Mar, 6,1916 
Flow through Weir Notches 
1101 
1 to 3 and 1 to 6, it was assumed that similar plottings for such notches 
would lie on the same straight line as those for the rectangular and 
Cipolletti notches. Lines B pass through the origin and have a slope of 
45°. The discharges through a 2-foot notch with the various heads that 
would fulfill the condition of being twice the discharge through a i-foot 
notch with the same head must lie on this 45 0 line. Curves C were 
obtained by plotting the discharges through the 2-foot notches of dif¬ 
ferent shapes against the decimal expression of the side slope of the 
notches. 
In each set of curves the point of intersection with the C curve of a 
vertical line drawn through the point of intersection of lines A and B 
indicates the side slopes which are necessary with a given head in order 
that the discharge through a 2-foot notch shall be twice that through a 
1-foot notch. The slopes found expressed as ratios of the horizontal to 
the vertical distance are given in Table XVI and indicate that the sides 
of a 2-foot notch which would give twice the discharges of a similar 
1-foot notch with heads up to 1 foot at least must be curves and must 
approach the vertical as they go up. 
Tabi^e XVI .—Side slopes necessary in order that a 2-foot notch discharge twice the amount 
of water from a i-foot notch 
Head. 
Slopes. 
Feet . 
I. 0 
•9 
•7 
.6 
•5 
•4 
. 2 
1 to 18. 5 
I to 18. 2 
i to 14. 7 
I to 12. I 
i to 6. 5 
I to K. 2 < 
a i to 4. 0 
a Obtained from data for 0.2 head. 
No attempt was made to determine the exact shape of the sides of the 
notch. They would be so complex, however, that their construction 
would render impracticable the use of such notches on the farm. 
Because of the appreciable difference in the effects of contraction with 
notches of different sizes, a similar comparison of the discharges through 
larger notches with those through a i-foot notch would probably give 
results different from those obtained for the 2-foot notch. 
SUBMERGED RECTANGULAR AND CIPOLLETTI NOTCHES 
A notch is said to be submerged or “drowned” when the water level 
on the downstream side is higher than the crest of the notch. To deter¬ 
mine the effect of submergence upon the discharges 757 experiments 
were made with the 1-, 2-, 3-, and 4-foot rectangular and Cipolletti 
notches used in the free-flow experiments. The conditions on the up- 
