THE SERVICE 
 
 OF 
 
 COAST ARTILLERY 
 
 BY 
 
 FRANK T. MINES 
 
 1 XITED STATES ARMY 
 Captain, Coast Artill* / Corps- Honor Graduate, Tnifd : ' 'tes Coast Artillery S( 
 
 FRANKLIN \V. WARD 
 
 NATIONAL GUARD OF NEW YORK 
 
 Major, Coast Artillery Corps, Nititft Artillery District; Member Division J'J.r<t>ttini>/</ l> 
 
 Artillery Officers 
 
 PUBLICATION AUTHORIZED BY THE WAR DEPARTMENT 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
 NEW YORK 
 GOODENOUGH & WOGLOM COMPANY 
 
 122 NASSAU STREET 
 
GENERAL 
 
 Copyright, 1910, 
 By FRANK T. HINES AND FRANKLIN W. WARD 
 
 All rights reserved 
 
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PREFACE 
 
 FEW words are needed to state the purpose of this work. It 
 represents an earnest attempt to furnish an informative book for 
 the use of coast artillerists with special reference to militia duty in 
 coast defense. 
 
 The organization of the United States Coast Artillery presents 
 a need which the National Government is not wholly able to supply. 
 The Coast Artillery Corps of the United States Army at its present 
 strength cannot provide at the utmost for more than one-half of 
 one manning detail for the armament of our far-reaching coast 
 fortifications. To supply this deficiency in personnel Congress has 
 authorized the development of a Coast Artillery Reserve to which 
 various coastwise states have transferred specially qualified regiments 
 of infantry from their militia organizations. 
 
 In these regiments, and in other organizations not so transferred 
 whose services will be required as Coast Artillery Supports and Coast 
 Guard, are many officers and men desirous of fitting themselves for 
 the technical service of coast defense. A complete programme of 
 instruction has been issued by the War Department, and it is to 
 supplement this, as well as to furnish a suitable reference book *for 
 the Regular personnel, that the present work was prepared. 
 
 The authors believe they have brought together in simple form 
 and compact shape the detailed information indispensable to efficiency 
 on the part of the coast artillerist, be he officer or man. In the 
 descriptions of armament and material, they have held strictly to 
 information procured from Ordnance Department publications; as 
 well as Coast Artillery orders, memoranda and circulars. In most 
 cases the information given here is transcribed from official documents. 
 No pretense is made that the work is exhaustive or conclusive, but 
 so far as it goes it has the kindly approval of Brigadier-General 
 Arthur Murray, Chief of Coast Artillery, and other distinguished 
 officers of the Army. 
 
 iii 
 
 204111 
 
IV PREFACE 
 
 The authors indulge the hope that the order and arrangement of 
 the text may be helpful to every patriotic student of coast defense , 
 and if the hope shall be realized they will consider themselves amply 
 repaid for their labors. Their thanks are due and gratefully tendered 
 to Major William G. Haan, Coast Artillery Corps, for his consistent 
 encouragement, generous advice and valuable suggestions. They 
 desire to express their obligations to Colonel Erasmus M. Weaver, 
 Chief of Division of Militia Affairs; Lieutenant-Colonel Charles J. 
 Bailey, Assistant to the Chief of Coast Artillery; Lieutenant-Colonel 
 Adclbert Cronkhite, Coast Defense Officer, Department of the East; 
 Major Thomas W. Winston, Coast Artillery Corps, editor of the 
 Journal of the United States Artillery; and Mr. Samuel L. Williams. 
 
 It is believed that this book is better illustrated than any on the 
 subject which has preceded it; an advantage mainly due to the skill 
 of Captain Bruno F. Wetzelberg, Coast Artillery Corps, N. G., N. Y., 
 by whom the original photographs and many of the drawings were 
 made, and to whom the authors are deeply indebted. They also desire 
 to express their thanks to Master Gunner George D. Meece, Coast 
 Artillery Corps, for drawings. 
 
 The volume has no other motive than to contribute to the efficiency 
 of a most important arm of the United States military service, The 
 United States Coast Artillery Corps. 
 
 FORT WADSWORTH, N. Y., September, 1909. 
 
CONTENTS 
 
 CHAPTER I 
 
 DEFINITIONS, ABBREVIATIONS AND SIGNS 
 
 PAGE 
 
 Including Approved Interpretations of all Technical Terms and Phrases 
 used in the Coast Artillery Service, together with Explanations, 
 Descriptions and Simplified Outlines of all Elements of Coast Defense 
 and Related Subjects 1 
 
 CHAPTER II 
 THEORY AND PRINCIPLES OF COAST DEFENSE 
 
 Theory of Defense, Attacks from Sea, Plan of Land Defense, Field Com- 
 bat, Fire in Field Combat and Night Attacks 66 
 
 CHAPTER III 
 ORGANIZATION AND PERSONNEL 
 
 The Tactical and Administrative Organization, Personnel, Staff Officers, 
 Coast Artillery Reserve Officers, Commands Appropriate to Grade, and 
 Non-commissioned Officers, etc 76 
 
 CHAPTER IV 
 GUNNERY AND BALLISTICS 
 
 Gunnery, Method of Gun Construction, Rifling and its Twist, The Pro- 
 jectile in the Gun, The Projectile in its Flight or the Trajectory, Aim- 
 ing and Laying. Accuracy of Fire and Practice, Ballistic Symbols 
 and Simple Formulas, Geometrical Magnitudes, etc 79 
 
 CHAPTER V 
 ARMAMENT 
 
 Detailed Description and Classification of the Primary, Intermediate and 
 Secondary Armament, Firing Mechanisms, Subcaliber Guns, - Recoil 
 
 Systems, etc 107 
 
 v 
 
vi CONTENTS 
 
 CHAPTER VI 
 EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 PAGE 
 
 Low Explosives, High Explosives and Fulminates, their Chemical Properties 
 and Method of Manufacture. Preparation and Blending of Charges, 
 Weights, Velocities, Pressure, etc. Service Projectiles, Color Scheme 
 and Method of Painting, Weights, Penetration, etc. Composition, 
 Construction and Action of all Types of Primers and Fuses 245 
 
 CHAPTER VII 
 INSTRUMENTS, DEVICES AND CHARTS 
 
 Depression Position Finders, Telescopes, Azimuth Instruments, Sur- 
 veyor's Transit, Plotting Boards, Mortar Predicter, Range Board, 
 Deflection Boards, Wind Component Indicator, Aeroscope, Time- 
 interval Clock, Interrupter, Telautograph, Telephone, Thermometer, 
 Mercurial and Aneroid Barometers, Anemometer, Atmosphere 
 Board, Open and Telescopic Sights, Gunner's Quadrant, Crusher 
 Gauge, Time-range Board and Powder Chart 304 
 
 CHAPTER VIII 
 SEARCHLIGHTS 
 
 Tactical Location and Use, Types of Projectors, Effective Ranges, Nomen- 
 clature and Operation 402 
 
 CHAPTER IX 
 SUBMARINE MINES, SMALL BOATS, ETC. 
 
 Mechanical and Electrical Types of Mines, Mine Fire-Control System, 
 Mining Casemate, Loading Room, Method of Making Turk's Head, 
 Telegraph Joint, Okonite Joint, etc. Loading Mines, Duties on the 
 Water, Care and Preservation of Mine Material, Small Boats and 
 Boat Drill . . 414 
 
 CHAPTER X 
 SEACOAST ENGINEERING 
 
 Theory of, Location and Measurement of Base Lines, Triangulation in 
 Connection with the Location of Horizontal Base Lines, Gun Centers 
 and Directing Points of Batteries, Determination of the True Azimuth, 
 Location of Pintle Centers, Orientation of Gun and Mortar Azimuth 
 Circles (with problems), Leveling and Hydrographic Surveying 431 
 
CONTENTS vii 
 
 CHAPTER XI 
 CORDAGE 
 
 PAGE 
 
 Types of Ropes, Method of Making Splices, Knots, Hitches and Straps, 
 Blocks and Tackle, Power of Tackle, Levers, Differential Pullies, 
 Gins, Shears, Derricks and Cranes, and Hydraulic Jacks 460 
 
 CHAPTER XII 
 MAGAZINE RIFLE 
 
 Points in Handling, Dismounting and Assembling, Cleaning and Care, 
 Gun Sling, Ammunition, Ball Cartridge, Blank Cartridge, Dummy 
 Cartridge and Guard Cartridge 483 
 
 CHAPTER XIII 
 POINTS FOR COAST ARTILLERISTS 
 
 Battle Commanders, Battle Command Drill, Fire Commanders, Fire 
 Command Drill, Orders of Fire, Searchlight Commands, Communica- 
 tion Officer, Battery Commanders, Solution of Target Practice 
 Problem, Adjustments of Gun and Carriage, Training of Personnel, 
 Calibration, Observation of Fire, Emplacement Officers, Range Offi- 
 cers, Tug Officer and Observer, Shore Tug Signals, Maneuver Signals, 
 Sound Signals, Wig-wag Signals, Night Signals, Wireless Communi- 
 cation, Observers, Gun Pointers, Range Setters, Meteorological 
 Observers, Tide Observers, Camp Sanitation, and Types of War 
 Vessels . 494 
 
THE 
 
 SERVICE OF COAST ARTILLERY 
 
 CHAPTER I 
 DEFINITIONS, ABBREVIATIONS AND SIGNS. 
 
 INCLUDING APPROVED INTERPRETATIONS OF ALL TECHNICAL TERMS AND 
 PHRASES USED IN THE COAST ARTILLERY SERVICE, TOGETHER WITH 
 EXPLANATIONS, DESCRIPTIONS AND SIMPLIFIED OUTLINES OF ALL ELE- 
 MENTS OF COAST DEFENSE AND RELATED SUBJECTS. 
 
 "A" Row. See HOOPS. 
 
 Abatis. In field fortification, rows of felled trees, with the smaller branches 
 lopped off, and the others sharpened and turned towards the enemy. 
 
 Abbreviations. See page 63. 
 
 Absolute Deviation. The distance measured in a straight line from the 
 center of the target to the point of impact. 
 
 Accumulator Room. A room in the battery provided for a storage battery. 
 
 Adjutant. See ARTILLERY DISTRICT ADJUTANT, POST ADJUTANT. 
 
 Aeroscope. A device used in the meteorological station and the fire, mine, 
 and battery primary stations for the indication of the azimuth of the wind in 
 in degrees, the velocity of the wind and the density of the atmosphere by refer- 
 ence numbers. In the latter stations it may also contain a dial indicating the 
 height of tide. 
 
 Aiming. The operation, with the aid of a sight, of giving a cannon the 
 direction and elevation necessary to hit the target. 
 
 Air Spaces. The galleries and narrow spaces around interior rooms to 
 facilitate ventilation and assist in keeping the rooms dry. 
 
 All-Round-Fire. Fire delivered through the entire circumference of an 
 azimuth circle. 
 
 Ammunition. Any material used in charging ordnance, as powder, shot, 
 shell, etc. 
 
 Ammunition Hoist. The device by means of which ammunition is raised 
 to the loading platform. Separate hoists are used for projectiles and powder, 
 or the latter is served by hand. 
 
 Ammunition Recess. The space built in the parapet wall at loading plat- 
 form level for the temporary storage of ammunition. 
 
2 THE SERVICE OF COAST ARTILLERY 
 
 Ammunition Shoes. Any type of slipper made entirely of a non-metallic 
 substance. 
 
 Ammunition Truck. A steerable three-wheeled truck, with suitable space 
 for carrying a complete charge from the delivery or reserve table to the breech 
 of cannon. 
 
 Anemometer. An instrument used in the meteorological station to deter- 
 mine the velocity of the wind in miles per hour. 
 
 Aneroid Barometer. A watch-shaped instrument used in the meteoro- 
 logical station to determine the pressure or density of the atmosphere. 
 
 Angle. The figure made by two straight lines that meet or would meet if 
 sufficiently prolonged, or, two straight lines starting from the same point. It 
 is measured by the arc of a circle included between its sides, the center of the 
 circle being its vertex. An angle of 90 degrees is known as a right angle; an 
 angle of more than 90 degrees is known as an obtuse angle; one less than 90 
 degrees as an acute angle. 
 
 Angle of Departure. The angle between the line of departure and the line 
 of sight. This is the angle given in range tables. See QUADRANT ANGLE OF 
 DEPARTURE. 
 
 Angle of Fall. The angle of fall is the angle which the tangent to the 
 trajectory at the point of impact makes with the line of shot. In practical 
 gunnery the angle of fall is often expressed as a slope, i.e., 1 on 10, meaning 
 that for one foot of drop in vertical height the projectile would travel ten feet 
 horizontally. 
 
 Angle of Impact. The complement of the angle of incidence. 
 
 Angle of Incidence. The angle between the line of impact and the normal 
 to the surface at the point of impact. 
 
 Angle of Jump. See JUMP, ANGLE OF. 
 
 Angle of Position (or Depression). The angle between the line of sight 
 and a horizontal plane through the axis of the trunnions. 
 
 Angle, Quadrant. See QUADRANT ANGLE. 
 
 Angle, Striking. See STRIKING ANGLE. 
 
 Angular Elevation or Depression. The angular elevation or depression 
 of the target includes the depression due to the curvature of the earth. It is 
 sometimes called position angle. 
 
 Angular Velocity. The ratio of the angular travel or motion of a body, to 
 the time consumed in describing the angle. 
 
 Approaches. The water area over which the enemy may be expected. In 
 fortification, roadways entering the battery parade. 
 
 Apron. The reinforced concrete or metal portion of the superior slope of a 
 parapet and the interior slope of a mortar pit designed to protect against blast. 
 Also called blast slope. 
 
 Arc. Any part of a circumference. 
 
 Area. An extent of surface. 
 
 Armament. Guns and mortars of various sizes and powers, including their 
 carriages. In the coast artillery service armament is classified as primary, 
 in ermediate, arid secondary. 
 
 Armor. The protection afforded the sides and decks of warships. It is 
 classified as wrought iron, compound, all steel and face-hardened armor. 
 
