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Title: Micrographia
       Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon


Author: Robert Hooke

Release Date: March 29, 2005  [eBook #15491]

Language: English

Character set encoding: ISO-646-US (US-ASCII)


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       *       *       *       *       *

By the Council of the ROYAL SOCIETY of London
for Improving of Natural Knowledge.

Ordered, That the Book written by Robert Hooke, M.A. Fellow of this
Society, Entituled, Micrographia, or some Physiological Descriptions of
Minute Bodies, made by Magnifying Glasses, with Observations and Inquiries
thereupon, Be printed by John Martyn, and James Allestry, Printers to
the said Society.

Novem. 23. 1664.

BROUNCKER. P.R.S.

       *       *       *       *       *


MICROGRAPHIA:

OR SOME

Physiological Descriptions

OF

MINUTE BODIES

MADE BY

MAGNIFYING GLASSES

WITH

OBSERVATIONS and INQUIRIES thereupon.

       *       *       *       *       *

By R. HOOKE, Fellow of the ROYAL SOCIETY.

       *       *       *       *       *






  _Non possis oculo quantum contendere Linceus,
  Non tamen idcirco contemnas Lippus inungi._ Horat. Ep. lib. 1.



[Illustration]

       *       *       *       *       *


LONDON, Printed by Jo. Martyn, and Ja. Allestry, Printers to the
ROYAL SOCIETY, and are to be sold at their Shop at the Bell in S.
Paul's Church-yard. M DC LX V.

       *       *       *       *       *


TO THE

KING.

SIR,

I Do here most humbly lay this _small_ Present at _Your Majesties_ Royal
feet. And though it comes accompany'd with two _disadvantages_, the
_meanness_ of the _Author_, and of the _Subject_; yet in both I am
_incouraged_ by the _greatness_ of your _Mercy_ and your _Knowledge_. By
the _one_ I am taught, that you can _forgive_ the most _presumptuous
Offendors_: And by the _other_, that you will not _esteem_ the least work
of _Nature_, or _Art_, unworthy your _Observation_. Amidst the many
_felicities_ that have accompani'd _your Majesties_ happy _Restauration_
and _Government_, it is none of the least considerable that _Philosophy_
and _Experimental Learning_ have _prosper'd_ under your _Royal Patronage_.
And as the calm prosperity of your Reign has given us the _leisure_ to
follow these _Studies_ of _quiet_ and _retirement_, so it is just, that the
_Fruits_ of them should, by way of _acknowledgement_, be return'd to _your
Majesty_. There are, Sir, several other of your Subjects, of your _Royal
Society_, now busie about _Nobler_ matters: The _Improvement_ of
_Manufactures_ and _Agriculture_, the _Increase_ of _Commerce_, the
_Advantage_ of _Navigation_: In all which they are _assisted_ by _your
Majesties Incouragement_ and _Example_. Amidst all those _greater_ Designs,
I here presume to bring in that which is more _proportionable_ to the
_smalness_ of my Abilities, and to offer some of the _least_ of all
_visible things_, to that _Mighty King_, that has _establisht an Empire_
over the best of all _Invisible things_ of this World, the _Minds_ of Men.

Your Majesties most humble
and most obedient
Subject and Servant,

ROBERT HOOKE.

       *       *       *       *       *

TO THE

ROYAL SOCIETY.

After my _Address_ to our _Great Founder_ and _Patron_, I could not but
think my self oblig'd, in consideration of those _many Ingagements_ you
have laid upon me, to offer these my _poor Labours_ to this MOST
ILLUSTRIOUS ASSEMBLY. YOU have been pleas'd formerly to accept of these
rude _Draughts_. I have since added to them some _Descriptions_, and some
_Conjectures_ of my own. And therefore, together with YOUR _Acceptance_, I
must also beg YOUR _pardon_. The Rules YOU have prescrib'd YOUR selves in
YOUR Philosophical Progress do seem the best that have ever yet been
practis'd. And particularly that of avoiding _Dogmatizing_, and the
_espousal_ of any _Hypothesis_ not sufficiently grounded and confirm'd by
_Experiments_. This way seems the most excellent, and may preserve both
_Philosophy_ and _Natural History_ from its former _Corruptions_. In saying
which, I may seem to condemn my own Course in this Treatise; in which there
may perhaps be some _Expressions_, which may seem more _positive_ then YOUR
Prescriptions will permit: And though I desire to have them understood only
as _Conjectures_ and _Quaeries_ (which YOUR Method does not altogether
disallow) yet if even in those I have exceeded, 'tis fit that I should
declare, that it was not done by YOUR Directions. For it is most
unreasonable, that YOU should undergo the _imputation_ of the _faults_ of
my _Conjectures_, seeing YOU can receive so _small advantage_ of reputation
by the _sleight Observations_ of

YOUR most humble and
most faithful Servant

ROBERT HOOKE.

       *       *       *       *       *


THE

PREFACE.

It is the great prerogative of Mankind above other Creatures, that we are
not only able to _behold_ the works of Nature, or barely to _sustein_ our
lives by them, but we have also the power of _considering_, _comparing_,
_altering_, _assisting_, and _improving_ them to various uses. And as this
is the peculiar priviledge of humane Nature in general, so is it capable of
being so far advanced by the helps of Art, and Experience, as to make some
Men excel others in their Observations, and Deductions, almost as much as
they do Beasts. By the addition of such _artificial Instruments_ and
_methods_, there may be, in some manner, a reparation made for the
mischiefs, and imperfection, mankind has drawn upon it self, by negligence,
and intemperance, and a wilful and superstitious deserting the Prescripts
and Rules of Nature, whereby every man, both from a deriv'd corruption,
innate and born with him, and from his breeding and converse with men, is
very subject to slip into all sorts of errors.

The only way which now remains for us to recover some degree of those
former perfections, seems to be, by rectifying the operations of the
_Sense_, the _Memory_, and _Reason_, since upon the evidence, the
_strength_, the _integrity_, and the _right correspondence_ of all these,
all the light, by which our actions are to be guided is to be renewed, and
all our command over things it to be establisht.

It is therefore most worthy of our consideration, to recollect their
several defects, that so we may the better understand how to supply them,
and by what assistances we may _inlarge_ their power, and _secure_ them in
performing their particular duties.

As for the actions of our _Senses_, we cannot but observe them to be in
many particulars much outdone by those of other Creatures, and when at
best, to be far short of the perfection they seem capable of: And these
infirmities of the Senses arise from a double cause, either from the
_disproportion of the Object to the Organ_, whereby an infinite number of
things can never enter into them, or else from _error in the Perception_,
that many things, which come within their reach, are not received in a
right manner.

The like frailties are to be found in the _Memory;_ we often let many
things _slip away_ from us, which deserve to be retain'd, and of those
which we treasure up, a great part is either _frivolous_ or _false_; and if
good, and substantial, either in tract of time _obliterated_, or at best so
_overwhelmed_ and buried under more frothy notions, that when there is need
of them, they are in vain sought for.

The two main foundations being so deceivable, it is no wonder, that all
the succeeding works which we build upon them, of arguing, concluding,
defining, judging, and all the other degrees of Reason, are lyable to the
same imperfection, being, at best, either vain, or uncertain: So that the
errors of the _understanding_ are answerable to the two other, being
defective both in the quantity and goodness of its knowledge; for the
limits, to which our thoughts are confin'd, are small in respect of the
vast extent of Nature it self; some parts of it are _too large_ to be
comprehended, and some _too little_ to be perceived. And from thence it
must follow, that not having a full sensation of the Object, we must be
very lame and imperfect in our conceptions about it, and in all the
proportions which we build upon it; hence, we often take the _shadow_ of
things for the _substance_, small _appearances_ for good _similitudes_,
_similitudes_ for _definitions;_ and even many of those, which we think, to
be the most solid definitions, are rather expressions of our own misguided
apprehensions then of the true nature of the things themselves.

The effects of these imperfections are manifested in different ways,
according to the temper and disposition of the several minds of men, some
they incline to _gross ignorance_ and stupidity, and others to a
_presumptuous imposing_ on other mens Opinions, and a _confident
dogmatizing_ on matters, whereof there it no assurance to be given.

Thus all the uncertainty, and mistakes of humane actions, proceed either
from the narrowness and wandring of our _Senses_, from the slipperiness or
delusion of our _Memory_, from the confinement or rashness of our
_Understanding_, so that 'tis no wonder, that our power over natural causes
and effects is so slowly improv'd, seeing we are not only to contend with
the obscurity and _difficulty of the things_ whereon we work and think, but
even the _forces of our own minds_ conspire to betray us.

These being the dangers in the process of humane Reason, the remedies of
them all can only proceed from the _real_, the _mechanical_, the
_experimental_ Philosophy, which has this advantage over the Philosophy of
_discourse_ and _disputation_, that whereas that chiefly aims at the
subtilty of its Deductions and Conclusions, without much regard to the
first ground-work, which ought to be well laid on the Sense and Memory; so
this intends the right ordering of them all, and the making them
serviceable to each other.

The first thing to be undertaken in this weighty work, is a _watchfulness
over the failings_ and an _inlargement of the dominion_, of the Senses.

To which end it is requisite, first, That there should be a _scrupulous_
choice, and a _strict examination_, of the reality, constancy, and
certainty of the Particulars that we admit: This is the first rise whereon
truth is to begin, and here the most severe, and most impartial diligence,
must be imployed; the storing up of all, without any regard to evidence or
use, will only tend to darkness and confusion. We must not therefore esteem
the riches of our Philosophical treasure by the _number_ only, but chiefly
by the _weight_; the most _vulgar_ Instances are not to be neglected, but
above all, the most _instructive_ are to be entertain'd; the footsteps of
Nature are to be trac'd, not only in her _ordinary course_, but when she
seems to be put to her shifts, to make many _doublings_ and _turnings_, and
to use some kind of art in indeavouring to avoid our discovery.

The next care to be taken, in respect of the Senses, is a supplying of
their infirmities with _Instruments_, and, as it were, the adding of
_artificial Organs_ to the _natural_; this in one of them has been of late
years accomplisht with prodigious benefit to all sorts of useful knowledge,
by the invention of Optical Glasses. By the means of _Telescopes_, there is
nothing so _far distant_ but may be represented to our view; and by the
help of _Microscopes_, there is nothing so _small_, as to escape our
inquiry; hence there is a new visible World discovered to the
understanding. By this means the Heavens are open'd, and a vast number of
new Stars, and new Motions, and new Productions appear in them, to which
all the ancient Astronomers were utterly Strangers. By this the Earth it
self, which lyes so neer us, under our feet, shews quite a new thing to us,
and in every _little particle_ of its matter; we now behold almost as great
a variety of Creatures, as we were able before to reckon up in the whole
_Universe_ it self.

It seems not improbable, but that by these helps the subtilty of the
composition of Bodies, the structure of their parts, the various texture of
their matter, the instruments and manner of their inward motions, and all
the other possible appearances of things, may come to be more fully
discovered; all which the ancient _Peripateticks_ were content to
comprehend in two general and (unless further explain'd) useless words of
_Matter_ and _Form_. From whence there may arise many admirable advantages,
towards the increase of the _Operative_, and the _Mechanick_ Knowledge, to
which this Age seems so much inclined, because we may perhaps be inabled to
discern all the secret workings of Nature, almost in the same manner as we
do those that are the productions of Art, and are manag'd by Wheels, and
Engines, and Springs, that were devised by humane Wit.

In this kind I here present to the World my imperfect Indeavours; which
though they shall prove no other way considerable, yet, I hope, they may be
in some measure useful to the main Design of a _reformation_ in Philosophy,
if it be only by shewing, that there it not so much requir'd towards it,
any strength of _Imagination_, or exactness of _Method_, or depth of
_Contemplation_ (though the addition of these, where they can be had, must
needs produce a much more perfect composure) as a sincere _Hand_, and a
_faithful_ Eye, to examine, and to record, the things themselves as they
appear.

And I beg my Reader, to let me take the boldness to assure him, that in
this present condition of knowledge, a man so qualified, as I have
indeavoured to be, only with resolution, and integrity, and plain
intentions of imploying his _Senses_ aright, may venture to compare the
reality and the usefulness of his services, towards the true Philosophy,
with those of other men, that are of much stronger, and more acute
_speculations_, that shall not make use of the same method by the Senses.

The truth is, the Science of Nature has been already too long made only a
work of the _Brain_ and the _Fancy_: It is now high time that it should
return to the plainness and soundness of _Observations_ on _material_ and
_obvious_ things. It is said of great Empires, That _the best way to
preserve them from decay, is to bring them back to the first Principles,
and Arts, on which they did begin_. The same is undoubtedly true in
Philosophy, that by wandring far away into _invisible Notions_, has almost
quite destroy'd it self, and it can never be recovered, or continued, but
by returning into the same _sensible paths_, in which it did at first
proceed.

If therefore the Reader expects from me any infallible Deductions, or
certainty of _Axioms_, I am to say for my self, that those stronger Works
of Wit and Imagination are above my weak Abilities; or if they had not been
so, I would not have made use of them in this present Subject before me:
Whenever he finds that I have ventur'd at any small Conjectures, at the
causes of the things that I have observed, I beseech him to look, upon them
only as _doubtful Problems_, and _uncertain ghesses_, and not as
unquestionable Conclusions, or matters of unconfutable Science; I have
produced nothing here, with intent to bind his understanding to an
_implicit_ consent; I am so far from that, that I desire him, not
absolutely to rely upon these Observations of my eyes, if he finds them
contradicted by the future Ocular Experiments of other and impartial
Discoverers.

As for my part, I have obtained my end, if these my small Labours shall be
thought fit to take up some place in the large stock, of _natural
Observations_, which so many hands are busie in providing. If I have
contributed the _meanest foundations_ whereon others may raise nobler
_Superstructures_, I am abundantly satisfied; and all my ambition is, that
I may serve to the great Philosophers of this Age, as the makers and the
grinders of my Glasses did to me; that I may prepare and furnish them with
some _Materials_, which they may afterwards _order_ and _manage_ with
better skill, and to far greater advantage.

The next remedies in this universal cure of the Mind are to be applyed to
the _Memory_, and they are to consist of such Directions as may inform us,
what things are best to be _stor'd up_ for our purpose, and which is the
best way of so _disposing_ them, that they may not only be _kept in
safety_, but ready and convenient, to be at any time _produc'd_ for use, as
occasion shall require. But I will not here prevent my self in what I may
say in another Discourse, wherein I shall make an attempt to propose some
Considerations of the manner of compiling a Natural and Artificial History,
and of so ranging and registring its Particulars into Philosophical Tables,
as may make them most useful for the raising of _Axioms_ and _Theories_.

The last indeed is the most _hazardous_ Enterprize, and yet the most
_necessary_; and that is, to take such care that the _Judgment_ and the
_Reason_ of Man (which is the third Faculty to be repair'd and improv'd)
should receive such assistance, as to avoid the dangers to which it it by
nature most subject. The Imperfections, which I have already mention'd, to
which it is lyable, do either belong to the _extent_, or the _goodness_ of
its knowledge; and here the difficulty is the greater, least that which may
be thought a _remedy_ for the one should prove _destructive_ to the other,
least by seeking to inlarge our Knowledge, we should render it weak, and
uncertain; and least by being too scrupulous and exact about every
Circumstance of it, we should confine and streighten it too much.

In both these the middle wayes are to be taken, nothing it to be_
omitted_, and yet every thing to pass a _mature deliberation_: No
_Intelligence_ from Men of all Professions, and quarters of the World, to
be _slighted_, and yet all to be so _severely examin'd_, that there remain
no room for doubt or instability; much _rigour_ in admitting, much
_strictness_ in comparing, and above all, much _slowness_ in debating, and
_shyness_ in determining, is to be practised. The _Understanding_ is to
_order_ all the inferiour services of the lower Faculties; but yet it is to
do this only as a _lawful Master_, and not at a _Tyrant._ It must not
_incroach_ upon their Offices, nor take upon it self the employments which
belong to either of them. It must _watch_ the irregularities of the Senses,
but it must not go before them, or _prevent_ their information. It must
_examine_, _range_, and _dispose_ of the bank which it laid up in the
Memory: but it must be sure to make _distinction_ between the _sober_ and
_well collected heap_, and the _extravagant Ideas_, and _mistaken Images_,
which there it may sometimes light upon. So many are the _links_, upon
which the true Philosophy depends, of which, if any one be _loose_, or
_weak_, the whole _chain_ is in danger of being dissolv'd; it is to _begin_
with the Hands and Eyes, and to _proceed_ on through the Memory, to be
_continued_ by the Reason; nor is it to stop there, but to _come about_ to
the Hands and Eyes again, and so, by a _continual passage round_ from one
Faculty to another, it is to be maintained in life and strength, as much as
the body of man it by the _circulation_ of the blood through the several
parts of the body, the Arms, the Feet, the Lungs, the Heart, and the Head.

If once this method were followed with diligence and attention, there is
nothing that lyes within the power of human Wit (or which is far more
effectual) of human Industry, which we might not compass; we might not only
hope for Inventions to equalize those of _Copernicus_, _Galileo_,
_Gilbert_, _Harvy_, and of others, whose Names are almost lost, that were
the Inventors of _Gun-powder_, the _Seamans Compass_, _Printing_,
_Etching_, _Graving_, _Microscopes_, &c. but multitudes that may far exceed
them: for even those discoveries seem to have been the products of some
such method, though but imperfect; What may not be therefore expected from
it if thoroughly prosecuted? _Talking_ and _contention of Arguments_ would
soon be turn'd into _labours_; all the fine _dreams_ of Opinions, and
_universal metaphysical natures_, which the luxury of subtil Brains has
devis'd, would quickly vanish, and give place to _solid Histories_,
_Experiments_ and _Works._ And as at first, mankind _fell_ by _tasting_ of
the forbidden Tree of Knowledge, so we, their Posterity, may be in part
_restor'd_ by the same way, not only by _beholding_ and _contemplating_,
but by _tasting_ too those fruits of Natural knowledge, that were never yet
forbidden.

From hence the World may be assisted with _variety_ of Inventions, _new_
matter for Sciences may be _collected_, the _old improv'd_, and their
_rust_ rubb'd away; and as it is by the benefit of Senses that we receive
all our Skill in the works of Nature, so they also may be wonderfully
benefited by it, and may be guided to an easier and more exact performance
of their Offices; 'tis not unlikely, but that we may find out wherein our
Senses are deficient, and as easily find wayes of repairing them.

The Indeavours of Skilful men have been most conversant about the
assistance of the Eye, and many noble Productions have followed upon it;
and from hence we may conclude, that there it a way open'd for advancing
the operations, not only of all the other Senses, but even of the Eye it
self; that which has been already done ought not to content us, but rather
to incourage us to proceed further, and to attempt greater things in the
same, and different wayes.

'Tis not unlikely, but that there may be yet invented several other helps
for the eye, at much exceeding those already found, as those do the bare
eye, such as by which we may perhaps be able to discover _living Creatures_
in the Moon, or other Planets, the _figures_ of the compounding Particles
of matter, and the particular _Schematisms_ and _Textures_ of Bodies.

And as _Glasses_ have highly promoted our _seeing_, so 'tis not
improbable, but that there may be found many _Mechanical Inventions_ to
improve our other Senses, of _hearing_, _smelling_, _tasting_, _touching._
'Tis not impossible to hear a _whisper_ a _furlongs_ distance, it having
been already done; and perhaps the nature of the thing would not make it
more impossible, though that furlong should be ten times multiply'd. And
though some famous Authors have affirm'd it impossible to hear through the
_thinnest plate_ of _Muscovy-glass_; yet I know a way, by which 'tis easie
enough to hear one speak through a _wall a yard thick_. It has not been yet
thoroughly examin'd, how far _Otocousticons_ may be improv'd, nor what
other wayes there may be of _quickning_ our hearing, or _conveying_ sound
through _other bodies_ then the _Air_: for that that it not the only
_medium_, I can assure the Reader, that I have, by the help of a _distended
wire_, propagated the sound to a very considerable distance in an
_instant_, or with as seemingly quick a motion as that of light, at least,
incomparably swifter then that, which at the same time was propagated
through the Air; and this not only in a straight line, or direct, but in
one bended in many angles.

Nor are the other three so perfect, but that _diligence_, _attention_, and
many _mechanical contrivances_, may also highly improve them. For since the
sense of _smelling_ seems to be made by the _swift passage_ of the _Air_
(_impregnated_ with the steams and _effluvia_ of several odorous Bodies)
through the grisly _meanders_ of the Nose whose surfaces are _cover'd_ with
a very sensible _nerve_, and _moistned_ by a _transudation_ from the
_processus mamillares_ of the Brain, and some adjoyning _glandules_, and by
the moist _steam_ of the _Lungs_, with a Liquor convenient for the
reception of those _effluvia_ and by the adhesion and mixing of those
steams with that liquor, and thereby affecting the nerve, or perhaps by
insinuating themselves into the juices of the brain, after the same manner,
as I have in the following Observations intimated, the parts of Salt to
pass through the skins of Effs, and Frogs. Since, I say, smelling seems to
be made by some such way, 'tis not improbable, but that some contrivance,
for making a great quantity of Air pass quick through the Nose, might at
much promote the sense of smelling, as the any wayes hindring that passage
does dull and destroy it. Several tryals I have made, both of hindring and
promoting this sense, and have succeeded in some according to expectation;
and indeed to me it seems capable of being improv'd, for the judging of the
constitutions of many Bodies. Perhaps we may thereby also judge (as other
Creatures seem to do) what is wholsome, what poyson; and in a word, what
are the specifick properties of Bodies.

There may be also some other mechanical wayes found out, of sensibly
perceiving the _effluvia_ of Bodies; several Instances of which, were it
here proper, I could give of Mineral steams and exhalations; and it seems
not impossible, but that by some such wayes improved, may be discovered,
what Minerals lye buried under the Earth, without the trouble to dig for
them; some things to confirm this Conjecture may be found in _Agricola_,
and other Writers of Minerals, speaking of the Vegetables that are apt to
thrive, or pine, in those steams.

Whether also those steams, which seem to issue out of the Earth, and mix
with the Air (and so to precipitate some _aqueous_ Exhalations, wherewith
'tis impregnated) may not be by some way detected before they produce the
effect, seems hard to determine; yet something of this kind I am able to
discover, by an Instrument I contriv'd to shew all the minute variations in
the pressure of the Air; by which I constantly find, that before, and
during the time of rainy weather, the pressure of the Air is less, and in
_dry weather_, but especially when an _Eastern Wind_ (which having past
over vast tracts of Land is heavy with Earthy Particles) blows, it is much
more, though these changes are varied according to very odd Laws.

    The Instrument is this. I prepare a pretty capaceous Bolt-head AB, with
    a small stem about two foot and a half long DC; upon the end of this D
    I put on a small bended Glass, or brazen _syphon_ DEF (open at D, E and
    F, but to be closed with cement at F and E, as occasion serves) whose
    stem F should be about six or eight inches long, but the bore of it not
    above half an inch diameter, and very even; these I fix very strongly
    together by the help of very hard Cement, and then fit the whole Glass
    ABCDEF into a long Board, or Frame, in such manner, that almost half
    the head AB may lye buried in a concave Hemisphere cut into the Board
    RS; then I place it so on the Board RS, as is exprest in the first
    figure of the first Scheme; and fix it very firm and steady in that
    posture, so as that the weight of the _Mercury_ that is afterwards to
    be put into it, may not in the least shake or stir it; then drawing a
    line XY on the Frame RT, so that it may divide the ball into two equal
    parts, or that it may pass, as 'twere, through the center of the ball.
    I begin from that, and divide all the rest of the Board towards UT into
    inches, and the inches between the 25 and the end E (which need not be
    above two or three and thirty inches distant from the line XY) I
    subdivide into Decimals; then stopping the end F with soft Cement, or
    soft Wax, I invert the Frame, placing the head downwards, and the
    Orifice E upwards; and by it, with a small Funnel, I fill the whole
    Glass with Quicksilver; then by stopping the small Orifice E with my
    finger, I oftentimes erect and invert the whole Glass and Frame, and
    thereby free the Quicksilver and Glass from all the bubbles or parcels
    of lurking Air; then inverting it as before, I fill it top full with
    clear and well strain'd Quicksilver, and having made ready a small ball
    of pretty hard Cement, by heat made very soft, I press it into the hole
    E, and thereby stop it very fast; and to secure this Cement from flying
    out afterward, I bind over it a piece of Leather, that is spread over
    in the inside with Cement, and wound about it while the Cement is hot:
    Having thus softned it, I gently erect again the Glass after this
    manner: I first let the Frame down edge-wayes, till the edge RV touch
    the Floor, or ly horizontal; and then in that edging posture raise the
    end RS; this I do, that if there chance to be any Air hidden in the
    small Pipe E, it may ascend into the Pipe F, and not into the Pipe DC:
    Having thus erected it, and hung it by the hole Q, or fixt it
    perpendicularly by any other means, I open the end F, and by a small
    _Syphon_ I draw out the _Mercury_ so long, till I find the surface of
    it AB in the head to touch exactly the line XY; at which time I
    immediately take away the _Syphon_, and if by chance it be run somewhat
    below the line XY, by pouring in gently a little _Mercury_ at F, I
    raise it again to its desired height, by this contrivance I make all
    the sensible rising and falling of the _Mercury_ to be visible in the
    surface of the _Mercury_ in the Pipe F, and scarce any in the head AB.
    But because there really is some small change of the upper surface
    also, I find by several Observations how much it rises in the Ball, and
    falls in the Pipe F, to make the distance between the two surfaces an
    inch greater then it was before; and the measure that it falls in the
    Pipe is the length of the inch by which I am to mark the parts of the
    Tube F, or the Board on which it lyes, into inches and Decimals: Having
    thus justned and divided it, I have a large Wheel MNOP, whose outmost
    limb is divided into two hundred equal parts; this by certain small
    Pillars is fixt on the Frame RT, in the manner exprest in the Figure.
    In the middle of this, on the back side, in a convenient frame, is
    placed a small Cylinder, whose circumference is equal to twice the
    length of one of those divisions, which I find answer to an inch of
    ascent, or descent, of _Mercury_: This Cylinder I, is movable on a very
    small Needle, on the end of which is fixt a very light Index KL, all
    which are so pois'd on the Axis, or Needle, that no part is heavier
    then another: Then about this Cylinder is wound a small Clew of Silk,
    with two small steel Bullets at each end of it GH; one of these, which
    is somewhat the heavier, ought to be so big, as freely to move to and
    fro in the Pipe F; by means of which contrivance, every the least
    variation of the height of the _Mercury_ will be made exceeding visible
    by the motion to and fro of the small Index KL.

But this is but one way of discovering the _effluvia_ of the Earth mixt
with the Air; there may be, perhaps many others, witness the _Hygroscope_,
an Instrument whereby the watery steams volatile in the Air are discerned,
which the Nose it self is not able to find. This I have describ'd in the
following Tract in the Description of the Beard of a wild Oat. Others
there, are, may be discovered both by the Nose, and by other wayes also.
Thus the _smoak_ of burning _Wood_ is _smelt_, _seen_, and sufficiently
_felt_ by the eyes: The _fumes_ of burning _Brimstone_ are _smelt_ and
discovered also by the destroying the Colours of Bodies, as by the
_whitening of a red Rose_: And who knows, but that the Industry of man,
following this method, may find out wayes of improving this sense to as
great a degree of perfection at it is in any Animal, and perhaps yet
higher.

'Tis not improbable also, but that our _taste_ may be very much improv'd
either by _preparing_ our taste for the Body, as, after eating _bitter_
things, _Wine_, or other _Vinous liquors_, are more sensibly tasted; or
else by _preparing_ Bodies for our tast; as the dissolving of Metals with
acid Liquors, make them tastable, which were before altogether insipid;
thus _Lead_ becomes _sweeter_ then Sugar, and _Silver_ more _bitter_ then
Gall, _Copper_ and _Iron_ of most _loathsome_ tasts. And indeed the
business of this sense being to discover the presence of dissolved Bodies
in Liquors put on the Tongue, or in general to discover that a fluid body
has some solid body dissolv'd in it, and what they are; whatever
contrivance makes this discovery improves this sense. In this kind the
mixtures of Chymical Liquors afford many Instances; as the sweet Vinegar
that is impregnated with Lead may be discovered to be so by the affusion of
a little of an _Alcalizate solution_: The bitter liquor of _Aqua fortis_
and _Silver_ may be discover'd to be charg'd with that Metal, by laying in
it some plates of Copper: 'Tis not improbable also, but there may be
multitudes of other wayes of discovering the parts dissolv'd, or dissoluble
in liquors; and what is this discovery but a kind of _secundary tasting_.

'Tis not improbable also, but that the sense of _feeling_ may be highly
improv'd, for that being a sense that judges of the more _gross_ and
_robust motions_ of the _Particles_ of _Bodies_, seems capable of being
improv'd and assisted very many wayes. Thus for the distinguishing of
_Heat_ and _Cold_, the _Weather-glass_ and _Thermometer_, which I have
describ'd in this following Treatise, do exceedingly perfect it; by each of
which the least variations of heat or cold, which the most Acute sense is
not able to distinguish, are manifested. This is oftentimes further
promoted also by the help of _Burning-glasses_, and the like, which collect
and unite the radiating heat. Thus the _roughness_ and _smoothness_ of a
Body is made much more sensible by the help of a _Microscope_, then by the
most _tender_ and _delicate Hand_. Perhaps, a Physitian might, by several
other _tangible_ proprieties, discover the constitution of a Body as well
as by the _Pulse_. I do but instance in these, to shew what possibility
there may be of many others, and what probability and hopes there were of
finding them, if this method were followed; for the Offices of the five
Senses being to detect either the _subtil_ and _curious Motions_ propagated
through all _pellucid_ or perfectly _homogeneous_ Bodies; Or the more
_gross_ and _vibrative Pulse_ communicated through the _Air_ and all other
convenient _mediums_, whether fluid or solid: Or the _effluvia_ of Bodies
_dissolv'd_ in the _Air_; Or the _particles_ of bodies _dissolv'd_ or
_dissoluble_ in _Liquors_, or the more _quick_ and _violent shaking motion_
of _heat_ in all or any of these: whatsoever does any wayes promote any of
these kinds of _criteria_, does afford a way of improving some one sense.
And what a multitude of these would a diligent Man meet with in his
inquiries? And this for the helping and promoting the _sensitive faculty_
only.

Next, as for the _Memory_, or _retentive faculty_, we may be sufficiently
instructed from the _written Histories_ of _civil actions_, what great
assistance may be afforded the Memory, in the committing to writing things
observable in _natural operations_. If a Physitian be therefore accounted
the more able in his Faculty, because he has had long experience and
practice, the remembrance of which, though perhaps very imperfect, does
regulate all his after actions: What ought to be thought of that man, that
has not only a perfect _register_ of his own experience, but it grown _old_
with the experience of many hundreds of years, and many thousands of men.

And though of late, men, beginning to be sensible of this convenience,
have here and there registred and printed some few _Centuries_, yet for the
most part they are set down very lamely and imperfectly, and, I fear, many
times not so truly, they seeming, several of them, to be design'd more for
_Ostentation_ then _publique use_: For, not to instance, that they do, for
the most part, omit those Experiences they have made, wherein their
Patients have miscarried, it is very easie to be perceiv'd, that they do
all along _hyperbolically extol_ their own Prescriptions, and vilifie those
of others. Notwithstanding all which, these kinds of Histories are
generally esteem'd useful, even to the ablest Physitian.

What may not be expected from the _rational_ or _deductive Faculty_ that
is furnisht with such _Materials_, and those so readily _adapted_, and
rang'd for use, that in a moment, at 'twere, thousands of Instances,
serving for the _illustration_, _determination_, or _invention_, of almost
any inquiry, may be _represented_ even to the sight? How neer the nature of
_Axioms_ must all those _Propositions_ be which are examin'd before so many
_Witnesses_? And how difficult will it be for any, though never so subtil
an error in Philosophy, to _scape_ from being discover'd, after it has
indur'd the _touch_, and so many other _tryals_?

What kind of mechanical way, and physical invention also is there requir'd
that might not this may be found out? The _Invention_ of a way to find the
_Longitude_ of places is easily perform'd, and that to as great
_perfection_ as is desir'd, or to at great an _accurateness_ as the
_Latitude_ of places can be found at Sea; and perhaps yet also to a greater
certainty then that has been hitherto found, as I shall very speedily
freely manifest to the world. The way of _flying_ in the Air seems
principally unpracticable, by reason of the _want of strength_ in _humane
muscles_; if therefore that could be suppli'd, it were, I think, easie to
make twenty contrivances to perform the office of _Wings_: What Attempts
also I have made for the supplying that Defect, and my successes therein,
which, I think, are wholly new, and not inconsiderable, I shall in another
place relate.

'Tis not unlikely also, but that _Chymists_, if they followed this method,
might find out their so much sought for _Alkahest_. What an _universal
Menstruum_, which dissolves all sorts of _Sulphureous Bodies_, I have
discover'd (which hat not been before taken notice of as such) I have shewn
in the sixteenth Observation.

What a prodigious variety of Inventions in _Anatomy_ has this latter Age
afforded, even in our own Bodies in the very _Heart_, by which we live, and
the Brain, which is the seat of our knowledge of other things? witness all
the excellent Works of _Pecquet_, _Bartholinus_, _Billius_, and many
others; and at home, of Doctor _Harvy_, Doctor _Ent_, Doctor _Willis_,
Doctor _Glisson_. In _Celestial Observations_ we have far exceeded all the
Antients, even the _Chaldeans_ and _Egyptians_ themselves, whose _vast
Plains_, _high Towers_, and _clear Air_, did not give them so great
advantages over us, as have over them by our _Glasses_. By the help of
which, they have been very much outdone by the famous _Galileo_,
_Hevelius_, _Zulichem_; and our own Countrymen, Mr. _Rook_, Doctor _Wren_,
and the great Ornament of our Church and Nation, the _Lord Bishop of
Exeter_. And to say no more in _Aerial Discoveries_, there has been a
wonderful progress made by the _Noble Engine_ of _the most Illustrious Mr.
Boyle_, whom it becomes me to mention with all honour, not only as my
particular Patron, but as the _Patron_ of _Philosophy_ it self; which he
every day _increases_ by his _Labours_, and _adorns_ by his _Example_.

The good success of all these _great Men_, and many others, and the now
seemingly great _obviousness_ of most of their and divers other Inventions,
which from the beginning of the world have been, as 'twere, trod on, and
yet not minded till these last _inquisitive_ Ages (an Argument that there
may be yet behind multitudes of the like) puts me in mind to recommend such
Studies, and the prosecution of them by such methods, to the _Gentlemen_ of
our Nation, whose _leisure_ makes them fit to _undertake_, and the _plenty_
of their fortunes _to accomplish_, extraordinary things in this way. And I
do not only propose this kind of _Experimental Philosophy_ as matter of
high _rapture_ and _delight_ of the mind, but even as a _material_ and
_sensible Pleasure_. So vast it the _variety of Objects_ which will come
under their Inflections, so many _different wayes_ there are _of handling_
them, so great is the _satisfaction_ of _finding_ out _new things_, that I
dare compare the _contentment_ which they will injoy, not only to that of
_contemplation_, but even to that which most men prefer of _the very Senses
themselves_.

And if they will please to take any incouragement from so mean and so
imperfect endeavours as mine, upon my own experience, I can assure them,
without arrogance, That there has not been any inquiry or Problem in
_Mechanicks_, that I have hitherto propounded to my self, but by a certain
method (which I may on some other opportunity explain) I have been able
presently to examine the possibility of it; and if so, as easily to
excogitate divers wayes of performing it: And indeed it is possible to do
as much by _this method_ in _Mechanicks_, as by _Algebra_ can be perform'd
in _Geometry_. Nor can I at all doubt, but that the same method is as
applicable to _Physical Enquiries_, and as likely to find and reap thence
at plentiful a crop of Inventions; and indeed there seems to be no subject
so barren, but may with this good husbandry be highly improv'd.

Toward the prosecution of this method in _Physical Inquiries_, I have here
and there _gleaned_ up an _handful_ of Observations, in the collection of
most of which I made use of _Microscopes_, and some other _Glasses_ and
_Instruments_ that improve the sense; which way I have herein taken, not
that there are not multitudes of useful and pleasant Observables, yet
uncollected, obvious enough without the helps of Art, but only to promote
the use of Mechanical helps for the Senses, both in the surveying the
already visible World, and for the discovery of many others hitherto
unknown, and to make us, with the great Conqueror, to be affected that we
have not yet overcome one World when there are so many others to be
discovered, every considerable improvement of _Telescopes_ or _Microscopes_
producing new Worlds and _Terra-Incognita's_ to our view.

The Glasses I used were of our English make, but though very good of the
kind, yet far short of what might be expected, could we once find a way of
making Glasses Elliptical, or of some more true shape; for though both
_Microscopes_, and _Telescopes_, as they now are, will magnifie an Object
about a thousand thousand times bigger then it appears to the naked eye;
yet the Apertures of the Object-glasses are so very small, that very few
Rays are admitted, and even of those few there are so many false, that the
Object appears _dark_ and _indistinct_: And indeed these inconveniences are
such, as seem inseparable from Spherical Glasses, even when most exactly
made; but the way we have hitherto made use of for that purpose is so
imperfect, that there may be perhaps ten wrought before one be made
tolerably good, and most of those ten perhaps every one differing in
goodness one from another, which is an Argument, that the way hitherto used
is, at least, very uncertain. So that these Glasses have a double defect;
the one, that very few of them are exactly true wrought; the other, that
even of those that are best among them, none will admit a sufficient number
of Rayes to magnifie the Object beyond a determinate bigness. Against which
Inconveniences the only Remedies I have hitherto met with are these.

    First, for _Microscopes_ (where the Object we view is near and within
    our power) the best way of making it appear bright in the Glass, is to
    cast a great quantity of light on it by means of _convex glasses_, for
    thereby, though the aperture be very small, yet there will throng in
    through it such multitudes, that an Object will by this means indure to
    be magnifi'd as much again as it would be without it. The way for doing
    which is this. I make choice of some Room that has only one window open
    to the South, and at about three or four foot distance from this
    Window, on a Table, I place my _Microscope_, and then so place either a
    round Globe of Water, or a very deep clear_ plano convex_ Glass (whose
    convex side is turn'd towards the Window) that there is a great
    quantity of Rayes collected and thrown upon the Object: Or if the Sun
    shine, I place a small piece of oyly Paper very near the Object,
    between that and the light; then with a good large Burning-Glass I so
    collect and throw the Rayes on the Paper, that there may be a very
    great quantity of light pass through it to the Object; yet I so
    proportion that light, that it may not singe or burn the Paper. Instead
    of which Paper there may be made use of a small piece of Looking-glass
    plate, one of whose sides is made rough by being rubb'd on a flat Tool
    with very find sand, this will, if the heat be leisurely cast on it,
    indure a much greater degree of heat, and consequently very much
    augment a convenient light. By all which means the light of the Sun, or
    of a Window, may be so cast on an Object, as to make it twice as light
    as it would otherwise be without it, and that without any inconvenience
    of glaring, which the immediate light of the Sun is very apt to create
    in most Objects; for by this means the light is so equally diffused,
    that all parts are alike inlightned; but when the immediate light of
    the Sun falls on it, the reflexions from some few parts are so vivid,
    that they drown the appearance of all the other, and are themselves
    also, by reason of the inequality of light, indistinct, and appear only
    radiant spots.

    But because the light of the Sun, and also that of a Window, is in a
    continual variation, and so many Objects cannot be view'd long enough
    by them to be throughly examin'd; besides that, oftentimes the Weather
    is so dark and cloudy, that for many dayes together nothing can be
    view'd: And because also there are many Objects to be met with in the
    night, which cannot so conveniently be kept perhaps till the day,
    therefore to procure and cast a sufficient quantity of light on an
    Object in the night, I thought of, and often used this, Expedient.

    I procur'd me a small Pedestal, such as is describ'd in the fifth
    Figure of the first _Scheme_ on the small Pillar AB, of which were two
    movable Armes CD, which by means of the Screws EF, I could fix in any
    part of the Pillar; on the undermost of these I plac'd a pretty large
    Globe of Glass G, fill'd with exceeding clear Brine, stopt, inverted,
    and fixt in the manner visible in the Figure; out of the side of which
    Arm proceeded another Arm H, with many joynts; to the end of which was
    fastned a deep plain _Convex glass_ I, which by means of this Arm could
    be moved too and fro, and fixt in any posture. On the upper Arm was
    placed a small Lamp K, which could be to mov'd upon the end of the Arm,
    as to be set in a fit posture to give light through the Ball: By means
    of this Instrument duly plac'd, as is exprest in the Figure, with the
    small flame of a Lamp may be cast as great and convenient a light on
    the Object as it will well indure; and being always constant, and to be
    had at any time, I found most proper for drawing the representations of
    those small Objects I had occasion to observe.

    None of all which ways (though much beyond any other hitherto made use
    of by any I know) do afford a sufficient help, but after a certain
    degree of magnifying, they leave us again in the lurch. Hence it were
    very desirable, that some way were thought of for making the
    Object-glass of such a Figure as would conveniently bear a large
    Aperture.

As for _Telescopes_, the only improvement they seem capable of, is the
increasing of their length; for the Object being remote, there is no
thought of giving it a greater light then it has; and therefore to augment
the. Aperture, the Glass must be ground of a very large sphere; for, by
that means, the longer the Glass be, the bigger aperture will it bear, if
the Glasses be of an equal goodness in their kind. Therefore a six will
indure a much larger Aperture then a three foot Glass, and a sixty foot
Glass will proportionably bear a greater Aperture then a thirty, and will
as much excel it also as a six foot does a three foot, as I have
experimentally observ'd in one of that length made by Mr. _Richard Reives_
here at _London_, which will bear an Aperture above three inches over, and
yet make the Object proportionably big and distinct; whereas there are very
few thirty foot Glasses that will indure an Aperture of more then two
inches over. So that for _Telescopes_, supposing we had a very ready way of
making their Object Glasses of exactly spherical Surfaces, we might, by
increasing the length of the Glass, magnifie the Object to any assignable
bigness. And for performing both these, I cannot imagine any way more
easie, and more exact, then by this following Engine, by means of which,
any Glasses, of what length soever, may be speedily made. It seems the most
easie, because with one and the same Tool may be with care ground an Object
Glass, of any length or breadth requisite, and that with very little or no
trouble in fitting the Engine, and without much skill in the Grinder. It
seems to be the most exact, for to the very last stroke the Glass does
regulate and rectifie the Tool to its exact Figure; and the longer or more
the Tool and Glass are wrought together, the more exact will both of them
be of the desir'd Figure. Further, the motions of the Glass and Tool do so
cross each other, that there is not one point of eithers Surface, but has
thousands of cross motions thwarting it, so that there can be no kind of
Rings or Gutters made either in the Tool or Glass.

    The contrivance of the Engine is, only to make the ends of two large
    _Mandrils_ so to move, that the Centers of them may be at any
    convenient distance asunder, and that the _Axis_ of the _Mandrils_
    lying both in the same plain produc'd, may meet each other in any
    assignable Angle; both which requisites may be very well perform'd by
    the Engine describ'd in the third Figure of the first _Scheme_: where
    AB signifies the Beam of a Lath fixt perpendicularly or Horizontally,
    CD the two Poppet heads, fixt at about two foot distance, EF an Iron
    _Mandril_, whose tapering neck F runs in an adapted tapering brass
    Collar; the other end E runs on the point of a Screw G; in a convenient
    place of this is fastned H a pully Wheel, and into the end of it, that
    comes through the Poppet head C, is screwed a Ring of a hollow
    _Cylinder_ K, or some other conveniently shap'd Tool, of what wideness
    shall be thought most proper for the cize of Glasses, about which it is
    to be imploy'd: As, for Object glasses, between twelve foot and an
    hundred foot long, the Ring may be about six inches over, or indeed
    somewhat more for those longer Glasses. It would be convenient also and
    not very chargeable, to have four or five several Tools; as one for all
    Glasses between an inch and a foot, one for all Glasses between a foot
    and ten foot long, another for all between ten and an hundred, a fourth
    for all between a hundred and a thousand foot long; and if Curiosity
    shall ever proceed so far, one for all lengths between a thousand and
    ten thousand foot long; for indeed the principle is such, that
    supposing the _Mandrils_ well made, and of a good length, and supposing
    great care be used in working and polishing them, I see no reason, but
    that a Glass of a thousand, nay of ten thousand foot long, may be as
    well made as one of ten; for the reason is the same, supposing the
    _Mandrils_ and Tools be made sufficiently strong, so that they cannot
    bend; and supposing the Glass, out of which they are wrought, be
    capable of so great a regularity in its parts as to refraction: this
    hollow _Cylinder_ K is to contain the Sand, and by being drove round
    very quick to and fro by means of a small Wheel, which may be mov'd
    with ones foot, serves to grind the Glass: The other _Mandril_ is
    shap'd like this, but it has an even neck instead of a taper one, and
    runs in a Collar, that by the help of a Screw and a joynt made like M
    in the Figure, it can be still adjustned to the wearing or wasting
    neck: into the end of this _Mandril_ is screwed a Chock N on which with
    Cement or Glew is fastned the piece of Glass Q that is to be form'd;
    the middle of which Glass is to be plac'd just on the edge of the Ring
    and the Lath OP is to be set and fixt (by means of certain pieces and
    screws the manner whereof will be sufficiently evidenc'd by the Figure)
    in such an Angle as is requisite to the forming of such a Sphere as the
    Glass is design'd to be of; the geometrical ground of which being
    sufficiently plain, though not heeded before, I shall, for brevities
    sake, pass over. This last _Mandril_ to be made (by means of the
    former, or some other Wheel) to run round very swift also, by which two
    cross motions the Glass cannot chuse (if care be us'd) but be wrought
    into a most exactly spherical Surface.

But because we are certain, from the _Laws of refraction_ (which I I have
experimentally found to be so, by an Instrument I shall presently describe)
that _the lines of the angles of Incidence are proportionate to the lines
of the angles of Refraction_, therefore if Glasses could be made of those
kind of Figures, or some other, such as the most incomparable _Des Cartes_
has invented, and demonstrated in his Philosophical and Mathematical Works,
we might hope for a much greater perfection of Opticks then can be
rationally expected from spherical ones; for though, _caeteris paribus_, we
find, that the larger the _Telescope_ Object Glasses are, and the shorter
those of the _Microscope_, the better they magnify, yet both of them,
beside such determinate dimensions, are by certain inconveniences rendred
unuseful; for it will be exceeding _difficult_ to make and _manage_ a Tube
above an _hundred foot long_, and it will be as difficult to _inlighten_ an
Object less then an hundred part of an inch distant from the Object Glass.

I have not as yet made any attempts of that kind, though I know two or
three wayes, which, as far as I have yet considered, seem very probable,
and may invite me to make a tryal as soon as I have an opportunity, of
which I may hereafter perhaps acquaint the world. In the Interim, I shall
describe the Instrument I even now mention'd, by which the _refraction_ of
all kinds of Liquors may be most exactly measur'd, thereby to give the
curious an opportunity of making what further tryals of that kind they
shall think requisite to any of their intended tryals; and to let them see
that the laws of Refraction are not only notional.

    The Instrument consisted of five Rulers, or long pieces placed
    together, after the manner exprest in the second Figure of the first
    _Scheme_, where AB denotes a straight piece of wood about six foot and
    two inches long, about three inches over, and an inch and half thick,
    on the back side of which was hung a small plummet by a line stretcht
    from top to bottom, by which this piece was set exactly upright, and so
    very firmly fixt; in the middle of this was made a hole or center, into
    which one end of a hollow cylindrical brass Box CC, fashion'd as I
    shall by and by describe, was plac'd, and could very easily and truly
    be mov'd to and fro; the other end of this Box being put into, and
    moving in, a hole made in a small arm DD; into this box was fastned the
    long Ruler EF, about three foot and three or four inches long, and at
    three foot from the above mention'd Centers PP was a hole E, cut
    through, and cross'd with two small threads, and at the end of it was
    fixt a small sight G, and on the back side of it was fixt a small Arm
    H, with a Screw to fix it in any place on the Ruler LM; this Ruler LM
    was mov'd on the Center B (which was exactly three foot distance from
    the middle Center P) and a line drawn through the middle of it LM, was
    divided by a Line of cords into some sixty degrees, and each degree was
    subdivided into minutes, so that putting the cross of the threads in E
    upon any part of this divided line, I presently knew what Angle the two
    Rules AB and EF made with each other, and by turning the Screw in H, I
    could fix them in any position. The other Ruler also RS was made much
    after the same manner, only it was not fixt to the hollow cylindrical
    Box, but, by means of two small brass Armes or Ears, it mov'd on the
    Centers of it; this also, by means of the cross threads in the hole S,
    and by a Screw in K, could be fastned on any division of another line
    of cords of the same radius drawn on NO. And so by that means, the
    Angle made by the two Rulers, AB and RS, was also known. The Brass box
    CC in the middle was shap'd very much like the Figure X, that is, it
    was a cylindrical Box stopp'd close at either end, off of which a part
    both of the sides and bottomes was cut out, so that the Box, when the
    Pipe and that was joyned to it, would contain the Water when fill'd
    half full, and would likewise, without running over, indure to be
    inclin'd to an Angle, equal to that of the greatest refraction of
    Water, and no more, without running over. The Ruler EF was fixt very
    fast to the Pipe V, so that the Pipe V directed the length of the Ruler
    EF, and the Box and Ruler were mov'd on the Pin TT, so as to make any
    desirable Angle with the Ruler AB. The bottom of this Pipe V was stop'd
    with a small piece of exactly plain Glass, which was plac'd exactly
    perpendicular to the Line of direction, or _Axis_ of the Ruler EF. The
    Pins also TT were drill'd with small holes through the _Axis_, and
    through those holes was stretcht and fastned a small Wire. There was
    likewise a small Pipe of Tin loosly put on upon the end of V, and
    reaching down to the sight G; the use of which was only to keep any
    false Rayes of light from passing through the bottom of V, and only
    admitting such to pass as pierced through the sight G: All things being
    placed together in the manner describ'd in the Figure; that is, the
    Ruler AB being fixt perpendicular, I fill'd the Box CC with Water, or
    any other Liquor, whose refraction I intended to try, till the Wire
    passing through the middle of it were just covered: then I moved and
    fixt the Ruler FE at any assignable Angle, and placed the flame of a
    Candle just against the sight G; and looking through the sight I, I
    moved the Ruler RS to and fro, till I perceived the light passing
    through G to be covered, as 'twere, or divided by the dark Wire passing
    through PP: then turning the Screw in K, I fixt it in that posture: And
    through the hole S, I observed what degree and part of it was cut by
    the cross threads in S. And this gave me the Angle of Inclination, APS
    answering to the Angle of Refraction BPE: for the surface of the Liquor
    in the Box will be alwayes horizontal, and consequently AB will be a
    perpendicular to it; the Angle therefore APS will measure, or be the
    Angle of Inclination in the Liquor; next EPB must be the Angle of
    Refraction, for the Ray that passes through the sight G, passes also
    perpendicularly through the Glass _Diaphragme_ at F, and consequently
    also perpendicularly through the lower surface of the Liquor contiguous
    to the Glass, and therefore suffers no refraction till it meet with the
    horizontal surface of the Liquor in CC, which is determined by the two
    Angles.

By means of this Instrument I can with _little trouble_, and a very small
quantity of any _Liquor_, examine, most accurately, the _refraction_ of it
not only for one inclination, but for all; and thereby am inabled to make
very accurate Tables; several of which I have also experimentally made, and
find, that _Oyl of Turpentine_ has a much greater Refraction then _Spirit
of Wine_, though it be _lighter_; and that _Spirit of Wine_ has a greater
Refraction then _Water_, though it be lighter also; but that _salt Water_
also has a greater Refraction then _fresh_, though it be _heavier_: but
_Allum water_ has a less refraction then common _Water_, though heavier
also. So that it seems, as to the _refraction_ made in a Liquor, the
_specifick gravity_ is of no efficacy. By this I have also found that look
what _proportion _the _Sine_ of the Angle of _one Inclination_ has to the
_Sine_ of the Angle of _Refraction_, correspondent to it, the same
_proportion_ have all the _Sines_ of other Inclinations to the _Sines_ of
their appropriate Refractions.

    My way for measuring how much a Glass magnifies an Object, plac'd at a
    convenient distance from my eye, is this. Having rectifi'd the
    _Microscope_, to see the desir'd Object through it very distinctly, at
    the same time that I look upon the Object through the Glass with one
    eye, I look upon other Objects at the same distance with my other bare
    eye; by which means I am able, by the help of a _Ruler_ divided into
    inches and small parts, and laid on the _Pedestal_ of the _Microscope_,
    to cast, as it were, the magnifi'd appearance of the Object upon the
    Ruler, and thereby exactly to measure the Diameter it appears of
    through the Glass, which being compar'd with the Diameter it appears of
    to the naked eye, will easily afford the quantity of its magnifying.

    The _Microscope_, which for the most part I made use of, was shap'd
    much like that in the sixth Figure of the first _Scheme_, the Tube
    being for the most part not above six or seven inches long, though, by
    reason it had four Drawers, it could very much be lengthened, as
    occasion required; this was contriv'd with three Glasses; a small
    Object Glass at A, a thinner Eye Glass about B, and a very deep one
    about C: this I made use of only when I had occasion to see much of an
    Object at once; the middle Glass conveying a very great company of
    radiating Pencils, which would go another way, and throwing them upon
    the deep Eye Glass. But when ever I had occasion to examine the small
    parts of a Body more accurately, I took out the middle Glass, and only
    made use of one Eye Glass with the Object Glass, for always the fewer
    the Refractions are, the more bright and clear the Object appears. And
    therefore 'tis not to be doubted, but could we make a_ Microscope _to
    have one only refraction, it would, _caeteris paribus_, far excel any
    other that had a greater number. And hence it is, that if you take a
    very clear piece of a broken _Venice_ Glass, and in a Lamp draw it out
    into very small hairs or threads, then holding the ends of these
    threads in the flame, till they melt and run into a small round Globul,
    or drop, which will hang at the end of the thread; and if further you
    stick several of these upon the end of a stick with a little sealing
    Wax, so as that the threads stand upwards, and then on a Whetstone
    first grind off a good part of them, and afterward on a smooth Metal
    plate, with a little Tripoly, rub them till they come to be very
    smooth; if one of these be fixt with a little soft Wax against a small
    needle hole, prick'd through a thin Plate of Brass, Lead, Pewter, or
    any other Metal, and an Object, plac'd very near, be look'd at through
    it, it will both magnifie and make some Objects more distinct then any
    of the great _Microscopes_. But because these, though exceeding easily
    made, are yet very troublesome to be us'd, because of their smallness,
    and the nearness of the Object; therefore to prevent both these, and
    yet have only two Refractions, I provided me a Tube of Brass, shap'd
    much like that in the fourth Figure of the first _Scheme_; into the
    smaller end of this I fixt with Wax a good _plano convex_ Object Glass,
    with the convex side towards the Object, and into the bigger end I fixt
    also with wax a pretty large plano _Convex_ Glass, with the _convex_
    side towards my eye, then by means of the small hole by the side, I
    fill'd the intermediate space between these two Glasses with very clear
    Water, and with a Screw stopp'd it in; then putting on a Cell for the
    Eye, I could perceive an Object more bright then I could when the
    intermediate space was only fill'd with Air, but this, for other
    inconveniences, I made but little use of.

