, 1872-10-11
THE LONGEST BRIDGE.
Constructed Of q Passzge-"1y Acroos
the River Tay, Scotland

Constructed of a PasszEc-Wny AcroB8
the River Tag, Scot1and-
From ttz Mechanics Acga-tne.
The new Tay. Bridge. now in course Of con, :,
struction, Will be the longest bridge IN the world
longer even than the Viceoaa Bridge, Mon
t1eal. The Tictora Bridge is 9,194 feet long,
while the Tav Bridge Will be 10,3o1, maling :
Difference IN favor % q TIE LAY brage % OF 11So ;.
longer, it would be two miles exactly, and for Ill
infants and purposes it n1sy therefore, e.cal1ed
two-mile bridge, and Will have ninety pie1s and
eighty-niue spans-
Ihe details OF this vast undertaking n1e OF
interest. The work vas to oe finished in threo
years from May, 1871, and the dimensions In d.
tail are as follows:
Between the abutme1s. on the Fife shor and
sho1e. there are to be eishty-nine spans, three
OF vhich-connting from Newport-wll: he 90
feet wide; two OF so feet; twenty-five CT l2D
fest; fourteen OF 200 feet; si1teen-cor in1:ag
side-of 100 feet: twenty-five Of 66 feet; 'one OF
1855 feet, and si1 OF q feet Tho -eateeE
height Of the bridge VIII be s. feet zhoV high
water mark. The bridge is slightly IN II 9 form
Of an arch Leaving from the Newport 'de, tho
gradient is one in 100 for three spans ar d from
this point it is only ore in 351 until the cen:1e'
of the bridge is reached. and drops again with =
gradient Of oce in 13 end continues ut tn Is 1inS
the Dundee shore is reached The 2: :e1s are
1nede double, and a1o in the foT1c Of cE ilndeis,
made Of cast iron, which ia again TILED IN with
bricEs. Tho quaniity OF cast iron 1equired
for tile cylinders is ,6U0 tons. while tht. super
structure ia all n1sl'eabIe iron, 5000 tons Of
which is required There ere at present about
uiuety men employed ut the works. U,e con-
tract for the whole bridge was taken by Mr. De
Berge, for E217. .0G1.
Tie hraeed pies that will be used from the.
north side weigh go tons in all There VII be
about Ihir:y-6;I Thousand yards OF brick and
concrete work, nrd some cighty-Ee7en Thousand
cubic feet Of timber. The operatanns IN the
construction Of tie bridge are peculiar: The
usual manner q laying piers OF the Kind used
from which cylinders of the pie- are guided in:o
their places. But in this case there is nos
depth Of coil for Pile-drivins. The cast-iron
cylinders and brick works are tirst built on the
their places By means Ct ,pontoons and lowered
into position By hydraulic apparatus The ex-
ca5ating for the foundation must be done with
great care, and is accomplished BY the oIsll-
stoiidity 1a'f & :na 'gaA s4sbiIiiy OF he Whole
structure must depend ON the frmness
Of the base Of the cylinders; and there must be
great exaciuess i'll the fitting and strength II
the cement used in the br1ck-work and concrete.
1 piece of the cement, one and half inch
square, which l,sd been used on Dec. IS, and
SINCE then kept in water: WIS submitted to
strain, breaking at i, ,l2o pounds This cement
becomes stronger tho longc. 1t IL Kept IN fne
water: up to period Of FIVE years; when it
reaches its maximum strength: The first cyliu-
der Nss Hoe.ed into it's p1aee in October of last
year, and IVES finished by NOT ~ The three
rectangular piarB arc s:z:x-elsht feet hlgh Meas~
ured from hish-wster mark. Two Of the e2ans,
or superstructmes, Of the rectangular piers are
already placed, while mere are about ready
-Four pier foundations are finished, Ealcn are
the most tedious part Of the work. The new
plsn adopted in the construction Of these paeta:
which joins the two cylinders into one, gives
craat compactness and strength IN the simplest
Way. The laying OF the first SIX or eight pier