 Armor Belt. The side protection of the vitals of warships. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 3 
 
 Armor-Piercing Projectiles. Shot and shell designed to penetrate heavy 
 side and turret armor of war vessels. 
 
 Armstrong Guns. The built-up gun construction of Great Britain, the 
 germ of which is to be found in the coiled welded system of Sir William Arm- 
 strong, introduced in 1852. 
 
 Armstrong Rapid-Fire Gun. A seacoast cannon usually 40 to 50 calibers 
 long and of 6-inch and 4.72-inch caliber. The latter is usually called "four 
 point seven. " 
 
 Artillery. The name given to all firearms discharged from carriages ashore 
 in contradistinction to "small arms," which are discharged from the hands. 
 It also denotes the particular troops employed in the service of such fire- 
 arms. 
 
 Artillery in the U. S. military service is known as coast artillery and field 
 artillery, the latter being classified as light artillery, horse artillery, siege artillery, 
 and mountain artillery. 
 
 Artillery District. An artillery district is a subdivision of the coast line, 
 including the entire personnel of coast artillery troops proper, and coast artillery 
 supports assigned to duty in connection with the fixed defenses thereof. 
 
 For tactical purposes it consists of those battle commands which are within 
 supporting distance of one another. 
 
 For administrative purposes, forts not within supporting distance may be 
 included in the district. 
 
 In the regular service, districts are designated by name, as " Eastern Artil- 
 lery District of New York, " "Artillery District of the Columbia/' etc. In the 
 organized militia it is customary to designate them by number, as "Thirteenth 
 Artillery District, N. G., N. Y." 
 
 Artillery District Adjutant. A coast artillery officer responsible, under 
 the district commander, for the various reports, returns, rosters, details, records, 
 orders and communications pertaining to the administration of an artillery dis- 
 trict, together with all other duties prescribed for regimental adjutants so far 
 as they are applicable to artillery districts. His tactical duties are those of a 
 communication officer of a battle command, unless otherwise assigned by the 
 district commander. 
 
 Artillery District Commander. District commanders are assigned to 
 artillery districts in orders from the War Department. The command of an 
 artillery district devolves upon the senior regular coast artillery officer present, 
 whether he has been assigned in orders or not. However, with the sanction of 
 higher authority a district commander may continue to exercise the more 
 important functions of his command when absent temporarily from his district 
 on artillery duty. 
 
 The district commander assigns field officers as battle, fire and mine com- 
 manders, and staff officers as searchlight and communication officers. In 
 detailing officers other than staff officers as searchlight and communication 
 officers no battery should be left with less than the number of officers required 
 by its manning table. If officers are not available, non-commissioned officers 
 should be detailed. 
 
 The district commander is responsible for the efficiency of his district. He 
 has control within its limits of all matters relating to artillery instruction, drill 
 and practice, and is responsible for the procurement of the proper supplies and 
 
4 THE SERVICE OF COAST ARTILLERY 
 
 accessories. He sees that orders prescribing drills and other exercises are 
 properly and uniformly carried out. 
 
 Accompanied by members of his staff, he inspects all forts in his district at 
 prescribed periods. During the period for out-door instruction he inspects all 
 armament, fire-control equipment, light equipment, all necessary material and 
 fort record books and battery emplacement books. On these occasions the 
 personnel are required to be at their posts and the inspection includes drills of 
 the various elements of the defense, as well as the physical condition, clothing 
 and equipment of the personnel. 
 
 Within the time specified in orders after the last inspection of each quarter, 
 he submits his quarterly report on the prescribed form, through military chan- 
 nels, to The Adjutant General of the Army. 
 
 The operation of all means of water transportation, assigned by competent 
 authority, for exclusive use of the artillery district, including harbor vessels, 
 tugs, lighters, dispatch boats and landings is under his supervision. He sees 
 that economy is exercised in their maintenance and operation. He makes the 
 -official visits required to foreign and naval officers visiting in the harbor. 
 
 He conducts combined artillery drill and tactical exercises of all the elements 
 of defense of his district, in accordance with existing orders. 
 
 He regulates the boat service so that a target may be towed one day each 
 week for each post during the out-door period. 
 
 He is charged with the preparation of all plans of defense for his district 
 against hostile attack, and forwards a copy thereof through military channels, 
 to the Chief of Coast Artillery, for approval and makes such suggestions as to 
 the modification thereof as may, in his opinion, be required by new conditions. 
 
 He should have knowledge of the plans of the general defense of the coast 
 line in the vicinity of his district and be instructed by the general officer com- 
 manding as to his duties in connection therewith. 
 
 During hostilities he is charged with the supervision of all military operations 
 in his district and in connection therewith. He establishes and maintains a 
 system of security and information on both the water and land fronts. He 
 keeps the various subordinate commanders informed as to conditions. He 
 appoints the artillery district staff officers; and upon proper recommendation 
 and examination appoints the non-commissioned officers and men of the several 
 grades and ratings serving in companies, in the district. 
 
 In the organized militia the commanding officer of an organization assigned 
 to the coast artillery reserve, when at home station, receives this title. 
 
 Artillery District Commander's Flag. See FLAG OF ARTILLERY DIS- 
 TRICT COMMANDER. 
 
 Artillery District Engineer. See DISTRICT ARTILLERY ENGINEER. 
 
 Artillery District Ordnance Officer. A coast artillery officer charged with 
 the requisition, accountability, inspection and repair of all ordnance property 
 and stores pertaining to the seacoast armament and equipment of an artillery 
 district. He has immediate supervision and control of the district machine 
 shop and resident machinists. His tactical duties may be those of communi- 
 cation or searchlight officer of a battle command, unless otherwise assigned by 
 the district commander. 
 
 Artillery District Quartermaster. An officer of the Quartermaster's 
 Department, or a coast artillery officer, who is accountable and responsible for 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 5 
 
 all quartermaster property used in connection with district headquarters, and 
 all water transportation assigned for use of the artillery district, including 
 harbor vessels, etc. Under the district commander he is responsible for their 
 maintenance and supply, personnel, and operation. If a coast artillery officer, 
 his tactical duties are prescribed by the district commander. 
 
 Artillery Engineer. See DISTRICT ARTILLERY ENGINEER. 
 
 Artillery Garrison. The personnel assigned to duty at a coast artillery fort. 
 
 Atmosphere Board. A device pertaining to the equipment of the meteor- 
 ological station. A graphic table by means of which the reference numbers to 
 be recorded on the dial of the aeroscope indicator can be determined from read- 
 ings of the barometer and thermometer. 
 
 Automatic Firing. A term applied to one of three methods of exploding 
 submarine mines, i.e., where the apparatus is so arranged that the mine ex- 
 plodes upon contact. 
 
 Automatic Machine Guns. Rapid-fire guns in which the force of recoil is 
 used to operate the breechlock and to load and fire the piece. 
 
 Auxiliary Horizontal Base System. When either the battery primary 
 or secondary station becomes inoperative, the battery commander's station is 
 used as a base end station in place of the disabled station. 
 
 Auxiliary Power Plant. See SECONDARY OR AUXILIARY POWER PLANT. 
 
 Axial Vent. A vent in which the opening is parallel with the axis of the 
 bore. It is the type of vent used in modern seacoast cannon. 
 
 Axis. A straight line, real or imaginary, passing through a body, on which 
 it revolves or may be supposed to revolve. 
 
 Axis of Gun. The axis, or central line, of the bore. 
 
 Axis of Trunnions. That axis, or central line of the trunnions. 
 
 Azimuth of a Point. In coast artillery, the horizontal angle measured 
 in a clockwise direction from south to a line from the observer to the point. 
 For example, the azimuth of a point R from A is the angle (measured clockwise 
 from the south) between the north and south line through A and the line from A 
 to B. The north point has an azimuth of 180 degrees. 
 
 Azimuth Difference. The difference between two azimuths of a point as 
 read from two other points, as, for example, the difference between the azimuth 
 of the target as read from the primary station and the azimuth of the target as 
 read from the directing gun or point of a battery. 
 
 Azimuth Instrument. An instrument for determining azimuths. It is 
 sometimes used as a position-finding instrument in secondary stations. 
 
 Azimuth Setter. The member of a mortar detachment who lays the 
 mortar in azimuth. 
 
 "B" Row. See HOOPS. 
 
 Backlash. The play between a screw and its nut where the latter is loosely 
 fitted. A reverse movement of any part of a mechanical gear, caused by 
 irregularities, without moving other connecting parts. 
 
 Bale. That part of an assembled submarine mine used for the attachment 
 of the mooring cable to the mine case ; also provided for the protection of the 
 joint where the single conductor cable enters the mine. 
 
 Ballistic Board. See RANGE BOARD. A device used to determine the 
 total range corrections to be applied to the range found on the plotting board. 
 
 Ballistic Tables. Tables of data used in connection with ballistic formula 
 
6 THE SERVICE OF COAST ARTILLERY 
 
 in the solution of ballistic problems; certain functions used in the various 
 formulas are previously calculated for the certain velocities and then tabulated. 
 
 Ballistics. That branch of the science of gunnery which treats of the motion 
 of projectiles. 
 
 Bandoleer. A khaki-colored small arms ammunition belt, consisting of 
 six pockets, each containing two clips or ten rounds. Worn over one shoulder 
 and under the opposite arm. 
 
 Banquette. The step between the truck and loading platform. 
 
 Banquette Tread. In field fortification, a tread or foot bank running 
 along the inside of the interior slope upon which soldiers stand to fire over the 
 parapet. 
 
 Bar and Drum Sight. An open sight used on rapid-fire guns. 
 
 Barbette. A mound of earth or a platform on which guns are mounted to 
 fire over a parapet. In field fortification this level is distinguished by the 
 name of Banquette Tread. 
 
 Barbette Carriage. See CARRIAGE OR MOUNT. 
 
 Barometer. See ANEROID BAROMETER and MERCURIAL BAROMETER. 
 
 Base-end Station. An observing station located at either end of a base 
 line, designed to contain an azimuth instrument or depression position finder. 
 Base-end stations are designated as primary, secondary, or supplementary. 
 
 Base Fuse. A firing device inserted in the base of cored shot and armor- 
 piercing shell to ignite the bursting charge. Base fuses are used when the 
 point of shell requires great strength, as for penetrating armor. 
 
 Base Line. A horizontal line the length and direction of which has been 
 determined. This line is used in position finding, especially for long ranges ; 
 the stations at its ends are called base-end stations. It is called "right" or 
 " left " handed, depending on whether the primary station is to the right or left 
 of the secondary facing the field of fire. 
 
 Battery. The entire structure erected for the emplacing, protection and ser- 
 vice of one or more guns or mortars, together with the guns and mortars so 
 protected. The guns of a battery are of the same size and power, and are 
 grouped with the object of concentrating their fire on a single target and of their 
 being commanded directly by a single individual. 
 
 Normally a battery of the primary armament consists of two guns or two 
 pits of mortars. Under exceptional circumstances a single gun with its fire- 
 control service may constitute a battery. 
 
 In the case of intermediate and secondary armament a battery may consist 
 of any number of guns assigned to it. 
 
 Battery Commander. The senior artillery officer present for duty at a 
 battery. 
 
 The battery commander exercises both administrative and tactical command. 
 
 As an administrative officer he is responsible that every effort is made to 
 keep the battery supplied with the proper equipment, implements and ammu- 
 nition. He keeps a record of the daily attendance at drill and instruction, with 
 names of absentees, reason and authority for such absence. 
 
 As a tactical officer he is responsible that the personnel of his battery is 
 efficient in drill, in practice and in action, that the.equipment and fire-control 
 installation provided for his battery are in serviceable condition and that no 
 permanent modifications are made therein without proper authority. He is 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 7 
 
 required to see that the officers and men of his battery are instructed in the care, 
 preservation and use of artillery material, and that records are kept and reports 
 rendered as prescribed in orders and regulations. 
 
 He is authorized to modify the manual of the piece within the limits pre- 
 scribed by the drill regulations and to make temporary modifications or changes 
 ia the fire-control installation, provided such modifications or changes per- 
 mit of prompt return to their original condition. Permanent changes may be 
 made in the provisional installations upon the approval of the district com- 
 mander, the changes to be reported to the War Department. Changes in the 
 standard installation can only be made with the approval of the War Depart- 
 ment. 
 
 He should be encouraged by his superiors to improvise devices and methods 
 that will simplify the fire-control system or increase the efficiency of his 
 command. 
 
 He is responsible that the plotting-room details for the fire and battle 
 commanders' stations are kept in practice during the period of indoor instruction. 
 
 He should inspect his battery and make a test of the fire-control system 
 thereof weekly. 
 
 In battle command or fire command drill or action he exercises limited 
 fire control, acting on orders received from higher commanders. When " battery 
 commander's action" is ordered he exercises independent fire-control and 
 fights his battery in accordance with his own judgment. In cases of emergency 
 he acts without waiting for orders, in accordance with instructions previously 
 given. 
 
 Battery Commander's Station. An observing station at or near the battery, 
 usually in rear of the center traverse. The new type is a combined observing 
 room, emergency instrument room, plotting room, etc., at the rear of the 
 traverse. 
 
 Battery Commander's Walk. The elevated walk leading from the battery 
 commander's station along the rear of the battery. 
 
 Battery Emplacement Book. A loose-leaf record book provided for each 
 battery, in which all important data relating to the emplacements, guns, fire- 
 control equipment, etc., of a battery are kept. 
 
 Battery Field of Fire. The area covered by the armament of a battery; 
 it covers that portion of the fire area which can be most conveniently defended 
 by the battery in question. 
 
 Battery Manning Table. A table containing a list of names detailing 
 the personnel of a battery to their posts. 
 
 Battery Parade. The area in rear of the emplacements of a battery where 
 the sections form. 
 
 Battle Area. The area covered by the armament of a battle command. 
 
