The origin of metalliferous deposits has long been a subject of discussion. Professor Joseph Le Conte, however, seems to have arrived at a very decided opinion on this question, for in a contribution to the “American Journal of Science” (3rd series, xxvi. p. 1—19, July, 1883), after referring to Sulphur Banks and Steamboat Springs in California, he says: “Thus then subterranean waters of any kind, but especially alkaline, at any temperature, but mostly hot, circulating in any direction, but mainly upcoming, and in any kind of waterway, but mainly in open fissures, by deposit, form metalliferous veins.”