CHARLES, JACQUES ALEXANDRE CESAR (1746 1823), French mathematician and physicist, was born at Beau gency, Loiret, on Nov. 12, 1746. From being a clerk in the min istry of finance, he turned to scientific pursuits, and became one of the most acute of physical researchers and inventors. He was the first, in 1783, to employ hydrogen for the inflation of balloons (see AERONAUTICS), and about 1787 he anticipated Gay Lussac's law of the dilatation of gases with heat, which on that account is sometimes known by his name. He improved the Gravesand heliostat and the aerometer of Fahrenheit and invented a "thermometric hydrometer," a "goniometer by reflection" and many other ingenious physical devices. In 1785 he was elected to the Academy of Sciences, and subsequently he became profes sor of physics at the Conservatoire des Arts et Metiers. He died in Paris on April 7, 1823. His published papers are chiefly con cerned with mathematical topics.