474 



SCIENCE. 



[Vol. XIII. No. 333 



capable of measuring up to 3,000 volts. The generator circuits 

 are led to a switch-board in the same dynamo-room, where any 

 generator can be thrown on to any one of the outgoing motor cir- 

 cuits. 



Leaving this subterranean power station, and ascending the 



The electric-motor room is shown in one of the large illustra- 

 tions. The six motors are of the regular Brush constant-current 

 type, each of 80-horse-power capacity, and are arranged in a 

 single row parallel with the main driven shaft, to which they are all 

 belted in the ordinary manner. The surface water-wheel is also 



Choilar shaft, are the circuits of copper wire, one to each generator. 

 At one point these circuit wires pass through a shower-bath of 

 spray, but the insulation is so perfect that no leakage has yet devel- 

 oped. The wires issue from the mine shaft, and are carried above 

 ground to the electric-motor room at the Nevada Mill. The total 

 length of each circuit is a little more than a mile. 



connected to this same shaft. It will be noted that there is here a 

 very novel and interesting feature. This surface wheel uses the 

 water in the first instance, and furnishes part of the power to drive 

 the main shaft. The waste water, after this primary use, is carried 

 down the Choilar shaft to the underground chamber, where it 

 drives the dynamos which generate the electric current and ener- 



