The Manchester journal. [volume] (Manchester, Vt.) 1861-current, 1913-02-06

pits, which are frequently termed gla'
clal gravels on account OF their direct
or Indirect association with ice action,
are quite widely distributed, and these
have been and may be used TO a
greater or less extent In road Improve
ment.
During recent geological history of
the continent the Atlantic and gull
borders have been submerged AT inter
walls. The ocean has advanced inland
a number Of times. During each OF
these periods of continental submer-
gence the harder rock remanents along
the inner margins Of the oceans al
vance have been rounded, worn down
deposited and redeposlted with vary
ing proportions OF sands and loans
and clays, thus forming beds OF gray
eli. which are today available for road
building purposes.
Gravel roads and macadam roads
alike have often received sweeping con
formations 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 I'm the construction of macad-
am roads is being quite generally rec
ognlzed. but unfortunately many anna
teur road builders seem TO think that
gravel roads may be constructed by
simply piling gravel on the surface and
leaving II 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 in the
case OF a macadam road. Moreover, In
the one case ms In the other speeifica'
tIons must be adapted to varying local
conditions. or course. the gravel itself
must he selected with care. That which
contains a sufficient quantity OF bind
ing material so that II stands as yer.
deal wall when II Is being excavated
5 generally the best. for the reason
hat this same binding material viii
re-cement the gravel when used for
road building
There are three important qualities
which should be possessed by road
building gravel hardness. toughness
md cementing or binding power. CT
these three qualities the last is the
most important This binding quality
is due IN part TO the presence OF oxide
IL iron, lime or ferrugineous clay and
In part 10 the angular shape and size
u the pebbles composing the gravel
Blue gravel Is universally conceded to
be the best for road construction, be.
cause IL Is usually derived from trap
rock As the pebbles composing the
gravel retain the characteristics which
they formerly possessed as a part OF
The larger rock itself, It follows that as
trap rock is considered an excellent
paterial for road building. trap rock
gravel should occupy the same relative
rank among the gravels Limestone n.
generally speaking. a soft rock, and
Consequently limestone gravel. which
Is quite rare, will usually be found
soft and win wear rapidly, Quart2
possesses practically no binding power,
although II Is very hard Therefore
gravel which contains an exception.
ally large percentage Of quartz VIII not
prove successful. as II viii fan 10 con
.olidaie unless II contains binding ma
erial. or unless good binder Is added
In order that the maieria may bind
readily the pebbles should be angular
and shanla vary IN size 80 that the
smaller fragments Uar fill the void,