The Sun.
London, England, 1866-10-20 00:00:00

however, each engine is distinct in itself, having its
own throttle and discharge valves, air, feed, and
bilge pumps, and the ordinary condenser and india-
rubber foot and delivery valves.
The combined nominal power of the three engines
is 160 horses. Steam is supplied to the engines by
two ordinary tubular boilers, each containing three
furnaces, with 350 brass tubes. The heating surface
per nominal horse-power is 16.7 square feet of
tube surface, and 725 square feet of grate bar sur-
face. Every part of the machinery is iu beautiful
proportion to other parts in design, and is as beau-
tifully finished in point of work. The hydraulic
wheel and its casiag and copper propulsion pipes are
all marvels of workmanship, the wheel and casing,
as iron work,reflecting the highest possible credit on
the Messrs. Dudgeon, the manufacturers. The cop-
per propulsion pipes were manufactured to the Messrs.
Dudgeon's order by the Messrs. G. and T. Blundell,
the present representatives of the well-known Down-
ton Patent pump firm, of London. Connected

with this part of oar notice of the machinery of
the Waterwitch it is necessary to state that, in addi-
tion to the sluice valves leading to the hydraulic
wheel from the perforated box-canal in the bottom
of the ship there are also two side sluices which con-
nect the wheel only with the bilge of the ship. These
side sluices are intended to pump out any water from
the ship's hold—the sea sluice valves being closed—
that may gain sudden access through shot or tor-
pedo-holes, or other damage to the ship's hull below
the water line. As it is calculated that with the
engines making 45 revolutions per minute the
hydraulic wheel would eject 300 tons of water per
minute from the ship, the damage done must be of
a very extraordinary nature indeed that would sink
the ship in spite of the clearing powers of so huge a
bilge pump.
In so novel an application of propulsion there is,
necessarily, yet very much to learn, and, as a con-
sequence of this immature knowledge, opinions, even
among professional men, are very much divided as
to the possible extent of its application and of its
working value, and this diversity of opinion has even
extended into the question as to the precise point at
which the propelling force is first brought to bear
upon the vessel. Without, however, entering fur-
ther upon this subject we may say that the propell-
ing force brought into action upon the vessel's hull,
by the ejection of the water from the hydraulicwheel
through the propelling pipes and the nozzles over the
ship's sides, is best described by Mr. Ruthven as
" similar to the recoil produced by the firing of a
gun." In describing this more' ully Mr. Ruthven
says:--

" Were a gun placed on a line with the keel and
fired towards the stern, there would result a pressure
forcing the vessel forward equal to the force with
which the ball left the gun, and if a continuous firing
were kept up, there would thus result an availrble
propelling force. The water column issuing from
the nozzles on the ship's side resembles the ball from
the gun, and the reacting force which propels the
vessel presses on the bent arm of the nozzle in the
contrary way to the discharge. With this hydraulic
power the propelling force presses directly on the
vessel. The paddle and the screw press the vessel
ahead by pushing back the water, so that the pro-
pelling force acts indirectly on the vessel through
the yielding water."
The Admiralty wisely determined in carrying out
so important and costly an experiment to provide

reliable data with which to weigh the results ob-
tained from the Ruthven hydraulic, as fitted in the
Waterwitch, against the ordinary principle of screw
propulsion, and for this purpose selected the trial
figures of her Majesty's armour-plated twin-screw
gunvessel Viper, a vessel precisely similar to the
Waterwitch in tonnage, displacement, &c., and in
ratio of horse power of engines to tonnage. The
Viper in her full boiler power runs over the mea-
sured mile attained a mean speed of nine knots, and

against this rate the speed attained by the Water-
witch, with her hydraulic machinery, has to be
placed, and considered as indicating the success or
non-success of the system as regards its suitability
for the propulsion ofsships of war.
The Watcrwitch left Woolwich for Tilbury, where

the Admiralty officials appointed to watch and re-
port upon the trial were to join her, at 8 30 a.m.
yesterday, in charge of Staff-Commander Dillon,
her Majesty's ship Fitzgard, her draught of water
being 9ft. Bin. forward and 9ft. 10in. aft., the lower

