WILLIAM R. PERKINS LIBRARY DUKE UNIVERSITY Digitized by the Internet Archive in 2016 with funding from Duke University Libraries https://archive.org/details/textbookofnavalo01cook A TEXT-BOOK II OP NAVAL ORDNANCE AND GUNNERY. PREPARED POR THE USE OF THE CADET AIIDSHIPMEN f AT THE LKited States Xaa^al Academy. M V BY V>0 A. f: gooke, COiniANDER, U.S.X., IN CHARGE OF INSTHUCTION IN ORDNANCE AND GUNNERY AT THE U. S. NAVAL ACADEMY. Aew-York : JOHN WILEY & SON, 15 ASTOR PLACE. 1875. Entered, according to Act of Congress, in the }'ear 1875, by A. P. COOKE, In the Office of the Librarian of Congress, at Washington. 31 FEh 141945 ^ Serial hecord Division Ths Llbrarir of CongroM Copy Tt.t.itkthattonS ENSR.A.VBD ON WOOD BY CH.YKLES AIcRRAY, XEW YOltK. John F. Trow & Son, Printers, 205-213 East i2th St., New York. C77Z PREFACE. Tins work was undertaken hy tlie Instructors in the Department of Ordnance and Gunnery at the Naval Academy, to supply a deficiency which has long heen felt, and to I'ender available, as far as possible, in a sin- gle volume the course of instruction hitherto pursued l;)y the Cadet JMidshipmen; thus relieving them from the necessity which at present exists, of copying manuscript notes on the subject. The unsettled condition of various rpiestions relating to ordnance, makes it necessary to prepare suitable text- books for to-day, which should be I'evised as often as the progressive development of the suliject seems to re- quire, Explosive-agents, rilled ordnance, gun-carriages, and many other branches of the subject, are in a state of transition, and it is impos.sible at the present mo- ment to produce a com])lete and entirely satisfactory treatise on these subjects. It is thought that no intelligent progress can be made in the subject of the manufacture of cannon, and of many of the stores used in their service, without some preliminary knowledge of the metallurgy of iron, and of the means of producing the metals employed. As this sul)ject is not taught in an}' other department of the Academy it is given a place here. IV PREFACE. A sufficient knowledge of niatheinatics, physics and chemistry, is attained hythe students in tlieir previous course, to enaT>le them to grasp all the subjects treated in this work. The sul)ject of Field Fortifications ’was formerly taught in this department, l)ut for want of time and an appropriate text-l)ook it was taken out of the course. The last chapter, entitled “Naval Operations on Shore,” has Ijeen arranged with a view of covering briefly the necessary ground in this l)ranch. In the compilation of the material employed, the writer is greatly indebted to Lieut.-Commanders C. Ab Tracy, G. W. Coffin, N. Ludlow, and C. F. Goodrich, to Lieut. J. C. Soley, and to Professors J. M. Eice and D. Fisher. The advice, assistance, and manuscript notes of many other officers have likewise aided materially in the pre2:>aration of this work. Department of Ordnance and Gunnery, U. S. Naval Academy, Annapolis, March, 1875. CONTENTS. CHAPTER I. CANNON METALS. Section 1. — Metallurf/y of Iron. Preparation of Iron Ores — Smelting;— Fluxes — Fuel — The Blast-furnace — Charging — Temperature of Blast — Hot-hlast — Method of Heating the Blast — Blowing in — Working of the Furnace — Chemical Action in the Furnace-^Pro- duction of Gun-iron. Section II. — Cast-iron. Composition of Cast-iron — Varieties of Cast-iron — Gray Cast-iron — White Cast-iron — -Mottled Cast-iron — Classification of Pig-iron — Variations in Composition of Cast-iron. Section III . — WrougM-iron. Peculiarities — How produced — Conversion of Crude into Malleable Iron — Various Processes — Chemical Reactions — Kind of Iron most suitable for Con- version — Variation in Quality — The Puddling-furnace — Proce.ss of Paddling— The Puddle-balls — Shingling or Blooming— Rolling-mills — Rolled Armor- plates — Weldi ng — U psett i n g. Section IV. — Steel. Peculiarities — Definitions — How obiained — Classification — Process of Cementation — Blister-steel — Spring steel — Shear-steel — Cast-steel — Steel Ingots — Bessemer Process — Annealing — Tempering Steel in Oil. Section V. — Bronze. Bronze for Cannon — Pure Copper — Pure Tin — Circumstances affectin the Production of Bronze — Constitution of the Alloy — Difficulty of makin Sound Castings. Section VI. — General Qualities. Qualities necessary in Metals for Cannon — Properties of Metals — Density — Hardness — Brittleness — Tenacity — Porosity — Elasticity — Limit of Elasti- city — Permanent Set — Malleability — DuctiliQv— Rupture — Qualities of Cast- iron — Qualities of Wrought iron — Qualities of Steel — Qualities of Bronze. be be VI CONTENTS. CHAPTER II. GENERAL DESCRIPTION OF ORDNANCE. Section, I. — Terms and Definitions. Classification — Nomenclature — Interior Form — Length of Bore — Wind- age — Seat of the Charge — I'he Vent — Exterior Form — Force to be restrained — Experiments — Devices — Mortars — Hcwitzers — Percussion Lochs — The Uai ■ ling Gun. Section II. — Theory of 'Gun Construction. The Kinds of Strains upon a Gnn — Tangential Strain — Longitudinal Strain — Crushing- force — Transverse Strain — Total Bursting Tendency — Determination of the Exterior JModel of Guns. Preponderance — To determine the Preponderance — To determine the Po- sition of the Trunnions — To determine the Effect on the Preponderance of a Change in the Position of the Trunnions. CHAPTER III. CAST GUNS. Section I. — Standard of Iron. Smelting of Iron for Cannon — Difference in Quality — Effects of different Treatment — Practical Treatment in Fusion — Tests while in Fusion— Crys- tallization — Development of Crystals — Chilled Castings — Effects of Crystalliza- tion on Strength — Size of Crystals — Contraction of Casting — Effect of sudden Change of Form — Effect of Irregular Cooling — Effect of Age on Endurance — Improvement in Casting — Standard of Quality — Comparison with Standard Samples — To Determine the Density — The Hydrometer — Wurdemann Balance for Specific Gravities. Section II. — Mechanical Tests. The Testing-machine — Capacity of the Machine — Working the Machine — Adjusthients- -Tensile Strain — Crushing-force — Errors of the Machine — Modification of the Machine. 1 Section III. — Fabrication. Fabrication of Cast-iron Guns — Charging the Furnace — Fusions — Mold- ing.? — Models— The Flask — The Core-barrel — The Pit — Melting D.own the Charge — Tapping the Furnace — Cooling the Casting — Withdrawing the Core- barrel — Trimming Down the Casting — Removing the Sinking-head — Cutting out Specimens — Boring — Cutting Hole for Elevating-screw — Drilling the Vent — Marking Guns — Fabrication of Bronze Howitzers — The Flask — Molding — The Pit — Charging the Furnace— Melting down the Charge — Casting. Section IV. — Inspcciic n . Inspection of New Guns — The Inspecting Instruments — Vent Impres- sions — Gutta-percha Impressions — Powder-proof — Water-proof — Extreme Proof of Trial Guns — Enlargement of Vents — Endurance of Guns in Service — Injuries from the Powder — Injuries from the Projectiles — Descriptive List of Guns — Inspection of, at Termination of a Cruise — Inspection of Vents. CO^'TE^^TS. Vi I CHAPTER IV. r-UILT-UP GUXS. . Section I — Principles of Construction. DeSnitinni— Nature of the Force to 1)3 Restrained — Limit of Thickness of Jtetal — Methods of Equallizing the Strain — System of Initial Tension— De- fects of the System— Methods of Application — System of Varying Elasticity — Defects of the System. Section IT. — The Parrott Gun. General Description — The Barrel — Tlio Hoop — Placing the Reinforce. Section III. — British Guns. The Armstrong System — IMethod of Manufacture — The Frazer System — Tlie "Woolwich Gun — Details of Manufacture — Palliser System of Conversion — Experimental Guns — The Wliitworth Gun — The Blakely Gun — The Vavas- seur System. Section IV. — French Hatal Guns. General Description — Manner of Casting — Hoops — Breech-screw — Gas- check. Section V. — Gernyin Haval Guns. Nomenclature — Features of tlie Manufacture — The Central Tube — The Hoops — Breech-plug — Gas-chsck — Vent-tubs. CHAPTER V. KIFLING. Section I. — Principles. Definitions — Origin of Rifling — Introduction of Rifle-cannon — Progress in Construction — Object of Rifling — Method of Rifling — Uniform Twist — In- creasing Twist — Velocity of Rotation — Character of Grooves — Cutting the Grooves. Section II— Systems. Definitions — Classification — Centring — Wliitworth’s, Vavasseur’s, Scott’s, Lancaster's — Studs or Ribs to fit the Grooves — The "Woolwich System — The Shunt System — Expansion System — Parrott’s — Compressing Systems — Krupp’s — Breech-loading. CHAPTER VI. PROJECTILES. Section I. — General Description. Classification — Spherical Projectiles — Elongated Projectiles — Length — Form of Head — Studded Projectiles — Expanding Projectiles — Parrott’s— Dahlgren’s — Schenkla’s — Hotchkiss’ — Lead-coated Projectiles — Solid Projec- tiles — Hollow Projectiles — -Shells — Case Shot — -Shrapnel — Rifle- shrapnel — Grape-shot — Canister — Htfie-canister — Fabrication of Projectiles — Shot — Shell — Bouching— Chilled Projectile.s— Steel Projectiles — Inspection — Object — Condition of Loaded Shell — Removing Fuzes — Piling. CONTENTS. viii Section II. — Deviation. General Consideration — Effect of Wind — Variable Projectile Force — Rotation of the Earth — Faulty Disposition of the Line of Sio-]it — Influence of tlie State of the Air — Deviation of Spherical Projectiles — Windage — Eccen- tricity — Deviation of Elongated Projectiles — Friction against the Air — Centre of Gravity — Couoidal-headed Projectiles — Flat-headed Projectiles — Drift. Section III. — Effects. General Consideration — Impact of Projectiles — Compression — Elongation — Shearing — Bending — Pulverizing — Friction — Heat — Penetration — General Tlieory — Penetration of Spherical Projectiles — Penetration of Elongated Projectiles — Formula for Penetration of Iron Plates— Form of Head — Oblique Impact — Concussion — Armor-piercing Projectiles— Shape — Spherical — Elong- ated — The Effect of Hardening Projectiles — Advantages of Steel over Chilled Projectiles — Experiments against Armor— Armor-plates and Backing — Wood Backing — Effects on Wood — Effects on Earth — Effects on Masonry — Punching and Racking — Force of Imijact — The Punching Effects of Projectiles. CHAPTER VII. GUN-CARRIAGES. Section I . — United States Naval Carriages. General Considerations — Marsilly Broadside-carriage — Pivot-carriages — Xl-inch Iron Pivot- carriage — 20-pdr. Rifle Pivot-carriage — XV-inch Turret-car- riage — Mortar-carriage — • Howitzer Boat-carriage, wood — Iron Boat-carriage, Howitzer — Field-carriage. Section II. — English Naval Carriages. The Broadside Scott Carriage — Advantages of Mechanical Carriages — High and Low Carriages — The Depression-carriage — The Engli.sh Turret-car- riage — The Turret Indicator — The Moncrieff System — Hydraulic Appliances. CHAPTER VIII. , EXPLOSIVE AGENTS. Section I. — General Consideration of E.rplosives. Definition — Explosive Compounds — Explosive Mixtures — Intensity of Explosion — Detonation. Section II. — Manufacture of Gunpowder. Ingredients of Gunpowder — Refining Saltpetre — Description of the Pro- cess — Solution — Filtering — Crystallization — Washing — Testing — Drying — Extraction of Saltpetre from Damaged Powder — Sulphur — Refining Appara- tus — Process of Refining — Testing— — Converting Wood into Char- coal — Effect of Temperature Employed in Conversion — Qualities of Charcoal — Proportions of Ingredients — Preparing and Mixing Ingredients — Incorpora- tion — Mill-cake — Pressing — Hniformity of Results — Graining — Dusting and Glazing — Drying — Special Powders — Explosion — Inflammation — Combustion. COXTEXTS. IX Section Ill.—Inspection of Gunj)owder. General Qualities — Examination by Hand — Flasbing — Size of Grain- Gravimetric Density — Specific Gravity — The Mercury Densimeter — Initial Velocity — ■ Ballistic Pendulum — Electro-ballistic Machines — Xavez-Leurs Chronoscope— Benton's Thread Velociiiieter — Le Boulenge’s Chronograph — Schultz’ Chronoscope — Basht'orth’s Chronograph — Noble’s Chronoscope — Le Boulenge’s Electric Clepsydra — Strain upon the Gun — Pressure Gauges — Hygrometric Qualities — Analysis — Marking Barrels. Section IV. — P reservation of Qui^ooicder. Magazines on Shore — Classification of Powder — Service of the Magazine — Ships’ Magazines — Powder-tanks — System of Marking Tanks — Service of the Magazine— Transportation of Powder. Section V. — Explosive Compounds. Gun-cotton — Nitro-glycerine — Uses — Compounds of Nitro-glycerine — Dynamite — Lithofracteur — Dualiue — Fulminates. CHAPTER IX. ^ PYROTECHNT. Section I. — Materials. Buildings — Classification of Materials — Compositions — Cases — Drifts. Section II. — Means of Firing Gannon. Percussion-primers — Friction -primers — Spur-tubes — Quick-match — Slow- match — Port-fires. Section III. — Fuzes. Time-fuzes — Tlie Navy Time-fuze — Times of Burning — To Shorten Fuzes — Testing Fuzes — Time-fuze for Rifle-prujectiles — Imperfection of Time-fuzes — Premature Explosion — The Bormanu Fuze — Concussion-fuzes — Percussion-fuze.s — Schenkle Fuze — Parrott Fuze — German Percussion-fuze — Mortar-fuzes — Electric-fuzes. Section IV. — Signals. Kinds — Signal Rockets — C.osten Signal-lights — Holders. Section U . — Preparing Ammunition. jVfeking Cartridge-bags — Filling Cartridge-bags — Service-charges — Strapping Shells — Filling Shells — Packing — Wads — Boat Ammunition- Stand of Ammunition — Metallic Cartridges — Incendiary Preparations. CHAPTER X. PR.\CTICE OF GtrXNERY. Section I. — Service of Ordnance. Loading— Pointing — Sighting Cannon— Tangent Firing — Tangent Sights — Adjustment of Sights — Marking Sights— Determining Distances — Use of Plane-tables — Accuracy of Fire — The Inclination of the Target — Transferring R cord of Firing from Horizontal to Vertical Target — Record of Target Practice at Sea — Elevating Quoins and Screws. X CONTENTS. Section II. — Different Kinds of Fire. Classification— Direct Fire— Ricociiet Fire — Carved Fire— Plunging Fire — Solid-shot Firing — Shell Firing — Shrapnel Firing — Grape and Canister Firing— Horizontal Fire— Vertical Fire— Falling Velocity— Small-arm Firing. Section III. — Gun Irnfflements. Staves — Sponges — Hammers — Ladleg — W orms — Sectional Staves. CHAPTER XI. TUE JIOTION OF PROJECTILES. Equation of the Path of a Projectile in a Non-resisting Medium — To find the Time of Flight of a Projectile on a Horizontal Plane — To find the Elevation necessary to cause the Projectile to pass through a Point given by its Co ordinates — To find the Velocity of a Projectile at any Point of its Path — To obtain an Expression for the Direction of the Path at any Point — To find the Co-ordinates of a Point where a Projectile will strike an In- <-lined Plane, passing through the Point of Projection, the Range on the Inclined Plane, and the Time of Flight — Examples — The Motion of a Projec- tile in Air — Analytical Expre.ssion for the Cubic Law of Resistance — Equation of Motion for the Cubic Law of Resistance — Use of the Tables — Examides — To find the Range on a Horizontal Plane — Law of Penetration of Projectiles. CHAPTER XII. NAVAL OPER.tTIONS ON SHORE. Section I. — General Considerations. Employment of a Naval Force on Shore — The Base — Preparations. Section II. — Landing. Details — Equipment — The Boats — Land! ng. Section III. — On the March. The Advance — .\dvance guard3— Rear-guards — Bivouac — Encampment — Guards. Section IV. — Engaging. The Attack — The Skirmishers — The Infantry — The Artillery — The De- fence. Section V. — Field Fortifications. Definitions — Plans — Profiles — To Distribute the Workmen — Aj'tillery in Eiehl-works — Defence of Walls — Defence of a Building — Defence of a Village — Defence of a Bridge — Attack of Works — Surprises — Open Attack — Defence — Sorties. Section VI. — The Detreat. Rear guards — Destruction of Bridges — Passage of a Defile — The Em- barkation. LIST OF BOOKS QUO'IFD. XI THE FOELOWIXG IS A LIST OF THE PRIXCTPAL BOOKS AND DOCUMENTS • WHICH HAVE BEEN CONSULTED OR QUOTED IN THIS VOLUAIE A Course of Instruction iR Ordnance and Gunnery, prepared for the use of tin; Cadets of the United States Military Academy, by Brevet-Col. J. G. Benton, Major Ordnance Department, U.S.A. ; late Instructor of Ord- nance and Science of Gunnery, Military Academy, West Point. 3d edi- tion. (Kew York : D. Van IS'ostrand, 1867.) The Principles and Practice of Ulodern Artillery, including Artillery Material. Gunnery, and Organization and Use of Artidery in Warfare. By Lieut. - Col. (1. n. Owen, B.A., Prof, of Artillery, Koyal Military Academy, Woolwich. (London : John Murray, Albemarle street, 1871.) A Text-hoolc of the Construction and Manufacture of the Pifled-ordnance in the BritiAi Seroice. ByCaptdnF. S. Stoney, R.A., Asst.-Supt. Royal Gun Factories, and Lieut. Charles Jones, R.A., Instructor, Royal Gun Fac- tories. A Treatise on Ordnance and Armor, embracing Descriptions, Discussions, and Professional Opinions concerning the Material, Fabrication, Require- ments, Capabilities, and Endurance of European and American Guns, for Xaval, Sea-coast, and Iron-clad Warfare, and their Rifling, Projectiles, and Breech-loading ; also results of Experiments against Armor. By Alex. L. Holley. (Xew York : D. Van Xostrand, 1865.) A Treatise on Ordnance and JTaixd Gunnery. Compiled and arranged as a Text-book for the Ltnited States Xaval Academy. By Lieut. Edward Simpson, U. S. Xavy. (Xew York : D. Van Xostrand, 1863.) The Artillerist's Mmual. Compiled from various sources, and adapted to the Service of the United States. By Brig-Gen. John Gibbon, U. S. Vols., Captain 4th Artillery U. S. Army. 2d edition. (Xew York : D. Van Xostrand, 1863.) Gunnery Instructions U. S. Xavy. Detail Drill, 1870. A Treatise on the M trdlurgy of Iron, containing Outlines of the History of Iron Manuflicture, Methods of Assay and Analyses of Iron Ores. Pro- cesses of Manufacture of Iron and Steel. By H, Bauerman, F.G.S. (New York ; Virtue & Yorston, Dey street, 1868.) Metals : their Prop'>rties and Treatment. By Charles Loudon Bloxam. 2d edi- tion. (London : Longmans, Green & Co., 1871.) Ordnance Instructions for the United States Wavy. Published by order of the Xavy Dept. (Washington : Gov'ernment Printing-office.) The Ordnance Manual, for the use of the Officers of the U. S. Army. (Phila- delphia : J. B. Lippincott & Co., 1861.) Ammunition. A Descriptive Treati.se on the Different Projectiles, Charges^. Fuze, Rockets, etc., at present in use for the Land and Sea-service, and on other War Stores manufactured in the Royal Laboratory. By Capt. V'^iviau Dering Majendie, R. A., Asst.-Supt. Royal Laboratory, Woolwich. (London : W. Mitchell & Co., Military Publishers, 39 Charing-cross, 1867 ) Part I. Ammunition for Smooth-bore Ordnance. LIST OF BOOKS QUOTED. xil Pakt II. Ammunition for Eified Ordnance. By Captain diaries Orde Brown, R.A., Capt. -Instructor Eoyal Laboratory, Woolwich. , Part II. — Continued. By Capt. C. 0. Brown. d Treatise on JVaval Gunnery. Dedicated by special permission to the Lords Commissioners of the Admiralty. By Gen. Sir Howard Douglas, Bart. 5th edition. (London : John Murray, Albemarle street, 1860.) Shells and Shell Guns. By J. A. Dahlgren, Commander in Charge of Experi- mental Ordnance Department, Navy Yard, Washington. (Philadelphia : King & Bird, 1857.) On the Physiced Conditions Involved in the Construction of Artillery, with an Investigation of the Relative and Absolute Values of the Materials princi- pally employed, and some hitherto unexplained Causes of the Destruction of Cannon in Service. By Robert Mallet. (London : Longman, Prime, Green, Longmans, & Roberts, 1856.) Reports of Experiments on the Properties of Metals for Cannon, and the Qualities of CcLhnun Powder, with an Account of the- Fabrication and Trial of a 15-iuch Gun. By Capt. T. J. Rodman, of the Ordnance De- partment U. S. Army. (Boston : Charles H. Crosby, 1861.) Reports of Experiments on the Strength and other Properties of Metals for Cannon, with a Description of the Machines for testing Metals, and of the Classification of Cannon in Servdee. By Officers of the Ordnance De- partment U. S. Army. (Philadelphia : Henry Carey Baird, 1856.) Report on the Fabrication of Iron for Defensive Purposes, and its use in Modern Fortifications, especially in Works of Coast Defence. Professional Papers of the Corps of Engineers LI. S. Army. No. 21. (Washington : Government Printing-offices, 1871.) Report on Certain Experimented and Theoretical Investigations relative to the Quality, Form, and Combination of Materials for Defeeisive Armor, together with Incidental Facts relative to their use for Industrial Pur- poses. By Brevet-Major W. R. King, Capt. of Engineers, U. S. Army. (Washington : Government Printing-office, 1870.) Professional Papers Corps of Engineers U. S. Army. No, 17. A Manual of Gunnery for Her Majesty’s Fleet. Corrected up to 1st Januarv, 1872.) The Le Boadenge Chronograph. By Brevet-Capt. O. E. Michaelis, First Lieut. Ord. -Corps U. S. Army. (New-York : D. Van Nostrand, 1872.) Traite cVArtillerie Theorique et Pratique. Par G. Piobert. (Paris : Gauthier 1869.) Electro-ballistic Machines and the Schidtze Chronoscope. By Brevet Lieut. - Col. S. V. Benet, Capt. of Ordnance U. S. Army. (New York : D. Van Nostrand, 1866.) Holes on Gunpowder, prepared for the use of the Gentlemen Cadets of the Royal Military Academy. By Capt. Goodenough, R.A. , Instructor in Artillery, Royal Military Academy. (London ; Mitchell & Co., Charing-cross, 1868.) Ure’s Dictionary of Arts, Manufactures, and Mines. Edited by Robert Hunt, F.R.S. 6tii edition. (London : Longmans, Green & Co., 1867.) LIST OF BOOKS QUOTED. xiii Journals of the Royal United Service Institution. (London : W. Mitcliell & Co., Charing- cross.) Inspection and Proof of Cannon for the United States Navy. (Washington : Government Printing-office, 1804.) United Stales Navy Gunnery Notes. (Washington : Government Printing- office, 1871.) United States Navy Laboratory Notes. (Washington : Government Printing- office, 1871.) Gunpoinder as an Mement in the Problem of Modern Ordnance, the Influence ot Density on its Explosive Action, and the Densimeter it uses, and Ad- justments. Naval Ordnance Papers No. 1. By Lieut. -Commander J. D. Marvin, U. S. N. (Washington : Government Printing-office, 1872.) Mode of Fabricating the XV.-in. Guns contracted for by the Chief of the Bureau of Ordnance, Navy Department, with the “ Knap Fort Pitt Foundry, ’ Pittsburg, Pa., 1870 and 1871. Naval Ordnance Papers No. 3. By Com- mander R. F. Bradford, U. S. N. (Washington : Government Printing- office, 1872.) A Concise Treatise on the Theory and Practice of Naval Gunnery. By M'in. N. Jeffers, Jr., passed Midshipman U. S. Nav3^ (New York : D. Apple- ton & Co.) Recent Investigations and Applications of Explosive Agents. By F. A. Abel, F.R.S. (Washington : Government Printing-office, 1871.) A Mathematical Treatise on the Motion of Projectiles. By Francis Bashforth, Prof. Mathematics, Woolwich. (London : Asher & Co., 13 Bedford Street' Covent Garden, W.C. , 1873.) Nicaise’s Belguin Field Artillery. Translated with an Appendix and Notes, by 0. E. Michaelis, Cap. Ordnance U. S. A. (W. C. & F. P. Church' New York, 1872.) American Breech-loading Small-arrhs. A Description of late Inventions, in- cluding the Gatling Gun, and a Chapter on Cartridges. Compiled by Brig. -Gen. C. B. Norton, U. S. Vols. (New York : F. W. Christeru, 77 University place, 1872.) Instructions for Officers and Non-Commissioned, Officers on Outpost and Patrol Duty. Authorized and adopted by the Secretarv of War. (Philadelphia : J. B. Lippincott & Co., 1863.) Practiced Treatise on Strengthening and Defending Outpost Villages, Houses, Bridges, etc. By J. Jebb, Lieut. -Col., Corps Royal Engineers. 3d edi- tion. (London : W. Clowes & Sous.) An Elementary Course of Military Engineering — Part I. Comprising Fixed Fortifications, Military, Mining, and Siege Operations. By D. H.'iMahan, LL.D., Prof. Military and Civil Engineering, U. S. Military Academv' (New York : John Wiley & Sou, 1806.) The Soldier's Pocket-book for Field Service. By Col. G. J. Wolseley, Deputy Quartermdster-Geueral in Canada. (London: MacMillan & Co'., 1869.) ' Comp and Outpost Duty for Infantry with Standing Orders. Extracts from the Revised Regulations for the Armv, Rules for Health, Maxims f..r Soldiers and Duties of Officers. By Daniel Butterfield, Mai -Gen U S Vols. (New York : Harper & Brothers, 1863.) XIV LIST OF BOOKS QUOTED. Report to the Government of the United States on the Munitions of War ex- hibited at the Paris Universal Exhibition, 1807. By Chas. B. Xorton, late Lieut. -Colonel U. S. Vols., and \V. J. Valentine, Esq., President of U. S. Com., 1855, United States Commissioners. (Xew-York : Office ot Army and Navy Journal, 39 Park row, 1868.1 {Jhemieal Phenomena of Iron Smelting. An Experimental and Practical Ex- amination of the Circumstances which determine the Capacity of the Blast-furnace, Temperature of the Air, and the proper Condition of the Material to be operated upon. Bj^ J. Lowthian Bell. (New York : D. Van Nostrand, 23 Murray street, 1872.) Boat Armament of the United Slates Navy. Designed by and executed under the direction of J. A. Dahlgren, Commander U. S. N. in Charge of the Ordnance Department, U. S. Navy Yard, ^Vashington, D. C. 2d edition. (Philadelphia : King & Baird, 1850.) The Management of Steel. By George Ede, employed at the Royal Gun Factories Department, Woolwich Arsenal. (New York : D. Appleton & Co., 1867.) Dictionnaire vies Matliematiqu'es AppUquees. Par H. Sonnet. (Paris : Libraire de L. Hacliette et Cie., Boulevard Saint-Germain, No. 77, 1807.; Report on a Naval Mission to Europe. Especially devoted to the Material and Construction of Artillery. By Captain E. Simpson, U. S. N. 2 vols. (Washington: Government Printing-office, 1873.) Annual Report of the Chief of Ordnance to the Secretary of War, for the years 1872 and 1873, (Washington : Government Printing-office.) Spans’ Dictionary of Engineering : Civil, Mechanical, Military, and Naval. Oliver Byrne, editor. (Loudon : E. & F. N. Spon, 48 Charing-cross, 1873.) A Handbook of the Manufacture and Proof of Gunpoicdcr as carried on at the Royal Gunpowder Factory, Walth.un Abbey. By Capt. F. M. Smitli, R.A., Assistaut-Saperintendent. (L.mdon, 1870.) Instructions for the Care and Preparettion of Ammunition. (Published by the United States Naval Ordnance Bureau, 1874.) The Determination of the Time of Flight of Projectiles, etc., by Means of the Electric Clepsydra, from Researches in Experimental Ballistics. By .\iajor P. Le Boulenge, Belgian Artillery. Translated from the French by Lieut. -Commander J. D. Marvin, U. S. Navy. (Washington : Govern- ment Printing-office, 1873.) United States Naval Ordnance Notes. The Reffye Gun. 1873. MYAL ORDNANCE AND GUNNERY. CHAPTER I. CANNON METALS. Section I — Metallurgy of Iron. 1. Metallurgy of Iron * is the art of extracting iron from its ores. This metal is nsed in the mannfaeture of most of the engines of destruction that modern science has intro- duced into the art of war. In its pure state it is rarely found in nature, hut its ores exist in great abundance in all parts of the world. The natural compounds of iron which are available as ores of the metal, are chiefly oxides and carbonates. These scarcely ever occur in a state of purity, but associated with clay and other silicious minerals, or with limestone, which substances are useful as slag-forming components; and also with com- pounds of sulphur and phosphorus, which are deleterious im- purities. 2. PEEPAEATIOlSr OF IEOH ORES.— The ironstone, or ores of iron, w'hen extracted from the mines, being in a very rough state, and intermixed with earthy substances, it is first necessary to prepare them for the Ijlast or smelting fur- nace. Ores are subjected to different treatment in different coun- tries and at different mines, depending upon their value and quality. 3. Dressing. — Some ores are not subjected to any partic- ular dressing, while others are separated from a portion of the intermingled clay and sand by sifting, crushing, stamping and washing. * B.auerman. 1 2 NAVAL ORDNANCE AND GUNNERY. These processes are usually accomplished hy breaking- machinery and roller-crushing-mills. The machinery used for washing the ores generally consists of a horizontal staff armed with projecting knives or paddles, revolving in a cylindrical trough, through which a stream of Avater is kept flowing. The rough ore, after being well mixed up Avith the Avater by the action of the paddles, is carried by the stream into a settling- pit, where the heavier masses of clean ore deposit, while the flnely divided earthy matter is carried off with the Avaste water. Washing of ores is rarely practised, except in countries where labor is very cheap, or facilities for waslaing very great. 4. Weathering. — At some mines the ores are exposed to the action of the air for some time. Superflcial oxydation takes place, the adherent fragments of foreign substances disintegrate, and can be readily removed ; and impurities are also partially removed by rain. 5. Ironstone Breakers. — In order to attain the greatest regularity in the process of smelting, it is advisable that all charges of ores and fluxes should be reduced to fragments of nearly uniform dimensions. The size of the fragments should be proportioned to the height of the furnace and the greater or less susceptibility to reduction of the ore, varying from cubes of one to two inches in the side, to as ranch as four to six inches in the side. The limits are determined by the con- ditions required : the larger masses being only adapted for tall furnaces, Avhen by the sIoav descent of the charges, suflicient time is allowed for the heat to penetrate to the interior, at the same time that a free passage is afforded to the upper curi-ent of the gas. Smaller pieces, on the other hand, although expos- ing a greater surface to the action of the reducing gases, pack closer together and offer greater resistance to the blast. The reduction in size is effected by various mechanical means of breaking, the most advantageous of which arc crushing^ollers and lever-machines called h'reakers. The ma- terial operated upon is sometimes raw ore and sometimes Avashed ore. 6. Roasting or Calcination of Iron Ores. — In this coun- try roasting of ores is much less practised than in England and on the Continent ; partly on account of the higher price of labor here, but chiefly because our principal ores — hematites and magnetites — are anhydrous. The object of roasting is to expel the Avater, sulphur, arse- nic and other impurities AAotli Avhich the ores are combined ; all volatile matters are thus remoA'ed, the amount of iron is concentrated into a smaller weight, and as the fragments of CANNON METALS. 3 mineral retain their form they are rendered porous and more readily susceptible of being changed in the subsequent opera- tions in the smelting-furnace. The roasting is eUected in various ways, which may be classified generally under two dif- ferent heads. 7. First. Roasting in the Open Air. — This is done by dis- tributing the ore in alternate layers with waste coal, wood or charcoal, and the pile tlius formed is igTiited and burned. This anethod is used in localities where fuel is cheap, when compared with labor, but is in many respects disadvantageous on account of the waste of fuel and the imperfect distribution of the heat, the interior of the pile often being heated to excess, with a partial fusion of the ore, when the outer parts have only at- tained the proper temperature. 8. Second. Roasting in Furnaces or Kilns. — This method is generally to be preferred when economy of fuel is of impor- tance, as the heat of combustion is more perfectly applied, and a more uniform product is obtained, than is the case with the more rude method of roasting in the air. The construction of the kilns in different localities varies considerably, but the principle of working is, in the main, the same everywhere. The ore is piled above a thin bed of fuel at the bottom of the kiln shaft, which may be conical, cylindrical, barrel or wedge shaped, and when ignited is covered with layers of ore and fuel alternately until the shaft is full to the top or throat. The ore roasted by the combustion of the fuel at the bottom, where the air has access to the kiln, is withdraAvn, and the next layer falls ; the deficiency be- ing made good by fresh charges at the tojx (Fig. 1.) 9. SMELTTMG is the process by which the iron is reduced to the metal- lic state, and separated from the refrac- tory substances with which it is com- bined in the ore. It consists in raising the ore to a high heat, in contact with carbon and a suitable flax, in the blast or smelting furnace. The flux unites with the earthy matter of the ore, forming a glassy substance called slag or cinder, and the carbon as carbonic oxide unites with the oxy- gen of the ore, setting the iron free ; which in turn unites with a portion of the carbon and forms a fusible compound called pig or cast-iron. Fig. 1. 4 NAVAL OEDNANCE AND GUNVSTEEY. 10. Fluxes used in Ieon-smelting. — Tn practice, very few ores are found to contain earthy ingredients in proportions suf- ficient to form readily fusible slags alone, and it therefore be- comes necessary to supply the deficiency. This may be done, either by mixing ores of dissimilar composition in such quanti- ties as shall yield slags of the desired composition, or by the addition of calcareous or aluminous minerals not containins^ O iron. The first of these methods is certainly to be preferred, as by it the slag is formed without unnecessarily reducing the percentage of iron in the charge or burden, taken as a whole : whereas, the addition of fluxes increases the weight of material to be passed through the furnace for the same produce of metal ; but it can only be carried out in localities having a large and varied command of minerals. Usually, therefore, a combination of both methods is used, the best mixture of ores obtainable being supplemented by the addition of earthy min- erals. 11. Difficulty of Obtaining Puee Metal. — The reduction of iron ores can be effected practically only by carbon or car- bonic oxide. The ]UTneipal flux employed in iron smelting is carbonate of lime in the form of limestone. As a very high temper- ature is necessary to effect the reduction, the metal almost always combines with a greater or less proportion of the reduc- ing agent, as well as of other elementary substances; such as silicon, sulphur and phosphorus, that may be present either in the ore, the fuel or the flux ; so that the ultimate result is never a pure metal, but a compound of iron with carbon, silicon, sul- phur, phosphorus and sometimes manganese, and occasionally traces of other baser elements, as titanium, etc. Small traces of foreign elements exert a very marked influ- ence on the metal, and it is these small and in many cases unnoticed differences of composition, that render so many points in the chemistry and practical working of iron obscure and difficult to be understood. 12. Composition of Fluxes. — The composition of the lime- stone to be used is of considerable importance, and depends upon the kind of ores employed. Chemical analysis alone can determine to which class a particular limestone belongs, as there is often nothing in the external appearance by which a pure limestone may be distinguished from one containing forty or fifty per cent, of foreign matter. Magnesium limes'tone is especially to be avoided as producing a very refractory slag. The addition of fluxes to the blast-furnace is regulated by CANNON METALS. 5 several considerations. When the ores are of good quality, the chief point to be considered is the production of the most fusi- ble slag, with the smallest addition of non-ferriferous matters ; this is more especially the case with charcoal-furnaces. When mineral fuel is used, however, it is necessary to form a slag that is capable of absorbing sulphur, which would otherwise be taken up by the iron ; and, for this purpose, a larger quantity of flux is used than that indicated by theory, as giving the most fusible product. The quality of the iron produced, depends greatly upon the kind of flux employed. 13. Slag is the vitreous mass wdiich covers the fused metal in the smelting-hearth. It is commonly called cinder. The physical character of slag, such as color, texture, fluid- ity, etc., varies with the composition and the working condition of the furnace, so that it is not possible from inspection alone, to determine the character of the metal produced, except after con- siderable experi- ence of the in- dividual furnace ; and the relation between the slag and metal in one locality may be to- tally different in another. II. Fuel. — The fuel used in iron-smelting va- ries in dilferent localities and with the purposes for wdiich the iron is intended. Char- coal is said to make the most su- perior iron, and is always used in the manufacture of iron for ordnance purposes. Coke is very generally used, and bituminous and anthracite coals are also employed. Fig. 2. — Blast-fumace for Smelting Iron Ores. 6 NAVAL ORDNANCE AND GUNNERY. 15. THE BLAST-FURlSrACE. — The means of reducin'? iron ore now almost universally in use, is the blast or smelting furnace. (Fig. 2.) CoNSTEDCTioN. — This consists mainly of a tall shaft of brick and stone or of iron, and generally of the form of a truncated pyramid, but sometimes cylindrical or rectangular. The, construction of blast-furnaces varies considerably in different localities in regard to size and proportions of parts to each other, as well as material employed. The height and dimensions vary with the nature of the ores and fuel used. 16. The Stacli . — The interior has the forai of two trun- cated cones, united at their bases. The upper one, C, which is the larger and more acute, is placed upright ; it constitutes the furnace proper, and is knoAvn as the stach. 17. The Boshes.— lower cone, B, which is inverted, is shorter and more obtuse than the other; their line of junction forming the widest part of the furnace. A, is called the hashes, and it terminates below in a space called the hearth, E. 18. The Hearth . — The hearth, properly speaking, is that part of the furnace only which receives the fluid metal and cin- der as they fall 'below the level of the twyers, o. Three of the sides of the hearth descend to the bottom of the furnace, or to the hearth-stone, while the fourth side, called the tymp, t, does not go all the way down, but leaves an open- ing, and is supported by an arch or by strong bars of iron let into the sides of the furnace. 19. Furnace-lining . — The interior of the furnace has a double lining of fire-brick, i, I, the space between them being tilled with sand or broken slag to prevent injury to the outer wall by the expansion of the lining from the heat. The hearth and hearth-stone and boshes are built of refractory material because of the great heat which they have to endure. 20. Details of the lower Part of the Furnace. — Arched openings ar-c built on each side of the shaft at the bottom, three of which are called the twyer-arches, and the other the tymp- arch. 21. The Twyers, or blast-pipes, are the ends of the pipes through which the blast is admitted to the hearth, and as they are exposed to a high temperature, they are east so as to enclose a coil of wrought-iron tubes, through which a stream of cold water continually circulates. Fig. 3 represents a section of a twyer-nozzle thus protected, the cold water en- CANNON METALS. 7 tei’ing the casing by the tube and the hot water running off by the tube t' . 22. Twyer-lioles . — Passages for the introduction of these ])ipes are perforated through the wall of the hearth, o, a short distance above the hearth-stone. These are known as twyer- holes, and vary in number. The smaller charcoal-furnaces have often only two, placed on opposite sides of the hearth. Three is a more usual number, one leing placed at the back, opposite to the tymp, and the others at the sides of the hearth. When a larger number is used they are generally placed at equal intervals all around the hearth. 23. The Fore-hearth is the front or working side of the hearth. This side is constructed difPerently from the others, its upper part being formed by a heavy block of stone, g (Fig. 4), called the tymp-stone, which is supported by a east- iron tymp-plate, built into the mason- ry of the furnace ; while the lower part is enclosed by the dam-stone, b, faced externally by a thick cast-iron dam-plate, m. That portion of the hearth which is shut in by the dam-stone is called the oricchble, for it is here that the cast-iron produced in the furnace accumulates in a melted state covered with slag. 24. The Cinder-notch. — A semi-circular furrow in the top edge of the dam, known as the cinder-notch, forms a passage for the slag. In charcoal and other small furnaces the front of the dam is generally formed into a gently sloping, inclined plane, or cinder-fall, where the slag, as it runs out, solidities in a compara- tively thin layer, and may be broken up and removed by hand. 25. Tap-hole. — The tap-hole for withdrawing the molten iron from the hearth is a narrow vertical slit pierced through the darn, and extending from the hearth-stone upwards. Dur- ing the time that the hearth is tilling it is stopped by a pack- ing of sand, rammed iia tight, which can be easily perforated by a pointed bar at the time of casting. 20. Tymp-stopping . — The space between the top of the 8 NAVAL ORDNANCE AND GUNNERY. dam and the tymp-stone is also stopped with sand or brick, a small passage being left for the escape of slag ; this is called the tymp-stopping. 27. Details of the Top of the Furhace. — The top, or throat, of the furnace is surrounded by a platform for the con- venience of charging, and is in many cases covered with a . short cylindrical chimney which leads off the flame escaping at the throat, F. (Fig. 2.) 28. Throat, Cup, and Cone . — When it is desired to collect the gases given off at the top of the furnace, it is necessary to work with a closed throat. The most simple contrivance for this purpose, and that most generally used, is known as the cup and cone. (Fig. 5.) It con- sists of an in- verted, conical cast - iron fun- nel, A, fixed to the top of the furnace, whose lower aperture is of about one- Iialf the diam- eter of the throat. An upright cast-iron cone, B, is placed in the furnace be- low the cup ; it is suspended by a chain attached to its apex, so that it may he, raised or lowered at pleasure. In the former position it hears against the bottom of the cup and forms an air-tight stopper, preventing the escape of gas from the top of the furnace ; which then finds its way out by the proper passage through the wall of the furnace, C. 29. How suspended . — The cone is suspended by an arch- headed lever, carrying a counterbalance at the end of the op- posite arm. The raising or lowering is effected by a pinion moved by a hand-wheel gearing into a ratchet attached to the counter-bal- ance weight. The gas passes through a lateral flue into a wrought-! ron main-pipe, which distributes it to the various pipes feeding the boiler fires and hot-blast stoves. Fig. 5. — Cup and Cone for closing the Blast-furnace, in order that the waste gases may pass into the lat- eral tlue, as shown by the arrow. CAXJfOJir METALS. 9 30. Chaeging. — The charges are thrown into the space enclosed by the cup, then by lowering the cone, it allows the charges in the cup to be dropped into the furnace and at tlie same time acts as a distributer ; only the small amount of gas that is lost during the time of charging is allowed to escape, and as the operation is very quickly performed the current through the main-pipe is kept up with great regular] tju 31. The Blast, or draft, in the furnace is iutroduced through the twyers, and is maintained by means of blowing- engines of various constructions. 32. Pressure of Blast . — The working-limits of blast-press- ure vary with the nature of the fuel employed, and the burden of the furnace, etc. A steady current in the furnace is accomplished by arrange- ments for equalizing the pressure, and its amount and force are indicated by means of gauges. 33. Tejipekatuee of Blast. — How Determined . — In prac- tice the temperature of the blast is generally determined by its power of fusing metals, mercurial thermometers not being reli- able for temperatures much above 400° or 500° F.-, owing to the irregular expansion of the mercury when near its boiling- point. This is done by exposing a thin rod of the metal to the current in the twyer, a hole being made for the purpose in the elbow of the branch-pipe connecting the twyer with the main blast- pipe. 34. The following table, from “ Bloxam on Metals f con- tains the melting points of various metals : TABLE OF FUSEBmiTY. Tin melts at 442° F. Cadmium “ “ 442° “ Bismuth “ “ 507° “ Lead “ “ 617° “ Zinc “ “ 773° “ Antimony* “ “ 1,150° “ Silver “ “ 1,800° “ Copper “ “ 1,990° “ Gold “ “ 2,000° “ Cast-iron “ “ 2,780° “ Steel “ “ 4,000° ‘‘ Wrought-iron “ above 4,000° “ * Estimates of temperature above the fusing-point of zinc caimot be regarded as exact, on account of the difficulty of ascertaining them. 10 NAVAL ORDNANCE AND GUNNERY. 35. Hot-blast. — When tlie stream of air forced tlirougli a furnace is heated above 300° or 400° F., it is called a hot-blast. 36. Effects of IIotMast. — Whenever a forced stream of air is employed for combustion, the resulting temperature must evidently be impaired by the coldness of the air injected upon the fuel ; fires fed with hot air should, with the same fuel, rise to a higher temperature than fire fed with common cold air. Furnaces blown with heated air exert greater reductive power than those in which a cold-blast is used. This has led, since tlie introduction of hot-blast, to the extensive use in iron- smelting of refractory ores not formerly smelted ; a large part of which have been ores of a class calculated to produce inferior iron ; and it is to the use of ores of this nature, far more than from any detei’ioration in quality, arising from a heated blast, that the frequent inferiority of hot-blast iron is to be ascribed. As the fusing metal is brought in contact with less fuel, and as less air is passed through the furnace, the chemical reac- tions are probably somewhat modified, hut it is thought the quality of the product is not injured. 37. Excessive Heat of Eurnace. — An excessive temperature in the furnace is injurious, because unnecessary heat of fusion injures the quality of the metal produced ; dark-gray graphitic iron resulting always from intensity of heat. But this can be regulated as well with the hot-blast as with the cold : since it depends on the fuel employed, the burden of ore, and the pressure of the blast, as Avell as its temperature. 38. Advantages of Hot-blast. — With fuels difiicult of ignition, and with refractory ores, the advantages of the hot- blast are most marked. It effects a saving of heat, and accom- plishes the reduction of the most refractory ores in less time and with a less expenditure of fuel than the cold-blast. It is therefore employed at the present day almost to the exclusion of cold-blast, the latter being retained only for cer- tain special makes, such as for gun-founding, which command an extra price, and may therefore be produced without strict regard to economy. 39. AYakm-blast. — E ven for purposes where it is desirable to produce the best possible quality of iron without regard to cost it is now customary to use a warm-hlast rather than the cold ; that is to say, a blast varying from 100° to 200° F., so as to obtain uniformity of temperature at all seasons of the year ; which is not possible when using a blast absolutely cold. 40. Some of the latest experiments upon the comparative strengths of hot-blast and cold-blast irons appear to warrant the CANNON IIETALS. 11 conclusion, that so far as the temperature of the blast only is concerned, the hot-blast tends slightly to injure the quality of the softer (gray) irons, wliilst it improves, sometimes in a very remarkable degree, the character of the harder (white) cast- irons. 41. Method of Heating the Blast. — The combustible gases from the stack are generally used to heat the air. For this purpose a kind of oven is built near the stack, and the inflammable gases are drawn off from the top and passed through it. In this oven are series of pipes through which the air is forced before it enters the stack ; sometimes this oven is heated independently of the stack. 42. The amount to which the temperature of the blast may be raised with advantage does not appear to have any practical limit, except that arising from the necessity of keeping the apparatus tiglit, and avoiding its rapid destruction by excessive heat. Yet, Bell says 1,000° F. should be the limit even in the largest furnaces. (Art. 45.) 43. Blowing in is the operation of starting the furnace. In manufacturiug gun-iron charcoal is used with limestone as a flux. To commence blowing in, first put a quantity of good dry v/ood in the bottom, raising it to a height of three or four feet, and then several tons of charcoal ; over this are introduced regu- lar layers of charcoal, flux, and a very light burden of ore. AVhen the furnace is thus filled, to about one-third its lieight, the wood at the bottom is ignited. When the upper layers be- come incandescent the charging is resumed until the furnace is two-thirds lull, the burden of ore being gradually increased, up to that necessaiy for producing gray iron of the proper quality in the ordinary working. AVhen the Are reaches the top of the minerals the furnace is filled up to the top, and the blast turned on to about two-thirds its full force. This continues for a time, when the blast is turned full on, and the chavging goes on regularly. The weight of the charges as well as the temperature and pressure of blast must be gradually increased so as to get to the proper burden by degrees. 44. AVoeking of the Fuenace. — When the furnace is at work or in blast it is kept filled to the top or throat, with alter- nate layers of fuel, ore and flux, the latter being mixed in proper proportions, to produce the most fusible combination of the earthj^ matters ; a constant stream of air being maintained through the twyers, at a sufficient pressure to pass freely through the contents of the furnace. 12 NAVAL ORDNANCE AND GDNNEET. 45. Chemical Action in the Furnace.^ — The oxygen of the blast coming in contact with a great excess of incandescent fuel is saturated, so to speak, at once with carbon, and carbonic oxide is formed. The heat thus generated, though not the maximum which the fuel would produce if burnt with excess of air, suffices to fuse the carburetted iron, and the silicious compounds descending from above ; and they fall into the hearth when they separate by liquation into metal and slag. The latter, being specifically lighter, rises to the surface, and protects the former from the decarbonizing action of the blast. The carbonic oxide produced, together -with the inert nitro- gen, rises through the incandescent materials of the furnace and at a certain Tieight, within ten or fiften feet of the top -of a fifty or sixty-five feet stack, where the temperature is compara- tively low (probably not exceeding the melting-point of zinc), the reduction of the oxide of iron takes place. The reaction may be approximately expressed thus: — Fe^Oj -j- SCO = 2Fe + SCO,. The CO, formed reacts immediately on the hot coal, and is converted again to CO, and this reduces more ii’on oxide, and thus the interaction continues until certain proportions of CO and CO, obtain, wlien the reducing action of CO becomes less powerful than the tendency of CO, to oxydize the newly formed metal. The power of CO, to oxydize iron over that of CO to reduce it increases with the temperature. At a liigh heat, too, an excess of CO is produced, as carbon reduces CO, better at high temperatures. These facts, according to Bell, set a limit to the degree of heat at which the blast can be advantageously used. The escaping gases scarcely ever contain more than forty parts of CO, to one hundred CO by volume, and this is diluted with about two hundred parts of nitrogen. It follows that only one-fifth of tbe carbon is wholly con- sumed in the blast-furnace. Another important reaction takes place below the reducing- zone, depending on the fact that carbonic oxide is itself reduced with the elimination of carbon, or decomposed according to the formula 2CO = C -|- CO, in the presence of metallic iron, and the lower oxides of iron at a certain temperature somewhat higher than that most favorable for the reduction of the iron oxide. The spongy metallic iron, probably not wholly reduced, * Bell’s Chemical Phenomenon of Iron-smelting. CANNON METALS. 13 descends nnmelted into the bottom portions of the furnace where the reduction is perfected, probably by the finely divided carbon resulting from the reaction described above. At the zone of fusion, just above the twyers, the iron combining wfitli a portion of this carbon, and with varying quantities of silicon, etc., melts and falls into the hearth below as cast-iron. 46. Production of Gun-iron. — It is very necessary that this should be of uniform strength and density. In order to produce the best quality of iron the greatest care is required. All the materials which enter the furnace should be of the best and purest quality, and kept dry ; regularly and uniformly mixed, and supplied to the furnace at regular intervals. The temperature of the blast should be kept as nearly uni- form as possible, without using what is termed the hot-hlast, which is on no account to be used. 47. Tapping. — The molten metal accumulating in the hearth of the furnace is removed at regular intervals by tap- ping, or piercing a hole through the lower part of the dam, and allowing the metal to flow into sand or cast-iron moulds placed in front of the furnace. Before tapping, the blast is shut off and the tymp-stopping removed. The tap-hole is opened by driving in the point of a wrought- iron bar, which is held by one man while another strikes the end with a sledge-hammer if necessary. 48. The molds, or pig-beds, usually consist of a series of furrows in the sand of the casting-floor, molded by a wooden core having the name or mark of the foundry attached to it. The molds are arranged in parallel series on either side of a central feeder, known as a sow y and as soon as one series is tilled the current is allowed to flow into the next, and so on, until the cast is completed. For gun-iron sand-molds should be used. When this operation ceases the tap-hole is again secured, and the work proceeds as before. In this manner a furnace may be kept continually going night and day for years, until rejiairs render Mowing out neeessar}. 49. Piling Pigs. — Each pig of any one run should be placed in a separate pile, aiid each of these piles should be kept sepa- rate in transportation, and be re-piled in the foundry yard in the same order as at the smelting-furnace. These precautions are necessary in order to have an accurate history of the metal of which each gun is made. 14 NAVAL ORDNANCE AND GUNNERY. Section II . — Cast-Iron. 50. Composition of Cast-Ikon.'^ — The only substance with which iron is invariably and indispensably associated in cast- iron is carbon. By fusing finely divided iron with charcoal until the metal has taken up as much carbon as it will dissolve, a dark-gray mass is obtained, which is so brittle that it may be powdered in a mortar. That carbon forms any definite compound with iron is very doubtful. Iron seems to have the power of dissolving carbon at a high temperature, and on slow cooling the carbon is separated in dis- tinct graphitic scales. If the cooling is very slow large crystals one-half to three-fourths of an inch long are formed, and graphite may be readily removed from the faces with a knife. On chilling gray iron the carbon is retained in a more intimate state of combination or solution, and cannot be separated. As to whether the carbon is chemically combined, or whether it is carbon in another form than graphite simply dis- solved in the iron, difierent opinions exist. The percentage of carbon in the best varieties of pig-iron varies from three to rather over four per cent., except, perhaps, in the variety of iron known as sj>iegeleisen, which sometimes contains nearly five per cent. 51. YAPaETiES OF Cast-Ikon. — On examining the fractures of freshly broken pieces of cast-iron, it will be found that some specimens have a silvery-white and others a gray color, caused by the presence of very minute particles of carbon, which are interspersed among the lighter-colored particles of the metal. When the gray samples of cast-iron are acted upon by acid (diluted sulphuric or hydrochloric) the iron is dissolved, but the black particles of carbon are left, and these are found to possess the same propeidics as the natural variety of carbon, known as black-lead, or graphite, of which pencils are made. When the white cast-iron is dissolved in acids very little black residue of carbon is left, because the greater part of the carbon, being intimately combined with the iron, is dissolved by the acid, or eliminated as gaseous hydro-carbons, and very little is presented in the form of graphite. 52. When a sample of gray cast-iron is melted, the particles of the free carbon are dissolved by the liquid metal becoming intimately combined with the iron ; and if the melted mass be Bloxam. CANICON METALS. 15 suddenly cliilled by throwing water npon it, or by running it when near its point of solidification into a thidv iron mould, the carbon does not separate again, so that a mass of white cast- iron is thus produced. 63. It is more difficult to convert the white into the gray variety of cast-iron, but this can be done by exposing the melted metal to a high temperature, and allowing it to cool down very slowly, when a portion of the carbon separates from the iron, and the gray variety of cast-iron is produced. The relative grayness or whiteness of pig-iron furnishes no real standard of quality as compared with the produce of other localities, but is rather an indication of the wmrking condition of the furnace. 51. The variable qualities of ore, fuel, and limestone may exercise such an influence on the resulting crude iron as to ren- der a lofv denomination of one manufacbire of greater commer- cial value than a higher denomination of other makes. Other things being equal white cast-iron can be more readily and cheaply produced than gray, as the same amoiint of fuel is made to carry a larger burden of ore, and the charges are driven more rapidly. As, however, it can only l)e used for forge purposes, while the more expensive gray metal is available for making castings or malleable iron, it is usually sought to diminish its production as much as possible, except in special cases, Avhere quantity of make or an extreme economy of fuel is desired. 55. Gray Cast-iron. — Since in gray cast-iron a smaller pro- portion of the iron is in combination with carbon, and more of it in the true metallic state, this variety would be expected to exhibit more of the properties of metallic iron. Accordingly the gray cast-iron is much softer and less brittle than white iron ; it is in a slight degree malleable and flexible. The larger proportion of metallic iron contained in the gray cast-iron causes it to require a higher degree of heat before it begins to show signs of fusion, but it is capable of becoming very liquid at a sufficiently high temperature, so as to be easily run into molds. It becomes more fluid and preserves its fluidity longer than white iron ; it expands on becoming solid so as to be capable of Ailing up the smallest cavities and depressions of a mold. Gray cast-iron is about one-twentieth lighter than the white variety ; its average speciflc gravity is 7.1. The gray iron rusts more easily in air and is more readily acted upon Avith acids than Avhite iron, Avhich may be ascribed partly to its containing more iron in an uncombined form, and partly to the acceleration of chemical action caused by the voltaic disturbance excited by the contact of the particles of graphite Avith the par- IG NAVAL ORDNANCE AND GUNNERY. tides of iron in the presence of the acid ; in the ease of air, car- bonic acid. This variety of iron is used for ordnance purposes 56. White Cast-ieon. — Since in white cast-iron a considera- ble proportion of the iron is in intimate combination with car- bon, this variety would be expected to present the characters of the compound of carbon with iron, described above (Art. 50j ; accordingly the white cast-iron is very brittle and extremely hard, so that a lile will scarcely tonch it, whereas gray iron is much softer, and admits of being filed and turned. White cast-iron is softened at a lower temperature than gray, but becomes less perfectly fluid ; in cooling it passes through the pasty or semi-fluid state, and contracts very considerably on solidification. It scintillates or throws off sparks, as it runs from the furnace, to a much greater extent than gray iron. Its average specific gravity is 7.5. White iron usually, but by no means invariably, contains less total carbon than gray iron. Its qualities generally are the reverse of those of gray iron, and it is therefore unsuitable for ordnance purposes. 57. There are two distinct kinds of white iron. First, That obtained from ores containing a larger proportion of manganese crystallizing in large plates; this variety, called spiegeleisen, is highly prized for making steel ; and Second, Tliat resulting from a heavy mineral burden of the furnace, or from a general derangement of its working, and that caused from the rapid chilling of fused gray iron. 58. Mottled Cast-ieox is composed of a mixture of the ■white and the gray varieties in varying proportions, the gray iron sometimes appearing in specks, like minute flowers upon a white ground, whilst in other specimens the mass is composed of gray iron and the white iron appears in spots. Fine gray mottled iron from its great tenacity is known to be the best fitted for large castings where great strength is required, and is employed for gun-founding. It may be made by mixing white and gray iron, or by continuing gray iron in fusion for some time, until it gets the proper color. The kind of mottle will depend much upon the size of the castings. (Art. 364.) 59. Classification of Pig-ieon. — Generally a medium-sized gram, light-gray color, lively aspect, fracture sliaiq) to the touch, and a close, compact texture indicate a good quality of iron; while a grain either very large or very small, a dull earthy aspect, loose texture, dissimilar crystals mixed together indicate an inferior quality. The produce of the blast-furnace is di-visible into several qualities, which for practical purposes are determined by the CANXON EIETALS. 17 appearance presented by a freshly fractured surface — a num- ber of pigs taken from each cast being broken for the purpose. The numerous gradations in the scale are mainly dependent on color or degree of grayness, texture or size of crystals, and their uniformity and lustre. The largest-grahmd, brilliant, and graphitic dark-gray metal is known as hfo. 1 pig, while the smaller-grained varieties, with diminishing lustre and color, are designated by the higher numbers as far as ISlo. 4. IBeyond this point, when the metal ceases to be gray, it is usual to omit the numerical scale, and denominate the remain- ing qualities by their color, as mottled^ weak and strong mottled, and white, the last being the lowest. This classification is subjected to variations in different locali- ties. The gray numbers as far as ISTo. 3, are also called melting or foundry -pigs / the lower qualities, wTieh are only adapted for conversion into malleable iron, coming into the class of forge- pigs. 60. Yakiatioxs in Composition of Cast-ieon. — Although carbon appears to be the only substance mdispensably associated with the metal in cast-iron, the commercial varieties of this material always contain silicon, phosphorus, sidphur, and manganese, v’hich are often present in considerable proportion, and are known to exercise an influence upon the character ol; the cast-iron ; other substances, such as titanium, cobalt, nickel, chromium, copper, vanadium, calcium, magnesium and arsenic may also be discovered by a careful analysis of considerable quantities of cast-iron, but they are generally present in very small proportion, and are, not known to produce any effect on the metal. The following table illustrates the general composition of the three principal varieties of cast-iron : Gray. Mottled. WMte. Iron . . 90.24 89.31 89.86 Combined carbon . . . . . 1.02 1.79 2.46 Graphite . . 2.64 1.11 0.87 Silicon . . 3.06 2.17 1.12 Sulphur . . 1.14 1.48 2.52 Phosphorus . . 0.93 1.17 0.91 Manganese . . 0.83 1.60 2.72 99.86 93.63 100.46 61. The difiicillties attending the chemical analysis of cast- 2 18 NAVAL OEDNANCE AND GDNNERT. iron are very great on account of the large quantity of iron which has to he separated from small quantities of the other constituents, so that, although numerous analyses are recorded, their results do not exhibit that agreement which is necessary in order that the composition of this material may be considered to be thoroughly established. There appears to be little knowledge of a thoroughly satis- factory character with respect to the eifect of different propor- tions of foreign matter upon the quality of iron, for the exact analysis of this material is tedious and difficult ; and those who are competent to execute it in a trustworthy manner have rarely the opportunity of becoming practically acqiiainted with the behavior of the metal. 62. Silicon. — 1ST ext to carbon silicon, or silicum, is the com- monest and most abundant constituent of cast-iron ; its effect is very similar to that of carbon, and its tendency is to reduce the percentage of carbon. It is an element that is always present in every form of iron, although at times its quantity is very minute ; the proportion of silicon being higher in the gray than in the white variety, and the greater the quantity of graphite in the crude iron, the larger the amount of silicon. The best common iron contains from one to one and one- fourlli per cent, of silicon. Such iron has a smoother face than inferior pig, and when struck with a hammer rings ; it is brit- tle and crystalline ; whereas inferior pig contains only two to four-tenths of silicon, is rough on the face or surface, breaks with less ease than the crystalline pig, and when struck sounds dead like lead, without ringing at all. Silicon exists in cast-iron sometimes combined and some- times separate, and is derived from silica in the ore or in the fuel ; silica is a combination of silicon with oxygen, and when the latter is abstracted by the carbon at the high temperature of the blast-furnace, the silicon enters into combination with the iron. The presence of a large proportion of silicon in cast-iron is generally considered injurious to its quality, the strongest cast- irons being those which contain a small quantity of that ele- ment. Iron which has been smelted with coke contains a larger proportion of silicon than that smelted with charcoal, and hot- blast iron commonly contains more than that smelted by cold- blast. The presence of silicon in pig-iron affects in a remarkable degree the yield as well as the strength of the bar-iron produced therefrom. It is necessary that this element should be removed CANlSrOIT METALS. 19 as inncli as possible bv a refining process, before the crude iron is submitted to the puddling process ; but as this involves a great waste of material and trouble, it becomes an object of much practical importance to prevent, as far as possible, the presence of this element in the crude iron. In refining iron the silicon is oxydized before the carbon, and in some cases the silicon is separated completely from the metal, existing only as traces. The time required to refine iron seems to depend upon the amount of silicon present in the pig ; thus, gray iron requires much longer time than white, and when very silicious white iron or glazed gray pig is used, it is almost impossible to refine it. It has always been the general impression that any amount of silicon in steel reduces its quality and seriously impairs its strength ; good steel may, however, contain two per cent, of sili- con, and its presence makes steel castings more solid.* 63. Maxoaxksu is seldom if ever absent from cast-iron, for it is a metal which very nearly resembles iron in its chemical properties, and is commonlj^ found in iron ores, so that the same operation which reduces the iron in the blast-furnace also reduces the manganese, and this metal becomes alloyed or closely mixed with the melted iron. The manganese has been found in the large proportion of one-sixteenth of the weight of the cast-iron, but it seldom ex- ceeds one-fortieth. The influence exerted by the manganese upon the character of the cast-iron is very decided, tending to the production of the white variety, the manganese diminishing the tendency of the carbon to separate in the form of graphite. AVhite east-iron, therefore, is found to contain the largest proportion of manganese. The spathic iron ores yield a cast-iron containing a particu- larly large quantity of manganese, sometimes exceeding one-tenth of the weight of the cast-iron. Such an iron is capable of con- taining upwards of one twenty-fifth of its weight of carbon in combination with it, and the compound thus formed ciy stall izes in large and shining plates, whence it is named by the Germans sjyiegeleisen, or mirror-iron. It is largely employed in the man- ufacture of Bessemer steel. It has been asserted that the presence of manganese in iron ores encourages the passage of phosphorus, sulphur, and silicon into the slag, thus reducing the proportion of those injurious impurities in the metal. Eilej. 20 NAVAL ORDNANCE AND GUNNERY, 04. PiiospnoEUS is one of the most unwelcome ingredients in iron ores, from tlie ease with which it passes into the metal during the smelting process, producing the most injurious effects, if present in more tlian a very small proportion. Practically speaking, all the phosphorus in the ore and in the fuel passes into the pig-iron made ; like silicon it makes pig- iron weak, although it is thought that when the amount is not more than one-half to three-fourths per cent., the strength of the pig-iron is not materially affected by it. Phosphorns occasionally forms between one-fiftieth and one- sixtieth part of the weight of cast-iron, but about one-hundredth part is a more common proportion of phosphorus. It exists in combination with a portion of the metal as j>hospMde of iron, and is derived either from phosphate of iron contained in the ore, or from phosphate of lime, which is frequently present in the limestone employed as a flux, and in minute quantity in the coal. These phosphates contain phosphorus in a state of com- bination with oxygen, which is abstracted by the carbon of the fuel in the blast-furnace, and the phosphorus thus set free enters into combination witli the iron. So completely is the phos- phorus taken up by the metal, that only traces of that element in the form of phosphates are usually found in the slag from the blast-furnace. The effects of phosphorus are to harden cast-iron, decrease its strength, and increase its fusibility. Iron made from ores containing much phosphorus is always cold-short, or incapable of being wrought cold under the hammer without breaking. G5. SuLPiiiJE, though almost invariably contained in cast- iron, rarely forms as much as OTie-fiftieth of its weight. It is chiefly derived from ironpyrites, which is the yellow substance, of metallic appearance, so common in lumps of coal, and may be found in rusty globular masses on the sea-beach. It is composed of iron combined with sulphur in nearly equal proportions, and since crystals of ironpy rites are found in many iron ores, it is the chief source of the sulphur, which is the most objectionable impurity in iron. The most prejudicial form in Avhich sulphur can exist in the blast-furnace is when it occurs as sulphide of iron ; it has no prejudicial effect when it exists as sulphide of calcium. Large quantities of sulphur may be present as a sulphate of an alkaline earth without having any effect on the quahty of the iron produced. The white varieties of cast-iron contain a larger proportion of sulphur than the gray, and it will make gray non white. It is thought that slightly different amounts of it may modify the CAis^NON METALS. 21 pig-iron, and produce tlie difference we find in it, for practically there is a very great difference in the Avorking of the different grades of iron, Avhen chemically speaking there may be no dif- ference apparent. Tlie percentage of sulphur usually increases as the quality of the pig decreases, and its presence tends to red-shortness in bar-iron, rendering it incapable of being worked at a red heat under the hammer. This element also imparts to crude iron the property of becoming viscid and of solidifying c^uickly with cavities and air-bubbles. Iron may be both red-short and cold-short at the same time. Such iron is the worst possible iron, and is made from ores con- taining a high percentage of sulphur and phosphorus. Section III.— WrougJit-lron. 66. "WnouGnT ok Malleable Ikon.* — This is the nearest approach to the chemically pure metal that can be obtained on the large scale, and may be almost absolutely free from carbon. It never contains more than one-fourth per cent. 67. It is a soft, malleable, and extremely tenacious substance, infusible except at extreme temperatures obtainable in furnaces of special construction, but capable of being agglomerated by pressure, when at a white heat, to a compact state by the pro- cess of Avelding. 68. IIoAV Peoduced. — It may be produced either directly from the ore, or by the conversion of pig-iron. Varieties. — TheA’arietiesof malleable iron are distinguished by many different names, but they have reference rather to form and destination than to difference of composition. 69. CoNVEESiox OF Ckude INTO Malleable Ieon. — This is effected by one or more operations, which are necessarily of an oxydizing nature, the object being to eliminate from the cast- iron the carbon in the form of carbonic oxide gas, and the sili- con, sulphur, phosphorus, and other foreign bodies in the form of oxydized products which pass either partially or wholly into slag or cinders. 70. T aeiotjS Peocesses. — The numerous processes em- ployed in the production of malleable from cast-iron are divisi- ble into two classes, according to the nature of the furnaces employed. First. The ogpen-jire.^ or hearth-furnaces, where the pig-iron * Bauerman. 22 NAVAL ORDNANCE AND GUNNERY. is melted and decarbonized in a shallow hearth before the blast of an inclined twyei’. Secondly. The yyxoddling-furnaces, where the same operation is performed on the bed of a reverberatory fm-nace. 71. Chemical Reactions. — The reactions going on during the process are similar in either case. The carbon, if it exist originally as graphite, first passes into the combined state, and is then converted into carbonic oxide either by the oxygen of the blast dmectly, or indh’eetly by the oxide of iron dissolved in the slag. Oxydizing agents for the indirect conversion may be derived from the pig-iron under treatment, which is always oxydized to a certain extent under the influence of the blast cluiing the melting, or they may be added in the form of ore, forge-scales, or slags. According to the relative importance of the parts played by these agents, the process is divided into dry and xcet puddling, the former being dependent mainly on the exposure pf the metal to the action of the air, while in the latter, which is more generally known as the pig-hoiling process, the slag and oxide of iron added are the most important oxydizing agents. The removal of the foreign matter in combination with the iron takes place in the following order : — ^flrst, silicon, then manganese, then phosphorus, and lastly sulphur, the latter ele- ment being most difficult of removal. In the treatment of gray pig-iron, the graphitic carbon is transformed into the combined condition after the removal of the silicon during the melting of the charge. 72. Kind of Ikon most suitable for Conteesion. — White cast-iron is more suitable for conversion into malleable iron than gray, as in it the whole of the carbon in combined with the iron, and it does not, when raised to a high temperatm’e, pass imme- diately from the solid to the liquid state, but assumes, when near its melting point, an intermediate or pasty condition favorable to the more effectual action of the air or other agents employed in the removal of the combined carbon. Gray metal, on the other hand, though recpiiring a higher temperature for fusion, becomes very liquid, and in a deep hearth sinks below the level of the blast, and, becoming covered with a coating of slag, is completely protected against the action of the air, unless it is brought under the influence of the blast by stirring or hftmg with an iron bar, an operation which involves great labor and de- lay, as well as an increased expenditure of fuel and waste of ii’on. JSTo sensible amount of decarburation takes place until the whole of the graphitic carbon has entered into combination with CANNON 5IETALS. 23 the iron, or, what amounts to the same tiling, until the metal has passed from the gray to the white state ; and this conversion is an essential preliminary in all refining processes where the air is introduced above the surface of the melted metal. 73. Refining. — Gray pig-ii’on is often subjected, as a first step in the process of making malleable iron, to a preliminary decarburation in the oxydizing Mast-hearth^ or rejinery • this process is called refining. 7d. The Puddling Furnace is of the reverberatory form, one in which the flame is made to pass over a bridge and then beat down again or reverberate upon a hearth or surface on which the materials to be heated are placed. It consists of an oblong casing of iron plates (Fig. G), firmly bound together by iron tie-bars, and lined with fire-brick. The fireplace, F, is separated from the hearth, A, by a jire- hridge over which the heated products of combustion with a surplus of oxygen play upon the sm’face of the molten metal, effecting its conversion, and thence pass through the flue to a Fig. 6. — Puddling Furnace. lofty chimney, C, in which is suspended a metal damper-plate, by which the draught can be regulated. The Fireplace varies in depth with the nature of the fuel employed, being greatest with the hard kinds of coal. 24: NAVAL ORDNANCE AND GUNNERY. The fire-grate is niade of plain wronght-iron bars. A forced draught, produced by blowing air in below the grate, is some- tunes used. The surface of the grate should be between one- half and one-thh*d of that of the bed or hearth. The charging or fire hole is about a foot above the grate. T/ie hearth . — The bottom of the bed is formed of cast-u’on hearth-plates resting upon cast-iron beams. The hearth is covered with cinders or sand, and is tenni- nated at either end by a straight wall or bridge, called respec- tively the fire-hridge and the jiue-T)ridge. The Flue . — The roof of the furnace is curved to a flat arch, and is generally made to slope at a small angle towards the flue, which slopes towards the stack. The sectional area of the flue varies with the nature of the fuel, being larger for soft coal. The mainworldng-door, D, is made of brick set in a cast-iron frame ; it may be readily lifted and lowered by means of a lever. It is only opened during the introduction of the charge and the removal of the puddled balls. The sill of the door is about a foot above the level of the bed. There is sometimes a second work- ing-door near the flue for introducing the cast-iron, so that it may soften slowly till it be ready for drawing towards the bridge. The Stoj)per-hole . — A small rectangular or arched notch, called the stopper-hole, is cut out of the lower edge of the door for the introdiiction of the tool used in stirring the metal, and through which the workman can observe the state of the fm- nace. It may be closed air-tight. The Tap-hole., through which the slag, or tap-cinder, is with- drawn from the hearth, is placed below the door-sill. It is plugged iip with sand. A portion of the cinder also overflows the flue-bridge, and runs down the inclined surface of the flue to the bottom of the stack, h. 75. Process of Puddling. — Although the process of pud- dling is susceptible of considerable modification according to the nature of the pig-metal employed and that of the iron wliich it is desired to produce, it may be generally stated to include the following operations : 1st. Melting down of the charge with or without the previ- ous heating. 2d. Incorporation of osydizing fluxes with the charge at a low heat. 3d. Elimination of carbon by stmlng the contents of the furnace at a high temperatm’e. 4th. Consolidation of the reduced fion to masses or balls fit for hammerino;. O CANNON METALS. 25 7G. CnAKGiNG THE FtTKXACE. — Pieces of metal are succes- sively introduced with a long shovel, and laid one over another on tlie sides of the hearth in the form of piles rising to the roof, the middle being left open for puddling the metal as it is successively fused. The piles are kept separate to give free cir- culation of air round the metal. The working-door of the fur- nace is now closed, fuel is laid on the grate, and the mouth of the fireplace is filled up with coal ; at the same time the damper is entirely opened. In puddling refined metal, or in dry puddling, the furnace is charged with metal alone, hut in puddling, gray metal, that is, in wet puddling, or boiling, as it is tai'meU, forge-cinder is charged along with the metal, and the temperature rises much higher. 77. PuDDLiNG-TooLS. — ^The tools employed are principally of two kinds, namely, long, straight, chisel -edged bars, or pad- dles, and hooked bars with similar fiat ends, called rccbbles. The number of tools used in the working of one charge depends on the quality of the iron, and may vary from four to eight, according to the amount of work required. When withdrawn from the furnace, the points are coated with molten cinder, which is removed by quenching the bar in a cistern of cold water. 78. In order to lessen the great amount of labor involved in working the chaige, various mechanical appliances have been proposed in substitution for manual puddling, but these as yet have not been adopted to any great extent. They may be gen- erally classified under two heads, namely, those imitating the motions of hand-sthring, and those usina: rotatina; or oscillatina: o o o hearths. Dank’s rotatory puddling-furnace is the most successful of these, and is being introduced quite extensively. It produces a better quality of iron with much less labor, and in less time than is possible by hand-puddling. 79. Manipulation of the Molten Iron. — When the metal begins to soften, the workman or puddler introduces the rab- ble through the stopper-hole for the purpose of working the metal. The amount of handling required in this part of the process dejiends upon the nature of the iron operated upon. 80. White or Refined Iron . — When this is used it requires a continuous operation, which calls for much care and skill on the part of the w’orkman. The pieces of metal that begin to melt are detached from the piles with the rabble, and new surfaces opposed to the action of the heat ; as it softens it is removed from the vicinity of the fire-bridge, to prevent the metal from run- ning together. When the whole of the metal is reduced to a pasty condition, 2G NAVAL OKDNANCE AND GUNNERY. the temperatiu-e of the furnace is lowered to prevent its heconi- iug more fluid. The puddler now works about with his rabble the clotty metal, which swells up exhibiting a kind of fermenta- tion, occasioned by the discharge of carbonic oxide, burning with a blue flame as if the bath were on fire. The metal becomes finer by degrees and less fusible, or, in the language of the work- man, it begins to dry. The disengagement of carbonic o.xide diminishes and soon stops. The workman continues meanwhile to puddle the metal till the whole charge is I'educed to the state of incoherent sand ; the damper is then progressively opened. With the return of heat the particles of metal begin to aggluti- nate, the charge becomes more difficult to raise, or, in the lan- guage of the workman, it works heavy. The refining is now finished, and nothing remains but to gather the mon mto balls. 81. Gray Pig-iron . — With this variety of iron, which re- quires a higher temperature for fusion, but which runs very liquid, the fragments may be melted clown without being moved, if the furnace is sufficiently hot. Oxydizing agents are charged with the iron. In order to bring about the reaction of the slag upon the melted metal it is necessary to incorporate the whole contents of the furnace well together after melting. For this purpose the temperature is lowered by checking the draught or even throwing water upon the metal, the charge being stirred at the same time. The slag is also reduced to a more basic condition by the addition of scale., or mill-einder, to compensate for the silica produced from the oxydation of silicon in the pig. When the mixture is complete and the mass somewhat stif- fened, the reaction of the oxide and silicate of u-on upon the combined carbon is apparent by the escape of blue flames of car- bonic oxide, and as the teinj^erature is increasdtl by opening the damper the whole surface commences to boil, from the rapid escape of gas, and at the same time a portion of the molten slag flows out. The action is facilitated by constant sthring with the rabble. As the carbon diminishes the ebullition becomes less violent, and the bath from its reduced fusibility in spite of the high tem- perature begins to stiffen, and malleable iron separates, or, as it is called, comes to naUire. At this point of the process the whole contents of the furnace require to be well stirred and broken iqa, so that every part may be brought imder the influence of the high temperatiu-e. The reduced mass is subject to a final heat in order to facilitate the separation of the cinder by rendering it perfectly fluid. CANNON JIETALS. 27 82. The Puddle Balls. — Tlie last operation consists in forming np the balls, Avhich is done by detaching from the re- duced iron masses from sixty to eighty pounds weight each, and pressing them together with the tool until they are sufficiently coherent to be moved without falling to pieces. This may be done either by pressing against the bottom and sides of the fur- nace, or by a rolling motion, the iron being gathered up around a small nucieus like a snow-ball. As soon as a ball is made, it is placed close against the fire- bridge to keep it hot and out of the draught of air between the working-door and the line ; the second is proceeded with until the whole of the charge has been balled up ; the stopper-hole is then closed, and the final heat is given to facilitate the operation of shirt gling. The removal of the balls, which are of a roughly spherical form, after they are drawn to the working-door with the tool, is effected by means of a long pair of tongs with curved jaws. , They are first lifted to the iron table in front of the working- door, and afterwards either dragged along the floor or carried on a wrought-iron truck to the hammer, or such other maehme as may be employed for shingling. 83. SiiiNGLTNG, OK Bloomixg, is the process of converting the puddle balls into malleable stuff by hammering or com- pressing. A Bloom is a rough lump or bar of wrought-iron which results from the slfingliug process. 8d. Shingling Machines . — The machines used in the com- ])ression and welding of the rough balls of malleable iron into blooms are of two different kinds, namely, hammers and squeez- ers.^ the former acting by percussion, and the latter by compres- sion. In addition to these, it is usual to reduce the blooms so obtained to short rough bars by passing them at the same heat throtigh a rolling-mill. 85. The Flxisiied Bak. — The rough bars, or slabs, of malle- able iron obtained in the process of puddling and shingling, require to be subjected to other treatment in order to produce finished, or merchant iron. For this purpose they are cut into short lengths, which are made into nearly cubical packets or piles and subjected to a further consolidation by hammering and rolling, at a welding- heat, imtil a bar Avith a uniformly smooth surface, free from flaws or cracks, is obtained. 86. Eolling-mills. — These are used in the production of finished iron from the blooms. In its simplest form a rolling- mill consists of two cast-h'on cylinders placed with them axes 28 NAVAL ORDNANCE AND GUNNERY. horizontally one above the other, and connected by spur-geaiing, so as to revolve at the same velocity, (big. 7.) The surface of the rolls may be either smooth, as is the case in the plate-mfUs, or grooved into various patterns, as in those used for the produc- tion of merchant bars. (Fig. 7.) The reduction in the size of the bloom is effected by regu- lating the vertical distance between the two rolls, by the use of grooves diminish- ini-piec6. (Fig. 19.) This amingeinent allows the vent to be renewed when too much en- larged by continued use. Copper vent-pieces are especially neces- sary in rifle-guns, in consequence of the prolonged action of the gas arising from the resistance of tlie projectile. In the largest calibre the interior orifice is lined with platinum. The upper portion of the copper i's replaced by steel to obtain a harder surface for receiv- ing the blow of the hammer. 217. Position . — All smooth- bore guns of the Dahlgren pattern have two unbouched vents, situated on opposite sides of the axis of the bore, and inclined at an angle of 70° with that axis. (Fig. 76.) The one on the right side is bored entirely through ; the other is simply initiated to give it direction. When the open vent is too much enlarged by wear for further use it is closed with melted zinc, and the other is bored out. Each vent should endure about live hundred service rounds. (Art. 603.) In smooth-bore cast-guns the vent enters the bore v‘ery near the bottom ; the vmnts of heavy built-up guns are usually bored vertically, and in such a position as to strike the cartridge at about four-tenths of its leng-th from the bottom of the bore, it having been ascertained by experiment that the ignition of the charge at about this point realizes the greatest projectile force that can I'e produced by a given charge. Experiment shows that the actual loss of force by the escape of gas through the vent, as compared to that of the entire charge, is inconsiderable, and may be neglected in practice. 218. Extekior Form. — In designing a gun it is necessary in the first place to endeavor to determine what thickness of metal is required for that part of the gun surrounding the seat of the charge, for it is here where the greatest strain from the explosion of the charge is exerted. ISTo precise rules can be laid down for tlie regulation of this thickness in various kinds of oi’dnance, as so much depends upon the physical properties of the material used. The general results of experience, or of experiments, car- 68 NAVAL ORDNANCE AND GUNNEET. ried on for the pm-pose of establishing this point, can alone fur- nish ns with the recpiisite data. (Art. 221.) The amount of metal in a gun must depend upon the charge, Fig. 20. — IX-in. Dahlgren. the weight, and form of the projectile, the material used, and the method of construction. 219. Foece to be kesteaixed. — ^TFhen a charge of gunpow- der is ignited in the bore of a gun, the gas exerts ecpial pressm-es in all directions, and therefore neglecting windage, the pressure in the bottom of the bore is equal'to that on the base of the pro- jectile, and the pressures on the top and bottom as well as those on the sides of the bore balance each other. 220. The metal of a gun is subjected to two principal strains (Art. 308), one, a transverse or tangential, which tends to rend the metal lengthwise, or from end to end, through A, B (Fig. 21), and the other, a longitudinal, tending to fracture the gim across, as through C, D (Fig. 21), or to chive out the g breech. As the projectile moves towards the muzzle so will the space in which the gas is confined be increased, and the pressure be decreased ; the portion of metal surrounding the space originally occupied by the cartridge, and a little in front of it, is that upon which the maximum pressure from the gas is exerted. The maximum pressure will be influenced by the nature^ of the powder, the resistance ofl’ered by the projectile to motion, and by the absence or amount of windage. 221. Expeeijients. — Many experiments have been made to determine the gradual decrease of strain upon the metal of a piece of orchmnce, from breech to muzzle. The first were D. — 1 C Eig. 21. GENERAL DESCRIPTION OF ORDNANCK 69 accomplished bj perforating a gun in several places from the ex- terior to the bore, at right angles with the bore, and successively screwing a pistol-barrel, containing a steel ball, into each perfora- tion, and discharging the gun with the pistol-barrel at the diJier- Fig. 22 . — Heavy Twenty-Pounder Bronze Rifle, 1,950 lbs. ent perforations, the relative velocities with which the pistol-ball (received by a pendulum) is forced out at these different positions indicate the force exerted there to burst the gun ; and conse- quently the relative strength of metal necessary in the various parts to resist explosion. The results of these experiments are relatively as follows, in decimal parts : At a calibre in rear of centre of projectile 98 “ centre of projectile 1. “ one calibre in front of projectile 81 “ two “ “ “ 68 “ three “ “ “ 62 “ five “ “ “ 53 “ seven “ “ “ 44 “ nine “ “ “ 40 “ eleven “ “ “ 37 “ fifteen “ “ “ 29 These decimals show the relative strength necessary at differ- ent parts to resist explosion. The dimensions here given are intended to apply to cast-iron ordnance, which it was assumed should have a thickness of one calibre round the seat of the charge where the greatest strain is exerted. 70 KAVAL OEDNAIfCE AND GUNNERY. 22'2. Other experiments have been made hj using Rodman’s pressure gauge (Art. 1332) in the holes instead of a pistol-barrel, Fig. 23. — Navy XV-incli. also using electricity by connecting a chronoscope rvith wh-es in plugs titted in the holes of the gun. (Art. 1302.) 223. In cast-iron guns of more recent construction tire metal is distributed on diherent principles, viz. : in giving a greater thickness of metal, and consequently more strength about the seat of the charge, vdiile the amount of metal in the chase is diminished, this part having to sustain but a small proportion of the strain from the discharge of the piece; also, in increasing the proportional thickness of metal, as the calibre of the gun is greater. (Art. 311.) 221. iMPnovEJiENTS. — Gun-making is no longer the simple matter which it continued to he while the Avorld was content vrith wooden ships and round shot. There are now almost as many ways of making a gun as of making a steam engine. In-' genuity has been exercised upon the material, the construction, the rifling, and the mounting of the gun, as also in regard to the kind of powder with which it is to be loaded, the structure of the projectile which is to he fired, and the appliances by which the gun is to be worked. Everything is changed since the days when simple smooth-bores and cannon-balls were deemed sutii- ciently formidable and destructive. After many years of experiment and millions of expenditure foreign powers have established two or three systems of I'ifled ordnance as worthy of confidence. These are the German sys- tem (Art. 701', the Erench system (Art. (573), and the English system (Art. 6(51). In our country appropriations have been made for carrying on experiments with a view to establishiug the best system of heavy rifled ordnance. The Army has been entrusted with this GENERAL DESCRIPTION OF ORDNANCE. 71 important duty, and experimental guns on different plans are now in course of construction. 225. Devices. — Formerly cannon were liiglily ornamented with figures representing some fanciful design, together with the national coat-of-arms and cypher of the reigning monarch. Each Fig. 21. — DaUgren Shell Gun. piece also bore a particular name, borrowed from some animal or passion ; and sometimes mottoes were inscribed upon them. The most recent models are characterized by an entire absence of molding or ornaments, and by the utmost simplicity of ffgure. 22G. (See Table facing jiage 71, and marked 71'^.) 227. MORTARS. — Mortars are short pieces of ordnance with large bores, used to throw shells at high angles, generally forty-five degrees, for reaching objects by their vertical fire. They are used in the navy only under exceptional circum- stances. 228. CoxsTEcrcTioN.— They are constructed stronger than guns, on account of the high elevation at which they are fired ; and shorter, because the difficulty of loading would be increased by their length. In the new patterns, the axis of the trunnions passes through the centre of gravity, if the piece and the bore is unchambered. The only mortar used in the naval service, is the thirteen inch of 17,000 lbs., made of cast-iron. (Fig. 25.) 229. ITowitzers. — Properly, howitzers are a description of shell-guns ; shorter, lighter, and more cylindrical in shape than 72 NAVAL ORDNANCE AND GUNNERY. a gun of tlie same calibre, and having a chamber for the recep- tion of the powder. They are employed to fire large projec- tiles at low angles, with comparatively small charges of powder. Fig. 25. 230. Kaval rioAvuTZERS are bronze shcll-gnns, adapted to field and boat service. They are made of bronze on account of their comparative lightness for the same strength, and from their being less liable to burst than iron guns of the same calibre. 231. The Bo.^t Howtizees are both smooth-bore and ride. Fig. 23. — Light Twelve-Pounder Boat Howitzer. They are alike in the principle of construction and general appearance, and differ only in weight and dimensions. GENERAL DESCRIPTIOiSr OF ORDNANCE. 73 Around the charge the metal is distributed in form of a cyl- inder (Fig. 26), extending sufficiently in front of the seat of the projectile ; thence to the muzzle it is continued as a truncated cone. The breech is a portion of a sphere. The bore is terminated by a conical chamber (Fig. 18), and the piece is mounted on its carriage by a loop. Fig. 27. — Rifled Twelve- Pounder Bronze Howitzer. 232. Pekcussion-Locks ”^foe Naval Okdnance. — The ham- N. An iron nipple with a case-hardened face screwed into the head. A. The hole for the axial bolt of the hammer. A B. The extension of the hole, termed a slot, in the direction of the head H; its length is such as to admit of the hammer’s receding one inch, which takes it entirely clear of the vent-blast. L. A laniard entering beneath the rear end of the shank, which is rounded for that purpose, then through a perforated stud (Y) on the under-side of the shank. mer has its revolution about the axial bolt traversing the hole A, and the force is applied by the laniard passing about the rounded rear end of the shank. When the hammer is thrown hack, the laniard being steadily and quickly drawn, compels the hammer to turn on its holt until down on the vent. Aow, if there were no other perforation for the bolt than that at A, the hammer could not escape from the gas issuing out of the vent, and must be thrown otf by it. But when the ham- mer is down, if the force of the laniard he continued, the effort L Fig. 28. — H. Tbe head of the hammer. ' S. The shank. 74 NAVAL ORDNANCE AND GUNNERY. is to withdraw directly from the vent, and the slot or extension of A permits this to he done until the end of the slot at B is arrested by the axial bolt. The receding motion thus obtained has the extent of one inch, which is sufficient to take the ham- mer-head clear of the blast of the vent. A lock-mass is cast with the gnn near the vent (Fig. 22). It is slit so as to form studs, between which the hammer is se- cured and has its move- ment. On boat-howitzers the lock has no slot, and does not recede from the vent. The vent-blast is avoided b}' having a perforation in the head of the liammer ; which allows for its escape without throwing back the lock. 233. THE GATLIHG-GUH — (Fig. 32) — is a machine-gun consisting of a set of ten barrels. A, in combination witli a grooved cartridge carrier, M, and a lock-cylinder, O and O' (Fig. 36). The whole being rigidly secured to a centre-shaft, H. The grooves in the carrier, the holes in the lock-cylinder, and the barrels, all correspond in number. Each barrel is pro ■ vided with a lock, F (Fig. 37), which works in a chamber formed in the lock-cylinder; O and O', in a line with the axis of the barrels. The lock-cylinder is surrounded by an outer casing, II, connected to the framing, B, which is carried along on each side of the barrels and across the front of the gun ; the rear end of each side frame forming a support for the breech-casing, II. In the breech-casing is a verticle trans- THE GATLIXG-GIESr. 75 ’s^erse partition, D (Fig. 39), into wliicli tire main central shaft, 17, n'liich carries the loch-cylinder, O, carrier M, and barrels. A, is journalled. At its front end the main shaft is also journalled into the cross-piece of the frame, B. 23-1:. On the rear end of the main shaft is fixed the revolt- ing gear (Fig. 39), which is worked by a crank, G, on the right side of the breech-casing, H. The rear of the chamber in which the gear is placed is closed by a cascabel plate, C (Fig. 37), having an opening through which the lock may be entered Fig. 33. and withdrawn when necessary. This opening is closed by a plug of special construction, E, attached to the cascabel plate by a chain. In front of the breach-casing and hinged to the frame, B, is a curved plate, I (Fig. 31), called the hopper^ through which the cartridges are fed to the gun. 76 NAVAL ORDNANCE AND GUNNERY. The gun is mounted on a swivel block, L (Fig. 32), on which are formed seats to receive the trunnions of tlie gun ; this block is secured to the carriage by a centre-pin, which allows it to turn and bring the gun to bear upon any object within the arc of twelve degrees, the trunnions permitting vertical motion of the muzzle of the gun, 235. The IIoppek (Fig. 34) is a brass curved plate, I, hinged to the frame-work of the gun on the right side and encasing the chambers of the barrels. It is pro- vided with an aperture, K, through which the cartrid- ges descend to their places in the grooves of the car- rier or chambers of the bar- rels ; Avhereupon they are instantly taken possession of by the locks, forced into the barrels, and bred. A short distance in fi’ont of the cartridge aperture, is an upright pin I', in which the feed drum, Y (Fig. 42), rests and revolves. The upper side of the hopper is flat and circular. 236. The Apertuke, K (Fig. 42), for the cartridges, is nearly of the form of a cartridge and tapered downward. Its sides serve to guide the cartridges into the carrier singly, so that they can be removed one by one. The front end of the aperture is projected downward nearly into the carrier next the barrels, and thus serves to cut otf the entrance to that particular barrel which is in front of it, Avhile in this position; and prevents the cartridge which lies upon the one already in the groove from sliding forward and prematurely entering the opposite barrel. 237. The Carrier, M (Fig. 35), is a metal cylinder, attached to, and revolving with, the main shaft ; its for- ward edge being sutficiently near the rear end of the barrels to insure the cartridges entering with- out jamming (Fig. 42). On its circumference are as many grooves as there are barrels, in Avhich the cartridges rest and are pushed forward into the Fig. 35. barrels by the locks ; thus the grooves of the car- rier act as chambers for the barrels (Fig. 33). 238. The Lock-cylixder, O and O' (Fig. 36), is a metal piece, consisting of tivo cylinders of different diameters, 0, and O'. On the circumference of the smaller and parallel with the THE GATLING-GHH. 77 Fig. 30. axis of tlie barrels, are as many slots as there are lochs, and in these slots, the lug on the underside of the loch-case, P (Fig. 37), travels. In the larger cylinder.' and in line with the axis of the barrels, are the same number of holes, in which the lochs move for- ward and bach. A slot or opening is made between the holes and the circumference of the cylinder, form- ing a guide for the lug, cc, on the firing-pin, Z (Fig. 37), of the loch. 239. The Locks consist of hollow steel cylindi’ical cases of different diameters, F (Fig. 37); the larger cylinder, or rear part of the loch- case being open at the top for a portion of its length. In this portion is placed the firing-pin and spring, Z, the for- mer, which Fig 37. IS re- duced in diameter at its forward end to about one-eighth of an inch, passes through the smaller portion of the loch-case, W, and projects very slightly beyond it. The spring, Z, is confined between the end of the slot and a lug, cb, formed at the forward end of the larger part of the firing-pin. This lug is designed to tahe against the coching-plate in the breach-casing and gradually press the spring and firing-pin bachward, until the proper moment, when it is released and the firing-pin is thrown violently forward, exploding the cartridge. Attached to the loch-case, on the under side, are two lugs, P, intended to travel in the slot on the circumference of the small- er portion of the loch-cylinder O' (Fig. 36). At the rear upper side of the case is a lug, y?, which tahing against the cam sur- face, P, in the breach-casing, (Fig. 38), communicates a for- ward and bachward motion to the loch. On the upper left-hand side of the loch-case (Fig. 37), is fixed a piece of steel, a, about four inches long, called the Ex- tractor^ having its forward edge rounded on the upper side and a shoulder on the latter, strihes a cam just at the edge of the barrel, drops over the rim of the cartridge, and when the loch moves bach, brings the cartridge-shell with it and di’ops it on the ground beneath the gun. 78 NAVAL ORDNANCE AND GUNNERY. 2-10. The Breech-casing, II (Fig. 38 and Fig. 39), is a hollow cylinder extending from the front end of the lock-cylin- der to the rear portion of the frame, B. Flanges, A A, on its sides rest on and are screwed to the frame (Fig. 32); near the rear end is a partition called the dia_phragm-plate, D (Fig. 39), which divides the cylinder into two parts and separates the lock- cylinder and worm gear, which is placed in the rear portion of the casing. A cascabel plate, C (Fig. 37), screws to the rear end of Fig. 38. the casing and serves to en- case and protect the worm or revolving-gear. In the forward division of the casing are placed the cams, B (Fig. 38), for forcing forward and drawing back the locks. In the upper left-hand side of the diaphragm-plates is an aperture, d (Fig. 39), through which the lock passes when entered or withdrawn ; a brass tube, e, screwed to the aperture, serving as a guide to the lock and breach-plug. At the proper distance from the front end of the casing, and on the right side, is placed a cocking-plate, which will be explained under the heacl of cocking apparatus. 2-11. The Bevolving or 'Worm-gear (Fig.39 ). — To the rear end of the main staff passing through the diaphragm-plate, D, is fixed a worm-wheel, W, worked by a shaft, S, extending across the rear portion of the casing. On this shaft is a worm, s, which works in the worm-wheel, W. A crank, G, at the right end of the transverse shaft conveys motion by means of the -worm to the worm-wheel, and thus the lock-cylinder, carrier, and barrels are revolved. 212. Traversing-gear. — To the opposite side of the trans- verse shaft on which the crank, G (Fig. 39), is fitted, is keyed a sleeve, t, having cut on its exterior a right and left- hand screw, on -which works the tapered end of a forked piece, T. This is dropped into a socket, in the outer end of a brass casting, FT, against which the upper end of the elevating- screw presses at Ub The fork, T, passes through the upper socket, then through a brass ring fitted with a clamji, T', and finally through the lower socket of the casting, by which means the fork is permitted to turn as it passes along the cross-cut thread, t, in either direction. Fig. 10 represents the THE GATLIXG-GUN. 79 fork detached and enlarged, and also in its proper position on the sleeve. On the onter end of the sleeve is keyed a ring, capable of adjustment at every half turn of the cross-cut-thread. This is ef- fected by a pin on the ring, and correspond- ing holes midway be- tween the intersec- tion of the threads of the screws, thus reg- ulating the range of motion of the breach of the gun. This ring serves to close one end and thus make the screw endless, and also to turn the fork into the return groove, the inner end of the sleeve being arranged so as to ac- complish the same object. ' As the firing-crank, G, is turned, the bands, carrier, lock-cyl- inder and right and left-hand screw are revolved. The latter, Avorking on the fork, T, gives the piece a continuous lateral trav- erse which may be enlarged or contracted as desired, by means of the ring, t ' ; thus sjareading the fire over a wide range, or contractnig it. Elevating or depressing the gnn does not interfere with the lateral traverse, as the elevating screw presses against the bottom of the casting to which the fork is attached, and thus both run up or doAvn alike. 2±3. The Elevating-gear (Eig. 32) consists of a screw Avhose loAver part rests npon the trail of the gun, and whose upper part ends in a ball, Avorking in a socket, tJ^ (Fig. 39), on the under side of the brass-casting, U. On the upper surface of the casting is a rib which Avorks in a corresponding slot, in a square brass plate, U", screwed to the under side of the breech- casing. By referring to Fig. 39, the arrangement of the ele- vating and revolving gear Avill be readily understood. 2f4. The movement of the Locks is accomplished bv means of two spiral cams, E, (Fig. 38), placed in the breech-casing and 80 NAVAL ORDNANCE AND GUNNERY. a slot in the casing itself, along the edge of the cams. As the crank, G (Fig. 39), is turned, the rear Ing,^ (Fig. 37), on the lock-case travels in the slot along the spiral cam, forcing the lock forward on the lock-cylinder and carrier. The front end taking against the cartridge in the carrier, pnshes it into the barrel. At the moment that the cartridge has fully entered the barrel the lug, x (Fig. 37), in the firing-pin takes against the cocking-plate and forces back the spring, z. When the lug, a?, on the pin passes the highest point of the cocking-plate, the pin flying forward explodes the cartridge. The rear Ing, having then reached the highest point of the spiral-cam, R, moves straight forward a short distance and then enters the slot of the other cam and is drawn back to its original position. The same occurs as each lock arrives at the cam and slot. 245. Removing the Locks. — The locks are removed and in- serted through an aperture, cut in the cascabel and dia- phragm plates (Figs. 37 and 39). Both these apertures are closed by a brass breech-plng, E (Fig. 37), which is inserted from the rear through the cascabel-plate, C. This plug carries at its front end a sleeve, E', which has a projecting cone,/) on the under side of which is cut a slot. When the plug is in position in the gun, this slot forms a continuation of a groove cut in the rear chamber, and in which a lug formed on tlie rear end of each lock revolves. When the lock is brought into line with the plug, by means of the outside handle, G, which is indicated by an arrow on the hopper, I, and a line on the rear brass barrel- plate, the Ing, y>, on the lock engages in the slot on the arm of the ping, and on the latter being ivithdrawn, the lock follows. The sleeve, E^ is connected to the body of the ping by a pin formed with the ping, and around which it is just free to re- volve without being a close fit. To withdraw the plug, it is first partially rotated so as to bring the lug by which it is locked opposite the aperture, the sleeve still retaining its hold on the lock to be extracted, and being retained against it by a spiral spring, which is interposed between the plug and the sleeve. The lock and sleeve are guided into the aperture in the dia- phragm-plate by a tube, having a slot in its upper side, through which the sleeve, E', of the plug passes, carrying the lock with it. 246. Cocking the Locks is accomplished by means of an inclined spiral cocking-plate, projecting on the inner side of the breech-casing, so that when the lock is moved forward, a luir, a?, formed on the tiring-pin, is arrested by it, the spring of the loclc is gradually contracted, and the firing-pin drawn back into the lock-case. When the lug, x, passes the end of the stationary THE GATLING-GUN. 81 Fm. 41. The cartridges coehing-plate, it is suddenly released, relieving the spring, s, which forces the pin violently forward and explodes the car- tridge. As the cocking-plate is stationary and the lugs, x, re- volve with the locks, tlie cocking-plate acts upon the firing-pins, in the several locks successively, causing the discharge of each barrel, as its lock-lug passes the plate. 217. The Feed-dkum Y (Fig. 41), consists of a metal fram- ing of cylindrical shape, hav- ing any convenient number of divisions or slots (usually sixteen) around its circumfer- ence, radiating from the cen- tre. Each division, Y', con- tains twenty-five cartridges, placed one above the other in a horizontal position, Y" (Fig. 42). A hole in the een- ti’e of the drum fits over a pin, I', on the hopper, I. The cartridges are fed to the carrier, M, below, and thence to the barrels, A. pass to the hopper through an aperture at the bottom of each division of the drum. On the bottom face of the drum and to the left of the hopper is a projecting rib, which fits into the slot, li', on the hopper-plate to steady the drum when firing. On its lower periphery the drum has a series of thumb-lugs, m (Fig. 41), by which it is re- volved. A small brass weight in each division is caused to bear upon and slide down a groove provided for it, so that it follows the cartridges as they descend, and prevents their becoming choked in the divisions. In firing the gun the man at the drum brings one of the thumb-lugs, m, coincident 6 Fig. 43. 82 NAVAL OEDNANCE AND GENNERT. with the rib on the hopper-plate, the one at the crank revolves the barrels and carrier, and the cartridges drop into the hop- per from one division nntil it becomes empty. The operator then reverses the drum one-sixteenth part of its circumference, bringing the next lug over the rib, and at the same time the next division of cartridges over the hopper ; the feed thus con- tinues until the whole number of divisions are emptied, when a full drum replaces the empty one, and the firing continues. A locking arrangement is provided for retaining the drum in posi- tion when not in use. 2d8. To Fill the Feed-drum. — Invert and unlock it, turn the bottom-plate, Y (Fig. 42), until the hole in the plate comes directly over a division of the di-um, then raise the brass weight and fill in the rtirtridges regularly, letting the weight descend slowly until the division is full. Proceed in like manner witli the remaining divisions ; then lock the plate and place the drum upright. 249. The Working of the Gun. — One man places the feed- drum filled with cartridges on the hopper-plate, with the two apertures coinciding ; another, at the firing-crank, revolves it, which, by means of tlie worm-gear, revmlves the main shaft, carrying with it the lock-cylinder, carrier, barrels, and locks. As the carrier revolves the cartridges in the drum drop one by one into the grooves of the carrier. Instantly the lock, by its impingement on the spiral cam in the breech-casing, moves for- ward, pushing the cartridge into the barrel, and when the lug on the firing-pin passes the highest point of the cocking-plate the charge is fired. As soon as this occurs, the lock is drawn back by the sphal cam in the breech-casing, bringing with it the shell of the cartridge, after it has been fired, which is di’opped upon the ground beneath. 250. Thus, when the gun is revolved, the locks in rapid suc- cession move forward to load and fire, and returning extract the cartridge-shells. The whole operation of loading, closing the breech, discharging, and expelling the empty cases is thus con- ducted while the barrels are kept in continuous revolving move- ment. In operating the, gun, firing in succession, there is no accumulation of recoil, and therefore no resighting, or relaying the gun, necessary between each discharge. When once sighted its carriage does not moi'e, except at the will of the operator. The gun can be moved laterally while firing is going on so as to sweep the sector of a chcle of 12°, or more, without moving the trail or changing the -wheels of the carriage. 251. Its locks are made interchangeable, strong, and durable ; but should they get out of order, they can be replaced by new THE GATLIXG-GXJN. 83 ones in a very few moments. The loch mechanism is the only portion liable to derangement, the other parts being protected, or of sufficient strength to withstand all usage incident to the service. 253. The feed-drums are not absolutely necessary, except at close-quarters, and are likely to cause a wasteful expenditure of ammunition; the drums being liable at any time to become deranged and wmrk badly. The crew should therefore be exercised at feeding the gun by hand, in which ease, all that is necessary is for one man, A^ hen the hopper is turned back, to lay the cartridges, one at a time, into the grooves of the carrier. The revolving of the crank loads and lires the gun. 253. When rapid lire is continued, the piece becomes heated, and the barrels are liable to bind and prevent the free working of the gun; recourse is then had to the adjustment-nuts in the front of the barrels. These must be eased up sufficiently to en- able the barrels to revolve freely, care being taken that the crank is fastened to prevent the possibility of the piece being fired while the adjustment is being made. 254:. In firing, the crank must be turned steadily, in a uni- form manner, and not too rapidly ; otherwise the cartridges will jam in the carrier, and thus elfectually stop the fire until they can be removed. The cartridge used is the same as that of the ISTavy Hifle, .5 in., and the arm is efiective to the same distance — about 1,200 yards. 255. In exercising on board ship the locks should be removed to avoid unnecessary snapping of the spring, and the cartridges can then be run through the hopper at Avill, familiarizing the men Avith the use of the arm Avithout Avasting ammunition. 256. It is believed that the “ Gatling ” cannot be substituted for the “IIoAvitzer” in boats, therefore no boat-carriage is pro- vided, the instability of the boat causing the continuous fire (the great feature of the gun) to be extremely scattering, Avhile the shrapnel or canister from its Howitzer is delivered only Avhere the gun points. In smooth Avater it may be used as a boat-gun by removing the wheels, resting the axles on the gunwale, Avith the trail of the carriage under the fonvard thwart. 257. Theseevation. — The Gatling Gun, although an intri- cate piece of mechanism to put into the hands of seamen, is not liable to get out of order in use, or have its parts deranged, un- less tinkered Avith by the quarter-gunner. It is not injured by being Avet in handling, or liable to be clogged with sand or mud, provided it is cleaned and dried before the next firing. 84 NAVAL OEDNANCE AND GUNNERY. 258. The gun should never be taken apart unless absolutely necessaiy, and then, if possible, by a competent mechanic, under the supervision of an oliicer. It should be kept free from mst, dust, and moisture, and oiled frecpiently, using line sperm-oil. When it is possible, before firing, the barrels and can-ier should be wiped and cleaned ; in doing this the crank should be reversed to avoid unnecessary snapping. 259. DlliECTIONS FOE TAEIING THE GuN APAET. 1st. Take out the locks. To do this, turn the breech-plug so that the marks upon it and the cascabel-plates correspond ; then turn the crank until one of the marks on the rear brass barrel- plate is brought in line witli the arrow on the hopper, and then pull out the plug, which will bring out a lock. Ee-insert the plug, and repeat the operation, until all the locks are removed. 2(^. Take off the cascabel-plate, which is screwed to the breech-casing. Zd. Eemove the crank-axle ; first taking off the traversing- screw and worm, which are fastened to the shaft by a screw and a taper-pin through it ; then remove the worm gear. \th. Take out the screws that fasten the casing to the frame. 5^A. Eaise the barrels a very little by means of the assem- hling^est ; then remove the breech-easing. 260. Dieections foe purriNG the Gun togethee. 1st. Put the axis in its place through the plates which hold the barrels, and then put to their places the carrier-block, lock- cylinder, and large rear-nut. The last should be screwed up tight, and have the taper-pin put through the nut and sliaft. 2f?. Place the gun within the frame, and let the front end of the axis rest in tlie hole designated for it, in tlie front of the frame; then adjust the assembling-rest, and, in this position, the breech-casing can be shoved over the lock-cy Linder to its proper place ; then screw the casing to the frame. Zd. Put on the worm-gear, replace the crank-axle, etc., and then prrt on the cascabel-plate. Eevolve the crank to the right or left until one of the marks on the barrel-plate is brought in line with the arrow on the hopper, and then insert a lock, which is shoved to its place by the plug. Eemove the plug, and re- peat the operation until all the locks are in their places. 201. THE AEMAMENT OF SHIPS OF WAE."— The main points to be considered in determining the armaments of ships are : * Extracts from a paper on “ The Armament of our Ships of TTa?\” by Captain W. N. JefEers, U. S. N., in “The Record of the United States Navjd Institute,” Vol. I., 1874. AK3IAMENT OF SHIPS. 85 First. The proportion of the aggregate weight of the guns to the tonnage. Second. To dispose of this weight in such a manner as shall develo]) the greatest power of which it is susceptible. Third. The relation of the battery to the speed of the vessel. 262. I. The relations of weight of battery to tonnage of ship depends upon the aggregate assigned to ordnance by the constructor in distributing his weights ; and the weight of bat- tery Avhich experience shows can be safely and conveniently carried, is from one-third greater to double that allowed on the given displacement. 263. II. Having a ship of a certain tonnage, draft of water, and speed, with so many tons of displacement assigned to ord- nance ; the question is, how to dispose of that weight to the best advantage, distributing it with a due regard to the neces- sary power and range of the guns. 261. In every case our practice is, to assign the smallest number of the heaviest guns to form the weight ; preferring pivot-guns to those in broadside when the deck arrangements will permit, because the former are always more under com- mand than the latter ; and it is thoroughly established that a small number of large pieces will inflict injuries beyond the power of a large number of small ones. The smallest number and heaviest pieces which can be conveniently handled will then form the armament. 265. One of the first elements to be considered is the abil- ity to handle the projectile in the confined quarters of a ship subject to violent motions of rolling and pitching. Only one man can conveniently handle the projectile of a broadside gun, and but two that of a pivot ; and experiment proves that the nine-inch and eleven-inch are the largest shells which can be so handled with ease. 266. Ho effort should be spared to use the heaviest calibre which can be conveniently carried, and any obstacles that are removable ought to be made to give way without scruple. The celerity of fire will not be materially affected, and the su- perior calibre always possesses superior range, accuracy, and power. 267. III. It is absolutely necessary that a ship of war should exercise a full power of offence and defence, Avithin the circle of which she is the centre : next to this, and to this only, in importance is her ability to transfer this power to an- other point. 268. In order that a ship may exercise her full measure of offence, speed has become an indispensable attribute. Without 86 NAVAL ORDNANCE AND GUNNERY. it lier powers are altogether incomplete ; and expenence appe . . to have determined that it is jndieions to sacrilice a large por- tion of the armament in order to procnre great speed at any cost. 269. When a vessel of war encoimters a superior force, speed should he ahle to make her safe, hut the necessary dimi- nution of offensive power should not be so great as to disable a lirst-class steamer from watching any vessel of her own class, of inferior speed, but provided with a proper armament. 270. Our vessels of war sliould have equal speed with those of other nations, for it is only by this equality that they can select and retain the distances preferred. If, however, our ship is inferior in speed, then the choice of distance is with the enemy, who is supposed to prefer close quarters ; but if our ship is properly armed he can only reach this position after pass- ing through the deliberate fire of powerful guns. 271. Kind of Gun. — The armament of our ships of war con- sists mainly of smooth-bore guns. These cannot compete with rifle-guns, except at short ranges, their eihciency depending on high velocities, which the resistance of the air greatly diminishes ; besides, spherical projectiles are deficient in weight, and their form is not favorable for penetration. 272. With wooden shijDS, the mere lodgment of a shell, in the side, before its explosion, is sufficient to inflict serious injury ; but against armored ships complete perforation is essential. Since the general introduction of armored vessels, the conditions of war- fare hav'e been altered, and the subject of penetration has be- come of paramount importance. This necessitates the intro- duction of ride-cannon as the entire armament of our ships. 273. The principal advantage of ride-cannon consists in their greater penetration, due to the concentration of effect on a smaller and better form of surface ; next, in greater explo- sive contents for the same weight; then range, and lastly, accuracy. 271. It is comparatively easy to obtain accuracy to such au extent as is sufficient for the purposes of naval warfare. Under the ordinary circumstances of a naval action, the probability of striking an enemy’s ship is dependent far more on an accurate knowledge of the distance, on the steadiness of the ship carry- ing tlie gun, and the skill of the man who dres it, than on the qualities of the gun itself. 275. Great extent of range is one of the especial merits claimed for rided ordnance. But the instances in which a great range would be valuable in naval war are of such rare and ex- ceptional occurrence, that it is not an important requirement in a good naval gun. THEORY OF GUN CONSTRUCTION. 8T Section II — Theory of Oun Construction! 276. THE KIHDS OF STRAIHUPOH A GUH.— There are : 1st. A tangential strain., tending to split the gun open lon- gitudinally, and similar in its action to the force which bnrsts the hoops of a barrel. 2c?. A longitudinal strain, tending to pull the gnn apart in the direction of its length. This tendency is a maxiinnm at the bottom of the bore, and diminishes to zero at the muzzle. 2>d. A strain of compression, exerted from the axis outward, tending to crush the truncated wedges of which a unit of length of the gun may be supposed to consist, and to diminish the thickness of the metal to which it is applied. 1th. A transverse strain, tending to break transversely the staves of which the gun may be supposed to consist, and similar in its action to the force which breaks the staves of a barrel. 277. Tangential Strain. — Barlow shows that the strain, produced on any cylinder by the action of a central force, diminishes as the square of the distance from the centre increases. The demonstration of this law is based upon the hypothesis that the area of the cross section of the cylinder to which the force is applied remains the same before and during the application of the central force. Assuming this to be true, call A the area of the cross section of the gun. In Fig. 43, let r — the radius of the bore, li — the radius of the exterior, h = the increase of the internal radius, B — the increase of the exterior radius. Evidently, TtE^ — n! = 7t{ir — = A ( 1 ) or IP — ! — ^ (2) * Compiled by Lieutenant-Commander C. F. Goodrich, United States Navy. ’ 88 NAVAL ORDNANCE AND GUNNERY. Differentiating eq. (2), bearing in mind that A and tt are constants, gives ’iltdR — %'dr = o (3) Hence RdR — rdr t4) Multiplying and dividing the first member of eq. (4) by R, and the second member by r, and substituting for dR and dr tlieir values B and h, gives R r ^ ' whence the proportion -:^ = Rd:r^ (a) 278. But the strain produced on any two pieces of the same material will be proportional to the increase in length divided by the original length of each respectively — the absolute strain, for a given increase of length, depending upon the coefficient of elasticity of the material strained. Hence, if ^ be the strain on the exterior, then - is that on the interior. It will therefore be seen from the proportion (a) that the strain diminishes as the square of the distance from the centre increases. 279. To find the whole resistance of the gun-cylinder to the tangential strain. Let Fig. 44 represent a section of a homogeneous gun-eyhn- der. Take C, the centre of the bore, as the origin, and two lines at right angles to each other as the co-ordinate axes. Denote CA, the radius of the bore, by r, and CB, the exter- nal radius, by R. Me may represent the de- gree of expansion of the metal at any point in the line AB. caused by an explosion at C, bj an ordinate, erected at the given point proportional in length to the number of pounds’ strain at that point, as AH ; similarly we may represent a compres- sion by a negative ordinate, as AM. 280. Erecting ordinates in this manner at every point in the THEORY OF GUH CONSTRUCTION. 89 line AB, and draAving a line tlirougli their extremities, Ave have the curve HL. From BarloAv’s LaAv Ave have for the equation to this curve y = ,( 6 ) Avhere c is a constant depending upon the force exerted. To obtain the form of this curve Avhen the expansion is at its limit, i.e., AA’hen the tenacity of the metal is just sufficient to overcome the strain at A, Ave have for the co-ordinates of the point X — r, y = S, where 8 denotes the maximum strain in pounds. Substituting these values of x and y in eq. (6), Ave find > 5=4 G = 88^ and the equation to the curve is therefore 88 y = ^ (b) 281. Taking 8 = 30,000 pounds, r = 3 inches, Ave find for a? = 3 in., y = 30,000. a? = 4 in., y = 16,875. £c = 5 in., y = 10,800. X — Q in., y — 7,500. a? = 7 in., y = 5,510. Thus the resistance offered by each part of the cylinder diminishes very rapidly as the distance from the axis increases. 282. As the ordinate at each point of the line AB measures the resistance of the gun at that point, the sum of all the ordi- nates, or the area of the curve AHLB, represents the entire tenacity of the gun-cylinder. To find this area Ave have ^ =fydx (7) Substituting the value of y from eq. (b), 88 «/ 00 Intewratino: betAveen the limits H and r, O O ' ( 8 ) “1 -41 L Xjr 1 or A = 8r R — r ~~W' (0) 90 NAVAL OEDNANCE AND GUNNEEV. 283. Takins’ tlie same numerical values of S and r as kefore. giving different values of ^ — the gun), Jo — r = 1 inch, J2 — r — 2 inches, Jo — r = S inches, Jo — r = 4: inches, Ji — r = 5 inches, Ji — r = Q inches. (the thickness of the wall of A = 22,500 lbs. A = 36,000 lbs. A = 45,000 lbs. A = 51,429 lbs. A = 56,250 lbs. A - 60,000 lbs. If we integrate between oc and r, or, what is the same thing, make the wall of the gun infinitely thick, A = Sr (9) 284. ISTow it may be shown that the whole force developed by an explosion, to burst a gun tangentially, is where is the pressure of the gas per sqiiare inch, and r the radius of the bore. But we see from eq. (9) that the greatest possible resistance of the cylinder is Sr ; therefore when an explosion takes place, and p is greater than S, the cylinder must give way. That is, thickness of metal, however great, in a homogeneous! y constructed gun-cylinder, can withstand an expanding force greater than the absolute tenacity of a bar of the same metaV' 285. To find the tohole force exerted oy an explosion in a cylinder to rend it longitudinally. Let Fig. 45 represent a section of a cylinder, and let it be required to find the force ex- erted by an expanding gas to rend the cylinder along the line AB. Let OA = r, the interior radius of the cylin- der, and p denote the force the gas exerts upon a unit of surface. At any point, as P, the gas acts in the line OP. and the force may be resolved into tlie components Py and Tx, respectively perpendicu- lar and parallel to the line AB. The sum of all the forces acting perpendicularly to AB is the force requh’ed. Let 0 = the angle POA, then Py = p sin d. The element of surface is rdd. The required force F = f pr sbi Odd — pr f sin Odd . . (10) THEORY OF GUN CONSTRUCTION. 91 Taking tlie integral between and o, 2i F = pr (d) At the limit of endurance the rupturing effort will be equal to the whole resistance offered. ^ R — r pr — hr — — ( 11 ) or ^ = ^ It (e) /p Should p become greater than 8 ^ 5 — , the gun will burst. J-i As a particular case, let the wall of the gun be one calibre in thickness, i.e., R = S?*, then = (f) Eupture will hence ensue in this gun when the pressure per square inch exceeds two-thirds of the tensile strength per square inch of the metal of which it is constructed. 28G. Longitudinal Stkain. — The tendency of this strain is to blow the breech off. Expressions for the rupturing effort of tliis strain, and the resistance 01 the gun to it, can be readily found based upon the assumption, in itself highly probable, that the law of diminution of strain from the interior outward will be the same for any central section of the sphere of which the breech may be sup- posed to consist as for any cross section of the gun. 287. To find the Imigitudinal rupturing effort . — If ^ be the pressure per square inch at the bottom of the bore, the whole rupturing effort in the direction of the axis of the gun will be p multiplied by the number of square inches in the area of the bore, or E = rcr'^P (g) 288. To find the resistance of the gun to the longitudinal rupturing effort . — This will evidently be the sum of the resist- ances to longitudinal separation of the rings of metal composing the cross section of the gun, at the juncture of the breech and cylinder. Let r be the radius of the bore. R be the radius of the exterior of the gun. 8 be the tensile strength of the metal per square inch. 92 NAVAL ORDNANCE AND GITNNERY. Let X be the radius of any ring. dx be its breadth. We have already seen that the resistance to an internal ex- plosive force at any point of the wall of the gun is S Hence, that of a ring whose radins is x, and breadth dx, will be S — X ^TTxdx, or 27tr^S — . The whole resistance of the wall X‘ X of the gun will be found by integrating this expression between the Innits and : J %Ttr^ = 27 ir^ S iWj?. Log. R — Nap. Log. r J . . (12) = 2/Tr' S Nap. Log. R T (h) At the limit of endurance the whole resistance will be equal to the whole rupturing effort, or Ttr'^p =. 27tr^ S Nap. Log. ^ (13) hence, p — Nap. Log. ^ (i) 289. As a special case, assume, as before, that the wall of the gun is a calibre in thickness, or R — Zr. Expression (i) now becomes p = 2S Nap. Log. Z — 28 X 1.09S6 (11) or, in round numbers, p =■ 28 (j) Comparing this with eq. (f), we see that this gun would be three times as strong longitudinally as tangentially — if the bm-st- ing-effort were resisted by its tangential strength alone. The tangential and longitudinal strains are in directions at right angles to each other, and hence, probably, neither affects the ability of the metal to resist the other — wliile the compres- sibility of the metal tends to diminish its capacity to resist either. 290. Ceushixg-foece. — T his force diminishes from the bore outward, while the area of resistance increases. The effect of this upon a compressible truncated wedge would be to change its form from that of Fig. 16 to that of Fig. 17. And the appearance of a cross section of the gun after rupture would be that of Fig. 18. If the metal were in- THEORY OF GUFT CONSTRUCTION. 93 compressible, the appearance of a rupture would be that of Fig. bore would result from the crushing of the metal ; and any enlargement caused by the action of a central force would be ac- companied by an equal enlarge- ment of the exterior diameter of the gun ; and hence the strain upon the metal at the inner and outer surface of the gun would be inversely as the radii of those as their squares (as in the case of ( cross section of the gun after , and no enlargement of the Fig. 46. Fig. 47. surfaces instead of inversely :ompressible metal). 291. To find an expression for the effect of a crushingfiorce. Lety> = the pressure per square inch of gas on the siu’face of the bore, G = the compression per inch in length, due to y>, of a prism one square inch in area of cross section, r — the radius of the bore of the gun, X = the radius of one of the thin cylinders which com- pose the gun. The elementary compression of any prism taken in the metal of the gun will be = cdx. If the pressure were uni- form (or G constant) throughout the length of this prism, the integral of this expression, or cx^ would give the entire compres- sion or increase in the radius of the bore. But, in a gun, the pressure per square inch against the interior of each consecutive, elementary cylinder of which we may suppose it to consist, will vary according to some law which must lirst be determined. Suppose a thin, hollow cylinder, and let a = the tangential resistance per imit of length of one side of this cylinder, r' = its interior radius, p' = the pressure per square inch against its interior siu’face winch would just produce rupture. 94 NAVAL ORDNANCE AND GUNNERY. Formula (cl), already obtained for tbe bursting-effort of a central force, gives j)'r' — a, or 2 ?' = ^ (15) Or, tbe pressure per square inch against the interior of a hol- low cylinder necessary to develop a constant amount of tangen- tial resistance in its sides, varies inversely as its interior radius. It has been shown that, at the limit of endurance. P - S li — T ~~IT' The tangential resistance developed in that cylinder of the gun whose interior radius is x will be equal to the total tangen- tial resistance of the wall of the gun less that developed in the cylinder whose exterior radius is a?, or by eq. (c). Sr VR-r V R Hence the pressure per square inch against the interior sur- face of the elementary cylinder, whose interior radius is cr, will be 292. Supposing the compression per inch in length of the same metal to be directly proportional to tbe pressure per square inch, we shall have p \ G — Sr r R — r 1 X : c / where c' is the compression per inch of length due to the force p acting at the distance x from the origin. Solving the propor- tion with reference to c'. , _ Scr r R — r 1 ^ 2) \- R X ,(16) The expression for the elementary compression now becomes du — c'dx. Substituting the value of o' from eq. (16), du = Scr r — r 1 2) R X Integrating between the limits R and r, ( 1 ‘) THEORY OF GUN CONSTRUCTION. 95 Scr r T u .(k) As before, in a special case, assume the gun to be one cali- bre in thickness, or R = 3r, ,(18) w ^ [i ^09- i + I ] = Log. 3] (19) Jr But the ITaperian logarithm of 3 is 1.0986. as 1, cr ¥ Assuming this ( 1 ) 293. Now supposing^ = 8., or that the pressure per srpiare iuch on the bore of the gun is ocpial to the tensile strength of cv the metal, we have u = -g , or, the increase in radius of the bore, due to the compression of the metal, in a gun, one calibre in thickness is equal to one-third of the total compression which a prism, whose height equals the radius of the bore would undergo under a pressure per square inch equal to that against the bore of tlie gun. 29d. Now if we suppose a given pressm’eto be exerted upon the surface of the bore of a gun, while its exterior diameter is prevented from undergoing any increment, the total eularg- ment of the bore and the consequent extension of the metal will be wholly due to comj)ression, and all the effects of compres- sion will be produced as if the exterior of the gun were uncon- strained. 295. If we now suppose the exterior restraint removed, the interior and exterior diameters would undergo precisely equal increments. Or the gun would expand in the same manner as one of which the metal is incompressible, the metal having al- ready undergone all the compression which this pressure could produce, and the extension of the metal at the two surfaces of the gun, which would take place after the removal of the exte- rior restraint, would therefore be inversely as their radii. 296. It has just been shown that in a gun one calibre thick the total enlargement of the bore due to compression is the total extension of the surface of the bore due to this enlarge- 96 NAVAL ORDNANCE AND GUNNERY. ment is 27zr-, and tlie extension per inch of the same surface is o 0 2 7T r S c 2 7tr ~‘6' If a he the total extension per inch of which the metal is susceptible, then a—x will he the extension per inch which the O surface of the bore underwent after the removal of the exterior restraint, and the extension per inch of the exterior surface is 29Y. To exemplify : a cylinder was taken the total extension per inch of which was .00303, the compression per inch .OOTil, one-third of which is .00117 ; and .00303 — .00147 =.00156, one- third of which is .00052, the extension per inch of the exterior of a gun one calibre thick, made of this metal, at the moment of interior rupture. But the strain necessary to produce an extension of .00054 was found to be 11,000 poimds ; hence the exterior of the gun would be under a strain of between 10,000 and 11,000 pounds per square inch at the moment of interior rupture ; while, if the metal were perfectly incompressible, it would, at the same mo- ment, be under a strain of 18,000 pounds. 'Z* 0 298. The expression -x was derived from the hypothesis that the compression per inch of east-iron is directly proportional to the pressure. Experiment shows the compression of this metal to increase in a higher ratio, so that the effects of compressibility will be even greater than those just determined. 299. This example suffices to establish the importance attach- ing to the property of compressibility in gun metal, its action being to prevent the full development of both the transverse and the tangential resistances, and to that degree it is believed (in guns of large calibre, and consequently of great pressure of gas) as to cause internal longitudinal rupture before the trans- verse resistance is fully developed, even for the shortest practi- cable length of surface pressed. 300. Transverse Strain. — In estimating the resistance which a gun can offer to a tendency to transverse ruptime, it will THEORY OF GUN CONSTRUCTION. 97 be more simple to regard it as composed of staves, firmly se- cm'ed at their ends, the rear ends being supposed to be secured to a central cylinder ; and, in this case, it will be only necessary to consider a single stave, as all others of equal width and length would be subjected to similar and equal strain. 301. Let us, therefore, consider the action upon a single stave, whose breadth is one inch. If the gun be one calibre in thickness, the exterior breadth Avill be three inches. We shall be something below the actual resistance which the stave can offer, if we consider it as of rectan- gular section of two inches in breadth ; this is ap- parent from inspection of Fig. 50, Let the stave a be acted upon by the pressure of gas along its inner surface, and suppose the pressure to be applied between the points h and V. Now this stave is secured at both ends, and the pie. 50 . rupturing-force equally distributed along its length between the points of support. It suffers a tendency to rupture at three points, as shown in Fig. 51 by the lines be, o,"' c', b' c". 302. The formula for the resistance which a bar thus strained can offer is in which w is the breaking-weight distributed equally along the bar, 5 the breadth of the bar, d its depth, I its length, and S' the weight required to break a bar of the same material one inch square, firmly secured at one end, when applied at one inch from the point of support. If p be the pressure of gas per square inch, the whole pres- sure on the stave be^ and the tendency torujpture (i. e., the 7 98 NAVAL OEDNANCE AND GUNNERY. ratio of tlie bursting-effort to the resistance) will be represented 7 7 . pi pr L It thus appears that tbe tendency to transverse ruptui’e in- creases as tbe squ.are of the length of the bore underpressure, and that the resistance offered to this kind of strain increases as the square of the thickness of metal. 303. The resistance offered by the transverse strength of the staves acts in concert with the tangential resistance, and when the length of the bore under pressure is such that the increase of its diameter due to the bending of the staves that due to the compression of the metal at the moment of rupture, shall be equal to that which it would attain at the same moment from the action of the tangential strain alone, then will the resistance to rnptiu’e be equal to the sum of the transverse and tangential resistances. 301. This can only occur for one particular length of surface pressed and, for any greater length, the staves would require to be bent out beyond the breaking diameter for the tangential resistance before reaching their breaking ti-ansverse strain ; and the transverse resistance would only be equal to the pressure necessary to bend the staves out to the position of tangential rup- ture, mmifsthe compression of the metal. Thus the tangential resistance would be overcome and the gun split longitudinally before the transverse resistance would be brought fully into action 305. The effect of the crushing force on compressible metal is to prevent the development of the transverse resistance in the same manner as it did that of the tangential resistance : to di- minish the amoimt of aid Avhich the transverse resistance can bring to the tangential for any greater length of bore. 306. When the length of surface pressed becomes less than that which develops the joint action of both resistances, the diameter due to transverse rupture will be less than that due to tangential ruj)ture, and transverse rupture would first ensue; or, what is more probable, in guns of any considerable thick- ness of metal, rupture Avill occur by splitting through the breech, or by forcing the rear ends of the staves outward, caus- ing rupture along the lines be and de (Fig. 51). 307. Eecm-ring to the expression for the tendency to trans- verse ruptm’e, pV THEORY OF GUN CONSTRUCTION, 99 and supposing tlie transverse strength of iron to he one-fourth the tensile or S' /S, and substituting for S' this value, vre have pP SSbd^' Then supposing 5 = 2 in., c? = tendency to transverse rupture 10 2p in., Z = 20 in., we have the — — ^ or the transverse strength o o alone, supposing the tensile strength to he 30,000 Ihs. per square inch, would resist a pressure of 45,000 lbs. per square inch for two calibres in length of a 10-inch gun, if it could be brought fully into action. This, for reasons already given, cannot, how- ever, be done; but the transverse is doubtless a powerful auxiliary to the tangential resistance for short lengths of bore and where the pressure is greatest. 308. The Tendencies to Rupture in Guns of One Calibre IN Thickness, each considered as independent of all others, will be as follows, viz. : — Tangential or rupture will ensue when 3 > 2 /S’. Longitudinal , I 2i o or rupture will ensue when p S. Trcmsverse — 3 b or rupture will ensue when 2 y? > 3 /S. 309. Total Burstino- Tendency, — As already indicated, the bursting tendency is the ratio of the bursting effort to the total resistance which the gun can offer. The bursting effort against one side of the gun is, from what has already been shown, eq. (d), the product of the pressure per square iucb multiplied by the radius of the bore and the length of the bore to which pressure is applied. Let R be the exterior radius of the gun. r “ radius of the bore. L “ length of the . bore to which pressure is applied. I “ length of the surface pressed which fully develops both transverse and tangential resistance. pressure per square inch. V ' 100 NAVAL ORDNANCE AND GUNNERY. Let S be tbe tensile strength of the metal. Then p r L is the bursting effort. The whole tangential resistance will be equal to that for an element of the gun cylinder one unit in length multiplied by the length of surface pressed, or, from eq. (c). LSr E — r ~E~' The foramla for the transverse resistance of a bar of rect- angular cross section is (Art. 302) 12 S' h(P 310. By mechanics it is known that the resistances which bars of the same material can offer when the strain is equally distributed along their lengths, and the bars tent to their treah- ing deflection, are to each other directly as the fourth powers of their length. But in the case of the staves forming a gun cylinder, except for short distances, tangential will ensue before transverse rupture. In order to determine, therefore, the transverse resistance, calling x the transverse resistance due to that length, the following proportion may be instituted : 12 S’ tcP L whence : x = r 12 hcV V ^=~7T— ( 20 ) S' may be taken as one-fourth of the tensile strength, or - ; h is the mean breadth of the stave, or — , when the inner 2 r breadth is one unit ; d is the thickness of the stave, or E — r. Substituting these values, the whole transverse resistance of a bar thus strained whose length is L, is 3 + {E-rYV 2/- JJ The total bursting tendency is, hence, C= — - LSr E-r 2> S{E^r){E -iflr E ^rE 2y? r’ E L 2 L Sr' {E -r)-\-3 SE {E -f r) {E - THEORY OE GUET COXSTRUCTIOX. 101 '^pr^ R L S{R — r)^r- L ^ R {R -{- r) {R — r)^,J..(m) 311. DETEKMIIfATION OF THE ExTEEIOE MoDEL OF GuNS. In order that the gun may be equally strong throughout, the bursting tendency must be the same at all points of the bore ; or, in other words, for all values of Z, G, in the foregoing paragraph, must be constant. Equation (m) then becomes that of a portion of the curve of intersection of one side of the gun by a plane con- taining the axis of the bore. In this formula, y? will obviously be a function of Z; and if we suppose the maximum pressure to be exerted upon a length l,oi the bore, and the pressure from the forward extremity of V to the muzzle to be inversely as the volume occupied by the gas (and hence, in this case, as the length of the bore thus occupied), then the pressure at any distance Z from the bottom of the bore should be expressed by p'V L {p' being the maximum pressiu'e), and the foregoing forimda would become (7=2 P'tH' 8 R (7?— r) j^2 G Z -f- 3 i? (i? -f- 7*) (Z — J • •(if) Now since 2 — is constant, the other factor is constant also, so that this last expression need alone be regarded in de- termining the relative values of R corresponding to the as- sumed values of Z. 312. From the great excess of the transverse over the tan- § ential resistance for the smaller values of Z, and from the rapid iminution of the transverse resistance as Z increases, the value of this expression, with a constant value of Z, will first in- crease to a maximum and then decrease as Z increases. In order, therefore, to determine the proper exterior model of a gun, we first decide upon the volume of the charge ; and, from the qiiality of the powder, and the form and weight of the projectile, determine the length of the bore subjected to maxi- mimi pi’essure and the value of this pressure. 313. We then establish the relation betwen V and Z, or the law of variation of pressure, and then assume I equal to or a little less than two calibres, since experiment has shown the 102 NAVAL ORDNANCE AND GUNNERY. transverse resistance to be fuby developed for about that length of surface pressed. Then take R equal to or a little less than the greatest exte- rior radius of the gun and determine the value of L that renders R {R - + 3i? (7? + r) (i? - r) ^ J (o) a maximum. Then if R have been assumed equal to the great- est exterior radius, the gun will be cylindrical from this point back to the curve of the breech ; and the curve of that portion forward of this point will be determined by assuming values for L and determining for R such corresponding values as will cause expression (o) to remain constant and equal to its max- imum. 314. Illtjsteatiox. — On account of the influence of com- pression in preventing the development of the full strength of the material, only one-third of the theoretical transverse resist- ance was used in computing the exterior radii of the fifteen- inch gun, and the pressure was assumed to vary not as L but as V L, The formula used was 2y?r^ R v/x c = X p rn S {R- r)V2r"-L -f R^R -f r){R - (i?) The value of R used in determining the value of L which rendered the bursting tendency a maximum was 22.5 inches. The outer and extreme inner dotted lines in Fig. 52 give the exterior form and proportions and the diameter of the bore of the gun as cast. The curved dotted lines give the form and proportions of a gun of the same bore and maximum exterior diameter computed on the hypothesis that the pressure of the gas is inversely as the space behind the projectile (or p varies inversely as L). The middle dotted lines give the form THEORY OF GUY COYSTRUCTIOY. 103 and proportions of a gun of tlie same diameter of bore and maximum exterior diameter on the hypothesis that the pressure is inversely as the square root of the space behind the projectile, (or ]) varies inversely as The full lines show the form and proportions of this gun as finished. 315. It will be observed that this gun is heavier in the chase than the hypothesis would make it. This was done purposely, for the reason that it was intended to use charges of such char- acter as would produce a more uniform pressm’e in the chase of a gun, for a given maximum pressure, than is obtained by the use of ordinary powder. , 316. It should be here remarked that even for guns in which a quick powder is to be used, the lines due to the law that the pressm’e is inversely as L should not be strictly adhered to, in that part where the most rapid diminution of exterior diameter occurs ; for the reason that, in so doing, the front ends of the staves for those lengths of bore subjected to the greatest press- ure would be deprived of their proper support and the trans- verse resistance would be greatly diminished just where it is most needed, and where its value is gi’eatest in a properly mod- elled gun. The beginning of the taper should be, therefore, say half a calibre farther forward and the taper less rapid than the loss of pressure in this part of the gun would make it. 317. Experiment has not yet satisfactorily established the law of variation in pressure due to the ordinarj’ cannon powder. But it is thought that no powder is fit for use in guns of large calibre that will not so far approximate to uniformity of press- ure as to conform to the law that the pressm’e is inversely as VT> 318. PREPOl^DEIlAlSrCE. — Defistitioys. — The moment of a solid with reference to a plane is equal to the product of the weight of the solid multiplied by the pei’pendicular distance of its centre of gravity from the plane. If moments tending to produce rotation with the hands of a watch are considered positive, evidently those tending to pro- duce rotation against the hands of a watch are 'negative. The preponderance of a gun is the moment of the weight of the gun about the axis of the trunnions divided by the distance between the axis of the trunnions and the centre of the elevat- ing-screw-hole. It is the pressure in pounds on the screw when the gun is level. 319. To DETEEinsTE THE Peepondeeance. — It is thus seen that the weight of the gun and its moment about the axis of the trunnions must be determined. 104 NAVAL OKDNANCE AND GUNNEET. As tlie measurements in guns are made from the base-ring, it will be convenient to take its plane for tbe plane of reference. Having obtained tbe moment of tbe weight of tbe gu7i with ref- erence to this plane, to deduce that about tbe axis of tbe trun- nions involves but a simple transformation. The gun being assmned homogeneous, the weights of its parts are proportional to their volumes. Tlie latter can there- fore be used in tbe calculation, and only changed into weights at the last step. In the accompanying figure (Ho. 53), let A, B, C, and D be the positions of the elevating-screw-hole, the plane of the base-ring, the centre of gravity of the gun, and the axis of the trunnions respectively ; P, the preponderance acting at the ele- vating-screw-hole, and W, the weight of the gun acting at the centre of gravity. By the principle of the lever, the moments of these forces must be equal ; or P X AD = "W X CD Letting AB = h, BD = a, and BC=a? P X (a + &) — TV X {a — x), . • . P TVa — Wa?. Since TV ; by substitution, Ya — \x P = a -[-h -d,. .(a) TVhere Y is the volume of the gun in cubic inches. Yx, the moment of the volume of the gun with refer- ence to the plane of the base-ring. a, the distance of the axis of the trunnions from the plane of the base-ring. THEORY OP GUY CONSTRUCTIOY. 