to which Effect I conceive the Heat of the Climate must have Concurr'd with the Disposition of the Black Surface to Reflect the Sun-beams Inward for I remember that having made that among other Tryals in England though in Summer-time the Eggs I Expos'd acquir'd indeed a considerable Degree of Heat but yet not so Intense a One as prov'd sufficient to Roast them 10. Seventhly and Lastly Our Conjectures at the Nature of Blackness may be somewhat Confirm'd by the formerly mention'd Observation of the Blind Dutch-man that Discerns Colours with his Fingers for he says that he Feels a greater Roughness upon the Surfaces of Black Bodies than upon those of Red or Yellow or Green And I remember that the Diligent Bartholinus says that a Blind Earl of Mansfield could Distinguish White from Black only by the Touch which would sufficiently Argue a great Disparity in the Asperities or other Superficial Textures of Bodies of those two Colours if the Learn'd Relator had Affirm'd the Matter upon his own Knowledge 11. These Pyrophilus are the chief things that Occurr to me at present about the Nature of Whiteness and Blackness which if they have Rendred it so much as Probable that in Most or at least Many Cases the Causes of these Qualities may be such as I have Adventur'd to Deliver it is as much as I Pretend to for till I have Opportunity to Examine the Matter by some further Tryals I am not sure but that in some White and Black Bodies there may Concurr to the Colour some peculiar Texture or Disposition of the Body whereby the Motion of the Small Corpuscles that make up the Incident Beams of Light may be Differingly Modify'd before they reach the Eye especially in this that White Bodies do not only Copiously Reflect those Incident Corpuscles Outwards but Reflect them Briskly and do not otherwise Alter them in the manner of their Motion Nor shall I now stay to Enquire whether some of those other ways as a Disposition to Alter the Velocity the Rotation or the Order and Manner of Appulse to the Eye of the Reflected Corpuscles that Compos'd the Incident Beams of Light which we mention'd when we consider'd the Production of Colours in General may not in some Cases be Applicable to those of White and Black Bodies For I am yet so much a Seeker in this Matter and so little Wedded to the Opinions I have propos'd that what I am to add shall be but the Beginning of a Collection of Experiments and Observations towards the History of VVhiteness and Blackness without at present interposing my Explications of them that so I may assist your Enquires without much Fore-stalling or Biassing your Judgment EXPERIMENT IN CONSORT Touching Whiteness Blackness EXPERIMENT I. HAving promis'd in the 114 and 115. Pages of the foregoing Discourse of Whiteness and Blackness to shew that those two Colours may by a change of Texture in bodies each of them apart Diaphanous and Colourless be at pleasure and in a trice as well Generated as Destroy'd We shall begin with Experiments that may acquit us of that promise Take then what Quantity you please of Fair Water and having Heated it put into it as much good Common Sublimate as it is able to Dissolve and to be sure of having it well glutted continue putting in the Sublimate till some of it lye Untouch'd in the bottom of the Liquor Filter this Solution through Cap-paper to have it cleer and limpid and into a spoonfull or two thereof put into a clean glass vessel shake about four or five drops according as you took more or less of this Solution of good limpid Spirits of Urine and immediately the whole mixture will appear White like Milk to which mixture if you presently add a convenient proportion of Rectifi'd Aqua Fortis for the number of drops is hard to determine because of the Differing Strength of the liquor but easily found by tryal the Whiteness will presently disappear and the whole mixture become Transparent which you may if you please again reduce to a good degree of Whiteness though inferiour to the first onely by a more copious affusion of fresh Spirit of Urine N. First That it is not so necessary to employ either Aqua Fortis or Spirit of Urine about this Experiment but that we have made it with other liquors instead of these of which perhaps more elsewhere Secondly That this Experiment though not made with the same Menstruums nor producing the same Colour is yet much of Kin to that other to be mentioned in this Tract among our other Experiments of Colours about turning a Solution of Praecipitate into an Orange-colour and the Chymical Reason being much alike in both the annexing it to one of them may suffice FOR both EXPERIMENT II. Make a strong Infusion of broken Galls in Fair Water and having Filtred it into a clean Vial add more of the same liquor to it till you have made it somewhat Transparent and sufficiently diluted the Colour for the credit of the Experiment lest otherwise the Darkness of the liquor might make it be objected that 't was already almost Ink Into this Infusion snake a convenient quantity of a Cleer but very strong Solution of Vitriol and you shall immediately see the mixture turn Black almost like Ink and such a way of producing Blackness is vulgar enough but if presently after you doe upon this mixture drop a small quantity of good oyl of Vitriol and by shaking the Vial disperse it nimbly through the two other liquors you shall if you perform your part well and have employ'd oyl of Vitriol Cleer and Strong enough see the Darkness of the liquor presently begin to be discuss'd and grow pretty Cleer and Transparent losing its Inky Blackness which you may again restore to it by the affusion of a small quantity of a very strong Solution of Salt of Tartar And though neither of these Atramentous liquors will seem other than very Pale Ink if you write with a clean Pen dipt in them yet that is common to them with some sorts of Ink that prove very good when Dry as I have also found that when I made these carefully what I wrote with either of them especially with the Former would when throughly Dry grow Black enough not to appear bad Ink. This Experiment of taking away and restoring Blackness from and to the liquors we have likewise tryed in Common Ink but there it succeeds not so well and but very slowly by reason that the Gum wont to be employed in the making it does by its Tenacity oppose the operations of the above mention'd Saline liquors But to consider Gum no more what some kind of Praecipitation may have to do in the producing and destroying of Inks without it I have elsewhere given you some occasion and assistance to enquire But I must not now stay to do so my self only I shall take notice to you that though it be taken for granted that bodies will not
