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TO THE EDITOR OF THE LAUNCESTON
EXAlI1NER.
IRON versus Wool).
Smn,-The subject of iron versus wood for ship
building purposes having during the last week
been pretty fully discussed in Launceston in con
nectlion with proposals which have been brought
before the public for increasing the number of
steamers on the Tamar, it has occurred to me that
some of your readers may be interested by the
perusal of a few facts on the subject of iron ship
building. I propose to direct attention to the
rise, progress, and present extent of iron ship
building, and specially to the peculiar suitability
of iron as a material for the construction of vessels
intended for river navigation.
The first iron vessels were those built in Eng
land, and completed in 1801, for a canal in Staf
fordshire, since which time the superiority of iron
over wood for canal boats has been so fully demon
strated, that two-thirds of the entire number of
canal boats, built since I830, and now in use inl
the United Kingdom, are of iron. It most here
be remembered that the wear and tear to which
a canal boat is subject are excessive, when com
pared to what a sea-going or river craft is exposed.
Canal boats are constantly coming into collision
with the banks of the canal or with other boats,
they frequently take the ground, and are also
much knocked about in the locks. Several iron
boats on the Grand Junction Canal have been in
constant use for twenty years, during which time
they have required very trifling repairs, and are
still in efficient order,
Tihe first sea.going iron steam vessel was the
Aaron Mltanby, built for Mr. Manby, at Horsley,
in 1821, which traded between London and Paris
via Havre and Rouen, and Is, I believe, the only
vessel which has ever made the voyage between
the two great capitals of Europe. Mr. Mauby
subsequently placed three other small steamerson
the Seine, and continued running the four vessels
until 1830, when they fell intto other hands. The
first of these steamers is alluded to in Le Consti.
tutionnel, published int Paris on 13th June, 1822,
in the following terms:--" The bateau A vapeur
en fer i'Aaron lhlanby, Capt. Anglais Napier,* eat
arriv hire, Lundi, bluit heures du soir an Port
St. Nicholas, avre mitn clhargement de graine de
I tt fle, qu'il avait pris A Rouen, et de quelques
pieces de fonte et de mecaniques, venant d'An
i gleterre."
Iron vessels were introduced on the river
I Shannon in Ireland, in 1835, by the Inland Steam
I Navigation Company, their first iron steam vessel
was built by the Horsley Company, and within
I" ten years (viz., fromt 1825 till 1835) their fleet of
iron steam vessels was increased to seven, whlich
maintained a regular line of steam communication
a front Kilrush, at the month of the Shannon, to
Limerick, and thence upwards through Lough
Derg to the junction of the river wilth the grand
canal, which affords communication with Dublin;
these latter vessels, and their machinery, were
t constructed in Liverpool by Messrs. Fawecett .and
t Preston, and by Messrs. Mather, Dixon & Co.
About the year 1828 Mr. John Laird, of Birken
head, whose business had till then been chiefly
confined to hoiler making, began to build several
large vessels of iron, and has since been perhaps
more extensively and more successfully engaged
in iron shlip-building than any other builder in the
world. The fame of the iron war-steamer Ne
mesis, built by this gentleman for the Honorable
East India Company, has been extensively circut
Slated throughout the world, and it is only here
requisite to state that site is still (though more
than ten years old) as efficient as ever, and the
a dread of the Malay pirates .about Singapore, at
r which port site is stationed at present. Mr.
Laird snbsequently built tihe Phlegethon, the Fame,
&e,, for the Hon. East India Company. The
steamers employed in exploring the month of the
t Niger, and many others,-lt may also here he
mentioned that he is at present building a splendid
steamer for the Sydney and Wollongong trade.
Mr. Fairbairn, the celebrated engineer of Man
I chester, who had devoted much attention to the
Ssnubject, submitted to the British Assoiciation in
1840 ithe results af a long series of experiments
on the comparative values of iron and wood for
r shipbuilding purposes, and in 1842 he thns noticed
e the subject iin a letter to a friend at Liverpool:
" That iron is a stronger, safer, anid more durable,
j material for ship-building, there cannot exist a
I doubt, and that for tihe following reasons :--First.
Because the strength of iron plates is to English
a oak as 49'05 to 10'01, being in the ratio of nearly
5 to 1. Secondly. An iron-built ship is safer,
e from the circumstances that the material of which
r * Now Admiral Sir Charles Napier.

site Is composed not only admits of great strength,
but the joints heing all united by rivets, effect a
degree of security which cannot be attained in a
timber ship. On the other hand, a vessel coin
posed of wood has all her joints open, and instead
of the whole being united en masse, the sheathing
or planking presents a series of joints, which, in
order to make water-tight, miust undergo the
process of canulking, and thus, although consoli
dating the parts by bard wedging, has nevertheless
a tendency to start the sheathing, and probably
cause a greater strain on the joints. Is, the iron
built ship these counteracting forces are tnot in
operation, as the joints are the same as the solid
plates, minms only the loss of strength sustained
by the perforations of the rivets. Lnstly,-An
iron vessel is more durable and more serviceable
than a timber one, because (unlike wood) it is not
subject to the dry rot; nor do the repairs, as far as
my experience goes, exceed one-third of those to
which a timber-built vessel is subject. In the use
of iron for the purposes of ship-building, we
possess many advantages which cannot possibly be
obtained by any other material. It receives any
impression, will mould to any shape, and from its
flexure, ductility, and strength, it is admirably
adapted for the construction of vessels, where
lightness and strength form a whole or part of the
constituents."
The great wonder of iron slhip-lllding, the
Great Britain steamer, built at Bristol by Mr.
Guppy, is of the following dimensions:
feet. in.
Length of keel - - - - - - - 289 0
Length from figure-head to taffrail - 320 0
Beam ------ -- - 5 1 0
Depth . .- . .- . .- . . - 31 4
Draught of water when loaded - - 10 0
Tonnage per old mneasuremnent, 3,500 tons
The plates of the keel are f of an inch thick in
the middle to I inch at the ends, and all the
plates under water are from I to f an inch at the
top. She is clencher built, and double rivetted
throughout; towards the extremities, and quite
aloft, the thicknesses are reduced gradually to
7.16thss; the ribs are of angle iron--6 inches by 31
by 7j inch thick at the bottom of the vessel, and
7.10ths at the top ; the distance of the ribs from
centre to centre is 14 incites. The history of this
vessel, and of Iher wonderful release from her po
sition on the northl coast of Ireland, where she was
stranded, will still be fresh in the recollection of
your readers. Parties who have seen this vessel
in Liverpool, within the last 12 months, declare
her hull to be in excellent order, and not in the
least the worse for the severe usage she has re.
ceived. That a wooden vessel, of similar dimen.
slons, could never have survived a similar mishap,
is the opinion of all the professional talent of the
day who were engaged in that great engineering
triumph--the release of the Great Britain.
I propose in my next letter to direct attention
to the commercial advantages held out by iron
ships, and to the proportions which ought to exist
between thle several parts of such vessels when
built for steam navigation, as well as to the most
correct proportions of power to tonnage, in iron
steam vessels.-I am Sir, youear's faithfilly,
ScauTATOR.
Angnst 12.

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