16 charts illustrating ocean temperatures at different depths, taken from Reports of the Challenger cruise, 1872-76

The Challenger Expedition, organised by the Royal Society and UK Hydrographic Office, circumnavigated the globe in order to study the physical, chemical and biological characteristics of the deep sea. Culminating in a series of detailed scientific reports, the expedition has sometimes been claimed to be the origin of modern oceanography. HMS Challenger, after which the expedition was named, was captained by Captain George Strong Nares; Scottish naturalist Charles Wyville Thomson led the six-man scientific team.