Torpedoes and Torpedo Warfare
by Charles William Sleeman · English · Gutenberg #44990 · 783,082 chars · public domain (US)
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Title: Torpedoes and Torpedo Warfare
Author: Charles William Sleeman
Release date: February 24, 2014 [eBook #44990]
Most recently updated: October 24, 2024
Language: English
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*** START OF THE PROJECT GUTENBERG EBOOK TORPEDOES AND TORPEDO WARFARE ***
[Transcriber's Notes: Mathematical problems could not be represented as
in the original as we cannot stack numbers. The following rules were
used:
Parentheses added to groupings of numbers.
Bracket and "rt" square roots. [3rt]
Carets and curly brackets indicate a superscripted number, letter or
symbol. 4^{3}
An underscore and curly brackets indicate a subscript. H_{2}O
Bold text is surrounded by =equal signs= and italic text is surrounded
by _underscores_.]
[Illustration: _The "Suna" before the Explosion._]
[Illustration: _The Torpedo._]
[Illustration: _The "Suna" after the Explosion._]
Griffin & C^{o.} Portsmouth. W.F. Mitchell del.
TORPEDOES
AND
TORPEDO WARFARE:
CONTAINING A
COMPLETE AND CONCISE ACCOUNT OF THE
RISE AND PROGRESS OF SUBMARINE WARFARE;
ALSO A
DETAILED DESCRIPTION OF ALL MATTERS APPERTAINING THERETO,
INCLUDING THE LATEST IMPROVEMENTS.
BY
C. W. SLEEMAN, ESQ.,
LATE LIEUT. R.N., AND LATE COMMANDER IMPERIAL OTTOMAN NAVY.
_WITH FIFTY-SEVEN FULL-PAGE ILLUSTRATIONS, DIAGRAMS,
WOODCUTS, &c._
PORTSMOUTH:
GRIFFIN & CO., 2, THE HARD,
(_Publishers by Appointment to H.R.H. The Duke of Edinburgh._)
LONDON AGENTS: SIMPKIN, MARSHALL, & CO.
1880.
_All Rights reserved._]
PREFACE.
IN the following pages the Author has endeavoured to supply a want,
viz. a comprehensive work on Torpedo Warfare, brought down to the
latest date.
The information has been obtained while practically engaged in torpedo
work at home and abroad, and from the study of the principal books
which have already appeared on the subject, and to the authors of which
he would now beg to express his acknowledgments, viz.: "Submarine
Warfare," by Lieut.-Commander Barnes, U.S.N.; "Notes on Torpedoes," by
Major Stotherd, R.E.; "Art of War in Europe," by General Delafield,
U.S.A.; "Life of Fulton," by C. D. Colden; "Torpedo War," by R.
Fulton; "Armsmear," by H. Barnard; "Treatise on Coast Defence," by
Colonel Von Scheliha; Professional Papers of the Royal Engineers; "The
Engineering"; "The Engineer"; "Scientific American"; "Iron"; &c., &c.
The Author is also desirous of thanking the following gentlemen, to
whom he is indebted for much of the valuable information contained
herein:--
Messrs. Siemens Brothers, Messrs. Thornycroft and Co., Messrs. Yarrow
and Co., Captain C. A. McEvoy, 18 Adam Street, W.C., Mr. L. Lay,
Messrs. J. Vavaseur and Co.
LONDON, 1879.
CONTENTS.
PAGE
Preface iii
CHAPTER I.
The early History of the Torpedo--Remarks on the existing
State of Torpedo Warfare 1
CHAPTER II.
Defensive Torpedo Warfare--Mechanical Submarine
Mines--Mechanical Fuzes--Mooring Mechanical Mines 13
CHAPTER III.
Defensive Torpedo Warfare (_continued_)--Electrical
Submarine Mines--Electrical Fuzes--Insulated Electric
Cables--Electric Cable Joints--Junction Boxes--Mooring
Electrical Submarine Mines 27
CHAPTER IV.
Defensive Torpedo Warfare (_continued_)--Circuit
Closers--Firing by Observation--Voltaic
Batteries--Electrical Machines--Firing Keys and Shutter
Apparatus--Testing Submarine Mines--Clearing a Passage
through Torpedo Defences 60
CHAPTER V.
Offensive Torpedo Warfare--Drifting Torpedoes--Towing
Torpedoes--Locomotive Torpedoes--Spar Torpedoes--General
Remarks on Offensive Torpedoes 115
CHAPTER VI.
Torpedo Vessels and Boats--The _Uhlan_--The _Alarm_--The
_Destroyer_--Thornycroft's Torpedo Boats--Yarrow's
Torpedo Boats--Schibau's Torpedo Boats--Herreshoff's
Torpedo Boats--Torpedo Boat Attacks--Submarine Boats 158
CHAPTER VII.
Torpedo Operations--The Crimean War (1854-56)--The
Austro-Italian War (1859)--The American Civil War
(1861-65)--The Paraguayan War (1864-68)--The Austrian
War (1866)--The Franco-German War (1870-71)--The
Russo-Turkish War (1877-78) 187
CHAPTER VIII.
On Explosives--Definitions--Experiments--Gunpowder--Picric
Powder--Nitro-Glycerine--Dynamite--Gun-cotton--Fulminate
of Mercury--Dualin--Lithofracteur--Horsley's
Powder--Torpedo Explosive Agents--Torpedo Explosions 204
CHAPTER IX.
Torpedo Experiments--Chatham, England,
1865--Austria--Carlscrona, Sweden, 1868--Kiel,
Prussia--England, 1874--Copenhagen, Denmark,
1874--Carlscrona, Sweden, 1874-75--Portsmouth, England,
1874-75--Pola, Austria, 1875--Portsmouth, England,
1876--Experiments with Countermines--The Medway, England,
1870--Stokes Bay, England, 1873--Carlscrona, Sweden, 1874 220
CHAPTER X.
The Electric Light--The Nordenfelt and Hotchkiss Torpedo
Guns--Diving 239
CHAPTER XI.
Electricity 265
APPENDIX.
McEvoy's Single Main Systems 283
Siemens' Universal Galvanometer Tables 287
Synopsis of the Principal Events that have occurred in
connection with the History of the Torpedo 290
Index 297
LIST OF PLATES.
DESTRUCTION OF TURKISH GUNBOAT "SUNA" (_Frontispiece_).
I. FULTON'S TORPEDOES.
II. FRAME TORPEDOES, BUOYANT MECHANICAL MINES.
III. SINGER'S AND MCEVOY'S MECHANICAL MINES.
IV. EXTEMPORE MECHANICAL MINE, MECHANICAL PRIMERS.
V. MECHANICAL FUZES.
VI. FORM OF CASE OF SUBMARINE MINES.
VII. ELECTRIC FUZES.
VIII. ELECTRIC CABLES, EXTEMPORE CABLE JOINTS.
IX. PERMANENT JOINTS FOR ELECTRIC CABLES.
X. JUNCTION BOXES, MECHANICAL TURK'S HEAD.
XI. MOORINGS FOR SUBMARINE MINES.
XII. STEAM LAUNCH FOR MOORING SUBMARINE MINES.
XIII. MATHIESON'S CIRCUIT CLOSER.
XIV. AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.
XV. MCEVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.
XVI. RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.
XVII. APPARATUS FOR FIRING BY OBSERVATION.
XVIII. SYSTEMS OF DEFENCE BY SUBMARINE MINES.
XIX. FIRING BATTERIES, TESTING BATTERIES.
XX. FIRING KEYS, SHUTTER APPARATUS.
XXI. SHUTTER APPARATUS.
XXII. GALVANOMETERS FOR TESTING.
XXIII. SIEMENS' UNIVERSAL GALVANOMETER.
XXIIIA. DITTO DITTO.
XXIV. DITTO DITTO.
XXIVA. DITTO DITTO.
XXV. SHUNT, COMMUTATOR, RHEOSTAT.
XXVI. WHEATSTONE'S BRIDGE.
XXVII. TEST TABLE, DIFFERENTIAL GALVANOMETER.
XXVIII. METHODS OF TESTING--ARMSTRONG--AUSTRIAN.
XXIX. DRIFTING TORPEDOES.
XXX. HARVEY'S TOWING TORPEDO.
XXXI. DITTO DITTO.
XXXII. SYSTEMS OF ATTACK WITH HARVEY'S SEA TORPEDO.
XXXIII. DITTO DITTO.
XXXIV. DITTO DITTO.
XXXV. GERMAN AND FRENCH TOWING TORPEDOES.
XXXVI. WHITEHEAD'S FISH TORPEDOES.
XXXVII. THORNYCROFT'S BOAT APPARATUS FOR FISH TORPEDOES.
XXXVIII. LAY'S LOCOMOTIVE TORPEDO.
XXXIX. DITTO DITTO.
XL. DITTO DITTO.
XLI. DITTO DITTO.
XLII. DITTO DITTO.
XLIII. DITTO DITTO.
XLIV. MCEVOY'S DUPLEX SPAR TORPEDOES.
XLV. THE "ALARM" TORPEDO SHIP.
XLVI. THE "DESTROYER" TORPEDO SHIP.
XLVII. THORNYCROFT'S TORPEDO BOATS.
XLVIII. DITTO DITTO.
XLIX. YARROW'S TORPEDO BOATS.
L. DITTO DITTO.
LI. RUSSIAN TORPEDO BOAT, HERRESHOFF'S TORPEDO BOAT.
LII. SUBMARINE MINE EXPLOSION.
LIII. DITTO DITTO.
LIV. MCEVOY'S SINGLE MAIN SYSTEM.
[Illustration]
Torpedoes and Torpedo Warfare.
CHAPTER I.
THE EARLY HISTORY OF THE TORPEDO.--REMARKS ON THE EXISTING STATE OF
TORPEDO WARFARE.
THE earliest record we have of the employment of an infernal machine
at all resembling the torpedo of the present day, was in 1585 at the
siege of Antwerp. Here by means of certain small vessels, drifted down
the stream, in each of which was placed a magazine of gunpowder, to be
fired either by a trigger, or a combination of levers and clockwork, an
Italian engineer, Lambelli, succeeded in demolishing a bridge that the
enemy had formed over the Scheldt.
So successful was this first attempt, and so tremendous was the effect
produced on the spectators, by the explosion of one of these torpedoes,
that further investigation of this new mode of Naval warfare was at
once instituted.
But it was not until some two hundred years after that any real
progress was effected, though numerous attempts were made during this
period, to destroy vessels by means of sub-marine infernal machines.
It was owing to the fact, that the condition which is now considered as
essential in torpedo warfare, viz., that the charge must be submerged,
was then entirely ignored, that so long a standstill occurred in this
new art of making war.
_Captain Bushnell, the Inventor of Torpedoes._--To Captain David
Bushnell, of Connecticut, in 1775, is most certainly due the credit
of inventing torpedoes, or as he termed them submarine magazines. For
he first proved practically that a charge of gunpowder could be fired
under water, which is incontestably the essence of submarine warfare.
_Submarine Boat._--To Captain Bushnell is also due the credit of first
devizing a submarine boat for the purpose of conveying his magazines to
the bottom of hostile ships and there exploding them.
_Drifting Torpedoes._--Another plan of his for destroying vessels, was
that of connecting two of his infernal machines together by means of a
line, and throwing them into the water, allowing the current to carry
them across the bows of the attacked ship.
_Mode of Ignition._--The ignition of his magazines was generally
effected by means of clockwork, which, when set in motion, would
run for some time before exploding the machines, thus enabling the
operators to get clear of the explosion.
Captain Bushnell's few attempts to destroy our ships off the American
coast in 1776 and 1777, with his submarine boat, and his drifting
torpedoes were all attended with failure, a result generally
experienced, where new inventions are for the first time subjected to
the test of actual service.
_Robert Fulton._--Robert Fulton, an American, following in his
footsteps, some twenty years after, revived the subject of submarine
warfare, which during that interval seems to have been entirely
forgotten.
A resident in France, in 1797, he is found during that year making
various experiments on the Seine with a machine which he had
constructed, and by which he designed "to impart to carcasses of
gunpowder a progressive motion under water, to a certain point, and
there explode them."[A]
_Fulton's Failures._--Though these first essays of his resulted in
failure, Fulton thoroughly believed in the efficacy of his schemes, and
we find him, during that and succeeding years, vainly importunating the
French and Dutch Governments, to grant him aid and support in carrying
out experiments with his new inventions, whereby he might perfect
them, and thus ensure to whichever government acceded to his views, the
total destruction of their enemy's fleets.
_Bonaparte aids Fulton._--Though holding out such favourable terms, it
was not until 1800, when Bonaparte became First Consul, that Fulton's
solicitations were successful, and that money was granted him to carry
out a series of experiments.
In the following year (1801), under Bonaparte's immediate patronage,
Fulton carried out various and numerous experiments in the harbour of
Brest, principally with a submarine boat devised by him (named the
_Nautilus_), subsequently to his invention of submarine carcasses as
a means of approaching a ship and fixing one of his infernal machines
beneath her, unbeknown to the crew of the attacked ship.
_First Vessel destroyed by Torpedoes._--In August, 1801, Fulton
completely destroyed a small vessel in Brest harbour by means of one of
his submarine bombs, then called by him for the first time, torpedoes,
containing some twenty pounds of gunpowder. This is the first vessel
known to have been sunk by a submarine mine.
_Bonaparte's patronage withdrawn._--Notwithstanding the apparent
success, and enormous power of Fulton's projects, on account of a
failure on his part to destroy one of the English Channel fleet, at the
end of 1801, Bonaparte at once withdrew his support and aid.
Disgusted with this treatment, and having been previously pressed by
some of England's most influential men, to bring his projects to that
country, so that the English might reap the benefit of his wonderful
schemes, Fulton left France, and arrived in London, in May, 1804.
_Pitt supports Fulton._--Mr. Pitt, then Prime Minister, was much struck
with Fulton's various schemes of submarine warfare, and after examining
one of his infernal machines, or torpedoes, exclaimed, "that if
introduced into practice, it could not fail to annihilate all military
marines."[B]
Though having secured the approval of Mr. Pitt, and a few other members
of the Government, he was quite unable to induce the English to accept
his schemes in toto, and at once employ them in the Naval service.
Twice Fulton attempted to destroy French men-of-war, lying in the
harbour of Boulogne, by means of his drifting torpedoes, but each time
he failed, owing as he then explained, and which afterwards proved
to be the case, to the simple mistake of having made his machines
specifically heavier than water, thus preventing the current from
carrying them under a vessel's bottom.
_Destruction of the "Dorothea."_--Though in each of the above-mentioned
attempts Fulton succeeded in exploding his machines, and though on the
15th October, 1805, in the presence of a numerous company of Naval
and other scientific men, he completely demolished a stout brig, the
_Dorothea_, off Walmer Castle, by means of his drifting torpedoes,
similar to those employed by him at Boulogne, but considerably
improved, still the English Government refused to have anything further
to do with him or his schemes.
England, at that time, being mistress of the seas, it was clearly
her interest to make the world believe that Fulton's schemes were
impracticable and absurd.
Earl St. Vincent, in a conversation with Fulton, told him in very
strong language, "that Pitt was a fool for encouraging a mode of
warfare, which, if successful, would wrest the trident from those who
then claimed to bear it, as the sceptre of supremacy on the ocean."[C]
Wearied with incessant applications and neglect, and with failures, not
with his inventions, but in inducing governments to accept them, he
left England in 1806, and returned to his native country.
_Application to Congress for Help._--Arrived there, he lost no time in
solicitating aid from Congress to enable him to carry out experiments
with his torpedoes and submarine boats, practice alone in his opinion
being necessary to develop the extraordinary powers of his invention,
as an auxiliary to harbour defence.
By incessant applications to his government, and by circulating his
torpedo book[D] among the members, in which he had given detailed
accounts of all his previous experiments in France and England, and
elaborate plans for rendering American harbours, etc., invulnerable
to British attack, a Commission was appointed to inquire into and
practically test the value of these schemes.
They were as follows:--
1.--_Drifting Torpedoes._--Two torpedoes connected by
a line floated in the tide at a certain depth, and
suffered to drift across the bows of the vessel to
be attacked; the coupling line being arrested by the
ship's cable would cause the torpedoes to be forced
under her bottom; this plan is represented and will be
readily understood by Fig. 3.
2.--_Harpoon Torpedo._--A torpedo attached to one end
of a line, the other part to a harpoon, which was to be
fired into the bows of the doomed vessel from a piece
of ordnance mounted in the bows of a boat, specially
constructed for the purpose; the line being fixed to
the vessel by the harpoon, the current, if the vessel
were at anchor, or her progress if underweigh, would
carry the torpedo under her bottom. Fig. 2 represents
this type of Fulton's submarine infernal machine.
3.--_Spar Torpedo._--A torpedo attached to a spar
suspended by a swivel from the bowsprit of a torpedo
boat, so nearly balanced, that a man could easily
depress, or elevate the torpedo with one hand, whilst
with the other he pulled a trigger and exploded it.
4.--_Block Ship._--Block ships, that is vessels from
50 to 100 tons, constructed with sides impervious to
cannon shot, and decks made impenetrable to musket
shot. A spar torpedo _a, a, a_, to be carried on each
bow and quarter Fig. 4 represents this curious craft.
_Stationary Mines._--Stationary buoyant torpedoes
for harbour defence, to be fired by means of levers
attached to triggers. This kind of mine is shown at
Fig. 1.
5.--_Cable Cutters._--Cable cutters, that is submarine
guns discharging a sharp piece of iron in the shape of
a crescent, with sufficient force to cut through ship's
cables, or other obstructions.[E]
_Practical Experiments._--Various and exhaustive experiments were
carried out in the presence of the Commissioners, tending generally to
impress them with a favourable view of Fulton's many projects.
