Jacques Charles

Jacques Alexandre César Charles was born in 1746 at Beaugency in the Loiret. He began as a clerk in the finance ministry and came to science largely self-taught, drawn in by the popular lecture-demonstrations of the day, which he later gave himself with great flair at the Conservatoire des Arts et Métiers in Paris.

Inspired by the Montgolfier brothers' hot-air ascents, Charles realised that the newly isolated 'inflammable air' — hydrogen — would lift far more for its weight. In August 1783 he launched the first unmanned hydrogen balloon, and that December he and Nicolas-Louis Robert made a manned ascent from the Tuileries before a crowd of hundreds of thousands, rising to some 3,000 metres. The hydrogen balloon was for a century afterward called a charlière in his honour.

Around 1787, working with gases, Charles found that at constant pressure different gases all expand by the same fraction of their volume for a given rise in temperature — the proportionality of volume to temperature now called Charles's law. He never published it. The result became widely known only when Joseph Louis Gay-Lussac, crediting Charles's unpublished work, established and printed it in 1802.

Charles was elected to the Académie des Sciences in 1795 and became a professor of physics, remembered as much for his showmanship and instrument-making as for his research. He died in Paris in 1823.