No attempt will be made in this paper to enter upon the discussion of the progress which has been made in medical, pharmaceutical, and physiological chemistry. The discussion outlined under the above heads does not by any means embrace the whole subject. It will be sufficient to indicate only the lines of progress along which the greatest advances have been made. I. INORGANIC AND PHYSICAL CHEMISTRY. [Illustration: H Davy Pres RS.] The three propositions established by Lavoisier, which serve as the foundation for inorganic and physical chemistry, are the following:— 1. Bodies burn only in contact with pure air. 2. The air is consumed in the combustion, and the increase in weight of the burnt body is equal to the decrease in weight of the air. 3. In combustion the body is generally changed, by its combination with the pure air, into an acid, and metals are changed into metal calx. The total number of elementary bodies known at the beginning of the century was probably less than thirty. Many had been recognized as such since remote antiquity, but none of the non-metallic elements, except oxygen and sulphur, was known, and even their properties were not established with any degree of precision. Not only did Lavoisier establish the fundamental principles of modern chemistry, but in connection with Fourcroy (1755–1809), Berthollet (1748–1822), and Guyton de Morveau (1737–1816), laid the foundation of modern chemical nomenclature. The contributions to chemical knowledge at this time were greatly increased by the works of the Swedish chemist, Scheele (1742–1786), and in the beginning years of the century the great work which was accomplished by Sir Humphry Davy advanced very rapidly the general knowledge of chemical science. Davy’s first works served to elucidate the connection between electricity and chemical processes, and it was through the classical experiment with an electric current that he isolated (1807) the metals sodium and potassium, and described their properties. This achievement of Sir Humphry Davy’s was the second great step in the progress of chemistry, after the one taken by Lavoisier. By means of the metals sodium and potassium other metallic elements were separated, notably aluminium by Wöhler (1845). Basing his work upon the above experiment, Sainte Claire Deville developed the metallurgy of aluminium (1854), and Bussy isolated magnesium (1830). In 1811 iodine was discovered by Courtois, and its properties examined simultaneously (1814) by Davy and Gay-Lussac. The contributions made by Berzelius (1779–1848), who was a contemporary of Davy and Gay-Lussac (1778–1850), were of the most important character. Berzelius not only added to the knowledge of inorganic chemistry but also established many of the important theories on which chemical action depends. His elaboration of the employment of the blowpipe in chemical analysis was of the greatest practical value.