THE CONQUEST OF NATURE 



plained that there is loss of energy when the steam 

 engine operates the dynamo. At Niagara, of course, no 

 steam is involved ; it is the energy of falling water that is 

 transformed into the energy of the electrical current. 

 Moreover, the revolving dynamo is attached to the same 

 shaft with the turbine water-wheel, so that there is no 

 loss through the interposition of gearing. Yet even so, 

 the electric current that flows from the dynamo repre- 

 sents somewhat less of energy than the water current 

 that flows into the turbine. This loss, however, is com- 

 pensated a thousandfold by the fact that the energy of 

 the electric current may now be distributed in obedience 

 to man's will. 



"STEP UP" AND "STEP DOWN" TRANSFORMERS 



The dynamos in operation at Niagara do not differ in 

 principle from those in the street-car power-house, ex- 

 cept in the fact that they are not supplied with commuta- 

 tors. We have seen that these dynamos are of enor- 

 mous size. Those already in operation generate five 

 thousand horse-power; others in process of construction 

 will develop ten thousand. The generator which pro- 

 duces this enormous current is about eleven feet in 

 diameter, and it makes two hundred and fifty revolu- 

 tions per minute. The armatures are so wound that the 

 result is an alternating current of electricity of twenty- 

 two hundred volts. This current represents, it has been 

 said, raw material which is to be variously transformed 

 as it is supplied to different uses. To factories near at 

 hand, indeed, the current of twenty-two hundred volts 



