The San Francisco call. [volume] (San Francisco [Calif.]) 1895-1913, 1895-12-08
HUDSON RIVER BRIDGE.
The Greatest Engineering Work UNDER
taken in the World.


taken in the world.
Scientific American.
The Secretary of War recently ap-
pointed board of officers of the Corps OF
Engineers to Investigate and report their
conclusions as to the maximum length or
span practicable for suspension bridges,
and consistent with an amount OF trafnc
probably sufficient to warrant the expense
of construction The leading features of
the design upon which the estimates were
made were as follows; A steel suspension
bridge having clear span of 5000 feet be-
tween the towers and carrying six railroad
tracks placed side by side. The floor OF
the bridge to be provided with stiffening
truss, which shall be hinged at the center
and be 100 feet in depth; the bridge to be
carried on sixteen cables, arranged eight
on each side; each cable to consist OF 5000
parallel steel wires wrapped together and
having a breaking strength of 2S,440 tons;
the diameter, inclusive of wrappings, be.
ing 21H inches. The estimated cost OF
the bridge is SO, 1S6,540.
From an engineering standpoint 1t Is not
the total length of a bridge that deter
mines its magnitude, but the length OF the
individual spans. The cost and construct
i've difficulties of rebuilding increase
at rapidly increasing ratio as tue span IS
heightened. The Tay bridge in Scotland
is twice the length of the Forth bridge to
zion of its TWO miles of short girders did
not call for the exercise of one-ffth part of
the skill and courage required in throwing
the huge spans of the Forth bridge across
the mile of deep water at the Firth of
Forth. In a like increasing ratio win the
difficulties multiply in stretching this
mammoth structure across the Hudson
River.
The seven wonders of the world, that ap
pealed so strongly to the ancents, will be
com pletely overshadowed on every point
of com parison by this GROWING feat of the
nineteenth century. If mere bulk or mass
be taken as a standard of comparison, 1t
will be bigger and heavier than the great
est of the works of the ancients; and in the
scientific knowledge involved in its con-
struction it will embody truths in chem
istry mathematics and mechanics that
would bewilder the Egyptian builders of
the pyramids even more than its vast
stretch of steel cables and Interlacing grid
ers.
The two masses of masonry that will
have to be built on shore to resist the enor-
nous pull of the sixteen cables will i'll
their united weight and bulk rival the
great pyramid of Ghizeh. The four steel
towers that carry the cables will each, IN
all probability, overtop the lofty Washing
ton monument and will be exceeded in
| height only by one structure, the Elffel
| Tower. Ethically, if we may so speak,
| they will stand loftier than the last named,
| inasmuch as the Eiffel Tower is merely
spectacular ''freak," whereas the four
great towers of this bridge will reach their
full stature as a part of great mechanical
structure erected for useful mechanical
| purpose.
When loaded to its full working capacity
the bridge can carry in midair, at height
OF $50 feet above the river, seventeen
heavily loaded freight trains, which, If
strung out in line, would be two miles IN
length. This would represent total load
of $4,000 tons. Moreover, it could carry
this load with large margin of safety in
a tempest of wind that would endanger
the stability of many of the adjacent
buildings in New York City.
1t is fortunate, judged from the esthetlc
point of view, that the great structure is
to be built on the suspension principle In
stead of the cantilever, as was at one time
proposed. Apart from the much greater
weight and cost of a cantilever bridge,
there is by comparison everything to be
said in favor of the light and graceful
appearance of the suspended bridge. The
lofty and tapering steel towers, with the
cables rising in long, sweeping curve to
meet them 500 feet in ny,dair, will form a
picture at once ma jestic aud beautiful.