Mower County transcript. [volume] (Lansing, Minn.) 1868-1915, 1873-02-13
LONGEST BRIDGE IN THE WORLD.
The Construction Of n Passn xc.way
Across the River Toy, Scotland.
From tho Mechanics Magazine,

OF cOnStructlCn, Will bo longest bridge
in the world-longer even than the
Victoria Bridge, Montreal. The VIC
toria Bridge is 9,194 feet long, while
fthe Tay Bridge will be 10, 321. making
difference in favor of the lay Bridge
of 4, l36. If the Thy Bridge were eighty
yards longer, it would be tvs miles ex-
actly, and for all intents and purposes
it may therefore be called q two mile
bridge, and will have ninety piers and
eighty-nine spans.
The details of this vast undertaking
are of interest. The work was to be
finished IN three years from May, 1871,
and the dimensions in detail are "a
follows:
Between the al,utment on the Fife
shore and the abutment at Magdalen
Point, on the Dundee shore, there are
to be eighty-nine spans, three of which
coming from Newport-wiu be 60
feet wide; two of 80 teet Twenty-Five
of 120 feet fourteen of 200 feet; sixteen
counting from the center of the
bridge to the Dundee side-of 12O feet {;
twenty five of 66 feet one of 100 feet :;
and six of 27 feet. The greatest height
of the bridge will 88 feet above high.
water mark. The bridge is slightly in
the form of an arch. Leaving from
the Newport side, the gradient is
one in 100 for three spans, and
and from this point it is only one in
353 until the centre of the bridge
is reached, and drops again with gra-
dient of one in: 73, and continues at this
until the Dundee shore is reached.
The piers are made double, and ere in
the form of cylinders, made of cast
iron, which are again filed in with
bricks. The quantity of cast iron re-
quired for the cylinders IS 1900 tons,
while the superstructure is all ma!lea.
BILE iron, $500 tons of which is requir-
ed. There are at present about ninety
men employed at the works. The con-
tract for the whole bridge was taken
by Mr.. DeBergue for 92l7, 1000.
The braced piles that will be used
from the north side weigh six hundred
and fifty tons in all. There will be
about thirty-six thousand yards of
brick and concrete work, aid some
eighty-seven thousand cubic feet of
timber. The operations IN the con-
struction of the bridge are peculiar.
The usual manner of laying piers of
the kind used for the Tay Bridge is to
erect heavy staging, from which cylin-
ders of the pier are guided into their
places. But in this case there is not
depth of soil for pile driving. The
cast-iron cylinders and brickworks are
first built on the shore, at the waters
edge, then doated into their places by
means of pontoons, and lowered
into position by hydraulic ap-
paratus. The excavating for the
foundation must be done with
great care, and is accomplished by the
ordinary air compression system. The
solidity and stability of the whole
structure must depend On the firmness
OF the base of the cylinders, and there
and strength in the cement used in the
brick-work and concrete. A piece of
the cement, one and a half inch square,
which had been used Oh December 10th,
and since then kept in water, was sub.
mitted to strain, breaking at eleven
hundred and twenty pounds, This
Gem ent becomes stronger the longer it
is kept in the water, up to q period of
five years, when it reaches its maxi
mum strength.
The first cylinder was foated into its
place on October of last years, and was
finished by November 29th. The three
rectangular piers are sixty-eight feet
high, measured from high water mark.
Two of the spans or superstructures of
therectangular piers are already placed,
while more are about ready. Four
Fier foundations are finished, which
are the most tedious part of the work.
The new plan adopted in the construc-
tion of these piers, which joins the two
pactness and strength in the simplest
way. The laying of the first six or
eight pier foundations is made more
difficult FROM the depth of the water,
which at full tide is about tbirty-two
feet and eighteen feet at low tide. The
bridge is for single line.