expensive
than the tunnel. After the shaft demonstrates that the dirt is rich,
and precisely the altitude at which it lies, a tunnel is cut to strike
it. The shaft may be the cheaper for prospecting, but the tunnel is
usually the cheaper if any large amount of dirt is to be taken out.

The shaft is dug by one man in the hole, and one or two are employed at
a windlass in hauling up the dirt. Mining-shafts in placer diggings are
rarely over one hundred feet deep; but one was dug in Trinity county to
the depth of six hundred feet, for the purpose of prospecting, but it
found neither pay-dirt nor the bed-rock.

_River-Mining._--River-mining is mining for gold in the beds of rivers,
below low-water mark. The only practicable method of doing this is by
damming the stream, and taking the water out of its bed, in a ditch or
flume. It has been proposed by persons who never saw the mines, to get
the gold by dredging, or with a diving-bell; but such schemes are
absurd in the eyes of miners. The rivers in which the gold is found are
mountain-torrents, in which a canoe can scarcely float in summer, much
less a dredging machine; and any large scoop working under water would
miss the crevices and corners in the rocks, where most of the gold is
found. As the water is very seldom more than a couple of feet deep, a
diving-bell would be of little service. The flume, the ditch, and the
wing-dam, are the chief tasks of the river-miner. The ditch is rarely
used, because the banks of the mining-streams are usually so steep,
high, rocky and crooked, that a flume is cheaper. The wing-dam is not
often used, because the river-beds are in most places too narrow. The
flume is almost universally employed.

The work of river-mining can be done only during the summer and fall,
while the water is low, and while the miner can have confidence that it
will not rise. It may be as low in January as in August, but the winter
is the season of rains; and when the flood comes, it sweeps dams,
flumes and every thing before it. If the dam and flume be commenced too
early in the season, they may be carried off before they are finished;
and it frequently happens that they are destroyed in the fall just when
the miners are commencing to reap the reward of their summer's labor.

River-mining has many disadvantages, as compared with other branches of
mining. The miner cannot work at it more than half the year; he cannot
prospect the dirt which is hidden under water