    My way for fixing both the Glass and Object to the Pedestal most
    conveniently was thus: Upon one side of a round Pedestal AB, in the
    sixth Figure of the first _Scheme_, was fixt a small Pillar CC, on this
    was fitted a small Iron Arm D, which could be mov'd up and down, and
    fixt in any part of the Pillar, by means of a small Screw E; on the end
    of this Arm was a small Ball fitted into a kind of socket F, made in
    the side of the Brass Ring G, through which the small end of the Tube
    was screw'd; by means of which contrivance I could place and fix the
    Tube in what posture I desir'd (which for many Observations was
    exceeding necessary) and adjusten it most exactly to any Object.

    For placing the Object, I made this contrivance; upon the end of a
    small brass Link or Staple HH, I so fastned a round Plate II, that it
    might be turn'd round upon its Center K, and going pretty stiff, would
    stand fixt in any posture it was set; on the side of this was fixt a
    small Pillar P, about three quarters of an inch high, and through the
    top of this was thrust a small Iron pin M, whose top just stood over
    the Center of the Plate; on this top I fixt a small Object, and by
    means of these contrivances I was able to turn it into all kind of
    positions, both to my Eye and the Light; for by moving round the small
    Plate on its center, could move it one way, and by turning the Pin M, I
    could move it another way, and this without stirring the Glass at all,
    or at least but very little; the Plate likewise I could move to and fro
    to any part of the Pedestal (which in many cases was very convenient)
    and fix it also in any Position, by means of a Nut N, which was screw'd
    on upon the lower part of the Pillar CC. All the other Contrivances are
    obvious enough from the draught, and will need no description.

Now though this were the Instrument I made most use of, yet I have made
several other Tryals with other kinds of Microscopes, which both for
_matter_ and _form_ were very different from common spherical Glasses. I
have made a _Microscope_ with one piece of Glass, both whose surfaces were
_plains_. I have made another only with a _plano concave_, without any kind
of reflection, divers also by means of _reflection_. I have made others of
_Waters_, _Gums_, _Resins_, _Salts_, _Arsenick_, _Oyls_, and with divers
other _mixtures of watery_ and _oyly Liquors_. And indeed the subject is
capable of a great variety; but I find generally none more useful then that
which is made with _two Glasses_, such as I have already describ'd.

What the things are I observ'd, the following descriptions will manifest;
in brief, they were either _exceeding small Bodies_, or _exceeding small
Pores_, or _exceeding small Motions_, some of each of which the Reader will
find in the following Notes, and such, as I presume, (many of them at
least) will be _new_, and perhaps not less _strange_: Some _specimen_ of
each of which Heads the Reader will find in the subsequent delineations,
and indeed of some more then I was willing there should be; which was
occasioned by my first Intentions to print a much greater number then I
have since found time to compleat. Of such therefore as I had, I selected
only some few of every Head, which for some particulars seem'd most
observable, rejecting the rest as superfluous to the present Design.

What each of the delineated Subjects are, the following descriptions
annext to each will inform, of which I shall here, only once for all, add,
That in divers of them the Gravers have pretty well follow'd my directions
and draughts; and that in making of them, I indeavoured (as far as I was
able) first to discover the true appearance, and next to make a plain
representation of it. This I mention the rather, because of these kind of
Objects there is much more difficulty to discover the true shape, then of
those visible to the naked eye, the same Object seeming quite differing, in
one position to the Light, from what it really is, and may be discover'd in
another. And therefore I never began to make any draught before by many
examinations in several lights, and in several positions to those lights, I
had discover'd the true form. For it is exceeding difficult in some
Objects, to distinguish between a _prominency_ and a _depression_, between
a _shadow_ and a _black stain_, or a _reflection_ and a _whiteness in the
colour_. Besides, the transparency of most Objects renders them yet much
more difficult then if they were _opacous_. The Eyes of a Fly in one kind
of light appear almost like a Lattice, drill'd through with abundance of
small holes; which probably may be the Reason, why the Ingenious _Dr.
Power_ seems to suppose them such. In the Sunshine they look like a Surface
cover'd with golden Nails; in another posture, like a Surface cover'd with
Pyramids; in another with Cones; and in other postures of quite other
shapes; but that which exhibits the best, is the Light collected on the
Object, by those means I have already describ'd.

And this was undertaken in prosecution of the Design which the _ROYAL
SOCIETY_ has propos'd to it self. For the Members of the Assembly having
before their eys so many _fatal_ Instances of the errors and falshoods, in
which the greatest part of mankind has so long wandred, because they rely'd
upon the strength of humane Reason alone, have begun anew to correct all
_Hypotheses_ by sense, as Seamen do their _dead Reckonings_ by _Coelestial
Observations_; and to this purpose it has been their principal indeavour to
_enlarge & strengthen_ the _Senses_ by _Medicine_, and by such _outward
Instruments_ as are proper for their particular works. By this means they
find some reason to suspect, that those effects of Bodies, which have been
commonly attributed to _Qualities_, and those confess'd to be _occult_, are
perform'd by the small _Machines_ of Nature, which are not to be discern'd
without these helps, seeming the meer products of _Motion_, _Figure_, and
_Magnitude_; and that the _Natural Textures_, which some call the _Plastick
faculty_, may be made in _Looms_, which a greater perfection of Opticks may
make discernable by these Glasses; so as now they are no more puzzled about
them, then the vulgar are to conceive, how _Tapestry_ or _flowred Stuffs_
are woven. And the ends of all these Inquiries they intend to be the
_Pleasure_ of Contemplative minds, but above all, the _ease and dispatch_
of the labours of mens hands. They do indeed neglect no opportunity to
bring all the _rare_ things of Remote Countries within the compass of their
knowledge and practice. But they still acknowledg their _most useful_
Informations to arise from _common_ things, and from _diversifying_ their
most _ordinary_ operations upon them. They do not wholly reject Experiments
of meer _light_ and _theory_; but they principally aim at such, whose
Applications will _improve and facilitate_ the present way of _Manual
Arts_. And though some men, who are perhaps taken up about less honourable
Employments, are pleas'd to censure their proceedings, yet they can shew
more _fruits_ of their first three years, wherein they have assembled, then
any other _Society_ in _Europe_ can for a much larger space of time. 'Tis
true, such undertakings as theirs do commonly meet with small
incouragement, because men are generally rather taken with the _plausible_
and _discursive_, then the _real_ and the solid part of Philosophy; yet by
the good fortune of their institution, in an Age of all others the most
_inquisitive_, they have been assisted by the _contribution_ and _presence_
of very many of the chief _Nobility_ and _Gentry_, and others who are some
of the _most considerable_ in their several Professions. But that that yet
farther convinces me of the _Real esteem_ that the more _serious_ part of
men have of this _Society_, is, that several _Merchants_, men who act in
earnest (whose Object is _meum & tuum_, that great _Rudder_ of humane
affairs) have adventur'd considerable sums of _Money_, to put in practice
what some of our Members have contrived, and have continued _stedfast_ in
their good opinions of such Indeavours, when not one of a hundred of the
vulgar have believed their undertakings feasable. And it it also fit to be
added, that they have one advantage peculiar to themselves, that very many
of their number are _men of Converse and Traffick_; which is a good Omen,
that their attempts will bring Philosophy from _words_ to _action_, seeing
the men of Business have had so great a share in their first foundation.

And of this kind I ought not to conceal one particular _Generosity_, which
more nearly concerns my self. It is the _munificence_ of _Sir John Cutler_,
in endowing a Lecture for the promotion of _Mechanick Arts_, to be governed
and directed by This _Society._This _Bounty_ I mention for the
_Honourableness_ of the thing it self, and for the expectation which I have
of the _efficacy_ of the _Example_; for it cannot now be objected to them,
that their Designs will be esteemed _frivolous_ and _vain_, when they have
such a _real Testimony_ of the _Approbation_ of a _Man_ that is such an
_eminent Ornament_ of this renowned City, and one, who, by the _Variety_,
and the _happy Success_, of his negotiations, has given evident proofs,
that he is not easie to be deceiv'd. This Gentleman has well observ'd, that
the _Arts_ of life have been too long _imprison'd_ in the dark shops of
Mechanicks themselves, & there _hindred from growth_, either by ignorance,
or self-interest: and he has bravely _freed_ them from these
_inconveniences_: He hath not only obliged _Tradesmen_, but _Trade_ it
self: He has done a work that is worthy of _London_, and has taught the
chief City of Commerce in the world the right way how Commerce is to be
improv'd. We have already seen many other great signs of Liberality and a
large mind, from the same hand: For by his _diligence_ about the
_Corporation for the Poor_; by his honorable _Subscriptions_ for the
rebuilding of St. Paul's; by his chearful _Disbursment_ for the replanting
of _Ireland_, and by many other such _publick works_, he has shewn by what
means he indeavours to _establish_ his Memory; and now by this last gift he
has done that, which became one of the _wisest Citizens_ of our Nation to
accomplish, seeing one of the _wisest of our Statesmen, the Lord Verulam_,
first propounded it.

But to return to my Subject, from a digression, which, I hope, my Reader
will pardon me, seeing the Example is so rare that I can make no more such
digressions. If these my first Labours shall be any wayes useful to
inquiring men, I must attribute the incouragement and promotion of them to
a very _Reverend_ and _Learned Person_, of whom this ought in justice to be
said, _That there is scarce any one Invention, which this Nation has
produc'd in our Age, but it has some way or other been set forward by his
assistance_. My Reader, I believe, will quickly ghess, that it is _Dr.
Wilkins_ that I mean. He is indeed a man born for the _good_ of _mankind_,
and for the _honour_ of his _Country_. In the _sweetness_ of whose
_behaviour_, in the _calmness_ of his _mind_, in the _unbounded goodness_
of his _heart_, we have an evident Instance, what the true and the
_primitive unpassionate Religion_ was, before it was _sowred_ by particular
_Factions._ In a word, his _Zeal_ has been so _constant_ and _effectual_ in
advancing all good and profitable _Arts, that_ as one of the Antient
_Romans_ said of _Scipio_, _That he thanked God that he was a _Roman_;
because whereever _Scipio_ had been born, there had been the seat of the
Empire of the world_: So may I thank God, that _Dr. Wilkins_ was an
_Englishman_, for whereever he had lived, there had been the chief Seat of
_generous Knowledge_ and _true Philosophy_. To the truth of this, there are
so many worthy men living that will subscribe, that I am confident, what I
have here said, will not be looked upon, by any ingenious Reader, as a
_Panegyrick_, but only as a _real testimony_.

By the Advice of this _Excellent man_ I first set upon this Enterprise,
yet still came to it with much _Reluctancy_, because I was to follow the
footsteps of so eminent a Person as _Dr. Wren_, who was the first that
attempted any thing of this nature; whose original draughts do now make one
of the Ornaments of that great Collection of Rarities in the _Kings
Closet_. This _Honor_, which his first beginnings of this kind have
receiv'd, to be admitted into the most famous place of the world, did not
so much _incourage_, as the _hazard_ of coming after _Dr. Wren_ did
_affright_ me; for of him I must, affirm, that, since the time of
_Archimedes_, there scarce ever met in one man, in so great a perfection,
such a _Mechanical Hand_, and so _Philosophical_ a _Mind_.

But at last, being assured both by _Dr. Wilkins_, and _Dr. Wren_ himself,
that he had given over his intentions of prosecuting it, and not finding
that there was any else design'd the pursuing of it, I set upon this
undertaking, and was not a little incourag'd to proceed in it, by the
Honour the _Royal Society_ was pleas'd to favour me with, in approving of
those draughts (which from time to time as I had an opportunity of
describing) I presented to them. And particularly by the Incitements of
divers of those Noble and excellent Persons of it, which were my more
especial Friends, who were not less urgent with me for the publishing, then
for the prosecution of them.

After I had almost compleated these Pictures and Observations (having had
divers of them ingraven, and was ready to send them to the Press) I was
inform'd, that the Ingenious Physitian _Dr. Henry Power_ had made several
_Microscopical_ Observations, which had I not afterwards, upon our
interchangably viewing each others Papers, found that they were for the
most part differing from mine, either in the Subject it self, or in the
particulars taken notice of; and that his design was only to print
Observations without Pictures, I had even then _suppressed_ what I had so
far proceeded in. But being further _excited_ by several of my Friends, in
complyance with their opinions, that it would not be unacceptable to
several inquisitive Men, and hoping also, that I should thereby discover
something New to the World, I have at length cast in my Mite, into the vast
Treasury of _A Philosophical History_. And it is my _hope_, as well as
_belief_, that these my _Labours_ will be no more comparable to the
_Productions_ of many other _Natural Philosophers_, who are now every where
busie about _greater_ things; then my _little Objects_ are to be compar'd
to the greater and more beautiful _Works of Nature_, A Flea, a Mite, a
Gnat, to an Horse, an Elephant, or a Lyon.


       *       *       *       *       *


MICROGRAPHIA,

OR SOME

Physiological Descriptions

OF

MINUTE BODIES,

MADE BY

MAGNIFYING GLASSES;

WITH

OBSERVATIONS and INQUIRIES thereupon.

       *       *       *       *       *


Observ. I. _Of the Point of a sharp small Needle._

As in _Geometry_, the most natural way of beginning is from a Mathematical
_point_; so is the same method in Observations and _Natural history_ the
most genuine, simple, and instructive. We must first endevour to make
_letters_, and draw _single_ strokes true, before we venture to write whole
_Sentences_, or to draw large _Pictures_. And in _Physical_ Enquiries, we
must endevour to follow Nature in the more _plain_ and _easie_ ways she
treads in the most _simple_ and _uncompounded bodies_, to trace her steps,
and be acquainted with her manner of walking there, before we venture our
selves into the multitude of _meanders_ she has in _bodies of a more
complicated_ nature; lest, being unable to distinguish and judge of our
way, we quickly lose both _Nature_ our Guide, and _our selves_ too, and are
left to wander in the _labyrinth_ of groundless opinions; wanting both
_judgment_, that _light_, and _experience_, that _clew_, which should
direct our proceedings.

We will begin these our Inquiries therefore with the Observations of Bodies
of the most _simple nature_ first, and so gradually proceed to those of a
more _compounded_ one. In prosecution of which method, we shall begin with
a _Physical point_; of which kind the _Point of a Needle_ is commonly
reckon'd for one; and is indeed, for the most part, made so sharp, that the
naked eye cannot distinguish any parts of it: It very easily pierces, and
makes its way through all kind of bodies softer then it self: But if view'd
with a very good _Microscope_, we may find that the _top_ of a Needle
(though as to the sense very _sharp_) appears a _broad_, _blunt,_ and very
_irregular_ end; not resembling a Cone, as is imagin'd, but onely a piece
of a tapering body, with a great part of the top remov'd, or deficient. The
Points of Pins are yet more blunt, and the Points of the most curious
Mathematical Instruments do very seldome arrive at so great a sharpness;
how much therefore can be built upon demonstrations made onely by the
productions of the Ruler and Compasses, he will be better able to consider
that shall but view those _points_ and _lines_ with a _Microscope_.

Now though this point be commonly accounted the sharpest (whence when we
would express the sharpness of a point the most _superlatively_, we say, As
sharp as a Needle) yet the _Microscope_ can afford us hundreds of Instances
of Points many thousand times sharper: such as those of the _hairs_, and
_bristles_, and _claws_ of multitudes of _Insects_; the _thorns_, or
_crooks_, or _hairs_ of _leaves_, and other small vegetables; nay, the ends
of the _stiriae_ or small _parallelipipeds_ of _Amianthus_, and _alumen
plumosum_; of many of which, though the Points are so sharp as not to be
visible, though view'd with a _Microscope_ (which magnifies the Object, in
bulk, above a million of times) yet I doubt not, but were we able
_practically_ to make _Microscopes_ according to the _theory_ of them, we
might find hills, and dales, and pores, and a sufficient bredth, or
expansion, to give all those parts elbow-room, even in the blunt top of the
very Point of any of these so very sharp bodies. For certainly the
_quantity_ or extension of any body may be _Divisible in infinitum_, though
perhaps not the _matter_.

But to proceed: The Image we have here exhibited in the first Figure[1],
was the top of a small and very sharp Needle, whose point _aa_ nevertheless
appear'd through the _Microscope_ above a quarter of an inch broad, not
round nor flat, but _irregular_ and _uneven_; so that it seem'd to have
been big enough to have afforded a hundred armed Mites room enough to be
rang'd by each other without endangering the breaking one anothers necks,
by being thrust off on either side. The surface of which, though appearing
to the naked eye very smooth, could not nevertheless hide a multitude of
holes and scratches and ruggednesses from being discover'd by the
_Microscope_ to invest it, several of which inequalities (as A, B, C,
seem'd _holes_ made by some small specks of _Rust_; and D some
_adventitious body_, that stuck very close to it) were _casual_. All the
rest that roughen the surface, were onely so many marks of the rudeness and
bungling of _Art_. So unaccurate is it, in all its productions, even in
those which seem most neat, that if examin'd with an organ more acute then
that by which they were made, the more we see of their _shape_, the less
appearance will there be of their _beauty_: whereas in the works of
_Nature_, the deepest Discoveries shew us the greatest Excellencies. An
evident Argument, that he that was the Author of all these things, was no
other then _Omnipotent_; being able to include as great a variety of parts
and contrivances in the yet smallest Discernable Point, as in those vaster
bodies (which comparatively are called also Points) such as the _Earth_,
_Sun_, or _Planets_. Nor need it seem strange that the Earth it self may be
by _Analogie_ call'd a Physical Point: For as its body, though now so near
us as to fill our eys and fancies with a sense of the vastness of it, may
by a little Distance, and some convenient _Diminishing_ Glasses, be made
vanish into a scarce visible Speck, or Point (as I have often try'd on the
_Moon_, and (when not too bright) on the _Sun_ it self.) So, could a
Mechanical contrivance succesfully answer our _Theory_, we might see the
least spot as big as the Earth it self; and Discover, as _Des Cartes_[2]
also conjectures, as great a variety of bodies in the _Moon_, or _Planets_,
as in the _Earth_.

But leaving these Discoveries to future Industries, we shall proceed to add
one Observation more of a _point_ commonly so call'd, that is, the mark of
a _full stop_, or _period_. And for this purpose I observed many both
_printed_ ones and _written_; and among multitudes I found _few_ of them
more _round_ or _regular_ then this which I have delineated in the third
figure of the second Scheme, but _very many_ abundantly _more disfigur'd_;
and for the most part if they seem'd equally round to the eye, I found
those points that had been made by a _Copper-plate,_ and Roll-press, to be
as misshapen as those which had been made with _Types_, the most curious
and smothly _engraven strokes_ and _points_, looking but as so many
_furrows_ and _holes_, and their _printed impressions_, but like _smutty
daubings_ on a matt or uneven floor with a blunt extinguisht brand or
stick's end. And as for _points_ made with a _pen_ they were much _more
ragged_ and _deformed_. Nay, having view'd certain pieces of exceeding
curious writing of the kind (one of which in the bredth of a _two-pence_
compris'd _the Lords prayer, the Apostles Creed, the ten Commandments, and
about half a dozen verses besides of the Bible_, whose _lines_ were _so
small_ and _near together_, that I was unable to _number_ them with my
_naked eye_,) a very ordinary _Microscope_, I had then about me, inabled me
to see that what the Writer of it had asserted was _true_, but withall
discover'd of what pitifull _bungling scribbles_ and _scrawls_ it was
compos'd, _Arabian_ and _China characters_ being almost as well shap'd, yet
thus much I must say for the Man, that it was for the most part _legible_
enough, though in some places there wanted a good _fantsy_ well _preposest_
to help one through. If this manner _of small writing_ were made _easie_
and _practicable_ (and I think I know such a one, but have never yet made
tryal of it, whereby one might be inabled to write _a great deale_ with
_much ease_, and _accurately_ enough in a very _little roome_) it might be
of very good use to convey _secret Intelligence_ without any danger of
_Discovery_ or _mistrusting_. But to come again to the point. The
_Irregularities_ of it are caused by three or four _coadjutors_, one of
which is, the _uneven surface_ of the _paper_, which at best appears no
smother then a very course piece of _shag'd cloth_, next the _irregularity
of the Type_ or _Ingraving_, and a third is the _rough Daubing_ of the
_Printing-Ink_ that lies upon the instrument that makes the impression, to
all which, add the _variation_ made by the Different _lights_ and
_shadows_, and you may have sufficient reason to guess that a _point_ may
appear much more _ugly_ then _this_, which I have here presented, which
though it appear'd through the _Microscope_ _gray_, like a great splatch of
_London_ dirt, about three inches over; yet to the _naked eye_ it was
_black_ and no bigger then that in the midst of the Circle A. And could I
have found Room in this Plate to have inserted an O you should have seen
that the _letters_ were not more distinct then the _points_ of Distinction,
nor a _drawn circle_ more exactly _so_, then we have now shown a _point_ to
be a _point_.

       *       *       *       *       *


Observ. II. _Of the Edge of a Razor._

The sharpest _Edge_ hath the same kind of affinity to the sharpest _Point_
in Physicks, as a _line_ hath to a _point_ in Mathematicks; and therefore
the Treaty concerning this, may very properly be annexed to the former. A
Razor doth appear to be a Body of a very neat and curious aspect, till more
closely viewed by the _Microscope_, and there we may observe its very Edge
to be of all kind of shapes, except what it should be. For examining that
of a very sharp one, I could not find that any part of it had any thing of
sharpness in it; but it appeared a rough surface of a very considerable
bredth from side to side, the narrowest part not seeming thinner then the
back of a pretty thick Knife. Nor is't likely that it should appear any
otherwise, since as we just now shew'd that a _point_ appear'd a _circle_,
'tis rational a _line_ should be a _parallelogram_.

Now for the drawing this second Figure[3] (which represents a part of the
Edge about half a quarter of an inch long of a Razor well set) I so plac'd
it between the Object-glass & the light, that there appear'd a reflection
from the very Edge, represented by the white line abcdef. In which you may
perceive it to be somewhat sharper then elsewhere about d, to be indented
or pitted about b, to be broader and thicker about c, and unequal and
rugged about e, and pretty even between ab and ef. Nor was that part of the
Edge ghik so smooth as one would imagine so smooth bodies as a Hone and Oyl
should leave it; for besides those multitudes of scratches, which appear to
have raz'd the surface ghik, and to cross each other every way which are
not half of them exprest in the Figure, there were several great and deep
scratches, or furrows, such as gh and ik, which made the surface yet more
rugged, caus'd perhaps by some small Dust casually falling on the Hone, or
some harder or more flinty part of the Hone it self. The other part of the
Razor ll, which is polish'd on a grinding-stone, appear'd much rougher then
the other, looking almost like a plow'd field, with many parallels, ridges,
and furrows, and a cloddy, as 'twere, or an uneven surface: nor shall we
wonder at the roughnesses of those surfaces, since even in the most curious
wrought Glasses for _Microscopes_, and other Optical uses, I have, when the
Sun has shone well on them, discover'd their surface to be variously raz'd
or scratched, and to consist of an infinite of small broken surfaces, which
reflect the light of very various and differing colours. And indeed it
seems impossible by Art to cut the surface of any hard and brittle body
smooth, since _Putte_, or even the most curious _Powder_ that can be made
use of, to polish such a body, must consist of little hard rough particles,
and each of them must cut its way, and consequently leave some kind of
gutter or furrow behind it. And though Nature does seem to do it very
readily in all kinds of fluid bodies, yet perhaps future observators may
discover even these also rugged; it being very probable, as I elsewhere
shew, that fluid bodies are made up of small solid particles variously and
strongly mov'd, and may find reason to think there is scarce a surface _in
rerum natura_ perfectly smooth. The black spot mn, I ghess to be some small
speck of rust, for that I have oft observ'd to be the manner of the working
of Corrosive Juyces. To conclude, this Edge and piece of a Razor, if it had
been really such as it appear'd through the _Microscope_, would scarcely
have serv'd to cleave wood, much less to have cut off the hair of beards,
unless it were after the manner that _Lucian_ merrily relates _Charon_ to
have made use of, when with a Carpenters Axe he chop'd off the beard of a
sage Philosopher, whose gravity he very cautiously fear'd would indanger
the oversetting of his Wherry.

       *       *       *       *       *


Observ. III. _Of fine Lawn, or Linnen Cloth._

This is another product of Art, A piece of the finest Lawn I was able to
get, so curious that the threads were scarce discernable by the naked eye,
and yet through an ordinary _Microscope_ you may perceive[4] what a goodly
piece of _coarse Matting_ it is; what proportionable cords each of its
threads are, being not unlike, both in shape and size, the bigger and
coarser kind of _single Rope-yarn_, wherewith they usually make _Cables_.
That which makes the Lawn so transparent, is by the _Microscope_, nay by
the naked eye, if attentively viewed, plainly enough evidenced to be the
multitude of square holes which are left between the threads, appearing to
have much more hole in respect of the intercurrent parts then is for the
most part left in a _lattice-window_, which it does a little resemble,
onely the crossing parts are round and not flat.

These threads that compose this fine contexture, though they are as small
as those that constitute the finer sorts of Silks, have notwithstanding
nothing of their glossie, pleasant, and lively reflection. Nay, I have been
informed both by the Inventor himself, and several other eye-witnesses,
that though the flax, out of which it is made, has been (by a singular art,
of that excellent Person, and Noble Vertuoso, M. _Charls Howard_, brother
to the _Duke of Norfolk_) so curiously dress'd and prepar'd, as to appear
both to the eye and the touch, full as _fine_ and as _glossie_, and to
receive all kinds of colours, as well as Sleave-Silk; yet when this Silken
Flax is twisted into threads, it quite loseth its former luster, and
becomes as plain and base a thread to look on, as one of the same bigness,
made of common Flax.

The reason of which odd _Phenomenon_ seems no other then this; that though
the curiously drest Flax has its parts so exceedingly small, as to
equallize, if not to be much smaller then the clew of the Silk-worm,
especially in thinness, yet the differences between the figures of the
constituting filaments are so great, and their substances so various, that
whereas those of the _Silk_ are _small_, _round_, _hard_, _transparent,_
and to their bigness proportionably _stiff_, so as each filament preserves
its proper _Figure_, and consequently its vivid _reflection_ intire, though
twisted into a thread, if not too hard; those of Flax are _flat_, _limber_,
_softer,_ and _less transparent_, and in twisting into a thread they joyn,
and lie so close together, as to lose their own, and destroy each others
particular reflections. There seems therefore three Particulars very
requisite to make the so drest Flax appear Silk also when spun into
threads. First, that the substance of it should be made more _clear_ and
_transparent_, Flax retaining in it a kind of opacating brown, or yellow;
and the parts of the whitest kind I have yet observ'd with the _Microscope_
appearing white, like flaw'd Horn or Glass, rather then clear, like clear
Horn or Glass. Next that, the filaments should each of them be _rounded_,
if that could be done, which yet is not so very necessary, if the first be
perform'd, and this third, which is, that each of the small filaments be
_stifned_; for though they be square, or flat, provided they be
_transparent_ and stiff, much the same appearances must necessarily follow.
Now, though I have not yet made trial, yet I doubt not, but that both these
proprieties may be also induc'd upon the Flax, and perhaps too by one and
the same Expedient, which some trials may quickly inform any ingenious
attempter of, who from the use and profit of such an Invention, may find
sufficient argument to be prompted to such Inquiries. As for the _tenacity_
of the substance of Flax, out of which the thread is made, it seems much
inferiour to that of Silk, the one being a _vegetable_, the other an
_animal_ substance. And whether it proceed from the better concoction, or
the more homogeneous constitution of _animal_ substances above those of
_vegetables_, I do not here determine; yet since I generally find, that
_vegetable_ substances do not equalize the _tenacity_ of _animal_, nor
these the _tenacity_ of some purified _mineral_ substances; I am very apt
to think, that the _tenacity_ of bodies does not proceed from the _hamous_,
or _hooked_ particles, as the _Epicureans_ and some modern _Philosophers_
have imagin'd; but from the more exact _congruity_ of the constituent
parts, which are contiguous to each other, and so bulky, as not to be
easily separated, or shatter'd, by any small pulls or concussion of heat.

       *       *       *       *       *


Observ. IV. _Of fine waled Silk, or Taffety._

This[5] is the appearance of a piece of very fine Taffety-riband in the
bigger magnifying Glass, which you see exhibits it like a very convenient
substance to make Bed-matts, or Door-matts of, or to serve for Beehives,
Corn-scuttles, Chairs, or Corn-tubs, it being not unlike that kind of work,
wherewith in many parts in _England_, they make such Utensils of Straw, a
little wreathed, and bound together with thongs of Brambles. For in this
Contexture, each little filament, fiber, or clew of the Silk-worm, seem'd
about the bigness of an ordinary Straw, as appears by the little irregular
pieces, ab, cd, and ef; The _Warp_, or the thread that ran crossing the
Riband, appear'd like a single Rope of an Inch Diameter; but the _Woof_, or
the thread that ran the length of the Riband, appear'd not half so big.
Each Inch of six-peny-broad Riband appearing no less then a piece of
Matting Inch and half thick, and twelve foot square, a few yards of this,
would be enough to floor the long Gallery of the _Loure_ at _Paris_. But to
return to our piece of Riband: It affords us a not unpleasant object,
appearing like a bundle, or wreath, of very clear and transparent
_Cylinders_, if the Silk be white, and curiously ting'd; if it be colour'd,
each of those small horney _Cylinders_ affording in some place or other of
them, as vivid a reflection, as if it had been sent from a _Cylinder_ of
Glass or Horn. In-so-much, that the reflexions of Red, appear'd as if
coming from so many _Granates_, or _Rubies_. The loveliness of the colours
of Silks above those of hairy Stuffs, or Linnen, consisting, as I
else-where intimate, chiefly in the transparency, and vivid reflections
from the _Concave_, or inner surface of the _transparent Cylinder_, as are
also the colours of Precious Stones; for most of the reflections from each
of these _Cylinders_, come from the _Concave_ surface of the air, which is
as 'twere the foil that incompasses the _Cylinder_. The colours with which
each of these _Cylinders_ are ting'd, seem partly to be superficial, and
sticking to the out-sides of them; and partly, to be imbib'd, or sunck into
the substance of them: for Silk, seeming to be little else then a dried
thread of Glew, may be suppos'd to be very easily relaxt, and softened, by
being steeped in warm, nay in cold, if penetrant, juyces or liquors. And
thereby those tinctures, though they tinge perhaps but a small part of the
substance, yet being so highly impregnated with the colour, as to be almost
black with it, may leave an impression strong enough to exhibite the
desir'd colour. A pretty kinde of artificial Stuff I have seen, looking
almost like transparent Parchment, Horn, or Ising-glass, and perhaps some
such thing it may be made of, which being transparent, and of a glutinous
nature, and easily mollified by keeping in water, as I found upon trial,
had imbib'd, and did remain ting'd with a great variety of very vivid
colours, and to the naked eye, it look'd very like the substance of the
Silk. And I have often thought, that probably there might be a way found
out, to make an artificial glutinous composition, much resembling, if not
full as good, nay better, then that Excrement, or whatever other substance
it be out of which, the Silk-worm wire-draws his clew. If such a
composition were found, it were certainly an easie matter to find very
quick ways of drawing it out into small wires for use. I need not mention
the use of such an Invention, nor the benefit that is likely to accrue to
the finder, they being sufficiently obvious. This hint therefore, may, I
hope, give some Ingenious inquisitive Person an occasion of making some
trials, which if successfull, I have my aim, and I suppose he will have no
occasion to be displeas'd.

       *       *       *       *       *


Observ. V. _Of watered Silks, or Stuffs._

There are but few _Artificial_ things that are worth observing with a
_Microscope_, and therefore I shall speak but briefly concerning them. For
the Productions of art are such rude mis-shapen things, that when view'd
with a _Microscope_, is little else observable, but their deformity. The
most curious Carvings appearing no better then those rude _Russian_ Images
we find mention'd in _Purchas_, where three notches at the end of a Stick,
stood for a face. And the most smooth and burnish'd surfaces appear most
rough and unpolisht: So that my first Reason why I shall add but a few
observations of them, is, their mis-shapen form; and the next, is their
uselessness. For why should we trouble our selves in the examination of
that form or shape (which is all we are able to reach with a _Microscope_)
which we know was design'd for no higher a use, then what we were able to
view with our naked eye? Why should we endeavour to discover mysteries in
that which has no such thing in it? And like _Rabbins_ find out
_Caballisms_, and _aenigmas_ in the Figure, and placing of Letters, where
no such thing lies hid: whereas in _natural_ forms there are some so small,
and so curious, and their design'd business so far remov'd beyond the reach
of our sight, that the more we magnify the object, the more excellencies
and mysteries do appear; And the more we discover the imperfections of our
senses; and the Omnipotency and Infinite perfections of the great Creatour.
I shall therefore onely add one or two Observations more _artificial_
things, and then come to the Treaty concerning such matters as are the
Productions of a more curious Workman. One of these, shall be that of a
piece of water'd Silk, represented in the second Figure of the third
_Scheme_,[6] as it appear'd through the least magnifying Glass. _AB_
signifying the long way of the Stuff, and _CD_ the broad way. This Stuff,
if the right side of it be looked upon, appears to the naked eye, all over
so waved, undulated, or grain'd, with a curious, though irregular variety
of brighter and darker parts, that it adds no small gracefulness to the
Gloss of it. It is so known a propriety, that it needs but little
explication, but it is observable, which perhaps everyone has not
considered, that those parts which appear the darker part of the wave, in
one position to the light, in another appears the lighter, and the
contrary; and by this means the undulations become transient, and in a
continual change, according as the position of the parts in respect of the
incident beams of light is varied. The reason of which odd _phaenomena_, to
one that has but diligently examin'd it even with his naked eye, will be
obvious enough. But he that observes it with a _Microscope_, may more
easily perceive what this _Proteus_ is, and how it comes to change its
shape. He may very easily perceive, that it proceeds onely from the variety
of the _Reflections_ of light, which is caus'd by the various _shape of the
Particles_, or little protuberant parts of the thread that compose the
surface; and that those parts of the waves that appear the brighter, throw
towards the eye a multitude of small reflections of light, whereas the
darker scarce afford any. The reason of which reflection, the _Microscope_
plainly discovers, as appears by the Figure. In which you may perceive,
that the brighter parts of the surface consist of an abundance of large and
strong reflections, denoted by a, a, a, a, a, &c. for the surfaces of those
threads that run the _long way_, are by the Mechanical process of watering,
_creas'd_ or _angled_ in another kind of posture then they were by the
weaving: for by the weaving they are onely _bent round_ the warping
threads; but by the watering, they are _bent with an angle, or elbow_, that
is in stead of lying, or being bent _round_ the threads, as in the third
Figure, a, a, a, a, a, are about b, b, b (b, b, b representing the ends, as
'twere, of the cross threads, they are bent about) they are creas'd on the
top of those threads, with an _angle_, as in the fourth Figure, and that
with all imaginable variety; so that, whereas before they reflected the
light onely from one point of the round surface, as about c, c, c, they now
when water'd, reflect the beams from more then half the whole surface, as
de, de, de, and in other postures they return no reflections at all from
those surfaces. Hence in one posture they compose the brighter parts of the
waves, in another the darker. And these reflections are also varied,
according as the particular parts are variously bent. The reason of which
creasing we shall next examine; and here we must fetch our information from
the Mechanism or manner of proceeding in this operation; which, as I have
been inform'd, is no other then this.

They double all the Stuff that is to be water'd, that is, they crease it
just through the middle of it, the whole length of the piece, leaving the
right side of the Stuff inward, and placing the two edges, or silvages just
upon one another, and, as near as they can, place the wale so in the
doubling of it, that the wale of the one side may lie very near parallel,
or even with the wale of the other; for the nearer that posture they lie,
the greater will the watering appear; and the more obliquely, or across to
each other they lie, the smaller are the waves. Their way for folding it
for a great wale is thus: they take a Pin, and begin at one side of the
piece in any wale, and so moving it towards the other side, thereby direct
their hands to the opposite ends of the wale, and then, as near as they
can, place the two opposite ends of the same wale together, and so double,
or fold the whole piece, repeating this enquiry with a Pin at every yard or
two's distance through the whole length; then they sprinkle it with water,
and fold it the longways, placing between every fold a piece of Pastboard,
by which means all the wrong side of the water'd Stuff becomes flat, and
with little wales, and the wales on the other side become the more
protuberant; whence the creasings or angular bendings of the wales become
the more perspicuous. Having folded it in this manner, they place it with
an interjacent Pastboard into an hot Press, where it is kept very violently
prest, till it be dry and stiff; by which means, the wales of either
contiguous sides leave their own impressions upon each other, as is very
manifest by the second Figure, where 'tis obvious enough, that the wale of
the piece ABCD runs parallel between the pricked lines ef, ef, ef, and as
manifest to discern the impressions upon these wales, left by those that
were prest upon them, which lying not exactly parallel with them, but a
little athwart them, as is denoted by the lines of, oooo, gh, gh, gh,
between which the other wales did lie parallel; they are so variously, and
irregularly creas'd that being put into that shape when wet, and kept so
till they be drie, they so let each others threads, that the Moldings
remain almost as long as the Stuff lasts.

Hence it may appear to any one that attentively considers the Figure, why
the parts of the wale a, a, a, a, a, a, should appear bright; and why the
parts b, b, b, b, b, b, b, should appear shadowed, or dark; why some, as d,
d, d, d, d, d, should appear partly light, and partly dark: the varieties
of which reflections and shadows are the only cause of the appearance of
watering in Silks, or any other kind of Stuffs.

From the variety of reflection, may also be deduc'd the cause why a small
breez or gale of wind ruffling the surface of a smooth water, makes it
appear black; as also, on the other side, why the smoothing or burnishing
the surface of whitened Silver makes it look black; and multitudes of other
phaenomena might hereby be solv'd, which are too many to be here insisted
on.

       *       *       *       *       *


Observ. VI. _Of Small Glass Canes._

That I might be satisfied, whether it were not possible to make an
_Artificial_ pore as _small_ as any _Natural_ I had yet found, I made
several attemps with small _glass pipes_, melted in the flame of a Lamp,
and then very _suddenly_ drawn out into a great length. And, by _that
means_, without much difficulty, I was able to draw some almost as small as
a _Cobweb_, which yet, with the _Microscope_, I could plainly perceive[7]
to be _perforated_, both by looking on the _ends_ of it, and by looking on
it _against the light_ which was much the _easier way_ to determine whether
it were solid or perforated; for, taking a small pipe of glass, and closing
one end of it, then filling it _half full_ of water, and holding it
_against the light_, I could, by this means, very easily find what was the
_differing aspect_ of a _solid_ and a _perforated_ piece of glass; and so
easily distingish, without seeing either end, whether any _Cylinder_ of
glass I look'd on, were a _solid stick_, or a _hollow cane_. And by this
means, I could also presently judge of any small _filament_ of glass,
whether it were _hollow_ or _not_, which would have been exceeding tedious
to examine by looking on the end. And many such like ways I was fain to
make use of, in the examining of divers other particulars related in this
Book, which would have been no easie task to have determined meerly by the
more common way of looking on, or viewing the Object. For, if we consider
first, the very _faint light_ wherewith the object is enlightened, whence
many particles appear _opacous_, which when more enlightned, appear very
_transparent_, so that I was fain to _determine_ its _transparency_ by one
glass, and its _texture_ by another. Next, the _unmanageableness_ of most
_Objects_, by reason of their _smalness_, 3. The _difficulty of finding_
the desired point, and of _placing_ it so, as to reflect the _light
conveniently_ for the Inquiry. Lastly, ones being able to view it but with
_one eye_ at once, they will appear no small _obstructions_, nor are they
easily _remov'd_ without many _contrivances_. But to proceed, I could not
find that water, or some _deeply ting'd_ liquors would in small ones rise
so high as one would expect; and the _highest_ I have found it yet rise in
any of the pipes I have try'd, was to 21 _inches_ above the level of the
water in the vessel: for though I found that in the small pipes it would
_nimbly enter_ at first, and run about 6 or 7 _inches_ upwards; yet I found
it then to move upwards _so slow_, that I have not yet had the _patience_
to observe it above that height of 21 _inches_ (and that was in a pretty
_large Pipe_, in comparison of those I formerly mentioned; for I could
observe the _progress_ of a _very deep ting'd liquor_ in it with my _naked
eye_, without much trouble; whereas many of the _other pipes_ were so _very
small_, that unless in a _convenient posture_ to the light, I could not
perceive _them_:) But 'tis very probable, that a greater _patience_ and
_assiduity_ may discover the liquors to _rise_, at least to remain
_suspended_, at heights that I should be loath now even to _ghess_ at, if
at least there be any _proportion_ kept between the height of the ascending
liquor, and the _bigness of the holes_ of the pipes.

_AN ATTEMPT FOR THE EXPLICATION OF THIS EXPERIMENT._

My Conjecture, _That the unequal height of the surfaces of the water,
proceeded from the greater pressure made upon the water by the Air without
the Pipes_ ABC, _then by that within them_[8]; I shall endeavour to confirm
from the truth of the two following _Propositions_:

The first of which is, _That an unequal pressure of the incumbent Air, will
cause an unequal height in the water's Surfaces_.

And the second is, _That in this experiment there is such an unequal
pressure_.

That the first is true, the following _Experiment_ will evince. For if you
take any Vessel so contrived, as that you can at pleasure either _increase_
or _diminish_ the _pressure_ of the Air upon this or that part of the
_Superficies_ of the _water_, the _equality_ of the height of those parts
will presently be _lost_; and that part of the _Superficies_ that sustains
the _greater pressure_, will be _inferior_ to that which undergoes the
_less_. A fit Vessel for this purpose, will be an inverted Glass _Syphon_,
such an one as is described in the _Sixth Figure_. For if into it you put
Water enough to fill it as high as _AB_, and gently blow in at _D_, you
shall _depress_ the Superficies _B_, and thereby _raise_ the opposite
Superficies _A_ to a _considerable height_, and by gently _sucking_ you may
produce clean _contrary_ effects.

Next, That there is such an _unequal pressure_, I shall prove from this,
_That there is a much greater incongruity of Air to Glass, and some other
Bodies, then there is of Water to the same_.

By _Congruity, I mean a property of a fluid Body, whereby any part of it is
readily united with any other part, either of itself, or of any other
Similar, fluid, or solid body: And by Incongruity a property of a fluid, by
which it is hindred from uniting with any dissimilar, fluid, or solid
Body._

This last property, any one that hath been observingly conversant about
fluid Bodies, cannot be ignorant of. For (not now to mention several
_Chymical Spirits_ and _Oyls_, which will _very hardly_, if at _all_, be
brought to _mix_ with one another; insomuch that there may be found some 8
or 9, or more, several distinct Liquors, which _swimming_ one upon another,
will not presently _mix_) we need seek no further for Examples of this kind
in _fluids_, then to observe the _drops of rain_ falling through the _air_
and the _bubbles of air_ which are by any means conveyed under the surface
of the _water_; or a drop of common _Sallet Oyl_ swimming upon water. In
all which, and many more examples of this kind that might be enumerated,
the _incongruity_ of two _fluids_ is easily discernable. And as for the
_Congruity_ or _Incongruity_ of Liquids, with several kinds of _firm_
Bodies, they have long since been taken notice of, and called by the Names
of _Driness_ and _Moisture_ (though these two names are not comprehensive
enough, being commonly used to signifie only the adhering or not adhering
of _water_ to some other _solid Bodies_) of this kind we may observe that
_water_ will more readily _wet some woods_ then _others_; and that _water_,
let fall upon a _Feather_, the whiter side of a _Colwort_, and some other
leaves, or upon almost any _dusty_, _unctuous_, or _resinous_ superficies,
will not _at all adhere_ to them, but easily _tumble off_ from them, like a
solid _Bowl_; whereas, if dropt upon _Linnen_, _Paper_, _Clay_, _green
Wood_, &c. it will not be taken off, without leaving some part of it behind
_adhering_ to them. So _Quick-silver_, which will very _hardly_ be brought
to _stick_ to any _vegetable body_, will _readily adhere_ to, and _mingle_
with, several clean _metalline bodies_.

And that we may the better finde what the _cause_ of _Congruity_ and
_Incongruity_ in bodies is, it will be requisite to consider, First, what
is the _cause_ of _fluidness_; And this, _I conceive_, to be nothing else
but a certain _pulse_ or _shake_ of _heat_; for Heat being nothing else but
a very _brisk_ and _vehement agitation_ of the parts of a body (as I have
elswhere made _probable_) the parts of a body are thereby made so _loose_
from one another, that they easily _move any way_, and become _fluid_. That
I may explain this a little by a gross Similitude, let us suppose a dish of
sand set upon some body that is very much _agitated_, and shaken with some
_quick_ and _strong vibrating motion_, as on a _Milstone_ turn'd round upon
the under stone very violently whilst it is empty; or on a very stiff
_Drum_-head, which is vehemently or very nimbly beaten with the Drumsticks.
By this means, the sand in the dish, which before lay like a _dull_ and
unactive body, becomes a perfect _fluid_; and ye can no sooner make a
_hole_ in it with your finger, but it is immediately _filled up again_, and
the upper surface of it _levell'd_. Nor can you _bury_ a _light body_, as a
piece of Cork under it, but it presently _emerges_ or _swims_ as 'twere on
the top; nor can you lay a _heavier_ on the top of it, as a piece of Lead,
but it is immediately _buried_ in Sand, and (as 'twere) sinks to the
bottom. Nor can you make a _hole_ in the side of the Dish, but the sand
shall _run out_ of it to a _level_, not an _obvious property_ of a fluid
body, as such, but this dos _imitate_; and all this meerly caused by the
vehement _agitation_ of the conteining vessel; for by this means, _each_
sand becomes to have a _vibrative_ or _dancing_ motion, so as no other
heavier body can _rest_ on it, unless _sustein'd_ by some other on either
side: Nor will it suffer any Body to be _beneath_ it, unless it be a
_heavier_ then it self. Another Instance of the strange _loosening_ nature
of a violent jarring Motion, or a strong and nimble vibrative one, we may
have from a piece of _iron_ grated on very strongly with a _file_: for if
into that a pin _screw'd_ so firm and hard, that though it has a convenient
head to it, yet it can by no means be _unscrew'd_ by the fingers; if, I
say, you attempt to unscrew this whilst _grated on by the file_, it will be
found to undoe and turn very _easily_. The first of these Examples
manifests, how a body actually _divided_ into small parts, becomes a
_fluid_. And the latter manifests by what means the agitation of heat so
easily _loosens_ and _unties_ the parts of _solid_ and _firm_ bodies. Nor
need we suppose heat to be any thing else, besides such a motion; for
supposing we could _Mechanically_ produce such a one _quick_ and _strong_
enough, we need not spend _fuel_ to _melt_ a body. Now, that I do not speak
this altogether groundless, I must refer the Reader to the Observations I
have made upon the shining sparks of Steel, for there he shall find that
_the same_ effects are produced upon small chips or parcels of Steel by the
_flame_, and by _a quick and violent motion_; and if the body of _steel_
may be thus melted (as I there shew it may) I think we have little reason
to doubt that almost _any other_ may not also. Every Smith can inform one
how quickly both his _File_ and the _Iron_ grows _hot_ with _filing_, and
if you _rub_ almost any two _hard_ bodies together, they will do the same:
And we know, that a sufficient degree of heat causes _fluidity_, in some
bodies much sooner, and in others later; that is, the parts of the body of
some are so _loose_ from one another, and so _unapt to cohere_, and so
_minute_ and _little_, that a very _small_ degree of agitation keeps them
always in the _state of fluidity_. Of this kind, I suppose, the _AEther_,
that is the _medium_ or _fluid_ body, in which all other bodies do as it
were swim and move; and particularly, the _Air_, which seems nothing else
but a kind of _tincture_ or _solution_ of terrestrial and aqueous particles
_dissolv'd_ into it, and agitated by it, just as the _tincture_ of
_Cocheneel_ is nothing but some finer _dissoluble_ parts of that Concrete
lick'd up or _dissolv'd_ by the _fluid_ water. And from this Notion of it,
we may easily give a more Intelligible reason how the Air becomes so
capable of _Rarefaction_ and _Condensation_. For, as in _tinctures_, one
grain of some _strongly tinging_ substance may _sensibly_ colour some
_hundred thousand_ grains of _appropriated_ Liquors, so as every _drop_ of
it has its proportionate share, and be sensibly ting'd, as I have try'd
both with _Logwood_ and _Cocheneel_: And as some few grains of _Salt_ is
able to infect as great a quantity, as may be found by _praecipitations_,
though not so easily by the _sight_ or _taste_; so the _Air_, which seems
to be but as 'twere a _tincture_ or _saline substance, dissolv'd and
agitated by the fluid and agil AEther_, may disperse and _expand_ it self
into a _vast space_, if it have room enough, and infect, as it were, every
part of that space. But, as on the other side, if there be but some _few
grains_ of the liquor, it may _extract all_ the colour of the tinging
substance, and may _dissolve_ all the Salt, and thereby become _much more
impregnated_ with those substances, so may _all_ the air that sufficed in a
_rarfy'd state_ to fill some _hundred thousand_ spaces of AEther, be
compris'd in only _one_, but in a position proportionable _dense_. And
though we have not yet found out such _strainers_ for Tinctures and Salts
as we have for the Air, being yet unable to _separate_ them from their
dissolving liquors by any kind of _filtre_, without _praecipitation_, as we
are able to _separate_ the Air from the AEther by _Glass_, and several
other bodies. And though we are yet unable and ignorant of the ways of
_praecipitating_ Air out of the AEther as we can Tinctures, and Salts out
of several _dissolvents_; yet neither of these seeming _impossible_ from
the nature of the things, nor so _improbable_ but that some happy future
industry may find out ways to effect them; nay, further, since we find that
Nature _does really perform_ (though by what means we are not certain) both
these actions, namely, by _praecipitating_ the Air in Rain and Dews, and by
supplying the Streams and Rivers of the World with fresh water, _strain'd_
through secret subterraneous Caverns: And since, that in very many other
_proprieties_ they do so exactly _seem_ of the _same nature_; till further
observations or tryals do inform us of the _contrary_, we may _safely
enough conclude_ them of the _same kind_. For it seldom happens that any
two natures have so many properties _coincident_ or the _same_, as I have
observ'd Solutions and Air to have, and to be _different_ in the rest. And
therefore I think it neither _impossible_, _irrational_, nay nor
_difficult_ to be able to _predict_ what is _likely_ to happen in other
particulars also, besides those which _Observation_ or _Experiment_ have
declared thus or thus; especially, if the _circumstances_ that do often
very much conduce to the variation of the effects be duly _weigh'd_ and
_consider'd_. And indeed, were there not a _probability_ of this, our
_inquiries_ would be _endless_, our _tryals vain_, and our greatest
_inventions_ would be nothing but the meer _products_ of _chance_, and not
of _Reason_; and, like _Mariners_ in an Ocean, destitute both of a
_Compass_ and the sight of the _Celestial guids_, we might indeed, _by
chance_, Steer _directly_ towards our desired Port, but 'tis _a thousand to
one_ but we _miss_ our aim. But to proceed, we may hence also give a plain
reason, how the Air comes to be _darkned_ by _clouds_, &c. which are
nothing but a kind of _precipitation_, and how those _precipitations_ fall
down in _Showrs_. Hence also could I very easily, and I think truly, deduce
the cause of the curious _sixangular figures_ of Snow, and the appearances
of _Haloes, &c._ and the sudden _thickning_ of the Sky with Clouds, and the
_vanishing_ and _disappearing_ of those Clouds again; for all these things
may be very easily _imitated_ in a _glass of liquor_, with some slight
_Chymical preparations_ as I have often try'd, and may somewhere else more
largely relate, but have not now time to set them down. But to proceed,
there are other bodies that consist of particles more _Gross_, and of a
more _apt_ figure for _cohesion_, and this requires _somewhat greater_
agitation; such, I suppose [Mercury], _fermented vinous_ _Spirits_, several
_Chymical Oils_, which are much of kin to those Spirits, &c. Others yet
require a _greater_, as _water_, and so others _much greater_, for almost
infinite degrees: For, I suppose there are very _few_ bodies in the world
that may not be made _aliquatenus_ fluid, by _some_ or _other_ degree of
agitation or heat.

