24 
MEASUREMENT AND DIVISION OF WATER. 
Seventh—The approaching channel should be made 
much larger than the weir opening, to bring the velocity 
of approach within low limits. 
A fuller consideration of the proper conditions and 
the effects of their neglect is given with the Yilloresi 
module on page 27. These apply equally well to the rec¬ 
tangular weir. The experimental foundation of the 
formula is shown in the following 
ABSTRACT OF FRANCIS’ EXPERIMENTS ON WEIRS. 
[Depth lias in all cases been corrected for velocity. Supply canal 14 feet wide. | 
Serial No. 
Depth of Water on 
Weir in Feet. 
Coefficient for the 
Experiments. 
Length of Weir, ft. 
No. Contractions. 
COMMENTS. 
1-4 
1.56 
3.318 
10 
2 
5-10 
1.25 
3.334 
10 
2 
SERIES A. 
11-33 
1.00 
3.322 
10 
2 
Crest of weir is 5 feet above bottom of channel of 
approach. 
56-61 
0.80 
3.325 
10 
2 
72-78 
0.62 
3.328 
10 
2 
36-43 
1.06 
3.353 
10 
2 
SESIES B. 
62-68 
0.83 
3.340 
10 
2 
Same as A except that crest is only 2 feet above 
79-84 
0.65 
3.328 
10 
2 
bottom of channel. 
41-50 
0.98 
3.341 
10 
0 
SERIES O. 
Canal made same width as weir, suppressing con- 
67-71 
0.80 
3.339 
10 
0 
traction, otherwise as in A. 
51-5 
1.00 
3.327 
10 
0 
SERIES D. 
Water cannot expand after passing weir. 
SERIES E. 
34-5 
1.02 
3.360 
8 
4 
Water 5' deep. 
85-8 
0.68 
3.337 
8 
4 
Water 2' deep. 
Two bays, separated by partition 2' wide, giving 4 
_ 
contractions. 
Series C and D correspond to weirs erected in flumes, C at the lower end, D 
in the middle, each of full width of flume. 
