20 
points, it may be so made that the opening will be reduced in 
such proportion as the head increases. 
This module would seem to be satisfactory. There is 
little or no friction, but it has the disadvantage of requiring 
considerable loss of fall. If condition u is not important, the 
module doubtless will be very satisfactory. 
For a discharge of 1.44 cubic ,feet per second, generally 
estimated in Colorado enough for 80 acres, with a hole 12 
inches in diameter, the following would be the diameter of 
the plug for the given distances from the top of the plug: # 
Depth. Diameter in feet. 
3 inches.0.53 
6 “ 0.70 
12 “ .0.80 
2 feet .0.87 
4 “ 0.91 
9 “ 0.94 
SPILL-BOX OR EXCESS WEIR. 
Another means of preserving a constant head is due to 
A. D. Foote of Idaho, Past President of the American Soci¬ 
ety of Irrigation Engineers. 
