28 BULLETIN 1026, TJ. S. DEPABTMENT OF AGBICULTUBE. 
farmer's pocket whether it is in the form of an assessment or a car- 
riage charge. 
The canal structures of the valley show various designs and types 
of construction, but in general permanent structures of reinforced 
concrete are replacing the old timber structures. Diversion dams 
are rock and brush, timber, or concrete. Rock and brush dams 
are used by only a few of the small ditches on the lower reaches of 
the river. The majority of the dams are simple structures consist- 
ing of piles of rock cribs topped by heavy timber decks on which 
there are permanent crests or standards for flashboards. Wings 
may be of masonry, concrete, or timber and seepage underneath is 
usually cut off by a row of sheet piling. A dam of this type is shown 
in Plate II, figure 1. The majority of the newer dams are of rein- 
forced concrete set on piles or rock crib, and having well- designed 
overflow lips and suitable sluices to scour the channels past the canal 
intakes. A dam of this type is shown in Plate I, figure 1. The crest 
of the Larimer County Dam (PL I, fig. 1) was found to be too 
low for certain stages of the river and was raised 12 inches with 3 
by 12 planks fastened to iron pins sunk in the crest. In Plate I, 
figure 2, is shown another type of concrete dam in which the water is 
held up by flashboards. 
The drift guard at the head of the Larimer and Weld Canal, 
shown in Plate II, figure 2, is of the same general design as others in 
the valley. The structure itself and the individual timbers of the 
grating are placed at such an angle that the drift tends to slide 
downstream instead of lodging. A few canals depend on booms of 
logs chained end to end and anchored so that they swing out in front 
of the gates. 
Headgates are made of timber, concrete, or stone and are fitted 
with wooden or iron gates raised by some combination of screw 
and lever, or rack and pinion. A type of gate and lifting device 
is shown in Plate III, figure 1. Wasteways and sand sluices are of 
similar design. Some of the canals use an adaptation of the Land 
sand gate with diagonal ducts to cut out the greater part of the sand 
near the bottom of the canal. # 
In the construction of the canals of the valley flumes are avoided 
even at great expense as is evidenced by the construction shown in 
Plate III, figure 2. Some of those which were built are being elimi- 
nated by the construction of tunnels or inverted syphons, the longest 
in the valley, a half-mile flume along the side of the canon at the 
head of the North Poudre Canal, being replaced by a tunnel 1,600 
feet in length through solid rock. There still remain a number of 
timber or concrete flumes for crossings of less than 200 feet, and one 
of these is shown in Plate IV, figure 1. Rating flumes at the head 
of canals are usually of concrete or timber, though a few of masonry 
