The Sun.
London, England, 1859-11-10 00:00:00

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PUCE 41). STAMPED, 51-1.

cording to present arrangements, to bring out, at
the lowest computation, 1,000 guns a-year, with the
prospect of a considerable addition to that number,
in case of actual demand. A number of cast-iron
guns will be made in the factories and by the trade
for experimental use, to be encased in a kind of net-
work, termed a " chemise," composed of wrought-
iron, which it is suggested will add to the endur-
ance of the inner metal of which the gun is cast,
and render it sufficiently strong for the pur-
pose. The new department has received instruc-
tions to bring out as speedily as possible a batch
of 40 6-pounder rifle guns to carry the don-
gated shot for field service in China, to be trans-
ported overland. It is stated that, as a neces-
sary consequence of the whole of the gun factories
being employed for the manufacture of Sir
William's guns, the shot and shell foundries
will be ultimately handed over to the same direc-
tion, and that the superintendence of the laboratory
will merge into that of the gun factories, which
will create a reduction of no insignificant import-
ance in the gene al expenditure.

IRON scREw STEAM-SHIPS'.

(From Mitchell' Steam-Shipping Journal.)

Iron ships, like brick mansions, can be built to

last a few Sears, or to hold together for a century.
All depends upon tho weight and strength of mate-
rial employed, and the architectural design. It has
been asserted by the awner of an iron yacht that he
paid at the rate of £4O per ton, builder's measure-
ment, but there are persons wbo advertise to com-
plete ships in hull, rigging, and machinery, at from
£9 to £l3. Iron ships, therefore, may be purchased
to suit the capitalist. He may have solidly built
vessels of good metal, or he may have common
plated ships, constructed expressly to sell. The
weakly built ship, when smartly rigged and painted,
will look as good to the uninitiated as the one more
substantially put together. Thu Tyne and the
Clyde have a reputation for turning out cheap iron
ships, but we suspect that good strong vessels of
the very first class can be had from off the banks of
those rivers if a remunerative price is paid. Where
honest and independent surveyors arc engaged to
overlook the work, it is their fault if material of the
right substance is not employed, though they can-
( not be present at all times to see the metal fused.
There is a great variation in the cohesion of diffe-
rent irons. Old metal, transmuted, perhaps, some
thousands of times, till its properties deteriorate, is
sLghtly mixed with bars of virgin iron, and plates
are turned out, by contract, of a given thickness,
which may by chance stand the atmosphere pres-
sure applied to test its strength. Well coated, these
plates may last for years ; but if, from some parti-
cular cause, an equal strain is brought to bear on
one, or several of them, they fall to pieces like, as
was once described by the shipwrecked mate of a
steamer, " the tearing of a sheet of paper ;" or, to
apply the simile of another seaman saved from the
wreck of a screw collier, " like a pack of cards."
The boatswain's mate of the Royal Charter states
that that ship " broke up like a bend-box." In some
instances this strange destruction is less owing to
the fault of the iron than to the peculiar build of
the ship. It is almost impossible to award to each
their proper share of the blame ; but it has always
been observed that when iron ships do begin to
break up there are no half measures ; the rivets
start, a few plates go, and the rest follow. Where
they do hold, their tenacity is great if a ship is
faithfully built. But the durability of a ship de-
pends not so much on the quantity as on the quality
of the metal. A ship built of the best Low Moor
iron, with cold hammered plates, and well strength-
ened horizontally, will stand an enormous strain.
As between Scotch, Welsh, and English iron of
various descriptions, there is a difference in value of
about io per ton, more or less, according to the
place of delivery.

The tenacity of metals depends very much upon
their purity. Professor Wallace gives the specific
cohesion and strength of different sorts of iron as

Specific cohesion.
Iron (Bar) ....... from 8.964 to 5.839
f f Best quality ' 7.006
99 German BR from 9.880 t 1 6.514
~ Swedish
~ Liege. from 8.791 to 6.621
~ German L
f 1 Spank% 8.635
„ Oosement
„ Fine grained 5.306
„ Medium fineness
„ Coarse grained 2.712
Iron (Cast) French
~German 7-250
„ English front 5.521 to 4.331

Here we have the tenacious union of the particles
of the multifarious descriptions of iron proved to
demonstration. When, therefore, we speak of an
iron-built ship, if we would rightly understand her
bt:ild, we must know something of the composition
of the metal used in her construction. But to il-
lustrate the utter impracticability of thoroughly
understanding the relative strength of samples of
iron, we will also give the experiments made by
Rennie to ascertain the direct cohesion of bars one
inch square, in tons.

