Rogue River courier. (Grants Pass, Or.) 1886-1927, 1903-10-29
A PERILOUS CALLING
Difficulties and Dangers Met With
In Bridge-Building.
Mammoth steel sinews Must lie
Woven Into the Dissy structures
with Mathematical Accur-
paoy At All Tfaes.

The design OF long bridge span is
one OF the most elaborate mathemat-
ical problems that arises in construc-
tive work. The stresses produced by
its own weight, by the weight Of traf-
fc, by locomotive drivers, by the ham
mering of hattened 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
contraction Of the steel in summer
and winter, are all accurately calcu-
lated. The definition Of the loaded
and unloaded bridge is determined,
and complete drawings are made Of
every member Of 1t. 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 will crush an egRshell or a
steel column, and accurately measure
the stress in each case. The differ
ent kinds Of members are forged, riv-
eted bored or planed in perhaps half
a dozen remote shops, and although
usually not fitted together there, are
examined and measured by special
lists TO see that they are correct,
and are then shipped by scores Of
car loads TO the site OF the proposed
structure. where steam derricks un-
load them and pie them many feet
high in stacks covering acres OF
ground.
The huge piers may rise above the
wnter. hundreds Of feet apart. II re-
mains to place on them a l0O0-ton
structure, high above savage chasm,
over an impossible current OF roar
ing tide, where the water is deep, the
bottom Of Jagged rocks or treacher'
GUS quicksand. or where an old bridge
must be removed and the new one
built in it's place without interrupting
navigation or obstructinR continuous
traffic on the bridge. To accomplish
this the engineer has timber, bolts
and ropes, hoistinR engines, derricks
and 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, writes Frank w. Skin
ner. in Century.
The complicated framework OF .
great span is a skeleton with many
accurate joints and thousands Of stee
Einews and bones, each Of which mus
go in exactly the right place in eK
nctly the right order The builder
must weave into the trusses piecei
larger. heavier and far more inhex
ible than whole tree-trunks; swiftly
hoist and swing them to place hun
dreds OF feet high; fiji together thu
massive girders and huge forged bar
with watchmaker's accuracy; supper
the unwieldy masses until they ar,
keyed together and self-sustaining
and under millions Of pounds Of stres
must adjust them, at dizzy heights
TO mathematical lines. This he ma,
need to do, not deliberately in n com
Portable shop or on a solid platform
but in dangerous emergencies, at Mt
most speed. putting forth his Who'll
strength on narrow, sprinFng plank
In furious tempest, in bitter cold o
in blazing heat. lie may be in tn
heart Of an African desert, mennce
by blood-thirsty fanatics, or in
gorge of the Andes hundreds Of mile
from tools or supplies, where there i
absolutely no supplement to his ow
resources. Under such condition
bridge building is one OF the mos
fascinating and difficult OF engineer
ing problems, and requires n diner
ent solution for almost every case.