The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1872-10-16
The Longest Fridge in the THorid--Fhc
Construction Of "a Pa&snse-N y
Across ti,e Riycr Tay, Scotland.

The new Tay bridge, now in course OF
construction, will be the longest bridge IN
tie word-longcr even than the Victoria
bridge, Montreal. The Victoria bridge Is
9,194 feet long, while the 'fay bridge will be
1921, making Il difference in favor o. the
Tav bridge of 1876 feet. If the lay bridge
were eighty yards longer it would he two
miles exactly, and for all intentS and pur-
poses it may therefore be called two-ml!c
bridge, and will have ninety piers and eighty
nine spans.
TIE details of this vast undertaking arc OF
interest. The work was to be finished III
three wears from May, 1871. aud the d!nlen.
si0ns in detail are d follows:
Between the abutmcnt on the Fife shore
ana the abutmeai at MagdalGn Point, on the
Dundee shore. there are to be cighly-Nnc
spa,i.-thrce Of Which. counting from New
nar;. will be Ga feet wide; tWo OF 81 feet
tweutv.two Of 100 feet fourteen OF 200 feet ::
sixteen, counting from the centre OF Tue
bridge 10 tie Dundee ,idc, Of l2O feet tWeli.
tv-uYc of GG feet; oic Of $50 feet; ana SIX
OF q feet. The greatest hci-l OF Tie Drlu2c
will be IS feet above hl%h-Wulci marx. 1he
bridge i. slightly in the iorIn ola arch. LeaE-
Ing from the Newport side. tine gradient IL
one in 100 Tor thee spans. and from TINS
point it Is only one III 353 until the centre CT
the bridge is reached, and drops again vita
q Gradient of one in Is. and continues ut ms
until the Dundee shore Is reached. 1De
piers are made double, and are in the form
Of cylinders, made Of cast-lron, when are
again filled in with bricks. Tue quantity OF
rVst-iron required for the cylinders Is LOW
tons, while The superStructllrc Il all miIea-
bic iron. $500 tons OF which Is required.
There are ut present about ninety lnen en-
ploved ut the works. The contract for the
whole bridge was takcn BY Nr. De BerSle
for E21T ,0G0.
Tue buced piles that will lie used from
the north side weigh six hundred aud htlS
tons in all. There will bc about thir!y-slz
thousand yards OF brick and concrct" "oIk,
and some eiXhty-seEen thousand cubic lcct
Of timber. The operations in the e0DstrHc,
ton of the bridge are peculiar Tue usuul
manner of laying piers of the kind used for
the Tay bridge is to erect heavy staging,
from which cylinders Of the pier are guided
into their places. But in this case there is
not depth OF soil tor pile-driviny. The cast
iron cylinders and bllck-work are first built on
the shore, at the waters edge, then lloatcd
into their places by means of pontoons,
and lowered into position hy hvdr0u'
Tic apparatus. The cxcavatirg for tie
foundation must be done with great care,
and is accomplished by the ordinary cir
compression system. The solidity and sta.
bility of tie whole structure must depend
on the firmncSs of the base OF the cylinders,
and there must he great eXactness in the
fitting and strength in the cement used in
the brick-work and concrete. \ piece OF
the cement Zone and n half inch square,
which had been used on December 18th, and
since then kept IN water, was submitted 10
grain, breaking ut l,l20 pounds. Thi:
cement becomes stronger the longer 1t i:
kept in the water, until 8 period OF
five years, when it reaches its maxi
mum strength. The first cylinder was
floated In lis place on October Of
last year, and was finished by November 29th,
| The three rectangular plers are sixty-eisht