Indiana State sentinel. [volume] (Indianapolis) 1841-1853, 1847-03-04
a Novel undertaking.

A London correspondent Of the New York Journal
Of Commerce mentions undertaking. remarkable
alike for its novelty and vasiness. which is in pro-
gress a, the Menai Straits:
The bodest idea yet started by any living Eng neer,
is that Of Robert Stephenson, engaged upon the
construction Of the Chester and Holyhead Railway,
who proposes and is now executing a tubular iron
bridge the Menai Straits, Ito connect the shores
of Caeruarvonshire with the island of Anglesca-a
feat accomplished previously by TelfOrd, but the
old and well tested plan Of suspension brldges Mr.
Stephenson's project Is purely original, and OF
gigantic proportions. He proposes to construct tu
buar bridge Of plate iron, one inch hckthe plates
20 be riveed together in the form of a rectangular
tube or tunnel, having section II by % feet
outside measurement, and 10 extend the Straits
in three spans of $50 each. Two lofty piers will be
erected in the water to support the central span, at
sufficient height the channel to allow the largest
class OF shipping to pass free, without striking their
royal mast heads There be two of these tubes
laid parallel TO each oiher the entire length Of each
being 1850 feet and thus allowing free transit Of the
trains in opposite directions at the same time
The clear space left in each tube for the passage
of the train is Ia by II feet leaving feet of vertical
dimensions given above to be accounted for. This
Is appropriated to the purpose of rendering the tube
sufficiently stiff 10 bear its own weight and that Of
the train, by dividing by IA feet Of the upper por
ton of the tube into smaller tubes, arranged in two
horizontal rows resist compression and the lower
-
ded into similar small tubes to resist tension. The
two grand tubes, containing the separate roadways
for each train of cars be boted together side
by side, to resist lateral pressure from the heavy
gales Of wind to this region. Ii is not 10 be
supposed that any board of directors would have
cePted such formidable project this, without first
being well satisfied of the feasibility of executing
it. and the sufciency of the work for its intended
purpese when DONE Careful and most elaborate ex-
periments were undertaken by Messrs. Fairbairn g.
1frkf llu G. H..
cal and scientific knowledge of the strength of iron
a building material-and upon their joint verdict
Of approval the tubular bridge is now going on the
;racted for in part.
In conducting these experiments, the gentlemen
above named discovered some valuable facts. They
found that 1t was necessary to provide much larger
amount Of strength in the tubes to resist compression
than TO resist tension; that wrought and cast iron
stand directly opposite to each other this particular
resist weight applied horizontally than tubes of
the square or rectangular section Hence, adopting
the latter form, and siening by making the depth
of the tube nearly double its width, (26 by IA feet
and then adding nteriory two rows of smaller tubes
above and one below, they arrived at form capable
Of sustaining $50 tons the of space of $50
feet and they state IN their report, fully compe-
tent for the purposes of railway viaduct, tunnel or
bridge
The experiments were tried on largesscale, tubes
of by Is inches square and 80 feet long being used
The successful issue of this great project will place
Mr.. Stephenson in the same rank Telford BroneI,
and Smeatone.