that divers Chymical Notions about Matters Philosophical are taken for granted and employ'd, and so adopted by very eminent Writers both Naturalists and Physitians. Now this I fear may prove somewhat prejudicial to the Advancement of solid Philosophy: For though I am a great Lover of Chymical Experiments, and though I have no mean esteem of divers Chymical Remedies, yet I distinguish these from their Notions about the causes of things, and their manner of Generation. And for ought I can hitherto discern, there are a thousand_ Phaenomena _in Nature, besides a Multitude of Accidents relating to the humane Body, which will scarcely be clearly & satisfactorily made out by them that confine themselves to deduce things from Salt, Sulphur and Mercury, and the other Notions peculiar to the Chymists, without taking much more Notice than they are wont to do, of the Motions and Figures, of the small Parts of Matter, and the other more Catholick and Fruitful affections of Bodies. Wherefore it will not perhaps be now unseasonable to let our_ Carneades _warne Men, not to subscribe to the grand Doctrine of the Chymists touching their three Hypostatical Principles, till they have a little examin'd it, and consider'd, how they can clear it from his Objections, divers of which 'tis like they may never have thought on; since a Chymist scarce would, and none but a Chymist could propose them. I hope also it will not be unacceptable to several Ingenious Persons, who are unwilling to determine of any important Controversie, without a previous consideration of what may be said on both sides, and yet have greater desires to understand Chymical Matters, than Opportunities of learning them, to find here together, besides several Experiments of my own purposely made to Illustrate the Doctrine of the Elements, divers others scarce to be met with, otherwise then Scatter'd among many Chymical Books. And to Find these Associated Experiments so Deliver'd as that an Ordinary Reader, if he be but Acquainted with the usuall Chymical Termes, may easily enough Understand Them; and even a wary One may safely rely on Them. These Things I add, because a Person any Thing vers'd in the Writings of Chymists cannot but Discern by their obscure, Ambiguous, and almost AEnigmatical Way of expressing what they pretend to Teach, that they have no Mind, to be understood at all, but by_ the Sons of Art _(as they call them) nor to be Understood even by these without Difficulty And Hazardous Tryalls. Insomuch that some of Them Scarce ever speak so candidly, as when they make use of that known Chymical Sentence;_ Ubi palam locuti fumus, ibi nihil diximus. _And as the obscurity of what some Writers deliver makes it very difficult to be understood; so the Unfaithfulness of too many others makes it unfit to be reli'd on. For though unwillingly, Yet I must for the truths sake, and the Readers, warne him not to be forward to believe Chymical