=Nicolas Lemery=, also born in 1645, wrote a _Cours de Chimie_, one of the best text-books of the time, which passed through as many as thirteen editions, and was translated into English, German, Latin, Italian, and Spanish. In this book he strove, as he says, to express himself clearly, and to avoid the obscurities which were to be found in the authors who had preceded him. The fine imaginations of other philosophers concerning their physical principles may elevate the spirit by their grand ideas, but they prove nothing demonstratively. And, as chemistry is a science of observation, it can only be based on what is palpable and demonstrative. Nicolas Lemery, who is not to be confounded with his son Louis, also a chemist, made a considerable number of contributions to pharmaceutical chemistry; and his _Pharmacopée Universelle_, _Dictionnaire Universel des Drogues Simples_, and _Traité de l’Antimoine_ were standard works in their day. Lemery was at one time a Protestant, and on the revocation of the Edict of Nantes fled to England; but, embracing Catholicism, he returned to Paris, re-established his pharmacy, and was elected into the Academy in 1699. He died in 1715. =William Homberg=, born in Batavia in 1652, was originally intended for the profession of law, but, becoming attached to science, studied botany and medicine in Padua, chemistry at Bologna and in London, mechanics and optics at Rome, and anatomy at Leyden. In the course of his travels he visited the mines of Germany, Hungary, Bohemia, and Sweden. In 1682 he was invited to Paris by Colbert, and in 1691 was made a member of the Academy and was placed by the Duke of Orleans in charge of his laboratory—then one of the finest in Europe. Homberg married the daughter of Dodart, the physician. She became an expert _préparateur_, and was of great assistance to him in his experimental inquiries. He first made known the existence of phosphorus in France, discovered by Brand, of Hamburg, and he described the phosphorescent salt associated with his name. He made important observations on the saturation of alkalis by acids, and was aware that they combined in different proportions. He was an industrious worker, and, with the exception of Cassini, was the most active member of the Academy. He died on September 24th, 1715. Next to Boyle, perhaps the most active agent in emancipating chemistry from the yoke of alchemy was Boerhaave, who, by his teaching as Professor of Physic, raised the University of Leyden to the summit of its fame.