~1 §0lnjj;t p«ttt;jj ©hursito ^ mn to 1303 AlHi^^. ^,;e.r university Ubrarv 007^-^ VfflT^ lUQolSL •M>» GAYLORD PRINTED IN U.S.A. The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924030896850 J^ TREATISE ORDNANCE NAVAL GTJNlSrEET, COMPILED AND ARRANGED TEXT BOOK FOR THE U. S. MYAL ACADEMY. LIEUT. EDWAKD SIMPSON, u. a. NATY. SECOND EDITION, EETISED AND ENLARGED. NEW YORK : D. VAN NOSTRAND, 192 BROADWAY, 1862. VF Entered according to Act of Congress, in tlie year 1861. By D. VAN NOSTRAND, In the Clerk's Offioe of the District Court of the United States, for the Southern District of New Torlc. V. A. ALTORD, STBRBOTYI'BE AND PRINTRR. Bureau of Oednanck and Hydeogkaphy, Jidy Wi, 1859. Sm: The manuscript on Grnnnery, compiled by Lieut. Edward Simpson, U. S, Navy, which was sent to tliis Bureau with your letter of the 15th ultimo, is herewith returned. The Secretary of the Navy approves of the use of this work as a text book for the Academy. ******** Respectfully, Tour obd't serv't, D. N. mGEAHAM, CJdrf of the Bureau. Captain G, S. Blake, Superintendent of Naval Academy ., Anaapolis, Md. DEDICATION. TO THE HON. GEORGE BANCROFT, TO WHOM THE NAVY IS INDEBTED F O K THE UNITED STATES XAVAL ACADEMY, THIS WORK EESPECTFULLT DEDICATED. rilEFACE. This work, originally designed merely as a text-book for the Naval Academy, has been allowed to depart from the essential character of such a work, in the hope that it might prove more ac- ceptable to the Navy generally. The compiler of this volume, when ordered to take charge of the instruction in Naval Gunnery at the Naval Academy, could find no single work that would cover the ground necessary for an ele- mentary course in this branch. Many good works were at hand, but each bore on some speciality of the author, which it seemed to have been his object to set forth ; no one volume was sufficiently comprehensive to supply the want ; it became necessary to compile from each such parts as, when united, might embrace the whole subject. This volume is the result of the author's effijrts to achieve this object. In submitting his work to the Navy, the author desires to be understood as simply making an eflTort to circulate information which many officers, owing to constant service afloat, may not have been able to collect. This information he has endeavored to throw together in a readable and familiar form, and has avoided as much as j)ossible all scientific demonstrations, making the work elemen- tary in its charactei". He is well aware that, had this duty devolved on many of his brother officers, it would have been better executed ; but, trusting to the generous character of the profession, he believes that his V, ork will be generously dealt with. 8 PREFACE. The text is chiefly drawn from the writings of the following authors, viz. : Sir Howard Douglas, Naval Gunn-ery. Captain J. H. Wabd, U.S. IST., Ordnance and Gunnery. Major Alfred Moedbcai, TJ. S. A., Notes on Gunpowder. Captain Miner Knowlton, U. S. A., Notes on Construction of Cannon., &c. Captain Johx GiBBOif, U. S. A., Artillerists Ifanual. Captain C. M. Wilcox, U. S. A., Mijles and Bifle Practice. Lieutenant W. 11^. Jefpers, TJ. S. IST., Theory and Practice of Naval Gunnery. Professor Trbadwell, Cannon of Large Calibre. M. Thiroux, Instruction d'' Artillerie. Mr. W. C. E. Geeenee, Gunnery in 1858. Professor Magnus, Deviation of Elongated Projectiles. Mr. J. M. B. Scoffern, Projectile Weapons of War. Mr. Ltnall Thomas, Rifled Ordnance. M. Panot. Lieutenant Stevens, R. N., Pointing at Sea. M. Page, Theorie du Pointage. Extracts have been made also from the foUowine; works, viz. : Ordnance Manual of the XT. S. Army. Ordnance Instructio7is of the U. S. Navy. Aide-M6moire to Military Sciences. '■'■SrnallArms^^ {Reports of Experiments, Ordnance Department^. The writings of Major J. G. Barnard, Commander J. H. Dahlgken, and Captain J. G. Benton, U. S. Army, have also been consulted, and a few extracts made from the works of the last two authors. E. Simpson, Lieutenant U. S. Navy. TJ. S. Naval Academy, Newpobt, R.I., Ociobw 16, 1861. CONTENTS. CHAPTER I. AKT. Review op Ancient Arms 4 Anciest Engines op War 9 Ancient Men-op- War 14 Ancient Artillery 15 Intention op Gunpowder and Ancient Cannon, with account op their EARLIESr USES 16 Advance in Gun-Making, &c 18 Battle op Lepanto 23 Mortar 27 Introduction op Carronades 29 Resume op the History op Calibre 33 Experience of War of 1812 34 Maximum Calibres now in use in the United States Navy 35 CHAPTER II. PABIilCATION OP CANNON. Cast-Iron, Wrought-Ibon, Beokzb 37 Fabrication of Cannon 56 Boring 68 Casting on a Core 72 Turning .' 13 Vent-Pieces 75 Weakness op Wrought-Ieon Cannon 78 Nomenclature op Cannon 80 Inspection op Cannon 81 Proof op Cannon 95 Marking Cannon 99 CHAPTER III. cannon. Form op Cannon 100 Bompord's Plan for determining Form 100 Recoil, Effect op, on Cannon and Small Arms 106 ■WflNDAGE 110 Preponderance 115 10 CONTENTS. ABT 119 Phenombka in Bore on Combustion of the Chaege Pbofessor Teeadwbll on Lodgements Increase of Strain due to increase of Calibre " Injury to Bronze Cannon ; drooping at the Muzzle 12 Injury to Cannon in Proof Strengthening Bands on Cannon ■jqo Mr. Eobert Mallet on Planes of TfEAKNESS 133 Professor Theadwell on Fractures 140 Effect of Vibration 142 Effect of Shrinking in Cooling Casting on a Core, or Hollow Casting ^^^ 145 Effect op Trunnions - - 14*7 Effect of Age on Endurance To render Cannon unserviceable '^ Presertation of Cannon 151 CHAPTER IT. gun-carriages. Conditions sequiree of a Gun-Caseiagb "152 Friction Carriages 155 Bseeching. Compound Breeohin© 156 Effect of Height of Carriage 159 Iron Carriages 161 Navy Four-Truck Carriage 164 Ward's GuN-CAEiaAGB 1T3 Marsilly (Navy Two-Truck) Carriage 115 EoMME Carriage lie Marshall Carriage lit Bheestham Carriage 118 Pivot Carriages 119 Van Brunt's Carriage 182 Bed and Quoin 18S Elevating Screw 181 ■Ward's Screw-Quoin 188 Porter's Quoin 189 Rule for mounting Guns 190 CHAPTER V. sunpowdee. Discovery of Gunpowder 192 Nitre "Walls, Beds 194 Charcoal 198 Sulphur 201 Manufacture of Gunpowder 204 Packing Gunpowder 213 Phenomena attending the Change from a Solid to a Gaseous State.. 216 Combustion, Causes that influence the Rapidity of 213 Harmlbssness of Non-Elastic Fokoe 234 CONTENTS. 11 AUT, Proof op Powder 240 Eprouvette 241 Balustic Pendulum 244 Loss OP Force by ■Wikdage 246 Effect of Junk Wads 247 Effect of reduoino Wimdaoe 249 Rotary Machine 260 Natez's Machine , 261 Storaoe of Gunpowder 280 Damaged Gunpowder 282 GuN-COTTON 283 CHAPTBE TI. projectiles. Casting 287 Inspection 293 Bar-Shot 304 Chain-Shot 305 Grape-Shot 306 Canister Shot 307 Shells 309 Spherical Case , 310 Carcasses 313 Sabots 315 Martin's Shell 316 Norton's Liquid Fire 317 Resistance op the Atmosphere 319 Windage, &c '. 320 Devtations 321 Magnus' Experiment 325 Eccentricity, Effect of 328 Advantage op Large Calibre 338 Advantages op the Spherical and Elongated Form 340 Penetration 346 Rockets 347 Manufacture 349 CoNGREVE Rocket 361 Motive Power of Rockets 362 Uncertainty of Rocket Practice 367 Rockets fired prom Cannon 371 Hale's Rocket 372 Hale's Rocket Tube for Broadside Firing 375 CHAPTER VII. FUZES. Fuze-Case 381 Safety Plug 384 Water Cap 385 12 CONTENTS. JIET English Fuze ^^^ Splingaed's Shrapnel Fuze ^^" boemann i'oze ^^-' French Shrapnel Fuze oaf] CoNcrrssiON Fuzes Peussian Fuze SOHONSTEDT FuZE Snoeck Fuze *"" Splingard's Concussion Fuze Percussion Fuze 413 Moorsom's Fuze ^^^ Bourbon Fuze ^^^ Fuze used during Experiments at "West Point 418 CHAPTER Till. locks and primers. Early Methods of firing Cannon 419 First Application of Locks to Cannon 423 Percussion System 424 Natt Percussion Primer 428 English Primer 429 Navy Locks 430 Late Improvement in Mounting the Hammer 432 Friction Primers ■ 433 English Navy Friction Primer 434 CHAPTER IX. theory of pointing guns. Preliminary 435 Trajectory in a Tacuum 449 Height of the Curve 452 Range 456 Resistance of the Air 459 All Deviations not due to Errors of Pointing 462 Trajectory in the Air 463 Height of the Curve 468 Angle of greatest Range 469 Direct Fire 411 Pointing 472 Point Blank 474, 476 and 485 Tangent Scale • 475 Negative Hausse ^80 Dispart Sight 481 Use of Graduations between " Level" and Range at Level 487 Marking Breech Sights 488 Relation between Total Hausse and Time of Flight 491 Deviations resulting from a Difference of Level in the Trucks .... 492 Chase Firing 495 CONTENTS. 13 ABT. Pendulum Hausse 496 Side Pointikg .' 49t Pointing by means of the Handles 498 Tangent Firing 499 Ricochet Firing 500 CHAPTER X. rifles. Inaccuracies that the Rifle is intended to Correct 503 Object of the Rifle Motion 505 Methods of imparting the Rifle Motion 506 Breech Loading, Matnard's Rifle 508 Deltigne's Rifle 509 Rifle a Tige 510 Gaining Twist • 513 The Helix 515 Ball a Culot 516 Pritchet Bullet 518 United States Naty Bullet 5l3 Greener's Expansive Bullet 520 Theory of Rifle Motion, Drift 521 Advantages op the Elongated Form of Bullet 523 Grooves on the Bullet, French Theory 525 Magnus' Theory op the Deviation of Elongated Projectiles 530 Rifled Cannon 538 French Rifled Cannon 539 Lancaster Gun 540 Cavalli Gun 541 "Wahrbndorpf Gun 543 The Armstrong Gun 545 The Armstrong Shell 550 The Armstrong Carriage for Broadside Use 555 Professor Treadwell's Plan for Constructing Cannon 558 The Wihtworth Gun 560 Advantages of Rifled Cannon limited to Long Ranges 566 Comparison op the Armstrong and Whitworth Guns 569 Objections to Breech-Loading Cannon 570 James's Rifle Shot 571 Sawyer's Shell 512 Pareott's Rifled Cannon and Shell 573 The Schenkl Rifle Shell 577 , CHAPTER XI. practice of gunnery. Double Shotting 580 Effect of Shot on Iron 584 Iron-cased Ships 588 Jones's Inclined Sides 591 Cole's Revolving Towers 592 14 CONTENTS. ART. "La Gloiee" 593 The " Wabrior" 596 Deteemining Distance of Objects at Sea 597 PeAOIICE of FlElNS AT SeA 603 "Hoenet" and "Peagogk" 612 "A70N" AND "Wasp" 613 "Frolic" and "Wasp" 614 Loading in one Motion 617 Explosion of Shells on Concussion 618 concknteation of fire 628 Effect of Projectiles 633 Naval Duels 639 " Guebrieee" and " Constitution" 640 Receiving an Attack from to "Wind-ward 641 " Macedonian" and " United States" 646 Receiving an Attack feom to Leeward 647 NAVAL GUNIsTERT. CHAPTER I. 1. Ordnance and Gunnery. Under tke tead of Ord- nance is classed all that relates to tlie construction, equipment and preservation of guns,' and the fabrication and cai-e of sliot and ammunition. Under the head of Gunnery is classed the drill of the personnel attached to a gun, and its skilfiil and most effective use. 2. Importance of Gnnnerj. In preparing a ship, and disciplining her crew for service, the fitness of her bat- tery, skilfalness of her crew in its use, and the preserva- tion of her military stores, should be regarded as among the objects of paramount importance; for she may in other respects be well provided, be clean, neatly rigged, and have an active crew, but if her battery be imperfect in its constBttctioB, condition or appointments, or if, through carelessness, or want of a proper estimate of its importance, the instruction and exercise be neglected, so that her gnanery is bad, she will most imperfectly ful- fil, in action, the chief purposes for which she is to be employed. 3. -Des^n of Chapter I. In opening the instruction proposed, it may not be uninteresting, or without its use m exciting a spirit of inquiry, to give an account of «moi?eiit arms in general, to notice briefly the ancient 16 NAVAL GUNNEEY. modes of sea fighting, to give some accomit of tlie artil- lery employed by tlie Greeks and Komans, and during the middle ages until the application of gunpowder to cannon, and trace the invention of, and improvements in, cannon from their earliest use, through intervening maritime wars, to the present time. 4. Arms. Arms, in a general sense, include all kinds of Aveapons, both offensive and defensive; and among the earliest may be classed the bow and arrow, and the sling, they being the first means invented for pi'ojecting bodies with an offensive aim. The term Artillery, as formerly applied, was nearly synonymous with Archery. 5. The Sling. To the bow and sling were soon added spears, swords, axes and javelins. The invention of the sling is attributed by ancient wiiters, to the Phoenicians, or the inhabitants of the Balearic Islands; the great fame that these islanders obtained arose from their assiduity in its use; their children were not allowed to eat until they struck their food from the top of a pole with a stone from a sling. From the accounts left us (probably fabulous), it ap- pears that the immense force with which a stone could be projected can only be, exceeded by modem gunnery. Even at that early age, leaden balls were in use as pro- jectiles. 6. The Bow. The bow is of equal if not greater an- tiquity. The first account we find of it is in Genesis xxi. 20, Avhere the Lawgiver, speaking of Ishmael, says, " and God was with the lad, and he grew and dwelt in the wilderness, and became an archer." 1. The Cross-Bow. To the Normans appears to be awarded the invention of the cross-bow, an instrument NAVAi GUira'EEY. 17 whicli afterward became of great repute in England. It is said of the cross-bow that quarrels* could be pro- jected from tliem 200 yards, so that we may imagine the force with which one of these lumps of iron would strike even the strongest armor, as, to range that distance, the initial velocity would be not far short of 900 or 1,000 feet per second, nearly equal to the effect of a ball from a musket. 8. Ancient illusqueteer. This being the case, it is not to be wondered at that the musket had to struggle so many years before it grew so much into favor as to su- persede the bow ; for the musqueteer was formerly a most encumbered soldier. He had, besides the unwieldy weapon itself, his coarse powder for loading in a flask, his fine powder for priming in a touch-box, his bullets in a leathern bag with strings to draw in order to get at them, whilst in his hand were his musket rest and his burning match ; and, when he had discharged his piece, he had to draw his sword in order to defend himself. 9. Ancient Engines of War. The structure of fortifica- tions and that of offensive engines must mutually influ- ence each other. In ancient times, before the invention of fire-arms, the strength of cities depended on the height of their walls ; at the present time this would constitute a weakness ; whilst, on the other hand, our modem low fortified walls would have been no defence against the ancient mode of attack. The forms of ancient engines of war may be included in the following classes : 1. — Catapulta, for projecting stones. 2. — Ballista, for projecting beams and darts. 3. — The Battering Kam. * Oarreaux, from their heads, which were square pyramids of iron. 2 18 NAVAL GUNWEEY. 4. — The Tower of War, from wMcli projectile weap- ons were tlirown. 10. Catapulta and Ballista. The Catapulta and Ballista are botli engines of the cross-bow kind, but employed for throwing different projectiles. In making these enormous cross-bows, instead of making the bow out of one piece, it was formed in two parts, each of which was merely a straight arm. To form the machine, each piece at its mesial extremity was closely matted in amongst the fibres of a rope placed vertically and firmly secured at either end. From this arrangement, the bow could not be bent without producing great tension of the rope, thus . adding another force to that of the rebounding steel. A windlass or capstan was employed to bend these enormous bows, and when bent, the string was se- cured by a catch and iron pin. In order to discharge this machine, the pin was suddenly knocked out by the blow of a mallet. Catapultse have occasionally been employed in mod- ern warfare. There was one erected at Gibraltar, by General MelviUe ; it was for the purpose of throwing stones a short distance over the edge of the rock in a particular place where the Spaniards used to fre- quent, and where they could not be annoyed by shot or shells. 11. Battering Ram. Of aU the ancient offensive weap- ons none were so efficacious as the Battering Ram. It consisted of a long pole or spar, headed with a huge mass of iron or brass, usually shaped like the head of the animal from which its name was derived. The spar was sometimes mounted on wheels, but more frequently suspended by cords from a triangle of stout beams. In NAVAL GUNWEET. 19 either case, the intention was to impel it violently for- ward against an opposing wall, not with a view of its penetrating the mass, or even of dislodging a portion ty its immediate shock, but to generate a vibration that, continually repeated, would shake the strongest walls to their foundation, and eventually make them fall. 12. Principle of the Ram. It will be perceived, that the principle on which the Ram acted against walls was very different from that involved in the impact of shot fired from cannon ; the latter impels a projectile with great velocity against the object, and penetrates and shatters, without much disturbing the repose of masses situated near its point of impact ; the former possessed comparatively little penetrating force, but shook the strongest walls to their foundations. One of the most familiar instances of the effects produced by periodic vi- brations is the well known result of marching a regiment of soldiers over a suspension bridge, when the bridge, responsive to the measured step, begins to rise and fall with excessive violence, and if the marching be stiU. con- tinued, most probably separates in two parts. More than one accident has occurred in this way, and has led to the order that soldiers in passing these bridges must not march, but simply walk out of time. The difficulty of destroying fortifications with modern artillery is lead- ing the mind of artillerists to the invention of some way of operating on the principle of the Ham, ; it is supposed that this object will be, in a measure, reached by in- creasing the size of the projectile and diminishing the velocity with which it is fired, thus increasing its shat- tering, but diminishing its penetrating effects. 20 NAVAL GUNNBET. 13. The Tower. The Battering Ram was generally employed in connection with the fourth engine enumer- ated above, the Tower. This tower was called testudo. The walls of ancient cities, as has been stated, were of great height. Against defenders stationed on high walls, soldiers attacking, armed with manual weapons, fought at a great disadvantage from the ground ; the object, then, was to gain an elevation that commanded the city walls. This object was accomplished by means of towers of enormous magnitude. These towers were supported on wheels, the lower story was devoted to the battering-ram, all the others were filled with archers and light-armed soldiers generally. These large towers be- ing brought up close to the wall, put the besiegers on a more equal footing with the besieged, in that they could discharge their missiles from the same height, and even, by means of a drawbridge, engage in hand to hand en- counters on the top of the wall, while the ponderous ram would be, the while, thundering at the wall below. It was, of course, a great effort with the besieged to destroy these engines by fire, to guard against which the machine was usually covered with raw hides or metal scales, hence the name of testudo (tortoise), which, event- ually, the whole engine acquired. 14. Ancient Mcn-of-War. The Greeks, and subse- quently the Eomans and other ancients, fought at sea in galleys propelled by oars, which were arranged in banks, one, two, and sometimes three deep. Their con- tests were principally decided by boarding, and depend- ed much on personal prowess as well as on numbers. The galleys were constructed with heavy iron beaks, in order to destroy an opponent by piercing or crushing NAVAL GUBTNEEY. 21 its sides.* It was customary however to use a species of artillery. Ancient Artillery. The Greeks threw, by means of a machine, a composition known as Greek fire, which is represented to have been inextinguishable, and with which they destroyed an enemy while at a distance. It is now supposed that naphtha was the basis of Greek fire. Sometimes suffocating mixtures in earthen jars were thrown upon an enemy's deck to stifle and blind the crew, and venomous reptiles were thrown in the same way to produce terror and dismay. The catapulta was the light artillery of the ancients, which was fitted for use on their light vessels. In the middle ages, especially during the crusades, va- rious other means of annoying a distant enemy from vessels were devised ; the English galleys used wind- mills, which, turning rapidly, threw, by centrifugal force, heavy stones, combustible balls, and other missiles. There are enumerated no less than twelve different ma- chines for throwing missiles which had come into use in the 11th and 12th centuries, but their forms, construc- tion, and manner of use, are entirely lost to history. 15. Inycntion of Gunpowder. In 1320, gunpowder was invented by Friar Schwartz, a German. There is reason to believe that an English monk, Roger Bacon, was acquainted with its jDroperties in the preceding cen- * This method of destroying an enemy is not without favor in some minds even at the present time, particularly vphere a harbor is to be defended. Notwithstanding the high pitch of perfection to which the projectile system has been advanced, the desire of tlie combatant to close with his enemy is always apparent ; even in the last Italian campaign of the French, although much execution was done with the mini6 rifle and rifled cannon, the most decisive advantages were gained by a resort to the charge of bayonets. 22 NAVAL GTJNlfEEY. tmy, but Schwartz seems to have the credit of apply- ing it to military uses. ' It is said that he' was operating in a mortar on a mixture of nitre, charcoal and sulphur • (gunpowder in fact), and accidentally firing the mixture it exploded, urging the pestle to a considerable distance; that hence onginated cannon, and also the military term mortar, as applied to a particular variety of cannon. 16. Ancient Cannon. The term cannon is derived from carina (a reed) ; the first cannon were called homhardcs, from the great noise which the firing of them occasioned. The first cannon employed were nothing more than bars of iron arranged in such a manner that their in- ternal aspects should form a tube ; the bars were not welded, but merely confined by hoojDS. On some occa- sions, expedients much less efficient than this have been had recourse to, cannon having been made of coils of rope arranged in a tubular form, and even of leather oi' wood. 17. Earliest uses of Cannon. The earliest uses of this new description of artillery are noticed as having occurred at Cressy in 1346, where they were employed on land by the Black Prince; and at sea in 1350, in an action between the Moorish king of Seville and the king of Tunis, and again by the Venetians in 1380. On this last occasion it is remarkable that nations generally ex- claimed against its use as unfair in war. It was not then foreseen, as has since proved the case, that gunpow- der would render war, especially in naval battles, less sanguinary. Formerly, the great object in sea engage- ments was to board the enemy, and in hand to hand combats destroy life; but the chief effort now in fighting ships with guns, is to cripple or destroy the ship, which NAVAL GTJNlSrEET. 23 being accomplished, men are compelled by necessity to surrender. 18. Advance in Gun Making. The second step in gun making produced brass ordnance of enormous calibre, throwing stone balls of a weight equal to 600 pounds, and in some instances, it is said, reaching to 1,200 pounds. Louis XI. had a celebrated gun of this calibre, and Mahomet II. breached the walls of Constantinople, at the siege of that city in 1449, with a gun of this de- scription. Next, both wrought-iron and brass cast guns came into use, of a much reduced size, throwing cast- iron balls. 19. Ancient Wrouglit-iron Cannon. These wrought- iron guns were composed of a tube of iron, whose joint or overlap was in the direction of the length ; upon this is a succession of iron hoops, composed of iron three inches square, being, in fact, immense rings ; these ap- pear to have been driven on while redhot, and thus, by their contraction, forming a much stronger gun when combined with the interior tube than the generality of accounts given of ancient guns would lead us to expect. There have been recovered from the " Mary Eose," an English vessel of war sunk by a French fleet on the coast of England in 1545, several guns, some of wrought iron, constructed as just described, and others of brass, cast. One of the brass guns contained an iron ball. Some of these iron guns are in an excellent state of pres- ervation, considering that they have been immersed above 300 years. 20. Ancient Breech-loading Cannon. These guns all appear to have been loaded by removing a breech part or chamber, inserting the charge at the breech, replacing 24 NAVAL GUNNEEY. the chamber, and securing it by wedging it behind. ISTo means of raising or depressing the muzzle appear avail- able, the barrel or gun being sunk in a large block of timber, and secured there by bolts, as a musket barrel is secured in its stock, while a large piece of iron, or wood, was inserted perpendicularly into the deck to prevent recoil. The advantage of cJiamhers was under- stood even at this early period ; they were apparently slightly conical, with a spherical bottom. 21. Introduction of Cast-iron Cannon. It was not until so late as 1558, when cast-iron guns were introduced, more than two hundred years after the discovery of gunpowder, that cannon were so securely made as not to produce, by their liability to burst, as much appre- hension amongst those who served them as amongst the enemy, and until that time had not entirely superseded the ancient artillery. The method of constnicting the ancient artilleiy, as described above, seeming to have been sufficiently strong, the inference appears reason- able that the danger attending the serving of the pieces arose from the rude system of breech-loading which was then practised. It has tasked all the ingenuity of the present day to make a su.ccessful application of the breech-loading system, and even the specimens that we see in service are considered by many as inferior in strength to pieces loading at the muzzle. 22. Causes tending to increase the importance of Maritime Wars. Late in the thirteenth, or early in the fourteenth century, the polarity of the needle was di'scovered. The Portuguese had, by aid of it, ventured largely on the ocean, but its great effects were developed in the voyage of Columbus, which resulted in the discovery of the NAVAL GUNWEEY. 25 western world in 1492. The Portuguese had, six years before this, coasted the whole western shore of Africa and doubled the Cape of Good Hope, and six years later, 1498, the same people discovered the passage to India. The ocean, which had been a banier between nations, now, through these discoveries and by aid of the com- pass, became a convenient highway of communication. The Venetians in the, Mediterranean, the Portuguese in the East, and Spaniards in the West, held possession and attempted a monopoly of the commerce of those regions. Nations contended for and against this mo- nopoly ; maritime wars, in consequence, assumed an im- portance they had never before held, and gunpowder rendered them formidable and destructive. 23. Battle of Lepanto. The first great naval combat, growing out of this state of things, was fought at Le- panto between the Turks and Venetians in 1577 ; the vessels on both sides were mostly galleys armed with light cannon, the Venetians, however, had six ships showing, through port-holes, three long heavy guns on each side. These ships withstood the whole Ttu"Msh force, and contributed mainly to the result of that bloody day. This is the first notable instance on record of the decisive effect of a small number of heavy ordnance over a larger number of smaller calibre. 24. Armada of Philip II. In the year 1588, Philip II. of Spain astonished the world with the celebrated "Armada," which threatened the coast of England, but was defeated and finally wrecked or otherwise destroyed in the British seas. That fleet consisted of 132 vessels, with an aggregate tonnage of 63,120, carried 3,165 guns and 30,000 people, including soldiers. The largest of 26 NAVAL GUSrWEET. these vessels measured 1,550 tons, carried 50 guns and 422 persons; anotlier of them, of 1,200 tons, carried 50 guns and 360 persons; this last was about the prevailing proportion of tonnage, guns, and men throughout the fleet. The English force opposed, consisted of 175 ships of 29,740 tons, and 14,500 men. 25. The Royal Prince. The "Royal Prince," a Brit- ish ship built in 1610, twenty years after the " Armada" was destroyed, was of 1,500 tons burden, and car- ried 55 guns; of these pieces 2 were cannon petrond, or 24-pounders, 6 were demi-cannon (medium 32-pound- ers), 12 were culverins or 18-pounders, which were nine feet long with 177 pounds of metal to 1 of shot, 18 were demi-culverins or 9-pounders, 13 were rakers or 5- pounders, 6 feet long with upwards of 200 pounds of metal to one of shot, and 4 were port-pieces^ probably swivels. These guns were disposed as follows : on the lower gun-deck two 24-pounders, six medium 32's, and twelve 18's; on the up j)er gun-deck the battery was en- tii'ely of 9-pounders ; and the quarter-deck and forecas- tle were armed with 5-pounders ; and the brood of pop- guns that, in those days, swelled the nominal armament of ships. 26. The Sovereign of the Seas. In 1637, Charles I. built the " Sovereign of the Seas," more famous than any ship which had preceded, and unequalled by any afloat in her time. She mounted on three gun-decks 86 guns. On the lower deck were thirty long 24's and me- dium 32's; on her middle deck thirty I2's and 9's ; on the upper deck " other lighter ordnance ;" and on her quarter-deck, forecastle and elsewhere, " numbers of murdering pieces." This shows an increase in the size NAVAL GUNNEET. 27' of ships and number of guns since the preceding reign, but it may be remarked that the increase is principally in lighter ordnance and "other murdering pieces," so that according to our modern estimation, little addition was made to real and substantial efficiency. 2*7. Mortar. It may here be remarked, in the chain of improvement in naval ordnance, that the mortar was first used afloat in 16*79, at the French attack on Algiers; it was then discharged from a bomb ketch, precisely as at the present time ; the ketch rig was invented then, and is continued without change. 28. CharacteroflVaTal Conflicts in the time of Cromwell. In the severe and obstinately protracted contests between Blake and Van Tromp in Cromwell's time, it does not appear that the ships or batteries differed in any mate- rial degree, from those cotemporaneous in construction with the " Sovereign of the Seas." Indeed, with a single exception, that ship remained at the time of the British revolution, a whole reign after Cromwell's death, the most formidable ship, both in size and battery, in the British navy. This, if the Dutch ships were similarly armed, explains how those ships could fight a battle that was protracted through three days ; for, as will hereafter be seen, there were few guns in either fleet capable of penetrating a heavy ship's side and sinking her, even at close quarters. Armed as ships now are, and with tolerable gunnery, one or both must be destroy- ed in a few hours at most. 29. Introduction of Carronades. No marked alteration in the batteries of ships appears to have occurred down to the destruction of the French and Spanish maritime power at Trafalgar, in 1806. Carronades of small 28 JTAVAI. GiriTNEBT. weight and great calibre had taken the place in many cases of the 9 and 12-pounder long guns. Carronades are a short description of ordnance without trunnions, but having a loop under the reinforce which sets be- tween lugs on a bed, a bolt passing through the lugs and the loop ; the bed is mounted on a slide. The name is derived from the Carron foundry in Scotland, the first pieces of the kind having been cast there in 1119. They were of large calibre and of light propor- tional weight, the charge of powder was small, but at close quarters they were very effective. In the compo- sition of the batteries of the ships already cited, one great objection is the variety of calibres that were crowded together in the same ship, and sometimes on the same deck ; of course each calibre had its own ammu- nition, which was required to be stowed separate from the ammunition of the other calibres, thus multiplying ■ difficulties of stowage, and complicating the work of the powder division ; the introduction of carronades oper- ted to a considerable degree in bringing about an ap- proach to uniformity of calibre. How far this is true will appear by stating the batteries of the " Santissima Trinidada," the heaviest ship of the combined fleet, and of the " Victory" and others of the British fleet. 30. The Santissima Trinidada. The " Santissima Trin- idada" was built in Havana, in 1769 ; she then mounted 126 guns, viz. : on the lower gun-deck thirty long 36- pounders; on the second deck thirty-two long 18's; on the third deck thirty-two long 12's ; and on the spar-deck thirty-two 8-pounders ; at Trafalgar she is said, in the British accounts, to have had 140 guns, which number must have included swivels mounted for the occaaoa. NAVAL GUNNERY. 29 The Spanisli '74's in that action had fifty-eight long 24-pounders on the gun-decks; on the spar-deck ten iron 36-pounder caironades, and four long 8-pounders ; and on the poop six iron 24-pounder carronades, total Y8 guns. The French and Spanish ships had coehorns* mounted in the tops, and one or two field-pieces were movable on the spar-deck. 31. The Victory. The "Victory," the English flag- ship, on board of which Lord Nelson fell, mounted on her three gun-decks ninety long 32, 24 and 12-pound- ers ; and on the quarter-deck and forecastle ten long 12-pounders, and two 68-pounder carronades. 32. The Tamerlane. The British ship " Tamerlane," the best armed for her rate in the fleet, had fifty-six long 32-pounders, and thirty long 1 8-pounders on her gun- decks, and on the spar-deck twelve 32-pounder carron- ades, and four long 1 8-pounders. At a single broadside the weight of metal thrown by the " Santissima Trinidada," was 1,190 pounds, by the "Victory," 1,180 pounds. The United States ship Minnesota throws a weight of 1,700 pounds of metal at a broadside. 