To him, also, we owe the first knowledge of barytes, and of the characters of manganese. He determined the nature of the constituents of ammonia and prussic acid: he first determined the compound nature of common air, and the properties of the two elastic fluids of which it is composed. What other chemist, either a contemporary or predecessor of Scheele, can be brought in competition with him as a discoverer? And all was performed under the most unpropitious circumstances, and during the continuance of a very short life, for he died in the 44th year of his age. CHAPTER III. PROGRESS OF SCIENTIFIC CHEMISTRY IN FRANCE. I have already given an account of the state of chemistry in France, during the earlier part of the eighteenth century, as it was cultivated by the Stahlian school. But the new aspect which chemistry put on in Britain in consequence of the discoveries of Black, Cavendish, and Priestley, and the conspicuous part which the gases newly made known was likely to take in the future progress of the science, drew to the study of chemistry, sometime after the middle of the eighteenth century, a man who was destined to produce a complete revolution, and to introduce the same precision, and the same accuracy of deductive reasoning which distinguishes the other branches of natural science. This man was Lavoisier. Antoine Laurent Lavoisier was born in Paris on the 26th of August, 1743. His father being a man of opulence spared no expense on his education. His taste for the physical sciences was early displayed, and the progress which he made in them was uncommonly rapid. In the year 1764 a prize was offered by the French government for the best and most economical method of lighting the streets of an extensive city. Young Lavoisier, though at that time only twenty-one years of age, drew up a memoir on the subject which obtained the gold medal. This essay was inserted in the Memoirs of the French Academy of Sciences, for 1768. It was during that year, when he was only twenty-five years of age that he became a member of that scientific body. By this time he was become fully conscious of his own strength; but he hesitated for some time to which of the sciences he should devote his attention. He tried pretty early to determine, experimentally, some chemical questions which at that time drew the attention of practical chemists. For example: an elaborate paper of his appeared in the Memoirs of the French Academy, for 1768, on the composition of _gypsum_--a point at that time not settled; but which Lavoisier proved, as Margraaf had done before him, to be a compound of sulphuric acid and lime. In the Memoirs of the Academy, for 1770, two papers of his appeared, the object of which was to determine whether water could, as Margraaf had pretended, be converted into _silica_ by long-continued digestion in glass vessels. Lavoisier found, as Margraaf stated, that when water is digested for a