Alexandria gazette & daily advertiser. [volume] (Alexandria [Va.]) 1817-1822, 1818-02-04

Extract from the Report Of l.. Baldwin,
Esq. Principal Engineer to the board
of Public Works, Tor the state OF Viz
GINA.
- The next Important objects are,
to shew the manner of construction and
expence Of q road, on the most improved
modern plan.
In France and England, great atten.
ton has been bestowed upon this subject
within few years. The roads are most
" from 25 to 50 feet wide, and construct
ed with great care,with foot-paths, dra'ns'
&c. Of the ost convenient and Perma-
nent kind. In the neighbOrhood ct great
towns, they are made wider. The con-
ssruction and form OF the road are adapt
ed to the nature Of the soil, the character
Of the country, and the facility with
which the materials can be furnished.
There seems to be three principal
forms in Europe. Others, or modliica-
tons Of these, are occasionally adopted.
The frat is a convex read, in which the
transverse section presents segment OF
a circle Of large radius for the upper sur
face, with bitches and drains on each
,iLe.-This is most generally practsed
in England aud France, and al'nsst with
out exception in this country. The Sc
conL is that in which the road is conca'e
instead Of convex that is, cross sec
ton OF the road gives curve line Of large
radius, drawn from centre above the
road tor surface. In this form, the wa
ter is drained off along the middle to side
drains, or over falls at convenient dis
tances, and is preferable to that made
convex, where there are small decll'it'es
and little water to collect on the road
This form i. sometimes used in paving
streets in town. This is the form OF the
pavements in Paris and some roads In
France constructed in this way have been
found very good-but believe it has ne
YER been in use here. The third kind
presents straight line from one side to
the other, 10 transverse section, having
small slope to lead Of the water to one
side only. This is seldom adopted in ie'
vel countries but where the road lies a.
long the side of hills or mountains, it is
the best form that can be applied.
If the making road and keeping it in
repair, were considered merely on me-
chanical principles, we should easily con-
clude that q perfectly level line would
be the best for the transverse surface,
making all wheels wide and perfectly cy-
lindrical to roll in parallel plains. But
natural difficulties prevent the former,
and use and inveterate habits render the
latter hopeless. Rains, snow, sc. falling
upon the road, increase the resistance,
and would soon destroy it if not divert
ed. All wheel carriages are formed with
narrow wheels, declining from the centre
of gravity of the load, and pitched gath
ering, so a. generally to throw up the
soft substance in its track, and deposit it
on the outside Of the ruts. To avoid the
Inconvenience which the water produ-
ces, a coucave, convex, or sloPing form,
has been adopted, BY which the water
may be drained of. But, as in moving
along an Inclined surface, the weight OF a
loaded wagon is not equally distributed
on the four wheels. but is lessencd on the
higher aud increased on the lower wheels
in proportion to the slope, by which ruts
are more easily formed, the conveIity or
lateral inclination Of the road ought to be
the least possible. This convexity has
been various in general it is from IL to
81 iuches-that is; where the road is so
feet wide, it is ls or 81 inches higher in
the middle than at the sides. For road
Of that width, 1s inches is enough and
where it is 10 be made Of hard and po.
rous materials, even less would do. 1t is
often observed, that Notwithstanding the
curvature in the surface Of a new road,
The carriaoe wheels soon wear out deep