The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1883-08-02

I'VE MARVELLOUS STRUCTURE WHICH u n
spAX TVS RUSHING sCorCu CHANNEL.

wr90Kum& b1n0 = OEesss
rur MARVELLOUS STRUCTURE WHICH Is TO
SPAN THE RUSHING SCOTCH CHANNEL.
fsoston Advcrtsscr.I
new bridge, whose structure seems al !
most wonderful, Is TO be thrown across the
River Forth, Eve miles west OF Edinburgh'
scotland. This has been In contemplation
for wears. but the width and depth OF the
channel have until lately proved 100 much
for the engineers. Its necessity Is avpa.
rent. All the railroads on the east side OF
Scotland from the South hod a termhus al
Edinburgh. but. In order to make con-
rccs,on with the roads TO Perth, Dundee.
ynverness. and Aberdeen, y has been ne
~.ssarv either TO 60 due west Twenty-Five
miles 70 Stirring, where the Forth Is
hr;dcea, or 10 have FIVE miles ferry
transfer across the river Just above Edin-
burgh. .,
che occasional danger and inevitable incon.
yepience az ierriage across roadstead OF
that width open TO the easteriy winds.
In these DAYS OF rapid transit this Is no
longer endurable. The plan adopted by
the engineers, Messrs. Fowler and Baker.
"a striking example that necessity IL the
mother OF invention" The bridge will be
stretched between North and South Queens
ferry. six miles above Edinburgh. AT this
point the river Is one mile and one haiti
broad, and half mile from the north
shore Is the small island OF Inch
vpryjeld. This would make compare.
fiyely easy problem were II not that the
sleuth OF water precludes any piers for
more than half the distance. On the north
the channel Is 210 feet deep. and on the
south at least $50 feet. IL is out OF Inc
question TO try TO sink caissons so Jar. SIR
Thomas Burch. who built the ill-starred
Tay bridge, proposed SUSPENSION. This
would have required for the cables two
stone towers on the island, each 500 feet in
height, and on either bank OF the river one
YS4f feet high. They can be better appreci-
ated when il Is said that the towers OF the
BROOKLYN bridge rise but 271 feet above the
East river. This idea was speedily given
up. and the present one adopted. 1t
should be said that as yet Ii Is only plan.
Several hundred men are ut work prepar-
ing the approaches, but the bridge is not
constructed. The plans, however, have
been approved by the best English engi--
neers. and there is no reason to apprehend
failure.
The principle is a very simple one. An
ordinary pier structure runs out O little
way on either bank, On the edge OF the
deep channel near both banks four stone
piers are placed in a group, and similar
cluster will stand on the south side OF the
island. Upon these three supports Will rest
the entire weight OF the bridge. Upon
each one will be poised an immense cap OF
steel, made in the form OF an elongated
lozenge, with the long axis representing
the line of railroad. The middle one
will rest on the four island piers, which af
D. nil n,
out on either side SO feet. The two
from the shore piers will come within $50
feet OF meeting the centre one. and. TO fill
the gaps aud resting upon the cages, two
steel lattice girder bridges will be hung.
The middle cage will exactly balance upon
its support, but the other two will have to
reach out further over the channel than to-
ward land, and the balance will be made
up by weights. In order TO give the neces-
sary stiffness to such span from single
base, the structure has to be stiflened in
every manner. The plan OF the elong-
ated lozcnges gives each one height
above the pier OF $50 feet, soping up
from the pier and down from the top to
the connecting lattice-bridges. These
lozenge-sbaped affairs are really steel
cages, 100 feet wide at the bottom and only
30 feet at the top. This inward slope gives
the strength OF trestle support, for all the
weight falls upon the piers by uprights, and
now by the arch principle from the side.
The upper sides OF the lozenges will be
straight and the lower ones curved, while
the tracks will run along their horizontal
axes. 165 feet above the top Of the riers,
which will also be the altitude of the two
connecting steel girders. This balance, or
cantlever, principle has never been used
on large bridges before, and its introduce
ton here will make one which will eclipse
as an engineering wonder the famous Br-
tannia and Victoria tubular bridges. Some
idea Of the magnitude Of the work can be
gained by knowing that it will take
$4,000, 900 and several years. time.
At present the piers on the south side
are being put ina gigantic undertaking
i'm itself. On the north side, they are
nearly completed. The bridge will he Of
steel in every part except the piers. 1t
viii thus be more costly, but lighter and
more durable. When done it will work a
revolution in the manner Of building long
spans across deep-water channels.