Relations of chemistry to physics. Relations of heat to chemical phenomena. Improvements in the mercurial thermometer. Newton. Shuckburgh. Brooke Taylor. Cavendish. Black. Discovery of latent heat by Black. Discovery of specific heat. Experiments of Lavoisier and Laplace. Law of Dulong and Petit: its value in determining atomic weights. Specific heat of compounds. Neumann. Discovery of isomorphism by Mitscherlich. Foreshadowing of the kinetic theory of gases. Discovery of the law of gaseous diffusion by Graham. Liquefaction of gases. Monge and Clouet. Northmore. Faraday. Value of a knowledge of weights of unit volumes of gases in determining their molecular weights. Methods of vapour-determination by Dumas and Gay Lussac. Dalton and Henry’s law of gaseous solubility. Work of Schröder and Kopp on volume relations of liquids and solids. Connection between the chemical nature of a liquid and its boiling-point. BIBLIOGRAPHY 183 INDEX 187 HISTORY OF CHEMISTRY CHAPTER I THE CHEMISTRY OF THE ANCIENTS Chemistry, as an art, was practised thousands of years before the Christian era; as a science, it dates no further back than the middle of the seventeenth century. The monumental records of Egypt and the accounts left us by Herodotus and other writers show that the ancient Egyptians, among the earliest nations of whom we have any records, had a considerable knowledge of processes essentially chemical in their nature. Their priests were adepts in certain chemical arts, and chemical laboratories were occasionally attached to their temples, as at Thebes, Memphis, and Heliopolis. It is to be supposed, too, that in a cultured class, as the priesthood undoubtedly was, there would be now and again curious and ingenious persons who would speculate on the nature and causes of the phenomena which they observed. But there is no certain evidence that the Egyptians ever pursued chemistry in the spirit of science, or even in the manner in which they and the Chaldæans followed, for example, astronomy or mathematics. The operations of chemistry as performed by them were of the nature of manufacturing processes, empirical in character and utilitarian in result. It was comparatively late in the world’s history that men were found willing to occupy themselves in chemical pursuits in order to gain an insight into the nature of chemical change, and to learn the causes and conditions of its action.