DEFENSIVE TORPEDO WARFARE.--MECHANICAL MINES.--MECHANICAL
FUZES.--MOORING MECHANICAL MINES.
BY defensive torpedo warfare is meant the protection of harbours,
rivers, etc., by means of various descriptions of torpedoes moored
beneath the surface of the water.
Submarine, or sea mine, is the term that has been generally adopted to
designate this particular species of torpedo.
_Submarine Mines.--Defence in Future Wars._--The very conspicuous part
played by submarine mines, in the many wars that have taken place
since the introduction of the torpedo as a legitimate mode of Naval
warfare, when their manipulation was comparatively little understood,
and construction very imperfect, proves that, with the experience so
gained, and the vast improvements that have been, and are daily being
effected, in all that appertains to the art of torpedo warfare, the
protection of harbours, etc., will in future wars depend in a great
measure on the adoption of a systematic and extensive employment of
submarine mines.
The utility and power of this mode of coast defence has been fully
exemplified in actual war, more especially during the Franco-German war
(1870-1) and the late Turco-Russian war (1877-8).
_Torpedoes in the Franco-German War._--In the former instance, the
superiority of the French over the Germans, in the matter of ships,
was more than neutralised, by the use on the part of the latter of
electrical, mechanical, and dummy mines for the protection of their
harbours, etc. In regard to the utility of the latter, it is on record
that a certain German port was entirely defended by dummy mines, the
Burgomaster of that place having been unable to obtain men to place the
active mechanical ones in position, owing to the numerous and serious
accidents that had previously occurred in other German ports at the
commencement of the war, in mooring the latter kind of submarine mine.
The effect, so far as keeping the French fleet at a distance was
concerned, was precisely the same, as though active instead of dummy
mines had been employed, thus still further proving the vast moral
power possessed by torpedoes.
_Torpedoes in the Russo-Turkish War._--In the war of 1877, the Turks,
though possessing a powerful fleet in the Black Sea and flotilla on the
Danube, made little or no use of their superiority over the Russians in
this respect. They failed to even attempt to destroy the bridges formed
by the Russians over the Danube, nor did they make any attempt to
capture Poti, re-take Kustendje, or to create diversions on the Russian
coast in the Black Sea. Had the latter service alone been effectually
carried out, by which means, a large force of the enemy would have been
held in check, immense help would have been afforded to the Ottoman
armies in Europe and Asia. Again, during the whole of the war, the
Russian port of Odessa was never sighted, and Sebastopol only once by
the Ottoman fleet.
_Cause of Failure of the Ottoman Fleet._--The cause of this repeated
neglect on the part of the Turkish fleet may be traced almost entirely
to the assumption (which in nine out of ten cases was an erroneous one)
on the part of the Naval Pashas and Beys that every Russian harbour,
etc., was a mass of submarine mines, and this in several instances
extending many miles to seaward.
So also, some of the many failures experienced by the Russians in
their numerous torpedo boat attacks, were due in a great measure
to an erroneous supposition on the part of the captain of the Russian
steamer, _Constantine_ (employed to convoy the torpedo boats), that
the Turks had defended the entrance, to a distance of some miles to
seaward, of their harbours, etc., and thus the torpedo boats were
dispatched to the attack some miles off the entrance, causing them,
owing to the darkness, to enter the harbour in which the Turkish
vessels were lying, in a very straggling manner. And to a similar
reason the failure of the Russians to capture Sulina, in the attack
made on that place in October, 1877, was principally owing to their not
daring to send their Popoffkas to attack from the sea.
One of the chief points of usefulness of an extensive and systematic
employment of submarine mines, will be to minimise the number of
vessels necessary for the protection of harbours, etc., thus enabling
a far larger number of ships to operate at sea against those of an
enemy, this especially applies to countries like England and America
possessing a large extent of seacoast, numerous harbours, rivers, etc.,
which it would be necessary to defend in the event of war.
_Science of Torpedo Warfare._--The science of defensive torpedo warfare
may be considered to consist of:--
1.--The arrangement of the mines in positions, such
that it would not be possible for a hostile vessel
attempting to force a passage into a harbour, etc.,
defended by such means, to pass more than one line of
them, without coming within the destructive radius of
some one or other of the remaining mines.
