Bismarck daily tribune. [volume] (Bismarck, Dakota [N.D.]) 1881-1916, 1911-12-15
NATURAL BRIDGES
We Can Boast Of at Least Nine
Of Them In This Country.

Of Them In This Country.
OUR FIRST WOODEN BRIDGES.
They Were Built About 1900 In the
Eastern and Central States. and Then
Came the Covered Strueturss-Fe~
Iron Bridges Prior to 1850.
Nature has provided this country
with at least nine natural bridges. one
in Virginia with span Of about nine
ty-three feet and about 200 feet high:
one in Alabama with span Of about
seventy feet and about 1870 feet high:
five in California. the largest of which
has span Of about eighty feet and is
about twenty feet high; one in Ken
lucky with span of about seventy
feet and about 100 feet high. and one
in southern Florida Of somewhat
smaller dimensions.
Bridge building In the United States
Is Of comparatively recent accomplish
ment. The early settlers were com.
PEELED to ford the streams or cross
them on RATS or in dugouts. When
Washington crossed the Delaware with
his army there were no bridges over
that river. and history records many
Instances Of streams being forded with
untold hardship and the consequent
disasters and delays Such incidents
become serious matters when. for ex-
ample. physicians are unable to reach
the sick or injured because Of impass-
able fords or are compelled to expose
themselves to unnecessary danger.
Traffic conditions in general are de-
moralized by unsafe bridges or cu|.
verts.
Pontoon bridges have served tempo
rary need in many instances. but espe.
cially in warfare. Mention is made of
their use very early in history, and one
Of the most notable occasions was
when the Persian army under Xerxes
crossed the Hellespont on two pontoon
bridges consisting, one of 800 vessels
and the other Of 314. These were an
chored head and stern alongside of
each other, with their keels in the d.
rection Of the current.
The Romans had wickerwork vessels
covered with hides destined to support
the timber platform Of bridge. These
formed a part of the train Of their ar.
mics throughout the history Of the en-
pire until 476 A. D.
The construction Of highway bridges
In this country began to assume prac-
teal proportions about the year 1900,
when many wooden bridges were built
in the eastern and central states by
Theodore Burr and Timothy Palmer.
The wooden lattice truss was intro
duced about 1920 by 1thiel Towne.
Many Of these bridges. consisting of
'planks pinned together In lattice work.
were built from this time on. and they
became we'll known as "Towne' or
covered" bridges. It IS doubtful If
much attention was given to econom-
ical design. An effort was made to
protect the trusses from the weather
by wooden roofs and sides in some in.
stances. but very few were ever paint
ed to preserve the timber This early
type of bridge did service for many
years, and some are still in existence
in Indiana and elsewhere.
The FIRST covered bridge to be built
In Tippecanoe county and one Of the
first In central Indiana was the
Brown street bridge over the Wabash
river at Lafayette. according to the
records on file in the Office Of public
roads. department Of agriculture. This
old structure. that had been condemn.
ed for a good many years. has long
since disappeared. However. a mum.
Der Of covered wooden bridges that
were built more than a half century
ago are still being used within ra-
dius Of fifty miles Of Indianapolis.
Few iron bridges were built in this
country prior to 1850. and it was only
in 1e47 that the first publication In the
United States. discussing the rational
design of bridge members, was issued
by Squire Whipple Of Utica. N. 7.
Wrought Iron began to replace cast
iron about 1868. but steel was not used
until about ten years later. The ad-
vantage of steel over cast or wrought
iron lies in it's greater tensile strength.
Foremost among structures repre-
senting some Of the attractive as we'll
a. substantial features in good bridge
designing Of the present age may be
mentioned the Washington bridge over
the Harlem river in New York." said
the superintendent Of construction Of
bridge engineering. Office Of public
roads. Washington. This bridge has
two middle arches Of steel. each $40
feet in clear span. and seven masonry
arches, each with a sixty foot span
1ts total length II 2,375 feet. while
the width Of its roadway IL eighty
feet, and its height above mean high
water Is Isl feet 1t was built at q cost
Of Observation-Disclosures News.