nied its advantages.

In building roads very few iron-clad rules can be laid down for
universal application; skill and judgment must be exercised in designing
and building each road so that it will best meet the requirements of the
place it is to occupy. The relative value of the telford and macadam
systems can most always be determined by the local circumstances,
conditions, and necessities under which the road is to be built. The
former system seems to have the advantage in swampy, wet places, or
where the soil is in strata varying in hardness, or where the foundation
is liable to get soft in spots. Under most other circumstances
experienced road builders prefer the macadam construction, not only
because it is considered best, but also because it is much cheaper.

The macadam road consists of a mass of angular fragments of rock
deposited usually in layers upon the roadbed or prepared foundation and
consolidated to a smooth, hard surface produced by the passage of
vehicles or by use of a road roller. The thickness of this crust varies
with the soil, the nature of the stone used, and the amount of traffic
which the road is expected to have. It should be so thick that the
greatest load will not affect the foundation. The weight usually comes
upon a very small part of the surface, but is spread over a large area
of the foundation, and the thicker the crust the more uniformly will
the load be distributed over the foundation.

Macadam earnestly advocated the principle that all artificial
road-building depended wholly for its success upon the making and
maintaining of a solid dry foundation and the covering of this
foundation with a durable waterproof coating or roof of broken stone.
The foundation must be solid and firm; if it be otherwise the crust is
useless. A road builder should always remember that without a durable
foundation there is no durable road. Hundreds of miles of macadam roads
are built in the United States each year on unimproved or unstable
foundations and almost as many miles go to pieces for this same reason.
Says Macadam:

"The stone is employed to form a secure, smooth, water-tight flooring,
over which vehicles may pass with safety and expedition at all seasons
of the year. Its thickness should be regulated only by the quality of
the material necessary to form such a flooring and not at all by any
consideration as to its own independent power of bearing weight.... The
erroneous idea that the evils o