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

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. J. 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 llebe and
Kate, of about the same dimensions and power, the
trials of which were carried out under the. bupervision

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-

:ory, and in yesterday's trial of the Aurora, while
:he 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; copse-

quently the adoption of the principle in feeir 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 as 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. 6in., an area
of midahip 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, 71t. 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 which 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 M. 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 14.5:6 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. 2es,, hay-
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. From the Mouse the
Aurora was run out between the Maplin and the
Barrow es 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 Swin the vessel's bead
wasbrought round and laid homeward, it having been
decided not to lengthen the trial by
making circles,
See, owing tothe high state of the wind, the light con-
dition of the vessel, and the very satisfactory manlier
in which she had already turned both to port end star-
board in answer to her rudder or screwa, proving that
she possessed the same facilities in that respee., as
were possessed by the Flora, Hebe, and Kate, a faci-
lityn ily
,
of manoeuvring, in fact,
which must necessarily
he by every vessel built for end
fitted with
double screws driven by independent engines.
Southend was passed at 4h. 151 n., and about two
miles
e ahead was seen the Sea Swallow, ono of the
fastest paddle steamers on the Thu-nr--. PI-in, be-
tween London, Southend, and Sheerness, and a hot
chase naturally ensued, the Aurora eventually pass-
ing the clipper at 4h. 40m. in the midst of a heavy
squall of wind and rain, and subsaguse,tly during
the run up to Blackwall passing everything under
steam she came across. GraVESelld was passed at
sh. 15m., the engines making on the average at the
81w,*,..05-411 Fier, the cleeie g
time 127 revolutlowi,