June 21, 1889 ] 



SCIENCE. 



475 



gize the electric motors above ground, which in turn furnish addi- 

 tional power to the main shaft. 



Each electric motor has its own independent circuit fed from 

 one of the generators. The well-known Brush centrifugal gov- 

 ernor, with which each motor is fitted, regulates the speed sensi- 



none was encountered. The motors have not given a moment's 

 trouble or annoyance of any kind from the start. 



Some idea of the economic value of this electric power plant to 

 the mine-owners may be got from a statement of the saving effect- 

 ed by it. The surface wheel alone requires 312 miner's inches of 



lively, and all or any number of the motors work perfectly in a 

 battery together or with the water-wheel. In the motor-room there 

 is also an ammeter for each electric motor, to show at all times the 

 current flowing in each circuit. The motors run at a speed of S50 

 revolutions per minute. Some difficulty was anticipated in oper- 

 ating the motors together on one shaft in the manner described, but 



water to develop power sufficient to drive 40 of the 60 stamps with 

 which the mill is equipped. Moreover, this amount of water is 

 seldom available. Two of the electric motors, working in addition 

 to the surface wheel, will perform the same service with but 72 

 miner's inches of water, thus effecting a saving of about 77 per 

 cent. 



