The Project Gutenberg EBook of Experiments and Considerations Touching
Colours (1664), by Robert Boyle

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Title: Experiments and Considerations Touching Colours (1664)

Author: Robert Boyle

Release Date: December 28, 2004 [EBook #14504]

Language: English

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                   EXPERIMENTS
                       AND
                 CONSIDERATIONS
                     Touching
                     COLOURS.

  First occasionally Written, among some other
   _Essays_, to a Friend; and now suffer'd to
                 come abroad as

                       THE
                    BEGINNING
                      Of An
               Experimental History
                       OF
                     COLOURS.

         By the Honourable ROBERT BOYLE,
          Fellow of the ROYAL SOCIETY.

_Non fingendum, aut excogitandum, sed inveniendum,
quid Natura faciat, aut ferat._ Bacon.

                    _LONDON._

     Printed for _Henry Herringman_ at the
    _Anchor_ on the Lower walk of the _New
              Exchange._ MDCLXIV.

       *       *       *       *       *

                       THE
                     PREFACE.

Having in convenient places of the following Treatise, mention'd the
Motives, that induc'd me to write it, and the Scope I propos'd to my self
in it; I think it superfluous to entertain the Reader now, with what he
will meet with hereafter. And I should judge it needless, to trouble
others, or my self, with any thing of Preface: were it not that I can
scarce doubt, but this Book will fall into the hands of some Readers, who
being unacquainted with the difficulty of attempts of this nature, will
think itn strange that I should publish any thing about Colours, without a
particular Theory of them. But I dare expect that Intelligent and Equitable
Readers will consider on my behalf: That the professed Design of this
Treatise is to deliver things rather _Historical_ than _Dogmatical_, and
consequently if I have added divers new _speculative_ Considerations and
hints, which perhaps may afford no despicable Assistance, towards the
framing of a solid and comprehensive Hypothesis, I have done at least as
much as I promis'd, or as the nature of my undertaking exacted. But another
thing there is, which if it should be objected, I fear I should not be able
so easily to answer it, and that is; That in the following treatise
(especially in the Third part of it) the Experiments might have been better
Marshall'd, and some of them deliver'd in fewer words. For I must confess
that this Essay was written to a private Friend, and that too, by snatches,
at several times, and places, and (after my manner) in loose sheets, of
which I oftentimes had not all by me that I had already written, when I was
writing more, so that it needs be no wonder if all the Experiments be not
rang'd to the best Advantage, and if some connections and consecutions of
them might easily have been mended. Especially since having carelessly laid
by the loose Papers, for several years after they were written, when I came
to put them together to dispatch them to the Press, I found some of those I
reckon'd upon, to be very unseasonably wanting. And to make any great
change in the order of the rest, was more than the Printers importunity,
and that, of my own avocations (and perhaps also considerabler
solicitations) would permit. But though some few preambles of the
particular Experiments might have (perchance) been spar'd, or shorten'd, if
I had had all my Papers under my View at once; Yet in the most of those
Introductory passages, the Reader will (I hope) find hints, or
Advertisements, as well as Transitions. If I sometimes seem to insist long
upon the circumstances of a Tryall, I hope I shall be easily excused by
those that both know, how nice divers experiments of Colours are, and
consider that I was not barely to _relate_ them, but so as to teach a young
Gentleman to make them. And if I was not sollicitous, to make a nicer
division of the whole Treatise, than into three parts, whereof the One
contains some Considerations about Colours in general. The Other exhibits a
specimen of an Account of particular Colours, Exemplifi'd in Whiteness and
Blackness. And the Third promiscuous Experiments about the remaining
Colours (especially Red) in order to a Theory of them. If, I say, I
contented my self with this easie Division of my Discourse, it was perhaps
because I did not think it so necessary to be Curious about the Method or
Contrivance of a Treatise, wherein I do not pretend to present my Reader
with a compleat Fabrick, or so much as Modell; but only to bring in
Materials proper for the Building; And if I did not well know how Ingenious
the Curiosity and Civility of Friends makes them, to perswade Men by
specious allegations, to gratifie their desires; I should have been made to
believe by persons very well qualify'd to judge of matters of this nature,
that the following Experiments will not need the addition of accurate
Method and speculative Notions to procure Acceptance for the Treatise that
contains them: For it hath been represented, That in most of them, as the
Novelty will make them surprizing, and the Quickness of performance, keep
them from being tedious; so the sensible changes, that are effected by
them, are so manifest, so great, and so sudden, that scarce any will be
displeased to see them, and those that are any thing Curious will scarce be
able to see them, without finding themselves excited, to make Reflexions
upon Them. But though with me, who love to measure Physical things by
their _use_, not their _strangeness_, or _prettiness_, the partiality of
others prevails not to make me over value these, or look upon them in
themselves as other than Trifles: Yet I confess, that ever since I did
divers years ago shew some of them to a Learned Company of _Virtuosi_: so
many persons of differing Conditions, and ev'n Sexes, have been Curious to
see them, and pleas'd not to Dislike them, that I cannot Despair, but that
by complying with those that urge the Publication of them, I may both
gratifie and excite the Curious, and lay perhaps a Foundation whereon
either others or my self may in time superstruct a substantial theory of
Colours. And if _Aristotle_, after his Master _Plato_, have rightly
observ'd Admiration to be the _Parent of Philosophy_, the wonder, some of
these Trifles have been wont to produce in all sorts of Beholders, and the
access they have sometimes gain'd ev'n to the Closets of Ladies, seem to
promise, that since the subject is so pleasing, that the Speculation
appears as Delightful! as Difficult, such easie and recreative Experiments,
which require but little time, or charge, or trouble in the making, and
when made are sensible and surprizing enough, may contribute more than
others, (far more important but as much more difficult) to recommend those
parts of Learning (Chymistry and Corpuscular Philosophy) by which they have
been produc'd, and to which they give Testimony ev'n to such kind of
persons, as value a pretty Trick more than a true Notion, and would scarce
admit Philosophy, if it approach'd them in another Dress: without the
strangeness or endearments of pleasantness to recommend it. I know that I
do but ill consult my own Advantage in the consenting to the Publication of
the following Treatise: For those things, which, whilst men knew not how
they were perform'd, appear'd so strange, will, when the way of making
them, and the Grounds on which I devis'd them, shall be Publick, quickly
lose all that their being _Rarityes_, and their _being thought Mysteries_,
contributed to recommend them. But 'tis fitter for Mountebancks than
Naturalis to desire to have their discoverys rather admir'd than
understood, and for my part I had much rather deserve the thanks of the
Ingenious, than enjoy the Applause of the Ignorant. And if I can so farr
contribute to the discovery of the nature of Colours, as to help the
Curious to it, I shall have reach'd my End, and sav'd my self some Labour
which else I may chance be tempted to undergo in prosecuting that subect,
and Adding to this Treatise, which I therefore call a _History_, because it
chiefly contains matters of fact, and which History the Title declares me
to look upon but as _Begun_: Because though that above a hundred, not to
say a hundred and fifty Experiments, (some loose, and others interwoven
amongst the discourses themselves) may suffice to give a _Beginning_ to a
History not hitherto, that I know, begun, by any; yet the subject is so
fruitfull, and so worthy, that those that are Curious of these Matters will
be farr more wanting to themselves than I can suspect, if what I now
publish prove any more than a _Beginning_. For, as I hope my Endeavours may
afford them some assistance towards this work, so those Endeavours are much
too Vnfinish'd to give them any discouragement, as if there were little
left for others to do towards the History of Colours.

For (first) I have been willing to leave unmention'd the _most part_ of
those Phænomena of Colours, that Nature presents us of her own accord,
(that is, without being guided or over-ruld by man) such as the different
Colours that several sorts of Fruites pass through before they are
perfectly ripe, and those that appear upon the fading of flowers and
leaves, and the putrifaction (and its several degrees) of fruits, &c.
together with a thousand other obvious Instances of the changes of colours.
Nor have I _much_ medled with those familiar Phænomena wherein man is not
an Idle spectator; such as the Greenness produc'd by salt in Beef much
powder'd, and the Redness produc'd in the shells of Lobsters upon the
boyling of those fishes; For I was willing to leave the _gathering_ of
_Observations_ to those that have not the Opportunity to _make
Experiments_. And for the same Reasons, among others, I did purposly omit
the Lucriferous practise of Trades-men about colours; as the ways of
making Pigments, of Bleanching wax, of dying Scarlet, &c. though to divers
of them I be not a stranger, and of some I have myself made Tryall.

Next; I did purposely pass by divers Experiments of other Writers that I
had made Tryall of (and that not without registring some of their Events)
unless I could some way or other improve them, because I wanted leasure to
insert them, and had thoughts of prosecuting the work once begun of laying
together those I had examin'd by themselves in case of my not being
prevented by others diligence. So that there remains not a little, among
the things that are already published, to imploy those that have a mind to
exercise themselves in repeating and examining them. And I will not
undertake, that _none_ of the things deliver'd, ev'n in this Treatise,
though never so faithfully set down, may not prove to be thus farr of this
Sort, as to afford the Curious somewhat to add about them. For I remember
that I have somewhere in the Book it self acknowledged, that having written
it by snatches, partly in the Counntrey, and partly at unseasonable times
of the year, when the want of fit Instruments, and of a competent variety
of flowers, salts, Pigments, and other materials made me leave some of the
following Experiments, (especialy those about Emphatical Colours) far more
unfinish'd than they should have been, if it had been as easie for me to
_supply_ what was wanting to compleat them, as to _discern_. Thirdly to
avoyd discouraging the young Gentleman I call Pyrophilus, whom the less
Familiar, and more Laborious operations of Chymistry would probably have
frighted, I purposely declin'd in what I writ to him, the setting down any
Number of such Chymicall Experiments, as, by being very elaborate or
tedious, would either require much skill, or exercise his patience. And yet
that this sort of Experiments is exceedingly Numerous, and might more than
a little inrich the History of Colours, those that are vers'd in Chymical
processes, will, I presume, easily allow me.

And (Lastly) for as much as I have occasion more than once in my several
Writings to treat either porposely or incidentally of matters relating to
Colours; I did not, perhaps, conceive my self oblig'd, to deliver in one
Treatise _all_ that I would say concerning that subject.

But to conclude, by summing up what I would say concerning what I _have_
and what I _have not_ done, in the following Papers; I shall not (_on the
one side_) deny, that considering that I pretended not to write an accurate
Treatise of Colours, but an Occasional Essay to acquaint a private friend
with what then occurrd to me of the things I had thought or try'd
concerning them; I might presume I did enough for once, if I did clearly
and faithfully set down, though not _all_ the Experiments I could, yet at
least such a variety of them, that an attentive Reader that shall consider
the Grounds on which they have been made, and the hints that are purposely
(though dispersedly) couched in them, may easily _compound_ them, and
otherwise _vary_ them, so as very much to increase their Number. And yet
(_on the other side_) I am so sensible both of how much I have, either out
of necessity or choice, left undone, and of the fruitfullness of the
subject I have begun to handle; that though I had performed far more then
'tis like many Readers will judge I have, I should yet be very free to let
them apply to my Attempts that of _Seneca_, where having spoken of the
Study of Natures Mysteries, and Particularly of the Cause of Earth-Quakes,
he subjoins.[1] _Nulla res consummata est dum incipit. Nec in hac tantum re
omnium maxima ac involutissimá, in quâ etiam cum multum actum erit, omnis
ætas, quod agat inveniet; sed in omni alio Negotio, longè semper à perfecto
fuere Principia._

  [1] L. Annæ Senecæ Natur. Quest. l. 6. c. 5.

       *       *       *       *       *

         _The Publisher to the_
                 READER.

_Friendly Reader,_

Here is presented to thy view one of the Abstrusest as well as the
Gentilest Subjects of Natural Philosophy, the _Experimentall History of
Colours_; which though the Noble Author be pleased to think but _Begun_,
yet I must take leave to say, that I think it so well begun, that the work
is more than half dispatcht. Concerning which I cannot but give this
advertisement to the Reader, that I have heard the Author express himself,
that it would not surprise him, if it should happen to be objected, that
some of these Experiments have been already published, partly by Chymists,
and partly by two or three very fresh Writers upon other Subjects. And
though the number of these Experiments be but very small, and though they
be none of the considerablest, yet it may on this occasion be further
represented, that it is easie for our Author to name several men, (of whose
number I can truly name my self) who remember either their having seen him
make, or their having read, his Accounts of the Experiments delivered in
the following Tract several years since, and long before the publication of
the Books, wherein they are mentioned. Nay in divers passages (where he
could do it without any great inconvenience) he hath struck out
Experiments, which he had tryed many years ago, because he since found them
divulged by persons from whom he had not the least hint of them; which yet
is not touched, with design to reflect upon any Ingenious Man, as if he
were a Plagiary: For, though our Generous Author were not reserved enough
in showing his Experiments to those that expressed a Curiosity to see them
(amongst whom a very Learned Man hath been pleased publickly to acknowledge
it several years ago[2]; yet the same thing may be well enough lighted on
by persons that know nothing of one another. And especially Chymical
Laboratories may many times afford the same _Phænomenon_ about Colours to
several persons at the same or differing times. And as for the few
_Phænomena_ mentioned in the same Chymical writers, as well as in the
following Treatise, our Author hath given an account, why he did not
decline rejecting them, in the Anotations upon the 47th Experiment of the
third part. Not here to mention, what he elsewhere saith, to shew what use
may be Justifiably made of Experiments not of his own devising by a writer
of Natural History, if, what he employes of others mens, be well examined
or verified by himself.

  [2] He that desires more instances of this kind and matter, that
  according to this doctrine may much help the Theory of colours, and
  particularly the force both of Sulphureous and volatile, is likewise of
  Alcalizate and Acid Salts, and in what particulars, Colours likely depend
  not in the causation from any Salt at all, may beg his information from
  M. Boyle who hath some while since honoured me with the sight of his
  papers concerning this subject, containing many excellent experiments,
  made by him for the Elucidation of this doctrine, &c Dr. R. Sharrock in
  his ingenious and usefull History of the Propagation and Improvement of
  Vegetables, published in the yeare 1660.

