trench
method is used and wet weather prevails. If it is possible to close
the road against traffic until the road is dry the method is
applicable. Moreover, in long-continued dry weather, the dispersion
and loss of considerable gravel from the action of automobile traffic
is avoided because the gravel is held between substantial earth berms
and the gravel will pack better and hold its shape longer when
constructed by the trench method than otherwise.

=Surface Method.=--The surface method is one in which the gravel is
placed on the graded earth road surface without earth shoulders to
hold the gravel in place. It is also sometimes called the feather-edge
method. Except for the manner of placing as just mentioned, the
several operations are conducted in the same general manner as for the
trench method. The gravel does not compact as quickly as in the trench
method and a considerable loss of material is likely to result from
the effect of automobile traffic while the gravel is loose. But it has
the advantage of being free from difficulties in wet weather and in
some locations is therefore preferable to the trench method. It is
particularly applicable to those projects on which the placing of
gravel continues throughout the winter, the gravel being dumped and
spread, to be finally smoothed and finished in the early summer.

=Bonding.=--Where gravels deficient in binder are utilized, clay for
binder is sometimes added as the gravel is placed on the road. This
may be done by spreading the clay on top of the lower course of
gravel, placing the upper layer and sprinkling and rolling until the
clay squeezes up through the surface layer. It may also be
accomplished by spreading dry clay on the upper course before it is
harrowed and then harrowing to mix it with the gravel. Both methods
are practiced, but the former is believed to be preferable. A third
method is to separate the sand and pebbles and to mix the clay binder
with the sand and then spread the sand on top of the pebbles and mix
by harrowing.

=Maintenance.=--Gravel surfaces require careful maintenance,
especially during the first season the road is used. The gravel will
compact slowly and during the process will be rutted and otherwise
disturbed by traffic. It is important during this period to restore
the shape once a week or at least twice a month. The light blade
grader is usually employed for the purpose so long as the gravel is
somewhat loose. Later a drag of