105 5, tlie distance of the centre of tlie elevating-screw- hole from the plane of the base-ring. d, the weight of a cubic inch of the gnn-metah 320. The volume of the gan is obviously the sum of the volumes of the parts of the gun, regarded as solid, diminished by the sum of the volumes of all its cavities. From Mechanics, it is known that the moment of a solid with reference to a plane is equal to the algebraical sum of the moments' of its parts Avith reference to the same plane. In applying this principle to the case of preponderance, the following smnmary may he taken as a guide ; subject, of course, to such modification as the form of the particular gun considered necessitates. The portion of the gun forward of the base-ring is divided into parts whose volumes and moments can be computed, the gun being considered solid. Generally speaking, the gun may be divided into a cylinder, a solid of revolution having an odd number of equidistant sections, and therefore coming under “ Simpson’s Rule,” and one or more frustums of a cone. These moments and those of the trunnion and rim-bases are expressed and marked 'positive. The moments of the bore and chamber are expressed and marked negative. In rear of the base-ring are the breech and cascabel, whose moments are expressed and marked negative. Should there be any cavities here Avhose moments need be considered, these are expressed and positive. This distinction of signs flows from the definition of positive and negative moments. Since Yx = sum of the moments, sum of the moments . ^ sum of the volumes 321. The formula is Avritten in this manner merely to saAm space. The division indicated in the second member is not per- formed, as the terms of the fraction, and not its value., are sought. The moments are collected and placed in the numerator with their appropriate signs ; the denominator being similarly made up of tlie Amlumes. Factors common to the two tenns are then taken out, and written before the algebraical sum of the residting quotients — and, in turn, such of these quotients as contain common factors are combined into one. By thoroughly carrying out the princi- lOG NAVAL ORDNANCE AND GUNNERY. pie of factoring and combination, much time and labor may be saved in comj)nting. The indicated additions in the numerator and denominator are performed, and the results used in the expression for the preponderance. It must be borne in mind that we have assumed the metal to be homogeneous, though in practice, the breech is more dense than the chase, owing to the mode of casting ; hence, the pre- ponderance, as calculated, is always somewhat less than in reality. This excess of weight, in rear of the trunnions, is reduced to a minimum to allow the breech to be easily elevated or depressed. It is practically impossible to place the trunnions so that there shall be no preponderance ; nor has it been deemed advisable to dispense with it entirely in ISTavy guns, as the weight of the projectile in loading would depress the muzzle, and even when home, the breech would not readily follow down the screw for elevation. Example. 322. The form and dimensions of a XY-inch gun being given in the accompanying diagram (Fig. 51) and table, to com- pute its preponderance. Dimensions. Weight in Pounds. Lexgtii rx rxcHES of AC AD AE AF AG AE AN AT AU AL AM AO AP 42,000 25 35 37.5 45 55 65 75 85 95 14G 24 .3 31 THEORY OF GUN CONSTRUCTION. 107 Diameter^ in inches, at r A C D F G H K T U L 0 P 48 48 47.8 45 39.8 36.2 33.2 30.8 29.0 21.0 12.0 12.0 Trunnions. Bore and Chamber. Lengtli. Span of Rim-bases. • Diameter at Length of Diameter at QR QS Q R ac ab b c 5.5 48 12 12 146 15 15 15 Taking tlie moments of the parts of the gnn with reference to the plane of the base-ring, due regard being had to the signs, gives ecpiation ( 1 ) [from formula (b)]. 323. a. Volume of cylinder = nrh = tt X X 35. Its centre of gravity is distant or 17.5 from its base. Its moment, therefore, is x 24* X 17.5 X35. 324. b. By Simpson’s Rule, the moment of the solid DY with reference to the plane of its first section is equal to d -f 44 % -f 2^3*3 + Vh^x, + Th,x^ + Vh^e^ + h,x^, and its volume is equal to + 4/q -[- 2/^3 -[- 4A^ -(- 2 A 3 -}- 4Aj -|- hi), the A’s being the areas of the sections, the a?’s their distances respectively from the first section, and d, the common interval. Substituting the numerical values of these quantities, the expres- sion for the moment becomes -V"-^(23.9* X 0 -f 4 X 22.5* X 10 + 2 X 19.9* x 20 + 4 X 18.1* X 30 + 2 X 16.6* X 40 + 4 X 15.4* X 50 + 14.5* X 60), and that for the volume 108 NAVAL ORDNANCE AND GUNNERY. i3f-<23.9" + 4 X 22.5“+ 2 X 19.9“ + 4 X 18.1“+ 2 X 1C.6“ + 4 X 15.4“ + 14.5“), which reduce to -+7T x 157,495.4 and -+/T X 6,408.7. Dividing the moment by the volume gives the distance of the centre of gi-avity of the solid from the first section, equal to 24.58. Hence tlie moment of the solid with reference to the j)lane of the base-ring is -+;r X 6,408.7(35 + 24.58) == KJ>-7t X 6,408.7 X 59.58. 325. c. Volume of a frustrum = + Rr + r“), and its centre of gravity is distant from its larger base h ^“ + 2^r+ 3r“ 4 + /tV + ?'“ ’ where A is the altitude of the frustrum, R and t the radii of the larger and smaller bases respectively; hence the moment of the frustrum with reference to the base-ring is equal to I X 51(14.5“ + 14.5 X 10.5 + 10.5“) X (o5 + + X 14.5“ + 2 X 14.5 X 10.5 + 3 X 10.5 14.5“ + 14.5 X 10.5 + 10.5“ 17/T X 55,691.3, and ^ts volume 177t x 472.7. 526. d. The trunnions are cylinders whose volumes are 7T X X A = 7T X 6“ X 5.5, and their centres of gravity are distant from the base-ring 37.5. Their moment is 2/T X 6“ X 5.5 X 37.5. 327. e. The rim-bases are sections of cylinders by cones. Tlie expressions for tlieir volumes and the positions of their cen- tres of gravity are integrals of such complicated forms, that, in practice, the rim-bases are taken as'cylinders; on account of their small volume and their proximity to the centre of gravity of the gun, the error introduced through this assumption is so small as to 1)0 inappreciable. Volume of each rim-base = X 7.5“ X .75. Moment of both rim-bases ~ tt x 7.5“ X -75 X 37.5. 328. + The breech is a hemisphere whose volume h and moment with reference to the plane of the base is |-r x d X or X 24“ == 2r X 2-4“ X 8, and -|r X 24“ X |- X 24 — Ir X 24“ X 8 X 9, respectively. 329. g. The cascabel is taken as a cylinder whose height is THEORY OF GUX CONSTRUCTION. 109 T, and its radius 5. Its volume^ therefore, is tt X 5“ X I, and its moment tt x 5^ X 1(2-1 3.5) = X 5’ X I X 27.5. 330. h. The metal of the juncture of the cascahel with the hreech may he assumed, in practice, to compensate that taken from the screw-hole ; both are neglected. 331. {. The hore is a cylinder whose height is 131, its radius 7.5. Its volume, therefore, is tt x 7.5^ X 131, and its moment 7t X 7.5^ X 131(15 G5.5) =: ;r X 7.5^ X 80.5 X 131. 332. j. The chamber is taken as a paraboloid of revolution whose height is 15, and radius 7.5. Its volume, being half that of the circumscribing cylinder, is 7 t 7.5’“ X 7.5. Its centre of gravity is distant its height from the vertex. Its moment, therefore, is tt x 7.5''‘ X 7.5 X 10. 333. Substituting these numerical expressions in equation (1) gives equEttion (2). (See page 110 for equations.) 331. To Determine the Position of the Trunnions. — In designing a gun, the preponderance is decided upon beforehand, thus giving rise to the inverse problem, “ For a desired pre- ponderance, where should the trunnions be placed ? ” The weights and moments of the trunnions and rim-bases are neglected, as being at the axis about wliich the gun rotates, these cannot perceptilny affect the result. The remaining vol- umes and moments are obtained as before. Eeferring to equation (a) (Art. 319), P is now known, and BD = a becomes the unknown cpiantity to be determined. Solving this equation with reference to a gives equation (c). Ph V xd ^ Yd-P ' (e) For convenience P may be assumed equal to Qd. With this substitution and the cancelling of d in numerator and denominator _ Qb Vx V-Q (d) Example. 335. In the XV-inch gun already computed, where should the trunnions be placed that the gun may have a preponderance of 1,781 lbs. ? Here Q = ^ 6,861.51, h = 28, Vx = 5,980,271.2, and V = 162,087.7. 110 NAVAL ORDNANCE AND GUNNERY. 2'^ + I ci;?o + + II 'd PIS ol I + S II wo wow ^ o II II II II w So L' O o , I o w II II II w o' j * j a II E » r; GENERAL DESCRIPTION OF ORDNANCE. Ill Substituting these numerical values in e'^^uation (d), and solving, _ 6861.54x 28 + 5980271.2 _ 6172394.3 _ on 162087.7 — 6861.54 “ 155226.2 ~ ' Hence the axis of the trunnions must he placed at the dis- tance of 39.76 inches from the base-ring in order that the gun may bear the desired preponderance. 336. To Deteemint3 the Effect on the Peepondeeance of A Change in the Position of the Tehnnions. Different values of P are taken, and the coiTesponding val- ues of a computed. P and a are assumed to vary proportion- ally, and the variation in pounds of P for a change of a tenth of an inch of a thus obtained. This assumption is not absolutely true, but nearly enough so for all practical purposes. Example . — Had we taken 780 lbs. for the desired prepon- derance of the 'KY4nch gun, a would have been found equal to 38.12. Hence changiug the position of the axis of the trunnions by 1.64 inches, has caused the preponderance to vary by 1004 lbs. — or 61.2 lbs. for each tenth of an inch. CHAPTER III. CAST GTTXS. Section I. — Standard of Iron. 337. Smelting of Iron for C^vnnon.^ — It is in tlie smelt- ing furnace that the character of the iron is fixed. Iron of good chai-acter and high susceptilhlitj may he spoiled by its treatment at the foundry ; but this, ivith ordinary experience and intelligence, ought rarely to occur. It is impi’acticable, with our present knowledge, to make good and reliable guns from iron that leaves the smelting-fur- nace with bad qualities. 338. The smelting of iron is a purely chemical process, and should be conducted with the same regularity and precision as any other important chemical process. There are so many dis- turbing causes tending to affect its character and qualities, that, after every precaution shall have been taken to remove them, perfect uniformity in the quality of the iron produced from day to day cannot be effected, yet a near approximation to uniform- ity is practicable. 339. All the stock for a “blast” of gun-iron should be carefully prepared and housed before beginning to “ blow.” The ore should all be i-oasted and well mixed so as to be as nearly uniform, as to size of lumps and all other qualities, as possible. The charcoal should all be made as nearly as possible from the same kind of wood, of the same uniformity as to quality, and well mixed together after charring. All the stock shoulcl CD O be carefully weighed and supplied to the furnace at regular in- tervals of time. 310. The pressure, temperature, and hygrometrical condition of the “ blast,” should be kept as nearly constant as possible. The temperature of the blast may be kept very nearly constant without usmg what is termed a “ hot-blast,” by warming it just enough to bring it above the highest summer temperature. * Rodman. CAST GUNS. 113 341. The quantity of moisture may, it is believed, be kept neai-ly constant by passing the blast some distance over water heated to the proper temperature. And this may be readily done by passing the blast through a long horizontal tube, like a cylindrical steam-boiler, partly tilled with water, and kept at a constant temperature by the waste heat from the furnace. The temperature of the water should be such as to saturate the blast with moisture, and thus render it hygrometrically inde- pendent of atmospheric changes. 342. Piling the Pigs. — Supposing a standard of quality to have been determined (Art. 374), with the stock all prepared for a given number of guns, and having determined by com- parison with the standard the quality of iron required, a fur- ther approximation to identity in quality of the metal in the guns may be made by casting each run of metal from the smelting-furnace into a number of pigs of equal size, some- thing greater than the number of the guns to be made, and piling them in separate piles — each run of metal furnishing one pig to each pile. 343. Each pile should contain metal enough for one gun and one test-cylinder ; and be kept separate and distinct from all others in transportation, and be repiled in the foundry-yard in the same order as at the smelting-furnace : one gun being made from each pile, after the treatment which the iron should receive at the foundry shall have been determined by experi- - ments made on the iron in the surplus piles. The pigs should be cast in molds as prepared from a pattern, so as to be smooth and free from adhering sand as possible. 344. Diffeeence in Quality. — The difference between iron as it exists when presented for use in “ pigs ” and when in the body of the finished gun is very great, sometimes amount- ing to a difference in density of more than 20 pounds per cubic foot, and in tenacity more than as 1 to 2. This serves to show how unreliable the tests of the first fu- sion pig-iron are, as means for determining the quality of iron and its suitableness for making cannon. 345. The quality of cannon may be improved by endeavor- ing to ascertain the different qualities of the metal used in making them, and the best methods of treating it in the pro- cesses of melting, casting, and cooling. 346. It is found that some kinds of iron are susceptible of very great improvement, by different methods of treatment at the foundries ; while other kinds are at their maximum strength in the crude pigs. The cause of this difference in the suscepti- bility for change and improvement will doubtless be found in 8 114 NAVAL ORDNANCE AND GUNNERY. the qualities of ores used, and in the processes of smelting them. 347. The following table enables us to compare the various cpialities of cast-iron and bronze, and see the variations which occur in each. VARIOUS QUALITIES OF CANNON METALS.* Trans- COMPRES- Metals. DEKSITY. Tenacity. VEKSE SITE Hardness. Strenoth. STRENGTn. Cast-iron.. • Least . . . Greatest 6,900 7,400 9.000 45,970 5,000 11,500 84,529 174.120 4 57 33.51 Wrought- Least. . . 7,704 38,027 6,500 40,000 10.45 iron Greatest 7,858 74.592 127,720 12.14 Bronze • Least. . . 7,978 17,698 4.57 Greatest 8,953 56,786 .... 5.94 Cast-steel . ■ Least. . . 7,729 198,944 Greatest 7,862 128,66o 23,000 391,985 .... A prominent feature of this table is that which shows the gi-eat difference between the lower and higher grades of the same metal. In cast-iron the density differs as 0.9 to 7.4, a .. difference equal to 31 pounds per cubic foot ; in tenacity it dif- fers as 45,970 to 9,000 pounds per square inch, or as 5 to 1, and in hardness as 7 to 1. The bronze varies iii tenacity from 56,786 to 17,698, more than 3 to 1, and in density it is as 8.953 to 7.978, equal to 61 pounds in the cubic foot. 348. Effects of different Treatment. — Usually the quality of iron is greatly modified and improved by remelting and long continuance in fusion. But all lands of iron are not affected in like manner by these processes. In examining the effects of the different treatment of iron at the foundry, such samples should be chosen as will best ex- hibit the following particulars and characteristics, viz. ; 1st. Tlie properties which distinguish the different gi’ades of iron made from the same ores at the same furnace. 2d. The changes in the mechanical properties of iron pro- duced by repeated meltings of one of these grades, separately, showing the changes effected at each melting. 3d. "The changes produced by repeated meltings of the dif- ferent irrades of iron and of different fusions mixed. o Reports of Experimeuts on Metals for Cannon. — U. S. Ordnance Dept. CAST GUNS. 115 Itli. The changes produced in iron of the same melting and quality, by casting it into masses of different bulk, and by dif- ferent methods of cooling. 319. The softest kinds of iron will endure a greater num- ber of meltings with advantage than the higher grades. It ap- pears from Major Wade’s experiments with Greenwood iron that when it is in its best condition for casting into proof-bars of small hulk, it is then in a state which requires an additional fusion to bring it up to its best condition for casting into the massive bulk of cannon.* In selecting and preparing iron for cannon, we may proceed by repeated fusion, or by varying the proportions of the differ- ent grades and different fusions, until the maximum tenacity is attained. 350. Vakiation of Density and Tenacity. — An increase of density is a consequence which invariably follows the rapid cooling of cast-iron, and as a general rule, the tenacity is in- creased by the same means. The density and tenacity usually vary in the same order. It appears that the tenacity generally increases quite uniformly with the density, until the latter as- cends to some given point; after which an increased density is accompanied by a diminished tenacity. The turning-point of density at which the best qualities of gun-iron attain their maximum tenacity appears to be about 7.30. At this point of density, or near it, whether in proof- bars or in gun-heads, the tenacity is greatest. As the density of iron is increased its liquidity when melted is diminished. This causes it to congeal cpickly, and to form cavities in the interior of the casting. 351. If in pi-eparing iron for guns it is carried too Jiig\ either by long continuance in fusion or by using a large portion of a hard grade of iron, the casting will be lost. High Iron . — The condition of the iron at casting is said to be too high, when the process of decarbonization has been car- ried too far ; and the result will be a very hard iron. 352. Pkactical Tkeatment in Fusion. — In the practical treatment of iron in fusion while preparing it for casting into cannon, it may be safely continued in fusion, with increasing improvement of its quality, so long as sufficient liquidity is retained to insure an exemption from cavities in the interior of the casting. The point at which such cavities of a fatal character will form, will be reached before arriving at the point of density for maximum tenacity. * Eeports of Experiments on Metals for Cannon ; 1856. 116 NAVAL OEDNANCE AlID GUNNERY. 353. Tests while in Fusion. — A convenient method for determining the condition of the iron while in fusion, and whether it has arrived at the proper condition for casting, or should be longer continued in fusion, is found, in dipping from the melted pool of iron and easting into small bars about 10 inches long and from 1 to 2 inches square at one end, and tapering to a point at the other end. The first one is taken from the furnace and cast soon after the iron is all melted, and others are cast at such intervals afterwards as may be judged proper. They are cast vertically, point downwards, in sand- molds, and cooled rapidly. 351:. Great care must be taken in the preparation of the molds for these samples, as upon sample-bars so small, even a little, more or less moisture of the sand of the molds will make a difference as to the rate of progress towards white iron. 355. As samples cannot be obtained from the heads of large guns (Art. 367) until several days after they are cast, separate proof-bars are made and tested, to aid in directing the progress of the work. This enables the founder to determine the relative quality of the iron soon after it is cast, and in the intervals between each successive daily casting. 356. The proof-bars are broken in different places, and the condition of the iron is judged by the appearance of the several fractures. These fractures will exhibit various aspects, from white at the small end to dark gray at the large end ; and the bars at the latter periods of the fusion will exhibit the white at a greater distance from the small end, and the mottle, bright, and lighter shades will be found adv’ancing towards the large end. This method, although much less reliable than that of an actual measure of density and strength, is convenient, because of its ready application at short intervals, while the iron is in fusion ; and a practical eye will soon be able to mark the prog- ress of the changing quality of the non, and to determine the proper time for casting the gun. 357. ORYSTALLIZATIOA. — Of the various circumstances which affect the strength of cannon-metal, the most important appear to be those which connect themselves with crystalliza- tion. General Law . — It is a law of the molecular aggregation of crystalline solids, that when their particles consolidate under the iniluence of heat in motion, their crystals arrange and group themselves with their principal axis in lines pei'pendicu- lar to the cooling or heating surfaces of the solid; that is, in the lines of direction of the heat-wave in motion, which is the CAST Ginsrs. 117 direction of least pre:snre within the mass ; and this is true, whether in the ease of heat passing; from a previously fused solid in the act of cooling and crystallizing on consolidation, or of a solid not having a crystalline structure, hut capable of assuming one upon its temperature being sufficiently raised, by heat applied to its external surfaces, and so passing into it."" 35y. Moleculak Constitution of C.vnnon Metals. — The metals used in gun construction are crystallizing bodies, which in consolidating obey more or less perfectly, according to their conditions, this law; so that in castings of these metals, the planes of crystallization group themselves perpendicularly to the surfaces of external contour; that is, in the directions in which the heat of the fluid metal has passed outwards from the body in cooling and solidifying. Because the crystals of these metals are always small and are never very well pro- nounced, these directions are seldom very apparent to the eye, but they are not the less real. 359. Development of Ceystals. — Their development de- pends upon ; First. The character of the metal itself ; all irons that pre- sent a coarse, large-grained, dark, or spangled fracture, contain a large proportion of uncombined carbon or graphite, and form in castings of equal size the largest crystals. Second. The size or mass of the castings — -the largest cast- ings presenting for any given variety of metal the largest and coarsest aggregation of crystals; but by no means the most regular arrangement of them, which depends chiefly upon — Third. The rate at which the mass of the casting has cooled, and the regularity with which heat has been carried off by conduction from its surfaces to that of the mold adjacent to them. 360. Chilled Castings. — Those castings in which the fluid iron is poured into a nearly cold and very thick mold of cast-iron, whose high conducting power rapidly carries off the heat, present the most complete and perfect development of the crystalline structure perpendicular to the chilled surfaces of the casting. In such, crystals are often found penetrating more than an inch into the substance of the metal, clear and well-defined. 361. Illustrations. — These prevailing directions of crystal- line arrangement may be made more clear to the eye by the ac- companying Figure 55, which shows sections of a round and a square bar of cast-iron where the crystallization is well devel- * Mallet. 118 NAVAL ORDNANCE AND GLDTNERT. oped. In the round bar the crystals all radiate from the cen- tre ; in the square bar they are arranged perpendicularly to the four sides, and hence have four lines in the diagonals of the Fig. 55. square — in which the terminal planes of the crystals abut or interlock, and about which the crystallization is always con- fused and irregular. The result of this arrangement is to create planes of weak- ness where the difierent systems of crystals intersect. 362. Effect of Ckystallization on Stuength. — The size and arrangement of the crystals of a metal have an important influence on its strength. This arises from the fact that the adhesion of the crystals by the contact of their faces is less than the cohesion of the particles of the crystals themselves, and that consequently rupture takes place along the larger or principal crystalline faces. A metal will therefore be strongest where its crystals are small. 363. Size of Crystals. — The size of the crystals of a par- ticular metal depends on the rate of cooling of the heated mass; the most rapid cooling giving the smallest crystals. The size of the crystals or coarseness of grain in castings of iron depends, for any given make of iron and given mass of castings, upon — First. The high temperature of the fluid iron above that just necessary to its fusion, which influences — Second. The time that the molten mass takes to cool down and assume again the solid state. The lower the temperature at which the fluid iron is poured into the mold, and the more rapidly the mass can be cooled down to solidiflcation, the closer will be the grain of the metal, the smaller its crystals, the fewer and least injurious the planes of weakness, and the greater the speciflc gravity of the castings. Slow cooling develops a coarse, uneven grain, with large but thoroughly irregiflar aud confused crystallization ; cast-ii’on CAST GUNS. 119 with such a grain is never strong or cohesive, though soft and extensible. 361. The more rapidly a casting once consolidated can be cooled, without introducing injurious effects, the finer, closer, and more even will be its grain on fracture, and with any given metal the greater will be its strength. The rate of cooling cannot be accelerated beyond a moderate limit. If this limit be exceeded, as by casting in a cold, thick, highly conducting metallic mold, the iron is “ chilled,” its constitution changed, and the carbon, not having time to crystallize out, remains com- bined or diffused through the mass. It cannot be so fast as to endanger unequal contraction, nor must it be so fast in large castings, such as guns requiring to be “ fed,” from a feeding or sinking-head, with fresh portions of hot fluid metal during consolidation to All up the internal cavities or porosity due to contraction and crystallization, that this feeding cannot be accomplished. The larger the mass of the casting, with any given quality of iron, generally the coarser is the grain ; that is, the larger are the crystals that develop themselves in the mass. The same metal that shall produce a fracture bright gray, mottled, and without a crystal visible, in a small bar, will in a large casting produce a dark, confusedly crystalline surface of fracture as coarse as granite rock. 365. Contkactiojst of Castings. — A certain amount of con- traction, on becoming solid from the liquid state, occurs in all castings. For iron this is variable, and depends upon the mass of the castings; being greatest for small and least for large castings, of the same make of iron, and poured at the same temperature. There are two conditions that principally affect the degree of contraction, namely, the extent to which the fluid metal as entering the mold has been expanded by elevation of tempera- ture, and the state of final aggregation of the particles, depend- ing upon the size of the mass. 366. Effect of Sudden Change of Form in Castings. — Sudden changes of form or of dimensions in the parts of cast- guns, besides the injury they do to the crystalline structure of the mass, introduce violent strains, due to the unequal contrac- tion of the adjoining parts, whose final contraction has been difiierent. For this reason, in the method of easting heavy guns as adopted in Sweden, it is considered necessary to form the ex- terior of the casting as a perfect cylinder. 367. Time REQumED for Cooling Castings. — The enormous 120 KAVAL ORDXAN-CE AXD GTJXXERT. time required by a lar^e casting for cooling is not generally known. A solid casting sufficiently large for a XV-indi gen weighs about 35 tons ; it is reddiot three days after having been east, and only becomes cold enough to handle after affiortnight. The cooling of a casting must be uniform, so far as uniformity is possible. This is impossible strictly in any easting; the approach to it is most difficult in heaA'y solid castings, and hence the great advantage of the practice of hollow casting upon a suitably made core, admitting of internal cooling by artificial means. 368. Effects of Ieeegelve Cooling of Castings. — The contraction of cast-iron in becoming solid introduces strains into the mass by consolidation of one portion of the casting before another. When a large gun is east solid and the metal cools in the ordinary way, the external portions solidify long before the interior has ceased to be liquid, and the process of solidifica- tion is propagated as it were, in parallel layers from the outside to the centre of the mass. When the first layer or thickness of solid crust has formed in the exterior, it forms a complete arch all round, so that the contraction between fiuidityand solidifica- tion of each subsequent layer is accommodated by portions of matter withdrawn radially from the interior towards the still cooling exterior ; that is to say, from a smaller towards a larger circumference. 369. The final effect of this, propagated to the centre of the mass, is two-fold. First. To produce a violent state of internal tension in the particles of the metal in radial lines from the axis of the gnu inwai'd as a cylinder, tending to tear away the external portions of the mass from the internal nucleus. Second. To produce about the centre or along the axis a line of weakness, and one in which the texture of the metal is soft, porous, and of extremely low specific gravity. 370. The effect of this unequal contraction may be so great as to crack the interior metal of cast-iron cannon, even before it has been subjected to the force of gunpowder, and large masses of iron which have been cooled very rapidly by casting them in iron molds, have been known to split open longitudinally, from no other cause than the enormous strains to which they are thus subjected. 371. Sinking-head. — Guns have long been cast in a verti- cal position and with a certain amount of head of metal above the topmost part of the gun itself. From this head the casting is fed with fresh portions of fluid metal during consolidation ; it also affords a gathering-place for all scoria or other foreign CAST GUN'S. 121 matter. But tlie great value of increased Lead of metal is in adding to the density of castings, and so also to tlieir strength. Fineness of grain, smallness of crystal, density, increased cohe- sion and elasticity, are all induced by casting under lai-gely in- creased statical heads of fluid metal. By appa^-atus not difficult to contrive, atmospheric pressure or that of condensed air might easily be brought to aid that of the head of metal, with economy in reducing the labor and cost of the mass of metal to be melted, and with the advantage of enabling the pressure on the solidifying mass to be varied. 372. Effect of Age on Endukance. — The length of time that a piece has been cast influences its endurance. A gradual adjustment takes places of the internal strains produced in cooling, and like many other substances iron possesses the property of accommodating itself to an unnatural position, and Anally of adopting this as its natural one. 373. Impeovement en Castings.- — The principal improve- ment in the fabrication of cast-iron guns, is Captain Eodman’s process of cooling them as far as possible from the interior, and for this purpose casting them hollow. The design is to .remedy the various defects of the old process; principally to obviate the tendency of solid castings to burst by their own initial strains, by reversing the process of cooling and shrinking described above. Since there would then be no force opposed to the contraction of the inner layers of metal, except the trifling cohesion of tlie liquid or pasty mass that they shrink away from, they would not be left in tension, and therefore they could not exert any power to pull the ex- terior layers into compression. The method employed is, to carry off the internal heat by passing a stream of water through a hollow core, inserted in the centre of the mold-cavity before casting, and to surround the flask with a mass of burning coals to prevent too rapid radiation from the exterior. (Art. M5.) Extensive trials have l?een made to test the merits of this plan, and the results show that cast-iron cannon made by it are not only stronger but are less liable to enlargement of the bore from continual firing, the surface of the bore being the hardest and densest part of the casting, and best calculated to resist pressure and abrasion.- 374. STANDARD OF QUALITY. — Before proceeding to execute a contract for cannon, a trial-gun should be made and ex- posed to extreme proof with service charges. After undergoing this proof in a satisfactoiy manner, the trial-gun should serve as a standard, and the proportions of the several kinds of metal 122 NAVAL ORDNANCE AND GUNNERY. used, and the methods employed in its manufacture should be followed in all respects in the fabrication of other guns. With the trial-gun should be cast a samjple-gun or a cylinder of equal diameter, and at least half the length of the gun, from which test specimens should be cut and tested. 375. The sample-gun or cylinder should be of the same diameter as the guns to be made, and should be made under the same cii’cumstances which are to attend the preparation of the iron for, and the casting and cooling of, the guns themselves. The object of the sample is to obtain specimens which have not been subjected to previous strain and vibration, as would be the case if taken from the fragments of the broken trial- gun. For it is impossible to reason back to what would have been either the capacity for work or the work due to elasticity of an unstrained specimen by knowing to what extent these proper- ties were possessed by that specimen after it had been sub- jected to both strains and vibrations of unknown intensity and number. And although it is interesting to know to what extent these properties are possessed by the fragments of a worn-out gun, yet it would be of far greater practical utility and importance to know the value of these properties in the new untried guns. Specimens thus obtained would afford reliable results ; and in connection with the powder-proof with service-charges of guns, cast at the same heat, these results would become stand- ards with which to compare other lots of iron or other guns, and thus determine beforehand the number of rounds which a gun will stand. 376. Comparison with Standard. — "While the cannon are making, the inspecting officer examines and tests the metal be- fore it is used, witnesses its melting and casting, and tests the metal in the first gun made, before the second one is cast. If the first proves unsatisfactory, such changes are made, either in the material or in its treatment, as will tend to produce the desired result. This practice of ascertaining the quality of the material used, and of the casting made from day to day, as the work proceeds, enables the founder to distinguish the material, to select those of best quality, and to treat them in the best manner. If these tests are satisfactory, the inspecting officer is assured of the good quality of the guns, before any proof by firing is made. And this supersedes the necessity of using excessive proof-charges in the final proof, which may do serious and even CAST GUNS. 123 fatal injury to guns, witliout bursting them or leaving any vis- ible marks of the injury. • 377. Means, of Comparison. — The testing-instrument (Art. 396) furnishes to the founder a convenient and accurate method of comparing the qualities of iron. It therefore enables him to select his materials before casting, with greater certainty and safety. lie can also by this means determine the comparative utility of different methods of melting and casting the gun. As the quality of the iron is essentially changed by the different ways of treating it while in the melted state, and by the differ- ent means adopted for cooling it after it is cast into the mould, the testing-instrument enables one to ascertain the effect pro- duced by these processes in all their several stages of progress, and to decide upon that which is found most suitable for mak- ing the guns of the best quality. 378. Contract with Founder. — The metal of guns made for the naval service is subjected to tests to ascertain its hard- ness, specific gravity, and tensile strength. The particular hardness, density, and strength which the metal must possess is specified m the special contracts with the Founder. Each foundry keeps an accurate record of the character, mixture, and mode of working the metal of each gun, so that its foundry number will at once refer to its class, date, weight, etc. 379. Samples. — The quality of the iron as it exists in the gun is more accurately represented by samples taken from its sinJdng-liead than by any which can be obtained from other parts of the casting without injury to the gun. These samples are taken from the lower end of the sinking-head, next to the muzzle of the gun, and are cut out so that their axes will be parallel to the axis of the casting, at a distance from the centre of the head equal to the distance between the axis of the bore and the middle of the metal in the wall of the piece when bored. When guns burst from extreme proof, samples are taken from different parts to test the strength of the metal. The radial specimens are generally found to be somewhat stronger than the longitudinal from the same cross-section of the gun. (Art. 362.) 380. Marking-samples. — The sinking-head and the gun to which it belongs have the same foundry-number. The samples have the foundry-numbers and the letter II stamped upon both ends of them. All samples taken from any gun-easting, whether from the 124 NAVAL ORDNANCE AND GUNNERY. sinking-lieacl, the proof-bars, or other casting, from the same melting, bear the founchy-nnmber of the gun. The letter II, added to the number, denotes that the sample is taken from the head. OH denotes a sample from near the outer or ex- terior surface. Ill an inner sample, and other letters are used denoting the locality from which the specimen has been taken. The letter B on any sample, denotes that it was taken from a proof-bar. The figures which follow the letter indicate the fusion or the number of times the iron has been melted. 381. Value oe Tests. — The samples are tested as soon as practicable. The tests are carefully made and recorded Avith the other proofs and inspections, and afford the means of com- parison betAveen the metal of different guns and of different foundries. Ho particular Amlue is attached to these tests as an indication of the absolute endurance of the gun, but only as exhibiting the similarity that the several guns bear to the standard. Ex- perience has shown that a variation of about 2,000 pounds more or less, in the tensile strength, is a sufficient limit to be allowed, and within Avhich to confine the founders ; an exact adherence being impossible. 382. Staetdaed Specimen. — In order to obtain a suitable sample for de- termining the density and strength ; a cy- lindrical piece about four inches long and tivo in- ches in diameter is taken, and pre- pared by reduc- ing it to a form that will fit the holders of the testing - machine (Fig. 56), and of such bulk as will be conveni- ent for ascertaining its density. In order to obtain reliable comparatiA'e results, it is necessary that tlie specimens shall all conform to the standard in size and shape. 383: To Determine the Density. — The sample is weighed in air and in pure distilled AA'ater ; clear rain or river water may be substituted, if its relative density be first accurately determined. Fig. 56. CAST GUN'S. 125 In taking the speeihc gravity of iron, the operations are nn- avoidably performed with water at different temperatures, varying with the state of the weather at the time ; and as the density of the water varies with its temperatui’e, it is necessary to note the temperature of the water at the time of w^eighing tlie sample, and to reduce the ascertained density to what it would have been if the sample had been weighed in water at the temperature of the assumed unit. A thermometer is suspended in the water, and its temperature is noted at each weighing. The temperatiu’e of 60° F. is taken as the standard ; and when a sample is weighed in ^Yater of any other temperature, the weight of water displaced by it is corrected by the table compiled for that purpose. The instruments employed for determining the density of speci- mens are — The Hydrometer and the Densimeter^ or Balance for specific gravities. 384. The Hydkometek. — Fig, 57 exhibits the form of the instru- ment. The bulb B is of thin cop- per about 7 inches diameter at top, and 8 inches high, having a brass handle, II, and a solid stem of brass, S, screwed into the bot- tom. A vertical index-stem made of steel, I, is inserted in the upper part of the handle. The upper end of this stem receives the weight-pan, W, which is sup- ported in its place by a conical socket on its under side. The height of the hydrometer, from the bottom of the ball to the weight-pan, is 21 inches. Its gen- eral form and the distribution of the metal within it, place the centres of gravity and buoyancy so far apart that it readily takes a vertical position, when im- mersed, and will deviate very little from it, however irregularly it may be loaded. Fig. 57. 126 NAVAL ORDNANCE AND GUNNERY. Its maximum buoyancy is about 14,000 grains ; but this may be reduced when weighing lighter samples, by adding at the bottom one or more adjusting-weights, which may vary it one-half. The index-stem is of very small diameter, a length of one inch displacing one grain of water. The zero-mark is in the middle of the length of the stem. The weights are marked in grains, decimally divided, vary- ing from one-tenth of a grain to 4,000 grains. The vessel which contains the water is a glass jar about a foot in diameter and two feet in height. It must be placed on a level support, and the height of the water in the jar should be such that when the hydrometer descends to the bottom, the weight-pan shall still be above the sm-face of the water. The weight-pan is attached to the index-stem by an open socket, so that it may be removed with its load, and placed on a table, where the weights may be more safely and accurately counted. 385. To DETEKinxE the Density of Watek. — The hy- drometer may be employed to determine the relative density of distilled and any other kind of Avater. The weight of the hydrometer, added to its balance-weight in distilled Avater, at the temperature of 60°, gives the weight of a quantity of pure standard Avater, Avhich is equal in bulk to the immersed part of the instrument. The Aveight of the liA-drometer and its load when immersed in like manner, in other kind of Avater at the salne temperature, gix’es the weight of an equal bulk of the lat- ter, and this Aveight divided by the former, gives the multiplier for correcting the density, Avhen ascertained in any other than pure distilled water. At the foundries generally, river-water is found to be suf- ficiently pure for use Avithout needing any correction. 386. To Use the Instedjient. — First load the pan with grain Aveights until the instrument rests at its zero, and record the sum of these weights, as the halance of the hydrometer. Next, place in the pan the samples together Avith as many weights as Avill again bring the instrument to its zero, and re- cord these Aveights, as the sample balance in air. The differ- ence betAveen these balances is equal to the Aveight of the sam- ple in air. Then place the sample on the bulb of the instru- ment at P, and immerse both until the hydi’ometer again rests at zero, and record the weights on the pan, as the sample bal- ance in water. The difference between this balance and that in air is equal to the weight of the water displaced by the immersed sample. The temperature of the Avater at the time CAST GUN’S. 127 of weighing is rioted, and if it is not at 60°, divide the weight displaced by sample, by that number in the table which is op- posite the noted temperature, and the quotient will give the corrected displacement for the temperature of 60°. Then, the weight of the sample in air divided by the corrected displace- ment gives the density of the sample. 387. Example. Sample No. 4, H. Grains. Balance of the hydrometer 11485.0 Balance with sample in air 923.0 Difference = weight of sample in air 10562.0 Balance with sample in water 2370.4 Balance with sample in air 923,0 Difference = weight of water displaced Noted temperature, 72^°. Tabular number, 72J = .998912. 1447.4 -- na .n-io “ 1449.0 coi’rected displacement, , 10562 == 7.289 = density. 1449 Or by Logaritlims — Water displaced at 72J° =: 1447.4.. Tabular number for 72J° = .998912, 1447.4 Logarithms. 3.1605886 1.9995274 Logarithm of corrected displacement 3.1610612 Weight of sample in air = 10562 4.0237461 Corrected displacement 3.1610612 Density = 7.289 = 0.8626849 The determination of densities by the hydrometer requires much practice to arrive at correct results, and is, moreover, very tedious. The densimeter^ or halance^ may therefore be advantageously substituted for it, the results being occasionally checked by the hydrometer. 128 NAVAL ORDNANCE AND GUNNERY, 388. The Densimetee,'-’' or Balan-oe for Specific Gravities, is in principle a simple beam scale of accurate workmanship. As made by W urdemann, it consists of an open beam of German silver, A (Fig. 58), fitted Avitb knife-edge bearings, and mounted Fig. 58 . in a hollow standard, B. The central knife-edge, (7, upon which the beam is balanced is l.d inch long, and those at extremities, d, from Avhich the scale-pans are suspended are 0.9 in. long ; all bearing their lengths on steel plates. When not in use the beam rests on its Y’s, e e, on a cross- bar, F, at the top of the standard. This cross-bar also supports the scale-pans on separate rests, (j y, free from contact Avitli their knife-edges. Through the standard a rod passes for lifting the beam Avhen in use ; it connects v’itli the crank, h. The standard is set on a brass plate furnished ivith a circu- hir spirit-level and foot-screws, o o, for accurately levelling it. Inspection and Proof of Cannon — U. S. Navy. CAST GUNS. 129 The whole apparatus is enclosed in a glass case to protect it from dust or currents of air; the case is fitted with a sliding front which is counterpoised for convenient manipulation. 3S9. When not in use the glass case should be kept closed to protect the balance from dust, and a vessel containing crystalized chloride of calcium^ to absorb the moisture of the air, ought to be always placed inside the case. The best arrangement for this pirrpose is a glass funnel, containing the chloride set in a beaker-glass. The beaker should always be emptied before the water reaches the end of the funnel-stem. 390. Ad.justments. — The heam is balanced by two adjust- ments placed above it. First, by the horizontal screws, Avith milled heads, for the zero of the index below r, and, second, by the lai'ge nut, s, on the pei-pendicular sereAV for vertical balance. Thi^ last, when once set, it is seldom necessary to touch. 391. The Arms are adjusted to equal length. There is to each knife-edge end a steel screAv with capstan-head, which when screwed forward will spring out the part upon which the kiiifc- edge rests, and thus lengthen its distance from the centre. Both ends are made tlius adjustable, by which means perfect symmetry of the trvo parts of the beam is obtained and the ne- cessity of screwing back during the adjustment is obruated, since it will merely be necessary to lengthen the arm Avhich proves to be shortest. To test this the relative place of the scales should be changed after first balancing them exactly, if, after the change either preponderates, it proves that arm to be the longest. One half the difference is to be corrected with weights, and the other half Avith the adjusting-screws. Great caution must, hoAvever, be observed in not screwing up too much at a time. A correct result in weighing may be obtained Avithout this adjustment being absolutely exact, by fii’st balancing the speci- men to be weighed, with any coiiA^enient substance, then re- moving the specimen and substituting in its place knoAvn Aveights until equilibrium with the counterpoise is restored. 392. Use of the IxsTEUiiExx. — By the crank, K, placed in front of the case, the centre bearing is gently raised, which, lifting the beam off its Y’s, also takes up the scales. Y hen the beam is completely raised the oscillations of the scales are arrested by touching the spring-lever, Y, on the right of the crank, which works the steadying-pins, w w, under each pan. On abandoning the lever the preponderance of the specimen 9 ISO NAVAL ORDNANCE AND GUNNERY. or tlie -weiglit, will immediately be manifested, and additional weights may be added or removed iintil they are in. equilibrium. When placing the specimen and estimated counterbalancing weights in the scales, the beam should always be let down on the siipports ; but small weights may be added or changed whilst simply arresting the scales with the lever. The door should not be pushed up higher than is just neces- sary to obtain convenient access, as the balance is very sensitive. Care should be taken not to abrade the pans by carelessly put- ting in the specimens or rubbing to remove dust. 393. Detekjiination of Specific Gkatitt. — For the deter- mination of specific gravities a German-silver vessel is used just large enough to conveniently hold the specimen, and open at the top, which is planed off perfectly straight so that a plate- glass provided for the purpose can be slid over it, and will shut air-tic^t. This vessel is filled with distilled water, carefully re- moving air-bubbles from inside the vessel, or drops mechani- cally adhering to the outside. Weight and temperature are noted, and a table may be computed, so that tliis element constitutes for the instrument used a constant. It will be convenient to keep the water in a reservoir of considerable size, to avoid the inconvenience of frequent changes of temperature. The absolute weight of the specimen having been previ- ously taken and noted, it is then submerged in the vessel, a small pair of tongs being used for the purpose, when it will dis- place a quantity of water equal to its volume. The vessel is again covered with the plate-glass, using the same precautions as before, and the weight taken. 39T. Since specific gravity is represented by the ratio of the absolute weights of the same volume of water, and of the article to be determined, we have to divide the weight of specimen by a quantity obtained, by deducting the wei_^t of the vessel, with specimen inserted, from the sum of weight of vessel filled with water, and of the weight of specimen. Therefore if — C— Weight of vessel filled with water (constant), W= Absolute weight of specimen, W,= Weight of vessel with specimen submerged, S = Specific gravity. We have Grains. CAST GUNS. Example. Logarithms. c = 8618.5 w = 9888.0 3.9951085 ■ c + w = 18506.5 17137.7 c + W - w, = 1368.8 3.1363400 s = 7.223 . 0.8587685 395. Fokm of Recokd of Comptjtatioit. By Densimeter. Calibre. No. Spec. Tem. Weight. Grains. Grains. Tem. Logarithms. |sp. Gr. IX-in. 1910. H.I. 63° Tank filled Spec, in air. .... Spec, in water . . Water disijlaced . 8963.1 9845.5 18807.6 17465.0 1343.6 63° 1.9999020 3.9932378 3.9931398 3.1279466 .8651932 7.332 IX-in. 1910. H.I. 63° Water displaced. 8962.1 9787.2 18749.3 17416.5 1332.8 63° f. 9999020 3.9906585 3.9905605 3.1247650 .8657955 7.343 132 NAVAL ORDNANCE AND GUNNERY. By IIydeo^ietee. Calibre. No. 1 Spec.jTem. ■Weight. Grains. Grains. Tem. Sp. Gr. IX-in. 1910 H.I. 64“ Bal. of liyd Bal. with Spec, in air Spec, in water. . Water displaced. 12784.2 2938.5 9845.7 1342.8 64° r.9998660 3.9932463 7.330 4281.3 3.9931126 3.1280113 .8651013 IX-in. 1910. H.2. G4° Water displaced. 12784.2 2996.7 4329.6 9787.5 i332!o 64° 1.9998660 3.9906718 3.9905378 3.1247976 .8657402 7.341 Section II. — Mechanical Tests. 396. THE TESTIHG-HACHIHE affords the means of ascertaining those properties of metals on which the endurance of guns is believed mainly to depend. As yet, however, no standard of properties has been deter- mined, nor is it believed to be practicable to fix such standard except by connecting the mechanical tests of a metal with the endurance under the powder-proof of the <>:uns made from it. 397. The Rodman Testexg-machine. — This instrument is used to determine the capacity of any metal to resist a tensile, transverse, torsional, or crushing force. It is also used to ob- tain the indenting-force, and an internal force can be applied for bursting hollow cylinders, 398. Bowee Exerted. — By a combination of levers and cog-wheels the action of the power employed is greatly aug- mented and transmitted to the specimen under trial. CAST GUXS. 133 The machine consists essentially of a system of three levers, AC, A'C' and A"C". (Fig. 59.) The position of the fulcrum in each of these cases is denoted by F, F' and F'' respectively. The power is applied at P, and the position of the weight is denoted by W. The levers are connected by rigid rods. > A a F c Fro. 59. The mechanical advantage of the lever AC is 10 to 1 ; that of A'C' is 20 to 1, and that of A"C" is 10 to 1. AYe have, therefore, ])y the formula for compound levers : 5 = ^ + 1 + 15 = 2000 . 399. EXPLANATION OF THE HODMAN MA- CHINE. — The MroDLE Levee, so called because it is inter- mediate between the other two, is the upper lever, A'F' (Fig. CO). All its bearing knife-edge pivots are in the same hor- izontal plane. Its fulcrum, F', is supported by an interior frame which is attached to the screw, D, above it. The knife-edge A' connecting by means of a long vertical rod, A'C, with the small lever ^ AF, is ninety -seven inches from the fulcrum, F', and the knife-edge C' connecting by means of a strap, A'H', with the main lever, A"F'', is four inches and eighty-hve hundredths from the fulcrum F', making a proportion between the two arms of the lever as 20 to 1. 400. The Maest Lever, A'^F'', is the one which acts directly upon the specimen under trial, and is acted upon by the middle lever through a long iron strap, A"C', wEich connects them. All'its knife-edges are in the same plane. Its fulcrum, F^', is supported by a pair of heavy iron stan- chions, BP, fitted to the bed-piece, EE. The knife-edge K" which is liidved with the middle lever is ninety inches from the fulcrum, F", and the knife-edge C^, w'hich acts upon the speci- I 134 NAVAL OKDNANCE AND GUNNEET. men under trial is nine inches from the fulcrum, F", making the power of this lever as 10 to 1. 401. The Small Levee, AF, is the one to which the weights are attached. All its bearing knife-edge pivots are in the same plane. Its fulcrum, F, is supported by the lower end of the guide, G.G', attached to the main lever stanchions. The knife-edge C, con- necting with the middlelever, is turn and twenty-five hundredths inches from the fulcrum, F, and the knife-edge A, to which the weights are attached, is twenty-two and five-tenths inches from the fulcrum, F, making the power of this lever as 10 to 1. 402. Tue Combikatiox of Levees. — A combination of the small lever with the middle lever gives a proportion of two hundred to one ; and a combination of all three of the levers gives a proportion of two tjiousand to one. A weight of one pound, therefore, applied to the platforms of the suspending rod, T, on the small lever exerts a force of two hundred pounds on the strap, A'^C', connecting with the main lever, and of two thousand pounds at C", where the strain acts upon the sample. 403. Capacity of tue Maciilxe. — The weights used are of two denominations, viz., half pounds and five pounds, repre- senting respectively one thousand and ten thousand pounds. Smaller increments of strain than one thousand pounds are noted on the small lever, Avhich is provided with a sliding weight and graduated from zero to ten ; each number repre- senting an additional hundred pounds. Of the first denomination, tliere are ten weights, represent- ing a strain of ten thousand pounds, and of the second, there are nine weights, representing a strain of ninety thousand pounds. The aggregate strains of all the weights or the capacity of the machine being one Inmdj'ed thousand jiounds. 404. The Cog-wuieel Geaeixg. — The lai-ge vertical frame, EH, at one end of the machine (Fig. 00), supports the cog-wheel gearing wdiich is set in motion by a craidv. To the heavy main lever stanchions, BB, a guide, G.G., is attached ; through the u]>per end of which the small end, G', of the middle lever passes. This guide ascends and descends evenly with the screw, D, and tlie fulcrum, F', of the lever, by means of a rack and pinion, U'L", at each end of the revolving- rod, L. A mortise through the guide receives the lever and allows it a free motion to a limited extent. The lever is thus maintained in a position always nearly horizontal, while it re- mains free to oscillate on its fulcrum in either direction, as the strain or the weights may preponderate. The supports of the CAST GUA"S. 135 small lever are attached to the guide, G.G', so that it ascends or descends with the middle lever. O 405. lIuLTiPLicATioisr OF Power. — Fifty timns of the hand- crank, I, gives one turn to the horizontal wheel, M, at the top of the frame, E. A screw nut is cut in the axis of this wheel, through which the vertical screw, D, passes. This wheel, when turned, ele- vates or depresses the screw, and sets in motion all the mov- able parts of the machine. Two turns of this horizontal wheel move the vertical screw one inch, and this requires one hundred turns of the hand- crank, and gives one-tenth of an inch of motion to the knife edge of the main lever, where the strain on the samole is ex- erted. 136 NAVAL ORDNANCE AND GUNNERY. The cranh to which the power is first communicated moves distance of seve.ity-two seventy- each inches at each turn, and two hundred inches for tenth of an inch of motion at the straining-point of the ma- chine. Such a great power is needed only when heavy strains are exerted. Wlien heojinniuo: a strain, or Avhen loweringdown the levers, the small pinion, o, on the crank shaft is thrown ont of gear, by lifting the latch, X, and shifting the shaft ; tlius bringing into action the large pinion, R, which change of gearing gives a velocity nine times as great to all the mov- able parts of the machine, but the force exerted whl be only one-ninth as great as before. 4-06. The Torsion Lever, L', works between two heavy pillow-blocks, B', fitted on the bed-frame, E, and within these pillow-blocks the journals of the torsion-lever revolve. Its axle has a cylindrical aperture concentric with its axis. This lever is set in motion by a chain, S, whicli connects di- rectly with the middle lever through the strap, S. 407. Pedestals for Trans- verse Strains.— Two hollow movable pedestals, TT, are at- tached to the bed-frame, E, fitted with steel knife-edges, which serve as points of sup- port for the test-bars. Horizontal braces secure the stability of the frame-work of tll6 408. W(3rKIHG the MACHIXE.— Adjustments.— All the working knife-edges, and the seats on which they hear, are made of hardened cast-steel ; the other principal parts of cast-iron. Fig. 01. — Testing--macMne. Eleyation. ) (End CAST GUNS. 137 Before beginning a test, it is necessary to see that all the knife-edges are properly adjnstecl, and that 'the vertical screw through the horizontal wheel on the top of the machine is run down its full length, to obtain all its scope. To adjust the equilibrium, there is a small horizontal rod, B', with a weight working upon it, which is attached to the upper end of the slide, G.Gr', supporting the small lever. Before the specimen is secured in its place, the machine must be accurately balanced by moving the weight, W', of the adjusting-rod either in or out, as it may require. The final and accurate adjustment is made with the small brass weight, W", attached to the end of the small level’. 409. The Sample Holdees in all forms of strain, excepting that of torsion, are attached at one end to a stirrup, C'', on the main lever, and at the other to the bed-frame. "To apply the strain to the specimen, the hand-crank, I, is turned with regu- larity in the direction which raises the screw, and sets in motion all the movable parts of the instrument. The slide on the small lever, S", is moved gradually, just keeping its equipoise ; as the strain is increased, weights are supplied at P, in such manner as will keep the lever erenly balanced, so that the force applied at the instant of breaking may be accurately determined by counting the weights then on the platforms. • 410. Texsile Steaix. — After the density of a specimen has been ascertained, and before it is inserted in the holders, its smallest diameter is accurately measured and recorded. This is done by sliding-calipers, an instrument provided with a Yenier, which measures hundredths of an inch, and thousandths of an inch may be readily determined by a practiced eye. The specimen is now fitted between the holders used for the purpose; one of which is attached to the shackle hung on the stirrup of the main lever ; the screw, U, connecting with the bed-frame, is then run up by the handles, II', underneath, . until the specimen can be caught between the holders that fit on its upper end. After the sample is secured between the holders, the screw is run down until a sufficient strain is obtained, to keej) them in place. Then proceed with the test. The breaking-weight is divided by the area of the smallest diameter of the specimen, and the -quotient gives the tenacity, or the strength per square-inch. That is, let a represent the breaking weight, & the area, and X the tenacity per square-inch. 5 ; 1 sq. in. ~ a x. I 138 NAVAL ORDNANCE AND GUNNERY. Examples. Sample No. 4. H. Logs. Brealdng-weiglit, 50500 4.7032914 Diameter, 1.25 in.; area (^r^), 1.22719 in. .0.0889099 Tenacity per sq. in., 41151 lbs 4.6143815 411. The following table contains the area and the log- arithms for aU the variations of diameter likely to occur in tensile samples : Diam. Area. Logs. Diam. Area. Logs. Diam. Area. Logs. 1.190 1.11220 .0461839' 1.204 1.13853 .0563429 1.297 1.32120 .1209093 1.191 1.11407 .0469135 1.205 1.14042 .0570639 1.298 1.32324 .1210393 1.192 1.11594 .0476425 1.206 1.14231 .0577845 1.299 1.32528 .1223083 1.193 1.11782 .0433707 1.207 1.14421 .0585045 1.300 1.32732 .1229707 1.194 1 11909 .04909851 1.208 1.14610 .0592237 1.301 1.32937 .1230446 1.195‘ 1.12157 .0493257 1.209 1.14800 .0599425 1.302 1.33141 .1243120 1.196 1.12345 .0505523 1.210 1.14990 .06060071 1 303 1.33346 .1249788 1.197 1.12533 .0512783 1.290 1.30698 .11626931 1.304 1.33550 .1256451 1.198 1.12721 .0520035 1.291 1.30901 .1169423 1.305 1.33755 .1263109 1.199 1.12909 .0527283 1.292 1.31104 .1176148 1.303 1.33960 .1269763 1.20» 1.1 S 097 .0534523 1.293 1.31307 .1182868 1.307 1.34165 .1276411 1.201 1.13280 .0541759 1.294 1.31510 .1189583 1.308 1.34370 .1283033 1.202 1.1347.5 .0548989 1.295 1.31713 .1196293 1.309 1.34570 .1289091 1.203: 1.13664 1 .0556211 1'296 1.31617 .1202998 1.310 1.34782 .1296325 412. Transvekse Strain. — For determining the transverse strength of metals, a specimen-bar is taken two or three feet long, and about two inches square. It is prepared for the test with a slight dressing with the hie or grind-stone, on one of its faces near each end, in order that the bar may bear more evenly against the supports when under the strain. The middle of the bar — the' part where the fracture occurs — is dressed in like manner on each of its four faces, in order that its breadth and depth in this part may be accurately measured. 413. To Place tue Bar. — Run the screw, U, down nearly level with the bed-frame, out of the way ; slide the pedestals to the proper distance on either side, to accommodate the length of the specunen. Suspend the long link, S (Fig. 62), from the same shackle used in the tensile-strain, and pass the bar through the pedestals and the long link, so that it rests in the middle of its length on the knife-edge in the bottom of the link. The latter is then drawn upward until the ends of the bar bear CAST GUXS. 139 firmly against the knife-edge supports in the pedestals, which must be at equal distances from the link. 411. The Deflection. — The breaking-force is applied on the under side of the bar, in the middle, and forces it upwards against the supports at the ends. The deflection is measured by inserting a graduated, tapered metallic scale between the upper surface of the bed-frame and the under side of the bar-holder, directly beneath the forcing- line of the latter, against the centre of the bar. The space enlarges as the bar bends, and the graduated wedge measures minutely the deflection of the bar at any stage of its progress. A record is kept of the deflection’’’' and which shows the quantity of deflection and permanent set under a given pressure, which is designed to lie near to, but somewhat less than, the minimum breaking-weight. Also of the “ last deflec- tion,” which gives the amount of deflection under the pressure of the breaking-weight. i 415. The q/" represents the weight in pounds required to break a bar one inch square, rigidly supported at one end ; the weight being ai^plied at a distance of one inch from the point of support. For square bars it is determined by the formula — =: S, the unit of strength. 46 a* I = the length between the supports. TF = the breaking-weight. 0 = the breadth of the bar. d — the depth of the bar. The breadth and depth are accurately measured near the fracture ; and, as the dimensions are irregular, it is proper to measure in three places for each ; one measure to be taken in the middle of the bar, and the other two near the corners. The mean of the three measures to be taken as the true dimen- sion. If the bar is defective, the results cannot, of course, be relied on. Example. Proof Ear No. 4S4. Logs. 6 =: 1.969 (mean of three measurements) 0.2942457 d =: 1.9683 (mean of 3) log. 0.2940913 X 2 = . . 0.5881826 — 0.8824283 i Z X TF= 2^0 X 13900 = 69500 4.8419848 Transverse strength = S = 9111 lbs 3.9595565 O 140 NAVAL ORDNANCE AND GUNNERY. 416. Torsional Strain. — For determining the torsional strain, or the weight required to break hj twisting, a specimen- bar is used, wliich is long enough to project hejmnd the jour- nals of the torsion-lever, and receive the indices, <3', whicli are attached to its ends, a. The parts against which the holding- keys, k', are pressed are made square. All the other parts are round. The part between the keys is dressed to a true cylinder, the length of which should not be less than three diameters. This length is necessary to allow' a full development of the fracture to occur within the dressed part of the specimen. The distance between the keys is nineteen inches. 417. . To Place the Specimen. — The bar passes through the axle of the torsion-lever. One end is held tirmly to the pillow-block of the bed-frame, and the other to the journal of the torsion-lever, L', by means of keys, Kb The axis of the bar is made to coincide with the axis of the torsion-lever, by passing its ends through concentric rings, r, inserted in recesses provided for the pui-pose, before the keys are fixed in their places. Indices, are attached to the projecting ends of the bar and adjusted to the zero of the are beneath, before the strain is commenced. The diameter of the specimen is carefully measured before it is secured in the journal. Bring the keys up on the bottom, until the bar rests firmly upon them, then key up from the top to keep it firmly in its place. Connect the chain on the tor- sion-lever to the strap communicating with the middle lever, and proceed with the test. IVhen a bar is in the machine for torsion, the lever. Lb is placed at its lowest point, but sometimes the screw, D, ascends to its highest limit before the bar breaks. AVhen this happens the lever is propped up, the chain is detached and shortened by removing its upper link ; then, on its being again attached, the work is resumed and the strain extended until the bar breaks. 418. liecovcling the Strain. — In torsional strains the main lever of the testiug-machine is inoperative. The recorded breaking-weight then is only two hundred times greater than the actual weights on the platforms, which is equal to one-tenth of the usual reading in other tests. But as the torsion-lever is thirty inches long from its axis to the point where the centre of the chain acts upon it, the weight as above ascertained is multiplied by thirty, and the product represents the strain ex- erted at a point one inch from the axis of the strained bar. In practice it is found more convenient to read off the weights CAST GUNS. 141 for torsion in the same manner as in other tests, and to multiply that reading by three. 419. The Deflection . — Although one end of the bar is firml y fixed, it will yield a little by its compression on the heys, and Fig. G2. — Stirrap for Holding Indenting Apparatus. therefore its angular deflection is determined by the diffenmce between the reading on the arcs. The deflection of the bar is noted at each addition of a cer- 142 NAVAL OEDNANCE AND GUNNERY. tain numbez' of pounds of pressure ; and at eaeli addition of, say, five hundred or a thousand pounds, the bar is released from strain and the permanent set ascertained. The greatest anffle of deflection and the breaking-weight are also recorded. The torsional strength is Q tor in which w = breaking-weight, T — radius of torsion-lever, d — diameter of specimens. 420. Crushtno-fokce. — T he samples submitted to the test of compression are small cylinders, the lengths of which are generally two and a half times their diameters. Bars of greater length than these diameters are liable to bend under the pressure before the fi’acture occurs ; and if the length be less than two diameters, the fracture in its regular form may not be fully developed, and a portion of the sample may be pulverized or reduced to small grains. The ends of each sam- ple are made perfectly parallel and pei’pendicular to the axis, so that all parts of the sample will be equally pressed. 421. Placing the Specimen. — Fig. 62 shows the form of the stirrup used in holding the instruments for crushing.^ burst- ing, and indenting samples when the straining force is applied. /S' is a stirrup attached at its upper end to the straining-stirrup, C" , on the main lever ; and P is attached to the bed-frame by means of the screw U. y is a block of kon upon which the sample may rest. The samples or the instruments for holding them are inserted in the space, T. 422. llecording the Compression. — The dimensions of the sample are carefully measured before placing it. The depres- sion or permanent set at every five thousand pounds, for instance, are then carefully noted. The breaking-weight is recorded as well as the angle of fracture of the specimen. The strength per square inch AviU be g _ weight area 423. Indenting-force. — T he comparative softness or hard- ness of metals is determined by the bulk of the cavities or in- dentations made by equal pressure; the softness being as the bulk directly, and the hardness as the bulk in\’ersely. 424. Indenting-tool. — Of the different forms of cavity CAST Ginsrs. 143 made by indenting-tools, that of the pyramid is preferred, because of its simplicity and the ease with which its volume may be computed. The instrument used for making indentations is represented by Fig. 63. Fi^. G3. The indenting part of the tool is in the form of a pyramid, having a rhombus for its base, the diagonals of Avhich are respectively one inch and two-tenths of an inch ; the height of tlie pyramid one-tenth of an inch. In late experiments the form of the pyramid has been changed and improved somewhat, by causing it to make a longer line, and mark minute diiferences more accurately. 425. Standard of Comparison . — The volume of an indenta- tion made with this tool is taken as the measure of the work required to produce it, and is inversely proportional to the hardness of the specimen, that is (denoting by II the hai’dness of any specimen). n=\ (I.) V I denoting any convenient constant, and r the volume of the indentation corresponding to II. It has been found by experiment that a pressure of 10,000 pounds on the base of the pyramid, makes an indentation, in 144 NAVAL ORDNANCE AND GUNNERY. the softest metals used in guns, about nine-tenths of an inch long. The maxiimim indentation, one inch in length, of the in- strument is therefore assumed as the unit of hardness ; there- fore, denoting by V the volume corresponding to an indenta- tion one inch in length, we obtain from equation (1), ^ = ^or and in general, or, putting I = the number of tenths of an inch in the length of any given indentation, V 1000 v~ r ’ since pyramids are to each other as the cubes of any similar di- mensions. A pressure of less than 10,000 will probably be found better suited to the purpose, with the improved*tools. Abetter stand- ard of comparison may be found in some metal of uniform density and hardness, easily obtainable in all places. The silver coin of the country best fullils these conditions. The volume of the cavity made in this, by the adopted unit of pressure, may be assumed as the unit of hardness; and this divided by the volume of the cavity in any sample tested, will denote the hardness of that sample as compared with that of silver coin.* 426. Ekeoes of the Eodman Machixe. — The errors inci- dental to the use of this machine are due to three causes : 1st. AVeight of its different movable parts. 2d. Motion of the centres of gravity of the levers towards or from their fulcrnms. 3d. Friction. The First cause of error is avoided in practice by means of the adjusting-weights, already described. The system is brought into perfect equilibrium, so that any increase of AV will be balanced by a proportionate increase of P. The Second cause of error is comparatively unimpoi-tant, Rodman. CAST GUA^S. 145 because the levers AC and A'C', are so adjusted as never to make a large angle with a horizoTital line passing through the fulcrum, and in the case of the lever A"C^', which makes a lai’ger angle, the shape is such as to bring the centre of gravity very near the centre of motion. Let D denote the distance through which the centre of gravity moves. a denote the distance of the centre of gravity from the centre of motion. L denote the angle described by the lever during the breaking of a specimen. In general the levers are so adjusted that the line connect- ing the centres of gravity and of motion is horizontal when the movement of the lever is half completed. . ■ . D = a versine ^ L. It is evident that one or both of these factors is very small in each case. The Third cause of error is made as small as possible by the use of knife-edges and steel plates, and is practically inconsid- erable. The determination of the absolute breaking and other strains involve the elimination of errors due to friction, etc., but for obtaining the comparative strength of specimens, the machine is all that can be desired. 427. MoDiFicATioisrs of the Machine. — This machine is arranged for shoi't tensile specimens only, and as the power is at present applied, admits of only a very slight stretch, which is unsuifed to the breaking of specimens giving elongations of several inches. A change has therefore been tried in the lower fastening of the specimen, by which the power was applied at that point,, through a screw and cogwheels, and tins arrangement was foimd to answer the pmgiose in the most satisfactory manner.* Another change was made in order to get a continuous in- crease in the weight upon the scale-beam, instead of adding one weight at a time as is generally done. This was accom- plished by using a chain for a weight, which, being wound upon a reel, was reaclily reeled into the scale as fast as required to balance the strain upon the specimen. The principal advan- tage of this method is in working the indicator. 428. The Indicator. — In connection with the testing- machine it has been found desirable to have an instrument which would give a continuous curve representing the elonga- 10 * King. 14G NAVAL ORDNANCE AND GUNNERY. tions and corresponding tensile-strains for specimens of various kinds, in order to arrive at the exact dynamical value of the metal. 429. A.n instrument has been devised for this purpose (Fig. 64). It consists of a brass frame, AB, supporting a vertical cy- linder, C, revolved by the endless screw, S. This screw being turned by the tape, T, which draws around the pulley, P, as the weight, AY, is iNDic.VTOE wound along the (for tensUe strains and elongation.) SCale-beUm AYhen the chain was used as a weight, the cy- linder revolved as the chain was paid into the scale. This arrange- ment causes the cylinder to re- volve as the weight or strain upon the speci- men increases or diminishes, and if the mark- er, M, remains stationary, it will describe a horizontal circle upon the paper with which the cylinder is covered. Starting from the zero-point of the scale, the length of any arc of the circle will represent the strain upon the specimen at the instant the marker has arrived at the end of the arc. 430. If now the elongation of a given portion of the speci- men carries the marker in a direction parallel to the axis of the cylinder, it is clear that the curve, NO, described upon the paper, will accurately and continuously represent the relation between the elongation of the specimen and the corresponding strain upon it. In order to move the marker in this manner, it is connected with one end of the specimen by the clamp, Q', which tits into a centre-punch-mark on the specimen, while the frame and cylinder are attached to the other end, Q, of the specimen in a similar manner. 431. The portion of the specimen between the two centre- CAST GIIN'S. 147 puncla-marks is evidently the only portion wliose elongation will move the marker along the paper, and the space passed over by the marker divided by the original length of this por- tion, will give the elongation per unit of length of the speci- men, or the per cent, of elongation ; and the area hounded by the curve, NO, and the co-ordinates, NR and RO, measures the worli, of breaking the specimen. 432. Fig. G5 shows examples of the record made by the Indicator. It will be seen that in the specimens indicated, the first part of the elongation gives a very slight curve, which shows that the elongation increases rather more rapidly than the strain upon the specimen. This part of the curve extends from the origin to the point a. When the specimen begins to elongate freely, and there is a well-defined change in the rate of increase, the point a proba- bly coincides with the elastic limit. The strain increases as the elongation continues almost up 148 NAVAL ORDNANCE AND GIINNEET. to tlie breaking-point, h. Tliis shows that the tenacity of metai, which has been stretched beyond the elastic limit, is not en- tirely destroyed, as is commonly believed, bnt the work of the rupture has ljut just commenced. 433. Just before rupture takes place, in case of good wrought-iron, the specimen is observed to suddenly contract at some point, sometimes at two, and very rarely at a greater number; strain slightly diminishing at the instant, and the specimen breaks generally with a sudden snap, though very soft iron sometimes breaks so cpiietly as not to be heard at all. 434. The effect of the elongation of specimens in this man- ner is to change the smooth surface of the specimen to a I'ough and scaly appearance, and in case of bronze the specimen be- comes so irregular as to resemble a roll of putty flattened in various directions between the Angers. The elon 2 :ation of steel develops innumerable fine cracks nearly perpendicular to the surface. 435. In breaking a specimen a second or third time, it would seem that the metal must get weaker, especially since the sudden breaking produces a violent shock ; but on the con- trary, the specimen evidently breaks at the weakest point, and the shock and previous stretching have not been sutiicient to reduce the strength of the next weakest part of the specimen below that of the first one. It is sometimes found that even the third breaking requires a greater strain than the second. 436. Much labor in turning out specimens may be saved by the use of sockets with conical wedges (Fig. GG), which have been devised for the purpose of taking hold of the middle por- tion of broken specimens, and breaking them a second time. It will be seen that by cutting out the specimen barely large enough to turn up to the required diameter, a great saving may be effected over the usual method which requires the ends of the specimen to be quite large, while the middle portion, for nearly the whole length, has to be turned do^m to a much smaller diameter. Quite a number of specimen of each kind should, if possi- ble, be tested under as nearly identical circumstances as practi- cable, in order to get reliable mean results. 437. The usual form of specimens for tensile strain is such, that unless the weakest point happens to occur at the smallest section of the specimen, the fractured area will be larger than the measrired section. By using longer cylindical specimens this source of error will be avoided, in all but exceptional cases, arising from flaws or other defects. Besides, the usual or standard form of specimen admits of transverse strains due to CAST GUNS. 149 the iineqiial bearing of the ends in the sockets of the testing- machine. This defect is greatly improved by using longer specimens. 438. The simple measure of the strain required to break a piece of metal, without regard to the elongation produced before rupture takes place, is not a measm*e of what occurs in practice ; for when a bar of ^ iron is broken, a certain space is passed over by the breaking-force in separating the fibres, and as this space bears no analogy whatever to the tensile strength of the metal, it must come in as an independent factor. For example, the metal of cannon is stretched at every discharge ; and when- ever metal is subject to a variable strain, there must be a corresponding change of length. These elongations may be very small in amount ; so small, in fact, as to be inappreciable in ordinary measurements, but it is no less certain that they exist. 439. EIEIILE’S TESTIEG-MA- CEillsE. — This is a good example of a horizontal testing-machine adapted to testing rope, chain, wire, bar or plate iron, etc. The iron frame, CC (Fig. 67), and the timbers which support the iron guides, SS, are all firmly secured to a solid foundation of ma- sonry. 440. The Levees. — Enclosed in the frame, CC, is a heavy intermediate lever, A, one fulcrum of which bears against a Fig. G6. smooth steel surface composing a part of the frame. - The lower fulcmm, D, presses against the clevis, E, which connects directly with the clamps holding one end of the test specimen. This lever is suspended at the larger end by clevises, F, swinging from the iron frame, C, and at the smaller end by a link or rod connecting with the differential lever, or scale-beam, G. 441. Eecoedixg the Stkain. — On this beam is an ordinary weight-dish, H, upon which standard weights are placed for recording the strain to which the specimen is being subjected. A weight of one pound on the weight-dish indicates a strain of one thousand pounds on the specimen under trial. 442. Application of Powee. — At the other end of this 150 NAVAL OKDNANCB AND GUNNEET. machine is placed a hydraulic pump and jack, I ; the cross-head, L, carrying the clamps for one end of Ihe specimen, being at- tached to this by the bolts MM, The whole arrangement Fig 67. — Eiehlc Testing-macliine. travels along a railway, SS, on low, strong wheels, and may be secured in any position, to accommodate the length of the speci- men, by keys dropping into slots on the railway. The power is applied to the jack, I, by the pump, J, while the scale-beam is kept horizontal by the use of the weights ; its equipoise being indicated by a pointer attached to the centre fulcrum of the beam. 413. Adjustment. — When the specimen is in position, the lever and beam must be balanced by means of the balance-cup, K, hanging from the extreme end of the scale-beam. All the knife-edge bearings and fulcrums are made of steel, and are CAST GUNS. 151 very strong and true. As each part swings perfectly free, there is comparatively no friction, and the strain on a specimen can he weighed to within a few pounds. 444. The Diffekential Lever. — Fig. 68 represents the differential lever and scale-beam used in tliis instrument. The link O is connected with the intermediate lever, A (Fig. 67). If a weiglit of one hundred pounds he suspended from the link O, one half, or fifty pounds, will be suspended by the hearing P, and fifty pounds by the hearing P'. These weights being transmitted through links to the hearings Q and Q', P and P' are equidistant from the bearing T, while Q and Q' are at unequal distances from the centre bearing or fulcrum, R. If the distance Q' R be 6^ inches, and Q R be inches, and the weight at Q and Q' 50 pounds, then the moment on the side Q will be 50 X 5|- =: 275 ; and the moment on the side Q' will be 50 X 6|- = 325. The difference of these moments, or 325 — 275 = 50, will be the unbalanced moment; and if a weight of 5 pounds be suspended on the scale-beam at a distance of 10 inches from the fulcrum, R, it will counter-balance the extra moment on the side Qb The vertical planes passing through R and T are one-half inch apart ; therefore if a one-hundred-pound weiglat be suspended at one-half inch from R, acting as a simple lever, it will be under precisely the same conditions as the differ- ential lever with the above dimensions.* Section III. — Fahrication. 445. FABRIC ATIOFT OF CAST-IROFT GUNS.— The details of the casting of a XY-inch gun, as practiced at the Fort Pitt Foundry, Pittsburgh, Pa., will be taken as an example, f 446. The Furnaces. — Two reverberatory air furnaces are used for melting the iron of which the gun is made, the draught being produced by high chimneys instead of by a blast. Fig. 69 represents the Fort Pitt Air Furnace, the peculiarity being that, as the iron melts, it runs backwards toward the bridge-wall, C ; the crown of the furnace being so constructed as to cause the flame to impinge against the surface of the pool of melted metal, while at its greatest temperature ; thus it is melted with- out coming in direct contact with the carbon, as in the blast- * See a description of Kirkaldy’s machmes in the London Mechanics' Magazine of the 9th March, 1866. f Conamdr. R. F. Bradford, U. S. Navy. — Navy Ordnance Papers, No. 3. 152 NAVAL OKDNANCE AND GUNNERY. furnace — where the fuel aTid fire are mixed together. Bitu- minous coal is used in these furnaces. 417. In the Fig. 69, A represents the metal-chamher, being that part of the furnace where the iron, for what is termed a “ heat,'’’ is placed. The bed of this chamber is first prepared by covering it with a layer of sand, Avhich is hardened down, giv- ing it at the same time the desired curve ; then boards are laid, upon which the pigs of iron to be melted (or charged) are piled; B repi-esents the fuel chamber, or fireplace, the name passing over the bridge-wall, C, and through the metal chamber on its way to the chimney, I) ; ^ is the tap-hole ; X, the charg- ing-door, made of fire-brick bound together by iron bands ; E is the ash-pit ; and f, the grate-bars. The dotted line represents the surface of the metal when “ doicn^’’ or melted. 448. In the charge used for a XV-inch gun, the greatest depth of metal, when down, is about nine inches, exposing about one hundred square feet of surface to the flame. It is very necessary, in castiug a lot of guns, to have the bed CAST GUNS. 153 of the fiu’nace prepared, in every instance, the same as with the standard gun, as the treatment of a given charge of iron may he varied by the manner of dressing the bed of the furnace. By exposing the same amount of iron in a broad, shallow pool, it is more eilectu dly brought under the influence of the flame than when collected in a narrow, deep pool. 449. Charging the Furnaces . — In charging the furnace for a “ heat,” the ditferent grades of iron which have been decided upon are weighed and piled, in the proper proportions, in the metal-chamber of the furnace, always having the second-fusion iron nearest the Are. 450. Fusions. — The iron, as it comes from the smelting-fur- nace, is termed ‘■Faw pig,” and is a first fusion. The second- fusion iron (as understood by founders) is produced by a com- bination of raw pig and second-fusion, melted in an ordinary fir-furnace, and then run out. These pigs are usually of a dif- ferent shape than the raw pig, but to prevent confusion, and at the same time to distinguish different second-fusion irons one from another, each should be distinctly marked and piled separately. 451. The object of using a second-fusion iron in a casting is to obtain greater density than can be produced from the raw pig alone ; it also increases the tensile strength. (Art. 349.) 452. The Charge.— In casting the XV -inch gun, the fur- naces were each charged as follows : Bloomfield raw pig 21,143 lbs. Bloomfield second fusion (red-dot) 13,214 “ Bloomfield second fusion (red-cross) 2,043 “ 37,000 “ Total in both furnaces 74,000 “ The second fusion, marked ‘‘red-dot,” consisted of the fol- lowing combinations, viz. : Bloomfield raw pig 50,000 lbs. Bloomfield second fusion 19,575 “ . Run into pigs and marked “ red-dot ” 69,575 “ The proportions of the other grade, marked “ red-cross,” are as follows, viz. : Bloomfield raw pig 29,410 lbs. Bloomfield second fusion 32,590 “ Run into pigs and marked “red-cross”. . ..62. 0(io “ 154 NAVAL ORDNANCE AND GUNNERY. The second-fusion iron used in these combinations is pro- duced by melting two parts of raw pig with one of second fusion- 453. Molding, in general terms, is the process by which a cavity of the form of the gun is obtained, by embedding a model in sand and then withdrawing it. 454. Moldhuj-composition . — The sand most nsed for this purpose is a kind of loam, which contains a sufficient quantity of clay to i-ender it moderately cohesive when damp. Sand, possessing all the qualities required for molding, is seldom, if ever, found in a state of nature; but when the requisite cpiali- ties are known the materials may be selected, and an artificial composition produced without difficulty. The sand should be principally of silex, very refractory, and of the kind commonly called sharp-sand. When not sufficiently refractory, the sand is vitrified by the high temperature of the melted metal, and pro- tuberances are found upon the casting which are not easily removed. 455. The method of preparing the molding-composition artificially, varies according to the kind of casting for which it is to be used. In preparing it for cannon, great care is taken to introduce the exact quantity of clay required. When too little is used, the composition is not sufficiently adhesive ; when too much is used, the mold is injured by contraction iii drying. The sand is first carefully sifted, then properly mixed and moistened with water in which clay has been stu-red ; the composition is considered sufficiently adhesive when it will retain its form after having been taken in a moist state and squeezed in the hand. 45G. The same composition may be repeatedly used for mold- ing, but as the adhesive property of the clay is destroyed by the heat to wdiich it is exposed in casting, more clay must be added every time, in the same manner as when the composition is first formed. 457. Models. — The wmoden model is technically called the pattern. Models for casting should be made of one or several pieces, according to the form of the mold required. When the form is sucli that the whole model can be withdrawn from the sand at once, without injuring the mold, a single piece will suffice; but generally the model is composed of several pieces, so fitted that "they can be put together in succession as the molding progresses, and finally taken apart and removed by piecemeal when the molding is complete. 458. The Flask. — The mold is formed in a case of cast-iron, called a flash, consisting of several pieces, each of which has CAST GUNS. 155 I 1 i 156 NAVAL ORDNANCE AND GUNNERY. flanges perforated with holes for screw-bolts and nuts, to unite the parts flrmly. In casting the XY-inch gun, a circular flask (Fig. TO) is used, consisting of live upright sections, secured together by clamps fitting over flanges, AAA, at either end of the sections ; its thickness is one inch, and it is pierced Avith holes. (Art. 481). 459. Divisions of the Flask. — The breech, or loAver section, BB, is made of sufflcient length to cast the base of breech, cascabel, and square knob ; the ne^t above, CC, is tAventy-five inches in length and cylindrical, being the part which embraces the cylinder of the gun ; the next is the trunnion-sections, DD, fitted Avith trunnion-boxes having movable plates on their ends, that the trunnion pattern may he placed and removed after the mold is finished ; then there are two sections above this, £E and FF, the upper being about three feet longer than the required length of the gun, to admit of a “ sinldng-lieadr The entire length of the flask is tAventy feet. 460. Pkocess of Molding. — The pattern is in five sections, each slightly tapered, that the mold might he uninjured in its withdraAval. The average thickness of sand forming the mold is about eight inches. 461. In making the mold, the lower section is placed upon a plate of iron in an upright position ; the pattern being intro- duced and centred, the space hetAveen the pattern and the flask is then filled with molding-sand, using thin layers, which are rammed uniformly until the Avhole of that section is complete. The patterns for the “ runners,” ER, and their branches, h, b, h, are introduced as the Avork progresses ; the latter, being tapered, are easily removed. 462. After the mold for the breech, or lower section, is finished, the next section of the flask is placed upon it and secured, the pattern for which is introduced, and, being fitted with doAvels, held accurately in place. The molding is continued with this section as Avith the first, and when completed is lifted off, care being taken not to break the mold (the pattern being left in the mold). 463. The third or trunnion section is then placed upon the second, the model being adjusted as Avith the second, and the molding is continued in this Avay, until the whole is completed, thus insuring a perfect mold throughout, free from irregulari- ties at the junction of the sections. 464. The patterns are then Avithdrawn, and the molds fin- ished and smoothed about the lock-lugs, sight-masses, and side- gates, after Avhich it is placed in the drying-oven, the two lower CAST Gims. 157 sections being clamped together, the others singly ; and -^hen thoroughly dry, withdrawn. 465. A wash composed of pulverized coke-cinders, molasses, and water is then applied ; this dries qiiickly, and produces a smooth, hard surface, thus preventing the molten metal from entering into the sand of the mold, and it insures a smooth, clean- coating. 466. The Coee-bakkel; — The core-barrel (Fig. 71) consists of a water-tight iron tube, AD, about fifteen feet long, and Cap uith journal used when making Core. SEOTIOH AT A-U. Journal and Ring-bolt put in I to tui n barrel on in maldng ® Core. Fig. 71. — Core-barreL three-fourths of an inch thick, its exterior diameter at the head being twelve inches, and tapering one-fourth of an inch, at the lower extremity, to facilitate its withdrawal after the cast. It is rounded at its lower end, D, and fiuted throughout the 158 NAVAL ORDNANCE AND GUNNERY. cylindrical part, to allow the escape of gas generated by tlie burning of the composition with which it is covered. 467. Pkepaeing the Coee. — To prepare the core for cast- ing, journals (Pig. 71) are first fitted, at either extremity of the barrel ; it is then placed in a horizontal position upon an iron truck, being supported by the journals, which rest in bearings. AVhile so supported it is easily turned by means of a crank attached to one of the journals, and is first wrapped or served with white-hemp stuff (18-thread), covering that portion of the barrel which comes in contact with the molten iron. 468. Over this a coating of molding-composition is applied quite wet, which is wrapped with twine, to insure its adhering. When about half di-y, the outer or last layer of composition is applied, which, being made quite sticky, adheres readily. Great care is taken to have the surface of the core perfectly smooth, and the composition of unifonn thickness. The diameter of the core-barrel for a XV-inch gun, when complete, is 13.75 inches at the top, and slightly tapered at the bottom. 469. When ready, the truck supporting the core-barrel is rolled into the drying-oven, and' when perfect!}' dry removed; the usual time required being eighteen hours. The Composi- tion then receives a coating of coke-wash, when it is again j)laced in the oven, where it remains until thoroughly dry. Upon its final removal the journals at either extremity are removed, being replaced by the regular cap on top, and a tight- fitting screw-plug at the bottom, which is covered with mold- ing-composition, and dried by a fire built under it. 470. The Pit. — The pit (Fig. 70) is circular in fonn, nine- teen feet deep, and twelve feet in diameter ; the walls are of brick, and the bottom, an iron tank of one-half inch sheet-iron, extending upwards eight feet. The mouth of the pit is provided with iron covers, made to fit closely to prevent escaping of heat from the fire built around the flask. 471. Placing xhe Flask. — The mold being thoroughly dry, the two lower sections, clamped together, are lowered and secured in an upright position in the centre of the pit — a layer of sand having been previously placed in the bottom, for the flask to rest upon ; the other sections are lowered singly, and secured in their places, the whole being braced from the sides of the pit to retain it in a vertical position. 472. Cranes. — Cranes are employed for moving cannon, molds, and other heavy masses about a foundry. They are fitted Avith cog-wheel gearing to obtain power at the expense of time, and are often worked by steam. Care must be taken CAST GUNS, 159 to give great sti*engtli to this machine, and to caiioe its motion to be easy on its pivot. When properly adjusted a weight may he lifted and transported from one point to another, anywhere within the limits of the circle described by the arm. 473. AnjtiSTixG the Core. — The core is then lowered into the mold of the gun. To centre and secure the core-barrel in position it is necessaiy to have a frame, usually termed a “ spider to support and hold rigidly in place the core when properly centred. The spider, SS (Fig. 70), is of cast-iron, about two and one- half feet high, having three legs, each of wliich having a projec- tion at the bottom, fitted with an adjustable screw, which rests upon the upper flange of the flask ; there is also a funnel or sleeve fitted in the central part of the top, through which the core-barrel passes and fits closely, holding it firmly, so that any movement of the frame will produce a change in the position of the core. 474. The Gauge, for centering the core, consists of a long, wooden rod, on the end of which a piece of board is fixed at right-angles, and on this board a light is placed. The length of this projecting board, previously determined, is the distance the core should be from the mold when in the centre. Having adjusted the core in the mold, by means of the screws fitted in the legs of the spider, it is secured firmly by clamps, FI (Fig. 70), made to fit over the top of the frame and under the flange of the flask. 475. Meeting down the Charge. — The mold and core-bar- rel being in readiness, and the furnaces charged, the fires are started and regulated so that the iron will be “ down ” in both furnaces at about the same time. Particular attention is paid to the manner of firing, that it be uniform and steady ; also that the fires be kept clean to produce not only the best, but uniform, results. The length of time required to obtain complete fusion of the charge depends in a great measure upon the state of the atmosphere, etc., being from five to eight hours. 476. When nearly down^’’ it is necessary to work or pud- dle it, that any lumps or balls of unmelted iron may be brought in contact with the flame. This is done by inserting long iron rods or green saplings in the air-holes of the metal-chamber. Saplings are preferred, as the steam generated from the sap in the wood causes the molten iron in the pool to boil, and the more dense iron at the bottom is mixed with that of the surface, while many of the impurities are dispelled at the same time. 160 NAVAL ORDNANCE AND GDNNEET. 477. When the charge is “clown” specimens are taken out to ascertain if the iron is in proper condition, or sufficiently “ IvKjli ” (Art. 351) ; that is, sntiiciently decarbonized ; these spe- cimens are run in dry-sand molds, and are about six inches in length, varying in size from one-quarter of an inch to one inch square. When cold they are broken, and the appearance of the fracture indicates whether the iron is sufficiently ’■'■high'' (Art. 356). The three-cpiarters of an inch specimen is required to he well mottled. 478. As the density and tensile strength of the iron depends in a great ineasui’e upon the “highness ” to which it is brought, extreme care is required in this operation. Where the first spe- cimens proved are unsatisfactory, the iron is kept in fusion still longer, during which time it is puddled v/ith green-poles. 476. Tapping the Fuknace. — When eveiy thing is in readi- ness the furnaces are tapped, and the molten metal conducted by runners or troughs coated with fire-clay directly to the side- gates of the mold, EE. It flows into these and down to the bottom, entering the mold by branch-gates, b, b, b, at intervals of one foot apart from bottom to muzzle. Tlie branch-gates are cut so that the metal will enter the mold in a direction toward the axis, upward, care being taken to keep the molten iron after it enters the mold well stirred with long poles to prevent scoria from entering the trunnion- holes, and also to assist in mixing the metals from the different furnaces. 480. When the mold is nearly full the tap-holes are stopped, and the surface of the metal in the gun-head covei-ed by a layer of pulverized charcoal, to prevent its chilling. The time of till- ing the mold is about fourteen minutes. The surplus iron remaining in the furnaces is run into pigs, but is not used again for gun-metal. 481. Heating the Pit. — During the casting, the gas which is generated and passed out through the holes in the flask is ignited by dropping small quantities of molten metal into the pit, and as soon after the “ cast ” as possible, a fire is built in the pit, about the bottom of the flask — wood and bituminous coal being used in sufficient quantities to burn four or five days ; the mouth of the pit being covered, after the mass is thoroughly ignited. 482. Cooling the Casting. — The water for cooling is taken from a hydrant, where the supply is constant and uniform, the connections being made by rubber hose. It is conducted to the bottom of the core-barrel by means of a copper tube, one and a half inches in diameter, TT (Fig. 70). This tube passes through CAST GUNS. 161 a water-tiglit joint in the centre of the cap, and extends to vrithin a few inches of the bottom of the barrel ; being open at its lower end, the water passes ont and ascends through the aiinidar space between the tubes, and is discharged from the core-barrel at a point above the casting, Y. 483. The water for cooling the core is started before the furnaces are tapped, and allowed to run through the barrel, and off by the discharge-pipe, Y, Y, to ascertain if every part is per- fectly tight ; it continues thus to circulate until the core is re- moved, at about the rate of forty gallons per minute. 484. Withdrawing the Core-harrel . — This is done about eighteen hours after the casting, as soon as the metal becomes sufficiently cool to permit of its removal. The withdrawal causes no delay or trouble, as the rope with which it is wrapped is consumed, and therefoi’e leaves the barrel detached from the composition surrounding it, the latter adhering to the bore of the gun. 485. Cooling log air . — After the withdrawal of the core-bar- rel the cooling is continued by forcing a continuous stream of air into the cavity thus left, by means of a rotary blower, driven by a small steam-engine, the air being conducted from the blower to the gun through an eight-inch sheet-iron pipe, which is introduced into the bore and to within one calibre of the bottom. 486. A record of the rate of cooling is kept by noting at regular intervals of time the temperature of the water or air on entering and leaving the core. When the temperature of the air in the bore is nearly down to that of the outside atmosphere, the blower is stopped, and the pipe removed. Time of Cooling . — The time of cooling is about eight days. For XY-iuch guns it usually varies from seven to nine days, depending mainly upon the temperature of the air and the speed of the blower. 487. Removestg the Casting. — The gun is hoisted from the pit ten days from the time of casting. Preparations for re- moving the ffask commence the day before. Transporting-lugs are cast on the sinking-head, to which slings are attached for hoisting and landing the casting in the foundry, where all irregularities are chipped off, and the sur- face thoroughly cleaned of sand or foreign substances, and pre- pared for the lathe. Weight of rough casting, including sinking- head, etc 66,000 lbs. Weight of rough gun. ... 61,000 “ Weight of finished gun 43.000 “ 488. Condition of the Casting. — This mode of casting, by 11 163 NAVAL ORDNANCE AND GUNNERY. means of side-gates, is resorted to in order to preserve the form of the mold. If the metal was conducted into the upper open- ing of the ixiold itself, its fall upon the sides and bottom would injure their forms. The condition of the casting in reference to smoothness depends in a great measure upon the state of the mold when the metal is run. It should be perfectly dry and hard, otherwise the metal mixes with the sand, and adheres in clumps, produc- ing a I’ough and irregular casting, the cleaning of which is a dithcult and laborious job. 489. TIeading-lathe. — The easting is next placed in what is called the '■^heading-lathe (Fig. 72), where it is prepared for the horing-lathe. The cascab el-bearing, base of breech, and a section of the chase are all turixed down to finished dimensions while in this lathe, as the chase and rounded part of the cascabel- knob form the bearings for the boring-lathe. The cut at the muzzle, or place Avhere the sinking-head is to be broken off, is also made in this lathe. A (Fig. 72) represents the muzzle-ring with adjustable screws; B, the bearing in which the muzzle-ring revolves; C, the chuck, or mortise, into which the square knob of the casca- bel is inserted and secured ; D, the tools or cutters with rests. The bearing in which the muzzle-ring revolves is a heavy cast- ing, the bottom of which fits into grooves in the rack, andean be moved to or from the chuck, being adaptable to long or short guns. 400. Ad.justmext ix Lathe. — The gun is lowered into place, the square knob in rear of the cascabel fitting into the chuck, while the muzzle is introduced and projects several inches beyond the face of the muzzle-ring, in which position it is approximately centred, and held firmly in place by adjustable screws in the chuck and muzzle-ring. 491. The breech is adjusted by placing a shaiqx-pointed in- strument in the rest, and bringing it in contact with the surface of the easting near the base-line, and while turni 112 : the gun — which is done by machinery — -the screws in the chut^c are moved nntil coincidence of the line around the gim is obtained. CAST Guisrs. 163 492. At the muzzle a bar of iron is laid upon blocks, so that it shall be just inside the bore, and nearly in contact with its interior siu’face. As the gun turns, the distance between this point and the metal of the bore is observed, and equalized ap- proximately, by the screws in the muzzle-ring beariug. 493. A Avooden disk turned to fit the bore accurately, bear- ing a string attached to its centre, is then pushed to the bottom of the bore, and made to assume a position in a plane perpen- dicular to its axis. The string from the centre of the disk is long enough to reach some distance outside of the muzzle ; the outer end being made fast to an upright the same height as the inner end or centre of disk ; the string is now hauled perfectly taut, and the gun again tuimed, a square being placed upon blocks about one foot in front of the muzzle, close to the string ; and as the gun revolves, the distaiiee, if any, which the string deA'iates from the square is observed and corrected by again moving the screws in the muzzle-beariug. 494. When properly centred, the string will remain in the same position in the square and be the same distance from the interior surface of the gun, throughout an entire revolution, showing that the axis of the gun and lathe coincide. "With the holloAV cast-gun it is necessary that it shoidd be centred from the bore, as it sometimes happens that its axis does not coincide with the axis of the casting, which is one rea- son for casting them above the true size, to admit of being fin- ished by the interior, or so that the axis of the cast bore shall coincide Avith that of the gun when turned. 495. Measuring the Casting. — The casting is next meas- ured, taking diameters at the principal points, length of the casting, sinking-head, diameter and length of trunnions, distance from centre of trunnions to base-line, size of lock and sight- masses ; also excess of metal over finished dimensions at points ten inclies apart, commencing at forty -five inches ahead of base- line. Shoidd cavities or defects of any kind he discovered, their depth and full extent will he ascertained and noted, thus pre- venting useless subsequent labor in case they exceed the limits of toleration. 496. Turning down the Casting. — The gun being centred, the turning commences at the muzzle ; this is done by placing a tool in the rest, Avhich is brought in contact with the surface at the desired point, the metal being turned off as the gun re- volves. The rest^ or support which holds the tool, is arranged to move in two directions, one toAvard the gun, or at right an- gles to the axis of the lathe, by which means the depth of cut is 16i NAVAL ORDNANCE AND GUNNERY. regulated, and the other in line parallel with the axis, that is, from muzzle to breech. 497. This last movement is effected by means of s,fecd, the motion being given by a fork attached to one of the trunnions, and at every revolution of the gun the rest is made to advance. The first cut is usually an inch deep, commencing at the muzzle where the sinking-head is to be cut off and extending thirty inches towards tlie trunnions. The second and third cuts are commenced at the same point as the first, and are about one and one-eightli of an inch deep ; increasing as the tool advances in the gun, other cuts are made until the metal is reduced to the finishing diameter. 498. Eemoving the Sinkixg-iiead. — The cut at the muzzle, or the place where the “sinking-head” is to be broken off, is next made ; its depth is usually about seven inches or to within three or four inches of the cast bore. The gun is now taken from the lathe, and the “ sinking- head ” broken or wedged off, at which time the appearance of the metal at the fracture should be examined as to color, form, and size of crystals, texture, and whether sharp to the touch ; it is also necessary to ascertain its degree of hardness, and how the metal works under the tools, in the different stages of its fabrication ; all of which should be duly noted and form part of the record of the gun. 499. Cu'mxG out Specimens. — Three specimens for densi- tj, tensile strength, etc., are taken from the face of the “ sink- ing-head,” next the muzzle, at points equally distant from each other around the circle and as near as possible to the outer crust of the casting (about one-fourth of an inch), the axis of the sam- ple being parallel to the axis of the gun. These specimens are of the standard size, and are marked on each end with the letter II, to denote head-specimens ; also number of gun from which taken, and the number of specimen. (Art. 3S0.) 500. IloRixG-LATUE. — Tliis lathe (Fig. 73) consists of the rack, EE, two journals, AA, and the boring-rod, B, the supports CAST GUNS. 165 of wliicla rest upon tlie rack, and are of suck a heiglit tliat the axes of the journals and horing-rod shall be in the same hori- zontal plane. 501. The gun while in the lathe rests in the journals at the cascabel bearing and chase; the metal at these points having been turned down to the finished size while in the heading- lathe, the square knob or cascabel is secured in the chuck by tightening the screws equally in all directions. 502. Adjustment iisr the Latue. — The boring-rod is first introduced a short distance into the bore of the gun, and the space between the exterior surface of the boring-rod, and the exterior surface of the gnn at the muzzle, observed. For this purpose a thin wooden gauge is used, pointed at one end and having a notch at the other, which takes the outer surface of the gun at the muzzle, the gauge being laid on the face of the mu^&zle, and, of course, perpendicular to the axis of the bore. As the gun revolves, the distance above, below, and on either side is observed, thus verifying the perfect concentricity of the axis of the gun at the muzzle. The adjustment is completed at the breech, by slackening the bolts at the cascabel bearing, leaving it free to move on the rest ; and should any lateral motion be perceptible, it is correct- ed by adjusting the screws in the chuck, after which the con- centricity is complete from breech to muzzle. 503. Boring. — In boring, the first tool or cutter used is fourteen inches in diameter, being secured on the end of the boring- rod, or arbor, C, which is made to advance by machinery as the gun revolves, until arriving at the bottom of the cylin- drical part of the bore. The chamber is next roughed out, and then the “ reamer,” or finishing-tool (fifteen inch), for the bore is used ; and lastly the chamber “ reamer.” 50i. During the process of boring, the turning continues, and the exterior is finished, except between the trunnions and about the lock and sight-masses ; the former being planed off by a machine for the purpose, and the latter reduced by chip- ping and filing. To insure a smooth surface in the bore, all the work on the exterior surface of the gun is suspended while the reamer, or finishing-tool, is being used. 505. The boring being completed, the cylinder-guage is in- serted before removing the gun from the lathe, to ascertain if it passes freely to the bottom of the bore ; the chamber-reamer should also be measured after use in each gun, and, if found correct, the gun is moved from the lathe. 506. Trunnion-lathe. — The gun is next placed in the 166 NAVAL ORDNANCE AND GUNNERY. trunnion-lathe, which consists of the rack, two journals, and the trunnion-head, or shaft. The gun is placed in the journals, which are of such a height that the axis of the gun, when properly adjusted, shall be level, the gun being supported at the chase and cascabel. 507. The trunnion-head consists of a hollow shaft in which the cutters are placed, and is supported irpon a rack previously placed at right angles to the axis of the gun, and of such a height that it shall he in the same horizontal plane as the axis of the gun . 508. In turning and finishing the trunnions, the hollow shaft of the trunnion-machine is made to revolve about the trunnion, the gun being stationary ; and, as the turning pro- gresses, the shaft moves on its rack towards the gun, its speed being regulated as circumstances require. One trunnion and rim-base being finished, the gun is turned over, bringing the other trunnion in the same position as the first, and is turned in like manner. 509. The Planing-machine. — The metal in excess between the trunnions is removed by the planing-machine (Fig. TI), which is placed on the side opposite the trunnion-machine, and is so arranged that the movable point in which the cutter is se- cured, A, traverses forward and back in a horizontal plane over that portion of the gun between the trunnions that has not been turned down. The cutter is secured in a spring-set, B, by which means it cuts only while moving forward, the gun being ttirned the tvidth of the cut after each passage of the planer. 510. The desired curve of metal is obtained by introducing a guide-plate of tlie proper form, C, in rear of the cuttei’-rest. After the planing is finished, the gun is removed from the CAST GUNS. 167 lathe, and placed upon the skids, where the surplus metal about the rim-bases, lock, and sight-masses is reduced by chipping, and finished by hand. 511. Cutting- PIole for Elevating-screw. — The gun being carefully levelled, and the trunnions placed horizontal, the po- sition of the centre of the serew-hole, which in the guns of the Dahlgreii pattern is tangent to the radius of the breech, is marked on the neck of the cascabel with a centre-punch. 512. The Boring and Screvycutting Machine, which is a con- venient, portable hand-drill press, is then placed on the cascabel, the boring-shaft inserted in the hollow leading-bar, and its mova- ble centre placed in the mark. The instrument is then set verti- cal, by a spirit-level, on the cogged driving-wheel and the four pairs of set-screws on the clamp-head embracing the cascabel. 513. The centre is then removed, and a drill inserted in the lower extremity of the boring-shaft, which, being held firmly by a shoulder and turned by a four-armed wrench, while pressed up to the metal by slowly turning the cogged driving-wheel, cuts the hole. This is successively enlarged, by two or more counter-bits, to the size of the body of the screw. The cutter is then inserted in the leading-bar, and the thread cut. 514. Drilling the Yent. — The proper position for the ex- terior orifice of the vent having been determined and marked upon the base-line, the drill is set at the required angle by the \84T' \70& yent-guide (Art. 566), and held in position by a frame of cast- iron, which is secured on the gim. 1G8 NAVAL ORDNANCE ANT) GENTNERT. After the vent is fairly started, the g;im is tirmed over, that the cutting may not obstruct the drill. The left vent is simply indicated, being bored two inches. The scpiare knob of the cascabel is now brohen off and the end of the cascabel rounded and finished ; also the foundry number is stamped on the right rim-base in one-fom-th-ineh figures. 515. Marking Guns. — Guns for the ISfaval service, received by authority of the llureau of Ordnance, are to be marked in the following manner, viz. : On the cylinder, in the line of sight near the sight-mass, all accepted guns are to have stamped an anchor two inches long. On the base ring or line, the initials of tne foundry, the register inamber, and weight of gun in pounds. On the right trunnion, the calibre and year of fabrication. On the left trunnion, the letter P, and the initials of the In- specting Officer ; all the above in one-inch letters. Oil the upper jaw of the cascabel, the preponderance in pounds to be stamped lightly with half-inch figures. On the end ot the upper jaw, the cascabel block, and head of pin, the foundry number in quarter-inch figures. The foundry number is also to be marked on the right rim- base. Guns rejected for imperfections of any kind will have the letter 0 stamped on the anchor, so as to partiallv obliterate it. 510. PABEICATIOJI OF BEOAZE IlOAVITZEES.— A model or pattern of the gun is first prepared ; to do this it is first necessary to lay down on paper an exact draAviug of the gun de- sired ; showing, on a convenient scale, its general appearance and the relative proportions of its different parts, both exterior and interior ; the full dimensions being put down opposite each part. 517. A drawing of the gun is now made on a smooth board, full size, the dimensions taken from the draught, but laid down by a rule, Avhichfis larger than an ordinary one by 0.15 of an inch to the foot, which alloAvs for the shrinkage of the metal in cooling. 518. Two pieces of clear, well-seasoned white pine are se- lected of such proportions that, Avheu joined, they will form a sqiiare piece of timber, considerably larger, and of greater di- ameter, than the gun itself. The two corresponding faces being smoothed, so that a perfect junction may be formed, four holes are made in the face of one, Avhile corresponding pins, termed steadijing-pim^ are fitted in the face of the other ; this is for the purpose of insuring the vCxaet adjustment of the parts while molding. CAST GUXS. 169 The pieces are then joined face to face, the extremities rounded otf, and iron bands driven over the ends, for the pur- pose of uniting them tirmlv. Thus fitted, the wliole is carefully adjusted in a lathe, so that the axis shall fall directly in the plane dividing the two parts. It is then turned down to the required form. _ 519. The pattern consists of three parts: the model of the gun itself, the sinking-head, and knob of the cascabel, which is enlarged to form a square projection by which the piece can be held while being turned and bored. When the pattern is detached from the lathe these parts are separated with a saw. Pieces of wood representing tlie sight-masses, the lock-lug, and the loop are tacked on in their proper places, and the whole is sand-papered and varnished. The pattern is now complete, and the parts will represent the appearance of two semi-cylindrical bodies exactly similar in size and shape. 520. The Flask is a long, rectangular box, P (Fig- T6), made of iron-plates bolted together, the top and bottom ones, whicli are movable and called lids^ being of one-quarter inch wrought-iron and the sides of half-inch cast-iron. It consists of two equal parts, each of which is large enough to contain half the mold ; these parts are each fitted with a flange, extending entirely around the flask, and perforated with holes for screw-bolts and nuts to unite the two parts firmly. They are also fitted with joimnals at the ends for conveni- ence in suspending them ; and with eye-bolts for the pur- pose of moving them about, lowering the flask into the pit, etc. The head of the flask has a large hole and two small ones, in wliich to pour the metal and to permit the escape of gases. The flask has strengthening pieces at different places, and inside is divided into compartments by iron plates having a score cut in them to receive the pattern. These plates serve to make the mold more compact. 521. Moldixg. — A smooth, flat board, whose dimensions are a little larger than the flask, is placed on the ground, and the half-model is placed upon it flat side down. The corre- sponding half-flask with its lid removed is then placed around it and clamped to the board. Molding-composition is intro- duced in small quantities at a time and rammed compactly around the model. This is continued until the flask is fllled ; the lid is then bolted on, the flask hoisted, turned over, and again deposited on the ground with the lid down. The board is then undamped ; the face of the mold then brushed off, and 170 NAVAL ORDNANCE AND GUNNERY. sprinkled with a kind of wdiite sand, called parting-sand, to kee]3 the two parts of the mold from sticking together. The other ha If -model is then placed in position on top of the first, and tlie corresponding half-flask with its lid removed secured in place to the under one. The sand is again introduced and rammed compactly around the upper half-model as before, the steadying-pins hold- ing it firmly in jflace ; when the flask is filled the second lid is bolted on. The half-flasks are now separated and each is found to con- tain one-half of the mold with the corresponding parts of the model embedded. The latter are then carefully withdrawn and all imperfec- tions on the face of the mold are repaired, w’hen it is coated with a composition of brick-dust, pipe-clay, molasses, and water, which gives the interior of the mold a smooth, hard surface. 522. A runner is made on one side with a single branch at the bottom for the purpose of introducing the molten metal. This channel is made by embedding a rod in the sand between the two half -flasks in molding the piece. The branch runner enters the mold in an oblicpie direction. The entrance of the metal to the mold at its bottom is at an angle which gives a rotary-motion to the liquid, the effect being to produce a depression in the centre and a gravitation to it of all scoria. A narrow channel is cut in the molding-composition some- what larger than the small hole in the head of the flask, and leading from it to the channel left by the rod. Another nar- row channel is cut from the other small hole, intersecting the mold about a foot from the top, by which the height of the metal in the mold can be ascertained during the casting. 523. The drying-oven is a rectangular apartment built of brick, with an arched roof and iron doors, having tracks led into it for the ears upon which the flasks rest. It is heated by an open fireplace which is fed from the outside with coal. 521. Drying the JSLold . — The half-flasks are securely bolted together, when the whole is placed upon a car and run into the oven or drying-room, where it is allowed to remain three or four days, or until it is perfectly dry. The temperature of the oven ranges from 200° to 250° F. 525. The Pit. — The pit is of a circular form and lined throughout with water-proof cement. It is situated directly in front of the furnace, and is fitted with an adjustable apparatus for receiving the flask, and sustaining it in an upright position. 526. Plachstg the Flask. — T he flask is lowered uito the pit, CAST GUNS. in breecli down, until tlie upper end is about twelve inches below the spout at the mouth of the furnace ; it is then secured in this position, and boards are placed over the mouth of the pit for the convenience of the founder. 527. Chaegestg the Fuehace. — A reverberatory furnace is used. The proportions of the metals selected for this species of bronze are such as to produce the toughest and most inde- structible alloy. It consists generally of ninety parts of copper and ten of tin. Lake Superior copper is preferred on account of its toughness, ^nd German tin for its purity. The greatest care is necessary to keep the compound free from sulphur, lead, iron, and arsenic, for any of these would lessen the value of the alloy for the required purpose. (Art. 135.) 528. In consequence of the different fusibility of copper and tin, the perfection of the alloy depends much upon the treatment of the melted metal. If the tin be not quickly uni- ted with the copper, it will be burned, and converted into scoria ; but such are the affinities of the metals, that the loss which might be expected from the burning of the tin is pre- vented by its being retained by the more stable copper. It is very essential that the metals be thoroughly incorporated, for the tin, being the lighter, would remain on the surface, and there would be no union of the metals whatever. 172 NAVAL ORDNANCE AND GUNNERY. The copper is first introduced into the furnace through the side-door, I), in the form of ingots of about eighteen pounds Aveight : tAvo tliousand pounds of copper being required in cast- ing the lieavy twelve-pounder howitzer of seven hundred and fiity pounds Aveight. 523. Melting down the Chaege. — T he fuel used for melt- ing is spruce pine, three-fourths of a cord being required for each ton of copper ; Avood is used in preference to coal, because the gases evolved are not so injurious to the copper. The furnace being closed, the fire is started ; from three to four hours are required to fuse the copper, depending upon the force and direction of the wind and the state of the atmos- phere. 530. At the moment at which fusion takes place, the tin, Avhich is prepared in the form of ingots, each Aveighing about seven pounds, is throAvn into the furnace through a door, one at a time ; care being taken to submerge the ingot thus intro- duced ill order that it may not spread itself on the surface of the copper and become oxydized ; the Avhole mass being kept in a state of agitation bv means of a rabble introduced through the same door. The molten mass is thus puddled until the metals arc thor- oughly incorporated, Avhich operation requires about four min- utes ; the rabble is then AvithdraAvn, the door closed, and the damper raised. 531. The compound is uoav subjected to an intense heat for about thirty minutes, or until the founder is satisfied that the mass has been reduced to the required state of liquefaction. It is almost impossible to give any rule as to Avhen the metal is ready for running, as those Avho are experienced in the matter tell by its color and general appearance ; Avhich is defined as a yellow-red color. 532. When the pure metals are not used, the charge is made up of remnants of other castings and shaAungs from the lathe, etc., Avliich are re-melted Avith a sufficient quantity of zinc and tin to preserve the proper proportions. (Art. 138.) In a light 12-pdr., cast in 1871, the furnace was charged with : One 2I-pdr., Howitzer 1,280 lbs. Lake Copper 75 “ A gun muzzle 100 “ Ingots (Bronze) 115 “ Total 1,600 “ CAST GUNS. 173 In a light 12-pdr., cast in 1872, the furnace was charged with : Two Heads 1,420 lbs. Ingots (Bronze) 205 “ Tin 2 “ Zinc 2 ‘‘ Total 1,G29 “ In a heavy 12-pdr., cast in 1865, the furnace was charged with : Lake Copper 800 lbs. Ingots (Bronze) 1,000 “ One Head GOO “ Total 2,400 “ 533. Casting. — In casting it is customaiy to allow the melted metal to run first through the side-runner until it rises two or three inches above the loop ; the stream is then trans- ferred directly through the top of the mold and allowed to run in until the mold is filled. This is done to prevent the upper part of the casting from cooling too rapidly, and thereby ctius- mg an unequal distribution of the tin, this metal being found always in the greatest quantities in that part of the casting which retains heat the longest. (Art. 137.) It is considered impossible to render the alloy perfectly homogeneous, because of the difference of fusibility and specific gravity of the con- stituent metals. (Art. 140.) 534. To ti’ansfer the stream of melted metal, a simple device is resorted to. It consists of two rionner-hoxes of cast-iron. A, B (Fig 7G). The lower one has a partition dividing it into two chambers, with an orifice in the bottom of each, so fitted that Avhen it is placed on the flask, F, one orifice Vvdll lead fair into the runner, and the other directly into the mold. 535. The upper runner-box slides on the upper edge of the lower one, and is furnished with handles to facilitate the opera- tion. Its bottom is pierced with a single orifice to allow the stream of metal to flow successively into the inner and outer chambers of the lower one. The upper runner-box is also fitted with a spout, which, when they are in position, comes directly under the spout, S, at the gate of the furnace ; it is long enough to allow for the distance between the first and second positions of the upper runner-box. 174: NAVAL ORDNANCE AND GUNNERY. 536. Tlie spouts and runner-boxes, well lined with clay, be- ing secured in position, and tbe furnace ready to tap, an orifice is made in its gate and tbe metal allowed to run in tbe mold. From the gate it is conducted by the spoilt into the upper runner-box ; flowing from thence through the orifice, it passes into the inner chamber of the lower runner-box, and down through the side-runner and its branch into the bottom of the mold. 537. At the moment the founder, who is looking down into the mold, discovers that the metal has arisen above the loop, he causes the upper runner-box to be shifted, so that the stream is transferred to the outer chamber of the lower runner-box. When the mold is filled the gate is plugged up, the runner- boxes are removed, and the casting allowed to cool. When the casting has become sufficiently solid to be removed, the mold is hoisted out. The remaining metal in the furnace is drawn ofl; in ladles, and cast into rough ingots for future use. The casting having become sufficiently cool to be handled, the flask is opened, the gun taken out, and with a hammer and chisel the sand and rough projections removed. The gun is then ready for the lathe. Section IV. — Inspection. 538. Inspection of New Guns.— New guns are to be closely examined and measured inside and out, for defects of metal or manufacture, as soon after being finished as possible, if it has not already been done in the various stages of manufacture. For this purpose the gun is placed on skids, so that it may be easily moved, and its foundry number is noted so as to identify the jiiece. As rust tends to conceal defects, this examination is to take place before exposure to the weather ; and previously to the final examination and proof of the guns, they are not to be covered with paint, lacquer, oil, or any material which may conceal defects of metal. 539. If it is ascertained that any attempt has been made to conceal defects, the gnus so treated are to be rejected without further examination. The water-proof, which is of great importance in detecting defects of metal, not otherwise developed, necessarily succeeds immediately the powder-proof, and can only be effectively em- ployed in fine weather, and when the temperature is above the freezing-point; final inspections are to be made at such times only. INSPECTION OF GUNS. 175 540. THE IHSPECTIHG-IHSTRUMENTS.— The in- specting-instruments are first carefully verified before any measurements are taken. Tliey may be described and their uses explained as follows : 541. A Mieeoe, for reflecting the sun’s raj^s. TJse . — The interior of the bore fs to be examined by reflect- ing the rays of the sun into it from the mirror or mirrors ; or, if the sun is obscured, and there can be no delay, by means of a spirit-lamp or of a wax-taper on the end of a rod, taking care not to smoke the sui’face of the bore. 542. The Seaechee consists of a long staff of wood, fitted with a head of six or seven steel points (Fig. 77). The points are arranged at equal intervals around the head, and attached with a tendency to spring out and increase their diameter ; this ten- dency is restrained by a hoop of iron embrac- ing them, and capable of being worked in and along the staff. 543. TJse . — The searcher is used for detecting the presence of small cracks or flaws. To use the instrument the hoop is pushed out on the head, thus contracting the points; it is then introduced in the gun to the bottom of the bore, and the hoop being pidled back allows the points to spring out and take against the surface of the bore. The searcher is then slowly with- drawn, turning it at the same time ; if one of the points catches, its distance from the muzzle is measured on the staff, and its position in the bore noted, and marked on the exterior of the gun. The size and figure of the cavity is then determined by taking an impression of it in wax. 544. The Cyltndee-gauge. — This is a hollow cylinder of iron, turned to the least allowed diameter of the bore, and one calibre in length (Fig. 78). It has a cross-head at each end, one of which has a smooth hole through its axis to fit the staff, and the other is tapped to receive the screw in the end of it. Fig. 78. — Cylinder-gauge. 176 NAVAL ORDNANCE AND GUNNERY. 545. Use . — The cylinder-gauge is introduced in the hore of the gnn, and must pass freely to the bottom of the hore. This instrument shows that the bore is not too small. 546. A Measuking-staff. — This is a stalf of steel or iron (Fig. 79), in joints of suitable lengths, connected togetlier by screws. Each joint is provided with a light brass disk, DD, the diameter of which is 0.05 inches less than that of the bore. Through the centre of the disk there is a hole which fits upon the shoulder at the joint ; the whole is so arranged that udien the joints are screwed together the disks between them ai’e held firmly in place, while tlie length of the staff is not affected by them. A steel point, P, is screwed on to the end. When pushed to the bottom of the bore, the staff coincides very nearly with its axis. The outer joint is graduated to inches and tenths. A slide, S, is made to play upon it with a vernier scale, graduated to hundredths of an inch. On the inner end of the slide, a branch, B, projects at a right angle, sufficiently long to reach across the muzzle-face, and, when in contact with it, to indicate the precise length obtained from that point to the end of the measuring-point on the other end of the staff. 547. Use . — The instrument is introduced until the point reaches the bottom of the boi-e, and the branch placed so that it takes across the muzzle-face, and the reading shows the length of the bore of the gun. 548. CiiAjiBEK-GAUGE. — The head should be made of close- grained, well-seasoned wood, and of the exact dimensions of the chambe]’. Two planes crossing each other at a right angle, coinciding with the vertical and horizontal central sections, have been found better than a solid block. The edge should be bevelled. A socket in its centre connects it with the measuring-stiiff. 549. Use . — Being pushed to the bottom of the bore, if the length coincides with that obtained by the point, it is obvious that the chamber is large enough, provided the cylindrical pare has not been bored too deep, in which case a shoulder would be found at the junction. I INSPECTION OF GUNS. 177 The edges of the gauge should he chalked before inserted. When withdrawn, if the chalk-marks are visible all around the chamber, it is evident the chamber is not too large. An e.xamination of the chamber-reamer (Art. 503) will be very satisfactory, and if found correct in size and shape, the impossibility of making the chamber too large will be apparent. 550. Stak-gauge. — This instrument is composed of the staff, the head, and the handle (Fig. 80). Fig. 80. — Star-gauge. The staff is a brass tube, S, made in three pieces, for con- venience of storage, and connected, when required, by screws. It is graduated to inches and cj^uarters, so that the distance of the head from the muzzle of the gun may always be known. A centre-line, starting from the centre of the upper socket in the head, is marked upon the statf throughout its length. 551. The Head . — The inner end of the staff expands into a head, H (Figs. 81 and 82), in which are placed four steel Fig 81. — Head of Star-gauge. sockets, K, at equal distances from each other ; two of the sock- 13 178 NAVAL OKDNANCE AND GUNNERY. ets opposite to eacli other are secured permanently, and the other two are movable. 552. A wedge, or tapering plate, "W, the sides of which are cylindrical, runs through a slit in the head (Fig. 82) ; an aper- Fig. 83. tnre in the inner end of the movable sockets, AA, embraces the cylinders, so that when the wedge is moved forward or back- ward, the sockets are projected or withdrawn. The tapering of the wedge has a certain known proportion to its length, so that if it is moved in either direction a given distance, a proportional movement is imparted to the sockets. The sides of the wedge incline 0.35 inch in a length of 2.2 inches, so that by pushing it the thirty-fifth part of this dis- tance (about 0.06 inch), the distance between the two sockets is increased .01 inch. 553. There are four steel measuring-points, P, for each cal- ibre, fitted with strong shoulders at one end, below which threads are cut for screwing into the sockets in the head. A wrench is made to fit the shoulders, so as to turn the points INSPECTION OF GUNS, 179 firmly into tlieir places ; when two of these are screwed into the fixed sockets, the distance between their extremities is equal to the true diameter of the bore. 551. A square steel sliding-rod, R, is connected with the wedge in the head, and runs through the whole length of the staff, projecting some inches beyond the outer end. This rod has as many parts as there are joints in the staff (three), and, like them, connects by screws. 555. The Handle (Fig. 83) is attached to the projecting end of the sliding-rod. It is a short hollow tube of brass, MB, made to fit over the outer end of the staff, S, and connect with the sliding-rod, R, by a screw at its outer extremity fitted with a large milled-head, M. The handle is divided into two parts, one fitting and working closely over the other. On each side of the inner part is a small tube, CD ; a thread is cut in one, D, through which a fine screw, held by a stud on the outei’ part, E, works and gives it motion ; a guide, F, runs through the other. A slit, Gr, through the inuer part of the handle permits a part of the staff near the end to be seen beneath, and a scale is placed on one side of the slit graduated with the distance that the wedge moves to throw the points .01 inch apart. 556. Adjusting the Instrument . — There is a steel adjusting- ring (Fig. 84) for each calibre, reamed out to the exact minimum diameter of the bore. The fixed measuring-points of the head will just pass into the adjusting- ring of the corresponding calibre ; the movable points are made to touch the in- ner circumference of the ring by pressing in the wedge; and this is accomplished by moving in the handle., which works the sliding-rod. Seen through the slit of the handle, G, is a small plate of silver, I, in- serted in the staff, and a fine mark upon it to show the place of zero when the measuring-points are adjusted. 180 KAVAL ORDA^ANCE AAD GUA'XEET. The zero-mark on the scale along the slit is made to cori'e- spond with it by means of the line screw, ED. 557. A Muzzle-rest in the form of T is employed to keep the staff of the star-gange in the axis of the Lore while it is be- ing used (Fig. 85). It contains a groove, A, in the centre of the transverse branch, to receive the lower half of the staff, and can be used with any c I 55 Cored Shell 400 “ 3 Xl-indi. . . ..10,000 “ (25 ( Solid Shot Shell 100 127 (( (( 1 10 X-inch . . . . ..12,500 “ jl8 112 Sohd Shot Shell 124 05 U ii 1 10 IX-inch.... ...9,000 “ jl5 (10 Solid Shot Shell 90 08 u 1 10 Vlll-inch of. . ...0,500 “ 10 Shot , 65 (( 10 32-pdr. of . . . ...4,500 “ 8 Shot 32 (( 10 The cannon-powder for pi’oof is of not less than 1,500 feet initial velocity. It is tilled in service-cylinders and well settled. For chambered pieces the increased charges should fill the chamber and necessary portion of the bore. The projectiles are of full weight, and not below the mean gauge ; the shells filled with a mixture of sand and ashes, to 'bring them up to the weight of the filled shells. Sabots for the shell, and a grommet wad over the shot. The gun should be fired on skids or a proving-carriage to test the trunnions. If five per cent, out of any lot offered for ordinary proof under a contract fails to sustain it, the whole may be rejected, as may be stipulated in the contract. 599. Water-pkoof. — The pressure to be applied in the water-proof is two atmospheres, or thirty pounds to the square inch. The penetration of water in this proof through the metal of the piece, in any place, will cause the rejection of the gun ; and if, on examination after the water-jjroof, there are any defects indicated by weeping or dampness in the bore, the gun is rejected. The water-proof is alone to be depended on to detect minute clusters of cavities in the bore, which for this jiurpose INSPECTIOjST of guns. 193 should be perfectly dry, and examined by sunlight. All in- spections, consequently, sliould take place in fair weather, and when the temperature is above the freezing-point. 600. IlydmuliG Pump and Apparatus for the water-proof, — Any of the various patterns of this macliiue may be applied to the proof of guns. An iron cross-head is secured to a stout wooden block which fits into the muzzle, and which has a flange or shoulder to cover the muzzle-face ; rings of gutta- percha are plncecl between them ; an iron rod with a ring in one end, to lit over the trunnion, and with a thread cut on the other end, is used on each side of the gun, to connect the trun- nions with the cross-head. The whole is set up Avith nuts, and the pressure on the rings makes a tight joint ; a coupling on the cross-head receives the hose, and the water is forced into the gun through a hole in the Avooden block. Care should be taken that the valve is loaded Avith the proper Aveight for proof. In the construction of the huilt-tcp steel-lined cannon of the English service, the steel tubes are subjected, after toughening in oil, to a water-pressure in the interior of 8,000 lbs. per square inch, to detect any latent cracks ; and after the powder- proof they are subjected to a presstire of 120 lbs. on the square inch, to make sure that the end has not been split at proof. 601. Extreme Pkoof of Tkial-gujsts.— The extreme proof of guns intended for trial of metal is conducted as follows : A suitable butt is erected to arrest the flight of the projectiles used in proof, and to admit of their easy recoAmry, and a bomb- proof, readily accessible, for the protection of the tiring-party. After undergoing the ordinary proof established for its calibre' and class, the gun selected for extreme proof is subjected to at least 1,000 rounds Avith service-charges. It may be tired from skids or suspended. During the trial the gun is frequently and critically exam- ined, inside and out, for cracks or defects, especially about the interior orifice of the A^ent, of which impressions are taken in Avax at regular intervals. If they show that the vent is corroded in furroAvs, and en- larged considerably in diameter at its juncture with the bore, a permanent impression is to be taken in lead, to show the conical enlargement. 602. Enlargement of Yents. — When, from the appear- ance of the bore at the interior orifice of the vent, it is evident that the latter has enlarged beyond the limit of safety, and es- pecially Avhen a crack or cracks appear to be extending rapidly, the vent so enlarged may be filled with melted tin or zinc ; a 13 194 NAVAL OEDNANCE AND GUNNEKT. tiglit-fitting sponge-liead being pnsbed to tbe bottom of the cbamber to close the interior orifice — and the other vent bein'^ drilled through for the pui-pose of continuing the firing. The precise time at which this is to be done will vary according to circumstances ; such as quality of metal, charge, and eleva- tion. 603. The endurance of a smooth-bored gun with seiwice- charges may be surely predicted by oljservation of the progres- sive wear of the interior orifice of the vent. There are certain general forms in which this enlargement takes ]3lace. They may be classed as triangular, lozenge, quadrilateral, star, circu- lar, and elliptic. (See Plates in Ord. Ins.) With the lateral vent of the Dahlgren system, it usually takes the lozenge form'^ the cracks extending from the opposite angles lengthwise of the bore. AVith those rifled-cannon in which the vent is bouched, the cracks appear around the bouching, and although the bouching preserves the vent, yet the formation of fissures around the en- larged orifice, when once commenced, causes a greater tendency to rapture. AYith the vent not bouched, the wear in rifle-can- non is about double that of the smooth bore. So long as the wear of the vent is regular and without cracks, a mere enlargement is not indicative of danger; but when it reaches a diameter of four-tenths of an inch, the vent should be closed and a new one opened. 604. A gun of ^ large calil^re should not in service be expected to stand more than 400 or 500 rounds before it will be necessary to open the new vent, which, ho^rever, Avill be of no advantage unless the old one be closed at its interior orifice, on which the gases otherwise would continue to act as a wedge. The first distinct appearance of the cracks, as shown by the button, is the proper limit. After the gun bursts, a sketch or draft is made showing the lines of fracture, and specimens are reserved for trial of density and tensile strength ; and, if practicable, a photograph is taken. 605. Exdtjeakce of Guxs in Service. — The principal in- juries caused by service are internal, arising from the separate action of the powder and the projectile. They increase in extent with the calibre, whatever may be the nature of the gun, but are modified by the material of Avhich it is made. 606. In,iueies from the Powder. — The injuries from the powder generally occur in rear of the projectile. They are, 1st. Enlargement of that portion of the bore vdiich contains the poAvder, arising from the compression of the metal. This INSPECTION OF GUNS. 195 injury is more marked when a sabot or wad is placed between the powder and tlie projectile, and is greatest in a vertical direction. 2d. Cavities produced Ijy the melting away of a portion of the metal by the beat of combustion of the charge.^ 3d. Cracks arising from the tearing asunder of the particles of the metal at the surface of the bore. At first a crack of this kind is scarcely perceptible, but it is increased by continued firmg until it extends completely tbrougb the side of the piece. It generally commences at the junction of the chamber with the bore, as this portion is less supported than the others. 4th. Furrows or scoring produced by the' erosive action of the inflamed gases. Tliis injury is most apparent where the cur- rent of the gas is most rapid, oi‘ at the interior orifice of the vent, and on the surface of the bore, immediately over the seat of the projectile. 607. Scoring commences very early in large guns ; at first, it is only a mere roughness, which gradually increases in depth and forms lines along the bore ; but it is not until a gun has been fired very considerably that it becomes of importance. The impressions of deep scoring resemble the bark of an old elm-tree, the metal being eaten awtay into irregular furrows and ridges. Even when it has reached this extreme case, however, scoring has not caused the destruction of the gun, though in some instances, acting like a wedge, it has split the bore at that part. Some experimental guns, excessively scored on the upper side of the bore, have been turned over, vented and sighted on the under side, but this has not been found necessary until the gun has been used more than is probable under ordinary cir- cumstances. 608. Injuries feow the Projectile.— The injuries ailsing from the action of the projectile occur around the projectile and in front of it. They are : 1st. — Indentation in the lower side of the bore, pro- duced by the pressure on the projectile by the escape of gas through the windage, before the ball has moved from its seat. The elasticity of the metal, and the burr, or crowd- ing up, of the metal in front of the projectile, cause it to rebound, and, being carried forward by tlie force of the charge, to strike against the upper side of the bore, a short distance in front of the trunnions. From this it is reflected against the bottom, and again reflected against the top of the bore, and so on until it leaves the piece. The first is called “ indentation,” and the others are called “ enlargements.” 196 NAVAL ORDNANCE AND GITNNERT. In pieces of ordinaiy length, there are generally three en- largements when this injury tii'st makes its appearance, but their number is increased as the “indentation ” is depressed and the angle of incidence increased. The effect of this bounding motion is alternately to raise- and depress the y^iece in its trun- nion-holes, and to diminish the accuracy of fire, until finally the piece becomes unfit for service. It is principally from this injury that bronze guns become unserviceable. Mortars and howitzers are not much affected by it. The principal means used to prevent this injury are to wrap the projectile with cloth or paper, and to shift the seat of the projectile.’ v. The latter may be done by a wad or lengthened sabot, or by reducing the diameter and increasing the length of the cartridge. The last of these methods is considered tlie most practical as well as the most effective ; and it has the additional advantage of decreasing the strain on the bore, by increasing the space in which the charge expands before the ball is moved. 2d. Scratches or furrows made upon the surface of the bore by rough projectiles, or by case-shot. 3d. Cuts made by the fragments of projectiles which break in the bore. 4th. AVearing away of the lands of rifle-cannon, especially at the dividing edges. A little rubbing of the side of the grooves from the filction of hard bearings is of little importance. 5th. Enlargement of the muzzle, arising from the forcing outAvard of the metal by the strikiiig of the projectile against the side of the bore as it leaves the piece. By this action the shape of the muzzle is elongated in a vertical direction. Gth. Cracks on the exterior. Tliese arc formed by the com- pression of the metal Avithin, generally at the chase, where the metal is thinnest. This portion of a bronze gun is the first to give Avay by long firing, Avhereas cast-iron guns usually burst in fear of the trunnions, and the fracture passes through the vent, if it be much enlarged. 609. Dkscriptiv]': List of Guxs. — Before sailing, the In- spector of Ordnance furnishes the Commander with a descrip- ti\ e list of his battery, together with a statement of the number of times each gun on board has been fired, in the following form (a copy of Avdiieh the Commander transmits to the Bu- reau of Ortlnance before sailing; this list is returned to the In- spector of the yard to which she may return, Avith all additional firing, noted opposite the number of each gnu, certified correct by the Commander) ; INSPECTION OF GUNS, 197 Class of Marks on ba.se-ring. Trunnions. Pivot or ' Where No. of fires Gun. Kegr. No. j Weight. Fouatiry. Right. Left. Broadside. Received. to date. 610. Set of Vent Impressions . — The Inspector also fur- nishes the Commander with a set of leaden impressions of the interior orifice of the vents of the guns, secured in a suitable box, that he may be able to compare the wear and gradual en- largement. These are transferred with the guns to other ships, or when landed. (Fig. 97.) 611. Inspection at Termination of a Cruise. — At the ter- mination of a cruise the guns are carefully examined by the Ordnance Officer of the Yard, and such others as may be di- rected, with the view to discover and report any injuries which they may have sustained in service, or any defects which may not have been developed in the original ■proof. Before proceeding to ex- amine a gun the bore should be thoroughly cleaned; it will generally be sufficient- ly prepared for examina- tion by washing, sponging, and drying. If, however, there be hard rust or a coating of any kind on the surface of the bore, it may be cleansed either by firing, if circumstances admit, one or two scaling-charges, about one-third the full charge, without projectiles, which will usually loosen the scale ; or the bore may be scrubbed out with hot water and potash. Ho sharp-edged or pointed scraper should be employed for cleansing the bores of rifled-guns, as they are unnecessary and liable to injure the rifling. 612. In this examination the attention of the Inspecting Officers is directed to the following points, viz. : Fig. 97. — Vent Impressions. 198 NAVAL ORDNANCE AND GUNNERY. Enlargement of the interior orifice or exterior orifice of the vent. Indentations or hollows produced by the projectile Ijollot- ing against the surface of the bore, or by the action of the gases. Cuts or scratches in the bore, produced by fragments of broken, or roughness of imperfect, projectiles. Roughness or corrosion of the metal on the exterior, pro- duced by neglect or exposure. Similar injuries in the bore, or any enlargement of the bore, which is to be ascertained by measuring with the star-gauge, at every one-fourth of an inch, from the bottom of the cylindrical part to the seat of the projectile, every inch from that point to the trunnion, thence every five indies to the muzzle, and the results recorded in the usual form, and reported to the Bui-eau, that they may be compared with those noted at the original in- spection. In rified-cannon, cracks or injuries produced by firing, or the mpture of shells, are to be sought for, around and in the rear of the vent bouching ; on the top of the bore, between the trunnions and reinforce-band ; on the lower side of the bore, near the seat of the projectile, at the junction of the lands and the grooves ; near the inside of the muzzle, caused by explosion of shells. Care is to be taken that the distinguishing marks and num- bers are always accurately noted, that the correct history of each gun may be preserved. 613. Inspection of Vents. — As the best indication of the amount of fii'ing to which any smooth-bored gun has been ex- posed, when it is not otherwise known, is given by the enlarge- ment of the vent ; particular attention is paid, in the re-inspection of the guns, to this point. The standard gauge is used to ascer- tain the general enlargement, and the searcher to detect defects which may have been developed in firing. Impressions are taken of the lower orifice of the vent with softened wax, and if they show that the vent is corroded in furrows and enlarged considerably in diameter at its junction with the bore, a perma- nent impression is to be takeli in lead to show the conical en- largement. 01-1. When the number of rounds fired is not known, an estimate may be made from an examinaiion of the vent by cy- liudricad gauges, difl'eriug from each other by .01 inch, passed through it. In all the guns of the Dahlgren pattern the vents are two- tenths of an inch in diameter. INSPECTION OF GUNS. 199 Observation of the wear of the vent in proof-firing of smooth-bored guns gives tlie following as the average diameter of the vent, after the under-mentioned number of fires : No. of Eounds 100, 200, 300, 400, 500. Diameter of Vent 24, .26, .30, .35, .40. These combined with examination of the interior orifice, will enable a very correct judgment to be formed of the proba- ble number of fires sustained and duration of the gun. The larger the calibre and the heavier the charge, the more promptly the wear is manifested on the interior and exterior. The enlargement does not extend very far from the lower orifice until the enlargement of the exterior has reached a di- ameter of .3 of an inch. So long as the wear is regular, and the cracks, although numerous, do not exceed .5 of an inch in length, the indications are good. If the cracks are but few or diminish in number, running into each other and extending rapidly, it is a very unfavoi’able sign. In the rifie-cannon (Par- rott’s) cracks athwart the bore, either running into the benching or into the rear of it, are very unfavorable to the gun’s endu- rance. CHAPTEE lY. BUILT-UP GUNS.* Section I-^Princijples of Construction. 615. GEYEEAL COJ^SIDEEATIOISrS. — modern the- ory of constructing guns can be called new, since guns are in existence that have been either recovered from wrecks, or pre- served in other ways, showing every variety of coils, hoops, casting, wire-binding, and so on, as far as the appliances then in use could furnish the quondam inventors with means of car- rying their inventions into effect. That in which novelty has been attained, is the improve- ment of processes by which large castings or forgings, accurate turning and boring, can be secured, or by which chemical knowledge can be brought to bear on the manipidation of metals ; but no such progress can make a built-up gun, or ma- chine of any sort, stronger than a perfectly homogeneous one, in which the varying strains are closely calculated and properly met by the scientific disposition of the necessary strength. 616. DEFINITION. — The terms ‘■^huilt-vp’’^ and ‘•'hoojped'' are applied to those cannon in which the principal parts are formed separately, and then united in a peculiar manner. They are not necessarily composed of more than one kind of metal ; some of the most important are made of steel alone ; and they may be made by welding or by screwing the parts together, and by shrinking oi’ forcing one part over another. 