In the mean time, this Treatise is such, that there needs no other
invitation to peruse it, but that tis composed by one of the Deepest & Most
indefatigable searchers of Nature, which, I think the World, as far as I
know it, affords. For mine own part, I feel a Secret Joy within me, to see
such beginings upon such _Themes_, it being demonstratively true, _Mota
facilius moveri_, which causeth me to entertain strong hopes, that this
Illustrious _Virtuoso_ and Restless Inquirer into Nature's Secrets will not
stop here, but go on and prosper in the Disquisition or the other principal
Colours, _Green, Red_, and _Yellow_. The Reasoning faculty set once afloat,
will be carried on, and that with ease, especially, when the productions
thereof meet, as they do here, with so greedy an Entertainment at home and
abroad. I am confident, that the ROYAL SOCIETY, lately constituted by his
MOST EXCELLENT MAJESTY _for improving Natural knowledge_, will Judge it
their interest to exhort our Author to the prosecution of this Argument,
considering, how much it is their design and business to accumulate a good
stock of such accurate Observations and Experiments, as may afford them and
their Offpring genuine Matter to raise a Masculine Philosophy upon, whereby
the Mind of Man may be enobled with the Knowledge of solid Truths, and the
Life of Man benefited with ampler accommodations, than it hath been
hitherto.

Our Great Author, one of the Pillars of that Illustrious Corporation, is
constantly furnishing large _Symbola_'s to this work, and is now falln, as
you see, upon so comprehensive and important a theme, as will, if insisted
on and compleated, prove one of the considerablest peeces of that
structure. To which, if he shall please to add his Treatise of _Heat_ and
_Flame_, as he is ready to publish his Experimental Accounts of _Cold_, I
esteem, the World will be obliged to Him for having shewed them both the
_Right_ and _Left Hand_ of Nature, and the Operations thereof.

The considering Reader will by this very Treatise see abundant cause to
sollicit the Author for more; sure I am, that of whatever of the
Productions of his Ingeny comes into _Forein parts_ (where I am happy in
the acquaintance of many intelligent friends) is highly valued; And to my
knowledge, there are those among the French, that have lately begun to
learn English, on purpose to enable themselves to read his Books, being
impatient of their Traduction into Latin. If I durst say all, I know of the
Elogies received by me from abroad concerning Him, I should perhaps make
this Preamble too prolix, and certainly offend the modesty of our Author.

Wherefore I shall leave this, and conclude with desiring the Reader, that
if he meet with other faults besides those, that the Errata take notice of
(as I believe he may) he will please to consider both the weakness of the
Authors eyes, for not reviewing, and the manifold Avocations of the
Publisher for not doing his part; who taketh his leave with inviting those,
that have also considered this Nice subject experimentally, to follow the
Example of our Noble Author, and impart such and the like performances to
the now very inquisitive world. _Farewell._

_H. O._

       *       *       *       *       *

                       THE
                    CONTENTS.

       *       *       *       *       *

CHAP. I.

_The Author shews the Reason, first of his Writing on this Subject_ (1.)
_Next of his present manner of Handling it, and why he partly declines a
Methodical way_ (2.) _and why he has partly made use of it in the History
of_ Whiteness _and_ Blackness. (3.)

Chap. 2. _Some general Considerations are premis'd, first of the
Insignificancy of the Observasion of Colours in many Bodies_ (4, 5.) _and
the Importance of it in others_ (5.) _as particularly in the Tempering of
Steel_ (6, 7, 8.) _The reason why other particular Instances are in that
place omitted_ (9) _A necessary distinction about Colour premis'd_ (10,
11.) _That Colour is not Inherent in the Object_ (11.) _prov'd first by the
Phantasms of Colours to_ Dreaming _men, and_ Lunaticks; _Secondly by the
sensation or apparition of Light upon a Blow given the Eye or the Distemper
of the Brain from internal Vapours_ (12.) _The Author recites a particular
Instance in himself; another that hapn'd to an Excellent Person related to
him_ (13.) _and a third told him by an Ingenious Physician_ (14, 15.)
_Thirdly, from the change of Colours made by the Sensory Disaffected_ (15,
16.) _Some Instances of this are related by the Author, observ'd in
himself_ (16, 17.) _others told him by a Lady of known Veracity_ (18.) _And
others told him by a very Eminent Man_ (19.) _But the strange Instances
afforded by such as are Bit by the_ Tarantula _are omitted, as more
properly deliver'd in another place_. (20.)

Chap. 3. _That the Colour of Bodies depends chiefly on the disposition of
the Superficial parts, and partly upon the Variety of the Texture of the
Object_ (21.) _The former of these are confirm'd by several Persons_ (22.)
_and two Instances, the first of the Steel mention'd before, the second of
melted Lead_ (23, 24.) _of which last several Observables are noted_ (25.)
_A third Instance is added of the Porousness of the appearing smooth
Surface of Cork_ (26, 27.) _And that the same kind of Porousness may be
also in the other Colour'd Bodies; And of what kind of Figures, the
Superficial reflecting Particles of them may be_ (28.) _and of what Bulks,
and closeness of Position_ (29.) _How much these may conduce to the
Generation of Colour instanc'd in the Whiteness of Froth, and in the
mixtures of Dry colour'd Powders_ (30.) _A further explication of the
Variety that may be in the Superficial parts of Colour'd Bodies, that may
cause that Effect, by an example drawn from the Surface of the Earth_ (31.)
_An Apology for that gross Comparison_ (32.) _That the appearances of the
Superficial asperities may be Varied from the position of the Eye, and
several Instances given of such appearances_ (33, 34, 35.) _That the
appearance of the Superficial particles may be Varied also by their Motion,
confirm'd by an Instance of the smoaking Liquor_ (35.) _especially if the
Superficial parts be of such a Nature as to appear divers in several
Postures, explain'd by the variety of Colours exhibited by the shaken
Leaves of some Plants_ (36.) _and by changeable Taffities_ (37, 38, 39.)
_The Authors wish that the Variety of Colours in Mother of Pearl were
examin'd with a_ Microscope (40.) _And his Conjectures, that possibly good_
Microscopes _might discover those Superficial inequalities to be Real,
which we now only imagine with his reasons drawn partly from the
Discoveries of the_ Telescope, _and_ Microscope (41.) _And partly also from
the Prodigiously strange example of a Blind man that could feel Colours_
(42.) _whose History is Related_ (43, 44, 45.) _The Authors conjecture and
thoughts of it_ (46, 47, 48, 49.) _and several Conclusions and Corollaries
drawn from it about the Nature of Blackness and Black Bodies_ (50, 51, 52.)
_and about the Asperities of several other Colour'd Bodies_ (53.) _And from
these, and some premis'd Considerations, are propos'd some Conjectures;
That the reason of the several Phænomena of Colours, afterwards to be met
with, depends upon the Disposition of the Seen parts of the Object_ (54.)
_That Liquors may alter the Colours of each other, and of other Bodies,
first by their Insinuating themselves into the Pores, and filling them,
whence the Asperity of the Surface of a Body becomes alter'd, explicated
with some Instances_ (55, 56.) _Next by removing those Bodies, which before
hindred the appearance of the Genuine Colour, confirm'd by several
examples_ (57) _Thirdly, by making a Fissure or Separation either in the
Contiguous or Continued Particles of a Body_ (58.) _Fourthly, by a Union or
Conjunction of the formerly separated Particles; Illustrated with divers
Instances of precipitated Bodies_ (59.) _Fifthly, by Dislocating the parts,
and putting them both into other Orders and Postures, which is Illustrated
with Instances_ (60, 61.) _Sixthly, by Motion, which is explain'd_ (62.)
_And lastly, and chiefly, by the Union of the Saline Bodies, with the
Superficial parts of another Body, whereby both their Bigness and Shape
must necessarily be alter'd_ (63, 64.) _Explain'd by Experiments_ (65, 66.)
_That the Colour of Bodies may be Chang'd by the concurrence of two or more
of these ways_ (67.) _And besides all these, Eight Reflective causes of
Colours, there may be in Transparent Bodies several Refractive_ (68, 69)
_Why the Author thinks the Nature of Colours deserves yet a further
Inquiry_ (69.) _First for that the little Motes of Dust exhibited very
lovely Colours in a darkned Room, whilst in a convenient posture to the
Eye, which in other Postures and Lights they did not_ (70.) _And that
though the smaller Parts of some Colour'd Bodies are Transparent, yet of
others they are not, so that the first Doubt's, whether the Superficial
parts create those Colours, and the second, whether there be any Refraction
at all in the later_ (71, 72, 73.) _A famous Controversie among
Philosophers, about the Nature of Colour decided_. (74. 75.)

Chap. 4. _The controversie stated about Real and Emphatical Colours_ (75,
76.) _That the great Disparity between them seems to be, partly their
Duration in the same state, and partly, that Genuine Colours are produc'd
in Opacous Bodies by Reflection, and Emphatical in Transparent by
Refraction_ (78.) _but that this is not to be taken in too large a Sense,
the Cautionary instance of Froth is alleged and insisted on_ (78, 79.)
_That the Duration is not a sufficient Characteristick, exemplify'd by the
duration of Froth, and other Emphatical Colours, and the suddain fading of
Flowers, and other Bodies of Real ones_ (80.) _That the position of the Eye
is not necessary to the discerning Emphatical Colours, shew'd by the seeing
white Froth, or an Iris cast on the Wall by a Prism, in what place of the
Room soever the Eye be_ (81.) _which proceeds from the specular Reflection
of the Wall_ (82.) _that Emphatical Colours may be Compounded, and that the
present Discourse is not much concern'd, whether there be, or be not made a
distinction between Real and Emphatical Colours_. (83.)

Chap. 5. _Six Hypotheses about Colour recited_ (84, 85) _Why the Author
cannot more fully Speak of any of these_ (86.) _nor Acquiesce in them_ (87,
88.) _What_ Pyrophilus _is to expect in this Treatise_ (88, 89.) _What
Hypothesis of Light and Colour the Author most inclines too_ (90.) _Why he
thinks neither that nor any other sufficient; and what his Difficulties
are, that make him decline all Hypotheses, and to think it very difficult
to stick to any._ (91, 92.)

       *       *       *       *       *

Part the Second.

_Of the Nature of Whiteness and Blackness,_

CHAP. I.

_The reason why the Author chose the Explication of Whiteness and
Blackness_ (93.) _Wherein_ Democritus _thought amiss of these_ (94.)
Gassendus _his Opinion about them_ (95.) _What the Author approves, and a
more full Explication of White, makinig it a Multiplicity of Light or
Reflections_ (96, 97.) _Confirm'd first by the Whiteness of the_ Meridian
_Sun, observ'd in Water_ (98.) _and of a piece of Iron glowing Hot_ (99.)
_Secondly, by the Offensiveness of Snow to the Travellers eyes, confirm'd
by an example of a Person that has Travell'd much in Russia_ (100.) _and by
an Observation out of_ Olaus Magnus (100.) _and that the Snow does
inlighten and clear the Air in the Night, confirm'd by the Mosco Physician,
and Captain_ James (101.) _But that Snow has no inherent Light, prov'd by
Experience_ (102.) _Thirdly, by the great store of Reflections, from white
Bodies observ'd in a darkned Room, and by their unaptness to be Kindled by
a Burning-glass_ (103.) _Fourthly, the Specularness of White Bodies is
confirm'd by the Reflections in a dark Room from other Bodies_ (104.) _and
by the appearance of a River, which both to the Eye and in a darkned Room
appear'd White_ (105, 106.) _Fifthly, by the Whiteness of distill'd_
Mercury, _and that of the_ Galaxie (107, 108.) _and by the Whiteness of
Froth, rais'd from whites of Eggs beaten; that this Whiteness comes not
from the Air, shew'd by Experiments_ (109, 110.) _where occasionally the
Whiteness of Distill'd Oyls, Hot water, &c. are shew'd_ (111.) _That it
seems not necessary the Reflecting Surfaces should be Sphærical, confirm'd
by Experiments_ (112, 113.) _Sixthly, by the Whiteness of the Powders of
transparent Bodies_ (114.) _Seventhly, by the Experiment of Whitening and
Burnishing Silver._ (115, 116.)

Chap. 2. _A Recital of some Opinions about Blackness, and which the Author
inclines to_ (117.) _which he further insists on and explicates_ (118,
119.) _and shews for what reasons he imbrac'd that Hypothesis_ (120.)
_First, from the contrary Nature of Whiteness and Blackness, White
reflecting most Beams outwards, Black should reflect most inward_ (120.)
_Next, from the Black appearance of all Bodies, when Shadow'd; And the
manner how this paucity of Reflection outwards is caus'd, is further
explicated, by shewing that the Superficial parts may be Conical and
Pyramical_ (121.) _This and other Considerations formerly deliver'd,
Illustrated by Experiments with black and white Marble_ (122, 123.)
_Thirdly, from the Black appearance of Holes in white Linnen, and from the
appearance of Velvet stroak'd several ways, and from an Observation of
Carrots_ (124, 125.) _Fourthly, from the small Reflection from Black in a
darkned Room_ (125, 126.) _Fifthly, from the Experiment of a Checker'd Tile
expos'd to the Sun-beams_ (127.) _which is to be preferr'd before a Similar
Experiment try'd in_ Italy, _with black and white Marble_ (128.) _Some
other congruous Observations_ (129.) _Sixthly, from the Roasting black'd
Eggs in the Sun_ (130.) _Seventhly, by the Observation of the Blind man
lately mention'd, and of another mention'd by_ Bartholine (130.) _That
notwithstanding all these Reasons, the Author is not absolutely Positive,
but remains yet a Seeker after the true Nature of Whiteness and Blackness._
(131, 132.)

Experiments _in Consort, touching_ Whiteness _and_ Blackness.

_The first_ Experiment, _with a Solution of Sublimate, made White with
Spirit of Urine_, &c. (133, 134.)

_The second_ Experiment, _with an Infusion of Galls, made Black with
Vitriol_, &c. (135, 136.) _further Discours'd of_ (137.)

_The third_ Experiment, _of the Blacking of Hartshorn, and Ivory, and
Tartar, and by a further Calcination making them White_ (138, 139.)

_The fourth_ Experiment, _limiting the_ Chymist's _principle_, Adusta nigra
sed perusta alba, _by several Instances of Calcin'd Alabaster, Lead,
Antimony, Vitriol, and by the Testimony of_ Bellonius, _about the white
Charcoles of_ Oxy-cædar, _and by that of_ Camphire. (140, 141, 142.) _That
which follows about Inks was misplac'd by an Errour of the Printer, for it
belongs to what has been formerly said of Galls_ (142, 143.)

_The fifth_ Experiment, _of the black Smoak of Camphire_ (144.)

_The sixth_ Experiment, _of a black_ Caput Mortuum, _of Oyl of Vitriol,
with Oyl of Worm-word, and also with Oyl of Winter-Savory_ (145.)

