Measurement and Division oe 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 
Q (sec. ft.) =.0798 L (in inches) H 3/2 (in inches). 
Where the depth is measured in inches, but the length is given 
in feet. 
Q (sec. ft.) = .006675 L (in feet) H 3 ' 2 (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. 
Serial Number. 
Depth of Water on 
Weir in Feet 
Coefficient for the 
Series 
C 
u 
•H 
V 
jq 
-M 
bo 
c 
<u 
►4 
Number of Contrac¬ 
tions 
COMMENTS 
1- 4 
1.56 
3.318 
10 
2 
SERIES A. 
5-10 
125 
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 
0.83 
3 340 
10 
2 
Same as A except that crest is only 2ft. abovefloor. 
79-84 
0.65 
3 326 
10 
2 
44-50 
0 98 
3 341 
10 
0 
SERIES C. 
67-71 
0 80 
3 339 
10 
0 
Canal made same wirith 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. 
