A few words as to the work laid out for the _Challenger_, and how she did it. She is a 2,000-ton corvette, of moderate steam-power, and was put into commission, with a reduced complement of officers and men, Captain (now Sir) George S. Nares, later the commander of the Arctic expedition, having complete charge and control. Her work was to include soundings, thermometric and magnetic observations, dredgings and chemical examinations of sea-water, the surveying of unsurveyed harbours and coasts, and the resurveying, where practicable, of partially surveyed coasts. The (civil) scientific corps, under the charge of Professor Wyville Thomson, comprised three naturalists, a chemist and physicist, and a photographer. The naturalists had their special rooms, the chemist his laboratory, the photographer his “dark-room,” and the surveyors their chart-room, to make room for which all the guns were removed except two. On the upper deck was another analysing-room, “devoted to mud, fish, birds, and vertebrates generally;” a donkey-engine for hauling in the sounding, dredging, and other lines, and a broad bridge amidships, from which the officer for the day gave the necessary orders for the performance of the many duties connected with their scientific labours. Thousands of fathoms of rope of all sizes, for dredging and sounding; tons of sounding-weights, from half to a whole hundredweight apiece; dozens of thermometers for deep-sea temperatures, and gallons of methylated spirits for preserving the specimens obtained, were carried on board. [Illustration: THE “ACCUMULATOR.”]