MEASUREMENT AND DIVISION OF WATER. 
17 
reptitious enlargement and furnishing a groove for the gate 
to slide in. Mr. Foote thinks that the main ditch need 
not lose more than a few inches fall—enough to have the 
excess spill back. Mr. Graves prefers at least a foot. 
These have been introduced on the canals of which 
Mr. Graves is the Chief Engineer—the Monte Vista or 
Citizens’ canal, the Rio Grande or Del Norte, the Grand 
River and the Montrose, which include the largest canals 
in the State. The farmers whom I questioned in the San 
Luis Valley expressed themselves as perfectly satisfied with 
its fairness. 
SttXvon through CD 
F? - 
A 
i 
. 
JS 
m 
_Bj 
i 
. 
. 
Fig. 4 . —plans of the spill-box. 
S«Uot\ 
lVuo vxg\\ i© 
C is the entrance of water from the ditch ; G a gate which serves to admit as 
much water as is desired ; B the outlet furnishing water to the user. 
The success of the device for maintaining the head con¬ 
stant is nearly perfect. Under circumstances purposely 
made unfavorable—when there was a strong head of 
water in the canal, no regulation of the gate B, and with 
obstructions so placed on the weir as to force nearly all the 
water into the upper end of the box—the depth flowing over 
opposite the orifice w T as less than two inches. Under normal 
conditions the variations in head in the box will be verv 
t/ 
slight and the flow practically constant. When the flow from 
openings of different sizes are compared, however, besides 
the difference in favor of the larger user from causes already 
spoken of, there must be a velocity of approach which 
