Firſt occaſionally Written, among ſome other
Eſſays, to a Friend; and now ſuffer'd to
come abroad as
By the Honourable ROBERT BOYLE,
Fellow of the ROYAL SOCIETY.
Non fingendum, aut excogitandum, ſed inveniendum,
quid Natura faciat, aut ferat. Bacon.
Printed for Henry Herringman at the
Anchor on the Lower walk of the New
Exchange. MDCLXIV.
Aving 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.
Friendly Reader,
Ere 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
ago2; 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.
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.
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.)
Of the Nature of Whiteneſs and Blackneſs.
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)
Concerning Promiſcuous Experiments about Colours.
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 
and 
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 
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 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.
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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, [pg 2] 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. [pg 3]
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.
[pg 4]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 [pg 5] 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 [pg 6] 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 [pg 7] 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, [pg 8] 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 [pg 9] 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 [pg 10] 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 [pg 11] 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 [pg 12] 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 [pg 13] 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 [pg 14] 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 [pg 15] (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 [pg 16] 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 [pg 17] 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 [pg 18] 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 [pg 19] 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.
[pg 20]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.
But, Pyrophilus, I would not by all that I have hitherto diſcours'd, be thought to have forgotten the Diſtinction [pg 21] (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, [pg 22] 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 [pg 23] 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 [pg 24] 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, [pg 25] 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 [pg 26] 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 [pg 27] 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 [pg 28] 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 [pg 29] 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 [pg 30] 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 [pg 31] 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.
7. And I hope, Pyrophilus, you will not think it ſtrange or impertinent, that I employ in divers paſſages of theſe Papers, [pg 32] 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 [pg 33] 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 [pg 34] 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 [pg 35] 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 [pg 36] 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) [pg 37] 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 [pg 38] 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, [pg 39] 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 [pg 40] 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