Three manganese nodules from the Pacific Ocean have been analysed for 35 elements by using ma.inly spectrophotometric a.nd spectrogra.phic methods. Cu, Co, Ni, Zn, and Pb were found in amounts approaching 1 %, which far exceeds their average concentrations in igneous rocks. On the other hand, elements having readily hydrolysable ions, such as Ga, Sc, Zr, Y, La and Ti, are present only in amounts comparable with their concentrations in igneous rocks....