—21 — 
A cut of this was given in the Engineering News of No¬ 
vember, 1886, and it has been more fully described in the 
ransactions of the Am. Society of Civil Engineers, Vol. XVI. 
In Fig 3, A is the main ditch, with a gate forcing a pro¬ 
ion of the water through box B. This has a board on the 
ide towards the main ditch, with its upper edge at such a 
might as to give the required pressure at the orifice. Then 
f the water be forced through B, the amount in excess of 
his pressure will spill back into the ditch. If the box B is 
nade long enough, and the spill-board be sharp edged nearly 
til the excess will spill back into the ditch, thus leaving a con¬ 
stant head at the orifice. Mr. Foote calls this the excess weir, 
de constructed one for trial purpose. To Mr. W. H. Graves 
>f Monte Vista, is due the credit of its introduction into use 
>n large canals, with the necessary modifications. He terms 
t the spill-box, a more suggestive name than that proposed 
PA cm 
SttLerv through CD SuUotv 
1 
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c; 
1 
1 
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G 
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Figure 4 —plans of the spill-box. 
C is the entrance of water from the ditch; G a gate which serves to admit as 
auch water as is desired; B the outlet furnishing water to the user. The small 
rrows show where the water spills back into the main ditch. 
)y Mr. Foote. In use, Mr. Graves constructs a weir in the 
:anal, and places the box at one side, always using two, if 
)ossible, one at each side, to save fall and expense. The 
;pill-box is about 16 feet long, 14 inches wide, set perfectly 
evel. The crest next the canal is brought to a sharp edge, 
ind so are the 2x4 pieces on that side of the box. The gate 
or opening the orifice is of galvanized iron, worked by a rod 
md wing nut from the end of the box, so that it may be ad- 
usted to any desired size of opening, and locked. The side 
)f the opening is protected by strips of galvanized iron, with 
Redouble purpose of protecting the orifice from surreptitious 
mlargement and furnishing a groove for the gate to slide in. 
VIr. Foote thinks that the main ditch need not lose more than 
1 few inches fall—enough to have the excess spill back. Mr. 
Graves prefers at least a foot. 
