VITRIFIED BRICK PAVEMENTS FOR COUNTRY ROADS. 9 
down in layers not over 8 inches thick, and each layer should be 
thoroughly rolled. In excavation care should be exercised, if the 
material is earth, not to permit plows or scrapers to penetrate below 
the subgrade. The subgrade in both excavation and embankment 
should be brought to its final shape by means of fine grading with 
picks and shovels and rolling. 
When completed the subgrade should be uniform in grade and 
cross section, otherwise the foundation must be made unnecessarily 
thick where depressions occur, in order that its grade and cross 
section may be uniform and its thickness not less at any point than 
that required. The subgrade should be repeatedly rolled and re- 
shaped until the desired shape is secured. If curbs are constructed 
independent of the base they should be set before the final finishing, 
in order that they may be made to serve as a guide for this work. 
The shoulders should never be less than 4 feet wide and should 
consist of some material which compacts readily under the roller and 
does not readily absorb water. Not infrequently one of the shoulders 
is made sufficiently wide to form an earth roadway parallel to the 
brick pavement. Such an arrangement serves to relieve the pave- 
ment of considerable traffic during favorable seasons and also affords 
some advantage to horse-drawn traffic. The general method of con- 
structing shoulders for brick roads is not essentially different from 
that employed for other types of pavements. 
CURBING. 
All brick pavements should be supplied with strong, durable 
curbing, both on the sides and at the ends. Otherwise the marginal 
brick will soon become displaced by the action of traffic, and their 
displacement will, of course, expose the brick next adjoining, so that 
deterioration might eventually spread over the entire pavement. 
Properly constructed curbing, on the other hand, will hold the pave- 
ment as in a frame and enable the brick to present their combined 
resistance to the destructive influences of traffic. 
Satisfactory curbs may be constructed of stone, Portland cement 
concrete, or vitrified clay shapes made especially for this purpose. 
Wood has also been used for curbs to a limited extent, but when it is 
considered that the life of a brick pavement under ordinary condi- 
tions should far exceed the life of any wood curb which might be 
devised, the economy of employing a more durable material is 
readily apparent. 
Stone curbing may be made from any hard, tough stone which is 
sufficiently homogeneous and free from seams to admit being quar- 
ried into blocks not less than 4 feet long, 5 inches thick, and 18 
inches deep. On account of their ordinarily homogeneous structure, 
92742°— 15 2 
