21 
A cut of this was given in the E 7 ig;ineerin^ News of No¬ 
vember, 1886, and it has been more fully described in the 
transactions of the Am. Society of Civil Engineers, Vol. XVL 
In Fig 3, A is the main ditch, with a gate forcing a pro- 
tion of the water through box B. This has a board on the 
side towards the main ditch, with its upper edge at such a 
height as to give the required pressure at the orifice. Then 
if the water be forced through B, the amount in excess of 
this pressure will spill back into the ditch. If the box B is 
made long enough, and the spill-board be sharp edged nearly 
all the excess will spill back into the ditch, thus leaving a con- 
stant head at the orifice. Mr. Foote calls this the excess weir. 
He constructed one for trial purpose. To Mr. W. H. Graves 
of Monte Vista, is due the credit of its introduction into use 
on large canals, with the necessary modifications. He terms 
It the spill-box, a more suggestive name than that proposed 
SicUorv CD 
j 
1 
m. . 
n 
I 
. ‘ 62 ,—--- 
Figure 4 —plans op the spill-box. 
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i C is the entrance of water from the ditch; G a gate which serves to admit as 
I much water as is desired; B the outlet furnishing water to the user. The small 
arrows show where the water spills back into the main ditch. 
I by Mr. Foote. In use, Mr. Graves constructs a weir in the 
I canal, and places the box at one side, always using two, if 
I possible, one at each side, to save fall and expense. The 
■ spill-box is about i6 feet long, 14 inches wide, set perfectly 
■ level. The crest next the canal is brought to a sharp edge, 
; and so are the 2x4 pieces on that side of the box. The gate 
for opening the orifice is of galvanized iron, worked by a rod 
and wing nut from the end of the box, so that it may be ad¬ 
justed to any desired size of opening, and locked. The side 
of the opening is protected by strips of galvanized iron, with 
1 the double purpose of protecting the orifice from surreptitious 
I 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. 
