GEOLOGICAL SUEVEY OF THE TEREITOEIES. 215 



tion not quite as liigii as its sides, over which the water i^ours from, the 

 former into the latter division, thereby clearing itself. An elevator 

 conveys it from here to the cistern. By this arrangement the same 

 water can be used two or three times. 



One engine of thirty-five horse-power drives two six-stamp and two 

 five-stamp batteries. The stamps of the former weigh six hundred 

 pounds each, and those of the latter four hundred and fifty pounds 

 each. 



There is a separate bin opposite each battery for sorting the custom 

 ores. The four-liundred-and-fifty-pound stamps are intended to drop 

 thirty-five, and the six hundred pounders twenty-five times per minute. 



There are in this mill eight feet of coppers and four feet of blankets ; 

 but besides this the water runs over four and one-half feet of small 

 blankets to the tail-sluice. Two pumps keep the water constantly 

 supplied to the cistern. The blankets are washed, according to circum- 

 stances, every fifteen to thirty minutes. 



These tailings are brought into the Bartola pans and polished by 

 arastras, nitrate of mercury and cyanide of potassium being added in 

 small quantities to assist the process. 



From this they are brought to the dolly-tub for amalgamation. These 

 three pans save $15 of the gold, which would otherv/ise run out and be 

 thrown away, per day ; and Mr, Bradley hopes to be able, by the use of 

 three additional i)ans, which he contemplates adding, to pay the daily 

 wages of the whole mill personal. 



The two five-stamp batteries are always workecl together, but the six- 

 stamp batteries are provided with a clotch, by disconnecting which 

 fasteuiug they can be worked separately, 



Cleveland mine. — Excelsior lead. 



Trail CreeJc, afeiv miles from Idaho City. — I visited the mill belonging 

 to this company for the purpose of witnessing the trial of a^ new two- 

 staaip steam stamp, the invention of Mr. Wilson, of Philadelphia. Two 

 steam cylinders are mounted on heavy framework, the piston-rods pro- 

 longed below are shod, thus forming the two stamp-rods. The weight 

 of each stamp is 500 pounds, the impinging force of the steam 1,700 

 pounds 5 which, deducting the necessary amount for friction and other 

 losses, leaves an available blow of over 1,700 pounds. These stamps 

 can be run 170 to 212 per minute. This velocity was not attained 

 during the trial, but the working was so satisfactory as to leave the 

 impression on all who witnessed it that this kind of stamij mill, with 

 certain modifications, bids fair to supersede all others. Great attention 

 must, of course, be paid to the feeding, to avoid throwing upon the 

 table imperfectly crushed quartz, because from twice to twelve times as 

 much ore as in an ordinary mill passes in a given time under each one of 

 these stamps. 



The smelting tcorlcs of Professor Sill. — These works are favorably sit- 

 uated on Clear Creek, half a mile below the western extremitj^ of the 

 town of Black Hawk, There are two reverberatory furnaces, a set of 

 rollers for crushing, and attached to the works is an assay office for 

 valuing the ore bought. 



This ore is of all kinds and comprises the richest produced by the 

 mines. Seven tons are matted in one day, and this matt is then sent by 

 Professor Hill to Swansea and sold. The lump ore is roasted in heaps 

 six to eight weeks, to get rid of the greater part of the sulphiu' ; it is 

 then crushed in the rolling-mill and mixed with the other ores. 



The tailings, consisting mainly of pyrites, are roasted in the reverbe- 

 ratory furnaces. 