617. OBJECT. — The object of this method of manufacture is to correct the defects of one material by uniting with it op- posite qualities of the same or other materials. The defects Avhich follow tlie working of large masses of iron or steel, such as crystalline structure, false welds, cracks, etc., are avoided by first forming the parts in small masses of good quality and then uniting them separately. 618. Nature of the Eokce to be kestkatned. — In consider- ing the effect upon a yielding material of any force which may be applied, the rate of application of the force, or the time which elapses from the instant when the force begins to act, until it attains its maximum, should not be neglected; for, with equal ultimate pressures per square inch of surface, that force * Compiled by Lieutenant J. C. Solcy, U. S. Na\y. il BiriLT-UP GUNS. 201 ■will be most severe upon the gun which attains this pressure in the shortest period of time. (Chap. II.) 619. HOW TO INCREASE THE STRENGTH OF A GUN. — The most obvious method of enabling a gun to sustain a greater elastic pressure is simply to thicken its side?, thus in- creasing the area of the parts to be torn asunder. This rule has been found to work practically with guns of small calibre, but in larger guns it does not work, from the fact that, in cast guns, of whatever metal, the outside helps but very little in restrain- ing the explosive force of the powder, the strain not being communicated to it by the intervening metal. The consequence is that, in large guns, the inside is split while the outside is scarcely strained. This split rapidly increases, and the gun ultimately bursts. 620. Example. — If we make equidistant ch’cular marks on the end of an India-rubber cylinder (Fig. 98), and stretch if, we can plainly see how much more the inside is strained than the outside, or even the intermediate parts ; the spaces between the marks will become thin- ner, each space he- coming less than that outside of it ; but the inner spaces, much thinner than the others (Fig. 99), showing that when the inside is strained almost to breaking, the intermediate parts are doing much less work, and those far removed almost none. 621. Limit to TnicKisrEss of Metal. — Now, if we take any transverse section of a gun, any unit in length, and suppose the metal to be divided into any number of concentric rings, it will be evident that the greater the distance of any ring from the axis of the gun, the less will it be stretched by the expansion of the bore when the piece is discharged, and consequently the less will it contribute to the general strength of the gun. If the strain upon the bore from the discharge he considered merely as a pressure, — statical force, — the resistance offered to it by any two rings will be inversely proportional to the square of then* cu’ciunferences or distances from the axis of the ffun. Fig. 98. — India-rabber cylinder, with equi- distant concentric marks. Fig. 99. — The same cyiin- der, stretched by inter- nal pressure ; the con- centric marks show the inferior stretch of the exterior. 202 NAVAL ORDNANCE AND GUNNERY. G22. It will, therefore, appear that there is a certain limit beyond M'hich it would be useless to increase the thickness of the metal, viz. ; When the force exerted on the surface of the bore would be sufficient to rupture the interior portions of the metal before the strain acted to any extent upon the exterior parts. Any arrangement of the parts by which the explosive strain is distributed equally over the entire thickness of the piece, necessarily brings a greater amount of resistance into play. In order to obtain the requisite resistance, and with a moderate thickness of metal, it is desirable to equalize, as far as possible, the strain upon every portion of the metal. C23. METHODS OF EQUALIZING THE STEAINS. — There are two general methods of accomplishing this, viz. : First, l)y giving the exterior portions a certain initial tension, gradually decreasing and passing into compression towards the interior, which is done by shiinking heated iron bands or tubes around the parts to be compressed, or by slipping a tube into the bore, which has been slightly enlarged by heat. Secondly, by means of the system of varyiluj elasticity ; this is accomplished by placing that metal which stretches most within its elastic limit around the surface of the bore, so that, by its enlargement, the ex])losive strain is transmitted to the other parts. These two methods of ecpializing strains without an inordi- nate increase of thickness, are so important that they deserve more than a passing notice. They are called tire systems of In- itial Tension and Varying Elasticity. Some gun-makers use the one, some the other, some a combination of the two, and even in our own hollow-cast guns the idea of Initial Tension is one of primary importance. 02i. PuixciPLKS OF System of Ixttial Texsiox. — The sys- tem of Initial Tension consists in making a gun of concentric tubes, by putting (.m each snccessive layer, proceeding outward from the centre, with an initial tension exceeding that of those below it ; in other words, so that each hoop shall compress the one within it. The inner layer is thus in compression while the outer layer is in the highest tension. The innei’ layer is able to sustain the tii’st and greatest stretch, and the outer layer, although sti'etched less by the explosion of the powder, has already been stretched into high tension, and thus has to do an equal amount of work. The intermediate layers bear the same relation to the initial strain, and to the strain of the powder, so that, in short, all the layers contribute equally of their tensile strength to resist the strain of the explosion. 625. Defects of tue System. — Each hoop, or tube, has this BUILT-UP GUNS. 203 element of weakness that its inner circumference is more stretched than its onter one. Absolute perfection would necessitate infinitely thin hoops, and, practically, the thinner the layei’s the greatei' will be the strength, provided the mechan- ical difficulties in constracting, and more especially in applying, a great number of thin strata with the proper tension do not outweigh the advantages. G26. M]5thods of Application. — The two principal methods of applying the system are by shrinliing on, or by forcing on, the hoops. 627. SJirinldng. — If the hoops are put on by shrinking, two embarrassments arise : Firsts the hoops must be accurately bored, and after each layer has been put on, the gun must be put in a lathe and tlie outside turned. Great accuracy of labor is required — labor of tbe most expensive class. Secondlg, the process of shrinking on is not to l)e depended upon ; not only is there a difliculty in insuring the exact tem- perature required, but scai’cely any two pieces of iron will shrink identically. The fitting of hoops Avith nice adjustment Avoiild be difficult, theoretically; practically, it Avould not bo done. But the chief embarrassment is the unequal effect of heat. In the first place, heating the layers over a fire to expand them subjects one part to more heat than another ; the tempera- ture of the surface and interior are unequal, thus causing irregular strains. This may be remedied by boiling the hoops in oil, Avhich Avould toughen as Avell as expand the lioops. in the second j)lace, the hoops are often heated to redness Avhen oxydation takes place. The internal diameter of the hoop is increased, and scale is left betAveen some parts and not betAveen others. In the third place, cast-iron and steel sensibly and per- manently eidarge in proportion to the amount of carbon they contain Avheii subjected to the heat. 628. Forcing on. — WhitAvorth and Blakely advocate the method of forcing the hoops on Avith hydrostatic pressure. The forcing of a slightly conical ring over a correspondingly conical tube obviates the necessity of great accuracy in the diameter of either pieces. The truth of the cone depends upon the correct- ness of the lathe. Tbe truth of the surfaces is also a question of good tools. The tension of the ring depends on the distance to Avhich it is forced in the conical tube, and this may be regu- lated by the saf ety-Auil ve of the hydrostatic press. With special tools, and Avhen correctness depends upon the mechanical appliances, Avhich can be adjusted Avith the utmost nicety, an inexpert Avorkman could hardly fail to do Avell. 204 NAVAL ORDNANCE AND GUNNERY. 629. Principles of Syste^i of Yaeting Elasticity. — Lotus now suppose the hoops or tubes forming a gun to be fitted to- gether accurately, but without tension. If the inner hoop is very elastic, and the next less elastic, and so on throughout the series, the outer hoops being the least elastic, and the degree of elasticity being exactly proportioned to the degree of elongation by internal pressure, all the hoops will be erpially strained by the powder, and none of their strength wasted. If the inner hoops be stretched by the powder-pressure of an inch, and the outer hoop of an inch, the material of the in- ner hoop should have such elasticity that it should be no nearer its breaking-point when stretched -jL of an inch than the less elastic outer hoop when stretched -yj-y of an inch. Both hoops would then be equally strained by the powder, and oppose an equal resistance to it. 630. Defects of the System. — It has been found difficult to obtain materials having the respective ranges- of elasticity necessary to perfectly cany out this system. For this reason the outer tube or tubes are sometimes put under an initial ten- sion equal to the working load, in order that the work done may be equal for all. This severe and permanent strain on the outer tube, of course, tends to relax it; but if the inner tube can stretch very much without injury, and the outer tube can only stretch a little, the permanent strain upon all parts of the gun, in order that it may be uniformly strained under fire, will be slight, and the tendency to relaxation limited. 631. Longitudinal Steength. — Care must be taken to have sufficient longitudinal strength. The theoretical resistance of a cylinder under internal pressure to cross fractui-e is four times as great as its resistance to splitting longitudinalh’, if the tenacity of the metal is the same in all directions. To obtain strength in this direction, some circumferential strength may be sacrificed by making one part the length of the entire gun. and of adequate thickness. It is probably better that this single large piece should be inside, and this is the general practice. 632. Length of Hoops. — Hoops of considerable length are desirable to add to the frictional surface, thus giving longitudinal strength to the gun. But length or continuity is chiefly desir- able to transfer the strain upon one point to a large resisting area. 633. Huviber of Hoops. — An obvious disadvantage of a large number of hoops is that the transverse strength of the gun is much reduced. 634. Want of Continuity. — A hooped gim must always BUILT-UP GUNS. 205 possess the defect of want of continuity of substance. How- ever perfect the workmanship at first, in large guns the jar of repeated firing would soon shake them loose. The great defect in the Armstrong guns Avas developed in the shaking loose and fracturing of some of the hoops under the tremendous vibration due to filing large charges. 635. Yibeation. — Both the means, that have been con- sidered, of increasing the resistance of a gun to mere pressure, are perfected only in proportion to the number of separate tiihes or layers employed ; hut on the other hand, increasing the number of parts lessens the resistance of the body - to tlie effect of sudden strain. When a gun is fired the shock is propagated from layer to layer in a wave; if the layers are already detached tubes, the outer one has no help from the rest in i-esisting the Aubration, and the only way to modify the effect of the Avave of force upon the outer lajmr is to give that layer great mass and thence inertia. 636. CONCLUSIONS. — To sum up briefly tlie principles of gun construction, merely thickening the walls of a gun beyond a certain point adds very little to its resistance to internal pressure. A homogeneous gun, in a state of initial repose, hoAvever thick it may be, cannot sustain permanently a pressure per square inch greater than the tensile strength of a square inch of the metal of Avhich it is conqAosed. The reason is that the inner layers of metal are more stretched and strained by an internal press- ure than the outer layers, in the inverse ratio of the squares of their diameters. Therefore, the layers must be placed under such initial strain, or must possess such A^arying elasticity that all parts of the gun will he equally Avorked at the instant of firing. Both these conditions are perfectly carried out in proportion to the number of separate layers or tubes thus treated ; but the AA^ave of force (in distinction from statical pressure), and the effects of unequal vibration, distress a gun in proportion to the number of its parts, so that the building-up principle cannot be carried far Avithout depriving the gun of the necessary mass and continuity of substance. 637. The system of hoops Avith initial tension, although the- oi’etically perfect and an acknowledged improvement in the construction of ordnance, involves certain practical difficulties. When several thicknesses of hoops are used, it is difficult to maiiitaiiA the proper longitudinal strength, and it has been found that a gun composed of tAvo or three tubes, although not so strong to resist statical pressure as one composed of five or six tuhecimen guns under- went, and in virtue of which the Frazer system superseded the original single coil system of Armstrong, towards the close of 1866. 661. THE "WOOLWICH GUH. — The name “ Woolwich Gun ” is the term applied to all the guns manufactured in England since 1866. The term is a comprehensive one, and might be expanded into “ Wrought-iron-muzzle-loading-guns, built on Sir William Armstrong’s principle, modified by Mr. Frazer, improved by Mr. Anderson’s method of hooking the coils with solid-ended steel tubes toughened in oil, rifled on the French system, modified as recommended by the Ordnance Select Committee, for projectiles studded according to Major Palliser’s plan.” 662. Details of the Gun. — The gun consists of : (1.) An A tube. (2.) A B tube. (3.) A breech-coil. (4:.) A cascabel. 663. (1.) The A tube, or inner barrel (Fig. 109), is made from a solid forged cylinder of cast-steel, which is supplied to the Royal Gun Factory bjr Messrs. Firth, of Shefiield. Cast- ing is necessary, not only for the purpose of obtaining a suffi- ciently large block of steel, but also of making the block homo- 212 NAVAL ORDNANCE AND GUNNERY. Fig. 109. geneoiis and uniform in density. Forging imparts to it tlie properties of great solidity and density. A piece is cut from the block at the breech end, and divided into small pieces which are tested for tensile strength and elasticity in the natural state, and also to ascertain at what temperature the block can be immersed in oil to the best ad- vantage. A steel-block which stands all the tests, is rough-turned, in which operation a lip is foianed on the muzzle to farilitate lift- ing the tube into or out of the furnace or oil-bath. It is then bored roughly from the solid. The tube thus formed is heated from four to six hours to the approved temperature in a vertical furnace, and then plunged into an adjacent bath of oil, in which it is allowed to cool and soak, generally twelve hours. It must then be turned and bored to make it straight inside and outside, and to re- move any flaws. It is then subjected to the water-test of 8,000 pounds per square inch, and, if no flaw is detected, the barrel is considered safe, and remains in this condition until the B tube is ready to be shrunk over it. CGI. (2.) The B tube is composed of two single and slightly taper coils united together (Fig. 110). The two coils, being made and welded in the usual man- ner, are faced and recipro- cally recessed to the depth of about one inch, and then united together endways by expanding the recess of a heat, and allowing it to shrink the shoulder of the other (Fi coil by around 111 ). This holds the two coils together enough to allow the tube thus formed, to be placed upright in a furnace ; when it arrives at welding-heat, it is removed to a steam-hammer, and receives on its end six or seven blows, Fig. 110. Fig. 111. BUILT-UP GUNS. 213 Fig. 112. wliicli weld tlie joint completely. The tube is next rough- turned, in which process a rim is left near the muzzle for con- venience in lifting, and then rough and fine bored (Fig. 112). The interior of the B tube having been brought to the required smoothness for contact with the steel barrel, it is gauged every twelve inches down the bore, and at the shoulder. To the measurement the calculated amount of shrinkage is added, and the exterior of the A tube is turned so that it shall be exactly larger than the interior of the B tube by the recpiired amount of shrinkage. 665. (3.) The Breech-coil is composed of a triple-coil, a douUe-coil, and a trunnion-ring. The triple-coil (Fig. IIS') is made of three bars, all of the same section, but diliering, of course, in length ; the middle one is coiled in a reverse direction so as to break joints. To weld the folds, it is raised to welding-heat in a furnace, and hammered on end ; then a man- drel is forced down inside from either end, and it is hammered on the out- side, being heated before each opera- tion. When cold, the ends are faced, and the outer coil is turned down at the muzzle end to form a shoulder for the reception of the trunnion- fig. 113. ring. The double coil (Fig. 114) is made of two bars of the same section as those of the triple coil, but of dilferent lengths. It is made in the same manner as the triple coil, and it has a shoulder formed at its lower end, so that it may overlap the trun- nion-ring. The trunnion-ring (Fig. 115) is made like all wrought-iron trun- nion-rings, being built up on the end of a porter-bar. All these parts, triple-coil, double-coil, and trunnion-ring, being thus prepared, the trunnion-ring is heated to redness and dropped on the shoulder of the triple- Fig. 114. 214 NAVAL ORDNANCE AND GUNNERY. Fig. 116. coil, whicli is placed upright on its breecli end for this pni-pose ; while the trunnion-ring is still hot, the douhle-coil is dropped down on the front of the triple-coil through the upper portion of the trunnion-ring, which thus forms a band over the joint, and in cooling grips the two coils (Fig. 116) sufficiently to admit of the whole mass being placed bodily in the furnace, where it is raised to welding- heat. It is then placed on its breech end under a heavy ham- mer ; six or seven blows suffice to amalgamate all the parts; hut to make the weld more perfect in the interior, a_cast-iron man- drel is forced down the bore to within 20 inches of the breech. The mass is then reversed, and the mandrel driven out again. It is then turned and bored. The front of the d.ouble coil is recessed to a distance of nine inches, and deep enough to overlap the B tube. Finally the thread is cut for the cascabel. (Fig. 117.) 6G6. (4.) The eascaljel is made of the best scrap-iron. It is first forged into a single cylinder, then turned, and a bevel thread cut on it. A hole which is after- ward enlarged to a loop is drilled through the end. (Fig. IIS.) One round of the thread is turned off at the end of the cas- cabel, so that there may be an annular space there, which, in connection with the channel now cut along the cascabel and across the threads inch in depth, forms the gas-escape which comes out at the right side of the loop. This will give notice, in ease FORGED SCREWED ^hc stecl tiibe should split. 667. Buildeng up the Gun. — The A tube and the B tube, being pi’e- pared as described, are shrunk together in the following manner : the B tube is placed over a grating, and heated for about two hours by a wood-fire, for which the tube itself forms the flue, until it is Fig. 118. BUILT-UP GUNS. 215 Fig. 119. sufficiently expanded to drop easily over tlie muzzle-end of the A tube, which is placed upright in a pit ready to receive it. The B tube is then raised, the ashes brushed from its in- terior, and it is dropped over the steel barrel (Fig. 119). During the process of shrinking, a stream of cold water is poured into the ' steel barrel by means of a pipe and sj^ihon — to keep it as cool as possible. A ring of gas is placed at the muzzle-end of the B tube to pre- vent its coohug prematurely, and jets of cold water play on the other end, and are gradually raised to the muzzle for the pur- pose of cooling the whole tube consecutively from the breech end, which it is desirable should grip first. The method of cooling the tube prevents it from being drawn out into a state of longitudinal tension. The A and B tubes, shrunk up, are placed in a lathe, and while one cutter fine-turns the B tube to its proper shape, an- other cutter fine-turns the breech end of the A tube according to the plan of the breech-coil. The half-formed gun, composed of the A and B tubes, is placed on its muzzle in the shrinking-pit, and the breech-coil is heated and shrunk on in the same manner as the B tube ; it is, however, being nearly of the same thickness throughout, allowed to cool naturally, and cold water is forced up into the bore of the gun by a jet round which the muzzle rests. The cascabel is next screwed in, which operation requires great care, as the front of it must bear evenly against the steel barrel. After it is screwed in, it is splined to prevent it from turning. 668. The above method of construction is now applied to Fig. 120. the 7-inch and 8-inch guns (Fig. 120). It has been modified 216 NAVAL ORDNANCE AND GUNNERY. for the 9-inch guns (Fig. 121), and upwards, hy using a slightly thinner steel tube and two double coils on the breech instead of one tri])le coil. Fig. 121 . The higher natures have an intermediate B noil in addition (Fig. 122),\nd the 12-inch 35-ton gun has a button instead of a cascabel hole. r—1—; 669. Yent. — The vent enters at a point two-fifths the length of the seiwice-cartridge from the end. The vents are lined with copper, specially hardened, and bored vertically in the 7-inch, 8-inch, and 9-inch guns; but in the 10-inch and 12- iiicli gnus they are bored at an angle of 45° with the vertical, and on the right side of a broadside gun, but on the most con- venient side in a turret-gun. 670. Nomenclature . — The guns are named as follows : The 12-inch 12-inch 10-inch 400-pdr. 9-inch 12-ton S-inch ...... ISO-pdr. 7-inch 115-pdr. BUrLT-HP GTJXS. 217 671. PALLISEE SYSTEM OE COEYERSIO]Y.— This system of Major Palliser depends on the principle of Yarying Elasticity, and recourse has been had to it in order to utilize the smooth-bore cast-iron guns. Some smooth-bore 6d-pdrs. are the only ones which have been converted. 672. Tlieorxj of the System . — A barrel or hollow cylinder of coiled wrought-u’on is introduced into a cast-iron gun, the barrel being of such thickness in proportion to its calibre that the residual strain borne by this tube shall bear a relation to the strain it transmits to the surrounding cast-iron which shall be best proportioned to their respective elasticities. The pre- cise proportions will depend on various circumstances, the prin- cipal of which are the excessive expansion of wrought-iron due to heat, and great range between the limits of elasticity and rupture. The cast-iron will have to do nearly all the longitudinal work. By varying the thickness of the tube, the transmitted strains can be regulated to the greatest nicety. 673. Method of Gonsteuctiox. — The gim having been bored, a coiled wrought-iron tube is inserted (Fig. 123). The tube consists of two thin wrought-iron ban-els, the outer one being much shorter than the inner one, and shrunk to it at the breech end. Two are used for the pui-pose of obtaining the benefit of the tension, and also to break the continuity of any internal fracture. The end of the tube is closed by a solid wrought-iron breech-screw. The tube is made slightly taper, and the bore of the gun is tapered correspondingly ; the tube is placed in the bore, and as soon as it comes in contact through- out its length, a screw-locking-ring A, which takes against a shoulder on the tube, is screwed into the muzzle, and sets the tube home ; and since in practice it has been found that the elasticity of the wrought-iron inner tube is not proportioned to its greater elongation, the deficiency is supplied by putting the tube under a slight compression, which is effected by perma- nently stretching the wrought -u’on in the gun by heavy proof- 218 NAVAL ORDNANCE AND GUNNERY. charges. The tube is further secured in the gun by means of a screw which passes through the cast-iron shell a short distance before the trunnions at right-angles to the bore, and screws into the tube. 674. PAKSOdd’S SYSTEM OF CONYEESIOX.— Mr. Parsons has proposed that the tube should be made of steel, having a solid breech, A (Fig. 124), the ingot not being bored through its entire length. He proposes to reinforce the tube M'ith jackets of steel shrunk on, B, and to insert the whole, tube and jacket, from the rear of the iron casting, the cast-iron gun being so bored out as to recpiire force to insert the tube in its place. The tube being inserted, a steel plug, C, is to be screwed in from the rear, which presses against the rear of the tube, and the breech is then closed by a cast-iron plug repre- senting the cascabel of the piece, I). Various projects have been brought forward to convert our present smootii-bore guns into rifles, but these are all make- shifts. All of our smooth-bore guns are of too high a calibre, I’elative to their length of bore and weight, to be usefvdly con- verted. 675. EXPEPIMENTAL GUXS. — TheMhitwoeth Gux is made of a substance called compressed steely which is said to be obtained by melting short bars of Swedish iron with a small quantity of carbonaceous matter in crucibles, after which it is cast into round ingots and compressed by hydraulic presses while fluid. The smaller Whitworth guns are forged solid; the larger ones are built up with hoops (Fig. 125). The barrel is made by casting an ingot hollow. A taper mandrel is inserted in the hole, and the whole tube is hammered until it is of the desired size and shape. The hoops are flrst cast hollow, and then hammered over a steel mandrel or rolled in a revolv- ing-machine. Before receiving their flnal finish they are an- nealed. The hoops are screwed together to form a tube, and BUILT-UP GUNS. 219 the tubes are bored with a slight taper and forced on over each other by hydraulic presses, in order to secure initial tensiou. In the larger guns the breech is hooped with a harder and a higher steel than the barrel. The breech-plug is made with offsets in such a way as to screw into the barrel and the two adjoining hoops. 676. The Blakely Gun. — The most approved pattern of the Blakely Gun combines in its construction the principles of Initial Tension and Varying Elasticity, in order to call all the metal of the piece into simultaneous play (Fig. 126). The inner tube is made of low steel having considerable elasticity, but not quite enough. The next tube is made of high steel with less elasticity, and is shrunk on to the inner tube with just sufficient tension to compensate for the want of elasticity. It is hooked at the breech end over the inner tube. The outer cast-iron jacket, to which the trunnions are attached, is the least elastic of all, and is put on only with the shrinkage obtained by warming it over a lire. It is hooked over the tube within. The steel tubes are cast hollow and hammered over steel man- drels, by which the tenacity of the metal is much increased. All the steel parts are annealed. 220 NAVAL ORDNANCE AND GUNNERY. 677. The Yavasseur Systeji consists of a steel tube with hoops of the same material. The strength is cast more upon the hoops and less upon the tube, Avhich is quite thin and jacketed from the breech to a short chstance in front of the trunnions, with a second tube shrunk upon it ; the hoops en- circle the jacketed and unjacketed parts, extending to the muzzle. (Fig. 127.) The figure represents a 7-inch gun of this make. It is built entirely of Fiidh steel, except the trunnion-band, F, which is Fig. 137. — ^VavasBeur 7-inch [steel]. made of wrought-iron. The tube. A, the jackets, B, C, D, and the breech-plug, G, are of cast-steel, the tube. A, being oil- tempered. The exterior rings, E, are forged and rolled like railway tires (Art. 706). The A'ent is at a distance from the bot- tom of the bore eqtial to two-fifths length of the cartridge. Section IV. — French JVavcd Guns. 678. General Description. — ^Breech-loading, rifled cast- iron guns liooped with steel Avere introduced into the French navy about 1860. On these being considered deficient in poAver, elforts to olitain increased strength AA’ere made, which resulted, in 1871, in the adoption of the system now in use. 679. Model of 1871. — The model of 1871 comprises the calibres of 12.18 inches, 9.36 inches, 7.32 inches, and 5.16 Fig. 128. inches. They are all cast-iron breech-loading guns, hooped and lined with steel. BUILT-UP GLWS. 221 680. Casting. — Second-fusion gray cast-iron is used exclu- sively in the manufacture of these guns. They are cast in a mold with a hollow core, and cooled from the interior. The chase occupies the lower part of the mold. 681. Lining. — The tubes to line the bore are made of Bessemer steel, forged and tempered in oil, furnished by Messrs. Petin & Gaudet. The tube is introduced into the gun from the rear or breech end, and has welded on its after-end a collar having a thread on the outside which screws into the metal of the gun ; on the inside of the collar is the thread for the breech-screw. The tube is introduced into a lodgment about .007 inches less in diameter than the exterior diameter of the tube ; the length of the lodgment is also about .007 inches less than that of the tube. 682. To insert the tube, that part of the gun which is to contain it, is raised to a certain heat which will insure the right amount of expansion. The tube is inserted cold and screwed up, and the cast-iron in cooling compresses it, both longitudinally and transversely. The greatest objection is the difficulty of making the joint tight. Tubes extending the whole length of the gnu have been used, but without such good results. 683. The Hoops. — The hoops are rings of puddled steel, very strong and elastic ; mild steel, homogeneous, with a regu- lar libre, is generally chosen. The body of the gun is turned perfectly cylindrical, and of a diameter slightly greater than the interior diameter of the hoops ; they are then heated and shrunk on, and the gun is cooled interiorly by running water through the bore. 68d. The gun is cast without trunnions, and they are built upon one of the hoops, which is called the trunnion-hoop. The larger calibres have a double row of hoops breaking joints. 685. Gxis-CHECK. — The Broadmell Ming forms the gas- check for these guns. This is the invention of Mr. Broadwell, an American, and it is adopted generally as the gas-check in all successful breech-loading systems. 686. The Broadwell Ring is an arrangement illustrated by Pig. 129. It consists of a curved ring, I, and flat bearing- plate, II. The curved ring is fitted in a correspondingly shaped chamber, and like a steam-valve, for instance, may be made perfectly gas-tight, independently of the expansive force of the gas, by being pressed tightly into the chamber by the breech-closing apparatus. The curved self-adjusting gas-ring and adjustable bearing- plate are exceedingly simple, — the ring completely filling the chamber, and being free to move in any direction that may be 222 NAVAL ORDNANCE AND GLTNNERY. necessary in order to bear accurately upon the plate, witbout in the least impairing its mechanical ht in its chamber. Fig. 129. 687. The French Gum of old model had the gas-check fixed to the axis of the breech-plug, but this led to difiiculties of Avorldng, particularly when using very quick powder, and when the initial velocities became considerable. Tliese guns had two lodgments for the gas-check, the one nearest^ the breech being reserved for the time when degradations of the bore at the other, had occurred sufiiciently to prevent a com- plete closure. This change was very efficacious in prolonging the life of the piece, and only required a shorter axis for the new gas-check. 688. In the model of 1871, only one lodgement is made in the gun ; the gas-check, DE (Fig. 130), is of the same shape, but is i^iaced by hand in the lodgement, and driven up by the breech-screw, S. It remains in place throughout the tirina’. The central opening is.made of the same diameter as the pow- der-chamber, and the side is strengthened b}’' a projection. It freely admits the passage of the ammunition. In the larae guns the gas-checks are made of copper, and in the small ou"es of steel. If destroyed, they are easily renewed. 689. Beeecii-sceew. — The breech is closed with a screw- plug of cast-steel, having fourteen threads, which is screwed into the rear part of the bore. Were it necessary in firing to screw and unscrew the whole length of this plug at every round, much time would be BUILT-UP GUNS. 223 wasted ; but tliis is obviated by dividing the screw into six parts, in the direction of its axis, the threads being removed Fig. 130 . from every other one, both from the ping and from the breech of the gnn. When the breec-h is to be closed, the threaded portions of the ping are presented so that they come opposite the smooth parts of the breech-hole. The plug is then pushed in, when a sixth of a turn with a handle brings the screw of both parts together. (Fig. 132.) 690. This system of closing the breech by means of a slotted screw, or one having interrupted threads, was first pro- posed by an American named Eastman, and has been adopted by the French with excellent results. 691. In the model of 1871 the threads are inclmed so that the plug will be better supported from the rear. (Fig. 130.) There is a slight hollow in the front end of the plug opposite the central opening of the gas-check. To make the closm-e still more complete, a cop]jer ring, AB, projecting .01 inches, is sunk into the front end of the plug. This ring, on which the bottom of the gas-check rests, oilers a surface of softer metal, and assists in making the contact more perfect. 692. The ring, as well as the base of the gas-cheek, has three concentric grooves, .05 inches wide and deep, which fur- nish lodgements for any gas that may escape, and prevent it from 224 NAVAL ORDNANCE AND GUNNERY. reacliing tlie metal of the gun. To reserve a place of deposit for the residuum from the bore, the part, AC, between the lodgement of the gas-cheek and the threads of the collar, is bored out to the same diameter as the bottom of the thi-eads. 693. To close the Breech . — A strong cranked lever serves to manipulate the hreech-plug, by turning which the threads of the screw enter the corresponding grooves. The movement in the contrary direction disengages them. 694. The breech being closed, the lever-handle is prevented from moving back, and thus al- lowing the plug to he unscrewed by a short metal catch, a (Fig. 131), working freely on a stud placed in the upper part of the right side of the breech. This catch lifts as the lever-handle reaches it, and allows it to pass, hut drops by the action of a spring when the handle has passed, and thus prevents the lever from moving to the left, a stud on the breach prevents it from moving to the right. 695. To open the Breech . — The weight of the breech-plug for a 9-|-inch gun is about 500 pounds ; therefore a support, or col- lar, is used to hold it, when withdrawn. This is a metallic frame carrying a bracket, A (Fig. 132), hinged to the side of the breech near the open- ing. It has a kind of gut- ter in which slides the screw portion of the plug. This support being placed in a line with the bore, the hand gripe at the mid- dle of the breech-plug is seized, and the screw being disengaged, a strong pull will bring the whole to the rear. The impulse given swings it open, the breech- screw remaining fixed in its support, or collar. A safety-catch held by a spring secures the collar fair in a line with the bore. BUILT-UP GXmS. 225 696. Loading. — The breech-plug being swung round at right angles to the bore on its support, an iron bearer is intro- duced to facilitate the loading of the projectile, and prevent the cartridge from being torn by the threads of the screwn It is kept in position by a lever and stud fixed to the under side of the breech. The bearer has a groove to guide the projectile, and it is long enough to clear the tapped portion of the breech. It is readily moved in and out by hand. The projectile is placed on this bearer and pushed into the bore ; a Avad of dried sea-Aveed is then pushed in, and aftenvards the cartridge ; the plug is then pushed in, and sci’ewed up. 697. Safety-catch . — To obviate the danger resulting from a neglect to screw up the plug when the breech is closed, the lock-lanyard, which has a bob on it, is made to pass through the eye, c (Fig. 131), of a piece of iron fixed to the breech. When the handle is not in its place, that is, wdien the plug is not properly screwed in, a spring, 5, closes the eye and does not allow the bob to pass. When the handle is in position with the plug screwed up, it opens the eye and allows the bob to pass, Avheii the gun can be fired. 698. The linFEVE Gux. — This is a small bronze breech- loader, introduced during the war of 1870 by Col. De Kefiye. Its distinctive feature seems to be its metallic cartridge, which is interesting because it is proposed to introduce in our service a breech-loading 3-inch rifled howitzer using a metallic cartridge- case. 699. The Iteffye Cartridge. — This is composed of com- pressed powder enclosed in a metallic case. The rigidity of the cartridge-ease offers the valuable adA’antage of permitting the employment of powder pressed in cakes, which preserve that form and condition calculated to produce the best effect from the expanding gases. Besides, the ease furnishes a lining to the chamber, and also serA'es as a gas-check. (Fig. 133.) The cartridge cylinder is made from a sheet of tin, rolled on a mandrel and covered with seAmral layers of paper rolled on, using glue betAveen all surfaces. The head, AB, is a brass cup contracted at the open end and slightly enlarged at the bottom. A depression is formed in its base, called the yjriming-charriber, which also serves as a compartment for the vent gas-check arrangement, CD. A hole is drilled in the centre of this indentation, E, for the rivet of the gas-check, and the sides are pierced at the point where the bottom joins- with six holes, hh, to permit the passage of the flame to the charge. A brass disk or gas-check, CD, is riveted to the bottom of the priming-chamber, and it is chamfered at 15 226 NAVAL ORDNANCE AND GUNNERY. the edges, so as to avoid closing the holes communicating with the charge. A brass cup fits snugly in the depression of the head, fomfing a part of the priming-chamber, and it is pierced to correspond with the axis of the vent. The wad, GII, is made by rolling sheets of paper in cylin- ders, which are then cut up into the required sizes. These serve as wedges, binding the tube and head close together. In making up the case, the lower edge of the cylinder, having been slit^with hand- shears, is inserted in the head and shoved down until the edge takes against the priming- chamber. The cylindrical paper wad is now dropped in the ease, just fitting over the priming- chamber, and pressed down with a punch, which forces it against the sides and upon tlie bottom of the bent tin. The head is secured by rivets. Ell, to the bent edges of the tin, and to the wad, securing all firmly together. The charge is made up of six cakes or rings of compressed powder having central holes. The bottom cake is slightly convex at its lower surface, to take the form of the pressed paper wad. The cartridge is charged by rolling the six cakes in a paper envelope, and inserting the cylinder thus formed in the case. By a certain degree of compression a greater force is developed, when an appropriate surface of ignition is presented, by the explosion of a given quantity of gunpowder, than in a loose state ; therefore a charge of powder when compressed should give a greater velocity than an ordinary charge tired in the ordinary way. BUILT-UP GUNS. 227 A pasteboard cup, L, is placed over the powder and filled wfith lubricating material, having first inserted a wad of tow. The end of the case is covered with a cloth patch secured with a ribbon, to keep the pasteboard cup in place. The edges are then slightly crimped. The priming-chamber, CD, is filled with musket-powder, the vent-hole being closed with a small patch, one corner of which is left free. The gas-check arrangement operates as follows : The pow- der in the priming-chamber being ignited by the primer, the flame will immediately reach the charge through the small holes pierced for the purpose, when the gases from the latter pressing in the opposite direction flatten out the indented brass, which carries with it the gas-check, and the whole closes down upon the vent, forming a metallic obstruction to the escape of the gases. 700. In the forward face of the breech-screw of this gun, a cupped recess 0.4 in. in depth is snnk to receive the head of, tlie metallic case. This recess has three left-handed spiral grooves, in which the head of the case is firmly grasped, and as if embedded after firing. On opening the mechanism and withdrawing the movable breech, these projections bring with them the cartridge-case. The latter strikes with its open end at the rear opening in the breech, and falls to the ground. In case it is too firmly held, it may be readily detached by un- screwing. The Eastman breech-closing arrangement operates Avell in this gun, except a slight upsetting will sometimes appear in the threads of the screw-box. In our gun several important modifications will be made in the details of the screw-breech by increasing the length of the screw, adopting a better form of thread, and the insertion of a steel thimble containing the screw-box, in the rear of the gun. At the cen- tre of the I’ecess, in the body of the breech-screw, is the vent, hy which the flame from the primer passes to the centre of the cartridge.* Section Y. — German Naval Guns. 701. Nomenclature. — The heavy rifled guns for vessels are breech-loaders, of Krnpp’s cast-steel, all hooped, and with round breech closure and axial vent. The calibres of the guns, that is, diameters of rifled part of bore from land to land, are as follows : * U. S. Naval Ordnance Notes, 1873.— T/jfi Eeffye Gun. 228 NAVAL ORDNANCE AND GUNNERY. 11-inch, or 28 centimetre, 96-pdr. lU-inch, - or 2G 9-inch, or 23^ “ 90-pdr. 8-inch, or 21 “ T2-pdr. 6.6- inch, or 17 “ 3G-pdr. 5.7- inch, or 15 “ 21-pdr. Fig. 134. 702. Features of the Maxufactcee. — The great fea- tures of the manufacture are tlie forging of large masses from single homogeneous ingots without seams or welds, the forging and rolling of hoops without welds, the use of very heavy ham- mers, and the quality of tlie steel which contains one-half per cent, of carbon and a considerable quantity of silicon. 703. Old Krupp Coxstructiox. — The guns are made at the factory of Krui)p, at Essin, in Prussia, lie supplies all tbe cast-steel guns that are used in the German service. Until within a few years, he made all his heavy guns of a single ingot, cast, forged, and turned ; but this method left the gun open to the serious objection of liability to bursting explosively or without Avarning. No matter Avhat care has been used in the manufacture, cast-steel is a treacherous metal, likely to burst Avithout warning ; and in many instances the failiu’e of Krupp’s guns have been attended with disastrous consequences. 704. Neav Krupp Coxstructiox. — Mr. Krupp has aban- doned the precedmg method, and now builds up all his larg-e guns by shrinking hoops of steel over a central tube with initial tension. BUILT-UP GUNS. 229 Tlie guns consist of a central tube, and the single (in guns of 9-inches calibre, and nji'U’ards double) layer of hoops protect- ing those parts most exposed to damage by the expansion of the powder-gas. The 6.6-inch and S-inch gnus of the old construction have been altered to the new on account of its greater durability. The outside parts are named : the breech or bottom-piece, li (Fig. 135), the hooped or middle piece. A, and the cone, or chase, C. The length is measured between the planes of the base of the breech and the muzzle. The breech-piece imme- diately abaft the hooped piece contains the wedge-hole, H, cut- ting through at right angles to the axis of the bore. In the base of the breech is the hole for loading, L (I ig. 140) ; on each side of the hole is a hook, V, with two slots for the hinges of the loading-box, and hooks of shell-bearer ; farther forward are the holes for the sights. The hooped piece, diminishing in fi'ont by steps towards the chase, has in its rear the protruding end-hoop^ D (Fig. 135). In its front part, on a broad hoop, are the rim-bases and trun- nions, whose axes pass through the axis of the piece. On top of the trunm'ous are the screw-holes for sights. The after- edges of the end-hoop and of the bottom-piece are considerably rounded off. The bore extends to the wedge-hole, and includes the chamber, the seat of the projectile and rifling. The cham- ber is equal in diameter to the diameter of the bottoms of the grooves. 230 IsAVAL OEDNAIfCE AND GUNNERY. forging Fig. 136. 705. The Central Thbe, T, is very massive ; almost a gun by itself. It is forged and turned from a single ingot, and loses half its weight in the lathe. The gun-blocks are cooled slowly by throwing them, after hammering, into the hot ashes and cinders from the furnaces, where they are allowed to remain. Tins tube supplies all the longitudinal strength, and projects far enough to the rear to accommodate the breech closure. It is not tempered. The walls are 0.8 of a calibre thick from a point over the middle of the charge to the point wliere the rings terminate. 700. Hoors. — The hoops are made with an endless fibre by an ingot into the shape shown in Fig. 136, with a slot through the middle ending in holes. This slot is pressed with wedges into a ring, which is half the diameter and twice the thickness of the finished ring. The ring, having been heated, is put over the central roll of a machine like the tire-rolling- machine (Fig. 137). The rolls, while revolving, gradually approach each other, and thus the hoop is rolled to its proper size, and at the same time an endless fibre is developed in the direction of the circumference ; they are cooled by a jet of water while on the rolls; this prevents distortion. They are then heated and shrunk on with initial ten- sion. They are kept from work- ing on the gun by key-rings, a (Fig. 135), which are lialf-hoops laid into scores cut to receive them. 707. Breech-plug. — For the hooped guns which with heavy charges had not sufficient durability, the cylindro-pris- Fig. V61 . — Machine for Rolling Hoops. Fig. 138. matic wedge, P (Fig. 139), has been adopted. It slides in a BUILT-UP GUNS. 231 horizontal inortiso of the same shape in the breech-piece. The plug is made of steel, the wedge and cylinder forming one body ; the rounded part is on the rear side, as that gives a greater bearing-snrfaee. It is generally drawn ont on the left side, except in turrets or when the position of the gnns may jecpiire a change. The front side is Hat and forms the bottom of the bore. The wx'dge has small grooves parallel to its after- edge oil the top and l)ottom for the leading-lasts, which keep it in position while it is being moved ont and in. In the gnns of 8-ineh calibre and upwards, the ping is moved in and ont by a transporting-screw, a. In the smaller gnns it is moved by hand. The transporting-screw rests in a groove on the npper side of the wedge, and has a shoulder which takes against 'the locking-plate, h, and a rounded end which turns in a ring at the other end of the wmdge and keeps the screw in position. The screw works in a nut, c, on the npper side of the wedge-hole. (Fig. 139.) The transporting-screw has a scpiare end to which a crank. Fig. 139 . f, is fitted for turning it. The end projects through a plate, 0 , called the locking-plate. This plate is screwed on to the extreme end of the wedge. In a hollow on the after-side of the wedge is the loching- screw, d, with its joint against the locking-plate, ont of which one end protrudes square, for shipping the crank, while the other end rests in the wedge and is held by a pin. ' It may be turned, but cannot be moved in the direction of its axis. Upon it is the nut, e, shorter than the hollow, with several rino’s cut away on one side, but with one full end ring at the outer 232 NAVAL ORDNANCE AND GUNNERY. Fig. 140. end. Upon the latter a projection, u, is formed, Tvhich, coming out of a segment of the locking-j)Jate, may be turned about one-third of a circle. As soon as the projection stops the turning of the nut, it can be pushed forward or back. ^Vith closed breech, the ring parts of the nut fit into cuts, 17 , < 7 , p, in the gun ; but when open, the part not having rings turns to the rear. The same crank, f, fits both screws. The locking-chain, o, on the gun, with the hook on the locking- plate, limits the movements of the wedge. 708. Gas-chece. — To pre- vent the escape of gas breech- wards without a perfect me- chanical fit of the parts of the breech, a Broadwell-j)late, h (Fig. 129), and ring, i, are used. The ring is a circle of steel, which fits into a groove or chamber at the bottom of the bore close to the wedge- mortise. As an aid to the Fig. 141. steel Broadwell-ring of the chamber, a circular, slightly hol- lowed out Broadwell-plate, h (Fig. 138), is entered into the wedge, which is cut out for this pui'pose on its front side at h (Fig. 138), so that, at the closing of the breech, its liin, projecting a little over the wedge, meets the ring, which also projects over the front side of the wedge-hole. At the discharge this check is closed by the action of the pow- der-gas, which presses the thin edges of the ring against the gim and plate. The plate has circular plates of thin brass be- hind it, for an equalizing spring support; and the plate is kept BUILT-UP GLmS. 233 in position bj a pin wbicb is screwed into tlie wedge at tlie centre, for wliicb tlie plates of brass are pierced. 709. The Yent-tube. — The vent is in the direction of the axis of the bore, and is tilled with a vent-tube; this is made of steel, cylindrical, and is lined with copper, more or less conical, and tits exactly into its place in the wedge ; this place is en- larged at the rear, and fitted with a thread for \h.Q primer-hibe screw. It has also a broad fiange upon whose rear side the lock for confining the friction-primers is placed, A (Fig. 112). This consists of a fiat cover which has a cut in it for the wire of the friction-primer, and it has a button on toji for handling it, a. It turns easily on its hinge, and is hollowed out on the side of the vent, so that it may be raised by the escaping gas, and thrown aside. The whole lock is placed in a hollow of the wedge, so that it can be moved at pleasure without inter- CHAPTER Y. - EITLIN^G-. Section I. — Principles. 710. Definition. — A rifle is a fire-arm which has cerlain spiral grooves or “rifles’' cut into the surface of its bore, for the purpose of communicating a rotary motion to' a projectile around an axis coincident with its flight. 711. Oeigin of Rifling.— The rifle-principle was first developed in small-arms. W ith the smooth-bore gun the wind- age which allowed the ball to be entered freely at the muzzle of the piece gave rise to great inaccuracy of flight, from the fact that the projectile was thereby caused to ballot along the boi’e, and be projected in a direction due to its last contact, and this deviation was complicated by a motion of rotation gen- erated at the instant of the last contact of the ball with the bore, and pei-petiiated throughout the entire flight of the projectile. 712. To avoid the bad effects of the shocks in the bore, windage was suppressed, the ball made of a calibre equal to that of the piece, and straight grooves cut in the barrel ; which diminished the surface in contact with the projectile, thus ena- bling it to be pushed home with slight pressure. By accident- ally making these grooves inclined, it was immediately seen that increased accuracy was given to the weapon ; but the science of the day "was unable to assign a reason for tins superi- ority. 713. About the year 1600 the rifle-musket began to be used as a military weapon for flring spherical bullets. It is well known, however, that this means of obviating the effects of the irregular rotary movement of the projectile was applied long before the nature of the difficulty wdiich it remedied was itself apprehended. 711. The rotation of the ball upon a given axis, by means of the tight-fltting spiral groove, and the consequent invariable presentation to the resistance of the atmosphere, of the surface originally placed in that direction, would seem to indicate be- yond the possibility of misconception, the advantage that was to be obtained from it. And yet it is only in our own time that the round ball has given way in the rifle to the conical or RIFLING. 235 elongated projectile. The great merit of the arm was conse- quently of little account, because the resistance experienced by the round ball from the atmosphere was nearly the same, whether tired from one piece or another; while with light charges there was a certain decrease of initial velocity from the friction in the rifle. But with the conical or elongated projec- tile the surface of the transverse section was decreased, while the weight remained; therefore there was less resistance to overcome with the same power. 715. It is obvious, however, that the introduction of elon- gated projectiles would follow that of rifled-bores; and, indeed, it is very doubtful if cannon would ever have been rifled were it not for the sake of firing such projectiles — for the advan- tage of such accuracy as might be given to a spherical projectile would very probably be counterbalanced by the curved and irregular ricochet that rotation imparts to it, and the increased strain on the gun. Thus rifling being necessary for the employ- ment of elongated projectiles, and such projectiles being essen- tial to the success of rifled cannon, the two have become insep- arably connected in the mind. 716. Difficulty of Loading . — The great difficulty of loading the rifle prevented it for a long time from being generally used in regular warfare, but the improvements which have been made of late have entirely overcome this difficulty, and rifles are now used almost univei'sally in place of smooth-bored small-arms. 717. INTRODUCTIOJI OF RIFLE-CARROR.— The general adoption of rifled small-arms necessitated the introduc- tion of rifled-cannon. It is plain that the principle has applica- tion to all sizes of projectiles, and would therefore be used for the heaviest ordnance as well as for the smallest. Contempora- neous attempts so to adapt it have not been wanting, but they are in many cases isolated in point of time and connection. The first persevering and rational efforts to apply the rifle- principle to cannon were initiated some twenty years since, and the names of Wahrendorff, Cavalli, Lancaster, and others, are identified with the first efforts to overcome the difficulties — of no ordinary character — that beset the question. 718. Difficulty of Construction. — The yielding nature of lead renders the application of the rifle-principle of easy accom- plishment in the case of small-ainns ; but such is not the case with rifle-cannon, where the projectiles are made of iron. The application of this principle to cannon also required an increase of strength in the piece. 719. The greater the Aveight and the length of a projectile, the greater is the opposition from inertia and friction which it 236 NAVAL ORDNANCE AND GTJNNERT. offers in the bore to the expansion of the ignited charge, and this opposition is considerably augmented if the projectile is constrained to travel through the bore in a spiral course. Hence it is not difficult to comprehend why a rined-gun must he of a stronger, tougher, and more elastic material than is necessary for a smooth-bore gun in which the spherical projec- tile yields promptly to the first impulse of the powder-gas to which it presents half its surface, and hounds freely forward through the bore, almost unimpeded by friction ; while the sti’ain on the gun is immensely relieved by the comparatively great windage. 720. Again, as the explosive power of a cartridge, as well as the inertia and friction of a projectile, increase" as the cubes of their respective weights, while the surface of the chamber and the base of the projectile against which the powder-gas acts increase only as the squares, it folloAvsthat the larger the charge and the heavier the projectile, the harder and stronger mxist be the inner barrel, or else the slower must be the combustibility of the powder used. 721. The difficulty of perfecting more powerful guns for rifle-cannon than previously existed, has been very great ; nor have we by any means reached perfection in the construction of such guns. The successful application of the rifled principle and the possibility of throwing enormous shells with the great- est initial velocity have exhibited the importance of the strong- est cannon and the utility of the largest calibres, but their development must be in harmony with the progress of the manufacturing arts. 722. Progress nsr Coxstetjction. — The progress of the art of war depends essentially upon that of the sciences and manu- factures, for the manner of hghting depends upon the character of the arms which we possess. These will be more effective, as their mode of construction is more perfect, and as the means employed in their manufacture produce greater strength and precision. This is particularly the case with reference to cannon, in evidence of which we have only to call to mind the great revo- lution in warfare which has taken place since their introduc- tion, and which is continually taking place as the means of per- fecting cannon increase. It is only of late years that our knowledge of the metalhirgy of iron, and" our ability to manufacture and handle large masses of that metal, have rendered possible the fabrication of the enormous pieces of the present day. But now the great improvements which have been intro- EIFLING. 237 duced in the manufacture of iron, in the fabrication of cannon, and in the facilities for the transportation and handling of heavy guns, render possible the success of cannon of mammoth proportions. 723. Designing Rifle-cannon. — In designing rifle-cannon, the practicability of manufacture and the durability of struc- ture must be ascertained. The weight, calibre,' length, system of rilling, weight and shape of projectile, etc., etc., must be all scientifically calculated so as to ensure excellence in range, ac- curacy, and penetration ; and then each and all of these con- structional details are liable to alteration, should the thorough trial of a specimen gun render any amendment advisable. 721. Early Experiments.^ — The first comprehensive experi- ment with rified-cannon appears to have been made in Russia, about 1836, on the invention of a Belgian, but did not prove successful. In 1815, Cavalli, a Sardinian officer, experimented with a breech-loading cannon which was rifled with two grooves, for a plain iron projectile, adapted to fit them. In the next year, Wahrendoj’ff, of Sweden, fitted heavy projectiles to take the- rifling by affixing lead to their elongated sides by means of grooves cut in them. And not long after this, Timmerhaus, of Belgium, invented an expanding sahut, which, being fitted to the base of the projectile, was forced into the rifle-grooves and thus gave rotation. ' In these early experiments we find the germs of the leading systems of the present day. The solid projectile, fitted to enter the grooves of the gun ; the compression of a soft covering on the projectile by the lands of the gun ; and the expansion of the rear of the projectile by the press me of the powder to till the grooves of the gun. 725. OBJECT OF RIELINGr. — The object of rifling a gun is to increase its accuracy of fire, and, by enabling elongated to be substituted for spherical projectiles, to obtain from it longer ranges. Rifling diminishes the deviations of ordinary projectiles, due to the following causes : 1st. Want of uniformity, in figure and weight, around the longitudinal axis of the projectile, passing through the centre of gravity. 2d. Position of the centre of gravity, before or behind the centre of figure. 3d. Resistance of the air. I. By rotating the projectile around its longitudinal axis, the direction of these deviations is so rapidly shifted from side 238 NAVAL ORDNANCE AND GUNNERY. to side, that the projectile has no time to go far out of its course either way. II. The velocity of this rotation is such as to make the axis stable on leaving the bore, and to counteract the pressure of the air tending to turn the projectile over, or render it unsteady in liiglit. III. A given weight of projectile can he put into such a form as to oppose the least practicable cross-sectional area to the air, and thus to receive the least practicable retardation of velocity. 726. Advantages of Elongated Peojectiles. — Certain peculiar advantages follow from the rotation of the projectile, causing it to present the same part to the front throughout its flight. It becomes possible to make a much simpler percussion-fuze, because it is only necessary to provide for action in one dii’ec- tion in place of every possible direction. Shells required to act towards the front in any peculiar way have their bursting-charge and metal placed with a view to this object. So, again, the centre of gravity may be brought to any desired part of the shell ; and this is an important feature in the construction of projectiles. Pilling gives the power of altering the form of projectiles at will. The head may be made of any desired shape, for penetra- tion or flight. The projectile may be elongated so as to give a diminished surface for any resisting medium to act upon ; thus in flight, velocity is kept up and the range extended, or on im- pact greater penetration is obtained. Weight for weight, the same effect may generally be pro- duced with an elongated projectile by using a smaller charge of powder than Avith a spherical one. It follows from the flight of an elongated projectile meeting Avith less resistance from the air, and keeping up its A'elocity better, that at all but A'ery short ranges the trajectory is flatter ; hence the probability of hitting an ordinary object is greater. The poAver to vary the length of the elongated projectile en- ables all those for the same gun to be made of the same Aveight, and hence to require the same elevations Avith the same charge of poAvder. Or it is possible to make a projectile specially lieaA-y if required. This obviously camiot be the case Avith spherical projectiles, AAdiich must be of the same size. 727. Disadvantages of Elongated Peojectiles. — The chief disadvantages are, bad ricochet, increased complication, and ex- pense of manufacture, liability to injury arising from the neces- sity of soft studs, expanding rings, or a soft lead coat ; increased RIFLING. 239 strain on tlie gun, besides greater probability of jamming and injury to tbe bore, uncertainty of time-fuzes. 728. METHOD OF EIFLIbTG. — To rifle a flre-arm, spiral grooves are cut in tbe surface of tbe bore, into wliicb the pro- jections or soft metal coating of the projectile are made to enter. The grooves may be of any number, and may extend par- tially around the bore, or once, twice, or several times in its length. They may be of the same pitch or curvature through- out, or the twist, if desired, may increase in curvature towards the muzzle. It is essential, however, that all the grooves be of the same curvature, and exactly parallel to each other ; their object being to impress upon the projectile a rotating motion about its axis of progression, and thus keep it in a straight line as it spins forwai'd. The motion of a top holding itself upright while rapidly spinning, illustrates the principle of the rifle. 729. Lands. — -The spaces between the grooves are called ‘■'•landsP Where the grooves are very wide, and the lands very narrow, they are termed “ riljsP 730. Calibre . — The calibre of a rifle-gun is measured across the lands. In the ease of a rib-rifled-gun, it is measured to the bottom of the grooves. 731. Fokm of Gkoove.- — -The form of the grooves and their number vary very much according to the method of rifling. The form of the groove is determined by the angle which the tangent makes at any point with the corresponding element of the bore. If the angles be equal at all points, the groove is said to be uniform. If they increase from the breech to the muzzle, the grooves are called increasing., or the rifling has a gaining twist. 732. Twist is the term generally used to express the inclina- tion of a groove at any point, and is measured by the length of a cylinder corresponding to a single revolution of the spiral. This, however, does not convey a correct idea of the inclination of a groove. A correct measure of the inclination of a rifle-groove at any point, is the tangent of the angle which it makes with the axis of the bore ; and this is always equal to the circumference of the bore divided by the length of a single revolution of the spiral, measured in the direction of the axis. 731. Unifokii Twist. — Let ABC (Eig. 113) be a right-an- gled triangle, in which — EC = circumference of the bore of a gun, AB = length of the bore. How suppose the triangle ABC to be wrapped around the 240 NAVAL ORDNANCE AND GUNNERY. surface of tire bore as in Fig. 143, so that B and C meet. AC will be the lielix^ or curve of the groove. IS^ow in Fig. 143 the groove makes a complete turn in the length of the bore ; but in ordinary Fig. 143. rifle-guns the twist is more gradual, making less than one turn in the boi’e. In the ease before us, AB equals the length of ilfling due to one turn, that is, the distance travelled by the projectile while it is turning on its axis. AC is the total length of spiral and Q the angle of twist, or angle of the rifling. Let n = number of cah- bres in which the projectile makes one turn. tan Q ^ _ AB “ Tt X calibre number of calibres X calibre 7t Tt number of calibres n 735. Uniformly Increasing T^VIST. — Wlien this system is adopted, the grooves start in a direction parallel to the axis of the bore, and the twist increases uniformly towards the muzzle. In the Fig. 144, ABCO denotes the development of the bore, and CM that of a groove. The origin of the co-ordinate axes is taken at the commencement of the groove at the bottom of the bore ; the axis of Y is parallel to the axis of the bore. The curve OM is tangent to OA at O, since the projectile starts in the direction OA. Let

osition; the gun to be operated upon is fixed in front of it. in line with the rifiing-bar, which has a motion of translation along its bed as well as a certain ainoimt of rotation on its own axis, EIFLIiSTG. 249 regulated to the required pitch. An automatic reverse motion is contrived for the bar, so that when once set in motion the machine is self-acting. Section II. — Systems. 752. A System: of Hifleyg consists essentially in the means of giving rotation to the 'projectile. The twist of the grooves, the length, diameter, or form of the projectile, must depend upon the purpose for which a gim is required, no matter upon what system it may be rifled. In- ventors often claim principles which are as applicable to one as to another system. As regards precision of Are, one system will give as good results, for all practical purposes, as another, pro- vided the conditions of charge, projectile, and twist of grooves are alike, and the rifling of the bore and the manufacture of the projectiles have been performed with the same amount of care and skill in both cases. The conditions that are especially desirable in a system of rising for ordnance are Accuracy of tire, simplicity and dura- bility in both projectile and gun, non-liability of projectile to jam in the bore in loading or tiring. It must not cause too great strain, and for heavy ordnance, must allow of the use of large charges. It will be observed that in many of the systems of rifling in use, one or more of these conditions have been saeriticed to some extent, to secure a closer compliance with others thought to be of greater importance, or of easier attainment. 753. Great numbers of rifled guns, with projectiles to corre- spond have been proposed, but most of the systems of rifling that have been adopted by any service, or tried on the i.'raetice- ground, may be divided into the following classes, each of which has its advantages and its disadvantages, and none are without objections. First. Muzzle or breech-loading guns, having projectiles of hard metal, fitting the peculiar form of the bore mechanicall}^ Second. Muzzle or breech-loading guns, with projectiles having soft metal studs or ribs, to tit the grooves. Third. Muzzle-loading guns, with projectiles, having a soft metal envelope or cup, which is expanded by the gas in the bore. Fourth. Breech-loading guns, with projectiles having a soft metal coating larger in diameter than the bore, but which is compressed by the gas into the form of the bore. 250 NAVAL ORDNANCE AND GUNNERY. 754. First Class. — In this class, the hard metal projections are so shaped as to fit the peculiar form of the bore mechani- cally. The gaiuing-twist is obviously impracticable with this form of lifling. Centring . — In consequence of windage, which is nece.?sary in all muzzle-loading guns, the axis of the projectile does not always coincide with that of the bore ; in firing, this leads to inaccuracy of fire. In order to secure accuracy of fire, it is essential that the axis of the projectile should correspond with that of the bore of the gun ; for, otherwise, the axis of rotation will be variable, and the dellection of the projectile uncertain. Should the axis of the projectile on leaving the bore be unsteady, the projectile will have the 'MCiUbling motion so frecpiently observed in ex- perimental pi’actice. A projectile is said to be centred when the grooves of the rifling are so constructed as to bring the axis of the projectile in line with that of the bore Avhen the piece is fired. Centring may embody the compressing or expanding sys- tems in any required degree. While the projectile is rotated by the solid projections formed upon it, and fitting into the grooves of the gun, the exterior of these projections, or of the whole projectile, maybe covered with a soft substance which may, in the case of a breech-loader, be largei- than the bore, and thus be compressed while passing out of the gun; or which may be expanded, by the pressure of the powder, to fill the gun. When the projectile is well centred, windage cannot afiect its straight passage throngh the bore. Usually, in the first class, the hard surface of the projectile is dressed to bear directly on the surface of the bore, leaving a little windage. The systems of Whitworth, Y avasseur, Scott, and Lancaster are examples of this practice. 755. WiiiTWOETii’s SxsTEji. — The Whitworth gun has a hexagonal spiral bore, the corners of which are rounded off. The form of the bore is not, however, strictly hexagonal. The interior of each gun is first bored out cylindrically, and when the rifling is completed, a small portion of the original cylindrical bore is retained along the centre of each of the sides of the hexagonal bore, and the other parts of each side recede or incline outw.irds towards the rounded angles ; hence the diameter of the hexagonal hore is greatest at the rounded angles. This description will be readily understood by reference to Fig. 153. EIFLING. 251 The reasons for thus modifying the general form of the rifling are, to facilitate loading, and thus allow of a reduction of windage, and also to ensure, if possible, the bearing of the sides of the projectile on sur- faces instead of on mere lines, as would be the tendency with a plain hexagonal bore having windage. A hexagonal bolt revolved on its axis Avithin a slightly larger hexagonal orifice would not bear upon its side, but only upon its six corners. The points of contact Avould be mere Fm. 103. lines. In this system, the bore must obviously be slightly larger than the projectile. In Fig. 151, while the face, a e, of the pro- jectile is flat, the face, d e, of the bore is so inclined, that the Fig. 154. projectile in coming out Avill bear upon the whole of it, as shown. If the face, a e, of the bore was also plain, the projec- tile Avould bear only on the corners e 1), etc. The following table gives the particulars of the Whitworth guns and rifling ; 252 NAVAL ORDNANCE AND GUNNERY. !.a -g- t5rd C O ti) ^ a • o .S ^.a c ^5 to Ch O CO CO CJ o £h H . o o ^ c. S The peculiarities of this system are the polygonal rifling and comparatively small bore. It has great range and penetration, bnt has never been adopted for heavy gnns by any nation ex- cept Brazil. The polygon has twenty-four surfaces with six grooves, each .4 inch deep. Though the long iron bearing diffuses the strain over a large surface, and enables a rapid twist with great rotation to be RIFLING. 253 V f5}. fcl) S o g cj & o' "SiwWtofcCs.V^.-i.IiaA. 254 NAVAL ORDNANCE AND GUNNERY. given, yet the hearing is really on a mere line in each groove, and is ninch nearer the axis of the projectile than in systems with projecting flanges, and tlie leverage for rotating is there- fore much less. In muzzle-loading gnns of this system it is difficult to thor- oughly sponge the bore. A patent lubricating cartridge in a metallic case is used with the breech-loaders. 756. Yavasseue’s System. — This method comes under the head of rih-rijling (Art. 729) — the rotation being given by means of raised ribs in the bore, while the projectile itself has corresponding grooves cut along its cylindrical surface. The ribs are three in number ; their shape, and also that of the coiTesponding grooves, are shown in Fig. 156. There are no sharp angles either in the projectile or the bore of the piece. The dimensions and particulars concerning the guns and rifling are given in the following tables : RIFLING, 255 The twist of the rifling is one turn in thirty calibres for all sizes. The angle of the twist is 5°, 58', 41'h6, and is thus obtained : In the light-angled triangle ABC (Fig. 157), let AB = n = the number of calibres in which the projectile makes one revo- lution = 30 = BC = circumference of bore, d = angle of rifling ; 256 NAVAL ORDNANCE ziND GUNNERY. Then tan 0 = Ali 7T 11 3.1416 30 nat.no. 0.10472 log 9.020029 = 5°.58', 41A6. Fio. 157. To find the Width of Tib . — Having width of rib for one ^nn, to hnd that of another gun, when r' of the latter is known, w' — width of i-ib. v' = diam. inside of rib (col. e. of Tab). 1.5 = width of rib of 12- in. gun. 5.7 — r' for 12-in. gun. Then w' ; 1.5 = r' : 5.7. Suppose w' is required for 10-in. gun, when r' = 4".75, w' = r' X ^ - .263r' 5.1 = .263 X 4.75 == Fig. 158. 1". 24925, or l'b25 (col. e of Table). In this system the bore of the gun is not weakened by hav- ing grooves cut into it, and the projectile is also considerably stronger than those fitted with studs, because the metal cut out of the body of a tivelve-iuch projectile, for instance, by the coun- tersinks for fixing the stucls (Art. 782), is more than that cut out of the same projectile by the three grooves. There is also considerable less scoring in the bore, as the part most aHected by the rush of the gas in the part between tlie ribs, nearly one-third the whole circumference in width ; the scoring is, therefore, much less local and takes place in a part not weakened by grooves cut into it, as is the case in grooved guns, where the grooves being the highest part of tlie bore act as channels along which the gas rushes. It is claimed that as the ribs in this system project froin the RIFLING. 257 surface of the bore, they are mucli more effectnany cleaned than are grooves, by sponging, so that much less windage can be allowed. Late experiments to determine the relative values of long and of short rifle-bearuigs have demonstrated the great superior- ity of the system. This arrangement necessarily involves a considerable amount of friction, the more so as both the metals which come into con- tact are hard. It is necessaiy that the projectiles should be fitted with peculiar precision, .so as to preclude jamming on the one hand, and too much windage on the other. 757. Scott’s Sys- tem. — In this method | the bore is rifled with i narrow, s h a 1 1 o w grooves (Fig. 159), deeper on the driving than on the loading side. The projectile is one iron ribs almost casting having triangular in section, extending the whole length of the the drivin 2 ;-side. O cylin- drical body, and set to the angle of the rifling. In cross sec- tion the ribs give a deep bearins’-surface on (Fig. 160.) By shallowing the loading-side of the groove, the ribs rest on inclined planes so that the projectile, when forced into its seat, has a natural tendency to slip round so as to cling to the driving- side before the mm is fired, to start easily, and to mount into the centring position the moment it begins to move out. Less windage is given to the ribs on the jirojectile than to its body, so that it rests upon its projections, and its body does not touch the bore at all. The ribs almost till up the grooves, and check the escape of the gas, with its consecjuent erosion of the bore, and unecj^ual 17 258 NAVAL ORDNANCE AND GirNNT:E,T. action on the projectile. While hy striking the curve of the cross section of the groove and of the rib with two different radii, the latter is driven up into the centre of the bore at once, causing the axis of the projectile and of the bore to coin- cide. (Fig. 161.) In this system there are 3 grooves for 9-ton guns and un- der; 5 grooves for 12 and IS-tnn guns; and 7 grooves for 25- ton guns and upwards. The grooves are of the same size for all guns. lYidth, 0.8 inch ; depth, 0.125 inch. This system has not, as yet, been generally adopted by any nation. 758. Lancaster’s Systew. — This method may be described as that of the usual circular bore with two wide grooves, each about one-third the circumfer- ence in width, the shoulders of the grooves being shaved off so as form an ellipse. (Fig. 1G2.) Tlie cross section of tlie bore is oval, only a trace of the ongiual bore being left at the minor axis. The absence of shoulders to the two grooves converts the two places of contact of the jarojectile with the rifling, into circular wedges tending to burst the gun or to compress the pro- jectile. This system has much to commend it, on account of its simplicity, but it has never obtained success ; on the contrary, it has been very unsuccess- ful in competition with other systems. 759. CV»n>AKATiVE Advantages of the First Cl.vss — , The advantages of this class are : economy, simplicity, and d’u- ahility of p.'ojectile. The rilie-motion is communicated with great certainty and regularity. The projectile does not expand Fiff. 103. — Lancaster’s Riflino RIFLING. 259 Aviuclage the c as as the here Jims expands by the explosion, and hence get's more warms, so that its safety-valve gets larger and gets weaker. The chief objections are, that hotli projectile and bore being hard, fracture of one or the other is liable to oeenr from a pro- jectile and that unless the bore be made of very hard material, it will be rapidly worn by the friction of the projec- tile on it. The obvious mechanical advantages of the Gentrinfj System recommend it. It decreases the strain upon the gim by allow- ing windage without affecting the accuracy of the flight of the projectile ; and when so applied as to bring the minimum wedg- ing-strain and friction upon the gun, and to place and hold the projectile in the centre of the bore without shock, and to allow its centre of gravity to be in the centre of figure, and to sup- port the projectile at or on both sides. of its centre of gravity, thus promoting velocity and accuracy, it woidd seem that this system must be the best to be adopted for heavy ordnance. 760. Second Class. — In this class the body of the projectile is composed of a hard metal, as cast-iron, and there are attached to it projections of soft metal in the form of ribs, or rounded buttons so arranged as to enter the grooves of the rifling. The Woolwich or French rifling, and the Shunt system are exam- — The present English service It is a modification of the deep broad grooves (Fig. 163), pies of this class. 761. The Woolwich System. rifling is called by this name. French System, and consists of each of which receives two soft metal circular studs attached to the pro- jectile. The grooves are three or more in number, ac- cording to the calibre of the piece ; they are 1.5 inches wide, and 0.18 inches deep, with curved edges, both the loading and driving edg bottom of the grooves is eccentric to with a radius of 3 inches ; they are of natures of heavy guns, but are a little gun and upwards ; the grooves are also widened at the muzzle in the larger guns, in order to faciliate lc>ading by cutting away the loading side slightly for two inches from the muzzle. being struck with the the the deeper same radius. The bore, being struck same width for all for the 10-inch 260 NAVAL ORDNANCE AND GUNNERY. This system embraces imiform and increasing twists, the latter being preferred. Both the direction and twist are given by the bearing of the studs on the grooves, the body of the projectile never being in- tended to come into contact with the bore. The windage is 0.8 inch in all calibres. The projectiles have two studs for each groove in all in- stances ; both studs in the case of the uniform twist, and the rear one where tlie twist is increasing, are nearly of the size of the groove, with their faces corresponding to the curved bot- tom of the groove. The rear stud is four inches from the bottom of the pro- jectile, and the studs of each groove are ecjuidistant from the centre of gravity. (Art. 783.) Particulars of the Riflincj : 12-inch gun, 9 grooves ; twist increasing from 1 in 100 to 1 in 50 calibres at muzzle. 10-inch gun, 7 grooves; twist in- creasing from 1 in 100 to 1 in 40 calibres at muzzle. 9-inch gun, 6 grooves ; twist increasing from 0 to 1 in 45 calibres at muz- zle. 8-inch gun, 4 grooves ; twist inci’easing from 0 to 1 in 40 calibres at muzzle. 7-inch gun, 3 grooves ; twist uniform 1 in 35 calibres. The 7-inch gun has a uniform twist because, at the time of its introduction, the uniform was preferred to the increasing spiral. 762. The Shunt Systew. — This is one of Armstrong's systems of rifling. The peciiliarity of this system is that the depth and width of the grooves vary at dilierent parts, the ob- ject aimed at being to provide a deep groove for the studs of the projectile to travel down when tlie gun is being loaded, and a shallow groov^e through which they must pass when the gun is fired, so that the projectile may be gripped and perfectly centred on leaving the muzzle. This is obtained by making pne side of the groove (the driving-side) near the muzzle, shal- low, as shown in Fig. 164, the unshaded j)ortion representing the shallow part, or grip. The projectiles have soft copper studs, which fit easily with a windage of 0.025 inch into the deep portion of the groove ; when the gun is loaded, the studs travel down this deep portion until they reach about the middle of the bore, where they meet with an incline, by which they are ‘‘ shunted,” or switched off, into a narrow part of the groove, still of the same depth, down which they travel to the chamber. On discharge the studs bear against the other side of the groove, until they come to the incline, up which they travel, RIFLING. 261 the studs being thereby compressed. With this compression they pass through the remaining part of the bore. 7(fl Fig. 164 . There are three grooves with a uniform pitch of one turn in 4-0 calibres, the edges being angular. This system was introduced with certain guns of the Arm- strong pattern in the English service, after the repeated fail- ures of his heavy breech-loading guns, because, it carried out two favorite theories of Sir William Armstrong, viz., the centring of the projectile and its retardation. The last is now generally conceded to be a disadvantage. It has been abandoned, because it was not found to answer well in prac- tice. It was complicated ; the projectile was gripped at the muzzle when at its highest velocity, thus greatly straining the piece, and the sharp angles at the edge of the grooves rendered the tube liable to split. 763. CoMPAKATivE Advaisttages of the Second Class. — In this class the studs being soft, the bore is not liable to in- jury from the projectile, if, as should always be the case, the height of the stud is rather greater than the depth of the groove, so that the projectile moves through the bore on the studs alone. Also if a jam should occm’, the studs will give away, and so prevent injury. 262 NAVAL ORDNANCE AND GUNNERY. Studs in tlie middle of the projectile instead of long hear- ings on its cylindrical portion, or expanding material at its base, allow tlie rifling to stop farther away from the chamber ; so that the gun is not weakened by it, at the point of greatest powder-pressnre. On the other hand, the studs cause additional expense in mannfactnre, and they are liable to injnry in transport or store. And the}" are a frecpieiit canse of injnry to the bore from over- riding the grooves. 76-f. Third Class.- — In this class the body of the projectile is composed of a hard metal, and there is attached to it, gener- ally at the base, a cup, band, or other arrangement of soft metal, by the expansion of which into the grooves of the gim the projectile is given rotation. The expansion system is carried out on the most extensive scale in this country. The plan of rifling which has heretofore been almost nniversally adopted in the United States consists of lands and grooves of the same or nearly ecpial width. As the standard Army and Navy projectiles are of the expanding class, they may all be used in any gnu of the proper calibre, irrespective of the width or depth of the gi-oove. The Parrott, Hotchkiss, and Shenkle, and many other jirojectiles, belong to this class. The Parrott system will illus- trate it. (Art. TSo.) 105. Tue Par- rott System. — In the rifling of the Parrott guns the grooves and lands are of equal width, the former be- ing one-tenth inch deep for all calibres. The bottom corners of the grooves are rounded to facilitate cleaning and to do away with the me- chanical disadvantage of a sharp corner. (Fig. 165.) , The jwojectiles are recessed around the corner of the base to receive a brass ring which is expanded into the grooves of the gun by the explosion of the powder. RIFLING. 263 All calibres are rifled with an increasing-twist. The following table gives the particulars of the Parrott guns and lifling. The calibres in use in the naval service are the 100-pdr. and the 60-pdr. The 30-pdrs. and 20-pdrs. have been withdrawn, and a new bronze 20-pdr. rifle substituted. Pound shot can readily lie used in these guns when advan- tageous, as for the ricochet. They should be wrapped in canvas or other suitable material, with the object of bringing their centre as nearly in the axis of the bore as practicable. PARTICULARS AND A3LMUNITION OF TFIE PARROTT GNNS. NA5IE OP GUN. Length of Boro. Diameter of Bore. | 1 Diameter over lleinforce. -fcS No. of Grooves. 1 Depth of Grooves. | -- cb ^ -3 o 'o o "k m H Charge. 1 U ‘o' % ^ A o 1 turn Ins. Ins. Ins. Lbs. Ins. in ft. ut Lbs. Lhs. mu'zzie. 1 1 Shot, lOl p lO-pdr 70 3 11.3 890 o o 1 0 10 1 ■( Shed, 9f i 20-pdr 79 3.67 14.5 1750 5 1 1 u 10 2 j Shot, 194 ) ( Shell, 18| y 30-pdr. Army. 120 4.20 18.3 4200 1 12 3J 30-pdr.' Navy. 96.8 4.20 18.3 3550 60-pdr. Navy. 105 5.3 21.3 5360 7 1 15 6 55 100-pclr 130 6.4 25.9 9700 9 V 18 10 70 to ICO 8-inch 136 8 32 1C300 11 1-U 23 16 132 to 175 10-inch 144 10 40 26500 15 1 1 0 30 25 230 to 250 766. Comparative Advaxtages of Third Class. — Ex- panding projectiles cannot be tired with as heavy a charge of powder as others, for fear of breaking, nor are they ajwa^-s sure to receive the rifle-motion. The windage being greatly reduced or entii’ely stopped, the strain on the gun is increased,, and an ordinary time-fuze will not always be lighted by the flame from the charge of the gun. Fragments of the expand- ing attachment are liable to fly otf and injure those in advance. The centre of gravity is almost necessarily behind the centre 264 NAVAL OEDNANCE AND GUNNEKY. of figure, and the bearing of the projectile is usually behind the centre of gravity. 767. Foukth Class. — With this class the projectile is larger than the bore, and is squeezed or planed to fit the V)ore b}^ the lands of the rifiing. The projectile, therefore, must have a soft coating, and be entered at the breech into a cham- ber larger than the rest of the bore ; and whatever escape of gas there may be around the breech-closing apparatus reduces its range and velocity. This plan was early adopted and perfected by the Germans, wdio obtained great accuracy and range with charges of one- ten tli weight of the projectile. The rifling consisted of numerous shallow rectangular grooves. The Armstrong system of rifling for breech-loaders for- merly used in the Englisli service does not differ in principle from this. The rifling consists of a great number of shallow, narrow grooves (the 7-inch has 76), the object being to give the soft metal coverino; a verv larve bearino- on the drivin»;-side of the grooves, and thus prevent stripping, and make up for want of depth. This system has been abandoned. The German system will illnstrate this-class. 768. The Geioian Systew, or Krupp's Method. — In this system the grooves are thirty in number for all calibres, quite shallow, and of the form shown in Fig. 166, their sides being rachal and forming sharp angles with the bore. The rifling has a uniform-twist of one turn in 25 feet. The grooves are wider at the bottom of the bore than at the muzzle, so that the compression of the lead-coated projectile is gradual, and less force is expended in changing the shape of the projectile. This change of shape is effected by making the whole groove of the same size as at the muzzle, and then cutting away gradually on the loading-edge of the groove. Of course, as the twist is uniform, the driving-side of the groove cannot vary. Tim outer surface of the lead coating of the projectile is in naised rings with grooves between, to allow space for its being drawn down in passing through the bore. (Fig. 182.) 769. Comparative Advantages of the Fourth Class. — The compressing system unduly strains the gun by suddenly stop- ping windage, by fouling, and b}’' forcing the projectile into a bore of smaller diameter. The compressed projectile must be fired from a breech-loading gun, and the increasing-twist is im- practicable from the great length of the soft-metal bearing. Tlie soft coating of the projectile is liable to injury in handhug and in store; also to be stripped on firing. RIFLING. 265 Its adv'antages are that the projectile is centred during its passage through the bore, which prevents balloting ; the angles of departure and the initial velocities are therefore more uni- A form, and the stability of the axis of rotation on leaving the bore is better assured ; from w'hich result great regularity and precision of tire. There is little or no ditficulty as to erosion of the metal caused by the gas forcing its way between the pro- jectile and the bore. The lead jacket of the forced projectile does not prevent the employment of heavy charges. Forced projectiles do not wedge in the bore. The regularity of the movement of these projectiles does not wear or injure the bore. The soft-metal coating prevents damage to the lands. The bursting of a projectile covered with soft metal has comparatively no baneful etfect on the gun. 770. BliElfCH-LOADIlSlG. — Intimately connected with the subject of the different systems of rifling is that of the ad- 2G6 NAVAL ORDNANCE AND GUNNERY. vantages and disadvantages of Ijreech-loading for cannon. There are strong arguments both for and against tlie use of the breeehdoaders — some nations using them altogether and others not at all. 771. Advantages . — A principal advantage claimed for breech-loading guns is rapidity of tire, bnt the result does not seem to have been attained in the large guns. The gun can be loaded when run out, without exposing the men, and worked in a smaller space by limiting the recoil. Any ignited substance left in the bore can be seen and removed ; and there is no danger of the projectile not being home. The breech-loading gun may be made longer, occasionally, which is a great advantage Avhere there is difficulty in burning the powder; moreover, a large powder-chamber may be em- ployed for the better burning of the charge. The advantages of the I'ourth Class of Eifiing (Art. 769) may be claimed in favor of breech-loading. 772. Disadvantages . — The breech-loading cannon is heavier and more expensive than one loading at the muzzle. There are more parts to be damaged. In heavy guns, far from there being any increased facility in loading, considerable force has to be used and applied in a very careful way to the breech-closing apparatus, or the gun may be rendered tempora- rily unserviceable. Escape of gas, fouling or corrosion of the closing surfaces, and injury to the delicate Broadwell-riug or gas-check, are among the contingencies that may arise in ser- vice. Much additional labor and outlay are required to construct and tit up interchangeable hollow screws or sliding stoppers; to fit and renew gas-checks; to apply opening and closing apparatus, which cannot be very simple, but which must be very strong and durable; to fabricate, keep clean, and main- tain all these parts on such a plan that two or three men can manipulate them with ease and certainty, and without unusual risk of disaster from excitement or carelessness ; and of such size and strength that the heaviest projectiles can be fired, with large charges of powder. ' 773. Conclusions .- — The adoption of a system of working and loading guns by hydraulic power (Art. SS6)must have an important bearing upon the question of the comparative merits of breech and muzzle loaders. One of the chief advan- tages claimed for breech-loaders is that any length of bore can be adopted without increasing the difficidty of loading, and that, therefore, a higher duty can be obtained from the RIFLING. 267 powder. It lias also been urged that a gun of larger size can be worked in a given turret as a breecli-loader. Successful niecbauical methods for loading at the muzzle would seem to negative these advantages. The suppression of wdndage and the power of placing the vent in the breech-block are important advantages claimed for hreeclidoaders. It has now become very important to suppress windage, which tends much more rapidly to score and cut up the bore in very heavy guns, tired with large charges of slow burning powder, than in small guns tired with light, quick-burning charges. Tlie vent is also a serious trouble in A*ery heavy guns, from its rapid erosion by the same cause. But it is claimed that the windage can be etfect- ually suppressed in many muzzledoading systems of rifling and projectiles, and an arrangement lias been devised for stop- ping altogether the passage of gas through the vent, thus removing the difliculty of its erosion.''^ In view of these facts, the relative merits of the two systems must remain undetermined fof the present. * lu some experiments made in England by Capt. Noble upon the force of fired gunpowder, be succeeded in effectually closing the vent, as follows ; The stoppage of the vent was effected by an apparatus consisting of a steel plug screwed into the body of the gun. immediately over the copper vent. This remained a fixture, but was capable of easy removal in case it should he desirable to fire by the ordinary process. The interior of the plug was bored out and screwed, so that another plug could be fitted inside of it. The inner plug had half the thread cut away as in the screw of the French breech-loading gun, so that it went in at once and by a quarter of a turn was rendered fast. Inside of the iimer plug a little plunger worked in a cylindri- cal chamber, into which a primer representing the common friction-rube was dropped. In the centre of the plunger, there was a pin to fire the primer by detonation, and surrounding it a steel gas-check, which, when the powder was exploded, expanded so as to stop the escape of gas. The charge was fired by striking the external head of the plunger. The recoil of the plunger was stopped by a shoulder. CHAPTEE VI. PROJECTILES. Section I. — General Descrijytion. 774. Classieication. — Projectiles may be classified — accord- ing to their form, as spherical and elongated ; according to their structure and mode of operation, as solid^ holloio, and case shot. 775. SPIIEEICAL PEOJECTILES. — Spheiical projec- tiles are commonly nsed in smooth-bore-gnns, and for tbis pur- pose possess certain advantages over those of an elongated form. 1st, they present a uniform surface to the resistance of the air as they turn over in their flight; 2d, for a given weight they offer tiie least extent of surface to the resistance of the air ; 3d, the centres of figure and inertia coincide ; 4th, they touch the surface of the bore at only one point ; they are therefore less liable to wedge in the bore and endanger the safety of the piece. 5th, their rebound on land and water being certain and regular thev are Avell suited to ricochet-firing. 77G. ELONGATED PEOJECTILES.— The great im- provements Avhich have been made of late, in the accuracy and range of cannon, consist simply in the use of the elongated in- stead of the spherical form of projectile. To attain accuracy of flight and increase of range with an elongated projectile, it is necessary that it should move through the air in the direction of its length. Experience seems to show that the only sure method of affecting this is to give it a rapid rotary motion around its long axis by the grooves of the rifles. 777. Length. — This necessaiily varies in the different de- scriptions of j)i’ojectiles for the same gun, inasmuch as it is to some extent subordinate to the consideration of bringing them all, with certain exceptions, to the same weight ; but experiments go to prove that a length of two calibres at least is necessary for very accurate firing, and it is desirable for good “ vis viva,'’ or destructive effec-t on impact at any but very short ranges, to have the weight great in proportion to the calibre, or, in fact, to the surface of resistance, and of course this is favored by an in- creased length of projectile. As a rule, the best length for PEOJECTILES. 269 accurate firing with any ordinary twist, has been found to he from two to three calibres. 778. Form of Head. — The form of head is governed by two considerations, flight and penetration. The latter gives difierent forms in different instances. (Art. 851.) The question of flight affects all equally, and on this many experiments have been made, which have resulted in the general adop- tion of wliat is termed an ogival head, or figure generated by the revolution of an ogival, or pointed arch, about its axis. It has been found that the total pressure on a nine-inch spherical projectile, moving with a velocity of 1150 feet per second, is about 555 lbs. AHBM representing the spherical nine-inch pi'ojec- same diameter rep- ^ resented by AC.D Fig. 167. BM, and moving with the same velocity, is -187 lbs. — ^^thus showing a difference of 681bs. total pressure.* How supposing the elongated projectile to move steadily, point first, the pressure' on the respective heads, AMB, must be the same ; therefore the difference of the total pressure, viz., 681bs., must be due to the difference of minus pressure on the bases AHB, ACDB respectively, thus showing that the form of base of a projectile, materially influences the total pres- sure which it meets with, when moving through the air at a high velocity. The total pressure on an ordinary ogival-headed projectile of nine-inch diameter, represented by ACDBM', is only 3891bs'., thus showing the great difference of pressure, viz., 1661bs., on an elongated ogival-headed projectile and a spheri- cal projectile of the same diameter when moving at the same velocity through the air. Another great advantage which the elongated projectile possesses over the spherical, is that, for the same calibre, the momentum of the former is much greater, varying, of course, in proportion to their respective weights, which would be nearly three to one, depending on the length of the elongated projectile. 779. The construction of ogival heads of radii of 1, and 1|- diameter respectively, may be seen in Figs. 168, 169, and 170 — tile (Fig. 167), and _ the total pressure on a hemispherical- ^ headed, elongated projectile of the * Bashforth. 270 NAVAL ORDNANCE AND GUNNERY. C and C' being tlic centres and K the length of the radii in each case. It ■whl be seen in the case of diameters radius that the head is exactly 1 calibi'e long. 780. hiewton gives the form of body (Fig. 171) whicli vould, in passing through a tlnid, experience the least resist- ance. This form, it is seen, is very simi- lar to the ogival. 781. Piobert says that the figure (172) will experience the least resistance fiom the air. Its lengrh is five times its greatest diameter, and its largest section is placed of the length from the hind part. Fig. 173. The shape of some of the '^Vhitworth projectiles approach more nearly to this form than those of any elongated projectiles hitherto used. (Art. .) 6 4 ^ d- -b Fig. 173. 782. Studded Peo.tectiles. — These are fitted for rifling of- the second class. (Art. 760.) The studs arc usually of bronze, the proportions of the alloy being from seven to ten parts of copper to one of tin, which is sufficiently soft to enable the stud to be attached to the projectile by pressing it into under-cut holes in the latter, causing the end, which is cupped or hollowed out, to expand and rivet itself firmly in ; it is swedged cold into the holes. (Fig- 173.) PROJECTILES. 271 Tn studding a projectile, two rings of eircular holes are usu- ally cast in tlie walls, the number of holes in each ring corre- sponding to the number of grooves in the gun. The weaken- ing of the walls by so many holes, arid the concentration of the effort of rotation at these points, seriously affects the endurance of the projec- tile. 7S3. The system of studding to accommodate the increasing spiral, c;m be readily understood by Fig. ITd, and the following explanation. FE', DD' represent the groove at seat of projectile ; AA', BB' repre- sent the groove at the muzzle. O and O' are the studs. The object sought is to combine a double bearing with an accelerated spiral. The chtliculty lies in the fact, that since the angle at wdiich the grooves are inclined is continu- ally increasing, the gun would he trying to turn the fore part of a rigid projectile faster than the hinder part, which would be impos- sible. To overcome this difficulty, the rear stud is made larger than the front one. Thus, at starting, the three rear studs do all the work of turning the projectile, since EE' is the driving-edge of the groove when it commences to move. This work is inconsiderable, as the angle of the twist at first is zero. But as the projectile travels along the bore, the friction will wear down the rear studs, and the assistance of those in front will he gradually called into play.^ The rear studs are made large enough to fill the grooves ; the size and position of the front stud is thus determined. Draw AA' tangent to A'AII ' a the makino- an an 2 ;le O O AA' tangent final angle of larger rifling. stud at C, and From O, the / 272 NAVAL ORDNANCE AND GUNNERY. centre of the rear stud draw 00^, maliing O'OH = ^ A'AII. It Avill readily he seen that a circle described with any point O' as a centre along the line 00', and the perpendicular O'P let fall upon BB' as a radius, will touch DD', and that the projectile will freely enter the gun, and that the bearing-edges of the stud will all press equally on the driving-edges of the grooves as the projectile approaches the muzzle. The front stud touches the dilving-edge on entering the bore, and the loading-edge when well home ; and the reverse action occurring in bring, the share it takes in the work of rotation is very small, for until the driving-edge meets it, the whole pres- saire is on the rear studs. Its chief use appears to be to steady the projectile. 781. These projectiles must he handled and stored with great cai'e to prevent the studs being bruised and injured so as to jam in the bore, or fail to grip on the grooves in bring. They are liable to break up in the bore if bred a second time, and the studs are liable to sheer and thus prevent the cen- tring of the projectile. 785. Exi’anding Beojectiles. — These are used with ribing of the Third Class. (Art. 761.) All the projectiles used in the naw)" for ribed ordnance are of the Expanding Class ; being forced to take the grooves by the action of the charge of powder, and require no other pre- caution in loading than spherical shell. It is essential, how- ever, that the base-ring of every ribe projectile, especially the Parrott, shall be greased before entering it into the gun, to prevent the formation of a hard deposit in the grooves. Parrott Projectile.— V&i'voith projectile is composed of a cast-iron body and brass ring cast into a rabbet formed aroimd its base. The ring is from 1 in. to 11 in. in width, and about 1 in. in maximum depth. The gas presses against the bottom of the ring and underneath it, so as to expand it into the grooves of the gun. (Eig. 175.) To prevent the ring from turning in the rabbet, the latter is recessed at several points of its circumference, like the teeth of gearing. The diameter of the rabbet is greatest at the extreme rear of the shot, so that the brass ring cannot by off without break- ing. Tdie entire projectile is slightly smaller than the bore, so as to be easily rammed home. Very few of the rings have been broken in practice ; they should be separated from the iron base of the projcctbe at PEOJECTILES. 27a three or four parts of the circumferenee, in case any fail to ex- pand and take tlie grooves. This should be done very lightly with a cold-chisel, so as not to interfere with loading. It is only necessary to sever the contact of the two metals. The use of a little grease or lubricating material around the rinc firing, is advantageous. other of the projectile, before Fig 176. 186. Dalilgren Projectile . — Dahlgren’s rifie projectile con- sists of a cast-iron cylindro-coui- cal projectile with a leaden cup attached to its base ; offsets from the cup entering into recesses in the iron securely attach the cup to the projectile. (Fig. 176.) There are projections cast on the cylindrical portion which are but slightly raised from the surface of the shot ; and in the groove around the cup is placed a mixture of tallow and lamp-black, which lubricates the bore after each discharge. 787. The ShenJde Projectile. — s> projectile is com- posed of a cast-iron body, having its greatest diameter a little/ more than -J- of its length from the forward end, from which point, to the rear end, it presents the form of a truncated cone, with straight projections cast upon it. (Fig. 178.) Around the rear portion is placed a ring of jgapier^iaclie (Fig. 179), the interior of which is made conical and grooved, to fit the projections on the casting ; so that there shall be no lateral slipping ; the exterior is cylindrical and slightly smaller than the bore, so as to run home easily. The powder-gas drives jga'pier-mache ring forward upon the case, whence it. 18 274 NAVAL ORDNANCE AND GIINNERT. is jammed into the grooves of the gun, and made so compact as to rotate the projectiles without strippiirg. On issuing from Fig. 177. the bore the ring is blown to pieces, leaving the projectile unen- cumbered in its flight. A great difficulty has been found in practice in always get- ting a proper quality of material for the sabot ring. These projectiles have gone out of use, as the papier-mache case was found to swell and e.xpand upon being exposed to dampness and moisture. 788. IIotchHss Projeciile . — The Hotchkiss projectile is ■composed of three parts. It consists of a cast-iron body with a cylindrical base of diminished diameter, over which a cast-ii-on cap is fitted. These parts are slightly less in diameter than the 'bore of the gun. The groove between the body and the cap contains an expanding ring of lead ; offsets from the lead enter- ing into recesses in both the iron parts, and holding all secure. (Fig. 181.) The first power of the powder, befoi’e the inertia of the whole projectile is overcome, is devoted to driving the cap farther upon the body, thus squeezing out the intermediate lead into the grooves of the gun, and at the same time holding the lead, as in a vice, so that it cannot revolve on the projectile. AYhen discharged, the base-piece is dri\-en forward upon the Tront piece to an extent which is definitely limited by its con- tact with the extreme rear, and by this movement expands the soft-metal ring to an amount jnst sufficient to fill the gun and take the grooves. PROJECTILES. 275 789. Lead-coated Peojectiles. — These are used with rifling of the fourth class. (Art. 767.) To attach the lead-coat the surface of the iron is well cleaned, and covered with a zinc solder, when the lead is cast directly on that. The zinc amalgamates sufficiently with the iron and lead to give a very complete attachment. In order to get a clean metallic surface to wdiich the zinc may adhere, the projectile is dipped into a sal-ammoniac solution ; the next operation con- sists in dipping the projectile into molten zinc. The lead-coat occasionally becomes detached in spots, where the lead has risen up into blisters from the for- mation of gas underneath it, occasioned by vol- taic action between the different metals. Such blisters are generally very small, and may be pricked and then hammered down, without affecting the fitness of the projectile for service. If left to develop th.emselves they have been known to attain a large size. In the German service, the lead-coat is covered with a mixture of beeswax and benzine applied warm, and rubbed smooth with flannel rags. This does away with any necessity for lubricating the bor^ (Fig. 182.) ^ Fig. 182. 790. The lead-coating is preserved from in- jury by two grommets which are nearly cut in two to facilitate V. 276 NAVAL ORDNANCE AND GUNNERY. removal, and the projectiles are stored in racks fitted in the shell-room. Sometimes the body of the projectile is not strictly cylindri- cal, but rather smaller at the base, the lead-coating bringing the finished body into a cylinder. This form is considered good for j)enetration, but any lead-coating must considerably retard the projectile in endeavoring to force its way tlmougii armor. This lead-covering causes a great waste of power, as it is the iron part alone, of the shell, that can do work against the iron plates, and consequently a considerable force is expended in projecting a part of the projectile which is useless for the work which has to be performed. 791. SOLID PROJECTILES. — Solid projectiles when used in heavy guns are known as solid-shot, round-shot, or shot. They are employed to destroy, fracture, or penetrate an object by the mere force of impact, and are used when great range, ac- curacy, and penetration are required. Solid shot are classified according to their weight. 792. HOLLOW PROJECTILES. — Under the head of Hollow Projectiles are included shells for guns, howitzers, and mortars. These are usually made of cast-iron, and are classified according to the diameter of the bore of the piece. 793. Shell. — A shell is a hollow pi’ojectile filled with gun- powder, which is ignited by a fuze at the required moment, the bursting of the shell causing destruction by its explosive force and by the fragments, and, if the object be combustible, by set- ting it on fire. The thickness of metal must be such that the shell may contain as large a bursting-charge as possible, but that it be strong enough to withstand the shock of the discharge within the bore of the gun. The thickness of metal in a spherical shell is about one- sixth of the diameter, and the weight of the shell is about three-fourths that of the solid-shot of the same calibre. Crane’s IX-in. Shell consists of a shell within a shell. The advantage claimed is that upon bursting it separates into double the number of pieces. It is made by first casting an Ylll-in. shell with a IX-in. core ; this casting (when sumciently set, and before cold) is used as the core for a IX-in. shell. Pevet’s Shell is made similar to the Crane’s, excepting that there is a space of about seven-tenths (7-lOths) of an inch between the two shells, which is filled with small-sized iron balls. PKOJECTILES. 277 The shell of a I’ifle-gnn, being elongated, is, hy giving it a greater length than the shot, brought up to the same weight as the latter. 794. Moktae-shells are fired from Mortars at high angles, being intended to fall upon and set fire to buildings, vessels, or other combustible constructions ; to destroy earth-works, or by their great penetration before bursting to explode maga- zines protected from other projectiles. They are fitted with two lugs placed one on each side of the fuze-hole, which serve for attaching a pair of sliell- hoolcs. The fuze-holes of mortar-shells are larger in diameter than those of other common shells, and they are not countersunk or bouched with composition. 795. CASE-SHOT. — Case-shot are a collection of small projectiles enclosed in a case or envelope. The envelope is mtended to be broken in the piece by the shock of the discharge, or at any point of its flight by a charge of powder enclosed within it ; in either case the contained pro- jectiles continue to move on after the rupture, but scatter out into the form of a cone ; so as to cover a large surface and at- tain a great number of objects. The three principal kinds of case-shot in use are grajje, caiv- ister^ and shrapnel. They are adapted to all guns, and receive their names froin the pieces in which they are used. 796. Shrapnel. — Shrapnel are thin-sided shell, in which are placed, besides the bursting-charge of powder, a number of small balls embedded in sulphur. The}" are cast in the same maimer as ordinary shell, excepting that their sides are made thinner to allow for a greater number of balls. The charge of powder is quite small, being only sufficient to rupture the case and liberate the balls. The thickness of the metal should be such that it will resist the explosion of the charge within the bore of the gun, but open readily with a small bursting-charge. The bursting-charge should be merely sufficient to open the shell without affecting the flig ht of the bullets. A spherical shell of this class has a less thickness of metal than a common shell, viz., about one-tenth of its diameter, and its weight when empty is about half that of a solid shot of shni- lar diameter. (Fig. 183.) 797. Filling . — -To fill a shrapnel a funnel is screwed into the fuze-hole, and the ease filled with the recpiisite number of balls. A round, hollow steel mandrel, made slightly tapering 278 NAVAL ORDNANCE AND GUNNERY. towards the lower end, which is ronnded oS, and harins: a score cut on either side throughout its length to admit of a free pas- sage for the melted sulphur to the interior of the shrapnel, is driven and worked through the fuze-hole to the bottom of the case. The projectile is then thoi’oughly warmed, generally in warm water, to prevent the cold metal from solidifying the sul- phur before it has filled all the interstices. It is then filled with melted sulphur, and as soon as the sul- phur is set the mandrel is withdrawn : this is accomplished by first heating it from the interior by the insertion of a hot rod. wdien it is readily removed. The funnel is also removed, and the inagazine formed by the mandrel is cleaned and the fuze- hole carefully tapped out. ' In this magazine is deposited the charge of powder, where it is protected against all injury from the movement of the balls. By this arrangement the cpiantity of powder required to open the shrapnel is very small, and the bullets are prevented from striking by tlieir inertia against the sides of the case and crack- ing it when the piece is fired. Lead being much more dense than iron, the shrapnel is, when loaded, nearly as heavy as a solid shot of the same calibre Fig. 183. — Section of 12-pdr. shrapnel, with Bormann fuze and filling of sulphur. for the lighter guns. A shell of this class is, in fact, simply a canister-shot adajrted to long range. The rupture may be made to take place at any point of its flight, and in this respect it is superior to canister and grape shot, wluch begin to separate the moment they leave the piece. PEOJECTILES. 279 Table of contents and weights of spherical shrapnel for navy guns. Calibre. Weight of empty shell. Contents. ^ t) -2* ^ o No. o£ balls. Size o£ balls. I>bs. of sulphur. Bursting- charge. XV-inch .... 178 lbs. 1,000 iron. 1 inch. 30. 10 oz. 358 lbs. Xl-inch 76 “ 625 iron. 0.85 “ 10. 6 141 “ X-incli 57 “ 435 iron. 0.85 “ 8.5 4 “ 101 “ IX-inch .38 “ 350 iron. 0.85 “ 7. 3 7o ‘‘ Vlll-inch... . 29 “ 220 iron. 0.85 “ G . 2.5 “ 52 “ 32-pdr 15 “ 235 lead. 0.65 “ 2.25 1.25 “ 32 “ 24-pdr 11 “ 175 lead. 0.65 “ 1.5 450 grs. 24 “ 12-pdr 6.5 “ 80 lead. 0.65 “ 0.75 350 grs. 12 “ 798. Rifle-siieap^'el. — In the Boxer shrapnel for tlie riiiec]- ordnance of the English service tlie es- sential features of a shrapnel-shell are einhocliecl. This shell (Fig. 181) has a cylindri- cal iron body, with a chamber at the hot!-om, and four longitudinal grooves inside to facilitate breaking up; it is cast without a head. A tin case for the bursting-charge tits into the chamber, on the shoulder of which rests a wrought- iron disk. The shell is lined with paper, and filled with halls embedded in rosin. A wrought-irou tube passes down the middle of the shell and through a hole in the centre of the iron disk, to lead the flame from the fuze to the burstim;- charge. K disk is placed over the top of the bullets. The wooden head is ogival in form, and made of elm covered with thin wrought-iron, which is riveted to the shell. This head contains a socket and bouchino' for the fuze. 799. GnAPE-snoT. — A grape-shot is Fig. 184. composed of a number of small shot ar- ranged around a spindle on an iron disk. Formeily the shot were 280 ' NAVAL OEDNANCE AND GUNNERY. 1 la m (7 Fig. 185. enclosed in a canvas-bag, which was drawn together between the balls, or “quilted ” by a strong line; but the present method is more simple and durable. It consists of nine shot of a size appro- pi'iate to the calibre used, which are held together by two rings and a plate at each end of the stand connected by a rod. (Fig. 185.) The diameter of balls for grape-shot varies wdth the calibre, being in all cases larger than those used for canister. Grape-shot are now nearly obsolete, it being considered that canister-shot are sufficient for short ranges ; and the canister-shot possesses the advantage of striking a great many more points at one discharge than grape. There is an advan- tage, too, in not having so many different kinds of ammunition. It is the intention to abolish grape as soon as the stock on hand is exhausted. 800. Canistee-siiot. — A canister-shot is a metallic cylinder about one calibre in length, filled with balls and closed at both ends with woodeir or metal disks. They are supplied for all guns. For 8-inch canister, and all those of less calibre, the envelope is made of tin, while canister for the larger calibres have an en- velope of iron. The bottom of XY-ineh canister is made of two thicknesses of 1-inch hard wood, crossing each other, and put together with wrought-iron nails clinched. A spindle, with a wrought-iron handle passing through the centre of the canister, is riveted on the bottom through a square plate. All other canister have bottom-heads of one thickness of hard wood. Top-heads are all made of white- pine. The case is notched, turned over the heads, and tacked down. The balls for all canister are 1.3 inch dia- meter, and the number used varies with the calibre. To give more solidity to the mass, and prevent the balls from crowding upon each Other when the piece is fired, the inter- stices are closely packed with sawdust. 801. Eifle-canister. — These are very sim- ilar in general appearance to those used in smooth-bore cannon. (Fig. 186.) The case is of sheet-iron, or tin, with frmged ends which are turned over and soldered or riveted to iron or zinc disks. PEOJECTILES. 281 The balls are of iron or zinc packed in rosin or coal-dust, sometimes in disks of wood. (Fig. 187.) Eig. 187. They are fitted with solder studs or rings of lead on the out- side to take the rifling (Fig. 187), or with an expanding cup (Fig. 186). dlATXD-GEENADEs consist of Small cylindrical shaped shell, with conical ends, fitted with a plunger at the striking-end, and a directing-feather at the other. The plunger fits loosely into the cavity in the forward part of the shell, and is made to pro- ject two or three inches beyond its face, being retained in place by a slight spring ; it has attached to its outer end a circular piece of sheet-iron several inches in diameter. At the bottom of the cavity in which the plunger is placed a nipple is fixed, communicating with the bursting-charge, on which is placed an ordinary percussion-cap, whidi is exploded when the plunger is driven in violently, thereby igniting the charge. There are three sizes of grenades, one (1), three (3), and five (5) pounds, and are intended to be thrown by hand, and may be very effectively used in repelling attacks by boats or by persons well sheltered against others completely exposed. 802. FABE1CATIOJ7 OF PROJECTILES.— They are usually made of gray or mottled cast-iron of good quality. Shells should be made of the best cpiality of iron, and with par- ticular care, in order that they may not break in the gun. 803. Patteen. — The pattern of a spherical projectile is com- posed of two hollow cast-iron hemispheres, which unite in such a manner as to form a pei’fect sphere ; on the interior of each lieraisphere is fastened a handle to enable the operator to ch-aw it from the sand when the half-mold is completed. The fla-sJcs which contain the mold are made of iron, in two ecpial parts, united by means of hooks at their larger bases. The other ends are fitted with movable covers. (Fig. 188.) 282 NAVAL OEDNANCE AND GIJXXERT. 804. Molding. — This operation is performed by placing the flat side of one of the hemispheres on the molding-board and Fig. 188 . corering it -rdth a flask. Sand is then poured into the flask, filling np the entire space between it and the hemisphere, and well rammed. Tlie cover is then attached, and the flask turned over, the hemisphere is withdrawn, and the entire surface of the sand painted with coke-wash and dried. The remaining half of the mold is formed in the same way, except that a channel for the introduction of the melted iron is made by inserting a round stick in tlie sand before it is rammed and withdrawing it afterwards. A, dig. ISS. 805. Hollow, Pbojectiles. — TTms far the operations of molding and casting solid and hollow projectiles are the same. The cavity of a hollow projectile is formed by inserting a core of sand. This is a sphere of the proper size, made by compres- sing the molding-composition on a half-inch hollow non spindle by means of two hemispherical cups. (Tig. The requisite compression being given by screws. The core is by means of a gauge placed exactly in the centre of the mold and supported in that position by the stem Avhich forms the PEOJECTILES. 2S3 fuze-hole. The stem is perforated witli small holes to allow of the escape of steam and gas generated by the heat of the melted metal, that part of it which comes in contact with the melted iron, and forms the fuze-hole is coated with sand. In pouring the melted iron into the mold with the ladle cai-e should be taken to prevent scoria and dirt from entering, with it, and for this purpose the surface should be skimmed with a wooden stick. After the iron has become sufficiently hardened the flasks are opened and the sand knocked from the casting. Then the core is broken up and removed, and the interior surface cleaned by a scraper. The greatest care is to be taken to remove every particle of sand or fragment of iron from the interior. The sinking-head or projecting portion at the gate, and around the base where the two halves join, are taken olf with a file or chisel if necessary. A number of the balls are now placed in a large revolving iron cylinder, which by friction polishes and makes the surface more uniform. 806. Bouching. — The fuze-holes of all shell are bouched with gun-metal to receive the Is avy -fuze-stock. In fitting the shell to receive the borrohing, the bore should be tapped with a full thread, and the proper shoulder left at the bottom to pre- vent the bouching from being driven in by the shock of firing and causing premature explosion. The object of the bouching is to prevent ruct, and to have 284 NAVAL OEDNANCE AND GUNNERY. the same kind of metal in contact ,with the fnze-stock, so that there will he less danger in extracting or exchanging a fuze. The fuze-holes of heavy riile-shell are necessarily cast larger than the diameter of the regular fuze-stock, wliich can, however, be used wdth the aid of an adapting-ring of gun- metal, which is screwed in to reduce the diameter of the hole to the proper dimensions. The fifteen -inch spherical shell are cast with three fuze- holes ecpially distant from each other, and situated in the an- gles of a triangle 4 inches apart. 807. CHILLED PROJECTILES. — Chilled-iron projec- tiles have been profitably employed to pierce armor-plates, on account of their intense hardness. 808. Pallisee Peojectiles. — The English projectiles rec- ommended by Major Palliser may he described as an example of chilled projectile. The form of these are cylindro-conoidal, the head being ogival, struck with a radius of diameters. The total length varies between 2 and 2|- calibres. The bottom is flat, and in the centre of the bottom is a filling- hole for shells, closed with a com- position screw-plug. (Fig. 190.) All Palliser shells are lacquered internally to give them a smooth, clean lining, Avhich prevents the iron from either oxydizing at the expense of the powder, or firing it from friction by rapid rotation during flight. As the lacquer does not always hold well to the metal, serge-bags are introduced to con- tain the bursting-charge as an additional prevention against pre- mature ex|)losion. These bags are made bottle-shaped, and are intro- duced through the filling-hole. Palliser shot are cored. The hollow up the centre enables them to cool more uniformly, and ren- ders them less liable to split. It also slightly hnproves its proportions and its regularity of flight. The bottom is closed with a plug. 809. How made . — These projectiles are made of carefidly selected iron, which, if run in sand-molds, woidd solidify as mot- tled, iron. Fig. 190. PEOJECTILES. 285 The projectiles are east point down, for the sake of density and soundness in the head. The mold is formed of a metal- chill at the bottom extending up past the junction of head and body ; the remainder of the mold is formed of sand, as also is the case for the formation of the interior. The chilling action therefore extends a little past the head of the projectile, which thus has a mottled body and a white head. The Griison projectiles are east with a dead-head on the base, which is afterwards cut off, the object being to obtain a solid bottom to stand well under the shock of the discharge. The chilling is effected by the metal molds, in virtue of their great conducting-power, their thickness greatly affecting the ex- tent of their action. The head thus chilled white, possesses generally the quality of Avhite-irou, intense hardness, crushing- strength, considerable brittleness, and increased density. The tip or point of a chilled projectile, is occasionally broken off by the impact of a shell or shot rolled or struck ob- liquely against it ; for the point which may penetrate directly through many inches of armor without injury, may be frac- tured by a very slight transverse blow. 810. Steel Peojectiles have proved more efficient than those of any other metal, but their expense has heretofore been too great to warrant their general use. For rifle projectiles they are made from solid ingots of steel turned to form, and bored out for shells. They are hardened by heating and cool- ing quickly, the head being to a certain extent chilled. The manufacture is expensive and tedious, and the tempering is a matter of difficulty, the shells being liable to crack. In or- der to overcome this difficulty hollow shot have been devised, the hole through the centre allowing the sudden shrinkage to take place without the injurious effects above alluded to. 811. WhitwortNs Steel Shell we m. 2 i 6 .Q ivom. m.got& oi steel cast in the form of hoops, and drawn down to the necessary size under the hydraulic press. The ends are closed with screw plugs. They are therefore less costly than might be supposed. 812. ITSISPECTIOIT. — Object of Ikspection. — The prin- cipal points to be observed in inspecting projectiles are, to see that they are of proper size in all their parts, that they are made of suitable metal, and that they have no defects, con- cealed or otherwise, which will endanger their use or impair the accuracy of their fire. As it would be impracticable tc make all projectiles of exact dimensions, certain variations are allowed in fabrication, which are specified in the “ Ordnance Insti’uetions.” 813. Inspection oe Solid Pkojectiles. — The projectile is 286 NAVAL ORDNANCE AND GENNERT. inspected while nnlaccjnered, perfectly clean, and before be- coming rnsty, so tliat the eye can detect any flaws or imperfec- tions in the metal. Each projectile is placed npon a table and examined to see that its surface is smooth, and that the metal is sound and free from- seams, flaws, and blisters. If clusters of cavities - or small holes appear on the surface, strike the point of the hammer into them, and ascertain their depth with the searcher. If the depth of the cavity exceeds 0.2 inch, the projectile is rejected ; it is also rejected if any attempt has been made to conceal defects by plugging or filling holes in any mode whatever. The projectile must pass in every di- rection through the large gauge (Fig. ] 91), and not at all through the small one ; the calipers and scale will deter- mine exactly the difference of diameters of the same projectile. The ring and cylinder gauges are examined before each inspection, and when found to have en- larged 0.01 of an inch, ai’e laid aside and marked as unservice- able. The projectiles are next passed through the cylinder-gauge, placed at an inclination of about two incmes between the ends, and supported in such a manner as to be easily turned from time to time, to prevent its being worn in furrows. Projectiles which slide or stick in the cylinder are rejected. The next proof is to drop a few taken indiscriminately from the lot under inspection from a height of twenty feet on a solid platform of iron, or roll them down an inclined plane of the same height against a mass of iron, after which they are again examined for defects of metal. The average weight of solid projectiles is determined by ' weighing at least three parcels, of from 20 to 50 each, taken in- discriminately from the lot. As many of the lightest are weighed separately as the In- specting Officer deems necessary, and all found to fall below the least weight allowed by the Ordnance Instructions are re- jected. 811. Inspection of Hollow Pkojectiles. — The surface of the shell and its exterior dimensions, form, weight, and strength, are examined and tested as in the case of solid projectiles, and subject to all the conditions there specified. PROJECTILES. 287 The shell is next struck with a hammer (Fig. 192), to judge by the ring or sound whether it is free from cracks ; and the exterior and interior diameters of the fuze - hole (which should be accurately reamed) are verified, and the soundness of the metal about the inside of the f u z e - h 0 1 e ascer- tained. To determine the thickness of the metal, three points, at least, on the great circle at right angles to the axis of the fuze-hole are measured (Fig. 192.) ; also one at the fuze-hole (Fig. 193), and one at bottom. No shell is received which deviates more than one-tenth of an inch from the proper thickness in any part. The shell is next placed in a tub of water, which should be Fro. 193. — Gauge for thickness opposite fuze hole. deep enough to completely cover it. A pair of hand-bellows and a wooden plug are inserted into the fuze-hole, the plug to fit the fuze-hole and the nozzle air-tight. Air is then forced by the bellows into the shell. If there are any air-holes in it, air-bubbles will rise on the surface of the water, and the shell is rejected. This occasionally occurs from the escape of air from porous spots which do not extend to the interior of the shells. In this case the action of the bellows produces 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 likewise cause the rejection of the shell. 288 NAVAL ORDNANCE AND GUNNERY. The Inspecting OtEcers stamp the shell at one inch from tlie fuze-hole with their intials, also those of the foundry at which they are cast. The Inspector or one of his assistants innst be present when shot or shell are inspected ; and the stamps and marks are always retained^ in the possession of the Inspector. shells are mutilated by chipping a piece out of the 815. Inspectiojt of Gkape and Canistee. — The dimensions are verified by means of a large and small gauge. Table of Gauges for Smooth-bore Projectiles. SHOT. Dimensions, ■Weight. XV. XIII. XI. X. IX. 8. 32. Mean Diameter (in. ) 14.80 12.80 10.80 9.80 8 80 7.85 6 25 TVTenrt Wp.ijvht Hhs. ^ 440. 276. 1G6. 124. 90. 65. 32.5 SHELL. Dimensions, Weight. XV. XIII. XI. X. IX. 8. 32. 24. 12. Mean Diameter (in.) 14.80 12.80 10.85 9.85 8.85 7.85 6.25 5.67 4.52 Thiclcne^s (in.) 2.85 2. ST 2. 1.80 1.60 1.50 1.25 .90 .70 Diameter of fuze-hole .65 .65 .65 .65 ■ .65 .65 .65 Mean weight, empty (lbs.) 3.30. 208. 127. 95. 68.50 50. 25. 17. 8.4 Weight of filled andsaboted (lbs.) 1352. 216.5 135.5 101.50 73.50 52.75 26.5 Rejected fuze-holes. GEAPE. Dimensions, Weight. XV. XI. X. IX. 8 . 32. Weight of Stand (lbs.) 34.75 26.10 20.4 S.75 S9.10 71.70 52.20 37.12 21.80 15. 15. IS. IS. 12. 3.65 3.34 2.80 2.50 2.50 125.08 98.02 74.10 53.25 33.60 PEOJECTILES. 289 SHARPNEL. Dimensions, Weight. Mean of empty case. Balls Sulphur Bursting Weight complete, saboted (lbs. ). . . } Gauge (m.) Thickness (in.). Weight (lbs.) 'v Number ( Diameter (in.).. , i Weight (lbs.)..., (lbs.) -charge loz.) XV. XI. X. IX. 8. 39. 24. 14.80 10.85 9.85 8.85 7.86 0.25 5.07 1.25 1. .87 .75 .69 .60 .55 178. 76. 67. 38. 29. 15. 11. 1000. 625. 435. 350. 220. 235. lead 175 .lead 1. .85 .85 .85 .85 .65 .65 140. 51. 33.5 27. 17. 14. 10.5 30. 10. 8.5 7. 5. 2.95 1.5 10. 6. 4. 3. 2.5 1.25 450 . grs. 358. 141. 101. 75. .52 32. 24. 19. 4.53 .45 6.5 80. lead .65 4.T5 .75 350. grs. 12 . CANISTER. Dimensions, "Weiglit. XV. XI. X IX. 8. 32. 24. 12. .25 .25 .25 9K .25 .15 6. .35 1.90 39 .15 5. .3 1.90 39. 1 Height, finished (in.) 14. 1. 19. 5-8 10.5 6-8 9.5 5-8 > lO iT. ! t- CO 7.75 .50 Thictoess ( (in.) Head. T (j^ ) 1. 2. 5-8 1. 1. 1, 50 600. 315. 290. 230, 162. 100. 1.30 1.30 1.30 1.30 1 30 1 30 1.30 12 5 Balls y. 1 Weight (lbs.) 150. 83. 70. 45. 23. 5 85 207. 120. 98. 70. 50. 30. 14.55 7 7.5 816. PKESERYATIOlSr OE PEOJECTILES.— They are cleaned from rust and covered with a thin lacquer, when they are first received and when they are stored. The following colors are established when put on board ship : all shot, black ; shell, red ; and sharpnel, white. The length of fuze is stencilled on the shell. Covers of boxes containing projectiles are painted the same color as their contents, and the length of the fuze of a loaded pro- jectile is stencilled in black on the box. Empty shell, whether in store or in transportation, are most carefully protected from dampness. They have the fuze-bo aching coated with compo- 19 290 NAVAL ORDNANCE AND GUNNERY. sition, and the fuze-hole is stopped hy a plug of very soft ^vood which is well coated with a mixture of oil and tallow, and screwed in. The ends of the plugs are not sawed off even with the shell, but left square and project sufficiently to allow them to he imscrewed by means of a wrench ; and when these plugs are removed for the purpose of fitting the shells for service, they are not thrown away, but preserved for future use. 817. Stowage. — They arc piled with the fuze-holes down, and free from contact ; under cover, when practicable, but with free ventilation. Projectiles in boxes must be stowed in tiers with thin battens of wood between the tiers, so that there may be free circulation of air. Platforms of masonry, or of condemned projectiles, are pre- pared to pile them on. Square piles are to be preferred where there is room. Projectiles, after having been piled, are so far examined each yeai', as to ascertain if they require to be cleaned, re- lacquered, and repiled to secure their proper preseiwation. For the proper stowage and preservation of projectiles on board ship, shell-rooms are provided, the same care and atten- tion being given to their construction, location, and means of lighting and flooding as in magazines. The loaded shell, being either in boxes or bags, are stowed in the shell-room in tiers or ranges, held in place by wooden battens if necessary ; and when there are various kinds, they are to be stowed on separate tiers, with pieces of plank between them, in such manner that each kind can be readily obtained. It is seldom that the shell-room will contain the full allowance boxed ; the remainder will be put on board empty. Empty shell are to be stowed on board ship by themselves, in a dry place, unsaboted, in bulk. A sabot, straps, tacks, and lashing is furnished for each empty shell; after target practice the number of loaded shells is to be made complete. 818. Lacqueeixg. — Whenever projectiles are to receive lacquer, care is taken that the quantity applied does not increase the diameter more than is indispensably necessary, and in no case above established high gauge. Old lacquer and rust are removed b}^ scraping, as far as can be conveniently done, before a new coating is applied. neither hammering nor beating is resorted to for this pur- pose. After numerous experiments upon different lacquers em- ployed for the preservation of projectiles from rust, the French have abandoned all of them. The projectiles are simply piled, under sheds when practica- PROJECTILES. 291 ble, or in tlie open air, and, when pnt on hoard of ship, cleaned of rnst and ruhhed over with whale-oil : the same means adopted every three months of the cruise. 819. The Condition of Loaded Shell, and especially of their fuzes, is frequently examined into, taking out a fuze occa- sionally so as to detect any injury which may arise from moist- ure, and such as may he found damaged are replaced hy spare fuzes. Projectiles returned from cruising ships are emptied, cleaned, and plugged. In emptying shell they are handled carefully and placed on a bench with a hole in it to receive and support the inverted shell. A wooden vessel placed below receives the powder. The powder which has been removed from shells is only used for filling shell, as it always contains a small quantity of grit, which renders it unfit for general service. All powder taken from shell is sifted, and all dust and par- ticles of dirt removed, as far as possible, before putting it into barrels. Should the powder have become caked, so as not to be easily removed by washing out the shell, a handful of small iron shot put in the shell facilitates this operation. 820. Removing Fuzes. — Whenever it is expedient or neces- sary to examine the fuzes and loading of shell wliich have been already prepared, great care is observed in removing the fuze, and it is never done in the shell-room. The fuze-stock may generally be safely unscrewed Avith the fuze-wrench, taking care, in the first place, to strike the side of the shell gently ivith a wooden mallet, to detach the powder from the fuze, to work very slowly, and not to endea\'or to overcome any unusual resistance. ISTo attempt should be made to open a shell, for the purpose of unloading it or destroying its charge, in any other way than by unscrewing the fuze-stock. In doing this, if the stock do not yield at once to an ordi- nary effort with the wrench, then the shell should be marked and immediately set aside, to be thrown overboard. 821. To find the number of halls in a pile ^ multiply the sum of the three parallel edges by one-third of the number of balls in a triangular face. In a square-pile, one of the parallel edges contains but one ball ; in a triangular pile, two of the edges have but one ball in each. — V ^ bemg ttie number in the bottom row. 292 NAVAL ORDNANCE AND GUNNERY. The sum of the three parallel edges in a triangular pile is £c + 2 ; in a square pile, 2x -j- 1 ; in an ohlong pile, 3X + 2a? — 2 ; X being the length of the top row, and a? the width of the bottom tier ; or 3m — a? -)- 1 ; m being the length, a? the width of the bottom tier. If a pile consist of two piles joined at a right-angle, calcu- late the contents of one as a common oblong pile, and of the otlier as a pile of which the three parallel edges are equal. Section II. — Deviations I 822. Geneeal Consideeations. — The term deviation must be understood to mean not only the deflections, right or left, of the line of fire, but also the differences between the ranges of similar projectiles fired under like condition from the same guns. Very great irregularities occur in the paths of spherical pro- jectiles. If a number of projectiles be fired from the same gun, with equal chaiges and elevations, and with gunpowder of the same quality, the gun-carriage resting upon a platform, and the piece being pointed Avith the greatest care before each round, very few of the projectiles will range to the same distance ; and, moreover, the greater part will be found to deflect consid- erably, unless the range be very short, to the right or left of the line in which the gun is pointed. With elongated projectiles the fire is far more accurate, but still the ranges and deflections are subject to variations of greater or less amount. The causes of the deviations of projectiles, whether fired from smooth-bore or rifle guns, and independent of inaccuracy in pointing, and variable position of the gun-carriage, rcrowind, varialjle projectile force, and rotation of the earth. 823. Effect of Wind. — Should the wind be blowing in gusts and be changeable in direction, it is difficult to allow for it in pointing the gun ; but with a steady breeze, in a pretty constant direction, a feAV rounds will generally be sufficient to shoAv the allowance necessary. The velocity of the wind is very low compared with that of the projectiles, but it remains usually nearly the same throughout its flight, whereas the ve- locity of the projectile decreases rapidly ; it therefore fre- quently happens that the Avind appears to have greater effect toAvards the end of the range, and it may be often noticed in * Owen. PROJECTILES. 293 practice, tliat projectiles deviate in a rapidly increasing curved line. The wind, if strong, will greatly affect the ranges of projec- tiles; decreasing or increasing the range according as it may be blowing with or against the projectile. The lower the velocity of a projectile, the greater will be its deflection caused by the wind, as, for instance, upon mortar- shells, on which, having low velocities and long times of flight, the Avind exercises a very disturbing influence. The greater the density of the projectile, the less will its motion, during flight, be affected by the wind ; and thus shells ai-e more influenced by wind than shot. The wind exercises a very great deflecting influence upon an elongated projectile during its flight, rendering it difficult to obtain accuracy of fire at long ranges, even from rifled guns, excepting in very calm weather. If the centre of gravity be placed very near tlie centre of the long axis, the force of the Avind Avill be pretty evenly distrib- uted over the Avhole length of the projectile. Should, hoAveA^er, the centre of gravity be placed far in advance of or beliind the centre of figure, the force of the wind Avill press unequally upon the shot, and uncertain deflections Avill most probably occur. 821. Yaeiable Pkojectile-fokce. — It is impossible Avith our present facilities to manufacture large quantities of poAvder of a perfectly uniform quality ; but supposing it could be ac- complished, the force from a given charge Avould be liable to variation according to the state of the atmosphere, and the con- dition of the poAvder as affected by the time it has been in store ; it will also be frequently found in practice that the charges have not been Aveighed out with perfect accuracy, nor the gun loaded so that the projectile is ahvays in the same posi- tion Avith reference to the charge. The consequence is, that very few projectiles fired from the same gun Avith Avhat are called e(pial charges, leave the bore with exactly the same ini- tial velocity. 825. Rotation of the Eaeth. — The deviation of a pro- jectile caused by the rotation of the earth is a complicated problem. The principle that this rotation will impress upon the projectile a tendency, upon leaving the bore, to move Avith the same velocity in the same direction as the point upon the surface from which the gun is fired, is readily comprehended, but not its application to some particular cases.* The devia-' ■* For a general discussion of this subject, see an Article by Prof. Wm. Ferrel in The Mathematical Monthly for August, I860. 294 NAVAL ORDNANCE AND GUNNERY. tion due to tins cause is too sliglit to be regarded iu prac- tice. 826. Faulty Dispositioit of the Ll\e of Sight. — The line of sight may he improperly placed and situated out of the vertical plane, either in consequence of the constnictiou of the gun or its carriage, or hy the etfect of the inclination of the plane upon which it is placed. In these two cases the line of fire maintaining a fixed and determined position, in respect to the axis of the gun and the vertical plane of fire, the deviations are constant for equal distances and equal inclinations, and it becomes easy to correct them after a few trials. 827. Influence of the State of the Air. — The haro- raetic state of the atmosphere may also produce an effect upon the ranges ; for the greater the density and elasticity of the displaced fluid, the greater will be the retardation of the pro- jectile. The phenomenon of refraction also slightly modifies the range, hut these last causes are scarcely appreciable in practice. 828. DEYIATIOX OF SPIIEEICAL PEOJECTILES. — The principal causes of the deviations of projectiles fired from smooth-bore guns, are 1st. Windage. 2d. The imperfect form and roughness of the surface of the projectile. 3d. Eccentricity of projectiles arising from their not being homogeneous. 829. Windage. — Windage causes irregularity in the flight of a projectile, from the fact of the elastic gas acting in the first instance on the upper portion of the projectile and di-iving it against the bottom of the bore. The projectile reacts at the same time that it is impelled forward by the charge, and strikes the upper surface of the bore some distance in advance, and so on, by a succession of re- bounds until it leaves the bore in an accidental direction and with a rotatory motion, depending chiefly upon the position of the last impact against the bore. (Fig. 194.) PEOJECTILES. 295 Thus, should the last impact of a concentric projectile, Avhen fired from a gun, be on the right-hand side of the bore, as rep • resented in the figure, it will have a tendency to deflect to the left in the direction 5, while at the same time a rotation will be given to it in the direction indicated by the arrows, or to the right. The effect of this rotation being to cause the projectile itself to deviate to the right during its flight, so that the deflec- tion will not be to the left, but to the right, unless the range is very short. If the projectile leave the gun, rotating on a vertical axis, with its forward part moving from left to right — supposing the observer to be behind the piece — there will be a diminished pressure on the right side and an increased one on the left side, which will therefore cause it to deviate to the right. If a projectile strike the bottom of the bore, the rotation of the fore-part would be from up downwards, and instead of de- flecting to the right, the range would be decreased. Suppose the projectile to rotate in an opposite direction, the results would be reversed. Should it, on leaving, strike any intermediate part of the bore, a compound effect would be produced, according to the position of the point of impact. It appears from these explanations, that a projectile leaving the gun, rotating on any axis, except one parallel to that of the bore, will deviate according to the direction of the rotation. 830. Eccenteicity. — Should the centre of gravity of a pro- jectile not coincide with the centre of figure, it is termed eccentric, and is found to deviate according to the position of the centre of gravity when the ball is placed in the bore of the gun ; should the line joining the centre of gravity and the centre of figure of a projectile be not parallel to the axis of the bor*e, the charge of powder will act on a larger surface on one side of the centre of gravity than on the other, so that there will be a rotation from the lightest towards the heaviest side. If Fig. 195 represent an eccentric shot, the centre of gravity, Gr, of which is below the centre of figure F, the powder, acting on a larger surface above than below G, will give it a rotation as indicated Iry the arrow, and from what has been previously said, the deviation will be to the side on which the centre of gravity lies ; this is the ease in practice, for it has been ascertained by experiment that if a projectile be placed in a gun so that its centre of gravity is to the right of the vertical plane passing through the axis of the bore, it will deviate towards the right, and vice-versa ; also if the centre of gravity be upwards, the range will be increased; and if downward, di- minished. 296 NAVAL ORDNANCE AND GUNNERY. It is found in practice that projectiles deviate in a curved line, either to the right or to the left, the curve rapidly in- creasing towards the end of the range. This probably occurs from the velocity of rotation decreasing hut slightly compared to the velocity of translation ; or if a strong wind is blowing steadily across the range during the whole time of its flight, this deflecting cause being constant, while the velocity of the projectile diminishes, the curve will manifestly increase with the range ; the trajectory is, therefore, a curve of double curva- ture, its projection on either a horizontal or vertical plane be- ing a curved line. 831. Conclusion . — From the foregoing considerations it fol- lows, that the smoother the surface of the projectiles and the less their windage and eccentricity, other things being equal, the greater will he their accuracy. Experiments show that the preponderating side should be put next the charge, and. the line joining the centre of gravity and the centre of flgure should be parallel to the axis of the bore. The position of the preponderating side is found by float- ing the projectile in a bath of mercmy, and the degvee of promptness with which an eccentric shot, floated as above, assumes the position due to its preponderance, is regarded as the measure of that jireponderance. 832. DEVIATION OF ELOA^GATED PEOJECTILES. — If the projectile come out of the gun perfectly centred, that is, rotating round its longest axis, and having that axis coincident with the line of flight, there will be no tendency, either of the axis of rotation, or of the projectile itseE, to deflect, so long as the motion is in a straight line, because the resistance of the air will act uniformly all around. As soon, however, as the trajectory has begun to curve downwards under the influence of gravity, the resistance of the air acts more on the under side than on the upper, and effects will be pro- PEOJECTILES. 207 duced depending on tlie resultant direction of the resistance of the air in relation to the centre of gravity. 833. Practically, the path of the projectile is found to re- sult in a deviation, increasing uniformly with the distance from the gun, and depending, as to its direction, on the direc- tion of the deilectiug-force at the moment of its first applica- tion. If the deflecting- force act on the projectile in a vertical direction upwards, the horizontal projection of the line of flight will he a line deviating to the right or left, of the plane of Are, according as the twist is right or left handed. If the deflecting-force act in the opposite direction, the projectile will he deflected to the left or right, according as the twist is right or left; and whatever be the direction of the deflecting- force, the deviation will be a uniformly increasing one at right angles to it. 83d. These effects may be illustrated experimentally by means of a gyroscope provided with a small elongated projectile instead of the disk used for ordinary experiments. (Fig 197.) The projectile must be made with the greatest care, so that its centre of gravity coincides exactly with that of the two rings within which it is placed ; tho rings are so arranged that one can turn round a vertical axis, and the other round a horizontal axis, the projectile being there- fore free to turn in any direction. A cylindrical portion of metal extends be- yond the base of the projectile, in prolong- ation of its longer axis, round which the string is wound to give the required rota- tory motion. As the projectile in the gyroscope has no motion of translation, a strong current Fig. 197. of air must be chrected upon it, so as to represent the resistance of the atmosphere to a projectile mov- ing with a high velocity. The diameter of the nozzle of the blower should be equal to, or rather larger than, that of projectile, and the centre of the blast should be directed low the point of the projectile in the position indicated E in Fig. 145. 835. If Fig. 145 represent the elongated projectile of the be- bj gyroscope, it will where between a be found that a pressure, E, and h will produce a similar the exerted any- effect to an 298 NAVAL OEDNANCE AND GUNNERY. upward pressure exerted at tlie point E. Supposing, however, the projectile to be rotating rapidly in the direction indicated by the arrow in Fig. 197, and the pointed end is facing the spectator : then, if a pressure be exerted at 5, corresponding to E in Fig. 145, the point of the projectile will not rise (at least perceptibly), but will move laterally in the direction c, that is, to the right, with reference to an observer behind the gyro- scope ; if a pressure be exerted at d (Fig. 197), the point will fall ; if at a, the point will move laterally in the direction c7, or to the left, with reference to an observer behind the gvro- scope; lastly, if a pressure acts upon the rotating body at c, the point Avill rise. ISlow should a pressure be exerted in anv intermediate part of the circle abed, as, for instance, between b and d, then the motion of the point of the projectile will be compounded of the motions caused by respective pressures at b and d, that is to say, the point Avill move laterally to the right (with reference to an observer behind the gyroscope), and droop at the same time. 836. If a strong blast of air be directed on the fore part of the rotating projectile, the centre of the current being a little below the point, but in the same vertical plane with it, as showm by the dotted lines in Fig. 145, so as to represent the resistance of the air to a projectile moving with a high velo- city, the pointed end will first move slowly to the right (towards G, Fig. 197), effects being afterwards successively produced by the blast similar to those wliich would be caused by a press- ure acting gradually round the circle aebd (Fig. 197), as already described. If pressure be exerted behind the centre of gravity in- stead of in front, or on the fore part of a projectile rotating with a left-handed rotation, the above effects will be reversed. 837. The line of flight is therefore not absolutely a straight line, but becomes a curve of double curvature ; and if project- ed on a vertical plane at right angles to the plane of tire, w'ould consist of a series of cj’cloidal curves, were the time of flight sufficiently great, increasing the distance of the ])rojec- tile from the plane of fire by the length of one of them at each revolution. The length of these curves depends upon the amount of the deflecting-force, and their number is equal to the number of revolutions made by the projectile in its flight. 