The Coolidge examiner., 1937-07-15

THE completion of the new
Il steel bridge across the
Golden Gate recalls some of
the old metal spans, many of
which have been in use for
two or more centuries.
To England, in 1776. fell the honor
Of erecting the first iron bridge.
There Abraham Darby cast bridge
at the Coalbrookdale Iron works and
erected it across the Severn.
Thomas Telford, a Scotsman who
lived between 1857 and 1884, is
known to students of engineering
the world over for his achievements
in canal, harbor. road. and bridge
construction. He was engineer for
the parliamentary commissioners
for road making and bridge build
ing in the highlands of Scotland, un-
der which organization ]. 200 bridges
were erected In England he helped
build FIVE bridges over the Severn,
and was employed on canals and
highways by the Swedish and Polish
governments.
The Menai suspension bridge in
Wales. connecting Carnarvonshire
with the island of Anglesey. is the
best-known monument to his pio-
neering genius. 1t was opened in
1926. after seven years of work. and
was. at that time. the worlds larg-
est suspension bridge, being lilo
feet long. with a main span of 57e
feet.
Ancestors of Brooklyn Bridge.
Telford was a shepherds son. Ap-
prenticed TO stonemason at fifteen,
he studied engineering in his spare
time and published verse. A man Of
amazing industry and versatility,
Telford invented the pavement
which bears his name.
Gables spun in place to swing a
suspension bridge were tried in 1881
by Vicat. a French engineer, for
bridge across the Rhone. Later
Roebling developed this method at
Niagara Falls. Cincinnati. and final
ly at the Brooklyn bridge.
In Europe. as in America, the
Nineteenth century saw vast ad-
vance in iron bridge building, espe-
cially stimulated by new railways.
The Newcastle and Berwick railway
alone required ITO. Progress in de-
sign sometimes was costly. A new
iron bridge across the Firth Of Tay,
near Dundee, Scotland. collapsed in
a gale. Rushing at night into the
open gap a mail train was wrecked,
killing some four-score passengers.
Today's bridge excels not only in
design. foundations, and methods of
erection. but especially in materials.
Now iron yields to steel. The Besse-
mer, and later Siemens-Martinp proc
esses, gave bridge builders some
thing new and stronger-a steel
cheaply produced.
At any army field day you may
SCC G4C SPECIFY WI OA D.
showing how emergency bridges are
built, wrecked, and repaired in war
time.
Washington Bridge Beats George.
Homer tells about pontoon bridges
used in war. Darius, Cyrus, Xer-
xes, Alexander the Great. all en-
ployed them.
In 1871, it took General Washing
ton four days to ferry only 1000
men across the Hudson when he
moved his army south from New
York to Virginia. Now, over the
George Washington bridge at New
York, a whole army corps-or 97,-
600 men. 23.105 animals, and more
than 1000 gun carriages, trucks,
and other vehicles-could be put
across in eight hours!
Chinese classics relate that a GER
tain king once crossed river by
walking over a bridge formed by
the backs of a long line of big, ac-
commodating turtlesl
In west China and Tibet, to this
day, men coast" across rivers on
tightropes. sitting in a seat slung
under the rope and sliding along II.
To make the underslung seat slide
faster the rope is often creased with
butter. DR.. Joseph Rock, exploring
for the National Geographic society,
reports his own use of yak butter
on such bridges. II always tried to
find a bridge made of new rope"
says DR.. Rock. for the rope soon
wears out"
In his Voyage to South Ameri-
ca" written many decades ago,