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 





