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diff --git a/44990-0.txt b/44990-0.txt new file mode 100644 index 0000000..f972560 --- /dev/null +++ b/44990-0.txt @@ -0,0 +1,15860 @@ +*** 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 + +J. GRIFFIN & CO., + +Naval Publishers, + +(_By Appointment, to H.R.H. The Duke of Edinburgh_.) + +2, THE HARD, PORTSMOUTH. + +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. + + "In addition to the English terms used in connection + with the Sea, we have the same in French, German, + Spanish and Italian.... Not merely to the seafaring + man, but also to the ordinary traveller, this book + recommends itself."--_U.S. Gazette._ + + "It is handy in size and complete in all respects, + provision having been made by blank leaves between + each page for any additions that may have to be + made."--_Broad Arrow._ + + +PROBLEMS IN NAVAL TACTICS. + +By VICE-ADMIRAL RANDOLPH, C.B. With four Full-Page Diagrams. 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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._ + + "The book is invaluable as a brief but accurate + description of the fighting powers of the Ironclads + of England and other European powers of the present + day."--_Broad Arrow._ + + "The whole volume possesses a deep interest. Its + details are trustworthy."--_John Bull._ + + +THE ARMIES OF EUROPE AND ASIA + +Demy 8vo. Illustrated. 14s. + +By Major-General UPTON, U.S.A. Embracing Official Reports on the Armies +of Japan, China, India, Persia, Italy, Russia, Austria, Germany, +France, and England. 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A Collection of Practical Rules, +Notes, and Tables, for the use of the Royal Navy, the Mercantile +Marine, and Yacht Squadrons. With Colored Signal Flags, Charts, and +Illustrations. Bound in leather, 500 pages, and carefully compiled +Index. + + "A Nautical Cyclopædia."--_Liverpool Albion._ + + "The most perfect and complete of any publication of + the kind."--_U.S. Gazette._ + + "A valuable addition to a yachtsman's library."--_Land + and Water._ + + "Valuable and excellently arranged little work."--_Pall + Mall Gazette._ + + "A volume quite indispensable."--_The Graphic._ + + "An admirable and much wanted little book."--_Edinburgh + Review._ + + +CAPT. SIR GEORGE S. NARES' SEAMANSHIP + +=5th Edition.= Demy 8vo. 21s. + +400 beautifully engraved Woodcuts, and Plates of Flags, accurately +Colored. + + '_It is the best work on Seamanship we + have._'--_Standard._ + + '_Is a book for the instruction of young officers, and + of reference for older ones it cannot be excelled, many + most valuable additions are made in this edition. The + book should be the officers' vade mecum._'--_United + Service Gazette._ + + '_Every necessary particular is given so fully + and completely as to leave nothing to be + desired._'--_Shipping Gazette._ + + +CAPTAIN ALSTON'S "SEAMANSHIP" + +=2nd Edition.= Crown 8vo. Cloth, 12s. 6d. + +Contains 200 Illustrations of Rigging, Sails, Masts, &c.; with +Instructions for Officers of the Merchant Service, by W. H. 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Being the best and only complete +book of the Rigging of Ships. + + "This is a valuable little book, adapted to suit every + class of ship, whether steam or sailing vessel, and + should form part of the kit of every youngster adopting + the profession of the sea. Many oldsters will also find + it valuable, from the general information it contains. + The present is the sixth edition, which has been + carefully revised and corrected."--_U. S. Gazette._ + + +_Griffin & Co., Publishers, 2, The Hard, Portsmouth._ + + +THE NAVY OF TO-DAY; + +Its Moral and Intellectual Condition. + +Crown 8vo. Sewed, 2s; Cloth, 2s. 6d. + + "In the Navy of To-Day, we have a number of + thoughtfully written essays which deserve to obtain the + widest publicity."--_Broad Arrow._ + + "A little work which all should peruse who have the + interests of the Navy at heart."--_Christian World._ + + "We can with confidence recommend the Navy of To-Day as + a book well worthy of attentive reading. We recommend + chap. v. more particularly to the earnest consideration + of Naval Officers."--_U.S. Gazette._ + + +SEA TERMS AND PHRASES. + +ENGLISH AND FRENCH. By Lieut. E. PORNAIN, French Navy. For the use of +Officers of Royal and Mercantile Navies, Engineers, Shipbuilders, Ship +Owners, Merchants, Ship Brokers. + +Crown 8vo. 4s. + + "A copy should be possessed by everyone whose + profession, occupation, or interests bring them + into relationship with a seafaring life."