As a final test, the sloop _Argus_ was ordered, under the
superintendence of Commodore Rodgers, to whom Fulton had previously
explained his mode of attack, to be prepared to repel all attempts made
against her by Fulton, with his torpedoes.
_Defence of the "Argus."_--Though repeated attempts were made, none
were successful, owing to the energetic, though somewhat exaggerated
manner in which the defence of the sloop had been carried out. She
was surrounded by numerous spars lashed together, nets down to the
ground, grappling irons, heavy pieces of metal suspended from the yard
arms ready to be dropped into any boat that came beneath them, scythes
fitted to long spars for the purpose of mowing off the heads of any who
might be rash enough to get within range of them.
As Robert Fulton very justly remarked, "a system, then only in its
infancy, which compelled a hostile vessel to guard herself by such
extraordinary means could not fail of becoming a most important mode of
warfare."
Three of the Commissioners reported as favourably as could be expected,
considering its infancy, on the practical value of Fulton's scheme of
torpedo warfare.
_Congress refuse aid._--But on the strength of Commodore Rodgers's
report, which was as unfair and prejudiced, as the others were fair
and unprejudiced, Congress refused Fulton any further aid, or to
countenance any further experiments that he might still feel inclined
to prosecute.
Though undeterred by this fresh instance of neglect, and still having a
firm belief in the efficacy of his various torpedo projects, yet other
important matters connected with the improvement of the steam engine
occupied his whole time and prevented him from making any further
experiments with his submarine inventions.
_Mode of Firing, 1829._--Up to 1829, that is to say for nearly sixty
years after the invention of torpedoes, mechanical means only were
employed to effect the ignition of the torpedo charges, such as levers,
clockwork, and triggers pulled by hand; with such crude means of
exploding them, it is not extraordinary to find, that all the attempts
made to destroy hostile ships, resulted in failure.
[Illustration: FULTON'S TORPEDOES.
PLATE I]
Briefly reviewing the history of the torpedo during its first period
of existence, viz., from Captain Bushnell's invention of submarine
magazines in 1775, down to the introduction of electricity, as a
means of exploding submarine mines, by Colonel Colt, in 1829, we
find that due to the unwearied exertions, and numerous experiments
carried out by Captain Bushnell, Mr. R. Fulton and others, the
following very important principles in the art of torpedo warfare were
fully proved:--
1.--That a charge of gunpowder could be exploded under
water.
2.--That any vessel could be sunk by a torpedo,
provided only the charge were large enough.
3.--That it was possible to construct a boat which
could be navigated, and remain for several hours under
water, without detriment to her crew.
4.--That a ship at anchor could be destroyed, by means
of drifting torpedoes, or by a submarine or ordinary
boat, armed with a spar torpedo.
5.--That a vessel underweigh could be destroyed by
means of stationary submarine mines, and by the harpoon
torpedo.
These principles, which at the time were fully admitted, laid the
foundations of the systems of torpedo warfare, that are at the present
day in vogue, all over the world.
_Second Epoch._--The second epoch in the life of the torpedo dates from
1829, when Colonel Colt, then a mere lad, commenced experiments with
his submarine battery.
_Colt's Experiments._--His first public essay, was on the 4th June,
1842, when he exploded a case of powder in New York harbour, while
himself standing at a great distance off.
Having by numerous successful experiments satisfactorily proved that
vessels at anchor could be sunk by means of his electrical mines,
Colonel Colt engaged to destroy a vessel underweigh by similar means,
which feat he successfully accomplished on 13th April, 1844.
_Colt's Electric Cable._--The electric cable as used by Colonel Colt,
was insulated by cotton yarn, soaked in a solution of asphaltum and
beeswax, and the whole enclosed in a metal case.
_Colt's Reflector._--On examining Colt's papers after his death, one
was found illustrating one of his many devices for effecting the
explosion of a submarine mine at the proper instant.
_Description of Reflector._--One set of conducting wires from all the
mines is permanently attached to a single pole of a very powerful
firing battery, the other wires lead to metal points which are attached
to marks on a chart of the channel in front of the operator and which
marks correspond with the actual positions of the mines in the channel.
A reflector, is arranged to throw the image of a hostile vessel on the
chart, and as this image passes over either of the wire terminations
on it, the operator with the other battery wire, completes the
circuit, and explodes the torpedo, over which by her image thrown on
the chart, the vessel is supposed to be at that precise moment.[F] In
his experiment with a vessel under weigh, Colt had probably taken the
precaution of laying down several circles of mines, and thus aided by
cross staffs, ensured the experiment being a success.
With regard to the invention of the word torpedo, for submarine
infernal machines, Dr. Barnard in his life of Colt says, "that Fulton
used the word torpedo, probably on account of its power of stunning or
making torpid, and that a long way through the water,--in so naming it,
he buildeth better than he knew, for Colt's torpedoes being fired by
electricity may with special fitness take its name from the electric
eel."[G]
_Theoretical Knowledge._--Though many opportunities have occurred
during the last thirty-five years for practically testing the
effectiveness of torpedoes when employed on actual service, especially
during the American Civil War (1861-65) and the late Turco-Russian
War (1877-78), yet in so far as the offensive and electrical portion
of submarine warfare is concerned, our knowledge of them is still
principally theoretically.
_Failure of Offensive Torpedoes._--The manipulation of the ordinary
spar or outrigger torpedo boats, and of the various automatic
torpedoes, appears simple enough, when practice is made with those
submarine weapons during peace time, also the results of such practice
is without doubt uniformly successful, yet when the crucial test of
actual service is applied, as was the case during the war of 1877, with
the Whitehead and spar torpedoes, then a succession of failures had to
be recorded.[H]
The cause of this want of success in war-time with offensive torpedoes,
lies in the fact, that during peace time the experiments and practice
carried out with them, are done so, under the most favourable
circumstances, that is to say in daylight, and the nerves of the
operators not in that high state of tension, which would be the case,
were they attacking a man-of-war on a pitch dark night, whose exact
position cannot be known, and from whose guns at any moment a sheet of
fire may be belched forth, and a storm of shot and bullets be poured on
them, whilst on actual service, this would in nine out of ten instances
be the case.
Some uncertainty must and will always exist in offensive torpedo
operations when carried out in actual war, where, as in this case, the
success of the enterprise depends almost wholly on the state of a man's
nerves, yet this defect, a want of certainty, may to a considerable
extent be eradicated were means to be found of carrying out in time of
peace, a systematic practice of this branch of torpedo warfare, under
circumstances similar to those experienced in war time, and this is not
only possible, but practicable.
_Moral Effect of Torpedoes._--We now come to the moral effect of
torpedoes, which is undoubtedly the very essence of the vast power of
these terrible engines of war. Each successive war that has occurred,
in which the torpedo has taken a part, since Captain Bushnell's futile
attempt in 1775 to destroy our fleet by drifting numerous kegs charged
with gunpowder down the Delawarre, teem with proofs of the great worth
of torpedoes in this respect alone.
That such a dread of them should and always will be met with in future
Naval wars, at times creating a regular torpedo scare or funk, is not
extraordinary, when it is remembered that these submarine weapons of
the present day, are capable of sinking the finest ironclad afloat, and
of launching into eternity without a moment's warning or preparation,
whole ships' crews.
The torpedoes existing at the present day have, without doubt, reached
a very high degree of excellence, in so far as their construction,
fuzes, cables, &c., both electrically and mechanically, is concerned,
but much has yet to be done to develop their actual effectiveness.
The result of the numerous and exhaustive experiments that have of
late years been carried out by England, America, and Europe prove that
the necessary distances between stationary submarine mines are by far
greater than those within which the explosions are effective.
Therefore it will be found necessary to supplement those submarine
harbour defences, by automatic torpedoes that can be controlled and
directed from the shore, as well as by specially constructed torpedo
boats.
_Automatic Arrangements._--And to ensure certainty, which is the
desideratum in torpedo warfare, circuit closers, or other automatic
arrangements for exploding the submarine mines, must be employed, as
the system of firing them by judgment is not at all a sure one.
_Ship Defence._--The problem, which occupies the attention of Naval
and other scientific men, at the present day, is how best to enable a
ship to guard herself against attacks from the fish and other automatic
torpedoes, and this without in any way impairing her efficiency as a
man-of-war.
The means of such defence, should most certainly be inherent in the
vessel herself, outward methods, such as nets, booms, etc., are
to great extent impracticable, besides one of the above mentioned
torpedoes, being caught by such obstructions would, on exploding, most
probably destroy them, thus leaving the vessel undefended against
further attacks.
_Mechanical Mines._--Several ingenious methods have of late been
devised for the purpose of obviating one of the principal defects
common to all kinds of mechanical submarine mines, the most efficient
and practical of which will be found fully described in the following
pages, viz., the great danger attendant on the mooring of such mines;
but as yet, no really practical mode of rendering mechanical mines
safe, after they have once been moored and put in action, has been
discovered, were such to be devised, a very difficult and extremely
important problem of defensive torpedo warfare would be solved.
_Electrical Mines._--In regard to electrical submarine mines, much
has been done by torpedoists in general to simplify this otherwise
somewhat complicated branch of defensive torpedo warfare, by adopting
the platinum wire fuze, in the place of the high tension one, by the
employment of Leclanché firing batteries, by the simplification of
the circuit closer, and discarding the use of a circuit breaker, by
altering the form of torpedo case, and whenever possible by enclosing
the circuit closer in the submarine mine.
The necessity of a very elaborate system of testing should, if
possible, be overcome, for a system of submarine mines that requires
the numerous and various tests that are at the present day employed,
to enable those in charge of them to know for certain that when wanted
the mines will explode, cannot be considered as adaptable to actual
service. It must be remembered that the safety of many ports, etc.,
will in future wars depend almost entirely on the practical efficiency
of electrical and mechanical mines. As yet, in actual war, little or
no experience has been gained of the real value of a mode of coast
defence by electrical mines, excepting from a moral point of view,
though in this particular they have most undoubtedly been proved to be
exceedingly effective.
A submarine mine much wanted on active service, is one that can be
carried on board ships, capable of being fitted for use at a moment's
notice, and of being easily and rapidly placed in position by the
ordinary boats of a man-of-war. It should be a self-acting electrical
mine, with the circuit closing apparatus enclosed in the torpedo case,
and capable of carrying about 100 lbs. of guncotton. This form of mine
would be found extremely useful to secure the entrance to a harbour,
etc., where ships might happen to be anchored for the night, or which
might have been wrested from the enemy, etc.
They should be capable of being placed in position and picked up again,
in the shortest possible space of time.
_Offensive Torpedoes._--Coming to the question of offensive torpedoes
there still seems to be a great difference of opinion as to the real
value of the Whitehead fish torpedo, and this point will never be
finally settled until that weapon has been more thoroughly tested on
actual service; from a specially built torpedo boat, by which is meant
a Thornycroft or Yarrow craft, the spar torpedo would seem to be the
most effective weapon. Torpedo vessels for the special purpose of
experimenting with the Whitehead torpedo have been built by England,
America, and several continental governments, so that we may soon hope
to get some more decided opinion as to the utility of that weapon.
When manipulated from the shore, or large ships, the Lay torpedo boat,
if only its speed be increased will prove an exceedingly effective
submarine weapon, for the purposes of offence, active defence, or
clearing harbours, etc., of mines, in fact, it may be more truly said
of this weapon, than of the Whitehead, "that it can do everything but
speak." Captain Harvey has greatly improved his towing torpedo, but it
is still a somewhat complicated and difficult weapon to manipulate by
ordinary persons, that is, those not specially trained for the work.
Drifting torpedoes under certain circumstances should prove invaluable,
but little or no improvement has been effected in this direction.
Submarine boats have also remained _in statu quo_, though for the
purpose of clearing an enemy's harbour of mines, it seems impossible to
devise any better method.
Electric lights are now universally adopted for use on board ship, and
will play a very important part in the defence of ships against torpedo
attacks in future wars. Glancing back on what has been effected in the
matter of improving the system of torpedo warfare in all its branches
during the last few years, with the exception of the vast improvements
in the form and construction of steam torpedo boats, their engines,
etc., very little has been done, owing principally to the want of that
practical knowledge which unfortunately can only be gained from their
employment in actual war.
The late Turco-Russian war afforded a splendid opportunity for applying
the crucial test of actual service to both the offensive and defensive
branches of torpedo warfare, yet little or no light was thrown on the
somewhat shadowy subject of submarine warfare. The present struggle
between Peru and Chili may furnish some experience, but it will not be
very satisfactory, as hardly any knowledge of manipulating torpedoes is
possessed by either side.
FOOTNOTES:
[Footnote A: C. D. Colden's "Life of Fulton."]
[Footnote B: C. D. Colden's "Life of Fulton."]
[Footnote C: C. D. Colden's "Life of Fulton."]
[Footnote D: "Torpedo Warfare," by R. Fulton, 1810.]
[Footnote E: C. D. Colden's "Life of Fulton."]
[Footnote F: Johnston's Cyclopædia.]
[Footnote G: Armsmear.]
[Footnote H: See Chapter VII.]
CHAPTER II.
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.]
CHAPTER III.
DEFENSIVE TORPEDO WARFARE--_continued_.
BY electrical submarine mines is meant those whose charges are ignited
by the agency of electricity.
_Submarine Mines during the Crimean and American Wars._--It was during
the Crimean war (1854-6) that this description of defensive torpedoes
was for the first time employed on actual service. Several of the
principal Russian harbours were protected by this form of submarine
mine, but owing to the smallness of their charges, and to the want of
electrical knowledge on the part of the Russian officers and men in
charge of them, none of the ships of the Allies were sunk, or even
rendered _hors de combat_ by this mode of harbour defence, though in
several instances ground known to be covered with submarine mines was
passed over by both English and French vessels of war.
Subsequently the Confederates, during the American civil war, employed
electrical submarine mines in considerable numbers for the defence
of their numerous harbours, rivers, &c.; but though in so far as the
size of the torpedo charges was concerned, they did not make the same
mistake as the Russians, yet, owing to the absence of proper electrical
apparatus, and the want of any practical knowledge of the manipulation
of electrical sea mines, on the part of the Confederate torpedoists,
they were almost entirely unsuccessful in destroying the Federal
warships; the _Commodore Jones_ being the sole instance, out of the
large number of vessels belonging to the Northerners which were sunk
and severely injured by torpedoes, of a war steamer being sunk by means
of electrical submarine mines.
In the Franco-German and Russo-Turkish wars which have lately occurred,
electrical sea mines were very extensively used in coast defence, but
with the exception of the loss of the gunboat _Suna_ to the Turks,
during the latter struggle, by this form of defensive torpedo, no other
damage to vessels resulted from their use, yet owing to the vast moral
power possessed by these submarine weapons, they were enabled to most
effectually carry out the work of defence entrusted to their care.
Of late years many important discoveries have been made in the science
of electricity, and vast improvements have been effected in electrical
apparatus, to which causes may be traced the vastly improved system of
electrical submarine mines as adopted by the English, American, and
principal European governments at the present day, as compared with
those that have hitherto been employed.
The certainty of action when required of electrical submarine mines,
which is of course the desideratum of all torpedoists, has, by the
improved mode and manner of ascertaining the exact electrical condition
of each particular mine, and of the system as a whole, which is at
present in vogue, been made almost absolute.
_Advantages of Electrical Submarine Mines._--This form of defensive
torpedo possesses numerous important advantages, the principal of which
are as follows:--
1.--They are always absolutely under control.
NOTE.--By detaching or connecting the firing battery, which is effected
by means of a plug, key, &c., they may be respectively rendered
harmless, or dangerous. Thus friendly ships may pass over them in
safety, whilst those of the enemy are debarred from so doing. On this
account harbours, &c., protected by such mines are termed "Harbours of
refuge."
2.--Fresh mines may be added to a system of such
defensive torpedoes, thereby allowing an exploded mine
to be replaced.
NOTE.--This is a very important point in connection with a system of
defence by submarine mines, as in the case of a deep water channel,
a hostile vessel being sunk by one of them, would not become an
obstruction, as, were the channel a comparatively shallow one would
most probably be the result, and therefore it would be necessary to put
a fresh mine in the place of the exploded one; this would also apply
were a mine to be prematurely ignited, or if any portion of its firing
apparatus were injured.
3.--At night, or in a fog, no vessel can pass through a
channel, &c., so protected without affording a means of
ascertaining her presence.
NOTE.--This is also a very important advantage of a system of defence
by electrical sea mines, affording as it does a complete safeguard
against surprise.
4.--The power of obtaining proof, without going
near it, by a system of testing that the electrical
condition of the mine, &c., is perfect.
NOTE.--This again is an extremely important point. For were a charge to
become wet, one of the electric cables of the mine broken, or damaged,
&c., it would instantly be made apparent at the firing station, and
could be at once remedied.
5.--They can be raised for examination, or removed when
no longer required, with ease and safety.
Such are some of the chief advantages of employing the agency of
electricity to effect the ignition of the charge in a system of defence
by submarine mines.
_Defects of Electrical Submarine Mines._--The following are the chief
defects connected with the use of electrical mines:--
1.--The number of wires that are required to be used
with them.
2.--The necessity of employing specially trained men in
their manipulation.
In time there seems little doubt but that the former obstacle will be
to a considerable extent overcome, but the latter must always be a flaw
in an otherwise perfect system of coast defence by submarine mines.
_Rules to be observed in using Electrical Submarine Mines._--In
connection with a system of electrical submarine mines the following
rules should be carefully observed:--
1.--They should be moored in deep channels, that is
to say, where the larger class of vessels would in
attempting to force a passage be obliged to go.
NOTE.--Mechanical submarine mines should never be used under these
circumstances, as the difficulties of mooring them and keeping them in
position would be very considerable, also a vessel being sunk in a very
deep channel would not necessarily block it, and as a mechanical mine
cannot be replaced, a gap would be left in the defence.
