remember _Philoponus_ recited out of _Aristotle_ himself, when he lately disputed for his Chymists against _Themistius_. And here we may on this occasion consider, that since a Body from which the Fire hath driven away its looser parts is wont to be look'd upon as Earth, upon the Account of its being endow'd with both these qualities, Tastlessenesse and Fixtnesse, (for Salt of Tartar though Fixt passes not among the Chymists for Earth, because 'tis strongly Tasted) if it be in the power of Natural Agents to deprive the _Caput Mortuum_ of a body of either of those two Qualities, or to give them both to a portion of matter that had them not both before, the Chymists will not easily define what part of a resolv'd Concrete is earth, and make out, that that Earth is a primary, simple, and indestructible Body. Now there are some cases wherein the more skilful of the Vulgar Chymists themselves pretend to be able, by repeated Cohobations and other fit Operations, to make the Distilled parts of a Concrete bring its own _Caput Mortuum_ over the Helme, in the forme of a Liquor; in which state being both Fluid and Volatile, you will easily believe it would not be taken for Earth. And indeed by a skilful, but not Vulgar, way of managing some Concretes, there may be more effected in this kind, then you perhaps would easily think. And on the other side, that either Earth may be Generated, or at least Bodies that did not before appear to be neer Totally Earth, may be so alter'd as to pass for it, seems very possible, if _Helmont_[34] have done that by Art which he mentions in several places; especially where He sayes that he knowes wayes whereby Sulphur once dissolv'd is all of it fix'd into a Terrestrial Powder; and the whole Bodie of Salt-Petre may be turn'd into Earth: Which last he elsewhere sayes is Done by the Odour only of a certain Sulphureous Fire. And in another place He mentions one way of doing this, which I cannot give you an Account of; because the Materialls I had prepar'd for Trying it, were by a Servants mistake unhappily thrown away. [Footnote 34: _Novi item modos quibus totum Salpetiae [Errata: sal-petrae] in terram convertitur, totumque Sulphur semel dissolutum fixetur in Pulvearem terreum. Helmont in Compl. atque Mist. Elementor. Sect. 24._]