The Sun.
London, England, 1862-01-06 00:00:00

THE ARMY.

The following troops are ordered to be held in
readiness to embark at Portsmouth to join head-
quarters on foreign service :—For Gibraltar, 100th
Foot (Prince of Wales' Royal Canadian)-1 officer
and 50 men. For Malta, Ist battalion 22d Foot-1
officer and 45 men.

Tenders for the proposed cavalry barracks at Col-
chester are to be delivered on Friday at the War-
office. The officers' quarters will be three storys in
height, but the barracks generally will be two-
storied, and the quarters for the troops will be built
in blocks, accommodating 72 men each. The build-
ings now about to be proceeded with will be placed
on the north-west corner of the Abbey Farm land
some time since purchased by the Government, and
near the site of the artesian well, the commencement
and progress of which has been previously noticed.
The site secured will not be fully occupied by the
proposed new works, so it is surmised that further
erections:are contemplated at a future time. Various
drainage works which have been some weeks on
hand in connection with the proposed new building
have been completed.
Major the Hon. C. J. Addington, of the 38th,
is discharging the duties of acting brigade-major at
the camp at Colchester, in the temporary absence of
Brigade-Major Cooch. Capt. Annesley, 2d Bat-
talion, 6th, is under orders to join the headquarters
of his regiment at Gibraltar. Staff-Assist.-Surgeon
Hope has been attached to the medical staff of the
10th depot battalion. In the course of last week
between 60 and 70 men who had volunteered for
service on the American continent left the camp for
Pembroke, Belfast, Limerick, and Athlone, to join
the 15th, 17th, 36th, 47th, 62d, and 63d Regiments.

The examination for the admission of candidates
for the Royal Artillery and Royal Engineers to the
Royal Military Academy, Woolwich, under the
Horse Guards regulations of the sth of April, 1861,
will commence at Chelsea Hospital this morning,
before the Vice-President and members of the Coun-
cil of Education. The first day will be devoted to
the medical examination of the candidates.

Lieut.-Colonel Brise, commanding the West
Essex Militia, recently tendered the services of that
regiment for garrison or colonial duty in the event
of a war, and has received a letter of thanks for the
offer.

IOULING OF THE SCREW.

TO THE EDITOR OF THE TIMES.

Sir,—As all matters connected with steam navi-
gation are invested with more than ordinary in-
terest at the present juncture, and especially those
having reference to steamers for war purposes, I beg
to offer the following remarks in the hope that they
may tend to some improvement in the present sys-
tem of screw propulsion.
It appears to me that the great desideratum to be
aimed at in constructing a war steamer is light
draught, combined with a steady platform for
fighting her guns, with good speed, and a power
of steering easily and manceuvring rapidly under
all circumstances, having, moreover, a screw that
will not foul.