2.--They should be placed in the narrowest parts of the
channel.
NOTE.--The object of this rule is evident, fewer mines being required,
and consequently in the case of electrical ones, a far less number
of wires are needed, which gives an increase of simplicity, and
consequently more effectiveness. This point should be observed in
connection with mechanical, as well as electrical submarine mines.
3.--They should where practicable be moored on the
ground.
NOTE.--The advantages attendant on an observance of this rule are:--
_a._--Increased vertical effect.
_b._--Avoidance of mooring difficulties.
_c._--Less liability of shifting from its original
position.
_d._--Less chance of its being discovered and rendered
useless by an enemy.
_e._--By far heavier charges may be conveniently
employed.
4.--Where possible, no indication whatever should be
given of the position of the mines by their circuit
closers, or in the case of small buoyant ones, by the
mines themselves.
NOTE.--In some instances this will be almost impracticable, as for
example, where there is a very great rise and fall of tide. For
instance, at Noel Bay in the Bay of Fundy, the rise is over fifty feet.
Here, when circuit closers, or small buoyant mines are used, both of
which ought never to be more than twenty feet below the surface, long
before low water they would be found floating on the surface in full
view. Many attempts have been made to overcome this difficulty, but as
yet no really practicable means have been devised.
5.--The stations where the firing batteries, &c., are
placed, should be in the defensive work likely to
be held the longest, thus enabling the mines to be
commanded up to the last moment.
6.--The electric cables should be laid in positions
such that their discovery by the enemy would be
extremely difficult, and almost impossible.
NOTE.--This may be to a certain extent effected by leading them from
the mines to the firing and observing stations by circuitous routes,
and by burying them in trenches.
7.--They should not be thrown away on boats.
NOTES.--As they can in all cases be fired by will, even when circuit
closers are used, this rule is easily observed. But to prevent an
enemy's boats from rendering the mines useless, a line of small
torpedoes might be placed in advance of the large ones, or the circuit
closers themselves might be charged.
At night, or in foggy weather it will be necessary to employ
guard-boats, electric lights, &c., to protect them against damage by an
enemy's boats, &c.
In the foregoing pages of this chapter will be found the requirements
and conditions essential to a perfect system of electrical submarine
mines for the defence of a harbour, river, &c.; in the following
pages a general description of the component parts of such defensive
torpedoes, under the following heads--Form and Construction of Case;
Electrical Fuzes; Electric Cables; Watertight Joints; Junction Boxes;
and Mode of Mooring, will be considered.
_Form and Construction of Torpedo Case._--The case of a submarine mine
should be capable of fulfilling the following conditions:--
1. It must be able at great depths to withstand a great
pressure of water, and remain perfectly watertight.
NOTE.--This in the case of a charge of gunpowder being an imperative
necessity.
2. As a buoyant mine, it must be capable of affording
a considerable excess of buoyancy, by which it may be
rendered stationary when moored.
NOTE.--This is generally obtained by having an air space within
the torpedo, thus requiring a much larger case in which the charge
is enclosed than would otherwise be necessary, causing increased
difficulties in transportation, mooring, and raising them for
examination, &c.
3. When explosive agents which require a certain time
for thorough combustion are used as the charge, such
as gunpowder, picric powder, gun-cotton (not fired by
detonation), &c., a much stronger case is necessary
to obtain the full explosive effect than would be the
case were detonated charges, under the same conditions,
employed.
NOTE.--This is an extremely important point, for if a weak case is
employed with a charge of gunpowder, &c., fired by a fuze primed with
powder only, a portion of it on being fired would generate a sufficient
quantity of gas to burst the case, thus blowing out the remainder of
the charge before its ignition had been effected.
4. It should be of such a form that the complete
ignition of the charge is obtained by the employment
of the least number of fuzes possible to effect this
result.
NOTE.--This point is especially to be observed when gunpowder is the
explosive agent.
The various forms of defensive torpedo cases may be classed under the
following heads:--
1.--Spherical shape.
2.--Cylindrical shape.
3.--Conical shape.
_Spherical Shape._--This form of case is theoretically the very
best one possible to devise, but on account of the difficulty of
constructing it, and its comparative costliness, such a form may be put
aside as being impracticable.
_Cylindrical Shape._--Torpedoists in general have hitherto adopted the
cylindrical form of case as being the best adaptable for both ground
and buoyant mines containing a heavy charge.
The Confederates employed exclusively this shape for their electrical
submarine mines, which were ground ones, and the Austrians in the war
of "66" approved of this form of case for their electrical submarine
mines, which were buoyant ones. Figs. 19 and 20 represent respectively
the American and Austrian mines.
In England the cylindrical shape has up to quite lately found most
favour with her torpedoists for both buoyant and ground mines. At Fig.
21 is represented a 100-lb. buoyant electrical mine, surrounded by a
wooden jacket, _e_, and having its circuit closer, _C_, enclosed within
it; and at Fig. 22 is shown a 250-lb. electrical mine, which may be
used either as a buoyant or ground one.
For large ground mines, the best form of torpedo case seems to be that
of the turtle mine, which is shown at Fig. 9. A heavy charge may be
contained in it; it forms its own anchor; and it would withstand an
explosion of an adjacent mine without sustaining any injury. At present
the cylindrical shape is the form generally used, though as far as
retaining its position on the ground in a strong tide, it cannot be
compared to the turtle form.
[Illustration: FORM OF CASE OF SUBMARINE MINES.
PLATE VI.]
_The Conical Shape._--Hitherto this shape of submarine mine case was
only used in connection with mechanical mines, but now it is the
form considered most suitable for all buoyant mines, electrical or
mechanical. At Fig. 23 is shown the conical shaped mechanical mine,
employed by the Confederates for use with sensitive fuzes. The conical
form of torpedo case lately approved of by the English torpedo
authorities is somewhat similar to that one, the charge being contained
in a kind of box hung from the top of the case, and the circuit closer
is screwed into the bottom of the case; surrounding the upper part
of the case is a thick buffer of wood, by which damage to the mine
is prevented by the passage of friendly ships. This is altogether a
very neat and serviceable form of torpedo case. This form of case is
also more difficult to discover by dragging, and easier to retain in
position.
_Electrical Fuzes._--The fuzes employed in connection with electrical
submarine mines may be divided into two classes:--
1. Platinum wire bridge fuzes.
NOTE.--That is where the evolution of heat is caused by a large
_quantity_ of the electric force flowing through a good conductor
of large section, such as the copper core of electric cables, being
suddenly checked by a very thin wire composed of a metal which compared
with the conductor offers a very great resistance, such as _platinum_.
2. High tension fuzes.
NOTE.--That is where the evolution of heat is caused by the electric
spark, or by the electric discharge taking place through a substance
which offers very great resistance to the passage of the electric force.
_Platinum Wire Fuze._--This is the form of electrical fuze most
commonly used, and which will most certainly supersede altogether the
high tension fuze.
There are numerous advantages accruing from the use of platinum wire
fuzes, the chief of which are here enumerated:--
_a._--Great facilities for, and entire safety whilst
testing the circuit.
_b._--Extreme simplicity of manufacture.
_c._--Non-liability to deteriorate.
_d._--Perfect insulation of the electric cables used in
connection with submarine mines not necessary.
_English Service Platinum Wire Fuze._--The following is a description
of the platinum wire fuze of the form adopted in the English service, a
section of which is shown at Fig. 24. It consists of a head of ebonite
_a_, hollowed out, in which a metal mould is fixed, the wires which
have been previously bared are inserted into holes in this mould, and
firmly fixed thereto by means of a composition poured into the mould,
whilst hot; this is shown at _b_. The two bared ends of the wires which
project beyond the metal mould, as _c_, _c_, are connected by a bridge
of platinum-silver wire ·0014" in diameter and weighing ·21 grs. per
yard. This is effected as follows:--
A very fine shallow groove is made in the flat ends of the bare wires
_c_, _c_, and the platinum-silver wire is laid across in the incisions,
and fixed there by means of solder. The length of the bridge _d_ is
·25."
A tube _e_, made of tin, and soldered to a brass socket _f_, is fixed
by means of cement to the ebonite head _a_; in this tube is placed the
fulminate of mercury, the open end of the tube _g_ being closed with a
pellet of red lead and shellac varnish; around the bridge of the fuze
is placed some loose gun-cotton.
_McEvoy's Platinum Wire Fuze._--Another form of platinum wire fuze,
which has been devised by Captain McEvoy, formerly of the Confederate
Service, is shown at Fig. 25. It consists of the head _a_, formed of
a mixture of ground glass, or Portland cement, worked up with sulphur
as a base: this mixture when hot is poured into a mould, in which the
two insulated copper wires, _b_, _b_, have been previously placed; when
cold, the mixture with the wires affixed is removed from the mould,
and the platinum wire bridge _c_ being secured to the bare ends of the
copper wires, the whole is firmly fixed in a brass socket _d_, by means
of cement; the space _e_ is filled with loose dry gun-cotton, so as
to surround the bridge _c_; a copper tube _f_, closed at one end, is
partly filled with fulminate of mercury, and when the fuze is required
for service, this tube is secured to the brass socket _d_ by means of
cement.
In this form of low tension fuze there is no liability whatever of
any injury being caused to the bridge by the working of the wires in
the head, or by damp even after lying in the water for a month or
more. One peculiarity of this fuze is that the composition is run over
the insulated wires without materially softening the dielectric, or
affecting in the slightest degree the insulation of the wires.
_High Tension Fuzes._--The high tension fuze was devised for use with
electrical submarine mines, in the place of the platinum wire fuze,
on account of the little knowledge possessed, in the early days of
submarine warfare, in regard to the manipulation of Voltaic batteries.
Platinum wire requires a temperature of some 500° F. to heat it to
incandescence, and therefore necessitates the use of a powerful Voltaic
battery, both in intensity and power, to effect the ignition of
gunpowder by this means at considerable distances.
The Grove and Bunsen pile were the only suitable form of Voltaic
battery known at the period of the introduction of high tension fuzes,
both of which possessed the defects of uncertainty and inconstancy, and
also were by far too cumbersome and too difficult to keep in effective
working order to be of any real practicable value.
High tension fuzes may be ignited by means of either an electro-magneto
machine, an electro-dynamo machine, a frictional machine, or by a
Voltaic battery, generating an electric current of high intensity.
Various kinds of this form of electrical fuze have been designed, the
principal of which are as follows:--
1.--Statham's fuze.
2.--Beardslee's fuze.
3.--Von Ebner's fuze.
4.--Abel's fuze.
5.--Extempore fuze.
_Statham's Fuze._--A section and elevation of this electric fuze are
shown at Fig. 26; _a_, _b_ is a gutta percha tube, with an opening cut
in it, as shown in figure. The interior of this vulcanised gutta percha
tube is coated with a thin layer of sulphide of copper, which coating
is obtained by leaving a bare copper wire for some time in connection
with the above-mentioned tube. The extremities of two insulated copper
wires _c_, _c_, considerably smaller than the conducting wires, are
uncovered, scraped, and then inserted into the tube _a_, _b_, with an
interval of ·15 inch between them. The wires are then bent as shown in
the figure, and the priming placed between the terminals. The whole
is covered with a gutta percha bag, which is filled with fine grained
gunpowder. The priming substance is composed of fulminate of mercury
worked up with gum water. The objection to this fuze, which was used
by the Allies in their destruction of the Russian fortifications at
Sebastopol, is the want of sensitiveness of sulphide of copper, and the
consequent necessity of a very powerful firing battery.
_Beardslee's Fuze._--This high tension fuze is shown at Fig. 27.
It consists of a cylindrical piece of soft wood a, which is about
three-quarters of an inch in length and in diameter; two copper nails,
_b_, _b_, are driven through this piece of wood _a_, in such a way
that while the two heads come together as close as possible without
absolutely touching, the pointed ends are some distance apart from
each other, and project through the wood _a_; two insulated copper
wires, _c_, _c_, are firmly soldered to these projecting ends, and
a piece of soft wax, _d_, is pressed around the junction points. In
a groove, across the heads of the copper nails, is placed a little
black lead, to which is added a minute quantity of some substance, the
nature of which is known only to Mr. Beardslee. Several folds of paper
are wrapped round the wooden cylinder, forming a cylinder about 2-1/2
inches long, one end of which is tightly fastened round the insulated
wires as at _e_. The other end of the cylinder is then filled with
powder, _f_, and closed by a piece of twine. The whole fuze is then
coated with black varnish. Though not highly sensitive, Beardslee's
fuze is exceedingly efficient, and extremely simple.
_Von Ebner's Fuze._--This form of fuze was devised by Colonel Von Ebner
of the Austrian Engineers. A section and elevation of it is shown at
Fig. 28. It consists of an outer cylinder, _a_, of gutta percha, and an
inner one of copper, _b_, which latter encloses a core formed of ground
glass and sulphur, _c_, which core is cast round the two conducting
wires _d_, _d_ in such a way that they are completely insulated from
one another. In the first instance the wire is in one continuous
length, the opening _e_ being subsequently made, and carefully gauged,
so as to ensure a uniform break, or interval in the conductor of
each fuze. The priming composition, which consists of equal parts of
sulphide of antimony and chlorate of potash, is placed in the hollow
_f_, to which is added some powdered plumbago, for the purpose of
increasing the conducting power of the composition. This mixture is
put into the hollow, _f_, of the fuze under considerable pressure, the
terminals being connected with a sensitive galvanometer, in circuit
with a test battery, and the pressure applied so as to obtain, as far
as possible, uniformity in the electrical resistance of each fuze.
The Austrians employed this form of high tension fuze in connection
with a frictional machine for the electrical mines used in their
defence of Venice, &c. during the war of 1866.
_Abel's Fuze._--Mr. Abel devised a high tension fuze, which in 1858 was
extensively experimented with; the Beardslee and Von Ebner fuze being
based upon the principles applied for the first time in Abel's fuze.
[Illustration: ELECTRICAL FUZES.
PLATE VII]
Many modifications of it have been from time to time devised by Mr.
Abel; a section and elevation of the more recent form of his fuze
is shown at Fig. 29. It consists of _b_, _b_, a body of beech wood,
hollowed for half its length, in which space the priming charge
is placed; it is also perforated by three holes, one vertical for
the reception of the capsule of sensitive mixture, the other two
horizontal, in which the conducting wires are placed; _a_, _a_ are two
insulated copper wires, passing into the vertical hole, and resting
on the sensitive mixture; in a cavity, _d_, of the body of the fuze
is placed some mealed powder, which is fired by the ignition of the
sensitive mixture on the passage of the electrical current.
The insulated wires used in connection with this fuze consist of two
copper wires, about 2 inches long, and ·022 inch in diameter, enclosed
in a covering of gutta percha ·13 inch in diameter, and separated about
·06 inch from each other.
At one end the wires are bared to 1·25 inch, at the other they are
merely cut across by a very sharp pair of scissors. This end of the
double covered wire is inserted into a paper cylinder _c_, _c_, which
holds a small quantity of the priming mixture. This capped end of
the wires is inserted into the wooden body of the fuze through the
vertical hole _i_, and projects ·15 inch into the cavity _d_. The bare
ends of the double covered wires are pressed into small grooves in the
head of the cylinder _e e_, and each extremity is bent into one of
the small channels _d' d'_, which are at right angles to the vertical
perforation. _d' d'_ are two small copper tubes driven into these
channels over the wire ends, to keep the wires in position, and to form
the opening into which the conducting wires _f_ are inserted and bent
round, as at _e'_.
The priming mixture of Abel's original fuze, which was the one used
by the Confederates, was composed of 10 parts of subphosphide of
copper, 45 parts of subsulphide of copper, and 15 parts of chlorate of
potash. These ingredients reduced to a very fine state of division, and
intimately mixed, in a mortar, with the addition of a little alcohol,
are dried at a low temperature and preserved in bottles until required
for use. The sensitive mixture used by Mr. Abel more recently for his
submarine electrical high tension fuzes, is composed of an intimate
mixture of graphite and fulminate of mercury. By the process of
ramming, the electrical resistance of the fuze is regulated.
_Extempore Fuzes._--It may be necessary in some cases, when a specially
manufactured fuze is not attainable, to make a fuze on the spot. The
following is a neat and simple method of constructing an extempore high
tension fuze.
_Fisher's Extempore Fuze._--This form of fuze was devised by
Lieutenant now Captain Fisher, R.N. It consists of a small disc of
gutta percha, through which the ends of two wires are inserted about
1/4 inch apart, their ends terminating in small copper plates formed
by hammering down the wire. These flat ends should be fixed parallel,
and in the first place in contact with one another, also should be
level with the surface of the gutta percha. The other two extremities
of the wires are then placed in circuit with a sensitive galvanometer
and a test battery; the needle of the former deflects violently, there
being a complete metallic circuit; the flat ends of the wires or poles
of the fuze are then separated very carefully, until the needle just
ceases to deflect. In the space thus formed, a little scraped charcoal
is placed, and rammed in by a piece of wood. By the application of
pressure, any degree of sensitiveness may be attained, merely observing
the deflection of the galvanometer needle. Over the charcoal a little
powdered resin is shaken, and pressed down, by which means the charcoal
is fixed in position, and owing to the inflammability of the resin, the
ignition of the gunpowder priming is ensured. The disc of gutta percha
is then placed in an empty Snider ball cartridge, &c., and by the
application of a little warm gutta percha applied externally, the holes
where the projecting ends of the wires pass are closed, and the disc is
fixed and insulated. The case is then filled with some mealed powder
and fine grained powder, on the top of which is placed a little cotton
wool, and the whole pressed down tightly with the finger, the open
end of the case being then choked, as in Beardslee's fuze and Abel's
extempore one. The apex is then covered with some warm gutta percha,
and the whole of the fuze coated over with red sealing-wax dissolved in
methylated spirits.
