Sample of ‘Chocolate clay’collected by HMS Challenger, 1872-1876

Sample of ‘Chocolate clay’, collected by HMS Challenger from the South Pacific Ocean, south of Tahiti, at a depth of 2385 fathoms, 1872-1876. Collection site was station 281.

The Challenger Expedition (1872-1876), 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.

Prior to the expedition, HMS Challenger was specially fitted out in order to accommodate the many thousands of specimens and samples collected en route. Geological samples collected from the sea floor, such as this one, were carefully labelled with information about the depth and location from which they had been gathered.