# Encyclopædia Britannica, Ninth Edition/Jean Baptiste Joseph Delambre

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​ DELAMBRE, JEAN BAPTISTE JOSEPH (1749–1822), an eminent mathematician and astronomer, was born at Amiens, September 19, 1749. He commenced his studies in the gymnasium of that town under the celebrated poet L^elille, with whom he maintained an intimate friendship till his death. Having obtained an exhibition founded by one of his ancestors for the benefit of the town of Amiens, he waa enabled to prosecute his studies for a time at the College du Plessis in Paris. The expiry of this privilege, however, left him to struggle with great privations. During the interval in which he was awaiting permanent employment he devoted himself to historical and literary studies. He undertook extensive translations from Latin, Greek, Italian, and English, and at the same time entered on the study of the mathematical sciences. For about a year he supported himself by teaching at Compiegne. On his return to Paris in 1771 he obtained the situation of tutor in the family of D Assy, the receiver-general of finance. By this time he had resolved to give himself specially to the study of physics and astronomy. At the College of France he attended the lectures of Lalande, on whose works he had even at 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 intrusted to him the most complicated astronomical calculations, and prevailed on D Assy to establish an observatory at his house, where Delambro applied himself to astronomical observations. In 1781 tho discovery of the planet Uranus by Herschel 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 con struction 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 1m 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 tables 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, wlroL 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 under taking, 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 his Base du Systcme Metrique Decimal (3 vols. 1806-10), for which he obtained, by a 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 1 807 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 lie 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 cf others. His literary and scientific labours 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 Connaissances des Temps, and his Astronomic Theorique et Pratique exhibit the finest applications of modern analysis to astronomy and geography. It is a remarkable fact that Delambre did not apply him self to astronomical observations until he had reached the comparatively late age of thirty-five. He was appointed a member of the Royal Council of Public Instruction in 1814; but he lost the place in 1815. He was in Paris when it was taken by the allied armies ; and, in a letter written at tha,t time to a friend and pupil, he says that on the day of the siege, in the hearing of the cannon ade, he laboured with tranquillity in his study from eight in the morning till midnight. He had a happier fate than Archimedes in a like position, for he was not molested by the victors, and no one was billeted on him, probably from respect to his high reputation. At the creation of the Legion of Honour in 1802 Delambre was made a member of that order. He was appointed chevalier of St Michael in 1817, an officer in the Legion of Honour in 1821 ; but a long time before, he had been created an hereditary chevalier, with an endowment, which was decreed as a national reward. The life of continued and hard study which Delamt&gt;re led at last affected his health. The disease by which he was cut off became apparent in the month of July 1822. His total loss of strength, with frequent and long continued fainting-fits, gave warning of a fatal result, which occurred on the 19th August 1822. The following is a list of his works which appeared separately : Tables de Jupiter et de Saturn (1789) ; Tables du Soleil, de Jupiter, de Saturn, d Uranus, ct dcs Satellites de Jupiter, pour scrvir d la 3mc edition I Astronomic dc Lalandc (1792) ; Mithodcs Analytiques pour la Determination d un Arc du Meridien (1799) ; Tables Trigonometriques Decimates, par Borda, revues, augmentees, et publites par M. Delambre, (1801) ; Tables du Soleil, publiees par le Bureau dcs Longitudes (1806) ; Base du Systeme Metrique De cimal, &c. (3 vols. in 4to, 1806-1810) ; Rapport Historique sur les Progres des Sciences Mathematiques depuis 1789, &c. (1810) ; Abrcge d Astronomic, ou Lecons JtZlemcntaires d Astronomic Theorique ct Pratique, in 8vo ; Astronomic Theorique ct Pratique (3 vols. in 4to, 1814); Tables Ediptiqucs dcs Satellites de Jupiter (1817) ; Histoire de V Astronomic Ancienne (2 vols. in 4to, 1817) ; Histoire dc I Astronomic du Moyen Age (1819, 1 vol. in 4to) ; His toire dc V Astronomic Moderne (1821, 2 vols. in 4to) ; Histoire de T Astronomic au Dixhuitiemc Siecle (1 vol. 4to, 1827). In addition to these, he furnished a very considerable number of memoirs (about 28) on various points of astronomy to the Connaissances de Temps, beginning with the year 1788. He also contributed to the Memoirs of the Academies of Stockholm, St Petersburg, Berlin, and Turin, and to those of the first class of the French Institute ; and he composed eloges on many of his contemporaries at their death.