The Sun.
London, England, 1856-10-14 00:00:00

The steam troop-ship Urgent, Commander Phillips,
arrived at Portsmouth yesterday from Ireland, with part
of the 33d and 50th Regiments, which she landed at the
dockyard.
Her Majesty's ship Retribution, 22, Capt. Barker, had
steam up at 6 o'clock last night ready for leaving for the
Mediterranean.

Her Majesty's steam troop-ship Simoom was taken
into dock at Portsmouth yesterday for a refit.
The steam store ship Hesper arrived at Portsmouth,
yesterday from Woolwich to ship stores and medical
comforts for the island of Madeira.

The following appointments were made yesterday at
the Admiralty :—C. W. Talbot, naval cadet, to the Prin.
cess Royal ; C. R. Harris, ditto, to the Colossus ; J. T.
Bedford, ditto, to the Retribution ; R. D. Campbell,
ditto, to the Cesar ' • E. F. Keppel and U. E. Eyre,
ditto, to the Raleigh, and J. D. Webb, ditto, to the . Sa-
tellite.

TEE NEW AMERICAN STEAM-SHIPS OP WAR

The visit of the large American steam-frigate Merri-
mac to Southampton having occasioned considerable
interest we think it may now be a proper time to lay be-
fore our readers such information as we have from time
to time obtained respecting her, and the Wabash, the
Minnesota, the Raanoke, and the Colorada—four ships
of much the same size and power of the Merrimac—
and also respecting the huge steam-corvette the Niagara.
In order to render the information which follows per-
fectly reliable, in so far, at !east, as the Merrimac is
concerned, we have visited that vessel, and verified by
personal observation the facts hereafter stated. In mak-
ing this verification we were favoured with the utmost
courtesy and co-operation on the part of the officers of
the ship, and particularly of first lieutenant G. W. Har-
rison, who was in command of her at the time of our
visit, and to whose kindness we are much indebted.

The principal dimensions of the five frigates above
enumerated are so nearly alike that they may, for all
ordinary purposes, be considered the same, and may be
to ken as follows :

Feet. Ins.
Length of keel
Length on load-water line
Length over all 3OO 0
Breadth extreme
Breadth moulded 5O 2
Depth of hold (to gun deck) 26 4
Draught of water forward
Draught of water aft
As our examination of the Merrimac was made for the
purpose of estimating her merits as a ship of war, we must
add to the above the following details, which are of im-
portance in such a ship. When the vessel is at her load
line the height of the gnn-deck ports above the water
are, amidships, 9 feet, and forward and aft 12 feet, or
thereabouts. The height from her gun deck to the lower
sides of her spar-deck beams is 6 feet. The height of
her bulwarks is such, that when the hammocks are
stowed, they reach 8 feet 8 inches above the upper deck.
Her gun-deck ports are 3 feet 8 inches long, and nearly
8 feet 6 inches apart. Her load displacement is esti-
mated at 4,000 tons ; but this we could not, of course,
test.

The Men:mac was designed by Mr. Lenthall, who is
at the head of the Bureau at Washington, and was built
by Mr. Delano, the master shipwright of the navy yard
at Boston (or the officer who corresponds to a master
shipwright of our own dockyards). Her frame is of live
oak, crossed on the inside with two sets of diagonal iron
plates, which are inclined in opposite directions. She is
also strengthened by similar plates on the outside, at bow
and stern. Her plank is also of oak, and, like our own
ships of war, she is copper-fastened up to a few feet

