But if this lava flow took place in a pre-existing valley, we ought to find under the rocky covering beds of gravel, rolled stones, and other _débris_ peculiar to a river bed. Such, in fact, we do find extended along directly underneath the lava, about fifteen hundred feet above the general level of the country. These old river gravels are found to be very rich in gold, and miners have tunneled into them in numerous places in search of the valuable metal. In order to determine the geological age of these gravels, and subsequent lava flow, a careful examination of portions of plants and bones of animals found therein has been made. The plants are pronounced by competent authority6 to be Pliocene, totally distinct from any specimens now growing in California. The animal remains are rhinoceroses, camels, and an extinct species of horse. The age of these gravels is, therefore, pronounced to be Pliocene. We would say in this connection that the auriferous gravels of California have been the object of a very careful research by Prof. Whitney. He adds to his conclusions that of another of the State geologists. We need not give in detail his arguments, but he reaches the conclusion that the auriferous gravels of the Pacific slope represent the whole of the Tertiary Age.7 We have seen that in the ancient gravels of European rivers archæologists have found the materials wherewith to build a fascinating story of man’s appearance in Quaternary times. We have underneath the lava flow of California the gravel beds of rivers far antedating the gravels of the Somme. It is therefore not a little interesting to learn from Prof. Whitney that he finds many proofs of the existence of man in the gravels of the Pliocene Age in California. Under the solid basalt of Table Mountain have been found many works of men’s hands, as well as the celebrated “Calaveras Skull.” Calaveras Skull. This skull was taken from a mining shaft at Altaville, at a depth of one hundred and thirty feet from the surface, beneath seven different strata of lava and gravel. Prof. Whitney was not present when it was found. He, however, made it his business to examine into the facts of the case, and he thus speaks of it: “That the skull was found in these old, intact, cemented gravels has been abundantly proved by evidence that can not be gainsaid.” And again: “So far as human and geological testimony can at present be relied on, there is no question but that the skull was found under Table Mountain, and is of the Pliocene Age.”8