NOTE.--The difficulty of attaining the above effect, lies in the fact
that the destructive radius of a submarine mine, is considerably less
than the distance that must be maintained between them, to prevent
injury by concussion to the cases, circuit closers, electric cables,
etc., of such mines on the explosion of an adjacent one.
As an illustration of the above, take the case of a 500 lb. guncotton
submarine mine. Now the destructive radius of a sea-mine is found by
the formula R = [3rt](32 × C), where R is the destructive radius in
feet of a mine moored at its most effective depth, and C is the charge
(guncotton) in lbs.
In the above case R would be about 24 feet, which in so far as the
actual destruction of a ship is concerned, may be taken as correct,
but if injury to a vessel's engines, boilers, etc., be also taken into
consideration, and as the vessel would most probably be underweigh
on such an occasion, this would be a very vital and important
consideration, R would under those circumstances be more than doubled.
Now the necessary interval for safety between such mines, according
to torpedo authorities, is equal to 10 R, and should certainly be not
less than 8 R, which in this case would give about 200 feet, therefore
assuming the radius of destruction to be 50 feet, it is seen that there
would be under those conditions a clear undefended space of about 100
feet between each couple of 500 lb. mines in the same line.
2.--The combined arrangement of submarine mines with
forts and batteries, in such a manner, that every one
of the former shall be well covered by the guns of
the latter, and also that it would be impossible for
an enemy's ships to get within effective range of the
forts, or batteries, without moving over ground where
mines were laid.
NOTE.--This applies to the defence of the more important harbours,
etc., in which case the submarine mines (which would be chiefly
electrical ones) would only act as auxiliaries to the land defences. To
effectually carry out the above, there can be no question but that they
who plan the forts, etc., should also plan the systems of submarine
defence.
A harbour, river, etc., which it is necessary to protect by electrical
submarine mines, etc., and where no land defences exist, should have
its mines supported by a powerful ship or ships, as maybe thought
desirable.
_Success in Torpedo Warfare._--The two most important conditions
essentially necessary to the successful employment of torpedoes, both
offensive and defensive, are:--
1. CERTAINTY OF ACTION.
2. SIMPLICITY OF MANIPULATION.
Without the former this mode of Naval warfare is comparatively useless,
while without the latter the former condition is rarely obtained, more
especially in the case of offensive torpedoes.
Submarine mines are divided into separate classes, viz.:--
1. MECHANICAL MINES.
2. ELECTRICAL MINES.
_Mechanical Mines._--By this description of submarine mines, is meant
those whose charges are fired by mechanical means alone.
_Mechanical Mines in the American Civil War._--During the civil war
of America (1861-5), the Confederates depended almost entirely on
mechanical submarine mines for the protection of their harbours,
rivers, etc., and to this extensive use of such mines may be traced
nearly the whole of the Federal disasters afloat.
In the principal wars that have subsequently occurred, though this
form of submarine mine has been to a certain extent used, it has
generally been only as an auxiliary to the more effective electrical
torpedo, and owing to the deterrent effect produced by the numerous
torpedo successes that characterised the American Civil War, on Naval
Commanders, etc., few vessels have been destroyed by their means, the
effect of the employment of defensive torpedoes having been almost
wholly a moral one.
_Mechanical Mines for Coast Defence._--The experience hitherto gained,
with regard to the employment of mechanical mines for coast defence in
actual war, proves that they will be found exceedingly valuable in the
following positions:--
1.--In combination with booms or other obstructions
placed in defence of narrow channels, etc., which are
intended to be completely blocked up.
2.--In shallow water on the flanks of electrical mines.
3.--In protecting unfrequented bays, channels, etc.,
and a long line of seacoast, which may otherwise be
entirely undefended.
NOTE.--In this latter instance, though the mines may not be covered
by any guns, still they will be of great use, in so far, that being
mechanical ones, they cannot be rendered useless by the process of
cutting cables, etc., but must be destroyed, which in time of peace
is a work of considerable labour and danger, and, therefore, would in
the time of war, cause at the very least, serious delay to an enemy
desirous of effecting a landing, etc., at a point so protected.
