MEANS OF COMMUNICATION. 15 
The width of the roadway will depend on the number of tracks, but it is 
advisable always to grade for two tracks, even where only one is to be laid 
at first; because a subsequent widening of the embankments is always 
attended with a want of firmness, which is not counterbalanced by the 
advantage of transporting the material on the finished track. The distance 
between two tracks is made a little greater than the width or gauge of the 
track. From 4 to 5 feet are generally allowed from the end of the supports 
of the track to the beginning of the side slopes. In cuttings, at least 4 feet 
should be left between the longitudinal supports of the rails and the side- 
drains. To preserve the side slopes they should be sown in grass seed or 
sodded ; low bushes may also be planted to advantage. 
In order to keep the road dry, drains are made along the foot of embank- 
ments. In excavations, drains are necessary not only by the sides of the 
roadway, but also above the side slopes, in order to carry off the surface 
water. PI. 2, jig. 3, gives an idea of such an arrangement when walled 
drains, 6 df e, run along the road 272; & is the ordinary ditch, 2 a second 
one on the hill side. In England gutters of earthenware or other drains, g, 
are sometimes used under the middle of the track to carry off the water from 
the superstructure. 
Cross-drains or culverts are constructed in various ways, of which’ some 
examples are given in figs. 4, 5,6, and 7. In wet or marshy soil drains must 
be made under the body of the road emptying into the side drains; an 
example of this is given in jig. 3. 
In localities where land is very expensive, and stone can be obtained 
at moderate cost, the extent of the side slopes both in cutting and filling 
may be diminished by building sustaening walls, of which jigs. 11 and 12 
show examples. They may be built of dry masonry, and should have a 
batter of at least 1 upon 10. 
The best materials for embankments are gravel, sand, and clay; clay, 
which mixes very readily with water, and earth containing vegetable sub- 
stances, are least adapted to the purpose. In marshy localities it is often 
requisite to remove the upper stratum to the depth of several feet, and to 
fill in solid material, such as gravel. When this is not sufficient, and the 
subsoil will not sustain the weight of the road and trains, it is best to drive 
wooden piles on which the superstructure for the railroad is placed. F%g. 
24 shows a road partially sustained by piles. 
In regions where timber is abundant, the use of wooden trestles or truss- 
work in the place of embankments is sometimes resorted to. Structures of 
this kind are required to be very firm in order to withstand the racking 
caused by the passage of the trains. Embankments are generally filled in 
afterwards to take the place of the woodwork as it decays, and this system 
is found very suitable in cases where the funds for the construction of a 
road are not abundant, and it has to be built in part from its income. 2. 
2, jigs. 18, 14, and 15, represent a structure of this kind; jig. 13 is a side 
view, jig. 14 a top view without the superstructure, and jig. 15 a cross- 
section. The sleepers aa support the three uprights 0b), sustained by the 
side-braces dd, which form a kind of truss with the cross-tie c¢; on the 
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