a ae ee oe 
AREA OF MINING OPERATIONS IN THE SIERRA, 301 
or washing the detritus either in or closely adjacent to the beds of the pres- 
ent rivers; and second, /gh or deep gravel mining, ordinarily carried on by the 
hydraulic process; third, tunnel muning or drifting, that is, working out the 
rich portions or “leads” on the bed-rock by means of drifts, as already ex- 
plained ;* and fourth, what may be called — for want of a better name — 
surface miming, which includes those shallow workings, or ordinary placer 
mines, which are carried on in the modern and usually thin detrital covering 
of the bed-rock, not immediately in the beds of the rivers, but on the rolling 
uplands between them, and chiefly in the foot-hills of the Sierra. The class 
of “diggings” designated as surface is intermediate in character between 
the river and the hydraulic mining operations. The latter require a large 
outlay for plant, and are expected to be quite permanent in character, the 
enormous quantity of material handled more than compensating for the 
moderate yield per cubic yard. River and bar mining, so extremely produc- 
tive in the early days, are now almost entirely a thing of the past. Surface 
mining is of a transient character, the superficial deposits being too thin, 
usually, to justify heavy expenditures for bringing water from a distance, so 
that in such cases temporary reservoirs are mostly used, which are filled by 
the winter rains, the supply from which is soon exhausted, when the work is 
discontinued, to be resumed during the next season if sufficiently profitable. 
As the more superficial kinds of mining operations — river and surface — 
have long since ceased to be of any great importance in the Sierra Nevada, 
it is not easy to designate the precise area over which such washings have 
been successfully carried on. From the point where the first discovery of 
gold was made by the Americans, on the South Fork of the American River, 
the gold-seekers spread themselves with rapidity far and wide; and but very 
few years had passed before every stream between the Kern and the Klamath 
had been “ prospected.” While it is true that some gold has been washed 
from detrital material lying on the granitic bed-rock, it is safe to say that, 
almost without exception, the area covered by the slaty rocks in the Sierra 
is that over which the detrital formations have been found sufficiently rich in 
gold to be worked with profit; and where, also, veins occur in the bed-rock 
which can be successfully mined. 
Of course it is easy to see that gold may have been swept from its original 
place of occurrence in the slates downward on to rocks of a different charac- 
ter; and where the formations are much mixed together, as is the case from 
* See ante, p. 78. 