There are numerous objections against their employment, the principal
ones being:--
1.--That they are all, more or less dangerous to place
in position.
2.--That they cannot be tested when moored.
3.--That they are as dangerous to friend as to foe,
when once placed in action.
4.--That an exploded, or known damaged mine cannot be
replaced.
NOTE.--The above objections, especially 2 and 3, constitute without
doubt very serious defects in a system of defence by mechanical mines,
and in the case of purely mechanical ones, it seems almost impossible
to eradicate any of them, though, notwithstanding, under the particular
circumstance before-mentioned, these species of defensive torpedo will
be found extremely useful.
_The Advantages of Mechanical Mines._--They possess a few advantages,
which are as follows:--
1.--They are comparatively cheap.
2.--They can be kept in store and ready for use at a
moment's notice.
3.--They do not require specially trained men to
manipulate them.
4.--Extempore ones can be easily and readily made.
_Best Kinds of Mechanical Mines._--Among the very numerous and various
kinds of mechanical submarine mines that have been devised the
following may be considered as the most effective, and practicable of
them all:--
1.--FRAME TORPEDOES.
2.--BUOYANT MINES.
This includes:--
_a._--BARREL MINE.
_b._--BROOK'S MINE.
3.--SINGER'S MINE.
4.--MCEVOY'S IMPROVED MINE.
5.--EXTEMPORE MINE.
_Frame Torpedoes._--This form of defensive mine is shown at Fig. 6. It
consists of a frame work which is formed of four strong timbers _a_,
_a_, _a_, _a_, these being kept parallel and only a few feet apart by
means of cross timbers _b_, _b_. A cast-iron torpedo _c_, _c_, _c_, in
the shape of a shell, is bolted to the head of each of the timbers _a_,
_a_, _a_, containing about thirty pounds of fine grained gunpowder, and
fitted with a percussion fuse, which is so placed that it would come
into contact with a vessel striking against the framework, directly
or not. One end of the frame is securely anchored, the other, that on
which the torpedoes are fixed, is kept at its proper distance below
the surface of the water by means of chains, _d_, _d_, and anchors. To
prevent the frame from sinking when sodden with water, the uprights
_e_, _e_, are provided.
This form of mechanical mine, which performs the double function of
torpedo and obstruction, was much used by the Confederates, and found
extremely useful, no passage was attempted to be forced by the Federals
where these torpedoes were known to be placed.
_Stake Torpedo._--Fig. 7 represents another form of the frame torpedo.
It consists of a piece of timber, _a_, its heels secured by a heavy
metal shoe _b_, working in a universal joint in the mooring, _c_. At
the head of the piece of timber is secured a torpedo _d_, containing
about fifty pounds of gunpowder, and fitted with four or five sensitive
fuzes. The proper angle of inclination is obtained by securing the
upper end of the timber to an anchor as shown at _e_. As a proof of the
efficiency of this species of mechanical mine, even though having been
in position for a great length of time, the U.S. gunboat, _Jonquil_,
was nearly destroyed whilst attempting to remove some similar torpedoes
which had been in position for two years.
[Illustration: FRAME TORPEDOES, BUOYANT MECHANICAL MINES.
PLATE II.]
_The Barrel Torpedo._--One description of this form of mechanical
submarine mine is shown at Fig. 8. It consists of a barrel _a_, to the
ends of which are attached two cones of pine _b_, _b_, for the purpose
of preventing the current from turning the mine over.
To ensure its being watertight, pitch is poured into the interior
through the bunghole, and the barrel rolled about, so that the inside
may be evenly covered. The outside was also thoroughly coated with
pitch. These mines usually contain about 100 lbs. of gunpowder, and
are exploded by means of percussion or chemical fuzes (_c_, _c_, _c_,)
generally five in number, screwed into sockets on each side and on the
top of the bilge of the barrels. To keep them upright a weight _d_ is
hung below the mine.
This kind of mechanical mine was much used by the Confederates, and to
some extent by the Turks in their late war with Russia.
