The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1889-09-28

Spanish frontier His views were adopt
ed by all French engineers at the enc
of the last century, and it was in accord
ance with them that the Simplon and othe
great roads over the Alps as well as tn,
principal roads to France, were built unde
Napoleon.
The excellence of broken stone road
caused their universal adoption in the first
half of this century, and in only two parti-
culars have any Improvements been mad,
upon them to the present day. The frs
is in regard to the manner of breaking tn,
stone Maeadam caused the stone to b,
broken by hand on the side of the road
the size and weight of the hammer being
carefully specified. Now they are much
more quickly aud cheaply broken by
machine. These machines are driven by
steam engines and are of various sizes
capable of crushing from ten to two hun.
dred tons per day BY regulating the
width Of opening between the jaws, OF
within the cone, the sizes to which the
stone can be broken Is scorrespoudingly regu-
lated. and by the use of revolving screens
with openings of various size, the stones
of different sizes eau be separated and de-
hvered in separate piles of one-half inch,
one inch. two and one-half inches. etc.
The other improvement Is in the use Of
rollers 10 consolidate the road and give a
smooth. uniform surface instead of allow
ing this work to be slowly aud painfully
/ performed BY the vehicles using IL Horse
rollers we're introduced about 1884 and
steam rollers about 1860 There was for
some time discussion as to the relative
/ economy and merits of the two kinds Of
/ rollers. but this has now been settled in
/ favor Of the steam rollers. OF steam rol-
lers there are three principal varieties, the
/ first, known as'the Ballaison, or Gellcrat,
[ designed in France. the second known as
the Aveling and Porter, designed in En-
gland. and the. third, known as the Liudelof
I designed in America OF these the Ayel-
{ ing and Porter Is the best for macadam
roads. and the Lindelof Cor rolling plastic
{ pavemcnts.
Macadam roads are now everywhere Goa
s;ructed on substantially the same pTinCi-
ples. The ground IS tirsl cleared and level
ed Of the prescribed width, and If neccs-
sary. excayated 10 the depth of the road
covering. All ro1ts Of trees, aud soft aud
spongy spaces not aforiing a firm bearing
are removed and their places hllcd with
good gravel or broken stone The surface
Is then rolled wi,h heavy roller, in order
10 thoroughly compact il, If the Tcliord
foundation : uscd, 1t Is placed on the roll-
ed earth IN the form Of irregular stones
from SIX to eight inches ia size, carefully
placed in position and forming rough
pavement. on whjch the msesdam metal Is
placed. Ii the Telfarl foundation Is not
uscd, the metal Is placed directly on the
earth. in a uniform layer no, exceeding sIx
inches in depth. This Is then thoroughly
compactcd hy rolling with heavy roller
for several hours. uniil the metal will NOT
Weld under the ruler Another LAYER IT
broken stone 81 the same depth is then
placed on the iirsi aud cumpacted IN the
same manner Fiaallya layer of from enc
70 Two inches in depth Of very tine broken
stones or gravel. not exceeding thrcc-
fourshs 1t an inch in the largest iimcu.
siuns. IS spread on The surface. aad this in
turn ! eompae,ej by rolling. The rad is
then Ees,iy foF use. The rolling Is gre4lly
facilitated and the oompac,ness Of the rad
increased by thoroughly sPrinkliag each
layer in eonacction with the rolling. la
many cases the total thickness cf the maca-
dam ) only eight inches, instead oi lxelyc
To thirsocn inshcs
The Gust Of such ryssds depends chiefly
on two factors, the prioc OF labor and the
priee Of broken stone. In addition 80 this
i the COS, of culyerts and bridges, which
must be provided for any rad, whatever
the rad surface may be The price Of
broken stone varies from 20 cents "a s.
per ton, depending On the character of the
stone and the distance which !, has 30 be
hauled For a road 80 feet wide aud 9
inches thick. about ) 500 tons are rcquircd
for each mile in length. The cst Of the
road surface alone Is about $4,000 per
mile The cost Uf erabankment, cxcaya-
ton. eulverts, dnins, stone cutters, etc,
may carry the Gust up 20 s7o,0a0 pcr
mile
These fgnnz nigh, even be increased
in the ease Of roads tFaycrsing noun
tainous distric,, where expensive cnlhank-
menis. cuttings in rock and earth, retain.
ine sails, etc, would b. Necessary The
laying out Of such roads calls for the same
surveys aud the same engineering skill as
in the laying out Of railways.
The shape or eross- section 20 BE- given
TO the road has been the subject of mach
discussion in the past Roads which are
much rounded in the centre shed the water
very easily, but, on the other hand. they
are very uncomfortable for vehicles. There
has also been much dispute as TO whether
the cross shape Of the road should be
curve. or should consist Of two straight
lines meeting at the centre It Is now
generally conceded that the cross- section
should be a curve, and that the height Of
the road should be about one sixtieth Of
It's width, 1 2, in roads 30 feet wide the
centre should be inches higher than the
sides, in roads 40 feet wide it should be 5
inches, aud so on in proportion TO its width.
The great cost Of macadam roads, and
the comparative lack of necessity for them
in consequence of the enormous develop
ment of railways, has prevented their con
struction TO any great extent in America.
The National Road, which was intended
to form the great highway across the Ale
ghauies from the Potomac to the Ohio,
was begun under authority of Congress
about sixty years ago, but it had only pro
gressed a short distance beyond Cumber-
land, Maryland, when its construction was
abandoned, in consequence of the building
of railways for the same purpose. Macad-
amized roads have therefore been confined
to city or suburban streets, and to a few
of the older States in the East Even the
turupikes, or toll roads, originally built by
corporations which made their profit by
levying toll on each passing horse or vehicle,
were macadamized only for small portion
of their width in the centre, leaving earth
roads on each side. These latter were
habitually used in summer, leaving the
+; hard central portion, whose surface was
seldom kept smooth, for use during the
rains and mud in winter.
With the exception of these few turn
pike high-roads, American roads have been
built of whatever material was nearest at
hand. Frequently, if not generally, they
were made by simply plowing ditch on
| each side and throwing the earth into a