_Insulated Electric Cables._--For the work of defence by electrical
submarine mines, the wires along which the electric current flows have,
on account of their being led underground and through the water, to be
covered with some substance which shall prevent the current during its
passage from escaping to earth, or in other words, they (the wires)
must be insulated.
The substances in general use for such purposes are as follows:--
1.--Gutta percha.
2.--Ordinary india rubber.
3.--Hooper's material.
_Gutta Percha._--This substance was used by Messrs. Siemens in the
cables manufactured by them for the Austrian government in 1866, and is
to some extent still employed, though Hooper's material or vulcanised
india rubber, has been found to be more suitable. The dielectric, gutta
percha, possesses the following advantages:--
_a._--It can be put on the conducting wire, as an
unbroken tube.
_b._--It only absorbs 1 per cent. of water.
_c._--It has the property of clinging to the metallic
conductor, by which is meant, that should it
(conductor) be cut through, and any strain be brought
on the cable, there is a tendency on the part of the
gutta percha to cling to the conducting wire, thereby
not increasing the fault.
The defects of such an insulator are:--
_a._--Its liability to become hard and brittle when
exposed to dry heat, and consequently it requires to be
stored under water.
_b._--It becomes comparatively a bad dielectric at 100°
F.
_c._--It becomes plastic at high temperatures, which
causes the conducting wire to alter its position.
In some particulars ordinary india rubber is a better insulator than
gutta percha, but this substance is equally inferior to Hooper's
material, &c. The advantages possessed by this substance are:--
_a._--It is not easily affected by a dry heat.
_b._--It is a very excellent dielectric.
The defects of this mode of insulation are:--
_a._--It must be put on the conducting wires in a
series of jointed pieces.
_b._--It does not cling to the conducting wire, so that
if the electric cable be cut, and any strain be brought
on it (cable), the previous fault is increased.
_c._--It absorbs 25 per cent. of water.
_Hooper's Material._--This insulating material consists of an inside
coating of pure india rubber, then another similar coating in
conjunction with oxide of zinc, which is termed the separator, and
an outside coating of india rubber combined with sulphur. The use of
the separator is to prevent any damage to the conducting wires by the
action of the sulphur. The three coatings are then baked for some
hours at a very high temperature, which fuses the whole into a solid
mass, and vulcanises the outer coating. The properties of the pure
india rubber which is in contact with the metallic conductor are thus
preserved, while any decay of the outer covering is prevented by the
vulcanising process.
The advantages claimed by Mr. Hooper for this mode of insulating
electric submarine cables, are:--
_a._--High insulation.
_b._--Flexibility.
_c._--Capability of withstanding the bad effects of dry
heat.
The qualifications essential to a perfect insulated electrical cable
for use with submarine mines are as follows:--
1.--Capacity to bear a certain amount of strain without
breaking.
2.--Perfect insulation, or at least as nearly so as
it is possible to obtain, and composed of a substance
capable of being readily stored, and kept for a
considerable length of time without being injured.
3.--Pliability so that it may be wound on, or paid out
from, a moderately sized drum without injury.
4.--Provided with an external covering capable of
protecting the dielectric from injury when used in
situations where there is a rocky or shingly bottom, &c.
The insulated wire of a submarine cable is technically spoken of as its
_core_.
By a _cable_ is meant to be understood any piece of covered wire.
Several forms of submarine electrical cables have been devised, all of
which more or less possess the qualifications enumerated above. The
following are some of the most effective:--
1.--Siemens's cable.
2.--Hooper's cable.
3.--Gray's cable.
4.--Service cable.
_Siemens's Cable._--This form of cable is represented at Fig. 30. It
consists of a strand _a_, which is composed of three or more copper
wires formed by laying up the several single copper wires spirally,
several layers of gutta percha, or india rubber, _b_, two coverings of
hemp, saturated with Stockholm tar, _c_ and _d_, and several plies of
copper tape _e_, wound on, so that each strip overlaps the preceding
one, as shown at Fig. 30. The conductivity of the copper employed for
the strand is equal to at least 90 per cent. of that of pure copper.
This exterior covering of copper tape is a patent of Messrs. Siemens
Brothers, and when once laid down, the cable so covered is very
efficiently protected, and of course it is little affected by the
action of the sea water. This mode of protection has one great defect,
viz., that in the event of a kink occurring in paying out the line, and
at the same time a sharp strain being applied, the copper tape at that
point is extremely likely to destroy the insulation by being drawn in
such a way as to cut through the dielectric. On this account great care
must be observed in handling this form of cable.
In practice precautions must be taken to prevent the copper tape
covering from being brought into contact with any iron, for were such
to happen, electrical action would at once ensue, causing the iron to
corrode with enormous rapidity.
In some of Siemens's cables, vulcanised india rubber replaces the gutta
percha insulation. Iron covered cables, either galvanised or plain, are
manufactured as well as the copper tape covered ones by that firm.
_Hooper's Cable._--This form of cable is represented at Fig. 31. It
consists of a metal conducting wire, generally copper, _a_, covered
with an alloy to protect it from chemical action, the insulating
substance _b_, known as Hooper's material, previously described at page
39, a covering of tarred hemp _c_, and an outer covering of iron wires
(No. 11 B. W. G.), each of which is separately covered with tarred hemp
and wound on spirally, _d_.
Gray's cable is very similar to the one just described, the chief
difference in it as compared with Hooper's being the absence of the
separator.
_Silvertown Cables._--The following is a description of the core of an
electrical submarine cable, which is used by the English government,
and is supposed to contain all the advantages of the foregoing, and
none of their defects. It consists of a strand conductor of four copper
wires (No. 20 B. W. G.) of quality not less than 92 per cent. of pure
copper, and possessing an electrical resistance of not more than 14
ohms per nautical mile. This strand is tinned and insulated with
vulcanised india rubber to a diameter of ·24 inch, and then covered
with a layer of felt, and the whole subjected to a temperature of 300°
F. under steam pressure. This forms the core of the various kinds of
cables employed in connection with a system of defence by electrical
submarine mines, which are enumerated as follows:--
1.--Single core armoured cable.
2.--Multiple cable.
3.--Circuit closer cable.
4.--Single core unarmoured cable.
5.--Special cables for firing by cross bearings.
_Single Core Armoured Cable._--This form of cable is used in connection
with each mine of a group or system, and also to connect forts,
&c. across an arm of the sea. Over the core, which has been fully
described, is laid a spiral covering of tanned, picked Russian hemp,
over this are laid ten galvanised iron wires (No. 13 B. W. G.),
each one of which is covered with a similar hemp, which is laid in
an opposite spiral to the former similar covering, with a twist of
one revolution in about thirteen inches; in order to prevent these
wires from gaping when the cable is kinked, a further covering of two
servings of hemp passed spirally in opposite directions is laid, and
the whole passed through a hot composition of a tar and pitch mixture.
Exterior diameter of this cable is 7/8 inch. Its weight in air is
27-50/112 cwt., and in water 14-40/112 cwt. per nautical mile. The
breaking strain of a cable thus manufactured is 62-1/2 cwt., and its
cost about £47 per nautical mile. A diagram of this cable is shown at
Fig. 32.
_Multiple Cable._--This form of cable is employed in cases where it is
necessary to carry a large number of cables into the firing station,
&c. It consists of seven single cores formed into a strand, over which
a padding of hemp fibres is laid longitudinally, and over this again
is laid an armouring of sixteen (No. 9 B. W. G.) galvanised iron
wires, each one of which is covered with a layer of tarred tape put
on spirally with a twist of one revolution in 15 inches. The exterior
covering consists of two layers of hemp and composition, which is
laid on with a short twist, and in opposite directions. The external
diameter of this cable is 1-1/4 inch. Its weight in air and water is
78-25/112 cwt., and 45-32/112 cwt. respectively per nautical mile.
Its breaking strain is 135 cwt., and cost about £357 per nautical
mile. This form of cable is used in connection with a junction box,
from which the single armoured cables leading to the different mines
radiate, and is shown at Fig. 33.
_Circuit Closer Cable._--This cable, which connects the mine and
circuit closer, has been found to be subjected to exceptional wear and
tear, and therefore requires a special form of exterior protection. The
core of this cable is the same as the one described at page 41, also
it is covered with a similar padding of hemp, but instead of the iron
wires as in the case of the multiple cable, &c., nine strands, each of
which is composed of fourteen No. 22 Bessemer Steel Wires, are wound
on, each such strand being covered with hemp, which is put on with a
twist of one revolution in every 7-1/2 inches, the external covering
being the same as in other cables.
This form of armouring for an electric cable possesses the
qualifications of pliability, lightness, and great tensile strength.
Its weight in air is 52-106/112 cwt., and in water 28-4/112 cwt. per
nautical mile. Its breaking strain 65 cwt., and cost about £127 per
nautical mile.
_Single Core Unarmoured Cable._--This form of cable is used in a system
of defence by submarine mines to connect the detached works of a
maritime fortress, &c., for the purpose of telegraphing.
It consists of the ordinary service core, over which are laid two
servings of tarred hemp, put on spirally. The weight of this cable in
air is 4-13/112 cwt., and in water 1-36/112 cwt. per nautical mile; its
breaking strain is 7-1/2 cwt., and its cost per nautical mile is about
£35.
_Special Cables._--In firing electrical submarine mines by means of
cross bearings, a special cable is employed. As a general rule there
would be three lines of mines placed to converge on one of the stations.
Each of these lines would be provided with a conducting wire in
connection with the firing arrangements, while one line of wire in
connection with the firing station would be required for telegraphing.
For the purpose in question a four cored cable is used.
_Land Service Cable._--The cable employed for this service consists
of a core formed similar to that of the multiple cable, described at
page 41; over which is laid a padding of hemp, and finally two servings
of tarred hemp laid spirally in opposite directions are wound on. Its
weight in air is 16 cwt., and in water 4-50/112 cwt. per nautical mile.
Its breaking strain 17-1/2 cwt., and cost per nautical mile about £137.
_Sea Service Cable._--This consists of a similar core to the land
service cable, and padding of hemp, over which is laid an armouring
of fifteen No. 13 galvanised iron wires, each one being covered with
tarred tape, and finally the ordinary servings of tarred hemp. Its
weight in air is 49-101/112 cwt., and in water 25-109/112 cwt. per
nautical mile. Its breaking strain 65-100/112 cwt., and cost per
nautical mile about £202.
When frictional electricity is used to fire high tension fuzes, it has
been found by experiment that if several lines of insulated cables
are laid in the same trench for a few hundred yards, the inductive
effect of the electrical charge generated by a frictional machine is so
great that its discharge through one cable is sufficient not only to
fire the fuze in immediate connection with it, but by induction every
other fuze in connection with the remaining wires laid in the trench.
And this effect equally occurs when the electric cables are some feet
apart, provided they run parallel for a few hundred yards, and whether
the shore ends of the cables, the fuzes in connection with which are
not intended to be fired, are insulated, or put directly to earth,
the connections beyond the fuzes being to earth, or even insulated,
provided a very few yards of conductor exist beyond the fuze.
The length of wire which it is necessary to use between the mine
and its circuit closer would be quite sufficient for the purpose of
effecting ignition by induction. With platinum wire fuses there is no
danger whatever of the above happening, nor in the case of high tension
fuzes is there so much danger of ignition by induction, when a constant
instead of a frictional electric battery is used to generate the
current.
Another mode of protecting an insulated cable is to place it, as it
were, in the core of a hempen cable. In forming the rope on the cable,
great care is necessary to prevent any serious amount of torsion,
or tension coming on the insulated wire, either of which would most
assuredly result in injury to the cable. This form of cable might in
connection with obstructions, &c., be of great use, as on account of
its closely resembling an ordinary rope, it would be very unlikely to
excite suspicion, and so would most probably be cut, the result of
which, by previous arrangement, would be an explosion of a mine, or by
means of a galvanometer, &c., an indication that the obstructions, &c.,
were being interfered with.
_Jointing Electrical Cables._--This is a very important point in
connection with a system of defence or offence by electrical torpedoes.
In many instances it will be found necessary to join either two lengths
of cable, or an insulated wire and a cable, together, in both of which
cases, great care must be used in making the joints, so that the
insulation and the continuity of the circuit may be perfect.
[Illustration: ELECTRIC CABLES, EXTEMPORE CABLE JOINTS.
PLATE VIII]
Many species of junctions have been from time to time devised, the most
practical and generally employed of which are:--
1.--India rubber tube joint.
2.--Mathieson's joint.
3.--Beardslee's joint.
4.--McEvoy's joint.
5.--Permanent junction.
_India rubber Tube Joint._--This form of joint is a very useful one
for extempore purposes, being easily and quickly made, and being very
effective. At Fig. 34 is shown a sketch of such a junction. About 1·5
inches of the copper conductor of the two insulated cables are laid
bare and connected together by means of Nicoll's metallic joint, as
shown at Fig. 36, or by turning one of the conductors round the other,
their ends being carefully pressed down by means of pliers, to prevent
any chance of the india rubber tube being pierced; over the splice thus
formed serve some twine, and over the whole put a coating of india
rubber cement, grease, &c., then draw the vulcanised india rubber
tube, which has been previously placed on one of the insulated cables,
over the splice _a_, as shown at _b_, and secure it firmly by means of
twine, _c_, _c_, and then to prevent any strain being brought on the
joint, form a half-crown as shown in Fig. 35 at _A_.
In forming the splice, it is very important that the metallic ends
should be perfectly clean. The danger to this mode of jointing of the
piercing of the tube by the ends of the conductors is entirely removed
by employing the Nicoll metallic joint, which is formed as follows:--
_Nicoll Metallic Joint._--One of the conducting wires, as _a_, Fig. 36,
is formed into a spiral twist by means of a very simple instrument,
and the other wire _b_, which is left straight, is inserted into the
spiral, the whole being placed on an anvil, and pressed closely and
securely together by a single blow of a hammer.
_Mathieson's Joint._--This somewhat complicated, though very effective
mode of jointing, which is adopted in the English torpedo service, is
shown at Fig. 37, in elevation and section. It consists of two ebonite
cylinders _a_, _a_, through which the cables to be connected are
passed. Within these cylinders an ebonite tube _b_, _b_ is placed, the
ends of which are wedge-shaped, and which press against two vulcanite
rings _c_, _c_; in the interior of this tube _b_, _b_ is the metallic
joint _d_ of the two cables. The centre of the tube _b_, _b_ is of
square section, and fits into a hollow of similar form in the cylinders
_a_, _a_, the object of this being to prevent any twisting of the
wires during the process of screwing up, which would be liable to
injure the metallic joint _d_.
The manner of making this joint will be easily understood from the
figure. With this, as with all other temporary joints, it is advisable
to form a half-crown in the cable, including the joint.
_Beardslee's Joint._--This form of temporary joint when used with
strand conductors, which are composed of a number of small wires, has
been found to be exceedingly useful and effective, the only defect of
such a joint being the liability of straightening the wires of the
conductors should a direct strain be brought upon the wire extremities.
Fig. 38 represents a section of this joint; it consists of an ebonite
cylinder _a_, one end of which is solid, and the other open and fitted
with a screw thread, into which is screwed a plug _b_; through both the
plug _b_, and the solid end of the cylinder _a_, perforations are made
just large enough to admit the insulated wires _c_, _c_; about half an
inch of the extremities of these wires are bared and cleaned, and then
passed, the one through the plug _b_, a disc of vulcanised india rubber
_d_, and a metal disc _e_, and the end of the strand conductor turned
back on the face of this metal disc, the other through the perforation
in the solid end of the cylinder _a_, then through similar discs _d_
and _e_, and the end of the strand conductor treated in the same
manner as the former one; then by means of the screw plug _b_, the two
metallic discs _b_, _b_, and consequently the bare extremities of the
strand conductors are brought into close metallic contact.
_McEvoy's Joint for Iron Wire covered Cable_.--This form of joint is
shown in section at Fig. 39. Two brass caps _a_, _a_ are slipped over
the ends of the cables required to be joined, then the iron wire and
other coverings of the cables down to the insulating substance are
removed, the former being bent back close against the bottom of the
caps _a_, _a_, as shown in Fig. 39 at _b_, _b_; the cores of the cables
are then joined by an india rubber temporary joint _c_, which has been
described at page 45: the whole is then placed in the body of the
joint, and the brass caps _a_, _a_ screwed up, jamming the bent back
iron wires against a solid piece of brass _d_, _d_, by which means a
firm and perfect joint is made in the cables.
[Illustration: PERMANENT JOINTS FOR ELECTRIC CABLES.
PLATE IX]
Fig. 40 represents a section of a McEvoy temporary joint for single
cored unarmoured cables, which seems to fulfil all the conditions
necessary to a perfect joint of that description. This joint is, with
the exception of there being two screw plugs instead of one, very
similar to Beardslee's joint described at page 46; this alteration is a
great improvement, remedying as it does the one defect of Beardslee's
joint, viz., the liability of the cables to be drawn apart due to any
great tension being brought on them.
A permanent joint in electrical submarine cables, which from its nature
requires to be an exceptionally good one, is a somewhat difficult and
troublesome operation, and also requires a considerable time to form a
thoroughly reliable one.
_Siemens's Methods of Jointing._--The following methods, and
instructions for forming such joints, are those adopted by Messrs.
Siemens Brothers in connection with their telegraph cables, and which
will be found generally applicable to all insulated cables.
_The Formation of a Joint in the Conductor of an Insulated Cable._--The
conductor is either covered with a gutta percha or an india rubber
dielectric. In both cases cut off the dielectric so as to bare the
conductor-wire for a length of about three inches, taking care never to
cut at right angles to the conductor-wire, for fear of injuring it with
the cutting-knife or scissors.
Then clean the wires forming the strand with file-card and emery-paper,
and solder them into a solid bar for a length of about one inch.
