EARTH, SAND-CLAY, AND GRAVEL ROADS. 
31 
keep the above force busy. With such a force the number of wagons 
for maximum efficiency varies from about 3 for a 500-foot 
haul up to about 12 for a haul of 1 mile. Ordinarily, one of the 
plow teams may be employed in hauling for at least a part of the 
time, 
Under average conditions such a force as that described above 
should move about 150 cubic yards of earth per 10-hour day. 
BUILDING EMBANKMENTS. 
One of the most important considerations connected with the 
grading of an earth road is the stability of the embankments. 
Where a road is situated in a cut and is well drained, it is not likely 
Fig. 19.— Steam shovel at work. 
to be affected seriously by such agencies as shrinkage, settlement, and 
slipping, any one of which may injure or destroy a road situated on 
a poorly constructed embankment. In grading a road, therefore, 
the methods employed in building the embankments are deserving 
of much more careful scrutiny than those employed in making 
excavations. 
To prevent a road over an embankment from being damaged by 
shrinkage of the material forming the embankment, the material 
must be free from vegetable matter and uniformly compacted as it 
is deposited. Where the road surface is to be of earth, the embank- 
ment usually may be compacted sufficiently to prevent injury from 
shrinkage by spreading the material in relatively thin horizontal 
layers and letting each layer be compacted by the grading teams as 
the succeeding layer : s being spread. Layers of ordinary earth, not 