Having therefore in short set down my Notion of a Fluid body, I come in the
next place to consider what _Congruity_ is; and this, as I said before,
being a _Relative property_ of a fluid, whereby it may be said to be _like_
or _unlike_ to this or that other body, whereby it _does_ or _does not mix_
with this or that body. We will again have recourse to our former
Experiment, though but a rude one; and here if we mix in the dish _several
kinds_ of sands, some of _bigger_, others of _less_ and finer bulks, we
shall find that by the agitation _the fine sand_ will _eject_ and _throw
out_ of it self all those _bigger_ bulks of small _stones_ and the like,
and those will _be gathered_ together all into _one_ place; and if there be
_other_ bodies in it of other natures, those also will be _separated_ into
a place by themselves, and _united_ or _tumbled_ up together. And though
this do not come up to the _highest property_ of _Congruity_, which is a
_Cohaesion_ of the parts of the fluid together, or a kind of _attraction_
and _tenacity_, yet this does as 'twere _shadow_ it out, and somewhat
resemble it; for just after the same manner, I suppose the _pulse_ of heat
to _agitate_ the small parcels of matter, and those that are of a _like
bigness_, and _figure_, and _matter_, will _hold_, or _dance_ together, and
those which are of a _differing_ kind will be _thrust_ or _shov'd_ out from
between them; for particles that are _similar_, will, like so many _equal
musical strings equally stretcht_, vibrate together in a kind of _Harmony_
or _unison_; whereas others that are _dissimilar_, upon what account
soever, unless the disproportion be otherwise counter-ballanc'd, will, like
so many _strings out of tune_ to those unisons, though they have the same
agitating _pulse_, yet make quite _differing_ kinds of _vibrations_ and
_repercussions_, so that though they may be both mov'd, yet are their
_vibrations_ so _different_, and so _untun'd_, as 'twere to each other,
that they _cross_ and _jar_ against each other, and consequently, _cannot
agree_ together, but _fly back_ from each other to their similar particles.
Now, to give you an instance how the _disproportion_ of some bodies in one
respect, may be _counter-ballanc'd_ by a _contrary disproportion_ of the
same body in another respect, whence we find that the subtil _vinous
spirit_ is _congruous_, or does readily _mix_ with _water_, which in many
properties is of a very _differing nature_, we may consider that a _unison_
may be made either by two _strings_ of the same _bigness_, _length_, and
_tension_, or by two strings of the same _bigness_, but of _differing
length_, and a _contrary differing tension_, or _3ly._ by two strings of
_unequal length_ and _bigness_, and of a _differing tension_, or of _equal
length_, and _differing bigness_ and _tension_, and several other such
varieties. To which _three properties_ in _strings_, will correspond _three
proprieties_ also in _sand_, or the _particles_ of bodies, their _Matter_
or _Substance_, their _Figure_ or _Shape_, and their _Body_ or _Bulk_. And
from the _varieties_ of these _three_, may arise _infinite varieties_ in
fluid bodies, though all agitated by the _same pulse_ or _vibrative_
motion. And there may be as many ways of making Harmonies and Discords with
these, as there may be with _musical strings_. Having therefore seen what
is the cause of Congruity or Incongruity, those relative properties of
fluids, we may, from what has been said, very easily collect, what is the
_reason_ of those Relative proprieties also between _fluid bodies_ and
_solid_; for since all bodies consist of _particles_ of such a _Substance_,
_Figure_, and _Bulk_; but in some they are _united_ together more _firmly_
then to be _loosened_ from each other by every _vibrative_ motion (though I
imagine that there is no body in the world, but that some degree of
agitation may, as I hinted before, agitate and loosen the particles so as
to make them fluid) those _cohering_ particles may _vibrate_ in the same
manner almost as those that are _loose_ and become _unisons_ or _discords_,
as I may so speak, to them. Now that the _parts_ of all _bodies_, though
never so _solid_, do yet _vibrate_, I think we need go no further for
proof, then that _all_ bodies have some _degrees_ of _heat_ in them, and
that there has not been yet found any thing _perfectly cold_: Nor can I
believe indeed that there is any such thing in Nature, as a body whose
particles are at _rest_, or _lazy_ and _unactive_ in the great _Theatre_ of
the _World_, it being quite _contrary_ to the grand _Oeconomy_ of the
Universe. We see therefore what is the reason of the _sympathy_ or uniting
of some bodies together, and of the _antipathy_ or flight of others from
each other: For _Congruity_ seems nothing else but a _Sympathy_, and
_Incongruity_ an _Antipathy_ of bodies, hence _similar_ bodies once
_united_ will not _easily part_, and _dissimilar_ bodies once _disjoyn'd_
will not _easily unite_ again; from hence may be very easily deduc'd the
reason of the _suspension_ of _water_ and _Quick-silver_ above their usual
_station_, as I shall more at large anon shew.

These properties therefore (alwayes the concomitants of fluid bodies)
produce these following visible _Effects_:

First, They _unite_ the parts of a fluid to its _similar_ Solid, or keep
them _separate_ from its _dissimilar_. Hence _Quick-silver_ will (as we
noted before) _stick_ to _Gold_, _Silver_, _Tin_, _Lead_, &c. and _unite_
with them: but _roul_ off from _Wood_, _Stone_, _Glass_, &c. if never so
little scituated out of its _horizontal level_; and _water_ that will _wet
salt_ and _dissolve_ it, will _slip_ off from _Tallow_, or the like,
without at all _adhering_; as it may likewise be observed to do upon a
_dusty_ superficies. And next they cause the parts of _homogeneal fluid_
bodies readily to _adhere_ together and _mix_, and of _heterogeneal_, to be
exceeding _averse_ thereunto. Hence we find, that _two_ small _drops_ of
_water_, on any superficies they can roul on, will, if they chance to touch
each other, _readily unite_ and _mix_ into one 3d _drop_: The like may be
observed with two small _Bowls_ of _Quick-silver_ upon a Table or Glass,
provided their surfaces be not _dusty_; and with two drops of _Oyl_ upon
fair water, _&c_. And further, _water_ put unto _wine_, _salt water_,
_vinegar_, _spirit_ of _wine_, or the like, does immediately (especially if
they be shaken together) _disperse_ it self all over them. Hence, on the
contrary, we also find, that _Oyl of Tartar_ poured upon _Quick-silver,_
and _Spirit of Wine_ on that _Oyl_, and _Oyl of Turpentine_ on that
_Spirit_, and _Air_ upon that _Oyl_, though they be stopt closely up into a
Bottle, and _shaken_ never so much, they will by no means long suffer any
of their bigger parts to be _united_ or included within any of the other
Liquors (by which recited Liquors, may be plainly enough represented the
four _Peripatetical Elements_, and the more subtil _AEther_ above all.)
From this property 'tis, that a drop of _water_ does not mingle with, or
vanish into _Air_, but is _driven_ (by that Fluid equally protruding it on
every side) and forc't into as little a space as it can possibly be
contained in, namely, into a _Round Globule_. So likewise a little _Air_
blown under the _water_, is _united_ or thrust into a _Bubble_ by the
ambient water. And a parcel of _Quick-silver_ enclosed with _Air_, _Water_,
or almost any other _Liquor_, is _formed_ into a _round Ball_.

Now the cause why all these included Fluids, newly mentioned, or as many
others as are wholly included within a heterogeneous fluid, are not
_exactly_ of a _Spherical Figure_ (seeing that if caused by these
Principles only, it could be of no other) must proceed from some other kind
of _pressure_ against the two opposite flatted sides. This _adventitious_
or _accidental pressure_ may proceed from _divers causes_, and accordingly
must _diversifie_ the Figure of the included heterogeneous fluid: For
seeing that a body may be included either with a fluid only, or only with a
solid, or partly with a fluid, and partly with a solid, or partly with one
fluid, and partly with another; there will be found a very great variety of
the terminating _surfaces_, much differing from a _Spherical_, according to
the various resistance or pressure that belongs to each of these
encompassing bodies.

Which Properties may in general be deduced from two heads, _viz._ _Motion_,
and _Rest_. For, either this Globular Figure is altered by a _natural
Motion_, such as is _Gravity_, or a _violent_, such as is any _accidental
motion_ of the fluids, as we see in the _wind_ ruffling up the water, and
the _purlings_ of _Streams_, and _foaming_ of _Catarracts_, and the like.
Or thirdly, By the _Rest_, _Firmness_ and _Stability_ of the ambient
_Solid_. For if the including _Solid_ be of an _angular_ or any other
_irregular_ Form, the included _fluid_ will be near of the _like_, as a
Pint-_Pot_ full of _water_, or a _Bladder_ full of _Air_. And next, if the
including or included fluid have a greater _gravity_ one than another, then
will the _globular_ Form be deprest into an _Elliptico-spherical_: As if,
for example, we suppose the Circle _ABCD_, in the _fourth Figure_, to
represent a _drop of water_, _Quick-silver_, or the like, included with the
_Air_ or the like, which supposing there were no _gravity_ at all in either
of the _fluids_, or that the _contained_ and _containing_ were of the _same
weight,_ would be _equally comprest_ into an exactly _spherical_ body (the
ambient fluid _forcing equally_ against every side of it.) But supposing
either a greater _gravity_ in the included, by reason whereof the parts of
it being _prest_ from _A_ towards _B_, and thereby the whole put into
_motion_, and that _motion_ being _hindred_ by the _resistance_ of the
_subjacent_ parts of the ambient, the _globular_ Figure _ADBC_ will be
_deprest_ into the _Elliptico-spherical_, _EGFH_. For the side _A_ is
_detruded_ to _E_ by the _Gravity_, and _B_ to _F_ by the _resistance_ of
the subjacent medium: and therefore _C_ must necessarily be thrust to _G_;
and _D_ to _H_. Or else, supposing a greater _gravity_ in the _ambient_, by
whose more then ordinary _pressure_ against the under side of the included
globule; _B_ will be forced to _F_, and by its _resistance_ of the motion
_upwards_, the side _A_ will be _deprest_ to _E_, and therefore _C_ being
thrust to _G_ and _D_ to _H_; the _globular_ Figure by this means also will
be made an _Elliptico-spherical_. Next if a fluid be included _partly_ with
one, and _partly_ with another fluid, it will be found to be shaped
_diversly_, according to the proportion of the _gravity_ and _incongruity_
of the 3 _fluids_ one to another: As in the _second Figure_, let the upper
_MMM_ be _Air_, the middle _LMNO_ be common _Oyl_, the lower _OOO_ be
_Water_, the _Oyl_ will be form'd, not into a _spherical_ Figure, such as
is represented by the _pricked Line_, but into such a Figure as LMNO, whose
side LMN will be of a flatter _Elliptical_ Figure, by reason of the great
disproportion between the _Gravity_ of _Oyl_ and _Air_, and the side LOM of
a rounder, because of the smaller difference between the weight of _Oyl_
and _Water_. Lastly, The _globular_ Figure will be changed, if the
_ambient_ be partly _fluid_ and partly _solid_. And here the termination of
the incompassed _fluid_ towards the incompassing is shap'd according to the
proportion of the congruity or incongruity of the _fluids_ to the _solids_,
and of the gravity and incongruity of the _fluids_ one to another. As
suppose the subjacent _medium_ that hinders an included fluids descent, be
a _solid_, as let KI, in the _fourth Figure_, represent the smooth
superficies of a _Table_; EGFH, a parcel of _running Mercury_; the side GFH
will be more flatted, according to the proportion of the incongruity of the
_Mercury_ and _Air_ to the _Wood_, and of the _gravity_ of _Mercury_ and
_Air_ one to another; The side GEH will likewise be a little more deprest
by reason the subjacent parts are now at rest, which were before in motion.

Or further in the _third figure_, let AILD represent an including _solid_
medium of a cylindrical shape (as suppose a small _Glass Jar_) Let FGEMM
represent a contain'd _fluid_, as water; this towards the bottom and sides,
is figured according to the concavity of the _Glass_: But its upper
_Surface_, (which by reason of its gravity, (not considering at all the Air
above it, and so neither the congruity or incongruity of either of them to
the Glass) should be terminated by part of a _Sphere_ whose diameter should
be the same with that of the earth, which to our sense would appear a
straight _Line_, as FGE, Or which by reason of its having a greater
congruity to Glass than Air has, (not considering its Gravity) would be
thrust into a _concave Sphere_, as CHB, whose diameter would be the same
with that of the concavity of the Vessel:) Its upper Surface, I say, by
reason of its having a greater gravity then the Air, and having likewise a
greater congruity to Glass then the Air has, is terminated, by a _concave
Elliptico-spherical Figure_, as CKB. For by its congruity it easily
conforms it self, and adheres to the Glass, and constitutes as it were one
containing body with it, and therefore should thrust the contained Air on
that side it touches it, into a _spherical_ Figure, as BHC, but the motion
of Gravity depressing a little the Corners B and C, reduces it into the
aforesaid Figure CKB. Now that it is the greater congruity of one of the
two _contiguous fluids_, then of the other, to the containing _solid_, that
causes the separating surfaces to be thus or thus figured: And that it is
not because this or that figurated surface is more proper, natural, or
peculiar to one of these fluid bodies, then to the other, will appear from
this; that the same _fluids_ will by being put into differing _solids_,
change their _surfaces_. For the same water, which in a Glass or wooden
Vessel will have a concave surface upwards, and will rise higher in a
smaller then a greater Pipe, the same water, I say, in the same Pipes
greased over or oyled, will produce quite contrary effects; for it will
have a _protuberant_ and _convex_ surface upwards, and will not rise so
high in small, as in bigger Pipes: Nay, in the very same solid Vessel, you
may make the very same two contiguous _Liquids_ to alter their Surfaces;
for taking a small Wine-glass, or such like Vessel, and pouring water
gently into it, you shall perceive the _surface_ of the water all the way
_concave_, till it rise even with the top, when you shall find it (if you
gently and carefully pour in more) to grow very _protuberant_ and _convex_;
the reason of which is plain, for that the _solid_ sides of the containing
body are no longer extended, to which the water does more readily adhere
then the air; but it is henceforth to be included with air, which would
reduce it into a _hemisphere_, but by reason of its _gravity_, it is
flatted into an _Oval_. _Quicksilver_ also which to _Glass_ is more
incongruous then _Air_ (and thereby being put into a _Glass-pipe_, will not
adhere to it, but by the more _congruous air_ will be forced to have a very
_protuberant_ surface, and to rise higher in a greater then a lesser Pipe)
this _Quicksilver_ to clean _Metal_, especially to _Gold_, _Silver_, _Tin_,
_Lead_, &c. _Iron_ excepted, is more _congruous_ then _Air_, and will not
only stick to it, but have a _concave_ Surface like _water_, and rise
higher in a less, then in a greater Pipe.

In all these Examples it is evident, that there is an _extraordinary_ and
_adventitious force_, by which the _globular_ Figure of the contained
_heterogeneous_ fluid is altered; neither can it be imagined, how it should
otherwise be of any other Figure then _Globular_: For being by the
_heterogeneous_ fluid equally _protruded_ every way, whatsoever part is
_protuberant_, will be thereby _deprest_. From this cause it is, that in
its effects it does very much resemble a _round Spring_ (such as a _Hoop_.)
For as in a _round Spring_ there is required an additional _pressure_
against two opposite sides, to reduce it into an _Oval_ Form, or to force
it in between the sides of a _Hole,_ whose _Diameter_ is less then that of
the _Spring_, there must be a considerable force or _protusion_ against
_the concave_ or inner side of the _Spring_; So to alter this _spherical_
constitution of an included fluid body, there is required more pressure
against opposite sides to reduce it into an _Oval_; and, to press it into
an _Hole_ less in _Diameter_ then it self, it requires a greater
_protrusion_ against all the other sides, What degrees of force are
requisite to reduce them into longer and longer _Ovals_, or to press them
into less and less _holes_, I have not yet experimentally calculated; but
thus much by experiment I find in general, that there is alwayes required a
greater pressure to close them into longer _Ovals_, or protude them into
smaller _holes_. The necessity and reason of this, were it requisite, I
could easily explain: but being not so necessary, and requiring more room
and time then I have for it at present, I shall here omit it; and proceed
to shew, that this may be presently found true, if Experiment be made with
a _round Spring_ (the way of making which trials is _obvious_ enough.) And
with the fluid bodies of _Mercury_, _Air_, _&c_, the way of trying which,
will be somewhat more difficult; and therefore I shall in brief describe
it. He therefore that would try with _Air_, must first be provided of a
_Glass-pipe_, made of the shape of that in the _fifth Figure_, whereof the
side AB, represents a straight _Tube_ of about three foot long, C,
represents another part of it, which consists of a _round Bubble_; so
ordered, that there is left a _passage_ or _hole_ at the top, into which
may be fastened with _cement_ several _small Pipes_ of determinate
_cylindrical_ cavities: as let _hollow_ of

  F.       1/4
  G.       1/6
  H.       1/8
  I.  be   1/12   of an inch.
  K.       1/16
  L.       1/24
  M.       1/32
  &c----
There may be added as many more, as the Experimenter shall think fit, with
holes continually decreasing by known quantities, so far as his senses are
able to help him; I say, so far, because there may be made _Pipes_ so small
that it will be impossible to perceive the _perforation_ with ones naked
eye, though by the help of a _Microscope_, it may easily enough be
perceived: Nay, I have made a _Pipe_ perforated from end to end, so small,
that with my naked eye I could very hardly see the body of it, insomuch
that I have been able to knit it up into a knot without breaking: And more
accurately examining one with my _Microscope_, I found it not so big as a
sixteenth part of one of the smaller hairs of my head which was of the
smaller and finer sort of hair, so that sixteen of these _Pipes_ bound
faggot-wise together, would but have equalized one single hair; how small
therefore must its _perforation_ be? It appearing to me through the
_Microscope_ to be a proportionably _thick-sided Pipe_.

To proceed then, for the trial of the Experiment, the Experimenter must
place the _Tube_ AB, perpendicular, and fill the _Pipe_ F (cemented into
the hole E) with water, but leave the _bubble_ C full of _Air_, and then
gently pouring in water into the Pipe AB, he must observe diligently how
high the water will rise in it before it protrude the _bubble_ of Air C,
through the narrow passage of F, and denote exactly the height of the
_Cylinder_ of water, then cementing in a second Pipe as G, and filling it
with water; he may proceed as with the former, denoting likewise the height
of the _Cylinder_ of water, able to protrude the _bubble_ C through the
passage of G, the like may he do with the next _Pipe_, and the next, &c. as
far as he is able: then comparing the several heights of the _Cylinders_,
with the several _holes_ through which each _Cylinder_ did force the _air_
(having due regard to the _Cylinders_ of water in the small _Tubes_) it
will be very easie to determine, what force is requisite to press the _Air_
into such and such _a hole_, or (to apply it to our present experiment) how
much of the pressure of the _Air_ is taken off by its ingress into smaller
and smaller _holes_. From the application of which to the entring of the
_Air_ into the bigger _hole_ of the _Vessel_, and into the smaller _hole_
of the _Pipe_, we shall clearly find, that there is a greater pressure of
the air upon the water in the _Vessel_ or greater _pipe_, then there is
upon that in the lesser _pipe_: For since the pressure of the _air_ every
way is found to be equal, that is, as much as is able to press up and
sustain a _Cylinder_ of _Quicksilver_ of two foot and a half high, or
thereabouts; And since of this pressure so many more degrees are required
to force the _Air_ into a smaller then into a greater _hole_ that is full
of a more congruous fluid. And lastly, since those degrees that are
requisite to press it in, are thereby taken off from the _Air_ within, and
the _Air_ within left with so many degrees of pressure less then the _Air_
without; it will follow, that the _Air_ in the less _Tube_ or _pipe_, will
have less pressure against the superficies of the _water_ therein, then the
_Air_ in the bigger: which was the minor Proposition to be proved.

The Conclusion therefore will necessarily follow, _viz._ That _this unequal
pressure of the Air caused by its ingress into unequal holes, is a cause
sufficient to produce this effect, without the help of any other
concurrent_; therefore is probably the principal (if not the only) cause of
these _Phaenomena_.

This therefore being thus explained, there will be divers _Phaenomena_
explicable thereby, as, the rising of _Liquors_ in a _Filtre_, the rising
of _Spirit of Wine_, _Oyl_, _melted Tallow_, &c. in the _Week_ of a _Lamp_,
(though made of small _Wire_, _Threeds_ of _Asbestus_, _Strings_ of
_Glass_, or the like) the rising of _Liquors_ in a _Spunge_, piece of
_Bread_, _Sand_, &c. perhaps also the ascending of the _Sap_ in _Trees_ and
_Plants_, through their small, and some of them _imperceptible pores_, (of
which I have said more, on another occasion) at least the passing of it out
of the earth into their roots. And indeed upon the consideration of this
Principle, multitudes of other uses of it occurr'd to me, which I have not
yet so well examined and digested as to propound for _Axioms_, but only as
_Queries_ and _Conjectures_ which may serve as _hints_ toward some further
_discoveries_.

As first, Upon the consideration of the _congruity_ and _incongruity_ of
Bodies, as to _touch_, I found also the like _congruity_ and _incongruity_
(if I may so speak) as to the _Transmitting_ of the _Rates_ of Light: For
as in this regard, _water_ (not now to mention other Liquors) seems nearer
of affinity to _Glass_ then _Air_, and _Air_ then _Quicksilver_: whence an
_oblique Ray_ out of _Glass_, will pass into _water_ with very little
_refraction_ from the _perpendicular_, but none out of _Glass_ into _Air_,
excepting a _direct_, will pass without a very great refraction from the
perpendicular, nay any oblique Ray under thirty degrees, will not be
admitted into the Air at all. And _Quicksilver_ will neither admit oblique
or direct, but reflects all; seeming, as to the transmitting of the Raies
of Light, to be of a quite differing constitution, from that of _Air_,
_Water_, _Glass_, &c. and to resemble most those opacous and strong
reflecting bodies of Metals: So also as to the property of cohesion or
congruity, Water seems to keep the same order, being more congruous to
Glass then Air, and Air then Quicksilver.

A Second thing (which was hinted to me, by the consideration of the
included fluids globular form, caused by the protrusion of the ambient
heterogeneous fluid) was, whether the _Phaenomena_ of gravity might not by
this means be explained, by supposing the _Globe_ of Earth, Water, and Air
to be included with a _fluid_, heterogeneous to all and each of them, so
subtil, as not only to be every where _interspersed_ through the _Air_, (or
rather the _air_ through it) but to _pervade_ the bodies of _Glass_, and
even the _closest Metals_, by which means it may endeavour to _detrude_ all
earthly bodies as far from it as it can; and partly thereby, and partly by
other of its properties may move them towards the Center of the Earth. Now
that there is some such fluid, I could produce many Experiments and
Reasons, that do seem to prove it: But because it would ask some time and
room to set them down and explain them, and to consider and answer all the
Objections (many whereof I foresee) that may be alledged against it; I
shall at present proceed to other _Queries_, contenting my self to have
here only given a hint of what I may say more elswhere.

A Third _Query_ then was, Whether the _heterogeneity_ of the _ambient
fluid_ may not be accounted a _secondary cause_ of the _roundness_ or
_globular form_ of the _greater bodies_ of the world, such as are those of
the _Sun_, _Stars_, and _Planets_, the _substance_ of each of which seems
altogether _heterogeneous_ to the _circum-ambient fluid aether_? And of
this I shall say more in the Observation of the Moon.

A Fourth was, Whether the _globular form_ of the _smaller parcels_ of
matter here upon the _Earth_, as that of _Fruits_, _Pebbles_, or _Flints_,
&c. (which seem to have been a _Liquor_ at first) may not be caused by the
_heterogeneous ambient fluid_. For thus we see that melted _Glass_ will be
naturally formed into a _round Figure_; so likewise any small Parcel of any
_fusible body_, if it be perfectly enclosed by the _Air_, will be driven
into a _globular_ Form; and, when cold, will be found a _solid Ball_. This
is plainly enough manifested to us by their way of making _shot_ with the
_drops of Lead_; which being a very pretty curiosity, and known but to a
very few, and having the liberty of publishing it granted me, by that
_Eminent Virtuoso_ Sir _Robert Moray_, who brought in this Account of it to
the _Royal Society_, I have here transcribed and inserted.

To make small shot of different sizes; Communicated by his Highness _P.R._

_Take Lead out of the Pig what quantity you please, melt it down, stir and
clear it with an iron Ladle, gathering together the blackish parts that
swim at top like scum, and when you see the colour of the clear Lead to be
greenish, but no sooner, strew upon it _Auripigmentum_ powdered according
to the quantity of Lead, about as much as will lye upon a half Crown piece
will serve for eighteen or twenty pound weight of some sorts of Lead;
others will require more, or less. After the _Auripigmentum_ is put in,
stir the Lead well, and the _Auripigmentum_ will flame: when the flame is
over, take out some of the Lead in a Ladle having a lip or notch in the
brim for convenient pouring out of the Lead, and being well warmed amongst
the melted Lead, and with a stick make some single drops of Lead trickle
out of the Ladle into water in a Glass, which if they fall to be round and
without tails, there is _Auripigmentum_ enough put in, and the temper of
the heat is right, otherwise put in more. Then lay two bars of Iron (or
some more proper Iron-tool made on purpose) upon a Pail of water, and place
upon them a round Plate of Copper, of the size and figure of an ordinary
large Pewter or Silver Trencher, the hollow whereof is to be about three
inches over, the bottom lower then the brims about half an inch, pierced
with thirty, forty, or more small holes; the smaller the holes are, the
smaller the shot will be; and the brim is to be thicker then the bottom, to
conserve the heat the better._

_The bottom of the Trencher being some four inches distant from the water
in the Pail, lay upon it some burning Coles, to keep the Lead melted upon
it. Then with the hot Ladle take Lead off the Pot where it stands melted,
and pour it softly upon the burning Coles over the bottom of the Trencher,
and it will immediately run through the holes into the water in small round
drops. Thus pour on new Lead still as fast as it runs through the Trencher
till all be done; blowing now and then the Coles with hand-Bellows, when
the Lead in the Trencher cools so as to stop from running._

_While one pours on the Lead, another must, with another Ladle, thrusted
four or five inches under water in the Pail, catch from time to time some
of the shot, as it drops down, to see the size of it, and whether there be
any faults in it. The greatest care is to keep the Lead upon the Trencher
in the right degree of heat; if it be too cool, it will not run through the
Trencher, though it stand melted upon it; and this is to be helped by
blowing the Coals a little, or pouring on new Lead that is hotter: but the
cooler the Lead, the larger the Shot; and the hotter, the smaller; when it
it too hot, the drops will crack and fly; then you must stop pouring on new
Lead, and let it cool; and so long as you observe the right temper of the
heat, the Lead will constantly drop into very round Shot, without so much
as one with a tail in many pounds._

_When all is done, take your Shot out of the Pail of water, and put it in a
Frying-pan over the fire to dry them, which must be done warily, still
shaking them that they melt not; and when they are dry you may separate the
small from the great, in Pearl Sives made of Copper or Lattin let into one
another, into as many sizes at you please. But if you would have your Shot
larger then the Trencher makes them, you may do it with a Stick, making
them trickle out of the Ladle, as hath been said._

_If the Trencher be but toucht a very little when the Lead stops from going
through it, and be not too cool, it will drop again, but it it better not
to touch it at all. At the melting of the Lead take care that there be no
kind of Oyl, Grease, or the like, upon the Pots, or Ladles, or Trencher._

_The Chief cause of this Globular Figure of the Shot, seems to be the
_Auripigmentum_; for, as soon as it is put in among the melted Lead, it
loses its shining brightness, contracting instantly a grayish film or skin
upon it, when you scum it to make it clean with the Ladle. So that when the
Air comes at the falling drop of the melted Lead, that skin constricts them
every where equally: but upon what account, and whether this be the true
cause, is left to further disquisition._

Much after this same manner, when the Air is exceeding cold through which
it passes; do we find the drops of Rain, falling from the Clouds, congealed
into round Hail-stones by the freezing Ambient.

To which may be added this other known Experiment, That if you gently let
fall a drop of _water_ upon small _sand_ or _dust_, you shall find, as it
were, an artificial _round stone_ quickly generated. I cannot upon this
occasion omit the mentioning of the strange kind of _Grain_, which I have
observed in a _stone_ brought from _Kettering_ in _Northamptonshire_, and
therefore called by Masons _Kettering-Stone_, of which see the Description.
Which brings into my mind what I long since observed in the fiery Sparks
that are struck out of a Steel. For having a great desire to see what was
left behind, after the Spark was gone out, I purposely struck fire over a
very white piece of Paper, and observing diligently where some conspicuous
sparks went out, I found a very little black spot no bigger then the point
of a Pin, which through a _Microscope_ appeared to be a perfectly round
Ball, looking much like a polisht ball of Steel, insomuch that I was able
to see the Image of the window reflected from it. I cannot here stay
(having done it more fully in another place) to examine the particular
Reasons of it, but shall only hint, that I imagine it to be some small
parcel of the Steel, which by the violence of the motion of the stroke
(most of which seems to be imprest upon those small parcels) is made so
glowing hot, that it is melted into a _Vitrum_, which by the ambient Air is
thrust into the form of a Ball.

A Fifth thing which I thought worth Examination was, Whether the motion of
all kind of Springs, might not be reduced to the Principle whereby the
included _heterogeneous fluid_ seems to be moved; or to that whereby two
Solids, as Marbles, or the like, are thrust and kept together by the
_ambient fluid_.

A Sixth thing was, Whether the Rising and Ebullition of the Water out of
Springs and Fountains (which lie much higher from the Center of the Earth
then the Superficies of the Sea, from whence it seems to be derived) may
not be explicated by the rising of Water in a smaller Pipe: For the
Sea-water being strained through the Pores or Crannies of the Earth, is, as
it were, included in little Pipes, where the pressure of the Air has not so
great a power to resist its rising: But examining this way, and finding in
it several difficulties almost irremovable, I thought upon a way that would
much more naturally and conceivably explain it, which was by this following
Experiment: I took a Glass-Tube, of the form of that described in the sixth
Figure, and chusing two _heterogeneous fluids_, such as Water and Oyl, I
poured in as much Water as filled up the Pipes as high as AB, then putting
in some Oyl into the Tube AC, I deprest the superficies A of the Water to
F, and B I raised to G, which was not so high perpendicularly as the
superficies of the Oyl F, by the space FI, wherefore the proportion of the
gravity of these two Liquors was as GH to FE.

This Experiment I tried with several other Liquors, and particularly with
fresh Water and Salt (which I made by dissolving Salt in warm Water) which
two though they are nothing heterogeneous, yet before they would perfectly
mix one with another, I made trial of the Experiment: Nay, letting the Tube
wherein I tried the Experiment remain for many dayes, I observed them not
to mix; but the superficies of the fresh was rather more then less elevated
above that of the Salt. Now the proportion of the gravity of Sea-water, to
that of River-water, according to _Stevinus_ and _Varenius_, and as I have
since found pretty true by making trial my self, is as 46. to 45. that is,
46. Ounces of the salt Water will take up no more room then 45. of the
fresh. Or reciprocally 45 pints of salt-water weigh as much as 46 of fresh.

But I found the proportion of Brine to fresh Water to be near 13 to 12:
Supposing therefore GHM to represent the Sea, and FI the height of the
Mountain above the Superficies of the Sea, FM a Cavern in the Earth,
beginning at the bottom of the Sea, and terminated at the top of the
Mountain, LM the Sand at the bottom, through which the Water is as it were
strained, so as that the fresher parts are only permitted to transude, and
the saline kept back; if therefore the proportion of G M to FM be as 45 to
46, then may the Cylinder of Salt-water GM make the Cylinder of Fresh-water
to rise as high as E, and to run over at N. I cannot here stand to examine
or confute their Opinion, who make the depth of the Sea, below its
Superficies, to be no more perpendicularly measured then the height of the
Mountains above it: 'Tis enough for me to say, there is no one of those
that have asserted it, have experimentally known the perpendicular of
either; nor shall I here determine, whether there may not be many other
causes of the separation of the fresh water from the salt, as perhaps some
parts of the Earth through which it is to pass, may contain a Salt, that
mixing and uniting with the Sea-salt, may precipitate it; much after the
same manner as the _Alkalizate_ and _Acid Salts_ mix and precipitate each
other in the preparation of _Tartarum Vitriolatum._ I know not also whether
the exceeding cold (that must necessarily be) at the bottom of the Water,
may not help towards this separation, for we find, that warm Water is able
to dissolve and contain more Salt, then the same cold; insomuch that Brines
strongly impregnated by heat, if let cool, do suffer much of their Salt to
subside and crystallize about the bottom and sides. I know not also whether
the exceeding pressure of the parts of the Water one against another, may
not keep the Salt from descending to the very bottom, as finding little or
no room to insert it self between those parts, protruded so violently
together, or else squeeze it upwads into the superiour parts of the Sea,
where it may more easily obtain room for it self, amongst the parts of the
Water, by reason that there is more heat and less pressure. To this Opinion
I was somewhat the more induced by the relations I have met with in
_Geographical Writers_, of drawing fresh Water from the bottom of the Sea,
which is salt above. I cannot now stand to examine, whether this natural
perpetual motion may not artificially be imitated: Nor can I stand to
answer the Objections which may be made against this my Supposition: As,
First, How it comes to pass, that there are sometimes salt Springs much
higher then the Superficies of the Water? And, Secondly, Why Springs do not
run faster and slower, according to the varying height made of the Cylinder
of Sea-water, by the ebbing and flowing of the Sea?

As to the First, In short, I say, the fresh Water may receive again a
saline Tincture near the Superficies of the Earth, by passing through some
salt _Mines_, or else many of the saline parts of the Sea may be kept back,
though not all.

And as to the Second, The same _Spring_ may be fed and supplyed by divers
_Caverns_, coming from very far distant parts of the _Sea_, so as that it
may in one place be _high_, in another _low water_; and so by that means
the _Spring_ may be equally supply'd at all times. Or else the _Cavern_ may
be so straight and narrow, that the water not having so ready and free
passage through it, cannot upon so short and quick mutations of pressure,
be able to produce any sensible effect at such a distance. Besides that, to
confirm this _hypothesis_, there are many _Examples_ found in _Natural
Historians_, of _Springs_ that do ebb and flow like the Sea: As
particularly, those recorded by the Learned _Camden_, and after him by
_Speed,_ to be found in this _Island_: One of which, they relate to be on
the Top of a Mountain, by the small Village _Kilken_ in _Flintshire_,
_Maris aemulus qui statis temporibus suos evomit & resorbet Aquas_; Which
at certain times riseth and falleth after the manner of the Sea. A Second
in _Caermardenshire,_ near _Caermarden_, at a place called _Cantred
Bichan_; _Qui (ut scribit Giraldus) naturali die bis undis deficiens, &
toties exuberans, marinas imitatur instabilitates_; That twice in four and
twenty hours ebbing and flowing; resembleth the unstable motions of the
Sea. The _Phaenomena_ of which two may be easily made out, by supposing the
_Cavern_, by which they are fed, to arise from the bottom of the next Sea.
A Third, is a Well upon the River _Ogmore_ in _Glamorganshire_, and near
unto _Newton_, of which _Camden_ relates himself to be certified, by a
Letter from a Learned Friend of his that observed it, _Fons abest hinc,
&c._ The Letter is a little too long to be inserted, but the substance is
this; That this Well ebbs and flows quite contrary to the flowing and
ebbing of the Sea in those parts: for 'tis almost empty at Full Sea, but
full at Low water. This may happen from the Channel by which it is
supplied, which may come from the bottom of a Sea very remote from those
parts, and where the Tides are much differing from those of the approximate
shores. A Fourth, lies in _Westmorland_, near the River _Leder_; _Qui
instar Euripi saepius in die reciprocantibus undis fluit & refluit_, which
ebbs and flows many times a day. This may proceed from its being supplyed
from many Channels, coming from several parts of the Sea, lying
sufficiently distant asunder to have the times of High-water differing
enough one from the other; so as that whensoever it shall be High water
over any of those places, where these Channels begin, it shall likewise be
so in the Well; but this is but a supposition.

A Seventh _Query_ was, Whether the _dissolution_ or mixing of several
bodies, whether fluid or solid, with saline or other Liquors, might not
partly be attributed to this Principle of the congruity of those bodies and
their dissolvents? As of Salt in Water, Metals in several _Menstruums_,
Unctuous Gums in Oyls, the mixing of Wine and Water, &c. And whether
_precipitation_ be not partly made from the same Principle of Incongruity?
I say _partly_, because there are in some Dissolutions, some other Causes
concurrent.

I shall lastly make a much more seemingly strange and unlikely _Query_; and
that is, Whether this Principle, well examined and explained, may not be
found a _co-efficient_ in the most considerable Operations of Nature? As in
those of _Heat_, and _Light_ consequently of _Rarefaction_ and
_Condensation_, _Hardness_, and _Fluidness_, _Perspicuity_ and
_Opacousness_, _Refractions_ and _Colours. &c._ Nay, I know not whether
there may be many things done in Nature, in which this may not (be said to)
have a Finger? This I have in some other passages of this Treatise further
enquired into and shewn, that as well _Light_ as _Heat_ may be caused by
_corrosion_, which is applicable to _congruity_, and consequently all the
rest will be but _subsequents_: In the mean time I would not willingly be
guilty of that _Error_, which the thrice Noble and Learned _Verulam_ justly
takes notice of, as such, and calls _Philosophiae Genus Empiricum, quod in
paucorum Experimentorum Angustiis & Obscuritate fundatum est_. For I
neither conclude from one single Experiment, nor are the Experiments I make
use of all made upon one Subject: Nor wrest I any Experiment to make it
_quadrare_ with any preconceiv'd Notion. But on the contrary, I endeavour
to be conversant in divers kinds of Experiments, and all and every one of
those Trials, I make the Standards or Touchstones, by which I try all my
former Notions, whether they hold out in weight, and measure, and touch,
&c. For as that Body is no other then a Counterfeit Gold, which wants any
one of the Proprieties of Gold, (such as are the Malleableness, Weight,
Colour, Fixtness in the Fire, Indissolubleness in _Aqua fortis_, and the
like) though it has all the other; so will all those Notions be found to be
false and deceitful, that will not undergo all the Trials and Tests made of
them by Experiments. And therefore such as will not come up to the desired
_Apex_ of Perfection, I rather wholly reject and take new, then by piecing
and patching, endeavour to retain the old, as knowing such things at best
to be but lame and imperfect. And this course I learned from Nature; whom
we find neglectful of the old Body, and suffering its Decaies and
Infirmities to remain without repair, and altogether sollicitous and
careful of perpetuating the _Species_ by new _Individuals_. And it is
certainly the most likely way to erect a glorious Structure and Temple to
_Nature_, such as she will be found (by any _zealous Votary_) to reside in;
to begin to build a new upon a sure Foundation of Experiments.

But to digress no further from the consideration of the _Phaenomena,_ more
immediately explicable by this Experiment, we shall proceed to shew, That,
as to the rising of Water in a _Filtre_, the reason of it will be manifest
to him, that does take notice, that a _Filtre_ is constituted of a great
number of small long solid bodies, which lie so close together, that the
Air in its getting in between them, doth lose of its pressure that it has
against the _Fluid_ without them, by which means the Water or Liquor not
finding so strong a resistance between them as is able to counter-ballance
the pressure on its superficies without, is raised upward, till it meet
with a pressure of the Air which is able to hinder it. And as to the Rising
of Oyl, melted Tallow, Spirit of Wine, &c. in the Week of a Candle or Lamp,
it is evident, that it differs in nothing from the former, save only in
this, that in a _Filtre_ the Liquor descends and runs away by another part;
and in the Week the Liquor is dispersed and carried away by the Flame;
something there is ascribable to the Heat, for that it may rarifie the more
volatil and spirituous parts of those combustible Liquors, and so being
made lighter then the Air, it maybe protruded upwards by that more
ponderous fluid body in the Form of Vapours; but this can be ascribed to
the ascension of but a very little, and most likely of that only which
ascends without the Week. As for the Rising of it in a Spunge, Bread,
Cotton, &c. above the superficies of the subjacent Liquor, what has been
said about the _Filtre_ (if considered) will easily suggest a reason,
considering that all these bodies abound with small holes or pores.

From this same Principle also (_viz. the unequal pressure of the Air
against the unequal superficies of the water_) proceeds the cause of the
accession or incursion of any floating body against the sides of the
containing Vessel; or the _appropinquation_ of two floating bodies, as
_Bubbles_, _Corks_, _Sticks_, _Straws_, &c. one towards another. As for
instance, Take a Glass-jar, such as AB in the seventh _Figure_, and filling
it pretty near the top with water, throw into it a small round piece of
Cork, as C, and plunge it all over in water, that it be wet, so as that the
water may rise up by the sides of it, then placing it any where upon the
superficies, about an inch, or one inch and a quarter from any side, and
you shall perceive it by degrees to make _perpendicularly_ toward the
nearest part of the side, and the nearer it approaches, the faster to be
moved, the reason of which _Phaenomenon_ will be found no other then this,
that the Air has a greater pressure against the middle of the
_superficies_, then it has against those parts that approach nearer, and
are _contiguous_ to the sides. Now that the pressure is greater, may (as I
shewed before in the explication of the third _Figure_) be evinced from the
flatting of the water in the middle, which arises from the gravity of the
under _fluid_: for since, as I shewed before, if there were no gravity in
the under _fluid_, or that it were equal to that of the upper, the
terminating Surface would be _Spherical_, and since it is the additional
pressure of the gravity of water that makes it so flat, it follows, that
the pressure upon the middle must be greater then towards the sides. Hence
the Ball having a stronger pressure against that side of it which respects
the middle of the _superficies_, then against that which respects the
_approximate_ side, must necessarily move towards that part, from whence it
finds least resistance, and so be _accelerated_, as the resistance
decrease. Hence the more the water is raised under that part of its way it
is passing above the middle, the faster it is moved: And therefore you will
find it to move faster in E then in D, and in D then in C. Neither could I
find the floating substance to be moved at all, until it were placed upon
some part of the _Superficies_ that was sensibly elevated above the height
of the middle part. Now that this may be the true cause, you may try with a
blown Bladder, and an exactly round Ball upon a very smooth side of some
pliable body, as _Horn_ or _Quicksilver._ For if the Ball be placed under a
part of the Bladder which is upon one side of the middle of its pressure,
and you press strongly against the Bladder, you shall find the Ball moved
from the middle towards the sides.

Having therefore shewn the reason of the motion of any float towards the
sides, the reason of the incursion of any two floating bodies will easily
appear: For the rising of the water against the sides of either of them, is
an Argument sufficient, to shew the pressure of the Air to be there less,
then it is further from it, where it is not so much elevated; and therefore
the reason of the motion of the other toward it, will be the same as
towards the side of the Glass, only here from the same reason, they are
mutually moved toward each other, whereas the side of the Glass in the
former remains fixt. If also you gently fill the Jar so full with water,
that the water is _protuberant_ above the sides, the same piece of Cork
that before did hasten towards the sides, does now fly from it as fast
towards the middle of the Superficies; the reason of which will be found no
other then this, that the pressure of the Air is stronger against the sides
of the Superficies G and H, then against the middle I; for since, as I
shewed before, the Principle of congruity would make the terminating
Surface Spherical, and that the flatting of the Surface in the middle is
from the abatement of the waters pressure outwards, by the contrary
indeavour of its gravity; it follows that the pressure in the middle must
be less then on the sides; and therefore the consecution will be the same
as in the former. It is very odd to one that considers not the reason of
it, to see two floating bodies of wood to approach each other, as though
they were indued with some magnetical vigour; which brings into my mind
what I formerly tried with a piece of Cork or such like body, which I so
ordered, that by putting a little stick into the same water, one part of
the said Cork would approach and make toward the stick, whereas another
would discede and fly away, nay it would have a kind of verticity, so as
that if the _AEquator_ (as I may so speak) of the Cork were placed towards
the stick, if let alone, it would instantly turn its appropriate Pole
toward it, and then run a-tilt at it: and this was done only by taking a
dry Cork, and wetting one side of it with one small stroak; for by this
means gently putting it upon the water, it would depress the superficies on
every side of it that was dry, and therefore the greatest pressure of the
Air, being near those sides, caused it either to chase away, or else to fly
off from any other floating body, whereas that side only, against which the
water ascended, was thereby able to attract.

It remains only, that I should determine how high the Water or other Liquor
may by this means be raised in a smaller Pipe above the Superficies of that
without it, and at what height it may be sustained: But to determine this,
will be exceeding difficult, unless I could certainly know how much of the
Airs pressure is taken off by the smalness of such and such a Pipe, and
whether it may be wholly taken off, that is, whether there can be a hole or
pore so small, into which Air could not at all enter, though water might
with its whole force, for were there such, 'tis manifest, that the water
might rise in it to some five or six and thirty English Foot high. I know
not whether the capillary Pipes in the bodies of small Trees, which we call
their _Microscopical pores_, may not be such; and whether the congruity of
the sides of the Pore may not yet draw the juyce even higher then the Air
was able by its bare pressure to raise it: For, Congruity is a principle
that not only unites and holds a body joyned to it, but, which is more,
attracts and draws a body that is very near it, and holds it above its
usual height.

And this is obvious even in a drop of water suspended under any Similar or
Congruous body: For, besides the ambient pressure that helps to keep it
sustein'd, there is the Congruity of the bodies that are contiguous. This
is yet more evident in Tenacious and Glutinous bodies; such as Gummous
Liquors, Syrups, Pitch, and Rosin melted, &c. Tar, Turpentine, Balsom,
Bird-lime, &c. for there it is evident, that the Parts of the tenacious
body, as I may so call it, do stick and adhere so closely together, that
though drawn out into long and very slender Cylinders, yet they will not
easily relinquish one another; and this, though the bodies be _aliquatenus_
fluid, and in motion by one another, which, to such as consider a fluid
body only as its parts are in a confused irregular motion, without taking
in also the congruity of the parts one among another, and incongruity to
some other bodies, does appear not a little strange. So that besides the
incongruity of the ambient fluid to it, we are to consider also the
congruity of the parts of the contein'd fluid one with another.

And this Congruity (that I may here a little further explain it) is both a
Tenaceous and an Attractive power; for the Congruity, in the Vibrative
motions, may be the cause of all kind of attraction, not only Electrical,
but Magnetical also, and therefore it may be also of Tenacity and
Glutinousness. For, from a perfect congruity of the motions of two distant
bodies, the intermediate fluid particles are separated and droven away from
between them, and thereby those congruous bodies are, by the incompassing
mediums, compell'd and forced neerer together; wherefore that
attractiveness must needs be stronger, when, by an immediate contact, they
are forc'd to be exactly the same: As I shew more at large in my _Theory_
of the _Magnet_. And this hints to me the reason of the suspension of the
_Mercury_ many inches, nay many feet, above the usual station of 30 inches.
For the parts of _Quick-Silver,_ being so very similar and congruous to
each other, if once united, will not easily suffer a divulsion: And the
parts of water, that were any wayes _heterogeneous_, being by _exantlation_
or rarefaction exhausted, the remaining parts being also very similar, will
not easily part neither. And the parts of the Glass being solid, are more
difficultly disjoyn'd; and the water, being somewhat similar to both, is,
as it were, a medium to unite both the _Glass_ and the _Mercury_ together.
So that all three being united, and not very dissimilar, by means of this
contact, if care be taken that the Tube in erecting be not shogged, the
_Quicksilver_ will remain suspended, notwithstanding its contrary indeavour
of Gravity, a great height above its ordinary Station; but if this
immediate Contact be removed, either by a meer separation of them one from
another by the force of a shog, whereby the other becomes imbodied between
them, and licks up from the surface some agil parts, and so hurling them
makes them air, or else by some small heterogeneous agil part of the Water,
or Air, or Quicksilver, which appears like a bubble, and by its jumbling to
and fro there is made way for the _heterogeneous AEther_ to obtrude it self
between the Glass and either of the other Fluids, the Gravity of _Mercury
precipitates_ it downward with very great violence; and if the Vessel that
holds the restagnating _Mercury_ be convenient, the _Mercury_ will for a
time _vibrate_ to and fro with very large _reciprocations_, and at last
will remain kept up by the pressure of the external Air at the height of
neer thirty inches. And whereas it may be objected, that it cannot be, that
the meer imbodying of the _AEther_ between these bodies can be the cause,
since the _AEther_ having a free passage alwayes, both through the Pores of
the Glass, and through those of the Fluids, there is no reason why it
should not make a separation at all times whilst it remains suspended, as
when it is violently dis-joyned by a shog. To this I answer, That though
the _AEther_ passes between the Particles, that is, through the Pores of
bodies, so as that any chasme or separation being made, it has infinite
passages to admit its entry into it, yet such is the tenacity or attractive
virtue of Congruity, that till it be overcome by the meer strength of
Gravity, or by a shog assisting that Conatus of Gravity, or by an agil
Particle, that is like a leaver agitated by the _AEther_; and thereby the
parts of the congruous substances are separated so far asunder, that the
strength of congruity is so far weakened, as not to be able to reunite
them, the parts to be taken hold of being removed out of the attractive
Sphere, as I may so speak, of the congruity; such, I say, is the tenacity
of congruity, that it retains and holds the almost contiguous Particles of
the Fluid, and suffers them not to be separated, till by meer force that
attractive or retentive faculty be overcome: But the separation being once
made beyond the Sphere of the attractive activity of congruity, that virtue
becomes of no effect at all, but the _Mercury_ freely falls downwards till
it meet with a resistance from the pressure of the _ambient_ Air, able to
resist its gravity, and keep it forced up in the Pipe to the height of
about thirty inches.

Thus have I gently raised a Steel _pendulum_ by a Loadstone to a great
Angle, till by the shaking of my hand I have chanced to make a separation
between them, which is no sooner made, but as if the Loadstone had retained
no attractive virtue, the _Pendulum_ moves freely from it towards the other
side. So vast a difference is there between the attractive virtue of the
_Magnet_ when it acts upon a contiguous and upon a disjoyned body: and much
more must there be between the attractive virtues of congruity upon a
contiguous and disjoyned body; and in truth the attractive virtue is so
little upon a body disjoyned, that though I have with a _Microscope_
observed very diligently, whether there were any extraordinary
_protuberance_ on the side of a drop of water that was exceeding neer to
the end of a green stick, but did not touch it, I could not perceive the
least; though I found, that as soon as ever it toucht it the whole drop
would presently unite it self with it; so that it seems an absolute contact
is requisite to the exercising of the tenacious faculty of congruity.

       *       *       *       *       *


Observ. VII. _Of some _Phaenomena_ of Glass drops._

These _Glass Drops_ are small parcels of coarse green Glass taken out of
the Pots that contain the _Metal_ (as they call it) in fusion, upon the end
of an Iron Pipe; and being exceeding hot, and thereby of a kind of sluggish
fluid Confidence, are suffered to drop from thence into a Bucket of cold
Water, and in it to lye till they be grown sensibly cold.

Some of these I broke in the open air, by snapping off a little of the
small stem with my fingers, others by crushing it with a small pair of
Plyers; which I had no sooner done, then the whole bulk of the drop flew
violently, with a very brisk noise, into multitudes of small pieces, some
of which were as small as dust, though in some there were remaining pieces
pretty large, without any flaw at all, and others very much flaw'd, which
by rubbing between ones fingers was easily reduced to dust; these dispersed
every way so violently, that some of them pierced my skin. I could not find
either with my naked Eye, or a _Microscope_, that any of the broken pieces
were of a regular figure, nor any one like another, but for the most part
those that flaw'd off in large pieces were prettily branched.

The ends of others of these drops I nipt off whilst all the bodies and ends
of them lay buried under the water, which, like the former, flew all to
pieces with as brisk a noise, and as strong a motion.

Others of these I tried to break, by grinding away the blunt end, and
though I took a seemingly good one, and had ground away neer two thirds of
the Ball, yet would it not fly to pieces, but now and then some small rings
of it would snap and fly off, not without a brisk noise and quick motion,
leaving the Surface of the drop whence it flew very prettily branched or
creased, which was easily discoverable by the _Microscope_. This drop,
after I had thus ground it, without at all impairing the remnant that was
not ground away, I caused to fly immediately all into sand upon the nipping
off the very tip of its slender end.

Another of these drops I began to grind away at the smaller end, but had
not worn away on the stone above a quarter of an inch before the whole drop
flew with a brisk crack into sand or small dust; nor would it have held so
long, had there not been a little flaw in the piece that I ground away, as
I afterwards found.

Several others of these drops I covered over with a thin but very tuff skin
of _Icthyocolla_, which being very tough and very transparent, was the most
convenient substance for these tryals that I could imagine, having dipt, I
say, several of these drops in this transparent Glue whilst hot, and
suffering them to hang by a string tied about the end of them till they
were cold, and the skin pretty tough; then wrapping all the body of the
drop (leaving out only the very tip) in fine supple Kids-leather very
closely, I nipped off the small top, and found, as I expected, that
notwithstanding this skin of Glue, and the close wrapping up in Leather,
upon the breaking of the top, the drop gave a crack like the rest, and gave
my hand a pretty brisk impulse: but yet the skin and leather was so strong
as to keep the parts from flying out of their former posture; and, the skin
being transparent, I found that the drop retained exactly its former figure
and polish, but was grown perfectly opacous and all over flaw'd, all those
flaws lying in the manner of rings, from the bottom or blunt end, to the
very top or small point. And by several examinations with a _Microscope_,
of several thus broken, I found the flaws, both within the body of the
drop, and on the outward surface, to lye much in this order.

Let AB in the Figure X of the fourth Scheme represent the drop cased over
with _Icthyocolla_ or _Isinglass_, (by being ordered as is before
prescribed) crazed or flawed into pieces, but by the skin or case kept in
its former figure, and each of its flawed parts preserved exactly in its
due posture; the outward appearance of it somewhat plainly to the naked
eye, but much more conspicuous if viewed with a small lens appeared much
after this shape. That is, the blunt end B for a pretty breadth, namely, as
far as the Ring CCC seemed irregularly flawed with divers clefts, which all
seemed to tend towards the Center of it, being, as I afterwards found, and
shall anon shew in the description of the figure Y, the Basis, as it were,
of a Cone, which was terminated a little above the middle of the drop, all
the rest of the Surface from CCC to A was flawed with an infinite number of
small and parallel Rings, which as they were for the most part very round,
so were they very thick and close together, but were not so exactly flaw'd
as to make a perfect Ring, but each circular part was by irregular cracks
flawed likewise into multitudes of irregular flakes or tiles; and this
order was observed likewise the whole length of the neck.

Now though I could not so exactly cut this _conical Body_ through the
_Axis_, as is represented by the figure Y; yet by _anatomizing_, as it
were, of several, and taking notice of divers particular circumstances, I
was informed, that could I have artificially divided a flaw'd drop through
the _Axis_ or _Center_, I should with a _Microscope_ have found it to
appear much of this form, where A signifies the _Apex_, and B the blunt
end, CC the Cone of the Basis, which is terminated at T the top or end of
it, which seems to be the very middle of the blunt end in which, not only
the conical body of the Basis CC is terminated, but as many of the parts of
the drop as reach as high as DD.

And it seemed to be the head or beginning of a Pith, as it were, or a part
of the body which seemed more spungy then the rest, and much more
irregularly flawed, which from T ascended by EE, though less visible, into
the small neck towards A. The Grain, as it were, of all the flaws, that
proceeds from all the outward Surface ADCCDA, was much the same, as is
represented by the black strokes that meet in the middle DT, DT, DE, DE,
&c.

Nor is this kind of Grain, as I may call it, peculiar to Glass drops thus
quenched; for (not to mention _Coperas-stones_, and divers other
_Marchasites_ and _Minerals_, which I have often taken notice of to be in
the very same manner flaked or grained, with a kind of Pith in the middle)
I have observed the same in all manner of cast Iron, especially the coarser
sort, such as Stoves, and Furnaces, and Backs, and Pots are made of: For
upon the breaking of any of those Substances it is obvious to observe, how
from the out-sides towards the middle, there is a kind of Radiation or
Grain much resembling this of the Glass-drop; but this Grain is most
conspicuous in Iron-bullets, if they be broken: the same _Phaenomena_ may
be produced by casting _regulus_ of _Antimony_ into a Bullet-mold, as also
with _Glass of Antimony_, or with almost any such kind of _Vitrified
substance_, either cast into a cold Mold or poured into Water.

Others of these Drops I heat red hot in the fire, and then suffered them to
cool by degrees. And these I found to have quite lost all their
_fulminating_ or flying quality, as also their hard, brittle and springy
texture; and to emerge of a much softer temper, and much easier to be
broken or snapt with ones finger; but its strong and brittle quality was
quite destroyed, and it seemed much of the same consistence with other
green Glass well nealed in the Oven.

