378 MINING ESTDUSTRY. 



desired, and the roasted charge raked through it, faUing into a vaulted space or 

 chamber below the hearth, and thence removed to the cooling floor. The newer 

 furnaces are discharged through a door in the side, opposite to the stirring door, 

 and falling directly upon the cooling floor. The furnaces are built of common 

 brick. The hearth is 9 feet wide and 11 feet long, composed of hard bricks 

 laid on their edges and closely together. The furnaces are built in sets of two 

 each, having their fireplaces at opposite ends and a common flue between them, 

 which in the newer lot leads down under the floor and thus to the stack. The 

 charge of one of these furnaces is about 1,000 pounds, which, if consisting of 

 ores of most common occurrence in the district, requires about six hours' roast- 

 ing. Twelve per cent, of salt is generally added to the charge, and usually 

 nothing else. In most cases the salt is mixed with the ore in the hopper, and 

 so enters the furnace with it; but if the ore contains a large amount of sulphur 

 the salt is not added until the ore has been for some time subjected to the 

 roasting process, that the sulphur may first be partially oxidized and the for- 

 mation of sulphates commenced. During the roasting the charge is constantly 

 stirred, and turned repeatedly. Three men for each furnace are required for 

 this work every twenty-four hours. Two men for twenty-four hours, one each 

 shift, can attend to the discharge of the ore for the whole number of furnaces. 

 Each furnace consumes about seven-eighths of a cord of wood per day. After 

 being discharged and cooled the ore is taken to the pans for amalgamation. 

 The pans, fourteen in number, are known as the Varney Pan, but they are 

 made of wood. The flat bottom is furnished with dies of cast iron, and the 

 iron muller, which is a flat, circular disk, is caused to revolve by machinery 

 similar to that which has been described already in the chapter referring to 

 Washoe processes. 



The charge for each pan is 800 or 1,000 pounds. It is put into the pan 

 with sufficient water to bring the pulp to the desired consistency. The muller 

 is caused to revolve at the rate of 42 revolutions per minute. The muller does 

 not need shoes, as no more grinding is necessary than to break up the lumps 

 formed by caking in the furnaces ; it revolves as an agitator, or stirrer, to keep 

 the material in constant circulation, and is hardly suffered to touch the bottom. 

 The iron of the muller serves as a chemical agent in the same manner as that 

 which is put into the barrels, where these are in use, and the duration of the 



