kind. For example, the commander of the United States steamer
_Housatonic_ reported the loss of that vessel by a rebel torpedo off
Charleston on the evening of the 17th February, 1864, stating that about
8·45 p.m. the officer of the deck discovered something in the water
about 100 yards from, and moving towards, his ship. It had the
appearance of a plank moving in the water. It came directly towards the
ship, the time from when it was first seen till it was close alongside
being about two minutes; and hardly had it arrived close to the ship
before it exploded, and the ship began to sink. The torpedo-boat, with
its commander and crew, were lost, having, it is supposed, gone into the
hole made by the explosion, and sunk with the _Housatonic_. In general,
however, the performance of submarine boats has been unsatisfactory.
There is the difficulty of determining accurately the course of the
boat; there is great danger to the men manning it, as exemplified in the
case above; and there is again the problem of providing a means of
propulsion which shall enable such a boat to advance or retreat for,
say, a mile or more, without making its presence conspicuous by smoke or
otherwise. The latter condition would appear to exclude the use of steam
for such purposes, as the inevitable smoke and vapour would betray the
presence of the wily craft. Another power which has been proposed is air
strongly compressed, and recently a still more portable agent has been
suggested in solid carbonic acid, which is capable of exerting a
pressure of forty atmospheres by passing into the gaseous form. A
locomotive form of torpedo, invented by Mr. Whitehead, has the explosive
charge, which consists of about 18 lbs. of glyoxyline, placed in the
front part of a cigar-shaped vessel, the other part containing mechanism
for working a screw-propeller, by means of compressed air contained in a
suitable reservoir. This torpedo having been sunk a few feet below the
water, the motive power may be set in action by drawing a cord attached
to a detent, when the mechanical fish proceeds in a straight line under
the water. It is said that this torpedo is effective at 500 yards from
the ship attacked, and may even be made sufficiently powerful to travel
1,000 yards under the water. The great objection to such arrangements is
the uncertainty of the missile arriving at its destination, for even
supposing that the water were without currents, the least deviation from
the straight course would cause the torpedo to pass wide of the mark at
1,000 yards distant. It is said that at the experimental trials more
than one projector of such war engines has been startled by his machine,
after pursuing a circuitous submarine course, exploding in dangerous
proximity to the place whence it was sent off, the engineer narrowly
escaping being “hoist with his own petard.” The experiments which have
been made with Whitehead’s torpedo in smooth water appear, however, to
have been so far successful that we may probably hear of this invention
being put in practical operation in certain cases. Fig. 109 shows the
upthrow of water produced by the explosion of one of these torpedoes
against an old hulk. The large mass of water thus heaved up is a proof
of the mechanical energy of the explosion, and the effect on the hulk is
shown in Fig. 110, which exhibits the damage done to her timbers, from
the effects of which, it need hardly be said, she immediately sank. In
Fig. 112 we have the representation of the explosion of one of
Whitehead’s torpedoes containing 67 lbs. of gun-cotton, instead of the
glyoxyline. The accurate delineation of these pyramids of water could
not have been obtained but by the aid of instantaneous photography, and
it constitutes a good example of the great value of such an application
of that art, for the instantaneous photographs obtained in these
experiments enabled the engineers to calculate accurately the volume and
height of the column of water, which thus furnishes a measure of the
power of the explosion.
