The Sun.
London, England, 1859-04-29 00:00:00

The following details respecting the4ran
theatre of hostilities in Italy are interesting at this
moment
" If Alessandria, which was dismantled by the-
Austrians in 1835, when they gave it up to Pied-
mont, bat which has recently been fortified, were
made the basis of operations of an invading ate,
against Milan, the army would have two: routes -to
follow :—the first, in which there are a numbe4.
torrents, up to the Ticino, which separates: ,X4o4b-
hardy from Piedmont; and.-the second, the efthe
one, presenting an obstacle in the Po, which is.the
soutk n limit of Lombardo-Venetia. Now Airs.
tria, whice occupies Piacenza, on the right bank of
that river, has established an entrenched camp at
that place. Lower down are Cremona, and on
the left bank Mantua, to defend the passage
against an army which should leave Piacenza in
its rear. On the first road to Milan, behind the
Ticino, is Pavia, which seems to have been lately
fortified in order to be made a base of operations
against Alessandria, if besieged; on the north are
Bergamo and Brescia, strong places, but not im-
pregnable, and able to disquiet an army passing
them to attack Verona and Mantua, which are the
keys of the country. This territory was the theatre
of the campaign of 1796, and Austria has accumu-
lated defences there in the belief that in a future
war the same plan of attack would be followed ;
but that is perhaps doubtful. On the Mincio,
which is only ten leagues long from the Lake of
Gardo in which it rises to the marshes which
surround Mantua, where it falls into the Po,
and which can be forded in several places, means of
defence have been accumulated, and Peschiera and
Mantua protect its two extremities. The Adige is
in the rear, and flows parallel to the Po for a cer-
tain distance. It is perpendicular to it behind the
Lake of Gardo from Verona to Legrano, a length of
fifteen leagues. It can nowhere be forded, and its
banks, on the side of Verona, are covered with gar-
dens and vineyards, and those on the side of Man-
tua with rice fields and marshes. The road from
Verona to Legrano runs between the Adige and a
canal; and an army placed within the square
formed by Peschiera, Mantua, and Legrano, pro-
tected by the water which is found on the east and
west, by mountains to the north, and by the marshes
to the south, is free in its movements, and can
march on any point that may be menaced. Pes-
chiera, of which the defences are somewhat scat-
tered, is the refuge of the flotilla which, acting on
the Lake of Gardo, would menace a cops d'arntee,
desiring to cross the Mincio, and protects the locks
which enable the banks of the lower part of the
river to be inundated. By an inundation the fly-
ing, brides constructed by the enemy would be car-
ried away. Mantua is, like Peschiera, on an island
in the Mincio, surrounded by a lake, which should
be drained in order to allow the town to be taken,
and draining would leave a pestilential marsh
which would render the place uninhabitable. Tho
fortress is reached by raised causeways protected
by forts. It is very difficult to take, but can be
easily blockaded. As this place appears to Aus-
tria too unhealthy and too far from the Tyrol, she
has established her head-quarters at Verona, and.
has disbursed a large sum in fortifying the place.
Verona, like all the positions fortified by Austrian
engineers, comprises in addition to numerous forti-
fications an entrenched camp, capable of containing
an army. It is believed that the fate of the place
will be decided rather by a battle than by a siege,
which last would require a vast force. Legrano is a
tete-de-pont fortified by Napoleon, which would
enable the army of Verona to proceed to Mantua,
as Peschiera on the north would give it an issue on
Brescia and the northern part of the Milanais.
Moreover, an Austrian army, defeated and obliged
to remain at Verona, could be relieved by troops
arriving from the Tyrol on the front and rear of the
besiegers. The numerous roads in the Tyrol are pro-
tected by forts which a handful of men would be
capable of defending against a victorious army. If,
however, Verona were to be taken, the conquest of
Venetia would not be difficult. As to the Adriatic,
Austria has taken the caution of protecting herself
against an attack on its coasts. From the banks of
the Po to the frontiers of Istria, the shores of the
Adriaticlare very insalubrious. In some places it
is impossible to pass a night without being attacked
by fever, and the sea is shallow to a considerable
distance from the coast. Venice, in fact, is the
only place which can receive vessels even of a
secondary size, and they must enter by passeswhich
are protected by strong forts. If the city were
taken, Fort Malghera would remain, and it cannot
be approached either by land or water. In 1848,
the insurgents in that fort resisted the besieging
Austrian army until men and ammunition were
exhausted."

HOW GREAT GUNS ARE MADE.