They are cheap, convenient, and under certain circumstances very
effective. One of the objections to their use is the difficulty of
mooring them securely in strong currents, as otherwise they are very
liable to shift their positions. Three Confederate vessels were
"hoisted by their own petards," from this cause.[I]
_Brook's Torpedo._--Another form of buoyant mechanical mine is
represented at Fig. 9. It was designed for the express purpose of
preventing its discovery by dragging, etc., by the enemy. It consists
of the torpedo case _a_, formed of copper, which is attached to a
spar _b_, the lower end of which is secured to an universal joint in
its anchor _c_. Five percussion or chemical fuzes _d_, _d_, _d_, are
screwed into the head of the copper case.
_Turtle Torpedo._--To increase the danger and uncertainty of any
attempt to remove this form of buoyant mine, a turtle torpedo _A_, is
attached to it by a wire _e_. This torpedo contains about 100 lbs. of
gunpowder, and is exploded by means of a friction primer which passes
through a watertight joint _f_, and is attached to the wire _e_.
Whether this combination would prove effective, has yet to be seen, but
the buoyant mine alone was considered one of the most dangerous used by
the Confederates.
_Singer's Mechanical Mine._--An elevation and section of this form of
mechanical mine is shown at Fig. 10. It consists of an air chamber
_a_, and a powder chamber _b_; in the latter is fixed a rod of iron
_c_, one end of which rests in a cup formed in a lug _d_, where there
is a screw by means of which the rod _c_ may be screwed against the
bottom of the torpedo case, on the interior. In the cup is placed the
fulminating substance. A heavy cast iron cap _A B_ rests upon the top
of the case and is prevented from falling off by a low rim of tin,
which enters an aperture in the cap as at _e_: a wire _f_ connects
this cap with a pin _g_, which keeps a plunger _h_ at rest. The head
of this plunger _h_ is directly beneath the bottom of the rod _c_,
within the case; by means of a spring _i_, directly the pin _g_ is
drawn out, which is done by a hostile vessel striking against the mine
and knocking off the cap _A B_, the plunger _h_ is forced against the
bottom of the case and drives the rod _c_ into the cup containing the
fulminate, and so explodes the torpedo. The case of these mines, as
used by the Confederates, was formed of tin, and they contained from
50 to 100 lbs. of powder. A safety pin _k_ is provided to prevent a
premature explosion due to the pin _g_ being accidentally withdrawn.
This form of submarine mine was one of the most successful and most
extensively employed of all, on the part of the Confederates.
Though no accidents are stated to have occurred in placing this mine
in position, yet the fact of the iron rod _c_ having to be fixed for
action, and that close against the interior of the bottom of the case,
before the charge of powder has been put in, is an element of great
danger, for a comparatively slight blow beneath it, which might easily
occur in transport, etc., would explode the torpedo prematurely.
_McEvoy's Improved Singer's Mine._--To obviate this defect Captain
McEvoy has designed an improved mode of ignition for Singer's mine.
This is shown at Fig. 11. The form of case, and arrangement of heavy
cap are similar to those in Singer's mine. The mode of ignition is
as follows:--In the powder chamber _b_ is fixed a friction fuze _f_,
which by means of a piece of wire secured to a length of chain _k_,
_k_, is connected with the heavy cast iron cap _A B_. The piece of wire
passes through a diaphragm of thin metal _h_, which is soldered all
around, thus forming a complete watertight joint. Premature explosion
is prevented by passing a link of the chain, through a slot in the bolt
_c_, securing it there by a pin of bent wire _l_. The dotted line of
chain _k_, _k_, shows its position during the process of mooring this
form of Singer's torpedo. The manner of lowering this and also Singer's
mine is shown at Fig. 12. A buoy _x_, is attached by means of a line,
in the former case to the pin _l_, Fig. 12, in the latter case to
the pin _k_, Fig. 10, the pulling out of either, sets their respective
mines in action.
[Illustration: SINGER'S AND M^{c}EVOY'S MECHANICAL MINES.
PLATE III.]
_Mathieson's Cement Safety Plug_.--In the place of the safety pin _l_,
Fig. 11, employed by Captain McEvoy in his improved form of Singer's
mine, Quartermaster-Sergeant Mathieson, late Royal Engineers, employs
a plug or disc of soluble cement, so arranged that the action of the
sea-water after the mine has been placed in position destroys the plug
or disc, and so frees the chain which is connected with the fuze and
the heavy cap of the torpedo. This plan does away with the necessity of
using a buoy and line as shown in Fig. 12, and also affords ample time
for the men engaged in mooring the mine to get far away before it is
ready for action.
