The citizen. (Frederick City, Md.) 1895-1923, 1902-12-12
FASCINATING DANGER.
The Perils That Beset the Builders
of Big Bridges.

of Big Bridges.
The design of long bridge span is
one of the most elaborate mathemat-
zeal problems that arise in constructive
work. The stresses produced by it's
own weight. by the weight of traffic
by locomotive drivers, by tae hammer
ing of fattened wheels. By the action
of brakes on an express Grain. by the
high speed on a curved crack. by the
wind and by the expansion and con-
traction of the steel in summer and
winter are all accurately calculated
The detection of the loaded and I'M
loaded bridge is determined. and com
plete drawings are made of every men,
Der of IT, The bars of steel are tested
IN machines which will pull in two a
horsehair or a steel bar strong enough
to lift half score of the heaviest To-
comoives at once. and which will
crush an eggshell or steel column.
and accurately measure the stress in
each case. The different kinds of men,
bers are forged. riveted, bored or
planed in perhaps half dozen remote
shops. and. although usually not fitted
together there. are examined and meas
ured by specialists to see that they are
correct. and are then shipped by scores
Of carloads to the site of the proposed
structure. where steam derricks unload
them and pile them many feet high in
stacks covering acres of ground.
The bridge piers may rise above the
water hundreds of feet apart. 1t re-
mains to place them on a thousand ton
structure. high above a savage chasm.
over an impossible current or roaring
tide. where the water is deep. the bot
tom of Jagged rocks or treacherous
Quicksand. or where an old bridge must
be removed and the new one built in
its place without interrupting traffic
on the bridge. To accomplish this the
engineer has timber. bolts and ropes,
hosting engines. derricks and a band
of intrepid builders who have perhaps
followed him for years through more
hardship and danger than fall to the
lot of almost any other calling.
The complicated framework of
great span is skeleton with many
accurate joints and thousands of steel
sinewS and bones. each of which must
go in exactly the right place in exact
ly the right order. The builder must
weave into the trusSes pieces larger.
heavier and far more infiexible than
whole tree trunks. swiftly hoist and
swing them to place hundreds of feet
high. fit together the massive Orders
and huge forged bars with watchmak-
er's accuracy, support the unwieldy
masses until they are keyed together
and self sustaining. and under mil
lions of pounds of stress must adjust
them at dizzy heights to mathematical
lines. This he ruay need to do not de-
Rberately. but in dangerous emergen-
cies at utmost speed putting forth his
whole strength on narrow. springing
plankS in a furious tempest. in bitter
cold or in blazing heat. He may be
in the heart of an African desert, men,
accd y" hloodthrSty fanatics. or in a
gore IF the Andes. hundreds of miles
FROM I DIS OF supplies. where there is
ahso ~ no supplement to his own
rcso ..S. Under such conditions
ride builoing is one of the most fas
cina''H% and difficult of engineering
probls: : and requires Il different so.
luticn for almost every case.-Frank
w. Skinner in Century.