The Neihart herald. [volume] (Neihart, Mont.) 1890-1901, 1893-04-08
S SYSTEM.
Principles Upon which He Worked--The
Repair of Roads.

Pr1ncIpies Upon which He WOrked--The
Repair of Roads.
Macadam's plan of roadmaking diff
fered as much from the old way which
he found in operation as a bridge does
from a ford. Instead Of going deep for
a "bottoming" he worked solely on the,
top. Instead of producing a peaked
roof1ike mass of rough, soft rubbish, he
got a fiat, smooth and solid surface. In
lieu OF a road AZ feet through he made
one of at most ten inches in thickness,
and for rocks and powders he substi-
tuted stone broken small. His leading
principle was that a road ought to oe
considered as an artificial flooring, SO
strong and even as to let the heaviest
vehicles pass over it without impedi-
ment. Then people began to hear with
wonder of roads thirty to forty feet wide,
rising only three inches in the center,
and he propounded the extraordinary
heresy that a better and more lasting
road could be made over the naked sur
face of a morass than over solid rock,
Another of his easy first principles
was that the native soil was more resist
ant when dry than when wet, and that as
a reality, as it had to carry not alone the
traffic, but the road also, it ought to be
kept in a condition of the greatest re-
sistance; that the best way of keeping
it dry was to put over it q covering i'm
pervious to rain-the road in fact-and
that the thickness of this covering was
to be regulated solely in its relation to
ifs mnerUIO11Cnncc on1 NIT ~ al ,c -
its bearing of weights, to which the ma
tive soil was quite equal. Instead of
digging a trench, therefore, to do away
with the surface of the native soil, he
carefully respected it, and raised the
road sufficiently above it to let the water
run off. 1mpermeability he obtained by
the practical discovery that stones
broken small and shaken and pressed
together, as by the traffic on a road,
rapidly settled down face to face and
angle with angle, and made as close a
mass as a wall. Mankind now believe
that this last is all that Macadam in
vented; the rest is forgotten.
Surprise followed surprise. Roads
which We're mere layers of broken ston.
six, four and even as little as three
inches in thickness. passed through the
worst winters without breaking I'D,
while. as the coachman used to say,
they ran true; the wheel ran hard upon
them; it ran upon the nail"
For the repairs of his road when once
made he always chose wet weather and
''loosened the hardened surface with a
pick" before putting on the first broken
something's familiar enough to lis now,
but paradoXes then to all the confrater-
mites of the roads.
The size to which the stone should be
broken he determined in a practical way
by the area of contact of an ordinary
wheel with a smooth road. This be
found to be about an inch lengthwise,
and therefore he laid it down that a
''stone which exceeds an inch in any of
its dimensions is mischievous'-.that is
to say, that the wheel in pressing on one
end of it tends to lift the other end out
OF the road. In practice he found il
simplest to fix a weight of six ounces,
and his surveyors carried about scales
to test the largest stones in each heap.
He would allow no large stones even for
the foundation of his roads, for he found
that they constantly worked upward by
the pressure and vibration of the traffic.
The whole road was small broken stone,
even over swampy ground Southern
Planter.