The Figure and bigness of these for the most part was the same with that of
the Figure Z; that is, all the surface of them was very smooth and polisht,
and for the most part round, but very rugged or knobbed about D, and all
the length of the stem was here and there pitted or flatted. About D, which
is at the upper part of the drop under that side of the stem which is
concave, there usually was made some one or more little Hillocks or
Prominences. The drop it self, before it be broken, appears very
transparent, and towards the middle of it, to be very full of small
Bubbles, of some kind of aerial substance, which by the refraction of the
outward surface appear much bigger then really they are, and this may be in
good part removed, by putting the drop under the surface of clear Water,
for by that means most part of the refraction of the convex Surface of the
drop is destroyed, and the bubbles will appear much smaller. And this, by
the by, minds me of the appearing magnitude of the _aperture_ of the
_iris_, or _pupil_ of the eye, which though it appear, and be therefore
judged very large, is yet not above a quarter of the bigness it appears of,
by the _lenticular_ refraction of the _Cornea_.

The cause of all which _Phaenomena_ I imagine to be no other then this,
That the Parts of the Glass being by the excessive heat of the fire kept
off and separated one from another, and thereby put into a kind of sluggish
fluid consistence, are suffered to drop off with that heat or agitation
remaining in them, into cold Water; by which means the outsides of the drop
are presently cool'd and _crusted_, and are thereby made of a loose
texture, because the parts of it have not time to settle themselves
leisurely together, and so to lie very close together: And the innermost
parts of the drop, retaining still much of their former heat and
agitations, remain of a loose texture also, and, according as the cold
strikes inwards from the bottom and sides, are quenched, as it were, and
made rigid in that very posture wherein the cold finds them. For the parts
of the _crust_ being already hardened, will not suffer the parts to shrink
any more from the outward Surface inward; and though it shrink a little by
reason of the small parcels of some Aerial substances dispersed through
the matter of the Glass, yet that is not neer so much as it appears (as I
just now hinted;) nor if it were, would it be sufficient for to consolidate
and condense the body of Glass into a _tuff_ and close _texture_, after it
had been so excessively rarified by the heat of the glass-Furnace.

But that there may be such an expansion of the aerial substance contained
in those little _blebbs_ or bubbles in the body of the drop, this following
Experiment will make more evident.

       *       *       *       *       *

Take a small Glass-Cane about a foot long, seal up one end of it
_hermetically_, then put in a very small bubble of Glass, almost of the
shape of an Essence-viol with the open mouth towards the sealed end, then
draw out the other end of the Pipe very small, and fill the whole Cylinder
with water, then set this Tube by the Fire till the Water begin to boyl,
and the Air in the bubble be in good part rarified and driven out, then by
sucking at the smalling Pipe, more of the Air or vapours in the bubble may
be suck'd out, so that it may sink to the bottom; when it is sunk to the
bottom, in the flame of a Candle, or Lamp, nip up the slender Pipe and let
it cool: whereupon it is obvious to observe, first, that the Water by
degrees will subside and shrink into much less room: Next, that the Air or
vapours in the Glass will expand themselves so, as to buoy up the little
Glass: Thirdly, that all about the inside of the Glass-pipe there will
appear an infinite number of small bubbles, which as the Water grows colder
and colder will swell bigger and bigger, and many of them buoy themselves
up and break at the top.

From this _Disceding_ of the heat in Glass drops, that is, by the quenching
or cooling Irradiations propagated from the Surface upwards and inwards, by
the lines CT, CT, DT, DE, &c. the bubbles in the drop have room to expand
themselves a little, and the parts of the Glass contract themselves; but
this operation being too quick for the sluggish parts of the Glass, the
contraction is performed very unequally and irregularly, and thereby the
Particles of the Glass are bent, some one way, and some another, yet so as
that most of them draw towards the Pith or middle TEEE, or rather from that
outward: so that they cannot _extricate_ or unbend themselves, till some
part of TEEE be broken and loosened, for all the parts about that are
placed in the manner of an Arch, and so till their hold at TEEE be loosened
they cannot fly asunder, but uphold, and shelter, and fix each other much
like the stones in a Vault, where each stone does concurre to the stability
of the whole Fabrick, and no one stone can be taken away but the whole Arch
falls. And wheresoever any of those radiating wedges DTD, &c. are removed,
which are the component parts of this Arch, the whole Fabrick presently
falls to pieces; for all the Springs of the several parts are set at
liberty, which immediately extricate themselves and fly asunder every way;
each part by its spring contributing to the darting of it self and some
other contiguous part. But if this drop be heat so hot as that the parts by
degrees can unbend themselves, and be settled and annealed in that posture,
and be then suffered gently to subside and cool; The parts by this nealing
losing their springiness, constitute a drop of a more soft but less brittle
texture, and the parts being not at all under a flexure, though any part of
the middle or Pith TEEE be broken, yet will not the drop at all fly to
pieces as before.

This Conjecture of mine I shall indeavour to make out by explaining each
particular Assertion with _analogous_ Experiments: The Assertions are
there.

    First, That the parts of the Glass, whilst in a fluid Consistence and
    hot, are more rarified, or take up more room, then when hard and cold.

    Secondly, That the parts of the drop do suffer a twofold contraction.

    Thirdly, That the dropping or quenching the glowing metal in the Water
    makes it of a hard, springing, and rarified texture.

    Fourthly, That there is a flexion or force remaining upon the parts of
    the Glass thus quenched, from which they indeavour to extricate
    themselves.

    Fifthly, That the Fabrick of the drop, that is able to hinder the parts
    from extricating themselves, is _analogus_ to that of an Arch.

    Sixthly, That the sudden flying asunder of the parts proceeds from
    their springiness.

    Seventhly, That a gradual heating and cooling does anneal or reduce the
    parts of Glass to a texture that is more loose, and easilier to be
    broken, but not so brittle.

That the first of these is true may be gathered from this, That _Heat is a
property of a body arising from the motion or agitation of its parts_; and
therefore whatever body is thereby toucht must necessarily receive some
part of that motion, whereby its parts will be shaken and agitated, and so
by degrees free and extricate themselves from one another, and each part so
moved does by that motion _exert_ a _conatus_ of _protruding_ and
displacing all the adjacent Particles. Thus Air included in a vessel, by
being heated will burst it to pieces. Thus have I broke a Bladder held over
the fire in my hand, with such a violence and noise, that it almost made me
deaf for the present, and much surpassed the noise of a Musket: The like
have I done by throwing into the fire small glass Bubbles hermetically
sealed, with a little drop of Water included in them. Thus Water also, or
any other Liquor, included in a convenient vessel, by being warmed,
manifestly expands it self with a very great violence, so as to break the
strongest vessel, if when heated it be narrowly imprisoned in it. This is
very manifest by the _Sealed Thermometers_, which I have, by several
tryals, at last brought to a great certainty and tenderness: for I have
made some with stems above four foot long, in which the expanding Liquor
would so far vary, as to be very neer the very top in the heat of Summer,
and prety neer the bottom at the coldest time of the Winter. The Stems I
use for them are very thick, straight, and even Pipes of Glass, with a very
small _perforation_, and both the head and body I have made on purpose at
the Glass-house, of the same metal whereof the Pipes are drawn: these I can
easily in the flame of a Lamp, urged with the blast of a pair of Bellows,
seal and close together, so as to remain very firm, close and even; by this
means I joyn on the body first, and then fill both it and a part of the
stem, proportionate to the length of the stem and the warmth of the season
I fill it in with the best rectified _Spirit of Wine_ highly _ting'd_ with
the lovely colour of _Cocheneel_, which I deepen the more by pouring some
drops of common _Spirit of Urine_, which must not be too well rectified,
because it will be apt to make the Liquor to curdle and stick in the small
perforation of the stem. This Liquor I have upon tryal found the most
tender of any spirituous Liquor, and those are much more sensibly affected
with the variations of heat and cold then other more flegmatick and
ponderous Liquors, and as capable of receiving a deep tincture, and keeping
it, as any Liquor whatsoever; and (which makes it yet more acceptable) is
not subject to be frozen by any cold yet known. When I have thus filled it,
I can very easily in the forementioned flame of a Lamp seal and joyn on the
head of it.

Then, for graduating the stem, I fix that for the beginning of my division
where the surface of the liquor in the stem remains when the ball is placed
in common distilled water, that is so cold that it just begins to freeze
and shoot into flakes; and that mark I fix at a convenient place of the
stem, to make it capable of exhibiting very many degrees of cold, below
that which is requisite to freeze water: the rest of my divisions, both
above and below this (which I mark with a [0] or nought) I place according
to the Degrees of _Expansion_, or _Contraction_ of the Liquor in proportion
to the bulk it had when it indur'd the newly mention'd freezing cold. And
this may be very easily and accurately enough done by this following way;
Prepare a Cylindrical vessel of very thin plate Brass or Silver, ABCD of
the figure Z; the Diameter AB of whose cavity let be about two inches, and
the depth BC the same; let each end be cover'd with a flat and smooth plate
of the same substance, closely soder'd on, and in the midst of the upper
cover make a pretty large hole EF, about the bigness of a fifth part of the
Diameter of the other; into this fasten very well with cement a straight
and even Cylindrical pipe of Glass, EFGH, the Diameter of whose cavity let
be exactly one tenth of the Diameter of the greater Cylinder. Let this pipe
be mark'd at GH with a Diamant, so that G from E may be distant just two
inches, or the same height with that of the cavity of the greater Cylinder,
then divide the length EG exactly into 10 parts, so the capacity of the
hollow of each of these divisions will be 1/1000 part of the capacity of
the greater Cylinder. This vessel being thus prepared, the way of marking
and graduating the _Thermometers_ may be very easily thus performed:

Fill this Cylindrical vessel with the same liquor wherewith the
_Thermometers_ are fill'd, then place both it and the _Thermometer_ you are
to _graduate_, in water that is ready to be frozen, and bring the surface
of the liquor in the _Thermometer_ to the first marke or [0]; then so
proportion the liquor in the Cylindrical vessel, that the surface of it may
just be at the lower end of the small glass-Cylinder; then very gently and
gradually warm the water in which both the _Thermometer_ and this
Cylindrical vessel stand, and as you perceive the ting'd liquor to rise in
both stems, with the point of a Diamond give several marks on the stem of
the _Thermometer_ at those places, which by comparing the expansion in both
Stems, are found to correspond to the divisions of the cylindrical vessel,
and having by this means marked some few of these divisions on the Stem, it
will be very easie by these to mark all the rest of the Stem, and
accordingly to assign to every division a proper character.

A _Thermometer_, thus marked and prepared, will be the fittest Instrument
to make a Standard of heat and cold that can be imagined. For being sealed
up, it is not at all subject to variation or wasting, nor is it liable to
be changed by the varying pressure of the Air, which all other kind of
_Thermometers_ that are open to the Air are liable to. But to proceed.

This property of Expansion with Heat, and Contraction with Cold, is not
peculiar to Liquors only, but to all kind of solid Bodies also, especially
Metals, which will more manifestly appear by this Experiment.

Take the Barrel of a Stopcock of Brass, and let the Key, which is well
fitted to it, be riveted into it, so that it may slip, and be easily turned
round, then heat this Cock in the fire, and you will find the Key so
swollen, that you will not be able to turn it round in the Barrel; but if
it be suffered to cool again, as soon as it is cold it will be as movable,
and as easie to be turned as before.

This Quality is also very observable in _Lead_, _Tin_, _Silver_,
_Antimony_, _Pitch_, _Rosin_, _Bees-wax_, _Butter_, and the like; all
which, if after they be melted you suffer gently to cool, you shall find
the parts of the upper Surface to subside and fall inwards, losing that
plumpness and smoothness it had whilst in fusion. The like I have also
observed in the cooling of _Glass of Antimony_, which does very neer
approach the nature of Glass,

But because these are all Examples taken from other materials then Glass,
and argue only, that possibly there may be the like property also in Glass,
not that really there is; we shall by three or four Experiments indeavour
to manifest that also.

And the First is an Observation that is very obvious even in these very
drops, to wit, that they are all of them terminated with an unequal or
irregular Surface, especially about the smaller part of the drop, and the
whole length of the stem; as about D, and from thence to A, the whole
Surface, which would have been round if the drop had cool'd leisurely, is,
by being quenched hastily, very irregularly flatted and pitted; which I
suppose proceeds partly from the Waters unequally cooling and pressing the
parts of the drop, and partly from the self-contracting or subsiding
quality of the substance of the Glass: For the vehemency of the heat of the
drop causes such hidden motions and bubbles in the cold Water, that some
parts of the Water bear more forcibly against one part then against
another, and consequently do more suddenly cool those parts to which they
are contiguous.

A Second Argument may be drawn from the Experiment of cutting Glasses with
a hot Iron. For in that Experiment the top of the Iron heats, and thereby
rarifies the parts of the Glass that lie just before the crack, whence each
of those agitated parts indeavouring to expand its self and get elbow-room,
thrusts off all the rest of the contiguous parts, and consequently promotes
the crack that was before begun.

A Third Argument may be drawn from the way of producing a crack in a sound
piece or plate of Glass, which is done two wayes, either First, by suddenly
heating a piece of Glass in one place more then in another. And by this
means _chymists_ usually cut off the necks of Glass-bodies, by two kinds of
Instruments, either by a glowing hot round Iron-Ring, which just
incompasses the place that is to be cut, or else by a _Sulphur'd_ Threed,
which is often wound about the place where the separation is to be made,
and then fired. Or Secondly, A Glass may be cracked by cooling it suddenly
in any place with Water, or the like, after it has been all leisurely and
gradually heated very hot. Both which _Phaenomena_ seem manifestly to
proceed from the _expansion_ and contraction of the parts of the Glass,
which is also made more probable by this circumstance which I have
observed, that a piece of common window-glass being heated in the middle
very suddenly with a live Coal or hot Iron, does usually at the first crack
fall into pieces, whereas if the Plate has been gradually heated very hot,
and a drop of cold Water and the like be put on the middle of it, it only
flaws it, but does not break it asunder immediately.

A Fourth Argument may be drawn from this Experiment; Take a Glass-pipe, and
fit into a solid stick of Glass, so as it will but just be moved in it.
Then by degrees heat them whilst they are one within another, and they will
grow stiffer, but when they are again cold, they will be as easie to be
turned as before. This Expansion of Glass is more manifest in this
Experiment.

Take a stick of Glass of a considerable length, and fit it so between the
two ends or screws of a Lath, that it may but just easily turn, and that
the very ends of it may be just toucht and susteined thereby; then applying
the flame of the Candle to the middle of it, and heating it hot, you will
presently find the Glass to stick very fast on those points, and not
without much difficulty to be convertible on them, before that by removing
the flame for a while from it, it be suffered to cool, and when you will
find it as easie to be turned round as at the first.

From all which Experiments it is very evident, that all those Bodies, and
particularly Glass, suffers an Expansion by Heat, and that a very
considerable one, whilst they are in a state of Fusion. For _Fluidity_, as
I elsewhere mention, _being nothing but an effect of very strong and quick
shaking motion, whereby the parts are, as it were, loosened from each
other, and consequently leave an interjacent space or vacuity_; it follows,
that all those shaken Particles must necessarily take up much more room
then when they were at rest, and lay quietly upon each other. And this is
further confirmed by a Pot of _boyling Alabaster_, which will manifestly
rise a sixth or eighth part higher in the Pot, whilst it is boyling, then
it will remain at, both before and after it be boyled. The reason of which
odd _Phaenomenon_ (to hint it here only by the way) is this, that there is
in the curious powder of Alabaster, and other calcining Stones, a certain
watery substance, which is so fixt and included with the solid Particles,
that till the heat be very considerable they will not fly away; but after
the heat is increased to such a degree, they break out every way in
vapours, and thereby so shake and loosen the small corpusles of the Powder
from each other, that they become perfectly of the nature of a fluid body,
and one may move a stick to and fro through it, and stir it as easily as
water, and the vapours burst and break out in bubbles just as in boyling
water, and the like; whereas, both before those watery parts are flying
away, and after they are quite gone; that is, before and after it have done
boyling, all those effects cease, and a stick is as difficultly moved to
and fro in it as in sand, or the like. Which Explication I could easily
prove, had I time; but this is not a fit place for it.

To proceed therefore, I say, that the dropping of this expanded Body into
cold Water, does make the parts of the Glass suffer a double contraction:
The first is, of those parts which are neer the Surface of the Drop. For
Cold, as I said before, contracting Bodies, that is, _by the abatement of
the agitating faculty the parts falling neerer together_; the parts next
adjoyning to the Water must needs lose much of their motion, and impart it
to the Ambient-water (which the Ebullition and commotion of it manifests)
and thereby become a solid and hard crust, whilst the innermost parts
remain yet fluid and expanded; whence, as they grow cold also by degrees,
their parts must necessarily be left at liberty to be condensed, but
because of the hardness of the outward crust, the contraction cannot be
admitted that way; but there being many very small, and before
inconspicuous, bubbles in the substance of the Glass, upon the subsiding of
the parts of the Glass, the agil substance contained in them has liberty of
expanding it self a little, and thereby those bubbles grow much bigger,
which is the second Contraction. And both these are confirmed from the
appearance of the Drop it self: for as for the outward parts, we see,
first, that it is irregular and shrunk, as it were, which is caused by the
yielding a little of the hardened Skin to a Contraction, after the very
outmost Surface is settled; and as for the internal parts, one may with
ones naked Eye perceive abundance of very conspicuous bubbles, and with the
_Microscope_ many more.

The Consideration of which Particulars will easily make the Third Position
probable, that is, that the parts of the drop will be of a very hard,
though of a rarified Texture; for if the outward parts of the Drop, by
reason of its hard crust, will indure very little Contraction, and the agil
Particles, included in those bubbles, by the losing of their agitation, by
the decrease of the Heat, lose also most part of their Spring and Expansive
power; it follows (the withdrawing of the heat being very sudden) that the
parts must be left in a very loose Texture, and by reason of the
implication of the parts one about another, which from their sluggishnes
and glutinousness I suppose to be much after the manner of the sticks in a
Thorn-bush, or a Lock of Wool; it will follow, I say, that the parts will
hold each other very strongly together, and indeavour to draw each other
neerer together, and consequently their Texture must be very hard and
stiff, but very much rarified.

And this will make probable my next Position, That _the parts of the Glass
are under a kind of tension or flexure, out of which they indeavour to
extricate and free themselves_, and thereby all the parts draw towards the
Center or middle, and would, if the outward parts would give way, as they
do when the outward parts cool leisurely (as in baking of Glasses) contract
the bulk of the drop into a much less compass. For since, as I proved
before, the Internal parts of the drop, when fluid, were of a very rarified
Texture, and, as it were, tos'd open like a Lock of Wool, and if they were
suffered leisurely to cool, would be again prest, as it were, close
together: And since that the heat, which kept them bended and open, is
removed, and yet the parts not suffered to get as neer together as they
naturally would; It follows, that the Particles remain under a kind of
_tension_ and _flexure_, and consequently have an indeavour to free
themselves from that _bending_ and _distension_, which they do, as soon as
either the tip be broken, or as soon as by a leisurely heating and cooling,
the parts are nealed into another posture.

And this will make my next Position probable, that _the parts of the Glass
drops are contignated together in the form of an Arch_, cannot any where
yield or be drawn inwards, till by the removing of some one part of it (as
it happens in the removing one of the stones of an Arch) the whole Fabrick
is shatter'd, and falls to pieces, and each of the Springs is left at
liberty, suddenly to extricate it self: for since I have made it probable,
that the internal parts of the Glass have a contractive power inwards, and
the external parts are incapable of such a Contraction, and the figure of
it being spherical; it follows, that the superficial parts must bear
against each other, and keep one another from being condens'd into a less
room, in the same manner as the stones of an Arch conduce to the upholding
each other in that Figure. And this is made more probable by another
Experiment which was communicated to me by an excellent Person, whose
extraordinary Abilities in all kind of Knowledg, especially in that of
Natural things, and his generous Disposition in communicating, incouraged
me to have recourse to him on many occasions. The Experiment was this:
Small Glass-balls (about the bigness of that represented in the _Figure
&._) would, upon rubbing or scratching the inward Surface, fly all
insunder, with a pretty brisk noise; whereas neither before nor after the
inner Surface had been thus scratcht, did there appear any flaw or crack.
And putting the pieces of one of those broken ones together again, the
flaws appeared much after the manner of the black lines on the Figure, _&._
These Balls were small, but exceeding thick bubbles of Glass, which being
crack'd off from the _Puntilion_ whilst very hot, and so suffered to cool
without nealing them in the Oven over the Furnace, do thereby (being made
of white Glass, which cools much quicker then green Glass, and is thereby
made much brittler) acquire a very _porous_ and very brittle _texture_: so
that if with the point of a Needle or Bodkin, the inside of any of them be
rubbed prety hard, and then laid on a Table, it will, within a very little
while, break into many pieces with a brisk noise, and throw the parts above
a span asunder on the Table: Now though the pieces are not so small as
those of a _fulminating_ drop, yet they as plainly shew, that the outward
parts of the Glass have a great _Conatus_ to fly asunder, were they not
held together by the _tenacity_ of the parts of the inward Surface: for we
see as soon as those parts are crazed by hard rubbing, and thereby their
tenacity spoiled, the springiness of the more outward parts quickly makes a
divulsion, and the broken pieces will, if the concave Surface of them be
further scratcht with a Diamond, fly again into smaller pieces.

From which preceding considerations it will follow Sixthly, That the sudden
flying asunder of the parts as soon as this Arch is any where disordered or
broken, proceeds from the springing of the parts; which, indeavouring to
_extricate_ themselves as soon as they get the liberty, they perform it
with such a quickness, that they throw one another away with very great
violence: for the Particles that compose the Crust have a _Conatus_ to lye
further from one another, and therefore as soon as the external parts are
loosened they dart themselves outward with great violence, just as so many
Springs would do, if they were detained and fastened to the body, as soon
as they should be suddenly loosened; and the internal parts drawing inward,
they contract so violently; that they rebound back again and fly into
multitude of small shivers or sands. Now though they appear not, either to
the naked Eye, or the _Microscope_, yet I am very apt to think there may be
abundance of small flaws or cracks, which, by reason the strong reflecting
Air is not got between the _contiguous_ parts, appear not. And that this
may be so, I argue from this, that I have very often been able to make a
crack or flaw, in some convenient pieces of Glass, to appear and disappear
at pleasure, according as by pressing together, or pulling asunder the
contiguous parts, I excluded or admitted the strong reflecting Air between
the parts: And it is very probable, that there may be some Body, that is
either very rarified Air, or something _analogous_ to it, which fills the
bubbles of these drops; which I argue, first, from the roundness of them,
and next, from the vivid reflection of Light which they exhibite: Now
though I doubt not, but that the Air in them is very much rarified, yet
that there is some in them, to such as well consider this Experiment of the
disappearing of a crack upon the _extruding_ of the Air, I suppose it will
seem more then probable.

The Seventh and last therefore that I shall prove, is, _That the gradual
heating and cooling of these so extended bodies does reduce the parts of
the Glass to a looser and softer temper_. And this I found by heating them,
and keeping them for a prety while very red hot in a fire; for thereby I
found them to grow a little lighter, and the small Stems to be very easily
broken and snapt any where, without at all making the drop fly; whereas
before they were so exceeding hard, that they could not be broken without
much difficulty; and upon their breaking the whole drop would fly in pieces
with very great violence. The Reason of which last seems to be, that the
leisurely heating and cooling of the parts does not only wast some part of
the Glass it self, but ranges all the parts into a better order, and gives
each Particle an opportunity of _relaxing_ its self, and consequently
neither will the parts hold so strongly together as before, nor be so
difficult to be broken: The parts now more easily yielding, nor will the
other parts fly in pieces, because the parts have no bended Springs. The
_relaxation_ also in the temper of hardned Steel, and hammered Metals, by
nealing them in the fire, seems to proceed from much the same cause. For
both by quenching suddenly such Metals as have _vitrifed_ parts
interspers'd, as Steel has, and by hammering of other kinds that do not so
much abound with them, as Silver Brass, &c. the parts are put into and
detained in a bended posture, which by the agitation of Heat are shaken,
and loosened, and suffered to unbend themselves.

       *       *       *       *       *


Observ. VIII. _Of the fiery Sparks struck from a Flint or Steel._

It is a very common Experiment, by striking with a Flint against a Steel,
to make certain fiery and shining Sparks to fly out from between those two
compressing Bodies. About eight years since, upon casually reading the
Explication of this odd _Phaenomenon_, by the most Ingenious _Des Cartes_,
I had a great desire to be satisfied, what that Substance was that gave
such a shining and bright Light: And to that end I spread a sheet of white
Paper, and on it, observing the place where several of these Sparks seemed
to vanish, I found certain very small, black, but glittering Spots of a
movable Substance, each of which examining with my _Microscope_, I found to
be a small round _Globule_; some of which, as they looked prety small, so
did they from their Surface yield a very bright and strong reflection on
that side which was next the Light; and each look'd almost like a prety
bright Iron-Ball, whose Surface was prety regular, such as is represented
by the Figure A. In this I could perceive the Image of the Window prety
well, or of a Stick, which I moved up and down between the Light and it.
Others I found, which were, as to the bulk of the Ball, prety regularly
round, but the Surface of them, as it was not very smooth, but rough, and
more irregular, so was the reflection from it more faint and confused. Such
were the Surfaces of B. C. D. and E. Some of these I found cleft or
cracked, as C, others quite broken in two and hollow, as D. which seemed to
be half the hollow shell of a Granado, broken irregularly in pieces.
Several others I found of other shapes; but that which is represented by E,
I observed to be a very big Spark of fire, which went out upon one side of
the Flint that I struck fire withall, to which it stuck by the root F, at
the end of which small Stem was fastened-on a _Hemisphere_, or half a
hollow Ball, with the mouth of it open from the stemwards, so that it
looked much like a Funnel, or an old fashioned Bowl without a foot. This
night, making many tryals and observations of this Experiment, I met, among
a multitude of the Globular ones which I had observed, a couple of
Instances, which are very remarkable to the confirmation of my
_Hypothesis_.

And the First was of a pretty big Ball fastened on to the end of a small
sliver of Iron, which _Compositum_ seemed to be nothing else but a long
thin chip of Iron, one of whose ends was melted into a small round Globul;
the other end remaining unmelted and irregular, and perfectly Iron.

The Second Instance was not less remarkable then the First; for I found,
when a Spark went out, nothing but a very small thin long sliver of Iron or
Steel, unmelted at either end. So that it seems, that some of these Sparks
are the slivers or chips of the Iron _vitrified_, Others are only the
slivers melted into Balls without vitrification, And the third kind are
only small slivers of the Iron, made red-hot with the violence of the
stroke given on the Steel by the Flint.

He that shall diligently examine the _Phaenomena_ of this Experiment, will,
I doubt not, find cause to believe, that the reason I have heretofore given
of it, is the true and genuine cause of it, namely, That _the Spark,
appearing so bright in the falling, is nothing else but a small piece of
the Steel or Flint, but most commonly of the Steel, which by the violence
of the stroke is at the same time sever'd and heat red-hot, and that
sometimes to such a degree, as to make it melt together into a small
Globule of Steel; and sometimes also is that heat so very intense, as
further to melt it and vitrifie it; but many times the heat is so gentle,
as to be able to make the sliver only red hot, which notwithstanding
falling upon the tinder_ (that is only a very curious small Coal made of
the small threads of Linnen burnt to coals and char'd) _it easily sets it
on fire_. Nor will any part of this _Hypothesis_ seem strange to him that
considers, First, that either hammering, or filing or otherwise violently
rubbing of Steel, will presently make it so hot as to be able to burn ones
fingers. Next, that the whole force of the stroke is exerted upon that
small part where the Flint and Steel first touch: For the Bodies being each
of them so very hard, the puls cannot be far communicated, that is, the
parts of each can yield but very little, and therefore the violence of the
concussion will be _exerted_ on that piece of Steel which is cut off by the
Flint. Thirdly, that the filings or small parts of Steel are very apt, as
it were, to take fire, and are presently red hot, that is, there seems to
be a very _combustible sulphureous_ Body in Iron or Steel, which the Air
very readily preys upon, as soon as the body is a little violently heated.

And this is obvious in the filings of Steel or Iron cast through the flame
of a Candle; for even by that sudden _transitus_ of the small chips of
Iron, they are heat red hot, and that _combustible sulphureous_ Body is
presently prey'd upon and devoured by the _aereal_ incompassing
_Menstruum_, whose office in this Particular I have shewn in the
Explication of Charcole.

And in prosecution of this Experiment, having taken the filings of Iron and
Steel, and with the point of a Knife cast them through the flame of a
Candle, I observed where some conspicuous shining Particles fell, and
looking on them with my _Microscope_, I found them to be nothing else but
such round Globules, as I formerly found the Sparks struck from the Steel
by a stroke to be, only a little bigger; and shaking together all the
filings that had fallen upon the sheet of Paper underneath and observing
them with the _Microscope_, I found a great number of small Globules, such
as the former, though there were also many of the parts that had remained
untoucht and rough filings or chips of Iron. So that, it seems, Iron does
contain a very _combustible sulphureous_ Body, which is, in all likelihood,
one of the causes of this _Phaenomenon_, and which may be perhaps very much
concerned in the business of its hardening and tempering: of which somewhat
it said in the Description of _Muscovy-glass_.

So that, these things considered, we need not trouble our selves to find
out what kind of Pores they are, both in the Flint and Steel, that contain
the _Atoms of fire_, nor how those _Atoms_ come to be hindred from running
all out, when a dore or passage in their Pores is made by the concussion:
nor need we trouble our selves to examine by what _Prometheus_ the Element
of Fire comes to be fetcht down from above the Regions of the Air, in what
Cells or Boxes it is kept, and what _Epimetheus_ lets it go: Nor to
consider what it is that causes so great a conflux of the atomical
Particles of Fire, which are said to fly to a flaming Body, like Vultures
or Eagles to a putrifying Carcass, and there to make a very great pudder.
Since we have nothing more difficult in this _Hypothesis_ to conceive,
first, as to the kindling of Tinder, then how a large Iron-bullet, let fall
red or glowing hot upon a heap of Small-coal, should set fire to those that
are next to it first: Nor secondly, is this last more difficult to be
explicated, then that a Body, as Silver for Instance, put into a weak
_Menstruum_, as unrectified _Aqua fortis_ should, when it is put in a great
heat, be there dissolved by it, and not before; which _Hypothesis_ is more
largely explicated in the Description of Charcoal. To conclude, we see by
this Instance, how much Experiments may conduce to the regulating of
_Philosophical notions_. For if the most Acute _Des Cartes_ had applied
himself experimentally to have examined what substance it was that caused
that shining of the falling Sparks struck from a Flint and a Steel, he
would certainly have a little altered his _Hypothesis_, and we should have
found, that his Ingenious Principles would have admitted a very plausible
Explication of this _Phaenomenon_; whereas by not examining so far as he
might, he has set down an Explication which Experiment do's contradict.

But before I leave this Description, I must not forget to take notice of
the Globular form into which each of these is most curiously formed. And
this _Phaenomenon_, as I have elsewhere more largely shewn, proceeds from a
propriety which belongs to all kinds of fluid Bodies more or less, and is
caused by the Incongruity of the Ambient and included Fluid, which so acts
and modulates each other, that they acquire, as neer as is possible, a
_spherical_ or _globular_ form, which propriety and several of the
_Phaenomena_ that proceed from it, I have more fully explicated in the
sixth Observation.

One Experiment, which does very much illustrate my present Explication, and
is in it self exceeding pretty, I must not pass by: And that is a way of
making small _Globules_ or _Balls_ of Lead, or Tin, as small almost as
these of Iron or Steel, and that exceeding easily and quickly, by turning
the filings or chips of those Metals also into perfectly round _Globules_.
The way, in short, as I received it from the _Learned Physitian Doctor_
I.G. is this;

Reduce the Metal you would thus shape, into exceeding fine filings, the
finer the filings are, the finer will the Balls be: _Stratifie_ these
filings with the fine and well dryed powder of quick Lime in a _Crucible_
proportioned to the quantity you intend to make: When you have thus filled
your _Crucible_, by continual _stratifications_ of the filings and powder,
so that, as neer as may be, no one of the filings may touch another, place
the _Crucible_ in a _gradual fire_, and by degrees let it be brought to a
heat big enough to make all the filings, that are mixt with the quick Lime,
to melt, and no more; for if the fire be too hot, many of these filings
will joyn and run together; whereas if the heat be proportioned, upon
washing the Lime-dust in fair Water, all those small filings of the Metal
will subside to the bottom in a most curious powder, consisting all of
exactly round _Globules_, which, if it be very fine, is very excellent to
make Hour-glasses of.

Now though quick Lime be the powder that this direction makes choice of,
yet I doubt not, but that there may be much more convenient ones found out,
one of which I have made tryal of, and found very effectual; and were it
not for discovering, by the mentioning of it, another Secret, which I am
not free to impart, I should have here inserted it.

       *       *       *       *       *


Observ. IX. _Of the Colours observable in Muscovy Glass, and other thin
Bodies_.

Moscovy-glass, or _Lapis specularis_, is a Body that seems to have as many
Curiosities in its Fabrick as any common Mineral I have met with: for
first, It is transparent to a great thickness: Next, it is compounded of an
infinite number of thin flakes joyned or generated one upon another so
close & smooth, as with many hundreds of them to make one smooth and thin
Plate of a transparent flexible substance, which with care and diligence
may be flit into pieces so exceedingly thin as to be hardly perceivable by
the eye, and yet even those, which I have thought the thinnest, I have with
a good _Microscope_ found to be made up of many other Plates, yet thinner;
and it is probable, that, were our _Microscopes_ much better, we might much
further discover its divisibility. Nor are these flakes only regular as to
the smoothness of their Surfaces, but thirdly, In many Plates they may be
perceived to be terminated naturally with edges of the figure of a
_Rhomboeid_. This Figure is much more conspicuous in our English talk, much
whereof is found in the Lead Mines, and is commonly called _Spar_, and
_Kauck_, which is of the same kind of substance with the _Selenitis_, but
is seldom found in so large flakes as that is, nor is it altogether so
tuff, but is much more clear and transparent, and much more curiously
shaped, and yet may be cleft and flak'd like the other _Selenitis_. But
fourthly, this stone has a property, which in respect of the _Microscope_,
is more notable, and that is, that it exhibits several appearances of
Colours, both to the naked Eye, but much more conspicuously to the
_Microscope_; for the exhibiting of which, I took a piece of
_Muscovy-glass_, and splitting or cleaving it into thin Plates, I found
that up and down in several parts of them I could plainly perceive several
white specks or flaws, and others diversly coloured with all the Colours of
the _Rainbow_; and with the _Microscope_ I could perceive, that these
Colours were ranged in rings that incompassed the white speck or flaw, and
were round or irregular, according to the shape of the spot which they
terminated; and the position of Colours, in respect of one another, was the
very same as in the _Rainbow_. The consecution of those Colours from the
middle of the spot outward being Blew, Purple, Scarlet, Yellow, Green;
Blew, Purple, Scarlet, and so onwards, sometimes half a score times
repeated, that is, there appeared six, seven, eight, nine or ten several
coloured rings or lines, each incircling the other, in the same manner as I
have often seen a very _vivid Rainbow_ to have four or five several Rings
of Colours, that is, accounting all the Gradations between Red and Blew for
one: But the order of the Colours in these Rings was quite contrary to the
primary or innermost _Rainbow_, and the same with those of the secondary or
outermost Rainbow; these coloured Lines or _Irises_, as I may so call them,
were some of them much brighter then others, and some of them also very
much broader, they being some of them ten, twenty, nay, I believe, neer a
hundred times broader then others; and those usually were broadest which
were neerest the center or middle of the flaw. And oftentimes I found, that
these Colours reacht to the very middle of the flaw, and then there
appeared in the middle a very large spot, for the most part, all of one
colour, which was very vivid, and all the other Colours incompassing it,
gradually ascending, and growing narrower towards the edges, keeping the
same order, as in the _secundary Rainbow_, that is, if the middle were
Blew, the next incompassing it would be a Purple, the third a Red, the
fourth a Yellow, &c. as above; if the middle were a Red, the next without
it would be a Yellow, the third a Green, the fourth a Blew, and so onward.
And this order it alwayes kept whatsoever were the middle Colour.

There was further observable in several other parts of this Body, many
Lines or Threads, each of them of some one peculiar Colour, and those so
exceedingly bright and vivid, that it afforded a very pleasant object
through the _Microscope_. Some of these _threads_ I have observed also to
be pieced or made up of several short lengths of differently coloured
_ends_ (as I may so call them) as a line appearing about two inches long
through the _Microscope_, has been compounded of about half an inch of a
Peach colour, 1/8 of a lovely Grass-green, 3/4 of an inch more of a bright
Scarlet, and the rest of the line of a Watchet blew. Others of them were
much otherwise coloured; the variety being almost infinite. Another thing
which is very observable, is, that if you find any place where the colours
are very broad and conspicuous to the naked eye, you may, by pressing that
place with your finger, make the colours change places, and go from one
part to another.

There is one _Phaenomenon_ more, which may, if care be used, exhibit to the
beholder, as it has divers times to me, an exceeding pleasant, and not less
instructive Spectacle; And that is, if curiosity and diligence be used, you
may so split this admirable Substance, that you may have pretty large
Plates (in companion of those smaller ones which you may observe in the
Rings) that are perhaps an 1/8 or a 1/6 part of an inch over, each of them
appearing through the _Microscope_ most curiously, intirely, and uniformly
adorned with some one vivid colour: this, if examined with the
_Microscope_, may be plainly perceived to be in all parts of it equally
thick. Two, three, or more of these lying one upon another, exhibit
oftentimes curious compounded colours, which produce such a _Compositum_,
as one would scarce imagine should be the result of such _ingredients_: As
perhaps a _faint yellow_ and a _blew_ may produce a very _deep purple_. But
when anon we come to the more strict examination of these _Phaenomena_, and
to inquire into the causes and reasons of these productions, we shall, I
hope, make it more conceivable how they are produced, and shew them to be
no other then the natural and necessary effects arising from the peculiar
union of concurrent causes.

These _Phaenomena_, being so various, and so truly admirable, it will
certainly be very well worth our inquiry, to examine the causes and reasons
of them, and to consider, whether from these causes demonstratively
evidenced, may not be deduced the true causes of the production of all kind
of Colours. And I the rather now do it, instead of an Appendix or
Digression to this History, then upon the occasion of examining the Colours
in Peacocks, or other Feathers, because this Subject, as it does afford
more variety of particular Colours, so does it afford much better wayes of
examining each circumstance. And this will be made manifest to him that
considers, first, that this laminated body is more simple and regular then
the parts of Peacocks feathers, this consisting only of an indefinite
number of plain and smooth Plates, heaped up, or _incumbent_ on each other.
Next, that the parts of this body are much more manageable, to be divided
or joyned, then the parts of a Peacocks feather, or any other substance
that I know. And thirdly, because that in this we are able from a
colourless body to produce several coloured bodies, affording all the
variety of Colours imaginable: And several others, which the subsequent
Inquiry will make manifest.

To begin therefore, it is manifest from several circumstances, that the
material cause of the _apparition_ of these several Colours, is some
_Lamina_ or Plate of a transparent or pellucid body of a thickness very
determinate and proportioned according to the greater or less refractive
power of the _pellucid_ body. And that this is so, abundance of Instances
and particular Circumstances will make manifest.

As _first_, if you take any small piece of the _Muscovy-glass_, and with a
Needle, or some other convenient Instrument, cleave it oftentimes into
thinner and thinner _Laminae_, you shall find, that till you come to a
determinate thinness of them, they shall all appear transparent and
colourless, but if you continue to split and divide them further, you shall
find at last, that each Plate, after it comes to such a determinate
thickness, shall appear most lovely ting'd or imbued with a determinate
colour. If _further_, by any means you so flaw a pretty thick piece, that
one part does begin to cleave a little from the other, and between those
two there be by any means gotten some pellucid _medium_, those _laminated_
pellucid bodies that fill that space, shall exhibit several Rainbows or
coloured Lines, the colours of which will be disposed and ranged according
to the various thicknesses of the several parts of that Plate. That this is
so, is yet _further_ confirmed by this Experiment.

Take two small pieces of ground and polisht Looking-glass-plate, each about
the bigness of a shilling, take these two dry, and with your fore-fingers
and thumbs press them very hard and close together, and you shall find,
that when they approach each other very near, there will appear several
_Irises_ or coloured Lines, in the same manner almost as in the
_Muscovy-glass_; and you may very easily change any of the Colours of any
part of the interposed body, by pressing the Plates closer and harder
together, or leaving them more lax; that is, a part which appeared coloured
with a red, may be presently ting'd with a yellow, blew, green, purple, or
the like, by altering the appropinquation of the terminating Plates. Now
that air is not necessary to be the interposed body, but that any other
transparent fluid will do much the same, may be tryed by wetting those
approximated Surfaces with Water, or any other transparent Liquor, and
proceeding with it in the same manner as you did with the Air; and you will
find much the like effect, only with this difference, that those comprest
bodies, which differ most, in their refractive quality, from the
compressing bodies, exhibit the most strong and vivid tinctures. Nor is it
necessary, that this _laminated_ and _ting'd_ body should be of a fluid
substance, any other substance, provided it be thin enough and transparent,
doing the same thing: this the _Laminae_ of our _Muscovy-glass_ hint; but
it may be confirm'd by multitudes of other Instances.

And first, we shall find, that even Glass it self may, by the help of a
Lamp, be blown thin enough to produce these _Phaenomena_ of Colours: which
_Phaenomena_ accidentally happening, as I have been attempting to frame
small Glasses with a Lamp, did not a little surprize me at first, having
never heard or seen any thing of it before; though afterwards comparing it
with the _Phaenomena_, I had often observed in those Bubbles which Children
use to make with Soap-water, I did the less wonder; especially when upon
Experiment I found, I was able to produce the same _Phaenomena_ in thin
Bubbles made with any other transparent Substance. Thus have I produced
them with Bubbles of _Pitch_, _Rosin_, _Colophony_, _Turpentine_,
_Solutions_ of several _Gums_, as _Gum-Arabick_ in water; any _glutinous_
Liquor, as _Wort_, _Wine_, _Spirit of Wine_, _Oyl of Turpentine_, _Glare of
Snails,_ &c.

It would be needless to enumerate the several Instances, these being enough
to shew the generality or universality of this propriety. Only I must not
omit, that we have instances also of this kind even in metalline Bodies and
animal; for those several Colours which are observed to follow each other
upon the polisht surface of hardned Steel, when it is by a sufficient
degree of heat gradually tempered or softened, are produced, from nothing
else but a certain thin _Lamina_ of a _vitrum_ or _vitrified_ part of the
Metal, which by that degree of heat, and the concurring action of the
ambient Air, is driven out and fixed on the surface of the Steel.

And this hints to me a very probable (at least, if not the true) cause of
the hardning and tempering of Steel, which has not, I think, been yet
given, nor, that I know of been so much as thought of by any. And that is
this, that the hardness of it arises from a greater proportion of a
vitrified Substance interspersed through the pores of the Steel. And that
the tempering or softning of it arises from the proportionate or smaller
parcels of it left within those pores. This will seem the more probable, if
we consider these Particulars.

First, That the pure parts of Metals are of themselves very _flexible_ and
_tuff_; that is, will indure bending and hammering, and yet retain their
continuity.

Next, That the Parts of all vitrified Substances, as all kinds of Glass,
the _Scoria_ of Metals, &c. are very hard, and also very brittle, being
neither _flexible_ nor _malleable_, but may by hammering or beating be
broken into small parts or powders.

Thirdly, That all Metals (excepting Gold and Silver, which do not so much
with the bare fire, unless assisted by other saline Bodies) do more or less
_vitrifie_ by the strength of fire, that is, are corroded by a saline
Substance, which I elsewhere shew to be the true cause of fire; and are
thereby, as by several other _Menstruums_ converted into _Scoria_; And this
is called, _calcining_ of them, by Chimists. Thus Iron and Copper by
heating and quenching do turn all of them by degrees into _Scoria_, which
are evidently _vitrified_ Substances, and unite with Glass, and are easily
_fusible_; and when cold, very hard, and very brittle.

Fourthly, That most kind of _Vitrifications_ or _Calcinations_ are made by
Salts, uniting and incorporating with the metalline Particles. Nor do I
know any one _calcination_ wherein a _Saline_ body may not, with very great
probability, be said to be an agent or coadjutor.

Fifthly, That Iron is converted into Steel by means of the incorporation of
certain salts, with which it is kept a certain time in the fire.

Sixthly, That any Iron may, in a very little time, be _case hardned_, as
the Trades-men call it, by casing the iron to be hardned with clay, and
putting between the clay and iron a good quantity of a mixture of _Urine_,
_Soot_, _Sea-salt_, and _Horses hoofs_ (all which contein great quantities
of Saline bodies) and then putting the case into a good strong fire, and
keeping it in a considerable degree of heat for a good while, and
afterwards heating, and quenching or cooling it suddenly in cold water.

Seventhly, That all kind of vitrify'd substances, by being suddenly cool'd,
become very hard and brittle. And thence arises the pretty _Phaenomena_ of
the Glass Drops, which I have already further explained in its own place.

Eighthly, That those metals which are not so apt to vitrifie, do not
acquire any hardness by quenching in water, as Silver, Gold, &c.

These considerations premis'd, will, I suppose, make way for the more easie
reception of this following Explication of the _Phaenomena_ of hardned and
temper'd Steel. That Steel is a substance made out of Iron, by means of a
certain proportionate _Vitrification_ of several parts, which are so
curiously and proportionately mixt with the more tough and unalter'd parts
of the Iron, that when by the great heat of the fire this vitrify'd
substance is melted, and consequently rarify'd, and thereby the pores of
the Iron are more open, if then by means of dipping it in cold water it be
suddenly cold, and the parts hardned, that is, stay'd in that same degree
of _Expansion_ they were in when hot, the parts become very hard and
brittle, and that upon the same account almost as small parcels of glass
quenched in water grow brittle, which we have already explicated. If after
this the piece of Steel be held in some convenient heat, till by degrees
certain colours appear upon the surface of the brightned metal, the very
hard and brittle tone of the metal, by degrees relaxes and becomes much
more tough and soft; namely, the action of the heat does by degrees loosen
the parts of the Steel that were before streached or set _atilt_ as it
were, and stayed open by each other, whereby they become relaxed and set at
liberty, whence some of the more brittle interjacent parts are thrust out
and melted into a thin skin on the surface of the Steel, which from no
colour increases to a deep Purple, and so onward by these _gradations_ or
consecutions, _White, Yellow, Orange, Minium, Scarlet, Purple, Blew,
Watchet,_ &c. and the parts within are more conveniently, and
proportionately mixt; and so they gradually subside into a texture which is
much better proportion'd and closer joyn'd, whence that rigidnesse of parts
ceases, and the parts begin to acquire their former _ductilness_.

Now, that 'tis nothing but the vitrify'd metal that sticks upon the surface
of the colour'd body, is evident from this, that if by any means it be
scraped and rubb'd off, the metal underneath it is white and clear; and if
it be kept longer in the fire, so as to increase to a considerable
thickness, it may, by blows, be beaten off in flakes. This is further
confirm'd by this observable, that that Iron or Steel will keep longer from
rusting which is covered with this vitrify'd case: Thus also Lead will, by
degrees, be all turn'd into a litharge; for that colour which covers the
top being scum'd or shov'd aside, appears to be nothing else but a litharge
or vitrify'd Lead.

This is observable also in some sort, on Brass, Copper, Silver, Gold, Tin,
but is most conspicuous in Lead: all those Colours that cover the surface
of the Metal being nothing else, but a very thin vitrifi'd part of the
heated Metal.

The other Instance we have, is in Animal bodies, as in Pearls, Mother of
Pearl-shels, Oyster-shels, and almost all other kinds of stony shels
whatsoever. This have I also sometimes with pleasure observ'd even in
Muscles and Tendons. Further, if you take any glutinous substance and run
it exceedingly thin upon the surface of a smooth glass or a polisht
metaline body, you shall find the like effects produced: and in general,
wheresoever you meet with a transparent body thin enough, that is
terminated by reflecting bodies of differing refractions from it, there
will be a production of these pleasing and lovely colours.

Nor is it necessary, that the two _terminating_ Bodies should be both of
the same kind, as may appear by the _vitrified Laminae_ on _Steel_, _Lead_,
and other Metals, one surface of which _Laminae_ is contiguous to the
surface of the Metal, the other to that of the Air.

Nor is it necessary, that these colour'd _Laminae_ should be of an even
thickness, that is, should have their edges and middles of equal thickness,
as in a Looking-glass-plate, which circumstance is only requisite to make
the Plate appear all of the same colour; but they may resemble a _Lens_,
that is, have their middles thicker then their edges; or else a _double
concave_, that is, be thinner in the middle then at the edges; in both
which cases there will be various coloured rings or lines, with differing
consecutions or orders of Colours; the order of the first from the middle
outwards being Red, Yellow, Green, Blew, &c. And the latter quite contrary.

But further, it is altogether necessary, that the Plate, in the places
where the Colours appear, should be of a determinate thickness: First, It
must not be more then such a thickness, for when the Plate is increased to
such a thickness, the Colours cease; and besides, I have seen in a thin
piece of _Muscovy-glass_, where the two ends of two Plates, which appearing
both single, exhibited two distinct and differing Colours; but in that
place where they were united, and constituted one double Plate (as I may
call it) they appeared transparent and colourless. Nor, Secondly, may the
Plates be _thinner_ then such a determinate _cize_; for we alwayes find,
that the very outmost Rim of these flaws is terminated in a white and
colourless Ring.

Further, in this Production of Colours there is no need of a determinate
Light of such a bigness and no more, nor of a determinate position of that
Light, that it should be on this side, and not on that side; nor of a
terminating shadow, as in the Prisme, and Rainbow, or Water-ball: for we
find, that the Light in the open Air, either in or out of the Sun-beams,
and within a Room, either from one or many Windows, produces much the same
effect: only where the Light is brightest, there the Colours are most
_vivid_. So does the light of a Candle, collected by a Glass-ball. And
further, it is all one whatever side of the coloured Rings be towards the
light; for the whole Ring keeps its proper Colours from the middle outwards
in the same order as I before related, without varying at all, upon
changing the position of the light.

But above all it is most observable, that here are all kind of Colours
generated in a _pellucid_ body, where there is properly no such refraction
as _Des Cartes_ supposes his _Globules_ to acquire a _vertuity_ by: For in
the plain and even Plates it is manifest, that the second refraction
(according to _Des Cartes_ his Principles in the _fifth section of the
eighth Chapter of his Meteors_) does regulate and restore the supposed
_turbinated Globules_ unto their former uniform motion. This Experiment
therefore will prove such a one as our _thrice excellent Verulam_ calls
_Experimentum Crucis_, serving as a Guide or Land-mark, by which to direct
our course in the search after the true cause of Colours. Affording us this
particular negative Information, that for the production of Colours there
is not necessary either a great refraction, as in the Prisme; nor Secondly,
a determination of Light and shadow, such as is both in the Prisme and
Glass-ball. Now that we may see likewise what affirmative and positive
Instruction it yields, it will be necessary, to examine it a little more
particularly and strictly; which that we may the better do, it will be
requisite to premise somewhat in general concerning the nature of Light and
Refraction.

And first for Light it seems very manifest, that there is no luminous Body
but has the parts of it in motion more or less.

First, That all kind of _fiery burning Bodies_ have their parts in motion,
I think, will be very easily granted me. That the _spark_ struck from a
Flint and Steel is in a rapid agitation, I have elsewhere made probable.
And that the Parts of _rotten Wood_, _rotten Fish_ and the like, are also
in motion, I think, will as easily be conceded by those, who consider, that
those parts never begin to shine till the Bodies be in a state of
putrefaction; and that is now generally granted by all, to be caused by the
motion of the parts of putrifying bodies. That the _Bononian stone_ shines
no longer then it is either warmed by the Sun-beams, or by the flame of a
Fire or of a Candle, is the general report of those that write of it, and
of others that have seen it. And that heat argues a motion of the internal
parts is (as I said before) generally granted.

But there is one Instance more, which was first shewn to the _Royal
Society_ by Mr. _Clayton_ a worthy Member thereof, which does make this
Assertion more evident then all the rest: And that is, That a _Diamond_
being _rub'd_, _struck_ or _heated_ in the dark, shines for a pretty while
after, so long as that motion, which is imparted by any of those Agents,
remains (in the same manner as a Glass, rubb'd, struck, or (by a means
which I shall elsewhere mention) heated, yields a sound which lasts as long
as the vibrating motion of that _sonorous_ body) several Experiments made
on which Stone, are since published in a Discourse of Colours, by the truly
honourable Mr. _Boyle_. What may be said of those _Ignes fatui_ that appear
in the night, I cannot so well affirm, having never had the opportunity to
examine them my self, nor to be inform'd by any others that had observ'd
them: And the relations of them in Authors are so imperfect, that nothing
can be built on them. But I hope I shall be able in another place to make
it at least very probable, that there is even in those also a Motion which
causes this effect. That the shining of _Sea-water_ proceeds from the same
cause, may be argued from this, That it shines not till either it be beaten
against a Rock, or be some other wayes broken or agitated by Storms, or
Oars, or other _percussing_ bodies. And that the Animal _Energyes_ or
Spirituous _agil_ parts are very active in _Cats eyes_ when they shine,
seems evident enough, because their eyes never shine but when they look
very intensly either to find their prey, or being hunted in a dark room,
when they seek after their adversary, or to find a way to escape. And the
like may be said of the shining _Bellies of Gloworms_; since 'tis evident
they can at pleasure either increase or extinguish that Radiation.

It would be somewhat too long a work for this place _Zetetically_ to
examine, and positively to prove, what particular kind of motion it is that
must be the efficient of Light; for though it be a motion, yet 'tis not
every motion that produces it, since we find there are many bodies very
violently mov'd, which yet afford not such an effect; and there are other
bodies, which to our other senses, seem not mov'd so much, which yet shine.
Thus Water and quick-silver, and most other liquors heated, shine not; and
several hard bodies, as Iron, Silver, Brass, Copper, Wood, &c. though very
often struck with a hammer, shine not presently, though they will all of
them grow exceeding hot; whereas rotten Wood, rotten Fish, Sea water,
Gloworms, &c. have nothing of tangible heat in them, and yet (where there
is no stronger light to affect the Sensory) they shine some of them so
Vividly, that one may make a shift to read by them.

It would be too long, I say, here to insert the discursive progress by
which I inquir'd after the proprieties of the motion of Light, and
therefore I shall only add the result.

And, First, I found it ought to be exceeding _quick_, such as those motions
of _fermentation_ and _putrefaction_, whereby, certainly, the parts are
exceeding nimbly and violently mov'd; and that, because we find those
motions are able more minutely to shatter and divide the body, then the
most violent heats _menstruums_ we yet know. And that fire is nothing else
but such a _dissolution_ of the Burning body, made by the most _universal
menstruum_ of all _sulphureous bodies_, namely, the Air, we shall in an
other place of this Tractate endeavour to make probable. And that, in all
extreamly hot shining bodies, there is a very quick motion that causes
Light, as well as a more robust that causes Heat, may be argued from the
celerity wherewith the bodyes are dissolv'd.

