TAILINGS AND DUMP. 24I
alluvions
are being washed daily from their position, places must be provided at
lower elevations where the gravel can be deposited. A much larger
superficial area is usually required for this than was primarily
occupied by the material removed, as the dumps seldom have the depths
of the original deposits.
Working on different Bed-rock Levels with same Dump.—It
sometimes happens in adjacent claims with small dump-room that the
bed-rock of one is lower than the other. Where this occurs the claim
with the highest bed-rock should be the last run off.
An
illustration of this was afforded at Patricksville, in Stanislaus
County, where three claims were worked, one tailing over the other.
During the years 1876 and 1877 the lowest claim, called the "Chesnau,"
was closed each fall, the dump giving out, while the upper ones
continued work. With the return of spring freshets the canon was
cleared of the debris, and washing was regularly resumed in the
Chesnau, continuing as long as the dump lasted. The highest claim was
closed while the Chesnau was working, to avoid the too rapid filling-up
of the creek. If both upper claims had been worked at the same time the
Chesnau would soon have been closed.
Tailing into Streams.—The
want of dump is remedied only in exceptional cases by discharging into
a current or mountain torrent. This occurs where the gold placers are
on the borders of large, rapid, and well confined streams ; but in the
mountains, where the gold-bearing deposits are found, the rivers are
narrow and shallow, only running water in quantity during the winter
and early spring.
Experience at La Grange, on the Tuolumne.—
Some of the annoyances and difficulties arising from tailing into a
stream can be seen on the Tuolumne River below La Grange. The river, a
large mountain stream which runs over a hard slate bottom, has for 17
miles above the town a fall approximating 18 feet to the mile,
