CHASLES, MICHEL (1793-1880), French mathematician, was born on Nov. 15, at Epernon. He was educated at Paris, and engaged in business, which he later gave up for the study of mathematics. Chasles, was made professor of geodesy and mechanics at the Polytechnic school and later professor of higher geometry at the Sorbonne. He and Steiner independently elaborated modern projective geometry, but the interchange of scientific ideas was so poor that the former did not know of the work of the latter. Chasles used his "method of characteristics" and his "principle of correspondence" to solve many problems; the solutions were published in a series of papers in Comptes Rendus. The problem of the attraction of an ellipsoid on an external point was solved by him in 1846. Many of his original memoirs were later published in the Journal de l'Ecole Poly technique. Chasles wrote two text-books, Higher Geometry (185 2) and Conic Sections (1865) . His A percu historique sur l'origine et la developpement des en geometrie (1837) is a standard work, the subject being continued in Rapport sur le progres de la geometrie (1870). Chasles died in Paris on Dec. 18, 1880.