 Battle Chart. A chart used in battle, fire, and mine command stations 
 which covers their respective areas. It is constructed to show the channels 
 and different depths of water passable by the several types of war vessels; i.e., 
 the sector of any water area navigable by battleships, cruisers, torpedo 
 boats and smaller craft. It also shows the sectors of fire of the several batteries 
 in the particular command, and in the case of mine commands the position of 
 the fields, etc. It also sho^s the penetration in Krupp armor for each 1,000 
 yards of range for the several classes of armament. It is provided with an 
 
8 THE SERVICE OF COAST ARTILLERY 
 
 azimuth circle the center of which marks the location of the station to which 
 the chart belongs. 
 
 Battle Command. A battle command includes that portion of the arma- 
 ment assigned to any particular portion of the water area of an artillery district 
 in which a naval attack may be expected and over which one man may exercise 
 efficient control of the artillery fire and other means provided for defense. 
 
 Two or more fire commands and one mine command usually constitute a 
 battle command. There may be one or more battle commands in an artillery 
 district. 
 
 Two or more artillery forts or posts situated so that their armament covers 
 the same or adjacent water areas may constitute one battle command. 
 
 Responsibility for the sufficiency and condition of the material of a battle 
 command devolves upon the commanding officers of districts or posts in which 
 the battle command is located. 
 
 Battle Commander. A coast artillery officer assigned as such in orders 
 from district headquarters. He commands, for tactical purposes only, the 
 personnel of a battle command and is responsible for its tactical efficiency. 
 
 A battle commander sees that all orders prescribing battle-command driUs 
 and other exercises are properly and uniformly carried out. By frequent visits 
 to the fire commands he keeps posted as to the condition of the material and 
 personnel, so as to be able to report at all times as to their drill efficiency and the 
 condition of his battle-command service. He should exercise in battle-command 
 drill and in action, fire control throughout his command and over the battle 
 area, and command the fire action from his station from which the whole 
 battle area and approaches thereto should be visible. 
 
 He should have full knowledge of the nature and position of the mine fields 
 and any obstructions in his battle area and should be in communication with 
 the district commander, and his fire and mine commanders. He should be 
 informed of the general scheme of land defense, and after a careful study -of his 
 battle area, prepare plans of defense against the forms of attack liable to be 
 adopted by the enemy. He should be prepared to prevent reconnaissance in 
 force on the part of the enemy calculated to determine the strength and location 
 of the batteries. 
 
 At night the searchlights assigned to his battle area are under his immediate 
 control. Searchlights intended primarily for the mine service remain ordinarily 
 under the control of the mine commander, but when the battle commander 
 deems it necessary to use a mine-field light for searching, such light is under 
 control of the searchlight officer temporarily. 
 
 Battle Commander's Station. A station overlooking a battle area, occupied 
 by the battle commander, and necessary assistants, during drill or action. 
 
 Battle Flag. The national flag (garrison flag) displayed at a seacoast or lake 
 fort at the beginning of and during an engagement, whether by day or night. 
 It is also flown from the mainmast of vessels engaged. 
 
 Battleships. War vessels of massive appearance with broad beam as 
 compared with length. They have heavily armor-plated turrets and belt from 
 8 to 18 inches in thickness; deck and other armor 3 to 6 inches in thickness. 
 Average displacement 10,000 to 26,000 tons; length 375 to 550 feet; beam 60 
 to 75 feet; draft 24 to 30 feet; speed 16 to 21 knots (the measure of a nautical 
 mile or knot is 6080.27 feet, as against a statute mile, which measures 5280 feet). 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 9 
 
 Armament consists of: Main, 14-inch, 13-inch, 12-inch. Intermediate, 8-inch, 
 7-inch, 6-inch guns, and torpedo tubes. Secondary, 3-inch and smaller rapid- 
 fire guns. 
 
 Battle Tactics. As pertaining to fortress warfare, the science of the 
 disposition and handling of coast artillery units in action. 
 
 Berm. In field fortification, a moulding of natural ground between the 
 foot of the exterior slope and the scarp. 
 
 Bevel Wheel. A wheel having teeth cut on a bevel or conical surface called 
 a face ; where the inclination of the face is 45 degrees it is called a miter wheel. 
 Two of these wheels with teeth engaged at right angles to each other form a 
 bevel or miter gear. 
 
 Bivouac. A temporary place of repose for troops, in which they are shel- 
 tered by shelter-tents, bowers, or improvised shelter of any kind, or sleep in the 
 open air. 
 
 Blast. See POWDER BLAST. 
 
 Blast Slope or Apron. See APRON. 
 
 Blasting-Gelatine. The most powerful of the detonating and disrupt"' ve 
 explosives. It is only suitable for purposes of demolition. 
 
 Blending Powder. The process of mixing powders of the same or different 
 lots so as to obtain charges of uniform characteristics. 
 
 Blending Room. A dry, well-lighted and ventilated room in which several 
 charges of the same lot of smokeless powder are taken from the powder storage 
 cases and thoroughly mixed and blended. 
 
 Blind Shell. A shell which does not explode upon impact or when 
 intended to do so. 
 
 Boat Telephone. A simple type of telephone used in communicating over 
 cable between boats at distribution boxes in the mine field and the mining 
 casemate. 
 
 Bomb. A missile which also receives the names of bombshell and shell. 
 The use of the word is practically obsolete in gunnery. 
 
 Bomb-Proof. A term applied to military structures of such immense 
 thickness and strength that shells can not penetrate them. 
 
 Booth or Recess. Any recess or construction for the accommodation of 
 telautograph, telephone, etc. 
 
 Bore. The interior of a cannon forward of the front face of the breech 
 block. It is composed of the powder chamber, the centering slope, the forcing 
 cone, and the rifled portion, called the main bore. 
 
 Bore, Length of. See LENGTH OF BORE. 
 
 Bore-Plug. See CLINOMETER REST. 
 
 Bore-Sighting. In coast artillery, the process by which the line of sight 
 and axis of the bore prolonged are caused to converge on a point at or beyond 
 mid-range. 
 
 Bottom of the Bore. The surface of the powder chamber formed by the 
 face of the obturator-head when the breech-plug is home. 
 
 Bound. The path of a shot comprised between two grazes. 
 
 Bourrelet. That part of a projectile between the main body and the head, 
 which includes the beginning of the ogive. 
 
 Brackets. Metal supports for telautograph cases, etc. 
 
 Breech. The mass of metal behind the plane of the bottom of the bore. 
 
10 THE SERVICE OF COAST ARTILLERY 
 
 Breechblock. The metal plug which closes the breech. 
 
 Breech Bushing. That part of the breech which contains the threaded 
 and slotted sectors of the breech recess. 
 
 Breech Detail. A detail of the gun detachment charged with the duty of 
 opening and closing the breech. 
 
 Breech, Face of See FACE OF BREECH. 
 
 Breech Mechanism. The breechblock, obturating device, firing mechanism, 
 and mechanism for operating the breechblock. 
 
 Breech Recess. That part of the cannon which receives the breechblock. 
 
 Breech Reinforce. The part of the cannon in front of the breech and in 
 rear of the trunnion band. 
 
 Brown Prismatic Powder. A brown gunpowder of translucent celluloid 
 appearance, in the form of a six-sided prism with a hole in the center. 
 
 Building up Charges. The operation of preparing charges of brown pris- 
 matic, nitro-cellulose or spero-hexagonal powder, by properly placing the 
 grains in silk bags. 
 
 Built-up Cannon. Types of cannon in which the parts are built up of 
 either cylindrical forgings or a single forging wrapped with a rectangular Or 
 ribbon form of wire. 
 
 Buoy. A floating object moored to the bottom, used for temporarily 
 marking the positions of mines, junction and distribution boxes, channels, and 
 target positions. 
 
 Bursting Charge or Shell Filler. The charge of explosive required for 
 bursting a projectile ; it may be poured in loose or by melting. 
 
 Butt. In gunnery, a solid earthen parapet, to fire against in the proving 
 grounds or in practice. 
 
 Button Drill Primer. A form of primer so called from the fact that the 
 head of the friction wire is formed in the shape of a button. 
 
 " C Row. See HOOPS. 
 
 Cake Powder. Gunpowder which has become lumpy from having absorbed 
 moisture. 
 
 Caliber. A name given the minimum diameter of the bore of a firearm; 
 it is the diameter of the main bore in inches measured at the top of diametrically 
 opposite lands, or minimum diameter of the rifled portion of ihe bore. Also 
 used to express the length of cannon; e.g., a 12-inch gun 42 calibers long 
 would be 42 feet long ; a 6-inch gun 52 calibers long would be 26 feet long. 
 
 Calibration. The operation of adjusting the range scale so that the range 
 reading at any particular elevation of the gun will indicate the true distance 
 to the center of impact of a group of shots fired from that particular gun and 
 mount at that elevation with the standard velocity and under normal atmos- 
 pheric conditions. 
 
 It is desirable to calibrate the guns of a battery under the same atmospheric 
 conditions, although this is not absolutely necessary. It is absolutely necessary 
 that uniform ammunition be used for calibration firing of all guns of a particular 
 battery. When the individual guns of a battery are calibrated the battery is 
 calibrated, for the centers of impact of a series of shots from each gun under 
 normal atmospheric conditions will coincide at the point indicated by any 
 range setting. When guns of a battery " shoot together " (that is, give the same 
 range for the same range setting) they may be fired on the same data, but are 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 11 
 
 not calibrated unless the range under normal atmospheric conditions is that 
 indicated by the range setting. 
 
 It is not feasible to dete mine by actual firing all the points of a range scale, 
 and therefore it is assumed that the gun is calibrated when a range scale con- 
 structed from a computed range table is adjusted on the gun so as to give the 
 proper setting for a mid-range. 
 
 Call to Arms. A musical signal at which, if practicable, each man goes 
 direct to his post at a run. 
 
 Cannister. A projectile with a thin wall inclosing a number of small steel 
 balls but without a bursting charge, the case being ruptured by the shock of 
 discharge as the projectile leaves the gun. Designed for use against infantry 
 at short range. 
 
 Cannon. A general term for artillery weapons and firearms not carried nor 
 fired in the hands, from which projectiles are thrown by the force of expanding 
 powder gases. 
 
 Guns are long (generally from 30 to 50 calibers) have flat trajectories, and 
 are used for low-angle fire (less than 15 degrees), with high velocities (from 
 2000 to 3000 f.s., about). 
 
 Mortars are short (generally about 10 calibers), and are used for high-angle 
 fire (from 45 degrees to 70 degrees), with low velocities (from 550 to 1300 f.s., 
 about) . 
 
 Howitzers are intermediate between guns and mortars. 
 
 The term " piece" is used when referring to a cannon of any class. Cannon 
 in the United States land service are classified according to their use into coast, 
 siege, and field. 
 
 Cannon Ball. Properly speaking, this term should only be applied to 
 spherical solid projectiles which are fired from cannon. 
 
 Cannon Powder. A term applied to large-grained black or brown gun- 
 powder to distinguish it from rifle, mortar or mammoth powder. It is used 
 as a base in the manufacture of prismatic powders. 
 
 Cannonade. The act of discharging shot and shell from cannon for the 
 purpose of destroying an enemy. To discharge cannon. Also written can- 
 nonry. 
 
 Cannoneer. An artilleryman engaged in the firing, or one who manages or 
 assists in managing a cannon. 
 
 Canopy. The projecting roof over delivery tables of ammunition hoists of 
 modernized gun batteries. 
 
 Cap-Square. That portion of the iron work of a gun or mortar carriage 
 which folds or laps over the exterior portion of the trunnions to keep the piece 
 from jumping out of the trunnion bed. 
 
 Capital. The line through the gun pintle perpendicular to, or bisecting the 
 arc of the interior crest. 
 
 Capped Projectile. A projectile having a soft iron cap over its point to 
 give stability to the point when commencing penetration and to give the armor 
 an initial pressure at the point of penetration. 
 
 Carriage or Mount. The means provided for supporting a cannon. It 
 includes the parts for giving elevation and direction, for taking up the recoil 
 on discharge, and for returning the piece to the firing position. They are 
 classified as follows: 
 
12 THE SERVICE OF COAST ARTILLERY 
 
 1. Fixed. A mount provided for guns and mortars in permanent works 
 and not designed to be moved from place to place. 
 
 2. Movable or Wheeled. A carriage or mount provided with wheels for 
 ready transportation of the piece mounted thereon. Guns of the movable 
 armament are mounted on this type of carriage. 
 
 COAST CARRIAGES. Those used for coast artillery cannon. They may be 
 divided into four classes, depending upon the nature of cover afforded by the 
 emplacements : 
 
 a. Barbette. Where the gun remains above the parapet for loading and 
 firing. 
 
 b. Disappearing. Where the gun is raised above the parapet for firing, 
 and recoils under cover for loading. 
 
 c. Masking mount. Where the gun remains above the parapet for loading 
 and firing but can be lowered below the level of the crest for concealme-it. 
 
 d. Casemate. Where the gun fires through a port. 
 
 RAPID-FIRE GUN CARRIAGES (except the 6-inch on disappearing carriage) 
 are constructed so that the gun recoils in a sleeve and returns to the loading 
 position immediately after firing. 
 
 Note. If the carriage can be traversed so that the gun may be fired in all 
 directions it is said to have all-round fire. If it can not be traversed so that 
 the gun can be fired in all directions, it is said to have limited fire. 
 
 Cartridge. A complete charge contained in or held together by a case or 
 shell of metal. 
 
 Cartridge Bags. Bags made of a special quality of silk and sewed with 
 silk thread; used to contain the powder charge for cannon. This material 
 burns rapidly and completely, thus avoiding the danger of a smouldering 
 residue in the powder chamber. 
 
 Cartridge Extractor. That part of a breech-loading gun which ejects the 
 empty cartridge case from its seat in the bore. 
 
 Cartridge Room. A room of the magazine for the storage of cartridges. 
 
 Case. The charge holder of a submarine mine. 
 
 Case I. In gunnery, a class of gun pointing where direction and elevation 
 are both given by the sight. 
 
 Case II. In gunnery, a class of gun pointing where direction is given by 
 the sight and elevation by the range scale on the carriage. 
 
