The Sun.
London, England, 1863-08-26 00:00:00

TRIAL TRIP OF TUB AURORA.

Since 1840-1, when the screw may be considered
to have been definitely adopted in this country for
both the Royal and mermitile navies, there has
been no incident connected with its subs&quent his-
tory which has created so great a degree of interest
in the minds of scientific men and the ufruers of
both services as the introduction of the double, or
" twin" screw principle, each screw worked by in-
dependent engine power. The reason of this is suffi-
ciently obvious to the initiated, although perhaps
not to the general public. The fact is, we are enor-
mously increasing the tonnage of our shipi and
their engine power, and, as a natural sequence to
this course, the draught of water of these large
vessels has to be increased in proportion to
their tonnage, in order to fully develope their
screw's power, for, as the engine power
is increased so also increases the diameter
of the screw, and so aleo must increase in
the same ratio the ship's draught of water. The
natural result of this general increase in size and
driving power is that the deep-loaded merchant
single-screw steamer can only move in certain direc-

Lions in narrow and tortuous rivers, and conse-
quently incurs a considerable degree of extra ex-
pense under such circumstances, exclusive of loss of
time, which in the present day is acknowledged to
be of more real value than monby itself. Our War-
rior and Black Prince are, and our Minotaur and
Northumberland will be, from their great draught
of water and the great space they require to
turn in, perfectly use!ess to attack such for-
tresses as Cronstadt, New York, or even Cher-
bnurg ; or to run into such a place as Spithead,
passing the proposed marine forts on the Noman and
Horse, and tackle a ship or two inside the forts.
The use of a single screw is, in fact, attended
with so many dangers and difficulties, which may
possibly be avoided by the use of two screws
both in the Royal and mercantile marine, that it
can be no matter of wonder that the subject should
have acquired a degree of importance second only
to the universal adoption of the screw itself in pre-
ference to the paddle. The practical introduction
of the " twin" screw principle in this country is
owing to the enterprise of Messrs. S. and W.
Dudgeon, shipbuilders and engineers, of Limehouse,
who, in November last, tried their first vessel fitted
in this way on the Thames, the Flora, of 400 tons
and 130 horse power of engines (collectively), fol-
lowed after wards by two other vessels, the liebe and
Kate, of about the same dimensions and power, the
trials of which were carried out under the supervision
of Admiralty officials, and were fully reported on each
occasion in The Sun. The success of the trials
were in each instance most unequivocal and satisfac-
tory, and in yesterday's trial of the Aurora, while

the value of the twin screw principle was again de-
monstrated in the most satisfactory manner possible,
it was also on this occasion developed more fully
than in either of the previous trials. The double
screw was adopted by the Admiralty some years
since in the construction of the iron-cased floating
batteries, but they were driven in those vessels by
collective, not independent engine power ; conse-
quently the adoption of the principle in their case
only enable the Admiralty to construct vessels that
float at a moderately light draught of water, and
carry an immense (for their tonnage) weight of
armour and armament, in addition to the weight of
their engines, but it gave the vessels no increased
powers of turning, or manoeuvring rapidly under
steam in any circumscribed space, which they would
have possessed had their screws been driven by in-
dependent engines, as were the Aurora's in yester-
day's trial. It is these increased facilities which
the double independent screws offer to ships
of war for manoeuvring rapidly, whether engaged
with an enemy afloat or with a shore battery, that
has brought the subject so prominently before the
notice of the Admiralty and the general public,
and to these military purposes our report of yester-
day's trial more especially refers.
The Aurora is an iron vessel, 165 ft. in length,
with a beam of 23ft., a depth of 13ft. Gin., an area
of midship section of 150 square feet, and a dis-
placement of 400 tons. Her engines have a collec-
tive nominal power of 120 horse, and drive two
three-bladed screws, each independently of the
other, 7ft. in diameter, and with a pitch of 14ft. Gin.
The cylinders have a diameter of 26in., and a 21in.
stroke. The Aurora is a smart looking vessel, with
much finer lines forward and aft than were pos-
sessed by either of her predecessors. She carries
two short masts, rigged for fore and aft canvas, and
altogether, although " light as a bladder" on the
water, has the appearance of a thorough steam
" clipper." Her draught of water at starting yes-
terday was 7ft. 3in. aft, and sft. 3in. forward.
A large party of gentlemen left town yesterday
morning by the 10.52 train from Fenchurch-street
or Tilbury station pier. alongside waich the Aurora
lay with her steam up. Immediately on the party
embarking the screws were set to work in opposite
directions, and the vessel slewed round with her
head down river and started on her trial at
12.20 p.m., under the charge of Mr. Leigh,
Trinity pilot, the wind being strong at S.W., and
the tide at half ebb. In running past the mea-
sured mile, in the Lower Hope, with the engines
not up in the number of their revolutions, she was
timed and found to go over the ground in 4 min.
8 sec., giving the vessel a speed of 14.516 knots.
At 1.30 p.m. the Aurora was approaching the
Nore Light vessel, the engines averaging 120 revo-
lutions, with 271 b. of steam and a vacuum of 25in.,
and every part working with the greatest possible
smoothness. At 137 the Nore was passed, the dis-
tance from Tilbury, 20 nautical miles, having been
done in 1 hour and 17 minutes, an almost unparal-
leled rate of speed, considering the vessel's horse
power of engine and hull displacement. From the
Nore to the Mouse Light the vessel continued her
course, the wind still fresh from the same quarter,
and the movement of the water which necessarily
accompanied it giving the vessel, from her light
draught and hold upon the water,
sufficient " roll"
to detract from the efficient acting of her only just
submerged screws. Notwithstanding this disad-
vantage, however, she ran past the " mile" on
the Maplin Sands in 4 minutes 10 seconds, giv-
ing a speed of 14.400 knots, it being now about
slack water, and the tide of little moment
either way, and accomplished the distance
to the Mouse Light at 2h. sm. 225., hav-
ing been 28 minutes and 23 seconds from the Nore
—eight nautical miles. During the latter part of
the run down a small jib had been set to steady the
vessel, but no other help was given by the vessel's
canvas to her engines in attaining this somewhat
extraordinary rate of speed. Frem the Mouse the
Aurora was run out between the Maplin and the
Barrow as far as the S win Light, passing the James
Dixon, a fine screw collier under sail and full steam,
with her head in the same direction as the aurora's
on the way. On reaching the S win the vessel's head
was brought round and laid homeward, it having been
decided not to lengthen the trial by making circles,
&c, owing to tho high state of the wind,
thu
light con-
dition of the vessel, and the very satisfactory manner
in which she had already turned both to port and star-
board in answer to her rudder or serowe, pr"ving that
she possessed the same facilities in that respect as
were possessed by the Flora, Hebe, anal Bate, a faci-
lity of manoeuvring, in fee, which must
,tted with
necessarily
be possessed by every vessel built for and fitted
double screws driven by independent en ;fires.
Southend was passed at 4h. 15m and about two
miles ahead was seen the Sea Swallow, one of the
fastest paddle steamers on the Thames, plying be-
tween
chase
at London,uraly
ensued, the Aurora eventually pass-
ing the clipper at 4h. 40m. in the midst of a heavy
nl
Southend, and Sheerness, and a hot
and ly during
the run up to Blackwell passing eee,ith,lig
under
squall osfheweinamd
carne access.
rain,ero and subs,:qaentss. Gravesand. WEiS passed at
steam
5h.15m., the engiues making on the average at the
Pier, the closing 127 revolutlmsa