Next, it must be a _Vibrative motion_. And for this the newly mention'd
_Diamond_ affords us a good argument; since if the motion of the parts did
not return, the Diamond must after many rubbings decay and be wasted: but
we have no reason to suspect the latter, especially if we consider the
exceeding difficulty that is found in cutting or wearing away a Diamond.
And a Circular motion of the parts is much more improbable, since, if that
were granted, and they be suppos'd irregular and Angular parts, I see not
how the parts of the Diamond should hold so firmly together, or remain in
the same sensible dimensions, which yet they do. Next, if they be
_Globular_, and mov'd only with a _turbinated_ motion, I know not any cause
that can impress that motion upon the _pellucid medium_, which yet is done.
Thirdly, any other _irregular_ motion of the parts one amongst another,
must necessarily make the body of a fluid consistence, from which it is far
enough. It must therefore be a _Vibrating_ motion.

And Thirdly, That it is a very _short-vibrating motion_, I think the
instances drawn from the shining of Diamonds will also make probable. For a
Diamond being the hardest body we yet know in the World, and consequently
the least apt to yield or bend, must consequently also have its
_vibrations_ exceeding short.

And these, I think, are the three principal proprieties of a motion,
requisite to produce the effect call'd Light in the Object.

The next thing we are to consider, is the way or manner of the _trajection_
of this motion through the interpos'd pellucid body to the eye: And here it
will be easily granted,

First, That it must be a body _susceptible_ and _impartible_ of this motion
that will deserve the name of a Transparent. And next, that the parts of
such a body must be _Homogeneous_, or of the same kind. Thirdly, that the
constitution and motion of the parts must be such, that the appulse of the
luminous body may be communicated or propagated through it to the greatest
imaginable distance in the least imaginable time, though I see no reason to
affirm, that it must be in an instant: For I know not any one Experiment or
observation that does prove it. And, whereas it may be objected, That we
see the Sun risen at the very instant when it is above the sensible
Horizon, and that we see a Star hidden by the body of the Moon at the same
instant, when the Star, the Moon, and our Eye are all in the same line; and
the like Observations, or rather suppositions, may be urg'd. I have this to
answer, That I can as easily deny as they affirm; for I would fain know by
what means any one can be assured any more of the Affirmative, then I of
the Negative. If indeed the propagation were very slow, 'tis possible
something might be discovered by Eclypses of the Moon; but though we should
grant the progress of the light from the Earth to the Moon, and from the
Moon back to the Earth again to be full two Minutes in performing, I know
not any possible means to discover it; nay, there may be some instances
perhaps of Horizontal Eclypses that may seem very much to favour this
supposition of the slower progression of Light then most imagine. And the
like may be said of the Eclypses of the Sun, &c. But of this only by the
by. Fourthly, That the motion is propagated every way through an
_Homogeneous medium_ by _direct_ or _straight_ lines extended every way
like Rays from the center of a Sphere. Fifthly, in an _Homogeneous medium_
this motion is propagated every way with _equal velocity_, whence
necessarily every _pulse_ or _vitration_ of the luminous body will generate
a Sphere, which will continually increase, and grow bigger, just after the
same manner (though indefinitely swifter) as the waves or rings on the
surface of the water do swell into bigger and bigger circles about a point
of it, where, by the sinking of a Stone the motion was begun, whence it
necessarily follows, that all the parts of these Spheres undulated through
an _Homogeneous medium_ cut the Rays at right angles.

But because all transparent _mediums_ are not _Homogeneous_ to one another,
therefore we will next examine how this pulse or motion will be propagated
through differingly transparent _mediums_. And here, according to the most
acute and excellent Philosopher _Des Cartes_, I suppose the sign of the
angle of inclination in the first _medium_ to be to the sign of refraction
in the second, As the density of the first, to the density of the second.
By density, I mean not the density in respect of gravity (with which the
refractions or transparency of _mediums_ hold no proportion) but in respect
onely to the _trajection_ of the Rays of light, in which respect they only
differ in this; that the one propagates the pulse more easily and weakly,
the other more slowly, but more strongly. But as for the pulses themselves,
they will by the refraction acquire another propriety, which we shall now
endeavour to explicate.

We will suppose therefore in the first Figure ACFD to be a physical Ray, or
ABC and DEF to be two Mathematical Rays, _trajected_ from a very remote
point of a luminous body through an _Homogeneous_ transparent _medium_ LLL,
and DA, EB, FC, to be small portions of the orbicular impulses which must
therefore cut the Rays at right angles; these Rays meeting with the plain
surface NO of a _medium_ that yields an easier _transitus_ to the
propagation of light, and falling _obliquely_ on it, they will in the
_medium_ MMM be refracted towards the perpendicular of the surface. And
because this _medium_ is more easily _trajected_ then the former by a
third, therefore the point C of the orbicular pulse FC will be mov'd to H
four spaces in the same time that F the other end of it is mov'd to G three
spaces, therefore the whole refracted pulse GH shall be _oblique_ to the
refracted Rays CHK and GI; and the angle GHC shall be an acute, and so much
the more acute by how much the greater the refraction be, then which
nothing is more evident, for the sign of the inclination is to the sign of
refraction as GF to TC the distance between the point C and the
perpendicular from G on CK, which being as four to three, HC being longer
then GF is longer also then TC, therefore the angle GHC is less than GTC.
So that henceforth the parts of the pulses GH and IK are mov'd ascew, or
cut the Rays at _oblique_ angles.

It is not my business in this place to set down the reasons why this or
that body should impede the Rays more, others less: as why Water should
transmit the Rays more easily, though more weakly than air. Onely thus much
in general I shall hint, that I suppose the _medium_ MMM to have less of
the transparent undulating subtile matter, and that matter to be less
implicated by it, whereas LLL I suppose to contain a greater quantity of
the fluid undulating substance, and this to be more implicated with the
particles of that _medium_.

But to proceed, the same kind of _obliquity_ of the Pulses and Rays will
happen also when the refraction is made out of a more easie into a more
difficult _mediu_; as by the calculations of GQ & CSR which are refracted
from the perpendicular. In both which calculations 'tis _obvious_ to
observe, that always that part of the Ray towards which the refraction is
made has the end of the _orbicular pulse_ precedent to that of the other
side. And always, the oftner the refraction is made the same way, Or the
greater the single refraction is, the more is this unequal progress. So
that having found this odd propriety to be an inseparable concomitant of a
refracted Ray, not streightned by a contrary refraction, we will next
examine the refractions of the Sun-beams, as they are suffer'd onely to
pass through a small passage, _obliquely_ out of a more difficult, into a
more easie _medium_.

Let us suppose therefore ABC in the second Figure to represent a large
_Chimical Glass-body_ about two foot long, filled with very fair Water as
high as AB, and inclin'd in a convenient posture with B towards the Sun:
Let us further suppose the top of it to be cover'd with an _opacous_ body,
all but the hole ab, through which the Sun-beams are suffer'd to pass into
the Water, and are thereby refracted to cdef, against which part, if a
Paper be expanded on the outside, there will appear all the colours of the
Rain-bow, that is, there will be generated the two principal colours,
_Scarlet_ and _Blue_, and all the _intermediate_ ones which arise from the
composition and dilutings of these two, that is, cd shall exhibit a
_Scarlet_, which toward d is diluted into a _Yellow_; this is the
refraction of the Ray, ik, which comes from the underside of the Sun; and
the Ray ef shall appear of a deep _Blue_, which is gradually towards e
diluted into a pale _Watchet-blue_. Between d and e the two _diluted_
colours. _Blue_ and _Yellow_ are mixt and compounded into a _Green_; and
this I imagine to be the reason why _Green_ is so acceptable a colour to
the eye, and that either of the two extremes are, if intense, rather a
little offensive, namely, the being plac'd in the middle between the two
extremes, and compounded out of both those, _diluted_ also, or somewhat
qualifi'd, for the _composition_, arising from the mixture of the two
extremes _undiluted_, makes a _Purple_, which though it be a lovely colour,
and pretty acceptable to the eye, yet is it nothing comparable to the
ravishing pleasure with which a curious and well tempered _Green_ affects
the eye. If removing the Paper, the eye be plac'd against cd, it will
perceive the lower side of the Sun (or a Candle at night which is much
better, because it offends not the eye, and is more easily manageable) to
be of a deep _Red_, and if against ef it will perceive the upper part of
the luminous body to be of a deep _Blue_; and these colours will appear
deeper and deeper, according as the Rays from the luminous body fall more
_obliquely_ on the surface of the Water, and thereby suffer a greater
refraction, and the more distinct, the further cdef is removed from the
trajecting hole.

So that upon the whole, we shall find that the reason of the _Phaenomena_
seems to depend upon the _obliquity_ of the _orbicular pulse_, to the Lines
of Radiation, and in particular, that the Ray cd which constitutes the
_Scarlet_ has its inner parts, namely those which are next to the middle of
the luminous body, precedent to the outermost which are contiguous to the
dark and _unradiating_ skie. And that the Ray ef which gives a _Blue_, has
its outward part, namely, that which is contiguous to the dark side
precedent to the pulse from the innermost, which borders on the bright
_area_ of the luminous body.

We may observe further, that the cause of the _diluting_ of the colours
towards the middle, proceeds partly from the wideness of the hole through
which the Rays pass, whereby the Rays from several parts of the luminous
body, fall upon many of the same parts between c and f as is more manifest
by the Figure: And partly also from the nature of the refraction it self,
for the vividness or strength of the two terminating colours, arising
chiefly as we have seen, from the very great difference that is betwixt the
outsides of those _oblique undulations_ & the dark Rays circumambient, and
that disparity betwixt the _approximate_ Rays, decaying gradually: the
further inward toward the middle of the luminous body they are remov'd, the
more must the colour approach to a white or an undisturbed light.

Upon the calculation of the refraction and reflection from a Ball of Water
or Glass, we have much the same _Phaenomena_, namely, an _obliquity_ of the
undulation in the same manner as we have found it here. Which, because it
is very much to our present purpose, and affords such an _Instancia
crucis_, as no one that I know has hitherto taken notice of, I shall
further examine. For it does very plainly and positively distinguish, and
shew, which of the two _Hypotheses_, either the _Cartesian_ or this is to
be followed, by affording a generation of all the colors in the Rainbow,
where according to the _Cartesian Principles_ there should be none at all
generated. And secondly, by affording an instance that does more closely
confine the cause of these _Phaenomena_ of colours to this present
_Hypothesis_.

And first, for the _Cartesian_, we have this to object against it, That
whereas he says (_Meteorum Cap. 8. Sect. 5._) _Sed judicabam unicam
(refractione scilicet) ad minimum requiri, & quidem talem ut ejus effectus
alia contraria (refractione) non destruatur: Nam experientia docet si
superficies _NM_ & _NP_ (nempe refringentes) Parallelae forent, radios
tantundem per alteram iterum erectos quantum per unam frangerentur, nullos
colores depicturos_; This Principle of his holds true indeed in a prisme
where the refracting surfaces are plain, but is contradicted by the Ball or
Cylinder, whether of Water Or Glass, where the refracting surfaces are
Orbicular or Cylindrical. For if we examine the passage of any _Globule_ or
Ray of the primary _Iris_, we shall find it to pass out of the Ball or
Cylinder again, with the same inclination and refraction that it enter'd in
withall, and that that last refraction by means of the _intermediate_
reflection shall be the same as if without any reflection at all the Ray
had been twice refracted by two Parallel surfaces.

And that this is true, not onely in one, but in every Ray that goes to the
constitution of the Primary Iris; nay, in every Ray, that suffers only two
refractions, and one reflection, by the surface of the round body, we shall
presently see most evident, if we repeat the _Cartesian Scheme_, mentioned
in the tenth _Section_ of the eighth _Chapter_ of his _Meteors_, where
EFKNP in the third Figure[9] is one of the Rays of the Primary Iris, twice
refracted at F and N, and once reflected at K by the surface of the
Water-ball. For, first it is evident, that KF and KN are equal, because KN
being the reflected part of KF they have both the same inclination on the
surface K that is the angles FKT, and NKV made by the two Rays and the
Tangent of K are equal, which is evident by the Laws of reflection; whence
it will follow also, that KN has the same inclination on the surface N, or
the Tangent of it XN that the Ray KF has to the surface F, or the Tangent
of it FY, whence it must necessarily follow, that the refractions at F and
N are equal, that is, KFE and KNP are equal. Now, that the surface N is by
the reflection at K made parallel to the surface at F, is evident from the
principles of reflection; for reflection being nothing but an inverting of
the Rays, if we re-invert the Ray KNP, and make the same inclinations below
the line TKV that it has above, it will be most evident, that KH the
inverse of KN will be the continuation of the line FK, and that LHI the
inverse of OX is parallel to FY. And HM the inverse of NP is Parallel to EF
for the angle KHI is equal to KNO which is equal to KFY, and the angle KHM
is equal to KNP which is equal to KFE which was to be prov'd.

So that according to the above mentioned _Cartesian_ principles there
should be generated no colour at all in a Ball of Water or Glass by two
refractions and one reflection, which does hold most true indeed, if the
surfaces be plain, as may be experimented with any kind of prisme where the
two refracting surfaces are equally inclin'd to the reflecting; but in this
the _Phaenomena_ are quite otherwise.

The cause therefore of the generation of colour must not be what _Des
Cartes_ assigns, namely, a certain _rotation_ of the _Globuli aetherei_,
which are the particles which he supposes to constitute the _Pellucid
medium_, But somewhat else, perhaps what we have lately supposed, and shall
by and by further prosecute and explain.

But, First I shall crave leave to propound some other difficulties of his,
notwithstanding exceedingly ingenious _Hypothesis_, which I plainly confess
to me seem such; and those are,

First, if that light be (as is affirmed, _Diopt._ cap. 1. Sec. 8.) not so
properly a motion, as an action or propension to motion, I cannot conceive
how the eye can come to be sensible of the _verticity_ of a _Globule_,
which is generated in a drop of Rain, perhaps a mile off from it. For that
_Globule_ is not carry'd to the eye according to his formerly recited
Principle; and if not so, I cannot conceive how it can communicate its
_rotation_, or circular motion to the line of the _Globules_ between the
drop and the eye. It cannot be by means of every ones turning the next
before him; for if so, then onely all the _Globules_ that are in the odd
places must be turned the same way with the first, namely, the 3. 5. 7. 9.
11, &c. but all the _Globules_ interposited between them in the even
places; namely, the 2. 4. 6. 8. 10. &c. must be the quite contrary, whence,
according to the _Cartesian Hypothesis_, there must be no distinct colour
generated, but a confusion. Next, since the _Cartesian Globuli_ are
suppos'd (_Principiorum Philosoph._ Part. 3. Sec. 86.) to be each of them
continually in motion about their centers, I cannot conceive how the eye is
able to distinguish this new generated motion from their former inherent
one, if I may so call that other wherewith they are mov'd or _turbinated_,
from some other cause than refraction. And thirdly, I cannot conceive how
these motions should not happen sometimes to oppose each other, and then,
in stead of a _rotation_, there would be nothing but a direct motion
generated, and consequently no colour. And fourthly, I cannot conceive, how
by the _Cartesian Hypothesis_ it is possible to give any plausible reason
of the nature of the Colours generated in the thin _laminae_ of these our
_Microscopical Observations_; for in many of these, the refracting and
reflecting surfaces are parallel to each other, and consequently no
_rotation_ can be generated, nor is there any necessity of a shadow or
termination of the bright Rays, such as is suppos'd (_Chap._ 8. Sec. 5. _Et
praeterea observavi umbram quoque, aut limitationem luminis requiri:_ and
_Chap._ 8. Sec. 9.) to be necessary to the generation of any distinct
colours; Besides that, here is oftentimes one colour generated without any
of the other appendant ones, which cannot be by the _Cartesian Hypothesis_.

There must be therefore some other propriety of refraction that causes
colour. And upon the examination of the thing, I cannot conceive any one
more general, inseparable, and sufficient, than that which I have before
assign'd. That we may therefore see how exactly our _Hypothesis_ agrees
also with the _Phaenomena_ of the refracting round body, whether _Globe_ or
_Cylinder_, we shall next subjoyn our _Calculation_ or _Examen_ of it.

And to this end, we will calculate any two Rays: as for instance;[10] let
EF be a Ray cutting the _Radius_ CD (divided into 20. parts) in G 16. parts
distant from C, and ef another Ray, which cuts the same _Radius_ in g 17.
parts distant, these will be refracted to K and k, and from thence
reflected to N and n, and from thence refracted toward P and p; therefore
the Arch Ff will be 5.d 5'. The Arch FK 106.d 30'. the Arch fk 101.d 2'.
The line FG 6000. and fg 5267. therefore hf. 733. therefore Fc 980, almost.
The line FK 16024. and fk 15436. therefore Nd 196. and no 147 almost, the
line Nn 1019 the Arch Nn 5.d 51'. therefore the Angle Nno is 34.d 43'.
therefore the Angle Non is 139.d 56'. which is almost 50.d more than a
right Angle.

It is evident therefore by this _Hypothesis_, that at the same time that ef
touches f. EF is arrived at c. And by that time efkn is got to n, EFKN is
got to d and when it touches N, the pulse of the other Ray is got to o. and
no farther, which is very short of the place it should have arriv'd to, to
make the Ray np to cut the _orbicular pulse_ No at right Angles: therefore
the Angle Nop is an acute Angle, but the quite contrary of this will
happen, if 17. and 18. be calculated in stead of 16. and 17. both which
does most exactly agree with the _Phaenomena_: For if the Sun, or a Candle
(which is better) be placed about Ee, and the eye about Pp, the Rays EFef
at 16. and 17. will paint the side of the luminous object toward np _Blue_,
and towards NP _Red_. But the quite contrary will happen when EF is 17. and
ef 18. for then towards NP shall be a _Blue_, and towards np a _Red_,
exactly according to the calculation. And there appears the _Blue_ of the
Rainbow, where the two _Blue_ sides of the two Images unite, and there the
_Red_ where the two _Red_ sides unite, that is, where the two Images are
just disappearing; which is, when the Rays EF and NP produc'd till they
meet, make an Angle of about 41. and an half; the like union is there of
the two Images in the Production of the _Secundary Iris_, and the same
causes, as upon calculation may appear; onely with this difference, that it
is somewhat more faint, by reason of the duplicate reflection, which does
always weaken the impulse the oftner it is repeated.

Now, though the second refraction made at Nn be convenient, that is, do
make the Rays glance the more, yet is it not altogether requisite; for it
is plain from the calculation, that the pulse dn is sufficiently _oblique_
to the Rays KN and kn, as wel as the pulse fc is _oblique_ to the Rays FK &
fk. And therefore if a piece of very fine Paper be held close against Nn
and the eye look on it either through the Ball as from D, or from the other
side, as from B. there shall appear a Rainbow, or colour'd line painted on
it with the part toward X appearing _Red_, towards O, _Blue_; the same also
shall happen, if the Paper be placed about Kk, for towards T shall appear a
_Red_, and towards V a _Blue_, which does exactly agree with this my
_Hypothesis_, as upon the calculation of the progress of the pulse will
most easily appear.

Nor do these two observations of the colours appearing to the eye about p
differing from what they appear on the Paper at N contradict each other;
but rather confirm and exactly agree with one another, as will be evident
to him that examines the reasons set down by the ingenious. _Des Cartes_ in
the 12. _Sect._ of the 8. _Chapter of his Meteors_, where he gives the true
reason why the colours appear of a quite contrary order to the eye, to what
they appear'd on the Paper if the eye be plac'd in steed of the Paper: And
as in the Prisme, so also in the Water-drop, or Globe the _Phaenomena_, and
reason are much the same.

Having therefore shewn that there is such a propriety in the _prisme_ and
water _Globule_ whereby the pulse is made _oblique_ to the progressive, and
that so much the more, by how much greater the refraction is, I shall in
the next place consider, how this conduces to the production of colours,
and what kind of impression it makes upon the bottom of the eye; and to
this end it will be requisite to examine this _Hypothesis_ a little more
particularly.

First therefore, if we consider the manner of the progress of the pulse, it
will seem rational to conclude, that that part or end of the pulse which
precedes the other, must necessarily be somwhat more _obtunded_, or
_impeded_ by the resistance of the transparent _medium_, than the other
part or end of it which is subsequent, whose way is, as it were, prepared
by the other; especially if the adjacent _medium_ be not in the same manner
enlightned or agitated. And therefore (in the fourth _Figure_ of the sixth
_Iconism_) the Ray AAAHB will have its side HH more deadned by the
resistance of the dark or quiet _medium_ PPP, Whence there will be a kind
of deadness superinduc'd on the side HHH, which will continually increase
from B, and strike deeper and deeper into the Ray by the line BR; Whence
all the parts of the triangle, RBHO will be of a dead _Blue_ colour, and so
much the deeper, by how much the nearer they lie to the line BHH, which is
most deaded or impeded, and so much the more _dilute_, by how much the
nearer it approaches the line BR. Next on the other side of the Ray AAN,
the end A of the pulse AH will be promoted, or made stronger, having its
passage already prepar'd as 'twere by the other parts preceding, and so its
impression wil be stronger; And because of its _obliquity_ to the Ray,
there will be propagated a kind of faint motion into QQ the adjacent dark
or quiet _medium_, which faint motion will spread further and further into
QQ as the Ray is propagated further and further from A, namely, as far as
the line MA, whence all the triangle MAN will be ting'd with a _Red_, and
that _Red_ will be the deeper the nearer it approaches the line MA, and the
_paler_ or _yellower_ the nearer it is the line NA. And if the Ray be
continued, so that the lines AN and BR (which are the bounds of the _Red_
and _Blue diluted_) do meet and cross each other, there will be beyond that
intersection generated all kinds of _Greens_.

Now, these being the proprieties of every single refracted Ray of light, it
will be easie enough to consider what must be the result of very many such
Rays collateral: As if we suppose infinite such Rays _interjacent_ between
AKSB and ANOB, which arc the terminating: For in this case the Ray AKSB
will have its _Red_ triangle intire, as lying next to the dark or quiet
_medium_, but the other side of it BS will have no _Blue_, because the
_medium adjacent_ to it SBO, is mov'd or enlightned, and consequently that
light does destroy the colour. So likewise will the Ray ANOB lose its
_Red_, because the _adjacent medium_ is mov'd or enlightned, but the other
side of the Ray that is _adjacent_ to the dark, namely, AHO will preserve
its _Blue_ entire, and these Rays must be so far produc'd as till AN and BR
cut each other, before there will be any _Green_ produc'd. From these
Proprieties well consider'd, may be deduc'd the reasons of all the
_Phaenomena_ of the _prisme_, and of the _Globules_ or drops of Water which
conduce to the production of the Rainbow.

Next for the impression they make on the _Retina_, we will further examine
this _Hypothesis_: Suppose therefore ABCDEF, in the fifth _Figure_, to
represent the Ball of the eye: on the _Cornea_ of which ABC two Rays GACH
and KCAI (which are the terminating Rays of a luminous body) falling, are
by the refraction thereof collected or _converg'd_ into two points at the
bottom of the eye. Now, because these terminating Rays, and all the
_intermediate_ ones which come from any part of the luminous body, are
suppos'd by some sufficient refraction before they enter the eye, to have
their pulses made _oblique_ to their progression, and consequently each Ray
to have potentially _superinduc'd_ two proprieties, or colours, viz., a
_Red_ on the one side, and a _Blue_ on the other, which notwithstanding are
never actually manifest, but when this or that Ray has the one or the other
side of it bordering on a dark or unmov'd _medium_, therefore as soon as
these Rays are entred into the eye and so have one side of each of them
bordering on a dark part of the humours of the eye, they will each of them
actually exhibit some colour; therefore ADC the production of GACH will
exhibit a _Blue_, because the side CD is _adjacent_ to the dark _medium_
CQDC, but nothing of a _Red_, because its side AD is _adjacent_ to the
enlightned _medium_ ADFA: And all the Rays that from the points of the
luminous body are collected on the parts of the _Retina_ between D and F
shall have their _Blue_ so much the more _diluted_ by how much the farther
these points of collection are distant from D towards F; and the Ray AFC
the production of KCAI, will exhibit a _Red_, because the side AF is
adjacent to the dark or quiet _medium_ of the eye APFA, but nothing of a
_Blue_, because its side CF is _adjacent_ to the enlightned _medium_ CFDC,
and all the Rays from the intermediate parts of the luminous body that are
collected between F and D shall have their _Red_ so much the more diluted,
by how much the farther they are distant from F towards D.

Now, because by the refraction in the _Cornea_, and some other parts of the
eye, the sides of each Ray, which before were almost parallel, are made to
_converge_ and meet in a point at the bottom of the eye, therefore that
side of the _pulse_ which preceded before these refractions, shall first
touch the _Retina_, and the other side last. And therefore according as
this or that side, or end of the pulse shall be impeded, accordingly will
the _impressions_ on the _Retina_ be varied; therefore by the Ray GACH
refracted by the _Cornea_ to D there shall be on that point a stroke or
impression confus'd, whose weakest end, namely, that by the line CD shall
precede, and the stronger, namely, that by the line AD shall follow. And by
the Ray KCAI refracted to F, there shall be on that part a confus'd stroke
or impression, whose strongest part, namely, that by the line CF shal
precede, and whose weakest or impeded, namely, that by the line AF shall
follow, and all the intermediate points between F and D will receive
impressions from the _converg'd_ Rays so much the more like the impressions
on F and D by how much the nearer they approach that or this.

From the consideration of the proprieties of which impressions, we may
collect these short definitions of Colours: That _Blue is an impression on
the Retina of an oblique and confus'd pulse of light, whose weakest part
precedes, and whose strongest follows._ And, that _Red is an impression on
the Retina of an oblique and confus'd pulse of light, whose strongest part
precedes, and whose weakest follows._

Which proprieties, as they have been already manifested, in the Prisme and
falling drops of Rain, to be the causes of the colours there generated, may
be easily found to be the efficients also of the colours appearing in thin
_laminated_ transparent bodies; for the explication of which, all this has
been premised.

And that this is so, a little closer examination of the _Phaenomena_ and
the _Figure_ of the body, by this _Hypothesis_ will make evident.

For first (as we have already observed) the _laminated_ body must be of a
determinate thickness, that is, it must not be thinner then such a
determinate quantity; for I have always observ'd, that neer the edges of
those which are exceeding thin, the colours disappear, and the part grows
white; nor must it be thicker then another determinate quantity; for I have
likewise observ'd, that beyond such a thickness, no colours appear'd, but
the Plate looked white, between which two determinate thicknesses were all
the colour'd Rings; of which in some substances I have found ten or twelve,
in others not half so many, which I suppose depends much upon the
transparency of the _laminated_ body. Thus though the consecutions are the
same in the scumm or the skin on the top of metals; yet in those
consecutions in the same colour is not so often repeated as in the
consecutions in thin Glass, or in Sope-water, or any other more transparent
and glutinous liquor; for in these I have observ'd, _Red, Yellow, Green,
Blue, Purple; Red, Yellow, Green, Blue, Purple; Red, Yellow, Green, Blue,
Purple; Red, Yellow, &c._ to succeed each other, ten or twelve times, but
in the other more _opacous_ bodies the consecutions will not be half so
many.

And therefore secondly, the _laminated_ body must be transparent, and this
I argue from this, that I have not been able to produce any colour at all
with an _opacous_ body, though never so thin. And this I have often try'd,
by pressing small _Globule_ of _Mercury_ between two smooth Plates of
Glass, whereby I have reduc'd that body to a much greater thinness then was
requisite to exhibit the colours with a transparent body.

Thirdly, there must be a considerable reflecting body adjacent to the under
or further side of the _lamina_ or _plate_: for this I always found, that
the greater that reflection was, the more vivid were the appearing colours.

From which Observations, is most evident, that the reflection from the
under or further side of the body is the principal cause of the production
of these colours; which, that it is so, and how it conduces to that effect,
I shall further explain in the following Figure, which is here described of
a very great thickness, as if it had been view'd through the _Microscope_;
and 'tis indeed much thicker than any _Microscope_ (I have yet us'd) has
been able to shew me those colour'd plates of Glass, or _Muscovie-glass_,
which I have not without much trouble view'd with it, for though I have
endeavoured to magnifie them as much as the Glasses were capable of, yet
are they so exceeding thin, that I have not hitherto been able positively
to determine their thickness. This Figure therefore I here represent, is
wholy _Hypothetical_.

Let ABCDHFE in the sixth Figure be a _frustum_ of _Muscovy-glass_, thinner
toward the end AE, and thicker towards DF. Let us first suppose the Ray
aghb coming from the Sun, of some remote luminous object to fall
_obliquely_ on the thinner plate BAE, part therefore is reflected back by
cghd, the first _Superficies_; whereby the perpendicular pulse ab is after
reflexion propagated by cd, cd, equally remote from each other with ab, ab,
so that ag + gc, or bh + hd are either of them equal to aa, as is also cc,
but the body BAE being transparent, a part of the light of this Ray is
refracted in the surface AB, and propagated by gikh to the surface EF,
whence it is reflected and refracted again by the surface AB. So that after
two refractions and one reflection, there is propagated a kind of fainter
Ray emnf, whose pulse is not only weaker by reason of the two refractions
in the surface AB, but by reason of the time spent in passing and repassing
between the two surfaces AB and EF, ef which is this fainter or weaker
pulse comes behind the pulse cd; so that hereby (the surfaces AB, and EF
being so neer together, that the eye cannot _discriminate_ them from one)
this confus'd or _duplicated_ pulse, whose strongest part precedes, and
whose weakest follows, does produce on the _Retina_, (or the _optick nerve_
that covers the bottom of the eye) the sensation of a _Yellow_.

And secondly, this _Yellow_ will appear so much the deeper, by how much the
further back towards the middle between cd and cd the spurious pulse ef is
remov'd, as in 2 where the surface BC being further remov'd from EF, the
weaker pulse ef will be nearer to the middle, and will make an impression
on the eye of a _Red_.

But thirdly, if the two reflecting surfaces be yet further remov'd asunder
(as in 3 CD and EF are) then will the weaker pulse be so farr behind, that
it will be more then half the distance between cd and cd. And in this case
it will rather seem to precede the following stronger pulse, then to follow
the preceding one, and consequently a _Blue_ will be generated. And when
the weaker pulse is just in the middle between two strong ones, then is a
deep and lovely _Purple_ generated; but when the weaker pulse ef is very
neer to cd, then is there generated a _Green_, which will be _bluer_, or
_yellower_, according as the _approximate_ weak pulse does precede or
follow the stronger.

Now fourthly, if the thicker Plate chance to be cleft into two thinner
Plates, as CDFE is divided into two Plates by the surface GH then from the
composition arising from the three reflections in the surfaces CD, GH, and
EF, there will be generated several compounded or mixt colours, which will
be very differing, according as the proportion between the thicknesses of
those two divided Plates CDHG, and GHFE are varied.

And _fifthly_, if these surfaces CD and FE are further remov'd asunder, the
weaker pulse will yet lagg behind much further, and not onely be
_coincident_ with the second, cd, but lagg behind that also, and that so
much the more, by how much the thicker the Plate be; so that by degrees it
will be _coincident_ with the third cd backward also, and by degrees, as
the Plate grows thicker with a fourth, and so onward to a fifth, sixth,
seventh, or eighth; so that if there be a thin transparent body, that from
the greatest thinness requisite to produce colours, does, in the manner of
a Wedge, by degrees grow to the greatest thickness that a Plate can be of,
to exhibit a colour by the reflection of Light from such a body, there
shall be generated several consecutions of colours, whose order from the
thin end towards the thick, shall be _Yellow, Red, Purple, Blue, Green;
Yellow, Red, Purple, Blue, Green; Yellow, Red, Purple, Blue, Green;
Yellow_, &c. and these so often repeated, as the weaker pulse does lose
paces with its _Primary_, or first pulse, and is _coincident_ with a
second, third, fourth, fifth, sixth, &c. pulse behind the first. And this,
as it is _coincident_, or follows from the first _Hypothesis_ I took of
colours, so upon experiment have I found it in multitudes of instances that
seem to prove it. One thing which seems of the greatest concern in this
_Hypothesis_, is to determine the greatest or least thickness requisite for
these effects, which, though I have not been wanting in attempting, yet so
exceeding thin are these coloured Plates, and so imperfect our
_Microscope_, that I have not been hitherto successfull, though if my
endeavours shall answer my expectations, I shall hope to gratifie the
curious Reader with some things more remov'd beyond our reach hitherto.

Thus have I, with as much brevity as I was able, endeavoured to explicate
(_Hypothetically_ at least) the causes of the _Phaenomena_ I formerly
recited, on the consideration of which I have been the more particular.

First, because I think these I have newly given are capable of explicating
all the _Phaenomena_ of colours, not onely of those appearing in the
_Prisme_, Water-drop, or Rainbow, and in _laminated_ or plated bodies, but
of all that are in the world, whether they be fluid or solid bodies,
whether in thick or thin, whether transparent, or seemingly opacous, as I
shall in the next Observation further endeavour to shew. And secondly,
because this being one of the two ornaments of all bodies discoverable by
the sight, whether looked on with, or without a _Microscope_, it seem'd to
deserve (somewhere in this Tract, which contains a description of the
Figure and Colour of some minute bodies) to be somewhat the more intimately
enquir'd into.

       *       *       *       *       *


Observ. X. _Of _Metalline_, and other real Colours._

Having in the former Discourse, from the Fundamental cause of Colour, made
it probable, that there are but two Colours, and shewn, that the _Phantasm_
of Colour is caus'd by the sensation of the _oblique_ or uneven pulse of
Light which is capable of no more varieties than two that arise from the
two sides of the _oblique_ pulse, though each of those be capable of
infinite gradations or degrees (each of them beginning from _White_, and
ending the one in the deepest _Scarlet_ or _Yellow_, the other in the
deepest _Blue_) I shall in this _Section_ set down some Observations which
I have made of other colours, such as _Metalline_ powders tinging or
colour'd bodies and several kinds of tinctures or ting'd liquors, all
which, together with those I treated of in the former Observation will, I
suppose, comprise the several subjects in which colour is observ'd to be
inherent, and the several manners by which it _inheres_, or is apparent in
them. And here I shall endeavour to shew by what composition all kind of
compound colours are made, and how there is no colour in the world but may
be made from the various degrees of these two colours, together with the
intermixtures of _Black_ and _White_.

And this being so, as I shall anon shew, it seems an evident argument to
me, that all colours whatsoever, whether in fluid or solid, whether in very
transparent or seemingly _opacous_, have the same efficient cause, to wit,
some kind of _refraction_ whereby the Rays that proceed from such bodies,
have their pulse _obliquated_ or confus'd in the manner I explicated in the
former _Section_; that is, a _Red_ is caus'd by a duplicated or confus'd
pulse, whose strongest pulse precedes, and a weaker follows: and a _Blue_
is caus'd by a confus'd pulse, where the weaker pulse precedes, and the
stronger follows. And according as these are, more or less, or variously
mixt and compounded, so are the _sensations_, and consequently the
_phantasms_ of colours _diversified_.

To proceed therefore; I suppose, that all transparent colour'd bodies,
whether fluid or solid, do consist at least of two parts, or two kinds of
substances, the one of a substance of a somewhat differing _refraction_
from the other. That one of these substances which may be call'd the
_tinging_ substance, does consist of distinct parts, or particles of a
determinate bigness which are _disseminated_, or dispers'd all over the
other: That these particles, if the body be equally and uniformly colour'd,
are evenly rang'd and dispers'd over the other contiguous body; That where
the body is deepest ting'd, there these particles are rang'd thickest, and
where 'tis but faintly ting'd, they are rang'd much thinner, but uniformly.
That by the mixture of another body that unites with either of these, which
has a differing refraction from either of the other, quite differing
effects will be produc'd, that is, the _consecutions_ of the confus'd
pulses will be much of another kind, and consequently produce other
_sensations_ and _phantasms_ of colours, and from a _Red_ may turn to a
_Blue_, or from a _Blue_ to a _Red_, &c.

Now, that this may be the better understood, I shall endeavour to explain
my meaning a little more sensible by a _Scheme_: Suppose we therefore in
the seventh _Figure_ of the sixth _Scheme_, that ABCD represents a Vessel
holding a ting'd liquor, let IIIII, &c. be the clear liquor, and let the
tinging body that is mixt with it be EE, &c. FF, &c. GG, &c. HH, &c. whose
particles (whether round, or some other determinate Figure is little to our
purpose) are first of a determinate and equal bulk. Next, they are rang'd
into the form of _Quincunx_, or _Equilaterotriangular_ order, which that
probably they are so, and why they are so, I shall elsewhere endeavour to
shew. Thirdly, they are of such a nature, as does either more easily or
more difficultly transmit the Rays of light then the liquor; if more
easily, a _Blue_ is generated, and if more difficultly, a _Red_ or
_Scarlet_.

And first, let us suppose the tinging particles to be of a substance that
does more _impede_ the Rays of light, we shall find that the pulse or wave
of light mov'd from AD to BC, will proceed on, through the containing
_medium_ by the pulses or waves KK, LL, MM, NN, OO; but because several of
these Rays that go to the constitution of these pulses will be slugged or
stopped by the tinging particles E, F, G, H; therefore there shall be
_secundary_ and weak pulse that shall follow the Ray, namely PP which will
be the weaker: first, because it has suffer'd many refractions in the
impeding body; next, for that the Rays will be a little dispers'd or
confus'd by reason of the refraction in each of the particles, whether
_round_ or _angular_; and this will be more evident, if we a little more
closely examine any one particular tinging _Globule_.

Suppose we therefore AB in the eighth _Figure_ of the sixth _Scheme_, to
represent a tinging _Globule_ or particle which has a greater refraction
than the liquor in which it is contain'd: Let CD be a part of the pulse of
light which is _propagated_ through the containing _medium_; this pulse
will be a little stopt or impeded by the _Globule_, and so by that time the
pulse is past to EF that part of it which has been impeded by passing
through the _Globule_, will get but to LM, and so that pulse which has been
_propagated_ through the _Globule_, to wit, LM, NO, PQ, will always come
behind the pulses EF, GH, IK, &c.

Next, by reason of the greater impediment in AB, and its _Globular_ Figure,
the Rays that pass through it will be dispers'd, and very much scatter'd.
Whence CA and DB which before went _direct_ and _parallel_, will after the
refraction in AB, _diverge_ and spread by AP, and BQ; so that as the Rays
do meet with more and more of these tinging particles in their way, by so
much the more will the pulse of light further lagg behind the clearer
pulse, or that which has fewer refractions, and thence the deeper will the
colour be, and the fainter the light that is trajected through it; for not
onely many Rays are reflected from the surfaces of AB, but those Rays that
get through it are very much disordered.

By this _Hypothesis_ there is no one experiment of colour that I have yet
met with, but may be, I conceive, very rationably solv'd, and perhaps, had
I time to examine several particulars requisite to the demonstration of it,
I might prove it more than probable, for all the experiments about the
changes and mixings of colours related in the Treatise of Colours,
published by the _Incomparable_ Mr. _Boyle_, and multitudes of others which
I have observ'd, do so easily and naturally flow from those principles,
that I am very apt to think it probable, that they own their production to
no other _secundary_ cause: As to instance in two or three experiments. In
the twentieth Experiment, this _Noble Authour_ has shewn that the deep
_bluish purple-colour_ of _Violets_, may be turn'd into a _Green_, by
_Alcalizate Salts_, and to a _Red_ by acid; that is, a _Purple_ consists of
two colours, a deep _Red_, and a deep _Blue_; when the _Blue_ is diluted,
or altered, or destroy'd by _acid Salts_, the _Red_ becomes predominant,
but when the _Red_ is diluted by _Alcalizate_, and the _Blue_ heightned,
there is generated a _Green_; for of a _Red_ diluted, is made a _Yellow_,
and _Yellow_ and _Blue_ make a _Green_.

Now, because the _spurious_ pulses which cause a _Red_ and a _Blue_, do the
one follow the clear pulse, and the other precede it, it usually follows,
that those _Saline_ refracting bodies which do _dilute_ the colour of the
one, do deepen that of the other. And this will be made manifest by almost
all kinds of _Purples_, and many sorts of _Greens_, both these colours
consisting of mixt colours; for if we suppose A and A in the ninth Figure,
to represent two pulses of clear light, which follow each other at a
convenient distance, AA, each of which has a _spurious_ pulse preceding it,
as BB, which makes a _Blue_, and another following it, as CC, which makes a
_Red_, the one caus'd by tinging particles that have a greater refraction,
the other by others that have a less refracting quality then the liquor or
_Menstruum_ in which these are dissolv'd, whatsoever liquor does so alter
the refraction of the one, without altering that of the other part of the
ting'd liquor, must needs very much alter the colour of the liquor; for if
the refraction of the _dissolvent_ be increas'd, and the refraction of the
tinging particles not altered, then will the preceding _spurious_ pulse be
shortned or stopt, and not out-run the clear pulse so much; so that BB will
become EE, and the _Blue_ be _diluted_, whereas the other _spurious_ pulse
which follows will be made to lagg much more, and be further behind AA than
before, and CC will become _ff_, and so the _Yellow_ or _Red_ will be
heightned.

A _Saline_ liquor therefore, mixt with another ting'd liquor, may alter the
colour of it several ways, either by altering the refraction of the liquor
in which the colour swims: or secondly by varying the refraction of the
coloured particles, by uniting more intimately either with some particular
_corpuscles_ of the tinging body, or with all of them, according as it has
a _congruity_ to some more especially, or to all alike: or thirdly, by
uniting and interweaving it self with some other body that is already
joyn'd with the tinging particles, with which substance it may have a
_congruity_, though it have very little with the particles themselves: or
fourthly, it may alter the colour of a ting'd liquor by dis-joyning certain
particles which were before united with the tinging particles, which though
they were somewhat _congruous_ to these particles, have yet a greater
_congruity_ with the newly _infus'd Saline menstruum_. It may likewise
alter the colour by further dissolving the tinging substance into smaller
and smaller _particles_, and so _diluting_ the colour; or by uniting
several _particles_ together as in precipitations, and so deepning it, and
some such other ways, which many experiments and comparisons of differing
trials together, might easily inform one of.

From these Principles applied, may be made out all the varieties of colours
observable, either in liquors, or any other ting'd bodies, with great ease,
and I hope intelligible enough, there being nothing in the _notion_ of
colour, or in the suppos'd production, but is very conceivable, and may be
possible.

The greatest difficulty that I find against this _Hypothesis_, is, that
there seem to be more distinct colours then two, that is, then Yellow and
Blue. This Objection is grounded on this reason, that there are several
Reds, which _diluted_, make not a Saffron or pale Yellow, and therefore
Red, or Scarlet seems to be a third colour distinct from a deep degree of
Yellow.

To which I answer, that Saffron affords us a deep Scarlet tincture, which
may be _diluted_ into as pale a Yellow as any, either by making a weak
solution of the Saffron, by infusing a small parcel of it into a great
quantity of liquor, as in spirit of Wine, or else by looking through a very
thin quantity of the tincture, and which may be heightn'd into the
loveliest Scarlet, by looking through a very thick body of this tincture,
or through a thinner parcel of it, which is highly _impregnated_ with the
tinging body, by having had a greater quantity of the Saffron dissolv'd in
a smaller parcel of the liquor.

Now, though there may be some particles of other tinging bodies that give a
lovely Scarlet also, which though _diluted_ never so much with liquor, or
looked on through never so thin a parcel of ting'd liquor, will not yet
afford a pale Yellow, but onely a kind of faint Red; yet this is no
argument but that those ting'd particles may have in them the faintest
degree of Yellow, though we may be unable to make them exhibit it; For that
power of being _diluted_ depending upon the divisibility of the ting'd
body, if I am unable to make the tinging particles so thin as to exhibit
that colour, it does not therefore follow, that the thing is impossible to
be done; now, the tinging particles of some bodies are of such a nature,
that unless there be found some way of comminuting them into less bulks
then the liquor does dissolve them into, all the Rays that pass through
them must necessarily receive a tincture so deep, as their appropriate
refractions and bulks compar'd with the proprieties of the dissolving
liquor must necessarily dispose them to empress, which may perhaps be a
pretty deep Yellow, or pale Red.

And that this is not _gratis dictum_, I shall add one instance of this
kind, wherein the thing is most manifest.

If you take Blue _Smalt_, you shall find, that to afford the deepest Blue,
which _caeteris paribus_ has the greatest particles or sands; and if you
further divide, or grind those particles on a Grindstone, or _porphyry_
stone, you may by _comminuting_ the sands of it, _dilute_ the Blue into as
pale a one as you please, which you cannot do by laying the colour thin;
for wheresoever any single particle is, it exhibits as deep a Blue as the
whole mass. Now, there are other Blues, which though never so much ground,
will not be _diluted_ by grinding, because consisting of very small
particles, very deeply ting'd, they cannot by grinding be actually
separated into smaller particles then the operation of the fire, or some
other dissolving _menstruum_, reduc'd them to already.

Thus all kind of _Metalline_ colours, whether _precipitated_, _sublim'd_,
_calcin'd_, or otherwise prepar'd, are hardly chang'd by grinding, as
_ultra marine_ is not more _diluted_; nor is _Vermilion_ or _Red-lead_ made
of a more faint colour by grinding; for the smallest particles of these
which I have view'd with my greatest Magnifying-Glass, if they be well
enlightned, appear very deeply ting'd with their peculiar colours; nor,
though I have magnified and enlightned the particles exceedingly, could I
in many of them, perceive them to be transparent, or to be whole particles,
but the smallest specks that I could find among well ground _Vermilion_ and
_Red-lead_, seem'd to be a Red mass, compounded of a multitude of less and
less motes, which sticking together, compos'd a bulk, not one thousand
thousandth part of the smallest visible sand or mote.

And this I find generally in most _Metalline_ colours, that though they
consist of parts so exceedingly small, yet are they very deeply ting'd,
they being so ponderous, and having such a multitude of terrestrial
particles throng'd into a little room; so that 'tis difficult to find any
particle transparent or resembling a pretious stone, though not impossible;
for I have observ'd divers such shining and resplendent colours intermixt
with the particles of _Cinnaber_, both natural and artificial, before it
hath been ground and broken or flaw'd into _Vermilion_: As I have also in
_Orpiment_, _Red-lead_, and _Bise_, which makes me suppose, that those
_metalline_ colours are by grinding, not onely broken and separated
actually into smaller pieces, but that they are also flaw'd and brused,
whence they, for the most part, become _opacous_, like flaw'd Crystal or
Glass, &c. But for _Smalts_ and _verditures_, I have been able with a
_Microscope_ to perceive their particles very many of them transparent.

Now, that the others also may be transparent, though they do not appear so
to the _Microscope_, may be made probable by this Experiment: that if you
take _ammel_ that is almost _opacous_, and grind it very well on a
_Porphyry_, or _Serpentine_, the small particles will by reason of their
flaws, appear perfectly _opacous_; and that 'tis the flaws that produce
this _opacousness_, may be argued from this, that particles of the same
_Ammel_ much thicker if unflaw'd will appear somewhat transparent even to
the eye; and from this also, that the most transparent and clear Crystal,
if heated in the fire, and then suddenly quenched, so that it be all over
flaw'd, will appear _opacous_ and white.

And that the particles of _Metalline_ colours are transparent, may be
argued yet further from this, that the Crystals, or _Vitriols_ of all
Metals, are transparent, which since they consist of _metalline_ as well as
_saline_ particles, those _metalline_ ones must be transparent, which is
yet further confirm'd from this, that they have for the most part,
_appropriate_ colours; so the _vitriol_ of Gold is Yellow; of Copper, Blue,
and sometimes Green; of Iron, green; of Tinn and Lead, a pale White; of
Silver, a pale Blue, _&._

And next, the _Solution_ of all Metals into _menstruums_ are much the same
with the _Vitriols_, or Crystals. It seems therefore very probable, that
those colours which are made by the _precipitation_ of those particles out
of the _menstruums_ by transparent _precipitating_ liquors should be
transparent also. Thus Gold _precipitates_ with _oyl of Tartar_, or _spirit
of Urine_ into a brown Yellow, Copper with spirit of _Urine_ into a Mucous
blue, which retains its transparency. A solution of sublimate (as the same
Illustrious Authour I lately mention'd shews in his 40. Experiment)
_precipitates_ with oyl of _Tartar_ _per deliquium_, into an Orange
colour'd _precipitate_; nor is it less probable, that the _calcination_ of
those _Vitriols_ by the fire, should have their particles transparent: Thus
_Saccarum Saturni_, or the _Vitriol of Lead_ by _calcination_ becomes a
deep Orange-colour'd _minium_, which is a kind of _precipitation_ by some
Salt which proceeds from the fire; common _Vitriol_ _calcin'd_, yields a
deep Brown Red, etc.

A third Argument, that the particles of Metals are transparent, is, that
being _calcin'd_, and melted with Glass, they tinge the Glass with
transparent colours. Thus the _Calx_ of Silver tinges the Glass on which it
is anneal'd with a lovely Yellow, or Gold colour, &c.

And that the parts of Metals are transparent, may be farther argued from
the transparency of Leaf-gold, which held against the light, both to the
naked eye, and the _Microscope,_ exhibits a deep Green. And though I have
never seen the other Metals _laminated_ so thin, that I was able to
perceive them transparent, yet, for Copper and Brass, if we had the same
conveniency for _laminating_ them, as we have for Gold, we might, perhaps,
through such plates or leaves, find very differing degrees of Blue, or
Green; for it seems very probable, that those Rays that rebound from them
ting'd, with a deep Yellow, or pale Red, as from Copper, or with a pale
Yellow, as from Brass, have past through them; for I cannot conceive how by
reflection alone those Rays can receive a tincture, taking any _Hypothesis_
extant.

So that we see there may a sufficient reason be drawn from these instances,
why those colours which we are unable to _dilute_ to the palest Yellow, or
Blue, or Green, are not therefore to be concluded not to be a deeper degree
of them; for supposing we had a great company of small _Globular_ essence
Bottles, or round Glass bubbles, about the bigness of a Walnut, fill'd each
of them with a very deep mixture of Saffron, and that every one of them did
appear of a deep Scarlet colour, and all of them together did _exhibit_ at
a distance, a deep dy'd Scarlet body. It does not follow, because after we
have come nearer to this _congeries_, or mass, and divided it into its
parts, and examining each of its parts severally or apart, we find them to
have much the same colour with the whole mats; it does not, I say,
therefore follow, that if we could break those _Globules_ smaller, or any
other ways come to see a smaller or thinner parcel of the ting'd liquor
that fill'd those bubbles, that that ting'd liquor must always appear Red,
or of a Scarlet hue, since if Experiment be made, the quite contrary will
ensue; for it is capable of being _diluted_ into the palest Yellow.

Now, that I might avoid all the Objections of this kind, by exhibiting an
Experiment that might by ocular proof convince those whom other reasons
would not prevail with, I provided me a _Prismatical Glass_, made hollow,
just in the form of a Wedge, such as is represented in the tenth _Figure_
of the sixth _Scheme_. The two _parallelogram_ sides ABCD, ABEF, which met
at a point, were made of the clearest Looking-glass plates well ground and
polish'd that I could get; these were joyn'd with hard cement to the
_triangular_ sides, BCE, ADF, which were of Wood; the _Parallelogram_ base
BCEF, likewise was of Wood joyn'd on to the rest with hard cement, and the
whole _Prismatical_ Box was exactly stopt every where, but onely a little
hole near the base was left, whereby the Vessel could be fill'd with any
liquor, or emptied again at pleasure.

One of these Boxes (for I had two of them) I fill'd with a pretty deep
tincture of _Aloes_, drawn onely with fair Water, and then stopt the hole
with a piece of Wax, then, by holding this Wedge against the Light, and
looking through it, it was obvious enough to see the tincture of the liquor
near the edge of the Wedge where it was but very thin, to be a pale but
well colour'd Yellow, and further and further from the edge, as the liquor
grew thicker and thicker, this tincture appear'd deeper and deeper, so that
near the blunt end, which was seven Inches from the edge and three Inches
and an half thick; it was of a deep and well colour'd Red. Now, the clearer
and purer this tincture be, the more lovely will the deep Scarlet be, and
the fouler the tincture be, the more dirty will the Red appear; so that
some dirty tinctures have afforded their deepest Red much of the colour of
burnt Oker or _Spanish_ brown; others as lovely a colour as _Vermilion_,
and some much brighter; but several others, according as the tinctures were
worse or more foul, exhibited various kinds of Reds, of very differing
degrees.

The other of these Wedges, I fill'd with a most lovely tincture of Copper,
drawn from the filings of it, with spirit of _Urine_, and this Wedge held
as the former against the Light, afforded all manner of Blues, from the
faintest to the deepest, so that I was in good hope by these two, to have
produc'd all the varieties of colours imaginable; for I thought by this
means to have been able by placing the two _Parallelogram_ sides together,
and the edges contrary ways, to have so mov'd them to and fro one by
another, as by looking through them in several places, and through several
thicknesses, I should have compounded, and consequently have seen all those
colours, which by other like compositions of colours would have ensued.

But insteed of meeting with what I look'd for, I met with somewhat more
admirable; and that was, that I found my self utterly unable to see through
them when placed both together, though they were transparent enough when
asunder; and though I could see through twice the thickness, when both of
them were fill'd with the same colour'd liquors, whether both with the
Yellow, or both with the Blue, yet when one was fill'd with the Yellow, the
other with the Blue, and both looked through, they both appear'd dark,
onely when the parts near the tops were look'd through, they exhibited
Greens, and those of very great variety, as I expected, but the Purples and
other colours, I could not by any means make, whether I endeavour'd to look
through them both against the Sun, or whether I plac'd them against the
hole of a darkned room.

But notwithstanding this mis-ghessing, I proceeded on with my trial in a
dark room, and having two holes near one another, I was able, by placing my
Wedges against them, to mix the ting'd Rays that past through them, and
fell on a sheet of white Paper held at a convenient distance from them as I
pleas'd; so that I could make the Paper appear of what colour I would, by
varying the thicknesses of the Wedges, and consequently the tincture of the
Rays that past through the two holes, and sometimes also by varying the
Paper, that is, insteed of a white Paper, holding a gray, or a black piece
of Paper.

Whence I experimentally found what I had before imagin'd, that all the
varieties of colours imaginable are produc'd from several degrees of these
two colours, namely, Yellow and Blue, or the mixture of them with light and
darkness, that is, white and black. And all those almost infinite varieties
which Limners and Painters are able to make by compounding those several
colours they lay on their Shels or _Palads_, are nothing else, but some
_compositum_, made up of some one or more, or all of these four.