Blackness the one far Darker than the other of which Disparity the Reason seems to be that in the Less obscure part of the Velvet the Little Silken Piles whereof 't is made up being Inclin'd there is a Greater part of each of them Obverted to the Eye whereas in the other part the Piles of Silk being more Erected there are far Fewer Beams Reflected Outwards from the Lateral parts of each Pile so that most of those that Rebound to the Eye come from the Tops of the Piles which make but a Small part of the whole Superficies that may be cover'd by the piece of Velvet Which Explication I propose not that I think the Blackness of the Velvet proceeds from the Cause assign'd since each Single Pile of Silk is Black by reason of its Texture in what Position soever you Look upon it But that the Greater Blackness of one of these Tuffts seems to proceed from the Greater Paucity of Beams Reflected from it and that from the Fewness of those Parts of a Surface that Reflect Beams and the Multitude of those Shaded Parts that Reflect none And I remember that I have oftentimes observ'd that the Position of Particular Bodies far greater than Piles of Silk in reference to the Eye may notwithstanding their having each of them a Colour of its own make one part of their Aggregate appear far Darker than the other For I have near Great Towns often taken notice that a Cart-load of Carrots pack'd up appear'd of a much Darker Colour when Look'd upon where the Points of the Carrots were Obverted to the Eye than where the Sides of them were so 7. Fourthly In a Darkned Room I purposely observ'd that if the Sun-beams which came in at the Hole were receiv'd upon White or any other Colour and directed to a Convenient place of the Room they would Manifestly though not all Equally Encrease the Light of that Part whereas if we Substituted either a piece of Black Cloth or Black Velvet it would so Dead the Incident Beams that the place newly mention'd whereto I Obverted the Black Body would be Less Enlightned than it was before when it received its Light but from the Weak and Oblique Reflections of the Floor and Walls of a pretty Large Room through which the Beams that came in at the Hole were Confusedly and Brokenly Dispers'd 8. Fifthly And to shew that the Beams that fall on Black Bodies as they do not Rebound Outwards to the Eye so they are Reflected towards the Body it self as the Nature of those Erected Particles to which we have imputed Blackness requires we will add an Experiment that will also confirm our Doctrine touching Whiteness Namely that we took a Broad and Large Tile and having Whitened over one half of the Superficies of it and Black'd the other we expos'd it to the Summer Sun And having let it lye there a convenient time for the Difference is more Apparent if it have not lain there too long we found as we expected that whilst the Whited part of the Tile remained Cool enough the Black'd part of the same Tile was grown not only Sensible but very Hot sometimes to a strong Degree And to satisfie some of our Friends the more we have sometimes left upon the Surface of the Tile besides the White and Black parts thereof a part that Retain'd the native Red of the Tile it self and Exposing them to the Sun we observ'd this Last mention'd to have Contracted a Heat in comparison of the White but a Heat Inferiour to that of the Black of which the Reason seems to be that the Superficial Particles of Black Bodies being as we said more Erected than those of White or Red ones the Corpuscles of Light falling on their sides being for the most part Reflected Inwards from one Particle to another and thereby engag'd as it were and kept from Rebounding Upwards they communicate their brisk Motion wherewith they were impell'd against the Black Body upon whose account had they fallen upon a White Body they would have been Reflected Outwards to the Small parts of the Black Body and thereby Produce in those Small parts such an Agitation as when we feel it we are wont to call Heat I have been lately inform'd that an Observation near of Kin to Ours has been made by some Learned Men in France and Italy by long Exposing to a very Hot Sun two pieces of Marble the one White the other Black But though the Observation be worthy of them and may confirm the same Truth with Our Experiment yet besides that our Tryal needs not the Summer nor any Great Heat to succeed It seems to have this Advantage above the other that whereas Bodies more Solid and of a Closer Texture though they use to be more Slowly Heated are wont to receive a Greater Degree of Heat from the Sun or Fire than Caeteris paribus Bodies of a Slightet Texture I have found by the Information of Stone-cutters and by other ways of Enquiry that Black Marble is much Solider and Harder than White so that possibly the Difference betwixt the Degrees of Heat they receive from the Sun-beams will by many be ascrib'd to the Difference of their Texture rather than to that of their Colour though I think our Experiment