18 



GEOLOGY AXD MINING INDUSTRY OF LEADV1LLE. 



product is calculated according to the mint valuation ($1.2929 per ounce 

 of silver), which, as is well known, is in the case of silver considerably 

 higher than the fluctuating market value, and increases the value given for 

 the total product by about seven million dollars above that which would 

 be obtained by using the market value, if it were possible to obtain it in 

 each case. The price of lead is assumed at 4 cents a pound as an aver- 

 age for the whole period involved : 



Production of LeadriUe mines from Ib77 /o 18 J 4, inrlii*ire. 



In the time that has elapsed since the census year, although, owing 

 partly to decline in value of the metals and partly to a lower average tenor 

 of the ore, the total value of the annual product has decreased, the amount 

 of ore extracted from the mines of the district has very- considerably 

 increased, this having been in the census year (1879-1880) 152,241 tons, 

 and in the year 1884, according to the report of the Director of the Mint, 

 232,000 tons. 



