MINING. 239 
nature of the material in which they are found. In placer 
mining, the earthy matter containing the gold, called the “ pay- 
dirt,” is washed in water, which dissolves the clay and carries 
it off in solution, and the current sweeps away the sand, gravel, 
and stones, while the gold, by reason of the higher specific 
gravity, remains in the channel or is caught with quicksilver. 
In quartz mining the auriferous rock is ground to a very fine 
powder, the gold in which is caught in quicksilver, or on the 
rough surface of a blanket, over which the fine material is 
borne by a stream of water. About two-thirds of our gold is 
obtained from the placers, and one-third from the quartz. 
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 subter- 
raneous ; 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 ele- 
ment of his power; its amount is the measure of his work, 
and its cost is the measure of his profit. With an abundance 
cf 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 scien- 
tific or literary education is necessary to mastery in it. Amal- 
gamation is a chemical process it is true, but it is so simple 
that after a few days’ experience, the rudest laborer will man- 
age 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 
