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+*** START OF THE PROJECT GUTENBERG EBOOK 44990 ***
+
+[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 the lever attached
+to the shutter _d_, which by its own weight falls into the position
+shown by the dotted lines. _f_ and _g_ are two mercury cups, the former
+being in connection with the signalling current, and the latter with
+the firing current. When the lever is horizontal and the shutter drawn
+up and ready for action, the circuit of the signalling battery _s_ is
+completed through the mercury cup _f_, along an arm _h_ of the lever
+to the pivot _e_, and thence to the mine by the line wire _w_. When
+the circuit closer is struck by a passing vessel, and consequently the
+shutter thrown into the position shown by the dotted lines, another
+arm _k_, a prolongation of the lever, falls into the mercury cup _g_,
+which latter is in connection with the firing battery _F_. The armature
+_a_ is prevented from coming into actual contact with the horns of the
+electro magnet by two small studs. The object of this is to prevent any
+effect of residual magnetism which might otherwise interfere with the
+rapidity of action of the armature when released and drawn back by the
+spring _c_.
+
+[Illustration: FIRING KEYS, SHUTTER APPARATUS.
+
+PLATE XX]
+
+_The object of employing Mercury Cups._--Mercury cups were devised in
+the place of the springs used in connection with the original design of
+a shutter apparatus, for the reason that electrical circuits dependent
+on the pressure of springs are always liable to interruption from dirt
+or oxide intervening between the points of contact.
+
+_Shutter Apparatus used with a Circuit Breaker._--When the circuit
+breaking system is used with the shutter signalling apparatus, the
+action of the armature in releasing the lever must be reversed; that is
+to say, that when the current is passing and the armature _a_ attracted
+to the electro magnet _b b_, the shutter _d_ must be held up, and when
+the current ceases, and the armature _a_ drawn back by the spring _c_,
+the lever must be released, and the shutter allowed to fall. This is
+effected by altering the end of the lever, so that it hooks into,
+instead of abutting against the armature _a_.
+
+To each shutter apparatus an electric bell is fitted, by which notice
+is given when a circuit closer has been struck. For general service, a
+box containing seven such shutter signalling and firing apparatus has
+been adopted, a plan of which is represented at Figs. 81, 82 and 83.
+The connections of the different circuits are as follows:--
+
+The insulated wire of the upper bobbin of the electro magnet is
+connected to the spring of the armature; the pivot of the lever is
+connected with the right-hand terminal _B_, or main line connection
+on the top of the box; the insulated wire from the lower bobbin is
+connected to the middle brass plate _k_ in the front ledge of the
+apparatus, the circuit from _B_ to _k_ being thus completed. The front
+adjoining brass plate _A_, provided with a terminal, is connected with
+the negative pole of the signalling battery, the positive pole being
+put to earth.
+
+On a brass plug being put in the hole _l_, the signalling current will
+flow to the plate _k_, thence through the lower and upper bobbin to
+the spring of the armature, along the latter to the shutter lever, and
+from the pivot through the main line wire to the mine. The innermost
+brass plates _H H_ are all connected in the same metallic circuit, and
+to them are attached by means of the binding screw _D_ the test battery
+and galvanometer. Thus on the brass plug being removed from _l_, and
+placed in _m_, the signalling battery is cut out of circuit, and the
+test battery thrown in. In this way the condition of each individual
+mine may be ascertained while the connections of the remaining mines
+are left undisturbed. The positive pole of the firing battery (the
+negative being to earth) is connected to the terminal _S_ at the
+right-hand corner of the lower ledge of the box; the plate to which the
+terminal _S_ is fixed is divided at _G_, the left-hand portion being
+connected to a bar which runs horizontally the whole length of the
+box, and in metallic connection with each mercury cup _g_, Fig. 80. A
+brass plug is placed in the hole _G_, and when from any cause the lever
+drops, the firing battery will be thrown into circuit, and the mine to
+which the lever that has fallen is attached will be exploded.
+
+_Shutter Instrument and Observing Telescope._--Each mine is given a
+number, which is put on the disc of the shutter instrument connected
+to it, and also on the corresponding tablet _C_. From the brass plate
+in connection with the spring _c_, Fig. 80, a wire is taken to the
+terminal _f_, Fig. 81, on top of the box. From this terminal a wire is
+led to the connections of the observing telescope, and thus the mines
+can be fired by judgment if required, without the aid of the circuit
+closer.
+
+The signal battery current is always circulating, even when the system
+is in a state of rest, but in consequence of the resistance placed in
+this circuit, which may be either a resistance coil in the circuit,
+added to the resistance of the fuzes, when high tension fuzes are used,
+or only the former resistance in the case of low tension fuzes, this
+current is too feeble to form an electro magnet; directly, however,
+a circuit closer is struck, this resistance is cut out, and thus the
+signal battery current becomes sufficiently powerful to work the
+electro magnet of that particular mine.
+
+The circuit of the signal battery, and that to the observing telescope,
+are broken the instant the lever commences to fall.
+
+To enable the apparatus to be used on the circuit breaking system, a
+spare lever _E_ is provided for that purpose with each box.
+
+The object to be gained by a system of testing is to ascertain the
+condition of the electrical submarine mines placed in the defence of
+a harbour, &c., and should there exist any fault, not only to detect
+its exact position and cause, but also its magnitude, so that it may
+be at once determined whether it is necessary to remedy the fault, or
+whether the electrical apparatus is sufficiently powerful to overcome
+the defect.
+
+_Tests._--There are two distinct kinds of tests, viz.:--
+
+    1.--Mechanical tests.
+    2.--Electrical tests.
+
+[Illustration: SHUTTER APPARATUS.
+
+PLATE XXI]
+
+Mechanical tests are applied to ascertain that the mechanical
+arrangements of the shutter apparatus, circuit closers, and all similar
+appliances work efficiently and easily; that the several parts of the
+mine case when put together for service are thoroughly watertight;
+that the chains, wire cables, and ropes in connection with the mooring
+apparatus are of sufficient strength to perform the work required of
+them; that the weights of the anchors, or sinkers, are such as to keep
+the mines in position after submersion; and that the case of the mine
+be sufficiently strong to enable it to bear the external pressure due
+to the depth at which it may be submerged for a considerable time
+without any leakage.
+
+The foregoing tests of the mine case and moorings would of course be
+performed during the process of manufacture, but to prevent any chance
+of failure they should be repeated before being employed on actual
+service.
+
+_Electrical Tests._--Electrical tests are those which are applied
+to the several component parts of the system, to ascertain that the
+electrical conditions necessary to a successful result exist.
+
+The importance of being able to carry out the above in its entirety
+is understood when it is remembered that a submarine mine becomes
+practically valueless unless it acts efficiently at the single instant
+of time that it would be required so to do.
+
+_List of Instruments used in Testing._--The following are some of the
+instruments that are employed in connection with a system of electrical
+tests:--
+
+     1.--Thomson's electrometer.
+     2.--Thomson's reflecting galvanometer.
+     3.--Astatic galvanometer.
+     4.--Differential galvanometer.
+     5.--Detector galvanometer.
+     6.--Three coil galvanometer.
+     7.--Thermo galvanometer.
+     8.--Siemens's universal galvanometer.
+     9.--A shunt.
+    10.--Commutator.
+    11.--Rheostat.
+    12.--Resistance coils.
+    13.--Wheatstone's balance.
+
+Electrometers indicate the presence of a statical charge of
+electricity, by showing the force of attraction or repulsion between
+two conducting bodies placed near together. This force depending in the
+first place on the quantity of electricity with which the conducting
+bodies are charged, ultimately depends on the difference of potential
+between them; an electrometer is therefore strictly an instrument for
+measuring difference of potential.[J]
+
+Sir William Thomson's quadrant electrometer is the most perfect form
+of electrometer yet constructed, and the one usually employed in cable
+testing. It consists of a very thin flat aluminium needle spread out
+into two wings, and hung by a wire from an insulated stem inside a
+Leyden jar, which contains a cupful of strong sulphuric acid, the outer
+surface of which forms the inner coating of the Leyden jar. A wire
+stretched by a weight connects the aforesaid needle with this inner
+coating. A mirror, rigidly attached to this needle by a rod, serves
+to indicate the deflection of the needle by reflecting the image of
+a flame on to a scale. The needle hangs inside four quadrants, which
+are insulated by glass stems: each pair of opposite quadrants are in
+electrical connection. Above and below the quadrants two tubes, at
+the same potential as the needle, serve to screen it and the wires in
+connection with it from all induction except that produced by the four
+quadrants. Suppose the needle charged to a high negative potential (-),
+then if the quadrants are symmetrically placed, it will deflect neither
+to the right nor to the left, so long as the near quadrants are at the
+same potential. If one of these be positive relatively to the other,
+the end of the needle under them will be repelled from the negative
+quadrant to the positive one, and at the same time the other end of the
+needle will be repelled from in the opposite direction. This motion
+will be indicated by the motion of the spot of light reflected by the
+mirror, and the number of divisions which the spot of light traverses
+on the scale measures in an arbitrary unit the difference of potential
+between the + and - quadrants.
+
+The reflecting electrometer being a very delicate instrument, requires
+careful handling, and should only be used by a practised electrician.
+Its use would therefore be restricted to important stations, and
+special tests of a delicate nature.
+
+_Thomson's Reflecting Galvanometer._--A galvanometer is an instrument
+intended to detect the presence of a current and measure its magnitude.
+
+The most sensitive galvanometer as yet constructed is the reflecting
+galvanometer of Sir William Thomson, a diagram of which is shown at
+Fig. 84.
+
+A small piece of magnetised steel watch spring, 3/8ths of an inch long,
+is fastened with shellac on the back of a little round concave mirror,
+and of about the size of a fourpenny piece. This is suspended by a
+piece of unspun silk thread in the centre of a coil of many hundred
+turns of fine copper wire insulated with silk, and well protected
+between the turns with varnish. The two ends of the coils are soldered
+to terminal screws _a_, _b_, so that any conducting wire can be joined
+up to it as required. The little mirror hangs in the middle of its
+coil, with the magnet lying horizontally. By means of a lamp _L_ placed
+behind the screen, the light of which passes through a slit _M_, and is
+thrown on the face of the mirror, a spot of light is reflected on the
+scale _N_.
+
+When a current passes through the coil, the little magnet is deflected,
+and since the magnet is attached to the mirror, which is very light,
+both are deflected as forming one body, and the spot of light moves
+accordingly along the scale _N_.
+
+A powerful steel magnet _S_ is placed above the coil, and can be moved
+up or down, whereby the directive force of the earth may be increased
+or weakened. This magnet _S_ is used to steady the spot of light, which
+otherwise would shake about, and there would be no certainty about
+the measurement. A second magnet _T_ is placed perpendicular to the
+magnetic meridian, to adjust the zero of the instrument, i.e., to bring
+back the spot of light to a fiducial mark at the centre of the scale
+when no current is passing.
+
+This instrument should only be used at important stations, and when
+special tests of a delicate nature are required to be applied.
+
+_Astatic Galvanometer._--An astatic galvanometer is that in connection
+with which an astatic needle is employed, by the use of which the
+sensitiveness of a galvanometer is greatly increased.
+
+An astatic needle is a combination of magnetised needles _with their
+poles turned opposite ways_.
+
+At Fig. 85 a diagram of such an instrument is shown. Two magnets _D_
+and _C_ are joined, with the north pole of one over the south pole
+of the other, forming one suspended system. In the ordinary form of
+astatic galvanometer the needles _D_ and _C_ are about two inches long,
+and are each covered by a coil, these latter being so joined that the
+current must circulate in opposite directions round the two so as to
+deflect both magnets similarly. The deflection of the needles _D_ and
+_C_ is observed by means of a pointer or glass needle _A_, _B_, rigidly
+connected with the astatic system by a prolongation of the brass rod
+connecting the needles _D_ and _C_. The coils are flat and of the shape
+indicated in Fig. 85, and are also made in two halves, placed side by
+side with just sufficient space between them to allow the rod to hang
+freely.
+
+This form of galvanometer, though less delicate than the preceding one,
+is still a very sensitive one, and should only be applied in the case
+of fine and delicate tests.
+
+_Differential Galvanometer._--A differential galvanometer consists of
+a magnetic needle surrounded by two separate coils of equal length and
+material carefully insulated from each other and wound in opposite
+directions. In using it one circuit acts against the other. If a
+current of equal strength were passing through each there would be no
+deflection of the needle, because the influence in both directions is
+equal. If one current were stronger than the other, the needle would be
+deflected by the stronger.
+
+This form of galvanometer will be found extremely useful in connection
+with a system of electrical tests.
+
+Latimer Clark's double shunt differential galvanometer is the
+instrument best adapted for submarine mine tests.
+
+_Detector Galvanometer._--A detector galvanometer is usually made with
+a vertical needle, and is employed to detect and roughly estimate the
+strength of a current where no particular accuracy is required.
+
+It consists of a magnetic needle pivoted in the centre of a coil of
+insulated wire, and having an index needle attached to move with
+it, the latter appearing on a dial, divided into 360 equal arcs or
+portions: a diagram of such an instrument is shown at Fig. 86.
+
+This instrument should be of small size and portable form, and as
+sensitive as it is possible to make it, under such conditions.
+
+_Three Coil Galvanometer._--The three coil galvanometer is provided
+with a vertical needle, and is in other respects very similar in
+appearance to the detector galvanometer before described. It is formed
+with three coils of 2, 10, and 1000 ohms resistance; each coil is
+connected with a brass plate on the top of the box which encloses the
+whole, and may be switched into circuit by means of a plug at will. The
+object of the three resistances is to suit the different resistances
+that may occur, with a perfect, or imperfect state of the electrical
+combination in connection with each mine. A diagram of this instrument
+is shown at Fig. 87, the dotted portions are inside the case.
+
+_Thermo Galvanometer._--A thermo galvanometer is an instrument used to
+ascertain the power of a firing battery which is employed to ignite
+platinum wire or low tension fuzes.
+
+The form of thermo galvanometer generally used in connection with a
+test table, is arranged as follows:--
+
+Two ebonite studs, fitted with brass connecting screws, are fixed
+to the lid of a box containing some resistance coils, and placed in
+circuit with them; these studs, placed about ·3 of an inch apart, are
+arranged to receive a piece of platinum wire which is stretched from
+one stud to the other; the firing battery being placed in circuit with
+the platinum wire, and the resistance coils, its working power would
+then be tested by the fusion of the wire through a given electrical
+resistance, as indicated by the resistance coils put in circuit.
+
+Another form of thermo galvanometer, which is very compact and
+portable, is shown at Fig. 88. It consists of a wooden box _a_, with
+a cover of ebonite _b_, within the box is placed a resistance coil
+_c_; _d_ and _e_ are two ebonite standards ·3" apart, the former of
+which is connected by a copper wire with the terminal _f_, the latter
+to the terminal _g_; the terminal _h_ is similarly connected to the
+contact piece _k_, and the terminal _l_ to the firing key _m_, at
+_n_; the resistance coil _c_ is connected to the terminal _g_ and to
+the copper wire _n_; the platinum wire (of which several lengths are
+used, according to the resistance of the coil _c_) is placed between
+the standards _d_ and _e_. To test a battery, it is only necessary to
+connect it to the terminals _f_ and _h_, when by pressing down the key
+_m_ the power of the battery, according as to its fusing or not the
+platinum wires, will be ascertained; the use of the terminals _g_ and
+_l_ is to cut out the resistance, which is effected by connecting them
+by means of a copper wire.
+
+_Siemens's Universal Galvanometer._--Siemens's universal galvanometer
+is an instrument combining in itself all the arrangements necessary for
+the following operations:--
+
+    1.--For measuring electrical resistances.
+    2.--For comparing electromotive forces.
+    3.--For measuring the intensity of a current.
+
+The instrument which is shown in elevation and plan at Pl. xxiii.,
+Figs. 1 and 2 respectively, consists of a sensitive galvanometer which
+can be turned in a horizontal plane, combined with a resistance bridge
+(the wire of which bridge instead of being straight is stretched round
+part of a circle). The galvanometer has an astatic needle, suspended
+by a cocoon fibre, and a flat bobbin frame wound with fine wire. The
+needle swings above a cardboard dial divided in degrees; as however,
+when using the instrument the deflection of the needle is never read
+off, but the needle instead always brought to zero, two ivory limiting
+pins are placed at about 20 degrees on each side of zero.
+
+The galvanometer is fixed on a graduated slate disc, round which the
+platinum wire is stretched. Underneath the slate disc three resistance
+coils of the value of 10, 100, and 1000 Siemens' units are wound on a
+hollow wooden block, which protrudes at one side, and on the projection
+carries the terminals for the reception of the leading wires from
+the battery and unknown resistance. The adoption of three different
+resistance coils enables the measuring of large as well as small
+resistances with sufficient accuracy.
+
+[Illustration: GALVANOMETERS FOR TESTING.
+
+PLATE XXII]
+
+The whole instrument is mounted on a wooden disc, which is supported
+by three levelling screws, so that it may be turned round its axle.
+On the same axle a lever is placed which bears at its end an upright
+arm, carrying a contact roller. This roller is pressed against the
+platinum wire round the edge of the slate disc by means of a spring
+acting on the upright arm, and forms the junction between the _A_ and
+_B_ resistances of a Wheatstone's bridge, which resistances are formed
+by the platinum wire on either side of the contact roller, one of the
+three resistance coils forming the third resistance of the bridge.
+_G_ is the galvanometer, _k_ a milled head from which the needles
+are suspended, and by turning _k_ they can be raised or lowered, _m_
+is the head of a screw which arrests or frees the needle when in
+motion. _h__{1}, _h__{2}, _h__{3}, _h__{4}, are the terminals of the
+respective ends of the three resistance coils, viz., 10, 100, and 1000
+units, which are wound on the wooden block _C_; these terminals may be
+connected to each other by means of stoppers, and therefore one or
+more of the resistances may be brought into circuit as desired, and to
+the ends of these terminals the wires of the artificial resistances
+are connected as shown on diagrams Pl. xxiv., Figs. 1, 2, 3_a_ and
+3_b_; _f_ is the graduated slate disc, round which the platinum wire is
+stretched in a slight groove at the edge of the disc, and is inserted
+in such manner that about half its diameter protrudes beyond the slate.
+The ends of the platinum wire are soldered to two brass terminals _l_
+and _l_^{1}, which are placed at the angles formed by the sides of
+the gap in the slate disc, and which form the junctures, as in the
+ordinary resistance bridge, between _A_, _n_, and the galvanometer on
+one side, and _B_, _X_, and the galvanometer on the other side, of the
+parallelogram. The terminal _l_ is permanently connected by a thick
+copper wire or metal strip to terminal _h__{1}, and the other terminal
+_l_^{1} is connected in a similar manner to terminal III.
+
+Slate is adopted for the material of which to make the disc _f_,
+because it is found by experience to be the material which is the least
+sensitive to variations in the weather or temperature.
+
+The slate disc is graduated on its upper edge through an arc of 300
+degrees, zero being in the centre, and the graduations figured up to
+150 on each side at the terminals _l_ and _l_^{1} of the bridge wire.
+
+In the centre of the circular plate _E_ of polished wood, supported
+upon three levelling screws _b_, _b_, _b_, a metal boss is inserted,
+in which turns the vertical pin _a_ which carries the instrument. This
+pin, being well fitted to the boss, supports the instrument firmly, but
+at the same time allows it to be turned freely round its vertical axis
+without losing its horizontal position when once obtained.
+
+On the arm _D D_, which turns on the pin _a_, and somewhat behind the
+handle _g_, there is a small upright brass arm _d_ turning between
+two screw points _r_, and carrying in a gap at its upper end a small
+platinum jockey pulley _e_ turning on a vertical axis. This pulley
+forms the movable contact point along the bridge wire, against which it
+is kept firmly pressed by means of a spring acting on the arm _d_. The
+arm _D D_, which is insulated from the other parts of the apparatus, is
+permanently connected with the terminal I. On the top of _d_ a pointer
+_Z_ or a vernier is fixed, which laps over the upper edge of the slate
+disc and points to the graduations.
+
+To the pin _a_ is attached a circular disc of polished wood _C_,
+about one inch thick, and having a groove turned in its edge for the
+reception of the insulated wires composing the resistances. The disc
+_C_ has a projection _c_, which carries the five insulated terminals
+marked I., II., III., IV., V., as shown on Figs. 1 and 2, Pl. xxiii.
+Terminals III. and IV. can be connected by a plug, II. and V. by the
+contact key _K_. Terminal I. is in connection with the lever _D D_.
+
+Figs. 3 and 4, Pl. xxiii. show the shunt box supplied with the
+galvanometer if specially desired; the copper connecting arms _a_,
+_a_ are screwed to the terminals II. and IV. By inserting a plug at
+_c_ (Fig. 4, Pl. xxiii.), the galvanometer is put out of circuit
+altogether, whilst by plugging either of the other holes shunts of the
+value of 1/9, 1/99, or 1/999, are introduced into the circuit, and
+the effect upon the galvanometer is reduced to 1/10, 1/100, 1/1000,
+respectively of what it would have been without the insertion of the
+shunt.
+
+Figs. 5 and 6, Pl. xxiii., show a battery commutator allowing to bring
+into the circuit four different amounts of battery power. It is placed
+in the battery circuit whenever consecutive tests with different
+batteries are desired to be made, it being only necessary to change
+the place of the stopper in the battery commutator, the terminal screw
+_a_ of the battery commutator being connected to terminal V. of the
+galvanometer, and the screws _b_, _b_, _b_, _b_ to various sections of
+the battery: see diagram of connections, Fig. 4, Pl. xxiv.
+
+The application of the universal galvanometer will be clear from the
+diagrams on Pl ii.; instructions, however, for its practical use are
+added further on, and also tables for use when measuring conducting
+resistances.
+
+As will be seen from diagram, Fig. 1, Pl. xxiv., the proportion between
+the unknown resistance X, and the artificial resistance _n_ is, when
+the deflection is read off on the side of the slate disc marked _A_:
+
+    X : _n_ = 150 + _a_ : 150 - _a_
+
+    or, X = ((150 + _a_) / (150 - _a_)) × _n_.
+
+but if read off on the _B_ side of the disc--
+
+    X = ((150 - _a_) / (150 + _a_)) × _n_.
+
+The values of these two fractions, for every half degree, will
+be found in the columns headed _A_ and _B_ of the table in the Appendix.
+
+[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.
+
+PLATE XXIII]
+
+[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.
+
+PLATE XXIII^A]
+
+[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER.
+
+PLATE XXIV]
+
+[Illustration: SIEMEN'S UNIVERSAL GALVANOMETER
+
+PLATE XXIV^A]
+
+_Measuring Electrical Resistances._--For this purpose the instrument is
+arranged as a Wheatstone's balance. The connections are made as shown
+at Pl. xxiv., Figs. 1 and 5, where _X_ is the unknown resistance.
+
+    _a._--The needle _i_ is to be brought to the zero
+    point of the small cardboard scale by turning the
+    galvanometer _G_ round its vertical axis, taking care
+    that the needle moves with perfect freedom.
+
+    _b._--The pointer or vernier _Z_ is to be brought, by
+    means of the handle _g_, to the zero point of the large
+    scale on the slate disc.
+
+    _c._--A plug is to be inserted between the terminals
+    marked III. and IV.
+
+    _d._--The holes 10, 100, and 1000 are, two of them, to
+    be plugged, and one left open, according to the extent
+    of the unknown resistance to be measured; either 10 or
+    100 must be left open if the resistance is small, and
+    1000 if it is large.
+
+    _e._--The two ends of the unknown resistance are to be
+    connected to terminals II. and IV.
+
+    _f._--The two poles of some galvanic battery are to be
+    connected to terminals I. and V.
+
+When the above-mentioned connections have been made, and on depressing
+the key _K_, the battery current is sent into the combination and
+deflects the needle, say, to the right-hand or _B_ side of the
+instrument, the pointer or vernier _Z_ must then be pushed, by means of
+the handle _g_, to the _B_ side of the instrument. If this is found to
+increase the deflection of the needle _i_, the pointer _Z_ should be
+pushed to the other or _A_ side of the instrument beyond the zero point
+of the large scale until the needle remains stationary when the key _K_
+is depressed.
+
+The number indicated by the vernier _Z_ should be read off carefully,
+and notice taken whether it is on the _A_ or _B_ side of the large
+scale. This number must then be referred to the galvanometer table,[K]
+when the figure opposite to the number, multiplied by the resistance
+unplugged, is the resistance of _X_. The value of the resistance to be
+determined will be thus found by a single operation.
+
+Supposing the reading to be 50 on the _A_ side of the large scale, the
+resistance _n_ unplugged having been 100 units, we get according to the
+before-mentioned law of resistance bridge the following proportion (see
+Fig. 5, Pl. xxiv.):--
+
+    X : 100 = 150 + 50 : 150 - 50
+
+          X = ((150 + 50) / (150 - 50)) × 100
+
+          X = 200 units.
+
+For measuring very small resistances a single cell will be found
+sufficient; but for large resistances more should be used, say, 15 to
+20. If very accurate measurements of small resistances are to be taken,
+the screw at the end of the moving arm _D D_ should receive one battery
+wire, terminal V. receiving the other.
+
+_Comparing Electromotive Forces._--For this purpose Professor E. du
+Bois-Reymond's modification of Poggendorff's compensation method is
+used.
+
+The connections are made as shown at Pl. xxiv., Figs. 2 and 6.
+
+For comparing two electromotive forces _E__{1} and _E__{2}, a third
+electromotor of higher electromotive force _E__{0} is used, and two
+separate tests taken.
+
+The manipulations _a_ and _b_ are to be the same as before.
+
+    _c._--The hole between III. and IV. to be left
+    unplugged.
+
+    _d._--Plugs to be inserted in 10, 100 and 1000.
+
+    _e._--The two poles of the electromotor of an
+    electromotive force _E__{0} are to be connected to the
+    terminals III. and V.
+
+    _f._--The poles of the battery whose electromotive
+    force _E__{1} is to be compared are connected to
+    terminals I. and IV. in such a manner that the similar
+    poles of the two electromotors are joined to terminals
+    I. and III., and to IV. and V. respectively.
+
+When depressing the key _K_ the galvanometer needle will be deflected
+and can be brought back to zero by turning the pointer _Z_ either to
+the right or to the left. Should for instance the pointer have to be
+brought to 30° on the _A_ side we have the following equation--
+
+    E_{1} = E_{0} × ((150 - 30) / ( 300 + _n_))      (1),
+
+where _n_ is the resistance of the battery _E__{0}.
+
+The electromotor _E__{2} is now to be inserted in the place of _E__{1},
+and the galvanometer needle, when it deflects, again brought back to
+zero by moving the pointer _Z_. If for instance the pointer has to be
+pushed to 40° on the _B_ side to obtain equilibrium we have--
+
+    E_{2} = E_{0} × ((150 + 40) / ( 300 + _n_))     (2).
+
+By eliminating _n_ from equations 1 and 2 we have
+
+    E_{1} : E_{2} = (150 - 30) / (150 + 40) = 12 : 19    (3).
+
+The two electromotive forces are in the same proportion as the two
+observed distances of the pointer _Z_ from 150° on the _A_ side of the
+instrument.
+
+_For measuring the Intensity of a Current._--For this purpose the
+instrument is simply used as a sine galvanometer. The connections are
+made as shown at Pl. xxiv., Figs. 3_a_ and 7.
+
+The manipulations _a_, _b_, _c_, and _d_ same as in the second case.
+
+    _e._--Connect one pole of a battery to terminal II. and
+    put the other pole to earth.
+
+    _f._--Connect the line to terminal IV.
+
+The galvanometer is then to be turned in the same direction as the
+needle is deflected until the needle coincides with the zero point.
+Whilst this is being done the large scale on the slate disc will move
+under the pointer _Z_, which must be left stationary; the sine of the
+angle indicated by _Z_ will thus give the value proportionate to the
+strength of the current. Should the shunt box be required, it has to be
+connected with terminals II. and IV.
+
+Fig. 4 shows the same connections as Fig. 7, but without the shunt box,
+and with the battery commutator. Fig. 3_{a} shows diagram of the same
+connections but with the key _K_, and Fig. 3_{b} the same without the
+key.
+
+_A Shunt._--A "Shunt" is a second path offered to a current traversing
+a given circuit, or portion of a circuit, so as to diminish the amount
+of the current flowing through that portion of the circuit. In the
+diagram shown at Fig. 89 the shunt diminishes the amount of the current
+flowing along the circuit between _A_ and _B_.
+
+If only 1/Nth of the current is to pass along the circuit between _A_
+and _B_ (of resistance _R_) then the resistance of the shunt must equal
+R/(N - 1).
+
+By the aid of shunts it is quite possible to make use of very sensitive
+instruments to measure powerful currents.
+
+_Commutators or Switch Plates._--A commutator or switch plate is an
+apparatus by which the direction of currents may be changed at will, or
+by which they may be opened or closed. Bertin's commutator, which is
+represented at Fig. 90, consists of a small base of hard wood on which
+is an ebonite plate, this by means of the handle _m_ is turned about a
+central axis between two stops _c_ and _c'_. On the disc are fixed two
+copper plates, one of which _o_ is always positive, being connected by
+the axis and by a plate (+) with the binding screw _P_, which receives
+the positive electrode of the battery; the other copper plate _i_,
+_e_, bent in the form of a horse-shoe, is connected by friction below
+the disc with a plate (-), which plate is connected with the negative
+electrode _N_. On the opposite side of the board are two binding screws
+_b_, and _b'_, to which are attached two elastic metal plates _r_, and
+_r'_.
+
+On the disc being turned as shown in the figure, the current coming by
+the binding screw _P_ passes into the piece _o_, the plate _r_, and
+finally the binding screw _b_, which by means of a copper wire leads
+the current to the apparatus in connection with _b_; then returning to
+the binding screw _b'_, the current reaches the plate _r'_, the piece
+_i_, _e_, and so to the battery by the binding screw _N_.
+
+If the disc is turned so that the handle _m_ is half way between _c_
+and _c'_, the pieces _o_ and _i_, _e_, being no longer in contact with
+the plates _r_ and _r'_, the current will not pass. If _m_ is turned as
+far as _c_, the plate _o_ will then touch _r'_, and the current pass to
+_b'_, and return by _b_, thus reversing its direction.
+
+"Peg" switches are also often used; they are arranged so that the
+removal or insertion of a brass peg or plug cuts out, or completes a
+circuit.
+
+_Rheostat._--A rheostat is an instrument used for the comparison of
+resistances.
+
+[Illustration: SHUNT, COMMUTATOR, RHEOSTAT.
+
+PLATE XXV]
+
+Wheatstone's rheostat, which is shown in elevation at Fig. 91,
+consists of two cylinders _A_ and _B_, one of brass and the other of
+non-conducting material, so arranged that a copper wire can be wound
+off the one on to the other by turning a handle _C_. The surface of
+the non-conducting cylinder _B_ has a screw thread cut in it for its
+whole length, in which the turns of the copper wire lie, so that
+its successive convolutions are well insulated from each other. Two
+binding screws _D_, _D'_ connected with the ends of the copper wire are
+provided, to which the circuit wires are connected. A scale is attached
+at _E_, by means of which the number of convolutions on _B_ can be read
+off; and parts of a revolution are indicated on a circle at one end.
+The handle _C_ can be shifted from one cylinder to the other.
+
+Supposing the rheostat introduced into a circuit, and the whole of the
+copper wire wrapped on the metal cylinder _A_, then, on account of the
+large section of this metal cylinder, its resistance may be entirely
+neglected, but for every convolution of the wire on the non-conducting
+cylinder =B=, a specific resistance is introduced into the circuit.
+The amount of resistance can thus be varied as gradually as desired by
+winding on and off the cylinder _B_. This instrument is often used in
+connection with the thermo galvanometer.
+
+_Resistance Box._--The general arrangement of a resistance box is shown
+in the diagram Fig. 92.
+
+Between two terminal binding screws _T_ and _T__{1} secured on a
+vulcanite slab are fixed a series of brass junction pieces _a_, _b_,
+_c_, _d_; each of these is connected by a resistance coil to its
+neighbour, as shown at 1, 2, 3, and 4. A number of brass conical
+plugs with insulating handles of vulcanite are provided, which can be
+inserted between any two successive junction pieces, as between _T_ and
+_a_, or _a_ and _b_.
+
+With all the plugs inserted, the electrical current will flow direct
+from _T_ to _T__{1}, the large metallic junction pieces directly
+connected by the plugs would offer no sensible resistance; but if all
+the plugs were removed, then the current would flow through each of the
+coils 1, 2, 3, and 4, and the resistance in the circuit would be the
+sum of the resistances of those four coils. With the plugs arranged
+as in the figure, the current would flow through coil 4 only, and the
+resistance in the circuit would be equal to the resistance of that coil.
+
+_Wheatstone's Balance._--The electrical conductivity of a body is
+determined by ascertaining the ratio between the resistance of a
+certain length of the conductor in question, having a given section, to
+that of a known length of a known section of some substance taken as a
+standard.
+
+For this purpose Wheatstone's bridge in connection with a box of
+resistance coils is the most convenient method.
+
+At Fig. 94 is shown Wheatstone's balance (Post-office pattern), and
+at Fig. 93 the apparatus is reduced into the form of a parallelogram,
+which is the usual diagram of Wheatstone's bridge. The theory of the
+bridge is as follows:
+
+Four conductors _A B_, _B C_, _A D_, and _D C_ are joined at _A_ and
+_C_ to the poles of a battery _Z_; the resistance between _A_ and _B_
+is _R_; that between _A_ and _D_ is _r_; that between _D_ and _C_ is
+_R__{1}; and that between _B_ and _C_ is _x_, the unknown resistance to
+be measured. A convenient constant ratio is chosen for _R__{1} and _r_,
+such as equality 1 to 10, 1 to 100, or 1 to 1000; and then _R__{1} is
+adjusted until no current flows through the galvanometer _G_; when this
+is the case we have R : _r_=R_{1} : _x_, or _x_ = (_r_/R) × R_{1}; so
+that if _r_ = R/100, _x_ will be equal to R_{1}/100.
+
+Two keys _a_ and _b_ are inserted; the current is wholly cut off the
+four conductors until contact is made at _a_; and then after the
+currents in the four conductors have come to their permanent condition,
+contact is made at _b_ to test whether any current flows through the
+galvanometer. The three resistances _R_, _R__{1} and _r_ and the
+resistance of the galvanometer should be small if _x_ is small, and
+great if _x_ is great.
+
+The conductors _A B_ and _A D_ of the bridge are each formed of
+three resistance coils having a resistance of 10, 100, and 1000 ohms
+respectively, inserted between the terminals _B_ and _D_ of the
+balance, Fig. 94.
+
+The conductor _D C_ is formed of a set of resistance coils from 1 up
+to 4000 ohms, amounting altogether to 11,110 ohms, inserted between
+the terminals _D_ and _C_ of the balance; in the balance, a brass plug
+being inserted between the terminals _D_ and _D__{1}, they may be
+considered as one terminal _D_. The conductor _B C_ is the wire to be
+tested, and is connected to the terminals _B_ and _C_ of the balance.
+
+_Measurement of Resistances._--When a resistance is to be measured
+that is within the range of the coils in _R__{1}, _R_ and _r_ are
+made equal. The needle of the galvanometer will move in a different
+direction, either to the right or to the left, according as the
+resistance in _R__{1} is greater or less than the line wire _x_. The
+needle remains at zero only when the resistance in _R__{1} is equal to
+that in _x_. For _r_ : _R_ :: _R__{1} : _x_.
+
+[Illustration: WHEATSTONE'S BRIDGE.
+
+PLATE XXVI]
+
+When the resistance of _x_ is greater than that of _R__{1}, as in an
+insulation test, the resistance in _r_ is made _less_ than that in _R_,
+in order that _r_ and _R_ may have such a proportion one to the other
+as will enable the coils in _R__{1} to balance a resistance in _x_,
+greater than their own, that is to say, greater than 11,100 ohms; thus
+_r_ : _R_ :: _R__{1} : _x_, or 10 : 1000 :: 10,000 : 1,000,000, the
+resistance in the line to be tested would be 1,000,000 ohms, supposing
+the values of _r_, _R_ and _R__{1} to be respectively 10, 1000, and
+10,000 ohms.
+
+When the resistance to be tested is less than that of the least coil
+in _R__{1} (1 ohm), then the resistance in _r_ is made greater than
+in _R_. Thus _r_ : _R_ :: _R__{1} : _x_, or 100 : 10 :: 2 : 0·2; the
+resistance of the line to be tested would in this case be 1/20 of an
+ohm.
+
+_Manipulation._--In all cases the key in connection with the battery
+should first be depressed, then the galvanometer key, making very short
+contacts by the latter, just sufficient to show the direction of the
+deflection, until the coils in _R__{1} are nearly adjusted, otherwise
+considerable time will be lost in making a series of tests, owing to
+the swing given to the needle, which will take some little time before
+it again remains steady at zero. When once the coils in _R__{1} are
+adjusted, and a balance obtained, it should be ascertained whether the
+needle will remain steady when contact is made and broken.
+
+_Test Tables._--In connection with a system of testing electrical
+submarine mines, for the sake of convenience and simplicity it is
+necessary to use a table (termed a "Test Table"), on which all the
+apparatus used for the purpose of testing are fixed. Several forms of
+tables have been designed for such a purpose. At Fig. 95 is shown the
+method of arranging such a table.[L]
+
+_A_ is an astatic galvanometer placed between two switch plates, _B_
+and _C_; ten other similar switch plates, 1, 2, 3, 4, _D_, 5, 6, 7,
+_E_, and 8, are arranged in front of the galvanometer _A_; _F_, _G_,
+and _H_ are three terminal plates; _K_ is a box of resistance coils
+used in connection with the thermo galvanometer _M_; _L_ is a firing
+key, and _N_ a battery commutator; _O_ is a three-coil galvanometer;
+_R_ is a Wheatstone balance (Post-office pattern).
+
+The ten switch plates, 1, 2, 3, 4, _D_, &c., are used for the
+connection of any particular line to be tested, as well as for the
+earth connections and instruments employed in that operation.
+
+_"Sea Cell" Tests._--The arrangement shown in the figure is that
+required in connection with the sea cell test, and Mr. Brown's method
+of keeping certain earth plates in a bucket instead of in the sea.
+
+If two plates of suitable metal to form a Voltaic battery are placed in
+salt water and connected by a metallic conductor, a battery is at once
+formed capable of producing considerable deflection on a moderately
+delicate galvanometer. Testing by this arrangement has been termed the
+"sea cell" test.
+
+_Arranging Earth Plates._--Mr. Brown's, Assistant-Chemist to the War
+Department, method of arranging the earth plates is as follows:--
+
+A series of earth plates, such as copper, carbon, tin, zinc, &c., are
+placed in a bucket filled with sea water, and which is placed in the
+testing room. The water in the bucket is put in connection with the
+water of the sea by means of a conducting wire, terminating at one end
+with a zinc plate in the bucket, and at the other with a zinc plate in
+the sea. By this means the tests made with the different earth plates
+in the bucket are identical with those made with corresponding earths
+placed absolutely in the sea, and therefore these latter may be done
+away with, the sea cell tests being entirely carried out by means of
+the bucket earth plates.
+
+In addition to the bucket earth plates there will be several other
+earth plates in connection with the testing room, these being placed in
+the sea, such as the zinc earth for the firing battery, the zinc earth
+for the signalling battery, &c.
+
+_Connections of Switch Plates._--The switch plate _D_ is used for the
+connection of any particular mine cable which it may be required to
+test. The switch plate _E_ is connected with a zinc earth plate used
+for testing the firing battery. This must always be in the sea. The
+switch plate 1 is in connection with a zinc earth in the bucket; 2 is
+attached to a copper earth plate in the bucket; 3 is attached to a
+carbon earth plate in the bucket; 4 to a tin earth plate in the bucket;
+5 is used for connection with the zinc signalling earth connection in
+the sea; 6 is attached to a copper earth plate used for the sea cell
+test, or any other purpose required, in the sea; 7 is attached to a
+zinc earth plate in the sea; and 8 is a common zinc earth in the sea.
+
+The terminal plates _G_ and _H_ are used for the connection, for
+testing purposes of the negative and positive poles, of the firing
+battery, and _F_ is connected with a zinc earth in the sea, for a
+similar purpose. These plates are in connection with the resistance
+coils _K_ and the thermo galvanometer _M_, employed for testing the
+firing battery, the circuit being closed by the firing key _L_. Other
+ways of using these plates may of course be adopted if desired. The
+resistance coils _K_ range from 0·5 to 100 ohms, and are composed of
+wire adapted for the passage of a quantity current. A reversing key is
+generally used in connection with a testing battery and the three-coil
+galvanometer _O_. This reversing key would consist of two bridges
+completely insulated from each other, the upper one attached to the
+negative, the lower one to the positive pole of the test battery. In
+their normal position both keys press against the upper bridge, and
+until one or other of the keys is pressed down no current will pass,
+the direction of the current being altered by pressing down a different
+key. The point of each key is provided with a terminal and connected,
+the one to a zinc earth through the switch plate 8, the other to one
+terminal of the three-coil galvanometer when the tests are to be
+applied.
+
+The Wheatstone balance _R_ is used in finding the resistances of
+electrical cables, balancing fuzes, &c. By means of a commutator, _N_,
+the necessary number of cells for any particular test may be thrown in
+circuit when required.
+
+_Test of Platinum Wire Fuze for Conductivity._--The platinum wire fuze
+may be tested electrically as follows:--
+
+If placed in circuit with a few cells of a Daniell or Leclanché
+battery and a detector galvanometer, before the platinum wire bridge
+of the fuze is fixed, there should be no deflection of the needle,
+for no metallic circuit exists; if it did, such would be fatal to the
+efficiency of the fuze. If similarly placed in circuit after the bridge
+has been fixed, a considerable deflection of the needle should result,
+such deflection being due to the current passing through the metallic
+bridge, which to be efficient ought to be the sole medium through which
+the circuit is completed.
+
+_Test of Resistance of Platinum Wire Fuze._--The electrical resistance
+of a platinum wire fuze is ascertained by means of the Wheatstone's
+balance _R_ and galvanometer _A_, Fig. 95. The terminals of the fuze
+are connected to the binding screws of the balance, the commutator _N_
+and galvanometer _A_ being connected up in circuit. The resistance of
+the coils is then adjusted by taking out plugs until the needle of the
+galvanometer _A_ is brought to zero, when the sum of the resistances
+indicated by the unplugged coils will be equal to that of the fuze. The
+resistance of a platinum wire fuze might also be ascertained by means
+of a differential galvanometer instead of a Wheatstone balance.
+
+The electrical resistance of 3/10" of fine platinum wire, weighing 1·9
+grains to the yard, is 3/10 of an ohm nearly (Schaw).
+
+_Testing High Tension Fuzes._--High tension fuzes require very delicate
+and careful management in testing them, due to the high electrical
+resistance of such fuzes, which ranges from 1500 to 2000 ohms, combined
+with the danger of premature explosion when testing even with a small
+number of battery cells. Very sensitive galvanometers, such as the
+reflecting galvanometer, should if possible be used, otherwise the mode
+of making the tests for conductivity and resistance of a high-tension
+fuze is similar to that already given for a platinum wire fuze.
+
+Detonating fuzes should always be placed in an iron case during the
+process of testing.
+
+_Insulation Test for Electrical Cables._--To test an electrical cable
+for insulation, it should first be put in a tank of water, or in the
+sea, and allowed to soak for at least forty-eight hours. The object of
+this is to allow the water to penetrate the outer protection of hemp
+and iron wires, &c., and to search out and get into any weak places
+there may be in the insulation under the armouring. At Fig. 96 is
+shown the method of performing this test. _A_ is a tank holding the
+electrical cable, which has been in soak for forty-eight hours; _B_ is
+an astatic galvanometer; _C_, _Z_ a Leclanché or Daniell battery of
+great power; and _C_ is an ordinary firing key. One end of the electric
+cable _D_ is connected to the galvanometer _B_ through the firing key
+_C_; the other end of the cable is very carefully insulated; one pole
+of the battery is connected to the galvanometer _B_, the other is put
+to earth in the tank at _F_; should the insulation be perfect, no
+deflection of the needle should follow on the key being pressed down.
+A very slight deflection might be observed on a moderately sensitive
+galvanometer, due to the current passing through the insulation; its
+whole length being immersed, the surface through which such a current
+would pass would be large, and the sum of the infinitesimally small
+quantities escaping over the whole length, would in the aggregate be
+sufficient to deflect the needle to a small extent in completing the
+circuit of the battery. Should any considerable deflection occur,
+it would indicate a defect or leak in the insulation of the cable,
+the extent of which would be roughly measured by the amount of such
+deflection.
+
+By using a reflecting galvanometer a very much more delicate test
+would be obtained, but for the comparatively short lengths of electric
+cables used in connection with submarine mines, such accuracy is hardly
+necessary.
+
+To test an electric cable for conductivity, it would be only necessary
+to expose the metallic conductor _G_, and put it in the water of the
+tank. If the conductivity were good, then the whole of the current
+would pass through the cable and the needle of the galvanometer would
+be violently deflected. If the continuity were broken, no deflection
+would be observed.
+
+_Defects observed in the Conductivity of the Cable._--To ascertain the
+position of a defect in the insulation of a cable, as indicated by the
+tests above described, it would be only necessary to keep a continuous
+current flowing through the cable, and gradually take it out of the
+tank. If the fault existed at a single point, the deflection of the
+needle would be suddenly reduced at the moment of that point of the
+cable being lifted out of the water, and therefore its position would
+be determined with considerable accuracy. Should several defects exist
+as each was lifted out, a sudden reduction of the deflection would
+occur.
+
+_Discharge Test._--The conductor of an electrical cable may be broken
+without destroying the insulation, and on applying the foregoing
+tests, good insulation would be indicated, but no conductivity, and no
+information would be given as to the position of the fault. Under such
+circumstances the following test must be applied:--
+
+Put one pole of a very powerful battery to earth, and charge one
+end of the defective cable, then immediately discharge it through a
+reflecting galvanometer, and note the extreme limit of the swing of the
+needle, then, charge the other end of the cable in a similar manner,
+and discharge it through the same galvanometer, noting as before the
+swing of the needle. This should be done three or four times, and the
+average of the deflections taken. Then the position of the fault would
+be indicated by the proportion between the average deflections in each
+case, and the cable might safely be cut at that point. Should the
+precise position of the fault not be discovered in thus cutting the
+cable, each section should be tested again for conductivity, and that
+in which a fault was still found to exist should be again tested by the
+discharge as before.
+
+_Test of Electrical Resistance of Cable._--This is effected by
+balancing it against the Wheatstone balance, in a similar manner to
+that explained for a fuze. The electrical resistance of the conductor
+of a cable affords a very correct indication of the quality of the
+metal of which it is composed. For a very delicate test the reflecting
+galvanometer should be used.
+
+_Electrical Test of Insulated Joints._--Insulated joints and
+connections, whether of a permanent or temporary nature, should be
+tested electrically, in a precisely similar manner to that explained
+for electric cables.
+
+They should be soaked for forty-eight hours, and then tested for
+insulation, conductivity, and electrical resistance.
+
+In testing permanent joints special tests are carried out, which are
+described by Mr. Culley in his 'Handbook of Practical Telegraphy.'
+
+Voltaic batteries should be subjected to the following tests:--
+
+    1.--For potential.
+    2.--For internal resistance.
+    3.--For electromotive force.
+
+For the purpose of testing the potential of a battery, one pole should
+be put to earth, and with the other one pair of the quadrants of a
+Thomson's reflecting galvanometer should be charged; when this is done,
+a certain deflection of the spot of light will occur, and the amount
+of such deflection, as compared with that produced by a standard cell
+applied to the instrument in a similar manner, would give the relative
+value of the potential of the battery.
+
+The following method of determining the internal resistance of a
+battery is that recommended by Mr. Latimer Clark in his book on
+electrical measurements.
+
+The instrument employed is a double shunt differential galvanometer,
+a diagram of which is shown at Fig. 97. Connect the battery and a set
+of resistance coils in circuit between the terminals _A_ and _D_, and
+insert plugs in the resistance coils so that they give no resistance;
+insert plugs at _A_ and _C_, and also both the shunt plugs at _A_ and
+_D_. The current will now flow through one half of the galvanometer
+circuit only, being, however, reduced to 1/100 of its amount by the
+shunt _D_; the deflection of the needle must be carefully read. The
+plug _A_ must now be removed to _B_, which causes the battery current
+to flow through both halves of the galvanometer (each being shunted).
+The circuit will now be as shown in the figure, and the needle will
+of course be deflected somewhat more than before. Now unplug the
+resistance coils which are in circuit with the battery until the
+deflection of the needle is reduced to its original amount, and the
+resistances unplugged will be equal to the internal resistance of the
+battery.
+
+The following is another method of ascertaining the internal resistance
+of a battery cell.
+
+A circuit is formed, consisting of the battery cell, a rheostat, and
+a galvanometer, and the strength _C_ is noted on the galvanometer.
+A second cell is then joined with the first, so as to form one of
+double the size, and therefore half the resistance, and then by adding
+a length _l_ of the rheostat, the strength is brought to what it
+originally was, _C_.
+
+Then if _E_ is the electromotive force, and R the resistance of cell,
+_r_ the resistance of the galvanometer, and other parts of the circuit,
+the strength _C_ in the one case is C = E / (R + _r_), and in the other
+= E / ((1/2)R + _r_ + _l_), and since the strength in both cases is the
+same, R = 2_l_, i.e., the internal resistance of the cell is equal to
+twice the resistance corresponding to the length _l_ of the rheostat
+wire.
+
+The comparative electromotive force of a battery may be determined by
+means of a double shunt differential galvanometer in the following
+method, as recommended by Mr. Latimer Clark.
+
+"This can only be done relatively in terms of some other standard
+battery. First determine the resistance of the standard and of the
+other cells to be measured; then insert the shunt plugs at _A_ and _D_,
+Fig. 97, and also at _C_ and _B_, and join up the standard cell in
+circuit with a resistance coil to the terminals _A_ and _D_, and unplug
+the resistance coils until a convenient deflection is obtained, say
+15°; note the sum of the resistances in circuit, including that of the
+battery galvanometer, resistance coil and connecting wires; now change
+the battery for another, and by unplugging the resistance coils bring
+the needle again to the same deflection, 15°; having again found the
+total resistance in the circuit, the relative electromotive force will
+be directly proportional to these resistances."
+
+The electromotive force of a battery may also be measured statically
+by means of Thomson's quadrant electrometer, the poles of the battery
+being connected with the two chief electrodes of the instrument, in
+which arrangement no current will pass, and the electromotive force
+will be directly indicated by the difference of potential observed.
+
+In the case of a quantity battery, that is, a battery capable of fusing
+a fine platinum wire, its electromotive force and internal resistance
+may be determined by means of the resistance coils _K_, and thermo
+galvanometer _M_, shown at Fig. 95.
+
+_Tests after Submersion._--After an electrical submarine mine has
+been placed in position, it should be immediately tested to ascertain
+that all is right, and similar tests should be applied at intervals
+to ascertain that the charge remains dry; that the insulation and
+conductivity of the electric cable remains the same; and that its
+electrical resistance indicates a state of efficiency.
+
+The nature of the tests applied to determine these points will depend
+upon the nature of the combination in which the mine is arranged.
+
+The manner of applying the "sea cell" test, by which is ascertained the
+condition of a system of electrical submarine mines, will be readily
+understood from the following examples.
+
+The arrangements for testing to ascertain whether a charge is dry, or
+wet, is shown at Fig. 98.
+
+_z_ is a plate of zinc introduced in the circuit within the charge, and
+between the fuze and the shore; another earth plate of carbon _x_ is
+connected with the electric cable beyond the fuze, forming the ordinary
+earth connection of the system at that point; and at home a copper
+earth plate _c_ is used.
+
+First, in the case of a dry charge with the insulation and conductivity
+of the cable, good; under these circumstances there would be formed a
+sea cell between the earth plates _x_, and _c_, which would produce a
+certain deflection of the needle of a galvanometer _g_, which is placed
+in the circuit, and in a certain direction.
+
+Secondly, in the case of a charge becoming wet, through leakage,
+with the insulation and conductivity of the cable, good; under these
+circumstances, a sea cell would be formed between the plates _c_ and
+_z_, causing a different deflection of the needle in amount and in
+direction, by which it would be at once indicated that the charge had
+become wet.
+
+[Illustration: TEST TABLE, DIFFERENTIAL GALVANOMETER.
+
+PLATE XXVII]
+
+_"Sea cell" Test for Insulation._--Again, in the case of the insulation
+of the electric cable being damaged to such an extent as to expose
+the copper conductor. Under these circumstances there would be
+formed a sea cell between the copper earth plate _c_, and the exposed
+copper conductor of the cable, by which a certain definite deflection
+of the galvanometer would be observed, which deflection would differ
+in character from that produced by the copper carbon sea cell, when
+the insulation of the cable was good, and the system in working order,
+and therefore it would indicate that some change in the electrical
+conditions of the system had occurred. The fact that a leak existed in
+the insulation would be proved by changing the earth plate at home from
+copper to zinc, carbon, tin, &c.
+
+In the case of no deflection being produced on the galvanometer, on
+applying the sea cell test, a want of continuity, or inefficient
+connections would be indicated.
+
+The foregoing afford examples of the vast utility of the "sea cell"
+in connection with a system of electrical tests for submarine mines,
+numerous variations of which may be effected by employing a series of
+earth plates, of different metals, at the home end of the circuit, in
+connection with a carbon and zinc earth plate at the other end. And
+the mode of manipulating these tests may, by means of numerous switch
+plates, as shown at Fig. 95, be made extremely simple and efficient.
+
+_Armstrong's System of Electrical Testing._--A very simple method of
+testing electrical submarine mines, with which low tension fuzes are
+used, has been devised by Captain Armstrong, R.E., and is shown at
+Fig. 99. _a_ is the electric cable leading from the shore; _b_ the
+cable attached to a polarised relay _c_, and connecting the charge
+through the fuze _f_ to the earth; _b'_ the cable, attached to another
+polarised relay _c'_, and connecting the mine with the circuit closer;
+the polarised relay _c_, in the mine, is arranged to be worked by a
+positive current, that is to say, the wire surrounding the core is
+so wound as to increase the polarity of the electro magnet, near the
+armature _d_, when a positive current is passed through it, and to
+diminish the polarity when a negative current is passed through the
+wire surrounding the core; the polarised relay _c'_ within the circuit
+closer is arranged to be worked by a negative current, the coil being
+so wound as to produce an influence exactly the reverse of _c_.
+
+Then, a positive current passing along the line wire _a_, the
+armature _d_ in the charge will be attracted, while _d'_ will remain
+unaffected; again, if a negative current be circulated, the armature
+_d'_ within the circuit closer will be attracted, while the armature
+_d_ will remain unaffected. Two insulated wires forked together are
+wound round each electro magnet, one a thin wire (_g_ and _g'_) having
+a considerable resistance, about 1000 ohms, being connected direct to
+the earth plates _e_ and _e'_, and the other a thick wire (_h_ and
+_h'_) offering a very small resistance, and so arranged that when the
+armature is attracted, they may be in contact with and complete the
+circuit through the armature to earth.
+
+The thin wire coils are so arranged that a certain number of Leclanché
+cells (ten or twelve, as may be desired) will make the electro magnets
+act, while with fewer cells the current would be too weak, and would
+therefore pass through them to earth without affecting the armature.
+
+By means of the three-coil galvanometer, a table of the deflections,
+obtained by the foregoing system of testing, should be carefully
+recorded, when the circuit is known to be in good working order, so
+that any defect in the circuit would be at once indicated on the
+application of the various tests, by the results so obtained differing
+from those originally recorded. When a system of submarine mines is
+placed in position for the purposes of practice and experiment, every
+trouble should be taken to endeavour to fix the exact position of
+any defect that may exist, also to ascertain its magnitude, &c., but
+in time of war, should a defect exist in the system, no time must be
+lost in such operations, but the mine at once lifted, and the fault
+repaired, or a fresh one laid in its place, unless the presence of an
+enemy or other imperative cause should prevent such work being done.
+
+_Austrian Testing Table._--The following is a description of the
+Austrian testing table, and their mode of making electrical tests with
+it, in connection with their system of self-acting electrical submarine
+mines.
+
+[Illustration: METHODS OF TESTING.--ARMSTRONG,--AUSTRIAN.
+
+PLATE XXVIII]
+
+Its design is shown at Fig. 100; _c z_ represents the battery with one
+pole to earth at _e_, and the other in connection with an intensity
+coil _a_, through which the current passes to the contact plate _b_.
+When it is desired to put the system of mines in connection with the
+table, in a state of preparation to be fired by the contact of a
+vessel, a plug is inserted between the contact plates _b_ and _f_,
+and the current passes through the galvanometer _g_, and electrically
+charges the conducting wires connecting the mines with the battery,
+through the several binding screws on the contact plates, numbering
+1, 2, 3, &c. The fact that the charge has been fired is also at once
+indicated on the galvanometer _g_.
+
+_Test to discover an Exploded Charge._--It then becomes necessary to
+ascertain which particular mine of the system has been exploded; for
+this purpose a separate circuit in connection with a single cell _d_
+is employed. This cell is in connection through a galvanometer _g'_ (a
+more sensitive instrument than the galvanometer _g_) with the pivot of
+the key _h_, and rheotome _R_, which latter is connected, as shown by
+the dotted lines, with each individual mine of the system attached to
+the contact plates numbered 1, 2, 3, &c. The handle of the rheotome is
+moved round, to each number in succession and directly it is placed in
+contact with that corresponding to the exploding mine, the electrical
+circuit is completed through the exposed end of the fractured wire, and
+this is indicated by the galvanometer _g'_. During the testing process
+the firing battery _c z_ must be disconnected; this is done by raising
+one of the bridges _i i_ with which each group of ten mines is provided.
+
+_Insulation Test._--The rheotome and testing galvanometer _g'_ are
+also used to test the insulation of the electric cables connecting
+the mines to the testing table. This is done in precisely the same
+manner as testing for an exploded mine: the handle of the rheotome is
+turned round, and each cable connected in succession with the testing
+circuit as before; should the galvanometer _g'_ remain stationary,
+the insulation is good; but should a defect of insulation exist, the
+current passing through it would act on and deflect the galvanometer,
+indicating the particular line in which it exists, and, roughly, its
+extent in proportion to the deflection shown; should the fault be
+considerable, the defective cable should be at once detached, as the
+current lost through it might so diminish the working power of the
+firing battery, as to prevent it exploding any of the fuzes attached
+to the group in connection with it. By the above arrangement, the
+insulation of each line can be tested at any moment required.
+
+In making the delicate test for insulation, which should invariably
+be done at leisure, and, if possible, when an enemy's vessels are
+not in the vicinity of the mines, a large number of Daniell's or
+other cells of suitable form should always be used. To do this,
+it would only be necessary to connect such a battery in place of
+a single cell permanently arranged, as described, in the testing
+circuit, and to proceed with the details of the operation as before.
+As the cable would, in actual work, always be charged with the full
+power of a firing battery, the value of its insulation to resist an
+electrical charge at such a high potential would be an important
+point to determine. The fuzes being entirely out of the circuit till
+the moment of the action arrives, no danger of a premature explosion
+need be apprehended; if a fuze were in such a position as to be fired
+prematurely, it would be exploded, in connection with the firing
+circuit, independently of the operation of testing the insulation of
+the cables.
+
+_To render a Channel Safe._--In order to render the channel safe for a
+friendly vessel, it is only necessary to remove the plug from between
+the contact plates _b_ and _f_; this disconnects the firing battery
+from the circuit.
+
+_Defence of Harbours by Booms, &c._--Booms or cables supported by rafts
+may also be employed in the defence of harbours, or rivers, either by
+themselves, or in combination with submarine mines; in the latter case,
+the booms, &c., may be moored either in advance of the mines, or in
+rear of the front row, this last method of mooring them being the most
+effective one.
+
+There are a great variety of forms in which a boom may be constructed.
+The qualities essential for a good and practicable boom are:--
+
+    1.--Great strength.
+    2.--Great power of resistance.
+    3.--Convenience in handling.
+    4.--Easy to manipulate.
+    5.--Its materials easily procurable.
+
+_Construction of a Boom._--The general construction of a boom consists
+of a main cable, buoyed up at intervals by floats. The main cable may
+be either wire, chain, or rope, the former being very much superior for
+this purpose to chain or rope. The floats consist of balks of timber
+built round the main cable and bound together by means of iron hoops
+&c. A space is left between each float, by which a certain amount of
+flexibility in the boom is obtained, without which it would be of
+comparatively little use, as it might be easily overrun.
+
+It must be borne in mind, in constructing all such booms, that the
+smaller the proportion of timber used in forming the floats to the
+cable, consistent with buoyancy, the stronger will be the structure.
+
+A very important feature in connection with such a mode of defence is
+the manner of mooring it; for if it be moored so as to be unyielding,
+then its sole power of resisting a vessel charging it is the actual
+strength of the materials composing the structure, but if it be moored
+so that it is capable of yielding to a sudden blow, this force will
+be to some extent absorbed, and resistance of the defence greatly
+increased.
+
+The raft employed to support the main cable should be moored by means
+of very heavy chains (without anchors) in the direction of the attack,
+and with ordinary anchors and cables on the other side.
+
+As a rule, the booms should be moored obliquely to the direction of the
+current, where there is any, as the tendency of the current to overrun
+the boom when so placed will be less, and also a ship ramming it must
+place herself athwart the current to attack the boom at right angles.
+
+_Clearing a Passage through the Torpedo Defences of an Enemy._--The
+subject of clearing a passage through the torpedo defences of an
+enemy is one fraught with innumerable difficulties, on account of the
+varied nature and impracticability of obtaining accurate and _certain_
+information of such defences, and thus it is impossible to lay down any
+fixed rule or plan for carrying out such an operation.
+
+In fact, it will be only under the most favourable circumstances that
+such a service will be successfully accomplished, that is to say,
+in the case of a harbour or river defended by submarine mines but
+unsupported by guns, or guard boats, or where the electric light is
+used.
