The Sun.
London, England, 1864-04-25 00:00:00

tirely under the supervision of the dockyard officials.
Her engines have been manufactured by Messrs.
John Penn and Sons. They are nominally of 3
horse power, but being on the highepressure prin-
ciple they can be worked up to ten times that power.
The entire machinery occupies a space of 6ft. by 4ft.,
and the engines are so constructed that the whole
machinery can be bodily lifted out of the launch and
placed on the deck of the vessel to which she is ate
tached. The weight of the whole is 3 tons 17cwt.
2qrs. 201 b. There are four cylinders, each with a
diameter of 4in., and a length of stroke of 6in. The
connecting rod is 12in. in length, and the diameter
11; the piston rod is Zia. The diameter of the
crank axles is ltin„ and the diameter of the screw
shaft the same. The ,",screw propeller is 3ift. in
length. The fire-grate is 2ft. by 2ft. and the length
of eaeh of the boiler tubes, of which there are 19,
3ft. 3in., and their external diameter 21in. The
total fire-bar surface is sft. ; surface of flue, 21ft. ;
and surface of tubes, 40ft.; the total heating sur-
face is Gift. The two screws are 4-bladed, and have
a diameter of 2ft., the set of the pitch being 3ft.
4in. Each screw is driven by its own indepen-
dent shafting, which thus enables both to be worked
in contrary directions. The quantity of coals on
board was 13 cwt. At starting the draught of
water, both fore and aft, was 2ft. 6in. From the
above figures it will be seen that the engines are
probably the smallest ever supplied to one of her
Majesty's vessels, nevertheless the results achieved
were somewhat astonishing, and appeared to take
all the spectators by surprise. At 10 o'clock the
screw launch steamed from the dockyard pier,
having on board Captain Stewart, C. 8,, superin-
tendent of the dockyard ; Capt. Colin Campbell, of
the Bombay; Captain Stokes, Queen's harbour..
master; Mr. Thornton and Mr. Hutchens, master-
shipwrights, and others of the officials. The engines
were in charge of Mr. Wiggell, from:Messrs. Penn's
establishment, who superintended their working.
Prior
.to the launch undergoing the most impor-
tant portion of her day's tr;als Captain Stewart
directed her to he taken to the most crowded
portion of the harbour, in order to test her mat ceav-
ring capabilities in and out among the vessels,
boats, and other craft about the dockyard. At this
time there was a pressure of steam of upwards of
601 b, and the screws each making upwards of 200
revolutions per minute. Before she had been out
any great distance it soon became evident that the
twin-screw principle enabled a vessel to be almost
independent of her rudder. Acting upon this Capt.
Stewart boldly directed the tiller of the rudder to
be removed, and henceforward the vessel was steered
solely by her screws. 'With a strong flood tide
running, the vessel was manceavred by means of
her screws with as much ease as when her rudder
was brought into use, and, indeed, the remarkable
ease with which she was turned round boats, buoys,
and other objects pointed out by Capt. Stewart, as
well as the surprising steaming powers of the minia-
ture craft, elicited the admiration no less than the
astonishment of all on board, as well as of the per-
sons who watched her progress from the dockyard
and pier. After fully demonstrating to the officials
the steaming and steering capacities of the screw
launch she went alongside the dockyard, where some
slight alterations were effected in the machinery,
after which the miniature vessel's hoed was turned
down the harbour, and a ran taken towards the
Nore, duricg which numerous experiments were
made in steering the launch solely by means of her
screws, with the most complete success. The time
occupied in the run from Chatham Dockyard to the
Camber was two hours, which would give an ave-
rage speed of rather over six knots per hour. The
boat was also tried in making circles, when with
the port screw going ahead at fall speed and
the starboard screw working astern the circles
were made as nearly as possible on a pivot,
the average time occupied being 1'247 of a
minute with the engines making 310 revolutions
per minute. During the run to and from the Nora
the engines worked with the utmost freedom and
regularity, the boilers giving a pressure of 601 b. of
steam, the average number of revolutions of the
screws being 320 per minute. Altogether, the trials
were deemed a complete success as establishing the
superiority of the double screw principle:
The Geyser, 6, paddle, Commander Thrupp, ar-
rived at Spithead yesterday, from Dovonport, with
men paid off from the Nile.