CLAIRAULT (ALEXIs C LAUDE), a ce lebrated French mathematician and aca demician, was born at Paris the 13th of May, 1713. His father, a teacher of ma thematics at Paris, was his sole instructor, teaching him even the letters of the al phabet on the figures of Euclid's Ele ments, by which he was able to read and write at four years of age. By a similar stratagem it was that calculations were rendered familiar to him. At nine years of age he *put into his hands Guisnee's Application of Algebra to Geometry ; at ten he studied l'Hospital's Conic Sec tions ; and between twelve and thirteen he read a memoir to the Academy of Sci leaces, concerning four new geometrical curves of his own invention. About the same time he laid the first foundation of his work upon curves that have a double curvature, which he finished in 1729, at sixteen years of age. He was named Ad joint-Mechanician to the Academy in 1731, at the age of eighteen, Associate in 1733, and Pensioner in 1738. During
his connexion with the Academy, he had a great multitude of learned and ingeni ous communications inserted in their me moirs, besides several other works which he published separately. In the year 1750, the Academy of Petersburg pro posed a prize on the subject of the lunar motions, which Clairault obtained : and in a few years lie obtained another prize on the same subject. He was during life a most active and indefatigable man. He died in 1765, at the age of 52. His works are numerous, and his papers, inserted in the Memoirs of the Academy, may be found in the year 1727, and also for al most every year till 1762; being upon a variety of subjects, astronomical, mathe matical, optical, &c.