 Case III. In gunnery, a class of gun pointing where direction is given by 
 the azimuth scale and elevation by quadrant or by the range scale on the 
 carriage. 
 
 With mortars this Case is used exclusively. It is used with guns, (1) in fir- 
 ing by battery, (2) when the position of the target is known but the target is 
 not visible from the gun on account of smoke, fog, etc., (3) in predicted firing 
 by piece when for any reason direction cannot be accurately given by the 
 sight. 
 
 Casemate. An obsolete bombproof chamber, usually of masonry, in which 
 cannon were placed to be fired through embrasures or portholes ; or one capable 
 of being used as a magazine. See MINING CASEMATE. 
 
 Casemate Battery. A storage battery in the mining casemate provided 
 as a means of furnishing direct current for the mine system. 
 
 Casemate Electrician. A specially qualified member of a mine command 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 13 
 
 assigned to the care and operation of the mining casemate. Insignia: Red 
 mine case with red bar below within a yellow circle, all to be of cloth. 
 
 Casemate Officer. A coast artillery officer stationed at the mining case- 
 mate who controls its operation. 
 
 Casernes. In a general acceptation, casernes signify barracks. 
 
 Cast-iron Shot. Projectiles made of cast iron, used in service target 
 practice. 
 
 Castramentation. The art or act of encamping, or the act of marking or 
 laying out a camp. 
 
 Cathead. A projecting piece of timber or iron with a pulley at the head, 
 attached to either side of the bow of mine planters, by which anchors and 
 mine cases are hoisted or lowered. 
 
 Center of Gravity. That point in a body, or system of bodies rigidly 
 connected, upon which the body or system will balance itself in all positions, 
 though acted upon by gravity. 
 
 Center of Gravity Band. A painted band one-half a caliber wide on gun 
 projectiles, and six inches wide on mortar projectiles. The center of gravity 
 of the projectile is the center of the band. It also indicates where the shot 
 tongs are placed. 
 
 Center of Gravity of Cannon. The center of gravity of a cannon is near 
 the intersection of its axis and the axis of the trunnions. The preponderance 
 is the excess or moment of weight in rear of the axis of the trunnions over 
 that of the front, or the converse. 
 
 Center of Impact. The mean point of impact, or the mean of all the 
 hits. When a projectile strikes the target a number of times, it is the mean 
 trajectory. 
 
 Center Pintle. A term applied to a seacoast carriage when its axis of 
 rotation is approximately through the center, that is, when it traverses about 
 a point at its center. 
 
 Centering Slope. The conical part of the powder chamber between the 
 main chamber and the forcing cone. 
 
 Centrifugal Force. A force whose direction is from a center. For instance, 
 water is thrown from the blades of a propeller from the force issuing from its 
 center. 
 
 Centrifugal Fuses. Firing devices, the action of which depend upon cen- 
 trifugal force ; inserted either in the base or point of an armor or deck-piercing 
 shell to ignite the bursting charge. 
 
 Chamber. See SHOT OR POWDER CHAMBER. 
 
 Charge. The charge consists of the powder and the projectile. The powder 
 for all large cannon, to include 4.7-inch guns, is enclosed in silk or serge bags 
 and is separate from the projectile. In guns of greater caliber than six inches 
 it is put up in two or more sections or bags. For smaller calibers the projectile 
 and powder are not separate; such ammunition is called "fixed." 
 
 Charts. See HARBOR, DIFFERENCE, POW T DER, VESSEL, BATTLE AND SYMBOL 
 CHARTS. 
 
 Chase. The part of a cannon in front of the trunnion band. 
 
 Chassis. The traversing base frame of a gun carriage upon which the top 
 carriage moves backward and forward. 
 
 Chief Loader. A non-commissioned officer in charge of the loading of sub- 
 
14 THE SERVICE OF COAST ARTILLERY 
 
 marine mines. Insignia: Red mine case within a yellow circle, all to be of 
 cloth. 
 
 Chief of Ammunition Service. A non-commissioned officer in charge of 
 the magazines, galleries, and service of ammunition for a gun battery, or a 
 mortar emplacement. 
 
 Chief of Coast Artillery. A general officer of coast artillery charged with 
 the duty of keeping the War Department advised of the efficiency of the coast 
 artillery personnel and material, and making such recommendations as will 
 tend to promote its efficiency; to confer with and advise the chiefs of bureaus 
 in all matters relating to coast artillery; to correspond direct with command- 
 ants of artillery service schools and the president of the Artillery Board on 
 questions of a technical character not involving matters of command, discipline, 
 administration or the status or interests of individuals; to make recom- 
 mendations as to the instruction, examination, promotion, assignment, special 
 duty, and transfer of coast artillery officers and men, as well as methods and 
 courses for their instruction ; to issue direct to coast artillery officers bulletins 
 and circulars on technical matters. He is a member of the General Staff 
 Corps and the Board of Ordnance and Fortifications. 
 
 Chief of Coast Artillery's Flag. See FLAG OF CHIEF OF COAST ARTILLERY. 
 
 Chief Planter. A non-commissioned officer in charge of the service of a 
 mine planter. Insignia: Red mine case within a yellow circle, all to be of 
 cloth. 
 
 Chronograph. An instrument for measuring the velocity of projectiles. 
 
 Chronometer. An instrument for accurately measuring time. 
 
 Circle. A plane figure bounded by a curved line, called its circumference, 
 which returns into itself, and which is everywhere equally distant from a point 
 within it called a center. A circumference is divided into 360 equal parts, 
 each of which is known as a degree', each degree into 60 parts, each of which 
 is known as a minute ; each minute into 60 parts, each of which is known as a 
 second. In the coast artillery service degrees are divided into hundredth*, and 
 the minutes and seconds eliminated. 
 
 Circuit-Closer. A device by which submarine mines are fired electrically 
 by the vessel closing the circuit. 
 
 Circumference. See CIRCLE. The circumference of any circle is 3.1416 
 times the length of its diameter. 
 
 Cleaner. An artilleryman charged with the care of armament out of service. 
 
 Clinometer. An instrument for measuring accurately the inclination of the 
 axis of the bore to horizontal. 
 
 Clinometer Rest. The support for a clinometer inserted in the muzzle of 
 the gun; it is also called bore-plug. 
 
 Coast Artillery Board. A board, consisting of such number of coast 
 artillery officers as the War Department may direct, to which may be referred 
 from time to time all subjects pertaining to the coast artillery upon which the 
 War Department or the Chief of Coast Artillery may desire the board's opinion 
 and recommendations. 
 
 Coast Artillery Company. An integral part of the Coast Artillery Corps, 
 assigned to some portion of the armament. The strength is fixed in orders; 
 the present authorized personnel of a gun company of the primary armament 
 is, Captain, 1 First Lieutenant, 1 Second Lieutenant, 1 First Sergeant, 1 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 15 
 
 Quartermaster Sergeant, 8 sergeants, 12 Corporals, 2 Mechanics, 2 Musicians, 
 2 Cooks, and 81 Privates. The number of privates may be varied in com- 
 panies depending upon the armament to which it is assigned; this is partic- 
 ularly the case in companies of the mine defense. 
 
 Coast Artillery Fort. The coast defenses at any military post and tho 
 garrison assigned thereto. Its command devolves upon the senior regular 
 coast artillery officer present. 
 
 Coast Artillery Garrison. The personnel, to include regular coast artil- 
 lery, coast artillery reserves, and coast artillery supports, assigned to a coast 
 artillery fort. 
 
 Coast Artillery Material. Coast artillery material is classified as arma- 
 ment, range equipment, power and light equipment, and submarine defense 
 equipment. 
 
 Coast Artillery Reserves. Militia troops organized as coast artillery for 
 the purpose of supplementing the regular coast artillery. 
 
 Coast Artillery Supports. Infantry or other troops assigned to coast 
 artillery forts to support the artillery in repelling land attacks in the immediate' 
 vicinity of the fortifications. 
 
 Coast Carriage. See CARRIAGE or MOUNT. 
 
 Coast Defense. The military and naval dispositions and operations neces- 
 sary to resist a naval attack on any part of the coast line. 
 
 Coast Defense Officer. A coast artillery officer assigned to duty on the 
 staff of division or department commanders to act in an advisory capacity 
 with respect to matters pertaining to the efficiency of coast artillery material 
 and to the drill, instruction and employment of coast artillery in connection 
 with coast defense generally. 
 
 Coast Defense Ships. Ships of the monitor or gunboat type, supple- 
 menting the shore defenses at points where the latter do not give adequate 
 protection, by reason of the width of the approaches or the nearness of the 
 harbor, city, or anchorage, etc., to the sea. 
 
 Coast Guard. Mobile troops placed at strategical points near fortified 
 portions of the coast line. 
 
 Collar. A device made of wood, placed upon the chase of a gun to make 
 the diameter equal to that of the body of the piece, to enable it to be rolled 
 with facility. 
 
 Colors. The silken national, and district or regimental flags carried by 
 regiments or battalions of engineers, troops comprising coast artillery districts, 
 and regiments of infantry. The word is used in contradistinction to standards, 
 which are smaller in dimension and are carried by regiments of cavalry, and 
 regiments of field artillery. They are carried in battle, campaign, and on all 
 occasions of ceremony at district or regimental headquarters where two or more 
 companies of the district or regiment participate. 
 
 Each coast artillery post, where two or more companies of coast artillery 
 are stationed, is furnished with a service color, which is the national color made 
 of bunting or other suitable material, but in all other respects similar to the 
 silken national color. Garrisons of coast artillery posts other than district 
 headquarters may use them upon all occasions. 
 
 Colors of the Coast Artillery Corps. The national color is of silk 5 feet 
 6 inches fly, 4 feet 4 inches on the pike, which is 9 feet long, including spear- 
 
16 THE SERVICE OF COAST ARTILLERY 
 
 head and ferrule; the union is 2 feet 6 inches long, with stars embroidered in 
 white silk on both sides of the union; the edges are trimmed with knotted 
 fringe of yellow silk 2^ inches wide; there are two cords 8 feet 6 inches long, 
 having tassels, and composed of red, white, and blue silk strands. The official 
 designation of the artillery district is engraved on a silver band placed on the 
 pike. 
 
 The corps color, of the same dimensions as the national color, is of scarlet silk, 
 having embroidered upon it in colors the official coat of arms of the United States, 
 of suitable size. Below the coat of arms, in the middle, embroidered in yellow 
 silk, are two cannon, crossed; also a scroll embroidered in yellow silk and 
 bearing the inscription, "U. S. Coast Artillery Corps," embroidered in red 
 silk; the edges are trimmed with knotted fringe of yellow silk 1\ inches wide; 
 cord and tassels same size as those of the national color, but of red and yellow 
 silk strands. Both sides of the color are embroidered alike. 
 
 One set of national and corps colors is issued to the headquarters of each 
 artillery district. 
 
 Colors on Projectiles. See PAINTS ON PROJECTILES. 
 
 Combination Electric Friction Primer. A primer combining the prin- 
 ciples of friction and electric primers, the electric features being modified. 
 
 Combination Fuse. A fuse inserted in the point of shrapnel which ignites 
 the bursting charge either upon impact or at the completion of the set time 
 interval; it contains both a time and percussion fuse, thus increasing the 
 chance of bursting. 
 
 Commissary Sergeant. See POST COMMISSARY SERGEANT. 
 
 Common Electric Primer. A primer whose action depends upon the 
 ignition of a small charge of fulminate fired by means of a platinum bridge 
 heated to incandescency by an electric current. 
 
 Common Friction Primer. A primer which operates solely by friction. 
 
 Communication Officer. A coast artillery officer charged with the duty of 
 receiving and transmitting communications during drill or action. 
 
 The communication officer of a battle command has entire charge of the 
 system of communication, inspects the equipment of the station, excepting 
 the equipment pertaining to the searchlight system, verifies the adjustment of 
 the position-finding instruments, receives the report of details and reports to 
 the battle commander when the station is in order, or reports any defects that 
 he cannot immediately correct. He receives all orders from and transmits 
 all communications to the district commander, and all orders to and com- 
 munications from the fire and mine commanders. He sees that an accurate 
 record is kept of all orders of the battle commander and all communications of 
 whatever character received at the station. 
 
 The communication officer of a fire command is in charge of the station 
 under the fire commander. He inspects the equipment of the station, verifies 
 the adjustment of the position-finding instrument, plotting board, etc. Re- 
 ceives the reports of the battery commanders and transmits them to the fire 
 commander. He transmits the orders of the fire commander to range officers, 
 or through the latter to the battery commanders; receives all orders from the 
 battle commander, and immediately transmits same to the fire commander. 
 He sees that an accurate record is kept of all orders and communications to 
 and from the station. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 17 
 
 Communications. Means of transmitting orders or messages through the 
 tactical chain of artillery command. In the case of mobile troops it includes 
 all routes, such as roads, railroads, etc., by which an army communicates with 
 its base, or by which several parts of an army communicate with each 
 other. 
 
 Composite Artillery Type Telephone. A special type of telephone pro- 
 vided for permanent artillery communications. 
 
 Computer. A member of the fire-control section who operates a range or 
 deflection board. 
 
 Concentric. That which has a common center with something else. A 
 stone thrown in a motionless pool of water would cause concentric circles to form 
 on its surface. 
 
 Cone of Dispersion. See ("ONE OF SPREAD. 
 
 Cone of Spread. The imaginary cone containing the diverging bullets or 
 fragments upon the explosion of a shrapnel shell. This cone is very long. 
 
 Conical. Round and tapering to a point. 
 
 Console. A bracket whose projection is not more than half its height ; any 
 small bracket. 
 
 Contact Firing. The electrical firing of a submarine mine when it is struck 
 by an enemy's ship. 
 
 Converted Gun. A smooth-bore gun in which a tube containing rifling 
 has been inserted. 
 
 Cordage. Ropes and cord collectively. See chapter on CORDAGE. 
 
 Cored Shot. A projectile the center of which is partly hollowed. It can 
 be filled with a bursting charge and used the same as a shell. 
 
