A PRÆFACE INTRODUCTORY To the following Treatise.

belonging to the second of the following Discourses, which I could not possibly retrive, though it were the chief of them all. And having once more try’d the Opinion of Friends, but not of the same, about this imperfect work, I found it such, that I was content in complyance with their Desires; that not only it should be publish’d, but that it should be publish’d as soon as conveniently might be. I had indeed all along the Dialogues spoken of my self, as of a third Person; For, they containing Discourses which were among the first Treatises that I ventur’d long ago to write of matters Philosophical, I had reason to desire, with the Painter, to latere pone tabulam, and hear what men would say of them, before I own’d my self to be their Author. But besides that now I find, ’tis not unknown to many who it is that writ them, I am made to believe that ’tis not inexpedient, they should be known to come from a Person not altogether a stranger to Chymical Affairs. And I made the lesse scruple to let them come abroad uncompleated, partly, because my affairs and Præ-ingagements to publish divers other Treatises allow’d me small hopes of being able in a great while to compleat these Dialogues. And partly, because I am not unapt to think, that they may come abroad seasonably enough, though not for the Authors reputation, yet for other purposes. For I observe, that of late Chymistry begins, as indeed it deserves, to be cultivated by Learned Men who before despis’d it; and to be pretended to by many who never cultivated it, that they may be thought not to ignore it: Whence it is come to passe, 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 Phænomena 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