40 THOMAS COMMERFORD MARTIN 



and dynamos furnishing power for the hauhng plant both in- 

 side and outside of the mine. About a mile and a half from 

 the coke ovens is situated the washing and crushing plant, 

 with a capacity of 800 tons in ten hours. All the machinery 

 from tipple to mine opening is driven by electric motors, a 

 trolley line with electric locomotives bringing the pit cars from 

 the main entry to the tipple. This idea of the utilization of 

 waste gas in coke fields and blast furnaces has of late occupied 

 considerable thought and attention on the part of mechanical 

 and mining engineers, and important developments are result- 

 ing from the employment of electricity as a means of lessening 



waste. 



In most mining districts, however, the work is inter- 

 mittent, machinery is widely scattered in places difficult of 

 access, fuel is expensive, and the economical use of steam is not 

 possible. Compressed air, as a means of transmitting power, 

 is handicapped by loss in the compressor and the piping, and 

 is limited to short distances and to the operation of appa- 

 ratus requiring power regardless of cost. 



Under the modern conditions of power transmission from 

 waterfalls, etc., electricity has shown itself to be largely in- 

 dependent of distances, so that, as was pointed out by Mr. 

 F. O. Blackwell, before the American Institute of Mining 

 Engineers, in February, 1903, a given amount of power can 

 be delivered either 528 feet away, at 100 volts, or 50 miles 

 away at 50,000 volts, with the same total amount of copper 

 per horsepower and exactly the same loss of power in the 

 transmission circuit. With proper choice of potential and 

 system, this loss need not exceed 10 per cent, even when the 

 current is carried as far as 150 miles. 



So much has been done in the matter of power trans- 

 mission for mining purposes that it is difficult to pick out any 

 specific case as thoroughly typical. But it would be hard to 

 find an instance more notable than that of the Standard and 

 Bay Counties Power companies, in California. These, con- 

 solidating other systems, have a remarkable network of cir- 

 cuits of which one of the largest begins at Colgate, in the foot- 

 hills of the Sierras, on the North Yuba river, a second at Fol- 

 som City, a third at Electra, and a fourth at De Sabla. From 



