CHAPTER XII 

 KTJTTER'S FORMULA 



IN the endeavor of Ganguillet and Kutter to construct 

 a new formula which by proper variation of its constants should 

 be applicable to all streams, small as well as large, to pipes as 

 well as to rivers, the original Chezy formula was used as a basis. 

 The way in which their complicated formula was made up is 

 here roughly outlined, both to indicate more clearly the mean- 

 ing of and reason for its terms, and also to show a method by 

 which other empirical formulae can be constructed. Their 

 method was to assume and demonstrate that the value of 

 " c " would be best formulated by an expression of the form 

 used by M. Bazin, but into which the element of roughness 

 should be introduced. M. Bazin's formula was 



or, making i/a equal y and g/a equal x, it would read 



Ganguillet and Kutter at first thought that y could be made 

 constant, that is, independent of roughness, which would be 

 made a function of x, equal to n-y, or n-y 2 , etc. To check 

 this assumption and at the same time find the value of y, a num- 

 ber of the gagings of Bazin were selected and curves drawn 

 with values of i/\/R for abscissae and i/c as ordinates. Aver- 



175 