+
+Numerous methods have been devised from time to time to effect the
+destruction of an enemy's submarine defences, among which are the
+following:--
+
+    1.--Projecting frames, &c., from the bows of a vessel.
+    2.--Creeping and sweeping by boats.
+    3.--Countermining.
+
+_Projecting Frames, &c., from the Bows of a Vessel._--This method
+was adopted by the Federals during the American civil war of 1861-5,
+and in many instances it was the means of saving their ships when
+proceeding up rivers which had been torpedoed by the Confederates,
+though notwithstanding this precaution several vessels were sunk. The
+submarine mines against which this mode of defence was used, were in
+nine cases out of ten mechanical ones, and therefore the framework
+defence afforded a better means of protection then, than would be the
+case now that electrical ground mines and circuit closers are used, as
+the framework would catch the circuit closer only, and the vessel would
+probably be over the mine when the explosion took place. The Americans
+moor their circuit closers in rear of their mines, so that a vessel
+fitted with a bow frame or not, coming in contact with the former must
+be right over the charge at the instant of explosion.
+
+Against ground electrical mines fired at will, the bow net, &c., is
+no protection whatever, still under certain circumstances it would be
+found extremely useful.
+
+_Sweeping for Submarine Mines._--This method of clearing a channel of
+submarine mines could not possibly be carried out under artillery fire,
+but in waters not so defended it would prove of some value.
+
+Where only buoyant mines, or ground mines with circuit closers are
+to be cleared away, two or more boats dragging a hawser between them
+would be sufficient to discover them, and so lead to their destruction;
+but where dummy mines and inverted creepers are moored in addition,
+another method of sweeping must be resorted to, viz., that of bringing
+an explosive charge of gun-cotton to act on the obstruction grappled,
+and thus destroy it. This is effected by lashing a charge to each end
+of the sweep, so that whatever is grappled may slide along it, until
+caught by hooks, which are attached for this purpose to the centre
+of the charge. On grappling an obstruction, the two boats drop their
+anchors, one hauling in, the other veering out the sweep, until the
+charge is hooked by the obstruction; this being effected, the boats
+move out of range, and the charge is fired.
+
+_Creeping for Electrical Cables, &c._--Creeping is the method employed
+for picking up the electric cables of the enemy's submarine mines, and
+is effected by boats towing an ordinary grappling iron, or specially
+prepared creeper on the ground.
+
+In both sweeping and creeping it would be found necessary to employ
+a diver, who would ascertain the nature of the grappled obstructions
+which could not be easily raised by the boats.
+
+The Lay torpedo boat, which is fully described in the chapter on
+offensive torpedoes, is capable of being used for the foregoing
+purposes.
+
+_Countermining._--Countermining, that is, the destruction of submarine
+mines by the explosion of other mines dropped close to them, will
+under certain conditions prove of great use in clearing harbours of
+mines. This method could not be operated in waters properly guarded and
+swept by artillery fire.
+
+There are two distinct methods of laying out countermines, viz.:--
+
+    1.--In a boat, which may be either towed, or hauled out
+    to its destination, or may be steered, and controlled
+    by electricity.
+
+    2.--By attaching them to buoys so that they are
+    suspended at the proper depths, and then hauled out by
+    means of a warp to an anchor which has been previously
+    placed in position.
+
+Both of the foregoing methods have been successfully manipulated in
+practice, the first method, where the boat carrying the countermines is
+towed either by a pulling or steam boat being the most practicable one.
+A large amount of material would be required for clearing a channel by
+means of countermines: for example, if the mines to be attacked require
+500-lb. gun-cotton charges to be used, 7-1/2 tons of the explosive,
+besides cables, buoys, &c., would be required to clear a passage about
+one mile in length and 200 feet in width.
+
+A ship's launch will carry about twelve of these 500-lb. countermines,
+with all the gear attached thereto.
+
+Experiments to ascertain the effect of countermining have been carried
+out in England and Europe for the last five years, some of which are
+given at length in the chapter on "Torpedo Experiments." During the
+Turco-Russian war, a portion of the Danube was swept in the ordinary
+and most simple manner by the Turks, and five Russian electro contact
+buoyant mines were picked up; one other exploded during the process of
+dragging it to the surface, but no injury occurred to those at work.
+
+_Destruction of Passive Obstructions._--To clear away booms, or other
+passive obstructions, if not possible to cut them away, they may be
+destroyed by outrigger boats exploding their torpedoes underneath, and
+in contact, or by attaching charges of gun-cotton at intervals, and
+then exploding them simultaneously. When a chain is horizontal, and
+therefore somewhat taut, a charge of 3-1/2 lbs. of gun-cotton (this
+explosive, being the most effective and convenient for such purposes,
+should always be used) will be found sufficient to destroy it, no
+matter what size, and whether the chain is in or out of the water, the
+charge being of course placed in contact with it. Great uncertainty
+must always attend the supposed clearance of a channel, or passage
+of submarine mines, as was exemplified during the American civil war,
+when most of the Northerners' vessels were destroyed while moving over
+ground which had been previously carefully dragged, and buoyed, and
+this fact, coupled with the tediousness and danger of performing such a
+service, proves the enormous value of a system of defence by submarine
+mines.
+
+FOOTNOTES:
+
+[Footnote J: 'Electricity and Magnetism,' by Professor F. Jenkins.]
+
+[Footnote K: See Appendix.]
+
+[Footnote L: As constructed by Mr. J. Mathieson, late R.E., at the
+Silvertown Telegraph Works, Essex.]
+
+
+
+
+CHAPTER V.
+
+OFFENSIVE TORPEDO WARFARE.
+
+
+THE term "Torpedo" is applicable more particularly to offensive
+submarine mines than to those employed for the purposes of defence, and
+therefore by _torpedoes_ will be understood every kind of submarine
+explosive weapon designed to be used for active attack against vessels,
+&c., no matter how they may be manipulated.
+
+_Offensive Torpedo Warfare still in its Infancy._--Though during the
+seventeen or eighteen years that torpedoes have been considered as a
+legitimate mode of naval warfare there have occurred three big wars,
+in each of which submarine weapons, offensive and defensive, have
+played an important part, still the subject of _offensive_ torpedo
+warfare must be even now considered as in its infancy, and therefore
+any opinions expressed as to the merits and demerits of the various
+apparatus in connection therewith can but be based on the theoretical
+capabilities of each torpedo, and on the results of experiments carried
+out with them during peace time, which latter as a rule are conducted
+under far too favourable conditions to be relied upon.
+
+_Their Use during the Civil War in America._--During the American
+civil war, the only offensive submarine weapon that was used was
+the outrigger or spar torpedo, which in those days was a crude and
+imperfect machine, and manoeuvred from boats possessing all the
+features which a torpedo boat should _not_ possess. Still under these
+unfavourable conditions ships were sunk by such means by both Federals
+and Confederates, proving that in future wars this mode of attack,
+favoured by the vast and important improvements that have lately been
+effected both in connection with the torpedoes and torpedo boats,
+should play a prominent part, and prove a most destructive mode of
+attack.
+
+_Their Use in the Franco-German and Russo-Turkish Wars._--In the
+Franco-German war of 1870-1, offensive torpedo warfare was not
+resorted to by either side, the French fleet being deterred from
+entering German waters by the submarine mines placed, or at least
+supposed to be placed, in position.
+
+From the Russo-Turkish war much light was expected by torpedoists
+to be thrown on the subject of torpedo warfare, but alas, little or
+nothing was done to settle any of the many vexed questions which exist
+in regard to offensive submarine weapons. The torpedo experience of
+that struggle tended rather to prove that the vast importance hitherto
+attached to torpedo attack was much exaggerated.
+
+One of the causes which led to the failure of offensive submarine
+weapons, when employed on active service, seems to be due to the fact
+that, owing to the extremely small radius of the destructive effect
+of such weapons, it is absolutely necessary for complete success to
+explode the mine in actual contact with the attacked vessel; to ensure
+which, at night time, in an unknown harbour, with the position of the
+vessel attacked somewhat uncertain, and even without the additional
+obstacles of guard boats, booms, electric lights, &c., is a service of
+infinite difficulty, and one which may easily terminate in a failure.
+The foregoing would more especially apply to the spar torpedo attack,
+but in an attack with the Whitehead fish, or towing torpedo, there
+would be an additional cause of failure, viz., the complicated nature
+of their manipulation.
+
+Torpedoes may be divided into four classes, viz.:--
+
+    1.--Drifting or floating torpedoes.
+    2.--Towing torpedoes.
+    3.--Locomotive torpedoes.
+    4.--Outrigger or spar torpedoes.
+
+_Drifting or Floating Torpedoes._--By "drifting" or "floating"
+torpedoes are meant all those submarine machines which are dependent on
+the tide or current of a stream for their action and motion.
+
+During the American civil war this mode of attacking vessels was
+constantly employed by the Confederates, and though not successful in
+destroying any of the Federal ships, was the means of considerably
+hampering the movements of their river flotillas.
+
+Drifting torpedoes might be advantageously used for the destruction of
+pontoon bridges, booms, &c., and in this way, had the Turks in their
+late war used them, the Russians would have found the crossing of
+the Danube a matter of infinite danger and difficulty; in fact, by
+a systematic use of such weapons, combined with a little dash on the
+part of the Ottoman flotilla on the Danube, that river should have been
+to the Russians an impassable barrier. To use these torpedoes most
+effectively, especially against a single vessel, a thorough knowledge
+of the force and direction of currents should be gained before
+proceeding to undertake an operation in which these submarine weapons
+are used.
+
+Another point to be remembered is, that if such a torpedo were started
+with the flood, for example, towards an enemy, and did not explode,
+there would be a chance of its being returned to the starting-place by
+the ebb tide.
+
+In this class the following torpedoes seem the most practicable:--
+
+    1.--Lewis's drifting torpedo.
+    2.--McEvoy's drifting torpedo.
+    3.--American extempore drifting torpedo.
+
+_Description of Lewis's Drifting Torpedo._--"Lewis's" drifting torpedo,
+designed for the express purpose of destroying booms or other floating
+obstructions placed round a vessel at anchor for the purposes of
+defence, is shown at Fig. 101. It consists of a box _a_, containing the
+charge and fitted with several detonating fuzes. This box is attached
+to one side of a beam _b_, and within 6 inches of one extremity, the
+beam being about 20 feet long and 7 inches square; to the opposite
+side, of the same end of the beam _b_ a heavy weight _c_, resting in
+a shoe _d_, is attached by a long iron rod _e_, which reaches to the
+other extremity of the beam, and is there connected to a bell-crank
+lever and spring _f_, a pressure on which detaches the weight _c_; a
+chain _g_, 18 feet long, connects the weight loosely with the upper
+end of the beam, and another chain _h_, 9 feet 6 inches long, connects
+it with a point more than 2 feet below the centre of the beam. The
+apparatus is so constructed that it floats nearly vertical with the top
+of the beam just above the surface of the water.
+
+On the machine drifting against the boom or other obstruction, the
+spring or lever _f_ at the upper extremity is pressed down, thus
+releasing the weight _c_, which falling, becomes suspended by the two
+chains _g_ and _h_, and brings the beam into an inclined position. The
+weight of this mass of iron and the chain suspending it are suddenly
+brought to bear on the top of the beam, dragging it under water and
+clear of the boom, &c. At the same time the lower end, released from
+the weight, rises, and the whole apparatus is carried forward by the
+current against the side of the vessel, on striking which the torpedo
+is exploded.
+
+_Description of McEvoy's Drifting Torpedo._--"McEvoy's" drifting
+torpedo is intended to be floated, singly or in groups, by the aid of
+tides or currents against vessels at anchor, bridges, &c.
+
+At Fig. 102 is shown a plan of this form of drifting torpedo.
+
+It consists of the body of the torpedo _a_, which contains the charge,
+at the side of which is placed the loading hole _b_; _c_ is the tube
+containing the priming charge; _d_ is the framework surrounding and
+protecting the wheel or screw _e_; _f_ is the fuze pillar, in the
+centre of which is a steel rod _g_, and on the top a thin steel plate
+_h_ is placed; _i_ is the nipple for the percussion cap; _k_ is a
+horizontal bar, turning and resting on top of the fuze pillar _f_; _m_
+is the lever for supporting the hammer _n_ when it is set; _l_ is the
+screw barrel supporting the wheel or screw _e_; _o_ is a safety pin;
+_q_ is the supporting chain, and _p_ the spring for working the hammer
+_n_.
+
+By means of a buoy or log of wood, from which the torpedo is suspended,
+it can be adjusted so that the explosion shall occur at the requisite
+depth.
+
+To prepare the torpedo for use, unscrew the fuze pillar _f_, take off
+the horizontal bar _k_, place a percussion cup on the nipple _i_, and
+screw it tightly against the end of the steel rod _g_. The fuze pillar
+is then ready for use, and should be screwed into the body _a_. Then
+fill the torpedo with the explosive and close the loading hole _b_. The
+hammer _n_ is then set by drawing it back and bringing the end of the
+lever _m_ against it, at the same time running the screw barrel _l_
+under the lever _m_, so that its end catches the screw of the barrel,
+as shown in the figure. The safety pin _o_ is then put in its place and
+secured by a few parts of thread, which by a sharp jerk on the safety
+line will be easily broken.
+
+[Illustration: DRIFTING TORPEDOES.
+
+PLATE XXIX]
+
+The horizontal lever _k_, which carries the lever _m_ and propeller
+_e_, rotates on the top of the fuze pillar _f_, and is prevented from
+rising by means of a screw. The torpedo being let go, the safety pin
+_o_ is pulled out by means of a line which is attached to it. The
+propeller will not revolve whilst the torpedo is drifting with the
+current, but the instant it is stopped by the action of the current
+the wheel will be caused to revolve, and after a few revolutions it
+will unscrew the barrel from under the end of the lever _k_, and
+the latter, dropping the hammer _n_, will be forced by the spring _p_
+into contact with the thin steel plate _h_ on the top of the fuze
+pillar, which blow is transmitted by means of the steel rod _g_ to the
+percussion cap, and the torpedo exploded.
+
+_American Extempore Drifting Torpedo._--This form of drifting torpedo,
+which is readily made, was used in great numbers by the Confederates,
+and though not successful in sinking any Federal ships, caused their
+vessels considerable annoyance and delay.
+
+At Fig. 103 is shown a sketch of this torpedo. It consists of a tin
+case containing about 70 lbs. of powder. A stiff wire _a_, _b_ passes
+through a hole punctured in a strip of tin _c_, and a stuffing box _d_;
+the end _a_ of the wire is covered with fulminate, and so arranged
+that the friction caused by its passage through the strip of tin _c_
+will ignite it; a number of wires lead from _b_ to pieces of driftwood
+on the surface _e_, _e_, _e_, and the case is supported at the proper
+depth by a line attached to a section of log.
+
+_Towing Torpedoes._--By towing torpedoes are meant those submarine
+machines which are so shaped and arranged, that when towed from a ship
+or boat in motion they will diverge to a considerable extent, thus
+enabling the towing vessel to pass clear of the ship attacked, and yet
+near enough to allow of the torpedo being brought in contact with some
+part or other of her hull.
+
+Towing torpedoes were for the first time employed on actual service
+during the late Russo-Turkish war, when a modified form of the
+well-known Harvey torpedo, designed by a German officer, was used by
+the Russians, but in no case was it successful.
+
+In this class of submarine offensive machines may be placed the
+following:--
+
+    1.--Harvey's towing torpedo.
+    2.--Menzing's towing torpedo.
+    3.--The French towing torpedo.
+
+_Harvey's Torpedo._--This form of towing torpedo was invented
+conjointly by Captain John Harvey and Commander Frederick Harvey,
+R.N., and is intended to be used at sea both as a means of offence and
+defence.
+
+At Fig. 104 is shown in elevation the small sized Harvey towing
+torpedo, in which all the latest improvements that have been devised
+are represented.
+
+_a_ is the case of the torpedo, formed of Muntz's metal, but not
+provided, as the original ones were, with an exterior case of wood; by
+this alteration greater capacity combined with extreme lightness is
+obtained, which undoubtedly much enhances the value of the small size
+torpedo which is intended to be carried by and manoeuvred from boats;
+_b_ is the principal or after lever, hinged on the top of torpedo at
+_c_, and rests, when ready for action, in a crutch formed in the top of
+the exploding bolt _d_; _e_ is the foremost lever, hinged at _f_, and
+kept in position on the after lever _b_ by a groove formed in it and a
+lashing which passes through a slot in the principal lever, as at _g_;
+_h_ is the side lever, pivoted at _i_, and exerting a pressure on the
+firing bolt _d_ by means of a lanyard which is passed through the bolt
+_k_ and over the principal lever _b_; _l_ is the top lever, pivoted
+at _m_, and exerting a pressure on the bolt _d_ by means of a lanyard
+which is passed through the bolt _n_ and over the principal lever _b_;
+this top lever _l_ has been added to ensure the action of the torpedo,
+on its striking sideways against a vessel; _o_ and _t_ are handles, to
+the former of which the lashings of the levers _h_ and _l_ are secured;
+_p_ is the ring used for attaching the buoy rope; _r_, _r_ are two
+loading holes, made in the side of the torpedo case, by which a charge
+of gun-cotton may be quickly and efficiently stowed; this also is a new
+feature in the small size torpedo; _s_ is the rudder formed for the
+purpose of controlling the direction of the torpedo when the tow line
+is suddenly slacked.
+
+In regard to the large size torpedo, the construction of the case
+remains as in the original ones, the improvements being, the
+enlargement of the loading and fuze holes, and the addition of the top
+lever _l_, as shown at Fig. 104.
+
+The small size torpedo is capable of holding 47 lbs. of water, whilst
+the large size one will contain 76 lbs. of water, or about 33 lbs. and
+58 lbs. of gun-cotton respectively.
+
+The slings are made of best Italian hemp, and consist of a span of
+four legs, which are secured to lugs at the corners of the torpedo and
+connected to an iron thimble, which is shown at Fig. 105; this thimble
+is made suitable for either wire or hemp rope, and is so arranged that
+should the seizing become slack, the parts of the slings cannot become
+detached from the thimble.
+
+[Illustration: HARVEY'S TOWING TORPEDO.
+
+PLATE XXX]
+
+The legs of the slings should be so fitted that when stretched
+alongside the torpedo they extend 1 foot beyond the stem for the
+large torpedo and 8 inches for the small one; the four legs should be
+so fitted that when an equal strain is brought on them, the thimble
+should be on a level with the upper lugs, and the upper fore span form
+an angle of 80° to 85° with the side of the torpedo; this is shown at
+Fig. 106. This arrangement gives the best divergence with the least
+strain on the tow rope, and is suitable when the torpedo is kept at
+short scope, as well as when a long length of tow line is out.
+
+The mode of attaching the foremost and side levers is shown at Fig.
+107. Before reeving the lanyards they should be well greased in the
+wake of the fair leads, but not where they are made fast. The lanyards
+should be made up like a reef point. Care should be taken that the
+short arm of the side lever _h_ is brought close into the fair lead,
+and its lanyard should be set up sufficiently taut to give a slight
+spring in the principal lever _b_ by the strain thus brought on it.
+This lever _b_ has a steel fish on the top, in order to prevent it
+taking a permanent bend. If the side lever lanyard is properly set up,
+the bolt will spring down about 1/8th of an inch when the safety key is
+withdrawn, owing to the spring in the lever, and the shrinking of the
+lanyard; this brings the muzzle 1/8th of an inch nearer the pin without
+disturbing the side lever.
+
+The bolt is so arranged that the torpedo can be fired by either of the
+following methods:--
+
+    1.--Mechanically.
+    2.--Electrically at will.
+    3.--Electrically on contact or at will.
+
+_Mechanically._--In this case the bottom of the inner cylinder, as at
+_a_, Fig. 108, is fitted with the ordinary mechanical chemical fuze,
+ignition being effected by the breaking of the glass vessel containing
+the sulphuric acid on being forced into contact with the needle _n_, by
+the action of the levers on the torpedo striking a vessel.
+
+_Electrically at Will._--For this purpose a platinum wire fuze is used,
+one terminal being connected to earth through the bolt, the other to a
+wire leading up through the core of the bolt, and connected by means of
+an ebonite joint with a single cored electrical cable leading from the
+torpedo vessel.
+
+_Electrically on Contact, or at Will._--In this case, a resistance
+coil is inserted in addition to the fuze, and is so arranged that on
+the bolt being forced down a short circuit is formed, cutting out the
+resistance coil (about 20 ohms), and thus enabling the battery to fire
+the fuze, which, owing to the 20 ohms resistance in the circuit, it was
+previously unable to effect. Should the bolt so arranged be required to
+be fired at will, it is only necessary to put a more powerful battery
+in circuit, and so fire the fuze through the 20 ohms resistance.
+
+_Exploding Bolt._--The exploding bolt is fitted to act with a pressure
+of from 30 to 40 lbs. on its head for the large size torpedo, and from
+15 to 20 lbs. for the small size one.
+
+The bolts are all the same size, and differ only in the direction
+of the slot for the safety key _k_, being port or starboard bolts
+accordingly. The muzzle of the exploding bolt stands 1 inch off the pin
+when in the safety position, that is, when the safety key rests on the
+brass work of the priming case.
+
+The safety key is secured in the slot of the exploding bolt, as shown
+at Fig. 108, by eight or nine parts of strong whitey-brown thread
+secured to the key, passed round the bolt, and securely knotted; the
+parts of the thread should come away with the key, in order that none
+of the parts may be worked down the tube by the exploding bolt.
+
+In the event of the large torpedo being cut away in deep water after
+the withdrawal of the safety key, it will explode by pressure on the
+head of the bolt at about sixty fathoms depth; the small one at about
+thirty fathoms.
+
+_Buoys._--The buoys are of two sizes, and are made of solid cork
+(such cork only being used as will ensure great floating power after
+being immersed for a time); each buoy is built upon a galvanised iron
+tube running longitudinally through; on the ends of the tube are
+screwed wooden cones, which bind all together, and render the buoy
+indestructible.
+
+Two buoys are used for each torpedo, the larger buoys for the large
+size torpedo, and the smaller buoys for the small size torpedo. The
+buoy rope is of hemp, about five or six fathoms in length and two
+inches in circumference, an eye being spliced in the end nearest the
+torpedo; to this eye is bent the tow rope, with a single or double
+sheet bend forming the knot by which the torpedo is towed; the other
+end of the buoy rope is passed through one of the rings in the stern
+end of the torpedo (according to whether working in deep or shallow
+water), then through the tube of the first buoy, and an overhand knot
+made in the rear; then through the next buoy, and a knot in the rear
+of that. Recently, Captain Harvey has adopted a large and a small buoy
+for each torpedo, the large one being practically sufficient, the
+smaller one being added in the event of the other one becoming sodden.
+
+_Brakes._--The brakes are used for the purpose of controlling the tow
+ropes; they can be fixed by screws into the deck at the most convenient
+place for command, and in a properly constructed torpedo vessel would
+be placed below the water line, to prevent exposure of the men working
+them. They are so arranged as to admit of the tow rope being quickly
+veered, and at the same time are sufficiently powerful to bring the
+torpedo to the surface when required. Success greatly depends on the
+skilful handling of these brakes, for in conjunction with the cork
+buoys they give the operator command of the depth at which the enemy
+is to be struck. Unless a very high rate of speed is required, one
+handspike will control the tow rope; the other strap can be thrown off
+the drum, and the handspike allowed to lie on the deck ready to be
+thrown into gear, if necessary. The surface of the drum in contact with
+the strap should be powdered with rosin to increase the friction. The
+tow rope should be so reeled up that in veering the reel may revolve
+towards the men at the handspike. The spindle will contain several tow
+ropes, that, in the event of one torpedo being cut away, another can be
+immediately bent.
+
+The brake for small torpedo requires only one drum and handspike. It
+can be fitted to a steam launch by placing an extra thwart across near
+one of the others.
+
+Care should be taken that the riding turns lie fairly over each other,
+to prevent a jamb when veering.
+
+The brakes, both large and small, are so made as to ensure durability,
+they being considered a part of the ship's furniture.
+
+Brake for safety key line is a small reel on the same principle. When
+going a slow speed, it may not be necessary, as the safety key line
+can be attended by hand; but when going ten or eleven knots, it will
+be found of considerable advantage, both in keeping the bight of the
+safety key line from dragging astern, thereby lessening the divergence
+of the torpedo, and also in drawing the safety key when a strong stop
+is used.
+
+_Arrangements for Launching and Towing the Torpedoes._--A yard across
+either the main or mizen mast of a torpedo vessel, from 20 to 25 feet
+above the water line, is a very convenient method for launching and
+towing. The leading block on the yard, through which the tow rope is
+rove, may be fitted to a traveller on the yard with an inhaul and
+outhaul, that the distance out from the ship's side may be regulated as
+convenient.
+
+In a large vessel, the leading block for tow rope can be fixed to
+the end of the quarter-boat's davits. The brakes for commanding the
+tow rope should be screwed firmly to the deck. In a vessel properly
+constructed for the service, they would be on the lower deck, the tow
+rope having been led along the yard, and down each side of the mast.
+
+A leading block for the tow rope is placed on the deck by span or bolt
+a few feet in front of the brake. The safety key reel, if used, must
+be fixed in a convenient position on deck, that the man attending it
+can see how to control it; in a properly constructed vessel he would be
+in the pilot house. The safety key line leads through a small leading
+block on the ensign staff or some convenient point abaft the lead of
+the tow rope, 15 to 20 feet above the water. The leading block on
+the yard may be fitted with a lizard, if thought necessary. A sharp
+instrument should be kept by the brakes ready to sever the tow rope.
+
+In large men of war, arrangements are made for carrying a loaded
+torpedo and two buoys in a convenient position on each side of the
+vessel, in such a manner that the tow line can be bent, the exploding
+bolt screwed in, the levers adjusted, and the torpedoes and buoys
+dropped simultaneously when required.
+
+_Preparing the Torpedoes for Use._--The torpedoes, port and starboard,
+loaded and ballasted, having been hoisted out of the torpedo room, are
+placed on the deck on their own sides, with their heads forward under
+the leading block, and the buoys placed abaft them and strung together;
+the exploding bolts are now entered into the torpedoes, and forced down
+until their safety keys rest on the brass work, taking care that each
+safety key points in the direction of the eye through which its lanyard
+has to pass; the levers are now secured by their lanyards, as explained
+at pages 120 and 121. The eye at the end of the buoy rope is now rove
+through the large or small ring in the stern end of the torpedo. The
+tow rope having been previously rove through the leading block on the
+deck and on the yard, is rove through the thimble of the slings from
+forward aft, and bent, with a single or double sheet bend, to the
+eye of the buoy rope. The safety key line having been previously rove
+through the leading block on the ensign staff, and the lanyard on the
+safety key having been led through the eye of the handle, making a fair
+lead with the slit in the bolt, are bent together with a double sheet
+bend, and stopped to the eye of the handle by a split yarn of suitable
+strength, the yarn having been first secured to the line by a round
+turn outside the bend.
+
+The line should also be stopped with another split yarn round all parts
+of the slings close up to the thimble, having first made an overhand
+knot in the line at a distance a few inches longer than that between
+the eye bolt and the thimble.
+
+The crew having been stationed at their respective posts, the handles
+having been shipped on the tow reel, the tow line is then reeled up
+until the torpedo will launch clear, and swing out under the leading
+block on the yard. Hold the torpedo by the handspikes, and take off the
+handles of the brake. In swinging out, care should be taken that in
+starting from the deck the fore slings do not foul the fore top lever.
+The stern of the torpedo can be steadied by keeping a slight strain on
+the buoy rope. The safety key line must be kept clear, and not checked,
+or it might break the stop and draw out the key before intended. The
+buoys must be placed in a proper position and hands stationed by them
+to launch them overboard the instant the torpedo takes the water. It
+would be better to stop the screw, if circumstances would allow of it,
+when lowering the torpedo and buoys into the water, to prevent the
+chance of the buoys fouling the screw. The torpedo, on reaching the
+water, will _immediately_ diverge clear of the ship; the buoys being
+launched, as the strain comes on the buoy rope, they will be towed
+clear away from the screw, and full speed may be put on at once. The
+men at the handspikes must veer steadily, occasionally checking the
+torpedo, that it may be kept near the surface, and not allowed to dive,
+which it will do if the tow rope is slacked up altogether, and then a
+sudden strain brought on it.
+
+Eventually it will come to the surface, when the bow is pointed up
+by the strain on the tow rope; greater the speed the more quickly
+will it be brought to the surface. In shallow water this should be
+particularly attended to, as in diving it might strike the bottom and
+injure the levers, and, if the safety key has been withdrawn, explode;
+moreover, it brings an undue strain on the tow rope. The torpedo can
+now be gradually veered out to the distance required, the safety key
+line so attended that a sufficient strain is kept on it as not to
+allow of a long bight of line dragging astern of the torpedo; at the
+same time having due regard to the strength of the yarn by which the
+line is stopped to the handle of the torpedo. The distance veered must
+depend upon the nature of attack. The tow line should be marked with
+knots every 10 fathoms: under some circumstances the torpedo would be
+close to the ship until passing the enemy; at other times veered to 40
+fathoms it will be found most suitable.
+
+The full divergence of 45° is obtained up to 50 fathoms; beyond that
+the bight of the tow rope in the water drags the torpedo astern, unless
+the tow rope is triced much higher up, which has its disadvantage;
+40 to 50 fathoms of tow rope gives the best command of the torpedo,
+veering 2 or 3 fathoms of tow line suddenly will always sink the
+torpedo some feet below the surface. Should it become necessary to use
+the torpedoes with a stern board, they can be so used, but in this case
+the port torpedo is used on the starboard, bow and starboard on the
+port; all other arrangements being exactly the same. In rough weather,
+advantage should be taken of the roll, and the torpedo allowed to swing
+out from the yard, and be let go by the run, checking the tow rope
+immediately the torpedo is in the water. It is not absolutely necessary
+to ease the vessel when launching; the torpedo can be launched at full
+speed. In the event of its being found necessary to cut adrift the
+torpedo, in consequence of coming suddenly across a friendly vessel,
+the tow rope should be cut near the brake, and if the buoy rope has
+been rove through the large stern ring, the torpedo will sink and be
+lost, the buoy only remaining. If the buoy rope has been rove through
+the small stern ring, the torpedo will be suspended by the buoy rope;
+and should the safety key not have been withdrawn, can be recovered
+with safety.
+
+In the event of wishing to recover it when the buoy rope has been rove
+through the large ring, a toggle must be lashed on the tow rope abaft
+the leading block on the yard, when it can be recovered by the buoy
+rope; as a general rule, however, it will be found best to expend the
+torpedo, and not attempt its recovery.
+
+[Illustration: HARVEY'S TOWING TORPEDO.
+
+PLATE XXXI]
+
+[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.
+
+PLATE XXXII]
+
+_Recovering the Torpedo._--Should the safety key have been withdrawn,
+great caution is necessary. Tongs, shown at Fig. 109, for going round
+the upper part of the bolt, to take the place of the safety key,
+when once clasped and secured round the bolt, render the torpedo
+safe to handle; this could only be done from a boat. With the safety
+key in, there is no danger in hoisting it inboard again by its own tow
+rope, and hoisting up the buoys at the same time with a grapnel.
+
+_Different Methods of Using the Torpedo._--There are two methods of
+employing the torpedo, either of which may be adopted, according to
+circumstances.
+
+    1.--When it is towed with a length of line varying from
+    25 to 60 fathoms, and dipped when in position to strike
+    the attacked vessel.
+
+    2.--When it is kept suspended from the yard, &c., and
+    dropped at the spot, where according to the first
+    method it would have been dipped.
+
+In the first method, it is not necessary to withdraw the safety key
+till just before dipping; in the second method the safety key line is
+belayed at about twenty fathoms, and the key withdrawn when the line is
+tautened by the ship going ahead.
+
+_Tactics._--Description of the various attacks that may be made with
+the Harvey torpedo against a ship at anchor or under way. In the
+following diagrams _T_ is the torpedo vessel, _S_ the ship attacked.
+
+[Illustration]
+
+    ...... The track.
+    ------ The tow rope.
+    O-o-o  The torpedo.
+
+_Attacking a Vessel moored Head and Stern._--In this case the torpedo
+vessel steers in for the bow or quarter of the vessel attacked,
+according to the direction of the current, and on the side approached
+launches the torpedo between the moorings, as at _A_; leaving the tow
+rope slack, the torpedo vessel proceeds ahead or astern against the
+current, and when at a sufficient distance off, the tow rope is held
+fast, which will cause the torpedo to diverge into contact with the
+vessel attacked, as shown by Fig. 110.
+
+_Attacking a Vessel at Anchor by Crossing her Bow._--In this case
+the torpedo is sufficiently diverged when near to the vessel with a
+good scope of tow rope out. After having crossed her bow, proceeding
+onwards, the tow rope will be brought obliquely across her cable, and
+the torpedo will swing into her, as shown at Fig. 111. It may be here
+remarked, that in all cases the depth of the explosion can be obtained
+by the sudden slacking of the tow rope; and the tow rope once under
+the keel, causes the torpedo to be hauled down near to it before
+exploding.
+
+_Attacking a Vessel at Anchor by coming up from Astern on either
+Side._--In this case the torpedo is launched when on the quarter of the
+vessel attacked, as at _A_, the tow rope left slack. After steaming
+ahead some distance, hold fast the tow rope, when, by continuing to
+steam on, the torpedo will diverge into contact with the bottom of the
+vessel attacked, as shown at Fig. 112. _When skilfully performed_,
+the total destruction of the enemy is certain, since the torpedo is
+springing from a depth to the surface, and will, in consequence, strike
+near her keel. The torpedo vessel can pass at her greatest speed, and,
+if thought necessary, near enough to clear away any of the ordinary
+obstructions, such as booms, nets, &c.
+
+_Passing Down between Two Lines of Vessels at Anchor._--In this case it
+would be impossible to fire at the torpedo vessel, for fear of injury
+to their friends. Two or more torpedo vessels following each other with
+preconcerted signals would cause great destruction. See Fig. 113.
+
+_Attacking a Vessel in Motion from Right Ahead._--In this case two
+torpedoes are launched, port and starboard, each diverging to its full
+extent; when passing the vessel attacked, one or the other of the tow
+ropes is brought across the cut-water, and by the simultaneous motion
+of the two vessels in opposite directions, the torpedo is brought
+alongside of or under the bottom of the vessel attacked, as shown at
+Fig. 114. The torpedo vessel should keep the masts of her enemy in
+one until close to, when either torpedo will be used, according to
+the movement of the enemy. At the time of the tow rope taking the
+cut-water, the brake is suddenly eased up; the tow rope will then pass
+under the bottom, when by checking the tow rope the torpedo will be
+hauled under the bottom.
+
+To execute this attack, judgment, skill, and nerve of the highest order
+will be required, as the risk of being run down will be imminent.
+
+_The Attack from Astern._--In this case two torpedoes are launched, and
+diverged as in the previous case; it is assumed in this instance that
+the torpedo vessel can outspeed the vessel attacked, which will enable
+her to bring a torpedo under the run of the attacked vessel, as shown
+at Fig. 115.
+
+[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.
+
+PLATE XXXIII]
+
+[Illustration: SYSTEMS OF ATTACK WITH HARVEY'S TOWING TORPEDO.
+
+PLATE XXXIV]
+
+_If Chased by a Hostile Vessel, and unable to Face her._--In this case
+veer a torpedo astern, having first obtained a position a little on
+the bow of the chasing vessel. When it is known by the length
+of the tow rope out that the torpedo is about abreast of her bow,
+hold fast the tow rope, which will cause the torpedo to diverge, and
+be brought into contact, as shown at Fig. 116. As a last resort drop
+spanned torpedoes.
+
+Torpedoes can be used with a stern board, if necessary. The port
+torpedo, in this case, will be launched on the starboard side, and the
+starboard on the port side.
+
+It should be here remarked that, although great speed is essential in
+the torpedo vessel to come up with the enemy and choose an advantageous
+position, it is not advisable to tow the torpedoes, if it can be
+avoided, at a greater speed than 11 knots; because the strain brought
+upon the towing gear is excessive, and the torpedo would require a
+large addition of ballast to keep it sufficiently immersed to attain
+the full divergence.
+
+There is, however, one style of attack in which the highest speed can
+be maintained, viz. by dropping the torpedo alongside in passing.
+
+This mode of attack is one of the best, particularly under cover of
+darkness, against a ship at anchor.
+
+The position of the torpedo is known, and the tow line is never in
+contact with the enemy during the operation; a skilled hand at the
+brakes is all that is required, the vessel keeping a straight course at
+the highest speed, passing as close as possible to the enemy, in order
+to clear away all obstructions. The tow rope must not be checked by the
+brake too suddenly.
+
+_Defensive Purposes._--The Harvey torpedo may be used as a means of
+defence by large ships against a torpedo vessel attacking with that
+species of submarine weapon, as the latter would be forced to pass
+outside the former vessel's torpedo, and thus decrease the chance of
+a successful dip. Again, in the case of an attack by the ram, these
+torpedoes afford some protection, as a deterrent.
+
+_Night time._--Though a dark night and tempestuous are favourable to a
+surprise, yet in the case of a Harvey torpedo attack it is essential
+that the weapon should be seen to dip it at the proper time, therefore
+daylight is necessary to this species of torpedo attack.
+
+_Value of the Harvey Torpedo._--The Harvey torpedo is undoubtedly of
+considerable value when _ably handled_, yet the skill and judgment
+required is very great, and can only be acquired by _constant_
+practice.
+
+_Description of the Menzing Towing Torpedo._--This modified form of the
+Harvey towing torpedo was designed by Captain Menzing, of the German
+navy, to remedy what is considered by the Germans as the chief defect
+of that weapon, viz. its liability to injure friendly vessels, and also
+to do away with the necessity of using two torpedoes, one for each side
+of a ship.
+
+At Fig. 117 is shown a plan and elevation of this towing torpedo.
+_a_ is the body of the torpedo, somewhat similar to the Harvey, but
+narrower at the stern, and bevelled on both sides towards the bow; _b_
+is an iron frame placed in the bow, capable of being turned either to
+the right or left; _c_ is the hole for the introduction of the fuze,
+and _d_ is the loading hole; _e_ is a rudder placed at the stern of the
+torpedo; _f_, _f_ are levers, by pressure against which the torpedo
+may be fired mechanically, or electrically at will; these levers are
+connected to a block of wood fitted with stops to prevent them being
+pushed too far over; _s_ and _p_ are two towing ropes, one on each side
+of the torpedo, which pass from its stern through the point of the
+frame _b_, and thence to the vessel, these are also connected to the
+rudder _e_ in such a manner that on either of the ropes _s_ and _p_
+being tautened the rudder _e_ is turned in the opposite direction; _w_
+is an electric cable, strong enough to bear the whole pressure of the
+torpedo when being towed right aft.
+
+To diverge the torpedo on the starboard quarter of the ship, the line
+_s_ must be slackened, and the whole towing strain brought on the rope
+_p_, causing the frame _b_ to be pulled over to a knot _k_ in the
+rope _p_, made at the proper position to ensure the torpedo towing at
+the correct angle from the course of the vessel, and at the same time
+causing the rudder _e_ to be turned to starboard; this is shown at Fig.
+117 by the dotted lines.
+
+To diverge the torpedo on the port quarter, the towing rope _p_ would
+be slackened and the whole strain brought on the rope _s_, and an
+action opposite to that already described would be the result.
+
+Two cork buoys are used, similar to those employed with the Harvey
+torpedo; one being attached at a distance of 10 feet from the stern of
+the torpedo, and the other at such a distance astern that the torpedo
+would be placed at a distance below the surface to allow of safety to a
+friendly vessel.
+
+[Illustration: GERMAN AND FRENCH TOWING TORPEDOES.
+
+PLATE XXXV]
+
+The torpedo is manipulated in a similar manner to the Harvey, the
+circuit being closed at the moment of the first buoy disappearing, at
+which time the torpedo would be about ten feet below the surface. The
+two buoys are together capable of supporting the torpedo, and thus by
+means of the second one it may be picked up, should it be necessary to
+cut the towing ropes.
+
+_Description of the French Towing Torpedo._--The towing torpedo used by
+the French is represented in section and plan at Fig. 118.
+
+_a_ is the body of the torpedo, formed of wood enclosed in a thin steel
+case; _b_ is the head made of cork; _c_ is the case containing the
+charge, which is generally 33 lbs. of dynamite, this case is supported
+by the bolt _d_ resting on the plate _e_; _f_, _f_ are whiskers, which
+are connected to the plate _e_; _g_ and _h_ are hollow tubes, one end
+of _g_ being attached to the case _e_, and one end of _h_ to the rear
+end of the body of the torpedo _a_, and they are so arranged that when
+the case _c_ is released, its weight will draw out the tube _g_, which
+slides along the tube _h_ to nearly the full extent of the latter; _k_,
+_k_ are bolts, to which the towing sling is attached; _l_ is the fuze,
+and _n_ is a small gun used for firing the torpedo at will. The hole
+in the plate _e_ through which the bolt _d_ passes is larger than the
+latter, so that when the plate is moved backwards by pressure being
+applied to the whiskers the bolt is freed from support, and case _c_
+attached to it falls.
+
+The modes of firing are as follows:--
+
+    1.--The automatic plan of firing is effected by the
+    tube _h_, after it has fallen a certain distance,
+    corresponding to a depth of 9 feet for the case _c_,
+    drawing down by means of a line attached to it a plug
+    contained in the body _a_, which completes the circuit
+    of the firing battery.
+
+    2.--The plan of releasing the charge at will is
+    effected by means of the small gun _n_, which is fired
+    by electricity, and by its firing forces back the plate
+    _e_, thus releasing the charge, which is then exploded,
+    as previously explained.
+
+_Locomotive Torpedoes._--By "Locomotive" torpedoes are meant those that
+possess within themselves the power to move through the water, when
+once started in a given direction.
+
+Of this species of submarine weapons, the following are the most
+efficient and are the ones most generally used:--
+
+    1.--The Whitehead fish torpedo.
+
+    2.--The Lay torpedo.
+
+_Invention and Adoption of the Fish Torpedo._--The idea developed by
+the fish torpedo is due to an Austrian marine artillery officer, who
+is now dead. In 1864, Mr. Robert Whitehead, then superintendent of
+iron works at Fiume, acting upon the suggestions of a Captain Lupuis
+of the Austrian army, commenced a series of experiments to ascertain
+the practical value of the above idea, the result being a fish torpedo,
+commonly called "The Whitehead," which though far inferior to the fish
+torpedo of the present day, was then considered to be a fearful and
+wonderful weapon.
+
+The Austrians were the first to purchase this weapon, and two years
+later, in 1870, Mr. Whitehead came to England, and prosecuted numerous
+experiments with his fish torpedo under the supervision of several
+English officers, and on the 8th of October of the same year he
+succeeded in completely destroying an old hulk moored at the mouth of
+the Medway. The fairly successful results of these experiments induced
+the English government to purchase the secret and several of Mr.
+Whitehead's fish torpedoes, under the following conditions:--
+
+    1.--The right of manufacturing them in England.
+
+    2.--To be kept fully informed of all improvements, as
+    soon as made.
+
+    3.--The right of using all such improvements.
+
+And the total amount paid to Mr. K. Whitehead at that time was the
+sum of seventeen thousand five hundred pounds, which did not include
+the sum of two thousand five hundred pounds claimed for the expenses
+attendant on the Medway experiments. Since then a large number of
+Whitehead's fish torpedoes have been purchased from time to time,
+especially during the Turco-Russian war, when some two hundred were
+ordered, also great numbers have been manufactured at Woolwich. The
+English fish torpedo, as far as can be ascertained, is a vastly
+superior weapon to the Whitehead fish torpedo, possessing as it does
+increased speed, and therefore far greater accuracy.
+
+Besides Austria and England, nearly all the European governments have
+purchased the Whitehead secret and torpedoes, but in the case of some
+of them, the last two clauses of the English conditions of purchase
+were omitted.
+
+[Illustration: WHITEHEAD'S FISH TORPEDO.
+
+PLATE XXXVI]
+
+The Turkish is the only government that has obtained the Whitehead
+secret and torpedoes without paying for it. This was managed as
+follows:--
+
+"On the night of the 20th of December, 1877, the Russians made an
+attack with Whitehead torpedoes on an Ottoman squadron lying in the
+harbour of Batoum, but owing to a want of practical knowledge of the
+manipulation of such weapons, no vessels were sunk or damaged, but two
+fish torpedoes, one in perfect condition, were found the next morning
+high and dry on the beach at that place."
+
+The American government have up to the present time not sanctioned
+the purchase of the costly Whitehead torpedo, preferring their own
+locomotive torpedo, which will be fully described further on. On a
+government purchasing the fish torpedo, a certain number of their
+naval or military officers are sent to Fiume in Austria, where Mr. R.
+Whitehead's manufactories are situated, and where the necessary very
+exhaustive experiments with his torpedoes are carried out, and are
+there thoroughly instructed in the manipulation of these machines, and
+are also supplied with a double set of drawings of the various parts of
+the torpedo. These officers, and all others whom it may be necessary to
+initiate into the mysteries of the Whitehead secret, are bound on their
+honour not to divulge it.
+
+_Employment of Fish Torpedoes in War._--The fish torpedo has been
+employed on actual service on three known occasions only, in two of
+which it failed to fulfil its deadly mission.
+
+On the 29th of May, 1877, a Whitehead fish torpedo was fired by H.M.S.
+_Shah_ against the Peruvian ironclad _Huascar_, but failed to strike
+her, owing to the latter vessel altering her course at the moment of
+the torpedo being discharged. The next instance of the employment of
+the Whitehead torpedo was that one mentioned at page 132. The last
+and only successful attempt yet made occurred on the 26th of January,
+1878, when the Russian steamer _Constantine_ fired a Whitehead
+torpedo against a Turkish guard vessel off the harbour of Batoum, and
+completely destroyed her.
+
+_Description of Torpedo._--A general view of the Whitehead fish torpedo
+is shown at Fig. 119. It is divided into three parts, connected
+together by screws.
+
+    1.--The charge chamber.
+
+    2.--The adjustment chamber, in which is placed what is
+    known as the secret.
+
+    3.--The air and engine chamber.
+
+Vertical and horizontal steel fins are fitted for the purpose of
+maintaining the torpedo in an upright position whilst passing through
+the discharge tube, or frame; the former fins run nearly the whole
+length of the weapon, while the latter are considerably shorter. The
+motive power of the torpedo is compressed air, forced by means of a
+powerful steam air compressing pump into a portion of the steel chamber
+(3) at a tension of upwards of 1000 pounds to the square inch, which
+is equivalent to about sixty atmospheres, and which by means of a set
+of small three cylinder Brotherhood engines, contained in the steel
+chamber (3), drives two screw propellers. These engines are capable
+of exerting a force of forty indicated horses, and yet only weigh
+about thirty-five pounds, from which it will be understood that to
+attain these results the workmanship and materials employed in their
+manufacture are of the very highest order and fineness.
+
+The torpedo is made of various sizes, ranging from 14' long and 14"
+maximum diameter to 19' long and 16" maximum diameter.
+
+_Capabilities of the Fish Torpedo._--The capabilities of the fish
+torpedo are as follows:--
+
+    1.--If adjusted for a certain depth, from 5 to 15 feet,
+    and projected from above water, or if started from the
+    surface, or if discharged from a submerged tube, it
+    will rapidly attain that depth, and maintain it during
+    the run.
+
+    2.--If fired in still water, it will make a straight
+    run in the line of projection, provided that an
+    allowance has been made for the deflection due to
+    transverse currents.
+
+    3.--It can be adjusted to stop after having run any
+    distance up to its extreme range, and after stopping to
+    sink, float, or explode.
+
+    4.--Its range and speed vary considerably, according to
+    the pattern of the torpedo.
+
+  -------+----------------------------------------------+-----------------
+         |           Whitehead Fish Torpedo.            |  Woolwich Fish
+         |                                              |    Torpedo.
+         +--------------+---------------+---------------+-----------------
+         |14' long, 16" | 14' long, 16" | 14' long, 14" | 14·5' long, 14"
+         |  max. diam.  |   max. diam.  |   max. diam.  |    max. diam.
+  Yards. |  one screw.  |  two screws.  |  two screws.  |   two screws.
+  -------+--------------+---------------+---------------+-----------------
+    200  |      ..      |      ..       |     20 knots. |   25-1/4 knots.
+    250  | 9-1/2 knots. |      ..       |       ..      |        ..
+    300  |      ..      | 12-1/4 knots. | 19-1/4 knots. |   24-1/2 knots.
+    400  |     8 knots. |      ..       |     18 knots. |       23 knots.
+    600  |      ..      |     11 knots. |       ..      |       20 knots.
+    750  |      ..      | 10-1/2 knots. |       ..      |        ..
+    800  |     7 knots. |      ..       | 16-1/2 knots. |       18 knots.
+   1000  |      ..      |      9 knots. |       ..      |   15-1/2 knots.
+  -------+--------------+---------------+---------------+-----------------
+
+    Pressure of air in engines varies for distance and
+    speed from 40 atmospheres to 140 atmospheres.
+
+_Placing the Charge._--The explosive is generally placed in what is
+termed the cartridge case, which case is similar in shape to the
+interior of the charge chamber (1), and is fixed thereto by means of
+wooden wedges.
+
+_Ignition._--The method of ignition is mechanical, and is arranged as
+follows:--Extending from the nose of the torpedo to the cartridge case
+is a tube terminating in a copper case, in which is placed the priming
+charge and detonating composition; within this tube is a steel rod
+some 2 feet long, fitted with a needle point at its inner end, and its
+outer end screwed into a frame; this frame is capable of moving in and
+out, and is connected with a spiral spring which tends to force it, and
+consequently the steel rod, or striker, inwards. By compressing this
+spiral spring, the inner end of the frame is butted against a catch,
+by which it is prevented from acting. On this catch being released,
+no matter by what means, the spring is brought into action and forces
+the frame and steel striker inwards, the needle point of the latter
+coming into contact with the detonator fires the priming charge, and so
+explodes the torpedo. The foremost extremity of the torpedo, which is
+termed the nose piece, is so fitted that it is capable of being forced
+inwards, but in a position of rest its inner edge is just clear of
+the catch. On a pressure being brought on the nose piece in a direct
+line with the length of the torpedo, it will be forced inwards, the
+result being the releasing of the catch and explosion of the torpedo.
+In addition to the nose piece, horizontal and vertical levers, or
+whiskers, may also be used, a slight pressure on either of which
+will similarly effect the explosion of the torpedo; also cutters for
+penetrating nets, &c., are fitted to the nose piece when desired.
+
+_Safety Wedge and Key._--For safety purposes a wedge is employed, which
+when in the safety position prevents the catch from acting; this wedge
+is so arranged that it may be withdrawn by the action of the machinery
+after the torpedo has run a certain distance, and also may be replaced
+by similar means in the safety position on the completion of the run.
+As an additional precaution a safety key is used, which is inserted in
+the head of the torpedo through the spring of the frame.
+
+_Description of Adjustment Apparatus._--For adjusting the length
+of range for withdrawing and replacing the safety wedge, &c., the
+following apparatus is employed.
+
+Two cog wheels, a large and a small one, are fixed on the upper part of
+the after end of the torpedo, just in front of the screw propellers:
+the small wheel is fitted with a certain number of teeth, thirty for
+instance, which gears into an endless screw attached to the propeller
+in such a manner that one revolution of the propeller moves the wheel
+one tooth, therefore thirty revolutions would turn the wheel one
+complete revolution. The big wheel is fitted with much larger teeth
+than the small one, and by means of a pin on the latter wheel is moved
+round one tooth for every complete revolution of the small wheel, and
+clamped in this new position by a spring catch, which is also worked by
+the pin on the small wheel. In front of these wheels is a stud which
+works fore and aft in a slot, and attached to a spring which tends
+to draw it to the after end of the slot. This stud is connected by
+means of a wire rod to the valve that admits the compressed air to the
+engines; when the stud is in the fore part of the slot the valve is
+open, and when in the after part it is closed.
+
+_Adjusting Length of Range._--By means of a lever the spring of the
+stud is compressed, and the stud moved to the fore part of the slot;
+then the big wheel is moved round until a stud on its face is the
+required number of teeth above the lever. For every thirty revolutions
+of the propeller, and consequently one tooth of the big wheel, a
+certain known distance is traversed, which varies according to the
+pattern of the torpedo.
+
+_Adjusting Apparatus._--When the propeller has made the number of
+revolutions corresponding to the length of range required, and
+consequently has moved the big wheel the number of teeth it was set
+above the lever, the stud on the big wheel presses against the lever
+and so releases the spring in the slot, causing the slot stud to fly
+from the fore part to the after part of the slot, by which action
+the valve admitting the compressed air to the engines is closed, and
+consequently the engines cease to work.
+
+Attached to the axle of the big wheel is a small brass arm, which
+is connected by means of a brass rod to the safety wedge, and is
+so arranged that after the required number of revolutions of the
+propeller, the safety wedge will be drawn out; or it may be drawn out
+at the instant of the torpedo leaving the tube, carriage, &c. Also by
+means of an additional lever at the fore part of the torpedo, which is
+connected by means of a wire rod to the valve that admits the air to
+the engines, and by arranging the attachment of the safety wedge to
+the brass rod from the big wheel, so that on the wedge being withdrawn
+it is released from that brass rod, on the torpedo having completed
+its run, the action of closing the valve which admits the air to the
+engines causes the additional lever to force the wedge into the safety
+position.
+
+_Torpedo to Float at End of Run._--This is due to the difference of
+buoyancy at the end of a run from what it was at the commencement,
+owing to the compressed air being used in working the engines.
+
+_Torpedo to Sink at End of Run._--This is effected by means of the
+adjustment chamber (2), in the after end of which there is a spiral
+spring valve, which can be attached to the brass rod on the outside of
+the torpedo that works the valve which admits air to the engines, in
+such a way that on the valve being closed, and therefore the run of the
+torpedo completed, the spiral spring valve is opened, admitting water
+to the adjustment chamber (2) of sufficient amount to sink the torpedo.
+
+_To Explode the Torpedo at End of Run._--This is effected by connecting
+the vertical firing whisker to the rod which otherwise would be
+connected to the safety wedge lever, by which means, on the valve
+admitting air to the engines being closed, a force is transmitted
+to the vertical whisker instead of to the safety wedge lever, and
+consequently the torpedo is exploded.
+
+_Adjusting the Depth._--A small wheel, the face of which is marked in
+feet, is placed on the left side of the fore part of the adjustment
+chamber (2). To adjust for depth, by means of a key turn the wheel
+until the number corresponding to the depth of run required is opposite
+the pointer.
+
+The torpedo is maintained at the desired depth by means of certain
+mechanical apparatus contained within the adjustment chamber (2), and
+which constitutes what is termed the secret of the fish torpedo. This
+chamber is connected by screws to the foremost and after chambers of
+the torpedo, in such a manner that by means of a number of small holes
+bored round the circumference, as shown at (2), Fig. 119, the faces
+of the chamber are exposed to the pressure of the water, which varies
+with the depth to which the torpedo descends. Within the adjustment
+chamber is an endless strong spiral spring, attached to the after face
+of the chamber, and so arranged that after being set to a certain
+tension, capable of resisting an equivalent pressure on the outside
+of the aforesaid face, any increase or decrease in this exterior
+pressure will cause the spiral spring to work a rod by which the
+horizontal rudders of the torpedo are regulated, and thus the desired
+depth for which the spring is set is maintained. The course of the
+torpedo is represented by a series of curves, above and below the line,
+representing the depth it is set for, these curves gradually decreasing
+until at 100 yards' distance from where the torpedo was started the
+curves are so small that the path of the torpedo is almost identical to
+that of a straight line.
+
+Within this adjustment chamber is also placed an automatic balance,
+which also assists to maintain the torpedo at the desired depth, by
+reason of its swinging forward on the torpedo descending, and swinging
+aft on its rising, which motion is used to regulate the horizontal
+rudders. The above is merely a general idea of the arrangement used in
+the Whitehead fish torpedo, to enable it to reach and maintain whatever
+depth it may be necessary to use it at from 5 to 15 feet.
+
+_Projecting the Torpedo._--The fish torpedo may be projected in various
+ways, viz.:--
+
+    1.--Through a submerged tube in the stem, or on the
+    broadside.
+
+    2.--From a carriage above the surface.
+
+    3.--From the surface.
+
+_Discharging Torpedo through a Submerged Tube in the Stem._--In this
+case a tube is fitted to an orifice in the stem; this opening is as
+far below the water line as possible, and is closed by a watertight
+cap and a sluice valve; the inner end of the tube is fitted with a
+watertight door; the torpedo being prepared for action is placed inside
+the tube, the inner door closed, and the tube filled with water; then
+the watertight cap and sluice valve are opened, and the torpedo started
+by means of a piston which is worked by compressed air. This piston can
+be worked from deck, and so the torpedo fired at the proper instant.
+To prevent the torpedo from slipping out of the tube, a stop is placed
+in the fore end of it, which can be withdrawn at the same time as the
+compressed air is admitted behind the piston. The torpedo being clear
+of the tube, the sluice valve and watertight cap are closed, and the
+tube emptied of the water, the projecting piston being at the same time
+forced back.
+
+_On the Broadside._--In this case, the discharging tube works inside an
+iron casing, through a stuffing box at the inner end, and in a shield
+attached to the outer end of the tube. This shield, placed on the fore
+side of the orifice, is of such a length as to protect the torpedo from
+the pressure of the water passing the vessel. The mode of discharging
+the torpedo in this case is similar to that used when projecting it
+through the stem.
+
+_Comparison of the Stem and Broadside Methods of Projecting the
+Torpedo._--The former method of projecting the torpedo seems the most
+suitable to specially built torpedo vessels, but not so to large
+ironclads, on account of the difficulty of fitting a tube to the stem
+of such a ship, and also that in so doing the efficiency of the vessel
+as a ram would be impaired.
+
+In regard to the accuracy of the firing of the above methods, both seem
+equally good, though in the case of firing on the broadside it would
+be necessary to prepare carefully calculated tables of deflection, any
+mistake in the using of which would be fatal to a successful torpedo
+shot.
+
+_Projecting a Torpedo from above Water._--In this case an iron carriage
+is used, which is fitted with a frame, in which the torpedo rests; the
+outer end of this frame is provided with a lip, some few feet long,
+by which means the rear end of the torpedo is slightly canted up on
+leaving the frame, and any undue strain on the tail of the torpedo is
+prevented. The frame is mounted in the iron carriage in such a way that
+it can be elevated or depressed by means of a screw, as in the case of
+a gun mounted in an ordinary carriage. The torpedo is ejected from the
+frame by means of a piston as previously explained, a small reservoir
+of air being attached to the carriage, so that it can be used at any
+port.
+
+_Firing a Torpedo from the Surface._--The torpedo possesses sufficient
+buoyancy to float with a small portion of its upper surface above
+water; such being the case, it is only necessary to set the various
+adjustments, point it in the required direction, and by hand turn back
+the lever on the upper part of the weapon (which opens a communication
+between the air chamber and the engines), when it will instantly dart
+off and very rapidly attain the depth it is set for.
+
+_Method of Firing a Fish Torpedo from a Boat._--To manipulate a fish
+torpedo from a boat, it may be carried in a light frame, which can
+be lowered or raised by means of a pair of davits. When required to
+discharge the torpedo, the frame containing it is lowered into the
+water, so as to bring the torpedo about two feet below the surface, the
+head being somewhat lower than the tail.
+
+_Thornycroft's Method of Firing Fish Torpedoes from a Boat._--Another
+method, which has been patented by Mr. J. I. Thornycroft, of the firm
+of J. I. Thornycroft and Co., steam launch builders, and which is
+fitted to the torpedo boats built by them for foreign governments, is
+shown in elevation and plan at Figs. 120 and 121.
+
+The apparatus consists of two or more bent levers _A_ securely and
+rigidly fixed on a shaft _B_, which works in bearings fixed on the deck
+of the vessel _C_ from which the torpedo is to be discharged. On the
+ends of the levers _A_ furthest from the shaft _B_ are pivoted other
+levers _D_, to which the cradle or case _E_ for sustaining the torpedo
+is suspended. The other ends of each of these levers are connected to
+the vessel by means of rods or tubes _F_, jointed at each end in such
+a way that when the shaft _B_ is made to revolve in its bearings, the
+case containing the torpedo is guided over the side of the vessel and
+close to it, and is held in a position convenient for discharging the
+torpedo, as shown at Fig. 120.
+
+The shaft _B_ may be made to revolve by means of ropes _G_ and pulleys
+_H_ attached to the levers _A_, or by hydraulic or steam pressure, as
+may be found most convenient.
+
+The torpedo case can be towed alongside the vessel if necessary without
+deranging the apparatus. The torpedo case is carried in the angles
+of the bent levers, and is stowed away so that neither it nor the
+suspending levers project at all beyond the hull of the vessel; also
+when lowered, the levers and suspending rods fold over one another so
+as to occupy very little space, and the torpedo is suspended close to
+the hull.
+
+Also the torpedo during the operation of lowering as well as when in
+a firing position remains close to the side of the vessel, thereby
+obviating any risk or inconvenience from excessive leverage which would
+have a tendency to capsize the boat.
+
+For especially built torpedo launches, the above mode of carrying and
+launching the fish torpedo is certainly the best yet devised.
+
+_Woolwich Fish Torpedo._--In the Woolwich torpedo, the engines exert a
+force of nearly 60 indicated horses, and work up to 1000 revolutions
+per minute; the total weight of the torpedo fully charged (33 lbs. of
+gun-cotton) is about 500 lbs.
+
+[Illustration: THORNICROFT'S BOAT APPARATUS FOR FISH TORPEDOES.
+
+PLATE XXXVII]
+
+The Whitehead fish torpedo costs about 380_l._, while the Woolwich one
+costs only 300_l._
+
+_The Lay Torpedo Boat._--Priority of invention of this torpedo was on
+the 13th of June, 1873, awarded by the Commissioners of Patents to Mr.