will make it Probable enough that the greater part of that Difference may well be ascrib'd to that Disposition of Parts which makes the one Reflect the Sun-beams Inward and the other Outwards And with this Doctrine accords very well that Rooms hung with Black are not only Darker than else they would be but are wont to be Warmer too Insomuch that I have known a great Lady whose Constitution was somewhat Tender complain that she was wont to catch Cold when she went out into the Air after having made any long Visits to Persons whose Rooms were hung with Black And this is not the only Lady I have heard complain of the Warmth of such Rooms which though perhaps it may be partly imputed to the Effluvia of those Materials wherewith the hangings were Dy'd yet probably the Warmth of such Rooms depends chiefly upon the same Cause that the Darkness does As not to repeat what I formerly Noted touching my Gloves to satisfie some Curious Persons of that Sex I have convinc'd them by Tryall that of two Pieces of Silken Stuff given me by themselves and expos'd in their Presence to the same Window Shin'd onby that Sun the White was considerably Heated when the Black was not so much as Sensibly so 9. Sixthly I remember that Acquainting one Day a Virtuoso of Unsuspected Credit that had Visited Hot Countries with part of what I have here Deliver'd concerning Blackness he Related to me by way of Confirmation of it a very notable Experiment which he had both Seen others make and Made himself in a Warm Climate namely that having carefully Black'd over Eggs and Expos'd them to the Hot Sun they were thereby in no very Long time well Roasted
Colour principally under that Notion for there is in the bodyes we call Colour'd and chiefly in their Superficial parts a certain disposition whereby they do so trouble the Light that comes from them to our Eye as that it there makes that distinct Impression upon whose Account we say that the Seen body is either White or Black or Red or Yellow or of any one determinate Colour But because we shall God permiting by the Experiments that are to follow some Pages hence more fully and particularly shew that the Changes and consequently in divers places the Production and the appearance of Colours depends upon the continuing or alter'd Texture of the Object we shall in this place intimate and that too but as by the way two or three things about this Matter 2. And first it is not without some Reason that I ascribe Colour in the sense formerly explan'd chiefly to the Superficial parts of Bodies for not to question how much Opacous Corpuscles may abound even in those Bodies we call Diaphanous it seems plain that of Opacous bodies we do indeed see little else than the Superficies for if we found the beams of Light that rebound from the Object to the Eye to peirce deep into the Colour'd body we should not judge it Opacous but either Translucid or at least Semi-diaphanous and though the Schools seem to teach us that Colour is a Penetrative Quality that reaches to the Innermost parts of the Object as if a piece of Sealing-wax be broken into never so many pieces the Internal fragments will be as Red as the External surface did appear yet that is but a Particular Example that will not overthrow the Reason lately offer'd especially since I can alleage other Examples of a contrary Import and two or three Negative Instances are sufficient to overthrow the Generality of a Positive Rule especially if that be built but upon One or a Few Examples Not then to mention Cherries Plums and I know not how many other Bodies wherein the skin is of one Colour and what it hides of another I shall name a couple of Instances drawn from the Colours of Durable bodies that are thought far more Homogeneous and have not parts that are either Organical or of a Nature approaching thereunto 3 To give you the first Instance I shall need but to remind you of what I told you a little after the beginning of this Essay touching the Blew and Red and Yellow that may be produc'd upon a piece of temper'd Steel for these Colours though they be very Vivid yet if you break the Steel they adorn they will appear to be but Superficial not only the innermost parts of the Metall but those that are within a hairs breadth of the Superficies having not any of these Colours but retaining that of the Steel it self Besides that we may as well confirm this Observation as some other particulars we elsewhere deliver concerning Colours by the following Experiment which we purposely made 4. We took a good quantity of clean Lead and melted it with a strong Fire and then immediately pouring it out into a clean Vessel of a convenient shape and matter we us'd one of Iron that the great and sudden Heat might not injure it and then carefully and nimbly taking off the Scum that floated on the top we perceiv'd as we expected the smooth and grossie Surface of the melted matter to be adorn'd with a veâ— glorious Colour which being as Transitory as Delightfull did almost immediately give place to another vivid Colour and that was as quickly succeeded by a third and this as it were chas'd away by a fourth and so these wonderfully vivid Colours successively appear'd and vanish'd yet the same now and then appearing the second time till the Metall ceasing to be hot enough to afford any longer this pleasing Spectacle the Colours that chanc'd to adorn the Surface when the Lead thus began to cool remain'd upon it but were so Superficial that how little soever we scrap'd off the Surface of the Lead we did in such places scrape off all the Colour and discover only that which is natural to the Metall it self which receiving its adventitious Colours only when the heat was very Intense and in that part which was expos'd to the comparatively very cold Air which by other Experiments seems to abound with subtil Saline parts