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Page:Popular Science Monthly Volume 35.djvu/574

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THE POPULAR SCIENCE MONTHLY.

new discoveries, still rules. The "muriatic radicle" gave Lavoisier some trouble, for he could find no oxygen in muriatic acid, and his experiments upon it with oxygen resulted in the production of a neutral substance which must be its calx; and so he called chlorine oxidized muriatic acid. Such mistakes were natural in the early days of chemistry. The decomposition of volatile alkali, or ammonia, by Berthollet, led to the suggestion which Lavoisier gave out with great modesty, that many earths, still regarded as simple, might be compound; and that their apparent indifference to oxygen should be attributed to their being already saturated with it.

On the nature of gases and vapors, which had not been understood before, Lavoisier asserted, in a memoir published in 1777, that most bodies were capable of existing in three different states—those of solids, liquids, and vapors, or aëriform fluids. The terms airs, vapors, and aëriform fluids express only a single form of matter—a class of bodies infinitely extended; and this principle "gives the key to nearly all the phenomena relative to the different kinds of air and to vaporization." While heat tends to change volatile bodies into vapor, the pressure of the air has a contrary effect; and "the tendency of volatile bodies to evaporate is in direct ratio to the heat to which they are exposed, and inverse to the weight or pressure brought to bear upon them." Lavoisier's memoirs on heat, expansion and contraction under changes of temperature, and latent heat, show an insight into the accepted principles. He discussed with much sagacity the question whether heat is a fluid or a force; and it would not be hard, for one who is determined to look for it, to find in his essays on this subject a prevision of the current constitutional chemistry. Lavoisier's later labors were physiological. They include papers on the production of carbonic acid in respiration and the office of the lungs in the process, in which the present theory is proposed as a secondary hypothesis, and on cutaneous transpiration. In his physiological studies, M. Dumas has found that he had arrived at a remarkable anticipation of modern views concerning the relations of organic to inorganic nature.

Lavoisier carried his energy into several other fields, and made his mark in all. He cultivated an estate of two hundred and forty arpents in the Vendôme, and in nine years doubled its production. His name is associated with a number of propositions looking to the public welfare or economical reform. In 1789 he presented in the National Assembly a report of the "Caisse d'Escompte," to which he had been attached for one year. As commissioner of the treasury he proposed in 1789 a new plan for the collection of imposts, which he elaborated in a special essay entitled "The Territorial Wealth of the Kingdom of France," a work which, accord-