TEEATMENT OF THE COMSTOCK OEES. 255 



Twelve pounds of the sulphate of copper and thirty-six pounds of salt 

 are put into the pan with each charge, and the whole is worked for two hours 

 before putting in the quicksilver. Little or no grinding is required, as the 

 material is already exceedingly fine ; the muller is raised high enough above 

 the bottom to avoid unnecessary friction, but is revolved at about the same 

 speed as in working ore, the main object being to keep up a rapid and perfect 

 circulation of the pulp. After two hours the quicksilver is added, and in large 

 quantity, usually 300 pounds. The charge is then worked for four hours 

 longer, and afterward drawn off into the settler, from which the amalgam is 

 collected in the manner already described, while the residue is allowed to 

 pass through large agitators, before finding its way to the tailing stream, in 

 order to save as much as possible of the escaping amalgam and quicksilver. 



The quantity of quicksilver employed in this process is so large that the 

 loss of that metal in the operation is proportionally great, especially as it is 

 believed that the clayey condition of the slimes greatly facilitates its escape. 

 This loss is stated at about five pounds of quicksilver to the ton of slimes. 

 This item, together with the cost of the chemicals, which, by reason of their 

 liberal use, amounts to a considerable sum, makes the treatment of slimes 

 quite expensive, probably not less than $12 per ton. 



The supply of slimes is obtained by purchase from the neighboring crush- 

 ing mills, their value being previously determined by assay. This value 

 varies from $25 to $50 per ton, and the purchase price, for some time past, 

 has been from $3 to $5 or more per ton, according to their contents. It is 

 said that the method of working just described extracts upward of sixty, and 

 frequently eighty, per cent, of the assay value. 



In Mr. Parke's mill, in the same neighborhood, the method of operation 

 is very similar to that just described. He uses, however, large wooden pans 

 or tubs, having cast-iron bottoms but wooden sides. The tubs have large 

 capacity. The wooden sides of the tub, which are 3 inches thick, are fur- 

 nished on the inside with a lining, also of wood, 1 inch thick, which, when 

 worn down, may be replaced by new pieces without reconstructing the tub. 

 In addition to this inner lining it has been found advantageous to attach strips 

 of wood, 2 by 4 inches thick, to the inner circumference of the tub ; these 

 strips stand vertically, and about 2 inches apart, producing a rough or corru- 



