APTER IV

THE SELECTION OF MATERIALS FOR MACADAM ROADS[7]

No one rock can be said to be a universally excellent road material. The
climatic conditions vary so much in different localities, and the volume
and character of traffic vary so much on different roads, that the
properties necessary to meet all the requirements can be found in no one
rock. If the best macadam road be desired, that material should be
selected which best meets the conditions of the particular road for
which it is intended.

The movement for better country roads which has received such an impetus
from the bicycle organizations is still felt, and is gaining force from
the rapid introduction of horseless vehicles. To this demand, which
comes in a large measure from the urban population, is to be added that
of the farmer, who is wakening to the fact that good roads greatly
increase the profits from his farm produce, and thus materially better
his condition; and to the farmer, indeed, we must look for any real
improvement in our country roads.

In considering the comparative values of different rocks for
road-building, it must be taken for granted in all cases that the road
is properly laid out, constructed, and maintained. For if this is not
the case, only inferior results can be expected, no matter how good the
material may be.

In most cases the selection of a material for road-making is determined
more by its cheapness and convenience of location than by any properties
it may possess. But when we consider the number of roads all over our
country which are bad from neglect and from obsolete methods of
maintenance that would be much improved by the use of any rock, this
regard for economy is not to be entirely deprecated. At the same time,
as a careless selection leads to costly and inferior results, too much
care cannot be used in selecting the proper material when good roads
are desired at the lowest cost. When macadam roads are first introduced
into a district they are at worst so far superior to the old earth roads
that the question is rarely asked, whether, if another material had been
used, better roads would not have been obtained, and this at a smaller
cost. When mistakes are made they are not generally discovered until
much time and money have been expended on inferior roads. Such errors
can in a great measure be avoided if reasonable care is taken in the
selection of a suitable material. To select a material in a haphazard
way, wit