Chapter 10

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 (_Cæteris paribus_) Bodies of a Slightest 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 Sunbeams 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 Sunbeams 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 on by 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 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, to which Effect I conceive the Heat of the Climate must have Concurr'd with the Disposition of the Black Surface to Reflect the Sunbeams 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,[9] 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.

[9] Hist. Anatom. Cent. 3. Hist. 44.

II. These, _Pyrophilus_, are the chief things that Occurr to me at present, about the Nature of Whiteness and Blackness, which it 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 so 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 Observation towards the History of Whiteness 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.

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EXPERIMENT IN CONSORT, Touching Whiteness & Blackness.

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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 Præcipitate 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 'twas already almost Ink; Into this Infusion shake 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 Præcipitation 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 be Præcipitated by Alcalizat Salts, that have not first been dissolved in some Acid _Menstruums_, yet I have found upon tryals, which my conjectures lead me to make on purpose, That divers Vegetables _barely infus'd_, or, _but slightly decocted in common water_, would, upon the affusion of a Strong and Cleer _Lixivium_ of Potashes, and much more of some other Præcipitating liquors that I sometimes employ, afford good store of a Crudled matter, such as I have had in the Præcipitations of Vegetable substances, by the intervention of Acid things, and that this matter was easily separable from the rest of the liquor, being left behind by it in the Filtre; and in making the first Ink mention'd in this Experiment, I found that I could by Filtration separate pretty store of a very Black pulverable substance, that remain'd in the Filtre, and when the Ink was made Cleer again by the Oyl of Vitriol, the affusion of dissolv'd _Sal Tartari_ seem'd but to Præcipitate, and thereby to Unite and render Conspicuous the particles of the Black mixture that had before been dispers'd into very Minute and singly Invisible particles by the Incisive and resolving power of the highly Corrosive Oyl of Vitriol.

And to manifest, _Pyrophilus_, that Galls are not so requisite as many suppose to the making Atramentous Liquors, we have sometimes made the following Experiment, We took dryed Rose leaves and Decocted them for a while in Fair Water, into two or three spoonfulls of this Decoction we shook a few drops of a strong and well filtrated Solution of Vitriol (which perhaps had it been Green would have done as well) and immediately the mixture did turn Black, and when into this mixture presently after it was made, we shook a just Proportion of _Aqua Fortis_, we turn'd it from a Black Ink to a deep Red one, which by the affusion of a little Spirit of Urine may be reduc'd immediately to an Opacous and Blackish Colour. And in regard, _Pyrophilus_, that in the former Experiments, both the Infusion of Galls, and the Decoction of Roses, and the Solution of Copperis employ'd about them, are endow'd each of them with its own Colour, there may be a more noble Experiment of the sudden production of Blackness made by the way mention'd in the Second Section of the Second Part of our Essays, for though upon the Confusion of the two Liquors there mention'd, there do immediately emerge a very Black mixture, yet both the Infusion of _Orpiment_ and the Solution of _Minium_ were before their being joyn'd together, Limpid and Colourless.