+John Louis Lay, several other persons having claimed the invention,
+among whom was Colonel Von Scheliha, an officer of the Russian army.
+
+This locomotive torpedo, or more properly called torpedo boat, has been
+for several years adopted by the American government, during which time
+it has undergone a series of exhaustive experiments, which has proved
+it to be a most valuable and efficient weapon of offence and defence.
+Lately the Russian government have adopted it, and intend using it
+extensively in the defence of their harbours, &c.
+
+_General Description of the Torpedo._--At Fig. 122 is shown a
+longitudinal section of a Lay torpedo boat constructed and provided
+with guiding and controlling apparatus, and with means for propelling
+it by ammoniacal gas. Fig. 123 is a horizontal section of the same;
+_A_ is the hull or body of the boat, which has conical ends _A_^{1},
+_A_^{2}, and is formed of thin plate iron, or steel, or other suitable
+material. The section in the end _A_^{1} forms the magazine containing
+the charge of dynamite or other explosive material; _A_^{3} is the
+section containing the gas reservoir or holder; the compartment _A_^{4}
+contains the apparatus for holding and paying out the electric cable;
+the compartment _A_^{5} in the end _A_^{2} contains the motor engine,
+the steering apparatus, and other parts to be hereinafter described.
+All of these compartments or sections are separated from each other by
+means of air-tight bulkheads _A_^{6}. The torpedo boat may be propelled
+by means of a single screw, double screw, or two screws. In the latter
+method, which is shown at Figs. 122 and 123, the propellers _B_ and
+_C_ are made to revolve in opposite directions; the shaft _D_ of the
+propeller _B_ is hollow or tubular, and the shaft _E_ of the screw
+_C_ passes through the same; these screws are actuated by an engine
+shown at _F._ _H_, _H_ are the horizontal rudders, or side wings, two
+forward and two aft; these wings are mounted on shafts or spindles
+passing transversely through the boat; these rudders may be set to
+occupy a horizontal position, or a more or less inclined position in
+the proper direction, to cause the submerging of the boat by the action
+of the water on the said rudders as the boat moves forward, and they
+are adjusted before starting. _N_, _N_ are two guide rods, one aft
+and one forward, which project up from the boat to enable the operator
+to determine its position at any part of its run, and in the case of a
+night attack they are provided with lights; the said rods can be raised
+or lowered at the will of the operator. _Q_ is the electric cable,
+which affords a medium of communication between the operator on shore,
+&c., and the torpedo boat, whereby it may be started, stopped, steered,
+fired, and has her position ascertained; this cable is carried in the
+boat in a coil arranged longitudinally in the air-tight chamber _A_^{4}
+in the reel frame _R_, and is payed out as the torpedo progresses
+through a tube _S_, projecting aft under the boat and beyond the
+rudders and propellers, so that the said cable will not be fouled by
+the same; or it may be payed out through a hollow shaft in the centre
+of the boat. One end of this cable is connected to a keyboard at the
+station on shore or on board of the ship or other structure from which
+the torpedo boats are controlled. This keyboard is provided with a
+suitable battery or other means for generating the electric current, as
+hereinafter described.
+
+The said cable is composed of several wires, each of which is insulated
+from the others. One of these wires is connected with the mechanism
+for starting and stopping the boat, one is connected with the steering
+apparatus, one serves for indicating to the operator at all times the
+exact position of the rudder, one is connected with mechanism for
+elevating and depressing the said guide rods, and one serves for firing
+the charge in the magazine.
+
+The motive power for effecting the necessary movements of the mechanism
+or apparatus in performing the above operations is obtained from the
+aforesaid engines, which are provided with suitable valves arranged in
+combination with electro magnets, shunts, and the devices connected
+with the said wires of the cable, as hereinafter set forth.
+
+This form of cable has since been replaced by one which consists of two
+wires only, the one for performing all of the necessary operations,
+exclusive of the firing or exploding of the magazine, and the other
+exclusively for this latter purpose. This improvement is effected by
+employing a series of relays or resistance coils, or a multiple, or
+compound relay in the boat. The advantages gained by this improved form
+of cable are:--
+
+    1.--Increased flexibility.
+
+    2.--A greater length of cable may be coiled in a given
+    space.
+
+    3.--A thicker coat of insulating material may be used,
+    thereby more perfectly insulating it.
+
+    4.--It is much cheaper.
+
+Two rudders are generally used, one below and one above the boat, as
+shown at _U_, Fig. 122. These rudders are operated and controlled by
+means of a small auxiliary engine _T_, Fig. 122, which is started,
+stopped, and reversed by the electric current conducted through the
+cable _Q_ in connection with magnets attached directly to a valve
+forming part of the said engine. This valve is so actuated by the
+magnets that when the current passes in one direction the engine _T_
+will move the rudder to starboard, and when the current acts in the
+opposite direction it will turn the rudder to port.
+
+The mechanism for firing the charge in the magazine _A_^{1} is clearly
+shown in Fig. 124, and operates as follows:--Projecting from the front
+extremity or stem of the boat is a rod or pin _V_, which extends
+through a suitable packing box _W_ into the said magazine or charge
+chamber; when the boat strikes an object, the said rod is forced
+inward into contact with the springs or points _X_, thereby closing
+an electrical circuit and igniting a cartridge, shown at _Y_, in the
+magazine.
+
+The charge in the magazine can also be fired at any moment by the
+operator on shore closing a circuit on the keyboard and thereby
+cutting out one of two resistance coils placed in the circuit to
+prevent accidental or premature discharge--that is to say, there are
+two resistance coils. The battery is not sufficiently powerful to
+fire through both resistance coils at the same time. When the boat
+strikes an object, the resistance coil in the magazine is cut out by
+the driving inward of the rod _V_, as above described; the battery
+then fires through the one on the keyboard. On the other hand, if
+the operator desires to fire the torpedo boat before she touches the
+object of attack, he manipulates the switch to cut out the coil in the
+keyboard, the charge then being fired through the coil in the magazine.
+This arrangement of the two resistance coils is very effectual in
+preventing accidents.
+
+In some instances the magazine is made detachable from the hull of the
+boat, so that on striking an object it will descend or drop down in the
+water before exploding. This modification is shown at Figs. 125 and 126.
+
+The magazine _A_* is attached at its lower side to the boat by a chain
+or other suitable connection. At its upper edge it is held by a rod
+_a_*, as shown in Fig. 125. This rod is fitted to slide in dovetailed
+bearings, as shown at _b_*, and when this magazine is in its place
+on the boat the said rod is engaged with a catch or stop _c_*, but
+when the said rod is driven against any object it is forced back and
+released from the said catch or stop, and the magazine then drops, as
+in Fig. 126, and is fired.
+
+To effect the firing a ball _d_* is used and placed in a tube
+containing two springs or plates _e_* and arranged in an upwardly
+inclined position, as shown in Fig. 125, one of the said springs being
+connected with the cable and the other with a wire that passes through
+the cartridge to earth.
+
+While the magazine is in the position shown in Fig. 125 the circuit
+is incomplete, but when the magazine drops the said ball falls into
+the position shown in Fig. 126; the circuit is then completed, and the
+magazine is fired.
+
+The electrical or electro-magnetic apparatus for generating, directing,
+and controlling the currents, whereby the above-described operations
+are effected, may be of any suitable kind, the following being the form
+of apparatus usually employed.
+
+A battery _r_, shown at Fig. 127, consists of any desired or requisite
+number of cells constructed and arranged in any suitable manner, and
+connected by proper conducting wires with the keyboard _s_. The latter
+is provided with a series of pole changers _s_^{1}, _s_^{2}, _s_^{3},
+_s_^{4}, and switches _s_^{5}, _s_^{6}, and is shown in Fig. 128.
+
+Each of these pole changers is arranged to effect and control one of
+the above-named operations, and is therefore connected with one of the
+aforesaid insulated wires forming the cable. For instance, the pole
+changer _s_^{1} effects the starting and stopping of the propelling
+engine; _s_^{2} controls the steering apparatus; _s_^{3} is connected
+with the steering index; _s_^{4} operates or adjusts the aforesaid
+guiding rods; and the switches _s_^{5}, _s_^{6} control and effect the
+firing of the charge in the magazine.
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XXXVIII]
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XXXIX]
+
+The connections between these pole changers and switches, and
+the apparatus they operate or control on board the boat, are as
+follows--that is to say, the said propelling engines have a throttle
+valve, which controls the admission of the gas from its generator or
+reservoir to the cylinders of the said engine, and in combination
+with this valve in the boat there is a shunt and set of electro
+magnets. The armature of the latter is connected with a lever, which
+is pivoted so that the action of the electric current in one direction
+through these magnets will pull one end of the said lever down, and the
+action of the current in the other direction will pull its other end
+down--that is to say, by reversing the current through these magnets
+the movement of the said lever is reversed; and this lever, connected
+by suitable means with the slide of the said throttle valve, will open
+or close the same, and thereby start or stop the engine as required.
+
+For operating and controlling the above-described steering apparatus,
+and indicating the position of the rudder to the operator on shore, the
+following devices are employed, in combination with the pole changers
+_s_^{2}, _s_^{3} on the keyboard:--The pole changers are geared
+together by insulated toothed wheels, which are fixed on the spindles
+or axes of the said pole changers, so that the latter work accurately
+together and maintain the same relative positions to each other. The
+pole changer _s_^{2} is connected by one of the said insulated cable
+wires with a shunt on board the boat, which shunt is connected with a
+set of magnets arranged in combination with the valve of the engine
+that drives the steering apparatus, and which valve is reversed or
+opened and closed by the reversal of the currents through the said
+magnets, as above described, and the said engine moves the rudder
+to port or starboard at the will of the operator. In order that the
+operator may know the exact position of the rudder at any moment, a
+series of pins or projections fixed on an arc or other portion of the
+rudder stock, and arranged in combination with an insulated spring
+projecting into the path of the said series of pins, are employed. This
+spring is connected by one of the cable wires with the pole changer
+_s_^{3} on the keyboard, which is geared with and moves in unison with
+the pole changer _s_^{2}, so that the electric current that controls
+the steering engine, and the current that returns the indication of the
+rudder's position, will both be reversed simultaneously. A separate
+battery is connected with the index on the said keyboard, whereby a
+constant current is maintained between this index and the indicating
+apparatus on the boat.
+
+The current passing from the said spring to the shore is made to
+indicate the position of the rudder by the index on the keyboard by
+the contrivance shown in Fig. 129. This contrivance consists of a
+set of magnets _w_, which have a vibrating armature _w_^{1} pivoted
+to oscillate between them. One end of the armature lever is provided
+with insulated spring pawls _w_^{2}, which take into ratchet wheels
+_w_^{3}. On the same shafts on which these ratchet wheels are fixed are
+wheels _w_* formed with insulated teeth and geared with each other. The
+shaft of one of these wheels is geared by bevel pinions _w_^{4} with a
+vertical shaft _w_^{5}, to which is attached the index needle or finger
+_x_**, Fig. 128. Therefore it will be obvious that this index finger
+is placed in connection with the aforesaid spring and series of pins
+attached to the rudder yoke on board the boat.
+
+Now it will be obvious that when the rudder is turned in either
+direction these pins will come successively in contact with the said
+spring, and at each contact and separation the circuit will be made and
+broken, and an impulse will be transmitted through the cable, whereby a
+corresponding movement will be transmitted to the said index finger or
+pointer _x_** on the keyboard.
+
+The pole changer _s_^{4} is connected with another of the insulated
+wires of the cable, which on board the boat is connected with a shunt
+and set of magnets arranged in combination with the aforesaid cylinders
+that operate the said guiding rods, so that by sending the current in
+one direction the said rods will be raised, and by sending the current
+in the opposite direction the said rods will be lowered.
+
+The switch _s_^{5} is connected with another of the said insulated
+wires of the cable, which forms the circuit, including the aforesaid
+two resistance coils.
+
+By adjusting this switch the operator completes the circuit through the
+two resistance coils, and then, but not till then, the charge can be
+exploded, either by the operator, or by the action of the firing pin or
+rod when the same is driven in and cuts out the other resistance coils
+as above described. The resistance coil _X_^{1}, Fig. 124, is connected
+to the binding screws 9, 10 by the wires 7 and 8. These binding screws
+are in metallic connection with the two springs _X_, but otherwise they
+are carefully insulated. One pole of the fuze _Y_ is connected to the
+binding screw 10, the other put to earth through the body of the boat,
+as at _E_; the main wire 11 is connected to the binding screw 9. Now
+when the operator cuts out the resistance coil at the firing station,
+which is done by moving the switch _s_^{6}, the electric current is
+sufficiently powerful to ignite the fuze _Y_ through the resistance
+coil _X_^{1}, so that at any moment the torpedo may be exploded by
+the operator on shore, or by the contact between the torpedo and the
+attacked vessel the rod _V_ will be driven in, and, coming in contact
+with the springs _X_, will bridge over the space that originally
+existed between them and so cut out the resistance coil _X_^{1}, and
+the torpedo will be exploded automatically.
+
+_Capabilities of the Lay Torpedo Boat._--The capabilities of the Lay
+torpedo boat are as follows:--
+
+    1.--It may be launched from the shore, a vessel,
+    or a structure, and be kept under observation, and
+    accurately guided or directed to the ship or other
+    object to be attacked; and it may be exploded at any
+    desired moment, or it may be caused to return to the
+    original point of departure without being fired.
+
+    2.--It may be totally and instantaneously submerged to
+    prevent its destruction or capture by the enemy, and it
+    may be raised to the surface, as soon as the danger has
+    passed, in a condition fit for immediate action.
+
+    3.--It may be used as a tug or towing boat to take out
+    a number of torpedoes, which may be sunk and exploded
+    when desired.
+
+    4.--It may be used in connection with certain apparatus
+    to clear away obstructions found to prevent the
+    entrance of ships into harbours, and it may also be
+    used to clear harbours of mines, &c.
+
+_Launching the Lay Torpedo Boat._--For facilitating the launching and
+controlling of the Lay torpedo boats, a structure or submarine fort
+is used. This structure may be square, or oblong, and may be made to
+carry any number of the torpedo boats. The body is constructed of plate
+or sheet iron of suitable strength and stiffened with angle iron, or
+otherwise, and divided longitudinally or transversely into watertight
+compartments, into which the water is admitted to sink the said
+structure. At the top or upper side, cylinders or tubes are placed,
+each of which is capable of containing and launching one of the torpedo
+boats. At the forward end of each tube is a door, or cover secured to a
+rod or shaft fitted to turn in suitable bearings; this rod or shaft is
+provided with an arm which is connected to the piston rod of an engine
+worked by gas contained in a reservoir, or by other suitable means.
+The slide or other valve which controls the admission of the gas,
+&c., to this engine is arranged in connection with electro magnets,
+connected by a suitable cable with a keyboard on shore, or wherever
+the operator's station may be. By sending an electric current through
+this cable in one direction through the electro magnets, the door is
+closed; and by sending such a current in the opposite direction it is
+opened. The cables carried in the torpedo boats, and through which the
+mechanism on board each torpedo boat is operated and controlled, are
+also in this case connected with the keyboard, which must be provided
+with a number of sets of pole changers and switches, or equivalent
+devices, corresponding with the number of boats to be controlled by
+means of the said keyboard.
+
+This apparatus will form a very convenient adjunct to fortifications or
+stations liable to be attacked by sea. The said fort may be prepared
+for use by placing torpedo boats in the said tubes, and may be kept
+floating until the enemy's ships have arrived closely enough to
+permit the determination of the point where the said fort can be most
+advantageously located for operating against the said ships. The fort
+is then towed to this point, or taken as near as possible thereto on
+rails, and towed the remainder of the distance. It is then submerged,
+and will be ready for immediate operation. The said fort is provided
+with suitable valves for the admission of water to sink the same, and
+with means for forcing in air through the pipe _P_* to expel the water
+when the fort is to be raised.
+
+When it is desired to launch either of the said torpedo boats, the door
+of its tube or cylinder is first opened by sending a current through
+the cable that controls the door, as above described. Then the current
+is sent through the boat's cable to start her propelling engines. The
+said boat will then emerge from the cylinder or tube and will rise to
+the surface, or as near the surface as may be desired, and may then be
+directed and controlled by the operator at the keyboard, as previously
+described. And one after another of the said torpedo boats may be thus
+launched and exploded, without giving to the enemy any clue to the
+point or position from which they are being sent.
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XL]
+
+_Launching the Torpedo from a Ship._--The method of launching the Lay
+torpedo boat from an ironclad or other large ship is shown at Fig.
+130. The tubes or cylinders _S_ in which the torpedo boats _A_ are
+held are, in the apparatus shown at Fig. 130, closed at their inner
+ends by plates, or covers _S_^{1}, which are provided with suitable
+water-tight and insulating packing boxes _S_^{2} for the passage of the
+electric cables of the said torpedo boats, each cable being connected
+with the keyboard, which is placed in any convenient part of the ship,
+and at their outer ends the said tubes are furnished with strong and
+well-fitted slide valves, or sluice gates _S_^{3}, which are opened
+by screws, connected by gearing with a hand wheel, and shaft _S_^{4},
+_S_^{5}, for the admission and exit of the said torpedo boats. Also
+these cylinders are provided with packing pieces at their sides,
+arranged to be pressed by screws or otherwise up to the sides of the
+torpedo boats in these cylinders, and thereby hold them firmly and
+immovably in rough weather.
+
+_The Method of Sinking and Raising a Lay Torpedo Boat._--The apparatus
+by which this is effected is shown at Fig. 131, which is a longitudinal
+section of a portion of a torpedo boat. The hull _A_ of the torpedo
+boat is provided with a water chamber _l_, which has holes or apertures
+_l_^{1} in the bottom of the same, and is also provided with an air
+cock at _l_^{2}. In connection with this chamber is arranged a small
+cylinder _m_, provided with a piston _m_^{1}, whose rod _m_^{2} is
+attached to the lever of the said cock. A spiral spring _m_^{3} is
+provided to resist the inward movement of the said piston. The said
+small cylinder _m_ is connected by a pipe _m_^{4} with a valve chest,
+in which is arranged a slide valve _m_^{5}. The said slide valve is
+connected by a rod or rods to the lever or levers _m_^{6}, whose
+fulcrum is at _m_*, and the said levers are connected by the links
+or rods _m_^{7} with the armatures of electro magnets _n_, which are
+included in the circuit of the cable, whereby the boat is controlled
+from the keyboard at the station; _o_ is a pipe extending from the said
+valve chest to the aforesaid water chamber _l_; _p_ is a feed pipe by
+which gas is conducted from the reservoir or generator to the valve
+chamber.
+
+When it is desired to sink the torpedo boat an electric current is sent
+in one direction through the said magnets, and thereby operates the
+slide valve to admit gas to the cylinder _m_ in front of the piston
+_m_^{1}, which is thus forced inward and opens the air cock _l_^{2}.
+The opening of this cock permits the escape of the air from the water
+chamber _l_, and consequently the entrance of water through the
+apertures _l_^{1}, and the boat then immediately sinks.
+
+When it is desired to raise the boat a current is sent in the opposite
+direction through the said electro magnets, thereby operating the said
+valve and piston in such a manner as to close the cock _l_^{2} and
+open the port _o_^{1} and the pipe _o_, thereby allowing the gas to
+pass from the valve chamber into the compartment _l_; this gas by its
+pressure expels the water from the said compartment, and the boat then
+having its normal buoyancy restored immediately rises to the surface.
+
+_The Lay Torpedo Boat used as a Tug to take out a Number of Small
+Torpedoes._--This arrangement is shown at Figs. 132 and 133. The
+small vessels or torpedoes are designed to be first sunk and then
+exploded, chiefly for clearing harbour or the like of mines or other
+obstructions. These results are accomplished by means of the following
+devices and arrangements, that is to say, each of the small vessels
+or torpedoes _F_ is provided with apparatus which is included in an
+electrical circuit formed by a suitable insulated cable _G_, extending
+throughout the train of small vessels or torpedoes _F_. One vessel of
+this train, preferably the rear one, is connected with the station by
+an electrical cable _H_, which is payed out from a coil or coils, or
+a reel or reels, in the said vessel as the same travels through the
+water. This cable _H_ connects with the cable _G_, which is connected
+with the towing boat _A_, and passes through the series of boats
+_F_ to the said cable _H_. One wire of the said cable is arranged
+in combination with sealed or covered apertures in the bottom of a
+compartment or compartments of these small vessels _F_, as shown at
+_I_, the covers of these apertures being so formed as to be ruptured
+or destroyed by the explosion of a cartridge or cartridges placed in
+the said compartment or compartments. When a current of electricity is
+sent through the aforesaid wire of the cable it will explode the said
+cartridges and open the apertures, thereby admitting water into the
+said compartments so that the vessel _F_ will sink.
+
+The cable _G_ that passes through the train of torpedoes or vessels _F_
+is so arranged that when a current passes through the other wire of the
+said cable it will fire cartridges placed in the charge chambers or
+magazines of the said small vessels, as shown at _J_. The part of the
+cable or towing line _G_, which connects the towing boat _A_ with the
+train of small boats or torpedoes _F_, is attached to a hook or other
+device, which can be disengaged by sending a current through the cable
+_K_, connecting the boat _A_ with the shore or other station. It will
+be understood that when being used for this purpose the said boat _A_
+is not or need not be charged with explosive material.
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XLI]
+
+The aforesaid towing boat _A_ takes the train of torpedoes _F_ to any
+required position. It is then disengaged from the train, leaving the
+said small vessels or torpedoes _F_ floating in such position. Then by
+sending a current first through one wire of the cable _H_ the boats _F_
+are first sunk by the explosion of the cartridges and opening of the
+apertures, as above described. They may then be discharged immediately
+by sending a current through the other wire of said cable _H_ and
+firing the cartridges in their magazines, or they may be left submerged
+to form mines which may be exploded at any desired moment.
+
+The said small vessels or torpedoes may be provided with vertical rods
+to indicate their position to the operator at the station; these rods
+are shown at _L_, and they should be made hollow to allow the air in
+the water compartments or chambers to escape to permit the water to
+enter the same when the vessels _F_ are to be sunk; or other suitable
+provision may be made for the escape of the air from these compartments.
+
+The said vessels _F_ are preferably made cylindrical with conical ends,
+and are provided with suitable insulating and water-tight packing
+boxes, as shown at _F_^{1} for the cable _G_ to pass through at the
+stem and stern of each vessel.
+
+_The Lay Torpedo in Clearing Obstructions._--For this purpose the
+torpedo boat is provided with an apparatus, shown at Figs. 134 and
+135, in combination with the electric cable, whereby the said boat
+is controlled and guided, and there is arranged in the boat _A_ a
+compartment _A_^{3}, from which extends down into the water a line
+or rod _U_, provided at its outer end with a hook or claw _U_^{1},
+properly formed to take hold of any chain or bar with which it may come
+in contact. In the said compartment _A_^{3}, and upon the upper end of
+the said line or rod _U_, is placed a small case or cylinder _U_^{2}
+containing a charge of dynamite or other explosive material and a
+cartridge or fulminating cap, or a bottle of sulphuric acid, surrounded
+with a certain quantity of chlorate of potash and sugar. This case
+or cylinder _U_^{2} is shown detached and drawn to an enlarged scale
+at Fig. 135, and it will be seen that the said case is provided with
+a tube 1 containing a cartridge, or a phial filled with explosive
+substance at 2, and a ball or weight at 3. The said case is fitted
+to slide upon the said line or rod _U_, and when placed at the upper
+end thereof and not held or retained will slide to the lower end of
+the same. In the said compartment _A_^{3} is arranged at _U_^{4} an
+electro-magnetic apparatus, included in the circuit of the said cable,
+and connected with a bolt or catch which in its normal position holds
+the said explosive case and prevents its running down on the grappling
+line or rod _U_. This explosive case is also provided at its lower end
+with a grappling hook _U_^{5}.
+
+When the grappling hook _U_^{1}, on the lower or outer end of the line
+or rod _U_, engages with any obstruction the boat will be stopped, and
+this stoppage will be indicated on the keyboard. The operator by this
+indication is apprised of the stoppage of the boat by an obstruction,
+and by sending a current through the cable by means of a switch
+provided for this purpose on the keyboard he can immediately release
+the explosive case _U_^{2}, which runs down the line or rod _U_, and
+engages by its grappling hook _U_^{5} with the hook _U_^{1}. The line
+or rod _U_ is then disengaged from the boat _A_, and the explosive
+case _U_^{2} turns or falls over. As it turns over the ball or weight
+3 contained in the tube 1 drops on the said phial 2, fractures it, and
+thereby allows the acid to mix with the explosive or fulminating charge
+and explode the case _U_^{2}. This explosion will rupture or destroy
+the obstructing chain or bar, so that the ironclad ships or other
+vessels can pass freely and safely into the harbour or beyond the point
+where it was intended to stop them.
+
+_Used to clear away Mines and Electric Cables._--For this purpose there
+is an implement _V_ provided, Fig. 136, somewhat of an anchor form, but
+with four or any desired number of arms _V_^{2} extending outward at
+a suitable angle from its shank _V_^{1}. In the neck of each of these
+arms are fitted two small plain or toothed discs _V_^{3}, which are so
+arranged as to present their teeth to any object lying in the angle or
+corner formed by and between the arms _V_^{2} and shank _V_^{1} of the
+said implement, as shown at _W_.
+
+In using this implement it may be attached to a line or cable coiled
+in the torpedo boat, which, in this case, is used without being
+charged with explosive material, and is sent in advance of any ship
+that has to enter or pass through the suspected water. This line must
+be arranged in combination with a detaching apparatus controlled by
+electro-magnetic apparatus included in the circuit of the cable which
+connects the torpedo boat with the keyboard at the operating station.
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XLII]
+
+By sending a current from the station the operator releases the said
+implement or its line from the detaching hook or holding device. The
+said implement then sinks to the bottom; then the said boat returns
+to the ship, paying out the said line as she so returns. The end of
+this line is then taken by a steam tug or other vessel, and the said
+grappling implement is thereby dragged along through the water over
+which the ships are to advance, thus breaking any wires or cables that
+may be in its course. This operation is shown at Fig. 137, in which _A_
+is the towing boat, _K_ the controlling cable, _V_ the said implement,
+_V_* the line attached to the implement _V_, _X_ _X_ submerged mines,
+and _X_^{1} _X_^{1} are the mine cables.
+
+In some instances it may not be practicable to reach the enemy's
+ship or other object of attack directly from the station to which
+the torpedo boat is connected, and from which it is controlled. In
+this case a small boat, &c., is used in addition, which should be so
+arranged as to present to the enemy's view as slight a surface as
+possible. This mode of attack is shown at Fig. 138, where _A_ is the
+torpedo boat, and _N_ is the small auxiliary boat. This boat _N_ is
+provided with a keyboard and battery like that described at page 144,
+and the electric cable _L_, carried on and payed out from the torpedo
+boat _A_, is connected with the keyboard. The boat _N_ is also attached
+to and towed by the torpedo boat _A_ by the tow line _O_; and the
+torpedo boat is steered and guided by means of the said keyboard in the
+boat _N_. The auxiliary boat is designed to contain two men, who lie
+down, one at the bow, the other in any convenient position abaft him;
+the latter has control of the keyboard, while the former by the aid of
+a telescope keeps the torpedo boat in view, and transmits his orders to
+the man at the keyboard. On arriving at such a distance from the enemy
+as to render an attack practicable, the tow line _O_ is disengaged,
+and the torpedo boat _A_, guided and controlled, and fired from the
+boat _N_. The torpedo boat being exploded, the auxiliary boat can be
+rowed back to the station or ship to which it belongs. By this means
+the range of action of the torpedo boat is greatly extended, and with
+comparatively slight danger to those employed in making the attack.
+
+A more recent form of the Lay torpedo boat is shown at Figs. 139, 140,
+and 141, where Fig. 139 is a plan or top view of such a boat, Fig. 140
+is a side elevation of the same, and Fig. 141 is a midship section on
+the line _x x_. _A_ is the hull of the boat, _a_ is the main or central
+portion of the said hull, _b_, _b_ are side or auxiliary portions of
+the same. These parts _a_ and _b_ may be oval or circular in transverse
+section; they are constructed of thin steel or other suitable sheet
+metal, and secured together by riveting or bolting. The side or
+auxiliary portion _b_ form the reservoirs or chambers for the gas; they
+also serve to contain the propelling engines. _c_ is the magazine, _d_
+the chamber or compartment for containing the coiled cable, _e_ is the
+compartment containing the electrical steering and other apparatus, _f_
+is the firing rod or pin, _g_ is the water ballast chamber, _h_ is the
+cable, _i_ the paying-out tube, _j_, _j_ are the screws or propellers
+which rotate in opposite directions, and _k_, _k_ are the sight or
+guiding rods.
+
+The parts of the apparatus or mechanism whereby the various operations
+of the torpedo boat are effected are connected to the cable and
+controlled by electric currents transmitted from the station through
+the cable, as previously described. The Lay torpedo boat weighs about 1
+ton, its length is 23 feet, and speed 12 knots per hour.
+
+_Spar or Outrigger Torpedo._--By a spar or outrigger torpedo is meant a
+torpedo which is carried at the end of a pole or spar projecting from a
+boat or vessel, and which may be fired either by contact or at will.
+
+This system of submarine offence has up to the present time been the
+only one that has successfully stood the crucial test of actual warfare.
+
+During the civil war in America the spar torpedo attack was resorted to
+by the Confederates and Federals, principally by the former, the result
+being the loss of two large men of war and severe injury to several
+other ships composing the Federal fleet, and the loss of one vessel of
+war belonging to the Southerners.
+
+The spar torpedo was also used on several occasions by the Russians in
+their attacks on the Turkish ships in the war of 1877-8, but in only
+one attempt was it the means of sinking a Turkish vessel.
+
+_Description of McEvoy's Duplex Spar Torpedo._--At Fig. 142 is shown a
+sketch of Captain McEvoy's improved patent duplex spar torpedo, which
+is the form most generally used at the present time, and which seems to
+fulfil all the requirements of such a submarine weapon, viz.:--
+
+    1.--Handiness, at the same time capable of containing a
+    charge of gun-cotton sufficient in contact to destroy
+    the most powerful vessel afloat.
+
+    2.--Certainty of action.
+
+    3.--Capable of being fired either on contact or at will.
+
+    4.--Mode of attaching the spar simple and very secure.
+
+[Illustration: LAY'S LOCOMOTIVE TORPEDO.
+
+PLATE XLIII]
+
+In Fig. 142, _a_ is the case, capable of containing some 33 lbs. of
+gun-cotton; _b_ is the tube through which the three wires _w_, _w_^{1},
+and _w_^{2} are led; _c_ is the socket in which the wooden or steel
+spar is introduced and secured, _d_ is the striker, which is attached
+to a brass contact plate within the head of the case _a_ in such a
+manner that any pressure either on the head or side of the striker _d_
+will force the aforesaid plate in contact with the two studs to which
+the battery wires are attached; _e_ is a cradle affixed to the striker
+_d_ to ensure its action on contact being made by the torpedo with the
+attacked vessel; the explosive is inserted at _f_, the socket _c_ being
+made to screw on and off.
+
+When a hollow steel spar is used, the battery wires are sometimes led
+through the interior of the torpedo and the spar, by which means they
+are well protected; the only objection to this method of leading the
+wires being the probability of injury to them, should the spar be
+broken on contact, or by a shot.
+
+_McEvoy's Arrangement of Torpedo Wires._--At Fig. 143 is shown the
+arrangement of wires as devised by Captain McEvoy, whereby the spar
+torpedo may be exploded at will or on contact. _c_ and _z_ are the
+poles of the firing battery, to which are attached respectively the
+wires _d_ and _d_^{2}; _f_ is the fuze, which is placed in the centre
+of the charge, and to the poles of which the wire _d_^{2} is attached,
+the other end of this wire being connected with the stud _s_; to the
+stud _s_^{1} is attached the other end of the wire _d_, and at the
+point _c_ in the same wire is inserted a contact breaker; another wire
+_d_^{1} is connected to the wires _d_ and _d_^{2} at the points _r_
+and _r_^{2} respectively, and at the point _k_ in this same wire is
+inserted a firing key, which latter is shown in section at Fig. 144,
+from which the mode of connecting the two ends of the wires and of
+using the key will be at once apparent. The contact breaker is somewhat
+similar to the firing key, but there is no spring in it, contact being
+made or broken by screwing the two parts together or apart. The object
+of the contact breaker is to prevent the torpedo being exploded by
+contact, and so to place the control of the weapon entirely in the
+hands of the operator. As will be seen from Fig. 143, if contact is
+broken at _c_, it is impossible to fire the torpedo unless the firing
+key _k_ be pressed in; but should contact be made at _c_, then either
+by means of the firing key _k_, or by the torpedo striking the hostile
+vessel, its ignition will be effected.
+
+The foregoing method of arranging the spar torpedo wires is certainly
+very neat and effective, and is at the present time in extensive use.
+As yet it has not been adopted by the English government, they still
+preferring to fire the spar torpedo at will alone.
+
+The different methods of manipulating the spar torpedo from boats will
+be described in the following chapter.
+
+_General Remarks on Offensive Torpedoes._--The torpedoes that have been
+described in this chapter are the only ones that at the present time
+can be considered as having been proved to be practically useful, and
+which in future wars may be employed against ships with some chance of
+success.
+
+The spar, the Whitehead fish, and the Harvey towing torpedo have each
+been subjected to the test of actual service, the former weapon being
+the only one that has under those conditions been successfully used.
+Taking this fact into consideration, also the high pitch of excellence
+that has been attained in the construction of steam torpedo boats, and
+also the results of the numerous exhaustive experiments that have been
+from time to time carried out in England, America, and Europe, with
+various modifications of the locomotive, towing, and spar torpedoes,
+there can be no two opinions as to which of the numerous species of
+offensive submarine weapons is the most practicable and effective, and
+that is the spar or outrigger torpedo.
+
+To manipulate successfully locomotive and towing torpedoes in an attack
+against hostile vessels, the operators must be not only unusually
+fearless and self-possessed, but also must possess a thorough practical
+knowledge of the complicated method of working and manoeuvring those
+weapons--in fact, they must be specialists; whilst in the case of the
+spar torpedo, which may be fired by contact, it is only necessary to
+employ men capable of handling a boat well, and possessed of dash and
+pluck, to ensure an attack by such means being generally successful.
+Of course under some circumstances, such as in a general action, when
+the locomotive and towing torpedoes are manipulated from specially
+constructed torpedo vessels, they will prove of great value, and the
+fish torpedo fired from a boat, in close proximity to the attacked
+vessel, in smooth water, and unmolested, would sink a vessel which
+under the same circumstances, owing to her being protected by booms,
+might prove impregnable to a spar torpedo attack; but such favourable
+conditions will not often occur in war time.
+
+[Illustration: M^{c.} EVOY'S DUPLEX SPAR TORPEDO.
+
+PLATE XLIV]
+
+As an offensive submarine weapon of defence, the Lay torpedo boat
+should prove of real value; and also manoeuvred from specially
+constructed vessels, it seems capable of being used in a variety of
+ways. As yet little is known of this weapon, all the experiments
+carried out with it having been confined to America; but now that
+Russia has adopted it, and one or two have also been secured by the
+Peruvians, its practical value will become more generally known.
+
+
+
+
+CHAPTER VI.
+
+TORPEDO VESSELS, BOATS, AND SUBMARINE BOATS.
+
+
+_EMPLOYMENT of Torpedo Ships._--Torpedo ships, that is to say,
+sea-going vessels, very fast, handy and impregnable, specially
+designed to carry and operate offensive submarine weapons, such as
+locomotive, towing, and the spar torpedoes, especially the former, are
+now considered as a necessary and valuable adjunct to a fleet, their
+special work being to give the coup de grâce to disabled ironclads
+in a general action; they will also be used to attack the ships of
+a blockading force, and against rival torpedo vessels. As a general
+rule these torpedo ships will be armed with the ram and torpedoes
+only, heavy guns being dispensed with, though the Nordenfelt and other
+machine guns will be considered necessary.
+
+_The German Torpedo Vessel Uhlan._--This torpedo vessel was built in
+Germany by the Stettin Engine Company, and launched in 1876.
+
+She is armed with a contact torpedo charged with dynamite carried on a
+10-foot ram, lying deeply under the water line. To protect the vessel
+from the effects of the discharge of the torpedo, she is built with two
+complete parts, sliding one within the other, and having a considerable
+extent of intermediate space between them. This space is filled with a
+tough and elastic material (cork and marine glue), which even in the
+case of the bows being carried away, would afford a second line of
+resistance. The _Uhlan_ carries an engine of one thousand indicated
+horse power. The steam is supplied by Belleville's tubular generator.
+These engines occupy by far the greater space of the vessel, only a
+very small portion being left for her crew and coal. This great power
+of the engines is necessitated by the fact that she has to be driven
+at a very high speed, at the same time she has a very great draught,
+also the greatest facility of steering has to be attained; hence the
+proportion of width to length, 25 to 70 feet. In order to save the
+crew at the worst, a raft is constructed, which is also filled with a
+mixture of cork and marine glue, and is placed near the helm. The mode
+of operating with the _Uhlan_ is as follows:--
+
+The dynamite torpedo is affixed to the point of the ram by the aid of
+divers. The rudder is then fixed, and the crew opening a wide port on
+the vessel's side, jump on the aforesaid raft. The steamer then rushes
+forward, and explodes its torpedo in contact with the hostile vessel.
+The crew hold on to the torpedo ship, and in case she is not injured
+board her again and repeat the manoeuvre, if necessary.[M]
+
+This is a novel form of torpedo boat, but does not seem to be a very
+practicable method of torpedo attack.
+
+_Admiral Porter's Torpedo Ship Alarm._--The _Alarm_ torpedo ship was
+built from plans designed by Admiral David D. Porter, U.S.N. Her
+total length, which includes a ram 32 feet long, is 172 feet; her
+beam is 27 feet 6 inches, and her draught of water is 11 feet. She is
+built of iron on the bracket plate system, that is to say, she has a
+double hull, one shell being constructed inside the other. Her double
+bottom is divided into a number of water-tight compartments. The whole
+interior of the vessel is also built in compartments, which may be
+hermetically closed, so that in case of both the shells being ruptured,
+it would still be impossible to fill the entire ship with water. She is
+steered by the same apparatus which propels her, viz. the Fowler wheel,
+which is illustrated at Fig. 145.
+
+This wheel turns on a vertical shaft, and its paddles are feathered by
+an eccentric cam in such a manner that at one part of their revolution
+they have a pushing and drawing action on the water, while at another
+part they present only their edges. In fact it is simply a feathering
+paddle wheel, turned horizontally instead of vertically. By suitably
+turning the cam wheel, which is done from the helm, the feathering of
+the paddles is caused to occur at different points; and in this way
+the vessel may be turned, or rather her stern twisted around, as if
+on a pivot. At the same time, by suitably adjusting the paddles, the
+ship goes ahead, or astern, the engine meanwhile running in the same
+direction.
+
+By the apparatus above described it is considered that the _Alarm_ is
+afforded not only a means of speed, but of being handled with the
+utmost readiness, which latter is absolutely essential in such a
+vessel, as she must always meet her antagonist bows on.
+
+The steering is accomplished from the wheel house located aft on the
+deck, or below deck, as all the appliances in the wheel house for
+steering, &c., are duplicated below. By means of a hand lever beneath
+the wheel, steam is admitted to a small auxiliary engine which works
+the cam that adjusts the paddles. Then by turning the horizontal hand
+wheel in either direction, the helmsman controls the movement of
+the cam, as desired. Just above the wheel is a dial with a pointer,
+which enables him to note the position of the paddles, and so adjust
+them as ordered. Inside the wheel house there are also devices for
+communicating with the men working the bow gun, and with those managing
+the torpedoes.
+
+_Her Armament--Engines._--At Fig. 146 is shown the spar and mode of
+working it. It consists of a long hollow iron cylinder lying on its
+supports between decks. Its outboard end rests in a kind of trough, and
+to this extremity the torpedo is fixed. The spar is controlled by means
+of tackles and a steam winch. The side spars are 18 feet, and the bow
+spar 32 feet in length. If the hostile vessel is defended by torpedo
+guards, by means of a mechanical contrivance the torpedo signals the
+fact, and is not exploded until the vessel has forced the obstructions.
+The engines of the _Alarm_ are compound, with four cylinders, the
+condenser being placed between them. There are four cylindrical tubular
+boilers with an aggregate heating surface of 4,600 square feet. Her
+speed is about 16 knots. Her upper deck is only 3 feet above the water.
+She is fitted with an electric light, and also with machine guns on her
+broadside.[N]
+
+This is undoubtedly a most formidable vessel, both as a ram and a
+torpedo ship, and if capable of performing all that is expected of her,
+will prove a valuable addition to the United States Navy.
+
+[Illustration: THE "ALARM" TORPEDO SHIP.
+
+PLATE XLV]
+
+_Captain Ericsson's Torpedo Vessel "Destroyer."_--This torpedo vessel
+was devised and built by Captain John Ericsson. The _Destroyer_ is
+130 feet long, 11 feet deep, and 12 feet beam, extreme; both ends of
+her hull are precisely alike, and terminate with very fine wedges.
+The rudder is attached to a vertical wrought iron post welded to a
+prolongation of the keel, just abaft the propeller, as shown at Fig.
+147. The tillers consist of thin plates of iron riveted on opposite
+sides of the rudder, a few inches from its bottom. These tillers are
+operated by straight rods connected to the pistons of horizontal
+hydraulic cylinders of 5 inches diameter, which are attached to the
+sides of the keel. The steering gear by the above arrangement is placed
+10 feet below the water line, while the top of the rudder is 6 feet
+below the same, and thus perfect security is afforded to this most
+important feature of a torpedo vessel. The intention of the designer
+in constructing this vessel is to render her so far impregnable, that
+in attacking bow on she can defy the opponent's fire, at the same
+time offering absolute protection to her commander and steersman, and
+also protecting the base of her funnel. The leading feature of the
+construction of the hull of the _Destroyer_ is its being provided
+with an intermediate curved deck, which extends from stem to stern,
+and which is composed of plate iron strongly ribbed, and perfectly
+water-tight. This intermediate deck supports a heavy solid armour
+plate, fixed transversely to the line of keel, and 32 feet from the
+bow, inclined at an angle of 45°, and supported on its after side by
+a wood backing 4 feet 6 inches in thickness. Behind this formidable
+shield the steering wheel is manipulated, a wire rope extending from
+its barrel to a four-way cock placed near the stern, by means of which
+water pressure is admitted alternately to the hydraulic cylinders,
+previously mentioned, the motion of whose pistons actuate the rudder.
+The lower division of the vessel is ventilated by powerful blowers, and
+contains the machinery; it also affords a safe retreat for the crew
+during the attack. The upper division is filled with blocks of cork,
+excepting a small part near the bow, occupied by the aforesaid armour
+plate and wood backing.
+
+The deck house is 70 feet long, and composed of plate iron, riveted
+water-tight to the upper part of the hull. As there are no openings in
+the sides of this deck house, the vessel may be run with her upper deck
+under water.
+
+_Armament of the "Destroyer."_--The _Destroyer_ is to be armed with
+torpedoes somewhat similar to the projectile torpedo, drawings of
+which were submitted by Captain Ericsson, the inventor, to Emperor
+Napoleon III. in 1854. The present weapon is composed of a solid block
+of light wood, the explosive charge being contained in a metallic
+vessel inserted at its forward end. Instead of being circular, as was
+the case with the original torpedo, its transverse section is square,
+with parallel top and bottom and vertical sides, forming very sharp
+wedges at both ends, cased with steel plates. The extreme length of
+the _Destroyer_ torpedo is 23 feet. Ignition is effected by means of a
+percussion fuze placed in the head of the weapon.
+
+_Operating the Torpedo._--The method of operating the torpedo is that
+of inserting it into a horizontal tube near the bottom of the vessel,
+provided with valves for keeping out the sea during the process of
+insertion, as shown at Fig. 148. When near the hostile vessel, this
+valve is opened, and the torpedo expelled by a piston actuated by steam
+power, the expulsion being effected without recourse to gunpowder
+or other explosive agent. The area of the actuating piston of the
+_Destroyer_ is 314 square inches, while the sectional area of the
+projectile is only 196 square inches; this difference in size of the
+two areas is a special and important feature of the invention, as will
+be understood from the following: the tension of the acting medium in
+the _Destroyer_ exceeds 200 lbs. per square inch, therefore the torpedo
+will be pushed out by a force of (314 × 200) / 196 = 320 lbs. per
+square inch, and as the distance passed by the piston while impelling
+the torpedo is 30 feet, an energy of nearly 2,000,000 foot-pounds will
+be imparted to the projectile.
+
+When making an attack, it is intended that the vessel should at the
+instant of firing her torpedo reverse her engines, this retrograde
+motion being greatly assisted by the recoil, which must attend the
+discharge of a body weighing some 1,400 lbs. impelled by the aforesaid
+enormous force, and moving through a distance of 30 feet before
+reaching the water.[O]
+
+Certainly this new system of submarine attack seems feasible, but it
+has yet to prove, in common with all other new inventions, whether its
+theoretical capabilities are also practical ones. At Fig. 149 is shown
+a general view of this novel torpedo vessel under weigh.
+
+[Illustration: THE "DESTROYER" TORPEDO SHIP.
+
+PLATE XLVI]
+
+_Torpedo Boats._--In offensive torpedo warfare, whether using the
+spar, locomotive, or towing torpedo, especially in the case of the
+former class of submarine weapons, to ensure a successful attack it
+is absolutely essential to operate those weapons from steam boats,
+which are capable of fulfilling as near as possible the conditions
+herein enumerated:--
+
+    1.--They should be capable of steaming at least 18
+    knots per hour.
+
+    2.--Their engines should be noiseless, and easily
+    managed.
+
+    3.--They should be extremely handy.
+
+    4.--No smoke should enable their approach to be
+    detected, or glare from their fires.
+
+    5.--That it should be possible to raise steam in them
+    in a few minutes.
+
+    6.--They should be built in water-tight compartments,
+    and covered fore and aft to prevent being swamped.
+
+    7.--The crews should be protected as far as practicable
+    from rifle fire.
+
+In addition to the foregoing, for the purpose of rendering these craft
+capable of defending themselves against the attack of guard boats, and
+also of being employed as such, and on river expeditions, &c., they
+should be built sufficiently strong to enable them to carry a small gun
+either in the bows or stern; this would apply more especially to those
+torpedo boats which are part of a ship's stores.
+
+During the last four years a very large number of torpedo boats have
+been built, which more or less fulfil the aforesaid conditions, nearly
+the whole of which have been constructed by the two English firms, viz.
+Messrs. Thornycroft and Co. and Messrs. Yarrow and Co., and to the
+latter firm is due the honour of constructing the fastest vessel as yet
+in the world.
+
+Up to the present time, a specially built torpedo boat has on only one
+occasion been used on active service, viz. at the attack on a Turkish
+monitor on the 20th of June, 1877, which is detailed at length in the
+following chapter. This boat was one of Messrs. Thornycroft and Co.'s
+launches, and from all accounts she behaved wonderfully well under the
+most untoward circumstances.
+
+_Thornycroft Torpedo Launches._--Messrs. Thornycroft and Co., of
+Chiswick, London, have during the last six years built a large number
+of torpedo launches for the English government and for several of the
+principal European governments.
+
+_Norwegian Launch._--The first torpedo boat ever built by this firm was
+the one shown at Fig. 150, for the Norwegian government. This boat was
+57 feet in length by 7 feet 6 inches beam, drew 3 feet of water, and
+the stipulated speed was 16 English statute miles, or nearly 14 knots
+per hour; which speed was not to be ascertained by a mere measured mile
+trial, but was to be 16 miles through the water in a run of one hour's
+duration.
+
+The hull of the vessel was constructed entirely of steel plates and
+angle bars, and, as may be seen from the diagram, was divided into six
+water-tight compartments, _A_, _B_, _C_, _D_, _E_, _F_.
+
+The compartments marked _A_ and _F_ in the stem and stern were for
+stores; those marked _B_ and _E_ were fitted with seats for the crew,
+and were provided with movable steel covers, so that on going into
+action, or during rough weather, they might be completely covered.
+
+The compartments _C_ and _D_ are for the steersman and the machinery
+respectively, and were covered completely by steel plating 3/16 of
+an inch in thickness--a thickness sufficient to withstand Snider or
+Martini-Henry bullets, fired from a distance of twenty paces.
+
+The compartment _D_ was furnished with a hood, having slits 1/4 of
+an inch wide, all round, through which the steersman could see with
+sufficient distinctness to direct his course easily. Motion was
+communicated from the wheel to the tiller by means of steel wire ropes,
+which it was originally intended should be encased in wrought iron
+tubes.
+
+The possibility however of these tubes being bent by a shot, and so
+jamming the wire ropes, led to this arrangement being abandoned, and
+the ropes were simply run through eyes at intervals along the side.
+
+The armament consisted of a cylindro-conical shaped torpedo towed from
+the top of the funnel, round which a ring was fitted with two pulleys
+for the towing rope, the strain being taken off by means of two stays
+attached forward.
+
+The length of this torpedo was 13 feet and the diameter 9 inches, and
+with a speed of 11 knots it has diverged to about 40 degrees from the
+direction of the boat's motion when running in smooth water.
+
+The torpedo is worked by means of a small winch and brake fixed on
+the after part of the engine room skylight; davits are provided for
+dropping the torpedo overboard.
+
+The engines were compound, of the usual inverted double cylinder direct
+acting type, capable of developing about 90 indicated horse power, and
+were fitted with a surface condenser, so that the vessel could run in
+salt water, without danger of injuring her boiler.
+
+A small tank contained a supply of fresh water, to make good
+deficiencies arising through leakage, and from steam escaping at the
+safety valves, &c.
+
+The circulating, air, and feed pumps were driven by a separate engine.
+
+The boiler was of the locomotive type, the shell being made of Bessemer
+steel; the fire box and its stays of copper, and the tubes of solid
+drawn brass.
+
+On the official trial, which took place on the Thames on the 17th of
+October, 1873, the number of revolutions done in the hour was found
+to be 27,177, and the number required to do a mile in still water was
+1578. The distance run in the hour was then, 27,177/1578 = 17·22, or
+very nearly 17-1/4 miles.
+
+The steam pressure during the trial averaged 85 lbs. per square inch,
+and the vacuum 25-1/2 inches.
+
+_Swedish and Danish Boats._--Boats of the same size and similar in all
+particulars to the foregoing one--excepting the engines, which are
+improved by driving the air pump, feed pump, and circulating pumps off
+the main engines, and abolishing the auxiliary engine, which performed
+these duties in the case of the Norwegian boat--were made for the
+Swedish and Danish governments. The result was an increase of speed to
+17·27 miles in the case of the Swedish boat, and to 18·06 miles, or
+15-5/8 knots, in the case of the Danish boat.
+
+There is no information regarding the armament of the Swedish boat, but
+the Danish boat was armed with two spindle-shaped torpedoes 12 feet
+long and 11-1/2 inches diameter, somewhat like the Whitehead torpedo.
+They were placed on deck longitudinally near the funnel, so as to
+facilitate launching, and were arranged to be towed from an upright
+pole 8 feet high, placed about 6 feet from the stem.
+
+A small winch was fixed on either side aft, to pay out the towing line,
+and to bring back the torpedo. By these arrangements the torpedo could
+be projected at a large angle from the direction of the boat's motion,
+and at considerable velocity. The speed of the boat when towing one of
+these torpedoes is about 10 knots.
+
+_Austrian and French Boats._--The next size of torpedo vessel is that
+supplied to the Austrian and French governments, which is shown at
+Fig. 151. The dimensions are:--length, 67 feet; beam, 8 feet 6 inches;
+draught of water, 4 feet 3 inches. The guaranteed speed in the case of
+the Austrian boat was 15 knots in a run of one hour's duration, and in
+the case of the French boats 18 knots, in a run of two hours' duration.
+These boats were built of somewhat thicker plating than the 57 feet
+type, and the armour was extended.
+
+They were divided into six water-tight compartments, and they differed
+from the Scandinavian boats in having the spaces forward and aft of the
+machinery permanently decked, instead of being covered with movable
+steel covers only.
+
+The machinery was somewhat similar to that in the Scandinavian boats,
+excepting that the engines were capable of developing 200 indicated
+horse power, and that the air was supplied to the furnace by being
+forced into an air-tight stoke hole, instead of being forced directly
+under the fire grate.
+
+The armament of these vessels consisted of two torpedoes attached to
+the end of wooden poles, 4-1/2 inches diameter and about 43 feet long,
+connected to the battery by insulated wires, and arranged to be fired
+either by coming in contact with the enemy's vessel or at any distance
+from it, at the will of the operator.
+
+The torpedoes themselves were simply copper cases, of sufficient size,
+in the case of the Austrian boat, to contain 11,000 cubic centimetres
+of explosive, and in the case of the French boats, to contain 25
+kilogrammes of dynamite.
+
+The mode of arranging the wires is similar to that explained at page
+155. The method of manipulating the torpedo poles consists of two tubes
+riveted together at right angles, so as to form something like the
+letter T. The torpedo pole is put through the horizontal tube, which is
+free to move round the centre of the vertical tube, and the vertical
+tube is free to move through a quarter circle at right angles to the
+centre line of the vessel.
+
+In attacking in front, the vertical tube is laid over till it is
+parallel to the water surface, and the horizontal tube is allowed to
+incline sufficiently far to allow of the end of the pole, when run out,
+to be depressed from 8 to 10 feet below the water-line. It is held in
+this position by a pair of blocks attached to the top of a short mast.
+
+In attacking on the broadside, the vertical tube is laid over till it
+assumes a position such as to allow of the pole, when swung round, to
+touch an enemy's vessel at about 8 or 10 feet below the water line.
+
+The speed trials of the Austrian boat took place on the 11th of
+September, 1875, when she did 24,700 revolutions on her hour's run
+on the Thames, and the number of revolutions required to do a knot
+in still water was found to be 1357. This gives the distance run in
+the hour as 18·202 knots, or 3·202 knots over the contract speed. The
+steam pressure averaged 105 lbs. per square inch, and the vacuum 25-1/2
+inches during the run.
+
+In the case of the French boats, the total number of revolutions done
+in the two hours' run in the roadstead off Cherbourg was 49,818, and
+the number required to do a knot in still water was found to be 1382,
+so that the distance run in the two hours was 36·05 knots, or just over
+the contract speed. During the two hours, the average steam pressure
+was 108 lbs. per square inch, and the vacuum 25 inches.
+
+The Austrian boat was sent to her destination on board a steamer, but
+the French boats, under the command of an experienced captain, steamed
+by themselves from Chiswick to Cherbourg, not crossing at the nearest
+points and running along the shore, but going boldly from Dover direct
+to Cherbourg.
+
+Shortly after the arrival of the French boats in Cherbourg, they were
+altered so as to attack in front only, as the French authorities found
+that these small vessels were better adapted for resisting the effects
+of an explosion at the bow than at any other part.
+
+The arrangement adopted is shown at Fig. 152, and consisted of a steel
+pole about 40 feet in length, having one end about 6 inches diameter,
+and solid, and the other about 1-1/2 inches diameter, and hollow; this
+pole was mounted at its solid end on small pulleys, which ran upon two
+ropes stretched fore and aft of the vessel; the other end, to which
+the torpedo was attached, was led over a pulley fixed on the bow.
+Ropes passing over pulleys to a windlass in the after compartment were
+attached to the inboard end, and by turning the windlass the pole was
+drawn backwards or forwards as required.
+
+It will be observed that as the pole is drawn forward, the inboard end
+being constrained to move in a line parallel to the deck, the outer end
+is depressed in the water, and is so adjusted that when the pole is run
+out to its full extremity, the torpedo is depressed to about 8-1/2 feet
+below the water level.
+
+_Dutch and Italian Boats._--The third size of boat built by this
+firm for the Dutch and Italian governments are 76 feet long and 10
+feet beam, and are guaranteed to do a speed of 18 knots. These boats
+are similar in design to the Austrian and French boats previously
+described, but differ from them in having engines of 250 indicated
+horse power, and in having more free board forward, so as to make them
+better sea boats.
+
+The Dutch type are armed with the outrigger torpedo, as fitted to the
+French boats, and the Italian type with the Whitehead fish torpedo.
+
+_The "Lightning" Type of Boat._--Now comes the _Lightning_ type of
+vessel, which is shown at Fig. 153. This vessel, built for the English
+government, is 84 feet long over all, 10 feet 10 inches beam, and
+draws about 5 feet of water. The machinery on board the _Lightning_
+is similar in design to that already described, and is capable of
+indicating 350 horse power. The hull of the _Lightning_ is made of
+heavier plating than usually employed, and her lines are fuller, as
+she is intended for use in a tolerably rough sea if necessary; and
+in order that she may be able to remain at sea for some time, cabin
+accommodation on a scale larger than in any of the other boats is
+provided for the officers and crew. The steering gear is arranged so
+that the vessel may be steered from the deck, or from the conning
+tower, and the usual telegraph gear is fitted to communicate from the
+deck, or from the conning tower, to the engine room.
+
+The top of the conning tower is supported on three screws, so arranged
+that it may be raised or lowered, and the space for sight adjusted
+according to the range of vision required, or the risk to be run from
+the enemy's missiles.
+
+The _Lightning_ is armed with fish torpedoes, which are discharged from
+her deck forward by means of a discharging apparatus.
+
+The torpedoes are charged with air, by means of one of Mr.
+Brotherhood's air-compressing pumps.
+
+The _Lightning_ on her preliminary runs attained a speed on the
+measured mile of 19·4 knots per hour, a speed which will be somewhat
+reduced when she has her torpedoes, &c., on board, but which will then
+be over 18 knots per hour.
+
+Several torpedo boats have been built and are in process of
+construction by this firm for the English government.
+
+[Illustration: THORNYCROFT'S TORPEDO BOATS.
+
+PLATE XLVII]
+
+_French Boats._--The next size of boats is the 87 feet type, as shown
+at Fig. 154. Of this type of torpedo launch several have been built and
+are now under construction for the French government.
+
+These vessels are 10 feet 6 inches beam; draught of water about 5
+feet. They are built of heavier plating than the _Lightning_, and are
+guaranteed to maintain a speed of 18 knots. The propellers in these
+boats are placed in front of the rudder, so as to give increased
+readiness in steering. In order to prevent oxidation as far as
+possible, the plates and frames below the water line are galvanised. A
+spark-catching apparatus is fitted to the base of the funnel, so as to
+prevent the position of the boat being betrayed to the enemy at night.
+
+The armament of these vessels consist of an outrigger arrangement
+similar to that described at page 167. They are also well adapted for
+the Whitehead torpedo. They are also provided with a strong buffer in
+the bows for deadening the shock, in the event of their coming into
+contact with an enemy's vessel at too high a rate of speed.
+
+_"Second Class" Boats and Mode of Manipulating the Fish Torpedoes
+from them._--Another type of Thornycroft torpedo boats, several of
+which have been built for continental governments, and which is termed
+"Second class," is shown at Fig. 155. These boats are 60 feet long, 7
+feet 6 inches beam, and draw some 3 feet of water; their guaranteed
+speed being 16 knots per hour. The mode of carrying the Whitehead fish
+torpedo, and manipulating it from such a boat by means of Mr. J. I.
+Thornycroft's invention, which has been fully described at page 140, is
+shown at Figs. 155 and 156, where Fig. 155 represents both torpedoes
+housed, and Fig. 156 one torpedo in the firing position, the other one
+being housed.
+
+Four of this type of Thornycroft torpedo boats were attached to H.M.S.
+_Hecla_ during her recent cruise in the Mediterranean, and have been
+very favourably reported on as follows:--They do not suffer from the
+blows of the sea, nor from the strains incident upon hoisting in and
+out; nor yet when they are suspended ready for lowering, in which
+latter position they have frequently remained for twenty-four hours;
+that under careful management they are perfectly safe in a heavy sea,
+and they possess good manoeuvring powers.
+
+The Thornycroft torpedo frames were found to perform well the services
+for which they are intended. When proceeding at ordinary speed they
+are nearly noiseless, and cannot be seen on a dark night at a distance
+of 100 yards.
+
+_The Thornycroft Propeller._--All the torpedo boats built by this firm
+are fitted with the propeller invented by Mr. Thornycroft, and which
+bears his name. It is a modification of what is known as the Dundonald
+propeller, the principal difference being that in the Dundonald
+propeller the blades are inclined backward in straight lines, while in
+the Thornycroft propeller they are curved.
+
+_Experiment at Cherbourg._--The following account of an experiment
+which took place at Cherbourg in March 1877, whereby to test the
+efficiency of a Thornycroft torpedo boat in exploding a spar torpedo
+under the bottom of a vessel proceeding ahead at the time, is taken
+from the _Times_, under date the 13th of March, 1877.
+
+[Illustration: THORNYCROFT'S TORPEDO BOATS.
+
+PLATE XLVIII]
+
+"Admiral Jaurez, who commands the squadron, ordered a disabled ship,
+the _Bayonnaise_, during a rather rough sea, to be towed out by a
+steamer belonging to the navy. A second lieutenant, M. Lemoinne, was
+sent for, and informed that he had been selected to make the experiment
+of launching the Thornycroft against the _Bayonnaise_ while both were
+in full sail. He accepted the mission without hesitation, picked out
+two engine men and a pilot, and went down with them into the interior
+of the Thornycroft, of which only a small part was above water; this
+visible portion being painted of a greyish colour, so as to be easily
+confused with the sea. The torpedo was placed so as to project from
+the bow of the vessel, at the extremity of which were two lateen
+sailyards about three metres in length. The towing steamer then took
+up its position in front of the squadron, and the Thornycroft also
+assumed the position assigned for it; an interval of three or four
+marine miles separating the torpedo boat and the _Bayonnaise_. On a
+signal being given, both were set in motion, the steamer advancing
+in a straight line, and the Thornycroft obliquely, so as to take the
+_Bayonnaise_ in flank. The steam tug went at 14 knots an hour, going at
+full speed in order to escape the Thornycroft. The latter went at 19
+knots an hour, a rate not attained by any vessel in the squadron. The
+chase lasted about an hour, the squadron keeping in the rear, so as to
+witness the operations. At the end of that time the distance between
+the Thornycroft and the _Bayonnaise_ had sensibly diminished, and at
+a given moment the former, in order to come up with the latter at the
+requisite distance, had to slacken speed to 8 knots an hour. The
+whole squadron watched this last phase of the struggle with breathless
+interest, and people asked themselves whether the shock of the torpedo
+would not infallibly destroy the little vessel which bore it. It was
+feared that the lives of the second lieutenant, Lemoinne, and his
+three companions were absolutely sacrificed. However, the two vessels
+got visibly nearer. All at once the Thornycroft put on a last spurt,
+and struck the _Bayonnaise_ with its whole force on the starboard
+bow. The sea was terribly agitated, a deafening report was heard, and
+the _Bayonnaise_, with a rent as big as a house, sank with wonderful
+rapidity. As for the Thornycroft, rebounding by the shock about fifteen
+metres off, even before the explosion occurred, it went round and round
+for a few moments, and quietly resumed the direction of the squadron.