Having soldered the wires, forming the ends of the two lengths of
conductors to be joined, into two solid rods, file each of them off
in a slanting manner, so that they will form a scarf-joint when put
together.
Place the two ends of strand in the two small vices on a stand which
is supplied for the purpose, so that the two scarfed ends overlap each
other, and bind them round with a piece of fine black iron wire, in the
shape of a spiral, so as to keep the ends close together, then solder
the two ends together by applying a hot soldering iron.
Then remove the iron binding wire and clean up the joint, filing off
all unnecessary solder.
And make a band of four fine tinned copper wires, and bind them tightly
side by side round the joint, covering the whole length of the scarf,
and then solder the band and joint solidly together.
Then make another band of four fine tinned copper wires and bind them
round the joint in the same manner as before, but extending about a
quarter of an inch beyond each end of the other binding wire, the
parts only of this second binding which project beyond the end of the
first binding are to be soldered, so that the centre part remains loose
and may keep up a connection between the two ends by forming a spiral
between them in the event of the scarf giving way and the two ends of
the conductor separating slightly.
This form of joint is called the "spring" joint.
The finished joint should be washed with spirit of wine and brushed, so
as to take away all particles of soldering flux, and to avoid oxidation
of the wire. The washed joint should then be dried with a piece of
cloth and exposed to the flame of a spirit lamp to dry it thoroughly.
A cable conductor ought never to be jointed with the help of soldering
acid, but with that of resin, sal ammoniac, or borax only, so that any
chance oxidation, and consequently destruction, of the conducting wire
may be avoided.
There are other modes of jointing conductors, such as the twisting and
scale joint, but the foregoing method will sufficiently explain this
part of electric cable work.
_The Formation of a Joint in an India rubber Insulated Cable._--In
making a joint in any insulated cable, the very greatest care must be
taken to keep the hands, tools, and materials clean and dry.
Remove the felt for about twelve inches from each end of the core by
soaking it with mineral naphtha and then rubbing it off clean with the
file-card. The cleaned surface sear with a red-hot iron, to burn off
all remaining fibres of the felt. Wash these seared ends clean with
naphtha.
Then cut off about four inches of the insulating material (taking
care never to cut at right angles to the conducting wire for fear of
injuring it) so as to leave enough of the conductor bare to join and
solder in the manner described at page 47.
After the conductor is jointed and soldered, clean again the seared
parts of the insulator with the glazed side of the squares of cloth
moistened with mineral naphtha, so as to leave a clean adhesiveness
only; taper again the insulating material down to the conductor for
about two inches on each side of the conductor-joint with a pair of
curved and very clean scissors.
The tapering must be completed in such slanting way that the different
layers of the dielectric are so far exposed as to enable a secure
laying on of the new jointing material.
India rubber core consists chiefly of three layers of insulating
material: the first layer next to the strand is called the pure or
brown; the second layer is the white or separating; the third layer is
the light red or jacket rubber.
Coat the conductor with a pure (brown) rubber tape tightly laid on
in a spiral form, commencing at the spot where the separator (white)
ends, across the corresponding place on the opposite side of the joint
and back again in a contrary direction. The ends are fastened down by
pressing a clean, heated searing-iron or a heated knife on them. By
doing so the band will stick; the remaining portions of the band to be
cut off with the scissors.
Lay on tightly the separating india rubber tape in the same manner, but
beginning where the jacket or outer layer of rubber ends. One lap will
be sufficient.
Complete the insulation by lapping on tightly two layers of red india
rubber tape: the last lap must cover each end of the core to four
inches on each side of the conductor-joint, or extend to the searing or
tackiness, but not beyond it.
Lay on three tight bindings of the cloth tapes, all in the same
direction, care being taken to avoid wrinkles. The ends of the cloth
tapes are cemented down with a thin coating of india rubber cement.
Immerse the joint in the jointing-bath at 150° to 200° F. and gradually
raise the heat so that in half an hour the temperature will be 320° F.,
at which temperature keep the joint for twenty minutes: then take it
out and let it cool in the open air.
_The Formation of a Joint in a Gutta percha Insulated Cable._--Having
jointed the conducting wires in the manner described at page 47, clean
and dry the joint well and cover the bare conductor with a thin layer
of compound. This is best done by heating a small stick of compound to
nearly its melting point, and rubbing it over the bare conductor, which
has been previously heated with the flame of a spirit-lamp.
Heat the gutta percha covering of both ends gently until it is quite
soft, without, however, causing it to bubble or burn. Draw, then, with
the fingers, the gutta percha coverings of both ends down, tapering
them off until they meet in the middle of the joint; heat them
sufficiently to make them adhere together.
Apply a layer of compound on the tapered-off gutta percha in the same
manner as described for coating the bare conductor, and cover it with
a first coating of gutta percha sheet to about half the thickness
necessary to finish the joint. This is done by heating a small sheet
of gutta percha, of about one-eighth of an inch in thickness, until it
is quite soft, and by pressing it in that state round the joint to the
required size; the greatest care to be taken to expel all the air.
The projecting lips are then cut off with a pair of curved scissors.
The seam thus produced is to be rubbed with a hot iron until it is
completely closed and the joint well rounded off.
Apply another layer of compound and a second layer of gutta percha
in exactly the same manner as described for the first layer; care,
however, is to be taken to get the seam in this second layer of gutta
percha not over, but as nearly as possible right opposite to, the seam
in the layer underneath.
The whole to be worked as cylindrical as possible, and to a size not
exceeding the original core. The joint, so far finished, is then to be
cooled with water until the gutta percha is quite consolidated.
Another, the overlapping gutta percha joint, is made in the following
manner:--
Cut off the two ends of the core, so that the gutta percha and the
conductor-wire are flush. Warm the gutta percha for a distance of
about three inches from each of the ends with the flame of a spirit
lamp, and, when sufficiently soft, push it back until it forms an
enlargement. The two ends of the conductor are then to be soldered
according to instructions for making joint in conductors.
To have a perfectly clean surface of the two gutta percha enlargements,
remove all impurities by the way of peeling them with a sharp knife.
Warm gently both knobs and the copper joint, and cover the whole length
of the bare wire with compound, planing it with a warm smoothing-iron.
Draw then with the fingers one of the warmed and softened knobs
carefully up to the other knob or enlargement, leaving on its way
a perfect tube of gutta percha upon the wire, decreasing gradually
to the thickness of the copper strand towards the other knob. Any
superfluous gutta percha is removed. This scarf is finished with a warm
smoothing-iron, so as to unite it to the compound on the wire strand,
and a thin layer of compound is also put over the scarf in the same
manner as before.
The other knob is then warmed and drawn in the same way over the tube
already formed, which is at the same time heated sufficiently to make
the two adhere.
Apply a layer of compound on the second scarf of gutta percha, covering
it in the same manner as described for coating the bare conductor,
and cover it with a small sheet of gutta percha in the same manner as
described above, so as to make the finished joint to the size of the
core as manufactured.
_Rules to be observed in forming Joints._--The following rules must be
carefully observed in forming either a temporary or permanent joint:--
1.--In laying bare the conductor, the dielectric should
be warmed and then pulled off, so preventing any chance
of it being damaged, which might be the case were the
dielectric to be cut off.
2.--For a perfect junction, soldering is necessary.
3.--The wires before connection should be carefully
cleaned, and the hands of those performing the work
must be dry.
4.--Gutta percha should not be given too much heat,
for it then becomes oily and will not, in that state,
properly adhere.
5.--Grease and dirt must be scrupulously avoided.
Great care is absolutely necessary in making junctions, as they are the
principal sources of defect in the insulation of electrical submarine
cables.
_Junction Boxes._--When it is necessary to employ a multiple cable,
a junction box is used to facilitate the connection of the several
separate wires diverging from the extremities of such a cable. In
one angle of such a box the multiple cable is introduced, while the
separate cables make their exit on the opposite sides and pass to the
different mines. Different views of a junction box are shown at Fig.
41, where _A_ is a plan of the top or lid, _B_ a plan of the bottom,
with the lid off, _C_ an elevation, and _D_ a section of the box.
The manner of using the junction box is as follows:--
The multiple cable is put in at _a_, and secured there by means of a
nipping hook, shown at Fig. 42, which hook passes through the bottom
of the junction and is made secure by means of a nut. The single core
cables radiating from the junction box pass through the openings _b_,
_b_, _b_ on the sides, and angle opposite to where the multiple cable
a enters. Each multiple cable is composed of seven cores, and each of
these is connected by means of joints with the mine cables within the
junction box, and each of these seven cables is secured by means of a
nipper similar to, but smaller than, the one shown at Fig. 42, which
are also secured by means of nuts, as in the case of the multiple cable
nipping hook. When all the connections are made, the lid _A_ is placed
so as to rest on the studs _c_, _c_, _c_, and firmly secured by a bolt
_d_, which is made water-tight by means of a washer and nut.
By means of the nipping hooks, which take any strain that may be
brought on the cables, the connections within the box are ensured
against injury by such a cause.
To enable the whole to be lifted together for the purposes of
examination of the cables, &c., a buoyed rope is connected to the
eye-bolt _e_. For this service a dummy circuit closer is the best form
of buoy, it having great buoyancy and resembling in appearance an
active circuit closer.
A junction box should be placed in such a position as to be easily
attained, even in the presence of an enemy, and its buoy should, if
possible, not be seen. It is also very essential that it should be in
a safe and guarded position, for any injury to the junction box or
multiple cable would be fatal to the group of mines in connection.
In the following cases, special junction boxes are used:--
1.--A seven cored armoured cable to be connected direct
to another length of the same.
2.--A single armoured cable to be connected as in
foregoing instance.
3.--A T junction box for the branch system of
electrical contact mines.
_Junction Box for Multiple Cables._--At Fig. 43 is represented a plan
of lower half of this form of junction box. It consists of a pair of
cast iron plates of precisely similar form to the one shown at Fig.
43, and so made as to be capable of being fastened tightly together by
means of four bolts and nuts passing through the holes _a_, _a_. The
grooves _b_, _b_ at the two extremities are just large enough to grip
the armoured cable firmly, when the upper and lower parts are screwed
together. A larger space is provided in the hollow for the joint.
_Junction Box for Single Cored Cables._--For this purpose a junction
box similar to, but smaller than the one above described is employed.
_T Junction Box._--This form of junction box is employed when the
system of electrical contact mines on branches from a single cable is
used. This system is dependent on the use of a platinum wire fuze in
connection with a platinum wire bridge in each branch close to its
junction with the main cable.
This form of junction box, which is shown at Fig. 44 is very similar
to the one used for the connection of two multiple cables, only
differing in its shape, which is that of a T. _a_ is a disconnector,
which will be described further on; _b_, _b_, _b'_ are the armoured
electric cables, _b_, _b_ being the main, and _b'_ the branch cable in
connection with the forked joint formed within the T junction box; _c_,
_c_, _c_ are Turk's heads formed to prevent any strain being brought on
the forked joint. This form of Turk's head is made by turning back the
wires of the cable armouring, and frapping them round with spun yarn
until the necessary size and shape is attained.
_McEvoy's Turk's Head._--Another form of Turk's head, devised by
Captain McEvoy, is shown at Fig. 45. It consists of two separate pieces
of brass, _a_ and _b_, the former screwing over the latter. The mode of
using it is as follows:--
Slip the piece of brass _b_ over the cable _c_, and turn back the wires
of the cable _d_, _d_, &c., so that they lie against the shoulder of
the brass piece _b_, then slip the other piece of brass _a_ over the
cable and screw it on the piece _b_, firmly jamming the turned back
wires _d_, _d_, &c. This is a very neat and quick method of forming
a Turk's head, and it should be invariably used in preference to the
foregoing method, which is clumsy, and which takes some time to form.
The section of a disconnector is shown at Fig. 46. It consists of an
iron cover, or dome _a_, which is provided with a screw fitting on
to another screw on the ebonite body _b_ of the apparatus. When the
dome _a_ is screwed tightly down on the washer _i_, the whole is made
perfectly watertight. _c_, _c_ are insulated terminals for connecting
the cores of the branch and main cables after their armouring has been
removed, as shown at Fig. 44. _d_, _d_ are two copper conducting wires
(No. 16 B. W. G.) passing through the centre of the ebonite body _b_,
and projecting into the interior of the apparatus. These wires are
held in position and insulated by means of a composition formed of a
mixture of pitch, tallow, beeswax and gutta percha. This composition
is put on whilst hot and allowed to cool gradually, when it becomes
hard and durable. Great care is necessary to ensure the cavity within
the ebonite body _b_ being completely filled, as otherwise a leakage
might occur, owing to the great pressure of water at depths where the
disconnection would be generally used. _f_ is a boxwood cover which is
slipped on, and fits fairly tight to the ebonite body _b_; _g_ is a
piece of thin platinum wire, weighing 1·6 grains to the yard, and being
4/10 inch in length; _h_ is an ebonite pin, which passes through two
small holes in the boxwood cover _f_, into which it fits tightly, and
in such a position as to be directly beneath the platinum wire bridge
_g_, when the boxwood cover _f_ is fixed on. The pin _h_ is pushed
through the holes in the cover _f_ from the outside, so as to pass
beneath the bridge _g_ after the priming has been inserted, and the
cover has been placed on.
When prepared for use, the platinum wire bridge _g_ is surrounded by
some loose gun-cotton priming, sufficient in quantity to blow off the
boxwood cover _f_, without destroying the dome _a_; the cover _f_
being blown off, carries the ebonite pin _h_ with it, and through
the platinum wire bridge _g_, thereby rupturing it, and breaking the
continuity of the circuit. The object of so doing is to cut off the
connection of an exploded mine, so that the full amount of the firing
current is available for the other mines, and not suffered to be wasted
by passing through the exposed wire of the broken circuit, which, were
the disconnector not employed, would be the case.
When any particular mine of a system is struck, the current passes
through the main cable _b_, the disconnector _a_ (which is in
connection with that mine), and branch cable _b'_ to the fuze, and so
explodes the mine, and destroys the platinum wire bridge _g_ of the
disconnector at practically the same instant. The effect of the latter
operation would be to cut off and insulate the branch cable of the
exploded mine, and so prevent any loss of the electrical current, when
another mine of that system is required to be fired.
The platinum wire bridge _g_ is 4/10 inch long, while that of the fuze
is 3/10 inch, the object of this difference in length of the bridges
being to ensure the former one _g_ being fired, and thus the insulation
made doubly sure. Many other forms of disconnectors have been devised,
but none have proved in practice so effective as the one just described.
[Illustration: JUNCTION BOXES. MECHANICAL TURK'S HEAD.
PLATE X]
_Mooring Electrical Submarine Mines._--This is one of the most
difficult problems to be solved in connection with a system of
submarine mines. The objects to be attained in mooring are as follows:--
1.--The mines should preserve the exact positions in
which they are laid down.
NOTE.--From the comparatively small radius of destructive effect,
of even heavily charged submarine mines, it will be understood how
absolutely essential, in the case of mines fired by judgment, it is
that this object should be attained.
2.--The mooring chains, or ropes, must be so arranged
that no twisting whatever should occur, as otherwise
fracture of the insulated wire would be likely to
happen.
3.--In the case of buoyant mines, their distance from
the bottom must be so adjusted, that at no time shall a
vessel passing over them be out of their vertical range
of destruction, nor shall they be visible.
The difficulties attendant upon the efficient mooring of submarine
mines are immense, as will be understood when the action of gales
of wind, and strong tides, which latter vary continually in their
direction and in their rise and fall, are taken into consideration.
The foregoing remarks apply more particularly to a system of buoyant
submarine mines, as those placed on the ground are comparatively easy
to moor.
Several modes of mooring buoyant submarine mines have been suggested,
the most practicable of which are as follows:--
1.--Ladder moorings.
2.--Fore and aft moorings.
3.--Austrian method of mooring.
4.--Single rope mooring.
_Ladder Mooring._--This is a method of mooring, which in places where
it may be necessary to place the anchors far apart will be found useful.
The circuit closer is connected to the mine by two ropes which lead
thence to two anchors, the ropes being separated by wooden rounds,
or spreaders, 1 to 3 feet long, by which the tendency to twisting is
prevented.
The anchors are placed some 12 feet apart.
The only defect of the ladder mooring is the quantity of sea-weed, &c.,
that is liable to be lodged on the rounds, thus causing the circuit
closer to be drawn out of its proper position.
_Fore and aft Mooring._--This mode may be advantageously employed in a
tideway where the current runs very strong, that is to say, five knots
per hour, or more. It consists simply of two anchors, one of which is
moored up, and the other down the stream.
_Austrian Method of Mooring._--This method of mooring, adopted by the
Austrians during the war of 1866, is shown at Fig. 47. It consists of
a wooden triangular platform on which several heavy weights _a_, _a_,
_a_ are placed; the mine is attached to this platform by means of three
wire ropes _b_, _b_, _b_, connected to the angles of the latter, and
fastened to three chains, which by means of a catch holds the mine at
the position required.
This catch consists of a pulley attached to the extremity of the wire
rope of the platform, through which the mooring chain of the mine is
passed, and fastened by a key at the required depth by means of a
self-acting arrangement.
This key, which is of considerable weight, slips down as the mine is
being hauled into position, but the moment the chain is slacked, two
arms catch into a link of the chain, and so hold the mine in position.
The weight of such a key is about 60 lbs. It is fitted with nuts, &c.,
to enable it to be taken to pieces.
This plan of mooring proved very effective in the harbours of the
Adriatic, where there is hardly any tide or current to twist the
mooring ropes, or otherwise disturb the mines. The Austrians have
lately adopted the mushroom sinker in place of the wooden platform and
weights, for their anchor.
