46 BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
1 to 2 miles in 10 hours. It is very useful on projects where the 
yardage per 100-foot station is small and where there are many short 
laterals. 
A dry-land dipper dredge made of steel but equipped with a dif- 
ferent device for walking than the machine just described is illus- 
trated in Plate LX, Figure 2. The machine when working rests 
on two skids, each 3 feet wide by 30 feet long. The auxiliary skids 
each measure 3 feet wide by 28 feet long. When being moved the 
weight of the machine is shifted to the auxiliary skids, and the ma- 
chine is skidded ahead. The auxiliary skids are then pulled forward. 
The machine will move either forward or backward. It is made 
with various widths of span from 14 feet up to 45 feet and in three 
sizes, 3, 1, and 14 cubic yards. The length of boom varies for the 
different sizes from 25 feet to 55 feet. 
A dry-land dipper dredge which employs the same method of 
walking as the machine illustrated in Plate VITI, Figure 2, but which 
is equipped with a different type of bucket, is used to some extent 
on drainage work. This machine (Pl. X, Fig. 1) is built almost en- 
tirely of wood, longleaf yellow pine being used, as this wood has 
greater resiliency than fir. The boom is of wood reinforced by truss 
rods. This machine as ordinarily built will span a ditch with a top 
width of 28 feet. It has a 40-foot boom and a 1#-yard dipper. 
Booms of 30 or 50 feet can be used. For power a 60-horsepower 
internal-combustion engine is used. The dipper or scoop (Pl. X, 
Fig. 2) is 5 feet wide at its cutting edge. By virtue of the peculiar 
shape of the scoop, 2? cubic yards are easily removed at each dip. 
‘This excavator 1s mounted on six shoes or feet, one at each corner 
of the platform and one on each side of the machine at the center. 
The four corner shoes are attached directly to the framework of the 
machine and move with it. The machine moves by shifting its 
weight to the center feet and sliding forward on the four corner 
shoes. The center feet are then pulled forward by means of chains 
attached to a drum. The machine in operation weighs 160 tons, but 
on account of the large bearing surface of the shoes the pressure 
per square inch is slightly less than 10 pounds. The front shoes are 
6 by 10 feet; the rear shoes, 6 by 9 feet; while the middle shoes are 
7 by 14 feet; these sizes, of course, can be varied. When operating, 
the entire weight is on the four corner shoes. 
To dismantle or assemble an old machine of this type takes 15 men 
about 30 days. To build an entirely new machine would take the 
same number of men from 60 to 90 days. The machine can be 
shipped on four cars. 
For this machine the minimum economical yardage of any one job 
is 1,000,000 cubic yards. The machine will excavate an average of 