838. When an elongated projectile is fired from a rifle-gun, it leaves the bore rotating rapidly round its longer axis ; and if the initial velocity wmre very low, the projectile experiencing but PROJECTILES, 299 slight resistance from tlie atmosphere, the larger axis would remain (as in vacuo) during the whole time of flight parallel or nearly so to its primary direction, as shown in Fig. 198. In explaining the effect produced by the resistance of the air upon an elongated projectile moving with a high velocity, tlie projectile will be supposed to have what is termed a right- handed rotation : that is, the upper part turns from left to right, with reference to an observer placed behind the gun ; for the direction of the grooves of rifled pieces are almost inva- riably so as to give such rotation. After the projectile has left the bore, the residtant of the resistance of the air will, unless the centre of gravity be very far forward, act upon a point in front of the centre of gravity and below the longer axis, at all angles of elevation given in practical gunnery. The effect produced by this pressure will depend chiefly upon the form of the head of the projectile ; therefore, let us first consider the effect ujion a conoidal head. 839. Deviation of the Conoidal-headed projectile. The pressure E. (Fig. 145), exerted anywhere between a and h, will have a tendency to raise the point a or to produce a similar effect to an upward pressure exerted at the point E. This will result in giving tlie point a a lateral movement to the right. (Art 833.) As this lateral movement of the point proceeds so will the resultant act more and more to the left of the vertical plane, passing through the longer axis of the projectile. And as the deviation continues at right angles to the direction of the deflecting-force, the point will soon begin to droop. The point of the projectile first moves to the right, then downwards, still keeping to the right, then to the left, and so on, describing a portion of the circle, the continuance of the motion depending upon the time of flight and velocity main- tained. As the velocity becomes low, the circular motion of the point will gradually cease ; but in practice, during the few seconds of flight which generally elapse, as the velocity is 300 NAVAL ORDNANCE AND GUNNERY. pretty high throughout, there is prohahly sufficient time and pressure not only to turn the point to the right, hut to bring it down on to the trajectory, or even below it. 840. Of course the longer axis of an elongated projectile does not remain, during flight, continually a tangent to the trajectory, unless the centre of gravity, as in an arrow or rocket, is very near the face end ; yet, practically, on account of the drooping of the point, the longer axis may throughout a considerable portion of the time of flight approximate very nearly to a tan- gent to the trajectory, as in Fig. 199, Fig. 199. The effects on targets furnish most satisfactoiy evidence of this ; it is almost invariably found that the holes made in targets are circular, even when elongated jirojectiles descend at consid- erable angles. The most probable explanation of this fact must evidently be, that the point of the projectile has drooped during flight, so that, on striking the longer axis is nearly perpendicular to the plane of the target. (Fig. 199.) This drooping of the point is of importance, fordid the axis remain parallel during flight to its primary direction, the pro- jectile would most probably, when fired at any hut a very low angle, on striking an object of hard material and solid structure turn up against it lengthways, and therefore produce but trifling effect. This has not, however, been found to take place in practice, but on the contrary the penetration of elongated pro- jectiles at considerable ranges, are always remarkably great. There is little fear of the projectile turning up against an object unless the velocity of translation and rotation be very low, and the angle of fire very high. 841. Deviation of tlie Flat-headed Projectile . — A pressure ex- erted upou the head and below the larger axis, as (K Fig. 146), will have a tendency to cause the head to droop ; or will produce PEOJECTILES. 301 an effect similar to a downward pressure, acting at C ; just the opposite of what is observed with a conoidal-pointed projectile. Therefore (Art. 833), the projectile will he deflected to the left or right, according as the twist is right or left handed. It is found in practice that conoidal-headed projectiles fired from rifled guns giving a right-handed rotation, always deviate to the right ; and in the few’ cases tried with guns giving a left- handed rotation, the deviation is to the left ; wdth flat -headed projectiles, these deviations are reversed. 812. Drift . — This peculiar deviation is called drift., and is generally constant for the same ranges — so that it can he allow’ed for in pointing the gun, hy using a horizontal slide grad- uated and attached to the tangent scale, or by inclining the tan- gent scale to the left. Section III.— Effects. 813. General Considekation. — A knowledge of the de- structive effects of projectiles is of very great importance. In general, these effects depend upon a variety of circumstances, such as the velocity of the projectile at the moment of impact, its weight, form, diameter, the material of which it is made, the nature of the object struck, and the relative position of this lat- ter with regal’d to the trajectory of the projectile. When a projectile strikes an object, its energy is expended, not only in penetrating, fracturing, or producing vibration in the material -of the object, but, when the latter offers great re- sistance, in breaking up or changing the form of the projectile. 841. Ijipact of Projectiles. — In order to arrive at a clear understanding of Avhat takes place when the motion of a projec- tile is arrested by any resisting medium, it is necessary to recall some of the elementary prmciples upon which these phenomena depend.* The manner in which a projectile acquires its velocity, is a good illustration of the manner in which its motion is de- stroyed. If the mean pressure, P, of the gas be multiplied by the space, S, passed over by the projectile while acquu’ing its veloc- ity, the result will be the measure of the work done by the charge of powder ; and it will also be equal to thp work of stopping the same projectile, no matter how or by what means it may be brought to rest. King. 302 NAVAL ORDNANCE AND GUNNERY. The same result is generally arrived at by measuring the veloc- ity imparted to the projectile under the circumstances men- tioned, and multiplying the square of the velocity by one-half of the mass of the projectile ; or, since the mass is equal to the weight divided by the force of gra^nty, the expression for the work stored in the projectile, and which must be expended in AV v“ bringing it to rest, = — ^ — , where W = weight of the projec- tile in pounds, v velocity of the projectile in feet, and g = the force of gravity in feet, or the velocity which a body will ac- quire by its own weight in one second of time. This expression involves indirectly the same quantities as that first mentioned ; namely, the mean pressure of the gas and the distance passed over bj'^ the projectile ; assuming this meas- ure for the work stored in the projectile, it remains to consider how this work is expended. 84:5. The following are the different effects produced by the impact of a projectile upon any solid body ; some of these being so connected as to render their relative importance extremely doubtful. Comjpression . — The first effort of impact is to compress or drive back those portions of both projectiles and target first coming in contact upon those immediately behind them ; the amount of this compression depending upon the material and velocity of impact, as well as upon the form of the projectile. Elongation. — The greater part of the work of the pro- jectile in penetrating wrought-iron and similar materials is expended in overcoming the tenacity of the material, or in elongating the fibre. This is evident when we consider that punching or shearing consists not so much in cutting the fibre, as in bending it, and afterwards pulling it in two lengthwise. Shearing. — This, as just stated, consists chiefly in the two strains already mentioned. Bending. — This also implies tension and compression ; the back of the target being elongated, and the front compressed. Pulverizing — a portion of the material. This takes place only in case of hard materials, as stone or cast-iron, and it then absorbs a very great amount of work. Like bending and shearing, it involves compression and elongation, the material being compressed until it yields laterally to a tensile strain. Motion. — While the work is being expended, a certain amount of time is allowed for the force of the projectile to im- part motion to the target, especially that portion immediately in front of the projectile. Friction. — T\\q friction is very great, especially in the case PROJECTILES. 303 of the more pointed form of projectile, and varies inversely with the velocity of the projectile. Heat. — This is due to friction, both external and internal, that is, of the projectile and fragments against the target, and against each other during the distortion of the material, from compression, bending, etc. The suddenness with which this heat is generated is almost unequalled by any known source of heat. It is well known that the heat developed in the interior of loaded shells, on striking violently a thick iron plate, is sufficient to ignite the powder, and this fact has been utilized in dispensing with fuzes for ex- ploding armor-punching shells. The effect of a projectile on striking a mass or target of any form or material, may be divided into two general portions, one being entirely local, while the other is distributed over more or less surface according to circumstances. The former is penetration.^ and the latter may be called the concussion. 816. PENETRATIOlSr. — General Theory. — The most common substances encountered by projectiles are arranged in the following series, in the order of their resistances to penetra- tion : — water, sand, wood, lead, copper, wrought-iron, soft steel, cast-iron, chilled iron, hardened steel, etc. All other sub- stances may be arranged between these, or in continuation of the series. Air opposes the motion of a projectile by its inertia, elastic force, and the pressure due to its weight. The projectile com- presses the air in its front and disperses it laterally, while the rear of the projectile is relieved by its motion of the normal pressure of the air. A small amount of resistance is also met with in the shape of friction. Water. — In the case of water these resistances are increased by the greater density and weight of this substance, and there is also a slight additional resistance due to the cohesion among the particles. Sand, being a solid, or at least made up of solid elements, presents the additional resistance of crushing-strength.” It cannot be penetrated at a high velocity without crushing some of the grains, and the higher the velocity the greater the amount of Avork expended in this manner. This resistance to crushing implies a continuation of the elastic force beyond the elastic limits, and involves indirectly tensile strength, since a solid in being crushed must enlarge laterally and finally yield to a strain of tension. Wood. — In penetrating wood, lead, or any of the other 304 NAVAL ORDNANCE AND GUNNERY. materials, “tensile strength ” forms the chief element of the re- sistance, while inertia and friction become of minor importance. 847. J^asticity . — The office of elasticity in all these cases is to transmit the effect of the projectile from those particles first acted upon to those more remote, and thus calling into play their inertia or tensile strength, as the case may he ; and were it not for this property, the statical resistance of a plate of any material to perforation Avould be entirely independent of the thickness of the plate ; a thick plate would offer no greater resistance than a thin one, since each layer or unit of thickness would be perforated AAuthout receding any assistance from its neighbors. The worh of penetration woiild then vary directly with the distance penetrated, or the thickness of the plate; elasticity, however, has its maximum point of usefulness in resisting pen- etration, and beyond this it becomes a great disad^'antage. While increasing the number of fibres or elementary portions of the material broken at once, thereby increasing the statical resistance, it diminishes the time dxiring Avhich this resistance opposes the motion of the projectile in like ratio; and the amount of motion destroyed or generated increases with the time as Avell as Avith the force or resistance. For this reason hardened steel and chilled iron are less efficient in stopping projectiles than soft iron, although they offer a much greater statical resistance to penetration. There are many reasons for helieAung that a general for- mula for the penetration of projectiles in all materials may be deduced, Avhen experiments have been sufficiently extended, in Avhich tlie constants will simply require changing to suit any particular case under consideration. 848. Peneteation of Spherical Projectiles. — The area presented by a ball may be taken as equal to that of its great circle ; if, then, R = the mean resistance per square inch offered by the object throughout the penetration, and r = the radius of the shot, R 7t =z resistance to he overcome by shot — the formula for accumulated worlc being ; and putting y? for S, the space penetrated P.S = P = PEOJECTILES. 305 _ Let d = weight of a cubic inch of the materia] of the shot ; then w = ^7tT^d, , . rrd d'o 'irdv^ This formula, although answering for low velocities, gives too great penetration for high velocities ; it is, however, sufB- ciently accurate for the deduction of the simple laws stated below. R, which will vary with the nature of the material fired at, whether wood or masonry, or other substances, must be found by experiment. 'When the resisting material is the same, P varies r d or the penetration is proportioned to the diameter and density of tire sliot, and to the square of its velocity on impact — so that the larger the diameter of the ball, and the greater its density, the deeper will be the penetration ; especially as the final velocity for the same initial velocity will be higher. When projectiles of the same density are fired into the same material, P varies as r v‘‘, or with the diameter of the shot and the square of its velocity on impact.^ 8-19. Peneteation of Elongated Pkojectiles. — The pen- etration of an elongated projectile is greater than that of a spherical projectile of equal weight, when both are fired with the same initial velocity ; for the former presents a less area to the resistance of the object; it can have a pointed head, and it will have a greater final velocity, being less retarded during flight. In general, however, an elongated projectile is fired with a lower initial velocity than a spherical projectile of equal weight from a smooth-bore gun ; and, therefore, at a short distance, the latter will most probably produce more effect as regards penetration than the former ; but as the range is increased, so will the penetrating power of the elongated projectile be greater conqrared with that of the spherical, for the former will maintain a high velocity much longer than the latter. 850. Formula for Perforation of Iron Plates. — One of 20 306 NAVAL ORDNANCE AND GUNNERY. tlie first questions to present itself in connection with annor- plating is the relation between the thickness of the plate and the diameter, Aveight, and velocity of the projectile recpiired to perforate it ; or, having given the diameter, weight, and veloc- ity of a projectile, required the thickness of a single wrought- iron plate which it will just perforate. Several formulre have been proposed for this purpose, but the great ditficulty has been the want of experimental results sufficiently accurate and comprehensive to verify the principles upon which they are based ; and to give the correct values for the constants or co-efficients Avhich enter them. Captain I^oble, li. A.,* gives the following formula for the penetration of wrought-iron plates by steel shot, the impact being direct : = 27rE/r5\ Avhere ^ . W = weight of shot in pounds, -y = velocity on impact, in feet, g — the force of gravity, 2E. :=: diameter of shot in feet, 1) — thickness of unbacked plate in feet, = a coefficient depending on the nature of the AAwought-iron in the plate, and the nature and form of head of the shot. Solving the above equation for J, giA^es : In order to determine h the following series of equations can be formed : The variable quantities in these equations are E, 5, w, and r ; * ‘ ‘ Report on various experiments carried.out under the direction of the Ord- nance Select Committee, relative to the penetration of iron-armor plates by steel shot.” By Capt. W. H. Noble, R. A. London : I860. and for /o, ^ 47rlvv/Z»' ^Tt^gjVh — W,Aq'‘ =r 0. 47rR„y5"Z; — W„a'„‘ = o. 4:7tYv,gh-k — = o. etc., etc., etc. I PROJECTILES. 307 7 t being tbe usual representative of the ratio of diameter to cir- cumference of the circle, and g representing the force of grav- ity in dynamical terms. Having determined the value of Tc, the “ work ” necessary to penetrate any unbacked plate of given thickness may be calculated. This formula is only claimed to give a near approximation, as the case is one which does not admit of absolute accimacy, involving, as it does, many sources of error and uncertainty, which it is impossible to eliminate without an almost intermin- able series of experiments. 851. Fokm of Head. — That the penetration of an elon- gated projectile is influenced by the form of its head has been shown by experiment, many clifEerent forms of head having been tried. The flat head has been strongly advocated, because it is asserted to be a better form for pimching than any of the pointed heads, and because it is also asserted that it will bite into an iron plate at such an oblique angle as would cause a pointed head to merely glance. But the truth of these asser- tions has not been generally admitted. The flat-headed projec- tile is objectionable both as regards accuracy and velocity, and it has also a tendency to upset or bulge at the head on impact, and this result is very marked. The pointed projectile is superior in accuracy and range, and does not upset on impact to anything like the same ex- tent. It is asserted that it cuts through an iron plate to a better advantage, or rather tears through blending back the plate. 852. OijLiQUE Impact. — -Another point in connection with the penetration of elongated projectiles is the effect of different forms of head upon the rotation of the projectile when the im- pact is oblique. If the axis of the projectile is tangent to the trajectory on impact, and at the same time normal to the target, there will be no tendency to rotate about any axis parallel with the plane of the target. In Fig. 200, if we suppose a projectile to arrive at A, under these conditions it will undoubtedly penetrate the plate directly. But let one arrive at D or E, and there will be a tendency to rotate, and this tendency will depend upon the form of the projectile as well as upon the angle between the trajectory and its axis. Now it is asserted, on the one hand, that the advantage in the latter case will be in favor of the flat-headed projectile, since the moment of the rotating force will be the variable resistance of the plate multiplied by the lever arm Dd, for the pointed 308 NAVAL OEDNANCE AND GUNNERY. projectile, and the same multiplied hy a much shorter lever arm, Ee, in case of the flat-headed projectile, and this may be negative ; or in other words, there may be a tendency to rotate towards the normal, which would be a decided advantage. This would take place when the line of the trajectory passed within the base of the shot. In the third case, represented at B and C, a projectile is moving with its axis tangent to the trajectory, but oblique to the target ; here there is also a tendency for the flat-headed projec- tile to rotate toward the normal, but it is questionable whether such rotation would be advantageous. The pointed projectile would have a less tendency to such rotation. On the other hand the respective motions of a flat and pointed headed projectile on oblique impact are explained as follows : It is asserted that the flat-headed projectile on striking (Fig. 201), cuts out a portion of the face of the plate, which it carries along in front, thus increasing the thickness to be pen- etrated, and, remaining nearly parallel to its original direction, it has to pass through the plate obliquely. While if the projectile has a pointed head (Fig. 202), the point enters at flrst more deeply into the plate than the flat head, and the centre of gravity moving forward, the projectile turns around more readily than with the latter, so that its axis becomes perpendicular, or nearly so, to the face of the plate, having then only the least thickness to penetrate. It is ditficult to obtain for comparison the results of practice with the flat and pointed headed projectiles of the same mate- rial tired at targets inclined to the line of the range ; the former having been so little used, as its form is so objectionable, both as regaixls accuracy and velocity. On the whole it may be said that in the case when the pro- PEOJECTILES. 309 jeetile onglit to be capable of piercing tbe plate or target, there is little difference between the effect of a flat head and a hemispherical head ; but when the target is beyond the power of the projectile, the hemispherical head makes the deepest indent. 853. Concussion. — The impact of a projectile, in addition to indenting or penetrating a target, produces more or less bend- ing, tearing, and other damage at a distance from the point of impact ; which effects may be classed under the term “ Con- cussion.” The effect of concussion is transmitted from the point of im- pact in all directions, in the same manner as sound-waves and in- creases with the elasticity of the material. Whatever tends to diminish the elasticity of the structure, as dividing it into many pieces, or using soft ductile material to receive the projectile, will diminish the effect of concussion. This effect is expended in two ways : First, in giving motion to the structure or in developing inertia ; and, second, in overcoming the tenacity of the material, either in bending or tearing those portions first acted upon from those more remote. Both of these components, increase with the whole amount of work expended by the projectile, other conditions being equal. The first component, being motion converted into motion, is nearly independent of the amount of penetration ; it would be absolutely independent but for the fact that where the penetra- tion is very slight the projectile or pieces of it may be thrown Fig. 201 Fig. 202. 810 ITAVAL ORDNANCE AND GUNNERY. to the ]-eai’ by the elasticity of the target, and this effect, re-act- ing upon tlie target, vrould be in addition to that due to the stop- ping of the projectile. Taking an extreme case, suppose the target and projectile to be perfectly elastic, and to resist all pen- etration ; the projectile would be thrown to the rear with nearly the velocity with which it struck, and the velocity imparted to the target woidd be double what it would have been had the target and projectile been perfectly inelastic. The second component will increase as the amormt of pene- tration diminishes, since the less the penetration, the greater must be the force exerted by the structm*e to absorb a given amount of work from the projectile. But the amount of pene- tration for the same form of projectile, and with other condi- tions equal, diminishes nearly as the diameter of the projectile increases ; and since the work stored in a projectile va- ries directly with its weight, or the cube of the diameter, we may conclude that that xjortion of the effect of concussion ex- pended in overcoming the cohesion of the material varies di- rectly with the fourth power of the diameter of the projectile / on this supposition this effect, for the X, XA^, and XX inch spherical shot, would be as 1, 5 and 16, respectively, while the relative penetration of these projectiles would be only about as 1, 1-|-, and 2. The same effect may also be shown to vary directly with the velocity of impact. For a given amount of work expended by the projectile, it is evident that the lower the velocity, or the longer the time allowed for the force or resistance of the target to work, and the concussion to be transmitted to distant points, the greater will be the effect in bending the target, breaking bolts, and otherwise shattering the structure ; but the whole work arises with the square of the velocity, and this, divided by the velocity, leaves the first power of the velocity as before stated. The form of projectile is supposed to be the same in all cases. The effect of changing the form would depend upon the change in penetration, those forms which give the greatest pene- tration giving the least effect of concussion. 854. Aemoe-piekcing Projectiles.* — Projectiles intended for practice at objects composed of Avood, masonry, or earth, are made of cast-iron, but since the introduction of iron for the defence of ships and fortifications, a material possessing greater hardness than ordinary cast-iron is required to overcome the resistance opposed by thick wrought-iron plates. Both elou- * Mallet. PROJECTILES. 311 gated and spherical projectiles for use against armor should he of the hardest and toughest material possible. The power of a projectile to stand up to its work and de- liver its full blow on the target depends on the shape as much as on the quality of the metal of which it is composed. 855. Shape. — Spherical Projectiles . — The resistance of the plate, neglecting friction, acts as a normal to each point of the surface of contact of the projectile ; thus, in Fig. 203 it will be seen that the portion of a spherical projectile included be- tween A and B, which we may term the zone of compression, is subject to a crushpig pressure towards the centre, O, but it may be said to be under no tensile strain. While the posterior portion of the projectile is suddenly cheeked by it in the form of a wedge, when a portion of the work stored up in it — (the amount depending on the tensile strength of the material of the projectile) — is im- pressed on the tdrget through the front por- tion, A O B, while the remainder is car- ried off unprofitably in the fragments into which the posterior portion breaks. On examining the projectile after im- pact, a part very nearly corresponding to A 0 B in form, will be found intact (Fig. 203), with the fractured surface scored and polished, while the remainder will be dispersed in small fragments. We know that any casting fractures most easily in the direc- tion of a normal to its surface, the crystals settling themselves so as to form lines on this direction. Theoretically, the portion represented by Fig. 203 ought to be smaller as the penetration is less — except in the case of Fig. 203. — Anterior Fragment of round shot after impact against armor coinciding nearly ■with zone of compression. the entire blow being too small to overcome the tensile streugth of the metal in the manner described : — when the projectile woidd only split irregiilai'ly or in an extreme case remain entire. In all instances, obviously a great amount of tlie work 312 NAVAL OKDNANCE AND GUNNBET. Stored np in the projectile is wasted ; not that actually em- ployed in breaking it, for such work is clearly the result of the reaction from the target ; hut whatev^er power remains stored up in the fragments, after they sever themselves from the mass of the projectile. Since it is impossible to predict what part of a spherical projectile fired from a smooth-bore gun will come in contact with the target on impact, it is necessary that the material should be such as will offer the greatest union of hardness, crushing-strength, and tenacity ; therefore steel has been re- sorted to in some instances, and may be regarded as the cul- minating point of development of the smooth-bore projec- tiles. 856. Elongated Projectiles . — The flat-ended form possesses a peculiar advantage as regards the projectile, and another as concerns the plate. As to the projectiles, it may be seen (Fig. 204:) that in direct impact the whole of the resistance of the target acts in lines j>arallel to the projectile’s axis, which direction is the most favorable to the projectile retaining its mass and delivering its full blow on the target, and again, if the target is to be punched by actual shearing, the flat- head is the form best adapted to effect it. The flat-head would probably be best in the case of direct firing against plates composed of hard iron, for it is easy to conceive of a hard material offering very great resistance to the forcing open of a pointed head, which might be punched by the clean shearing of a flat-headed projectile. 857. The power given by rotation, of keeping the same portion of a projectile presented to the front, is of peculiar value in punching armor-plates ; it enables the head of a pro- jectile to he made of any desired form, while the power of re- diicing the calibre of a projectile in proportion to its weight, which is perhaps the principal advantage obtained by rifling, is also most important here, the depth of penetration being in in- verse proportion to the circumference. 858. In shells, however, this stability of the axis of rotation PEOJECTILES. 313 tells more fully, for it enables every part of the projectile to be made of such proportions as will give the maximum power at the moment of impact. The walls of an elongated shell being chiefly subjected to a longitudinal strain, an interior hollow may be made without entailing the great weakness existing in spherical shells as compared wdth solid shot. Hence it follows that while smooth-bore shells have seldom or never been fired at armor, rifled shells have proved very successful. 859. There are two causes which contribute to give shells peculiar power against iron plates. The first is that it is not necessary to weaken the head of a shell by making a fuze-hole in it ; because no fuze is reqirired, the heat generated on the impact of a projectile against the armor being sufficient to fire the bursting-charge. To such an extent ]s light as well as heat generated, that on firing at target after dark, a pale flash is seen to follow the impact. The second cause that operates to favor the action of shells, is the fact that when the shell has penetrated to a depth of even a few inches before rupture occurs, the sides are supported by the armor around them, and the explosion, being confined at the sides, acts to the front with greatly increased force. 860. In a conical head (Fig. 205), the normal pres- sures throughout form a zone of compression acting as a wedge towards the body of the projectile, whose angle is the supplement of that of the cone of the head. This is better than that formed in the spherical head, because the angle is less acute, and because the apex of the wedge, instead of being a fixed point throughout (the centre of the sphere), moves along the axis of the projectile as it enters deeper and deeper into the target. In the ogival head (Figs. 206 and 207), it will easily be seen how much superior is the action. In this the wedge" is at the commencement slightly acute, but then the resistance acts on a small surface and is comparatively small, and the angle in- creases, till, at the junction of head and body, it becomes 180°, or a straight line (Fig. 207), so that we then have the body of the projectile in much the same condition as the flat-hea"ded 314 NAVAL ORDNANCE AND GUNNERY. bolt driving before it an ogival wedge, winch opens the armor by wedging rather than by clipping or pnnching, 861. It is possible, no doubt, to conceive of a material that might be sheared by the flat projectile more easily than opened by the ogival ; but it would be to contradict the results of ex- perience to say that plate-iron was such a substance ; and as the softer and more plastic natures of plate-iron have been found to hold their bolts the best, and stand the longest, and so have been universally adopted, the ogival has become obviously the correct form of head. 8G2. The Effect of Haedexixg Pkojectiles is probably much greater than is generally supposed ; that is, the amount of work gained is much greater than the increase of strength of the projectile. It is well known that a very small force may under certain circumstances determine the performance or non-performance of a very large amount of work. In like manner a very slight addition to the rigidity of a projectile, by hardening or other- Avise, may deteianine Avhether a very large amount of Avork shall be Avasted upon the projectile or expended upon the plate. 863. Another means of increasing the work done upon the armor-plate in comparison Avith that done ipmn the projectile is by increasing the velocity of the latter. That is, a projectile moving at a Ioav A’elocity may be smashed up or flattened against the plate, Avhile the same projectile fired at a higher A’elocity may go through the same plate almost uninjimed. On this principle a lead shot may be fired through an iron plate, or a tallow candle through a pine board. PEOJECTILES. 315 861. For the larger calibre of rifled guns, but one style of armor-pnncbing projectile is usually suppbed ; this being a shell with thick walls, which may be fired empty as a shot, or with the biu’sting-charge to give tlie explosive action of a shell. It is found to penetrate best when fired as a shot ; the action of the bursting-charge, generally taking place before the pro- jectile reaches its full depth, interferes with penetration when the armor is very strong ; but when the front-plates are not very thick, the backing may be shattered to a greater extent from the explosion of a bursting-charge. 865. ADTANTxiGES OF - StEEL OVER ClIILLED PROJECTILES. — Late trials have sho'wn a superiority of steel projectiles over those made of chilled cast-iron, and although the former are somewhat more expensive than the latter, on the principle that the best is at the same time the cheapest, it would be misplaced economy to leave any means imavailed of to increase the penetrating power of projectiles. The quality of chilled projectiles, from the nature of their manufacture (Art. 809), is necessarily unreliable ; whereas this is not the case with hammered cast-steel, or at least not to the same extent by far, even w'hen large masses are produced, and the difliculty of manufacture increases with the calibre. The most essential difl:erence in the behavior of steel and chilled projectiles on striking the target, consists in the reaction on the ]irojectile showing itself in the latter by breaking up, while the former are only set up. As the breaking up of the chilled shells may take place before the bursting-charge comes into operation, whereby the rending effect is considei’ably prej- udiced, this material appears far less adapted for shells than steel. The superiority of steel in this respect is still further in- creased by the fact that the steel shell, can have thinner walls, consequently a larger chamber, and can thus hold a larger bursting-charge than the chilled metal. 866. EXPEPJMENTS AGAINST AEMOP.— The ex- periments made of late years, although numerous and costly, have not been carried out in such a manner as to afford the necessary data for establishing the laws of penetration. In these ex'periments numerous circumstances have been approx- imated to, or assumed, and there have been generally many points of absolute difference between the experimental struc- tures and those to be built for service. By far the larger number of all the experiments of which we have record, were made upon targets small in area, al- though representing the entire thickness of parts to be used in 316 NAVAL ORDNANCE AND GUNNERY. practice ; these small targets being held and braced up in var- ious ways, generally different from the manner in which the same targets would be supported were they to fonn integral parts of a permanent structure. ISTor have the tests applied to these targets been as a rule correct imitations of what they would probably receive in seiwice; having been fired at delib- erately with the guns and projectiles of the same countrj^, as the targets. 867. Aemor-Plates and Backing. — The following deduc- tions have been made from trials with armor-plates extending over several years. The best material to resist projectiles is soft, tough wrought- iron ; and to attain these qualities it should be pure, free from sulphur, phosphorus, and carbon. Steely-iron, commonly known as homogeneous iron, puddled steel, etc., when in large masses is easily cracked by projectiles, and is not, therefore, suitable for armor-plates. Soft-steel may be used for armor- plates ; but when cost is taken into consideration, it is doubtful if it possesses any advantages over wrought-iron. Boiled iron does not offer quite so much resistance as ham- mered iron, 3 ’et if the size of the plate admit of it, it is to be preferred on the score of economy. Plates should be as large as possible to reduce the number of joints which are lines of weakness. A solid plate offers for the same thickness a greater resist- ance to a projectile than a laminated one, or one made up of several thinner plates ; but when the surface is rounded in shape, and of small extent, as in the Monitor turrets, the latter may be used to great advantage, as great thickness may thereby be easil}^ obtained. It is difficult in practice to obtain very large and thick masses in great numbers of uniformly good quality and at a moderate cost. With targets made up of several plates, the chief difficulty has been to contrive bolts of suitable form, and to dispose them so that the strength of fhe target is not quickly impaired by the shearing of the bolts from the vibrations of the separate plates, or by their fracture on being struck by projectiles. 868. Wood-backing alone, unless combined with rigid hori- zontal angle iron stringers, affords but little support to the plate ; that is to say, a projectile which is capable of penetrating a plate unbacked, v/ill also be capable of doing so if it be backed with wood alone. Wood-backing is, however, of great value because it distributes the blow ; it deadens the vibrations and saves the fastenings ; also it stops the splinters. PROJECTILES. 317 The best form of backing appears to be that in which wood is combined with strong horizontal angle-iron attached to the inner skin, and extending to the armor-plates ; this, by giving rigidity, very considerably assists the plate to resist penetra- tion. An inner skin of iron is of the greatest possible advantage ; it renders the backing more compact, and prevents the passage of many splinters. Oak and teak are the most suitable timbers for backing- plates, and are used as such on vessels. A yielding backing is found to occasion less strain on the fastenings than a very hard one. Where projectiles are made of the same material, and are similar in shape, their penetration into unbacked plates is nearly in proportion to their living force, or their weight multigylied ly the squares of the velocity of impact. 869. The resistance which an unbacked plate offers to pen- etration is nearly in proportion to the square of its thickness, provided this thickness be confined within ordinary limits. In the case of oblique plates the penetration diminishes nearly with the sine of the angle of incidence. 870. The most suitable material for shells to be used against iron plates is tempered steel. These projectiles should be made of cylindrical shape, with thick sides and bottom to direct the explosive effect of the charge forward after penetration is ef- fected. The most suitable material for solid shot is hard, tough cast-iron. Palliser’s chilled shot are made of this material, and so are the shot made for our service. 871. It follows from the preceding, that the most suitable covering or shield for cannon is a conical-shaped turret made of Avrought-iron plates, as large as it is practicable to make them, backed Avith oak or teak. To pi’otect the men from the fragments of projectiles Avhich may penetrate completely through this covering, there should be an “inner skin” of thick boiler-plate placed behind the wood. 872. With our XY-inch cast-iron projectiles, made of the best charcoal-iron, poured and worked in a peculiar manner so as to obtain hard and solid masses, the penetration is quite as great and uniform as that obtained with steel shot of equal Aveights propelled by similar charges, the only difference being that the ii’on breaks after passing through, Avhile the steel is only compressed or flattened, a result rather in favor of the iron 318 NAVAL ORDNANCE AND GUNNERY. shot, if entrance is made between-decks, where men are exposed to its fragments. 873. Effects on Wood. — The effect of a projectile fired against wood varies with the nature of the wood and the direction of the penetration. If the projectile strike perpendicular to the fibres, and the fibres be tough and elastic, as in the case of oak, a portion of them are crushed, and others are bent under the pressure of the projectile, but regain their form as soon as it has passed by them. It is found that a hole formed in oak by a hall of four inches in diameter closes up again, so as to leave an opening scarcely large enough to measure the depth of the penetration. The size of the hole and the shattering effect increases rap- idly for the large calibres. A nine-inch projectile has been found to leave a hole that does not close up, and to tear away large fragments from the back portion of an oak target repre- senting the side of a ship-of-war, the effect of which on a vessel would have been to injure the crew stationed around ; or, if the hole had been situated at or below the water-line, to have endangered the vessel. If penetration take place in the direc- tion of the fibres, the piece is almost always split, even by the smallest shot, and splinters are thrown to a considerable dis- tance. In consequence of the softness of white-pine, nearly all the fibres struck are broken, and the orifice is nearly the size of the projectile ; for the same reason the effects of the projectile do not extend much beyond the orifice. When a round-shot strikes against a surface of oak, as the side of a ship, it will not stick if the angle of incidence he less than 15°, and if it do not penetrate to a depth nearly equal to its diameter. 874. Effect on Eaktii. — Earth possesses advantages over all other materials as a covering against projectiles ; it is cheap and easily obtained, it offers considerable resistance to penetra- tion, and to a certain extent regains its position after displace- ment. It is found by experience that a projectile has very lit- tle effect on an earthen parapet unless it passes completely through it, and that injury done by day ca'n he promj)tly repaired by night. The powers of resistance of pure, compact quartz-sand to the penetration of projectiles has been found very much to ex- ceed that of ordinary earth. The size of the openings formed by the passage of a pro- jectile into earth is about one-third larger than the projectile, increasing, however, toward the outer orifice. PEOJECTILES. 319 Elongated projectiles are easily deflected from their course in earth. They are sometimes found lying in a position at right-angles to their course, and sometimes Avith the base to the front. Unless a shell be very large in proportion to the mass of earth penetrated, its explosion Avili produce but little displacement. 875. Effect on Masonka’. — The effect of a projectile against masonry is to form a truncated conical hole terminated by another of a cylindrical form. The material in front of and around the projectile is broken and shattered, and the end of the cylindrical hole even reduced to poAV'der. Pieces of the masonry are sometimes thrown 50 or 60 yards from the Avail. The elasticity developed by the shock reacts upon the pro- jectile, sometimes throwing it back 150 yards. The exterior opening varies from four to fix'e times the diameter of the projectile, and the depth varies Avith the size and density of the projectile and its velocity. Solid cast-iron shot break against gmnite, but not against freestone or brick. Spherical shells are broken into small fragments against each of these materials. The most destructive projectile against masonry is the elon- gated percussion shell. 876. PuNGiiiNG AND PACKING. — It lias been shoAim that the penetration of a projectile depends more upon velocity than weight, and that the elongated is a better form than the spherical for mere penetration ox ]?uncliing. It must, hoAvever, be remembered that A’ery heavy shot, tired with A^elocities which might not enable them to penetrate or punch holes in iron armor, may still do great damage, especially if many ai'e fired successively, by breaking bolts and shaking the whole fabric ; also, that a spherical shot, having a larger diameter than an elongated projectile, may often do more damage in cracking or shattering a plate, than the latter in punching it, the work done by the ball being distributed over a larger area ; the same argument Avill apply to the case of tivo elongated pro- jectiles, having different diameters, striking a target Avith the same force, as measured by Hence there are two general methods of attempting the destruction of iron-clad vessels, termed respectively racking and punching. We have pre- ferred the racking system. 877. The Racking System requires heavy projectiles of large diameters, fired Avith Ioav velocities, to destroy and shake off the armor by repeated shocks Avithout penetration, and thus to expose the vessel to the effects of ordinary projectiles. 320 NAVAL OEDNANCE AND GUNNEEY. 878. The Punching System requires elongated projectiles of moderate weight, fired with high velocities, so as to perforate the armor, and, if near the water-line, to sink the vessel, or at any part to injure men or machinery, or explode the magazine within the vessel. 879. The Two Systems ComMned. — The two forces may prepare the way for each other, so as to produce a more for- midable result than when they are independently exercised. The defect of the light-shot system when the range is very long or the armor very thick, and of the heavy-shot system when the range is even very short and the armor is laminated or so constructed as to suffer little from racking and shaking, is the waste of power in producing local effect, that is fmitless because it is incomplete. By combining the two systems, the light fast shot may weaken the armor by the loss of substance and continuity, until the heavy shot can carry in a large section of it bodily ; and at the same time the general straining and cracking of plates produced by the heavy shot will make punching all the easier. 880. Force of Impact. — In order to estimate the probable effect of a projectile upon an object, it is necessary to calculate the total energy in the projectile at the moment of impact. The “ms viva,^' or total energy of a body in motion, is the whole mechanical effect or work which it will produce on being brought to a state of rest, without regard to the time occupied ; and it varies as the weight of the body multiplied by the square of its velocity. This work, accumulated in the moving body, is represented by the weight which it is capable of raising one foot high, and is equal to the weight in pounds of the moving body multiplied by the square of its velocity in feet, and divided by twice the accelerating force of gravity. Or, Total Energy wv^ - V where w =■ weight of projectile, V = final velocity, g = force of gravity. (32.2 ft.) Example. — Thus, if a projectile of 165 lbs. weight be mov- ing with a velocity of 1170 feet per second, the work accumu- lated in it, or the power it will actually exert on impact, is 165 X (1170)’ PROJECTILES. 321 881. The Punching Effects of Pkojectiles are iisuallj compared by calculating wbat is termed the energy ])er inch of circumference in foot-tons, which is found by dividing the total energy by the number of inches in the circumference of the projectile. Enero-y per inch of circum. = - . — ^ — 7 -,, ^ 2y X 27 t K’ where R = radius of projectile. It will be readily seen that more force is required to drive a large projectile through a plate than a small one. Therefore, if the object is to know the depth to which pro- jectiles will penetrate, size must enter as an element in the question. It has been found that an approximate standard of comparison is furnished by dividing the total energj^ stored up in a projectile by its circumference. Tlie reason of this is plain. Suppose the projectile to act literally as a punch, and to clip a round disk out of the plate of sufficient size to allow it to enter ; it is clear, in such a case, that the work performed is simply that of shearing the plate round the edge of the projectile. Thus the energy of the pro- jectile will be met b}’ the resistance required to shear the tar- get in this manner, in a line which coincides with the exact circumference of the projectile. Ro doubt this supposition is not correct, as any one knows who has seen plate-liring. It is, however, sufficiently near the truth to furnish a standard of comparison between projectiles of various calibres. 21 CHAPTER YII. GUN-CAEEIAGES.* Section I — United States Na/oal-gun-carriages. 882. Geneeal Consideeations. — The first of all consider- ations as to the mounting of the battery, is that it should admit of the utmost possible rapidity of fire, united with accuracy of aim. It is important to secure the greatest possible efficiency of the weapon under the conditions in which it is required to be employed. The daty of providing the most perfect means of working guns seems to be second only in importance to that of adopting the best material, form, and construction for the gun itself. Of two shnilar guns, that which can tire the greatest number of rounds in a given time is certainly most efliective, and rapidity of fire depends much more on the gun-carriage and conveniences for loading, than upon any peculiarity attaching only to the gun. 883. Owing to the increase in the size and power of ordnance since the introduction of armor, gun-carriages have gradually be- come elaborate machines; and mechanical science, in the hands of naval experts, has produced carriages and slides which enable the heaviest guns to be easily, accurately, and safely worked on the broadsides of ships. The great superiority of wrought-iron to timber as a material for gTin-carriages is now universally ac- knowledged. 881. Although the mechanism has been greatly improved, the physical force of the gun’s crew is still the source of the power by which the gun is worked. As long as this is the ease a practical limit to the weight of glin that can be efficiently worked is imposed, and it would seem that this limit has been already reached. As still larger guns are in prospect, the necessity naturally presents itself for substituting an inanimate and unlimited power — like that of steam acting directly or through the medium of Avater under pressure. 885. The heat and elasticity of steam, and the difficulty of conveying it from place to place, render it unsuitable for direct apjjlieation to the AArnrhing of guns ; but in the hydraulic system, so successfully developed for commercial purposes, steam is * Compiled by Lieut. Commander G. W. Coffin, TJ. S. Navy. GUX-CARRIAGES. 323 made available as a central source of power, by employing a steam-eaglns to pump crater into pipes, wliicb transmit it at bigli pressure to the various points of application of the force where it acts in hydraulic pressure to produce the different movements required. It is this system which has been applied to the loading and working of heavy guns. 886. The application of this system to naval guunery was put in successful practice in some of our iron-clads during the late war. Loading from below deck by depressing the muzzle (Art. 1028) was devised by Mr. Stevens and practised on board one of our vessels. Taking up the recoil on a steam or air cylinder (Art. 102G), and running out and in by steam as recommended by Captain Eads, was also successfully practised. Muzzle-pivoting the guns so as to obtain 25 deg. elevation and lateral train in a fixed turret with a port no larger than the muzzle was practised on some of our monitors with entire success. 887. Requirements of Mechanical Carphages. — These arp : powerful moving-machinery so contrived as to be unaffected by the concussion of firing; self-acting controlling gear, almost independent of human carelessness ; the gradual absorption of, rather than ridgid re.-istance to, shocks ; Lie dispersion of con- cussious over large surfaces ; independence of distortion of, or other injuries to, the ship’s side ; smoothness and ease of motion in every direction, and safety under all conditions of the sea. 888. Disappearing Systems. — Guns mounted on the disap- pearing principle, are arranged to drop when fired into a position in which they can be loaded under cover, and from which they are only raised when required again to deliver their fire. (Art. 1022 .) It is yet undecided how far this principle is generally appli- cable in substitution of turrets for the protection of guns at sea. One great difficulty would seem to be that of effectually closing the opening, by which the gun must pass up and down, through the deck so as to prevent the entry of water, and it is difficult to conceive how rapidity or accuracy of fire can be attained in this way. 889. In this system the gun must not only be loaded while lowered and under cover, but it is usually fitted to be trained and aimed while there, by indirect methods, such as by teles- copic apparatus adapted to the gun’s axis, and so arranged that it can enable an observer to look over and above the cover. It is not probable that any such indirect instrumental apparatus 324 NAVAL OEDNANCE AND GUNNEEY. can be constracted which, when adapted to a heavy rifled gun shall admit of the accuracy of fire of the piece being adequately met by a corresponding exactness of aim. The disappearing principle was first recommended by Cap- tain J. B. Eads, and was adopted for trial in several of our western iron-clads. 890. The MAKsmuy Beoahside Caeeiage (W ood). Nomenclature. A. — Brackets. B. — Bear Transom. C. — Breast Piece. D. — Sweep Piece. I. — Saucer. F. — Front Transom L. — Boss of EoUer Handspike. M. — ^Trucks. N. — Cap Squares. 9. — Side Tackle-bolt. 10. — Train “ “ 11. — Transporting Tackle-bolt. K. — EoUer Handspike. P. — Washer and pin. Dimensions. Height of Trunnions Extreme length of Caniage Width of Front Width of Eear Thickness of Wood 34 inches. 68 39.5 “ 44 7 r. “ 891. The Braclcets, A, are made of heavy white oak, jogged and dowelled together as in Figure 208, and firmly secured to each other by the bolts 1, 2, 3, 4, 5 — 1 and 2 cap- stpiare bolts; 3, 4, and 6, bracket bolts. The rear portion of the brackets are extended dotvnward to the deck, the upper descending by a curve and two steps ; the latter being faced by strips of metal, to take the chafe of the handspikes when used on them. The brackets are joined by the Front (F) and Rear Transoms (B), which are jogged into them, the front transom having two bolts (7 and 8), and the rear, one (6) ; the Front Transom, F, is scored out to permit vertical motion of the chase of the gun in the carriage. 892. The Breast Piece, C, is firmly bolted to the front transom and works against the Sweep Piece, D, fitted to ship and nnship from the ship’s side by composition pins and sockets. 893. The Socket Plate consists of a metal plate, with in- dentations or sockets for the boss, F, of the Roller Handspike, K, to take in. It is placed under and at the rear edge of the Transom B. 894. The Roller Handspike, K, consists of a bronze head GUi!f-CAERIAGES. 325 and socket with a hickory handle ; in the head are placed two lujnum-vitm rollers, four inches in diameter, working on a line through the sides of the head. A boss, L, is cast at the junc- ISll iLEPji 41 |I';I ■,ILJ ll':| kM IB ff '': ° i' 1>W rill K r"' ‘1 M <5001- ^ socket, making an angle of 70 ° with the socket is placed the hickory handle, hen in use, the lift of the carriage is greatest with thp OSS, L,- vertical, as it is then raised i inch above the deck. In 326 NAVAL ORDNANCE AND GUA^NERT. service the best result is obtained with the handle at the hip ; care must be used to maintain the axis of the roller perpendicu- lar to the motion of the carriage, otherwise the weight cants the head, causing the rollers to deface the deck. 895. The Truch Axle is let into the Brackets, A, and secured to them by the cap-square bolts, 1, and the brace, 12, through which the other cap-square bolt passes and is set up by a nut. 896. The Tr^iclcs, M, are of lignum^itoe, one calibre in thickness, and retained on the axle Ijy a washer and flange- pin, P. 897. The Saiccer, I, is of composition, and secured to the Rear Transom, B. From its shape it permits a horizontal movement of the lower end of the screw, due to its deviation from the perpendicular, in elevation or depression. 898. Resistance to Recoil. — As the recoil of the gun is to the rear and downward, considerable resistance is offered by the friction excited between the carriage brackets and deck ; the recoil is thus checked in proportion to the 'friction exerted. 899. Manoeuvring the Carriage. — To run the carriage in and out, or transport it about the deck, the Roller Handspike, K (Fig. 208), is shipped under the rear transom, B,and the gun readily moved on its trucks and the roller handspike. 900. Elevation Chtainahle. — Broadside carriages are so con- structed as to give 11° elevation and 7° depression to the gun, and for four different heights of the lower port-sill above the deck, viz., 24, 20, 18, and 16 inches, according to the require- ments of their position. 901. Preservation. — Hew carriages should be kept well painted, and the trucks, axle-trees, and trunnion-holes oiled. Staining or keeping them bright is strictly prohibited. 902. Gun Tacldes are to be of well-stretched manilla, cut of suflicient length to allow' of full recoil, and with end enough to hitch around the straps of their inner blocks. 903. Metallic Gun Taclde Blocks are supplied to all Har- shly and heavy pivot carriages; these have ribs on the hooks, which keep the blocks fair with the falls, and prevent their fouling on recoil. Breechings are of the best three-strand, shroud-laid, and soft, hemp rope, 9 and 10 inch for the larger guns, from 6 to 9 for the smaller; they should be long enough, when fitted, to allow the muzzle of the gun to come one foot inside of the port. Breechings are never to be covered, blackened, or in any way rendered less pliable than when first fitted. 904. Wkodght ieon Caekiage fok VIIITnch Gun. GTIN-CAEIIIAGES. 327 Fig. 209 . 328 NAVAL ORDNANCE AND GUNNERY. Nom.endature. A. — Brackets. B. — Rear Transom. C. — Breast Piece. D. — Sweep Piece. P. — Front Transom. K. — Composition Shoes. L. — Elevating Screw. M. — Trucks. N. — Cap Squares. O. — Angle Iron. 9. — Side Tackle-bolt. 10. — Train “ 11 . — Transporting-bolt. Principal Dimensions. Height of Trunnion 36 inches. Extreme Length of Carriage 56 ‘‘ Width of Carriage 27 “ Thickness of Iron f “ Weight of Carriage 981 lbs. 905. The Brackets, A, are made of f inch Tvronglit-iron ; on tlieir rear lower portion are placed composition shoes, K, which rest npon the depk. 906. The Transoms, BF, of the iron carnage, are of wronght-iron plate, and occupy the same position as in the wooden carriage ; the front transom, F, and rear, B, are riveted to the brackets by angle-iron, O. 907. The Truck iVxle passes throngh the forward lower ends of the brackets, shown in the figure by the dotted line; on these axles composition trucks, M, one calibre in thickness, are placed. 908. Blevating Gear. — At the height of the Breast Piece, D, and just in rear of the Trunnion Holes, are rods connecting the brackets; on these are pivoted a bar, P, whose rear end rests on the head of the male and female screw, L, which works in the bed-plate of the carriage to such an extent that when the gnn has extreme elevation, the screw is considerably below the Bed-plate, B, yet does not touch the deck. 909. Side (9), Train-tackle (10), and Transporting Bolts (11) are of composition, and occupy the same position as in the wood carriage. 910. The Breast Piece, C, is of wood and arranged to be at the height of, and work on, the Sweep Piece, D. The Socket Plate is very similar to that on the wood car- riage, occupying the same position. 911. Cap Sguares, N, are of composition, and secured to the brackets by screw nuts. 912. The Recoil is checked by the friction exerted between the deck and the composition shoes, K, whose rear edges are curved upward to prevent injury to the deck on recoil. GUX-CAERIAGES. 329 913. Wroiiglit-iron is employed in the mannfactnre of gun- carriages for the reason tliat it does not splinter like cast-iron on the impact of shot. Because of their less weight, less space occupied, and iron-liability to injury in service, these carriages promise to entirely supersede the wood carriages. 914. When Parrott guns are mounted in broadside, a Mar- silly carriage is employed, differing from the ordinary carriages in that the brackets are extended farther to the rear to accom- modate the additional length of gun. 915. Pitot Cakeiages. — Object. — Guns whicli are expected to be fired at greater elevations than the ordinary port will admit of, are mounted upon pivot-carriages, which give an elevation of 20° to the gun, and a much larger arc of train than the broadside carriage, the bulwarks of the ship being arranged to let down in order to accomplish it. On Spar Declcs the slide may usually be pivoted amidships, and on both bows when placed forward ; if aft, astern and on both quarters ; and there being fewer obstructions aft, the gun in some cases has a full sweep from one beam to the other. On Gun Declcs the arc of train is somewhat limited, yet con- siderably greater than with the broadside carriage ; tlie ship’s side is arranged to let down like the bulwarks on spar-decks, the fighting pivot being at the ship’s side. 916. The XI-Inch Pivot Caekiage (Wood) is composed of two principal parts, the slide and the carriage proper (Fig 210), the former being secured at one of its ends by a pivot bolt, P. Fig. 212 is traversed by tackles, to bring the guns to bear upon the object, or to change position in firing. 917. The Carriage differs from the Broadside in the suppres- sion of trucks, and the substitution, therefor, of three transoms B (Fig. 214), front, middle, and rear ; the lower sides of which rest upon the slide, and by their friction modify the recoil. 918. The Brackets.^ A, are in two parts, gogged and dowelled together, and they and the transoms, B, are firmly secured to each other by the bolts, O. 919. The Transoms., B, extend beyond the brackets and slide-rails, C, the forward being for the compressors, f, and the rear for the double eye bolted to it, to which the blocks of the in and out tackles hook ; a third called the Breast Transom J is bolted between the front ends of the brackets, and is scored out as in the Broadside carriage. 920. The Journal Plates (g) attached to the brackets, carry rollers on an eccentric axle, extending across, between, and beyond the brackets; levers are supplied to be shipped on 330 NAVAL ORDNANCE AND GUNNERY. (L O H WOODEN PAKT9. N. Battens and Slats. Y. Preventer Breechings METAL PARTS. Z. Upper Pivot-plate. 1. IMiddle Boiler-plate. 2. Eyes for Tackles. 8. Harter Straps. 4. Rail-plates. Fig. 210. — Plan of Xl-Inch Gun-carriage and Slide. BOTTOM VIEW. GUJSr-CAERIAGES, 331 tlie end of the axles, throwing the eccentrics in and out of action. Fig. 211— Plan of SUde for Xl-Inch Gun-carriage. Note . — All metal parts are composition, except bo us. METAL PARTS. 5. Transporting journals. 6. Pivot-plates & guide-flanges. 7 Middle roller screw and bracket- the axles, levers, elevating 921. The Compressor, 214 ), is placed upon the project- ing portion of the Front Transom B, and is worked by means of a screw and handles, binding the transom and compressor-batten D, closely together, by which the recoil is restrained, and kept with- in the limits of the slide. On the rear transom is placed a metal 332 NAVAL ORDNx\NCE AND GUNNERY. saucer, L, on wliich the lower end of the Elevating Screw, K, rests, the upper portion working in the cascabel of the gun. 922. The Slide consists of two wooden rails, C, jogged into transoms, front, middle, and rear (E, Fig. 21d), and connected beneath by slots, and at their ends by cross-pieces called Hurters. (F, Fig. 214.) CARRIAG-E. WOODEN PADTS, J. Breast Transom scored for elevation, as is also the middle transom. XTET.AL PARTS. K. Elevating Screw. L. Saucers. K. Inside journal-plate. 0. Bracket-bolts, SLIDE. METAL PARTS. P. Bossed Sockets, Plates, & Pivot Bolts. R. Middle Training Truck, with Journals. S. Transporting Trucks, Axles, «S: Journals. T. Guide Plates inside of rails. Fig. 213. — Sectional Vie-w of XI- Inch Gun-carriage and Slide. The transoms, E, three in number, project beyond the slide- rails, and have attached to them rollers, G, on eccentric axles ; GUN-CAEKIAGES. 333 the rear for training, ancf the front for shifting the slide, or traversing it. At the proper position in each of the transoms, front and rear, is placed a metal plate, with hole for the pivot- bolt (Fig. 211), 6. 923. The Compressor Battens^ D (Fig. 211), are two strips of oak equal in length to the distance between pivots, which are attached to the slide-rads, C, on the outside ; against these the under lip of the compressor, f, takes when set taut. Fig. 213. — Pivot Compressor. 924. The Ilurters^ F, are the two cross-pieces bolted to the rails, and haAng their inner sides curved for the carriage- rollers to run against, should the carriage get beyond control, going out or in. To these and the slide are attached composition eyes for the blocks of the in-and-out training and traversing tackles. 923. Metal Tracks are laid upon the deck for the slide-roll- ers, G and II (Fig. 214), to run upon, being struck with a radius equal to the distance between their rollers and the opposite pivot. For each position of the slide, in traversing^ bossed sockets, P (Fig 212), are inserted in the deck for the front and rear pivot-bolts. 926. The Bossed SocketyY (Fig. 212), consists of a raised rim of metal around the pivot-hole, a corresponding slot in the slide transom securing the coincidence of the hole in the slide with that in the socket, thus facilitating the entrance and re- moval of the pivot-bolt, W. 927. The Eccentrics y G- and FL (Fig. 214), when out of action 334 NAVAL ORDNANCE AND GUNNERY. allow the slide-transoms, E, to rest upon the deck, and those of the carriage upon the slide. In order to ti-ain or shift the slide, the levers are shipped upon their axles, the rollers, G and H, put in action, thus lifting the slide from the deck, and leaving it free to be moved by its tackles. In the same way the car- riage is lifted from the slide to run in or out. 928. Recoil . — Before firing, the compressor, f, is set taut by the screw, binding the carriage transom, B, and compressor- batten, D, together. When the gun is fired, the recoil is ab- sorbed by the friction exerted between them. 929. The Compressors, f (Figs. 213 and 211), are not intended to eiitii’ely supersede the use of breechings, but rather as an aux- iliary ; the main reliance being placed on the Breeching, which should be shackled to the ship’s side, and not to the slide, as in the latter position unnecessary strain is brought on the pivot- bolt. CARRIAGE. WOODEN PARTS. METAL P.VETS. A. Brackets of two pieces, with jog, d. Cap Squares. a, and dowels, b. e. Trunnion Plates. B. Transoms, projecting beyond the f. Compressor, with screw and lever, rails, front, middh', and rear, g. Rollers and Journal Plates, jogged into brackets. SLIDE. WOODEN PARTS. MET.VL P.VRTS. C. Rails. , U- Shifting Trucks. D. Compressor Battens. H. Training Trucks, both uith jour- E. Transoms ; front and rear, each nals, and eccentric axles, in two parts, middle in one part. F. Hurters, front and rear. Firing to Windward, the compressor, f, should be set just taut eiioiurh to check the recoil and ease the strain on the O breeching. GUN-CARRIAGES. 335 Firing to Leeward^ the gun on recoil has to run up an in- clined plane ; consequently the compression required is very slight. ^YitK the Yessel on an Even Keel, it is usual to set tlie Compressor a certain number of turns, which is known to give the proper compression. 930. Shipping the Levers. — In order that this may be done expeditiously, both axle and lever are marked with a cold- chisel, and should always be hove up past the centre and rest against the wood of the slide or carriage. 931. Transporting. — For transporting the pivot-carriage and slide f]-om one end of a vessel to the other, composition sockets, S, are attached to the under side of each slide-rail ; through these pass square axles, carryiiig at their extremities metal rollers. The axle, being passed through the slide, is lifted on its rollers, the transporting trucks shipped, and the slide lowered ; it now rests on the transporting trucks, S, and may he readily moved to any desired position. (5, Fig. 211.) A Middle Roller, 7 (Fig. 211), has in some cases been pro- vided for the slide of the Xl-ineh gun, which from its great length is liable to sag at the centre. 932. Running out to Leeward in a sea-way, even with pre- cautions and a well drilled crew, there is liability of the gun breaking away and doing damage. To guard against this. Fig. 216. Preventer Breechings, T, are fitted (Fig 210), of such a length as to he just taut when the gun is out, and allow the front carriage trucks to reach but not ascend the curve of the front hurter, F ; for if the trucks should ascend this curve, the compressor-straps must surely give way to the power exerted to separate the carriage and slide by such a heavy weight moving with its velocity. 3G NAVAL ORDNANCE AND GUNNERY. 933. XI-iNCH Ikon Pivot-Cakeiage. — Nomenclature. A. — Slide rails. B. — Transoms. C. — Front and Rear Hurters. D. — Pivot-holes. SLIDE. E. — Transporting Trucks. F. — Slide Rollers. 1, 2, ?}. — Tie Bolts. 4 . — Transporting Axle. CARRIAGE. G. — Brackets. II. — Front Bed-plate. I. — Bear Bed-plate. K. — Eccentric Rollers. L. — I'ront Rollers. M. — Cap Square. N. — Composition plates to increase friction. O. — Angle iron connecting brackets, etc. P. — Bolts for Preventer Breeching. Q — Compressor Plate. R. — Bolts of In-and-Out Tackles. S. — Vertical Transom. P'. P'. — Journal Plates. V Compressor, PRINCIPAL DIJIENSIOXS. Extreme length 15 ft. 7 in. Length between Pivots 11 ft. 10 in. Width of Slide 3 ft. G in. Width of Rails 0 ft. 5 in. Radius of Training Track 10 ft. 10 to, Radius of Traversing Track 12ft. G in. 934. The Slide, A, consists of two rails of double T rolled wroiiglit-iron, 8.87 inches high by 5 inches wide, connected by the tie-bolts, 1, 2, 3. GTJIT-CAERIAGES. 337 935. Hie Transoms, B, are of 1-^ineli wroiiglit-iroTi of the form shown in the figm’e, and riveted to the under side of the rails, A ; they project beyond and have fitted to them composi- tion rollers, F, on eccentric axles, the latter being secured by plates and iDolts ; levers shipped on the projecting ends of the axles put the rollers in and out of action. 936. The Hurters, (7,-are the brass castings riveted to each end of the slide-rails for the carriage-trucks to run against. Each of these carries bolts for the blocks of the in-and-out tackles he- 338 NAVAL ORDNANCE AND GUNNERY. neath them, and to the vertical part of the T rail, are attached brass plates with bolts for the blocks of the shifting and train- ing tackles. 937. Coincidence of the Pi/oot-holes, D, is secured by plates screwed to the slide transoms, B, and distant from each other a little more than the diameter of the bossed socket, indicated in the figure by the dotted circle around the pivot-hole, D. 938. Fo7‘m of Bail. — The wrought-iron rails. A, when first manufactured have the form shown in Fig. 215, but before be- ing placed for the slide the under side of the upper outer por- tion of the T is removed, giving it the form of Fig. 216, in order that the compressor may have a fiat surface to act on. 939. Transporting. — Aboiit ten inches in rear of the front and the same distance in front of the rear trucks are placed the sleeves for the transporting axle and trucks, E, the latter of such a diameter as to sustain the slide clear of the deck when let down from its eccentric rollers, F. 940. The Carriage. — All iron parts of the carriage are made of 1-J-ineh wrought-iron, the journal-plates, rollers, eap-scpiare, trunnion-rests, and preventer-breeching-bolts being of brass. Immediately beneath the trunnion-hole is a vertical iron plate, S, extending down between the brackets to the bed- plate, II. 941. The Brackets, G-, rest on the bed-plates, and they and the vertical transom, S, and bed-plates, II and I, are riveted together with the angle iron, O. 942. The Bed-plates, II and I, extend beyond the brackets, the rear, I, being shaped to a doiible eye, for the blocks of the in-and-out tackles, the front, II, contracting into a plate for the compressoi-screw to work upon. 943. The Journal Plates, P', for the eccentric axle and rollers are riveted to the rear end of the brackets, G, the axle extending across, between, and beyond the plates and carrying rollers, K, revolving in the jfiates. These axles are eccentric in order that, by the use of level’s, the trucks may be placed in or out of action at pleasure. In the former ease the carriage is raised and rests on its rollers, K ; in the latter, it rests on the slide, A. 944. Form of Eccentric Axle. — An ordinary cylindrical axle has cast on it an eccen- tric (Fig. 219), that is, instead of the two cylin- ders being concentric, the axle passes on one side of the centre, X, of Fig. 219 . GUiSr-CAERIAGES. 339 the larger circle. "With the axle at its lowest position, the rollers are out of action ; at its upper position, the carriage is raised by the action of the rollers, a height corresponding to the eccen- tricity of the axle. The front trucks, L, are like those of an ordinary carriage, always resting on the slide and revolving on any movement of the carriage. 9d5. The Compressor^ Y (Fig. 220), consists of a composi- tion casting, Y, having a vent, V', at the centre of the upper arm, through which works a screw bolt, W, with handles. It is placed on the compressor plate, O, its under lip, x, taking against the under side of the upper, T, of the rail. When the « ib". screw is turned, the rail is compressed between the compressor plate, O, and the lip of the compressor, x. The recoil is thus limited by the friction of the different parts. 946. Recoil . — As the bed-plates, II and I, and rail are each of iron, acting alone, sufficient friction would not be excited to keep the recoil within the desired limits. To correct this deti- ciency, after the brackets, G, have been riveted to the bed-plates, plates of composition, 1ST, are screwed to that portion of the bed- plates in contact with the slide, thus increasing the friction to the required point. As the compressors are placed as near as possible to the brackets, the latter are cut out to allow space in turning the handles of the compressor. 947. Necessitij of Eccentric Rollers in the Slide.— slide-rollers, F, are all eccentric for the reason that when shift- ing the slide at sea, with much motion on the ship, it is abso- lutely necessary to have complete control of it ; for should it once get away from the crew, it becomes a serious matter to again confine it. When this is likely to occur, the levers are at once let down, throwing the rollers out of action and the slide upon the deck, when, from the great weight, the friction of the transoms on the 340 NAVAL OEDNANCB AND GUNNERY. deck will almost immediately stop it. This would be impossi- ble were the slide always free to move on its roUerSj and only confined by tackles. ^ 948. 20-pde. Eifle Pivot Caeeiage. — Principal Dimensions. Estreme length f)7 inches. Length between Pivots 88 inches. Width of Slide 23.G inches. Thickness of iron. f inch. Radius of Training Track 83 inches. Radius of Shifting Track 90 inches. Extreme length of Carriage 48 inches. Its construction is essentially the same as the Xl-inch car- riage, the only difference being that the bed-plates of the twen- ty-pounder are of bronze cast with two upright pieces, to which the iron bi’ackets are riveted, while in the Xl-inch, angle iron is used to connect their brackets and bed-plates. Only one tie bolt is used to connect the slide-rails at their centres. As the beds are of bronze the requisite amount of friction can always be obtained by the compressor. (Figs. 221 222.) 949. XY-iNcn Tukket Carriage. — ■ Nomenclature. a. — B ox Bracket. B. — Bed Plate. C. — In-and-out gear. D. — Compressor. E. — Cog-wheel. F. — Guides. G. — Carriage-braces. II. — ‘‘ RoUers. I. — Iron rails. K. — Balance-wheel. L ' . — El e vator- rest. M. — Curved lever. N. — Front Transom. O. — Rear “ O'. — Sleeve. O”.— Nut. P. — Small Cog- wheel R. — Compressor Plates. GUN-CAERIAGES. 341 950. The Slide consists of two heavy iron rails, I, extend- ing from one circumference of the Tm*ret to the other, and firmly secured to it ; on these run the carriage rollers, II. Be- tween the two iron rails, and parallel to them, are four wooden joists, L, called compressor-battens, each six inches square. (Fig. 225.) 951. The Carriage is of wrought-iron. The brachets. A, being of the box form, while the bed-plate, B, and front, N, and rear O, transoms, are of single plate-iron. All parts of the carriage being riveted together, and the brackets. A, sup- ported by the two traces, G. At each under corner of the bed- plate, B, is placed an angular metal plate, F, called a guide, pre- venting lateral motion of the carriage on the rails. 952. The Li-and-Out Gear, C, consists of an axle extend- 34:2 NAVAL ORDNANCE AND GUNNERY. ing across the front end of the carriage, caiTjing rollers, H, placed in the brackets. Just inside the outer bracket, the axle lias on it a large cog-wheel, E, a shorter axle placed hio-her in tlie bracket, working the larger cog-wheel bj means ”of the smaller cog, P, in its inner end. To the outer end is fixed a crank, C', to be worked by hand. 953. The Carriage Rollers, II, are four in number : the for- ward two attached to the axle of the “ In-and-Out Gear,” and the rear to short axles in each bracket. GUN-CAERIAGES. 343 954. The Compressor Gear, D.— To the bottom of the carriage is piveted an iron plate (P. Fig. 225), whose ends project doAvn- ward through the Bed-plate, B ; on these are hung curved levers, M. To one is pivoted a sleeve. O', and to the other a nut, O". A rod passing through the bracket and the sleeve has on its end a thread, which works in the nut on the opposite lever ; lateral motion of the sleeve on the rod being prevented by collars outside the bracket. The rod has attached to it a bal- ance-Avheel and crank, K. 955. The Compressor Plates, R, five in number, are of ^ inch iron (Fig. 224) ; their ends project through the Bed-plate and are keyed ; tlieir lower portions extending downward between the wooden joice or battens, L (Fig. 225), parallel with them and the iron rails. 956. Action of the Compressor Gear. — As the balance- wheel, K, is revolved it carries the rod with it, causing the upper ends of the curved levers, M, to separate, and the lower to approach ; the latter press against the two outer compressor- battens, L, forcing them out of parallelism, and binding the iron plates, R, and battens, L, firmly together. When the gun is fired its recoil is absorbed by the friction of the several parts. Reversing the motion of the wheel separates the plates and battens, leaving the carriage free to move on its rollers. 957. Elevator-Pest. — Idie elevating screw usually rests on the projecting portion, L', of the bed-plate. In some carriages a semicircular plate is riveted to the rear transom, having on 344 ORDNANCE AND GUNNERY. its circnmference a vertical plate connected to a fore and aft plate, tlie two supporting an iron saucer, on whicli the lower end of the elevating-screw rests, the upper end passing through the cascahel of the gun. 958. The Ilurters are flat plates of iron bolted to the rails, to prevent the carriage going beyond the proper point, out or in. 959. Ele/vation. — The port is cut from the circumference, of the turret, of such dimensions as to allow of 10° elevation and 5° depression, and permit only vertical motion of the muzzle of the gun in it. 960. The Port Stopper, S (Fig. 226). — ^When the gun re- coils after firing, the open poi't, Z, is free to the entrance of an enemy’s shot. To protect those in the turret while loading the gun, a heavy mass of iron, S (Fig. 226), curved to allow the gun to pass going in and out, is pivoted at the top and bottom of the Turret, and worked by a lever and tackle. As the gun recoils, the Port Stopper is swimg around, covering the port, and swinging sufliciently near to the inner circumference of the Turret to prevent shot fired at an angle from entering the Turret between it and the port. The gun being loaded the port-stopper is swung around and the gun run out. 961. Loading. — The loading hatches, T, are placed abreast the rear of each carriage when in, the communication between the turret and below being open when the guns are pointed abeam. As the projectiles are very heavy and the space in the turret limited, mechanical appliances are made use of to carry the projectile to the muzzle of the gun. These consist of a long iron rod, U, pivoted above the loading-hatch, the movable end being fitted to slide on a guide at the top of the turret abreast the muzzle of the gun. The shell-tackle is hung on the ]’od by its strap, which carries a roller travelling on the rod. When the gun is to be loaded, the shell is whipped u]^ to the requisite height, the whip hitched, and the projectile run to the muzzle of the gun on the rod. After each tire, the turret is revolved so as to bring the gun abeam and leave the loading-hatches open. 962. The Hammer and Sponge. — The port being closed by the port-stopper, S, an ordinary handle cannot be used, hence that in use consists of a number of sections which con- nect with each other by a spring catch. The rammer or sponge, beiirg fixed to the first section, is entered and the next section prrt on ; in this way the whole is made up and the gun sponged or the projectile^ pushed home. In removing the sjronge or rammer, each section is taken off as its catch comes to the muzzle. 963. Pointing. — The guns being fixed in the tuiTet, point- GUN-CAIIRIAGES. 345 ino- is effected by revolving it until the guns bear upon tlie ob- ject, which is determined by the person at the sight-hole, T. This consists of a circular opening of about two and a half or three inches diameter cut through the turret, parallel to the rails 346 NAVAL ORDNANCE AND GUNNERY. on which the carriage runs. In this opening is placed an in- strument (Fig. 227), consisting of a hollow cylinder of brass, having a portion of its circumference at the outer end cutaway, and a vertical piece soldered to it. The inner end of the cyl- inder is closed, and a vertical slit cut in it. The officer at the sight-hole, loohing through the sHt, brings the vertical piece on the object, when the engineer at the starting-bar ceases to re- volve the turi'et. 964. Sights . — The gun besides being fitted with the ordi- nary sight has a trunnion-ledge and level (Fig. 228). This con- Fig. 228. — Trunnion-ledge and Level for XV-incli Gun. sists of a brass plate pivoted to the centre of the trunnion, the upper portion ending in a pointer, the lower having a slot and thumb-screw working in it. A ledge projects from the plate, on which is placed a spirit-level. The upper face of the trun- GUN^-CAEIIIAGES. 347 nion is graduated for a certain number of degrees of elevatiou and depression. To elevate the gun, loose the thumb-screw and move the pointer to the number of degrees desired ; tighten the screw and lower the breech until the bubble of the spirit-level marks zero. The gun then has the elevation indicated by the pointer ; re- versing the operation, depression is obtained. 965. The Turret when not in use rests upon the deck, a raised rim of metal protecting its lower edge from being jammed by shot. A. shaft, L, passes down through the vessel to the kelson, with arrangements at its lower end for being raised by a wedge and ram. When this is done the turret is raised from the deck and rests on the shaft, and is revolved by steam gearing. The turret is composed of a number of one- inch wrought-iron plates, firmly bolted together, making a total thickness from eleven to thirteen inches. The people in the turret are protected from the fastening bolts, which ai-e likely to fly out on the impact of heavy shot, by a casing of iron placed a few inches from the inner circumference of the turret. 966. Above the turret is placed an iron pilot-house, from which those controlling the movements of the vessel may see by the bevelled openings in its circumference. In some moni- tors the guns and their carriages have been arranged to work by steam, and the turret to be raised by an hydraulic-pump at- tached to the lower end of the shaft, instead of the wedge and rams. This would seem to be a decided improvement over the old method, or that generally in use. 967. Moktae Caekiage (Fig. 229). Nomenclature. 1. — Circle. 2. — Bracket. 8. — Mortar. 4 — Face. 5. — Trarmion. 6. — Carriage Steps. 7. — Eccentric Socket. 8. — Carriage Boiler. 9. — Circle Eccentric. 10. — Hurter. 11. — “Ratchet. 12. — Clovis lug. 18. — Stringers. 14. — Rear Transom. 15. — Heavy Cro.ss-bolt. IG. — Lever (eccentric). 17. — Circle-lever. 18. — Guides. Principal Dimensions. Length of Carriage 9 ft. 4 inches. IVidth of Carriage, Front 4 “ 9 “ Vv'idth of Carriage, Rear 4 “ G “ Height of Trunnion 3 “ 2 “ Diameter of Circle 11 “ G “ 968. The Carriage . — In consequence of the high angles at which mortars are fired, their carriages differ from ordinary gun- 348 NAVAL ORDNANCE AND GUNNERY. carnages in tliat they rest for their whole length on the circle or platform. 969. The Brackets, 2, are each made of two pieces of boiler- iron, separated from each other by flat bars of iron placed at suitable intervals, to stiffen the brackets in the direction in vdiich the weight and recoil bear upon them. All parts are held together by screw-bolts. The brackets are united to each othei by the steps, 6, axle-tree, 8, two ii’on stringers, 13, crossing 20 Fig. 229. diagonally under the piece near the bottom of the brackets, a rear transom, 14, and a heavy cross-bolt, 15. 970. 27ie Transoms . — The steps, 6, serve the purpose of front transoms, and are made by laying plates of boiler-iron hor- izontally ; the lower being nearly twice the size of the upper, and bolted to the brackets. The upper is scored out in the rear to allow for the curved form of the piece. The rear transom, 14, is a plate of iron placed vertically between the brackets in rear of the piece, and is fitted with an elevating loop, which serves as a fulcrum for the elevating lever. 971. llunning In and Out . — The motion of the carriage in running in or out is obtained by a pair of rollers, 8, on an eccen- tric axle, placed underneath and a little in front of the curve GTJiSr-CAKRIAGES, 319 of the ti’unnions. On the projecting end of the axle a lever, 16, ships, by which the rollers may be thrown in or out of ac- tion. The motion of translation of the carriage is given by handspikes placed in holes in the circumference of the trucks, 8 ; the latter being first thrown in action by the lever in the socket, 7, The movements of the carriage are directed by com- position guides, 18, screwed to the circle and fitting over flanges at the bottom of the brackets. A heavy piece of oak, called the Hurter bolted to the circle, limits its outward movement, the brackets being curved to fit the slope of the hurter. 972. The Mortar Circle, (Fig. 230). — The naval mortar is , Fig. 230. generally used on board schooners built for the purpose. It is carried amidships, and that part of the deck on which the cir- cle rests is raised about three inches above the remainder. The circle is a circular platform made by two thicknesses of oak beams ; the upper, called the deck planks, are laid at right angles to the direction of the recoil ; the lower layer, called sleepers, being laid parallel to the axis of the piece. The two layers are bolted to each other horizontally and vertically, and strength- 350 NAVAL ORDNANCE AND GUNNERY. ened circumferentially by two steel hoops, 19 and 20, one at the top and bottom. This disposition of the planks offers the greatest resistance to recoil. On its upper surface are bolted composition tracks, 22, for the carriage rollers. A heavy bolt through its centre, working in a frame-work beneath, keeps it in position. 973. Eaentric Rollers (23) are four in number, and placed at equal distances in the circumference of the circle. (3n the ends of the axles, curved levers (IT) ship, by which the circle is raised on its rollers, and may be revolved about its central pivot by tackles hooked to eye-bolts in the circle and deck. 971. The Deck is strengthened underneath the circle by a column of heavy beams laid across each other, and extending from the kelson up to the under side of the deck. 975. Howitzer Boat-carriage. (Wood.) Fig. 231. Nomenclature. A. — Bed. B. — Slide. C. — Compressor Plate. D. — Compressor Bolts. E. — Compressor Handlea. F. — Lugs for Loop. G. — Bed-plate. H. — Elevating Serew. K — Ath wart-ship Sweep L. — Pivots. M. — Pivot Plates. N. — Fore and aft Sweep Piece. ' 976. The Slide consists of a wooden top-piece resting on two side pieces tvliich are slightly inclined from the vertical and slope at each end towards the end of the top-piece, where metal plates are attached for the pivot-bolts, of the carriage. In the top-piece, and extending iiearly its whole length, is a slot in which move the bolts, D, and wooden guide of tlie Bed- plate. The bolts, 1), are square at their lower ends and pass through the bed-plates, up the slot, and through the bed, A. On their upper ends a thread is cut, and corresponding nuts GTm-CAEEIAGES. 351 ■with handles, E, work on a composition plate let into the wood, flush with it. On this the nuts press when screwed down, compressing the slide, B, between the bed. A, and bed-plate, G, and controlling the recoil by the friction of the difi'erent parts. 977. The Compressor is composed of the several parts C, D, E, G, and A ; that is, it consists of a combination of all, resulting in friction between certain parts and modiflcation of the recoil. When the compressor handles are set as taut as the strength of an ordinary man will allow, it always suffices to keep the recoil within the limits of the stop in the slide. In order that the compressors shall invariably perform their func- tion, the surface of the parts in contact must be plain but not smooth. The Bolts, D, being passed through the bed-plate loosely, were the handles taken off, they would drop out ; to prevent this, small buttons are placed on the under side of the bed- plate, G. The Lugs, E, are cast of composition ■with a cavity to re- ceive the loop of the gun, which rests in it, and is retained there by a bolt passing through the lug and loop ; the latter being secured by a pin and washer. 978. Elevation is obtained by a screw, II, passing through the caseabel of the gun ; its lower end has a knob Avorking in a box fitted to the bed; a disk a few inches above the knob serves to turn the screw. 979. The Boat-carriage should be so placed in the bow of the boat as to carry the muzzle of the Howitzer just above and clear of the gunwale and stern of the boat. Two pieces of yellow pine, K, are laid athwart-ships so as to bear the carriage at that height, and on these it traverses when pivoted at the stem. 980. Pivots . — Six pivots, are pivoted to each boat ; stem, each bow, stern, and each quarter. The tAvo iron plates, M, of each pivot, being Avelded together and bolted to their positions, the distances between the stem pivot-plate, and that of either bow, must correspond to the distances betAveeu the pivot-holes in each end of the slide ; they are thus at the points of an equilateral triangle, which enables a rapid and certain manage- ment of the gun in changing its position. (Fig. 232.) 981. Pivoting . — If the carriage be pivoted at the stem, it may be brought to either boAv, by pi\*oting the rear end of the slide to one boAv, remoA'ing the stem pivot, and training the forward end to the opposite bow ; to change it from the bow to 352 NAVAL ORDNANCE AND GUNNERY. the stem pivot, the process is reversed. To sustain the carriage when pivoted at the how in sweeping-, a piece of yellow pine scantling, N, is placed fore and aft amidships and mortised into the rear cross-pieces. The stern of the boat is similarly arranged, bnt from the form of the boat at that part there is more space, and the gnn can always be worked easier there than forward. 982. The Ikon Boat-carkiage.— (Fig. 233.) Wrouglit-iTon J3 oat-carriages are now being made and supplied to vessels in service, the dimensions being tlie same as those of the wooden carriage, in order that they may replace them and not entail any change in the present fittings of boats. 983. Nomenclature. A. — Slide B. — Bed. C. — Bed-plate. D. — Lugs for Loop. E. — Elevator Box. F. — Compressors. G. — Rests of Slide. Principal Dimensions. Extreme length Length between Pivots Length of Bed Length of Bed- plate Width of Bed Extreme width of Slide Height of Loop-bolt GSil inches. 64.1 “ 87 “ 26.3 “ 7.75 “ 11.75 “ 13.05 “ 981. The Slide. A, consists of a wrought-iron plate, riveted to two wrought-iron Z-shaped sides, the heads of the rivets GUN-CARRIAGES. 353 bein^ taken oS to present a plain surface to tbe bed, B. The iipper plate of tbe slide contains a slot extending nearly its whole lena:tb. Between the ends of the slot and slide are holes for the front and rear pivot bolts. 985. The Bed Plate . — Between the side pieces, a composi- tion bed-plate, C, travels forward and back ; to this plate are attached bolts, having a thread cnt on their upper ends ; these pass through the slot in the slide and holes in the bed, and 0 D \d ik ,u Fig. 233 . have working on them corresponding nuts with handles by which the necessary compression of the slide between the bed and bed-plate is produced, thus modifying the recoil. 986. The Bed., B, which rests on the slide, A, is a bronze cast- ing, consisting of a plate having on its upper surface projecting pieces, D, called the lugs, which have a cavity in them for the loop of the gun ; the elevator box, E, and holes for the compres- sor-screws. 987. Fiecoil.—K^i\xQ slide is of wrought-iron, while the bed 354 NAVAL OEDNANCE AND GUNNEET. and bed-plate are of bronze, advantage is taken of the friction exerted between the different metals to check recoil. This is accomplished more effectually by having the frictional sur- faces of different kinds of metal, than when only one kind is emplojmd. 988. The Sides curve upward at each end to allow space be- tween the carriage and pivot-plate, and to facilitate its move- ments. By reference to the rear elevation of the carnage (Fig 233;, the manner of riveting the top plate to the Z-shaped sides will be readily understood, and that the slide rests on the lower por- tions of its sides, which, being 2-| inches wide, give abundant stability to the carriage in training. Three tie-bolts, not shown in the figure, placed at the front, rear, and centre of the slide, connect the sides and prevent lat- eral motion. As these are placed low down, they do not inter- fere with the movements of the bed-plate, C. These carriages are considerably lighter than the wooden carriages ; and being of iron, are consequently less liable to injury from exposure in service. 989. The Howitzek Field-caeeiage. (Fig 234.) 990. The Carriage is of wrought-iron, its weight being re- duced to the least limit, about 500 lbs. ; the axle, has cast at its centre lugs to receive the loop of the gun. 991. The Trail, B, is curved, being bolted to the axle, and supported on either side by the rod braces, C, which bolt to the trail and axle. At its rear end the trail expands, and is slotted for the trail-wheel, E. This is hung on a hollow axle, to which is attached on each side a guide that is hinged at the forward part of the seat ; this allows the trail-wheel to be thrown back on the trail and put out of action. A pin chained to the trail passes through it and the hollow axle. With the wheel in the slot and confined by the pin, the trail of the carriage rests on it, as in Fig. 234. Beyond the slot is a socket for the trail hand- spike. 'The elevator-box is like that in the boat-carriage. 992. The Field Carriage ashore. — As it is designed to oper- ate independently of a limber, light composition frames, having pins projecting upward, are attached to the ti*ail and axle on Nomenclature. B. — Trail. C. — Trail-braces. D. — Lags. H. — Elevator-box. E. — Trail- wheel . F. — Socket. G. — Elevator. K. — Ammunition boxes. 6TUT-CARRIAGES. 355 each side, on which the ammunition boxes rest. Their bottoms are fitted with metal sockets for the projecting pins of the frames. The carriage is di’awn by means of a drag-rope hooked to a becket near the sockets ; this rope has inserted at suitable intervals wooden handles for the crew to hold. At the hook are two shorter ropes, called guide ropes, by which the direction of the trail is governed when on the march. To the axle is hooked a short drag-rope, which is used as a check, or holding- back rope in steep d^escents. Fig. 234. "When in action, the trail-pin is removed, and the trail-wheel thrown back on the trail, allowing the trail to rest upon the ground, which serves to check the recoil. 993. The Field Carriage in the Boat is placed aft wdth its trail over the quarter (Fig. 235), so as not to impede the move- ments of the coxswain. For convenience in running it forward or aft, as when shifting the gun from the boat to the field-car- riage, or the reverse, three wooden tracks or skids are laid fore and aft on the thwarts, and bolted. The centre being for the trail, the other two for the carriage-wheels. 994:. For Landing the Field Carriage^ short skids projecting ahead to the beach or landing are provided ; these hook to the bows of the boat, and are braced at the shore end by a long iron rod and hook ; on these the carriage- wheels run. 995. Implements. — With the field and boat carriage are sup- plied Eammer, Sponge, Ladle, W orm^ and Handspike ; two of 35G NAVAL ORDNANCE AND GUNNERY. tliose mentioned being on the same handle, one at each end. The latter answering a double pui-poss, first as a trail hand- spike, and second as a shifting-spar ; having fitted to its centre a metal hook used in the groin et around the neck of the cascabel in shifting, mounting, and dismounting the Howitzer. Section II. — English If aval Gun-Carriages. 996. The BKOADsmE Scott Cakkiage. Nomenclature. A. — Bracket. B. — Bow Compressor. C. — Elevating Gear. c. — Releasing Lever of Elevat- ing Gear. D. — Chain Nipper of In-and- Out Gear. E. — Carriage Wedges of Bow Compressor. b. — Eccentric Lever and Gear. F. F. — Coned and Grooved Rollers. G. — Metal Hook for lip of Front Track. H. H.H. ' — Raised Metal Tracks. K. — Cogged Training Track. L. — Preventer Pivot Bar. M. — Slide Wedges of Bow Compressor. N. — In-and-out Gear. O. — Endless Chain. P. P. — Winches of Training Gear. R — Shaft of Training Gear. S. — Training MTieeL S'. — Cog-track. T. — Shaft Support. W. — Training Brake. X- — Hydraulic Jack. Y. — Compressor Pawl. Z. - — Buffer Blocks. 997. The Carriage is of the box girder description, of mixed wrought and cast iron (wrought outside, and cast inside). GUjST-CAEEIAGES. 35T and, unlike tlie old pattern, is long and low, thus remedying the rearing back tendency of short and high carriages, and the con- sequent downward strain on the deck and slide, and giving a Fig. 236. much greater surface to absorb the concussion or shock of re- coil. As the carriage is made so much lower, the slide is corre- spondingly raised, thus maintaining the same heiglit of the axis of the trunnion above the deck, and allowing room for tlie cogged gear beneath the slide. 998. The Slide is of girder wrought-iron, filled in on each side with teak (see Fig. 239), with no head- plate, thus allowing the gun to be run farther out and facilitating point- The upper surface of the slide is an inclined plane, having an angle of from 3° to 5° for ordinary broad- side guns, which serves to check the recoil, and facilitates the running out of the gun. 999. The Dech (Fig. 237) beneath the slide has bolted to it four (4) metal tracks, H, H, II', and K ; the first two, H, are usually solid, and have cast on them upper surface a rib to take the groove of the slide-rollers F. These tracks are raised at their extremities, to allow for the deck curv- ature, and thus prevent alteration of the sights in extreme training. The track, K, is cogged fo)’ the cog-training wheel, and may be of brass or iron, usually the former. The track H' is of metal, having cast on its forward side a strong projecting lip, under which the metal hook, G, attached to the slide, takes. NAVAL ORDNANCE AND GUNNERY. 358 1000. The Pivot (Fig. 238) is independent of the ship’s side and any accident that might occur to it, as -the recoil is received from the coned and grooved rollers, F, of the slide, Fig. 338. and the metal hook, G, by the three metal tracks, H. Were the shock received by a pivot at the side, a heavy shot impinging there might and probably would prevent the further service of the gun. 1001. The Dimensions of a 12-inch 25-ton Broadside Gun- carriage are as follows : Length of slide, 15 ft. 6 in. ; width, 6 ft. ; length of carriage, 8 ft. 9 in. ; height of trunnion above the deck, 5 ft. 1^ in., the relative length of slide and carriage permitting a recoil of 6 feet. Fig. 239. — Section at Compressor. Fig. 340. — Rear view of Carriage. Fig. 241. — ^Rear view of Slide. Fig. 243. — Front view of Slide. GUN-CAKRIAGES. 359 For other guns the dimensions are similarly proportioned. 1002. TliJi Self-Acting Bow Compressor^ B, consists of strong metal bows hung by their centi-es through a hole in each side bracket. (See Fig. 24:6, B.) From the carriage short wedge-shaped plates, E, are suspended between hard wooden haulks, and wedge-shaped iron plates fixed to the girders of the slide M. A wheel with screw attached works through the outer end of the metal bow, setting the plates firmly together (Fig. 239). The circumference of the wheel is notched to re- ceive pawl, Y, attached to the bow at the height of the wheel. The weight of the gun, when let down from its eccentric rollers, drives the up])er wedge, E, tight between the lower ones, M, and^the downward concussion of firing tends to drive them still more together, while the action of lifting the gun- carriage on its eccentric rollers, to run it out, releases the wedges because of their shape. 1003. The Elevating Gear, C (Fig. 238), consists of a cogged arc attached to the side of the breech of the gun, acted on by a cog-wheel inside, and drum outside the bracket, and fixed to the same pinion. Through it, sockets are pierced in the periphery of the drum, into which pointed handspikes are placed in elevating or depressing the gun — a clamp outside the drum nipping it at the desired elevation ; a holding-pin attached to the bracket assists the clamp. 1004:. The Eccentric Gear, h (Fig. 238), consists of a shaft across the rear end of the carriage, car- rying the eccentric rollers, placed in the under and rear side of the brackets. A cog-wheel on the inside, worked by levers on the outside, acts on a V -shaped cog when on the eccentric axle, throw- ing the eccentric rollers in and out of action. A pawl, or releasing lever (Fig. 238), is provided for holding the eccen- tric in action. The latest carriages have their eccentric rollers worked by an hy- draulic jack, X, on one side, and cog- wheels and drum on the other (Fig. 24:3) ; with the jack the heaviest gun may be easily lifted by one man. 1005. The In-and-Out Gear (X, Fig. 237). —The carriage, being lifted oiit on its rear eccentrics as before described, is run in and out by means of spur wheels and pinions fixed to the rear end of the slide on each side, worked by Avinch-han- dles, which drive a shaft across the rear end of the slide. Two Fig. 243. 360 NAVAL OEDNANCE AND GTLNNTEET. endless chains, O, run around spockePioheels fitted to this shaft, and the forward end of the slide (that foi*ward having an elastic shackle) by which the chain is kept taut at all times, the upper part of tlae chain passing through holes in the car- riage, When not in use, the chains are not attached to the carriage ; but when required, the upper part of each chain, 0, is caught by an arrangement called the chain-dipper. (See hig. 244, D.) This consists of an eccentric in the bottom of the carriage, worked by a lever, by which the eccentric catches the chain in the teeth fitted to the upper side of the box in the bottom of the carriage, and through which the chain passes. When the In-and-Out Gear is moved with the chain caught, it cari-ies the carriage with it, either in or out. By throwing the lever up, the chain is released, and the carriage ceases to move. Buffer Blochs, 2i (Fig. 237), of india rubber are placed at each end of the slide to receive the carriage should it move out with tackles should occasion require it. 1006. The Training Gear, li, S, T, W, (Figs. 238, 241, 245), GUN’-CAIIRIAGES. 361 consists of a crown-wheel and bevel pinions, taxed to the rear end of the slide, woi’ked by winch-handles, which drive a shaft, R, extending forward beneath the slide, and armed at its for- ward end with a cog-wheel, woi’king in the cogged ti’ack, K, on the deck. For Extreme Train, when the vessel is rolling deep, or at any time that additional power is reqnii-ed, a second driving- pinion is provided, giving twice and a half the power of the single pinion ; a pawl, to lock the training-geai’, when the gnn is stationai-y, and a bi’ake, W, to control the rapidity of train- iiag. The latter consists of a dimiiuitive bow compressor applied to the training-geai*, near the winch-handle (Fig. 21-5, W). Eye-bolts for trahaing are fitted to the slide to be used with tackles. 1007. Advantages of Mechanical Caueiages. — The shocJc of recoil is I’eceived by metal ribs cast on tlie npjaer surface of the heavy solid metal tracks, H, and by a sti’ong metal hook, G, attached to the front end of the slide, whicli ties it down to the deck by the hook, taking under the strong metal lip of the front ti’ack, H'. By this means the shock of recoil is not received at any single point, but is distributed over the sui’face of the three tracks, and thence to the deck, and thus the tear- ing or rending effect is much less at any one of these points than it would be on a single pivot-bolt. Again, the compressor wedges, E and M, are not only wedge-shaped vertically, but are slightly so longitudinally, by which arrangement the I'ecoil is gradually checked or absoi’bed, instead of being suddenly re- sisted as with ordinai’Y compressors. 1008. The Bow Compressor, B, is self acting, fi’om its pecu- liar construction. The compi’essoi’-plates being wedge-shaped both vertically and horizontally, lifting the carriage must nec- essarily ease them ; lowei’ing the carriage, the reverse occurs. Therefore the wheel being set to a point (determined by practice) and pawled, the mere running out of the gun, in one case, and firing in the othei’, operates the compressor. So that the com- pression by the wheel having once been determined, the gam may be fii-ed a long time with- out the compression being altered. Experiments prove that one man may set the wheel so taut 362 NAVAL ORDNANCE AND GUNNERY. as to reduce the recoil to 3 feet, one half that allowed by the slide. By this arrangement the danger occurring with most compressors, viz., that the compressor-man will set the com- pressor too taut or not enough, is entirely obviated ; and any compressor not self-acting is liable to be worked so, and the gun and carriage seriously injured thereby. 1009 Training Gear . — As this gear is attached to the rear end of the slide, it is much less exposed to an enemy’s shot than at the ship’s side, or in any other position about the slide. And at night, or when smoke and noise would liinder the men at the side of a gun worked by tackles from seeing or hearing their gun-captain, the captain of a gun, fitted with mechanical training gear, regulates the movements of the slide with the greatest ease, as the motive power, viz., the men at the winch- handles, are within a few feet of him. Again this position of the motive power enables him to train and keep his gun on the object as it is being run out, and save much valuable time, especially in firing at a moving object. In practice the con- trolling brake, W, has answered its purpose very well, and the training gear greatly increases the rate of firing under any conditions, its advantages being best shown in bad weather. AVith it and the in-and-out gear, much manual labor is saved, the crew being reduced thereby to one-third. In training guns by tackles and handspikes, the motion is verjmrregular, the guns being many times jumped beyond the desired point, while with the Mechanical Gear the greatest nicety is obtained. 1010. High and Low Carriages . — The effect of reducing the height and increasing the length of carriages may be il- lustrated by assuming an extreme case. Imagine a very high and short carriage on one slide, and a very long and low car- riage on another. The gun being fired horizontally, the shock of recoil in the first instance will be communicated by a lever, represented by the vertical height and length of the car- riage, and the leverage being great, the shock will be more powerful, while with the long, low carriages the leverage is much reduced, and consecpiently the shock on the slide, and a longer surface is provided for absorbing the recoil. Hence the same decks will sustain the firing of heavier guns by the use of long, low carriages and high slides, preserving the axis of the gun at the same height above the deck. 1011. The Didpkessiox Cakeiages (Fig. 21T). — These were designed by Capt. Scott, 11. JS[., for the smaller upper guns of Broadside vessels, as an auxiliary defence against Torpedo or at- tacking boats very near or alongside the vessel, as at such times the main-deck guns do not possess sufficient depression to protect GTJN-CAERTAGE9. 363 her against them. Referring to Fig, 2i7, the slide, A, is of iron and has an inclination of 10° to the front. To the slide is at- Fiq. 247. tached the cylinder of an hydraulic compressor, B, the piston being fixed to the front end of the carriage, which is of iron; an elevating arc, 0, attached to the gun and worked by a pinion and wheel instead of the drum and handspikes in use with heavy guns, permits of 20° elevation and 30° depression. A clamp fitted to the axle fixes the gun as desired. Tlius with the ship on an even keel, projectiles may be thrown 100 ft. high, at 100 yards’ dis- tance, or into a boat as near as 13 yards from the ship’s side. The great amount of depression obtained makes them a very use- ful addition to Broadside Iron-clad armament, as with the ut- most depression obtainable with the Broadside carnages, the shot would fall over twice as far from the ship’s side. Without these depression carriages, there would be left around the ves- sel a free zone of fire of considerable size, in which attacking 364 NAVAL ORDNANCE AND GUNNERY. boats might lie with perfect immunity from the vessel’s hea’^y guns. 1012. The Eng- lish Tueeet Cae- EiAGE. (Figs. 248, 249.) The Slide con- sists of four wrought- iron girder beams, A, built into the Turret below the deck (see Fig. 248), consti- tuting strengthening struts, and forming a part of the ship. These fixed girders have an inclination of about 3°, and form slides on which are mounted two com- pound pivoting gnn- carriages, the train- ing being effected by the revolution of the Turret itself. The only point of piinciple in which the Turi-et differ from the Broadside carriages, is in their possessing compound vertical pivoting gear, to minimize the vertical area of the port. To accomplish this, the carriage and slide with tlie gun were lifted bodily to set heights by means of screws working irregu- larly, involving considerable loss of time. It is now obtained by lifting the gun only. This is effected by supporting the gun in wrought-iron blocks, susceptible of vertical motion in the brackets. These blocks are united beneath the gun by a curved transom acted on beneath its centre by the ram of an hydraulic jack attached to the bottom plate of the carriage, which raises the gun bodily about 6 inches per minute. Iron props of different lengths are used to support the trunnion-blocks in the different positions in which it is intended to fire. 1013. Elevation . — On each step the elevation and depres- sion is regulated by elevating gear, differing from the Broad- Gim-CAERIAGES. 365 side gear, in that it is adapted to use with the axis of the gun at the three different heights ; a single man at the eascabel of the gun works the pinion and spur-wheel, which raise or lower the gun along the cogged arc, or elevating-bar. The steps are so arranged that the upper gives no elevation and 7° depres- sion, the bottom step 15° elevation and. no depression ; the middle or ordinary fighting step gives 9° elevation and 2° de- pression. This division of step may be changed at any time, by substituting iron props of other heights. 1014. The Carriages are adapted to the circular form of the tiu’ret by lengthening the minor bi’acket of each, and both are so reduced in front as to leave considerable space betw^een them and the turret, thus rendering them, like the broadside car- riage, independent of concussions or indentations of the armor*. 1015. Recoil . — The shock of recoil on the trunnion-blocks is distributed over large bracket sirr-faces by the wrought -iron guides in w’hich they move. That from the carriage is conveyed to the girders by the long brackets of the carriage, whose inner plate of cast-iron resting on the girders form excellent frictional surfaces. 1016. The Turret has a spindle at its bottom extending downward a short distance into a strong framework built for it ; the lower edge of the turret rests on coned rollers, connected by rods with a tiange or collar on the spindle. The whole being protected by a shield (Fig. 218). It is revolved by machinery worked by steam or by hand power ; usually both are provided. If worked by hand, the handles by which the power is applied are placed on the deck below, outside the turret, requiring with eighteen men about eighty seconds to perform one-half revolu- tion ; with steam, eighteen seconds. 1017. The In-and-Out Gear consists of a shaft canying two endless chains, connected and detached from the carriage in the same way as with the Broadside carriage. The shaft extends through the iron girders and the sides of the turret, to which handles are fixed to be worked by the men outside. It is arranged in halves and connected by a coupling, so that each gun may or may not be worked separately. As nearly twice the power is required to run in and out a Turret gun as a Broadside, the gearing is arranged to multiply the manual labor to the desired extent, with the Turret one hundred and fifty times and Broadside ninety. Elastic Buffers are placed at each end of the girders or slide, to check the gun should it go in or out violently. 1018. Pointing is efiected by sights on top of the turret, on which allowance is made for the heio-ht abov*e the sun. Inaceu- O O SG6 NAVAL ORDNANCE AND GUNNERY, racies in the parallelism of the sights and axis of the gnn are so far compensated for hy the greater distance between the front and rear sight (Turret), that with rolling motion, better shooting is sometimes made than with the short radius sights on the gun itself. By reference to the figure, it will he seen that the same compressor and in-and-out gear are used with both Turret and Broadside carriages. When the Turret is fixed and the gun movable, the latter rests on a turn-table worked by steam, which brings the gun to the port, the training being effected by the mechanical gear. 1019, The Theket Indicatoe. — With Turret guns, extreme depression can only be given when aiming directly abeam, and as the gun is pointed forward or abaft the beam, a correspond- ing reduction of the extreme beam depression occurs. Tliere is also great liability of firing through the decks or shooting away ngging, etc. To obviate this danger and enable the person Gim-CAERIAGES. 367 pointing tlie gun, either on top or in the turret, to point the gun at night or in the day-time, clear of the deck and all obstruc- ELEVATION OF INDICj IN DAVUCKT SEEN Fig. 250 . tions, an instrument has been devised called the TuiTet Indicator, (Fig. 250), fixed either on the turret or in it. By which is seen at a glance, by day or night, the angle of depression at which both'or either of the guns can be fired at every bearing, clear of the deck and all obstructions. 1020. Eeferring to Fig. 250, it will be seen that the indica- tor consists of a hollow disk, with a rod through its centre carry- ing a pointer ; it is graduated near its outer circumference to 368 NAVAL ORDNANCE AND GUNNERY. indicate the arc of train that the gun makes with the beam. The number of degrees marked on the inner circle, as seen by day- light, indicate the amount of safe depression which maybe given at that arc of train, the gun right or left being marked on the disk ; also the fore and aft and beam points, the black spaces in- dicating the obstructions to fire. 1021. For use at nighty the clear space of the disk as seen by daylight is illuminated, by which, although it appears blank by day, at night it shows the same graduated arc of train and corresponding amount of depression as the outer disk, the fore and aft points being indicated by illuminated letters seen through the open space in the upright piece. By machinery or hand power the pointer is made to follow the movements of the Tur- ret, recording the arc of train and correspondino: depression. 1022. THE MONCEIEFF SYSTEM O'E GUX-CAE- EIAGE. — The principle on which this carnage is constructed may be shortly stated as that of utilizing the force of the recoil in ordei’ to lower the whole gun, so that it can be loaded out of sight and out of exposure, while retaining enough of that force to bring the gun up again into the bring position. This principle belongs to all the carriages ; but the forms of these carriages, as well as the method in which this principle is applied, vary in each case. For instance, in siege guns, where weight is an element of importance, the recoil is not met by counterpoise. With heavy garrison gims, on the other hand, which wdien once mounted remain permanent in their positions, there is no objection to weight. In that case, therefore, the force of gravity is used to stop the recoil, because it is a foi’ce always the same, easily managed, and not likely to go wrong. The great difficulty arising from the enormous destructive force of the recoil of heavy guns is here overcome. 1023. That part of the carriage, E (Fig. 251), which is called the elevator, may be spoken of and treated as a lever; this lever has the gun-carriage axle at the end of the power-arm, and the centre of gravity of the counter-weight, C, at the end of the weight-arm, there being between them a moving fulcrum. When the gun, G, is in the firing position, the fulcrum on which this lever rests is almost coincident with the centre of gravity of the counter-weight, C, and when the gun is fired the elevators roll on the platform and consecprently the fulcrum, or point of support, travels away from the end of the weight-arm towards the end of the power-arm, or in other words, it passes from the counter-weight, C, towards the gun, G. When the gun is Fred, its axle passes backwards on the up- per or fiat part of a cycloid. It is free to recoil, and no strain GUN-CAEEIAGES. 369 is put upon any part of the structure, because the counter- weight commences its motions at a very low velocity. As the recoil goes on, however, the case changes completely, for the moving fulcrum travels towards the gun, making the weight- arm longer and longer every inch it travels. Thus the resist- ance to the recoil, least at lirst, goes on in an increasing pro- gression as the gun descends, and at the end of the recoil it is seized by a self-acting pawl, or clutch. The recoil takes place without any jar, without any sudden strain, and its force is retained under control by the men at the gun, to bring it to the tiring position at any moment they may choose to release it. The recoil, moreover, however violent at first, does not put injurious horizontal strain on the platform. 1024. Hydkaulic Appliances. — The hydraulic system of Fig. 252. — Turret with two 38-ton guns, showing loading from below under port, and hydraulic buffer. loading and working guns as applied to the turret of the Thunderer^ is illustrated by Fig. 252. 24 370 NAVAL OEDNANCE AND GUNNEET. The principal mechanism of a gun-camage monnted on a slide is that for absorbing and regulating the force of recoil, and for moving the gun from loading to firing position, or back. In the usual English type of carriage the former office is performed by a peculiar and very powerful brake, known as the compressor, and the latter usually by winch-gear, giving motion to an endless chain so placed beneath the carriage that it may be seized at any point by a clutch on the carriage. 1025. In the hydraulic arrangement all this mechanism is replaced by the press or cylinder seen in the figure ; this press acts both to check recoil and to give motion to the gun-carriage on the slide. It is fixed on the slide in the line of recoil, with its piston-rod permanently attached to the carriage. 1026. Running In or Out . — To run the carriage in or out it is only necessary to admit to one side or other of the piston the water delivered from the steam-pumps. When the gun recoils the w^ater is di-iven out of the press through a loaded and partly balanced valve, the resistance of which to its passage arrests the recoil, and can be adjusted at a moment’s notice, so as to regulate the extent of recoil under different conditions. In its office of checking recoil it is self-acting, and always ready for use without any preparation. Whatever the weight of the gun, no men are required for running in or out beyond the one whose duty it is to open and close the valves which allow the water-pressure to act. 1027. The gun is made partial muzzle-pivoting by hinging the slide horizontally at the rear, the front end being free to be raised or lowered upon suitable chocks from the floor of the tur- ret, at the different heights required to give the desired range of elevation to the gun in the port. 1028. Loading . — The loading is effected by turning the turret so as to bring the muzzle of the gun opposite either one of two distinct sets of loading-gear placed on the main deck, and locking it in this position by a catch. The gun is at the same time depressed, so that the charge may be raised to the muzzle and pushed home in the bore at an inclination from below the upper deck. The projectile is brought up to the loading-place on a small railway-truck controlled by a friction-plate, which clamps it to the rails whene^•er the truck-handle is lowered. It is then run on to a hoist which rises with it out of the main deck until arrested by stops placed so as to bring the hoist to rest when the projectile is in line with the bore of the gun. It is then pushed off the truck into the muzzle, and raimned home by an GUN-CAEEIAGES. 371 hydraulic rammer, consisting of a parallel tube in which runs a piston-rod armed with a rammer-head. 1029. Sjponging . — The same rammer is used for pushing home the charge and also for cleaning the bore after each round. For this purpose the head of the rammer is formed like an ordinary sponge, and it contains a self-acting valve, which opens when pushed against the end of the bore, so as to discharge a strong jet of water within the gun. In loading, this valve does not act, because it does not then come in contact, owing to the peculiar form of the rammer-head. The same form of rammer has been made telescopic to re- duce its length. A wad pushed home with the projectile pre- vents it from running forward when the rammer is withdrawn. 1030. Advantages . — The advantages claimed for this method are ; 1. The loading operation is transferred from a confined space and exposed position in the port, to a roomy and conve- nient place on the main deck, where the apparatus is completely protected. 2. The dimensions, and consequently the weight, of the tur- ret required to protect any given gun are greatly reduced, be- cause the minimum diameter that will take m the length of the gun is all that is necessary, without additional space for loading. 3. Instead of a large gun’s crew, one man in the turret and one outside may direct and control all the movements of the heaviest gun, and may load and fire it wfithout other help than that involved in bringing up the ammunition ; and, finally, far greater rapidity of fire is obtained than would be possible by manual power. The loading positions are duplicated, to give a reserve in case of accident, or to enable that one to be selected which may best keep the turret-port out of the line of the enemy’s fire. In the event of accident to the hydraulic loading-gear, the gun may be loaded from below by hand. The carriages are arranged so that recourse may be had to hand-power for working the guns, should any accident to, or failure of, the hydraulic system occur. For this purpose the mechanical means of working by hand have been retained side by side with the hydraulic apparatus, and it has been nec- essary to adhere generally to the usual mode of mounting a gun. But it is thought that w'here this condition is not im- posed, great advantages in simplicity and strength of the appa- ratus required, and in the safety with which exceptionally heavy guns may be worked, can be obtained by a radical change in the method of mounting the gun. CHAPTEE YIIL EXPLOSIVE AGENTS. Section I. — General Consideration of Explosives.^ 1031. Definitions. — An explosion may be considered as the result of a chemical change in the solid or liquid body, by which is suddenly, or very rapidly, produced from it a gi’eat volume of highly expanded gas. Explosives may be defined as a class of bodies, the mole- cules of which are in such a state of unstable equilibrium, that a slight disturbing agency will cause chemical change among them ; the effect of which change is to produce suddenly a very large volume of highly expanded gas. 1032. Explosive Effect. — Explosive reaction is the tei-m applied to the chemical change which takes place in explosive bodies when their equilibrium is destroyed, while the blow or impulse given by the sudden production of the large volume of highly heated gas is termed explosive effect. KJ33. Explosive Compounds. — An explosive compound is a single definite chemical compound, the particles of which re- arrange themselves to form the gases evolved by explosion. The more important of the explosive compounds in exten- sive use for '\ arious purposes are : Eulminate of Mercury Evlminate of Silver, Nitro-glycerine, Gun-cotton. Explosive compounds are much more sudden and violent ill their action than explosive mixtures. 1031. Explosive Mixtuees. — An explosive mixture consists of combustibles and supporters of combustion, mixed so that by their mutual action a large quantity of gas is developed. The most important ex]ilosive mixture is gunpowder. 1035. The combustible bodies that maj’ be used are very numerous, but practically there are only two bodies which are used to supply the oxygen necessary for burning the combusti- * Extracts from Lectures of Prof . TF. H. Hill, IF. S. Torpedo Station. EXPLOSIVE AGENTS. 373 ble. These are potassium nitrate or saltpetre, and potassium, chlorate. Therefore all mixtures may be divided into two classes, namely : nitrate and chlorate mixtures. Nitrate Mixtures. — The most important one under tliis head is that composed of saltpetre, sulphur, and charcoal (Art. lOdT). Ill various proportions this mixture is employed for very many purposes ; the action is the same in all cases, so that the explosion of gunpowder fully illustrates them all. Nitra e mixtures are not greatly susceptible to friction, concussion, or percussion. In general the explosion of these mixtures is com- paratively slow. 1036. Chlorate Mixtures. — In general, the explosion of these mixtures is much more sudden and violent than that of nitrate mixtures, and they are also much more sensitive to per- cussion, concussion, and friction. Glenerally speaking, all chlor- ate mixtures are unsafe, and dangerous to handle or transport on account of their susceptibility to accidental explosion. 1037. As examples of this class may be mentioned, potas- sium chlorate mixed with resin, galls, gambia, tan, .etc. ; such as Hosley’s, Oriental, Erhardt’rs powders, etc. ; with sugar, potas- sium ferrocyanide, or ferricyanide ; such as white or German gunpowder ; with sulphur as used in explosive bullets. 1038. A gaseous explosive mixture is nearly as sudden in its action as an explosive compound, for it contains particles in a state of perfect mixture, each gas acting as a vacuum to the others. This is not the case with solid explosive mixtm-es ; therefore these latter are less sudden and violent in their action than either gaseous mixtures or explosive compounds. 1039. Intensity of the Explosion. — Explosion may be of different degrees of intensity, from that where the body is con- verted into gas by gradual combustion up to detonation, where the whole mass of the body is suddenly and violently converted into gas ; as for example : when gunpowder is ordinarily fired, each grain commences to burn on the sui’face, the burning gradually extending to the interior, until the whole is con- sumed, while nitro-glycerine seems always to detonate, which partially accounts for its excessive violence. 1040. Means of Causing Explosion. — The application of heat either directly or indirectly is the principal means of caus- ing an explosion. Directily, as by a match, a red-hot iron, etc. Indirectly, by friction, where the mechanical energy of rubbing is converted into heat ; by percussion, where heat is generated by the direct application of a blow ; or by concussion, where heat is generated by a jar or shock communicated through a second body. 374 NAVAL OEDNANCE AND GUNNEET. 1041. Method of Peodtjcing Explosion. — The circum- stances under which an explosion takes place create a marked difference in the effect produced. Every one is familiar with the different effects produced by firing gunpowder in the open air and firing it in a confined space ; but, apart from this, the mode by which it is fired exercises immense infiuences, both upon the force and the rapidity of its explosion. Suppose that a quantity of fulminate of mercumj be ex- ploded within a mass of any other explosive ; apart from the name produced, a blow will be given by the gas suddenly formed by the fulminate, which will act upon the sm-rounding explosive percussively, like the blow of a hamme'r upon an anvil. The very rapid motion of the particles of gas will give them a force, as regards any resisting body, similar to that exercised by a solid, having a great velocity, against any obsta- cle in its path. 1042. DETONATIOhr. — "When the flame of the fulminate is applied directly to the explosive, the chemical change is initiated at the point of application, and, if the flame alone were considered, would gradually spread from this point through the mass ; but the percussive blow is extended through all parts of the body with very great rapidity, enormously expediting the speed of the explosive charge. In certain cases the effect is practically simultaneous throughout the whole mass of the body exploded, thus producing detonation, the effect of which is mueh more powerful than that of an ordinary explosion. 1043. Explosives Capable of Detonation. — Each explo- sive body that has been experimented with seems to have a particular mode of detonation, and probably all explosives may be detonated if the right method of doing so be known. Gun- cotton seems to have a greater range of susceptibility to differ- ent inodes of firing than any other explosive agent. It can be made to burn slowly without explosion, and the rapidity of its combustion can be increased up to the point of detonation. Nitro-glycerine, as before stated, appears always to detonate. (It is not sensitive to flame as directly applied.) Fulminate of mercury is a detonating substance, but the quantity of gas given off is comparatively small, hence the limited range of its de- structive effect. Gunpowder is said to be capable of detona- tion, but it is more difficult to obtain detonating effects with it than with any of the others. 1044. Detonation, now Pkoduced. — Detonation can only be produced by the application of the requisite blow or shock, and this is usually accomplished by means of a detonating fuze EXPLOSIVE AGENTS. 375 containing the required amount of fulminate of mercury, the amount differing for each explosive. Fulminate of mercury has been found to be by far the best agent for producing detonation ; less of it is required than of any other explosive. Nitro-glycerine is much more powerful than fulminate of mercury, but while a certain amount of the latter will detonate gun-cotton, seventy times as much nitro- glycerine will not accomplish it. Chloride of Nitrogen and Iodide of Nitrogen are much more violent than fulminate of mercury, yet a larger quantity of them are required to produce detonation. These facts indicate that there is some peculiarity in the impulse given by the firing of fulminate of mercury that affects other explosives more powerfully than that given by any other body, though the latter may he the stronger. It may be considered that this isowing to a peculiarity of vibration, or wave motion, due to the explosion of fulminate of mercury, which causes greater disturbance among the molecules of other explosives than the vibrations produced by any other explosives. 1045. Hatuke of Detonation. — Detonation is really only an exceedingly rapid explosion. In an ordinary explosion like that of powder in a gun, much force is lost by the slowness of the action. As gases expand heat is absorbed, so that if the gases can expand as they are formed, much of the heat of the chemical reaction is absorbed, diminishing the shaiqmess of the explosive effects, Avhich is therefore not sudden but gradual. With a force gradually generated and exerted, we have a propulsive effect, but a detonation has a disruptive violence, which may become almost irresistible. 1046. Illustrations op Explosion by Detonation. — The practical value of this mode of developing the force of explo- sive agents is very great. The necessity of confining gun- powder and other explosive materials in strong receptacles for the purpose of developing their explosive force, is greatly re- duced, and indeed entirely dispensed with in the case of charges fired under water, when detonating fuzes are used as the ex- ploding agents. Masses of hard material of great size or strength, such as blocks of hard rock, large iron castings, or thick bars of iron, may be broken up by simply placing upon one of their surfaces a comparatively small charge, quite unconfined, of compressed gun-cotton, or of a nitro-glycerine preparation, and exploding it by means of a detonating-fuze. In such operations the destructive effect of the detonation will be increased by covering the charge with sand or other material, but in hurried operations good results may be obtained 376 NAVAL ORDNANCE AND GUNNERY. with either of the materials specified by detonating them when freely exposed to air. For hasty demolition of buildings and of military works, the explosion by detonation affords most important facihties, reducing the difficulties, dangers, and cost of such operation to a minimum. Section II — Ma/nufacture of Gunpowder. 1047. Gunpowdee is the agent employed for the firing- charge of all ordnance, and for the bm’sting-charge of all pro- jectiles. Its use depends upon the fact, that at the moment of igni- tion, violent deflagration takes place, accompanied by the evo- lution of a large volume of gas. It is evident that if the ex- plosion occur in a limited space, a vast pressure accumulates and becomes a propulsive foi’ce. The gas produced by the ex- plosion of good gunpowder occupies nearly 900 times the vol- ume of the powder itself ; but, owing to the high temperature, the space occupied by the gas at the moment of formation is probably 3,000 times greater than the volume of the powder. It has been found that no comj)osition fulfils so many requi- sites for charging fire-arms as a mixture in due proportions of nitre.) charcoal^ and sulphur ^ and it is this composition which constitutes gunpowder. The ingredients should be of the greatest possible purity, both for the quality of the powder and the prevention of disas- trous accidents in the manufacture. 1048. mGKEDIEXTS OF GUhrP01YDEE.--The in- gredients for the manufacture of gunpowder should be sup- plied in the rough state, and refined and prepared for use at the factory, in order to insure as far as possible uniformity of results in manufacture and safety in carrying it on. It is manifestly useless to attempt to obtain powder possess- ing uniform qualities unless measures are taken to insure the uniform purity of its constituent elements ; and although pres- ence of chemical impurities may be readily detected in samples of refined saltpetre and sulphur supplied by contract, and though it might be possible to devise a series of practical tests for the various physical qualities by purchase, there can be no guarantee for the purity of the former and uniformity of the latter equal to that of careful supervision during the actual processes of prep- aration and refining. * Smith. MANTJFACTUIIE OF GUNPOWDER. 377 A manufacturer wlio refines liis own saltpetre and sulpliur, and burns liis own charcoal, has means of insuring the purity and uniformity of the ingredients of which he makes use, far supe- rior to that of any system of testing, however careful. 1049. The additional security against accidents in the course of manufacture, gained by careful exclusion of all ^loreign mat- ter from the ingredients during the processes of refining, is of even greater consequence in the manufacture of gunpowder. The question, how far the too frequent explosions in powder factories are dependent on the presence of minute particles of foreign bodies introduced into the ingredients after refining and before they come into the hands of the mixer, has not received the attention which it deserves. But it is too often found that though care be taken to exclude any fragments of sand, grit, etc., from the powder from the time it leaves the mixing-house till the time that it is finished, the same vigilance is not exei’- cised in excluding minute particles of foreign substances from the unmixed ingredients, by which negligence the subsequent precaution is altogether thrown away. 1050. Those engaged in removing saltpetre from the refin- ery to the mixing-house should be scrupulously careful not to step into the bins where it is stored without putting on clean magazine shoes, and should not make use of any shovels, bar- rels, etc., but those kept specially clean and free from grit for the purpose ; and the same precautions should be taken in hand- ling sulphur and charcoal, the latter of which should be picked over by hand, piece by piece, before being ground, and after that treated with the same care as the other ingredients. If pre- cautions to avoid accidents are worth taking at all, they must, to be effectual, be commenced whenever the ingredients are taken in hand, and maintained to the end of the manufacture. 1051. Eefinixg Sautpetee. — -The principle on which the process depends, is that saltpetre is greatly more soluble in hot than in cold water, while the impurities generally found in it do not present the same disparity in their solubility at dif- ferent temperatures. Thus a saturated cold solution of crude saltpetre Avill, as its temperature is raised, take up a much greater additional quantity of saltpetre proportionately than it Avill of the other salts present. Hence if a boiling saturated solution of the impure salt be made and allowed to cool, it will deposit the excess of saltpetre and retain the other salts in solu- tion. Boiling Avater will take up 39. G1 parts of chloride of so- dium, and about 240 of saltpetre. W ater at the temperature of 70° will take up about 36 of the former and about 32 of the latter. Consequently, if a boiling solution saturated with salt- 378 NAVAL OEDNANCE AND GUNNEEY. petre and chloride of sodium he cooled to 70°, it will deposit about 208 parts of the former to about 3.6 of the latter. All, therefore, that has to be done in refining saltpetre is to make a concentrated solution of this crude material at a high temperature, to run the solution into fiat troughs, to keep it in constant agitation as it cools down, and then to renaove from it the saltpetre as it crystalizes out of the mother litpior. 1052. Desceiption of the Refixixg Peocess. — Solution. — About two tons of crude saltpetre are pressed in a large open copper pan capable of holding about 500 gallons of water, and about 270 gallons of water are added to it. This is generally done over night, and the fires are lighted under the copper early the following morning. Over the bottom of each pan is placed a false bottom of iron perforated with holes of an inch in diam- eter, to allow the sand and insoluble impurities to fall to the bottom. In about two hours the Avhole of the saltpetre will be found to be dissolved and the solution boiling, and the specific gravity of the solution being about 1.49, it reaches the tempera- ture of 230° F. The false bottoms are pulled out jrast before the solution begins to boil, and the scum, containing the greater part of organic, impurities, is removed from the surface. The solution is allowed to boil for about half an hour longer, until no more scum rises to the surface ; the copper is then filled up with cold water, and the solution again boiled briskly for a few minutes, after which it is allowed to cool down to become of a proper temperature for being pumped into coolers. 1053. Filtering . — The filtering process is almost always used when refining saltpetre for gunpowder-making, but is sometimes omitted when refining for other pm-poses. In tlie latter case the solution is made of extra strength and conse- quently denser, and the cooler being placed below the level of the coppers, the solution is run directly into it through a pipe, the orifice of which in the copper is placed at a certain height above the bottom, to prevent the sediment running out with the clear liquor. But filtering affords a much more certain plan of obtaining a clear liquor for crystallization, and presents little difficulty and causes very little loss of time. 1054. When the temperature of the solution has fallen to 220° F., with a specific gravity of about 1.53, it is ready for pumping into the filters. AVhen the solution has arrived at the proper temperature for the ]U’Ocess, a common hand-pump is lowered into the copper, and the solution is pumped into a wooden trough leading to another larger one, termed the supply- trowjh, furnrshed with six holes in the bottom, beneath which the iilteriug-bags are suspended. AVooden plugs are provided MANUFACTURE OF GUNPOWDER. 379 for these holes in the bottom of the supplj-trongh, so that if the hags become clogged, the flow of solution maj be stopped till they are replaced by clean ones. 1055. The bags are suspended on iron hooks underneath the holes in the supply-trough. They are always rinsed with hot water before the Altering commences, and require occasion- ally a little poured over them to prevent the formation of crystals during the process, which would clog the canvas and prevent the solution running. Occasionally a solution is found to contain so much organic impurity, that it will not run through the Alters. In this case a little glue, about 1 lb. to 2 tons of saltpetre, is added to the so- lution in the copper, which has the effect of throwing up a great part of the impurity as a scum, which can be removed be- foi'e the liquor is pumped oirt. 1056. The Altering of a copperful of liquor, of the strength described (Art. 1052), takes about three-quarters of an hour. As soon as it is all removed from the copper, the pumps, which are suspended overhead on a small pulley, are pulled up and the coppers, if necessary, cleaned out. The sediment, consisting piincipally of sand in the proportion of about ^ per cent, of the crude, is washed and the washing reserved for evaporation. A wooden trough placed directly underneath the flltering-bags receives the solution as it runs from them, and conducts it directly into the cooler. When all the solution is Altered, the bags are i-insed with hot water into the evaporat- ing-pots, and then washed and hung up to dry. 1057. Crystallization . — The cooler, or crystallizing cistern, is a large, shallow, flat trough of sheet copper, being about 12 feet long, 7 feet wide, and 1 foot deep. By the time the solu- tion runs into it the temperature will have fallen to between 190° and 180° F. As the temperature continues to fall, the ex- cess of saltpetre crystallizes out, leaving, of course, a considerable quantity still in solution, and along with it the chemical impu- rities of the crude salt, the chlorides and sulphates. If the solution were left to crystallize without agitation, the salt would be deposited in the form of large crystals, each of which would pnclose a small quantity of this impure mother liquor. To prevent this, the liquor in the coolers must be kept in constant agitation, to cause it to deposit the salt in the form of flour., or minute crystals. This is effected by a workman who, for the Arst hour or so, until the temperature of the liquor falls to about 90°, keeps it constantly stirred by means of a large wooden hoe, with which also the flow is drawn to the side of the cooler, to be shovelled out with a copper shovel. 3S0 NAVAL ORDNANCE AND GUNNERY. As it is removed, it is fii’st thrown into an inclined board, or drainer^ to allow the excess of lic[uor to run back into the cooler. It remains on the drainer for some minutes, after which it is transferred to the washing-vat. 1058. When the liquor falls in temperature to about 90° F., the agitation is discontinued, because the crystals are deposited much more slowly, so that the cost of labor would he considera- bly increased. The crystals which are deposited at a tempera- ture below this also contain a much larger quantity of mother liquor. About three quarters of the entire Cjuaiitity of saltpetre is removed from the solution, if the agitation he stopped at 90° F. The crystallizing process may he very materially hastened by artificial cooling. In some refineries, where a good fall of water can he obtained, a stream of cold water is made to ran under the bottom of the cooler. This reduces its temperature very rapidly, and causes the flour to he deposited with less loss of time. 1059. The mother liquor is left to cool down after the proper amount of flour has been removed from it. As soon as its temperature approaches that of the atmosphere, large crystals are deposited in the cooler. The liquor, still, of course, a satu- rated solution containing all the original soluble impurities, is run off and reserved for subsequent evaporation. The crystals are scraped off and transferred to the refinery copper with the next charge of crude salt. The following is an analysis of a sample of the salts left in solution in the liquor : Saltpetre 77.10 Chi. Sodium 18.51 Sulphate of Soda 3.39 99.30 — which should be compared with the anaysis of the crude salt. 1060. Washing. — The washing-vat, to which the saltpetre flour is transferred, is of wood, about 6 feet long, i wide, and 3|- deep. It is provided with a false bottom pierced with small holes, underneath which is a plug-hole which can be closed or opened as required. In tliis vat the saltpetre receives three waslfiugs, the first being given at once, as soon as it is raked from the strainers into the vat, to remove the excess of mother liquor still adhering to it. About 70 gallons of water are run through the vat, and, escaping from the plug-hole un- derneath the false bottom, are conducted into an underground IiIANTJFACTURE OF GUNPOWDER. 381 tank. The second washing is done by covering the crystals with water and allowing it to stand for half an honr, the ping being in, and then allowing it to rnn off into a second nnder- gTonnd tank. The crystals are allowed to drain for half an honr after this washing. The third washing is given by run- ning about 100 gallons of Avater through the crystals, as in the first Avashing, the plug-holes remaining open. The Avater from the third washing runs into the tank which receives the second, the contents of which, being comparatively free of impurities, are used in the refining coppers. The water from the first Avashing is only used in the evaporating-pots. It is, of course, most important that the purest water should be used for these AAmshings. Distilled Avater shoidd, if possible, be alone employed. The washings, as they run off, are saturated solutions of saltpetre ; but they take up, in passing through the salt, any traces of chlorides remaining in it. 1061. Tests. — Supposing all the foregoing operations to have been properly carried on, the saltpetre will be found to be perfectly pure. Should it be deemed necessary to test it for impurities, it should be subjected to the folloAving. A solution should be tested : 1. With blue and red litmus paper, for the presence of an acid or alkali. 2. With a solution of nitrate of silver, for the presence of chlorides, which Avould throw down the insoluble chloride of silver. 3. With a solution of chloride of barium, for the presence of sulphates, which would give the insoluble sulphate of baryta. I. With a little oxalate of ammonia, for lime, AAdiich would give oxalate of lime. In the ordinary practice of a refinery, the second test, viz., that for chlorides, more especially the chloride of sodium, is the only one ever used. 1062. The saltpetre is transferred to the store bins gener- ally the day after it is refined. In removing it from the wash- ing vats, about six inches deep at the bottom is left, as it con- tains a great deal of Avater. After remaining in the bins three or four days, it will be found to contain from three to five per cent, moisture, according to the season. It remains in the bins till required for use in the mixing-house, the saltpetre used for poAvder-making being always used moist. 1063. Drying . — Should a supply of refined saltpetre be re- quired for storage or transport, the salt is generally dried before being placed in ban’els. This is done in a hot-chamber : a small room with a stone floor, underneath Avhich runs a flue ; and pro- 382 NAVAL ORDNANCE AND GUNNERY. vided with racks inside, on whick are placed the flat copper trays containing the saltpetre. The hot-chamber is capable of containing two or three tons of saltpetre, and the teinperatnre is generally raised to about 220° F., which dries it completely in from four to six hours. The salt is covered in a flat tray, placed outside the store before being baiTelled up. 1064. Extraction of Saltpetre from Damaged Powder. — The extraction of saltpetre from powder sweepings, a consider- able cpiantity of which accumulates in the course of manufacture, and from powder which may have been accidentally wetted or damaged by long storage in damp magazines, forms a part of the ordinary nature of duties in a refinery of saltpetre. Copper pans are used for stirring the sweepings, and any damaged powder which may be sent to the factory is also placed in pans. As a precaution, the contents of each pan are carefully and thoroughly melted, and the supply is not allowed to become dry by evaporation. 1065. The Operation . — About 240 gallons of water are pumped into a copper of 400 gallons capacity, and brought nearly to the boiling-point. Pure water must be used for the first day’s operation, but afterwards the liquors obtained in fil- tering the previous day’s work. About 900 bbls. of the dam- aged powder are then thro^vn in, care being exercised that it is thoroughly wetted throughout before being brought into the extracting-house. The mixture is stiiTcd and boiled for three- quarters of an hour, after which the fire is damped and the solution ladled into filters of coarse sheeting. From the first series of filters, the solution passes to a second row, through which it passes, clear, into a tank. From the tank it is subsequently pumped into the evaporating-pots and boiled down. The saltpetre being of course pure, the boiling is merely to drive off a certain quantity of water. AYhen suffi- ciently reduced it is again filtered and crr-stallized in small cop- per pans. The crystals obtained are used a s crude saltpetre. The carbon and sulphur obtained are thrown on the waste-heap, being of no value. 1066. The whole process of extraction is dirty and trouble- some, and the expediency of carrying it on to any great extent depends on the price of saltpetre at the time, and the price which can be obtained in the market for damaged powder. Powder sweepings should of course always be extracted, as they are liable to contain particles of foreign substances ; but pro- vided powder be merely old and dusty, it may still be well adapted for blasting operations, and may command a good price. MANUFACTURE OF GUNPOWDER. 383 1067. About 94 per cent, of the saltpetre contained in pow- der can always be obtained by extraction, against the value of which must be set otf the cost of the men’s wages employed in the process, the amount of fuel expended, etc. 1068. Sulphur. — The sulphur used in gnnpowder-making is imported from Sicily. The finest quality is alone employed. As imported, the sulphur contains from three to four per cent, of earthy impurities, having already undergone a rough purifi- cation by distillation before it comes into the merchant’s hands. It is finally and carefully purified at the factories by a second distillation. 1069. The substance exists in several distinct conditions or forms, two of which require special notice, viz., the soluble, or electi’o-negative form, and the insoluble, or electro-positive. Dis- tilled sulphiu’ consists almost entirely of the former. Sublimed sulphur, contains a large proportion of the latter. Distilled sulphur, as used in the manufacture of gunpowder, consists of masses of clear yellow crystals in the form of rhombic-octahe- dra, and is readily soluble in bisulphide of carbon. Sublimed sulphur, known a.?, flowers of sulphur^ is a pale yfellow powder, composed of minnte particles wdiich do not present a crystalline structure, but which are merely minnte granules consisting of insoluble sulphur, enclosing a small portion of the soluble variety. This latter form of sulphur is to a great extent insol- ble in the bisulphide. 1070. Description of Refining Apparatus. — The apparatus employed consists of a large pot of cast-iron, A (Fig. 253), set in brick work, the metal being very thick. Round the top edge is shrunk a strong ring or tire of 'wrought-iron, to prevent split- ting by explosion. On the top is fitted a large dome-shaped cover, also of cast-iron, secured to the pot by three wrought-iron tie-rods, which are secured by screw-bolts to a wrought-iron ring passing round the neck of the cover. At the top of the cover is a circular opening fitted with a heavy cast-iron lid, the w'eight of which is sufficient to keep it in its place during the refining process. In this lid is an iron plug-hole having con- siderable taper, through which the pot is charged. The cast- iron plug which closes it fits sufficiently tight to prevent escape of sulphur-vapor, particularly if a little sand be thrown over it ; but at the same time it acts as a safety-valve, being lifted out if an unusual pressure of vapor is exerted inside the pot. 1071. From the dome-shaped cover two pipes proceed at right angles to each other, one to the subliming-dome, the other to the distilling-tank, or receivingpot. The first pipe is fur- nished with a throttle-valve (Fig. 254), D, which can be closed 384 NAVAL ORDNANCE AND GUNNERY. or opened by a handle from without. The other pipe is encased in a water-jacket, and can also be closed or opened by means of Fig. 253. — Ground Plan of Sulphur-refining’ Apparatus. A. Melting Pot. B. Pipe with Water Jacket leading to C. 0. The Receiving Pot. D. Pipe leading to Subliming Dome. a valve. When distilling, a constant flow of water is main- tained through the water-jacket (Fig. 255). An escape pipe fltted to tliis jacket allows of the escape of water when tliere is a sudden development of steam caused by the heat of the sulphur vapor. 1072. The receiviug-pot, C, is merely a large circular vessel of cast-iron, which is set on a frame inserted in small trucks, to allow of a slight movement Avhen the pipe which connects it with the melting-pot becomes expanded and lengthened by the heat of the sulphur vapor passing through it. There is a large circular opening in the lid through which the melted sulphur can be ladled out when necessary. This opening is closed by an iron lid similar to that of the melting-pot, in which is also a small plug-hole through which the depth of melted sulphur in ' the receiving-pot can be ganged witii an iron rod. A small pipe leads from another opening in the lid of the receiving-pot into a square wooden chamber lined with lead to receive any new condensed vapor, and saves it to deposit its sulphur in the form of flowers. This chamber is provided with a tall chim- ney, also of wood, containing a series of steps or traps to catch as much of the flowers sls, possible. MAinJFACTTJEE OF GENPOWDEE. 385 1073. The siTbliming-dome is a large dome-shaped building of brick, E (Fig. 251). The pipe for the sulphur-pot enters it Fig. — Sulpur Eefinmg Pot and Dome. near the top. The chamber is lined with flag-stones, and the floor is covered with sheet-lead. It is provided with two doors, an inner one of iron, an outer one of wood lined with sheet- lead, both close fitting, through which passes a pipe to allow tlie escape of air. This pipe terminates in a vessel of cold water. 1071:. Process of Refining . — If distillation alone is to be carried on, about 5|- cwt. of crude sulphur are placed in the pot each morning. An extra hundred-weight must be put in, if both distillation and subliming are to be carried on together. The fire being lighted, the conical cast-iron plug is left out of the hole in tlie lid of the pot, the passage into the dome is opened, and that into the receiving-pot closed. The heat is maintained for three hours till the sulphur is of a proper temperature for distillation. The vapor which first rises from the pot is of a pale yellow color, and as much of it as passes into the dome falls down condensed as flowers of sulphur. But at the end of three hours the vapor becomes of a deep reddish-brown color, showing that the temperature of the melted sulphur has reached the proper point. The plug must then be inserted in the lid, the communi- cation to the dome closed, and that leading to the receiving- pot opened, allowing the heavy vapor to pass through the pipe surrounded with the water-jacket, by means of which a con- stant circulation of cold water is kept up round it. In this way the sulphur vapor is condensed, and runs down into the 25 386 NAVAL ORDNANCE AND GUNNERY. receivin,o;-pot as a clear orange liquid resembling molasses in color and consistency. 