[Illustration:
FIG. 111.—_Experiment made by the Royal Engineers with a Torpedo
charged with 10 lbs. of Gun-Cotton._
]
The ordinary torpedo adopted by the British authorities for coast
defence consists of a cylinder of boiler plate, 4 ft. long and 3 ft. in
diameter. It is intended to contain 432 lbs. of loose gun-cotton,
equivalent in explosive energy to about a ton of gunpowder. The effect
of one of these torpedoes exploded 37 ft. beneath the surface of the
water is depicted in Fig. 113, and in Fig. 114 is shown the effect
produced when the same charge was exploded at the depth of 27 ft. below
the surface. Gun-cotton appears to be the most effective explosive for
torpedoes, if we may judge by the large volume of water heaved up, as
witness Fig. 111, which shows the result with a small torpedo,
containing only 10 lbs. of gun-cotton, exploded at a less depth than
those already mentioned. The ordinary torpedoes are moored by an anchor
attached to the torpedo, and floating above it is a buoy shaped like an
inverted cone. This cone contains a mechanical arrangement of such a
nature that when it is struck by a passing vessel, an electric circuit
is closed by bringing into contact two wires connecting the torpedo with
a voltaic battery on shore. While the apparatus may thus be at any
moment made fatal to a hostile vessel touching it, from the control it
is under by the engineer having the management of the battery contacts,
friendly vessels may pass over it with impunity.
[Illustration:
FIG. 112.—_Explosion of Whitehead’s Torpedo, containing 67 lbs. of
Gun-Cotton._
]
The employment of torpedoes develops, as a matter of course, a system of
defence against them. Nets spread across a channel will catch drifting
torpedoes, and stationary ones may be caused to explode harmlessly by
nets attached to spars pushed a great distance forward from the
advancing ship.
Before the final adoption of Whitehead’s torpedo, presently to be
described, the British Government had, after various official trials,
approved of a towing torpedo designed for offensive operations. It is
the invention of Commander Harvey, and is worthy of a detailed
description for the ingenuity of its construction.
[Illustration:
FIG. 113.—_Explosion of 432 lbs. of Gun-Cotton in 37 feet of Water._
]
[Illustration:
FIG. 114.—_Explosion of 432 lbs. of Gun-Cotton in 27 feet of Water._
]
The shape of Harvey’s torpedo, as may be noticed on reference to Fig.
118, is not symmetrical, but it has some remote resemblance to a boat,
though constructed with flat surfaces throughout. The outside case is
formed of wood well bound with iron, all the joints being made
thoroughly water-tight. The length is 5 ft. and the depth 1¾ ft., while
the breadth is only 6 in. Within this wooden case is another water-tight
case made of thick sheet copper, from the top of which two very short
wide tubes pass upwards to what we may term the deck of the wooden case.
These are the apertures through which the charge of gunpowder or other
explosive material is introduced; and when the tubes have been securely
stopped with corks, brass caps are screwed on. The centre of the
internal case is occupied by a copper tube, _g_, Fig. 115, which passes
the entire depth, and is soldered to the top and bottom of the copper
case, so that the interior of the tube has no communication with the
body of the torpedo, the principal charge merely surrounding it. Thus
the tube forms a small and quite independent chamber in the midst of the
large one, which latter is capable of containing 80 lbs. of gunpowder.
The copper tube or priming-case contains also a charge, _a_, which when
exploded bursts the tube, and thus fires the torpedo in its centre. The
priming charge is put in from the lower end of the tube, which is
afterwards closed by a cork and brass cap, _h_; for the centre of the
priming-case is occupied by a brass tube, _b_, closed at the bottom, but
having within a pointed steel pin projecting upwards. In this tube works
the exploding bolt _c d_, which requires a pressure of 30 or 40 lbs. to
force it down upon the steel pin. This pressure is communicated to the
bolt by the straight lever working in the slot at its head, _d_, and
itself acted on at its extremity by the curved lever to which it is
attached. Thus from the mechanical advantage at which the levers act a
moderate downward pressure suffices to force the exploding bolt to the
bottom of the brass tube. The lower end of this bolt has a cavity
containing an exploding composition sufficient in itself to fire the
torpedo, even independently of the priming charge contained in the
copper tube. This composition is safely retained in the end of the bolt
by a metallic capsule, _c_, which, when the bolt is forced down, is
pierced through by the steel pin at the bottom of the brass tube, and
then the explosion takes place. The bolts are not liable to explosion by
concussion or exposure to moderate heat, and they can be kept for an
indefinite period without deterioration.
