The science of chemistry, as it is known to-day, had its real origin towards the end of the eighteenth century. Before and up to that time it is true there were many great workers in chemistry, whose names are associated with investigations in chemical science, such as Boyle, Stahl, Black, and Scheele. Contemporary with the close of the eighteenth century and the beginning of the nineteenth must also be mentioned particularly the names of Priestly (1733–1804), Cavendish and Humphry Davy (1778–1829). All these workers had to contend, first of all, with erroneous theories, which made it difficult to rightly interpret the data of experiment. The old theory of phlogiston produced an environment in which it was difficult for true scientific methods to survive. The great investigator, who did more than any other one man to overturn this false theory and place chemistry on a firm foundation, was Lavoisier (1743–1794). Born near the middle of the eighteenth century, his scientific activity began about 1770, and before he was twenty-five he was made a member of the French Academy of Sciences. At the age of forty he was recognized as the foremost scientist of his age. Priestly discovered oxygen in 1774, but failed to recognize its true relations to other bodies. It was Lavoisier who discovered oxidation (1776), an achievement which meant more to chemistry than the discovery of oxygen. The observation that metals when heated in confined air increased in weight while the volume of the confined air decreased, is the crucial experiment upon which the whole science of chemistry rests. This experiment was made most rigorously by Lavoisier, and the apparatus which he used is still preserved in the Museum of L’École des Arts et Métiers in Paris. This apparatus, simple in character and yet almost perfect in construction, has for the chemist a peculiar significance and sacredness, producing an impression similar to that inspired in the devout Christian by the relics of the Cross and the Holy Sepulchre. In the brief space which is assigned for a discussion of the progress of chemistry during the nineteenth century, economy of words will be secured by briefly tracing some of the salient points in the progress of some of the more important branches of chemical science. In the following pages, therefore, will be found a brief statement of what has been accomplished, of the most important character, in the science of chemistry, under the following heads:— Inorganic chemistry; physical chemistry; organic chemistry; analytical chemistry; synthetical chemistry; metallurgical chemistry; agricultural chemistry; graphic chemistry; didactic chemistry; chemistry of fermentation; and lastly electro-chemistry.