Mexico weekly ledger., 1878-02-28

HINTS ON ROAD MAKING.

Il go - RE
HINTS ON ROAD MAKING.
Roads are essential to the devet-
opment of the natural resources of
| all countries, and therefore, consti-
tute y primary element of progress.
In America the rail road has super.
seeded the extended thoroughfaTes
of former systems. Nevertheless,
rock roads still maintain their I'M
portance as feeders and auxillaries
to the highways of modern transport
tation. On this account we may De
pardoued for advancing a few hints
on road making.
In laying out new roads great care
should be expended on securing easy
grades. There should be also, as lit
tie deviation as possible from a
straight line between commencing
and ending. The importance of easy
grades is often not as highly appre-
ciated, nor as well attended TO as it
ought to be. 1t requires only a force
of 264 pounds to move a wagon weigh
ing 6 tons along a level macadamized
road, and yet on one having an as
cent of one foot in seventy, a force
| of 400 pounds is requisite for the
| same rate of speed. The declivities
| down which horses can trot with
safety, vary with their character. In
paved roads they may be l in 63. In
macadamized, l in So; in those con-
| structed of gravel, l ia 10, have been
allowed. r
Engineers have differed o good
! deal as to the best traverse form OF
| road beds. Undoubtedly the center
| should be more elevated than the
| sides, but roads can he kept free OF
both water anl mud by a slight in
clination lengthwise, than by any
form that can be given to their cross
sections. Roads but little raised in
the middle arc easiest OH Wagons
and do not as readily cut into routes
as those that confine transportatien
to their centres. Perhaps the best
rule for crop sections is an inclina-
ton of one foot in thirty on the sides
| with q few feet i'm the centre ON a fiat
curv0
Different opinions also obtain as t"
whether the bed for the material OF
which the road is to be constructed,
should be fiat or rounded. Those
that prefer it TO be fiat consider that
there should be a greater depth uf
material at the centre than ut the
sides, while others are of the opinion
that the covering ought to be Of uni
form thickness.
The first thing to bc attended TO in
constructing a road is its foundation.
The great majority of our roads have
no artificial foundations. In most
instances the surface on which the
material is laid is in its natural con-
ditIon.
Teeford aud Macadam held differ
ent opinions as to the propriety of
such construction. Teeford consid-
cred that it was highly Important to
have Il good foundation. lie made it
OF stones varying in depth from 8
inches in the centre to 3 inches at the
sides. These he placed upon their
broadcast surfaces and upon them,
spread IA coating of broken rock, not
exceeding six inches in thickness.
On the other hand Macadan pre-
ferred soft and Welding foundation.
His roads were formed entirely OF
angular pieces of stone, capable of
being passed through a ring of two
and q half inches ia diameter. Ills
plan has now fewer advocates than
that of Teeford's, or than the one
subsequently, proposed by Mr..
Hughes, who insisted on a concrete
o~fgrayel and lime for foundations, at
the same time experience shows that
broken rock on Macadam's plan is the
best covering, whether roads havearti
fetal foundations or not. The streets
of ST. Louis are constructed Of Maca-
dam, but as they are toe level to
drain, they are covered with mud in
winter and dust in summer. The
same Inconvenience are experienced
in Mexico.
Little need be said further ofdrain-
age. The Importance of attending to
it is generally apparent. In addition
to what has been already advanced
on that head, we will only add that
bitches should be constructed from
every depression where water has n
tendency to accumulste.