 Corrected Range. The fictitious range which determines the elevation to 
 be given the gun, in order to hit the target. 
 
 Corridor or Truck Corridor. The elevated passageway in rear of the 
 traverse connecting adjacent gun emplacements at the loading platform level. 
 
 Corridor Wall. The traverse wall along the corridor. 
 
 Counter Attack. A counter attack, during an engagement of mobile 
 troops, is directed against the enemy's attack, i.e., it meets him before, or at 
 the moment of, arrival at the defended position. The term also applies to an 
 attack made after a prior defensive attitude and directed against troops not 
 previously engaged, for example, in turning the flank of an attacking force. 
 This is called the decisive counter attack, although, properly speaking, it is 
 the assumption of the offensive. 
 
 Countermining. The operation of clearing a channel of mines, by exploding 
 large charges sufficiently near the mines to cause their destruction. The usual 
 method consists of dropping in succession two or more parallel straight lines 
 of countermines at such distance from each other that their simultaneous 
 explosion will destroy all mines within their destructive radius. 
 
 Note. The success of this is very doubtful, however, under the present 
 mine system. 
 
 Counter Recoil. The return of the gun in battery, immediately after recoil. 
 
 Counterscarp. Sae SCARP. 
 
 Counterweight. The weight used on disappearing carriages to take up 
 part of the force of recoil, and to carry the gun to the firing position. The 
 term is also applied to the weight on masking parapet mounts. 
 
18 THE SERVICE OF COAST ARTILLERY 
 
 Counterweight Well. The pit in the front end of a gun platform for the 
 reception of the counterweight of a disappearing carriage. 
 
 Cover Post. Positions for the members of a mortar detachment at the 
 command " Take Cover." 
 
 Cradle. A device employed for transporting heavy guns a short distance. 
 
 Crane. A mechanical device for raising ammunition by means of differen- 
 tial or other blocks. 
 
 Critical Dimension. A term used in connection with powder grains. It is 
 the dimension or thickness of the web between the perforations in a 
 multi-perforated grain. Also called least dimension. See chapter on BAL- 
 LISTICS. 
 
 Cross Fire. Cross fire is where the projectiles from guns in different posi- 
 tions cross one another at a particular point. 
 
 Crow's Nest. The name commonly applied to the observing station located 
 in the parapet or traverse. 
 
 Cruiser. A war vessel of graceful and regular outline. Armored Cruisers 
 have a narrow beam as compared with length, a high freeboard, armor-plated 
 turrets and belt. Average length about 400 feet, beam 60 to 70 feet, draft 
 22 to 24 feet, speed 22 to 24 knots, displacement 13,000 to 15,000 tons, armor 
 3 to 6 inches in thickness, armament 10-inch, 8-inch, 6-inch, and smaller rapid- 
 fire guns, and torpedo tubes. 
 
 Protected Cruisers differ from armored cruisers in having only protected 
 deck at water line. Average length 300 to 430 feet, beam 40 to 50 feet, draft 
 17 to 27 feet, speed 19 to 23 knots, displacement 3,000 to 9,000 tons, armor 
 of deck \\ to 4 inches, armament 8-inch, 6-inch, 5-inch, 4-inch, and smaller 
 rapid-fire guns, and torpedo tubes. 
 
 Scout Cruisers differ from other types in having no armor protection. Aver- 
 age speed 22 to 26 knots, armament small rapid-fire guns. 
 
 Cruiser Battleship. A war vessel the armament of which is equal in power r 
 or nearly so, to a battleship, but which cannot fight in a naval "battle line" 
 owing to the lightness of its armor protection. This type of war vessel carries, 
 as its capital caliber, eight 12-inch guns; its armor, however, is only about one- 
 half the thickness of that of battleships. This saving in weight being given 
 to motive power, their speed being about 26 knots. Their functions are to 
 drive in or destroy the enemy's armored cruisers and discover the strength 
 of his battle front. They may also be used to harass the enemy's battleships 
 either before or during an action. 
 
 Crusher Guage. A device inserted in the mushroom head of the breech- 
 block, or in the bottom of the bore, to determine the maximum pressure of 
 the bore. Commonly called pressure gauge. 
 
 Curvature of the Earth. A term applied in gunnery to define the amount 
 of bending of the water surface of the earth from the normal due to the earth's 
 shape. This bending of the water surface causes the target to be on a lower 
 level than that of the gun, i.e., the apparent difference of level between the 
 axis of the gun and mean low water as the position of the target is increased 
 in proportion to the range. 
 
 Curve or Curved Line. A line that changes direction at every point. 
 
 Curved Fire. See FIRE. 
 
 Cut-off Jack Set. A form of telephone bridged on lines to primary sta- 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 19 
 
 tions and booths to enable communication officers to talk direct to any primary 
 station in the fire command. 
 
 Cylindrical. Having the form of a cylinder; uniformly circular. 
 
 Cylindro-Conical. Having the form of a cylinder the forward portion of 
 which is conical. 
 
 "D" Row. See HOOPS. 
 
 Danger Range. See DANGER SPACE. 
 
 Danger Space. The horizontal distance within which a target of given 
 height would be hit by a projectile. It is usually computed for the standard- 
 size target. The danger space varies with the range, the flatness of the tra- 
 jectory, the height of the target, and the height of the gun above the target. 
 
 Data Line. See INTELLIGENCE LINE. 
 
 Datum Point. A fixed point in the field of fire the true azimuth and range 
 of which has been determined by the Engineer Corps. Such point or points 
 are used in proving the accuracy of range and position finding instruments. 
 
 Deflection. The horizontal angle between the plane of sight and plane of 
 departure; it is expressed as a reference number and is set off on the sight 
 deflection scale. 
 
 Deflection Board. A device for determining the algebraic sum of the 
 deflection corrections for wind, drift and travel of target during the time of 
 flight and the predicted interval. It is used to determine the reference numbers 
 for the deflection scale of the sight in Cases I and II, and the azimuth correc- 
 tion reference number in Case III; and, for mortars, the corrected azimuth. 
 
 Deflection Scale. A scale provided on sights, graduated in degrees and 
 hundredths for the purpose of obtaining and applying corrections for deviation. 
 
 Delayed Automatic Firing. A term applied to one of the three methods 
 of exploding submarine mines, i.e., where the apparatus is so arranged that the 
 mine is exploded when a signal is given which indicates that it has been struck. 
 
 Delivery Table. The table from which ammunition is delivered to the 
 truck. 
 
 Density of Loading. The mean density of the whole contents of the 
 powder chamber. It is the ratio of the weight of the powder charge to the 
 weight of a volume of distilled water at a temperature of 39.2 degrees F., which 
 would completely fill the powder chamber. The formula for computing it is 
 A (density of loading) = (27. 7W") / V, in which W is equal to the weight of the 
 powder in pounds and V the volume of the chamber in cubic inches. 
 
 Department Artillery Officer. See COAST DEFENSE OFFICER. 
 
 Department Commander. A general officer assigned by order of the 
 President to command all the military forces of the government within the 
 limits of territorial divisions and departments which are not excepted from 
 his control by the War Department. 
 
 Department Commander's Flag. See FLAG OF DEPARTMENT COMMANDER. 
 
 Depression Position-Finder. A telescopic instrument used in the primary 
 and secondary stations of a fire-control base line, to read either vertical or 
 horizontal angles. When used in the first instance it is a depression-position 
 finder, while in the second it is used the same as an ordinary azimuth instru- 
 ment. Objects when viewed from an elevation appear under different angles 
 of depression according to their distance from the point or points of observa- 
 tion; this fact is taken advantage of in the vertical base system and is the 
 
20 THE SERVICE OF COAST ARTILLERY 
 
 principle upon which depression-position range finders are constructed. The 
 depression-position range finder solves, mechanically, the problem of determin- 
 ing one side of a vertical right triangle, having given a side and two adjacent 
 angles. The given, or base side, is the distance above sea level of the axis about 
 which the telescope is elevated or depressed. The lower angle is constant and 
 equal to 90 degrees. The depression angle varies with the distance of the 
 observed target. 
 
 Detonation. The practically instantaneous combustion or decomposition 
 of a disruptive explosive of high order. 
 
 Deviation. Distances measured either in the horizontal plane at the level 
 of the target or in a vertical plane through the center of the target at right 
 angles to the plane of direction. If from the point of impact of a shot a per- 
 pendicular be drawn to the plane of direction, the length of this perpendicular 
 is the lateral deviation, and it is plus or minus according as the point of 
 impact is to the right or left of the line of direction looking from the gun. 
 The distance from the foot of this perpendicular to the center of the target 
 is the longitudinal deviation. It is plus when the point of impact is beyond 
 the tanget and minus when it is short. 
 
 Deviation at the Target. If from the target a line be drawn perpendicular 
 to the plane of direction intersecting the plane containing the line of shot, the 
 length of this perpendicular is the "deviation at the target." 
 
 Deviation, Absolute. See ABSOLUTE DEVIATION. 
 
 Deviation, Mean Lateral. See MEAN LATERAL DEVIATION. 
 
 Deviation, Mean Longitudinal. See MEAN LONGITUDINAL DEVIATION. 
 
 Deviation, Range. See RANGE DEVIATION. 
 
 Diameter. A line passing through the center and terminating at both ends 
 in the circumference of a circle. 
 
 Difference Chart. A graphic device constructed upon geometric principles 
 by which information as to range and azimuth of a target from one point the 
 primary station is converted mechanically into similar information with re- 
 spect to any other point, as the directing gun or point of a battery. 
 
 Direct Fire. See FIRE. 
 
 Directing Gun. See DIRECTING POINT. 
 
 Directing Point. A point at or near the battery for which relocation is 
 made at the plotting room. It is the point over which the gun center of the 
 plotting board is adjusted. When the pintle center of a gun of a battery is 
 taken as the directing point, such gun is called the directing gun. 
 
 Disappearing Carriage. A gun carriage so constructed that it witl carry 
 its gun to a firing position above the parapet and upon discharge carry it back 
 to the original loading position behind the parapet. 
 
 Displacement. The horizontal distance from the vertical axis of the posi- 
 tion finder of the battery primary station to the pintle center of the directing 
 gun, or some other directing point. 
 
 In a marine sense the word implies the quantity of water displaced by the 
 hull of a ship, the weight of the displaced liquid being equal to that of the 
 displacing body. 
 
 Displacement of any Point. The horizontal distance in yards of that 
 point from the directing point. 
 
 Distribution Box. A cast-iron case through which the cables of a group 
 
DEFINITIONS/ABBREVIATIONS AND SIGNS 21 
 
 of submarine mines are distributed from the multiple-core cable which runs 
 to the mining casemate. 
 
 District Artillery Engineer. A coast artillery officer charged with the 
 requisition, supervision, maintenance, inspection and accountability of the 
 signal, submarine mine and engineer installations, property and stores of an 
 artillery district. He inspects all such installations, property and stores at 
 each post in his district at least once a month. His tactical functions are 
 those of a searchlight officer of a battle command, unless otherwise assigned 
 by the district commander. 
 
 District Commander. See ARTILLERY DISTRICT COMMANDER. 
 
 District Drill. A drill conducted by the district commander in which all 
 the artillery elements of defense of the district take part. 
 
 Ditch. In field fortification, the trench in front of the parapet, designed as an 
 obstacle to the assailant. It was formerly called also a moat or a, fosse. 
 
 Double Primary Station. A building so constructed as to contain under 
 one roof two primary stations with their plotting rooms. 
 
 Double Secondary Station. A building so constructed as to contain under 
 one roof two secondary stations. 
 
 Drift. The divergence of the projectile from the plane of departure due to 
 its rotation, its ballistic character and the resistance of the air. It is generally 
 in the direction of rotation, except for extreme elevations of high-angle fire, 
 in which case it may be opposite to the original direction of rotation. For the 
 United States service rifled guns it is to the right. It may be expressed either 
 in yards or angular measure. 
 
 Driggs-Schroeder Rapid-Fire Gun. A rapid-fire gun of 2.24-inch caliber, 
 commonly called 6-pounder. They are distinguished by two models of breech 
 mechanism, namely, screw-block and drop-Week. 
 
 Driggs-Seabury Rapid-Fire Gun. A rapid-fire gun of 2.24 and 3-inch 
 caliber, commonly called 6 and 15-pounders respectively. 
 
 Drill Primer. A primer provided for reloading, used for drill purposes. 
 
 Dunnite. See EXPLOSIVE "D." 
 
 Dynamite. A detonating and disruptive explosive of high order used for 
 filling submarine mines and demolitions of all kinds. 
 
 Earthworks. In fortification, a general term for all military constructions, 
 whether for attack or defense, in which the material employed is chiefly 
 earth. 
 
 Ecrasite. A high explosive compound of foreign manufacture. 
 
 Eight-inch Gun. A seacoast cannon usually 40 calibers long and of 8-inch 
 caliber. 
 
 Elasticity. That property by which bodies recover their former shape and 
 volume after having yielded to some force. Elasticity of steel permits its 
 extension to a certain limit, beyond which a permanent set would take place. 
 This limit is known as the limit of elasticity. 
 
 Electric Ballistic Machine. See CHRONOGRAPH. 
 
 Electric Firer. See EXPLODER. 
 
 Electric Mines. Submarine mines fired by electric current; they are of 
 two classes, controllable and non-controllable. 
 
 Electric Primer. See COMMON ELECTRIC PRIMER. 
 
 Electrician Detachment. A detachment consisting of the electrician ser- 
 
22 THE SERVICE OF COAST ARTILLERY 
 
 geants and necessary assistants detailed from the enlisted personnel, charged 
 with the care and preservation of the electrical installations, etc., of a fort. 
 
