FLOW IN OPEN CHANNELS 291 



These channels were of many different forms and dimensions ; were 

 lined with different materials, and had slopes varying from *001 to '01. 



Prony, from experiments by Chezy and Dubuat on earthen channels 

 and on wooden channels of small section put 



a v -\- b v 2 = m i 



or C = 



The corresponding value of / = 2 g b -f ^-j A + 



! i = 22,472. .4 = "00607. 



i I a 



where ^ 



i = 10,607. 5 = '00286. 

 I b 



Eytelwein, from experiments on the Ehine channel, gave the same type 

 of formula, his coefficients being 



- = 41,211. A = '00719. 

 a 



- = 8,975. B = -00156. 



In both these cases the unit of length is 1 foot. With moderate 

 velocities a r is small compared with b v* and may be neglected, when 

 the formulae reduce to 



Prony v = -j=- VmT= 103 Vm~i. f = '00607. 



Eytelwein v = - - = 95 \/mT. / = '00714. 



These coefficients, being independent of the condition of the surface, 

 are obviously only applicable to channels having the same physical 

 characteristics as those experimented upon. 



Bazin (1897), as the result of a very large number of experiments on 

 canals and conduits of all sections and dimensions, deduced for C the 

 value 



157-6 



N 



in foot units. 



N varying with the character of the surface. 



Values of N for different types of surface are given on p. 293. 



This gives a value of/ = '000259 jl + *-= + ^} - 



u 2 



