Page:Philosophical Transactions - Volume 003.djvu/187

 The Curious are hereby advertised, that the Author hath thought fit to lodge with the Publisher a number of Copies both of this Cometography, and of all his former Works, viz, the Selenography, Mercurius in sole visus, Venus in sole visa, Epistolæ de motu Libratorio Lunæ, and the Prodromus and Mantissa concerning the two Comets of An. 1664, and An. 1665. All which Books being order'd by the Author to be vended here, for an Exchange into the longest and best Telescope, that can be made by English Artists; those that are desirous to be furnisht with them, may please to address themselves to the Publisher, who is ready to give them further information herein.

Hough some few of these Letters were by the Author himself written in Latin, yet the farr greater part of them having been by him written in French, they are now come abroad all Translated into Latin, for the benefit of those, that are unskilful in the other Language. They contain very many Philosophical questions and matters, of all forts, and an Explication of many difficulties, to be met with in the other Works of the Illustrious Author, and were written to some of the most Eminent persons for knowledge and learning of this Age. The intelligent Reader will find here an incredible and exceedingly delightful variety of Subjects, Geometrical, Arithmetical, Musical, Optical, Mechanical, Physiological, Medical, Metaphysical and Moral.

There is a Third part of the same Authors Letters yet remaining un-translated, which is like to follow very shortly, with some other Tracts, concerning Man, and the Union of the Rational Soul with the Body; whereof the former was written by Descartes himself, the latter by the Ingenious-D. Dela Forge, upon Cartesian Principles.

His Author endeavours in this small Tract to shew the Nature, Difference, Choice, Qualities and Vertues, (especially in Physick) of Vitriol, together with the various wayes of preparing both dry and liquid Medicins out of that Mineral Juyce. The way of making Vitriol used at Goslar in Germany (the Authors Native Country) we shall thence extract and give here verbatim, as follows; Rh