_Mechanical Mine_.--The extempore mechanical submarine mine, shown at
Fig. 13, will be found to possess all the qualities which are necessary
to a perfect mine of that description.
It is extremely simple, it can be readily and quickly made, all the
materials of which it is constructed are at hand on board every
man-of-war, and it is certain in its action.
It consists of a barrel _a_, which is thoroughly coated inside and
out with hot pitch, etc., to make it watertight, a block of wood _b_,
secured to the top of the cask _a_, and having a recess cut in it to
receive a round shot _c_, also a hole through which a strop _d_, is
passed, and another hole to receive a toggle _e_. At the bottom of the
cask on the inside, is fixed a wooden frame work _f, f_, to the top of
which two ordinary gun friction tubes are fixed _g_, _g_. A piece of
wood _h_, is secured to the bottom of the cask on the outside, bored
with two holes, one to receive a thin iron rod _i_, the other for the
safety pin _k_. Wires _x_, _x_, secure the gun tubes _g_, _g_, to
one end of the iron rod _i_, the other end of which is connected by
means of a rope lanyard to the shot _c_. Weights are slung beneath the
barrel to keep the mine upright. The principle of action of this form
of mechanical mine is precisely similar to that of Captain McEvoy's
improved Singer's mine, and need not, therefore, be described.
_McEvoy's Mechanical Primer_.--A sectional view of this apparatus
is represented by Fig. 14. It consists of two brass tubes fitting
accurately one within the other, of which _a_, _a_, is the inner one.
To this inner tube are affixed two brass diaphragms _b_, _b_. A brass
spindle _c_, carries a weight _d_, which is regulated by a spring, _e_.
A locking rod, _f_, moves in a ball and socket joint at _g_. A hammer
_h_, which is shown in Fig. 14, at full cock, is kept in that position
by the rod _f_. A vessel, striking the mine, in which this apparatus is
placed causes the weight, _d_, to cant over, allowing the rod, _f_, to
be forced upwards by means of the spring _e_, and so frees the hammer
_h_, which falls on a nipple _i_, on which is placed the percussion
substance, and so explodes the mine.
_McEvoy's Papier Maché Safety Plug._--To prevent a premature explosion
during transport, etc., of a mine in which this apparatus is placed, a
plug of papier maché, which is soluble in water, is inserted in the two
spaces _p_, _p_, by which the spindle _c_, is prevented from moving to
one side or the other. The use of a papier maché, instead of a cement
plug for the purposes of safety, is a great improvement, as by the
simple process of pressure, any period of time that it is necessary
should elapse before the complete destruction of the plug, can be
readily and certainly obtained, which when a cement plug, formed of
different ingredients is used, is not always the case.
_McEvoy's Mechanical Mines._--Captain McEvoy has also devised a plan,
whereby a mechanical mine of the foregoing form may be placed in a
state of safety, even after it has been rendered active. In the place
of the aforesaid papier maché wad at _p_, Fig. 14, he uses a plunger
which fits into the cavity _p_, of the heavy weight _d_. This plunger
is always kept in a position clear of the weight by means of a spiral
spring, unless it is desired to render the mine inactive when the
plunger is forced into the aforesaid cavity and kept there by means of
a pin inserted above it. Above this there is another plunger, acted
on by a spiral spring sufficiently powerful to enable it to force
the previous mentioned plunger into the safety position; this upper
plunger is rendered inactive by means of a pin. The mine being placed
in position, that pin which is keeping the lower plunger inserted in
the cavity _p_, of the weight _d_, is withdrawn and the mine rendered
active. To the pin of the upper plunger is attached a line which is
anchored some distance from the mine in a known position. Then to
render the mine inactive for the purpose of picking it up, etc., it
is only necessary to raise the aforesaid line, and draw out the pin
of the upper plunger, which by means of the strong spiral spring will
force the lower plunger into the safety position, and render the mine
inactive.
