The great economy of this method is manifest from the fact that
many old deposits in the river-beds, the gravel of which had been already
washed by hand, have again been washed with profit by the hydraulic
method.
'In California the whole art of working the diluvial gold-deposits was
revolutionised by this new method. The auriferous earth lying on hills and
at some distance above the level of the watercourses would in the ordinary
methods be excavated by hand and brought to the water, but by the present
system the water is brought by aqueducts to the gold-deposits, and whole
square miles which were before inaccessible have yielded up their precious
metal. It sometimes happens from the irregular distribution of the gold in
the diluvium in California that the upper portions of a deposit do not
contain gold enough to be washed by the ordinary methods, and would thus
have to be removed at a considerable expense in order to reach the richer
portion below. By the hydraulic method, however, the cost of cutting away
and excavating is so trifling that there is scarcely any bank of earth
which will not pay the expense of washing down in order to reach the rich
deposits of gold beneath.
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