The record-union., 1893-08-22


Also Used in London and Other
Large CIties-Good Eighteen-Foot
Roads in Scotland Cost $500 Per
Mile.
In 1916 John Loudon Macadam began
his system OF putting broken stone upon
a road which shall unite by its own angles
so as to form solid, hard surface. 1t
must remain in the situation in which it
is placed, whereas gravel must be III con-
stant motion" The choice Of angular
stones, 80 as to form a sort Of mosaic or
interloclling system" the care to secure
proper foundations, and a thorough roll
ing, are the three great clements in mod
ern British roadmaling. says the New
York SHn. Macadam, in his testimony
before a House of Commons Committee,
held that road should be as fiat as pos
sibIe, with only just enough slope to al
low the water to escape. Carriages need,
he said. to stand upright, and if you
make the read too convex they will go
for the center, and there the wear will be
the greatest, so that the water win soon
collect there. His own practice was to
make roads only about three inches
higher i'll the center than on the sides.
and TO make all parts OF the road equally
hard.
lie often built road in what he called
three tlmes''-that is, with a layer Of
broken stone about four inches thick,
worked until 1T WAS set. then second,
then a third. Whinstoue, used much in
the north OF England and in Scotland
1.ar f.,y-Dvifo al
the most durable, but he accepted as ado-
qUate flint in Essex and Sussex; lime
stone III the west, which cOnsUlidates
quickly and makes a smooth road but
not the most lasting; the hard pebbles OF
Shropshire and so on. In maintenance
and repair the difference between a town
and a country maCadamiZed road is, as
Consul Daniels expresses it, that the for
mer is hacked over, spread with enough
broken WhnstOne 10 raise it to its proper
Level and cumber, and rolled with a
heavy roller, ioamy gravel being used
as binding material for the Iuterstices,
whereas on country roads the old surface
is not hacked over, nor the new material
rolled, but left to be consolidated by
travel.
Macadam substituted for the old high
curved road, consisting OF about four feet
OF large stones and other material, an al
most ltat and smooth road about a foot
( thick. He chose wet weather for repairs
He introduced the plan OF loosening the
hardened surface with a pick before put
ting his first layer Of broken stone. He
had his stone breakers sit down to their
work. In short, he introduced many
new details, which are now familiar.
And his plan OF using old material en-
aDled his roads to be built and repaired
with unprecedented economy. In time
machine broken stones came in. His
/ TlFnGantpA tO ISarliny,,ny,+ ~,
1919, but not until 1884 was it supple
mented by Nj. PolonCeau's introduction
OF the steam roller. The elder Macadam
lived 10 see great changes wrought bv
his system.
PAVE3IENTs N LARGE CITIES.
The streets of London have many va
rieues Of pavement. In kensington
there is a great deal Of wood pavement.
which is laid on concrete and usually
consists OF creosoted deal blocks. Most
Of the wood is SIX inches deep, but of late
years fve-inch blocks have been substi-
tuted, aud Engineer Weaver thinks that
live inches Will be the usual depth here
AFTER in order to effect a saving in cost,
and that tive-inch WOOD paving will last
ten years. Surveyor HAYWOOD Of Green
witch, however puts the life OF wo0d-cube
paving at four to i've years, that of as
pnalt at fifteen to twenty, il it could be
I left Uudisturbed, and that of granite
cubes at tWenty-one years. 4 most vaIu-
able set OF comparisons between wood.
asphalt and granite pavements is made by
Engineer HAYWOOD. Eruu.'a series OF ex-
periments he reached these conclusions:
That asphalt was most slippery when
merely damp and safest when perfectly
dry; That a horse might be expected to
travel on the asphalt without an accident
nearly twice the distance when the pave
ment was dry that it could do when
damp. and that the difference between
the safety OF asphalt when wet and dry
was not considerable.
THAT granite was most slippery when
I dry and safest when wet; that q horse
might be expected 10 travel on granite
without accident nearly seven times the
distance when the pavement was wet
than when dry, and that the granite was
about twice as safe when merely damp as
when dry.
hat wood was most slippery when
damp and safest when dry; that q horse
might be expected to travel on wood
more than three times the distance when
the pavement was dry than when damp,
and that the wood was more than twice
as sale when wet as when damp"
The material used for paving the streets
Of Dublin is from the Wicklow uuarries
and is very durable, it being, in fact. SO
hard as'sOmetimes to become dangerously
smooth in dry weather. There are also
wood pavements. something like the
/ Nicholson, and macaGamized streets
( The country roads are hardly as good. on
the average, as those OF England and
Wales, as the frequent raiuialls make the
soil spongy and less suitable for road
ways. on the other hand, they suffer
little from frost.
BEST WORK DONE BY CORPORATE WORK
MEN.
Out Of $50 miles Of streets in Belfast
about fifty are macadamized ten paved
with granite sets, and ninety with sea
pebbles. The best paving is done by cor
poration workmen, not by contract. The
sets are laid on a concrete ued composed
OF four parts broken stone two parts
broken brick. two parts gravel and one
part best Portland cement. This con-
crete may be six, nine or twelve inches
thick, according to traffic and the nature
of the ground. All the material must be
clean. For macadanlzing whinstone is
mostly used.
(