Now, whereas it may here again be objected, that neither can the Reds be
made out of the Yellows, added together, or laid on in greater or less
quantity, nor can the Yellows be made out of the Reds though laid never so
thin; and as for the addition of White or Black, they do nothing but either
whiten or darken the colours to which they are added, and not at all make
them of any other kind of colour: as for instance, _Vermilion_, by being
temper'd with White Lead, does not at all grow more Yellow, but onely there
is made a whiter kind of Red. Nor does Yellow _Oker_, though laid never so
thick, produce the colour of _Vermilion_, nor though it be temper'd with
Black, does it at all make a Red; nay, though it be temper'd with White, it
will not afford a fainter kind of Yellow, such as _masticut_, but onely a
whiten'd Yellow; nor will the Blues be _diluted_ or deepned after the
manner I speak of, as _Indico_ will never afford so fine a Blue as
_Ultramarine_ or _Bise_; nor will it, temper'd with _Vermilion_, ever
afford a Green, though each of them be never so much temper'd with white.

To which I answer, that there is a great difference between _diluting_ a
colour and whitening of it; for _diluting_ a colour, is to make the
colour'd parts more thin, so that the ting'd light, which is made by
trajecting those ting'd bodies, does not receive so deep a tincture; but
whitening a colour is onely an intermixing of many clear reflections of
light among the same ting'd parts; deepning also, and darkning or blacking
a colour, are very different; for deepning a colour, is to make the light
pass through a greater quantity of the same tinging body; and darkning or
blacking a colour, is onely interposing a multitude of dark or black spots
among the same ting'd parts, or placing the colour in a more faint light.

First therefore, as to the former of these operations, that is, diluting
and deepning, most of the colours us'd by the Limners and Painters are
incapable of, to wit, _Vermilion_ and _Red-lead_, and _Oker_, because the
ting'd parts are so exceeding small, that the most curious Grindstones we
have, are not able to separate them into parts actually divided so small as
the ting'd particles are; for looking on the most curiously ground
_Vermilion_, and _Oker_, and _Red-lead_, I could perceive that even those
small _corpuscles_ of the bodies they left were compounded of many pieces,
that is, they seem'd to be small pieces compounded of a multitude of lesser
ting'd parts: each piece seeming almost like a piece of Red Glass, or
ting'd Crystal all flaw'd; so that unless the Grindstone could actually
divide them into smaller pieces then those flaw'd particles were, which
compounded that ting'd mote I could see with my _Microscope_, it would be
impossible to _dilute_ the colour by grinding, which, because the finest we
have will not reach to do in _Vermilion_ or _Oker_, therefore they cannot
at all, or very hardly be _diluted_.

Other colours indeed, whose ting'd particles are such as may be made
smaller, by grinding their colour, may be _diluted_. Thus several of the
Blues may be _diluted_, as _Smalt_ and _Bise_; and _Masticut_, which is
Yellow, may be made more faint: And even _Vermilion_ it self may, by too
much grinding, be brought to the colour of _Red-lead_, which is but an
Orange colour, which is confest by all to be very much upon the Yellow.
Now, though perhaps somewhat of this _diluting_ of _Vermilion_ by overmuch
grinding may be attributed to the Grindstone, or muller, for that some of
their parts may be worn off and mixt with the colour, yet there seems not
very much, for I have done it on a Serpentine-stone with a muller made of a
Pebble, and yet observ'd the same effect follow.

And secondly, as to the other of these operations on colours, that is, the
deepning of them, Limners and Painters colours are for the most part also
uncapable. For they being for the most part _opacous_; and that
_opacousness_, as I said before, proceeding from the particles, being very
much flaw'd, unless we were able to joyn and re-unite those flaw'd
particles again into one piece, we shall not be able to deepen the colour,
which since we are unable to do with most of the colours which are by
Painters accounted _opacous_, we are therefore unable to deepen them by
adding more of the same kind.

But because all those _opacous_ colours have two kinds of beams or Rays
reflected from them, that is, Rays unting'd, which are onely reflected from
the outward surface, without at all penetrating of the body, and ting'd
Rays which are reflected from the inward surfaces or flaws after they have
suffer'd a two-fold refraction; and because that transparent liquors mixt
with such _corpuscles_, do, for the most part, take off the former kind of
reflection; therefore these colours mixt with Water or Oyl, appear much
deeper than when dry, for most part of that white reflection from the
outward surface is remov'd. Nay, some of these colours are very much
deepned by the mixture with some transparent liquor, and that because they
may perhaps get between those two flaws, and so consequently joyn two or
more of those flaw'd pieces together; but this happens but in a very few.

Now, to shew that all this is not _gratis dictum_, I shall set down some
Experiments which do manifest these things to be probable and likely, which
I have here deliver'd.

For, first, if you take any ting'd liquor whatsoever, especially if it be
pretty deeply ting'd, and by any means work it into a froth, the
_congeries_ of that froth shall seem an _opacous_ body, and appear of the
same colour, but much whiter than that of the liquor out of which it is
made. For the abundance of reflections of the Rays against those surfaces
of the bubbles of which the froth consists, does so often rebound the Rays
backwards, that little or no light can pass through, and consequently the
froth appears _opacous_.

Again, if to any of these ting'd liquors that will endure the boiling there
be added a small quantity of fine flower (the parts of which through the
_Microscope_ are plainly enough to be perceiv'd to consist of transparent
_corpuscles_) and suffer'd to boyl till it thicken the liquor, the mass of
the liquor will appear _opacous_, and ting'd with the same colour, but very
much whiten'd.

Thus, if you take a piece of transparent Glass that is well colour'd, and
by heating it, and then quenching it in Water, you flaw it all over, it
will become _opacous_, and will exhibit the same colour with which the
piece is ting'd, but fainter and whiter.

Or, if you take a Pipe of this transparent Glass, and in the flame of a
Lamp melt it, and then blow it into very thin bubbles, then break those
bubbles, and collect a good parcel of those _laminae_ together in a Paper,
you shall find that a small thickness of those Plates will constitute an
_opacous_ body, and that you may see through the mass of Glass before it be
thus _laminated_, above four times the thickness: And besides, they will
now afford a colour by reflection as other _opacous_ (as they are call'd)
colours will, but much fainter and whiter than that of the Lump or Pipe out
of which they were made.

Thus also, if you take _Putty_, and melt it with any transparent colour'd
Glass, it will make it become an _opacous_ colour'd lump, and to yield a
paler and whiter colour than the lump by reflection.

The same thing may be done by a preparation of _Antimony_, as has been
shewn by the Learned _Physician_, Dr. _C.M._ in his Excellent Observations
and Notes on _Nery's Art of Glass_; and by this means all transparent
colours become _opacous_, or _ammels_. And though by being ground they lose
very much of their colour, growing much whiter by reason of the multitude
of single reflections from their outward surface, as I shew'd afore, yet
the fire that in the nealing or melting re-unites them, and so renews those
_spurious_ reflections, removes also those whitenings of the colour that
proceed from them.

As for the other colours which Painters use, which are transparent, and
us'd to varnish over all other paintings, 'tis well enough known that the
laying on of them thinner or thicker, does very much _dilute_ or deepen
their colour.

Painters Colours therefore consisting most of them of solid particles, so
small that they cannot be either re-united into thicker particles by any
Art yet known, and consequently cannot be deepned; or divided into
particles so small as the flaw'd particles that exhibit that colour, much
less into smaller, and consequently cannot be _diluted_; It is necessary
that they which are to imitate all kinds of colours, should have as many
degrees of each colour as can be procur'd.

And to this purpose, both Limners and Painters have a very great variety
both of Yellows and Blues, besides several other colour'd bodies that
exhibit very compounded colours, such as Greens and Purples; and others
that are compounded of several degrees of Yellow, or several degrees of
Blue, sometimes unmixt, and sometimes compounded with several other
colour'd bodies.

The Yellows, from the palest to the deepest Red or Scarlet, which has no
intermixture of Blue, are _pale and deep Masticut, Orpament, English Oker,
brown Oker, Red Lead, and Vermilion, burnt English Oker, and burnt brown
Oker,_ which last have a mixture of dark or dirty parts with them, &c.

Their Blues are several kinds of _Smalts_, and _Verditures_, and _Bise_,
and _Ultramarine_, and _Indico_, which last has many dirty or dark parts
intermixt with it.

Their compounded colour'd bodies, as _Pink_, and _Verdigrese_, which are
Greens, the one a _Popingay_, the other a _Sea-green_; then _Lac_, which is
a very lovely _Purple_.

To which may be added their Black and White, which they also usually call
Colours, of each of which they have several kinds, such as _Bone Black_,
made of _Ivory_ burnt in a close Vessel, and _Blue Black_, made of the
small coal of _Willow_, or some other Wood; and _Cullens earth_, which is a
kind of brown Black, &c. Their usual Whites are either artificial or
natural _White Lead_, the last of which is the best they yet have, and with
the mixing and tempering these colours together, are they able to make an
imitation of any colour whatsoever: Their Reds or deep Yellows, they can
_dilute_ by mixing pale Yellows with them, and deepen their pale by mixing
deeper with them; for it is not with _Opacous_ colours as it is with
transparent, where by adding more Yellow to yellow, it is deepned, but in
_opacous_ _diluted_. They can whiten any colour by mixing White with it,
and darken any colour by mixing Black, or some dark and dirty colour. And
in a word, most of the colours, or colour'd bodies they use in Limning and
Painting, are such, as though mixt with any other of their colours, they
preserve their own hue, and by being in such very smal parts dispers'd
through the other colour'd bodies, they both, or altogether represent to
the eye a _compositum_ of all; the eye being unable, by reason of their
smalness, to distinguish the peculiarly colour'd particles, but receives
them as one intire _compositum_: whereas in many of these, the _Microscope_
very easily distinguishes each of the compounding colours distinct, and
exhibiting its own colour.

Thus have I by gently mixing _Vermilion_ and _Bise_ dry, produc'd a very
fine Purple, or mixt colour, but looking on it with the _Microscope_, I
could easily distinguish both the Red and the Blue particles, which did not
at all produce the _Phantasm_ of Purple.

To summ up all therefore in a word, I have not yet found any solid colour'd
body, that I have yet examin'd, perfectly _opacous_; but those that are
least transparent are _Metalline_ and _Mineral_ bodies, whose particles
generally, seeming either to be very small, or very much flaw'd, appear for
the most part _opacous_, though there are very few of them that I have
look'd on with a _Microscope_, that have not very plainly or
circumstantially manifested themselves transparent.

And indeed, there seem to be so few bodies in the world that are _in
minimis_ opacous, that I think one may make it a rational _Query_, Whether
there be any body absolutely thus _opacous_? For I doubt not at all (and I
have taken notice of very many circumstances that make me of this mind)
that could we very much improve the _Microscope_, we might be able to see
all those bodies very plainly transparent, which we now are fain onely to
ghess at by circumstances. Nay, the Object Glasses we yet make use of are
such, that they make many transparent bodies to the eye, seem _opacous_
through them, which if we widen the Aperture a little, and cast more light
on the objects, and not charge the Glasses so deep, will again disclose
their transparency.

Now, as for all kinds of colours that are dissolvable in Water, or other
liquors, there is nothing so manifest, as that all those ting'd liquors are
transparent; and many of them are capable of being _diluted_ and compounded
or mixt with other colours, and divers of them are capable of being very
much chang'd and heightned, and fixt with several kinds of _Saline
menstruums_. Others of them upon compounding, destroy or vitiate each
others colours, and _precipitate_, or otherwise very much alter each others
tincture. In the true ordering and _diluting_, and deepning, and mixing,
and fixing of each of which, consists one of the greatest mysteries of the
Dyers; of which particulars, because our _Microscope_ affords us very
little information, I shall add nothing more at present; but onely that
with a very few tinctures order'd and mixt after certain ways, too long to
be here set down, I have been able to make an appearance of all the various
colours imaginable, without at all using the help of _Salts_, or _Saline
menstruums_ to vary them.

As for the mutation of Colours by _Saline menstruums_, they have already
been so fully and excellently handled by the lately mention'd Incomparable
_Authour_, that I can add nothing, but that of a multitude of trials that I
made, I have found them exactly to agree with his Rules and Theories; and
though there may be infinite instances, yet may they be reduc'd under a few
Heads, and compris'd within a very few Rules. And generally I find, that
_Saline menstruums_ are most operative upon those colours that are Purple,
or have some degree of Purple in them, and upon the other colours much
less. The _spurious_ pulses that compose which, being (as I formerly noted)
so very neer the middle between the true ones, that a small variation
throws them both to one side, or both to the other, and so consequently
must make a vast mutation in the formerly appearing Colour.

       *       *       *       *       *


Observ. XI. _Of _Figures_ observ'd in small Sand._

Sand generally seems to be nothing else but exceeding small Pebbles, or at
least some very small parcels of a bigger stone; the whiter kind seems
through the _Microscope_ to consist of small transparent pieces of some
_pellucid_ body, each of them looking much like a piece of _Alum_, or _Salt
Gem_; and this kind of Sand is angled for the most part irregularly,
without any certain shape, and the _granules_ of it are for the most part
flaw'd, through amongst many of them it is not difficult to find some that
are perfectly _pellucid_, like a piece of clear Crystal, and divers
likewise most curiously shap'd, much after the manner of the bigger
_Stiriae_ of Crystal, or like the small Diamants I observ'd in certain
Flints, of which I shall by and by relate; which last particular seems to
argue, that this kind of Sand is not made by the comminution of greater
transparent Crystaline bodies, but by the _concretion_ or _coagulation_ of
Water, or some other fluid body.

There are other kinds of courser Sands, which are browner, and have their
particles much bigger; these, view'd with a _Microscope_, seem much courser
and more _opacous_ substances, and most of them are of some irregularly
rounded Figures; and though they seem not so _opacous_ as to the naked eye,
yet they seem very foul and cloudy, but neither do these want curiously
transparent, no more than they do regularly figur'd and well colour'd
particles, as I have often found.

There are multitudes of other kinds of Sands, which in many particulars,
plainly enough discoverable by the _Microscope_, differ both from these
last mention'd kinds of Sands, and from one another: there seeming to be as
great variety of Sands, as there is of Stones. And as amongst Stones some
are call'd precious from their excellency, so also are there Sands which
deserve the same Epithite for their beauty; for viewing a small parcel of
_East-India_ Sand (which was given me by my highly honoured friend, Mr.
_Daniel Colwall_) and, since that, another parcel, much of the same kind, I
found several of them, both very transparent like precious Stones, and
regularly figur'd like Crystal, _Cornish_ Diamants, some Rubies, &c. and
also ting'd with very lively and deep colours, like _Rubys_, _Saphyrs_,
_Emeralds_, &c. These kinds of granuls I have often found also in _English_
Sand. And 'tis easie to make such a counterfeit Sand with deeply ting'd
Glass, Enamels and Painters colours.

It were endless to describe the multitudes of Figures I have met with in
these kind of minute bodies, such as _Spherical_, _Oval_, _Pyramidal_,
_Conical_, _Prismatical_, of each of which kinds I have taken notice.

But amongst many others, I met with none more observable than this pretty
Shell (described in the _Figure_ X. of the fifth _Scheme_) which, though as
it was light on by chance, deserv'd to have been omitted (I being unable to
direct any one to find the like) yet for its rarity was it not
inconsiderable, especially upon the account of the information it may
afford us. For by it we have a very good instance of the curiosity of
Nature in another kind of Animals which are remov'd, by reason of their
minuteness, beyond the reach of our eyes, so that as there are several
sorts of Insects, as Mites, and others, so small as not yet to have had any
names; (some of which I shall afterwards describe) and small Fishes, as
Leeches in Vineger; and smal vegetables, as Moss, and Rose-Leave-plants;
and small Mushroms, as mould: so are there, it seems, small Shel-fish
likewise, Nature shewing her curiosity in every Tribe of _Animals_,
_Vegetables_, and _Minerals_.

I was trying several small and single Magnifying Glasses, and casually
viewing a parcel of white Sand, when I perceiv'd one of the grains exactly
shap'd and wreath'd like a Shell, but endeavouring to distinguish it with
my naked eye, it was so very small, that I was fain again to make use of
the Glass to find it; then, whilest I thus look'd on it, with a Pin I
separated all the rest of the granules of Sand, and found it afterwards to
appear to the naked eye an exceeding small white spot, no bigger than the
point of a Pin. Afterwards I view'd it every way with a better _Microscope_
and found it on both sides, and edge-ways, to resemble the Shell of a small
Water-Snail with a flat spiral Shell: it had twelve wreathings, a, b, c, d,
e, &c. all very proportionably growing one less than another toward the
middle or center of the Shell, where there was a very small round white
spot. I could not certainly discover whether the Shell were hollow or not,
but it seem'd fill'd with somewhat, and 'tis probable that it might be
_petrify'd_ as other larger Shels often are, such as are mention'd in the
seventeenth _Observation_.

       *       *       *       *       *


Observ. XII. _Of _Gravel_ in Urine._

I Have often observ'd the Sand or Gravel of Urine, which seems to be a
_tartareous_ substance, generated out of a _saline_ and a _terrestrial_
substance _crystalliz'd_ together, in the form of _Tartar_, sometimes
sticking to the sides of the _Urinal_, but for the most part sinking to the
bottom, and there lying in the form of coorse common Sand; these, through
the _Microscope_, appear to be a company of small bodies, partly
transparent and partly _opacous_, some White, some Yellow, some Red, others
of more brown and duskie colours.

The Figure of them is for the most part flat, in the manner of Slats or
such like plated Stones, that is, each of them seem to be made up of
several other thinner Plates, much like _Muscovie Glass_, or _Englsh Sparr_
to the last of which, the white plated Gravel seems most likely; for they
seem not onely plated like that, but their sides shap'd also into _Rhombs_,
_Rhomboeids_, and sometimes into _Rectangles_ and _Squares_. Their bigness
and Figure may be seen in the second _Figure_ of the seventh _Plate_, which
represents about a dozen of them lying upon a plate ABCD, some of which, as
a, b, c, d seem'd more regular than the rest, and e, which was a small one,
sticking on the top of another, was a perfet _Rhomboeid_ on the top, and
had four _Rectangular_ sides.

The line E which was the the measure of the _Microscope_, is 1/32 part of
an _English_ Inch, so that the greatest bredth of any of them, exceeded not
1/128 part of an Inch.

Putting these into several liquors, I found _oyl of Vitriol_, _Spirit of
Urine_, and several other _Saline menstruums_ to dissolve them; and the
first of these in less than a minute without _Ebullition_, Water, and
several other liquors, had no sudden operation upon them. This I mention,
because those liquors that dissolve them, first make them very white, not
_vitiating_, but rather rectifying their Figure, and thereby make them
afford a very pretty object for the _Microscope_.

How great an advantage it would be to such as are troubled with the Stone,
to find some _menstruum_ might dissolve them without hurting the Bladder,
is easily imagin'd, since some _injections_ made of such bodies might
likewise dissolve the stone, which seems much of the same nature.

It may therefore, perhaps, be worthy some Physicians enquiry, whether there
may not be something mixt with the Urine in which the Gravel or Stone lies,
which may again make it dissolve it, the first of which seems by it's
regular Figures to have been sometimes _Crystalliz'd_ out of it. For
whether this _Crystallization_ be made in the manner as _Alum_, _Peter_,
&c. are _crystallized_ out of a cooling liquor, in which, by boyling they
have been dissolv'd; or whether it be made in the manner of _Tartarum
Vitriolatum_, that is, by the _Coalition_ of an _acid_ and a _Sulphureous_
substance, it seems not impossible, but that the liquor it lies in, may be
again made a _dissolvent_ of it. But leaving these inquiries to Physicians
or Chymists, to whom it does more properly belong, I shall proceed.

       *       *       *       *       *


Observ. XIII. _Of the small _Diamants_, or _Sparks_ in _Flints_._

Chancing to break a Flint stone in pieces, I found within it a certain
cavity all crusted over with a very pretty candied substance, some of the
parts of which, upon changing the posture of the Stone, in respect of the
_Incident_ light, exhibited a number of small, but very vivid reflections;
and having made use of my _Microscope_, I could perceive the whole surface
of that cavity to be all beset with a multitude of little _Crystaline_ or
_Adamantine_ bodies, so curiously shap'd, that it afforded a not unpleasing
object.

Having considered those vivid _repercussions_ of light, I found them to be
made partly from the plain external surface of these regularly figured
bodies (which afforded the vivid reflexions) and partly to be made from
within the somewhat _pellucid_ body, that is, from some surface of the
body, opposite to that superficies of it which was next the eye.

And because these bodies were so small, that I could not well come to make
Experiments and Examinations of them, I provided me several small _stiriae_
of Crystals or Diamants, found in great quantities in _Cornwall_ and are
therefore commonly called _Cornish Diamants_: these being very _pellucid_,
and growing in a hollow cavity of a Rock (as I have been several times
informed by those that have observ'd them) much after the same manner as
these do in the Flint, and having besides their outward surface very
regularly shap'd, retaining very near the same Figures with some of those I
observ'd in the other, became a convenient help to me for the Examination
of the proprieties of those kinds of bodies.

And first for the Reflections, in these I found it very observable, That
the brightest reflections of light proceeded from within the _pellucid_
body; that is, that the Rays admitted through the _pellucid_ substance in
their getting out on the opposite side, were by the contiguous and strong
reflecting surface of the Air very vividly reflected, so that more Rays
were reflected to the eye by this surface, though the Ray in entring and
getting out of the Crystal had suffer'd a double refraction, than there
were from the outward surface of the Glass where the Ray had suffer'd no
reflection at all.

And that this was the surface of the Air that gave so vivid a
_re-percussion_ I try'd by this means I sunk half of a _stiria_ in Water,
so that only Water was contiguous to the under surface, and then the
internal reflection was so exceedingly faint, that it was scarce
discernable. Again, I try'd to alter this vivid reflection by keeping off
the Air, with a body not fluid, and that was by rubbing and holding my
finger very hard against the under surface, so as in many places the pulp
of my finger did touch the Glass, without any _interjacent_ air between,
then observing the reflection, I found, that wheresoever my finger or skin
toucht the surface, from that part there was no reflection, but in the
little furrows or creases of my skin, where there remain'd little small
lines of air, from them was return'd a very vivid reflection as before. I
try'd further, by making the surface of very pure Quicksilver to be
contiguous to the under surface of this _pellucid_ body, and then the
reflection from that was so exceedingly more vivid than from the air, as
the reflection from air was than the reflection from the Water; from all
which trials I plainly saw, that the strong reflecting air was the cause of
this _Phaenomenon_.

And this agrees very well with the _Hypothesis_ of light and _Pellucid_
bodies which I have mention'd in the description of _Muscovy-glass_; for we
there suppose Glass to be a _medium_, which does less resist the pulse of
light, and consequently, that most of the Rays incident on it enter into
it, and are refracted towards the _perpendicular_; whereas the air I
suppose to be a body that does more resist it, and consequently more are
_re-percuss'd_ then do enter it: the same kind of trials have I made, with
_Crystalline Glass_, with drops of fluid bodies, and several other ways,
which do all seem to agree very exactly with this _Theory_. So that from
this Principle well establish'd, we may deduce severall Corollaries not
unworthy observation.

And the first is; that it plainly appears by this, that the production of
the Rainbow is as much to be ascribed to the reflection of the concave
surface of the air, as to the refraction of the _Globular_ drops: this will
be evidently manifest by these Experiments, if you _foliate_ that part of a
Glass-ball that is to reflect an _Iris_, as in the _Cartesian_ Experiment,
above mention'd, the reflections will be abundantly more strong, and the
colours more vivid: and if that part of the surface be touch'd with Water,
scarce affords any sensible colour at all.

Next we learn, that the great reason why _pellucid_ bodies beaten small are
white, is from the multitude of reflections, not from the particles of the
body, but from the _contiguous_ surface of the air. And this is evidently
manifested, by filling the _Interstitia_ of those powder'd bodies with
Water, whereby their whiteness presently disappears. From the same reason
proceeds the whiteness of many kinds of Sands, which in the _Microscope_
appear to be made up of a multitude of little _pellucid_ bodies, whose
brightest reflections may by the _Microscope_ be plainly perceiv'd to come
from their internal surfaces; and much of the whiteness of it may be
destroy'd by the affusion of fair Water to be contiguous to those surfaces.

The whiteness also of froth, is for the most part to be ascribed to the
reflection of the light from the surface of the air within the Bubbles, and
very little to the reflection from the surface of the Water it self: for
this last reflection does not return a quarter so many Rays, as that which
is made from the surface of the air, as I have certainly found by a
multitude of Observations and Experiments.

The whiteness of _Linnen_, _Paper_, _Silk_, &c. proceeds much from the same
reason, as the _Microscope_ will easily discover; for the Paper is made up
of an abundance of _pellucid_ bodies, which afford a very plentifull
reflection from within, that is, from the concave surface of the air
contiguous to its component particles; wherefore by the affusion of Water,
Oyl, Tallow, Turpentine, &c. all those reflections are made more faint, and
the beams of light are suffer'd to traject & run through the Paper more
freely.

Hence further we may learn the reason of the whiteness of many bodies, and
by what means they maybe in part made _pellucid_: As white Marble for
instance, for this body is composed of a _pellucid_ body exceedingly
flaw'd, that is, there are abundance of thin, and very fine cracks or
chinks amongst the multitude of particles of the body, that contain in them
small parcels of air, which do so _re-percuss_ and drive back the
penetrating beams, that they cannot enter very deep within that body; which
the _Microscope_ does plainly inform us to be made up of a _Congeries_ of
_pellucid_ particles. And I further found it somewhat more evidently by
some attempts I made towards the making transparent Marble, for by heating
the Stone a little, and baking it in Oyl, Turpentine, Oyl of Turpentine,
&c., I found that I was able to see much deeper into the body of Marble
then before; and one trial, which was not with an unctuous substance,
succeeded better than the rest, of which, when I have a better opportunity,
I shall make further trial.

This also gives us a probable reason of the so much admired _Phaenomena_,
of the _Oculus Mundi_, an _Oval_ stone, which commonly looks like white
Alabaster, but being laid a certain time in Water, it grows _pellucid_, and
transparent, and being suffer'd to lie again dry, it by degrees loses that
transparency, and becomes white as before. For the Stone being of a hollow
spongie nature, has in the first and last of these appearances, all those
pores fill'd with the obtunding and reflecting air; whereas in the second,
all those pores are fill'd with a _medium_ that has much the same
refraction with the particles of the Stone, and therefore those two being
_contiguous_, make, as 'twere, one _continued medium_, of which more is
said in the 15. _Observation_.

There are a multitude of other _Phaenomena_, that are produc'd from this
same Principle, which as it has not been taken notice of by any yet that I
know, so I think, upon more diligent observation, will it not be found the
least considerable. But I have here onely time to hint _Hypotheses_, and
not to prosecute them so fully as I could wish; many of them having a vast
extent in the production of a multitude of _Phaenomena_, which have been by
others, either not attempted to be explain'd, or else attributed to some
other cause than what I have assign'd, and perhaps than the right; and
therefore I shall leave this to the prosecution of such as have more
leisure: onely before I leave it, I must not pretermit to hint, that by
this Principle, multitudes of the _Phaenomena_ of the air, as about
_Mists_, _Clouds_, _Meteors_, _Haloes_, &c. are most plainly and (perhaps)
truly explicable; multitudes also of the _Phaenomena_ in colour'd bodies,
as liquors, &c. are deducible from it.

And from this I shall proceed to a second considerable _Phaenomenon_ which
these Diamants exhibit, and that is the regularity of their _Figure_, which
is a propriety not less general than the former, It comprising within its
extent, all kinds of _Metals_, all kinds of _Minerals_, most _Precious
stones_, all kinds of _Salts_, multitudes of _Earths_, and almost all kinds
of _fluid bodies_. And this is another propiety, which, though a little
superficially taken notice of by some, has not, that I know, been so much
as attempted to be explicated by any.

This propriety of bodies, as I think it the most worthy, and next in order
to be consider'd after the contemplation of the _Globular Figure_, so have
I long had a desire as wel as a determination to have prosecuted it if I
had had an opportunity, having long since propos'd to my self the method of
my enquiry therein, it containing all the allurements that I think any
enquiry is capable of: For, first I take it to proceed from the most simple
principle that any kind of form can come from, next the _Globular_, which
was therefore the first I set upon, and what I have therein perform'd, I
leave the Judicious Reader to determine. For as that form proceeded from a
propiety of fluid bodies, which I have call'd _Congruity_, or
_Incongruity_; so I think, had I time and opportunity, I could make
probable, that all these regular Figures that are so conspicuously
_various_ and _curious_, and do so adorn and beautifie such multitudes of
bodies, as I have above hinted, arise onely from three or four several
positions or postures of _Globular_ particles, and those the most plain,
obvious, and necessary conjunctions of such figur'd particles that are
possible, so that supposing such and such plain and obvious causes
concurring the _coagulating particles_ must necessarily compose a body of
such a determinate regular Figure, and no other, and this with as much
necessity and obviousness as a fluid body encompast with a _Heterogeneous_
fluid must be protruded into a _Spherule_ or _Globe_. And this I have _ad
oculum_ demonstrated with a company of bullets, and some few other very
simple bodies; so that there was not any regular Figure, which I have
hitherto met withall, of any of those bodies that I have above named, that
I could not with the composition of bullets or globules, and one or two
other bodies, imitate, even almost by shaking them together. And thus for
instance may we find that the _Globular_ bullets will of themselves, if put
on an inclining plain, so that they may run together, naturally run into a
_triangular_ order, composing all the variety of figures that can be
imagin'd to be made out of _aequilateral triangles_; and such will you
find, upon trial, all the Surfaces of _Alum_ to be compos'd of: For three
bullets lying on a plain, as close to one another as they can compose an
_aequilatero-triangular_ form, as in A in the 7. _Scheme_. If a fourth be
joyn'd to them on either side as closely as it can, they four compose the
most regular Rhombus consisting of two _aequilateral triangles_, as B. If a
fifth be joyn'd to them on either side in as close a position as it can,
which is the propriety of the _Texture_, it makes a _Trapezium_, or
four-sided Figure, two of whole angles are 120. and two 60. degrees, as C.
If a sixth be added, as before, either it makes an _aequilateral triangle_,
as D, or a Rhomboeid, as E, or an _Hex-angular Figure_, as F, which is
compos'd of two _primary Rhombes_. If a seventh be added, it makes either
an _aequilatero-hexagonal_ Figure, as G, or some kind of six-sided
_Figure_, as H, or I. And though there be never so many placed together,
they may be rang'd into some of these lately mentioned Figures, all the
angles of which will be either _60_. degrees, or 120. as the figure K.
which is an _aequiangular hexagonal_ Figure is compounded of 12.
_Globules_, or may be of 25, or 27, or 36, or 42, &c. and by these kinds of
texture, or position of globular bodies, may you find out all the variety
of regular shapes, into which the smooth surfaces of _Alum_ are form'd, as
upon examination any one may easily find; nor does it hold only in
superficies, but in solidity also, for it's obvious that a fourth _Globule_
laid upon the third in this texture, composes a regular _Tetrahedron_,
which is a very usual Figure of the _Crystals_ of _Alum_. And (to hasten)
there is no one Figure into which _Alum_ is observ'd to be crystallized,
but may by this texture of _Globules_ be imitated, and by no other.

I could instance also in the Figure of _Sea-salt_, and _Sal-gem_, that it
is compos'd of a texture of _Globules_, placed in a _cubical_ form, as L,
and that all the Figures of those Salts may be imitated by this texture of
_Globules_ and by no other whatsoever. And that the forms of _Vitriol_ and
of _Salt-Peter_, as also of _Crystal_, _Hore-frost_, &c. are compounded of
these two textures, but modulated by certain proprieties: But I have not
here time to insist upon, as I have not neither to shew by what means
_Globules_ come to be thus context, and what those _Globules_ are, and many
other particulars requisite to a full and intelligible explication of this
propriety of bodies. Nor have I hitherto found indeed an opportunity of
prosecuting the inquiry so farr as I design'd; nor do I know when I may, it
requiring abundance of time, and a great deal of assistance to go through
with what I design'd; the model of which was this:

First, to get as exact and full a collection as I could, of all the
differing kinds of Geometrical figur'd bodies, some three or four several
bodies of each kind.

Secondly, with them to get as exact a History as possibly I could learn of
their places of Generation or finding, and to enquire after as many
circumstances that tended to the Illustrating of this Enquiry, as possibly
I could observe.

Thirdly, to make as many trials as upon experience I could find requisite,
in Dissolutions and Coagulations of several crystallizing Salts; for the
needfull instruction and information in this Enquiry.

Fourthly, to make several trials on divers other bodies, as Metals,
Minerals, and Stones, by dissolving them in several _Menstruums_, and
crystalizing them, to see what Figures would arise from those several
_Compositums_.

Fifthly, to make Compositions and Coagulations of several Salts together
into the same mass, to observe of what Figure the product of them would be;
and in all, to note as many circumstances as I should judge conducive to my
Enquiry.

Sixthly, to enquire the closeness or rarity of the texture of these bodies,
by examining their gravity, and their refraction, &c.

Seventhly, to enquire particularly what operations the fire has upon
several kinds of Salts, what changes it causes in their Figures, Textures,
or Energies.

Eighthly, to examine their manner of dissolution, or acting upon those
bodies dissoluble in them; The texture of those bodies before and after the
process. And this for the History.

Next for the Solution, To have examin'd by what, and how many means, such
and such Figures, actions and effects could be produc'd possibly.

And lastly, from all circumstances well weigh'd, I should have endeavoured
to have shewn which of them was most likely, and (if the informations by
these Enquiries would have born it) to have demonstrated which of them it
must be, and was.

But to proceed, As I believe it next to the Globular the most simple; so do
I, in the second place, judge it not less pleasant; for that which makes an
Enquiry pleasant, are, first a noble _Inventum_ that promises to crown the
successfull endeavour; and such must certainly the knowledge of the
efficient and concurrent causes of all these curious Geometrical Figures
be, which has made the Philosophers hitherto to conclude nature in these
things to play the Geometrician, according to that saying of _Plato_,
[Greek: Ho Theos geometrei]. Or next, a great variety of matter in the
Enquiry; and here we meet with nothing less than the _Mathematicks_ of
nature, having every day a new Figure to contemplate, or a variation of the
same in another body,

Which do afford us a third thing, which will yet more sweeten the Enquiry,
and that is, a multitude of information; we are not so much to grope in the
dark, as in most other Enquiries, where the _Inventum_ is great; for having
such a multitude of instances to compare, and such easie ways of
generating, or compounding and of destroying the form, as in the _Solution_
and _Crystallization_ of Salts, we cannot but learn plentifull information
to proceed by. And this will further appear from the universality of the
Principle which Nature has made use of almost in all inanimate bodies. And
therefore, as the contemplation of them all conduces to the knowledg of any
one; so from a Scientifical knowledge of any one does follow the fame of
all, and every one.

And fourthly, for the usefulness of this knowledge, when acquir'd;
certainly none can doubt, that considers that it caries us a step forward
into the Labirinth of Nature, in the right way towards the end we propose
our selves in all Philosophical Enquiries. So that knowing what is the form
of Inanimate or Mineral bodies, we shall be the better able to proceed in
our next Enquiry after the forms of Vegetative bodies; and last of all, of
Animate ones, that seeming to be the highest step of natural knowledge that
the mind of man is capable of.

       *       *       *       *       *


Observ. XIV. _Of several kindes of frozen _Figures_._

I have very often in a Morning, when there has been a great _hoar-frost_,
with an indifferently magnifying _Microscope_, observ'd the small
_Stiriae_, or Crystalline beard, which then usually covers the face of
most bodies that lie open to the cold air, and found them to be generally
_Hexangular prismatical_ bodies, much like the long Crystals of
_Salt-peter_, save onely that the ends of them were differing: for whereas
those of _Nitre_ are for the most part _pyramidal_, being terminated either
in a point or edge; these of Frost were hollow, and the cavity in some
seem'd pretty deep, and this cavity was the more plainly to be seen,
because usually one or other of the six _parallelogram_ sides was wanting,
or at least much shorter then the rest.

But this was onely the Figure of the _Bearded hoar-frost_; and as for the
particles of other kinds of _hoar-frosts_, they seem'd for the most part
irregular, or of no certain Figure. Nay, the parts of those curious
branchings, or _vortices_, that usually in cold weather tarnish the surface
of Glass, appear through the _Microscope_ very rude and unshapen, as do
most other kinds of frozen _Figures_, which to the naked eye seem exceeding
neat and curious, such as the Figures of _Snow_, frozen _Urine_, _Hail_,
several _Figures_ frozen in common Water, &c. Some Observations of each of
which I shall hereunto annex, because if well consider'd and examin'd, they
may, perhaps, prove very instructive for the finding out of what I have
endeavoured in the preceding Observation to shew, to be (next the _Globular
Figure_ which is caus'd by _congruity_, as I hope I have made probable in
the sixth _Observation_) the most simple and plain operation of Nature, of
which, notwithstanding we are yet ignorant.

I.

_Several Observables in the _six-branched_ Figures form'd on the surface of
Urine by freezing._

1 [11]The Figures were all frozen almost even with the surface of the
_Urine_ in the Vessel; but the bigger stems were a little _prominent_ above
that surface, and the parts of those stems which were nearest the center
(a) were biggest above the surface.

2 I have observ'd several kinds of these Figures, some smaller, no bigger
then a Two-pence, others so bigg, that I have by measure found one of its
stems or branches above four foot long; and of these, some were pretty
round, having all their branches pretty neer alike; other of them were more
extended towards one side, as usually those very large ones were, which I
have observ'd in Ditches which have been full of foul water.

3 None of all these Figures I have yet taken notice of, had any regular
position in respect of one another, or of the sides of the Vessel; nor did
I find any of them equally to exactness extended every way from the center
a.

4 Where ever there was a center, the branchings from it, ab, ac, ad, ae,
af, ag, were never fewer, or more then six, which usually concurr'd, or met
one another very neer in the same point or center, a; though oftentimes not
exactly; and were enclin'd to each other by an angle, of very near sixty
degrees, I say, very neer, because, though having endeavoured to measure
them the most acurately I was able, with the largest Compasses I had, I
could not find any sensible variation from that measure, yet the whole
six-branched Figure seeming to compose a solid angle, they must necessarily
be somewhat less.

5 The middle lines or stems of these branches, ab, ac, ad, ae, af, ag,
seem'd somewhat whiter, and a little higher then any of the _intermediate_
branchings of these Figures; and the center a, was the most _prominent_
part of the whole Figure, seeming the _apex_ of a solid angle or _pyramid_,
each of the six plains being a little enclin'd below the surface of the
_Urin_.

6 The lateral branchings issuing out of the great ones, such as op, mq, &c.
were each of them inclin'd to the great ones, by the same angle of about
sixty degrees, as the great ones were one to another, and always the bigger
branchings were _prominent_ above the less, and the less above the least,
by proportionate _gradations_.

7 The _lateral_ branches shooting out of the great ones, went all of them
from the center, and each of them was parallel to that great branch, next
to which it lay; so that as all the branches on one side were parallel to
one another, so were they all of them to the _approximate_ great branch, as
po, qr, as they were parallel to each other, and shot from the center, so
were they parallel also to the great branch ab.

8 Some of the stems of the six branches proceeded straight, and of a
thickness that gradually grew sharper towards the end, as ag.

9 Others of the stems of those branches grew bigger and knotty towards the
middle, and the branches also as well as stems, from Cylinders grew into
Plates, in a most admirable and curious order, so exceeding regular and
delicate, as nothing could be more, as is visible in ab, ac, ad, ae, af,
but towards the end of some of these stems, they began again to grow
smaller and to recover their former branchings, as about k and n.

10 Many of the _lateral_ branches had _collateral_ branches (if I may so
call them) as qm had many such as st, and most of those again
_subcollateral_, as vw, and these again had others less, which one may call
_laterosubcollateral_, and these again others, and they others, &c. in
greater Figures.

11 The branchings of the main Stems joyn'd not together by any regular
line, nor did one side of the one lie over the other side of the other, but
the small _collateral_ and _subcollateral_ branches did lie at top of one
another according to a certain order or method, which I always observ'd to
be this.

12 That side of a _collateral_ or _subcollateral_, &c. branch, lay over the
side of the _approximate_ (as the feathers in the wing of a Bird) whose
branchings proceeded parallel to the last biggest stem from which it
sprung, and not to the biggest stem of all, unless that were a second stem
backwards.

13 This rule that held in the branchings of the _Sexangular Figure_ held
also in the branchings of any other great or small stem, though it did not
proceed from a center.

14 The exactness and curiosity of the figuration of these branches, was in
every particular so transcendent, that I judge it almost impossible for
humane art to imitate.

15 Tasting several cleer pieces of this _Ice_, I could not find any
_Urinous_ taste in them, but those few I tasted, seem'd as _insipid_ as
water.

16 A figuration somewhat like this, though indeed in some particulars much
more curious, I have several times observ'd in _regulus martis stellatus_,
but with this difference, that all the stems and branchings are bended in a
most excellent and regular order, whereas in _Ice_ the stems and branchings
are streight, but in all other particulars it agrees with this, and seems
indeed nothing but one of these stars, or branched Figures frozen on
_Urine_, distorted, or wreathed a little, with a certain proportion: _Lead_
also that has _Arsenick_ and some other things mixt with it, I have found
to have its surface, when suffer'd to cool, figured somewhat like the
branchings of _Urine_, but much smaller.

17 But there is a _Vegetable_ which does exceedingly imitate these
branches, and that is, _Fearn_, where the main stem may be observ'd to
shoot out branches, and the stems of each of these _lateral_ branches, to
send forth _collateral_, and those _subcollateral_ and those
_laterosubcollateral,_ &c. and all those much after the same order with the
branchings, divisions, and subdivisions in the branchings of these Figures
in frozen _Urine_; so that if the Figures of both be well consider'd, one
would ghess that there were not much greater need of a _seminal principle_
for the production of _Fearn_, then for the production of the branches of
_Urine_, or the _Stella martis_, there seeming to be as much form and
beauty in the one as in the other.

And indeed, this Plant of _Fearn_, if all particulars be well consider'd,
will seem of as simple, and uncompounded a form as any _Vegetable_, next to
_Mould_ or _Mushromes_, and would next after the invention of the forms of
those, deserve to be enquir'd into; for notwithstanding several have
affirm'd it to have seed, and to be propagated thereby; yet, though I have
made very diligent enquiry after that particular, I cannot find that there
is any part of it that can be imagin'd to be more seminal then another: But
this onely here by the by:

For the freezing Figures in _Urine_, I found it requisite,

First, that the Superficies be not disturbed with any wind, or other
commotion of the air, or the like.

Secondly, that it be not too long exposed, so as that the whole bulk be
frozen, for oftentimes, in such cases, by reason of the swelling the of
_Ice_, or from some other cause, the curious branched Figures disappear.

Thirdly, an artificial freezing with _Snow_ and _Salt_, apply'd to the
outside of the containing Vessel, succeeds not well, unless there be a very
little quantity in the Vessel.

Fourthly, If you take any cleer and smooth Glass, and wetting all the
inside of it with _Urine_, you expose it to a very sharp freezing, you will
find it cover'd with a very regular and curious Figure.

II.

_Observables in figur'd _Snow_._

Exposing a piece of black Cloth, or a black Hatt to the falling _Snow_, I
have often with great pleasure, observ'd such an infinite variety of
curiously figur'd _Snow_, that it would be as impossible to draw the Figure
and shape of every one of them, as to imitate exactly the curious and
Geometrical _Mechanisme_ of Nature in any one. Some coorse draughts, such
as the coldness of the weather, and the ill provisions, I had by me for
such a purpose, would permit me to make, I have here added in the Second
_Figure_ of the Eighth _Scheme_.[12]

In all which I observ'd, that if they were of any regular Figures, they
were always branched out with six principal branches, all of equal length,
shape and make, from the center, being each of them inclin'd to either of
the next branches on either side of it, by an angle of sixty degrees.

Now, as all these stems were for the most part in one flake exactly of the
same make, so were they in differing Figures of very differing ones; so
that in a very little time I have observ'd above an hundred several cizes
and shapes of these starry flakes.

The branches also out of each stem of any one of these flakes, were exactly
alike in the same flake; so that of whatever Figure one of the branches
were, the other five were sure to be of the same, very exactly, that is, if
the branchings of the one were small _Perallelipipeds_ or Plates, the
branchings of the other five were of the same; and generally, the
branchings were very conformable to the rules and method observ'd before,
in the Figures on _Urine_, that is, the branchings from each side of the
stems were parallel to the next stem on that side, and if the stems were
plated, the branches also were the same; if the stems were very long, the
branches also were so, &c.

Observing some of these figur'd flakes with a _Microscope_, I found them
not to appear so curious and exactly figur'd as one would have imagin'd,
but like Artificial Figures, the bigger they were magnify'd, the more
irregularites appear'd in them; but this irregularity seem'd ascribable to
the thawing and breaking of the flake by the fall, and not at all to the
defect of the _plastick_ virtue of Nature, whose curiosity in the formation
of most of these kind of regular Figures, such as those of _Salt_,
_Minerals_, &c. appears by the help of the _Microscope_, to be very many
degrees smaller then the most acute eye is able to perceive without it. And
though one of these six-branched Stars appear'd here below much of the
shape described in the Third _Figure_ of the Eighth _Scheme_; yet I am very
apt to think, that could we have a sight of one of them through a
_Microscope_ as they are generated in the Clouds before their Figures are
vitiated by external accidents, they would exhibit abundance of curiosity
and neatness there also, though never so much magnify'd: For since I have
observ'd the Figures of _Salts_ and _Minerals_ to be some of them so
exceeding small, that I have scarcely been able to perceive them with the
_Microscope_, and yet have they been regular, and since (as far as I have
yet examin'd it) there seems to be but one and the same cause that produces
both these effects, I think it not irrational to suppose that these pretty
figur'd Stars of _Snow_, when at first generated might be also very regular
and exact.

III.

_Several kinds of Figures in _Water_ frozen._

Putting fair Water into a large capacious Vessel of _Glass_, and exposing
it to the cold, I observ'd after a little time, several broad, flat, and
thin _laminae_, or plates of _Ice_, crossing the bulk of the water and one
another very irregularly, onely most of them seem'd to turn one of their
edges towards that side of the Glass which was next it, and seem'd to grow,
as 'twere from the inside of the Vessel inwards towards the middle, almost
like so many blades of _Fern_. Having taken several of these plates out of
water on the blade of a Knife, I observ'd them figur'd much after the
manner of _Herring bones_, or _Fern blades_, that is, there was one bigger
stem in the middle like the back-bone, and out of it, on either side, were
a multitude of small _stiriae_, or _icicles_, like the smaller bones, or
the smaller branches in _Fern_, each of these branches on the one side,
were parallel to all the rest on the same side, and all of them seem'd to
make an angle with the stem, towards the top, of sixty degrees, and towards
the bottom or root of this stem, of 120. See the fourth _Figure_ of the 8.
_Plate_.

I observ'd likewise several very pretty Varieties of Figures in Water,
frozen on the top of a broad flat Marble-stone, expos'd to the cold with a
little Water on it, some like feathers, some of other shapes, many of them
were very much of the shape exprest in the fifth Figure of the 8. _Scheme_,
which is extremely differing from any of the other Figures.

I observ'd likewise, that the shootings of _Ice_ on the top of Water,
beginning to freez, were in streight _prismatical_ bodies much like those
of _roch-peter_, that they crost each other usually without any kind of
order or rule, that they were always a little higher then the surface of
the Water that lay between them; that by degrees those _interjacent_ spaces
would be fill'd with _Ice_ also, which usually would be as high as the
surface of the rest.

In flakes of _Ice_ that had been frozen on the top of Water to any
considerable thickness, I observ'd that both the upper and the under sides
of it were curiously quill'd, furrow'd, or grain'd, as it were, which when
the Sun shone on the Plate, was exceeding easily to be perceiv'd to be much
after the shape of the lines in the 6. _Figure_ of the 8. _Scheme_, that
is, they consisted of several streight ends of parallel Plates, which were
of divers lengths and angles to one another without any certain order.

The cause of all which regular Figures (and of hundreds of others, namely
of _Salts_, _Minerals_, _Metals,_ &c. which I could have here inserted,
would it not have been too long) seems to be deducible from the same
Principles, which I have (in the 13. _Observation_) hinted only, having not
yet had time to compleat a _Theory_ of them. But indeed (which I there also
hinted) I judge it the second step by which the _Pyramid_ of natural
knowledge (which is the knowledge of the form of bodies) is to be ascended:
And whosoever will climb it, must be well furnish'd with that which the
Noble _Verulam_ calls _Scalam Intellectus_; he must have scaling Ladders,
otherwise the steps are so large and high, there will be no getting up
them, and consequently little hopes of attaining any higher station, such
as to the knowledge of the most simple principle of Vegetation manifested
in Mould and Mushromes, which, as I elsewhere endeavoured to shew, seems to
be the third step; for it seems to me, that the Intellect of man is like
his body, destitute of wings, and cannot move from a lower to a higher and
more sublime station of knowledg, otherwise then step by step, nay even
there where the way is prepar'd and already made passible; as in the
_Elements of Geometry_, or the like, where it is fain to climb a whole
_series_ of Propositions by degrees, before it attains the knowledge of one
_Probleme_. But if the ascent be high, difficult and above its reach, it
must have recourse to a _novum organum_, some new engine and contrivance,
some new kind of _Algebra_, or _Analytick Art_ before it can surmount it.

       *       *       *       *       *


Observ. XV. _Of _Kettering-stone_, and of the pores of _Inanimate_ bodies._

[13]This Stone which is brought from _Kettering_ in _Northampton-Shire_,
and digg'd out of a Quarry, as I am inform'd, has a grain altogether
admirable, nor have I ever seen or heard of any other stone that has the
like. It is made up of an innumerable company of small bodies, not all of
the same cize or shape, but for the most part, not much differing from a
Globular form, nor exceed they one another in Diameter above three or four
times; they appear to the eye, like the Cobb or Ovary of a _Herring_, or
some smaller fishes, but for the most part, the particles seem somewhat
less, and not so uniform; but their variation from a perfect globular ball,
seems to be only by the pressure of the _contiguous_ bals which have a
little deprest and protruded those toucht sides inward, and forc'd the
other sides as much outwards beyond the limits of a Globe; just as it would
happen, if a heap of exactly round Balls of soft Clay were heaped upon one
another; or, as I have often seen a heap of small Globules of
_Quicksilver_, reduc'd to that form by rubbing it much in a glaz'd Vessel,
with some slimy or sluggish liquor, such as Spittle, when though the top of
the upper Globules be very neer spherical, yet those that are prest upon by
others, exactly imitate the forms of these lately mention'd grains.

Where these grains touch each other, they are so firmly united or settled
together, that they seldom part without breaking a hole in one or th'other
of them, such as a, a, a, b, c, c, &c. Some of which fractions, as a, a, a,
a, where the touch has been but light, break no more then the outward
crust, or first shell of the stone, which is of a white colour, a little
dash'd with a brownish Yellow, and is very thin, like the shell of an Egg:
and I have seen some of those grains perfectly resemble some kind of Eggs,
both in colour and shape: But where the union of the _contiguous granules_
has been more firm, there the divulsion has made a greater Chasm, as at b,
b, b, in so much that I have observ'd some of them quite broken in two, as
at c, c, c, which has discovered to me a further resemblance they have to
Eggs, they having an appearance of a white and yelk, by two differing
substances that envelope and encompass each other.

That which we may call the white was pretty whitish neer the yelk, but more
duskie towards the shell; some of them I could plainly perceive to be shot
or radiated like a _Pyrites_ or _fire-stone_; the yelk in some I saw
hollow, in others fill'd with a duskie brown and porous substance like a
kind of pith.

The small pores, or _interstitia_ eeee betwixt the Globules, I plainly saw,
and found by other trials to be every way pervious to air and water, for I
could blow through a piece of this stone of a considerable thickness, as
easily as I have blown through a Cane, which minded me of the pores which
_Des Cartes_ allow his _materia subtilis_ between the _aethereal_ globules.

The object, through the _Microscope_, appears like a _Congeries_ or heap of
Pibbles, such as I have often seen cast up on the shore, by the working of
the Sea after a great storm, or like (in shape, though not colour) a
company of small Globules of Quicksilver, look'd on with a _Microscope_,
when reduc'd into that form by the way lately mentioned. And perhaps, this
last may give some hint at the manner of the formation of the former: For
supposing some _Lapidescent_ substance to be generated, or some way brought
(either by some commixture of bodies in the Sea it self, or protruded in,
perhaps, out of some _subterraneous_ caverns) to the bottom of the Sea, and
there remaining in the form of a liquor like Quicksilver, _heterogeneous_
to the ambient _Saline_ fluid, it may by the working and tumblings of the
Sea to and fro be jumbled and comminuted into such Globules as may
afterwards be hardned into Flints, the lying of which one upon another,
when in the Sea, being not very hard, by reason of the weight of the
incompassing fluid, may cause the undermost to be a little, though not
much, varied from a globular Figure. But this only by the by.

After what manner this _Kettering-stone_ should be generated I cannot
learn, having never been there to view the place, and observe the
circumstances; but it seems to me from the structure of it to be generated
from some substance once more fluid, and afterwards by degrees growing
harder, almost after the same manner as I supposed the generation of Flints
to be made.

But whatever were the cause of its curious texture, we may learn this
information from it; that even in those things which we account vile, rude,
and coorse, Nature has not been wanting to shew abundance of curiosity and
excellent Mechanisme.

We may here find a Stone by help of a _Microscope_, to be made up of
abundance of small Balls, which do but just touch each other, and yet there
being so many contacts, they make a firm hard mass, or a Stone much harder
then Free-stone.

Next, though we can by a _Microscope_ discern so curious a shape in the
particles, yet to the naked eye there scarce appears any such thing; which
may afford us a good argument to think, that even in those bodies also,
whose _texture_ we are not able to discern, though help'd with
_Microscopes_, there may be yet _latent_ so curious a _Schematisme_, that
it may abundantly satisfie the curious searcher, who shall be so happy as
to find some way to discover it.

Next, we here find a Stone, though to the naked eye a very close one, yet
every way perforated with innumerable pores, which are nothing else but the
_interstitia_, between those multitudes of minute globular particles, that
compose the bulk it self, and these pores are not only discover'd by the
_Microscope_, but by this contrivance.

I took a pretty large piece of this stone, and covering it all over with
cement, save only at two opposite parts, I found my self able, by blowing
in at one end that was left open, to blow my spittle, with which I had wet
the other end, into abundance of bubbles, which argued these pores to be
open and pervious through the whole stone, which affords us a very pretty
instance of the porousness of some seemingly close bodies, of which kind I
shall anon have occasion to subjoyn many more, tending to prove the same
thing.

