The Findlay Jeffersonian. [volume] (Findlay, Hancock County, Ohio) 1870-1881, 1872-10-25
THE LONGEST BRIDGE IN THE
WORLD.
The Construction of a Passage WAY
Across the River Tay, Scotland.

The new Tay Bridge, now in cours,
of construction, will be the longes
Bridge in the world-longer ever
| than the Victoria Bridge, Montreal
The Victoria Bridgeis 6, 9,l94 feet long
while the Tay Bridge will be lo,s2l
making a difference IN favor of the
TaY Bridge of l,l36 feet. If the Tay
Bridge were eighty yards longer il
would be two miles exactly, and fol
all intents and purposes it may there.
fore ce called two-mile bridge, and
will have 90 piers and SO spans.
The details of this vast undertak.
ing are Of interest. The work was to
be finished in three years from May,
1871, aud the dimensions in details
are as follows:
Between the sbutment On the Fife
shore and the abutment at Mag
dalen Point, on the Dundee shore,
there are to be eighty-nine spans,
three of which, counting from New.
port, will be 60 feet wide; two of 80
feet; twenty-five OF 120 feet; fourteen
Of 200 feet; sixteen, counting from
the centre of the bridge to the Dun
dee side, OF 12O feet; twenty-five of
SO feet; and six of 27 feet. The
greatest height of the bridge will be
SO 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 one hundred
for three spans, and from this point it
is only enc in thre hundred and fifty
lhree until the centre of the bridge is
reached, and drops again with a grs-
dent of one in seventy-three, and
continues at this until the Dundee
shore is reached. The piers are dou-
BILE, and are IN the form of cylinder,
made of cast-iron, which are again
filed in with bricks The quantity
of cast-iron for the cylinders is 1900
while the superstructure is all mallea-
Bile iron, 5000 tons of which is re-
quired. There are at present about
ninety men employed at the works.
The contract for the whole bridge
was taken by Mr. De Bergue for
Ell, 900.
The braced piles that will be used
from the north side weigh six hun |
dred and fifty tons in all. There will
be about thirty six thousand yards OF
brick and concrete work, and 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 Bride 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
,ast-iron cylinders and brick-works
are first built on the shore, at the
waters edge, then foated into their
places by means of pOntoons, and low
sred into position by hydraulic ap-
oaratus- The excavating for the
oundation must be done with great
,aIe, and is accomplished by the Or
binary air compression system. The
'olidity and stability of the whole
structure must depend on the frmness
of the base of the cylinders, and there
must be great exactness in the itting
md strength in the cement used in the
orick-work and concrete.
A piece OF cement, one and q half
inches square, which had been used on
December 10, and since then Kept in
water, was submitted to strain, break
ng at eleven hundred and twenty
pounds. This cement becomes
tronger the longer IL is kept in water,
lp to period Of five years, when it
caches its maximum strength. The
irst cylinder was hoated into its
,lace in October OF last year, and
vas finished by Nov vember 20. The
hree rectangular piers are sixty
light feet high, measured from high
Vater mark. Two of the spans, or
uperstructures, Of the rectangular
'iers are already placed, while more
re about ready, four pier founda-
ion are finished, which are the most
edious part Of the work. The new
Ian adopted in the construction of
hese piers, which joins the two cyl
nders into one, gives great compact
less and strength in the simplest
Fay. The laying OF the first six or
light pier foundations is made more
iificult from the depth Of water,
7hich q: full tide is about thirty-two
eet, and eighteen feet at low tide
'he bridge is for q single line.
Mechanics Magazine.