162 



HYDRAULICS AND ITS APPLICATIONS 



An examination by the author, of experiments by G. S. Williams 1 on 

 such weirs, with widths ranging from '48 foot to 16*8 feet and with heads 

 from '5 foot to 4*0 feet, shows that, adopting the Francis formula, the 

 discharge is given within about 3 per cent, for all widths and heads, so 

 long as 



iv>2H, by writing K' = K '75 + "1 

 Fteley and Stearns, using crest widths of from 2 to 10 inches, and heads 



B'O" 



n'3" 



FIG. 89B. 



from -116 to '894 feet, deduced the formula Q = Kb (H + k)%, where 

 / = "2016 V ('807 b - H)* + '2146 6 2 - '1876 b, and K is the coefficient 

 for a thin-crested weir. 



The most reliable experiments on flow over broad-crested weirs and 

 dams are those by Bazin 1 and those carried out at Cornell University 

 between 1898 and 1904 under the supervision of Professor G. S. Williams. 1 

 In the latter experiments which were made for the United States Geological 



1 For a full discussion of these results, as well as those of Bazin, see " Water Supply and 

 Irrigation," Paper No. 200, U.S. Geological Survey; "Weir Experiments, Coefficients and 

 Formulas,' 1 by R. E. Horton. Also see " Rafter," "Trans. Am. Soc. C.E.," vol. 44, 1900. 



