FACTS IN AMEEICAN MINING. 83 



centage of the men employed at reduction works would be com- 

 petent to cope with the chemical complications which would be 

 likely to bar their way to success in the employment of this process. 



The yard, barrel, and pan processes for the extraction of gold 

 and silver from their ores have repeatedly been made the subject 

 of comparative experiment, and the following published result of 

 some trials, in the Ophir Mine affords valuable and interesting 

 information : — The yard process cost £6 per ton, and lost 20 per 

 cent, of the metal ; the barrel process cost £5 14s. per ton, and 

 lost 15 to 20 per cent, of the metal ; the pan process cost £3 per 

 ton, and lost 35 to 40 per cent, of the metal. But this series of 

 experiments did not reveal the whole truth ; it was found that 

 the loss by the barrel process was principally gold, and that by 

 the pan principally silver, and the bullion from the pan was found 

 to be worth just twice as much as that from the barrel process. 



The Stetefeldt Furnace. — This is the only desulphurizing 

 furnace which appears to claim notice in this paper. The one 

 used at Reno, near Virginia, for desulphurizing and chloridizing 

 the ore, consists of a shaft 20 feet high, by 3 or 4 feet square. 

 At its base there are two fire-places, in opposite sides, with short 

 flues leading into the stacks. The ore having been mixed with 3 

 to 6 per cent, of salt is crushed under stamps and passed through 

 No. 40 screens. This finely pulverized ore is fed in a continuous 

 stream by machinery from the top of the shaft. Just below the 

 top of the shaft is a flue for the escape of the gases, leading into 

 dust chambers, where any portion of the fine material carried up 

 by the draught may deposit. The main shaft at the end of the dust 

 chambers is 40 feet high. As the fine ore descends, mixed with 

 salt, against the current of hot air ascending in the shaft, it 

 becomes chloridized, giving off sulphurous and sulphuric acid ; 

 every atom of the ore being exposed to oxidizing and chloridizing 

 influences. The furnace is said to perform its work with less cost 

 for fuel, labour, and salt, than the ordinary reverberatory — one 

 furnace treating 20 tons in a day, with the labour of eight men, 

 which would require ten reverberatory furnaces and thirty-six men. 

 The fuel used is two cords of wood a day, while the ten reverbe- 

 ratories would require five times the quantity, and the saving in 

 salt is one-half. The bullion produced is larger and richer, and 

 the cost of treatment only about 26s. per ton. 



The loss on the Colorado ores has been pretty well ascertained: 

 it is about 30 per cent. Of the quantity saved, 55 per cent, is 

 obtained in the battery and appliances, and 15 per cent, by con- 

 centration and treatment of tailings. 



Statistics. 



The gold yield of California in 1853 exceeded eleven millions 

 sterling. The gross yield from quartz mines is increasing slowly. 