1075. The person who watches tlie operation knows, bv gauging the depth of the melted sulphur in the receiving-pot, when the greater part of the material has distilled over. He then lowers the fire, opens the communication into the dome. and cuts off that leading to the receiving-pot, allowing the re- maining sulphur to pass off into the dome as flowers. A low fire is maintained till the whole has been driven off, leaving the eartliy residue quite free from it, and consequently loose like coal-ashes, so that it may be easily ladled out before recharging the pot. 1070. When both subliming and distillation are cairied on at once, the first part of the process would be exactly as described above ; but when the distillation was finished the fire would be maintained for the remainder of the day, but somewhat lower, to dnve off the quantity required into the dome. And in this case the subliming process would be carried on for several days, and the pot and dome never allowed to cool down altogether till the required (piantity of flowers of sulphur had been ob- tained. 1077. It is of the greatest consequence that the fires should mmrFACTURE of gunpowder. 387 be carefully regulated in all cases, for if the heat become too great and the temperature of the melted sulphur be allowed to rise to 836°, the vapor disengaged at that temperature is highly explosive when mixed with common air ; and if the ping be driven out by the pressure of the vapor, or if air be drawn into the pot through some leakage in the pipes, an explosion invari- ably happens. 1078. When the distilled sulphur in the remaining pot has cooled down sufSciently, which it will do in the course of an hour or two, it is ladled by hand into wooden tubs and allowed to solidify. These tubs are constructed of a number of loose staves held together by broad wooden hoops, which can be struck off when the sulphur has set, allowing the staves to fall asunder and leave it as a solid cylindrical mass. 1079. Distilled sulphur immediately after being removed from the tubs is placed within a boarded-otf enclosure, to guard against coming in contact with any fragments of grit or sand which might thus enter the powder, and is broken up into larger lumps, which are sent up to the factory to be ground under a small pair of millstones. After being ground it is reeled through 32-mesh wire-cloth, and is then fit for the mixing-house. 1080. Testing. — Its fitness for use as an ingredient of gun- powder may be readily tested : 1st. By burning a small quantity on porcelain, when the amount of residium should not exceed 0.25 per cent. 2d. By boiling with water and testing with blue litmus pa- per, which it should only very feebly redden. 1081. Use as an Ingredient of Gunpowder. — As an ingre- dient of gunpowder, sulphur is valuable on account of the low temperature (560° F.), at which it inflames, thus facilitating the ignition of the powder. Its oxydation by saltpetre appears also to be attended with the production of a higher temperature than is obtained with charcoal, which would have the effect of accelerating the combustion, and of increasing by expansion the volume of gas evolved. 1082. Chaecoal. — The woods from which charcoal is now manufactured for powder-making, appear to have been in use from a very early period. Modern research has shown that there was a good reason for their selection, and that the cause of their superiority over all other woods is probably that their charcoal when burnt with saltpetre and sulphur yields larger volumes of gas than any others. 1083. TJie Woods tlsed. — The woods generally used for the best gunpowders are the willow, the alder, and what is popiilarly known as the hlack dogwood. The more rapidly a wood has 388 NAVAL ORDNANCE AND GUNNERY. been grown, the less dense will it be, and the better for powder- making when converted into charcoal. The vnllovj is one of the sottest and lightest of woods ; it is of very rapid growth, nearly white, and has a tolerably large circnlar white pith. The alder is somewhat harder and denser in texture than the willow, and is not of such rapid growtln Its color is reddish-brown, and the pith is triangular in section. The dogwood i?, dense and tough, of slow growth, and having circular pith of a reddish color. 1081. Small wood of about ten years’ growth is preferred for powder-making. Alder and willow of this age will be probably four or five inches in diameter, dogwood about one. The wood must be straight, perfectly sound, and entirely free from bark, and must be felled in the spring. Great sti-ess is laid on the cleanliness of the wood. Any traces of bark adhering to it are not to be tolerated. If the wood is cut in the spring when the sap is rising, the bark is easily removed, and the wood is left ])erfectly clean. Wood cut at any other season of the year is ■just as good, only in this case the removal of the bark is a much more difficult matter. 1085. To Convert the Wood into Charcoal. — W ood is con- verted into charcoal in iron retorts or cylinders, set into bnck- work. Fig. 256 shows a transverse section of a set of cylindere, MANUFACTURE OF GUNPOWDER. 389 giving tlie arrangement of tlie fines, by wliieli tlie flame is made to play all around them ; and Fig. 257 shows a longitudinal section of one cylinder, showing how the second cylinder, or slip. A, containing the wood is placed in its interior, and the ar- rangement of pipes hy which the gaseous matter evolved from the wood is conducted into the fire. 1086. Each cylinder is made of cast-iron, having two pipes passing out at the inner end of it. When set, the lower one of these is closed with hrick-work, the upper one only being used, and the lower one being only intended for use should the cylin- der be turned round and reset. To the uppermost pipe is at- tached a branch pipe leading to a horizontal pipe extending be- hind the whole set of cylinders, from one end of which another pipe descends perpendicularly, joining another leading directly into the former. Each cylinder has a false bottom of brick- work, in front of which is bolted on a piece of wrought-iron plate having a cylinder hole corresponding to the uppermost pipe of the cylinder. The cylinders are closed with tight-fitting iron doors secured by a powerful screw, much in the same way as the ends of gas retorts are fastened. 1087. For convenience of handling, the wood is placed in MM MM MM MM iMM MM MM MM M MM MM MM MM MM MM MMM 5 I MMMMMiM -MM^ MM MM Ml AMMMMMMI ^MMMMSMMMi MMsMMMMMM i^MMMiMMMM W M>M MM M:M| 4^'^ MM >MM MM M MM 'MMMMMMM MMMMMMiM MmI Tig. 257. — Longitudinal Section of Retort, email cylinders of sheet-iron, A, termed slips^ which are placed on small iron travelling carriages, on which they can be run up 390 NAVAL ORDNANCE AND GUNNERY. dii’eetly to tlie month of the cylinders and shot in. The back end of each slip is provided with a handle to facilitate with- drawal. The slips are a little over three feet in length so as just to take the cord-w'ood in easily. 1088. Provided the cylinders are hot, the wood is thoroughly charred in two or three hours. The plan of conducting the gas and tar from the wood into the fire is found greatly to economize fuel, and to he the readiest means of ascertaining when the char- ]-ing is properly and thoroughly done. This is shown by the flame wliieh issues from the pipe leading into the fire becoming of a v^iolet tint, indicating the formation of carbonic oxide. As soon as this is observed the doors of the cylinders are opened, the slips are hoisted out and lowered into large iron extinguishers having close-fitting lids, in which they remain for half a day, after which the ehai'coal is shot into coolers — large cylindrical eases of sheet-iron fitted with lids — and sent to the cliarcoal store. Wood yields about 25 per cent, of charcoal. 1089. Effect of Temperature employed in Conversion . — It is of the higliest importance that the charring of the wood should always he conducted as neaily as possible at the same temper- ature ; for the chemical composition of the charcoal and the temperature at which it will igirite is undoubtedly affected by the temperature at which it has been charred. Charco.al pre- pared at a low temperatm-e is softer, more inflammable, and contains more gaseous elements than charcoal pi-epared at a higher heat, and the gunpowders made from these charcoals wmuld be similarly affected. It is hopeless, therefore, to at- tempt to ohtai]i uniform results in manufacturing powder, unless means be taken to insure uniformity in the preparation of char- coal. 1090. Qualities of Charcoal . — The fitness of charcoal for gunpowder depends on its chemical composition, which is indi- cated by its physical cpialities. If properl}- made it should be jet-black in color, its fracture should show a clear, velvet-like surface, and it should be light and sonorous when dropped on a hard surface. Underburnt charcoal, that is, charcoal that is prepared at a very low temperature, is at once known by its reddish-brown color ; overburnt charcoal, by its hardness and density. The former is greatly more infiammal)le than the latter, charcoal prepared at a temperature of 500° F. being readily ignited at a temperature of G10° F., while charcoal prepared at 1800° F. requires a temperature neaily double the last to inflame it. 1091. Underbunit charcoal has found favor for some small- arm powders. It certainly appears to render the powder more MANUFACTUEE OF GTJNPOWDEE. 391 inflammable, and consequently quicker, but it has the disadvan- tage of being more hygroscopic thau denser charcoal, and of rendering the powder therefore more liable to suffer damage from damp. That underburnt charcoal produces a very marked effect on gunpowder there can be no doubt. Recent experi- ments have proved that if two powders be made identical in all other qualities, the one with black charcoal, the other with red or underburnt charcoal, the latter will give a higher velocity to the projectile than the former. Powder made from underbiu’nt charcoal can be readily distinguished, when crushed to line dust, by its color. 1092. Peopojstions of Ingeedients. — In determining the proportions in which the constituents should be mixed, the circumstances in which it is to be used must be considered. A. vast number of experiments have been made at various times to discover the proportions of nitre, sulphur, and charcoal best adapted for the production of gunpowder. It has been found that no general rule can be given which shall fulfil every requirement, yet all nations appear to have found by trial the proportions most generally useful for ordinary purposes, and they all approximate to the percentages required by the formula 2KRO, + S -f 3C, supposing the charcoal to be pure carbon. The percentage composition is generally thus : Kitre 74.8 Sulphur 11.9 Charcoal 13.3 The percentage of nitre varies from 70 to 80 ; that of sul- phur and charcoal from 10 to 15 each. The best powder is intended for war and sporting purposes, and contains usually a little less sulphur and a little more char- coal than the above. 1003. The proportions required by regulation for gunpow- der in the United States services are : Nitre 75 Charcoal 15 Sulphur 10 These proportions are not those which theoretically would give the greatest amount of gas. The charcoal is in excess, to allow for ash, and the sulphur is diminished, as it acts injuri- ously on the metal of the piece by the formation of a sulphide of iron, which eats away the surface of the bore. When the proportion of charcoal is greater than that con- tained in commoir powder it will be less completely and rapidly burned. 392 NAVAL ORDNANCE AND GUNNERY. 1094. Blasting Powder, for example, contains a greater proportion of charcoal and less nitre ; its action is consequently slower, and if used in fire-arms, not only is the piece very soon rendered foul, but the hall is projected to a much less distance. This alteration in the proportions is mainly on account of the great reduction in price thereby effected. 1095. Preparing and Mixing the Ingredients. — Before the ingredients can be mixed, they must be reduced to a pow- der sufficiently tine for the purpose. It is important to bear clearly in mind the meaning of the terms mixing and incorpo- rating, as they are used by gunpowder-makers. Though gun- powder is really only a mixture, very intimate, no doubt, of the three ingredients, and not a new chemical substance formed out of them, yet by mixing is understood only the stirring to- gether for a few minutes of the saltpetre, sulphur, and charcoal, to get them perfectly distributed amongst each other; and by incorporating, the long-continued trituration and grinding wliich the mixture undergoes under heavy edge-runners, by which a mass of the ingredients becomes transformed, from a mere mixture of three different substances into gunpowder. A pre- liminary mixing, such as is employed at most gunpowder- works, may be dispensed with ; incorporation, wliether per- formed by pestle and mortar, in the stamping-mill, or under edge-runners, never. 1096. If the saltpetre is used moist, an allowance for this must be made in weighing. The percentage of moisture in the cpiantity used is ascertained by drying and pressing a sample, and comparing the weight before and after the operation. In this country it is found highly advantageous to have the salt- petre dried and pulverized before weighing out. 1097. Occasionally dried, refined saltpetre may be employed for manufacture in the case of a stoppage in the saltpetre re- finery. In this case the dried salt is first ground under a pair of small stone-edge runners, fitted vdth scrapers to iirevent the salt adhering to them, and then passed through a slope reel covered with 28-mesh wire, that which passes through the wire being used for mixing, the larger fragments being re- ground. 1098. The sulphur is ground in quantities of 2-^- cwts. at a time, under a pair of iron edge-runners, also fitted with scra- pers, and sifted in a slope-reel covered with 32-mesh wire. 1099. Charcoal, after being carefully hand-picked, to guard against the introduction of any fragments of foreign matter and underburut knots of wood, is groimd in a mill resembling MANUFACTURE OF GUNPOWDER. 393 a coffee-mill in action. (Fig. 258.) It consists of a cone work- ing in a cylinder, each being firmished with diagonal ribs, or teeth, wliich are widely apart at top, but approach closely to- A. — Cylinder. B.- — Cone. K.— Reel. gether at bottom. The charcoal, which is shot in at the top, passes out at the bottom into a slope-reel, covered with 32-mesh wire, all fragments which do not pass throxigh being trans- ferred again to the mill. 1100. An important caution must be mentioned in connec- tion with the grinding of chai'coal. After being burnt it should be allowed to stand for a considerable time — ten days to a fortnight — before being ground ; for when ground fresh after burning, the finely powdered charcoal absorbs and condenses oxygen so rapidly as to generate a great amount of heat ; enough, in so bad a conductoi’, to cause spontaneous combustion. In- stances of fires in gunpowder factories from this cause are on record, fresh-ground charcoal having been left overnight in wooden bins. 1101. Mixing-Machine . — The relative proportions of the three ingredients are weighed out in quantities of 50 lbs., and 394 NAVAL ORDNANCE AND GUNNERY. transferred to tlie mixing-machine. ("Fig. 259.) This consists of a hollow drum of gun-metal, which is made to revolve at a Fig. 259. — Mixing-machine. speed of 40 revolutions per minute. The hearings of this drum are hollow, to receive a shaft which passes through them. This shaft carries in the interior of the drum a series of 44 arms, or diers, tlie points of which just clear the interior of the drum, and revolves at twice the speed of the drum, and in the opposite direction. 1102. A 50-lb. hag of ingredients is emptied into the drum through a scpiare opening at the top of it, and the drum and shaft carrying the lliers being set in motion for five minutes, the saltpeti-e, sulphur, and charcoal are thoroughly mixed to- gether. The opening at the bottom of the drum allows the mixed ingredients to fall down the shoot into a tub, from which they ai’e transferred to an 8-mesh wire sieve placed over another shoot having a composition-bag placed beneath it. On the sieve the charge is carefully sifted by hand, to guard against any foreign matter, such as splinters of wood from the saltpetre bins, etc., pas.smg into it, and falls through into the bags, in which it is tied up tightly and transferred to the charge- house, ready for the incorporating-mill. 1103. Incorpokation. — Incorporation is unquestionably the M/il^UFACTuRE OF GUNPOV/DER, 395 most important of all the operations in the manufacture of gunpowder. Without it there Avould he no manufacture, for the charge of saltpetre, sulphur, and charcoal goes to the in- corating-mill a mere mixture, and leaves it gunpowder, l^oth- ing that can he done to it afterwards will add to its strength or explosiveness ; no future treatment can remedy defective in- corporation. By incorporation is, of course, meant the long- continued grinding together of the ingredients which hlends them together and brings them into such close juxtaposition, that they appear to form a new substance. Unless this be done perfectly, perfect mutual decomposition of the con- stituents of the gunpowder cannot be expected on combustion. The more thoroughly it is effected, the stronger will be the resulting gunpowder. 1104. Upon the thorough and effectual mcorporatiou wliich it receives depends mainly the excellence of powder. Great attention is paid to the process, not only for military, but for sporting purposes, and the most powerful mills are always used. It has been carried to the highest pitch of excellence, and in many eases it is carried on for an unnecessary length of time; some of the liner sporting powders are said to be incor- porated for twelve hours. Provided the iucorporating-mill is sufficiently powerfid, and is worked at a sufficient speed, a most thorough incorporation can be effected in a few hours, after which there is no object in continuing the process. But as imperfectly incorporated powder cannot fail to be of inferior (quality, and to foul the gun under most circumstances, it is best to incorporate the materials as thoroughly as possible ; and if the powder is thus rendered too explosive, this quality can be reduced by increasing its density and hardness, and by vary- ing the shape and size of its constituent grains. (Art. 1114.) 1105. Imperfect Incorporation . — What may be expected of an imperfectly incorporated powder may be at once seen by burning small quantities of different powders, varying in the amount of incorporation they have undergone, on plates of glass or porcelain. A perfectly made powder flashes off, leav- ing nothing but some smoke-marks ; an imperfectly worked powder will coat the plate with specks of un decomposed salt- petre. 'Y\x\^ flashing test is a simple and effectual way of ascer- taining the amount of working which has been bestowed on the powder in the mills, and is the only safe and infallible test of incorporation. This test must be performed by an ex- perienced person, and no powder which does not stand it can be expected to shoot either strongly, uniformly, or cleanly. 1106. -The Incokpoeating-mill. — In order to effect a close 396 NAVAL ORDNANCE AND GUNNERY. and intimate reunion between the saltpetre, the sulphur, and the charcoal, they must be rolled and ground together for a Fig. 260. — Incorporating-mill. (Elevation), length of time ; and the gunpowder-maker finds the most effectual way of accomplisliing this, is to grind the materials together under heavy edge-runners of stone or iron, which by their motion — a compound of rolling and twisting — soon work them into a homogeneous mass. 1107. The mill generally used consists of apair of large, heavy edge-runners of iron or stone, which revolve on a strong circii- MANUFACTURE OF GUNPOWDER. 397 lar bed, the bed being, of course, stone for the stone, and iron for the iron runners. (Figs. 260 and 261.) Tlie runners are of various sizes, weighing from 3 to 4 tons each, and being from 4 to 7 feet in diameter. Those of the smaller diameter are better than the larger, as the latter caiise a greater twist on the bed, and are therefore more apt to cause accident. The face of the runners should be nearly flat, with a slight bevel towards the edge. 1108. The runners are connected by a powerful spindle of wrought-iron, which rests in brass bouches placed in the cross- head, so as to allow the spindle and runners to rise and fall according to the thickness of the layer of material on the bed. The spindle is placed in the cross-head, so as to bring one runner nearer to it than the other, and therefore cause them to describe different paths when in motion. 1109. The cross-head is flxed on a vertical shaft, on which is fixed, underneath the flooring of the mill, a wheel driven by 398 NAVAL ORDNANCE AND GUNNERY. a pinion on the driving-shaft, which passes underneath the whole group of mills, By this arrangement the whole of the Fig. 2G3. — Incorporating' MiU. (Section.) machinery is kept underneath, and out of reach of damage from explosion. The cross-head is fitted with a bracket on each side, to carry 2. plow ^ or wedged-shaped piece of wood shod with felt and leather, which travels round on the bed immediately in MANUFACTURE OF GUNPOWDER. 399 front of the rnimers, and thus keeps the composition from working away from them. The bed has a curb or edge round the outside, formed by a sloping rim or casing fixed all round it ; that on the inside is formed by the circular base of the conical socket, down which the vertical shaft of the cross-head passes. Both the inside and the outside curbs have gun-metal rings round them for the plows to work against. Every fitting and bolt is arranged witii the greatest care, so as neither to break nor become loose from the jolting of the mill, and thus drop into the charge. illO. Tools Used. — The instruments used are a wooden ral:e, to distribute the charge over the bed ; a shaver, or flat board on the end of a staff, to push off the charge from the bed occasionally ; a copper chisel, to be used in getting the charge off the bed when finished ; a brush for brushing the materials into the centre of the bed ; a wooden mallet, to break up any caked powder which may adhere to the runners or bed ; and a copper watering-pot, used for watering the charge. fill. The Operation. — The charges, which have been care- fully sifted in order to avoid the possibility of foreign matters - getting into the mill-bed, are thrown one half on each side of the bed, and distributed evenly over it. The runners are then moved round a quarter I’evolution, and the piece of mill-cake left under them from the former charge is broken off and dis- tributed over the fresh charge. 1112. This portion of mill-cake is of course finished powder, and quite hard, if the nmners have been left standing on it. It is broken up and distributed to prevent its adhering to the bed and causing too much friction. The runners are usually left on the portion of powder on which they stop when the in- corporation is complete, as the attempt to move them off on to a leather placed on the mill-bed involves the risk of a portion of the runner coming down in contact with the bed, and thereby igniting some of the powder-dust with which every crevice is filled. 1113. Before starting the mill about two pints of pure water are sprinkled over the charge. The runners are then started at a speed of about eight revolutions a minute. The millinan does not remain in the mill, but only goes in from time to time to push up the charge from the bed and to add a little more water according to the state of the charge. From two to three pints are generally found to be necessary in very damp weather, and as many as eight or ten in very bright days. The watering of the charge is left to the millman’s judgment. 1114. Time Iteguired for Incorporation. — The times of in- 400 NAVAL ORDNANCE AND GUNNERY. corporation vary with the power of the mills. Thns, cannon powder requires 3|- hours working under stone lumners weigh- ing 3|- tons, and making 7^ revolutions a minute, but only "2^ under iron runners of 4 tons, making 8 revolutions a minute. Small-arm (dog-wood) powders require 5^ hours in the former mills, and 4 in the latter. Taking about 50 lbs. as the maximum amount which it is best to incorporate at one time imder one pair of runners, it is easy to calculate the capacity of a gunpowder factory. A cer- tain amount of work can be obtained from them, and no expe- dient can produce more ; no extra time or work can be ex- pended on the process. 1115. The powers of a gunpowder factory are therefore known, being regulated by the numbers of pairs of incorporating runners which it possesses. The manufacture of gunpowder cannot be hastened, and even if it could, an explosion may happen at any moment which may cripple a factory for the greater part of a year, so that an extensive store of gunpowder is always required to be kept on hand in case of war. 1116. Mill-calce . — As the process of incorporation ap- proaches completion, the charge requires to he carefully watched, in order to ensure each finished charge leaving the mill in as nearly as possible the same state as regards moisture. The appearance of the powder when finished depends mainly on the state in which the charges leave the mill. The finished charge usually has from two to three per cent, of moisture. If too much moisture be present as the incoiq)oration draws to a close, the charge must be repeatedly pushed up with a shover ; if too little, some more must be added from the watering-pot. The color of the charge gives a very good indication of the amount of moisture present. 1117. When the process is finished, the charge, now known mill-calce — being partly in the state of soft cake, and partly of dust — is scraped and swept up from the mill-bed, placed in wood- en tubs, and transferred to the charge-houss to await inspection. If the charges are found to be of a proper color and consistency, samples from each are taken, which, after being roughly granu- lated by hand, and dried, are flashed on a glass plate to ascertain the thoroughness of the incoiq)oration which they have under- gone. This flashing is more a matter of form than anything else, for the mill-cake seldom fails to give satisfactory results. 1118. Danger of Incorporation . — As incoi-poration is the most important of all the operations in the manufacture of gun- powder, so it is by far the most dangerous. Accidents in the subsequent processes, where large quantities of powder are sub- MANUFACTURE OF GUNPOWDER. 401 Jeeted to treatment at one time, are fortunately rare ; but in the incorporating-mills tliey may be expected from time to time. It is hardly possible it can be otherwise, considering the enormous friction to which the powder is subjected in them. 1119. Tlie amount of water added to the charge does not re- duce the ingredients to a pasty mass, and so lessen their explosive- ness; on the contrary, the charge when it approaches comple- tion is highly explosive. If a large amount of water Avere added, the saltpetre Avould be partly dissolved, and all the in- corporation preAdously etfected would be undone. 1120. It is difficult to conjecture how accidents do happen, unless it be from the charge adhering to the runners and leaving the bed bare, in which case the friction betAveen the runner and the bed is so great as to cause a spark. Of course the more obvious causes of accident, such as some foreign body falling into the bed, are not alluded to here, but only those causes which are as yet unknown, and Avhich no amount of vigilance can altogether avert. 1121. Drencliing-apjyaratus. — Admitting, therefore, that occasional explosions in the incorporating-mills are inevitable, the object of the manufacturer is to render them as harmless as possible. As the mills are generally built in groups, an explo- sion in one, is very apt to spread amongst all the others round it. To prevent this a drenching-aj>j>aratu8 (Fig. 263), is erected over each pair of runners. 1122. The apparatus consists of a large shutter pivoted on a spindle, which runs through the whole group of mills. To this spindle the shutter in each mill is attached, and the spindle passes through bearings in the partition-walls, so that the lifting of the shutter lifts all the others. Balanced on the pivot-edge of the shutter is a large copper vessel full of water. This A-essel is so arranged that the slightest lift of the shutter capsizes its contents into the bed of the mill beneath it. 1123. An explosion in one mill, therefore, lifts the shutter above it and throws down the water into the mill-bed, and though, of course, too late to do any good in the mill which has exploded, the movement of the shutter turns the spindle and drowns the charges in all the adjacent mills, and thus saves them from explosion. This drenching-apparatus is found to answer very Avell. 1124. The explosion of a green charge does not, in some cases, do much damage to the structure of the mill or the machinery ; that of a Avorked charge is very violent, and leaves generally no part of the structure standing. Consequently all mills should be made of very strong framework, covered with 26 402 NAVAL ORDNANCE AND GUNNERY. light hoards, which can he quickly replaced if destroyed hy an explosion. Fortunately the men do not requme to he always in A. — Cistern made of copper to hold 40 {jallons. B. — Vf eight made of cast-iron to balance the shutter. C. — Shutter made of wood. When lifted by an explosion relieves the foot of the cistern, A, causing it to turn over, drenching the mill, and also turning over ail the cisterns in connection with the shaft, D, which passes through the .stufinng-box, E, it being built in the walL F. — Couplings connecting.the shafts on both sides of the wall. the mills ; on the contrary, they only enter them from time to time for a minute or so — either to liquor the charge, or to see that all is going on well. 1125. PRESSING. — Gunpowder leaves the incorporating- mill partly in the state of soft cake, partly dust. The cake hardens very considerably, if allowed to stand for a few days. In this form it would be unfit for use. The cake may be broken up into grains, but such grains are too soft to stand much handling or transport without crumbling to dust. Powder made from mill-cake will always be found to be dusty, and such powder must always be irregular in action. It will also be much more liable to absorb moisture, and therefoi'e to cake and become lumpy. 1126. To ensure uniformity and good-keeping qualities, and freedom from dust, powder must be converted into firm grains. This is done by compressing the soft material into hard masses by pressure alone, and then crushing up these masses into the description of grain required. The object of ])ressing, then, is MAircrFACTUEE OF GIJXPOWDEE. 403 Fig. 264. — Press. Elevation and section showing press in action. A. — Cylinder. B. — Earn. C. — Press-box. D. — Overhead-block. E E. — Standard. dranlic gunpowder-press is shown in Figs. 264 and 265. The to convert the soft dusty mass of ineorpotated ingredients, now gunpowder, into hard cakes of the particular density which is found to give the best results when the powder is finished. After the cakes are formed they can be broken up by various contrivances into grains of any size, all of which will have a uniform density and hardness, and which can be freed from dust, and glazed and polished so as to bear handling and trans- port without breaking or crumbling. 1127. Gunpowder is generally pressed in layers between plates of gun-metal or copper, in a hydraulic press. Screw- presses are sometimes used, and there are different ways of placing the powder in the presses used. The best results are found to be obtained by pressing in thin layers. 1128. DESCEiPTion of Press. — A convenient form of by- 404 NAVAL ORDNANCE AND GUNNERY. press-box Is made of gun-metal, lined inside and out -with oak boards, and is of great strength. The bottom and one side are Fig. 265 — Press. Elevation and section showing press partly unloaded. permanently attached to each other. The other three sides are liinged to the bottom, so that they can be opened out to facili- tate unloading. When closed tbey are secured with short, coarse-threaded screws of gun-metal. The box has two project- ing gun-metal claws, which hinge on to a fixed horizontal rod of the same metal, so that the box can be turned on it, on the table of the hydraulic press, when filled and ready for pressing, or outwards when it has to be unloaded. 1129. Loading the Press . — Being first turned down on its side, the open top is closed temporarily with a piece of board which is fitted to it. What is now the uppermost side is un- covered and raised, and the other two sides are fastened in their places. Gun-metal racks to hold the press-plates, having per- MANUFACTURE OF GUNPOWDER. 405 pendiciilar grooves in them inch apart, are then slid in on each side, and the plates being put in, the powder-meal is shov- elled in and falls down readily between the plates till the box is full ; the racks are then drawn out, leaving the plates free, with layers of powder between them. The excess of powder being carefully swept off the edge of the box, the upper side is lowered and screwed to the other three ; an overhead-block and tackle are made fast to the gun-metal eye on the side of the box, and the box is turned over on the press-table. 1130. The box now stands on its bottom, and the temporary board with which the top has been closed dui'ing charging being lifted off, the powder and plates will be found to have settled down several inches by their own weight. The vacant space at the top is tilled up by shovelling in a few more layers of meal, placing a plate by hand on each in succession, till the press-box is full. The overhead-block, which exactly fits into the press- box, is now run into its place, over and nearly touching the con- tents of the box, and secured there, when everything is ready to apply the pressure until the box rises to a sufficient height. 1131. Unloading the Press . — After the designated pressure has been attained, the press-table, carrying the press-box, is allowed to descend. The pumps are in another building, separated from the press-house by large traverses, and here the workmen remain while the pressure is being applied. The workmen now re-enter the press-house and proceed to unload the box. The overhead-block is first run out of the way, and the block and tackle being attached to the box, it is turned over on its side. The fixing-screws are now taken out of their sockets, and the three hinged sides of the boxes opened out, leaving the powder and press-plates standing in a solid mass. Each plate, with a layer of hard slate-like cake adhei’ing to it, is separated from the one beneath it, and, being lifted into a wooden bin, gets a few knocks with a wooden mallet, which cause the cake to fall off in irregular fragments, which are broken into pieces of the size of a man’s hand, shovelled into tubs, and removed. 1132. Uniformity of Residts . — To obtain pressings of equal density, equal quantities of powder-meal must be compressed equal distances. It is a matter of considerable difficulty to en- sure, uniformity of results in pressing powder. It is of the highest importance that the density obtained should be uniform, for recent experiments have proved conclusively that the quali- ties and explosive effect of gunpowder are materially affected by comparatively slight variations in density. It is perfectly possible to manufacture powder of uniform density, and such powder will give accurate and uniform results, both as regards 406 NAVAL ORDNANCE AND GUNNERY. pressure in the gun and, consequently, velocity imparted to the projectile. The density of powder is given in the press ; the importance of accuracy in pressing, in which the shooting qualities of powder therefore entirely, or at least mainly, de- pend, is evident. 1133. As the powder-meal possesses varying degrees of elas- ticity and resistance to pressure, depending to a great extent on the moisture it contains, and, as far as can be judged by experi- ence, on the state of the atmosphere at the time, equal pressures will not always have equal effects. It is therefore very neces- sary to have all the conditions made as nearly as possible the same in each experiment. If equal quantities of meal contain- ing equal quantities of moisture could be compressed to the same amount in equal times and under the same atmospheric conditions, then there is little doubt that tolerable uniformity of density would be attainable. But it must be always a matter of the greatest difficulty to fulfil all these conditions exactly. In the ffi’st place, the moisture in the powder-meal depends mainly on the amount of liquoring the charges have received. This is usually left to the judgment of the workman, who is “guided by the state of weather. And though the charges may be unifomi as regards moisture, on leaving the mills, it is obvi- ous that variations of temperature between the days of incorpor- ation and pressing will affect them unequally. In the next place, the bulk of the meal is affected by the moisture contained in it, so that fill the press-box as carefully as we can, we do not get equal quantities to be subjected to pressure each time. 1134. If the quantities operated on were very small, it might be possible to devise some method of equalizing the moisture contained in them ; but when large charges are required to fill the press-box, it becomes a much more difficult matter. It is necessary, when examining the densities of press-cake in order to ascertain if it is fitted for the manufacture of a particular ])owder, to have it previously dried. 1135. It is found in practice that though absolute uniform- ity cannot be guaranteed in pressing, very close results can be obtained. To attain absolute uniformity in the finished pow- der, the density of every pressing, after it has been converted into grain, is taken, and the different pressings are then mixed in the proportions to give the density required. Thus if the density fixed for the powder be 1.07, and the densities of the pressings be found to be 1.70 and 1.04, they would be mixed iu equal proportions, and would give a powder of 1.67 density. Powders which differ to a great extent in density are never mixed. MANTJFACTUEE OF GUFTPOVtTDER. 407 1136. GRAINI?7G. — The press-cake must now be converted into the particular size of grain required. And the means em- ployed to break uja the press-cake must be so arranged as to crush it up as nearly as possible into the size or sizes of grain wanted, without reducing much of it to dust. The smaller the size of grain, the larger will be the percentage of it obtained from granulated press-cake ; hence with the small size of grain formerly used with cannon, any of the older and ruder appli- ances for effecting granulation gave good percentage of grain. But as recent experiments have conclusively proved that much larger-sized grains should be employed in large charges for heavy ordnance, new and improved granulating-machines have been introduced. Large powders have been made by tlirowing the press-cake on a table and breaking it up by hand with mallets ; but there is little doubt that arrangements and alterations can be made in the machines so as to enable them to granulate powders of any size of grain. 1137. Geanulating-machine. — The granulation is effected by passing the press-cake between revolving toothed rollers of gun-metal. The machine contains four pairs of such rollers ar- ranged in a slanting direction, one above the other. (Fig. 266.) A. — Hopper witli raising arrangement. EE. — Long Screen. B. — Endless Band. F. — Box for Dust. CCCC. — The 4 pairs of Rollers. G. — Box for Grain. EBB. — The Short Screens. H. — Box for “ Chucks.” These rollers are set in the two strong side-frames of gam- metal which form the framework of the machine. Each ]>air is adjusted at the proper distance apart by set-screws; but the back roller of each pair works in a sliding bearing, which is kept up against the bearing of the other roller by a weighted lever, so as to admit of the rollers opening out and admitting an excess of material to pass through without injury to the ma- 40S NAVAL ORDNANCE AND GUNNERY. chine. The two upper pairs of rollers have coarser teeth than the lower pairs. 1138. Slanting rectangular sieves or screens are placed un- derneath each of the three upper pairs of rollers to the top of the next, to convey any fragments which escape proper crashing in one pair into the teeth of the next pair. Underneath the whole is a long rectangular frame carrying two long screens to separate the proper size of powder, and a board underneath to receive the dust and carry it down into a tub placed to receive it. Both the short screens and the long frame are attached to the framework of the machine, and receive a vibratory motion by means of appro j)ri ate mechanism. 1139. Attention must be paid to the angles at which the different screens are placed ; this varies in different machines, and the proper inclination can only be ascertained by experi- ment. These screens will of course require to be changed for each different size of powder that is being made. 1140. Action of the Machine . — The general action of the machine will be understood from Fig. 266. The press-cake is placed in a hopper at the back of the machine, and earned up by means of an endless band of canvas having strips of leather sewed to it to catch the cake. The band passes under a scraper which prevents too much cake being carried up at once. The cake falls between the first pair of rollers, which work at a speed of about thirty revolutions per minute, and is immediately crashed up into granular fragments which fall in the first short screen. The whole of the grains, except the fragments which are too large, fall through this screen directly on to the surface of the upper long screen underneath, and fall through it like- wise to the second, Avhich permits the dust and minuter parti- cles to fail through on to the sloping board underneath, down which they slide into the tub placed to receive them, but Avhich retains the proper size of grain, which in turn rolls down it mto another receptacle at the bottom. 1141. The larger pieces Avhich escaped proper crushing in the first pair of rollers are shaken down by the first short screen into the second pair, to undergo the same process as at first, and so on Avith the third and fourth pairs of rollers. Some fi*ag- ments of too coarse a size Avill escape all the rollers, and conse- quently require a third box to receive them in front of the other two placed to receive the dust and grain respectively. These pieces, termed chuchs, require to be passed through the machine again. 1142. TFhen the hopper has reached the limit of its travel upAvards, and all the cake has fallen out into the band and been MAyUFACTIJEE OF GUNPOWDER. 409 conveyed up to the machine, a clutch is relieved which stops the upward travel of the hopper, and a hell is rung in the watch- house where the workmen remain during the time the machine is working. The machine, being self-supplying, requires no watching when working. As soon as the bell rings the work- men re-enter the house and place tlie grain and dust in tubs ready for transmission to the proper store-rooms. 1143. Danger of the Process . — To judge from the large proportion of accidents which take place in granulating-houses, the process-would appear to be specially dangerous. It is diffi- cult to account for the fatality which accompanies granulating- houses. In any well-regulated factory the operation is not con- sidered to be any more dangerous than any of the other pro- cesses, but statistics show beyond doubt that it must be specially dangerous. The probable explanation appears to be that if there has been any negligence anywhere in keeping fragments of foreign matter from the powder as it progresses through the various stages of manufacture, the granulating-house, in which the powder undergoes more crushing and grinding than it does anywhere else, anrl where there are a number of metal axles and bearings at work, is the place where such negligence will most surely tell. 1144. Dusting AND Glazing. — The granulated powder as it comes from the machine contains amongst it a large cpiantity of dust. This is formed by the crushing action of the granulating machine, and must of course pass through the various sieves and screens with which the machine is provided along with the grain. The grain itself is not in a condition to be made use of as powder, being rough and porous on the surface and very an- gular in shape ; and moreover, the presence of a large quantity of fine dust amongst it would render it not only most incon- venient to handle, but would also render it more liable to absorb moisture, and to deteriorate. 1145. A rough, unpolished angular grain would also very speedily rub down into dust, if subjected to much shaking in transport. It becomes necessary, therefore, to free the granu- lated powder from all traces of dust, and to polish or give a sur- face to the grains themselves to enable them to bear a great deal of friction without deterioration. 1146. Powder is freed from dust by placing it in revolving reels covered with cloth or wire mesh of various degrees of fineness, through which the dust escapes. It is glazed by caus- ing the grains to rub against each other in revolving wooden barrels. The extent to which the operations of dusting and glazing are carried, and the nature of the appliances used, de- 410 NAVAL ORDNANCE AND GUNNERY. pend entirely on the density, hardness, and size of grain of the powder operated on. 1147. Large-grained, dense, hard powder will hear a great deal of knocking abont in tire reels without becoming disinte- grated and forming fresh dust; and will, moreover, bearagi’eat deal of friction in the glazing barrels, acquiring speedily a high degree of polish. But when operating on a small-grained, soft powder of low density, the dusting must be carefully conducted, as the process will develop as much fresh dust as it removes; and the amount of friction the grains will bear in glazing must be likewise carefully regulated. 11-18. It is found in practice that powder may be divided into two general classes, each of which requires different treat- ment in dusting and glazing, viz., the cannon jpovcd^cr of all (‘lasses, and the small-arm powder of all classes. The former is not only pressed to a higher density, but is made of a larger size of grain ; the latter generally is of lower density and much smaller size. Modern cannon powder, being of large-sized grains and of firm consistency, admits of a comparatively open-ineshed reel- covering being used in dusting, and of the process being contin- ued as long as required without risk of injury to the grain. The powder can therefore be rendered perfectly free from dust, and sufficiently glazed at the same time, coming out of the reel as finished powder at one operation. 1140. The Dusting-eeel. — There are two classes of reels in use, the horizontal and the slope, the former usually employed with j:)owder of large grain, and the latter with fine-grain pow- der. Different powders take different lengths of time to be freed from dust, and require different descriptions of reel-cover- ings. It is impossible, therefore, to lay down exact rules in such matters, and it would be tedious to go over all the particu- lars of the numerous dustings that all kinds of powders undergo. 1150. A horizontal reel (Fig. 2GT), consists of a cylindrical skeleton of wooden hoops supported on a shaft by radial arras, the skeleton being covered with canvas or wire cloth. The reels are made in Mves for convenience of repair and re-cover- ing. The shaft is of iron, covered with wood ; the radial arms are of gun-metal ; the ends are formed of two short disks of wood screwed upon the shaft. One end can be unscrewed and drawn back. The bearing of the reel-shaft next this movable end is fixed in a block which can be lowered if necessary, so as to put the reel for the time being on a slope. In the middle of the reel is a square opening closed with a wooden door, through which the powder is placed in the reel, being run through a MAlSrCTFACTURE OF GUNPOWDER, 411 hopper at the top of the parallel wood-casing in which the reel is placed to coniine the dust which escapes from it. Fig. 267. — Ilorizontal Reel. (Section.) AA.— Reel Covering. D.— Opening for loading. B.— Shaft. E.— Hopper for loading. CO.— Movable End. FF.— Reel Case. G.— Block carrying the bearing of the lower end, which can he raised or lowered by means of the rope, K, and Lever, L. 1151. Horizontal re^ls are intended to receive a quantity of powder for a certain length of time, and to revolve with it, shaking it against the reel covering, and thus forcing the dust through the meshes, When a reel has run the required time, say a half-hour, making forty revolutions, with a charge of powder, the driving-wheel is made to revolve very slowly, the end of the reel is lowered by means of a rope and lever, and the movable end of the reel is unscrewed and drawn back. As the reel slowly revolves the powder runs out into a hopper and is conducted into the baiTels. 1152. Slope reels are not intended to retain the powder, but only to extract a certain portion of dust as it runs through them. They resemble the horizontal reels in general construc- tion, except they have no ends and the shaft is set at a perma- nent slope. Each reel is provided with a feeding-hopper at its upper end ; attached to which is a loose spout for guiding the powder into the reel. 1153. The Glazing-barkel. — Glazing-barrels consist of 412 NAVAL ORDNANCE AND GUNNERY. large strong wooden baiTels (Fig. 268) supported on an iron shaft Avhich runs through their centre. The barrels, tAvo of which are generally placed in line on one shaft, are made of oak, and are aboiAt 5 feet long and 2|- in diameter ; the shaft is eased with wood where it passes through the barrels. Each barrel is provided with a small square door for charging and uncharging. 1154. The barrels are found to be peculiarly well adapted for the purpose, oAving to their shape. Formerly wooden cylin- ders with straight sides were used, but it was found that the ditferent sizes of grain had a tendency to separate in them, so that all did not receiA^e an equal amount of polishing. But in the barrels, which are larger in diameter at the centre, there fs a constant intermingling of the grain and a more uniform action. 1155. With large-grained powders sometimes a little graphite is used to obtain a better surface. This gives a line silvery surface to the grain, but care must be taken to use the proper description of black lead. This is really an impurity, and should therefore be sparingly supplied to powder. It is never used Avith any of the fine small-arm powders, but only with poAA'ders intended to be used in large charges and Avith the express intention of giving them a surface which will, if any- thing, retard rather than quicken ignition. Inferior blasting- poAvder is sometimes polished in this way to a high degree of brilliancy, but the lustre is no test of its quality. 1156. The friction of the grains in the glazing-bai’rels MAOTJFACTUKE OF GUNPOWDER. 413 necessarily generates a good deal of heat. Some of the fine- grain powders which require a long time in glazing come out so hot as hardly to admit of the hand being plunged in them. In all cases the heat generated is so great as to cause the powder to part with almost all its moisture ; but as there is little or no escape for it, it condenses on the interior of the barrels and forms a hard coating with the powder-dust.* 1157. The glazing process not only polishes the grains, but tends to rub off their more prominent angles and to bring them to a rounded form. It generates a little dust, and requires, therefore, a second dusting, after which it has only to be dried to be ready for use. 1158. Drying. — The drying-rooms consist of large cham- bers having an arrangement of steam-pipes running along the floor, and provided with double doors which can be closely shut, and with ventilators at top and bottom which can be closed or opened from without. The temperature is main- tained at from 125° to 130° F., and regulated by a large ther- mometer inside, which can be read from without. The chambers are fitted with wooden racks, on which are placed the trays containing the powder. The powder is gener- ally kept one day in the drying-room. In the case of large- grain powder, wFen withdrawn it is placed in barrels and headed up for issue. But in the case of fine-grain powders, a third dusting is sometimes requisite to remove all traces of dust and fit them for service. This is teYmed Jmishing, and is done in a horizontal reel. Explosions of drying-rooms are comparatively rare. 1159. Special Powders. — On the introduction of the mammoth modern ordnance it became apparent that the ordi- nary powders in use were too sudden in their action for the power of the guns. This led to the making of special powders in the shape of prisms, cylindrical pellets, spheres, etc., with a view of modifying the explosiveness of the charges. 1160. Large-grain powder for heavy guns was first adopted in this country in 1861, at a time when other nations continued the use of small-grain. This great improvement in the mode of manufacture was the result of careful study and experiment. The invention of Hodman’s “ perforated cake,” or prismatic powder, which has been adopted by, and is now in use in both Russia and Germany, and the “ pebble ” powder, similar to our “mammoth,” adopted by England, created that revolution in the manufacture of gunpowder, based upon purely scientific * Glazing barrels are now fitted with ventilating bungs which open at each revolution, and aUow the heated air, surcharged with moisture, to escape ; thus preventing ‘‘ sweating.” NAVAL OKDNANCE AND GUNNEET. il4 principles of combustion and evolution of gases, that has ena- bled all nations to increase the size of their ordnance. The question of variations of the density of powder and of the effect whieli such, especially when combined with variations in shape and size of grain, could not fail to produce, soon began to attract general attention. Those who studied the subject soon became aware of the immense advantage to be derived, not only from increasing the density of powder, and thereby lessening e.xplosiveness and consequent strain on the gun, hut from uniformity of density and shape of grain as affecting reg- ularity of effect. IIGI. Experiments are still being made with a view of de- termining the description of gunpowder whose employment in large charges is attended with the least risk of overstraining the heavy gnns in service. The projecting charge should be so related, in its rate of combustion to the form of the gun from which it is fired, that, with a given convenient thickness of metal and length of bore, the maximum velocity of projectile attainable from such gan should be produced. In comparing one gunpowder with another, the radical question is, which contains the best supply of gases, and which maintains this supply most advantageously at the required ten- sion. The tension may be too low as well as too high ; what is wanted is an elastic force which will not strain the gun more than is needed to give to the projectile the required terminal speed. The causes which affect the quality and character of gun- powder, and the phenomenon which attends its application to projectile purposes, depend upon the concurrence of a variety of conditions, not a few of which are unknown. Ill powder-making, ability to reproduce results will always be the important question ; so many disturbing causes tend to affect its final qualities that, after every precaution has been taken to remove them, perfect uniformity in the finished arti- cle produced from day to day cannot, with our present means and knowledge, be surely counted upon. 1162. TERMS APPLIED TO DIFFEREXT KIXDS OF POWDER. — Dunpowder for the Xaval Service is known and designated under the following heads : Hexagonal, Mam- moth, Rflle, Cannon, Shell, and Small-arm ; classed according to the size of the grain. They are all, as a general rule, made of the same proportion of ingredients, although the size and den- sity of the grains, hardness, and amount of glazing is different with each. MANUFACTURE OF GUNPOWDER. 415 PLAN •0 ■ a-— These points are now being experimented on, and change of classification about to be made. 1163. Majoiotii Powder. — This is an irregular, large- grained powder about 0.8 inch in diameter, which is used for large charges in heavy guns. The large-grain powder greatly diminishes the strain on the gun, in producing a given velocity, from that due to ordi- nary cannon powder, because of the longer time required for the complete combustion of each grain. The larger the grain, other things being equal, the less v/ill the maximum exceed the mean pressure, and the greater will be the charge required to produce a given velocity. 1164. Prismatic Powder, or perforated cake-powder (Fig. 269.) — This is ordinary powder made in the form of regular hexagonal prisms about one inch thick and 0.8 inch in the side, perforated with seven holes about 0.1 inch in diameter. The cakes are formed by plac- ing mealed powder, moistened sutficiently with water, in a mold of the proper form, and subject- ing it to the required pressure. In making up charges of this powder the prisms are built up regularly in the cartridge-bags like honeycomb, which are then tightly tied at the mouth, so that the grains are kept in place. These perforations thus form long tubes through the charge, b,7 which the gas permeates the whole mass. This powder, originally from the United States, has been in- troduced into the German, Rus- sian, and Austrian services, and finds many advocates elsewhere. This form of powder is based on the theory that the grains, being ignited through the perforations, burn outwardly, pro- ducing a progressively increasing surface of ignition, thereby evolving greater volumes of gas, as the velocity of the projec- tile is increased, and the space through which the gas develops is augmented. 1165. Hexagojxal, Powder. — This powder, represented in ELEVATION Fig. 2G9. 4:16 NAVAL ORDNANCE AND GUNNERY. Fig. 270, is about 0.7 inch in diameter, and made by Dupont & Co. It has lately been introduced, and has given very good results. The granula- tion is veiy unifonn. It is called “ Hex- agonal ” by the manufacturers probably be- cause it is nearly so in cross-section. 1166. Waffle Powder. — This powder proposed by Commodore Jeffers, has been experimented with to some extent in the navy, with excellent results. It is pressed between plates with projecting ribs similar to “ waffle-irons,” which furnish a simple means of obtaining regular granulation, and thus controlling tlie sur- face. The fracture of the press-cake takes place along the grooves thus formed, dividing the cakes into squares, or rather truncated Fig. 270. its resemblance powder, similar pyramids, precisely as in Fig. 271, and of about the same general size as the hexagonal powder. 1167. Pebble Powder — so called from to small black pebbles. This is an English to onr Mammoth powder. It consists of irregular cubes, having edges from five-eighths to four-eighths inch in length, made by cutting up the press-cake into the re- quired form. 1168. Pellet Powder. — This is an English term applied to a large-grained powder. The pieces of the , Pellet powder are all of uniform size and cylin- drical shape, about one-half inch long and three-c[uarter inch diameter, with a perfora- tion at one end to give greater igniting siu- face. (Fig. 272.) 1169. lIiFLE Large Gralx powder, or ‘‘K. L. G.” powder, is an English service powder, in grains which pass through a sieve of four meshes, but are retained in one of eight meshes to the inch. 1170. Macheves for Maxixg Special Pow- ders. — The fundamental parts of every ma- chine, for making this class of powder, are: 1st, a mold in which to place the powder-mer.l ; 2d, a punch accurately fitting the mold, Avith which to compress the poAvder ; 3d, some appli- ance for pressing the finished pellets out of the molds. Fig. 272. MANUFACTURE OF GUNPOAVDER. 417 1171. A safe arrangement for combining these three is sho’wn in Fig. 273. A is a small charge of powder placed in the mold, B, which, fits it accuratelj. This punch has a shoul- der on it on which it rests loose on a second plate, C, under- neath the mold-plate. The lower end of this pundi rests on the upper surface of the hydraulic ram, D. An upper descend- ing punch, E, of larger diameter than the mold, can be brought 27 418 NAVAL OKDXANCE AND GUNNERY. down to the surface of the mold-plate either bj a screw or by a hydraulic pressure, so as to close the mold. With siich an arrangement a pellet can he safely made, firstly, by bringing the top punch down on the plate and fixing it there so as to confine the povrder ; secondly, by raising the lower punch, by means of the ram, till a proper amount of compression has been given to the powder ; thirdly, by stop- ping the ])ressure from beneath and raising the upper punch ; and, fourthly, by raising the finished pellet out of the mold by the pressure of the ram underneath. 1172. It is plain that any form caii be given to the pellets by altering the shape of the molds and punches, and that hob lows or perforations can be made in the pellet if recpiired. There is no difiei'ence really in any of these jmwders. except in the shape. A machine exactly similar to this could be used for making powder into hexagonal prisms perforated with holes. However, machines of different descriptions are em- ployed in different countries and by different makers. ATiat- ever arrangement is used, it must be always remembered that the only safe Avay of ensuring tolerable uniformity of density is to compress a certain amount of meal into a certain space ; and that giving each pellet the same amount of pressure in |)ounds does not necessarily turn out powder of uniform density. 1173. EXPLOSION. — The phenomenon of explosion of gunpowder may be divided into three parts, viz. : ignition, in- jiammatiov , and combustion. By ignition is luiderstood the setting on fire of a particular part of the charge; by inflammation, the spread of ignition from grain to grain ; and by combustion, the burning of each grain from its surface to centre. 1174. Ignitiox.— Gunpowder may be ignited by the electric spark, by contact with an ignited body, or by a sudden heat of 572° F. ' A gradual heat decomposes powder without explosion, by subliming the sulphur. Flame will not ignite gunpowder unless it remains long enough in contact with the grains to heat them to redness. Thus the flame from burning paper may be touched to grains of powder without igniting them, owing to the slight intensity of the flame and the cooling effect of the grains. " 1175. It inay be ignited by friction, or a shock between two solid bodies, even when they are not very hard. Experiments show that gunpowder may be ignited by the shock of copper against copper, copper against iron, lead against lead, and even lead against wood ; in handling gunpowder, therefore, violent shocks between all solid bodies should be avoided. EXPLOSION OF GUNPOVvDER. 419 1176. The time necessary for igniting powder varies accord- ing to circumstances. For instance, damp powder requires a longer time than powder perfectly dry, owing to the loss of heat consequent on the evaporation of the water; a powder the grain of which has an angular shape and rough surface will be more easily ignited than one of rounded shape and smooth surface; a light powder more easily than a dense one. 1177. IjsrFLA3J3X.\.Tiox. — When grains of powder are united to form a charge, and tire is communicated to one of them, the heated and expansive gases evolved insinuate themselves into the interstices of the charge, envelop the grains, and ignite them one after another. This propagation of ignition is called inflammation, and its velocity, the velocity of inflammation. It is much greater than that of combustion, and it should not be confounded with it. When powder is burned in an open train, fine powder inflames more rapidly/ than coarse ; such, however, is not the case in ii re-arms, owing to the diminution of the interstices. If a charge were composed of mealed-powder, the flame could no longer find its way through the interstices, and the velocity of inflammation and combustion would become the same. 1178. How supposing one grain or particle alone be ignited, it will first be inflamed over its whole surface, and the pro- gressive combustion will take place from the exterior to the in- terior. Itsrafc of comhustionw^W^ therefore depend upon both its shape and size, leaving out entirely, for the present, the question of density and hardness. A particle of spherical or cubical form ■will expose less surface to ignition in proportion to its volume than one of an elongated or flat shape, and will con- sequently require a longer period for the combustion of its en- tire mass ; the larger the particle, also, the longer will be the time required for its combustion. 1179. Looking, then, at one grain of powder by itself, we may say that the larger it is, and the more nearly its form ap- proaches a sphere, the longer will its combustion take and the slower will be the evolution of the gas. When, however, we come to regard the action of an aggregation of such particles, as in the charge of a gun, the rate of ignition of the whole charge is also aii’eeted by the size and shape of the grain. 1180. The part of the charge first ignited is that near the vent, and the remainder is inflamed by contact with the heated gas generated by the combustion of this portion, so that the rate of igmition of the whole mass will be regulated by the gi'eater or less facility with which the gas can penetrate thi’oughout the charge, which is itself dependent upon the 420 NAVAL ORDNANCE AND GUNNERY. shape and size of the interstices between the erains. If tlie grains be spherical and regular in form, the interstices will 1)C comparatively laige and uniform, and the gas will penetrate the mass with facility ; again, the larger tlie grains, the larger the interstices between them. If, on the other hand, they be hat or flaky and irregular in shape, the passage of the gas will be more chflicult, and the rate of inflammation of the charge reduced. 1181. We see, therefore, that the considerations which affect the more or less rapid combustion of an individual grain of gunpowder, also affect the rate of ignition of a charge of such grains, but in an opposite direction ; so that a form of grain which will individually burn rapidly may ofier an increased resistance to tlie passage of the heated gas tln-ough the charge, and thereby retard its ignition, while a grain which will burn more slowly may allow of the charge being more rapidly ignited. 1182. i>y varying the size and shape of the grain alone, a powdei' may therefore be obtained, a charge of which shall be ignited rapidly throughout, but burn comparatively slowly, or one wliich shall be ignited more slowly, but when once inflamed burn very rapidly. It is necessary to draw a clear distinction be- tween a rapidly-igniting and a cpiickly -burning powder. 1183. Ratio of the Charge. — The heat developed increases with the charge, and as the velocity of the gases increases with their temperature, it is tlierefore evident that a large charge is consumed cpricker than a small one ; it is also true that the loss of heat absorbed by the sm-face of the bore is much less sensible when the charge is great than when it is small, that is, the cpnantity absorbed is proportional to the surface, or the scpiare of the calibre of the gun and the heat developed increases as the cube of the calibre. 1184. The Resistance to he overcome. — When the projectile offers a great resistance it is not so quickly displaced as when the resistance is slight; its motion in the first instance is then less rapid, and it evidently follows that the inflammation takes place in a space more confined as the resistance to be overcome is greater. The smaller this space is, the more heat is concentrated, the higher the temperature of the gases is raised, and consequent- ly their velocity is increased, the inflamed gases have a less dis- tance to e.xpand. through, and there follows from all these causes a train of effects which accelerates the inflammation of the charge. 1185. The Place where the Fire is Communicated to the Charge. — When a cpiantity of powder is contained in an cii- closerl space, all the sides of which offer an equal resistance, EXPLOSION OF GUNPOWDER. 421 it is evident that the complete inflammation will be the qnieh- est possible when the fire is applied to the centre of the charge. In cannon, however, the force developed does not meet with the same resistance in all directions ; the projectile yields as soon as sufficient force acts tipon it, and as the combustion of tlie powder requires a definite interval of time, it follows that a great part of the charge is not consiuned until after the dis- placement of the projectile. In'ow the position of the interior orifice of the vent may influence the time required to displace the projectile, and this influences the inflammation of the charge. For example, with the regulation vent, it is the upper part of the charge which first takes fire ; the inflammation is communicated to the adja- cent parts and promptly reaches the projectile ; the gases ex- panding displace it, and the inflammation takes place in a larger space than that at first occupied by the charge. 1186. The Glazing of the grains facilitates the rapid trans- mission of the flame through the mass. 1187. — CowBUSTiox. — The velocity of combustion is the space passed over by the surface of combustion in a second of time, measured in a direction perpendicular to this surface. The diameter of the grains in “ cannon powder ” does not ex- need 0.15 inch ; the time required for combustion of such grains, therefore, is altogether too transient to be ascertained by direct observation. 1188. The velocity of combustion may be determined l)y compressing the powder composition into a tube and burning it, or by burning \h.Q press-calie. In the latter case take a prism of the cake of convenient length and about one inch square at the base, smear the sides with hog's-lard and place it on end in a shallow dish of water. The object of the lard is to prevent the spread of the flame to the sides, and the water is to prevent the lower end from being ignited by burning drops of powdei\ Set the upper end on fire and note the time of burning of the column with a stop-watch beating tenths of seconds. In either way it will be shown that the composition, if homogeneous, burns in parallel layers, and that the velocity of combustion is uninfluenced by the size of the columns or by the temperature and pressure of the surrounding gas. 1189. Now take a spherical grain of powder of homogene- ous structure, and so hard jrressed that the gas cannot penetrate it. Apply fire to any part of its surface ; the flame will imme- diately envelop it, and burn away the first spherical layer; the radii of the grain undergoing equal reductions in equal 422 NAVAL ORDNANCE AND GDNNERT. successive portions of time. T"lien at the end of half the time required for the total combustion of the whole grain, there will remain uneonsnmed a sphere of which the radius is one half the original radius, but the volume will be only one-eighth the original volume (spheres being to each other as the cubes of their radii.) At this epoch, therefore, seven-eighths of the grain will have been consumed. 1190. It will be seen from this, that for equal intervals of time, those taken in the first period of combustion givm forth very much larger amounts of gas than those taken in the last ; and that with a charge of such grains the gas is evolved in the inverse order desired : the evolution being greatest while the velocity of the projectile is least, and least Avhile that velocity is the greatest ; thus giving rise to excessive pressure at and near the seat of the charge. This may be remedied in some degree l)y inci'easing the size of the grain, the effect of wh.ich will be to diminish the amount of gas evolved in the first inffant of time, and thereby diminish the pressure in the gun. 1191. It may be shown by direct experiment that the burn- ing of a grain of powder in a fire-arm is progressive, and that the size of the grain exerts a great influence on the velocity of the projectile. For instance, if piece of iXiQ press-calce was placed in a small mortar and fired, little or no motion Avoukl be given to the projectile. If this piece be divided into seven or eight parts, the projectile will be thrown a short distance, and by increasing the number of the parts or grains, so will the effect of the powder on the projectile also increase. 1192. The progressive burning of powder is further con- firmed by the fact, that burning grains are sometimes projected from the gun with sufficient force to perforate screens of paper and wood at considerable distance. It is even found that they are set on fire in the gun and afterward extinguished in the air before they are completely consumed. The large grains of pow- der used in the fifteen-incli gun are sometimes thrown out burn- ing to a distance of one hundred yards. 1193. The Velocity of Combustion varies with the jyio- rity, proportions, trituration, density, and condition of the in- gredients, also with the pressure under which the powder is burned. Purity of Ingredients. — To secure the greatest velocity of combustion, it is necessary that the nitre and sulphur should be pure or nearly so. This can always be effected by a proper attention to the pre- scribed modes of refining ; but with charcoal it is different, for the part which it plays in combuscion depends upon certain EXPLOSION OF GUNPOIYDER. 423 cliaractenstics wliicli are indicated by its color and texture. Tlie velocity of combustion will be greater for red charcoal than for that which is black and strongly calcined; and for light airl friable charcoal, than that which is hard and compact. 1194. Proportiom . — By varying th.e proportions tlie velocity of combustion is varied. The increase of sulphur tends to make a more violent explo- sion and a more Cjuickly kindling mixture, as the sulphur is tlie kindling ingredient. Too much charcoal causes too slow burn- ing. The diminution of the snlphur.or nitre checks the rapidity of combustion, but may be made up by using more inflamma- ble charcoal. The quality of the charcoal is powerfully affected by the temperature at vdiich it is made. That made at a low temperature, or red charcoal, contains more hydrogen and less carbon, is more inflammable, and burns more rapidly, but, fro7ii its smaller proportion of carbon, must be used in greater quan- tity. It may be said that the charcoal is the varying ingredi- ent ; so that the proportions used at any time will depend upon the quality of the charcoal. In all naval ]iowder, great cai'e is taken to get a uniform quality of black coal, giving the nearest attainable approach to pure carbon. 1195. Trituration. — Gunpowder, unlike nitro-glycerine, ful- minate of mercury, and other detonating substances, is not a. chemical compound but only a mechanical mixture. By the' incorporating process during manufacture the three substances- of which powder is composed are so intimately mingled that the eye cannot detect the presence of any particular one. They are,, notwithstanding, only mixed, and the saltpetre can be readily dissolved out by water, or the sulphur sublimed in the form of a vapor, by the application of a moderate heat, leaving in either case the other two ingredients chemically unchanged. The more intimate the mixture, the more nearly does gunpowder approach to a chemical compound, and the more violent is its combus- tion ; but there always must remain a vast ditference between the most complete mechanical mixture and the most unstable- chemical compound. For this reason the combustion of gun- powder is only very rapidly progressive and not instantaneous,, as is the case with the violent explosives mentioned above. It is this difference that renders gunpow'der so valuable as a pro- pelling agent, for were it not for its comparatively mild action, no gun could be made sufficiently strong to resist its force. The material of the cannon would be broken before the inertia of the projectile could be overcome. 1196. Demit ]). — The density and hardness of the grains of powder are of quite as vital importance as their size and form, in determining the rate of ignition and combustion of a charge. 42i NAVAL ORDNANCE AND GUNNERY. By density is meant the quantity of powder actually present in a given hulk. It is important that this quality should not be confounded with hardness. A substance may he very liard and yet he of a low density. A powder with a very hard surface may be really less dense than anotlier, the surface of wliich is softer. Of course very high density cannot he communicated without pro- ducing a considerable degree of hardne.ss ; hut powder can be made hard without rendering it very dense, by pressing the dost in a comparatively dry state. 1107. Hardness seems to bear a direct relation to the power exerted in compressing, while density does not. Powder-dust, at a high degree of moisture, say G per cent, can he made very dense by application of moderate pressure, while that of 1 per cent, can only he brought to the same point in density by the exertion of enormous force. Of the two the latter will be the harder j^owder. 1198. Explosive Fouce. — By using a slower burniug pow- der less heat and pressure are evolved at first, and, the waste of heat in the stage of initial pressure being less, more heat remains for expansive action. Hence the slower burning powder is weaker at first but stronger afterwards ; and although tlie total quantity of gas be only the same and the pressure not so great at any point, yet the aggregate pressure throughout the bore may equal that of the more energetic and more dangerous powders. 1199. The cpiestiou of the instantaneous e.xplosion of gun- poAvder is one of extreme importance, for, independently of the increase of the actual amount of pressure Avhich it would cause in a gun, this pressure Avhen suddenly applied Avill have tAviee the destructive effect that the same pressure AA’ould have if • sloAvly applied. 1200. The objects to be attained in regulating the size and •density of the grains are, the greatest possible Amlocity of pro- jectile combined with the least strain on the gun. These can- not be obtained by one set of conditions for all natures of ord- liance. A small projectile moves quickly and relieves the strain in a still greater ratio. A heavy projectile not only moves sloAAdy, but even a considerable motion does not relieve the • strain in a proportionate manner, because the column of pow- der is larger in a large gun than in a small gun. IVitli small- arms, consequently, Ave must use fine-grain poAvdei’, but large- grain poAvder Avith heavy guns. 1201. Owing to the effect Avhich heat and pressure have in accelerating combustion, the size and density of grain that will suit any particular gun, and as a consequence the actual pressure lin the gun itself, can only be determined ])ractically. 12Q2. The explosive force of gunpowder may be calcidated EXPLOSION OF GUNPOWDER. 425 from the products of combustion, on the assumption that certain laws hold good, such as that the tension of a gas varies with its density and also with its temperature. It must, however, he re- memhered that these laws have been verified only within certain limits of pressure and temperature ; and therefore, Avheii Ave come to such Amrv great pressures and temperatures as are met with in the explosion of poAvder, any conclusions founded on them must he received Avith caution, until the results have been confirmed by experiment. 1203. It is of little practical utility to attempt to determine the exact value of the explosive force of gunpowder, for the na- ture of the action in charges of equal weights Avill vary consid- erably not only from atmospheric causes, or in consec[uence of imperfections in the manufacture or in the qualities of the in- gredients, but with the size, form, and density of the grains and \heform of the cartridge. 1204. PEODUCTS OF COMBUSTIOH._It was form-' erly supposed that in the combustion of gunpowder the Avhole of the oxygen of the nitre entered into combination with the carbon, forming carbonic acid, the nitrogen being set free, while the potassium combined with the sulphur, forming potas- sium sulphide, thus: 2KNO3 + S + 30 = Iv„S + + 3CO„_. Although the proportions indicated by the first term of this formula would coincide very closely Avith the proportions in which the ingredients are ordinarily mixed, if the charcoal used were pure carhon, that coincidence disappears when the actual composition of the brown charcoal generally used is taken into account. Thus the formula Avould give : 2KEO3 202.1 = 74.84 per cent. S 32. = 11.84 “ “ 30 36. = 13.32 “ “ If, however, Ave substitute for 0 the constituents of broAvn charcoal as given below, we have : Eitre ; 74.84 per cent. Sulphur 11.84 “ Oarbon 9.69 “ “ Ilydi’ogen 39 “ “ Oxygen... 2.97 “ “ Ash. . . .27 “ “ Wherein the O 2.97 per cent, corresponds to 6.2 per cent, additional nitre. . It has been found, too, that the actual products of the com- bustion are much more complicated than this theory Avould in- dicate, and that they vary greatly Avith the conditions of the pressure and temperature under which the explosion takes place. 42G NAVAL OKDNANCE AND GUNNERY. 1205. Tlie elaborate investigations of tlie precincts of com- bustion of gunpowder made some years since by Vogel, Ijy Bunsen and Scbiscbkotf, by Link, and by Koi'olye, all coincided in proving that very little potassium sulphide is formed, but that it becomes oxydized to potassium snlphate and hypo-sul- phate, and that notable quantities of potassium carbonate are produced. It results from this that a much smaller volume of gas is gen- erated than the old theory calls for ; only ^ as much, according to Bunsen. Bunsen found that one gramme of gunpowder yielded 193 cubic centimetres of gas reduced to o°C, at the normal atmos- pheric pressure. 1206. The experiments referred to above were made under conditions differing widely from those obtained in actual prac- tice, and since the above researches were made, experiments have been instituted both in America and Enssia so as to imi- tate the condition of pressure and temperature which exist where powder is fired in guns. They agree in finding that when gunpowder is exploded at a low temperature, K„SO^ is formed, but under high pressure and great heat the sulphate is partially reduced to sulphide, thus accounting for the well- known fact, that if a gun be washed out after a discharge a large amount of potassium sulphide is found in the solution. Potas- sium carbonate seems to be formed under all conditions. 1207. The following is the result of an analysis of the residue obtained from firing a cannon loaded with shot, with a charge of 3 pounds of powder : IVSO, 15.00 Iv„C03 37.00 K:SA 8.29 K„S . . iCCyS c:.... Sand. . 3S.1S .33 .09 .82 Composition of the powder used : KNO3 S Charcoal Moisture 99.71 7-1.175 9.890 1BS35 1.000 99.900 INSPECTION OF GUNPOWDER. 427 Composition of the Charcoal : C II o Ash 72.5 2.9 22.3 2.3 100.0 The composition of the residue was found to vary consider- ably in experiments made with different kinds of fire-arms, and with different charges of powder and shot, but the general con- elusion was, that the increased pressure, by prolonging tlie time of interaction of the ingredients, and by augmenting the heat, gives rise to more gas and leaves less oxygen fixed in the residue. 1208. Berthelot, in an important research made during the late war in France, “ On the Explosive Force of Gunpowder,” draws attention to the importance of bearing in mind the phe- nomena of dissociation, according to which, the products found after cooling do not exist at the high temperature pi'oduced by explosion, but are replaced by more simple compounds. Section III. — Inspection of Gimpowder. 1209. Inspection. — Before gunpowder is received from the manufacturer it is inspected and proved. As it may have the required strength and still be incapable of bemg long preserved, it is necessary to inquire into the manner in which the mixing, pounding, and other manipulations have been performed, for upon these the powder depends in a great measure for the preservation of its qualities. 1210. General Qualities. — Gunpowder should be of an even-sized grain, angular and irregular in form, without shaiqi corners, and very hard. It should be free from dust ; and when Hashed in small quantities in a copper plate, it should leave no bead or fouling. It should give the required initial velocity to the projectile, and not more than the maximum pressure on the gun, and should absorb but little moisture from the air. 1211. Examination by Hand will determine the firmness, crispness, and shape of the grains, and their freedom from dust ; which cau also be ascertained by pouring a portion of powder quickly from one vessel to another. 1212. Flashing. — This is done by firing about ten grains with a red-hot iron. Should there be many sparks, or should white globules or beads appear, or any spots be left on the plate, it would indicate that the incorporation had not been 428 NAVAL ORDNANCE AND GUNNERY. effectually performed, or that the proper proportion of ingredi- ents had not been employed. 1213. Size or Grain. — The size of the grain is tested hy standard sieves made of sheet-brass pierced vrith round-holes. These sieves are five in number, two being used for each kind of powder. ISTos. 1 and 2 for rifie, 2 and 3 for cannon, and 4 and 5 for shell powder. The holes are of the following diameters, viz. : jSTo. 1, .3 of an inch ) hs^o. 2, .1.5 “ f Xo. 2, .15 “ ] ^ No. 3, .10 » f No. 4, .06 » I Q, „ No. 5, .02 “ [ The size of the grain is required to confoim to the follow- ing : Passthrough No. 1 all ] -p-fl Eemain on No. 2 all f Passthrough No. 2 all) ^ Remain on 3 j Cannon. Passthrough No. 4 all | q-, Eemain on No. 5 alU Ten jier cent, of variation is tolerated. 1214. Geaviaietric Density is the weight of a given meas- ured quantity ; it is usually ex'pressed by the weight of"a cubic foot in ounces. The cube box is constructed with great accuracy, and the powder is simply poured into it until filled. A hat ruler is then drawn across the surface, and the box with its con- tents weighed. The weight of the box when empty being de- ducted, that of a cubic foot of the powder under examination is ascertained. This cannot be relied on for the true density, as the size and shape of the grain may make the denser powder seem the lighter. Cannon-powder should have a gravimetric density of about 875 oz., and not exceeding 900 oz., to the cubic foot. It varies with different makers from 875 to 975. 1215. Specific Geavita'. — Assuming the usual values as- signed to the elements of gunpowder in the scale of specific gravity, the absolute density of a homogeneous mass of the mixt ire is 1.985. This point is never reached in practical manufacture, and even in GoA'ernment supplies the variation from this standard is such that frequently in a given hidk, poAvder consists of 25 per cent, of pores, in addition to all air- spaces between the grains. INSPECTION OF GUNPOAVDER. 429 The specific gravity of gunpowder is generally between 1.65 and 1.75. It is important that it should be determined with the greatest accuracy. 1216. The MEECunT DENsniETEK,'" invented by Colonel Mallet, of the French army, is the best apparatus yet devised for this purpose, and has, with slight inodifi- cations,' been adop- ted for testing Navy powder. It is an instrument by means of Avhieh, in con- nection with an air- pump and a delicate b,ilance, the density of a solid may be obtained. (Fig. 274.) It consist of two principal parts — the immo\uxble standard, A, with various fit- tings, and a hollow ellipsoidal glass ves- sel, A', called the vase, having tubular extremities, each furnished with a metallic cap or col- lar, B, into which is screwed a short iron plug, C, per- forated in the di- rection of its length, and fitted with a stop-cock. The up- per orifice of the ping, which screws into the lower end of the vase, is cov- ered with a dia- phragm of chamois leather, the lower Fig. 274. end of the upper plug being similarly fitted with one of v’cry fine metallic gauze. * Naval Ord. Papers, No. 1. Lieut. Comtnauder J. D. Marvin, U. S. Navy. 430 NAVAL ORDNANCE AND GUNNERY. The leather diaphragm strains the mercury, that of wire prevents grains of powder from being sucked up into the barometer-tube. A nozzle, d, screwed to the lower end of the bottom ping, dij)S into the mercmy in the dish, e. The standard is a bracket of wrought-iron mounted on a table of convenient height. It is fitted with a thermometer, g, a gi’adnated scale for the barometer-tube, h, and a socket with a stop-cock, i, into which the barometer-tnbe and upper connection of the v'ase are screwed. A long bulb, which forms a part of the barometer-tnbe, sur- rounds and encloses the upper end of the stem. This acts as a receiver for the overflow of mercmy, which is liable to be thrown up when leaks occur about the connections of the vase or tube. The bulb, which is in general outline a cylinder, contracts at its top, terminating in a conical point, over which the open end of a flexible India-rubber hose is slipped, thus connecting the tube, and through it the vase, with the air-])ump. 1317. I 'lie Ajusiments . — As all of the different connections of the v'ase where air-tight joints are made, are -fitted with leather washers of constantly changing thickiress, it follows that a variable degree of screwing up is rerpfired in order to make the junctions absolutely perfect. AYitli the plugs which screw into the ends of the vase, it is of great importance tliat the ex- tent to wliich they enter should be uniform for any given num- ber of trials with the same powder, that is, they should be run into the same distance when each sample of powder is tried, that they were when the vase was filled with mercury alone ; for if not in far enough the capacity of the vase is increased. In or- der to control this source of error as far as possible, set-marks are put on the collars and on the plugs. So long as these are either brought together or kept separated by a fixed and con- stant amount at different trials the experiment will be accurate. As coincidence will probably only occur when the washers are new, the separation, as they wear away or become compressed, mnst be estimated and carefully retained the same at different trials, so long as the same value is assumed for the weight of the vase filled with mercury alone. In screwing on the nozzle and in screwing in the plugs, both wrenches should be used — one as a spanner, to hold against the other used as a wrench, otherwise the cementing of the col- lars may be started and leaks produced. The" zero of the barometer-scale is the lower end of the noz- zle. The quantity of mercury in the dish and the level on which the dish i-ests shoiild be so regulated that the immersion of the nozzle will not be greater, when the vase is full, thaii is neces- INSPECTION OF GUNPOWDEK. 431 sary to prevent tlie admission of air. If tins precantion be dis- regarded, the fluctuations in the iieight of the barometic column ai’e very liable to mislead by attacliing suspicion to the working of the pumns or to the cioseness of the densimeter connections. 121S. When leaks in the connections of the vase occur they are indicated by air-bubbles, which can be distinctly seen pass- ing up through the enclosed mercury. They can generally be located, if about the junctions, by closing the cocks in sucecession from down lap, meantime working the ]nnnp. If about tlie tube-connections, the flow of air will continue with all the cocks closed; if below this, the leak can be located between the two cocks. By tightening the junctions with the wrenches, or, if in the cocks, by screwing them up with a screvr-driver, the difficulty is readily overcome. It sometimes happens that the cement Avhich holds the collar to the neck of the vase becomes cracked and produces a leak. This can be located by filling the vase, closing both cocks, and then expanding the mercury by holding the vase in the hands or by wrapping a warm cloth around it, the effect of which is to foi'ce globules of mercury out at the point where the ' leak has occurred. A mixture of tallow and beeswax, applied at the same time that the pump is worked, will stop a leak of this kind. 1219. When the vase is unscrewed after the filling, the mercuiy which remains in the fine tubes of the end plugs must he carefully jarred out. This precaution is very important ; for as the amount of mei'cury which thus remains varies at differ- ent trials, the accuracy of the weight taken is sensibly affected, if care is not taken to remove all the mercury outside the cocks. For this reason the globules which adhere to the vase and its fittings should be removed by brushing, before an^^ attempt is made to get the weights. In testing line powder, both plugs should be unscrewed, and, with the vase, carefully wiped after each trial ; with mammoth this is only occasionally necessary. 1220. Whenever the barometer-tube or vase become coated on the inside with sulphuret of mercury, they should be dis- mounted .and washed with aqua i-egia (by measure, two parts liydrochloric acid to one part of nitric acid). In tlie event of breaking the barometer-tnbe, expose the metallic socket, which holds the lower end, to the flame of a lamp, until the cement softens ; remove the broken tube, and then screw the socket in ]flac3 again. Coat the end of the new tube witli cement, and insert it in the socket before the latter cools off, taking care that it stands vertical when in place; for if at all inclined it will be difficult to unscrew it for the purpose of cleaning or emptying the overflow-bulb. 432 NAVAL ORDNANCE AND GUNNERY. 1221. The Aie-pdmp. — The air-pump used with the densime- ter is of the ordinary construction, and is mounted on a li 2 ;ht table. (Fig. 275.) The vacuum-gauge, a, is in. an air-tight glass case, which is Pig. 275 . placed between the standards on -which the brake works. It can be shut off from connection with the cylinder by the cock and air is admitted to it ; and thence to the cylinder, etc., by unscrewing the glass covei-, which can be turned by means of a chamfered ring on the brass collar into which it iits. Connec- tion with the densimeter is controlled by the cock c. The cylinder, cZ, of brass, oscillates on trunnions at its base; its con- nections with the vacuum-gauge and .the hose leading to the densimetei’ are through the curved pipe, e, which is held agaiint its several bearings by set-screws. The upper cylinder head is fitted with an oil-hole closed by the screw-ping,/", and has an overdow-can g, to catch oil forced out in exhausting. 1222. The Precautions to be observed in using the pump, INSPECTION OF GUNPOTTOEE. 433 are : 1. AlTzays keep the piston-rod and piston well oiled. 2. Keep the cocks h and c, and the connections of the tube, e, air- ti 2 ;ht. 3. Screw down the Tacuum-gauge case securely before commencing to exhaust. To determine whether the pump is tight and working well, close the cock c under the bell-glass table, A, and Avork the brake. The vacuum-gauge Avill show whether air is admitted, and the leak may be located by the hissing sound made by the air rushing in. The connections of the India-rubber hose require occasional looking to. The air-pump end is tightened by scTewing up; the other can always be made perfect by cutting off a short sec- tion, thus getting a ubav and unstretched portion to adjust over the end of the barometer-tube of the densimeter. 1223. The Balance. — The balance employed in the pro- cess of determining density, is a simple beam-scale, constructed with great accuracy. (Art. 388.) The great convenience of a decimal system of weights has led to the adoption of the scale of grammes in ascertaining the density of powder. The set of weights used is of 5,000 grammes ; approximately 11 pounds. The heaviest, 1 kilogramme, 2,204 pounds ; the lightest, 5 centigrammes, 0.75 giains. 1224. The Feogess of taking the Density.— The powder to be tested, if of mammoth size, will require breaking up to a smaller granulation ; for in its natui’al state it will not readily enter the vase, which is of but one-half-inch interior diameter at the neck. This is readily and safely done by using a light steel hammer, the powder resting on a table of wood. For convenience of computation, it is advisable to use sam- ples of 100 grammes ; or, if employing grain weights, of 1543.3 grains. Recourse may then be had to tables (see Appendix II.) for finding the density. 1225. To tal'e the Density . — Weigh out the sample with great accuracy, taking 100 grammes, if practicable. The vase being mountecl, with the nozzle screwed in place and well im- mersed in the mercury, close the lower cock, opening both the others, and exhaust the air from the tube and A^ase. When the gauge shoAvs nearly a perfect A^acuum, open the lower cock. The mercury from the dish aahU then enter and fill the A-ase, rising in the tubs to nearly the barometic height, the vacuum meanwhile being kept up by continuous pumping. As soon as the column becomes stationary, close the loAver stop-cock and re-admit the air to the top of the tubs by unscrewing the casing 28 434 NAVAL ORDNANCE AND GUNNERY. of tlie vaciuim-guage ; close the other coehs and unscrew the nozzle ; dismount the vase, jar out the mercury from the tubular spaces outside the cocks, brush the outside clean, an I then jtlace the vase on its rest and weigh it. Call this weight of vase and mercury YM = W. Empty the vase by opening the cocks, and allow the mercury to return to the dish ; also let the mercury run out of the barometer-tube. If the inside of the vase is coated, unscrew both plugs and wipe it out with a cloth ; or, if necessary, wash it with acqua regia. TCith clean mercury, washing is rai’ely required. 1226. In general practice, after having emptied the vase, one plugis unscrewed, and the sample of powder previously weighed out is poured in. The plug being again securely in place, the vase is mounted and the mercury pumped into it, passmg up through the powder, tilling its interstices, driving out the air, and rising to the same height in the tube as before. When this point is reached, close the cocks, admit the air, unscrew and weigh the vase as before, calling the weight of powder, vase, and mer- cury PV ]\I= W'. From these two weights, together with that of the powder sample, the density is calculated by the propor- tion : Density of mercury : density of powder = weight of mer- cury displaced by powder : weight of powder : or, if — W n= weight of vase and mercury, W' — weight of powder, vase, and mercury, w — weight of powdei’, D = density of mercury, d — density of powder, then W' — = weight of mercury, vase, and powder, less the weight of powder, and W — — w) = weight of mercury displaced by the powder, and the proportion becomes — D : eZ = W — "W' vj \ w, ^ _ D X vj or, a - The weight of W should be determined at the beginning and end of each set of trials, and the mean be used to correct the result of the whole scries. 1227. The occasions will be rare when the accuracy of the results given in the table will be sufficiently atfected by tem- perature to require correction ; but if the thermometer varies materially from GG° Fahrenheit, and great accuracy is required, the density of the powder may be calculated by the formula already given, in which D will be the density of the mercury at the'temperature of the time of observation, to be taken from ESrSPECTIOIT OF GUNPOWDER. 435 the table ; or, if no table is at hand, the effect of the tempera- ture can be computed by the formula — _ Do X 5550 ^ 5550 + t ’ in which Do — density of mercury at zero centigrade, and t = any temperature above zero ; or the correction may be attained with suthcient accuracy for ordinary practice by multiplying the decimal .00245 by the temperature expressed in degrees (centigrade). This product, subtracted from 13.596, gives the density for the temperature under consideration. The propor- tion given above, viz., D : = W — W' -\-w.w, must be used to compute the density of the sample, if its weight be other than 100 grammes or 1543.3 grains ; and the actual value of D should also enter into the calculation when the temperatime varies materially from 66° Fahrenheit. For example : Suppose W = 4120 grammes. Suppose W' = 3400 grammes. Suppose 90 grammes, and the temperature = 90° Fahrenheit, then D = 13.52, ap- proximately, and the density of the sample is 1.502. 1228. Test of the Quality of the Mercury. — The mercury used should be of specilic gravity — 13.55055 at 66° Fahrenheit. Its purity can be tested by comparison with distilled water by the follovvung process : Clean the vase and its connections thoroughly, and weigh it. Call this weight a. Mount the vase and fill it with mercury, and again weigh it, calling the result h. Empty clean, and connect it again, substi- tuting a dish of distilled water for that of mercury ordinarily used. Fill the vase by pumping slowly to avoid overflowing. Detach and weigh it again, calling this last weight c ; then — G — a the density of the mercury, which, if up to the standard, will coiTCspond to that given in the table for the temperature at the time of trial. Tlie mercury used with the densimeter should frecpiently be strained through chamois-leather to remove impurities which are accidentally introduced into it in experimenting. 436 NAYAL ORDNANCE AND GUNNERY. Form for recording exjperiments with the densimeter. Record Nomber. Date. Class or Chorac- ter of Sample. S CJ-, 9 . <=> si ■s i Density. 1 Thermometer. 1 1229. Use of the Tables. — Tables I. and II. are arranged for nse precisely like a table of logaritbms of numbers. (Ap- pendix II.) Fxample., Table I — Uequired tbe density corresponding to W — lY' -\-w = 824.5. Opposite 824, in tbe left-baud column, will be found in tbe column beaded o= for tbe first three fig- ures, 1.G4 ; and looking to tbe right in the column beaded .5, tbe remaining figures 348 are taken, giving 1.G4348 for tbe den- sity. If "W — TY' -|- w = 821.6, tbe first figures are taken from below, as indicated by tbe bar over 928 in tbe column beaded G. Example, Table II. (Appendix II.) 732. G grammes = 11304.1 grains. 734.5 grammes = 11333.3 grains. 1230. MUZZLE VELOCITY. — A projectile on leaving tbe bore of a gun will have acquired its maximum velocity, gener- ally termed tbe initial velocity. This essentially depends upon tbe powder, and is an important test of its quality. 1231. ELECTRO-BALLISTIC MACIIIXES.— Tbe accu- rate determination of tbe velocity of a projectile at any point of its trajectory, lias been one of tbe most difficult problems in tbe science of gunnery. It has exercised tbe talents and in- ELECTRO-BALLISTIC MACHINES. 437 gemiity of tlie bsst scientific minds of tlie age, and has given rise to much interesting discussion and many valuable experi- ments. The ■wondrous mechanical skill of the day, and our mastery over the powers of electricity, have, however, recently given ns instruments which, in their results, more than realize the brightest dreams of the experimenters of a century ago. Their bulky, unwieldy, and expensive machines have given place to the neat and compact chronoseope, which, witli its pencil of electrical light, now notes with unerring certainty in- finitesimal intervals of time. 1232. BALLISTIC PENDULUM.— The ballistic pendu- lum invented by Kobins, who is justly held to be tlie pioneer of modern gunnery, was first used in 1740, with the object of measuring the velocity of projectiles and the resistance of the air. It consisted of a tripod, from the top of which was sus- pended a pendulum vibrating freely on its axis of suspension. The bob was arranged, and of a size, to receive the impact of the projectile. Its prolongation below the bob was so con- trived as to register the degree of vibration. If such a pendulum, being at rest, is struck by a body of known weight, and the vibration which it makes after the blow is known, the velocity of the striking body may thence be de- termined. The quantity of motion of the body before impact is equal to that of the pendulum and body after impact. 1233. GUN PENDULUM. — The use of the gnu pendu- lum seems to have been suggested by Robins, although Count Rumford first reported, in 1781, the results of various experi- ments made with it for the determination of the initial velocity of projectiles, and the most advantageous position of the vent. It consisted of a gim suspended in a horizontal position, and vibrating freely ; the arc of its recoil being accurately measured when the gun was fired. The quantity of motion of the gun as a pendulum is equal to that of the projectile, charge of powder, and the air. Prom this the velocity of the projectile may be deduced. Extended experiments ■with both the ballistic and gun pendulums Avere made in England, from 1775 to 1791, by Hutton ; at Metz in 1839 and 1840 ; and in the United States from 1843 to 1848, by Major Mordecai of the Ordnance De- partment. The instruments used in this country Avere the most perfect of their kind, and the importance of the results obtained cannot be too highly estimated. The instraments Averc, however, A^ery expensive, had to be erected on perma^ nent structures, and* were rather limited in their application. 1234. ELECTRICITY. — Professor Wheatstone, in 1840, 438 NAVAL ORDNANCE AND GUNNERY. first suggested the employment of electricity in determining the velocity of projectiles. It Avas tried in the folloAviug man- ner : Two screens or targets of wire were so placed as to be cut by the ball during its flight. Each screen formed part of the circuit connecting a galvanic battery and an electro-magnet. This last suspended a pencil over a cylinder made to revolve uniformly. The rupturing of the target wire by the ball in- terrupted the current, and caused the magnet to release the pencil, which made a mark on the revolving cylinder. The time of revolution being known, the angle between these two marks determined the time of the ball’s passage between the two targets ; and knoAving the distance of the targets apart, the velocity coidd be readily ascertained. 1235. The application of electricity, as seen in this first attempt, depends upon its very great velocity, Avhich may be considered instantaneous for shoit distances. The greatest difficulty to be overcome lies in the manner of recording and preserving the time of flight, or, rather, of registering the in- stant the projectile strikes each target. When this is per- formed Avith the necessary accuracy, and the time it takes a projectile to pass over a certain distance thus obtained, the mean velocity Avill be the cpiotient of the space divided by the time. It may be said, Avithout appreciable error, that this mean velocity is the actual velocity of the projectile at the middle point of the space passed over. 123G. In May, 1843, Professor Henry, now secretary of the Smithsonian Institirtion, presented and read a paper before the American Philosophical Society, “ On a ucav method of de- termining the velocity of projectiles.” It consisted in the a}> plication of the instantaneous transmission of an electrical action. Two Avire screens placed in the path of the projectile were made to form piarts of galvanic currents, connected with the axis and surface of a revolving cylinder Avhich Avas covered by a graduated paper. The terminal point of the AA-fi’e at the surface did not quite touch the paper, and the interruption of the primary current by the rupture of the Avire of the screen by the projectile, induced an intense secondary current, on the principle of the common coil machine, Avhich gave a sp)ark that pierced the paper at the instant of the rupture. To Professor Henry belongs the credit of first proposing the use of the spark from Avhat is now knoAvn as the Euhm- korff coil, Avhich has been since adopted in the most improved and successful instruments. Attention was thus early drawn to the novel question of devising and constructing a machine based on the employment ELECTRO-BALLISTIC JIACHINES. 439 of electricity, and to serve in solving the most difficnlt problems in gunnery. We will describe the most successful of the vari- ous instruments in use. 1237. Navez-Leuks Chbonoscope. — This is probably the most successful of all the pendulum instruments, where the value of the time is expressed in arc. It may be said to consist of two separate instruments : the pendulum and the dis- jvnctor. 1238. The Pendulum. — An upright plate of vulcanite with a graduated arc, A (Fig. 276), mounted on a stand, snpjjorts two pendulums, two electro-magnets, a pair of springs, and the Circuit from the battery wMch magnetizes the chronometer electro-magnet. Circuit from the battery ■which magnetizes the register electro-magnet. Arrangement of the second circuit to investigate the valve of the coefficient x. pivot upon which the escapement system works. One of the pendulums, a, is termed the chronometer pendulum., and tlie other, h, the register pendulum and the magnets are so ad- justed, one behind each pendulum, that when magnetized by a current of electricity they will just sustain the bobs of their respective pendulums, into both of which a piece of soft h’on is inserted. 440 NAVAL ORDNANCE AND GUNNERY. 1239. An index-needle, having a vernier at the end to slide along the graduated arc, is riveted to a steel disk, c, working in the same axis as the chronometer pendulum, with which it oscillates, simply by friction, until clamped by the action of the escapement. 1240. The springs are attached to the vertical plate, and pass one on each side of the steel disk, c ; near the ends of the springs are two cleats, one on each spring, between which a wedge-lever, e, can be adjusted to keep the springs apart ; two other cleats close on the disk of the index-needle, which is be- tween the springs, when the wedge-lever, e, is displaced by the face of the stirrup, d. 1241. The rod of the register pendulum is provided with aii arc canying a stirrup, d, which, in its descent when the pendu- lum is released, knocks away the wedge-lever, e, from between the springs, and so closes them upon the disk, c, of the index- needle, thus clamping it. 1242. The TJisjunctor. — Thi?, consists of a small stand, B, on which are two pieces of brass, /y, each provided with a pres- sure-screw, a brass spring, g, fastened by another pressure- screw, and a cam, 4, to work the spring ; the brass pieces have platinum points, separated from each other by a very short in- terval, and the spring has also a platinum point below it, which, when pressed down by the action of the cam, connects the two other points ; thus connecting, when requisite, the circuits through the apj^aratus. 1243. The Electric Currents are obtained by means of Bunsen’s voltaic batteries, there being two circuits for an ordi- nary experiment, one (Fig. 276) passing through the magnet of the chronometer pendulum and the first screw, the other through the magnet of the register pendulum and the second screw ; as both pass through the disjunctor, the simultaneous disjunction of l)oth circuits can be effected by turning the cam, releasing the spring, and so disconnecting the platinum points. 1244. Arrangement of Targets. — TAq apparatus is placed in a small house at a distance of about 130 yards from the gun, so that it may not be effected by the firing, and the arrange- ment of the gun and targets is as follows : The first target (Fig. 276) is placed at a distance of 10 yards in front of the muzzle of the piece, and the second target 40 yards beyond the former ; both targets are of the same construction and dimen- sions; each consisting of a wooden frame having copper wires stretched across in parallel rows by means of pins in the sides of the frame, and these wii’es are broken by the passage ELECTRO-BALLISTIC MACHINES. 441 of tlie projectile throiigli them. In order to protect the wires of the first target from the action of the gas, a ivooden screen is placed about 40 inches from this target, between it and the gun ; the screen has a circular hole, about 1^ calibres in diam- eter, through which the projectile passes. 1245. "Operation of the Instrument . — The gun is fired the projectile passes through the first target, breaks the first cir- cuit, and demagnetizes the magnet of the chronometer pendu- lum ; the boh begins to fall, carrying with it the index-needle. When the projectile cuts the wires of the second target, the second circuit is broken, and the magnet of the register pendu- lum is demagnetized ; the bob falls, carrying with it the arc and stirrup, which in its descent knocks away the wedge-lever and clamps the index-needle. 1246. The time due to this arc of vibration can, by the theory of the pendulum, be readily ascertained, but it must be greater than the time taken by the projectile to pass from one target to the other ; for a certain small interval of time elapses between the rupture of the second circuit and the clamping of the index-needle. This small portion of time is found by means of the disjuuctor, before the gun is fired, by breaking both circuits at once, and the small arc so found must be de- ducted from the arc determined by firing the gun. 1247. Benton’s Thread YELOcniETEu. — This is a gra\dty instrument in which the weights are suspended by the tension of a cord, and it may be worked with common thread in place of the usual electro-magnetic currents. The principle involved in this arrangement is, that the loos- ening eSect of cutting a taut tlmead is transmitted to equal dis- tances along the thread from the point of rupture, in equal, or sensibly equal, times. It is a principle that can be applied to others of the large class of machines for measuring small inter- vals of time. The peculiar advantages found in the use of threads over electricity are, simplicity and cheapness of the apparatus, free- dom from acid and water for the batteries, and the certainty and ease with which it can be operated by a single person, and that person the one wdio fires the gun. The Velocimeter may be depended upon to give results suf- ficiently accurate for all the practical purposes of proving pow- der and making ballistic calculations. For the purpose of explanation, the appai’atus may be divided into the time-marker, oy pendulrnn^machine, the targets Ho. 1 and Ho. 2, and the threads. 1248. Pendulum FIachine. — The pendidum machine is 442 NAVAL ORDNANCE AND GUNNERY. shown in Fig. 277. is a bed-plate of metal, which supports a graduated aiv, l>. This arc is placed in a vertical position by means of thumbscrews and spirit-levels attached to it ; and it is graduated into degrees and fifths, commencing at the lowest point of the arc, and ending at 90°. p p' are two pendulums having a common axis of motion passing through the centre, and perpendicular to the plane of the arc. The bob of the pendulum^.?' is hxed, but that oi p can be moved up and down with a thmnb-screw, so as to make the times of vibration equal. 1249. The aj)paratus to record the point at which the pen- dulums pass each other Avhen they fall is attached to the pro- longation of the suspeiisi on-rod p\ and consists of a small pin enclosed in a brass tube ; the end of the pin near the arc has a sharp point, and the other is terminated with a head the sur- face of which is oblique to the plane of the arc. As the pendulums pass each other, a blunt steel point attached to the lower extremity of the suspension-rod p strikes against the oblique surface of the head of the pin, which presses the point into a piece of paper clamped to the arc, leaving a small puncture to mark the point of passage. An improvement to the foregoing consists in attaching to the pendulum yi' a delicate bent lever, which carries on its point a small quantity of print er's-ink ; the pendulum y? presses upon this lever, causing the point to touch the arc and leave a small dot opposite to the point where the pendulums pass each other. 1250. The Compressors . — The leve^'-compressors., A A', are made to hold up the pendulums by tightening the threads, B B', leading to the two targets. When the threads are severed at the targets by the projectile and slacken, the compressors are ELECTEO-BALLISTIC MACHINES. 443 forced back by their springs, and the penduiums are released and immediately begin to tall. The compressors are shown in detail in Fig. 278. They have each a slight notch at the lower end to re- ceive the sharp end of the pendulum-rod, D, and hold it firmly in a horizontal posi- tion. At the upper end is also a notch for attaching the thread. G represents the spring which presses the compressor away from the pendulum when the thi’ead is severed. 1251. The pendulum ma- chine should be placed equi- distant from the two targets, and sufficiently remote from the piece not to be affected by the jar of the discharge before both pendulums have commenced to fall. In the case of small-arms, it may be placed directly in the plane of fire ; but in the case of cannon, it should be at least 100 feet to the right or left of it. (See Fig. 279.) In the figure, target Flo. 1 is placed 125 feet from the muzzle of the piece. At this distance the thread will be severed by the ball before it can be broken by burning grains of powder. For ordinary purposes, how- ever, target F7o. 1 may be placed directly in the muzzle of the piece, by attaching it to a vertical string stretched across the muzzle. A board supported on two posts may be used to 444: NAVAL ORDNANCE AND GUNNERY. d<, Fig. 280 . screen the thread leading to the pendulum from target No. 2. 1252. Targets for Ca/rmon are similar in construction, and composed of a single post fixed in the ground, to which are at- tached horizontal arms, as shown in Fig. 279. A thread, d d (Fig. 280), is stretched vertically between these arms, to which is attached the thread leading to the pendulum at one side. The point of attachment of this tliread should he a little below where the projectile cuts the vertical thread, and is shown at i. Both threads to the pendulum passthrough the loops of the compressors, and are fastened to posts set in the ground, in such relative positions to each other and the pendulum that the compressors will sustain the pendulums vrhen the threads are tightened, and will relax their hold when broken. 'When can- non are carefully aimed, the projectile will cut both vertical threads directly ; hut in the case of small-arms, it is found diffi- cult to ensure the cutting of the thread of No. 2 target without a special arrangement. 1253. Targets for Small-arms.— No. 1, for small- arms, consists of a piece of board (Fig. 281) with a vertical opening to serve as a rest for the muzzl e of the gun. Across this open- ing, and directly in front of the muzzle, is stretched a short hori- zontal thread secured to two leather washers. The thread a to pendulum No. 1 is drawn around the mid- dle of the horizontal thread, and secured at the leather washer, b. The muzzle of the piece is in contact Avith the intersection of the threads, which should he a little below the centre of the bore. The thread J) is cut the instant the bullet reaches the muzzle, and the thread a slackens, generally, Avithout breaking. ELECTRO-BALLISTIC MACHINES. 445 Target ISTo. 2, for small-arms (Fig. 282), is composed of an iron target-plate, B, 1 inch thick, which swings freely on The lower back edge hori- of Fig. zontal trunnions at its upper edge, the plate rests lightly against the back of a sharp knife- blade, D, hinged at E. The thread, I, leading to pendulum hi o. 2 is wrapped around the slitted part in which the knife-blade oper- ates, and fastened to the leather washer, F. 0 C are two flat-iron bars bolted to a post of wood let into the ground, and serve as sup- ports of the trunnions of tlie target-plate, B. When the bullet strikes the plate, B, the knife-blade, D, is pressed back- wards, cutting the thread, I, and releasing the pendulum. C and F[ are screens of boiler-plate to protect the thread and knife from fragments of the bullet. The target-plate, B, is made of tough wrought-iron about 6 inches wide, 6 inches deep, and 1 inch thick. The knife should be made as sharp as possible, so that a slight tap of the finger on the target-plate will suffice to cut the . thread. 1254. To Deteemtne the Time. — It is considered that each pendulum begins to move at the instant the projectile cuts the thread, and that the interval of time corresponds to the diflerence of the ai’cs described by the pendulums up to the time of meeting. Let m and m' (Fig. 283) represent the positions of the two pendulums before rupture, and let the interval between the rup- ture be such that the m ^ m' centres of oscillation will pass each other at L As the times of vibration are equal, the interval of time will correspond to the arc i i', the arc m' i being equal to m i'. A vertical line through the centre of motion bisects the are i i'. The reading, therefore, corresponds to one-half of the 1 V / V: V ^ 1 i n Fig 283. 446 NAVAL ORDNANCE AND GUNNERY. required time, or time of passage of the projectile between the threads. To determine a formula for the time that it takes for one of the pendulums to pass over a given arc, let I be the length of the equivalent simple pendulum, v the velocity of the centre of oscillation, or point m', y the vertical distance passed over by this point, x the variable angle which the line of suspension makes with the horizontal, and t' the time necessary for the point ml to pass over an entire circumference, the radius of which is Z, with a uniform velocity, v, we have. V = V2gy. Siabstituting for y its value in terms of the constant angle of half -oscillation and the variable angle x, the above expression becomes V = V'igl cos. (90°— x) ’ from which we see that the velocity of the pendulmn increases from its highest to its lowest point, and vice versa. The time t' is equal to the circumference of the circle, the radius of which is I divided by the velocity, v ; again dividing this by 360, we have the time of passing over each degree, or ^ 2 7T Z 360 2yZ cos. (90° — x) To determine Z, it is necessary to change the cylindrical anns of suspension to knife-edges, in order to determine the time of vibration through a very small arc. The mean of 500 vibra- tions will be very near the exact time of a single vibration. Knowing the time of a single vibration, the length of the equiv- alent simple pendulum can be obtained by the relation Z=Z' t"“, in which t" is this time, and V is the length of the simple second’s pendul um at the place of observation. In this way all the constants of the expression for t are known, and by assigning difierent values to a?, a table can be formed from which the times corresponding to the different arcs can be obtained by simple inspection. 1255. Le Boulexge’s CHKONOGKXPn. — In Captain Le Bou- lenge’s instrument, the shot is made successively to cut two currents, and thus to demagnetize two electro-magnets which liad previously supported two heavy bodies ; the faU of these bodies, under the action of gravity, is the measure of tlie time taken by the shot to pass over a known distance. 1256. In the Kavez-Leurs instrument tlie weight liberated by the shot is a pendulum oscillating in front of a graduated arc, the angle described by the pendulum being the measm-e of ELECTRO-BALLISTIC MACHINES. 447 Fig. 284. 443 NAVAL ORDNANCE AND GUNNERY. * The instrament is here represented mounted on its transporting box. For accurate work from fixed positions it should be placed upon a pedestal resting upon masonary ; and should be established with all the care which characterizes the setting up of astronomical instruments. This point has received great at- tention at the U. S. Naval Experimental Battery. ELECTRO-BALLISTIC MACHINES. 449 The column stands on a triangular base, upon ivhich is fixed the Trigger^ T. (Fig. 287.) 1259. — The electro-magnet^ A, supports a long cylindrical rod (Fig. 284) suspended vertically and called the Chronometer. This rod is partially covered with two zinc tubes, D £, called Registers. The electro-magnet., B, sustains a shorter rod, F, named the Registrar. The Trigger (Fig. 287) consists of a circular steel knife, G, fixed in a recess of the spring, H, by means of the screw, FT, which forms an axle upon which it can be turned so as to bring a fresh portion of the edge opposite the chronometer. The spnnc H, can be “cocked,” or restrained, by means of the catch on one end of the lever, I. The other end of this lever carries a disk, 0, fixed to a screw, by means of which it can be raised or lowered as required. 1260. This disk is verti- cally below the registrar when suspended to its electro-mag- net ; consequently, when the current through the second screen is broken, the registrar falls on the disk and releases the spring, IT. The tube, L (Fig. 284), retains the registrar after its fall. If it be required to alter the time taken by the regis- trar to release the knife, it is done by raising or lowering the disk of the trigger by turning it in the direction with the sun to hxarease the time, and against the sun to reduce it. The screw has a pitch of one millimetre, and tlie circmnference of the disk is divided by notches into ten equal parts in which the pawl, r, works ; by this arrangement the disk can be moved any required number of tenths of a millhnetre (within certain lim- its), and is retained in the required position by the pawl. 29 ^ 450 NAVAL OEDNANCE AND GUNNERY. 1261. Tlie screw, M, passes tlirougli tlie lever and acts against the fulcrum supporting it ; it is intended for regulating the hold of the catch of the lever on the spring, whi.h should always be as light as possible. Tliis is regulated once for all, hut should the spring at any time sliow a tendency to escape of itself, this defect can he remedied hy slightly withdrawing the screw, M. 1262. — The Disjunetor (Fig. 288) is composed of a main- spring, t, cari-ying a cross-piece, covered with insulating ma- terial, and passing under the two steel plates, q q'. By pressing the milled-headed screw, z, the spring is compressed and held hy the catch, x, allowing the plates, c[ q', to come into con- tact with the metal pins, r F, and thus complete the circuits hy bringing the screws s v and s' v' into connection with one another. W hen the catch, x, is pressed, the mainspring being released, its cross-piece strikes the two plates exactly at the same instant, raises them from the screws, and thus breaks both currents identically at the same time. Should it be thought at any time that the disjunetor is Avorking inaccurately, the method of testing it, and of correct- ing it Avhen out of order, is very simple, and will be described under the heading of “ Method of correcting irregularities.” 1263. The arrangement of the screws and electric current is precisely the same as when using the Isavez-Leurs instru- ment, except that the chronometer battery must be increased in strength (because its electro-magnet is requu’ed to support a greater Aveight than in the hlavez-Leiu’S instrument), and a dif- ferent method adopted for introducing the disjunetor into the circuit. With the Le Boulenge chronograph, the two Avires from the positive poles of the batteries are not joined as Avith the Navez-Leurs, but are taken to the two connecting screAvs, s s', of the disjunetor; and thus the two currents, though passing through the disjunetor, are kept entirely separate. 1264. The electro-magnet. A, is magnetized by the current passing through the first screen ; consequently when the shot cuts this screen, the chronometer is released and falls freely in a vertical direction. The other electro-magnet is in the circuit through the second screen, so that the registrar falls A\-hen this screen is cut, and, striking the disk on the free end of the lever of the trigger^ liberates the spring, which carries forward the knife until it sti’ikes the chronometer in its fall and makes an indent in the upper zinc tube. 1265. A very simple relation exists (as Avill be seen here- after) betAA^een the height of this indent and the velocit_y of the projectile. It is evident that the time which elapses after the fall of the chronometer before the registrar is released, is the ELECTEO-BALLISTIC MACHINES. 451 time taken by tbe projectile in passing over the distance between the screens; the less, therefore, the velocity of the projectile, the further in advance will the -chronometer be, and the higher will be the indent. Fia. 287. — The Trigger. 1266. A Graduated Rule is used for measuring the height of the indent above the zero-point. It is of brass, and is grad- uated on both edges ; the upper edge is a scale of equidistant parts, divided into millimetres, reading to tenths Avith a ver- nier, and is intended for use in connection with the tables. Tlie loAver scale is for reading off the velocity of the qirojectile without any calculation; it is graduated in metres fora distance between the screens of 50 metres. The zero-point on the scale 452 NAVAL OEDNANCE AND GUNNEET. corresponds with the origin^ or the point at which the knife marks the chronometer, if the trigger is set in action when it is at rest. The rule is fitted at the zero-end with a jointed piece having a slightly conical projection, which enters into a recess in the bob of the chronometer, when applied for measuring the marks. Care must be taken not to injure this portion of the scale, or the measurement may be rendk’ed inaccurate.* 12G7. Tiieoky of the Insteumeht. — As stated above, if the trigger be set in action when the chronometer is at rest, a mark will be made by the knife on the zinc, which point we will call the origin, as it is the zero-point from which the height of fall of the chronometer must be calculated. Let II be the height above the origin of the mark obtained by firing a projectile through the screens. Since the chronom- eter follows the law of the fall of heavy bodies, _ p' 2 H ~ y will be the time it was in motion before receiving the impres- sion. How T' would be the time required by the projectile to traverse the distance between the screens, supposing that the chronometer commences to fall the instant the projectile passes through the first screen, and further, supposing that it is struck by the knife at the precise instant the shot cuts the second screen. Blit tills is not the case. In fact, after the rupture of the first screen, a certain time, 6, elapses before the electro-magnet is demagnetized sufficiently to free the chronometer ; the movement of the chronometer will therefore be delayed, and the observed time consequently diminished, by the quantity 0. 1268. Again, some time elapses between the cutting of the second screen and the moment when the knife reaches the chronometer, viz., the time required for the following opera- tions : 6' for the demagnetization of the electro-magnet support- ing the registrar. t' for the fall of the registrar to the disk of the trigger. t" for the disengagement of the catch. t'" for the knife to pass over the horizontal distance which separates it from the chronometer. How it is evident that the chronometer, before it is stnick by the knife, will have been in motion dmlng the sum of the above time in addition to the time taken by the shot in passing * The rule, being a proportional scale, can be used for any distance between Bcrcens. At the U. S. Naval Experimental Battery the interval is a hundred feet, and the reverse face of the rule is graduated to inches and decimals, and tables corresponding are used. ELECTRO-EALLTSTIC MACHINES, 453 over tlie distance between tlie screens. Consequently tlie ob- served time, T', is too great by the sum of {O' -\-t' t" -j- t'"'). We have also shown above that T' is too small by the quantity d, the time required to demagnetize the chronometer electro- magnet. Therefore, to ascertain tlie true time, T, Ave must deduct from T' the quantity {O' -\-t' 1" + t'" — 0), Avhich we We have then T = T' — 12G9. Now suppose T = O, or, in other words, suppose the shot to cut both screens simultaneously, then Ave should have 454: NAVAL ORDNANCE AND GUNNERY. T' = t. From wliieh it appears that t sFould be the time re- corded on the chronometer if both currents were cut identically at the same instant. Tliis we can do by using the disjunctor, and we thus obtain a mark, on the lower ziuc tube, at a height above the origin ecpual to the space passed over in the time which we call xlxQdisjunctor-reading • the time corresponding to this read- ing must bo deducted from the whole time recorded on the chro- nometer, to arrive at the time taken by the shot to traverse the distance between the screens. As before stated, the disk of the trigger can be raised or lowered so that the disjunctor-readiiig can be altered (if required) within certain limits, and we can thus regulate the instrument so that the time t shall have a con- stant value. The value of t for which the velocity scale has been calculated is 0".15, and the height of the corresponding mark above tlie origin is 110.370 mill. (4.248 inches). Start- ing with this assumption, a scale has been calculated for a dis- tance between the screens of 50 metres, by means of which the velocity of the projectile can be at once determined without the aid of any calculation. Should it be necessary to place the screens nearer to one another, the velocity can be found by multiplying the number read off on the scale by the frac- tion — , D being the actual distance between the screens in 50 metres. 1270. The method of calculating this scale is as follows : Suppose the shot to have a velocity of 500 metres a second, 50 it would take — ^ = 0".l to traverse the distance between the screens. The instrument will, therefore, mark 0".15 (disjunctor-read- ing) -)- O'hl, or 0".25, and the corresponding height of fall from the origin will be H = ip T' pX(0.2o) ^^ Conversely, if the mark on the chronometer is 613.17 mill, above the origin, we know that the velocity of the projectile is 500 metres a second. The disjunctor-reading being at a height corresponding to 0".15, and the screen 50 metres apart. This calculation has been made for a series of velocities in- creasing from metre to metre for all ordinary velocities, and the corresponding heights engraved on the scale supplied with the instrument. This scale is inconvenient, as it is necessary to use a multi- plier in order to ascertain the velocity in feet corresponding to ELECTRO-BALLISTIC MACHINES. 455 tlie number read off, and this multipler varies with the distance between the screens. 1271. Method of Adjusting the Insteumen’'. — Setting up the Chronograph . — For transport the different portions of the instrument are packed in a box, wdiich can be made to serve the purpose of a stand by means of an iron tripod supplied with it. This arrangement is no doubt very convenient in cases where it is recpiired to move the instrument constantly and set it up in different positions. For proving powder, or in similar cases, where the instrument is stationary it is advisable to have recourse to a more permanent arrangement, as at the Experi- mental Battery, Annapolis. 1272. The triangular piece which supports the trigger and the column is fastened to a heavy cast-iron base by the three screws supplied with the instrument. This base is 13 inches square and 1 inch thick, and is supported on four milled- headed levelling-screws, which ivork in brass Y’s let into the oak block. 1273. The instrument is permanently fixed to the stand, and is covered, when not in use, by a glass case to protect it from injury, a small beaker containing calcined chloride of cal- cium heing used to absorb the moisture under the case. 1274. The electro-magnets are fixed in position by passing the screwed stems through the column and fastening them with milled-headed nuts (Fig. 286). Two zinc tubes, or registers, are placed on the chronometer ; to put on the small one the bob at the lower end must first be unscrewed. The tubes should be pressed slightly out of shape before being put on, to cause them to fit tightly on the rod, and not to shift too easily. It is well to see, from time to time during the operation, that the bottom of the tube is resting against the bob. 1275. The connections with the battery and the screens having been established, and the cuiTents found to pass cor- rectly, and to be of sufficient strength, the next step is to ad- just and regulate the instrument. This consists of three operations, viz. : 1st. Levelling the instrument. 2d. Eegulating the power of the electro-magnets. 3d. Regulating the height of the disjunctor-reading.' 1276. 1st. Levelling the Instrument . — For this purpose the chronometer is used. After having cocked the trigger, sus- pend the chronometer to its elect)'o-magnet, and bring it into its proper position by means of the levelling-screws. In levelling from front to rear see that the inclined plane 456 NAVAL ORDNANCE AND GUNNERY. on the bob, on the side opposite the number, rests very lightly against the projecting edge of the triangular base. To level laterally, the right face of the hob is brought exactly in line with the salient angle formed by tlie projection above referred to. In this position the left face of the bob is a short distance from the screw, E ; the edge of the knife is opposite and slightly behind the zinc tube ; and when the chronometer falls, the projecting ring passes clear of the knife- edge. To test whether this is the case, break the circuit, by means of the disjunctor, and notice whether there is any fric- tion, or if anything catches during the fall. To ascertain whether the chronometer is properly levelled from front to rear, see that the inclined plane on the bob rests along its whole length against the projecting edge ; then remove it sideways out of the vertical, by pushing the bob against the screw, E, when it will return into its original position, if prop- erly levelled. The levelling being completed, and the registrar suspended to its electro-magnet, the inclined plane on the bob, on the side opposite the number, should rest very lightly against the edge of the arm, K. This arm is fitted in a bracket, and its position can be altered by means of an adjusting-screw. This adjust- ment need only be performed once for all ordinary positions of the instrument when used in taking velocities. If the electro-magnet and the bracket be removed to the upper part of the column, as shown in Fig. 285, it may be nec- essary to readjust the arm in order that the registrar may still hang vertically. The levelling of the registrar is verified in the same manner as in the case of the chronometer, viz., by ascer- taining — 1st. That when moved laterally it returns to its origi- nal position; 2d. That it falls freely without touching the tube, L. 1277. 2d. Regulating the Electro-magnets . — This is done (as with the Navez-Leurs instrument) by withdrawing the core of the magnets until they are only capable of just supporting the rods. It is always an advantage to work with weak mag- nets, as the variation in the time required to demagnetize them need not be taken into account ; should, however, their power be insufficient, the operator will experience some difficulty in suspending the I’ods. The following method has been adopted for making the electro-magnets of just sufficient power : The chronometer, with its zinc tubes, is increased in weight by means of a brass tube, which is slipped over the upper zinc. It is then suspended to the magnet, and the core gradually ELECTEO-BALLISTIC MACHINES. 457 witlidrawn until the power is insufficient to support the weight, wlien it falls. The core must be turned slowly and gently, so as not to free the rod by any jar or vibration. The extra weight is then removed, and the chronometer can be suspended without difficulty. The other magnet is regulated in the same manner, a smaller brass tube being supplied for increasing the weight of the registrar. In order to suspend the chronometer to its electro-magnet without difficulty, the folloiving method should be adopted : Hold it lightly in the left hand at the centre, the fingers open and towards the body ; allow the bob to rest upon the second joint of the first finger of the right hand, the hand being half open, the palm vertical and turned towards the body, and the fingers together ; the chronometer is thus held in a vertical position, the numbered face of the bob being turned towards the operator. Bring it in this position to the electro-magnet, by placing the exterior surfaces of the two cones in contact, and, as soon as attraction is perceived, let go with the left hand, still keeping the fingers near to catch the chronometer should it fall. Then slowly lower the right hand, so that the two cones, sliding over one another, remain with their points only in con- tact, and place the bob in its proper position by moving the first finger of the right hand, upon which it still rests. This done, withdraw the support of the right hand by lowering it vertically, when the chronometer will remain suspended in its proper position. If there should be any vibration it will soon cease from the friction against the rest. The registrar is suspended in the same manner, but the chronometer is always placed in position first. Difficulty is sometimes experienced by beginners in sus- pending the parts of the chronograph ; minute details have thei'efore been given as to the best way of doing so. The other operations are exceedingly simple. To cock the disjunctor, so as to establish the currents, press the milled-headed screw, z (Fig. 288), with the centre finger of the right hand, until the spring is held by the catch, x. To break the currents pi’ess the catch, x, with the forefinger of the right hand, the thumb being placed against the sup- port, y. In cocking the trigger care must be taken not to disturb the level of the instrument ; consequently the left hand only is used, the fingers being placed against the support of the tube, L, and the spring drawn back with the thumb imtil it is held by the claw of the lever. 458 NAVAL OEDNANCB AND GTJNNEET. The trigger must always he coclzed before attempting to sus- pend the chronometer. 1278. 3d. Regulating the Disjunctor Reading . — As we have said before, this reading shonld represent a time = 0” .15, and the mark shoidd consequently be 110.37 mill. al)ove the origin. This height is shown on the scale by a special inark called disjunction. To facilitate the operation, commence by ti’acing on the small zinc tube a circle at the required height. For this purpose fasten the vernier by means of the clamping- screw, with the index opposite the line marked “ disjonction.” Place the chronometer flat on a table with the numbered face next the body, and apply the rale to it by inserting the conical point of the hinge in the recess of the bob, allowing the index of the vernier to rest on the zinc. Support the end of the rule in the i-ight hand, and Avith the left turn the tube, taking care to keep it pressed against the bob at the lower end of the chro- nometer. In this manner a fine line is traced on the tube, with which, when the instrument is well regulated, the disjunctor- marks ought to correspond. The indent made by the knife is a notch, clearly cut in the metal, the base of which is in a plane pei’pendicular to the axis of the tube. It is the section of this plane with the tube which must be taken as the mark, and the index of the vernier must always be brought against it when reading the height of the indent. The point of the vernier index is of the same form as the edge of the knife, and consequently fits accurately against the plane (or lower) side of the indent, so that there can be no un- certainty in the measurement. The instrument having been prepared, a disjunctor-reading is taken ; if the mark is exactly on the circle previously traced, no alteration is necessary, and the experiments can be proceeded with at once. Should the mark, however, be above the circle, the space through Avhich the registrar falls must be diminished by raising the disk of the trigger ; if below, the disk must be lowered. In the former case it is turned in the contrary direction to the sun, and in the latter case Avith the sun. The arrangement by which the amount of alteration in the height of the disk is regulated has already been pointed out when describing the trigger. 'When the height of the disk has been regulated for some previous experiments, the reading Avill not vary on another occasion more than a few tenths of a millimetre, and this can be (at once) corrected by turning the ELECTEO-BALLISTIC MACHIlSrES. 459 disk, in tlie proper direction, tlirongli the required miinber of divisions of the circle. 1279. Method of Takestg Velocities. — The instrument is prepared for measuring velocities in the same maimer as for taking the disjunctor-reading. First cock the disjunctor, then the trigger, and aftervrards suspend the chronometer and reg- istrar. Before suspending the rods, however, it is advisable, in order to prevent the possibility of errors in measuring the indents given by ditierent rounds, to make ink-marks round the lower edge of the upper zinc tube, about one-twentieth of an inch apart, and to turn the tube after each round so as to bring these marks successively opposite the line on the centre ring. Equidistant lines are thus obtained, upon which the marks of successive rounds will be registered. The same may be done with the lower (or disjunctor) tube ; by this means each tube can be made to register about twenty indents at each end, and can be turned end for end when the circle at one extremity is completed. An indent having been obtained on the upper tube by firing a projectile through the screens, the velocity may be ascertained in two ways : 1st, by measuring the height of the mark above the origin, and calculating the time and corresponding velocity from the tables ; 2d, by measuring the velocity on the scale adapted for that purpose. The former method is the more accurate, while the latter takes less time, and, for ordinary purposes, such as the proof of powder, indicates the velocity within sufficiently narrow limits. 1280. Method of Coekectixg Irkegulaeities. — When the foregoing directions for adjusting and regulating the instru- ment are adhered to, not only do successive disjunctor-readings taken between the rounds agree within very narrow limits, but the readings generally remain constant from one round to another. It is therefore sufficient, when accustomed to the chronograph, in order to ensure its regularity, to take a reading of the disjunctor after every three or four rounds. The operator must judge from the regularity of these read- ings whether he should repeat them, and whether it may be necessary to readjust the instrument. The following directions will assist him. If the reading is too high or too low, repeat it ; and if the difference remains constant, and is small, the height of the disk of the trigger need only be altered. Should, however, the error be considerable, indicating that there is a variation in the force of one of the magnets, this force must be regulated. 4G0 NAVAL ORDNANCE AND GUNNERY. 1281. Should the disjunctor-readings become irregular, the following points must be looked to, viz. : 1st. If one of the magnets has not become too strong. 2d. If the instrument is properly levelled ; that is, if the rods hang vertically, and do not rest too heavily against the support. 3d. If there be not an imperfect connection in the circuits, including the battery and the screens. Should the mark obtained be indistinct, the chronometer must be brought nearer to the knife (by means of the levelling- screws), care being taken that it still falls freely and without friction. 1282. If, during the experiments, one of the currents be- comes broken without any apparent cause, try (after ascertain- ing that the screens are properly mended), whether there is contact between the plates, q q', of the disjunctor (Fig. 288), and the pins, r r', by removing the wire from the binding-screw at one extremity of the plate, and bringing it into contact with the screw at the other end. If the current is thus re-estab- lished, it shows that the break occurs at the point of contact of this plate with the screw, which should be cleaned by passing a piece of paper between them. 1283. The only parts of the instrument that require special attention are the points of contact between the rods and the electro-magnets. These four points ought to be kept clean and polished, and it is as well never to touch them with the fingers, and to rub them frequently with a chamois-leather. . The rest of the instrument may be covered with rust and dirt without affecting its working, whilst a single spot of rust on one of these points may cause irregularity in the disjunctor-readings. If by acci- dent they should get rusty, very tine emery cloth must be used to clean them, care being taken to rub round the point so as not to alter its form. 1281. From the nature of the instrument itself nothing can affect the chronometer while falling, and the rate of falling being according to a well-known and invariable law, it is evi- dent that there can be no constant error in the measurement of velocities, provided that the scale is correctly graduated, and the disjunctor in proper working order. 1285. The accidental errors which may he committed cor- respond to those which odcur when a series of disjunctor-read- ings are taken, after the instrument has been properly regu- lated ; and any one at all accustomed to using the instrument will see at once that the errors in determining velocities (inclu- ELECTRO-BALLISTIC MACHINES. 461 ding errors in reading the scale) do not exceed a few decime- tres, and that the I’csnlts are snthciently accurate for ordinary experiments, the variations being far less than those due to other causes. 1280. If the two currents are not broken by the disjunctor identically at the same instant, there will be a constant error in the readings. The disjunctor is not liable to get out of order, but, if required, its accuracy can at any time be verified as follows : Determine the height of the disjunctor-reading, and then invert the currents by removing the wires which were first at s and V to s' and v', and those at s' and v' to s and v (Fig. 288), so as to send the chronometer current through the side on which the registrar current first passed, and vice versa. Having done this, take several readings, and ascertain whether they agree with those previously taken, which will be the case if the dis- junctor is correct. If there should be any difference between the height of these two series, it represents double the error of the disjunctor, and from the relative position of the marks it can be seen on which side contact is first broken ; i. e., which plate is raised before the other. To correct this error, it is only necessary to elevate or lower one of the screws, v v', until both plates are raised by the cross-piece of the spring exactly at the same moment. 1287. SCHULTZ CHROHOSCOPE.-This instrument, invented by Captain Schultz, of the French artillery, is de- signed for measuring very short intervals of time. By means of it, periods varying from thu’ty seconds to the part of a second have been measured with very great approximation, and with great ease and accuracy. It was introduced into the United States by Colonel Laidley for the purpose of deter- mining the initial velocity of projectiles in the proof of gun- powder. A tuning-fork, making an ascertained number of vibrations per second, is arranged to trace on the blackened surface of a revolving cylinder a sinuous line, showing the beginning and end of each vibration. This sinuous trace will be an actual scale of time. If, then, the instant the projectile reaches each of the two given points in its trajectory be marked upon the cylinder, beside the sinuous line or scale of time, the number of vibrations comprehended between the two marks will be an exact measurement of the time required. The important parts of the machine (Fig. 289) are thj Cylinder^ Vihratiny-forh, Electric Interrujyter, Ruhmlzorff 462 NAVAL OEDNANCE AND GUNNEEY. ^7o^7, Pendulum^ and Micrometer / and, while experimenting, the Gcdvanic Batteries and Targets. 1288. The Cylinder, with its connections, forms the most 1. Cylinder. 2. Clock-work. 3. Pendulum. 4. Tibra ting-fork. 5. Eubmkora CoiL C. Interrupter. 7. Micrometer. 8. Target. bulky of the working parts. A double motion of rotation and translation is given it by means of a cord and weight acting on a system of clockwork. These motions can also be given sep- ELECTKO-BALLISTIO MACHINES. 463 arately by band, independent of the weights. The cylinder is detached from or connected with the clockwork by a thumb- screw that clamps one of the wheels ; and the sliding motion is produced or stopped by closing or opening the nut in which the translating-screw works. The silver face of the cylinder is covered with a thin coat- ing of lamp-black, which is removed by the ti’ace and spark, and the bright surface exposed in strong contrast to the blackened parts. 1289. The Yibrating Forh stands immediately in front of the cylinder. It is clamped tightly to the bed-plate of the ma- chine, Avhieh is of iron, resting on a stout oak tiible. On each side of the fork, supported on a stand, are two small electro- magnets, meant to originate, sustain, and equalize its vibrations, and can be set at any required distance from it. The left hrauch of the fork is armed Avith a flexible quill point, Avhich can be made to touch the e}dinder at pleasure, and thus trace upon it both the middle line and the line of vibration, in the form of a helix ; the former AA^hile the fork is at rest, and the latter while it is vibrating. 1290. The Interrupter is the point of termination of the poles of the battery Avhich supplies the current for the small electro-magnets. It consists of a light beam one end of which is fixed, and the other end, extending beneath two electro-mag- nets and over a small cup containing mercury and alcohol, has a platinum blade attached wliich rises from or descends to the surface of the mercury as the beam is affected by the electro- magnets above it. One pole of the battery passes through a platinum wire into the mercury ; the platinum blude at the end of the beam becomes the other pole, and each time it touches the surface of the mercury, completes the circuit and excites the electro-magnets on each side of the fork, as well as those Avhich act on the beam itself. The magnets lift the blade out of the mercury by attractuig the beam and thus rupture the cui’rent. This done the magnets lose their magnetic force, release the beam, and the blade descends to the mercury, completing the circuit, and so on. All the electro-magnets being in the same current, are subject to a change of condition Avith each motion of the beam, Avh'ich must rise and fall as often as the fork vi- brates, accommodating itself to and acting in unison with it, in order that the small electro-magnets shall always assist and neAmr retard the vibration of the fork. Small sliding Aveights are attached to the beam, which, Avhen moved, change its time of rise and fall ; the mercury-cup, Avhen raised or loAvered, has the same effect. Should the above means 464 NAVAL ORDNANCE AND GUNNERY. fail, recourse is had to the nuts that clamp the beam, and these are tightened or loosened until the proper movement is obtaiued. If the fork vibrates for twenty or thu'ty seconds without appar- ent change, the beam is supposed to be moving in unison with it, as there can be no permanent vibration of the fork unless this condition be fulfilled. 1291. The RuhmJcorff Coil . — The secondary currents ob- tained by magnetic induction possess a high degree of intensity, and if the circuit be broken at the moment the current is pass- ing, a brilliant spark will be obseiwed at the point at which the interruption is occasioned. The secondary currents are rendered efficient by means of the Ruhmkorfl; coil. It consists of two concentric helices of copper wire ; the primary or inner coil consisting of a stouter and shorter wire than the secondary or outer coil, which is made of a very thin Avire, insulated by silk, and each layer of coils is carefully insulated from the adjacent layer; a bundle of soft iron Avire is placed in the axis of the coils. The primary coil is not continuous through its length, but admits of being broken. So long as the current circulates uninterruptedly through it, the iron core becomes an artificial magnet. As soon as the current is broken, however, the iron core ceases to he a magnet, but a powerful secondary current is induced in the secondary coil, which Avill emit a spark at any point in its circuit Avhere broken. The power of the instrument, and the intensity and striking distance of the spark, may be much increased by connecting the primary Avire Avith the modification of the Leyden jar, com- monly called a condenser. This consists of a pile of alternate sheets of broAvn paper or oU-silk and tin-foil. To use the Ruhinkorfi coil, the primary wire is connected wdth a battery and the targets ; the secondary Avire Avith the instrument; one of the ends is brought tlu’ongh a glass tube close to the cylinder just over the fork, the other end is con- nected with the bed-plate and thence Avith the cylinder and other parts of the machine, except the support for the glass tube, Avhich is carefully insulated. By this arrangement, when the primary current is broken by rupturing the target Avire, a sec- ondary current is induced and a spark is projected from the end in the glass tube to the face of the cylinder, Avhich represents the other end, where a bright spot beside the trace indicates the exact instant the rupture took place. 1292. The Pendulum is used to determine the exact num- ber of vibrations of the fork in a second of time, a matter of the greatest importance. It is connected A\dth an ordinary clock-work, and should be regulated to beat half seconds ELECTEO-BALLISTIC IIACHINES. 465 ■with accuracy. Below it is an insulated upright spring, the movable end of which is in contact with a metallic stand. To determine the number of tbe fork’s vibrations, the Ruhmkortf coil is put in connection, no longer with the targets, but with the pendulum, one pole of the primary current being attached to the spring, and the other pole to the metallic stand. A spring is fixed to the end of the pendulum itself, which, at every double beat, strikes the insulated spring from its place, thus breaking the current and giving a spark on the cylinder to mark each second of time. As the cylinder can run for thirty sec- onds, the nmnber of vibrations sought can be obtained wu'th close approximation, by dividing the entire number of vibra- tions registered on the cylinder by the number of seconds. 