I believe it will be conceded by all impartial per-
sons that very few, if any, of our war ships can
pretend to more than one of these qualities—viz.,
speed ; and that, moreover, they are all liable to be
crippled by " fouling of the screw," such fouling
being as likely to proceed from the wreck of other
ships' masts and rigging in an action as their own.
Impressed with this belief, it has been my study for
several years to discover some means of accomplish-
ing the above ends without sacrificing any other
point of efficiency, and my own convictions having
the support of many scientific officers of my own
profession and other competent judges, I have less
hesitation in troubling you with them. First, as
to "fouling the screw." There are too many instances
on record of fatal accidents and constant inconve-
nience arising from the fouling of the screw to need
special cases being cited on this occasion. In Mr.
Bannister's letter to the 7inzes of the 26th Novem-
ber last he justly observes that "guard bars are not
a sufficient protection ;" indeed, they rather aggra-
vate than reduce the evil. The method he pro-
poses of putting knives or teeth on the boss was
suggested by the late lamented Sir Howard
Douglas in 1859, and, as stated in my letter to the
Times in September of the same year, " might be
well enough did not chain and wire form a part of
all ships' rigging ;" added to which it must be re-
membered that ropes, &e., do not always come into
direct contact with the boss whereon these knives
are fitted, but are caught by the arms of the pro-
peller, and often knot themselves around the root,
which, being narrower than at the periphery, pre-
vents their slipping off or being disentangled, unless
the screw is lifted, which, under some circumstances
I propose to notice, may not be possible, especially
in action. In addition to the liability to foul the
present mode of fitting the screw is open to several
grave objections.
First, to attain great speed, it has been deemed ne-
cessary to have a screw of great diameter, which
entails great draught of water, notwithstanding
which the screw in most instances is so near the
surface that it must catch every floating object
within its reach, and being lifted out of water by
the slightest pitching motion, or bared by the un-
dulation of the wave, loses a large proportion of its
effect, and if not fitted with a good governor the
engines are liable to be strained by " racing."
Being thus near the surface the screw is liable to
injury from shot, and being within a few inches of
the bottom may be broken by striking a rock when
in shallow water.
As has been seen in several remarkable instances
of late, the Great Eastern to wit, the after stern-
post (on which the rudder and after-bearing of
the screw shaft depend) and rudder-head are
liable to be broken or bent by the sea striking
the exposed part of the rudder. This may
often arise from a defective forging, or a wrong
proportion in that long unsupported bar of iron
which is E 0 costly and difficult to forge, and
which with its appurtenances adds materially
to the weight at the extremity where all
should be as light as possible ; it is also liable to
be twisted or bent by a blow from heavy shot, or by
striking the ground aft, in either case the rudder
and screw-lifting frame might be jammed, thes crew
shaft thrown out of centre, and the ship, to all in-
tents and purposes, crippled.
It is to the prevention of these evils I desire to
draw attention, and I believe that may be accom•
plished by the adoption of a slight modification of
the propeller referred to in my letter of September
2, 1859, which was invented by Mr. Richard
Roberts, of Manchester, described by him as his
" spiral vane propeller, calculated to throw off
ropes, weeds, and wreck," and may be thus de-
scribed :—The vanes, or blades, are of wrought iron
or steel, secured to spiral Ranges on a cycloidal boss
of large diameter ; hence the root of the blades is
long, and therefore, being well supported, admit of
being much thinner than those of the ordinary
shape in cast metal ; being thinner they displace
less water, and consequently absorb less power; they
are also far less liable to injury, are readily replaced
or repaired when injured, and may be estimated at
half the weight and one-third the cost of those made
in gun metal (cast metal blades of this form would
be far less liable to injury than those of the present
type). These blades are tapered on
be said
and when in rotation may the leading edge
to form a " cone"
that will throw off all passing wreck without injury
to the propeller, or any mass of cordage, chain, or
wire rope that may come in contact or even fall
across it. This form of blade will also ensure a more
constant and equable action on the water under all

circumstances, and consequently remove one cause
of vibration. The method of attaching this propeller
to the shaft enables it to be readily unshipped at
sea, and being comparatively light, the after bearing
may be safely dispensed with, thus removing an-
other cause of vibration and entanglement. Although
it may be readily applied to ships of the present form,
and the chances of fouling materially reduced, it
cannot be altogether prevented as in a ship specially
constructed or altered to suit it.
This leads to the consideration of the second
portion of the subject—viz., " steering and ma-
noeuvring war steamers," and the construction of
light draught ships either for war or mercantile
purposes, in which steam is the principal agent, as
would, I apprehend, be the case iu vessels intended
to operate in shore on an enemy's coast, or up
rivers, or in defence of our own ; also, for merchant
vessels making passages under steam having tidal or
bar harbours to deal with, as in the Dutch and
other Northern ports, where much detention and
loss is incurred by waiting for water. All seamen
will appreciate the advantages of a light draught of
water in such cases. It would also effect conside-
rable saving of time and inconvenience now felt at
Spithead ; for instance, where a ship has to wait
till high water spring tides to go into harbour;
and make present dock accommodation available
without the enormous expenses consequent on alte-
ration to suit it to the present draught of large war
steamers.