_Single Rope Mooring._--This simple method of mooring has after
numerous exhaustive experiments been adopted as the most practicable
and effective of all others. Whenever possible, a wire instead of
hempen cable should be used to connect the mine and its circuit closer
to the mooring anchor, as the former is less liable to twist, kink, or
wear from friction than the latter.
A ground mine with circuit closer attached is represented at Fig. 48,
where _a_ is the wire mooring rope, _b_ the electric cable leading from
the mine to the circuit closer, _C_, and _c_ the cable leading from
the firing station to the mine; _d_ is the oblong sinker attached to
the mine, and _e_ the tripping chain leading to the shore, to which
the cable _c_ is attached at intervals, so that by underrunning the
electric cable, the tripping chain may be easily picked up, and the
mine raised.
[Illustration: MOORINGS FOR SUBMARINE MINES.
PLATE XI]
At Fig. 49 is shown a buoyant mine. The only difference in the mooring
of this and the one before described, is that instead of resting on
its anchor on the ground, it is moored at a certain distance above its
anchor _d_, to which it is secured by a chain _e_.
Fig. 50 represents an electro contact mine. _M_ is the mine with
circuit closer enclosed, _a_ the wire mooring rope, _d_ the mushroom
anchor, and _b_ the electric cable leading from the mine to the
disconnector _D_.
The mushroom sinker or anchor, which is undoubtedly the most effective
of all other forms of mooring anchors used for the purposes of
anchoring submarine mines, is shown at _e_, Fig. 49; the legs are added
for use on rocky or hard bottoms, under which circumstances the weight
of the anchor should also be increased.
For ground mines the form of sinker shown at _d_, Fig. 48 is employed;
it is of an oblong shape, and hollowed out in the centre to allow of
its being lashed close up to the mine.
Large blocks of stones with their bases slightly hollowed are useful as
extempore moorings, so also is the one shown at Fig. 51, which consists
of a strong heavy wooden shaft _a_, with a number of wooden arms _b_,
_b_ attached to its base; this form of extempore sinker was considered
very efficient by the American authorities.
The wooden weighted platform, which was described at page 56, is also a
very useful form of extempore sinker.
For dead weight moorings, pigs of ballast, heavy stones, &c., may be
used.
The weight of the anchor or sinker for mooring submarine mines is a
very important consideration. It will depend on the amount of buoyancy
of the mine, on the strength of current, and on the nature of the
bottom, also whether the mines are to be hauled down to, or moored with
the anchor.
Stotherd uses the following formula:
W = [2rt](B^{2} + P^{2})
where B is the excess of the flotation over the weight of the charge of
a given submarine mine;
P is the pressure exerted by any given current on the same buoyant mine;
W the weight of sinker necessary to overcome the tendency of the
mine to move. In still water P becomes nothing, and therefore W equal
to 2 B, that is, in still water double the buoyancy of a mine is a
sufficient weight for its anchor.
The value of P may be found from the formula P = 4·085 × V^{2}, where V
is the velocity of the current in miles per hour.
From this equation P will be found in terms of pressure in pounds per
square foot of flat surface, which is nearly double that on the curved
surface of a cylinder.
In regard to the amount of buoyancy of a submarine mine, it has been
found by actual practice that in the case of a mine moored in still
water it should certainly be not less than the weight of the charge,
whilst if subjected to the lateral pressure due to a current, it should
be not less than three times the pressure exerted by the current.
It is always necessary to allow an excess of buoyancy over the
calculated amount to counteract any leakage, or other disturbing cause
which might otherwise materially affect the efficiency of the mine.
There are two modes of placing a mine in position; either by attaching
the anchor, with the cable necessary for the depth of water, to the
mine, and lowering both together, or by placing the anchor first, and
then hauling the mine down to it, and by means of a catch, fastening it
at the required depth.
The first mode is exceedingly simple, but except under very favourable
circumstances cannot be relied on when firing by observation is the
means adopted to explode a system of submarine mines. The second plan
is practically easy to carry out, and by it a mine may be placed more
accurately. To enable either of the above methods to be properly
carried out, specially fitted steamboats, &c., are requisite.
At Fig. 52 is represented a 42 feet launch fitted for laying down a
submarine mine by the first of the two modes enumerated above.
[Illustration: STEAM LAUNCH FOR MOORING SUBMARINE MINES.
PLATE XII.]
_a_ is the mine; _b_ is the electric cable carried from the drum _c_
to the charge, and connected for use; _d_ is the circuit closer, which
is attached to the mine by its electric cable and mooring rope; _f_
is the mushroom sinker attached by means of its mooring chain to the
mine, it is suspended by a slip rope _g_, which passes over a small
crutch fitted with a sheave _h_; _i_ is a hollow iron derrick, and _k_
the tackle and fall for lifting mine into boat; this derrick is formed
of an iron tube about 3 inches diameter, 3/8 inch thick, and 10 feet 6
inches long; it is attached to an iron tube mast of similar diameter
and thickness to the derrick, but 12 feet 3 inches long, an iron chain
6 feet 6 inches long and 5/8 inch diameter, connects the derrick to
the mast; _m_ is a leading sheave to keep the cable clear whilst it is
being paid out; _l_ is a crab, for working the tackle _k_, &c., and _c_
is the drum on which the electric cable is wound.
In connection with the defence of a harbour by a system of electrical
submarine mines of large size, it will be necessary to employ a service
of steamtugs, steamboats, mooring-barges, &c., specially fitted for
such work. One of the great advantages of the hauling down method
of placing mines in position, is, that the anchors, with the cables
connected thereto, may be carefully and accurately got into position
during the time of peace, and the mines themselves, which should be
kept in store ready fitted for immediate use, need not be placed in
position until they are actually required. The drums used for reeling
a multiple cable on, are capable of holding half a nautical mile in
length. That used for a single core armoured cable is similar to but
smaller than the aforesaid drum, and is capable of stowing one nautical
mile of such a cable. For transportation wooden drums are ordinarily
used.
CHAPTER IV.
DEFENSIVE TORPEDO WARFARE--_continued_.
_CLOSING the Electric Circuit._--In connection with the system of
coast defence by means of electrical submarine mines, there are two
distinct methods of effecting the closing of the electric circuit, and
consequently, the firing battery being connected, the explosion of the
mine or mines, which methods may be used separately, or in combination,
and are as follows:--
1.--The self-acting method.
2.--The firing by judgment, or observation method.
During the early days of submarine defensive warfare, the latter method
alone was used, owing to the absence of anything like a practicable
form of self-acting apparatus; but within the last few years, the
former has almost entirely superseded the latter method, except in very
exceptional cases; this revolution being due to the vast improvements
that have been, and still are being effected in the system of firing
electrical submarine mines automatically.
_Use of Circuit Closers._--Electrical submarine mines may by means of
an apparatus, termed a _circuit closer_, be rendered self-acting; that
is to say, by the action of a vessel coming in contact with such an
apparatus, which may be either within the mine itself, or within a buoy
attached to the mine, the electric circuit is closed, and the mine in
connection with the circuit closer so struck, exploded. The essential
feature of such a mode of closing the electric circuit is, that
electrical submarine mines may be rendered either active or harmless,
at the will of the operator, which is effected by the putting in, or
taking out of a plug, by which means the firing current is either
thrown in, or out of the circuit.
_Circuit closers._--Many different forms of circuit closers have been
devised, among which the following seem the most suitable and are those
generally used:--
1.--Mathieson's inertia circuit closer.
2.--Mathieson's spiral spring circuit closer.
3.--Austrian self-acting circuit closer.
4.--McEvoy's mercury circuit closer.
5.--McEvoy's weight magneto circuit closer.
_Mathieson's Circuit Closer._--This form of circuit closer has been
adopted by the English government in connection with their system of
defence by electrical submarine mines.
The details of this apparatus are shown at Pl. xiii.
Fig. 53, _a_ is a gun-metal dome screwed on to a metal base _b_, its
foot resting on a gutta percha washer _c_, so as to exclude any water;
_d_ is a cap screwed on to the top of the dome, and made watertight
by the leather washer _e_; _f_ is a guard cap screwed into the cap
_d_, this is to keep the spindle of the circuit closer steady during
transport, and would be removed when the apparatus is prepared for
service; _g_ is the ebonite base plug through which pass the insulated
wires _E_ and _L_; _h_ is an hexagonal collar, working in the metal
base plate _b_, by means of which, and the brass collar _i_, and the
leather washer _k_, the base plug is secured, and water is excluded
from the interior of the circuit closer; _l_, _l_, _l_ are brass
columns supporting a circular ebonite piece _m_; _n_ is a metal bridge
screwed on to the base plate _b_, into which is screwed the spindle
_p_, both of which are prevented from moving after being screwed up by
the set screws _r_ and _s_.
The spindle _p_ carries a leaden ball _t_, which is supported upon the
rest _v_, and is secured in position by the screw nut _w_; _x_ is an
india rubber ring, the object of which is to prevent any damage being
done to the spindle should the ball when set in action by a heavy
blow from a passing vessel be brought into contact with the dome; 2
is a brass disc attached to the spindle carrying an ebonite disc 4,
connected to it by screws; 6 is a brass contact ring also fixed to the
ebonite disc 4, provided with a screw 8, for the attachment of one of
the base plug wires, and with platinised projections 3, 3, 3, Fig.
56. The contact ring 6 is completely insulated from the spindle and
brass disc 2. Three contact springs 5, are attached to the circular
ebonite piece _m_, and the faces opposite to the platinised projections
of the disc 2 are also platinised. 7 shows the contact screws of the
connecting pieces, which serve also as adjusting screws to regulate the
sensitiveness of the apparatus, the points of which as well as their
bearings on the springs are platinised.
The springs are connected together by means of the wires 9, Fig. 55,
one end of which is secured to the connecting piece by the screw 10,
and the other passes through to the top of the ebonite piece, and is
attached to the top of the spring next in succession to that to which
it is fixed below.
One terminal of a coil of 1000 ohms resistance (which is used for
testing purposes) is attached to the line _L_, terminal of the
ebonite base plug, which latter is also connected to the screw 8, on
the circumference of the contact ring 6; the other terminal of the
resistance coil is connected to the earth, _E_ terminal of the base
plug.
A bare copper wire of No. 16 B. W. G. connects the top of the last
contact spring with the set screw _s_; a piece of similar wire jointed
to it is passed round one of the brass collars and connected to the
screw _r_. As a precaution against bad contact, the contact springs
are connected together by bare wires _A_, _B_, _C_. This completes the
connections for the signalling circuit, the earth being formed by the
body of the instrument; _D_ is a hole left in the metal base for the
passage of the insulating wire which connects the earth plate to the
earth _E_ terminal of the base plug.
_Testing Current._--For testing purposes the current from the test
battery arrives by the line wire _L_, and passes thence through the
resistance coil to earth by means of the wire _E_, which is attached
to a zinc earth plate placed in a recess in the jacket of the circuit
closer.
_Action of the Circuit._--The action of the apparatus is as follows:--
_Closer._--On the circuit closer being struck, the weight of the lead
ball _t_ causes the steel rod _p_ to be deflected and brings the brass
ring 6 in contact with one of the springs 5; the signalling current
which up to this moment has been passing through the 1000 ohms coil
to earth, then passes to the contact ring 6 (avoiding the resistance
coil) thence to the spring which is in contact with it, and from there
by means of the wire connections to the set screws _s_ and _r_, and so
to earth through the metal body of the apparatus; the effect of the
resistance coil being thus eliminated, is to strengthen the signalling
current, and thus enable it to work the shutter apparatus, by which
means the firing current is thrown into circuit and the mine exploded.
[Illustration: MATHIESON'S CIRCUIT CLOSER.
PLATE XIII]
_Circuit Breaker._--By altering the mode of connecting the wires, the
above apparatus may be used as a circuit breaker, that is to say, the
signal may be given, and the mine exploded by the cessation of a
passing current, instead of by the closing of the electric circuit.
This system was specially designed for use with platinum wire fuzes,
but is rarely used.
_Circuit Closer of Electro Contact Mines._--When the inertia circuit
closer is employed in connection with electro contact mines, the
circular ebonite piece _m_ is replaced by a similar shaped piece of
brass, and which is in metallic connection through the brass pillars
_l_, _l_, _l_ with the mass of the metal of the apparatus which forms
the earth plate.
The insulated wire of the base plug is connected to one pole of a
platinum wire fuze, the other pole of which is connected by another
wire to the outer metal rim of the disc of the spindle. As long as the
circuit closer remains undisturbed, a break will remain in the circuit,
which is due to the ebonite insulation between the spindle and the
outer metal rim of the disc; but the moment the apparatus is struck,
which causes the spindle to vibrate, the outer metal rim will come in
contact with one of the springs completing the circuit, through the
circular metal portion and the pillars of the circuit closer to earth.
_Adjustment of Circuit Closer._--The sensitiveness of Mathieson's
inertia circuit closer is determined by the distance between the
disc 4 and the springs 5, 5, 5, which is regulated by means of the
adjusting screws 7, 7, 7, which press against the inner faces of the
springs. Owing to the great weight of the leaden ball, when by any
cause the circuit closer is inclined for a length of time, a permanent
set is given to the spindle, thereby destroying the adjustment of the
instrument.
_Improvements in the Inertia Circuit Closer._--To remedy this very
serious defect, a cylinder of india rubber is substituted for the
leaden ball; a circuit closer so fitted is also less affected by the
action of counter mines, which is a very important advantage.
_Mathieson's Spiral Spring Circuit Closer._--A sectional elevation of
this form of circuit closer is shown at Fig. 57. It consists of a brass
base _a_, provided with a grooved flange for carrying a gutta percha
washer, and it has also an hexagonal projection for the purpose of
screwing the circuit closer into the gun-metal mouth of its air-tight
cylinder, or buoy; _b_ is a brass dome enclosing the apparatus for the
purpose of protecting it from injury, and also by means of india rubber
washers to prevent an ingress of water, should the circuit closer case
become injured, and leak; _c_ is a brass collar to which the brass
contact springs _i_, _i_ are attached, and which are regulated by the
set screws _j_, _j_; a brass spiral spring _d_ carries a metal rod _e_,
which supports a brass ball _f_, surrounded by an india rubber band
_h_. A contact disc _g_ is secured to the base of the spindle _e_, but
insulated from it by an ebonite boss; _k_ is an ebonite base plug with
two channels in it, through which the wires _m_, _m^{1}_ pass.
_An Improvement on the Inertia Circuit Closer._--This instrument is
a vast improvement on the inertia apparatus previously described,
being more simple and more certain in its action, a desideratum in
all circuit closers; but notwithstanding, up to the present time
Mathieson's inertia apparatus has been used by our government, to the
exclusion of all other instruments of a similar nature, some of which
were proved to be far superior when subjected to the crucial test of
actual practice.
_Austrian Self-acting Circuit Closer._--This form of circuit closing
apparatus, which is purely a self-acting one, that is to say, a mine so
fitted cannot be fired at will, is shown at Fig. 58.
It consists of several buffers _a_, _a_, _a_, which by means of
strong springs are held in position, their heads projecting outside
the torpedo case _b_; on being pressed in by the contact of a passing
vessel, the ends of these buffers would be forced against a ratchet
wheel _c_, which is also kept in position by means of a spring. Several
strong pieces of wood _d_, _d_ within the case keep the buffers and
their attached arms in the proper direction, and also afford rigidity
to the torpedo case. The brass ratchet wheel _c_ being put in motion
carries round with it a central arrangement _e_, the lower part of
which is shown at Fig. 58, _A_.
This portion consists of a cylinder of brass _f_ divided into two parts
insulated one from the other by a piece of ebonite _g_; on one side of
this cylinder there are three arms of brass, _h_, _i_, and _k_, and on
the other there are two arms, _l_ and _m_, all of which are insulated
from each other.
[Illustration: AUSTRIAN CIRCUIT CLOSER, MERCURY CIRCUIT CLOSER.
PLATE XIV]
The arm _h_ is close to, but insulated from a metal plate _n_, which
latter is permanently connected with the conducting wire leading from
the firing battery, and thus while in a state of rest is electrically
charged; beyond the arm _i_ is a spring _o_, which is connected with
the earth, and in such a position that when the central portion is
moved round, this spring _o_ comes in contact with the arm _i_, and
the plate _n_ with the arm _h_ simultaneously, and the circuit is thus
completed through earth to the battery, but the current of electricity
does not pass through the fuze. The arms _k_, _l_ on the opposite
sides of the cylinder, and consequently insulated one from the
other, are connected with the fuze, and the arm _m_ is connected with
the earth.
On a further pressure of the vessel on the buffer, the arm _i_ is
pushed beyond the spring, and in contact therewith, and consequently
the circuit by earth to the battery is broken, while the contact of the
arm _h_ and plate _n_ is still retained, and the current is passed by
the arm _k_ through the fuze to the arm _l_, and then to earth through
the arm _m_, thus completing the electric circuit of the firing battery
through the fuze, and to exploding the mine.
The spring acts as a circuit breaker, and by means of an intensity
coil in connection with the firing battery, the current is only passed
through the fuze when at the point of greatest intensity.
By detaching the firing battery, the channel defended by such submarine
mines may be rendered safe.
_Fuze only in Circuit at Moment of Firing it._--One of the principal
objects to be gained by the employment of such an arrangement for the
closing of the electric circuit in connection with submarine mines, is
the prevention of premature explosion from induction which might be
caused by the proximity of any atmospheric electricity, the fuze in
this system being entirely cut out of circuit until the moment when it
is necessary to fire it.
The Austrians employed this form of circuit closing instrument during
the war of 1866, and still continue to use it in connection with their
coast defence by submarine mines.
_McEvoy's Mercury Circuit Closer._--At Fig. 59 is represented a
longitudinal section of a circuit closer of this construction.
It is placed in the mine in such a manner that when undisturbed it
maintains an approximately upright position.