I must not here omit to take notice, that in this body there is not a
_vegetative_ faculty that should so contrive this structure for any
peculiar use of _vegetation_ or growth, whereas in the other instances of
vegetable porous bodies, there is an _anima_ or _forma informans_, that
does contrive all the Structures and _Mechanismes_ of the constituting
body, to make them subservient and usefull to the great Work or Function
they are to perform. And so I ghess the pores in Wood, and other
vegetables, in bones, and other Animal substances, to be as so many
channels, provided by the Great and Alwise Creator, for the conveyance of
appropriated juyces to particular parts. And therefore, that this may tend,
or be pervious all towards one part, and may have impediments, as valves or
the like, to any other; but in this body we have very little reason so
suspect there should be any such design, for it is equally pervious every
way, not onely forward, but backwards, and side-ways, and seems indeed much
rather to be _Homogeneous_ or similar to those pores, which we may with
great probability believe to be the channels of _pellucid_ bodies, not
directed, or more open any one way, then any other, being equally pervious
every way. And, according as these pores are more or greater in respect of
the _interstitial_ bodies, the more transparent are the so constituted
concretes; and the smaller those pores are, the weaker is the _Impulse_ of
light communicated through them, though the more quick be the progress.

Upon this Occasion, I hope it will not be altogether unseasonable, if I
propound my conjectures and _Hypothesis_ about the _medium_ and conveyance
of light.

I suppose then, that the greatest part of the _Interstitia_ of the world,
that lies between the bodies of the Sun and Starrs, and the Planets, and
the Earth, to be an exceeding fluid body, very apt and ready to be mov'd,
and to communicate the motion of any one part to any other part, though
never so far distant: Nor do I much concern my self, to determine what the
Figure of the particles of this exceedingly subtile fluid _medium_ must be,
nor whether it have any interstitiated pores or vacuities, it being
sufficient to solve all the _Phaenomena_ to suppose it an exceedingly
fluid, or the most fluid body in the world, and as yet impossible to
determine the other difficulties.

That being so exceeding fluid a body, it easily gives passage to all other
bodies to move to and fro in it.

That it neither receives from any of its parts, or from other bodies; nor
communicates to any of its parts, or to any other body, any impulse, or
motion in a direct line, that is not of a determinate quickness. And that
when the motion is of such determinate swiftness, it both receives, and
communicates, or propagates an impulse or motion to any imaginable distance
in streight lines, with an unimaginable celerity and vigour.

That all kind of solid bodies consist of pretty massie particles in respect
of the particles of this fluid _medium_, which in many places do so touch
each other, that none of this fluid _medium_ interposes much after the same
mannner (to use a gross similitude) as a heap of great stones compose one
great _congeries_ or mass in the midst of the water.

That all fluid bodies which we may call _tangible_, are nothing but some
more subtile parts of those particles, that serve to constitute all
_tangible_ bodies.

That the water, and such other fluid bodies, are nothing but a _congeries_
of particles agitated or made fluid by it in the same manner as the
particles of _Salt_ are agitated or made fluid by a parcel of water, in
which they are dissolv'd, and subsiding to the bottom of it, constitute a
fluid body, much more massie and dense, and less fluid then the pure water
it self.

That the air on the other side is a certain company of particles of quite
another kind, that is, such as are very much smaller, and more easiely
moveable by the motion of this fluid _medium_; much like those very subtile
parts of _Cochenel_, other very deep tinging bodies, where by a very small
parcel of matter is able to tinge and diffuse it self over a very great
quantity of the fluid dissolvent; or somewhat after that manner, as smoak,
and such like minute bodies, or steams, are observ'd to tinge a very great
quantity of air; onely this last similitude is deficient in one propriety,
and that is a perpetuity or continuance in that state of commixture with
the air, but the former does more neerly approach to the nature and manner
of the air's being dissolv'd by this fluid or _AEther_. And this Similitude
will further hold in these proprieties; that as those tinctures may be
increased by certain bodies, so may they be precipitated by others, as I
shall afterwards shew it to be very probable, that the like accidents
happen even to the Air it self.

Further, as these solutions and tinctures do alter the nature of these
fluid bodies, as to their aptness to propagate a motion or impulse through
them, even so does the particles of the Air, Water, and other fluid bodies,
and of Glass, Crystal, &c. which are commixt with this bulk of the _AEther_
alter the motion of the propagated pulse of light; that is, where these
more bulkie particles are more plentifull, and consequently a lesser
quantity of the _AEther_ between them to be mov'd, there the motion must
necessarily be the swifter, though not so robust, which will produce those
effects, which I have (I hope) with some probability, ascribed to it in the
digression about Colours, at the end of the _Observations_ on
_Muscovy-glass._

Now, that other Stones, and those which have the closest and hardest
textures, and seem (as far as we are able to discover with our eyes, though
help'd with the best _Microscopes_) freest from pores, are yet
notwithstanding replenish'd with them, an Instance or two will, I suppose,
make more probable.

A very solid and unflaw'd piece of cleer white _Marble_, if it be well
polish'd and glaz'd, has so curiously smooth a surface, that the best and
most polish'd surface of any wrought-glass, seems not to the naked eye, nor
through a _Microscope_, to be more smooth, and less porous. And yet, that
this hard close body is replenish'd with abundance of pores, I think these
following Experiments will sufficiently prove.

The first is, That if you take such a piece, and for a pretty while boyl it
in Turpentine and Oyl of Turpentine, you shall find that the stone will be
all imbu'd with it; and whereas before it look'd more white, but more
opacous, now it will look more greasie, but be much more transparent, and
if you let it lie but a little while, and then break off a part of it, you
shall find the unctuous body to have penetrated it to such a determinate
depth every way within the surface. This may be yet easier try'd with a
piece of the same _Marble_, a little warm'd in the fire, and then a little
Pitch or Tarr melted on the top of it; for these black bodies, by their
insinuating themselves into the invisible pores of the stone, ting it with
so black a hue, that there can be no further doubt of the truth of this
assertion, that it abounds with small imperceptible pores.

Now, that other bodies will also sink into the pores of _Marble_, besides
unctuous, I have try'd, and found, that a very Blue tincture made in
_spirit of Urine_ would very readily and easily sink into it, as would also
several tinctures drawn with _spirit of Wine_.

Nor is _Marble_ the only seemingly close stone, which by other kinds of
Experiments may be found porous; for I have by this kind of Experiment on
divers other stones found much the same effect, and in some, indeed much
more notable. Other stones I have found so porous, that with the
_Microscope_ I could perceive several small winding holes, much like
Worm-holes, as I have noted in some kind of _Purbeck-stone_, by looking on
the surface of a piece newly flaw'd off, for if otherwise, the surface has
been long expos'd to the Air, or has been scraped with any tool, those
small caverns are fill'd with dust, and disappear.

And to confirm this _Conjecture_, yet further, I shall here insert an
excellent account, given into the _Royal Society_ by that Eminently Learned
Physician, Doctor _Goddard_, of an Experiment, not less instructive then
curious and accurate, made by himself on a very hard and seemingly close
stone call'd _Oculus Mundi_, as I find it preserv'd in the Records of that
Honourable Society.

    A small stone of the kind, call'd by some Authours, _Oculus Mundi_,
    being dry and cloudy, weigh'd 5-209/256 _Grains_.

    The same put under water for a night, and somewhat more, became
    transparent, and the superficies being wiped dry, weighed 6-3/256
    _Grains_.

    The difference between these two weights, 0-50/256 of a _Grain_.

    The same Stone kept out of water one Day and becoming cloudy again
    weighed, 5-225/256 _Graines_.

    Which was more then the first weight, 0-16/256 of a _Grain_.

    The same being kept two Days longer weighed, 5-202/256 _Graines_.

    Which was less then at first, 0-7/256 a _Grain_.

    Being kept dry something longer it did not grow sensibly lighter.

    Being put under water for a night and becoming again transparent and
    wiped dry, the weight was, _6-3/256 Grains_, the same with the first
    after putting in water, and more then the last weight after keeping of
    it dry, 0-57/256 of a _Grain_.

    Another Stone of the same kind being variegated with milky _white_ and
    _gray_ like some sorts of _Agates_, while it lay under water, was
    alwaies invironed with little Bubbles, such as appear in water a little
    before boyling, next the sides of the Vessel.

    There were also some the like Bubbles on the Surface of the water just
    over it, as if either some exhalations came out of it, or that it did
    excite some fermentation in the parts of the water contiguous to it.

    There was little sensible difference in the transparency of this Stone,
    before the putting under water, and after: To be sure the milky-_white_
    parts continued as before, but more difference in weight then in the
    former. For whereas before the putting into the water the weight was
    18-97/128 _Graines_. After it had lyen in about four and twenty hours
    the weight was 20-27/128 _Graines_, so the difference was, 1-58/128
    _Graines_.

    The same Stone was infused in the water scalding hot, and so continued
    for a while after it was cold, but got no more weight then upon
    infusing in the cold, neither was there any sensible Difference in the
    weight both times.

In which Experiment, there are three Observables that seem very manifestly
to prove the porousness of these seemingly close bodies: the first is their
acquiring a transparency, and losing their whiteness after steeping in
water, which will seem the more strongly to argue it, if what I have
already said about the making transparent, or clarifying of some bodies, as
the white powder of beaten Glass, and the froth of some glutinous
transparent liquor be well consider'd; for thereby it will seem rational to
think that this transparency arises from the insinuation of the water
(which has much the same refraction with such stony particles, as may be
discover'd by Sand view'd with a _Microscope_) into those pores which were
formerly repleat with air (that has a very differing refraction, and
consequently is very reflective) which seems to be confirm'd by the second
Observable, namely, the increase of weight after keeping, and decrease upon
drying. And thirdly, seem'd yet more sensibly confirm'd by the multitude of
bubbles in the last Experiment.

We find also most Acid Salts very readily to dissolve and separate the
parts of this body one from another; which is yet a further Argument to
confirm the porousness of bodies, and will serve as such, to shew that even
Glass also has an abundance of pores in it, since there are several
liquors, that with long staying in a Glass, will so _Corrode_ and eat into
it, as at last, to make it pervious to the liquor it contain'd, of which I
have seen very many Instances.

Since therefore we find by other proofs, that many of those bodies which we
think the most solid ones, and appear so to our sight, have notwithstanding
abundance of those grosser kind of pores, which will admit several kinds of
liquors into them, why should we not believe that Glass, and all other
transparent bodies abound with them, since we have many other arguments,
besides the propagation of light, which seem to argue for it?

And whereas it may be objected, that the propagation of light is no
argument that there are those atomical pores in glass, since there are
_Hypotheses_ plausible enough to solve those _Phaenomena_, by supposing the
pulse onely to be communicated through the transparent body.

To this I answer, that that _Hypothesis_ which the industrious _Mersennus_
has publish'd about the slower motion of the end of a Ray in a denser
_medium_, then in a more rare and thin, seems altogether unsufficient to
solve abundance of _Phaenomena_, of which this is not the least
considerable, that it is impossible from that supposition, that any colours
should be generated from the refraction of the Rays; for since by that
_Hypothesis_ the _undulating pulse_ is always carried perpendicular, or at
right angles with the Ray or Line of direction, it follows, that the stroke
of the pulse of light, after it has been once or twice refracted (through a
Prisme, for example) must affect the eye with the same kind of stroke as if
it had not been refracted at all. Nor will it be enough for a Defendant of
that _Hypothesis_, to say, that perhaps it is because the refractions have
made the Rays more weak, for if so, then two refractions in the two
parallel sides of a _Quadrangular Prisme_ would produce colours, but we
have no such _Phaenomena_ produc'd.

There are several Arguments that I could bring to evince that there are in
all transparent bodies such atomical pores. And that there is such a fluid
body as I am arguing for, which is the _medium_, or Instrument, by which
the pulse of Light is convey'd from the _lucid body_ to the enlightn'd. But
that it being a digression from the Observations I was recording, about the
Pores of _Kettering Stone_, it would be too much such, if I should protract
it too long; and therefore I shall proceed to the next _Observation_.

       *       *       *       *       *


Observ. XVI. _Of _Charcoal_, or burnt _Vegetables_._

Charcoal, or a Vegetable burnt black, affords an object no less pleasant
than instructive, for if you take a small round Charcoal, and break it
short with your fingers, you may perceive it to break with a very smooth
and sleek surface, almost like the surface of black sealing Wax; this
surface, if it be look'd on with an ordinary _Microscope_, does manifest
abundance of those pores which are also visible to the eye in many kinds of
_Wood_, rang'd round the pith, both a in kind of circular order, and a
radiant one. Of these there are a multitude in the substance of the Coal,
every where almost perforating and drilling it from end to end; by means of
which, be the Coal never so long, you may easily blow through it; and this
you may presently find, by wetting one end of it with Spittle, and blowing
at the other.

But this is not all, for besides those many great and conspicuous irregular
spots or pores, if a better _Microscope_ be made use of, there will appear
an infinite company of exceedingly small, and very regular pores, so thick
and so orderly set, and so close to one another, that they leave very
little room or space between them to be fill'd with a solid body, for the
apparent _interstitia_ or separating sides of these pores seem so thin in
some places, that the texture of a Honey-comb cannot be more porous. Though
this be not every where so, the intercurrent partitions in some places
being very much thicker in proportion to the holes.

Most of these small pores seem'd to be pretty round, and were rang'd in
rows that radiated from the pith to the bark; they all of them seem'd to be
continued open pores, running the whole length of the Stick; and that they
were all perforated, I try'd by breaking off a very thin sliver of the Coal
cross-ways, and then with my _Microscope_, diligently surveying them
against the light, for by that means I was able to see quite through them.

These pores were so exceeding small and thick, that in a line of them, 1/18
part of an Inch long, I found by numbring them no less then 150. small
pores; and therefore in a line of them an Inch long, must be no less then
2700. pores, and in a circular _area_ of an Inch diameter, must be about
5725350. of the like pores; so that a Stick of an Inch Diameter, may
containe no less then seven hundred and twenty five thousand, besides 5
Millions of pores, which would, I doubt not, seem even incredible, were not
every one left to believe his own eyes. Nay, having since examin'd _Cocus,
black and green Ebony, Lignum Vitae_, &c. I found, that all these Woods
have their pores, abundantly smaller then those of soft light Wood; in so
much, that those of _Guajacum_ seem'd not above an eighth part of the
bigness of the pores of Beech, but then the _Interstitia_ were thicker; so
prodigiously curious are the contrivances, pipes, or sluces by which the
_Succus nutritius_, or Juyce of a Vegetable is convey'd from place to
place.

This _Observation_ seems to afford us the true reason of several
_Phaenomena_ of Coals; as

First, why they look black; and for this we need go no further then the
_Scheme_, for certainly, a body that has so many pores in it as this is
discover'd to have, from each of which no light is reflected, must
necessarily look black, especially, when the pores are somewhat bigger in
proportion to the intervals then they are cut in the _Scheme_, black being
nothing else but a privation of Light, or a want of reflection; and
wheresover this reflecting quality is deficient, there does that part look
black, whether it be from a porousness of the body, as in this Instance, or
in a deadning and dulling quality, such as I have observ'd in the _Scoria_
of Lead, Tin, Silver, Copper, &c.

Next, we may also as plainly see the reason of its shining quality, and
that is from the even breaking off of the stick, the solid _interstitia_
having a regular termination or surface, and having a pretty strong
reflecting quality, the many small reflections become united to the naked
eye, and make a very pretty shining surface.

Thirdly, the reason of its hardness and brittleness seems evident, for
since all the watery or liquid substance that moistn'd and toughn'd those
_Interstitia_ of the more solid parts, are evaporated and remov'd, that
which is left behind becomes of the nature almost of a stone, which will
not at all, or very little, bend without a _divulsion_ or _solution_ of its
_continuity_.

It is not my design at present, to examine the use and _Mechanisme_ of
these parts of Wood, that being more proper to another Enquiry; but rather
to hint, that from this Experiment we may learn,

First, what is the cause of the blackness of many burnt bodies, which we
may find to be nothing else but this; that the heat of the fire agitating
and rarifying the waterish, transparent, and volatile water that is
contain'd in them, by the continuation of that action, does so totally
expel and drive away all that which before fill'd the pores, and was
dispers'd also through the solid mass of it, and thereby caus'd an
universal kind of transparency, that it not onely leaves all the pores
empty, but all the _Interstitia_ also so dry and _opacous_, and perhaps
also yet further perforated, that that light onely is reflected back which
falls upon the very outward edges of the pores, all they that enter into
the pores of the body, never returning, but being lost in it.

Now, that the Charring or coaling of a body is nothing else, may be easily
believ'd by one that shall consider the means of its production, which may
be done after this, or any such manner. The body to be charr'd or coal'd,
may be put into a _Crucible_, Pot, or any other Vessel that will endure to
be made red-hot in the fire without breaking, and then cover'd over with
Sand, so as no part of it be suffer'd to be open to the Air, then set into
a good fire, and there kept till the Sand has continu'd red hot for a
quarter, half, an hour or two, or more, according to the nature and bigness
of the body to be coal'd or charr'd, then taking it out of the fire, and
letting it stand till it be quite cold, the body may be taken out of the
Sand well charr'd and cleans'd of its waterish parts; but in the taking of
it out, care must be had that the Sand be very neer cold, for else, when it
comes into the free air, it will take fire, and readily burn away.

This maybe done also in any close Vessel of Glass, as a _Retort_, or the
like, and the several fluid substances that come over may be receiv'd in a
fit _Recipient_, which will yet further countenance this _Hypothesis_: And
their manner of charring Wood in great quantity comes much to the same
thing, namely, an application of a great heat to the body, and preserving
it from the free access of the devouring air; this may be easily learn'd
from the History of Charring of Coal, most excellently describ'd and
publish'd by that most accomplish'd Gentleman, Mr. _John Evelin_, in the
100, 101, 103, pages of his _Sylva_, to which I shall therefore refer the
curious Reader that desires a full information of it.

Next, we may learn what part of the Wood it is that is the _combustible_
matter, for since we shall find that none, or very little of those fluid
substances that are driven over into the Receiver are _combustible_, and
that most of that which is left behind is so, it follows, that the solid
_interstitia_ of the Wood are the _combustible_ matter. Further, the reason
why uncharr'd Wood burns with a greater flame then that which is charr'd,
is as evident, because those waterish or volatil parts issuing out of the
fired Wood, every way, not onely shatter and open the body, the better for
the fire to enter, but issuing out in vapours or wind, they become like so
many little _aeolipiles_, or Bellows, whereby they blow and agitate the
fir'd part, and conduce to the more speedy and violent consumption or
dissolution of the body.

Thirdly, from the Experiment of charring of Coals (whereby we see that
notwithstanding the great heat, and the duration of it, the solid parts of
the Wood remain, whilest they are preserv'd from the free access of the air
undissipated) we may learn, that which has not, that I know of, been
publish'd or hinted, nay, not so much as thought of, by any; and that in
short is this.

First, _that the Air_ in which we live, move, and breath, and which
encompasses very many, and cherishes most bodies it encompasses, that this
Air is the _menstruum_, or universal dissolvent of all _Sulphureous_
bodies.

Secondly, _that this action_ it performs not, till the body be first
sufficiently heated, as we find requisite also to the dissolution of many
other bodies by several other _menstruums_.

Thirdly, _that this action_ of dissolution, produces or generates a very
great heat, and that which we call Fire; and this is common also to many
dissolutions of other bodies, made by _menstruums_, of which I could give
multitudes of Instances.

Fourthly, _that this action_ is perform'd with so great a violence, and
does so minutely act, and rapidly agitate the smallest parts of the
_combustible_ matter, that it produces in the _diaphanous medium_ of the
Air, the action or pulse of light, which what it is, I have else-where
already shewn.

Fifthly, _that the dissolution_ of sulphureous bodies is made by a
substance inherent, and mixt with the Air, that is like, if not the very
same, with that which is fixt in _Salt-peter_, which by multitudes of
Experiments that may be made with _Saltpeter_, will, I think, most
evidently be demonstrated.

Sixthly, _that in this dissolution_ of bodies by the Air, a certain part is
united and mixt, or dissolv'd and turn'd into the Air, and made to fly up
and down with it in the same manner as a _metalline_ or other body
dissolved into any _menstruums_, does follow the motions and progresses of
that _menstruum_ till it be precipitated.

Seventhly, That as there is one part that is dissoluble by the Air, so are
there other parts with which the parts of the Air mixing and uniting, do
make a _Coagulum_, or _precipitation_, as one may call it, which causes it
to be separated from the Air, but this _precipitate_ is so light, and in so
small and rarify'd or porous clusters, that it is very volatil, and is
easily carry'd up by the motion of the Air, though afterwards, when the
heat and agitation that kept it rarify'd ceases, it easily condenses, and
commixt with other indissoluble parts, it sticks and adheres to the next
bodies it meets withall; and this is a certain _Salt_ that may be extracted
out of _Soot_.

Eighthly, that many indissoluble parts being very apt and prompt to be
rarify'd, and so, whilest they continue in that heat and agitation, are
lighter then the Ambient Air, are thereby thrust and carry'd upwards with
great violence, and by that means carry along with them, not onely that
_Saline concrete_ I mention'd before, but many terrestrial, or indissoluble
and irrarefiable parts, nay, many parts also which are dissoluble, but are
not suffer'd to stay long enough in a sufficient heat to make them prompt
and apt for that action. And therefore we find in _Soot_, not onely a part,
that being continued longer in a competent heat, will be dissolv'd by the
Air, or take fire and burn; but a part also which is fixt, terrestrial, and
irrarefiable.

Ninthly, that as there are these several parts that will rarifie and fly,
or be driven up by the heat, so are there many others, that as they are
indissoluble by the _aerial menstruum_, so are they of such sluggish and
gross parts, that they are not easily rarify'd by heat, and therefore
cannot be rais'd by it; the volatility or fixtness of a body seeming to
consist only in this, that the one is of a texture, or has component parts
that will be easily rarify'd into the form of Air, and the other, that it
has such as will not, without much ado, be brought to such a constitution;
and this is that part which remains behind in a white body call'd Ashes,
which contains a substance, or _Salt_, which Chymists call _Alkali_: what
the particular natures of each of these bodies are, I shall not here
examine, intending it in another place, but shall rather add that this
_Hypothesis_ does so exactly agree with all _Phaenomena_, of Fire, and so
genuinely explicate each particular circumstance that I have hitherto
observ'd, that it is more then probable, that this cause which I have
assign'd is the true adequate, real, and onely cause of those _Phaenomena_;
And therefore I shall proceed a little further, to shew the nature and use
of the Air.

Tenthly, therefore the dissolving parts of the Air are but few, that is, it
seems of the nature of those _Saline menstruums_, or spirits, that have
very much flegme mixt with the spirits, and therefore a small parcel of it
is quickly glutted, and will dissolve no more; and therefore unless some
fresh part of this _menstruum_ be apply'd to the body to be dissolv'd, the
action ceases, and the body leaves to be dissolv'd and to shine, which is
the Indication of it, though plac'd or kept in the greatest heat; whereas
_Salt-peter_ is a _menstruum_, when melted and red-hot, that abounds more
with those Dissolvent particles, and therefore as a small quantity of it
will dissolve a great sulphureous body, so will the dissolution be very
quick and violent.

Therefore in the _Eleventh_ place, it is observable, that, as in other
solutions, if a copious and quick supply of fresh _menstruum_, though but
weak, be poured on, or applied to the dissoluble body, it quickly consumes
it: So this _menstruum_ of the Air, if by Bellows, or any other such
contrivance, it be copiously apply'd to the shining body, is found to
dissolve it as soon, and as violently as the more strong _menstruum_ of
melted _Nitre_.

Therefore twelfthly, it seems reasonable to think that there is no such
thing as an Element of Fire that should attract or draw up the flame, or
towards which the flame should endeavour to ascend out of a desire or
appetite of uniting with that as its _Homogeneal_ primitive and generating
Element; but that that shining transient body which we call _Flame_, is
nothing else but a mixture of Air, and volatil sulphureous parts of
dissoluble or combustible bodies, which are acting upon each other whilst
they ascend, that is, flame seems to be a mixture of Air, and the
combustible volatil parts of any body, which parts the encompassing Air
does dissolve or work upon, which action, as it does intend the heat of the
_aerial_ parts of the dissolvent, so does it thereby further rarifie those
parts that are acting, or that are very neer them, whereby they growing
much lighter then the heavie parts of that _menstruum_ that are more
remote, are thereby protruded and driven upward; and this may be easily
observ'd also in dissolution made by any other _menstruum_, especially such
as either create heat or bubbles. Now, this action of the _menstruum_, or
_Air_, on the dissoluble parts, is made with such violence, or is such,
that it imparts such a motion or pulse to the _diaphanous_ parts of the
Air, as I have elsewhere shewn is requisite to produce light.

This _Hypothesis_ I have endeavoured to raise from an Infinite of
Observations and Experiments, the process of which would be much too long
to be here inserted, and will perhaps another time afford matter copious
enough for a much larger Discourse, the Air being a Subject which (though
all the world has hitherto liv'd and breath'd in, and been unconversant
about) has yet been so little truly examin'd or explain'd, that a diligent
enquirer will be able to find but very little information from what has
been (till of late) written of it: But being once well understood, it will,
I doubt not, inable a man to render an intelligible, nay probable, if not
the true reason of all the _Phaenomena_ of Fire, which, as it has been
found by Writers and Philosophers of all Ages a matter of no small
difficulty, as may be sufficiently understood by their strange
_Hypotheses_, and unintelligible Solutions of some few _Phaenomena_ of it;
so will it prove a matter of no small concern and use in humane affairs, as
I shall elsewhere endeavour to manifest when I come to shew the use of the
Air in respiration, and for the preservation of the life, nay, for the
conservation and restauration of the health and natural constitution of
mankind as well as all other aereal _animals_, as also the uses of this
principle or propriety of the Air in chymical, mechanical, and other
operations. In this place I have onely time to hint an _Hypothesis_, which,
if God permit me life and opportunity, I may elsewhere prosecute, improve
and publish. In the mean time, before I finish this Discourse, I must not
forget to acquaint the Reader, that having had the liberty granted me of
making some trials on a piece of _Lignum fossile_ shewn to the Royal
Society, by the eminently Ingenious and Learned Physician, Doctor _Ent_,
who receiv'd it for a Present from the famous _Ingenioso Cavalliero de
Pozzi_, it being one of the fairest and best pieces of _Lignum fossile_ he
had seen; Having (I say) taken a small piece of this Wood, and examin'd it,
I found it to burn in the open Air almost like other Wood, and insteed of a
resinous smoak or fume, it yielded a very bituminous one, smelling much of
that kind of sent: But that which I chiefly took notice of, was, that
cutting off a small piece of it, about the bigness of my Thumb, and
charring it in a _Crucible_ with Sand, after the manner I above prescrib'd,
I found it infinitely to abound with the smaller sort of pores, so
extreamly thick, and so regularly perforating the substance of it
long-ways, that breaking it off a-cross, I found it to look very like an
Honey-comb; but as for any of the second, or bigger kind of pores, I could
not find that it had any; so that it seems, whatever were the cause of its
production, it was not without those small kind of pores which we have
onely hitherto found in Vegetable bodies: and comparing them with the pores
which I have found in the Charcoals that I by this means made of several
other kinds of Wood, I find it resemble none so much as those of Fire, to
which it is not much unlike in grain also, and several other proprieties.

And therefore, what ever is by some, who have written of it, and
particularly by _Francisco Stelluto_, wrote a Treatise in _Italian_ of that
Subject, which was Printed at _Rome_, 1637, affirm'd that it is a certain
kind of Clay or Earth, which in tract of time is turn'd into Wood; I rather
suspect the quite contrary, that it was at first certain great Trees of Fir
or Pine, which by some Earthquake, or other casualty, came to be buried
under the Earth, and was there, after a long time's residence (according to
the several natures of the encompassing adjacent parts) either rotted and
turn'd into a kind of Clay, or _petrify'd_ and turn'd into a kind of Stone,
or else had its pores fill'd with certain Mineral juices, which being
stay'd in them, and in tract of time coagulated, appear'd, upon cleaving
out, like small Metaline Wires, or else from some flames or scorching forms
that are the occasion oftentimes, and usually accompany Earthquakes, might
be blasted and turn'd into Coal, or else from certain _subterraneous_ fires
which are affirm'd by that Authour to abound much about those parts
(namely, in a Province of _Italy_, call'd _Umbria_, now the _Dutchie_ of
_Spoletto_, in the Territory of _Todi_, anciently call'd _Tudor_; and
between the two Villages of _Collesecco_ and _Rosaro_ not far distant from
the high-way leading to _Rome_, where it is found in greater quantity then
elsewhere) are by reason of their being encompassed with Earth, and so kept
close from the dissolving Air, charr'd and converted into Coal. It would be
too long a work to describe the several kinds of pores which I met withall,
and by this means discovered in several other Vegetable bodies; nor is it
my present design to expatiate upon Instances of the same kind, but rather
to give a Specimen of as many kinds as I have had opportunity as yet of
observing, reserving the prosecution and enlarging on particulars till a
more fit opportunity; and in prosecution of this design, I shall here add:

       *       *       *       *       *


Observ. XVII. _Of _Petrify'd wood_, and other _Petrify'd bodies_._

Of this sort of substance, I observ'd several pieces of very differing
kinds, both for their outward shape, colour, grain, _texture_, hardness,
&c. some being brown and redish; others gray, like a Hone; others black,
and Flint-like: some soft, like a Slate or Whetstone, others as hard as a
Flint, and as brittle. That which I more particular examin'd, was a piece
about the bigness of a mans hand, which seem'd to have been a part of some
large tree, that by rottenness had been broken off from it before it began
to be _petrify'd_.

And indeed, all that I have yet seen, seem to have been rotten Wood before
the petrifaction was begun; and not long since, examining and viewing a
huge great _Oak_, that seem'd with meer age to be rotten as it stood, I was
very much confirm'd in this opinion; for I found, that the grain, colour,
and shape of the Wood, was exactly like this _petrify'd_ substance; and
with a _Microscope_, I found, that all those _Microscopical_ pores, which
in sappy or firm and sound Wood are fill'd with the natural or innate
juices of those Vegetables, in this they were all empty, like those of
_Vegetables charr'd_; but with this difference, that they seem'd much
larger then I have seen any in _Char-coals_; nay, even then those of Coals
made of great blocks of Timber, which are commonly call'd _Old-coals_.

The reason of which difference may probably be, that the charring of
Vegetables, being an operation quickly perform'd, and whilest the Wood is
sappy, the more solid parts may more easily shrink together, and contract
the pores or _interstitia_ between them, then in the rotten Wood, where
that natural juice seems onely to be wash'd away by _adventitious_ or
unnatural moisture; and so though the natural juice be wasted from between
the firm parts, yet those parts are kept asunder by the _adventitious_
moystures, and so by degrees settled in those postures.

And this I likewise found in the _petrify'd_ Wood, that the pores were
somewat bigger then those of _Charcoal_, each pore being neer upon half as
bigg again, but they did not bear that disproportion which is exprest in
the tenth _Scheme_, between the small specks or pores in the first Figure
(which representeth the pores of Coal or Wood charr'd) and the black spots
of the second Figure (which represent the like _Microscopical pores_ in the
_petrify'd_ Wood) for these last were drawn by a _Microscope_ that
magnify'd the object above six times more in Diameter then the _Microscope_
by which those pores of Coal were observ'd.

Now, though they were a little bigger, yet did they keep the exact figure
and order of the pores of Coals and of rotten Wood, which last also were
much of the same cize.

The other Observations on this _petrify'd_ substance, that a while since,
by the appointment of the _Royal Society_, I made, and presented to them an
account of, were these that follow, which had the honour done them by the
most accomplish'd Mr. _Evelin_, my highly honoured friend, to be inserted
and published among those excellent Observations wherewith his _Sylva_ is
replenish'd, and would therefore have been here omitted, had not the Figure
of them, as they appear'd through the _Microscope_ been before that
engraven.

This _Petrify'd_ substance resembled Wood, in that

First, all the parts of it seem'd not at all _dislocated_, or alter'd from
their natural Position, whil'st they were Wood, but the whole piece
retain'd the exact shape of Wood, having many of the conspicuous pores of
wood still remaining pores, and shewing a manifest difference visible
enough between the grain of the Wood and that of the bark, especially when
any side of it was cut smooth and polite; for then it appear'd to have a
very lovely grain, like that of some curious close Wood.

Next (it resembled Wood) in that all the smaller and (if I may so call
those which are onely visible with a good magnifying Glass) _Microscopical_
pores of it appear (both when the substance is cut and polish'd
_transversly_ and _parallel_ to the pores of it) perfectly like the
_Microscopical_ pores of several kinds of Wood, especially like and equal
to those of several sorts of rotten Wood which I have since observ'd,
retaining both the shape, position and magnitude of such pores. It was
differing from Wood:

First; in _weight_, being to common water as 31/4 to 1. whereas there are
few of our _English_ Woods, that when very dry are found to be full as
heavie as water.

Secondly, in _hardness_, being very neer as hard as a Flint; and in some
places of it also resembling the grain of a Flint: and, like it, it would
very readily cut Glass, and would not without difficulty, especially in
some parts of it, be scratch'd by a black hard Flint: It would also as
readily strike fire against a Steel, or against a Flint, as any common
Flint.

Thirdly, in the _closeness_ of it, for though all the _Microscopical_ pores
of this _petrify'd_ substance were very conspicuous in one position, yet by
altering that position of the polish'd surface to the light, it was also
manifest, that those pores appear'd darker then the rest of the body, onely
because they were fill'd up with a more duskie substance, and not because
they were hollow.

Fourthly, in its _incombustibleness_, in that it would not burn in the
fire; nay, though I kept it a good while red-hot in the flame of a Lamp,
made very _intense_ by the blast of a small Pipe, and a large Charcoal, yet
it seem'd not at all to have diminish'd its extension; but only I found it
to have chang'd its colour, and to appear of a more dark and duskie brown
colour; nor could I perceive that those parts which seem'd to have been
Wood at first, were any thing wasted, but the parts appear'd as solid and
close as before. It was further observable also, that as it did not consume
like Wood, so neither did it crack and flie like a Flint, or such like hard
Stone, nor was it long before it appear'd red-hot.

Fifthly, in its _dissolubleness_; for putting some drops of distill'd
_Vinegar_ upon the Stone, I found it presently to yield very many Bubbles,
just like those which may be observ'd in spirit of _Vinegar_ when it
corrodes _corals_, though perhaps many of those small Bubbles might proceed
from some small parcels of Air which were driven out of the pores of this
_petrify'd_ substance by the insinuating liquid _menstruum_.

Sixthly, in its _rigidness_, and _friability_, being not at all flexible
but brittle like a Flint, insomuch that I could with one knock of a Hammer
break off a piece of it, and with a few more, reduce that into a pretty
fine powder.

Seventhly, it seem'd also very differing from Wood to the _touch_,
_feeling_ more cold then Wood usually does, and much like other close
stones and Minerals.

The Reasons of all which _Phaenomena_ seem to be,

That _petrify'd_ Wood having lain in some place where it was well soak'd
with _petrifying_ water (that is, such a water as is well _impregnated_
with stony and earthy particles) did by degrees separate, either by
straining and _filtration_, or perhaps, by _precipitation_, _cohesion_ or
_coagulation_, abundance of stony particles from the permeating water,
which stony particles, being by means of the fluid _vehicle_ convey'd, not
onely into the _Microscopical_ pores, and so perfectly stoping them up, but
also into the pores or _interstitia_, which may, perhaps, be even in the
texture or _Schematisme_ of that part of the Wood, which, through the
_Microscope_, appears most solid, do thereby so augment the weight of the
Wood, as to make it above three times heavier then water, and perhaps, six
times as heavie as it was when Wood.

Next, they thereby so lock up and fetter the parts of the Wood, that the
fire cannot easily make them flie away, but the action of the fire upon
them is onely able to _Char_ those parts, as it were, like a piece of Wood,
if it be clos'd very fast up in Clay, and kept a good while red-hot in the
fire, will by the heat of the fire be charr'd and not consum'd, which may,
perhaps, also be somewhat of the cause, why the _petrify'd_ substance
appear'd of a dark brown colour after it had been burnt.

By this _intrusion_ of the _petrifying_ particles, this substance also
becomes hard and _friable_; for the smaller pores of the Wood being
perfectly wedg'd, and stuft up with those stony particles, the small parts
of the Wood have no places or pores into which they may slide upon bending,
and consequently little or no flexion or yielding at all can be caus'd in
such a substance.

The remaining particles likewise of the Wood among the stony particles, may
keep them from cracking and flying when put into the fire, as they are very
apt to do in a Flint.

Nor is Wood the onely substance that may by this kind of _transmutation_ be
chang'd into stone; for I my self have seen and examin'd very many kinds of
substances, and among very credible Authours, we may meet with Histories of
such _Metamorphoses_ wrought almost on all kind of substances, both
_Vegetable_ and _Animal_, which Histories, it is not my business at
present, either to relate, or _epitomise_, but only to set down some
Observation I lately made on several kind of _petrify'd_ Shels, found about
_Keinsham_, which lies within four or five miles of _Bristol_, which are
commonly call'd _Serpentine-stones._

Examining several of these very curiously figur'd bodies (which are
commonly thought to be Stones form'd by some extraordinary _Plastick
virtue_ _latent_ in the Earth itself) I took notice of these particulars:

First, that these figured bodies, or stones, were of very differing
substances, as to hardness: some of Clay, some Marle, some soft Stone,
almost of the hardness of those soft stones which Masons call Fire-stone,
others as hard as Portland stone, others as hard as Marble, and some as
hard as a Flint or Crystal.

Next, they were of very differing substances as to transparency and colour;
some white, some almost black, some brown, some Metalline, or like
Marchasites; some transparent like white Marble, others like flaw'd
Crystal, some gray, some of divers colours; some radiated like those long
_petrify'd drops_, which are commonly found at the _Peak_, and in other
_subterraneous caverns_, which have a kind of pith in the middle.

Thirdly, that they were very different as to the manner of their outward
figuration; for some of them seem'd to have been the substance that had
fill'd the Shell of some kind of Shel-fish; others, to have been the
substance that had contain'd or enwrapp'd one of those Shels, on both
which, the perfect impression either of the inside or outside of such
Shells seem'd to be left, but for the most part, those impressions seem'd
to be made by an imperfect or broken Shell, the great end or mouth of the
Shell being always wanting, and often times the little end, and sometimes
half, and in some there were impressions, just as if there had been holes
broken in the figurating, imprinting or moulding Shell; some of them seem'd
to be made by such a Shell very much brused or flaw'd, insomuch that one
would verily have thought that very figur'd stone had been broken or brused
whilst a gelly, as 'twere, and so hardned, but within in the grain of the
stone, there appear'd not the least sign of any such bruse or breaking, but
onely on the very uttermost superficies.

Fourthly, they were very different, as to their outward covering, some
having the perfect Shell, both in figure, colour, and substance, sticking
on upon its surface, and adhering to it, but might very easily be separated
from it, and like other common _Cockle_ or _Scolop-shels_, which some of
them most accurately resembled, were very dissoluble in common _Vinegar_,
others of them, especially those _Serpentine_, or _Helical stones_ were
cover'd or retained the shining or Pearl-colour'd substance of the inside
of a Shel, which substance, on some parts of them, was exceeding thin, and
might very easily be rubbed off; on other parts it was pretty thick, and
retained a white coat, or flaky substance on the top, just like the
outsides of such Shells; some of them had very large pieces of the Shell
very plainly sticking on to them, which were easily to be broken or flaked
off by degrees: they likewise, some of them retain'd all along the surface
of them very pretty kind of _sutures_, such as are observ'd in the skulls
of several kinds of living creatures, which _sutures_ were most curiously
shap'd in the manner of leaves, and every one of them in the same Shell,
exactly one like another, which I was able to discover plainly enough with
my naked eye, but more perfectly and distinctly with my _Microscope_; all
these sutures, by breaking some of these stones, I found to be the
_termini_, or boundings of certain _diaphragms_, or partitions, which
seem'd to divide the cavity of the Shell into a multitude of very
proportionate and regular _cells_ or _caverns_, these _Diaphragms_, in many
of them, I found very perfect and compleat, of a very distinct substance
from that which fill'd the cavities, and exactly of the same kind with that
which covered the outside, being for the most part whitish, or
_mother-of-pearl_ colour'd.

As for the cavities between those _Diaphragms_, I found some of them fill'd
with Marle, and others with several kinds of stones, others, for the most
part hollow, onely the whole cavity was usually covered over with a kind of
_tartareous petrify'd_ substance, which stuck about the sides, and was
there shot into very curious regular Figures, just as _Tartar_, or other
dissolv'd Salts are observ'd to stick and _crystallize_ about the sides of
the containing Vessels; or like those little _Diamants_ which I before
observed to have covered the vaulted cavity of a Flint; others had these
cavities all lin'd with a kind of _metalline_ or _marchasite-like_
substance, which with a _Microscope_ I could as plainly see most curiously
and regularly figured, as I had done those in a Flint.

From all which, and several other particulars which I observ'd, I cannot
but think, that all these, and most other kinds of stony bodies which are
found thus strangely figured, do owe their formation and figuration, not to
any kind of _Plastick virtue_ inherent in the earth, but to the Shells of
certain Shel-fishes, which, either by some Deluge, Inundation, Earthquake,
or some such other means, came to be thrown to that place, and there to be
fill'd with some kind of Mudd or Clay, or _petrifying_ Water, or some other
substance, which in tract of time has been settled together and hardned in
those shelly moulds into those shaped substances we now find them; that the
great and thin end of these Shells by that Earthquake, or what ever other
extraordinary cause it was that brought them thither, was broken off; and
that many others were otherwise broken, bruised and disfigured; that these
Shells which are thus _spirallied_ and separated with _Diaphragmes_, were
some kind of _Nautili_ or _Porcelane shells_; and that others were shells
of _Cockles_, _Muscles_, _Periwincles_, _Scolops_, &c. of various sorts;
that these Shells in many, from the particular nature of the containing or
enclos'd Earth, or some other cause, have in tract of time rotted and
mouldred away, and onely left their impressions, both on the containing and
contained substances; and so left them pretty loose one within another, so
that they may be easily separated by a knock or two of a Hammer. That
others of these Shells, according to the nature of the substances adjacent
to them, have, by a long continuance in that posture, been _petrify'd_ and
turn'd into the nature of stone, just as I even now observ'd several sorts
of Wood to be. That oftentimes the Shell may be found with one kind of
substance within, and quite another without; having, perhaps, been fill'd
in one place, and afterwards translated to another, which I have very
frequently observ'd in _Cockle_, _Muscle_, _Periwincle_, and other shells,
which I have found by the Sea side. Nay, further, that some parts of the
same Shell may be fill'd in one place, and some other caverns in another,
and others in a third, or a fourth, or a fifth place, for so many differing
substances have I found in one of these _petrify'd_ Shells, and perhaps all
these differing from the encompassing earth or stone; the means how all
which varieties may be caus'd, I think, will not be difficult to conceive,
to any one that has taken notice of those Shells, which are commonly found
on the Sea shore: And he that shall throughly examine several kinds of such
curiously form'd stones, will (I am very apt to think) find reason to
suppose their generation or formation to be ascribable to some such
accidents as I have mention'd, and not to any _Plastick virtue_: For it
seems to me quite contrary to the infinite prudence of Nature, which is
observable in all its works and productions, to design every thing to a
determinate end, and for the attaining of that end, makes use of such ways
as are (as farr as the knowledge of man has yet been able to reach)
altogether consonant, and most agreeable to man's reason, and of no way or
means that does contradict, or is contrary to humane Ratiocination; whence
it has a long time been a general observation and _maxime_, that _Nature
does nothing in vain_; It seems, I say, contrary to that great Wisdom of
Nature, that these prettily shap'd bodies should have all those curious
Figures and contrivances (which many of them are adorn'd and contriv'd
with) generated or wrought by a _Plastick virtue_, for no higher end, then
onely to exhibite such a form; which he that shall throughly consider all
the circumstances of such kind of Figur'd bodies, will, I think, have great
reason to believe, though, I confess, one cannot presently be able to find
out what Nature's designs are. It were therefore very desirable, that a
good collection of such kind of figur'd stones were collected; and as many
particulars, circumstances, and informations collected with them as could
be obtained, that from such a History of Observations well rang'd, examin'd
and digested, the true original or production of all those kinds of stones
might be perfectly and surely known; such as are _Thunder-stones_, _Lapides
Stellares_, _Lapides Judaici_, and multitudes of other, whereof mention is
made in _Aldonandus_, _Wormius_, and other Writers of Minerals.

       *       *       *       *       *


Observ. XVIII. _Of the _Schematisme_ or _Texture_ of _Cork_, and of the
Cells and Pores of some other such frothy Bodies._

I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen
as a Razor, I cut a piece of it off, and thereby left the surface of it
exceeding smooth, then examining it very diligently with a _Microscope_, me
thought I could perceive it to appear a little porous; but I could not so
plainly distinguish them, as to be sure that they were pores, much less
what Figure they were of: But judging from the lightness and yielding
quality of the Cork, that certainly the texture could not be so curious,
but that possibly, if I could use some further diligence, I might find it
to be discernable with a _Microscope_, I with the same sharp Penknife, cut
off from the former smooth surface an exceeding thin piece of it, and
placing it on a black object Plate, because it was it self a white body,
and casting the light on it with a deep _plano-convex Glass_, I could
exceeding plainly perceive it to be all perforated and porous, much like a
Honey-comb, but that the pores of it were not regular; yet it was not
unlike a Honey-comb in these particulars.

First, in that it had a very little solid substance, in comparison of the
empty cavity that was contain'd between, as does more manifestly appear by
the Figure A and B of the XI. _Scheme_, for the _Interstitia_, or walls (as
I may so call them) or partitions of those pores were neer as thin in
proportion to their pores, as those thin films of Wax in a Honey-comb
(which enclose and constitute the _sexangular celts_) are to theirs.

Next, in that these pores, or cells, were not very deep, but consisted of a
great many little Boxes, separated out of one continued long pore, by
certain _Diaphragms_, as is visible by the Figure B, which represents a
sight of those pores split the long-ways.

I no sooner discern'd these (which were indeed the first _microscopical_
pores I ever saw, and perhaps, that were ever seen, for I had not met with
any Writer or Person, that had made any mention of them before this) but me
thought I had with the discovery of them, presently hinted to me the true
and intelligible reason of all the _Phaenomena_ of Cork; As,

First, if I enquir'd why it was so exceeding light a body? my _Microscope_
could presently inform me that here was the same reason evident that there
is found for the lightness of froth, an empty Honey-comb, Wool, a Spunge, a
Pumice-stone, or the like; namely, a very small quantity of a solid body,
extended into exceeding large dimensions.

Next, it seem'd nothing more difficult to give an intelligible reason, why
Cork is a body so very unapt to suck and drink in Water, and consequently
preserves it self, floating on the top of Water, though left on it never so
long: and why it is able to stop and hold air in a Bottle, though it be
there very much condens'd and consequently presses very strongly to get a
passage out, without suffering the least bubble to pass through its
substance. For, as to the first, since our _Microscope_ informs us that the
substance of Cork is altogether fill'd with Air, and that that Air is
perfectly enclosed in little Boxes or Cells distinct from one another. It
seems very plain, why neither the Water, nor any other Air can easily
insinuate it self into them, since there is already within them an _intus
existens_, and consequently, why the pieces of Cork become so good floats
for Nets, and stopples for Viols, or other close Vessels.

And thirdly, if we enquire why Cork has such a springiness and swelling
nature when compress'd? and how it comes to suffer so great a compression,
or seeming penetration of dimensions, so as to be made a substance as
heavie again and more, bulk for bulk, as it was before compression, and yet
suffer'd to return, is found to extend it self again into the same space?
Our _Microscope_ will easily inform us, that the whole mass consists of an
infinite company of small Boxes or Bladders of Air, which is a substance of
a springy nature, and that will suffer a considerable condensation (as I
have several times found by divers trials, by which I have most evidently
condens'd it into less then a twentieth part of its usual dimensions neer
the Earth, and that with no other strength then that of my hands without
any kind of forcing Engine, such as Racks, Leavers, Wheels, Pullies, or the
like, but this onely by and by) and besides, it seems very probable that
those very films or sides of the pores, have in them a springing quality,
as almost all other kind of Vegetable substances have, so as to help to
restore themselves to their former position.

And could we so easily and certainly discover the _Schematisme_ and
_Texture_ even of these films, and of several other bodies, as we can these
of Cork; there seems no probable reason to the contrary, but that we might
as readily render the true reason of all their _Phaenomena_; as namely,
what were the cause of the springingess, and toughness of some, both as to
their flexibility and restitution. What, of the friability or brittleness
of some others, and the like; but till such time as our _Microscope_, or
some other means, enable us to discover the true _Schematism_ and _Texture_
of all kinds of bodies, we must grope, as it were, in the dark, and onely
ghess at the true reasons of things by similitudes and comparisons.

But, to return to our Observation. I told several lines of these pores, and
found that there were usually about threescore of these small Cells placed
end-ways in the eighteenth part of an Inch in length, whence I concluded
there must be neer eleven hundred of them, or somewhat more then a thousand
in the length of an Inch, and therefore in a square Inch above a Million,
or 1166400. and in a Cubick Inch, above twelve hundred Millions, or
1259712000. a thing almost incredible, did not our _Microscope_ assure us
of it by ocular demonstration; nay, did it not discover to us the pores of
a body, which were they _diaphragm'd_, like those of Cork, would afford us
in one Cubick Inch, more then ten times as many little Cells, as is evident
in several charr'd Vegetables; so prodigiously curious are the works of
Nature, that even these conspicuous pores of bodies, which seem to be the
channels or pipes through which the _Succus nutritius_, or natural juices
of Vegetables are convey'd, and seem to correspond to the veins, arteries
and other Vessels in sensible creatures, that these pores I say, which seem
to be the Vessels of nutrition to the vastest body in the World, are yet so
exceeding small, that the _Atoms_ which _Epicurus_ fancy'd would go neer to
prove too bigg to enter them, much more to constitute a fluid body in them.
And how infinitely smaller then must be the Vessels of a Mite, or the pores
of one of those little Vegetables I have discovered to grow on the
back-side of a Rose-leaf, and shall anon more fully describe, whose bulk is
many millions of times less then the bulk of the small shrub it grows on;
and even that shrub, many millions of times less in bulk then several trees
(that have heretofore grown in _England_, and are this day flourishing in
other hotter Climates, as we are very credibly inform'd) if at least the
pores of this small Vegetable should keep any such proportion to the body
of it, as we have found these pores of other Vegetables to do to their
bulk. But of these pores I have said more elsewhere.

To proceed then, Cork seems to be by the transverse constitution of the
pores, a kind of _Fungus_ or Mushrome, for the pores lie like so many Rays
tending from the center, or pith of the tree, outwards; so that if you cut
off a piece from a board of Cork transversly, to the flat of it, you will,
as it were, split the pores, and they will appear just as they are
express'd in the Figure B of the XI. _Scheme_. But if you shave off a very
thin piece from this board, parallel to the plain of it, you will cut all
the pores transversly, and they will appear almost as they are express'd in
the Figure A, save onely the solid _Interstitia_ will not appear so thick
as they are there represented.

So that Cork seems to suck its nourishment from the subjacent bark of the
Tree immediately, and to be a kind of excrescence, or a substance distinct
from the substances of the entire Tree, something _analogus_ to the
Mushrome, or Moss on other Trees, or to the hairs on Animals. And having
enquir'd into the History of Cork, I find it reckoned as an excrescency of
the bark of a certain Tree, which is distinct from the two barks that lie
within it, which are common also to other trees; That 'tis some time before
the Cork that covers the young and tender sprouts comes to be discernable;
That it cracks, flaws, and cleaves into many great chaps, the bark
underneath remaining entire; That it may be separated and remov'd from the
Tree, and yet the two under-barks (such as are also common to that with
other Trees) not at all injur'd, but rather helped and freed from an
external injury. Thus _Jonstonus_ in _Dendrologia_, speaking _de Subere_,
says, _Arbor est procera, Lignum est robustum, dempto cortice in aquis non
fluitat, Cortice in orbem detracto juvatur, crascescens enim praestringit &
strangulat, intra triennium iterum repletur: Caudex ubi adolescit crassus,
cortex superior densus carnosus, duos digitos crassus, scaber, rimosus, &
qui nisi detrahatur dehiscit, alioque subnascente expellitur, interior qui
subest novellus ita rubet ut arbor minio picta videatur_. Which Histories,
if well consider'd, and the tree, substance, and manner of growing, if well
examin'd, would, I am very apt to believe, much confirm this my conjecture
about the origination of Cork.

Nor is this kind of Texture peculiar to Cork onely; for upon examination
with my _Microscope_, I have found that the pith of an Elder, or almost any
other Tree, the inner pulp or pith of the Cany hollow stalks of several
other Vegetables: as of Fennel, Carrets, Daucus, Bur-docks, Teasels, Fearn,
some kinds of Reeds, &c. have much such a kind of _Schematisme_, as I have
lately shewn that of Cork, save onely that here the pores are rang'd the
long-ways, or the same ways with the length of the Cane, whereas in Cork
they are transverse.

The pith also that fills that part of the stalk of a Feather that is above
the Quil, has much such a kind of texture, save onely that which way soever
I set this light substance, the pores seem'd to be cut transversly; so that
I ghess this pith which fills the Feather, not to consist of abundance of
long pores separated with Diaphragms, as Cork does, but to be a kind of
solid or hardned froth, or a _congeries_ of very small bubbles consolidated
in that form, into a pretty stiff as well as tough concrete, and that each
Cavern, Bubble, or Cell, is distinctly separate from any of the rest,
without any kind of hole in the encompassing films, so that I could no more
blow through a piece of this kinde of substance, then I could through a
piece of Cork, or the sound pith of an Elder.

But though I could not with my _Microscope_, nor with my breath, nor any
other way I have yet try'd, discover a passage out of one of those cavities
into another, yet I cannot thence conclude, that therefore there are none
such, by which the _Succus nutritius_, or appropriate juices of Vegetables,
may pass through them; for, in several of those Vegetables, whil'st green,
I have with my _Microscope_, plainly enough discover'd these Cells or Poles
fill'd with juices, and by degrees sweating them out; as I have also
observed in green Wood all those long _Microscopical_ pores which appear in
Charcoal perfectly empty of any thing but Air.

Now, though I have with great diligence endeavoured to find whether there
be any such thing in those _Microscopical_ pores of Wood or Piths, as the
_Valves_ in the heart, veins, and other passages of Animals, that open and
give passage to the contain'd fluid juices one way, and shut themselves,
and impede the passage of such liquors back again, yet have I not hitherto
been able to say any thing positive in it; though, me thinks, it seems very
probable, that Nature has in these passages, as well as in those of Animal
bodies, very many appropriated Instruments and contrivances, whereby to
bring her designs and end to pass, which 'tis not improbable, but that some
diligent Observer, if help'd with better _Microscopes_, may in time detect.