perhaps not uncapable of working upon Lead so dispos'd These things I say together with my observing that whatever parts of the so strongly melted Lead were expos'd a while to the Air turn'd into a kind of Scum or Litharge how bright and clean soever they appear'd before suggested to me some Thoughts or Ravings which I have not now time to acquaint You with One that did not know me Pyrophilus would perchance think I endeavour'd to impose upon You by relating this Experiment which I have several times try'd but the Reason why the Phaenomena 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 Phaenomena I mention'd will scarce at all disclose themselves And we have also observ'd that this successive appearing and vanishing of vivid Colours was wont to be impair'd or determin'd whilst the Metal expos'd to the Air remain'd yet hotter than one would readily suspect And one thing I must further Note of which I leave You to search after the Reason namely that the same Colours did not always and regularly succeed one another as is usually in Steel but in the diversify'd Order mention'd in this following Note which I was scarce able to write down the succession of the Colours was so very quick whether that proceeded from the differing degrees of Heat in the Lead expos'd to the cool Air or from some other Reason I leave you to examine Blew Yellow Purple Blew Green Purple Blew Yellow Red Purple Blew Yellow and Blew Yellow Blew Purple Green mixt Yellow Red Blew Green Yellow Red Purple Green 5. The Atomists of Old and some Learned men of late have attempted to explicate the variety of Colours in Opacous bodies from the various Figures of their Superficial parts the attempt is Ingenious and the Doctrine seems partly True but I confess I think there are divers other things that must be taken in as concurrent to produce those differing forms of Asperity whereon the Colours of Opacous bodies seem to depend To declare this a little we must assume that the Surfaces of all such Bodies how Smooth or polite soever they may appear to our Dull Sight and Touch are exactly smooth only in a popular or at most in a Physical sense but not in a strict and rigid sense 6. This excellent Microscopes shew us in many Bodies that seem Smooth to our naked Eyes and this not only as to the little Hillocks or Protuberancies that swell above that which may be conceiv'd to be the Plain
other 14. And perhaps Pyrophilus it may prove some Illustration of what I mean and help you to conceive how this may be if I Represent that where the Particles are so exceeding Slender we may allow the Parts expos'd to the Sight and Touch to be a little Convex in comparison of the Erected Particles of Black Bodies as if there were Wyres I know not how many times Slenderer than a Hair whether you suppose them to be Figur'd like Needles or Cylindrically like the Hairs of a Brush with Hemisphaerical or at least Convex Tops they will be so very Slender and consequently the Points both of the one sort and the other so very Sharp that even an exquisite Touch will be able to distinguish no greater Difference between them than that which our Blind man allow'd when comparing Black and White Bodies he said that the latter was the less Rough of the two Nor is every Kind of Roughness though Sensible enough Inconsistent with Whiteness there being Cases wherein the Physical Superficies of a Body is made by the same Operation both Rough and white as when the Level Surface of clear Water being by agitation Asperated with a multitude of Unequal Bubbles do's thereby acquire a Whiteness and as a Smooth piece of Glass by being Scratch'd with a Diamond do's in the Asperated part of its Surface disclose the same Colour But more perchance of this elsewhere 15. And therefore we shall here pass by the Question whether any thing might be consider'd about the Opacity of the Corpuscles of Black Pigments and the Comparative Diaphanëity of those of many White Bodies apply'd to our present Case and proceed to represent That the newly mention'd Exiguity and Shape of the extant Particles being suppos'd it will then be considerable what we lately but Hinted and therefore must now somewhat Explane That the Depth of the little Cavities intercepted between the extant Particles without being so much greater in Black Bodies than in White ones as to be perceptibly so to the Gross Organs of Touch may be very much greater in reference to their Disposition of Reflecting the imaginary subtile Beams of Light For in Black Bodies those Little intercepted Cavities and other Depressions may be so Figur'd so Narrow and so Deep that the incident Beams of Light which the more extant Parts of the Physical Superficies are dispos'd to Reflect inwards may be Detain'd there and prove unable to Emerge whilst in a White Body the Slender Particles may not only by their Figure be fitted to Reflect the Light copiously outwards but the intercepted Cavities being not Deep nor perhaps very Narrow the Bottoms of them may be so Constituted ' as to be fit to Reflect outwards much of the Light that falls even upon Them as you may possibly better apprehend when we shall come to treat of Whiteness and Blackness In the mean time it may suffice that you take Notice with me that the Blind mans Relations import no necessity of Concluding that though because according to the Judgment of his Touch Black was the Roughest as it is the Darkest of Colours therefore White which according to us is the Lightest should be also the Smoothest since I observe that he makes Yellow to be two Degrees more Asperous than Blew and as much less Asperous than Green whereas indeed Yellow do's not only appear to the Eye a Lighter Colour than Blew but by our first Experiment hereafter to be mention'd it will appear that Yellow reflected much more Light than Blew and manifestly more than Green