1293. The Micrometer serves to divide a vibration on the cylinder into very small parts for close reading. It magnifies the trace, and, by means of movable cross hairs, fixes the posi- tion of the spark. A double vibration of ordinary length may be divided into 2,000 parts, and as each of the former is about the portion of a second, the readings of the micrometer may approximate to the -s-Tnmnr portion of a second of time. 1294. The Batteries .- — A Bunsen’s batteiy of eight cups, the zinc cylinders of wdiich are seven inches long and three inches in diameter, is connected with the interrupter and tuning- fork ; and another battery of two, three, or four cups is con- nected with the liuhmkortf coil. The number of cups used with the latter will depend on the size and distinctness of the spark required, and on the length of the wire iised. The wire need not be more than .06 inch in thickness. By using a solution of bi-chromate of potash instead of ni- tric acid in the porous cups, a saving in the cost of the liquid is effected and the injurious fumes of nitrous acid avoided, with- out loss of strength in the battery. The liquids in the cups should be renewed, and the parts of the battery cleaned, ©ace a week. 1295. The Targets . — In working the instrument it is essen- tial that the current pass only through one target at a time, there being but one coil and one battery, no matter how many targets may be used. After the first target is ruptured,,the cur- rent must be transferred to tbe succeeding one before the' pro*- jectile reaches it, and so on throughout the series. The- targets must therefore be so made and arranged as that each shall trans- fer the current to the succeeding target the instant its wires are ruptured ; and that the transfer shall be completed before the projectile reaches the latter. To effect this, a wdre from one pole of the battery connects- 30 466 NAVAL OEDNANCE AND GUNNERY. both targets on one side. From the other pole a ■wire leads to the first target, and is attached to one of two brass rods that are on the top of the frame. A wire from the second brass rod leads to the second target. If the rods he connected by resting a piece of metal on both, the current will pass continuously through both targets ; but if the rods be disconnected, the cur- rent, being interrupted by their separation, will pass through the first target only. A series of brass levers are placed on the top of the frame, extending directly over the two rods. From their lower ends a wire passes down and up to foimi the target ; when the wire is tightened, the levers are raised from contact with the two rods. JSTow, the first target being broken, the lev- ers are released by the slackening of the wire and are instantly pressed down upon the two rods by a series of steel springs, and the connection made with the second target. In the experiments made at the Frankford Arsenal, with targets one foot apart, the current was transferred from one to the other by means of a simple brass spring, in less than xowo of a second of time. 1296. Principles of the Machine . — From the above description of its parts, it will be understood that the Forh., when vibrating, traces a scale of time on the coated surface of the revolving cylinder, the unit of which is the duration of a double vibration. The value of the unit for this machine is ^ second of time. The Interrupter originates, sus- tains, and equalizes the lateral c.xtent of the vibrations of the fork ; and the Coil, in connection with the targets, de- posits a spark beside the traced scale of time, to indicate the instant the wire of a tarijet is broken, thus markino; the begin- ning and end of each interval to be meas- urecl. The Pendulum serves to detennine the number of vibrations made by the fork in a second of time. The measurement of time by this instru- ment, then, depends on the equality of dmation of the vibrations made by the fork. These vibrations are known to be isochronal for the same fork, when their am- plitude is constant, and are in no way affected by the motions of the other parts of the machine. The vibrations made by the fork are recorded on the cylin- c d Fig. 290 . ELECTKO-BALLISTIC MACHINES. 467 JfG- der in the form of a sinuous line, as in Fig. 290, making th6 scale of time. The middle line, c d, traced hj the fork when at rest, is of great importance, as it divides the sinuous line and gives the exact points of the origin and end of each vibration. Even when not in the middle, no error can occur when double vibrations are counted. As expressed on the cylinder, each of the double vibrations is sutiiciently large to admit of being divided into tenths by the eye ; when greater accuracy is required, the micrometer must be used. To determine the value of the interval between two sparks, the number of double vibrations are counted. Where both sparks fall immediately opposite the intersections of the two lines, the value will be summed up in entire double vibrations, as in Fig. 290, X and y being the sparks. When one or both of the sparks do not fall opposite an intersection, the value of the interval, is thus arrived at. In Fig. 291 the sparks are at x and y. From a to T) are twenty-three double vibrations. By the eye or the microme- ter, the distances a x and h y are found to be .8 and .25 of a double vibration. Therefore x y — 23 -|- .8 -|- .25 == 24.05 24.05 double vibrations = 7: ,.. = .096565 Fig. 291 . 249.055 seconds of time. As the velocity space time ’ suppose the space between the targets to be one hundred feet, then the velocity of projectile will be equal to = 1035.5 feet per second. .096565 ^ 1297. To Use the Chronoseope . — The cylinder is coated by revolving it over the flame of an oil-lamp with a flat wick. This takes ten minutes, and twelve or fifteen rounds may be fired before the coating needs renewal.' The operator, standing in front of the instrument, releases the translating-screw, pushes the cylinder to the right, clamps it to the wheel-work, and throws the translating-screw into gear again. He then sets the point of the quill, at the extremity of the fork, very lightly 468 NAVAL OEDNANCE AND GUNNEET. against the face of the cylinder, and releases the brake. While rotating, the cylinder will be removed toward the left by the Fig. 292. translating-screw, and receive the trace of the middle line in the form of a helix. This done, the quill is raised and the cylin- der is pushed to the right as before. The quill is again set with ELECTEO-BALLISTIC MACHINES. 469 ils point exactly on the middle line, the translating-serew thrown into gear, the circuit of the battery and the interrupter closed, and the beam touched gently to start it vibrating. At this point the caution “ Ready ! ” is given, the circuit of the battery and the RuhmkorfE coil promptly closed, and the cylinder started rotating when the command “ Fire ! ” is given. As soon as the report is heard, the machine is stopped by the brake, both currents opened and interrupted, the quill point removed, and the cylinder detached from the wheel-work ; when the operator counts the result, while the gun is being reloaded, and the tar- gets mended preparatory to another round. 1298. The Bashfokth Chkonogkaph. — Profr. Rashforth, of the Artillery School, Woolwich, England, has made extensive ex- periments to determine the resistance of the air to the motion of rifle projectiles, with a chronograph of his own invention. Fig. 292 gives a general view of the instrument. 1299. Description . — The fly-wheel. A, is capable of revolv- ing about a vertical axis, and carrying with it the cylinder, K, which is covered with prepared paper for the reception of the clock and screen records. The length of the cylinder is 12 or 14 inches, and the diameter 4 inches. B is a toothed wheel which gears with the wheel-work, M, so as to allow the spring, CD, to be slowly unwrapped from its drum. The other end of CD, being attached to the platform, S, allows it to descend slowly along the slide, L, about J inch for each revolution of the cylinder. E E' are electro-magnets ; d d' are frames supporting the keep- ers ; and ^ ' are the ends of the springs, which act against the- attraction of the electro-magnets. When the current is interrupted in one circuit, as E, the magnetism of the electro-magnet is destroyed, the spring, y, car- ries back the keeper, which, by means of the arm, a, gives a blow to the lever, h. Thus the marker, m, is made to depart from the uniform spiral it was describing. When the current is restored the keeper is attracted, and thus the marker, m, is brought back, which continues to trace its spiral as if nothing had happened. E' is connected with the clock, and its marker, m', records the seconds. E is connected with the screen, and records the passage of the projectile through the screens. By comparing the marks made by m m' the exact velocity of the projectile can be calculated at all points of its course. The slide. L, is flxed paralled to F, and the cylinder, K, by the brackets, G II. Y is a screw for drawing back the wheel-work, M ; and J, a stop to regulate the distance between M and B. The depression of the lever. A, raises the two springs, 5, which act as levers, and bring the diamond points, m m' , down upon the paper. ,^70 NAVAL ORDNANCE AND GUNNERY. When an experiment is to be made, care is taken to see that the two currents are complete. The fly-wheel, A, is set in motioji by hand, so as to make about three revolutions in two seconds. The markers, m m' , are brought down upon the paper, and after four or flve beats of the clock the signal to tire is given, so that in about ten seconds the experiment is completed and the in- strument is ready for another. Tlie pendulum of a half-seconds ■clock strikes once, each double-beat a very light spring, and so interrupts the galvanic current in E' once a second. 1300. The Targets. — Fig. 293 gives the details of the screen. It represents a piece of hoard 1 inch thick and 6 or 7 inches wide, and rather larger than the width of the screen to be formed. Transverse grooves are cut at ecpial dis- tances, something less than the diameter of the projectile. Staples of hard brass spring- wire are flxed with their prongs in the continuation of the grooves. Pieces of sheet copper, ace, are provided, having two elliptical holes the distance of whose centres ecjuals the dis- tance of the grooves. The pieces of copper are used to connect each wire staple, J, d, f, with its neighbor on each side. These copper connections hold down the wire springs, which, when free, are in contact with the tops of the holes ; hut when properly w’eighted, they rest on the lower edge of the holes. Thus the copper c forms a connection between the staples h and d \ the copper e joins d and/", and so on. ^ A galvanic stream will therefore take the following course, whether the springs he weighted or unweighted : copper a, brass 1) ; copper c, brass d ; copper , limits the play of the spring ; the bottom surface of the disjunctor is covered with a sheet of India-rubber, for the purpose of deadening the vibrations, which permits it to be set up on the same table as the instrument. Experience has proved that this disjunctor is without fault ; once regulated, it is not liable to be deranged ; its regularity is perfect, for with the chronograph it gives identical disjunctions, and as to its exactitude it can be verified whenever desired, by establishing that inversion of the currents does not produce any change in the disjunction. 1312. Basis of the Calculation of the Times . — We will now explain how the time is deduced from the weight of mer- cury run out. We have supposed the flow constant; but it is not so in reality, for in proportion as the liquid runs out the height of the level diminishes, and with it the discharge. In order that the flow may always commence under the same conditions, before each trial the mercury is brought to a fixed level, which is done 478 NAVAL ORDNANCE AND GUNNERY. by a very simple operation. For this purpose, the instrument being levelled by means of an air-bubble level, whicli is laid in two directions at right angles to each other on the upper disk, a fresh quantity of mercury is added to that in the receiver ; then an overflow is opened (called level-escajpe) formed by a simple screw, o. The orifice being opened, the excess runs out into a little bucket, s, hung under the level-escape. The level thus obtained, which we will call the original level, is always of the same height ; for the determining experi- ments show that in the first unit of time the same Amlume always runs out. But the weight of this volume will vary with the temperature ; consequently, to reduce all experi- ments to the same terms, each weighing must be brought to a uniform temperature. They are reduced to 0° by the formula = P ( 1 -|- « t\ a being the coefficient of the ex- pansion of mercury, 0”.00018, and t the temperature of the receiver. This temperature is indicated by a thei’mometer, which forms a part of the apparatus, the bulb of which is im- mersed in the mercury-reservoir by passing it through an open- ing, U, in the upper disk. Tlie rapidity of flow will vary at each instant by reason of the lowering of the level, but on account of the great surface of the receiver as compared with that of the orifice, this lowering during the interval of a second is very small (about one-tenth of a millimetre,) and the time may be calculated without errors in the results by supposing — 1. That the flow is constant during the interval of one second. 2. That in passing from one second to another, the amount of flow decreases by a constant quantity. 1313. We will support this method of calculation by an ex- ample, the data for which are given by the instrument itself. Let II be the height of the original level above the orifice, and P the weight run out during tlae first second. At the end of this time the level will have been lowered by a quanity. A, which will be the altitude of a cylinder having for a base the "P surface of the upper reservoir, and for volume—, d being the density of mercury, 13.598. We shall have then h = — R being the radius of the ;r li 0 ° reservoir. At the beginning of the second second the height of the level will be H' II — A. Let us call A the surface of the orifice, and m the co- - ELECTRO-BALLISTIC MACHINES. 479 efficient of the contraction of the stream, we will have, by the laws of hydraulics — _ P = m A Since from second to second the level falls only by an almost inappreciable fraction, the coefficient, m, will not change, and Fiff. 297. we shall have also the weight run out during the second second, P' = m A fTylP- j fj7 Consequently -r. / -o- P'= P H is the formula which enables us to calculate the weight of the second second ; that of the first, the height of the original level, and the radius of the reservoir being known. 480 NAVAL OEDNANCE AND GUNNEET. Having calculated P', we may deduce from it in the same way V" Y'", etc., the weights run out during the thii-d, fourth, and following seconds. The data given by the instmment are H = 0”. 20, P =: 0™. 10, and P = 6200 centigrammes." 1314. Applying these values to the preceding calculation, we have the following results : Seconds. Height of Level. Discharge. 1st. Dif. 2d. Dif. First Millimitrea. 0. 2000C0000000 CentigrammeH. 6200. 000000 Centgr, 2.250042 Centgr. Second 0. 199854862317 6197. 749958 2. 250032 0. 000011 Third 0. 199709777705 6195. 499927 2. 250020 0. 000011 Fourth 0. 199564745545 6193. 249907 2. 250008 0. 000012 Fifth 0. 199419766096 6190. 999899 2. 249995 0. 000D13 Sixth Seventh 0. 199274839298 0. 199129965171 6188. 749904 6186. 499922 2. 249982 0. 000013 The figures of this table prove that it is permissible to con- sider the difference of weis:hts run out from one second to an- other as absolutely constant. The column of second differences shows, in effect, that they are so, to nearly the ten-millionth of a gramme, or in time ^ or 0^'.000000002, a quantity ten thousand times smaller than the fraction of time which we can hope to measure in practice. In the second place, the difference between the weights run out in two consecutive seconds being but 2'.25, which represents in time 0'h0003, no appreciable error is committed in calculat- ing the time as though the flow were constant duriiig the in- terval of one second. 1315. In order to compute the table of times of the clepsy- dra according to the principles indicated, it will be seen that we must know the height of the original level. Owing to the convex curve formed by the mercury, it is very difficult to measm-e this height exactly, but fortunately tiffs exact measure is unnecessary, as will be shown. The weight of the first sec- ond being 6,200".00, we have, by supposing H = 0 .200, found * In the use of the instrument the centigramme is adopted as the unit of weight. ELECTEO-BALLISTIC MACHINES. 481 for the second, 6,197'.T5. Suppose that in the measurement of H a mistake of a millimetre is made, and that in reality H = 0“.201, the weight of the second second, calculated with this new value, would be 6197.76 ; for H = 0“.202 it would be 6197.77 for H = 0.203 it woidd be 6197.78 for H = 0.204 it would be 6197.79 That is to say, an ei’ror of a millimetre in the measurement of H brings into the calculation of the second second only an error of. 0'b000002, a quantity which can clearly be neglected in practice. 1316. Experimental Determination of the Table of Times. — In order to determine experimentally the weight of mer- cury which runs out in the first second, the two currents of the apparatus must be broken at intervals, separated by exactly one second. A first method would consist in pass- ing the current through a plate rheotome^ which we will describe farther on, and by bearing on the plates in fol- lowing the beats of a seconds pendulum. From the weight obtained we would subtract the weight of disjunction, and thus have the weight of the first second. But by this method even a very experienced operator could never obtain in his observations the precision of which the instrument is sus- ceptible ; for this reason, a more exact method has been sought out, which consists in causing the currents to be broken by the pendulum itself, which divests the process of all personal skill. A system of two small metallic circuit-closers, ab c and d ef (Fig. 299), are fastened to the lower part of the case of a seconds-beating regulator, and in the vertical plane of the pen- dulum. Each of these closers is movable around an axis, b and perpendicular to the plane of oscillation. The pendulum terminates in a cutter, O, which, meeting in its course the points of the closers, causes them to fall alternately to the right and to the left of their respective vertical positions. Let ? s be the opening circuit, and let a point, of this circuit be united by a conductor to the connection Ti, and a point, p to the connec- tion 1. 1317. The base,^y>, which supports the whole system is in- sulated, but the connection h communicates through metal with the axis b, and the connection I with the screw g / consequently, when the pendulum is at m m, that is to say, at the end of its beat to the left, the closer ab c being in contact with the screw < 7 , the diverted circuit, r hi gf\^ complete. If in this state of things the circuit be cut in the part g r, the opening current will not be destroyed ; it will pass entirely by the diversion 31 482 NAVAL ORDNANCE AND GUNNERY. r Tcl q, but the pendulum continuing its course will destroy the continuity of the diversion, and consequently the opening cur- rent, at the instant when, arrived at z z, it touches the arm c. It must be remarked that so long as the circuit between q and r is not interrupted, the movement of the pendulum cannot break the current. Let an analogous diversion, xij v, be es- tablished by means of the closer d ef, in the closing circuit u y. The pendulum, having arrived at ml m', will have met the army, pressed dowm the closer d upon its screw of con- tact, A, and closed the diversion of the closing current. If at this instant a rupture be made between v and x, the closing cir- cuit will not be broken ; but this rupture will take place when the pendulum, arriving at z' z', touches the arm d. 1318. It is apparent, then, that the operator can break the opening current by means of the pendulum, when it, in passing ELECTRO-BALLISTIC MACHINES. 483 to the left, arrives on tlie line z z, and in the same way he can break the closing current at the moment when the pendulum coming to the right, arrives on the line z' z' . To accomplish the breaking of the circuits g’ r and -y a rheotome (Fig. 298) is used having two plates, A and B, which close the circuits by their contact with C and D. These contacts established, the opening current passes at the same time through the general circuit t q K r s, and through the diversion qlic r, which in- cludes the contact of the closer. If the finger he pressed on the extremity, E, of the plate A, the general circuit is inter- rupted between q and and the closing current passes as a whole through the diversion. The same effect is produced in the closing circuit by means of the plate B. The circuits be- ing established in the manner which has just been explained, and the clepsydra being in readiness, that is to say, the mercury at the level-mark and the two levers raised, the operator follows with the eye the movement of the pendulum. When he has taken up the cadence accurately, he places the forefinger on E when the pendulum is nearly in the position m m ; then the pendulum, arriving at z s, breaks the opening current, and the running out commences. Toward the end m' ml of the same oscillation, the operator presses down the second plate, B, and the pendulum, repassing to z' z\ breaks the closing current, and the flow is arrested. Let us call a the weight of mercury ob- tained by this operation, and /J that which would have been obtained if the two currents had been broken at exactly the same instant ; then a — f3 will be the weight run out while the pendulum is passing over the angular space z m' m' z' . This space will correspond exactly to one second, if the two oblique lines z z and z' z' are equidistant from the vertical ; but this condition is realized with difficulty in practice, and if we were to bind ourselves to its acceptance, the process would he subject to serious errors ; therefore we have made the process independent of it, by proceeding in the following way: 1319. After having obtained the weight or, as has just been explained, the mercury is again raised to the level-mark, and the instrument put in readiness ; then the operation is recom- menced, but a longer time is measured. After having broken the first current, the second is not ruptured at the end of the oscillation ; on the contrary, the pendulum is allowed to return, and it is not until its arrival for the second time at m! m' that the second plate, B, is pressed down. Let y be the w'eight ob- tained in this second operation y — /3 will be the w'eight which runs out while the pendulum is passing over zm! -\-m! m NAVAL OKDNANCE AND GUNNEEY. z' 3 ' m m m' m' z’ . If from tire time (;^ — /?) we sub- tract the time (« — /3) which is required by the pendulum to pass over z m' -\-m! z\ there will remain y — a, which will be the time employed by the pendulum to pass over the space {z m' m' z' z' m ^ m m' m' z')—{z m! -f- mf z') or z' m m mf m' z' ^ m m\ that is to say, two complete oscilla- tions, and Y — -will be the weight run out in one second. By this method we obviate the determination of the weight /?, corresponding to a simultaneous disjunction. The electrical conditions not varying from one trial to another, this weight will remain the same, and since it is included in each of the above partial operations, it is eliminated by the subtraction. ELECTRO-BALLISTIC MACHINES. 485 1320. Knowing the weight, of one second, we can cal- culate the weight of the following by the process which has been explained, and we will discover in consequence the con- stant ditference oj, from one second to another. These two quantities suffice for calculating the weights P,, Pj, P3, P4, P„, corresponding to the 1'‘, 2% S'*, 4“*, tz,*** second. Let it be re- marked, first, that the system of closers being established as far as possible in the vertical plane of the pendulum, the weight y — /? will be very nearly that which runs out during the first three seconds. a — /? will in the same way be the weight of the first sec- ond ; consequently the weight y — a will be that which flows during the second and third seconds. We will have then — • P 2 X P 3 = (r — and P2 — P3 = S whence -D _ (r — «) + ■O _{r— a) ~a> ^ , The first second will be Ps go, the fourth P 3 — cq and the w'" P,„_„ - _ Before giving the results furnished by this process, a re- mark in relation to its nse remains to be made. The contact between the closer and the bearing-screw not 'being very close, this point presents a great resistance to the passage of the cur- rent, and it often happens that when the direct circuit is cut by the rheotome, the current does not retain sufficient force to hold the armature of the magnet ; it is for this reason that one should, in this experiment, give to the magnets a great force of attraction, in order that they may preserve a sufficiency when the current passes through the diversion alone. 1321. Use of the Instrument in Experimental Firing . — The clepsydra is set up in a place in close proximity to the firing-ground, and on the same table are placed the disjunc-' tor, B, and the balance, C (Fig. 300). The batteries are on the floor or elsewhere near by. They are formed of Bunsen’s elements, arranged in the ordinary way, that is, with nitric acid in the porous cup, and a mixture of sul- phuric acid and water in the glass. Two or tlnee cells gen- erally suffice for the opening current, the number necessary for 486 NAVAL ORDNANCE AND GUNNERY. the closing current varying with the extent and resistance of the circuit. In certain special cases Bunsen cells, such as are used for telegraphy, have been employed. In these cells the carbon is replaced by a plate of copper, riveted to the zinc cylinder ; the glass contains only water, and the porous cup a mixture of water and sulphuric acid. This system has the ad- vantage of being serviceable for two months without its being necessary to touch it, but the electro-motive force which it de- velops is very rapidly exhausted. When the current is allowed to circulate during any time, the battery is very sensibly weak- ened ; if the circuit be interrupted, it stores up a fresh force, and the current returns to its original intensity. These battei’- ies are very irregular, and much inferior in this respect to the ordinary Bunsen batteries, the action of which can be consid- ered constant during the same series of experiments. 1322. The opening-circuit, ahcdefg (Fig. 300), includes the first target, the disjunctor, and the opening electro-magnet ; it passes in front of the muzzle of the gun, whether on an ordi- nary target-frame placed at 10” from the muzzle, or in a simple wire stretched across the face of the muzzle. In this latter case it must be ascertained whether the wire used is strong enough to resist the blast of gas which precedes the projectile. 1323. The second ch'cxxit, hi j him n oj> qr s, the second target, the disjunctor, and the closing electro-magnet. In the trials at the ISTaval Experimental Battery, Annapolis, Md., there is used in forming this circuit a telegraphic line parallel to the line of lire. The current is brought to the second target, h I, by a conductor, i /r, united to the line at the top of the target. After its passage through the target the current reaches the earth through a plate, m, thrust into the ground near by, the circuit being continued by a second plate, n, planted near the location of the instrument ; the current returns from this plate to the battery by passing through the instrument. By this arrangement, when the range is changed, it suffices to simply move the second target and its earth-plate. These plates, which are formed of a simple plate of copper or of zinc of a few decimeters long, or of a coil of wire, ought to be placed either in water or in a damp stratum of soil. If by the nature of the ground this kind of soil is difficult to reach, the current should be retmmed to the battery by a second metallic conductor. 1324. All these dispositions being made, it is ascertained whether the currents pass, and whether they have sufficient force to hold the levers of the clepsydra in position. The magnets are then regulated by running the movable ELECTRO-BALLISTIC LIACHINES. 487 core more or less inside the coil. The force of attraction is regulated so that the levers Avill be held with tlie least power necessary to prevent their being subject to accidental release. The operator then tills to level by pouring a cup of mercury into a glass funnel placed in the orifice, Y, and then opening the overflow. It is to be remarked that by this operation the mercury, which forms the surface of the bath, is drawn from the receiver, and this is the only portion which can contain im- purities. This mercury is poured into a flannel strainer, from which it comes out freed from oxide and dust. This process is necessary, for experience has proved that the mercury em- ployed ought to be perfectly clean ; it must then be improved in quality by use in the instrument, owing to these successive filtrations. 1325. To make ready the instrument, the currents are first made to circulate, by pressing on the button of the disjunctor I j until the spring is caught in the catch ; then with the fore- finger the catcli, T, is disengaged, while the closing-lever is brought in contact with its magnet by using the thumb. As to the opening-lever, it is self-acting, for it is raised against its magnet each time the mechanism operates. 1326. To cause disjunction, the spring of the disjunctor is released by bearing with the forefinger on the trigger, x, and with the thumb on the guard, v. These operations, as will be seen, are extremely simple and rapid; the principle has there- fore been adopted of making three disjunctions before each fire, which requires hardly a half minute. The mercury being received each time in the same vessel, the total weight, divided by three, will be that of the disjunction obtained by a mean of three trials. After having made the disjunctions, the original 488 NAVAL ORDNANCE AND GUNNERY. level is not restored preparatory to the firing, for the quantity of mercury run otf is too small to alter, in a sensible degree, the height of the liquid in the reservoir. At the instant of firing, the levers I and J fall successively, hut if the magnets be regulated too “ fine,” it will follow that the shock produced by the fall of the first lever will cause that of the second. This effect is avoided in the following way : If the time to be measured exceeds one second, which is generally the case, be- fore giving the order “fire,” the closing-lever is held against its magnet by the finger until the opening-lever has fallen. Operating in this way in the measure of a time less than a second, there would not be time to remove the finger before the rupture of the second target ; therefore, in this case, suffi- cient force is given to the magnet to prevent its releasing its hold when the first lever falls. 1327. The weights are taken by means of a balance form- ing a part of the apparatus, which is constructed with a view to this special use. For convenience of transport, it can be dismounted and placed in the instrument-case. This balance not being sensitive beyond a half centigram, the weights are easily taken. This degree of precision is quite sufficient, for the half centigram represents a time less than the twelve- thousandth of a second. Immediately after firing, the disjunc- tion is weighed; then the discharge during the passage of the shot, and tlie mercury poured back into the instrument, restores the original level. In this way the operation of levelling need be done but once at the commencement of the practice ; if, however, the temperature changes sensibly, it ought to be done over. As the two-fold weighing is quite a long operation, a mon- grel process is used which possesses very nearly the same ex- actness. In the experiments the weight which will be obtained is always approximately known, and this weight, varying but very little from fire to fire, a counter-balance is used which balances this approximate weight placed in one of the scale- pans with the vase in which the mercury is to be weighed. At each trial it is only necessary to replace the approximate weight by the mercury obtained, and to balance the scale with small weights, which are the amount to be added or subtracted in order to get the weight sought. In order to simplify this operation, the counter-balance is adjusted for the minimum which can be obtained, and in this way the difference is always to be added. A counter-balance is also used in weighing the disjunctions. Experience has shown that, with a little practice at the balancej the operation of weighing is easily done within INSPECTION OF GUNPOWDEE. 489 the time required for repairing the targets and the serving of the piece. 1328. Force of Gravity. — In the use of nearly all electro- ballistic machines, the force of gravity enters as a necessary element in the calculation. The following formula* may be employed to calculate the most probable value of the apparent force of gravity — being the resultant of true gravitation and centrifugal force — in any locality where no pendulum observa- tions of sufficient accuracy have been made. This formula with the two coefficients which it involves, corrected according to modern pendulum observations, is as follows : Let G be the apparent force of gravity on a unit mass at the equator, and g that in any latitude A : then The value of G in terms of the absolute unit is 32.088. When the point of observation is materially above the sea level, the true gravity may be derived with sufficient accuracy for all practical purposes from in which g' represents the force of gravity at the height. A, above the sea, and r, the radius of the earth. {Army Ordnance Manual^ p. 469.) The formulae given by different standard authorities will give somewhat varying results for the same station. Tliat used at the Naval Experimental Battery, Annapolis, and deduced from what are considered the most reliable data, is g = 32.1533. Lxj. vvxxat aio v>uiiOiU.ci cu. tllc lllUOL icilciuiu uata, lo ^ 1.0KJK}* 1329. STEAIN UPON THE GUN.— The resistance op- posed to the motion of a projectile in the bore of a gun, and which tends to increase the explosive force of the powder, de- pends upon the form and weight of the projectile, upon the circumstance of the piece being smooth-bored or rifled, and upon the system of rifling adopted. The projectile will commence to move when the force of the gas has become equal to the resistance offered to motion. The time necessary for the conversion into gas of the quantity of powder required to move the projectile, will depend upon the nature of the gunpowder used, the form of the cart- ridge, and the point of ignition of the latter. * EiemenU of Natural Philosophy, by Professor Sir W. Thompson and P. G. Tait. Oxford ; 1873. y G (1 + .00513 Siffi A). 490 NAVAL ORDNANCE AND GUNNERY. The maximum strain upon the metal of the gun will mainly depend upon the rapidity of the conversion of the powder into gas. 1830. The initial velocity of the projectile may not, how- ever, be in proportion to the maximum strain, hut it varies as the work done on the projectile, or as the pressures into the spaces through which they act, or : PS= where P= pressure of gas, S = space through which P acts, W^iweight of j)rojectile, V=: velocity of projectile, g=r force of gravity. And if S be a very small interval, a fair approximation to the mean strain exerted through it in the bore of a smooth- bored gun may be calculated by this formula. 1331. Pkessuee-gauges. — These are instruments used for determining, by the method of indentation^ the pressure exerted within the bore of the gun by the ignition of the powder. 1332. PoDMAxr’s Pkessure-gauge is shown in Fig. 301, and in using it, a hole is drilled through the gun at any point or points in the bore whei'e it is desired to ascertain the pressure exerted by the exploding charge. Into this hole the tube, A, is screwed, its lower end, which is open, being flush with the bore. The other end is closed with the piston, or indenting-tool, B, the joint being rendered tight by means of the gas-check, g. The piston carries a knife, 13 . (Art. 424), and upon the knife rests a piece of copper, E, which is held tightly against it by the screw, S. The hole in the tube shown at C, and the recess around the stem of the indenting-tool, are made for the purpose of letting the piston, and thus prevent its Fig. 301. — Capt. Rodman’s pressiu-e piston. (Section.) out any gas that might acting against the shoulder of pass the indenting-tool. INSPECTION OF GUNPOWDER. 491 B 1333. Use. — In nsing this apparatus the shank or piston of the indenting-tool and the hole in the tube into whicdi it is in- serted for use are well cleaned and oiled, and the indenting-tool inserted into the tube, which is then screwed into the gun, and a disk of soft copper placed on the point of the indenting-tool, the disk being held in position by the screw, S, acting either upon a second copper disk or upon a piece of iron having a plain surface next the disk to be indented. The pressure on the inner end of the indenting-piston forces the point of the indenting-tool into the copper disk when tlie gun is fired. This disk is then removed to the testing-machine, and the pressure required to produce an equal indentation with the same tool. / [jl ilif] \ in the same disk, or one from the same bar of copper, is accurately weighed; then, knowing the area of a cross-section of the indenting-pis- ton, the pressure per square inch is calculated. For the purpose of get- ting greater accuracy of results the indenting-point is veiy broad and thin so as to make a very long cut as compared with its breadth and depth. 1334. Ikteknal Pressure-gauge. — This apparatus is placed wholly within the bore of the gun, being inserted in the bottom of the car- tridge-bag, and having the charge filled in over it so that no powder will get under it and come between it and the bottom of the bore when rammed home in the gun. Fig. 302 shows the construction of this instrument. A, outer cylinder; B, screw-plug for closing mouth of outer cylinder ; G, copper gasket to form gas-tight joint ; C, specimen of copper to be indented ; I, indenting-tool ; P, in- denting piston ; y, gas-check. 1335. Use. — All its parts except the exterior of the outer cylinder are carefully cleaned before each fire, and the threads of the screw-plug and the indenting-piston carefully oiled ; the 492 NAVAL ORDNANCE AITO GUNNERY. copper specimen is then placed in the bottom of the cylinder, the indenting-piston inserted into the screw-plug, and with the outer cylinder horizontal, the plug is screwed home ; being afterwards tightly set in with a wrench while the cylinder is held in a vice. The cylinder is then carefully set down upon the closed end, and the indenting-piston gently pushed down till the point of the indenting-tool rests upon the copper speci- men ; a small gas-check is then inserted, mouth outwards, till it rests upon the end of the indenting-piston. 1336. At the Naval Experimental Battery, a gauge called the “ double ping,” from its giving two indications, has been designed for use with disks of pure silver, and the records of pressure obtained are very reliable. The instrument is inserted into the gun with the screw-plug towards the muzzle, and is generally found in the bore of the gun or near the piece after its discharge, when the screw- plug is withdrawn, and the specimen removed, having an in- dentation in its surface, due to the pressure that has been exerted upon the outer end of the indenting-piston. 1337. The indications of pressure by thus instrument are generally found to be something less, for equal charges of powder, than those by the external gauge. One reason for this is probably owing to the fact that in the external gauge the gas has a considerable space to travel through between the powder-chamber and the indicating parts, so that before reaching the piston the gases have attained a high vis-viva, especially with quick-burning powders. To enable those who have not the means of detennining the pressure corresponding to a given length of indentation to obtain approximate results from the pressure-gauge, tables are constnicted by accurately measuring the length of cut due to each 100 lbs. of pressure. 1338. Makvin’s Estimator * is an instrument for measur- ing and verifying indentations in the disks used with the pres- sure-gauge. Description. — Fig. 303 is a profile, and Fig. 304 a midship vertical section of the Estimator. The instrument consists (Fig. 304) of a cutter-stein, ABC, cylindrical as far as B, and from B to C rectangular, as per cross-section. This stem carries two nuts, E and F, and one disk, D ; E, working on a left-handed screw of 12 the inch pitch • F, on a right- handed thread cut accurately to inch pitch. The lower end of the cutter-stem is grooved to receive the Designed by Comdr. J. D. Marvin, U. S. Navy. INSPECTION OP GCJNPOWDER. 493 feather of a knife, m, about 1 inches long. G is cylindrical from a to 5, hut square from h to c, and has through it a slot in which the lower end of the cutter-stem, ABC, fits accu- rately. H is a square plate having in its centre a circular recess to contain the disk, I. J is the saucer which centres the plate, H, and guide-block, G] e e (Fig. 304) are holes in which to place a punch, to drive out the disk or plate in case they jam. K (Fig. 303) is a pointer with a bob on its end, pivoted at d, in a slot cut in G ; it is horizontal when the nut, F, rests on G, but drops down by its own weight when they are separated. The nut, F, is of precisely 3.183 inches diameter on the out- Cross section on x y. Fig. 304. side, the circumference being 10 inches; this has a scale of inches marked upon it, and is graduated to .02 inches. The cutter has a trifle over 0.2 inch vertical play, which exceeds the depth of an ordinary cut. When the point of the cutter is tangent to the disk, I, the zero of the scale on F should be opposite the point L ; F resting firmly on G, and the pointer, K, horizontal. 494 NAVAL OKDNANCE AND GTINNEET. The length of cut coiTesponding to any given projection of the cutter beyond the lower face of G may be determined either mathematically or by experiment. The pitch of the screw on which F works being inch, and the diameter of F being 3.183 inches graduated to liftieths of an inch on the circumference, it follows that the extension of the cutter can be read by the index, L, to ^ ^ ^ of an inch. By applying inside calipers between D and F at f and y, a check can always be had on the setting of the cutter. 1339. Use. — Place the disk in the recess of the plate, H, and place H in the saucer, J. Adjust the guide-block, G, on the top of H, slack up the locking-nut, E, and revolve F the number of times necessary to give the play between F and G needed to make the required cut. Bun down the locking-nut firmly, to relieve the thread of F of as much strain as possible. Insert the cutter-stem in the slot, G, and the instrument will now be ready to place in the testing-machine, where weights are applied, until the pointer, K, comes horizontal as shown by a mark on the index, L. As soon as the pointer is up, reverse the crank and relieve the pressure. The pressure comes upon the point indicated by the arrow. A graduated scale of lengths of cut corresponding to readings on the circular scale F, is used with the estimator. The reading corresponding to the length of the cut to be duplicated is brought opposite to the point L. The cutter actually used in the pres- sure gauge, is used in the estimator, on a fresh uncut disk. The power required to force the knife down to duplicate the cut is the measure of the pressure. 1340. The Ckusuer-gauge. — This is a term applied to the English pressure-gauge. (Fig. 305.) It consists of a tube or cylinder of steel wdnch admits of the insertion of a small cylinder of copper, B, which is retained in the centre of the chamber, c d e by a small w'atch-spring. One end of this cylinder rests against an anvil. A, and the other is acted upon by a movable piston, C, which is kept tight against the cylinder by the spring, i. A gas-check, D, is inserted against the lower extremity of the piston, and should any gas get past this, there are passages by which it can escape into the open air. In this apparatus the method of compression is used for ascertaining the pressures. The crusher-gauge is used in exactly the same way as the Kodman-gauge. "Upon the explosion of the charge the gas acts upon the area of the piston and crushes the copper cylin- der against the anvil. The amount of compression the copper thus sustains becomes an indication of the pressm-e exerted upon the piston. INSPECTION OF GENPOWDEE. 495 .1341. In order to obtain data whereon to base tbe calcula- tions of tbe pressures, a series of experiments is made by means of a testing-instrument to determine the pressure required to produce a definite amount of compres- sion on copper cylinders similar to those used in the instrument. The results of these experiments are tabulated, and they furnish a means of comparison whereby the amount of compression produced in the crusher becomes a direct indication of the pressure exerted by the gases at that part of the bore where the gauge is placed. 1342. The results of experiments show that the copper disks cannot be depended upon to give uniform re- sults, but latterly disks of pure silver have been employed, and the margin of error has been much reduced. 1343. One great obstacle to the attainment of correct pressui’e indica- tions is the ditficulty of obtaining per- fect uniformity in the quality of the metal upon which the pressures are re- corded. To this possible defect as well as the probable imperfect action of the piston may be attributed the very wide differences between the results some- times obtained with equal charges of the same kind of powder. 1344. Pkessuke-cukves. — Having obtained the pressures and velocities pressures as they actually occur in the bore, we may make a graphic representation of them by constructing a curve which would have for abscissas the times, and for ordinates the pressures, of the gases. We would find it somewhat similar to Fig. 306. That is, the tension increases with great rapidity in the first moments of combustion ; it attains promptly the maximum, and then decreases with less rapidity. It is to this circumstance that are due the bursting properties of the powder and the destructive effects which it sometimes exerts upon the bore of the piece. Fig. 305. — ^Sectional elevation of Crashing-in- strument. 496 NAVAL OEDNANCE AND GUNNERY. But with equality of charge the curve is found to vary very much with difEerent powders ; therefore it is desirable to pro- duce such a powder that the curve O M B may he replaced by a curve such as O M' B', in which the maximum may he less elevated, but whose total area may be equal or even superior. Thus we should endeavor to take away from the pow- der its bursting pro- perties and preserve to the projectile the same velocity in leaving the bore, or even impress upon it a greater velocity. In order to accom- plish this it is neees- , sary to consider what has been said under -X the head of Exjplo- Fig. 306. si'-oQ Force of Gun- 2 )owder 1198). 1345. IIYGEOMETBIC QUALITIES. -If the powder be made of pure materials and have the required density, its hygroinetric quality follows as a matter of course. It may be determined by exposing the powder to air saturated with moist- ure. For this purpose, samples of about 1,500 grains weight may be placed in a shallow tin pan, nine inches by six inches, set in a tub the bottom of which is covered with water. The pan of powder should be placed about one inch above the sur- face of the water, and the tub covered over. In this manner any sample of powder may be compared with another of known good quality. Good powder, made of pure materials, will not absorb more than two and a half per cent, of moisture in twenty- four hours. 1316. ANALYSIS. — Whatever may be the mode of proof adopted, it is essential, in judging of the qualities of gunpow- der, to know the mode of fabrication, and the proportions and degree of purity of the ingredients. The latter point may be ascertained by analysis. The following plan is recommended by Fresenius : Determination of the Moisture. — A\teigh two or three grams of the substance (not reduced to dust or pulverized) between two well-litting watch-crystals, and dry in the desic- cator, over concentrated sulphuric acid, or at a gentle heat. INSPECTION' OF GEIs^POWDEE. 497 not exceeding 69° centigrade, till tlie weight remains con- stant. Deter mmation of the Saltpetre. — Place an accurately v/eighed quantity (about live grams) on a lilter and moisten with water; then saturate w'th water, and after some time, repeatedly pour small quantities of hot water upon it, until the nitrate of potassium is completely extracted. Eeceive the first filtrate in a small weighed platinum dish, and the washings in a beaker. Evaporate the contents of the platinum dish cautiously, adding the Avashings from time to time ; heat the residue cautiously to incipient fusion, and Aveigh it. Determination of the Sulphur. — Oxydize tAvo or three grams of the powder with pure concentrated nitric acid and c'llorate of potassium, the latter being added in small portions, Avhile the fluid is maintained in gentle ebullition. If the opera- tion is continued long enough, it usually happens that both the charcoal and sulphur are fully oxydized, and a clear solution is finally obtained. Evaporate with excess of pure hydro chloric acid in a water-bath to dryness; filter, if undissolved charcoal should render it necessary, and then precipitate the sulphuric acid by barium chloride with the usual precautions. Determination of the Charcoal. — Digest a weighed portion of the powder repeatedly with sulphide of ammonium, till all the sulphur is dissolved ; collect the charcoal on a filter (previ- ously dried at 100° and Aveighed), wash it first Avith Avater con- taining sulphide of ammonium, then with pure Avater ; dry at 100° and Aveigh. The charcoal so obtained must, under all circumstances, be tested for sulphur by the method glA'en above, and, if occasion require, the sulphur must be determined in an aliquot part. These operations can only be performed with accuracy, in a properly appointed chemical laboratoiy, by one someAvhat ex- perienced in quantitative analysis. 1347. IXSFECTIOX DEPORT. — The report of inspection should shoAv p>lace and date of fabincation and of proof; the hind of powder and its general equalities, as the number of grains in 100 grs. ; whether hard or soft, round or angular ; of uni- form or irregular size ; whether free from dust or not ; the ini- tial velocities obtained in each fire ; the amount of qiressure for each charge ; the amount of moisture absorbed ; and, finally, the height of the barometer and hygrometer at the time of the proof. 1348. Marks on the Barrels. — Barrels must be marked on the head (Fig. 307) with maker’s name, date of manufac- •32 498 NAVAL ORDNANCE AND GUNNERY. ture, initial velocity when manufactured, density, pressure, kind of powder, lot, class, last initial velocity and pressure ob- 1349. Restokixg TJnseevice-ujle Powder. — When powder lias been damaged by being stored in damp places, it loses its strength. If the quantity of moisture absorbed does not exceed seven per cent., it is sufficient to dry it, to restore it for service. This is done by exposing it to the sun. 1350. Condemned Powder. —"Wlien powder has absorbed more than seven per cent, of water, it is condemned, and sent to the powder-mills to be worked over. When it has been damaged with salt water or become mixed with foreign matter which cannot be separated by sifting, the nitre is dissolved out from the other materials and collected by evaporation. When powder is condemned by survey, it should be turned into store ; as the nitre contained, which forms three-fourths of the powder, is still perfectly good, and can be made serviceable in making new powder. (Art. 1066.) 1351. Purchasing Powder Abroad. — In case of necessity, powder for saluting may be purchased abroad in order to pre- serve a supply of our own proof-powder for battle. Should it become necessary to use powder for service charges which has not been regularly inspected and proved in the man- ner required by regulations, such tests of it must be made as circumstances will admit. The ranges given by it may be com- pared with those of service powder of good quality under the same circumstances. If deficient in strength, the quantity of the charges should be increased, until the ranges are equalized, in order that the sight-bar may still indicate the proper ele\ a- tions for each charge and distance. Fig. 307 . Section IV. — Preservation and Storage of Gunpowder. 1352. PEESERYATIOX AXD STORAGE.— In the stowage of powder, both ashore and afloat, especial pains should be taken to secure it from the dangers of explosion and the effects of moisture ; and to this end great care is observed in the construction and locality of magazines and shell-rooms, par- STORAGE OF GUNPOWDER. 499 ticiilarly on board ship, where many details have to he consid- ered, and every possible precaution taken to accommodate the full allowance of powder completely, to guard it to the utmost against injury and accidental explosion, and to deliver it from the magazine as required, with facility and certainty. 1353. Magazines on Shore for the storage of gunpowder are generally built of brick or stone in a very substantial man- ner, and in places free from moisture, and should be remote from danger. The magazine should be fire-proof and dry, and protected by lightning-rods, which are attached to masts or poles planted from six to ten feet from the walls of the build- ing ; the mast should be of such height that the point of the stem may be about fifteen feet above the building. Magazines should never be opened while there is thunder and lightning. For the preservation of the powder, and of the floors and lining of the magazine, it is of the greatest importance to pre- serve nnobstrueted the circulation of air under the flooring as well as above. The windows should have inside shutters of copper wire-cloth. The ventilators must he kept free. JSTo shrubbery or trees should be allowed to grow so near as to protect the building from the sun. The magazine-yard should be paved and well drained, and kept scrupulously clean. 1354. Storage. — Powder barrels in magazines on shore, when there are no racks, should be stowed on their sides, with their marked ends towards the alleys, three tiers high, or four tiers if necessary, with small skids on the floor and between the several tiers of barrels, using chocks at intervals on the lower skids to prevent the barrels from rolling. If it is necessary to pile the baiTels more than four tiers high, the upper tiers should he supported by a frame resting on the floor ; or the barrels may be placed on their heads with boards between the tiers. Whenever practicable, the barrels should be arranged in double rows, with a passage-way between the rows, so that the marks on each barrel may be seen at a glance, and any barrel easily reached. Barrels must be carefully examined before putting them into the magazines, to see that they are perfectly tight ; that the hoops are not fastened with iron nails ; that there is no iron or anything objectionable about the barrel. 1355. The powder should be separated - according to its kind, the place and date of fabrication, and the proof-range. Each parcel of powder should be inscribed on a ticket and attached to the pile, showing the entries and the issues. Powder, when stored in magazines on shore, must be 500 NAVAL ORDNANCE AND GUNNERY. kept only in barrels, and arranged in lots, being cdassed as follows : Class 1. New powder. Class 2. Powder returned from skips and otlier sources wbicb has been found after proof to be up to the recpiired standard for servdee. Class 3. Returned powder, fit only for filling projectiles. (Powder taken from projectiles shall be used again only for filling projectiles.) Class 4. Returned powder fit only for saluting. Class 5. Powder unfit for use. There should be an unencumbered space of six or eight feet square at the door or doors of the magazine. 1356. Peesekvation. — Powder-houses or magazines on shore are to be inspected by the ordnance officer at least once in every week, and every precaution taken to guard them against explosion, and to preserve the powder dry and in good condi- tion. Magazines should be opened and aired in clear, dry weather, when the temperature of the air outside is lower than that inside the magazine. The moisture of a magazine may be ab- sorbed by chloride of lime or charcoal, suspended in an open box under the arch of the door, and i-enewed from time to time. The use of quicklime is dangerous and forbidden. The powder in barrels should be turned from time to time, at least as often as every three months, and being arranged as mentioned before, the oldest powder will always be accessible for first delivery, without disturbing that of more recent man- ufacture. 1357. Seevice of the Magazine. — Mhen powder is han- dled in powder-houses or magazines on shore, either for the purpose of inspection or preparation for delivery to ships, the baize-cloth is to be spread, and the people before entering the magazine must divest themselves of every metal implement, empty their pockets, — that nothing likely to produce fire may escape detection, — and put on the magazine-dresses and slip- pers. Neither loose powder nor open barrels will be jaermitted to remain in a magazine, nor shall barrels on any account be opened in a magazine. Should a barrel-head start, the barrel must be immediately removed to the shif tiny-house, and the powder shifted into a sennceable barrel. The barrels must be opened only on the fiooi’-cloth in the shiftiug-honse, and no metallic setter used in driving either copper or wooden hoops. Powder-barrels should never be opened except when required for use, as grains of powder falling between the staves would STORAGE OF GUOTOWDER. 501 prevent tlieir being tightened. Samples must always be taken from tlie bungs. Magazine-dresses . — They are to be of worsted, like a simple shirt, to reach to the knees ; no metal buttons to be worn. Magazine-slippers . — They must be made wholly of cotton, cloth or buckskin. In hot or warm climates the naked feet are generally preferred. India-rubber and woolen-slippers are pro- hibited. 1358. Fixed Ammunition should not be put in the same magazine with powder in barrels. Fireworks should never be stored in a powder-maga- zine. 1359. llhe 2Lagazine Ledger should show at all times the quantity of powder on hand, the number of barrels, the marks on each barrel, and, in fact, a complete history of ail the pow- der in the inai>;azine. 1360. Issuing Poioder . — When powder is to be issued for use to any vessel, it shall be selected as far as practicable from dehveries made by the same manufacturer, at the same time or date. The powder is measiued in copper measures and put into cartridge-bags, and the cartridges stowed in powder-tanks. A correct history of all powder issued must accompany it. When powder is shifted from one barrel or tank to another, care must be taken to remove all old marks, and to mark the barrel correctly for its contents. Great irresrularities bavin<; been discovered in the weijrht of cartridges supplied from the difterent magazines, it is ordered that at least teir measures shall be weighed at each filling, and allowance made for different densities, by using a small com- pensating measure to supply the deticieney or to remove the excess. 1361. Ships’ MAGAzixrES.— All powder, wliether public or private, must be safely stowed in the magazine. Form . — In view of the fact that all the powder for use on board of ships is now put up in carti idge-bags and stowed in cubical copper tanks made water-tight, the form of magazines sliould be as nearly rectangidar as the shape of the vessel will admit. Strength . — They should be built strong enough to resist sufficiently the effect of the working of the vessel in heavy weather, and also the pressure of water they will have to sustain in case of being flooded. Situation . — When there is only one magazine, it is always in the after part of the vessel; but when two, one aft, the other forward ; and they are to be as nearly equal iu regard 602 NAVAL ORDNANCE AND GUNNERY. to capacity as the shape of the vessel and other ch’cumstances will admit. 13G2. Construction. — The magazine con.sists of three parts: (Fig. 308.) The room where the charges are stowed ; a small delivery- Lil Fig. 308 . room or passage, nsnally athwartship, immediately outside of this, into which the charges are passed before going on deck ; and the light-rooms, or boxes. The magazine and its passage, considered as one, must he made perfectly water-tight, by caulking the bottom and sides, and then lining them internally, first with white-pine boards, tongued and grooved, and again with sheets of lead of extra thickness, soldered together over these boards. Both these lin- ings are to extend entirely over the bottom, or floor, and all the way up to the crown on all sides. When the magazine reaches the ceiling of the ship it must he battened oft' two inches ; the lining of the floor must be battened up one inch, and also the magazine-deck, so that water leaking through the sides of the vessel may run by and under, and not into, the magazine. An external lining of sheet-iron must he resorted to as a pi’otection against Are, and to prevent the intrusion of rats. When it is impossible to avoid extending the sides of the STOEAGE OF GUNPOWDER. 503 magazine so far out towards tlie skin of the ship as to leave only an air-passage on either side, the crown should be at least six feet below the deep load-line. In all cases where this crown is less than six feet below that line, the sides should he made susceptible of protection by allowing a space to interpose materials, such as sand, coal, or water in tanks, between them and the interior planking of the ship. An average space of six feet or more on both sides will be sufficient. Under no circumstances, however Avell the side be guarded, should the crown of the magazine, if it can he avoided, he less than four feet below the load-line. Their floors may rest on the kelson, hut should not come below it. 1363. Their height should he equal only to an exact num- ber of times the height of a powder-tank when lying on its side, in addition to the thickness of the shelving ; an additional inch should he allowed for play or spring. The whole height in the clear should be limited by the con- dition that a inan standing on the floor may reach the upper tier of tanks with ease. Four tiers of 200-pound tanks, three of them resting on shelves two inches thick, and the other on inch-battens on the magazine-floor, with an allowance of one and a half inch for play, will require a height, in the clear, of six feet two Inches. Both safety and convenience would suggest this as the maxi- mum limit m height, even for the largest magazine. If, however, in a ship of great draft of water, it should he found practicable to have height enough for live tiers of tanks, then the lower tier may he laid so as to occupy the whole of the magazine-floor ; and on the top of this tier, in the alley- way, a light false bottom is to be placed for the men to stand upon to enable tliem to reach the upper tier, which is the one that should he exhausted flrst. Thisialse bottom should be made of gratings, and in sections convenient for speedy removal. ' A magazine aft in a ship is to have its passage for deliver- ing powder adjoining its forward part ; and one forward in a ship is to have this passage adjoining its after part, in order that it may never be necessary to pass powder over the light- box scuttle. 1361. As many doors, D (Fig. 309), are to be cut in the hulk-head, I II (Fig. 308), separating this passage from the magazine-room, as there are alle_ys to be left in the latter, be- tween the racks or shelves on which the tanks are stowed ; and 504 NAVAL ORDNANCE AND GUNNERY. these doors must correspond -with those alleys. They are not only to afford a means of entrance to the magazines, but also for passing the tanks in and out. Section on H I, Fig. 308. Fig. 309. Through the upper part of each door a small scuttle, S, is to be cut,— two, if necessary, — for the purpose of passing the cartridges out of the magazine-room with the door itself closed ; and is to have a lid so arranged as to open outwards only, and to close of itself when the scuttle is not actually in use. Frigates should have two alleys for each magazine. In screw- vessels of large size, where the shaft will interfere with this ar- rangement, two alleys for the forward magazine. In smaller vessels one alley will suffice. In all cases the alley is not to be less than two feet and ten inches in breadth, and it ought to be more, if practicable, to prevent confusion and delay. Each alley (A E, Fig. 308) is to be illuminated by a separate light. If there be room in the magazine, there should be space left at one end for a man to pass from one alley to the other with- out going into the passage. All the metallic fixtures about a magazine, delivering- passage, and light-room mnst be of copper. In order to increase secnrity against the effects of lightning, a magazine should be placed, if jaracticable, so as not to include a part of a mast. 1305. Flooding the Magazine. — Each magazine as a whole, that is, including the delivery-passage, being made as stated be- fore, water-tight, is to be provided with an independent cock, T, for filling it rapidly with water; a waste-pijie leading from the upper tier of tanks to carry off the snpei'fiuoiis water, and a cock just at the floor to empty the magazines after having been flooded. Both the cocks must be turned from the decks above, each having a lever attached to its spindle for the ])iir])ose, dis-. tinctl}'^ marked with engraved letters what it is and how it is to be used, and kept secured by a proper lock, the key of which is to be kept among those of the magazine. A perforated disk or strainer is to be secured inside of the hole, at the upper part STORAGE OF GTJXPOWDER. 605 of tlie magaziue, for tlie -waste-pipe ; tlie deli very -pipes are trapped to prevent vermin or vapor entering. Section on A-E, Fig. 308. Fig. 310. 1366. Lighting tge Magazine. — The magazine is to be lighted by means of one regulation lantern, to correspond with each alley of the magazine-room, placed in a box arranged for the purpose, E (Fig. 310). The lantern, is fitted to hold a regulation candle of large diameter. The box, of which a portion of the magazine bulk- head forms a part, is lined internally with soldered sheets of copper. The entrance to it is at the top, through a scuttle in the deck large enough to admit the lantern. For single-decked vessels this scuttle may be surrounded by a composition cover- ing pierced with holes one-fourth of an inch in diameter, on the forward and after sides, near the top. The cover must be so arranged that, when placed on in one position, all the holes will be closed ; by turning it half round, they are all open, thus supplying air to the lantern and carrying off the smoke. A small dome or reversed funnel of copper, when it can be con- veniently done, is to be placed above the lantern and fitted with a pipe of the same metal to convey the smoke off. This pipe may pass up through the covering of the light-box, which is to have a plug-hole lined with brass for the purpose, and then led farther, if necessary, taking care, however, to consult perfect safety throughout. The admission of air to the light-box may be from the divi- sion of the hold in which it is placed, by small holes near its top, through its side or bacly protected with copper-wire gauze, in- side and outside of the box. In the portion of the magazine bulkhead before alluded to, and so as to throw as much light as possible into the magazine- room, an opening with great bevelling is cut, which is covered by two plain glasses of suitable thickness, somewhat separated from each other, one of wFieh, W (Fig. 311), that next to the 506 NAVAL ORDNANCE AND GUNXERY. lantern, must be permanently fixed ; and the other, that next to the magazine, X, is to be let into a wooden frame so that it may be easily removed, and thus both glasses cleaned with convenience and safety. These glasses are held in place by brass screws, after being closely fitted, having their edges made perfectly tight. 1367. Stowing the Magazine. — Ledges on the shelves, Section on F L, Fig. 303. or a bar of wood (Fig. 310), to ship and imshij) with facility, will be provided for each tier of tanks on both sides of the alleys, to secure them from getting out of place when the ship rolls. The powder-tanks containing charges for each class of guns are stored on their sides with the lids next to the alleys and hinges down, near the magazine-scuttles through which these charges are delivered. When tanks are emptied they are stowed on the upper shelves in order that the powder may be kept as much as possible below the water-line. Before the tanks are filled they must be thoroughly cleaned, and before stowing them in the magazine the exteriors are care- full}' cleaned and the Kds examined. 1368. Powder T^vxks. — The powder-tanks, for the recep- tion, and safe storage of the powder on board ship, are rectan- gular metallic cases, the sides and bottom being of sheet-copper, zinc-coated, and the top of composition. They have a circular hole or opening in the top, which is closed by a composition lid on hinges, c (Fig. 31i), and made water-tight by means of a rubber-gasket inserted in an annular groove on the lower side of the lid, shutting down upon a knife-edge around the opening, and when closed is retained in place by a screw-bolt fitted in the lid opposite the hinges. There is also a circular copper disk, or cover. A, fitting over the charges, inside the composition lid. On the same end are two handles for transporting the tank. All tanks before issue should be thoroughly tested, to see STORx\GE OF GUNPOWDER. 507 that they are water-tight. This is done by immersing them in water six feet in depth, for twenty-four hours. They are made of four sizes and are de- nominated as 200 lb., 150 lb., 100 lb., and 50 lb. tanks respec- tively, this being their capacity for powder in grain ; but the 200- pound tank is consid- ered the standard size for service, the others being used only in exceptional cases, and to nil up small vacant spaces. 1369. The System OF Marking Powdee- TANKs is as follows : The lid end is painted wlhte, and is marked with the weight of Fig, 313, cartridge, number of cartridges, and calibre of gun for which they are intended, thus : the lower part of the lid end, as the tank lies in the rack (Art. 1367), is marked with the number of charges contained (Fig. 313). Tlie upper right-hand corner is marked with the number of pounds in each charge. The upper left-hand cor- ner of tanks for supplying the battery, is marked with the calibre of the gun for which the contents is intended, and the calibre is also marked in red on the lid, in large Roman num- erals, for all smooth-bore guns. They are marked on their upper sides, next the lid end, with the name of the manufacturer, kind of powder, initial velocity, density, pressure, and date of manufacture. And in order to distinguish more readily those tanks con- taining “Service,” “Saluting,” “Torpedo,” or other charges from each other, the following plan of painting the lids has been adopted: Tanks containing sal uting-charges have one-half of the lid painted red, and “ Saluting ” is marked on the other half. Tanks containing shell-charges have a red circle painted on the lid, and inside the circle is marked “ Shell.” 508 NAVAL ORDNANCE AND GUNNERY. Tanks containing powder for torpedoes ai’e marked on tlie upper left-hand corner of tlie lid end “ Toi'pedo,” and on the lid is marked in red a large letter T. Powder for torpedoes is put in cartridge-bags properly stencilled. Tanks containing howitzer charges are marked on tlie upper left-hand corner of the lid end Howitzer,” and on tke lid is painted in red a large letter II. Tanks containing sliell-poicder have a large letter S painted in red on the lid. This kind of powder is put up in any cou- veitient size of bag which will make the best storage, the bags being properly stencilled. Tanks containing ride-charges, beside having the calibre marked on the upper left-hand corner of the lid end, have also on the lid a large letter P painted in red. A history of the powder contained in each is to be pasted or stencilled on the inside of the tank-lid. Ho loose powder is ever to be taken or carried on board ship. STOKAGE OF GUNPOWDER. 509 1370. Seetice of the Magazine. — Whenever the maga- zinos are opened, every precantioii is to be taken to guard against accident by fire ; to examine tliat all the men stafioned in any way, in or about the magazine, embracing all stationed witliin the magazine-screen, put on the magazine-dress and shoes, and on no account liave anything metallic about them, and that no improper articles are introduced ; and to see that all the articles required for sweeping and removing loose powder are at hand, and that these operations are performed before the magazine is closed. The tanks are never to be opened unless by special order, or when powder is actually required for service, and then no more of the lids are to be unscrewed than the immediate supply necessitates. The strictest attention to this is rec[uired, as ex- perience has proved that the preservation of the powder in good condition depends upon the entire exclusion of damp air. No coopering is ever to be done in the magazines of ships. Should powder be received on board in barrels, the hoops and heads must be started on the orlop, or berth-deck, before enter- ing the magazine. 1371. Dampness of Magazine. — Sponge dipped in a solu- tion of salt water, dried and weighed, is a means of ascertaining if dampness exists in these places. If it becomes heavier the magazine is damp. Ventilation. — Provision must be made by means of grat- ing-hatches for sufficient ventilation in action, to supply the men with fresh air, and allow the dampness caused by perspira- tion to pass off ; and fan-blowers are to be fitted to increase the supply of fresh air, and to assist the v^entilation. The magazine should be opened and aired at least once a fortnight, for a few hours, on bright, clear days. 1372. Magazine Screens. — They are made of thick fear- naught or double-baize, with holes through which to pass the powder ; these holes to be covered with fiaps of the same material. One screen is to be hung abaft, and another forward of the magazine passing-hatch, and scuttles in sloops-of-war ; in frigates, one is usually hung abaft the fore, and one forward of the after magazine-scuttle; but as ships are differently ar- ranged, two to each magazine are allowed, if they are neces- sary. 1373. Transpoktation of Powder. — Barrels of powder should not be rolled for transportation ; they should be carried in hand-barrows, or slings made of rope or leather. In moving powder in the magazine a cloth or carpet should be spread ; 510 NAVAL OKDNANCE AND GUNNERY. all the implements used there should he of rrood or copper, and the barrels should never be repaired in the magazine. When it is necessary to roll the powder for its better preser- vation, and to prevent its caking, it should be done with a small cpiantitj at a time, on boards in the magazine yard. In wagons, barrels of powder must be packed in straw, secured in such a manner as not to rub against each other, and the load covered with thick canvas. In transportation by railroad, each barrel should be carefully boxed, and packed so as to avoid all friction. The barrels should have a thick tar- paulin under them. The cars should have springs similar to those of passenger-cars. 1374. V essels-of-war always receive their powder and loaded shell in the stream. When receiving powder the red flag is always to be hoisted at the fore,' and all proper precaution taken to guard against accidents from fires and lights. The tanks should be passed through the ports most convenient to the magazines, and landed on mats to prevent injiiry. The red flag is always to be hoisted at the powder-houses when they are open, and kept flying until they are closed. Tlie wharf or landing-place must be spread with old canvas, so that the barrels or tanks may not come in contact with, and convey, sand or gravel to the magazines. When avoidable, gunpowder is not to be sent from vessels to powder-houses, nor from powder-houses to vessels, in wet weather, nor when there is a probability of wetting the ban-els or tanks ; and the packages must be conveyed in covered boats or wagons showing a red flag. The powder-boat, before being used, must be swept thor- oughly clean, and the bottom covered with mats. Before shipping powder by a vessel, the hold must be ex- amined to see that all iron bolt-heads, etc., are covered with sheet lead, leather, or old canvas ; that the hold is clean swept and free from grit or dust. A cushion (stuffed with oakum) covered with leather is to be used for landing all powder barrels or tanks upon, whether in the hold of a vessel, or on a wharf, when loading or dis- charging powder. Section V. — Explosive Compounds. 1375. Genekal Consideratioxs. — Numerous as have been the attempts to apply other explosive agents as substitutes for EXPLOSIVE COJIPOtnSTDS. 511 gunpowder in fire-arms, no rival of the latter has established any good claims to success as a prop>elling agent, except for sporting pui-poses. The various fulminating substances known to chemists are unfit for use in fire-arms, owing to a variety of circumstances ; one of which is the extreme rapidity of their explosion, the vdiole mass appearing to be converted into gas at once. The action of fulminates is also too local ; if a portion of any of the more violently explosive substances be fired on a jriece of metal, the latter will be perforated or depressed exactly at the spot occupied by the substance ; and if it be attempted to use it to clrarge fire-arms, they will be destroyed, yet in all probability the ball not projected ; moreover, these substances are not ser- viceable for charging shells, because the latter, instead of being blown into pieces of moderate size capable of inflicting great damage, become converted into fragments so small as to be far less destructive. But, although gunpowder is still the only propelling agent susceptible of general application, it no longer enjoys a mo- nopoly in connection with some equally important applications to naval, military, and industrial purposes, such as blasting, demolition of walls, buildings, or wrecks, and destruction of vessels by torpedoes. 1376. GUbT-COTTOI^.’'^ — This is obtained by the action of concentrated nitric acid on cotton. Cotton is nearly pure cel- lulose, which is the principal part of the ligneous fibre or woody matter of plants. Cotton, linen, and hemp fabrics and unsized white-paper are nearly pure cellulose. When cellulose, cotton wool for instance, is acted upon by a strong mixture of nitric and sulphuric acids, its external ap- pearance remains unchanged, but its chemical composition is very much altered, being formed. This is a nitro- substitution prodirct. A certain n;nnber of equivalents of hy- drogen being abstracted from the cellulose, and their place sup- plied by an equal number of equivalents of nitryl. There are a number of these substitution prodircts in which the substitution is more or less complete, and they differ more or less in their pi’operties. The pyroxyline used to make collodion is a mixture of several of the lower ones. The lower products decompose more readily than the higher ones, and at a lower temperature they are more prone to spontaneous decomposition and more inhammable, and will explode, but with less violence than the higher ones. * EUl. 512 NAVAL OEDNANCE AND GUNNERY. The term Gun-cotton slionld he restricted to the liighest one of the products ; and in making it, the substitution must be carried as far as possible, so that none of the lower and less stable compounds may be obtained mixed with the higher ones. The cotton used must be perfectly dry, and free from grease or other impurities. Only the very strongest nitric acid must be used, and the treatment must be prolonged until the conver- sion has become complete. The gun-cotton must be finally freed from every particle of acid. 1377. Manufacture. — The various details connected with the manufacture of gun-cotton are frecpiently changing, and, therefore, only a general description of the mode of prepara- tion will be given. 1378. Purification of the Cotton — Long-staple raw cotton of the finest quality is the best to use. It is first cleaned and then w^ashed in an alkaline solution to get rid of all oily matters, which would otherwise prevent the complete saturation of the cotton by the acids used in its preparation. xVfter being purified, it must be again thoroughly washed and then dried before going through the subsequent operations. 1379. Treatment with Acid. — The perfectly dry cotton is converted into gun-cotton by immer.sion in a mixture of strong nitric and sulphuric acids, in the proportion by weight of one part of nitric'to three parts of sulphuric acid. The sulphuric acid does not act at all in forming the gun- cotton, but only takes up the Avater that is formed during the process, thus preserving the strength of the nitric acid. The nitric acid is of the strength not less than spec. grav. 1.50. The sulphuric acid is the ordinary oil of vitriol, spec. grav. 1.83. The cotton is fiijst dipped in this mixture, and exposed to its action for a feAV moments. It is then taken out, and as much as possible of the acid that has been taken up removed by pressure. It is then put in fresh acid, Avhere it I’emaini 48 hours. The vessels are kept cool during this time by a stream of cold water. In the first acid the cotton is nearly all converted, but it is a matter of the greatest importance that the coiiAmrsion should be complete. It is therefore necessary that the second and prolonged operation should be made. 1380. To Remoa'e the Acid. — To remove all the acid from the gun-cotton thus made, it is jdaced m a centrifugal drying machine, and then thoroughly steeped for a^ considerable time in running Avater, and subsequently dried. It is finally treated Avith an alkaline solution, as carbonate of soda, and again Avashed, thoroughly dried, and packed. 1381. Abel’s Method. — In the manufacture of gun-cotton. EXPLOSIVE COMPOUXDS. 513 there is great difficulty in thoroughly washing the cotton, be- cause the long, hollow fibres get twisted and bent, so that it is very hard to free them from the acid. Abel has instituted the pulping process, by which the cotton is so torn as to be easily washed ; and instead of raw cotton of high quality and long staple, any description of cotton can be employed; and the waste cuttings from spinning-machines, such as are used for cleaning machinery, are more suitable than cotton in any other form. The pure, fine pulp is pressed into compact masses while wet. 1382. Pulping. — The cotton, after being washed and strained, is carried to a long tub, or heater, filled with water, in which a wheel revolves, armed on its periphery with steel cut- ters. From the bottom of the tub under the wheel extend sim- ilar projections of steel, and as the motion of the wheel carries the cotton around, all parts are driven through the contracted space between the cutters, thus reducing the whole to a pulp. From the beater the entire contents is run into poacher, or large tub in which a paddle-wheel revolves. The object being to continue the washing of the cotton, after being reduced to pulp, so as to secure the perfect cleansing of the material. All parts of the pulp are carried over and over by the wheel, and this operation is continued several hours. The operations of the preparation of the cotton are now complete, and it only re- mains to di'ain off the water and press the pulp into the required shape. 1383. Compressing . — In order to drain off the water, the first operation is to draw off the pidp and water from the poacher to a large n-on cylinder, or stuff-chest, where it is agi- tated by paddle-wheels. From the bottom of the stuff-chest there runs a pipe to lead the pulp to the press for forming the cakes. This press is a circular machine consisting of a shelf having thirty-six circular perforations about two and a half inches in di- ameter, which have cylindrical continuations extending about one foot below. Beneath these hollow cylinders are a corresponding number of solid cylinders fitted so as to enter them, which are attached to a plate that is actuated from below by a hydraulic force. The solid cylinders being entered into their correspond- ing hollow ones, the pulp is allowed to run in through a mova- ble trough, and fill the recesses. The upper orifices are now covered with a weight, the solid cylinders forced up, and the pulp compressed, tlie water being allowed to escape through strainers or perforations in the pressing cylinders. The cylinders of gun-cotton thus formed are removed to a 33 514 NAVAL ORDNANCE AND GUNNERY. second press having only fonr cylindrical recesses, in each of which are placed three of the cylinders, separated from one another hy disks of iron having scored edges to allow the escape of water. The operation is repeated, the pressure being six tons to the sqnare inch. This press produces cylinders about three inches in length hy two and one-half inches in diameter, and weighing one-half pound ; about six per cent, of moisture being still retained. 1384. General Properties. — Gun-cotton is entirely insol- uable and unaffected by water, so it may remain in it any length of time without injury. Its permanency has been a matter of doubt, and for this reason the more extended use of gun-cotton has been greatly hindered. Of course if it is liable to spontaneous decomposition, it cannot he used with any degree of confidence, hut the late improvements in its manufacture seem to give a very stable and safe product. If so regarded, it possesses many advantages over gunpowder, as follows : less danger in making ; unaffected by moisture, or even immersion in water ; easier transportation ; it leaves no residue and makes no smoke. 1385. Forms in which Ghn-cotton is Used. — It can he worked into many forms for different uses. The process of manufacture when not pulped leaves it in the loose state, re- sembling ordinary cotton. It can then be run into threads and ropes, and the threads into webs or hollow cylinders. For ordnance purposes it is made into disks from the pulp, or the yarn is wound on a hollow tube or core. Besides this, the com- pact masses pressed from pulp can, while still moist, be cut, saw’ed, or drilled into any shape, granulated or mixed with other bodies. Potassium nitrate or chlorate, is usually mixed with the pulped article. Abel has proposed a mixture called Glyoxiline composed of compressed nitrated gun-cotton saturated with nitro-glycerine. 1386. Uses oe Ghn-cotton. — It is much used for mining purposes and submarine explosions, since it is more readily handled than gunpowder, is not injured by water, and less is required to do the same work. Compressed gun-cotton is much used for torpedoes and large engineering operations, for which it presents very gi-eat advantages. It is very effective when great destructive effects are to be produced very quickly, as blowing up bridges and military works. For instance, to de- .‘^troy a bridge it is only necessary to place upon it a charge of gun-cotton and fire it with a detonating fuze. In the same way large (piantities of rock may be broken up and guns may be disabled. EXPLOSIVE COMPOUNDS. 515 1387. Mode of Firing. — Dry gun-cotton when nneonfined flashes off without explosion ; when ignited, therefore, to obtain its force it must be confined in strong vessels so that the gases first generated will he driven through the whole mass envelop- ing every particle with flame before the case is ruptured. Under these circumstances great explosive effects may he obtained. The explosion is very much influenced by the manner in which it is effected. It can be readily detonated, and then it is un- necessary to have it strongly confined. The more powerfully it is compressed the more readily it can be detonated, since the particles are less able to move on one another, and therefore offer a greater resistance, causing more rapid evolution of heat. Compressed gun-cotton can be fired while moist, or even when saturated with water, by exploding in it a disk of the dry, by means of a fulminate fuze. AV^hen dry and unconfined, if ignited by a flame, it burns steadily and quietly until consumed ; but if fired by a detonator, it explodes violently. 1388. UITRO-GLYCEEINE. — This is a nitro-substitution product of glycerine ; it is a violently explosive substance pro- duced by the action of nitric-acid on glycerine. Its formation resembles that of gun-cotton, three equivalents of hydrogen being removed frotn the glycerine by the nitric acid, and three equivalents of nitre introduced in their place. 1389. Gdyoeeine is the sweet principle of oils and fats. It is a sweet, viscid, colorless liquid, soluble in water and alco- hol in all proportions. In this country it is principally derived from the fats of hogs. That of commerce contains more or less water, and is slightly colored. Sometimes it also contains small quantities of fatty acids. This is a very dangerous impurity, if it is to be used in making nitro-glycerine, and must be guarded against. 1390. Method of ManijFxVctuee. — It is produced by the ac- tion of strong nitric-acid on glycerine at a low temperature. As in making gun-cotton, the nitric-acid is mixed with a large proportion of strong sulphuric acid, — one part of the for- mer to two parts of the latter, by weight, — which acts in taking up the water that results from the reaction, and so keeps the nitric acid at its full strength. Glycerine is mixed slowly with the acid mixture, which is constantly agitated during the operation, and great pains is taken to keep down the temperature. AVhen all the glycerine has been added, the mixture composed of nitro-glycerine and the remaining acid is poured in a thin stream into a large vol- ume of water, where the nitro-glycerine is precipitated as a white, opaque, heavy oil. AVhen it has subsided the water may 516 NAVAL ORDNANCE AND GUNNERY. be poured off. It must be thorougUj washed, as too much stress cannot be laid upon the importance of a complete removal of the acid from the nitro-glycerine. After some time, depending on the temperature, the white, opacpxe, thick fluid changes to a clear, pale amber, somewhat thinner liquid, and then should be entirely free from acid. If so, it Avill x-emain unaltex’ed, not becoming acid again. Converting glycerine into nitro-glycerine must be carefully and properly conducted, if good results are to be obtained. It must be carried on at as low a temperature as possible, and a gi-eat rise of temperature must be prevented during the opera- tion. The glycerine must be free from dangerous impurities. The strongest nitric acid must be used ; if weak acid is used, the quality of the product may greatly vary. 1391. General Properties. — Nitro-glycerine is more vio- lent in its explosive effects than gun-cotton, more nearly re- sembling the fulminates, though not so easily exploded. When not piu’e, it undei’goes spontaneous decomposition with evolu- tion of nitrous fumes, frequently causing explosions ; but when well purified, it may be kept for a long time without alteration. It is unaffected by, and does not mix with, water, so that it can be exploded when in direct contact with it. It is a light yellow, oily liquid, has a faint, peculiar smell, and a sweet, pun- gent aromatic taste. A drop of it is said to cause veiy violent headache, and in large doses it appears to be decidedly poison- ous. 1392. Mode of Firing. — To explode nitro-glycerine it is necessary to use what is technically called & strong exjglodcr. that is, one that in itself gives a strong blow or shock. Therefore, fulminate of mercury is generally employed for that purpose. Nitro-glycerine explodes only locally by percussion. If placed upon an anvil and struck with a hammer, the particles receiving the blow detonate, not exploding, but scattering the rest of it. It is not exploded hy friction or concussion in the ordinary sense of the words, that is, by an ordinary or reasonable friction or concussion. Simple application of flame will not fire it, though, of course, it may be heated to explosion ; but it is not sensitive, that is, not easily exploded by slight causes, therefore an ordi- nary fuze or slow match is useless. However exploded, it seems always to be instantaneous through the whole mass. When fulminate is used, this is evi- dently by direct detonation. In other cases, probably by initial detonation of a small particle. It is more easil}" detonated than any other body, and less fulminate is required. It can readily be fired by this means, when imconfined ; but as is al- EXPLOSIVE COMPOUNDS. 517 ways the case, greater effects are obtained if it is confinech however slightly. It is with the greatest difficulty that it is bred when frozen ; therefore it is used in the liquid state. 1393. Teanspoetatiojst. — It is usually kept in cans and frozen for transportation or preservation, and must be melted before it is used. It solidifies at 40° Fahr., which can readily be accomplished by keeping it in melting ice a sufficient time. It freezes to a nearly pure white crystalline mass. When frozen, it can be melted by means of hot water not above 90° or 100° Fahr. 1394. Stability oe Peemanence. — The history of nitro- glycerine closely resembles that of gun-cotton. The manufac- ture has been carried on before it had been properly studied or its characteristics known. As to its stability, the little exact knowledge obtained of it has caused the opinion to be formed that it is very unstable. Even yet we have very little precise knowledge of it, but it is believed that its permanency depends upon its purity, and that if pure and well made it is sufficiently stable, provided proper care is taken of it. As an explosive it is so valuable that it would still be used even were it much more dangerous. 1395. Uses of ISTirEo-GLYCEEixE.— It has generally been used for submarine and other blasting. For heavy work it surpasses any other agent, being so much more powerful than gunpowder; less is required and less drilling is necessary. It is a powei-ful shattering agent, and breaks up the rocks finehx It leaves no residue and gives no smoke. It is well adapted to many kinds of submarine work ; good results are obtained by placing it on the surface of rocks under water, the latter acting as a tamping. 1396. COMPOUFIDS OF XITKO-GLYCEPmE.— The successful application of the remarkable explosive liquid, nitro- glycerine, has been developed chiefly in the last few years, and the existence of several most serious obstacles to its use in the pure liquid condition has been practically demonstrated ; in several in- stances,. indeed, by most disastrous accidents; therefore, many attempts have been made to devise some method of promoting safety, and also certainty of action in its employment. These ends have been attained to a great extent by mixing nitro-glycerine with some solid substance of perfectly inert na- ture, and of absorbent character, through the medium of which the liquid is susceptible of employment in a condition assimi- lating to that of other explosive agents in practical use. 1397. Dynamite. — This is the name given to a compound of nitro-glycerine formed by absorbing it in a light silieious 518 NAVAL ORDNANCE AND GUNNERY. earth, which may he mixed with about three times its weight of uitro glycerine without becoming more than moist to the touch, and is therefore readily susceptible of manipulation as a solid material. This mixture is as readily susceptible of explosion through the initiative agency of a detonating fuze as nitro-gly- cerine itself, and though it obviously cannot he so powerful an explosive agent as that substance when successfully applied in its undiluted state, its destructive powers are still greatly in ex- cess of those of gunpowder. Dynamite is applicable to all the uses for which nitro-gly- cerine is employed. When properly applied it does nut need confinement for the development of its explosive forces, and it is especially applicable for military purposes. It is by far the best of the nitro-glycerine mixtures, and is probably the best form for its use in torpedoes. Certain defects are inherent in the material, such as its los- ing its susceptibility to detonation by the ordinary means at a low temperature,* and the tendency of the nitro-glycerine to partial separation from the silicious earth during transport and storage ; hut in balancing its advantages against those of other explosive agents, the special defects of these have also to he taken into account, so that, provided the uniform stability of the material becomes established, and the apprehensions as to its comparatively dangerous character, to which certain accidents have given rise, are allayed by further experience in its storage and use, and, possibly, by improvements in its manufacture, a high position may be assigned to dynamite among the most use- ful explosive agents of the present time. It is the best of all the nitro-glyceilne preparations. 1398. Lithofracteue. — Several other methods of applying nitro-glycerine as a destructive agent have been brought for- ward. Among these is the substance to which the inventor has given the name, lithofracteiir, and which contains, in addition to nitro-glycerine and an absorbing medium of the description used in dynamite, some proportion of other explosive materials, such, for example, as the constituents of gunpowder. This sub- stance is of a plastic and almost pasty nature, and is employed in the form of rolls made up in paper. Lithofracteur may be considered a dynamite to which has been added about twenty per cent, of bad gunpowder contain- ing an enormous excess of carbon. The addition of the con- stituents of gunpowder lowers its tiring-point, which is of * If finely divided, it may be exploded when frozen ; but this fact is practi- cally of Uttle value. EXPLOSIVE COMPOUNDS. 519 doubtful advantage and makes it more liable to be injured by moisture. Its force must be less than dynamite, for it depends on the amount of nitro-glycerine in it ; no additional force be- ing derived from the other ingredients. 1399. Dualixe. — Sawdust and similar absorbent materials have also been used as vehicles for the application of nitro-gly- cerine, under the name of dualine. This mixture also contains about twenty per cent, of saltpe- tre. It, however, owes its explosive qualities to the uitro-glyce- rine, and the only thing in its favor is that it is not liquid. In other respects there are serious objections to it. The slight ab- sorbent power of the sawdust makes the amount of nitro-glyce- rine taken up comparatively small, while holding feebly what is absorbed. The mixture of nitre and wood makes dualine more sensitive to flame or blows, and lowers the tiring-point. It contains less nitro-glycerine tlian dynamite, and hence is weaker. It is much lighter than dynamite, and for equal vol- umes has much less force. It has an excess of carbon from the wood, so that great amounts of that deleterious gas, carbonic-ox- ide, are formed, diminishing the force of the reaction. 1400. FULMINATES. — Fulminate is the general name for a class of explosive bodies which are compounds of fulminic acid with a base. They are all more or less explosive by the action of heat or friction ; of these the fulminates of mercury and silver are the most important. 1401. Fulmixate of Mekcuey is prepared by dissolving one part of the mercury in twelve of nitric acid, sp. gr. 1.42, aided by a gentle heat. As' soon as the mercury is dissolved add eleven parts of alcohol sp. gr. 0.87. A brisk action will ensue and the solution will become turbid from the separation of crystals of the fulminate. Dense, white clouds are also evolved at the same time. When the action has subsided the vessel may be filled with water and the fulminate allowed to settle, after which it is collected on a filter, washed, and dried by exposure to the air. When dry, it must be handled cau- tiously, as it explodes by friction or percussion, especially when in^contact with particles of sand or glass. It is also exploded by heating to about 300°, by the electric spark and by contact with concentrated nitric acid or sulphuric acid. When wet it will not explode. Its explosive force is not much greater than that of gunpowder, but it is much more sud- den in its action. The readiness with which it is fired makes it an excellent agent for exploding other substances, and this gives it its value. It is used in percussion-caps, primers, and fuzes — not pure, but 520 NAVAL OEDNANCE AND GUNNEET, mixed with nitre, mealed-powder, and other substances, because it is necessary to moderate its explosive property, since it is otherwise too rapid and violent for the purpose. It is some- times mixed with chlorate or nitrate of potash, and ground glass is often added to increase the sensibility of the mixture to explosion by percussion. 1402. Fulminate of Silver is prepared by a process simi- lar to that for fulminate of mercury, but as its explosive quali- ties are far more violent it is advisable to prepare it only in minute quantities. When dry, it must be handled with the greatest caution. Notliing harder than paper should be used in manipulating it, or for Avrappers. It is exploded in the same way as fulminate of mercury, but is of no practical value on account of its sensitiveness. 1403. Picric Acid and Picrates. — Picric Powder. — Picric, or tri-nitrophenic acid, is another nitro-substitution compound. It is formed by the action of nitric acid upon phenol, or phenylic alcohol, better known as carbolic acid. It is used as a dye-stuff. It has but feeble explosive properties, yet many of its salts are highly explosive. Potassium picrate is so verj" sensitive to friction or percus- sion as to be practically useless. Abel’s picric-powder is a mixture of ammonium picrate with saltpetre. It is very little affected by blows or friction, possesses considerably more explosive force than gunpowder, and can he worked in a moist state like ordinary powder. It is said to be useful for torpedoes. CHAPTER IX. PTEOTECHNT. Section 1. — Materials.'^ 1404. Definition. — Pyrotecliny is the art of preparing ammunition and fireworks for military and ornamental jnir- poses. Buildings. — To conduct the operations of tlie laboratory witb safety and convenience, tbe following rooms are necessary, viz. ; 1st. Furnace-room, for operations requiring tbe use of fire. 2d. Cartridge-room , for making all kinds of cartridges. 3d. Filling-room, for filling cartridges wdtb powder. 4tb. Con^ositiomroom, for mixing compositions. 5tb. Driving-room, for driving rockets, fuzes, etc. 6tb. PacTiing-^'oom, for putting up articles for transporta- tion. 7tb. Carpenter' s and Tinner' s-shop. 8tb. Magazine, for storing powder and ammunition. A laboratoiy, like a powder-mill, should be situated apart from inhabited buildings ; and for convem'ence of communica- tion, the rooms, with the exception of the furnace-room, carpen- ter’ s-shop, and magazine, should be situated under one roof. 1405. Furnaces. — A furnace is composed of a cast-iron ket- tle 2 feet in diameter set in a fireplace of brick. In the field, sods may replace the brick, if the latter cannot be obtained. Two kinds of furnaces are employed in a laboratory ; in tbe first, the fiaine circulates around both bottom and sides of the kettle ; in the second, it only comes in contact with the bottom ; the latter is used for compositions, in which gunpowder forms a part. 1406. Precautions. — To prevent accidents in the operations of a laboratory, avoid as much as possible the use of iron in the construction of the buildings, fixtures, etc. ; sink the heads of iron-nails, if used, and cover them with putty ; cover the floor with oil-cloth or carpets, and have it frequently swept. Let the Benton's Ordnance and Gunnery. 522 NAVAL ORDNANCE AND GUNNERY. workmen in the powder-room wear socks, and take them off when they go out. Keep no more than the requisite amount of powder in the laboratory, and have the ammunition and finished work taken to the magazine. Let powder-barrels be carried in hand-barrows made with leather, or with slings of rope or canvas, and the ammiinition in boxes. Let everything that is to be moved be lifted, not dragged or rolled on the floor. Never drive rockets, port-flres, etc., in a room where there is any powder or composition except that used at the time. Never enter the laboratory at night, xmless it is indispensable, and then use a close lantern, or wax or oil light well trimmed. Allow no tobacco to be smokod, nor friction-matches to be car- ried in or around the laboratory. 1407. Mateeials.— -Laboratory materials may be divided in- to four classes, viz. : 1st. Those for producing light, heat, and explosion. 2d. Those for coloring flames and producing bnlliant sparks. 3d. Those used in preparing compositions. 4th. Those used in making cartridge bags, cases, etc. 1408. 1st Class. — Nitre .- — For laboratory use, nitre must be reduced to a tine powder or very minute crystals. It is best pulverized in rolling-barrels at the powder-mills, but it may be pulverized by hand, in the laboratory, with a rolling-barrel, or by pounding in a brass mortar, or by stirring a crystallizing so- lution. 1409. Chlorate of Potassa . — Chlorate of potassa is formed by passing a current of chlorine, in excess, through lime-water, and then treating the mixture with the chloride of potassium, or by the carbonate or sulphate of potassa. The chlorate of potassa and chloride of calcium are formed ; the former crystallizes, the latter remains in solution. It is soluble in water, but not sensibly so in alcohol. As before stated, it is a more powerful oxydizing agent than nitre ; and when mixed with a combusti- ble body, easily explodes by shock or friction. It is inflamed by simple contact with sulphuiic acid, and thus affords a simple means of exploding mines. A convenient form of apparatus for this purpose is a glass vmssel with two compartments; one containing sulphuric acid, and the other chlorate of potassa and gunpowder. It is placed near the surface of the ground, and when broken under the feet of the enemy, the two substances are brought in contact, pro- ducing fire, which explodes the mine. 1410. Charcoal . — For laboratory use, charcoal may he made by charring wood in an iron kettle buried in the ground. It may be pulverized by rolling in a barrel with bronze balls, or PRYOTECHNY. 523 by beating in a leatber bag with a maul. It slionbl be kept in close barrels in a dry place. nil. Sulphur. — When melted sulphur is to be used, care must be taken that it does not become thick, which occurs at about 400°, It may be pulverized in a rolling-barrel, or by be- ing pounded in a mortar and sifted. Eoll brimstone is better for melting than flowers of sulphur. When flowers of sulphur are to be mixed wdth chlorate of potassa, it should be washed to remove the free sulphui'ie acid. Sulphur hastens the com- bustion of compositions to which it is added. 1412. Antimony — Antimony, or regulus of antimony, is a grayish-white metal, easily reduced to a powder, and by its com- bustion with sulphur produces strong light and heat ; the color of the flame is a faint blue. 1413. Sulphuret of Antimony. — Sulphuret of antimony is mixed with inflammable substances to render them more easily ignited by flame or friction. 1414. Gunpowder. — For compositions, gunpowder is pulver- ized, or mealed, by the rolling-barrel, or by grinding with a muller on a mealing-table, or by beating in a leather bag. The simple incorporation of the ingredients of gunpowder does not answer the desired purpose. 1415. Lampblack. — Lampblack is the result of the incom- plete combustion of resinous substances. It is composed of about 80 parts of carbon and 20 of impurities. It is employed to quicken the combustion of certain mixtures ; but before it is used, it should be washed with a strong alkaline solution, to re- move all traces of empyreumatic oil. 1416. 2d Class. — Coloring Materials. — Aflame is colored by introducing into the composition which produces it a sub- stance the particles of wdiich, on being interspersed through the flame, and heated to the incandescent state, give it the recpdred color. Coloring substances do not generally take part in the combustion, and their presence more or less retards it ; it is for this reason that chlorate of potassa, a more pow’erful oxydizing agent than nitre, is used in lieu of it, in compositions for colored fires. 1417. Colors. — There are a great variety of substances which give color to flames, the principal of which axe nitrate and sul- phate of strontium, and chloride of strontium, for red ; the ni- trate of barium, for green ; the bicarbonate of soda, for yellow ; the sidphate, carbonate, and acetate of copper, for blue Lamp- black is employed to give a train of rose-colored fire in the air; powdered flint-glass, for white flames ; and oxide of zinc, for blue flames. 524 NAVAL ORDNANCE AND GUNNERY. 1418. Sj)arhs. — ■Briniant sparks are produced by introducing into the composition filings or thin chips of either wrought-iron, cast-iron, steel, or copper, or by fragments of charcoal; the effect depends upon the si/e of the particles introduced. The j)articles should be freshly prepared, or shoidd have been -we]! preserved from rust. 1419. 3d Class. Peepauing CoMPOsmojrs. — Turpentine is the substance which exudes from the freshly cut surface of a pine- tree in warm weather. The first year’s running is called virgin, or white, turpentine : after this it becomes more hard and yellow. 1420. Spirits oj Turpentine. — This is the essential oil ob- tained by distilling native turpentine. 1421. liosin. — This substance is sometimes called colo- phony., and is the residiuum of the distillation of tui-pentine. 1422. Tar. — Tar is a semi-fluid substance, obtained from the heart of the pine-tree by a smothered combustion, as in charcoal -pits. 1423. Pitch. — Pitch is obtained by boiling down tar to the requisite consistency, either by itself or combined with a por- tion of rosin ; it becomes solid on cooling, but is softened by the heat of the hand. 1424. Venice Pcrpentine. — Yenice tui’pentine is obtained from the larch ; but what is commonly known by that n.nne is a compound of melted rosin and spirits of turpentine. The fore- going substances are chiefly employed in the preparation of compositions for producing light. 1425. Alcohol, etc. — Alcohol (spirits of wine), hrandy, whtis- Tcey, or vinegar, is used for mixing compositions in which nitre enters, because this salt is but slightly soluble in these liquids. 1426. Gum-Arabic.— -Gmxi-^LYSLhic. in solution is employed to give body to certain compositions. It retards combustion ; and as the solution is liable to spontaneous decomposition, it should only be prepared as wanted. 1427. Beeswax and 2£utton-taIlow are employed chiefly in mixing compositions intended to produce heat and light. 1428. 4tii Class. — Pkepaelxg Caeteddges, etc. — The mate- rial of which cartridge-bags are made is woven expressly for the purpose. The color is white, and the calibre of the gun and the weight of the charge must be stencilled on the bag in figures two and a half inches long. AYhen procured of necessity else- where, the stutf should be chosen of wool entirely free from any mixture of thread or cotton, and of sufficiently close texture to prevent the finer powder from sifting through. 'Wild-hoar, satinet, merino, and bombazette are named as proper materials for cartridge-bags ; of these the thinnest stuff, not twilled, hut PYEOTECHIfY, 525 having the requisite strength and closeness of texture, is the best. Fabrics of cotton and flax are not used, because the powder sifts through them, and they are more apt to leave fire in the gun than Avoollen stuffs. 1429. Compositions. — The term composition is applied to all mechanical mixtures which by combustion produce the effects sought to be attained in pyrotechny. If these composi- tions be examined, it will be found that many of them are de- rived from gunpowder, by an admixture of sulphur and nitre, in proportions to suit the required end. 1430. Preparation . — Compositions are prepared in a dry or liquid form ; in either case it is necessary that the ingredients should be pure and thoroughly mixed. 1431. Yor dry compositions, the ingredients are pulverized separately, on a mcaliny-tcible, with a wooden midler y they are then weighed and mixed with the hands, and afterwards passed three times through a wire sieve of a certain fineness. lYhen a highly oxydizing substance, as the chlorate of potassa, is present, great care must be observed in mixing to a^mid friction or blows which might lead to an explosion. When coarse char- coal or metals in grains are used, they should be added after the other ingredients have been mixed and sifted. 1432. For the liquid form . — When it becomes necessary to use fire to melt the ingredients, the greatest precaution is nec- essary to prevent accident, especially when gunpoivder enters. The dry parts of the composition may be generally mixed to- gether first, and put by degrees into the kettle, when the other ingredients are fluid, stirring well all the time. When the dry ingredients are very inflammable, the kettle must not only be taken from the fire, but the bottom must be dipped in water, to prevent the possibility of accidents. 1433. Foem. — To give a portable form to compositions, they are inclosed in eases, cast in moulds, or attached to cotton- yarn, rope, etc. 1434. Cases. — Cases are generally paper tubes, made by covering one side of a sheet of o paper with paste, or gum-arabic, wrapping it around informer, and rolling it under a flat surface until all the layers adhere to each other. The quality of the paper and the thickness of the sides of the case should depend upon the pressure of the gases evolved in the burning. (Fig. 314) 1435. Filling . — To fiU a case, it is first cut to the proper Fig. 314. 526 NAVAL OEDNANCE AND GUNNEET. length and placed in a mould ; the composition is then poured in, a ladleful at a time, and each ladleful is packed bj striking a certain number of blows on a drift with a mallet of a given weight. The height of each ladleful of composition should he about ecpial to a single diameter of the bore of the case. 1436. Drifts^ etc . — Small drifts receiving heavy blows should he made of steel, and tipped Avith bronze (Tig. 315); large di-ifts may be made of wood or bronze, depending on the force of the blow. In driving highly inflammable compositions, as that of the rocket, care should be taken to settle the drift so as to exclude the air before striking with the mallet, as the heat gen- erated by the sudden condensation of air might be euftieient to ignite the composition. Preliminary tests of all new materials should he made by burning one or more specimens of the composition, and the proportions of the ingredients corrected, if necessary. 1437. Yent . — The length of the flame from a given compo- sition depends on the size of the vent and the extent of the burning-surface. The vent is made small b}' chohing the end of the case with stout twine ; and the bmaiing-surface is in- creased by driving the composition around a spindle which, on being withdrawn, leaves a conical-shaped cavity. A vent may be also formed by driving in moist plaster of Paris or clay, and boring a hole in it with a gimlet. If the end of the case is to he closed up entirely, the boring is omitted. Fig. 315. Section II.— Means of Finng Cannon. 1438. Pkimeks. — One of the most important subjects to he considered in connection with the efficiency of the ship's battery, is that of providing a simple and efficient means of discharging the guns instantaneously and with certainty ; to this end num- erous contrivances and inventions have been suggested and tried. Percussion and friction primers are now used in the ser- vice, although elective primers, tubes, port-tire, and slow-match are manufactured, and may be used in special cases. 1439. Pekcussiox-puimees. — The percussion-primer has a Avafer or flat-head attached to a quill-harrel. The process usu- ally observed in selecting the material and manufacturing the primers is as follows : PEIMERS. 527 Each quill must be clarified and furnish a barrel at least two and a half inches long. The barrel is to be round, free from flaws, pith, and brittleness occasioned by clarifying, or any other defect which may render it unfit for the purpose required. (Flatness of the quill-barrel will subject it to be rejected at the discretion of the Inspecting Officer.) It must not exceed in diameter nineteon-hundreths of an inch at any part, nor be less than seventeen-hundreths of an inch, within one and one-half inches of the end that is cut from the quill. The small end must not be broken or bruised. 1440. Fabrication . — Cut the barrels of the quills close from the feather, aud insert them into the socket of a wooden block made two inches deep and two tenths of an inch in diameter. A punch, having ten cutters radiating from the stem, is entered into each quill- barrel, and driven down with a smart tap, so as to slit the upper end of the barrel into ten prongs, and as far as the upper surface of the block permits. (Fig. 316.) Turn back the prongs, so that they will lie on the surface of the block ; a circular punch is applied to each, and made by a blow to cut off the prongs to its own diameter (0.52 inch). 1441. Yery stout paper, previously pre- pared by tw’o coats of shellac varnish (gum- lac dissolved in alcohol), is punched witli holes 0.17 inch in diameter, and so ar- ranged as to correspond with the sockets of the wooden block. The quill-lDarrels are freed from pith, the punched paper laid on the block, the holes corresponding and the varnished side up, the quill-barrels put Fig. 316. through the paper into the sockets of the block, filled with grained powder, seven grains Troy, and pressed firmly down with their prongs fiat on the varnished side of the sheet of stout paper. 1442. Brush the shellac-varnish over the spaces of paper be- tween the heads of the quill-barrels, and spread a sheet of good writing-paper, slightly moistened with water, over the entire surface of the stout sheet and the prongs of the quills. Put the block and the sheets thus stuck together, with the quill prongs between them, into a pi-ess, apply a foi’ce of about thirty tons, and keep them long enough to set the prongs and make the sheets of paper adhere firmly. 528 NAVAL ORDNANCE AND GUNNERY. 1443. Each quill is separated from tlie card bj means of a circular punch, which cuts out a disk 0.62 inch in diameter, and of course includes the prongs enclosed between them. A stellated disk to C'over the head of the primer is punched out of linen-made paper of the finest and closest fabric. This disk has twelve points — diameter from exterior points, 1.25 inches, from interior 0.700 inch. Metal plates are at hand with superficial recesses about 0.65 inches in diameter. On each of these a stellated cover is placed, and four grains of fulminate deposited on it. This is composed of five parts of fulminating mercury and one of mealed-powder, both dry. Place the head of the primer on the charge of fulminate, holding it by the quill-harrel and pressing it down firmly ; brash good wLeat paste on the points of the cover and on the interior surface of the head, turn the points over, and unite them neatly and closely on the paper head. 1444. The primer is now made and only requires to he pro- tected from moisture. Eor this purpose, shellac is dissolved in alcohol, so as to he thin enough to he laid on with a brash. This is of a brownish yelloAv ; a portion is pre- pared with lamp-black. Coat over the quill-barrel with shellac, then the under side of the wafer with the black shellac-varnish. Then shellac the upper surface of the wafer. Tip the end of the quill-harrel with black varnish, and apply a second coat of uncolored shellac thickly about the primer. (Fig. 317.) 1445. The primers, being put in tin boxes made to hold fifty of them, are ready for inspection. After which the lids are coated with shellac to ex- clude moisture, until wanted for immediate use. These boxes are intended to fit in and form a lin- ing to the primer-boxes which slip on the waist- belts worn by the Gun Captains. 1446. When primers have been returned from cruising ships, or have remained in store for one or more years, they must he tested by firing five per cent, of the number, and not issued again without special orders. The date of manufacture or re-inspection, with the initials of inspecting officer, are to he legibly written and pasted Avithin the cover of the laboratory cases, and, when issued for service, the date and station to which sent is to he added. 1447 FniCTiON-PiirMEKS. — The friction-primer for cannon is a small brass tube 1-J inches in length, and 0.19 inch in diam- Fig. 317. PRniERS. 529 eter, filled with fine-grained powder, wliicli is ignited by di-aw- ing a roiigb wire briskly tbrongb friction composition contained ill a smaller tube inserted into tbe first near the top, and soldered at right-angles to it. Tbe short tube is 0.44 inch long, and 0.15 inch in diam- eter. The wire is 3.4 inches long, of brass, annealed, the end in the small tube flattened, and fitted with dentated edges, a ; while the other end is doubled on itself and twisted, leaving a loop 0.2 inch in diameter, and then bent alongside the long tube for packing. (Fig- 318.) 1448. Friction Comjyosition . — This is made of two parts of the sulphiiret of antimony and one part of the chlorate of potassa moistened with gummed water, 50 grains of gum-arabic in two ounces of water to one pound of composition. The materials are first pulverized separately, mixed together dry, moistened with gum-water, and ground in an iron mill such as is used for I’imers are packed in tin boxes in the same manner as percussion-primers. Fra. 318. 1449. In case either lock or percussion-primer should entirely fail, recourse will be had to the friction-primer. In using them, the Gun Captain, after taking the primer from the box, will raise the twisted wire loop until it is on a line with the spur ; place the tube in the vent with the spur towards the muzzle of the gun, then hook the lanyard into the raised loop, and pull it, when otherwise ready to fire ' the gun, as though it were a lock-string, using, however, a less degree of force. The lanyard may be hooked to the loop before the tube is put into the vent. 1450. Stobage of Pelsiees. — Percussion and friction prim- ers and all other articles containing fulminating matter are kept in boxes prej>ared for the purpose, and the boxes are stored, separately fi-om other articles, in a dry, secure, and safe place, under lock and key, and are on no account to be put in the maga- zines — being distributed in two or thi'ee places, and a portion kept constantly at hand. 1451. Allowance of Peimees. — The allowance of percus- sion-primers to ships fitting for sea is three hundred for each one hundred rounds, and fifty per cent, additional for practice- in pulhng the lock-string. 84 grinding pai Friction- 630 NAVAL ORDNANCE AND GUNNERY. The allowance of friction-primers is fifty to each gnn on hoard ship. 1452. Spue-tubes. — These are quill priming-tubes (Fig. 319) filled with inflammable composition, and ignited by applying the match. The body of the tube is fill ed with a composition of mealed-pow- der moistened with camphorated alcohol until a thick paste is formed ; the composition is introduced into the qnill by pressing its lower end into the paste, thus taking up a portion of it, and repeating the operation xmtil the quill is filled. A small wire is then run through the axis of the tube, and allowed to remain there until the paste is dry ; when it is withdrawn, leaving the composition perforated throughout its entire length. Tlie object of piercing the composition is to ex- pose more surface to the action of the flame ; the ignition of the whole contents of the quill is thus rendered instantaneous. 1453. The head of the tube, or is formed by insert- ing a strand of quick-match, about an inch long, into the com- position, through a hole near the head of the quill. This is protected by a small tube of stiff paper lashed at right angles to the quill. The end of the quick -match is covered with a paper cap. The whole is shellaced over to protect it from moisture. Spur-tubes are packed in tin boxes in the same manner as percussion-primers. When spur-tubes are used the Gun Captain exposes the priming, and the 2d Captain applies the match. 1454. Slow-match is used to preserve fire. It may be made of hemp, flax, or cotton rope. The rope is saturated with the acetate of lead or the lye of wood ashes ; if it is made of cotton it is only necessary that the strand be well twisted. It burus from four to five inches in an hour, forming a hard-pointed coal, which readily communicates fire to any inflammable ma- terial with Avhich it comes in contact. For the Navy, loosely laid, one-inch flax-rope is used. . It is placed in a solution of one pound of acetate of lead to five gal- Fig. 319. PEIMERS. 531 Ions of water, for twenty-foiir hours'; then taken ont, rove through blocks and well stretched. It is left on a stretch for eight or ten hours, and rubbed down smooth with rags ; when it is cut in lengths of about two fathoms each, and packed in boxes ready for issue. For service a piece of this rope two or three feet long is wound around a match-staffs having a slit in one end and a point of iron on the other, which can be stuck in a match-tub. 1155. Quick-match is used to communicate fire. It is made of cotton-yarn (lamp-wick) saturated in alcohol and then put into a composition formed of mealed-powder and gummed spirits ; after saturation the yarn is Avound on a reel or hung up until perfectly dry. The burning of quick-match is A'ery irregular, varying Avith the condition of the match and the quantity of powder over its surface. One yard in thirteen seconds is about the mean rate of burning of new match Avhen not confined. The rate of burning may be much increased or rendered almost instantane- ous by enclosing it in a tube of any description. The ignition of any combustible AAdiich it is not safe to ap- proach may be readily effected by enclosing quick-match in a paper case or leader of the required length. 115G. PoRT-FiEE. — Fort-fire is a cylindrical paper case con- taining a composition which burns with an intense flame. It is used for firing guns in the absence of other means, and also em- ployed, as its name implies, to carry jire Avhenever required. In order to stop the combustion in a port-fire it is best to cut it off as near as possible to the flame. Port-fire is used for life- Ijiioy lights, because of its ability to resist Avater. The poAver of a burning composition to resist the penetration of Avater to the mass is in direct proportion to the A'olume of gas evoh'ed and to the rapidity of its escape, and consequently to the rapidity with AA'hich it burns. Port-fire cut up into small pieces and placed in a shell forms a very good incendiary material. 1157. In an emergency Avheu port-fire cannot be procured, a substitute may be made by impi-egnating paper with a solu- tion of 12 oz. of saltpetre to 1 gallon of Avater. When dried, the paper is rolled up into a solid cylinder about the size of the ordinary port-fire. It burns sloAvly, or rather smoulders. The finished port-fires are 18 inches long and ^ inch in diameter. The composition is composed of : nitre, 4 lbs. ; sulphur, 1 lb. 10 oz. ; mealed-poAA'der, 12 oz. ; and burns at the rate of about one inch in a minute. The bottom of the case is filled Avith clay and the top Avith 532 KAVAL OEDNAXCE AND GTJXXERY. inealed-powder. Tlie case is painted black and the top tipped with red, to show wliicli end to light. When dry, the port-fires are packed in laboratoiw boxes, 50 or 100 in a box. 1158. FinrxG Cannon by ELBCTEicrrr. — Many methods have been proposed with this object in view. Such, for example, as if in the percussion-primer (Art. 1139) there was substituted for the fiat-head an arrangement for electrical ignition con- structed in the manner descilbed under the head of Electric Fuzes (Art. 1509). Several contrivances on this principle have been brought forward, but experiment has not decided upon the best. A satisfactory mode of discharging cannon by electricity would be very serviceable in simultaneous and concentrated firing. Firing salutes by electricity may be veiy simply and easily performeJ by placing an electric fuze in each cartridge and leading the wires out of the muzzle of the gun to their a}> propriate connections. 1159. Electric Prijier. — The electric primer chiefly used consists of a cpfill tube filled with fine-grained powder or pierced composition, to the top of which is secured a small hard-wooil plug, in which is placed a small quantity of priming composi- tion, and the copper wires so arranged as to ignite the compo- sition upon the passage of the electrical current, by which means the jiowder in the tube is fired. The head of the primer is arranged with pi’oper connections for attaching the ends of the circuit-wires leading from the bat- tery or electrical machine. Tliese primers are useful in firing time-guns, and also those subject to extreme proof. Section III. — Fuzes. 1160 . Fezes are the means used to ignite the bursting- charges of hollow projectiles at any desired moment of their flight. There are a great many varieties of fuzes. They may be classed according to their mode of operation, percussion, con- cussion, and time fuzes. 1161. The Time-fuze consists of a column of inflammable composition which, being ignited by the charge in the gun. burns for a certain space of time, at the end of which it com- municates its flame to the bursting-charge in the shell. In the Navy, all spherical shells except those for howitzers and for shrapnel are fitted with the Navy Time-fuze. FUZES. 533 1462. Bequirements. — The conditions required to consti- tute a good time-fuze are, that it should ignite with certainty ; that it should burn regularly, and that when ignited it should not be liable to extinction. Time-fuzes haye the adyantage of being independent of the object, and of furnishing a core of dispersion whose aj)ex is aboye the target. But they are entirely dependent upon the exactness of their adjustment, and eyen when properly adjusted they somethnes giye premature or tardy explosions without assigned reasons ; be- sides, they atford no means of estimating at sight the distance at which the pro- jectiles hurst, and consequently no cri- terion for correcting them, which is a great disadyantage. 1463. The Jfxyy Time-fcze (Fig. 320). — This fuze is composed of a composition driyen in paper case and then inserted in a mBcil stocTc, which screws into the fuze-hole ; so that one end of the composition lies eyen Avith the exterior smdace of the shell, and is exposed to the flame of the charge in the gun, the other end being Avithin, amidst the charge of the shell. The composition is coyered with a safety- cap, Avhich protects it from moistime and accidental ignition ; also with a xoater- cap of peculiar construction, intended to protect the flame from being extin- guished on ricochet. 1404. A Safety-plug at the loAxer exti’emity preA'ents the communication of Are to the jDowder in the shell, in the eyent of the accidental ignition of the fuze after being uncapped. 1405. Composition . — The ingredi- ents of all thu e-fuze compositions are the same as for gimpoAyder, but the proportions are A'aried to suit the re- quired rate of burning. Pure mealed- poAvder giAms the quickest composition, and the others are derived from it by the addition of nitre and sidphur in cer- tain quantities. The rate of Fig. 320. — Xavy Time- fuze. bm-ning of a fuze composition 534 NAVAL ORDNANCE AND GUNNERY. depends on tlie purity and tliorongh incorporation of the materials, and on its density. These qualities are best secured by procuring tbe materials from the powder-mills ready mixed and gi-anulated like powder, in which form it is not more liable to deteriorate than gunpow- der, and can be preserved for a long time without the possibility of alteration. The three compositions used are manufactured at Dupont's Powder-mills, and are known by the letters Z, JZ, and JV. These compositions have the appearance of ordinary un- glazed cannon-powder, but tlie proportions of tbe ingredients tliffer from those composing cannon-powder. By combining these compositions in different proportions and adding small quantities of mealed-powder, driving a few fuzes and burning them for trial, the several compositions for driving the various fuzes are found. 1466. The Paper Fuze-case . — The case into which composition is driven is made of strong white paper, which is cut into slips leaving one end square, the other tapered to a point (Fig. 321). These pieces of paper are placed on a smooth board and covered Avith a refined glue, used rather thin and kept warm in a suitable vessel. They are then rolled on a steel cylindrical former., beginning Avith the square end, the gradual diminu- tion of the other end of the paper producing the required taper on the exterior of the case. If one of these cases is cut in any part, the several layers of paper are not perceptible, but appear as if resolved into a perfectly firm and homogeneous material. The finished case (Fig. 323) is put in a gauge to see that it is of the proper dimensions and both of its ends cut off even with the faces of the gauge. 1467. The Safety-plugs are made of the softest lead wire. This wire is cut into short lengths and put through molds to bring them to the proper diameter. They are then put into the plug-making machine, which cuts and forms the lead wire into the proper shape and length for safety -plugs. 1468. Before the composition is driven into the case, the safety-plug, P (Fig. 322), is inserted with its cavity end in the smaller end of the paper case, and the solid portion of it pro- jecting beloAv the tapering end of the case. A steel punch with a conical-shaped end, being introduced into the case and enter- ing the cav^ity of the safety-plug, is struck a smart blow with a mallet, which forces the soft lead out, pressing it hard against the sides of the paper case. Fig. 321. FUZES. 535 1469. Tlie jar of concnssion consequent upon the explosion of the charge in the bore is so great as to detach the plug from Fig. 323. the case,, so that from the moment the shell leaves the gun the communication is open between the burning composition in the fuze and tlie bursting- charge in the shell, and as soon as the composi- tion is consumed the shell will explode. 1470. Fuze-driving Fig. 323. Machine .— is done bj a macliine. It is a screw-press requiring two persons to work it. The driving-shaft moves vertically through a metal tube on the exterior of which is a strong square thread. A nut works upon this by means of a large disk attached to it, of sufficient diameter to create the requisite power, and npon the upper side of this disk are established two levers, attached to the head of the shaft. By adjusting the weights upon the levers a bell is rung, when a pressure of 2,000 pounds is obtained with the screw. 536 NAVAL OKDNANCE AND GUNNEEY. 1471. The paper case is secured in a steel mold or socket, which is made to adjust so closely to the exterior of the case as to sustain it and also protect the safety-plug against the pressure applied in condensing the composition. Two or more of these molds are placed around the edge of the cu’cular plate carried upon the lower part of the frame, and revolving so as to bring the molds in turn to the shaft. 1472. Driving the Composition . — The composition, being first pulverized to a fine powder, is put into the case by a small scoop which holds eight or ten grains. Each charge is driven by a steel drift which fits snugly into the case, the workman moving aroxiud the lower plate so as to bring the didft under the driving-shaft of the machine, the positions being determined by a spring and catch wmrking into a notch in the edge of the plate. The disk is now given a cpiick whirl by means of the handles on its periphery, and the dri\dng-shaft descends on the drift ; the movement is sustained and the pressure increased until the sound of the bell indicates that the lever has risen and the action of the machine has ceased. 1473. The motion of the disk is now reversed and the shaft sufficiently raised to allow the woi’kman to revolve the lower plate and biiug in place another mold, which has meanwhile been charged. The operation proceeds until the column of condensed composition is rather larger than required. In this way the composition is solidified until its density is doubled and it becomes as hard as stone. The paper cases ai-e removed from the driving-mold and placed in another of the exact length required ; the projecting portion is then cut oif evenly wdth a sharp knife. 1474. The Water-caj) is made of copper, and is cylindrical in shape (C, Fig. 322). The upper end has a recess .10 inch deep, in which there are three holes, one going down to the centre of the cap and connecting with the side-holes ; the other two are made to hold a small piece of quick-match. There are two holes in the sides of the cap opposite to each other and connecting, but leading at different angles; and one hole lead- ing from the bottom of the cap to those through the sides. Thus the water-cap is perforated with a channel, Avhich is filled with mealed powder. This communicates fire to the composi- tion in the paper case, and the angles of the channel prevent the enti-ance of any matter, such as sand or water, over which the shell may ricochet. The recess on top lias two small pieces of quick-match, each secured in its own hole, and a small cpiantity of powder poured into the recess and pressed down, so that the outer surface is FUZES. 637 primed with mealed-powder and strands of qnick-match, which are ignited by the scorching flame that rushes ovmr the projec- tile at the tiring of the charge in the gun. 1475. The Safety-cap is a circular leaden patch with a lip or lug attached (S, Fig. 322), cut out of soft sheet-lead that is about .06 inch thick. It is punched out with a cutter of the proper shape and dimensions. This patch, with a thin piece of parchment of the same shape and size under it, is put on over the top of the water- cap and driven down into the recess in the head of the fuze- stock with a punch made for the purpose, having the length of the fuze in raised letters on the end, so as to leave this mark on the leaden j>atch. 1476. The Fuze-stoclx. is made of tough bronze, with a stout shoulder or flange at the outer end (F, Fig. 322). Its length over all is 2.44 inches. The filled paper case, or fuze proper, is placed in the metal stock, safety-plug-end first, and then pressed down until the end of the paper case is nearly even with the lower end of the stock, the safety-plug projecting below the stock. The water-cap is screwed in on top of the fuze and covered with the safety-patch. A circular label is pasted on over the patch showing the length of the fuze, the date of fab- rication, and tlie initials of the inspector. A little shellac is brushed around the safety-plug and lower end of fuze-stock ; also around the leaden patch and top of stock. A pasteboard cap is put on over the safety-plug-end of the fuze-stock to prevent the i)lug from being broken off, and the fuzes thus prepared are stowed in boxes. 1477. Time of Buknixg. — The Navy Tlme-fazes are of 3-|, 5, 7, 10, 15, and 20 seconds time of burning ; which times are supposed to offer a sufficient variety for most of the exigencies of the service, and a certain proportion of each are supplied to each ship. There are also supplied for special purposes paper-case fuzes of greater length, which when used are always to be in- serted in metal stocks. Gexeral Working-fuze. — All loaded spherical shell sup- plied are fitted with the five-seconds fuze, which is to be regarded as the general working-fuze. This fuze may be drawn and any of the others substituted. The XV-iiich shell are fitted with three fuzes, each 3^, 5, and 7 seconds. One-half of the shell allowed for rifled guns are fitted with time-fuzes, and the remainder with percussion-fuzes. 1478. To Shorten Fuzes. — For special firing any 'time- fuzes may be shortened. To do this, unscrew the water-cap 538 NAVAL ORDNANCE AND GUNNERY. and back the paper case out from the lower end with a diift and mallet, cut off from the lower end with a line saw, oi’ shai-p knife struck with a mallet, the proportional part recpiired, and insert the upper part in the stock, forcing it down with a few gentle blows with the drift ; screw in the water-cap. It is preferable, however, when circumstances will admit, to take up such distance as will correspond with the time of flight of one of the regulation lengths. In shortening the fuzes there is danger of disturbing the cohimn of composition. 1179. Testing Fuzes. — Fuzes are tested by securing them in some convenient place, lighting them, and noting the time of burning. In testing the ISTav}’- time-fuze, the safety -plug must be removed. Being intended for use under a water-cap, they burn a longer time in the open air. Under the water-cap the gases are so confined that the combustion is augmented. 1180. Time-fuzes foe Rifle-pkojectiles.- — Time-fuzes are very unreliable in rifle-guns in consequence of the flame being cut otf from the fuze ; with the Parrott shell, however, the Navy time-fuze is the most certain of ignition and regular in its time of burning. For rifle-projectiles, where the flame of the charge is entirely cut off from the fuze, the time-fuzes are fitted with a detonating arrangement at the top. This consists of a small hollow cylinder of metal, termed the detonator^ containing a small quantity of detonating composition, and having a flre-hole communicating with the fuze-composition. K 2 ?lunger \?> sus- pended in the detonator by means of a wire, and when the gim is fired the suspen ding-wire is broken, and the plunger coming in contact with the detonating composition e.xplodes it, thus firing the fuze-composition. 1181. Imperfection of Time-fuzes. — It is impossible that any species of fuze should be absolutely perfect. AVhen suita- ble opportunities for observation occur, it is noticed that in firing a number of shells many do not explode. The failure of the composition to ignite is probably generally due to the ab- sorption of moisture ; and therefore all fuzes taken from shell or returned from ships, which have been more than one year in service, are to be returned to the Laboratory in the Ordnance Yard at AVashington, where all fuzes are prepared. Fuzes of over two years’ date of manufacture are not to be issued for service. Sometimes the fuze is extinguished after having been ignited. This may occur Avhen the shell ricochets on soil or water'. AVater is not so detrimental as sand, and the fuze is rarely extinguished by several ricochets upon it. FUZES. 539 Generally tlie gases evolved by tlie combustion of the eom- j)osition will repel with great energj’ any obtrusive matter which would extinguish the fuze if once in contact with the ignited surface. 1482. Peematcre Explosion.— This may be caused by the increase of the ignited surface of the composition resulting from cracks in the case or composition itself, or by interstices between the case and com]3osition ; and in proportion to the extent of this cause so will be the increased celerity of the combustion. Crevices may occur in the composition from some defect in the tools or in the mode of using them, or they may be created by bending the case. It may also happen that the displacement of the shell by the charge of the gun will force in the column of composition or the case with it. This would of course cause the shell to explode ^•ery quickly. The shell may be defective in thickness or quality of metal, and be crushed by the force of the discharge, when the explo- sion will take place in or near the gun. The bursting of shell near the muzzle of the gun is some- times attributed to the detonating qualities of the powder in tlie shell. It is manifest that the premature explosion of shells is far more detrimental to their efficiency than the failure to explode at all. 1483. Commanders of vessels are required to observe care- fully the action and result of all fuzes, and report in detail to the Bureau of Ordnance whenever opportunities may occur, particidarly specifying the number and kind fired, elevation of gun, failure to explode, and satisfactory action ; also whether the fire was ricochet or direct. 1484. The question of a good fuze for all conditions of service is still to be determined. For ordinary firing with smooth-bore projectiles, the service time-fuze, as made for many years past, continues to give good results, but the greatly in- creased range and time of flight at present obtainable with heavy guns render it desirable to adopt a principle of shell- explosions independent of the time of flight and of the preser- vation in good order of a long column of composition. 1485. The Boemanh Fuze was invented by Captain Bor- mann of the Belgian army. The case is a metallic disk about 1.6 inches in diameter and half an inch thick (Fig. 324), made of lead, hardened suffi- ciently for the pui'pose by the infusion of some tin. It is cast without the thread by which it is to be screwed into the'fuze- hole, and this is afterwards cut in an ordinary slide-lathe. 540 NAVAL OKDNANCE AND GUNNEEY. The metallic fuze is screwed in flush with the shell, and well luted around the edge on the exterior surface. The composition is firmly con- densed into an interior canal, or horseshoe-shaped indentation, east in the disk around its periphery and as near to it as possible, open- ing below, a strand of quick-match being first placed in the bottom of the channel. The canal is closed, after the composition is driven, by a piece of the same metal, correspond- ing in shape (Fig. 325). the cross- section of it being wedge-shaped. This is pressed down upon the composition by a machine sealing it hermetically. 1486. The upper surface of the disk above the composition is very thin, so as to yield readily to the cutting-tool employed to open it, its whole external correspond- ing of course with the composition below. It is graduated into seconds and fourths of seconds. The end of the composition where the enu- meration begins communicates with a small magazine at the centre of the disk, which is charged with grained powder, and closed on the inner side with a very tliin disk of sheet-lead so as to yield in that direction to the explosion. A pin-liole is sometimes punched in this disk to insure the escape of the flame into the shell. 1487. The Operation of the Fuze occurs thus : The thin covering of metal above the composition is cut so as to lay bare the upper surface of the composition, and to afford the flame access to it at the part desired. The cut should be made with the' fuze-cutter close to the right of the mark in the index- plrfe ; and it is best made in two or three efforts instead of try- in^to effect the cut at once. Under lire, the Bormann fuze, though perfectly simple, is very liable not to be cut to the desired time ; it is often done incorrectly, and sometimes not at all. Fig 324. TOP VIEW Fig. 325. FUZES. 541 Shell fitted with this fuze should he placed in the gun with the cut of the fuze up, because in this position it is more cer- tain of being touched hj the flame of the charge as it rushes over the top of the shell. The combustion occu- pies the assigned time in passing from the incision towards the origin of the graduation, when it trav- erses the orifice leading into the magazine, the contents of which ex- plodes smartly towards the interior, and then encoun- ters instantly the charge in the shell. 1488. The metal of this fuze being soft and its diameter great, there is danger of its screw-thread being stripped, and its being driven in by the shock of firing, or of its being driven out on the ignition of the bursting-charge, thus afi^ording a means of escape for the gas evolved, without bursting the shell. To prevent the former, a broad shoulder, aa (Fig. 326), is left when the fuze-hole is tapped. To avmid the possibility of the lat- ter, and at the saane time to increase the effect of a small burst- ing-charge, the fuze-hole below the shoulder is closed by screwing in a composition disk, J, Avith a small hole in its centre through which the tire from the fuze is communicated to the charge. 1489. Advantages . — The peculiar excellence of this fuze consists in the driving of the Avhole mass of the composition by a single pressure, and its disposition in such wise that the com- bustion occurs not Avith the stratification of the mass, but trans- versely to it, while in the ordinary fuzes the solidification and the process of combustion are just the reA^erse ; that is, the column is composed of a number of la^’ers solidified succes- sively liy an equal pressure ; but as the inferior layers have, l)esides the pressure applied to them, to bear that of the super- incumbent layers, it folloAvs that the mass is not homogeneous, but increases in density with the inferior position of the layers. The Avhole error of fabrication, whatever it may be, in the JBorrnann fuze, is only experienced when the fuze is opened at its extreme duration. At all inferior times it is reduced proportionally. The regularity of this fuze burning is very great. The Bormann fuze is fitted to all shrapnel and howitzer ammunition. Fig. 326. 542 NAVAL ORDNANCE AND GUNNERY. 1490. Percussion and Concussion Fuzes. — A percussion or concussion fuze is one wliicli is independent of tlie element of time of fliglit, and wliicli depends wholly upon imjxict for its ultimate action. The distinction between percussion and concussion fuzes has been somewhat arbitrary, and the application of the terms has depended upon the sense in which the inventor of any par- ticular fuze chose to apply them. 1491. Concussion-fuze. — A concussion -fuze is one which is put in action by the discharge, but the effect of that action is restrained until it strikes the object. 1492. Requirements . — Such a fuze, in order to be service- able, must not only produce explosion on striking, but it must not produce it on the shock of the explosion of the gun-charge, nor of that produced by the ricochets of the projectile in or out of the gun. These fuzes have usually con- sisted of some combination of the highly explosive fulminates, but the extreme danger of using them lias been a great obsta- cle to their adoption. Thei’e is no fuze of this kind in use in the Navy. 1493. The Splingard Fuze is both a concussion and time fuze ; the appearance of the paper case is similar to that of the Navy time-fuze, but the internal arrange- ment is different. The case is filled with fuze-composition, and a long cavity is formed in the lower part of the composi- tion by driving it around a spindle as in a rocket ; this cavity is filled Avith moist plas- ter-of-Paris, and a long needle is inserted in it, nearly to the bottom of the plaster, form- ing a tube enclosed in and supported by the composition. (Fig. 327.) The composition is ignited in the usual way at the top. and as it burns away, leaves a portion of the plaster tube unsupported. 'When the shell strikes its object, the stock breaks off the unsupported ]iart of the tube, and the flame of the composition immedi- ately communicates with the bursting- charge ; if the tube does not break the com- position burns up, and the bursting-charge is ignited as in an ordinary time-fuze. 1494. The Bacon and McIntyre Fuze is A'ery similar to this, except that the internal tube is differently formed. In this fuze a thin copper tube, E (Fig. 32S), extends thi’ough Fro. 327. FUZES. 643 Fig. 328. — A, outside paper case. B, pow, der composition. C, inside paper case. D. coating of plaster of Paris. E, conical tube- F, baU on tube. the centre of tlu; fuze-composition, and lias a solid copper head, F, secured in its upper end by a little soft sol- der. The copper tube is enveloped with paper, C, and between the pa- per and the tube is a thin layer of plaster-of- Paris, D. The fuze being ig- nited by the flame from the gun, the upper part of the com- position burns away in the flrst second or two of time, melting the solder and leaving the head of the tube free to be displaced by the shock of impact. Under ordinary circumstances this fuze acts like the time- fuze, the stopper, F, being kept in place by the plaster-of- Paris ; but upon impact, the plaster breaks, the ball falls, and the flame passing through the tube at once ignites the bursting- charge. 1495. — Peecussion-fxjze. — A percussion-fuze is one which is prepared for action by the discharge, and put in action by the shock on striking the object. Like the concussion-fuzes, they have usually been dangerous from the fulminate employed, or from their complicated and delicate construction. The embarrassments that beset the efforts to realize an efticient percussion-shell of the ordinary spheri cal , form arise from the impossibility of having the projectile present a given point to the impact, and no reliable fuze of this nature has yet been arranged for spherical shells. In elongated rifle-projectiles this is more easily accomplished, and there are on trial for the rifled-cannon the percussion-fuzes of Schenkle, Parrott, and others. Perhaps the case most completely illustrating the advan- tages that may accompany the use of percussion-fuzes is that of vessels firing shell at short and frequently changing ranges. 1496. Requirements . — The essential requirements of a good percussion-fuze are : that it should not be ignited by the shock of discharge or on striking water ; that it shall be ignited on the impact of the shell against the object, and that it may not be liable to explode by handling or during transport. The percussion-fuze has many points in its favor : it assures the bursting of the projectile ; it can be used for all ranges, be they never so great ; it admits — a very important desideratum in war — of estimating distances, and of correcting the error of the estimation ; it augments the result of firing by adding great 544 NAVAL ORDNANCE AND GUNNERY. moral to pliysical effect, due to the explosion of tlie projectile in the midst of the enemy. Its only inconvenience is its inability to cause the hurstin*; of the projectile before it has touched the object, thus render- ing the effects of fire dependent upon the nature and confor- mation of the target at the point of impact. 1497. SciiEXKLE-FTTze. — One of the simplest forms of this kind of fuze is the Schenkle percussion-fuze, vrhich has been found very reliable, and is now the only one issued in the l^avy. It is a metal fuze-stock (Fig. 329), enclosing a movable core-piece, or steel plunger, bearing a musket-cap. The plunger, primed and capped, is confined inside the stock, in which it fits loosely, by a screw or pin, which passes through a hole in the side of the stock and plunger, to prevent it from moving. A safety-cap is screwed into the top of the fuze- stock, and its bottom is closed by a cork or leather stopper. 1498. When the projectile is set in motion, the plunger by its inertia carries away the pin which confines it, and pi-esses against the bottom of the fuze-stock. When its motion is arrested, the inertia of the plunger causes the percussion- cap to impinge against the safety-cap, which ignites the priming, Avhen the stopper in the bottom of the fuze-stock is blown out and the shell exjfioded. 1499. As a precaution against danger while handling, the brass safety-cap is countersunk on one end and fiat on the other. It is kept with the countersunk end down at all times except when loading ; Avhile this end is down, should the plunger become loose, the percussion cap is prevented from coming in contact with the hard surface of the safety cap, but on being turned end for end a plane surface is opposed to the percussion cap, upon Avhich it may strike. There is a slit cut in the top of the fuze-stock and cap which is designed for the entrance of the fuze- wrench. These fuzes are made of two sizes, the smaller size being fitted to 20 and 12 pdr. rifle-shell, while the larger ones are used for the heavier shell. 1500. Paeeott Pekcussion-fttze. — This consists of a metal fuze-stock, A B (Fig. 330), enclosing a plunger, P ; but the ar- FUZES. 645 rangement is different from tlie Selienkle. In the Par- rott fuze the plunger closes the bottom of the stock, and is prevented from slij^ping through by a shoulder, c d, on the plunger, taking against a projection on the interior of the stock. The plunger is surmounted by a long nipple, H, armed vith a per- cussion-cap, which strikes against a safety-cap, S, screwed into the top of the fuze-stock. The ring, R, being placed over the plunger, its lugs, xx, take against the lip, R, and in this position the cap of the fuze-stock screws close down on the ring, holding the shoulder of the plunger at cd firmly against the projectile on the inside of the stock. The plunger, capped and primed, is held firm until the projectile strikes the object, when its inertia carries away the lugs, x x, and the plunger impinges against the safety -cap, producing the explosion. 1501. Geema:x PEECussiOjsr-FrzE (Tig. 331). — In this fuze the plunger, a h, having a central fire-hole, is let into the fuze- hole and rests against the shoulders, c c. This plunger is sur- mounted by a perforated cap, having a terminating point on the top side. The plunger is retained in its place by a pin, E, which passes tranversely into the fuze-hole, the side of which is put in con- tact with the point of the cap. The outer end of the pin projects on the side of the shell, the projection being limited by the line of the cylindrical por- tion. The fuze-hole is closed by a screw-cap, f f, having a small central screw-hole into which the fulminate-cap, g, is screwed. When fired from a rifle-piece, the centrifugal force generated by the revolution of the shell throws out the pin, E ; the plunger by its inertia is retained at the bottom of the chamber during the flight of the projectile ; at the moment of impact the plunger impinges against the fulminate, which, exploding, ignites the charge in the shell. 35 Fig. 330. — Parrott Percussion-fuze. 546 NAVAL ORDNANCE AND GUNNERY. 