And that this may be so, seems with great probability to be argued from the
strange _Phaenomena_ of sensitive Plants, wherein Nature seems to perform
several Animal actions with the same _Schematism_ or _Orginization_ that is
common to all Vegetables, as may appear by some no less instructive then
curious Observations that were made by divers Eminent Members of the _Royal
Society_ on some of these kind of Plants, whereof an account was delivered
in to them by the most Ingenious and Excellent _Physician_, Doctor _Clark_,
which, having that liberty granted me by that most Illustrious Society, I
have hereunto adjoyn'd.

_Observations on the _Humble_ and _Sensible Plants_ in _M Chiffin's_ Garden
in Saint _James_'s Park, made _August_ the _9th, 1661_._ _Present, the_
Lord _Brouncker_, Sr. _Robert Moray_, Dr. _Wilkins_, Mr. _Evelin_, Dr.
_Henshaw_, _and_ Dr. _Clark_.

    There are four Plants, two of which are little shrub Plants, with a
    little short stock, about an Inch above the ground, from whence are
    spread several sticky branches, round, streight, and smooth in the
    distances between the Sprouts, but just under the Sprouts there are two
    sharp thorny prickles, broad in the letting on, as in the Bramble, one
    just under the Sprout, the other on the opposite side of the branch.

    [14]The distances betwixt the Sprouts are usually something more then
    an Inch, and many upon a Branch, according to its length, and they grew
    so, that if the lower Sprout be on the left side of the Branch, the
    next above is on the right, and so to the end, not sprouting by pairs.

    At the end of each Sprout are generally four sprigs, two at the
    Extremity, and one on each side, just under it. At the first sprouting
    of these from the Branch to the Sprig where the leaves grow, they are
    full of little short white hairs, which wear off as the leaves grow,
    and then they are smooth as the Branch.

    Upon each of these sprigs, are, for the most part, eleven pair of
    leaves, neatly set into the uppermost part of the little sprig, exactly
    one against another, as it were in little _articulations_, such as
    Anatomists call _Enarthrosis_, where the round head of a Bone is
    received into another fitted for its motion; and standing very fitly to
    shut themselves and touch, the pairs just above them closing somewhat
    upon them, as in the shut sprig; so is the little round _Pedunculus_ of
    this leaf fitted into a little cavity of the sprig, visible to the eye
    in a sprig new pluck'd, or in a sprig withered on the Branch, from
    which the leaves easily fall by touching.

    The leaf being almost an oblong square, and set into the _Pedunculus_,
    at one of the lower corners, receiveth from that not onely a _Spine_,
    as I may call it, which, passing through the leaf, divides it so
    length-ways that the outer-side is broader then the inner next the
    sprig, but little _fibres_ passing obliquely towards the opposite
    broader side, seem to make it here a little muscular, and fitted to
    move the whole leaf, which, together with the whole sprig, are set full
    with little short whitish hairs.

    One of these Plants, whose branch seem'd to be older and more grown
    then the other, onely the tender Sprouts of it, after the leaves are
    shut, fall and hang down; of the other, the whole branches fall to the
    ground, if the Sun shine very warm, upon the first taking off the
    Glass, which I therefore call the _humble Plant_.

    The other two, which do never fall, nor do any of their branches flagg
    and hang down, shut not their leaves, but upon somewhat a hard stroke;
    the stalks seem to grow up from a root, and appear more _herbaceous_,
    they are round and smooth, without any prickle, the Sprouts from them
    have several pairs of sprigs, with much less leaves then the other on
    them, and have on each sprig generally seventeen pair.

    Upon touching any of the sprigs with leaves on, all the leaves on that
    sprig contracting themselves by pairs, joyned their upper superficies
    close together.

    Upon the dropping a drop of _Aqua fortis_ on the sprig betwixt the
    leaves, ff all the leaves above shut presently, those below by pairs
    successively after, and by the lower leaves of the other branches, ll,
    kk, &c. and so every pair successively, with some little distance of
    time betwixt, to the top of each sprig, and so they continu'd shut all
    the time we were there. But I returning the next day, and several days
    since, found all the leaves dilated again on two of the sprigs; but
    from ff, where the _Aqua fortis_ had dropped upwards, dead and
    withered; but those below on the same sprig, green, and closing upon
    the touch, and are so to this day, _August_ 14.

    With a pair of Scissers, as suddenly as it could be done, one of the
    leaves bb was clipped off in the middle, upon which that pair, and the
    pair above, closed presently, after a little interval, dd, then ee, and
    so the rest of the pairs, to the bottom of the sprig, and then the
    motion began in the lower pairs, ll, on the other sprigs, and so shut
    them by pairs upwards, though not with such distinct distances.

    Under a pretty large branch with its sprigs on, there lying a large
    Shell betwixt two and three Inches below it, there was rubbed on a
    strong sented oyl, after a little time all the leaves on that sprig
    were shut, and so they continued all the time of our stay there, but at
    my returne the next day, I found the position of the Shell alter'd, and
    the leaves expanded as before, and closing upon the touch.

    Upon the application of the Sun-beams by a Burning-glass, the more
    _humble Plant_ fell, the other shut their leaves.

    We could not so apply the smoak of _Sulpher_, as to have any visible
    effect from that, at two or three times trial; but on another trial,
    the smoak touching the leaves, it succeeded.

    The _humble Plant_ fell upon taking off the Glass wherewith it was
    covered.

    Cutting off one of the little Sprouts, two or three drops of liquor
    were thrust out of the part from whence that was cut, very cleer, and
    pellucid, of a bright greenish colour, tasting at first a little
    bitterish, but after leaving a licorish-like taste in my mouth.

    Since, going two or three times when it was cold, I took the Glasses
    from the more _humble Plant_, and it did not fall as formerly, but shut
    its leaves onely. But coming afterwards, when the Sun shone very warm,
    as soon as it was taken off, it fell as before.

    Since I pluck'd off another sprig, whose leaves were all shut, and had
    been so some time, thinking to observe the liquor should come from that
    I had broken off, but finding none, though with pressing, to come, I,
    as dexterously as I could, pull'd off one whose leaves were expanded,
    and then had upon the shutting of the leaves, a little of the mention'd
    liquor, from the end of the sprig I had broken from the Plant. And this
    twice successively, as often almost as I durst rob the Plant.

    But my curiosity carrying me yet further, I cut off one of the harder
    branches of the stronger Plant, and there came of the liquor, both from
    that I had cut, and that I had cut it from, without pressure.

    Which made me think, that the motion of this Plant upon touching, might
    be from this, that there being a constant _intercourse_ betwixt every
    part of this Plant and its root, either by a _circulation_ of this
    liquor, or a constant pressing of the subtiler parts of it to every
    extremity of the Plant. Upon every pressure, from whatsoever it
    proceeds, greater then that which keeps it up, the subtile parts of
    this liquor are thrust downwards, towards its _articulations_ of the
    leaves, where, not having room presently to get into the sprig, the
    little round _pedunculus_, from whence the _Spine_ and those oblique
    _Fibres_ I mentioned rise, being dilated, the _Spine_ and _Fibres_
    (being continued from it) must be contracted and shortned, and so draw
    the leaf upwards to joyn with its fellow in the same condition with it
    self, where, being closed, they are held together by the implications
    of the little whitish hair, as well as by the still retreating liquor,
    which distending the _Fibres_ that are continued lower to the branch
    and root, shorten them above; and when the liquor is so much forced
    from the Sprout, whose _Fibres_ are yet tender, and not able to support
    themselves, but by that tensness which the liquor filling their
    _interstices_ gives them, the Sprout hangs and flags.

    But, perhaps, he that had the ability and leisure to give you the exact
    _Anatomy_ of this pretty Plant, to shew you its _Fibres_, and visible
    _Canales_, through which this fine liquor circulateth, or is moved, and
    had the faculty of better and more copiously expressing his
    Observations and conceptions, such a one would easily from the motion
    of this liquor, solve all the _Phaenomena_, and would not fear to
    affirm, that it is no obscure sensation this Plant hath. But I have
    said too much, I humbly submit, and am ready to stand corrected.

I have not yet made so full and satisfactory Observations as I desire on
this Plant, which seems to be a Subject that will afford abundance of
information. But as farr as I have had opportunity to examine it, I have
discovered with my _Microscope_ very curious structures and contrivances;
but designing much more accurate examinations and trials, both with my
_Microscope_, and otherwise, as soon as the season will permit, I shall not
till then add any thing of what I have already taken notice of; but as farr
as I have yet observ'd, I judge the motion of it to proceed from causes
very differing from those by which Gut-strings, or Lute-strings, the beard
of a wilde _Oat_, or the beard of the Seeds of _Geranium_, _Mosscatum_, or
_Musk-grass_ and other kinds of _Cranes-bill_, move themselves. Of which I
shall add more in the subsequent Observations on those bodies.

       *       *       *       *       *


Observ. XIX. _Of a _Plant_ growing in the blighted or yellow specks of
_Damask-rose-leaves_, _Bramble-leaves_, and some other kind of leaves._

I have for several years together, in the Moneths of _June_, _July_,
_August_, and _September_ (when any of the green leaves of _Roses_ begin to
dry and grow yellow) observ'd many of them, especially the leaves of the
old shrubs of _Damask Roses_, all bespecked with yellow stains; and the
undersides just against them, to have little yellow hillocks of a gummous
substance, and several of them to have small black spots in the midst of
those yellow ones, which, to the naked eye, appear'd no bigger then the
point of a Pin, or the smallest black spot or tittle of Ink one is able to
make with a very sharp pointed Pen.

Examining these with a _Microscope,_ I was able plainly to distinguish, up
and down the surface, several small yellow knobs, of a kind of yellowish
red gummy substance, out of which I perceiv'd there sprung multitudes of
little cases or black bodies like Seed-cods, and those of them that were
quite without the hillock of Gumm, disclos'd themselves to grow out of it
with a small Straw-colour'd and transparent stem, the which seed and stem
appear'd very like those of common Moss (which I elsewhere describe) but
that they were abundantly less, many hundreds of them being not able to
equalize one single seed Cod of Moss.

I have often doubted whether they were the seed Cods of some little Plant,
or some kind of small Buds, or the Eggs of some very small Insect, they
appear'd of a dark brownish red, some almost quite black, and of a Figure
much resembling the seed-cod of Moss, but their stalks on which they grew
were of a very fine transparent substance, almost like the stalk of mould,
but that they seem'd somewhat more yellow.

That which makes me to suppose them to be Vegetables, is for that I
perceiv'd many of those hillocks bare or destitute, as if those bodies lay
yet conceal'd, as G. In others of them, they were just springing out of
their gummy hillocks, which all seem'd to shoot directly outwards, as at A.
In others, as at B, I found them just gotten out, with very little or no
stalk, and the Cods of an indifferent cize; but in others, as C, I found
them begin to have little short stalks, or stems; in others, as D, those
stems were grown bigger, and larger; and in others, as at E, F, H, I, K, L,
&c. those stems and Cods were grown a great deal bigger, and the stalks
were more bulky about the root, and very much taper'd towards the top, as
at F and L is most visible.

I did not find that any of them had any seed in them, or that any of them
were hollow, but as they grew bigger and bigger, I found those heads or
Cods begin to turn their tops towards their roots, in the same manner as I
had observ'd that of Moss to do; so that in all likelihood, Nature did
intend in that posture, what she does in the like seed-cods of greater
bulk, that is, that the seed, when ripe, should be shaken out and dispersed
at the end of it, as we find in Columbine Cods, and the like.

The whole Oval OOOO in the second _Figure_ of the 12. _Scheme_ represents a
small part of a Rose leaf, about the bigness of the little Oval in the
hillock, C, marked with the Figure X. in which I have not particularly
observ'd all the other forms of the surface of the Rose-leaf, as being
little to my present purpose.

Now, if these Cods have a seed in them so proportion'd to the Cod, as thole
of _Pinks_, and _Carnations_, and _Columbines_, and the like, how
unimaginably small must each of those seeds necessarily be, for the whole
length of one of the largest of those Cods was not 1/500 part of an Inch;
some not above 1/1000, and therefore certainly, very many thousand of them
would be unable to make a bulk that should be visible to the naked eye; and
if each of these contain the Rudiments of a young Plant of the same kind,
what must we say of the pores and constituent parts of that?

The generation of this Plant seems in part, ascribable to a kind of
_Mildew_ or _Blight_, whereby the parts of the leaves grow scabby, or
putrify'd, as it were, so as that the moisture breaks out in little scabs
or spots, which, as I said before, look like little knobs of a red gummous
substance.

From this putrify'd scabb breaks out this little Vegetable; which may be
somewhat like a _Mould_ or _Moss_; and may have its _equivocal_ generation
much after the same manner as I have supposed _Moss_ or _Mould_ to have,
and to be a more simple and uncompounded kind of vegetation, which is set a
moving by the _putrifactive_ and _fermentative_ heat, joyn'd with that of
the ambient aerial, when (by the putrifaction and decay of some other parts
of the vegetable, that for a while staid its progress) it is unfetter'd and
left at liberty to move in its former course, but by reason of its
_regulators_, moves and acts after quite another manner then it did when a
_coagent_ in the more compounded _machine_ of the more perfect Vegetable.

And from this very same Principle, I imagine the _Misleto_ of Oaks, Thorns,
Appletrees, and other Trees, to have its original: It seldom or never
growing on any of those Trees, till they begin to wax decrepid, and decay
with age, and are pester'd with many other infirmities.

Hither also may be referr'd those multitudes and varieties of _Mushroms_,
such as that, call'd _Jews-ears_, all sorts of _gray_ and _green_ Mosses,
&c. which infest all kind of Trees, shrubs, and the like, especially when
they come to any bigness. And this we see to be very much the method of
Nature throughout its operations, _putrifactive Vegetables_ very often
producing a Vegetable of a much less compounded nature, and of a much
inferiour tribe; and _putrefactive_ animal substances degenerating into
some kind of animal production of a much inferiour rank, and of a more
simple nature.

Thus we find the humours and substances of the body, upon _putrifaction_,
to produce strange kinds of moving Vermine: _the putrifaction_ of the
slimes and juices of the Stomack and Guts, produce Worms almost like
Earth-worms, the Wheals in childrens hands produce a little Worm, call'd a
_Wheal-worm_: The bloud and milk, and other humours, produce other kinds of
Worms, at least, if we may believe what is deliver'd to us by very famous
Authors; though, I confess, I have not yet been able to discover such my
self.

And whereas it may seem strange that _Vinegar_, _Meal_, musty _Casks_, &c.
are observ'd to breed their differing kinds of Insects, or living
creatures, whereas they being Vegetable substances, seem to be of an
inferiour kind, and so unable to produce a creature more noble, or of a
more compounded nature then they themselves are of, and so without some
concurrent seminal principle, may be thought utterly unfit for such an
operation; I must add, that we cannot presently positively say, there are
no animal substances, either mediately, as by the soil or fatning of the
Plant from whence they sprung, or more immediately, by the real mixture or
composition of such substances, join'd with them; or perchance some kind of
Insect, in such places where such kind of _putrifying_ or _fermenting_
bodies are, may, by a certain instinct of nature, eject some sort of
seminal principle, which cooperating with various kinds of _putrifying_
substances, may produce various kinds of Insects, or Animate bodies: For we
find in most sorts of those lower degrees of Animate bodies, that the
_putrifying_ substances on which these Eggs, Seeds, or seminal principles
are cast by the Insect, become, as it were, the _Matrices_ or Wombs that
conduce very much to their generation, and may perchance also to their
variation and alteration, much after the same manner, as, by strange and
unnatural copulations, several new kinds of Animals are produc'd, as
_Mules_, and the like, which are usually call'd Monstrous, because a little
unusual, though many of them have all their principal parts as perfectly
shap'd and adapted for their peculiar uses, as any of the most perfect
Animals. If therefore the _putrifying_ body, on which any kind of seminal
or vital principle chances to be cast, become somewhat more then meerly a
nursing and fostering helper in the generation and production of any kind
of Animate body, the more neer it approaches the true nature of a Womb, the
more power will it have on the by-blow it incloses. But of this somewhat
more in the description of the _Water-gnat_. Perhaps some more accurate
Enquiries and Observations about these matters might bring the Question to
some certainty, which would be of no small concern in Natural Philosophy.

But that _putrifying_ animal substances may produce animals of an inferior
kind, I see not any so very great a difficulty, but that one may, without
much absurdity, admit: For as there may be multitudes of contrivances that
go to the making up of one compleat Animate body; so, That some of those
_coadjutors_, in the perfect existence and life of it, may be vitiated, and
the life of the whole destroyed, and yet several of the constituting
contrivances remain intire, I cannot think it beyond imagination or
possibility; no more then that a like accidental process, as I have
elswhere hinted, may also be supposed to explicate the method of Nature in
the _Metamorphosis_ of Plants. And though the difference between a Plant
and an Animal be very great, yet I have not hitherto met with any so
_cogent_ an Argument, as to make me positive in affirming these two to be
altogether _Heterogeneous_ and of quite differing kinds of Nature: And
besides, as there are many _Zoophyts_, and sensitive Plants (divers of
which I have seen, which are of a middle nature, and seem to be Natures
transition from one degree to another, which may be observ'd in all her
other passages, wherein she is very seldom observ'd to leap from one step
to another) so have we, in some Authors, Instances of Plants turning into
Animals, and Animals into Plants, and the like; and some other very strange
(because unheeded) proceedings of Nature; something of which kind may be
met with, in the description of the _Water-Gnat_, though it be not
altogether so direct to the present purpose.

But to refer this Discourse of Animals to their proper places, I shall add,
that though one should suppose, or it should be prov'd by Observations;
that several of these kinds of Plants are accidentally produc'd by a casual
_purifaction_, I see not any great reason to question, but that,
notwithstanding its own production was as 'twere casual, yet it may
germinate and produce seed, and by it propagate its own, that is, a new
Species. For we do not know, but that the Omnipotent and All-wise Creator
might as directly design the structure of such a Vegetable, or such an
Animal to be produc'd out of such or such a _putrifaction_ or change of
this or that body, towards the constitution or structure of which, he knew
it necessary, or thought it fit to make it an ingredient; as that the
digestion or moderate heating of an Egg, either by the Female, or the Sun,
or the heat of the Fire, or the like, should produce this or that Bird; or
that _Putrifactive_ and warm steams should, out of the blowings, as they
call them, that is, the Eggs of a Flie, produce a living Magot, and that,
by degrees, be turn'd into an _Aurelia_, and that, by a longer and a
proportion'd heat, be _transmuted_ into a Fly. Nor need we therefore to
suppose it the more imperfect in its kind, then the more compounded
Vegetable or Animal of which it is a part; for he might as compleatly
furnish it with all kinds of contrivances necessary for its own existence,
and the propagation of its own Species, and yet make it a part of a more
compounded body: as a Clock-maker might make a Set of Chimes to be a part
of a Clock, and yet, when the watch part or striking part are taken away,
and the hindrances of its motion remov'd, this chiming part may go as
accurately, and strike its tune as exactly, as if it were still a part of
the compounded _Automaton_. So, though the original cause, or seminal
principle from which this minute Plant on Rose leaves did spring; were,
before the corruption caus'd by the Mill-dew, a component part of the leaf
on which it grew, and did serve as a _coagent_ in the production and
constitution of it, yet might it be so consummate, as to produce a seed
which might have a power of propagating the same species: the works of the
Creator seeming of such an excellency, that though they are unable to help
to the perfecting of the more compounded existence of the greater Plant or
Animal, they may have notwithstanding an ability of acting singly upon
their own internal principle, so as to produce a Vegetable body, though of
a less compounded nature, and to proceed so farr in the method of other
Vegetables, as to bear flowers and seeds, which may be capabale of
propagating the like. So that the little cases which appear to grow on the
top of the slender stalks, may, for ought I know, though I should suppose
them to spring from the perverting of the usual course of the parent
Vegetable, contain a seed, which, being scatter'd on other leaves of the
same Plant, may produce a Plant of much the same kind.

Nor are Damask-Rose leaves the onely leaves that produce these kinds of
Vegetable sproutings; for I have observ'd them also in several other kinds
of Rose leaves, and on the leaves of several sorts of Briers, and on
Bramble leaves they are oftentimes to be found in very great clusters; so
that I have found in one cluster, three, four, or five hundred of them,
making a very conspicuous black spot or scab on the back side of the leaf.

       *       *       *       *       *


Observ. XX. _Of _blue Mould_, and of the first Principles of Vegetation
arising from _Putrefaction_._

The Blue and White and several kinds of hairy mouldy spots, which are
observable upon divers kinds of _putrify'd_ bodies, whether Animal
substances, or Vegetable, such as the skin, raw or dress'd, flesh, bloud,
humours, milk, green Cheese, &c. or rotten sappy Wood, or Herbs, Leaves,
Barks, Roots, &c. of Plants, are all of them nothing else but several kinds
of small and variously figur'd Mushroms, which, from convenient materials
in those _putrifying_ bodies, are, by the concurrent heat of the Air,
excited to a certain kind of vegetation, which will not be unworthy our
more serious speculation and examination, as I shall by and by shew. But,
first, I must premise a short description of this _Specimen_, which I have
added of this Tribe, in the first Figure of the XII. _Scheme_, which is
nothing else but the appearance of a small white spot of hairy mould,
multitudes of which I found to bespeck & whiten over the red covers of a
small book, which, it seems, were of Sheeps skin, that being more apt to
gather mould, even in a dry and clean room, then other leathers. These
spots appear'd, through a good _Microscope_, to be a very pretty shap'd
Vegetative body, which, from almost the same part of the Leather, shot out
multitudes of small long cylindrical and transparent stalks, not exactly
streight, but a little bended with the weight of a round and white knob
that grew on the top of each of them; many of these knobs I observ'd to be
very round, and of a smooth surface, such as A, A, &c. others smooth
likewise, but a little oblong, as B; several of them a little broken, or
cloven with chops at the top, as C; others flitter'd as 'twere, or flown
all to pieces, as D, D. The whole substance of these pretty bodies was of a
very tender constitution, much like the substance of the softer kind of
common white Mushroms, for by touching them with a Pin, I found them to be
brused and torn; they seem'd each of them to have a distinct root of their
own; for though they grew neer together in a cluster, yet I could perceive
each stem to rise out of a distinct part or pore of the Leather; some of
these were small and short, as seeming to have been but newly sprung up, of
these the balls were for the most part round, others were bigger, and
taller, as being perhaps of a longer growth, and of these, for the most
part, the heads were broken, and some much wasted, as E; what these heads
contain'd I could not perceive; whether they were knobs and flowers, or
seed cases, I am not able to say, but they seem'd most likely to be of the
same nature with those that grow on Mushroms, which they did, some of them,
not a little resemble.

Both their smell and taste, which are active enough to make a sensible
impression upon those organs, are unpleasant and noisome.

I could not find that they would so quickly be destroy'd by the actual
flame of a Candle, as at first sight of them I conceived they would be, but
they remain'd intire after I had past that part of the Leather on which
they stuck three or four times through the flame of a Candle; so that, it
seems they are not very apt to take fire, no more then the common white
Mushroms are when they are sappy.

There are a multitude of other shapes, of which these _Microscopical_
Mushroms are figur'd, which would have been a long Work to have described,
and would not have suited so well with my design in this Treatise, onely,
amongst the rest, I must not forget to take notice of one that was a little
like to, or resembled, a Spunge, consisting of a multitude of little
Ramifications almost as that body does, which indeed seems to be a kind of
Water-Mushrom, of a very pretty texture, as I else-where manifest. And a
second, which I must not omit, because often mingled, and neer adjoining to
these I have describ'd, and this appear'd much like a Thicket of bushes, or
brambles, very much branch'd, and extended, some of them, to a great
length, in proportion to their Diameter, like creeping brambles.

The manner of the growth and formation of this kind of Vegetable, is the
third head of Enquiry, which, had I time, I should follow: the figure and
method of Generation in this concrete seeming to me, next after the Enquiry
into the formation, figuration; or chrystalization of Salts, to be the most
simple, plain, and easie; and it seems to be a _medium_ through which he
must necessarily pass, that would with any likelihood investigate the
_forma informans_ of Vegetables: for as I think that he shall find it a
very difficult task, who undertakes to discover the form of Saline
crystallizations, without the consideration and prescience of the nature
and reason of a Globular form, and as difficult to explicate this
configuration of Mushroms, without the previous consideration of the form
of Salts; so will the enquiry into the forms of Vegetables be no less, if
not much more difficult, without the fore-knowledge of the forms of
Mushroms, these several Enquiries having no less dependance one upon
another then any select number of Propositions in Mathematical Elements may
be made to have.

Nor do I imagine that the skips from the one to another will be found very
great, if beginning from fluidity, or body without any form, we descend
gradually, till we arrive at the highest form of a bruite Animal's Soul,
making the steps or foundations of our Enquiry, _Fluidity_, _Orbiculation_,
_Fixation_, _Angulization_, or _Crystallization Germination_ or
_Ebullition_, _Vegetation_, _Plantanimation_, _Animation_, _Sensation_,
_Imagination_.

Now, that we may the better proceed in our Enquiry, It will be requisite to
consider:

First, that Mould and Mushroms require no seminal property, but the former
may be produc'd at any time from any kind of _putrifying_ Animal, or
Vegetable Substance, as Flesh, &c. kept moist and warm, and the latter, if
what _Mathiolus_ relates be true, of making them by Art, are as much within
our command, of which Matter take the _Epitomie_ which Mr. _Parkinson_ has
deliver'd in his _Herbal_, in his Chapter of _Mushroms_, because I have not
_Mathiolus_ now by me: _Unto these Mushroms_ (saith he) _may also be
adjoyn'd those which are made of Art (whereof _Mathiolus_ makes mention)
that grow naturally among certain stones in _Naples_, and that the stones
being digg'd up, and carried to _Rome_, and other places, where they set
them in their Wine Cellars, covering them with a little Earth, and
sprinkling a little warm water thereon, would within four days produce
Mushroms fit to be eaten, at what time one will: As also that Mushroms may
be made to grow at the foot of a wilde _Poplar Tree_, within four days
after, warm water wherein some leaves have been dissolv'd shall be pour'd
into the Root (which must be slit) and the stock above ground._

Next, that as Mushroms may be generated without seed, so does it not appear
that they have any such thing as seed in any part of them; for having
considered several kinds of them, I could never find any thing in them that
I could with any probability ghess to be the seed of it, so that it does
not as yet appear (that I know of) that Mushroms may be generated from a
seed, but they rather seem to depend merely upon a convenient constitution
of the matter out of which they are made, and a concurrence of either
natural or artificial heat.

Thirdly, that by several bodies (as Salts and Metals both in Water and in
the air, and by several kinds of sublimations in the Air) actuated and
guided with a congruous heat, there may be produc'd several kinds of bodies
as curiously, if not of a more compos'd Figure; several kinds of rising or
Ebulliating Figures seem to manifest; as witness the shooting in the
Rectification of spirits of _Urine_, _Hart-horn_, _Bloud_, &c. witness also
the curious branches of evaporated dissolutions, some of them against the
sides of the containing Jar: others standing up, or growing an end, out of
the bottom, of which I have taken notice of a very great variety. But above
all the rest, it is a very pretty kind of Germination which is afforded us
in the Silver Tree, the manner of making which with Mercury and Silver, is
well known to the Chymists, in which there is an Ebullition or Germination,
very much like this of Mushroms, if I have been rightly inform'd of it.

Fourthly, I have very often taken notice of, and also observ'd with a
_Microscope_, certain excrescencies or Ebullitions in the snuff of a
Candle, which, partly from the sticking of the smoaky particles as they are
carryed upwards by the current of the rarify'd Air and flame, and partly
also from a kind of Germination or Ebullition of some actuated unctuous
parts which creep along and filter through some small string of the Week,
are formed into pretty round and uniform heads, very much resembling the
form of hooded Mushroms, which, being by any means expos'd to the fresh
Air, or that air which encompasses the flame, they are presently lick'd up
and devour'd by it, and vanish.

The reason of which _Phaenomenon_ seems to me, to be no other then this:

That when a convenient thread of the Week is so bent out by the sides of
the snuff that are about half an Inch or more, remov'd above the bottom, or
lowest part of the flame, and that this part be wholly included in the
flame; the Oyl (for the reason of filtration, which I have elsewhere
rendred) being continualy driven up the snuff is driven likewise into this
ragged bended-end, and this being remov'd a good distance, as half an Inch
or more, above the bottom of the flame, the parts of the air that passes by
it, are already, almost satiated with the dissolution of the boiling
unctuous steams that issued out below, and therefore are not onely glutted,
that is, can dissolve no more then what they are already acting upon, but
they carry up with them abundance of unctuous and sooty particles, which
meeting with that rag of the Week, that is plentifully fill'd with Oyl, and
onely spends it as fast as it evaporates, and not at all by dissolution or
burning, by means of these steamy parts of the filterated Oyl issuing out
at the sides of this ragg, and being inclos'd with an air that is already
satiated and cannot prey upon them nor burn them, the ascending sooty
particles are stay'd about it and fix'd, so as that about the end of that
ragg or filament of the snuff, whence the greatest part of the steams
issue, there is conglobated or fix'd a round and pretty uniform cap, much
resembling the head of a Mushrom, which, if it be of any great bigness, you
may observe that its underside will be bigger then that which is above the
ragg or stem of it; for the Oyl that is brought into it by filtration,
being by the bulk of the cap a little shelter'd from the heat of the flame,
does by that means issue as much out beneath from the stalk or downwards,
as it does upwards, and by reason of the great access of the adventitious
smoak from beneath, it increases most that way. That this may be the true
reason of this _Phaenomenon_, I could produce many Arguments and
Experiments to make it probable: As,

First, that the _Filtration_ carries the Oyl to the top of the Week, at
least as high as these raggs, is visible to one that will observe the snuff
of a burning Candle with a _Microscope_, where he may see an Ebullition or
bubbling of the Oyl, as high as the snuff looks black.

Next, that it does steam away more then burn; I could tell you of the dim
burning of a Candle, the longer the snuff be which arises from the
abundance of vapours out of the higher parts of it.

And, thirdly, that in the middle of the flame of the Candle, neer the top
of the snuff, the fire or dissolving principle is nothing neer so strong,
as neer the bottom and out edges of the flame, which may be observ'd by the
burning asunder of a thread, that will first break in those parts that the
edges of the flame touch, and not in the middle.

And I could add several Observables that I have taken notice of in the
flame of a Lamp actuated with Bellows, and very many others that confirm me
in my opinion, but that it is not so much to my present purpose, which is
onely to consider this concreet in the snuff of a Candle, so farr as it has
any resemblance of a Mushrom, to the consideration of which, that I may
return, I say, we may also observe:

In the fifth place, that the droppings or trillings of Lapidescent waters
in Vaults under ground, seem to constitute a kind of _petrify'd_ body,
form'd almost like some kind of Mushroms inverted, in so much that I have
seen some knobb'd a little at the lower end, though for the most part,
indeed they are otherwise shap'd, and taper'd towards the end; the
generation of which seems to be from no other reason but this, that the
water by soaking through the earth and Lime (for I ghess that substance to
add much to it _petrifying_ quality) does so impregnate it self with stony
particles, that hanging in drops in the roof of the Vault, by reason that
the soaking of the water is but slow, it becomes expos'd to the Air, and
thereby the outward part of the drop by degrees grows hard, by reason that
the water gradually evaporating the stony particles neer the outsides of
the drop begin to touch, and by degrees, to dry and grow closer together,
and at length constitute a crust or shell about the drop; and this soaking
by degrees, being more and more supply'd, the drop grows longer and longer,
and the sides harden thicker and thicker into a Quill or Cane, and at
length, that hollow or pith becomes almost stop'd up, and solid: afterwards
the soaking of the _petrifying_ water, finding no longer a passage through
the middle, bursts out, and trickles down the outside, and as the water
evaporates, leaves new superinduc'd shells, which more and more swell the
bulk of those Iceicles, and because of the great supply from the Vault, of
_petrifying_ wafer, those bodies grow bigger and bigger next to the Vault,
and taper or sharpen towards the point; for the access from the arch of the
Vault being but very slow, and consequently the water being spread very
thinly over the surface of the Iceicle, the water begins to settle before
it can reach to the bottom, or corner end of it; whence, if you break one
of these, you would almost imagine it a stick of Wood _petrify'd_, it
having so pretty a resemblance of pith and grain, and if you look on the
outside of a piece, or of one whole, you would think no less, both from its
vegetable roundness and tapering form; but whereas all Vegetables are
observ'd to shoot and grow perpendicularly upwards, this does shoot or
propend directly downwards.

By which last Observables, we see that there may be a very pretty body
shap'd and concreeted by Mechanical principles, without the least shew or
probability of any other seminal _formatrix_.

And since we find that the great reason of the _Phaenomena_ of this pretty
_petrifaction_, are to be reduc'd from the gravity of a fluid and pretty
volatil body impregnated with stony particles, why may not the _Phaenomena_
of Ebullition or Germination be in part possibly enough deduc'd from the
levity of an impregnated liquor, which therefore perpendicularly ascending
by degrees, evaporates and leaves the more solid and fix'd parts behind in
the form of a Mushrom, which is yet further diversify'd and specificated by
the forms of the parts that impregnated the liquor, and compose or help to
constitute the Mushrom.

That the foremention'd Figures of growing Salts, and the Silver Tree, are
from this principle, I could very easily manifest, but that I have not now
a convenient opportunity of following it, nor have I made a sufficient
number of Experiments and Observations to propound, explicate, and prove so
usefull a _Theory_ as this of Mushroms: for, though the contrary principle
to that of _petrify'd_ Iceicles may be in part a cause, yet I cannot but
think, that there is somewhat a more complicated caufe, though yet
Mechanical, and possible to be explain'd.

We therefore have further to enquire of it, what makes it to be such a
liquor, and to ascend, whether the heat of the Sun and Air, or whether that
_firmentiation_ and _putrifaction_, or both together; as also whether there
be not a third or fourth; whether a Saline principle be not a considerable
agent in this business also as well as heat; whether also a fixation,
precipitation or settling of certain parts out of the aerial menstruum may
not be also a considerable coadjutor in the business. Since we find that
many pretty beards _stiriae_ of the particles of Silver may be precipitated
upon a piece of Brass put into a _solution_ of Silver very much diluted
with fair water, which look not unlike a kind of mould or hoar upon that
piece of metal; and the hoar frost looks like a kind of mould; and whether
there may not be several others that do concurr to the production of a
Mushrom, having not yet had sufficient time to prosecute according to my
desires, I must referr this to a better opportunity of my own, or leave and
recommend it to the more diligent enquiry and examination of such as can be
masters both of leisure and conveniencies for such an Enquiry.

And in the mean time, I must conclude, that as far as I have been able to
look into the nature of this Primary kind of life and vegetation, I cannot
find the least probable argument to perswade me there is any other
concurrent cause then such as is purely Mechanical, and that the effects or
productions are as necessary upon the concurrence of those causes as that a
Ship, when the Sails are hoist up, and the Rudder is set to such a
position, should, when the Wind blows, be mov'd in such a way or course to
that or t'other place; Or, as that the brused Watch, which I mention in the
description of Moss, should, when those parts which hindred its motion were
fallen away, begin to move, but after quite another manner then it did
before.

       *       *       *       *       *


Observ. XXI. _Of _Moss_, and several other small-vegetative Substances._

Moss is a Plant, that the wisest of Kings thought neither unworthy his
speculation, nor his Pen, and though amongst Plants it be in bulk one of
the smallest, yet it is not the least considerable: For, as to its shape,
it may compare for the beauty of it with any Plant that grows, and bears a
much bigger breadth; it has a root almost like a seedy Parsnep, furnish'd
with small strings and suckers, which are all of them finely branch'd, like
those of the roots of much bigger Vegetables; out of this springs the stem
or body of the Plant, which is somewhat _Quadrangular_, rather then
_Cylindrical_, most curiously _fluted_ or lining with small creases, which
run, for the most part, _parallel_ the whole stem; on the sides of this are
close and thick set, a multitude of fair, large, well-shap'd leaves, some
of them of a rounder, others of a longer shape, according as they are
younger or older when pluck'd; as I ghess by this, that those Plants that
had the stalks growing from the top of them, had their leaves of a much
longer shape, all the surface of each side of which, is curiously cover'd
with a multitude of little oblong transparent bodies, in the manner as you
see it express'd in the leaf B, in the XIII. _Scheme_.

This Plant, when young and springing up, does much resemble a Housleek,
having thick leaves, almost like that, and seems to be somwhat of kin to it
in other particulars; also from the top of the leaves, there shoots out a
small white and transparent hair, or thorn: This stem, in time, come to
shoot out into a long, round and even stalk, which by cutting transversly,
when dry, I manifestly found to be a stiff, hard, and hollow Cane, or Reed,
without any kind of knot, or stop, from its bottom, where the leaves
encompass'd it, to the top, on which there grows a large seed case, A,
cover'd with a thin, and more whitish skin, B, terminated in a long thorny
top, which at first covers all the Case, and by degrees, as that swells,
the skin cleaves, and at length falls off, with its thorny top and all
(which is a part of it) and leaves the seed Case to ripen, and by degrees,
to shatter out its seed at a place underneath this cap, B, which before the
seed is ripe, appears like a flat barr'd button, without any hole in the
middle; but as it ripens, the button grows bigger, and a hole appears in
the middle of it, E, out of which, in all probability, the seed falls: For
as it ripens by a provision of Nature, that end of this Case turns downward
after the same manner as the ears of Wheat and Barley usually do; and
opening several of these dry red Cases, F, I found them to be quite hollow,
without anything at all in them; whereas when I cut them asunder with a
sharp Pen-knife when green, I found in the middle of this great Case,
another smaller round Case, between which two, the _interstices_ were
fill'd with multitudes of stringie _fibres_, which seem'd to suspend the
lesser Case in the middle of the other, which (as farr as I was able to
discern) seem'd full of exceeding small white seeds, much like the
seed-bagg in the knop of a Carnation, after the flowers have been two or
three days, or a week, fallen off; but this I could not so perfectly
discern, and therefore cannot positively affirm it.

After the seed was fallen away, I found both the Case, Stalk, and Plant,
all grow red and wither, and from other parts of the root continually to
spring new branches or slips, which by degrees increased, and grew as bigg
as the former, seeded, ripen'd, shatter'd, and wither'd.

I could not find that it observ'd any particular seasons for these several
kinds of growth, but rather found it to be springing, mature, ripe, seedy,
and wither'd at all times of the year; But I found it most to flourish and
increase in warm and moist weather.

It gathers its nourishments, for the most part, out of some _Lapidescent_,
or other substance corrupted or chang'd from its former texture, or
substantial form; for I have found it to grow on the rotten parts of Stone,
of Bricks, of Wood, of Bones, of Leather, &c.

It oft grows on the barks of several Trees, spreading it self, sometimes
from the ground upwards, and sometimes from some chink or cleft of the bark
of the Tree, which has some _putrify'd_ substance in it, but this seems of
a distinct kind from that which I observ'd to grow on _putrify'd_ inanimate
bodies, and rotten earth.

There are also great varieties of other kinds of Mosses, which grow on
Trees, and several other Plants, of which I shall here make no mention, nor
of the Moss growing on the skull of a dead man, which much resembles that
of Trees.

Whether this Plant does sometimes originally spring or rise out of
corruption, without any disseminated seed, I have not yet made trials
enough to be very much, either positive or negative; for as it seems very
hard to conceive how the seed should be generally dispers'd into all parts
where there is a corruption begun, unless we may rationally suppose, that
this seed being so exceeding small, and consequently exceeding light, is
thereby taken up, and carried to and fro in the Air into every place, and
by the falling drops of rain is wash'd down out of it, and so dispers'd
into all places, and there onely takes root and propagates, where it finds
a convenient soil or matrix for it to thrive in; so if we will have it to
proceed from corruption, it is not less difficult to conceive,

First, how the corruption of any Vegetable, much less of any Stone or
Brick, should be the Parent of so curiously figur'd, and so perfect a Plant
as this is. But here indeed, I cannot but add, that it seems rather to be a
product of the Rain in those bodies where it is stay'd, then of the very
bodies themselves, since I have found it growing on Marble, and Flint, but
always the _Microscope_, if not the naked eye, would discover some little
hole of Dirt in which it was rooted.

Next, how the corruption of each of those exceedingly differing bodies
should all conspire to the production of the same Plant, that is, that
Stones, Bricks, Wood, or vegetable substances, and Bones, Leather, Horns,
or animate substances, unless we may with some plausibleness say, that Air
and Water are the coadjutors, or _menstruums_, all kinds of
_putrifactions_, and that thereby the bodies (though whil'st they retain'd
their substantial forms, were of exceeding differing natures, yet) since
they are dissolv'd and mixt into another, they may be very _Homogeneous_,
they being almost resolv'd again into Air, Water, and Earth; retaining,
perhaps, one part of their vegetative faculty yet entire, which meeting
with congruous assistants, such as the heat of the Air, and the fluidity of
the Water, and such like coadjutors and conveniences, acquires a certain
vegetation for a time, wholly differing perhaps from that kind of
vegetation it had before.

To explain my meaning a little better by a gross Similitude:

Suppose a curious piece of Clock-work, that had had several motions and
contrivances in it, which, when in order, would all have mov'd in their
design'd methods and Periods. We will further suppose, by some means, that
this Clock comes to be broken, brused, or otherwise disordered, so that
several parts of it being dislocated, are impeded, and so stand still, and
not onely hinder its own progressive motion, and produce not the effect
which they were design'd for, but because the other parts also have a
dependence upon them, put a stop to their motion likewise; and so the whole
Instrument becomes unserviceable,, and not fit for any use. This Instrument
afterwards, by some shaking and tumbling, and throwing up and down, comes
to have several of its parts shaken out, and several of its curious
motions, and contrivances, and particles all fallen asunder; here a Pin
falls out, and there a Pillar, and here a Wheel, and there a Hammer, and a
Spring, and the like, and among the rest, away falls those parts also which
were brused and disorder'd, and had all this while impeded the motion of
all the rest; hereupon several of those other motions that yet remain,
whole springs were not quite run down, being now at liberty, begin each of
them to move, thus or thus, but quite after another method then before,
there being many regulating parts and the like, fallen away and lost. Upon
this, the Owner, who chances to hear and observe some of these effects,
being ignorant of the Watch-makers Art, wonders what is betid his Clock,
and presently imagines that some Artist has been at work, and has set his
Clock in order, and made a new kind of Instrument of it, but upon examining
circumstances, he finds there was no such matter, but that the casual
slipping out of a Pin had made several parts of his Clock fall to pieces,
and that thereby the obstacle that all this while hindred his Clock,
together with other usefull parts were fallen out, and so his Clock was set
at liberty. And upon winding up those springs again when run down, he finds
his Clock to go, but quite after another manner then it was wont
heretofore.

And thus may it be perhaps in the business of Moss, and Mould, and
Mushroms, and several other spontaneous kinds of vegetations, which may be
caus'd by a vegetative principle, which was a coadjutor to the life and
growth of the greater Vegetable, and was by the destroying of the life of
it stopt and impeded in performing its office; but afterwards, upon a
further corruption of several parts that had all the while impeded it, the
heat of the Sun winding up, as it were, the spring, sets it again into a
vegetative motion, and this being single, and not at all regulated as it
was before (when a part of that greater _machine_ the pristine vegetable)
is mov'd after quite a differing manner, and produces effects very
differing from those it did before.

But this I propound onely as a conjecture, not that I am more enclin'd to
this _Hypothesis_ then the seminal, which upon good reason I ghess to be
Mechanical also, as I may elsewhere more fully shew: But because I may, by
this, hint a possible way how this appearance may be solv'd; supposing we
should be driven to confess from certain Experiments and Observations made,
that such or such Vegetables were produc'd out of the corruption of
another, without any concurrent seminal principle (as I have given some
reason to suppose, in the description of a _Microscopical_ Mushrome)
without derogating at all from the infinite wisdom of the Creator. For this
accidental production, as I may call it, does manifest as much, if not very
much more, of the excellency of his contrivance as any thing in the more
perfect vegetative bodies of the world, even as the accidental motion of
the _Automaton_ does make the owner see, that there was much more
contrivance in it then at first he imagin'd. But of this I have added more
in the description of Mould, and the Vegetables on Rose leaves, &c. those
being much more likely to have their original from such a cause then this
which I have here described, in the 13. _Scheme_, which indeed I cannot
conceive otherwise of, then as of a most perfect Vegetable, wanting nothing
of the perfections of the most conspicuous and vastest Vegetables of the
world, and to be of a rank so high, as that it may very properly be
reckon'd with the tall Cedar of _Lebanon_, as that Kingly Botanist has
done.

We know there may be as much curiosity of contrivance, and excellency of
form in a very small Pocket-clock, that takes not up an Inch square of
room, as there may be in a Church-clock that fills a whole room; And I know
not whether all the contrivances and _Mechanisms_ requisite to a perfect
Vegetable, may not be crowded into an exceedingly less room then this of
Moss, as I have heard of a striking Watch so small, that it serv'd for a
Pendant in a Ladies ear; and I have already given you the description of a
Plant growing on Rose leaves, that is abundantly smaller then Moss;
insomuch, that neer 1000. of them would hardly make the bigness of one
single Plant of Moss. And by comparing the bulk of Moss, with the bulk of
the biggest kind of Vegetable we meet with in Story (of which kind we find
in some hotter climates, as _Guine_, and _Brasile_, the stock or body of
some Trees to be twenty foot in Diameter, whereas the body or stem of Moss,
for the most part, is not above one sixtieth part of an Inch) we shall find
that the bulk of the one will exceed the bulk of the other, no less then
2985984 Millions, or 2985984000000, and supposing the production on a Rose
leaf to be a Plant, we shall have of those _Indian_ Plants to exceed a
production of the same Vegetable kingdom no less then 1000 times the former
number; so prodigiously various are the works of the Creator, and so
All-sufficient is he to perform what to man would seem unpossible, they
being both alike easie to him, even as one day, and a thousand years are to
him as one and the same time.

I have taken notice of such an infinite variety of those smaller kinds of
vegetations, that should I have described every one of them, they would
almost have fill'd a Volume, and prov'd bigg enough to have made a new
Herbal, such multitudes are there to be found in moist hot weather,
especially in the Summer time, on all kind of putrifying substances, which,
whether they do more properly belong to the _Classis_ of _Mushrooms_, or
_Moulds_, or _Mosses_, I shall not now dispute, there being some that seem
more properly of one kind, others of another, their colours and magnitudes
being as much differing as their Figures and substances.

Nay, I have observ'd, that putting fair Water (whether Rain-water or
Pump-water, or _May-dew_ or Snow-water, it was almost all one) I have often
observ'd, I say, that this Water would, with a little standing, tarnish and
cover all about the sides of the Glass that lay under water, with a lovely
green; but though I have often endeavour'd to discover with my _Microscope_
whether this green were like Moss, or long striped Sea-weed, or any other
peculiar form, yet so ill and imperfect are our _Microscopes_, that I could
not certainly discriminate any.

Growing Trees also, and any kinds of Woods, Stones, Bones, &c. that have
been long expos'd to the Air and Rain, will be all over cover'd with a
greenish scurff, which will very much foul and green any kind of cloaths
that are rubb'd against it; viewing this, I could not certainly perceive in
many parts of it any determinate form, though in many I could perceive a
Bed as 'twere of young Moss, but in other parts it look'd almost like green
bushes, and very confus'd, but always of what ever irregular Figures the
parts appear'd of, they were always green, and seem'd to be either some
Vegetable, or to have some vegetating principle.

       *       *       *       *       *


Observ. XXII. _Of common _Sponges_, and several other _Spongie_ fibrous
bodies._

A Sponge is commonly reckon'd among the _Zoophyts_, or Plant Animals; and
the _texture_ of it, which the _Microscope_ discovers, seems to confirm it;
for it is of a form whereof I never observ'd any other Vegetable, and
indeed, it seems impossible that any should be of it, for it consists of an
infinite number of small short _fibres_, or nervous parts, much of the same
bigness, curiously jointed or contex'd together in the form of a Net, as is
more plainly manifest by the little Draught which I have added, in the
third _Figure_ of the IX. _Scheme_, of a piece of it, which you may
perceive represents a confus'd heap of the fibrous parts curiously jointed
and implicated. The joints are, for the most part, where three _fibres_
onely meet, for I have very seldom met with any that had four.

At these joints there is no one of the three that seems to be the stock
whereon the other grow, but each of the _fibres_ are, for the most part, of
an equal bigness, and seem each of them to have an equal share in the
joint; the _fibres_ are all of them much about the same bigness, not
smaller towards the top of the Sponge, and bigger neerer the bottom or
root, as is usuall in Plants, the length of each between the joints, is
very irregular and different; the distance between some two joints, being
ten or twelve times more then between some others.

Nor are the joints regular, and of an _equitriagonal Figure_, but, for the
most part, the three _fibres_ so meet, that they compose three angles very
differing all of them from one another.

The meshes likewise, and holes of this reticulated body, are not less
various and irregular: some _bilateral_, others _trilateral_, and
_quadrilateral_ Figures; nay, I have observ'd some meshes to have 5, 6, 7,
8, or 9. sides, and some to have onely one, so exceeding various is the
_Lusus Naturae_ in this body.

As to the outward appearance of this Vegetative body, they are so usuall
everywhere, that I need not describe them, consisting of a soft and porous
substance, representing a Lock, sometimes a fleece of Wooll; but it has
besides these small _microscopical_ pores which lie between the _fibres_, a
multitude of round pores or holes, which, from the top of it, pierce into
the body, and sometimes go quite through to the bottom.

I have observ'd many of these Sponges, to have included likewise in the
midst of their fibrous contextures, pretty large friable stones, which must
either have been inclos'd whil'st this Vegetable was in formation, or
generated in those places after it was perfectly shap'd. The later of which
seems the more improbable, because I did not find that any of these stony
substances were perforated with the _fibres_ of the Sponge.

I have never seen nor been enform'd of the true manner of the growing of
Sponges on the Rock; whether they are found to increase from little to
great, like Vegetables, that is, part after part, or like Animals, all
parts equally growing together; or whether they be _matrices_ or feed-baggs
of any kind of Fishes, or some kind of watry Insect; or whether they are at
any times more soft and tender, or of another nature and texture, which
things, if I knew how, I should much desire to be informed of: but from a
cursory view that I at first made with my _Microscope_, and some other
trials, I supposed it to be some Animal substance cast out, and fastned
upon the Rocks in the form of a froth, or _congeries_ of bubbles, like that
which I have often observ'd on Rosemary, and other Plants (wherein is
included a little Insect) that all the little films which divide these
bubbles one from another, did presently, almost after the substance began
to grow a little harder, break, and leave onely the thread behind, which
might be, as 'twere, the angle or thread between the bubbles, that the
great holes or pores observable in these Sponges were made by the eruption
of the included _Heterogeneous_ substance (whether air, or some other body,
for many other fluid bodies will do the same thing) which breaking out of
the lesser, were collected into very large bubbles, and so might make their
way out of the Sponge, and in their passage might leave a round cavity; and
if it were large, might carry up with it the adjacent bubbles, which may be
perceiv'd at the outside of the Sponge, if it be first throughly wetted,
and sufferr'd to plump itself into its natural form, or be then wrung dry,
and suffer'd to expand it self again, which it will freely do whil'st
moist: for when it has thus plump'd it self into its natural shape and
dimensions, 'tis obvious enough that the mouths of the larger holes have a
kind of lip or rising round about them, but the other smaller pores have
little or none. It may further be found, that each of these great pores has
many other small pores below, that are united unto it, and help to
constitute it, almost like so many rivulets or small streams that
contribute to the maintenance of a large River. Nor from this _Hypothesis_
would it have been difficult to explicate, how those little branches of
_Coral_, smal _Stones_, _shells_, and the like, come to be included by
these frothy bodies: But this inded was but a conjecture; and upon a more
accurate enquiry into the form of it with the _Microscope_, it seems not to
be the true origine of them; for whereas Sponges have onely three arms
which join together at each knot, if they had been generated from bubbles
they must have had four.

But that they are Animal Substances, the _Chymical_ examination of them
seems to manifest, they affording a volatil Salt and spirit, like
_Harts-Horn_, as does also their great strength and toughness, and their
smell when burn'd in the Fire or a Candle, which has a kind of fleshy sent,
not much unlike to hair. And having since examin'd several Authors
concerning them, among others; I find this account given by _Bellonius_, in
the XI. _Chap._ of his 2d Book, _De Aquatilibus_. _Spongiae recentes_, says
he, _a siccis longe diversae, scopulis aquae marinae ad duos vel tres
cubitos, nonnunquam quatuor tantum digitos immersis, ut fungi arboribus
adhaerent, sordido quodam succo aut mucosa potius sanie refertae, usque
adeo foetida, ut vel eminus nauseam excitet, continetur autem iis cavernis,
quas inanes in siccis & lotis Spongiis cernimus: Putris pulmonis modo
nigrae conspiciuntur, verum quae in sublimi aquae nascuntur multo magis
opaca nigredine suffusae sunt. Vivere quidem Spongias adhaerendo
_Aristoteles_ censet: absolute vero minime: sensumque aliquem habere, vel
eo argumento (inquit) credantur, quod difficillime abstrahantur, nisi
clanculum agatur: Atq; ad avulsoris accessum ita contrahantur, ut eas
evellere difficile sit, quod idem etiam faciunt quoties flatus
tempestatesque urgent. Puto autem illis succum sordidum quem supra diximus
carnis loco a natura attributum fuisse: atque meatibus latioribus tanquam
intestinis aut interaneis uti. Caeterum pars ea quae Spongiae cautibus
adhaerent est tanquam folii petiolus, a quo veluti collum quoddam gracile
incipit: quod deinde in latitudinem diffusum capitis globum facit.
Recentibus nihil est fistulosum, haesitantque tanquam radicibus. Superne
omnes propemodum meatus concreti latent: inferne vero quaterni aut quini
patent, per quos eas sugere existimamus_. From which Description, they
seem to be a kind of Plant-Animal that adheres to a Rock, and these small
_fibres_ or threads which we have described, seem to have been the Vessels
which ('tis very probable) were very much bigger whil'st the _Interstitia_
were fill'd (as he affirms) with a mucous, pulpy or fleshy substance; but
upon the drying were shrunk into the bigness they now appear.

The texture of it is such, that I have not yet met with any other body in
the world that has the like, but onely one of a larger sort of Sponge
(which is preserv'd in the _Museum Harveanum_ belonging to the most
Illustrious and most learned Society of the _Physicians_ of _London_) which
is of a horney, or rather of a _petrify'd_ substance. And of this indeed,
the texture and make is exactly the same with common Sponges, but onely
that both the holes and the _fibres_, or texture of it is exceedingly much