Manganese nodules were first discovered on the ocean floor 160 miles south-west of the Canary Islands on February 18, 1803, during the first complex oceano logical cruise of the Challenger. They surprised researchers by their unusual shape and also by their unusual chemical composition; nevertheless for many years after wards, they were considered merely as one of Nature's exotic marine tricks. After the Secpnd World War, a comprehensive investigation of the World Ocean started, and new data were obtained on a wide distribution of manganese nodules and their polymetallic composition, that...