299 
1908-9.] Discharge of Water from Circular Weirs. 
Some experiments were carried out in order to find the actual quantity 
of water passing over a circular weir under various heads, and to ascertain 
the value of the coefficient of discharge. The diameter of the orifice 
employed was 2J inches, and the aperture had the usual sharp edges, so as 
to leave the jet free to contract. The head of water was measured in the 
ordinary way, by means of a hook gauge. The results of the experiments 
Table II. 
Head. 
Inches. 
Actual Discharge 
by Experiment. 
Gallons per minute. 
Theoretical Discharge 
from Curve. 
Gallons per minute. 
Coefficient 
of 
Discharge. 
1-23 
5-66 
9-62 
•588 
1 -31 
6-69 
10-80 
•619 
1-42 
7-80 
12-50 
•624 
1-50 
8-73 
13-79 
•633 
1-56 
9-23 
14-66 
•630 
1-58 
9-49 
15-05 
•631 
1-70 
10-68 
17-03 
•627 
1-75 
11-40 
18-07 
•631 
1-83 
12-15 
19-40 
•626 
1-96 
13-59 
21-72 
•625 
2-02 
14-51 
22-85 
•635 
2*08 
14-82 
23-92 
•620 
2T0 
15-02 
24-32 
•618 
2T9 
16-06 
25-90 
•620 
2 *22 
16-75 
26-50 
•632 
2-30 
17-32 
27-90 
•621 
2-45 
19-17 
30-50 
•629 
2-52 
20-21 
31-50 
•642 
2-59 
20-53 
32-60 
•630 
2-69 
21-39 
34-00 
•629 
2-74 
22-11 
34-70 
•637 
2-85 
22-72 
36-10 
•629 
2-99 
23-68 
37-80 
•626 
313 
24-78 
39-25 
•631 
3-28 
25-81 
40-80 
•633 
3-40 
26-59 
42-00 
•633 
3-59 
27-63 
44-00 
•628 
3-76 
28-66 
45-65 
•628 
3-90 
29-63 
46-90 
•632 
4-03 
30-35 
48-20 
•630 
4T8 
30-87 
49-40 
•625 
4*35 
31-91 
50-80 
•628 
4-49 
32-74 
52-00 
•630 
are given in Table II., and are plotted in fig. 3. A scale of discharge in 
gallons per minute for the orifice employed is appended to the horizontal 
axis of the diagram, and the values of the theoretical discharge, given in 
the third column of Table II., were obtained by multiplying the lengths of 
the abscissae of the theoretical curve by this scale. The fourth column of 
the table gives the coefficient of discharge — that is, the ratio of actual dis- 
