Investigations into conditions in Arctic and Antarctic seas were carried out during the late 18th and 19th centuries by private as well as government-sponsored expeditions. While the French occupied themselves with exploration mainly within tropical and temperate waters, Britishinterests lay in the Arctic regions, where a possible route through to the Pacific might be found, and as the location for whaling and sealing operations. It was to the advantage of these industries to discover how deep the polar seas were, to determine the water temperature and quality, and to understand the tides and currents flowing round their shores. But for a long time scientists failed to grasp that the key to water quality and movement lay in elucidating thetemperature profile from surface to sea bed. The instruments available before 1874 were not capable of resolving this profile and it was not until the end of the 19th century that measurements were made of sufficient accuracy to enable the various water masses and their consequent movements to be calculated theoretically from intensive temperature studies. By this time initiative for such work had passed into the hands of Norwegian scientists and Britain was represented only as a member of the International Commission for Exploration of the Sea (ICES), established in 1902.