CHASLES, MICHEL

born Nov. 15, 1793, pernon, Fr. died Dec. 18, 1880, Paris French mathematician who, independently of the Swiss-German mathematician Jakob Steiner, elaborated the theory of modern projective geometry, the study of the properties of a geometric line or plane figure that remain unchanged when the figure is projected onto a plane from a point not on either the plane or the figure. Chasles was made professor of geodesy and mechanics at the cole Polytechnique, Paris, in 1841. His Aperu historique sur l'origine et le dveloppement des mthodes en gomtrie (1837; Historical Survey of the Origin and Development of Geometric Methods) is still a standard historical reference. In 1846 he became professor of higher geometry at the Sorbonne. In that year he solved the problem of determining the gravitational attraction of an ellipsoidal mass to an external point. In 1864 he began publishing in Comptes Rendus the solutions to an enormous number of problems based on his method of characteristics and his principle of correspondence. The basis of enumerative geometry is contained in the method of characteristics. Chasles was a prolific writer and published many of his original memoirs in the Journal de l'cole Polytechnique. He wrote two textbooks, Trait de gomtrie suprieure (1852; Treatise on Higher Geometry) and Trait des sections coniques (1865; Treatise on Conic Sections). His Rapport sur le progrs de la gomtrie (1870; Report on the Progress of Geometry) continues the study in his Aperu historique. Chasles is also remembered as the victim of a celebrated fraud. He is known to have paid nearly 200,000 francs (approximately $36,000) for various forged letters, some purported to be from famous men of science and one allegedly from Mary Magdalene to Lazarus.