50 BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
at the bottom, made an average distance of 2,250 linear feet in 10 
hours. The soil was a hard, yellow, sandy clay, overlain by a turfy 
muck varying in depth up to 24 feet. The total length of ditches 
dug was 165 miles, two machines of the same size being used. The 
maximum distance dug in 10 hours was 6,600 feet. The fuel con- 
sumption per shift of 10 hours was 50 gallons of gasoline. 
On another project a wheel machine of the same size was used. 
The soil was a silt loam, firm and uniform, but not tenacious. The 
average length of ditch cut per day was 800 feet, while the maximum 
was 1,950 feet. The total length of ditch cut was 117,000 feet. 
Wheel excavators are adapted to the excavation of ditches in soils 
free from stumps, buried timbers, bowlders, or rock. They have 
been used extensively in the Gulf States on flat, swampy prairie 
lands. 
THE HYDRAULIC DREDGE. 
The hydraulic dredge has been used only to a limited extent in 
the construction of drainage ditches, due to the fact that nearly 
all such ditches are too small to be dug economically by this method. 
Hydraulic dredges are suitable for digging ditches 800 or more 
square feet in cross section, for building levees under favorable con- 
ditions, and especially for building up tidal flats and lowlands. 
The principal parts of the hydraulic dredge are a centrifugal 
pump, the power machinery to drive the pump, and the hull on 
which the machinery is mounted. When the dredge is operating 
the material to be excavated, mixed with water, is drawn in through 
the suction pipe and discharged where desired through a line of 
pipe sometimes several thousand feet long. Coarse sand, gravel, 
muck, and silt are easily handled in this way, and by the use of a 
rotary cutter on the end of the suction pipe comparatively hard 
clay can be removed. The machine does not work well where there 
are stumps, logs, large stones, or other such obstructions. 
The dredge must be moved frequently. This is usually accom- 
plished by cables operated by a hoisting engine and attached to 
deadmen on the shore or, if working in a large stream, to anchors 
dropped into the stream. Either one or two spuds are arranged at 
the stern of the dredge, which hold that end of the hull in position. 
By swinging the head of the dredge the amount of material de- 
livered to the pump can be regulated so that the dredge will handle 
the maximum percentage of solids. 
To determine whether the dredge is working properly a vacuum 
gauge is attached to the suction pipe and a pressure gauge to the 
discharge pipe. The operator by means of the vacuum gauge can. 
tell when the pump is handling the proper amount of material, as 