Whether this invention is a practicable one or not, remains to be
proved, but anyhow it is a step in the right direction.
[Illustration: EXTEMPORE MECHANICAL MINE, MECHANICAL PRIMERS.
PLATE 4]
_Abel's Mechanical Primer._--This is shown in section and elevation at
Fig. 15 (A and B). _a_, _a_, is the powder chamber in which the priming
charge is placed; _b_ is a screw plug to close the chamber; _c_ is a
flexible india rubber tube; _d_, _d_, are screw bands; _e_ is a glass
tube containing oil of vitriol enclosed in a lead tube; _f_ which
contains the explosive mixture; _g_, an eye at the head of the primer
to receive the firing line; _h_, _h_ are segmental guards; _i_ is the
guard ring; and _j_ the safety screw pin. This apparatus is screwed
into a socket in the upper part of the torpedo case, as shown at Fig.
15 (C).
_Mode of Action._--When placed in position, to render the primer ready
for action, the guard ring, _i_, is pulled off, first having removed
the safety pin _j_, when the segmental guards _h_, _h_, will fall away,
leaving the india rubber tube _c_, _c_, exposed.
A sufficient strain being brought on the rope secured to the ring _g_,
the lead tube _f_ bends, causing the fracture of the glass tube _e_,
thus igniting the priming charge and exploding the mine.
A submarine mine so fitted may be fired at will, by bringing a line,
from the ring _g_, to the shore, or it may be made self-acting by
connecting two of them together, etc.
_Percussion and Chemical Fuzes._--Many forms of this mode of mechanical
ignition have been from time to time devised, of which the following
are the most important ones:--
_Sensitive Fuze._--It consists of an inner cylinder _a_, _a_, Fig. 15,
of composition metal, 1-1/2" diameter, and 2-1/2" long, having a thread
cut on its outside, and a bouching _b_, 2-1/4" diameter and 2" long
with a sexagonal projection _c_, for applying a wrench, also with an
external and internal thread. The upper end of the inner cylinder _a_,
is solid for 1", and is perforated by three holes _d_, _d_, _d_, in
each of which a percussion primer is placed _e_, _e_. A piece of thin,
soft and well annealed copper _f_ is soldered to the upper end of the
bouching _b_, to keep moisture from the primers, and is so thin that a
slight blow will crush without breaking it. A safety cap can be screwed
on to the external thread above the projection _c_.
_Rain's Detonating Composition._--The detonating composition employed
in this and many other forms of percussion fuzes by the Confederates,
etc., consisted of a combination of fulminate of mercury and ground
glass, and was invented by, and is named after, General Rains, Chief
of the Torpedo Bureau, at Richmond, during the Civil War (1861-5). So
sensitive was this composition that seven pounds pressure, applied to
the head of one of the primers, would explode it.
When required for use the internal cylinder _a_, containing the primers
_e_, _e_, is screwed up until contact between them and the copper cap
_f_ is secured.
_McEvoy's Percussion Fuze._--Fig. 16 represents a longitudinal section,
full size, of the mechanical percussion fuze, used by Captain McEvoy in
connection with his drifting torpedo, which latter will be hereafter
described. _a_ is a piece of metal, having an external and internal
thread, and a projection _b_, to which is applied the spanner for
screwing it into the torpedo case. This piece _a_ is hollow at its
upper end, and is closed by means of a thin copper dome _c_, which is
soldered to it. Screwed into the piece _a_ is the plug, or nipple _d_,
with a hole through it from end to end, it is rammed full of mealed
powder, and then a fine hole is drilled through the composition. A
cavity _e_ at the head of the plug, or nipple _d_, is filled with a
fulminating substance. A spiral spring _f_, encircles the plug _d_, on
which a cap _g_ rests; _h_ is a needle in this cap. The action of this
fuze will be readily understood from the plan of the fuze at Fig. 16.
A safety cap is provided, which fits into the slots _i_, _i_, and is
fixed there by means of a set screw.