A 681 b. gun, when finished, is 17ft. long, 28ins. in
diameter at the breech, and weighs 95 cwt. As suns
of this description are cast vertically, and require a
" dead head" of considerable magnitude in order to
insure sufficient density, it may be imagined that the
furnaces are matters of important consideration.
In practice it was found advisable to use two fur-
naces in the melting of a sufficient quantity of iron
for the production of one such gun as we have de-
scribed. The Woolwich furnaces would each hold
sufficient molten metal for the casting of one gun,
but as it was not possible to charge with ten tons
of pig iron at once, it was found better in every
way to charge two furnaces with five tons and melt
simultaneously. The quality of the iron produced
in this way was found to be superior to that result-
ing from one furnace, when a portion of the charge
must have been melted first, and the remainder
afterwards. Repeated tests proved this fact to de-
monstration, and it is a practical point of much
consequence. The Woolwich furnaces are partly
constructed of Stourbridge firebrick, but the beds
are of a different material. The throwing in
of old " carronades," " dead heads," and
" pigs," was found to chip off, or to crack and
destroy the fire bricks, and a substitute for these in
the construction of the furnace beds had to be found.
A cheaper substance, and one which admits of
easy repair, is now used. It is composed of equal
parts of glass-grinder's sand and blackfoot sand.
The former is the refuse from the Thames patent
glass works, and contains a considerable admixture
of fine particles of 'glass, and the latter is obtained
n
furnace
uuri.
aetorrlinnmi
recommend
aecctteceeehsdod:omb,
surface
esuarnmadbardnfeml
iaydns
acmdef Charlton.psiteinueidimttrpsphpetsoarahetiitrrrenoNdor.tinaoilogputpflopsoytoefficiencye
htaliquidhat
Withet
ono lf'
rfifre
foundationse ar e amal-
gamated, m
the al -
aeor heati:enp-d.
fire-brick,
rcTit
e hfktre smaat economynnh
ddae
dimensions of the furnaces, it may be stated
that they are about 22ft. long, from centre of fire
grate to centre of chimney ; sft. 2in. wide ; and
2ft. Gin, in height from bed to crown. The fire
grate is sft. 2in. square, and open for the admission
of air at the end of the furnace, and the chimney is
60ft. in height and 2ft. 6in. square. The furnaces
are always heated before receiving their charges,
and when the latter are sufficiently fluid and hot,
the molten streams from two furnaces, as we have
stated, are made to flow through separate channels
into one reservoir. Here they mingle and blend
for a little time in one harmonious whole, so as to
equalise any difference of temperature which may
have existed prior to their being tapped. Metal.
is now ladled in small quantities from the reser-
voir for the purpose of casting testing bars, and a
sluice door being opened the molten ceean courses
its way down river-like into the centre of the
gun mould, which is placed vertically, and muzzle
upwards, to receive it. Scoria and other impu-
rities float upwards as the metal rises, and great
precautions are taken to prevent their flowing
with the iron into the " trunnions," which they
cidsee
naa tdreh, greataa d buts
entirely,uthb sei dphTeeolihrl
would weaken, and thus make the whole casting.
fuseless.eNv i
nnhelaVhofen
thtehegtumdetealahruetaec,hetshetog.
3wodit!igianteas
the shute is removed, and then again opened
the mould. In cooling there
through which it flowed are sehtuati,foerspa.emeinlulyteinuntfthairel
the complete filling of
ethssetmhus produced is in the
by no means deteriorates
dfis suffered t• remain in statu
subsidence
mould
sl d
preparedis then opbeynelda,tahned
andt h e
the gun. Everything
and .
for about three days nights after the quo
boring-mill for proving, and mayhap for battle.
Such is some account of the gestation and birth of
a great gun, and which in these non-piping times
of war may be acceptable to the public generally,
pour-
ing
casting, ePe r usuallyt!n
and certainly must be tol the scientific reader.—
Mechanics' Magazine,

FATAL ACCIDENT DURING THE RECENT GALE.
—A fearful accident occurred at the bar of the Tyne, on
Wednesday. A Norwegian brig being about to enter the
harbour, two boats put off to her. They had got outside
the bar, and attempted to hook her, when they were both
swamped by a heavy sea. The Andrew Woodhouse steamer,
towing the Tossel, immediately let go the rope, and made to
the assistance of the men belciaging to the boats, who were
knocking about in the broken water. The master of the
steamer, who was twice washed from the wheel while trying
to save the poor fellows, got a life-buoy to three of them,
and they laid hold of it. They were washed away three
times by the sea ; and at last could make no further exer-
tions, and were swept away and drowned. The men in the
steamer then made a gallant attempt to save the fourth
man, and eventually rescued him from the boiling nves*
He was immediately brought into port, and is recovering .
The names of the drowned men are: Jere_p_ra;
wre7e'vali
of th
Thomas Thompson, and William Simpsont.sine
of e steam-
well-known Tyne Foy boatmen. The "Puct,—Nanchater
tug is highly praised for his gallant eend
Gy4rdian.