_EXPERIMENT III._

If pieces of White Harts-horn be with a competent degree of Fire distill'd in a Glass-retort, they will, after the avolation of the Flegm, Spirit, Volatile Salt, and the looser and lighter parts of the Oleagenous substance, remain behind of a Cole-black colour. And even Ivory it self being skilfully Burnt (how I am wont to do it, I have elsewhere set down) affords Painters one of the best and deepest Blacks they have, and yet in the Instance of distill'd Harts-horn, the operation being made in Glass-vessels carefully clos'd, it appears there is no Extraneous Black substance that Insinuates it self into White Harts-horn, and thereby makes it turn Black; but that the Whiteness is destroy'd, and the Blackness generated, only by a Change of Texture, made in the burnt Body, by the Recess of some parts and the Transposition of others. And though I remember not that in many Distillations of Harts-horn I ever sound the _Cap. Mort_. to pass from Black to a true Whiteness, whilst it continu'd in Clos'd vessels, yet having taken out the Cole-black fragments, and Calcin'd them in Open vessels, I could in few hours quite destroy that Blackness, & without sensibly changing their Bulk or Figure, reduce them to great Whiteness. So much do these two Colours depend upon the Disposition of the little parts, that the Bodies wherein they are to be met with do consist of. And we find, that if Whitewine Tartar, or even the white Crystalls of such Tartar be burnt without being truly Calcin'd, the _Cap. Mortuum_ (as the Chymists call the more Fixt part) will be Black. But if you further continue the Calcination till you have perfectly Incinerated the Tartar, & kept it long enough in a Strong fire, the remaining _Calx_ will be White. And so we see that not only other Vegetable substances, but even White woods, as the Hazel, will yield a Black Charcoal, and afterwards Whitish ashes; And so Animal substances naturally White, as Bones and Eggshels, will grow Black upon the being Burnt, and White again when they are perfectly Calcin'd.

_EXPERIMENT IV._

But yet I much Question whether that Rule delivered by divers, as well Philosophers as Chymists, _adusta nigra, sed perusta alba_, will hold as Universally as is presum'd, since I have several Examples to allege against it: For I have found that by burning Alablaster, so as both to make it appear to boyl almost like Milk, and to reduce it to a very fine Powder, it would not at all grow Black, but retain its Pure and Native Whiteness, and though by keeping it longer than is usual in the fire, I produced but a faint Yellow, even in that part of the Powder that lay nearest the top of the Crucible, yet having purposely enquired of an Experienced Stone-cutter, who is Curious enough in tryng Conclusions in his own Trade, he told me he had found that if Alabaster or Plaster of Paris be very long kept in a Strong fire, the whole heap of burnt Powder would exchange its Whiteness for a much deeper Colour than the Yellow I observ'd. Lead being Calcin'd with a Strong fire turns (after having purhaps run thorough divers other Colour) into _Minium_, whose Colour we know is a deep red; and if you urge this _Minium_, as I have purposely done with a Strong fire, you may much easier find a Glassie and Brittle Body darker than _Minium_, than any white _Calx_ or Glass. 'Tis known among Chymists, that the white _Calx_ of Antimony, by the further and more vehement operation of the fire, may be melted into Glass, which we have obtain'd of a Red Colour, which is far deeper than that of the _Calx_ of Burnt Antimony, and though common Glafs of Antimony being usually Adulterated with _Borax_, have its Colour thereby diluted, oftentimes to a very pale Yellow; yet not onely ours made more sincerily, was, as we said, of a Colour less remote from Black, than was the _Calx_; but we observ'd, that by Melting it once or twice more, and so exposing it to the further operation of the Fire, we had, as we expected, the Colour heightned. To which we shall add but this one Instance, (which is worth the taking notice of in Reference to Colours:) That, if you take Blew, but Unsophisticated, Vitriol, and burn it very slowly, and with a Gentle degree of Heat, you may observe, that when it has Burnt but a Little, and yet so far as that you may rub it to Powder betwixt your fingers, it will be of a White or Whitish Colour; But if you Prosecute the Calcination, this Body which by a light Adustion was made White, will pass through other Colours, as Gray, Yellowish, and Red; and if you further burn it with a Long and Vehement fire, by that time it comes to be _Perustum_, it will be of a dark purple, nearer to Black, not only than the first _Calx_, but than the Vitriol before it at all felt the fire. I might add that _Crocus_ _Martis_ (_per se_ as they call it) made by the Lasting violence of the Reverberated flames is not so near a Kin to White, as the Iron or Steel that afforded it was before its Calcinations; but that I suppose, these Instances may Suffice to satisfie you, that Minerals are to be excepted out of the forementioned Rule, which perhaps, though it seldome fail in substances belonging to the Vegetable or Animal Kingdome, may yet be Question'd even in some of these, if that be true, which the Judicious Traveller _Bellonius_ affirms, that Charcoales made out of the Wood of _Oxycæder_ are White; And I could not find that though in Retorts Hartshorn and other White Bodies will be Denigrated by Heat, yet Camphire would not at all lose its Whiteness, though I have purposely kept it in such a heat, as made it melt and boyl.

