Thomson, Sir Charles Wyville

(1830–82) British marine biologist and oceanographer: postulated the existence of a mid-Atlantic ridge and of oceanic circulation.

Educated at the University of Edinburgh, Thomson held a number of academic posts in Scotland and Ireland before being appointed professor of natural history at Edinburgh in 1870. He took part in several deep-sea expeditions, leading the 5-year circumnavigational Challenger expedition of 1872–6, a landmark in marine exploration which resulted in the discovery of 4717 new marine species.

Thomson disproved two accepted beliefs: that the oceans were lifeless below 300 fathoms (about 550 m); and that a fairly constant temperature of about 4°C existed at these depths. He found many animals by dredging at depth, and diverse temperatures at similar submarine depths in different regions. The expedition also showed that a clay bottom is usual at great depths and that nodules of nearly pure manganese dioxide (MnO 2 ) are found on the sea-floor.

All this work revitalized oceanography. On the basis of temperature measurements Thomson postulated the presence of oceanic circulation and the existence of a mid-Atlantic ridge, but the latter was not confirmed until 1925.