+No trace remained of the _Bayonnaise_; it was literally swallowed up by
+the sea."
+
+The experiment was a most complete success, the torpedo boat not being
+in the least degree injured.
+
+_The Power of Flotation of a Thornycroft Boat after being pierced by
+a Rifle Shot._--On the 5th of July, 1877, Messrs. Thornycroft and Co.
+made an experiment with one of their torpedo boats to ascertain under
+what conditions flotation is still retained after the boat has been
+pierced by a rifle shot.
+
+The torpedo boat experimented on was similar to the one which has been
+described at page 169. A Martini-Henry was fired through her side,
+about a foot under water in the stoke hole. Whilst at anchor the water
+entered in sufficient quantity to fill an ordinary size bucket in
+twenty-five seconds, but when she was driven ahead less water entered,
+and on the speed of 10 knots being reached, little or no water entered.
+The hole was a little more than three quarters of an inch in diameter.
+
+The engagement on the Danube between the torpedo boat _Schootka_
+and some Turkish vessels, in which the former vessel was pierced by
+bullets, but yet did not sink, led to the above experiment being
+carried out.
+
+_Efficiency of Thornycroft's Engines._--As a practical proof of the
+efficiency of the engines supplied by Messrs. Thornycroft and Co.
+to their torpedo boats, a similar engine has been used for over two
+years to work the various machines in connection with their works at
+Chiswick.
+
+_Torpedo Boats built by Messrs. Yarrow and Co._--Messrs. Yarrow and
+Co., of the Isle of Dogs, London, are also very well-known torpedo
+boat builders, and have during the last four years constructed a
+considerable number of such vessels for the English and different
+continental governments, and, as has been before stated, they are the
+constructors of the fastest vessel in the world.
+
+_Dutch Torpedo Launch._--In 1875 this firm built a torpedo launch for
+the Dutch government, specially designed for ocean purposes. It was 66
+feet long, 10 feet beam, and 5-1/2 feet deep. She was driven by a pair
+of inverted direct acting engines. The boiler was of the locomotive
+type, with a working pressure of 140 lbs. per square inch, and capable
+of exerting a force of some 200 indicated horses.
+
+_Russian Torpedo Boat._--This firm also constructed for the Russian
+government two torpedo steamers 85 feet in length. The guaranteed
+speed of these vessels being 20 knots per hour. In 1878 the Russian
+government ordered one hundred exactly similar boats to be constructed,
+mostly at St. Petersburg, thus proving the high estimation held by that
+government of Messrs. Yarrow and Co.'s torpedo boats.
+
+_Description of a Yarrow Torpedo Launch._--Figs. 157, 158, and 159 show
+an elevation, section, and plan of a torpedo boat, Yarrow type, a large
+number of which have been built for the Russian and other continental
+governments.
+
+The length of this boat is 75 feet, its beam 10 feet, and draught of
+water 3 feet. She is built of steel of the best quality, no other
+metal possessing the requisite strength and stiffness for scantling,
+and plates of such lightness. It is divided into eight compartments by
+seven transverse bulkheads, the forward and after compartments being
+used for stores, the two central ones enclosing the machinery, while
+the steersman and operator are placed in the compartment immediately
+abaft the engines.
+
+The steersman's head projects above the deck, and is protected by a
+rifle proof steel truncated cone, the top part of which is movable like
+the visor of a helmet. The hull is decked over from end to end with a
+curved shield, the midship plating of which is capable of resisting
+rifle shots, even at close quarters; its curved form being well adapted
+for giving the maximum strength to the structure, and quickly frees
+itself from any large body of water.
+
+[Illustration: YARROW'S TORPEDO BOATS.
+
+PLATE XLIX]
+
+The propelling machinery consists of a pair of inverted compound
+condensing engines. The revolutions per minute at full speed are about
+470, and the indicated horse power about 280. The propeller is of
+steel. The funnel is fixed at one side of the centre line, to be out of
+the way of the bow torpedo pole and gear.
+
+This type of torpedo boat attains a speed of from 17-1/2 to 18-1/2
+knots per hour.
+
+The armament of some of these boats consists of three spar torpedoes, a
+bow, and two quarter ones. The bow pole, which is strong and heavy, is
+hauled out and in by means of a small auxiliary engine.
+
+Boats similar to these, but of larger dimensions, viz. 84 feet long and
+11 feet beam, have also been constructed by this firm. Speed from 19 to
+20 knots per hour.
+
+_English Torpedo Boats._--The following account of two torpedo
+boats which had been originally built by this firm for the Russian
+government, but, owing to the proclamation issued by the English
+government at this time prohibiting torpedo boats leaving England, were
+seized by the Customs authorities when on the point of completion, and
+were ultimately purchased by the English government, is an extract from
+the _Times_ under date the 4th of July, 1878.
+
+"These vessels are each 85 feet long with 11 feet beam, and draw,
+when fully equipped for service, an average of 3 feet of water. They
+are strongly constructed of steel, and are fitted with compound
+surface condensing engines capable of indicating 420 horse power. The
+high pressure steam cylinder of these engines is 12-1/2 inches in
+diameter, and the low pressure 21-1/2 inches, both having a 12 inch
+stroke. These boats are at present known by their builders' numbers,
+one being No. 419 and the other No. 420. The former is propelled by a
+three-bladed screw, 5 feet 6 inches diameter and 5 feet pitch; and the
+latter by a two-bladed screw of similar proportions. Messrs. Yarrow
+adopt supplementary engines for driving the air pump, circulating
+pump, and feed pumps; they consider this plan preferable to that of
+working these pumps direct off the main engine, as is sometimes done.
+One advantage in having separate pumping engines is that, whether the
+vessel is in motion or stationary, a powerful means is available for
+pumping her out, should the necessity arise. It is estimated by her
+builders that if the air pump and circulating pump were both utilised
+for this purpose, the water could be pumped out as fast as it could
+enter either of these vessels through one hundred holes made in the
+skin by Martini-Henry rifle bullets. If this is the case, these craft
+may be deemed safe from sinking so long as their machinery is working
+efficiently. The boiler is of the locomotive type, placed in the
+forward part of each vessel, and has a closed stoke hole. In connection
+with the boiler a very important improvement has been introduced by
+Messrs. Yarrow. This consists in a means of rendering the closed
+stoke hole safe for the men in the event of the collapse of a boiler
+tube--a contingency which cannot be absolutely guarded against. Its
+efficiency was proved beyond all question upon a previous trial of
+one of these boats. This was No. 419, which was tried on the 24th of
+May last under the supervision of the Admiralty officials. Upon that
+occasion an accidental rupture of one of the boiler tubes occurred
+nearly at the close of the runs over the measured mile, which so far
+had been very successful. When the boiler tube gave way the steam
+rushed out of the foremost hatchway from the compartment in which the
+smoke box end of the boiler is situated, and soon after from the two
+funnels. The men in the stoke hole, however, being shut off from the
+boiler, were uninjured, and remained at their post several minutes
+after the first outburst of steam. The accident, although an untoward
+event, was considered by the Admiralty officials as affording a highly
+satisfactory proof of the efficiency of Mr. Yarrow's invention.
+
+"The engines are placed amidships, and each vessel has spacious cabin
+accommodation aft, as it is intended that they may be used either as
+despatch or torpedo boats. For the latter purpose the cabin framings
+above deck are removed and replaced by steel plating. They are steered
+from the cabin, there being a look-out for the steersman just above
+deck level. The deck is clear of all obstructions, the two funnels
+being placed one on either side. They are fitted with balanced rudders
+and steer well, answering their helms very quickly."
+
+The trials of these two torpedo boats are taken from the _Engineer_
+under date the 19th of July, 1878. At that time these boats completely
+eclipsed in speed everything that had hitherto been done. At Fig. 160
+is shown in elevation this type of torpedo launch.
+
+"The trials were personally conducted by Mr. Yarrow, under the
+superintendence of the authorities from Whitehall, and consisted in
+a two hours' run without stopping, during which time the boats were
+tested at the measured mile at Long Reach. Each boat was run six times
+over the mile, three runs with the tide and three runs against it. The
+boats and machinery are similar in every respect, excepting that No.
+419 is fitted with a three-bladed propeller, and No. 420 a two-bladed
+one, their diameters and pitch being the same in both cases. The
+weights on board were accurately weighed, and amounted to 6 tons in
+each boat, including coals, water, crew, and ballast.
+
+"_Trial of No. 419._
+
+                            Min. Sec.   Knots per hour.
+
+    1st run down occupied    2   36         23·076
+    1st run up      "        3   20         18·000
+    2nd run down    "        2   35         23·226
+    2nd run up      "        3   16         18·367
+    3rd run down    "        2   32         23·684
+    3rd run up      "        3   14         18·557
+      Mean of the six runs, 20·818 knots per hour.
+      Mean steam pressure, 115 lbs. per square inch.
+      Vacuum, 23-1/2 inches.
+      Mean revolutions of main engines per minute, 456.
+
+"_Trial of No. 420._
+
+                            Min. Sec.   Knots per hour.
+
+    1st run down occupied    2  33-1/2      23·452
+    1st run up      "        3  25-1/2      17·518
+    2nd run down    "        2  32-1/2      23·606
+    2nd run up      "        3  21          17·910
+    3rd run down    "        2  32          23·684
+    3rd run up      "        3  24          17·647
+      Mean of the six runs, 20·636 knots per hour.
+      Mean steam pressure, 115 lbs. per square inch.
+      Vacuum, 24 inches.
+      Mean revolutions per minute, 466.
+
+"The highest speeds were obtained by No. 419, during the third runs up
+and down, the mean of which give 21·12 knots, which is equal to 24-1/3
+statute miles per hour, during which time the engines were making 470
+revolutions per minute. At the close of the runs, the bearings were
+found to be in first-class condition, and there was not the least sign
+of anything getting warm during any part of the trials."
+
+_Spanish Torpedo Boat._--The following description of a torpedo boat
+built by this firm for the Spanish government, enumerating all the
+improvements that have of late been effected in the construction of
+such vessels by members of this firm, is taken from the _Engineering_
+under date the 21st of February, 1879.
+
+"The alterations have a twofold character, and have reference to the
+arrangements for discharging the products of combustion from the
+furnaces and to those for steering the vessel. In brief, the boat is
+funnelless and is fitted with two rudders, one at each end. The main
+object in dispensing with the funnel is to enable the torpedo boat
+to approach as closely as possible to an enemy without being seen,
+a secondary, although still an important, consideration, being the
+absence of any obstruction to the steersman's view, such as a funnel on
+deck. The outlets for the smoke in the present instance are two ports,
+one on either side of the vessel, and placed about 15 feet in from the
+bow. Each of these smoke ports is fitted with a damper, and the smoke
+can be turned through either or both of the passages as desired. The
+control of these dampers is given to the steersman, who, on approaching
+an enemy, can direct the products of combustion through the port on
+the unexposed side of the vessel. The emission of smoke by day and of
+the glare and sparks by night are thus to a very large extent hidden
+from view, thus enabling the torpedo boat to approach very closely to
+the point of attack without being observed. The outlets are fitted
+with valves which are kept open by the blast, but which close on being
+struck by a passing wave. Should the vessel have to be out when a heavy
+sea is running the ports are closed, and a spare funnel is rigged up on
+deck, on one side. Although the smoke ports are placed forward in this
+boat, it is intended to place them aft in the next that Messrs. Yarrow
+build, as that arrangement will obviate the inconvenience at present
+experienced by those on deck from the heated gases of the furnace being
+carried along it at times by the wind, when on a certain course.
+
+[Illustration: YARROW'S TORPEDO BOATS.
+
+PLATE L]
+
+"The steering powers of the boat have next had attention from Messrs.
+Yarrow, and they have sought to remedy the defective steering common to
+these large quick-speed torpedo craft. To do this they have fitted the
+vessel under notice with two balanced rudders, one of which is placed
+forward about 10 feet from the bow, and the other in its usual position
+at the stern with the screw abaft it. Both rudders are connected
+with the same steering gear, and are operated simultaneously by one
+steersman. The forward rudder can be raised out of the water into a
+casing inside the boat if desired by means of a screw cut on the upper
+part of its spindle. By the same means, by unscrewing the collar on the
+spindle, the rudder can be released and dropped into the water should
+the necessity arise for so doing, by reason of its becoming fouled or
+damaged. In trials which have been made with this double-steering
+system, it has been found that when steaming at high speeds the forward
+rudder has a much greater control over the motion of the boat than the
+stern one. The reason assigned for this is that at high speeds the
+forward part of the boat is lifted out of the water, and consequently
+offers a diminished side resistance to any turning motion brought to
+bear upon it.
+
+"The boat in which these improvements have been introduced is 86 feet
+long by 11 feet beam and 5 feet 6 inches deep. She is fitted with
+compound engines having 22 inch and 12-1/2 inch cylinders, with a 12
+inch stroke, and making 520 revolutions per minute when running at full
+speed. She is propelled by a three-bladed screw 5 feet 6 inches in
+diameter and 5 feet pitch. Put through some evolutions with the view of
+testing her steering powers, the double rudder arrangement was found to
+answer exceedingly well, and she turned a circle of a diameter equal
+to about three times her own length in 1 minute 15 seconds. She turned
+equally well either going ahead or astern, and in fact her steering
+capabilities were satisfactorily demonstrated. The new arrangement for
+carrying off the smoke also answered very well, with the exception
+that the heated gases occasionally swept the deck, which objectionable
+result will be avoided in future boats."
+
+These boats are to be armed with spar torpedoes, and with the Whitehead
+fish torpedo, the cradles and fittings for which are shown at Fig. 161.
+
+_The Fastest Vessel in the World._--Another type of torpedo boat, of
+which one of the same dimensions has been built by this firm for the
+English government, is shown at Fig. 162. This vessel is as yet the
+fastest vessel in the world. The trials with this boat were made in
+March of this year, and were as follows:--
+
+     Runs.     Time,      Knots                         Knots
+             Min. sec.  per hour.                     per hour.
+
+    First     2   37  =   22·93}
+    Second    3    2  =   19·78}  Mean of first pair   = 21·35
+
+    Third     2   33  =   23·53}
+    Fourth    2   55  =   20·57}  Mean of second pair  = 22·05
+
+    Fifth     2   30  =   24·00}
+    Sixth     2   56  =   20·45}  Mean of third pair   = 22·23
+
+giving as a mean 21·93 knots per hour, or 25-1/4 statute miles. The
+boat was fully equipped for active service, i.e. with a load of 6-3/4
+tons on board. It was found during the trial that at speeds of 17 and
+19 knots the vibration of the boat was considerable, but when running
+over 20 knots it was hardly perceptible; the excessive vibration taking
+place when the revolutions of the engines became a multiple of the
+natural vibration of the boat.
+
+Torpedo boats are at the present time being built by this firm for the
+English, French, Spanish, Austrian, and Italian governments.
+
+_Russian Torpedo Boats, built by Mr. S. Schibau, Prussia._--Mr. S.
+Schibau, of Elbing, Eastern Prussia, in 1878 constructed ten torpedo
+boats for the Russian government, similar to the one shown at Fig 163.
+
+These boats are each 66 feet long, and 11 feet 3 inches beam. They are
+built of steel plates about an eighth of an inch thick. Their engines
+consist of three cylinder compounds, with surface condensers; and they
+run at 380 revolutions per minute, at full speed, driving a screw 4
+feet in diameter. They have been variously armed, some with the spar,
+some with the Whitehead fish, and some with the Harvey towing torpedo.
+Their speed is about 18 knots per hour.
+
+_Messrs. Herreshoff's Torpedo._--Messrs. Herreshoff, of Rhode Island,
+U.S.A., have also constructed several torpedo boats. One of these,
+built for the English government, is shown in section at Fig. 164.
+This boat is 59 feet 6 inches long, 7 feet 6 inches beam, and 5 feet 6
+inches deep; she draws about 1 foot 3 inches of water.
+
+[Illustration: RUSSIAN TORPEDO BOAT, HERRESHOFF'S TORPEDO BOAT.
+
+PLATE LI]
+
+"The vessel is constructed with five water-tight bulkheads, and her
+hull is of composite construction below the water line, having a
+steel framing covered with wood planking. The upper part of the hull
+is wholly of steel, the plates being 1/16 inch thick, the top sides
+sloping inwards and the upper work forming a protective superstructure
+for the crew and machinery. She is propelled by a screw which is placed
+beneath the vessel in a central position, and which is driven by a
+direct acting condensing engine placed in the forward part of the boat.
+The diameters of the steam cylinders are 10-1/2 inches and 6 inches
+respectively, with 10 inch stroke, and they are of 100 horse power
+estimated. There is an independent feed pump and air pump. The stoke
+hold is enclosed and is supplied with air by a Sturtevant blower, which
+is driven by an independent engine of 2-1/2 horse power. The propeller
+is a two-bladed screw 38 inches in diameter and 5 feet pitch, the
+screw shaft being 23 feet in length. The vessel is steered by means
+of a balanced rudder placed a short distance from the stern and under
+the ship, the helmsman being located in a stern cabin with a protected
+look-out raised just above the deck. The hull and machinery together
+weigh 6 tons, but with the working crew of four men and fuel, stores,
+and two torpedoes on board, boat weighs about 7-1/2 tons.
+
+"Steam is supplied by a Herreshoff coil boiler, which constitutes
+another novelty in this boat. This boiler consists of a circular
+combustion chamber, which in the present instance is 4 feet in diameter
+internally, and within which is a coil of about 300 feet of 2 inch pipe
+coiled to nearly the diameter of the chamber. This coil is continued at
+the top so as to form a kind of dome under the cover of the combustion
+chamber. By the side of the boiler is a separator, into which the
+steam passes before it goes to the engine. The water from the feed
+pump is admitted at the top of the coil, and during its course to the
+bottom the greater portion of it becomes converted into steam. Having
+passed through the entire length of the coil, the steam and water are
+discharged together into the separator in such a manner that the water
+is entirely separated from the steam, and can be blown off as required.
+The steam is taken from the top of the separator, and returns through
+a short coil placed inside the combustion chamber, where it becomes
+superheated, and is led thence to the engines. It is claimed for this
+boiler that it cannot explode destructively, inasmuch as there is
+but a very small quantity of water in it at any time, and that it is
+distributed along the entire length of the coil. A rupture at any point
+would only be attended by a moderate blowing off of steam. The rapid
+circulation of the water is found to prevent the deposit of salts, the
+surplus water not converted into steam carrying with it all impurities.
+A good working pressure can be obtained within a few minutes of
+lighting the fire, and the boiler can be blown off in a few seconds.
+The large combustion chamber enables the full economy of the fuel to be
+realised."[P]
+
+This vessel is guaranteed for a speed of 16 knots per hour. She can
+be propelled ahead or astern with equal speed, and can be brought to
+a dead stop when going full speed within a distance equal to her own
+length. Her turning powers are equally good. Her armament will probably
+be the fish torpedo.
+
+_Ordinary Torpedo Boat._--The most efficient and simple method of
+fitting and working a spar torpedo from an ordinary steam launch or
+pinnace is shown at Fig. 165. This method will be readily understood
+from the figure; the dotted lines show the position of the spar and
+upright, when rigged in. The speed of this type of torpedo boat ranges
+from 6 to 9 knots. Occasions would no doubt occur in time of war when a
+torpedo attack by such boats would be a feasible matter, and therefore
+everything should be done to render these boats fit for that special
+service.
+
+_Defects._--The most important defects of such craft are:--
+
+    1.--The noise created by their engines, thus
+    rendering an undetected approach to a hostile vessel
+    impracticable.
+
+    2.--Their liability to be swamped by the explosion of
+    the torpedo.
+
+Of course there are many minor defects, but above are the principal
+ones, both of which might, to a considerable extent, be modified.
+
+_Torpedo Boat Attacks._--It is impossible to attempt more than a
+very general idea of how to conduct a torpedo boat attack, as so
+much depends upon the circumstances, ever changing, under which each
+particular attack would have to operate.
+
+The spar and the fish torpedo are the submarine weapons that can best
+be manipulated from boats, the towing torpedo requiring a more roomy
+craft than the torpedo boat generally is to operate it from with any
+chance of success.
+
+_Methods of Protecting Ships from Boat Torpedo Attacks._--The principal
+methods that exist at the present time of protecting a ship from a boat
+torpedo attack are as follows:--
+
+    1.--Booms by themselves, or supporting nets hung
+    vertically, surrounding the ship at a distance of 10 or
+    15 feet from the side of the vessel.
+
+    2.--A crinoline of wire, or chain, fixed by stays to
+    the vessel's side, but capable of being lifted out of
+    the water if required.
+
+    3.--The above methods supplemented by guard boats, and
+    a cordon of boats.
+
+    4.--A cordon of boats, that is, boats connected at
+    certain distances by means of hawsers, or chain cables,
+    and at a distance of some 200 or 300 yards from the
+    vessel, supplemented by guard boats, but without other
+    protection.
+
+    5.--Electric lights and torpedo guns. These latter are
+    small guns capable of penetrating the side of a torpedo
+    boat and of being depressed at a very small angle.
+
+As it is against these defences that torpedo boats would have to
+contend, therefore they have been described previous to explaining the
+mode of conducting a torpedo boat attack.
+
+The first two methods of defence are of course quite impracticable when
+the attacked vessel is one of a blockading squadron, and it is against
+such vessels that a torpedo boat attack will generally be used and
+oftenest be successful.
+
+In the case of a vessel forced to anchor in a harbour which is
+accessible to the torpedo boats of the enemy, by the application of
+either of the first two methods, supplemented by guard boats and
+electric lights, she would undoubtedly be almost impregnable against a
+torpedo boat attack, even were the boats armed with the fish torpedo,
+though she would of course not be in that state of readiness which
+is essential to a man-of-war's efficiency. As a general rule, no
+man-of-war should anchor unless absolutely necessary in the vicinity
+of an enemy's ports, and then should retain the power of moving in any
+direction in the quickest space of time possible, using the electric
+light and guard boats as a means of protection.
+
+An attack by boats armed with the spar torpedo must always partake of
+the nature of a forlorn hope, this especially applying to the boats
+themselves, the crews of which, provided they are supplied with good
+life belts, would seem to run a far greater risk of a wetting and a
+prison than of being shot.
+
+Not less than four torpedo boats should compose the attacking force.
+The crews of the boats, consisting of only those actually required,
+should fully understand "_that the hostile vessel is to be torpedoed_,"
+i.e. they are not to give up the attack on the vessel opening fire,
+nor in the case of one or more of the torpedo boats being sunk, but
+to remember that one boat is sufficient to effectually carry out the
+object of the attack, viz. the sinking of the ship.
+
+In making the attack, one boat should be directed on each bow, and
+one on each quarter, the final rush being as combined as possible.
+There must not be the _slightest hesitation_, and each boat must make
+_direct_ for her point of attack.
+
+The cause of the Russians failing so often in their torpedo boat
+attacks during the war of '77 may be traced to the absence of anything
+like a system, and to their giving up the attack directly they supposed
+themselves discovered.
+
+When using the towing torpedo, two boats only could be used, and they
+should make the attack, either coming down from ahead, one on each side
+of the vessel, or coming up from the stern, one on each side of the
+vessel, or by the boats crossing the bow and stern of the vessel in
+different directions.
+
+In the case of the fish torpedo the attack must be conducted in a
+different manner, the object in this case being to get within a certain
+distance only of the vessel undetected, and from thence send the
+missile on its deadly course. The distance should not be more than 500
+yards; the closer up to 200 yards the better. In connection with such
+an attack, the torpedo boats might be supported by guard boats, whose
+particular duty it would be to engage the enemy's guard boats and so
+leave the torpedo boats free to do their particular work.
+
+It has been suggested to use the electric light from the bows
+of torpedo boats, but this would do away with one of the chief
+characteristics of such boats, viz. their invisible and unknown
+approach, on which the whole success of the attack in a great measure
+depends.
+
+_Fosberry's Patent Torpedo Boat Protective._--To enable torpedo
+vessels and boats to remain afloat after being struck by shot from
+mitrailleuses, rifles, and other arms usually employed against such
+craft, and at the same time to retain their structural lightness,
+Colonel G. V. Fosberry, of the English army, has designed the following
+method, which is based upon the discovery that when india-rubber or
+the like is placed and secured on a metal plate, and is penetrated
+or punctured by a rifle bullet or similar projectile, which also
+passes through the metal plate, the hole or orifice so formed in the
+india-rubber will, after the projectile has passed through it and the
+metal plate, immediately be closed by the elasticity of the surrounding
+portions, so that no water can follow the projectile through the
+said hole or orifice. India-rubber or other elastic material, or
+a combination of such materials, in the form of sheets, belts, or
+coats, is placed upon or around those portions of the hull of the boat
+which are to be protected. Vulcanised or mineralised india-rubber
+is the material usually employed by Colonel Fosberry. Between the
+metal plates and the india-rubber covering an intermediate substance,
+generally kamptulicon, is interposed, which is cemented or riveted to
+the said metal plates, and to which the india-rubber is attached. This
+intermediate substance, which is the feature of the invention, must be
+of such a nature that it may be caused to adhere closely and tightly
+to all parts of the metal, and also to the india-rubber covering, while
+the same are unperforated, but when the said india-rubber covering and
+the metal plate under the same are perforated by a bullet, the portion
+of the said intermediate substance adjacent to the perforation must
+be detached from the elastic covering and metal plate, and leave the
+former free to act like a valve, and close up over the hole so that no
+water may enter; and this intermediate substance, as applied by the
+inventor in the immediate vicinity of the perforation, will by the
+effect of the shot be so broken up and detached from the india-rubber
+covering as to allow the same to recover its original position
+independently of the new shape or position of the injured and deformed
+metal plate.
+
+Should the india-rubber be placed upon the metal plates and be so
+attached to the said plates as to adhere and conform to them in
+or after their deformation, a hole made in the india-rubber would
+remain open; on the other hand, should the india-rubber without any
+intermediate substance be attached to the metal plate in such a manner
+that it will recover its position after perforation, water would
+penetrate between the metal and the india-rubber, and by the pressure
+of this water the india-rubber would be liable to be detached from
+a large area of the metal plate, and so become ineffective or even
+dangerous to the boat. Moreover, if the india-rubber is fixed directly
+upon the metal plates, in the case of a shot passing completely through
+the boat, that is to say, passing into the boat at one side and out at
+the other side, a large portion of the india-rubber adjacent to the
+hole made by the shot in leaving the boat will be torn or destroyed,
+but this will not be the case in boats constructed according to Colonel
+Fosberry's patent.
+
+The French government have recently applied this invention to one of
+their torpedo boats with very successful results, thereby proving that
+it is not merely a theoretical idea.
+
+_Submarine Boats._--Submarine boats, if they could be constructed to
+fulfil the conditions hereinafter enumerated which are essential to a
+perfect boat of that nature, would for many reasons be a very important
+point solved in connection with torpedo operations, and therefore it is
+most extraordinary that a practicable submarine boat has not yet been
+designed and built.
+
+_Bushnell's Submarine Boat._--The first submarine vessel built for
+torpedo purposes was designed and constructed by David Bushnell in
+1775. This vessel, operated by a Sergeant Esra Lee, was employed in an
+attempt in 1776 or thereabouts on the _Eagle_, an English man-of-war,
+which proved unsuccessful, owing to the sergeant not being thoroughly
+versed in the management of his curious craft. She was soon afterwards
+sunk in the Hudson river, but was subsequently recovered by the
+inventor, though never used again. This vessel was capable of holding
+one person, and air sufficient to support him thirty minutes without
+receiving fresh air, and is fully described in 'Barnes's Submarine
+Warfare.'
+
+_Qualifications essential to a Submarine Boat._--A submarine boat
+should possess the following qualifications:--
+
+    1.--It should be of sufficient displacement to carry
+    the machinery necessary for propulsion, and the men and
+    materials for performing the various operations.
+
+    2.--It should be of such a form that it may be easily
+    propelled and steered.
+
+    3.--It should have sufficient interior space for the
+    crew to work in.
+
+    4.--It should be capable of carrying sufficient pure
+    air to support its crew for a specified time, or of
+    having the means of purifying the air within the boat,
+    and exhausting the foul air.
+
+    5.--It should be able to rise and sink at will to the
+    required depth, either when stationary or in motion.
+
+    6.--It should be so fitted that the crew possess the
+    means of leaving the boat without requiring external
+    assistance.
+
+    7.--It should carry a light sufficient to steer by, and
+    to carry on the various operations.
+
+    8.--It should possess sufficient strength to prevent
+    any chance of its collapsing at the greatest depth to
+    which it may be required to manipulate it.
+
+The results of former experiments with such boats prove that manual
+power, which was the original mode of propulsion, is not the motive
+power best adapted to such a boat; compressed air, gas as used in the
+Lay torpedo boat, and steam, are all of them far preferable to the
+original method, but which of these modern ones is the most practicable
+has yet to be decided.
+
+The most difficult point to be overcome in connection with a submarine
+boat is that of steering it correctly when beneath the surface of the
+water.
+
+_Confederate Submarine Boat._--The Confederate submarine torpedo
+boat that sunk the Federal vessel of war _Housatonic_ on the 17th
+of February, 1864, was built of boiler iron, 35' long, 3' beam
+(extreme), 5' high in the centre. She carried a crew of nine men. She
+was propelled by means of a screw propeller worked by eight of the
+crew, her greatest speed being four knots an hour in smooth water.
+She carried a sufficient quantity of air to enable the crew to remain
+submerged for the space of two to three hours. Two fins were fitted on
+the outside for rising and falling at will, when in motion. There were
+two manholes provided, fitted with bull's-eyes. This boat was intended
+to pass under a vessel's bottom, towing a torpedo after her, which was
+arranged to explode on contact. She was the means of drowning fourteen
+men before she made her last attempt, when nine others were added to
+the above list. In her successful attack on the _Housatonic_, she was
+armed with the bow spar torpedo, and was sunk, owing to her running
+into the hole formed by the explosion of her torpedo. About three
+years after the American civil war was over, this submarine boat was
+recovered. Divers went down, and found her lying alongside the hull of
+the _Housatonic_, with the remains of the nine men in her.
+
+_French Submarine Boat "Plongeur."_--The boat termed the _Plongeur_
+was designed by Admiral Bougois and M. Brune, and was exhibited at
+the Paris Exhibition of 1867. She was 26' long, 9' deep, and fitted
+with centre and bilge keels. She carried two small tanks containing
+compressed air, and four large tanks were placed at the bottom of the
+boat for the purpose of sinking her, these latter tanks communicating
+with the water outside and the air tanks. She also was fitted with a
+compass for steering by, a water gauge to show the depth of submersion,
+and an air gauge to show the pressure of air in the boat. Rectangular
+valves were placed at the bottom of the boat for entrance or exit
+therefrom, for the use of divers, and to affix torpedoes to a ship's
+bottom. On the top a circular opening for entrance and exit was
+arranged, also an iron cupola fitted with bull's-eyes. She was also
+fitted with an apparatus for spraying water through the air in the
+interior of the boat on its becoming foul, and escape valves for
+releasing any foul air were placed at the top of the boat. The water
+tanks were filled by means of pumps, and emptied by means of the
+compressed air. She was propelled by a three-bladed screw worked by
+four men. Her rate of progression was about four knots per hour. The
+anchors consisted of two 15 inch shot, fitted with wire rope cables,
+working through watertight stuffing boxes.
+
+This vessel has been subjected to some experiments, but with what
+results is not generally known.
+
+One of the most important uses to which a submarine boat would be put
+in connection with torpedo operations would be "to discover the exact
+position and number of an enemy's submarine mines, and if necessary
+destroy them," the former being an operation in the present day quite
+impossible to perform, and the latter one rarely to be depended on.
+
+FOOTNOTES:
+
+[Footnote M: Extract from 'European Ships of War,' &c., by J. W. King,
+U.S.N., page 312.]
+
+[Footnote N: Extract from _Engineering_, under date April 13, 1877.]
+
+[Footnote O: Extract from letter of Captain Ericsson that appeared in
+_Engineer_, under date Nov. 8, 1878.]
+
+[Footnote P: Extract from the Engineering of the 10th of January, 1879.]
+
+
+
+
+CHAPTER VII.
+
+TORPEDO OPERATIONS.
+
+
+A REVIEW, however brief, of the numerous torpedo operations that have
+of late years been carried out in actual war, must prove not only of
+great interest, but of material aid to those who may be desirous of
+studying this branch of naval warfare, for the experience so gained
+ought alone to be the basis on which a system of submarine offence and
+defence should be constructed.
+
+No new torpedo invention should be adopted, however theoretically
+perfect it may be, until it has been subjected to a very severe
+practical test, under conditions as nearly analogous to those that
+would occur on active service as it would be possible to obtain. The
+vast importance of a carefully planned and executed system of submarine
+_defence_ is an established fact, and it only remains to discover what
+are the best weapons for, and most practicable mode of manipulating a
+system of submarine offence, to establish torpedo warfare in all its
+branches as a necessary function of naval warfare.
+
+It would be a mere waste of time to dwell on the Anglo-French and
+American wars of the beginning of this century (1797-1812); though
+during that period various attempts were made by Fulton and others
+to destroy hostile vessels by means of submarine infernal machines,
+inasmuch as they all partook more or less of the nature of experiments,
+and were all failures, but come at once to the Crimean war (1854-1856),
+when what may be termed a systematic employment of torpedoes for
+harbour defence was first employed.
+
+
+CRIMEAN WAR (1854-56).
+
+_Defence of Sebastopol Harbour, &c._--The Russians employed a large
+quantity of submarine mines, both electrical and mechanical,
+principally the latter, in their defence of the harbours of Sebastopol,
+Sveaborg, and Cronstadt.
+
+According to General Delafield, U.S.A., the arrangement of the
+mechanical mines was entirely new, the conception and idea of an
+eminent Russian chemist, Professor Jacobi.
+
+_Electrical Mines._--No mention is made by the General of the
+employment of electrical mines, but the fact of a hulk being captured
+by the Allies at Yenikale, with a number of torpedoes on board, and
+all the arrangements necessary to explode them by electricity, such as
+Voltaic piles, electric fuzes, several miles of conducting wire, &c.,
+is sufficient proof of this type of submarine mine being extensively
+used by the Russians in their harbour defences.
+
+Many of their mechanical mines were picked up by the Allies, several of
+which were found to have their safety caps on. Owing to this neglect,
+and the smallness of the charge of the torpedoes (only some 25 lbs. of
+gunpowder), it is not to be wondered at that no serious injury was done
+to any ships of the allied squadron.
+
+Deterred most probably by the failures of Bushnell, Fulton, and others
+in previous years with the submarine and other torpedo boat attacks,
+nothing of this description was attempted by either side.
+
+_Russian Mechanical Mines._--The Russian mechanical mines consisted
+of barrels of powder fitted with fuzes, so arranged that a blow would
+smash a glass tube containing sulphuric acid, causing the acid to mix
+with some chlorate of potash, resulting in combustion and the explosion
+of the mine.
+
+
+AUSTRO-ITALIAN WAR (1859).
+
+_Defence of Venice by Von Ebner._--During this brief struggle,
+defensive torpedo operations were carried out under the direction of
+Colonel Von Ebner, of the Imperial Austrian Engineers.
+
+The harbour of Venice was protected by a most elaborate system of
+submarine mines, devised by the above-named officer. Though the
+importance of his system was proved by the fact of no attempt being
+made on Venice, yet no opportunity was afforded of _practically_
+testing its efficiency.
+
+
+AMERICAN CIVIL WAR (1861-65).
+
+_Cause of the Present Importance of the Torpedo._--The prominent
+position the torpedo now holds as a most important and legitimate
+function of naval warfare is owing without doubt to the successful and
+extensive employment of them on the part of the Confederates during
+this long and bloody struggle.
+
+_Reasons which induced the Confederates to employ Torpedoes._--The
+numerous harbours and navigable rivers in the possession of the
+Southerners, the few ships of war at their disposal, the overwhelming
+fleet of the Northerners, and the introduction for the first time of
+ironclads in naval warfare, are the principal causes which forced the
+Confederates to resort to torpedoes as a means of offence and defence.
+
+Though a few rude and extempore submarine mechanical mines were met
+with by the Federals during the earliest part of the war, it was not
+until many months after the commencement of hostilities that the
+Confederates, finding themselves quite unable to cope with their rivals
+on the sea, set to work in earnest to organise a system of submarine
+warfare on a grand scale.
+
+_Torpedo Corps formed, &c.--Loss of "Cairo."_--By October, 1862, a
+secret service torpedo corps, with headquarters at Richmond, was in
+full swing, and the principal harbours and rivers of the Confederates
+were systematically protected by means of electrical and mechanical
+mines, also a scheme of offence by drifting and spar torpedoes was in
+preparation, and in December of the same year they experienced the
+first-fruits of their labour by the total destruction of the Federal
+war steamer _Cairo_.
+
+The following brief review of the numerous torpedo operations carried
+out by both sides, and the effect their use had on the war, will be
+sufficient to enable the general reader to gain some idea of the vast
+importance of this submarine weapon in future warfare.
+
+Fuller and more detailed accounts will be found in Commander S.
+Barnes's, U.S.N., Colonel Von Scheliha's, and Captain H. Steward's
+torpedo works.
+
+_Every Species of Torpedo used--Frame Torpedoes at Charleston,
+&c.--Federal Ship Disasters--Small Effect of Electrical Mines--Loss of
+the "Commodore Jones," &c._--Every species of submarine mine seems to
+have been used by the Southerners for their harbour and river defence,
+the most effectual of which were the barrel, frame, and Singer's
+torpedoes. These were all mechanical, fired by means of sensitive
+concussion fuzes. At Charleston and elsewhere the frame torpedo, which
+also acted as an obstruction, was largely used, and where this species
+of mine was known to be laid, the Northerners never attempted to force
+a passage. Out of some thirty or forty Federal ships sunk or injured by
+torpedoes, by far the larger proportion of such disasters was effected
+by means of the barrel and Singer's mines. Though electrical mines were
+very extensively used on the St. James River and at Charleston, &c.,
+yet only one Federal steamer, the _Commodore Jones_, was sunk, and only
+one other, the _Commodore Barney_, was injured.
+
+_Case of the "New Ironsides."_--The Federal ship _New Ironsides_, at
+the attack on Charleston in 1863, was anchored for one hour and a half
+exactly over a 5000 lbs. electrical mine, which despite all the efforts
+of the Confederates could not be exploded. The reason of this was owing
+to the deterioration of the primer, due to too constant testing.
+
+_Welden Railway._--A notable instance of the effect of torpedoes on the
+war was the saving of the Welden line of communication in December,
+1864. The Welden Railway was the principal artery of communication
+to Richmond for the Confederates. To intercept this, by destroying
+the railway bridges, a fleet of nine Federal gunboats was sent up the
+Roanoke river; when nearly arrived at their destination, and though
+every precaution in the shape of bow projecting spars, creeping, &c.,
+was taken, seven of the vessels were either sunk or severely injured by
+submarine mines. Thus the expedition ended in a most disastrous failure.
+
+_General Butler's Attack on Richmond._--Again, in April, 1864, General
+Butler's attack on Richmond utterly failed, owing to the Federal fleet
+being unable to co-operate with him, the destruction of the _Commodore
+Jones_ completely checking any further advance of Admiral Lee's ships,
+thus allowing the Confederates to employ the garrisons of their river
+batteries in their land line of entrenchments.
+
+_More than One Line of Torpedoes required._--The capture of the Spanish
+fort at Mobile in April, 1865, by a Federal fleet under Admiral Lee,
+proves the necessity of employing more than one line of torpedoes,
+where the safety of a position depends almost entirely on those means
+of defence, as this one did. Here, though several Federal vessels were
+either sunk or severely damaged, yet the fort was captured.
+
+_Boat Torpedo Attacks._--In regard to boat torpedo attacks, the
+Confederates were only successful in two out of many attempts made by
+them to sink Federal vessels.
+
+_The "Housatonic" and "Minnesota."_--These successes were the complete
+destruction of the Housatonic by a submarine boat, fitted with a spar
+torpedo, and serious injury caused to the _Minnesota_ by the explosion
+of a contact spar torpedo, carried by an ordinary gig, commonly termed
+"David's." In the former instance the attacking boat was sunk,[Q] in
+the latter instance she was uninjured.
+
+_Destruction of the "Albemarle."_--On the part of the Federals,
+Lieutenant Cushing with a steam launch fitted with a Wood and Lay
+torpedo, succeeded in sinking the Confederate ram _Albemarle_. The
+boat in this instance was swamped by the column of water thrown up on
+the explosion of the torpedo, she having been driven full speed at the
+Albemarle.
+
+_Ship Spar Torpedoes._--On both sides, spar torpedoes fitted to the
+bows of ships, and also on rafts slung over the bows, were somewhat
+extensively used, but on no occasion were they the means of injuring or
+sinking any vessels.
+
+To increase the difficulties of the Northerners in searching for
+submarine mines, the Southerners laid down a great number of dummy
+torpedoes, also erected false torpedo stations, and laid false wires.
+
+It must always be borne in mind, in connection with the torpedo
+operations above detailed, that the apparatus were very crude, and the
+operators at the commencement inexperienced.
+
+
+PARAGUAYAN WAR (1864-68).
+
+_Torpedoes employed by the Paraguayans._--During their protracted
+struggle with the Brazilians, the Paraguayans employed submarine mines
+for the protection of their river forts, &c.
+
+_Loss of the "Rio Janeiro"--Brazilian Fleet entrapped._--On the 2nd
+of September, 1866, the Brazilian ironclad _Rio Janeiro_, after
+being well-battered by the guns of the Curupaity fort, was sunk by a
+torpedo. Later on, near the same place, a whole fleet of Brazilian war
+ships were entrapped by the Paraguayans, between two rows of submarine
+mines, but owing to faulty arrangements they escaped unharmed.
+
+
+AUSTRIAN WAR (1866).
+
+_Venice, Pola, &c., protected by Torpedoes._--During this war,
+torpedoes for the defence of Venice, Pola, &c., were extensively used
+by the Austrians, under the direction of Baron von Ebner, but as in '59
+no opportunity was afforded of proving their practical worth, though
+morally they were of great value, the Austrian harbours so defended
+being considered impregnable by the enemy, and therefore no attempt was
+made to force them.
+
+
+FRANCO-GERMAN WAR (1870-71).
+
+Little or nothing in the matter of torpedo operations was attempted by
+the Germans, and on the part of the French nothing whatever.
+
+_Germans employed Submarine Mines._--Electrical and mechanical mines
+were placed in several of the German harbours, the former containing
+about 200 lbs. of dualine, the latter some 80 lbs. of gunpowder. The
+only attempt to destroy French ships by means of offensive torpedoes
+was made by the German vessel the _Grille_, off Rügen, which resulted
+in failure.
+
+In laying down and in picking up after the war was over their
+mechanical mines, several exploded, killing some ten to fifteen men.
+
+_Boats necessary._--Towards the end of the war, the Germans were
+constructing special torpedo boats, believing that such were necessary
+for the complete defence of harbours. This war added another proof of
+the moral worth of submarine mines; the French fleet not daring to
+approach German waters _supposed_ to be defended by such means.
+
+
+RUSSO-TURKISH WAR (1877-78).
+
+_Superiority of Turkey to Russia in the matter of Ships._--On the
+Danube, in the Black Sea, and Mediterranean, where the principal naval
+portion of the war was carried out, Turkey was possessed of a fleet
+of ships infinitely superior to Russia, both in point of numbers and
+strength, and therefore, to enable her to hold her own against this
+vast superiority of the Turks, the Russians resorted to an extensive
+employment of torpedoes, for both offensive and defensive purposes.
+
+_Russian Torpedoes._--For many years previous to the outbreak of
+hostilities in April, 1877, the Russians had been studying the subject
+of torpedo warfare in all its branches, a certain number of their
+naval and military officers and men having every year passed through
+a regular course of torpedo study, at a school specially formed for
+such a purpose; they had also laid in large stores of submarine mines,
+spar torpedoes, and were in possession of the Whitehead and towing
+torpedoes, and also several electric lights, and a few months after war
+was declared they obtained a fast Thornycroft torpedo boat.
+
+_Turkish Torpedoes._--On the other hand, the Turks were only in
+possession of a number of those huge, unwieldy 500 lbs. buoyant mines,
+and one electric light; circuit closers, contact mines, boats (steam or
+otherwise) fitted for use with torpedo, or offensive torpedoes, being
+conspicuous by their absence.
+
+Thus it will be seen that in the matter of submarine offence and
+defence, the Russians were as superior to the Turks as the latter were
+to the former in the matter of ships.
+
+_Turkish Defensive Torpedo Operations._--The defensive torpedo
+operations carried out by the Ottoman naval officers and men were as
+follows:--
+
+The harbour of Batoum in the Black Sea was protected by a few 500 lbs.
+buoyant mines, arranged to be fired by observation.
+
+The mouth of the Bosphorus and the Dardanelles were similarly defended.
+For this work great praise is due to those who executed the work, for
+the very strong current and great depth met with in those waters would
+render such a service a work of great difficulty, even when properly
+constructed mooring boats, and men trained to such, were employed, both
+of which in this particular instance were absent.
+
+Soulina, one of the mouths of the Danube, and Suda Bay (Candia) were
+also protected by similar means.
+
+_Russian Defensive Torpedo Operations._--The Russian defensive torpedo
+operations were very extensive, their principal harbours in the
+Baltic, as well as those in the Black Sea, were carefully defended by
+electro-contact mines of the latest type; so also they protected their
+numerous bridges across the Danube, double and sometimes treble rows
+of such mines being moored on either side, and in addition they also
+placed several mines in the Danube, on the chance of destroying the
+Turkish Danube flotilla.
+
+_Destruction of Turkish Gunboat "Suna" by a Russian Submarine
+Mine._--The only instance that occurred during this war of a vessel
+being sunk by a stationary submarine mine was that of the Turkish
+gunboat _Suna_, at Soulina, in October, 1877, on the occasion of the
+unsuccessful attack on that place made by the combined Russian and
+Roumanian flotilla.
+
+About 6 A.M. on the morning of the attack, a "loftcha" containing two
+of the enemy's electro-contact mines, fitted for laying down, was
+captured by the Turks, from which it was evident that the Russians had
+been employed during the night in torpedoing the reach immediately
+above the Turkish defences. However, not heeding this very practical
+warning, the Pacha in command of the Soulina squadron ordered the
+_Kartal_ (a paddle-wheel tug vessel) and the _Suna_ (an old wooden
+gunboat) to reconnoitre up the river; they accordingly started, the
+_Kartal_ leading the way. At 8.5 A.M., about fifteen minutes after the
+two vessels had left their moorings, an explosion was heard, and almost
+at the same instant the unfortunate gunboat _Suna_ was observed to go
+down head foremost, her masts only remaining above water. The _Kartal_,
+which at the time of the catastrophe was some distance in advance, at
+once turned back to the assistance of her consort, and managed to save
+a number of the gunboat's crew, this work having to be performed under
+a galling fire from the allied flotilla. Owing to this day being the
+"Feast of Bairam," the unfortunate gunboat was dressed with masthead
+flags, thus four Turkish ensigns fell into the hands of the enemy, the
+Pacha refusing permission for any attempt to be made to save them. The
+reason that the _Kartal_ escaped the fate of her consort was due to her
+only drawing some 5 feet of water, while the _Suna_ drew at least 8
+feet.
+
+The gunboat struck the mine that sunk her on her port bow, the effect
+of the explosion being to completely smash in that side of her bow,
+dismount her foremost guns, and carry away her foremast just above the
+deck (the mast remained standing, though inclined forward); the second
+lieutenant of the _Suna_, who was at the time of the explosion standing
+on her fore bridge, was thrown off and killed, and some twelve of
+the crew were killed and wounded. To complete the destruction of the
+_Suna_, another torpedo was exploded under her port quarter by the
+Russians. The torpedo that was used on this occasion is detailed at
+page 68.
+
+_Offensive Torpedo Operations._--The numerous boat torpedo attacks made
+by the Russians against the Turkish fleet will now be considered. The
+following accounts have been carefully compiled from two sources, viz.
+an article written by Captain Chardonneau, which appeared in the 'Revue
+Maritime et Coloniale,' 1878, and which has been recently translated
+for the Journal of the Royal United Service Institution by Lieutenant
+J. Meryon, R.N., and notes taken by the author during his service with
+the Imperial Ottoman Navy (1877-78).
+
+
+1ST AFFAIR.
+
+_The Batoum Attack._--The first torpedo boat attack occurred on the
+night of the 12th-13th of May at Batoum.[R]
+
+On the night of the attack there were lying in the harbour several
+vessels of the Ottoman fleet, including ironclads, transports,
+despatch-boats, &c. These vessels were totally unprotected by guard
+boats, booms, electric lights, &c., and only the usual number of
+sentries were posted, the Turks at that time not quite believing in
+such boat attacks, thus offering peculiar advantages for a torpedo
+attack.
+
+Four torpedo boats formed the attacking force, viz. the _Tchesme_,
+_Sinope_, _Navarino_, and the _Soukoum Kalé_.
+
+These boats were carried by a ship of the Maritime Company of Odessa,
+named _Grand Duke Constantine_. She was an iron screw steamer,
+able to steam about 10 knots per hour, and fitted to hoist up the
+above-mentioned torpedo boats. She was armed with four 4-pounders, and
+torpedoes.
+
+Early in the evening of the 12th the _Constantine_ left Poti, and
+proceeded off the harbour of Batoum, her captain (Lieutenant de
+Vaisseau Makaroff) deeming it advisable to lay to seven miles from the
+harbour, the supposition that the Turks had placed submarine mines off
+the entrance being the cause of his so doing.
+
+About 11 P.M. the four torpedo boats started to the attack, Makaroff
+being in command of one of them. They were all painted sea green,
+and possessed a high speed. The night being dark, and having been
+despatched some distance off, they reached the entrance in somewhat
+straggling order. The _Tchesme_, commanded by Lieutenant Zatzarennyi,
+and armed with a towing torpedo, was the first to enter the harbour,
+and, without waiting for her consorts, dashed at the Ottoman fleet, and
+succeeded in getting close to a large Turkish paddle-wheel transport,
+and her commander dipping his torpedo, struck the ship under her
+quarter; but that little something which so often causes a failure in
+this mode of warfare occurred, and no explosion followed the pressing
+down of the firing key, much to the chagrin and disgust of Zatzarennyi.
+As might be supposed, by this time an alarm had been raised, and guns,
+rifles, &c., were fired in and from every direction, causing the
+torpedo boats to beat a precipitate and hasty retreat. Fortunately the
+Turks were not possessed of any steamboats, nor were any of their ships
+ready to dash out, or the defeat would have been a far more disastrous
+one than was the case. Neither of the boats were damaged, nor any of
+the crews injured.
+
+The failure of this first attempt was due in a great measure to the
+mode of attack, no system or unanimity of action on the part of the
+four commanders being observable; and also to the somewhat half-hearted
+support given to the _Tchesme_, for had her three consorts only dashed
+at the Turkish ships as boldly, one at least of the Ottoman fleet would
+have been sunk, the only defence resorted to being their guns and small
+arms.
+
+The moral effect of torpedoes was displayed here, causing the
+_Constantine_ to lay too far off the entrance to the harbour, thus
+decreasing the chance of her boats making a successful attack.
+
+The Russian version finishes up by saying, "although this first
+endeavour was unsuccessful, the authors of it were received at
+Sebastopol with enthusiasm."
+
+
+2ND AFFAIR.
+
+_The Matchin Attack._--The second attempt was made on the 25th-26th of
+May on two Turkish monitors, the _Fettu Islam_ and the _Duba Saife_,
+and a small river steamer, the _Kilidj Ali_, lying at anchor off
+Matchin.[S]
+
+Four Russian torpedo boats were sent to the attack, viz. the
+_Czarowitch_, Lieutenant Doubasoff; the _Xénie_, Lieutenant Chestakoff;
+the _Djiquite_, Midshipman Persine; and the _Czarevna_, Midshipman
+Bali. The total number of officers and men carried by these boats on
+this occasion was forty-six.
+
+The night of the attack was rainy, but not completely dark, since the
+moon was above the horizon during nearly the whole of the expedition.
+
+The force left Brailoff at one o'clock on the morning of the 26th,
+and advanced in two columns up the river, finding great difficulty in
+stemming the strong current.
+
+A boat from the _Duba Saife_, rowing guard some 500 yards in advance of
+the squadron, observed the approach of the Russian boats, but allowed
+them to pass on their voyage of destruction without attempting to
+stop them, or alarm the vessels. On reaching within 150 yards of the
+_Duba Saife_, Dubasoff in the _Czarowitch_ was challenged, and failing
+to give the correct answer was immediately fired at; but, nothing
+daunted by the hail of shot and bullets, he dashed on, and succeeded
+in exploding one of his spar torpedoes on the port side of the _Duba
+Saife_, just under her quarter, a column of water and _débris_ being
+thrown up to a height of 120 feet, which partly filled his boat, but
+notwithstanding managed to get safely away. The monitor not sinking as
+soon as expected, Chestakoff in the _Xénie_ dashed in, and completed
+the work of destruction, the unfortunate ship sinking in a very few
+minutes after this last explosion. The _Djiquite_ was struck in the
+stern, and had to be run ashore for repairs, but eventually all four
+boats reached Brailoff in safety. The Russians allowed to neither
+killed nor wounded, which, when the time they were exposed to the fire
+of the three Turkish ships (about twenty minutes), the number of men
+(forty-six) engaged, and their very close quarters, seems miraculous.
+
+The _Duba Saife_, thus lost to the Turks, carried two 12 cm. Krupp
+guns, and a crew of some sixty officers and men, few of whom were
+saved. Lieutenants Dubasoff and Chestakoff were decorated with the
+4th Class of the Cross of Saint George, and three seamen received the
+insignia of the Order of Military Merit.
+
+This attack was conducted in a most gallant manner, and far more
+systematically than the Batoum affair. If instead of holding one of the
+boats in reserve, which was part of Dubasoff's plan, and the remaining
+three attacking one vessel, the force had divided itself into two
+parties, and had made a simultaneous attack on both the monitors, the
+probability is that the _Fettu Islam_ would have shared the fate of her
+consort.
+
+The officer of the Turkish guard boat was tried by court-martial,
+but what his ultimate fate was is not generally known. He certainly
+deserved nothing less than death.
+
+
+3RD AFFAIR.
+
+_The Soulina Attack._--The third attempt took place on the 9th-10th
+of June, 1877, on a Turkish squadron lying at anchor off Soulina.[T]
+This squadron consisted of the three ironclads _Feteh Bulend_,
+_Moocardemikhair_, and _Idglalieh_, and a tug, _Kartal_.
+
+The Russian attacking force consisted of six torpedo boats, viz. the
+No. 1, Lieutenant Poutschin; the No. 2, Lieutenant Rojdestvenski; the
+_Tchesme_, Lieutenant Zatzarennyi; the _Sinope_, the _Navarino_, and
+the _Soukoum Kalé_. The No. 2 was a specially constructed torpedo
+boat, 68 feet long, and very fast. All were armed with spar torpedoes,
+with the exception of the _Tchesme_, which carried a towing torpedo.
+The boats were convoyed from Odessa by the _Constantine_, some being
+carried, and some being towed; another steamer, the _Vladimir_,
+supported her. The Turkish squadron were anchored in quarter line,
+about one mile from the harbour; the _Kartal_, under weigh, being used
+as an advance guard, and a few boats rowing guard close to the ships
+being _the only means of protection_ adopted by the Turks. Passive
+obstructions, such as booms, nets, crinolines, &c., were not thought
+of, much less used.
+
+On arriving about five miles from Soulina, the boats were formed into
+two groups, the first consisting of the No. 1, the No. 2, and the
+_Tchesme_, and despatched on their way. The working of their engines
+was scarcely heard, and all lights were carefully hidden by tarpaulins.
+
+The first casualty that happened was the disabling of the _Tchesme_,
+by the electric wire of her towing torpedo fouling the screw, this
+obliging her to return to the _Constantine_. Aided by good fortune,
+and by the darkness of the night, the No. 1 and the No. 2 succeeded
+in getting close to (30 yards) one of the Turkish vessels, the
+_Idglalieh_, before being discovered, when they were at once hailed,
+and, not answering, a tremendous fire of big guns and rifles was
+directed on them from the _Idglalieh_, which was promptly followed by
+that of the whole squadron, though from the other ships nothing of the
+boats could be seen.
+
+According to the Russians, the No. 2 succeeded in exploding her
+torpedo close to, if not in contact with, a Turkish vessel, but from
+eyewitnesses on board the squadron only one explosion was heard, viz.
+that of Lieutenant Poutschin's torpedo. Any way, no damage whatever
+was experienced by the Ottoman squadron. The No. 1 came down on the
+_Idglalieh's_ starboard bow, fouled her cable, and swung alongside,
+exploding one of her torpedoes in so doing, but with no other result
+than a wetting to those of the ironclad's crew, who were on the
+forecastle. Alongside Poutschin remained for some minutes, but at last
+managed to get clear, and then was either sunk by the _Idglalieh's_
+fire, or, as he avers, on finding his screw foul, he sunk his boat,
+rather than let her fall into the hands of the Turks. Poutschin and
+four of his crew were picked up, after being some hours in the water,
+by the squadron's boats.
+
+The No. 2 seems to have suffered severely, her funnel being bent, the
+axle of the steering wheel damaged, sixteen rivets were started, and
+the iron keel plate had dropped some 18 inches, and finally the lower
+part of her rudder broken, and one of the blades of her screw bent aft;
+part of this damage was no doubt the effect of the explosion of her
+torpedo, which was probably not in position, but unless she ran over
+some loose stones of the Soulina breakwater, the damage to her keel and
+rudder cannot be accounted for.
+
+The second group of boats had followed up the first, but on hearing the
+noise of the explosions and roar of the guns and rifles they returned
+to the _Constantine_.
+
+That ship, on observing the firing, endeavoured to close the land, but
+she grounded, and remained until daylight in a difficult position, but
+at last got afloat, and returned to Odessa with five out of her six
+torpedo boats.
+
+Lieutenant Rojdestvenski, the Commander of the No. 2, received the 4th
+Class of the Cross of Saint George, and three seamen the insignia of
+the Order of Military Merit.
+
+On the part of the No. 1 and No. 2, this was a most gallant affair,
+though unsuccessful, but as regards the remainder of the boats the less
+said the better.
+
+Had the Turkish squadron slipped the instant the alarm was given, and
+steamed full speed in the direction of Odessa, the _Constantine_ and
+her convoy might have been cut off. Both the _Moorcademikhair_ and
+_Feteh Bulend_ were 13 knot ships, and therefore considerably faster
+than the enemy. But, as usual, the Turks were far too dilatory to take
+advantage of the occasion.
+
+
+4TH AFFAIR.
+
+_The Rustchuk Attack._--The fourth torpedo attack was made on the
+afternoon of the 20th of June, 1877, on a Turkish monitor off Rustchuk.
+
+The only Russian torpedo boat sent to the attack on this occasion was
+a Thornycroft named the _Choutka_, commanded by Lieutenant Skrydloff,
+and accompanied by a celebrated Russian artist, Verechtckaguine by
+name. The instant the torpedo boat was observed, so well directed and
+steady a fire was kept up by the monitor that both the lieutenant and
+the artist were badly wounded, and the electric wires of the torpedo
+severed, thus obliging the _Choutka_ to beat a retreat. According to
+the Russian account, the monitor was struck by the boat's torpedo
+spar, but the above seems the more likely version. This was certainly
+a most audacious attack, and had the Turks only succeeded in hitting
+the _Choutka_ with her big gun, it would have ended fatally for the
+Russians; as it was, the boat was struck by several bullets, but none
+of the crew were wounded.
+
+
+5TH AFFAIR.
+
+_The Aluta Attack._--The fifth attack was made on the 30th of June,
+1877, on a Turkish monitor off the mouth of the Aluta, in the river
+Danube. This attempt, like the last, took place in broad daylight. Four
+Russian boats were sent forward, but in spite of the captain of the
+Turkish vessel doing all he could to run the boats down, none of them
+succeeded in getting sufficiently near the vessel to enable a torpedo
+to be placed in contact. The captain of the monitor took the precaution
+to rig his lower booms out, and so managed to keep the enemy's boats
+at a respectful distance, they imagining that mines were fixed to the
+ends of the booms. After two hours of this dodging about, the Russians,
+finding the case hopeless, abandoned the attack.
+
+The Russian account states--1st, that the captain of the monitor was an
+Englishman; 2nd, that the vessel was protected by nets and torpedoes
+lashed to the extremities of her booms--both of which statements are
+radically wrong.
+
+The torpedo boats forming the attack were the _Choutka_, Midshipman
+Niloff, and the _Mina_, Sub-Lieutenant Arens, both armed with the spar
+torpedo.
+
+Unless indeed the Russians acted up to the old proverb which says
+"Discretion is the best part of valour," it is difficult to understand
+how four small easily handled boats could have been for one hour
+endeavouring to strike a ship (which ship was at the same time being
+manoeuvred with a view of running them down) without either effecting
+their object or being sunk or damaged in the attempt.