_Improved Form of Jacobi's fuze._--The section shown in Fig. 17 is an
improved form of the chemical fuze, invented by Professor Jacobi, and
used by the Russians in their land and sea mines during the Crimean war
(1854-5). It consisted of a small glass tube _a_, containing sulphuric
acid, enclosed in a lead cylinder _b_. A mixture of chlorate of potash
and white sugar surrounds the tube and holds it in position; _c_ is a
primer filled with mealed powder in connection with the charge of the
mine. The action of this fuze is as follows:--On a vessel striking
against the lead cylinder _b_, it is crushed in, breaking the glass
tube containing the sulphuric acid, and thus causes it (acid) to flow
into the mixture of chlorate of potash and white sugar, producing fire,
which by means of the primer _c_, passes into the charge, and explodes
the mine.
[Illustration: MECHANICAL FUZES.
PLATE V.]
_Defect of Chemical Fuze._--The defect of the chemical fuze just
described is its slow rate of ignition when compared to gunpowder. This
may be remedied by adding a small quantity of sulphuret of antimony or
perro cyanide of potassium.
Both the Turks and the Germans employed, as a mode of ignition for
their mechanical submarine mines, the chemical fuze described above,
with but slight modifications in the shape of the lead cylinder and
manner of fixing the fuze into the torpedo case.
Mechanical fuzes, both percussion and chemical, which require a blow
to effect their ignition, are to a certain extent defective when
applied to submarine mechanical mines (which are always buoyant ones)
in so far that a hostile vessel passing over ground supposed to be
defended by torpedoes of any description, would do so at as slow a
rate of speed as it would be possible to proceed at, and would, under
those circumstances, _push away_ rather than strike a buoyant mine,
with which she might come in contact. During the American civil war
and the Russo-Turkish war, especially in the former, there are several
instances on record of vessels passing over buoyant mechanical mines
unharmed, whilst similar vessels have afterwards been destroyed
by those self-same mines; and the only cause for such apparent
inconsistency being the above-mentioned one, viz., the pushing rather
than striking effect produced on a buoyant mine by a vessel under weigh
proceeding at a very slow speed, or merely drifting with the current.
_Steward's Safety-Cock Arrangements._--To obtain security to a certain
extent in placing mechanical submarine mines in position, which,
as has been previously stated, is one of the defects common to all
forms of such torpedoes, many ingenious methods have been devised,
such as safety caps to their fuzes, safety pins, soluble plugs, &c.
Another method, suggested by Captain Harding Steward, R.E., which
it is intended should be used in connection with the other safety
arrangements, is shown at Fig. 18. It consists of a stop-cock _A_,
which, in connection with a tube, is introduced between the fuze and
the charge. It is so arranged that when the cock is turned in the
direction of the tube, as shown in section _B_ at _e_, the gas on
formation can pass easily through and explode the charge; but when
the cock is shut off, the gas on formation escapes through the side
_d_, as shown in section _C_. To prevent destruction of the charge
through leakage under the pressure of the water, the cone in connection
with the stop-cock should fit very accurately, and, as an additional
preventive, the escape hole should be covered with a waterproof
plaster, which at a moderate depth would keep the water out and yet
offer no material resistance to the escape of the gas if the stop-cock
were shut off, as at _C_. The efficiency of this arrangement, as
far as relates to its cutting off the gas from the charge, has been
satisfactorily proved by practical experiments.
_Mooring Mechanical Mines._--This description of defensive torpedo
will rarely be used in deep-water channels, &c., and on account of
the impossibility of ascertaining whether such a mine has drifted or
otherwise, it should not be moored in a very rapid current. Such being
the case, an ordinary mushroom anchor, heavy stone, &c., and single
steel wire mooring-rope, will be generally found quite sufficient to
keep such mines in position.
When only a few mechanical submarine mines are moored in position, and
at some distance apart, it would be found a useful plan to moor them
each with three anchors, one anchor being up-stream. By this method,
at low water, on the up-stream anchor being raised, the mine would
show itself, and might in that position be approached and rendered
inactive. Were this plan to be adopted when several such mines are in
position, there would be the danger of the up-stream anchor on being
raised, bringing up to the surface, and probably in contact with the
boat at work, a mine to which that particular anchor does not belong,
an explosion being the result.
FOOTNOTES:
[Footnote I: "Submarine Warfare," by Commander S. Barnes, U.S.N.]