_The seventh_ Experiment, _of whitening Wax_ (146.)

_The eighth_ Experiment, _with Tin-glass, and Sublimate_ (147, 148.)

_The ninth_ Experiment, _of a Black powder of Gold in the bottom of_
Aqua-fortis, _and of the Blacking of Refin'd Gold and Silver_ (148, 149.)

_The tenth_ Experiment, _of the staining Hair, Skin, Ivory_, &c. _Black,
with Crystals of Silver_ (150, 151.)

_The eleventh_ Experiment, _about the Blackness of the Skin, and Hair of_
Negroes, _and Inhabitants of Hot Climates. Several Objections are made, and
the whole Matter more fully discours'd and stated from several notable
Histories and Observations_ (from the 151 to the 167.)

_The twelfth_ Experiment, _of the white Powders, afforded by Precipitating
several Bodies, as Crabs Eyes, Minium, Coral, Silver, Lead, Tin,
Quick-silver, Tin-glass, Antimony, Benzoin, and Resinous Gumms out of
Spirit of Wine_, &c. _but this is not Universal, since other Bodies, as
Gold, Antimony, Quick-silver_, &c. _may be Precipitated of other Colours_
(168, 169, 170.)

_The thirteenth_ Experiment, _of Changing the Blackness of some Bodies into
other Colours_ (171, 172.) _and of Whitening what would be Minium, and
Copper, with Tin, and of Copper with Arsnick, which with Coppilling again
Vanishes; of covering the Colour of that of_ 1/3 _of Gold with_ 2/3 _of
Silver melted in a Mass together_ (173, 174)

_The fourteenth_ Experiment, _of turning the black Body of Horn into a
White immediately with Scraping, without changing the Substantial form, or
without the Intervention of Salt, Sulphur, or Mercury_ (176.)

_The fifteenth_ Experiment, _contains several Instances against the Opinion
of the_ Chymists _that Sulphur_ Adust _is the cause of Blackness, and the
whole Matter is fully discuss'd and stated_ (from 176 to 184)

Part the Third.

_Concerning Promiscuous Experiments about Colours_.

Experiment the First.

_IN confirmation of a former Conjecture about the Generation of Colours
from diversity of Reflections are set down several Observations made in a
Darkned room_ (186, 187.)

Experiment _the second, That white Linnen seem'd Ting'd with the Red of
Silk plac'd near it in a light Room_ (188,189.)

Experiment _the third, Of the Trajection of Light through Colour'd Papers_
(189, 190.)

Experiment _the fourth, Observations of a Prism in a dark Room_ (191, 192.)

Experiment _the fifth, Of the Refracting and Reflecting Prismatical Colours
in a light Room_ (193.)

Experiment _the sixth, On the Vanishing of the_ Iris _of the Prism, upon
the access of a greater adventitious Light_ (194.)

Experiment _the seventh, Of the appearances of the same Colour'd Papers by
Candle-light_ (195, 196).

Experiment _the eighth, Of the Yellowness of the Flame of a Candle_ (197).

Experiment _the ninth, Of the Greenish Blew transparency of Leaf Gold_
(198).

Experiment _the tenth, Of the curious Tinctures afforded by_ Lignum
Nephriticum (from 199 to 203). _Several trials for the Investigation of the
Nature of it_ (from 204 to 206.) Kircher's _relation of this Wood set down,
and examin'd_ (from 206 to 212). _A Corollary on this tenth_ Experiment,
_shewing how it may be applicable for the Discovering, whether any Salt be
of an Acid, or a Sulphureous, and Alcalizate Nature_ (from 213 to 216).

_The eleventh_ Experiment, _Of certain pieces of Glass that afforded this
Variety of Colours; And of the way of so Tinging any Plate of Glass with
Silver_ (from 216 to 219).

_The twelfth_ Experiment, _Of the Mixing and Tempering of Painters
Pigments_ (219, 220, 221).

_The thirteenth_ Experiment, _Of compounding several Colours by Trajecting
the Sun-beams through Ting'd Glasses_ (from 221 to 224).

_The fourteenth_ Experiment, _Of the Compounding of Real and Phantastical
Colours, and the Results_ (224, 225, 226.) _as also the same of
Phantastical Colours_ (226, 227.)

_The fifteenth_ Experiment, _Of Varying the Trajected_ Iris _by a Colour'd
Prism_ (228, 229.)

_The sixteenth_ Experiment, _Of the Red fumes of Spirit of_ Nitre, _and,
the resembling Redness of the Horizontal Sun-beams_ (230, 231.)

_The seventeenth_ Experiment, _Of making a Green by nine Kinds of
Compositions_ (from 231 to 236.) _And some Deductions from them against the
necessity of recurring to Substantial forms and Hypostatical principles for
the production of Colours_ (from 237 to 240.)

_The eighteenth_ Experiment, _Of several Compositions of Blew and Yellow
which produce not a Green, and of the production of a Green by other
Colours_ (241, 242.)

_The nineteenth_ Experiment, _contains several instances of producing
Colours, without the alteration of any Hypostatical principle, by the
Prism, Bubbles, and Feathers_ ( from 242 to 245.)

_The twentieth_ Experiment _Of turning the Blew of Violets into a Red by
Acid Salts, and to a Green by Alcalizate (245, 246.) and the use of it for
Investigating the Nature of Salts_ (247, 248.)

_The one and twentieth_ Experiment, _of the same Changes effected by the
same means on the Blew Tinctures of Corn-flowers_ (249, 250.) _And some
Restrictions to shew it not to be so general a propriety as one might
imagine_ (251.)

_The twenty second_ Experiment, _of turning a Solution of Verdigrease into
a Blew, with Alcalizate and Urinous Salts_ (252, 253, 254.)

_The twenty third_ Experiment, _of taking away the Colour of Roses with the
Steams of Sulphur, and heightning them with the Steams Condens'd into Oyl
of Sulphur_ per Campanam (254, 255.)

_The twenty fourth_ Experiment, _of Tinging a great quantity of Liquor with
a very little Ting'd Substance, Instanced in_ Cochineel (from 255 to 257.)

_The twenty fifth_ Experiment, _of the more general use of Alcalizate and
Sulphureous Salts in the Tinctures of Vegetables, further Instanced in the
Tincture of Privet Berries, and of the Flowers of Mesereon and Pease_ (from
257 to 259.) _An_ Annotation, _shewing that of the three Hypostatical
principles, Salt according to_ Paracelsus _is the most active about
Colours_ (from 259 to 261.) _Some things Precursory premis'd to three
several Instances next following, against the fore-mention'd Operations of
Salts_ (261, 262.)

_The twenty sixth_ Experiment, _containing Trials with Acid and Sulphureous
Salts on the Red Tinctures of Clove-july-flowers, Buckthorn Berries,
Red-Roses, Brasil_, &c. (262, 263.)

_The twenty seventh_ Experiment, _of the changes of the Colour of Jasmin
flowers, and Snow drops, by Alcalizate and Sulphureous Salts_ (263, 264.)

_The twenty eighth_ Experiment, _of other differing Effects on Mary-golds,
Prim-roses, and fresh Madder_ (265.) _with an Admonition, that these Salts
may have differing Effects in the changing of the tinctures of divers other
Vegetables_ (266, 267.)

_The twenty ninth_ Experiment, _of the differing Effects of these Salts on
Ripe and Unripe Juices, instanced in Black-berries, and the Juices of
Roses_ (from 267 to 270.) _Two reasons, why the Author added this twenty
ninth_ Experiment, _the last of which is confirm'd by an Instance of Mr._
Parkinson, _consonant to the Confession of the Makers of such Colours_
(272.)

_The thirtieth_ Experiment, _of several changes in Colours by Digestion,
exemplify'd by an_ Amalgam _of_ Gold _and_ Mercury _and by Spirit of
Harts-horn. And (to such as believe it) by the changes of the_ Elixir.

_The thirty first_ Experiment, _shewing that most Tinctures drawn by
Digestion Incline to a Red, instanc'd in_ Jalap, Guaicum, _Amber, Benzoin,
Sulphur, Antimony_, &c. (276, 277.)

_The thirty second_ Experiment, _That some Reds with Diluting turn Yellow,
others not, exemplify'd by the Tincture of_ Cochineel, _and by Balsam of_
Sulphur, _Tinctures of_ Amber, &c. (277, 278, 279.)

_The thirty third_ Experiment, _of a Red Tincture of_ Saccarum Saturni _and
Oyl of_ Turpentine _made by Digestion_ (279.)

_The thirty fourth_ Experiment, _of drawing a Volatile red Tincture of
Mercury_, _whose Steams were white, but it would Tinge the Skin black_
(279, 280.)

_The thirty fifth_ Experiment, _of a suddain way of making a Blood red
Colour with Oyl of_ Vitriol, _and Oyl of_ Anniseeds, _two transparent
Liquors_ (280, 281.)

_The thirty sixth_ Experiment, _of the Degenerating of several Colours
exemplify'd in the last mention'd Blood red, and by Mr._ Parkinsons
_relation of_ Turnsol, _by some Trials with the Juice of Buck-thorn
Berries, and other Vegetables, to which several notable Considerations and
Advertisements back'd with_ Experiments _are adjoyn'd_ (from 281 to 288.)

_The thirty seventh_ Experiment, _Of Varying the Colour of the Tinctures
of_ Cochineel, _Red-cherries, and Brasil, with Acid and Sulphureous Salts,
and divers Considerations thereon_ (from 288 to 290.)

_The thirty eighth_ Experiment, _About the Red fumes of some, and White of
other distill'd Bodies, and of their Coalition for the most part into a
transparent Liquor_ (290, 291.) _And of the various Colours of dry
Sublimations, exemplify'd with several_ Experiments (292, 293, 294.)

_The thirty ninth_ Experiment, _Of Varying the Decoction of_ Balaustiums
_with Acid and Urinous Salts_ (294, 295.) _Some_ Annotations _wherein two_
Experiments _of_ Gassendus _are Related, Examined, and Improv'd_ (from 295
to 302.)

_The fortieth_ Experiment, _Of the no less Strange than Pleasant changes
made with a Solution of Sublimate_ (from 301 to 306.) _The difference
between a Chymical axd Philosophical Solution of a_ Phænomenon (307, 308.)
_The Authors Chymical Explication of the_ Phænomena, _confirm d by several_
Experiments _made on_ Mercury, _with several Saline Liquors_ (from 308 to
310.) _An Improvement of the fortieth_ Experiment, _by a fresh Decoction
of_ Antimony _in a_ Lixivium (311, 312, 313.) _Reflections on the tenth,
twentieth, and fortieth_ Experiments, _compar'd together, shewing a way
with this Tincture of Sublimate to distinguish whether any Saline Body to
be examin'd be of a Urinous or Alcalizate Nature_ (from 314 to 317.) _The
Examination of Spirit of_ Sal-armoniack, _and Spirit of_ Oak _by these
Principles_ (from 316 to 319.) _That the Author knows ways of making highly
Operative Saline bodies, that produce none of the before mention'd effects_
(319, 320.) _Some notable_ Experiments _about Solutions and Precipitations
of Gold and Silver_ (320, 321.)

_The one and fortieth_ Experiment, _Of Depriving a deep Blew Solution of
Copper of its Colour_ (322.) _to which is adjoyn'd the Discolouring or
making Transparent a Solution of Verdigrease, &c. and another of Restoring
or Increasing it_ (322, 323.)

_The forty second_ Experiment, _Of changing a Milk white Precipitate of_
Mercury _into a Yellow, by Affusion of fair Water, with several
Considerations thereon_ (from 323 to 326.)

_The forty third_ Experiment, _Of Extracting a Green Solution with fair
Water out of imperfectly Calcin'd Vitriol_ (327.)

_The forty fourth_ Experiment, _Of the Deepning and Diluting of several
Tinctures, by the Affusions of Liquors, and by Conical Glasses that
contain'd them, Exemplify'd in the Tinctures of_ Cochineel, Brasil,
Verdigrease, Glass, Litmus, _of which last on this occasion several
pleasant_ Phænomena _are related_ (from 328 to 335.) _To which are adjoyn'd
certain Cautional Corollaries_ (335, 336.) _The Waterdrinker and some of
his Legerdemain tricks related._(337.)

_The forty fifth_ Experiment, _Of the turning Rhenish and White Wine into a
lovely Green, with a preparation of Steel _(338, 339.) _Some further Trial
made about these Tinctures, and a Similar_ Experiment _of_ Olaus Wormius
(340.)

_The forty sixth_ Experiment, _Of the Internal Colour of Metalls exhibited
by Calcination_ (341, 342, 343.) Annotation _the first, That several
degrees of Fire may disclose a differing Colour_ (343.) Annotation _the
second, That the Glasses of Metalls may exhibit also other Kinds of
Colours_ (344.) Annotation _the third, That Minerals by several degrees of
Fire may disclose several Colours_(345).

Experiment _the forty seventh, Of the Internal Colours of Metalls disclos'd
by their Dissolutions in several_ Menstruums (from 345 to 350.)
Annotation _the first, The Authors Apology for Recording some already
known_ Experiments, _without mentioning their Authors_ (from 350 to 352.)
Annotation _the second, That some Minerals also by Dissolutions in_
Menstruums _may exhibit divers Colours_. Annotation _the third, That
Metalls disclose other Colours by Precipitations, instanc'd in_ Mercury
(from 353 to 355.)

_The forty eighth_ Experiment, _Of Tinging Glass Blew with Leaf Silver, and
with Calcin'd Copper, and White with Putty_ (from 355 to 358.) Annotation
_the first, That this white Glass is the Basis of Ammels_ (358.) Annotion
_the second, That Colour'd Glasses may be Compounded like Colour'd Liquors
in Dying Fats_ (359.) Annotation _the third, Of Tinging Glass with Minerel
Substances, and of trying what Metalls they contain by this means_ (from
360 to 362.) Annotation _the fourth, That Metalls may be Ting'd by
Mineralls_ (362, 363.) Annotation _the fifth, Of making several Kinds of
Amauses or Counterfeit Stones_ (from 363 to 365.) Annotation _the sixth, Of
the Scarlet Dye, of the Stains of dissolv'd Gold and Silver_ (366, 367) _Of
the Greenness of Salt Beef, and Redness of Neats Tongues from Salts; of
Gilding Silver with Bathe Water_ (368, 369.) _And Tinging the Nails and
Skin with_ Alcanna (369)

_The forty ninth_ Experiment, _Of making Lakes_ (369.) _A particular
example in Turmerick_ (370, 371.) Annotation _the first, That in
Precipitations wherein Allum is a Coefficient, a great part of them may
consist of the Stony particles of that Compound Body_ (from 372 to 375.)
Annotation _the second, That Lakes may be made of other Substances, as
Madder, Rue,_ &c. _but that Alcalizate Salts do not Always Extract the same
Colour of which the Vegetable appears_ (from 376 to 378.) Annotation _the
third, That the_ Experiments _related may Hint divers others_ (378)
Annotation _the fourth, That Alum is usefull for the preparing other than
Vegetable Pigments_ (379.)

