Wichita eagle. [volume] (Wichita, Kan.) 1886-1890, 1889-11-24
THE FORTH BRIDGE.

Sir Thomas Bouch had taken in hand the
job of spanning the Firth of Forth, had
planned e huge suspension bridge and had
considerable work done on it when the lay
disaster put an end to the project at once and
forever. Ia the natural reaction of horror
there was a general protest against any
bridge, and very extensive feeling that no
safe one could be built In due time, how
ever, the question wac submitted to three
eminent engineers, Messrs. John Fowler, W.
H. Barlow and T. E. Harrison. After care
full inquiry they decided upon a cantilever Of
plan jointly devised by Mr- Fowler and Mr..
Barker, and the bridge thus arranged for Is
now rapidly nearing completion.
By glance at the annexed engravings and
Che following figures the reader viii see what
enormous difficulties they had to overcome;
and but for the rocky little Isle of Inchgar-
vie, in the middle of the Firth, the new
bridge would have been an impossib ility
That island is but mere point of stone, but
it is enough. On each side of it the channel
is nearly /, 200 feet wide, the water is over
200 feet deep, and yet the railway track, on
a level with the approaches on each side, is
252 feet above average tide To span such a
chasm with bridge sufficient to support the
heaviest trains and proof against the great
est wind tension ever known in Scotland,
was indeed task for engineers. Yet all in
spectors and scientific visitors admit that
they have accomplished it.
The structure is briefly classified as "can-
tilever truss double span bridge, all steel, and
the largest Of its kind in the world" The
material used is tested for an ultimate resist
ance Of thirty tons per square inch in tension
trrtr
therefore, sustain four times the combined
strain of a wind pressure of fifty-six pounds
TO the square foot and a maximum running
load of two tons TO the foot or s, 400 tons to
the span. 1t might be well for the North
British Railway company to have cards
printed with engineers certificates to these
facts and have one handed to each passen-
ger on the line just before the train reaches the
bridge, as passengers will certainly feel the
need of such an assurance Of safety If they
see the structure they are about to pass over.
The cantilever has the shape Of an elon-
gated diamond, and there are four masonry
piers supporting the four gigantic Legs" on
which are poised the balancing arms, and
these extend out Go feet on each side of the
,Dase. The old ''parlor magic" trick Of stick
hing two devastating forks into a cork to
make III Daia,lce anu danCe Oh eIA my, CIV S
some faint idea of the necessity for such inn
mense balancing arms. The middle canti-
lever is longer than the other two, it's base
being 370 feet long, while theirs are 155 feet.
The greatest height of the bridge above the
piers is $50 feet and the ends of the cantilever
beams are still $50 feet apart, SO they are
joined by lattice girders resting on the ends
of the arms With these figures, the reader
can see the enormous size of the diamond"
and the daring and extent to which the canti-
lever principle has been carried. Neverthe-
less, as the extension each way is equal, the
safety is as great as if it were on a smaller
scala