It consists of a metal tube _a_ into which the cup _b_ of vulcanite,
or other insulating material is fixed. The cup is contracted at some
distance from the top by the perforated plug _c_, which is also of
insulating material; _d_ is a metal pin fixed into the bottom of the
cup _b_, it is connected with the wire _e_, which is insulated and
passes to the battery; _f_ is a metal plug closing the tube _a_ and the
cup _b_ at the top; _g_ is a wire attached to the plug _f_, and passing
from it to an earth connection. The cup _b_ is filled with mercury up
to the level of the plug _c_. By the contact of a passing vessel the
instrument would be tilted sufficiently to cause the mercury to flow
into contact with the metal plug _f_, thus completing the electric
circuit and exploding the mine.
This form of circuit closer, though not generally adopted, would, on
account of its being less liable to derangement by the motion of the
waves, or by the explosion of an adjacent or counter mine, seem to
fulfil the many requirements of a circuit closer for general service.
_McEvoy's Weight Magneto Circuit Closer._--This form of circuit closer,
which is shown in section and plan at Figs. 60 and 61, is one of
the most important improvements that has ever been effected in such
apparatus, and bids fair to become universally adopted.
A heavy metal conical shaped weight _a_ (Fig. 60), hollowed out in
its base and working in a ball and socket joint _b_, rests on a solid
brass base _c_, and is so arranged that on the apparatus being struck,
the weight _a_ will fall over, pivoting on one of its supports _d_,
_d_; _e_ is a band of india rubber, encircling the weight _a_, for the
purpose of preventing a jar on its falling against the sides of the
brass cylinder _f_, which contains the weight _a_ and joint _b_. A
brass rod _g_, connected to the ball and socket joint, passes through
the base _c_, through a strong spiral spring _h_ (which latter rests on
an adjusting screw _k_), through a piece of ebonite _l_, which supports
the bobbins and core _m_, _m_^{1}; then between these bobbins _m_,
_m_^{1} through an armature _n_, which is pivoted at _p_; and lastly
through a slight spiral spring _o_, which is kept in position by the
adjusting screw _i_.
The armature _n_ is fitted with a small piece of brass _r_, so arranged
that when it (the armature) is in the position shown in Fig. 60, this
piece of brass _r_ does not make contact with the two strips of metal,
_s_, _s_, between which it, _r_, works; but when the armature _n_ is in
contact with the cores of the bobbins _m_, _m_^{1}, then the piece of
brass _r_ makes contact with the metal strips _s_ _s_, and so makes a
short circuit for the electric current. An ordinary telephone _t_, Fig.
61, in which some small shot, bells, &c., are placed, is fixed to the
top of the brass cylinder _f_.
_Action of Circuit Closer._--The action of this apparatus is as
follows:--
On the mine carrying this form of circuit closer being struck by a
passing vessel, the weight _a_ is caused to fall over towards the side
of the brass cylinder _f_, thus allowing the strong spiral spring _h_
to act on the brass rod _g_ in an upward direction, by which means the
armature _n_ is brought into contact with the soft iron cores of the
bobbins _m_, _m_^{1}.
[Illustration: M^{c.}EVOY'S MAGNETO ELECTRO CIRCUIT CLOSER.
PLATE XV]
The connections of the wires are made as follows:--
The line wire _w_ is led through the base of the apparatus and
connected to a piece of brass under the ebonite support _l_, in
connection with one of the wires of the bobbin _m_, the other wire
of which is attached to the metal strip _s_; the wires of the bobbin
_m_^{1} are connected, the one to the metal strip _s__{1}, the other
to a piece of brass under the ebonite support _l_; from this latter
piece of brass a wire _w__{1} is led to the brass screw _x_. The wires
_w__{2}, _w__{3}, from the fuzes are led, the one to the brass screw
_x_, the other to a screw _y_, which forms through the metal of the
apparatus the earth plate. One of the wires of the telephone _t_ is
connected to the brass screw _x_, the other _w__{4} is connected to
the piece of brass to which the line wire _w_ is also attached. While
the circuit closer remains in a state of rest, the current from the
signalling battery flows along the line wire _w_, up the telephone wire
_w__{4}, through the telephone which has a high resistance, then by the
wire _w__{2} through the fuzes, and to earth by the wire _w__{3}.
On the circuit closer being struck, by which cause the armature _n_ is
brought up to the cores of the bobbins _m_, _m_^{1}, and the piece of
brass _r_ in contact with the metal strips _s_, _s__{1}, the signalling
current, instead of circulating through the high resistance of the
telephone _t_, passes round the bobbin _m_, down the metal strip _s_,
across the brass piece _r_, up the metal strip _s__{1}, round the
bobbin _m__{1} (thus forming an electro magnet of _m_, _m__{1}), and by
the wire _w_, direct through the fuzes to earth, and so explodes the
torpedo. The effect of the telephone resistance being cut out, is to
strengthen the signalling current, and enable it to work the shutter
apparatus and so throw the firing battery in circuit and explode the
mine.
The advantages of this circuit closing apparatus are:--
1.--Simplicity.
2.--Compactness.
3.--Increased certainty of action, due to the sustained
contact of the armature _n_, on the apparatus being
struck.
4.--Additional means of testing a system of electrical
submarine mines, which is afforded by the telephone:--
When this form of circuit closer is put in action by a friendly vessel
coming in contact with it, or when experiments are being made, the
signalling current must be reversed, so that no doubt may exist as to
the armature _n_ having dropped, on the apparatus coming to rest.
The telephone test indicates whether the circuit closer is in position
or not, the shot, &c., within the telephone being shaken about by the
movement of the buoyant circuit closer, the noise so created is readily
distinguished by the receiving telephone at the station.
Another form of submarine mine is that known as the "Electro
Mechanical" mine. The difference between this form and an ordinary
mechanical mine is, that the exploding agent is electricity, and that
it may be converted into an electro contact mine if desirable.
_Description of a Russian Electro._--The electro mechanical mine,
used by the Russians during the late Turco-Russian war, is shown in
elevation and section at Figs. 62 and 63.
_Mechanical Submarine Mine, used by them during the late Turco-Russian
War._--_A_ is the conical shaped case; _B_ the loading hole; _C_ the
base plug; _D_, _D_, &c., are five horns, screwed into the head of the
case _A_; these are composed of a glass tube _A_, containing a chlorate
of potash mixture, enclosed in a lead tube _B_, over which is screwed a
brass safety cylinder _C_; when ready for action this latter tube _C_
is removed; directly beneath each of the horns _A_, on the inside of
the case, as at _E_, is a thin brass cylinder, closed at one end by a
piece of wood _d_, and containing several pieces of zinc and carbon,
arranged in the form of a battery, the zinc and carbon wires _z_ and
_x_ being led through the piece of wood _d_; _F_ is a copper cylinder
containing the priming charge of gun-cotton _g_, and detonating fuse
_f_; the terminals of the fuze are connected to two insulated wires,
_w_ and _w__{1}, the former of which is led direct to the loading hole
_B_, and attached on the inside to the five zinc connecting wires _z_,
&c.; the latter is attached to one end of a safety arrangement _S_, the
other end of which is connected to the wire _w__{2}, which is attached
on the inside to the carbon wires _x_, &c.; the safety arrangement _S_
consists of an ebonite cylinder, containing a brass spiral spring fixed
to one end of it, and pressing against a brass plate at the other,
thus preserving a metallic connection between the wires _w__{1}, and
_w__{2}; the mine is rendered inactive by pressing the spring down, and
inserting a piece of ebonite between it and the plate.
_Its Action._--The action of this form of electro mechanical submarine
mine is very simple; the brass safety cylinders _c_, _c_, &c., being
removed on a vessel striking either of the horns, _D_, _D_, &c., the
lead tube _b_ is bent, causing the glass tube _a_ to be broken, and
the mixture contained therein to flow into the cylinder _E_, instantly
generating a current of electricity in the zinc carbon battery, and
exploding the mine.
_Mode of Converting into an Electro Contact or Observation Mine._--To
convert this mine into an electro contact one, it is only necessary to
connect the wires _w__{1} and _w__{2} to other wires leading from the
shore; also by replacing the horns _D_, _D_ by solid brass screw plugs,
the mine may be converted into an ordinary observation one. In this
case the two wires _w_ and _w__{1} attached to the fuze _f_, terminals
would have to be connected to the observation instruments on shore.
_Turkish Vessel sunk._--It was by means of one of these electro
mechanical mines, that the Turkish gunboat _Suna_ was sunk at Soulina.
Firing by observation, that is to say, effecting the ignition of an
electrical submarine mine at the precise moment of a hostile vessel
being vertically over it, through the agency of one or two observers
stationed at a very considerable distance from the mine, should, with
the very perfect self-acting circuit closers that exist at the present
time, be resorted to only in very exceptional cases, or in connection
with the self-acting system.
There are two defects, which are common to all methods of firing
submarine mines by observation, and these are:--
1.--At night time, or in foggy weather, it cannot be
employed.
2.--It is necessary to employ at least two observers,
at a considerable distance apart, who to effect a
proper action at the right moment, must work in perfect
unison. These defects alone are sufficient to explain
the preference given to a self-acting method of closing
the electric circuit at the precise moment of a vessel
being in position over a mine by those governments who
have adopted electrical submarine mines as a means of
coast defence.
_Methods of Firing by Observation._--There are several methods of
firing by observation, of which the following are the ones principally
used:--
1.--By pickets or range stakes.
2.--By cross bearings.
3.--By intersectional arcs fitted with telescopes.
4.--The Prussian system.
_Intersection by Pickets or Range Stakes._--In narrow channels and at
short distances, this system of ascertaining the relative position
of a hostile vessel and a submarine mine may be used, provided that
skilled and careful men are employed to work it. Two or more pickets
or stakes are arranged in front of the firing station in such a manner
that a vessel passing up the channel on the prolongation of these
stakes will be over a mine. This arrangement should of course always be
considered as an extempore one; it was used on several occasions by the
Confederates during the American civil war.
_Firing by Cross Bearings._--The simplest method of so determining
the relative position of a vessel and a submarine mine, and exploding
it at the right moment, is that in which observers are placed on
the prolongation of the mines. This mode is shown at Fig. 64, where
_m__{1}, _m__{2}, _m__{3}, &c., and _n__{1}, _n__{2}, _n__{3}, &c.,
are the mines; _A_ and _B_, the points in prolongation of the mines
where the observers are stationed; _D_ the firing battery, and _s_, and
_s__{1} two hostile vessels.
At the stations _A_ and _B_ firing keys are placed, at the former one
for each separate mine, perfectly distinct and insulated from each
other, at the latter a single key. The pivot points of the series of
keys at _A_ are connected by separate wires to one pole of the firing
battery _D_, the other pole of which is connected by a single cored
insulated cable to the pivot point of the key at _B_; the contact
points of the series of keys at _A_ are connected by separate line
wires as _A m__{1}, _A m__{2}, _A m__{3}, &c., to the different mines,
while the contact point of the key at _B_ is put to earth. Thus it will
be seen that, in the case of the row of mines, _m__{1}, _m__{2}, &c.,
unless the key at _B_, and the key at _A_, of either of those mines
are both pressed down at the same instant, no current can pass, and
therefore none of those mines can be exploded.
[Illustration: RUSSIAN SUBMARINE MINE, FIRING BY OBSERVATION.
PLATE XVI]
In the case of the vessel _S_, though at _C_, she is on the
prolongation of the line _A m__{5}, _C_, and therefore the key of the
mine _m__{5}, is pressed down at _A_, yet not being on the prolongation
of the line _B_, _E_, the key at _B_ is not pressed down, therefore the
firing battery is not thrown in circuit, or the mine _m__{5} exploded,
but when the vessel _s_ reaches the position _N_, that is over the mine
_m__{3}, she being on the prolongation of the lines _A m__{3}, and _B
E_, the key (_m__{3}) at _A_, and the key at _B_ would both be pressed
down, and therefore the mine _m__{3} exploded, and the ship destroyed.
In the case of a vessel passing through an interval between any two
mines at such a distance as to be out of the radius of destructive
effect of either of the mines belonging to the first row (which is
shown at _s__{1},) only the key at _B_ would be pressed down, and thus
the vessel enabled to pass safely through, but only to come to grief
at the second or third row of mines, provided they have been properly
placed, and separate though similar arrangements as in the case of the
line of mines, _m__{1}, _m__{2}, &c. have been made.
_Firing by a Preconcerted Signal._--At Fig. 65 is represented a
somewhat similar, though a much simpler plan of the foregoing system,
by employing a preconcerted signal at the station _B_ in the place of
the firing key and insulated cable, as in the former case. The only
material difference in the arrangement of these two methods, is that
in the latter case the pole of the firing battery at _A_, which in
the former case was connected to the firing key at _B_, is put direct
to earth. As will be readily understood, this latter system requires
great coolness and nerve on the part of the operator at _A_, who has
not only to watch the vessel passing across his intersections, but
also to be on the alert to receive the signal from the observer at
_B_. Should it ever be necessary to adopt this latter system, it will
be found advisable to employ two men at station _A_, one to watch
station _B_, the other to attend to the firing key and intersections.
A separate signal-flag for each line of mines, and also a separate
firing arrangement, would be required. As in many cases it would not
be practicable to have a station in such an advanced position as at
_B_, in Figs. 64 and 65, on account of the danger of its being cut off
by an enemy, another combination becomes necessary. In this instance
the station _B_ is placed on the opposite side of the river, &c.,
to that on which the station _A_ is placed, and a series of firing
keys, instead of a single one, is here used, necessitating a multiple
cable between the stations _A_ and _B_, in the place of single cored
cable; the manner of manipulating this method is very similar to that
previously described.
_Firing by Intersectional Arcs fitted with Telescopes._--The
foregoing methods of firing by cross bearings are replete with
many serious defects, to remedy which, to a considerable extent,
special arrangements have been devised, that is, the employment of
intersectional arcs fitted with telescopes at the stations _A_ and _B_.
Figs. 66 and 67 show the arrangements of these arcs, the former being
the one used at the firing station _A_, the latter at the converging
station _B_. At each station one arc is provided for each row of mines
placed in position. The firing arc Fig. 66 consists of a cast iron
frame _a_, with three feet _b_, _b_, _b_, these being provided with
levelling screws.
To ascertain when this frame is level, a circular spirit level is
attached thereto, a telescope _d_ provided with one horizontal and
three vertical cross wires, supported on Y's, admitting of vertical
motion and attached to an upright _e_. A mill-headed screw _f_ enables
the telescope _d_ to be raised or lowered; the telescope, which is
rigidly connected to a vernier _g_, traversing over a graduated arc
_h_, can be moved rapidly in a lateral direction by means of a rack
and pinion arrangement _i_, and it can be clamped in any position by
means of the screw _h_. Sights are fixed on the telescope in a vertical
plane passing through its axis. To the outer rim of the frame of the
arc, which is smooth, are secured the sights _l l_ (shown on a large
scale at Fig. 68), to give the direction of the mines. These sights are
provided each with a brass point of V form, _m_, and a binding screw,
_n_, in metallic connection with each other, but insulated by means of
an ebonite plate from the rest of the metal of the sight. One end of a
short piece of insulated wire is attached to the binding screw _n_, and
the other passes through a hole in the base of the sight and projects
below it; _o_ is a brass tube rigidly connected to and moving with the
upright carrying the telescope _d_, and projecting in front of this
latter. A brass spring _p_ (see Fig. 69) is attached to, but insulated
from the outer extremity of this tube, and is so arranged as to make
contact with the V point _m_ on the sight, by means of a corresponding
projection fitted to its under side. An insulated wire passing the tube
_o_, the outer end of which is connected to a screw on the spring _p_,
forms a metallic connection between this projection and the firing key.
At Fig. 68 is shown an enlarged view of the front of the sight; in
addition to the V projection _m_, and binding screw _n_, it is fitted
with a capstan-headed screw to bear against the inner rim of the frame,
and a thin wire upright _t_ for giving the alignment of the mine, to
which a disc is attached, on which the number of the mine is affixed.
When the distance between the station and the mine is only about one
mile, an ordinary eyepiece is used in the place of the telescope _d_.
At Fig. 67 is represented the arc employed at the converging station,
which with the exception of there being no tube _o_, and only one
sight, is precisely similar in construction to the one used at the
firing station, and which has been described.
[Illustration: APPARATUS FOR FIRING BY OBSERVATION.
PLATE XVII]
_Application of the Intersectional Arc Method._--The application of the
method of firing by observation, by means of intersectional arcs fitted
with telescopes, is shown at Fig. 70. _C_, _D_, and _E_ are three of
the larger kind of arcs, one being used for each row of mines at the
firing station _A_. At the converging station _B_, one of the smaller
arcs is used for each row of mines, as shown at _F_, _G_, and _H_.
_S_, _S__{1}, _S__{2}, are the signalling apparatus, the _F_ terminals
of which are connected to the sights _l_, _l_, _l_, Fig. 69, of arcs
_C_, _D_, _E_. Firing keys _a_, _a_, _a_ at station _A_ are connected
to each arc, and to three of the cores of the cable connecting the two
stations _A_ and _B_, respectively. At the converging station _B_,
three firing keys _b_, _b_, _b_ are connected to earth and to three
cores of the connecting cable respectively. The remaining core of this
cable is connected to the recording instruments _d_, _e_. The action of
the arcs, &c., will be readily understood from the diagram at Fig. 70.
This arrangement does not interfere with the action of the circuit
closer, as all that is effected by the observing arc circuit is to put
the signalling battery current at the converging station _B_ to earth
instead of at the circuit closer.
