This Doubt, you may remember, was formerly mention'd, but so transiently discours'd of, that it will now be fit to insist upon it; And manifest that it was not so inconsiderately propos'd as our Adversaries then imagin'd. But, before I enter any farther into this Disquisition, I cannot but here take notice, that it were to be wish'd, our Chymists had clearly inform'd us what kinde of Division of Bodies by Fire must determine the number of the Elements: For it is nothing near so easy as many seem to think, to determine distinctly the Effects of Heat, as I could easily manifest, if I had leasure to shew you how much the Operations of Fire may be diversify'd by Circumstances. But not wholly to pass by a matter of this Importance, I will first take notice to you, that _Guajacum_ (for Instance) burnt with an open Fire in a Chimney, is sequestred into Ashes and Soot, whereas the same Wood distill'd in a Retort does yield far other Heterogeneities, (to use the _Helmontian_ expression) and is resolv'd into Oyl, Spirit, Vinager, Water and Charcoal; the last of which to be reduc'd into Ashes, requires the being farther calcin'd then it can be in a close Vessel: Besides having kindled Amber, and held a clean Silver Spoon, or some other Concave and smooth Vessel over the Smoak of its Flame, I observ'd the Soot into which that Fume condens'd, to be very differing from any thing that I had observ'd to proceed from the steam of Amber purposely (for that is not usual) distilled _per se_ in close Vessels. Thus having, for Tryals sake, kindled Camphire, and catcht the Smoak that copiously ascended out of the Flame, it condens'd into a Black and unctuous Soot, which would not have been guess'd by the Smell or other Properties to have proceeded from Camphire: whereas having (as I shall otherwhere more fully declare) expos'd a quantity of that Fugitive Concrete to a gentle heat in a close Glass-Vessel, it sublim'd up without seeming to have lost any thing of its whiteness, or its Nature, both which it retain'd, though afterwards I so encreased the Fire as to bring it to Fusion. And, besides Camphire, there are divers other Bodies (that I elsewhere name) in which the heat in close Vessels is not wont to make any separation of Heterogeneities, but only a comminution of Parts, those that rise first being Homogeneal with the others, though subdivided into smaller Particles: whence Sublimations have been stiled, _The Pestles of the Chymists_. But not here to mention what I elsewhere take notice of, concerning common Brimstone once or twice sublim'd, that expos'd to a moderate Fire in Subliming-Pots, it rises all into dry, and almost tastless, Flowers; Whereas being expos'd to a naked Fire it affords store of a Saline and Fretting Liquor: Not to mention this, I say, I will further observe to you, that as it is considerable in the _Analysis_ of mixt Bodies, whether the Fire act on them when they are expos'd to the open Air, or