CLAIRAULT (or CLAIRAUT), ALEXIS CLAUDE (1713 1765), French mathematician, was born on May 7 or 13, 1713, at Paris. Under the tuition of his father, a teacher of mathe matics, he made such progress that at twelve years of age he read before the French Academy an account of the properties of four curves which he had discovered. His Recherches sur les courbes ci double courbure, finished in 1729 and published 1731, procured his admission into the Academy of Sciences, although he was still below the legal age. In 1736, with P. L. Maupertuis, he went on the expedition to Lapland, for the purpose of estimat ing a degree of the meridian ; and in r 743 he published his treatise Theorie de la figure de la terre, in which he promulgated the theorem known as "Clairault's theorem," which connects the gravity at points on the surface of a rotating ellipsoid with the compression and the centrifugal force at the equator (see EARTH, FIGURE OF THE). In 1750 he gained the prize of the St. Peters burg Academy for his essay Theorie de la lune; and in 1759 he calculated the perihelion of Halley's cornet. He also detected singular solutions in differential equations of the first order, and of the second and higher degrees. Clairault died at Paris on May 17, 1765.