+
+The Russians, though unsuccessful, behaved gallantly. Midshipman Niloff
+was severely wounded, but no mention is made as to the number of the
+crew that were killed and wounded, or of the damage received by the
+boats. Niloff received the 4th Class of the Cross of St. George, and
+Arens the Order of Military Merit.
+
+The Turkish captain, Ali Bey, behaved most pluckily and skilfully. The
+only wonder is that both the boats were not sunk by the monitor's fire.
+
+
+6TH AFFAIR.
+
+_The Soukoum Kaleh Attack._--The sixth attempt was made on the
+23rd-24th of August, 1877, on a Turkish ironclad, the _Assari Shefket_,
+at the time lying at anchor off Soukoum Kaleh.[U] Four torpedo boats
+composed the attacking force, viz. the _Sinope_, Lieutenant Pisarefski;
+the _Torpedoist_, Midshipman Nelson Hirst; the _Navarino_, Lieutenant
+Vichnevetski; and the _Tchesme_, Lieutenant Zatzarennyi, the latter
+officer being in command. These boats had been brought to the entrance
+of the harbour by the _Constantine_, and were despatched on their
+mission of destruction about half past ten.
+
+An eclipse of the moon occurred on this night, and, taking advantage of
+this fact, the four Russian torpedo boats dashed into the harbour at
+full speed and made for the Turkish vessel.
+
+Fortunately for the safety of his ship and lives of his crew, the
+captain of the Turkish ironclad had several boats rowing guard round
+his ship, and otherwise everything on board in readiness for immediate
+action. On the attacking flotilla nearing the guard boats, blue lights
+were burnt, rifles fired, &c., and the alarm given to those on the
+look-out in the _Assari Shefket_. The moment the enemy were within
+range, such a well-directed and heavy fire was poured on them that
+the attack was completely foiled. One of the Russian torpedoes was
+exploded, but failed to do more than throw a quantity of water up.
+The next morning a pole with torpedo fixed on it was found by the
+Turks, and on the strength of this and the numerous fragments of wood
+similarly found, one if not more of the enemy's boats it was supposed
+must have been sunk, or much knocked about.
+
+This was a much better planned and executed attack, but was
+unsuccessful owing to the extreme vigilance of the Turks.
+
+This attempt will always be remembered by the Turks, on account of the
+general order that appeared in the papers on the part of the Russians,
+in which "the brilliant exploit and successful destruction of the
+Turkish ironclad _Assari Shefket_" was set forth at great length; she
+at the time that this appeared being quietly at anchor off the dockyard
+at Stamboul, not having received any damage whatever.
+
+
+7TH AFFAIR.
+
+_The Second Batoum Attack._--The seventh attempt was made on the night
+of the 27th-28th of December, 1877, on several Turkish men-of-war
+anchored in the harbour of Batoum (the scene of the first Russian
+torpedo attempt and failure). Four boats composed the attacking force,
+viz. the _Tchesme_, Lieutenant Zatzarennyi, in command, armed with a
+Whitehead fish torpedo, containing 32 kilog. of gun-cotton, fitted
+to fire from a tube under the boat's keel; the _Sinope_, Lieutenant
+Stchelinski, armed with a similarly charged fish torpedo, fitted to
+fire from a raft, which was towed by the boat, and two other boats,
+armed with spar and towing torpedoes.
+
+The means employed at Batoum for the safeguard of the Ottoman fleet
+there against such an attack was that of guard boats and a barrier
+formed of logs of wood, with planks secured to them, so arranged by
+means of weights that the planks remained perpendicular to the surface
+of the water when in position.
+
+Owing to the extreme darkness of the night, the Russians managed to
+evade the guard boats, and when, as they imagined, some 60 to 65
+yards from a Turkish ironclad, the _Tchesme_ and _Sinope's_ Whitehead
+fish torpedoes were started on their deadly mission; but, owing most
+probably to the want of practice of manipulating these somewhat
+delicate instruments, also to the darkness, and the slight swell there
+was on at the time, both missed their mark, and were landed high and
+dry on the beach astern of the ship.
+
+One of these weapons was perfect, the other minus her fore compartment,
+this having been knocked off by the torpedo colliding with some hard
+object. No explosion was heard or seen by the Turks.
+
+This was the second time that the fish torpedo had been employed on
+actual service, and, as in the previous instance, failed.
+
+The guard boats and barrier of the Turks seem to have been of little
+avail.
+
+
+8TH AFFAIR.
+
+_The Final Attack._--The eighth and last attempt was made on the night
+of the 25th-26th of January, 1878.
+
+This was originally intended to be an attack on the Turkish fleet at
+Batoum, but on entering that harbour the two Russian torpedo boats,
+the _Tchesme_, Lieutenant Zatzarennyi, and the _Sinope_, Lieutenant
+Stchelinski, were met by a Turkish revenue steamer, against which the
+boats discharged their Whitehead torpedoes, resulting in her complete
+destruction, at the same time arousing the squadron, and causing the
+boats to beat a retreat.
+
+Though the vessel destroyed was not a frigate, yet the expedition
+was successful in so far as proving that it is possible to project
+Whitehead fish torpedoes from boats at a distance of 70 to 90 yards
+from an enemy's ship, on a dark night, and strike her with them.
+
+This concludes the whole of the offensive torpedo operations that were
+carried out during the war, of which two out of eight attempts were
+successful, which is without doubt a fair percentage.
+
+There seems every probability that the present struggle between Chili
+and Peru, in the Pacific, will afford torpedoists further experience of
+the various offensive torpedoes, when subjected to the test of active
+service.
+
+FOOTNOTES:
+
+[Footnote Q: See page 185.]
+
+[Footnote R: A Turkish port, situated on the east coast of the Black
+Sea, capable of holding several large ships when anchored head and
+stern, but otherwise only a few.]
+
+[Footnote S: A town situated on the south bank of the Danube, about
+eight miles from Brailoff.]
+
+[Footnote T: One of the principal mouths of the Danube.]
+
+[Footnote U: A place taken from the Russians in the early part of the
+war, situated on the east coast of the Black Sea.]
+
+
+
+
+CHAPTER VIII.
+
+ON EXPLOSIVES.
+
+
+EXPLOSION may be defined as the sudden or extremely rapid conversion of
+a solid or liquid body of small bulk into gas or vapour, occupying very
+many times the volume of the original substance, and which in addition
+is highly expanded by the heat generated during the action.
+
+This sudden or very rapid expansion of volume is attended by an
+exhibition of force which is more or less violent, according to
+the constitution of the original body and the circumstances of the
+explosion.
+
+Any substance capable of undergoing such a change on the application of
+heat or other disturbing cause is called an "explosive."
+
+_Explosive Force._--Explosive _force_ is _directly_ proportional to
+the heat of combustion and the volume of gas, and _inversely_ to the
+specific heat of the mixed products.
+
+Explosive _effect_ is _directly_ proportional to the volume of gas
+produced and the temperature of the explosion, and _inversely_ as the
+time required for the change to take place.
+
+_Explosive Effect and Force compared._--Explosive effect depends upon
+the rapidity with which the conversion is effected, while the same
+amount of explosive force may act suddenly or gradually.
+
+As before stated, explosions are more or less violent according to the
+_circumstances_ under which they take place. These may be considered as
+follows:--
+
+1.--The physical state of the explosive substance.
+
+2.--The external conditions under which the explosive body is fired.
+
+3.--The mode of firing.
+
+_The Physical State of the Explosive Substance._--Numerous instances
+may be cited to show the influence the physical condition of an
+explosive body has upon its explosion.
+
+Thus, gunpowder may, by merely varying the size, shape, and density of
+the grain, be made to ignite rapidly but burn comparatively slowly, or
+be made to ignite more slowly, but once inflamed to burn very rapidly.
+
+Again, gun-cotton in a loose, uncompressed state, will, if ignited,
+only flash off; if it is spun into threads or woven into webs, its rate
+of combustion may be so much reduced that it can be used in gunnery
+or for a quick fuze; while if powerfully compressed and damp it burns
+slowly. Wet gun-cotton requires a primer of dry gun-cotton and a
+fulminate fuze to explode; dry, it may be exploded by a fulminate fuze,
+&c.
+
+Then nitro-glycerine, when exploded by 15 grains of fulminate of
+mercury, and at a temperature above 40° F., is very violently
+detonated; below 40° F. it freezes and cannot be similarly exploded.
+
+To obtain the full effect of all explosives, confinement is absolutely
+necessary.
+
+The more rapid the explosion the less confinement required, approaching
+in the case of some explosives to so small an amount that it need not,
+for practical purposes, be considered.
+
+Thus a charge of nitro-glycerine or gun-cotton, when detonated in the
+open air, will destroy wrought iron rails, large blocks of stones,
+balks of timber, &c.
+
+In the case of the former body, the confinement of the atmosphere is
+sufficient.
+
+In the latter, the mechanical cohesion due to compression is sufficient
+restraint.
+
+Abel states that if the film of atmosphere surrounding the
+nitro-glycerine, not exceeding 1/1000 inch in thickness, be removed,
+the explosive effect is much lessened.
+
+A large charge of gunpowder fired in the ordinary way under water
+requires a strong case to retain the gases until the action has become
+general, or, owing to its slow rate of burning, the case would be
+broken before the whole of the charge had been ignited, and part of the
+charge drowned.
+
+This is often to be noticed when firing fine-grained powder in heavy
+guns.
+
+Igniting the charge at several points diminishes the confinement needed.
+
+_Mode of Firing._--The application of heat, directly or indirectly, is
+the principal means of causing an explosion.
+
+The flame from a percussion cap or primer, or a platinum wire heated to
+incandescence by an electric current, will _directly_ ignite a charge.
+Friction, concussion, &c., will _indirectly_ ignite a charge due to the
+conversion of mechanical energy into heat.
+
+It would appear that when one explosive body is used as a means of
+firing another, the resultant explosion is due to the blow suddenly
+formed by the gas of the firing charge acting percussively upon the
+mass to be exploded. If such were the case, then the most powerful
+explosive would be the best agent for causing an explosion. But it is
+not so.
+
+For example, nitro-glycerine, which is far more powerful than fulminate
+of mercury, requires more than 1000 grains to explode gun-cotton, while
+only 15 grains of the latter is needful for the same work, &c.
+
+A small quantity of an explosive substance which is sensitive to
+friction or percussion is often used to ignite the original charge.
+
+_Detonation._--The instantaneous explosion of the whole mass of a body
+is defined as "detonation."
+
+The essential difference between an explosion and a detonation is the
+comparative suddenness of the transformation of the solid or liquid
+explosive substance into gas and vapour.
+
+Some explosive bodies, such as the fulminates, &c., always detonate,
+while the detonation of others depends on the mode of firing.
+
+Nitro-glycerine always explodes violently, but when fired with an
+initiatory charge of fulminate of mercury it is much more powerful than
+when fired with gunpowder.
+
+Compressed gun-cotton in the air-dry state can be detonated by 2 grains
+of fulminate of mercury embedded in the material, but when it contains
+3 per cent. of water over and above the 2 per cent. which exists
+normally in the air-dry substance, 15 grains of the fulminate will not
+always do so.
+
+_Theory of Detonation._--The theory of detonation is not yet thoroughly
+understood. That it is not alone due to the heat caused by the impact
+of the mechanical energy of the particles of gas, set free from the
+initiatory charge on the principal mass, is proved by the fact of its
+being possible to detonate wet gun-cotton.
+
+Professor Bloxam terms detonation to be "sympathetic" explosion.
+
+Experiments carried on in England by Professor Abel, and in France by
+MM. Champion and Pellet, tend to show that it is due to the vibratory
+action of the detonating agent.
+
+Thus a glass may withstand a strong blow, though a particular note or
+vibration will smash it.
+
+All explosive compounds and mixtures, including gunpowder, are
+susceptible of violent explosion through the agency of a detonation.
+
+_Roux and Sarrau._--Roux and Sarrau divide explosions into two orders:--
+
+1st order.--Detonations.
+
+2nd order.--Simple explosions.
+
+Simple explosions are produced by direct inflammation, or by a small
+charge of gunpowder.
+
+Detonations are obtained from nitro-glycerine, gun-cotton, &c., by
+exploding with fulminate of mercury.
+
+They state that fulminate of mercury does not detonate gunpowder; but
+if the exploding charge is a small amount of nitro-glycerine, itself
+detonated by fulminate of mercury, then an explosion of the first order
+is obtained.
+
+The relative effects were approximately measured by determining the
+quantities necessary to rupture small cast iron shells of supposed
+equal strength.
+
+_Results of their Experiments._--The following are some of the
+results:--
+
+    +---------------+---------------------------+
+    |               |     Explosive Effect.     |
+    |               +---------------------------+
+    |               |  2nd Order. |  1st Order. |
+    +---------------+-------------+-------------+
+    |Gunpowder      |    1·00     |    4·34     |
+    |Gun-cotton     |    3·00     |    6·46     |
+    |Nitro-glycerine|    4·80     |   10·13     |
+    +---------------+-------------+-------------+
+
+According to the above table, nitro-glycerine is more than ten times,
+and gun-cotton more than six times, as powerful as gunpowder fired in
+the ordinary way (2nd order).
+
+The want of reciprocity between two detonating agents is shown in
+a remarkable degree by the following experiments, carried out by
+Professor Abel:--
+
+    1.--The detonation of 1/4 ounce of gun-cotton (the
+    smallest quantity that can be thus applied) induced the
+    simultaneous detonation of nitro-glycerine, enclosed
+    in a vessel of sheet tin, and placed at a distance of 1
+    inch from the gun-cotton.
+
+    2.--The detonation of 1/2 ounce of gun-cotton produces
+    the same effect with an intervening space of 3 inches
+    between the substances.
+
+    3.--The detonation of 2 ounces of nitro-glycerine in
+    _close contact_ with compressed gun-cotton failed to
+    accomplish the detonation of the latter, which was
+    simply dispersed in a fine state of division, in all
+    the instances but one, in a large number of experiments.
+
+Explosive agents are divided into explosive mixtures and compounds.
+
+In the former the ingredients are mechanically mixed, and can be
+separated by mechanical means.
+
+In the latter the ingredients are chemically combined, and can only be
+separated by chemical change.
+
+_Torpedo Explosive Agents._--The explosive agents that are practically
+the most important, as far as their employment as torpedo charges are
+concerned, are as follows:--
+
+_Explosive Mixtures._--A.--Explosive mixtures.
+
+    1.--Gunpowder.                          } Nitrate class
+    2.--Ammonium picrate, or picric powder. }
+
+_Explosive Compounds._--B.--Explosive compounds.
+
+    1.--Nitro-glycerine.
+    2.--Dynamite (No. 1).
+    3.--Gun-cotton.
+    4.--Fulminate of mercury.
+
+
+A.--EXPLOSIVE MIXTURES.
+
+_Gunpowder._--This explosive mixture is composed of seventy-five parts
+of nitre (saltpetre), fifteen parts of charcoal, and ten parts of
+sulphur.
+
+On being ignited, the oxygen which is feebly held by the nitrogen
+combines with the carbon, forming carbonic oxide gas, whilst the
+sulphur unites with the potassium of the nitre, the whole combination
+being accompanied by a great evolution of heat and expansion of gas,
+and the nitrogen is set free.
+
+_Properties, &c._--A spark, friction between hard bodies, or a
+temperature of 572° F., are any of them sufficient to cause an
+explosion of gunpowder.
+
+Slight moisture, due to damp air, &c., produces caking and
+deterioration.
+
+Wetting causes permanent destruction.
+
+Frost does not injure it.
+
+It can be fired by ordinary methods.
+
+It can be transported and handled with safety and great ease.
+
+It is not a suitable explosive agent for torpedoes, on account of its
+liability to be injured by damp, as well as its not being sufficiently
+violent, though for the sake of convenience, &c., it is often employed
+for such work.
+
+The effect produced by the explosion of a charge of gunpowder,
+ignited by the ordinary method, is that of an uplifting rather than a
+shattering effect.
+
+This evil may be greatly remedied, when gunpowder is used as the charge
+of a torpedo, by firing it with a detonator, by which means its fullest
+explosive effect is developed.
+
+_Picric Powder._--The picrates are salts of picric acid.
+
+Picric acid is formed by the action of nitric acid on carbolic acid.
+
+The picrate employed by Professor Abel is prepared from picric acid and
+ammonium. This preparation, or salt mixed with nitre (saltpetre), forms
+Abel's picric powder.
+
+_Properties, &c._--It is prepared for use in a similar manner to
+gunpowder, and it can be handled in the same way.
+
+It is less violent than dynamite or gun-cotton, though much more so
+than gunpowder.
+
+It is difficult to explode it by blows or friction.
+
+If flame be applied to it, the part touched burns, but the combustion
+does not become general.
+
+This explosive agent will probably be used for spar torpedoes, when
+gun-cotton or dynamite are not employed.
+
+
+B.--EXPLOSIVE COMPOUNDS.
+
+_Nitro-glycerine._--Nitro-glycerine is formed by the action of nitric
+acid upon glycerine at a low temperature.
+
+The manufacture of this compound consists, first, in the slow mixture
+of the glycerine with the acid, at a low temperature; secondly, in
+washing the nitro-glycerine from the excess of acid with water.
+
+The nitric acid before use is mixed with a certain proportion of strong
+sulphuric acid, so that the water formed during the reaction may be
+taken up, and thus any dilution of the nitric acid is prevented.
+
+Nitro-glycerine is composed of carbon, hydrogen, nitrogen, and oxygen,
+as indicated by the equation _C_{3}H_{5}N_{3}O_{9}_.
+
+_Properties, &c._--At ordinary temperatures nitro-glycerine is an oily
+liquid, having a specific gravity of 1·6. Freshly made it is creamy
+white and opaque, but clears and becomes colourless on standing for a
+certain time, depending on the temperature.
+
+It does not mix with, nor is it affected by, water. It has a sweet,
+aromatic taste, and produces a violent headache if placed upon the
+tongue.
+
+The opaque, freshly made nitro-glycerine does not freeze until the
+temperature is lowered to 3°-5° below zero, F., but, when cleared, it
+freezes at 39°-40° F. Nitro-glycerine freezes to a white crystalline
+mass, and in this state it can be thawed by placing the vessel
+containing it in water, at a temperature not over 100° F.
+
+If flame is applied to freely exposed nitro-glycerine, it burns slowly
+without explosion.
+
+Nitro-glycerine in a state of decomposition becomes very sensitive,
+exploding violently when struck, even when unconfined.
+
+Pure nitro-glycerine does not spontaneously decompose at any ordinary
+temperature, but if it contains any free acid, then decomposition
+may happen. When pure, it is not sensitive to friction, or moderate
+percussion. If struck with a hammer, only the particle receiving the
+blow explodes, the remainder being scattered.
+
+The firing point of nitro-glycerine is about 356° F., though it begins
+to decompose at a lower temperature.
+
+The mode of firing nitro-glycerine usually employed is that of a
+fulminate of mercury detonating fuse.
+
+Nitro-glycerine in the frozen state cannot be fired even by large
+charges of fulminate.
+
+In one instance, 1600 lbs. of liquid nitro-glycerine exploded in a
+magazine containing 600 lbs. of the same substance in a frozen state,
+but failed to fire the latter, only breaking it up and scattering it in
+every direction.
+
+_Dynamite._--This explosive compound is merely a preparation in which
+nitro-glycerine is itself presented for use, its explosive properties
+being those of the nitro-glycerine contained in it, as the absorbent is
+an inert body.
+
+Dynamite is formed of seventy-five parts of nitro-glycerine absorbed by
+twenty-five parts of a porous siliceous earth or "kieselguhr."
+
+The best substitute for "kieselguhr" is ashes of bog-head coal.
+
+Dynamite is a loose, soft, readily moulded substance, of a buff colour.
+
+The preparation of dynamite is very simple.
+
+The nitro-glycerine is mixed by means of wooden spatulas with the fine
+white powder (kieselguhr) in a leaden vessel.
+
+It freezes at 39°-40° F., and when solidly frozen cannot be exploded,
+but if in a pulverised state it can be exploded, though with diminished
+violence.
+
+It can be easily thawed, by placing the vessel containing it in hot
+water.
+
+Friction or moderate percussion does not explode it.
+
+Its firing point is 356° F.
+
+If flame be applied to it, it burns with a strong flame.
+
+It is fired by means of fulminate of mercury, and its explosive force
+is about seven times that of gunpowder.
+
+For ground and buoyant mines, where actual contact between the hostile
+vessel and the torpedo will be rarely achieved, this being next to
+nitro-glycerine the most violent of all known explosive agents, and
+being cheaply and readily procured, is the very best explosive for such
+torpedoes.
+
+That it is not generally adopted is owing to its containing a large
+proportion of that seemingly dangerous substance, nitro-glycerine,
+which makes the handling of dynamite a somewhat hazardous operation.
+
+According to Professor Abel, there are now as many as fifteen dynamite
+factories in different parts of the world (including a very extensive
+one in Scotland) working under the supervision of Mr. Nobel, the
+originator of the nitro-glycerine industry; and six or seven other
+establishments exist where dynamite or preparations of very similar
+character are also manufactured.
+
+The total production of dynamite in 1867 was only eleven tons, while in
+1878 it amounted to 6140 tons.
+
+This explosive compound is most extensively used for general blasting
+purposes all over the world, and for this purpose, owing to its
+cheapness and the convenience in manipulating it, is far superior to
+compressed gun-cotton.
+
+Gun-cotton is formed by the action of concentrated nitric acid
+on cotton, its composition being indicated by the formula
+_CH_{7}(NO_{2})_{3}O_{5}_.
+
+Professor Abel's process for manufacturing pulped and compressed
+gun-cotton is as follows:--
+
+Cotton waste is the form of cotton used; it is picked and cleaned,
+thoroughly dried at 160° F., and then allowed to cool.
+
+The strongest nitric and sulphuric acids are employed, mixed in the
+proportion of one part of the former to three of the latter by weight.
+These are mixed in large quantities, and stored in cast-iron tanks.
+
+The cotton in 1-lb. charges is immersed in the acid mixture, which is
+contained in a trough surrounded by cold water. After being subjected
+to the action of the acid for a short space of time, the cotton is
+taken up, placed upon a perforated shelf, and as much as possible of
+the acid squeezed out of it. It is then put into jars, covered with
+fresh acid, and the jars placed in fresh water, remaining there for
+twenty-four hours.
+
+To remove the acid, the gun-cotton from the jars is thrown into a
+centrifugal strainer, by which nearly all the acid is expelled. It is
+then diffused quickly in small quantities through a large volume of
+water, and again passed through a centrifugal machine.
+
+The next process is that of thoroughly washing the gun-cotton, for the
+purpose of removing the traces of the acid still adhering to it. By
+pulping, which operation is performed in pulping engines or beaters,
+the washing is expeditious and thorough.
+
+A _beater_ is an oblong tub in which is placed a revolving wheel
+carrying strips of steel on its circumference. From the bottom under
+the wheel project similar steel strips.
+
+The action of this machine is as follows:--
+
+By the rotation of the wheel, the gun-cotton which is suspended in
+water circulates around the tub, and is drawn between the two sets of
+steel projections, by which it is reduced to a state of _pulp_.
+
+The bottom of the tub is movable, and thus the space through which the
+gun-cotton must pass may be contracted, as the operation proceeds.
+
+The pulping being complete, the contents are run into _poachers_ for
+the final washing.
+
+A _poacher_ is a large oblong wooden tub. On one side at the middle is
+placed a wooden paddle-wheel, which extends half way across the tub.
+
+In the poacher the pulped gun-cotton is stirred for a long time with a
+large quantity of water. The revolution of the paddle-wheel keeps up a
+constant circulation, and care is taken that no deposit occurs in any
+part of the tub.
+
+Having converted the cotton into gun-cotton, reduced it to a state of
+pulp, and thoroughly washed it, the next process is to separate the
+water from the pulp, and compress it into cakes or discs.
+
+This is accomplished by means of two presses, the first of which has 36
+hollow cylinders, in which perforated plungers work upwards.
+
+These plungers having been drawn down, the cylinders are filled with
+the water-laden pulp, and their tops covered with a weight; the
+plungers are then forced up by hydraulic power, compressing the pulp,
+and forcing the water to escape through their perforations.
+
+The second one is used to more solidly compress the cylindrical masses
+of gun-cotton formed by the action of the first press, a pressure of 6
+tons to the inch being in this case applied.
+
+About 6 per cent. of moisture still remains in the discs, which can be
+readily removed by drying.
+
+_Properties._--Cotton converted into gun-cotton is little changed in
+appearance, though the latter is harsher to the touch than the former.
+
+If a flame be applied to dry loose gun-cotton, it flashes up, without
+explosion; if compressed it burns rapidly, but quietly.
+
+Moist compressed gun-cotton under the same circumstances burns away
+slowly.
+
+Gun-cotton containing 12 to 14 per cent. of water is ignited with much
+difficulty on applying a highly heated body. As it leaves the hydraulic
+press upon being converted from the pulped state to masses, it contains
+about 15 per cent. of water; in this condition it may be thrown on to
+a fire or held in a flame without exhibiting any tendency to burn;
+the masses may be perforated by means of a red-hot iron, or with a
+drilling tool, and they may with perfect safety be cut into slices by
+means of saws revolving with great rapidity. If placed upon a fire and
+allowed to remain there, a feeble and transparent flame flickers over
+the surface of the wet gun-cotton from time to time as the exterior
+becomes sufficiently dry to inflame; in this way a piece of compressed
+gun-cotton will burn away very gradually indeed.
+
+To test the safety of wet gun-cotton, the following two experiments
+among many have been made:--
+
+Quantities of wet gun-cotton, 20 cwt. each, packed in one instance in
+a large, strong wooden case, and in the other in a number of strong
+packing cases, were placed in small magazines, very substantially built
+of concrete and brickwork. Large fires were kindled around the packages
+in each building, the doors being just left ajar. The entire contents
+of both buildings had burned away, without anything approaching
+explosive action, in less than two hours.
+
+This comparatively great safety of wet gun-cotton, coupled with the
+fact that its detonation in that state may be readily accomplished
+through the agency of a small quantity of dry gun-cotton, termed a
+"primer," which, by means of a fulminating fuze, or detonator, is
+made to act as the initiative detonating agent, gives it important
+advantages over other violent explosive agents, when used for purposes
+which involve the employment of a considerable quantity of the
+material, on account of the safety attending its storage and necessary
+manipulation.
+
+From experiments conducted by engineer officers in Austria, it was
+found that if boxes containing dry compressed gun-cotton are fired into
+from small arms, even at a short range, the gun-cotton is generally
+inflamed, but never exploded, the sharpness of the blow essential to
+effect an explosion, which the bullet might otherwise give, being
+diminished by its penetration through the side of the box before
+reaching the explosive. Wet gun-cotton, containing even as little as 15
+per cent. of water, is never inflamed on these conditions.
+
+Dynamite, on the other hand, is invariably detonated when struck by a
+bullet on passing through the side of the box.
+
+Gun-cotton is insoluble in and unaffected by water.
+
+The firing point of gun-cotton is about 360° F.
+
+The temperature of explosion of gun-cotton is about 8700° F., being
+more than double that of gunpowder. Gun-cotton is not sensitive to
+friction or percussion.
+
+If not perfectly converted or thoroughly washed, gun-cotton is liable
+to spontaneous decomposition, which under favourable conditions may
+result in explosion.
+
+Compressed gun-cotton is free from such danger, as it may be kept
+and used saturated with water. It is stored in the wet state, care
+being taken that it is not exposed to a temperature that will freeze
+the water in the cakes, as if this occurs they are liable to be
+disintegrated by the expansion of the water in freezing.
+
+Gun-cotton is the agent most extensively used for all kinds of
+military engineering and submarine operations in Great Britain, it
+being especially manufactured by the English government for that
+express purpose; but in other countries it is not so manufactured, and
+therefore, as it is little used for other than military purposes, it
+is not to any extent privately manufactured, as is the case with other
+explosives, such as dynamite, dualine, lithofracteur, &c., and thus, in
+case of war, would be somewhat difficult to obtain out of England.
+
+Compared with dynamite, it is not so violent, and occupies more space,
+weight for weight, and also requires a more complicated means of
+detonating it. On the other hand, gun-cotton is infinitely safer to
+store and manipulate, and is not so subject to detonation by concussion
+(not being so sensitive) as dynamite.
+
+_Fulminate of Mercury._--Fulminate of mercury is formed by the
+action of mercuric nitrate and nitric acid upon alcohol. The mode of
+preparation is as follows:--
+
+Dissolve one part of mercury in twelve parts of nitric acid, and pour
+this solution into twelve parts of alcohol.
+
+Pour this mixture into a vessel which is placed in hot water until it
+darkens and becomes turbid and begins to evolve dense white fumes,
+then remove it from the water. The reaction goes on, with strong
+effervescence and copious evolution of dense white ethereal vapours. If
+red fumes appear, cold alcohol should be added to check the violence of
+the action.
+
+The operation should be performed at a distance from a fire or flame,
+and in a strong draught, so that the vapours may be carried off.
+
+When the liquid clears, and the dense white fumes are no longer given
+off, further action is stopped by filling up with cold water. The
+fulminate settles to the bottom of the vessel as a grey crystalline
+precipitate. The liquid is then poured off, and the fulminate washed
+several times by decantation or upon a filter.
+
+Dry fulminate of mercury explodes violently when heated to 367° F.,
+when forcibly struck by the electric spark, &c.
+
+When wet it is inexplosive, and therefore it is always kept wet, being
+dried in small amounts when required for use.
+
+Fulminate of mercury is applied in many ways, either pure or mixed with
+other substances, as in percussion caps, percussion powder, primers,
+detonators, &c.
+
+For the purpose of detonating nitro-glycerine or its preparations, 15
+grains of the fulminate are sufficient, but to detonate gun-cotton
+25 grains are necessary. The fulminate in detonating fuzes should
+be enclosed in a copper case or cap, and must never be loose. The
+fulminate should be wet when charging the detonators, as it is very
+dangerous to handle when dry.
+
+Great care is requisite in handling this explosive compound.
+
+In addition to the foregoing explosive compounds and mixtures, the
+following explosive agents have also been employed for the purposes of
+submarine operations, though only to a small extent.
+
+_Dualin._--Dualin is a nitro-glycerine preparation formed by mixing
+sawdust and saltpetre with that substance.
+
+This preparation, inferior to dynamite, was employed by the Germans as
+the explosive agent for their submarine mines during the Franco-German
+war (1870-71).
+
+_Lithofracteur._--Lithofracteur is also a preparation
+of nitro-glycerine. It is composed of the following
+materials:--Nitro-glycerine, kieselguhr, coal, soda, saltpetre, and
+sulphur.
+
+This explosive agent, also inferior to dynamite, is used, though not
+very extensively, by the French for their submarine mines.
+
+_Horsley's Powder._--Horsley's powder is a chlorate mixture formed of
+potassium, chlorate, and galls. This explosive mixture was formerly
+used by Captain Harvey for his towing torpedo, but has recently been
+discarded for compressed gun-cotton.
+
+_Abel's Detonation Experiments._--The following are the results of
+experiments carried out by Professor Abel, C.B., F.R.S., on the subject
+of detonation:--
+
+    1.--A fuze containing rather more than 1 ounce of
+    gunpowder, strongly confined, exploded in contact with
+    a mass of compressed gun-cotton, _only inflames it_,
+    although the explosion of the fuze is apparently a
+    sharp one.
+
+    2.--45 grains of fulminate of mercury, exploded
+    unconfined on the surface of a piece of compressed
+    gun-cotton, only inflames or disperses it.
+
+    3.--A fuze containing 9 grains of fulminate of mercury,
+    strongly confined, exploded in contact with compressed
+    gun-cotton, or dynamite, detonates it with certainty.
+
+    4.--An equal quantity of fulminate of mercury,
+    similarly confined, does not detonate _uncompressed_
+    gun-cotton in which it is imbedded, but merely
+    disperses and inflames it.
+
+    5.--150 grains of compressed gun-cotton, detonated in
+    proximity to dynamite, _detonates the latter_.
+
+    6.--3 ounces of dynamite, and very much larger
+    quantities, detonated in contact with compressed
+    gun-cotton, only disperses it.
+
+    7.--A wrought-iron rail can be destroyed by detonating
+    8 ounces of compressed gun-cotton placed unconfined on
+    the rail.
+
+    8.--A piece of wet gun-cotton, quite uninflammable,
+    removed from a fire, and detonated upon a block of
+    granite, using a small primer of dry gun-cotton,
+    shatters the block.
+
+    9.--A submerged charge of wet gun-cotton, open on all
+    sides to the water, and merely confined around the
+    dry initiative, or primer, by means of a net, can be
+    exploded.
+
+_Explosive Agents in Torpedoes._--The explosive agents that at the
+present time are most generally used in torpedoes are gunpowder,
+gun-cotton in the wet compressed state, and dynamite, and these may be
+compared as to their properties and their explosive effects.
+
+_Gunpowder._--Gunpowder is a familiar material, in general use for
+all military purposes. It can be handled and transported with safety
+and ease, and it can be fired by ordinary methods. But for submarine
+purposes it has the disadvantage of being very easily injured by water,
+so that it is absolutely necessary to enclose it in water-tight cases.
+
+_Gun-cotton._--Gun-cotton is free from liability to accidents, and in
+this matter, and the safety of its manufacture, it compares favourably
+with gunpowder.
+
+It is peculiarly adapted to submarine work, being unaffected by water.
+And as it may be kept in water, ready for use, it can be safely carried
+on board ship in large quantities. It is far more violent in its
+action when detonated than gunpowder. The chief objection to its use
+is, that being applied only for special purposes, it is not readily
+obtained. Also it requires a peculiar and somewhat complicated mode of
+firing it.
+
+_Dynamite._--Dynamite is more easily manufactured than the two
+foregoing explosives. The fact of it containing nitro-glycerine, which
+has a bad reputation, has militated against its use as a torpedo
+explosive agent, though for blasting purposes it is most extensively
+used. Though not directly affected by water, its firing is hindered
+when diffused through water. Another disadvantage is its high freezing
+point. Like gun-cotton, it requires special means to fire it, though
+much simpler, and also is much more powerful than gunpowder. The
+explosive effect of dynamite or gun-cotton is a rending or a shattering
+one, while that of gunpowder is an uplifting or heaving one.
+
+Again, it is necessary when using gunpowder that the object be in the
+line of least resistance, but with dynamite or gun-cotton the effect is
+nearly equal in every direction, therefore for submarine operations,
+either dynamite or gun-cotton is the explosive agent that should be
+invariably used.
+
+_Size of Torpedo Charges._--For permanent mines, a charge of 700 lbs.
+to 1000 lbs. of gun-cotton is quite sufficient, though too large a
+charge cannot be employed, except as regards the matter of convenience.
+
+For buoyant mines, 500 lbs. to 700 lbs. of gun-cotton is an ample
+charge, and for contact mines, 200 lbs. to 300 lbs. of gun-cotton is
+sufficient. In spar torpedoes, where lightness is a consideration,
+gun-cotton charges of 30 lbs. to 50 lbs. will be found ample, and
+similarly in the case of the towing or locomotive torpedoes. Of course,
+with regard to such a submarine weapon as the Lay torpedo boat, any
+size charge may be carried, according to the wish of the builder.
+
+_Torpedo Explosions illustrated._--At Fig. 166 is represented a sketch
+of a torpedo explosion, from a photograph taken at the moment the
+column of water was at its greatest elevation. The torpedo contained
+432 lbs. of gun-cotton, and was exploded under 27 feet of water.
+
+The height of the column thrown up measured 81 feet, and the diameter
+at the base 132 feet.
+
+[Illustration: SUBMARINE MINE EXPLOSION.
+
+PLATE LII]
+
+[Illustration: SUBMARINE MINE EXPLOSIONS.
+
+PLATE LIII]
+
+At Fig. 165 is shown a sketch of two submarine mine explosions from
+an instantaneous photograph; the schooner which is shown in
+the sketch happened to be passing at the moment of explosion, thus
+affording a comparison as to the size of the columns of water thrown up.
+
+The column on the left was due to the explosion of a submarine mine
+containing 100 lbs. gunpowder at a depth of 10 feet below the surface.
+That on the right was the result of an explosion of a similar mine, but
+at a depth of 41 feet below the surface. Its extreme height was 400
+feet.
+
+
+
+
+CHAPTER IX.
+
+TORPEDO EXPERIMENTS.
+
+
+THE following are some of the more important torpedo experiments that
+have been carried out in England and Europe, to investigate the subject
+of submarine explosions as applied to ships and to mines, &c., these
+experiments extending over a space of thirteen years.
+
+_Experiment at Chatham, England, 1865._--This experiment was carried
+out to ascertain the effect of gunpowder torpedoes on the bottom of a
+wooden ship.
+
+Target:--H.M.S. _Terpsichore_, a wooden sloop of war.
+
+Torpedo:--150 lbs. of fine-grained powder. Two were used. They
+were placed on the ground, about 13' below the ship's keel, and 2'
+horizontally clear of her side.
+
+Effect of explosion:--A hole of about 4' radius was made, about 19'
+nearly vertical from the charge; the _Terpsichore_ sinking a few
+minutes after the explosion.
+
+_Experiment in Austria._--The object of this experiment was to
+ascertain the effect of a very large charge of gun-cotton exploded at
+some distance from the side of a wooden vessel.
+
+Target:--A wooden sloop.
+
+Torpedo:--400 lbs. of gun-cotton, placed 10' below the surface of the
+water, and 24' horizontally from the bottom of the vessel.
+
+Effect of explosion:--Complete destruction of the vessel.
+
+_Experiments at Carlscrona, Sweden, 1868._--These experiments were
+made to investigate the effect of submarine contact mines, charged
+with dynamite, against a strong wooden vessel, as well as against
+a double-bottomed iron vessel. They were carried out under the
+supervision of Lieut.-Colonel Zethations, of the Royal Swedish Navy.
+
+Target:--The hull of a 60 gun frigate, which had been built in 1844;
+it had been cut down to the battery deck, and the copper removed.
+Her timbers and planking were quite sound; timbers of oak about
+13" square, and 1" apart; planking of Swedish pine, 5-1/2"; bottom
+strengthened inside with wrought-iron diagonal bands, 6" by 1-1/4";
+inside planking running half way up to the battery deck of oak; 6"
+thick. This completes the wooden target.
+
+On the port side a quadrangular opening was made, and fitted with a
+construction representing a strong double iron bottom, firmly fastened
+to an oaken frame that had been put on inside, on the four sides of the
+opening, and with through-going bolts, 1" in diameter, to the timbers.
+
+Torpedoes:--No. 1.--13 lbs. dynamite, enclosed in 1/12" iron case. It
+was placed on the starboard side, amidships, 7' below the water line,
+and 2' 2" from the bottom of the ship.
+
+No. 2.--16 lbs. dynamite, enclosed in a glass vessel. It was placed on
+the starboard side, 7-3/4' below the water line, 3' from the bottom of
+the ship, and 40' from her stern.
+
+No. 3.--16 lbs. dynamite, enclosed in 1/12" iron case. It was placed on
+the port side, 5-3/4' below the water line, 2' from the bottom of the
+ship, and 30' from her stern.
+
+No. 4.--10 lbs. dynamite, in a case as above. It was placed on the port
+side, 6-1/2' below the water line, 2-1/6' from the bottom of the ship,
+and 70' from her stern.
+
+No. 5.--13 lbs. dynamite, in case as above. It was placed 7-1/3' below
+the water line, 2-1/6' from the centre of the _iron_ bottom.
+
+These five torpedoes were fired at the same moment.
+
+Effect of explosion:--The hull of the ship was lifted about a foot, and
+sunk in 1-1/2 minutes.
+
+No. 1 Mine.--Timbers broken and thrown inside, into the hold, on a
+space of about 15' × 8'; three more timbers on one side of this hole
+broken; inside oak planking rent off on a length of 14'; two iron bands
+torn up and bent, one of them broken in two places; outside planking
+torn off on a space of 21' × 12'; several planks still higher up broken.
+
+No. 2 Mine.--Timbers blown away on a space of about 8' square; inside
+planking torn off on a length of 20'; two iron bands broken, and torn
+up and bent; and outside planking rent off on a space of 19' × 12'.
+
+No. 3 Mine.--Timbers blown away on a space of 10-1/2' × 12' at one end,
+and 6' at the other; inside planking off for a length of 14'; one iron
+band torn up, and one broken; outside planking off on a space of 18' ×
+25' × 15'.
+
+No. 4 Mine.--Timbers blown away on a space 4' × 16'; on the sides of
+this hole, ten timbers were broken; two iron bands torn up, and one
+broken; inside planking off for a length of 20'; outside planking off
+for a space of 20' × 23' × 10', and 13 feet.
+
+No. 5 Mine.--The gas sphere of this mine had hit the middle of the
+outside plates on one of the angle-iron ribs. This rib was torn from
+the timbers and bent up, nearly 2' in the middle, but not broken. There
+was an oval hole in the outside plates 4' × 3' between two ribs, which
+ribs, with the plates on edge riveted to them, were bulged out about
+5 inches. The inner plate, one large piece was blown up in a vertical
+position, after having cut all the bolts and rivets, sixty of 1", and
+thirty of 3/4", save those that fastened the lower side to the oaken
+frame and timbers. On a length of 30' and height of 20', the bottom, on
+all sides of the iron construction, had been bent inwards; the greatest
+bend was about 5"; three deck beams above had been broken.
+
+By the joint effect of all the mines, almost all the iron deck beam
+knees had been rent from the side, and there was an opening between
+deck and hull on both sides for a length of about 130 feet.
+
+_Experiment at Kiel._--Target:--A large gun-boat, greatly strengthened
+internally by solid balks of timber.
+
+Torpedo:--200 lbs. gunpowder. It was placed nearly under her keel, at a
+distance of 15 feet.
+
+Effect of explosion:--Complete destruction of the vessel.
+
+_Experiment in England, 1874._--Target:--A rectangular iron case 20'
+long, 10' high, and 8' wide, divided into six compartments by means of
+one longitudinal bulkhead midway between the front and rear faces of
+the target, and two athwartship bulkheads equidistant from the ends of
+the target. Thickness of front and rear faces 11/16", of longitudinal
+bulkhead 1/4", of athwartship bulkheads 3/8".
+
+Torpedo:--100 lbs. of gunpowder, enclosed in a spar torpedo case and
+fired by two detonators. It was exploded in contact with the target,
+7-1/2' below the surface of the water, and 7' from top of target.
+
+Effect of explosion on the target:--"Front of centre compartment
+destroyed and top blown off. Plate representing inner skin destroyed.
+Back of centre compartment (rear face of the target) much bulged, and
+penetrated; the hole measured 36' × 15". Large portions of the target
+were thrown to a height of 150 to 200 feet, and from 80 to 100 yards'
+distance."
+
+The effect of explosion on a ship's pinnace, which had been placed
+16 feet from and at right angles to the front face of the target,
+with steam up, and canopy and shield in position, was that a large
+quantity of water was thrown back in the boat, putting the fires out,
+and filling the boat up to her thwarts, but otherwise the boat was
+uninjured.
+
+_Experiments at Copenhagen, Denmark, in 1874._--The object of these
+experiments was to ascertain if a ship's armoured side would be
+seriously injured by a torpedo exploded in contact with it.
+
+
+1ST EXPERIMENT.
+
+Target:--1" thick, and 2' × 2', supported in a horizontal position on a
+substructure consisting of 8" timber resting on two pieces of 6" timber
+under two sides, and completely supported by earth up to lower edge of
+substructure.
+
+Torpedo:--33 lbs. of dynamite, enclosed in a square wooden case 2-1/4"
+high, and 5·5" × 5·5"; it was placed on the middle of the earth with 8"
+of earth tamping; this tamping representing the resistance of a thin
+stratum of water.
+
+Effect of explosion:--The plate was broken into four pieces, and
+substructure crushed.
+
+
+2ND EXPERIMENT.
+
+Target:--2" thick, and 2' × 2-1/2', supported in a horizontal position
+on a substructure as above, but resting on four piles of 6" x 6" timber.
+
+Torpedo:--8·9 lbs. of dynamite, enclosed in a wooden case 4" high, and
+5" × 10". It was laid with one edge on the plate, the other edge 3"
+above the plate; same tamping as above.
+
+Effect of explosion:--The plate broken into three pieces, and
+substructure crushed.
+
+
+3RD EXPERIMENT.
+
+Target:--5" thick, and 3' 8" × 4' 7", supported in a horizontal
+position on a substructure as above, but eight piles of 6" × 6" timber
+used. Plate bolted to the structure with eights.
+
+Torpedo:--44·4 lbs. of dynamite, enclosed in a wooden case, of same
+thickness as the Harvey torpedo, and 4" × 13" × 21"; it was placed with
+surface against the plate, one edge 2" and the other 5-1/2" from the
+plate; tamping as before.
+
+Effect of explosion:--Plate bulged 3-1/4" in the middle; substructure
+completely crushed.
+
+
+4TH EXPERIMENT.
+
+Target:--5" thick, and 3' 8" × 4' 7"; this was the same plate as used
+in the previous experiment, laid with bulge uppermost on two beams
+under the short sides.
+
+Torpedo:--44·4 lbs. of dynamite, enclosed in a cylindrical tin box
+7-1/2" × 2'; it was placed on top of plate 11" from one side and with
+ends 9-1/2" from edge of plate; tamping as before.
+
+Effect of explosion:--A corner of the plate broken off.
+
+
+5TH EXPERIMENT.
+
+Target:--Same plate placed vertically in the earth.
+
+Torpedo:--44·4 lbs. of dynamite, enclosed in a cylindrical tin box 8·5"
+× 18"; it was placed on timber, so as to rest against the face and
+centre of the plate; tamping as usual.
+
+Effect of explosion:--Plate broken into four pieces, two of which were
+large; pieces hurled over parapet, one fell at a distance of 400 feet.
+
+_Experiments at Carlscrona, Sweden, in 1874-75._--These experiments
+were carried out by the Swedish torpedo authorities, to ascertain the
+effect of different sized charges of dynamite and gunpowder, enclosed
+in divers cases, and exploded at various distances from a target which
+represented in all respects, with the exception of the armour, a
+section of the side of H.M.S. _Hercules_ before the boiler room, she
+being at that time one of the most powerful vessels afloat.
+
+Target:--32' in length, and fitted into the side of an old line of
+battle ship. Similar in shape to a wing tank, and comprised a double
+bottom in four water-tight compartments, a wing passage in two
+water-tight compartments, and two large water-tight compartments in
+rear of all. It extended from 2' above the water line to within about
+5' of the vessel's keel. The thickness of the plates forming the
+target were:--outer bottom, lower portion 13/16"; part where torpedo
+took effect, 3/4". Inner bottom, and wing passage bulkhead, 1/2".
+Vertical and longitudinal frames, both solid and bracket, 7/16". The
+longitudinal frames were bracket frames, with the exception of the
+second, which was solid and water-tight, with its outer edge about 8'
+below the water line. The vertical frames, of which there were seven,
+were placed 4' apart, the central one being solid and water-tight,
+the others being bracket frames. The ship was moored in 42 feet of
+water; the charges were detonated, one fuze being used in all but No. 3
+experiment, when five fuzes were employed.
+
+
+1ST EXPERIMENT.
+
+Torpedo:--33 lbs. of dynamite, enclosed in cylindrical steel case, no
+air space; height 10·75", diameter 10·75", and thickness 1/32". It was
+placed 25·5' from the target, opposite No. 7 frame, and 9·25' below the
+surface of the water.
+
+Effect of explosion:--Ship appeared to be lifted bodily. A rivet in the
+midship longitudinal bulkhead of fore compartment was loosened. The
+torpedo was fired from the ship, and the shock felt was not very great.
+
+
+2ND EXPERIMENT.
+
+Torpedo:--47·2 lbs. of dynamite, in cylindrical steel case, no air
+space; height 12", diameter 12", and thickness 1/32". It was placed
+25·5' from No. 5 frame, 9·25' below the surface of the water.
+
+Effect of explosion:--Ship appeared to be lifted bodily. A leak was
+started in the outer bottom opposite to charge, caused by the loosening
+of five rivets.
+
+
+3RD EXPERIMENT.
+
+Torpedo:--112 lbs. of gunpowder, rifle small grain, enclosed in
+cylindrical steel case placed inside an iron case, with an air space
+all round; steel case, 9-1/2" × 22-1/2" × 1/32"; iron case 33" × 25" ×
+1/4". It was placed 12' from No. 5 frame, 9·25' below the surface.
+
+Effect of explosion:--Centre of ship lifted bodily, as if her back was
+broken; ship then rolled heavily to port. On board fire engines and
+troughs displaced several feet: shores and struts started, showing
+that the shock was considerable. The outer bottom on each side of
+the centre dividing plate indented to a depth of 1 to 1-1/2 inches;
+numerous rivets started, and some sheared. The leak was considerable,
+owing to the number of rivets that were started. The strength of
+the plates was not considered to be materially affected by the
+indentations; the rivets, 239 in number, were replaced; and the target
+prepared for the next experiment.
+
+
+4TH EXPERIMENT.
+
+Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
+placed 15' from No. 7 frame, 9·25' below the surface of the water.
+
+Effect of explosion:--Ship rolled slightly to port. A bolt securing the
+midship transverse bulkhead to beam was sheared. No damage done to the
+target.
+
+
+5TH EXPERIMENT.
+
+Torpedo:--66 lbs. of dynamite, enclosed in steel cylindrical case, no
+air space, 13·5" × 13" × 1/32". It was placed 21' from No. 3 frame,
+9·25' below the surface of the water.
+
+Effect of explosion:--A rivet in outer bottom, above water line at
+fore end of target, was sheared. A few rivets in outer bottom opposite
+charge, and two in after compartment, were started, but no leak was
+perceptible. Several shores slightly displaced.
+
+
+6TH EXPERIMENT.
+
+Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
+placed 12·75' from No. 7 frame, 9·25' below the surface of the water.
+
+Effect of explosion:--Ship not lifted as much as was the case in No.
+3 experiment; but explosion much sharper. On board, fire engines were
+capsized, and vertical shores displaced. Outer bottom opposite charge
+indented to a depth of about 1/2 an inch, other parts less bulged, and
+many rivets started.
+
+
+7TH EXPERIMENT.
+
+Torpedo:--33 lbs. of dynamite, enclosed as in first experiment. It was
+placed 4' from No. 4 frame, 9·25' below the surface of the water.
+
+Effect of explosion:--Effect very great; ship hurled suddenly to
+starboard. On going on board two minutes after the explosion, the
+fore compartment was found full, the after compartment became full
+ten minutes later. Shores and struts were considerably displaced,
+and there was evidence that the ship had sustained a severe shock.
+Outer bottom injured over an area 14' × 16', the plates being split
+in all directions; one piece, 5' square, was torn completely off,
+and an irregular hole was formed in the outer skin 14' × 12'. In the
+inner bottom below the wing passage bulkhead a piece 6' × 9' was
+blown completely out; the wing passage bulkhead was torn from the
+longitudinal frame and split from top to bottom. The inner skin above
+the upper longitudinal frame was torn from the latter, and forced in
+and upwards, but was not otherwise damaged. The vertical bracket frames
+Nos. 3 and 4, the latter opposite the torpedo, were destroyed, but the
+solid frame No. 5 was almost uninjured. The outer bottom, where it was
+not torn off, was forced in 7', or 4' beyond where the _inner_ bottom
+had been.
+
+
+8TH EXPERIMENT.
+
+Torpedo:--660 lbs. of gunpowder, enclosed in a buoyant cylindrical
+1/4" iron case. It was placed 32·3' from No. 4 frame, 29·25" below the
+surface of the water.
+
+Effect of explosion:--The ship and target had been thoroughly repaired,
+and were in good condition when this experiment was made; the ship was
+in this case moored in 65 feet of water. No effect was produced on the
+target by the explosion.
+
+
+9TH EXPERIMENT.
+
+Torpedo:--19 lbs. of dynamite, enclosed in a cylindrical steel case
+with arched ends. It was placed 10·5' from No. 3 frame, 9·25' below the
+surface of the water.
+
+Effect of explosion:--Effect produced apparently equal to that by No. 3
+charge of 112 lbs. of gunpowder at 12'; indentation being from 1/2 to
+1-1/4 inches in the outer skin opposite the torpedo.
+
+
+10TH EXPERIMENT.
+
+Torpedo:--19 lbs. of dynamite, enclosed in a case similar to that used
+in the 9th experiment. It was placed 3·3' from No. 7 frame, 9·25' below
+the surface of the water.
+
+Effect of explosion:--Hole produced in outer skin, 6·5' × 2' to 5';
+inner skin only bulged and slightly cracked in two places. Above the
+longitudinal frame, a bulge was made in the outer skin 8' × 7', with
+the above-mentioned hole; below the longitudinal frame the indentation
+was 14' × 5' and 2·1" deep, with two horizontal cracks 10' x 13', and
+several inches broad.
+
+
+11TH EXPERIMENT.
+
+Torpedo:--112 lbs. of gunpowder, enclosed in a cylindrical case of
+3/64" steel, placed in a 3/16" steel case, with 223 lbs. of buoyancy.
+Ignition effected by a glass igniting bottle. It was placed 5·75' from
+No. 5 frame, 9·25' below the surface of the water.
+
+Effect of explosion:--There was but little upcast of water outside the
+ship, but a great upcast through the ship. She immediately lurched to
+starboard, and on boarding her five minutes after, the target was found
+full of water.
+
+The effect on the target was as follows, above the 2nd longitudinal
+frame, where strengthened by the wing passage bulkhead:--Outer bottom
+blown away from the 4th to the 6th frames for a length of 8 feet and a
+height of 4-1/2 feet, and bent in 6-1/2 feet. Inner bottom bent in and
+broken through between the 4th and 5th frames, with an irregular hole
+8' square, and between the 5th and 6th frames, a similar sized hole.
+Wing passage bulkhead was bent in 2" to 3", and riven for a length of
+29'; in the water-tight middle bulkhead athwartships the rivets in two
+vertical joints were completely torn away.
+
+Between the 2nd and 3rd longitudinal frames, and below the wing passage
+bulkhead, both the inner and outer bottoms were completely blown away
+for a length of 12 feet and a height of 4 feet. The vertical and
+horizontal frames between the two bottoms had kept their position
+unchanged, and excepting that the bracket plate by frame No. 6 was
+bent, cracked, and torn away, the damage they had sustained was limited
+to some comparatively slight bending. The open hole formed in the
+target measured 76 square feet in outer bottom, and 60 square feet in
+inner bottom.
+
+Comparing the effect of this torpedo with the 7th, 33 lbs. of dynamite;
+with the latter charge the breach was made at the cost of the bottom
+plates as well as the vertical and longitudinal frames, which were
+completely torn asunder and strained; with the gunpowder charge,
+only the bottom plates were broken through, whilst the plates whose
+directions were nearly parallel to the lines of explosive effect were
+but little affected.
+
+_Experiments at Portsmouth, England, 1874-75._--The object of these
+experiments was to ascertain the effect of 500 lbs. gun-cotton
+torpedoes exploded at various distances from a target representing the
+double bottom of H.M.S. _Hercules_.
+
+They were carried out in Stokes Bay, under the supervision of officers
+belonging to the torpedo department of the Royal Engineers, and a
+torpedo committee, composed of naval and military officers.
+
+The _Oberon_, the vessel chosen for these experiments, was fitted
+with a double bottom, representing as nearly as possible that of the
+_Hercules_ without the armour; also with a surface condenser, and its
+connections; a donkey Kingston feed-valve; and athwartship water-tight
+bulkheads, which divided the ship into seven water-tight compartments.
+The outer skin was composed of 3/16" and 7/8" iron plates. In her
+starboard side at different points were fixed forty-four crusher
+gauges, and over each side were suspended six shots, each fitted with a
+crusher gauge.
+
+Displacement of the _Oberon_ about 1100 tons.
+
+The ship was anchored head and stern. Her mean draught of water during
+the experiments was 11 feet.
+
+
+1ST EXPERIMENT.
+
+Torpedo:--500 lbs. of gun-cotton, in discs saturated with water, and
+enclosed in an iron cylindrical case, 34" × 30" × 1/4", with arched
+ends; the primer consisted of two dry discs, and two detonators. It was
+placed 101' horizontal from the target, and opposite the condenser on
+the starboard side; 47' below the surface of the water, on the ground.
+
+Effect of explosion:--No damage was done to the hull, or condenser, but
+light articles, such as bunker plates, gratings, tank lids, &c., were
+displaced.
+
+
+2ND EXPERIMENT.
+
+Torpedo:--As in first experiment. It was placed on the ground, 80'
+horizontal and opposite the condenser on the starboard side, 48' below
+the surface of the water.
+
+Effect of explosion:--No damage was done to the hull, of condenser,
+but the bunker plates, gratings, &c., were displaced to a greater
+extent than in the previous experiment.
+
+
+3RD EXPERIMENT.
+
+Torpedo:--As before. It was placed on the ground, 60' horizontal, and
+opposite the condenser on the starboard side; 47' below the surface of
+the water.
+
+Effect of explosion:--No damage was done to the hull. Flanges of the
+condenser inlet pipe were cracked, and several of the joint bolts were
+broken. The condenser had been thrown up bodily, and had torn away its
+holding down bolts; but it was not as well secured as it would have
+been had it formed part of the machinery of a ship.
+
+
+4TH EXPERIMENT.
+
+Torpedo:--As before. It was placed on the ground, 50' horizontal, and
+opposite the condenser on the starboard side; 48' below the surface of
+the water.
+
+Effect of explosion:--Outer bottom on starboard indented over a length
+of about 100', being forced in between the frames; maximum indentation,
+3/4". Many bracket frames were disturbed, and outer angle iron of
+water-tight longitudinal was started for a length of 30', and made to
+leak slightly. The shell of the condenser was cracked in two places,
+3' and 5' in length. Bolts securing condenser, and flanges of pipes
+and valves, were all more or less damaged. Condenser was rendered
+unserviceable.
+
+
+5TH EXPERIMENT.
+
+Torpedo:--Same charge as before, but the primer consisted of four dry
+discs, and two detonators. It was placed 28·5' horizontal, opposite
+No. 9 frame, on the starboard side, 36' from the stern; 48' below the
+surface of the water, and 22' from the ground.
+
+Effect of explosion:--Bow observed to be lifted several feet. Several
+angle irons and bracket frames were cracked, and numerous rivets in
+outer bottom were broken off. The outer bottom on the starboard side
+was indented between the frames, and brackets were disturbed over a
+space of 100 feet; inner bottom uninjured.
+
+
+6TH EXPERIMENT.
+
+Torpedo:--As in previous experiment. It was placed on the ground, 28·5'
+horizontal, opposite No. 36 frame on the starboard side, and 30 feet
+from the stern; 49·5' below the surface of the water.
+
+Effect of explosion:--Several plates in the outer bottom were cracked,
+and outer bottom made to leak in several places, owing to the
+fractures in the plates, rivets being started, and seams being opened.
+Considerably more damage was effected than in previous experiment, but
+inner bottom still remained uninjured.
+
+
+7TH EXPERIMENT.
+
+Torpedo:--As in the 5th experiment. It was placed on the ground,
+immediately under the edge of the outer bottom, 39-3/4' from the
+target, and opposite No. 18 frame, 70' from the stern; 50' below the
+surface of the water.
+
+Effect of explosion:--Outer and inner bottom broken entirely asunder
+at No. 19 frame on the starboard side, and between Nos. 16 and 17 on
+the portside. A fracture was caused in the outer bottom extending from
+the shelf plate to upper edge of strake next the keel on the starboard
+side, and from the shelf plate to upper edge of flat keel plate on the
+port side. A fracture was also caused in the inner skin extending from
+the topside to the outer edge of the garboard strake on the starboard
+side, and from the topside to upper edge of garboard strake on the port
+side; this including a fracture of the keel at No. 17. The vertical
+keel, the longitudinals, as well as numerous bracket plates and angle
+irons, were broken, and about 2000 rivets in the outer bottom were
+rendered defective.
+
+The outer bottom was indented over a considerable length, the
+indentation being greatest between the frames, and the maximum being
+8 inches. The inner bottom was not indented or damaged, with the
+exception of the fractures before mentioned.
+
+_Experiments at Pola, Austria, 1875._--These experiments were carried
+out to determine the effect of very heavy charges of dynamite on an
+iron pontoon fitted with a double bottom, similar to that of H.M.S.
+_Hercules_.
+
+Target:--An iron pontoon 60' long and 40' beam, with circular ends and
+fitted with a double bottom, also a condenser and two Kingston valves.
+
+
+1ST EXPERIMENT.
+
+Torpedo:--617 lbs. of dynamite. It was 62' horizontally from the keel,
+53' actual distance from the side, and opposite amidships, 40·5' below
+the surface of the water, and 20' from the ground.
+
+Pontoon:--Draught of water 19', and moored in 62' of water.
+
+Effect of explosion:--The pontoon moved away bodily a distance of 13
+feet; a few rivets in the outer bottom were started, and the outer skin
+was slightly indented between the frames; the maximum indentation being
+1·5". No other damage was sustained by the hull. Several of the screws
+securing the flanges of the Kingston valves were slightly loosened.
+
+
+2ND EXPERIMENT.
+
+Torpedo:--585 lbs. of dynamite. It was placed 60' horizontally from the
+keel, 48' actual distance from the side, and opposite amidships; 36'
+below the surface of the water, and 42' from the ground.
+
+Pontoon:--Draught of water 19·5', and moored in 74' of water.
+
+Effect of explosion:--The pontoon, which had been more rigidly moored
+than in the previous experiment, was moved bodily away a distance of 4
+feet. Many rivets were loosened, and a few connecting the angle irons
+were sheared; also the outer skin was slightly indented. No damage was
+done to the condenser or Kingston valves.
+
+_Experiment in the Sea of Marmora, 1875._--This experiment was carried
+out by Turkish officers attached to their naval school at Halki, an
+island in the Sea of Marmora, about eight miles from Stamboul. It
+consisted in destroying a Turkish schooner by the explosion of an
+100-lb. gun-cotton mine in contact with her, moored in 58 feet of
+water, and 10 feet beneath the surface.
