component Principles be so minute, and so strictly united, that the Corpuscles of it need less heat to carry them up, than is requisite to divide them into their Principles. So that of some Bodies the Fire cannot in close Vessels make any _Analysis_ at all, and others will in the open Air fly away in the Forms of Flowers or Liquors, before the Heat can prove able to divide them into their Principles. And this may hold, whether the various similar parts of a Concrete be combin'd by Nature or by Art; For in factitious _Sal Armoniack_ we finde the common and the Urinous Salts so well mingled, that both in the open Fire, and in subliming Vessels they rise together as one Salt, which seems in such Vessels irresoluble by Fire alone. For I can shew you _Sal Armoniack_ which after the ninth Sublimation does still retain its compounded Nature. And indeed I scarce know any one Mineral, from which by Fire alone Chymists are wont to sever any Substance simple enough to deserve the name of an Element or Principle. For though out of native Cinnaber they distill Quicksilver, and though from many of those Stones that the Ancients called _Pyrites_ they sublime Brimstone, yet both that Quicksilver and this Sulphur being very often the same with the common Minerals that are sold in the Shops under those names, are themselves too much compounded Bodies to pass for the Elements of such. And thus much, _Eleutherius_, for the Second Argument that belongs to my First Consideration; the others I shall the lesse insist on, because I have dwelt so long upon this. [Footnote 3: _Agricola_ de Natura Fossil. Lib. 9. Cap. 11. & 12.]