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diff --git a/44990.txt b/44990.txt deleted file mode 100644 index a854092..0000000 --- a/44990.txt +++ /dev/null @@ -1,16249 +0,0 @@ -Project Gutenberg's Torpedoes and Torpedo Warfare, by C. W. Sleeman - -This eBook is for the use of anyone anywhere at no cost and with -almost no restrictions whatsoever. You may copy it, give it away or -re-use it under the terms of the Project Gutenberg License included -with this eBook or online at www.gutenberg.org - - -Title: Torpedoes and Torpedo Warfare - -Author: C. W. Sleeman - -Release Date: February 24, 2014 [EBook #44990] - -Language: English - -Character set encoding: ASCII - -*** START OF THIS PROJECT GUTENBERG EBOOK TORPEDOES AND TORPEDO WARFARE *** - - - - -Produced by Chris Curnow, Emmy and the Online Distributed -Proofreading Team at http://www.pgdp.net (This file was -produced from images generously made available by The -Internet Archive) - - - - - - - -[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 Leclanche 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 Cyclopaedia.] - -[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 x 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 Mache Safety Plug._--To prevent a premature explosion -during transport, etc., of a mine in which this apparatus is placed, a -plug of papier mache, 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 mache, 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 mache 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 deg. 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 deg. - 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 deg. -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 L47 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 L357 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 L127 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 -L35. - -_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 L137. - -_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 L202. - -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 deg. to 200 deg. F. and gradually -raise the heat so that in half an hour the temperature will be 320 deg. 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 x 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.--Leclanche'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. - -_Leclanche Voltaic Battery._--This form of Voltaic battery was invented -by M. Leclanche, 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 Leclanche 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 Leclanche Firing Battery._--The advantages of the -Leclanche 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 Leclanche 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 Leclanche 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 Leclanche 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_)) x _n_. - -but if read off on the _B_ side of the disc-- - - X = ((150 - _a_) / (150 + _a_)) x _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)) x 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 deg. on the _A_ side we have the following equation-- - - E_{1} = E_{0} x ((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 deg. on the _B_ side to obtain equilibrium we have-- - - E_{2} = E_{0} x ((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 deg. 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) x 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 Leclanche -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 Leclanche 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 deg.; 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 deg.; 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 Leclanche -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 deg. to 85 deg. 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 deg. 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 grace 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 deg., 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 x 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 Ruegen, 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 Kale_. - -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 _Xenie_, 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 _debris_ 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 _Xenie_ 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 Kale_. 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 deg. F., is very violently -detonated; below 40 deg. 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 deg. 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 deg.-5 deg. below zero, F., but, when cleared, it -freezes at 39 deg.-40 deg. 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 deg. 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 deg. 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 deg.-40 deg. 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 deg. 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 deg. 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 deg. F. - -The temperature of explosion of gun-cotton is about 8700 deg. 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 deg. 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' x 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' x 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' x 12'. - -No. 3 Mine.--Timbers blown away on a space of 10-1/2' x 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' x -25' x 15'. - -No. 4 Mine.--Timbers blown away on a space 4' x 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' x 23' x 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' x 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' x 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' x 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" x 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' x 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" x 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" x 4' 7", supported in a horizontal -position on a substructure as above, but eight piles of 6" x 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" x 13" x 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" x 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" x 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" -x 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" x 22-1/2" x 1/32"; iron case 33" x 25" x -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" x 13" x 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' x 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' x 12'. In the -inner bottom below the wing passage bulkhead a piece 6' x 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' x 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' x 7', with -the above-mentioned hole; below the longitudinal frame the indentation -was 14' x 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" x 30" x 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' x 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' x 2' and 7' x 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" x 12" x 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 x 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 x 1.5' and 5' x .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" -x 12-1/2" x 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' -x 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" x 20" x 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" x 21-1/2" x 2"; (_b_) cylindrical cases, wrought iron, empty, -11-1/2" x 11-1/2" x 1/8"; (_c_) cylindrical cases, wrought iron, -charged, 11-1/2" x 11-1/2" x 1/8"; (_d_) cylindrical cases, wrought -iron, 30-1/4" x 30-1/4" x 1/8"; (_e_) spherical cases, wrought iron, -32-1/2" x 1/8"; (_f_) spherical cases, tinned steel, 12" x 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" x -28-1/4" x 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 deg. 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 deg. of surrounding water would be well illuminated at about 900 -yards' distance, while without the divergent lens there would be only -about 5 deg. 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 deg. 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 deg., of elevation 30 deg., and -of direction 360 deg. - -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 -versa_. 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 "Marie-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 -"Marie-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 _Marie-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 versa_. - -_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, Leclanche'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 Marie-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 Marie-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 - Leclanche'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 - Marie-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 mache 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 mache 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 mache 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 mache, 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, Leclanche'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. 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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 x 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 Marie-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. 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