res through
which the stream was passing.

[Illustration: FIG. 100.--HYDRAULIC MINING ON THE KLAMATH RIVER,
CALIFORNIA]

As the rocks upon the surface decay and the crumbling material is
carried away by running water, the gold, being very heavy, washes
down the hillsides and is at last gathered in the gulches. This
fact explains why we find gold both in veins and in the gravel of
the streams. Getting gold from the veins is called quartz-mining.
Washing it from the gravel is called placer-mining; and if the
gravel is deep and a powerful stream of water is required, the work
is called hydraulic mining.

[Illustration: FIG. 101.--MAY ROCK, A VEIN OF QUARTZ ON THE MOTHER
LODE]

Everyone has heard of the Mother Lode of California. Every miner
wishes that his mine were upon this famous lode, which is made
up of a large number of quartz veins extending along the western
slope of the Sierra Nevada mountains, and is marked by hundreds
of important mines. A line of towns marks the course of the Mother
Lode for over a hundred miles. They are almost entirely supported
by the gold which the lode supplies.

The gold first discovered in California was placer gold. After
the miners had worked over the stream gravels and had secured all
that they could in that way, they began to search for the home of
the gold. It could not always have been in the creek beds, and
the miners were correct in thinking that it must have been washed
from some other place. Gold was so frequently found in pieces of
loose or float quartz that this fact finally turned their attention
to the quartz veins which were numerous upon the mountain slopes.
Then came the discovery of the series of great quartz veins now
known as the Mother Lode.

[Illustration: FIG. 102.--AN ARASTRA]

When the miners first found the quartz flecked with gold, they
used the simplest means for separating the two substances. If the
quartz was very rich in gold, it was pounded and ground fine in
a hand mortar. Then the lighter quartz was washed away and the
gold left.

The miners also made use of the Mexican arastra. This is a very
crude apparatus, and is employed even now by miners who cannot
afford to procure a stamp-mill. To build an arastra, a circular
depression ten or twelve feet wide and a foot or more deep is made
in the ground. This depression is lined with stone, which forms
a hard bottom or floor. Four bars extend outward from an upright
post placed in the middle of t