THE CONQUEST OF NATURE 



where the turbine wheel is in operation. As we pass 

 down and down, our eyes all the time fixed on the ver- 

 tical revolving shaft, which is visible through a network 

 of bars and gratings, it becomes increasingly obvious 

 that to speak of this shaft as standing in "a hole in the 

 ground" is to do the situation very scant justice. A 

 much truer picture will be conceived if we think of the 

 entire power-house as a monster building, about two 

 hundred feet high, all but the top story being under- 

 ground. What corresponds to the ground floor of the 

 ordinary building is located one hundred and fifty feet 

 below the earth's surface; and it is the top story which 

 we entered from the street level, thus precisely reversing 

 the ordinary conditions. 



PENSTOCKS AND TURBINES 



As we descend now and reach at last the lowest floor 

 of the building, we step out into a long narrow room, 

 the main surface of which is taken up with a series of 

 gigantic turnip-shaped mechanisms, each one having a 

 revolving shaft at its axis; while from its side projects 

 outward and then upward a seven-foot steel tube, for all 

 the world like the funnel of a steamship. This seeming 

 funnel technically termed a penstock is in reality 

 the great tube through which the massive column of 

 water finds access to the turbine wheel, which of course is 

 incased within the turnip-shaped mechanism at its base. 



As you stand there beside this great steel mechanism 

 a sense of wonderment and of utter helplessness takes 

 possession of you. As you glance down the hall at this 



[188] 