above the load-water line. Her decks are of fir. On a
careful inspection, she seems to have been built with
very great skill and care, and is a very tight strong ship.
The large wooden knees (common in American ships,
because more approved of and more readily obtained
than iron) to some extent interfere with the beauty of
her appearance inboard ; but she is a very roomy and
handsome ship, and the appearance of her main deck is
unsurpassed.
`With all her sails set, she spreads 56,629 square feet
of canvas. Her engines are auxiliary only. Her rig is
in all respects like that of the largest American sailing
frigates, but from her great length she seems capable cf
carrying masts, spars, and sails even larger than those
she has. The mode in which the mainmast steps is
worthy of attention. The shaft of the propeller coming
immediately beneath it (since the engines are before the
mainmast), a step is formed to receive it above the shaft.
This step consists of a large thwartship beam of live oak,
supported near the middle by two 12-inch solid iron
columns which rest upon suitable keelsons. This ar-
rangement is perhaps as good as any other, although the
strength attending it must certainly be much less than
that in which the mast steps in a wooden step, sup-
ported immediately by the keelsons themselves, as is the
case where no screw shaft interferes. The modes adopted
in our own navy are various. In some cases tall forked
iron steps, which stride across the shaft, are employed,
and is others the heel of the mast itself is enlarged, and
the shaft allowed to pass through it, the lower piece of
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present armament is as follows :—On her upper deck
tons, and of 10 inches bore, and 14 8-inch guns, each
24 9-inch guns, each weighing nearly ,4 tons. The
whole of these guns, 40 in all, though strong enough to
discharge shot, if desired, are primarily intended to be
served with hollow shot or with shell--fur it is now a
practice with the Americans to supply their navy with
a quantity of empty hollow shot, which may be either
plugged and used as such, or charged, fitted with fuzes,
and used as shells. We must not, however, omit to
mention that she might carry a few additional 9 inch
guns on the main deck with perfect convenience. Her
gun-carriages on the main deck are similar to those used
in the French navy. They have, however, but two wheels
or trucks each, at the ship's end of the carriage. To
facilitate the running out of the gun the rear end of the
carriage is raised by a handspike fitted with a roller at
the end, on which roller the carriage runs out. At the
upper side of this handspike roller is a pin or stud which
takes into one or other of a series of recesses formed in
a plate on the underside of the rear end of the carriage.
The carriage slides of the large pivot guns differ from
our own chiefly in the fact that they are furnished at
each end with wheels or trucks (which run on the metal
circular bearing plates on the deck) mounted on
eccentric axles. These axles are turned by a spanner,
so as either to take the weight of the slide and allow
it to be run round upon them, or to ho raised clear
of the bottom of the slide, and allow it to rest imme-
diately upon the deck plates. The carriages which run
upon the slides have their rear trucks mounted upon
similar eccentric axles. The friction of the carriage upon
the slide when the piece is to be discharged (and when
the trucks are clear of the slide) is sometimes increased
by nipping the two together with screws.
The whole of the 9.inch guns, or main-deck guns, as
well as the two 10-inch pivot guns, are formed on Com-
mander Dahlgren's system, which consists in giving to
the gun, at each point of its length, a thickness propor
tioned to the direct pressure of the powder in the chase
at that point, supposing the gun to be fired with an ordi-
nary service charge. In order to carry out that principle
Commander (then Lieutenant) Dahlgren took an ordinary
Paixhan gun, and had bored in it a number of holes, each
of the size of a musket ball, extending from the outside
of the gun through into the chase. These holes were per-
pendicular to the axis of the gun. A musket ball was
then placed in the first hole (the rest of the holes being
plugged for the time), the gun fired with a service charge,
and the initial velacity communicated to the musket ball
measured by a ballistic
pendulum. This was repeated
with each hole successively, and lines representing the
initial velocities thus obtained were taken as the ordi-
nates"of a diirver (of which the distances apart of the
hole& represented the abscissa;), and this curve gave the
contour of the exterior of the gun. The Dahlgren guns
are of greatly increased thickness along the chase, and
suddenly increase their thickness near the breech, where
the great bulk of the metal of the gun is collected.
Before the adoption of them in their navy, the Ameri-
can Government had them severely tested, with highly
satisfactory results. Without doubt the principle of
Commander Dahlgren is correct, so far as it goes. There
are also eollatrale.advantages connected with the adop-
tion of it in naval ordnance, one of which is that the
centre of gravity
sideofmeuasethtendto m
ak eis,owing to the
her
battery
form of the guns, thereby brought nearer to the middle
of the ship, which
roll less hea-
vily than otherwise. Each gun is furnished with two
lock-lugs, or lugs for the gun-lock—one for use, and one
to supply its place if it should be knocked away.
There are a few other novel features in connection
with the guns of the Merrimac. One is that her guns
are fitted with elevating screws, which supply the place
of the quoin, Fac., in our own service. This arrangement
tends greatly to facilitate the sighting, and is certainly
an improvement, provided that it is not attended with
any defect in strength, and were assured that none had
been observed dating considerable Practice. Another