TREATMENT OP THE OOMSTOCK ORES. 2B5 



in Eastern Nevada, the heat from the roasting furnaces, on its way to the 

 stack, passes through the flues, saving a special firing. In the present in- 

 stance there are three kihis, able to dry about twenty-five tons per day, 

 consuming in all about a half cord of wood in twenty-four hours, and requiring 

 one man's attention to keep up fires and rake over the ore. 



Ceushing. — For crushing the rock, after drying, there are twenty stamps, 

 arranged in batteries of four, weighing about 600 pounds each, dropping 8 or 

 9 inches about 65 times per minute. The foundations and battery-frame are 

 not essentially different from those in wet-crushing batteries. The mortars 

 differ from the high ones used for wet-crushing, consisting of a bed-piece with 

 sides and ends that are only high enough to provide the means of bolting the 

 iron casting to the wood-work of the battery-frame, attaching the screen- 

 frames, &c. 



The dies are flat, circular pieces of cast iron, that fit into recesses in the 

 bottom of the mortar. Each die has two lugs or projections on its periphery, 

 which, being dropped into a groove in the bottom of the mortar, may then be 

 revolved 90 degrees, under a flange or lip with which the recess is cast. 

 Molten lead is then poured in to hold the dies firmly. When it is desired to 

 remove them, quicksilver is poured into the battery, dissolving the lead and 

 loosening the dies. By retorting the quicksilver, both metals are recovered. 



The discharge is at both sides and ends. Screens of brass wire-cloth 

 are used, having 40 meshes to the lineal inch, or 1,600 holes to the square 

 inch. The stamps crush from a half ton to one ton per head per day of 

 twenty-four hours. The batteries are inclosed by housings or closely fitted 

 boxes, which serve as receivers for the crushed material. The casings are 

 provided with doors, by means of which the workmen can enter and remove 

 the crushed ore by shovelling it into barrows. 



Roasting. — The fine ore is then roasted with salt in reverberatory 

 furnaces. These are built of common red brick. Figs. 1 and 2, on Plate 

 XXIV, show the method of their construction.^ Fig. 1 is a horizontal section 

 through the line, A B, on Fig. 2. In the drawings, H is the hearth ; D, the 



1 Erom drawings furnislied by Mr. J. B. Hiskey. 

 34 



