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 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, G'reek, Italian, and English, and at the same time entered on the study of the matheniatical 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 tirne 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 'natio 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 Delambre applied himself to astronomical observations. In 1.781 the 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 hi3 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 niore 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, wh'aL was awarded to him. In the same year (1792) he was elected a member of the Acadeiny.

I'mmediately afterwards he was appointed, along with Mtichain, by the French section of the joint English and Freneh commission to measure an arc froni 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. .M4chain 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 Systeme 21fetrique 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 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 uniTersity, 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 elves, 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 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 Jfithodes Analytiques pour he Determination, dun Arc du Meridien, his numerous memoirs in the additions to the Connaissances des Temps, and his Astronomie Theorique et Pratique exhibit the finest applications of modern analysis to astronomy and geography.

It is a remarkable fact that Delambre did not apply himself 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 that time to a friend and pupil, he says that on the day of the siege, in the hearing of the cannonade, 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 Delambre 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, et des Satellites de Jupiter, pour servir it la 3me edition l'Astronomie do Lalande (1792) ; Methocles Analytiques pour la Determination d'un Arc du Mericlien (1799) ; Tables Trigonometrignes Hgeimales, par Borda, revues, augmentecs, et publiees par M. Delambre, (1801) ; Tables du Soleil, publiees par le Bureau des Longitudes 6806) ; Base dzt Systeme Metrigue &c. (3 vols. in 4to, 1806-1810) ; Rapport Historique sur les Progres des Sciences Mathematiques depuis 1789, &c. (1810); Abrege d'Astronomie, Ott Lecons Elementaires d'Astronomie Theoriguc et Pratique, in 8vo ; • Astronomie Theorigue et Pratique (3 vols. in 4to, 1814) ; Tables Ecliptiques des Satellites de Jupiter (1817) ; Histoire de l'Astronomie Atzeienne (2 vols. in 4to, 1817) ; Histoire de l'Astronomie du Mayen Age (1819, 1 vol. in 4to) ; Histoire de l'Astronomie Modernc (1821, 2 vols. in 4to) ; Histoire de l'Astronomie au Dixhuitieme Siecle (1 Tel. 4to, 1827). In addition to these, he furnished a very considerable number of memoirs (about 28) on various points of astronomy to the Connaissanees 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 doges on many of his contemporaries at their death.