DESARGUES, GERARD (1593-1662), French mathe matician, was born at Lyons. By profession he was an engineer and architect, and was an army officer in the engineering section at the siege of La Rochelle. Between 1626 and 163o he gave a series of lectures on mathematics at Paris, and influenced Des cartes and Pascal. He died at Lyons in 1662. Most of his mathe matical work is on geometry, and the theory of involution and transversals is due to him. Desargues' most important writings are Traite de la section Perspective (1636) and Brouillon Project (1639). The latter book deals with conics and embodies most of his researches.