New-York tribune., 1873-05-10
WHY THE BRIDGE At DIXON FELL.


To the Editor Of The Tribune.
SIR: The Dixon bridge fell beneath the
weight Of a crowd Of people watching sacred rite IN
the stream below: there was no nood no gale OF wind
a Yush upon the bridge 10 simply broke under
the weight OF quiet mass; Zee fall and destroyed the
very load which it was buIt 70 carry and preserve
Weight is the thing which bridges are specially
built 20 resist and 70 the construction Of this bridge.
therefore. the disaster must be- referred.
The first telegraphc dispatch told what the bridge
was. It was bridge OF the Truesden pattern.
This statement alone is enough 70 indicate why the
accident occurred. While many wretched structures
have erected all parts OF the country there no
class Of bridge in which the correct laws OF bridge
construction have been 20 ruthlcssly violated the
Truesde bridge In II the material is SO liudciousy
distributed that than 0nehalf Of IT, effective
strength f. realized and danger made douhy great by
a multiplicity OF small parts and defective details And
yet t has erected Tor prices low tnat the besi
builders " the country constructing their bridges on
strict scientific principles and using plans n which every
piece OF iron s made perform It's fu share Of work.
have found 10 impossible compete with this bridge IN
contracts In brief not than Onehaf of the mate
rial in the TrCesde bridge performs any useful duty,
yet II the whole amount or material were worked 10
would be too weak IL contains less material than must
De put into the most economical form OF truss,
in which nothing is wasted 20 make that
bridge Of the kind that has fallen In the
nelghboring town OF Elgn similar structure has twice
been destroyed. It's defects OF construction arr 80
plaring that the wonder Is that this bridge has fallen
but that 80 many similar structures are now standing
There are hundreds Truesde bridges IN the United
States In western part Of Massachusetts, they are
specially common. and there is not one Of them which is
not a dangerous structure.
But the fall Of bridge should not lead 20 general
condemnation OF iron bridges No material mas YET
been discovered 50 well adapted Tor bridge building
iron is and the United States can now boast goody
share 0f the finest bridges In the world The laws
OF bridge construction definite and thoroughly IN
derstuod the strain upon every piece OF iron can be
calculated TO a nicety and II that iron s only made
large enough the structure perfectly safe IL D. now
Tie practice OF leading railroad and bridge engineers
10 limit the strain each part OF tie bridge o onenfth
and generally 20 one-siXth of tho strain required 20
break that part Special attention. given 10 details ana
an parts fitted together with the utmost care There
are parts a railroad which she traveller s safer
than on its new bridges, and the fall Of drstcass
iron bridge is an almost unneard-Of event. Bit. unfor
uuatey there are classes OF bridge builders There
are the leading bridge companies whose name enough
TO guarantee good work. ana who by their excellent
structures have done much 20 advance the science o
bridge building There also the Ignorant unprin
ciped bridge builders. whose work deserves the most
severe condemnation. The fields IN which these
tvo classes work well separated The
former find their customers M the leading
railway COMPANIES. They submit their plans 20
the scrutiny competent engineers, and get prices for
their work which large enough 10 pay for nrscass
structures The latter bud bridge upon streets and
Highways They seldom venture even 20 make "a bid fot
railway structures They deal with county officers 0f
road commissioners. who know hlJe nothing Ot
the merit plan offered them This class OF work 10
secured by undertaking an respectable builders. The
Truesde structure perhaps the'most unscenthc plan
on winch any large number Or bridges nave been erected
but a sufficient quantity OF material and good work
uauship is as important g.Od plan. ani there are
uutudes OF bridges whose skeleton plans are good hut
which bv their bad details and insufficient material are
rendered scarcely better than the Iruesdeh bridge
During the last six OF eight years thousands OF small
wrought-ron bridges have been built especially in tie
Western states general plan OF which mbes that
of some OF the most admired European bridges, but
which contain small amount OF ron that majority
OF them are dangerous structures from The rst and Few
OF them can be expected 10 last as lons as a gooh
wooden bridge. The writer has himself examined
a wroughtIron bow-string bridge Of span
OF 200 feet in which the ne that
connected the ends OF the arch consisted Of four
bands each four inches wide aud one-haf inch deep.
esh band being series OF dat bars welded mto ribbon
200 feet long The DC eh OF the truss at the center ald
NOT exceed % feet In such the weight Of the
bridge alone Amounted 20 more than One-hfth Of the
breakug strain or the iron. and ful load would In
crease 10 One-haf OF the l breaking strain tension
lar beyond the elastic limit OF the best iron and ulder
which = small imperfection OF workmanship would be
instantly perCepuDle. such bridge when USED out
little may stand FOR years bur II liable 10 break down
whenever drove Ot cattle crosses IT, and under the ex
oessive strain of its weight The iron De- Ie 10 De
terurate rapidly.
bridge Is seldom loaded without a portion OF ne
load consisting OF men ami w,sucu ana % cannot fall
without Iuhcting death on injury on those VINO are 90 IT,
while IN majority OF cases deep stream otOW adds 10
the certainty OF death the result OI such IN accident
To erect a dangerous budgo. IL not crime by law,
shows an atrOciOus disregard Of human ic compared
with which the creessness OF the captain OF the Al
lantic becomes par1lonable ofense II ever an aecl-
dent can Justly DE called murder, tue DiAnu
tragedy deserves this name. II the circumstances
which have secured the erection 0f good nrlages on
our railroads 10 not operate highways II shOsd ne
the duty OF the step IA. No legislation couu DC
uore simple and none effective than that which Is
needed for thls purpose the lsw prescribe the yari
me load ou each square foot for wneh highway
m ye are 10 be built and the limits 20 winch the iron may
te sfrained liz will be easy thlng 10 determine
whether tnese conditions fulfilled ana IN the hght OF
tn nixon Tragedy IL Is hardly much 10 say that very
severe penalties should be inflicted upon those who
neglect them. n
Nesc- York, May :, 1878.