The river press. [volume] (Fort Benton, Mont.) 1880-current, 1912-06-26

sbout Is per cent. The careful engi-
seer will set his grade stakes not
more than ffty feet apart. and In no
Ease should they be over a 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. A slope Of
not less than one and one-half to one
should be used. Care should also be
taken to have the gutter grades 50 fixed
that there will he at least a 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
ue. The specific gravity, weight per
cubic foot and water absorbed are also
determined. With such data as this in
hand and a 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 a 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 nae
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 N
half inch stone of varying thickness.
This foundation should be thoroughly
rolled with u steam roller and not more
than a thickness of five or six inches
rolled at q time. On top Of this Is
placed a three or four inch layer Of one
and one-half inch stone, and after thor
oughly rolling a layer Of rock screen
fngs below three-quarters Of an inch in
size Is spread. This layer of screenings
should be sufficient only to I'll the sur
face voids of the wearing course and
should not be applied all in n layer.
Each application of screenings should
be rolled in before the next application
is made. After the surface has been
thoroughly filled with screenings the
road should be we'll sprinkled with d
watering cart and rolled with a 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 If specially devised spread
ing wagons are not used the stone
should be dumped on boards and spreai
from them on to the road. The con
tractor should be required to place
about a hundred tons Of No. 2 stone
and 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 onl!
from the macadam road in that it ha
l a hand paved foundation course, con
: sisting Of coarse stone eight Or min
! inches in its greatest dimensions
l These stones are placed on edge in tn
J subgrade by hand on their broades
bases and at right angles to the line o
, the road, and all irregular portions ar
broken off with hammers.
This type of road was first designed
: by a French engineer named Tresague
forty years in advance of Telford. Th
roads built by Telford had fiat sub
grades, but those constructed by Ire
saguet had cambered subgrades, whic'
are supposed to have the effect of
r keystone arch, and this is the form i
e which they are constructed today. !
e is rather an interesting fact that i
t France practically all Of the broke
q stone roads are of the Macadam type
q while in England they are largely Q
o the Tresaguet or Telford type.
n Experience has proved that the onl
e way in which roads a be kept i
e good condition and at reasonable cos
is by continuous and intelligent mail
o tenance. 1t is a mistaken although III
fortunately general impression til;
certain types of road are permanent
No permanent road has ever been col
structed or ever can be.
Cutters, catch basins and culver
le ought by all means to be kept cleal
]. and small gullies in shoulders shout
g be filled before they become too larg
g The loose stone which nearly alway
A. appears on the surface Of a macada
II road the first spring after it is but
x should be raked up and stacked for f
. ture use. Small holes and incipiel
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