--_British + Mercantile Review._ + + "A Nautical Phrase Book in two languages ... + a completeness which leaves nothing to be + desired."--_Hampshire Telegraph._ + + +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. 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The Theory and Practice of avoiding Collision at +Sea; and the Regulations issued by Order in Council. + + +_Griffin & Co., Publishers, 2, The Hard, Portsmouth._ + + +NAUTICAL SURVEYING. + +By Commander MAY, R.N., F.R.G.S. + +Reprinted from "Alston's Seamanship." With Charts. 2s. 6d. + + "The treatise is simple and clear in arrangement, and + written with the especial object of instructing the + officers of the Naval Service in general, and only + deals with the use of such instruments as are found + on board of every man-of-war. We have never met with + any treatise on nautical surveying by any means so + well calculated to answer the purpose for which it was + written."--_Naval Science._ + + +THE MANUAL OF THE HYDROMETER. + +=2nd Edition.= Illustrated. Cloth. 3s. 6d. + +By LIONEL SWIFT, R.N. + + '... Has been treated in the clear and simple manner + which has been already manifested by Mr. Swift, in his + accurate description of the history and philosophy of + the Hydrometer.'--_Army and Navy Gazette._ + + 'Will be found of considerable interest to Engineers + and all those who are interested in the safe and + economical working of Steam Engines.'--_Shipping and + Mercantile Gazette._ + + +_By Authority of the Lords of the Admiralty._ + +QUESTIONS & ANSWERS ON THE AMMUNITION INSTRUCTION. + +For Officers passing through H.M. Gunnery Establishments. + +Paper 1s.; Cloth, 1s. 6d. + +By J. KITE, Instructing Gunner, H.M.S. "Excellent." + + "This book is a valuable _multum in parvo_. + All the multifarious details connected with + Ammunition Instruction, are dealt with ably and + concisely."--_Portsmouth Times._ + + +TRAVERSE TABLES + +Cloth, 5s. 6d. + +With simple and brief method of Correcting Compass Courses. + +By Commander R. E. EDWIN, R.N. + + "Lieutenant Edwin has been at great pains and trouble, + and he will probably save many hundreds of persons from + calculations which are frequently wearisome to the + flesh."--_Broad Arrow._ + + +DEFINITIONS IN NAVIGATION AND NAUTICAL ASTRONOMY. + +(FROM VARIOUS AUTHORITIES.) + +=New Edition.= With Diagrams. Demy 8vo. Cloth, 2s. 6d. + +For the use of the Naval Cadets, H.M.S. "Britannia." + + +_Griffin & Co., Publishers, 2, The Hard, Portsmouth._ + + +LAND OF THE WHITE BEAR. + +The Cruise of the "Pandora," to the Arctic Seas in 1875. + +By LIEUT. F. G. INNES-LILLINGSTON, R.N. + +With beautiful full-page Illustrations. + +Cloth Gilt, 5s. + + "The volume is prettily got up, and the views of Arctic + scenery are about the best we have seen in any recent + work of the kind."--_Athenæum._ + + "Thanks to English pluck and perseverance, combined, in + so many instances, with the ability to write a book, + we have become as familiar with Arctic-life scenes + and adventures as they can be made so by description. + In the present well-got-up little volume, we have an + account of the first voyage of the _Pandora_.... We + can heartily recommend Lieut. Innis-Lillingston's + 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 + exceedingly well illustrated, and both in letter-press + and binding is in the Messrs. Griffin's usually good + style."--_U.S. Gazette._ + + +THE LAST FOUR DAYS OF THE "EURYDICE." + +By Captain E. H. VERNEY, R.N. + +With Portrait of the "Eurydice." Cloth. 2s. 6d. + + "Capt. Verney has done his work remarkably well, and + with the best possible taste. He does not moralize + or try to improve the occasion, but, writing with a + restrained pathos and a graphic touch, he lets the + stern simple facts speak for themselves."--_Athenæum._ + + "The circumstances attending the foundering are given + as far as they are known, and also details of the ship + and its armament, with lists, of the officers and crew + who perished. The book forms an interesting souvenir of + the melancholy event."--_Court Journal._ + + +MEMOIR OF + +COMMODORE J. G. GOODENOUGH, C.B. + +BY CLEMENTS R. MARKHAM, C.B., F.R.S. + +WITH PORTRAIT. 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By Robert Kipping. 2s. + + +_Griffin & Co., Publishers, 2, The Hard, Portsmouth._ + + * * * * * + +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 *** |