Jean Baptlste Joseph Delambre, a French astronomer, born in Amiens, Sept. 19, 1749, died in Paris, Aug. 19, 1822. He was a pupil of Delille at the college in his native town, where he distinguished himself as a classical scholar. He studied rhetoric and philosophy in Paris, and on leaving college became a private tutor, occupying his leisure in reading Italian, English, and Greek literature, and studying mathematics at first only sufficiently to teach his pupils. From 1780 he devoted himself to astronomy, being first the pupil and then the collaborator of Lalande, who said that "Delambre was his best work." In 1790 he gained the prize of the academy of sciences for his tables of Uranus, though that planet had completed but a small arc of its orbit after its discovery by Herschel; and in 1792 another prize was given him for his tables of the satellites of Jupiter. For these labors he was unanimously elected a member of the academy in 1792. In the same year he was associated with Mechain in measuring an arc of the meridian from Dunkirk to Barcelona. The work was interrupted by the revolution, and was not finished till 1799. Delambre published the results in his Base du systeme metrique decimal (3 vols., 1806-'10). He entered the bureau of longitudes in 1795, the institute of France at its formation in the same year, became inspector general of studies in 1802, perpetual secretary of the institute for mathematical sciences in 1803, successor of Lalande in the college de France in 1807, and treasurer of the imperial university in 1808. The last office was suppressed at the restoration, and from that time he pursued his researches in retirement.

After having spent 30 years in the most severe astronomical and mathematical calculations, he undertook to write the history of astronomy from the remotest period, five volumes of which were published before his death (1817-21), and a posthumous volume on astronomy in the 18th century was issued in 1827. He also made a report on the progress of the mathematical sciences since 1789 (1810), and wrote Astronomie theorique et pratique (3 vols., 1814), and numerous papers for the Biographie universelle and the transactions of different European academies of science.