+
+_Experiment at Carlscrona, Sweden, 1876._--This experiment was a
+continuation of those previously carried out in 1874-75, and which have
+been detailed at page 224, &c.
+
+Target:--The same as had been used for the previous experiments
+(1874-75), and which had been thoroughly repaired.
+
+
+EXPERIMENT.
+
+Torpedo:--660 lbs. of gunpowder, enclosed in a buoyant cylindrical 1/4"
+steel case with domed ends, and contained in an inner 1/16" steel
+case. It was ignited by two Von Ebner fuzes placed in a charge of 1/4
+lb. of gunpowder and enclosed in a glass bottle. It was placed 5'
+horizontally from the water line, 23·75' actual distance from target,
+and opposite No. 5 (middle) frame of target, 29' below the surface of
+the water.
+
+Effect of explosion:--The ship was moored in 54' of water. She was
+lifted by the explosion, rolled over to port, and then settled to
+starboard, sundry large pieces of timber being thrown up in the
+air. The outer bottom of the target was broken through above the
+second longitudinal frame, from the fourth to the seventh frames
+laterally, and from the top of the target to the second longitudinal
+frame vertically, the hole made measuring about 9' high by 12' wide,
+or about 100 square feet in area. The inner bottom was also broken
+through between the top of the target and second longitudinal frame,
+and between the fourth and seventh vertical frames, the hole made
+being about 75 square feet in area. The bracket frames within the
+damaged area were but little damaged. The wing passage bulkhead was
+broken through opposite to Nos. 5 and 7 frames, the holes made being
+respectively 18 and 17 square feet in area. Through these holes the
+force of the explosion had made its way to the horizontal iron deck,
+forming the top of the target, which was completely broken through a
+little abaft No. 5 frame, the hole made measuring about 100 square feet
+in area. A piece of this iron deck, weighing, with the iron fastenings
+attached to it, about 1650 lbs., was thrown 16' against the upper deck
+beams. The target below the second longitudinal frame was comparatively
+but little injured. The outer bottom was indented and cracked in one
+or two places, but the inner bottom was uninjured. In addition to the
+damage to the target, the ship herself sustained serious injury, eleven
+of the lower deck beams, with their knees being broken (six being
+broken completely across). The main keel immediately under the target
+was also opened at the scarf, and the back of the ship was apparently
+broken. The hull had given out laterally to such an extent as to
+prevent the ship being taken into dock.
+
+_Experiments at Portsmouth, England, 1876._--The object of the
+following experiments was to determine the effect of comparatively
+small charges of gunpowder and gun-cotton exploded in actual contact
+with an ironclad, as would be the case in a torpedo attack either with
+locomotive towing or spar torpedoes.
+
+Target:--the same as used in the experiments of 1874-5, which have
+been detailed at page 229, &c., viz., the _Oberon_ fitted to represent
+H.M.S. _Hercules_ without the armour. Her mean draught was 11', and
+she was moored in 26-1/2' of water. The _Oberon_ had been placed in a
+thorough state of repair.
+
+
+1ST EXPERIMENT.
+
+Torpedo:--60 lbs. of gun-cotton in slabs, saturated with water. Total
+weight of charge 75 lbs. It was enclosed in a 1/4" iron case with cast
+iron ends. It was placed at 15' actual distance from the nearest side
+of the case to the target, and opposite No. 4 frame on the port side,
+10' below the surface of the water.
+
+Effect of the explosion:--The effect upon the vessel was unappreciable.
+This charge represented the large Whitehead fish torpedo, and its
+position corresponded to that of this torpedo when striking a net at a
+small angle with the keel.
+
+
+2ND EXPERIMENT.
+
+Torpedo:--The Harvey towing torpedo, charged with 66 lbs. of gunpowder,
+primed with gunpowder, and fired by means of an electric fuze. It was
+placed at 3' actual distance from the target, measuring from the centre
+of the torpedo, and opposite No. 4 solid frame on the starboard side,
+the vertical axis of the torpedo being at right angles to the vessel's
+side, 9-1/4' below the surface of the water.
+
+Effect of explosion:--This and the two following torpedoes were fired
+simultaneously. The outer bottom was blown in from the upper edge of
+the flat keel plate to the underside of the water-tight longitudinal,
+and fore and aft from No. 2 to No. 6 frames; an area 16' × 8-5/6'. Flat
+keel plates were broken between No. 2 and No. 4 frames, and the 4th
+strake of the bottom plating was broken, and the frames for that space
+blown in. Two holes were blown through the inner bottom, measuring
+respectively 2' × 2' and 7' × 1', making the total area of the inner
+bottom destroyed, 11 square feet.
+
+
+3RD EXPERIMENT.
+
+Torpedo:--33 lbs. of granulated gun-cotton, saturated with water; total
+weight of charge being about 41 lbs. It was enclosed in a 1/4" iron
+case, 12-1/2" × 12" × 12-1/2", the primer being 2-1/2 lbs. of slab
+gun-cotton, included in the 33 lbs. It was placed at 4' actual distance
+from the target, measuring from the centre of the case, and opposite
+No. 30-1/2 solid frame on the starboard side; 9-1/4' below the surface
+of the water.
+
+Effect of explosion:--Outer bottom blown in from upper edge of the
+lower longitudinal to the lower edge of the upper longitudinal between
+Nos. 28 and 32 frames; an area of 18 × 11 feet. The butts of the flat
+keel were started and the plating broken across No. 30-1/2 frame from
+the flat keel plate to the upper deck. Shelf plate at Nos. 30-1/2 and
+32-1/2 frames was broken. Nos. 29, 30, and 31 frames were blown in from
+first to third longitudinal; lower longitudinal from No. 28 to 31 also
+blown in. Two holes were blown through the inner bottom, measuring
+respectively 6 × 1·5' and 5' × ·25', making the total area of inner
+bottom destroyed 10 square feet. A steam launch with steam up and
+outrigger torpedo gear in place, one pole being rigged out, was placed
+with the stem of the boat 22' horizontally from the torpedo. She was
+uninjured and shipped very little water.
+
+
+4TH EXPERIMENT.
+
+Torpedo:--31 lbs. 14 oz. of gun-cotton in slabs, saturated with water,
+total weight about 40 lbs. It was enclosed in a 1/4" iron case 12-1/2"
+× 12-1/2" × 6"; primer being 20 oz. of gun-cotton, included in the
+31 lbs. 14 oz. It was placed at 4' actual distance from the target
+measuring from the centre of the case, and opposite No. 30-1/2 solid
+frame on the port side; 9-1/4' below the surface of the water.
+
+Effect of explosion:--Outer bottom and frames injured in a similar
+manner to that described in the third experiment. Outer angle irons of
+the 1st, 2nd, and 3rd longitudinals were started in the wake of the
+broken place. A hole was blown through the inner bottom, measuring 9·5'
+× 1', or about 10 square feet in area. The bolts of the outer bottom
+plate of stern post much open, and at Nos. 16 and 17 on the port side
+the upper two strakes were buckled and the shelf plate started.
+
+A steam launch, arranged in the same manner as in the fourth
+experiment, was uninjured, and shipped but little water.
+
+_Experiments with Countermine._--The following experiments have been
+carried out in England and other countries to ascertain some reliable
+data for countermining operations.
+
+
+1ST EXPERIMENT.
+
+_Experiments in the Medway, England, 1870._--Countermine:--432 lbs. of
+compressed gun-cotton, enclosed in a 3/16" iron case. It was moored at
+a depth of 37' below the surface of the water.
+
+Submarine mines:--A series of similar cases containing coal dust, &c.,
+were moored at distances of 50' to 100' from the countermine, and 37
+feet below the surface.
+
+Effect of explosion:--The submarine mine at 80' distance was completely
+destroyed; the dome of its circuit closer was dented in.
+
+
+2ND EXPERIMENT.
+
+Countermine:--As before, but moored 27' below the surface.
+
+Submarine mines:--As before, but moored at distances of 70' to 120'
+from the countermine, and 27' below the surface.
+
+Effect of explosion:--The submarine mine case at 120' distance was
+dented, but remained water-tight; the copper guard of fuze piece
+collapsed, and the earth connection of the fuzes was ruptured; the dome
+of its circuit closer was dented.
+
+
+3RD EXPERIMENT.
+
+Countermine:--As before, but moored 47' below the surface.
+
+Submarine mines:--As before, but moored at distances of 70' to 200'
+from the countermine.
+
+Effect of explosion:--The submarine mine case at 200' distance was
+dented, but it did not leak.
+
+
+1ST EXPERIMENT.
+
+_Experiments at Stokes Bay, England, 1873._--Countermine:--500 lbs. of
+gun-cotton, enclosed in a 3/16" iron case. It was placed on the ground,
+in 47' of water.
+
+Submarine mines:--Six ground mines, 1/4" thick cases, fitted with
+circuit, 10' below the surface, at distances of 100' to 200' from the
+countermine.
+
+Effect of explosion:--Submarine mines at 100' and 120' distance were
+destroyed, and their circuit closers thrown out of adjustment;
+submarine mines at 140' and 170' distance were much bulged, and leaked,
+and their circuit closer spindles were bent; submarine mine at 200'
+distance was uninjured, but its circuit closer was thrown out of
+adjustment.
+
+
+2ND EXPERIMENT.
+
+Countermine:--100 lbs. of gun-cotton enclosed in case, thickness No. 12
+B. W. G. It was moored 10' below the surface, in 35' of water.
+
+Submarine mines:--Five similar mines placed at same depth, at distances
+of 50' to 150' from the countermine.
+
+Effect of explosion:--The submarine mine at 50' distance showed
+continued or dead earth, two screws broken, and its case dented; the
+other mines were uninjured.
+
+
+1ST EXPERIMENT.
+
+_Experiments at Carlscrona, Sweden, 1874._--Countermines:--226 lbs. of
+dynamite, enclosed in a case 17-1/2" × 20" × 1/8". It was moored 9-3/4'
+below the surface, the depth of water being 41 feet.
+
+Submarine mines:--(_a_) cast iron ground 600 lb. mines, dome shaped,
+48-3/4" × 21-1/2" × 2"; (_b_) cylindrical cases, wrought iron, empty,
+11-1/2" × 11-1/2" × 1/8"; (_c_) cylindrical cases, wrought iron,
+charged, 11-1/2" × 11-1/2" × 1/8"; (_d_) cylindrical cases, wrought
+iron, 30-1/4" × 30-1/4" × 1/8"; (_e_) spherical cases, wrought iron,
+32-1/2" × 1/8"; (_f_) spherical cases, tinned steel, 12" × 1/8".
+
+Effect of explosion:--(_b_) mine, at 34' distance, was destroyed, and
+one at 92' distance was slightly bulged; (_c_) mine, 58' distance,
+mouthpiece injured and case leaky; (_d_) mine, 244' distance, a rivet
+started.
+
+
+2ND EXPERIMENT.
+
+Countermine:--As before, but moored at 29-1/4' below the surface; depth
+of water, 41 feet.
+
+Submarine mines:--As before.
+
+Effect of explosion:--(_a_) mine, at 146' distance, split in two; (_b_)
+mine, 34' distance, destroyed; at 49' distance, fractured; at 68'
+distance, indented but not fractured; (_c_) mine, 58' distance, case
+much bulged, and leaky; (_d_) mine, at 244' distance, rivets started,
+case half full of water; at 195' distance, sunk, several rivets
+started; (_e_) mine, at 195' distance, bolt loosened; (_f_) mine, at
+68' distance, not injured.
+
+
+3RD EXPERIMENT.
+
+Countermine:--453 lbs. of dynamite, enclosed in a case, 24-1/2" ×
+28-1/4" × 1/8". It was moored 9-3/4' below the surface; depth of water
+as before.
+
+Submarine mines:--As before.
+
+Effect of explosion:--(_b_) mine, at 49' distance, sunk and not
+recovered; at 58' distance, very much indented; (_c_) mine, at 58'
+distance, case much indented and leaky; (_f_) mine, at 48-1/2'
+distance, uninjured.
+
+
+4TH EXPERIMENT.
+
+Countermine:--As before, but moored 29-1/4' below the surface.
+
+Effect of explosion:--(_a_) mine, at 195' distance, completely stove
+in; (_c_) mine, at 58' distance, case indented but charge dry; (_e_)
+mine, at 175' distance, slightly leaky; (_f_) mine, at 48-1/2'
+distance, upper half indented in three places. It was also discovered
+during the above experiments that submarine mines charged with dynamite
+can be caused to explode by the detonation of a charge of the same
+explosive, at distances from it considerably beyond those at which
+the cases themselves are damaged by a similar charge. To prevent the
+foregoing, it is necessary to pack the dynamite very carefully, using
+at the same time special precautions.
+
+
+
+
+CHAPTER X.
+
+THE ELECTRIC LIGHT--TORPEDO GUNS--DIVING.
+
+
+ELECTRIC lights combined with fast steam launches as guard boats
+and specially constructed torpedo guns, such as the Nordenfelt and
+Hotchkiss machine guns, are at the present time the only _truly
+practicable_ means afforded to a man-of-war of defending herself
+against the attack of torpedo boats, whether these latter are armed
+with the spar, fish, or towing torpedo; the torpedo gun sinking the
+boats after the electric light and guard boats have detected their
+approach and position.
+
+As has been before stated, nets, shields, booms, &c., placed around
+a vessel of war, must, however slightly constructed, affect to a
+considerable degree her efficiency, by decreasing her power of moving
+quickly in any desired direction, which is essential to the utility of
+such a vessel in time of war; and thus on electric lights, guard boats,
+and torpedo guns must the safety of ships in future wars really depend,
+when attacked by torpedo boats.
+
+_The Electric Light._--The phenomenon of the _Voltaic arc_ was first
+discovered by Sir Humphry, then Mr., Davy at the beginning of the
+present century. The following is an account of the matter as given by
+him in his "Elements of Chemical Philosophy":--
+
+"The most powerful combination that exists, in which number of
+alternations is combined with extent of surface, is that constructed
+by the subscription of a few zealous cultivators and patrons of
+science in the laboratory of the Royal Institution. It consists of
+200 instruments, connected together in regular order, each composed
+of ten double plates arranged in cells of porcelain, and containing
+in each plate thirty-two square inches; so that the whole number of
+double plates is 2,000, and the whole surface 128,000 square inches.
+This battery, when the cells were filled with sixty parts of water,
+mixed with one part of nitric acid, and one part of sulphuric acid,
+afforded a series of brilliant and impressive effects. When pieces
+of charcoal about an inch long and one-sixth of an inch in diameter
+were brought near each other (within the thirtieth or fortieth part of
+an inch), a bright spark was produced, and more than half the volume
+of the charcoal became ignited to whiteness, and by withdrawing the
+points from each other, a constant discharge took place through the
+heated air, in a space equal at least to four inches; producing a most
+brilliant ascending arch of light, broad, and conical in form in the
+middle. When any substance was introduced into this arch, it instantly
+became ignited. Platina melted as readily in it as wax in the flame
+of a common candle; quartz, the sapphire, magnesia, lime, all entered
+into fusion; fragments of diamond, and points of charcoal and plumbago,
+rapidly disappeared, and seemed to evaporate in it, even when the
+connection was made in a receiver exhausted by the air pump; but there
+was no evidence of their having previously undergone fusion."
+
+The philosopher also showed that, when the Voltaic or electric arc is
+produced in the exhausted receiver of an air pump, the phenomena are
+as brilliant in character, and the charcoal points can be more widely
+separated, thus proving that the electric light is quite independent of
+the oxygen of the air for its support.
+
+Owing to the crude nature of the Voltaic batteries of that day, and
+also to the great expense of maintaining a large battery of that
+nature, nothing practical resulted from Davy's discovery of the
+electric or Voltaic arc. Professor Faraday, the great physicist, by
+his discovery of the principle of magneto-electricity, has enabled
+the electric light to be brought into practical use. As early as
+1833 Pixii applied the principle practically in the construction of
+a magneto-electric machine with revolving magnets; he was followed
+by Laxton, Clark, Nollet, Holmes, and others, who made machines with
+fixed magnets. In 1854 Dr. Werner Siemens, of Berlin, introduced the
+"Siemens' Armature," which, from its compact form, permitted a very
+high velocity of rotation in an intense magnetic field, giving powerful
+alternating currents, which, when required, were commutated into one
+direction.
+
+The latest improvement has been that from the magneto-electric to
+the dynamo-electric machine. It is due to both Dr. Siemens and Sir
+C. Wheatstone. Induced currents are directed through the coils of
+the electro-magnets which produce them, increasing their magnetic
+intensity, which in its turn strengthens the induced currents, and so
+on, accumulating by mutual action until a limit is reached.
+
+_Siemens' Electric Light._--The following is a description of
+Messrs. Siemens Brothers' dynamo-electric light apparatus, which,
+for use on board ship against boat torpedo attacks, &c., is equal,
+if not superior, to any similar apparatus yet produced, and which
+is extensively used in the German and other European navies. This
+apparatus was one of many others experimented on by Dr. Tyndal and Mr.
+Douglas, M.I.C.E., for the Trinity House.
+
+Dr. Tyndal says: "I entirely concur in the recommendation of Mr.
+Douglas, that the Siemens machine recently tried at the South Foreland
+be adopted for the Lizard. From the first I regarded the performance of
+this handy little instrument as wonderful. It is simple in principle,
+and so moderate in cost that a reserve of power can always be
+maintained without much outlay. By coupling two such machines together,
+a great augmentation of the light is moreover obtainable."
+
+_Principle._--When a closed electrical circuit is moved in the
+neighbourhood of a magnetic pole, so as to cut the lines of magnetic
+force, a current is generated in the circuit, the direction of which
+depends upon whether the magnetic pole is N or S; it also depends on
+the direction of motion of the circuit, and according to the law of
+Lenz, the current generated is always such as to oppose the motion of
+the closed circuit.
+
+All magneto-electric and dynamo-electric machines are based on the
+principle stated above, and are subject to many modifications.
+
+The name _dynamo_-electric machine is given to it, because the electric
+current is not induced by a _permanent magnet_, but is accumulated by
+the mutual action of electro-magnets and a revolving wire cylinder or
+armature. It is found that, as the dynamic force required to drive the
+machine increases, so also does the electric current; it is therefore
+called a dynamo-electric machine.
+
+_Description._--In the machine here described, of which Fig.
+164 is an elevation, Fig. 173 a part elevation, and Fig. 165 a
+longitudinal section, the electric current is produced by the rotation
+of an insulated conductor of copper wire or armature coiled in
+several lengths, 8, 12, 16, &c., up to 28, and in several layers,
+longitudinally, upon a cylinder with a stationary iron core _nn' ss'_,
+so that the whole surface of the armature is covered with longitudinal
+wires and closed at both ends, as in Fig. 165. This revolving armature
+is enclosed to the extent of two-thirds of its cylindrical surface by
+curved soft iron bars _NN__{1}, _SS__{1}.
+
+[Illustration: Fig. 164.]
+
+The curved bars are the prolongations of the cores of the
+electro-magnets _E E E E_. They are held firmly together by screws to
+the sides or bottom of the cast iron frame of the machine, making it
+compact and strong.
+
+The coils of the electro-magnet form with the wires of the revolving
+armature one continuous electric circuit, and, when the armature is
+caused to rotate, an electric current (which at first is very feeble)
+is induced by the remanent magnetism in the soft iron bars and directed
+through the collecting brushes into the electro-magnet coils, thus
+strengthening the magnetism of the iron bars,[V] which again induce a
+still more powerful current in the revolving armature.
+
+The electric current thus becomes stronger and stronger, and the
+armature therefore revolves in a magnetic field of the highest
+intensity, the limit of which is governed by the limit of saturation of
+the soft iron.
+
+At each revolution the maximum magnetic effect upon each convolution
+of the armature is produced just after it passes through the middle of
+both magnetic fields, which are in a vertical plane passing through the
+axis of the machine (i. e. _N__{1}_S__{1} in Fig. 173). The minimum
+effect is produced when in a plane at right angles to it, i. e.
+horizontal.
+
+[Illustration: Fig. 165.]
+
+According to the law of Lenz already referred to, when a circuit starts
+from a neutral position on one side of an axis towards the pole of a
+magnet, it has a direct current induced in it, and the other part of
+the circuit which approaches the opposite pole of the magnet has an
+inverse current induced in it; these two induced currents are, however,
+in the same direction as regards circuit. A similar current will also
+be induced in all the convolutions of wire in succession as they
+approach the poles of the magnets.
+
+These currents, almost as soon as they are induced, are collected by
+terminal rollers or brushes _B_, usually the latter, placed in contact
+with the commutator in the position which gives the strongest current.
+The position giving the strongest current gives also the least spark,
+so that when there are no sparks at the commutator the best lighting
+effect is produced. Fig. 166 shows position of brushes when the
+armature revolves in the direction indicated by the arrow.
+
+The circumference of the revolving armature is divided into an
+even number of equal parts, each opposite pair being filled with
+convolutions of insulated wire wound parallel to the axis of the
+armature.
+
+The ends of these wires are brought to a commutator and connected to
+the segments either by screws or by soldering.
+
+The brushes collect the electric currents as they are induced, which is
+nearly constant and continuous.
+
+The collecting brushes are combs of copper wire placed tangentially to
+the cylindrical commutator, and press lightly upon it with an elastic
+pressure.
+
+[Illustration: Fig. 166.]
+
+_Power and Light produced._--An increase of the armature speed produces
+a corresponding increase in the current produced, but not in the same
+proportion. The current increases more rapidly than the speed, and
+could be made to reach any intensity but for considerations explained
+below. With increase of current there is also increase of heat.
+
+The speed for continuous work must not be taken too high, because the
+heat developed at high velocities might destroy the insulation of the
+coils of the electro-magnet. The speed given for this machine produces
+no such injurious heating effect.
+
+The strength of the current is also influenced by the resistance of the
+electric lamp and its leading wires. With an electric lamp in a circuit
+of proper resistance the armature should revolve at the rate given in
+the following Table. The heating will then reach its maximum, which
+is very moderate, in about three hours after which there will be no
+further change.
+
+    ------------------------------------------------------------------
+                                TABLE.
+    -------+---------------------+---------------------+--------------
+     Size. |Number of revolutions|Intensity of light in|HP (actual) to
+           |    of armature.     |  standard candles.  |    drive.
+    -------+---------------------+---------------------+--------------
+    Medium |     800 to 850      |   4,000 to 6,000    |  3-1/2 to 4
+    -------+---------------------+---------------------+--------------
+
+The intensity of the unassisted light is given in standard candles. The
+standard here used is a stearine candle consuming 10 grammes per hour.
+
+_Regulation._--From the fact that a closed circuit rotating in a
+magnetic field experiences resistance to its motion which a broken
+circuit does not, motive power to any extent is only required when
+the circuit is closed. An interruption of the current is therefore
+equivalent to removing the load from the motor, which for mechanical
+reasons may be injurious to it and for electrical reasons to the dynamo
+machine.
+
+The sudden interruption of the circuit of the large machine produces
+an electric tension so dangerously high as to strain or destroy the
+insulation of the machine. When contact is again made after such
+interruption, the increase of speed resulting from the interruption
+causes a momentary current of great intensity, accompanied by sparks at
+the commutator.
+
+In order that the light may be quite steady the speed should be as
+uniform as possible. As too high an increase of speed may result in
+temporary extinction of the light, it ought never to be permitted. The
+motor should therefore be provided with a good and sensitive governor,
+that will keep the speed perfectly uniform however the steam and load
+may vary. A large and heavy fly-wheel is also very useful in keeping
+the speed nearly uniform during change of load.
+
+Although the circuit, when the machine is in full action, should never
+be suddenly interrupted, interruption arising from the extinction
+of the light is _not_ dangerous, because it is always preceded by a
+decrease in the strength of the current. When it is desired to divert
+the current into another circuit it is advisable to stop the machine.
+Although in practice with small machines this is rarely done, with
+large machines it is necessary.
+
+_Self-acting Shunt._--For great security, especially with the two
+machines coupled together, where the electric current is strong and
+the light equivalent to about 14,000 candles, it is advisable to insert
+in the circuit a self-acting shunt.
+
+[Illustration: Fig. 167.]
+
+This is placed between the lamp and machine and connected to both
+leading wires. Its principle is as follows:--
+
+The terminal _M_, Fig. 167, is joined by a short connecting wire to
+one terminal of the machine. The terminal _L M_ is connected to the
+remaining terminal of the machine and also to one of the lamp terminals.
+
+The terminal _L_ is connected to the other terminal of the lamp.
+
+The shunt contains a small electro-magnet _E_ mounted upon a square
+wooden slab or baseboard with its armature a, a contact c, and, below
+the slab, a resistance coil _W_, which is equal to the resistance of
+the electric arc of the light, about 1 S. _u._[W]
+
+As long as the lamp is burning well, the current circulates in the
+coils of the electro-magnet, and the armature _a_ being strongly
+attracted, there is no contact at _c_. The resistance coil _W_ is
+therefore not in electrical circuit. When the light is extinguished the
+current in the coils of the electro-magnet ceases, and the armature is
+withdrawn by the spring _f_ making contact at _c_. This offers to the
+electric current a path through _W_ of equal resistance to that of the
+lamp, and the current is subjected to scarcely any change, so that the
+motor has practically no cause to alter its rate.
+
+When the carbon points of the lamp again touch, the electric current
+returns to them, breaking contact at _c_, re-establishing the former
+conditions.
+
+_Direction of Rotation._--The armature may revolve in either direction.
+If it becomes necessary to drive it in the opposite direction to that
+for which the machine has been made, it is only necessary to reverse
+the brushes, placing their points in the direction of motion, and to
+change two of the wire connections, which operations can be effected in
+a few minutes. Fig. 166 shows the position of brushes for one direction
+of rotation and Fig. 168 that for the other.
+
+[Illustration: Fig. 168.]
+
+_Conducting or Leading Wires._--The leading wires are usually of copper
+of high electrical conductivity. They must be insulated from one
+another the whole of their length and not placed too close together.
+As their resistance affects the intensity of the light very much, the
+section must be carefully proportioned to the distance of the lamp from
+the machine.
+
+The best practical result is obtained when their resistance together
+with that of the lamp is equal to the total internal resistance of the
+dynamo machine. Wires of various sizes are therefore required.
+
+Decrease in strength of the current caused by a leading wire of too
+high resistance can be overcome by a higher velocity, which is obtained
+only by increased motive power, but if the wire is much too small, it
+will become heated. The proper remedy is to increase the sectional area
+of the leading wire.
+
+Bright sparks should never be allowed to appear at the commutator and
+brushes, as sparks result from a rapid burning of the metallic parts.
+They can easily be avoided by properly inclining the two arms which
+carry the brushes.
+
+The position of the brushes yielding the least spark at the commutator
+is that giving the highest intensity of light in the electric arc.
+
+The commutator should, while in motion, be freely oiled, to prevent the
+brushes wearing away too rapidly. The sticky oil should from time to
+time be removed by washing with paraffine oil or benzoline.
+
+_Wear and Tear._--The chances of stoppage so common to the old forms of
+electric light apparatus have in this form been reduced to a minimum,
+and now do not exceed those that arise with machines generally. The
+Trinity House Report states that the Siemens' machine worked well for
+a month without any necessity for stopping. The brushes are the only
+parts which wear away, and they are very easily replaced.
+
+In thick weather they should be connected in what is called parallel
+circuit (or parallel arc, or for "quantity"), because it has been
+found that when they are so arranged the intensity of the electric
+light produced exceeds by some twenty per cent. the intensity of the
+sum of the two when worked separately. Thus the two machines, giving
+respectively a candle power of 4,446 and 6,563 when worked separately
+(total 11,009), have given when coupled up in parallel circuit a light
+equivalent to 13,179 candles; just as in telegraphy it has been found
+that the rate of sending can be increased from 20 to 25 per cent. when
+the apparatus is coupled up in parallel arc. For this reason it is
+usual to employ two machines of medium size instead of one machine of
+large size. The intense light so produced is also much more uniform
+than from one large machine.
+
+_Automatic Electric Lamp._--Automatic electric lamps have been
+constructed with spring clockwork to cause the carbons to approach one
+another to a certain point, when, by means of an electro-magnet, the
+clockwork is checked, and the carbon points are allowed to burn away
+to such a distance that, by the decrease of current, the clockwork is
+released and the carbons caused to approach again. With such lamps the
+clockwork has been a source of trouble, and it is liable to get out of
+order.
+
+_Siemens' Patent Electric Lamp._--The lamp here described is actuated
+without clockwork; it also automatically separates the carbons after
+they have approached too closely or touch, and, by this combined action
+of approaching and separating, the carbon points are kept at a proper
+distance apart, and a steady light is obtained.
+
+The working parts are represented in the diagram Fig. 169, and at Fig.
+170 is shown the size employed on board ship.
+
+_E_ is the horse-shoe magnet with the armature _A_ placed in front of
+its poles a short distance from them. A regulating screw _b_ with the
+spiral spring _f_ is attached to the lever _A'_, forcing it against
+the stop _d_, and withdrawing the armature from the poles of the
+electro-magnet. When a current traverses the coils of the latter of
+sufficient strength to attract the armature and overcome the tension
+of the spring _f_, contact is made at _c_, which diverts the current
+from those coils. The consequent release of the armature breaks contact
+at _c_, the armature is again attracted, and this action is repeated,
+producing a vibrating motion of the lever and armature, which continues
+as long as there is sufficient current to overcome the tension of the
+spring.
+
+[Illustration: Fig. 169.]
+
+The spring pawl _s_ at the upper end of the lever _A'_, and oscillating
+with it, actuates a ratchet-wheel _u_, which is in gear with a train
+of wheels and the carbon holders; it thus opposes their tendency to
+approach by pushing them apart, tooth by tooth, until the current is
+so much weakened by the increased length of electric arc that the
+armature and lever cease to oscillate enough to move the teeth of the
+ratchet-wheel, and it rests near the stop _d_.
+
+While in this position the spring pawl is released from the
+ratchet-wheel and the preponderating weight of the upper carbon holder
+causes the carbon points to approach again. Increase of current follows
+decrease of resistance, the armature again oscillates, and this cycle
+of action is continuously repeated.
+
+When in action the movements of the carbons are scarcely perceptible,
+but when, by any external cause, the carbons are separated so as to
+extinguish the light, they immediately run together until they touch,
+when they ignite and separate to a proper working distance by means of
+the electro-magnet above described.
+
+The only operation requiring attention in the use of this lamp is the
+adjustment of the tension of the spring _f_. When this tension is once
+regulated to the current at disposal, the lamp will continue to give a
+steady light as long as the current remains uniform.
+
+The relative rate of consumption of the two carbon points differs. The
+positive carbon burns away rather more than twice as quickly as the
+negative carbon.
+
+[Illustration: Fig. 170.]
+
+The duration of the light depends mainly on the lengths and sizes of
+the carbons.
+
+Provision is made in this lamp that the rack which supports the
+negative carbon may be made to gear either into the teeth of the same
+pinion as that of the positive carbon, or into one of about half the
+size. By these means the light, when once focussed in a reflector,
+will remain in focus as long as the carbons last, whether permanent or
+reversed currents are employed.
+
+Besides its twofold application, the lamp is very compact, is simple in
+construction, and therefore not likely to get out of order, and it is
+capable of being regulated with great precision.
+
+There is no spring to be wound up. The contact need not be cleaned, as
+the sparks are scarcely perceptible.
+
+By removing two screws in the outside casing, all the chief working
+parts can be easily removed and inspected.
+
+Carbons are made from the hard carbon deposited in the interior of
+gas retorts, also from graphite. Various sizes, both square and round
+in section, of from 5 to 20 mm. in diameter, are used in the electric
+lamp according to the intensity of the electric current. Those commonly
+employed are from 10 to 12 mm. in diameter.
+
+The carbons supplied with the Siemens patent lamp are coated with a
+thin film of copper. This enhances the cost somewhat, but it greatly
+improves the result, as the carbons burn longer, and do not split, when
+so coated.
+
+By coating them the resistance is diminished, except at the points, so
+that all the heat is concentrated in the electric arc, and a brighter
+light is the result.
+
+When two dynamo machines are coupled together (see page 248), to give a
+very powerful current, the sizes up to 20 mm. are required.
+
+The consumption varies a little, but the average is from 3 to 4 inches
+per hour.
+
+[Illustration: Fig. 171.]
+
+_Concentration of Light._--Two kinds of concentrating apparatus are
+supplied in combination with the automatic lamp, both of which are
+capable of giving a powerful parallel beam, which will reach to an
+enormous distance, and are well adapted for naval purposes. The one
+kind consists of a parabolic reflector of stout metal, its concave
+surface being silvered and burnished. The apparatus is mounted with a
+ball-and-socket joint upon a wooden stand, as shown in Fig. 171.
+
+The other kind is the Fresnel catadioptric lens or holophote, Fig. 172,
+which may be substituted for the reflector, and gives a more powerful
+beam than one given by reflection. The lens is surrounded by a metal
+case or lantern, in which is placed the electric lamp upon a slide
+for focussing. Behind the carbon points a hemispherical reflector is
+placed, to catch all the back rays, and reflect them back through the
+lamp focus. The entire lantern is capable of revolving on horizontal
+rollers, and swings upon pivots. Two handles are placed at the back to
+manipulate it.
+
+[Illustration: Fig. 172.]
+
+As the electric arc is much too bright to be looked into with the naked
+eye, both concentrating apparatus are supplied with a lens, called a
+focus or flame observer, by means of which an image of the burning
+carbons is thrown upon small screens at the back, so that the lamp can
+be easily adjusted without fatigue to the eye. The focus observer is
+shown on the lamp in holophote, Fig. 172.
+
+_Precautions._--Before starting the apparatus, the electric lamp
+terminals and those of the dynamo machine must be _connected up_ by
+means of the leading wires provided with each set of apparatus. The
+terminals are marked _C_ and _Z_ respectively, and they should be
+connected, _C_ of machine to _C_ of the lamp, and _Z_ of the machine to
+_Z_ of the lamp, in order that the electric current may be sent in the
+proper direction through the carbons of the lamp. Should it, however,
+be found that the top carbon (which should consume twice as fast as
+that of the bottom one) does not consume so fast as the bottom one, it
+may be assumed that the dynamo machine has reversed its poles, and the
+leading wires will consequently require changing across. This reversal
+of poles, though possible, is of _very rare_ occurrence.
+
+[Illustration: Fig. 173.]
+
+The dynamo-electric machine should not be driven without its proper
+leading wires to lamp and lamp being connected up, or at least
+an external resistance equivalent to that of the lamp (which is
+approximately one Siemens' unit) must be inserted. In other words, the
+machine must not be driven when a wire of small resistance connects the
+two terminals _C_ and _Z_. This is expressed more briefly by saying the
+machine must not be _short-circuited_. If it is short-circuited when
+in motion the electric current becomes so powerful that it will leap
+from segment to segment of the commutator, where very bright and large
+sparks will be seen, and if continued would destroy the insulation,
+thus weakening the current generated.
+
+The leading wires should never be disconnected suddenly while the
+machine is revolving at its full speed, as such a sudden interruption
+will produce an intense spark, which will burn the ends of the wire
+where the contact is suddenly broken. When it becomes necessary to
+disconnect the wires, the belt should be pushed on to the loose pulley
+by means of the striking gear, or the steam engine should be stopped.
+
+It may be here stated that all connections should be cleaned bright and
+screwed tightly, to ensure perfect metallic contacts being made.
+
+_Coupling two Machines._--At Fig. 174 is shown a diagram of how to make
+the connections when coupling two machines in parallel circuit. _MM'_,
+_m_, _m'_, represent the ends of the wires of the electro-magnets;
+_BB'_ are the branches; _C_ and _Z_ are the terminals of each machine
+respectively.
+
+[Illustration: Fig. 174.]
+
+The three ways in which the various wire connections of these machines
+are joined up, and which are enough for all ordinary purposes, are
+given below in paragraphs (_a_), (_b_), and (_c_).
+
+(_a_) When the machine is working _singly_ and revolving in the
+direction indicated in Fig. 166, the following connections are made:--
+
+    _M_ is connected with _B_,
+    _M'_        "         _B'_,
+    _m_         "         _Z_,
+    _m'_        "         _C_,
+
+and the leading wires of the lamp are connected with _C_ and with _Z_
+as explained.
+
+(_b_) When working _singly_ and revolving in the direction indicated in
+Fig. 168:--
+
+    _M_ is connected to _B'_,
+    _M'_       "        _B_,
+    _m_        "        _Z_,
+    _m'_       "        _C_.
+
+Thus the only change necessary when the machine is to be driven in the
+opposite direction to that for which it is made, is to disconnect at
+_B_ the wire from _M_ to _B_ and at _B'_ the wire from _M'_ to _B'_,
+and to cross them. The machine will then be connected as above (_b_).
+
+(_c_) When working _two_ machines in parallel circuit, as in Fig. 174,
+they must be connected as follows (that on the left of the page being
+called the first machine, and that on the right the second machine):--
+
+    _C_ of first to _C_ of the second.
+    _Z_      "      _Z_        "
+    _M_      "      _B_        "
+    _B_      "      _M_        "
+    _M'_     "      _B'_       "
+    _B'_     "      _M'_       "
+
+and then connect _C_ and _Z_ of the second machine with the leading
+wires of the lamp.
+
+The connections _m_ to _Z_ and _m'_ to _C_ in each machine are the same
+as in cases (_a_) and (_b_). They do not require to be altered, and may
+therefore be left out of consideration in all three cases (_a_), (_b_),
+and (_c_). The whole of the connections here indicated can be quickly
+made by means of a cross-bar commutator or switch, which is supplied
+with the machines in cases where such changes are likely to be required
+frequently. This is usually attached to a wall, leading wires being
+taken to it from the dynamo machines separately, and others from the
+switch being led to the electric lamps.
+
+The leading wires from machine to lamp should, whenever possible, be
+kept _separate_, to prevent them rubbing together and making contact. A
+distance of two inches is quite sufficient to prevent accidents of any
+kind.
+
+When the leading wires are erected in places where they are likely to
+rub and chafe against hard substances, it is advisable to enclose each
+wire separately in india-rubber tubing at all the points where they are
+likely to be rubbed. This becomes very important on board ship, where
+everything is in motion, and special care is in consequence required.
+
+Some dynamo machines are coupled direct to the crank shaft of the steam
+engines; they require the same kind of attention as others, that is to
+say, they should be driven at a uniform speed, should be well oiled as
+well as the steam-engine, and they should be kept clean and free from
+sharp grit.
+
+_Application._--The electric light used in the case of a _direct_
+attack by torpedo boats, without the assistance of guard boats, will
+not prove of much assistance, on account of the very small space
+covered by the beam of light, and therefore if the direction of attack
+is not exactly known, the beam of light must be kept continually
+sweeping round the horizon on the chance of picking out the attacking
+boats, and thus, while flashing in one direction, they may be
+approaching in another, and effect their deadly mission.
+
+Every man-of-war should be fitted with at least three electric lights,
+whereby the above-mentioned want of space covered would be to a
+considerable degree obviated.
+
+If a powerful beam of light be thrown in a particular direction, and
+there kept stationary, all boats or vessels crossing its path at a
+distance not exceeding 1600 yards from the ship using the electric
+light, would become distinctly visible to observers placed behind the
+light; these vessels remaining visible as long as they continue in such
+a position that the beam of light acts as a background to them. Under
+very favourable circumstances, the distance at which the above effect
+may be observed is much increased.
+
+The parabolic reflector extends only about an arc of 33° at 540 yards'
+distance from the light.
+
+One defect of this form of reflector is, that it is rapidly dimmed by
+spray, rain, and by the particles given off by the carbons.
+
+The catadioptric lens, or holophote, gives a far more powerful but a
+more concentrated beam than the parabolic reflector. By means of such
+a beam of light, a torpedo boat may be discerned at about one mile
+distance. By adding divergent lens to the holophote, a less powerful
+and less concentrated beam of light will be thrown out; in this case
+about 20° of surrounding water would be well illuminated at about 900
+yards' distance, while without the divergent lens there would be only
+about 5° so illuminated but far more brilliantly.
+
+The distance at which objects can be detected by the electric light
+depends on their size and _colour_, more particularly on the latter.
+
+The observer should as a rule be well removed from the light.
+
+In the case of an electric light being thrown on the observer, the
+vessel, &c., using it would to that observer be invisible, the
+light only being seen; also when directed on any particular object,
+surrounding objects would be thrown into shade.
+
+The electric light will be found very useful for signal purposes by
+fitting a plane mirror in front of the catadioptric lens; so arranged
+that it be turned to any desired angle to the axis of the beam of
+light. By altering the angle of the mirror, the reflected beam of
+light can be swept from the horizon on one side, through the zenith,
+to the horizon on the other side. The time of passing the zenith being
+equivalent to the long and short flashes of the usual night signal code.
+
+In addition to using the electric light to detect the approach of
+torpedo boats, it may be used by the boats themselves to prevent the
+attacked vessel from discerning them.
+
+In turret ships, electric lights may be so arranged that the instant an
+object is brought into the field of the beam of light, the turret guns
+will be bearing on it.
+
+One great disadvantage of electric lights is the impossibility of
+protecting them from the enemy's fire, and this is a defect that cannot
+be eradicated, though it may be lessened, by manipulating them from the
+tops of a ship.
+
+_Torpedo Guns._--Hitherto by torpedo guns has been meant small guns
+mounted on carriages so constructed that a shot may be fired into
+the water only a few feet from the ship's side, or mitrailleuses,
+Gatlings, &c. Here the term is applied only to machine guns, which are
+constructed to fire either volleys, or, extremely rapidly, single shot,
+each shot of which would be capable of _penetrating_ and _sinking_
+torpedo boats, such as Messrs. Yarrow and Thornycroft are daily
+launching from their yards. Of such weapons there are at present only
+two, viz., the "Nordenfelt" and "Hotchkiss" gun. The former has, after
+very exhaustive experiments, been adopted by the English, Austrian,
+Swedish, and other naval authorities, while the latter has been adopted
+by the French government.
+
+_Nordenfelt Torpedo Gun._--This gun, as it at present is constructed,
+consists of four barrels of 1 inch calibre.
+
+The barrels are fixed in a horizontal plane, and are not moved during
+the firing; and the movement of the lever, the loading, the firing,
+and the extracting are all performed in the same plane, so that the
+_elevation_ of the gun is not disturbed by the firing.
+
+The gun is fed by means of hoppers, each of which contains ten rounds
+per barrel, _i. e._, forty shots.
+
+The continuous supply of cartridges, as well as the firing and
+extracting, are all performed by one motion of the lever, thus enabling
+the gunner to use his left hand to lay the gun.
+
+A volley of four shots can be fired at the same moment, or one shot can
+be fired separately. Eight shots can be fired in 1-1/4 seconds; twenty,
+thirty, or forty shots can be fired at a rapidity of two hundred shots
+per minute without difficulty.
+
+The recoil being taken up by the whole framework of the gun does not in
+the least disturb the aim.
+
+The entire mechanism of the gun can be opened up without undoing a
+single screw, in less than 20 seconds.
+
+All the four spiral firing springs can be taken out, without opening
+the rest of the mechanism, in 1-1/2 seconds.
+
+All the parts of the mechanism are made interchangeable, so that
+reserved parts can at any time be substituted. The gun can be placed on
+half cock, so that the strikers do not act; and for further security
+the lever can be locked. The carrier block, without which the gun
+cannot be fired, is loose, and can be taken away, in case it becomes
+necessary to abandon a gun, which is thus made useless to the enemy.
+
+The bullets are solid steel, weighing about 1/2 lb. At 1760 yards at
+right angles this gun will penetrate a 3/16 inch steel plate, which
+represents the thickness of the plates of a torpedo boat.
+
+At 200 yards at right angles it will penetrate one 3/16 inch steel
+plate placed in front of a 1/2 inch steel plate with a space of 3 feet
+between them, this target representing the plates and boiler of a
+torpedo boat.
+
+At the same distance, at 30° angle against the line of fire, it will
+penetrate a 1/2", 1/4", or 3/16" steel plate.
+
+The holes in some instances are from 6 to 11 inches in length, and
+2-1/2 inches in height. Angle of depression 20°, of elevation 30°, and
+of direction 360°.
+
+Weight of the gun 3-3/4 cwt., and weight of carriage 2-1/2 cwt.
+
+_Hotchkiss Torpedo Gun._--This gun consists of a group of five barrels,
+revolving on a central shaft, a breech block, containing the firing
+mechanism, a feeding hopper, and the necessary hand crank for training
+and firing. The gun is mounted on trunnions attached to a vertical
+column, which rests in a suitable socket bolted to the ship's side; by
+this means a universal motion is obtained.
+
+The essential difference between this and the Nordenfelt gun is, that
+the _barrels_ and mechanism are put into rotatory motion.
+
+Another point of difference is that single shots only can be fired, and
+not a volley, as in the Nordenfelt gun.
+
+With the Hotchkiss gun, only some thirty shots can be fired in one
+minute at an advancing torpedo boat. The weight of the Hotchkiss steel
+shot is about 1 lb., but owing to the low velocity of the gun, its
+penetrative power is little more than that of the Nordenfelt 1/2 lb.
+bullet.
+
+The object to be gained in firing at an attacking torpedo boat is to
+sink her, and not merely to kill or disable her crew, for supposing the
+attack to be made with a contact spar torpedo, and the boat to have
+reached within 300 yards' distance from the ship, then, even if all
+the crew (probably two or three men) were disabled or killed, the boat
+would, if not sunk, still carry out its work of destruction; therefore
+the projectiles to be used under such circumstances should be only
+those capable of penetrating a torpedo boat's plates, _i. e._, solid
+steel shot, not shells.
+
+_Diving._--In laying down and in picking up submarine mines, divers
+will be found extremely useful; also in clearing a passage in a
+river, &c., of an enemy's torpedoes in time of war. During the late
+Turco-Russian war, the harbour of Soukoum Kaleh taken by the Turks was
+_popularly_ supposed to have been cleared of its mines by native divers
+(Lazees), but as the torpedoes so captured were never seen at Stamboul,
+it must have been a stretch of imagination; probably such would have
+been done, had there been any mines in the harbour to clear away.
+
+The following is a general description of Messrs. Siebe and Gorman's
+improved diving apparatus.
+
+The apparatus consists of
+
+    1. An air-pump.
+    2. The diving dress.
+    3. The breast-plate.
+    4. The helmet.
+    5. The boots.
+    6. The crinoline.
+
+_Air-pump._--This improved air-pump consists of two double action
+cylinders, each cylinder capable of supplying about 135 cubic inches
+per revolution. The advantage of this air-pump is, that it can supply
+air to two divers, working independently and at different levels,
+each diver being in direct connection with one of the cylinders. The
+air-pipes are in lengths of 45 feet and 30 feet, made of vulcanised
+india-rubber with a galvanised iron wire imbedded; this protects from
+corrosion, and allows the air to pass through the pipes with less
+friction.
+
+_Diving Dress._--The diving dress is made of solid sheet india-rubber,
+covered on both sides with tanned twill; it has a double collar, the
+inner one to pull up round the neck, and the outer one of vulcanised
+india-rubber to go over the breast-plate and form a water-tight joint.
+The cuffs are also of vulcanised india-rubber, and fit tightly round
+the wrist, making, when secured by the vulcanised india-rubber rings, a
+water-tight joint, at the same time leaving the diver's hand free.
+
+_Breast-plate._--The breast-plate is made of tinned copper, and has a
+valve in front, by which the diver can regulate the pressure of air
+inside his dress and helmet. The outer edge of the breast-plate is of
+brass, and is secured by screws to the outer collar of the dress.
+
+_Helmet._--The helmet is made of tinned copper, and has a segment
+bayonet screw at the neck, corresponding to that of the breast-plate,
+which enables the helmet to be removed from the breast-plate by
+one-eighth of a turn. It has three strong plate glasses in brass
+frames, protected by guards; two oval at sides, and a round one on the
+front; the front one can be unscrewed, to enable the diver to give
+and take orders. At the side is an outlet valve, which, by inserting
+a finger, the diver can close, and so rise to the surface. The valve
+allows the foul air to escape, and prevents the entrance of the water.
+An elbow tube is securely fitted on the helmet, to which is fixed an
+inlet valve, to which the air-pipe is attached. The inlet valve is
+made that the air can enter, but in case of a break in the air-pipe it
+cannot escape.
+
+The front and back weights are of lead, heart-shaped, and weigh about
+40 lbs. each.
+
+_Boots._--The boots are made of stout leather, with leaden soles, and
+are secured over the instep by a couple of buckles and straps. Each
+boot should weigh at least 20 lbs.
+
+_Crinoline._--The crinoline or shackle is used for deep water; it is
+placed round the body and tied in the front of the stomach: being
+supported by braces, it affords protection to the stomach, and enables
+the diver to breathe more freely.
+
+_Ladder._--An iron ladder should be provided with stays to bear against
+the side of the boat from which the diving is carried on, to which may
+be attached (if working in deep water) an ordinary rope ladder, with
+ash rounds, and weighted at the end. Some divers have the ladder only
+20 feet long, to the last round a rope with a weight attached, which
+rests on the ground; by that means they descend.
+
+_Directions for using the Apparatus._--The ladder having been fixed,
+the position of the pump should be decided on, and it should be
+securely lashed by means of the ropes attached to the handles down to a
+stage, into which the _screw-eyes_ should be fastened if necessary; the
+pump should be placed out of the way of the divers, the men attending
+on them, and all the men employed. The best position for the pump is
+facing the head of the ladder, and about six feet from it.
+
+While the diver is dressing, the pump should be prepared for use,
+the winch handles should be taken out of the pump case, the nipples
+protecting the crank axles removed, the nuts being replaced on their
+screws. The nuts for the ends of the crank axles are taken off, the
+fly-wheel placed on the shaft, and the winch handles put on, and
+secured by the nuts, which are screwed home with the spanner. The pump
+is always worked in its case.
+
+The flaps covering the pressure gauges and that at the back of the
+pump case should be opened, the screw on the overflowing nozzle of the
+cistern removed, and the cistern filled with water; the caps of the air
+delivery pipes should be removed, the necessary lengths of air-pipe
+should be put together carefully with washers in place, and all the
+screws must be worked home by means of the _two_ double-ended spanners.
+The air-pipes should be tested by holding the palm of the hand to the
+end of the pipe, till the pressure shown on the pressure gauge is
+considerably above that corresponding to the depth the diver is to
+descend.
+
+_Dressing the Diver--Crinoline only for Deep Water._--The diver having
+taken off his own clothes, puts on a guernsey, a pair of drawers,
+very carefully adjusted outside the guernsey, and securely fastened
+by the tape round the waist, to prevent them from slipping down, and
+then a pair of inside stockings. If the water be cold, the diver may
+put on two or more of each of the above articles. He then puts on the
+crinoline and woollen cap, drawing the latter well over his ears; some
+divers find relief from putting cotton saturated with oil in their ears.
+
+The _shoulder pad_ is then put on, and tied under the diver's arms.
+He then gets into the diving-dress, which in cold weather should be
+slightly warmed, drawing it well up to his waist; he next puts his arms
+into the sleeves, an assistant opening the cuffs by means of the cuff
+expanders, or by inserting the first and second fingers of both hands,
+taking care to keep his fingers straight. The diver, by pushing, forces
+his hand through the cuff. He puts on a pair of outside stockings and a
+canvas overall to preserve the dress from injury.
+
+The diver then sits down, and the inner collar of the dress is drawn
+well up and tied round the neck with a piece of spun yarn, and the
+breast-plate put on, great care being taken that the india-rubber of
+the outer collar is not torn in putting it over the projecting screws
+of the breast-plate. The four pieces of the breast-plate band, which
+with the thumbscrews had been previously placed for safety in one of
+the boots, are then put over the outer collar, and secured to the
+projecting screws by means of the thumbscrews; the centre screw of each
+plate should be tightened first. It will generally be sufficient if the
+thumbscrews be screwed up hand-tight, the spanner being only used when
+necessary. The canvas overall is now adjusted and the boots are put on.
+
+The rings are passed over the cuffs, and the sleeves of the overall are
+drawn down to cover them. If gloves are to be used, the rings will be
+put on over them, as well as the cuffs. The helmet (without the front
+bull's-eye) is then put on; before doing so, the attendant should blow
+through the outlet valve of the helmet; he can do so by placing his
+head in the interior, and placing his mouth to the hole where the air
+escapes. Blow strongly; if in proper working order, the valve will
+vibrate. A loop of the life line is placed round the diver's waist, the
+line brought up in front of the man's body, and secured with a piece of
+small rope passing round his neck, or to the stud on the helmet. The
+waist-belt is buckled on with the knife on the left side, the end of
+the air-pipe being passed from the front, through the ring on the belt
+on the man's left, and up to the inlet valve on the helmet, to which it
+is secured; the upper part of the pipe is then made fast by a lashing
+to the stud on the left of the helmet. The diver then steps on the
+ladder, and two men are told off to _man the pump_.
+
+The weights are then put on, the front weight first, the clips being
+placed over the studs on the breast-plate. The back weights are then
+put on, and the clip lashings over the hooks on the helmet, and the two
+are secured to the diver's body by means of the lashing from the back
+weight, which is passed round the waist, through the thimble beneath
+the front weight, and tied to the other end of the lashing at the back
+weight.
+
+When the signalman is sure that all is right, and that the diver
+understands all the signals, he gives the word _Pump_, and screws the
+centre bull's-eye into the helmet securely; this done, he takes hold of
+the life line and "pats" the top of the helmet, which is the signal for
+the diver to descend.
+
+_Signals employed._--The signalman is the responsible person, and must
+be very vigilant all the time the diver is down; occasionally he will
+give one pull on the life line, and the diver should return the signal
+by one pull signifying "all right;" if the signal be not returned, the
+diver must be hauled up, but if the diver wishes to work without being
+interrupted by signal, he gives one pull on the line, independently,
+for "All right; let me alone." If the signalman feels any irregular
+jerks, such as might be occasioned by the diver falling into a hole, he
+should signal to know if he is all right, and if he does not receive
+any reply, he should haul him up immediately. If the diver from any
+cause is unable to ascend the ladder, and wishes to be pulled up, he
+gives four sharp pulls on the life line. If while being hauled up the
+diver gives one pull, it signifies "All right; don't haul me any more."
+The diver should be hauled up slowly and steadily. If the signalman
+wishes the diver to come to the surface, he gives four sharp pulls on
+the line, on which the diver should answer "All right," return to the
+foot of the ladder, and signal to be hauled up.
+
+_One_ pull on the air-pipe signifies that the diver wants more air.
+_Two_ pulls on the life line and _two_ pulls on the air-pipe in rapid
+succession, signify that the diver is foul and cannot release himself,
+and requires the help of another diver; on receiving such a signal, no
+attempt should be made to haul the diver to the surface.
+
+The above signals are to be invariably used; but other signals may be
+arranged as is most convenient for any particular work, as a great
+variety can be made with the life line and air-pipe. The diver can
+communicate with the surface by means of a slate.
+
+Further information on this subject, especially with regard to the
+foregoing diving apparatus, will be found in Messrs. Siebe and Gorman's
+"Manual for Divers."
+
+FOOTNOTES:
+
+[Footnote V: In wrought iron there is always some residual magnetism;
+there is therefore no necessity to start the magnetism with a permanent
+magnet.]
+
+[Footnote W: Siemens' unit.]
+
+
+
+
+CHAPTER XI.
+
+ELECTRICITY.
+
+
+_THEORY of Electricity._--The theory most readily understood, and which
+most satisfactorily explains the various electrical phenomena, is as
+follows:--
+
+"That every substance and every atom of the world is pervaded by a
+peculiar, subtle, imponderable fluid which is termed _Electricity_,
+but which is not known to exist, or remains in a state of _electrical
+equilibrium_, until evoked by certain causes."
+
+The effect of causing a disturbance of this equilibrium is to increase
+the normal, or natural, electricity in some particles, and to equally
+decrease it in other particles, i.e. what one loses the other gains.
+An excess of natural electricity is denoted by the term _positive_,
+or mathematical symbol (+) while a deficiency is denoted by the term
+_negative_, or symbol (-).
+
+_Like electricities repel each other._
+
+That is to say, two bodies charged with an excess of, or positive,
+electricity, being brought together repel each other, neither wishing
+to increase the excess that has been evoked in them.
+
+Similarly in the case of two bodies charged with a deficiency of, or
+negative, electricity, neither wish to add to the deficiency already
+there.
+
+In both these cases there can be no tendency to electrical equilibrium,
+which is the principle at work. In the former case, there being already
+too much, more will but increase the disturbance.
+
+In the latter case, further deficiency will but add to the irregularity.
+
+_Unlike electricities attract each other._
+
+That is to say, if two bodies, one charged with positive, or having an
+excess of electricity, the other charged with negative, or having a
+deficiency of electricity, be brought together, they will attract each
+other; both being desirous of altering their existing state, the one
+by decreasing its excess, and the other by decreasing its deficiency of
+electricity.
+
+In this case, there will be a tendency to equilibrium, caused
+by attraction. The earth is supposed to be a vast reservoir of
+electricity, from which a quantity can be drawn to fill up a
+deficiency, and which is always ready to receive an excess from
+other bodies. Every body in nature has its own natural quantity
+of electricity, and when an object is negatively electrified, or
+has a deficiency in its normal quantity, there is a tendency to
+receive a supply from any convenient source. Such an object would
+receive electricity from the earth if means were afforded; and a
+body _positively_ electrified, would tend to part with its excess in
+the same manner. Where such facilities for establishing electrical
+equilibrium are afforded, the result is the passage of a _current_ of
+electricity.
+
+_Conductors._--Sensible effects can be produced by electricity at great
+distances from the source, provided there be a medium of communication,
+that is, good _conductors_ to transfer it. When a glass rod is rubbed
+with a piece of silk, it becomes charged with an excess of, or
+positive, electricity, and at the same time the silk becomes charged
+with negative electricity.
+
+The glass rod will retain the positive electricity upon it for some
+time, unless touched with the wet hand, a wet cloth, a metal, &c., when
+it will instantly cease to be electrified. The electricity is then said
+to have been conducted away, and the bodies which allow it to run off
+the glass are called _conductors_ of electricity. Metals, water, the
+human body, charcoal, damp wood, and many other bodies are conductors.
+
+Those bodies which conduct electricity hardly at all, such as the air,
+silk, glass, sealing wax, gutta percha, india rubber, &c., are termed
+_nonconductors_ or _insulators_.
+
+Strictly speaking, all substances _conduct_ electricity in some degree,
+and a _nonconductor_ is merely a _bad_ conductor.
+
+In the following table the bodies are arranged in their order of
+conductivity, i.e. each substance conducts better than that which
+precedes it; the first-named body is the best insulator, and the
+last-named one is the best conductor.
+
+    Dry air.
+    Ebonite.
+    Paraffin.
+    Shellac.
+    India rubber.
+    Gutta percha.
+    Resin.
+    Sulphur.
+    Sealing wax.
+    Glass.
+    Silk.
+    Wool.
+    Dry paper.
+    Porcelain.
+    Dry wood.
+    Stone.
+    Pure water.
+    Rarefied air.
+    Sea water.
+    Saline solutions.
+    Acids.
+    Charcoal, or Coke.
+    Mercury.
+    Lead.
+    Tin.
+    Iron.
+    Platinum.
+    Zinc.
+    Gold.
+    Copper.
+    Silver.
+
+Though two substances are near one another in the above list, they do
+not necessarily approach one another in their power of conducting. For
+instance, taking the conducting power of pure silver as represented by
+the number 100, then
+
+    Pure Copper will be equal to 99·9,
+    Gold will be equal to 78·0,
+    while Zinc will be only equal to 29·0,
+
+and pure water, which is half-way down the list, will offer 6,754
+millions more resistance than silver to the passage of the electric
+current.
+
+The metals being the best known conductors, are usually employed as the
+means of transferring the electric current from one place to another.
+
+_Electric Circuit._--The conditions attending this operation are
+different from those of any other known method of transmission.
+
+A complete _circuit_ must always be formed by the electric current,
+i.e. it cannot start from one place _A_, travel to another place _B_,
+and cease there, but the current must be completed before it can be
+said to have reached _B_. There cannot be a current of electricity
+without a means of recombination, which recombination must be at the
+_source_, or place of original disturbance.
+
+This "place of disturbance" or _source_ must be considered as having
+two sides, i.e. at some spot the normal or natural electrical
+equilibrium is disturbed, and electricity is separated into too much
+(positive) on one side, and too little (negative) on the other side.
+If then no means of recombination be afforded, the electricities
+remain separated, and no current exists; but if a _conductor_ be made
+to connect the two sides, electricity is set in motion, and a current
+established. Originally to form a circuit between two stations _A_ and
+_B_, a conducting wire and a return wire were necessary, but in 1837
+Steinway discovered that the earth itself answered all the purposes of
+a return wire, in fact under favourable conditions much better. Thus,
+to form a circuit between _A_ and _B_, a conducting wire is required,
+and a buried metal plate at _A_ and _B_, the earth by these means
+taking the place of the return wire.
+
+The aforesaid metal plates are technically termed _earth plates_.
+The greater the size of the earth plates (up to certain limits), the
+deeper they are buried, and the better the conducting power of the soil
+surrounding them, the better conductors the plates become, or the less
+resistance the earth portion of the circuit offers. If either plate
+be not in communication with the earth, or else be separated from the
+wire, the circuit is not complete, or, as it is termed, "it is broken,"
+and no current will flow, the signal not made, torpedo not fired, &c.
+
+_"Short" Circuit._--Due to the fact that recombination, or a tendency
+to equilibrium, is always at work when electricity has been evoked, the
+conducting path along which the electric current flows must be covered
+with a nonconducting substance, or, as it termed, "insulated," or else
+the current would not perform its duty, but escape to earth, and so
+form what is termed a "short circuit."
+
+A current of electricity always chooses the _easiest path_ to effect
+recombination, or electrical equilibrium.