_The fiftieth_ Experiment, _Of the Similar effects of_ Saccarum Saturni
_and_ Alkalies, _of Precipitating with Oyl of_ Vitriol _out of_
Aqua-fortis, _and Spirit of_ Vinegar; _and of divers Varyings of the
Colours, with these Compounded_ (from 380 to 384.) _Another very pretty_
Experiment, _with a Solution of_ Minium (384, 385.) _That these_
Experiments _Skilfully digested may hint divers matters about Colours_
(386.) _The Authors Apologetick conclusion, in which is Cursorily hinted
the Bow or Scarlet Dye_ (387.) _The Authors Letter to Sir_ Robert Moray,
_concerning his Observations on the Shining Diamond_ (391. &c.) _And the
Observations themselves_.

       *       *       *       *       *

Errata.

Pag. 142. l. 20. These words, _And to manifest_, with the rest of what is
by a mistake further printed in this fourth Experiment, belongeth, and is
to be referred to the end of the second Eperiment, p.137. pag. 145. l. 1.
leg. _matter_. 146. l. 4. leg. _Bolts-head_. pag 161. in the marginal note
l. 2. dele _de_ ib. l. 3. lege lib 1. p 163. l. ult. insert _where_ between
the words _places_ and _the_. p. 164 l. 1. dele _that_. ibid, l. 8. leg
_Epidermis_. ibid. l. 19 leg. 300. for 200. p. 169. l. 22. leg. _into it_.
p. 170. l. 23. & 24. leg. _Some Solutions hereafter to be mentioned_, for
_the Solutions of Potashes_, and other _Lixiviate Salts_. p. 171. l. 6.
insert _part of_ between the words _most_ and _dissolved_ p. 176. l. ult.
insert the participle _it_ between the words _Judged_ and _not_ p. 234. l.
4. leg. _Woud-wax_ or _Wood-wax_. p. 320 l. 29. leg. _urine_ for _urne_.

       *       *       *       *       *

                      _THE_
             _EXPERIMENTAL HISTORY_
               _OF COLOURS BEGUN._

                THE FIRST PART.

CHAP. I.

1 I have seen you so passionately addicted, _Pyrophilus_ to the delightful
Art of Limning and Painting, that I cannot but think my self obliged to
acquaint you with some of those things that have occurred to mee concerning
the changes of Colours. And I may expect that I shall as well serve the
_Virtuosi_ in general, as gratifie you in particular, by furnishing a
person, who, I hope, will both improve my Communications, and communicate
his Improvements, with such Experiments and Observations as may both invite
you to enquire seriously into the Nature of Colours, and assist you in the
Investigation of it. This being the principal scope of the following Tract,
I should do that which might prevent my own design, if I should here
attempt to deliver you an accurate and particular Theory of Colours; for
that were to present you with what I desire to receive from you; and, as
farr as in mee lay, to make that study needless, to which I would engage
you.

2 Wherefore my present work shall be but to divert and recreate, as well as
excite you by the delivery of matters of fact, such as you may for the most
part try with much _ease_, and possibly not without some _delight_: And
lest you should expect any thing of Elaborate or Methodical in what you
will meet with here, I must confess to you before-hand, that the seasons I
was wont to chuse to devise and try Experiments about Colours, were those
daies, wherein having taken Physick, and finding my self as unfit to
speculate, as unwilling to be altogether idle, I chose this diversion, as a
kind of Mean betwixt the one and the other. And I have the less scrupled to
set down the following Experiments, as some of them came to my mind, and as
the Notes wherein I had set down the rest, occurr'd to my hands, that by
declining a Methodical way of delivering them, I might leave you and my
self the greater liberty and convenience to add to them, and transpose them
as shall appear expedient.

3 Yea, that you may not think mee too reserv'd, or look upon an Enquiry
made up of meer Narratives, as somewhat jejune, am content to _premise_ a
few considerations, that now offer themselves to my thoughts, which relate
in a more general way, either to the Nature of Colours, or to the study of
it. And I shall _insert_ an _Essay_, as well Speculative as Historical, of
the Nature of Whiteness and Blackness, that you may have a _Specimen_ of
the History of Colours, I have sometimes had thoughts of; and if you
dislike not the Method I have made use of, I hope, you, and some of the
_Virtuosi_, your friends, may be thereby invited to go thorow with _Red,
Blew, Yellow_, and the rest of the particular Colours, as I have done with
_White_ and _Black_, but with farr more sagacity and success. And if I can
invite Ingenious men to undertake such Tasks, I doubt not but the Curious
will quickly obtain a better Account of Colours, than as yet we have, since
in our Method the Theorical part of the Enquiry being attended, and as it
were interwoven with the Historical, whatever becomes of the disputable
Conjectures, the Philosophy of Colours will be promoted by the indisputable
Experiments.

       *       *       *       *       *

CHAP. II.

1 To come then in the first place to our more general Considerations, I
shall begin with saying something as to the Importance of examining the
Colours of Bodies. For there are some, especially _Chymists_, who think,
that a considerable diversity of Colours does constantly argue an equal
diversity of Nature, in the Bodies wherein it is conspicuous; but I confess
I am not altogether of their mind; for not to mention changeable Taffaties,
the blew and golden necks of Pidgeons, and divers Water-fowl, Rainbows
Natural and Artificial, and other Bodies, whose Colours the Philosophers
have been pleased to call not Real, but Apparent and Phantastical; not to
insist on these, I say, (for fear of needlesly engaging in a Controversie)
we see in Parrots, Goldfinches, and divers other Birds, not only that the
contiguous feathers which are probably as near in properties as place, are
some of them Red, and others White, some of them Blew, & others Yellow,
_&c._ but that in the several parts of the self-same feather there may
often be seen the greatest disparity of Colours; and so in the leaves of
Tulips, July-flowers, and some other Vegetables the several leaves, and
even the several parts of the same leaf, although no difference have been
observed in their other properties, are frequently found painted with very
different Colours. And such a variety we have much more admired in that
lovely plant which is commonly, and not unjustly call'd the _Marvayl of
Peru_; for of divers scores of fine Flowers, which in its season that gaudy
Plant does almost daily produce, I have scarce taken notice of any two that
were dyed perfectly alike. But though _Pyro_: such things as these, among
others, keep mee from daring to affirm, that the Diversity and change of
Colours does _alwaies_ argue any great difference or alteration, betwixt,
or in, the Bodies, wherein it is to be discerned, yet that _oftentimes_ the
Alteration of Colours does signifie considerable Alterations in the
disposition of parts of Bodies, may appear in the Extraction of Tinctures,
and divers other Chymical Operations, wherein the change of Colours is the
chief, and sometimes the only thing, by which the Artist regulates his
proceeding, and is taught to know when 'tis seasonable for him to leave
off. Instances of this sort are more obvious in divers sorts of fruits, as
Cherries, Plums, &c. wherein, according as the Vegetable sap is sweetned,
or otherwise ripened, by passing from one degree to another of Maturation,
the external part of the fruit passes likewise from one to another Colour.
But one of the noblest Instances I have met with of this kind, is not so
obvious; and that is the way of tempering Steel to make Gravers, Drills,
Springs, and other Mechanical Instruments, which we have divers times both
made Artificers practise in our presence, and tryed our selves, after the
following manner, First, the slender Steel to be tempered is to be hardened
by heating as much of it as is requisite among glowing Coals, till it be
glowing hot, but it must not be quenched assoon as it is taken from the
fire (for that would make it too brittle, and spoil it) but must be held
over a bason of water, till it descend from a White heat to a Red one,
which assoon as ever you perceive, you must immediately quench as much as
you desire to harden in the cold water. The Steel thus hardened, will, if
it be good, look somewhat White and must be made bright at the end, that
its change of Colours may be there conspicuous; and then holding it so in
the flame of a Candle, that the bright end may be, for about half an inch,
or more, out of the flame, that the smoak do not stain or sully the
brightness of it, you shall after a while see that clean end, which is
almost contiguous to the flame, pass very nimbly from one Colour to
another, as from a brighter Yellow, to a deeper and reddish Yellow, which
Artificers call a _sanguine_, and from that to a fainter first, and then a
a deeper Blew. And to bring home this Experiment to our present purpose, it
is found by daily Experience, that each of these succeeding Colours argue
such a change made in the texture of the Steel, that if it be taken from
the flame, and immediately quenched in the tallow (whereby it is setled in
whatever temper it had before) when it is Yellow, it is of such a hardness
as makes it fit for Gravers Drills, and such like tools; but if it be kept
a few minutes longer in the flame till it grow Blew, it becomes much
softer, and unfit to make Gravers for Metalls, but fit to make Springs for
Watches, and such like Instruments, which are therefore commonly of that
Colour; and if the Steel be kept in the flame, after that this deep Blew
hath disclosed it self, it will grow so soft, as to need to be new hardened
again, before it can be brought to a temper, fit for Drills or Penknives.
And I confess _Pyro._ I have taken much pleasure to see the Colours run
along from the parts of the Steel contiguous to the flame, to the end of
the Instrument, and succeed one another so fast, that if a man be not
vigilant, to thrust the Steel into the tallow at the very nick of time, at
which it has attain'd its due Colour, he shall miss of giving his tool the
right temper. But because the flame of a Candle is offensive to my weak
eyes, and because it is apt to either black or sully the contiguous part of
the Steel which is held in it, and thereby hinder the change of Colours
from being so long and clearly discern'd, I have sometimes made this
Experiment by laying the Steel to be tempered upon a heated bar of Iron,
which we finde also to be employ'd by some Artificers in the tempering of
such great Instruments, as are too big to be soon heated sufficiently by
the flame of a Candle. And you may easily satisfie your self _Pyro_: of the
differing hardness and toughness, which is ascribed to Steel temper'd at
different Colours, if you break but some slender wires of Steel so
temper'd, and observe how they differ in brittleness, and if with a file
you also make tryal of their various degrees of hardness.

2 But _Pyrophilus_, I must not at present any further prosecute the
Consideration of the importance of Experiments about Colours, not only
because you will in the following papers finde some instances, that would
here be presented you out of their due place, of the use that may be made
of such Experiments, in discovering in divers bodies, what kind the salt
is, that is predominant in them; but also because a speculative Naturalist
might justly enough allege, that as Light is so pleasing an object, as to
be well worth our looking on, though it discover'd to us nothing but its
self; so modifi'd Light called Colour, were worth our contemplation, though
by understanding its Nature we should be taught nothing else. And however,
I need not make either you or my self excuses for entertaining you on the
subject I am now about to treat of, since the pleasure _Pyro_: takes in
mixing and laying on of Colours, will I presume keep him, and will (I am
sure) keep mee from thinking it troublesome to set down, especially after
the tedious processes (about other matters) wherewith I fear I may have
tyr'd him, some easie, and not unpleasant Experiments relating to that
subject.

3 But, before we descend to the more particular considerations, we are to
present you concerning Colours, I presume it will be seasonable to propose
at the very entrance a Distinction; the ignorance or neglect of which,
seems to mee to have frequently enough occasioned either mistakes or
confusion in the Writings of divers Modern Philosophers; for Colour may be
considered, either as it is a quality residing in the body that is said to
be coloured, or to modifie the light after such or such a manner; or else
as the Light it self, which so modifi'd, strikes upon the organ of sight,
and so causes that Sensation which we call Colour; and that this latter may
be look'd upon as the more proper, though not the usual acception of the
word Colour, will be made probable by divers passages in the insuing part
of our discourse; and indeed it is the Light it self, which after a certain
manner, either mingled with shades, or some other waies troubled, strikes
our eyes, that does more immediately produce that motion in the organ, upon
whose account men say they see such or such a Colour in the object; yet,
because there is in the body that is said to be coloured, a certain
disposition of the superficial particles, whereby it sends the Light
reflected, or refracted, to our eyes thus and thus alter'd, and not
otherwise, it may also in some sense be said, that Colour depends upon the
visible body; and therefore we shall not be against that way of speaking of
Colours that is most used among the Modern Naturalists, provided we be
allowed to have recourse when occasion shall require to the premis'd
distinction, and to take the more immediate cause of Colour to be the
modifi'd Light it self, as it affects the Sensory; though the disposition
also of the colour'd body, as that modifies the Light, may be call'd by
that name Metonimically (to borrow a School term) or Efficiently, that is
in regard of its turning the Light, that rebounds from it, or passes thorow
it, into this or that particular Colour.

4 I know not whether I may not on this occasion add, that Colour is so far
from being an Inherent quality of the object in the sense that is wont to
be declar'd by the Schools, or even in the sense of some Modern Atomists,
that, if we consider the matter more attentively, we shall see cause to
suspect, if not to conclude, that though Light do more immediately affect
the organ of sight, than do the bodies that send it thither, yet Light it
self produces the sensation of a Colour, but as it produces such a
determinate kind of local motion in some part of the brain; which, though
it happen most commonly from the motion whereinto the slender strings of
the _Retina_ are put, by the appulse of Light, yet if the like motion
happen to be produc'd by any other cause, wherein the Light concurrs not at
all, a man shall think he sees the same Colour. For proof of this, I might
put you in mind, that 'tis usual for dreaming men to think they see the
Images that appear to them in their sleep, adorn'd some with this, and some
with that lively Colour, whilst yet, both the curtains of their bed, and
those of their eyes are close drawn. And I might add the confidence with
which distracted persons do oftentimes, when they are awake, think, they
see black fiends in places, where there is no black object in sight without
them. But I will rather observe, that not only when a man receives a great
stroak upon his eye, or a very great one upon some other part of his head,
he is wont to see, as it were, flashes of lightning, and little vivid, but
vanishing flames, though perhaps his eyes be shut: But the like apparitions
may happen, when the motion proceeds not from something without, but from
something within the body, provided the unwonted fumes that wander up and
down in the head, or the propagated concussion of any internal part in the
body, do cause about the inward extremities of the Optick Nerve, such a
motion as is wont to be there produc'd, when the stroak of the Light upon
the _Retina_ makes us conclude, that we see either Light, or such and such
a Colour: This the most ingenious _Des Cartes_ hath very well observ'd, but
because he seems not to have exemplifi'd it by any unobvious or peculiar
observation, I shall indeavour to illustrate this doctrine by a few
Instances.

