290 



MmrtsTG INDUSTET. 



pan, but also from the amount of iron disseminated, in a fine condition, through 

 the ore, produced by the wear of the stamps, shoes, and dies. 



This consumption of metal from the batteries and pans varies very much 

 in the different mills, depending partly upon the details of construction and 

 grinding effects of the pans and partly upon the hardness of the castings em- 

 ployed. The following figures from two mills serve to show the quantity of 

 iron reaching the pulp from this source, per ton of ore worked. The quantity 

 of ore treated is sufficiently large to afford a very fair estimate of the metal con- 

 sumed : 



Tons of ore worked. 



Loss of iron in batteries. 

 (Pounds per ton of ore.) 



Loss of iron in pans. 

 (Pounds per ton of ore.) 



Total. 



14,000 

 12,236 



2.76 

 2.10 



9.42 

 7.14 



12.20 

 9.24 



The fine iron coming to the ore in this way is very considerable in pro- 

 portion to the other minerals present. If ten pounds per ton are added from 

 this source it is equal to one-half of one per cent. In the Kentuck ore, of 

 which an analysis has been given, there is, including the iron from the bat- 

 teries, less than two and one-half per cent, of ore-bearing minerals present. 



Mercury and iron, under the proper conditions, undoubtedly are the principal 

 agents in the extraction of the precious metals by the Washoe method. The 

 results depend, however, in a great measure, upon the mechanical treatments 

 employed to reduce the ore to an exceedingly fine state of division, and to 

 maintain, with the proper degree of consistency, a constant agitation of the en- 

 tire mass ; the essential conditions of the amalgamation being that the mer- 

 cury should be thoroughly incorporated in the pulp, and every particle of the 

 reducible minerals brought in direct contact and triturated with the metal, in 

 the manner so well accomplished by the friction and grinding action of the pan. 

 The mercury should also at all times retain a bright, clean surface, free from 

 any film of metallic salts, such as sub-chloride of mercury or sulphate of lead, 

 and any coating of oil or grease. The slightest tarnish appears to retard very 

 greatly the activity of the metal. The iron seems to act as an electro-chemi- 

 cal agent ; the immediate contact of the two metals, aided by heat and fric- 



