6 GEOLOGY OF THE COMSTOCK LODE. 



D. Hague's admirable memoii-, "The Comstock Mines,'" and has undergone 

 no essential modification since the date of that work. The consumption of 

 timber in the mines up to the close of 1880 is estimated at 450,000,000 

 board feet. 



The only fuel used on the Comstock is wood, derived from the same 

 sources as the timber. The larger part reaches the town by rail, but a con- 

 siderable quantity is floated down the Carson River to convenient points, 

 and hauled to Gold Hill in wagons. The consumption of fuel at the mines 

 in hoisting and pumping is increasing rapidly, for the quantity of water is 

 greater year by year, as well as the distance through which it must be 

 forced. During the census year, ending May 3 1 , 1880, about 1 10,000 cords 

 were burned; and from 1860 to 1880 the consumption cannot have been 

 less than about 900,000 cords. The mills have burned about as much. 



Milling. — In the eai-ly days of mining on the Comstock considerable quan- 

 tities of very rich and complex ores occurred, and these were treated by roast- 

 ing and barrel-amalgamation. Later the ores became more facile, and the 

 system of pan-amalgamation was developed and applied with success. For 

 many years it has been found practicable to beneficiate all the ores met 

 with by this process, with the aid of "bluestone" (cuprous sulphate) and 

 salt. The success of the process is unquestionabl}' due in a large measure 

 to the chemical activity of the iron. Formerly the mills guaranteed a return 

 of 65 per cent, of the assay value of the ores, but of late years 72 per cent, 

 is guaranteed, and above 80 per cent, is often returned. The slimes and 

 tailings belong to the mills, which work them up for their own account or 

 sell them from time to time to other mills having especial facilities for their 

 treatment Tailings not caught by the mills and deposited at considerable 

 distances in the streams have also been treated with success in a small way. 

 On the whole, however, it is improbable that more than 75 per cent, of the 

 bullion contained in the ore has been recovered from it, and it is therefore 

 fair to estimate that the ore received has contained at least four hundred 

 million dollars, of which about three-quarters has reached the market. 



Relative quantities of gold and silver produced. The qUeStiOU of thc prOpOrtioU of 



gold to silver in the Comstock bullion is one of considerable importance in 



' iEsploration of the Fortieth Parallel, Vol. III. 