 Electrician Sergeant. A non-commissioned staff officer. Electrician ser- 
 geants are of two classes. The first class are charged with the immediate 
 supervision, care, and operation of a division of the electrical installations, 
 including searchlights and power plants when necessary, in addition to the 
 duties prescribed for electrician sergeants, second class. Any duty in con- 
 nection with the electrical installations, including the mechanical work of 
 repairing electrical apparatus and the care and operation of searchlights. 
 The second class are charged specifically with the care, repair and maintenance 
 of the electrical installations, including lines and means of communication, as 
 well as any duty in connection with the electrical installations, including 
 mechanical work necessary in repairing the electrical apparatus, and the care 
 and operations of searchlights and small power plants. Insignia : First Class. 
 Gold wreath with a white forked lightning within and a small red bar about 
 three-quarters of an inch long between the lightning and the wreath, all below 
 a sergeant's chevrons. The lightning, bar, and wreath to be of silk embroidery 
 thread. Second Class. Same as first class, omitting the small bar. 
 
 Elevation. A general term used to denote the inclination in a vertical 
 plane given to the axis of the'gun in pointing. See SIGHT ELEVATION, QUAD- 
 P.ANT ELEVATION. 
 
 Elevation Setter. The member of a mortar detachment who lays the mor- 
 tar in elevation. 
 
 Elliptical. Oblong with rounded ends. 
 
 Elongated Projectiles. The modern type of coast artillery projectiles. 
 
 Emergency Position Finder. A self-contained horizontal position finder, 
 or a d pression position finder constructed for use on low sights and suffi- 
 ciently accurate for emergency purposes. It is operated from the observing 
 station (crow's nest) at a battery in case the regular instrument or station is 
 destroyed. 
 
 Emergency Station. A range-finding station provided for use in case a 
 regular station of a permanent base line has been destroyed. These stations 
 are so located that they can be used to replace the primary or secondary station 
 of one or more base lines. The term is also applied to the observing station at 
 the battery, where an emergency depression position-finder is mounted. 
 
 Emergency System. A system of position-finding, used in an emergency. 
 It employs a self-contained position-finder located at the battery, with or 
 without a plotting board. 
 
 Emplacement. That part of a battery pertaining to the position, protection 
 and service of one gun or mortar, or a group of mortars. 
 
 Emplacement Book. See BATTERY EMPLACEMENT BOOK. 
 
 Emplacement Officer. A coast artillery officer in immediate charge of the 
 emplacements of a gun battery or one pit of a mortar battery. He is the bat- 
 tery commander's assistant at the guns to which he is assigned. He is respon- 
 sible to the battery commander for the condition of the emplacement and 
 material, as well as for the efficiency of its service. Upon arrival at the' em- 
 placement before a drill, practice or action, he makes a careful inspection of all 
 parts of the guns and carriages, the equipment and implements to be used, 
 giving special attention to the elevating and traversing devices as well as those 
 
DEFINITIONS. ABBREVIATIONS AND SIGNS 23 
 
 for running the piece in and from battery; recoil cylinders to see that they 
 arc properly filled with the right amount and kind of oil, and that the plugs 
 are properly inserted; obturators to see that they are properly adjusted; 
 pads in serviceable condition. In case of firing to see that the throttling 
 and buffer valves are properly set and locked; to see that the motor generator, 
 motors and controllers, firing attachments, firing batteries and circuits are in 
 order; that the sights, subscales of azimuth circles are in adjustment; that 
 sponges and rammers are of proper kind and gauge and in serviceable con- 
 dition; that suitable vessels are provided for the water necessary for sponging 
 out the bore; that all necessary charts are on hand; and that ammunition 
 hoists are in working order. 
 
 As the efficiency of a battery depends primarily on the correctness of ad- 
 justment of each of the devices mentioned above, the necessity of a thorough 
 inspection can not be too strongly recommended. 
 
 Emplacement officers of mortar batteries are charged with the corresponding 
 duties in so far as they pertain to a mortar battery. 
 
 Endurance of Cannon. The life of a cannon or the number of times a 
 piece is capable of being fired before relining is necessary. In the case of 
 heavy guns their life is assumed to be approximately 250 service shots. 
 
 Energy of the Projectile. The energy stored up in the projectile by the 
 force of expanding powder gases generated by the explosion of the charge. 
 It is expressed usually in foot-tons. When a projectile is in motion it is said 
 to have energy, i.e., it is capable of doing work and overcoming resistance. 
 The formula for computing it is: E = Wv 2 1 (4480y) , in which W is the weight 
 of the projectile in pounds, v is velocity in feet per second, and g the accelera- 
 tion due to gravity (mean value 32.16). 
 
 Energy of Recoil. An expression denoting the work done in recoil of a 
 gun when fired. The recoil may be reduced by decreasing the weight of the 
 projectile, decreasing the muzzle velocity, or by increasing the weight of the 
 gun. 
 
 Enfilade Fire. Fire which rakes a fighting line, the gun being on the 
 prolongation of the line. In naval or fortress engagements fire delivered on 
 the stern or bow of a ship so that the projectiles rake the whole length of the 
 deck. 
 
 Engineer. A non-commissioned staff officer whose duty it is to supervise, 
 care for, and operate the power plants, machine and repair shops, and such 
 mechanical and electrical apparatus used for power purposes as may be placed 
 under his charge. He may be required to perform such other technical duties 
 as may be necessary in the district or at the post to which assigned. Insignia : 
 Gold wreath with a red governor within and a small white star about one-half 
 of an inch above the governor, all to be of embroidery thread. 
 
 Equalizing Pipe. A pipe connecting corresponding ends of two recoil 
 cylinders for the purpose of equalizing the pressure therein. 
 
 Erosion of the Bore. The wearing away of the rifling of the bore. 
 
 Estuary. A passage, as at the mouth of a river or lake where the tide 
 meets the current ; an arm of the sea. 
 
 Exploder. An electrical machine operated by hand, used to fire electric 
 fuses and primers. 
 
 Explosive. A substance or a mixture of substances which, when heated, 
 
24 THE SERVICE OF COAST ARTILLERY 
 
 
 
 struck, or subjected to the shock of another explosive results in the rapid 
 formation of a great volume of highly heated gas. 
 
 Explosive Compound. An explosive whose ingredients are united chem- 
 ically. Nitro-glycerine and guncotton are explosive compounds. 
 
 Explosive "D," or Dunnite. A shell filler the exact ingredients of which 
 are secret. It is a high explosive compound. It is not fusible and shells are 
 filled by compression. It is the least sensitive to shock of all the explosives 
 used in the service. 
 
 Explosive House. A structure in which high explosives are stored on a 
 military post; frequently referred to as a magazine. Authorities do not agree 
 as to the most suitable type. Some advocate light wooden structures, the 
 debris of which in case of explosion would be thrown a comparatively short 
 distance; others recommend a building of corrugated iron with asphaltum 
 floors, making the house fireproof. Structures of this characte: are usually 
 protected by earthworks. 
 
 Explosive Mixture. An explosive whose ingredients are mixed mechanic- 
 ally. Gunpowder is an explosive mixture. 
 
 Exterior Crest. The line of intersection of the superior and exterior slopes. 
 
 Exterior Slope. The outer slope of the parapet of a battery. 
 
 Extreme Range. The greatest accurate range obtained by a projectile in 
 its flight. For example, the extreme range of the 16-inch breech-loading rifle, 
 model 1895, is approximately 21 miles. The extreme range against armor for 
 the 12-inch breech-loading rifle, model 1900, is approximately 13,000 yards, or 
 1\ miles. 
 
 Face of the Breech. The rear terminal plane of the gun perpendicular to 
 the axis of the bore. 
 
 Face of the Muzzle. The front terminal plane of the gun perpendicular 
 to the axis of the bore. 
 
 Faces of the Rimbases. The end planes of the rimbases perpendicular to 
 the axis of the trunnions. 
 
 Faces of the Trunnions. The end planes of the trunnions perpendicular 
 to their axis. 
 
 Field of Fire. The designation of the area covered by certain armament, 
 for example, that of a battery. 
 
 Fifteen-Pounder. Term applied to a 3-inch rapid-fire gun. It denotes 
 the proper weight of projectile for the piece. 
 
 Fillet. That portion of metal, filling the re-entrant angle formed by two 
 surfaces not tangent, thus avoiding a sharp corner. The term is also applied 
 to the metal cut away in removing the sharp edge formed by the intersection 
 of two surfaces. 
 
 Final Velocity. See REMAINING VELOCITY. 
 
 Fire. The discharge of firearms and the destruction caused by their pro- 
 jectiles. Artillery fire is classified as direct, curved and high-angle fire. Direct 
 fire is fire with high velocities and angles of elevation not exceeding fifteen 
 degrees. Curved fire is fire with low velocities and angles of elevation not less 
 than fifteen degrees. High angle fire is fire with low velocities and angles of 
 elevation not less than forty-five degrees. See ORDERS OF FIRE; ENFILADE 
 FIRE; FLANKING FIRE; FRONTAL FIRE; OBLIQUE FIRE; REVERSE FIRE. 
 
 Fire Area. The area covered by the armament of a fire command. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 25 
 
 Fire Command. A fire command consists normally of four batteries of 
 two guns each, or in the case of a mortar fire command, of two mortar bat- 
 teries consisting of two pits each. The batteries of a fire command should be 
 so located that their fire covers the same or adjoining water areas, and so 
 located that the artillery fire therein will not interfere with that of any other 
 fire command. 
 
 The armament of an artillery fort or post may be divided into two or more 
 fire commands. 
 
 Fire Commander. A coast artillery officer assigned in orders from district 
 headquarters to command a fire command. 
 
 A fire commander is responsible to the battle commander for the tactical 
 efficiency of his command. He is in direct communication with his battle 
 commander and each battery commander in his command. 
 
 He is both an administrative and tactical commander; his administrative 
 duties, however, are confined to those affecting the tactical efficiency of the 
 fire command. In general he exercises his administrative duties verbally or 
 informally. Generally orders to his fire command are issued from post head- 
 quarters. All communications to and from post headquarters affecting his fire 
 command are referred to him for his information and remark. His office is not 
 one of record; he consults the records at post headquarters for any needed 
 information. 
 
 On battery drill days he visits the batteries of his command during drill, 
 and on days of indoor instruction visits the companies during instruction 
 hours. He supervises battery target practice. 
 
 He requires a thorough knowledge of the installation, equipment and system 
 of fire control and drill on the part of the officers of his command, and en- 
 courages and recommends improvements in drill or material. 
 
 He should keep himself constantly informed as to the condition of the 
 material of each battery in his command as well as to the efficiency of all sup- 
 plies. 
 
 In battle command drill or in action, he takes up promptly the attack of 
 the targets assigned or indicated by the command of the battle commander. 
 When ordered to assume the exercise of independent fire action, he fights his 
 batteries in accordance with his own judgment. He is authorized by regula- 
 tions to order independent battery action whenever, in his opinion, the con- 
 dition of the naval attack renders such action advisable, provided independent 
 fire command action has been ordered, or urgency renders it necessary. He 
 uses his own judgment as to orders of fire and rate of fire, unless these have 
 previously been prescribed by the battle commander. 
 
 At night the illuminating light assigned to his fire area is under his immedi- 
 ate control. 
 
 Fire Commander's Station. A station overlooking a fire area occupied by 
 the fire commander and necessary assistants during drill or action. 
 
 Fire Control. The exercise of those tactical functions which determine: 
 (a) The objective of fire. (6) The volume and concentration of fire, (c) The 
 accuracy of fire. 
 
 The term /ire-control system includes the means employed in fire-control, 
 the scheme of its installation and method of its use. The material as installed, 
 which is employed in the fire-control of a battery or district, is called the fire- 
 
26 THE SERVICE OF COAST ARTILLERY 
 
 control installation for that battery or district. Installations are either standard 
 or provisional. 
 
 Fire-control material may be classified under the following heads: 
 
 a. Instruments for the observation and location of targets. 
 
 b. Instruments for the determination of firing data. 
 
 The personnel employed in fire control is called the fire-control personnel. 
 
 Fire-Control Installation. See FIRE CONTROL. 
 
 Fire-Control System. See FIRE CONTROL. 
 
 Fire Left. When marked on the deflection scales of telescopic sights 
 indicates minus deflection (muzzle pointed left). 
 
 Fire Right. When marked on the deflection scales of telescopic sights 
 indicates plus correction (muzzle pointed right). 
 
 Fired Standard Primer. See DRILL PRIMER. 
 
 Fireman. A non-commissioned staff officer charged with such duties as 
 pertain to the care and operation of boilers and accessories, including the police 
 of the boiler and engine room. He may be required to assist the engineer in 
 his work. Insignia: A bar and an arc of one bar of red cloth inclosing a red 
 governor made of yellow cloth. 
 
 Firing Interval. The interval of time between consecutive shots of the 
 same gun or mortar in continuous firing. 
 
 Firing Machine or Electric Firer. See EXPLODER. 
 
 Five-Inch Gun. A rapid-fire gun usually 45 to 50 calibers long and of 
 5-inch caliber. Made by the Ordnance Department. 
 
 Fixed Ammunition. When the cartridge case is attached to the projectile, 
 the two together are called fixed ammunition. It is not used in large calibered 
 guns on account of the disadvantage of handling and the difficulty of arranging 
 and preserving. 
 
 Fixed Armament. Guns and mortars of various sizes and powers, mounted 
 on stationary carriages. 
 
 Fixed Defenses. Defensive works ashore within the line of defense. 
 ' Fixed Mount. A mount or carriage provided for guns and mortars in 
 permanent works and not designed to be moved from place to place. 
 
 Fixed Light. A searchlight intended to demarcate the outer limit of a 
 battle area and illuminate any vessel entering it. 
 
 Flag of Admiral of the Navy. A flag consisting of four white stars, on 
 a blue field of bunting, placed at the corners of an imaginary square, whose 
 diagonals are horizontal and vertical. 
 
 Flag of Artillery District Commander. A flag of scarlet bunting, rectan- 
 gular in shape, 1-foot 6-inch hoist and 2-foot fly for small boats and launches, 
 and 2-foot 3-inch hoist and 3-foot fly for large boats. In the center of both 
 sides, crossed cannon in yellow, with a medallion at their intersection, in scarlet, 
 having an oblong projectile in yellow. The truck of the staff to be a gilt ball. 
 