5 And first, I remember, that having, through Gods goodness, been free for
several years, from troublesome Coughs, being afterwards, by an accident,
suddenly cast into a violent one, I did often, when I was awaked in the
night by my distempers, observe, that upon coughing strongly, it would seem
to mee, that I saw very vivid, but immediately disappearing flames, which I
took particular notice of, because of the conjecture I am now mentioning.

6 An excellent and very discreet person, very near ally'd both to you and
mee, was relating to mee, that some time since, whilst she was talking with
some other Ladies, upon a sudden, all the objects, she looked upon,
appeared to her dyed with unusual Colours, some of one kind, and some of
another, but all so bright and vivid, that she should have been as much
delighted, as surpriz'd with them, but that finding the apparition to
continue, she fear'd it portended some very great alteration as to her
health: As indeed the day after she was assaulted with such violence by
Hysterical and Hypocondrical Distempers, as both made her rave for some
daies, and gave her, during that time, a Bastard Palsey.

7 Being a while since in a Town, where the Plague had made great havock,
and inquiring of an ingenious man, that was so bold, as without much
scruple to visit those that were sick of it, about the odd symptomes of a
Disease that had swept away so many there; he told mee, among other things,
that he was able to tell divers Patients, to whom he was called, before
they took their beds, or had any evident symptomes of the Plague, that they
were indeed infected upon peculiar observations, that being asked, they
would tell him that the neighbouring objects, and particularly his cloths,
appear'd to them beautifi'd with most glorious Colours, like those of the
Rainbow, oftentimes succeeding one another; and this he affirm'd to be one
of the most usual, as well as the most early symptomes, by which this odd
Pestilence disclos'd it self: And when I asked how long the Patients were
wont to be thus affected, he answered, that it was most commonly for about
a day; and when I further inquired whether or no Vomits, which in that
Pestilence were usually given, did not remove this symptome (For some used
the taking of a Vomit, when they came ashore, to cure themselves of the
obstinate and troublesome giddiness caus'd by the motion of the ship)
reply'd, that generally, upon the evacuation made by the Vomit, that
strange apparition of Colours ceased, though the other symptomes were not
so soon abated, yet he added (to take notice of that upon the by, because
the observation may perchance do good) that an excellent Physician, in
whose company he was wont to visit the sick, did give to almost all those
to whom he was called, in the beginning before Nature was much weakened, a
pretty odd Vomit consisting of eight or ten dramms of Infusion of _Crocus
Metallorum_, and about half a dramm, or much more, of White Vitriol, with
such success, that scarce one of ten to whom it was seasonably administred,
miscarried.

8 But to return to the consideration of Colours: As an apparition of them
may be produced by motions from within, without the assistance of an
outward object, so I have observed, that 'tis sometimes possible that the
Colour that would otherwise be produced by an outward object, may be
chang'd by some motion, or new texture already produced in the Sensory, as
long as that unusual motion, or new disposition lasts; for I have divers
times try'd, that after I have through a Telescope look'd upon the Sun,
though thorow a thick, red, or blew glass, to make its splendor supportable
to the eye, the impression upon the _Retina_, would be not only so vivid,
but so permanent, that if afterwards I turned my eye towards a flame, it
would appear to mee of a Colour very differing from its usual one. And if I
did divers times successively shut and open the same eye, I should see the
adventitious Colour, (if I may so call it) changed or impair'd by degrees,
till at length (for this unusual motion of the eye would not presently
cease) the flame would appear to mee, of the same hew that it did to other
beholders; a not unlike effect I found by looking upon the Moon, when she
was near full, thorow an excellent Telescope, without colour'd Glass to
screen my eye with; But that which I desire may be taken notice of, because
we may elsewhere have occasion to reflect upon it, and because it seems not
agreeable to what Anatomists and Optical Writers deliver, touching the
relation of the two eyes to each other, is this circumstance, that though
my Right eye, with which I looked thorow the Telescope, were thus affected
by the over-strong impression of the light, yet when the flame of a Candle,
or some other bright object appear'd to me of a very unusual Colour, whilst
look'd upon with the Discompos'd Eye, or (though not so notably) with both
eyes at once; yet if I shut that Eye, and looked upon the same object with
the other, it would appear with no other than its usual Colour, though if I
again opened, and made use of the Dazled eye, the vivid adventitious Colour
would again appear. And on this occasion I must not pretermit an
Observation which may perswade us, that an over-vehement stroak upon the
Sensory, especially if it be naturally of a weak constitution, may make a
more lasting impression than one would imagine, which impression may in
some cases, as it were, mingle with, and vitiate the action of vivid
objects for a long time after.

For I know a Lady of unquestionable Veracity, who having lately, by a
desperate fall, receiv'd several hurts, and particularly a considerable one
upon a part of her face near her Eye, had her sight so troubl'd and
disorder'd, that, as she hath more than once related to me, not only when
the next morning one of her servants came to her bed side, to ask how she
did, his cloaths appear'd adorn'd with such variety of dazling Colours,
that she was fain presently to command him to withdraw, but the Images in
her Hangings, did, for many daies after, appear to her, if the Room were
not extraordinarily darken'd, embellish'd with several offensively vivid
Colours, which no body else could see in them; And when I enquir'd whether
or no White Objects did not appear to her adorn'd with more luminous
Colours than others, and whether she saw not some which she could not now
well describe to any, whose eyes had never been distemper'd, she answer'd
mee, that sometimes she thought she saw Colours so new and glorious, that
they were of a peculiar kind, and such as she could not describe by their
likeness to any she had beheld either before or since, and that White
Objects did so much disorder her sight, that if several daies after her
fall, she look'd upon the inside of a Book, she fanci'd she saw there
Colours like those of the Rain-bow, and even when she thought her self
pretty well recover'd, and made bold to leave her Chamber, the coming into
a place where the Walls and Ceeling were whited over, made those Objects
appear to her cloath'd with such glorious and dazling Colours, as much
offended her sight, and made her repent her venturousness, and she added,
that this Distemper of her Eyes lasted no less than five or six weeks,
though, since that, she hath been able to read and write much without
finding the least Inconvenience in doing so. I would gladly have known,
whether if she had shut the Injur'd Eye, the _Phænomena_ would have been
the same, when she employ'd only the other, but I heard not of this
accident early enough to satisfie that Enquiry.

9 Wherefore, I shall now add, that some years before, a person exceedingly
eminent for his profound Skil in almost all kinds of Philological Learning,
coming to advise with mee about a Distemper in his Eyes, told me, among
other Circumstances of it, that, having upon a time looked too fixedly upon
the Sun, thorow a Telescope, without any coloured Glass, to take off from
the dazling splendour of the Object, the excess of Light did so strongly
affect his Eye, that ever since, when he turns it towards a Window, or any
White Object, he fancies, he seeth a Globe of Light, of about the bigness
the Sun then appeared of to him, to pass before his Eyes: And having
Inquir'd of him, how long he had been troubled with this Indisposition, he
reply'd, that it was already nine or ten years, since the Accident, that
occasioned it, first befel him.

I could here subjoyn, _Pyrophilus_, some memorable Relations that I have
met with in the Account given us by the experienc'd _Epiphanius
Ferdinandus_, of the Symptomes he observ'd to be incident to those that are
bitten with the Tarantula, by which (Relations) I could probably shew, that
without any change in the Object, a change in the Instruments of Vision may
for a great while make some Colours appear Charming, and make others
Provoking, and both to a high degree, though neither of them produc'd any
such Effects before. These things, I say, I could here subjoyn in
confirmation of what I have been saying, to shew, that the Disposition of
the Organ is of great Importance in the Dijudications we make of Colours,
were it not that these strange Stories belonging more properly to another
Discourse, I had rather, (contenting my self to have given you an
Intimation of them here) that you should meet with them fully deliver'd
there.

       *       *       *       *       *

CHAP. III.

But, _Pyrophilus_, I would not by all that I have hitherto discours'd, be
thought to have forgotten the Distinction (of Colour) that I mentioned to
you about the beginning of the third Section of the former Chapter; and
therefore, after all I have said of Colour, as it is modifi'd Light, and
immediately affects the Sensory, I shall now re-mind you, that I did not
deny, but that Colour might in some sense be consider'd as a Quality
residing in the body that is said to be Colour'd, and indeed the greatest
part of the following Experiments referr to Colour principally under that
Notion, for there is in the bodyes we call Colour'd, and chiefly in their
Superficial parts, a certain disposition, whereby they do so trouble the
Light that comes from them to our Eye, as that it there makes that distinct
Impression, upon whose Account we say, that the Seen body is either White
or Black, or Red or Yellow, or of any one determinate Colour. But because
we shall (God permiting) by the Experiments that are to follow some Pages
hence, more fully and particularly shew, that the Changes, and consequently
in divers places the Production and the appearance of Colours depends upon
the continuing or alter'd Texture of the Object, we shall in this place
intimate (and that too but as by the way) two or three things about this
Matter.

2. And first it is not without some Reason, that I ascribe Colour (in the
sense formerly explan'd) _chiefly_ to the Superficial parts of Bodies, for
not to question how much Opacous Corpuscles may abound even in those Bodies
we call Diaphanous, it seems plain that of Opacous bodies we do indeed see
little else than the Superficies, for if we found the beams of Light that
rebound from the Object to the Eye, to peirce deep into the Colour'd body,
we should not judge it Opacous, but either Translucid, or at least
Semi-diaphanous, and though the Schools seem to teach us that Colour is a
Penetrative Quality, that reaches to the Innermost parts of the Object, as
if a piece of Sealing-wax be broken into never so many pieces, the Internal
fragments will be as Red as the External surface did appear, yet that is
but a Particular Example that will not overthrow the Reason lately offer'd,
especially since I can alleage other Examples of a contrary Import, and two
or three Negative Instances are sufficient to overthrow the Generality of a
Positive Rule, especially if that be built but upon One or a Few Examples.
Not (then) to mention Cherries, Plums, and I know not how many other
Bodies, wherein the skin is of one Colour, and what it hides of another, I
shall name a couple of Instances drawn from the Colours of Durable bodies
that are thought far more Homogeneous, and have not parts that are either
Organical, or of a Nature approaching thereunto.

3 To give you the first Instance, I shall need but to remind you of what I
told you a little after the beginning of this Essay, touching the Blew and
Red and Yellow, that may be produc'd upon a piece of temper'd Steel, for
these Colours though they be very Vivid, yet if you break the Steel they
adorn, they will appear to be but Superficial; not only the innermost parts
of the Metall, but those that are within a hairs breadth of the
Superficies, having not any of these Colours, but retaining that of the
Steel it self. Besides that, we may as well confirm this Observation, as
some other particulars we elsewhere deliver concerning Colours, by the
following Experiment which we purposely made.

4 We took a good quantity of clean Lead, and melted it with a strong Fire,
and then immediately pouring it out into a clean Vessel of a convenient
shape and matter, (we us'd one of Iron, that the great and sudden Heat
might not injure it) and then carefully and nimbly taking off the Scum that
floated on the top, we perceiv'd, as we expected, the smooth and glossie
Surface of the melted matter, to be adorn'd with a very glorious Colour,
which being as Transitory as Delightfull, did almost immediately give place
to another vivid Colour, and that was as quickly succeeded by a third, and
this as it were chas'd away by a fourth, and so these wonderfully vivid
Colours successively appear'd and vanish'd, (yet the same now and then
appearing the second time) till the Metall ceasing to be hot enough to
afford any longer this pleasing Spectacle, the Colours that chanc'd to
adorn the Surface, when the Lead thus began to cool, remain'd upon it; but
were so Superficial, that how little soever we scrap'd off the Surface of
the Lead, we did in such places scrape off all the Colour, and discover
only that which is natural to the Metall it self, which receiving its
adventitious Colours, only when the heat was very Intense, and in that part
which was expos'd to the comparatively very cold Air, (which by other
Experiments seems to abound with subtil Saline parts, perhaps not uncapable
of working upon Lead so dispos'd:) These things I say, together with my
observing that whatever parts of the so strongly melted Lead were expos'd a
while to the Air, turn'd into a kind of Scum or Litharge, how bright and
clean soever they appear'd before, suggested to me some Thoughts or
Ravings, which I have not now time to acquaint You with. One that did not
know me, _Pyrophilus_, would perchance think I endeavour'd to impose upon
You by relating this Experiment, which I have several times try'd, but the
Reason why the _Phænomena_ mention'd have not been taken notice of, may be,
that unless Lead be brought to a much higher degree of Fusion or Fluidity
than is usual, or than is indeed requisite to make it melt, the _Phænomena_
I mention'd will scarce at all disclose themselves; And we have also
observ'd that this successive appearing and vanishing of vivid Colours, was
wont to be impair'd or determin'd whilst the Metal expos'd to the Air
remain'd yet hotter than one would readily suspect. And one thing I must
further Note, of which I leave You to search after the Reason, namely, that
the same Colours did not always and regularly succeed one another, as is
usually in Steel, but in the diversify'd Order mention'd in this following
Note, which I was scarce able to write down, the succession of the Colours
was so very quick, whether that proceeded from the differing degrees of
Heat in the Lead expos'd to the cool Air, or from some other Reason, I
leave you to examine.

    [_Blew, Yellow, Purple, Blew; Green, Purple, Blew, Yellow, Red; Purple,
    Blew, Yellow and Blew, Yellow, Blew, Purple, Green mixt, Yellow, Red,
    Blew, Green, Yellow, Red, Purple, Green_.]

5. The _Atomists_ of Old, and some Learned men of late, have attempted to
explicate the variety of Colours in Opacous bodies from the various Figures
of their Superficial parts; the attempt is Ingenious, and the Doctrine
seems partly True, but I confess I think there are divers other things that
must be taken in as concurrent to produce those differing forms of
Asperity, whereon the Colours of Opacous bodies seem to depend. To declare
this a little, we must assume, that the Surfaces of all such Bodies how
Smooth or polite soever they may appear to our Dull Sight and Touch, are
exactly smooth only in a popular, or at most in a Physical sense, but not
in a strict and rigid sense.

