[59] “Mr. Cavendish,” says Dr. O. Gregory, “is the first who endeavored to establish that the proportions of the two principal elements of the atmospheric air were constant. The observations since made by M. de Mairy in Spain, M. Berthollet, in Egypt and in France; Mr. Davy, in England; and by Dr. Beddoes on the air brought from the coast of Guinea, seem to have confirmed this grand result. But one of the finest experiments made on this subject is that of Gay Lussac, in France, who, having been elevated alone in a balloon to the height of 6,900 metres, the greatest ever attained by any person, brought some atmospheric air from these regions. This air, being analysed at his return, comparatively with that on the surface of the earth, gave the same principles in the same proportions; a proof that the chemical constitution of the atmosphere at these great heights, is the same as at the surface of the earth. This result has been since confirmed by the experiments made by Messrs. Humboldt and Gay Lussac on eudiometry. The air of the surface of the earth, analysed at different days, at various hours and temperatures, presented no change in its composition: it always contained 0.21 of oxygen in volume, 0.783 of azote, 0.003 of hydrogen, and 0.004 of carbonic acid. Biot and Arrago have also lately verified this grand result. The atmospheric air, analysed in places the most distant from each other, in deep valleys, on high mountains, on banks of lakes, and in the glaciers of Chamouny, always presented to them the same composition.” Haüy’s Natural Philosophy, Note, vol. i. p. 218. [60] Sturm’s Reflections, vol. iv. p. 49.