THE CONQUEST OF NATURE 



grimed laborers; there is no glare of furnace, no glow of 

 heat, no stifling odor of burning fuel ; there is only the 

 restful hum of the machinery that responds to the cease- 

 less flow of the silent and invisible waters. Day and 

 night the mighty river here pulls away at its turbine 

 harness; and man, having once adjusted that harness, 

 may take his ease and enjoy the fruits of his ingenuity. 

 As we return now to the top of the building, we shall 

 view the spinning dynamos with renewed interest, and a 

 few facts regarding their output of energy may well claim 

 our attention. In their principle of action, as we have 

 seen, all dynamos are alike, depending upon the 

 mutual relations between the wire-wound armature and 

 a magnetic field. In the present case the magnets are 

 made to revolve and the armatures are stationary, 

 but this is a mere detail. There is one feature of these 

 dynamos, however, which is of greater importance, 

 the fact namely that they operate without commutators, 

 and therefore produce alternating currents. This fact 

 has an important bearing upon the distribution of the 

 current. Each of the dynamos before us generates the 

 equivalent of five thousand horse-power of energy. 

 There are eleven such dynamos here before us; there 

 are ten more in the power-house on the other side of the 

 canal, giving a total of one hundred and five thousand 

 horse-power for this single plant; and there are five 

 such plants now in existence or in course of construc- 

 tion to utilize the waters of Niagara, three being on 

 the Canadian shore. When in full operation the ag- 

 gregate output of these plants will be six or seven 

 hundred thousand horse-power. 



[190] 



