256 RESOURCES OF CALIFORNIA. 
a total expenditure of six hundred and forty dollars: and the 
gold obtained was three thousand dollars, leaving a clear profit 
of twenty-three hundred and fifty dollars. The dirt contained 
one cent and a fifth of gold in a cubic foot. The greater the 
amount of water used, the greater the proportionate amount 
of dirt that can be washed, and the greater the proportionate 
profits. It is far more profitable to have 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. 
§ 186. 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 bottum 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 explo- 
sion 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 hill- 
side, runs away without doing any service at washing. Blast- 
ing, 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. 
$187. TZail-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- 