[Illustration:
FIG. 115.—_Section of Priming-Case and Exploding Bolt._
]
The mode of producing the explosion is not stated: it consists probably
of an arrangement for bringing chemicals into contact. Besides the two
levers already mentioned, a shorter curved lever working horizontally
will be noticed. The object of this is to make a lateral pressure also
effective in forcing down the bolt—a result accomplished by attaching to
the short arm of the lever a greased cord, which, after passing
horizontally through a fairleader, runs through an eye (see Fig. 117) in
the straight lever, and has its extremity fastened so that a horizontal
movement of the short lever draws the other down. A very important part
of the apparatus is the safety key, _f_, Fig. 115, a wedge which passes
through a slot in the exploding bolt, and resting on the brass-work of
the priming-case, retains the muzzle 1 in. above the pin. Through the
eye of the safety key and round the bolts passes a piece of packthread,
_e_, which being knotted is strong enough to keep the key securely in
its place, but weak enough to yield when the strain is put on the line,
_d´_, used for withdrawing the safety key at the proper moment. This
line is attached to the eye of the key, and passes through one of the
handles forming the termination of the iron straps. As represented in
Fig. 117, it forms the centre one of the three coils of rope. The bottom
of the torpedo is ballasted with an iron plate, to which several
thicknesses of sheet lead can be screwed on as occasion requires. Fig.
117 shows the arrangement of the slings by which the torpedo is attached
to the tow-rope, and it will be seen that another rope passes backwards
through an eye in the stern to the spindle-shaped object behind the
torpedo. This is a buoy, of which two at least are always used, although
only one is represented in the figure. Each buoy, in length 4½ ft., is
made of solid layers of cork built up on an iron tube running through it
lengthways, so that the buoys admit of being strung upon the rope.
[Illustration:
FIG. 116.—_Harvey’s Torpedo._
]
Having thus described the construction of the torpedo, we proceed to
explain how it is used. It must be understood that if the torpedo and
its attached buoys are left stationary in the water, the tow-rope being
quite slack, the torpedo will, from its own weight, sink several feet
below the surface. But when they are _towed_, the strain upon the
tow-line brings the torpedo to the surface, to dip below it again as
often as the tow-line is slackened. There is another peculiarity in the
behaviour of the torpedo, and that is that, when towed, it does not
follow in the wake of the vessel, but diverges from the ship’s track to
the extent of 45°. Its shape and the mode in which it is attached to the
tow-line are designed so as to obtain this divergence. But, according as
the torpedo is required to diverge to the right or to the left, there
must be the corresponding shape and arrangement of tow-line and levers;
hence two forms of torpedo are required, the starboard and the port. The
figures represent the port torpedo, or that which is launched from the
left side of the torpedo-ship, and diverges to the left of its course.
The efficiency of the torpedo depends upon the readiness and certainty
with which it can be brought into contact with the hostile ship, and
this is accomplished by duly arranging the course of the torpedo vessel,
and by skilfully regulating the tow-line so as to obtain the requisite
amount of divergence, and to cause the torpedo to strike at the proper
depth. The tow-rope is wound on a reel, furnished with a powerful brake,
the action of which will be readily understood by inspection of Fig.
116, which represents also a similar smaller reel for the line attached
to the safety key. Leather straps, sprinkled with rosin to increase the
friction, encircle the drums of the reels, and can be made to embrace
them tightly by means of levers, so that the running out of the lines
can be checked as quickly as may be desired. Handles are attached to the
straps, so that they can be lifted off the drum when the line is being
drawn in by working the handles. When the torpedo is ready for action
and has been launched, a suitable length of tow-line, which is marked
with knots every ten fathoms, is allowed to run off its reel, while the
safety key-line is at the same time run off the small reel, care being
taken to avoid fouling or such strains on the line as would prematurely
withdraw the key. Fig. 106 will make clear the mode of controlling the
lines, but it is not intended to represent the actual disposition in
practice, where the men and the brakes would be placed under cover. On
the left of the figure a starboard torpedo is about to be launched; on
the right a port torpedo has been drawn under the ironclad and is in the
act of exploding, the safety key having been withdrawn by winding in its
line when the torpedo came into proximity to the attacked vessel.