It is however obvious that great speed cannot be
attained by one screw in a ship of very light
draught, if it is to be immersed sufficiently and
kept well clear of the ground. The principal objec-
tion to two screws hitherto has been that the chances
of fouling are doubled ; and the present form of
after section would not admit of sufficient diameter
being given, the dead wood offering a great obstruc-
tion to propulsion, and the rudder being still ex-
posed to shot or other accident.
It is now well proved that the increased bulk and
draught of water have not decreased the rolling of
our new war-ships, as was anticipated by some;
nor, indeed, is the Great Eastern herself less ad-
dicted to that pastime than her smaller sisters.
Now, you may as well put a rifleman in a swing to
fire at a long-range target as a rifled cannon in a
ship rolling from 16 to 20 degrees each way; it is,
therefore, nearly time that some remedy be found
whereby this rolling may be reduced.
First, then, to produce a steadier platform for these
rifled guns, and reduce the rolling to a minimum, I
propose to adopt a midship section of elliptical
form, which is maintained throughout full one-half
of the length, at a uniform depth (i. e., on an even
keel), whereby great capacity is obtained without
increasing the resistance, the lines of the
bow being composed of easy curves, on a principle
specially contrived for the purpose, by which the
best form for entering the water may be obtained,
and for laying on the plates without serious bend-
ing. This flat elliptical floor is continued to the
forefoot, and thus the fore section is made self sup-
porting (the heavy part of the sharp floor in other
ships being dispensed with), and is consequently
more buoyant, and, combined with the long flat
floor, will reduce the tendency to pitch, but will
lift going against a head sea. The after section is
composed of convex curves sufficiently fine to de-
liver the water freely, but not so lean as to remove
the necessary support in that quarter, the absence
of which induces " sending," or sinking aft, which
my observation teaches me is one of the causes of
rolling in ships of the present build. I believe such
a form is quite compatible with high speed in ships
of light draught, and the opinion is based on some
experience. That part known as the " dead
wood" in timber ships is dispensed with,
and with it all the cumbrous and costly
paraphernalia of sternposts, screw-lifting frame,
and, in fact, every forging of any consequence,
thereby reducing the weight at the after extremity,
and the cost of the ship. As a substitute for them
a broad cellular keel, of any required depth, tapered
at either extremity, is placed under each bilge, ex-
tending nearly the whole length of the floor; at
the after extremities of these keels are hung two
shallow rudders of sufficient area, that are always
immersed (balance rudders would, perhaps, be pre-
ferable). These act independently, or are geared
together by a simple contrivance that may be
worked by a wheel on deck or in the after part of
the engine-room; the engineer and helmsman thus
receiving orders simultaneously, both screws and
helm act together on the instant, the helmsmen
and steering apparatus being out of harm's way.
The keels are, in point of fact, cellular girders
of enormous strength, which will not only give
great longitudinal strength to the ship, but
will effectually defend the bottom on taking the
ground, especially if shod with timber, and the
space between and on either side being also de-
fended by plankings. They will give great sta-
bility, and that they do not interfere with speed or
steerage, but materially reduce rolling, has been
satisfactorily proved in Mr. Tovill's celebrated ship.
They will also keep the ship in an upright position
on taking the ground, facilitate docking, and re-
duce the risk in docking heavy ships, whether ar-
mour-plated or with cargo, the weight being thus
distributed over a large surface under each bilge.
Gunboats and all small vessels fitted thus might be
readily grounded without risk where there was no
dock, and their bottoms cleaned or repaired, the
keels being, in fact, a substitute for a gridiron.
The screws arc fitted to shafts led through cylin-
drical trunks under either quarter, which are, in
fact, that part of the after end of the keels between
the rudder and the ship's counter, the screws thus
working over and abaft the rudders, and quite
clear of them. As these screws will be driven at a
higher speed than a single screw of large diame-
ter, it is proposed to use gearing in large vessels,
each shaft being worked by two horizontal
high pressure condensing engines, with surface
condensers arid multitubular cylindrical boilers, the
whole of which, including the gearing, will be con-
siderably lower than the present ones, acting as
ballast and less exposed to shot. By this means
the ponderous engines now in vogue would be sub ,
divided into four parts—smaller, lighter, less liable
to accident, more readily replaced or repaired, and
less costly. By this arrangement a much longer
stroke is obtained, the port cylinders working the
starboard screw, and vice versa. In a small-class
vessel a single cylinder engine may be used to each
shaft with advantage, as I have seen in practice.
Being right and left screws, they turn in opposite
directions, and therefore correct that deviation
from a right line either would produce separately.
The helm is therefore unnecessary to counteract
that effect ; there is consequently less obstruction
to the ship's way. By reversing either screw the
ship may be turned rapidly on her centre, or
nearly so, without either head and stern way,
and may be steered, going either ahead
or astern, by these screws, without the aid
of the helm. This I have seen frequently.
The absence of the after sternpost the dead wood
will materially facilitate marimuvring and remove
obstruction to speed. These small screws, having
their centre much lower than with a single screw
of the same calculated power, will be working in
water of greater density, far less liable to accident,
and cannot be lifted out of water. Moreover, both
them and the rudders are in a more favourable posi-
tion for working, being well removed from the
centre, where there is an eddy or partial vacuum
caused by the water rushing into the space left by
the course of the ship.
The advantage that such a power of steering and
manoeuvring could give over a ship with one screw
in action in narrow waters, " where she would go
whichever way her bow takes" (as in the case of
the Warrior in this day's 'limes' Naval Intelligence),
is too obvious to need comment.

As the utility of efficient gunboats of very light
draught is now beyond all question, and as their
services may be required at no very distant period,
I conceive that this method of constructing them
would be attended with much advantage to the pub-
lic service ; their screws might be unshipped, and
the depth of the two keels increased by timber
" false keels," which might be readily removed, and
thus make the passage as sailing vessels, the keels
giving them the same stability and weatherly quali-
ties that the two large logs in a similar position
give to the Pernambuco catamaran.
I am furtkerniore of opinion that in the event of