The Emmett index. [volume] (Emmett, Idaho) 1893-1925, 1912-02-15
NATURAL BRIDGES
We Can Boast of at Least Nine
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 Struetures-Few
Iron Bridges Prior to 1850.

Eastern and Central States, and Then
Came the Covered Struetures-Few
Iron Bridges Prior to 1850.
Nature has provided this country
| with at least nine natural bridges. one
in Virginia with a span of about nine
ty-three feet and about POO feet high:
one in Alabama with span of about
seventy feet and about 1870 feet high;
! five in California, the largest of which
has a span of about eighty feet and is
about twenty feet high; one in Ken
| lucky with span of about seventy
feet and about 1870 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 We're 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
ullOlu udIuHllD anu lA4t NpAAE7N AN4AN
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 cul-
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 Heilespont on two pontoon
bridges consisting, one of 3G0 vessels
and the other of 314. These were an
chored head and stern alongside OF
each other, with their keels in the di
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 $500,
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 Ithiel Towne.
Many Of these bridges. consisting of
planks pinned together in lattice work.
were built from this time on, and they
became well known as ''TOwne" or
covered" bridges. 1t is doubtful II
much attention was given to econom-
icaI 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, num-
Der of covered wooden bridges that
were built more than a half century
ago are still being used within a ra-
dius of fifty miles Of Indianapolis.
Few iron bridges were built in this
country prior TO 1850. and it was only
in 1S4T that the first publication in the
United States. discussing the rational
design of bridge members. was issued
by Squire Whipple of Utica, n. Y.
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 its greater tensile strength.
Foremost among structures repre-
senting some of the attractive as well
as 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 I
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.
It's total length is 2,375 feet. while
he width OF its roadway is eighty /
'eet, and its height above mean high
water is 151 feet 1t was built at COST
# 50 S50.OO0 ."-Indianapolls News.