[Illustration:
FIG. 117.—_Harvey’s Torpedo._
]
[Illustration:
FIG. 118.—_Harvey’s Torpedo._
]
[Illustration:
FIG. 119.—_Official Trial of “Harvey’s Sea Torpedo,” February, 1870._
]
When the torpedo has been launched over the vessel’s side, the latter
being in motion, the torpedo immediately diverges clear of the ship; and
when the buoys have also reached the water, the men working the reels
pay out the line steadily, occasionally checking the torpedo to keep it
near the surface, but avoiding a sudden strain upon the slacked
tow-rope, which would cause the torpedo to dive, and in shallow water
this might lead to the injury or loss of the torpedo. The torpedo can be
gradually veered out to the distance required, at the same time that the
safety-key is so managed that sufficient strain may be put upon it to
prevent it from forming a long bight astern of the torpedo, but avoiding
such a strain as would break the yarn holding the safety-key in its
place. The distance to which the tow-line may be paid will depend upon
the circumstances of the attack. More than 50 fathoms is, however, a
disadvantage, as the long bight of tow-lines makes the torpedo drag
astern. The torpedo can always be made to dive several feet below the
surface by suddenly letting out two or three fathoms of tow-line. The
torpedo vessel should, of course, be a steamer of considerable
speed—able to outstrip when necessary all her antagonists, and, as a
rule, it is found best to make the attack at night. Let us imagine two
ships of war at anchor, and parallel to each other at perhaps a distance
of 60 fathoms; and suppose that, under cover of darkness, a hostile
torpedo vessel boldly steams up between them, having launched both its
starboard and port torpedoes. In such a case neither ship could fire at
the torpedo vessel for fear of injuring the other, while the torpedo
vessel would in all probability succeed in bringing its floating mines
into contact with both its enemies.
[Illustration:
FIG. 120.—_Model of Submarine Guns._
]
Another device for submarine attacks upon vessels on which much
ingenuity has been expended is the submarine gun. It has been sought to
propel missiles beneath the surface of the water, these missiles being
usually provided with a charge which, on contact with the vessel’s side,
would explode, and by making a hole below the water-line, cause the
certain destruction of the ship. It is obvious that such a mode of
attack would reach the only vulnerable parts of a thickly-plated
ironclad, and therefore the project has been recently revived in several
forms. Fig. 120 is taken from the photograph of a model of an invention
of this kind. The guns which are to propel the submarine projectiles,
have port-holes formed by valves in such a manner that the gun when
loaded can be run out without allowing water to enter; it can then be
fired while the muzzle is below the surface, and again drawn in without
the port being at any time so opened that water can pour into the
vessel. All contrivances of this kind have hitherto been failures;
indeed, it does not appear possible that they could succeed, except at
very close quarters, for the resistance offered by water to a body
moving rapidly in it is extremely great, and, as we have already had
occasion to state, the resistance increases as the square of the
velocity, and probably in even a higher degree for very great
velocities. Any one who will remember the effort it requires to move
one’s hand quickly backwards and forwards through water will easily
understand that the resistance it presents would, in a comparatively
short space, check the speed of a projectile, however great that speed
might be at first. A good many years ago Mr. Warner produced a great
sensation by an invention which appears to have been essentially a
floating torpedo. The cut below, Fig. 121, represents the result of an
experiment publicly made by him off Brighton, in 1844, upon a barque,
which was towed out by a steamer to a distance of a mile and a half from
the shore. Mr. Warner was on board the steamer, and the barque was 300
yards astern. Five minutes after a signal had been made from the shore,
the torpedo was caused to explode, striking the barque amidships,
throwing up a large column of water and _débris_, shooting the mainmast
clean out of the vessel, the mizen going by the board, and dividing the
hull into two parts, so that she sank immediately. Yet this invention,
though apparently so successful, does not seem to have ever been put in
practice.
