And I must not omit on this occasion to mention to you, _Eleutherius_, the memorable Experiment that I remember I met with in _Gasto Claveus_,[2] who, though a Lawyer by Profession, seems to have had no small Curiosity and Experience in Chymical affairs: He relates then, that having put into one small Earthen Vessel an Ounce of the most pure Gold, and into another the like weight of pure Silver, he plac'd them both in that part of a Glass-house Furnace wherein the Workmen keep their Metal, (as our English Artificers call their Liquid Glass) continually melted, and that having there kept both the Gold and the Silver in constant Fusion for two Moneths together, he afterwards took them out of the Furnace and the Vessels, and weighing both of them again, found that the Silver had not lost above a 12th part of its weight, but the Gold had not of his lost any thing at all. And though our Author endeavours to give us of this a Scholastick Reason, which I suppose you would be as little satisfied with, as I was when I read it; yet for the matter of Fact, which will serve our present turne, he assures us, that though it be strange, yet Experience it self taught it him to be most true. [Footnote 2: _Gasto Claveus_ Apolog. Argur. & Chrysopera.] And though there be not perhaps any other Body to be found so perfectly fix'd as Gold, yet there are divers others so fix'd or compos'd, at least of so strictly united parts, that I have not yet observ'd the Fire to separate from them any one of the Chymists Principles. I need not tell you what Complaints the more Candid and Judicious of the Chymists themselves are wont to make of those Boasters that confidently pretend, that they have extracted the Salt or Sulphur of Quicksilver, when they have disguis'd it by Additaments, wherewith it resembles the Concretes whose Names are given it; whereas by a skilful and rigid _Examen_, it may be easily enough stript of its Disguises, and made to appear again in the pristine form of running Mercury. The pretended Salts and Sulphurs being so far from being Elementary parts extracted out of the Bodie of Mercurie, that they are rather (to borrow a terme of the Grammarians) De-compound Bodies, made up of the whole Metal and the _Menstruum_ or other Additaments imploy'd to disguise it. And as for Silver, I never could see any degree of Fire make it part with any of its three Principles. And though the Experiment lately mentioned from _Claveus_ may beget a Suspition that Silver may be dissipated by Fire, provided it be extreamly violent and very lasting: yet it will not necessarily follow, that because the Fire was able at length to make the Silver lose a little of its weight, it was therefore able to dissipate it into its Principles. For first I might alledge that I have observ'd little Grains of Silver to lie hid in the small Cavities (perhaps glas'd over by a vitrifying heat) in Crucibles, wherein Silver has been long kept in Fusion, whence some Goldsmiths of my Acquaintance