lips of the nozzle pipes discharging the water on the
outside of the vessel being Bin. below the water-
line. The engines worked almost noiselessly, and
with a beautiful uniformity of action, as their three
connecting rods whirled round the immense water
wheel up to 39 revolutions per minute, that being
the maximum rate at v►hich it was attempted to
drive them between Woolwich and Tilbury. The
measured mile in Long Reach was passed at 9 30
a.m. in 6 minutes and 20 seconds, the speed of the
ship being 9.474 knob, with the revolutions of the
engines at 39 ; the pressure of steam, 171 b. ; and
the vacuum, 27in. Tilbury was reached at 13
minutes past 10, the time from Woolwich having
been 1 hour and 43 minutes. So far the amount of
success obtained was, without doubt, greater than
had been anticipated, and was a favourable omen
of the results of the day's trial. In running past the
mile in Long Reach the tide was at high water,
slack.

Tilbury was left at noon, the officials, &c., then
on board comprising Vice-Admiral George Elliot,
who may be considered as the main supporter and
advocate of the hydraulic principle of propulsion

with the Admiralty ; Mr. Andrew Murray, chief
engineer of Portsmouth dockyard ; Mr. Steel, in-
spector of machinery afloat to the Admiralty; Mr.
Barnes, from the office of the Controller of the
Navy ; Messrs. John and William Dudgeon, the
makers of the ship's machinery ; Mr. Ruthven, the
patentee of the hydraulic wheel ; Vice-Admiral Sir
Edward Belcher, Commander S. Brett, her Ma-
jesty's ship Vixen, and a number of naval officers
and gentlemen interested in marine engineering.
The ship's machinery was in . charge of Mr. Ham-
mock, managing engineer to the Messrs. Dudgeon,
assisted by Mr. Hefferman, the engineer of the
ship. The vessel was steamed down the river as far
as Southend, when, everything having proved to
be of the most satisfactory nature, the course was
reversed and laid up the river again, until the Ad-
miralty measured mile in the Lower Hope was
reached, when two runs were made with the con-
ditions and results annexed :
First Run.—A half-knot tide against the ship.
Wind, force of 3 on port-bow; time on the mile,
7 min. 15 sec. ; speed of ship, 8.276 knots ; revolu-
tions of engines, 41 ; steam pressure, 241 b. ;
vacuum, 27 inches.
Second Run.—Tide, half a knot in ship's favour ;
wind, nil; time on the mile, 6 min. 17 sec. ; speed
of ship, 9.549 knots ; revolutions of engines, 42 ;
steam pressure, 251 b. ; vacuum, 26in. ; mean speed
of the ship in two runs, 8.912 knots.
As neither the Admiralty, Vice-Admiral Elliot,
the patentee of the principle, the manufacturer of
the machinery, or the designer of-the ship can ever
have anticipated a greater rate of speed being at-
tained as a mean rate over the measured mile than
seven knots, the rate of 8.912, or say, in round
numbers, nine knots, attained by the Waterwitch
yesterday must have been a surprise as well as a
gratification to all concerned. This very agreeable
result, it is but fair to say, is as much due to the
unusual excellence of the ship's engines as to the
many acknowledged good qualities of the hydraulic
system of propulsion. The vessel, with slightly
more favourable conditions, which can readily
be given her, will certainly make a full half
knot in addition to her present rate as attained
yesterday, and this half knot may be increased
to a full three-quarters if she is sent to Portsmouth
to complete her trials under the same conditions as
is pursued with all other of her Majesty's ships
algirnt
si on
the Stokes' Bay mile. For instance, the
to
on the trial yesterday was not equal in
wqa';er,ynor,
the coal burnt on the Portsmouth trial
was the stoking of the furnaces—one of the most
important points in a trial of a ship's
speed—at all
approaching to the perfect system of fire-feeding
carried out at Portsmouth. The trial altogether
yesterday has also suggested manyo ideas which must
yet be practically tested pre:, as to any decided
at as to the
measure of opinion being safely arrived
exact value of the Ruthven principle. of hydraulic
propulsion.
We believe the ship will be further
tried on the Thames on two occasions, at light and
deep draught of water, at light draught carrying
her discharge nozzles clear above the water line, and