New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1850-08-14

A.. ,,... AR thefs,me load win not the ebsn-es OF
s,Iure be ecuoed almost Be ood tne rsnss OF PoOT'
A. far As wrought iron 10 concerned
The noip, there attempted to be established was,
a,, fbridges badly proporsioned with some parts
s,no,ed to excessive strain, would endure At al,
bov much more nigh. those be relied on 10 which
he greatest strain was only fraction Of what GER
tain parts Of the former were enduring.
Now the bridge which occasioned the catastro-
phe on the New.York and Erie Rlilrokt, on the
lot inst vas Of about the same length as that on
the Harlem road here referred 20, and PROBABLY
wss similarly proportioned, the lower chord 10 each
truss containing four square inches IN cross section
with one-fourth Of the same cut away IN forming
bolt holes, leaving only three square inches IN the
weakest parts The truss moreover suppose %
have had q depth equal 20 about onetenth me
length Of span and for such length and depth OF
truss, for q single track railroad bridge, shonsl
have put in a. least ten sq1are inches OF cross sec
ton OF wrought iron, in the middle OF the lover
chord, with other parts similarly proPortoned with
regard to the stress they were liable 70,
Now | suspect that the lower cnora IN tne me- sn-
hoybood NJ the center was the part tha. first gave
wav. in consequence Of being too small II It was
not 90 II only proves that there were other parts
still wesker than that TO which / had never given
attention Ny attention was TUNED 70 tnsI polnt
becsu,e that struck me as the most deceive IN
proportions and the most easily demonstrated 70
he al
satsfactiop, did not feel interested 10 go into fur
Their detail.
The cause Of the failure, therefore, conclude TO
Ia the had PROPORTIONS Of the structure, and weak
ness j. G. want OF proper size, in some OF the parts
detects noticed and frequently spoken oil by me
lin relation TO other bridges on the same PLAN years
ago; that the accident affords no just grounds OF
apprehension from iron bridges properly proper
toned and CONSTRUCTED, nor Of Encouragement from
the introduction OF such bridges on railroads
Now the most important practical lesson taught
by the sad catastrophe which gave occasion to TINS
article, Gs it appears 70 me- Is that better UNDER
stsDdiDg of the mechanical principles involved IN
the construction Of bridges should prevail among
engineers and those having charge OF such works,
and that no structures Of the kind either Of wood or
iron. should be adopted or admitted, unless scien
tifcally and systematically planned and proper
toned throughout
Since writing the above have seen the resolu
ton Of the directors Of that road FOR the dtsuse oil
iron bridges upon their road in future, and for the
removal Of two small bridges built by me near
Binghsmton.
The messure may be one Of policy or expeiiency
for the company, ss the public is lisble to reason
from the failure Of one iron 6Tl5ge that al IRON
bridges are unsafe, however differently planned
and proportioned But if any confidence can be
placed in the preceding statements, the folly OF
taking the failure here spoken Of ~ any evidence
Of unEaiety in those remaining viii be sufficiently
apparent .
il would seem that this summary condemnation
Of iron bridges by the directors Of the New. 1ofk
and Erie Railroad Co is founded on the fact tina
an iron bridge may break suddenly and without
any previous warning" Did it occur 70 them that
many Of the bridges considered as wooden bridges
depend for their support on iron bola aud iaSten
ipeF, which are equally liable 10 break suddenly,
without warning" and that their breakl1g "0uu
be equally as fatal to the structures 0. which they
compose parts as the breakage Of corresponding
part of an iron bridge!
Look at the Howe bridges on one Of the most
popular plans row in use for RAILROAD bridges 10
this country Think Of bridge Of so feet stretch,
with come go Of the structure, and all bat Ito
part Of the load land q railroad bridge should DO
able to bear with safety load Of 600 lbs to each
running FOOT suspended by iron bolts Of inches
in diameter, and this cut down by screw threads
TO trihe over / inches diameter leaving not to
exceed Is square inches to sustain the whoe
weight.
Now, 90 OF such a structure could not weigh
less than goo los. which, added to 2SOOOO
for the l4l5 Of the maximum load, gives
$4,000 lbs TO be sustained by Is square inches OF
wrought iron showing 1888 lbs. to the square
inch as the average stress upon all OF that set OF
6 bolts and those bolts being in pairs, one pair
near each corner Of the bridge are IN no wise GER
tain of sustaining the same stress, and the break
age OF any one Of them would suddenly throw
such A stress upon its fellow as would be almost
certain to break il and cause the immediate down
fall of the bridge.
Then look al those doomed iron bridges built by
me at Biz ghsmton, in which no man can point out
an important piece of wrought iron which, under
load Of 600 lbs 10 the running foot can be demon
streted 10 sustain tension exceeding 10000 los,
to the square inch Of cross section, or any other
part more severely taxed in proportion to its sale
capacity Having dolly contemplated thi. picture
and that, let US pause for a moment aud admire
the wisd1m, or commiserate the ignorance, OF
those who tremble at crossing the iron bridge,
while they feel fully az ease in passing over the
90 called, wooden structure whose stability de-
ponds on the same kind Of material exposed to
double and almost treble the stress which it sus-
tans in the other structure.
Utiea Augusf7, 1885, D. "hirfLh'
iI. read. = M printed art,e but 'an~1 am'rfa'
or O mistake .1 The copy.