45o 
“Hydraulic Mining” in California. [July, 
at intervals of twenty to forty days, and consists in removing 
the pavement and blocks from the bed of the sluice a 
then gathering all the amalgam of gold and rich dirt co 
ledted, and replacing the blocks in the same way as at hist. 
Advantage is taken on this occasion to reverse the positio 
of the blocks and stones when they are worn irregularly, 01 
substitute new ones for those which are worn though, lhe 
mechanical aftion of the washing process on the blocks is 
of course very rapid and severe, requiring complete renewal 
of them once in eight to ten weeks. Some miners piefer a 
pavement of egg-shaped stones set like a c . 0 ^ le - s ^ one 
flooring, the gold being deposited in the interstices. Most 
of the sluiceways are, however, paved with rectangular 
wooden blocks, with or without stones as described 
Standing at the mouth of one of the long tunnels in full 
action, any person unaccustomed to the process is stiuck 
with astonishment, amounting almost to terror, as the 
muddy mass sweeps onward, bearing in its course the great 
rolling boulders, which add their din to the loai of the 
water, the whole being precipitated down a series of falls, 
at each of which it is caught up again by new sluices of 
timber, lined like the first, and so onwards and downwards 
many hundreds of feet until the level of the river is reached, 
at a distance of about a half mile or more fiom the mouth 
of the first tunnel. , ,, . 
At each of these new falls of 25 to 50 feet the piocess of 
comminution begun in the first shaft is carried on and a 
fresh portion of gold obtained. Rude as this plan of saving 
gold appears to be, more gold is procured by it than by any 
other method of washing yet devised for this piocess of 
work, and the economical advantages obtained by it cannot 
be surpassed, as it would be impossible to handle such vast 
quantities of material in any other way, and we can compare 
the cost of washing and handling a cubic yard of aunfeious 
gravel by it as follows : 
By manual labour with the pan ... 
,, with rocker 
„ with the long tom 
By the hydraulic process 
Dollars. 
IS'OO 
375 
075 
0*15 
But this process, even if effective or profitable as a mining 
operation, may be prejudicial to the interests of the general 
public, if conducted on a large scale, as the vast quantity of 
material which it so suddenly removes is merely shifted into 
the shallows beneath, to be re-distributed by every freshet to 
