The Sun.
London, England, 1868-06-25 00:00:00

NG, JUNE 25, 1565,

EXPERI2IIENTS AT SHOEBURYNESS.

The great experiments at Shoeburyness oil iron
land defences entered on a new phaze on Tuesiay.
The public interest has in a great measure subsided
with the discontinuance of the trials of the Ply-
mouth shield and the destruction of the gre3t
15-inch plates ; but to those who watch these in-
vestigations with a desire to study fully their bear-
ing on the general mechanical question there are
still many facts to be carefully observed and many
important results to be recorded.
The objects remaining for attack at the com-
mencement of this week's practice were the " expe-
rimental casemate " (two simple walls faced with
iron) and the Millwall shield. The latter is the
most interesting, as it is a structure avowedly com-
petitive with others already tried ; but from the
situation in which it has been erected—consider-
ably to the west of the other targets, and facing an-
other part of the ground—it cannot be fired at till
the guns have been moved. This, with such an
enormous battery, is a troublesome operation, and
as it is desirable, therefore, to finish what they have
to do in their present position, the experiment tl
casemate has been selected as the next object of
attack. At the same time, the postponement of the
Milwall shield is to be regretted, as competitive
trials ought naturally to be as close as possible to-
gether, particularly when they are likely to have
any influence on the public mind.

During the practice at the Plymouth target th1:1
spectators have observed, standing immediately ad-
joining it on the right hand, a black iron wall,
larger and more imposing-looking even than its
formidable neighbour, and which, from its port-hole
in the centre, is at once identified as representing
generally a similar object—namely, the front wal
of a casemated battery. But the resemblance .is
only general and superficial. It is no massive iron
building, like the adjoining one ; it consists only of
concrete piers and walls, covered with what is com-
paratively a thin facing of iron. This is what is
called the "experimental casemate," and its object
is to exemplify and test various forms and arrange-
ments of defensive works formed by compounding
the two materials together. The iron work is light—
very light, indeed, as compared with the Plymouth
shield ; but its weakness has been assumed to be in
some measure compensated by the massiveness of
the concrete work behind. It represents nothing
that has yet been either built or designed ; it is
merely the embodiment of a series of mechanical
ideas that have sprung up from time to time for
some years past, and have been thought worthy
of a trial. And inasmuch as during the time these
ideas of defence have been slowly in cogitation
the practice of attack has been rapidly in ad-
vance, it will not be surprising that, now they
come to be pitted against each other, the guns
should win. The experimental casemate differs
essentially from the Plymouth fort in that the main
piers supporting the roof come to the front, and
are therefore exposed to fire. The target may
generally be described as consisting of two of
these piers, having a space between them for
the gun, protected by a shield, and roofed over
with brick arches covered with concrete. The
fronts of the piers, the front of the shield, and the
front of the arched work over the opening all
form one vertical wall, which is protected by a
facing of ironwork, and this ironwork is arranged
in various ways over the several parts of the area
of the wall in order to test, by actual firing, the re-
spective merits of the different forms of construe..
tion. It is altogether a very Complicated structure,
and very difficult to make intelligible without
figures.

The main piers measure 12ft. across, Bft. from
front to back, and 7f t. gin. in height. They are
formed of brickwortk to a height of 3ft. 9in. from
the floor level, and above that of Portland cement
concrete, all being enclosed on the sides and rear by
a casing of plate iron.

The part which we have called the shield, filling
up the space between the piers, and forming the
defence immediately in front of the gun, is 12ft.
wide and 9ft. high, with an embrasure in the
middle. It is (excluding the front iron armour,
which we shall speak of presently) 14in. thick, of a
sort of cellular structure, formed of thin iron
flanched ribs, filled in with cement concrete, and
backed with an iron skin plate three-quarters
of an inch thick on the rear side. The em-
brasure is strengthened with a massive iron
frame ; over this shield the roof arch i§ turned.
The most important part is the iron armour-facing
applied to protect the front wall. This wall is 28ft.
wide and 12ft. high, and is in the first place
covered entirely, except at the port-hole, by an outer
skin of iron-plating two inches thick, composed of
large plates, running horizontally. In front of this
skin are fixed six different varieties of external pro-
tecting armour, arranged in vertical divisions, each
division running the whole height of the wall and
occupying a certain portion of its width. We shall
call these Nos. 1 to 6 respectively, beginning from
the left hand of the spectator, or what is called the
" proper right" of the target.
Armour No. 1 is 4ft. Bin. wide, and consists of a
single 8-inch plate immediately in contact with the
2-inch skin, and bolted through the whole struc-
ture. This solid plate may be considered the stan-
dard as to weight for the whole of the varieties,
which are made up so as to contain equal weights of
iron for a given area.

Armour No. 2,4 ft. Sin, wide, is compound, con-
sisting first of ribs of what is technically called
" channel iron," set vertically against the 2-inch
skin, and faced with a plate 41-in. thick ; the spaces
between the ribs are filled up with bitumen.
Armour No. 3 is something like the last ; but in-
stead of the channel iron rib, there is used a pecu-
liar "hollow iron stringer" of the form of, Mr.
Brunel's well-known bridge-rail used on the Great
Western Railway, but much larger. This is a
contrivance proposed by Mr. Hughes, of the
Millwall Ironworks, and we shall have again to
mention it when we come to the Millwall shield.
The stringers are covered with 6-inch plates in
front. The armour division occupies a length of
10ft. 4in., part of it covering the main pier, and the
remainder extending over the cellular shield in front
of the gun.
Armour No. 4,3 ft. 3in, wide, is composed like
No. 2, but with the channel iron ribs closer to-
gether, and faced with a 4-inch plate ; this division
partly covers the cellular shield, and partly the roof
arching over it.
Armour No. 5 is a narrow strip like No. 4, but
with a 4i-inch facing ; and No. 6, extending to the
right-hand edge of the casemate and covering the
pier, is simply a 4i -inch plate backed by a filling
of 7in. of concrete between it and the 2-inch skin.

All :these armour facings are substantially bolted
through the work. and at the rear
.in many places
there are false casings of thin iron for the purpose
of covering up the nuts, and generally catching
splinters.
The order of firing against this casemate, as ori -
ginally settled, was to begin with the 12-inch gun
with charges representing XOO and 200 yards, going
on to the smaller guns successively ; but before the
day of trial this order was reversed, and the pro-
gramme was made to begin with the smaller guns,
going on afterwards to the larger. The practice ac-
cordingly commenced with a series of shell from the
smallest gun of the battery, the 7-inch, at 200
yards' distance, and with the full charge of 221 b. of
powder ; these were aimed low, and were intended
to hit successively the various divisions of the
armour, beginning with that on the left hand,
which we have called No. 1. Those were followed
by a second series from the 9-inch gun, aimed a
little higher; and these by a third from the 10-inch
gun, higher still.

The Journal des Debuts says that, :rumours hav-
ing gone abroad that the ex-Empress Charlotte in-
tended to return to Mexico at the call of a power-
ful party, it made inquiry on the subject of her
health, and ascertained from the most reliable
source that, though her condition is improved, her
reason is still profoundly affected."
MISSING SHIPS.—The Pharamond, which sailed
from Alexandria for Falmouth on the 9th of January ; the
Vesper, from London for Caen on the 13th of April ; the
Trial, from Newport for Wadebridge, from Ilfracombe on
ihe 21st of March ; and the Marion, from Havaunah for
Vow York, which was spoken off Charleston on the 17th
of March, kayo liQt Aince Don hoard vf. -- •

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