6. This, excellent _Microscopes_ shew us in many Bodies, that seem Smooth
to our naked Eyes; and this not only as to the little Hillocks or
Protuberancies that swell above that which may be conceiv'd to be the Plain
or Level of the consider'd Surface, for it is obvious enough to those that
are any thing conversant with such Glasses, but as to numerous Depressions
beneath that Level, of which sort of Cavities by the help of a
_Microscope_, which the greatest Artificer that makes them, judges to be
the greatest Magnifying Glass in _Europe_, except one that equals it, we
have on the Surface of a thin piece of Cork that appear'd smooth to the
Eye, observ'd about sixty in a Row, within the length of less then an 31
and 32 part of an Inch, (for the Glass takes in no longer a space at one
view) and these Cavities (which made that little piece of Cork look almost
like an empty Honey-comb) were not only very distinct, and figur'd like one
another, but of a considerable bigness, and a scarce credible depth;
insomuch that their distinct shadows as well as sides were plainly
discern'd and easiy to be reckon'd, and might have been well distinguish'd,
though they had been ten times lesser than they were; which I thought it
not amiss to mention to you _Pyrophilus_ upon the by, that you may thence
make some Estimate, what a strange Inequality, and what a multitude of
little Shades, there may really be, in a scarce sensible part of the
Physical superficies, though the naked Eye sees no such matter. And as
Excellent _Microscopes_ shew us this Ruggedness in many Bodies that pass
for Smooth, so there are divers Experiments, though we must not now stay to
urge them, which seem to perswade us of the same thing as to the rest of
such Bodies as we are now treating off; So, that there is no sensible part
of an Opacous body, that may not be conceiv'd to be made up of a multitude
of singly insensible Corpuscles, but in the giving these surfaces that
disposition, which makes them alter the Light that reflects thence to the
Eye after the manner requisite to make the Object appear Green, Blew, &c.
the Figures of these Particles have _a great_, but not _the only_ stroak.
'Tis true indeed that the protuberant Particles may be of very great
variety of Figures, Sphærical, Elliptical, Conical, Cylindrical,
Polyedrical, and some very irregular, and that according to the Nature of
these, and the situation of the Lucid body, the Light must be variously
affected, after one manner from Surfaces (I now speak of Physical Surfaces)
consisting of Sphaerical, and in another from those that are made up of
Conical or Cylindrical Corpuscles; some being fitted to reflect more of the
incident Beams of Light, others less, and some towards one part, others
towards another. But besides this difference of Shape, there may be divers
other things that may eminently concurr to vary the forms of Asperity that
Colours so much depend on. For, willingly allowing the Figure of the
Particles in the first place, I consider secondly, that the superficial
Corpuscles, if I may so call them, may be bigger in one Body, and less in
another, and consequently fitted to allay the Light falling on them with
greater shades. Next, the protuberant Particles may be set more or less
close together, that is, there may be a greater or a smaller number of them
within the compass of one, than within the compass of another small part of
the Surface of the same Extent, and how much these Qualities may serve to
produce Colour may be somewhat guess'd at, by that which happens in the
Agitation of Water; for if the Bubbles that are thereby made be Great, and
but Few, the Water will scarce acquire a sensible Colour, but if it be
reduc'd to a Froth, consisting of Bubbles, which being very Minute and
Contiguous to each other, are a multitude of them crowded into a narrow
Room, the Water (turned to Froth) does then exhibit a very manifest White
Colour,[3] (to which these last nam'd Conditions of the Bubbles do as well
as their Convex figure contribute) and that for Reasons to be mention'd
anon. Besides, it is not necessary that the Superficial particles that
exhibit one Colour, should be all of them Round, or all Conical, or all of
any one Shape, but Corpuscles of differing Figures may be mingled on the
Surface of the Opacous Body, as when the Corpuscles that make a Blew
colour, and those that make a Yellow, come to be Accurately and Skilfully
mix'd, they make up a Green, which though it seem one simple Colour, yet in
this case appears to be made by Corpuscles of very differing Kinds, duely
commix'd. Moreover the Figure and Bigness of the little Depressions,
Cavities, Furrows or Pores intercepted betwixt these protuberant
Corpuscles, are as well to be consider'd as the Sizes and Shapes of the
Corpuscles themselves: For we may conceive the Physical superficies of a
Body, where (as we said) its Colour does as it were reside, to be cut
Transversly by a Mathematical plain, which you know is conceiv'd to be
without any Depth or Thickness at all, and then as some parts of the
Physical Superficies will be Protuberant; or swell above this last plain,
so others may be depress'd beneath it; as (to explane my self by a gross
Comparison) in divers places of the Surface of the Earth, there are not
only Neighbouring Hills, Trees, &c. that are rais'd above the Horizontal
Level of the Valley, but Rivers, Wells, Pits and other Cavities that are
depress'd beneath it, and that such Protuberant and Concave parts of a
Surface may remit the Light so differingly, as much to vary a Colour, some
examples and other things, that we shall hereafter have occasion to take
notice off in this Tract, will sufficiently declare, till when, it may
suffice to put you in mind, that of two Flat-sides of the same piece of,
for example, red Marble, the one being diligently Polished, and the other
left to its former Roughness, the differing degrees or sorts of Asperity,
for the side that is smooth to the Touch wants not its Roughness, will so
diversifie the Light reflected from the several Plains to the Eye, that a
Painter would employ two differing Colours to represent them.

  [3] _See the Discourse of the Nature of Whiteness and Blackness._

7. And I hope, _Pyrophilus_, you will not think it strange or impertinent,
that I employ in divers passages of these Papers, examples drawn from
Bodies and Shadows far more Gross, than those minute Protuberances and
shady Pores on which in most cases the Colour of a Body as 'tis an Inherent
Quality or Disposition of its Surface, seems to depend. For sometimes I
employ such Examples, rather to declare my Meaning, than prove my
Conjecture; things, whom their Smallness makes Insensible, being better
represented to the Imagination by such familiar Objects, as being like them
enough in other respects, are of a Visible bulk. And next, though the Beams
of Light are such subtil Bodies, that in respect of them, even Surfaces
that are sensibly Smooth, are not exactly so, but have their own degree of
Roughness, consisting of little Protuberances and Depressions; and though
consequently such Inequalities may suffice to give Bodies differing
Colours, as we see in Marble that appears White or Black, or Red or Blew,
even when the most carefully Polish'd, yet 'tis plain by the late Instance
of Red Marble, and many others, that even bigger Protuberances and greater
Shades may likewise so Diversifie the Roughness of a Bodies Superficies, as
manifestly to concurr to the varying of its Colour, whereby such Examples
appear to be proper enough to be employ'd in such a Subject as we have now
in hand. And having hinted thus much on this Occasion, I now proceed.

8. The Situation also of the Superficial particles is considerable, which I
distinguish into the Posture of the single Corpuscles, in respect of the
Light, and of the Eye, and the Order of them in reference also to one
another; for a Body may otherwise reflect the Light, when its Superficial
particles are more erected upon the Plain that may be conceiv'd to pass
along their Basis, and when the Points or Extremes of such Particles are
Obverted to the Eye, than when those Particles are so Inclin'd, that their
Sides are in great part Discernable, as the Colour of Plush or Velvet will
appear Vary'd to you, if you carefully stroak part of it one way, and part
of it another, the posture of the particular Thrids, in reference to the
Light, or the Eye, becoming thereby different. And you may observe in a
Field of ripe Corn blown upon by the Wind, that there will appear as it
were Waves of a Colour (at least Gradually) differing from that of the rest
of the Field, the Wind by Depressing some of the Ears, and not at the same
time others, making the one Reflect more from the Lateral and Strawy parts,
than do the rest. And so, when Doggs are so angry, as to Erect the Hairs
upon their Necks, and upon some other parts of their Bodies, those Parts
seem to acquire a Colour vary'd from that which the same Hairs made, when
in their usual Posture they did farr more stoop. And that the Order wherein
the Superficial Corpuscles are Rang'd is not to be neglected, we may guess
by turning of Water into Froth, the beating of Glass, and the scraping of
Horns, in which cases the Corpuscles that were before so marshall'd as to
be Perspicuous, do by the troubling of that Order become Dispos'd to
terminate and reflect more Light, and thereby to appear Whitish. And there
are other ways in which the Order of the Protuberant parts, in reference to
the Eye, may much contribute to the appearing of a particular Colour, for I
have often observ'd, that when Pease are Planted, or Set in Parallel Lines,
and are Shot up about half a Foot above the Surface of the Ground, by
looking on the Field or Plot of Ground from that part towards which the
Parallel Lines tended, the greater part of the Ground by farr would appear
of its own dirty Colour, but if I look'd upon it Transversly, the Plot
would appear very Green, the upper parts of the Pease hindering the
intercepted parts of the Ground, which as I said retain'd their wonted
Colour, from being discover'd by the Eye. And I know not, _Pyrophilus_,
whether I might not add, that even the Motion of the Small Parts of a
Visible Object may in some cases contribute, though it be not so easie to
say how, to the Producing or the Varying of a Colour; for I have several
times made a Liquor, which when it has well settled in a close Vial, is
Transparent and Colourless, but as soon as the Glass is unstopp'd, begins
to fly away very plentifully in a White and Opacous fume; and there are
other Bodies, whose Fumes, when they fill a Receiver, would make one
suspect it contains Milk, and yet when these Fumes settle into a Liquor,
that Liquor is not White, but Transparent; And such White Fumes I have seen
afforded by unstopping a Liquor I know, which yet is it self Diaphanous and
Red; Nor are these the only Instances of this Kind, that our Tryals can
supply us with. And if the Superficial Corpuscles be of the Grosser sort,
and be so Framed, that their differing Sides or Faces may exhibit differing
Colours, then the Motion or Rest of those Corpuscles may be considerable,
as to the Colour of the Superficies they compose, upon this account, that
sometimes more, sometimes fewer of the Sides dispos'd to exhibit such a
Colour may by this means become or continue more Obverted to the Eye than
the rest, and compose a Physical Surface, that will be more or less
sensibly interrupted; As, to explane my meaning, by proposing a gross
Example, I remember, that in some sorts of Leavy Plants thick set by one
another, the two sides of whose Leaves were of somewhat differing Colours,
there would be a notable Disparity as to Colour, if you look'd upon them
both when the Leaves being at Rest had their upper and commonly expos'd
sides Obverted to the Eye, and when a breath of Wind passing thorow them,
made great Numbers of the usually Hidden sides of the Leaves become
conspicuous. And though the Little Bodies, we were lately speaking of, may
Singly and Apart seem almost Colourless, yet when Many of them are plac'd
by one another, so near, that the Eye does not easily discern an
Interruption, within a sensible space, they may exhibit a Colour; as we
see, that though a Slenderest Thrid of Dy'd Silk do's, whilst look'd on
Single, seem almost quite Devoyd of Redness, (for instance) yet when
numbers of these Thrids are brought together into one Skein, their Colour
becomes notorious.

9. But the same Occasion that invited me to say what I have mention'd
concerning the Leaves of Trees, invites me also to give you some account of
what happens in Changeable Taffities, where we see differing Colours, as it
were, Emerge and Vanish upon the Ruffling of the same piece of Silk: As I
have divers times with Pleasure observ'd, by the help of such a
_Microscope_, as, though it do not very much Magnifie the Object, has in
recompence this great Conveniency, that you may easily, as fast as you
please, remove it from one part to another of a Large Object, of which the
Glass taking a great part at once, you may thereby presently Survey the
Whole. Now by the help of such a _Microscope_ I could easily (as I began to
say) discern, that in a piece of Changeable Taffity, (that appear'd, for
Instance, sometimes Red, and sometimes Green) the Stuff was compos'd of Red
thrids and Green, passing under and over each other, and crossing one
another in almost innumerable points; and if I look'd through the Glass
upon any considerable portion of the Stuff, that (for example sake) to the
naked Eye appear'd to be Red, I could plainly see, that in that Position,
the Red thrids were Conspicuous, and reflected a vivid Light; and though I
could also perceive, that there were Green ones, yet by reason of their
disadvantagious Position in the _Physical Surface_ of the Taffity, they
were in part hid by the more Protuberant Thrids of the other Colour; and
for the same cause, the Reflection from as much of the Green as was
discover'd, was comparatively but Dim and Faint. And if, on the contrary, I
look'd through the _Microscope_ upon any part that appear'd Green, I could
plainly see that the Red thrids were less fully expos'd to the Eye, and
obscur'd by the Green ones, which therefore made up the Predominant Colour.
And by observing the Texture of the Silken Stuff, I could easisy so expose
the Thrids either of the one Colour or of the other to my Eye, as at
pleasure to exhibit an apparition of Red or Green, or make those Colours
succeed one another: So that, when I observ'd their Succession by the help
of the Glass, I could mark how the Predominant Colour did as it were start
out, when the Thrids that exhibited it came to be advanagiously plac'd; And
by making little Folds in the Stuff after a certain manner, the Sides that
met and terminated in those Folds, would appear to the naked Eye, one of
them Red, and the other Green. When Thrids of more than two differing
Colours chance to be Interwoven, the resulting changeableness of the
Taffity may be also somewhat different. But I choose to give an Instance in
the Stuff I have been speaking off, because the mixture being more Simple,
the way whereby the Changeableness is produc'd, may be the more easily
apprehended: and though Reason alone might readily enough lead a
considering Man to guess at the Explication, in case he knew how Changeable
Taffities are made: yet I thought it not impertinent to mention it, because
both Scholars and Gentlemen are wont to look upon the Inquiry into
Manufactures, as a _Mechanick_ imployment, and consequently below Them; and
because also with such a _Microscope_ as I have been mentioning, the
discovery is as well Pleasant as Satisfactory, and may afford Hints of the
Solution of other _Phænomena_ of Colours. And it were not amiss, that some
diligent Inquiry were made, whether the _Microscope_ would give us an
account of the Variableness of Colour, that is so Conspicuous and so
Delightfull in Mother of Pearl, in Opalls, and some other resembling
Bodies: For though I remember I did formerly attempt something of that Kind
(fruitlesly enough) upon Mother of Pearl, yet not having then the advantage
of my best _Microscope_, nor some Conveniences that might have been wish'd,
I leave it to you, who have better Eyes, to try what you can do further;
since 'twill be _Some_ discovery to find, that, in this case, the best Eyes
and _Microscopes_ themselves can make _None_.

