These have been introduced on the canals with which ; 
Mr. Graves was connected—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, 
and it is now, 1891, being introduced on the North Poudre 
canal. The farmers whom I questioned in the San Luis Val¬ 
ley expressed themselves as perfectly satisfied with its fairness. 
The success of the device for maintaining the head con-^. 
stant is very good, though it cannot be said to be perfect.^ It 
may be made much more sensitive. Under normal conditions 
(As usually placed in pairs.) 
The weir is placed across the ditch, making the ditch lower below than above, 
giving apportunity for the water to spill back into the ditch. G is a mo\cable gate 
to regulate the amount of water admitted at different stages of water in the canal, 
the variations in head will be confined within^ small limits. 
As the spill-box is especially a device for keeping the head 
constant it may be used either with the weir or with the inch 
system, or with any form of opening. It would be very eas¬ 
ily adapted to the Cippoletti form of weir. Unfortunately in 
its adoption by the companies with which Mr. Graves was 
connected the inch system of measurement was in use. With 
a single spill-box, when the opening is of different sizes, there 
will be caused a velocity of approach in the water which will 
tend still further to the favor of the larger opening. The ef- 
