VITEIFIED BRICK PAVEMENTS FOR COUNTRY ROADS. 13 
ordinary circumstances a satisfactory base may be constructed of 
concrete composed of 1 part of Portland cement, 3 parts of sand, and 
from 5 to 7 parts of broken stone or screened gravel. 
The sand should be clean and well graded in size, and the stone or 
gravel should conform to the usual requirements for coarse aggregate 
to be used in concrete construction. 
Foundations for brick pavements have also been constructed of 
planks laid on sand, and in some instances of sand alone. These 
foundations have seldom proved satisfactory for any great length 
of time, and can, therefore, be economically used only when the 
pavement is to be constructed of an inferior grade of brick. 
SAND CUSHION. 
Since it is practically impossible to construct an absolutely smooth 
base, and since there is always a slight variation in the size of pav- 
ing brick, owing to slight differences in the amount of shrinkage at 
the time of burning, it is necessary to provide an adjustable cushion 
of some kind between the base and the brick for correcting these 
slight irregularities, in order to secure an even surface and a uniform 
bearing for the brick. Sand has been found a most satisfactory 
material of which to construct this cushion, and is almost exclusively 
used for this purpose. The proper thickness for the sand cushion will 
of course depend on the extent of the inequalities above mentioned. 
Two inches is the most usual thickness, and has generally proved 
A T ery satisfactory. One and one-half inches, however, is in many 
cases entirely sufficient. 
The sand used in the cushion should be moderately clean and free 
from pebbles. If dirt or vegetable matter is present, it will soon be 
leached out and cause unevenness to develop in the pavement, while 
pebbles prevent the brick from securing a uniform bearing and ulti- 
mately produce the same result. It is also important that the sand 
should be dry when spread, especially if it is fine, because a compara- 
tively small amount of moisture increases the volume of fine sand con- 
siderably, and moisture when present is not, as a rule, uniformly 
distributed. Even if it were uniformly distributed at the start, some 
spots would dry out more rapidly than others while the spreading 
Avas under way, and a lack of uniformity would thus be produced in 
the cushion. 
In forming the cushion the sand is uniformly spread over the base 
to a depth slightly in excess of that desired, and is then smoothed off 
by drawing over it a template shaped to conform with the cross sec- 
tion of the finished pavement. The length of the template is ordi- 
narily made equal to the width of the pavement where this is less than 
about 25 feet, and equal to half the width for wider pavements. 
Timber guides may be laid in the same direction as the pavement for 
