— 37 — 
the allowance for contraction for 11 inches depth ; the eleventh column for a depth of ll^^ inches. 
For 1114 inches we then take a value intermediate between those for 11 inches and 1114 inches, ob¬ 
taining the correction .567, the amount by which the discharge is reduced. This, then, leaves the 
total discharge as 11.335 — .567 10.77 second feet. 
Table IV is used in exactly the same way. In this table the discharge is 
given for a portion of a weir 1 foot long, while No. Ill gives it for a weir 1 in. long. 
These two tables are consequently adapted to weirs of any length, but re¬ 
quire multiplication. ^ « txy. . 
Tables V and VI give the discharge for weirs of certain lengths, for different 
depths, and without multiplication. Where companies adopt weirs for measure¬ 
ment it is far more convenient to adopt certain standard lengths and make all weirs 
conform thereto. . „ , 
Table V gives the discharge over rectangular weirs for depths varying by 
.025 of a foot and for various lengths of weir. These tables give the discharge with 
two complete contractions. In case there is no contraction, then the amount in the 
right hand column may be added to the amounts given in the table. 
The amounts given in the boldface figures are for those cases where the con¬ 
ditions of depth and length of weir are such as to make the results the most reliable. 
Table VI is for rectangular weirs without contraction—which may also be 
found from table V, and for the Cippoletti trapezoidal weirs. It will be noticed 
here that the discharges given in the various columns are directly proportional to 
the length of the weir, while in table V they are not. The amounts are 1 per 
cent greater than given in table V. The quantities in table V were computed with 
the constant 31^ instead of 3.33 ordinarily used, making the quantities 1-10 of 1 per 
cent, greater than given by most tables. Table VI, intended for trapezoidal weirs 
is 1 per cent, greater than corresponding discharges of table V. 
Depth in all cases in the following tables is measured in still Avater. 
page 25 . 
TABLE I. 
See 
Auxiliary Table for Approximating to Velocity of Approach. 
Depth of water over 
weir. 
Average velocity 
in section of 
weir. 
Depth of water over 
weir. 
AA^erage velocity 
in section of 
weir. 
in ft. 
in in. 
in ft. per sec. 
in ft. 
. . 
. in in. 
in ft. per sec. 
.25 
3 
1.665 
1.75 
21 
4.400 
.50 
6 
2.351 
2.00 
21 
1.709 
.75 
9 
2.881 
2.25 
27 
1.995 
1.00 
12 
3.330 
2.50 
30 
5.265 
1.25 
15 
3.723 
2.75 
33 
5.510 
1..50 
18 
4.078 
3.00 
36 
5.765 
table II. 
Corrections in per cent, for velocity of approach, to be applied to values obtained 
from Tables III to VI. 
Veloc¬ 
ity. 
Head.* 
depth oveb weir, in 
FEET. 
.25 
.50 
.75 
1.00 
1.25 
1.50 
1.75 
,2.00 
2.25 
2.50 
2.75 
3.00 
25 
•.0010 
00.8 
00.4 
0.3 
0.2 
0.2 
0.1 
0.1 
0.1 
0.1 
0.1 
0.1 
0.1 
. 50 
.0039 
03.5 
1.8 
1.2 
0.9 
0,7 
0.6 
0.5 
0.4 
0.4 
0.3 
0.3 
0,8 
.75 
.0087 
08.0 
4.0 
2.6 
2.0 
1.6 
1.3 
1.1 
1.0 
0.9 
0.8 
0.7 
0.7 
i.oo 
.0155 
14.3 
7.1 
4.7 
3.5 
2.8 
2.3 
2.0 
1.8 
1.6 
1.4 
1.3 
1.2 
1.25 
.0243 
22.6 
11.1 
7.4 
5.5 
4.4 
3.7 
3.1 
2.7 
2.4 
2.2 
2,0 
1.8 
1..50 
.0350 
33.1 
16.1 
10.7 
8.0 
6.4 
5.3 
4.5 
4.0 
3.5 
8.2 
2.9 
2.6 
1.75 
.0176 
45.7 
22.2 
14.6 
10.9 
8.7 
7.2 
6.2 
5.4 
4.8 
4.3 
3.9 
S.b 
2.00 
.0622 
60.9 
29.2 
19.2 
14.3 
11.4 
9.5 
8.1 
7.1 
6.3 
5.6 
5.1 
4.7 
2 25 
.0787 
78.6 
37.4 
24.5 
18.2 
14.5 
12.0 
10.3 
9.0 
8.0 
7.2 
6.5 
6.0 
2.50 
.0971 
99.1 
46.7 
30.5 
22.6 
18.0 
14.9 
12.7 
11.1 
9.9 
8.9 
8.0 
7.4 
2.75 
.1175 
121.8 
56.9 
37.0 
27.4 
21.8 
18.0 
15.4 
13.4 
11.9 
10.7 
9.7 
S. J 
3.00 
.1398 
149.4 
69.1 
44.S 
33.1 
26.2 
21.7 
18.5 
16.1 
14.3 
12.8 
11.7 
10.7 
3 25 
.1611 
179.6 
82.3 
53.1 
89.1 
80.9 
25.6 
21.8 
19.0 
16.9 
1 15.1 
13.7 
12.6 
3 50 
.1903 
213.5 
96.9 
61.7 
45.7 
36.1 
29.9 
25.4 
22.2 
19.6 
1 17.6 
16.0 
14.6 
3.75 
.2185 
251.3 
113.0 
72.3 
53.0 
41.8 
34.5 
29.4 
25.6 
22.6 
1 20.3 
18.4 
16.8 
4.00 
.2486 
293.1 
130.7 
82.6 
60.9 
47.9 
39.5 
33.6 
29.2 
25.9 
1 28.2 
1 21.0 
19.2 
*Head=t54 36 
V being velocity in feet per second, in first column. 
