Touchstone, the Silver in the moistned part being immediately taken up and conceal'd by the Liquor, the Golden Particles would presently disclose that native Yellow, and look rather as if Gold, than if the above mention'd mixture, had been rubb'd upon the Stone. [15] See _Scaliger_ Exercit. 325. Sect. 9. _EXPERIMENT XIV._ 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.