 Flag of Assistant Secretary of the Navy. The same as that for Secre- 
 tary of the Navy, except the anchor and stars are blue on a white field of bunting. 
 
 Flag of Assistant Secretary of War. The same as that for Secretary of 
 War, except the stars are scarlet on a white field of bunting. 
 
 Flag of Chief of Coast Artillery. A flag of scarlet bunting, rectangular 
 in shape, 3-foot hoist and 4-foot 9-inch fly. The rank to be indicated by a 
 white star (or stars of appropriate number if above the rank of brigadier general) 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 27 
 
 of suitable size placed in the center line of the length of the flag. The truck 
 of the staff to be a gilt ball. 
 
 Flag of Department Commander. Same as that of Chief of Coast Artil- 
 lery, with rank indicated by appropriate number of stars. 
 
 Flag of Post Commander (Coast Artillery). A pennant of bunting, tri- 
 angular in shape, 1-foot hoist and 3-foot fly; the third nearest the staff to be 
 a blue field bearing thirteen stars and the remaining two-thirds to be scarlet. 
 The truck of the staff to be a gilt ball for post commanders above the rank of 
 captain, and for post commanders of a lower grade to be flat. 
 
 Flag of President of the United States. A flag consisting of the official 
 coat of arms of the United States, of suitable size, in the center of a blue field 
 of bunting. 
 
 Flag of Rear Admiral of the Navy. A flag consisting of two stars, on a 
 blue field of bunting, symmetrically placed on a vertical line in the center of 
 the flag. 
 
 Flag of the Secretary of the Navy. A flag consisting of four white stars, 
 on a blue field of bunting, symmetrically placed in the four corners, surrounding 
 a vertical white anchor. 
 
 Flag of the Secretary of War. A flag consisting of four white stars, on a 
 scarlet field of bunting, surrounding the official coat of arms of the United 
 States. 
 
 Flag of the United States. A flag with thirteen horizontal stripes, seven 
 red and six white, the red and white stripes alternating; the union of the flag 
 consists of white stars in a blue field placed in the upper quarter next the staff, 
 and extending to the lower edge of the fourth red stripe from the top, the 
 length of the union being 13/32 of the full length of the flag; the number of 
 stars is the same as the number of States in the Union. 
 
 Flag of Vice Admiral of the Navy. A flag consisting of three stars, on a 
 blue field of bunting, placed at the vertices of an imaginary isosceles triangle, 
 whose base is horizontal. 
 
 Flags. See BATTLE FLAG, COLORS, COLORS OF COAST ARTILLERY CORPS, 
 GARRISON FLAG, POST FLAG, STORM FLAG, SUBMARINE BOAT SIGNAL FLAG. 
 
 Flagship. The vessel which carries the commanding officer of a fleet or 
 squadron. It is distinguished by the flag of the officer in command, flying at 
 the main mast. 
 
 Flanking Fire. Fire directed along the front of or nearly parallel to the 
 enemy's line. 
 
 Floating Defenses. Vessels used for defensive purposes, including monitors, 
 gunboats, scout ships, torpedo boats, submarine boats, patrol and picket boats. 
 
 Foot-Ton. The energy expended or necessary to raise a weight equal to a 
 long ton, or 2,240 pounds, one foot. 
 
 Forcing. As applied to a projectile, forcing is the operation by which a 
 projectile is made to take hold of the grooves of the bore. 
 
 Forcing Cone. The part of the bore of a gun immediately in front of the 
 centering slope. It is formed by cutting away the lands so as to decrease their 
 height uniformly from front to rear. 
 
 Fort Commander. See COAST ARTILLERY FORT. 
 
 Fort Record Book. A permanent confidential record book containing the 
 history of the works, their object, armament, scheme of defense, and all infor- 
 
28 THE SERVICE OF COAST ARTILLERY 
 
 mation of value regarding the equipment and installation. It is supplemented 
 by the Fort Record Book Files, in which copies of all confidential papers and 
 maps are kept. 
 
 Fortified Point. A general term indicating a city, harbor, anchorage, 
 estuary, or any limited portion of the coast line that is defended by fixed 
 defenses. 
 
 Fosse. See DITCH. 
 
 Four-Inch Rapid-Fire Gun. A seacoast cannon, usually 40 calibers long 
 and of 4-inch caliber. 
 
 Friction. A force acting between two bodies at their surface of contact, 
 so as to resist their sliding on each other. Friction is of three kinds; sliding 
 and rolling friction, which act with solids ; and fluid friction, which acts with 
 liquids and gases. 
 
 Friction Primer. See COMMON FRICTION PRIMER. 
 
 From Battery. The position of a gun when withdrawn from its firing 
 position. 
 
 Front Pintle. A term applied to a coast carriage where its axis of rotation 
 is at or near its front end, i.e., where it traverses about a point in front of 
 its center. 
 
 Frontal Fire. Fire which is directed perpendicularly, or nearly so, to the 
 objects fired at. 
 
 Frustum. That part of a solid next to a base formed by cutting oft 7 the top. 
 
 Fulcrum. A means of support for a lever about which it turns in lifting or 
 moving a body. 
 
 Fulminate. A very sensitive explosive compound used in fuses, primers 
 and caps. 
 
 Fuse. A mechanical firing device used for exploding a bursting charge. 
 See chapter on FUSES AND PRIMERS. 
 
 Gabion. A wicker cylinder of strong basket-work open at both ends. Its 
 usual dimensions are 2 feet in diameter and 2| feet in height. They are filled 
 with earth and used for defensive purposes in field fortification. 
 
 Gallery. Any passage covered over head and at the sides. 
 
 Galvanometer. An instrument used for detecting the existence, and de- 
 termining the strength and direction of an electric current. 
 
 Garrison Flag. The national flag, 36 feet fly and 20 feet hoist. Hoisted 
 only on holidays, important occasions and during engagements. In the latter 
 case it is called the battle flag. 
 
 Garrison Gin. A lifting tackle used in mechanical maneuvers of coast 
 artillery armament.' 
 
 Gas Check. The essential mechanical feature of an obturator which enables 
 it to prevent the escape of gas. 
 
 Gas Check Pad. A pad made of asbestos and tallow enclosed in a canvas 
 cover and compressed under heavy pressure. Under the weight of firing the 
 plastic nature of the pad causes it to press outward against the gas check seat 
 and inward against the spindle, forcing the split rings firmly in their seats and 
 completely stopping the passage to the escape of gas. 
 
 Gear Wheel (or Cog Wheel). A wheel with teeth on the circumference to 
 mesh with a rack, worm ring, or another gear wheel. 
 
 General Defense Plan. The scheme of defense formulated prior to an at- 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 29 
 
 tack. A variety of these plans, based on the character of attack to be expected, 
 should be prepared and issued to the command. 
 
 Glacis. In field fortification a mound of earth which inclines from the 
 front of the ditch toward the foreground, thus forcing the assailant to full 
 exposure to the fire from the parapet before reaching the ditch. 
 
 Gravimetric Density. A term which refers to the ratio of the weight of a 
 unit volume of a standard powder to the weight of the same volume of any 
 other powder, i.e., the gravimetric density of a powder is the weight in pounds 
 of a volume of 27.68 cubic inches of the powder not pressed together by its own 
 weight. (27.68 is the number of cubic inches occupied by one pound of water). 
 
 Gravity. That force which tends to draw all bodies toward the earth with 
 uniformly increasing velocity. Its mean value equals 32.16 foot-seconds. An 
 example of gravity may be demonstrated as follows: A projectile thrown 
 from a mortar at, say, an angle of 90 degrees, would travel upward until the 
 propelling force under or behind it ceased to exist, it would then take a down- 
 ward course drawn by gravity and strike the surface at a velocity equal to 
 the original initial velocity which it had on leaving the muzzle. 
 
 Graze. The point at which a projectile strikes a surface and rebounds 
 onward. 
 
 Grooves. In ordnance, the spiral hollow cuts made in the surface of the 
 bore. 
 
 Guard Room. A room in the battery, or guard house, set aside for the use 
 of the guard. 
 
 Gun. A term applied in its most general application to any weapon which 
 throws or propels a missile to a distance ; any firearm or instrument for throwing 
 projectiles by the expanding force of powder gas, consisting of a tube or barrel 
 closed at one end. In a restricted sense, the term is applied to that class of 
 cannon in which the length of bore is great in comparison with the caliber. 
 
 Gunboat. Any boat of light draft carrying one or more guns. They 
 usually resemble cruisers, but are much smaller. Speed less than 14 knots, 
 displacement 2,000 tons or less. Armament, 6-inch, 5-inch, 4-inch and smaller 
 rapid-fire guns. 
 
 Gun Carriage. See CARRIAGE or MOUNT. 
 
 Gun Commander. A specially qualified non-commissioned officer in direct 
 charge of a gun section. When assigned in command of mortar pits they are 
 called pit commanders] to ammunition sections, chiefs of ammunition service. 
 
 Gun Commander's Range Scale. See RANGE SCALE. 
 
 Gun Company. A company assigned to the service of direct-fire guns only. 
 
 Gun Cotton. A detonating and disruptive explosive of high order made 
 of unspun cotton waste, used in shells, torpedoes and for demolitions of all 
 kinds. 
 
 Gun Differences. Differences in range and azimuth to the target from the 
 gun and from the directing point, due to gun displacement. 
 
 Gun Displacement. The horizontal distance in yards from the vertical 
 axis of the directing gun to the pintle center of any other gun of the battery, 
 or from the directing point to the pintle center of any gun of the battery. 
 
 Gun Lift. See CARRIAGE or MOUNT. 
 
 Gun Platform. That part of a battery upon which the gun carriage rests. 
 
 Gun Pointer. A specially qualified member of a gun section charged with 
 
30 THE SERVICE OF COAST ARTILLERY 
 
 the proper aiming or laying of a gun, or the chief of a mortar detachment who 
 supervises the loading and laying of a mortar. Insignia : Red crossed cannon 
 within a yellow circle, all to be of cloth. 
 
 Gun Section. A detail of the enlisted personnel, consisting of a gun com- 
 mander, a gun detachment, ammunition detachment and reserve. There is one 
 gun section for each piece assigned to a battery of the primary armament for 
 service or drill ; for batteries of the secondary armament, the detachment for 
 all of the pieces constitutes one gun section under a single gun commander. 
 
 Gunner. A specially qualified enlisted man who has passed the examination 
 in elementary gunnery. They are classified as first- and second-class gunners. 
 Insignia: First Class. In gun or mortar company; red projectile, with red 
 bar below. In mine company; red mine case, with red bar below. Second 
 Class. Same as first class, omitting the bar. All to be of cloth. 
 
 Gunner's Quadrant. An instrument usually used in laying mortars to give 
 quadrant elevation by either applying it at the breech or muzzle. 
 
 Gunnery. That branch of military science which comprehends the theory 
 of projectiles, and the manner of constructing and using ordinance. See 
 BALLISTICS. 
 
 Gunnery Specialists. Specially qualified enlisted men, such as Master 
 Gunners, Master Electricians, Engineers and Electrician Sergeants who have 
 successfully pursued the course of instruction at the Coast Artillery School. 
 
 Gunpowder. A black or brown granular explosive mixture of low order, 
 made of niter, charcoal and sulphur. 
 
 Hang Fire. A delayed ignition of the powder charge caused either by 
 defective primer or charge. See MISSFIRE. 
 
 Harbor Charts. Charts covering the water area of each fortified harbor 
 within the field of fire of the armament at that point. They are made on a 
 scale of 500 yards to the inch and the area covered is marked off in one -inch 
 squares which are numbered consecutively. The outlines of the harbor, depths 
 of water, channels, locations of batteries and stations are accurately indicated. 
 A chart mounted on a suitable board, with a range-scale arm pivoted at the 
 point indicating the station to which it pertains is furnished each Battle, Fire, 
 Mine and Battery Primary Observing Station. 
 
 High Angle Fire. See FIRE. 
 
 Hoist. See AMMUNITION HOIST. 
 
 Hoist Room. The room in the battery containing the receiving table of 
 the ammunition hoist. 
 
 Homogeneous. Of the same kind or nature ; consisting of similar parts or 
 of elements of like nature. 
 
 Hoops. In ordnance, hoops are cylindrical forgings concentric with the 
 tube of built-up cannon, superimposed upon the tube, jacket" or other hoops. 
 
 The "A" Row are over the jacket, extending from the breech to the trun- 
 nions. 
 
 The " B " Row when used are on " A " Row. 
 
 The "C" Row are all those hoops in contact with the tube in front of the 
 jacket. 
 
 The "D" Row are over the front end of the jacket and the " C " Row in front 
 of the trunnions. 
 
 Horizontal. On a plane parallel to the horizon. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 31 
 
 Horizontal Angle. An angle measured in the horizontal plane, or whose 
 sides lie wholly in such plane. 
 
 Horizontal Base System. The system of range -finding in which the posi- 
 tion and range of the target are definitely located by the use of the primary and 
 secondary arms of the plotting board, from azimuth readings taken simultane- 
 ously at the primary and secondary observing stations. 
 
 Horizontal Plane. That plane which passes through or contains the line 
 of the horizon. The horizontal plane referred to in the artillery position finding 
 service is the horizontal plane containing the water level. 
 
 Horizontal Position Finder. The Azimuth instrument. 
 
 Horizontal Range. The longitudinal distance from the muzzle of the gun 
 to the point of fall measured in the initial plane. It is the range given in all 
 fundamental range tables. 
 
 Horizontal Velocity. The component of the muzzle velocity parallel to the 
 horizontal plane passing through the muzzle of the gun. 
 
 Howitzers. Those cannon whose relative length and caliber range between 
 the gun and mortar classes. They are used principally by the mobile army. 
 
 Hydraulic Jack. A portable machine for exerting great pressure for lifting 
 or moving a heavy body through a small distance by hydraulic power. 
 
 Hygrometer. An instrument for measuring the degree of moisture in the 
 atmosphere. 
 
