The Sun.
London, England, 1855-09-25 00:00:00

WROUGHT V. CAST IRON GUNS.

The failure of wrought-iron guns of large calibre, says
Mr. J. Blackburn, of Erewash-valley, although much
to be regretted, is not surprising to practical men. The
Government of the United States of America, after the
lame❑table and fatal accident which occurred some
years since from the bursting of a wrought-iron gun of
large calibre on board the Princeton frigate, instituted a
vigorous inquiry, conducted by gentlemen of great ex-
perience and science in New York, when it was by
them for ever decided that wrought-iron guns of large
calibre were "unworthy and dangerous." A report of
these investigations was published in this country soon
afterwards, and• must have been seen by many of your
mechanical readers. There is, after all, no doubt but that
cast iron is the true material for large guns subject to
mighty concussions, simply from the fact of the great
facility of securing a sound gun, with only ordinary care
in the process of moulding and from the uniform crys-
talisation of the iron ; this great desideratum cannot he
obtained in such very heavy masses of iron as are neces-
sary for the wrought-iron guns of large calibre, on ac-
count of the great length of time they must necessarily
be under the action of the fire, for it is an ascertained
fact that wrought iron during this process, when in large
masses, undergoes what is termed a molecular change by
being kept so long in an incandescent and soft state. The
cohesive tenacity of wrought over cast, iron is about as 3
to 1, but from the cause assigned it cannot be estimated
fairly at more than as 2is to one,• if so much. The vast
expense necessarily incurred in the production of these
wrought-iron guns of large calibre gill, I am convinced,
be fatal to their permanent introduction and use, even
should they ever succeed to the utmost wish of their
most sanguine advocates ; at a moderate calculation 10
cast-iron mortars of 13in. calibre can be made for the
cost of one wrought-iron of the same dimensions. Taking
then, the data that 600 rounds fired will render an or-
dinary 13iu. cast-iron mortar hers de combat, 1,200
rounds or less would place the wrought-iron gun in the
like situation, while the cost has been in all probability
five times the cost of the two cast-iron rnr,rtars. Many
persons advocate the general adoption of a wrought-iron
gun on account of the supposed durability and the op-
portunity they present of reducing the weight. This,
however, is a known error; a light gun of the same
calibre as a heavy one cannot throw a shot or shell by
any means so far. The failure of our mortars used this
season in 4,11 e Baltic is much to be deplored, but bad
there been duplicates on board the ships of war which
could have been stowed as kentledge, and exchanged
when required, a more terrible blow might have been
inflicted upon our enemies. The question then arises—.
Can anything be done to make the cast metal guns and
mortars of large calibre, subject to mighty concussions,
of greater cohesive tenacity, and thereby more capable
of sustaining the tremendous expansive power of a heavy
charge of gunpowder? I answer decidedly yes, and at
a merly nominal increase of expense. This process was
fully explained to the Government of this country in
1850.