The Bennington evening banner. (Bennington, Vt.) 19??-1961, 1912-07-02

about 10 per cent The careful engi.
neer will set his grade stakes not
more than fifty feet apart. and in no
case should they be over hundred and
these will serve later for the macadam
work In grading ample material
should be left TO form the shoulders
Care should be used in properly slop-
ing cuts and fills to avoid as far as pos
sible settlement of material. slope OF
not less than one and one-half to one
should be used. Care should also be
taken 10 have the gutter grades SO fixed
that there will be ut least IA fall Of six
inches in each hundred feet in order To
provide surface drainage.
In general. any stone that is to be
used in road building should be test
ed for hardness, toughness, resistance
to wear and binding or cementing val
ne The specific gravity, weight per
cubic foot and water absorbed are also
determined. With such data as this in
hand and knowledge Of the volume
and character of traffic TO which the
road is subjected the engineer can
make an intelligent selection of the
best available material. While the dia-
bases. diorites and basalts, all com
monty known as traprock. in general
meet the conditions where macadam
roads are necessary. yet it is unwise to
select rock by species alone, as they
all vary greatly.
There are two distinct types Of bro
ken stone road in use today, known as
macadam and telford roads. The mac
adam road of today is so different from
the type specified by Macadam that the
relation is hardly recognizable. BY the
best practices used this road consists in
a foundation course of two and one
half inch stone of varying thickness.
This foundation should be thoroughly
rolled with steam roller and not more
than a thickness of five or six inches
rolled at u time. On top Of this is
placed three or four inch layer Of one
and one-half inch stone. and after thor
oughly rolling layer of rock screen
ings below three-quarters Of an inch i'll
size is spread. This layer Of screenings
should be sufficient only to fill the sur
face voids of the wearing course and
should not be applied all in one layer.
Each application of screenings should
be rolled in before the next application
is made. After the surface has been
thoroughly Glled with screenings the
road should be well Sprinkled with
watering cart and rolled with steam
roller until it is thoroughly bonded
This rolling should continue until the
surface ceases to wave in front of the
roller.
Stone should never be dumped on the
road and II specially devised spread
ing wagons are not used the stone
should be dumped on boards and spread
from them on to the road. The con
tractor should he required TO place
about a hundred tons Of No. stone
aud screenings at a convenient place
for each mile of road built for the pur
pose Of making future repairs
The telford road of today varies only
from the macadam road In that it has
hand paved foundation course. con
sistiug of cuorse stone eight or nine
Inches in it's greatest dimensions
These stones are placed on edge in the
suhcrade 10y hand on their broadcast
bases and at right angles TO the line Of
the road, and aii Irregular PORTIONS are
broken or with hammers
This type of road WAS first designed
boy "a French engineer named Tresaguet
forty years In advance of Telfoyd. The
roads built by Tcford had hat sub
grades but those constructed by Ire
saguot had cambered suhgrudes, which
are supposed TO have the effect of
keystone arch. and this is the form in
which they are constructed today. ID
is rather an interesting fact that in
France practically an Of the broken
stone roads are of the Macadam type.
while IN England they are largely Of
the Tresaguet or Telford type
Experience has proved that the only
way in which roads can be kept In
good condition and at reasonable cost
is 10y continuous and intelligent main
tenance 1t is a mistaken although I'M
fortunately general impression that
certain types Of road are permanent
No permanent road has ever been con
structcd or ever can be
Cutters catch basins and culverts
ought by all means TO be kept clean
aud small gullies in shoulders should
be filed before they become too large.
The loose stone which nearly always
appears on the surface OF macadam
road the FIRST spring after il Is built
should Doe raked mp and stacked FOR flu
ture use. Small holes and incipient