The Sun.
London, England, 1845-11-27 00:00:00

TO THE EDITOR OF THE TIMES.

Sir,—The various short paragraphs respecting the Janus
and her engines, which have found their way to the public
through your widely-circulated paper, having appeared to
me to proceed from uninformed persons, I have abstained
from troubling you to correct errors; but perceiving that
nearly half a column has this day been devoted to the sub-
ject, and that an insidious misrepresentation has been trans-
mitted to you, which may impose on the public, I claim of
your justice a space sufficient to rectify erroneous assertions,
and to place the forbearance of the Admiralty, wisely shown
towards the development of a machine (peculiarly adapted
to actuate the screw propeller) free from exposure to derange-
ment by shot, which is of the highest importance to the
naval service.—l am, Sir, your obedient servant,
8, Chesterfield-street, Nov. 26. DUNDONALD.

•
Memoranda, being Facts relative to the Progress and Per-
formance of the Revolving Engine on the Principle of those
in her Majesty's Sloop Janus.
The Earl of Minto, when First Lord of the Admiralty,
having learned from his brother, Rear-Admiral Elliott, that
rotatory engines had been successfully used (in two small
steam-boats), and that their compactness, levity, and celerity
of motion rendered that kind of engine peculiarly suited to
the naval service, ordered a trial to be made of the power of
a condensing engine on that principle by pumping water
from a well in Portsmouth Dockyard.
This engine had been at work for full twelve months when
the present Admiralty made their first official visit to that
yard, and their Lordships had an opportunity of witnessing
the energy and power it then displayed, which, by constant
work, has now increased to such a degree, that not one of the
thirteen engines in the yard (most of which are :on Watt's
principle) has produced a better vacuum, or required less re-
pair, as is testified by Mr. Taplin, the chief engineer and
mechanist of that yard.
This result was not, however, obtained without great
anxiety and trouble. Thirty times at least, within eighteen
months of its erection, was this engine taken to pieces, and at
times parts of it were sent to London to be altered, under the
impression that some defect or other prevented its efficient
performance. Such, indeed, was the prejudice originally
existing, augmented by repeated failures to work the engine,
that it was on the point of being finally rejected by the
authorities, when it occurred that, perhaps, the cold water-
pipe leading to the condenser might be choked. Admiral
Sir Edward Codrington, Rear-Admiral Bouverie, Captain Sir
Thomas Hastings, Mr. Taplin, and Mr. Blake, the master
shipbuilder, were present to witness the result of, perhaps,
the last trial; and they and others saw the injection-pipe
cut, and a plug of wood withdrawn, which blocked the pas-
sage, so that not one-fourth of the water required could enter
the condenser; indeed, after the pipe was rejoined on the fol-
lowing day, the engine could scarcely work two of the three
pumps it was destined to put into motion ; it was, therefore,
again pulled to pieces, and also the air-pump (which had
never before been suspected as a cause of obstruction); never-
theless it was found that the delivery valve was not only
open, but was retained open by its cover being screwed down
upon it, thereby effectually preventing the formation of a
vacuum, even by the most free introduction of injection
water, and the most complete condensation.
It may here be noticed that a ball of rope-yarn and a hank
of strands were subsequently extracted from the injection-
pipe ; and that within the last two months, on examining the
lower valve water-pumps at the bottom of the well, in the
middle suction-pipe a plug of solid elm wood was found,
which completely blocked up that pump, and consequently
during five years and a half defeated the trial of the engine
by the pumping of water. In confirmation of this Mr. Tap-
lin says, in a note dated the 18th of September—" The plug
must have been there from the time the pumps were first put
in motion. As a proof of this we never had such a supply of
water as at present."
It need, therefore, be no matter of surprise if the large
engines of the Janus have been delayed in the performance
of their duty, or that numerous trials failed to produce a
satisfactory result. On Saturday, the 15th, however, the
engines started well, and were accelerating, when the wedges
of the clutches of the paddle-wheels (being slackly driven)
slipped, and the engine flew round and broke the chain of
the air-pump, which being repaired on Monday, the Janus
proceeded down the Medway purposely at a moderate rate,
in order to ascertain if any damage had been done to the
engines themselves by the accident of Saturday. There being
no visible indication of derangement, the vessel proceeded,
and was anchored near the Mouse Light at dusk, on account
of the difficulty of passing through the shoals at night.
On the following morning, on setting the engines to work,
no vacuum could be formed in one engine, which having
thrown the whole labour on the other, it soon became mani-
fest that some partial derangement had taken place therein ;
and a search having been made, it was discovered that one of
the snift valves had been misplaced since the preceding even-
ing; consequently, the atmospheric air had thereby free ac-
cess to the condenser. This impediment having been de-
tected and removed, it was further discovered that the end
plate of the air-pump (lately withdrawn for inspection) had
been improperly jointed, so as to suspend its useful action.
Every person conversant with the mechanism of engines will
fully understand how totally independent these impediments
are of the principle of the engine, yet how fatal to its ope-
ration, which I have no doubt, like the Portsmouth engine,
will bo rendered perfectly efficient. Indeed, the brief spe-
cimen exhibited on Saturday confirms this opinion, having
accelerated from 18 to upwards of 20 revolutions before the
accident.
With regard to the boilers of the Janus, it is hereby fear-
lessly asserted, that having been first tested by authority of
the Admiralty, under the immediate inspection of the
officers of Chatham yards, and the greatly superior evapo-
rative power s having been doubted, an application was made
to the Admiralty to direct the engineer department of
Woolwich Dockyard to test the boilers. The result was
that their power amounted to 314 cubic feet of water eva-
porated per hour, at the economical rate of 12.9 pounds, by
each pound of Llangenneck coal—a result testified by the
engineer's official report of the trial, now in the records of
the Admiralty, dated the 19th of last November ; the im-
portance of which result, in a maritime point of view, every
person acquainted with steam navigation is competent: to
appreciate. Lastly, in regard to the temperature of the
"stoke-hole," although the furnaces are opposite, it may
truly be asserted, that the temperature is less than at the
same distance from any tubular boilers In her Majesty's ser-
vice. DUXDONALD.