10. I confess, _Pyrophilus_, that a great part of what I have deliver'd,
(or propos'd rather) concerning the differing forms of Asperity in Bodies,
by which Differences the incident Light either comes to be Reflected with
more or less of Shade, and with that Shade more or less Interrupted, or
else happens to be also otherwise Modify'd or Troubl'd, is but Conjectural.
But I am not sure, that if it were not for the Dullness of our Senses,
either these or some other Notions of Kin to them, might be better
Countenanc'd; for I am apt to suspect, that if we were Sharp sighted
enough, or had such perfect _Microscopes_, as I fear are more to be wish'd
than hop'd for, our promoted Sense might discern in the Physical Surfaces
of Bodies, both a great many latent Ruggidnesses, and the particular Sizes,
Shapes, and Situations of the extremely little Bodies that cause them, and
perhaps might perceive among other Varieties that we now can but imagine,
how those little Protuberances and Cavities do Interrupt and Dilate the
Light, by mingling with it a multitude of little and singly undiscernable
Shades, though some of them more, and some of them less Minute, some less,
and some more Numerous; according to the Nature and Degree of the
particular Colour we attribute to the Visible Object; as we see, that in
the Moon we can with Excellent _Telescopes_ discern many Hills and Vallies,
and as it were Pits and other Parts, whereof some are more, and some less
Vividly illustrated, and others have a fainter, others a deeper Shade,
though the naked Eye can discern no such matter in that Planet. And with an
Excellent _Microscope_, where the _Naked_ Eye did see but a Green powder,
the _Assisted_ Eye as we noted above, could discern particular Granules,
some of them of a Blew, and some of them of a Yellow colour, which
Corpuscles we had beforehand caus'd to be exquisitly mix'd to compound the
Green.

11. And, _Pyrophilus_, that you may not think me altogether extravagant in
what I have said of the Possibility, (for I speak of no more) of discerning
the differing forms of Asperity in the Surfaces of Bodies of several
Colours, I'l here set down a Memorable particular that chanc'd to come to
my Knowledge, since I writ a good part of this _Essay_; and it is this.
Meeting casually the other Day with the deservedly Famous[4] Dr. _J.
Finch_, Extraordinary _Anatomist_ to that Great Patron of the _Virtuosi_,
the now Great Duke of _Toscany_, and enquiring of this Ingenious Person,
what might be the chief Rarity he had seen in his late return out of
_Italy_ into _England_, he told me, it was a Man at _Maestricht_ in the
Low-Countrys, who at certain times can discern and _distinguish Colours by
the Touch_ with his Fingers. You'l easily Conclude, that this is farr more
strange, than what I propos'd but as _not Impossible_; since the Sense of
the _Retina_ seeming to be much more Tender and quick than that of those
Grosser Filaments, Nerves or Membranes of our Fingers, wherewith we use to
handle Gross and Hard Bodies, it seems scarce credible, that any
Accustomance, or Diet, or peculiarity of Constitution, should enable a Man
to distinguish with such Gross and Unsuitable Organs, such Nice and Subtile
Differences as those of the forms of Asperity, that belong to differing
Colours, to receive whose Languid and Delicate Impressions by the
Intervention of Light, Nature seems to have appointed and contexed into the
_Retina_ the tender and delicate Pith of the Optick Nerve. Wherefore I
confess, I propos'd divers Scruples, and particularly whether the Doctor
had taken care to bind a Napkin or Hankerchief over his Eyes so carefully,
as to be sure he could make no use of his Sight, though he had but
Counterfeited the want of it, to which I added divers other Questions, to
satisfie my Self, whether there were any Likelihood of Collusion or other
Tricks. But I found that the Judicious Doctor having gone farr out of his
way, purposely to satisfie Himself and his Learned Prince about this
Wonder, had been very Watchfull and Circumspect to keep _Himself_ from
being Impos'd upon. And that he might not through any mistake in point of
Memory mis-inform _Me_, he did me the Favour at my Request, to look out the
Notes he had Written for his Own and his Princes Information, the summ of
which Memorials, as far as we shall mention them here, was this, That the
Doctor having been inform'd at _Utrecht_, that there Lived one at some
Miles distance from _Maestricht_, who could distinguish Colours by the
Touch, when he came to the last nam'd Town, he sent a Messenger for him,
and having Examin'd him, was told upon Enquiry these Particulars:

  [4] Since for his eminent Qualities and Loyalty Grac'd, by his Majesty,
  with the Honour of Knighthood.

That the Man's name was _John Vermaasen_, at that time about 33 Years of
Age; that when he was but two years Old, he had the Small Pox, which
rendred him absolutely Blind: That at this present he is an _Organist_, and
serves that Office in a publick Quire.

That the Doctor discoursing with him over Night, the Blind man affirm'd,
that he could distinguish Colours by the Touch, but that he could not do
it, unless he were Fasting; Any quantity of Drink taking from him that
Exquisitness of Touch, which is requisite to so Nice a Sensation.

That hereupon the Doctor provided against the next Morning seven pieces of
Ribbon, of these seven Colours, Black, White, Red, Blew, Green, Yellow, and
Gray, but as for _mingled_ Colours, this _Vermaasen_ would not undertake to
discern them, though if offer'd, he would tell that they were _Mix'd_.

That to discern the Colour of the Ribbon, he places it betwixt the Thumb
and the Fore-finger, but his most exquisite perception was in his Thumb,
and much better in the right Thumb than in the left.

That after the Blind man had four or five times told the Doctor the several
Colours, (though Blinded with a Napkin for fear he might have some Sight)
the Doctor found he was twice mistaken, for he call'd the White Black, and
the Red Blew, but still, he, before his Errour, would lay them by in Pairs,
saying, that though he could easily distinguish them from all others, yet
those two Pairs were not easily distinguish'd amongst themselves, whereupon
the Doctor desir'd to be told by him what kind of Discrimination he had of
Colours by his Touch, to which he gave a reply, for whose sake chiefly I
insert all this Narrative in this place, namely, That all the difference
was more or less Asperity, for says he, (I give you the Doctor's own words)
Black feels as if you were feeling Needles points, or some harsh Sand, and
Red feels very Smooth.

That the Doctor having desir'd him to tell in Order the difference of
Colours to his Touch, he did as follows;

Black and White are the most asperous or unequal of all Colours, and so
like, that 'tis very hard to distinguish them, but Black is the most Rough
of the two, Green is next in Asperity, Gray next to Green in Asperity,
Yellow is the fifth in degree of Asperity, Red and Blew are so like, that
they are as hard to distinguish as Black and White, but Red is somewhat
more Asperous than Blew, so that Red has the sixth place, and Blew the
seventh in Asperity.

12. To these Informations the Obliging Doctor was pleas'd to add the
welcome present of three of those very pieces of Ribbon, whose Colours in
his presence the Blind man had distinguished, pronouncing the one Gray, the
other Red, and the third Green, which I keep by me as Rarities, and the
rather, because he fear'd the rest were miscarry'd.

13. Before I saw the Notes that afforded me the precedent Narrative, I
confess I suspected this man might have thus discriminated Colours, rather
by the Smell than by the Touch; for some of the Ingredients imployed by
Dyers to Colour things, have Sents, that are not so Languid, nor so near of
Kin, but that I thought it not impossible that a very Critical Nose might
distinguish them, and this I the rather suspected, because he requir'd,
that the Ribbons, whose Colours he was to Name, should be offer'd him
Fasting in the morning; for I have observ'd in Setting Doggs, that the
feeding of them (especially with some sorts of Aliments) does very much
impair the exquisite sent of their Noses. And though some of the foregoing
particulars would have prevented that Conjecture, yet I confess to you
(_Pyrophilus_) that I would gladly have had the Opportunity of Examining
this Man my self, and of Questioning him about divers particulars which I
do not find to have been yet thought upon. And though it be not incredible
to me, that since the Liquors that Dyers imploy to tinge, are qualifi'd to
do so by multitudes of little Corpuscles of the Pigment or Dying stuff,
which are dissolved and extracted by the Liquor, and swim to and fro in it,
those Corpuscles of Colour (as the _Atomists_ call them) insinuating
themselves into, and filling all the Pores of the Body to be Dyed, may
Asperate its Superficies more or less according to the Bigness and Texture
of the Corpuscles of the Pigment; yet I can scarce believe, that our Blind
man could distinguish all the Colours he did, meerly by the Ribbons having
more or less of Asperity, so that I cannot but think, notwithstanding this
History, that the Blind man distinguish'd Colours not only by the _Degrees_
of Asperity in the Bodies offer'd to him, but by _Forms_ of it, though this
(latter) would perhaps have been very difficult for him to make an
Intelligible mention of, because those Minute disparities having not been
taken notice of by men for want of touch as Exquisite as our Blind Mans,
are things he could not have Intelligibly express'd, which will easily seem
Probable, if you consider, that under the name of Sharp, and Sweet, and
Sour, there are abundance of, as it were, immediate peculiar Relishes or
Tasts in differing sorts of Wine, which though Critical and Experienc'd
Palats can easily discern themselves cannot make them be understood by
others, such Minute differences not having hitherto any Distinct names
assign'd them. And it seems that there was somthing in the Forms of
Asperity that was requisite to the Distinction of Colours, besides the
Degree of it, since he found it so difficult to distingush Black and White
from one another, though not from other Colours. For I might urge, that he
seems not consonant to himself about the _Red_, which as you have seen in
one place, he represents as somewhat more Asperous than the _Blew_; and in
another, very Smooth: But because he speaks of this Smoothness in that
place, where he mentions the Roughness of _Black_, we may favourably
presume that he might mean but a _comparative Smoothness_; and therefore I
shall not Insist on this, but rather Countenance my Conjecture by this,
that he found it so Difficult, not only, to Discriminate Red and Blew,
(though the first of our promiscuous Experiments will inform you, that the
Red reflects by great Odds more Light than the other) but also to
distinguish Black and White from one another, though not from other
Colours. And indeed, though in the Ribbonds that were offer'd him, they
might be almost equally Rough, yet in such slender Corpuscles as those of
Colour, there may easily enough be Conceiv'd, not only a greater Closeness
of Parts, or else Paucity of Protuberant Corpuscles, and the little extant
Particles may be otherwise Figur'd, and Rang'd in the White than in the
Black, but the Cavities may be much Deeper in the one than the other.

14. And perhaps, (_Pyrophilus_) it may prove some _Illustration of what I
mean_, and help you to conceive how _this may_ be, if I Represent, that
where the Particles are so exceeding Slender, we may allow the Parts
expos'd to the Sight and Touch to be a little Convex in comparison of the
Erected Particle of Black Bodies, as if there were Wyres I know not how
many times Slenderer than a Hair: whether you suppose them to be Figur'd
like Needles, or Cylindrically, like the Hairs of a Brush, with
Hemisphærical (or at least Convex) Tops, they will be so very Slender, and
consequently the Points both of the one sort and the other so very Sharp,
that even an exquisite Touch will be able to distinguish no greater
Difference between them, than that which our Blind man allow'd, when
comparing Black and White Bodies, he said, that the latter was the less
Rough of the two. Nor is every Kind of Roughness, though Sensible enough,
Inconsistent with Whiteness, there being Cases, wherein the Physical
Superficies of a Body is made by the same Operation both _Rough_ and
_white_, as when the Level Surface of clear Water being by agitation
Asperated with a multitude of Unequal Bubbles, do's thereby acquire a
Whiteness; and as a Smooth piece of Glass, by being Scratch'd with a
Diamond, do's in the Asperated part of its Surface disclose the same
Colour. But more (perchance) of this elsewhere.

15. And therefore, we shall here pass by the Question, whether any thing
might be consider'd about the Opacity of the Corpuscles of Black Pigments,
and the _Comparative_ Diaphaneity of those of many White Bodies, apply'd to
our present Case; and proceed, to represent, That the newly mention'd
Exiguity and Shape of the extant Particles being suppos'd, it will then be
considerable what we lately but Hinted, (and therefore must now somewhat
Explane) That the Depth of the little Cavities, intercepted between the
extant Particles, without being so much greater in Black Bodies than in
White ones, as to be perceptibly so to the Gross Organs of Touch, may be
very much greater in reference to their Disposition of Reflecting the
imaginary subtile Beams of Light. For in Black Bodies, those Little
intercepted Cavities, and other Depressions, may be so Figur'd, so Narrow
and so Deep, that the incident Beams of Light, which the more extant Parts
of the Physical Superficies are dispos'd to Reflect inwards, may be
Detain'd there, and prove unable to Emerge; whilst in a White Body, the
Slender Particles may not only by their Figure be fitted to Reflect the
Light copiously outwards, but the intercepted Cavities being not Deep, nor
perhaps very Narrow, the Bottoms of them may be so Constituted, as to be
fit to Reflect outwards much of the Light that falls even upon Them; as you
may possibly better apprehend, when we shall come to treat of Whiteness and
Blackness. In the mean time it may suffice, that you take Notice with me,
that the Blind mans Relations import no necessity of Concluding, that,
though, because, according to the Judgment of his Touch, Black was the
Roughest, as it is the Darkest of Colours, therefore White, which
(according to us) is the Lightest, should be also the Smoothest: since I
observe, that he makes Yellow to be two Degrees more Asperous than Blew,
and as much less Asperous than Green; whereas indeed, Yellow do's not only
appear to the Eye a Lighter Colour than Blew, but (by our first Experiment
hereafter to be mention'd) it will appear, that Yellow reflected much more
Light than Blew, and manifestly more than Green, (which we need not much
wonder at, since in this Colour and the two others (Blew and Yellow) 'tis
not _only_ the _Reflected Light_ that is to be considered, since to produce
both these, _Refraction_ seems to Intervene, which by its Varieties may
much alter the Case:) which both seems to strengthen the Conjecture I was
formerly proposing, that there was something else in the _Kinds_ of
Asperity, as well as in the _Degrees_ of it, which enabled our Blind man to
Discriminate Colours, and do's at least show, that we cannot in all Cases
from the bare Difference in the Degrees of Asperity betwixt Colours, safely
conclude, that the Rougher of any two always Reflects the least Light.

16. But this notwithstanding, (_Pyrophilus_) and what ever Curiosity I may
have had to move some Questions to our Sagacious Blind man, yet thus much I
think you will admit us to have gain'd by his Testimony, that since many
Colours may be felt with the Circumstances above related, the Surfaces of
such Coloured Bodies must certainly have differing _Degrees_, and in all
probability have differing _Forms_ or Kinds of Asperity belonging to them,
which is all the Use that my present attempt obliges me to make of the
History above deliver'd, that being sufficient to prove, _that_ Colour do's
much depend upon the Disposition of the Superficial parts of Bodies, and to
shew in general, _wherein_ 'tis probable that such a Disposition do's
(principally at least) consist.

