Jean Baptiste Joseph Delambre (1749-1822), an eminent mathematician and astronomer, was born at Aiens, September 19, 1749.
In 1771, at the College of France he attended the lectures of Lalande, on whose works he had even a that time made a complete commentary. This was first remarked when, in the course of instruction, an occasion presented itself of citing from memory a passage of Aratus. Lalande immediately entrusted to him the most complicated astronomical calculations, and prevailed on D'Assy to establish an observatory at his house, where Delambre applied himself to astronomical observations. In 1781 the discovery of the planet Uranus by Hershel led the Academy of Sciences to propose the determination of its orbit as the subject of one of its annual prizes. Delambre undertook the formation of tables of its motion, and the prize was awarded to him. His next effort was the construction of solar tables, and tables of the motions of Jupiter and Saturn. He took part in the sitting of the Academy of Sciences when Laplace communicated his important discoveries on the inequalities of Jupiter and Saturn; and he formed the design of applying the result of that profound analysis to the completion of table of the two planets. Delambre turned his attention more especially to the satellites of Jupiter - an undertaking of great difficulty and extent. He had been engaged for several years in the composition of his ecliptical tables, when the Academy of Sciences offered a prize for the subject, which was awarded to him. In the same year (1792) he was elected a member of the Academy.
Immediately afterwards he was appointed, along with Mechain, by the French section of the joint English and French commission to measure an arc from Dunkirk to Barcelona as a basis for the metric system. This undertaking, in itself laborious, was rendered highly dangerous to the personal safety of those engaged in it by the events of the Revolution. Mechain died whilst the work was proceeding; and its successful termination in 1799 was due to the ability and the prudence of Delambre. A full and interesting account of the work was published in the Base du System Metrique Decimal (3 vols. 1806-1810), of which he obtained, by unanimous vote, the prize awarded by the National Institute of France to the most important work in physical science of the preceding ten years.
Delambre, who had been chosen as an associate of almost every scientific body in Europe, was appointed in 1795 a member of the French Board of Longitude, and in 1803 perpetual secretary for the mathematical sciences in the Institute. In 1807 he succeeded Lalande in the chair of astronomy of the College of France, and he was appointed one of the principal directors (titulaires) of the university. For twenty years he performed faithfully and impartially the duties of his office in one of the classes of the Institute. His annual reports, his historical eloges, which have been published, and his exposition of the progress of science are eminently distinguished by profound erudition, literary skill, and, above all, by generous appreciation of the works of others. His literary and scientific labors were very numerous, and, in respect of excellence, of the highest order. His History of Astronomy, published at intervals, and forming when complete six quarto volumes, is a work of prodigious research. It puts the modern astronomer in possession of all that had been done, and of the methods employed by those who lived before him.
His Methodes Analytiques pour la Determination d'un Arc du Meridien, his numerous memoirs in the additions to the Commaissances des Temps, and his Astronomie Theorique et Pratique exhibit the finest applications of modern analysis to astronomy and geography.
Encyclopedia Britannica, 9th ed. (American Reprint), Vol. VII, 1880