I took a piece of Black-horn, (poliſh'd as being part of a Comb) this with a piece of broken glaſs I ſcrap'd into many thin and curdled flakes, ſome ſhorter and ſome longer, and having laid a pretty Quantity of theſe ſcrapings together, I found, as I look'd for, that the heap they compos'd was White, and though, if I laid it upon a clean piece of White Paper, its Colour ſeem'd ſomewhat Eclips'd by the greater Whiteneſs of the Body it was compar'd with, looking ſomewhat like Linnen that had been ſulli'd by a little wearing, yet if I laid it upon a very Black Body, as upon a Beaver Hatt, it then appear'd to be of a good White, which Experiment, that you may in a trice make when you pleaſe, ſeems very much to Disfavour both their Doctrine
that would have Colours to flow from the Subſtantial Forms of Bodyes, and that of the Chymiſts alſo, who aſcribe them to one or other of their three Hypoſtatical Principles; for though in our Caſe there was ſo great a Change made, that the ſame Body without being ſubſtantially either Increas'd or Leſſened, paſſes immediately from one extreme Colour to another (and that too from Black to White) yet this ſo great and ſudden change is effected by a ſlight Mechanical Tranſpoſition of parts, there being no Salt or Sulphur or Mercury that can be pretended to be Added or Taken away, nor yet any ſubſtantial Form that can reaſonably be ſuppos'd to be Generated and Deſtroy'd, the Effect proceeding only from a Local Motion of the parts which ſo vary'd their Poſition as to multiply their diſtinct Surfaces, and to Qualifie them to Reflect far more Light to the Eye, than they could before they were ſcrap'd off from the entire piece of Black horn.
EXPERIMENT XV.
And now, Pyrophilus, it will not be improper for us to take ſome notice of an Opinion touching the cauſe of Blackneſs, which I judged
it not ſo ſeaſonable to Queſtion, till I
I had ſet down ſome of the Experiments, that might juſtifie my diſſent from it. You know that of late divers Learned Men, having adopted the three Hypoſtatical Principles, beſides other Notions of the Chymiſts, are very inclinable to reduce all Qualities of Bodies to one or other of thoſe three Principles, and Particularly aſſign for the cauſe of Blackneſs the Sootie ſteam of adust or torrifi'd Sulphur. But I hope that what we have deliver'd above to countenance the Opinion we have propos'd about the Cauſe of Blackneſs, will ſo eaſily ſupply you with ſeveral Particulars that may be made uſe of againſt this Opinion, that I ſhall now repreſent to You but two things concerning it.
And Firſt it ſeems that the favourers of the Chymicall Theories might have pitcht upon ſome more proper term, to expreſs the Efficient of Blackneſs than Sulphur adust; for we know that common Sulphur, not only when Melted, but even when Sublim'd, does not grow Black by ſuffering the Action of the fire, but continues and aſcends Yellow, and rather more than leſs White, than it was before its being expos'd to the fire. And if it be ſet on fire, as when we make that acid Liquor, that Chymiſts call Oleum Sulphuris per campanam, it affords
very little Soot, and indeed the flame yeelds ſo little, that it will ſcarce in any degree Black a ſheet of White Paper, held a pretty while over the flame and ſmoak of it, which is obſerved rather to Whiten than Infect linnen, and which does plainly make Red Roſes grow very Pale, but not at all Black, as far as the Smoak is permitted to reach the leaves. And I can ſhew you of a ſort of fixt Sulphur made by an Induſtrious Laborant of your acquaintance, who aſſur'd me that he was wont to keep it for divers weeks together night and day in a naked and Violent fire, almoſt like that of the Glaſs-houſe, and when, to ſatisfie my Curioſity, I made him take out a lump of it, though it were glowing hot (and yet not melted,) it did not, when I had ſuffered it to cool, appear Black, the true Colour of it being a true Red. I know it may be ſaid, that Chymiſts in the Opinion above recited mean the Principle of Sulphur, and not common Sulphur which receives its name, not from its being all perfectly of a Sulphureous Nature, but for that plenty and Predominancy of the Sulphureous Principle in it. But allowing this, 'tis eaſie to reply, that ſtill according to this very Reaſon, torrifi'd Sulphur ſhould afford more Blackneſs, than moſt other concretes,
wherein that Principle is confeſs'd to be far leſs copious. Alſo when I have expos'd Camphire to the fire in Cloſe Veſſels, as Inflamable, and conſequenly (according to the Chymiſts) as Sulphureous a Body as it is, I could not by ſuch a degree of Heat, as brought it to Fuſion, and made it Boyl in the glaſs, impreſs any thing of Blackneſs, or of any other Colour, than its own pure White, upon this Vegetable concrete. But what ſhall we ſay to Spirit of Wine, which being made by a Chymical Analyſis of the Liquor that affords it, and being totally Inflamable, ſeems to have a full right to the title they give it of Sulphur Vegetabile, & yet this fluid Sulphur not only contracts not any degree of Blackneſs by being often ſo heated, as to be made to Boyl, but when it burns away with an Actual flame, I have not found that it would diſcolour a piece of White Paper held over it, with any diſcernable ſoot. Tin alſo, that wants not, according to the Chymiſts, a Sulphur Joviale, when throughly burned by the fire into a Calx, is not Black, but eminently White. And I lately noted to you out of Bellonius, that the Charcoals of Oxy-cedar are not of the former of theſe two Colours, but of the latter. And the Smoak of our Tinby coals here in England, has been
uſually obſerv'd, rather to Blanch linnen then to Black it. To all which, other Particulars of the like nature might be added, but I rather chooſe to put you in mind of the third Experiment, about making Black Liquors, or Inks, of Bodies that were non of them Black before. For how can it be ſaid, that when thoſe Liquors are put together actually Cold, and continue ſo after their mixture, there intervenes any new Adustion of Sulphur to produce the emergent Blackneſs? (and the ſame queſtion will be appliable to the Blackneſs produc'd upon the blade of a Knife, that has cut Lemmons and ſome kind of Sowr apples, if the juyce (though both Actually and Potentially Cold) be not quickly wip'd of) And when by the inſtilling either of a few drops of Oyl of Vitriol as in the ſecond Experiment, or of a little of the Liquor mention'd in the Paſſage pointed at in the fourth Experiment, (where I teach at once to Deſtroy one black Ink, and make another) the Blackneſs produc'd by thoſe Experiments is preſently deſtroy'd; if the Colour proceeded only from the Plenty of Sulphurous parts, torrify'd in the Black Bodies, I demand, what becomes of them, when the Colour ſo ſuddenly diſſappears? For it cannot Reaſonably be ſaid, that all thoſe that