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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

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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 _Quæries_ (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, _cæteris 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, _cæteris 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 _stiriæ_ 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 naturâ_ 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 _ænigmâs_ 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 _phænomena_, 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
phænomena 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 _Æther_,
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 _præcipitations_,
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 Æther_, 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 Æther, 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 _præcipitation_, as we
are able to _separate_ the Air from the Æther by _Glass_, and several other
bodies. And though we are yet unable and ignorant of the ways of
_præcipitating_ Air out of the Æther 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 _præcipitating_ 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
_Cohæsion_ 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_ a