But while so much uncertainty attends the consideration of the extent, richness, and durability of mines situated in the gold-bearing sands and gravels, something more precise and definite can be arrived at in regard to the gold-bearing rocks. In nearly all the gold countries of past times, the chief extraction of the precious metal, as we have said, has been from the drifted sands. It is so also now in Siberia, and it was naturally expected that the same would be the case in California. And as other countries had for a time yielded largely, and then become exhausted, so it was predicted of this new region, and it was too hastily asserted that the increasing thousands of diggers who were employed upon its sands must render pre-eminently shortlived its gold-bearing capability. This opinion was based upon the two considerations—_first_, that there is no source of reproduction for these golden sands, inasmuch as it is only in very rare cases that existing rivers have brought down from native rocks the metallic particles which give their value to the sands and gravels through which they flow—and _second_, that no available quantity of gold was likely to be found in any living rocks. But in respect of the living rocks, two circumstances have been found to coexist in California, which have not been observed in any region of gold-washings hitherto explored, and which are likely to have much effect on the special question we are now considering. These two circumstances are the occurrence of numerous and, it is said, extensive deposits of the precious metals in the solid quartz veins among the spurs of the Sierra Nevada, and of apparently inexhaustible beds of the ores of quicksilver. The discovery of gold in the native rock was by no means a novelty. The ancient Egyptians possessed mines in the Sahara and other neighbouring mountains. “This soil,” says Diodorus, “is naturally black; but in the body of the earth there are many veins shining with white marble, (quartz?) and glittering with all sorts of bright metals, out of which those appointed to be overseers cause the gold to be dug by the labourers—a vast multitude of people.”[18] At Altenberg also, in Bohemia, in the middle ages, the mixed metals (gold and silver) were found in beds of gneiss;[19] and, at present, in the Ural and Altai, a small portion of the gold obtained is extracted from quartz veins, which penetrate the granite and other rocks; but these and other cases, ancient and modern, though not forgotten, were not considered of consequence enough to justify the expectation of finding gold-bearing rocks of any consequence in California. It is to another circumstance that we owe the so early discovery of such rocks in this new country, and, as in so many other instances, to a class of men ignorant of what history relates in regard to other regions.