Stock Photo - Jean Baptiste Biot and Joseph Louis Gay-Lussac, French scientists, 1804 (1870). Biot (1774-1864) and Gay-Lussac (1778-1850) are shown making measurements at a height of 4000 metres during their balloon ascent of 20 August 1804. This was the first balloon ascent made specifically for scientific purposes, studying the composition of the air and the effect of altitude on terrestrial magnetism. From Les Merveilles de la Science by Louis Figuier. (Paris, 1870).

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