+
+_Insulators, &c._--On land, telegraph wires are as a rule laid above
+the ground, and therefore require supporting at every few yards; this
+is done by means of posts, and as these are formed of substances which
+are conductors of electricity, the wires require to be insulated
+from them. The insulators generally employed for such purposes are
+cup-shaped pieces of porcelain, or pottery, fixed to the head of
+the telegraph posts. By means of these insulators, the current of
+electricity is prevented from escaping to the earth by the post
+conductors.
+
+A certain amount of leakage, or loss of electricity, must occur at each
+of these posts, as there is no such thing as a perfect insulator. When
+the wires are laid on the ground or under ground, or under water, they
+are insulated by covering them with gutta percha, india rubber, &c.,
+and any loss of current is thus prevented.
+
+_Methods of generating Electricity._--For the purposes of torpedo
+warfare there are two methods of evoking electricity, viz.--
+
+1.--By _chemical action_.
+
+2.--By _friction_.
+
+_By Chemical Action._--_Chemical action_ is the chief source of free
+electricity, the representative of which is the galvanic, or Voltaic,
+battery.
+
+The electricity so generated is also termed dynamical electricity, due
+to there being a constant electric current, so long as the poles of the
+battery producing it are kept closed; the electricity being thus in a
+_dynamic_ or moving state.
+
+By chemical action is signified that which occurs when two or more
+substances so act upon one another as to produce a third substance
+differing altogether from the original ones in its properties, or when
+one substance is brought under such conditions that it forms two or
+more bodies differing from the original ones in their properties.
+
+_Definition and Properties of a Voltaic Cell._--The _Voltaic_ cell
+consists of an insulating jar, containing a liquid, in which are
+placed two plates or pieces of dissimilar metals; the liquid must be
+composed of two or more chemical elements, one of which at least tends
+to combine with one or other of the metals, or _with both in different
+degrees_.
+
+By a Voltaic _battery_ is meant a number of cells above one; this term,
+however, is often applied to a single cell when working by itself.
+
+A "_simple_ Voltaic cell," "element," or "couple," consists of two
+metals placed in a conducting liquid. If two metals--for instance, zinc
+and copper--are placed in water slightly acidulated, without touching
+each other, no effect is apparent; but if they be made to touch,
+bubbles of hydrogen gas are formed over the copper plate, and continue
+forming these until the plates are separated. After being in contact
+for some time, the copper plate will be found unaltered in weight,
+but the zinc plate will have lost weight, and the portion so lost
+will be found in the liquid in the form of sulphate of zinc. The same
+effects are also produced by connecting the two plates by means of some
+conducting substance, instead of placing them in contact.
+
+Zinc is invariably employed as one of the metal plates, on account of
+the ease with which it dissolves in dilute acids; and the greatest
+results are obtained when the second metal plate is not acted upon
+at all by the liquid, for then the whole effect due to the oxidation
+of the zinc plate is obtained; but when the second plate is also
+chemically acted upon, then only the effect due to the difference
+between the two chemical actions is obtained, for, as will be explained
+further on, they each act in directly opposite directions.
+
+_Voltaic Current._--The Voltaic current makes its appearance under the
+general laws of electrical action.
+
+When a body charged with an _excess_ of, or _positive_, electricity,
+is connected with the earth, electricity is transferred _from_ the
+charged body to the earth; and similarly when a body is charged with
+a _deficiency_ of, or _negative_, electricity, is connected with the
+earth, electricity is transferred _from_ the earth to the body.
+
+Generally whenever two conductors in different electrical conditions
+are put in contact, electricity will flow from one to the other.
+That which determines the direction of the transfer is the relative
+_potential_ of the two conductors. Electricity always flows from a body
+at _higher potential_ to one at _lower potential_, when the two are in
+contact, or connected by a conductor. When no transfer of electricity
+takes place under these conditions, the bodies are said to be at the
+_same potential_, which may be either _high_ or _low_. The _potential_
+of the earth is assumed to be _zero_.
+
+_Definition of Potential._--"The _potential of a body or point, is
+the difference between the potential of the body or point, and the
+potential of the earth_."
+
+Difference of potential for electricity is analogous to difference
+of level for water. Now, since, when a metal is placed in a vessel
+containing a liquid, electricity is produced, the liquid becomes of a
+different potential to the metal, each being electrified in an opposite
+way; and therefore, as above stated, there being a _difference_ of
+potentials, electricity will tend to flow from one to the other.
+
+This is evidence of a _force_ being in action, for there can be no
+motion without some force to produce it.
+
+_Electro-motive Force._--_Electro-motive force_ is the name given to a
+peculiar force to which is due the property of producing a difference
+of potentials. When it is said that zinc and water produce a definite
+electro-motive force, what is meant is, that by their contact a certain
+definite difference of potentials is produced.
+
+The _electro-motive force_ of a Voltaic element may be termed its
+_working_ power, in the same way as the pressure of steam is the
+working power of a steam engine, though this is not to be considered as
+the real source of power, which, as will be seen, is uncertain. Due
+to the difference of potential of the metal and the liquid, a current
+of electricity will flow from one to the other, causing the chemical
+decomposition of the liquid, and the reaction may be taken as the
+origin of the power employed.
+
+But while the expenditure of energy (which is necessary to produce a
+_force_) is accounted for by taking the chemical action as the source
+of power, the preceding cause of this chemical action, viz. the flowing
+of the current of electricity due to the difference of potential of the
+metal and the liquid, must also have first involved the expenditure of
+energy; thus the real source of power is very uncertain.
+
+_Electrolytes._--As before stated, a Voltaic cell consists of two
+plates of dissimilar metals, which must be immersed in a liquid
+composed of two or more chemical elements, one of which at least will
+combine with one or other of the metals, or both in a different degree.
+Those liquids which are thus decomposed by the passage of a current of
+electricity are termed _electrolytes_.
+
+The elements, then, forming the electrolyte may have chemical affinity
+for both metals, though in a greater degree for one than the other.
+
+"Oxygen" is the most important element of an electrolyte, and to the
+_affinity for oxygen of the metals_ is the magnitude of the result and
+effect.
+
+_Terms Electro-positive and Electro-negative._--All metals have a
+definite relation to each other as to the potential which any one may
+have when brought into contact with another. Thus, when zinc is brought
+into contact with copper, the former has a potential positive to the
+latter, i.e. a current of electricity will tend to flow from the zinc
+to the copper. The metals may be so placed in a list that each one
+would be positive to any of those that follow it; it is then said to be
+electro-positive to them, and they are electro-negative to it. As those
+metals which are electro-positive to others have a greater affinity for
+oxygen, and those that are electro-negative to others a less affinity
+for this element, the terms electro-positive and electro-negative
+signify, in effect, greater or less affinity for this element.
+Conversely, oxygen will combine more readily with the former than with
+the latter.
+
+The following list shows the commoner metals arranged in
+electro-chemical order.
+
+    + Zinc.
+      Lead.
+      Tin.
+      Iron.
+      Antimony.
+      Copper.
+      Silver.
+    --Gold.
+
+Take the case of a Voltaic cell composed of zinc and copper plates
+immersed in water.
+
+The passage of electricity through the water will decompose it into its
+elements hydrogen and oxygen, the latter having an affinity for both
+the plates, but considerably more so for the zinc plate.
+
+Then, an electro-motive force will be generated at each metal, and
+these forces will act in opposition to each other, but the greater
+strength of the one will overcome the weaker, and the real power of the
+electric current will be the difference between the two.
+
+_Definition of "Elements."_--The battery plates are termed the positive
+and negative _elements_. A Voltaic battery has two _poles_--a positive
+and a negative--which are the terminations of the plates.
+
+_Direction of Current._--The course of the current in a Voltaic cell
+is as follows:--_Within_ it leaves the electro-positive plate (or
+element), and flows to the electro-negative plate, but _outside_ the
+cell (or as it were on its return path) it flows from the positive
+_pole_ to the negative _pole_. The current always leaves the battery
+by the positive _pole_, and thus the copper is the negative _element_,
+but the positive _pole_, because the current leaves the battery by it;
+and the zinc is the positive element because the current begins there,
+_within_ the cell, and the negative _pole_ because it ends there,
+_outside_.
+
+The positive pole is the terminal of the negative plate, and _vice
+versâ_. There is but one current from a battery, viz. a positive one;
+what is called a negative current is merely the positive current
+passing in the reverse direction from the same pole, that is, the
+positive pole.
+
+_Single and Double Fluid Batteries._--Galvanic batteries may be divided
+into single fluid and double fluid batteries. The simplest form of
+galvanic cell practically in use is a single fluid cell, consisting of
+a zinc and a copper element, immersed in water slightly acidulated by
+the addition of a little sulphuric acid. In a battery of several cells,
+the zinc and copper plates are generally soldered together in pairs,
+and placed in a long stoneware or glass trough, divided into separate
+cells by means of partitions. By filling the cells with sand, this
+battery is made more portable, the plates being thus supported, and the
+liquid prevented from splashing about during transit.
+
+In this form it is called the _common sand battery_.
+
+_Action in a Single Fluid Cell._--The following process goes on in the
+single fluid cell when the circuit is closed--that is, when the battery
+is set to work.
+
+The water (composed of hydrogen and oxygen) is decomposed by the
+passage of the electric current, and oxide of zinc is formed. The
+oxygen of the water having greater affinity for the zinc, leaves the
+hydrogen. The zinc during the process is being consumed, as coal is
+consumed when it burns, while combining with the oxygen of the air.
+This oxide of zinc combines with the sulphuric acid, and forms sulphate
+of zinc; this salt is found to accumulate in solution in the liquid
+of the cell. At the same time the hydrogen of the water goes to the
+negative or copper plate, and gathers over it in bubbles.
+
+The process will be better seen by the accompanying plan of the
+chemical decomposition and recombinations.
+
+  Sulphuric Acid                 }
+  Zinc           }               }Sulphate of zinc found at
+       { Oxygen  } Oxide of Zinc }     positive plate.
+  Water{ Hydrogen                  Hydrogen found at negative plate.
+
+No _single fluid_ cell can give a constant electro-motive force because
+of the _polarisation_ of the plates.
+
+_Definition of the term Polarisation._--The word _polarisation_ means
+that the plates become coated with the products of the decomposition
+of the _electrolyte_, producing a diminution of current. In the above
+described battery, the hydrogen gathers on the surface of the copper
+plate, and an _electro-motive force_ is set up which counteracts
+the electro-motive force producing the current--the copper plate is
+said to be _polarised_. By the bubbles of hydrogen collecting on the
+face of the negative plate, the _surface_ in contact with the liquid
+is gradually decreased; thus the plate becomes practically smaller,
+and a single fluid cell which at starting gave a good current soon
+shows that it is really weakened. The consequence is that the zinc is
+consumed extravagantly as well as the acid, and the cell working with
+poor results. Also the _resistance_ of the cell is increased, due
+to the sulphuric acid, which is added to the water to increase its
+conductivity, being gradually used up, by combining with the oxide (see
+plan) and forming sulphate of zinc. Liquids are very bad conductors
+of electricity; the greater part of the ordinary internal resistance
+of a battery arises from this cause. The common sand battery is the
+worst of all batteries as regards constancy of electro-motive force,
+the _polarisation_ being greater in this battery than any other because
+the gas cannot readily escape. The common copper and zinc cell is the
+next in order of demerit. The _Smee_ single fluid cell, in which the
+negative plate is a platinum instead of a copper one, is better than
+the copper zinc cell, because the free hydrogen does not stick to the
+rough surface of the platinum plate so much as to the copper.
+
+_Double Fluid Batteries._--All the defects of the single fluid battery,
+which are as follows--
+
+1. Diminution of electro-motive force,
+
+2. Inconstancy,
+
+3. Increase of internal resistance,
+
+are remedied in the _double fluid_ battery, of which the _Daniell's
+cell_ was the first invented, and is a good example. Of this kind of
+cell many forms are in use, but the principle is the same throughout.
+There is a positive and negative element, and the cell is divided
+into two receptacles for the two fluids. In the most constant form
+of Daniell cell, the zinc is plunged into a semi-saturated solution
+of sulphate of zinc, the copper in a saturated solution of sulphate
+of copper, and these two solutions are separated either by a porous
+barrier, or by taking advantage of the different specific gravities of
+the two solutions. By a _saturated_ solution is meant a liquid which
+has dissolved as much of the substance as it possibly can.
+
+_The Chemical Action of a Daniell Cell._--The chemical action of this
+form of Daniell cell is as follows:--
+
+The zinc electrode combines with oxygen; the oxide thus formed
+combines with sulphuric acid and forms sulphate of zinc. Oxide of
+copper is separate from the sulphate; and the copper in this oxide
+is separated from the oxygen. The oxygen of the water is separated
+at the zinc electrode from the hydrogen, and at the other electrode
+this hydrogen recombines with the oxygen from the oxide of copper.
+This alternate decomposition and recombination of the elements of
+water can neither increase nor decrease the E.M.F. of the cell, the
+actions being equal and opposite. The result of the series of actions
+above described is that the sulphuric acid and oxygen of the sulphate
+of zinc are transmitted to the zinc, combine with it, and form fresh
+sulphate of zinc; the sulphuric acid and oxygen of the sulphate of
+copper are transmitted to the zinc set free by the above process, and
+reconvert it into sulphate of zinc; the copper of the sulphate of
+copper is transmitted to the copper electrode, and remains adhering
+to it. The whole result is therefore the substitution of a certain
+quantity of sulphate of zinc for an equivalent quantity of sulphate of
+copper, together with a deposition of copper on the copper or negative
+electrode.[X] The following is a plan of the process:--
+
+    Zinc............}                }  .{ Sulphate of Zinc found
+                    } Oxide of Zinc..} . {  at positive plate.
+    Water { Oxygen..}                }.
+          { Hydrogen.................}......}
+                { Sulphuric Acid.....}      } Water.
+    Sulphate of {                 { Oxygen..}
+     Copper     { Oxide of Copper {           { Copper at negative
+                                  { Copper....{  plate.
+
+_Description of the "Callaud" and "Marié-Davy" Batteries._--The Voltaic
+batteries in general use for the different purposes of torpedo warfare
+have been fully described in Chapter IV., and therefore it will be
+only necessary here to explain the construction of the "Callaud" and
+"Marié-Davy" batteries, these being much used abroad in connection with
+telegraphy.
+
+The _Callaud_ cell, named from the inventor, is a modification of the
+Daniell cell, and is also called a _gravity_ battery, the liquids
+being simply prevented from mixing by the law of gravity forbidding
+the heavier of the two from rising through the lighter. It consists
+of a thin plate of copper, which is laid on the bottom of a good
+_insulating_ jar having an _insulated_ wire leading up the side, and
+on this plate are placed crystals of sulphate of copper. A solution of
+sulphate of zinc is then poured in, and on the top is fitted a zinc
+plate, which forms the positive element. The vessel must not be shaken,
+or the sulphate of copper when dissolving will mix with the solution
+above it.
+
+The _Marié-Davy_ cell consists of a carbon electrode in a paste of
+proto-sulphate of mercury and water contained in a porous pot, and a
+zinc electrode in dilute sulphuric acid, or in sulphate of zinc.
+
+_The Circuit._--In connection with the manipulation of batteries,
+there is one important item to consider, viz. the _resistance_ in the
+_circuit_, which may be divided into _external_ and _internal_.
+
+_Resistances._--The _external_ resistance in practice is that which
+exists in the conducting line, and the various instruments connected
+with it.
+
+The _internal_ resistance is that which exists in the battery itself.
+All known conductors oppose a sensible _resistance_ to the passage
+of an electric current, and the strength of the current, or in other
+words, the quantity of electricity passing per second from one point to
+another, when a constant difference of potentials is maintained between
+them, depends on the _resistance_ of the wire on the conductor joining
+them. A bad conductor does not let the electricity pass so rapidly as a
+good conductor, that is, it offers more _resistance_.
+
+Resistance in a wire of constant section and material is _directly_
+proportional to the _length_, and _inversely_ proportional to the _area
+of the cross section_.
+
+The electrical resistance of a conductor must not be considered as
+analogous to mechanical resistance, such as the friction which water
+experiences in passing through a pipe, for this frictional resistance
+_is not_ constant when different quantities of water are being forced
+through the pipe, whereas electrical resistance is constant whatever
+quantity of electricity be forced through the conductor.
+
+_Application of Ohm's Law._--_Ohm's law_, which governs the strength of
+the current, is expressed by the equation
+
+    C = E / R or R = E / C or E = CR.
+
+Where C is the strength of the current;
+
+E is the E.M.F. or difference of potentials;
+
+and R is the resistance of the circuit. */
+
+In words, _Ohm's law_ means that the strength of the current is
+_directly_ proportional to the E.M.F., and _inversely_ proportional to
+the resistance of the circuit.
+
+As before stated, the resistance of the circuit consists of an
+_external_ and an _internal_ resistance, therefore when these
+resistances are separately considered, the equation C = E / R must be
+converted into C = E / (_x_ + _r_), where _x_ is the external, and _r_
+the internal, resistance.
+
+The resistance of the battery or the _internal resistance_ depends on
+the size of the plates and the distance between them, that is, it is
+_directly_ proportional to the distance, and _inversely_ proportional
+to the size.
+
+The _electro-motive_ force of a battery is dependent generally on
+the number of cells joined in _series_, and not on the _size_ of the
+plates. The cells of a battery may be joined in two ways, as follows:--
+
+    1. In series: that is, by connecting the negative
+    element of one cell to the positive element of another,
+    and so on.
+
+    2. In multiple arc: that is, by connecting negative to
+    negative, and positive to positive; which is the same
+    as increasing the size of the cells.
+
+If the conductor between the battery poles be such that the _external_
+resistance _x_ may be practically left out, then C = E / _r_, and no
+change in the strength of the current will be effected by adding any
+number of cells in series, as _r_ will increase equally with _E_, and
+therefore _C_ will remain the same; but if under the same conditions
+the cells be joined in _multiple arc_, then _r_ will decrease as _E_
+increases, and therefore _C_ will be increased.
+
+Thus with a short circuit of small external resistance, the strength of
+the current will be increased by increasing the size of the plates, or
+by joining the cells in multiple arc, but not in series.
+
+If the conductor between the poles of the battery be such that the
+external resistance _x_ becomes very great, then C = E / (_x_ + _r_),
+where _x_ is very great compared to _r_. By joining the cells in
+multiple arc _r_ is decreased, but _E_ and _x_ remain the same, and
+therefore _C_ is not materially altered, as _x_ is very great compared
+to _r_. By connecting the cell in series, _r_ is increased, and so is
+_E_, but as _r_ is still very small compared to _x_, the strength of
+the current _C_ is increased.
+
+Thus with a long circuit of great _external_ resistance, the strength
+of the current will be increased by joining the cells in series, but
+not in multiple arc.
+
+When the external resistance _x_ is neither very large nor very small
+in comparison with the battery or internal resistance _r_, then the
+strength of the current _C_ will be increased by adding the cells in
+series, and also in multiple arc. By the former process the E.M.F.
+_E_ is increased more than the resistance of the circuit _R_ or (_x_
++ _r_), and by the latter process, the E.M.F. _E_ is unaltered, whilst
+the circuit resistance (_x_ + _r_) is decreased. All the above may be
+practically demonstrated by the employment of suitable _galvanometers_.
+
+_Frictional Electricity._--_Frictional_ electricity is produced by the
+friction of two insulators. There is _no difference whatever in kind_
+between "Voltaic" and "frictional" electricity.
+
+_Comparison with Voltaic Electricity._--The electricity generated by
+friction possesses a great electro-motive force, producing on even
+a small conductor a large charge, whereas the electricity generated
+by the galvanic cell possesses a very small electro-motive force,
+and produces only a small charge on a small conductor. But when the
+conductor is large, the electricity produced by the galvanic cell will
+almost instantaneously charge the conductor to the maximum potential
+it can produce, the galvanic cell developing an immense quantity of
+electricity by the chemical reaction; whereas the quantity developed
+by friction between two insulators is so small, that if it be diffused
+over a large conductor the potential of the conductor will be very
+little increased.
+
+The late Professor Faraday has proved that one cell of a Voltaic
+pile possesses the same quantity of electricity as an ordinary sized
+frictional machine after being wound round 800,000 times, thus
+showing the contrast between the qualities of frictional and Voltaic
+electricity.
+
+The electricity of the frictional machine and that of the galvanic
+battery may be made to produce the same effect, there being no
+difference in kind between them. Frictional electricity can be made
+to pass in a current, but it is comparatively feeble. Again, Voltaic
+electricity can be made to produce a spark, but under ordinary
+circumstances it scarcely amounts to anything.
+
+_Description of a Frictional Electric Machine._--A frictional
+electrical machine consists of a vulcanite or glass disc or cylinder,
+which is made to revolve between cushions or rubbers of leather or
+silk. By the friction the (silk) rubbers become negatively, and the
+glass disc or cylinder positively, electrified. The revolving disc
+immediately after contact with the fixed rubbers passes close by a
+series of brass points, which are connected with a _condenser_. These
+points collect the positive electricity of the glass, the rubbers
+being put to earth. The positive electricity which the glass loses is
+supplied through the rubber; a stream of negative electricity flows
+from the rubbers to the earth during the charging of the conductor or
+condenser; in other words, the positive electricity flows from the
+earth to the rubber, whence it crosses to the glass disc and so to the
+condenser.
+
+_Definition of a "Condenser."_--A _condenser_ is an arrangement for
+accumulating a large quantity of electricity on a comparatively small
+surface.
+
+_The "Leyden Jar."_--The _Leyden jar_, which is the original type of
+the condenser, or accumulator, consists of a glass jar coated inside
+and out, up to within a few inches of the mouth, with tinfoil pasted
+on, but having no connection with each other. The mouth is usually
+closed by means of a wooden stopper, through which a brass rod passes,
+to the head of which is affixed a brass knob, &c., the rod and knob
+being metallically connected with the _inner_ coating by means of a
+chain.
+
+The "Leyden jar" may be charged either by connecting the _outer_
+coating to earth (the rubbers of the machine being also to earth),
+and the _inner_ coating to the conductor of the machine; or else by
+connecting the outer coating to the rubbers, and the inner coating to
+the conductor, a complete circuit being necessary to charge the jar as
+highly as the frictional electrical machine will admit of.
+
+The _conductor_ of the machine being charged, also forms a kind of
+Leyden jar, the conductor in this case being the inner coating, the
+air, the _dielectric_, and the nearest surrounding conductors, such as
+the walls of the room, &c., being the outer coating.
+
+_Meaning of "Dielectric."_--By _dielectric_ is meant a non-conducting
+medium, which in the case of the "Leyden jar" is the glass.
+
+_Frictional Electricity very little used for Torpedo
+Purposes._--Frictional electricity is now seldom used in connection
+with torpedo warfare, as on account of its very great power, or
+electro-motive force, a very perfectly insulated cable must be
+employed, which is somewhat difficult to obtain; it is also necessary
+to employ a condenser, which requires a certain time to charge. For
+these and other reasons, frictional electricity has been abandoned for
+the far more practical Voltaic electricity.
+
+_Magnetism._--A _magnet_ is a piece of steel, which has the peculiar
+property, among others, of attracting iron to its ends.
+
+Certain kinds of iron ore, termed the _loadstone_, have the same
+properties. The word "_magnet_" is taken from the country Magnesia,
+where the loadstone was first discovered.
+
+Magnetism in a body is considered to be a peculiar condition caused by
+electrical action. Both electricity and magnetism have the power of
+communicating their properties to other bodies without being in contact
+with them, i.e. _inducing_ the power, which on the bodies being placed
+far apart becomes insensible.
+
+_The "Poles" of a Magnet._--Every magnet has two _poles_, called the
+_north_ and _south_ poles. A magnetic steel needle if pivoted on an
+upright point, or suspended from its centre, will fix itself, pointing
+north and south; in England the end of the needle pointing to the north
+is termed the north pole, but in France it is termed the south pole.
+The reason of this difference is owing to the fact that the north pole
+of one magnet attracts the south pole of another, and therefore, as the
+earth is considered as one vast magnet, the end of the magnetic needle
+attracted to the north pole of earth magnet should be the south pole of
+the magnet; thus the French south pole in a magnet is the English north
+pole, and _vice versâ_.
+
+_Permanent Magnets._--A piece of steel when magnetised is termed a
+_permanent_ magnet, because it retains its magnetism for a considerable
+length of time; but soft iron cannot be permanently magnetised.
+
+A piece of soft iron rendered magnetic by induction retains a portion
+of its magnetism for some time after it has been removed from the
+magnetic field, by reason of what is called its _coercive force_. This
+remnant of magnetisation is called _residual magnetism_.
+
+_Effect of an Electrical Current on a Magnetic Needle._--A magnetic bar
+or needle pivoted on its centre will point north and south, but if an
+electric current is caused to flow along a wire parallel to and either
+over or under the magnetic needle, the latter will be turned from
+its position, and remain so as long as the current continues; on the
+current ceasing the needle will resume its original position.
+
+The magnetic needle can be turned either to the east or the west,
+according to the direction and course of the electrical current.
+
+Thus:--
+
+    Current from S. to N. _over_ deflects to W.
+    Current from N. to S. _under_ deflects to W.
+    Current from N. to S. _over_ deflects to E.
+    Current from S. to N. _under_ deflects to E.
+
+The Galvanometer, the "Mirror," and "Thomson's reflector" all depend on
+this principle for their usefulness. These instruments have been fully
+described in Chapter IV.
+
+_The Electro-Magnet._--If a piece of insulated wire be coiled round a
+rod of soft iron, and a current of electricity be made to pass through
+the coil, the iron core becomes magnetic as long as the current passes;
+when the current ceases the magnetism disappears.
+
+During the passage of the electric current, the iron core possesses all
+the properties of a magnet. Therefore if a piece of iron were placed
+near its poles it would be attracted and released from attraction as
+often as the current passed or ceased; and supposing such a piece
+of iron to be retained by a spring, &c., a series of movements,
+attraction, and drawing back would be effected.
+
+A piece of iron so arranged is termed an _armature_, and the instrument
+is called an _electro-magnet_.
+
+The coil of wire must be carefully insulated, or else the electric
+current will pass through the iron core to earth instead of performing
+its proper work.
+
+An electro-magnet is much more powerful than a steel magnet of equal
+dimensions, and depends on the strength of the current by which the
+magnetism is induced, and the number of turns of wire round the core.
+The north and south poles of an electro-magnet are determined by the
+direction in which the current flows through the wire.
+
+At the _south_ pole the current passes _with_ the hands of a watch, and
+at the _north_ pole _against_ the hands of a watch.
+
+_Definition of the "Ohm."_--The "ohm" is the standard used for
+electrical resistance; it is obtained by observing what effect is
+produced by a current of electricity on a certain conductor in a
+certain time.
+
+The ohm is a small coil of German silver wire representing the
+resistance overcome by a current in a certain time.
+
+FOOTNOTES:
+
+[Footnote X: Jenkins' 'Electricity.']
+
+
+
+
+APPENDIX.
+
+
+_McEvoy's Single Main System._--Hitherto in connection with a system
+of electrical submarine mines, it has been necessary to employ either
+a single cable between each submarine mine and the torpedo station, or
+a single cable, termed a "multiple cable," containing a limited number
+of insulated wires, leading from the station, and branching off from a
+junction box to each mine, by which considerable cost and complication
+is incurred. To remedy the above serious defects of such a system, and
+also to simplify the arrangement of electrical tests, Captain McEvoy
+has devised and patented the following apparatus; at the firing, or
+torpedo station, the end of the single main cable, that is, the single
+core cable leading to the junction box, is connected to a make and
+break contact apparatus, by which, by the movement of a dial or pointer
+around a fixed centre, a battery can be successively put in connection
+with the wire, and disconnected from it, in a somewhat similar manner
+to Wheatstone's step by step dial telegraphs. In the junction box at
+the opposite end of the single core main cable is an electro-magnetic
+apparatus for working a dial or pointer in exact unison with the
+aforesaid dial or pointer at the torpedo station. This junction box
+dial or pointer serves as a contact maker to put the wire of the main
+cable successively in contact with the branch wires leading to the
+several torpedoes, as it is caused to turn with a step by step motion
+by the sending of a succession of currents from the firing station.
+
+As the contact maker completes the circuit between the main cable and
+one of the branch wires, the current passes from the cable through the
+wire, and through the fuze of that particular torpedo to "earth"; but
+when any one or other of the torpedoes is to be exploded, the circuit
+between the main cable and the torpedo wire being completed, it is
+only necessary to send a current through the main cable of sufficient
+strength to ignite the fuze, and so explode the mine.
+
+The strength of the current used for giving the aforesaid step by step
+motion to the junction box dial or pointer is not sufficient to cause
+the ignition of the fuzes in the torpedoes.
+
+Again, if it be desired that the torpedoes should be so arranged that
+when any of them are struck by a passing vessel, the fact of its having
+been struck should be instantly signalled to the firing station. The
+dial apparatus in the junction box is arranged so that at one point of
+its revolution, termed the "zero point," all the torpedo branch wires
+are in circuit with the main cable, and that then a constant current
+is passing from the firing station through all the circuit closers,
+and out through resistance coils to "earth." In this case, if one of
+the circuit closers be struck, and therefore short circuit formed, the
+current passes direct to earth without going through the aforesaid
+resistance, and the fact of its having done so is at once indicated by
+a galvanometer at the firing point, by the movement of which a bell is
+rung at the station. The operator can then explode such torpedo at once
+by merely switching in the firing battery.
+
+At the same time the passage of the strong firing current may fuze a
+connection in the junction apparatus, by which the exploded torpedo
+is detached, i.e. the direct "earth" connection of such a torpedo is
+cut off, and the remaining submarine mines are left in proper working
+order; this effect may also be arrived at by other means.
+
+_General Description of Apparatus._--The following is a general
+description of this exceedingly clever and useful invention:--
+
+At Fig. 168 is shown a diagram view of the apparatus.
+
+_A_ is the instrument at the firing point on the shore or vessel; _B_
+is the cable wire led to a submerged box situated near the spot where
+the several torpedoes are grouped; _C_ is the instrument enclosed in
+the submerged box; _D_, _D_ are insulated wires led away from the box
+to the several torpedoes, there being a separate wire for each torpedo.
+
+Each of the wires _D_ is coupled to one or other of a series of
+metallic contact pieces _E_ ranged in a circle round the axis of
+a metallic pointer _F_, which can be turned with a step by step
+motion and successively brought into electrical contact with the
+several contact pieces _E_. The axis of the pointer is in electrical
+communication with the wire of the cable. The wire from the cable is
+first led to the coils of an electro magnet _G_, and thence passes to
+the axis of the pointer. _H_ is a magnetic armature in front of the
+electro magnet _G_; when a positive current of sufficient strength
+is sent through the cable the armature is rocked in one direction,
+and when a negative current is sent, it is rocked in the opposite
+direction. From the armature motion is transmitted to a pawl which
+works into the teeth of a ratchet wheel on the axis of the pointer _F_,
+so that by sending a succession of reversed currents of sufficient
+strength through the cable, the pointer _F_ is turned with a step by
+step motion and is successively brought into electrical contact with
+the several contact pieces _E_.
+
+[Illustration: M^{c.}EVOY'S SINGLE MAIN SYSTEM
+
+PLATE LIV.]
+
+In the instrument, at the firing point _a_ is a handle, by the turning
+of which a step by step motion is given to the pointer of a dial _b_
+and a simultaneous movement to the pointer _F_ of the instrument _C_
+in the submerged box. When the handle _a_ has made a half turn it
+couples one pole of the battery to the cable and the other to the earth
+connection, and when it has made a complete turn the connections are
+reversed. The pointer of the dial _b_ then moves forward from
+one division of the dial to the next, and simultaneously the pointer
+_F_ is turned in unison with it. The operator at the firing point can
+therefore always see which of the torpedoes is in electrical connection
+with the wire of the cable, and he can test each torpedo in succession
+by moving a handle, say at _h_, to cause the current passing back from
+the torpedo to pass through a galvanometer at _e_, and by the movement
+of the needle of the galvanometer it can be seen whether the resistance
+of the circuit through this torpedo is in its normal and proper working
+state.
+
+When the pointer of the dial _b_ is brought to zero, or as it is marked
+in the drawing to "signal," then the pointer _F_ of the apparatus _C_
+is in electrical communication with a contact point which is coupled to
+all of the branch wires _D_, and usually the apparatus is left in this
+condition, the handle _a_ being then locked and prevented from turning
+by a bolt actuated by a handle at _G_.
+
+The current from the battery at the firing point then passes to earth
+through the resistances in all of the torpedoes. If now any one or
+other of the torpedoes is struck by a passing vessel and the wire from
+its fuze put directly to earth, so that the current passes freely to
+earth instead of having first to pass through the resistance, the fact
+of the current passing freely to earth is notified at the firing point
+by the movement of the needle of a galvanometer _d_; the movement of
+the needle of this galvanometer effects an electrical connection by
+which a small battery is caused to sound a bell at _c_. The operator at
+the firing point can then if he pleases at once fire the torpedo that
+has been struck by moving a handle at _f_ and coupling up to the wire
+of the cable a battery of greater strength; the strong firing current
+will pass to earth through the fuze of the torpedo that has been
+struck, and will ignite this fuze, but will not affect the fuzes of the
+other torpedoes, as to pass through these fuzes it has also to pass
+through resistances which impede its passage and reduce its strength,
+so that the portion of the current which passes to earth through them
+is not of sufficient strength to ignite the fuzes.
+
+When the fuze of any one or other of the torpedoes is exploded by the
+passing of a strong firing current through it, the wire leading from
+the box _C_ to this torpedo is simultaneously cut off from electrical
+connection with the contact pin _E_ to which it was previously
+connected, and this pin is put to earth through a resistance either
+somewhat greater or less than the resistances in the torpedoes, so that
+the firing of one or more of the torpedoes does not interfere with the
+power of being able to turn the pointer _F_ of the apparatus _C_ in
+unison with the pointer of the dial _b_.
+
+Afterwards the operator at the firing point can ascertain which of the
+torpedoes has been fired by passing the pointer of the dial _b_ to
+each of the divisions of the dial in succession, and ascertaining by
+the galvanometer a the resistance of the circuit through each of the
+torpedoes, so that he at once ascertains which torpedo has been put to
+earth through the greater or less resistance.
+
+The cutting off of the wire _D_ from its contact _E_ when a strong
+current is passed through it may be effected by the wire being coiled
+around an iron core forming an electro magnet, which when a strong
+current is passed through the wire is of sufficient strength to shift
+the position of a contact apparatus and then effect the required
+alterations in the connections, but which is not of sufficient strength
+to effect any change when the weaker currents used for the signalling
+and testing operations are passed through the wire.
+
+It will be evident that with the above described apparatus any one or
+other of the torpedoes can if desired be exploded by the operator at
+the firing point whenever he desires to do so. To effect this he would
+by turning the handle _a_ bring the pointer of the dial _b_ opposite to
+the division of this dial; that would indicate that the cable had been
+brought into electrical communication with the torpedo required to be
+exploded, and then when it is ascertained by previously adjusted sight
+points that the vessel is above the torpedo, he can fire the torpedo by
+passing a strong firing current to the cable.
+
+In this way the apparatus can be used for firing any one or other of a
+group of sunken torpedoes, or if the torpedoes are buoyant ones, they
+need not be fitted with apparatus for putting the wire from their fuze
+directly to earth whenever the torpedo is struck by a passing vessel.
+The same arrangement of apparatus can also be used for firing any one
+or other of a number of mines or torpedoes on land and for separately
+testing the firing mechanism of each mine whenever desired.
+
+Captain McEvoy's single main system will shortly undergo a series of
+experiments under the supervision of the English torpedo authorities at
+Chatham, which will most probably result in its adoption by the English
+government, and also by the principal continental powers.
+
+
+TABLE[Y]
+
+SHOWING THE VALUE OF THE FRACTIONS A AND B FOR EVERY HALF DEGREE.
+
+    -------+-------------+-------------+
+           |      A      |     B       |
+     Arc.  |150 + [alpha]|150 - [alpha]|
+           +-------------+-------------+
+    [alpha]|150 - [alpha]|150 + [alpha]|
+    -------+-------------+-------------+
+     145   |    59·00    |    0·017    |
+     144·5 |    53·54    |    0·019    |
+     144   |    49·00    |    0·020    |
+     143·5 |    45·15    |    0·022    |
+     143   |    41·86    |    0·024    |
+     142·5 |    39·00    |    0·026    |
+     142   |    36·50    |    0·028    |
+     141·5 |    34·29    |    0·029    |
+     141   |    32·33    |    0·031    |
+     140·5 |    30·58    |    0·033    |
+     140   |    29·00    |    0·035    |
+     139·5 |    27·57    |    0·036    |
+     139   |    26·27    |    0·038    |
+     138·5 |    25·09    |    0·040    |
+     138   |    24·00    |    0·042    |
+     137·5 |    23·00    |    0·044    |
+     137   |    22·08    |    0·045    |
+     136·5 |    21·22    |    0·047    |
+     136   |    20·43    |    0·049    |
+     135·5 |    19·69    |    0·051    |
+     135   |    19·00    |    0·052    |
+     134·5 |    18·35    |    0·054    |
+     134   |    17·75    |    0·056    |
+     133·5 |    17·18    |    0·058    |
+     133   |    16·65    |    0·060    |
+     132·5 |    16·14    |    0·062    |
+     132   |    15·67    |    0·064    |
+     131·5 |    15·22    |    0·066    |
+     131   |    14·79    |    0·068    |
+     130·5 |    14·38    |    0·070    |
+     130   |    14·00    |    0·071    |
+     129·5 |    13·63    |    0·073    |
+     129   |    13·28    |    0·075    |
+     128·5 |    12·95    |    0·077    |
+     128   |    12·64    |    0·079    |
+     127·5 |    12·33    |    0·081    |
+     127   |    12·04    |    0·083    |
+     126·5 |    11·76    |    0·085    |
+     126   |    11·50    |    0·087    |
+     125·5 |    11·24    |    0·089    |
+     125   |    11·00    |    0·091    |
+     124·5 |    10·76    |    0·093    |
+     124   |    10·54    |    0·095    |
+     123·5 |    10·32    |    0·097    |
+     123   |    10·11    |    0·099    |
+     122·5 |     9·91    |    0·101    |
+     122   |     9·72    |    0·103    |
+     121·5 |     9·53    |    0·105    |
+     121   |     9·35    |    0·107    |
+     120·5 |     9·17    |    0·109    |
+     120   |     9·00    |    0·111    |
+     119·5 |     8·84    |    0·113    |
+     119   |     8·68    |    0·115    |
+     118·5 |     8·52    |    0·117    |
+     118   |     8·37    |    0·119    |
+     117·5 |     8·23    |    0·121    |
+     117   |     8·09    |    0·123    |
+     116·5 |     7·96    |    0·126    |
+     116   |     7·82    |    0·128    |
+     115·5 |     7·69    |    0·130    |
+     115   |     7·57    |    0·132    |
+     114·5 |     7·45    |    0·134    |
+     114   |     7·33    |    0·136    |
+     113·5 |     7·22    |    0·139    |
+     113   |     7·11    |    0·141    |
+     112·5 |     7·00    |    0·143    |
+     112   |     6·89    |    0·145    |
+     111·5 |     6·79    |    0·147    |
+     111   |     6·69    |    0·150    |
+     110·5 |     6·59    |    0·152    |
+     110   |     6·50    |    0·154    |
+     109·5 |     6·41    |    0·156    |
+     109   |     6·32    |    0·158    |
+     108·5 |     6·23    |    0·160    |
+     108   |     6·14    |    0·163    |
+     107·5 |     6·06    |    0·165    |
+     107   |     5·97    |    0·168    |
+     106·5 |     5·89    |    0·170    |
+     106   |     5·82    |    0·172    |
+     105·5 |     5·74    |    0·174    |
+     105   |     5·67    |    0·176    |
+     104   |     5·52    |    0·182    |
+     103·5 |     5·45    |    0·183    |
+     103   |     5·38    |    0·186    |
+     102·5 |     5·31    |    0·188    |
+     102   |     5·25    |    0·190    |
+     101·5 |     5·18    |    0·193    |
+     101   |     5·12    |    0·195    |
+     100·5 |     5·06    |    0·198    |
+     100   |     5·00    |    0·200    |
+      99·5 |     4·94    |    0·202    |
+      99   |     4·88    |    0·205    |
+      98·5 |     4·82    |    0·207    |
+      98   |     4·77    |    0·209    |
+      97·5 |     4·71    |    0·212    |
+      97   |     4·66    |    0·215    |
+      96·5 |     4·61    |    0·217    |
+      96   |     4·55    |    0·220    |
+      95·5 |     4·50    |    0·222    |
+      95   |     4·45    |    0·224    |
+      94·5 |     4·40    |    0·227    |
+      94   |     4·36    |    0·230    |
+      93·5 |     4·31    |    0·232    |
+      93   |     4·26    |    0·235    |
+      92·5 |     4·22    |    0·237    |
+      92   |     4·17    |    0·240    |
+      91·5 |     4·13    |    0·242    |
+      91   |     4·08    |    0·245    |
+      90·5 |     4·04    |    0·247    |
+      90   |     4·00    |    0·250    |
+      89·5 |     3·96    |    0·253    |
+      89   |     3·92    |    0·255    |
+      88·5 |     3·88    |    0·258    |
+      88   |     3·84    |    0·260    |
+      87·5 |     3·80    |    0·263    |
+      87   |     3·76    |    0·266    |
+      86·5 |     3·72    |    0·269    |
+      86   |     3·69    |    0·271    |
+      85·5 |     3·65    |    0·274    |
+      85   |     3·62    |    0·276    |
+      84·5 |     3·58    |    0·279    |
+      84   |     3·54    |    0·282    |
+      81·5 |     3·38    |    0·296    |
+      81   |     3·35    |    0·299    |
+      80·5 |     3·31    |    0·302    |
+      80   |     3·28    |    0·304    |
+      79·5 |     3·25    |    0·307    |
+      79   |     3·22    |    0·310    |
+      78·5 |     3·19    |    0·313    |
+      78   |     3·17    |    0·316    |
+      77·5 |     3·14    |    0·319    |
+      77   |     3·11    |    0·322    |
+      76·5 |     3·08    |    0·325    |
+      76   |     3·05    |    0·327    |
+      75·5 |     3·03    |    0·330    |
+      75   |     3·00    |    0·333    |
+      74·5 |     2·973   |    0·336    |
+      74   |     2·947   |    0·339    |
+      73·5 |     2·921   |    0·342    |
+      73   |     2·896   |    0·345    |
+      72·5 |     2·871   |    0·348    |
+      72   |     2·846   |    0·351    |
+      71·5 |     2·822   |    0·354    |
+      71   |     2·797   |    0·357    |
+      70·5 |     2·773   |    0·360    |
+      70   |     2·750   |    0·364    |
+      69·5 |     2·726   |    0·367    |
+      69   |     2·703   |    0·370    |
+      68·5 |     2·680   |    0·373    |
+      68   |     2·658   |    0·376    |
+      67·5 |     2·636   |    0·379    |
+      67   |     2·614   |    0·382    |
+      66·5 |     2·592   |    0·386    |
+      66   |     2·571   |    0·389    |
+      65·5 |     2·550   |    0·392    |
+      65   |     2·529   |    0·395    |
+      64·5 |     2·509   |    0·398    |
+      64   |     2·488   |    0·402    |
+      63·5 |     2·468   |    0·405    |
+      63   |     2·448   |    0·408    |
+      62·5 |     2·428   |    0·412    |
+      62   |     2·409   |    0·415    |
+      61·5 |     2·389   |    0·418    |
+      59   |     2·296   |    0·435    |
+      58·5 |     2·278   |    0·439    |
+      58   |     2·261   |    0·442    |
+      57·5 |     2·243   |    0·446    |
+      57   |     2·226   |    0·449    |
+      56·5 |     2·208   |    0·453    |
+      56   |     2·191   |    0·456    |
+      55·5 |     2·174   |    0·460    |
+      55   |     2·158   |    0·463    |
+      54·5 |     2·141   |    0·467    |
+      54   |     2·125   |    0·471    |
+      53·5 |     2·109   |    0·474    |
+      53   |     2·093   |    0·478    |
+      52·5 |     2·077   |    0·481    |
+      52   |     2·061   |    0·485    |
+      51·5 |     2·045   |    0·489    |
+      51   |     2·030   |    0·492    |
+      50·5 |     2·015   |    0·496    |
+      50   |     2·000   |    0·500    |
+      49·5 |     1·985   |    0·504    |
+      49   |     1·970   |    0·508    |
+      48·5 |     1·955   |    0·511    |
+      48   |     1·941   |    0·515    |
+      47·5 |     1·926   |    0·519    |
+      47   |     1·913   |    0·523    |
+      46·5 |     1·898   |    0·527    |
+      46   |     1·884   |    0·531    |
+      45·5 |     1·870   |    0·535    |
+      45   |     1·857   |    0·538    |
+      44·5 |     1·843   |    0·542    |
+      44   |     1·830   |    0·546    |
+      43·5 |     1·816   |    0·550    |
+      43   |     1·803   |    0·554    |
+      42·5 |     1·790   |    0·558    |
+      42   |     1·777   |    0·562    |
+      41·5 |     1·765   |    0·567    |
+      41   |     1·752   |    0·571    |
+      40·5 |     1·739   |    0·575    |
+      40   |     1·727   |    0·579    |
+      39·5 |     1·714   |    0·583    |
+      39   |     1·702   |    0·587    |
+      36·5 |     1·643   |    0·609    |
+      36   |     1·631   |    0·613    |
+      35·5 |     1·620   |    0·617    |
+      35   |     1·608   |    0·622    |
+      34·5 |     1·597   |    0·626    |
+      34   |     1·586   |    0·630    |
+      33·5 |     1·575   |    0·635    |
+      33   |     1·564   |    0·639    |
+      32·5 |     1·553   |    0·644    |
+      32   |     1·542   |    0·648    |
+      31·5 |     1·531   |    0·653    |
+      31   |     1·521   |    0·657    |
+      30·5 |     1·510   |    0·662    |
+      30   |     1·500   |    0·667    |
+      29·5 |     1·489   |    0·671    |
+      29   |     1·479   |    0·676    |
+      28·5 |     1·469   |    0·681    |
+      28   |     1·459   |    0·685    |
+      27·5 |     1·449   |    0·690    |
+      27   |     1·439   |    0·695    |
+      26·5 |     1·429   |    0·700    |
+      26   |     1·419   |    0·705    |
+      25·5 |     1·409   |    0·709    |
+      25   |     1·400   |    0·714    |
+      24·5 |     1·390   |    0·719    |
+      24   |     1·380   |    0·724    |
+      23·5 |     1·371   |    0·729    |
+      23   |     1·362   |    0·734    |
+      22·5 |     1·352   |    0·739    |
+      22   |     1·343   |    0·744    |
+      21·5 |     1·334   |    0·749    |
+      21   |     1·325   |    0·754    |
+      20·5 |     1·316   |    0·760    |
+      20   |     1·307   |    0·765    |
+      19·5 |     1·298   |    0·770    |
+      19   |     1·290   |    0·775    |
+      18·5 |     1·281   |    0·780    |
+      18   |     1·272   |    0·786    |
+      17·5 |     1·264   |    0·791    |
+      17   |     1·255   |    0·796    |
+      16·5 |     1·247   |    0·802    |
+      16   |     1·238   |    0·807    |
+      15·5 |     1·230   |    0·813    |
+      15   |     1·222   |    0·818    |
+      14·5 |     1·214   |    0·823    |
+      14   |     1·206   |    0·829    |
+      13·5 |     1·198   |    0·835    |
+      13   |     1·189   |    0·841    |
+      12·5 |     1·181   |    0·847    |
+      12   |     1·173   |    0·852    |
+      11·5 |     1·166   |    0·858    |
+      11   |     1·158   |    0·863    |
+      10·5 |     1·150   |    0·869    |
+      10   |     1·143   |    0·875    |
+       9·5 |     1·135   |    0·881    |
+       9   |     1·127   |    0·887    |
+       8·5 |     1·120   |    0·893    |
+       8   |     1·112   |    0·899    |
+       7·5 |     1·105   |    0·905    |
+       7   |     1·097   |    0·911    |
+       6·5 |     1·090   |    0·917    |
+       6   |     1·083   |    0·923    |
+       5·5 |     1·076   |    0·929    |
+       5   |     1·068   |    0·935    |
+       4·5 |     1·061   |    0·942    |
+       4   |     1·054   |    0·948    |
+       3·5 |     1·047   |    0·954    |
+       3   |     1·040   |    0·960    |
+       2·5 |     1·033   |    0·967    |
+       2   |     1·027   |    0·974    |
+       1·5 |     1·020   |    0·980    |
+       1   |     1·013   |    0·987    |
+       0·5 |     1·006   |    0·993    |
+    -------+-------------+-------------+
+
+
+A SYNOPSIS OF THE PRINCIPAL EVENTS THAT HAVE OCCURRED IN CONNECTION
+WITH THE HISTORY OF THE TORPEDO.
+
+  ---------+-------------+---------------------------+------------+---------------------------------
+    Date.  |Operator, &c.|          Event.           |  Place.    |             Remarks.
+  ---------+-------------+---------------------------+------------+---------------------------------
+    1585.  | Italian     | Attack on a bridge formed | Antwerp.   |Bridge completely destroyed.
+           |  Engineer,  |   over the Scheldt.       |            | Vessels, each carrying a heavily
+           |   Zambelli. |                           |            | charged magazine, fired by
+           |             |                           |            | clockwork, were carried by the
+           |             |                           |            | stream against the bridge.
+           |             |                           |            |
+    1775.  | Captain D.  | Numerous small experiments| America.   |By which he proved that a charge
+           |   Bushnell. |  with gunpowder charges.  |            | of gunpowder could be fired
+           |             |                           |            | under water.
+           |             |                           |            |
+    1776.  |      "      | Attack on the English     | New York.  |Boat managed by Sergeant E. Lee.
+           |             |  frigate H.M.S. _Eagle_ by|            | Attack failed, owing to his
+           |             |  his submarine torpedo    |            | inexperience in manipulating
+           |             |  boat.                    |            | this novel kind of craft.
+           |             |                           |            |
+    1777.  |      "      | Attack on the English     | New London.|Drifting torpedoes employed.
+           |             |  man-of-war H.M.S.        |            | Crew of a prize schooner astern
+           |             |  _Cerberus_ by his        |            | of the _Cerberus_ hauled one of
+           |             |  drifting torpedoes.      |            | the torpedoes on board, which
+           |             |                           |            | exploded, killing 3 men and
+           |             |                           |            | destroying a boat.
+           |             |                           |            |
+    1777.  |      "      | Attack on English ships by|    "       |This failed, owing to the ships
+           |             |  numerous floating        |            | having previously hauled into
+           |             |  torpedoes. Known by the  |            | dock to avoid the ice, but it
+           |             |  name of "Battle of Kegs."|            | created a great amount of
+           |             |                           |            | confusion and alarm among the
+           |             |                           |            | crews of the vessels.
+           |             |                           |            |
+    1797.  |  R. Fulton. | Experiments with torpedoes| France.    |These first attempts were
+           |             |  on the Seine.            |            | generally failures.
+           |             |                           |            |
+   July 3, |      "      | Experiments with his      | Brest,     |These experiments were successful
+    1801.  |             |  submarine boat named the |  France.   | in so far as proving that with
+           |             |   _Nautilus_.             |            | such a boat he could descend to
+           |             |                           |            | any given depth and reascend to
+           |             |                           |            | the surface at will, and that he
+           |             |                           |            | could remain below for a
+           |             |                           |            | considerable time.
+           |             |                           |            |
+   August  |      "      | Attempted to sink a small |     "      |Completely successful. This is
+    1801.  |             |  vessel by means of one of|            | the first vessel known to be
+           |             |  his torpedoes.           |            | destroyed by means of a torpedo.
+           |             |                           |            | Charge of submarine mine 20 lbs.
+           |             |                           |            | gunpowder.
+           |             |                           |            |
+    1801.  |      "      | Attempted to destroy one  | Off        |Owing to the ship altering her
+           |             |  of the English channel   |  Boulogne, | position at the moment of
+           |             |  fleet by means of his    |  France.   | setting the torpedo adrift, this
+           |             |  drifting torpedoes.      |            |  attack failed.
+           |             |                           |            |
+  Oct. 3,  |      "      |Catamarran expedition under| Boulogne,  |Failed, owing to a mistake in the
+    1804.  |             |  Lord Keith to destroy the|  France.   | construction of the torpedoes.
+           |             |  French fleet.            |            | The mines exploded, but did no
+           |             |                           |            | damage to the French ships.
+           |             |                           |            |
+  Oct.     |      "      | Similar expedition.       |     "      |Similar failure, owing to causes
+    1805.  |             |                           |            | above mentioned.
+           |             |                           |            |
+  Oct. 15, |      "      |Attempted to destroy a brig| Dover,     |The brig was completely
+    1805.  |             |  _Dorothea_ with his      |  England.  | demolished. Two torpedoes
+           |             |  drifting torpedoes.      |            | employed, each charged with 180
+           |             |                           |            | lbs. gunpowder and fired by
+           |             |                           |            | clockwork.
+           |             |                           |            |
+  July 20, |      "      | Experiment on a large hulk| New York,  |Finally successful, several
+    1807.  |             |  brig.                    |  America.  | attempts being necessary, owing
+           |             |                           |            | to faulty construction.
+           |             |                           |            |
+    Oct.   |      "      | Attack on the U.S. sloop  | New York.  |Failed, owing to the very
+    1810.  |             |   _Argus_ for finally     |            | ingenious though elaborate
+           |             |  testing the efficacy of  |            | defence of the vessel, carried
+           |             |  his torpedo schemes.     |            | out under the directions of
+           |             |                           |            | Commodore Rodgers.
+           |             |                           |            |
+    1812.  |  Mr. Mix.   | Attack on the English     | Lynn, Haven|Complete failure, though six
+           |             |  frigate H.M.S.           |  Bay,      | different attempts were made.
+           |             |  _Plantagenet_ with his   |  America.  |
+           |             |  drifting torpedoes.      |            |
+           |             |                           |            |
+  June 15, |      "      |Attack on H.M.S. _Ramilies_| New York.  | An utter failure.
+    1813.  |             | by blowing up a schooner  |            |
+           |             | alongside.                |            |
+           |             |                           |            |
+    1820.  | Captain     |Experiment with a submarine| Moulsford, |Idea was to fasten the torpedo by
+           |  Johnson.   |  boat carrying a torpedo  |  Berks,    | means of screws to the bottom of
+           |             |  on its back.             |  England.  | the hostile vessel. Trial proved
+           |             |                           |            | successful, but the English
+           |             |                           |            | government refused to sanction
+           |             |                           |            | the project as being too
+           |             |                           |            | diabolical.
+           |             |                           |            |
+   July 4, | Colonel     | Experiment on a raft with | Ware Pond, | Successful.
+    1829.  |  Samuel     |  his  submarine battery.  |  America.  |
+           |  Colt.      |                           |            |
+           |             |                           |            |
+    1839.  | General     | Destruction of the wreck  | Portsmouth,|He is stated to have employed
+           |  Paisley,   |  of the  _Royal George_ by|  England.  | galvanic firing to explode the
+           |  R.E.       |  submarine mines.         |            | mines.
+           |             |                           |            |
+    1840.  | Captain     | Experiment on the _John   | England.   | Successful. Details not known.
+           |  Warner.    |  O'Gaunt_.                |            |
+           |             |                           |            |
+   June 4, | Colonel S.  | Experiment to explode a   | New York.  |Successful. The operator was at a
+    1842.  |   Colt.     |  submarine  mine by       |            | great distance from the torpedo.
+           |             |   electricity.            |            |
+           |             |                           |            |
+   July 4, |      "      | Experiment on the U.S.    | Castle     |Successful. The operator was on
+    1842.  |             |  gunboat _Boxer_ with     |  Garden,   | board U.S. man-of-war at some
+           |             |  electric submarine mines.|  New York. | distance from the place where
+           |             |                           |            | the explosion occurred.
+           |             |                           |            |
+  Aug. 20, | Colonel S.  | Similar experiment on a   | Potomac    |Successful, the operator being
+    1842.  |   Colt.     |  schooner.                |  River,    | stationed at a distance of 5
+           |             |                           |  America.  | miles from where the mine was
+           |             |                           |            | placed.
+           |             |                           |            |
+  Oct. 18, |      "      | Similar experiment on the | New York.  |Successful. The operator being on
+    1842.  |             |  brig _Volta_, 300 tons.  |            | board the revenue cutter
+           |             |                           |            | _Ewing_, at a considerable
+           |             |                           |            | distance from the scene of the
+           |             |                           |            | explosion.
+           |             |                           |            |
+  April 13,|      "      | Experiment to destroy a   | Potomac    |Successful. The vessel was, at
+    1843.  |             |  vessel of 500 tons _under|  River,    | the time of the explosion,
+           |             |  weigh_ by electric       |  America.  | sailing at the rate of 5 knots
+           |             |  submarine mines.         |            | per hour, and to prevent the
+           |             |                           |            | possibility of any collusion
+           |             |                           |            | between the operator and crew,
+           |             |                           |            | they left the ship a few moments
+           |             |                           |            | before the catastrophe. Operator
+           |             |                           |            | 5 miles distant. Probably
+           |             |                           |            | several mines were placed in the
+           |             |                           |            | form of a circle.
+           |             |                           |            |
+   July,   | Captain     | Experiment with his       | Brighton,  | The vessel completely destroyed.
+    1844.  |   Warner.   |  invisible shell, on a    |  England.  |
+           |             |  barque of 450 tons.      |            |
+           |             |                           |            |
+   Jan. 1, | Colonel S.  |Experiment with an electric| New York.  |Successful. The operator being at
+    1845.  |    Colt.    |  submarine mine.          |            | a distance of 40 miles from
+           |             |                           |            | where the explosion took place.
+           |             |                           |            |
+    1846.  | Professor   | Discovered the explosive  |     ..     |Brought into use for military
+           |   Schonbein.|  agent "gun-cotton."      |            | purposes about 1863, by
+           |             |                           |            | Professor Abel.
+           |             |                           |            |
+    1846.  | Sobrero.    | Discovered the explosive  |     ..     |Brought into use about 1863, for
+           |             |  agent nitro-glycerine.   |            | blasting purposes by M. Alfred
+           |             |                           |            | Nobel, a Swede.
+           |             |                           |            |
+    1854.  | Russians.   | Attempted destruction of  | Cronstadt. |Several torpedoes were exploded
+           |             |  the English men-of-war   |            | near these ships, but with no
+           |             |  _Merlin_ and _Firefly_,  |            | other results than a wetting to
+           |             |  by stationary submarine  |            | some of their men.
+           |             |  mines.                   |            |
+           |             |                           |            |
+  Feb. 18, |Confederates.|Federal gunboats attempting| America.   |Considerably delayed, caused by
+    1862.  |             |  to force the Savannah    |            | the submarine mines, but no
+           |             |  river.                   |            | actual damage done. This was
+           |             |                           |            | their first appearance in a
+           |             |                           |            | practical form during the civil
+           |             |                           |            | war.
+           |             |                           |            |
+  Dec. 13, |      "      | Destruction of the Federal|Yazoo River,|Two torpedoes exploded under her;
+    1862.  |             |  ironclad _Cairo_, by     |  America.  | vessel much shattered, and sunk
+           |             |  stationary torpedoes.    |            | in 12 minutes. First vessel
+           |             |                           |            | destroyed in this war.
+           |             |                           |            |
+  Feb. 28, |      "      | The Federal monitor       | Ogeechee   |She was saved from sinking by
+    1863.  |             |  _Montauk_, severely      |  River,    | being run on the mud, thus
+           |             |  damaged by a submarine   |  Georgia.  | enabling the hole to be
+           |             |  mine.                    |            | temporarily closed, and the
+           |             |                           |            | vessel taken to Port Royal.
+           |             |                           |            |
+  July 22, |      "      | The Federal ironclad      |Yazoo River.|The vessel went down in 15
+    1863.  |             |  gunboat _Baron de Kalb_, |            | minutes. As she was sinking a
+           |             |  sunk by a submarine mine.|            | second torpedo exploded under
+           |             |                           |            | her stern. No lives were lost.
+           |             |                           |            |
+   Aug. 8, |      "      | The Federal gunboat       |James River.|The ship was, at the time of the
+    1863.  |             |   _Commodore Barney_      |            | explosion, steaming 9 knots, and
+           |             |  severely damaged.        |            | ran into it, losing 20 men, and
+           |             |                           |            | being some what severely
+           |             |                           |            | damaged. It was an electric
+           |             |                           |            | submarine mine charged with 1750
+           |             |                           |            | lbs. gunpowder.
+           |             |                           |            |
+   Oct. 5, |      "      | Boat torpedo attack on the| Charleston.|Failed. It was made by a boat
+    1863.  |             |  Federal ship _Ironsides_.|            | armed with a spar torpedo with
+           |             |                           |            | 60 lbs. gunpowder.
+           |             |                           |            |
+    1863.  |      "      | Confederate steamers      |            |Owing to the shifting of the
+           |             |  _Marion_ and _Ettiwa_    |     "      | position of barrel torpedoes.
+           |             |  destroyed by their own   |            |
+           |             |  mines.                   |            |
+           |             |                           |            |
+    1863.  |      "      | Confederate flag of truce |James River.| The same cause.
+           |             |  boat _Shultz_.           |            |
+           |             |                           |            |
+  Feb. 17, |      "      | Boat torpedo attack on the|Charleston. |Successful, the ship being sunk.
+    1864.  |             |  Federal frigate          |            | A submarine boat was employed on
+           |             |  _Housatonic_.            |            | this occasion, and owing to her
+           |             |                           |            | running into the hole made by
+           |             |                           |            | her torpedo, went down with the
+           |             |                           |            | ship.
+           |             |                           |            |
+  March 6, |      "      | Boat torpedo attack on the|North Edisto|Failed, owing to the torpedo spar
+    1864.  |             |  Federal ship _Memphis_.  |River, South| being broken by the vessel's
+           |             |                           |  Carolina. | screw.