33. Resume of the History of Calihre. In thus briefly tracing the history of ordnance, it will be observed that early fabricators, adopting the idea of the ancients in favor of missiles of the most ponderous practicable di- mensions, constructed guns of mammoth proportions to contain those missiles. It was soon found, however, * The Coehorn is a very light mortar, projecting a large projectile with a small charge of powder; it is probable that its projectile was intended to operate by means of the force of gravity virhen the ships should be within its short range. A heavy projectile falling from a great height and landing on a ship's deck might do much damage. 30 NAVAL GUNNEEY. that those guns were too heavy for transportation or ma- nceuvring, and their shot too heavy for handling with that facility essential to rapid firing. Both guns and shot were therefore reduced in calibre and dimensions, and for the shot a denser material, iron, was introduced. Iron shot first came in use about the year 1490. Lead- en shot, still more dense than iron, were, as has been re- marked, employed at an earlier date, but that substance proved too soft as well as too costly. In reducing the calibre of guns, the world proceeded from one extreme to another, and until within forty years regarded the 18-pounder as that which afforded the happy mean, between too light a gun on the one hand for effect, and too great weight on the other for convenient manoeuvring and rapid manipulation. Ac- cordingly the ISpounder came into use as the favorite battering piece. The next higher calibre was used oc- casionally on the lower decks of heavy ships, whose antagonists commonly had thick sides requiring shot of greater penetration than the 18-pounder. But for the upper decks of ships, this favorite gun was found too heavy, besides occupying, owing to its length, too much room. Nine-pounders were therefore substituted on these decks. But that calibre did not give momentum or weight of blow enough for effect; this suggested the carronade, of greater calibre and lighter weight, invented by General Melville, and intro- duced in ITOO. A 32-pound carronade and carriage weighs but little if any more than a long nine and car- riage ; no weight was added therefore by substituting the 32-pounder carronade for the long 9-pounder, but much was gained in effect, especially at short ranges, for NAVAL GUBTNEKT. 31 (momentum being equal to the product of weight and velocity) if the shot of 9 pounds were discharged with an initial velocity of 1,500 feet per second, and the 32-pound shot with a velocity of 750 feet per second, the momenta of the respective shot would be 13,500 for the 9-pound shot and 24,000 for the 32-pound shot, the 32-pound shot having almost double the percussive force, although discharged with an initial velocity of only half that of the smaller shot. What the carronade lacked in accuracy, in consequence of its reduced charge and length, was thought to be compensated by the greater niceness of its bore, and the reduced windage of its shot, for the art of boring guns was formerly so imperfect that a long gun could not be bored so uni- formly as to admit safely the reduced windage admissi- ble in a shorter carronade bore. This distinction be- tween the bores of carronades and long guns existed for some years, and, when existing, was not generally known. The carronades had from sixty to eighty pounds of metal for every pound of shot, few guns are now cast with less than one hundred pounds of metal to one of shot. This increase of metal admits of heavier charges, which give increased range of shot and still more increased accuracy. 34. Experience of the War of 1812. The experience of our war of 1812 with Great Britain taught another lesson, which was, that if the long 18-pounder be a happy medi- um, the long 24, with which our frigates were armed, was a still happier mean ; for the " United States," owing in a measure to this difference of calibre, cut up the "Mace- donian" most dreadfully, -without herself receiving a cor-, responding damage. 32 NAVAL GTJlSrWEET. Maximum Calibres now in use in the T. S. Navy. Profiting by this lesson, we have gone on steadily increasing the calibre of our naval batteries; the eight-inch shell gun and the 64-pounder, for throwing solid shot, have been intro- duced, and are acknowledged to be most efficient guns for the service required of them. We have not stopped at these, for the guns of nine-inch and even eleven-inch calibre which have been introduced into the service, are proved to possess, within their limited range, more ac- curacy and power than any guns that have preceded them, while the weight of the shells that they throw are not so great as to prevent rapid manipulation. Of course, if the former number of guns be retained, ships of increased capacity will be required to carry the heavier battery and the consequent increase of men, provisions, ! of an inch, must be laid aside as unserviceable. 296. Test of Strength. To test the strength or sound- ness of shot, they are dropped from a height of twenty feet on a solid platform of iron, or rolled down an in- clined plane of the same height against a mass of iron ; after which they are again examined for defects of metal. 297. Inspection of Shells. Shells are inspected in the same way as shot, except the test of strength by drop- ping, but require in addition the following instruments, viz. : Fig. ^ 298. Callipers, fig. 68, for mea- suring the thickness of the shell at points on the great circle, at right angles with the axis of the fuze-hole, which consists of two bent arms movable on a common pivot, and showing on a graduated arc the thickness of the metal ; or, 214 KAVAL aUNNEET. Kg. 69, fig. 69, of one straight arm wtich is placed tangent to the outside of the shell, and one bent, which is inserted in the shell, the thickness being shown on a graduated limb which joins the two. Fig. 70. 299. Callipers, fig. YO, for measuring the thickness of the shell opposite the fuze-hole, which consists of two straight arms connected by a circular piece. One of these arms is inserted in the shell, and the other, being movable, shows on a graduated side the thickness of the metal. 300. Gauges, fig. 71, for the dimensions of the fuze- hole, and thickness of metal at that point. These are PEOJECTILES. 215 Pig 11. pieces of plate metal having in- r \ I clined sides to fit the fuze-hole, ~] — ' with the proper dimensions mark- '^ ed ou them for each calibre. 301. A pair of hand-bellows, and a wooden plug to fit the fuze-hole, and bored through to receive the nose of the bellows. 302. The shell is sounded with the hammer, to see if it is free from cracks. The thickness of metal is measured at . several points on the great circle perpen- dicular to the axis of the fuze-hole, at the bottom, and at the fuze-hole. The diameter of the fuze-hole, which should be accurately reamed out, is measured with the gauge, and the soundness of the metal about the inside of the hole is ascertained by inserting the finger. The shell is then placed in a tub of water, which should be deep enough to cover the shell nearly to the fuze-hole. Air is then forced by the bellows into the shell. If there are any holes in it, air bubbles will rise on the surface of the water, and the shell shall be re- iected. This occasionally occurs from the escape of air from porous spots which do not extend to the interior or the shell. In this case the action of the bellows pro- duces no increase of bubbles, which cease rising as soon as the spots or cavities are filled with water. Porous spots are also detected by their absorbing water, and drying slowly when exposed to the air, and shall like- wise cause the rejection of the shell. Rejected shells are to be mutilated by chipping out a piece at the fuze- hole. Rejected shot are to be marked with an X near the grate, or point where the metal entered the mould. 303. Calibres. The calibre of solid shot or balls is 216 NAVAL GUNNERY. expressed by the round numbers of pounds contained in them. ' At present there are but two solid shot used in our naval service, viz., the 64 and the 32. The differ- ent varieties of shot may be classed as follows : Round shot, bar shot, chain shot, grape shot, and canister shot. Bar shot and chain shot are not now in use. 304. Bar Shot. Bar shot consists of two solid hemi- spheres connected by a bar. 305, Chain Shot. Chain shot consists of two hollow hemispheres, which when their bases are brought together, enclose a piece of chain which is attached to both hemi- spheres. When the shot is projected, the two parts sep- arate to the distance limited by the length of the chain, and sweep over considerable space ; a chain shot has been known to cut a foresail from its yard; they are particularly serviceable in dismantling an enemy at short distances. Of course they are very inaccurate in their flight. Fig. '2- 306. Grape Shot. A stand of grape liiiiwL-^lZ...- ":f!'ij consists of nine shot, fig. T2, of a size ap- \ ''■• 'A. '■ J pi'opriate to the calibre used, ■jvhich are held together by two rings, and a plate at each end of the stand connected by a ■VT ' f;?"'^" rod or bolt. V VJA,/' / Quilted arape consists of an iron plate ^•'^ and an upright spindle, around which balls are placed and held in their positions by a canvas bag, which is tied to the plate, and quilted on to the balls by means of strong twine, which is finally tied aroimd the mouth of the bag. 307. Canister Shot. Canister shot is a tin cylinder with iron heads, filled with balls packed in with saw- n PROJECTILES. Sit dust. The lieads are movable, and tlie edges of the tin are turned down over them to hold them in their places. The balls are made of such a size that seven of them can lie in a bed, one in the middle, and six around, mak- ing the diameter of the balls about one-third that of the bore. These balls are made of cast-iron. 308. Hollow Shot. Hollow shot are divided into shells, spherical case or shrapnel, and carcasses / all of which are made of cast iron. Their calibre is deter- mined either by the number of pounds contained in a solid shot of the same size, or by the number of inches in the diameter of the shell itself. 309. Shells. Shells are hollow shot, the interior space being formed of a sphere concentric with the outer surface, thus making the sides of equal thickness through- out. They have a conical opening, used to load the shell, and in which is inserted the fuze to communicate fire to the bursting charge. Formerly the shell was not fiUed through the faze-hole, but another hole was made, called the filling hole, through which the bursting charge was poured into the shell. The resistance offered by a shell to the force of the powder increases with the thick- ness of its sides. The number of pieces produced when it explodes is the greater, all else being equal, as the metal is more brittle. 310. Spherical Case. Spherical case or shrapnel, as they are called, after the English general who has the credit of having introduced them, are thin-sided shells, in which, besides the bursting charge, are placed a num- ber of musket balls. Their sides are much thinner than those of the ordinary shell, in order that they may con- tain a greater number of bullets ; and these acting as a 218 xIAVAL GUNNEEY. support to tlie sides of tlie shell prevent' it from being broken by the force of the discharge. The weight of the empty case is about one-half that of solid shot of the same diameter. Lead being much more dense than iron, the shrapnel is, when loaded, nearly as heavy as the solid shot of the same calibre. When the shrapnel bursts just in front of an object, the effect is terrific, being in fact pretty much the same as a discharge of grape from a piece at short range. The moment when the shrapnel will do most service is at that distance when grape ceases to be effective. The balls, liberated from the case, have no velocity except that due to the remaining velocity of the case, the charge contained in the case being only sufficient to rupture it, and liberate the balls ; in this consists its distinctive difference from the shell, the power of which lies much in the strength of the burst- ing charge that it may be able to contain. 311. Charging Shrapnel. Shrapnel, when first used, were loaded by simply dropping through the fuze hole a number of balls, and afterward pouring in a bursting charge of powder which disseminated itself in the inter- stices left by the balls ; the present method by confining the powder to a chamber, prevents the powder from being crushed by friction, and enables the bursting charge to be reduced. The present method of loading consists in dropping in the proper number of balls, and then pushing through them, until it rests on the bottom opposite the fuze-hole, a mandril grooved on both sides (first screwing a cup into the fuze-hole). Into this cup melted sulphur is poured, which enters the case through the grooves along the sides of the mandril, and when PROJECTILES. 219 the sulphur is cool, tlie mandril is withdrawn, leaving in the centre of the mass a small chamber in which the bursting charge is placed. Sometimes the mandril is not used, but the melted sulphur is poured in through the fuze-hole until the case is full, and when the sulphur has cooled, the space for the powder is bored out by a cutter, which removes both the sulphur and portions of the bullets from the space. This arrangement places the powder entirely free from contact with the bullets, and it is consequently not liable to be ground up by them while being transported or when the shell is fired. The powder can be placed in this chamber and allowed to remain without fear of damage or danger, and be all ready for use when required. Being, besides, in a com- pact mass, instead of scattered among the bullets, its power is much greater, admitting, as before stated, of a reduction of the bursting charge. 312. English Shrapnel. Figure IS represents the Kg. 73. shrapnel in use in the English service, where a portion of the shell is partitioned /"IK . ^ _ off by a diaphragm of sheet-iron, establish- ( \ *S^ '^ ^ ^^S ^^*^ chambers, one for holding the ^ VtV balls, the other for containing the burst- ^^^^^ ing charge. The spaces between the balls are packed with coal dust. The object of the diaphragm shell is to gaard against any chance of explosion of the bursting charge by concussion. In order that the balls may be released in a uniform manner, four grooves are cast in the interior of the shell, to determine the frac- ture, 313. Carcasses. Carcasses are shells having three additional holes, which are placed at equal distances 220 NAVAL GUNNERY. apart and tangent to the great circle of tlie shell wMcli is perpendicular to the axis of the fiize-hole. They are filled with a composition consisting of a solution of equal parts of white turpentine and spirits of turpentine, in- corporated with as much port-fire composition as will give the whole a compressible consistency ; the port-fire composition must be previously mixed with a small quantity of finely chopped tow. When properly incor- porated, this composition is compactly pressed into the carcass with a drift, so as to fill it entirely. Sticks of wood of about half an inch in diameter are then inserted into each hole of the carcass, in such a manner as to meet in the centre of the composition, in order that, when they are withdrawn, as many holes shall remain in the composition, in the same direction. In every hole thus formed, three strands of quick-match are inserted, of a length suflicient to allow of their being folded over the edge of the hole two or three inches ; some dry port- fire composition is pressed into the interstices to keep the quick-match fast in its place. The quick-match must be coiled into the holes and secured, until the car- cass is wanted, by fastening a small patch over the holes. Carcasses may be filled with the above compo- sition omitting the tow, and the holes may be bored with a gunner's gimlet before the composition becomes hard. Common shells may be loaded and used as carcasses in the following manner: the bursting charge is first placed in the bottom of the shell in a flannel bag, over which carcass composition is driven until the shell is nearly filled ; then insert four or five strands of quick- match, which must be secured by driving more compo PBOJECTILES. 221 sition upon it. These shells after burning as carcasses, explode. 314. Sabots. In order to preserve tlie shell in its proper position in a gun, a block of poplar, linden or other light close-grained wood is secured to the hemis- phere opposite the fuze-hole ; these sabots are strapped to the shells by straps of sheet-tin. Sheet-tin is made by coatiQg sheet-iron with tin. The iron is first scoured, or thoroughly cleaned by means of an acid, and then immersed in melted tin. 315. Hot Shot. Hot shot are sometimes used as pro- jectiles, particularly against ships when engaged with forts. Care is required in loading. The muzzle being sufficiently elevated to allow the ball to roll down the bore, the cartridge is inserted ; a dry hay wad is placed upon it, then a clay or wet hay wad, and rammed down ; and, if firing at angles of depression, a wad of clay or a wet hay wad is put over the ball. The charges for hot shot are from one-quarter to one- sixth the weight of the ball. With low velocities, the shot splits and splinters the wood, so as to render it fa- vorable for burning. With .great velocity, the ball sinks deep into the wood, is deprived of air by the closing of the hole, and chars instead of burning the surrounding wood. The shot should not penetrate more than ten or twelve inches. The wood is not ignited until some time after the penetration of the ball. The wads are made of hay or clay. Clay wads should consist of pure clay, or fuller's earth, free from sand or gravel, well kneaded with just enough moisture to work well. They are cylindrical, and one calibre in length. Hay wads should remain in soak at least ten or fif- 222 NAVAL GUNNERY. teen mimites. Before being used, tte water is pressed out of them. When hay wads are used, vapor may be seen escaping from the vent on the insertion of the ball ; but as this is only the effect of the heat of the ball on the water contained in the wad, no danger need be apprehended from it. With proper precautions in loading, the ball may be permitted to cool in the gun without igniting the charge. The piece, however, should be fired with as little delay as possible, as the vapor would diminish the strength of the powder. 316. Martin's Shell. Experiments have been made in England upon a new projectile, which is an ingenious substitute for redhot shot. It is styled Martinis Shell. It consists of an ordinary shell furnished with an iron screw stopper. Iron is melted in a furnace, and the shell filled with the molten ii-on before firing. To be effective it is necessary that the firing take place as soon as possible after the shell is charged, for the rapid cool- ing of the melted metal will so destroy its liquidity as to prevent the maximum effect from being exerted ; for, on impact, the shell is intended to break, scattering the liquid metal in every direction, setting fire to any thing in the vicinity at all inflammable. Should it fail to break and scatter its contents, it must still be very for- midable as a hot shot. 317. Norton's Liquid Fire. There is a composition, also, in England, known as '■'■JSTorton^s Liquid FifeP In the character of its effects, it rivals all that has been recorded of the old " Greek fire." The composition that Captain Norton uses consists of a chemical combination of sulphur, carbon, and phosphorus. He merely encloses PROJECTILES. 223 his composition in a metal, or even in a wooden shell, and its effects upon striking the sides or sails of a ship, a wooden building, or indeed any object at all combus- tible, is to cause its instant ignition. Captain Norton says, " Some months after Mr. Allison, civil engineer and chem- ist, had explained to me the component parts of his liquid fire, viz., phosphorus dissolved in bisulphuret of carbon, I contrived the following simple and safe means of demonstrating its working. I pierced a cork, some- what larger than that of a wine bottle, longitudinally through its centre, and large enough for the head of a stout arrow to enter ; in the other end I inserted a small glass vial filled with the liquid, and closely stopped with a wooden stopper broader on its outside end. The cork, thus prepared, I fixed on the head of an arrow, and shot it against a piece of loose canvas hung on a cord. On striking the canvas, the stopper was forced into the vial, and broke it in pieces, the liquid soaked into the can- vass, and in a few minutes set it in a blaze." 318. Form of Projectiles. The projectiles fired from smooth-bored cannon are generally of a spherical form, this being the only one which admits the great velocities which are impressed upon them ; if the sphere takes \ip a motion of rotation, the symmetry of its figure renders the effect of that resistance less irregular; and finally the centres of gravity and of figure are less removed than in any other figure, consequently the causes of irregularity are less numerous. If on the contrary, they have an elongated figure, they take up a very irregular motion of rotation, experience an increased resistance on the part of the atmosphere, and have but little accuracy of flight. 224 I^AVAL GTXPTNEKT. 319. Resistance of the Atmosphere. The resistance of the atmosphere, during the flight of the projectile, great- ly diminishes its effect, and it is the influence of its figure upon this resistance which we should consider. If the elasticity of the air were perfect, and if its particles were independent of each other, the moving surface would impress upon these molecules a velocity equal to that which itself possessed, and the resistance would be pro- portional to the square of the velocity; but this sup- position is not true, for experiment demonstrates that the resistance of the atmosphere increases in a higher ratio than the square of the velocity. Though not perfectly so, still the air is highly elastic, and when a projectile moves in it, the anterior strata, to a certain distance, are condensed, their pressure increas- ed, and a certain velocity communicated to them; these strata at first escape laterally, then rush in to fill the void in the rear of the body with an accelerated velocity, encountering the posterior hemisphere of the projectile with a less velocity, and exerting upon it a pressure proportionally less than that upon the anterior hemis- phere, as the velocity of the body is greater ; if the ve- locity of the body be sufficiently great, this displaced air will not return to its former position until after the passage of the body, and a vacuum will be left in its rear: in any case, the resistance to its motion is influenc- ed by the form of the posterior part of the projectile. These phenomena are similar to those when we move a body in the water, the waves and eddies being similar ; we see, then, that a rounded and elongated figure for both the anterior and posterior portions of the projectile would diminish the resistance. PEOJECTILES. 225 320. Windage. The windage of a stot is the diifer- ence between its diameter and the diameter of the bore of its gun. ■ Formerly the prescribed windage was the proportional windage of one-twentieth the diameter of the bore; now and since 1840, shot for the IT. S. Navy have a fixed windage of from one-tenth to two-tenths of an inch for all calibres. Shot of large windage, owing to their greater disposition to deflect, and the greater force with which they are deflected, produce the most serious lodgements in the gun. Shot are cast with less diameter than the bores they are intended for, in order, 1st, to allow for want«of spheri- city ; 2d, to allow for the formation of rust on the shot and in the bore; 3d, to allow for the fouling of the bore in long continued firing; and 4th, for the thickness of the straps which bind a shell to the sabot. If the windage ring be large, much of the force of the inflamed powder wiH escape past the ball, and be of no service ; to avoid this escape is one of the advantages of reduced windage. 321. Inaccuracies caused by Windage. Besides the es- cape and loss of fluid through the windage ring a great- er disadvantage arising from large windage is that it oc- casions inaccuracy in the flight of the shot, for instead of moving along the bore in a line parallel with its axis, and leaving the gun in the same line produced, the shot, if it have great windage, will deflect from the bottom to the top of the bore, or from side to side, and may leave the muzzle with a direction upward or downward, or lateral, which is altogether uncertain, depending upon the point of the muzzle on which the shot last impinged, and therefore necessarily interferes with the accuracy; 15 226 NAVAL GTJ^STNEBT. for suppose figure 74 a ball projected from a cannon, j,j ^^ and having a motion of rotation around a j^-^-^^ vertical axis, J, from right to left, due to '^ " b having impinged on the left side of the bore on leaving the muzzle. The deflection of the ball from left side of the muzzle will cause the ball to deviate toward the right, but the motion of rotation around a vertical axis having been established, the ball will before the end of its flight deviate toward the left; for the right side of the ball having its motion of rotation in conjunction with its' motion of translation, exceeds in velocity the left side of the ball, which has its motion of rotation in opposition to its motion of translation; the right side thus experiences greater resistance than the left side, the ball will incline to the direction of least resistance, hence a deviation to the left. 322. Direction of Deviations not Constant. The direction of this deviation will remain constant as long as the axis of rotation remains parallel to itself; but if, from the disturbing influence of the air combined with other causes in the ball itself, the axis of rotation changes its direction, the direction of the deviation will also change, and this explains why a ball may deviate on both sides of the plane of fire during the same flight. 323. The effect produced by this cause is analogous to that which makes a ship ardent, Avhen, from carrying sail hard, her lee bow being much buried in the water, she has a tendency to fly up into the wind. The com- pressed air in front of the projectile may be considered as an inclined surface, up which the shot is constrained to mount by reason of the reaction from the surface itself. PEOJECTILES. 22T Fig. 15. 324. As a general rule, tlie ball in balloting along tHe bore, strikes against tlie upper part of tlie bore about half way of tlie length, of the piece, and impinges for the last time on the lower part of the bore at the muzzle ; the general deflection, then, is upward, tending to in- crease the range. But the fact of the last contact being on the lower part of the bore, causes the ball to com- mence its flight with a rotation around a horizontal axis turning its front side from above downward ; the effect of this rotation will Tbe to diminish the range. Thus we see how, as a general rule, one motion tends to compen- sate the other, each acting as a corrective to the deviation of the other. 325. Magnus' Experiment. A very ingenious instrument to show the unequal pressure on different sides of a rotating body, has been invented by Professor Magnus, of Berlin. A small cylinder, fig. 75, with a vertical axis, is placed in front of a fan-wheel, by turning which a current of air is forced against the cylinder. Two light O vanes, a a', are balanced on points ^1 on each side of the cylinder by weights on the opposite sides of the pivots. So long as the cylin- der remains stationary, these little vanes are inclined at the same angle toward it, but the moment a rotary motion is given to the cylinder about its axis, the vanes are deflected at unequal angles, showing unequal pressure of the air, the greatest pressure being on that side where 228 NAVAL GUNNERY. the motion of tlie cylinder and cuiTent are in opposite directions. If, for example, the cylinder be rotating from right to left toward »', as indicated by the arrow head, the vane a wiU show the greatest deflection ; and were the cylinder free to move like a ball, it would be pushed, out of its direction, to the left by the increased pressure on the right. This is exactly the effect which experiment shows is produced on a projectile, which has a motion of rotation like the cylinder, and in which the blast from the fan-wheel is replaced by a motion of translation of the body itself If the rotation be from left to right, the same effect in a contrary direction would be observed. Thus we see that if the rotation were around a horizontal axis, the effect would be to lengthen or short^en the range, to lengthen it if the fi'ont part of the ball turned from down upward, and to shorten the range if the front part of the ball turned from up downward. 326. When the velocity of the current of air is very great in proportion to that of the revolving cylinder, the direction of the vane. fig. To, is but little different from what it was when the cylinder was stationary, whereas when the velocity of rotation is only a little inferior to the velocity of the current, one vane ap- proaches very near to the cylinder, whilst the other recedes correspondingly. This corresponds with what is observed in practice ; for the greater the velocity of rotation of a projectile in proportion to its velocity of translation, the greater will be the deviation. The flight of a ball may be considered, then, as being more accurate during the earlier parts of its flight than it is during the latter portion of its course ; for the PROJECTILES. 229 velocity of translation diminisliing very rapidly, wMlst that of rotation continues almost without alteration, the deviating influence of the rotation becomes more sensi- ble as the velocity of translation diminishes, or as the projectUe approaches the end of the trajectory. 327. That the remaining velocity of rotation in pro- jectiles is often very great, is shown by the fact that, after losing aU their velocity of translation, they are sometimes seen to roll on the surface of the ground ; and if any object be interposed to arrest the rotation, that motion is destroyed, wholly or in part, and all the force inherent in the ball is exerted to disengage it, and it will be thrown to a distance sometimes of 250 yards. 328. Eccentricity. In casting shot, short weight often arises from large cavities formed within the shot by confined air. These cavities also cause shot to have eGcentricity ^ or deviation of the centre of gravity from the centre of figure. This eccentricity is of very general occurrence, so much so that nearly every shot possesses what is tQsxajs.^ preponderance, that is, one section of it will be found to preponderate over every other section, if the shot itself be floated in a bucket of quicksilver. If no preponderance can be detected by this simple and accurate mode, no appreciable eccentricity can exist, the shot is then concent/i^ic. The degree of promptness with which an eccentric shot, floated as above, assumes the position due to its preponderance, is regarded as the measure of that preponderance. It was supposed that advantage could be taken of eccentricity in shot to obtain increased ranges, from the fact that when the preponderating side was placed ia different positions the range was sensibly affected. 230 ' NAVAL GUNNERY. 329. Effect of Eccentricity on Range and Accuracy. Be- tween 1835 and 1840, a series of experiments were car- ried on in Belgium, with grek,t care, and with ordnance of different calibres, from wMcli it was ascertained that, when the centre of gravity was above that of the figure, the range was greater than when it was below; and that when the centre of gravity was to the right or left, the deviation of shot was in like manner to the right or left. These results were confirmed by experiments carried on by Colonel Paixhans, at Metz, in 1841. The effects observed were : when the centre of gravity was above the centre of figure the ranges were the longest, and when below, the shortest ; when to the right hand or left hand, the deviations were also to the right or left. The mean range with the piece of ordnance used in the ex- periments, which, with the usual concentric shot, was 1,640 yards, was, with the eccentric shot (the centre of gravity being placed upward), equal to 2,140 yards, being an increase of 500 yards. 330. The reasoning used above in the case of the deviations resulting from the motion of rotation of a sphere in the air applies in the case of eccentric shot to explain the causes of these results of practice. After the motion of rotation in the air is once established, it is evident that the eccentricity of the projectile will tend to increase the resulting effects of rotation beyond what they would be were the ball concentric. It is, however, necessary in the first place to show in what direction the motion of rotation is taken up. Suppose the shot laid in the gun with the centre of gravity above the centre of figure ; any motion of rotation communicated PEOJEOTILES. 231 to an eccentric shot must take place around the centre of gravity ; now it is evident that there is much more surface for the charge to act upon below the centre of gravity than there is above it, consequently the lower portion of the ball will take up a higher initial velocity than wUl be imparted to the upper portion ; a motion of rotation is thus established around a horizontal axis, turning the front part of the ball from below upward. The shot retaining this motion on leaving the gun, the resistance of the atmosphere engendered by the rotation offers more resistance on the under side than on the upper side, the ball, inclining in the direction of least resistance, tends upward in its flight, and the range is lengthened. In like manner it may be shown how the range will be diminished if the centre of gravity be placed below the centre of figure, the ball in this case taking up a motion of rotation around a horizontal axis, turning its forward side from above downward. The same reason- ing will demonstrate that the deviation will be to the right or left, according as the centre of gravity is placed to the right or left of the centre of figure of the ball, the only difference being that in these cases the motion of rotation will be taken up around a vertical axis. 331. Effect of Rotation on Projectiles Fired en Ricochet. With respect to the ricochet of eccentric spherical pro- jectiles, there can be no doubt that the rotation which causes deflection in the flight must act in a similar manner to impede a straight-forward graze. When an ordinary, well-formed, homogeneous spherical projectile, having little or no eccentricity, upon which probably very little rotation is impressed, makes a graze, the 232 KAVAL GTJJSriraET. bottom of the vertical diameter first touclies the plane, and immediately the projectile acquires, by the reaction, a rotation upon its horizontal axis, by which the shot rolls onward throughout the graze favorably for a straight-forward second flight. But in the case of an eccentric spherical projectile, placed with its centre of gravity to the right or to the left, its rotation upon its vertical axis, during the graze, must occasion a fresh deflection in its second flight, and these fresh deflections have been shown by experiments to be always toward the same side of the plane of fire as the centre of gravity ; that is, if the shot was devi- ating to the right before the graze, the effect of the ricochet will be to continue the deflection in the same direction ; and it is only when the centre of gravity is placed in a vertical plane passing through the axis of the gun, that the rotation occasioned by touching the ground or water will not disturb the direction of the graze, though the extent of range to the first graze will be affected more or less, accordingly as the centre of gravity of the projectile may have been placed above or below the centre of figure. In the former case (Avhen placed above) the effect of the rotation, which is from below upward, tends to incline the ball to detach itself from the plane struck as soon as possible, the effect of the graze is also to make the ball bound up ; these two effects conform with each other, and the result is that the ricochet when the ball is rotating from below up- ward does not retard the progressive motion of the ball so much as when the centre of gra^dty is placed down which would impart a motion of rotation from above downward. In this latter case the effect of the graze is PEOJEOTILES. 233 to make tlie ball bound up, but tlie effect of tlie rotation is to make tlie ball have a tendency to remain in con- tact witk tlie plane struck, and to bury itself or to roll along on the surface; these two effects work against each other, and the result is to retard the forward mo- tion of the projectile. In neither of these cases, how- ever, is there any tendency to produce deflection to one side or the other, if the medium struck be a plane sur- face, 332. It would seem that no practical advantage can be gained from eccentricity in a projectile, where accu- racy is required, in consequence of the unequal intensity of the eccentricity in different projectiles. In bombard- ing a town, where it is desirable to have great range, but when it is indifferent where you hit, eccentric pro- jectiles might be of use, inasmuch as the extra range can be obtained by placing the preponderating side up; but in general the practical maxim, with smooth-bored cannon, holds good, that erroi's in sphericity and homo- geneity in a shot are causes of its deviation from a cor- rect path ; and it follows that spherical and homogene- ous projectiles, being the most simple, and quite in different to the position in which they are placed in the gun and rolled home, as well as to that in which they pass through the atmosphere, are decidedly to be pre- ferred to the others. 333. Eccentricity explaining Anomalies. The results of these experiments on eccentricity fully explain the ex- traordinary anomalies, as they have heretofore been considered, in length of range and in the lateral devia- tions; these have been attributed to changes in the state of the air, or the direction of the wind, to differ- 234 NAVAL GIJNNEET. ences in the strengtli of gunpowder, and to ineqiialities in the degrees of windage. All these causes are, no doubt, productive of errors in practice, but it is now clear that these errors are chiefly occasioned by the ec- centricity and want of homogeneity of the shot and the accidental positions of the centre of gravity of the pro- jectile with respect to the centre of figure. These ex- periments furnish decisive proof of the necessity of pay- ing the most scrujDulous attention to the figure and ho- mogeneity of solid shot, and the concentricity of shells. 334. Eccentricity in Stiells. In the shell it is still more evident that any eccentricity could not be control- led and turned to advantage, because in a number of shells the preponderating spot will occupy every variety of position, and as the shell must be placed in the gun in reference to the position of the faze-hole (which, in order that it may receive the flame rushing through the windage ring, is required to be placed "up and out"), it might be found that this would involve the placing of the preponderating spot in the worst possible position. The desire is, then, to make the centre of gravity of a shell coincide Avith the centre of figure, and to effect this a compensating mass is cast about the fuze-hole. 335. Best Position of tlie Preponderating Side. From the foregoing considerations it follows that the smoother the surface of balls, and the less their windage and eccentricity, other things being equal, the greater their accuracy. And when desiring to fire with unusual de- liberation" and accuracy, it is proper to select shot of least windage, least eccentricity and smoothest surface ; and, as it is almost impossible to obtain a ball perfectly concentric, experiments show that the preponderating or PROJECTILES. 235 heaviest side of the shot should be put next to the charge, in which position it interferes less with the accuracy of flight than when placed in any other. 336. Influence of Velocity on DcTiation. It follows, also, that when a ball is deflected from the line of aim by a blow on one side of the muzzle, the less the charge of powder, the greater will be the resultant angle of de- Adation produced by the blow ; and that, since the de- viations produced by friction of the atmosphere are in proportion to the times in which that friction operates, the ball which accomplishes a certain range in a given time has but half the angle of deviation that another ball will have if accomplishing the same space in double the time. Hence, high charges and high velocities arc essential to accuracy, especially in distant firing; and this constitutes the chief advantage of long guns, which bear and burn heavier charges; and accounts for the greater accuracy of larger and denser balls, which retain their velocities longer, and consequently accomplish their distances in less spaces of time. 337. Case of no Deriation. When the axis of revolu- tion makes no angle with the line of flight, but coincides with it, as in the rifle ball, there is, in theory, no devia- tion. 338. Advantage of Large Calibre. The resistance of the atmosphere to two projectiles moving with the same velocity, is respectively proportional to their surface, or to the square of their diameter, while the overcoming forces of these projectiles are proportionate to their weight, or the cube of their diameter; the effect of the resistance of the atmosphere will diminish as the pro- jectile has the greater overcoming force.. In short, the 236 l^AVAL GUNNEET. effect of atmosplieric resistance upon two projectiles moving witli tlie same velocity is in the inverse ratio of their diameters multiplied by their densities. For projectiles of .the same density, the effect of this resistance will l»e in the inverse ratio of their diameters ; take, for example, two balls of the same density, one of 3, and the other of 6 inches diameter ; these correspond nearly with 3-pounder and 24-pounder shot. The resis- tances to these shot are as the squares of 3 and 6, or as 9 to 36, or as 1 to 4. Their forces to overcome these resistances are as their weights, as 3 to 24, or as 1 to 8 (also as the cubes of their diameters, 27 to 216, which is likewise as 1 to 8) ; in other words, the larger of these balls meets a resis- tance four times as great as that of the smaller, but has eight times the power to overcome the resistance, and consequently is retarded in its flight but half as much as the smaller ball ; in other words, the effect of this resistance is in the inverse ratio of their diameters. 339. Advantage of Greater Density. For projectiles of the same diameter, but of different densities, the resis- tance wUl be in the inverse ratio of the densities, thus a shell will be retarded more than solid shot of the same diameter; finally, in order that two different projectiles shall experience the same resistance, it is necessary that the products of their diameters by their respective den- sities shall be equal. It results from this that a leaden ball would experience much less resistance than an iron ball of the same diameter, but balls of lead lose their form upon the first impact, even upon water, and have not a sufficient consistence to penetrate bodies which offer much resistance. PEOJECTILI^. 237 Wrouglit-iroii balls would have an advantage over cast-iron shot, but the expensive character of this ma- terial seems to present an insuperable obstacle to adopt- ing it for the purpose of projectiles. 340. Advantages of the Spherical Form. The projec- tiles first used in artillery were irregular in form, and con- sequently very inaccurate in fire, and it was not long before the advantages of the spherical form were demonstrated. The sphere, as before stated, presents the minimum surface for a given volume ; and the wind, which causes so much inaccuracy in elongated projectiles, has com- paratively but little eifect on the round one, which, having its centres of gravity and figure more nearly co- incident than any oth,er, presents, when it rotates, an equal surface always to the action of the air. If it strikes any object in its flight, it is less deflected from its course than one of any other form; an important fact at sea, where much of the firing must be en ricochet, also a very im- portant fact in sieges, since ricochet firing is sometimes the only means of reaching an enemy behind obstacles. 341. Advantage of the Elongated Form. When the de- sign is to strike an object direct, however, the sphere is no longer the most advantageous form. For, by making the projectile elongated and pointed, the resistance of the air is very much diminished, and additional weight can be added without increasing the cross-section of the projectile, thus increasing its power of overcoming the resistance, and favoring the penetration of the projectile when it strikes. 342. Requirement for Accuracy with Elongated Projectiles. Of course the elongated projectile, to be used Avith any advantage, must be preserved in its position of moving 238 NAVAL GTJinsrEET. through the air, point foremost ; otherwise, were it al- lowed to take up indiscriminate motions of rotation, it would tumble over and over, sometimes presenting its point, sometimes its side, and sometimes its base, to the resistance of the air, and would describe a trajectory totally at variance with accuracy ; on striking, also, it would be altogether uncertain what portion of its sur- face it would bring into contact with the object, thus, striking with its side or base foremost, its penetration would be insignificant. The elongated projectile is kept in the desired position of moving point foremost by de- termining its rotation around an axis passing lengthwise through the centre, in fact giving to it the rifle Tnotion, which is effected by cutting grooves in the bore of the piece, which impart the required motion to the ball dur- ing its passage along the bore, and the ball pursues its flight through the air retaining the acquired motion ot rotation. If the projectile be made of iron, it must be supplied with an outer coating of softer metal which can enter the grooves in the bore, but this subject will be dwelt on more at length under the head of Rifles; we remark again, however, that the use of the elongated ball must be disadvantageous if the rifle motion be not communi- cated to it ; but this motion being established, and the small diameter only being exposed to the resisting influ- ence of the atmosphere, the advantage derived from its increased weight is evident. 343. Resistance to the Spherical and Elongated Shot Com- pared. Taking the most approved form for elongated projectiles, the resistance to it is found to be about one- third of that offered to a spherical ball of the same dia- meter. The resistance to the spherical ball is one-halt PROJECTILES. 239 of what one of its great circles would experience ; so that the resistance to a projectile moving point foremost is just oneTsixth of what it would be were it moving with the base to the front. The resistance increases as the surface against which it acts becomes more nearly per- pendicular to the direction of this resistance. Hence, if this projectile becomes flattened by the rammer (as in loading a musket or rifle with a, leaden bullet) the resist- ance is very much increased. The resistance is, however, stiU. very great to even pointed projectiles, it being estimated that it reduced the range of a rifle bullet experimented on in Prance, to one-half of what it would be in vacuo. 344. One advantage possessedby the spherical figure is the manner in which it enters the gun; it rolls instead of sliding, and injures the bore less ; spherical shot can- not jam in the bore, which sometimes happens Vidth the elongated ball. 345. Influence of Wind on Accuracy. In addition to the injurious effects produced upon accuracy by windage and eccentricity, the action of the wind operates to interfere with the flight of projectiles; this cause pro- duces a gi'eater effect as the projectile increases in size and decreases in density, hence a shell will be more affected by it than a solid shot. With elongated projectiles the wind has a greater surface to act on, and produces a greater effect than on spherical balls. Elongated projectiles are some- times found to work up to windward instead of be- ing driven off to leeward. This is due to the fact that the part of the ball behind, being the lightest, is most easily acted on, and being thrown away from the wind, 240 NAVAL GtrWNEET. the point is tlu'ownin the opposite direction, giving a de- viation towa/rd the wind. The deviations arising from the action of the wind are very variable, and no rules can be laid down for correcting them. Practice and close ob- servation of the previous fires are the only correctives. 346. Penetration of IVavy Ordnance. The following table of penetrations maybe useful as a reference, as ex- hibiting the power in this respect of the ordnance of the United States Navy. It is the result deduced from nu- merous firings at a target of se9,soned white oak, made at the experimental battery at "Washington. The table is extracted from " Shells and Shell Guns," by Comman- der J. A. Dahlgren : INITIAL PEIIETEATION. GUN. MS. PROJECTILE, TELOCITY. 500 Yns. 1,000 YDB. 1,600 YDS. 2,000 YDS. PEBT. INCIIL'S. INCHES. INCHES. INCHES. 18 pdr. long 6 shot. 1,720 28.9 17.9 11.0 6.9 24 " 8 1,720 33.5 21.8 14.1 9.3 32 '• ofSScwt. 44 1,250 26.4 18.5 12.7 8.8 32 " of 42 " 6 1,450 32.0 22.0 15.0 10.3 32 " long 9 1,700 38.7 26.5 18.2 12.5 42 " 104 1,620 41.7 29.7 21.1 15.1 64 " 16 1,620 49.9 37.3 27.9 20.8 8-in. of 55 cwt. 7 shell. 1,350 29.2 20.2 14.0 9.7 8-in. of 63 cwt. 9 u 1,500 33.2 23.0 15.9 11.0 Coimnander Dahlgren remarks, "the penetration of the tables assumes the surface of the object to be placed rectangularly to the direction of the line of fire ; while in actual combat this will be an unfrequent occurrence ; for the opposing ships will be in constant motion in order to obtain or to preserve certain advantages of position, or to prevent the attainment of them by the other party; consequently the hulls, in the great major- ity of cases, will be presented more or less obliquely to the direction of fire, and the effort of the ball will be unfavorably exerted on the tough and elastic fibres of PEOJECTILES. 241 the oak, in proportion to the inclination of tlie surface with the direction of the ball's flight ; and when this 'angle is reduced to 15° the ball glances entirely." 347. Rockets. A rocket for military purposes con- sists of an inflammable composition contained in a cylin- drical case "of sheet iron. The head is of cast-iron, and may be either a solid shot, or a shell with a fuze com- municating with the rocket composition. The compo- sition consists of nitre, sulphur, and charcoal. When the rocket is used merely for making signals, the com- position is contained in a stout paper case, and the head, which is then conical, is flUed with a composition for producing, at the explosion, the decorations, such as stars, serpents, golden rain, &c. 348. Signal rockets are usually made of two sizes, 1.5-inch, and 2-inch, and are designated by the exterior diameter of the case. 349. The Former^ fig. 76, consists of two parts, the longest one being square at one end, and having at the other, where it is slightly rounded, a conical opening, into which fits the spindle of the second part, which is shorter than the first. Pig. 76. At the point where the two parts join, both being rounded, is a depression which is to form the choke of the rocket. The diameter of the former is two-thirds of the calibre of the rocket. To make the case, the former is enveloped with a sheet of the proper paper, cut to the required size and pasted after the first turn. It is then placed in the press 16 242 NAVAL GUNNEEY. and rolled tight, after whicli another piece of paper is rolled, pasted, and pressed on; and so on until the proper size is obtained. The press consists of a table' having grooves in the top, of a proper size to receive the cases. On top of this is placed a heavy platform with corresponding grooves, and this is hinged to the table and raised by a lever to put the cases in. The cases are then rolled by slipping a handle on the square end of the former and turning it. 350. The Choke. To choke the case, it is wrapped at the joint of the former with a piece of strong paper, to prevent the choking cord from chafing it. A strong, smooth cord is taken around the case at the joints of the former^ and a strong strain is brought on it. As the pa- per yields to the pressure, the short part of the/orwer is drawn out, until the case is sufficiently contracted, when the cord is taken off, the choke wrapped with strong tAvine and the former removed. When the case is per- fectly dry, it is trimmed to the proper length, so that the distance from the middle of the choke to the bottom shall be equal to that from the bottom of the spindle to the bottom of the mould, and the remaining portion equal in length to the distance between the bottom of the spindle and top of the mould. 351. Rocket Composition. The rocket composition should be well mixed, by passing it through fine sieves, and rubbing it in the hands. The charcoal, being the lightest ingredient, must be added after the nitre and sulphur have been mixed; and, Avhilst driving, the rocket composition must be frequently stirred to prevent these heavy materials from settling to the bottom. 352. Moulds. Moulds, for driving rockets, are cast in PKOJECTILES. 24J Fig. 11. a single piece, and bored out to the proper calibre. The spindle, wliicL. is made of cast steel, stands on and is connected -with the base, of cast iron, as is represented in fig. 77. The mould being passed down over the spindle, is secured by a pin, which runs through both. 353. Driving the Composition. The case is placed over the spindle, choke down, and settled with a mallet until it rests on the base of the spindle. The mould is then placed over it, and keyed to the base, which should rest on some solid foundation, as a large block of wood. The composition is placed in from a ladle, which is made of such a size as to contain enough to form a column, when driven, equal in height to one-half the interior of the case. In driving, four drifts are used, made of brass, or hard seasoned wood tipped with brass. The drifts have handles strengthened at the top by copper bands. The first drift is pierced, to receive the whole length of the spindle; the second to receive two-thirds of it; the third to receive one-third ; and the fourth is solid. 354. Mallets. Mallets for driving 1.5-inch and 2- inch rockets are turned, out of hard well-seasoned wood, and weigh about two and three pounds respectively. The force to be employed in driving depends on the size of the rocket, the larger receives thirty, and the smaller twenty-five blows, for each ladle full of compo- sition. The hollow drifts are fi:rst used, the shorter ones being taken as the case fills. When the composition 244 NAVAL GtrinsrEKT. Ms. 78. reaches tlie top of the spindle, one more diameter is driven with the solid drift, and covered with a patch of stiff paper, cut to fit the case ; and over this is driven a wad one-third of a diameter high, of clay, or plaster of Paris slightly moistened with water. This wad is after- ward pierced with a gimlet through to the composition, by means of which fire is communicated to the bursting charge in the pot containing the ornaments. -Rockets are sometimes driven solid throughout, and afterward bored out with a tap of the form of the spindle. 355. Pots. Pots are made of rocket paper, by roll- ing two or three turns of it upon a former of the same diameter as the rocket case, pasting it all well except the first turn on the former. The pot is two diameters long, and when attached to the rocket has an interior depth of one and a half diameters. In it are placed the or- naments of the rocket, and the charge of powder designed to blow them apart. 356. Cones. Cones are made of rocket paper, which is cut into circles of a diame- ter equal to twice the height of the cones to be made. Each of these cu-cles, cut in half, makes two cones. They are rolled upon the former, fig. 78, pasted and dried. 357. Priming. A rocket is primed by coiling a piece of quick-match, about two inches long, in the conical opening, and covering it with a cap of strong paper, )asted down or tied in the choke. 358. Making np tlic Rocket. To make up the rocket, the pot is placed in position, by pasting the upper part PROJECTILES. 245 of the case, and sliding it into tlie pot to the proper dis- tance ; or a ring of light wood may be used, wMcli, fit- ting inside the lower end of the pot, is placed over the upper end of the case, by taking off several folds of the paper down as far as is necessary. The plaster of Paris covering having been pierced with a gimlet, the hole is filled with mealed powder, and the bursting charge and ornaments placed in the pot with a slight covering of tow. The cone filled with tow (to assist in resisting the pressure of the air), and with its base cut to the same size as the pot, is placed on top of the latter, to which it is fastened by pasting over it a cone made of fine paper, the lower part being cut into slips, and pasted down over the pot. A slip of fine paper is then pasted around the joint to give a finish to the rocket. The cone decreases the opposition offered by the air, and as- sists the rocket in penetrating it. 359. Rocket Stick. As a guide to the rocket, a stick made of dry pine or other light wood, and nine times the length of the case, is attached to it with twine. The large end is fixed to the case, and is bevelled off so as to decrease the resistance of the air. The side next Fig. 19. the case is grooved out for a distance equal to two- thirds the length of the case which fits into it. Just below the bevel, and also opposite the choke, notches are cut to receive the twine by which the case is bound to the stick, fig. Y9. The other end of the stick is de- 246 NAVAL GUNWEBT. creased in tMckness to half tliat of the case end. The poise of rockets should be verified by balancing them on a knife-edge. Those under 1.25 inches should bal- ance at three diameters from the neck; between that and 2 inches at two-and-a-half diameters, and larger rockets at two diameters. If the stick is too light, the rocket will not rise vertically ; and if too long and heavy it rises slowly, and will not arrive at its proper height. 360. Decorations. Stars are the most beautiful dec- orations of rockets. They are made by driving the composition, moistened with alcohol and a small quan tity of gum-arabic solution, in port-fire moulds, without any paper case, and with a moderate number of blows ; they are cut into lengths of about three-quarters of an inch, and dredged with mealed powder. A more expe- ditious and better mode of making them is, to moidd them in a brass cylinder of the diameter desired for the stars, and push them out with a rammer, cutting them into proper lengths as they are formed. Stai's, after being dredged with mealed powder, must be dried in the shade. The gum-arabic, used in the star composi- tion, is intended to give such consistency to the stars that the explosion of the head of the rocket may not break them in pieces, and thereby destroy the effect. 361. Coagreve Rocket. The rod, attached to one side of the rocket, occasions irregularities in its flight, and the late Sir William Congreve, whose name is identified with this species of artillery, placed it in the direction of the axis of the rocket. This disposition, in a great measure, remedied the evil without interfering Vith the escape of the gas, for in the neck of British war rockets, PROJECTILES. 247 rig. 80. fig. 80 several apertures are formed for tlie admission of air ; at one of ttese in whicli is left a piece of quick- matcli, the fire is applied to the composition. The rocket, when about to be fired, is fitted in a tube, which is attached in a given position, to a rest ; when, on ap-' plying the match, the whole surface of the conical space is put in a state of slow combustion, and the rocket is propelled. The combustion continues until the compo- sition is entirely consumed, the elastic gas generated by the combustion escaping through the apertures. 362. Motive Power of the Rocket. The propelling power is produced by the expansion of the gas generated in the burning composition ; the force, thus originated, causes a pressure, outward, against the sides and ends of the rocket, but the apertures in the neck allowing the gas to escape there (being resisted only by the pressure of the atmosphere at the apertures), the pressure against that end is consequently less than that which is exerted by the gas against the head or anterior part of the rocket ; and the difference between the pressures at the opposite ends is a resultant force, acting against the head during all the time that the composition is burn- ing ; this constitutes, therefore, a pressive force by which the rocket moves onward, with a motion continually ac- celerated, till the resistance of the air against the head becomes equal to that force, or till the composition is burned out. This action of the gas is quite analogous to that which produces the recoil of a suspended gun when fired without shot or wad. 248 NAVAL GUNBTERT. 363. The Rod. The rod serves to guide the rocket in its flight, the lateral resistance of the air about it pre- venting, in some measure, its vibrations. In a one-pound rocket, before combustion begins, the common centre of gravity of the rocket and rod is about two feet from the head of the former, and about seven feet from the oppo- site extremity of the latter ; and then the resistance of the air, in checking the vibrations of the rocket, acts with considerable effect, like a power applied at the end of the longer arm of a leyer; but, in proportion as the composition is burned out, the centre of gravity ap- proaches the middle of the length of the whole missile ; the resistance of the air is then less able to counteract the accidental deviations of the rocket itself; the head at the same time begins to droop, and at length the whole comes obliquely to the ground. It has happened, even when the angle of elevation was small, that the weight of the rocket preponderated so far over that of the rod as to cause the missile to come to the ground in a direction tending toward the spot from whence it was fired. 364. Range. Signal rockets, whose diameters vary from one to two inches, will ascend verticaEy to a height of five hundred or six hundred yards ; and those whose diameters vary from two to three inches, to a height of twelve hundred yards. A 12-pounder rocket, fired at an elevation of 16°, and a 6-pounder rocket at an elevation of 142°, range about twelve hundred yards. The distances at which the explosion of rockets has been seen vary from forty to fifty miles. 365. British Rocltcts, The use of rockets was first introduced into the English military service by Sir PEOJEOTILES. 249 William Congreve. TMs officer caused them to be made to serve as shells or carcasses, and their weights, for these purposes, were 3, 6, 12, 24 and 32 pounds. When fired against timber or earth they penetrate to considerable depths. A 12-pounder rocket, after a range of 1,260 yards, has been known to enter to the depth of twenty-two feet into earth. 366. Every shell rocket in the English service is fitted at its head with a fuze, screwed into the base o± the shell. The fuze is as long as the size of the shell will admit of, so as to leave sufficient space, between the end of it and the inner surface of the shell, for admitting the bursting charge ; and the end of the fuze is cupped, to serve as a guide in the insertion of the boring bit, when it is desired to shorten the time of burning of the fuze by perforating the composition. There is a hole in the upper end of the shell, secured by a screw metal plug, for putting in the bursting charge, and for boring accord- ing to the different ranges at which it may be required to burst the shell. If the rocket is to be used as a shell rocket, at the longest range, the plug is to be taken out, and the shell filled, the fuze left at its full length, and the plug replaced. If at the shortest range, the fuze is to be entirely bored through, and the rocket composition bored into, to with- in one inch and a half of the top of the cone, in the 24-pounder rocket, and to within one inch in the 12, 6, and 3-pounder rockets. 36Y. Tncertainty of Rocket Practice. Experiments on shell rocket practice show the great uncertainty of that practice against troops in the field; and to this un- . certainty must be added the liability of the sticks to 2ol NAVAL GUNNEET. be broken on grazing tlie ground when fired at low angles. Tlie forward motion of a rocket is impeded by the resistance of the air at the head, and by the action of gravity. Again, in firing across the wind, the action of the air upon the stick causes the rocket to come up more to the wind instead of being driven -bodily to leeward, and the stronger the current of air is, the more the rocket points toward the quarter from whence the wind comes. When the rocket is fired against the wind the range is considerably shortened, and, when fired with the wind, it is lengthened. Thus, in firing across the wind, some allowance must be made for its effects, and the rocket must be pointed by so much to leeward of the object; in firing against the wind, greater elevation than that which the distance requires, must be given ; and, in firing with the wind, less elevation must be given, but the amount of these allowances can only be assumed approx- imatively, according to an estimate of the strength of the wind, and therefore the practice must be uncertain. 368. Limited Usefulness of Rockets. Rockets may be used, with some advantage, against cavalry, from the scaring effects of theblazing projectile upon horses; also against large masses of infantry; but they are totally inefficient in firing at small objects. Many exaggerated opinions were once entertained of the efficiency of this weapon, and it was believed that rockets would super- sede the use of artillery in the land service; but these opinions have generally sobered down to the idea, now prevalent, that they are only substitutes for field guns when these cannot be brought up. 369, Incendiary Property of Rockets. The most efficient PROJECTILES. 251 use, however, that can be made of rockets is as an incen- diary projectile, to set fire to towns or single buildings. From their want of penetration, rockets are powerless against the strong materials of ships of war, but they may- be used against places on the sea-coast, to protect land- ings, and against- crowds there assembled. For this pur- pose, in the English Navy, they are plentifully supplied to small steam vessels, which have light draught of water, and approach close to an enemy's coast. Rocket filing, however, from ships is a very dangerous practice ; the first rush of back fire, befor^ the rocket starts, is capable of igniting any combustible body upon which the flame may act. 370. Trajectory of the Rocket. The great uncertainty of rocket practice will be obvious from considering the causes which produce its trajectory. When it first starts from the tube, its velocity is so small that it is not sufficient to prevent the fore part of the rocket from drooping or dipping below the axis of the tube; the ac- tual angle of departure, therefore, is less than that at which the tube is set, and allowance for the error can only be made by a vague estimation. As the rocket proceeds, its velocity increases, and is supposed to be greatest at one-third or one-half the range. The common centre of gravity of a rocket and its stick, on starting, is situated near the propelling power, and the vibrations of the rocket during its flight take place about that point; this point is, however, continually changing its place in proportion as the composition is consumed, and this change causes continual irregularities in the devia- tions of the rocket during its flight. When the com- position is entirely burned out, the rocket proceeds under 252 NATAL GUNNERY. new and very different conditions; so tLat upon the whole it is utterly impossible to lay down the trajectory of a rocket, or to obtain good and sufficient rules for conducting the practice with that arm. 371. Rockets Fired from Cannon. The idea has been started of late of combining the rocket with a piece ot rifled ordnance, projecting it from the piece with a ve- locity sufficient to overcome all causes of deviation and inaccuracy which obtain at the commencement of the rocket's flight, and enabling it to range to much greater distances. Mr. Greener writes, "My experience with rockets goes to justify me in asserting that rockets dis- charged from a gun, under certain circumstances, can be as effectually controlled, and kept to a direct course, as a bullet fired from a rifle. The rocket, however, may be fired a much greater distance than we have ever been able to project a bullet; because, in addition to the force which projects it from the gun, its flight is maintained by the self-sustaining agency in the body of the rocket. Kockets require a much smaller charge of powder to project them than that which is required by a ball. A rocket, started by its own force, expends, in acquiring even an approximation to its highest velocity, at least one-third of the force with which it is charged ; but when projected by a small charge of gunpowder this force is saved, and the flight of the rocket is afterward sustain- ed by the force with which it is charged. " Firing rockets from cannon can only be practised under certain circumstances. A rocket suitable for ar- tillery should be cast of gun metal, with a frame of con- siderable strength; the composition should be more densely driven than is customary in the ordinary rocket ; PROJECTILES. 253 the outer frame of tie rocket should be cast with suita- ble projections to fit the grooves cut in the bore of the gun; the twist of these grooves should be considerable, as much as one turn in every three feet, in order to im- part to the rocket an effectual spinning motion when in a low state of velocity. The rocket, properly constructed, is then placed in the rocket gun, and fired in the usual way ; but it is essential that the gunpowder used should be of a suitable quality ; its combustion must be as slow as possible, a starting velocity of from five hundred to eight hundred feet per second being sufficient to insure the flight of the self-sustaining projectile to the end of its ranare." 372. Hale's Rocket. A very ingenious method of dis- pensing with the stick of the rocket has been proposed by Mr. Hale of England ; and, having been experimen- ted on by a board of United States officers, has been adopted into our service. This consists in causing the rocket to rotate on its axis during its flight, and, as in the case of an elongated shot, move steadily with the point foremost. For this purpose instead of permitting all the rush of flame to escape from the bottom orifice in a line with the axis of the tube, a portion of the inflamed gases issue from five orifices made near the neck, ob- liquely to the axis of the tube, the effect of which is that the body of the rocket is made to rotate while it is also propelled. In the experiments made with these rockets several modes of directing them have been tried ; first, by firing them from a small trough formed of wood in two inclined planes; secondly, from a frame carrying two portions of rings, which grasp the body of the rock- et, and retain it in one position until it has acquired, 254 NAVAL GUNNEEY. after ignition, sufficient force to overcome tlie pressure of a spring below it ; tMs force, suddenly releasing tlie body from tlie rings, permits tbe rocket to escape mtli a velocity sufficient to prevent tbe usual droop or dip mentioned before. 373. The appearance of tbe original Hale rocket was tte same as the Congreve rocket, to wMcli the Kg. 81. stick has not yet been attached, but it has undergone some modification since its first introduction. At pres- ent the tangential holes, of those in our service, are three in number, and, instead of being situated posteriorly at the neck of the rocket, are placed as far forward as the rear of the solid head, fig. 81, the perforation in the composition extending through the entire length of the case, and a small chamber being provided, within the rear part of the head, for the accumulation of the gas which issues through the tangential holes, 8*74. The English Hale rocket, fig. 82, has the tangen- tial holes also moved forward, they are two in number ; but the interior arrangement differs from that now in use in our service, in that the perforation in the composition is divided into two compartments by means of a diaphragm of iron which extends transversely across it, and which has a small hole through it coincident with the axis < f PEOJECTILES. 255 tlie case. The anterior chamber is exclusively concerned in furnishing gas for supplying the two tangential holes, while the posterior chamber is devoted to the evolution of the flame of propulsion. The use of the hole through the axis of the diaphragm is to obviate the necessity of igniting the rocket in two places. 375. Hale's Rocket Tube for Broadside Firin;^. Mr. Hale went so far in his enthusiasm in connection with his rocket, as to propose it for the armament of ships ; and, recognizing the injurious effect of the back fire which makes this weapon so dangerous in use on board ship, he devised a tube for broadside rocket service. It re- sembled a large tubular letter U, resting upon one bend, with both its heels sticking out of the port ; by this de- vice the back fire would be directed toward the enemy, and the rocket, acquiring strength, was to find its way around the U tube and fly in the direction of the enemy. 376. The Hale, like all other rockets, is liable to one very great objection, that is, that after the composition is burned out, it loses its directing power, because the rotation ceases when the composition is consumed ; no accuracy can, then, be expected from it beyond the dis- tance it has reached when the composition ceases to bum. 256 NAVAL GirifNEET. CHAPTEE YII. FUZES. 377. A Fuze is a contrivance by wMcli fire is com- municated to the bursting charge in a shell. Fuzes are divided into three classes, viz.: the common or time fuze, the concussion fuze, and the percussion fuze. 378. The Time Fuze consists of a column of inflam- mable composition which, being ignited by the charge in the gun, burns for a certain space of time, at the end of which it communicates its flame to the bursting charge in the shell. 379. The Concussion Fuze consists of an an'angement of inflammable composition, which is ignited by the charge in the gun, and in which the flame, by means of some interior contrivance, is admitted to the bursting charge in the shell at the moment of "la btrikiug ihc- object. 380. The Percussion Fuze receives no flame from the charge in the gun; but, at the moment of impact, a flame is generated, by means of fulminates, which pro- duces the explosion of the shell. 381. Fuze-Gase. The Fuze-case is a tube of suitable exterior and interior dimensions, for containing the fuze composition, which is compressed in it either by a drift and mallet, or by the force of a press ; the press used in the manufacture of the fuzes for our navy shells exerts a force of about 2,200 lbs. FUZES. 257 The oldest form of fuze-case was of wood, fig. 83, and Fig. 83. consists of a conical plug of wood of the proper ' 'iCj» i i|f^ size for tlie fuze-hole of the shell with which it i is to he fired. The axis of this plug is bored I out cylindrically, from the large down to with- i in a short distance of the small end, which is dM left solid. At the large end a cup is hollowed { i out, and the outside of the plug is divided into i. J inches and parts, generally tenths, commencing '— ' at the bottom of the cup. The cylindrical space is filled with composition, pounded or pressed hard as stone, the composition being solidified untU its den- sity is doubled, and the cup filled with mealed pow- der, moistened with whiskey or alcohol. The rate of burning is determined by experiments, and marked on a water-proof paper cap, which is tied over the cup. Knowing the time any shell is to occupy in its flight, the fuze is cut off with a saw, or bored, at the proper division, and firmly set in the fuze-hole with a mallet. If the wooden case should be set at an ang'le with the axis of the piece when fired, the jar of propulsion might bend it, thus breaking the column of composition, and cause a premature explosion of the shell by exposing an increased amount of surface to the flame ; in order to guard against this accident, it is necessary to place a wooden fuze-case in the axis of the bore. 382. Metallic Fnze-Case. It is very desirable, how- ever, that the fuze-hole of the shell should be placed up in the bore, in order to insure the inflammation of the fuze by the flame rushing through the windage ring ; in order the better to achieve this object, and also on ac- count of the rapid deterioration of wooden cases, we 17 258 JSTAVAL GTJNlSrEEY. have adopted in our naval service a metal fuze-case com- posed of copper and tin ; and the better to guard against the effect of moisture and against any chemical action that might be excited thereby between the composition and the metal, the composition is first driven in a papei- case which is afterward inserted in the metallic case. The metallic case is better able to resist the tendency to bend, which is induced by the effort of the shell to take up suddenly a rapid motion, and can be placed in that position in the bore where it is most certain to receive the full benefit of the flame. The fuze is generally* placed vjp and out. The metallic fiize-case of the navy is of such a length as to extend very little, if any, inside of the metal about the faze-hole ; in the 8-inch shell the fuze-case is supported by the metal of the shell thi-ough- out its entire length. The fazes of the United States navy are divided into five, ten, and fifteen seconds, a cer- tain proportion of each being supplied to each shell gun. 383. Paper Case. The paper case is made of stout paper cut in slips of the required size, having one end square and the other tapered to a point. The paper is rolled up on a cylinder of the required interior diameter of the case, and cemented where the surfaces come in contact. The taper with which the paper is cut gives a less exterior diameter at the bottom than at the top of the case. 384. Safety Plug, Before the composition is driven or pressed into the case, a safety plug is inserted which consists of a short solid cylinder of lead, surmounted by a shorter hollow cylinder of the same material and of the same diameter as the plug which it surmounts. The * The fuze in 9-indi, 10-inoh, and 11 -inch shells is placed in the axis of the bore. FUZES. 259 plug being inserted, and the solid portion of it project- ing below tlie tapering end of the case, a drift is intro- duced wMch, resting on tlie edge of the hollow cylinder or cylindrical cavity, is struck a smart blow with a mal- let, which, flattening out the sides of the lead, causes it to bind against the interior of the paper case, thus closing the end of the case, and preventing the issue of flame through that end of the case as long as the plug remains fixed. The shell, with its faze fitted with the safety plug, should be safe even were the fuze to be ig- nited on deck, but the jar of concussion, consequent upon the explosion of the charge in the bore, is so great as to detach the plug from the case at the moment that the shell commences its flight, so that from the moment the shell leaves the gun the communication is open be- tween the burning composition in the fuze and the burst- ing charge in the shell, and as soon as the composition is consumed the shell will explode. 385. Water Cap. The paper case, after the compo- sition is driven, is cut off to the required length and placed firmly in the metallic case. After the paper case is placed, a contrivance, called a water cap, is screwed in over the composition ; this contrivance has for its object the preventing the entrance of any matter, such as sand or water, over which the shell may ricochet, and is primed on its outer surface with a little powder and strands of quick-match. Over all is placed a leaden patch which securely guards the priming against mois- ture, and which must be removed at the time of enter- ing the shell in the bore, or the shell will not explode. 386.- Paper Cases. The paper case is sometimes used without being inserted in another case, but is, at the 260 NAVAL GUNWEEY. time of firing, inserted in the fuze hole, into wliich it is firmly set by blows of a wooden mallet, the fuze-hole having been previously bouched with wood or lead. When the fuze-hole is bouched with wood, the plug should be bored with a small drill at first, then driven in, and the hole afterward enlarged to receive the fuze ; were this precaution not taken, the plug would shrink and fall out. This use of the paper case was made with the United States boat howitzer ammunition, to every round of which a package was supplied containing five fazes, marked respectively in black circles around the case one, two, three, four and five seconds. The paper cases in use in the army are distinguished by the color, thus: Black burns 2 seconds to the inch. Red " 3 " " '' Green " 4 « • « « Yellow " 5 " " " Each fuze is made two inches long, and the yellow burns consequently ten seconds. This aiTangement is very objectionable as it involves the exercise of memory in selecting the color that may be required for immedi- ate use. At present the paper case is almost entirely super- seded by the Bormann fuze in the ammunition for the boat howitzers. 387. Fuze-Cases of other Nations. The fuzes of the English Navy have the metallic case ; but the French still adhere to the wooden case, from the belief that the metal • case, being raised to a high temperature by the burning composition may explode the bursting charge thus causing premature explosions. The Russians early FUZES. 261 adopted the metallic case, and proved at Sinope botli tlie terrific power of shells and the good quality of the fuzes. 388. English Fuze. The English fuze cases are made of brass, and are of three sizes, according to the calibres with which they are used. They differ from those of the U. S. Navy in having no safety plug, and no water cap. During the flight of the shell, the composition in the fuze is unprotected from the entrance of sand or water, over which it may ricochet, and is liable to fail- ure from this cause ; Sir Howard Douglas states that four fuzes out of five are extinguished on striking the water, and about one in three on striking a ship. The faze composition, however, is protected from moisture &c., by a brass cap which screws on outside the fuze case over the composition ; this cap is unscrewed by the loader at the time of entering the shell in the bore of the piece, and to guard against the danger of loosening the fuze case in the fuze-hole, the screw for the fuze case and that for the cap are cut in opposite directions ; the effect, then, of unscrewing the cap is to tighten the fuze case in the shell. The thread on the case, how- ever, projects beyond the surface of the shell after the cap is unscrewed, and must disturb the flight of the shell. 389. Injuries from Sliociis. It has long been recog- nized as a fact, that the fuze composition, driven in a wooden or metallic case, tightly fitting the fuze-hole of the shell, is liable to many injuries from shocks in and out of the bore, by which the composition is broken and cracked in such a way as to give passage to the flame, and cause premature explosions. Various means were 262 NAVAL GUNNEET. adopted to overcome this difficulty, and, among others, may be mentioned tlie cutting the inside of the case into grooves like a screw ; and afterward in the form of rings not communicating with each other, as the screw shape was found sometimes, after the wood had shrunk, not to fiiliil the object. Such a defect was more especially noticed in shrap- nel shells, the thin sides and short hearing surface for the fuze in them causing the shocks to be more forcibly transmitted to the composition. The conical form of the paper fuze case, and the bouching in the fuze hole, of the shrapnel supplied to the Navy howitzers obviates this objection in a great measure, but a more elaborate system of protecting the faze from the injurious effects of these shocks was in- vented by Captain Splingard of the Belgian Artillery. 390. Splingard Shrapnel Fuze. The Splingard shrap- nel fuze consists of two parts ; the fuze, properly so called, and the fuze-plug. The first is a small cylindri- cal tube of hammered copper, the upper end of which swells out so as to foi'm a kind of cup to hold the prim- ing, and prevent the case from being driven into the shell when the piece is fired. This tube is filled with composition in the usual way, a conical opening, one- tenth of an inch high, being left in the bottom, in order, when the flame reaches that point, that a larger surface may be ignited, thus rendering more certain the explo- sion of the shell. The fuze-plug is made of wood, and fits the faze-hole. The opening in the fuze-plug is in two parts, the upper conical in shape widening downward, the other cylindri- cal, and only a little greater in diameter than the copper FTJZES. 263 fuze, and mucli less than the tipper part of tlie opening. The upper part is fitted with, a cork, having an opening just large enough to allow the entrance of the fuze. The elasticity produced by the presence of the cork is the distinctive feature of the faze. 391. Boxer's Fuze. Fig. 84. Fig. 85. Pig. 86. e:^ The faze used by the English in connection with their diaphragm shrapnel, is the invention of Captain Boxer, the superintendent of the Laboratory Department at Woolwich, and is represented in figures 84 85 and 86. Figure 84 represents the fuze for spherical case, full size, and figures 85 and 86 sections of the same. The channel for composition (cg) is bored eccentric with re- gard to the exterior, and the two powder channels (dd) are bored on the thickest side. The exterior taper of the fuze is one-tenth of an inch to one inch. The fuze composition is made to burn one inch in five seconds. The upper part of the bore is charged with mealed powder, and a hole (h) is bored through this priming to a depth of 0.4 inch from the top to insure the ignition of the faze. The figures marked on the faze indicate tenths of an inch below the bottom of this hole, show- 264 NAVAL GUNNERT. ing the points at wMcli tlie fuze is to be pierced, accord- ing to the required time of bxirning ; the greatest length being one inch or five seconds. At each of these points a hole (e) is bored into the powder channel (d). The exterior of the faze is covered with paper pasted on and varnished. The lower hole (e) is pierced through into the composition. The other holes are filled with pressed powder and a little clay. In the bottom hole a strand of quick-match is inserted, which serves to retain the charge in the powder channel of the fuze. This quick match is continued from one channel to the other through a groove in the bottom of the fuze. A metallic cap covers the top of the fuze. Under this cap is placed a disk of pasteboard to which a piece of tape is attached to facilitate the uncapping of the fuze. When the fuze composition has burnt down to the hole, which has been bored through at the time of loading, the powder in the side channel is ignited, and the flame from the bottom of the fuze communicates, through a small groove, to the bursting charge. To fix the faze : the hole to regulate the time of bursting is bored, according to the range required ; the fuze is then placed in the bouche in the fuze-hole, and struck with a mallet ; the cap is not removed until the shell is placed in the muzzle of the gun, to protect the fuze from accident or wet. These fuzes have given great satisfaction by the regularity and certainty of their effect, but seem to be open to objection on the score of complication ; no reason is apparent why they should burn any more regularly than the common paper fuze, which was rijzEs. 265 formeiiy supplied to tlie TJ. S. Navy boat ammunition whilst the certainty of exploding the shell appears to be quite as great with these last, which also must be much the cheaper. Objection to Fnzes driven in tlic Direction of their Length. There exists an objection to all fuzes compressed in the direction of their axis ; as, it is urged, it is impossible to obtain perfect uniformity of combustion where the density of the mass is not uniform throughout. Fuze compositions, driven in the direction of the axis of the fuze, must have the lower layers more dense than the upper layers, in that the lower layers, in addition to the pressure which they receive on being driven, must re- ceive an additional pressure from the power which is exerted to compress the superincumbent layers. If the composition be consumed in the same direction in which it was compressed, it is evident that there must result iiTegularities in the duration of burning. The most im- portant invention, having for its object the correcting this defect in fuzes, is the Bormann fuze, invented by Captain Bormann of the Belgian Army. 392. Bormann Fuze. The essential improvement involved in the Bormann fuze consists in applying the Fig. 8T. pressure to the composition on the side, and burning it from the end. The fuze case, fig. 87, is made of metal (a com. position of lead and tin), and consists, fiyst, of a short cyl- inder, having at one end a horse-shoe shaped indentation, one end only of which com- 266 NAVAL GtrcnSTERT. municates witli the magazine of tlie faze ^placed in the centre. This horse-shoe indentation extends nearly to the other end of the cylinder, a thin layer of the metal Kg. 88. only intervening. This is gradu- ated on the outside into equal parts, representing seconds and quarter seconds as represented in fig. 88. In the bottom of this channel a smooth layer of the composition is placed, with a piece of quick-match underneath it. On this is placed the piece of metal represented in fig. 89, the cross section of it being wedge- shaped ; and this ■ is, by machinery, pressed down upon the composition, sealing it hermetically. The cylin drical openin j;-, represented at G, fig. 87, is filled wfth fine powder, and covered with a piece of lead, which is soldered in its place, closing the magazine from the external air. On the side of the fuze the thread ^^^ of a screw is cut which fits into one ^P cut on the inside of the fuze-hole, and the fuze is screwed into the shell with a wrench, the pro- jecting part of which fits into the indentation at b, tig. 88. The thin layer of metal over the composition is cut away with a gouge at the interval marked with the number of seconds which we wish the fuze to burn. The metal of this fuze being soft, there is danger of its being driven into the shell by the explosive force of the Fig. 89. T.oE.vra FTJZES. 267 charge. To prevent this, a circular piece of iron, of a less diameter than the fuze, with a hole through its cen- tre, and the thread of a screw on its outside, is screwed into the fuze-hole before the faze is placed in. 393. Operation of the Fuze. This fuze operates in the following manner; the thin covering of metal over the composition being cut at the required graduation, ex- poses the surface of quick-match which was placed in the horse-shoe indentation before the composition was pressed in; the composition is thus ignited by the charge in the gun, and it burns in both directions. The portion of the flame, which advances progressively with the graduation, is extinguished as soon as it reaches the termination of the channel in that direction; but the portion of the flame which burns toward the origin of the graduation communicates, through the connecting channel, with the powder in the magazine, which com- municates the flame, through the hole in the circular piece of iron, to the bursting charge in the shell, by blow- ing out the piece of lead soldered over the magazine. 394. Advantages of the Bormann Fuze. The regulari- ty and certainty of this fuze are very great ; and its use has, so far, been principally confined to light artillery in firing shells, and particularly shrapnel, in which these two requisites are so essential; but it has been applied to larger ordnance with every promise of complete success. One of the most important advantages of this fuze is the fact that the shells can be loaded, all ready for use, and remain so any length of time, perfectly safe from explosion, as the fuze can be screwed into its place, and the composition never exposed to external fire until the 268 NAVAL GUNNEET. metal is cut througli. The only operation, then, to be performed under fire is to gouge through the metal at the proper point, which may be done with any kind of chisel, knife, or other instrument. 395. Tests. The severest test to which this fuze has been subjected was in a series of experiments carried on in France, during which a number of shrapnels, with the fuzes not cut for bursting were fired and afterward re- covered, and again fired with the fazes properly cut. The results demonstrated that the fuzes resist completely all the shocks which the projectile receives, either when in the bore or when ricocheting on the ground, without injury and without detaching itself from the shell. In order to demonstrate this fact more clearly, several shots were fired with a rolling fire (en ricochet), without cutting the fuzes, and the same fuzes were fired over again after duly regulating them, giving the most satis- factory results. 396. French Shrapnel Fuze. The French, however, not having paid much attention to the perfecting of shrap- nel shot, are not known to have adopted the Bormann fuze ; in fact the only fuze that we have any account of as being applied to shrapnel by that nation is the one Fig. 90. represented in fig. 90. /'©"X The French shrapnel fuze is made of i( ^ ^° ) ^^^*^ wood, having three channels parallel j|\,,^^^|^_^| to its axis. These are filled to different heights with composition, corresponding thus to three -different bursting distances. Each of these channels is provided with a tin tube in which the composition is placed. FUZES. 269 The longest chaiiiiel is always left open. Tlie other two are closed with a covering of leather, over which is placed, for the shorter columns, a disk of rose-colored paper, for the other, one of blue. On these paper cover- ings ai"e marked the distances at which the columns will cause explosion. These distances are also placed on the face of the faze near the top of the channels. The fiize is capped with a rondelle of fringed paper, over which is placed a plain rondelle of parchment with a piece of tape attached, by means of which the fuze is uncapped. The proper channel is opened, and should a mistake be made, and the wrong one opened, it is only necessary to moisten the leather and replace it, opening the right one. The composition in the three channels burns in l^, 22, and 82 seconds. It is proposed to modify the fuze by adding a fourth column, intended to burst the shell at only 250 yards' distance, but at this short distance canister shot will do quite as well as, if not better than, shrapnel. This faze possesses one important advantage ; it may be regulated very promptly by men who do not know how to read. It might even be regulated in the dark by replacing the different colored paper disks by knota fixed to the priming cord. 397. Concussion Fuzes. Many and various attempts have been made to construct fuzes which, from the shock of a shell when striking, will communicate fire to the charge and explode it. A concussion fuze, as already defined, consists of an arrangement of inflammable com- position, which is ignited by the cha/rge in the gun, and in which the flame, by means of some interior contri- 270 NAVAL GUWNEET. vance, is admitted to the bursting charge in the shell at the moment of its striking the object. Such a fuze, in order to be serviceable, must not only produce explosion on striking, but it must not produce it from the shock of the explosion of the charge in the gun, nor of that produced by the ricochets of the pro- jectile in or out of the gun. These fuzes have usually consisted of some combination of the highly explosive fulminates. But the extreme danger of using these, and the fearful accidents which they are liable to cause, have been great obstacles to their adoption. 398. The definition for a concussion faze, as given above, is not without its objections; as undoubtedly the name is just as applicable to any other arrangement, not including a burning fv.ze, which sets fire to the charge on striking. The distinction is made for the sake of couvenience, and only such as are described by the defi- nition will be' included imder the head of concussion fuzes. The attempts made to construct these fuzes date from a very early period; and probably many of these at- tempts, although partially successful, never became known, on account of the very general disposition to keep secret such inventions, in order that the authors of them might derive all the benefits resulting from their discoveries. 399. Early Attempts at IiiTeiitioiii As early as the year 1637, mention is made of shells which took fire on striking the ground ; and at various periods since that time such shells have been experimented upon, many having the part near the fuze-hole made heaviest, from the belief that impact could be thus determined at this FUZES. 271 point. Could tMs principle liave been earned out with any thing like certainty with the spherical ball, the whole problem of concussion, or rather that of percus- don, fiizes would have been solved, for as soon as it is possible to determine the impact at a certain point, the simplest dispositions of fulminates can be made in order to generate a flame. But in experiments ma^le with shells, reinforced at the fuze-hole in order to give pre- ponderance at that point, it was found that the shell struck the target with the fuze-hole to the right, left, or rear, quite as frequently as to the front. The moment, however, that the principles of the rifle are applied to large guns, so as to project elongated projectiles point foremost, the means of exploding shells on striking, or at a very short time after striking, become as simple as those used to fire off a musket. It is not necessary to describe all the different at- tempts made to attain the desired object. Many of them proved successful, so far as the arrangement of the fuze was concerned ; that is, the shells exploded when, they happened to strike in a certain way ; but the great dif- ficulty still existed of compelling them to strike in that way. 400. In this country, an ingenious contrivance has been suggested and experimented on for some years, though, it is believed, mth no very decided success. It consists of a bronze fuze-case, solid at the outer end, and having in the body a square apartment, from which a vent leads into the interior of the shell. The sides of this little chamber are lined with a coating of percus- sion powder, with the exception of the parts in the an- gles, aAd a small portion of each of the faces which are 272 NAVAL G-XJWNERY. perpendicular to tlie axis of the fuze-case. In tlie face farthest from the head of the case, a small threaded hole is placed, for the purpose of holding in position a little metal haR with a threaded stem attached. This stem is screwed into the hole, the inner end of the plug be- ing movaUe for this adjustment ; the shell is attached to a sabot with the fuze-hole to the rem: When the shell is fired, the little ball breaks loose by the shock, strikes against the opposite face, where there is no ful- minate, and drops into the lowest part of the chamber of the fuze, where it rolls about until the shell strikes, when the concussion between it and the fulminating powder produces the explosion. This fuze is open to the objection of all fuzes in which percussion powder is used. It requires great nicety of adjustment to insure the breaking loose of the ball from its stem ; and if this last is too small, the ball may break from its position whilst the shell is being handled, and produce serious accidents. This fuze would be, under the definition, not a con- cussion, but a percussion fuze ; and it is mentioned here merely in giving a history of the different inventions for making shells explode on striking. 401. Prussian Fuze. From 1841 to 1847, numerous experiments were made in Prussia upon a concussion fuze invented in that country ; and although the success obtained with it has not been such as would warrant a very strong recommendation in its favor, a description of it may not be unproductive of benefit. The exterior aspect of the ftize-case is the same as that of the U. S. Navy fuze ; the interior of the case, howev- er, is divided into two cylindrical parts, the upper cylin- FUZES. 273 Fig. 91. der having a considerably greater diameter than the lower one. In other words, the perforation in the case commences with a cylinder of a certain diameter, and contin- ues for a certain distance, when it is suddenly contracted, forming a ledge in the interior of the case, and is continued through as a cylinder of less diameter. See fig. 91. 402. The percussion apparatus consists of a small glass tube, her- metically closed at both ends, partly filled with concentrated sulphuric acid, and wrapped with cotton thread soaked in a compo- sition composed of 70 parts, by weight, of chlorate of potassa, 10 " " " " flowers of sulphur, 20 " " " " white sugar, pulverized, sifted and moistened with alcohol. This covering is put on of such a thickness that the tube can just be inserted in a paper case which serves it as an envelope, and which is entered in the lower cylin- der of the fuze-case, a portion of it projecting above the ledge which unites the two cylindrical parts. A hreaker of lead, shaped like a thimble, is placed over the upper part of the tube which projects above the ledge, the base of the breaker resting upon the ledge. The explosive apparatus being in position, there re- mains between the thimble and the sides of the fuze- 18 274 KAVAL GUNNERY. case a vacant space, wliicli is filled with compressed meal-powder filled in by means of a hollow drift, the interior diameter of which is a little greater than the diameter of the thimble. When the composition reaches the top of the thimble, uncompressed meal powder is filled in to the top of the case. 403. Should the firing take place under such short ranges as to run the risk of not consuming all the com- position by the time the shell strikes the object, the time of combustion is shortened by piercing the composition with a small auger, in a direction parallel to the side ot the thimble, and to the depth deemed necessary ; or the rate of burning of the composition may be increased for short ranges by mixing with it 1| per cent, of pulverized charcoal. 404. On being fired, the thimble or breaker, being supported by the composition around it, is not disturbed. But as this takes fire like an ordinary time fuze, and burns down to the bottom of the breaker, it leaves this unsupported ; and if the composition is all consumed when the shell strikes the object, the shot causes the breaker to rupture the glass tube, setting free the sul- phuric acid, and exploding the shell. 405. The same objections may be urged against this fuze as against all those in which fulminating powder is used. It is of delicate construction and very dangerous, at least appears so to any one not experienced in its use, whilst the experiments made with it are far from demon- strating its success. 406. Schonstedt Fuze. In 1852, Captain Schonstedt, of Holland, invented a fuze very similar in its action to the Prussian, but had the advantage of acting both as PUZES. 275 an ordinary time fuze and as an explosive one, and in taving neither fulminating powder nor sulphuric acid in its construction. The principal points of difference between the two will be readily seen by inspecting Fig. 92. fig. 92. The case is made of a mixture of lead and tin, and the bottom part of it is made thick enough to allow the cutting of a side-channel which enters the central one near its end. The hreaker is similar to the one in the Prussian fuze. A tube of glass, open at both ends, and wrapped so as to fit, as in the Prussian fuze, takes the place of the closed tube. The side-channel is filled with ordi- nary fuze composition, and the space around the thimble with a compo- sition which burns out in two seconds. The glass tube is filled with fine powder, and a strand of quick-match, the lower end of which last is inserted in the mouth of the side-channel, where it enters the central one. When the shell is fired, the quick composition takes fire, and being consumed in two seconds sets fire to that in the side-channel, at the same time that it leaves the breaker unsupported. This upsets by the shock of striking, and the flame in the side-channel, communi- catino- with the powder and quick-match in the broken 276 WAVAL GtTNWEEY. glass tube, explodes the shell. In case the explosive apparatus does not act, the shell acts like one with a time faze, and explodes when the side-channel composi- tion burns out. Although this fuze has the advantage of dispensing with the dangerous contrivance in the Prussian fuze, the results obtained are not as satisfactory as those with the latter, and are not of such a nature as would recommend it as a reliable concussion fuze. 407. Snoeck Fuze. This faze, the invention of Cap- Fig. 93. tain Snoeck, of the Netherland Artillery, was tried in Holland in 1854. Its construction is based upon the property which cast zinc possesses, of being hard and tena- cious at ordinary temperatures, but very brittle when heated to from 417" to 482° Fahr. Hence, a zinc fuze might resist, when cold, the shocks of the charge and balloting in the bore ; but, when heated suf- ficiently by the burning composi- tion, would break from the shock of the impact of the projectile, and communicate fire to the charse. The fuze consists of a short wooden fuze-plug, fig. 93, fitted in the interior with a cork collar, through which the faze passes ; and the faze proper, which consists of a zinc tube of a truncated conical form, having at the top a projecting band, which secures the tube in its position, and at the bottom a solid part, which, by its weight, assists in breaking the FUZES. 211 tube when the shell strikes the object This tube is filled with ordiaary fuze composition. Many improvements are suggesled to this fuze, by adopting which it is supposed it might have proved a valuable and useful invention ; but a more perfect con- cussion fuze than any that had preceded it becoming known, experiments on the Snoeck fuze seem to have ceased. 408. Splingard Concussion Fuze. The more perfect concussion fuze alluded to, and which possesses quali- ties superior to all others, is the Splingard Concussion Fuze. This fuze, invented by the same Belgian captain whose admirable system of time fuzes has been already described, first became generally known in 1850, al- though it had then been invented twenty years. Dur- ing this period the knowledge of it was retained in Bel- gium as a state secret ; and it would probably still have remauied such but for the corruption of some agent not proof against the inducements offered to divulge it. It became known in England and Holland, when it was deemed advisable by the Belgian government to allow a description of it to be published ; which was done, as much as any thing else, for the purpose of forestalling the action of the speculators, who sought to sell the secret to foreign governments. 409. The fuze is characterized by its simplicity, and easy manufacture, by its general application to all shells, and by the total absence of all those dangerous fulmina- ting powders so generally used in concussion and per- cussion fuzes. The fuze consists of two parts, the fuze j)roper, fig. 94, 278 NAVAL GUNNEKY. Fig. 94. and the fuze-plug. The fuze-caSe is made of cartridge paper, nearly cylindrical in f^^X ~i WSM f*^^™! ^^^ filled with the ordinary fiize'^ v^ I ^m H composition, in the centre of which is a hollow conical cavity of plaster of Paris, open at the bottom, through which pass- es the flame when the cone, left unsup- ported by the burning away of the composition around it, breaks off from the shock of the impact of the projec- tHe. A strong paper is used, and is ren- dered incombustible by immersion in a solution of sulphate of ammonia. The fuze is filled, like a rocket, on a spindle, using small charges, and taking care to pack the composition well ; or it may be driven solid and bored out afterward. In the bottom part of the fuze a slow composition is used, next to that a quick- er one, and in the top part mealed powder. The surface of the opening in the composition is cov- ered with one or two coats of gum-lac varnish. When this is perfectly dry, plaster moistened with water is packed into the opening, so as to fill it completely ; and while it is still soft, a small spindle is thrust in along the axis to such a depth as not to pierce the top of the cone. The slow composition extends only a very little above the top of the plaster tube, in order to leave it unsup- ported very soon after fire is communicated to that part. In this way, the same fuze may be employed, either at very small, or at very great distances. The fuze-plug is of wood, and of the same form on ruzEs. 279 the exterior as an ordinary wooden fuze. The interior is formed of three parts: 1st. The upper and largest part, in which is fitted a cylindrical collar of cork, through which the fuze is passed, and held in its position there by friction, isolated from contact with the rest of the fuze-plug. This arrange- ment protects the composition from the shocks of the discharge and ballotings in the bore. 2d. The middle part, which slightly exceeds in diam- eter the diameter of the fuze-case; and 3d. The lower part, which is very narrow, with the double object of allowing the passage of the flame into the shell, and forming an offset for the lower end of the fuze to rest upon. The fuze-plug being fixed beforehand, the fuze is not in- troduced until just before firing. For the operation, no tool is required, it being pushed in simply with the hand. 410. Effect of a Shell Dependent on Penetration. It is evident that the effect of a shell upon the side of a ship must, in a great measure, depend upon the depth to which the shell has penetrated; if the shell should only , lodge in the outer planking and there explode, the effect would be superficial, and not much injury would be done to the ship ; if, however, the shell were to penetrate to ' such a depth as to imbed itself in the side, the efff3ct of the explosion would then be the greatest possible. The argument made against the use of concussion and per- cussion fuzes on board ship is that, if they answer the requirements of a fuze of this description, causing the shell to explode on impact, the effect of the shell must be superficial, as the shell will explode before it has pene- trated to any considerable depth. 280 NATAL GUNNERY. 411. TMs argument would be conclusive against the use of concussion fuzes, if tlie explosion took place simultaneously with impact, but it has been shown that a certain length of time is always required to elapse be- tween impact and explosion, and during this interval the shell penetrates to a considerable distance. In the case of the Splingard concussion fuze, it was shown by experiments made in 1853, vnth long guns of large call, bre and high charges, fired against heavy targets of tim- ber, that the time which elapsed between the striking of the projectile, the breaking of the tube, the transmission of fire to the charge, and the explosion of the shell, is precisely what it ought to be, in order to allow the shell to become properly imbedded in the wood. 412. Objection to Concussion Fuzes. Notwithstanding the advantages that do, without doubt, attach to the Splingard concussion fuze, it is proper to state, in jus- tice to the time-fuze, that the shell fitted with the con- cussion fuze cannot be expected to operate inboard ot the enemy, for the explosion will occur somewhere in the side. This limits the operation of the concussion system to the side ; while the shell fitted with the time- fuze, may explode in the side, or, having traversed the side, may explode inboard, cutting down guns' crews, disordering machinery, and even blowing up maga- zines. 413. Percussion Fuze. The percussion fuze receives no flame from the charge in the gun; but, at the moment of impact, a flame is generated, which produces the ex- plosion of the shell. Fuzes of this character have usually been constructed by making use of some of the dangerous fulminating powders; but even those which FUZES. 281 Fig. 95 have given the greatest promise of success, have this great objection against them, and are of a complicated and delicate construction. The English and French navies are both provided with a percussion fuze, but not to the exclusion of the time-fuze. 414. Moorsom's Fuze. The French percussion fuze is the invention of Captain Billette, but, as there are not many of them supplied to their ships of war, it is natural to infer that their ad- vantage is questioned. The English percussion fuze is the invention of Captain Moorsom of the English Na- vy, and seems to have been more successful than any other percussion fuze ever applied to spherical shells. The body of the fuze is made of bronze, and is screwed . into the faze-hole of the shell by means of a key fitting into two mortises made in the head. The lower part is not threaded, and projects into the chamber of the shell. In the body of the fuze, two cylindrical chambers are placed, one above the other, vsdth their axes perpendic- ular to each other. In fig. 95, which represents a section of the faze through the axis, the upper chamber is shown by a section through its axis, the lower one by a section perpendicular to its axis. These chambnM are both 282 NAVAL GUNWERT. alike, with similar percussion apparatus ; so that a de- scription of one will answer for both. In the chamber is placed a solid cylinder of bronze, h, terminating at each end by a small projection or pis- ton. One head of the chamber is movable, and when screwed into its place, its exterior is flush with the con- vex surface of the fuze. Holes are left on the exterior for the use of a key, and the head is screwed in after the hammer is placed in the chamber and suspended. In each end of the chamber is a small recess, a vent being bored through to it from the exterior of the fuze. These are both filled with fulminating powdei'. A hole is drilled through the hammer at its middle point, and perpendicular to its axis, and is used to sus- pend the hammer, by means of a copper wire, in the centre of the chamber. The wire passes through cor- responding holes in the body of the fuze, and is sol- dered at the ends in the curved portions of the holes near the surface of the fuze. In the lower end of the fuze, a third chamber is placed, with a percussion apparatus similar to the pre- ceding, acting, however, in the direction of the axis of the fuze, and having but one end of the chamber pro- vided with percussion powder, the vent leading from which communicates with a cross channel, having at each end a small chamber filled with powder. The hammer, a cylinder of bronze, with a piston like the others on its upper end, is suspended in the same way, by a copper wire passing through holes in the fuze, and soldered like the rest. At the bottom of this last chamber stands a cylinder of lead, fixed in its position by its base, which is pressed FUZES. 283 into a little offset between the bottom end of the fuze and the cap which closes the chamber. 415. When the shell strikes, the suspension wire of that hammer whose axis coincides with the diameter of the shell passing through the point of impact, or is parallel to it, is torn loose, releasing the hammer, and allowing it to plunge forward and explode the ful- minate, by striking it with the piston on its end. It is doubtful, even when the shell strikes in the most favorable way, if the action of the hammer is sufficiently powerful to always produce explosion : and, in support of this opinion, it may be mentioned that Sir Howard Douglas states that, in course of practice, it was noticed that they frequently failed to act even when new. Several 8-inch shells struck a hulk and passed without exploding ; and many of the fiizes were picked up en- tire among the splinters and fragments. He adds, however, that the problem is prosecuting with every prospect of success. For elongated projectiles, having the rifled motion, which move point foremost, and are always sure to strike at one place, the problem is an easy one of solu- tion. 416. Bourbon Fuze. The Bourbon Fuze, which is represented at fig. 96, is spoken of as being the type of all good fuzes for percussion projectiles. It con- sists of a bronze fuze plug screwed into the fuze-hole of the shell, with a head larger in diameter than the other part, and threaded on the exterior, by means of which a cap is screwed on, covering the fuze until just before it is used. A cap of copper, e e, is fixed to the head of the 284 NAVAL GUNNEEY. ^g- ^^- fuze. A threaded Lole is placed at the highest point of this cap, in which the ful- > minating cap, d^ is screwed ^ just Ibefore the fuze is used. \ A steel nipple is screwed into the body of the fuze just under the cap, which, when the cap is exploded, conveys fire to the charge, communicating it first to the powder contained in the channel of the fuze. The bottom of this chan- nel is closed with a cork stopper, which is blown out when the powder in the fuze takes fire. The projectile, being supposed to strike with the point first, the shock, in order to explode the cap, must be of sufiicient force to fiatten the cap, e e; and this cap has been made of such a thickness that nothing less than striking against the side of a ship, or other equally re- sisting body, is sufficient to cause explosion. No rico- chet, therefore, on water will cause the shell to burst. 417. Should it be found that shells ai'med with such fuzes burst too soon after striking, a small piece of fuze composition coiild easily take the place of the powder in the fuze, and delay the explosion of the shell any de- sired length of time ; and this modification may be ap- plied to any percussion fuze of this kind. It is now, however, pretty well established that the shell penetrates a sufficient distance to produce the proper effect, before the explosion takes place. FUZES. 285 Kg. 9'?. 418. In experiments made at West Point on elon- gated rifled projectiles, the exploding apparatus con- sisted simply of a nipple attached to a piece of met- al, and having on it a com- mon percussion cap, see fig. 97. This was dropped into a small chamber left in the point of the projectile, and a head piece screwed on. When the shell struck, the nij)ple piece continued to move to the front until arrested by the head piece of the chamber, when the cap was exploded, and fire com- municated to the charge. This gave a little more time for the projectile to penetrate than is allowed by the Bourbon fuze, and sometimes the shells appear to have passed through a solid target of beams three feet thick, bursting as they reached the opposite side. The de- struction produced by a projectile bursting in this way, after passing through a ship's side, would be very great, and would resemble that produced by the aid of the time-fuze. 286 NAVAL GUNNERY. CHAPTEE VIII. LOCKS AND PRIMEKS. 419. Early Methods of Firing Cannon. The means first used to communicate fire to the charge in the gun, were of course of the most primitive kind. Loose powder filling the vent, and the application of a coal of fire, were probably the first employed. 420. Match. The first step in the way of improve- ment for firing cannon, was the match, or slow-match to distinguish it from the quick-match. The vent was filled with powder, and a train laid on the vent-piece toward the muzzle; the object of this train was to avoid subjecting the match to the action of the blast through the vent, to which it Avould have been exposed if the match had been applied directly at the vent. Slow-match is made of hemp or cotton rope, about .06 in. diameter, with three strands, slightly twisted. Cotton rope, well twisted, forms a good match without any preparation. To prepare hemp rope, boil it ten minutes in water holding in solution one-twentieth of its weight of sugar of lead, or let it remain in the cold solution until it is thoroughly saturated ; run it through the hands, to take the water from it ; twist it by means of a winch ; smooth it by rubbing ; stretch it on poles to dry, and put it up in coils of twenty-five yards each. Match, so prepared, burns four inches to the hour. Plain LOCKS AND PEIMEES. 287 cotton matcli four and a half inches to the hour. Slow match, in burning, forms a hard-pointed coal, which readily communicates fire to any inflammable material "svith which it is brought in contact. A portion of this rope was supplied to each gun, the rope being wound around its wooden staffs which, having a point of iron, could be stuck in the deck or in its match-tub, which was an appendage formerly supplied, to all guns, answer- ing the double purpose of holding the match staff, as well as water for the gun's crew to drink during action. 421. Port-fire. The match being considered very slow in its action, and it being very desirable that there should be no delay between the ignition of the priming and the explosion of the charge, \h^ port-jvfe came to be much used for firing cannon, the match being retained iu order to ignite the port-fire. A port-fire consists of a small paper case, filled with a highly inflammable composition, the flame of which is very intense and penetrating, and cannot be extin- guished with water ; thus, in order to stop the combus- tion in a port-fire, it was always necessary to cut it ofl", as near as possible to the flame. The case is made on a steel former, twenty-two inches long and half an inch in diameter. The paper being cut to the proper dimensions, is rolled on the former. The composition is made of nitre, sulphur, and mealed powder. The port-fires are driven in a mould, fig. 98, made of brass, and in two parts, held together by a socket at the foot, and four strong bands. The bore in the mould is of the same length and diameter as the case. It having been put together, the case is put in position and the bands driven firmly down. Thi-ee drifts, of -283 NAVAL GtrWNEET. Fig. 98. different lengths, made of steel and tipped with brass at the lower end, are used for driving port-fires. The composition is introduced in small quantities, and the blows, struck with the mallet, are so arranged as to produce, as far as practicable, a uniform density. The shorter drifts are used as the case is filled up. Port-fires should not be primed. Before the driving is commenced, a piece of paper is introduced in the case, and driven like a plug at the bottom with the long drift ; and, when the case is full to the top, it is turned in, and beaten down, thus securing both ends. 422. Priming. The operation of priming cannon by filling the vent with powder from a flask, Avas slow, and objectionable for other causes ; to obviate these objec- tions there was introduced, for the purpose of priming, a quill priming tube, which, being filled with an inflam- mable composition, was placed in the vent, and a pri- ming of loose powder poured on top, forming a train, as before described, to keep the match from being affected by the blast. These tubes are made from quills, by cut- ting off the barrel at both ends, and splitting down the large end, for about half an inch, into seven or any other odd number of parts ; these are bent outward, perpen- dicular to the body of the quiU, and form the cup of the tube. Fine woollen yarn is then woven into these slits, like basket-work, fig. 99, the end being brought down and tied on the stem. The body of the tube is filled LOOKS AND PEnrEES. 289 Kg. 99. with a composition of mealed powder moistened with camphorated alcohol, until a thick paste is formed ; the composition is introduced into the quill by pressing the lower end into the paste, thus taking up a portion of it, and repeating this operation until the quill is filled. A strand of quick-match, two inches long, is now lai'd across the cup and pasted in there with the powder pastk A small wire is then run through the axis of the tube, and allowed to remain there, until the paste is dry; it is then withdrawn, leaving the composition perforated throughout its entire length. This is called j)ierced com- position ; the object of piercing the composition is to expose, more surface to the action of the flame; the igni- tion of the whole contents of the quill is thus rendered instantaneous, whereas, if the flame were required to ignite the composition through successive strata, much more time would be required to communicate the flame to the cartridge. 423. First Application of Locks to Cannon. This system of priming with the tube, and firing with the match was continued for many years. The first application of locks to cannon was made, as stated by Sir Howard Douglas, by Sir Charles Douglas, who, disappointed in having his propositions on this subject adopted by the Admiralty, out of his own funds bought a sufficient number of common musket locks to provide the entire battery of 19 SIMPSONS N AVA L G U N N E R Y. rurie 5. 'ii^ii^ii- ni//den.s i^^'avv Lock in u_.se. LiCh- uixnun x.r. D Van Nustian d Publi s h i- r. LOCKS AND PRIMERS. 291 liammer constructed on this simple principle was, in 1832, introduced into the French service by Colonel Jure and is yet the regulation lock of the French navy. j,;„ jQj^ Figure 101 represents the J~\ French naval lock, which, re- r""\ px|"i^3| -i£_, bounding from the blast of the \^'^^^^'^i'JS^- -r^-—7 vent, is caught, at its shcmk, ^ ( ^^ * cushion provided for the ^^ purpose. 425. Percussion Wafer. The earliest percussion prim- ers in use were made in the form of a wafer ; this wafer was placed in the vent of the piece, the metal of the gun being cut away in such a manner as to form a recess at the exterior orifice of the vent, in which the wafer was deposited, and was thus exposed to the direct action of the hammer. In spite of the apparent stability of the primer in this recess, it was found that the concussion of the air, caused by the discharge of other guns on the same deck, caused the wafer to leave its seat. An in- genious appendage intended to obviate this difficulty was attached to the loch plate, which is shown in figure 102, plate V. When the primer was placed in the vent this flat piece of metal, pivoted at one end on the lock plate, was moved so as to lie over the vent, thus preventing the wafer from jumping up ; as the hammer descended, the shank came in contact vrith a vertical projection from the flat piece of metal ; this projection had its side inclined, which produced a horizontal move- ment of the flat piece of metal, thus uncovering the primer as the hammer descended. This appendage answered very well the object for which it was intro- duced. 392 NAVAL GUNNEET. 426. Percussian Cap. Another plan for obviating the tendency of the wafer to jump out of the vent, was to change the form of the primer, substituting a cap for a wafer, and placing it on the nipple of the hammer ; this method obtained in the U. S. service, and was, for some time, the regulation primer of the U. S. Navy. 427. It will be seen that as soon as the percussion prin- ciple was adopted, all parts of the previous system disap- peared ; thus the tubes, which had established the com- munication between the priming and the charge, were dispensed with, it being thought that the flame of the fulminate was sufficiently intense to reach the cartridge without the aid of any connecting medium. The direct mannei', also, in which the hammer stnick over the vent had a tendency to determine the direction of the flame downward. This seems to have satisfied the require- ments of priming for guns of small calibre ; but, as the calibres were increased, the distance between the primer and the charge increased, and it was found necessaiy to restore the tube, placing on its top, or cup, an explosive wafer. This is the form of the present primer of the U. S. Navy. 428. Nary Percussion Primer. The quill is prepared as has already been described in the tube with pierced composition ; except that, in place of the basket work of woollen yarn, a perforated disk of paper is pasted under the prongs of the quill, and the pointed end of the quill is not cut off; fine-grained powder is substi- tuted for the pierced composition, and a piece of writing paper is placed over the iipper surface of the prongs, covering the powder in the quill, and preventing the detonating composition from entering the quill. The LOCKS AND PEIMEES. 293 explosive compound is the fulminate of mercury, niixed with a certain proportion of mealed powder, which, is added in order to give body to the flame, that of the fulminate alone being too volatile. The advantage of charging the tube with grained powder, instead of com- position, consists in its greater power to resist the effect of moisture. 429. English Primer, The English stiU retain the pierced composition, and deposit their fulminate in a smaller quill, which being passed through the larger quill near its upper end, at right angles to its axis, causes the primer to assume a cruciform shape. This form of primer enabled them to discharge the piece without bringing the hamnier down on the vent, it being only necessary to crush the fiilminating powder in one end of the cross-head ; but a great advantage, in causing certainty of ignition, was lost by the hammer not acting directly over the vent, tending to drive the. flame downward ; this last objection seems to have more than counterbalanced the advantage claimed before for the system ; for Sir Howard Douglas, writing on the subject, says " This construction was found to be so sluggish as not to accomplish the great desideratum in naval gunnery, which is, that the firing of the charge and the actual delivery of the shot from the gun shall take place as quickly as possible after pulling the trig- ger-line, in order that there may be little time for any alteration to take place, from the motion of the ship, in the aim of the gun. Thus it was necessarj^ to devise some means by which the hammer, after having struck fairly wpon the head of the tvbe placed iri the vent, should instantaneously slip or be drawn aside, so as to 294 NAVAL GUNNERY. be out of the way of the explosion tlirougli the vent. Various modes of effecting this have been devised iu the British and in other naval services, but the most efficient and simple implement of this nature is that', which was invented by an American named Hidden, and patented in 1842." 430. Navy Locks. This aEusion refers to the present tJ. S. Navy lock which will be, described farther on, and which has been adopted, with some alterations made by Colonel Dundas, into the British Na\^ ; but this lock was not the first one invented by Hidden, with a view to avoiding the effect of the blast. His first effort was to remove the hammer laterally from the vent, as shown in fig. 103, plate V. : as the hammer descended, thi'ough the action of the lock string and gravity, a projecting shoulder on the loch lug caused the hammer to fall at an angle with the lock plate, directly on the vent, thus exploding the primer; the shank, at this point, was found below the shoulder on the lug, and, the action of the lock string continuing, its effect was to remove the hammer laterally from the vent, bringing the shank parallel to the lock plate, thus avoiding the blast. This lock was very successful and was provided to batteries in the U. S. Navy in 1842. 431. The inventor continued his investigations, and in 1842 patented the lock referred to by Sir Howard Douglas, which, for simplicity and practical usefulness, stands without a rival. This lock is represented in fig. 104, plate V. A. The head of the hammer. B. The Shank. C. An iron nipple. LOCKS AlfD PEIMEES. 295 D. A slot in tte shank of sucL. a length as to allow the hammer to recede one inch. F. The lock-plate by which it is attached to the lock piece. G. The lock-lugs, forming the bearings for the axial bolt. The action of this lock may be described as follows. The first effect of the lock string is to cause the hammer to turn on its axial bolt, which it does until arrested by striking the primer ; the action of the lock string still continuing, the effect is to withdraw the hammer directly from the vent, and this effect is permitted through the instrumentality of the slot in the shank, the motion continuing until the bolt comes in contact with the op- posite end of the slot. 432. Late Improrement in Mounting the Hammer. In cannon of new construction the lock-piece is dispensed with, and lock-lugs are cast on the guns on each side of the vent. This arrangement admits of much simplifica- tion in the lock, dispensing with the lock-plate and the lugs upon it. The lock becomes a simple hammer with a slot in the shank, and is secured by its axial bolt to the lugs on the gun. The action of the lock string is also made more direct by placing the lock lugs to the rear of the plane passing through the vent at right angles to the axis of the piece. 433. Friction Primers. Friction primers are now al- most exclusively used for firing pieces in the field, * An objection to this plan is, that the shank and lock-lugs, being of different metals, expand unequally. At the late bombardment at Hatteras, the shank of the lock of one of the 10-inoh guns expanded so much as to make it necessary to re- move it from the gun and to file it down. 296 KAVAL GTnSTNERY. !« and could they be adopted on board ship, a still farther simplification in the firing of cannon could be brought about, as the locks could then be dispensed with. The friction primer, now used in our army, is repre- sented in fig. 105, the tube being made of sheet brass, Fis- 105. with a wire flattened at one end ^,__r~|rt^— ^s^^ and made rough and serrated, a, """"" ^ '^^ ^^-V £qp .j.|jg purpose of acting on the friction powder. The extremity is annealed in order to make it soft enough tp bend without breaking. The large tube is filled with the pierced composition, and the short tube with a mixture of two parts of chlorate of potassa and one of sulphuret of antimony moistened with gum- med water. A string is hooked to the eye, made by doubling the wire, and the friction of the rough end of the wire against the friction powder produces a flame which explodes the piece. The objection to adopting these primers on board ship, is the damage that may be done by the flying of the brass tubes, which issue from the vent with great force when the piece is discharged ; in action, also, the crew generally dispense with their shoes, and many might be seriously disabled by the sharp pieces of brass lying on the deck under their feet. The advantage to be derived, however, from a successful application of the system is pretty generally acknowledged, and efforts have been made to overcome the objectionable features of it. 434. English Friction Primer. Fig. 106, plate II., rep- resents the English friction primer which has been ex- LOCKS AND PEIMERS. 29*7 perimented oa in that service. The tu"be is a quill, but as the material has not sufficient strength or firmness to resist the force of the pull necessary to withdraw the friction wire, a loop of leather is attached to the quill which passes over a knob or projection cast on the gun just forward of the vent. The quill is destroyed by the combustion of the charge, and all accidents from the^ flying of the tube are obviated. The leather loop, how- ever, is perishable, and does not last for any length of time ; some other material will have to be substituted in its place. A solution of the problem is being at- tempted in that service, and it is said that it is also to be attempted in our service. 298 NAVAL GUNJSTEBT. CHAPTEE IX. THEORY OF POINTING GUNS. PEELIMLNAET. 435. Gravity. All bodies fall wlien they cease to be sustained; this general property of bodies is called gravity. 436. Tertical. Vertical is the direction that bodies follow in falling; this direction is indicated by the plumb line. We know, in fact, that a heavy body, sus- pended at the extremity of a flexible line, should draw this line in the same direction in which it would fall, if left free. 437. Horizontal. All planes, perpendicular to the vertical, are called horizontal planes. Horizontal planes may, therefore, be at any height whatever. 438. Resistance of the Air. When we observe the fall of bodies, we remark that those which have a large surface with little weight, such as paper, leaves of trees, feathers, &c., fall slowly ; whilst those which have a con- siderable weight, without presenting much surface, such as stones, metals, &c., fall rapidly. This difference arises from the unequal resistance which they encounter from the air, resistance which evidently ought to vary with the extent of surface upon which it is exerted. 439. Familiar Illustration. To prove that this differ- ence arises only from the resistance of the air, we intro- THEORY OP POINTING GUNS. 2 TO duce two very different bodies, a feather and a piece of lead for example, into a long glass tube ; from this tube we exhaust the air by means of an air pump, and then permit the bodies to fall ; we find that they fall with equal rapidity. 440. Velocity of a Falling Body. The velocity of a fall- ing body does not remain constant during its fall. We know that the blow produced by a heavy body is stron- ger in proportion to the height from which it falls. This comes from the fact, that the velocity which has been communicated to it by its gravity is greater in pro- portion to the time it is falling. At the instant the body commenced its fall, its veloci- ty was nothing ; from this moment its velocity goes on augmenting progressively in a continuous manner. At the end of one second, its velocity is 32.18 feet per second; at the end of two seconds, its velocity is 64.36 feet per second ; at the end of three seconds, its velocity is 96.54 feet per second, and so on in like manner, ad- diag 32.18 feet with each second of time ; that is to say, the velocity of falling bodies increases p^'oporPionally to the times. If we represent by g the velocity that a body has at the end of the first second, falling in a vacuum ;• and if we represent by v the velocity it has at the end of any number of seconds represented by t, the above law may be represented by the equation v=^gt.^ ffv,wK\ X<^-t.. ... ^vL Thus the velocity acquired by a body falling in a vacuum during ^''.S is, at the end of that time v=. g t= 32.18 X 7.5 = 241.37 feet per second. These results are given by experiment ; but they can. 300 NAVAL GUNNERY. very readily, he establislied by a course of reasoning. Thus, gravity acts constantly on all material particles ; when a body is sustained, the constant effort of gravity is continually destroyed by the resistance of the obsta- cle which opposes its action ; hence comes the pressure which heavy bodies exert upon the obstacles which pre- vent them from falling ; it is this pressure which consti- tutes their weight. When a body ceases to be sustained, gravity puts it in motion, and as this continues to act upon it while it is in motion, it impresses upon it at each iustant the same increase of velocity ; it follows, there- fore, that the total velocity which it impresses upon the body must increase proportionally to the time during which it acts. 441. Disregarding tlie Atmosplieric Resistance, all Bodies Pall with Equal Rapidity, Irrespective of Weight, Let us take two bodies perfectly equal ; gravity acts upon them in the same manner. If we permit them to fall during the same times, their movements should be identical ; conse- quently if they are together when they are abandoned to the action of gravity, they will remain together throughout their fall. It follows that their common movement would not be altered if they were joined to- gether ;• but, in that case, they would form but one body, of which the weight would be evidently double that of either taken separately. 442. The above remark applies to any number of bodies. Hence, if we suppose a body divided into any number of equal parts, the velocity impressed by grav- ity upon all the parts taken together is the same as would be impressed upon each of the parts taken sepa- rately ; from which we conclude that, in a vacuum, gra/o- THEOET OP POINTIWft GUNS. 301 ity impresses always the same velocity wpon all lodies, irrespective of their weight. 443. When we know the Law which governs the Telocity of a falling Body, we can calculate the Space that the Body passes over in a given Time. We remember that when the velocity of a body remains constant during its entire movement, the space passed over by the body is propor- tional to the product of the velocity by the times.^ Thus, Z'l^^jU. X, for example, if a body moving with a constant velocity f • <^t,-i of 5 feet per second, continues to move for 7 seconds, the space passed over is represented by the product 5 X 7= 35 feet. This result may be represented *by a diagram thus (fig. 107): upon an indefinite line A X, Fig. 107. take a length A B, pro- portional to the time, T) that is, which contains j the unit of length as j many times as the du- j ration of motion con- I tains the unit of time. I At the point A, erect a ^- ^ perpendicular A Y, and take upon this perpendicular a length A C proportional to the velocity; finally construct the rectangle A B D C upon these two lines. The surface of this rectangle is measured by A B x A C ; it is proportional to the space passed over, that is, it contains the unit of surface as many times as the space passed over contains the unit of length. 444. Let us next suppose that the velocity does not remain .constant during its motion; but that it varies in a continuous manner, proportionally to the time. Upon 302 NAVAL GUNNEET. Kg. 108- ^^f the indefinite riglit line A X, fig. 108, take lengths propor- tional to the time; thus A a! corres- ponds to one second; A aJ' to two seconds, \ / /J'3 THEOET OF POINTING GUNS. 305 ^^ = 16.09 feet; the space fallen through in two seconds is equal to 16.09x4 = 64.36 feet; in three seconds, 16.09x9 == 144.81 feet; in four seconds, 16.09 x 16 — 257.44 feet. ■Pig. 109. 449. Trajectory in a Vacnnm. We call the trajectory the path that a projectile passes over when thrown in any direction whatever. We will first determine the tra- jectory without considering the effect of the resistance of the air; that is, upon the supposition that the ball moves in a vacuum. Let the ball be projected from the point A (fig. 109), following a certain direction A Z, making with the hori- zontal plane an angle Z A X. The straight line A Z, in- dicating the direction of the motion at the origin, is called the line of fire ; this line is the continuation of the axis of the piece. The angle Z A X, which the line of fire makes with the horizontal plane, is called the angle of fire. The velocity of the projectile at 20 306 NAVAL GUNNEEY. the origin is called the initial velocity. Suppose the ini- tial velocity to be 100 feet per second. K the projectile were not acted upon by gravity, it would pass over the straight line A Z with a constant velocity of 100 feet per second ; consequently, at the end of one second, it would have arrived at a point c, the distance A c being taken equal to 100 feet ; but in consequence of gravity, it will have fallen in this time a vertical distance of 16.09 feet; hence, if we lay off, vertically below the point c, a dis- tance G h equal to 16.09, the point h will be the^oint re- ally occupied by the projectile at the end of one second. After two seconds, the projectile would have described, in virtue of its initial velocity, a distance A c' = 200 feet ; but in consequence of gravity will have fallen vertically a distance of 16.09 x 4 = 64.36 feet. Lay off vertically below the point c, a distance c' h' = 64.36 feet, and we have the point b' as the point occupied by the projectile at the end of two seconds. In general, at the end of a certain time t, the distance passed over in the direction of the line of fire, by virtue of the initial velocity, would be ^ X 100 feet, and the height through which the pro- jectile will have fallen vertically during the same time will be I ^ f. We can, then, construct as many points of the trajec- tory as we wish. The construction would always be th-? same for any initial velocity whatever, V. The space passed over in the line of fire, by virtue of the initial velocity, and at the end of any time t, would be Upon the line of fire A Z, take two points m and n; the corresponding distances A m and A n are propor- tional to the times t and t' during which these distances THEORY OF POINTIIirG GUNS. 307 would have been passed over hj virtue of the initial velocity. Thus Am = Yt, An = Yt'. V being constant, we have Am: An :: t : t' ; hence A jn' : An^ :: f \ t'\ The corresponding verticals m p and n q, which are the distances that the projectile has fallen below the line of fire at the end of the times t and t', are propor- tional to the squares of these times ; we have then mp : n q :: f : t"^; hence mp) : n q : : A n? : Ar^. 450. We thus see that, the verticals let fall from, the different points of the line of fire to meet the trajectory^ are to one another, as the squares of the distances of these verticals from the origin. ^ This property suffices to characterize the trajectory completely, and shows it to be a curve, known under the name oi parabola. 451. We proceed to demonstrate some of the leading properties of the trajectory in a vacuum. The projectile always falls vertically below the line oi fire ; consequently, in theory, it remains always in the vertical plane passing through this line. This vertical 'plane is called the plane of fire. The point B, fig. 110, where the trajectory cuts the horizontal A X, drawn from the point of origin, is the point of fall ; the angle which the direction of the tra- jectory makes at this point with the horizontal is the angle of fall. The portion A B of the horizontal, con- , NATAL GmSTNEET. J, tained between the origin I and the point of fall, is the f' horizontal range. Upon any point g taken upon the horizontal, draw a vertical g K until it meets the line of fire ; the triangles A ^ K, A B C, being similar, we have ^K:BC :: Kg : AB; hencj ^ BC.Aa again we have ^KA : BC:: AK^Ac^; but AK : AC::A^: AB, then KA :BC :: A/:AB^; hence BC.A./ <| *^^^~AB^ • For the height ^ A at which the projectile passes above the point A^.B^; and this will be the case whatever may be the position of the point g between the two points A and B. From which we conclude that : the greatest ordinate which we can draw between A and B, is the ordinMe erected upon the middle o/" A B. This ordinate, which is the greatest height attained by the projectile, is called the height of the trajectory. S-v,vJ'iv ., .t(f/>ef <:>i* «j tii/ t^l). 453. Take two points d and ^, equally distant from the point M ; we have for the ordinates d e and g h erect- ed at these points, B C B C J ^ = -^-^2- A (7. Be?, and^A = -^-jg2^ A^. By. 310 NAVAL GUNNERY. Since the points d and g are equally distant from the middle point M, we have A J = B ^, and K g = Yi d\ hence A c?. B 6? = A ^. B ^, consequently d e = g Ti^ that is to say, that : the ordi- nates equall/y distant from thrj middle ordinate are equal. We hence conclude that the middle 07'dinate divides the curve into two equal parts. 454. The portion of the curve contained between the origin A and the highest point N, is called the ascend ing branch ; the portion contained between the point N and the point of fall, the descending hranch. In a vacuum, these two branches are equal ; consequently the angle of fall is equal to the angle of fire. sif 455. The expression that we have already found for the middle ordinate gives the height of the curve, but we can find an expression for the height of the curve in terms of the horizontal i-ange and the angle of fire. The vertical M P, erected on the middle of A B, to meet the line of fire, is equal to —r- '■> on the other hand we have 4 now MN = MP-PN = -- — ^-^ = 5.-^ 2 4 4 In the right-angled triangle B A C, we have B C = A B. tang. A; then M N = J A B. tang. A, THEORY OF POINTIBTG GTJWS. 311 that is : in a vacuum, the height of the ciorve is eqiial to a quarter of the horizontal ramge multiplied hy the tan- . gent of the angle of fire. (s.,,^^,]I^XO.-l'L^, /-f- A- y^-uZo- ^ For an angle of fire of 45°,)'^^ ^7^' ^~ U'^^^^^^'^ B C = A B, *' ~ ~it/i ^ J a.^*'^ «, hence (H*^l*>.'-'^&^i*^ ^ '^*^ tang. A — ^ = 1, from whicli it follows that MN = i AB; we conclude then that : in a vacuum and for an angle of fire of 4^5°, the height of the cwrve is equal to a quar- ter of the horizontal range. 456. Range. We proceed now to calculate the hori- zontal range, when we know the initial velocity and the angle of fire. Suppose, first, an angle of 45". Fig. 111. Upon the line of A Z, fig. Ill, take a distance Ac, equal to the initial veloci- ty V; that is, that A G is just the dis- tance that the pro- jectile would pass over in the direc- tion of the line A Z, during; the first second of its motion, if it were not acted upon by gravity. The con-espond- ing vertical c J is the distance that the projectile will have fallen during the first second; consequently. 312 NAVAL GUNNERY. and we have c 5 : C B : : A c^ A C^ or 1 ^ : C B : : V^ : A CI The angle A being 45 °, we have B C = A B, consequently A C = A B^ + B C* = 2 A B^; it follows then i^: AB:: V^: 2 AB^ 2 V^ 2 A B = 9 that is, that : in a vacuum, and with an angle of fire of 45°, the horizontal range is equal to the square of the in- itial velocity divided hy the constant number 32.18. 457. Take any angle of fire, we have B C = A B. tang. A; we have also AC^ = AB^ + BC^; substituting for B C its value, we have A C^ = A B^ + A B.^ tang.^ A A C^ = A B^ (1 + tang.^ A); now substituting the values of B C and A C ^ in the proportion i^:CB:: V^: AC^ we have i ^ : A B. tang. A : : V^ : A B^ (1 + t mg.^ A), jfrom which AT./. . c A ^ 2 V^ tang. A A B (1 + tang.'' A) -^ , THEORY OF POINTING GUNS. 313 whence now 2Y.Mang.A . ^ (1 + tang.^ A)' . Bill. Xi tang. A = --^, sin. A COS. from wMch tang. A. cos.^ A = sin. A. cos. A ; but hence cos. ^ A = sec.^ A 1 + tang.^ A ' tang. A. — sin. A; COS. A; 1 + tang.^ A substituting this value in the equation 2 Y\ tang. A AB <7 (1 + tang.^ A)' we have ^ ^ 2 VI sin. A. cos. A A B = ; 9 but 2 sin, A. cos. A == sin. 2 A ; hence AB = — sin.2A, =- 2X <5wa.^ ^^ 9 that is, that : m tJie vacuum, the horizontal range is equal to the square of the initial velocity multiplied hy the sine of double the amgle of fire, and divided hy the constamt number 32.18. 458. If A = 45°, sin. 2 A = 1. For any other value of A greater or less than 45°, sin. 2 A is less than 1. We hence conclude that : in a vacuum,, the angle of 4:5° is the angle of greatest range, that is, it is the angle 314 NAVAL GUNNERY. wliich, with the same initial velocity, gives the greatest horizontal range. (^^ *<---.'-^ ''-^0 <^^ ^ Suppose the angle of fire taken equally distant above and below 45°, the horizontal range will be the same in the two cases. In the last equation take A = 45° + a; we have sin. 2 A = sin. (90 + 2 a), and, in taking A = 45° — wP-x ^n THEORY OP POINTING GUNS. 321 For the same projectile, the difference is so mucli the greater as the initial velocity and the angle of fire are greater. For two different projectiles, fired at the same angle and with the same velocity,- the difference is greater as the projectile is smaller, or as it is lighter for the same volume. 467. From the fact that the verticals increase more rapidly than the squares of the distances measured upon the line of fire, we can conclude that the trajectory in air must envelop completely, from the origin to the point of fall, the parabola which, with the same angle of fir6, would give the same horizontal range; below the point, however, marking the horizontal range, the contrary is the case, that is, that below this point the trajectory in air passes below the trajectory in a vacuum, 468. Height of the Curve. We have seen that, in a vacuum, the height of the curve is equal to a quarter of the horizontal range multiplied by the tangent of the angle of fire; we can, then, conclude that in the air, to give the same hoiizontal' range, the height of the curve must be greater than the quarter of the horizontal range multiplied by the tangent of the angle of fire. The smaller the projectile, the greater the difference. Thus, in military works, when mortars are fired at a given dis- tance and with a fixed angle of fire, the shell of the 8-inch mortar must rise highert han that of the 10-inch, and that of the 10-inch higher than that of the 13-inch mortar. We can also conclude that the greatest ordinate of the trajectory in air is nearer to the point of fall than to the origin; hence the ascending and descending branched of the trajectory are not equal in air; and the angle of fall is always greater than the angle of fire. 21 322 NAVAL GtrsrWEET. 469. Angle of Greatest Range, In the aii', tlie angle of greatest range is always less than 45", and decreases in proportion to the increase of the initial velocity, for different pieces of ordnance varying from 30" to 36°.. When the angle of fire is very small, the direction of the motion is very nearly horizontal in every part of the trajectory which is situated above the horizontal plane, and in that which diverges only a little below that plane. Now, the resistance of the air is always exerted in a di- rection exactly contrary to the motion; consequently, the direction of this resistance is very nearly perpendic- ular to gravity which is always vertical; it follows, then, that this resistance cannot alter, in a sensible manner, the vertical velocity produced by gravity. We deduce from this the fundamental principle which serves as the base of the theory of pointing. 470. Suppose a projectile fired in a certain direction A Z (fig. 113), making a very small angle with the hori- zontal plane. If this projectile were free from the action of gravity, but affected by the resistance of the air, it would move without quitting the line A Z, and at the end of a certain time t, it would have passed over, on this line, a certain distance A C. But, by virtue of grav- ity, it must fall, during the time t, a certain distance C B below the line of fire. Now suppose this same projectile to be fired with the same initial velocity, in a new direction A Z', differing but little from the first direction. If we admit that the resistance of the air is felt only along the direction of the line of fire, the projectile will, by virtue of the in- itial velocity and of the resistance of the air, have passed over, during the time t^ a distance A C == A C • but. THEOEY OF POINTING GUNS. 323 Fig. 113. ]by virtue of gravity, it must have t<; fallen, during the same time t, a dis- tance C B' = C B : from which we conclude that: with the same projectile and the same initial velo- city^ the distance that a projectile falls helow the line of fire is always the same, whatever may be the angle of fire, provided always that this angle remains very small. Thus we can admit that the ver- ticals C B and C B' are equal, only because we suppose -that the direc- tion of the motion being nearly hori- zontal, the resistance of the air is only exerted along th« line of fire, and has no effect whatever upon the motion produced by gravity. It follows that this principle, true in a vacuum for all angles of fwe, can be regarded a? a sufficient ap- proximation for practical purposes, only when the angles of fire do not exceed those which are usually employed in direct firing. We may also consider this principle as a sufficient ap- proximation when the angle of fire is moderately great, but the initial velocity quite small ; because, in this case, the curve described in the air does not differ much from the parabola which would give the same horizontal range for the same angle of fire. 471. Direct Fire. The fire is said to be direct when 324 NAVAL GUNNERY. Fig. 114. the projectile, fired uiider a certain angle, strikes, with- out grazing, an object which is 'uncovered and visible from the battery. 47 2. Pointing. We have already said that it was im- possible to take into consideration the lateral deviations resulting from the motion of rotation- we must then ignore these deviations, and suppose that the projectile always falls vertically below the line of fire ; consequent- ly, to point a piece, it is necessary to direct it in such a manner that the line of fire A Z (fig. 114), which is nothing more than the prolongation of the axis of the piece, shall pass vertically above the object B, a height B C equal to the distance that the projectile will fall below the line of fire while passing over the dis- tance A B. The plane of fire is thus made to pass through the object. This is termed lateral training. Cannon turn around their trunnions ; the axis of the trun- nions is perpendicular to the axis of the piece ; consequently, when the axis of the trunnions is hori- zontal, the axis of the piece can only move in a vertical plane; this plane is, then, the plane of fire for all the inclinations of the piece. "When the axis of the trunnions is not horizontal, there THEOEY OF POINTING GUNS. 325 will result errors in pointing, wliicli we will consider further on ; for tlie present we will consider this axis as perfectly horizontal. A plane drawn through, the axis of the piece, perpendiciilar to the axis of the trunnions, cuts the swell of the muzzle and the base-ring in two points, which determines the sight notches. The straight line which passes through these sight notches is called the line of metal sight or tlie natural line of sight. 473. Sight Notches. The sight notches are determined by the founder; the trunnions being horizontal, a square and plumb bob, d e (flg. 115), is set on the base-ring or Fig. 115. muzzle, ah G, d e being laid horizontal, and being made tangent to the surface of the gun at the point where the plumb line marks the perpendicular; the plumb line will then be in a vertical plane passing through the axis and perpendic- ular to the axis of the trunnions. The sight notch is then marked at the point where the plumb line touches the surface of the gun. This mark is made by the founder, but its correct- ness can be tested as follows ; place the trunnion square in such" a position that its legs, resting on skids support- ing the gun at the base-iing shall set closely against the two sides of the base-ring; "^adjust the pointer of the trunnion square so that it shall touch the notch on the upper surface of the base-ring, and clamp it in this position. Now shift the trunnion square, end for end, so that the legs shall set closely to the opposite sides of the base-ring; if the pointer now touches the notch cut in the base-ring, the notch is in the required plane; if the pointer does not touch the notch, the 326 NAVAL GtrKWEEY. notcli is not in this plane, and its error of position is eqnal to half the difference between it and the point touched on the base-ring at the second adjustment oi the trunnion square. 474. Point-Blank. When the axis of the trunnions is horizontal, the axis of the piece and the natural line of sight are situated in the same vertical plane; conse- quently if we point a piece in such a manner that the Fig. 116. natural line of sight is directed at the ; y^\ I object, we are certain that the vertical plane in which the axis of the piece moves, that is, the plane offire^ passes through the object; it remains then only to consider the inclination of the axis. The radius E Gr (fig. 116) of the base ring being greater than the radius A F of the swell of the muzzle, the line of s :;ht makes, with the axis of the piece, an angle E H G, which is called the natural angle of sight. This angle was formerly known as the angle of dispart. The trajectory departs at first very little from the line of fire; consequently, it cuts the line of sight in a point H, where that line is intersected by the prolongation of the axis; departing farther from the line of fire, it cuts the line of sight in a second point B, which is called the natural pointMank ; we have then this definition : The natural point-Uanh is the second THEORY OF POINTING GUNS. 327 point of intersection of the t/rajectory with the natv/ral line of sight. The distance of this point from tlie face of the muzzle is called the point-hlank range. It is evident that, for the same piece, the point blank varies with the initial velocity, consequently with the charge of powder; and that with a fixed charge, it depends upon the quality of the powder, method of loading, windage, state of bore, &c. When we speak of the point-blank range of a cannon, without indicating the charge, we understand the highest service charge. The first point of intersection H of the trajectory with the line of sight is called the first point-hlanh. A F is the radius at the swell of the muzzle ; D E is the difference between this radius and that at the base- ring, called the dispart; D A, the interval between these two radii, is called the length of the piece. The natural angle of sight can be determined by the angle E A D, which is equal to E H G, thus DE tang. A = ^ j^. The consideration of the first point blank serves only uselessly to complicate the theory of pointing ; we can easily omit it by supposing the axis of the piece to be raised in a direction parallel to itself, and passing over the sight notch on the muzzle in such a manner that the line of sight and the line of fire cut each other ex- actly at this point. This hypothesis, which greatly simplifies all questions relative to pointing, supposes that, at each point of the trajectory, the centre of the projectile is 'more elevated than it really is by a quan- tity equal to the radius of the greatest swell of the 328 WATAL GUNNERY. muzzle ; now, this radius is about a calibre ; it is then an error about equal to the diameter of the projectile ; such an error is entirely insignificant in practice. In all these cases it is easy to correct it by diriiinishing all the ordinates of the trajectory by a constant quantity equal to this radius. 475. Taogent Scale. When we wish to reach an ob- ject beyond the natural point-blank range, it is necessary Fig. 117. iq increase the inclination of the piece; that is, to increase the angle made cv 1/ by the line of sight with the axis ; in other words, to increase the angle of sight. This is done by increasing the radius of the base-ring by a quantity E K (fig. 117), varying according to the distance, and which is called tan- gent scale or h'eech sight. Represent this tangent scale E K by A. The two similar triangles K A D, ABC give BC hence B C = D K : : A B : A D DK. AB AD • The side D K is equal to (R — r) + Ji ; that is, the difference of the two radii increased by the length of the tangent scale. We represent this quantity by H, and call it the total hausse (from Jiausser^ to increase) ; then H.D BC = I THEOBY OF POINTING GTJNS. 329 hence H = — -f^ — • The line of sight K B, determined hj means of the hausse, is called' an artificial line of sight / and the point B the artificial point-hlanTc. We see, from this, that the application of the term point-blank is not limited, but that for every graduation on the breech sight we have a point blank, which is the second intersection of the tra- jectory with the lines of sight determined by means of the divisions on the breech sight, which are graduated to coincide with the distances of these point-blanks from the muzzle. The term is used frequently as synon- ymous with range, and is by some defined as such. 476. Point-Blank. The origin of the term point- hlank, seems to have been derived from the white point, or bull's eye, at which the line of sight of the marksman was directed ; and is also supposed to have some con- nection with the familiar order of " not to fire until you see the whites of the enemy's eyes ;" but all uses of it point to an understanding that tohen apiece was pointed at point-blanh the line of sight was directed upon the ob- ject. This understanding of the term agrees also with the use made of it in common parlance, it being used frequently adverlnally to express directly*. The defini- tion given above, is the one adopted by the French ; the English have another definition which will be given farther on in connection with front-sights; at present we will continue the subject of the tangent scale. 47Y. Tangent Scale. We have found that H : BC : Z : D expresses the relations that exist between these quan- * Worcester. 330 NAVAL GUKNEEY. titles, the object having "been supposed to be on the same level as the battery. It is desired to know if the proportion remains true if the object fired at be not on Kg. 118. . P_ M the same level as the battery; in other words, it is desired to know whether the angle of sight depends solely upon the dis- tance, and is altogether inde- pendent of the angle of eleva- tion of the object. Suppose that the object B is not on the same level with th«! batteiy, the line of sight A B (ilg. 118), which is always di- rected toward the object, makes with the horizontal plane an angle B A X, which we call the angle of elevation of the object, and which is positive or nega- tive according as the object is above or below the level of the battery. Represent this angle bye. The axis of the piece passes a certain vertical distance B C above the object. The angle C A X is the angle of fire ; represent it by P. The angle CAB, which the axis of the piece makes with the line of sight, is the angle of sight ; this angle is equal to the angle of fire C A X di- minished by the angle of elevation of the object B A X ; we represent it by a. THEORY OF POINTING GIJNS. 331 C A X = P, the angle of fire, C A B = a, the angle of sight. It may be remarked here that the angle of sight is equal to the angle of fire when the object is on the same level with the battery; for the angle of fire is the angle made by the line of fire (which is the axis produced) with the horizontal, and the angle of sight is the angle made by the line of fire with the line of sight, which is horizontal if the object be at the same level with the battery. In the present case they are unequal, and we have a = P-e. In the triangle B C A, we have B C : B A : : sin. a : sin. B C A. The angle B C A is the complement of the angle of fire P; consequently sin. B C A = COS. P = cos. (a + e) = cos. a. cos. e — -sin. a. sin. e Ave have then B C : B A : : sin. a : cos. a . cos. e — sin. a . sin e. In the right-angled triangle K A D, we have DK . AD sm. a= r-^^ and. cos. a = ATT "^^^"^•"'~ XX' moreover DK = H, AD = ?, AB = D. Putting these values in the preceding proportion, we have ^<^ -^ ■■■■ ^^ A-K -=»'•- ^™- B C : D : : H : ?. cos e — H. sin e from which D H -i- B C. H. sin. e = B C. ?. cos e II (D + B C. sin. e) = B C. I cos. e B C. I. cos. e H = D + B C. sin. e. 332 KAVAL GUNNERY. The angle of sight remaining very small, we can admit, without appreciable en-or, that so long as the distance of the object A B = D remains the same, the distance A C, measured upon the line of fire, remains also the same ; in this case the quantity B C, which the projectile falls below the line of fire, at the distance A C, does not vary. Now, the expression found for the value of H shows that, so long as D and B C do not vary (I being constant), H diminishes when the angle of elevation of the object, e, increases ; for, as the angle increases, the cosine decreases while the sine increases ; the value of H, then, will diminish ; but, in the ordinary limits of direct fire, this diminution is so small that it can be neglected in practice. Turning to the figure we see, on the other hand, that when the angle e increases, the dis- tance A C and consequently the height B C increase also ; there results a slight increase of the hausse, suffi- ciently small to be neglected. These two errors, either of which taken separately may be neglected, are in a contrary direction and compensate one another. We are able, then, to establish for practice this impor- tant principle ; that, in direct fire^ the liausse depends only ufpon the distance, and r6inains invariahle, whatever may he the angle of elevation of the object. Thus it appears that whether we fire upon an object upon the same level with the battery, or above or below it, the relation between the distance, length of piece, total hausse, and fall below the prolonged axis will be expressed by the proportion H : BC :: Z : D 478. When the total hausse H ia equal to the diifer- ence of the radii (R— r), the distance D is the point- THEOET OF POINTING GUNS. 333 blank range ; now, "from tlie foregoing, vre see that this distance ouglit not to vary with the height of the object ; from which we conclude that the point-blank range is always the same whatever may be the angle of elevation of the object; consequently in the definition of point blank, it is useless to introduce, as is sometimes done, this condition, viz. ; that the natural line of sight should be horizontal, that is, that the object must be on a level with the muzzle of the piece. 4Y9. Vertical Deviations corresponding to Errors of Ilausse. The proportion H : B C : : Z : D gives the relation between the total hausse and the distance B C which the axis passes abovp the object. If an error exist in one of these quantities, a corresponding error will exist in the other. If instead of using the hausse H, fig. 119, corres- pig. 119. ponding to the distance ^' D, we use a different hausse H', greater than' H, the axis of the piece will pass above the ob- ject a distance B C, dif- fering from B C, and we I : D, have from which H' : BC H' : B C : : H : B C, or H BC : BC. H' We draw from this (H'— H) : H :: (BC— BC) or (H'— H) : (B C— B C) :: H hence (H'— H) : (BC— BC) :: Z : D. BC, BC; 334 NAVAL GTJWNEET. Since H is the correct hausse corresponding to tlie dis tance D, B C is the distance that the projectile falls below the axis, at that distance ; it falls then below the point C a distance equal to B C, consequently it passes above the object a distance equal to B C — ^B C. If the hausse used, H', were less than the correct hausse H, the projectile would pass below the object a distance equal to BC — BC. H' — H is the error of hausse ; B C' — B C is the corre- sponding vertical deviation ; we have then between the error of hausse and the corresponding vertical deviation this relation ; that the error ofTiausse is to the correspond- ing vertical deviation as the length of the piece is to the distance from the object. The following table shows the vertical deviations, at the several distances indicated, for an error of hausse of .1 inch. fATT Girers. 32-pdr. 100 yds. feet. 27 200 yds. feet. .54 500 yds. feet. 1.35 1,000 yds. feet. 2.70 42 " .264 .528 1.32 2.64 Thus if, in practice with the 32-pounder at 1,000 yds., we should put up the breech sight too high by .1 inch, the ball would pass 2.7 feet above the object. 480. NegatiTC Hausse. In order to strike an object placed at a distance less than point-blank range, it will be necessary to diminish the angle that the axis of the piece makes with the natural line of sight. This must be accomplished by diminishing the difference between the radii of the muzzle and base-ring. This amount which it will be necessary to take from the radius of the base-ring, is called negative hausse. Represent it by h. The total hausse H is then equal to (R — r) — h. If THEORY OF POINTING- GTJNS. 335 Fig. 120. instead of pointing witL. this hausse H, we point at nat- ural point-blank, that is with a total hausse equal to E. — r, we commit an error of hausse equal to h ; conse- quently the projectile must pass at a certain distance y above the object, and we have (y being a vertical devi- ation corresponding to /;. the error of hausse) y\h::J):l Since the projectile passes at a certain distance y above the point aimed at, if, in- stead of pointing at the object, we aim at a point as much be- low the object as y is above it, the projectile will pass at the height of the object. Now it is impossible to short- en the radius of the base-ring ; we are then forced to point, by means of the natural line of sight, at a certain point below the object. We have then this relation : that the distance 'below the object^ to which we must aim, is to the negative hanisse as the distance of the object is to the length of the piece. It is not easy to determine, by the eye, a vertical distance below the object ; but we can, by means of the positive. hausse, determine a point of direction i upon which it will suffice to aim with the natural line of sight. 336 NAVAL GUNNERY. To do this, we commence by aiming at natural point- blank upon tlie object B (fig. 120); we take a positive liausse D E, equal to the negative hausse that it would be necessary to use corresjponding to the distance ; sight along this hausse and the sight notch on the muzzle ; this line of sight will meet the ground at a certain point G, which note carefully, and then direct the natural line of sight on this point. It is evident that the relation between the hausse and vertical fall is preserved by pointing in this manner, for continuing the line A G to B' vertically below B, and joining B and B', we have B B' : E D : : A B : A D. or B B' : 7i : : D : I 481. Dispart Sight. The practical difficulty attending the determining of the point to aim at, especially on board ship, has led to the adoption of a line of sight parallel to the axis. This line is produced by placing on the gun a front sight equal to the dispart. The old fi-ont sight was simply a piece of plank, having its lower edge fitted to the chase of the gun ; another form was to place a button on the highest point of the muzzle raiser] to the level of the base-ring. 482. A more elaborate arrangement of front sight was suggested by M. Koche, professor at the school of the French marine artillery. His front sight was com- posed of two uprights which were graduated, and be- tween which moved a horizontal plate ; by changing the height of this plate he changed the angle of sight. In order to render his system applicable to all distances, he placed upon the breech a fixed hausse corresponding to the greatest distance at which we are accustomed to fire THEOET OF POINTING GUNS. 337 at sea, that is to say, from 1,100 to 1,300 yards. He raised the uprights of his front sight to a level with this hauBse. When the movable plate was at the most ele- vated point, the line of sight was parallel to the axis. As the movable plate was lowered, the angle of sight increased until the line of sight became tangent to the muzde. 483. In the use of broadside guns, it was found very objectionable to place the front sight on the muzzle, in consequence of their liability to be knocked off or bro- ken by the port ; they are now placed on the second re- inforce. The height for the front sight is determined by means of a brass tompion which fits in the muzzle of the gun, and has an arm which is laid vertically, by lev- elling an offset of the tompion, which is fitted at right angles with the arm ; the length of the arm is equal to the radius of the base-ring plus the height of the notch, .in the breech sight when at level. From the end of this arm a thread is stretched to the breech sight, which thread lies in the vertical plane passing through the axis of the bore, and is parallel to the axis. The height of this thread above the surface of the gun determines the height of the front sight. 484. The line of sight, determined by means of the front sight, is called a dispart sight^ and was formerly expressed upon the gun as shown in fig. 121, the sight being made of wood strapped to the gun. The vis- ual ray was directed through a tubular opening bored longitudinally ; the upper portion of this tube was sub- sequently removed, leaving a groove on the top of the' sight along which the aim was taken. 485. Point-Blank. Cannon fitted with dispart sights 22 NAVAL GUNlirEET. had, of course, no natural angle of sight, consequently no Tiatural pointMank j hence the ra/nge at level began to be designated as point-blank, and this is the definition of the term adopted by the English, and generally received in the United States service as the~ signification of the term. The English de- fine the point-blank range as the distance from the muzzle of the gun to the intersec- tion of the trajectory with the horizontal plane on which the trucks of the carriage rest, the axis of the piece being laid hori- zontally; in the U. S. naval service it is understood as signifying the distance from the muzzle of the gun to the intersection of the trajectory with the surface of the water, the gun being raised a certain distance above this surface, always supposing the axis of the piece to be laid horizontally. This understanding of the term limits its application to one point, (which would be better defined as the range at level) and tends to prevent any clear and definite idea of the true meaning of the term from being fixed on the mind ; it would seem to be very de- sirable to abandon this definition altogether, and to accept the term as signifying all aims that are taken directly upon an object, no matter what may be the angle of sight on which depends the value of the point-blank. To aim at point-blank upon an object would, thus, simply imply that the line of sight THEORY OF POrNTING GUNS. 339 was to be directed iipoii it, the angle of sight giving such a direction to this line as to njake the intersection of the trajectory with the line of sight occur at the object. In all cases of direct fire, then, the aim would be taken at point^lanh ; whereas, in cases of rollmg fi/re or rwochet, the aim would not be taken at point-blank upon the object, but upon some -intermediate point. 486. Sights on U. S. Navy Cannon. Navy cannon are supplied with two sights, a breech sight, and a front sight on the second reinforce. When the mark level on the sight 'bar coincides with the upper surface of the sight box, a line drawn from the bottom of the notch to the top of the front sight is parallel to the axis of the bore, and thus supplies a dispart sight, with which we can aim at all points within the range at. level of the piece. It is however, in strictness, committing an error, ever to aim vnth the dispart sight, except when the ob- ject is very near to the muzzle ; to make this apparent, we will illustrate with a particular gun. 487. Use of Graduations between "Level" and Range at Level. The range at level of the 32-pounder of 33 cwt. is 288 yards, and this is the first graduation on the breech sight of which the value is expressed ; that is, suppose the gun to be laid level (breech sight down to " level ") and the line of sight to be directed at the side of a ship 288 yards distant on a point at the same height from the water as is the eye of the captain of the gun ; if the gun be fired, the shot, falling by virtue of gravity from the moment it leaves the muzzle, will strike the side at the water-line. Now it is evident' that the eye of the captain of the gun cannot see the water-line, hence he has struck a point that he did not aim at. Now, supposing 340 NAVAL GUNNBEY. tlie axis of the piece in the same position as before, if lie raise the breech sight until the graduation for 288 yards coincide with the upper surface of the sight box, he will find that the visual ray intersects the side of the ship at the water-line. This, then, should have been the position of the sight bar when he aimed at an object at the dis- tance of the range at level, in order that he might have aimed at the point that he wished and expected to hit. Suppose the ship at the distance of 144 yards; if the line of sight be taken at level, the ball will strike the side at a point about a quarter the distance between the level of the eye of the captain of the gun and the water, and if the breech sight be raised until the top of the sight box coincides with the graduation placed about a quarter of the distance between level and 288, the visual ray will be found to pass through the point struck. From this it is evident that, for all distances whether greater or less than the range at level, use should be made of the graduated breech sight, and that a positive error is com- mitted by ever pointing at level, without the object is close aboard. The necessity of this precaution becomes particularly apparent when we considei the object to be fired at as having but little magnitude, a boat for instance ; we see that, as the ball commences to fall, in obedience to grav- ity, from the moment it leaves the muzzle, we can never count on hitting' the object direct (except from the influ- ence of deviating causes), but that the ball will always fall short of the object, and the effect will have to be trusted to the chance of a lucky ricochet. 488. Marking Brecch-Sights. The breech sights of the THEORY OF POINTIJTG GUNS. 341 U. S. Navy cannon are secured at a fixed angle with the axis of the bore. The determination, then, of the grad- uation for degrees involves the solution of a triangle of which one side and the three angles are known. Thus, Fig. 122. in fig. 122, A is the position of the front sight; A B is the distance from the front sight to the rear face of the breech sight bar; this line being parallel to the axis of the bore, the angle B is 60°; the problem is, to determine the length of the side B C for all the values given to the angle A. Take, for example, the 32-pounder of 33 cwt. ; the length of the side A B is 2 feet 7 inches = 31 inches. Suppose angle A = 1° then C = 119" constant B = 60" we have sin. C : sin. A : : A B : B C ^ ^ A B. sin. A . _ . , „ B C = : — 7s — =^A B. sm. A. cosec. C sm. (J B C = 31 inch, x sin. 1" x cosec. 119". 1.49136 8.24186 .0624Y B C = 9.195&9 = .6247 of an inch. Suppose A = 2* B= 60" C = 118" B C == A B. sin. A. cosec. 342 KAVAL GUNNERY. 1.49136 8.54282 .05818 B C = 10.09236 = 1.23T of an incli. In like manner, taking A = 3°, we find B C = 1.8373 of an inch, so that we see that it will be sufficiently ac- curate, after having determined the value of B C for one degree, to multiply it by two, three, and four, in order to determine B C for these different values of A. 489. It is evident that, for the same value of A, the length of the side B C will increase with the length of the side A B; hence, when firing at great angles with pivot guns, it may become necessary to shift the front sight from the reinforce to the muzzle, the breech sight must be replaced by another, graduated in proportion to the increased length of the side A B. 490. The mode of marking breech sights at present adopted in the U. S. Navy, for practical convenience in pointing, is to mark lines on the sight bar, denoting angles of elevation, and to express, on them the corre- sponding ranges in yards. These ranges are determined by firing the gun at the different elevations, and noting the ranges with plane tables. The angles given by the plane tables are plotted on a projection of a convenient scale, and the distance of the graze from the gun is measured on the projection. 491. Relation between Total Hausse and Time of Flight. We have already seen, in direct firing, that, when the trajectory does not depart much from the horizontal, the resistance of the air remains always nearly pei-pendicular THEOEY OF POINTESTG GTTNS. 343 to the direction of gravity; consequently the vertical velocity of fall is not sensibly altered. Represent by t the time that a projectile takes to faU a distance B C be- low the line of fire, we have but hence BC=i"; gi thus..for a 12-pounder at 984 yards we have H = .076 yds., D = 984 yds., I = 2.2713 yds., and g = 10.723 yards; hence * 2.2713 X 10.723 "^ •*^^- We can verify the degree of exactness of this formula by means of a chronometer; but as we have not one al- ways at our disposal, a means of verification can be used founded upon the velocity of sound in the air. This velocity varies with the temperature; nevertheless , we may take 1,116 feet per second as a mean; consequent- ly an observer, placed at a distance from the piece equal to 1,116 feet multiplied by the time (in the case cited, 2'.478), should hear the sound of the explosion at the same instant that he sees the ball strike an object placed at 984 yards from the piece. 344 NAVAL GUNNERY. 492. Deviations Resulting from a Difference of Level in the Trucks. When the axis of the trunnions is horizon- tal, the line of sight and the axis of the piece are in the same vertical plane ; consequently there will be no cause of deviation, depending upon the pointing, except that which may result from the line of sight not being direct- ed with sufficient precision upon the object. Now, the alignment of three points is so simple an operation that no error should result from want of exactness in this particular. Deviations, then, lateral and vertical, when the trucks are on a level, must be attributed to causes independent of pointing. The principal cause is the motion of rotation of the projectile. It is far different when the axis of the trunnions is ' not horizontal. In this case, the line of sight and the line of fire are not in the same vertical plane; there re- sults from this a cause of lateral and vertical deviation depending upon the pointing. Fig- 123. Through the ob- ject B (fig. 123), draw a straight line m n parallel to the axis of the trun- nions ; take upon this line a distance m 71 equal to the width between the trucks. Through the lowest point m, draw a horizontal, and fi'om the high- est point n let fall a vertical to meet the horizontal line THEOKY OP POIKTIJSG GUNS. 345 at p. Tliis line np is tlie difference of level of the two trucks. The line of sight and the axis of the piece determine a plane which is always perpendicular to the axis of the trunnions; consequently, this plane cuts the vertical plane passing through m 7i, in the direction B C perpen- dicular to the line m n. The axis of the piece ought to meet this same vertical plane in a certain point C, situated upon this same per- pendicular. We have found before, for the expression of the length B C This quantity is the distance that the projectile falls vertically below the point C; consequently, if we let fall from the point C the vertical C equal to B C, the the point O will be the point struck by the projectile. Drawing through the point B a horizontal to meet this vertical in q, the line B q will be the horizontal devia- tion, and the line q O the vertical deviation. The point C being always situated above the point B, we see that the deviation always takes place on the side of the lower truck. The two triangles mn p, CB q are similar, as having their sides perpendicular. We have then B q : np : :B C : m n; hence t, B G.np ^ m n np is the difference of level of the trucks ; represent it hjd. m n is the width between the trucks ; represent it by W. 346 NAVAL GUNWEET. XT J\ Now substituting for B C its value — t — , we have ^ H. D. ^ The vertical deviation ^ O is equal to BC — C^ = BC— j/ BC^— B^"^; substituting for B C and B q their values, we have qO H. D ./ RM)^ RM>\cP I P W\ I' _ H. D _ .^/ H". Dl W^ _ HI B\ d H. D H. D /■ H. D. W H. D qO = -^j^ —^W'-d'). 493. It is evident that, for the same difference of level, the deviation is proportional to the distance of the object. 494. This cause of deviation is one that obtains on ship-board more than elsewhere, for the motion of the vessel renders it very uncertain that the axis of the tininnions will be horizontal at the moment that the gun is fired. The guns forward and aft are particularly sub- jected to the disadvantage arising from this cause, and experience may be made to show that, as a general rule, the best firing done from a ship is that done by her di- visions which are quartered in the waist, for these guns are not, like those forward and abaft of them, affected by the sheer of the ship. THEORY OF POINTING GUNS. 347 495. In chase fi/'ing, this deviation becomes a matter of great importance. Chases being necessarily made under a press of sail, the pursuing and pursued have generally a considerable heel (if sailing on a wind) ; in consequence of this the guns in the bow and stern ports of each are inclined to leeward ; the result will be that the shot will fall, or be apparently deflected to leeward of the object pointed at. The effect of this error may be avoided when chasing, or being chased, by the sim- ple practice of taking care to point the bow or stern guns, as the case may be, at the weathermost part of Pig. 124. the hull, the sights being, of course, adjus- ^~\ ted to the distance in the usual manner. 496. Some efforts have been made to overcome the effects produced by this cause, which can be described generally as follows: instead of the sight bar being secured in a box, preserving it in a plane perpendicular to the axis of the trunnions, it is pivoted in such a manner as to be placed, or to place itself, in a vertical position at all times. The line of sight is drawn through this sight tangent to the most'-elevated point of the muzzle. Fig. 124 represents a pendulum Jiausse ^ — ->-, in use in the United States Army for light field pieces ; it consists of an up- O right piece of sheet brass, and has a mova- ble slider and scale. At the lower end is placed a bulb or disk, filled with lead. The scale passes through a slit in a piece of steel, and is connected with it by a brass Al 348 NAVAL GUNNERY. screw, whicli serves as a point on wMcli the scale vi- brates laterally ; the slit is made long enough to allow the scale to assume a vertical position in any ordinary cases of irregularity of the ground on which the gun carriage may stand. The ends of the piece of steel are formed into journals or trunnions, by means of ivhich the hausse is supported on the seat attached to the base of the breech, and is at liberty to vibrate in the di- rection of the axis of the piece. Thus in any ordinary variations, either in the level of the wheels or in the elevation of the gun,' the scale is kept in the vertical position by the weight of the bulb at t'lie bottom. 497. Description of some Old Systems of Pointing. Side Pointing. Tixier de Norbec spe^-ks of a manner of point- ing by making use of a side line of sight. Since that time different systems of pointing, founded upon the same principle, have been proposed. All these systems may be summed up as follows : The axis of the piece and the axis of the trunnions being placed horizontally, imagine a horizontal plane tangent to the upper part of the trunnions (when side pointing was in use, guns were quarter hung) ; this plane cuts the greatest circumference of the muz- zle in two points ; at one of these points, the one on the right A (fig. 125), place a sight button ; through this point A draw a vertical plane parallel to the axis of the piece. Fig. 125. THEORY or POINTING GUNS. 349 This plane cuts the base ring in two points B B', which we suppose joined by a straight line. Trace the inter- section of this plane upon the base of the breech. The point of intersection of the straight line B B' with the plane tangent to the upper part of the trunnions is marked zero. From this point we graduate toward B on the line B B', and through each of these divisions we draw a horizontal plane, marking its intersection on the base of the breech. In order to point, we commence by directing the piece in such a manner that the sight button of the muzzle shall be situated in the vertical plane passing through the line B B' and through the object ; then we give the elevation by lowering the breech until the sight button lies in the plane determined by the object and by the horizontal mark on the base of the breech corresponding to the elevation that we wish to give to the piece. 498. Pointing by Means of tlie Handles. This means of Fig. 126. pointing consists in a thread A A' (fig. 126) extended be- tween the handles parallel to the axis of the trunnions. The eye being main- tained in the plane determined by this thread and the ob- ject, if we drop the breech until the thread appears tangent to the upper part of the muzzle, we have a positive hausse ; if, on the contrary, we raise the breech until the thread ap- 350 NAVAL GXJWWEEY. pears tangent to tlie base-ring, we have a negative hausse. In order to fix the thread at different heights, divi- sions, one-twentieth of an inch in depth, are cut on the rear side of the two handles. Two small buttons are fixed upon the outer sides. The thread, attached by a loop to one of these buttons, passes across the division on the handle corresponding to the hausse that we wish to use, and two or three turns are taken around the op- posite button. 499. Tangent-Firing. Before the introduction of the tangent scale or breech sight, all pointing at sea was done with the dispart sight ; thus, when desiring to strike an object beyond the range at level of the piece, the trajectory being always below the line of sight, it was impossible to determine a point-blank correspond- ing to the distance of the object. It became necessary, then, to direct the line of sight (which was parallel to the axis of the piece) at a point a certain distance above the object, this elevation being intended to allow for the space through which the projectile falls by the action of gravity in the time of flight. Now the verti- cal space through which the projected body, in its flight, Kg. 12Y. descends below the line of fire is equal to the tangent of the angle of elevation multiplied by the range or horizontal distance of the object from ip the gun ; in fig. 127, BD [D ^.c &-.- - ---"^' tang. A =■ AB' B D = A B. tang. A. THEORY OP POINTING isHTNS. 351 Ttus suppose a gun to be at A, at a known heiglit A A' above tlie level of the water, and at a known dis- tance A B from a vertical object B'C, as a ship's mast. For any particular nature of ordnance we know the elevation necessary to project the projectile a certain distance. Now in the equation B D = A B. tang. A A B, equal to the distance, is known, as is also tke an- gle A, which is the angle of elevation necessary to give the gun in order to project the ball the distance A B. But we have no means of laying the gun at this angle, except by finding the length of the vertical which will subtend this vertical angle at the distance of the object. The required length of vertical B D, is found by the equation B D = A B. tang. A; if then the line of sight, parallel to the axis be directed at the point D, we know that the gun has the elevation tkat is required in ca-der to make the ball reach to the distance A B. Adding to both sides B B', we have B' D = A B, tang. A + B B'. To strike an object, then, at the water line, at the distance A B greater than the range at level, the aim being taken with the dispart sight, it is necessary to di- rect the line of sight at a point situated at the distance B'D above the water line. The heights of certain points on the masts of foreign men-of-war being known, tables have been constructed, in the columns of which are designated the points at which the line of sight must be directed corresponding to certain distances of the object which it is desired to hit. In the Ordnance Instructions tables of this char- 352 NAVAL OUNWEET. acter will be found, calculated with reference to Britisli and Frencl; ships of war of four different classes. This mode of firing presents serious disadvantages, and is calculated to increase deviations depending upon en'ors in pointing; especially is this apparent in the effect that it would have upon deviations if the ships were, as in " chase firing," much careened, when the shot would not only be inclined to leeward on account of the difference of level of the trucks of your own gun, but the enemy's mast being also inclined to leeward the gim would be pointed to leeward, and evidently the error would be the greater the higher the aim is taken. Although this system of firing should never be adopt- ed except under necessity, it is very necessary that the principle of tangent firing should be understood, in order that a gun may not be considered as disabled if an accident should destroy the breech sight. 500. Ricochet Firing. By this term, when used afloat, is meant the causing shot to graze on the water short of the object, so that it may be reached by successive bounds or ricochets. A gun fired from a lower deck, when laid level*, will generally make more than eighteen ricochets before its extreme range is completed. This is a very proper mode to fire shot at a cluster of row boats &c., and even small craft of a slight scantling; but when so doing, two circumstances should be kept in mind — 1st, That causes, seemingly of little moment, will produce considerable deflection from the line of direction, for instance, shot gi'azing on a rough sea or on very shoal * On ship-board, a gun is supposed to he laid level when the line of sight, paral- lel to the axis, is directed at the horizon. THEORY OF POIKTIWG GUNS. 353 water, so that they may toucli the ground ; or even by the shot ricocheting on a current crossing the direction of the range. 2d. The power of the shot as to penetra- tion, after having made a certain number of grazes on the water; for as a shot evidently loses some force by every graze, it is desirable to know after how many, and under what circumstances of weight, elevation, and charge, it will retain sufficient force to penetrate. Ri- cochet firing should not be practiced over water at an- gles exceeding 4'* or 5". This system of firing should be, more properly, called rolling fire. Ricochet firing, properly so called^ is employed in order to reach objects placed behind a covering mass, such as a parapet or a traverse. The projectile can pro- duce its effect either by the first shock, or by rolling and bounding the length of the terreplein ; hence the name of ricochet firing. When a face of a work is exposed to this kind of fire, it is understood that its defences must be promptly ruined ; hence it has been the effort to guard against this kind of fire, as much as possible, by means of trav- erses, the object of which is to render the ricochet, or bounds of the shot, impossible. The angle of ten de- grees is regarded as the utmost limit of the angles favorable for ricochet firing; now, when a projectile grazes the crest of a parapet elevated two and a half yards, making an angle of 10° with the horizontal plane, it will strike the ten-eplein at fourteen yards from the foot of the parapet ; consequently, if the trav- erses be placed at distances of about fourteen yards' apart, the shot will bury itself in the ground at the foot of a traverse. Traverses are consequently placed at in- 23 354 NAVAL OUNNEET. tervals of about fourteen yards • and against a face pro- vided witli traverses we can only count upon the effect of the first shock. The problem proposed, then, in ri- cochet firing, is; to make the projectile pass through a fixed point hehind the covering mass. To do this, it is necessary that the projectile graze the interior crest of the parapet, which we call the object or the point of arrival, making with the horizontal plane an angle which we call the angle of arrival^ and the size of which depends upon the position of the objects which we wish to hit behind the covering mass. The difference between direct firing and ricochet fi/r- ing consists then in this : in direct firing, the initial velocity remains constant ; we propose only to make the projectile reach the object, no matter under what angle. In ricochet firing, the initial velocity and the angle of fire are variable ; we wish not only to make the pro- jectile reach the object, but we wish to make it reach it under a determined angle. In direct firing, we impose on ourselves a single condition ; in ricochet firing, we impose on ourselves two conditions. 501. The first problem which presents itself is to determine the angle of arrival, knowing the horizontal and vertical distances between the interior crest of the parapet and the point that we wish to hit. Angle of Arrival. Let A (fig. 128) be the interior crest of a parapet, B the point that we wish to hit. Let us consider as a straight line the small arc of the- trajec- tory comprised between the point A and the point B ; the angle CAB will be the angle of arrival ; represent it by i Call a the vertical distance C B from the point B to THEORY OF POINTHiTG GUNS. 355 Pig. 128. I gives Tis •-» / the crest, and h the horizontal distance ! A C ; the right-angled triangle CAB tang i == a T Nothing is easier than to calculate the angle * by means of the tahles of tan- gents ; l)ut the employment of tables, I however simple they may be, is imprac- I ticable in the field ; it is necessary then to seek some practical solution which I does not require the employment of any I table. Supposiag the angles proportional to their tangents, which gives an approxi- mation more than sufficient for the ques- tion under consideration, we have these two veiy simple relations : 1st. At the same distance from the crest, the fall of the projectile is propor- tional to the angle of a/rrival. 2d. For the sa/me angle of a/rriwal, the faU of the projectile is proportional to the distamxie from the crest. If now we remark that the tangent of the angle of 6° is 0.1051, that, consequently, for the angle of 6° and at the distance of 1 yard, the fall of the projectile is very nearly one-tenth of a yard, it is easy to find a very sim- ple formula in order to calculate approximately the angles of arrival. Call a! the distance D F (fig. 129) which the projec- tile falls below the crest at the distance A D = 1 yard, 356 NAVAL GmSTNEET. Fig. 129. and for the angle of arrival C A B = ^. sa The distance D E which it falls at the ,^| same distance of 1 yard for the angle of arrival of 6° is 0.1 yd. ; taking the tan- gents proportional to the angles we have, according to the first relation es- tablished above, a' : 0.1 :: ^ : 6". The two similar triangles D A F and C A B give CB:DF::AC:AD, or «:«':: Z* : 1, which expresses the 2d relation estab- lished above. Multiplying this proportion, term by term, with the first, it becomes a a' : a' x 0.1 : : h x i : 6" or a : 0.1 :: hxi : 6°xa= (0.1 x^>) / 6° i = 60" — , a That is, that in order to have the angle of arrival, it is necessary to multiply sixty degrees hy tlie vertical distance to the crest from the point which we wish to hit, and to divide by the horizontal distance. This angle being known, becomes one of the given quantities in the problem for the determination of the angle of fire and of the charge. The other given parts of the problem are the distance and the angle of elevation of the object. THEORY OF POINTING GUNS. 357 The distance is always known; as to the angle of elevation of the object, we can measure it directly from the battery. In order to do this, it is sufficient to direct a straight-edge toward the parapet to be leaped over, and to place the gunner's quadrant upon this straight- edge in order to measure its inclination. 502. The Angle of Fire. In ricochet firing, the dis- tance of the object is never very great, since, unless in exceptional cases, it never exceeds or even amounts to 550 or 650 yards. The angle of fire is always consider- able ; consequently, the initial velocity is quite small in fine, we only employ projectiles of a large calibre which suffer the least from the resistance of the air All these circumstances go to show that the trajectory, in this kind of fire, does not differ much from the para- bola. We can then obtain solutions sufficiently cor- rect by supposing that the motion takes place in a vacuum. We have seen that, in the case of the parabola, the angle of fall upon the horizontal plane passing through the point of departure, is equal to the angle of fire. We conclude from this that, in ricochet firing, when the object is at the level of the battery, it is necessary to employ an angle of fire equal to the angle of arrival which we wish to attain. But let us suppose that the angle of elevation of the object B A M = E (fig. 130) be appreciable. If the We A B were horizontal, the two angles CAB and C B A would be equal ; now, as the angle E is always ver^ small, we can, without sensible error, suppose these two angles equal. Let us place then 358 NAVAL GUNNEKY. Kg. 130. , C A B = C B A. Througli the point B draw the horizontal B D ; the angle C B D is equal to the angle of arrival i. Because of the parallels B D, A M, the angle D B A = E, then C B A== i + E, consequently C A B = *■ + E. The angle offlreCAM = CAB + E, then C A M = * + 2 E, that is, that the angle of fire is equal to the angle of a/rrival, plus twice the a/ngle of elevation of the object. This rule gives an angle of fire which is evidently too great ; con- sequently, the angle of arrival, which results from it, is too great. In ordinary circumstances of ri- cochet firing the error may go as high as 2°. But we remark, that, if we had an angle of arrival accurately calculated according to the position of the point to be struck, this point could be hit only by the projectile exay increasiag tlie rotary velocity of the stot vntliout increasing; its translatory velocity, a contrary effect is produced. Professor Magnus, of Ber- lin, has a theoiy on this sub- ject which satisfies the results of practice, he illustrates with the gyroscope (fig. 139). If, during the body's rotation, a force not passing through the centre of gravity, be ap- plied to the axis, for example, if, when the axis of the body is inclined to the horizon, a vertical force act on it near to the extremity of the axis, then the latter wiU. not be moved by it in a vertical plane, but will describe a cone, in that it begins to move veiy slowly and hori- zontd'ly toward one side. If the force act in a horizon- tal instead of a vertical di- rection, the axis describes stUl a cone, but commences moving very slowly and ver- UcaWy, upwards or down- wards. This motion has ail- 384 NAVAL GtrmSTEEY. ways a di/rection perpendicular , or approximately so, to the plane passing through the direction of the force and the axis of rotation. Suppose the observer placed in the production of the axis of rotation through the base, sees the body rotate in the same manner as the hands of a clock, or from left to right, and that the force acts from below upwards on the extremity of the axis turned from him, that is, on the apex, then this apex will move toward the right ot the observer ; if, on the other hand, the force acts from above downwards, the apex will move to the left. It the force be applied to the 'extremity nearest the obser- ver, then the apex moves to his left when the force acts from below upwards; to his right, however, when it acts from above downwards. If the rotation was in an opposite direction, or from right to left, then the ex- tremity, turned from the observer, would in each of the above cases move in an opposite direction to the one mentioned. 