i! a 
MEANS OF COMMUNICATION, 7 
level with the adjacent ground, as in jig. 1, the slopes of the side-channel 
abed may be 1 base tol perpendicular. When the road is on an embank- 
ment, as in jig. 2, its side slope should be 14 base to 1 perpendicular, and 
the same slope, or even a less inclination, is required for the sides of exca- 
vations. The bottom )c¢ 0 p of the*drains is two feet in width. At intervals 
walled drains, termed calverts, built of stone or brick, and usually arched 
at the top, pass under the road, and convey the water to the main drains 
which communicate with the natural courses. Shade-trees should not be 
planted on the road itself, as they are apt to keep it damp. 
When a road is to be made, the country through which it is to pass is 
carefully surveyed and mapped; profiles of the surface are obtained by 
means of the spirit-level, and from these data the location of the road is 
determined on, and estimates made of the required structures, such as 
bridges, culverts, and side-walks, and of the number of cubic yards of 
embankment and excavation. The line of road being thus marked on the 
ground, the grading and draining are done according to the plan proposed ; 
on each side of the road from 3 to 6 feet are marked off for the footpaths 
de and mn (jigs. 1 and 2), and two rows of curbstones placed at e and m. 
The paved bottom road covering (fig. 1) is formed of three layers of stone. 
The bottom layer, /, consists of small blocks of stone, about 6 inches high, 
packed together as closely as possible, the interstices being filled with small 
stones compactly set with a hammer. ‘The second layer, g, of broken stone, 
is made four inches high, and the convexity of the carriage-way is begun 
tobe formed. The third layer, / should consist of the hardest broken stone, 
of the size of a pigeon’s egg, and should again be from 4 to 6 inches high. A 
coating of clean gravel, two inches thick, termed a bending, is spread on the 
surface, and levelled by means ofa road-roller. The elevation of the centre 
of the carriage-way is about one eighteenth of its width. ‘The foot-paths are 
also covered with gravel, and serve as abutments for the body of the road. 
In order to diminish the wear and tear of the road as well as of the con- 
veyances, swmmer roads are sometimes laid out on the sides of stone roads. 
They are not covered with stone, and are closed by gates in wet weather 
and in winter. 
The materials for a good road-covering are the harder kinds of stone, 
quartz, the scorize of iron-furnaces, poor iron-ore, &c. Sandstone and all 
kinds of slate are too friable for the purpose. In Holland the so-called 
klinker roads are made, which are covered with brick baked very hard, 
called klinkers. 
Another mode of forming the road-covering was first brought into notice 
by McAdam; roads made according to his system are called Macadam- 
ized, and have been adopted in many states on account of the economy in 
their first construction. PJ. 1, fig. 2, represents a road of this kind; the 
covering consists entirely of broken stones, those of the bottom layer being 
about as large as hens’ eggs, and those on top of the size of a hickory-nut; 
gravel when it can be procured is preferable for the top-coating. Roads of 
this kind will only answer when the subsoil is very firm ; they require much 
care during the first years, as deep ruts are readily made, which must be 
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