which we need not much wonder at since in this Colour and the two others Blew and Yellow 't is not only the Reflected Light that is to be considered since to produce both these Refraction seems to Intervene which by its Varieties may much alter the Case which both seems to strengthen the Conjecture I was formerly proposing that there was something else in the Kinds of Asperity as well as in the Degrees of it which enabled our Blind man to Discriminate Colours and do's at least show that we cannot in all Cases from the bare Difference in the Degrees of Asperity betwixt Colours safely conclude that the Rougher of any two always Reflects the least Light 16. But this notwithstanding Pyrophilus and what ever Curiosity I may have had to move some Questions to our Sagacious Blind man yet thus much I think you will admit us to have gain'd by his Testimony that since many Colours may be felt with the Circumstances above related the Surfaces of such Coloured Bodies must certainly have differing Degrees and in all probability have differing Forms or Kinds of Asperity belonging to them which is all the Use that my present attempt obliges me to make of the History above deliver'd that being sufficient to prove that Colour do's much depend upon the Disposition of the Superficial parts of Bodies and to shew in general wherein 't is probable that such a Disposition do's principally at least consist 17. But to return to what I was saying before I began to make mention of our Blind Organist what we have deliver'd touching the causes of the several Forms of Asperity that may Diversifie the Surfaces of Colour'd Bodies may perchance somewhat assist us to make some Conjectures in the general at several of the ways whereby 't is possible for the Experiments hereafter to be mention'd to produce the suddain changes of Colours that are wont to be Consequent upon them for most of these Phaenomena being produc'd by the Intervention of Liquors and these for the most part abounding with very Minute Active and Variously Figur'd Saline Corpuscles Liquors so Qualify'd may well enough very Nimbly alter the Texture of the Body they are imploy'd to Work upon and so may change the form of Asperity and thereby make them Remit to the Eye the Light that falls on them after another manner than they did before and by that means Vary the Colour so farr forth as it depends upon the Texture or Disposition of the Seen Parts of the Object which I say Pyrophilus that you may not think I would absolutely exclude all other ways of Modifying the Beams of Light between their Parting from the Lucid Body and their Reception into the common Sensory 18. Now there seen to me divers ways by which we may conceive that Liquors may Nimbly alter the Colour of one another and of other Bodies upon which they Act but my present haste will allow me to mention but some of them without Insisting so much as upon those I shall name 19. And first the Minute Corpuscles that compose a Liquor may easily insinuate themselves into those Pores of Bodies whereto their Size and Figure makes them Congruous and these Pores they may either exactly Fill or but Inadequately and in this latter Case they will for the most part alter the Number and Figure and always the Bigness of the former Pores And in what capacity soever these Corpuscles of a Liquor
That there are divers other ways for the speedy Production even of True and Permanent Colours in Bodies besides those Practicable by the help of Liquors for proof of which Advertisement though several Examples might be alleged yet I shall need but Re-mind you of what I mention'd to you above touching the change of Colours suddenly made on Temper'd Steel and on Lead by the Operation of Heat without the Intervention of a Liquor But the other particular I am to observe to you is of more Importance to our present Subject and it is That though Nature and Art may in some cases so change the Asperity of the Superficial parts of a Body as to change its Colour by either of the ways I have propos'd Single or Unassisted yet for the most part 't is by two or three or perhaps by more of the fore-mention'd ways Associated together that the Effect is produc'd and if you consider how Variously those several ways and some others Ally'd unto them which I have left unmention'd may be Compounded and Apply'd you will not much wonder that such fruitfull whether Principles or Manners of Diversification should be fitted to Change or Generate no small store of Differing Colours 27. Hitherto Pyrophilus we have in discoursing of the Asperity of Bodies consider'd the little Protuberances of other Superficial particles which make up that Roughness as if we took it for granted that they must be perfectly Opacous and Impenetrable by the Beams of Light and so must contribute to the Variety of Colours as they terminate more or less Light and reflect it to the Eye mix'd with more or less of thus or thus mingl'd Shades But to deal Ingenuously with you Pyrophilns before I proceed any further I must not conceal from you that I have often thought it worth a Serious Enquiry whether or no Particles of Matter each of them singly Insensible and therefore Small enough to be capable of being such Minute Particles as the Atomists both of old and of late have not absurdly called Corpuscula Coloris may not yet consist each of them of divers yet Minuter Particles betwixt which we may conceive little Commissures where they Adhere to one another and however may not be Porous enough to be at least in some degree Pervious to the unimaginably subtile Corpuscles that make up the Beams of Light and consequently to be in such a degree Diaphanous For Pyrophilus that the proposed Enquiry may be of moment to him that searches after the Nature of Colour you 'l easily grant if you consider that whereas Perfectly Opacous bodies can but