A mine is defined and generally understood to mean "a subterraneous work or excavation for obtaining metals, metallic ores or mineral substances;" but this definition does not apply to our placer mines, which are places where gold is taken from diluvial or alluvial deposits. Most of the work is not subterraneous; it is done in the full light of day. In some of the claims the pay-dirt lies within two feet of the surface; in others it lies much deeper, but all the superincumbent matter is swept away. Water is the great agent of the placer miner; it is the element of his power; its amount is the measure of his work, and its cost is the measure of his profit. With an abundance of water he can wash every thing; without water he can do little or nothing. Placer mining is almost entirely mechanical, and of such a kind that no accuracy of workmanship or scientific or literary education is necessary to mastery in it. Amalgamation is a chemical process it is true, but it is so simple that after a few days' experience, the rudest laborer will manage it as well as the most thorough chemist. It is impossible to ascertain the amount of gold which has been taken from the mines of California. Records have been kept of the sums manifested at the San Francisco Custom House, for exportation, and deposited for coinage in the mints of the United States; and there is also some knowledge of the amounts sent in bars and dust to England; but we have no account of the sums carried by passengers to foreign countries and coined elsewhere than at London, or used as jewelry, or of the amount now in circulation in this state. According to the books of the Custom House of San Francisco, the sums manifested for export were as follows: In 1849, $4,921,250; in 1850, $27,676,346; in 1851, $42,582,695; in 1852, $46,586,134; in 1853, $57,331,034; in 1854, $51,328,653; in 1855, $45,182,631; in 1856, $48,887,543; in 1857, $48,976,697; in 1858, $47,548,025; in 1859, $47,640,462; in 1860, $42,303,345; in 1861, $40,639,089; a total of $551,603,904 in twelve years.