531. Now the elongated projectile is discharged from the piece with its axis coinciding with its trajec- tory, but, through the action of gravity, the trajectory deflects from its original direction, and from that of the axis. In consequence of this, the resistance of the air acts obliquely to the axis, and, with the ordinaiy forms of elongated projectiles without grooves, its resultant passes in front of and above the centre of gravity,* tending to raise the point, and from this results the conical motion of the axis to the right, if the rotation be to the right, to the left in the contrary case. As long as the resultant of resistance is in the same * This is satisfactorily shown to be the case in the Professor's experiments. RIFLES. 385 vertical plane witli tlie axis of the projectile, tlie motion of the apex will be to the right (supposing the rotation, to the right), for the deviation, as stated before, is per- pendicular to the plane passing through the direction of the force and axis of rotation ; but as soon as this mo- tion has commenced, the plane, passing through the re- sultant of resistance and through the projectile's axis, is no longer vertical, and the more this deviation of the appx increases, the greater becomes the inclination of this plane. But, as we have seen, the apex moves al- ways perpendicular to this plane, or approximately so ; hence, from the known direction of this motion, it fol- lows that the apex must be depressed. This depression of the apex can extend even so far that it becomes situated below the tangent through the centre of grav- ity. Then the resistance of the air, parallel to the tan- gent, acts from above downwards on the apex, and thereby a motion of the apex ensues in a direction op- posite to that just mentioned; continue the subject, and it will be seen that the axis will describe a helical revo- lution around the trajectory, if its flight last for a suffi- cient length of time. During the projectile's flight, however, owing to its short duration, so great a depression of the apex is not to be expected, and Major Barnard, of the United States Army, gives as his opinion, in a paper on this subject, that in most cases, if not in all, no complete revolu- tion takes place at all, but that the whole motion is confined to the first quadrant. In this case, the flight of the projectile would exhibit one continuous and con-, stantly increasing deviation to the right (supposing the rotation be to the right). 26 386 NAVAL GUNKERY. 532. This will account for the drift ; and moreover, the more rapid the rotation, the greater difficulty will there be in moving the axis of rotation (as can be readily tested by the gyroscope), hence the less must be the deviation, which satisfies the results of practice in that respect, where the French theory is found to be de- fective. 533. We have supposed the projectile without grooves, but it has been found that grooves around the cylindrical portion of the projectile promote accuracy. It is desirable then to determine in what manner they effect the object. Their object, according to Tamissier's theory, was to tilt the ball, bringing down the apex, thus preventing the axis from remaining parallel to its first position ; but it has been shown that this very drooping of the apex is a natural consequence of the rotation of the ball as soon as the apex deviates from the plane of fire. According to the theory described above, the mani- fest effect of the grooves is to increase the surface, in rear of the centre of gravity, exposed to the resisting in- fluence of the air ; this will have the effect of bringing the resultant of resistance more to the rear, in fact caus- ing it to pass through the centre of gravity instead of between it and the apex, and this will prevent the de- viation from the plane of fire consequent upon the result- ant of resistance passing through the axis between the centre of gravity and the apex. The tendency, then, of the grooves is to retain the axis parallel to its first posi- tion, making it comparatively rigid, and preventing the apex from deviating or drooping. 534. It is desirable, however, that the projectile should strike with its point foremost, but if the trajec- RIFLES. 387 tory be curved too rapidly in order to bring abotit tHs result, the range will be shortened. The tendency of the resistance, however, being to retain the axis parallel tO' its first position, the trajectory will be evidently flat- tened, and the range increased; while a judicious placing of the centre of gravity of the projectile before the centre of figure will have the effect of causing the apex to sink so gradually as not to interfere with the flattening of the trajectory. In all expansive bullets, the cavity formed at the base has the effect of thus throwing forward the centre of gravity, and the fact that the bullet strikes the object point foremost is due, mainly, to this cause, and not to the influence exerted by the grooves. This is e^ddent from the fact that the Pritchet bullet (fired from the Enfield rifle), which has no grooves around it, strikes the object point foremost. It is probable that the upper and rearmost side of the ball, experiencing less of the resistance than the lower side, may, in consequence of this, have a greater velocity of translation than the lower side, and may thus have the effect of gradually overcoming the rigidity of the axis ; this cause would operate in- the case of the bullet without grooves, as well as of the bullet with grooves. In fine, the grooves cannot have the effect of tilting the bullet, for, supposing that there was produced a ten- dency to lift the rear end of the ball, this force would be exhibited in inclining the apex to the left instead of causing it to droop (supposing always the rotation to be from left to right). 535. To recapitulate: Professor Magnus' experiments go to show that in elongated projectiles without grooves, 388 NAVAL GUNNEKY. the resultant of the resistance of the air passes through the axis between the centre of gravity and the apex ; that the effect, consequent upon this, is to incline the apex in a direction perpendicular to the pkne passing through the direction of the resistance and the axis of rotation; that the direction of this plane is constantly varying, causing the deviation of the bullet to describe a spiral around the general line of direction of the flight; that this motion, though constant, is slow, so much so that in the time occupied in the flight of the projectile there is described only a portion of the first quadrant. The grooves on the cylindrical part of the ball, by in- creasing the surface, in rear of the centre of gravity, sub- jected to the resistance of the aii', cause the resultant of the resistance to pass through the centre of gravity, thus preventing the deviation from the plane of fire which is caused when the resultant passes between the centre of gravity and the apex. No cause, then, operating to pro- duce a deviation to one side or the other, the rotation has an opportunity of developing its peculiar property, which is to preserve the axis rigid ; this rigidity, how- ever, is slowly overcome by the centre of gravity being situated before the centre of figure, the eflect of which is to bring down the apex slowly so as to permit the bullet to strike the object with the point foremost. 536. We see from this, that the effect produced by the grooves is the same as if we carried the centre of gravity farther. forM^ard in the bullet; and thus to make a bullet without grooves equal in accuracy to a bullet with grooves it is necessary that its forward part should be much more rounded ; and this is the case with the Pritchet bullet, used with the Enfield rifle, which has RIFLES. 389 its sides smooth and the centre of gravity thrown for- ward much farther than is the case with the French or United States bullets, both of which are more pointed in form at the forward end than is the English bullet. 537. The experiments of Professor Magnus with the gyroscope are so satisfactory that his conclusions may be safely taken as establishing the true theory of the rifle motion, and the deviations peculiarly due to it. The in- fluence of the grooves around the cylindrical part of the bullet, as just stated, seems to be a fair deduction from the results arrived at by Magnus, and is submitted as the probable manner in which they operate to promote accuracy. 538. Rifled Cannon. Many attempts have been made to apply the rifle principle to guns of large calibre, but up to the present time the success of inventors in this line has not been such as to warrant the introduction of rifled cannon, to any great amount, in the batteries of ships ; although for light pieces for the field, and boat howitzers, the application of the system seems to be ap- proved of to a considerable extent. The importance of the question is much enhanced by the fact that the mo- ment a successful plan is discovered, the problem of per- cussion shells is solved. Large projectiles, being made of iron, cannot, of course, be forced into the grooves of a gun like the leaden ball of small arms. All projectiles designed for rifled can- non are elongated in shape. Some have been made with spiral grooves, or projections, on the after surface, through which the gas, as it rushed, produced the rotary motion ; others have these grooves on the fore part of the ball, and the rotation is produced by the action of 390 ■ WAVAL GUNNEET. the air on tliem as tlie ball moves forward ; but although the effect was produced by these two methods in a slight degree, the force of rotation developed was not sufficient to insure the direction of the ball with any certainty, i Attempts have been made to cast on the outside of the cylindrical part of the shot some softer metal, such as lead, or composition, to take the groove and give the necessary rotation ; but it has generally been found that, although these metals take the grooves at first, they are torn off by the force of the powder. 539. French Rifled Cannon. The French have long been making experiments upon a cannon with two grooves, having an elongated projectile with buttons on the sides to fit into the grooves. Increased range and accuracy seem to be attained, but no dependence can be placed on them for any length of time, as the slightest obstruction or difficulty of the projectile in making its exit inevitably bursts the gun. 540. Lancaster Gun. The English I^ancaster ffun, so called from its inventor, and which was employed during the late war with Russia at an enormous expense to the British government, seems now to be acknowledged as a perfect failure, and has fallen entirely into disuse. To Fig. 140. get an idea of the form of the bore of this gun, suppose figure 140 the section of a rifle with two grooves, having a gaining twist; if we cut away the metal about the grooves until the bore will be represented by the dotted curve, we have a cross sec- tion of the elliptical bore of the Lan- caster gun. The "projectiles fired from this gun expe- RIFLES. 391 rienced great difficulty in forcing their way tlirougli, and tlie guns, consequently, frequently burst ; it was also noticed witt this gun that the projectiles were fre- quently broken, even when made of wrought iron. The manufacture of this gun was very difficult and expensive, the shell used with it was complicated and difficult of manufacture, and the serving of the gun was very trouble- some, requiring much habitual skill, or knack, in intro- ducing and setting the shell home through the turning of the bore; and it is not unlikely that, in some instances, the bursting of the Lancaster guns was oc- casioned by the oval ball leaving a space between it and the cartridge, or by getting fixed in the gun by change of position whilst it was being propelled through the oval bore. This plan of rifling has also been applied to small arms, but with much better success. Rifled Cannon Loaded at the Breech. The practice of loading guns at the breech is not of modern date, as will be seen by referring to the description, given in chap. I., of the guns recovered fi'om the "Mary Kose," sunk in 1545. 541. Caralli Gun. In 1846, iron rifled cannon, capable of being loaded at the breech, were invented by Major Cavalli, of the Sardinian artillery, and Baron Wahren- dorff, a Swedish noble, for the purpose of firing cylinclro- conical and cylindro-conoidal shot. In these guns the mechanical contrivances for securing the breech are very superior to the rude processes of earlier times, yet it is very doubtful whether, even now, they are sufficiently strong to insure safety when high charges are used in long continued firing. 392 NAVAL GUNNEET. Kg. 141. The length of the CavaJli gun (fig. 141) is 8 feet 10 inches, weighs 66 cwt., and its calibre is 6a inches. Two grooves are cut spirally along the bore, each of them making about half a turn in the length, which is 6 feet 9 inches. The chamber is cylindrical. With respect to windage, it must be observed that in all rifles with forced leaden shot of any shape, there is practically no windage, and, accordingly, no waste of the charge: but it is not so with iron shot fired from rifled cannon, since the iron cannot be made to expand so as to fill the bore and enter into the grooves; there must, consequently, be some windage; and, in fact, if there were not some, or if the charge were not greatly reduced, the blowing off the breech, an accident which happened to M. Cavalli's own gun, would be of frequent occurrence. Immediately behind the chamber there is a rectangu- lar perforation in a horizontal direction and perpendicu- lar to the axis of the bore; its breadth vertically is 9i inches, while horizontally it is 5.24 inches on the left side, and S.YS inches on the right side. This perforation is to receive a wrought-iron case-hardened quoin or wedge, which, when in its place, covers the extremity of the chamber which is nearest the breech. The projectile, cylindro-conical or cylindro-conoidal in form, being in- troduced through the breech and chamber into the bore RIFLES. 393 of the gun, and tlie cartridge placed behind it, a false breech of cast iron is made to enter 2i inches into the bottom of the chamber behind the cartridge; and a cop- per ring, which also enters the chamber, is placed over it. The iron wedge is then drawn toward the right hand till it completely covers the chamber. After being fired, the gun can be reloaded without entirely taking out the wedge; for the latter, which is shorter than the rectan- gular cavity in which it moves, can be withdrawn far enough to allow the new load to be introduced. Experiments made with this gun have given the following results, shells being fired from it with charges equal to one-tenth of the weight of the projectile: Mean Deviations. Elevation. Mean Range. To the Bight. To the Left. 10" 3058 yds. 3.4 yds. 3.39 yds. 15° 4128 " 11.0 " 1 ft. 11 in. 20" 4917 " 6.1 " 10 yds. 25° 5563 " 3.0 " 4 " These trials were considered highly satisfactory. 542. Wahrendorff Gun. The rifled gun constructed by Baron Wahrendorff differs in some respects from that oi Major Cavalli (fig. 142). Its whole length is 8 feet 11 inches, and its greatest diameter, A B, 2 feet 3 inches. The diameter a h oi the bore is 6.37 inches from the muzzle to within 6 inches of the chamber, in which space, G d e f,\t has a conical form, the diameter c d being 9.65 inches ; the diameter of the chamber cdgh\s*l.6 inches. A rectangular wedge, 12.2 inches long, 8.1 inches broad, and 4.25 inches thick, is made to slide toward the right or left hand, in a perforation formed transversely through the breech, for the purpose of covering, after the gun is 394 NAVAIi GUHNERT. Kg. 142. A /- L ^ ,c c ^-^ a J rr' Yi \ on even ^r ^^r terms, or stand on, and '^1/ y^ crossing his stem at D, keep his wind, and manoeuvre afresh. 643. Coming Down Abaft the Beam. But, it may be said, a cautious intelligent enemy, attacking from the windward, will come down abaft B's line of fire (fig. 173), Fig. 113. and when nearly in ,-^^ his wake, either run '^ up to windward, or / pass to leeward, as he may choose, if B B^ .'- will wait for him, or if A outsail B. But whether the action *? is to be thus fought or not, will neither depend upon B's sailing nor upon A's pleasure, if B manoeuvre properly, for if he have 31 482 NAVAL GUH-BTEEY. any reason for not desiring sucli a plan of action, and should not think proper to give A an opportunity of raking his stern, in passing to engage him to leeward, he should tack or wear at a convenient time while A is still out of range, and stand on slowly the other way. Thus if A 1 (fig. 174), perceiving B 1 lying to leeward, shape a Kg. IH. A! 3 2 "VX> \/A3 01 Hi: B3 course to run down into his wake, B 1 should tack or wear in time, and stand on, as B 2 toward A 2 ; and this manoeuvre will bring the case exactly to that which has been considered in figure 170. If B 1, neglecting or waiving this, stand on, and let A 1 get close in his wake, then A 1 may bear up, and raking B I's stern, engage him to leeward. 644. Danger of Allowing the Enemy to Approach in your Wake. There is no way in which B 1, having permit- ted A 1 to come close in his wake, can now avoid sus- Fig. 115. PRACTICE OF GDimEEY. 483 taining some previous disadvantage, if A 1 sliould try to rake Ms stern. For if B 1 tack to avoid it, he will first expose Hs stern, B (fig. 175), to be raked; lie will be severely punisked wkilst in stays by a fire in great part diagonal; if ke kang in stays, ke will be utterly destroyed ; and in coming around on tke otker tack, ke may fall off nearly end on toward A 2, as at B 3. No good officer, indeed, would attempt suck a metkod of avoiding being raked; and if, on tke contrary, B bear up, as B 2 (fig. 1*76), to prevent tkis, ker opponent A Pig. lis. Vb3 may luff up, and rake kim before B can get away, and tken manoeuvre for fresk advantage. Now if, on tke contrary, B skould kave tacked, as Fig. 177. ..'A A2 B*-^ 484 NAVAL GUNWEEY. suggested before, and stand on toward A, as B 2 (figs. 1Y4 and 177), then, if the offensive movement be con- tinued within range, B should deaden his way as much as ]30ssible, and open his fire upon A coming down, keeping his broadside, as at B 3,. B 4, steadily bearing, and thus follow the movement of A 2, A 3, gradually, till both ships come close together; and thus again the commander of B could have no objection to close action, the previous advantage homing been his. 645. Proper Plan of Receiving the Attack from to Wind- ward. If the reasoning be correct, the best way for a vessel, B (fig. 178), to leeward, to rec3ive an attack Fig. 178. v^p- ^ A2 AS-fff A* .i^ A5^ ,m"--^ %-s B5 „e% %- \ A7 with circumspection, from a vessel. A, to windward, is never to let A come down into his wake; but having PEACTICE OF GUNNEEY. 485 tacked in time, as B 2, stand on slowly till A ap. j)roacli within B's fire, from which time B should keep as stationary as possible. Supposing the vessels to be of nearly equal force, it may be assumed that A has no intention of avoiding action; but after he is once brought to the position A 4, it is evident he cannot approach nearer to B, manoeuvring thus, without re- ceiving a mass of fire which he cannot return. If he shape his course to cross B's bows, the counter man- oeuvre which B should apply is not velocity, but grad- ual change of position, in steady broadside bearing, with as little way as possible, following A's bows with the broadside so long as he tries to cross B's bow, an attempt which only can be continued until A come close to the wind on the port tack, and here again there v/ould be no objection to bring on close action in this way, the previous advantage having been to B. If, in thus coming to the wind, the vessels should get foul of each other, it will be in a position favorable to B, as E F (fig. 178), if the manoeuvre have been properly and steadily executed; and this will bring on a new char- acter of combat, viz. : boarding. These manoeuvres will, at all events, refuse to A the opportunities of which we have supposed him to be de- siroTis, viz.: previous distant cannonade on his own terms; and therefore it appears that this method of manoeuvring, in receiving an attack from the windward, is favorable for ships which are not at liberty to re- ceive battle under any disadvantageous tactical cir- cumstances. fi46. "Macedonian" and "United States." The action between the "Macedonian" and the "United States," 486 NAVAL GtrUNEKY. was, in tactical circumstances, of a nature difierent from those cases wMcli have been; considered. The British frigate was to windward, and ran directly down upon the "United States;" but, in doing this, she was so severely damaged that the upper deck was almost en- tirely disabled by the raking fire of the "United States," then lying steadily to leeward. In doing this, the British frigate committed a great en'or in tactics; she should have commenced with the ordinary manoeuvre of running down in the wake. 647. Receirifig am Attack from to Leeward* li] how- ever, the British frigate, represented by B (fig. 179), declining this, had been brought to, as at B 2, the " United States," A, fancying her rather shy, would cer- Fig. 179. 'A3 A2 tainl}', after some time have approached. This she probably would have done by tacking, as at A 2, and standing close upon the starboard tack into B's wake, and thence tacking toward her, as at A 3. Now if A taclc in B's wake, A cannot go to windward of B, nor vake him, except partially by luffing up in the wind, or PRACTICE OF GIINNERT 487 by keeping away, botli of wLich. would be random and very inefficient volleys. But if A should stand on, as at A 1 (fig. 180), and tack, as at A 2 to windward of Fig. 180. "/"^■""% J! E- --::,.--'A3 A 2 B's wake, then it would be advisable for B to tack also, as at B 2, because A, by acting thus, may be suspected of an intention of crossing B's stern in order to rake him before he engage him close to leeward, as at D. Now if B tack, it is evident that upon this course also he will go to windward of A ; and if A proceed to A 3, B 3 may lay across his bows and rake him. This A will not, of course, suffer ; and, to prevent it, must either wear or tack again. If he tack, and there wait, as at A 4, B may run alongside, and engage him to windward, at C, in close action ; or crossing A's stern, fight him to leeward, as at E. INDEX. AccDRAOY, Influence of wind on . . . 345 Age, Effect of on Endurance 147 Ancient Enoines of 'Wab 9 Angle, of Greatest Range in Air. . . 469 Of Arrival 501 Of Fire 502 Ancient Men-op-Wab 14 Akms 4 Ancient Musqueteer 8 Armada or Philip II 24 Armstrong- and Whitwobth Guns Compared 569 Atmosphere, Resistance of the 319 Ballista 10 Ballistic Pendulum 244 Battering Ram 11 Bunsen's Batteries 268 Bed aot) Quoin 167, 186 Porter's 189 Bolts Connecting Brackets and Axle- trees 169 Bore, Length of 89 Form of the Bottom of 113 Boring 68, 70, 75 Bow 6 Breast-Piece 166 Breech, Thickness at the 104 Loading 507 Loading Cannon, Objections to. . . 570 Sights, Marking 488, 489, 490 Breeching 156 Compound 157 Bronze 39 Bronze Cannon, Injuries to 124 Increasing DurabUity of .... 127 Bullets, Effect of 637 Calibre 303 Advantage of Large 460 Resume of the History of 33 Cannon, Nomenclature of 80 Ancient 16 Ancient Wrought-Iron 19 Cannon, Ancient Breech-Loading . . 20 Early Methods of Firing 419 Form of loO Exterior Form of. 105 Length of. 103 Model for 53 Introduction of Cast-iron for 21 Inspection of 81 Marking . . .' 99 Lifetime of. 130 Indication of Effect of Service in Iron 128 Substances Used in the Manufac- ture of 35 . Injuries to. ■ 121 Strengthening Bands on 131 Col. Bumford's Plan for Determin- ing Decrease in the Thickness of Metal for 101 Capt. Rodman's Improvement on the Plan of Col. Bumford 102 Effect of Re-entering Angles on. . 134 Effect of Irregularities on the Sur- face of 140 Preservation of 151 To Render Unserviceable 149 To Unspike a 150 Armstrong's Plan of Construction of, Identical with that of Prof. TreadweU 559 Babcock's Plan of Constructing. . . 576 Carriage, Navy Four-Truck . . .164, 165 Advantages of the Navy Four- Truck 171 Objections to the Navy Four-Truck. 172 Carcasses 313 Oareonades, Introduction of. 29 Cartridges, Effect of Varying the Length and Diameter of 248 Casting 64 On a Core 72 Rodman's Plan of Hollow 143, 144 Effect of Unequal Shrinking in the, 142 Shot and Shells 287, 288 490 INDEX. Catapult! 10 Chambers 112 Effect of Size of 239 Chaeooal 198 Obtaining by Distillation 199 Temperature at which Prepared. . 200 Coles' EEVOLvme Towbes .,. 592 Combustion 218 More Rapid in a Closed Space. . . . 219 Causes that Effect the "Velocity of 225, &c., to 232 C0MIN& Down Abaet the Beam. . . . 643 COMPOSITIOK, Moulding 56 OossiDBEATiONS, Referring to a Ves- sel Engaging to Leeward G01 Referring to a Vessel Engaging to Whidward 608 Referring to the Inclination of the Axis to the Plane of the Deck. 609 CoOLiir&, Effect of Unequal Rapidi- ty in 141 Arrangement of the Crystals of Iron in 135 Copper 38 Ceanbs 63 Oeoss-Bow 7 Danger op Allowing the Enemt TO Appeoaoh in Youe "Wake. . 644 Deviations, Direction of, not Con- stant 322 Magnus' Experiments on, 325, 326, 32"! Influence of Velocity on 336 Case of no Deviation 337 jSTot Due to Pointing 462 Vertical, Corresponding to Errors of Hausse 479 Resulting from Difference of Level of the Trucks 492 to 495 Magnus' Theory of, with Elongated Projectiles 530, 531, 532 DiEEOT FlEE 471 DiSPAET Sight 481 to 484 Dismantling an Enemy 615 Deteemining Distances op Objects at Sea 597 to 601 Distance op Object Determined by Bucknee's Plan 602 Double-Shotting 580 to 583 Drift ^ 522, 535 Erenoh Theory of 529 Drooping at the Muzzle 125 DuST-MiLL 206 Eccentricity 328, 332 In Shells 334 Effect of, on Range and Accura- cy 329, 330 Explaining Anomalies 333 Ehbestham Carriage 178 Elevating Screw 187 Elongated Foem op Bullet, Ad- vantages of 523 Epeouvettes 241, 255 Ranges by 242 Experience op the War or 1812, 34 Fire, Concentration of 628 to 632 General Conclusions on the Proper Time to 610 Firing .Low, Advantage of 611 " Hornet" and " Peacock" 612 "Avon" and "Wasp" 613 " Prohc" and "Wasp" 614 Flasks 59 Forging Wrought-Ieon Cannon. . 77 Peactures, Course of in Cast-iron Cannon 132 Friction Caeriages 155 Fuze 377 Time-Fuze 378 Concussion 379, 397, 398 Percussion 380, 413 Case 381 MetaUic Case 382 Paper Case 383, 386 Safety-Plug, Water Cap 384, 385 Cases of other Nations 387 BngUsh 388 Injuries to, from Shocks 389 Splingard's Shrapnel 390 Boxer's 391 Borniann, Operation of 392, 393 French Shrapnel 396 Prussian 401 to 405 Schonstedt 406 Snoeck 407 Sphngard's Concussion 408, 409 Moorsom's 415, 414 Bourbon 416 West Pomt 418 Objection to Concussion 412 Armstrong's 551 Gauge, Ring 294 Cylinder 84, 295 Star 85 Gun-Careiaoe, Conditions required of 152 Three Forms of 163 Ward's 173 Cast-iron 161 Wrought-lron 162 Wahrendorff's 543 Armstrong's 555 Deterioration of 160 Gravity 435 GeeENEE's EXPANSP^E BULLBT. . . . 520 Grooves, Want of, on the Pritchet Bullet Compensated by the more Forward Position of the Centre of Gravity ' 536 INDEX. 491 Gunnery, Ordnance and 1 GtUN-Pekdulum, Correct Eesults ob- tained with a Six-Pounder 256 Gunpowder, Origin of 191, 192 Invention of 15 Proportion of tlie Ingredients for, 204 Incorporation of 205 Graining 209 Advantages of Graining 215 Size of Grain of 212 Glazing 210 Effect of Glazing 211 Inspection of 224 Temperature Kecessaiy for the Inflammation of 221 Causes that will produce Inflam- mation of 222 Methods in Use for Inflaming . . . 223 Chemical Definition of the Ingre- dients of 216 Phenomena Attending the Change of, from a Solid to a Gaseous State 21'Z Character of the Gases of 233 Rate of Burning of 220 Proof of 240, 254 Proof of, for Small Arms 258 Storage of 280, 281 Packing 213 Markiug Barrels 214 Proportioning Charges of 284 Maximum Charge of 231 Advantage of Quick in Small Charges 236 Advantage of Slow in large Charges 235 Capacity of, for Resisting Moist- ure 259 Damaged 282 gun-cotton 283 Harmlessness of Non-Elastio Force 234 Heisht, Effect of, on Gun-Carriages, 159 Of the Curve in Tacuo 452 to 455 Of the Curve in Air 468 Helix 515 Hollow Casting 143 lifEFPIOIBNCT OE RANDOM BROAD- SIDE Firing 616 Inspection, of Cannon 81 Variations AUowed from True Di- mensions in 94 Iron, Cast . . . , 36, 46, 50 Wrought 37, 53 Cased Ships 588 La " Gloire" 593, 594, 595 The " Warrior" 596 Jones' Inclined Sides 591 Lepanto, Battle of 23' LoADma IN One Motion 617 Looks, First Application ot; to Can- non 423 Navy 430, 431 Improvement in Mounting the Hammer of ^. 432 Lodgements, ProfessorDanielTread- weU on 120 Marshall Carriage 177 Maesilly Carriage 175 Match [\ 420 Models _ 57 Mortar _' 27 Moulds [[[ 55 Moulding Composition 56 Moulding, Process of '. 60 Mounting Guns, Rule for ... . 190 Natal Duels 639 " Guerri^re" and •' Constitution" . 640 "Macedonian" and "United States" 646 Navez' Machine 261, 266, 267 The Pendulum 263 The Conjunctor 264 The Disjunotor 265 Manner of Using 269 to 279 Negative Hausse 48O Nitre 193 Walls 195 Method of Obtaining 196 Artificially Obtained 194 Pulverizing 197 Nomenclature of Cannon 80 Norton's Liquid Fire 317 Ordnance and Gunnery 1 Pendulum Hausse 496 Penetration 635 OfNavy Ordnance 346 Effect of a Shell dependent on, 410, 411 Percussion 424 Wafer 425 Cap for Cannon 426 Union of the Tube with the Wafer, 427 Navy Primer 428 Eughsh Primer 429 Phenomena in Bore on Combustion OP Charge. 119 Pivot Carriage 179, 180, 181 Point-Blane 474, 476, 485 Pointing 472 By means of the handles 498 Side 497 Port-fire 421 Pounding Mill 2O0 Practice of firing at sea 603 Preponderance 115 Priming Cannon 422 492 INDEX. Primers — Friction 433 English friction 434 Projectiles, moulds for 285 Models for 286 Perm of, 318 Polisliing 289 Advantage of large calibre of. . . . 338 Advantage of great density of . . . 339 Advantages of the spherical form for 340, 344 Advantages of the elongated form for 341 Requirement for accuracy with elongated 342 Resistance to elongated and spheri- cal compared 343 Best position for preponderating side of 335 Effect of on Wood 633 Effect of on Earth 634 Effect of on Masonry. 636 Effect of on Water 638 Pboop — Preliminary of Cannon. ... 96 Powder of Cannon 95 Water of Cannon 97 Injury to Cannon in 126 PuLVERizma Nitre 197 Quoin, Bed and 167, 186 Ward's Screw 188 Porter's Bed and 189 Ranse 456, 457, 458 In air 466, 467 Condemning as unserviceable .... 243 Receiving an Attack from to Windward 641, 645 Receiving an Attack from to Lee- ward 647 Rule fob Chasing to Leeward. . . 642 Recoil 106 Limit to 154 Necessity of 153 Effect of, on range 107, 108 Plan of controlling 579 Relation between total hausse and time of flight 491 Resistance op the Air 438, 459 Ricochet Firing 500 Rifle, Inaccuracies intended to cor- rect 503 Object of the motion 505 Methods of imparting the motion. 506 Maynard's 508 Delvigne'a 509 a tige 510 ftrooves 511 Twist 512 Gaining twist 513 Depth of Grooves 514 With ball i culot (wedge) 516 Rifle, Bullet without wedge 517 Pritchet bullet 518 United States Navy bullet 519 Theory of motion 521, 524 Grooves on the Bullet 525, 533 Influence causing the Bullet to strike point foremost 534 Cannon 538 French Cannon 539 Lancaster Cannon 540 Cavalh Cannon 541 Wahrendorff Cannon 542 Napoleon Cannon 544 Armstrong Cannon 545 to 557 Whitworth Cannon 560, 561, 562 Blakely Cannon 575 Parrott Cannon 573 Whitworth Projectile 563 Armstrong Projectile 550 James' Projectile 571 Sawyer's Projectile 572 Parrott's Projectile 574 Spanish Projectile 575 Napoleon Projectile 544 Schenkl Projectile 577 Advantage of, limited to long ranges 566, 567 Initial velocity of Projectiles 578 RiMBASES I] 6 Rocket 347 Signal 348 The Former 349 The Choke 350 Composition 351 Mould for 352 Driving the Composition 353 Pots 355 Cones 356 Making up the 358 Stick 359, 363 Decorations 360 Congreve 361 Motive power of the 362 Range of 364 British 365 SheU 366 Uncertainty of practice with 367 Limited usefulness of the 368 Incendiary properties of the 369 Trajectory of the 370 Fired from Cannon 371 Hale's 372, 373, 374 Hale's Tube for Broadside firing. 375 Roll, considerations of the 605, 606 Rolling Mill 207 RoMME Carriage 176 Rotation 461 Effect of, on projectiles fired en ricochet 331 Rotary Machine 260 "BoYAL Prince," Armament of the 25 INDEX. 493 Rule for determining 'Weight of Shot and Shells 292 Sabots 314 " Santissima Tkinidada," Arma- ment of the 30 Searcher 83 Shells 309 Brplosionof, on Concussion, 618 to 621 Care in the Use of 622 To Fill a Shell 627 Position of Shell-Rooms 624 Precaution in Passing 625 Premature Explosion of 626 Inspection of 297 to 302 Navy Shot and 290 Martin's 316 Shot, Weighing 291 Inspection of 293 Hot 315 Bar 304 Chain 305 Grape 306 Canister 307 Hollow 308 Effect of, on Iron 584 to 587 Spherical Case, or Shrapnel ... 310 Charging 311 English 312 Sight Notches 473 Sights fitted to Natt Cannon. . 486 Sight-Bar, Use of the Graduations between "Level" and Range at Level 487 Sling 5 Smelting 48 "Sovereign of the Seas," Arma- ment of 26 Steel, for Cannon 54, 79 Steps op the Carriage 170 Strain, Unequal on the Exterior and Interior of Cannon 133 Increase of, due to Increase of Cal- ibre 122 Strength, Test of, of Shot 296 Sulphur 201 Refinmg 202 The " Tamerlane," Armament of. . 32 Tangent Firing 499 Tangent Scale 475, 477, 478 The Tower 13 Trajectory, In Vacuo ... 449, 450, 451 In the Air 463, 464, 465 Teeadwell's Plan op Construct- ing Cannon 558 Trucks for Navy Gun-Carriage, 158 Trunnion 114 Effect of 145 Holes 168 Rule 88 Square 86 Turning 73 Tan Brunt's Carriage 182 Self-Compressing 184 Velocity, Of a Fallipg Body 440 Initial 257 Vent 117 Inclination of 91 Position of 90 Influence of Position of 118 Inspection of 129 The " Victory," Armament of ... . 31 Vibration, Effect of Irregularities on the Surface of Cannon 140 Wads, Effect of Junk 247 Ward's Gun-Carriage 173 Gun-Carriage compared with Four- Truck Carriage 1.74 Screw Quoin 188 Weakness of a Gun in the Direc- tion of its Length, as compared with its Power of resisting Longi- tudinal Strain 547 Whitworth and Armstrong Guns Compared 569 Reason for the Greater Range of the Smaller CaUbre 568 Windage 110, 320 Loss of Force by 246 Effect of Reducing 249 to 252 Effect of Escape of Gas through Ring 253 Inaccuracies Caused by 321 Suppression of '. ... 504 Wrought-Iron Cannon, Weakness of '78