TEEATMENT OF THE COMSTOCK ORES. 199 



the steam-chamber is that the exhaust-steam from the engine may be used in 

 it, while for use in the pulp it is better and customary to take steam directly 

 from the boilers, because that which conies fi-om the cylinder of the engine is 

 charged with oil and is injurious to amalgamation. The muller is gradually 

 lowered after the commencement of the grinding operation, and is allowed to 

 make about 60 or 70 revolutions per minute. In the course of an hour or 

 t\vo the sand should be reduced to a fine pulpy condition. When this has 

 been accomplished, and by some mill-men at a still earlier stage (even at the 

 beginning) of the operation, a supply of quicksilver is introduced into the pan, 

 the muller slightly raised from the bottom to avoid too great friction, which 

 would act to the disadvantage of the quicksilver, and the action continued for 

 two hours longer, during which the amalgamation is in progress. The quick- 

 silver is supplied by pressing it through canvass, so as to scatter it upon the 

 pulp in a finely divided condition. The quantity varies greatly in diiferent 

 mills, the ordinary supply being about 60 or 70 pounds to a charge of ore con- 

 sisting of 1,200 or 1,500 pounds. In some mills a quantity, varying from 75 

 to 200 or even 300 pounds, is put into a pan when starting up after a clean-up, 

 and subsequently a regular addition of 50 or 60 pounds made with each 

 charge. 



To promote amalgamation it is the general custom to add to the charge, 

 either at or soon after the beginning of the grinding, or at the time of supplying 

 the quicksilver, various materials generally described as "chemicals," and 

 usually consisting, at the present day, of sulphate of copper and salt. Since 

 the first introduction of the pan process a great variety of substances supposed 

 to effect the decomposition of the silver sulphurets and to facilitate amalgama- 

 tion have been suggested by process-vendors, and employed by men possessing 

 little or no knowledge of the science of chemistry. Even tobacco-juice, de- 

 coction of sage-bush, and various other equally absurd ingredients are said to 

 have been used by some operators and believed to be effective reagents in the 

 decomposition of the ore and amalgamation of the silver. The long list of mate- 

 rials once in use has now been reduced, excepting in few places, to sulphate of 

 copper and salt. The quantity used varies from a quarter or half a pound to three 

 or four pounds to each charge of ore; the two substances being employed in 

 very variable proportions in different mills. The action of these, however, 



