ELECTRICITY IN MININO 39 



Electric current for mining purposes is usually olUaiiiod 

 in one of two wa>'s, dcpendin^^ somewhat upon the nature of 

 the mine in the fii'st place, and secondly upon the environ- 

 ment. In coal mining regions it is natural that each mine 

 should draw upon its own fuel resources for power, the plant 

 being stationed at the pit mouth; but even in such ca^os, 

 where there is a group of mines it is sometimes found con- 

 venient to concentrate the power generating apparatus, trans- 

 mitting the current to a distance. This has been done in an 

 even more comprehensive way in western mining fields, one 

 steam plant which utilizes coal delivering its energj' to mines 

 no less than 26 miles distant, in districts where water power 

 is not available. Where the generating plant is at the mouth 

 of the mine it is customary to employ apparatus producing 

 low tension direct current; but where longer distances arc in- 

 volved the alternating current has been resorted to, in the 

 same manner as in central electric lighting and railwa}^ plants. 

 The current is generated at high potential by polyphase dyna- 

 mos and transmitted to substations, where it is lowered in 

 pressure and converted into direct current for use. 



One of the first plants of this kind for a mine haulage sys- 

 tem was installed at Ehrenfeld, Pa. The haulage in this mine 

 was accomplished by rope driving and mules until the main 

 heading, which should eventual^ extend 5 miles underground, 

 was nearly 2 miles long. This method was then replaced by 

 an electric system embodying the generation of a 3-phase, 25- 

 cycle, 5,600-volt alternating current near the pit mouth. This 

 current is transmitted by insulated cables to a substation in 

 the mine itself, near the center of the actual operations and 

 about 9,000 feet from the power house. Through the inter- 

 vention of static transformers and a rotary converter, direct 

 current at 275 volts is then delivered to the haulage circuits. 



An interesting variation of this plan is that embodied in 

 the plant constructed for the Raton Coal and Coke company, 

 at Blossburg, N. Mex. \Vhen built, in 1897, the coke plant in- 

 cluded some seventy five 3-foot ovens, in double banks. In 

 the center was erected a large batter}^ of boilers, to \\'hich the 

 waste gases from the coal are conducted through central flues; 

 the gas thus made available is employed to dri^'c gas engines 



