born April 13, 1892, Brechin, Scot.
died Dec. 5, 1973, Inverness
Scottish physicist.
He began as a meteorologist working on devices for locating thunderstorms. As head of the radio department of Britain's National Physical Laboratory (1935), he worked on aircraft radio location and could locate planes at a distance of about 80 mi (110 km) by beaming radio waves at them, receiving reflections of the waves, and calculating distance by elapsed time. This led to the design of the world's first practical radar system, a vital element in the defense of Britain against German air raids during World War II. His other contributions include a cathode-ray direction finder used to study atmospheric phenomena, research in electromagnetic radiation, and inventions used for flight safety.