One
of the most noted drift-mines in the State is the Bald Mountain, Sierra
County, where there is every facility for economical working. There
steam locomotives are used for transporting men and material through
the tunnel, which is over one and one-fourth miles long.
The
following sketches of the workings of the Sunny South .Mine, in Placer
County, will give a general idea of the method ot drift-mining. At this
place the main tunnel is below the channel, allowing the mine to be
opened and worked in a very convenient manner.
Drifting
was at one time the most extensively used method of deep mining, and
through it a very large amount of information has been obtained as to
the nature of the ancient river channels.
Hydraulic Milling.---Hydraulic
mining is that method of gold-mining in which the ground is excavated
by means of water discharged against it under pressure (hy-draulicked).
The
term in its limited sense, as generally applied, presupposes the
existence of, 1st, water, in sufficient quantity, which can be used
under pressure for mining ; 2d, gravel deposits containing gold which
can be worked profitably by the application of water in the manner
above mentioned.
Origin in California. —
The application of (he science of hydraulics to the mining of
auriferous gravels originated in California. The pressing necessity of
a more economical process of gold-washing became evident as the rich
surface deposits were exhausted, and led to the adoption of this
method, which was favored by the topography of the country.
Hydraulic vs. Drift Mining.—Deep
placers, if sufficiently rich, can be, and for various reasons
generally are, worked by drifting. But the results of actual practice
in Nevada County and elsewhere demonstrate that hydraulic mining,
compared with drifting, employs twice