1502. This is one of the simplest, and, at tlie same time, most safe and reliable percussion-fuzes jet invented. The fuh minate-cap, g, and pin, E, are not applied to the shell until the instant of loading, when the loader, who carries these articles in a pouch, screws in a fulminate-cap and inserts the pin, pre- viously feeling that the plunger does not stick. To keep the bursting-charge in place in the shell, a brass thimble, with a flange about the top, and a small hole in the bottom, is first pressed into the fuze-hole and takes agaiust the shoulder, c. It is made a trifle large, and a small slit on either side at the top gives it sufficient spring to lit snug and tight. A piece of cloth is pasted over the tire-hole in the bottom of the thimble. In this thimble the leaden plunger rests. Failure to Ignite. — Percussion-fuzes frequently fail if fired into a bank of soft earth, sand, or other material which does not offer a sufficiently sudden resistance ; also if fired at high eleva- tion, owing to the fact that the rifle-shells may not strike point foremost. 1503. Moktae-fuzes. — The mortar-fuze now used is a paper-case time-fuze, similar in general appearance to the ordi- nary paper-case fuze, of long time of burning. They are made up in packages and marked with the kind and length of fuze. For any shorter time the fuze is cut with a sharp knife or line saw. With this fuze is used a wooden fuze-plug, having a conical opening, which is reamed out to lit the paper case. FUZES. 547 When the shell is loaded, and the fuze cnt to the required length, it is pressed in the plug and the plug firmly set in the fuze-hole. Tlie head of the fuze having been covered with tow or something to prevent breaking the composition, the fuze-setter is placed on the plug, and it is driven with the mallet until the head is about of an inch above the surface of the shell. 1504. The old form of mortar- fuze consists of a conical plug of wood, of the proper size for the fuze-hole (Fig. 332). The axis of this plug is bored out cyliudrieally, from the large down to witliin a short distance of the small end, which is left solid. At the large end a cap is hollowed out, and the outside of the plug is divdded into inches and parts, commencing at the bottom of the cap. Seven inches extreme length, and each inch burning seven seconds, giving a total length of forty-nine seconds. The orifice is filled with composition pressed hard and evenly as possible. The cup is filled with mealed powder and moist- ened with alcohol. The rate of burning is determined by experiment, and marked on a water-proof paper cap, 'which is tied over the cup. This is removed when the fuze is used. Knowing the time of flight, the fuze is cut with a saw at the proper division, and firmly set in the fuze-hole with a fuze-setter and mallet. The great disadvantage of this fuze is its irregularity, it be- ing very difficult to press such a large column of composition so that equal lengths will burn in equal times. 1505. Running-fuzes for Mines and Blasting. — The running fuzes most used are those known in England as Bick- ford^ s fuze^ and in this country as safety-fuze and Tofs fuze. ^he common fuze ordinarily used in blasting with powder is of this kind. It consists essentially of a column of fine gunpowder enclosed in flax, hemp, or cotton, and made up with different coverings according to the use to which it is applied. When intended for immediate use on light work in dry ground, it is unprotected by additional coverings. W^hen intended for use in wet ground or under water, it is covered with varnished tape or gutta-percha. These fuzes cause ignition, by conveying flame to the charge to be exploded. They are somewhat uncertain in their rate of burning, but average about one yard in a minute. The ordinary varieties must be kept in a cool, dry place, and j)reserved from contact 'uuth grease or oil. Fig. 332. 548 NAVAL ORDNANCE AND GUNNERY. The gutta-percha-covered varieties are liable to become in- jured by keeping, from the deterioration of the gutta-percha. Before using, care must be taken that cracking of the gutta- percha has not occurred. They should be able to resist water for twenty-four hours. 1506. Quick-match Fuze is made by enclosing quick-match in a paper case with plaited cotton covering, and water-proofed. (Art. 1455.) Gun-cotton Fuze. — Gun-cotton thread or rope bums with great rapidity : not less than thirty feet per second. 1507. Detonati^tg-fuzes or Exploders. — By a detonating- fuze, or detonator, is meant one that causes a detonating explo- sion. The ordinary method of producing explosion is by the direct apj)lication of flame. By the detonating method, explo- sion of the main charge is caused by the concussion exerted by a small charge of explosive material in the fuze. Fulminating mercury seems to possess peculiar properties as a detonator, and practically is the only body so used. Detonating-fuzes are used when violent shattering explo- sions are desired. Thus nitro-glycerine, gun-cotton, and their preparations are always fired by means of a fulminate exploder. The ignition of the fulminate may be accomplished in the ordi- nary manner, or by the use of electricity. 1508. The simplest fulminate exploder is made by attach- ing a copper case or large cap containing the fulminate to the end of a piece of common running-fuze. If the fuze fits the cap closely, it may be retained in place, and the cap pro- tected against moisture by pressing round it wax, hard soap, or other similar substance. If the fuze is too small, it must be passed through a plug of wood or small cork fitting the cap, and the whole fastened on as above. Before it is fastened into the cap, the end of the fuze must be spread out so as to ensure contact with the fulminate. Fifteen grains is the usual amount of fulminate placed in the cap ; it should be put in when wet, with some gummy solution or varnish, so that it will dry to a solid lump which will not shake loose. Even in exploding powder there is often great advantage in using detonating-fuzes. It is difficult to prove that actual detonation of the powder is brought about, but experiment has shown that a much more violent action can be obtained by using this mode of firing. 1509. Electric Fuzes axd Exploders. — Evidently when ordinaiy running-fuze is employed as the means of iofuition. but one charge or mine can be exploded at a time. In large blast- ing ojperations, and in military engineering, simultaneous filing FUZES. 549 of many charges is constantly required. Again it is often de- sired to e.xplode charges from a distance, as in torpedo work. The applications of electricity to this purpose have become cj^uite extensive, and ofi'er many advantages in the greater certainty of their action, and the ease with which they can be employed under circumstances Avhero the ordinary running-fuze would be useless. Electric fuzes are always used with gun- cotton, nitro-glycerine, and their preparations, when any contin- uous or extensive work is to be done with them. Electric fuzes or exploders may be divided into two classes : those in which the heat is obtained by the passage of the elec- tric spark over a break in the circuit, and those in wliich the heat is obtained by the passage of the current over a conductor of great resistance. 1510. The first, or tension-fuzes, may be used with the Leyden jar, induction-coil, or any statical electric machine, such as Von Ebner’s, Smith’s, etc. The forms in which they are made are numerous, but essentially they are all alike. All that is necessary for a fuze or exploder of this class is, that there shall be a break in a circuit not greater than the spark can easily be made to pass over to is the usual distance), and that between the two points of the break shall be placed some composition that will be ignited by the passage of the spark. Gunpowder can be so fired, if packed closely between the points, but it is better to use some more sensitive material as a priming. Fulminating mercury is fired by the spark, and may be used for this purpose, either pure or mixed with other substances, as in percussion-cap composition. Abel’s composi- tion has been thus used. It is composed of sub-sulphide of copper, 64 parts ; subphosphide of copper, 14 parts ; and chlo- rate of potash, 22 parts. Other priming compositions are also employed. The wires of the fuze must be firmly held in a wooden block or similar contrivance, in such a manner that the priming cannot be displaced, or the distance between the points altered. Outside the priming-material is placed fulminating mercury, gunpowder, or other substance, and the Avdiole properly en- closed in a wooden or metallic case. In other respects the fuze may be made up as desired, by coating with water-proof com- position, varnishes, gutta-percha, etc. 1511. The principle difficulty connected with the use of statical electricity for causing explosion is the high insulation of the conducting-wires that is required. If the insulation is hnperfect, the loss is so great as to render the firing of the fuze 550 NAVAL OKDNANCE AND GUNNERY. uncertain or impossible. Some persons have tiied to avoid tliis need of perfect insulation by the use of very sensitive priming-compositions. Many fatal accidents have been occa- sioned by this recklessness. 1512. The second class of electric fuzes or exploders are those in which, by the passage of the current, a portion of the circuit having a great resistance becomes sufficiently heated to ignite some explosive or inflammable body in contact with it. Ifliese fuzes are used with the voltaic battery and the various magneto-electric machines, such as Farmer’s, Gramme’s, Wheat- stone’s, Beardslee’s, etc. For convenience, these may be divided into two divisions : those in which plnmbago, copper sulphide, Abel’s composition, or other similar highly resisting substance forms the part of the circuit which is to be heated, and those in which a fine platinum wire or other comparatively good conductor occupies that position. 1513. Of the first division are the fuzes made for Wheat- stone’s, Beardslee’s, or other similar machines. They consist essentially of a break in the circuit which is bridged by a layer of plumbago or composition which has a certain condnctins:- power, and which will burn when heated. In contact with this is placed the gunpowder, fulminating mercury, or other sub- stance which is the charge of the fuze. This anangement is made up in any desired shape. The difficulties connected with the use of these fuzes and the machines for which they are made are, that good insulation of the leading-wires is necessary, and that they are somewhat un- certain for various causes. The current from these machines has less intensity and greater quantity than the static, but is more intense, and has less volume than the voltaic current, or that generated by Far- mer’s or Gramme’s machines. Safe fuzes of this sort may be made, since no very sensitive composition is reqnired as a prim- ing. 1514. Of the second division are those known as platinum- wire fuzes or German-silver-wire fuzes. These are used with the galvanic battery and Farmer’s or Gramme’s machines. Several varieties are made in this country and in Europe. Of this kind are the fuzes made at the Toiqtedo Station, and issued for tor- pedo purposes, to be used with Farmer's dynamo-electric machine. The essential point in the construction of all the fuzes of this division is the placing of a short piece of very line metallic (platinum or German silver is generally used) wire in the cir- FUZES. 651 cuit, and in contact with it a priming-material which when tired ignites the fnze-mass, or the wire may be embedded in the fiize-m iss itself, and thus inflame it directly, without the inter- vention of a priming. 1515. This form of electric fuze has many advantages. The current with which it is used is one of great quantity and low intensity, so that the insulation of the conducting-wires need not be as complete as in the other cases. In fact, no insula- tion is recpiired,if the fuze is suflicieutly delicate and the whole circuit is not too long. As long as the fuze is whole, the current is complete, as may be shown by the passage of a weak current. It may, therefore, be tested at any time before using it, even when in the charge and the certainty of firing demonstrated, whereas with the other kinds, actual trial is necessary. Gi’eater uniformity is attained, since these fuzes can be made to conform to any standard of resis- tance. This point becomes of great importance when firing takes place at great distances, or when a great number of simultaneous explosions are to be made. These fuzes are safe to handle, since no highly sensitive composition is needed as a priming. 1516. The Dynamo-electetc Igniter now supplied to the service (Fig. 333) consists of a hard wooden plug, a, half an inch in length, inch in diameter, about its centre, and groove on either side (the bottoms of which are of an inch apart) for the reception of the copper wires. There are also two cotton-covered (braided) copper wires, which are twisted together for about an inch, and are stripped of their insulation almost to the twist ; these uncovered parts are pressed firmly into the grooves in the sides of the plug, and cut off, so that they pro- ject about one-eighth of an inch above the plug ; the ends of the wires are now split with a very fine saw, in the direc- tion of the plane passing through them, and the distance be- tween the ends carefully adjusted to IT of an inch, after which 05 ’ „ and about of an having a score cut longitudinal bottoms a Fig. 333. 552 NAVAL ORDNANCE AND GUNNERY. sinking it about an eighth of an inch, wire is next found and marked upon the platinum wire No. 40 is stretched between them, to form the bridge, and securely soldered to the ends of the split wires, i i. A wisp of gun-cotton,/’, is next wrapped around the platinum wire, and the ends of the copper wire pinched together sufficiently to take all strain off the platinum wire. The plug is now in- serted in a hollow wooden case, &, two inches long, counter- The resistance of the upon me case ; it should not vary more than five-tenths either side of 0.42 ohms. The upper part of the case is filled with rifie-powder, the top being closed with a disk of coi’k, over which is poured some water- proof composition, and the whole is properly coated with shellac to render it water-proof. 1517. The Dynawo-Electeic Fuze is made by enclosing one of the D. E. Igniters in a stout paper case about six inches in length, which is filled with rifle-powder to give more flame and consequently a more perfect igni- tion of the charge than can be obtained by the igni- ter alone. (Fig. 334.) The ends of the ease are properly closed, a wooden plug, B, with grooves cut in the sides for the wires, being used for the bottom, and a disk of cork for the top, which is coated with col- lodion, and seals the cork firmly into the case. The fuze is given two coats of brown shellac. The ends of the wires below the plug are stripped of their covering and brightened. Section lY. — Signals. 1518. Kixds. — The preparations employed for signals are ; rockets, signal-lights, navy red, white, and Hue lights. 1519. SiGXAL-EocKETS. — A signal-i’ocket is a cylindrical case of paper or metal, a (Fig. 335), at- tached to one extremity of a light wooden rod,^/, and containing an inflammable composition, h, which, being fired, shoots the whole of the arrangement thi’ough the air, by the principle that an unbal- anced reaction from the heated gases which issue from openings in fireworks, gives them motion in the opposite direction. The principal parts of a signal-rocket are: the ease, a\ the composition, Fig. 334. the head, c : the decorations, e \ and the stick,/! SIGNALS. 553 1520. Case . — The case is made by rolling stont paper covered on one side with paste around a former., and at the same time applying a pressure until all the layers adhere to each other. The vent is formed by choking one end of the case while wet, and wrapping it with twine. The paper case is covered outside with paste, and enclosed in a cylindrical case of tin, inches in diameter and 9 inches long. The lower edges of the tin case are turned under slightly, to keep the paper case from going through. 1521. Composition . — A variety of compositions are em- ployed for sign ah rockets ; the best can only be determined by trial, as it varies with the condition of the ingredients. The following proportions are used in the jSTaval Labora- tory : bTitre 4 lbs. 8 oz. Sulphur 1.2 oz. Charcoal 2 lbs. IVIealed-powder 4 oz. To increase the length and brilliancy of the trail, add steel or cast-iron tilings. 1522. Driving . — The case is placed in a steel mold, which has a conical spindle attached to the centre of its base to form the bore, g. This spindle is made of composition, 6^ inches long, and goes up through the vent into the centre of the case, having a hemispherical bottom to fit the choke, A. The composition is driven with a screw-press regulated to a pressui’e of about 5 tons. The first and second drifts are made hollow to fit over the spindle, and the third is solid. A small ladleful of pulverized clay is first put in and pressed down around the spindle, forming a bottom J inch thick. The composition is next put in, a ladleful at a time, each one pressed down separately. The top of the case is closed with clay, which is one diame- ter thick, and perforated with a small hole for the passage of the flame from the burning-composition to the head ; through this hole a strand of quick-match is placed. The rocket is primed by inserting one end of a strand of quick-match, eight or ten inches long, through the vent into the 554 NAVAL ORDNANCE AND GUNNERY. bore, and coiling tbe remainder in the recess formed by the choke. A piece of paper is pasted over the end to protect it. 1523. Head . — The head is formed by a tin cylinder inches diameter and 2^ inches long, joined to a hollow tin cone 2-| inches high, making the length of head 5 inches. (Fig. 336.) The long tin case goes about ^ inch into the cylindrical part of the head, and a piece of paper is pasted over the joint. The object of the head is to contain the decorations, which are scattered through the air by the explosion which takes place when the rocket reaches the summit of its trajectory. The explosion is produced by a small charge of rocket-composition, which is put into the head with the decorations. When the com- position is consumed, the bursting-charge explodes the head and ignites the decorations, which, fall- ing, produce a brilliant light that can be seen at a great distance. 1524. Decorations . — The decorations of rock- ets are of various kinds ; those used in the navy are white stars. Stars . — Stars are fonned by driving the com- position moistened Avith alcohol and gum-arabic in solution in port-lire molds, or molding it in brass cylinders of the desired diameter. It is then cut into short lengths and dredged (sprinkled) with mealed-powder. The gum-arabic is intended to give such consistency to the stars that the explo- sion of the head of the rocket may not break them in pieces, and thereby destroy the effect. White Star Composition. FTitre 3^ oz. Sulphur If oz. Mealed-powder f oz. 1525. Sticks . — The stick is a tapering piece of pine, about nine times the length of the case, and the large end is tied to the side of the case, to guide the rocket in its flight, as it has no rotary motion. The common centre of gravity of the rocket and stick is a little below the former. The stick counteracts by the resist I U Em. 336. SIGISTALS. 555 ance of tlie air upon it and tendency to turn over, and main- tains the rocket, during its flight, as nearly as possible in the di- rection in which it is hred. 1526. Motive-power . — The object of having the cavity or bore in the interior of the rocket is, that a large surface of com- position may be at once ignited when the rocket is fired, and so great a quantity of gas generated in the case that it cannot es- cape from the vent as quickly as formed, and therefore exerts a pressure in every direction on the interior surface of the rocket. The pressures on the sides of the rocket mutually bal- ance each other, but the pressure on the head is greater than that on the base, in consecpaence of the escape of gas from the vent ; it is this excess of pressure on the head over that on the base which causes the rocket to move forward, this being merely a similar action to the recoil of a gun. The force which produces motion in a rocket is therefore different from that which acts upon a projectile fired from a piece of ordnance; the former is a constant force producing ac- celerated motion in the rocket until the resistance of the air is equal to the force or the composition is consumed ; while the latter may be considered merely as an impulsive force, which ceases to act upon the projectile when it has left the bore of the piece. 1527. Packing Pockets — The cases are painted red and packed in laboratory-boxes, 30 to 50 in a box. The sticks are tied up in bundles and packed separately. 1528. Fikixg Rockets. — A few rockets are always kept mounted and ready for use. To fire a rocket, the stick is placed in a trough or tube, as a guide ; a musket-barrel will answer the purpose. The paper covering the bottom is torn off, exposing the priming. Holding the guide vertical or nearly so, a slow- match is applied to the priming, which ignites the composition. The inflamed gas issues violently from the bottom of the case as the rocket ascends. The time of ascent is from 7 to 10 seconds, and they will attain a height of about 500 yards. Under favorable circumstances, a signal-rocket may be seen within a circuit of from 30 to 40 miles. In mounting rockets the stick is attached so that it will hang end down, when sup- ported, close up along side the bottom of the rocket. 1529. CosTox SiGXAL-LiGHTS. — These are the usual night- signals of the Havy. They consist of red, green, and white lights, and their various combinations, representing the different numbers and pendants. The colors assimilate as far as possible with those of the day-flags. 556 NAVAL ORDNANCE AND GUNNERY. 1530. The case is made of fuze-paper three inches long and inches in diameter. A cylindrical block of soft wood 4' inch long forms the bottom, A, with a wooden nipple attached, to fit into the signal-holder, or firing-pistol. (Fig. 337.) Through Fig. 337. the centre of the bottom is a small hole, with a thin copper tube inch in diameter, B, extending through the middle of the case to withiu ^ incli of the top. Hollow drifts are used in filling, which are struck 15 moderate blows with a half-pound mallet for each charge. The ease is filled to the top of the cop- per tube ; the last charge being ^ ounce of mealed-powder. A small strand of quick-match is put through the copper tube and Avooden bottom, the upper end stitched to the side of the paper case above the mealed-powder, and the lower end split to Fig. 333. make sure of its ignition by the cap from the pistol. (Fig. 338.) 1531. The top of the ease is covered Avith a thin wafer of SIGNALS. 557 brown paper, immediately over the qnick-matcb and mealed- powder ; then over all is a pasteboard top, with a rim secured to the body of the case by a strip of paper pasted on both, C. The wooden bottom is covered with shellaced paper. The signal is finally covei’ed with white, red, or green paper, ac- coi’ding to the color of the composition, and packed in labor- atory-boxes for issue. The several colors in the Coston signals are intended to burn from 8 to 10 seconds. 1532. In a signal composed of three colors, 1^ charges of the composition of the last color to be burned are put in first and driven ; a thin circular disk of paper is pnt in the case on top of this composition, then 1|- charges of the second color are put in and driven, a piece of paper put on, and then 1|- charges of the first color to be burned are driven. When a signal is composed of but two colors, the lower thu’d of the paper case is filled with powdered clay, and driven the same as the composition, then on top of this clay the second colored composition is driven, and on that the first. AV^hen but one color forms a signal, two-thirds of the case is first filled with clay, and the composition driven in the upper third. 1533. Composition of ^Yhite Signals : 5 parts of Sublimate of Sulphnr, 5 “ “ Sulphuret of Antimony, 2 “ “ Eed Oxide of Lead, 3 “ “ Sulphuret of Arsenic, ^ “ “ Bleached Shellac, 21 “ “ ISTitrate of Potash. JCor the Red, Light. 16 parts of Chlorate of Potash, 6 “ “ Oxalate of Strontium, 2 “ “ Bleached Shellac, 2 “ “ Sugar of Lead, ^ “ Desiccated Lampblack. For the Green Light. 4 parts of Chlorate of Mercury, 2 “ “ Bleached Shellac, 12 “ “ Chlorate of Barium. Bed, White, and Blue Lights are made in the same man- 558 NAVAL OEDNANCE AND GUNNEET. iier as the Coston signals, and are of the same size. They only diifer in the burning composition, which is, for the Navy NJdte Light. Composed of 68 parts of Nitre, 18 “ “ Sulphur, 13 “ “ Mealed-powder, 4r^ “ “ Oi’piment, 3^ “ “ Antimony. Navy Red Light. Composed of 61 parts of Strontium, 20 “ “ Shellac, 37 “ “ Chlorate Potash, 3 “ “ Charcoal, 7 “ “ Sulphate Antimony.? Navy Blue Light. Composed of 21 parts of Ammoniated Copper, 18 “ “ Oxide of Copper, 12 “ “ Shellac, 6 “ “ Oaijiment, 68 “ “ Chlorate of Potash. 1531. Stowage of Ptrewoeks. — The fireworks, after care- fully remo^dng all fulminating matter, such as caps or primers, if any such he used to ignite them, are stowed in their proper packing-boxes, or other light boxes of suitable length, made water-tight and secured witir lock and key. These boxes are made to fit between the beams and carlines of the gun-decks of frigates and berth-decks of single-decked vessels. Those for instant use are placed near the after-hatch, and the remainder abaft that position, if possible, so as to be con- stantly under the care of the sentinel at the cabin-door. In no case, however, are they to be placed over any standing light or lantern on any deck. Section Y. — Preparing Ammunition. 1535. Coviposmox. — Ammunition is composed of projec- tiles, cartridges, etc. PEEPAKIXa AMMUNITION. 559 The cartridges and projectiles used with heavy ordnance are fitted and stored separately. 1536. MAKmG Cakteldge-bags. — Cartridge-bags are made of two shapes : conical, for gomer chambers, and cylindrical for other ordnance. The cartridge-cloth from which the bags are made is woven expressly for the pui’pose, being entirely of wool, and of close and uniform texture. It is manufactured in pieces varying in width from sixteen to thirty-six inches ; the different widths being adapted for the several lengths of cylin- ders to save waste in cutting. Cartridge-bags for cylindrical chambers are made of a rectan- gle to form the cylinder, and a circular piece to form the bot- tom. The flat patterns, by which the cartridge-bags for the 8-inch and 32-pounder guns are cut, are consecprently to be made rectangular for the cylindrical part of the bag, and circular for the bottom. The length of the rectangle is ecpial to the devel- opment of the cylinder, together with the allowance for seam ; and its width, to the whole length of the bag before sewing, including the allowance for seam and tie. S^recial patterns are furnished for those of XY-in., Xl-in., X in., IX-in., S-inch of 6,500 lbs., and 32-pounder of 4,500 lbs., shell-guns, all of which have gomer chambers. Cartridges for gomer-chambered ordnance are made conical in shape, and out of two pieces. In cutting, the length of the rectangle should be taken in the direction of the length of the stutf, as it does not stretch in that direction, and the material should be chosen, as nearly as possible, of the width rec[uired for the length of the bags, to save waste in cutting. The bags are to be sewn with worsted yarn, with not less than eight stitches to the inch ; they must be stitched within four-tenths of an inch of each edge, and the two edges of the seam felled down upon the same side, to prevent the powder from sifting through. The edges of the bottom are felled down upon the sides. The bags when filled must be tied with woollen thrums. 1537. Cartridge-bags for Saluting-charges . — Old cartridge- bags which have been condemned for service-charges are to be repaired and used for saluting-charges ; and whenever it is nec- essary to make bags expressly for the purpose, or for immedi- ate use, they may be formed by sewing together trvo rectaugii- lar pieces with semi-circular ends. 1538. Insjyeetion . — The material especially procured for car- tridge-bags is to be carefully inspected, to detect any mixture of cotton with the wool, by burning a few bits taken at hazard fi’om each piece, or by dissolving it in a solution of half an 560 NAVAL ORDNANCE AND GUNNERY. ounce of caustic potassa in a pint of water- — the cloth to be put in Avhen the water is boiling, which is to continue until dissolu- tion takes place. The texture of the stuff is also to he examined and its strength tried, such standard for the latter being estab- lished as may be found sufficient to ensure perfect efficiency. 1539. Preservation. — Cartridge-bags, as well as the material for making them, must be frequently examined, to prevent their being damaged by moisture, as well as to guard against moths. And they are never to be exposed on the shelves in store, but must be carefully packed by hydraulic press in linen cloth, or by enveloping them in water-proof paper hermetically sealed. 1540. IhLLiNG Carteh)ge-bags. — Standard powder-measures for filling cartridges for great guns are distributed as they may be required for the use of vessels and shore-magazines. As the gravimetric density of powder varies from 860 to 940, the weight of the contents of ten measures should be ascertained for each lot, and allowance made accordingly before filling the cartridges. In taking the weights, the powder is to be scooped up from the filling-chest with the measure until it is heaped, tapped twice moderately on the sides Avith the palms of the hands, and then struck with a wooden straight-edge. If the weight differs materially from that marked on the measure, a small compensating-measure should be used to supply the defi- ciency or remove the excess. When cartridges are filled for issue, the powder should be selected, as far as practicable, from dehveries made by the same person, and at the same time or date. 1541. Marking Cartridge bags . — The color of the cloth is white, and Avhen made up each bag is stencilled in black with the calibre of gun and weight of charge in figures two and a half inches long, for all service-charges. The cylinders, or cartridge-bags, in which the powder is put up for “ saluting,” “torpedo,” “howitzer,” “shell-powder,” or “ shell-charges ” are also to be distinctly stenciUed as such, in the same manner. 1542. Sekauce-chakges. — Tliere are certain fixed charges termed serMce charges for all guns. The amount of powder in tlieseiwice charge of a gun should be such that it will give the greatest initial velocity to the pro- jectile without too great strain on the metal of the piece, or a too violent recoil of the gun. The service-charges for the different calibres and classes of Naval smooth-bore guns noAv used in the Navy are as follows, and the cartridges are to he filled accordingly, viz. : PEEPAUmG AMMUNITION. 561 Service Charges for Naval Guns. Gnxs. CUAUGES. Calibre. Weight. Battering- charges — solivl shot. For clislant filing, 1-lOth. For ordinary fir'ng, O-lOths. O . B to w S) .S ^ 5 c ^ ci ^ OQ Shape of Cylinder. Shell guns. Vos, lbs. lbs. lbs. lbs. XV-in 43.000 10.000 100 M. P. 50 35 Conical Xl-in 30, rifle 20 15 7 X-in 12,500 9,000 6.500 4.500 15 13.5 6 IX-in 13 10 7 ( ( Vlll-in 7 7 4 (( G 6 4 (4 Vlil-in 03 cwt. 9 8 4 Cylindrical Vlll-in. 55 “ 7 7 4 Shot guns. X-in., or 130-pdr. . . (5 1-pflr 16,000 Iba. 30 18 6 U 106 cwt. 16 12 4 a 83 61 “ 10 8 4 n 33 “ 57 “ 9 8 4 ki 33 51 “ 8 7 4 a 33 “ 40 “ 7 7 4 a 32 “ 42 6 6 4 a 33 “ 33 “ 45 4.5 4 a 33 “ 27 “ 4 4 3 44 Charges for Naval Rifle Guns. Gan. Calibre. Weight. Diameter CriARGB OP POWDER. of bore. Weight. Kind. Diameter of guage. Parrott 100-pdr. Powids. 9,700 Inches. 6.40 Pounds. 8 Pifle Inches. 5.50 44 GO “ 5,400 5.30 6 44 4.60 44 30 “ 3,550 4.30 3.25 Cannon 3.70 44 20 “ 1,750 3.67 3 4 4 3.25 DaUgren »4 20 “ 1,340 4.00 2 44 12 “ 880 3.40 1 44 Witli the XV-inch guns at close quarters against iron-clads, 100 pounds of hexagonal or mammoth powder and a solid shot 36 562 NAVAL ORDNANCE AND GUNNERY. may be iissd for twenty rounds ; so also with the Xl-inch, 30 pounds of rifle and a solid shot. With all other guns, under like circumstances, and where penetration is desired, the distant firing-charges should be sub- stituted for the ordinary firing. Saluting charges are to be of under-proof powder. E.xperiinents have established the ability of our XV-iuch guns to endure charges of one hundred pounds of powder and a solid shot, and it is believed that they will stand even heavier charges. The service demanded of them requiring a wide range of charge, the seiwice-charge will vary with the object to be attained. 15T3. Fok Mortars. — The bag is only used to carry the powder, and when the piece is loaded the powder is poured into the chamber ; bags of any suitable size will answer for this service. 154T. For Hot-shot. — Cartridge-bags should be made doir- ble by putting one bag within another. The charge ought not to exceed three-fourths the service- charge, for in conse- quence of the expansion of the shot the windage is reduced and a greater strain will be exerted on the metal of the gun. The expansion of the gas will also be increased by the heat generated within the bore ; and, moreover, very great penetra- tion is not required, the object to be attained being that the shot shall merely lodge in the timber. 1545. Strappixg Shell. — All spherical shell and shrapnel are fitted with sdbuts. The sabot is a thick circular disk of wood, cut with the grain running plank-ways, about the diameter of the low gauge of the projectile, and with a cavity or saucer on one end to receive it. The projectile is secured to it with four straps of tin. The straps are fastened to a ring of tin encircling the fuze-hole by cutting four slits in the ring, into whicli the upper ends of the straps are hooked, turned down on the inside of the ring, and soldered. The lower ends of the straps are tacked to the side and under the bottom of the sabot, at equal distances from each other. A piece of twine is passed around between the sabot and projectile to frap the parts together. The Fnglish attach the sabot by a single expanding rivet through its centre, the hole in the projectile into which the rivet fits being under-cut, so that, on a blow being given, the end bulges out and grips the edge of it. This method is preferable to the straps. 1546. Advantages . — The sabot secures the position of the PREPAE,IXQ AMiMUI^ITION. 563 fuze in loading, which should he in the axis of the piece and from the cartridge. It tends to prevent tlie formation of a lodgment in the bore. It moderates the action of the powder on the projectile and helps to keep the projectile in its place. The fragments of the sabot are scattered as soon as the projec- tile leaves the bore of the piece. 1517. Filling Shells. — All shell are filled with shell- powder of the highest initial velocity. The shell must be filled and the powder well shaken down, leaving room only for the insertion of the fuze. A wooden plug the size of the lower part of the fuze will always determine this. For the purpose of increasing the effectiveness of hollow projectiles, a quick and strong bursting-charge is required to break the projectile into a large number of fragments. 1548. The Chakges of Powder foe Shell are as fol- lows : Charges for Spherical Shell. XV-inch. Xl-incb. a IX-inch. 1 VIII. inch. •O C. Boat and Field Howitzers. I3-in. Bomb. 24-pdr. 12 pdr. Full Charge. Bursting Charge. Blowing Charge. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. oz. lbs. oz. lbs. oz. Bursting or Ser^’ice Charge. 13. 6.00 4.00 3.00 1.85 0.90 1.0 0.5 11 0 6 0 0 6 Blowing Charge 1.0 0.25 0.25 0.25 0.25 0.25 Charges for ParrotCs Shell. 100-pdr. 60-pdr. 30-pdr. 20-pdr. lbs. oz. lbs. oz. 75s. os. lbs. oz. 3 11 2 2 1 8 1 0 Charges for Dahlgren Rifle-shell. 20-pdr 12-pdr 0.86 lbs. 0.50 lbs. 564 NAVAL OEDNANCE AND GTJNNEEY. The weight of charges for shells vai-ies slightly from those given in the tables, according to the size of the grain and den- sity of the powder. 1549. The Bursting-charges for Shell are made np in cot- ton bags and packed in separate tanks. Shells are tilled by capacity, and not by weight. When it is not required to burst the shell, but merely to blow the fuze out at practice, small charges called “ blowing-charges ” are used. In naval pi'aetice, however, it is seldom possible to recover the shells. 1550. Whenever it is necessary to load and fuze shell on board ship — a properly secured place being first prepared, not in the shell-room, and as far as convenient from the maga- zine — the shell, being strapped and saboted, are to be exam- ined to see that they ai’e clean, both inside and out, and thor- oughly dry. The greatest care is taken to remove every particle of sand or fragment of iron from the interior. The pi’escribed charge of powder is next poured into them through a proper funnel, care being taken that the end of the funnel passes below the screw-thread in the top, or bouching, to pre- vent any grains of powder from entering it. Any grains of it which may remain sticking to the thread of the bouching are brushed away carefully, and then, after putting a light coat of lacquer for small-arms, or sperm oil, on this thread and on that of the fuze, the latter is screwed in carefully with the fuze- wrench. The fuze must be screwed in tight, care being taken to have the proper leather washer under the head. The lacquer should be of the consistency of cream, and when, from evapora- tion, it becomes too stiff, should be thinned by adding more spirits of tmq)entine. 1551. The date when shell are fuzed nr filled, as well as that on which any of these arrangements are changed, or the shell are examined before issue, together with the initials of the offi- cer superintending these operations, should be legibly written and pasted on the shell. Projectiles are filled only as required for ships fitting for sea. ilo pi’ojectile should be fuzed until it has been filled, and they must be fuzed as soon as filled. 1552. Packing. — Loaded shell, as well as the sabots attached, are to be painted red and placed in boxes or bags marked with a red cross on the sides, and with the length of fuze in black. All spherical shell are packed singly. The smaller calibres of rifled shell are packed several in a box, and the larger cali- bres singly. 1553. Wads. — T^o wad is required over a shell, but a grommet-wad may be used in heavy rolling, or to prevent the PEEPAEING AMMUOTTIOlSr. 565 projectile moving forward slioiild the bore be depressed; also if it is shaken by the running out of the gun. When loading with shot, a grommet-^acl is placed oven it. No wad is placed between the charge and the projectile in ordinary service, and it is positivelj^ prohibited, to place a wad over an elongated projectile. 1554:. Geojimet-wad. — This consists of a selvagee, or circle of rope ecpial in diameter to the bore of the gun. They are made by a wad-machine. This consists of pairs of disks adapted to each calibre of guns, which, being placed face to face on a spindle and keyed, present an annular score grooved in such a way as to make, when fitted, a grommet of the re- quired size. Transverse notches are cut in the circumference of the disks to the bottom of the score, for the convenience of marling the wad before taking it off; the mold. In making the , wad, the end of a rope-yard is left in the score, and the mold is turned by a crank until the score is filled. The grommet thus formed is marled like a selvagee-strap, and a section of about an inch is taken out of it, in order to make the wad, when swelled by the dampness, enter the bore of the gun readily. Grommet-wads should be made neither too hard nor too soft ; and to avoid either of these two extremes, a sufficient number of hitches only will be taken to give the wad the consistency i-equired for service. Sections of one-third or one-fourth of these wads will answer as w’ell in case of need. 1555. Junk-wads. — They are now seldom used. They are made of oakum or cuttings of old “junk” compressed into a solid cylinder and bound around with spun yarn. They are of similar diameter to the bore of the gnu, and somewhat less than one calibre in thickness. 1556. Boat Ammunition. — -When the cartridge is attaclied to the projectile, the two together are termed '•'•fixed ammuni- tion ” • this is employed for service with boat-howitzers. It has the advantage of great convenience in the hiiriled prepara- tion that frequently precedes boat operations, and the guns can be served more rapidly with fixed ammunition, simultaneous loading is more simple, and the cartridge is sure to be placed correctly in the bore, and not with the choked end first, as is sometimes the case when the projectile and cartridge are sepa- rate. Fixed ammunition has, however, the disadvantage that in packing or stowing much greater space is required, and it is more difficult to arrange and to preserve. 566 NAVAL ORDNANCE AND GXJNNERT. The charges for “ Boat and Field Howitzers ” are : For the 2Fpdr. of 1300 lbs 2.00 lbs. For the medium 12-pdr. of 760 lbs . 1.00 “ For the light 12-pdr. of 430 lbs 0.625 “ The strength of the pieces would justify greater charges than these ; but the carriages, the fixtures, and the frame of the boat might be injured by the severe recoil of pieces so light, and even be disabled by the continued repetition of the firing with heavier charges. 1557. Stand of Ammunition. — A stand of ammunition is composed of the projectile, the sabot, the stra])s, and the cartridge-bag. (Fig. 339.) The projectiles used in howitzers are shell, shrapnel, and canister. For the two former the sabot has a sphencal cavity and a circular groove to which the cartridge-bag is tied ; in the latter the spherical cavity is omitted and a circular olfset is added. 1558. Packing. — As soon as the ammu- nition is finished it should be "ausred to see that it is of the proper calibre ; it is after- wards packed in well-seasoned pine boxes, so disposed that the sabot may rest on a ledge in the box, leavinij the chara:e below free from any pressure. The shell, shrapnel, and canister for the 24 and 12 pdr. howitzers are packed in boxes containing nine each. A fuze-cutter (for the Bormann fuze) is placed in the rim of each box containing loaded projectiles. The boxes are painted black and marked with the contents. The Hds are fitted with hinges and secured with screws. A key is becketed to each box for unscrewing the lid. 1559. In consequence of the objection to packing powder in wood on board ship, thereby rendering it more liable to de- terioration, various plans have been suggested for fitting the cartridge to be attached to the sabot at will, and stowing them separately ; and it has been lately ordered that this be done. The cartridge-bag has a brass wire ring sewed into the cloth outside of the tie, for the puipose of attaching it to the sabot of the projectile, the ring being made to open and fit into the fillet of the sabot, being retained in place by the force of the spring. Fig. 339 . PEEPAEZN-G AMMUNITION. 567 1560. Metallic Caeteidges. — ^Tlie metallic cartridge fur- nished the navy is a central-primed metallic carti'idge, and is manufactured by the United States Cartridge Company, Lowell, Mass, It consists of a brass case or shell having a solid head, made from one continuous piece, and by a peculiar process the metal throughout is of the same condition, and therefore not liable to burst at the head or rim, nor stick in the barrel of the gun after tiring. The method of priming is very simple and effective, being arranged so that the case or shell, which forms the greater part of the cost of the ammunition, can be reprimed and reloaded many times. The primer consists of two copper cups fitting inside of one another, fulminating compound being contained between them. TJie inside or smaller cup has two small perforations through the bottom to allow for the passage of the flame to the charge of powder, the bar formed between the perforations serving as an anvil against which the fulminate is exploded. The head of the case is made with a small circular cavity for the reception of the primer, the latter being applied from the outside ; there is also a perforation in the centre of the cav- ity to allow the flame from the primer to communicate with the powder-charge in the case. The charge of powder is 70 grains ; the bullet is cylindro- conical in shape, having three rings and a concave base, and is well lubricated ; the calibre .50, weighing 450 grains. They come in packages of 20 each, and weigh 2 lbs. 2 oz. The regular packing-box contains 50 packages, or 1,000 cartridges, and weighs 118 lbs. 4 oz. The empty shells or cases are to be carefully preserved, re- placed in their boxes, and returned to the navy-yards for re- loading. 1561. Duiiinr Caeteedges, made of the same size and form as the service cartridge, are supplied to ships, and must always be used during the manual exercise with the Remington rifle, in order to 2 ?i‘event injury to the striker by snapping the piece at “Fire.” 1562. Blank Caeteidges are supplied for funeral firing only ; they are not to be used in drill. 1563. Incendtaey Peepaeations are fire-stone, carcasses, incencliary-match, and hotshot. Fire-stone is a composition that burns slowly but intensely ; it is placed in a shell along with the bursting-charge, for the pm’pose of setting fire to ships, buildings, etc. 568 NAVAL ORDNANCE AND GUNNERY. Composition. — It is composed of ; 10 parts of Hitrej- 4r parts of Sulphur, 1 part of Antimony, 3 parts of Rosin. Preparation . — In a kettle in the open air, melt together one part of nmtton-tallow and one part of tui’pentine. The composition, having been pulverized and mixed, is added to the melted tallow and turpentine in small quantities. Each portion of the composition should he well stirred to prevent it from taking fire, and each portion should be melted before another is added. IIow used . — -When fire-stone is to be used in shell it is east into cylindrical molds, made by rolling fuze-paper around a former and securino; it with "lue. A small hole is formed in the composition by placing a paper tube in the centre of each mold. When the melted composition has become hard this hole is filled with a priming of fuze-composition. The object of this priming is to insure the ignition of the fire-stone by the flame of the bursting-charge. 15GI. Carcass. — A carcass is a hollow cast-iron projectile filled with burning-composition, the flame of which issues through several fuze-holes, to set fire to combustible objects. The fuze-holes are situated in the upper hemisphere, equi- distant from each other. Composition . — The composition is the same as for port-fires, mixed with a small quantity of finely chopped tow., and as much white turpentine and spirits of turpentine as avill give it a com- pressible consistency. Preparation. — The composition is compactly pressed into the carcass Avith a drift, so as to fill it entirely. Sticks of wood one-half inch diameter are then inserted into each fuze-hole Avith the points touching at the centre, so that when AvithdraAvn corresponding holes shall remain in the composition. In each hole thus formed tlu’ee strands of quick-match are inserted and held in place by dry port-tire composition, which is pressed around them. About three inches of the quick-match hang out Avhen the carcass is placed in the piece ; previously to that it is coiled up in the fuze-hole and closed with a patch. The metal of a carcass is considerably thicker than that of a common shell, because, being much Aveakened by the vents, there would be danger of the carcass breaking up under the shock of the dischaige ; and besides, as the carcass is not required to burst, PKEPARING AMMUNITIOIT. 569 it must have sufficient strength to withstand the pressure exerted upon it by the gas which is generated in the interior by the burning-composition. A Common Shell may be loaded as a carcass by placing a bursting-charge in first, and covering it with carcass-composi- tion driven in until the shell is nearly full, and then inserting strands of quick-match secured by driving more composition. This projectile, after burning as a carcass, explodes as a shell. 1565. — Incendiaiiy-matcii is made by boiling slow-match in a saturated solution of nitre, drying it, cutting it into pieces, and plunging it into melted fire-stone. It is principally used in loaded shells. 1566. IIoT-siiOT may be fired for the purpose of setting fire to vessels or buildings, though they are rarely used. Shot of low gauge should be chosen for this purpose with reduced charges. They can be made red-hot in from 15 to 30 minutes, but care must be taken not to bring them beyond a hright red, as they are then liable to fuze and become misshapen. Tlie part resting on the furnace-bars heats more quickly than the upper part, so they must frequently be turned. Shot expand •gig- of their diameter when brought to a red-heat therefore, to prevent accidents, each shot should be j^assed through a red-hot shot-gauge before being taken from the fire-room. Should the shot jam iu the bore it must be cooled by poiu'ing water in at the muzzle ; but if that fails, the charge must be drowned before attempting to blow out the shot. Precautions in Loading. — J unk and grommet wads which have been soaked in water for two or three hours, and the water pressed out of them, are to be used in loading. The junk-wads must bo small enough to fit easily when swelled by being soaked. The cartridge must be perfectly tight, so that powder will not be scattered along the bore. Sufficient eleva- tion having been given to enable the shot to roll home, first enter the cartridge, a dry junk- wad, and then a wet junk-wad, and ram them home. Briusr the shot in a bearer and enter it, With a wet grommet-wad on top; as it cools rapidly, no time should be lost. Quantities of smoke will come iq) through the vent, but a red-hot shot does not burn more than the outer yarns of a well-soaked junk-wad, even if left in the gun till it becomes cold. CHAPTEE X. PEACTICE or GUNNERY. Section I. — Service of Ordnance. 1567. LOADING. — The charge is placed in the muzzle with seams from the vent, small end in and tie outwards. It is pushed steadily to the bottom of the bore and on no account to be struck. The space which the powder occupies effects the initial velocity. Cartridges that have left the magazine are not to be returned until after the “ Eetreat ” is beaten, in order to prevent con- fusion. Powder-passers are to throw all cartridges that are injured in the slightest degree overboard, or in tubs of water prepared for that purpose. TliC cl tell is entered sabot first and fuze out. xkfter remov- ing the fuze-cap it is pushed gently to its place and never struck. 1568. ]\I.:iEKS ON EajMmee.— IVith the vieAv of affording tlie Loader a certain and independent means of knowing when tbe load is really home, the handle of the i-ammer has a mailc upon it, for the place of both charge and shell, easily distinguishable either by night or day. This mark is a narrow circular indentation, in a ]?ortion of which a strip of brass is secured, which is marked, for the outer one, with the charge in pounds, and for the inner one, with the projectile used. 1569. Eemoving Fuze-patcii. — In loading with shell, the cap is never to be removed until the shell is entered in the gun. IVitli high elevations, or when rolling, care should be taken that the shell does not slip down tlie bore before this is done. The cap or patch is removed by taking hold of the lug with the foreiinger and thumb, first raising it a little, and without twisting ; a pull readily removes it. The patch is passed to the Gun Captain, as an evidence that the piimiug lias been exposed; the patches are to be preserved juui accounted for at the end of the tiring. LOADING. 571 The Loader must be careful not to touch the fuze-composi- tion with iiis lingers, for fear of injuring it with moisture. In loading with percussion-shell, the screw-head of the fuze must be reversed. (Art. 1497.) 1570. The XY-inch Shell, being very heavy, is apt to slip in the straps by wliich it is secured to the sabot ; therefore, in load- ing, care must he taken to examine the position of the fuze-hole. When the distance is known to be less than the range of the shortest fuze, uncap all the fuzes. At other times uncap the fuze suited to the distance and the one of longest time of burn- ing. (Art. 1477.) 1571. lYrniDiiAwixG Peojectiles.— I f, in loading, a projec- tile jams in the bore, no attempt should be made to force it down, but it should be withdrawn. This may be done with the ladle^ by depressing and striking the muzzle against the lower sill of the port, or by running the gun out hard against the side, at extreme depression. Should these means fail to start the projectile, it will be necessary to destroy the charge by pouring water down the vent and muzzle, and then introduce a small quantity of powder and blow it out. Should a projectile jam in the bore in action, the Gun Cap- tain will not attempt to withdraw it, but discharge the piece at once. A gun is not to be loaded wdth more than a single projec- tile, and solid shot are not to be lired from shell-guns unless specially directed. 1572. Cake ix the Use of Shell. — In action, shell should never be allowed to accumulate on deck. Experiments have proved that any loaded shell at rest, when struck by a solid shot, tired with even a moderate charge will be exploded, with force sufficient to scatter in every direction, and to considerable dis- tances, any other shells that may be placed in near proximity. 1573. Keeping Guns Loaded. — Guns should never remain loaded longer than necessary, as the cartridge speedily deterior- ates by the effects of moisture. If a shell has been loaded twenty-four hours, it should be drawn and refuzed. 1574. Running Out. — As the projectile slides in the gun with very little friction, particular care should be talcen not to let the carriage strike wnth too great a shock in running out, as it will surely start the projectile from its seat. 1575. Closing the Yent. — After a piece has been dis- charged, the vent should be cleared with the priming-wire and the bore well sponged to extinguish any burning fragments of the cartridge that may remain. To prevent the current of air from fanning any burning 572 NAVAL ORDNANCE AND GUNNERY. fragments that may collect in the vent, it should be kept firmly closed with a thumb-stall in the operation of sponging. A moist sponge is always to be used. After sponging, the vent must again be cleared with the priming-wire and closed with the thumb-stall. These precau- tions are taken to prevent the possibility of the vent becoming obstructed. 157G. Cleaeing the Yent. — If at any time the Gun Cap- tain should find the veat obstructed, and be unable to clear it wdth i\\Q, primin'j-wire or l/oring-hit, he wall at once report to the officer of the division, who will order the vent-punch used ; or. if this should fail, have recourse to the vent-drill and l>race in charge of the Quarter Gunner. The boring-bit, vent-punch, and drills should be used with caution, as, being of steel, they are liable to be broken oil in the vent and thus eSectually spike the gun. After clearing the vent, the bore should be sponged. 1577. Spongers ^vnd Loaders should keep their bodies clear of the muzzle, and as much within the poi't as practicable for their own protection. 1578. li ARIDITY OF Loading. — Loading can not be executed with too much rapidity, provided neither the safety of the gun nor of its crew be compromised. 1579. Use of Projectiles not adapted to the Piece. — If it should become necessary to use a projectile much smaller than the bore, it is strapped to a stout sabot which fits the bore ; if a mortar-shell, it is placed in the centre of the bore with wedges and the surrounding space is filled up with earth or old junk. We may also fire fi-om a gun, shot of a greater calibre placed upon the muzzle ; this species of fire is generally at an angle of 45° ; the bomb placed upon the muzzle is secured by a cord which is broken by the first impulse ; the accuracy is nearly equal to that of shells from a mortar, and the rangeof an S-iuch shell fired from a 24-pdr. camion, with 8 lbs. charge of powder, is about GOO yards : the shorter the gnu, the greater the range. 1580. Loading Mortars. — The powder is to be emptied into the mortar from the cartridge-bag. which must be well shaken to remove dust and fine grains of powder. The bag is re- tained in the hands of the Loader to be used in wiping the shell before it is lowered into the bore. The powder is levelled off wdth a sjyatula, wdien the bomb, loaded and fuzed, is carefully lowered into the bore by the hooks, and allowed to rest upon the charge, keeping the fuze exactly in the axis of the bore. In mortars, where a sponge is seldom used, the stopping of the vent is not necessary ; but it should always be cleared out wdth LOADING. 573 the priming-wire before the powder is placed in. The bore is cleared with a scraper, and wiped out Avith an empty cartridge- b.ag or swab. If a sponge is used, it is much smaller than the bore. 1581. Loadustg Swall-aems.— Bring the piece to full-cock and open the breech-block ; if there be an empty sliell in the chamber, it Avill be removed by the extractor. The firing-pin may be made to protrude by being choked with rust, or by wedging of the firing-pin spring, and in this position lead to a premature explosion in closing the breech-block. Pass the fin- ger over the face of the breech-block, to ascertain that the firing- pin does not protrude. Place the cartridge in the chamber and close the breech- block. Should there be any difficulty in closing the breech- block, it is probable that the rim of the cartridge is too thick ; it should be AvithdraAvn and another tried. The chamber should be kept clean, and great care observed to prevent cartridges fouled with dirt, and particularly sand, from being inserted or discharged in the piece, as the expansion of the shell presses the sand into the metal and mars the surface of the chamber, and thus causes the shells to stick. Care should also be taken in cleaning the chamber for the same reason. The shell of an exploded cartridge should not be allowed to remain in the chamber any length of time, for fear it may adhere by corrosion. To prevent premature discharges, and to relieve the firing- pin spring, the piece should be always kept at half-cock. In coming to “ order arms,” the butt should be brought to the deck Avithout shock, as a jar may injure the piece. 1582. POINTING. — To point or aim a fire-arm is to give it such direction and eleA'ation that the projectile shall strike the object. To do this properly, it is necessary to understand the relations Avhich exist betAveen the line of sight, line of fire, tra- jectory, etc. 1583. DErnsrmoNS. — The line of sight is the right line con- taining the guiding points of the sights. The sights are two pieces on the upper surface of the gun, the situation of which with regard to the axis of the bore is known. H]xQ front sight is usually situated between the trunnions or * on the rim base, and is generally fixed ; the rear sight is placed on the breech, and is movable in a vertical plane. The natural line of sight is the line of sight nearest the axis of the piece ; the others are called artificial lines of sight. The line of fire is the axis of the bore prolonged in the di- rection of the muzzle. 574 NAVAL ORDNANCE AND GDNNEET. The angle of fire is the angle incliicled between the line of fire and horizon ; on account of the balloting of the projectile, the angle of the fire is not always ecpial to the angle of depart- ure or projection. T\xq angle of sight, or angle of elevation, is the angle in- cluded between the line of sight and line of fire ; angles of sight are divided into natural and artificial angles of sight, corre- sponding to the natm-al and artificial lines of sight which enclose them. T\xq plane of fire the vertical plane containing the line of fire. H\\Q plane of sight h the vertical plane containing the line of sight. 1584. Point-blank. — The term originated when it was imagined that a shot travelled for some distance in a straight line, or direct ; it is of no practical use, and is difter- entlv defined in diSerent countries. The French definitions oi pomt-hlanh scad, point-hlanh range are as follows : The point-hlanli is the second point at whicdi the line of sight intersects the traj ectory ; and the distance from the' face of the muzzle to this point is the point-hlanh range. The natural point-hlanli corresponds to the natural line of sight ; all other points-blank are called artificial pomts-hlanh. In the British service, as well as in our own, the point-blank distance is the distance at which the projectile strikes the hori- zontal plane on which the trucks of the carnage rest, the axis of the jiiece being horizontal. 1585. Eange is the distance from the muzzle of the gun to the second intersection of the trajectory with the line of sight. In practice the range is usually measured from the muzzle to the point of impact on the object, or to the first graze of the projectile. The ]-ange depends upon the initial velocity, the form, anrl density of the projectile, the angle of elevation of the gun. and the ditference of level between the planes upon which the gun and object respectrtely stand. Extreme range is the distance to the point at which the pro- jectile is brought to a state of rest. 1586. Range at Level. — The gun being placed a certain height above the water, depending on the class of vessel and the deck on which it is mounted, it is evident that, when the axis of the bore is horizontal, the projectile ■will have a range proportionate to this height. The distance to which the projectile wiU range in this case, SIGHTING CANNON. 575 before it grazes the Avater, is called the range-at-le.vel, and de- pends npon the class of gun, the cJiarge, and the height above the water. 1587. SIGHTIh7G CAhllSlOiSl. — In order that a projectile fired from a gun may strike a required object, it is necessary to adjust the line-of-fire with reference to the horizon and the ver- tical plane passing through the object in such a manner that the trajectory will reach it. The axis of the gun is not visible, and it is necessary to resort to notches or sights on the exterior surface to determine practically the position of the axis. The line of meial is a visual line, joining the notches cut on the highest points of the base-ring and swell of the muzzle. The inclination of the line of metal to the axis of the bore varies in guns of the same class as well as in those of different classes. Aiming, therefore, by the line of metal cannot be relied on for definite ranges ; besides that, within those ranges it is apt to mislead by giving too much elevation to the piece. If a gun be pointed at an object by means of a line of metal, it will be seen, by prolonging that line and the axis of the bore, that the latter will pass over the object. 1588. Dispart-sight. — A dispart is a piece of metal placed on the top of the gun to give a line-of-sight parallel to the axis of the bore. The dispart is generally defined as half the difference be- tween the diameters of those parts of the gun lopon which the sights are placed. Half the difference between the diameters of the gun at the base-ring and swell of the muzzle, or at any intermediate ])oint on the line of metal, will give the proper height of the dispart-sight at the point where the least diameter was taken. In the absence of other means of sighting, wooden dispart- sights lashed on the reenforce can be used. A narrow groove in the upper surface of the wooden sight, made to coincide with the plane of the line-of-sight marked on the gun, will assist in getting the true direction. The guns of the Dahlgren pattern are cylindrical for a cer- tain distance forward of the base-line, always giving a line-of- sight parallel to the axis of the bore. Guns are marked on the top of the base-ring, the sight- masses, and swell of the muzzle, by notches, wliicti indicate a vertical plane passing through the axis of the bore at right- angles to the axis of the trunnion. In range-at-level, the bore being horizontal, the dispart- 576 NAVAL ORDNANCE AND GUNNERY. sight is directed at a point above the water-line or point struck equal to its own distance above that line. If the gun is pointed by dispart directly at an object, the projectile will fall short, more or less, depending upon the distance. In pointing by dispart, therefore, it is necessary to direct the sight a certain height above the object, to allow for the fall of the projectile during flight ; the height to be pointed above must depend upon the distance of the object. 1589. Tangent Fieing. — Before the introduction of the tangent scale or breech-sight, all pointing at sea was done with the dispart-sight. When desiring to strike an object beyond the range-at-level of the piece, it was necessary 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 in- tended to allow for the space through which the projectile falls by the action of gravity in the time of flight. The vertical space through which the projected body in its flight descends below the line of fire is equal to the tangent of D the angle of elevation multiplied by the range or horizontal distance of the object from the gun. BD In the figure (310), tan A = BD = AB tan A. Thus, suppose a gun to be, at A, at a known height, AA', above the level of the water and at a known distance, AB, from a vertical object, B'D, as a ship’s mast. For any particular nature of ordnance we know the elevation necessary to project the projectile a certain distance. ISTow in the equation BD = AB tan A, AB, equal to the distance, is known, as is also the angle A, which is the angle of elevation necessary to give the gun in SIGHTING CANNON. 577 order to project the ball the distance, AB. But we have no means of pointing the gun at this angle, except by finding the length of the vertical, Avliich will subtend this vertical angle at the distance of the object. The required length of the vertical, BD, is found by the ecpiation, BD = AB tan 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 that is required in order to make the ball reach to the distance, AB. Adding to both sides, BB', Ave have B;D = AB tan A + BB'. To strike an object, then, at the water-line, at the distance AB, greater than the range at level, the aim being taken with the dispart-sight, it is necessaiy to direct 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. Such tables are to be found in the old editions of the Ordnance Instructions. This mode of firing presents serious disadvantages. The points arrived at have often to be estimated, as well as the dis- tance of the enemy’s vessel : the class of which can seldom be accurately determined. The men are taught to aim where they are not expected to hit, and the chances of the ricochet are lost ; hence, tangent firing should only be resorted to when there are no other means of regulating the elevation of the guns. 1590. Tangent Sights. — To facilitate the operation of pointing guns according to the distance of the object aimed at, sights are prepared and fitted to each gun. The ordinary sights consist of two pieces of bronze gun- metal, one of which, called the reenforce or dispart-sight, is a fixed point, firmly secured to the sight-mass, upon the upper surface of the gun between the trunnions. The other, or breech-sight, is a square bar or stem with a head, in the top of which is a sight-notch. It is set diagonally so as to expose two faces to the rear ; the rear angle chamf erred, to afford a bearing for the clamp-screw. This bar or stem is made to slide in a vertical plane, in the sight-box fixed to the breech-sight mass, and is held at the various elevations tor which it is graduated by means of a thumb-screw. Its length is sufficient for all the elevation which can be given — about 5° — before the muzzle appears above the front sight, after which 37 578 NAVAL ORDNANCE AND GUNNERY. a long wooden sight must be used, graduated for the whole length of the gun, using the notch in the muzzle. 1591. The brass tangent-scale or breech-sight may he said to be a tangent to an arc the radius of which is the distance from the outer point of the fore-sight to the fore part of the hind-sight, and the divisions are calculated accordingly ; this distance is called the short radius. The wooden tangent-scale may be said to be a tangent to an arc of which the radius is the distance from the notch on the swell of the muzzle to the front of the hind-sight ; this distance is called the long radius. The tangent-scale is set at an angle of 60°, so that it may slide up and down without touching the breech of the piece. Every gnu is furnished with two sight-bars, a long wooden and a short brass one ; the longer is used for ranges over 1,700 yards ; for all ranges less than this, which is the extreme dis- tance at which accurate practice may be expected at sea, the short bar is used. 1592. Pivot Guns have their tangent-scales fitted to be placed on the side of the breech, and the forward-sight is placed on the trunnion or rim-base. The advantage of this arrangement is that the tangent and trunnion sights can be used at any elevation ; for, being placed at the side of the gun, the muzzle of the piece does not inter- fere with the line of sight when pointing. The sights of all howitzers are fitted in this way : 1593. Sights for Pi fled Gions . — These consist of a fixed sight upon the right rim-base, and a brass movable sight in a socket which is screwed into the rear of the reenforce at the breech of the gim. The movable sight is furnished with a sliding eye-piece, and is graduated up to 10°. The eye-piece is also capable of lateral adjustment to allow for the drift as far as 10°, and for the effect of the wind. It is desirable that the sights should be placed on both sides of the breech ; other- wise, in firing from a port at extreme train, there may be con- siderable loss of lateral aim. 1594. The radius between the sights should bo as long as possible for sea-practice, with an unsteady platform, and where the eye is far removed from the rear-sight. In order to see the object in line with the outer sight, the eye must pass a certain vertical distance above the rear-sight. The amount of vertical height between the rear-sight and the line of vision depends upon the state of the weather, and upon the motion of the ship. When the shij) is steady it will prob- SIGHTING CANNON. 579 ably be 0.1 or 0.2 of axi incli. When the ship is very lively it may be half an inch. At all known distances, all considerable errors in firing at sea are dependent upon the height that the line of vision passes above the rear-sight. Take a given vertical height of visual error, say half an inch : the effect it will have upon the range depends upon the distance between the sights ; if they are but a few inches apart, the error will cause some thousands of yards increase of range. If they are as far apart as they can be placed, the same visual error will probably cause an error in range of less than a 100 yards with a IX-inch gun. 1595. Adjustment of the Sights.'^ — Roll the gun in the direction of its trunnions until the line of sight is uppermost. The cylindrical portion of gun forward of base-ring is supposed to be turned at the foundry parallel to axis of bore, so the next object is to trim down the reenforce and breech sight-masses un- til they are level with the cylindrical portion of gun. To do this, scrape off all the paint wdiich may be on the gun in line of sight. Place a straight-edge on the portion, its two ends rest- ing respectively on the reenforce and breech sight-masses. Trim down both masses until daylight cannot be seen between the straight-edge and the gnu along its whole length where the straight-edge takes, 1596. If possible, all sighting of guns should be done under cover, as the wind outside deflects the thread of the tompion-arm when fixing the point of the reenforce-sight. If the gun, how- ever, is out of doors and difficult to move, build a screen, fore and aft, the length of the gun to windward. The gun being in Gun Park, lying on wooden skids taking at chase and breech, build up with blocks under muzzle and at trunnions, using these in connection with chocks to bring the gun to an exact level both as to axis of bore of gun and axis of trunnions. 1597. The bore having been thoroughly cleansed, its axis is levelled by inserting a smalt steel T-scpiare in bottom of bore at the muzzle. The scpiare itself is first levelled by placing an or- dinary level on the transverse Ixrauch. When the T-square is levelled, the level is then placed on the longitudinal branch of the T-square lengthwise with the bore of gnu, and the axis of gun is then levelled by strilcing the chocks previously placed on each side under chase of gun, which of course either raise or lower the muzzle. When the gun has been levelled as to axis of bore, it is to be levelled as to axis of trunnions. By Lieutenant C. IL West, U. S. Navy. 580 NAVAL ORDNANCE AND GUNNERY. 1598, To level as to axis of trunnions; First, scrape o2 the paint on top of each trunnion, then place the trunnion-square as seen in h'ig. 311, and put the spirit-level on it as at s. Ad- Fig. 341. just the piece by means of the chocks under the tninnions until they are horizontal. This levelling the gun by axis of trunnions may throw out the axis of gun-level, in which case return to that, and then to the other, approximating closer and closer each time until the gun is levelled. If the gun be lying on wooden skids, the levelling must be verified from time to time, as the great weight will cause it to sink trifle by trifle, thus throwing the level out. 1599. Fitting Centee-sigiits. — The gun being levelled, next proceed to find initial point on base-ring. Encircle the breech of the gun at the base-ring with the trunnion-square, first scraping off the paint on gun where the legs of square take on either side, and level the square by a spirit-level. Then take the slid- ing pointer on transverse branch of square, and set it at a point exactly half way on the branch, by means of the graduated scale. Hit the gun on the base-ring a slight tap with the pointer. Take the square oS and turn the legs end for end, again em- bracing the gun, and again level square with spirit-level. Again hit the gun on the base-ring a slight tap with the jiointer. Should the pointer not strike in the same point as it did in the first instance, choose a point half way between the two for the initial point. IGOO, The initial point on base-ring being determined, place Fig. 342. the sighting-tompion (Fig. 3-12) in bore of gun. When the tompion is being placed in, be guided by the rings on the side to SIGHTING CANNON. 681 insert it evenly^ so as to prevent jamming. In large calibres it is also better to close the vent before inserting tlie tompion, as thus, Tvitli the compressed air, it can be taken ont more easily. Adjust the vertical arm of tompion by the spirit-level and tan- gent-screw. Extend the thread from vertical arm to the rear, resting for a second point on the initial point established by trunnion-square on base-ring. 1601. blow with a slight dent of the centre-punch, mark the point where the thread crosses the reenforce sight-mass. Take a straight-edge and lay it in the straight line determined by the two points, namely, the initial point on base-ring and the point determined on the reenforce sight-mass by thread of tompion- arm. Take a scriber and, with the straight-edge lying on these two points, scribe out a centre-line on the cylindrical portion of breech, also extending the line to the rear sight-mass. 1602. Proceed to cut out the breech sight-mass to its proper size (using as an initial line the line just described by means of straight-edge). For proper width, length, and bevels of breech sight-mass use templets and gatiges. There is a standard distance given for distance of front part of rear sight-mass from base-ring. 1603. As soon as the rear sight-mass is marked out by the templets, proceed to cut down the mass and lit rear sight-box. To tit the rear sight-box so as to bring the rear sight-box to proper angle, and also to a true plane perpendicular to axis of trunnions, use the levelling-bar. (Fig. 343.) Lay the reenforce- sight on the reenforce sight-mass. Then lay the levelling-bar with one end on the reeenforce sight, the sight taking in the line scribed on bottom of levelling-bar. 1604. The Levelling-har, B (Fig. 343), is a square steel bar with parallel faces, somewhat longer than the distance between the sights on the largest gun. The rear end is bevelled at an angle of 60°, the angle at which the sight is placed. It has a B S Fro. 343. central line marked on it throughout its length, on the under side, and along the bevelled end. It has also marked on its sides, near the forward end, the distance at which the sights should be placed for each class of gun. It is also fitted with screws’ for bringing it to a level. 582 NAVAL OEDNANCE AND GUNNERY. 1605. The levelling-bar being laid on the reenforce-sight, and its bevelled end taking against the rear-sight-bar, bring it to a level with the spirit-level and screws. This Avill give the true guide for angle of rear-sight-bar, and the latter’s proper plane. As soon as rear-sight-box is fitted, bore hole for same through rear-sight-mass. This hole is bored with the rear-sight- box on, and the latter is kept down in its place by a sling around cascabel set up by a handspike. 1606. The rear-sight being fitted tnie as to the levelling-bar, again level the arm of sighting-tompion, and stretch the thread back over gun, this time bringing the thread to the exact mid- dle of the rear-sight-bar notch. Kow in theoiy, the thread ought to come directly over the initial point of base-ring, and over the mark already laid off on reenforce-sight-mass ; but practically this is never the case, as it is almost irnpossihle to fit a rear-sight box so true as to bring the middle of the sight- notch in the exact line of sight already laid off. It will be found, upon stretching the thread the second time, that it will fall a trifie one side or other of the initial point on base-ring. 8o, virtually, it is necessary again to lay o3 a line of sight. 1607. With a measure take the distance that the thread falls to one side of the initial point on base-ring. Take this same distance that the thread is out, and lay it off horizontally on the cross-bar of the vertical sighting-arm. Of course when the thread is also moved this distance on the sighting-arm, the thread will fall the same distance to one side on the reenforce- sight-mass ; therefore mark this last point where the thread falls over the reenforce-sight-mass, and thus is established the second and final line of sight. Also mark the point where the thread now crosses the base-ring, and this is the final initial point to be marked for a fall due on the base-ring. Where the thread crosses the reenforce-sight-mass, hold the reenforce- sight itself directlj' under the thread. When the reenforce- sight-mass was lined out, at the same time with the breech- siace, making the practice more accurate. 1610. ACCURACY OF FIRE. — Firing for accuracy, whether with artillery or small-arms, may involve two entirely separate and distinct things ; 1st. The determination of the personal skill of the individ- ual using the weapon. 2d. The determination of the qualities as regards accuracy of the weapon itself. The most common way of determining the relative accu- racy of guns is to ascertain their mean differences of range and mean reduced deflection for a given mean range, and compare them — that gun being the most accurate for which these quan- tities are smallest. 1641. 2Iean Range . — The mean range is found by adding all the ranges together, and dividing the sum by the number of shots fired. 1642. Mean Difference of Range, or the mean error in range, may be found by taking the difference between each range nnd the mean range : add the differences together, divide by the number of shots fired, and the quotient will be the mean differ- ence of range. 1643. Mean Deflection.— KA2 together separately all the right deflections and all the left deflections ; subtract the smaller sum from the larger, and divide the difference by the niunber of shots flred ; the result will be the mean deflection. 1644. Mean reduced Deflection, or the mean error in di- ACCURACY OF FIRE. 597 rectiun, is found by taking the distance of each deflection from a line passing through the mean deflection add these distances, termed reduced deflections, together, and divide by the number of shot tired, for the mean reduced deflection. 16i5. Example . — Five shot fired under similar circum- stances give the following ranges and deflections : Ranges. reflections. ■yards. Yards. lUlO 4— Right. 1060 1— “ 1010 2 — Left. 1020 5— “ 1030 S — Right. O Sum of ranges 5160 , Number ot shot hred o j ^ a Tlie differences between each range and the mean range are 22, 28, 8, 12, and 2 = 72 yards. 11.1 yds., mean difference of range. Sum of right deflections = 8 yards. Sum of left deflections = 7 “ Difference = 1 “ ^ 0.2 yards, right mean deflection. Deflections from line through mean deflection : 3.8, 8, 2.2, 5.2, and 2.8 = 14.8. 11 8 — — = 2.96 yds., mean reduced deflection. 1616. An exact definition of the accuracy of a gun is a matter of no little difficulty. Of two guns fired from the same place, the same number of rounds, at the same target, Avith their axis in the same dh’ection, that would evidently be the more accurate which planted its shot more nearly together. But it is not always possible to test the practice of guns under precisely similar circumstances ; therefore Ave must seek a defi- nition equally true, but admitting, in addition, more elasticity in its application. Upon reflection, it becomes evident that an absolutely accu- rate gnu is one Avith Avhich, tired under identical circumstances, the chance or probability of striking the same spot twice amounts to certainty. Adopting the mathematical notion of probability, this Aviil be represented by unity — guns less accu- rate having probabilities represented by fractions. Such a mode, though suggested, has not been accompanied by the req- uisite tables to render it of general use. 598 NAVAL OEDNANCB AND GUNNERY. 1647. It is easier to determine, from tlie practice of the gun itself a rectangle with which there would be an equal chance of any shot from the gun striking or not striking ; or, if a given number of shots were fired, half the mmiber might be expected to fall within the area. The accuracies of two guns would be inversely as these rectangles for the same range. This method was proposed bv Captain Koble, E.. A., who furnished the following formula for application. If a be the length, and h the width of the area or rectangle required, then sum of differences of ranges. ft = 3.12 X .84.o3, ^ -j j 7 one less than number of ranges 7 0 7 Ko sum of reduced deflections. b — 3.12 X .8453, ; ^ , ^ one less than number ot detiections 1648. Accukacy of Small-aejis. — The I’elative precision of small-arms is decided by various methods. Centre of Impact.— T \iq point of impact of a ball is the point where it strikes the target, and the mean of all the hits is called the mean 'point of impact., or the centre of impact. To determine this point, let the piece be pointed at the cen- tre of a target stationed at the required distance, and fired a certain number of times, and let the positions of the shot-holes, measured in vertical and horizontal directions from the lower left-hand corner of the target, be arranged as in the following 0^0 o table ; No. of shot. Distances from lower left-hand comer in feet. Above. Right. 1 9 10 2 0 4 3 5 8 S') 14 S') 22 4.U7 7.3S The sum of all the vertical distances dixdded by the number of shots gives the height of the centre of impact above the origin. ACCURACY OP FIRE. 699 Similarly tlie sum of all the horizontal distances divided by the number of shots gives the horizontal distance from the origin to the centre of impact. Thus from the above table the co-ordinates of the centre of impact are 4.G7 and 7.33. The co-ordinates of the centre of the target being 6 each, the centre of impact is 1.33 below and 1.33 to the right of the centre of the target. 1649. Absolute Mean Deviation. — The co-ordinates of the centre of impact being known, the point itself is known, and its distance from the centre of the target is called the ahso- lute mean deviation. This is equal to the square-root of the sum of the squares of its vertical and horizontal distances from the centre of the target. 1650. Mean Deviation. — To obtain the mean deviation it is necessary to refer each shot-hole to the centre of impact as a new origin of co-ordinates, and this is done by taking the differ- ences between each tabular distance and the distance of the centre of impact and adding them. The sum of all the dis- tances thus obtained in one direction divided by the number of shots gives the mean deviation oy figure of merit. A shorter rule may be found : for if there ai-e m distances greater, and n distances less than the distance from the origin to the centre of impact, calling a the sum of the greater and & the sum of the less, we may write In using this formula, due care must be paid to the sign of (w — m). This method might be applied to the fire of cannon by re- ducing the grazes to an imaginary vertical target, the angles of descent being assumed equal for all shot fired at the same elevation. Applying this formula to the table given above, we get 3.11 feet vertically, 2.22 feet horizontally for the mean devia- tion OY figure of merit. 1651. Mean Horizontal and Mean Yertical Error. — The mean horizontal error is found by adding the horizontal distances by which the balls have missed the centre of the target, and dividing this sum by the number of balls ; this quotient indicates how much the average of the balls have missed horizontally the point aimed at. It may be directly and readily found by using the formula of the preceding article, substituting for ~x the horizontal dis- tance of the centre of the target from the origin. a — mx-\-nx—h m 4- n a — T) {n — m) X m -f- n = figure of merit. 600 I NAVAL ORDNANCE AND GUNNERY. Similarly the mean vertical error may he found, by using the same formula, with the substitution for ~x of the height of the centre of the target above the origin. The result shows evidently by how much the average of the shots have missed vertically. 1662. The Absolute Mean Ekeor. — To get this, there are two methods. The first is short and simple, and consists in cal- culating the hypothenuse of a right triangle, in which the other two sides are the mean horizontal and mean vertical errors. The second, which should be called the calculation of the meam, of the absolute errors^ consists in measuring for each ball its absolute error, a distance from the point aimed at, and to take the mean of these absolute errors by dividing then’ sum by the number of balls fired. This method is very long, since to have the absolute error of each ball it is necessary to square two numbers and then extract the square-root of these sums as the distance of the points struck have been measmed upon the vertical and hori- zontal lines passing through the point aimed at. The results are not exactly the same ; the mean of the abso- lute errors will be greater than the absolute mean error. 1653. Radius of a Circle Containing a Fraction of the Balls. — The radius of a circle containing a fraction of the balls, the third, half, or two-thirds is a common test of accuracy. Its centre is the point aimed at ; its radius is the absolute error of the third, half, or two-thirds of the other absolute errors arranged in order of size. Thus: 3, 4, 6, 7, 9, 15, IS, 21. 25, being the order in size of the absolute errors of nine balls. 6 will then be the radius of the circle containing the thi/'d of the best shots, 9 that containing the best half, and IS that containing the best two-thirds. If the number of balls fired be even, the circumference of the circle should pass equally distant from the two balls which limit it. For example, if we have twelve balls, and wish the circle containing the best third,\hG circumference should pass between the fourth and fifth balls at equal distances, the fourth within and the fifth without. If the number of balls be uneven. 9 for example, and we want the circle containing the best half of them, we pass it through the centre of the fifth ball. 1654. The Pee cent.— This test of accuracy indicates how many of one hundred balls fired have hit the target. To get the per cent., count the number of balls. A, that have hit the target, of the number, B, that have been fired, and from the proportion B ; a : : 100 : x., we have the per cent., JOO X a ACCURACY OF FIRE. 601 1655. CoiiPAKisoN OF THE DiFFEEENT Methods. — The de- termination of the mean point of impact can only he nsed in comparing tlie accuracy of two pieces that are of tlie same model and fired nnder precisely the same conditions; thus in general the mean point of impact gives only an imperfect idea of the accuracy of a piece. The mean horizontal error indi- cates only that the greatest nnmher of halls have gone too far to the right or left. Moreover, it may occur that two pieces have the same horizontal error, while the mean vertical error will he very different. The radius of a circle containing a fraction of the halls can- not give a perfect idea of the accuracy of a piece unless the halls are placed progressively distant, which cannot reasonahly he expected. The Per Cent. — If a piece he fired that has many causes of error, and we wish to test the skill of the marksman or the accuracy of the arm, only to the extent of ascertaining how many halls can he placed in the target, this method is simple and sufficiently exact. The surface covered hy the halls should, however, he taken into account, for it may occxir that with one arm the halls are scattered over the entire target, while with the other they are grouped in a small space ; this latter piece would he the more accurate. It would appear, then, that the method of the absolute mean error should he preferred : for it represents a quantity the ratio of which to the accuracy of the piece the mind can readily perceive ; and this quantity depending upon the posi- tion of each one of the halls varies when one of them varies, and thus gives a clear idea of the accuracy of the piece. 1650. The Inclination of the Target. — The most com- mon modes of recording target-practice are : rerticalVp as for smaU-arms, and horizontaThj as for great guns. Slight vertical errors on a vertical target are magnified into large errors in range, while the deviations are unchanged. Doubtless the fairest position of the target is that which would 602 NAVAL ORDNANCE AND GUN'N’ERT. receive the projectile at light angles to its own surface ; for witli this a normal target, there will be no distortion of errors either in favor of or against the gun. There is no real objection to anj of these positions of the target, as points on one can be transferred to each of the other two with facility, using the angles of fall from Bvclcner’s Tables, and assuming that the path of the projectile from the vertical target to the ground is a straight line. From an inspection of Fig. 354, it is seen that error on ver- tical target (Be) error on horizontal target (Ac) X tan A . . . (1) Error on normal target (cD) = error on horizontal target (Ac) X sin A (^2). If A, the angle of fall, be very small, there will be no apprecia- ble difference between its sine and tangent, and the vertical and normal targets will virtually coincide. If A be large, however, all determinations of the accuracy of the guns should strictly be made upon the normal target. 1657. Kecokd of Taeget-pkactice at Sea. — The record of a target-practice with great-guns should give for each shot the calibre and class of the gun, the weight of the charge, the nature of the projectile; if a shell, whether it biu’st before or after striking the water, or not at all, the observed distance of the target, the observed error in range, observed or estimated deviation, and the distance for which the sight was set. In the record should also appear the character of the wind and the sea, the motion of the ship, and the circumstances, so far as can be ascertained, attending any special occurrence. 1658. The following method of keeping the record is based upon suggestions by Capt. Jeffers, U. S. N. : An officer and a recorder are stationed at the topmast cross- trees. The former takes frequently the angles betiveen the sea horizon and the target, and gives them to the FTavigator, who looks out the corresponding distances and reports them to the executive officer. The officer aloft also takes the angles between the horizon and each point of impact. The recorder enters on a ruled form all the angles in suc- cession, denoting target angles by a check. He also has a paper divided into quarters by two lines at right angles to each other through the centre of the page. lYhenever a shot is fired, he notes in the appropriate quadrant the number of the shot ; his own estimation of the distance short, over, right, or left ; and the bursting of the shell as either before or after im- pact. Thus the diagram (Fig. 351) indicates that the fifth shell in the order of firing burst before impact, and the pieces struck ACCURACY OF FIRE. 603 ten yards short and fifteen to the left ; also that the seventh struck thirty yards over and five to the right, bursting after im- pact. Ricochet hits are marked by an R. An observer furnished with a similarly ruled paper, and stationed forward or aft, depending upon the wind, keeps an independent record of his estimation of the fall of the projectile and the ex- plosion of the sliell as a cheek upon the fi)’st I'ecorder. A competent person on the gun-deck records the number of the guns in their order of firing, and the dis- tances for which the sights were set. The clerk notes the time when firing began, and the dis- tance of the target, the time (by the order of firing) when changes of fuze or elevation are ordered and the observations of Fig. 351. the Captain. 1659. From tliese data a plan on the scale of one inch to sixteen yards should be made giving the positions of the several shot on the plane of the horizon. All shot not falling within 100 yards of the target should be rejected and reported in the aggregate as “ wild.” Accompanying this should be an elevation on tlm same scale, of the ship’s side, transferred to which are all the shot which would have struck it. This is easily made by means of tabulated angles of fall and eq (1) of the preceding article. (Art. IGbO.) In summing up, a proper proportional value should be al- lowed for any difference in distance. At 600 yds., the IX-in., Xl-in., and 100-pdr. are equal. At 1,300 yds., the proportion of hits for IX-in. should be 3, for T of Xl-in. or 100-pdr. in the same number of rounds. With the same guns, the hits at 600 yds. should be twice as many as those at 1200 yds., to maintain equality of firing. As the ordinary variation in range of a gun is about 50 yds., the sights should be altered only when the distance of the tar- get changes by more than that amount. It should be remembered that line shots over will appear to fall to the right or left of the target to observers on the right or left of the gun. 1660. QUOIXS AXD ELEVATIXG-SCREWS.— Most 604 NAVAL ORDNANCE AND GUNNERY. ]STaval guns are now fitted with elevating-screws, passing through a hole in the caseabel or attached to the carriages ; hut the ordi- nary beds and quoins are also still in use ; they are arranged to allow the extreme elevation and depression of the guns which the ports will admit with safety. "When the inner or thick end of the quoin is fair with the end of the bed in place, the gun is level in the carriage, or horizontal, when the ship is upright. The degrees of elevation above this level, which may be giveu to the gun by di’awing out the quoin when laid on its base, are marked on the side or edge, and those of depression on the fiat part of the quoin, so that when the quoin is turned on its side for depression the marks may be seen. The level mark on the quoin is to correspond with the end of the bed. When the quoin is entirely removed, and the breech of the gun rests on the bed, the gun has its greatest safe elevation ; and when the quoin is pushed home on its side, the gun has the greatest safe depression that the port will admit. Care must be taken that the stop on the quoin is always properly lodged, to prevent the quoin from fiying out or chang- ing its position, and that the bed is secured to the bed-bolt. Porter’s bed and quoin (Fig. 352) has been adopted for all carriages requiring quoins. This quoin, being graduated to whole degrees, requires a small additional quoin for slight dif- ference of elevation in smooth water. 1661. AVhen the elevating-screw is used, a quoin should he at hand to place under the breech of the gun, when at extreme elevation, to relieve the screw from the shock of the discharge, and prevent a change of the elevation, as well as to take the place of the screw if it should be disabled. 1662. When the fire is continuous at the same distance, the lever of the elevating-screw should be secured by a lanyard, to prevent the screw from tni'ning and altering the elevation. 1663. To obtain i-eadily the changes of elevation necessaiy in the use of rifie-guns, the heavier calibres are made with very POINTING. 605 small preponderance, and arc supplied -svitli an elevating-screw whicli is attached to the carriage at the lower end, while the nut is connected with the cascabel of the gun. Both screw and nnt admit of movements by which the screw can take any position required in the various degrees of elevation. The parts should be allowed a certain amount of play. 1664. Dahlgren’s screw is a single screw working through the cascabel and resting in a saucer in the carriage. 1665. Hart’s screw consists of a male and female screw at- tached to the carriage. 1666. Pointing Gtuns and Howitzers. — In ordinary firing it is not supposed that the trajectory changes its position with reference to the lines of sight and fire for angles of elevation and depression less than 15°. In aiming at any object, there- fore, the angle of elevation of which is less than 15°, aim as though it were in the same horizontal plane with the piece. 1667. In pointing guns and howitzers, under ordinary angles of elevation, the piece is first directed towards the object and then elevated to suit the distance. The accuracy of the aim de- pends, 1st : on the fact that the object is situated in the plane of sight. 2d : that the projectile moves in the plane of fire, and that the planes of sight and fire coincide or are parallel and near to each other. 3d : on the accuracy of the elevation. The first of these conditions depends on the eye of the gun- ner and the accuracy and delicacy of the sights ; the errors un- der this head are of but little practical importance. 1668. When the trunnions of the piece are horizontal and the sights are properly placed on the surface of the piece, the planes of sight and fire will coincide ; but when the axis of the trunnions is inclined and the line of sight is oblique to the axis of the bore, the planes are neither parallel nor coincident, and the aim will be incorrect. 1669. When the line of sight is parallel to the line of fire — as when the tangent-sight is at level — the planes of sight and fire will be parallel and at a distance from each other equal to the radius of the breech multiplied by the sine of the angle which the trunnions make with the horizon. To show this, let the circle, A B C D (Fig. 353), represent the ■section of the breech of the piece taken at right angles to the axis, and C the projection of the natural line of sight ; upon this plane let A' B'' be the inclined position of the trunnions. C' marks the revolved position of the’ line of sight, and C' D', the trace of the plane of sight Avhich is parallel to C D, the plane of fire. As the Ihies of sight and fire are parallel in their 606 NAVAL ORDNANCE AND GUNNERY. revolved position, tlie planes of sight and fire must also be parallel. The angle CO C' = B OB', therefore C C' = O C' sin B O B'. It is easily seen that in this case the error of pointing can never excejd the radius of the breech. By an inspection of the figure, it will also be seen that in the re- volved position of the line of sight, the elevation is diminished by a small quantity, which is equal to the versed sine of the arc C C'. 1670. When the tangent-scale is raised and the line of sight is no longer parallel to the line of fire, the planes of sight and fire intersect at a short distance from the muzzle ; hence it fol- lows, that as the object is situated in the plane of sight, the pro- jectile will deviate from the object to the side on which the lower trunnion is situated, and at a distance from it which is proportional to the distance of the object from the piece. This is shown in Fig. 3o4, where the piece is directed by the notches at A and C on the object, B. The shot will pro- ceed in the line, D E, to the right of the object, B, and at long range this deflection, B E, would be considerable. 1671. This cause of deviation is very common on ship-board, for the motion of the vessel renders it very uncertain that the axis of the trunnions will be horizontal at the moment that the gun is fii’ecl. The guns forward and aft are particularly sub- jected to the disadvantage arising from this cause, on account of the shear of the ship, and the guns amidships are usually more accurate in practice, because they rest ou a more level platform. POINTING. G07 1673. lu chase-fir in deviation must he tahen into con- sideration. . The pursuing and pursued have generally a consider- able heel or inclination to leeward ; in consecpienee of this, the trunnions of the guns in the bow and stern parts of each are in- clined, and in pointing them it will be necessary to aim at the weathermost part of the hull in order to avoid the effect of this error. The proper elevation due to the distance must be given ; as although the tangent-sight is slightly lowered by the heel of the ship, vet it is of no practical importance. These deviations will, of course, increase with the elevation of the gun and its distance from the target. To give an idea of their extent, suppose the plane to have an inclination of 10° ; distance of target, 900 yards ; elevation, 6° : the lateral de- viation will be six yards, and the projectile will strike too low by about 20 inches; if the inclination is but 5°, the lateral de- viation is reduced to 3 yards, and the fall to live inches. Then to correct for this source of error : point a little above the target and towards the side of the elevated trunnion, and make the corrections proportionally greater as the distance of the target and elevation of the gun are increased. 1673. PonsrxnsTG Sm^vll-arms and Moetaks.— In pointing small-arms and mortars the piece is first given the elevation, and then the direction necessary to attain the object. 1674. Pointing Small-aevis. — The rear-sights of small-arms are graduated with elevation-marks for certain distances, gener- ally every hundred yards; in aiming with these, as with all other arms, it is first necessary to know the distance of the ob- ject. This being known, and the slider being placed opposite the mark corresponding to this distance, the bottom of the rear- sight-notch and the top of the front-sight are brought into a line joining the object and the eye of the marksman. The term coarse-sight is used when a considerable portion of the front-sight is seen above the bottom of the rear-sight- notch ; and the tenn fine-sight when but a small portion is seen. The graduation marks being determined for a fine-sight, the effect of a coarse-si 2 :ht is to increase the true range of the • -1 ° ° projectile. 1675. Pointing Moetaes. — First give the elevation by ad- justing the quoin or ratchet until the required number of de- grees is obtained ; then the direction is given. The circle on wh.ieh the mortar stands, being fitted with eccentrics is made to revolve so as to point the mortar at the object without the trouble of swinging the vessel or moving the mortar around with handspikes. The elevation is given with gunner'' s quad- rant^ the sj)irit-level-quadrant, or the trunnion-sight. 608 NAVAL OEDNANCE AND GUNNERY. 1676. Gunner’s Quadrant. — This is made of brass and consists of a quarter of a circle fixed to a long arm. (Fig. 355.) Fig. 355. The edge of the circle is divided into degrees, and the inclina- tion of the arm to the horizon is determined hv a plummet which is fastened at the centre of the curve. This quadrant gives the elevation only to within a degree. To use it place the arm in the muzzle with the quadrant down ; raise tlie muz- zle until the plumb-line cuts the required augle on the gradu- ated arc. 1677. Spirit-level Quadrant. — This is similar to the gun- ner’s quadrant, having instead of the plumb-line a movable limb fastened at the centre of the arc, and a spirit-level attached to it. The end of this limb moves along the graduated arc, and has on it a vernier, by means of which parts of a degree can be read off. (Fig. 356.) This instrument is more especially intended for use with POINTING. 609 long pieces of large calibre, when firing at great elevations. To use it, insert the long arm into the bore, with the quadrant up ; there is a stop on the under side of the arm to prevent its slipping into the chamber ; the spirit-level attached to the graduated arc being set to the required angle, and the piece elevated until the spirit-level becomes horizontal, which will appear by the bubble resting in the centre of the glass tube. (Art. 964.) 1678. Trunnion-Sight. — This consists of a bar of mahogany or other hard wood not liable to warp (Fig. 346), of about forty inches in length, two inches wide, and one inch thick, with a brass notch at the rear end and a point at the other, so placed that an imaginary line from the top of the point to the bottom of the notch is parallel to the upper edge. A semicircular plate, graduated to degrees, is attached to the middle of the har, so that the bar’s upper edge corresponds to the 0 of the graduation. A small spirit-level is let into the upper surface of the rear end of the bar, and a stout thumb-screw passes through the bar and the centre of the semi-circulai*’ plate. To use this instrument a screw-hole is tapped in the axis of the left trunnion to receive the thumb-screw ; a line is marked on the trunnion perpendicular to the axis of the piece and passing through the axis of the trunnions. The sight is se- cured by the thumb-screw, with its rear end raised until the mark on the trunnion coincides with the degree of elevation re- quired. The piece is now elevated until the sight is level, which will be indicated by the spirit-level. This instrument is also designed to be used with pivot-guns when the required ele- vation passes the limits of the other sights. 1679. To give Lateral Train in mortar firing the trunnion- sight ma)" be used, or it can be done by a white line diuwn on the exterior of the mortar, in the same vertical plane as the axis of the piece when the trunnions are horizontal. The line is sometimes painted on the mortar-bed. In pointing mortars on shore it is an easy matter to get the direction, because the mortar is stationary ; but on ship-board, owing to the motion, it is attended with difficulty, especially when the vessel is rolling, and the line of fire can only be approximate. 1680. On shore, the plan of giving the direction is to de- termine practically, two fixed points, which shall be in a line "with the piece, and the object, and sufficiently near to be readily distinguished by the eye. A plummet is held in the hand im- mediately behind the mortar and the string made to coincide with these points. The mortar is then trained until the line of the plummet covers the central line on the mortar. 39 610 NAVAL ORDNANCE AND GUNNERY. 1681. In mortars, if the axis of the trunnions is not hori- zontal, the vertical plane passing through the line of sight vill still be parallel to the vertical plane of fire, and may be taken for it, so that it is not necessary to have the platform of mor- tars horizontal. 1682. Beaeing or the Eneihy. — It frequently happens in action that ships become quickly enveloped in a cloud of smoke so dense that when looking through the ports everything be- yond the muzzles of the guns will he invisible. But, though objects are thus shut out from the view of the battery, a mast or a spar may generally be seen from the upper deck sufficient- ly defined to mark the position of a vessel, and enable her bear- ings to be accurately taken either b}^ compass or by pointers. The principal care of the Commander must be to keep his guns always bearing on the enemy, and never pass the limits of extreme train for all his guns, unless absolutely necessary in mancBuvriug. 1683. Dieectoe. — This may be regulated by the aid of a hearing-plate, or director, fittecl in a convenient position on the upper deck. It is a species of alidade working on a graduated circle and giving the angular bearing of the object. The arc is marked in degrees and points, and the several bearings of con- centration are indicated as well as the dinlits of extreme train for all the guns. The sights of the alidade are graduated so as to be set to any degree of elevation or depression, according to the heel of the ship. 1681. In Pointing, the amount of lateral train required is usually designated by points, and the elevation by the corre- sponding number of yards of range. In tlie case of guns which work upon pivots or on centres, the motion of the rear of the gun-carriage being strictly con- fined to the arc of a circle, the position of the gun with refer- ence to the vessel can always be exactly defined by an arc di- vided into points, half-^ioints, and quarterqioints, being marked- on the deck. The ordinary broadside carriage, having no centres or pivots to work on, will rarely occupy the same place in the ports when the ffuns are run out for firiim, so that an arc marked on the deck would not be strictly applicable. 1685. CoNCENTEATED PiEE. — IVlieii all the guns of a bat- tery are directed to the same point and are discharged simul- taneously, it is called “ concentrated firing.” This kind of firing is used to the greatest advantage at short distances. One of the guns of the battery is selected as the directing-gun. POINTING. 611 To Concentrate a Ship’s Broadside^ the guns are trained in the direction of the object by means of The Directing-ljatten^ or The Converging-line^ and laid according to the heel of the ship and the distance of the object : the direction being given by the aid of the Director from the upper deck. . 1686. The Dieecting-battens. — These consist of metal or wooden battens, a (Fig. 357), sliding in two beckets attached to each of the brackets of the carriage, and retained in any position by a thumb-screw. They are arranged to slide out parallel to the deck, directly to the rear of the carriage. The upper sides of the battens are marked for the converg- ence on the bow, beam or quarter, and the outer sides in de- grees for parallel firing. To give direction, one of the battens is clamped at zero, the zero mark coinciding with the rear face of the becket in which it slides; the other batten is drawn out to the mark designating the points of convergence ordered, and clamped. A cord or bar is now placed over the ends of the two battens and the gun 612 NAVAL ORDNANCE AND GUNNERY. trained until this is parallel to a mark on the deck indicating the direction of the keel. 1687. The Converging-line. — This is a line hooked to tlie centre and near the outside of the upper port-sill, and held immediately under marks made on the beams or deck over- head, for the several bearings of a-beam, on the bow and ipiarter ; when the gun is trained until the sights are parallel to it. The midship gun is usually employed as the directing-gun, and the angles of training ascertained for the different bearings at a constant distance of say 500 yards. Tliough the calcnla- tions are made for this distance, yet this method of training will answer for all ranges within 1,000 yards. 1688. To Calculate the Angles for Concentration. — ■ On the Beam . — Let A (Fig. 358) be the midship gun trained right a-beam, B the foremost one, C the object at a constant distance of 500 yards. Let the distance from A to B, supposed known, ecpial 96 feet, and the distance from the centre of port in-hoard be taken as 11 feet, being the same for all the guns. Then the an- gle C can be easily found for ~ = Tan. C, the angle of training for the fore- most gnn. the the the tangent Again, in triangle B D E, we have D E = B D • Tan. C, the length of off overhead, from the point opposite For the intermediate guns divide to be set centre of the port, D E by the number of guns before the midship one, which will give the length of the tangent before the gun next to the midship one ; twice tins will be the length for the next gun, and so on : Thus, if D E = 10.7 inches, and the num- ber of giuis before A be 8, we have =1.3 inch, or the length for the gun next to A ; 2.6 in- ches = the length for the next gun, and so on. The same measurement answering for the guns abaft A. 1689. On the Bow or Quar- ter . — Let A (Fig. 359) be the midship gun trained 3 points abaft the beam, B the foremost one, C the object distant 500 yards. Let the distance from A 0 e Fig. 359. F C POINTING. 613 to B, supposed known, equal 96 feet, and the distance from the centre of the port in-board equal Id feet as before. Then from the expression, A C -f A B _ Tan. d (B -f C) A C - A B “ Tan. (B — C) the angle B can be easily found, which, taken from 90°, will give the angle of training for the foremost gun. Again, in tri- angles A i) E, B F G, we have D E = A D • Tan. A and F G = F B • Tan. B, which are the required lengths of the tangents to be set ofi overhead from the points opposite the centres of these ports. For the intermediate guns, divide the difference between the two lengths D E and F G by the num- ber of guns before the midship one, and add this common diffe- rence to the length D E for the gun next before the midship one, and so on to each gun in succession. Thus, let F G = 10 ft. 5 in., and D E = 9 ft. 4 in., tlie difference = 1 ft. 1 in.; let the number of guns before A be 8, then we have = 1.6 in., the common difference for each gun ; therefore 9 ft. 5.6 in. = the length for the gun before A ; 9 ft. 7.2 in. = the length for the next gun, and so on. The measnrements for the corresponding guns abaft the mid- ship one will be found by subtracting the common difference from D E, and so on, from each gun in succession. The calculation of the angles for 3 points before the beam, or for 1-|- points before and abaft the beam, is performed in the same manner. 1690. To jMaek the Beams. — Having a line parallel to the keel, overhead, at any convenient distance in rear of the guns, measure the assumed distance IF ft. from the centre of port in- board, and place a perfectly straight-edged batten there, parallel to the keel line ; then transfer the centre of the port to the bat- ten by stretching a line taut across from the centre of two op- posite upper port-sills ; or with any length of line as radius, from the centre of the port, describe an arc cutting the batten before and abaft the centre ; half the distance between these marks will give the point corresponding to the centre of the port. From this centre, measure off on the batten, to the right and left, the lengths of the tano;ents for the different bearings, as calculated above ; and then transfer these points to the beams or deck immediately over the batten. 1691. The Elevation. — Each turn of the elevating-screw represents 1° ; therefore, if the gun is once levelled, by stretch- ing a line across from tbe reinforce sights of opposite guns, and raising the screws until this line just touches the bottom of the 614 KAVAL ORDNANCE AND GUNNERY. sight-notch at level, and the number of threads above the cas- cabel noted, it is apparent that each turn raises or lowers the breech by 1°, and that the gun can be first made parallel witli the deck and then laid level to compensate for the degree of lieel given by the pendulum or director. 1692. Pendulums to Marh the Heel of the Ship . — The tangent sights give the elevation of the gun above the horizon- tal plane, and when the deck is steadily inclined from the hori- zontal line, by the pressure of the wind for instance, the tan- gent-scale will give the elevation of the gun above the plane of the deck, and not above the plane of the sea. Pendulums are fitted in convenient localities, working in a graduated arc, to indicate the amount of heel or inclination at any time, and show the nninber of degrees of elevation or de- pression required to bring a ship’s guns to a horizontal position. In practice, howevei’, very little reliance is placed upon these contrivances (Art. 1660). Section II.— Different Kinds of Fire. 1693. Classification. — The different kinds of fires are dis- tinguished, 1st. By the flight of the projectile, as direct., curved, ricochet, and plunging-fires y 2d. By the nature of the projec- tile, as solid-stiot, shell, shrapnel, grape, and canister fires ; and 3d. By the angle of elevation, as horizontal fire, or the fire of guns and howitzers under low angles of elevation, and verti- cal fire, or the fire of mortars under high angles of elevation. 1691. Dieect Fire. — A fire is said to be direct wlien the pro- jectile hits its object before striking any intermediate object, as the surface of the ground or water. This species of fire is employed where great penetration is required, as the force of the projectile is not diminished by pre- vious impact ; it is necessarily employed for shrapnel fire and for rifle-projectiles, which from their form are liable to be deflected by previously striking a resisting substance. This kind of fire requires a good knowledge of distance, and precision both of elevation and lateral direction, in order to strike an object which is comparatively a point. It is always to be preferred when the distance is accurately known, or when the object is so near that the chances of hitting it are very great ; also when the intervening surface between the gun and object is so rough or irregular that a projectile striking it would DIFFERENT KINDS OF FIRE. 615 have its velocity much diminished or destroyed, and its direction injuriously affected. 1695. Ricochet Fere. — When the angle of fall is small enough, the projectile rises and continues to move on, forming a' series of bounds or ricochets. A ricocheting ball makes a furrow in the surface struck, and each time the angle under which it leaves that surface is greater than that under Avhich it enters it ; for, having lost a portion of its velocity in passing over the first part of the curve, it has no longer the same power to overcome resistance, and must pass out hy a shorter path than the one it followed in entering, and consequently the angle is increased, which causes the more or less rapid extinction of the ricochet. The number, shape, and extent of the ricochets depend on the nature of the surface struck, the initial velocity, shape, size, and density of the projectile, and on the angle of fall. 1696. The most favorable circumstances under which this fire occurs are where the angle of fall is least, and the surface perfectly smooth. A 32-lb. spherical projectile will then roll 3000 to 3500 yards on water, rising hut little above the surface — never as high as the hull of a frigate — while the greatest range obtained from an elevation of 5 ° with the same gun and charge is less than 1800 yards. At first the bounds are of considerable extent, perhaps 350 to 400 yards between the first and second grazes ; they diminish gradually, so as to leave intervals not exceeding fifty yards as they approach the end of the range, and finallj' roll along the top of the water as if ploughing it. Long before this, how- ever, they are apt to curve off to the right or left from the true direction, so as to make an extreme deviation, often amounting to 100 or 200 yards. 1697. Ricochet firing, properly so called, is performed at level, or at most at three degrees of elevation ; shot Avill often ricochet at much greater angles, but it is not what is meant by ricochet firing. Upon smooth surfaces within certain distances this fire has some important advantages over direct firing. When the guns have very little or no elevation and are near the water, as they are in a ship's battery, theprojectile strikes the water at a very small angle ; its flight is not greatly retarded by the graze, and it rises but little above the surface in its course, but the penetra- tion is not to be depended upon beyond 1500 yards against ships of Avar. 1698. Ricochet firing at Ioav elevations requires only correct’ lateral direction, since the projectile would rarely pass over, and 616 NAVAL ORDNANCE AND GUNNERY. would probably strike a vessel, if within its effective rang-', whether the actual distance had been ascertained or not. The deviation of projectiles is, however, generally increased by ricochet, and in proportion to the roughness of the surface of the water. Even a slight ripple will make a perceptible dif- ference, not only in direction, but in range and penetration, and the height to which the projectile will rise in its bounds. 1699. Although these facts demand attention, yet when the estimated distance does not require an elevation of more than three degrees, projectiles from guns pointed rather too low for direct tiring will probably ricochet and strike the object with effect, even when the water is considerably rough. This may be called “ accidental ricochet.” When the water is not smooth, the most favorable circum- stances for ricochet-tiring are when the tlight of the projectile is with the I'oll of the sea, and the roll is long and regular. 1700. Ricochet will be effective against small objects up to 2000 yards, but should not commence at less than 600 yards ; at less distances it is preferable to tire direct. Ricochet is of no value from rifled guns firing elongated projectiles, as they lose all certainty of direction on the rebound. Projectiles rarely ricochet at all with elevations above 5°, and the bounds are always higher, with equal charges from the same gun, as the elevation of the gun is increased. 1701. Curved Eire. — W hen a projectile is fired so as just to clear an interposing cover and then descend upon tlie object without ricochets or rebounds, such j^i’^ctice is termed curved fire. Smallei- charges and higher angles are required than for ordinary direct fire. On shipboard it is more convenient to tire with service-charges from such distances as to obtain the proper angle of fall. 1702. Plunging Fire. — A fire is said to be plunging when the object is situated below the piece. This tire is particularly effective against the decks of A-essels. 1703. Solid-Shot Firing. — Solid shot are generally used when great accuracy at very long range and penetration are required. From their great strength they can be tired with a large charge of powder, Avhich gives them great initial velocity : and having great density, which diminishes the effect of the resistance of the air, they have great range and accuracy. In rifle-guns of large calibre it is found that solid shot s^'rain the guns from their weight, and shoot comparatively badly from their length, which is usually less than that of shell. It appears that the minimum length for good shooting is two calibres, and DIFFERENT KINDS OF FIRE. 617 that shell have an advantage from having the weight so diS' posed as to give a longer radius of gyration, and therefore a better spin. ITOd. Shell-Firing. — The diameter and velocity of two pro- jectiles being the same, the retarding effect of the air is inversely proportioned to their weight ; hence a shell has less accuracy and range than a solid shot of the same size. The shot has superior accuracy, lait the shell superior power, as it acts both by impact and explosion. If there be any difliculty in striking a given object, the shot will do so oftener than the shell ; or the shot will cluster more closely about any desired spot. On the other hand, the power exerted by a single exploding shell is infinitely more destruc- tive than that of many shot. The shot has greater penetration, but the shell does not require this property to the same extent, because the former must always perforate entirely to operate with effect, while the action of the latter will be materially lessened in its explosive power, if it does pass through instead of lodging. Hence, it may be assumed that the penetration of the shell is adequate to its special purpose at any distance ivhere shot of like weight are effective ; that is, if the shot pass entirely through, the shell may do likewise and explode in- board ; or it may lodge and work great destruction to the side. 1705. A shell may be made to burst either while in motion or when at rest ; in the first case, each of the fragments will have a forward velocity proportioned to that of the shell at the moment of fracture, and spreading out will act in the same way as a charge of grape; while, if the shell is stationary when it bursts, its effect Avill mainly depend upon the size of the burst- ing charge and the consequent violence of explosion. Shells may, therefore, be considered as having tivo distinct applications ; they may be used as missiles or as mines. As missiles they are most formidable, and most generally used against personnel of an enemy; but as mines they are most destructive against his materiel. The effects of shells depend in part upon the number of fragments produced by the explosion. Shells should be used against ships at all distances where the penetration Avoidd be sufficient to lodge them. They are of no service in breaching solid stone Avails, but are A’ery effective against eartliAvorks, ordinary buildings, and for bombarding. 1706. In firing shells with time-fuzes it is necessary to knoAv the time of flight, in order to regulate the burning of the fuze for the range required. The times of flight can be found with sufficient accuracy for such purposes by obsen-ation ; but they 618 NAVAL ORDNANCE AND GUNNERY. may be rotigbly calculated for low angles of elevation by the formula — • t — \ y" R (in feet) tan a. Where R = range, a — angle of elevation. Example. — An 8-inch shell is fired at an object 1400 yards distant, and for this raDge fom- degrees of elevation is required ; find the time of flight. t = \ y 4200 X = 4.3 second. The times of flight found by the above formula are, however, too short, the resistance of the air retarding the projectiles in their descent. 1707. At ranges from 1000 to 1100 yards, the 3^-second fuze is employed. The 5-second fuze is serviceable between . .1200 and 1400 yards. The 7-second fuze between 1500 and 1700 “ The 10-second fuze between 1800 and 2000 “ At ranges exceeding this, fuzes of longer time are em- ployed. It is best to employ the shortest time fuze that will reach the object, because its combustion is more powerful, and therefore less liable to extinction than the fuze of greater duration. Tlie times of flight and length of fuze for all projectiles, so far as ascertained, are given in the Table of Ranges, Ordnance Instructions. It is preferable, when circumstances will admit, to take up sucli distances as Avill correspond Avith the time c>f flight of one of the regulation lengths. When tiring against ships or earth- Avorks, the fuze should be a little longer than necessary in order to reach the object before bursting; but a little shorter wlien fir- ing against boats or masses of troops, in order to insure its burst- ing in front of them. 1708. Shrapnel Firing. — The shrapnel may be defined as a combination of the shell and the canister, by Avhich the former is made to serve as a case or envelope to the balls of the latter, carrying them to the desired point near the object, and then opening to permit their egress. Its sphere of operation can only begin Avhere the dispersion of the common canister becomes too great, and its effect feeble. With shrapnel the effect produced by the bullets will chiefly depend upon the bursting of the sliell at exactly the required in- stant ; no precise rule can be absolutely laid doAvn as to the dis- DIFFERENT KINDS OF FIRE. G19 tiiDce short of the object at Avhich the shell ought to hurst, as so much will depend upon the yelocity of the shell just before it opens, and otlier circumstances. They are fired with the hea- viest charges allowed for the guns. The bursting of a shrapnel at the proper distance is of the very greatest importance ; if the shell hursts too soon, the whole or greater part of the halls will fall short, the velocity and pene- tratmg power being greatly diminished in consequence ; if the shell pass the object before exjiloding, its effect as a shrapnel will be entirely lost. 1709. The effect of shrapnel greatly depends on the correct estimate of the results that are being produced, and in most cases on the judgment displayed in the constant efforts to improve on the shooting ; when used intelligently the effect is most excel- lent. It is possible generally from the gun to estimate the line and the height of the burst of the shell, but not the distance at which it occurs, and bad practice commonly arises from a too sanguine estimate of effects, judging from the appearance of the smoke of the burst alone ; particular attention slioidd therefore be paid to any visible marks of the bullets grazing; on water, splashes will be seen ; on dry ground, puffs of dust ; and the greater their velocity at the moment of bursting, the greater will be the effect. Shrapnel should be used from 300 to 900 yards with the 12-pdrs., and from 400 to 1500 yards with XTinch. A Avell-delivered shrapnel shell from a heavy gun must sweep away the crew of a pivot or other gun, on a spar-deck not protected by bulwarks. 1710. HiJte-iSla'ajpnel . — The effect of the oblong shrapnel is said to he inferior to that of the spherical, but this has been disproved by practice. At all ranges the effects of the oblong shrapnel are found to be superior to those of the spherical. Such a projectile fired from a rifled cannon, having previous to breaking up a rotatory motion, considerable lateral spread is given to the bullets when released. The charge is usually placed in a chamber at the base, so that on explosion there is no tendency to increase the lateral spread of the bullets, but rather to increase their velocity and penetration. 1711. Grape AND Canister Firixg. — In gi'ape and canister firing, the, apex of the cone of dispersion is situated in the muz- zle of the piece, and the destructive effect is confined to short distances. The shape of this cone is the same as in shrapnel ; its intersection by a vertical plane is circular, while that of a horizontal plane, as the ground, is oval, with its greatest dia- meter in the plane of fire. 620 NAVAL ORDNANCE AND GUNNERY. The greatest number of projectiles are found around tlie axis of the cone, while the extreme deviations amount to nearly one- tenth of the range. ' Grape and canister are effective at short distances against boats, exposed bodies of men, and the aigging of vessels. Grape being larger than canister, are effective at greater distances. Canister can only be used with effect at short ranges, on account of the rapid dispersion of the balls, and from the fact that their velocity is soon lost in consequence of their comparative light- ness. 1712. The fire of canister does not always ^produce the effect anticipated for it, because the object is often thought to be near- er than it really is, and the firing sometimes commences too soon ; also, the danger is often thought to be more imminent than it really is, and consequently proper care is not observed in aiming. On hard fiat ground, the effect of canister depends chiefly on its ricochet. The guns being level, the projectiles will effectual- ly sweep the ground for several hundred yards in front. When the men on the spar-decks of the enemy are exposed, by the heeling of the ship, grape or canister may be used against them, at distances ranging from 200 to 300 yards. Against light vessels a single stand of grape from heavy guns may be used at about 400 yards. 1713. liijled Canister . — It has been believed that the canis- ter practice of rifle-guns is inferior to that of smooth-bores, but the comparative trials instituted by various countries prove that the canister practice of rifle-guns is at least as effective as that of smooth-bores. The smooth-bore practice does not usually extend beyond the dangerous fire of modern small arms, so that generally at all distances where it can act usefully, the canister as well as the shrapnel practice of rifled-guns is superior to that of smooth- bores. 1714. Horizontal fire includes all kinds in which the pro- jectile strikes its object with a velocity due wholly, or nearly so, to the charve. In this fire the ranges are regulated bv alteration in the elevation of the axis of the piece, a fixed charge being generally used with each nature of gun ; this charge is the lar- gest the piece is capable of firing, so as to give very high velo- city to the projectile, and consequently a low trajectory, upon which accuracy of fire and the extent of ground effectively covered by the projectile mainly depend. 1715. Vertical fire includes all kinds in which the projec- tile strikes with a velocity due wholly, or nearly so, to gravity. DIFFERENT KINDS OF FIRE. 621 The usual angle of fire of mortars is 4:5 degrees, ■which cor- responds nearly with the maxiinuni range. The advantages of the angle of greatest range are : 1st. Economy of powder. 2d. Diminished recoil and strain on the piece, bed, and platfonn. 3d. More uniform ranges. When the distance is not great, and the object is to penetrate the roofs of magazines, buildings, etc., the force of fall may be in- creased by firing under an angle of 60 degrees. The ranges obtained under an angle of 60 degrees are about one-tenth less than those obtained wfith an angle of 4:5 de- grees. If the object be to produce effect by the bursting of the pro- jectile, the penetration should be diminished by firing under an angle of 30 degrees. When the object and the mortar are not on the same level, the angle of greatest range, instead of being 4:5°, is 4:5° ± 4- the angle of elevation or depression of the object. Thus, to reach an object elevated 15° above a mortar, the angle of greatest range would be 4:5° -j- 74"° = 524-° ; 'while, if the object was de- pressed 15°, the angle w'ould be 15° — 74-°=374-°. 1716. The angle of fire being fixed at 15° for objects on the same level with the piece, the range is varied by varying the charge of powder. The practical rule is founded on the know- ledge of the amount of powder necessary to diminish or increase the range a certain quantity. The 13-in. mortar with a charge of 3 lbs. of powder gives a range of 850 yards, and every additional 4- lb. increases the range about 180 yards. The elevation being 15°. 1717. A practical rule for finding the time of flight by which the length of the fuze is regulated, is to take the square- root of the range in feet, and divide it by four ; the quotient is the approximate time in seconds. 1718. The greatest dilficulty in firing mortars is to regulate the charges properly ; very great differences are found to exist between ranges obtained under the same circumstances, and these increase with the range, whilst the lateral deviations are much less. The utmost exactness is to be observed in measuring and filling the cartridges, as an ounce of powder makes an important variation in the range. Tables of charges, elevations, and ranges for the 13-in. mor- tar are given in the Ordnance Instructions. 1716. To estimate the distance by the bursting of the shell, where the flames can be seen, multiply the number of seconds 622 NAVAL ORDNANCE AND GUNNERY. that elapse hetvveen it and the report by 1100, and the product will be approximately the distance in feet." (Art. 1636.) 1720. Falliruj Yelocity. — The falling velocity of a mortar- shell at ordinary range may be found with sufficient accuracy for practical purposes as follows : The shell may be assumed to be rising during half the time of flight and falling during the other half ; therefore, if t be the time of flight, and Y the velocity required, the latter will be due to ; thus, if for 500 yards t = lO", Y = gt .’. Y = 32x5 = 160 feet. 1721. Mortars afloat are usually not to be much dreaded ; though mortar-vessels moored in smooth Avater may be A'ery efl'ecti ve. Large mortars should be used for the defence of navy yards, or other important stations on the sea-board ; for, although their inaccuracy of fire may cause many shells to be wasted, the chance of one or tAvo falling upon the deck of any A’essel Avould usually prevent its coming Avithin short range. 1722. Yertical fire is of all practice from ordnance the most uncertain as regards precision. The chief causes of inaccuracy of Amrtical fire are; that the shells having comparatively low velocity, but long times of flight, are peculiarly liable to considerable deviation from wind and other disturbing causes ; that the angles of descent of mortar sliells, fired at the usual angle of 15°, are so great that unless the object be of some extent, au error in range of a feAv yards might render the shell useless ; Avhereas, Avhen a projectile is fired at a Ioav angle of ele- vation, so much ground is covered by it before and after grazing that an error of some yards xmder or over Avould not generally be of mucli consequence ; also, that it is difficult in practice to ensure the requisite care in Aveighing out the charges, or to ob- tain poAvder of uniform quality. In vertical fire, as the object cannot generally be seen, and the piece is usually short, it is very difficult to point the mortar exactly in the same line for a number of rounds ; but if the pointing could be performed Avith the greatest accuracy, irregularities must always occur in practice Avitli projectiles iired at high angles and Avith low A'elo- cities. 1723. Saiall-Arai Firing. — The fire of the rifle-musket is not effective beyond 1200 yards ; the angle of fall, howe\'er, is so great that gi’eat care must be exercised in determining the exact distance of the object. If the ground be favorable, the * At the temperature of 33° the mean velocity of sound is 109'2..'5 feet in a second. It is increased or diminished half afoot for each degree of tem- perature above or below 33°. GUN IMPLEMENTS. 623 projectile M'ill ricocliet at 1000 yards, which increases the dan- gerous space, and therefore the chances of hitting the object. The limit of any fire is determined by the distinctness of vision. The effect of small-arm firing depends much on the skill and self-possession of the individual, for Avithout these quali- ties the most powerful and accurate arms will be of little a\'ail. Section III. — Gun Implements.'^ 1721. Staves. — The staves of all implements are made of tough ash, round, 2 in. in diameter for all lengths of over 150 in.. If in. for all other lengths above 100 in., and 1-|- in. for all below. A tenon is made on one end, f of an in. less in dia- meter than that of the staff. 1725. Sponges. — The sponge complete is 18 in. longer than the bore of the gun for Avhich it is intended. The staif is 2 in. shorter than the implement complete. The tenon is If in. shorter than the head. In the end of the tenon a Avorm is secured by means of a copper pin passing through a hole in its shank and the tenon. The worm, 2 in. in length and If in. in diameter, is made of elastic compo- sition AA'ire of in. in diameter, ta- pering at the points. It is riglit-han- ded in order to act Avhen turned to the right, or AA’ith the sun. (Fig. 360.) The sponge-head is made of poplar or other suitable light wood, and for smooth-bore guns consists of a cylin- drical body 1 in. in length, surmount- ed by a section Avhose surface is similar to that of the chamber of the gun. This section is fin. shorter than the chamber, and the diameter of the head at any point is 1 in. less than the diameter of the chamber, or bore, at that point. For unehambered guns the sponge-head conforms in shape to the bottom of the bore ; the radius of its curve being f in. less than that of the bore, the cylindrical body is retained. * Dimensions and Weights of Gun Implements. Bureau of Ordnance, 1874. Fig. 360. 624 NAVAL OKDNANCE AND GUNNERY. length 1726. Sponge-heads for all rifled guns are 2 calibres in A hole of the size of the tenon is bored througli the axis of the head, and the head is secured to the staff by means of a copper pin in. in diameter, through the cylindrical body. When the head is properly fixed to the staff it bears firmly against the shoulder of the tenon, allowing the end of the worm to project in. (Fig. 361.) Sponge-heads for greater calibres than Xlll-in. smooth-bore and Ylll-in. rifles are built up, hollow. All sponge-heads, when finished, are primed with several coats of boiled linseed oil or varnish. 1727. TAe woollen sponge is made of the shape and size requisite to tit the head, with an allowance of 1 in. in length for tackin2 1.75 9. length over the edge of the base. The wool sheared so as to allow no windaire. IS Fig. 361 . Sponge-caps for guns on covered decks are made of duck, of a size to tit the sponge snugly, lapping 1.5 in. over the base. The mouth is fitted with a draw-string, and a becket is fitted to the other end. These caps are not painted but kept scrubbed. For uncovered guns and all howitzers, the sponge- caps are similar to the others, except that they are long enough to gather around the staff. Ties are fitted to secure them in- stead of a draw-string ; and they are kept painted white. The cap is never put on the sponge unless both are clean and dry. 1728. Bristle sgionge-keads are 1.5 in. less in diameter than the chambers and bores of the gun for which they are intended. The bristles are sheared so as to work easily and leave no wind- age. Three spiral spaces are left the whole length of the sponge- head, in order to bring out unconsumed portions of cartridge ; these spaces are right-handed. Two-thirds of the head is covered with bristles, one-third bare ; the end of the sponge is entirely covered ; there is no worm in bristle sponges. 1729. R.:Vmmeks. — T he rammer complete is shorter than the sponge, by the length of the sponge-head. The rammer staff for smooth-bores is ecpial to the length of the complete rammer, minus one-third the length of the head. The rammer-head for smooth-hores (Fig. 362) is made of ash, birch, beech, or other tough wood, and consists of a cylindrical body and hemispherical neck. The neck is struck witli a radius GU2^ IMPLEMENTS. 625 of 2 in. Tlie necks of raminer-keads nbove 13 in. are cylindri- cal, 'vvitli tlie same radius, and one-third the length of the head. The diameter of the boclj is .25 in. less than that of the hore ; its length, two-thirds that of the Avhole head. The head of a 32-pdr. rammer is 1 calibre in length. I'or every change of calibre of 1 in. there is a corre- sponding change of .25 in. in the length of the head. The rear of the body is bevelled off to the neck, in a curve of 1 calibre. The front end is hollowed ont vuth the same ra- dius, the bottom of the curve be- ing bevelled oli where it meets the hole for the staff, leaving the exte- rior of the hole 2 in. in diameter. An annular sirrface is left around the face of the head, 1 in. in width, for calibres above Xl-in. ; .75 in. 75 Fig. 362 . for all others. The staff tenon is two-thirds the length of the head, its shoulder coming scpiare up to the base of the neck. The head is secured to the staff n by a copper pin .2 in. in diameter through the thickest part of the neck. Eamrner- heads for greater calibres than Xlll-in. are strengthened by copper hands .5 in. wide around the ends of the head and neck ; the copper is Xo. IT American wire-gauge. 1730. Rammer-heads f 07' rifled guns are made of composition (Fig. 363), cup-shaped, 1 calibre in length, with a neck two-thirds the length of the body, and tapering from 2 in. in diameter at the throat to 1.75 in. at the end. The extreme diameter of the head is .25 in. less than that of the bore. The diaplu-agm between the hollow of the head and neck is .2 in. in thickness. The hollow of the head, for a depth of 1.25 in., corre- sponds to the head of the projectile in shape ; the rest is cut away, so as to leave a shell .2 in. in thickness. The head is secured to the staff by two composition pins .2 in. in dia- meter through the neck. Metal rammer-heads for all guns above Tl-in. calibre are lightened kA Fig. 363. 40 by having segments cut out of the body. 626 NAVAL ORDNANCE AND GUNNERY. 1731. Ladles. — The ladle complete is of the same length as the rammer. The staff and head are of the same dimensions, except the length of the staff, which is calibres shorter than the rammer-staff. (Fig. 361.) The diameter of the head is reduced (to make a seat for the scoop) 1 in. in length for calibres above Xl-in. ; 3 in. for all others. The scoop is secured to the head by two rows of copper tacks. The copper used for making scoops is Xo. 11 for calibres above Xl-in., Xo. 13 forXI-in. and IX-in., Xo. 15 for Ylll-in. and 32-pdr.,and Xo. IT for all howitzers (American wire-gauge). 1732. IVoRMS. — The worm complete is the same length as the rammer. (Fig. 365.) The head consists of a round composition shaft, having a worm 2 in. in length at one end, and two straps 8 in. long at the other, the total length be- ing 20 in. At 8 in. from the end of the worm is a shoulder, for a disc of compo- sition .25 in. less in diameter than the bore for which it is intended. It is kept in its place by a key. The staff fits into a socket formed by the straps, and is kept in place __ Fig. 364. by two compo- sition pins pas- sing; througli both straps. Staves. — The casemate ffuns. 1733. Sectional staves for turret and where stoppers and shutters are used, are sectional, with spring connecting joints. (Fig. 366.) One section is permanently fixed to the head of the implement, projecting 12 in. beyond its base. As the length of the imple- ment is arbitrarily fixed, by the neces- sity of having a certain amount of staff beyond the end of the bore when the implement is home, one length is made longer or shorter than the average, ac- I 1 1 iiiha /4. 75 Fig. 365. GUN IMPLEMENTS. 627 cording to necessity. All other sections are 36 in. long exclu- sive of the tenons, which are 3 in. in length, a corresponding socket being fitted in the other end of the section. All detacha- 36 " 1 r;::;]: ^///////^//^ 36 " 1 ° i 36 " ' 1 r— -1: ' Fig. 366. hie sections are interchangeable. Each gun is supplied with three of the 36-in. sections. These, together with the fixed and odd sections, make the length of the different implements. CHAPTEE XL THE MOTION OF PROJECTILES. 173L A knowledge of the motion of projectiles in a non-re- slstinj medium is useful as an introduction to the discussion of the inotion of projectiles in air; the following iiivestigation, in which the resistance of the air is not considei'ed, is therefore in- troduced here. The attraction of gravitation is assumed to be constant and parallel to a fixed line. The Equation of the Path of a Projectile in a Xon- REsiSTiNO Medium. — Let the origin he taken at the. point of projection, and let the axis of y be vertical, and that of x hori- zontal and in the plane of projection ; x and y are the current co-ordinates of the centre of gravity of the projectile. It is evident that this point will continue to move in the plane xy, as it is projected in it, and is subject to no force tending to withdraw it from that plane, u denotes the initial velocitv, a the angle of projection, and t the time reckoned from the in- stant at which the projectile starts from 0. Y 0 Fig. 367. * By Professor J. M. Rice, United States Xavy. THE MOTION OF PROJECTILES. 629 Tlie equations of motion are d'x df and d^ df ac 2 eleration parallel to tlie axis of cb = 0 (1), acceleration parallel to tlie axis of y = — ^ . .(2). Integrating equations (1) and (2), we obtain = constant = cos a. dt and = constant — sin a — gt (3). Integrating again, X = ti cos a.t (4), and y = u sin a.t — ^ gf (o). Eliminating t between (4) and (5), we obtain the equation of the path or trajectory 2 / = £B tan a — ^ j— (a) 2 u cos a ^ or, putting li = , X' y = X tan a — s— (6), ^ 4A COS' a ^ h is evidently the height from which a body must fall to ac- quire the velocity u. {b) is the form in which this equation is usually employed. It is evidently the equation of a parabola. To FIND THE Vertex of the Trajectorv'. 1735. Multiplying (b) by 4A cos'’ a and transposing, we have X' — 4/i sin a cos a. x = — 4/i cos^ a.y. Completing the square by adding 4A'’ sin' a oof a, we have {x — 2/i sin a cos df = 4A' sin' a oof a — - 4A cos’ a.y, or (x ■ — A sin 2 af = 4A cos’ a (A siir a — y). If we pass to a new system of co-ordinate axes parallel to 630 NAVAL ORDNANCE AND GUNNERY. the old, by patting x^ — x — h sin 2 a, and y, = h sin'^ a — y, we obtain — 4A cos'* a.y„ the equation of a parabola referred to the vertex and principal axes. Tlie co-ordinates of the new origin, which is also the vertex, are x^ — x — a?, =: A sin 2a (6), and = y = h sin'* a (see diagram).. . . (7). Since the curve is symmetrical with reference to S2l, OR, which is called the range on a horizontal plane, is equal to 2x ^ ; but 2a?„ = 2A sin 2a = ^ (8), R denoting the range. 2A sin 2a is a maximum when 2a = ^, or a = y or 45°. That is, the greatest range is obtained, when the angle of ele- vation is 45° ; its value is 2A, and the corresponding maximum height is [see equation (7)]. When a is 45°, the range is 2i therefore four times the greatest height. Again, since sin 2a = sin (180° ■ — 2a) = sin 2 (90° — a), the complement of any angle gives the same range as the angle itself. To FIND THE TeVIE OF FlIGHT OF A PrOJECTFLE ON A HORI- ZONTAL PLxVNE. 1736. To find the time of flight, we divide the range [2A sin 2a] by tlie hoiizontal velocity \u cos a] thus, 2A2sinacosa 4Asina 2 sin a t = = (9). ?fcosc u g ^ ' This equation gives the time of flight in terms of u and a ; to obtain t in terms of R and a, which is sometunes desii’ahle. THE MOTION OF PROJECTILES. 631 we put a? = and y =: 0 in equations (4) and (5), wliicli then become R — u cos a. t and 0 =w6\na.t — ^ gf. Eliminating u, we obtain R tan a, = ^ gf^ or R tan a 9 ( 10 ). , 173Y. To FIND THE Elevation necessary to cause the Trajectory to pass through a Point given by its Co-or- dinates x' AND y', THE INITIAL YeLOCITY BEING GIVEN. x'^ We have y' = x' tan a — 77 7 -, to find tan a : ^ 4A cos a ’ putting tan a = z, we have — ^ ^ sec'’ a = 1 -I- tan'’ a = 1 4-s'’ ; cos a ' ‘ ’ substituting in the above equation, it becomes or 2 44 4A , 4A^ 4Ay' 4Ay' — ^ ^h^ — ^hy'—x'^ ( 11 ). If y' and x' have such values as to make 4:hy' -f- x'"‘ < 4A* there will be two real values of z, but if 4Ay'+»'“> 4A’ the values of z will be imaginary ; in this case it is therefore im- 632 NAVAL ORDNANCE AND GUNNERY. possible to so change a as to make the trajectory pass through the point. If (12), tliere will be one real value of z. Making x' and y’ variables in ecpiation (12), we have = 44= _ = 44 (A _ (1.3), the ecpiation of a parabola having its vertex on the axis of y at the height 4 above the origin. Since the co-ordinates of any point in this curve will give, when substituted in equation (11), a single value of 2 , all the tra- jectories thus formed totich^ but clo not cut the curve of ecpia- tion (13) ; this curve is called an envelop. 1738. To FIND THE Yelocity of a Projectile at any Point OF its Path. We have (|) = ()|) + 3- If substituting the values of and from equations (3) we de- duce qf — COS' a -|- [it sill a — gtf ; expanding and reducing — u‘ — 2y (lit sin a — ^gf), therefore, by equation (5), v' — tt" — 2yy. If we put for its value 2y4, we obtain v" = 2g {h -y) (14). 1739. To FIND THE DIRECTION OF THE PATH AT ANY POINT, we differentiate equation (b); thus dy dx = tana 24 cos^ a — tan c6 ( 15 ), 0 being the angle of inclination of the curve to the axis of x. THE MOTION OF PROJECTILES. 633 dy Putting ^ = 0, Ave have x = 2/i sin a cos a — h sin 2a, for the abscissa of the summit, or highest point of the path. The corresponding value of y is h sin“ a. which is therefore the greatest height the projectile attains ; it is also, as might have been aiiticipated, the ordinate of the ver- tex ; see equation (7). IT-iO. To FIND TiiE Co-ordinates of the Point where a Pro- jectile WILL STRIKE AN INCLINED PlANE PASSING THROUGH THE Point of Projection, the Range on the Inclined Plane, and THE Time of Flight. Let y—x tan (3 be the equation of the line OP, which is the inter- section of the inclined plane with the vertical jilane of the path of the centre of gravity of the body. 0 FIG. 368. Let a?, and y, be the co-ordinates of P, and let OP—r, the range ; then X, = r cos 13 and y, — r sin /3. Substituting in equation («) we have . _ r'cos"/? r sin [3 = r cos f3 tan a — ^ 5 — : •lAcos a’ whence r — 0, ov r — and reducing r — r cos (3 — X,— and r &in (3 = y, 4A cos° a (cos f3 tan a — sin f3) cod (3 ^ 4/i cos a sin (a — ff) cod (3 47; cos a sin (a — (3) cos (3 ’ 4/t COG a sin /3 sin (a — [3) cos^ (3 ( 14 ), 634 NAVAL ORDNANCE AND GUNNERY. If the inclined plane cnt the path of the projectile below the axis of £c, (3 will be negative. The time of flight is found by dividing by u cos a, the hori- zontal component of initial velocity ; thus, 4A cos a sin (a — j3) ~ u cos /3 cos a ’ putting for h its value — and reducing, 2wsin (a — S') t = (15). (J cos p ^ ’ 1741. The resistance of the air to the motion of spherical solid shot evidently increases with the square of the diameter, while the weight of the shot is proportional to the cube of the diame- ter. This resistance is therefore less effective with large spherical shot than with small shot ; but it is nevertheless so considerable, even in the case of the heavy shot now in use, as to render the above formulas inapplicable in practice, except to cases of low initial velocities not exceeding 400 ft. per second. It increases rapidly with the velocity, being nearly proportional to the cube. 1742. Equations (8), (9), and (10) are sometimes used in mor- tar practice. If in equation (10) we put ^=32 ft., we have ap- proximately t = ^ \/E tan a (16). If a is 45° t = (17). Example 10 will serve to show that the results obtained by these formulas are sufliciently accurate for some purposes, when the velocities are small. The charge of powder used in the ex- periments which furnished the data of Ex. 10, was a little less than two pounds in the flrst case, and a little more than two pounds in the second case. The following example, taken from Owen’s 2rodern Artillery, will show how entirely untrust- worthy these formulas are in the eases of ordinary practice. The range of a 32-lb. shot, tired with an initial velocity of 1600 ft., and with an angle of elevation of 4°, was 5070 ft. ; as comjjuted by formula (8) it should be 11,130 ft. THE MOTION OF PROJECTILES. 635 Examples. 1. The horizontal range of a projectile is 1000 ft. and the time of flight is 15 seconds. Eequired tlie angle of elevation, velocity of projection, and greatest altitude. Ans. a =: 74° 33' 09". V = 250.29 ft. II = 904.69 ft. 2. Find the velocity and angle of elevation of a ball that it may be 100 ft. above the ground at the distance of one quarter of a mile, and may strike the ground at the distance of one mile. Ans. a = 5° 46' 05. V = 921.566 ft. 3. What must be the angle of elevation of a body in order that the horizontal range may be equal to three times the greatest altitude ? What, that the range may be equal to the altitude? 4. A body is projected at an angle of elevation of 60°, with a velocity of 150 ft. ; And the co-ordinates of its position, its direction, and velocity at the end of 5 seconds. 5. A body is projected from the top of a tower 200 ft. high, at an angle of elevation of 60°, with a velocity of 50 ft. ; And the range on the horizontal plane passing through the foot of the tower, and the time of flight. 6. A body, projected in a direction making an angle of 30° with a plane whose inclination to the horizon is 45°, fell upon the plane at the distance of 250 ft. from the point of projection, which is also in the inclined plane ; required, the velocity of pro- jection and the time of flight. 7. At what elevation must a shot be fired with a velocity of 400 ft. that it may range 2500 yards on a plane which descends at an angle of 30° ? 8. Find the velocity and angle of elevation that a projectile may pass through two points whose co-ordinates are a?=300 ft., yr=60 ft., a?'=400 ft., and y'=40 ft. ; also find the horizontal range, greatest altitude, and time of flight. 9. Show that the maximum range on an inclined plane, of a projectile having a given initial velocity w, is — in which (3 denotes the inclination of the plane to the horizon. 636 NAVAL ORDNANCE AND GUNNERY. 10. The observed time of flight of an 8-in. mortar shell was 16*.0. the range being 3760 ft., and the angle of elevation 4:5° ; find the difference between this observed range and that obtained by computation Avhen the formulas of the preceding articles are employed. Find the difference when the range was 5S79.4: ft., ancl the observed time 20b8. Ans. —0.7 and —1.6. The Motion of a Projectile in Air. 1743. A complete and satisfactory solution of this problem has not hitherto been published ; in fact, the laiv of resistance of the air, which must be found by experiment, is not yet fully established. Some recent experiments made in England by Professor Francis Bashforth show that the resistance of the air to the mo- tion of a projectile is approximately proportional to the cube of its velocity. The direction of the resistance of the air at any point of the path of a projectile is evidently that of a tangent to the path draivn through the point. The following mathematical investigation is, with some changes in the notation, substantially that of Professor Bash- forth, and the accompanying tables which ivill be found in the appendix to this work are reprinted from his treatise" ; by means of these tables the trajectory of a projectile and its time of flight may be approximately found. 1744. R denoting the resistance of the air, and P the I'elo- city of the projectile, the cubic laiv of resistance is expressed thus — • R = ^l T\ In this expression % is a cpiantity to be determined by ex- periment; it is not the same for all Auilues of P, and has there- fore been tabulated. The following notation is adopted for the pui’pose of simplifying the formulas : Let u denote the horizontal component of the velocity, v the * A Mathematical Treatise on the Motion of Projectiles, founded chiefly on the Results of Experiments made icith the Author’s Chronograph. By Francis Bashforth, B.D. Aslier & Co., Loudon, 1873. THE MOTION OF PROJECTILES. 637 vertical component, and tlie inclination of the curve to the axis of cc, then u — V cos (j), and -y — sin (1) Eliminating V, and 'wi’itingy* for tan we have ^ = tan0 =^; to (2) differentiating, , tidv — vdti (3) Again, squaring and adding equations (1), y — tt" -\-v” — td (1 + a') (i) The equation s of motion are, in this case. d'x du 0 7 1^3 — — 2hV^cos(b df dt (5) and d'y dv m TTa ■ s ^-^--25Fsin<^-y.. (6) which may be written thus — ^ _ 25 Vht dt (7) and d'V -r7~2 , - — — V V — q dt ^ (8) Eliminating V, ndv — vdu dt - hence 1 11 1 or [equation (3)] dt S' IT (9) Combining equations (7) and (d), (10) and, eliminating dt between (9) and (10), 638 XAVAL ORDNAXCB AND GUNNERY. This equation involves but two variables, and is readily inte- grated. Denoting by the value of u corresponding to ^ = 0, or in other words the velocity at the highest point of the curve, and integrating, we obtain or therefore 1 = i { 1 - ^(3j, +^) * Putting r a ’ 1 u ( 11 ) ( 12 ) but [equation (9)] ^ therefore, eliminating or dt u, dp t ( 11 ) . . dx Again, dividing equation (13) by the identity u — THE MOTION OF PROJECTILES. 639 we obtain 'IC' dp gdx , or dx and, substituting tlie value of obtained from (12), and inte- grating, we have x= — Jp dp jy ll-r(3i^+y)} .(15) (15) Also, by means of the identity dy — pdx, we obtain from y =- ^ >i> pdp .(16) 2^ \i ^ The quantity ^ for “which y is substituted in equation ^1)77X>\C ^ (12) may be written thus, ; the numerator denoting the resistance of the air at the vertex of the trajectory, and the de- nominator the weight of the shot. Putting tan — p and tan — p' , dp — sec" (j) d = {l-\- p^) d

