The watchman and southron. [volume] (Sumter, S.C.) 1881-1930, 1911-08-30
Macadam, Road Maker.

1t has been said that the best roads
built since the days of the Romans
are those known as macadamized
roads.
Macadam was a Scotchman who
spent several years in America. on
his return TO his native land, to-
ward the close Of the eighteenth GEN.
tury. he devoted his attention to
road building. His leading principle
was that a road ought to be consider
ed as an artificial flooring SO strong
and even as to let the heaviest We
hicle pass over it without impedi-
ment.
People began to hear with wonder
Of roads thirty and forty feet wide
rising only three inches in the centre,
and he propounded the extraordinary
heresy that better and more lastiag
road could be made over the surface
of a morass than over solid rock.
Another of his principles was that
the soil is more resistant when dr.,
then when wet. In order to keep II
in condition Of the greatest re-
sistance-that Is to say dry-he ad-
N"cated the putting over 1t of a cov.
ering impervious to rain-the road,
la fact. The thickness Of this Gov
c:irg was TO be regarded In relation
to rs Imperviousness. and not at oil
as To its bearings Of weights.
Instead Of digging trench, there
fore, to do away with the surface OF
the native soil he carefully respected
II and raised the road sufficiently
above it to let the water run off.
Impermeatility he obtained by the
practical discovery that stones brok-
en- small and shaken and pressed to-
gether as by the traffic on a road
rapidly settle down face to face and
angle and make as close a mass as a
wall. Mankind in general now believes
that this last Is all that Macadam
invented; the rest is forgotten. That
important fraction OF his discoveries IL
what has given 20 Va the yerh to
and the French their
nouns macadam. macadamisage ana
the verb macadamiser.
1t was soon found that roads which
were mere layers Of broken stone. six.
four and even as little as three inches
In thickness passed through the
worst winters without breaking up.
while. as the coachman used to say.
they ran true"
Even in the breaking OF stones
Macadam effected a revolution. He
saw that able bodied men standing
up with heavy hammers wasted the
greater portion Of their strength. He
made his stone breakers sit, so tina.
all the force Of the blows took direct
effect on the stone; and the result
was that he found small hammers
lid the work perfectly well. and thus
vas able to confine 1t to old men past
hard labor. women and boys, which
reduced the cost Of the broken stone
by one-half.
The size to which the stone should
be broken he determined in a prac-
Iical way by the area Of contact Of IN
ordinary wheel with a smooth road.
This he found to be about an inch
lengthwise. and therefore he laid /,
down that stone which exceeds m
inch In any Of it's dimensions is mis-
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 1t simplest to
fix a weight of six ounces, and his
surveyors carried scales 20 test the
largest stones in each heap.
Macadam would allow no large
stones even for the foundtion OF his
roads, and he found that they con
s,antly worked upward 10y TIE preg-
sure and vibra tion Of the traffic The
whole road was of small, broken
stones even over swampy ground.-
IIarper's Weekly.