The Challenger Expedition of 1872-6 was conceived to examine the deep sea floor worldwide and disprove the theory of a 'dead zone' in the oceans below a certain depth. Using a modified Royal Navy ship, the expedition sailed nearly 70,000 nautical miles across the globe, collecting oceanographic data and marine specimens, and laying the foundations for the science of oceanography by later publishing fifty volumes of reports. The naturalist Henry Moseley (1844-91) recounts the voyage in this 1879 work, covering visits to many remote islands and the taking of samples at hundreds of locations. The voyage's achievements included the collection of over 4,000 new marine species and the discovery of the world's deepest ocean trench (Challenger Deep). Moseley's observations on native peoples also proved important as traditional cultures were changing rapidly at the time. Illustrated with numerous woodcuts, this narrative illuminates an adventure of great scientific significance.