THE MINERAL DEPTHS 



the element of danger is concerned between steam and 

 electric hoists. The difference is largely one of econ- 

 omy. The importance of this is shown by the recent 

 comparisons in a gold mine which has replaced its 

 steam apparatus by electricity. In this mine the hoist 

 moves through the shaft at a rate of over twelve hundred 

 feet per minute, elevating five hundred tons of ore 

 daily on double-decked cages. It is estimated that 

 this system shows an efficiency of 75 per cent, taking 

 into account losses of all kinds, with a resulting re- 

 duction of cost of from seven to twenty dollars per 

 horse-power per month. 



Results comparing very favorably with these have 

 been obtained also in some of the mines in Germany 

 and Bohemia, where electricity has been introduced ex- 

 tensively in mining. In one of these mines the daily 

 hoisting capacity is twenty-seven hundred tons from 

 a depth of over sixteen hundred feet, at a speed of over 

 fifty-two feet per second. In the Comstock mine, at 

 Virginia City, Nev., electric hoists are used which 

 obtain their power from a plant situated on the Tru- 

 chee River thirty-two miles away. 



ELECTRIC MINING PUMPS 



In pumping, which is always one of the important 

 items in mining, the use of electric power has been found 

 quite as advantageous as in the other fields of its 

 application. No special features are embodied in 

 most of the types of mining pumps over the rotary 

 and reciprocating types used for ordinary purposes, 



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