_Prussian System of Firing by Observation._--The principle on which
this system is based, depends upon the proposition that if _c d_, in
the triangle shown in Fig. 71, be always kept parallel to _H B_, then
_A c_, _c d_, _d A_ bear exactly the same proportion to each other as
_A B_, _B H_, _H A_ do to one another; so that by means of the small
triangle _A d c_, the lengths of the sides of the large triangle _A
B H_ can be obtained, and hence the position of the point _H_, the
base _A B_ being of course known. In Fig. 71 at _A_ there is a slate
table representing the roadstead, and upon it the exact position of
every torpedo is laid down, corresponding to their position in the
roadstead. At _A_ and _B_, 500 yards apart, telescopes having cross
wires are placed; at _A_ a long narrow straight-edged strip of glass
_A d_ is arranged to move in unison with the telescope at _A_; and by
the application of dynamo electricity, a similarly constructed piece of
glass _c d_ moves in exact unison with the telescope at _B_, and having
its pivot at _C_; that is to say, _C d_ keeps parallel with _B H_, the
line of sight of the observer at _B_.
Then if the observers at _A_ and _B_ have got a ship in their
telescopes, the point of intersection _d_ of the two pieces of glass _A
d_ and _C d_ gives the position of the ship on the slate table at _A_,
and when this point _d_ comes over the position of any one mine on the
slate, it is known that the ship is over that particular mine in the
harbour, and she may be destroyed accordingly, by throwing the firing
battery into circuit.
By the employment of electricity and a mirror, the great defect of this
method, viz., the necessity of employing four people to manipulate it,
would be remedied. The foregoing is a modification of Siemens's method
of ascertaining distances at sea, &c.
_Rules observed in Planting Mines._--In placing a system of submarine
mines in position, the following are some of the chief points to
be attended to, this work depending in a great measure on local
circumstances, and on the method that is to be adopted in exploding and
mooring them:--
1.--The plan of defence must be carefully laid down
on a chart, on a scale of not less than six inches
to the mile, and on this plan are to be marked the
sites of the observing stations, the positions of each
mine, circuit closer, and junction box, with their
corresponding numbers, and also of the electric cables.
2.--The position of each mine having been determined,
should be marked off by buoys.
3.--The utmost care should be taken to lay the electric
cables, so that they shall be as far as possible away
from the mines in the vicinity of which it may be
necessary to take them, so as to lessen the liability
of injury to them, by the explosion of the latter.
4.--The electric cables should be laid parallel, and
never be allowed to cross directly over each other,
otherwise the operation of underrunning them will be
much complicated, also a certain amount of slack should
be allowed to facilitate in picking the cables up for
repair, &c.
5.--Every manner of device is to be used to conceal the
electric cables, such as laying dummies, making detours
inland, &c.
6.--All marks indicating position of the mines to be
removed, after the mines have been placed in position.
7.--The identity of each cable and mine to be very
carefully preserved throughout, by means of a number.
8.--A number of electro contact mines should be
placed in advance of the leading line of mines, at
irregular intervals, to prevent the enemy, having once
ascertained the position of one mine of a line, from
knowing within limits the position of the others of
that line.
[Illustration: SYSTEMS OF DEFENCE BY SUBMARINE MINES.
PLATE XVIII]
In connection with a system of defence by electrical submarine mines,
the following batteries are required:--
1.--Firing battery.
2.--Signalling, or shutter battery.
3.--Testing battery.
4.--Telegraph battery.
_Firing Battery._--The firing battery should be suited to the nature of
the fuze employed, and should possess considerable excess of power to
enable it to overcome accidental defects, such as increased resistance
in the various connections, or defective insulation in the line wire,
&c.
As platinum wire or low tension fuzes are now universally adopted as
the mode of ignition for submarine mines, it will be only necessary
to describe those electrical batteries which are most suitable as an
exploding agent in connection with such fuzes; these are as follows:--
1.--Siemens's dynamo low tension machine.
2.--Von Ebner's Voltaic battery.
3.--Chromic acid or Bichromate Voltaic battery.
4.--Leclanché's Voltaic battery.
_Siemens's Low Tension Dynamo Electrical Machine._--This instrument
consists of an electro magnet and an ordinary Siemens armature, which,
by the turning of a handle, is caused to revolve between the poles of
the electro magnet. The coils of the electro magnet are in circuit with
the wire of the revolving armature, and during rotation the residual
magnetism of the soft iron electro magnet cores at first excites weak
currents which pass into the electro magnet coils, increasing the
magnetism of the core, thus inducing still stronger currents in the
armature wire. This accumulation by mutual action goes on until the
limit of magnetic saturation of the iron cores of the electro magnets
is reached.
By the automatic action of the machine, the powerful current so
produced is sent into the leading wire or cable to the fuze to be
exploded.
In this apparatus the electric current passes continuously through the
line wire until a sufficiently powerful current is generated to heat or
fuze the bridge of the fuze, and so ignite the gun-cotton priming. The
coils of the armature and electro magnets are wound with wire of large
diameter, to a total resistance of 8 to 10 Siemens units, or 7·6 to 9·5
ohms, in about 2,000 windings.
With a platinum wire weighing 1·65 grains per yard, 6-1/2 inches can be
fuzed on short circuit, and 14 inches can be heated to redness.
The total weight of this machine, which is manufactured by Messrs.
Siemens Brothers, is about 60 lbs.
_Advantages of Siemens's Dynamo Electrical Machine._--The advantages of
such a machine over Voltaic apparatus are:--
1.--The absence of chemical agents.
2.--There is less liability to get out of order.
3.--No special knowledge is required to work them, or
to keep them in order.
4.--Greater durability.
The great defect of this and all similar machines is that the electric
force has to be developed by turning a handle for a certain time
before it is possible to generate a current sufficiently powerful to
ignite a fuze, which defect, in connection with a system of defence
by self-acting submarine mines, particularly at night, renders them
inferior to Voltaic batteries, as under such circumstances, an
apparatus is required that will cause an electric current to flow at
any moment when the circuit is completed.
The application of steam power would to a certain extent remedy the
above-mentioned defect, but the cost of such a method, compared to
that of a Voltaic arrangement, would be far too great to allow of its
superseding the latter arrangement.
_Von Ebner's Voltaic Battery._--This form of Voltaic battery, which
may be considered as a modification of that known as Smee's, was
designed by Baron von Ebner, colonel of the Austrian imperial corps of
engineers, for use in connection with the Austrian system of submarine
defence, by self-acting electrical mines.
A section of one of these cells is shown at Fig. 72. It consists of a
glass vessel _a_, to contain the diluted sulphuric acid, within which
is suspended a plate _b_ of platinised lead, which is bent round into
a cylindrical form to fit close around the inner surface of the glass
vessel. In the centre of this latter is hung a porcelain perforated
cup _c_, containing some cut-up zinc and mercury to keep it (the zinc)
amalgamated. The top of each cell is furnished with a porcelain cover,
through which the wires attached to the positive and negative poles of
the cell project.
Due to the large quantity of liquid contained in the cell, the
tendency to alter its internal resistance is retarded; also by the
arrangement of the porcelain cup, above detailed, the consumption
of zinc and mercury, which in an ordinary Voltaic battery is very
considerable, is materially diminished.
_Chromic Acid or Bichromate Battery._--This form of battery is very
similar to Grove's, the difference being that, in the place of the
nitric acid as the exciting liquid, either chromic acid, or a solution
of bichromate of potash, sulphuric acid and water is substituted.
A form of this battery, as designed by Dr. Hertz, is used in connection
with the German system of torpedo defence.
_Leclanché Voltaic Battery._--This form of Voltaic battery was invented
by M. Leclanché, some twelve years ago. At Fig. 73 is shown a cell of
this battery in its original form. The positive pole _a_ consists of a
plate of graphite in a porous pot _b_, and surrounded by a mixture of
peroxide of manganese and graphite. The negative pole _c_ is a rod or
pencil of amalgamated zinc. The whole is enclosed in an outer vessel of
glass _d_ containing a solution of sal ammoniac.
A modified form of the Leclanché cell as used in a firing battery is
shown at Fig. 74. It consists of an ebonite trough or outer vessel _a_
about 16" long, 9" deep, and 2-3/4" wide. The negative pole or zinc
plate _b_ is of similar shape to the trough _a_, but with its base
removed, and does not fit the trough exactly, the space between it and
the trough being left to ensure the former being completely surrounded
by the sal ammoniac solution; the positive pole, or carbon element,
consists of four gas carbon plates _c_ attached together at their head
by means of lead, and enclosed in a flannel bag, in which they are
firmly embedded in the peroxide of manganese mixture; the positive
element is of such a shape that it fits loosely between the sides, and
is nearly of the same height as the zinc plate.
The object of such a form of cell was to obtain an electric current of
large _quantity_, with as few cells as possible, by which means the
loss of power which might occur from the employment of a great number
of small cells is avoided.
_Advantages of a Leclanché Firing Battery._--The advantages of the
Leclanché firing battery are:--
1.--The absence of chemical action when the battery
circuit is not complete, and consequently there is no
waste of material.
2.--Requires little or no looking after.
3.--It may be kept ready for action in store without in
any way deteriorating.
4.--It is comparatively very cheap.
These advantages combine to make a Leclanché battery the most suitable
of any other form of electrical battery for use as the exploding agent
for electrical submarine mines, and it is now universally used for such
purposes.
_Signalling Battery._--The signalling battery should be so constituted
as to be capable of working the electro magnet of the shutter apparatus
effectually when the circuit is closed direct to earth, and yet not so
powerful as by the continuous passage of the current generated by it to
fire the fuze in the mine. In the case of a platinum wire fuze being
in the circuit, plenty of power may be given to the battery without
fear of a premature explosion from this cause, but in the case of a
high tension fuze it is necessary to be very careful in order to guard
against such a contingency.
As in the case of a signalling or shutter battery, the electric current
will be continually flowing, it is necessary to employ a constant
battery, or one that requires least trouble and expense to maintain it
in working order, and it is for this reason that a modified form of
Daniell battery has been adopted to work the shutter apparatus.
_Daniell Signalling Battery._--At Fig. 75 is shown the manner of
arranging a Daniell cell. A glass or porcelain vessel _a_ contains a
saturated solution of sulphate of copper, in which is immersed a copper
cylinder _b_ open at both ends and perforated by holes; at the upper
part of this cylinder there is an annular shelf _d_, also perforated
by holes, and below the level of the liquid; this is for the purpose
of supporting crystals of sulphate of copper for the replacing of that
decomposed as the electrical action proceeds. Inside the cylinder _b_
is a thin porous vessel _c_ of unglazed earthenware; this contains
either water, or a solution of common salt, or dilute sulphuric acid,
in which is placed the cylinder of amalgamated zinc _e_. Two strips of
copper _p_ and _n_, fixed by binding screws to the copper and to the
zinc, serve for connecting the elements in series, or otherwise.
For the purposes of testing, either the Leclanché or Daniell battery
specially arranged, or the Menotti battery, which is really a
modification of the Daniell, may be used.
[Illustration: FIRING BATTERIES, TESTING BATTERIES.
PLATE XIX]
_Description of a Menotti Cell._--A Menotti cell, shown at Fig. 76,
consists of a copper cup containing some crystals of sulphate of copper
and covered with a fearnought diaphragm _a_, placed at the bottom of
an ebonite cell _b_; over this cup is put some sawdust, and resting on
top of this is a disc of zinc _c_ on another piece of fearnought. The
upper portion of the zinc and its connection with the insulated wire
are carefully insulated. Fresh water poured on the sawdust renders the
battery active.
_Description of a Menotti Test Battery._--Fig. 77 represents a plan
of the top of such a test battery with a 20-ohm galvanometer attached
thereto. The connections are made as follows:--
One of the wires _w_ of the object to be tested is attached to the
terminal _f_, which is also connected by an insulated wire to the
copper cup _a_; the other main wire _w__{1} is attached to the terminal
_g_ of the galvanometer; _h_, the other terminal of the galvanometer,
is connected by a short piece of wire _k_ to the terminal _l_ of the
contact key _m_; and the contact point _n_ is in connection with the
zinc plate _c_; thus the current from the battery flows along the wire
_w_ through the object to be tested, back along the wire _w__{1},
through the coils of the galvanometer, along the wire _k_ to the
contact key _m_, and if this is pressed down to the zinc plate _c_, so
completing the circuit.
To steady the needle of the galvanometer a bar magnet is used, which is
inserted in the space _r_. The whole of the apparatus is enclosed in a
leathern case fitted with a cover and strap.
This is a very compact and simple form of test battery, and will be
found extremely useful in boats, &c., when placing mines in position.
_Telegraph Battery._--For the purposes of telegraphing between torpedo
stations, &c., a form of Leclanché battery, known as No. 3 commercial
pattern, is generally used.
_Voltaic Batteries._--The following points in connection with the
use of voltaic batteries, which are taken from Beechey's 'Electro
Telegraphy,' should be carefully observed:--
1.--Each cell of a battery should be carefully
insulated.
2.--The floors and tables in the battery room should be
kept scrupulously clean and dry, so as to prevent the
least leakage or escape of the current.
3.--The plates of a battery should be clean.
4.--Porous cells should be examined, and cracked ones
replaced.
5.--No sulphate of zinc or dirt should be allowed to
collect at the lips of the cells.
In the case of a Daniell battery--
1.--The solutions should be inspected daily, and
crystals of sulphate of copper added as required.
2.--The zinc plate must not touch the porous cell, or
copper will be deposited on it (the zinc).
3.--The battery should be charged with sulphate of zinc
from the first.
4.--The copper solution must be watched and prevented
from rising over the edge of the porous jar, the
tendency of such solutions being to mix with each other
by an action termed _osmosis_.
These being in addition to foregoing general directions for Voltaic
batteries.
_Defects in a Voltaic Battery on its Current becoming Deficient._--On
the electric current of a Voltaic battery becoming deficient, the
following defects should be looked for:--
1.--Solutions exhausted; for instance, sulphate of
copper in a Daniell's entirely or nearly gone, leaving
a colourless solution.
2.--Terminals or connections between the cells
corroded, so that instead of metallic contact there are
oxides of almost insulating resistance intervening in
the circuit.
3.--Cells empty, or nearly so.
4.--Filaments of deposited metals stretching from
electrode (pole) to electrode (pole).
Also intermittent currents are sometimes produced by loose wires or
a broken electrode, which alternately makes and breaks contact when
shaken. Inconstant currents are also sometimes produced when batteries
are shaken. The motion shakes the gases off the electrodes, thus
increasing temporarily the electro-motive force of the battery.
_Firing Keys and Shutter Apparatus._--The following is a description of
the various firing keys and shutter signalling apparatus, which is used
in connection with a system of electrical submarine mines. By means of
the former the firing or other batteries may be thrown into circuit
at will, whilst by means of the latter the firing battery is thrown
in circuit without the aid of an operator, and a signal at the same
instant given, indicating that a certain mine of the system has been
struck.
_Description of a Series of Firing Keys._--At Fig. 78 is shown a plan
and section of a series of firing keys as arranged for firing several
mines by observation.
It consists of a strong wooden frame _a_, of a convenient form for
the purpose of attaching it to the firing table by screws through the
holes _b_, _b_. On this frame a series of keys _c_, _c_, _c_ are fixed
at convenient intervals. These consist of a strong brass spring firmly
screwed to a series of brass plates _d_, _d_, _d_ on the front of the
wooden box _a_. From these latter short copper wires pass through the
woodwork, and of such a length that, when required, the mine wires may
be easily attached by means of binding screws, as shown at _f_. The
inner end of each key is fitted with an ebonite knob (which is shown
at _c_ in the section) to insulate the hand of the operator when using
the key. On the frame, and directly under each of the ebonite knobs,
are arranged a series of metallic points _g_, _g_, _g_, so placed that
on either of the keys _c_ being pressed down, a perfect contact is made
between it and its respective metallic point; _h_, _h_, _h_ are copper
wires leading from the metallic points _g_, _g_, _g_ through the box,
and of such a length that binding screws _f_, _f_, _f_ can be easily
attached to them when necessary.
A single firing key of an improved form is shown at Fig. 79. It
consists of a strong wooden box _a a_, weighted at the bottom with
lead in order to steady the key on the table, &c., on which it may be
placed; on the inside of the bottom of the box is fixed a piece of
ebonite, by which means the metallic point _b_, and the terminal of the
firing key _c_, are insulated from each other; _d d'_ are two terminals
at the end of the box, to which the circuit wires are attached, one
of these terminals is connected in metallic circuit to the firing key
at _c_, the other one to the metallic point _b_; a wooden cover _h_,
fitted with a catch _k_, protects the connections of the wires; by
means of a plate, and catch _e e_, the key can be rendered inactive,
thus preventing the danger of a premature closing of the electric
circuit; by means of a spring _s_ a break is always established between
the key and the metallic point. It is immaterial to which of the two
terminals _d d'_ either wire is connected.
_The Morse Firing Key._--This form of key is so well known in
connection with the Morse telegraph, that it is not necessary to
describe it.
It is usually employed in torpedo work in connection with a testing and
firing table.
_The Shutter Apparatus._--The shutter signalling and firing apparatus
was devised to enable the firing battery current to be thrown in
circuit without the aid of a personal operator, the signalling current
(which is always kept in circuit) at the same instant ringing a bell,
by which is known the particular mine that has been struck.
At Fig. 80 is represented a diagram of such an apparatus. _a_ is an
armature working on a pivot between the two horns of an electro magnet
_b b_, and held in position by a spiral spring _c_; the latter is in
connection with a regulating screw, by which more or less pressure may
be brought to bear in an opposite direction to that of the attractive
action of the electro magnet. A stud _i_ regulates the distance to
which the armature may be drawn back; _d_ is a shutter on which a
reference number for each mine should be indicated, attached to a
lever pivoted at the point _e_, the inner arm of which is just long
enough to catch under the point of the armature _a_; when a current of
sufficient strength is passed through the coils _b b_ of the electro
magnet, the armature _a_ is attracted, releasing
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