Other changes in the earth's surface took place, and in the course of
time our streams of to-day were formed. As they cut their way through
the mountain ranges, some of them crossed the channels of old dead
rivers, and finding the gold hidden there, carried some of it along,
rolling it over and over, mixed with sand and gravel, down into the
lower lands under the bright sunlight. Here it was found by Marshall and
the gold hunters who followed him. These were the placer mines of which
we read in Chapter VII.
Gradually the best placer mines were taken up and the newcomers to the
gold fields traced the precious metal up the streams into the gravel of
the hillsides. Then was begun hydraulic mining, where water did the
work. In the canons great dams were constructed to catch the flow from
the melting snows of the mountains, and miles of flumes were built to
carry the water to the mining grounds. Immense pipes were laid and
altogether millions of dollars were invested in hydraulic mining. The
water coming down under heavy pressure from the mountain reservoirs
passed through giant hose which would carry a hundred miner's inches,
and, striking the mountain side with terrific force, washed away the
earth from the rocks.
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