Measurement and Division or Water. 25 
Sometimes it is convenient to make measurement of the depth 
in inches. Scales graduated in decimal parts of feet are not com¬ 
mon. In such case the following formula may be used. Q is 
the discharge in cubic feet per second in both cases. • 
Where depth is measured in inches, and length of the weir is 
given in inches, then 
0 (sec. ft.) =.0798 L (in inches) H 3 ~ (in inches). 
Where the depth is measured in inches, but the length is given 
in feet. 
0 (sec. ft.) = .006675 E (in feet) H 3 - (in inches). 
An additional word needs to be said regarding L. 
L is the effective length of the weir, which in case of the rec¬ 
tangular weirs, is not necessarily the same as the actual length. 
The various experiments made by Francis may finally all be 
classified and put in the following abstract: 
Summary of Francis’ Experiments on Weirs* 
Depth has in all cases been corrected for velocity. Supply canal 14ft wide. 
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1- 4 
1.56 
3.318 
10 
2 
SERIES A. 
5-10 
1.25 
3.334 
10 
2 
Crest of Weir is 5 ft. above floor of channel of ap- 
11-33 
1.00 
3.322 
10 
2 
proach. 
56-61 
0.80 
3.325 
10 
2 
72-78 
0.62 
3.328 
10 
2 
36-43 
1.06 
3.353 
10 
2 
SERIES B. 
62-66 
79-84 
0.83 
0.65 
3 340 
3.326 
10 
10 
2 
2 
Same as A except that crest is only 2ft. abovefloor. 
44-50 
0 98 
3.341 
10 
0 
SERIES C. 
67-71 
0.80 
3 339 
10 
0 
Canal made same width as Weir Suppressing- end 
Contractions. Otherwise as in A. 
51-55 
1.00 
3.327 
10 
0 
SERIES D. 
Water cannot expand after passing Weir. 
Water 5 feet deep. 
34- 5 
1.02 
3.360 
8 
4 
Water 2 feet deep. 
85- 8 
0 68 
3.337 
8 
4 
In both sets, two boxes separated by a partition 2 feet 
wide giving 4 contractions. 
*The author of this bulletin is responsible for the summary and the 
classification in these series. 
Comparison of series B and A shows the effect of nearness of floor 
on the vertical contraction. 
Series C and D correspond to the cases where weirs are erected in 
the middle of flumes; C to the case where the weir is at the lower end; 
D where at middle. 
