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very small, permitting of the treatment of about one and a half 

 tons a day. Six dry stamps, a steam arrastra, one reverberatory 

 roasting furnace, four barrels, a retort and one refining furnace, 

 together with a ten horse power engine, constitute the works. 



The second class ore, after being coarse stamped, is removed to 

 the arrastra, which is capable of grinding one ton per day to the 

 necessary fineness. The resulting slime, after drying, is pounded 

 and sifted. Five hundred pounds of the ore, after being mixed 

 with from eight to ten per cent, of salt, are subjected to the chlo- 

 ridizing roasting for about four hours. About one-half hour before 

 withdrawing the charge, two per cent, of unburnt limestone is 

 added to reduce the bichloride of copper to protochloride. In this 

 manner, six roastings are made in twenty-four hours. 



The barrels are charged with 1,000 pounds of the roasted ore ; 

 100 pounds metallic copper in metalHc balls, and 144 pounds of 

 water. After revolving two hours, to eifect the partial reduction of 

 salts injurious to the mercury, by the copper, five hundred pounds 

 of quicksilver are added. 



After revolving twenty-four hours in all, including the second 

 watering to collect the disseminated globules of quicksilver, the 

 whole is withdrawn and the amalgam separated and retorted. The 

 resulting silver is simply melted in a small reverberatory refining 

 furnace, with the addition of a little borax, and cast in bars of dif- 

 ferent sizes, having a fineness of 0.990 to 0.998. In the absence 

 of coin, these are used as a circulating medium, and find their way 

 to Sonora and, ultimately, to England. 



The defects of this process, as appHed at Arivaca, are very 

 great, and are attributable in part to the character of the ores and 

 absence of some facilities. The roasting is performed too hurriedly, 

 and the roving character of the Mexicans renders it very difficult 

 to make them good workmen at the furnace, where so delicate a 

 process, requiring long practice, is to be well executed. The per- 

 centage of sulphur in the ore subjected to this operation is so very 

 low, that the decomposition of the salt must be imperfect, causing 

 inordinate loss of this material, which is very expensive. Owing 

 to the small amount of lime added during the roasting there cannot 

 but be an unnecessarily large loss of quicksilver. The loss of silver 

 is said to be from twenty to thirty per cent., which destroys the 

 main advantage of the European barrel process over the cheaper 

 Mexican amalgamation ; but, by more carefully meeting the require- 

 ments of the method, this loss could probably be reduced to at least 

 ten per cent. These works were erected for temporary use, and 

 consequently the amount of manual labor is more than double that 

 which is necessary. 



The workmen at the furnace receive one dollar per day of twelve 



