GAY-LUSSAC, NICOLAS-FRANcOIS, was born at St. Leonard, in the department of Hauta-Vienne, on December 6th, 1778. He was educated at the Polytechnic School, where his assiduity and talents gained him the friendship of Berthollet. On leaving the school lie entered into the scientific department of Les Ponta et Chaussdes. The expansibility of the gases was at that time a subject exciting much attention ; and Gay-Lussac gave the law of dilatation, and showed its constant uniformity. His application to this subject led M. Charles, a scientific physician, to recommend him the use of the balloon, just previously invented, as an excellent means of testing some of his theories, of making fresh experiments, and of at least exciting public attention by his boldness and the novelty of the attempt. In conjunction with M. Biot, he made the proposal to the government ; Laplace and Berthollet supported it ; and M. Chaptal, then minister of the interior, gave them the balloon which had been constructed fur the use of the war-department, having had it refitted at the public expense. Furnished with chronometers, thermometers, barometers, hygrometers, electrometers, compasses, and paper and pencils, Messrs. Gay-Lussac and Biot ascended from the garden of the Conservatoire des Arts et Metiers, on August 23, 1804. Their highest elevation attained was 3977 metres (13,028 feet) above the Seine. M. Biot was affected with giddiness ; but Gay-Lussac, by hie expe riments, ascertained that the influence of terrestrial magnetism on the compass was nearly as great as on earth ; that the atmospheric elec tricity increased as they rose, and was always negative ; that the hygrometer showed increased dryness ; and the thermometer, which marked 14° Reauruur (64° Fahrenheit) on earth, sank to Si° (51°). The bold adventurers at last descended safely about 54 miles from Paris. On September 6, in the same year, M. Gay-Lussac made a second ascent alone, when be reached a height of 4i miles ; at which height he experienced a difficulty of breathing and an excessive cold, the thermometer being 6 degrees below 0 of Rdaumur (20° Fehr.). He calculated that the air lost 1 degree of heat for each additional height of 174 metres (571 feet). On this occasion he brought down, in bottles carefully prepared for the purpose, some air from the highest point reached, which on analysis was found to be composed precisely the same as at the surface. After a voyage of six hours he descended at a village about 21 miles from Rouen.
M. Charles had been correct in supposing these experiments would draw attention to his friend. It introduced him to honour, titles, and illustrious friends. Of the society of Arcueil, instituted by Laplace and Berthollet in 1804, consisting at first of only nine members, Gay Lussac was one. Here he met Alexander von Humboldt, with whom he joined in the investigation of the polarisation of light, several memoirs on which were furnished to the society. In conjunction also
with Von Humboldt he endeavoured to determine the position of the magnetic equator, and its intersection with the terrestrial equator. Gay-Luasat's chief attention however was directed to the Voltaic pile, and the decomposition of acids and alkalies. Napoleon I. had insti tuted a magnificent prize for the most important discovery made by means of the pile, hoping that it would be gained by some one con nected with the Ecole Polytechnique, but Sir H. Davy, by his discovery of the metallic basis of soda and potassium, was the suc cessful competitor in 1810. Bonaparte was dissatisfied ; he inquired why the members of the institute had suffered the prize to be taken by a stranger, and be was told there was no pile in France powerful enough to obtain any grand results. He ordered a colossal one to be constructed immediately, and with it Gay-Lussac and M. Thdnard commenced their experiments in 1808. The result was a work in 2 vols. pub lished in 1811, 'Recherches physico-chimiques our la pile, sur les abseils, eur les acidee, l'analyse v6g6tale, et animale; &c. Their dis coveries, and the improvements on methods of Davy, detailed in this work, were of great importance. In 1816 he was created Professor of Chemistry in the Polytechnic school.
Gay-Lussac's life was one of constant activity. Though he has only published two works, and those little more than pamphlets, 'Mr5moire cur l'Iode; and 'Mdmoire sur le Cyanogene,' both highly esteemed, he has written more than a hundred papers on various subjects, and all of great ability. Besides the subjects already mentioned, he wrote on hygrometry, on capillary attraction, on the distinction betweeu oxydes and hydratides ; and to him is due the discovery of the hydro-sulphurio and oxy-chloride acids. A course of chemical lectures delivered by him at the Sorbonne, taken down in short-hand, has been also published in two volumes.
The merits of Gay-Lussac were not unrewarded by his country. After 1830, he was repeatedly chosen a member of the Chamber of Deputies ; and in 1839 he was created a peer of France. He was a member of the Academy of Sciences, honorary professor of natural philosophy at the Sorbonne, professor of chemistry at the Jardin du Roi, verificator at the mint of works in gold and silver, editor, with Arago, of the 'Annales de Physique et de Chimie,' with several other official employments connected with the manufacturing industry of France. After a long life of useful labours, and in the enjoyment of excellent health till within a short period of his decease, he died on May 9, 1850, at the handsome mansion provided for him in the Jardin du Rol.