MINING. 311 



some claims, the pipe will tear down more dirt than the sluice 

 can wash ; in other claims, the sluice always demands more 

 dirt than the pipe can bring down. In the latter case, blast- 

 ing may be used to loosen the dirt, or the miners may under- 

 mine the bank, leaving a few columns of dirt for support ; 

 and then these being washed away by the pipe, the whole 

 bank comes tumbling down. 



In hydraulic claims all the dirt is washed; in all other 

 kinds of claims, such dirt as contains no gold is thrown to one 

 side, or " stripped off." " Hydraulic mining " is the highest 

 branch of placer mining ; it washes more dirt and requires 

 more water, and a larger sluice, than any other kind of min- 

 ing. The number of men employed in a hydraulic claim, 

 however, is usually small from three to six the water doing 

 nearly all the work. In some claims a man is constantly em- 

 ployed with a heavy sledge-hammer in breaking up large 

 stones, so that the pieces may be sent down the sluice. One 

 man attends to the sluice, and sees that the dirt does not 

 choke up in the sluice, or in the claim above it. 



The quantity of dirt that can be washed with a hydraulic 

 pipe depends upon various circumstances such as the supply 

 of water, the height of its fall, the toughness of the dirt, and 

 the amount of moisture in it. More can be washed in winter 

 than in summer, because the dirt is then moister, and requires 

 less water to loosen and dissolve it. The quantity of water 

 used in a hydraulic claim is from forty inches to three thous- 

 and. With one hundred inches, at least thirty cubic yards 

 can be washed in ten hours, on an average ; and three men 

 can do all the work. If there were a cent's worth of gold in 

 each cubic foot, the thirty cubic yards would yield eight 

 dollars and ten cents per day, or two dollars and seventy 

 cents to the man, exclusive of the cost of water. The water 

 usually costs ten cents an inch per day, so that one hund- 

 red inches would cost ten dollars. Allowing for the water 

 at that rate, a claim in which thirty cubic yards could be 