+           |             |                           |            |
+  April 1, |      "      | Destruction of the Federal| St. John's |This was effected by a floating
+    1864.  |             |  transport _Maple Leaf_.  |  River,    | torpedo.
+           |             |                           |  Florida.  |
+           |             |                           |            |
+  April 9, |      "      | Boat torpedo attack on the|James River.|The ship was severely damaged,
+    1864.  |             |  Federal ship _Minnesota_.|            | but not sunk. Spar torpedo,
+           |             |                           |            | charge 53 lbs. gunpowder.
+           |             |                           |            |
+  April 19,|      "      | Boat torpedo attack on the|Charleston. |Failed, owing to the boat being
+    1864.  |             |  Federal frigate _Wabash_.|            | discovered.
+           |             |                           |            |
+   May 6,  |      "      | Loss of the _Commodore    |James River.|Completely demolished by an
+    1864.  |             |  Jones_.                  |            | electric torpedo, 1750 lbs.
+           |             |                           |            | gunpowder. This part of the
+           |             |                           |            | river having been carefully
+           |             |                           |            | dragged.
+           |             |                           |            |
+  Aug. 5,  |Confederates.|Loss of the Federal monitor| Mobile Bay.|This occurred during the Federal
+    1864.  |             |  _Tecumseh_.              |            | attack on the defences of Mobile
+           |             |                           |            | Bay, the ship disappearing
+           |             |                           |            | almost instantaneously. The
+           |             |                           |            | captain and 70 of the crew were
+           |             |                           |            | killed.
+           |             |                           |            |
+  Oct. 27, |  Federals.  | Boat torpedo attack on the| Near       |The only Federal torpedo success
+    1864.  |             |  Confederate ironclad     |  Plymouth, | during the war. The boat was
+           |             |  _Albemarle_.             |  America.  | armed with the Wood and Lay
+           |             |                           |            | disconnecting spar torpedo. The
+           |             |                           |            | ship was sunk.
+           |             |                           |            |
+  Dec. 9,  |Confederates.| Loss of the Federal       | Roanoke    |The latter vessel was proceeding
+    1864.  |             |  steamers _Otsego_ and    |  River.    | to the assistance of the former.
+           |             |  _Bazeby_.                |            | Both were totally destroyed.
+           |             |                           |            |
+    1864.  | M. A. Nobel.| Introduction of dynamite. |    ..      |A modified form of the explosive
+           |             |                           |            |  nitro-glycerine.
+           |             |                           |            |
+    1864.  | Captain     |First series of experiments| Fiume,     |The idea of such a weapon
+           |  Lupuis and |   with the fish torpedo.  |  Austria.  | previously known, but not acted
+           |  Mr.        |                           |            | on.
+           |  Whitehead. |                           |            |
+           |             |                           |            |
+  Jan. 15, |Confederates.|Loss of the Federal monitor|Charleston. |Completely destroyed by a barrel
+    1865.  |             |  _Patapsco_.              |            | torpedo, sinking in a few
+           |             |                           |            | minutes. Sixty-two officers and
+           |             |                           |            | men drowned.
+           |             |                           |            |
+  March 1, |      "      |Loss of the Federal steamer|Near        |The place where this catastrophe
+    1865.  |             |  _Harvest Moon_.          | Georgetown.| occurred had been previously
+           |             |                           |            | swept for torpedoes.
+           |             |                           |            |
+  March 30 |      "      | Loss of two Federal       |Mobile Bay. |These losses occurred in the
+  to April,|             |  monitors, and three      |            | final attack on Mobile, at the
+   19 1865.|             |  gunboats.                |            | close of the war.
+           |             |                           |            |
+  Sept. 2, |Paraguayans. | Loss of the Brazilian war |Currupaity, |Completely destroyed by a
+    1866.  |             |  steamer _Rio Janeiro_.   |  Paraguay. | stationary torpedo at the
+           |             |                           |            | bombardment of Currupaity by the
+           |             |                           |            | Brazilian fleet.
+           |             |                           |            |
+    1874.  |  England.   | Adoption of the electric  |            |
+           |             |  light in the Navy.       |            |
+           |             |                           |            |
+   May 29, |  English.   | Torpedo attack by H.M.S.  |    ..      |This is the first Whitehead fish
+    1877.  |             |  _Shah_ on the Peruvian   |            | torpedo ever fired against an
+           |             |  ironclad _Huascar_.      |            | hostile ship. It failed, owing
+           |             |                           |            | to the _Huascar_ being at too
+           |             |                           |            | great a distance.
+           |             |                           |            |
+   May 12, |  Russians.  |Russian torpedo boat attack| Batoum.    |Failed. A Turkish ship was struck
+    1877.  |             |  on several Turkish ships.|            | by a towing torpedo, but it
+           |             |                           |            | failed to explode.
+           |             |                           |            |
+   May 26, |      "      | Russian torpedo boat      | Matchines, |Successful. A Turkish monitor,
+    1877.  |             |  attack on the Turkish    |  River     | _Duba Saife_, was sunk.
+           |             |  ships _Fettu Islam_,     |  Danube.   |
+           |             |  _Duba Saife_, and _Kilidj|            |
+           |             |  Ali_.                    |            |
+           |             |                           |            |
+   June 9, |      "      | Russian torpedo boat      | Sulina,    |Failed. The Russian torpedo boat
+    1877.  |             |  attack on the Turkish    |  mouth  of | No. 1 was sunk, and her
+           |             |  ironclads _Feteh Bulend_,|  the       | commander, Lieutenant Poutschin,
+           |             |  _Moocardemikhair_, and   |  Danube.   | with his crew, taken prisoner.
+           |             |  _Idglalieh_.             |            | The attack was made by six
+           |             |                           |            | boats.
+           |             |                           |            |
+  June 20, |      "      | Turkish monitor attacked  |Rutschuk, on|Failed. The officer in command of
+    1877.  |             |  by the Russian spar      | the Danube.| the boat being severely wounded,
+           |             |  torpedo boat_Choutka_.   |            | and the torpedo wires cut. This
+           |             |                           |            | attack was made in the daytime.
+           |             |                           |            |
+  June 23, |      "      | Two Russian torpedo boats |Mouth of the|Failed, owing to the spirited
+    1877.  |             |  attacked a Turkish       |  Aluta,    | defence on the part of the
+           |             |   monitor.                |  Danube.   | Turks. Another day affair.
+           |             |                           |            |
+  Aug. 22, |      "      | The Turkish ironclad      | Soukoum    |Failed. The captain of the
+    1877.  |             |  _Assari Shefket_ attacked|   Kaleh.   | _Assari Shefket_ had placed
+           |             |  by four Russian torpedo  |            | guard boats in advance of his
+           |             |  boats.                   |            | ship, by which he was warned of
+           |             |                           |            | the approach of the torpedo
+           |             |                           |            | boats, and so enabled to foil
+           |             |                           |            | the attack by a well-directed,
+           |             |                           |            | hot fire.
+           |             |                           |            |
+  Oct. 10, |      "      | Loss of Turkish gunboat   | Sulina.    |The gunboat was sunk by striking
+    1877.  |             |  _Suna_ at the Russian    |            | an electro-contactmine, placed
+           |             |  attack on Sulina.        |            | by the Russians about 3/4 mile
+           |             |                           |            | above the Turkish defences.
+           |             |                           |            | About fifteen officers and men
+           |             |                           |            | killed and wounded.
+           |             |                           |            |
+  Dec. 27, |      "      | Turkish squadron attacked | Batoum.    |Failed. The Russians fired two
+    1877.  |             |  by four Russian torpedo  |            | Whitehead fish torpedoes (the
+           |             |  boats, two being armed   |            | first attack of this nature
+           |             |  with the Whitehead fish  |            | during the war), both of which
+           |             |  torpedo.                 |            | were picked up by the Turks.
+           |             |                           |            |
+  Jan. 25, |      "      |Attack on Turkish ships by | Batoum.    |Successful. A Turkish revenue
+    1878.  |             | two Russian torpedo boats,|            | steamer on guard being sunk.
+           |             | armed with the Whitehead  |            | Final torpedo attack made in the
+           |             | fish torpedo.             |            | Russo-Turkish war (1877-78).
+  ---------+-------------+---------------------------+------------+---------------------------------
+
+FOOTNOTES:
+
+[Footnote Y: See page 92.]
+
+
+
+
+ERRATA.
+
+On Page 7 (line 11) insert words "could be destroyed" after "anchor."
+
+On Page 284, (Middle of page) "Fig. 176" should be "Fig. 168."
+
+On Page 285 (4th line from bottom) "e" should be "d."
+
+
+
+
+INDEX.
+
+
+A.
+
+  Abel, experiments by Professor, 207
+  Abel's detonation experiments, 216
+  ---- high tension fuzes, 37
+  ---- mechanical primer, 23
+  Action, chemical, 269
+  ---- ----, in a Daniell cell, 274
+  ---- ---- single fluid cell, 273
+  Adjustments of Whitehead's fish torpedo, the, 136
+  Admiral Porter's torpedo ship _Alarm_, 159
+  ---- ----, the armament of, 160
+  Adoption of the fish torpedo, the invention and, 131
+  Advantages of electrical submarine mines, the, 28
+  ---- ---- mechanical mines, the, 17
+  Agents, torpedo explosive, 217
+  Air pump, the, 260
+  _Alarm_, Admiral Porter's torpedo ship, 159
+  _Albemarle_, destruction of the, 191
+  Aluta, the Russian torpedo boat attack off the, 200
+  American Civil War, the, 189
+  ---- ----, mechanical mines in the, 16
+  ---- ----, torpedoes during the, 115
+  ---- ----, submarine mines during the, 27
+  ---- extempore drifting torpedoes, 119
+  Apparatus, directions for using the diving, 261
+  ----, firing keys and shutter, 80
+  ----, Siemens' electric light, 241
+  ---- ----, conducting wires for, 247
+  ---- ----, rotation of armatures in, 246
+  ---- ----, wear and tear of, 247
+  ----, the shutter, 82
+  ---- used with a circuit breaker, shutter, 83
+  Application of Ohm's law, the, 276
+  ---- ---- the electric light, the, 256
+  Arcs, firing by intersectional, 71
+  _Argus_, Fulton's attempt against the, 6
+  Armatures in Siemens' electric light apparatus, rotation of, 246
+  Armoured cables, single cored, 43
+  Armstrong's system of electrical testing, 107
+  Arrangement of earth plates, Brown's, 100
+  ---- ---- wires in McEvoy's spar torpedo, 155
+  Arrangements, Steward's safety cock, 25
+  Astatic galvanometer, the, 87
+  Attack with Harvey's torpedoes, methods of, 127
+  Attacks, boat torpedo, 191
+  ---- ----, methods of protecting ships against, 180
+  Austrian method of mooring, the, 56
+  ---- ---- testing, the, 109
+  ---- self-acting circuit closers, 64
+  ---- testing table, the, 108
+  ---- torpedo experiments, 220
+  ---- ---- launches, Thornycroft's, 165
+  ---- war, torpedo operations during the, 192
+  Austro-Italian war, torpedo operations during the, 188
+  Automatic arrangements, 10
+  ---- electric lamps, 248
+
+  B.
+  Balance, Wheatstone's, 97
+  ---- ----, manipulation of, 99
+  ---- ----, measurement of resistances by, 98
+  Barrel torpedoes, 19
+  Batoum, Russian torpedo boat attack at, 195, 202
+  Batteries, bichromate, 77
+  ----, double fluid, 274
+  ----, firing, 75
+  Batteries, Leclanché's Voltaic, 77
+  ----, Menotti test, 79
+  ----, signalling, 78
+  ---- ----, Daniell's, 78
+  ----, single and double fluid, 272
+  ----, telegraph, 79
+  ----, Voltaic, 79
+  ----, Von Ebner's, 76
+  Battery test for electro-motive force, Voltaic, 105
+  ---- ---- internal resistance, Voltaic, 104
+  ---- ---- potential, Voltaic, 104
+  Beardslee's high tension fuze, 36
+  ---- joint, 46
+  Bearings, firing by cross, 70
+  Bichromate batteries, 77
+  Boat, Bushnell's submarine, 2, 184
+  ----, Confederate submarine, 185
+  ----, experiment at Cherbourg, torpedo, 170
+  ----, French submarine, a, 185
+  ----, Lay torpedo, the, 141
+  ---- ----, capabilities of the, 147
+  ---- ----, clearing obstructions with the, 151
+  ---- ----, improved form of the, 153
+  ---- ----, launching the, 147
+  ---- ----, method of sinking and raising the, 149
+  ---- ----, used as a tug, 150
+  ---- ---- to clear away mines, 152
+  ----, _Lightning_, Thornycroft's torpedo, 168
+  ----, torpedo, attack at Batoum, 195, 202
+  ---- ---- Rustchuk, 200
+  ---- ---- Soukoum Kaleh, 201
+  ---- ---- Soulina, 198
+  ---- ---- off Matchin, 196
+  ---- ---- the Aluta, 200
+  ---- ----, the final, 203
+  ---- ----, attacks, 180, 191
+  ---- ----, methods of protecting ships against, 180
+  ---- ----, protective, Fosberry's patent, 182
+  Boats, submarine, 183
+  ---- ----, qualifications essential to, 184
+  ----, torpedo, 162
+  ---- ----, English, 173
+  ---- ----, Herreshoff's, 178
+  ---- ----, ordinary type of, 179
+  ---- ----, Schibau's Russian, 178
+  ---- ----, Spanish, 175
+  ---- ----, Thornycroft's, 163
+  ---- ----, Yarrow's, 172
+  Booms, construction of, 110
+  ----, defence of harbours by, 110
+  Boots for divers, 261
+  Boxes, junction, 51
+  ---- ----, for multiple cables, 52
+  ---- ---- single cored cables, 52
+  ----, resistance, 97
+  Brakes for Harvey's torpedoes, 123
+  Breaker, the circuit, 62
+  Breast-plate for divers, 260
+  Brook's torpedoes, 19
+  Brown's arrangement of earth plates, 100
+  Buoys for Harvey's torpedoes, 122
+  Bushnell, the inventor of torpedoes, 2
+  Bushnell's drifting torpedoes, 2
+  ---- mode of ignition, 2
+  ---- submarine boat, 2, 184
+
+  C.
+  Cable, Colt's electric, 7
+  ---- cutters, Fulton's, 5
+  Cables, circuit closer, 42
+  ----, creeping for electric, 112
+  ----, defects observed in the conductivity of, 103
+  ----, Hooper's, 41
+  ----, insulated electric, 38
+  ----, insulation test for electric, 102
+  ----, jointing electric, 44
+  ----, junction boxes for multiple, 52
+  ---- ---- single cored, 52
+  ----, land service, 43
+  ----, multiple, 42
+  ----, sea service, 43
+  ----, Siemens' electric, 40
+  ----, Silvertown electric, 41
+  ----, single cored armoured, 42
+  ---- ---- unarmoured, 43
+  ----, special, 43
+  ----, test of electrical resistance of, 104
+  _Cairo_, the loss of the, 189
+  Calland and Marié-Davy batteries, description of the, 275
+  Capabilities of Lay's torpedo boat, 147
+  ---- ---- Whitehead's fish torpedo, 134
+  Carlscrona, experiments with countermines at, 237
+  ----, torpedo experiments at, 220, 224, 232
+  Case, conical-shaped torpedo, 32
+  ----, cylindrical-shaped torpedo, 32
+  ----, form and construction of torpedo, 31
+  ----, spherical-shaped torpedo, 32
+  Cell, action in a single fluid, 273
+  ----, chemical action of a Daniell, 274
+  ----, definition and properties of a Voltaic, 269
+  ----, description of a Menotti, 78
+  ----, tests for insulation, sea, 106
+  ---- ----, sea, 100
+  Charges, size of torpedo, 218
+  Chatham, torpedo experiments at, 220
+  Chemical action, 269
+  ---- fuzes, 23
+  ---- ----, defects of, 24
+  Cherbourg, torpedo boat experiment at, 170
+  Circuit breakers, 62
+  ---- closer cables, 43
+  ---- closers, Austrian self-acting, 64
+  ---- ----, electro-contact mine, 63
+  ---- ----, Mathieson's inertia, 61
+  ---- ----, improvements in, 63
+  ---- ---- spiral spring, 63
+  ---- ----, McEvoy's mercury, 65
+  ---- ---- weight magneto, 66
+  ---- ----, the use of, 60
+  ----, closing the electric, 60
+  ---- resistances, 276
+  ----, short, 268
+  ----, the electric, 267
+  Civil war, torpedo operations during the American, 189
+  ----, torpedoes in the American, 115
+  Clearing a passage through torpedo defences, 111
+  Coil galvanometer, the three, 88
+  Colt, experiments by Colonel, 7
+  Colt's electric cable, 7
+  ---- reflector, 7
+  _Commodore Jones_, the loss of the, 189
+  Commutators or switch plates, 96
+  Comparing electro-motive forces, 94
+  Composition, Rain's detonating, 23
+  Compounds, explosive, 208
+  Concentration of the electric light, 251
+  Condenser, definition of a, 279
+  Conductivity of cables, defects observed in the, 103
+  ----, test of platinum wire fuze for, 101
+  Conductors, 266
+  Confederate submarine boat, 185
+  Connections of switch plates, 100
+  Construction of booms, 110
+  ---- ---- torpedo case, 31
+  Copenhagen, torpedo experiments at, 223
+  Countermining, 112
+  Countermines, experiments with, 235
+  ---- ---- at Carlscrona, 237
+  ---- ---- Stokes Bay, 236
+  ---- ---- in the Medway, 236
+  Coupling dynamo-electric machines, methods of, 254
+  Creeping for electric cables, 112
+  Crimean war, submarine mines during the, 27
+  ---- ----, torpedo operations during the, 187
+  Crinoline for divers, 261
+  Cross bearings, firing by, 70
+  Current, direction of, 272
+  ----, measuring the intensity of a, 95
+  ----, the Voltaic, 270
+
+  D.
+  Daniell's signalling battery, 78
+  Defects observed in the conductivity of cables, 103
+  ---- of chemical fuses, 24
+  ---- electrical submarine mines, 29
+  Defence of harbours by booms, 110
+  ----, ship, 10
+  Defences, clearing a passage through torpedo, 111
+  Defensive purposes, Harvey's torpedo for, 129
+  ---- torpedo operations, Russian, 193
+  ---- ----, Turkish, 193
+  ---- ---- warfare, 13
+  Definition and properties of a Voltaic cell, 269
+  ---- of a condenser, 279
+  ---- potential, 270
+  ---- the ohm, 281
+  ---- ---- term explosion, 204
+  ---- ---- explosive force, 204
+  ---- ---- polarization, 273
+  Description of a frictional electric machine, 278
+  ---- ---- series of firing keys, 81
+  ---- ---- Yarrow's torpedo boat, 172
+  ---- ---- Calland's and Marié-Davy's batteries, 275
+  ---- ---- Siemens' electric light apparatus, 241
+  ---- ---- Whitehead's fish torpedo, 133
+  _Destroyer_, Ericsson's torpedo vessel, 160
+  Destruction of passive obstructions, the, 113
+  ---- ---- the _Albemarle_, 191
+  ---- ---- _Duba Saife_, 197
+  ---- ---- _Suna_, 194
+  Detector galvanometer, the, 88
+  Detonating composition, Rain's, 23
+  Detonation, 206
+  ---- experiments, Abel's, 216
+  ----, theory of, 206
+  Dielectric, gutta percha as a, 38
+  ----, meaning of, 279
+  Differential galvanometer, the, 88
+  Direction of current, 272
+  Directions for using the diving apparatus, 261
+  Discharge test, the, 103
+  Disconnector, the, 53
+  Diver, dressing the, 262
+  Divers, boots for, 261
+  ----, breast plate for, 260
+  ----, crinoline for, 261
+  ----, helmet for, 260
+  ----, ladder for, 260
+  Diving, 259
+  ---- dress, the, 260
+  ----, signals employed in, 263
+  _Dorothea_, Fulton's destruction of the, 4
+  Double fluid batteries, 274
+  ---- ----, single and, 272
+  Drifting torpedoes, 116
+  ---- ----, American extempore, 119
+  ---- ----, Bushnell's, 2
+  ---- ----, Fulton's, 5
+  ---- ----, Lewis's, 117
+  ---- ----, McEvoy's, 118
+  Dualin, 216
+  _Duba Saife_, destruction of the, 197
+  Duplex spar torpedo, McEvoy's, 154
+  ---- ----, arrangement of wires in, 155
+  Dutch torpedo launches, Thornycroft's, 168
+  ---- ----, Yarrow's, 172
+  Dynamite, 211
+  Dynamo-electric machines, methods of coupling, 254
+  ---- machine, Siemens' low tension, 75
+
+  E.
+  Earth plates, Browne's arrangement of, 100
+  Effect compared, explosive force and, 204
+  Efficiency of Thornycroft's boat engines, 171
+  Electric cables, creeping for, 112
+  ---- ----, Hooper's, 41
+  ---- ----, insulated, 38
+  ---- ----, insulation test for, 102
+  ---- ----, jointing, 44
+  ---- ----, Siemens', 40
+  ---- ----, Silvertown, 41
+  ---- circuit, closing the, 60
+  Electric circuit, the, 267
+  ---- fuses, 33
+  ---- lamps, automatic, 248
+  ---- ----, Siemens' patent, 248
+  ---- light apparatus, Siemens', 241
+  ---- ----, conducting wires for, 247
+  ---- ----, light produced by, 244
+  ---- ----, rotation of armatures in, 246
+  ---- ----, wear and tear of, 247
+  ---- ----, application of the, 256
+  ---- ----, concentration of the, 251
+  ---- ----, precautions in manipulating, 252
+  ---- ----, self-acting shunt for Siemens', 245
+  ---- ----, the, 239
+  ---- machine, description of a frictional, 278
+  ---- machines, methods of coupling dynamo, 254
+  Electrical resistance of cables, test of the, 104
+  ---- resistances, measuring, 93
+  ---- submarine mines, 10, 27
+  ---- ----, advantages of, 28
+  ---- ----, defects of, 22
+  ---- ----, mooring, 54
+  ---- ----, rules for using, 29
+  ---- test of insulated joints, 104
+  ---- testing, Armstrong's system of, 107
+  ---- tests, 85
+  Electricity, frictional, 278
+  ----, methods of generating, 269
+  ----, theory of, 265
+  Electro-contact mines, circuit closers for, 63
+  Electrolytes, 271
+  Electro-positive and electro-negative, the terms, 271
+  Electro-magnet, the, 281
+  Electro-mechanical mines, Russian, 68
+  Electrometers, 86
+  ----, Thomson's quadrant, 86
+  Electro-motive force, 270
+  ---- ----, Voltaic battery test for, 105
+  ---- forces, comparing, 94
+  Employment of torpedo ships, the, 158
+  Engines, efficiency of Thornycroft's boat, 171
+  England, torpedo experiments in, 222
+  English service platinum wire fuse, the, 33
+  ---- torpedo boats, Yarrow's, 173
+  Ericsson's torpedo vessel _Destroyer_, 160
+  Experiment at Cherbourg, torpedo boat, 170
+  ---- with a torpedo boat, flotation, 171
+  Experiments, Abel's detonation, 216
+  ---- by Professor Abel, 207
+  ---- ---- Roux and Sarrau, 207
+  ----, Colt's torpedo, 7
+  ----, Fulton's practical, 5
+  ----, torpedo, at Carlscrona, 220, 224, 232
+  ---- ---- Chatham, 220
+  ---- ---- Copenhagen, 223
+  ---- ---- Kiel, 222
+  ---- ---- Pola, 231
+  ---- ---- Portsmouth, 229, 233
+  ---- ----, Fulton's French, 3
+  ---- ----, in Austria, 220
+  ---- ---- England, 222
+  ---- ---- Turkey, 232
+  ---- with countermines, 235
+  ---- ---- at Carlscrona, 237
+  ---- ---- Stokes Bay, 236
+  ---- ---- in the Medway, 236
+  Explosion, definition of the term, 204
+  Explosive agents, torpedo, 217
+  ---- compounds, 208
+  ---- force and effect compared, 204
+  ---- ----, definition of the term, 204
+  ---- mixtures, 208
+  ---- substance, physical state of the, 204
+  Explosions, illustrated torpedo, 218
+  Extempore drifting torpedoes, American, 119
+  ---- high tension fuzes, 37
+  ---- ----, Fisher's, 37
+  ---- mechanical mine, 21
+
+  F.
+  Failure of offensive torpedoes, the, 8
+  Fastest vessel in the world, the, 177
+  Final Russian torpedo boat attack, the, 203
+  Firing batteries, 75
+  ---- by cross bearings, 70
+  ---- ---- intersectional arcs, 71
+  ---- ---- observation, 69
+  ---- ---- preconcerted signal, 71
+  ---- Harvey's torpedoes, mode of, 121
+  ---- keys, 80
+  ---- ----, description of a series of, 81
+  ---- ----, Morse, 81
+  ----, mode of, 205
+  ---- ----, in 1829, 6
+  ---- Whitehead torpedoes, Thornycroft's method of, 140
+  Fish torpedo, adjustments of Whitehead's, 136
+  ---- ----, description of the, 133
+  ---- ----, invention and adoption of the, 131
+  ---- ----, methods of projecting the, 138
+  ---- ----, the mode of ignition of the, 135
+  Fish torpedoes in war, employment of, 133
+  ---- ----, Thornycroft's method of firing, 140
+  ---- ----, Woolwich, 140
+  Fisher's extempore high tension fuze, 37
+  Floating torpedoes, 116
+  Flotation experiment with a torpedo boat, 171
+  Fluid batteries, double, 274
+  ---- ----, single and double, 272
+  Fluid cell, action in a single, 273
+  Force compared, explosive effect and, 204
+  ----, definition of the term explosive, 204
+  ----, electro-motive, 270
+  ----, Voltaic battery test for electro-motive, 105
+  Forces, comparing electro-motive, 94
+  Fore and aft mooring, 56
+  Form of Lay's torpedo boat, an improved, 153
+  ---- ---- torpedo case, 31
+  Fosberry's patent torpedo boat protective, 182
+  Frame torpedoes, 18
+  Frames, projecting, 111
+  Franco-German war, torpedo operations during the, 192
+  ---- ----, torpedoes in the, 13
+  French submarine boat _Plongeur_, 185
+  ---- torpedo launches, Thornycroft's, 165, 169
+  ---- towing torpedoes, 131
+  Frictional electric machine, description of a, 278
+  ---- electricity, 278
+  Fulminate of mercury, 215
+  Fulton, Robert, 2
+  Fulton's attempt against the _Argus_, 6
+  ---- block ship, 5
+  ---- cable cutters, 5
+  ---- destruction of the _Dorothea_, 4
+  ---- drifting torpedoes, 5
+  ---- failures, 2
+  ---- French torpedo experiments, 3
+  ---- harpoon torpedoes, 5
+  ---- practical experiments, 5
+  ---- return to America, 4
+  ---- spar torpedoes, 5
+  ---- stationary submarine mines, 5
+  Fuzes, Abel's, 37
+  ----, Beardslee's, 35
+  ----, chemical, 23
+  ----, defects of chemical, 24
+  ----, electric, 33
+  ----, extempore, 37
+  ----, extempore, Fisher's, 37
+  ---- for conductivity, test of platinum wire, 101
+  ----, high tension, 34
+  ----, improved form of Jacobi's, 24
+  ----, McEvoy's percussion, 24
+  ----, percussion, 23
+  ----, platinum wire, 33
+  ----, ----, English service, 33
+  ----, ----, McEvoy's, 34
+  ----, sensitive, 23
+  ----, Statham's, 35
+  ----, test of resistance of platinum wire, 101
+  ----, testing high tension, 102
+  ----, Von Ebner's, 36
+
+  G.
+  Galvanometer, astatic, 87
+  ----, detector, 88
+  ----, differential, 88
+  ----, tables, Siemens' universal, 287
+  ----, thermo, 89
+  ----, Thomson's reflecting, 87
+  ----, three coil, 88
+  ----, universal, Siemens', 89
+  Generating electricity, methods of, 269
+  German torpedo vessel _Uhlan_, the, 158
+  Gun, the Nordenfelt torpedo, 257
+  ----, Hotchkiss torpedo, 259
+  Gun-cotton, 212
+  Gunpowder, 208
+  Guns, torpedo, 257
+  Gutta-percha as a dielectric, 38
+
+  H.
+  Harbours by booms, defence of, 110
+  Harpoon torpedoes, Fulton's, 5
+  Harvey's towing torpedo, 119
+  ---- ----, brakes for, 123
+  ---- ----, buoys for, 122
+  ---- ----, for defensive purposes, 129
+  ---- ----, launching, 123
+  ---- ----, methods of attack with, 127
+  ---- ----, mode of firing, 121
+  ---- ----, tactics with, 127
+  ---- ----, the value of, 129
+  Helmet for divers, 260
+  Herreshoff's torpedo boats, 178
+  High tension fuzes, 102
+  Hooper's electric cables, 41
+  ---- material, 39
+  Horsley's powder, 216
+  Hotchkiss torpedo gun, the, 259
+
+  I.
+  Ignition, Bushnell's mode of, 2
+  ---- of Whitehead's fish torpedo, mode of, 135
+  Illustrated torpedo explosions, 218
+  Improved form of Lay's torpedo, an, 153
+  India rubber tube joint, the, 45
+  Inertia circuit closer, Mathieson's, 61
+  ---- ----, improvements in, 63
+  Instrument and observing telescope, shutter, 84
+  Instruments used in testing, 85
+  Insulated electric cables, 38
+  ---- joints, electrical test of, 104
+  Insulation, sea cell tests for, 106
+  ---- test for electric cables, 102
+  Insulators, 268
+  Intensity of a current, measuring the, 95
+  Internal resistance, Voltaic battery test for, 104
+  Intersectional arcs, firing by, 71
+  Invention and adoption of the fish torpedo, the, 131
+  Italian torpedo launches, Thornycroft's, 168
+
+  J.
+  Jacobi's fuze, improved form of, 24
+  Jar, the Leyden, 279
+  Jointing electric cables, 44
+  Joints, Beardslee's, 46
+  ----, electrical test of insulated, 104
+  ----, india rubber tube, 45
+  ----, Mathieson's, 45
+  ----, McEvoy's, 46
+  ----, Nicholl's metallic, 45
+  ----, rules to be observed in forming, 51
+  ----, Siemens' permanent, 47
+  _Jones_, the loss of the _Commodore_, 189
+  Junction boxes, 51
+  ---- ---- for multiple cables, 52
+  ---- ---- single cored cables, 52
+  ---- ----, T, 53
+
+  K.
+  Keys, firing, 80
+  ---- ----, description of a series of, 81
+  ---- ----, Morse, 81
+  Kiel, torpedo experiments at, 222
+  Knowledge, theoretical, 8
+
+  L.
+  Ladder for divers, 261
+  ---- mooring, 55
+  Lamps, automatic electric, 248
+  ----, Siemens' patent electric, 248
+  Land service cables, 43
+  Launch, description of a Yarrow torpedo, 172
+  ---- for placing moorings, steam, 58
+  Launches, Thornycroft's torpedo, 163
+  ---- ---- Austrian and French torpedo, 165
+  ---- ---- Dutch and Italian torpedo, 168
+  ---- ---- French torpedo, 169
+  ---- ---- Norwegian torpedo, 163
+  ---- ---- Swedish and Danish torpedo, 165
+  ----, Yarrow's Dutch torpedo, 173
+  ---- ---- Russian torpedo, 172
+  Launching Harvey's torpedo, mode of, 123
+  ---- Lay's torpedo boat, 147
+  Law, the application of Ohm's, 276
+  Lay's torpedo boat, 141
+  ---- ----, an improved form of, 153
+  ---- ----, capabilities of, 147
+  ---- ----, launching, 147
+  ---- ----, method of sinking and raising, 149
+  ---- ----, used as a tug, 150
+  ---- ----, in clearing obstructions, 151
+  ---- ----, to clear away mines, 152
+  Leclanché's Voltaic battery, 77
+  Lewis's drifting torpedo, 117
+  Leyden jar, the, 279
+  Light, Siemens' electric, 241
+  ---- ----, conducting wires for, 247
+  ---- ----, concentration of, 251
+  ---- ----, precautions in manipulating, 252
+  ---- ----, rotation of armatures in, 246
+  ---- ----, wear and tear of, 247
+  ----, the electric, 239
+  ---- ----, application of, 256
+  _Lightning_, Thornycroft's torpedo boat, 168
+  Lithofracteur, 216
+  Locomotive torpedoes, 131
+  Loss of the _Cairo_, 189
+  ---- ---- _Commodore Jones_, 189
+
+  M.
+  Machine, description of a frictional electric, 278
+  ----, Siemens' low tension dynamo-electric, 75
+  Machines, methods of coupling dynamo-electric, 254
+  Magnet, the electro, 281
+  Magnetism, 279
+  Magneto circuit closer, McEvoy's weight, 66
+  Magnets, permanent, 280
+  Main system, McEvoy's single, 283
+  Manipulation of Wheatstone's balance, the, 98
+  Marié-Davy battery, description of the, 275
+  Matchin, Russian torpedo boat attack at, 196
+  Material, Hooper's insulating, 39
+  Mathieson's cement safety plug, 21
+  ---- circuit closer, inertia, 61
+  ---- ----, improvements in, 63
+  ---- ----, spiral spring, 63
+  ---- joint, 45
+  McEvoy's drifting torpedo, 118
+  ---- duplex spar torpedo, 154
+  ---- improved Singer's mine, 20
+  ---- joint, 46
+  ---- mechanical mine, 22
+  ---- ---- primer, 21
+  ---- ---- Turk's head, 53
+  ---- mercury circuit-closer, 65
+  ---- papier maché safety plug, 22
+  ---- percussion fuzes, 24
+  ---- platinum wire fuzes, 34
+  ---- single main system, 283
+  ---- weight magneto circuit-closer, 66
+  Measurement of resistance by Wheatstone's balance, 98
+  Measuring electrical resistances, 93
+  ---- the intensity of a current, 95
+  Mechanical mines, 10, 16
+  ---- ----, advantages of, 17
+  ---- ----, best kinds of, 17
+  ---- ----, extempore, 21
+  ---- ----, for coast defence, 16
+  ---- ----, in the American war, 16
+  ---- ----, McEvoy's, 22
+  ---- ---- improved Singer's, 20
+  ---- ----, mooring, 26
+  ---- ----, Russian electro, 68
+  ---- ----, Singer's, 19
+  Mechanical primer, Abel's, 23
+  ---- ----, McEvoy's, 21
+  ---- tests, 85
+  Medway, experiments with countermines in the, 236
+  Menotti cell, description of the, 78
+  ---- test batteries, 79
+  Menzing's towing torpedo, 130
+  Mercury circuit-closer, McEvoy's, 65
+  ----, fulminate of, 215
+  Metallic joint, Nicholl's, 45
+  Method of carrying fish torpedoes, Thornycroft's, 140
+  ---- ---- sinking and raising Lay's torpedo, 149
+  ---- ---- testing, the Austrian, 109
+  Methods of attack with Harvey's torpedoes, 121
+  ---- ---- coupling dynamo-electric machines, 254
+  ---- ---- generating electricity, 269
+  ---- ---- protecting ships against torpedo attacks, 180
+  ---- ---- projecting Whitehead's fish torpedo, 135
+  Mines, submarine, electrical, 10, 27
+  ---- ----, advantages of, 28
+  ---- ----, defects of, 29
+  ---- ----, mooring, 54
+  ---- ----, in the American war, 27
+  ---- ----, electro-contact, circuit-closers for, 63
+  ---- ----, Fulton's stationary, 5
+  ---- ----, mechanical, 10, 16
+  ---- ----, advantages of, 17
+  ---- ----, extempore, 21
+  ---- ----, McEvoy's, 22
+  ---- ----, improved Singer's, 20
+  ---- ----, mooring, 26
+  ---- ----, Russian electro, 68
+  ---- ----, Singer's, 19
+  ---- ----, rules to be observed in planting, 74
+  ---- ----, sweeping for, 112
+  Mixtures, explosive, 208
+  Mode of firing Harvey's torpedoes, 121
+  ---- ----, in 1829, 6
+  Monitor _Duba Saife_, destruction of the Turkish, 197
+  Mooring, Austrian method of, 56
+  ---- electrical submarine mines, 54
+  ----, fore and aft, 56
+  ----, ladder, 55
+  ----, launch for placing, 58
+  Mooring mechanical mines, 26
+  ----, single rope, 56
+  Morse firing keys, 81
+  Multiple cables, 43
+  ---- ----, junction boxes for, 52
+
+  N.
+  Nicholl's metallic joint, 45
+  Nitro-glycerine, 209
+  Nordenfelt torpedo gun, the, 257
+  Norwegian torpedo launches, Thornycroft's, 163
+
+  O.
+  Observation, firing by, 69
+  ---- ----, Prussian system of, 73
+  Observing telescope, shutter apparatus and, 84
+  Obstructions, destruction of passive, 113
+  ----, Lay's torpedo in clearing away, 151
+  Offensive torpedo operations, Russian and Turkish, 195
+  ---- ---- warfare still in its infancy, 115
+  ---- torpedoes, failure of, 8, 11
+  ---- ----, general remarks on, 156
+  Ohm, definition of the, 281
+  Ohm's law, application of, 276
+  Operations, torpedo, 187
+  ---- ----, during the American civil war, 189
+  ---- ---- Austrian war, 192
+  ---- ---- Austro-Italian war, 188
+  ---- ---- Crimean war, 187
+  ---- ---- Franco-German war, 192
+  ---- ---- Paraguayan war, 191
+  ---- ---- Russo-Turkish war, 192
+  ---- ---- defensive, Russian, 193
+  ---- ----, Turkish, 193
+  ---- ---- offensive, Turkish and Russian, 195
+  Ordinary type of torpedo boat, the, 179
+  Ottoman fleet, cause of failure of the, 14
+  Outrigger torpedoes, spar or, 154
+
+  P.
+  Papier maché safety plug, McEvoy's, 22
+  Paraguayan war, torpedo operations during the, 191
+  Passage through torpedo defences, clearing a, 111
+  Passive obstructions, destruction of, 113
+  Patent electric lamp, Siemens', 248
+  ---- torpedo boat protective, Fosberry's, 182
+  Percussion fuzes, 23
+  ---- ----, McEvoy's, 24
+  Permanent joint, Siemens', 47
+  ---- magnets, 280
+  Physical state of the explosive substance, the, 204
+  Picric powder, 209
+  Planting submarine mines, rules to be observed in, 74
+  Plates, Brown's arrangement of earth, 100
+  ----, connections of switch, 100
+  Platinum wire fuze for conductivity, test of, 101
+  ---- ----, test of resistance of, 101
+  ---- ---- fuzes, 33
+  ---- ----, English service, 33
+  ---- ----, McEvoy's, 34
+  _Plongeur_, French submarine boat, 185
+  Plug, Mathieson's cement safety, 21
+  ----, McEvoy's papier maché safety, 22
+  Pola, torpedo experiments at, 231
+  Polarization, definition of the term, 273
+  Porter's torpedo ship _Alarm_, Admiral, 159
+  Portsmouth, torpedo experiments at, 229, 233
+  Potential, definition of, 270
+  ----, Voltaic battery test for, 104
+  Powder, Horsley's, 216
+  ----, picric, 209
+  Precautions in manipulating the electric light, 252
+  Primer, Abel's mechanical, 23
+  ----, McEvoy's, 21
+  Projecting frames for torpedo ship defence, 111
+  ---- Whitehead's fish torpedo, methods of, 138
+  Propeller, Thornycroft's screw, 170
+  Properties of a Voltaic cell, definition and, 269
+  Prussian system of firing by observation, the, 73
+
+  Q.
+  Quadrant electrometers, Thomson's, 86
+  Qualifications essential to submarine boats, the, 184
+
+  R.
+  Rain's detonating composition, 23
+  Reflecting galvanometer, Thomson's, 87
+  Reflector, Colt's, 7
+  Remarks on offensive torpedoes, general, 156
+  Resistance boxes, 97
+  ---- of cables, test of electrical, 104
+  ---- platinum wire fuze, test of, 101
+  ----, Voltaic battery test for internal, 104
+  Resistances by Wheatstone's balance, measurement of, 98
+  ----, circuit, 276
+  ----, measuring electrical, 93
+  Rheostat, the, 96
+  Rope mooring, single, 56
+  Rotation of armatures in Siemens' electric light apparatus, 246
+  Roux and Sarrau, experiments by, 207
+  Rules in connection with submarine mines, 29
+  ---- to be observed in forming cable joints, 51
+  ---- ---- planting mines, 74
+  Russian and Turkish offensive torpedo operations, 194
+  ---- defensive torpedo operations, 193
+  ---- electro-mechanical mines, 68
+  ---- torpedo boat attack at Batoum, 115, 202
+  ---- ---- Matchin, 196
+  ---- ---- Rustchuk, 200
+  ---- ---- Soukoum Kaleh, 201
+  ---- ---- Soulina, 198
+  ---- ---- off the Aluta, 200
+  ---- ----, the final, 203
+  ---- ---- boats, Schibau's, 178
+  ---- ---- launch, Yarrow's, 172
+  ---- torpedoes, 193
+  Russo-Turkish war, torpedo operations during the, 192
+  ---- ----, torpedoes during the, 14, 115
+  Rutschuk, Russian torpedo attack at, 200
+
+  S.
+  Safety cock arrangement, Steward's, 25
+  ---- plug, Mathieson's cement, 21
+  ---- ---- McEvoy's papier maché, 22
+  Schibau's Russian torpedo boats, 178
+  Science of torpedo warfare, the, 15
+  Sea cell test for insulation, 106
+  ---- ---- tests, 100
+  ---- service cables, 43
+  Second class torpedo launches, Thornycroft's, 169
+  Self-acting circuit closer, the Austrian, 64
+  Sensitive fuzes, 23
+  Service cables, land, 43
+  ---- ----, sea, 43
+  ---- platinum wire fuze, English, 33
+  Ship _Alarm_, Admiral Porter's torpedo, 159
+  ---- defence, 10
+  ----, Fulton's block, 5
+  Ships against torpedo attacks, methods of protecting, 180
+  ----, employment of torpedo, 158
+  Shunt, definition of a, 95
+  ---- for Siemens' electric light, self-acting, 245
+  Shutter apparatus, firing keys and, 80
+  ---- ----, the, 82
+  ---- used with a circuit breaker, 83
+  ---- instrument and observing telescope, 84
+  Siemens' electric cables, 40
+  ---- ---- light apparatus, 241
+  ---- ----, conducting wires for, 247
+  ---- ----, description of, 241
+  ---- ----, power and light produced by, 244
+  ---- ----, rotation of armatures in, 246
+  ---- ----, self-acting shunt for, 245
+  ---- ----, wear and tear of, 247
+  ---- low tension dynamo machine, 75
+  ---- patent electric lamp, 248
+  ---- permanent joints, 47
+  ---- universal galvanometer, 89
+  ---- ---- tables, 287
+  Signal, firing by preconcerted, 71
+  Signals employed in diving, 263
+  Silvertown electric cables, 41
+  Singer's mechanical mine, 19
+  ---- ----, McEvoy's improved, 20
+  Single and double fluid batteries, 272
+  ---- cored armoured cables, 43
+  ---- ---- unarmoured cables, 43
+  ---- fluid cell, action in a, 273
+  ---- main system, McEvoy's, 283
+  ---- rope moorings, 56
+  Size of torpedo charges, 218
+  Soukoum Kaleh, Russian torpedo attack at, 201
+  Soulina, Russian torpedo attack at, 198
+  Spanish torpedo boats, Yarrow's, 175
+  Spar or outrigger torpedoes, 154
+  ---- torpedo, McEvoy's duplex, 154
+  ---- torpedoes, Fulton's, 5
+  Special cables, 43
+  Spherical shaped torpedo case, the, 32
+  Spiral spring circuit closer, Mathieson's, 63
+  Stake torpedoes, 18
+  State of the explosive substance, the physical, 204
+  Statham's high tension fuze, 35
+  Stationary mines, Fulton's, 5
+  Steward's safety cock arrangement, 25
+  Stokes Bay, experiments with countermines at, 236
+  Submarine boat, Bushnell's, 2, 184
+  ---- ----, Confederate, 185
+  ---- ----, French, 185
+  ---- boats, 183
+  ---- ----, qualifications essential to, 184
+  ---- mines 13
+  ---- ----, during the Crimean and American wars, 27
+  ---- ----, rules for using, 29
+  ---- ----, sweeping for, 112
+  ---- ----, electrical, 27
+  ---- ----, advantages of, 28
+  ---- ----, defects of, 29
+  ---- ----, mooring, 54
+  Submersion, tests after, 106
+  Success in torpedo warfare, elements of, 16
+  _Suna_, destruction of the Turkish vessel, 194
+  Swedish torpedo launch, Thornycroft's, 165
+  Sweeping for submarine mines, 112
+  Switch plates, commutators or, 96
+  ---- ----, connections of, 100
+  Synopsis, 290
+  System, McEvoy's single main, 283
+  ---- of electrical testing, Armstrong's, 107
+  ---- ---- firing by observation, Prussian, 73
+  ---- ---- tests, object of, 84
+
+  T.
+  T junction box, the, 53
+  Table, the Austrian testing, 108
+  Tables, Siemens' universal galvanometer, 287
+  ----, test, 99
+  Tactics with Harvey's torpedoes, 127
+  Telegraph batteries, 79
+  Telescope, shutter instrument and observing, 84
+  Tension dynamo machines, Siemens' low, 75
+  ---- fuses, testing high, 102
+  Term torpedo, definition of the, 115
+  Terms electro-positive and electro-negative, the, 271
+  Test battery, the Menotti, 79
+  ----, discharge, 103
+  ---- for electrical cables, insulation, 102
+  ---- of electrical resistance of cables, 104
+  ---- ---- insulated joints, electrical, 104
+  ---- ---- platinum wire fuze for conductivity, 101
+  ---- ---- resistance, 101
+  ---- tables, 99
+  Testing, Armstrong's system of electrical, 107
+  ----, Austrian method of, 109
+  ---- high tension fuzes, 102
+  ----, instruments used in, 85
+  ---- table, Austrian, 108
+  Tests after submersion, 106
+  ----, electrical, 85
+  ---- for insulation, sea cell, 106
+  ----, mechanical, 85
+  ----, object of a system, 84
+  ----, sea cell, 100
+  Theoretical knowledge of torpedoes, 8
+  Theory of detonation, the, 206
+  ---- ---- electricity, the, 265
+  Thermo galvanometer, the, 89
+  Thomson's quadrant electrometer, 86
+  ---- reflecting galvanometer, 87
+  Thornycroft's boat engines, efficiency of, 171
+  ---- method of carrying fish torpedoes, 140
+  ---- propeller, 170
+  ---- torpedo launches, 163
+  ---- ----, Austrian and French, 165
+  ---- ----, Danish and Swedish, 165
+  ---- ----, Dutch and Italian, 168
+  ---- ----, French, 169
+  ---- ----, Norwegian, 163
+  ---- ----, second class, 169
+  Three coil galvanometer, 88
+  Torpedo attacks, boat, 180, 191
+  ---- ----, methods of protecting ships against, 180
+  ---- boat, Lay's, 141
+  ---- ----, capabilities of, 147
+  ---- ----, an improved form of, 153
+  ---- ---- attack, Russian, at Batoum, 195, 202
+  ---- ---- ---- ---- Matchin, 196
+  ---- ---- ---- ---- Rustchuk, 200
+  ---- ---- ---- ---- Soukoum Kaleh, 201
+  ---- ---- ---- ---- Soulina, 198
+  ---- ---- ----, off the Aluta, 200
+  ---- ---- ----, the final, 203
+  ---- ---- experiment at Cherbourg, 170
+  ---- ---- for flotation, 171
+  ---- ---- _Lightning_, Thornycroft's, 168
+  ---- ---- protective, Fosberry's patent, 182
+  ---- boats, 162
+  ---- ----, Herreshoff's, 178
+  ---- ----, ordinary type of, 179
+  ---- ----, Schibau's Russian, 178
+  ---- ----, Yarrow's, 172
+  ---- ----, description of a, 172
+  ---- ---- Dutch, 172
+  ---- ---- English, 173
+  ---- ---- Russian, 172
+  ---- ---- Spanish, 175
+  ---- case, form and construction of, 31
+  ---- ----, conical shaped, 32
+  ---- ----, cylindrical shaped, 32
+  ---- ----, spherical shaped, 32
+  ---- charges, size of, 218
+  ---- defences, clearing a passage through, 111
+  ---- experiments at Carlscrona, 220, 224, 232
+  ---- ---- Chatham, 220
+  ---- ---- Copenhagen, 223
+  ---- ---- Kiel, 222
+  ---- ---- Pola, 231
+  ---- ---- Portsmouth, 229, 233
+  ---- ---- in Austria, 220
+  ---- ---- England, 222
+  ---- ---- Turkey, 232
+  ---- explosive agents, 217
+  Torpedo guns, 257
+  ---- ----, Hotchkiss, 259
+  ---- ----, Nordenfelt, 257
+  ---- invention and adoption of the fish, 131
+  ---- launches, Thornycroft's, 163
+  ---- operations, 187
+  ---- ---- during the Austro-Italian war, 188
+  ---- ---- Crimean war, 187
+  ---- ---- Franco-German war, 192
+  ---- ---- Paraguayan war, 191
+  ---- ---- Russo-Turkish war, 192
+  ---- ----, Russian defensive, 193
+  ---- ----, Turkish defensive, 193
+  ---- ---- and Russian offensive, 195
+  ---- ship _Alarm_, Admiral Porter's, 159
+  ---- ---- _Destroyer_, Ericsson's, 160
+  ---- ---- _Uhlan_, the German, 158
+  ---- ships, employment of, 158
+  ---- spar, McEvoy's duplex, 154
+  ---- ---- or outrigger, 154
+  ----, the term, 115
+  ---- warfare, defensive, 13
+  ---- ----, elements of success, 16
+  ---- ----, science of, 15
+  ---- ---- still in its infancy, offensive, 115
+  ----, Whitehead's fish, 133
+  ---- ----, adjustments of, 136
+  ---- ----, capabilities of, 134
+  ---- ----, methods of projecting, 138
+  ----, Woolwich fish, the, 140
+  ----, American extempore drifting, 119
+  ----, barrel, 19
+  ----, Brook's, 19
+  ----, Bushnell's drifting, 2
+  ---- ----, invention of, 2
+  ----, drifting, 116
+  ----, floating, 116
+  ----, frame, 18
+  ----, Fulton's drifting, 5
+  ---- ---- harpoon, 5
+  ---- ---- spar, 5
+  ----, general remarks on offensive, 156
+  ---- in war, the employment of fish, 133
+  ----, Lewis's drifting, 117
+  ----, locomotive, 131
+  ----, McEvoy's drifting, 118
+  ----, moral effect of, 9
+  ----, offensive, 11
+  ---- ----, failure of 8
+  ----, stake 18
+  ----, towing 119
+  ---- ----, French, 131
+  ---- ----, Harvey's, 119
+  ---- ----, methods of attack with, 127
+  ---- ----, the value of, 129
+  ---- ----, Mensing's, 130
+  ----, turtle 19
+  Turkey, torpedo experiments in, 232
+  Turkish defensive torpedo operations, 193
+  ---- monitor _Duba Saife_, destruction of the, 197
+  ---- offensive torpedo operations, 195
+  ---- ship _Suna_, loss of the, 194
+  ---- torpedoes, 193
+  ---- war, torpedoes during the Russo-, 115
+  Turk's head, McEvoy's mechanical, 53
+  Turtle torpedoes, 19
+
+  U.
+  _Uhlan_, the German torpedo vessel, 158
+  Unarmoured cables, single cored, 43
+  Universal galvanometer, Siemens', 89
+  ---- ----, tables, 287
+  Use of circuit closers, the, 60
+
+  V.
+  Vessel _Destroyer_, Ericsson's torpedo, 160
+  ---- in the world, the fastest, 177
+  ---- _Uhlan_, the German torpedo, 158
+  Voltaic batteries, 79
+  ---- battery, Leclanché's, 77
+  ---- ----, Von Ebner's, 76
+  ---- ----, test for electro-motive force, 105
+  ---- ---- internal resistance, 104
+  ---- ---- potential, 104
+  ---- cell, definition and properties of a, 269
+  ---- current, the, 70
+  Von Ebner's high tension fuze, 36
+  ---- ---- Voltaic battery, 6
+
+  W.
+  War, employment of fish torpedoes in, 133
+  ----, torpedo operations during the American civil, 189
+  ---- ---- Austrian, 192
+  ---- ---- Austro-Italian, 188
+  ---- ---- Crimean, 187
+  ---- ---- Franco-German, 192
+  ---- ---- Paraguayan, 191
+  ---- ---- Russo-Turkish, 192
+  ----, torpedoes during the American civil, 115
+  ---- ----, Russo-Turkish, 115
+  Warfare, defensive torpedo, 13
+  ----, elements of success in torpedo, 16
+  ----, science of torpedo, 15
+  ---- still in its infancy, offensive torpedo, 115
+  Wars, submarine mines in the Crimean and American, 27
+  Wear and tear of Siemens' electric light apparatus, 247
+  Welden railway saved by torpedoes, the, 190
+  Wheatstone's balance, 97
+  ---- ----, manipulation of, 99
+  ---- ----, measurement of resistances by, 98
+  Whitehead's fish torpedo, 133
+  ---- ----, adjustments of, 136
+  ---- ----, capabilities of, 134
+  ---- ----, methods of projecting, 138
+  ---- ----, mode of ignition of, 135
+  Wire fuze for conductivity, test of platinum, 101
+  ---- ----, test of resistance of platinum, 101
+  Wire fuzes, platinum, 33
+  ---- ----, English service, 33
+  ---- ----, McEvoy's, 34
+  Wires in McEvoy's spar torpedo, arrangement of, 155
+  Woolwich fish torpedo, the, 140
+
+  Y.
+  Yarrow's torpedo boats, 172
+  ---- ----, English, 173
+  ---- ----, Spanish, 175
+  ---- ---- launch, description of a, 172
+  ---- ---- launches, Dutch, 172
+  ---- ----, Russian, 172
+
+
+
+
+    GRIFFIN AND CO.,
+    PUBLISHERS BY APPOINTMENT TO H.R.H. THE DUKE OF EDINBURGH,
+    2, THE HARD, PORTSMOUTH.
+
+
+
+
+PUBLICATIONS OF
+
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+
+Naval Publishers,
+
+(_By Appointment, to H.R.H. The Duke of Edinburgh_.)
+
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+
+LONDON AGENTS:--Simpkin, Marshall, and Co., London.
+
+
+THE DUEL: A NAVAL WAR GAME,
+
+Invented and arranged by CAPT. PHILIP H. COLOMB, R.N., with
+Explanations and Rules of the Game, and the necessary Scales, and large
+Drawing Block. Price 10s. 6d.
+
+    "Captain Colomb's War Game will prove very useful to
+    all Executive Officers. It will become the Naval Chess."
+
+    "I think it will prove of much advantage to the
+    Service. It will open the eyes of many men who have
+    hitherto thought and talked of the subject perhaps
+    intelligently but not accurately."
+
+
+TORPEDOES AND TORPEDO WARFARE:
+
+Offensive and Defensive.
+
+Being a Complete History of Torpedoes and their application to Modern
+Warfare. By C. SLEEMAN, ESQ., late Lieutenant R.N., and late Commander
+Imperial Ottoman Navy. 1 vol., Royal 8vo., with Illustrations and
+Plates. Price 24s.
+
+
+VOCABULARY OF SEA WORDS.
+
+In ENGLISH, FRENCH, GERMAN, SPANISH, and ITALIAN. By Commander THE
+HON. A. C. LITTLETON, R.N. For the use of Officers of the Royal and
+Mercantile Navies, Yachtsmen, Travellers, &c. Strongly bound and
+interleaved throughout. Price 3s. 6d.
+
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+    with the Sea, we have the same in French, German,
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+    man, but also to the ordinary traveller, this book
+    recommends itself."--_U.S. Gazette._
+
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+    provision having been made by blank leaves between
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+    made."--_Broad Arrow._
+
+
+PROBLEMS IN NAVAL TACTICS.
+
+By VICE-ADMIRAL RANDOLPH, C.B. With four Full-Page Diagrams. Demy 8vo.
+2s.
+
+
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+
+
+CAPTAIN COLOMB'S NAVAL TACTICS
+
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+
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+QUEEN'S REGULATIONS AND ADMIRALTY INSTRUCTIONS--_New Edition_, 1879.
+2s.6d.
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+MANUAL OF GUNNERY,
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+
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+THE SHIPS OF THE ROYAL NAVY
+
+3rd Edition.
+
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+
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+
+    '_As an illustrated gift-book, independent of its
+    historic interest, "The Royal Navy," from the
+    truthfulness of its illustrations, cannot but recommend
+    itself, not only to the Royal Service, but also to the
+    public._'--_United Service Gazette._
+
+    '_This beautiful work does credit to all concerned in
+    its production._'--_Pall Mall Gazette._
+
+
+THE WAR SHIPS OF EUROPE
+
+Crown 8vo. Illustrated. 10s. 6d.
+
+By Chief-Engineer KING, U.S.A. Descriptions of the Construction, Armour
+and Fighting Power of the Ironclads of England and other European
+Powers of the present day. Revised and Corrected throughout, and with
+additional Notes by an English Naval Architect.
+
+    "A valuable and interesting contribution to maritime
+    literature ... interesting to the public ... and
+    instructive to the Naval Executive generally."--_United
+    Service Gazette._
+
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+
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+THE ARMIES OF EUROPE AND ASIA
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+
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+
+
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+THE SAILOR'S POCKET BOOK
+
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+
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+Notes, and Tables, for the use of the Royal Navy, the Mercantile
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+
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+
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+
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+
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+
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+CAPT. SIR GEORGE S. NARES' SEAMANSHIP
+
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+
+400 beautifully engraved Woodcuts, and Plates of Flags, accurately
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+
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+
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+    most valuable additions are made in this edition. The
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+
+    '_Every necessary particular is given so fully
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+
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+CAPTAIN ALSTON'S "SEAMANSHIP"
+
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+
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+
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+
+    "It has been revised and enlarged by Commander R. H.
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+
+
+THE RIGGER'S GUIDE.
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+
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+
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+    The present is the sixth edition, which has been
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+
+
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+
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+
+
+SEA TERMS AND PHRASES.
+
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+
+THE ACTIVE LIST
+
+Of ADMIRALS and CAPTAINS.
+
+By Capt. WILLIAM ARTHUR, R.N. Demy 8vo.
+
+With particulars exhibiting the progress, &c., of Officers, of the
+Royal Navy, from their entry into the Service to Jan. 1st, 1879.
+
+
+THE ACTIVE LIST
+
+Of all COMMANDERS and LIEUTENANTS:
+
+Corrected to July 1st, 1878.
+
+By Lieut. M. R. HAYES, R.N. Demy 8vo. 3s. 6d.
+
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+TIME, Causes of Special Promotions, Special Acquirements, Comparative
+Progress with other Officers, List of all Officers now on the Active
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+    narrative--his first attempt, as he tells us, at
+    book-writing--as giving a graphic account, in a
+    very unpretentious style, of his most interesting,
+    but perilous cruise.... As a gilt book, we can also
+    recommend the _Land of the White Bear_, for it is
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+       *       *       *       *       *
+
+Transcriber's Notes:
+
+Obvious punctuation errors have been repaired. Varied hyphenation was
+retained. The errors noted in the book's errata section have been
+repaired in the text except for the final one for page 285 where the
+transcriber could not find a "e" to change to a "d" at that location.
+
+Text uses both fuse and fuze. "Fuze" is usually used in the English
+language to mean more complicated fuses.
+
+Inconsistencies in italic usage was retained. For example, on page 98,
+"R" is referenced originally without italics in an equation and after
+on the same page is italicized when mentioned.
+
+Page 17, "principle" changed to "principal" (principal ones being)
+
+Page 77, "16'" changed to "16"" (about 16" long, 9" deep)
+
+Page 114, "Northerners'" changed to "Northerners'" (most of the
+Northerners' vessels)
+
+Page 132, "torpedos" changed to "torpedoes" (Whitehead's fish torpedoes
+have)
+
+Page 134, "14" changed to "140" (140 atmospheres)
+
+Page 162, equal sign added to equation ((314 × 200) / 196 = 320 lbs)
+
+Page 168, "THORNICROFT'S" changed "THORNYCROFT'S" on Plate XLVII.
+
+Page 170, "THORNICROFT'S" changed "THORNYCROFT'S" on Plate XLVIII.
+
+Page 199, "Poustchin" changed to "Poutschin" (Alongside Poutschin
+remained for some)
+
+Page 208, "spaces" changed to "space" (intervening space of)
+
+Page 212, subscript for O in chemical formula was unreadable. "5" was
+presumed and added. (the formula _CH_{7}(NO_{2})_{3}O_{5}_)
+
+Page 240, "Seimens" changed to "Siemens" (due to both Dr. Siemens)
+
+Page 241, "Seimens" changed to "Siemens" (that the Siemens machine)
+
+Page 271, this paragraph seems to be missing a word but was retained as
+printed as the word could not be presumed by research.
+
+    "Oxygen" is the most important element of an
+    electrolyte, and to the _affinity for oxygen of the
+    metals_ is the magnitude of the result and effect.
+
+Page 298, "Calland" changed to "Callaud" (Calland and Marié-Davy)
+
+Page 302, "dislectric" changed to "dielectric" (Gutta-percha as a
+dielectric)
+
+Page 11, advertising page, "Portsmouth." added to publisher line at
+bottom of page. Original ended with (_Griffin & Co Publishers, 2, The
+Hard,_)
+
+
+
+
+
+
+End of Project Gutenberg's Torpedoes and Torpedo Warfare, by C. W. Sleeman
+
+*** END OF THE PROJECT GUTENBERG EBOOK 44990 ***