58 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
At present it will be desirable to give a brief explanation of the methods 
by which the detrital deposits are worked for the gold they contain, as pre- 
liminary to a general account of their mode of occurrence. The terms which 
are made use of by the miners in describing their operations are so inti- 
mately connected with and dependent on the character of the deposits they 
are working, that it would be impossible to give a clear idea of the phe- 
nomena, without a knowledge of the different methods of getting at and 
making available the variously situated aggregations of auriferous detrital 
material in which the gold is found. It is not, however, the object of the 
writer to furnish a practical guide to the mechanical operations of gold wash- 
ing, in any of its departments; but only to convey a sufficiently clear idea 
of the methods employed in this kind of work to make the subsequent 
description of the geological conditions intelligible. 
All the methods of separating metalliferous particles from the sands or 
gravels through which they are disseminated depend, of course, on the 
simple principle of giving gravitation a chance to act on the heavier material; 
and this is done, almost exclusively, with the assistance of water. In the 
case of ordinary ores of the metals occurring mixed with the gangue, or of 
particles of gold in the solid quartz, the material must first be crushed or 
stamped to a fine powder, and then, the pulverized material, or “ slimes,” 
being agitated or in some way allowed to move in the presence of water the 
heavier particles have an opportunity to sink to the bottom. But the variety 
and the complexity of the machinery which has been contrived to do this 
simple work, especially in those cases where the ore is not much heavier than 
the rock with which it is associated, and to do it with the greatest amount 
of efficiency, rapidity, and economy of labor, is very great. In the case of 
gold, however, such complication is unnecessary; and, besides, in working” 
on any considerable scale the chemical affinity of quicksilver for gold is 
taken advantage of, as a most important assistance in helping to detain the 
precious metal. In the case of ordinary gold washing, the material operated 
on — sands and gravels — has already been pulverized by natural processes, 
and the miner has only to separate the valuable metal from the worthless 
portion. The simplest implement for effecting this is the pan, a sheet-iron 
or tin vessel with a flat bottom, a foot or more in diameter, which is partly 
filled with the material to be operated on, and then, with the repeated addi- 
tion of water, shaken with a peculiar motion not easily described, the earthy 
particles being allowed to pass over the edge of the utensil, until finally only 
