The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1912-08-08


pits, which are frequently termed gla
cial gravels on account of thei. diicc..
or indirect association with ice action.
are quite widely distributed. ana these
have been and may be used TO Il
greater or less extent in road improve
ment.
During recent geological history CT
the continent the Atlantic and gulf
borders have been submerged at ilte.'
vals The ocean has advanced inland
a number of times. During each of
these periods of continental subme:'
gence the harder rock remanents along
the inner margins Of the oceans ad
vance have been rounded, worn down.
deposited and redeposited with vary
ing proportions of sands and loans
and clays, thus forming beds Of gray,
ell, which are today available for road
building purposes.
Gravel roads and macadam roads
alike have often received sweeping con
demnations as unsatisfactory when the
cause of failure was poor construction
and not the character of the material
used. The need of care in grading and
drainage in the construction of macad,
am roads is being quite generally rec
ognized, but unfortunately many ANA
teur road builders seem to think that
gravel roads may be constructed by
simply piling gravel on the surface and
leaving it to be packed by the passing
traffic In point of fact. the grading
and drainage and other details In con
nection with the construction of a
gravel road should be done with as
much care and thoroughness as i'll the
case Of a macadam road. Moreover, III
the one case as In the other specifica
tions must be adapted to varying local
conditions. OF course, the grave! itself
must be selected with care. That which
contains sufficient quantity of bind
ing material so that it stands as a YER
teal wall when it is being excavatea
is generally the best, for the reason
that this same binding material will
re-cement the gravel when used for
road building.
There are three important qualities
which should be possessed by road
building gravel-hardness. touehnes.'
and cemcnting or binding power. OF
these three qualities the last is the
most important. This binding quality
Is due in part to the presence Of oxide
of iron, lime or ferrugineous clay and
in part to the angular shape and size
of the pebbles composing the gravel.
Blue gravel is universally conceded to
be the best for road construction, be-
cause it is usually derived from trap
rock. AS the pebbles composing the
gravel retain the characteristics which
they formerly possessed as part of
s1,o larger rock itself. it follows that as
rock is considered an excellent
=rial for road building, trap rock
.,vel should occupy the same relative
:'ank among the gravels. Limestone is.
generally speaking, soft rock. and
consequently limestone gravel, which
is quite rare, will usually be found
soft and will wear rapidly Quartz
possesses practically no binding power.
although it is very hard. Therefore
gravel which contains an exception
ally large percentage of quartz will not
prove successful. as it will fail to con
solidate unless it contains bindi:..r ~:
terial or unless a good binder is adG2 ID
In order that the material may b.n;l
readily the pebbles should be Angular
and should vary in size so that TIC
smaller fragments may gil the voide