ve a large sluice than a little one, if the water and dirt can be
obtained in abundance.

Usually, in a hydraulic claim, the dirt is washed down to the bed-rock;
but in some places the washing stops far above the bed-rock, because
there is no outlet for the water.

_Blasting._--In some hydraulic claims, the dirt, in dry seasons, is
blasted, so as to loosen it. A drift or hole is cut into the bottom of
a hill, one or two hundred feet high, and a number of kegs of powder
(from twenty to two hundred) are introduced, and they are fired with a
slow match. The explosion makes an earthquake in the vicinity; and the
ground is loosened to such an extent that there is a great saving of
labor. The breaking up of the dirt and the exposure to the air are
supposed to facilitate the washing greatly.

More water is required for piping down banks than for washing the dirt;
and often the sluice is almost idle for want of dirt, while the water,
after being thrown against the hillside, runs away without doing any
service at washing. Blasting, therefore, by loosening the earth,
enables the hydraulic miner to have an abundant and regular supply of
dirt in his sluice, at an expense much less than the cost of manual
labor to dig the bank down with pick and shovel.

_Tail-Sluice._--The tail-sluice is a large sluice made for rewashing
the tailings or dirt which has previously passed through other sluices.
It is placed ordinarily in the bed of a ravine or creek through which
tailings run, and it receives no attention for weeks or months at a
time, save to keep it from choking. The sluices emptying into it
furnish both dirt and water, and in the dirt there is always a large
amount of fine gold, as is plainly proved by the fact that some of the
tail-sluices have paid large profits to their owners. Tail-sluices are
always large, long and paved with stones; and sometimes they are
double, so that one side may be cleaned up while the other continues
washing. In a branch of the Yuba there is, or was not long since, a
tail-sluice twenty feet wide.

_Tunnel-Sluice._--A tunnel-sluice is a sluice in a tunnel. It sometimes
happens that a considerable body of water runs out through a tunnel;
and in such case, a sluice at the bottom of the tunnel offers the
easiest method of getting out and washing the dirt. The tunnels are
never cut level, but with a slightly ascending grade, so that the water
will always run out. The grade is so low, that transverse rif