California mines and minerals . ded and water-worn. Thereis also intermixed with it a small percentage of magnetic iron ore,in the shape of black sand. Fossils, both animal and vegetable, and,at some points in great quantity, occur in the middle and upper strataof gravel. These organic remains consist of the bones and teethof various animals, the trunks and branches of trees partially orwholly silicified, lignites and carbonized wood, in all of which latterthe vegetable structure is clearly apparent. Cords of petrified woodhave, in some places, been uncovered; also, Indian mortars and simi-lar
California mines and minerals . ded and water-worn. Thereis also intermixed with it a small percentage of magnetic iron ore,in the shape of black sand. Fossils, both animal and vegetable, and,at some points in great quantity, occur in the middle and upper strataof gravel. These organic remains consist of the bones and teethof various animals, the trunks and branches of trees partially orwholly silicified, lignites and carbonized wood, in all of which latterthe vegetable structure is clearly apparent. Cords of petrified woodhave, in some places, been uncovered; also, Indian mortars and simi-lar rude implements, proving the existence of man prior to the fillingin of these pliocene rivers. The Deep Gravels.—It is unnecessary at this place to enterinto a discussion of the origin of these deep gravels, but it may besaid that the blue lead theory, like the glacial and marine theoriesbefore it, has now been generally discarded by the investigators of theauriferous gravels, and there has been generally accepted the fluvi-. OiKN Cut, showing Early Workings uk thk Mklunk^ .Mi.\e, CalaverasCounty, from which $3,000,000 was taken. 22 CALIFORNIA MINES AND MINERALS atile theory in its essence, ascribing the origin of the gravel accu-mulations to the depositions of ancient rivers with courses similar tothe present rivers. The character of the deposits shows that therehas been an intermittent action. The torrential period and thequiescent period are both shown in alternating heavy and lightmaterial of the channels. But while there is this unanimity of opinionas to the origin of the gravel accumulations, there still exists a differ-ence of opinion regarding the geological age of the deposits. Sometimes the contents of these old river channels and hydraulicbanks are composed of gravel from bottom to top; oftener, however,they consist of layers of gravel, sand, volcanic ash or clay, and lava,occurring usually from the bottom up, in the order here we find this materia
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