"P.S. We may presume, that copies of Rey's work are rare. That which I have before me belongs to M. de Villiers, physician of the faculty of Paris, who has the best chemical library in France, and which he has sincere pleasure in laying open to the cultivators of the science. M. de Villiers's copy came from the library of the late M. Villars, physician at Rochelle, which was sold by his heirs in the course of last year. This copy was defective, it ended at p. 142, containing only the beginning of the 28th Essay. I requested M. Capperonier to allow me to transcribe, from the copy in the king's library, the two pages that are wanting in M. de Villiers's,—which he had the goodness to accede to. Thus, they who may wish to read John Rey's work, are informed, that there is a copy of it in the king's library, at the end of which they will find two manuscript letters; the first from Father Mersene to the physician, John Rey, in which he attacks the natural philosophy of that author,—the second, Rey's answer to Mersene, in which he defends himself with all his might."