164 SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



machinery, which as hitherto designed is somewhat complex and subject to 

 frequent stoppages for repairs. The steam is also in part decomposed at the 

 temperature maintained, and thus accomplishes a very considerable refine- 

 ment of the lead during the process of concentration, producing an excel- 

 lent market lead from comparatively hard bullion. 



conation. — The rich lead is cupelled in furnaces of the English model 

 with bone-ash tests. The test holds from a ton upwards. It is filled with 

 lead which is brought to a cupelling heat and an air-blast is turned on. 

 This blast is preferred to steam, as the 'latter becomes moist and also in- 

 creases the loss in silver, although the loss in any case is slight. The test 

 is kept full of lead by adding bars one by one at the back of the furnace 

 and allowing them to gradually melt down. It is tapped every twenty- 

 four hours, when from six to eight bars containing two-thirds silver are ob- 

 tained. Sixty such bars, on a second cupellation, give in about sixteen 

 hours 16,000 ounces of dore* silver, .965 fine in silver and .030 fine in gold. 

 A test lasts about ten days. In refining, concentrating, and cupelling 

 mountain mahogany wood is used. It is a very superior fuel, and costs 

 from $10 to $12 per cord. 



The poor litharge, containing about an ounce to the ton, is reduced to 

 market lead in reverberatory furnaces, with refuse charcoal from the bins. 

 The rich litharge, containing as high as 75 ounces, is resmelted with a fur- 

 nace charge, as there is almost always a dearth of lead in the ores. 



Advantages and disadvantages of refining. — It is a question whether Eureka is an 

 advantageous locality for refining bullion, fuel being high and labor $4 per 

 day. Refining on the spot obviates the necessity of paying interest upon 

 the money required to freight the unparted lead to a refinery in San Fran- 

 cisco or the East, and the market is frequently so overstocked with lead 

 that it is better to wait for a rise before shipping. On the other hand, high 

 charges are incurred in expressing the dord silver, which would be avoided 

 if the bullion were transported by freight as it comes from the furnaces. 



