The new era., 1890-08-28
written for THE NEW ERAl
Iron Bridae Construction.

Iron Bridge Construction.
The earliest bridge in the construction
Of which iron formed theprincipal part,
was, if we may believe Kirchen, in his
China illustrated product Of the civili-
zation of the great oriental empire, in
the days of antiquity, prior to the
christian era in the form OF a suspension
bridge, composed of chains, son which
the floor was directly laid, following
consequently the curvature of the sus-
pended CHAINS. We have no further
record of the use Of iron in bridge con-
struction until q. long time afterward
about the close of the last century
when cast iron was employed instead
of stone in the construction of an arch
bridge of one hundred feet span at
Colebrookdal, England. 1t has how
ever remained for the present. century
to develop the highly perfected forms
of wrought-iron and steel bridges which
we now have. OF these the enormously y
heavy tubular bridges across Menai
Strait and the st. Lawrence, are
among the principal pr ecursors, on the
one hand as to the material, and the
simple skeleton structures of Whipple,
on the other hand. AS to the type to
which the more elastic and trustworthy
material has been adapted, replacing
the crude mallable cast iron which so
largely entered into the earlier bridges
of this form, now to trace out simply
the development of that class.Rf bridges
which is a universaIs want OF $lA civi-
ized world for the common roads and
highways of the people. there were a
gfeal many bridges built of different
patterns, composed of cast and wrought
iron, which was quite heavy and cum
berson. They were however very ex-
pensiye, and in the country west OF
New York scarcely known, and could
hardly compete with such bridges as
men built of wood. This set the in
yentiye genius of the western country
to work, and some twenty five years
ago, several styles of iron superstruc-
lures were introduced at such prices as
to induce the highway authorities to
give them trial Almost all of these
bridges were built to sell, although the
material Of which they were made was
of sufficient size, so that they answered
the purpose of a bridge In most cases for
time. 1t should always be remembered
that the correct principles OF bridge
construction were but little known or
understood at this time. Soon, how
ever, there were immense strides taken
in the development of correct mathe-
matical principles governing bridge
construction, not only on general prin-
cipals, but also in those governing the
minutest details of construction, aud so
far has this progressed in the past
twelve or fifteen years, that it may
now be said with the majority of
builders, more attention is paid, and
more skill displayed than in almost any
other branch of mechanical construc-
tion. Now that there has been such a
high degree of perfection attained in
the construction OF iron bridges, and
the low price of iron and steel, il is false
economy for the supervisors of public
highways to even think of using wooden
superstructures for bridges, 1t is old
fogyism to think of erecting wooden
bridges in this enlightened day, when
timber is so scarce and iron SO plenti-
full, and the slight dtferance in the cost