[Illustration:
FIG. 121.—_The Warner Experiment off Brighton._
]
The stationary torpedoes of the kind mostly used in the American Civil
War were, as already stated, _self-acting_; that is, they exploded when
touched by a passing vessel. They would now be more generally called
_self-acting mines_, and are to be distinguished from that form of the
weapon in which the explosion is determined by some manipulation on
shore, such as the closing of an electric circuit, when the hostile
vessel comes within the area of destructive action. This form receives
the name of _observation mines_. Stationary mines are essentially
instruments of defence, and as such are employed for the protection of
rivers and harbours. The self-acting varieties usually contain a charge
of 70 lbs. to 80 lbs. of gun-cotton, and are commonly arranged in lines.
Of course, when the occasion for which such mines have been laid down is
past, they must be removed, and the operation of picking them up is one
of great danger. The observation mines, on the other hand, do not
require immediate removal, and they can be taken up with little risk. In
the British service the observation mine contains about 500 lbs. of
gun-cotton, and a line of these is sometimes moored in a water-way, from
35 feet to 50 feet below the surface. The area of destructive action in
this case is a circle of about 30 feet radius, and therefore a line of
seven such mines laid across a channel at intervals of 120 feet apart
would ensure the almost certain destruction of any war vessel of
ordinary breadth that might attempt to pass up a river of 840 feet in
width. This is about the distance across the Thames near the Tower of
London, but the depth of the river there being only 12 feet at low-water
and 33 feet at high-water, would not suffice to give effect to the full
energy of so large a charge of gun-cotton; for it has been found that,
for a given charge, there is a certain depth under water at which its
explosion will produce the maximum effect, and this depth will be
greater with heavier charges than with light ones. The regulation
“observation mine” of the British service has a cylindrical case of
stout plate-iron, 32 inches in diameter and 34 inches high, with domed
ends. Within this gun-cotton is contained, in a wet condition, in a
number of copper envelopes, which have holes for access of water to wet
the charge from time to time as occasion requires, the wet condition
being the safest for the carriage of gun-cotton. The centre of the case
is a tin charged with some discs of dry gun-cotton, and the detonator
required to bring about the explosion of the whole charge when the
electrical contact is made, fires the fuze contained within the primer.
These cases are arranged to have a certain buoyancy, and are moored with
wire ropes to heavy iron sinkers, the mooring ropes being of such length
as to keep the explosive case at the proper depth below the surface, and
of sufficient strength to resist the force of the currents in the
waterway. There is also another type of submarine mine, operated by an
electric current, the circuit of which is closed by contact of a passing
vessel, if at the time a battery on shore is included in the circuit. In
this way the mines can be made harmless or dangerous for passing vessels
at the will of the operator on shore. The passing vessel is made to
complete the circuit by tilting over the cylindrical case so far that
some mercury contained in a small part of it is upset, and makes the
requisite metallic contact. This arrangement is known as the
_electro-contact_ mine.
In former pages of this article on torpedoes will be found
representations of the effects produced by _Whitehead’s torpedo_, which,
being automobile and travelling altogether under the surface of the
water, was capable of being made a very formidable weapon of offence.
When the earlier editions of this work were going through the press, it
was understood that the Whitehead torpedo left much to be desired as
regards speed, certainty of direction through the water, and perhaps in
other points, the inventor being constantly engaged in effecting
improvements. At that time particular pains were taken to keep secret
the nature of the most important parts of the internal mechanism. The
work of construction was carried on in a room with locked doors,
blocked-out windows, and a military guard outside. The earlier
experimental forms of this automobile torpedo were constructed in
complete secrecy by the inventor himself, with the help of only one
trusted, skilled mechanic and a boy, who was no other than Mr.
Whitehead’s own son. The history of the invention is very interesting,
and exemplifies the power of skill and perseverance to overcome a
multitude of difficulties, the result being a machine which is simply a
marvel of ingenuity and of delicate nicety of adaptation.