Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-06-07

| OF the various stones and rock Iounu III
fields and forests. Many persons believe
| that there are to be found in Pennsylvanla
other stone almost as hard as Limestone
which, if it could be used, would reduce the
cost of maca6amizing very much in counties
where limestone is not found. The lnvestl-
CATION made by The DISPATCH brought
| ont the weight of evidence against sand
stone, and anything else than Limestone.
| Still there are many rocks and bouloers
| which people believe to be proof against the
weather and weight, which could be sub
| jected to tests thatfwould settle the ques-
tion at once. Certainly if a substitute could
| be found for limestone in those counties
where the material is scarce, the serious
question of cost could very materially be
| lessened. 1t is o point worth while consld-
ering.
The farmers of Western Pennsylvania are
about equally divided on the question OF
abolishing the system of working out road
taxes. Probably half of them are willing
that it should be abolished. To the dlsln-
terested mind there can be no doubt that to
do away with the system would greatly i'm
prove the condition OF roads. Road taxes
in Allegheny county annually amount to
about to $14e, 900, and it is estimated that in
the whole State the tax this levy of tax
aggregates S4, ,00O 900 annually. The great
that could be converted into money there
would not be half so much of q puzzle about
where the money is to come from for the re-
building of the roads.
HOW MAcADAM ROADS ARE MADE.
Macadam roads are constructed with sue
cessive layers of broken stone. If the best
quality of stone cannot be procured for the
whole of the road covering, care should be
faGan IN ealaof fba hardest and touphest
stone for the upper, or preferably for the
two upper layers, having an aggregate
thickness of about inches. The stone
should be broken into fragments, as nearly
cubical in form as possible, the largest OF
which should not exceed 2H inches In
longest diagonal dimensions. For inspect
ing the broken stone an iron ring ~ inches
in diameter may be used with advantage.
If the material be very tough and hard,
like most of the basaltic and trap rocks and
the sienitic GRANTEES, or if the traffic upon
the road be light and its amount not large,
the stone may be broken smaller without
danger of their crushing to easily or too
rapidly. The smaller the fragments the
less will be the volume of voids in the road
covering liable to become filled with water
and mud, and the sooner will the surface
become hard and smooth when opened to
traffic, or while being compacted with
rollers.
THE TELFoRD ROAD.
In Macadam's matured practice upon the
Bath and Bristol roads, England, he did
not allow any stone above three ounces in
weight (equal, with the material he had, to
cubes OF IL to inches in their longest
diagonal lengthy to be used. He caused
splinters and their spalls to be excluded as
far as possible, and laid considerable stress
upon uniformity of size and perfect clean
illness or freedom from dust, sand or earthly
matter.
Another road, named after Thomas Tel
ford, by whom it was first constructed in
Great Britain, is made with layers of broken
stone resting upon a sub-pavement OF stone
blocks. Telford's specifications for road
way 80 feet wide were as follows: Upon q
level bed prepared for the road, materials
a bottom course or layer of stones is to be
set by hand in the form of a claxe. firm
pavement. The stones set in the middle OF
the road are to be inches in depth; at
9 feet from center, inches; at II from the
center, 4 inches. and at 15 feet, 3 inches.
They are to be set on their proadest edges
and
LENGTHwIsE ACROSS THE ROAD
and the breadth of the upper edge is not to
exceed inches in any case. All the irreg-
ularities OF the upper part of the said pave
ment are to be broken off by the hammer,
and all the interstices are to be filled with
stone chips firmly wedged or packed by
hand with a light hammer, so that when
the whole pavement is finished there will
be convexity of inches in the breadth Of
Is feet from center.
The middle IS feet OF pavement is to be
coated with hard stones to the depth of
inches, of these inches ore to be first put
on and worked in by carriages and horses,
care being taken to rake in the ruts until
the surface becomes firm and consolidated,
after which the remaining inches are to be
put on. The whole of this stone is to be
broken into pieces as nearly cubical as pos
sible, so that the largest piece, in its longest
dimensions, may pass through a ring 2%
inches inside diameter.
The paved spaces on each side of the IS
middle feet are to be coated with broken
stones, or well-cleaned strong gravel, up to
the iootpath or other boundary Of the road.
so as to make the whole convexity of the
road inches from the center of the sides of
it. The whole OF the materials are to be
covered with a binding Of IL inches in
depth of good gravel, free from clay or
earth. L. E, STOFIEL,