Demoine courier., 1855-07-26
The Niagara Suspension Bridge.

The Buffalo Democracy Of Thursday
has a lengthy article upon the subject OF
the railway suspension bridge over The
Niagara river, from which WI gather
some int resting facts, not heretofore
published. The span Of the bridge is
S2l feet 4 inches; yet an engine. tender,
and passenger car, loaded with men. and
weighing altogether Al tone, depress the
long floor in the entire but 81 inches
The bridge, laden with a loaded freight
train, covering its whole length, and
weighing 326 tons, is DETECTED in the
MIDDLE only 10 inches A freigh, train
,raversing the bridge at the speed of five
miles an hour communicae YES no jar TO
passengers walking upon the carriage
way below. The land cables of the
bridge do not ,remble under 1.-THE slight
concussion of the superstructure do nc.
go over the SUBMITS Of the towers
Fas. anchored with stone, and grouted
in solid rock cut down TO the depth OF
twenty five feet, the great cables are i'm
movable by any mechanical force incl
dental to the use Of the bridge, or the
natural influences il will be subjec. to.
The ultimate strength of these cables is
10000 tons. The total weight Of the
material of the bridge, and OF the traffic
to which it will ordinarily be subjected.
is 2,262 tons, 10 sustain which the en-.
cineer has provided in his beautiful and
scientific structure, a strength Of 1900
tons. He demonstrates too, tina: while
The strength Of the cables is nearly six
times as grea,h as their ordinary tension,
that strength wiW never be impaired by
ribration. There are in the bridge ga
"~sus2enders," each capable Of sustain
ing 80 ,ons-and all CT sustaining 1920
tons. The weigh, they have ordinarily
to supper, is only, 1000 tons. Bot the
engineer has skillfully distributed the
weight of the bnr.hens. by the means of
'.girders'' and "trusses." These spread
the 81 tons heit of a locomotive and tend.
err over a length Of 200 feet. How am
pie is this provision against defective
iron or sudden straIhsl The rock upon
which the work relies on the New York
side of. the chasm is 100 feet long, 20
fee. wide, and 20 feet deep. 1t weighs
I60 pounds to the cubic foot, and pre-
SCENTS a resistance of $4,000 tons, exclu-
sive of The weight Of the superincumb-
ent masonry and embankment. The
limestone OF which the lowers are bull,
will support a pressure of 500 tons on
each square foot, without crushing
While The greatest weight that can fall
upon the lowers will rarely exceed 600
tons, a pressure of 80, 900 tons would be
required 10 crush the top course. There
are 400 tons weigh. IN each OF the ow
ers on the New York side. Among the
interesting CHARACTERISTICS OF the bridge
is it's elasticity. The depression under a
load commences at the end Of course. and
goes regularly across. After the passage
OF a train the equilibrium, is perfectly re
stored. The elasticity of the cables is
fully equal to the task. and wW never
be lost. The equilibrium of the bridge
is least afe in colo weather. Ii a
change of temperature Of 100 degrees
shouIG take place, the difference in the
level of the floor would be 2 feet 4 inch
es. So solid is this bridge ir its weight
its stiffness, and its staying, that not he
slightest motion is communicated to it by
the severest gales of wind that blow up
through the narrow gorge which it spans.
The cost of this great work was only
at is" saws the Democracy.
"Wquestionably the most admirable
Work Of art on this continent, and will
make an imperishable monument TO the
6femory of its enginineer JOHN A..
Free Press.