17. But to return to what I was saying before I began to make mention of
our Blind _Organist_, what we have deliver'd touching the causes of the
several Forms or Asperity that may Diversifie the Surfaces of Colour'd
Bodies, may perchance somewhat assist us to make some Conjectures in the
general, at several of the ways whereby 'tis possible for the Experiments
hereafter to be mention'd, to produce the suddain changes of Colours that
are wont to be Consequent upon them; for most of these _Phænomena_ being
produc'd by the Intervention of Liquors, and these for the most part
abounding with very Minute, Active, and Variously Figur'd Saline
Corpuscles, Liquors so Qualify'd may well enough very Nimbly after the
Texture of the Body they are imploy'd to Work upon, and so may change the
form of Asperity, and thereby make them Remit to the Eye the Light that
falls on them, after another manner than they did before, and by that means
Vary the Colour, so farr forth as it depends upon the Texture or
Disposition of the Seen Parts of the Object, which I say, _Pyrophilus_,
that you may not think I would absolutely exclude all other ways of
Modifying the Beams of Light between their Parting from the Lucid Body, and
their Reception into the common Sensory.

18. Now there seem to me divers ways, by which we may conceive that Liquors
may Nimbly alter the Colour of one another, and of other Bodies, upon which
they Act, but my present haste will allow me to mention but some of them,
without Insisting so much as upon those I shall name.

19. And first, the Minute Corpuscles that compose a Liquor may early
insinuate themselves into those Pores of Bodies, whereto their Size and
Figure makes them Congruous, and these Pores they may either exactly Fill,
or but Inadequately, and in this latter Case they will for the most part
alter the Number and Figure, and always the Bigness of the former Pores.
And in what capacity soever these Corpuscles of a Liquor come to be Lodg'd
or Harbour'd in the Pores that admit them, the Surface of the Body will for
the most part have its Asperity alter'd, and the Incident Light that meets
with a Grosser Liquor in the little Cavities that before contain'd nothing
but Air, or some yet Subtiler Fluid, will have its Beams either Refracted,
or Imbib'd, or else Reflected more or less Interruptedly, than they would
be, if the Body had been Unmoistned, as we see, that even fair Water
falling on white Paper, or Linnen, and divers other Bodies apt to soak it
in, will for some such Reasons as those newly mention'd, immediately alter
the Colour of them, and for the most part make it Sadder than that of the
Unwetted Parts of the same Bodies. And so you may see, that when in the
Summer the High-ways are Dry and Dusty, if there falls store of Rain, they
will quickly appear of a much Darker Colour than they did before, and if a
Drop of Oyl be let fall upon a Sheet of White Paper, that part of it, which
by the Imbibition of the Liquor acquires a greater Continuity, and some
Transparency, will appear much Darker than the rest, many of the Incident
Beams of Light being now Transmitted, that otherwise would be Reflected
towards the Beholders Eyes.

20. Secondly, A Liquor may alter the Colour of a Body by freeing it from
those things that hindred it from appearing in its Genuine Colour; and
though this may be said to be rather a Restauration of a Body to its own
Colour, or a Retection of its native Colour, than a Change, yet still there
Intervenes in it a change of the Colour which the Body appear'd to be of
before this Operation. And such a change a Liquor may work, either by
Dissolving, or Corroding, or by some such way of carrying off that Matter,
which either Veil'd or Disguis'd the Colour that afterwards appears. Thus
we restore Old pieces of Dirty Gold to a clean and nitid Yellow, by putting
them into the Fire, and into _Aqua-fortis_, which take off the adventitious
Filth that made that pure Metall look of a Dirty Colour. And there is also
an easie way to restore Silver Coyns to their due Lustre, by fetching off
that which Discolour'd them. And I know a _Chymical_ Liquor, which I
employ'd to restore pieces of Cloath spotted with Grease to their proper
Colour, by Imbibing the Spotted part with this Liquor, which Incorporating
with the Grease, and yet being of a very Volatile Nature, does easily carry
it away with it Self. And I have sometimes try'd, that by Rubbing upon a
good Touch-stone a certain _Metalline_ mixture so Compounded, that the
Impression it left upon the Stone appear'd of a very differing Colour from
that of Gold, yet a little of _Aqua-fortis_ would in a Trice make the
Golden Colour disclose it self, by Dissolving the other _Metalline_
Corpuscles that conceal'd those of the Gold, which you know that
_Menstruum_ will leave Untouch'd.

21. Thirdly, A Liquor may alter the Colour of a Body by making a
Comminution of its Parts, and that principally two ways, the first by
Disjoyning and Dissipating those Clusters of Particles, if I may so call
them, which stuck more Loosely together, being fastned only by some more
easily Dissoluble Ciment, which seems to be the Case of some of the
following Experiments, where you'l find the Colour of many Corpuscles
brought to cohere by having been Precipitated together, Destroy'd by the
Affusion of very peircing and incisive Liquors. The other of the two ways I
was speaking of, is, by Dividing the Grosser and more Solid Particles into
Minute ones, which will be always Lesser, and for the most part otherwise
Shap'd than the Entire Corpuscle so Divided, as it will happen in a piece
of Wood reduc'd into Splinters or Chips, or as when a piece of Chrystal
heated red Hot and quench'd in Cold water is crack'd into a multitude of
little Fragments, which though they fall not asunder, alter the Disposition
of the Body of the Chrystal, as to its manner of Reflecting the Light, as
we shall have Occasion to shew hereafter.

22. There is a fourth way contrary to the third, whereby a Liquor may
change the Colour of another Body, especially of another Fluid, and that
is, by procuring the Coalition of several Particles that before lay too
Scatter'd and Dispers'd to exhibit the Colour that afterwards appears. Thus
sometimes when I have had a Solution of Gold so Dilated, that I doubted
whether the Liquor had really Imbib'd any true Gold or no, by pouring in a
little _Mercury_, I have been quickly able to satisfie my Self, that the
Liquor contain'd Gold, that Mettall after a little while Cloathing the
Surface of the _Quick-silver_, with a Thin Film of its own Livery. And
chiefly, though not only by this way of bringing the Minute parts of Bodies
together in such Numbers as to make them become Notorious to the Eye, many
of these Colours seem to be Generated which are produc'd by Precipitations,
especially by such as are wont to be made with fair Water, as when Resinous
Gumms dissolv'd in Spirit of Wine, are let fall again, if the Spirit be
Copiously diluted with that weakning Liquor. And so out of the Rectify'd
and Transparent Butter of _Antimony_, by the bare Mixture of fair Water,
there will be plentifully Precipitated that Milk-white Substance, which by
having its Looser Salts well wash'd off, is turn'd into that Medicine,
which Vulgar _Chymists_ are pleas'd to call _Mercurius Vitæ._

23. A fifth way, by which a Liquor may change the Colour of a Body, is, by
Dislocating the Parts, and putting them out of their former Order into
another, and perhaps also altering the Posture of the single Corpuscles as
well as their Order or Situation in respect of one another. What certain
Kinds of Commotion or Dislocation of the Parts of a Body may do towards the
Changing its Colour, is not only evident in the Mutations of Colour
observable in _Quick-silver_, and some other Concretes long kept by
_Chymists_ in a Convenient Heat, though in close Vessels, but in the
Obvious Degenerations of Colour, which every Body may take notice of in
Bruis'd Cherries, and other Fruit, by comparing after a while the Colour of
the Injur'd with that of the Sound part of the same Fruit. And that also
such Liquors, as we have been speaking of, may greatly Discompose the
Textures of many Bodies, and thereby alter the Disposition of their
Superficial parts, the great Commotion made in Metalls, and several other
Bodies by _Aqua-fortis_, Oyl of _Vitriol_, and other Saline _Menstruums_,
may easily perswade us, and what such Vary'd Situations of Parts may do
towards the Diversifying of the manner of their Reflecting the Light, may
be Guess'd in some Measure by the Beating of Transparent Glass into a White
Powder, but farr better by the Experiments lately Pointed at, and hereafter
Deliver'd, as the Producing and Destroying Colours by the means of subtil
Saline Liquors, by whose Affusion the Parts of other Liquors are manifestly
both Agitated, and likewise Dispos'd after another manner than they were
before such Affusion. And in some _Chymical_ Oyls, as particularly that of
Lemmon Pills, by barely Shaking the Glass, that holds it, into Bubbles,
that Transposition of the Parts which is consequent to the Shaking, will
shew you on the Surfaces of the Bubbles exceeding Orient and Lively
Colours, which when the Bubbles relapse into the rest of the Oyl, do
immediately Vanish.

24. I know not, _Pyrophilus_, whether I should mention as a Distinct way,
because it is of a somewhat more General Nature, that Power, whereby a
Liquor may alter the Colour of another Body, by putting the Parts of it
into Motion; For though possibly the Motion so produc'd, does, as such,
seldome suddenly change the Colour of the Body whose Parts are Agitated,
yet this seems to be one of the most General, however not Immediate causes
of the Quick change of Colours in Bodies. For the Parts being put into
Motion by the adventitious Liquor, divers of them that were before United,
may become thereby Disjoyn'd, and when that Motion ceases or decays others
of them may stick together, and that in a new Order, by which means the
Motion may sometimes produce Permanent changes of Colours, as in the
Experiment you will meet with hereafter, of presently turning a Snowy White
Body into a Yellow, by the bare Affusion of fair Water, which probably so
Dissolves the Saline Corpuscles that remain'd in the _Calx_, and sets them
at Liberty to Act upon one another, and the Metall, far more Powerfully
than the Water without the Assistance of such Saline Corpuscles could do.
And though you rubb Blew _Vitriol_, how Venereal and Unsophisticated soever
it be, upon the Whetted Blade of a Knife, it will not impart to the Iron
its Latent Colour, but if you moisten the _Vitriol_ with your Spittle, or
common Water, the Particles of the Liquor disjoyning those of the
_Vitriol_, and thereby giving them the Various Agitation requisite to Fluid
Bodies, the Metalline Corpuscles of the thus Dissolv'd _Vitriol_ will Lodge
themselves in Throngs in the Small and Congruous Pores of the Iron they are
Rubb'd on, and so give the Surface of it the Genuine Colour of the Copper.

25. There remains yet a way, _Pyrophilus_ to be mention'd, by which a
Liquor may alter the Colour of another Body, and this seems the most
Important of all, because though it be nam'd but as One, yet it may indeed
comprehend Many, and that is, by Associating the Saline Corpuscles, or any
other Sort of the more Rigid ones of the Liquor, with the Particles of the
Body that it is employ'd to Work upon. For these Adventitious Corpuscles
Associating themselves with the Protuberant Particles of the Surface of a
Colour'd Body, must necessarily alter their Bigness, and will most commonly
alter their Shape. And how much the Colours of Bodies depend upon the Bulk
and Figure of their Superficial Particles, you may Guess by this, that
eminent antient _Philosophers_ and divers _Moderns_, have thought that all
Colours might in a general way be made out by these two; whose being
Diversify'd, will in our Case be attended with these two Circumstances, the
One, that the Protuberant Particles being Increas'd in Bulk, they will
oftentimes be Vary'd as to the Closness or Laxity of their Order, fewer of
them being contain'd within the same Sensible (though Minute) space than
before; or else by approaching to one another, they must Straighten the
Pores, and it may be too, they will by their manner of Associating
themselves with the Protuberant Particles, intercept new Pores. And this
invites me to consider farther, that the Adventitious Corpuscles, I have
been speaking of, may likewise produce a great Change as well in the Little
Cavities or Pores as in the Protuberances of a Colour'd Body; for besides
what we have just now taken notice of, they may by Lodging themselves in
those little Cavities, fill them up, and it may well happen, that they may
not only fill the Pores they Insinuate themselves into, but likewise have
their Upper Parts extant above them; and partly by these new Protuberances,
partly by Increasing the Bulk of the former, these Extraneous Corpuscles
may much alter the Number and Bigness of the Surfaces Pores, changing the
Old and Intercepting new ones. And then 'tis Odds, but the Order of the
Little Extancies, and consequently that of the Little Depressions in point
of Situation will be alter'd likewise: as if you dissolve _Quick-silver_ in
some kind of _Aqua-fortis_, the Saline Particles of the _Menstruum_
Associating themselves with the Mercurial Corpuscles, will make a Green
Solution, which afterwards easily enough Degenerates. And Red Lead or
_Minium_ being Dissolv'd in Spirit of Vinegar, yields not a Red, but a
Clear Solution, the Redness of the Lead being by the Liquor Destroy'd. But
a better Instance may be taken from Copper, for I have try'd, that if upon
a Copper-plate you let some Drops of weak _Aqua-fortis_ rest for a while,
the Corpuscles of the _Menstruum_, joyning with those of the Metall, will
produce a very sensible Asperity upon the Surface of the Plate, and will
Concoagulate that way into very minute Grains of a Pale Blew _Vitriol_;
whereas if upon another part of the same Plate you suffer a little strong
Spirit of Urine to rest a competent time, you shall find the Asperated
Surface adorn'd with a Deeper and Richer Blew. And the same _Aqua-fortis_,
that will quickly change the Redness of Red Lead into a Darker Colour,
will, being put upon Crude Lead, produce a Whitish Substance, as with
Copper it did a Blewish. And as with Iron it will produce a Reddish, and on
White Quills a Yellowish, so much may the Coalition of the Parts of the
same Liquor, with the differingly Figur'd Particles of Stable Bodies,
divers ways Asperate the differingly Dispos'd Surfaces, and to Diversifie
the Colour of those Bodies. And you'l easily believe, that in many changes
of Colour, that happen upon the Dissolutions of Metalls, and Precipitations
made with Oyl of _Tartar_, and the like Fix'd Salts, there may Intervene a
Coalition of Saline Corpuscles with the Particles of the Body Dissolv'd or
Precipitated, if you examine how much the _Vitriol_ of a Metall may be
Heavier than the Metalline part of it alone, upon the Score of the Saline
parts Concoagulated therewith, and, that in Several Precipitations the
weight of the _Calx_ does for the same Reason much exceed that of the
Metall, when it was first put in to be Dissolv'd.

26. But, _Pyrophilus_, to consider these Matters more particularly would be
to forget that I declar'd against Adventuring, at least for this time, at
particular Theories of Colours, and that accordingly you may justly expect
from me rather Experiments than Speculations, and therefore I shall Dismiss
this Subject of th