This is the oldest branch of chemical science, and naturally the one which was furthest advanced at the beginning of the century. Nevertheless, the advances which the past one hundred years have seen in this science are most surprising. Gold and silver are now secured from ores so poor as to have rendered them of no value a hundred years ago. The Bessemer process of steel making (1856) has revolutionized the world, and made possible railroads and steamships. The basic Bessemer process of making steel from pig-iron rich in phosphorus, has opened up rich mines of iron ore hitherto valueless. The basic phosphatic slag, resulting from this process, is of the highest value in the fields, and has brought agriculture and metallurgy into intimate relationship. The electric furnace has made aluminium almost as cheap as iron, bulk for bulk, and electric welding bids fair to take the place of the old process, with the cheapening of metals. VII. AGRICULTURAL CHEMISTRY. Sir Humphry Davy, in the beginning of the century, delivered a course of lectures on the relations of chemistry to agriculture, and these were published in book form. In France, important contributions were made to agricultural chemical science by Vauquelin, Chevreul (1786–1889), and Boussingault (1802–1887), who made important researches before the middle of the century. The most important work in agricultural chemistry, however, was done by Liebig. His achievements so overshadowed those of his predecessors that he is generally regarded, although improperly, as the father of that branch of the science. The early achievements of these workers showed the relatively small portions of the crops that were derived from the soil. The study of the ash constituents of plants laid the foundation of rational fertilizing, and the utilization of the stores of plant food preserved in great natural deposits. Beginning with the middle of the century, the attention of agronomists was called to the desirability of utilizing the deposits of guano, found in the islands along the west coast of South America; of the deposits of phosphate rock existing in many localities; and later, of the potash salts, discovered near Stassfurt, which completed the trio of available natural foods most useful to plants. The establishment of an agricultural experiment station by Sir John Lawes at Rothamstead (1834), before the middle of the century, set an example which has been followed by the establishment of experiment stations in all the civilized countries of the world. Under the great stimulus given to agricultural research by these stations, progress during the latter half of the century has been very rapid. There now exist in Europe nearly one hundred stations devoted to agricultural research, and in this country the number is half as great.