_EXPERIMENT V._

And now I speak of Camphire, it puts me in mind of adding this Experiment, That, though as I said in Clos'd Glasses, I could not Denigrate it by Heat, but it would Sublime to the sides and top of the Glass, as it was before, yet not only it will, being set on fire in the Free Air, send forth a Copious smoak, but having purposely upon some of it that was Flaming, clapt a Large Glass, almost in the form of a Hive, (but more Slender only) with a Hole at the top, (which I caus'd to be made to trye Experiments of Fire and Flame in) it continued so long burning that it Lin'd all the Inside of the Glass with a Soot as Black as Ink, and so Copious, that the Closeness of the Vessel consider'd, almost all that part of the White Camphire that did take Fire, seem'd to have been chang'd into that deep Black Substance.

_EXPERIMENT VI_

And this also brings into my mind another Experiment that I made about the production of Blackness, whereof, for Reasons too long to be here deduced, I expected and found a good Success, an it was this: I took Rectifi'd Oyl of Vitriol (that I might have the Liquor Clean as well as Strong) and by degrees mixt with it a convenient proportion of the Essential Oyl, as Chymists call it, of Wormwood, drawn over with store of Water in a Limbec, and warily Distilling the mixture in a Retort, there remain'd a scarce credible quantity of dry Matter, Black as a Coal. And because the Oyl of Wormwood, though a Chymical Oyl drawn by a _Virtuoso_, seem'd to have somewhat in it of the Colour of the Plant, I Substituted in its Room, the Pure and Subtile Essential Oyl of Winter-Savory, and mixing little by little this Liquor, with (if I mis-remember not) an Equal weight of the formerly mention'd Rectifi'd Oyl of Vitriol, and Distilling them as before in a Retort, besides what there pass'd over into the Receiver, even these two clear Liquors left me a Considerable Proportion, (though not so great as the two former) of a Substance Black as Pitch, which I yet Keep by me as a Rarity.

_EXPERIMENT VII._

A way of Whiting Wax Cheaply and in Great Quantity may be a thing of good Oeconomical Use, and we have elsewhere set down the Practice of Trades-men that Blanch it; But here Treating of Whiteness only in Order to the Philosophy of Colours, I shall not Examine which of the Slow wayes may be best Employ'd, to free Wax from the Yellow Melleous parts, but shall rather set down a Quick way of making it White, though but in very Small Quantities. Take then a little Yellow Wax, scraped or thinly sliced, and putting it into a Bolts-head or some other Convenient Glass, pour to it a pretty deal of Spirit of Wine, and placing the Vessel in Warm Sand, Encrease the Heat by degrees, till the Spirit of Wine begin to Simper or to Boyl a little; and continuing that degree of Fire, if you have put Liquor enough, you will quickly have the Wax dissolv'd, then taking it off the fire, you may either suffer it to Cool as hastily as with Safety to the Glass you can, or Pour it whilst 'tis yet Hot into a Filtre of Paper, and either in the Glass where it Cools, or in the Filtre, you will soon find the Wax and _Menstruum_ together reduc'd into a White Substance, almost like Butter, which by letting the Spirit Exhale will shrink into a much Lesser Bulk, but still retaining its Whiteness. And that which is pretty in the working of this Magistery of Wax, is, that the Yellowness vanishes, neither appearing in the Spirit of Wine that passes Limpid through the Filtre, nor in the Butter of Wax, if I may so call it, that, as I said, is White.

_EXPERIMENT VIII._