Wyville Thomson. Portrait of Sir Charles Wyville Thomson (1830-1882), Scottish marine biologist and oceanographer. In 1868-69 he led two deep-sea biological and depth-sounding expeditions, the results of which led him to postulate the exist- ence of deep-sea circulation and to challenge the belief that marine life existed only near the surface. During 1872-6 he headed the Challenger expedition which made soundings and observations at 362 points in the Atlantic, Antarctic & Pacific Oceans. He suggested the presence of the Mid- Atlantic Ridge. He began editing the 50 volumes of Challenger reports but was forced to retire through ill health, John Murray completing it.