Dionis Du Sejour, Achilles Peter

, one of the first French astronomers of the last century, was born at Paris Jan. 11, 1734, and appears to have been educated to the profession of the law, as he became a counsellor of parliament; but his fame is more solidly“established on his astronomical pursuits. In the former capacity, however, he was appointed a deputy from the noblesse of Paris as one of their representatives in the constituent assembly. His conduct here appears to have been moderate, and even praiseworthy, as he incurred the displeasure of the succession of tyrants who ruined their country, and was obliged to escape to some secure place of retirement, where he died in August 1794. During his more prosperous career, he was chosen a member of the royal societies of London (in 1775) and of Stockholm and Gottingen, and contributed many papers to Memoirs of the academy of sciences at Paris, of which he was also a member. His principal works, all of high value, are, 1.” Traite des courbes algebraiques,“1756, 12mo. 2.” Methode | generale et directe pour resoudre les problemes relatifs aux eclipses,“read in the academy. 3.” Recherches sur la gnomonique et les retrogradations des Planetes,“1761, 8vo. 4.” Traite“analytique des mouvemens apparens des corps celestes,” 1774, 2 vols. 4to. 6. “Essai sur les Cometes en general, et en particulier sur celles qui peuvent approcher de l'orbite de la terre,” 17“-”, svo; a work, says its reviewer, which deserves undoubtedly to be placed among astronomical productions of the first rank, and in which the learned author has omitted nothing that has the least relation towards the general theory of comets. Accordingly the commissaries, who were appointed by the royal academy of sciences at Paris to examine this work, declared that it contained the most complete theory of comets hitherto given. 6. “Essai sur les phenomenes relatifs aux disparitions periodiques del'anneaude Saturne,” 1776, 8vo. This work amply supported the character which the author had established by his former writings, and it received the unanimous approbation of D'Alembert, Borda, Vandermonde, Bezout, and La Place, the members of the academy who were appointed to examine it. ¹