Memphis daily appeal. [volume] (Memphis, Tenn.) 1847-1886, 1867-04-18
teonnusIcArED
I MEApHIs, April Is, 1867.
Editors Memphis Appeal

ItOMAAA III
MEMpHIs.A April I6, 1867.
Editors Memphis Appeal
find In your % local - of this morn
ing an unfair comparison Of the " ben
mead bridge y and the Clones iron-trus
BRIDGE in which ii is claimed that thl
former is the perfection Of human skill
aud ingenuity, while the latter is a fail
ure, and possesses faults that cannot b.
remedied. The inventor Of Jones
bridge is not here TO speak for himself
and I ask the privilege Of briefly an
swering this unjust criticism o
his invention, through your columns,
Both the structures Ia question are
essentialiyt the Howe plan, and the only
uoint TO be settled il as to the compara-
tive merits Of wood and iron, the Jones
bridge being all iron, The Denmead
bridge having w0oden-top chords and
braces. I cannot trespass upon your
space sufficient TO discuss at length and
10 detail this very nterestingsusjeet and
will content myself BY calling the atten-
ton to this subject of those VINO are
familiar with the improvements made In
bridge construction within the past
twenty wears, and by briefly abiding to
the nersistent fight that has been con-
stantIy made BY the old fossils Of q past
generation. against the Introduction Of
iron, either cast or wrought, In any pro-
portion, into such struetares. The elder
Campbell, of Pennsylvania, put the Burr
bridge in competition with Hewe's plan,
and always insisted that all wood was
preferable to wood and iron, but he
failed to convince railroad men of the
correctness Of this theory, and to-day
there are one hundred Howe
bridges in the United States to one
Burr bridge, and many of the younger
engineers az the country never saw
one Of the latter structures. Me-
Callum, with his great fame as an
engineer and with unlimited means at
his command, tried to drive the iron
| material from bridge construction, and
made an ingioriOus failure. Many other
plans Of wooden bridges have been tried,
since the introduction Of iron as an i'm
portant item of bridge construction
nearly all of which nave become obsO-
Iete, while the Howe bridge, with a
constantly increasing proportion Of iron,
has been growing in favor until at last
we Aud it perfected in strength and
beauty in Mr.. Jones complete iron truss.
The same arguments are used against
all iren that were used sgainst q part
iron, namely. that constant vibration
causes capitalization and final failure.
However true this may be in theory,
the hispory of the Howe bridge has
proved it to be of no Importance IN prac-
lice, and / predict the same will be the
case in bridges built Of all iron. The
writer's intimation that Jones' bridge IS
all cast iron is incorrect, cast iron being
used only where wood is used in the
Denmead bridge wrought iron being
used in the enc as In the other.
The failure of Bear creek bridge can
have little influence on the minds Of in
telligent engineers, who study the prin-
ciples of the plan and weigh the causes
that may have produced the result. The
failure of a Howe bridge upon the Fitch
burg railroad, in IS47, was as mysterious
as the fall of Bear creek bridge Oh the
Memphis and Charleston railroad, and
has never been explained still, thOus-
ands of Howe bridges have been built
since that time, and have stood the
severest tests OF strain and time.
II MI. Denmead's bridge has merit it
will be appreciated by discerning men,
and will receive the popularity he seeks
for it, without his attempting to detract
from the merits of other plans and II he
Is wise he will not try 10 build himself
M at the expense OF al honorable COM
petitOr whose invention may, in the
future, occupy the same relative position
to wooden structures, that iron loeOmo-
tives now do to the rude pony carts Of the
uncultivated inhabitants Of Pembina.
Our great forests are fast disappearing
and the iron mines that are being devel-
oped must eventually supply the mate
rial for rebuilding the thousands of fast
deGaying wooden bridges that have
always been a source of annoyance
ID railroad men in this country.
These facts are apparent to every
thinking mind, and the man who con-
tends, at this late day, that iron cannot
be made available for bridges, must be
Ignorant of the existence of the Victoria,
Menai, and other magnificent iron
bridges that have gained a wOEld-wide
reputation for the engineers who con-
structed them. IRON TRUSS.