reflect the incident Beams of Light those that are Diaphanous are qualified to refract them too and that Refraction has such a stroak in the Production of Colours as you cannot but have taken notice of and perhaps admir'd in the Colours generated by the Trajection of Light through Drops of Water that exhibit a Rain-bow through Prismatical glasses and through divers other Transparent bodies But 't is like Pyrophilus you 'l more easily allow that about this matter 't is rather Important to have a Certainty than that 't is Rational to entertain a Doubt wherefore I must mention to you some of the Reasons that make me think it may need a further Enquiry for I find that in a Darkned Room where the Light is permitted to enter but at One hole the little wandering Particles of Dust that are commonly called Motes and unless in the Sun-beams are not taken notice of by the unassisted Sight I have I say often observ'd that these roving Corpuscles being look'd on by an Eye plac'd on one side of the Beams that enter'd the Little hole and by the Darkness having its Pupill much Enlarg'd I could discern that these Motes as soon as they came within the compass of the Lumihous whether Cylinder or Inverted Cone if I may so call it that was made up by the Unclouded Beams of the Sun did in certain positions appear adorn'd with very vivid Colours like those of the Rain-bow or rathen like those of very Minute but Sparkling fragments of Diamonds and as soon as the Continuance of their Motion had brought them to an Inconvenient position in reference to the Light and the Eye they were only visible without Darting any lively Colours as before which seems to argue that these little Motes or minute Fragments of several sorts of bodies reputed Opacous and only crumbled as to their Exteriour and Looser parts into Dust did not barely Reflect the Beams that fell upon them but remit them to the Eye Refracted too We may also observe that several Bodies as well some of a Vegetable as others of an Animal nature which are wont to pass for Opacous appear in great part Transparent when they are reduc'd into Thin parts and held against a powerful Light This I have not only taken notice of in pieces of Ivory reduc'd but into Thick Leaves as also in divers considerable Thick shells of Fishes and in shaving of Wood but I have also found that a piece of Deal far thicker than one would easily imagine being purposly interpos'd betwixt my Eye plac'd in a Room and the clear Day-light was not only somewhat Transparent but perhaps by reason of its Gummous nature appear'd quite through of a lovely Red. And in the Darkned Room above mention'd Bodies held against the hole at which the Light enter'd appear'd far less Opacous than they would elsewhere have done insomuch that I could easily and plainly see through the whole Thickness of my Hand the Motions of a Body plac'd at a very near distance indeed but yet beyond it And even in Minerals the Opacity is not always so great as many think if the Body be made Thin for White Marble though of a pretty Thickness being within a Due distance plac'd betwixt the Eye and a Convenient Light will suffer the Motions of ones Finger to be well discern'd through it and so will pieces Thick enough of many common Flints But above all that Instance is remarkable that is afforded us by Muscovie glass which some call Selenites others Lapis Specularis for though plates of this Mineral though but of a moderate Thickness do often appear Opacous yet if one of these be Dextrously split into the thinnest Leaves 't is made up of it will yield such a number of them as scarce any thing but Experience could have perswaded me and these Leaves will afford the most Transparent sort of consistent Bodies that for ought I have observ'd are yet known and a single Leaf or Plate will be so far from being Opacous that 't will scarce be so much as Visible And multitudes of Bodies there are whose Fragments seem Opacous to the naked Eye which yet when I have included them in good Microscopes appear'd Transparent but Pyrophilus on the other side I am not yet sure that there are no Bodies whose Minute Particles even in such a Microscope as that of mine which I was lately mentioning
little heated upon the Fire and some beaten Allom put unto them and afterwards press'd forth the Juice or Liquor is usually put in great Bladders tied with strong thred at the Head and hung up untill it be Dry which is dissolv'd in Water or Wine but Sack he affirms is the best to preserve the Colour from Starving as they call it that is from Decaying and make it hold fresh the longer The third Colour where of none says he that I can find have made mention but only Tragus is a Purplish Colour which is made of the Berries suffer'd to grow upon the Bushes untill the middle or end of November that they are ready to drop from the Trees And I remember Pyrophilus that I try'd with a success that pleas'd me well enough to make such a kind of Pigment as Painters call Sap-green by a way not unlike that deliver'd here by our Author but I cannot now find any thing relating to that matter among my loose Papers And my Trials were made so many years ago that I dare not trust my Memory for Circumstances but will rather tell you that in a noted Colour-shop I brought them by Questions to confess to me that they made their Sap-green much after the ways by our Botanist here mention'd And on this occasion I shall add an Observation which though it does not strictly belong to this place may well enough be mention'd here namely that I find by an account given us by the Learned Clusius of Alaternus that even the Grosser Parts of the same Plant are some of them one Colour and some another For speaking of that Plant he tells us that the Portugalls use the Bark to Dye their Nets into a Red Colour and with the Chips of the Wood which are Whitish