The author, André LANGEVIN (1901-1977), was the second son of Paul Langevin and his wife Jeanne Desfosses. He was a student of physics at the École Supérieure de Physique et Chimie Industrielle where he became head of works in applied electricity in 1938. He was married to Luce Dubus, physicist, and communist activist, who assisted him writing this biography. He published on piezoelectricity and petrography, completing his doctorate in 1942. During the post-war period he was active in the National Union of Scientific Researchers and the National Education Federation. This biography of his father was written after his retirement in 1965.