Félix Savart

Félix Savart was born in Mézières in 1791 to a family of military engineers — the same École royale du génie de Mézières that had produced Coulomb a generation earlier. He trained as a military surgeon during the Napoleonic Wars, served in army hospitals along the Rhine, and earned his medical doctorate in Strasbourg in 1816 with a thesis on the construction of stringed musical instruments — an interest he never lost. After Waterloo he set up a small medical practice in Strasbourg, but the patients drifted away as he spent more and more of his time in his workshop, building violins by ear and measuring their acoustic properties with self-designed instruments.

Discouraged by his medical practice, Savart moved to Paris in 1819 to look for academic work. He was introduced to Biot, who recognised in him the rare combination of experimental dexterity and mathematical taste, and brought him on as a collaborator. The two were working together when Arago announced Ørsted's discovery to the Académie des sciences in September 1820. Within weeks they had built the apparatus that would let them measure the magnetic force on a small magnet at varying distances and angles from a long, current-carrying wire. Biot supplied the theoretical framework — that the force should derive from a sum over infinitesimal current elements, each contributing inversely as the square of distance — and Savart supplied the precise experimental geometry that pinned down the cross-product structure (the famous I dℓ × r̂ / r²). Their joint paper of 30 October 1820 beat Ampère's full electrodynamic theory by three weeks and, despite Ampère's later and more general framework, the field-element formula has carried both names ever since.

Savart's first love, however, was acoustics. He invented the toothed wheel that bears his name (the Savart wheel, used to determine the frequency of any periodic sound by comparison with a calibrated rotating cog); he measured the velocity of sound in solids; he showed that the human voice is produced by a vibrating membrane analogous to a violin string. Cherubini, the director of the Paris Conservatoire, hired him to advise on the acoustics of concert halls. In 1827 he was elected to the Académie des sciences and in 1836 he succeeded André-Marie Ampère in the chair of experimental physics at the Collège de France. He died in Paris in 1841 at the age of forty-nine, of a chronic illness that had been worsening for years. The Biot–Savart partnership had lasted only the autumn of 1820, but it was enough to put his name on every undergraduate magnetostatics textbook ever written.