Sydney Chapman, English mathematician, c 1930s.

Sydney Chapman (1888-1970) studied mathematics and engineering, and was a profesor at Manchester, Imperial College, London, and Oxford. He worked at the High Altitude Observatory at Boulder, Colorado, USA, and at the the Geophysical Institute in Alaska from 1954. Chapman developed the theory of thermal diffusion and made major advances in kinetic gases theory, as well as producing theories on geomagnetic storms, atmospheric tides, and geomagnetism. He was President of the Physical Society from 1949-1950.