THE COMSTOCK MINES. 159 



fully examined, and the total amount of their expenses divided by the num- 

 ber of tons of ore produced, the result will rarely fall below and generally 

 exceed the figures just given. 



Yield of Ores. — In connection with this subject the following tabular 

 statement is herewith presented, showing the number of tons of ore pro- 

 duced annually by several of the principal mines during four or five years 

 past, and the average yield per ton of their product. By comjjaring the fig- 

 ures of this table with those just given, the relation of cost of production to 

 the yield of ore may be easily seen. 



Concerning this table, it may be observed that the figures showing the 

 product include the whole quantity of ore raised from any given mine during 

 either of the years for which it is stated ; while the figures showing the yield 

 per ton apply simply to the quantity of ore reduced, during the given year, 

 by the company or mine in question. It is only in rare instances that the 

 number of tons reduced, or treated for the extraction of their precious metals, 

 is exactly the same as that produced from the mine, and, in some cases, the 

 difference is large. Thus, in the figures referring to the Savage and to the 

 Chollar-Potosi, during the last two years, there are, in the aggregate, many 

 thousand tons included in the stated product, to which the figures showing 

 the yield per ton do not apply, because the product comprises the quantity 

 of ore produced from the mine by the company and contractors together, 

 while the yield is only that of the ore treated by the company exclusively. 

 The table may not, therefore, be depended upon to show exactly the opera- 

 tions of the companies or mines named in it, its purpose being only to give a 

 general idea of the rate of production from the leading claims, and the aver- 

 age yield per ton of ore. 



The figures showing the yield express the value actually obtained, by 

 milling process, from the ore in question, averaging all classes. The relation 

 of this yield to the assay value, or that actually contained in the ore, as well 

 as the relative proportions of gold and silver, will be shown more clearly in 

 the following chapter. 



It is also to be observed that the great bulk of ore raised is of the qual- 

 ity generally denominated as third-class, yielding from $20 to $40 per ton; 

 the quantity of higher grades being generally insignificant, especially during 

 recent years. 



