1884. I “ Hydraulic Mining ” in California. 445 
traced the gold up the ravines to their sources in the lofty 
mounds and deposits, or hills of cemented conglomerate, 
near Eureka, in Nevada county, and by constructing canals 
from a higher level began the new system of “ hydraulic 
mining ” and washing, and gradually extended their opera- 
tions over the area of the metallic zone mentioned, of 
40 miles long by 20 wdde, using the Yuba River below Tim- 
buCtoo to receive and discharge the tailings, or refuse from 
their operations. The result in gold was considerable, but 
the system is from its violent nature difficult to control, by 
presuming to handle and remove such huge depositions in 
order to collect the richest material. The idea was bold, 
being an anticipation of Nature’s operations ; but the equi- 
table disposal of the “ tailings ” in a cultivated country is 
impossible, as the silt runs down the rivers, creating banks 
and bars in their channels, obstructing navigation and agri- 
cultural arrangements. 
General Description of Hydraulic Mining. 
The first work to be accomplished, after calculating that 
the amount or value of the material to be operated upon is 
sufficient to guarantee the cost of the undertaking in gene- 
ral, is the construction of a canal or canals, to convey the 
requisite volume of water from the fountain-head, and of 
sufficient elevation to command the ground to be worked 
upon, having also in view the levels of the necessary tunnels 
and shafts as outlets for the discharge of the gravel through 
them, these being engineering operations requiring much 
skill and labour to avoid useless after cost. 
AqueduCts of considerable elevation have to be constructed 
across deep valleys, and the speculation is at all times 
problematical, as the ground cannot be properly tested until 
the water arrives upon it, and disputes may arise between 
the shareholders of the canal and the mining company, 
ending frequently in the one devouring the other, unless the 
two interests be quickly amalgamated. 
The starting-point should be the lowest level, or “ Bed 
rock,” on the white cement in the ancient channel, which is 
probably the original silt collected in it, and is harder than 
the conglomerate above it, which is more easily removed. 
The courses of these beds can be easily traced by land- 
marks and indulations, and occasional exposures of the bed 
rock at low levels ; also trial shafts are sunk in various 
places in search of it, to a depth of .100 feet, passing through 
blue gravel. The grades of these beds are not steep, being 