- .
Toni.
iron bar, cast horizontally S 32
.ron bar, cast vertically

To this we may add—
Wrought iron, mean of 26 experiments by Brunel.— 31.20
Wrought iron, mean of 9 experiments by Telford.... 29-25
Wrought iron, mean of 8 experiments by 8r0wn.... 25.00
No two experiments, therefore, yield the same pro,
ducts ; but the average qualities of iron are so well
known that no purchaset need be at a loss in de-
signating in plain terms what sort of ircn he
wishes to be u,,.cd, though at the same time it rests
with the honour of a builder, or founder, to pro-
perly mix the metals. There are tricks and adul-
terations in every trade, and we fear the manipula-
tors of iron are not free from the universal vice.
Hence, as screw vessels built of iron are becoming
so common in several trades, supplanting clipper
sailing-vessels, it is essential that more attention
should be paid by intending owners of such ships
to the metal used, and to the principle of construc-
tion. Screw steam-ships do not appear to be fa-
vourites with the public as passenger-ships, though
they answer admirably for the conveyance of he avp
cargoes. The loss of the Royal Charter, which
could not stem the tempest even with her 300
horse-power auxiliary engines, has depreciated
them still further. But her case is an exceptional
one. When brought up by her anchor the masts
were cut away, and they fouled the screw, though
it must be admitted she was dragging before she
was dismasted. This fouling of the screw
appears difficult to overcome. Wire rigging,
chain sheets, and halyards are now so much used
that it is difficult to attach any cutting instru-
ment that will prove efficacious. A chain hanging
to a spar will sink under the ship's bottom, or be
drawn under by the ship's suction, and, when
seized by an arm of the screw, insinuate itself
round and round, till it either breaks off the fans
or stops the engine. The steamship Prince, when
caught in the gale off Sebastopol, it is said, was
working off the shore, when the order was given
to cut a 'ay the mizenmast. Immediately the mast
went by the board, the rigging fouled the screw, the
ship was disabled, and her loss followed. Many a
sailing ship has been saved by cutting away the
masts; but in screw steamers, uness care is taken
to see the rigging clear astern, the remedy is worse

than the disease.
The screw for first-class passenger ships, unless
as a mere auxiliary power for long voyages, is pos-
sibly doomed. It was prophesied that all steamers
would be propelled by screws before 1858, and the
adaptation of several of the Peninsular and Oriental
Company's ships from side wheels to stern screws
seemed, at one time, to give force to the prophecy ;
but the last new vessel of tho company, built to
order, was the Delta, with paddle wheels ; and their
vessel now on the stocks will also have side wheels.
In screw vessels there is so much noise in the after
section of the ship, by the rotation of the shaft,
that it is unpleasant to be quartered there. The
sleeping aecommodation is consequently placed
more amidships, and here you have the smell of the
oil from the engine-room, and the heat from the
boilers. Besides which, screw vessels roll badly,
and the vibration from the screw gives a tremulous
motion to the ship, to the sore aggravation of sea-
sickness. In the Great. Eastern, when the screw is
at work, the vibration is very great unless canvas
is spread, and the mastheads show this plainly by
their heavy quivering. When the screw stops and
the ship is driven by paddle only her motion is free
from all vibration, and she progresses smoothly.
On the Great Eastern's success or failure we appre-
hend will depend whether the double power will
be taken up and brought into use for passenger
steamers.

The unsold portion of the Australian gold in the
market, consisting of the £168,000 by the Orwell, has been
taken for the Continent, together with the 35,000 Sydney
sovereigns by the Placellician, and £4,000 in bars from the
Bank: