HYDROLOGY OF NEW YORK 



611 



The following are the approximate quantities of permanent 

 power in gross horsepower which may be realized at Kochester 

 from a flow of 1000 cubic feet per second : Gross 



horsepower 



Johnson and Seymour raceway 1,081 



Rochester, Carroll and Fitzhugh raceway 1,081 



Upper falls 10,418 



Middle falls 3,180 



Lower falls 10 ; 903 



UndeYeloped 1,931 



Total 28,624 



The total theoretical power is, as stated on a previous page, 

 28,840 gross horsepower, which under the conditions of 1904, 

 may be taken at over 31,000 gross horsepower. 



Why the gross horsepower has been adopted as the unit of power. 

 The unit of power adopted is the gross horsepower — that is, the 

 theoretical power produced by a given quantity of water falling 

 through a given space. The reasons for adopting this unit are as 

 follows : Water is easy to measure, while the actual power pro- 

 duced by water wheels — that is, the net power — is difficult to 

 measure. Again, the efficiency of water wheels varies greatly, the 

 best modern wheels yielding from about 70 per cent to To per 

 cent of the theoretical power of the water. On the other hand, 

 many of the cheaper wheels do not yield more than 40 per cent 

 to 50 per cent. With the gross horsepower adopted as the unit, 

 the onus of getting the largest possible net power out of the given 

 quantity of water is thrown where it belongs, namely, on the user. 

 On any other basis there would be an uncertainty as to the quan- 

 tity of water contracted for, with its attendant disputes. 



Quantity of water per gross horsepower. The following are the 

 quantities of water per gross horsepower on the several developed 

 powers at Rochester: Quantity 



of water in 

 cubic feet 

 per second 

 Head per gross 

 Name of dam in feet horsepower 



Johnson and Seymour 19 0.4630 



Upper falls 92 0.0957 



Middle falls 28 0.3140 



Lower falls 96 0.0917 



