Challenger expedition
The ship sailed from Portsmouth on December 21, 1872 and, under the command of Captain George Nares and the scientific supervision of Thomson himself, travelled nearly 70,000 miles surveying and sampling the Atlantic and Pacific Oceans and the southern reaches of the Indian Ocean. Their scientific brief, carried out at 362 sampling stations, was to determine the ocean depth, the composition of both shallow and deep water, the speed and direction of surface currents (and, where possible, subsurface currents), as well as noting the prevailing atmospheric conditions and taking samples of local plant and animal life.
After 1281 days away, many spent in foreign ports, the ship returned to Spithead in 1876, where the samples and measurements were collated and released over the next 20 years as the 50-volume Report Of The Scientific Results of the Exploring Voyage of H.M.S. Challenger during the years 1873-76, which, among many other discoveries, catalogued 4,000 previously unknown species of animal. John Murray, who supervised the publication, described the report as "the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries".
