Physicist (radioactivity, alpha particles, experimental nuclear physics) and administrator. On the physics faculty at Trinity College, University of Cambridge, Cambridge, England (1885-1898); McGill University, Montreal, Canada (1989-1907); Manchester University, Manchester, England (1907-1919); University of Cambridge, Cambridge, England (1919-1937); director, Cavendish Laboratory, Cambridge, England Industrial Research (1930-1937).