they Dye a Blackish Blew EXPERIMENT XXX Among the Experiments that tend to shew that the change of Colours in Bodies may proceed from the Vary'd Texture of their Parts and the consequent change of their Disposition to Reflect or Refract the Light that sort of Experiments must not be left unmention'd which is afforded us by Chymical Digestions For if Chymists will believe several famous Writers about what they call the Philosophers Stone they must acknowledge that the same Matter seald up Hermetically in a Philosophical Egg will by the continuance of Digestion or if they will have it so for it is not Material in our case which of the two it be of Decoction run through a great Variety of differing Colours before it come to that of the Noblest Elixir whether that be Scarlet or Purple or what ever other Kind of Red. But without building any thing on so Obtruse and Questionable an Operation which yet may be pertinently represented to those that believe the thing we may observe that divers Bodies digested in carefully-clos'd Vessels will in tract of time change their Colour As I have elsewhere mention'd my having observ'd ev'n in Rectify'd Spirit of Harts-horn and as is evident in the Precipitations of Amalgams of Gold and Mercury without Addition where by the continuance of a due Heat the Silver-Colour'd Amalgam is reduc'd into a shining Red Powder Further Instances of this Kind you may find here and there in divers places of my other Essays And indeed it has been a thing that has much contributed to deceive many Chymists that there are more Bodies than one which by Digestion will be brought to exhibit that Variety and Succession of Colours which they imagine to be Peculiar to what they call the True matter of the Philosophers But concerning this I shall referr you to what you may elsewhere find in the Discourse written touching the passive Deceptions of Chymists and more about the Production of Colours by Digestion you will meet with presently Wherefore I shall now make only this Observation from what has been deliver'd That in these Operations there appears not any cause to attribute the new Colours emergent to the Action of a new Substantial form nor to any Increase or Decrement of either the Salt Sulphur or Mercury of the Matter that acquires new Colours For the Vessels are clos'd and these Principles according to the Chymists are Ingenerable and Incorruptible so that the Effect seems to proceed from hence that the Heat agitating and shuffling the Corpuscles of the Body expos'd to it does improcess of time so change its Texture as that the Transposed parts do Modifie the incident Light otherwise than they did when the Matter appear'd of another Colour EXPERIMENT XXXI Among the several changes of Colour which Bodies acquire or disclose by Digestion it it very remarkable that Chymists find a Redness rather than any other Colour in most of the Tinctures they Draw and ev'n in the more Gross Solutions they make of almost all Concretes that abound either with Mineral or Vegetable Sulphur though the Menstruum imploy'd about these Solutions or Tinctures be never so Limpid or Colourless This we have observ'd in I know not how many Tinctures drawn with Spirit of Wine from Jalap Guaicum and several other Vegetables and not only in the Solutions of Amber Benzoin and divers other Concretes made with the same Menstruum but also in divers Mineral Tinctures And not to urge that familiar Instance of the Ruby of Sulphur as Chymists upon the score of its Colour call the Solution of Flowers of Brimstone made with the Spirit of Turpentine nor to take notice of other more known Examples of the aptness of Chymical Oyls to produce a Red Colour with the Sulphur they extract or dissolve not to insist I say upon Instances of this nature I shall further represent to you as a thing remarkable that both Acid and Alcalizate Salts though in most other cases of such contrary Operations in reference to Colours will with many Bodies that abound with Sulphureous or with Oyly parts produce a Red as is manifest partly in the more Vulgar Instances of the Tinctures or Solutions of Sulphur made with Lixiviums either of Calcin'd Tartar or Pot-ashes and other Obvious examples partly by this that the true Glass of Antimony extracted with some Acid Spirits with or without Wine will yield a Red Tincture and that I know an Acid Liquor which in a moment will turn Oyl of Turpentine into a deep Red. But among the many Instances I could give you of the easie Production of Redness by the Operation of Saline Spirit as well as of Spirit of Wine I remember two or three of those I have tried which seem remarkable enough to deserve to be mention'd to you apart EXPERIMENT XXXII But before we set them down it will not perhaps appear impertinent to premise That there seems to be a manifest Disparity betwixt Red Liquors so that some of them may be said to have a Genuine Redness in comparison of others that have a Yellowish Redness For if you take for example a good Tincture of Chochineel dilute it never so much with fair Water you will not
