Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1883-07-03
TIE NEW NIAGARA BRIDGE.
A Novel Principle In lis Con-
strucIiOn.
Toledo (Canada) Globe.

The Canada Southern railway bridge
over Niagara is to be built at a point
300 feet above the present suspension
bridge. The contractors have en-
gagged, under a very heavy penalty, to
complete the whole by the first of
December next, about eight months
from the time of beginning operations.
The time occupied in building the
suspension bridge was three years. A
comparison will give an idea of the
vast progress made in recent years in
the art of bridge building. The new
structure will embody a new princi
pie never before illustrated by aRy
large work actually flushed. Two
similar bridges, however, are now
being constructed-one the new Tay
bridge over Firth of Fourth, Scot.
land, and the second for the Canada
Pacific over the Braser river, British
Columbia.
Bridges built after the new design
are known as cantilever bridges. Each
end is made up of a section extending
from the shore nearly half way over
the chasm Each section is supported
about its center by strong tower.
The outer arm having no support, and
being subject like the other to the
weight of trains, counter advantage
is given by the shore arm being an
chOred or weighted.
This style of bridges has been
adopted so as to avoid the very great
expense involved in the construction
of suspension bridge. The towers
on either side will rise from the water 8
edge. Between them will be a clear
span of 500 feet over the river, the
longest double track truss span in the
world. The shore arm Of each can't
lever having been built and anchored,
the other arm will be constructed in
sections of % feet. the whole being
made self-sustainiDg as each section is
added.
The ends Of the cantilevers will
reach only 375 feet above the towers,
leaving a gap of l2b feet to be filed.
The link will be supplied by an ordi
nary truss bridge, which will be swung
into place and rested on the ends OF
the cantilevers. Here provision will
be made for expansion and contrac-
ton by allowing play between the ends
Of the truss bridge and of the camille.
vers. At the same time the bridge
will be thoroughly braced SO as to
prevent danger from the lateral pres.
sure of the wind. The wave" motion
perceptible on a suspension bridge will
not be felt on the new structure.
The total length Of the bridge will
be $50 feet. 1t will have a double
track and will be strong enough to
bear two of the heaviest freight trains
extending tho entire length OF the
structure, and under side pressure
Of wind at seventy five miles per hour,
aud even then it is to be strained to
only one fifth of its ultimate strength.
The towers will not rest on bed
rock, 40 thS rush of the river would
sweep any caissons " other works in
tended to be used for EXCAVATIONS, but
The foundation will Be In the large
bCHldere that have dropped from the
cliff during the past ages, the crevices
being GllSd in With espsnt, making a
sptid foundation. TIE pressure will
be SO divided that upon tbe 1oHnda
ton rock II viii bspRly twenty Gye
pounds to the square inch. The top
Of the stone structures will be Atty
feet above the water level, and from
these the steel towers supporting the
caatiisgers will rise 100 feet. From
the toyer topaSs.ious up the whole
bridge WiII'bs Of bteel, sAsTy inch of
which will be subject Vto ythe most
rigid tests from the time IL leaves
the ore iG the time it enters the
structure.