POWER DEVELOPMENT AT NIAGARA. 



625 



that amount. The reasons for this high frequency are mainly 

 two : The first, that with any given alternating-current dynamo 

 the number of alternations depends directly on the speed, and, as 

 this must usually be high in order to get as much work as pos- 

 sible out of the machine, the periodicity is also high. The sec- 

 ond reason is that in lighting work it is, of course, highly un- 

 desirable to employ a current of which the pulsations are so slow 

 as to leave the incandescent filament or the arc visibly dimmer 

 between separate beats, as we may call them, than during the 

 passage of the full current strength. In the case in hand one is 

 impressed with the effort that has been made to steer a middle 

 course in the design of the generators so as to obtain a portion of 



Turbine shaft 

 (broken away). 



Wheel case. 



FIG. 7. ELEVATION (PART SECTION) OF WHEEL CASE, PIT, AND PENSTOCK. 



the advantage of the direct current for motor work and of the 

 alternating for transformation. The periodicity for the first por- 

 tion at least of the electrical equipment is to be as low as twenty- 

 five per second, and this at once limits the scope of the use of the 

 current in the matter of electric lighting. Prof. Forbes states that 

 lighting by the current direct is a comparatively small portion 

 of the work in contemplation, and that the plant is rather to be 

 regarded as essentially for power distribution. The expression, 

 " lighting by the current direct," is used because a very impor- 

 tant branch of the power work will be the lighting of the city of 

 Buffalo. This is at present done by the ordinary direct-current 

 arc machines operated by engines of some three thousand horse 

 power. In changing over to the Niagara Falls power the whole 



VOL. XLV. 4*7 



