Fourier, Jean Baptiste Joseph, Baron, 1768-1830, French mathematician and physicist. He was noted for his researches on heat and on numerical equations. He originated Fourier's theorem on vibratory motion and the Fourier series, which provided a method for representing discontinuous functions by a trigonometric series. Fourier was professor (1795-98) at the École polytechnique, Paris; accompanied Napoleon I to Egypt; and was prefect of Isère (1802-15). In 1808 he was made a baron. He wrote Théorie analytique de la chaleur (1822; tr. 1878, repr. 1955). His scientific writings were collected in two volumes (1888-90).

Delambre, Jean Baptiste Joseph, 1749-1822, French astronomer and mathematician. He was a member of the bureau of longitudes from 1795 and professor at the Collège de France from 1807. With P. F. A. Méchain he measured (1791-99) for the French government an arc of the meridian between Barcelona and Dunkirk. He is noted also for astronomical computations, especially a table of the motions of Uranus, and for discovering four formulas in spherical trigonometry (Delambre's analogies). Delambre is known for his historical works, including Histoire de l'astronomie (6 vol., 1817-27).

See Felix-Jean-Baptiste-Joseph Nève