The Sun.
London, England, 1862-09-04 00:00:00

IRON-PLATE EXPERIMENTS.

Some interesting experimental firing has taken
place at Portsmouth recently with wrought and
cast iron shot and 8-inch shells from the 95cwt.
smooth-bore gun of the Stork gunboat, under the
supervision of Capt. R. S. Hewlett, C. 8,, command-
ing her Majesty's ship Excellent, the gunnery ship
at the port. One day's experiment consisted of the
testing of a cellular target built on a plan proposed
by Capt. Hewlett. The front and back plates of
this target were composed of 14-inch plate, sepa-
rated by f,-:-inch ribs, 15 inches in depth, to which
was attached the front and back plates of the target
by Finch angle irons, 4 inch by 4 inch. Thew',
ribs were placed vertically, and in six feet of the
target's length were eight inches apart only, in the
remaining six feet being 18 inches apart. The in-
terior of the target was thus composed of a series of
cells or flues, in one half of the target measuring
eight inches' breadth, 15 inches in depth, and eight
feet in length. In the remaining half of the target
they measured the same length and depth, but were
18 inches in breadth. The whole structure was 12
feet in length, 8 feet in breadth, and 15 inches in
depth (internally). It was fastened by the ordi-
dinary form of bolt, with nut and screw, from the
inner plate only to the ship's sides. This slight
structure was not expected to arrest the progress of
the 681 b. shot, with a velocity through the air of
2,000 feet per second ; but comparative results only
were sought, as a guide to the minimum thickness
of plate required to so crush the 681 b. cast-iron shot
in its passage through an armour plate that it
should afterwards be powerless to inflict any mate-
rial injury upon any substance within a certain dis-
ance of the plate's reverse side. To clearly illus-
trate this, suppose that, instead of clothing a ship
with its armour in slabs of iron of a certain thick-
ness, as is the case with our present iron-cased ships,
the same amount of metal was divided into two
slabs, separated by iron ribs of some 12 or 15 inches
in depth; the theory is that the outer plate of the
cellular side must be of sufficient thickness to de-
stroy the shot in its passage, and render it incapable
of inflicting any injury upon the inner armour plate,
or disturbing the fastenings which attach the armour
to the bhip's side. In fact, it is contended that this
form of armour should perform for the ship what the
Knight's shield did of old—it might be destroyed
without necessarily causing injury to the body it
was intended to protect. The result of the practice
at this target was, therefore, as already stated, only
of a comparative and purely experimental nature,
but still the data obtained must be of great value
with reference to the subject of ships' cellular ar-
mour.
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for shield ships his ship's sides were constructed on
the cellular plan, the inner armour plates being
Jones's angulated side, extending from the top of
the turrets or cylinders to below the water-line, and
the outer side being in the ordinary vertical posi-
tion. This proposed form, it was contended at the
time, would not only prevent the waves from wash-
ing up
platesh were angulated sides, but the
outer
angulated sides, with their fastenings, from any in-
jury by an enemy's shot, however close he might
bring his guns to bear. It is also obvious that an
immense addition of strength would be given to the
vessel's frame—a point of the greatest importance
to all iron-clothed, but more especially so to cupola
ships by this combination of angular and vertical
sides. Two other experiments made have a special
degree of interest attached to them, inasmuch as
they relate more particularly to the quality of the
metal of which the armour plates of our ships of
war are composed, rather than to any precise thick-
ness or form of plate. The two plates selected for
the experiment had each been previously fired at
several times on the day they were officially tested,
according to the usual mode, with a 95cwt. gun, at
200 yards' distance, throwing a 681 b. cast iron shot
with a charge of 161 b. of powder. In the experi-
ment referred to the gunboat was moored at a dis-
tance of 50 yards only, in lieu of the ordinary prac-
tice range of 200. The gun used was the Stork's
95 cwt. smooth bore, with wrought iron shot in
both instances.

The Thames Iron Works Company's plate of ham-
mered iron was first selected for trial, and the
wrought iron shot was sent against its least damaged
part with a charge of 221bs. of powder. The shot
buried it self two-thirds of its diameter in the plate,
but the latter had no cracks whatever extending be-
yond the immediate fracture caused by the pene-
tration of the shot---about 9 inches, or exceeding
the s'let,'s diameter by one inch. The second shot,
also of wrought iron, was directed against the least
damaged part of a rolled plate, manufactured by
Messrs. Brown, of Sheffield, with a charge of 251bs.
of powder, 31bs. additional to the last experiment.
The shot in this instance embedded itself in the
plate about three-fourths of its diameter, the platei