The Republican. [volume] (Oakland, Md.) 1877-current, 1895-05-30
BODYBUILDING MATERIALS.
Not So Much Depends on the Rock
Used as the Manner of Its Use,

ROAD metal! Road engineers gen.
orally seek the hardest rock they can
find, and the principle is generally,
but not always, a correct one. The
object to be sought is hard, smooth
surface that will not grind or cut
readily under wheels, so as to make
dust or mud. 1t is sometimes said
that all rocks harden when exposed
to weather. This is far from being
true of all rocks, though it is true
OF some of them. Syenite, for ex-
ample, decomposes when exposed, as
do many other rocks which contains
soluble constituents. 1t should
moreover, never be forgotten by
those who undertake to make good
roads that the arrangement of the
materials is of as much Importance as
the materials themselves. Clemens
Herschel, an authority on this sub
ject, covers the case exactly when
he says:
GA common gravel sieve often con-
stitutes the principal instrument
whose judicious use will make a
good road out of a miserable string
of ruts and cobbly elevations. 1t
would be only necessary to sift out
and separate the soil under the road
to sufficient depth into cobbles.
coarse gravel, fine gravel, and sand
then replace them in the order
named and with the proper thick
ness of layers each. Wet down and
roll, and the result will be a good
road"
Feldspar, When feldspar de-
Gays, or when 1t is finely powdered,
it forms clay or kaolin. Now, every
one knows that clay should not be
used for a top dressing for roads,
for when dry it forms fine dust,
and when wet it forms mud, both
of which are Objectionable, both on
their own account and because they
mark the beginning of the destruc-
ton of the roadway.
Shales. For roadbuilding pur-
poses the shales may be divided into
two classes, clay shales and sandy
shales. The clay shales are entirely
unfit for such purposes; the sandy
shales are the only ones that should
be used for top dressing, The rea-
son for this is sooner or later the
rocks are crushed and ground up,
and that which is made of clay only
forms fine dust when dry and a
pasty sticky mud when wet. The
arenaceous or sandy shales. on the
other hand, contains so much grit
that they usually pack hard and
make a firm roadbed.
Limestones. was for
merly regarded as one OF the best
rocks for top dressing, and it has
been exclusively used for such pur-
poses. Ithas, however, proved very
unsatisfactory in the long run, and
in many parts Of the country the
limestone macadamized roads are
being taken up and reconstructed of
more satisfactory materials. The
rock wears easily into an impalpable
powder when dry and forms sticky
paste when wet. Hard limestone
makes an excellent roadbed, but
should not be used for surface dres-
sing.
Sandstones.-As a rule, sandstone
is not good roadmaking rock, but
if roadbuilders will observe the be-
havior of sandstones of differe
varieties they will find that some of
them make fairly good roadbeds,
while others will not. This differ
ence is due to the absence or presence
of binding material, and no more
specific directions can be suggested
than that clean sandstone contain
ing no binding materials, as lime,
clay or iron, should not be used for
surface metals. John &. Banner.
GrantsvIIle,