Walker Lake bulletin. (Hawthorne, Nev.) 1883-1926, 1902-11-21
A PERILOUS CALLING
Difficulties and Dangers Met With
In Bridge-Building.
Mammoth steel sinewa Must Be
Woven Into the Dizzy Structures
with Math emstIcaI Accnr-
racy at All Times.

The design OF long bridge span 10
one of the most elaborate mathemat-
icnl problems that arises in eonstruc-
tive work. The stresses produced by
lis own weight. by the weight of traf-
fe. by locomotive drivers. by The ham
uerirg of iiattene1 wheels, by the
action of brakes on an express train.
by the high speed of curved track.
by the wind and by the expansion and
contra ctien of the steel in summer
and winter, are all accurately calcu
lated. TIE definition of the loaded
and unloeded bridge is determined.
and complete drawings are made of
every member 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 a score of
the heaviest locomotives at once, and
which vii crush an egg shell or
steel clinu, and accurately measure
the stress in each ease. The differ
cnt kinds Of members ale forged, riv-
eted. bored or planed in perhaps half
n dorm remote shops. and although
usually not fitted together there. are
examined aud measured by special
lists to see that they are correct,
and are then shipped by scores of
ear loads to the site of the proposed
structure, where steam derricks mn
lond them and pile them many feet
high in stacks covering acres of
ground.
The huge piers may rise above the
20 II g. IA
mains to place on them 1.O00-to
structure. liigh above a savage chasm,
over an impa ssahle current or roar
ing tide. where the water is deep. the
bottom If Jagged rocks or treacher-
Gus quicksand, or where an old bridge
must be removed and the new one
built in its place without interrupting
navigation or obstructing continuous
traffic on the bridge. To accomplish
this the engineer has timber. bolts
and ropes. hosting engines derricks.
and band of intrepid builders, who
hive perhaps followed him for years
through more hardship and danger
than fall to the lot OF almost any
other calling. writes Frank w. Skin
ner. in Century.
The complicated framework of
great span is skeleton with many
accurate joints and thousands of steel
sinews ard bones, each of which must
20 in exactly the right place in ex-
actly the right order. The builder
must weave into the trusses pieces
larger, heavier and far more inf,ex-
ible than whole tree-trunks: swiftly
hoist and swing them to place hun.
dreds OF feet high: fit together TIE
massive ri-.inrs ard huge forged bars
with W1;Hl enalicr's accuracy: support
the unNialiy masses until thew are
keyed tcgather and sele-sustaining
and under millions of pounds Of stress
must ADJUST them, at dizzy heights
to mathematical lines. This he may
need to do. not deliberat IL in eom-
Portable shop or on n solid platform,
but in dangerous emergencies, at ut
most speed. putting forth his whole
strength ON narrow. spria~,ng planks
in "A furious Tempest. in bitter cold or
In blazing heat. lie may he in the
heart Of an African desert, menaced
by blood thirsty fanatics, or in a
gorge of The Andes, hundreds OF miles
from tools or supplies. where there is
absolutely no supplement to his own
resources. Under such conditions
bridge building is one of the most
fascinating and difficult of engineer
ing problems. and requires q differ
ent solution for almost every case.