THE IMPROVEMENT OF RIVERS. 



where the coefficient m 

 and 



- j 0.405 



1 j 



i +0.55 



TT/J f 



Q - discharge in cubic feet per second ; 

 / length of weir in feet; 

 A height of water above crest in feet; 



p" height of crest in feet above bottom of channel of approach; 

 g - acceleration of gravity = 32.2. 



The height h is the head or distance from the top of the crest to the normal surface of 

 the approaching water, or the level at which the water would stand if the velocity 

 of fall over the crest had not reduced it. In Bazin's experiments it was measured at 

 16.4 feet, and in those at Cornell at 38 feet above the weir. 



The profile of the falling water is shown on the accompanying diagram platted 

 from measurements made during the work. 



Where h is between 4 inches and i foot Bazin gives #1 = 0.425 approximately. 

 Trautwine gives the following table of values of m:* 



Submerged Discharge. Where the weir is submerged, that is, where there is water 

 below to check the discharge, the formula generally employed assumes that the water 

 above the lower pool level discharges into free air and that that below discharges 

 through a submerged opening. It is as follows: 



Q = d(h + $d)^/2gd; (2) 



where Q = discharge in cubic feet per second ; 



actual discharge 



c = coefficient of discharge = -r . ; r L 



theoretical discharge 



/ = length of weir in feet; 



h = height of lower pool in feet above crest of weir; 



<f = difference between upper and lower pools, measured to still water, as in 



Bazin's experiments; ' 

 -32.2 feet. 



* Engineer's Pocket-book, p. 267*. 



