The Bavarian geologist Gümbel (Figure 1) was the first German scientist to study manganese nodules in some detail (1878). Gümbel studied nodules from expeditions of both the Gazelle and the Challenger, which operated in the North Pacific at the same time (1875), and he gave detailed descriptions. He generated a remarkable range of ideas to explain the origin of the nodules and concluded that most or all of the iron and manganese in deep ocean ferromanganese concretions have their source in submarine vents that emit gas and hot water. It seems that his choice between different hypotheses was strongly influenced by his experience with metal-bearing hot springs on land and his convictions regarding mechanisms of ore formation in general. In any case, contemporary experts did not find his reasoning compelling. Gümbel's hypothesis was essentially forgotten until it was recreated in the middle of this century.