44 BULLETIN 724, U. S. DEPARTMENT OF AGRICULTURE. 
especially true of macadam and, as a consequence, both V-drain and 
Telford foundations have been employed frequently in connection 
with the macadam surface. It is less true of Portland-cement con- 
crete only because its power of distributing pressure increases very 
rapidly with the depth and also may be greatly increased by prop- 
erly arranged steel reinforcement which is usually cheaper to employ 
than any form of foundation. 
Other types of road crust, such as blocks or setts, asphalt, and bitu- 
minous concrete, are intended only as wearing surfaces and in gen- 
eral must be supported on some form of artificial foundation. There 
are, of course, exceptional subgrade conditions where this is not true, 
as, for example, in the peninsular section of Florida, where the cli- 
mate is mild and the soil consists essentially of sand which, when 
properly confined, has a relatively high bearing power under all 
weather conditions to which it is subjected. In this section brick 
roads have been constructed directly upon the sand subgrade with 
fairly satisfactor}^ results. 
In this region where frost in the ground is unknown, it is neces- 
sary to provide only adequate bearing. The requirements of this 
nature should, however, receive careful consideration and types 
should be selected that can be repaired easily and successfully with- 
out loss of good material, in case the assumed bearing value of the 
soil is not developed in practice or decreases owing to deterioration 
of curbs, drying out of sand, or other strictly local causes. 
Under the conditions usually prevailing neither the thickness of 
the road crust nor the combined depth of surfacing and foundation 
is adequate to prevent entirely the upheaval by frost, providing this 
is sufficiently extreme. The question of combating frost action still 
remains unsettled and exceedingly difficult of solution. The damage 
caused by it is very great in some cases and the economic aspect of 
the matter is involved. In general, it is not advisable to prepare 
elaborate and costly foundations to save comparatively cheap roads 
from slight damage; on the other hand, a considerable expense in 
foundation construction would be warranted if assurances existed 
that the effect would be to save an expensive surface from all dam- 
age. The entire question doubtless hangs on the reduction of soil 
moisture in the premises and the removal of free water at all times. 
To effect this the various methods of drainage discussed will serve 
largely if judiciously applied. The use of shoulder drains and 
ample provisions for relieving the subgrade and foundation near the 
surface of melted snow and ice in periods of alternate thawing and 
freezing will go a long way toward accomplishing the results de- 
sired. Generally in the northern part of the United States, the gla- 
ciated areas have well drained soils and frost action tends to be 
