668 GEOLOGY AND MINING INDUSTEY OF LEADVILLE. 



the tymp stone removed, and the lieartL cleared from accretious by means of bars and 

 sledges; a little fuel is then thrown iu the hearth, the tymp-stone replaced, the blast 

 turned on, and smelting resumed. 



Blowing out of the furnace — When a furnace needs repairing or when an accident 

 interfering with a regular working of the furnace has occurred, the feeding is entirely 

 suspended, but the blast is kept on until the contents of the furnace are entirely molten. 

 The charge soon burns with a bright top and the furnace emits torrents of heavy white 

 fumes. When the whole charge lias reached the level of the tuyeres the furnace is 

 emptied of its fluid contents, first at the tap-hole, then the breast is removed and the 

 bullion taken out of the crucible. 



Length of runs — The lengtii of ruus or smelting campaigns is seldom less than 

 three months, but often reaches six, eight, and even twelve and thirteen months. The 

 lack of oi-e is one of the principal causes that shorten the smelting campaigns. 



COST AND PROFITS OF SMELTING. 



The discussion of profit and loss in smelting will be made for a smelter which 

 stands in intermediate conditions between the smelters which produce most and those 

 which produce least. This smelter works with two furnaces of a capacity of 35 to 40 

 tons each of ore per twenty-four hours. The discussion is based on data obtained at this 

 smelter for the month of July, ISSO, and which are to be found with the composition of 

 smelting charges, the other data being all derived from Table IV. The cost of smelting 

 per ton of ore. as estimated at each smelter, has been given also in the same table. 

 The calculations are made on cost and profit per twenty-four hours and per ton of ore. 



EXPENSES PER TWEXTY-FOUR HOURS. 



Potter. 



Cost of mechanical power per 24 hours, represented by 3J cords of pine wood burned under 



the boilers and driving engines, blowers, pumps, &c., at |4.75 per cord §15 44 



Lahoi: 

 Cost of manual labor per 24 hours : 



2 foremen, at .$4 and S6 §10 00 



8 head smelters, at §4 33 00 



26 helpers, at S3 78 00 



05 laborers, at |2.50 162 r>0 



282 50 



Aggregate salary of staff per 24 hours 46 50 



Ore. 



Forty-eight tons ore smelted in 24 hours, contents 34 per cent, of lead, 41.5 ounces 

 of silver to the ton, equivalent to 1,992 ounces, at .$1.15 per ounce (New York 

 quotations June 21, 1880) 2,290 80 



32,640 pounds of lead, equal to 1,632 units, at 15 cents per unit of 20 pounds 244 80 



2,585 60 



Deducting 5 percent, off price of silver $114 54 



Deducting cost of treatment at $20 per ton 960 00 



1,074 54 



1,461 06 