will add an Experiment of our own made before we met with That which though in many Circumstances very differing serves to prove the same thing for having taken of the deeply Red Juice of Buckthorn Berries which I bought of the Man that uses to sell it to the Apothecaries to make their Syrrup de Spina Cervina I let some of it drop upon a piece of White Paper and having left it there for many hours till the Paper was grown dry again I found what I was inclin'd to suspect namely That this Juice was degenerated from a deep Red to a dirty kind of Greyish Colour which in a great part of the stain'd Paper seem'd not to have so much as an Eye of Red Though a little Spirit of Salt or dissolv'd Alcaly would turn this unpleasant Colour as formerly I told you it would change the not yet alter'd Juice into a Red or Green And to satisfie my self that this Degeneration of Colour did not proceed from the Paper I drop'd some of the deep Red or Crimson Juice upon a White glaz'd Tile and suffering it to dry on there I found that ev'n in that Body on which it could not Soak and by which it could not be Wrought it nevertheless lost its Colour And these Instances Pyrophilus I am the more carefull to mention to you that you may not be much Surpris'd or Discourag'd if you should sometimes miss of performing punctually what I affirm my self to have done in point of changing Colours since in these Experiments the over-sight or neglect of such little Circumstances as in many others would not be perhaps considerable may occasion the mis-carrying of a Trial. And I was willing also to take this occasion of Advertising you in the repeating of the Experiments mention'd in this Treatise to make use of the Juices of Vegetables and other things prepar'd for your Trials as soon as ever they are ready lest one or other of them grow less fit if not quite unfit by delay and to estimate the Event of the Trials by the Change that is produc'd presently upon the due and sufficient Application of Actives to Passives as they speak because in many cases the effects of such Mixtures may not be lasting and the newly produc'd Colour may in a little time degenerate But Pyrophilus I forgot to add to the two former Observations lately made about Vegetables a third of the same Import made in Mineral substances by telling you That the better to satisfie a Friend or two in this particular I sometimes made according to some Conjectures of mine this Experiment That having dissolv'd good Silver in Aqua-fortis and Precipitated it with Spirit of Salt upon the first Decanting of the Liquor the remaining Matter would be purely White but after it had lain a while uncover'd that part of it that was Contiguous to the Air would not only lose its Whiteness but appear of a very Dark and almost Blackish Colour I say that part that was Contiguous to the Air because if that were gently taken off the Subjacent part of the same Mass would appear very White till that also having continu'd a while expos'd to the Air would likewise Degenerate Now whether the Air perform these things by the means of a Subtile Salt which we elswhere show it not to be destitute of or by a peircing Moisture that is apt easily to insinuate it self into the Pores of some Bodies and thereby change their Texture and so their Colour Or by solliciting the Avolation of certain parts of the Bodies to which 't is Contiguous or by some other way which possibly I may elsewhere propose and consider I have not now the leisure to discourse And for the same reason though I could add many other Instances of what I formerly noted touching the emergency of Redness upon the Digestion of many Bodies insomuch that I have often seen upon the Borders of France and probably we may have the like in England a sort of Pears which digested for some time with a little Wine in a Vessel exactly clos'd will in not many hours appear throughout of a deep Red Colour as also that of the Juice wherein they are Stew'd becomes but ev'n on pure and white Salt of Tartar pure Spirit of Wine as clear as Rock-water will as we elsewhere declare by long Digestion acquire a Redness Though I say such Instances might be Multiply'd and though there be some other Obvious changes of Colours which happen so frequently that they cannot but be as well Considerable as Notorious such as is the Blackness of almost all Bodies burn'd in the open Air yet our haste invites us to resign you the Exercise of enquiring into the Causes of these Changes And certainly the reason both why the Soots of such differing Bodies are almost all of them all Black why so much the greater part of Vegetables should be rather Green than of any other Colour and particularly which more directly concerns this place why gentle Heats do so frequently in Chymical Operations produce rather a Redness than another Colour in digested Menstruums not only Sulphureous as Spirit of Wine but Saline as Spirit of Vinegar may be very well worth a serious Inquiry which I shall therefore recommend to Pyrophilus and his Ingenious Friends EXPERIMENT XXXVII It may seem somewhat strange that if you take the Crimson Solution of Cochineel or the Juice of Black Cherries and of some other Vegetables that afford the like Colour which because many take but for a deep Red we do with them sometimes call it so and let some of it fall upon a piece of Paper a drop or two of an Acid Spirit such as Spirit of Salt or Aqua-fortis will immediately turn it into a fair Red. Whereas if you make an Infusion of Brazil in fair Water and drop a little Spirit of Salt or Aqua-fortis into it that will destroy its Redness and leave the Liquor of a Yellow sometimes Pale I might perhaps plausibly enough say on this occasion that if we consider the case a little more attentively we may take notice that the action of the Acid Spirit seems in both cases but to weaken the Colour of the Liquor on which it falls And so though it destroy Redness in the Tincture of Brazil as well as produce Red in the Tincture of Chochineel its Operations may be Uniform enough since as Crimson seems to be little else than a very deep Red with perhaps an Eye of Blew so some kinds of Red seem as I have lately noted to be little else than heightned Yellow And consequently in such Bodies the Yellow seems to be but a diluted Red. And accordingly Alcalizate Solutions and Urinous Spirits which seem dispos'd to Deepen the Colours of the Juices and Liquors of most Vegetables will not only restore the Solution of Cochineel and the Infusion of Brazil to the Crimson whence the Spirit of Salt had chang'd them into a truer Red but will also as I lately told you not