' (1 +y) d0 ^ p ~ g y X — — (1 +y) d0 _ _ V y ^ '0 y^-— / (p +p°) __ ^ J 0 (^P +P')> ^ ^ ] ] ] 4>' 9 not less than 60° or 45°, for values of y = 0.00, 0.01, (i. 02.. .0.18, O.iO, 0.2, 0.3, 0.4... 4.9, 5.0. The value of d<^ generally used Avas the cir- cular measure of 1°, but Avhen 1 — y (3yj< became small, the successive values of — ; — ^ Avere subiect to rapid i-r(3i^+y) ^ ^ variation ; in such cases intervals of ^° Avere used, and the re- sults have been given in preliminary tables (see Appendix). By the ordinary rule of proportional parts, or, Avhere great accuracy is rerpiired, by interpolation, it Avill not be difiicnlt to find the values of X, Y, and T for A'alues of y and (p intermediate to those given in the tables. Examples of the Methods of finding the Xumerical YaLUES of X, Y AND T, y being GIA'EN. From the tables, page 71, Appendix: X ~\'°-X T= .20430 - .09348 = .11082, 0.7 Jo 0.7 Jo r T - Y T= .013448 - .002299 = .011149, “■’J.O “•■’J4 .11027, r T = .07836. Suppose it Avas required to find the value of =A]>(u.]; X 0.41, = .004059 + (.006548 — .005196) X 0.41 = .004059 + .001352 X 0.41 = .004059 + .000554 = .004613. In the same Avay X^ ^ J * In tills example both limits are negative. and T may be found. 3.2 J 3 THE UOTIOH OF PEOJECTILES. 641 1716. In order that the tables may he nsed for the solution of problems, we see from the above examples that y must first be determined numerically* having found its value, we turn to the corresponding table, and obtain [see Fig. 369] OM=^ X 1 “ JIA = ^ r 1 “ g yjo’ g /Jo and the time in OA = ~ T , for the ascending branch. Kow for the descending branch we have for the co-ordinates of the point P' , where the direction of the curve is inclined at an angle /3 to the horizon, /3 being negative. an ' =^Xy g y J ^ , N'P' = ^ X/ 0 g 1 and the time in AP' = — X/~l^ . g r Jo To FLXD THE RaNGE OX A HoKIZOXTAL PlAKE. / A N Having computed OM, we make A2£ = N'P', whence By the help of the tables /3 can be found, and this value of /3 must be used in calculating 2Ip. Suppose it were required to tind the height at which the shot would strike a vertical target placed at the distance OL, and the time of flight. Here we have See article 1748. 41 642 NAVAL ORDNANCE AND GUNNERY. ML^ LO - OM xy , g rJo’ f = (ZO-OJ^)A, wliich gives (3 by the help of the tables. The value of /3 so found must be used to hnd X'P', whieh subtracted from AJ/, computed by the formula on page 641, gives the required height. W e must proceed in the same way if it be required to Hnd where the shot wdll be at a given time. may be obtained by putting (p = a in equation (19) below (a denoting the angle of projection) ; replacing and substituting the value of -jq, we can obtain from the same equation the value of U(j, {(p being known or assumed). 1747. Functions belonging to the descending branch are usually distinguished from those belonging to the ascending branch by a prime ; thus, cp' denotes the angle made by the de- scending branch of the curve with the horizontal plane. The symbol f-s is sometimes used to denote feet j)er se- cond. The relation between the horizontal component of the velo- city and the corresponding velocity in the curve is expressed thus : cos (p — or X and, consequently (a being the angle of projection, and ^ the initial velocity), V cos a = u. 1748. To DETERMIXE y. 2hu ’ We have y = — ^ (by definition, page 639) ; (17) Now, it is obvious that b must increase directly with the trans- verse section of the projectile, and inversely with its weight ; that is, it must be proportional to — , c denoting the calibre of the projectile; we therefore put THE MOTION OF PROJECTILES. 643 % =^s(»y in which K has been determined experimentally for snch ve- locities as are likely to occnr in practice ; the factor is introduced to save space in printing the tables. From equations (11) and (18) we obtain by eliminating 25 1 _ 1 3 tan 0 -j- tanV u,“ uj ' gw (1(JOO)“ (19) or /loooy fiooox \ w J ~~ V u, ) «/> K £= g' ^ .( 20 ) and introducing the value of from (20) in (12) and reducing, we have K ^ g_^ { ) -\ . — (3 tan 0 — tan ^) \ / g w ^ .( 21 ) X. Loir — is found in Tables I and II, and g Log (3 tan (p + tan® (f>)= Log in Tables III and Y. Examples. 1749. A 16-pounder fires an ogival-headed shot 16 lbs. in weight and 3.54 in. in diameter, the angle of projection being 2°, and the initial velocity 1358 ft. per sec. ; find the trajectory and time of flight. Putting IF = , and = (3 tan -j- tan® (p), (21) be- comes 644 NAVAL ORDNANCE AND GUNNERY. 1000 Kc^ g • to --P. g w u^ = u^ = Y cos 2° = 1358 cos 2°, w = 16 lbs., and c = 3.54 in. 1.358 ar. co. 9.86710 2°, sec 10.00026 ( 22 ) Log 9.86736 =0.40002 3 Log 9.60208 {v = 1358) Log 0.51793 (Table I.) K 9 c = 3.54 2 Log 1.09800 ar. CO. 8.79588 w = 16 K — ■ - Log 0.41181 Log 0.41181 g V) ^ ° P, (Table III.) Log 9.0203S 0.27051 Log 9.43219 / loop ' ^ V ) 0.67053 Log 9.82642 y - 3.85 Log 0.5S539 The value of — (for v = 1358), employed in the above computation, is too small ; a more accurate result may be ob- tained by taking the value corresponding to the mean of the initial velocity (1358), and the value of obtained from Loi ( 1000 \ = I I found above, thus : V -Wo / Io,(i^)-=0.S.6., THE MOTION OF PROJECTILES. 645 whence = 1143 ; hut u ^— 1357 i ("^^0+ '^ 2 ) = 1250 ; corresponding correction of Log — = -|- 0.01077. K & ^ — . - (1250) Log 0.42258 g w ^ ^ ° 0.27730 Log 9.44296* /1^0\ ^Q_4QQQ2 0.67732 Log 9.83079 y = 3.91 0.59179 . - = 1139. X 1 = 0.04118, and X \^x' = yY .X 1 = 1659.7 ft. 3«S -Jo - Jo denoting the angle of incidence, vre hare i:=^]r”p]:=por- V In the above example, y = 3.017 and y'= 2.822, 1 also hut Y — Y 2.622_Jo and Y 1'= 2.822_|o 2.822— I 0 = 8 ° °= 0.006910 = Y' 1*^, 5 2.822 Jo = 0.008329 - 0.006788 = 0.001511, 0.000122. 122 ’ — 8°. 079 the angle of incidence, loll * Bangs = x + a?' = 3559.7 + 2801.9 = 6361.6. In a similar manner rre obtain time of flight = 6". 58. 1752. A more accurate solution of the problem mar be ob- tained by dividing each branch of the trajectory into successive portions, and using a mean approximate A’alue of K for each por- tion ; the final values of a?, y and t will each be equal to the algebraic sum of the corresponding partial values thus obtained.. It will be convenient to change K at points of the curve where its direction is inclined to the horizon some entire number of degrees, because the values of Y, Y, and T are given for all those cases in the tables.* 1753. It will be found sufficient for many practical purposes to neglect the effect of gra'vity, and treat the motion of a shot as if its path were a straight line ; this will suffice for experi- mental pui’poses when it is desired to find the loss of velocity, or the time of flight for a limited space, the initial velocity being high. The less the shot is affected by the resistance of tlie air the more accurate will be the results; therefore this * For an example of tliis method, see Professor Bashforth’s Treatisa 648 NAVAL ORDNANCE AND GUNNERY. method will apply better to pointed elongated shot than to spherical shot, and better to solid shot than to shell of the same external form. The equation of motion for the cubic law of resistance is d'‘s dv 3 = - dv or — — % dt. Suppose that v — V when ^ = 0, 1 V then' =-2i F e/0 di , integrating and substituting value of 2d (page 643), ^ ~ -TVS = I - -—3 V V w (luutt) or c’ ^ _ 500 I ^lOOOy ^ 1000 w K [\ V ) \ r y f which connects t and v. d's dv . ds V S? = * ’ di = di dv _ vdv dt'~ ds' ■C) whence and therefore THE MOTION OF PROJECTILES. 64:9 or o’ (1000)’ j /lOOOx K I V -y y 1000 \ ~T^J .(3) ■which connects s and v. If in the equation i ^ = 2ls, -we substitute for — , ^ V y ’ as V ■we have and integrating, we have w’hich connects t and s. ^f we divide bj we obtain t — y-\- hs‘ P 4.U 1 V i — P = 2^5, V V 1 1 _ 2 ^ V y' ~ s •(F .(5) which connects v, t, and s independently of 2J, the coefficient of resistance. 1754. In determining the velocity of a shot it is usual to measure the time in which a given short range is described, and then, dividing the space in feet by the time in seconds, the result is adopted as the approximate velocity at the middle point. If the cubic law of the resistance of tlie air be supposed sufficiently near the truth, this may easily be shown to be strictly correct for any range, so long as the path of the shot may be considered to be a straight line. We have seen that when V is the initial velocity and v the velocity at the distance s, then ^ p+ 2Js, or if v' be the velocity at the distance then 650 NAVAL ORDNANCE AND GUNNERY. Also time in seconds s by equation (d), y+ i-S tlie true velocity at the middle point of the range s. } 1755. Inasmuch as the resistance of the air does not vary strictly as the cube of the velocity, Avhen formulae (2), (3), and (d) are used for considerable differences of T^and v. it is necessary to use several numerical values of K. But as this would be a troublesome operation to pei'form in each case, general tables of the values of ^ j “ \ spherical and ogival-headed shot [Tables IX and XI], and also of the values of | for spherical and elongated shot [Tables VIII and X], have been computed. It is manifest that these quantities depend upon v and V, which are quite independent of the nature of the shot, while K is a eoefficieut dependent on the fonn of the projectile. 1756. Suppose the initial velocity to be V, and that the velocity falls from Y to t\, in space s,, and in time t , ; from t\ to -u, in space s^, and in time t ; from v„ to v, in space ^ 3 , and in time ... and from to v„, in space and in time t„. Let A], IC, JY ■ ■ -K„ Le the particular values of K due to the mean of the velocities Fand -y,, y, and r,, and y„_, and r„. Then we have from equation (2) _ 500 j /ioooy_ /loooy ) w * ~ A] ( V n, / V F / ) ’ ^ ^ ^ ( / iooo y_ noooy ] w K„ \ \ v„ J V y, / ' ’ -zw ' ~ A", I V ^3 / \ v„ ) \ ' etc. etc., THE MOTION OF PROJECTILES. 651 _ ^ j |^ 1000 \^_ /^ lOOO ^ m “ K Adding these equations, we have W 5002 1 s /loooy U vj / loop y \ Vr,., J .(I.) Proceeding in the same Avay with equation (3), we have (loooy j 1000 w G W a; (loooy IC 1000 1000 } 1000 ■Wo etc. etc. therefore — = (lOOO)"* 2 ^ 1000 1000 (II.) In calenlating the nnmerical values of the right-liand mem- bers of the above equations, V Avas taken ^'or elongated shot) = 1700 /’-s; V, = 1690 ; v., = 1680 ; = 1670, etc., and A) the coefficient corresponding to the velocity 1695 J-s, to 1685, to 1675, etc. Tables of the values of — ^ and — s were thus formed corresponding to a loss of eAmry ten feet in (f (? the velocity. By interpolation, the values of — and of — 5 %0 which have been given in the tables, were then found for every foot lost in velocity. ExxVmples of the use of Tables YIII, IX, X, and XI. 1757. (1) Let it be required to find in what range an 11.52- inch ogival-headed shot Aveighing 600 lbs. Avould have its velocity reduced from 1400 to 1300/‘-.s. Let s denote the required space, then = 1865 - 1348 = 517, ^9 = = 2837 ft. (11.52)= 517 is the difference of the ranges opposite 1400 and 1300 y-s in Table YIII. 652 NAVAL ORDNANCE AND GUNNERY. (2) Let it be required to find in what time the velocity of the same shot would be reduced from 1400 to 1300 f-s. Here —t — 1".258 — 0".875 = 0".383, the difference of the w times opposite 1400 and 1300 f-s in Table IX. Hence t = 1L732. (3) If, on the other hand, the initial velocity being given 1350 it was required to find what would be the loss of velo- city in 1500 ft., w'e should have given (11.50) 600” - 1500 = 331.8, the reduced range. How opposite the initial velocity 1S50 f-s in Table VIII we find 1599, to which must be added the reduced range 331.8, making 1930,8 ; and corresponding to this we find the velocity 1288.2 by the same table; hence the velocity of an 11.52-in. 000-lb. elongated shot would fall from 1350 to 1 288.2 /-« in 1500 feet. (4) In like manner, if it was required to find how much the velocity of the same shot wonld be reduced in half a second, its initial velocity being 1334 f-s, we must find the reduced time, — ^ = .2212 X 0".5 = O'kllOG ; adding this to 1".120, the num- %o her opposite the velocity 1334 f-s in Table IX, we obtain l'’.230G ; and opposite 1".230G we obtain by proportional parts 1306.6 f-s, which is the velocity the shot will retain at the end of half a second. (5) Suppose a 15-in. spherical shot weighing 452 lbs. to be fired with an initial velocity of 1400/-S at a target 500 yards off; to find the striking velocity. Here e = 14.88 in. ; then w (14 88)^X15 - 45200 = the reduced range ; opposite the velocity 1400 in Table X we find 1501, and adding 734.7 to this, we have 2235.7, opposite which, in the same table, we find the velocity 1215.8_^/-s, which is the required striking velocity. THE MOTION OF PROJECTILES. 053 Table YIII was deduced from experiments made with ogival- headed shot struck with a radius of diameters. For high initial velocities and low angles of projection, ta- bles YIII to XI may be used to find approximately the time of flight and trajectory of the shot ; thus, suppose V the initial velocity, and v the velocity when the shot has described the space 01^' (Fig- 369) in time t, the effect of gravity not being considered; then, by tables YIII to XI, it is possible to And OP' and t. If X, y be the co-ordinates of P' at time then X = OP' cos a \ y = OP' sin a — \gt' j become known because OP' and t are known approximately. Table XII will be useful in finding the values of \gf. The Laav of Penetration of Projectiles.'^ 1758. A Commission, appointed by the French Minister of War, carried on experiments at Metz, in 1831 and 1835, Avith a vieAV to determine the hiAv of penetration of spherical shot into various kinds of wood, masonry, and earth. Tlie conclusions arrived at Avere, first, that the resistance of the same substance to spherical shot of different diameters Availed as the square of the diameter of the shot ; and, secondly, that the resistance of diffrerent substances to the same shot varied as a -)- /3 X (velo- city)“, Avhere a and j3 Avere constant for each substance. If, there- fore, G be the diameter of the shot in inches, w its Aveight in pounds, and v its velocity in feet per second, then the resistance to the shot Avill be expressed by (a -|- (id) — {X gv"), and the retarding force hj —d {X gv'). The following are the values of A, g, and — calculated from the values a and j3, as given by Didion,f and adapted to English measures. Baslifortli On the Motion of Projectiles, London, 1873, p. 74. t Didion, Traite, pp. 301, 303, and 304. 654 NAVAL ORDNANCE AND GUNNERY. Substances. A Oak, Beech, and Ash 2329.4 .004328 734 Elm 1787.5 .003322 734 Fir and Birch 1296.0 .002408 734 Poplar 1217.7 .002263 734 Sand, mixed with Gravel 486.0 .009031 232 Eartli, mixed with Sand and \ Gravel ( 670.3 .012456 232 Clayey soil 1167.5 .003799 554 Earth from an old Parapet 782.0 .004360 424 Dam]) Clay 297.2 .002209 367 Moistened Clay 102.4 .000762 367 Masonry of good quality 6166.9 .008595 847 Masonry of medium quality 4915.7 .006851 847 Brickwork 3530.4 .004920 847 1759. Suppose that is the striking velocity of a spherical shot, and that Avheii it has penetrated a distance s, its veloci- ty is V ; let S denote the value of s when the shot comes to rest, that is, when v — 0. AVe have (If vdv ds (ld_ w (A -j- /X v) ; or or w ^ f-, , f '■ W’ S = ^ wloge’“ -r— ^ — lo2r„ s= 2ticg loo- (1 2/xcVlog,/ CHAPTER XII. NAVAL OPEKATIONS ON SHOKE.'^ Section I — General Considerations. 1760. Considerations. — Tlie application of a naval force to tlie purposes of littoral warfare can only be considered as inci- dental to the general purposes for Avhicli the navy is created, and the character of the operations is necessarily limited by the char- acter and strength of the force. The squadrons Avhich the navy might collect ivould seldom be able to land a sufficient number of men to cope successfully ivith the forts or troops of any civi- lized nation with whom ive might be at war. When they have been employed by foreign nations against each other, or against ns, the operations have been desidtory and generally attended Avith deplorable results. 1761. The landing of seamen would rarely be resorted to Avhen opposed by good infantry, or Avhen the object to be attained Avould take them very far from their base of operations. It would be uuAvise, generally speaking, to expose them Amluntarily to measure force in the held Avith disciplined infantry and caval- ry. When necessity leads to such a measure, it should be based on the unquestioned superiority of the sailors and marines, both in numbers and appointments. Exceptional cases occur Avhere the strength of a ship or squadron may be landed Avith impor- tant effect, as AA'hen the rights of the ffag, of civilization, or of humanity require the use of a naval force for Avant of other means. The offences of savage nations or islanders, or of a pira- tical people, may be instanced as cases requh’ing punishment or intimida,tion. 1762. Should it be judged expedient, hoAvever, to prosecute this desultory kind of Avarfare, the commanders employed in it Avill do well to consider that a descent ought never to be hazarded Compiled by Ijieutenant J. C. Soley, United States Navy. G36 NAVAL ORDNANCE AND GUNNERY. into fin enemy’s country vitliout having taken proper precau- tions to secure a retreat; that the severest discipline ought to be preserved during all the operations of the campaign ; that a commander ought never to disembark but on a well-concerted plan, nor commence his military operations without some imme- diate point or object in vieAV ; that a re-embarkation ought never to he attempted, except from a clear, open beach, where the ap- proach of an enemy may be seen and the forces covered by the fire from the ships. 1763. The Base. — I n all naval operations on shore, the first point to consider and fix should he the base of operations. Whenever it is possible, this base should be the sipiadron ; but Avhen operating in shallow waters, the largest possible ship or ships, whose draught will admit of it, should accompany the boats and keep up a constant communication with the forces on shore, so as to be ready at all times to forward with dispatch supplies both of provisions and ammunition, and to send for- ward reinforcements if required. 1761. Preparations. — B efore landing, many points must pre- sent themselves for the consideration of the commander-in-chief : the means of approach, the opportunities for landing, the nature of the ground, the possibility of maintaining communications Avith a suitable base, the character and numbers of the opposing force, the possibility and probability of accomplishing the ob- jects of the expedition, and the safe Avithdraival of the forces. 1765. Taking it for granted that all the preliminary drills haAm been thoroughly taught, and that the men are fully acquain- ted Avith the manual of the hoAvitzer and Avith the skirmish drill, and have some knoAvledge of battalion drill, the first consider- ation is the means of approach. Every care should be taken to keep the men fresh for their Avork ; and to this end, the boats containing the landing-force should be tOAA’ed to the place of dis- embarkation by the steam launches and cutters of the fleet. 1766. The officer in command of the landing-force should be furnished Avith accurate information of the depth of Avater and the dangers of naA'igation. Care must be taken also to get as much knoAvledge as is possible of the character of the ground and the opportunities for landing. Generally speaking, an open beach Avhich may be SAvept by the fire of the shipping and Avill offer a firm footing, should be selected. Judicious means, Iioaa-- ever, must be used to get the force landed Avithont opposition ; aAmiding it either by keeping out of sight, or, if seen, 1)a' pulling rapidly to some point Avhich may be more readily reached bv the boats than by the party on shore, or by di\-idin'g the force and making false attacks upon different points. NAVAL OPERATIONS ON SHORE. 657 1767. If, however, such attempts are unavailing, then it only remains to land promptly in the face of the enemy ; and to this end, that part of the beach must be selected where the footing is most likely to be firm, the bank generally shelving, and the bot- tom freest from stones and mud, least exposed to tlie surf, and most especially where no cover of any kind for the enemy exists within some hundreds of yards from the shore. It is also of the utmost importance to keep up communication with the base, and for this purpose some vessels should be stationed to cover and protect the boats, and also to furnish assistance to the party on shore in whatever way it may be needed. Section II — Landing. 1768. Details. — Before landing, the station of each boat should be fixed, and every officer should be made acquainted with ttie details of the organization, and particularly with his position after landing. The small-arm men should be formed into companies of forty men, with four petty officers, and armed Avith breech-load- ing rifles and bayonets ; each company to be commanded by a lieutenant and two other officers. The howitzer crews should be composed of twenty-one men, each man being armed with a cutlass and breech-loading pistol. 1769. Each sliip landing two companies should also furnish twelve pioneers : four with a saw and axe each, four with a pick- axe and spade each, four with small crowbars and sledge-ham- mers each, or such intrenching or other tools as the nature of the expedition may require ; the men should be equipped ivith those tools to whose use they are most accustomed : carpenters with saws and axes, firemen with intrenching-tools. Vessels fumishing a smaller contingent of infantry should furnish a pro- portionate number of pioneers. An armorer, avIio ivill join the pioneers, should be sent with each landing party, and furnished with cleaning-rods, screiv-drivers, and gimlets. The ship’s bugler and the drummer and lifer should be sent with the men. 1770. Every man in the command should liave a canteen and haversack, and a blanket, folded and slung over his shoulder. 1771. Each division of boats should carry a distinguishino- flag; scaling-ladders, intrenching-tools, and other implements should be cariied by designated boats. 1772. If landing in a heavy surf, the ammunition should be put into small powder-tanks ivitli the lids ivell screived doivn. 658 NAVAL ORDNANCE AND GUNNERY. and the howitzers might be rafted on shore if they could not be carried safely in the boats. Fig. 370. 1773. Landing. — Should the distance to the point of landing be considerable, the boats should be towed to within a suitable distance of the beach, being careful to keep out of range. On ar- riving opposite the place of disembarkation, the tow-ropes should be cast off and the line fonned preparatory to landing. The boats containing the heavy howitzers should be on the extreme flanks, next the light howitzers which are to be landed, and the main body of infantry in the middle, with the skirmishers in the centre. There should be a reserve force of howitzers and infan- try ready to be dii’ected to either flank, or to reinforce any par- ticular part of the line. The howitzer divisions should be form- ed in echelon, so as to deliver a cross-fire on that part of the beach where the landing is to be made. IVlien all these disposi- tions have been made, the boats should pull in for the landing- place. 177L It should be borne in mind that the force will be at the greatest disadvantage when disembarking in the face of a strong opposition ; for in using all the celerity that is practicable with NAVAL OPERATIONS ON SHORE, 059 trained men, there must be a few minutes when the pieces to be put ashore must be inactive. Therefore it is necessary that, as soon as the howitzer fii-e has cleared the beach, a strona; body of skirmishers and infantry should be landed, to engage the enemy during the disembarkation of the howitzers. ISTo gun should be landed before there are at least forty men on the beach. 1775. Meanwhile the fire of the heavy howitzers should be discontinued, unless they can safely fire shell over the heads of the party on shore. The skirmishers should immediately advance and seize the nearest cover, while the main body of infantry will pull in and land, followed by the howitzers. Immediately the main body of infantry has landed they should be deployed into line of battle, with a strong skirmish line in advance, and they should take up the strongest position possible, the howitzers be- ing brought into position as fast as they are landed. The line should be formed in such a manner that the flanks will if pos- sible be protected by the nature of the ground, or by the fire from the ships. 1776. The Boats will always land a boat’s length apart. Be- fore leaving the ship, four boat-keepers should be appointed to each boat caiTying a howitzer, and two for the others, with an officer in charge of each division of boats, who should on no account leave them. The boats should be hauled off to their anchors with a long scope of cable, and a man left in each boat to veer in, that the troops may be readily embarked. The officer left in charge of the boats should be careful to avoid being sur- prised, and, if circumstances will admit, should strengthen his position by cutting down trees and throwing up small breast- works a short distance in front. There should be at least one boat with a full crew left with him, to enable him to keep up communication with his base ; he should also endeavor to keep up communication with the commander of the forces by means of signal-men. Section III. — On the March. 1777. The Advance. — If the force has landed without oppo- sition, the first duty wdll be to make a reconnaissance, in order to ascertain the position of the enemy, the situation of the nearest towns and villages, the direction of roads, streams, etc., and to obtain a general idea of the country. If it becomes necessary to advance into the country, the manner of advance must be deter- mined by the commanding officer. If the country be open, or if no opposition be met with, the column may take up the march in close order. 660 NAVAL ORDNANCE AND GUNNERY. 1778. Advance-guards. — If, on the other hand, the line of march should pass over hilly country, or through woods, or if there are any indications of the presence of an enemy, every precaution should he taken against a sui’prise, by throwing out advance-guards, rear-guards, and flankers, as may be deemed necessary. 1779. The object of these guards is to give time for the col- umn to make the necessary preparations for attack or retreat in case the enemy are discovered. 1780. The guards should each consist of at least one ofiicer. Rear k Guard, 0 Qfe, Offizcr Aovance a Guard. OpFiQta Par Off, o Fig. 371. one petty oflicer, and twenty men, arranged as in the figure. Generally speaking, the advance-guard should be from one-fifth to one-tenth of the whole force, and should be accompanied by a detachment of signal-men and pioneers. The advance-guard may be increased or diminished at the discretion of the com- manding oflicer. 1781. When tlie column halts, the advance-guard does the same, but the men at the head should occupy the neighboring heights, if there be any within four or five hundred yards. There should never be less than three men at the head, and dif- ferent divisions shoidd endeavor to keep their distance from the others. On coming to a wood, the men at the head should be reinforced, and some sent through, and others around it, the column halting until the wood has been patrolled. The same rule should be followed on coming to a Gllage. They should never enter a defile without previously occupying the heights on either side by flanking-parties. At night the distances should be reduced, and communication kept up with a chain of men just far enough apart to see each other. Should the advance-guard be attacked, it should engage with spirit, and never fall back until absolutely obliged to do so, and then the retreat should NAVAL OPERATIONS ON SHORE. 661 be made on either side of the column, and never on the column itself. 1782. Rear-gtjakds. — The object of rear-guards is to prevent the enemy from approaching the column unperceived, and the men composing it should be picked men. Should they be at- tacked, the men in rear should be reinforced by the other squads, aud the enemy must be held in check. If they retire, the same rules apply to them as to the advance-guard. Whenever the -X- -X — Com. Off. X ! AIDES. XXX Field Officers. X X Company Officers. X X X X X XX X X X X X XX XX X X X X X X XX X XX XX XXX X X X X X X X X X 5 >« X J>'X X ^XXx X X v. □ ^ D -^H Q-5. 0 Cooking Places. D-^ Sinks. Fig. 372. Bivouac of a force of 1 Comp. Pioneers. . ..70 '| 10 Howitzers 220 i 12 Companies 1008 f Officers 54 J 1352 men. 602 NAVAL ORDNANCE AND GUNNERY. column halts, the rear-guard should face to the rear. Flankers are placed as in the hgure, on either or both flanks, as may be necessary, and their movements are governed by the same gen- eral rules as the other guards ; all parties so thrown out should keep themselves concealed as much as possible. 1783. Bivouac. — In selecting a site for a bivouac, wood and water are the great requisites. In cold weather, woods are the warmest places, but in tropical climates it is better to bivouac in the open. Dry and sheltered positions should be chosen. If obliged to bivouac where one may have to engage, it is better to take a position in advance of the one which must be occupied in fighting. If obliged to bivouac near a marsh, there should be some rising ground between it and the position selected ; this should be done if possible some time before the arrival of the column. 1781. On arriving on th^ ground selected, the infantry and howitzers should wheel into open column by divisions, crews of howitzers formed to the rear and the men mustered, absentees reported to the commanding officer, and arms stacked. The men should sleep where they stand in ranks, officers sleeping opposite the flanks. Cooking places should be made on the other flanks, and sinks dug some two hundred yards off. The camp-guard should be immediafely posted, whose duty it is to prevent all persons from leaving, except officers and authorized persons. The advance-guard and rear-guard should be relieved in the afternoon, at tlie time of going into bivouac. 1785. Grand-guaed. — Besides the regular camp-guard, which is charged with maintaining order and discipline in the camp, there should be a grand-guard thrown out in the dh’ection of the Sentinels. aqpoaapqp ppppn^tnpnnpappcipap ''J jk '1-' Out':.: Posts ''J V M' jF cncpcp cpcpiziicincfaa PlCH.eTS. t : n Grand-Guard. Fig. 373. NAVAL OPERATIONS ON SHORE, 663 enemy. This should consist of one or two companies, aecord- ino- to the nature oi the service and the ground to be covered. The first line is the grand-guard, one-haii of whom may rest six hours, and the otner half be awake and ready for duty six hours. This is the post from which the pickets, outposts, and sentinels radiate. The picket-guards compose the second line, and are relieved from the grand-guard every eight hours ; one-half to be under arms half the time, the other half to rest half the time. The third line are the outposts, consisting of nine men, relieved from the pickets every two hours : these men should be always watchful. The fourth or front line of senti- nels are to be relieved from the outposts every hour : they patrol constantly, and connect with one another. 1786. The ofiicer commanding the grand-guard should be sta- tioned at the first line, visiting the second every six hours, and generally supervising. The other officers should be stationed with the pickets, and should visit the outposts and sentinels fre- quently. The petty officers command the outposts. It is not necessxry that the line should be straight, but the general princi- ples should always be canned out. it is generally advisable to have some howitzers with the grand-guard, on the first line, posted so as to command the approaches. 1787. When attacked, the outposts forming as skirmishers move to the support of the sentinels ; pickets may move forward to support the others, or all may retii'e skirmishing as the nature of the attack may suggest. Should the attack be so strong that the whole grand-guard is compelled to retire, then each line will retire fighting. When an attack commences, a message should be instantly sent to the commanding officer, detailing i s nature and giving any necessary information. Section 1 V. — Engaging. 1788. The Attack. — Thisj^peration must be considered un- der two phases : 1st. The column has halted within sufficiently easy distance of the enemy to make a march of from five to ten miles, with the intention of attacking as soon as it arrives. 2d. It has halted at too great a distance for that purpose, so it marches up to him, and bivouacs for the night to attack next morning. 1789. If the column has been closely pursuing the enemy, with the advance-guard continually in contact with the enemy’s rear, it may happen that the retreating force m xy be suddenly found drawn up to receive battle. Under su:‘h circumstances, it would be better to act as in the second case, particularly if it oc- curs late in the day, in which case all preparations for attack 661 NAVAL ORDNANCE AND GUNNERY. should be made late in the night ; hut should the enemy be de- moralized from previous defeats or other causes, he should be attacked when he turns to show fight, as in the first case. 1790. In either case, the nature of the country and its com- munications must determine the mode of the advance ; but it should resemble closely the order in which it is intended to fight, covered by swarms of skirmishers as an advance-guard. If it is impossible to advance in line of battle, the double column is sug- gested as being the easiest to deploy. In any case, the column should be kept closed up and ready to he deployed into line, followed in the rear by the reserve. Skirmish Line — 3 Companies. 12 a SI 10 Q Line l~ ^ I \ - ^ \ ^ \ l|l 22P Line f 7 Reserve Fig. 374 . — FoncE deployed, re.\dy to attack. Arrived within the fire of the enemy’s guns, the position should be reconnoitred, and the column deployed into line and placed in position. 1791. These aiTangemcnts should be made under cover of the advanced line of skirmishers. Having decided on what part of the enemy’s line to make his false and real attacks, the command- ing officer should attack as soon as possible, if the chances are in his favor : delays in such cases are very dangerous. The artil- lery should he massed opposite that part of the enemy’s line where the real attack is to he made. It is sometimes necessary to begin an action with all the guns available at the moment, in order" to keep the enemy at a distance while the troops are get- ting into position. NAVAL OPERATIONS ON SHORE. 665 1792. The commanding officer must decide whether the as- sault is to be made in line or in column. If in line, it must be remembered that the charge must occasion much disorder in the line, which, unless supported on the instant of its first success, is sure to be driven hack by a counter-charge. For this reason, a second line should be formed and placed so as to cover the assault. 1793. Taking it for granted that it was decided to attack the enemy’s left, the disposition would be as in the figure. Of Fm. 375. — Force attacking Enemy’s Left Flank. course, before the advance, all the available guns should be brought to bear on the left. When it was considered that the artillery fire had told sufficiently, the attacking-party should ad- vance. As soon as they become engaged a partial advance of the whole line should take place. The advance should be closely covered by skh’raishers, who should push on as near to the ener my’s lines as possible. 1794. If, however, during the march the enemy should be unexpectedly found in position, or when called upon to act as in the first case, more time will be required to deploy and to make arrangements for attacking. The advance-guard should take up some defensive position, and strengthen it if possible. The commander should hasten to the front and reconnoitre the 606 NAVAL ORDNANCE AND GUNNERY. ground. Having done so, orders must be sent to the command- ers of the several divisions, telling them where to deplbv, etc. These dispositions must depend entirely on whether it is intend- ed to await the enemy’s attack or to attack first, and in the latter case, on what part of the enemy’s line the attack is to be made. 1795. The Skirmishers. — Specially instructed men are ne- cessary for this work. In covering a line or a column advanc- ing to attack an enemy, their numbers should be increased according as the nature of the ground to be moved over affords cover ; every skirmisher of the enemy should be wiped out by them from the front of the attacking-liue, and a con- tinued fire maintained up to the last moment, as this will serve to screen the advance and to steady the men. They should move forward quickly as soon as the advance commences, keep- ing about 150 yards ahead, and under cover as much as they can, and press as close to the enemy’s line as possible, even up to 150 yards. Too much care cannot be taken in guarding against a waste of ammunition ; the firing should be deliberate and careful in the extreme, and not a shot thrown away. Ean- doni filing only encourages and gives confidence to the enemy, vdiile it depletes one’s own resources. 1796. The Infantry. — In advancing the main body of the infantry to the attack, they should be distributed in two lines, as above shown (Fig. 375). The lines should advance together at a steady quick march to within 150 yards of the enemy, when the order will be given to the first line, “ Prepare to charge.” If the skirmishers have pushed up close to the enemy, they will lie down, and the first line passing over them Avill commence their charge as they do so. The second line should continue the movement in qnick-step. At the order ‘‘Charge,” let the men cheer with a will, and take up the run with their pieces at a trail, seizing them with the left hand as they close with the enemy. 1797. The Artillery. — The ground in the vicinity of the point to be attacked must be swept by a heavy cannonade be- fore the attacking-force is launched forward. The heaviest pos- sible fire should be maintained up to the last moment, and when the attacking-force has advanced into such a position as to impede the nre, the howitzers should, if possible, be advanced into such a position that they can reopen. 1798. After the charge commences, they should devote themselves to the other part of the line, or be placed in such a position as best to repel a counter-charge, or they may be used as circumstances dictate, being careful to keep some companies with them. The skirmishers, after the charge has commenced, should form on the artillery NATAL OPERATIONS ON SHORE. 667 1799. The guns should always be massed Avhen it is possible, as the moral eliect is much greater than when they are scat- tered, and their lire should he directed to the enemy’s men rather than to Ins guns. They should always be supported by infantry on one or both flanks, but never in rear. 1800. The Defence. — Great care is necessary in the selection of a position where a defence is to be made. It shoidd afford a depth of live or six hundred yards on which to manoeuvre, with free communication from right to left, and with roads in rear by which to retreat. The protection of the flanks is a serious consideration ; one at least ought to rest on some impassable obstacle. Tlie general line of positions must either curve con- vexly or concavely towards the enemy, or there must be a mix- ture of both. If the flanks are strong and not easily ap- proached or turnecl, the concave is the stronger. If, on the contrary, the spots where the flanks rest present no feature of strength, it is better to have them retired, thus forming a con- vex front to the enemy. 1801. An obstacle, not actually an impassable one, running somewhat parallel to the general line of the position and about two or three hundred yards in front of it, adds greatly to its strength ; but such obstacles as high banks, hedges, etc., which would afford any cover, are most dangerous. Obstacles that cut up one’s own lines are to be avoided, and also positions with wooded ground in front of them. If there is but one road to retreat by, it should run from near the centre. 1802. The Infantry. — In distributing the troops along a chosen position, some parts of it will require to be held by a much greater number than others, and the commander must decide which is the impoi’tant point or key, and that point should be occupied in force, with the reserves near at hand. He should then set to work to strengthen himself artificially. The formation of the command into two lines instead of one has many advantages, as it keeps it more compact and renders it easier to support any particular point of the line ; but the second line should be used very sparingly, and only when the necessity is urgent. 1803. The front of the infantry will always be covered by skirmishers, so that no fire can be delivered till they' have been driven in : when the front has been cleared and the enemy is advancing, it is time for the infantry to open fire, kneeling and with volleys, hy word of command. File-firing should not be used at such a time, as it is so difficult to stop it. It will be for the commander to decide when it shall stop, and then the order should be given, “ Prepare to charge,” and let them go in with 668 NAVAL ORDNANCE AND GUNNERY, a cheer. An advancing enemy shonlcl never be awaited in tlie open plain : in all such attacks there is a moment when the defendant must charge. Immediately after charging the men should be reformed and led back to their original position with- out being allowed to go too far in their broken state. 1804. The Artillery. — In defence, as in attack, it is the duty of the artillery to devote itself to the enemy's men, and it should be placed on that flank which occupies the strongest posi- tion. When neither flank has any natural supports, the guns should be massed in the centre. These rules can be adhered to when the front does not exceed 1200 yards ; beyond that, bat- teries must occupy several parts of the position. 180.5. Squares to resist cavalry should only be formed when absolutely necessary, as the square is a mark for every descrip- tion of tire. In forming them, advantage should be taken of any favorable ground. If there is an obstacle, such as a small hedge, ditch, or fence, it is better to form at about twenty yards from it than to hug it closely. Section V. — Held Fortification. 1806. Definitions. — When an armed force is constrained to act on the defensive, from disparity of numbers or strength, it should endeavor to counterbalance this disparity by selecting a position on which to receive battle Avhich will atford everv military advantage to itself and prove, in a corresponding degree, unfavorable to the assailant Such a position should present natural obstructions to the advance of an assailant ; it should screen the assailed from tire ; it should command the ground over which the assailant must advance ; it should com- mand the lines of approach by a front and cross tire ; it should offer no obstructions to the free movements of the assailed ; it should have natural points of support both on the flanks and in the rear ; and its lines of retreat should be ample and secure. As natural defensive positions may rarely possess the most essen- tial of these advantages, their defects must be remedied by artiticial means. These means are fortifications. 1807. Fortification may therefore be detined as the art of so arranging a position selected for defence that an inferior force shall be able to resist with advantage the assaults of one supe- rior to it. The covering mass is termed a Parapet when it shelters tlie assailed from the view and tire of the assailant, and affords a sweeping fire over the lines of approach. NAVAL OPERATIONS ON SHORE. 669 1808. The Profile is the vertical section showing the thick- ness and height of the parapet and the slopes in front and rear. ABMN, Ground line. EF, Superior Slope. JK, Counterscarp. BO, Banquette Slope. FO, Exterior Slope. HIJK, Ditch. CB, Banquette. OH, Berm. LM, Glacis. BE, Interior Slope. HI, Scarp. The most nsnal obstruction to impede the enemy’s approach is the Ditch,, which is placed in front of the parapet, for which it furnishes the material. Any little ditch made behind a breastwork for the men to stand in for cover is called a Trench. The excavation of this also furnishes material for the parapet. 1809. A Banquette is a step on which men stand to fire over the parapet. It should generally be about 4- feet 6 inches below the top. 1810. A Bermi?, a narrow strip left between the parapet and the ditch to prevent the earth from falling into the ditch. 1811. The top of the parapet is termed the Superior Slope; the interior face, when arranged for infantry, is termed the Interior Slope ; when for artillery, the Ge7iouilleTe ; theextej’ior face is the Exterior Slope. 1812. The side of the ditch adjacent to the parapet is called the Scarp ; the side opposite, the Counterscarp. 1813. A mound of earth placed in front of the counterscarp, with a gentle slope outwards, is called a Glacis. 1811. All Abattis is an obstacle formed by felling trees and laying them side by side, with the branches pointed and turned towards the enemy. 1815. A Traverse is any mass Avhich is intei-posed to protect the men from fire which comes in any direction except the front. 1816. A Revetment consists of a facing of stone, wood, or sods, or any other material to sustain an embankment when it receives a slope steeper than is natural. They are used only for the interior slope of the parapet, and for the scarp. 1817. Relief the height of the crest of the parapet above the bottom of the ditch. 670, NAVAL ORDNANCE AND GUNNERY. 1818. Command is its height above the level of the surround- ing country. 1819. In order to establish mutual defensive relations between all the parts, certain parts may be thrown forward towards the enemy, and tliey are denominated advanced parts j other yjor- tions, denominated are withdrawn from the enemy and protected from their fire by the advanced parts. and TJ VW, Advanced Parts. QT, jSF". Lines of Defence. liSTU, Retired Parts. PQR.UVW, Salient An?^, the base = — ^ — ; and if the ditch is to be 10 feet deep. 44 + 114 the area, gfoh, X 3-|- = 28 sq. feet. aof : 4iX H- aheh = X 15 = lOU “ hek = 2 X H = 15i « Area of profile of parapet or ditch = 147|- “ 1471 Mean breadth of ditch = 10 = 14.775 feet. Breadth at top or bottom of ditch = 14.775 ^ = 18.9 or 10.6 feet. ^ NAVAL OPERATIONS ON SHORE. 677 14:7A Time required to execute X 6 = nearly 33 hours. To throw up a length of parapet of 100 yards would require a working-party of 100 men : 50 diggers, 3d shovellers, 16 ram- mers. 1839. Having selected a position on which a field-work is to be thrown up, and determined its dimensions, it is to be remem- bered that the salient angles should be directed towards points that are difficult of access ; the faces of the wmrk are then marked out by small pickets, and traced with a piece of tape and the arigles set off. To guide the workmen in the construc- tion, right profiles (Fig. 389), made with slips of board, are constructed along every face, about 10 yards apart. 1810. Experience has shown that, in ordinary soils, a man with a pick can furnish employment to two men with shovels, and that, not to be in each other’s way, they should be from to 6 feet apart, and, finally, that a shovelful of earth can be pitched by a man 12 feet horizontally or 6 feet vertically. 1841. To distribute the workmen, the counterscarp crest is divided into lengths of 12 feet and the scarp crest into lengths of 9 feet, the points being marked by pickets. In each area thus marked out, a working-party is arranged, consisting of a pick with two shovels near the counterscarp, two shovels near the scarp, and one man to spread and one to ram the earth for two parties. The pick commences by breaking ground so far from the counterscarp crest, that by digging vertically 3 feet, he will arrive at the position of the counterscarp. This is carried on at the same depth of 3 feet advancing towards the scarp, where the same precaution is observed. The earth is thrown forward and evenly spread and rammed. If the ditch is deeper than 6 feet, an offset, about 4 feet broad, should be left at the scarp at mid-depth of the ditch, to place a relay of shovels. W hen the ditch has been excavated to the bottom, the offsets are cut away, and the proper slope given to the sides. The earth furnished by the offsets, if not required to complete the parapet, may be formed into a small glacis. Care should be taken not to have any pebbles on top of the parapet, and also to have a drain to take the water off without letting it run down the scarp. 1842. Artillery in Field-works. — The proper positions for artillery are on the flanks and salients of a work, and the guns should be collected at these points in batteries of several pieces. The term battery is used of a collection of several guns, and it is named according as the parapet is arranged for firing over or Fig. 389. 678 NAVAL ORDNANCE AND GUNNERY. tlirongh it; in firing over.it is called a larbette battery - in firing throngli, an emJjrasure hattery. 18d3. The barbette consists of a mound of earth thrown up against the interior slope ; the upper surface is level and 1 foot 8 inches below the interior crest ; the earth at the sides and rear receives the natural slope. To ascend the barbette a con- struction termed a rainj? is made of earth ; it should be 5 feet wide on top, and the slope is G feet of base to 1 of perpen- dicular. It should be at some convenient point in rear, and take up as little I’oom as possible. 1841. An embrasure is an opening made in the parapet for a gun to hre through. The bottom of the embrasure is tei'ined the sole, and should be 1 foot 8 inches above the ground, and should slope outward. The interior opening is termed the mouth ; it should be 18 inches wide. The embrasure opens outwards ; the sides of it are called cheehs. 1845. Defence of WxVlls. — Walls are readily made available for purposes of defence by loop-holing them, the mode of doing it varying with their height and situation. It is a general rule that F G. 390. — Defence of Walls. 6. loop-holes must be so placed that an enemy, if he succeeds in rushing up, shall not be able to make use of them. To prevent this they should be 8 or 9 feet above the ground on the outside (Fig. 390, a), but on the inside (Fig. 390, V) the banquette from which the defenders are to lire should not be more than about 4 feet 6 inches below them. A portion of the wall not less than 18 inches high should be left above the loop-holes to screen the men’s heads when firing. 1846. These points are attainable in several ways ; if the walls are high, the loop-holes may be made near the top, and a tem- porary stage or earthen banquette might be placed inside; if the wall is not over 6 feet high, the loop-holes may be made at 4 feet 6 inches above the inside level, and a ditch made out- KAVAL OPERATIONS ON SHORE. G79 side. The quickest way of making a loop-hole is to break the wall down from the top for about 2 feet (Fig. 390, a\ and then to till it up at the top with a stone or sand-bag. If the wall should be low, a piece of timber supported on a couple of stones would be a ready expedient. If exposed to the tire of artillery, a wall will not afford good cover, but it may be improved by sinking a trench in rear and throwing the earth against the wall, or by digging a ditch in front and throwing the earth over the wall. 1817. Defence of a Building. — The great art of making a defensible post out of a building and the adjoining outhouses and walls, consists in selecting from all the objects in view only what will be useful in strengthening the work, and in sacriticing everything else, making use of the materials for fortifying. ISIS. A building proper for defensive purposes should be in a commanding position ; it should be substantial, and of a nature to furnish materials for placing it in a state of defence ; it should be of an extent proportioned to the number of defenders, and only require the time and means that can be devoted to complet- ing it ; it should have walls and projections that mutually tiank each other ; it should be ditiicult of access, and yet have a safe retreat ; and the walls should be of moderate thickness. Brick houses or walls are to be preferred to those of stone or Avood. 1 819. The number of men necessary for defence may be rough- ly estimated by alloAving 1 man to every 4 feet on the loAver tioor, 1 to every 6 on the next, and 1 to every 8 on the next. 1850. To put a building in condition to rep 1 an immediate attack, certain points AV'ould naturally claim primary attention, and they should be attended to in the order in Avhich they are given. 1st. To collect material and barricade the doors and windows on the ground floor, to make loop-holes in them, and to level any obstruction outside that Avould give cover to an enemy. 2d. To sink ditches opposite the doors on the outside, and to arrange loop-holes in the Avindows of the upper story. 3d. To loop- hole the Avails, generally attending first to the most exposed parts, and to make communications through all the Avails. 4th. To place abattis or any feasible obstructions on the outside. 5th. To place out-buildings and garden Avails in a state of de- fence, and to establish communications betAveen them 1851. Defence of aTillage. — In arranging the general plan, some substantial buildings Avithin musket-range of each other should be selected for the prominent or salient points of the line. These, Avith the intervening Avails, hedges, or open spaces, will be prepared for defence as has been already explained, so as to completely enclose the position. Care should be taken not Fio. ;{01. — Tiiic Dfkknce of a NAVAL OPERATIONS ON SHORE. 68L to attempt to enclose a larger space than can be manned and de- fended bj the available force. Anything ■which would afford cover to an enemy outside of the lines should he destroyed, burning houses, filling ditches, throwing down fences, etc. The roads by which an enemy can approach should be cut across by trenches. All obstructions on the inside which are perpendicu- lar to the line of defence should be removed so as to admit of manoeuvring. All streets and roads open to attack should be barricaded, or breastworks should be thrown up. If several bar- ricades are to be disputed in succession, the means of retreat through them must be preserved, and communications should be made from house to house on each side of the street. 1852. Some strong building or buildings should be selected in a central position, commandiTig the principal roads and streets, which should be strengthened and made to serve as rallying- points in case the assailants penetrate the outer defences. A reserve force should always be kept ready to reinforce any part of the walls. 682 NAVAL ORDNANCE AND GUNNERY. 1853. Defence of a Bridge. — If a body of troops had to re- tire over a bridge in the presence of a superior force, works- would naturally be thrown up in front of it for covering the re- treat and ensuring its being held until the passage was effected, and others might be placed in rear for giving support and pro- longing the resistance. If the protection of the bridge were the object, the same plan would be followed ; but if it were merely for disputing the passage in order to cover a line of operations or a flank march, works might be placed in rear, whicb is the proper position for defensive purposes. The annexed Fig. (393) may serve as an example of temporary works in front as well as in rear of a bridge for guarding and disputing the passage with a force of 600 men available for work and defence. The first consideration should be the distribution of the men. Three- fourths of them should be placed in advance, and one-fourth as a reserve in rear, and a small proportion of the former number NAVAL OPERATIONS ON SHORE. 683 as a support close to the front of the bridge. A file of men should be allowed to every yard of parapet in front, and the main reserve in other works in rear, which should be large enough to receive two-thirds of the whole number, if the force is obliged to fall back. 1854. This arrangement would give 400 men on the outer line in front, 50 men in rear of the outer line as a support, and 150 men partially occupying the works in rear as a reserve. This would require 200 yards on the outer line, 25 yards for the sup- port; in all, 225 yards in front. 1855. The next point to decide would be the plan; and a simple and serviceable one would be the one shown in Fig. 393, a priest-cap with a redan on each face. A ready way of laying this out would be, first of all, to trace a rough semicircle with pickets about one-sixth less in running length than the required breastwork. This could be done with a radius of 64 yards. The salient angles being fixed in the outline of the work so traced, and their lengths being disposed within the semicircle so as to flank each other, the total length, though it may vary with the figure adopted, will be near enough the required extent for practice. In rear of the bridge about 200 yards more would be required, but so disposed as to protect the men from enfilade. 1856. At a convenient distance in front, varying from 20 to 50 yards, an abattis or other obstruction should be placed parallel to the general contour of the works, and extending to the river on either side. This aiTangeinent of the works would require 212 men to throw up the parapet ; the rest might be emplojmd in making the abattis, in throwing down the parapet walls of the bridge, blocking up the roads, etc. 1857. If the force be very ranch smaller the Avorks should be executed of an extent to correspond ; a good breastwork with an abattis before it might be made across the front of the bridge, a barricade in the middle, and another one in rear flanked by strong breastworks. 1858. Attack of Works. — Having considered the various means of putting positions in a state of defence, it is in order to consider the various methods of attacking and defending such posts. An attack should either be by surprise or by open force. 1859. Surprise. — In the first case the strictest secrecy should be observed as to the intent : the enemy should be deceived by false manoeuvres, and the troops should be kept in ignorance of the movement until they are assembled for the attack. The most favorable moment for a surprise is about two hours before 684 NAVAL ORDNANCE AND GUNNERY. dayliglit. The troops should be divided into a storming-party and reserve, and the storming-party should consist of an ad- vance-party and a support. Several columns of attack should be formed, some for false and some for real attack, hut the columns formed for false attack should he strong enough to take advantage of any success. 1860. Pioneers should accompany each storming-party to remove obstacles, and they should be provided with hags of powder with fuses attached for blowing down gates, doors, or other obstructions. All operations should be carried on with des]iatch and in silence. The advance-party should he provided with ladders, ]danks, brush, or anything which would be ser- viceable in tilling up ditches or crossing them, and the charges should generally be made in column through whatever force was formed for the defence of the parapet. A strong reserve should be kept ready to follow up any successful attack. 1861. Open Ati'ack. — The general arrangements for an open assault comprehend the operations to gain possession of the works, the measures for maintaining possession, and the precau- tions to be observed in case of repulse. The troops should be drawn up in a sheltered position out of range of the assailed, and a heavy fire opened from the howitzers in the most favor- able positions to enfilade the faces and destroy all visible obsta- cles. When the fire of the works is silenced, the troops are thrown foi’ward and demonstrations made on several points, to divert the attention of the assailed fi-om the true point of attack, and to prevent him from concentrating his forces there. 1862. The disposition of the troops making an assault will depend very much on circumstances; generally, the parties should be arranged as in the preceding case ; the troops to sup- port and, if necessary, to reinforce the storming-parties, should advance in one or two lines, with the artillery on the flanks, disposed to repel sorties. When the assailed are driven from their main works the storming-party should press them closely, and endeavor to enter the interior works with them, leaving to the troops which follow the duty of retaining possession of the works already gained. If tlie storming-party has to retreat, its retreat should be covered by a strong body of infantry and artillery. 1863. Defence. — The essential point in defence is to have every part of the works guarded by a sufficient number of troops to resist an attack on all sides; this is of importance, not onlv in isolated works, but in continued lines. At least two ranks should be drawn up on the banquette throughout the entire extent of the line, with supports and a reserve proper- NAVAL OPERATIONS ON SHORE. 635 tioned to the importance of the work. The strictest vigilance should be exerted to guard against a surprise ; sentries should be posted on all the commanding points of the works, and on the outside patrols should be posted to watch the enemy’s movements, and to give notice of his approach. 1864. At night the number of sentries should be increased, and redoubled vigilance should be used, especially after mid- night. The reserve should be posted in the most convenient position to afford prompt assistance to any point in danger of being forced. If the enemy opens his attack by a warm can- nonade, the men should not be exposed to it if they can be sheltered at the posts they are to occupy when the columns of attack approach. The men should be instructed to reserve their lire until the enemy arrives at certain points mai’ked in front, which should not be more than 400 yards from the parapet. Should the enemy succeed in forcing his way in, the reserve should attack with the bayonet before he has time to form ; but the only well-grounded prospect that the assailed can have of repelling the assault, when tlie enemy has gained the top of the scai’p, is to meet him offensively with bayonet on top of the parapet. Large stones, heavy round logs, and hand-grenades should be in readiness to roll over on the enemy when he is in the ditch. 1865. Sorties. — If it should seem desirable, and the garrison is sufficiently strong to make a sortie, it is essential that it should be well timed and vigorously executed, and be in sufficient force to make some impression, either as a diversion in favor of tlie defenders of the parapet, or to drive the assailants back beyond the obstacles thev may have already surmounted. The party should be selected from the reserve, leaving the parapets fully manned. The men for the sortie shovdd be drawn up at the point where they are to go out, and at the critical moment when the speed of the assailants has been checked by the opposition they have met with in front, a furious onset with the bayonet should be made on one or both flanks, and when the object is effected, the troops should immediately retire within the works. The firing from the defences should cease when they come out, and be resumed the moment the front is clear again. Section VI. — The Retreat. 1866. Rear-guards. — After having accomplished the objects of the expedition, or if the forces have been defeated or re- pulsed, it becomes necessary to get them on board ship as G86 NAVAL ORDNANCE AND GUNNERY. quickly as possible. If the forces are at a cousiclerable distance from the boats, the retreat will be a matter requiring great care and judgment, particularly if the rear is closely pressed by the enemy in force. In this case, everything will depend on the rear-guard, which should be formed from the freshest men, and should number at least one-fifth or oiie-sixth of the whole force, including some howitzers. 1867. The great art of rear-guards is that of being able con- stantly to force an enemy to deploy and to attack, and then to get away safely without any serious fighting : its pui-pose is more fulfilled by threatening to fight than by fighting. If the pursuing enemy should become reckless and push on to attack with an insufficient force, it will then be for the rear-guard to pounce suddenly on him with all his available force, and having struck a severe blow, to at once resume the retreat. 1868. The officer commanding the main body should, from time to time, send to the commander of the rear-guard infor- mation as to the condition of the road, bridges, etc., to be passed, and every position suitable for the rear-guard to defend itself in should be especially noted. 1869. The distance that the rear-guard should be from the main body depends upon the nature of the country, its num- bers, and the manner in which the pursuit is conducted. It should not be more than a few hours’ march, and under all cir- cumstances communication should be kept up with the main body. The actual rear of the rear-guard should be a line of skirmishers. 1870. All villages on the line of retreat and all supplies of provision should be destroyed ; everything, in fact, on which the pursuers might subsist. If the country is so enclosed that the pursuers must travel on the roads, every thing should be done to retard their progress ; setting fire to houses or villages on the line of march, felling trees across the road, destroying bridges, should never be omitted when it can be dons. 1871. Destruction of Bridges. — Bridges may be destroyed by burning, if there is time ; if not, it would be sufficient to bore a hole in the main braces or lower chords of truss-bridges and put in a charge of powder with a fuze. To destroy a bridge of masonry, sink a shaft in the roadway near the centre arcJi, down to tiie haunch, with a short gallery ending in a chamber, so as to lodge the powder in the middle of the width of the bridge under the roadway. Five or six hom-s' labor and a charge of from 50 to 100 lbs. will probably be sufficient. If there is not time to sink a deep shaft, a hole may be sunk across the crown of the arch, and a charge of 250 or 300 lbs. of pow- KAVAL OPERATION'S ON SHORE. 687 der, placed over the crown and covered with stones, will answer the purpose. 1872. Passage of a Defile. — In case it becomes necessary for the retreating forces to pass through a detile, troops from the main body should be posted on the heights on eitlier side and deployed as skirmishers while the main body is passing through. As soon as the rear-guard is in position and the enemy has deployed, the supports should enter the detile, and the rear-guard should fall back, maintaining a heavy tire along the line. The skirmish-line of the rear-guard should, if possible, retire along the heights as well as by the detile ; if that is not pos- sible, they should dispute every inch of ground in the detile while the line of battle is being formed on the other side, howitzers being posted so as to entilade the pass, and troops ready to attack the advance of the enemy as they emerge. After having given the enemy a serious check, the line of march should be resumed, the rear-guard resuming their original duties. 1873. The Embarkation. — On arriving at the boats, if there is no enemy present or near, the troops and howitzers might all be embarked at once, and return to their ships. But if the enemy is pressing closely, the breastworks wliich have been prepared by the officer in charge of the boats should be manned, retaining some howitzers to keep the enemy at a distance. The main portion of the howitzers should be embarked, and the boats hauled into such a position that, by their cross-fire, they can sweep the approaches and cover the embarkation of the infantry, which should be proceeded with as expeditiously as possible, being careful to get all the howitzers embarked while there is still a large number of infantry on shore. The last who are. on the beach should retire in skirmishing order, keep- ing up a vigorous fire until the last moment, when they should lose no time in getting to their boats, the howitzers, boats, and vessels keeping up a continuous fire to prevent the enemy from making a sudden rush and capturing them. TABLES. I COEFFICIENTS FOE THE CUBIC LAW OF EESISTANCE. ELONGATED PROJECTILES WITH OGIVAL HEADS. Reprinted from Professor Fe.\kcis Bashportii’ s Motion of Projectiles. V Kv K, s Log 7 .274828 •74454 8 .14114 .009932 . 14084 38 .76197 .295012 ■77154 7 .12324 .007575 .12301 39 .78893 .316461 . 79926 6 •10543 •005547 .10527 40 .81659 •339267 •82774 5 .08772 .003841 .08760 41 .84500 -363530 .85702 4 .07008 .002452 .07000 42 .87419 •389362 .88716 3 .05249 .001376 •05245 43 .90423 .416885 .91822 2 .03496 .000611 •03494 4 ^ •93515 .446235 -95024 +i .01747 .000152 .01746 45 .96702 •477561 •98331 + _L + 46 .99991 .511027 I .01749 O 00000 000000 00000 47 1.03386 .546814 1.05286 0 — + — 48 1.06897 .585125 1.08950 — I •01745 .000152 •01745 49 l', 10529 .626186 I. 12750 2 .03488 .000609 .03490 50 I . I429I .670247 I . 16696 3 • 05?32 .001371 •05237 51 1.18193 • 7175^ 1.20799 4 .06978 .002438 .06985 52 I . 22243 .768515 1.25070 5 .08726 .003814 .08738 53 1.26452 .823382 1.29523 6 .10477 .005501 • 10494 54 I . 30S32 .882577 1-34171 7 .12233 .007501 . 12256 55 1-35393 •946541 I. 3903 I 8 •13995 .009820 . 14025 56 I. 40150 1.015767 1.44118 9 •15763 .012463 .15801 57 1.45116 I .090812 1-49453 lO •17540 .015437 •17587 58 1.50307 I . 172306 1-55055 II •19325 .018746 .19382 59 1-55738 1.260959 I , 60949 12 .21121 .022399 .21189 60 1.61429 1.357583 1.67159 13 .22928 .026405 .23007 14 •24747 •030773 . 24S40 0.04 15 .26580 •035514 .26687 r = i6 .28428 . 040640 .28551 9 1 X Y 'T* 17 18 .30202- .32174 .046163 .052098 .30432 •32333 i 0 19 .34076 .058462 •34255 60 1.96194 1.79302 1.84116 20 •35998 .065267 •36197 59 I . 86669 1.63124 1.7^82 21 .37942 .072536 .38163 58 1.77967 I .4S920 1.6S623 22 .39910 .080287 .40155 57 I . 69963 1-36351 I. 61666 23 .41903 .088543 .42174 56 1.62556 1.25157 I .55151 24 •43923 •097325 .44221 55 1-55667 1.15130 I . 49029 25 •45971 . 106662 .46299 54 I. 49231 1.06105 1.43256 26 .48050 .116579 .48410 53 1-43195 ■97945 1-37799 27 .50162 .127107 •50555 52 1-37514 •90540 1.32626 23 .52308 .138279 .52737 51 I. 32150 •83795 1.27711 29 •54490 .150130 •54958 50 I. 27071 •77632 1.23030 30 .56712 . 162699 .57220 ' 49 1.22249 •71985 1.1S563 11 •58974 .176029 •59527 48 1.17661 .66798 I. 14292 32 .612S1 . 190164 .61880 47 1.132S5 .62022 I . I 020 I 33 .63633 .205154 .64282 46 I .09102 .57614 1.06275 44 r - = 0.04 7 = 0.04 9 X Y T 9 X Y T u 45 1.05097 •53538 1.02503 0 — I •01745 .000152 .01745 44 1.01256 •49762 .98873 2 •03487 . 000609 .03490 43 .97564 .46258 •95373 3 .05230 .001370 •05235 42 .94011 .43002 .91996 4 .06973 .002435 .06983 41 .90587 •39971 .88731 5 .08719 .003809 .08734 40 .87281 •37147 .85572 6 . 10467 •005493 . 10488 39 . 84085 •34513 .82511 7 .12219 .007489 . 12249 38 .80992 .32052 •79542 8 •13976 .009802 .14015 37 •77995 •29752 •76659 9 .15739 .012437 .15788 36 .75086 .27599 •73856 10 .17510 .015401 •17571 35 .72261 •25584 .71128 II .19288 .018698 •19363 34 .69513 •23695 .68471 12 .21076 .022336 .21166 33 .66838 .21924 .65880 13 .22875 .026325 .22981 32 .64231 .20263 •63350 14 .24686 .030671 .24810 31 .61688 . 18704 .60879 15 . 26509 .035388 .26652 30 .59204 .172413 •58463 16 •28347 .040486 .28510 29 .56777 .158678 . 56098 17 .30200 •045976 .30386 28 . 54402 •145783 •53782 18 .32071 .051874 .32281 27 .52077 •133677 •51510 19 .33960 .058195 .34196 26 .49798 . I223I4 .49282 20 .35868 •064953 .36131 25 •47563 .111652 .47094 21 •37798 .072167 .38091 24 •45369 .101651 .44943 22 .39750 .079857 .40075 23 •43213 .092276 .42828 23 .41726 .0S8044 .42085 22 .41093 .083494 .40746 24 .43728 •096749 .44123 21 .39007 .075276 •38695 25 .45758 .105999 .46191 20 •36953 .067596 .36673 26 .47817 .115820 .48292 19 .34928 .060427 •34679 27 .49907 . 126241 . 50426 18 .32932 .053746 .32711 28 .52030 .137294 •52596 17 .30961 •047532 .30766 29 .54188 .149013 •54805 16 .29015 .041766 .28844 30 •56383 .161436 •57054 15 .27091 .036430 . 26942 31 .58618 . 174602 •59346 14 .25189 .031509 .25060 32 .60895 .188556 .61684 13 .23306 .026988 •23195 33 .63216 .203346 .64071 12 .21441 .022853 .21348 34 •65585 .219024 .66509 II .19592 .019092 •I9515 35 .68003 •235647 .69002 10 •17759 .015695 .17697 36 •70474 .253275 •71553 9 .15940 .012651 . 158S9 37 .73001 .271977 .74166 8 •14134 .009951 . 14094 38 .75588 .291827 .76844 7 .12340 .007588 .12309 39 •78237 .312903 .79592 6 •10555 .005555 .10532 40 .80953 •335295 .82414 5 .08780 .00384.“; .08764 41 .83740 .259099 •85314 4 .07012 .002454 .07003 42 . 86602 .384420 .88298 3 .05252 .001377 •05247 43 .89543 •411374 .91371 2 •03497 .000611 •03494 44 .92568 . 440090 ■94539 +i .01747 .000152 .01746 45 •95683 .470706 .97809 + + + 46 .98894 .503379 I .01186 0 00000 000000 00000 47 1.02205 .538280 1.04679 48 1.05624 •575598 1.08295 45 y = = 0.05 y = 0.05 f X Y T 9 X 1 i Y j T 0 49 1.09158 -615542 I . 12043 0 1 30 •59593 •173941 •58653 50 1 . 12813 .658346 I. 15932 29 •57131 . 160017 .56272 51 I . 16598 .704267 I. 19973 28 •54726 .146954 •53941 52 I. 20521 -753593 1.24176 27 .52372 . 134698 •51655 53 I. 24591 . 806644 1-28555 26 .50067 . I232OI .49414 54 1.28817 .863779 I. 33122 25 .47806 .112420 .47214 55 I. 33212 -925397 1.37891 24 •45589 .102314 .45052 56 1-37785 .991947 1.42879 23 •43412 .092847 .42926 57 1.42548 1.063932 1.48104 22 .41272 .083983 .40834 58 1-47515 1.141917 1-53584 21 .39168 .075692 •38774 59 1.52700 1.226536 r- 59342 20 .37096 .067948 •36744 60 1.58116 r. 318507 1.65401 19 .35056 .060724 •34742 18 .33045 •053993 .32767 = 0.05 17 .31061 •047737 .30815 y -- 16 .29103 .041934 .28887 T 15 .27167 .036566 . 26980 9 X Y 14 13 •25254 .23362 .031618 .027075 .25093 .23223 0 60 2.04361 I .90178 1.87718 12 .21488 .022920 .21372 59 1.93605 1.71908 1.79181 ir .19631 .019143 •19535 58 1.83932 1.56116 1.71316 10 .17791 •015733 •I77I3 57 1-75143 1.42316 1.64026 9 . 15966 .012678 . 15902 56 1.67093 I. 30150 1-57234 8 •14154 .009970 . I4I04 55 I . 59669 1.19344 1.50878 7 •12355 .007600 . 12316 54 1.52782 I .09686 I . 44908 6 . 10566 .005563 .10538 53 1.46362 I .01007 I . 39280 5 .08788 .003850 .08768 52 r -40351 .93171 1-33958 4 .07017 .002457 .07005 51 I. 34701 .86067 1.28914 3 •05255 .001378 .05248 50 1-29373 . 79602 I.24II9 2 .03498 .000612 •03495 49 1-24333 -73699 I -19552 .01747 .000152 .01747 48 1-19551 .68293 I . I5I92 + + + 47 I. 15004 .63329 I.II022 0 00000 000000 00000 46 I . 10669 .58760 1.07025 _ + 45 1.06527 •54544 1.03189 — I .01745 .000152 •01745 44 1.02563 .50647 .99501 2 .03486 .000609 •034S9 43 •9S759 •47039 -95949 3 .05227 .001369 •05234 42 .95106 .43690 .92524 4 .06968 .002433 . 06980 41 .91591 •40579 .89217 5 .08711 .003805 .0S730 40 .8S202 .37684 .86018 6 . 10456 .0054S5 .10483 39 .84931 •34987 .82921 7 . 12204 .007477 .12241 38 .81768 •32471 .79919 8 •13956 .0097S4 1 . 14005 37 -78707 .30122 .77006 9 •15714 .012411 j .15776 36 •75740 .27926 •74175 10 •17479 •015363 ' .17536 35 .72861 •25873 .71421 II .19251 .018651 ! .19345 34 . 70064 •23950 .68740 12 .21032 .022273 •21144 33 -67343 .22149 .66127 13 .22823 .026245 j .22955 32 .64694 .20461 •63577 14 .24625 .030571 1 .24779 31 .62112 1 .18878 .610S7 15 .26439 .035263 j .26616 46 y = = 0.05 Y — 0.06 f X Y T 9 X Y T u i6 .28267 -040334 .28470 0 60 2.14308 2.03739 1.91913 17 .30110 ’.045792 .30340 59 2.01825 1.82534 1.82716 18 .31969 .051653 .32229 58 1.90851 1.64619 1-74339 19 .33845 .057932 •34138 57 1.81053 1.49233 I . 66642 20 .35740 .064643 .36067 56 1.72199 1.35850 1.59520 21 .37655 .071804 .38018 55 1.64122 I . 24094 1.52890 22 .39592 .079434 •39995 54 1.56696 1.13679 I . 46690 23 .41552 .087553 .41996 53 1.49824 1.04390 1.40867 24 .43537 .096183 . 44026 52 1-43431 .96056 1-35379 25 .45548 . 105349 .46085 51 1 - 37454 ^ .88540 1.30191 26 .47587 .115076 •48175 50 1.31844 .81732 1.25271 27 .49656 .125393 •50299 49 1.26558 .75542 1 . 20594 28 .51757 .136330 .52457 48 1.21561 .69894 1.16137 29 .53891 . 147920 • 54654 47 1.16824 .64723 1.11881 30 .56061 . 160200 .56890 46 I. 12322 .59977 I .07808 31 .58269 . 173208 .59168 45 1.08031 .55610 1.03903 32 .60518 . 186988 .61492 44 1.03933 .51582 1.00153 33 .62809 .201584 .63863 43 I .00010 .47860 .96546 34 .65145 .217048 .66284 42 .96249 •44412 •93071 35 .67529 .233433 .68759 41 .92636 .41215 .89718 36 .69963 • 250799 .71291 40 .89158 •38245 .86478 37 .72451 .269211 .73884 39 .85807 .35481 -83343 38 .74996 .288738 .76540 38 .82571 .32907 . 80307 39 .77600 -309458 . 79264 37 •79443 . 30506 .77361 40 .80268 -331455 .82061 36 •76415 .28265 •74501 41 .83004 -354821 •84935 35 •73479 .26171 .71721 42 .85811 •379656 .87890 34 .70631 .24213 .69015 43 .88693 .406069 .90932 33 .67862 .22380 •66379 44 .91655 •434183 •94067 32 .65169 .20665 .63808 45 .94702 .464131 .97300 31 .62547 .19057 .61299 46 .97839 .496058 I .00639 30 •59990 •175509 .58847 47 I.01071 .530125 1.04089 29 •57494 .161389 .56449 48 1.04405 .566510 I .07660 28 .55057 .148151 . 54102 49 1.07846 .605410 1.11358 27 •52673 •135741 .51803 50 I .11401 . 647042 1.15194 26 - 50340 . I24IO7 .49548 sr 1.15077 .691646 I . 19176 25 .48054 .113204 •47335 52 1.18882 •739489 1.23316 24 •45813 . IO299I .45162 53 1.22824 . 790867 1.27625 23 .43614 .093428 .43025 54 1.26911 .846111 1.32116 22 ' .41454 .084480 .40923 55 1.31153 .905589 I . 36802 21 •39331 .076116 •38854 56 1-35559 .969709 1.41698 20 .37242 .068306 .36816 57 I. 401 39 r .038928 I .46821 19 .35186 .061024 . 34806 58 r. 44905 1.113758 I. 52190 18 .33160 •054244 .32823 59 I .4q86q 1.194772 1.57823 17 .31162 •047945 .30865 60 1.55041 1.282610 1.63744 16 .29191 .042104^ .28931 1 15 .27244 .036704 .27018 14 .25320 .031728 •25125 13 .23418 .027162 .23251 47 y — o.o6 y — 0.07 ^ ! X Y T

75 4665 4655 4645 4635 4625 4615 4605 86 4596 4586 4576 4566 4557 4547 4537 4528 4518 4509 87 4499 4490 4480 4471 4461 4452 4442 4433 4423 4414 88 4405 4395 4386 4377 4367 4358 4349 4340 4331 4321 89 4312 4303 4294 4285 4276 4267 4258 4249 4240 4231 90 4222 4213 4204 4195 4186 4177 4169 4160 4151 4142 91 4134 4125 4116 4107 4099 4090 4081 4073 4064 4056 105 V. 0 1 2 3 j * 5 6 7 8 9 F-s. Feet. Feot. Feet. Feet Feet. Feet Feet. Feet Feet. Feet. 92 4047 4039 4030 4022 4013 4005 3996 3988 3980 3971 93 3963 3954 3946 3938 3930 3921 3913 3905 3897 3888 ' 94 3880 3872 3864 3856 3848 3840 3832 3823 ■3815 3807 95 3799 3791 3784 3776 3768 3760 3752 3744 3736 3728 96 3721 3713 3705 3697 3689 3682 3674 3666 3659 3631 97 3643 3636 3628 3621 3613 3606 3598 3591 3583 3576 98 3568 3561 3553 3546 3539 3531 3524 3516 3509 3502 99 3495 3487 3480 3473 3466 3458 3451 3444 3437 3430 100 3423 3416 3409 3402 3395 3388 3381 3374 3367 3360 lor 3353 3346 3339 3332 3325 3319 3312 3305 3298 3291 102 3285 3278 3271 3265 3258 3251 3245 3238 3231 3225 103 3218 3212 3205 3199 3192 3186 3179 3173 3166 3160 104 3154 3147 3141 3135 3128 3122 3116 3109 3103 3097 105 3091 3084 3078 3072 3066 3060 3054 3048 3041 3035 106 3029 3023 3017 3011 3005 2999 2993 2987 2982 2976 107 2970 2964 2958 2952 2946 2941 2935 2929 2923 2918 108 2912 2906 2900 2893 2889 2883 2878 2872 2866 2861 109 2855 2850 2844 2838 2833 2827 2822 2816 2811 2805 no 2800 2794 2789 2784 2778 ^2773 2767 2762 2757 2751 III 2746 2741 2735 2730 2725 2719 2714 2709 2704 2698 II 2 2693 2688 2683 2678 2672 2667 2662 2657 2652 2646 113 2641 2636 2631 2626 2621 2616 2611 2606 2601 2596 114 2591 2586 2581 2576 2571 2566 2561 2556 2551 2547 115 2541 2536 2531 2526 2522 2517 2512 2507 2502 2497 II6 2492 2487 2483 2478 2473 2468 2464 2459 2454 2449 117 2444 2440 2435 2430 2426 2421 2416 2411 2407 2402 118 2397 2393 2388 2383 2379 2374 23C9 2365 2360 2356 1 19 2351 2346 2342 2337 2333 2328 2323 2319 2314 2310 120 2305 2301 2296 2292 22S7 2283 2278 2274 2269 2265 I 2 I 2260 2256 2252 2247 2243 2238 2234 ! 2229 2225 2220 122 2216 2212 2207 2203 2199 2194 2190 2185 21S1 2177 123 2172 21C8 2164 2159 2155 2151 2146 ; 2142 2138 2134 124 2129 2125 2121 2116 2112 2108 2104 2099 2095 2091 125 2087 2082 2078 2074 2070 2066 2061 2057 2053 2049 126 2045 2040 2036 2032 j 2028 2024 2020 2015 2011 2007 127 2003 1999 1995 1991 19S6 1982 1978 1974 1970 1966 128 1962 1958 1954 1949 1945 1941 1937 1933 1929 1925 129 1921 1917 1913 1909 1905 1901 1897 1893 1SS9 18S5 130 1881 1877 1873 1869 1 1865 1S61 1857 1853 1849 1S45 131 1841 1837 1833 1829 1825 1821 1817 1S13 1S09 1S06 132 i802 1798 1794 1790 17S6 1782 1778 1774 1770 1766 133 1763 1 1759 1755 1751 1747 1743 1739 1736 1732 172S 134 1724 1720 1716 1713 1709 1705 1701 1697 1694 1690 135 1686 16S2 1678 1675 ' 1671 1667 1663 1660 1656 1652 136 1648 1645 1641 1637 1633 1630 1626 1622 161S 1615 137 I6II 1607 1603 1600 1596 1592 1589 1585 1581 1578 133 1574 1570 1567 1563 1559 1556 1552 1548 1545 1541 139 1537 1534 1530 1526 : 1523 1519 1516 1512 1508 1505 140 1501 1497 1494 1490 1487 1483 1479 1476 1472 1469 141 1465 |i46r 1458 1454 1451 1447 1444 1440 1437 1433 106 I I V. 0 1 2 3 1 5 6 i 8 9 F-s. Feet. Feet Feet. Feet. Feet. Feet. Feet. Feet Feet. Feet. 142 1429 1426 1422 1419 1415 14x2 1408 1405 X4OI 1398 143 1394 1391 1387 1384 1380 1377 1373 1370 1366 1363 144 1359 1356 1352 1349 1345 1342 1338 1335 133X 1328 145 1324 1321 1318 1314 1311 1307 1304 1300 1297 1293 146 I 2 QO 1287 1283 1280 1276 1273 X270 1266 1263 1259 147 1256 1253 1249 1246 1242 1239 1236 1232 X22g 1225 148 1222 12x9 1215 12X2 1209 1205 1202 1199 1195 1192 149 1189 1185 1182 1179 1175 XX72 1169 1165 1162 1159 150 1155 1152 1149 1145 1142 1139 1135 1132 xx2g 1126 I51 1122 III9 1 1 16 IIT 2 1109 1106 1x03 1099 1096 1093 152 1090 1086 1083 1080 1077 1073 XO7O 1067 1064 1060 153 1057 1053 1051 1047 1044 XO4X 1038 1034 1031 1028 154 1025 1022 1018 1015 1012 1009 1006 X 002 999 996 155 993 990 987 983 980 977 974 971 968 964 156 961 958 955 952 949 945 942 969 936 933 157 930 9-7 924 920 917 914 911 908 905 go2 153 899 895 892 889 886 883 880 877 874 871 159 868 864 861 858 855 852 849 846 843 840 160 837 834 831 828 825 822 818 8x5 812 8og I6I 806 803 800 797 794 791 788 785 782 779 162 776 773 770 767 764 761 75S 755 752 749 163 746 743 740 737 734 731 728 725 722 719 164 716 713 710 707 704 701 698 695 692 689 165 686 683 6S0 677 674 672 66g 666 663 660 166 657 654 651 648 645 642 639 636 633 630 167 628 625 622 619 616 613 610 607 604 601 168 598 596 593 590 587 5S4 581 578 575 572 l6g 569 567 564 561 558 555 552 549 546 544 170 541 538 535 532 529 526 524 521 518 515 171 512 509 506 504 501 498 495 492 489 487 172 484 481 478 475 472 470 467 464 461 458 173 456 453 450 447 444 442 439 436 433 430 174 428 425 422 419 416 414 411 408 405 402 175 400 397 394 391 389 386 3S3 380 377 375 176 372 369 366 364 361 358 355 353 350 347 177 344 342 339 336 333 33 T 328 325 322 320 173 317 314 311 309 306 303 301 298 295 292 179 290 287 284 282 279 276 273 271 268 265 180 263 260 257 255 252 249 246 244 241 238 181 236 233 230 228 225 222 220 217 214 2 X 2 182 209 206 204 201 198 196 193 igo 188 185 183 182 180 177 174 172 169 166 164 x6i 158 184 156 153 150 148 145 143 X40 137 135 132 i8=i 129 127 124 122 119 xx6 114 XIX loS 106 186 103 XOI 98 95 93 90 88 85 82 80 187 77 75 72 69 67 64 62 59 57 54 188 51 49 46 44 41 39 36 33 31 28 189 26 23 21 18 15 13 xo 7 5 3 107 XI. A GENERAL TABLE OF VALUES OF 2^t w FOR 'SPHERICAL SHOT. Stars {*) indicate that the unit figure is to be taken from the line next below. V. 0 1 2 3 1 5 ' 1 8 9 F-s. Seconds. Secs. Secs. Secs. Secs. Secs. Secs. 1 Secs. Secs Secs. 50 13-414 .356 -299 .242 .185 . 129 -073 .017 *.962 *.907 51 12.852 -798 -744 .690 -637 -584 -531 -478 .426 -374 52 12.323 .272 .221 . 170 .119 .069 .020 *.970 *.921 *.872 53 11.823 -775 .726 -679 .631 -584 -537 1 .490 -443 -397 54 ir-351 -305 -259 .214 . 169 .124 .080 1 .036 *.991 *-948 55 10.904 .861 .818 -775 -732 .690 -647 .605 -564 .522 56 10.481 .440 -399 -358 -318 .278 .238 .198 .158 .119 57 10.080 .041 .002 *.964 '='.926 *.887 *-849 *812 ="-774 *-737 58 9.700 .663 .626 -589 -553 -517 .481 -445 .409 -374 59 9-338 •303 .268 -234 .199 .165 . 130 .096 .062 .02Q 60 8-995 .962 -929 -895 .863 .830 -797 -765 -733 .700 61 8.669 -637 .605 -574 .-542 .511 .480 -449 .419 -388 62 8.358 -327 -297 .267 -237 .208 .178 .149 . 120 .090 63 8.061 -033 .004 *-975 *-947 *.919 *.890 *.862 *-834 *.807 64 7-779 -752 .724 -697 .670 -643 .616 -5S9 .562 -536 65 7.510 -483 -457 .431 .405 -379 -354 .328 -303 -277 66 7.252 .227 .202 -177 -153 .128 .103 .079 -055 .030 67 7.006 ■••.982 *-958 *-935 *.911 *.887 *.864 *.841 *.817 *-794 68 6.771 -748 -725 -703 .680 -657 -635 .613 .590 .568 69 6.546 -524 .502 .481 -459 -437 .416 -394 -373 -352 70 6-331 .310 .289 .268 -247 .227 .206 .185 .165 -145 71 6.124 .104 .084 .064 .044 .025 .005 *-985 *.966 *.946 72 5-927 -,907 .888 .869 .850 .831 .812 -793 -774 .756 73 5-/37 .718 . 700 .681 .663 -645 .627 .609 .591 -573 74 5-555 -537 .519 .502 .484 .466 -449 -432 .414 -397 75 5.380 -363 -346 -329 .312 -295 .278 .261 -245 . 22S 76 5.212 -195 .179 .163 . 146 . 130 .114 .098 .0S2 .066 77 5.050 -034 .019 .003 1^87 *.972 *.956 *.941 *.926 *.gio 78 4-895 .880 .865 -849 -834 .819 .805 .790 • 775 .760 79 4-745 -731 .716 .702 .687 -673 -659 -644 .630 .616 80 4.602 -587 -573 -559 -545 • 532 .518 .504 .490 -476 81 4-463 -449 -436 .422 .409 -395 .382 -369 -356 -342 82 4-329 .316 -303 .290 -277 .264 •251 -239 .226 .213 83 4.200 .188 -175 . 163 .150 .138 • 125 -113 .101 .08S 84 4.076 .064 .052 .040 .028 .oi6 .004 *.992 *.980 *.968 85 3-957 •945 • 933 .921 .910 .898 .887 .875 .864 .852 86 3.841 .829 .818 .807 •796 .784 -773 .762 -751 .740 87 3-729 .718 .707 .696 .685 -675 .664 -653 .642 -632 88 3-621 .611 .600 .590 •579 -569 -558 -548 -537 -527 89 3-517 -507 -496 .486 •476 .466 .456 -446 -436 .426 90 3.416 .406 -396 .386 -377 -367 -357 -347 .33S .328 91 3-318 -309 -299 .290 .280 I -271 .261 .252 -243 -233 Y. 0 1 2 3 4 5 6 T 8 9 F-s. Seconds. Secs. Secs. Secs. Secs. Secs. Secs. Secs. Secs. Secs. 92 3.224 .215 .206 . 196 .187 .178 . 169 . 160 • 151 . 142 93 3-133 .124 .115 . 106 •097 .088 •079 .071 .062 •053 94 3-044 .036 .027 .OT9 .010 .001 *-993 *•984 *.976 *.967 95 2-959 - 95 r» .942 •934 .926 .919 .909 .901 • 893 .885 96 2.876 .868 .860 .852 •844 • 836 .828 .820 .812 .804 97 2.797 .789 .781 •773 •765 •758 •750 •742 • 734 •727 98 2.719 .712 • 704 .697 .689 .682 .674 .667 .659 .652 99 2.645 .637 .630 •623 .616 .608 .601 • 594 • 587 .580 100 2-572 -565 • 558 •551 •544 • 537 •530 • 523 • 517 .510 lOI 2-503 .496 • 489 .482 .476 .469 .462 .456 •449 •442 102 2.436 .429 •423 .416 .409 •403 •397 •390 •384 •377 103 2-371 .365 • 358 •352 •346 •339 •333 •327 .321 •315 104 2.308 .302 .296 .290 .284 .278 .272 .266 .260 •254 105 2.248 .242 .236 .231 .225 .219 .213 .207 .202 . 196 106 2.190 . 184 .179 • 173 . 167 . 162 • 156 •151 • 145 . 140 107 2.134 . 129 .123 .118 .112 .T07 . 102 .096 .091 .085 108 2.0S0 .075 .070 .064 •059 •054 •049 •043 •038 •033 109 2.028 .023 .018 •013 .008 •003 *.998 *•993 *.988 *.983 no 1.978 -973 .968 •963 • 958 •953 •948 •943 .938 •933 III 1.929 .924 .919 .914 .910 •905 .900 1 .895 .891 .886 II 2 1. 881 .877 .872 .867 .863 •858 •854 •849 •845 .840 113 1-835 .831 .826 .822 .817 .813 808 .804 .800 • 795 1 14 1. 791 .786 .782 •778 • 773 .769 .765 .760 • 756 • 752 115 1-747 -743 •739 •735 • 730 .726 .722 .718 .714 • 709 II6 1-705 .701 .697 .693 .689 .684 .680 .676 .672 .668 117 1.664 .660 .656 .652 .648 .644 .640 .636 .632 .628 118 1.624 .620 .616 .612 .608 .604 .600 .596 • 593 • 589 119 1.585 .581 • 577 •573 • 569 .566 .562 •558 • 554 .550 120 1-547 .543 •539 •535 • 532 • 528 • 524 .520 • 517 • 513 I 2 I 1.509 .506 .502 .498 •495 .491 .487 .484 .480 .476 122 1-473 .469 .466 .462 •459 •455 •451 .448 -444 .441 123 1-437 • 434 • 430 •427 •423 .420 .416 •413 •409 .406 124 1.402 •399 •395 •392 • 388 •385 .382 •378 •375 • 371 125 1.368 • 365 .361 •358 • 355 •351 •348 •344 •341 • 338 126 1-334 • 331 • 328 •325 .321 •318 •315 • 311 .308 • 305 127 1.302 .298 • 295 .292 .289 •285 .282 •279 .276 .272 128 1.269 .266 .263 .260 • 257 •253 .250 • 247 •244 .241 I 2 Q 1.238 • 234 .231 .228 .225 .222 .219 .216 .213 .210 130 1.206 .203 .200 .197 .194 .191 .188 .185 .182 .179 131 1.176 • T 73 .170 .167 . 164 .161 • 158 • 155 .152 .149 132 1 . 146 • 143 . 140 • 137 • 134 • 131 . 128 • 125 . 122 . 120 133 1.117 .114 .III . 108 • 105 . 102 .099 .096 •093 .091 134 1 .088 .085 .082 •079 .076 •073 .071 .068 .065 .062 135 1.059 -05^ •054 •051 .048 •045 .043 .040 •037 •034 136 1.032 .029 .026 .023 -020 .018 •015 .012 .010 .007 137 1.004 .001 *•999 *.996 *•993 *.991 *.988 >.985 *•983 *.980 138 0.977 •975 •972 .969 .967 .964 .961 •959 .956 •954 139 0.951 .948 .946 •943 • 940 •938 •935 •933 •930 .927 140 0.925 .922 .920 .917 • 915 .912 •909 •907 • 904 .902 141 0.899 .897 .894 .892 .889 .867 .884 .882 .879 .877 109 V. 0 1 2 3 4 : 5 6 7 8 9 F-s. Seconds. 1 Secs. Secs. Secs. Secs. Secs. Secs. Secs. Secs. Secs. 142 0.874 .872 .869 .867 .864 .862 •859 • 857 • 854 .852 143 0.849 •847 •844 .842 .839 .837 •835 .832 • 830 .827 144 0. 825 .822 .820 .818 •815 .813 .810 .808 .806 .803 145 0.801 •798 .796 • 794 •791 • 789 •787 .784 .782 .780 146 0.777 ■775 •773 • 770 .768 . 766 •763 .761 • 759 .756 147 0.754 ■ 752 •749 • 747 • 745 .742 •740 •738 • 736 • 733 148 0.731 .729 •727 • 724 .722 .720 .717 • 715 • 713 • 711 149 0.708 . 706 .704 .702 .700 .697 .695 •693 .691 .688 150 0.686 .684 .682 .680 .677 • 675 •673 .671 .669 .666 151 0.664 .662 .660 .658 .656 •653 .651 .649 .647 .645 152 0.643 .641 •638 •636 •634 .632 .630 .628 .626 .623 153 0.621 .619 .617 .615 .613 .611 .609 .607 •605 .602 154 0.600 .598 .596 • 594 .592 • 590 .588 .586 • 584 .582 155 0.580 .578 • 576 • 574 • 572 • 570 .568 .565 • 563 .561 156 0.559 .557 •555 • 553 •551 • 549 •547 • 545 • 543 .541 157 0.539 .537 • 535 • 533 • 531 • 529 •527 • 525 • 523 .521 158 0.519 • 517 •515 • 513 • 511 .510 .508 • 506 .504 .502 159 0.500 .498 .496 •494 •492 .490 .488 .486 •4S4 .482 160 0.481 •479 •477 •475 •473 •471 .469 .467 .465 • 463 I6I 0.462 .460 •458 .456 •454 •452 •450 •448 .446 •445 162 0.443 •441 •439 •437 •435 •433 •432 •430 .428 .426 163 0.424 .422 .421 •419 •417 •415 •413 •411 .410 .408 164 0.406 .404 .402 .401 •399 •397 •395 • 393 • 392 •390 165 0.388 .386 •384 • 383 •381 .379 •377 • 375 •374 •372 166 0.370 .368 .367 • 365 •363 .361 .360 •35S • 356 •354 167 0.353 • 351 •349 • 347 •346 .344 •342 •340 • 339 •337 168 0.335 • 333 •332 .330 .328 • 327 •325 •323 • 321 .320 i6g 0.318 .316 •315 •313 •311 .309 • 30S .306 • 304 •303 170 0.301 .299 .298 .296 •294 • 293 .291 . 289 .288 .286 171 0.284 .283 .281 • 279 .27S .276 •274 • 273 •271 .269 172 0.268 .266 . 264 .263 .261 .260 .258 .256 •255 •253 173 0.251 . 250 .248 • 247 •245 .243 . 242 .240 .238 •237 174 0.235 • 234 .232 .230 . 229 .227 .226 .224 .222 .221 175 0.219 .218 .216 .215 .213 .211 .210 CO 0 .207 .205 176 0.203 .202 .200 • 199 • 197 . 196 • 194 . 192 .rgr . 1S9 177 0. i88 .i8-6 '.185 .183 . 182 . iSo ■ 17S • 177 .175 • 174 178 0. 172 • I/I . 169 .168 . 166 .165 . 163 . 162 . 160 • 159 179 0.157 • 156 • 154 • 152 • 151 .149 . 148 .146 .145 .143 180 0. 142 .140 • 139 • 137 .136 •134 • 133 .131 .130 . 129 181 0. 127 . 126 • 124 . 123 . I 2 T . 120 . iiS • 117 .115 • 114 182 0. ri2 .III . 109 . io 3 .107 .105 • 104 . 102 . lOI .099 183 0.09S .096 •095 • 093 .092 .090 .0S9 .0S8 .0S6 .0S5 184 0.083 .082 .080 • 079 .078 .076 •075 •073 .072 .070 185 0.069 .06S .066 .065 .063 .062 ,o6r •059 .058 •056 186 0.055 • 054 .052 .051 .049 .04S • 047 • 045 .044 .042 187 0.041 .040 .038 • 037 .035 •034 • 033 •031 .030 .029 188 0.027 .026 .024 • 023 .022 .020 .019 .018 .oi6 .015 l8g 0.014 .012 .Oil .009 .008 .007 .005 .004 .003 .001 IIU XII. TABLE OF VALUES OF h = = 16 . 0954 FEET. t 0 1 2 3 4 5 6 T 8 9 n Feet. Feet. Feet. Feet, Feet, Feet, Feet. Feet. Feet. Feet. I.O 16.10 16.42 16.75 17.0S 17-41 17-75 18.08: 18.43 18.77 19.12 1. 1 19.48 19.83 20. 19 20.55 20.92 21.29 21.66 22.03 22.41 22.79 1.2 23.18 23.57 23.96 24.35 24-75 25-15 25-55 25.96 26.37 26.78 1-3 27.20 27.62 28.04 28.47 28.90 29-33 29-77 30.21 30.65 31.10 1-4 31.55 32.00 32.45 32.91 33-38 33-84 34.31 34-78 35-26 35.73 1-5 36.21 36.70 37.19 37.68 38.17 38.67 39-17 39.67 40.18 40.69 1.6 41.20 41.72 42.24 42.76 43.29 43.82 44.35 44.89 45.43 45.97 1-7 46.52 47.06 47.62 48.17 48.73 49.29 49 . 86 50.43 51.00 51-57 1.8 52.15 52.73 53.31 53.90 54-49 55-09 55.68 56.28 56.89 57-49 1 . 9 58.10 58.72 59.33 59-95 60.58 61.20 61.83 62.46 63.10 63.74 2.0 64.38 65.03 65.68 66.33 66.98 67-64 68 . 30 68.97 69.64 70.31 2.1 70.98 71.66 72.34 73-02 73-71 74.40 75-09 75.79 76.49 77-20 2.2 77.90 78.61 79.32 80.04 80.76 81.48 82.21 82.94 83.67 84.41 2.3 85.14 85.89 86.63 87.38 88.13 88.89 89.64 90.41 91-17 91-94 2.4 92.71 93.48 94.26 95.04 95.83 96.61 97.40 98.20 98.99 99-79 2.5 100.6 ] lOI .4 102.2 103.0 103.8 104-7 105.5 106.3 107.2 108.0 2.6 108.8 109.6 no. 5 111.3 II 2.2 113-0 113-9 114-7 115-6 116.4 2.7 117.3 118.2 119. 1 120.0 120.8 I21.7 122.6 123.5 124.4 125-3 2.8 126.2 127. I 128.0 128.9 129.8 130.7 131-6 132.6 . 133.5 134.4 2.9 135.4 136.3 137.2 138.2 139-1 140. I I4I .0, 142.0 142.9 143-9 3-0 144.9 145.8 146.8 147.8 148.8 149-7 150.7 151-7 152.7 153-7 3-1 154.7 155.7 156.7 157.7 158.7 159-7 160.7 161 . 7 162.8 163.8 3-2 164.8 165.8 166.9 167-9 169.0 170.0 171.1 172. 1 173.2 174.2 3-3 175.3 176.3 177.4 178.5 179.6 180.6 181.7 182.8 183.9 185 .0 3-4 186. 1 187.2 188.3 189.4 190.5 191.6 192.7 193.8 195.0 196.1 3-5 197.2 198.3 199.4 200.6 201.7 202.8 204.0 205.1 206.3 207.4 3-6 208.6 209.7 210.9 212 . I 213.3 214-4 215.6 216.8 218.0 219.2 3 -i 7 220.3 221.5 222.7 223.9 225.1 226.3 227.5 228. 8 230.0 231.2 3.8 232.4 233.6 234.9 236.1 237-3 238.6 239.8 241.0 242.3 243.5 3.9 244.8 246. 1 247.3 248.6 249.9 251.1 252.4 253-7 255.0 256.2 4.0 257.5 258.8 260. 1 261 .4 262.7 264.0 265.3 266.6 267.9 269.2 4.1 270.6 271.9 273.2 274.5 275-9 277.2 278.5 279.9 281 . 2 282.6 4.2 283.9 285.3 286.6 288.0 2S9.3 290-7 292.1 293-5 294.8 296.2 4.3 297.6 299,0 300.4 301.8 303.2 304.6 306.0 307.4 308.8 310.2 4.4 311.6 313.0 314.4 315.9 317-3 318.7 320.2 321.6 323-0 324-5 4.5 325.9 327.4 328.8 330.3 331-8 333-2 334-7 336.2 337-6 339-1 4.6 340.6 342.1 343.5 345-0 346.5 348.0 349-5 351-0 352.5 354-0 4.7 355.6 357.1 358.6 360. 1 361.6 363-2 364-7 366.2 367.8 369-3 4.8 370.8 372.4 373.9 375-5 377-1 378.6 380.2 381.7 383-3 384.9 4.9 386.5 388.0 389.6 391.2 392.8 394-4 396.0 397.6 399-2 400.8 5-0 402.4 404.0 405.6 407.2 408.8 410.5 412. i 413.7 415.3 416.9 ‘1 1 2 3 4 5 6 7 8 9 Feet. Feet. Feet. Feet. Feet. Feet. Feet. Feet. Feet. Feet. 5-1 418.6 420.3 421.9 423-6 425.2 426.9 428.5! 430.2 431-9 433-5 5-2 435.2 436.9 438.6 440-3" 442.0 443-6 445.3' 447.-0 448.7 450.4 5-3 452.1 453-8 455.5 457-3 458.9 460.7 462.4 464.1 465-9 467-6 5-4 469.3 471. 1 472.8 474-6, 476.3 478.1 479.8 481 .6 483.4 485.1 5-5 486.9 488.6 490.4 492.2^ 494.0 495-8 497 -^ 499-4 501.2 503.0 5-6 504.8 506.6 508.4 510.2 512.0 513.8 515-6 517-5 519-3 521.1 5-7 522.9 524.8 526.6 528.5* 530.4 532.2 534-0 535-8 537.7 539-6 5-8 541.4 543.3 545-2 547-1 549-0 550.8 552.7, 554-6 556.5 558.4 5-9 560.3 562.2 564-1 566.0 567-9 569.8 571-7 573-7 575-6 577*5 6.0 579.4 581.4 583-3 585-2 587.2 589.1 591 -I 593-0 595.0 597.0 6.1 598.9 600.9 602.9 604 . 8 . 606.8 608.8 610.7 612 . 7 614.7 616.7 6.2 618.7 620.7 622.7 624.7 626.7 628.7 630.7 632.8 634-8 636.8 6.3 638.8 640.9 642.9 644.9 647.0 649.0 651.1 653-1 655.2 657- 2 6.4 659-3 661.3 663.4 665.5 667.5 669.6 671 -7^ 673-8 675-9 677.9 6.5 680.0 682.1 684.2 686.3 688.4 690.5 692.6 694.8 696.9 699.0 6.6 701 . 1 703.3 705.4 707.5 709.7 711.8 713-9 716.1 718.2 720.4 6.7 722.5 724.7 726.8 729.0 731-2 733-4 735-5 737.7 739-9 742.1 6.8 744.3 746.4 748.6 750. 8j 753-0 755-2 757 - 5 759-7 761.9 764.1 6.9 766.3 ■768.5 770.8 773.0] 775-2 777.4 779-7 781.9 784.2 786.4 7.0 788.7 790.9 793-2 795-4'' 797-7 800.0 802.3 804.5 806.8 809. 1 7-1 811.4 813-7 816.0 818.2 820.5 822.8 825.1 827.5 829.8 S32. 1 7.2 834.4 836.7 839.0 841.3 843-7 846.0 848.4 850.7 853.0 855.4 7.3 857.7 860. 1 862.4 864.8 867.1 869.5 871.9! 874-3 876.6 879.0 7-4 881.4 883.8 886.2 888.5 890.9 893-3 895.7 898.1 900.6 903.0 7-5 905.4 907.8 910.2 912.6 915.1 917-5 919.9 922.4 924.8 927.2 7.6 929.7 932.1 934-6 937-0' 939-5 941.9 944-4 946.9 949-3 951.8 7-7 954.3 956.8 959-3 961.8 964.2 966.7 969.2. 971-7 974.2 976.7 7.8 979.2 981.8 984-3 986.8 989-3 991.8 994 j 996.9 999-4 1002 7-9 1005 1007 1009 1012] 1015 1017 1020 1023 1025 1028 8.0 1030 1033 1035 1038 1041 1043 1046 1048 1051 1053 8.1 1056 1059 1061 1064 1066 1069 1072 1074 1077 loSo 8.2 1082 1085 1088 1090'^ 1093 1095 1098 IIOI 1104 1106 8.3 1109 1112 1114 1117^ 1120 1122 1125 II2S 1130 1133 8.4 1136 1138 1141 1144 1147 1149 1152 1155 1157 ii6o 8.5 1163 1166 1158 II7I 1174 1177 1179 IIS2 1185 liSS 8.6 1190 1193 1196 1199 1202 1204 1207 1210 1213 1216 8.7 1218 1221 1224 1227 1230 1232 1235 123S 1241 1244 8.8 1246 1249 1252 1255 1258 1261 1264 1266 1269 1272 8.9 1275 1278 1281 1284 1286 12S9 1292 1295 129S 1301 9.0 1304 1307 1310 1*^12 1315 1318 1321 1324 1327 1330 9.1 1333 1336 1339 1342 1345 1348 1350 1353 1356 1359 9.2 1362 1365 1368 1371 1374 1377 13S0 1383 13S6 1389 9-3 1392 1395 1398 1401 1404 1407 1410 1413 1416 1419 9-4 1422 1425 1428 1431 1434 1437 1449 1444 1447 1450 9-5 1453 1456 1459 1462 1465 146S 1471 1474 1477 14S0 9.6 1483 i486 1490 1493 1496 1499 1502* 1505 150S 1511 9-7 1514 1518 1521 1524 1527 1530 1533 1536 1540 1543 9.8 1546 1549 1552 1555 155S 1562 1565 1568 1571 1574 9-9 1578 1581 1584 1587 1590 1593 1597 1600 1603 1606 112 APPENDIX II. TABLE I. Densities corresponding to different values of — W' -j- w, in grammes. Is umbers. 0 1 2 3 1 5 G T 8 9 DifF. 700 r -93579 551 523 496 468 1 413 385 358 330 27.6 701 303 275 247 220 192 165 137 109 082 054 27.6 702 027 997 972 944 917 890 862 835 807 7 So ' 27.4 703 1-92753 725 698 670 643 616 588 561 533 506 27-4 704 479 451 424 396 369 342 314 287 259 232 27-4 705 205 177 150 123 096 069 041 014 987 960 27.2 706 1-91933 905 878 851 824 797 770 743 716 6S9 27.1 707 662 634 607 580 553 526 499 472 445 418 27.1 708 391 364 337 310 283 256 229 202 175 148 27.0 709 I 2 I 094 067 040 013 986 959 932 905 878 26.9 710 1.90852 825 798 771 744 718 691 664 637 610 26.8 711 584 557 530 503 476 450 423 396 369 342 26.8 712 316 289 262 235 209 182 155 129 102 075 26.7 713 049 022 995 969 942 916 889 862 836 809 26.6 714- -...V... 1.89783 756 730 703 677 651 624 597 571 544 26.5 715 518 491 465 438 412 385 359 332 306 279 26.5 716 253 226 200 173 147 121 094 068 041 015 26.4 717 I .88989 962 936 910 883 857 831 804 778 752 26.3 718 726 699 673 647 620 594 568 541 515 489 26.3 719 463 436 410 384 358 332 306 280 254 228 26.1 720 202 175 149 123 097 071 045 019 993 967 26.1 721 1.87941 914 888 862 836 810 784 758 732 706 26.1 722 680 654 628 602 576 550 524 498 472 446 25-9 723 421 395 369 343 317 291 265 239 213 187 25-9 724 162 136 no 084 058 033 007 981 955 929 25-8 725 I . 86904 878 852 826 800 775 749 723 697 671 25.8 726 646 620 594 568 543 517 491 466 440 414 25-7 727 389 363 337 311 286 260 234 209 183 157 25-7 728 133 107 082 056 031 005 9S0 954. 929 893 25.6 729 1.85878 852 827 801 776 750 725 699 674 648 25-5 730 623 598 573 547 522 495 471 446 420 395 25-4 115 Table I. — Continued. Numbers. 0 1 1 2 3 4 K 0 6 7 8 9 Diff. 731 1.85369 344 318 293 267 243 217 192 167 142 25-2 732 II6 091 066 041 015 989 973 939 ^14 8go 24.9 733 I . 84863 839 813 786 762 737 714 6S7 653 637 25.7 734 612 587 562 536 511 486 461 436 411 389 25.0 735 361 336 311 286 260 235 210 185 150 135 25.0 736 no 085 060 035 010 985 960 935 910 8S5 25.0 737 1.83860 835 811 786 761 736 711 685 661 636 25.0 738. 612 586 560 536 510 487 461 437 412 38S 25.0 739 362 338 313 288 264 239 214 189 165 140 25.0 740 II4 090 064 041 016 991 967 942 917 893 25.0 741 1.82868 843 8lg 794 769 745 720 695 670 645 24.6 742 621 596 572 547 523 49S 474 449 425 400 24.5 743 376 351 326 302 277 253 228 203 179 154 24.6 744 130 105 081 056 032 008 983 959 934 910 24.6 745 I. 81886 861 837 812 78S 764 739 715 691 666 24.4 746 642 617 593 569 544 520 496 471 447 423 24.3 747 399 374 350 326 302 278 253 22 Q 205 iSi 24.2 748 157 132 108 084 060 036 on 987 963 939 24.2 749 I . 80915 890 866 842 818 794 770 746 722 69S 24.1 750 674 649 625 601 577 553 529 505 48 1 457 24.1 751 433 409 385 361 337 313 289 265 241 217 24.0 752 193 l6g 145 121 097 073 049 025 001 977 24.0 753 1-79953 929 905 881 857 833 S09 7S5 761 737 23-9 754 714 6go 666 642 619 595 571 54S 524 500 23-7 755 477 453 429 405 382 358 334 311 2S7 263 23.7 756 240 216 192 168 145 I2I 097 074 050 026 23.7 757 003 979 955 931 go8 S84 S60 837 S13 789 23.7 758 1.78766 742 719 695 672 648 625 601 57S 554 23-5 759 531 507 484 460 437 413 390 366 343 319 23*5 760 296 272 249 225 202 179 155 132 loS 085 23.4 761 062 039 015 992 g6S 945 921 89S ^74 851 23*4 762 1.77828 804 781 758 734 711 6SS 664 641 61S 23.4 763 595 571 54S 525 502 479 455 432 409 3S6 23.2 764 363 339 316 293 270; 247 223 200 177 154 2j).2 765 131 107 084 061 038 015 992 969 946 923 23.1 766 I . 76900 876 S53 S30 807 J-7S4 .3S . 715 1 692 23.x 116 Table I. — Continued. Numbers. 0 1 2 3 1 5 6 7 8 9 Diff. 767 I . 76669 646 623 600 577 554 531 508 485 462 23.0 768 439 416 393 370 347 324 301 278 255 232 22.9 769 210 187 164 141 118 095 072 049 026 003 22.9 770 1.75981 958 935 912 889 866 843 820 797 774 22.9 771 752 729 706 683 661 638 615 593 570 547 22.7 772 525 502 479 456 434 411 3S8 366 343 320 22.7 773 298 275 252 227 207 184 161 139 II6 093 22.7 774 071 048 025 003 980 958 935 912 890 867 22.6 775 I • 74845 822 800 777 755 732 710 6S7 665 642 22 . 5 776 620 597 575 552 530 507 4S5 463 440 418 22.5 777 395 372 350 327 305 283 260 238 215 193 22.4 778 171 148 126 104 081 059 037 014 992 970 22.3 779 1-73948 925 903 881 858 836 814 791 769 747 22.3 780 725 702 680 658 635 613 591 568 546 524 22.3 781 502 479 457 435 413 39X 368 346 324 302 22.2 782 280 257 235 213 191 169 147 125 103 081 22.1 783 059 036 014 992 970 948 926 W 882 860 22.1 784 1.72838 815 793 77X 749 729 705 683 661 639 22.1 785 617 595 573 551 529 507 485 463 441 419 21.9 786 39S 376 354 332 310 2S8 266 244 222 200 21.9 787 X79 X57 135 113 091 070 048 026 004 982 21.8 788 I . 71961 939 917 895 873 852 830 808 786 764 21.8 789 743 721 699 677 656 634 612 591 569 547 21.7 790 526 504 482 460 439 417 395 374 352 330 21.7 791 309 287 265 243 222 200 178 157 135 113 21.7 792 092 070 049 027 006 984 963 941 920 898 21.5 793 1.70887 855 833 812 790 769 747 725 704 682 21.6 794 661 639 618 596 575 554 532 511 489 46S 21.4 795 447 425 404 382 361 340 318 297 275 254 21.4 796 233 2II igo 168 147 126 104 083 061 040 21.4 797 019 997 976 954 933 912 890 869 847 826 21.3 79S 1.69806 784 763 742 721 700 679 658 639 616 21 . 1 799 595 573 552 531 509 488 467 445 424 403 21.2 800 382 360 339 318 297 276 254 233 212 191 21. 1 801 170 149 128 107 086 065 044 023 002 981 21.0 802 1.68959 938 917 896 875 854 8-33 812 791 770 21.0 117 Table I. — Continned. N umbers. 0 1 2 3 4 5 6 7 8 , [) DifF. 803 1.68749 728 707 686 665 644 623 602 581 560 21.0 804 539 518 497 476 455 434 413 392 371, 350 21.0 805 329 308 287 266 245 224 203 182 161 140 20.9 806 120 099 078 057 036 015 994 973 952 932 20.9 807 1.67912 891 870 849 828 808 787 766 745 724 20.8 808 704 683 662 641 621 600 579 559 538, 517 20.7 809 497 476 455 434 414 393 372 352 331 310 20.7 810 290 269 248 228 207 187 166 145 125 104 20.6 811 084 063 042 022 001 981 960 939 919 8g8 20.6 812 1.66878 857 837 816 796 775 755 734 714' 693' 20.5 813 673 652 632 61I 591 570 550 529 509 488, 20.5 814 468 447 427 406 386 366 345 325 304| 284^ 20.4 815 264 243 223 203 182 162 141 I2I loi oSo 20.4 816 060 039 019 999 978 958 938 917 897 877^ 20.3 817 1.65857 836 816 796 775 755 735 714 694' 674’ 20.3 818 654 633 613 593 573 553 533 512 492 472 20.2 819 452 431 411 391 371 351 330 310 290 27O; 20.2 820 250 229 209 189 169 149 129 109 089 069 20. I 821 049 028 008 988 968 948 928 go8 8SSj 868 20.1 822 1.64848 828 808 788 768 748 72S 70S 688 668 20.0 823 648 628 608 588 568 548 528 508 488 46S 20.0 824 448 428 408 388 368 348 328 308 288 268 19.9 825 249 229 209 189 169 149 129 109 089 069 19.9 826 050 030 010 990 970 950 930 910 890 870 19.9 827 1.63851 831 811 791 771 752 732 712 692 672 ig.S 828 653 633 613 593 574 554 534 515 495 475 19.7 829 456 436 416 396 377 357 337 318 29S 27S 19.7 830 259 239 219 200 180 I61 141 I2I 102 082 19.6 831 063 043 023 004 984 965 945 925 go6 886 19.6 832 1.62867 847 827 808 788 769 749 729 710 690 19.6 833 671 651 632 612 593 573 554 534 515 495' 19.5 834 476 456 437 417 398 379 359 340 320; 301 19.4 835 282 262 243 223 204 184 165 145 126 106 19.5 836 0S7 067 048; 029 009 990 971 951 932 913 19.3 837 I .61894 874 855 836 816 797 778 758 739 720 19.3 838 701 681 662 643 623 604 585 565 546 527 19.3 118 Table I. — Continued. Numbers. 0 1 2 3 4 5 6 7 8 9 Dm . 839 1 .61508 488 469 450 431 412 392 373 354 335 19.2 840. . . 316 296 277 258 239 220 200 181 162 143 19.2 841 124 104 085 066 047 028 009 990 971 952 19.1 842 1.60933 913 894 375 856 837 817 798 779 760 19.2 843 741 722 703 C84 665 645 627 608 589 570 19,0 844 551 532 513 494 475 456 437 418 399 380 19.0 845 361 342 323 304 285 266 247 228 209 igo 18.9 846 172 153 134 115 096 077 058 039 020 001 19.0 847 1.59982 963 944 925 906 888 869 850 831 812 18.8 848 794 775 756 737 718 700 681 662 643 624 18.8 849 606 587 568 549 530 512 493 474 455 436 18.8 850 418 399 380 361 342 324 305 286 267 248 i8.8 851 230 2 II 192 174 155 137 118 099 081 062 18.6 852 044 025 006 987 969 950 931 913 894 875 18.7 853 r. 58857 838 820 801 783 764 746 727 709 690 18.5 854 672 653 634 615 597 578 559 541 522 503 18.7 855 485 466 448 429 41 1 392 374 356 337 319 18.5 856 300 281 263 244 226 208 189 171 152 134 18.4 857 II6 097 079 060 042 023 005 986 968 949 18.5 858 I -57931 912 894 875 857 839 820 802 783 765 18.4 859 747 728 710 692 673 655 637 618 600 582 18.3 860 564 545 527 509 490 472 454 435 417 399 18.3 861 381 362 344 326 307 289 271 252 234 216 18.3 862 198 179 I6I 143 125 107 088 070 052 034 18.2 863 016 997 979 961 943 925 907 889 871 853 18. 1 S64 1.56835 816 798 780 762 744 725 707 68g 671 18.2 865 653 634 616 598 580 562 544 526 508 490 18. 1 866 472 454 436 418 400 382 364 346 328 310 18.0 867 292 273 255 237 2.19 201 183 165 147 129 18. 1 868 III 093 075 057 039 021 003 985 967 949 17.9 869 1-55932 914 896 878 860 842 824 806 788 770 17.9 870 753 735 717 699 681 663 645 627 609 591 17.9 871 574 556 538 520 502 485 467 449 431 413 17.8 872 396 378 360 342 324 307 289 271 253 235 17.8 873 218 200 182 164 146 129 III 095 075 051 17.8 874 040 022 004 986 969 951 933 916 898 880 17-7 119 Table I. — Continued Is umbers. 0 1 2 3 4 5 6 7 8 9 Diff. 875 I . 54863 845 827 809 792 774 756 739 721 703 17-7 876 686 668 650 633 615 598 580 562 545 527 17.6 877 510 492 474 457 439 422 404 386 369 351 17.6 878 334 r 316 298 281 263 246 228 210, 193 175 17.6 879 158 140 123 105 083 070 052 034 017 999 17.6 880 1.53982 964 947 929 912 895 877 860 842 825 17-4 881 808 790 773 755 738 721 703 686 668 651 17.4 882 634 616 599 581 564 547 529 512 494 477 17.4 883 460 442 425 407 390 373 355 338 320 303 17-4 884 286 268 251 234 216 199 182 164 147 130 17-3 885 113 095 078 061 043 026 009 991 974 957 17-3 886 I . 52940 922 905 888 871 854 836 S19 802 785 17.2 887 768 750 733 716 699 682 664 647 630 613 17.2 888 596 578 561 544 527 510 492 475 | 45S 441, 17.2 889 424 406 389 372 355 338 321 304 287; 270I 17. 1 8go 253 235 218 201 1 84 167 150 133 116 099; 17. 1 891 082 064 047 030 013 996 979 962 945 92S 17. I 892 1.51911 894 877 860 S43 826 809 792 775 758; 17.0 893 741 724 707 690 673 656 639 622 605 588; 16.9 894 572 555 53S 521 504 487 470 453' 436 419 17.0 895 402 3S5 368 351 334 317 300 2S3 266 249 16.9 896 233 216 199 182 165 149 132 115 09S oSr i6.S 897 065 048 031 0X4 ”^97 981 ^64 947 [ 930 913 16.8 898 1.50897 880 863 S46 S29 813 796 779' 762 745 16.8 899 729 712 695 678 661 645 628 611 594 577 16.8 900 561 544 527 510 494 477 460 444 427 41G 16.7 901 394 377 360 343 327 310 293 377, 260 243 16.7 902 227 210 193 177 160^ 144 127 no 094 077 16.6 903 061 044 027 Oil 994 ! 97S 944 92S 911 16.6 904 1.49895 878 862 845 829 812 796 779 763 746 16.5 905 730 713 696 6S0 663 647 630 613 597 5 So 16.6 906 564 547 531 514 498 48 1 465 448 432 415 16.5 907 399 3S2 366 349 333 317 300 2S4 267 251 16.4 908 235 218 202 185 169 152 136 II9 103 086 16.5 909 070 053 037 021 OO-^ 988 ^72 955 939 , 923 16.3 910 1.48907 890 857 S4. 825 S09 792 776 760 16.4 120 TABLE II. Tdble for the reduction of grammes and tenths of grammes to grains. [From 700 grammes to 910 grammes.] Numbers. 0 6 9 700. 701. 702. 703- 704. 705. 706. 707- 708. 709. 710. 711. 712. 713 714- 715- 716. 717- 718.. 719. . 720. . 721. . 722. . 723- • 724. . 725- • 726. . 727. . 728.. 729. . 730. . 10801.00 16.43 31-9 47-3 62.7 78.2 93.6 10909 . o 24.4 39- 9 55-3 70.7 86.2 1 1001 .6 17.0 32.5 47-9 63-3 78.7 94.2 11109.6 25.0 40- 5 55.9 71-3 86.8 I 1202. 2 17.6 33.0 48.5 63-9 02.5 17.9 04.1 19.5 05 .6 07.2 08 .740.3 ■ 8 ;i 3-4 22.6 24.1 25.7 27.2,28.8 •7j44-3 48.8 50.4I51.9 53.5 55.o's6.6 58.1,59-7 33-435-0 64.2 95-1 10.5 25.9 41.4 96.7J98.2 12. 1 13.6 I 27.5129.0 79-7 81.3 82.8 84.4 85.9:87.5 89.0^90.6 . 4 06 . o -8'2I.4 .2^36.8 38.3 43.044.5 46.1 47.649.2 50.7 52.3 53 56.8 58.4(59.9 61. 72.2 87-7 89.3(90-8 92-4 03.1 18.5 34-0 49-4; 64.8 80.2 95-7 II . I 26.5 42.0 57-4 72.8 36.5 38.1 65 .8,67.3 68. 9 70.4 72.0 99- 15- 30 632.133.7 73-8175-3 76 04.7jo6.2 20. 1(21 .6 35-637-1 5i-o'52.5 66.4^67.9 81.8 97-3 12.7 83-3 98.8 14.2 28.I|29.6 43.6^45-1 59.obo.5j62 74-475-9 77- 69 84. 00. 15- 31- 46. 88.3 89.9 9i.4'93.( 03-7 19. 1 34-5 50.0 65-4 05.3106.8 08 20.7^22.3123. 36.1 73-5,75-1 01.3 02.9 i 6.7 'i 8.3 47-6(49-2 5 63.oj64.6 9 78.4I80.0 93-9j95-5 8 09.3^10.9 4-7,26.3 40.2j4i.8 55-6;57-2 71.0*72.6 9 86.4188.0 oi-9jo3-5 17-3 18.9 I -7i34-3 14.9 30.3 45 - 8 61.3 76.6 92.1 07-5 22.9 .ij67.7 69.2 5j83-i 0,98.6 4 T4.0 8 29.4 344.946.4 7 60.3 61. ^ . I 75.7 05.0 20.4 35-8 48.3,49-9 51-4 7 I 63.6 65.2 79.0 80.6 94-5^96-1 09.9*11.5 25.3 26.9 40.7142.3 37.6.39.; 51.653.1 54. 756.2(57. s 67.068.5.70.1 7i.6j73.2 66 . 82. 97- 13- 28. 43- 59- 74- 91. 1 06.6 22.0, 37-4 53-0 68.3 83-7 6,99-2 0^14.6 4I30.0 84.6 00. 1 15-5 30.9 77-2 92.6 08.1 23-5 38.9 54-5 69.8 85-3 00.7 16.1 31-5 8(45.446.9 3,60.9 62.4 7176.3(77-8 121 Table II. — Continued. Numbers. 0 1 2 3 4 0 6 7 8 9 731 11279-3 80.8 82.4L3.9 85.5 87.0 88.6 1 90.1 91.7 93.2 732. 733 - . 734 - ■ 735 - 736. . 737 - 738. 739 - 740. 741. 742. 743 - 744 - 745 - 746. 747 - 748. 749 - 750. 751 - 752. 753 - 754 - 755 - 756. 757 - 758. 759 - 760. 761. 762. 763- 764. 765- 766. 94.8 11310.2 25.6 41.0 56.5 71.9 87-3 11402.8 18.2 33- 6 49.1 64.5 79-9 95-4 11510.8 26.2 41 .6 57-1 72.5 87.9 11603.4 18.8 34- 2 49-7 65.1 80.5 95-9 11711.4 26. 8 42.2 57-7 73-1 88.5 11803.9 19.4 96.3197.9199.4 01 .0 02. 5 04. 1 05 .6 07.2 08.7 II. 7 13.314.8 16.4 17.9 19.5 21.0 22.6 24.1 27.1 28.7 42.544.1 58.0^59.6 73-4j75-0 88.890.4 04 - 3 |o 5.9 19.721.3 35-1 36.7 50.6)52.2 66.0 67.6 81.4)83.0 30.2 31. 8 | 33- 3 34-9 36-4 38.039.5 45.647.248.7 50.3 51.8^53-4 54-9 I I I I I 61. 1 62.7 64. 76.5:78.1 5 o 22.8 24.4 38.2)39.8 53 . 7 | 55.2 69.1 70.7 I 84.5:86.1 91 . 993 . 07.409. I96.998.5 00.001. Ill 12.3.13.9 15.447. I27.7 29.3 30 . 8'32 * I ^ ! 43.1 44.746.247 I I 158.6 60.2 61 .7,63 I I 1 I ,74.075.677.1 78 189.491.0*92.5 94 I 1 04.9 06.5 08.009 |2o.32i.9'23.4 25 135. 7'37. 3 38.8^40 *5i.2'52.s'54.3 55 1 i 1 66.6 68.2 69.7 71 82 .0^83 .6 85.1 86 i I- I- 97.4'99.ooo.5 02 12.9 14.5 16.0 17 28.3 43.7 59.2 74.6 90.0 05.4 29.9'3I.4 33 45.346.8^48 60.8 62.3 63 76.2 77.7 79 91.693.1 94 07.0*08.5 10 I 120.9 22.5 24.0 25 i I I I 2 65.8167.3 68.9 70.4 79.6 81 .2:82.7 84.3 85.8 tit'— 95.0 96. 698. 1 99. 701. 2 10.5 12. I I3.6'i5.2 16.7 25.9 27.5 29.0 30.6 32.1 41.342.944.446.047.5 56.8 58.4 59.9 61.5 63.0 72.2 73.8'75.3 76.9 78.4 87. 6 89.2'90.7*92.3 93.8 6 03. 1 04.7:06.2 07.8 09.3 o 18.5 20.1 21.6 23.2 24.7 .4 33.9 35.5 37.o'38.640.t .8 49.3 50. 9 52.4 54.0 55.5 .3 64.8 66.4 67.9 69.5 71.0 .7 80.2 81.8 S3. 3 84.9 86.4 . I 95.6 97.2 98.7 00.3 01.8 .611.1 12.7 14.2 i^.S 17.3 I .0 26.5 28. 1 29.6 31.2 32.7 .441.943.545-046.648.1 ■9 57-V59-ot6o.5 62.1 63.6 .3*72.8 74.4 75.9 77.5 79.0 .788.289.891.392.994.4 . i'o 3.6 05 .2 06. 7 0S.3 09.8 .6 19. i'20. 7 22.2 23.8 25.3 .0 34.5 36.1 37-6 39-2 40.7 .449.951.5 53.054.656.1 .965.467.068.5 70.1 71.6 .3 80.8 82. 4 83.9 85.5 87.0 I I _i_ . 7 96 . 2 97 . 8 99 . 3 00 . 9 02 . 4 .1 II. 6 13.2 14.7 16.3 17. 8 .6 27.1 28.7 30.2 31.8 33.3 122 Table II. — Continued. N umbers. 767. 768. 769. 770 . 771- 772. 773- 774- 775- 776. 777- 778. 779- 780. 7S1. 782. 783. 784. 785. 786. 787. 788. 789. 790. 791. 792. 793- 794- 795- 796. 797- 798. 799- 800. 801. 802. 2 ! 3 11834.8 50.2 65.7 81. 1 96- 5 11911.9 27.4 42.8 58.25 73.68 89. 1 12004.5 19.9 35-4 50.8 66.3 81.7 97.1 12112.6 28.0 43-4 58.8 74-3 89.7 12205 . 1 20.6 36.0 51-4 66.9 82.3 97- 7 12313.1 28.6 44.0 59-4 74-9 36-3 37- 51-7 53- 67.2 68. I 82.6 84. I 98 .0 99 13-4 15 28.9 30 I 44-3 45 59-8|6 i 75.276 90.6 92 07 23 38 53 69 84 00 15 4 ! 5 C i 9 I 9 39-4 41 -042. 5 44- 1 45 -6 47 -2 48. 7 I ' I I 3 54.8 56.4 57.959.5 61.062.664.1 I ! ! I 8 70.3 71.9 73.475.0 76.5 78.1 79.6 I i : I ' I I 2 85.7 87.3 88.890.491.993.5 95.0 6 01 . I 02. 7 04.2 05 .8 07.3 oS.9'10.4 i ^ ' o ‘ a' ! i I o o 16. 5 i8. 1 19.6 21 .2 22. 7 24.3 25 .8 5 32 0 33.6'35.i 36.7^38.2'39.84i.3 ’ I ' ' i A 947.449.0 50.5 52.1 53-6 55-2 56.7 06.0 21 .4 36.9 ‘52.3 ,67.8 |83.2 '98.6 14. 1 29-5'3i 44.946 60.3 61 '75.8 77 I 91 . 2 92 06.6 08 22.1 23 37-5 39 52.9 54 68.4 70 83 .s '85 99 . 2 00 . 14.6 16. 4 62 . 8'78 2'93 6'og o 24.576.1 27.6 5'40.04I.643.i .3 79.981.4 .7 95.3 96.8 I I . I 10.7 12.2 .9 55- ■ 4'70. .8 86 . 2 01.7 I 7 17-2 57-058.5 72.5 74.0 87.989.4 03.3 04. 18.8 20. 83.0 84.5 86 98.499.9 i3-7'i5-3 29.2 30.7 44.746.2 60. i'6i .6 75-6j77-i 91.092.5 06.407.9 21.9 23.4 772.2 i'87.6 01.5 03.0 16.948.4 32. 47- 63- 78. 94- 777. 3^8. 840, I 52.7 54.2 55 . I 32.6 34.2 35. .5 48.049.6 51. .9 63.4 65.0 66. .4 78.9 80.5 82. o' 83. 6^85. 1 |s6 •8'94-395-9 97-4 99-0^do.5*02 8 5'68. i!69.6 71 .2 7 I 2 09. 7| 1 1. 342. 8 14. 4' 15. 9^7. 5 3 29.9*3i.4'35.o 7 45. 3^46. 9^48. 5 ‘ I I ! i I • 5 56.0 57.6 59. 1 bo. 7 62.2 63.8 I ■ . . 7 25 .2 26.8 28. I 40.642.2 43. I < Al A ■ 071.5 73.1 74.6 76.2 77.979 • J 4 86.9’8S . 5|go.ol9i .6 93. i'94. 7 4'o7.oo8.5 jo.i 8 02.3 03.905. I I ! 2 17.7,19.3 20. 8,22.4:23.9 25 30.131.7 33.2 34.8 36.3’37.9'39.4 4I I II I I 45-5 47-1 48.6 50.2 5 I -7 53-3 54-8 56 60.9 62.5 64.0 65 .6 67. 1 68. 7|7o. 2 71 -3:33-8 849-3 2j64-7 7I80.2 1I95-6 541-0 ! , 0|26.5 441-9 57-3 72.7 88.2 03.6 19.0 34-5 50.0 65-3 80.8 96.2 II .6 5 27-0 042.5 4 57-9 8:73-3 76.448.0,79.5 81.1,82.6,84.2 85.7,87.3 88.8 1 I 123 Tabi.e II. — Contmv.ed. Numbers. j 0 1 : 2 : 3 4 ^ 5 6 : T ; 8 : 9 1 803 12390.3 1 ' ' ’ ' 91.8 93.4 94.9 96.5 gS.o 99.6 01. 1 02.7 04. Sou 12405.7 07.208.8 10.3 1 1. 9 13.4 15.0 16.5 18. 1 19. 805 21 .2 22.7 24.3 25.8 27.4 28.9 30.5 32.033.6 35. 806 36.6 38. 139. 7 41.242.8^44.3 45.947.449.0 50. 807 52.0 53.5 55.1 56.6 58.2 59.7 61.3 62.8 64.465. 808 67.4 68.9^70.5^72.073.6 75.1 76.7 78.2 79.8 81. 8og 82.9 84.4 86.0 87. 5 89. 1 90.6 92.2 93.7 95 .3 96. 810 98-3 99.801.402.904.5 06^007.609.1 10.7 12. 8II 12513-7 15.2 16. S|i8. 3' 19. 9 21.4 23. 0 24. 5 26.1 27. 812 ^29.2 30.7 32.3 33.8 35.436.938.5 40.041.643. 813 44.6 46.1 47.7'49.2|5o.8 52.3 53-9 55-4 57 -O 58. 814 60.0 61.5 63.i'64.6 66.2 67.7 69.3 70.8 72.4 73. 815 75 ■ 5 77.0 78.6 80.1 81.7 83.2 84.8 86.3 87.9 89. 816 90.9 92.4^94.0 95.5 97.1 98. 6 00. 2 01. 7 03. 3 04. 817 12606.3 07.809.4 10.9 12.5 14.0 15.6 17. 1 18.7 20. 818 21 .7 23.2 24.8 26.3 27.9 29.4 31.0 32.5 34. T 35. 819 37-2 38. 740.3 41. 8^3-4 44- 9 46 -5 48.049.6 51. 820 52.6 54-1J55-7 57- 2I58.S 60.3 61 .9 63.465.066. 821 0 00 0 69.5 71.1^72.6 74.2 75.7 77.3 -8.8 So. 4 Si. 822 83-5 85.0 86.6 88.1 89.7 91 .2 92.8 94.3 95.9 97. 823 98.9 00.4 02.0 03.5 05.1 06.6 oS .2 09.7 II .3 12 824 12714-3 15 .817.4 iS .9 20. 5 22.0 23.6 25 . 1 26.7 28 825 29.7 31.2 32.8 34.3 35.9 37.439.040.5 42.143 826 45-2 46.7'48.3 49.8 51.4 52.9 54.5 56.057.6 59 827 60.6 62.1 63.7 65.2 66.8 68. 3 69.9 71-4 73-0 74 828 76.0 77-579-1 80.6 82.2 83.7 85.3 86.8 SS.4 89 829 91.5 93 . 0^94 . 6g6 . 1 '97 . 7 99 . 2 00 . 8 02 . 3 03 . 9 05 830 12806.9 oS.4|io.o^i.5^i3.i 14.6 16.2 17.7 19.3 20 831 22.3 '23.8 25.4 26.9128.5 30.031.6 33-1 34-7 36 832 37-8 : 39.3 40.9 42.4|44-oj45.5'47-i 48-6 50.2 51 833 53-2 54-7 56-3 57-8 59-460.962.5 64.065.667 834 1 68.6 70.171.7 73.2 74.8 76.3 77.9 79. 481. 0S2 835 ! 84.1 85.6'87.2 88.790-3 91-8 93-4 94-996-5 98 836 ' 99-5 01.002.6 04.1 05.7 07.2 08.8 10.3 1 1. 9 13 837 12914.9 a6.4 18.0 19.5 21. 1 22.624.2 25.7 27.3 28 838 1 30-3 3 T- 8 ! 33-4 34-9 36.5 38.039.641.1 42.7 44 1 1 i 1 ; 1 1 1 1 12i Table II. — Continued. Numbers. 839- 840. 841. 842. 843. 844. 845. 846. 847. 848. 849. 850. 851. 852. 853 - 854 - 855. 856. 857. 858. 859- 860. 861. 862. 863. 864. 865. 866 . 867. 868 . 869. 870. 871. 872. 873- 874. 0 1 2 3 12945.8 61.2 76.6 92.1 13007.5 22.9 38.4 53.8 69.2 84.6 13100. 1 15-5 30.9 46.4 61.8 77.2 92.7 13208.1 23.5 38.9 54 - 4 69.8 85.2 13300.7 16. 1 31-5 46.9 62.4 77.8 93-2 13405.7 24.1 39-5 55 - 0 70.4 85.8 3 48.9 50.4 52.o'53.5 7 64.3 65.8^67.4168.9 I 79.7 81.2 82.8:84.3 : I 1 695. 296. 798. 3^99. o 10.6 12.1 13.7 15.2 .4 26.0 27. 5 29. 1 .941-5 43-0 56.9 58.4 72-3 73-8 87.7 89.2 03.2 04.7 18.6 20. I 34-035-5 49-5 51-0 44.6 60.0 75-4 90.8 06.3 2I''. 7 37-1 30.6 46.1 61.5 76.9 92-3 07.8 23.2 38-6 52-6 54.1 64.9 66.4 68.0^69.5 80.3 81 .8183.4 84.9 1 I I- 95-8 97.3 98.900.4 I II. 2 12.7 14.3 15. 8 8 i 9 55.1 56.655.2 59.7 70. 572. 073-6, 75-1 85.9 87. 4 89. 090. 5 01 .4 02.9 04. 5 06.0 16.8 18.3 19.9 21 .4 32. 2 33. 7^35-3 36. 8 47.749.2 63.1^64.6 78.5 80.0 93-9 95-4 09.4 10.9 24.8 26.3 40.241.7 55 - 7 ' 57-2 71 .1 72.6 86.5 88.0 02.003.5 17.4^18.9 50.8 52.3 66.2 67.7 81 .6 83 . 1 97.098.5 12.5 14.0 27-gj29-4 43-3 44-8 58-8|6o.3 74-275-7 I 89. 6^91. 1 L 05.1 06.6 ! 20.5 22.0 3 7 I ,6 ,0 ■4 ■9 ■3 7 .2 .6 .0 26 . 6 ; 28 . 1 , 297 7131. 2 32 . 8 : 34.3 35-9 37-4 ! I I c o I i I Q • 442 - 043.5 45 . 1 46 . 6 ^ 48.2 49.7 51.3 52.8 ■ 9 57-5 59 - 060.6 62 . 1163.7 65 . 2 ^ 66 . S| 68. 3 : I : I I ,3 72.9 74.4 76 . 0 : 77.5 79.1 80.6 82.2 83.7 : : ' : : 1 7 88.3 89.8 91 . 4 ^ 92.9 94.5 96.0 97.6 99.1 ,2 03.8 05 .3 06.9 08.4 10 . o II . 5 13. 1 14.6 ' ; I I I : 1 .6 19.2 20.7 22.3 23.8 25.4 26.9 28.5 30.0 , 0 * 34.6 36.1 37 . 7 ' 39 . 2 ' 40 .s| 42.3 43 . 9 j 45.4 .4 50.0 5 i. 5 ' 53 .i' 54 . 6 | 56.2 57 - 7 , 59-3 60.8 .9 65 . 5 ' 67 .o 68.6 70 .i' 7 i .7 73.2 74 . 8 , 76.3 I I ' I I I ,3 80.9 82.4 84.0 85 . 5 87. 1 88.6 90.2 91 . 7 i , I o' i- !- I- i- c - 7 : 96.3 97.8 99.4 00.9 02.5 04 . 005.6 07.1 ,2 II. 8 13.3 14.9 16.4 18 . 019.5 21 . I 22.6 ,6 27 . 228 . 7 ^ 30.3 3 i.sj 33 . 4 ' 34.9 36.5 38.0 , 042 . 644.1 45.7 47.2 48.8 50.3 51.9 53.4 ,5 58.1 59.6 61.2 62.7 64.3 65.8 67.4 68.9 •9 73-5 75-0 76.6 78.1 79.7 81.2 82.8 84.3 ,4 89.0 90.5 92.1 93.6 95.2 96.7 98.3 99.8 i I ! I I I I 125 Table II. — Continued. Numbers. 875. 876. 877. 878. 879. 880. 881. 882. 883. 884. 885. 886 . 887. 888 . 889. 890. 8gi. 892. 893- 894. 895- 896. 897. 898. 899. 900. 901 . 902. 903. 904. 905. 906. 907. go8 909, 910 0 1 2 3 •i 5 CO 0 I350I.2 16.7 02.7 18.2 04.3 a 19.8 05.8 07.408.9 10.5 L2.0 21 .3 22.9 24.4 26.0 27. 5 13-6 15. 1 29.1 30.6 32.1 47-5 63.0 78.4 93-8 13609.3 24.7 40. 1 55-6 71.0 86.4 13701.8 17-3 32.7 48.1 63.6 79-0 94.4 13809.9 25-3 40.7 56.1 71 .6 87.0 13902.4 17.9 33-3 48.7 64.2 79.6 95-0 14010.4 25-9 41.3 33-6 35 - 2 , 36 - 7 38.3 39-8 41 - 4 ' 42 . 9 44- 5 46-0 49.o;5o.6’52.i 53-7 55-2 56.8 58.3 59.961.4 I , I 64.5 66.1 67.6 69.2 70.7 72.3 73.8 75.4 76.9 79.9 81 . 5 83.0 84.6 86. 1 87.7 89.2 go. 8 92.3 95-3 10.8 26.2 27 41-6 43-2 57-1 58.7 72.5 74-1 87.9 03-3 18.8 34.2 96.9 98.4 00. obi . 5 03. 1 04.6 06.2 07. 7 12. 4' 13. 9 15. 5 17.0 18. 6 20. 1 21. 7 23. 2 I C A 29.3 30.9 32.4 34-035-5 37-1 38.6 44.-746. 3 47-8 49-4|5 o. 952-5 54-0 60.2 61 .8 63.3 64.9 66.4 68.0 69.5 75.6 77.278.7 80.3 81.8 83.4^84.9 89.5 91.0 92.6 94.1 95.7 97.2 98.8 00.3 04.g'06.4 08.0 09.5 II. I 12.6 14.2 15.7 20.4 21 .9 23.5 25 .0 26.6 28. 1 29.7 31.2 35-8 37-3 38.940.442.043.5 45.1 46.6 49.6'5I.2'52.7'54.3 55.8 57.4 58.9’6o.5'62.o 65.i|66.7|68.2 69.8 71.3 72.9 74.4 76.0 77.5 80.5 82. 1 S3. 6 85 .2 86.7 88 .3 89.8 91 .4 92.9 95 . 9 97 . 5 99 . o 00 . 6 02 . 1 03 . 7 05 . 2 06 . 8 08 . 3 1 I ' 1 1. 4' 1 3.0 14.5 16. 1 17.6 19.2 20.7 22.3 23. 8 26.878.4 29. 9 31. 5 33-0 34.6 36.1 37.7 39.2 42. 273. 845. 346. 945. 4 50. 0 51. 5 53.1 54-6 I ' I ' ' ' 57 .6 59. 2 60. 7 62. 3 63 . 8 65 .4 66. 9 68. 5 70.0 73-1 88. 5 03-9 19.4 74.7 76.2 77.8 79.3 So. 9 82. 4 84.0,85.5 90.1 9I.6'93.2 94.7 96.3 97. 8 99.400.9 05.5^07.008.6 10. 1 II. 7 13.2 14. 8 16.3 28. 7 30.3 31. S 44-1 45-7 47-2 59.5 61. 1 62.6 21.022.5 24.1 25.6 27.2 34. 8|36. 4^37. 939. 541-042. 6 50.2 51.8 53.3 54.9 56.4 58.0 ; 65. 7^67. 3 68.8 70.4 71.9 73.5 75.0 76.6 7S.1 81. i'82. 7 84.2 85.8 87.3 S8.9 90.4 92.093.5 96.5 98.1 99.6^01.2 02. 7 04. 3 05.8 07.408.9 11.9 13.5 15.0 16.6 iS. I 19.7 21.2 22.8 24.3 27.4^29.030.5 32.1 33-635-2 36.7 3S-339-S 42.8 44.445.9 47-5 49-0 50.6 52.1 53-7 55-2 ! I I - 12G TABLE III. Density of mercury at different temperatures. {Centigrade^) Temperature. Density. o 13.59600 I 13-59355 2 13.59110 3 13-58865 4 13.58620 5 13-58375 6 13.58130 7 13-57885 8 13-57640 9 13-57395 10 13-57150 II 13-56905 12 13.56760 I2i 13.56638 13 13-56515 I 3 l 13-56393 14 13.56270 Temperature. Density. 14I- 13.56148 15 13.56025 15^ 13-55903 16 13-55780 i6i 13-55658 17 13-55536 17I 13-55413 18 13-55290 CO 13-55178 19 13-55055 I 9 i 13-54933 20 13.54810 20| 13.54688 21 13-54565 2li 13-54443 22 13.54320 224 13-54197 Temperature. Density. 23- - -t 13-54095 234 13-53952 24 13-53830 24I 13-53707 25 13-53585 25 i 13.53463 26 13-53340 264 13.53217 27 13-53095 274 13-52973 28 13.52850 284 13.52728 29 13.52606 294 13-52483 30 13-52361 127 TABLE lY, lieduction of Fahrenheit to Centigrade scale. Fahren- heit. Ceiiti- gi’ade. 2 0 3 5-10 34 I I-IO 35 1 6-10 36 2 2-10 37 0 M 1 38 3 3-10 39 3 9-10 40 4 4-10 41 5 42 5 5-10 43 6 i-io 44 6 6-10 45 7 2-10 : 46 7 7-10 47 8 3-10 48 0 i 8 9-10 Fahren- heit. Centi- grade. 49 9 4-10 50 10 51 10 5-10 52 II I-IO 53 II 6-10 54 12 2-10 55 12 7-10 56 13 3-10 57 13 9-10 58 14 4-10 59 15 60 15 5-10 61 16 I-IO 62 16 6-10 63 17 2-10 64 17 7-10 65 18 3-10 Fahren- heit. Centi- grade. 66 18 9-10 67 19 4-10 68 20 69 20 5-10 70 21 I-IO 71 21 6-10 72 22 2-10 73 22 7-10 74 23 3-10 75 23 9-10 76 24 4-10 77 25 78 25 5-10 79 26 I-IO 80 26 6-10 81 27 2-10 82 27 7-10 Fahren- heit. Centi- grade. 83.°.... 28 3-10 84 28 9-10 85 29 4-10 86 30 87 30 5-10 88 31 I-IO 89 31 6-10 90 32 2-10 91 32 7-10 92 33 3-10 93 33 9-10 94 34 4-10 95 35 96 35 5-15 97 36 I-IO 98 36 6-10 99 0 M 1 c<-) To reduce ceutigrade to Falireulieit ; — Falir. = Ceu. x 1.8-}- 32°. 128 IND E X Accuracy of fire, to determine the Art* the mean range ‘‘ mean difference of range “ mean deflection “ mean reduced deflection “ definition of the accuracy of a gun “ rectangle method. “ of small arms . . .• “ absolute mean deviation •“ mean deviation “ mean horizontal and mean vertical ^rror “ the absolute mean error “ radius of a circle containing a frac- tion of the balls “ the per cent “ comparison of differentrmethods. . “ the inclination of the target “ record of target practice at sea “ Angle of fire “ Angle of sight “ Armament of ships of war “ relation of weight of battery to tonnage. “ how to dispose of weight of battery to best advantage relation of battery to speed of vessel. . . kind of gun adapted to ships of war. . . . Armor, experiments against plates and backing laminated difficulty of bolting plates, resistance offered to penetration Armstrong system, principles of gun, description of number of parts barrel of breech piece of cascabel of shrinking on the coils coils and tubes of trunnion ring of Alloys used in the fabrication of cannon guns constructed of homogeneous one of great density >. experiments with, for cannon making 1640 1641 1642 1643 1644 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1583 . 1583 - 261 262 263 , 267 , 271 , 266 270 274 ' 866 867 867 867 869 646 , 647 648 649 650 651 652 653 654 655 141 143 144 145 2 INDEX. Alloys, advantages of those of iron Art. 146 Backing for armor ‘‘ 868 Ballistic machines, the ballistic pendulum “ 1263 the gun ijendulum “ 1263 application of electricity to ‘‘ 1234 Bar-iron “ 8.5 Blakely gun “ 076 Blast Furnace “ 15 the stack. “ 16 the boshes..' “ 17 the hearth “ 18 the tymp 18 lining of “ 19 twyer arches twyers twyer holes fire hearth cinder notch tap hole tymp-stopping throat cap and cone details of the top of the charging the draft of, how maintained pressure of blast. temperature of blast, how determined fusibility of metals, table of hot blast hot blast, effects of heat of furnace hot blast, advantages of w'arm blast heating the blast starting the working the chemical .action in the tapping the, to preserve uniformity of blast in the. !Boat howitzers Breech loading advantages of disadvantages of British naval guns Uroadwell ring Bronze tor cannon the copper the tin management of uniformity of the alloy effect of remelting, on the constitution of the alloy difficulty of making sound castings frour often remelted alloys upon wliat the perfection of the alloy depends qualities of strength of objections to rilled guns of comparative value of, as a cannon metal Blooming ( I a u ( ( (( (( u (( 20 21 23 23 24 25 26 28 27 30 31 33 S3 34 ' 35 SO" 37 38 39 41 ■ 43 44 45 47 340, 341 231 770 771 773 645 686 133 134 135 136 137 138 139 140 177 178 179 184, 185 83 INDEX. 3 Built-up gTins Art. G16 object of “ lI17 initial tension, principles of the system “ C24 defects of the system “ 625 methods of application of the system. “ 626 varying elasticity, principles of tlie system “ 629 defects of the system “ 6::i0 longitudinal strength of “ G'll length of hoops “ 682 number of hoops “ 633 want of continuity ‘‘ 634 vibration in “ 635 conclusions with regard to ‘‘ 636 Cannon construction, upon what depends the necessity for strength in “ 186 Cannon metals, qualities necessary in “ 147 properties “ 149 den.sity “ 150 hardness “ 151 brittleness “ 152 tenacity “ 153 tensile strength “ 154 porosity “ 155 elasticity- “ 156,157 permanent set “ 158 elasticity of torsion 159 malleability “ 160 ductility , “ 161 difficulty of selecting suitable material “ 148 various qualities of “ 347 qualities uiDon which then- fitness depend 180 C.anister shot “ 800 rifle “ 801 Calibre Case-shot Cast-iron, composition of varieties converting gray into white white into gray gray- white. diSerent kinds of white mottled Ca.st-iron, classification of variation in coinposition of difficulties attending the analysis of silicia in manganese in phosphorus in sulphur in want of uniformity of diiference in strength of chemical identity does not involve uniformity in mechani- cal properties cost of comparative value of, as a cannon metal qualities of comparative strength of, as a material for cannon con- struction 202 795 50 51 52 53 55 56 57 58 59 60 61 62 63 64 65 165 165 160 167 181, 185 ■ 164 164 4 INDEX. Cast-iron, tensile strength of the strongest, does not make the most enduring. . . variation of density and tenacity how improved effect of different treatment Castings, improvement in construction of ... rate of cooling time required for cooling effects of irregular cooling high iron practical treatment of iron in fusion pi'oof-bars molecular constitution of cannon metals crystallization development of crystals chilled effect of crystallization on strength size of crystals effect of sudden change of form in effect of age on endurance standard of quality in comparison with standard means of comparing. . . Charcoal woods used for conversion of wood irrto effect of temperatrrre employed in conversion qualities of .- how prepared as an ingredient of gunpowder danger of spontaneous combustion in fresh ground. . Cold-short iron Chamber Concussion, as an effect of the inrpact of a projectile Crusher gauge Dangerous space Densimeter adjrrstments of use of Determining density of gun iron position of trarnnions Detonation, explosion by explosives capable of how produced nature of illirstration of explosion by Deviation of projectiles effect of wind on effect of variable projectile force on effect of rotation of the earth on effect of faulty disposition of the line of sight on, influence of the state of the air on of spherical projectiles effect of windag-e on effect of eccentricity on of elongated projectiles of conoidal -headed projectiles of flat-headed projectiles Art. i ( U ( ( u (( ( ( (( (( (; C( u (( ( i u It u ii I ( <; ( i u ( ( i i u u i t u (6 u (( u u lfl4 1G4 3d0 SUi 348 3T3 36.) 3G4 3G7 368-370 3.71 3.53 35.5-3.50 358 3.59 359 360-361 363 363 366 373 374 376 377 1083 1083 1085 1089 1090 1099 1100 64 213-313 853 1340 ' 1639 388 390, 391 392, 394 38.3 334. 33.5 1042 1043 1044 1045 1046 823 823 824 825 826 827 828 829 830 833 839 841 INDEX. 5 Drift Art. 842 Dimensions of naval ordnance “ 22(j Descriptive list of guns “ (i09 Devices on cannon “ 22.) Dynamite “ 1397 Distances, determining “ 1G2S correcting by previous rounds “ 1G29 judging of “ 1029 determining by angle subtended by the mast of the enemy “ 1G30 horizontal angle taken at bow and stern . ‘‘ 10.31 using ship’s own mast as the given height “ 1632 observing the angular distance from horizon “ 1033 the velocity of sound “ 1634 three point problem “ 1635 Boulenge’s Telemeter “ 1636 plane tables ‘ 1637 Eastman’s breech closing system “ 690 Elevating screws “ 16(!0 Elongated projectiles, origin of “ .714,715 advantages of “ 726 disadvantages of ; “ 727 English experimental guns ‘‘ 675 Endurance of guns in service • 605 Electro-ballistic machines “ 1231 the Navez-Leurs chronoscope “ 1 273 the pendulum. “ 1238 the disjunctor “ 1242 the electric currents.. . . “ 1243 arrangement of targets. . . “ 1 244 operation of the instru- ment “ 1245 Benton’s thread velocimeter “ 1247 the pendulum machine 1248 the compres- sors “ 1250 the cannon targets “ 1252 the small-arm targets “ 1253 to determine the time... “ 1259 Le Boulenge’s chronograph “ 1255 the electro- magnets. “ 1259 the dis- junctor. . “ 1262 theory of the in- strument. “ 1267 method of adjust- ment. ... “ 1271 6 INDEX. Electro- ballistic maclimes, Le Boulenge’s cliroiiograpli, method of taking ve- locities. . . Art. 1279 method of correct- ing meg- ularities.. “ 1280 Schultz’s chronoscope “ 1287 the cylinder “ 1283 the vibrating fork. . “ . 1289 the interrupter “ 1290 the Euhmkorff coU. “ 1291 the pendulum. “ 1292 the micrometer. .. . “ 1293 the batteries “ 1294 the targets “ 1295 principles of the machine “ 1296 to use the chrono- ecope “ 1297 Bashforth’s chronograph “ 1298 description “ 1299 the targets “ 1300 arrangement of screens . “ 1301 Noble’s chronoscope, description. .■ “ 1302 rate of the discs. .. . ‘‘ 1303 to obtain the elec- trical record.s “ 1305 connection with the bore of gun “ 1306 Le Boulenge’s electric clepsydra “ 13o7 d escrip- tion.... “ 1308 basis of calcula- tion of times.. 1312 e X p e r i - ' m e ntal deter- mina- tion of times.. “ 1316 use of the i n stru- ment.. “ 1321 Force of gravity as an element in bal- listics Explosive agents Explosives, definition of Ex^rlosive effect compounds mixtures different classes of nitrate mixtures chlorate E.xplosion, ini.ensity of 1323 1031 1031 1 ') 2 10:3 10: 4 1025 10.5 io;lo 10,. 9 IXDEX. r Explosion, means of causing .Art. 1040 method of producing •' 1041 Explosive compounds, general consideration of “ 1375 guncotton “ 137(5 manufacture of 1377 purification of the cotton “ 137S treatment with acid “ 1379 to remove the acid 1380 Abel’s method *• 1380 pulping 1382 compressing: *• 1383 general properties “ 1384 forms in which used “ 1335 uses “ 138(5 mode of firing “ 1387 nitro -glycerine “ 1388 method of manufacture “ 1390 general projierties “ 1391 mode of firing “ 1392 transportation of... '• 1393 stability and permanence. .. .' “ 1394 uses “ 1395 compounds of nitro -glycerine “ 139(5 dynamite “ 1397 lithofracteur “ 1398 duaUne “ 1399 Exterior form of guns 215,311 Extreme proof of trial guns “ GOl Fabrication of Cast-icon CJuns “ 445 contract with gun formder “ 378 preparing stock for a blast of gun-iron “ 339 piling pigs, to obtain identity in quality of metal “ 34.2, 343 furnaces for melting gun^iron . , . “ 443, 447 charging the furnaces -149 first and second fusion iron “ 450 charge used “ 451 distribution of metat ‘‘ 223 molding “ 453 molding composition ” 454, 45(i models “ 457 flasks “ 458, 459 process of molding “ 4G0, 4(55 core baiTel in hollow casting ‘‘ 4(50 preparing the core “ 437, 439 casting pit “ 470 placing the flask “ 471 cranes “ 472 adju.sting the core “ 473 melting down the charge “ 475, 477 tapping the furnace “ 479 heating the pit 481 cooling heavy castings “ 482 withdrawing core-barrel ‘‘ 484 removing heavy castings from pit “ 487 condition of rough casting ‘‘ 488 heading lathe for heavy guns ..., “ 489 8 INDEX. Fabrication bf Cast-iron Guns, boring lathe, adjustment in Art. mea.suring gun-castings. “ turning down gun-castings “ removing the sinking-head “ cutting out specimen “ boring lathe “ adjustment in boring trunnion lathe planing machine cutting hole for elevating screw. . . drilling the vent Bronze Howitzers pattern flask molding runner drying oven drj'ing the mold pit for mold placing flask charging the furnace treatment of the melted metal melting down the charge made-up charges casting runner-box for casting tapping the furnace Firing means of by electricity different kinds of u U direct ricochet curved plunging solid-shot shell shrapnel grape and canister horizontal vertical small arm Fraser system of gun construction Form of gun, experiments to determine the French naval guns castings of the tubes of building up the the hoops of breech screw of safety-catch for to open the breech of , . . , loading the , . Field fortifications definitions plans profiles artillery in field works U (( u 490, 494 495 49(i 498 499 500 502 503, 505 500, 508 509 511, 513 514 516 517, 519 520 521 522 523 524 525 526 527 528 529, 531 532 533 534 536 1438 1458 1693 1694 1695 1701 1702 1703 1704 1708 1711 1714 1715 1723 656, 658 221 078 680 681 682 083 689 694, 697 095 696 1806 1807 1821 1830 1842 INDEX. 9 Field defence of walls . . . . building village. . bridge. . attack of works. ... surprise open attacks defence sorties Fulminates of mercury . . . silver Fuzes Tke time fuze requirements of Tke navy time fuze safety-plug for composition for paper case for driving the compo.sition, machine for’. . driving the composition wat;3r-cap for safety-cap- for fuze-stock tor time of burning varieties general working fuze to shorten the testing Time fuzes for rifle projectiles Time- fuzes, imperfection of Time fuzes, premature explosion of Their action and result to be reported The Bormann fuze operation of advantages of Percussion and concussion Concussioir The Splingard fuze The Bacon and McIntyre fuze Percussion advantages of Scheukle fuze. Parrott fuze . . German fuze . Art. 1845 1847 “ 1851 “ 1854 “ 1858 “ 1850 “ 1801 “ 1808 “ 1805 “ 1400 “ 1401 “ 1403 “ 1400 1461 “ 1463 “ 1463 “ 1404,1407 “ 1405 “ 1400 “ 1470 “ 1473 “ 1474 “ 1475 “ 1479 “ 1477 “ 1477 “ 1477 “ 1478 “ 1479 “ 1477,1480 “ 1481 “ 1483 “ 1484 “ 1485 “ 1487 “ 1489 “ 1490 “ 1491 “ 1493 “ 14;)4 “ 1195 “ 1490 “ 1497 “ 1500 “ 1501 Mortar. “ 1503 Itunniug, for mines and blasting ■“ 1505 Detonating “ 1507 Fulminate exploder “ 1508 Electric exploders “ 1509 Electric, “ 1509 Platinum- wire “ 151-4 advantages of “ 1515 The dynamo-electric igniter. “ 1510 The dynamo-electric ' “ 1517 Removing, from loaded shell “ 830 For 15 -in shell “ 1570 Gas- check for breech loaders “ 685 10 INDEX. Gatling German gun, description of revolving gear of hopper of carrier of lock cylinder of locks of breech casing of traversing gear of elevating gear of removing the locks of feed drum of working the comparison with howitzers Ijreservation of directions for taking apart putting together. . . naval guns features of the manafaclure old Krupp construction new the central tube the breech plug the gas check the vent tube Art. 233 “ 234, 241 233 “ 237 “ 238 Arts. 239, 244, 246, 231 '• 240 “ 242 “ 243 “ 245 247. 232 Arts. 249, 230. 253, 254, 235 “ 236 “ 237 “ 239 “ 260 “ 701 “ 703 703 “ 704 “ 703 “ 707 “ 708 “ 709 Gomer chamber “ 214 Grape shot ; “ 799 Guncotton “ 1376 Gun, general form of “ 189 construction, theory of “ 276 ' making, improvements in “ . 224 interior form of a “ 201 Guns, how distinguished “ 188 cast iron, detection of coming fracture of “ 170 Gunpowder “ 1047 ingredients of “ ' 1048 purity of ingredients necessary to security of manufac- ture ^ “ 1049 proportions of ingredients “ 1093 imeparing and mixing the ingredients “ 1095 mixing machine '■ 1101 incorporation of the ingredients, importance of the process ‘‘ 1103 time required for. . “1104,1114 the effect of imper- I feet “ 1105 miU used for “ 1106 the operation “ 1111 capacity of a factory for making " 1115 mill-cake “ 1116 danger of incorporatiom “ 1118 drenching apparatus, to prevent explosion in factory. . . “ 1121 pressing the mill-cake “ 1125 description of press “ 1127 dilficulty of obtaining uniformity of results in pressing. “ 1133 Gunpowder, method of obtaining powder of uniform density 1133 graining “ 1136 granulating- machine “ 1137 method of granulating powder “ 1140 INDEX. 11 Gunpowder, danger attending granulation dusting and glazing the dusting reel the glazing barrel drying special powders terms applied to different kinds of powder mammoth prismatic hexagonal watiie pebble i pellet rifle-large -grain machine for making special powder explosion of ignition of inflammation of combustion of xelocity of combustion explosive force of products of combustion . , inspection of general qualities of examination of. by hand by flashing size of grain gravimetric density of specific gravity of the mercury densimeter process of taking the density initial velocity of analysis of strain upon the gun pressure gauges r , curves hygro metric qualities of inspection report marks on the barrels preservation and storage storage on shore preservation of, in shore magazines classification of “ issue of, from shore magazines magazine ledger transportation of reception of, on board ship storing, on board ship tanks system of marking restoring unserviceable condemned purchasing abroad Gun carriages of United States Navy general considerations steam power for working * requirements of mechanical disappearing systems Art. <; u C ( u u u (4 U u u u ( 4 ic ti 1143 1144 1149 1153 1158 1159 1163 1163 1164 1165 1166 1167 1168 1169 1170 1173 1174 1177 1187 1193 1198 1304 1209 1310 1211 1213 1213 1214 1215 1316 1224 1230 1346 1329 1331 1344 1345 1347 1348 1353 1354 1356 1355 1360 1359 1373 1374 1367 1.368 1369 1349 1350 1351 883 883 885 887 888 12 INDEX. Gun carriages, Marsilly broadside, nomenclature Art. dimensions “ the brackets “ the breech piece “ the socket plate “ the roller handspike “ the truck axle “ the trucks “ the saucer “ resistance to recoil “ manoeuvering the carriage “ elevation obtainable “ preservation of “ tackles for “ metallic gun-tackle, blocks for. . “ breechings for “ wrought iron carriages for 8-iu. gun, nomenclature dimensions.. the brackets. “ the transoms “ the truck axle “ elevating gear “ side and train- ing bolts . . “ the breast piece. ... cap square.. “ . the recoil ... “ advantages of urought-iron. ... “ mounting Parrott rifles in broadside “ pivot carriages “ Wooden 11-iu. Pivot. the carriage the brackets the transoms the journal plates the compressor ' the slide the compressor battens the hurters the metal tracks the bossed sockets the eccentrics the recoil the breeching shipping the levers transporting pireventer breeching Iron 11 -in. Pivot. nomenclature dimensions the slide the transoms the hurters coincidence of pivot holes, how secured form of rail transporting (( a u u u 890 890 891 892 89.3 894 89.5 890 897 898 899 900 901 903 903 903 904 904 905 900 907 908 909 910 911 913 913 914 915 910 917 918 919 92P 921 923 933 924 925 920 927 928 929 930 931 933 933 933 934 935 936 937 938 939 rNDKX. 13 Gun carriages, Iron 11-in. Pivot, the caniage Art the brackets “ the bed -plates “ the journal-plates “ form of eccentric axle “ the compressor. “ recoil “ necessity of eccentric rollers in slide “ 20-Pdr. Rifle Pivot “ 15-in. Turret. nomenclature the slide the carriage / . . . the m-and-out gear the carriage rollers the compressor gear the compressor plates . . . . action of compressor gear. elevator rest the hurters elevation the port stopper loading appliances the rammer and sponge . ; pointing the turret turret sights the turret pilot house Mortar, nomenclature dimensions the carriage the brackets the transoms running in and out the mortar circle eccentric rollers the deck supports Howitzer, boat (wood), nomenclature. . . the slide ........ the compressor. . elevation the boat carriage pivots ihvoting Howitzer, boat (iron), nomenclature dimensions the slide the bed-plate. ... the bed recoil the sides C4 U u (( u u u (( (( u ( ( Howitzer, field, nomenclature the carriage. . u 940 941 943 943 944 945 946 947 948 949 950 951 953 953 954 955 956 957 958 959 960 961 963 963 964 965 966 967 967 968 969 970 971 973 973 974 975 976 977 978 979 980 981 983 983 984 985 986 987 988 989 990 14 IIO)EX. Gun carriages, Howitzer, field, the trail Art. 091 the carriage ashore ‘‘ 992 the carriage in the boat “ 992 skids for landing “ 994 implements ■ “ 995 Enghsh Naval 996 Scott’s Broadside (English), nomenclature “ 996 the carriage “ 997 the slide ‘‘ 998 deck tracks “ 999 the pivot “ 1000 the dimensions “ 1001 self-acting compressor. “ 1002 elevating gear “ 1003 eccentric gear “ 1004 in and out gear “ 1005 training gear “ 1006 advantages of mechan- ical carriages “ 1007 bow compressor “ 1008 training gear “ 1009 high and low carriages. “ 1010 depression carriages. .. “ 1011 English Turret the slide “ 1012 compound vertical pivoting gear . ‘‘ 1012 elevation “ 1013 the carriage '. “ 1014 recoil “ 1015 the turret “ 1016 in-and-out gear “ 1017 elastic buffers “ 1017 pointing “ 1018 turret indicator “ 1019 night firing “ 1021 Hydraulic Appliances (English) general description “ 1024, 1(>25 running in and out. “ 1026 loading “ 1028 sponging “ 1029 advantages “ 1030 Gun Implements “ 1724 staves “ 1724 sponges “ 1725 rammers 1729 ladles “ 1731 worms “ 1732 sectional staves 1733 Hand grenades “ 801 Howitzers “ 229 Hydrometer “ 384 use- of “ 386, 387 Hot blast iron “ 40 Hart’s elevating screw “ 1665 Impact, force of “ 880 Incendiary preparations “ 1563 carcass “ 1564 incendiary match “ 1565 INDEX. 15 Incendiary preparations, hot-shot Injuries to guns from the projectile powder Inspection of projectiles grape and canister guns at termination of cruise .... vents new guns Inspecting instruments for guns mirror searcher cylinder gauge . measuring staff, chamber guage star gauge head of measuring points sliding rod for. . handle for adjustment of. . . muzzle rest for. . disk . use of Art. U u (& ( ; (( vent guide verifying interior positions of vents vent gauges vent searcher profile boards ' beam calliper cascabel block trunnion guage trunnion square , trunnion rule templates impression taker for vents gutta-percha impressions Laboratory materials, classification of nitre chlorate of potassa charcoal sulphur antimony sulphuret of antimony gunpowder lampblack .' coloring materials substances which give color to flames substances which produce sparks turpentine rosin tar pitch alcohol gum-arabic beeswax ( I u u for preparing cartridges Laboratory buddings furnaoe 1506 cns 008 812 815 611 613 538 540 541 543 544 540 548 550 551 553 554 555 550 557 558 502 560 508 571 573 / 575 577 578 579 580 583 580 591 593 1407 1408 1409 1410 1411 1413 1413 1414 1415 1410 1417 1418 1419 1421 1422 1433 1425 1420 1-427 1428 1404 1405 16 INDEX. Laboratory operations Art. compositions “• - Landing a naval force tbe base “ preparations “ details “ the boats ‘• the landing ‘‘ on the march “ advance guards “ rearguards “ bivouac “ grand guard “ engaging the attack “ the skirmishers “ the infantry “ the artillery .... “ the defence “ field fortification “ the retreat “ destruction of bridges “ p.a.ssage of a defile “ the embarkation “ Length of bore Limit of thickness of cannon Line of sight Line of fire Line of metal Lithofracteur Loading ' rapidity of Loading .small arms mortars Loaded, keeping guns Magazines on shore service of on board ship. construction of flooding lighting seiTice of screens for dampness of ventilation of i Marking samples of gun iron Marking guns Marvin’s estimator hletallurgy of iron Mortars, definition of construction of Motion of projectiles, the equation of the path of a projectile in non-resisting medium co-ordmates of the vertex maximum range time of flight on a horizontal plane elevation necessar}' to cause a projectile to pass through a given point 140G 1429 1701 1703 1704 1708 1770 1773 1777 1778 1782 1783 1787) 1788 1789 179.1 1790 1797 1800 1800 1800 1871 1873 ' 1873 203 021 1183 1183 1187 1398 1107 1178 1181 1180 1173 1313 1317 1301 1302 1301 1306 1370 1371 1371 1371 380 11.1 1338 1 227 228 1734 1731 1731 1736 1737 INDEX. 17 Motion of projectiles, envelop of the trajectories Art. 1787 velocity of a projectile at any point of its path. “ 1738 direction of the path at any point “ 1789 co-ordinates of the point where a projectile will strike an inclined plane passing through the point of projection, the range and time of flight on the inclined plane “ 1740 Remarks on the utility of the formulas ob- tained when the resistance of the air is not con-sidered “1741, 1742 . Examples “ 1742 Motion of a projectile in air “ 1743 integrals for the determination of x, y, and f, deduced, “ 1744 computation and use of the tables for finding x. Y, and T “ 1745 determination of x, y, and and the range on a horizontal plane by means of the tables “ 174(5 ' determination of ?/ “ 1748- examples Arts. 17-49, 1750, 1751 motion of a projectile when the effect of gravity is not considered 1753, 1754 computation of tables I'lII, IX, X and XI “ 175G' examples of the use of tables YIII, IX, X and XI “ 1757 Naval operations on shore “ 1700- Naval howitzers “ 230 Nitro-glycerine “ 1388 Nomenclature of guns “ 190 breech “ 191 cylinder “ 192 curve “ 193 chase “ 194 muzzle “ 195 traunions “ 196 rim bases “ 200 Ordnance, definitions of the term “ 187 Palliser system of conversion “ 671 theory of “ 672 method of construction “ 673 Parson’s system of conversion “ 674 Parrot gun “ 639 barrel of “ 640 the hoops “ 641 placing the reinforce ‘ ‘ 642 Percussion locks for naval ordnance “ 232 Point blank “ 1584 Powder proof “ 598 Picric powder “ 1403 Plane of fire “ 1583 sight “ 1583 P'josphorus bronze “ 142 Pouching and racking “ 876, 879 Pyrotechny ' “ 1404 Pig-1. eds “ 48 Piling pigs “ 49 IS INDEX. Pig'S, difference in quality of Art. 344 Penetration of projectiles “ 84 metallic cartridges “ 1550 dummy cartridges for small arms ‘‘ 15(51 blank cartridges for smail arms “ 15G2 Preparation of iron ores “ 2 dressing “ 3 weathering “ 4 breaking “ 5 roasting “ (5 Preponderance “ 199,318 example to compute the, of a 15-in. gun .4rts. 322,333 effect on the, of a change in the position of the trunnions Art, 336 Pressure gauges “ 1332 Primers, percussion “ 1439 fabrication of ‘‘ 1440 ' pacldng “ 1443 testing “ 144(5 returned from ships “ 144(5 friction “ 1447 composition for 1448 when and how used 1449 allowance of “ 1451 stowage of “ 1450 spur tubes for “ 1452 how used “ 1453 electric “ 1459 Projectiles, fabrication of ‘‘ 802 pattern for “ SO ! molding of “ 804, 805 bouching of “ 806 chilled 807, 805 Palliser: “ SOS, 809 steel 810, 805, 870 Whitworth’s steel " 811 inspection of “ 812 sohd “ 813 hollow “ 814 .smooth bore, table of gauges for “ 815 preservation of “ 850 piling “ 817 lacquering “ 818 to find the number of balls in a pile “ . 821 deviations of “ 822 elongated, deviations of 832 line of flight of elongated “ 837 elongated, positions of axes during flight •• 838, 840 effects of “ 843 impact of " 844 different effects produce bj’ the impact of “ 845 concussion produced by impact of “ 853 armor piercing “ 854 spherical, for use against armor “ 855 20 IXDI5X. Projectiles, armor piercing, effect of shape on their power Art. effect of flat-ended form for armor-piercing. .. *• advantage of rifle projectiles for punching armor elongated, for use against armor “ effects of conical-ended form for armor-piercing “ the ogival, the best form of head for armor-piercing. .. effect of hardening “ advantage of steel over chiUed “ classification of “ spherical “ elongated “ length of form of heads ogival heads form of body which would experience the least resi-t- ance in passing through a fluid form of body which would experience the least resist- ance from the air elongated, studded system of .studding elongated, expanding Parrott’s '. Dahlgren’s rifle ' Shenkle’s Hotchkiss’ lead- coated solid hollow punching effects of, how compared withdrawing a Puddling furnace process furnace, charging the tools substitutes for manual manipulation of the molten iron in white iron gray iron balls Quoins Quick match Range at level Rammer, marks on Reffye gun cartridge Red short iron Running out cannon Rifle, difficulty of loading the Rifle cannon, introduction of difficulties of perfecting progress of construction of designing early experiments with calibre of form of groove in • having projectiles of hard metal, fitting the peculiar- form of the bore mechanically 8.o6 8()6 8.57 856 860 861 862 865 774 775 776 7TT 778 770 780 781 7S2 788 785 785 786 787 788 789 791 792 881 1571 74 75 76 78 79 80 81 82 1660 1455 1585 1586 1568 698 699 65 1574 716 717 721 722 724 724 780 731 754 INDEX. 21 Rifle cannon, with projectiles having soft metal studs, or ribs, to fit the grooves Art. with projectiles having a soft metal enveloi^e or cup, which is expanded by the gas in the bore with projectiles having a soft metal coating, larger in diameter than the bore, but which is compressed bj' the gas into the form of the bore '■ Rifling, definition of “ origin of ...... Arts. 71 1, ' difficulty of application to great guns Arts. object of “ method of ‘‘ lands “ twist “ uniform twist “ uniformly increasing tvvist “• increasing twist, advantages of the “ objections to the “ uniform twist, advantages of the “ character of grooves in “ the loading and driving edge “ advantages of radial bearing in “ rounded angles in “ cutting the grooves “ a system of ‘‘ different systems of, classified ‘‘ definition of centring “ 'Whitworth’s system of “ Yavasseur’s system of “ Scott’s system of “ Lancaster’s system of “ comparative advantages of systems of the first class ‘ ‘ the Woolwich system of “ the Shunt system of “ comparative advantages of the systems of the second class. “ the Parrott sy.stem of ■’ comparative advantages of the systems of the third class . . “ ICrupp’s method of “ the German system of “ cpraparativc advantages of the systems of the fourth class. ‘‘ Rifle projectile, to find the initial velocity of rotation of a “ upon what its velocity of rotation depends “ effect of its initial velocity on the velocity of rota- tion ... “ effect of its form on the velocity of rotation. ..... “ effect of its density upon its velocity of rotation . . effect of the distribution of its material, upon its velocity of rotation “ effect of the position of its centre of gravity, upon its velocity of rotation “ objections to high velocity of rotation . . . ‘ “ velocity of rota cion required in a ‘‘ S.xltpetre, refining of “ description of the process “ filtering of, in refining “ crystallization of. in refining “ washing, testing, etc., in refining “ testing for impurities “ 7G0 7u4 I 0 I 710 7i;i -710 725 728 72!) 722 724 725 72G 727 728 747 748 740 750 751 752 752 754 755 750 757 758 759 701 702 702 705 700 708 708 709 729 740 741 742 744 745 740 740 1051 1052 1052 1057 1000 1001 33 INDEX. Saltpetre, drying- for storage or transport extraction of, from damaged powder how prepared as an ingredient of gunpowder Sulphur, where obtained value as an ingredient of gunpowder soluble and insoluble form of flower of apparatus for refining process of refining testing how prepared as an ingredient of gunpowder. Shell Crane’s Pevey’s mortar loaded, examination of armor piercing care in the use of Smelting of iron fluxes used in difficulties of obtaining pure metal of iron, composition of fluxes slag cinder fuel used Strength of a gun, how to increase the Sinking head Sample gun Samples irom gun castings Standard specimens of gun iron Shingling ■ machines Scoring Spongers and loaders Seat of the charge Slow' match Sighting cannon Sight, dispart i . . . . tangent brass tangent wooden tangent Sights, pivot gun . for rifled guns advantage of long radius between adjustment of . breech, adjustment of reinforce, adjustment of side, adjustment of . . marking tangent using graduation for degrees trunnion spirit-level quadrant gunner’s quadrant Signals Signal rockets the case composition Art. lOGI 10()4 1006 1067 1081 1069 1069 1070 1074 1080 1098 7!b! 796 79;l 794 819 858 1572 9, 8:17 10 11 12 1-3 l:3 14 019 :171 375 379 382 83 84 607 1577 211 1454 1587 1583 1590 1591 1591 1.592 1593 1594 1595 1599 1608 1614 1622 1624 1625 1 (>55 Ph54 1 ()53 1518 1519 15-20 1521 INDEX. Signal rockets, driving head decorations stick motive power 7 pacldug. ... firing Signals, Goshen’s lights compositions for storage of Shrapnel to prepare rille Steel, its peculiarities its distinguishing properties various kinds liigh and low how obtained puddled "! cemented 1 converting furnace fur cementation process effect on physical properties of the iron ....... blister spring tilted shear cast process of manufacture ingots .... hammering, or drawing down the ingots Bessemer process to produce Bessemer steel Bessemer converter for charging' the Bessemer converter chemical action in Bessemer process admission of blast to Bessemer converter casting the ingots, in Be.ssomer process 1 hammering the ingots in Be.ssemer process AVhitworth metal annealing tempering tempering in oil qualities of '. high, its distinguishing properties low, distinguishing properties advantages strength of low, comparative value of as a cannon metal Strain, lands of, to'which a gun is subjected in firing the two principal strains, to which a gun is snbj_ected tangential to find the whole resistance of the gun cylinder. . to the to find the whole force exerted by an explosion in a cylinder rend it longitudinally longitudinal, tendency of longitudinal rupturing effort, to find the Art. 1523 “ 1533 “ 1534 “ 1535 153!) “ 1537 1538 “ 1529 “ 1533 “ 1534 “ 798 “ 797 798 “ 101 “ 103 “ 103, 108 “ 104 “ 105 “ 107 “ 108 “ 109 “ no. 111 “ 113 “ 113 “ 114 “ 114 “ 115 “ 118 “ 117 “ 118 “ 119 “ 120, 138 123 123 125 124 138 137 139 130 131 133 173 173 174 175 178 183, 185 376 230 377.378 373,334 285 388 287 24 INDEX. Strain, longitudinal rnpturmg effort, to find the resistance of the gun to the Art. 288, 289 crushing force “ ' 290 to find an expression for the effect of a ‘‘ 291.292 transverse “ 300 tendencies to rupture “ 308 bursting tendency “ 309 nature of the force to be restrained in cannon 018 method of equalizing the, in cannon 023 Testing machines ‘‘ 390 Testing machine, Rodman’s “ 397 power exerted “ 398 explanation of ‘‘ 399 main lever of ‘‘ 400 small lever of “ 401 combination of levers 402 capacity of “ 403 cog wheel, gearmg of “ 404 multiplication of power ‘‘ 405 torsion lever " 400 pedestals for transverse strain ‘‘ 407 adjustments of “ 408 s.ample holders “ 409 obtaining tensile strain of specimen with “ 410 table containing areas and logs, of va- riations of diameter in tensile sam- ples. “ 411 determining transverse strain with. . . . 412.413,414 torsional strain with. .410,417.418.419 test of compression with 420,421,422 to determine the indenting force with 423,424.425 errors of ‘‘ 420 modifications of “ 427 indicator for. ... “ 428,429 Riehlc’s the levers of recording the strain ajiplication of power adjustment the differential lever Testing specimens — elongation, examples of effect of repeated breaking of same specimen proposed shape of specimens advantage of long specimens value of tests Tests of iron while in fusion h39 440 441 442 443 444 4:2 433 435 430 437 381 353 Tables of fire Tangent firing Trunnions, size of ... . position of Vavasseur gun Vent, definition of . . . . piece position of ... . enlargement of. 1023 15S9 197 198.2.34 017 215 210 217 002,004 INDEX. 25 Vent, impression of closing- the clefiring- the ■Wrought iron, peculiarities of how produced conversion of crude into malleable iron chemical reactions dui’ing the conversion kind of iron most suitable for conversion refining process rolling mills reheating in rolling mills forge cinder mill cinder • piling puddled bars rolling bars, details of manipulation crop-ends rolled armor plates effect of rolling. . . : effect of powerful vibrations judging its quality by character of fracture. . . variations in quality • • . ■ ■welding poiter-bars upsetting scarfing welding large pieces qualities of strength of uniformity of comparative value of. as a cannon metal Wrought iron guns, detection of weakness -in inability to resist compression and wear- want of homogeniety Woolwich gun details of the A tube the B tube the breech coil the casoabel building up nomenclature of Whitworth gun Windage Water-proof Arts. 506,, Art. U Arts. Art, 597,610 1575 1576 66 67.91 68,70 69 71 72 73 86 87 87,100 87 88 89 89 90 92 93 94 95 96 97 98 99 100 168 168 169 182.185 170 171 172 661 662 663 664 665 666 667 670 675 208,210 599 9 ¥Wr.- % •h'i ■ '^"V 't ■•'1- - r. \ ' fit ‘ I V ■ >A . , S 1 ' /