The herald., 1896-07-26


scription, except tramways and the like. !
These roads may be classed In two main Y
subdivisions: Highways, whichEaVerse |
the agricultural districts, with their
tributary lanes, and the streets and al
leys of cities and towns. These two d.
visions require separate consideration,
not alone from the differing classes OF
traffic passing over them and the vary
ing conditions they have To fulhll, put
also from the difference OF materials
used in their construction. l VIII, there-
fore, here only attempt to treat or the
agricultural or country roads, nor will
| enter into any scientific discussion, bu.
endeavor to confine myself to facts ana
figures comprehensive to the unframed
mind. Having now briefly outlined the
history of road building from the time
of the Roman empire. it would not be
out of place to give few ideas as to the
proper methods to be followed in modern
road building. 1t is not AsWays adVlsa-
bic to economize too much IN the original
construction, as in that case the annual
expense of maintenance (Which should
bear the same relation to the construc-
tion expense that interest bears to in
vested capitaD will soon become so |
| ereat that the original amount sinks into |
| insigniflcance, even if the wear ana tear |
of the traffic does not soon necessitate
| a reconstruction of the entire work.
! Many persons imagine road building |
to be one of the simplest of works,
| whereas it is one of the most complex
| subjects that can engage the attention
| of an engineer, requiring much Juog-
ment and experience on his part to OBJ
| tain the best results at the least cost
| He has first to study the country through
| which the road is to be constructed, so as
| to select a line which, whilst being as
| short as possible, shall conform with the
accepted rules controlling grades, curves
| and drainage. The Romans built their
| OF atrht irrp obstacles.
and this would, without doubt, be the
| correct principle did it not almost al
| ways entail too great an expense in con-
| struction that the other requirements
might be fulfilled, or some obstacle sue
| cessfully passed. The conditions, there
fore, first to be considered are the align
| ment, proper gradients, curves and econ
| omy of construction. These conditions
must be carefully and judiciously con-
sidered and location fulfilling them
settled upon before an economical road,
| both as to cost of maintenance ana
TRANSFORMATION, can be constructed. Too
much care cannot be given to the sub
ject of grades, and especially as to the
maximum grade that should be admis-
sable. The Importance of this cannot
be more strongly impressed upon the
mind than by calling attention TO the
fact that upon a macadam raod in fair
condition, and on a level grade, the force
exerted by a horse to draw any load is
equivalent to about one-thirtieth OF the
weight of that load. whereas in ascend
ing q grade the horse is called upon to
exert force nearly equal to the load,
divided by the rate of grade For in
stance, If a horse can haul 5000 POUNDS
on a level road, the same horse could
haul only about 167 pounds up grade
of one in thirty.
! One of the greater expenses in con-
structing roads is the moving of ma
l toll II a q
be borrowed from the surrounding coun-
try for the purpose of filling, or disposed
| of from excavations, therefore the engi-
reer should balance the excavations and
the filings so that the superfluouus ma
terial in one place could supply the de-
ficiency in another. and the shorter the
distance for transporting this material
the better. The proper drainage of a
roab is another very important cohslu-
Grafton. 1t was formerly thought that
an alternate rise and fall in the grades
was advisable, even when artiicially
| made, it being claimed that thus the
drainage was facilitated, and that the
| alternate increasd and decreased exer-
ton was less firing 70 the horse. The
fallacy of the last of these suppositions
was, think, conclusively proved by
the example previously given, of tbs
comparative eXertion necessary for
horse to move a load on a level and OF
ar ascending grade. AS to the drainage
idea ii NAV he of soro .. ah5oa cdnc1, fei
once attained; besides which. ther,
should be no place on well located
road but could be Satisfactorily
drained by the means of side bitches.
The next point to be considered is the
necessary width of roadway. Varying
opinions have been expressed by au-
thorities upon this subject. but it would
seem that after minimum width has
been established, to be only a matte,
of how much traffic the road is designed
to accommodate. l belive a general
width of thirty-five feet for main roads
to be sufficient and for tributaries from
one-third to one-half of this width.
| select thirty-tive feet because it gives
: SUFFICIENT room for several teams to
: ! work in the same section and for the
. largest teams to pass on curves of 100
] feet radius. In close connection with
, this subject of widths is that of admis-
; sable curves. If we adopt the width of
{ thirty-fve feet, then the shortest radius
{ should be eighty feet for the interior
| curve
All highways on main roads should be
made of broken stone Cor metaled, as it
is called), although the subsidiary roads
may be built entirely of earth when too
heavy or constant traffic is not expected
Where it is intended to construct a road
of this class the ground along the line
Tor its entire width should be thoroughly
cleared off and the natural surface eX-
caVated to such a depth as will insure
the absence of all vegetable matter:
these excavations should be filed with
good clean earth and the entire surface
well watered and rolled. The material
to compose the roadway should then be
spread in layers of from four to five
irches deep and each layer, after moist
ening thoroughly, rolled to the desired
shape-this shape is a matter of much
Importance and will be described later.
All roads should where possible. be
raised above the surrounding country
and furnished with side bitches for
drainage, as will hereafter be de-
scribed.
In the construction of highways more
care is necessary than in the foregoing
class The foundation should be pre-
pared. as in the previous case. only at
intervals of every forty or fifty feet;
trenches should be dug across it one foot
wide and varying in depth from four
inches at the center to six inches at the
sides: these should be filled with coarse
gravel to facilitate the drainage of the
sub-grade; half pipes filled with gravel
would be better. but are too expensiye
After the bed is thus prepared broken
stone should be spread thereon as fol-
lows:
The stones of the bottom or foundation
course should not exceed two and one
| nalt inches and be as near cubical in
| form as possible. 1t is found that when
a NJ l,ax- IL 49,