 Hypothetical Targets. Imaginary targets of assumed dimensions, for 
 heavy guns. This target is outlined by two standard pyramidal targets towed 
 60 feet from center to center with a red streamer suspended from a wire or 
 hemp cord midway between them, the hypothetical target represented being a 
 vertical rectangle 30 by 60 feet. For mortars the hypothetical target is a 
 circle 100 yards in diameter the center of which is indicated by a pyramidal 
 target. 
 
 Identification of Target. The act or process of recognizing a target which 
 has been designated. 
 
 Igniter or Igniter Charge. A small charge of rifle powder placed in con- 
 tact with the propelling charge to insure the ignition of the latter. See PRIMER 
 CHARGE. 
 
 Igniting Primer. Primers used in cartridge cases for subcaliber tubes not 
 provided with percussion firing mechanism. They require for ignition an 
 auxiliary friction or electric primer which is inserted in the vent of the spindle 
 in the same manner as for service firing. 
 
 In Battery. The term used to indicate that a gun is in its proper position 
 for firing. 
 
 In Commission. The term used to indicate those batteries to which per- 
 sonnel is assigned. 
 
 In Service. The term used to indicate those batteries to which personnel 
 is assigned and at which daily drills are held. 
 
 Indication of a Target. Any method employed to designate a target. 
 
 Inflammation. The spread of flame over the surface and into the perfora- 
 tions of powder grains. 
 
 Illuminating Light. A searchlight whose primary function is to follow a 
 target that has been assigned to a fire command. 
 
 Initial Pressure. The first or starting pressure. The term is frequently 
 
32 THE SERVICE OF COAST ARTILLERY 
 
 applied in reference to initial tension, or the stress developed in the body of a 
 built-up gun, by the method of fabrication. Initial tension is produced by 
 shrinking over a tube or hoop a heated hoop that will have a slightly smaller 
 diameter when cooled, each hoop compressing the one beneath it. 
 
 Initial Velocity. The rate of travel at which a projectile leaves the muzzle 
 of a cannon. Generally called muzzle velocity. 
 
 Initial Velocity of Rotation. The rate of motion at which a projectile is 
 traveling around its longer axis at the instant it leaves the muzzle of the gun. 
 
 Initial Velocity of Translation. The rate of motion at which a projectile 
 is traveling in the direction of its flight at the instant it leaves the muzzle of the 
 gun. See MUZZLE VELOCITY. 
 
 Inside of a Beam. A point is so called when it lies between the battle 
 commander's station and a line passing through the axis of a searchlight beam. 
 
 Intelligence Line. A telephone line connecting a primary and secondary 
 station; used for the transmission of general information. The line over which 
 data are sent from the reader at the secondary station to the secondary arm 
 setter at the plotting board in the primary station plotting room is called the 
 data line. 
 
 Interior Crest. The line of intersection of the interior wall or slope with 
 the superior slope. 
 
 Interior Slope or Wall. The inner slope or wall of gun parapets or mortar 
 pits. 
 
 Intermediate Armament. The armament of a coast artillery fort used to 
 attack lightly armored or unarmored vessels; it may be employed effectively 
 to supplement the primary armament in the attack of armored vessels, or the 
 secondary armament in the defense of the mine fields. It includes the 6-inch, 
 5-inch and 4.72-inch guns. 
 
 Jacket. A cylindrical forging, concentric with and shrunk on the tube; 
 it generally extends from the breech of the gun to a plane beyond the trunnions. 
 
 Judgment Firing. See OBSERVATION FIRING. 
 
 Jump, Angle of. The angle included between the line of departure and the, 
 axis of the bore when the piece is pointed. Experience has shown that the 
 actual range for a given elevation does not correspond to the computed range. 
 For convenience it is assumed that the entire discrepancy is due to an increase 
 or decrease of the elevation of the gun at the instant the projectile leaves the 
 muzzle, and this small difference in angle is called the jump. Therefore in 
 determining the sight or quadrant elevation to be used to obtain a given range, 
 a correction, which differs for different guns, carriages and ranges, must be 
 applied to the angle of departure given in the range table. It may be deter- 
 mined by experiment. In practice it is included in the necessary range cor- 
 rections as determined by trial shots. 
 
 Junction Box. A device used in splicing cable, its object being to protect 
 the joint and cause the strain to come upon the armor of the cable rather than 
 on the joint itself. 
 
 The Single function box, small, consists of two rectangular plates of cast 
 iron ^-inch in thickness, 20 inches long and 6 inches wide, united by four ^-inch 
 bolts at the corners (the bolts having square shanks and hexagonal nuts to 
 facilitate clamping) ; the plates are hollowed in the middle to form a chamber 
 which receives the turks' heads and joint. The ends of the plates are curved 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 33 
 
 to admit the cable ends, and the turks' heads are clamped to the lower plate 
 by straps and screw bolts, the cavity of the upper plate covering them when 
 bolted in position. This type of box is used in splicing single conductor cable. 
 
 The Single junction box, large, is similar in construction and is used in 
 splicing multiple cables or cables of more than one core. 
 
 The Grand junction box, or junction box used as a distribution box when 7 
 conductor multiple cable is used, consists of two circular plates of cast iron, 
 f-inch in thickness and 21 inches in diameter, united by four 1-inch bolts at 
 tne corners. The joints and 7 conductors and multiple cable are clamped in 
 the box in a similar manner to thai described for the single junction boxes. 
 
 Kentledge. Old cast iron articles which have become unserviceable, such 
 as condemned guns, shot and shell, etc. 
 
 Laflin & Rand Firing Machine, or Electric Firer. See EXPLODER. 
 
 Land Front. Those portions of the defenses which are provided to repel 
 an attack from the land area in rear of or on the flank of permanent seacoast 
 works. 
 
 Lands. In ordnance, the surfaces or ribs of the bore between two adjacent 
 grooves of the rifling. 
 
 Lanyard. A strong cord to one end of which a brass hook is attached. 
 Used for exploding the friction primer when the piece is to be fired. See SAFETY 
 LANYARD. 
 
 Large Caliber Guns. The class of guns included in the primary armament. 
 
 Lateral. Of or pertaining to the sides. 
 
 Latrine. A closet for soldiers in camps or barracks. 
 
 Laying. The operation of giving a gun the direction and elevation neces- 
 sary to hit the target without the use of a sight. 
 
 Least Dimension. A term used in connection with powder grains. The 
 least dimension of a grain of powder is the dimension measured between the 
 perforations of a multi-perforated grain over or through which the fire spreads 
 in order to consume the entire grain. See CRITICAL DIMENSION. 
 
 Le Boulenge Chronograph. See CHRONOGRAPH. 
 
 Length of the Bore. The distance from the front face of the breechblock 
 when seated, to the face of the muzzle. 
 
 Limited Fire. Fire delivered through a restricted circumference of an 
 azimuth circle. 
 
 Limits of Fire. The terminating azimuths of the field of fire of a battery, 
 
 Line. A line is that which has length, but not breadth nor thickness. A 
 curve or curved line is a line having no finite portion of a straight line. 
 
 Line of Collimation. The line in which the optical axis of the telescope 
 should be when properly adjusted. The line of collimation and the line repre- 
 senting the axis of the telescope, when in proper adjustment, coincide. 
 
 Line of Defense. In coast artillery, the coast line; it consists of fortified 
 and unfortified portions. The fortified portions are those which include im- 
 portant harbors, cities, roadsteads, estuaries and approaches thereto. The 
 unfortified portions are those lying between or adjacent to the fortified portions. 
 
 Lines of defense for both the coast guard and coast artillery supports are 
 determined upon and planned in detail in time of peace for each fortification; 
 the works necessary for each line are surveyed and mapped out in detail. 
 
 Line of Departure. A line representing the prolongation of the axis of the 
 
34 . THE SERVICE OF COAST ARTILLERY 
 
 gun at the instant the projectile leaves the bore ; it is therefore tangent to the 
 trajectory at the muzzle. It is sometimes called the line of fire. 
 
 Line of Direction. A line in the vertical plane from the gun to the 
 center of the target at the instant the shot strikes. 
 
 Line of Impact. The line tangent to the trajectory at the point of impact. 
 
 Line of Shot. The line from the gun to the point of impact. 
 
 Line of Sight. A straight line passing through the sights of the piece; 
 at the instant of firing this line passes through the target. 
 
 Litmus. A dye stuff extracted from certain lichens as a blue amorphous 
 mass which consists of a compound of the alkaline carbonates, with certain 
 coloring matters relating to orcin and orcein. When litmus is used as a dye 
 it is turned red by acids and restored to its blue color by alkalies (common 
 salt is a good one). 
 
 Litmus Paper. Paper saturated with blue or red litmus, used in testing 
 for acids or alkalies. It is essential to the service in that it is used for testing 
 powder and explosives to determine whether or not they are deteriorating in 
 storage ; which fact is indicated when the blue litmus paper is turned red in the 
 presence of acid fumes which are given off to a greater or less extent when a 
 powder or explosive is deteriorating. The amount of deterioration is indicated 
 by the length of the time required for the paper to change color. 
 
 Loading Platform. That surface upon which the cannoneers stand while 
 loading the piece. 
 
 Loading Position. At gun batteries; breech closed, cannoneers at posts 
 for inspection, projectile and powder charges on truck near the delivery table. 
 
 At mortar batteries; mortars horizontal, breech closed, cannoneers except 
 No. 6, at post of inspection, projectiles on trucks about ten feet in rear of 
 mortars, powder at entrance to pit, No. 6 is at the entrance to the powder 
 magazine. 
 
 Loading Room. A room suitably equipped for the loading of submarine 
 mines. 
 
 Loading Tray. A device used to protect the breech while loading. 
 
 Location of a Target. The determination of its range and azimuth from 
 a given point. See RELOCATION OF A TARGET. 
 
 Longitudinal. Extending in length; running lengthwise. The longi- 
 tudinal extent of a gun would be its length from breech to muzzle. 
 
 Long Roll. A drum alarm signal, when, if practicable, each man goes 
 direct to his post at a run. 
 
 Lug. A projecting piece to which anything is attached, or against which 
 anything bears, or through which a bolt passes. 
 
 Lyddite. A high explosive of British manufacture. 
 
 Machine and Rapid-Fire Gun Mounts. Guns of this class used in coast 
 defense are mounted on moving or traveling carriages, and fixed mounts, called 
 rapid-fire mounts, which are disappearing or non-disappearing, recoil or non- 
 recoil. 
 
 Machine Guns. Guns of one or more barrels using fixed ammunition and 
 provided with mechanism for continuous loading and firing. The mechanism 
 may be operated by man power or by the force of recoil. They are designed 
 to deliver a strong, rapid, continuous and accurate fire of small projectiles. 
 See AUTOMATIC MACHINE GUNS and SEMI-AUTOMATIC MACHINE GUNS. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 35 
 
 Magazine. In a literal sense any place where stores are kept; as a military 
 expression a magazine signifies rooms and galleries for the storage of powder, 
 primers, fuses, etc. Magazines are classified as peace magazines and storage 
 magazines. 
 
 Main Bore. That part of the bore in front of the forcing cone. 
 
 Maneuvering Rings. Large cast iron rings fastened in the walls of em- 
 placements, designed for holdfasts in mechanical maneuvers. 
 
 Manning Party. The personnel assigned to the service of any specific 
 element of the defense. 
 
 Manning Table. A list of the names of those who constitute a manning 
 party, with the particular post to which each is assigned. 
 
 Mark One. A term used to indicate the first improvement of the original 
 model of a particular type of gun, mortar, etc. 
 
 Marine Obstructions. Sunken hulks, subwater piles, dams, booms, barri- 
 cades, rope entanglements and any other form of barrier that may delay the 
 enemy in navigating a defended water area. 
 
 Masking Mount. See CARRIAGE or MOUNT. 
 
 Master Electrician. A non-commissioned staff officer charged with the 
 general supervision of the electrical and power installations of an artillery 
 district or post. He assists the artillery engineer in his work and is required to 
 make inspections and tests of electrical plants and installations, and perform 
 such other technical duties as may be necessary. Insignia : Gold wreath with 
 red forked lightning within and a small white star about one-half of an inch 
 above the red lightning, all to be of silk embroidery thread. 
 
 Master Gunner. A non-commissioned staff officer employed in photo- 
 graphic work and seacoast engineering, in the preparation of tables, charts 
 and maps, and for such other technical artillery duties as he may be qualified 
 to perform. Insignia: Gold wreath, inclosing a red projectile and a small 
 white star about one-half of an inch above the projectile, all to be of silk em- 
 broidery thread. 
 
 Material Target. A target used for all subcaliber practice with guns. 
 When used as a fixed target it is moored fore and aft, as nearly broadside to 
 the battery firing as possible. For battle, fire and mine command practice 
 two or more targets are used on the same towline, separated by about 100 yards. 
 For record subcaliber practice at moving targets it is towed at the end of a 300- 
 yard towline. The standard material target for use as stated above consists 
 of a buoyant base upon which is mounted a vertical rectangular frame 10x24 
 feet, covered to within 2 feet of the bottom with white cotton cloth divided 
 into three panels, the middle panel being painted black. The base consists 
 of two parallel flotation sills each of a 10x10 inch timber, surmounted by a 
 3x10 inch plank nailed thereto; three cross-pieces, a prow and four diagonal 
 braces, the whole being fastened with a bridle for towing. 
 
 All record firing for rapid fire guns below 4.7-inch caliber is made with the 
 above size of target. For guns above 4-inch the standard material target 
 30 feet high by 60 feet long is used. See PYRAMIDAL TARGET, HYPO- 
 THETICAL TARGET. 
 
 Maul. A heavy wooden beater or hammer, used in driving stakes, tent 
 pegs, etc. Usually miscalled mallet by inexperienced soldiers. 
 
 Maximite. A high explosive shell filler. It is fusible and very suitable for 
 
36 THE SERVICE OF COAST ARTILLERY 
 
 armor piercing shell, which are charged by melting the maximite and pouring 
 it in. 
 
 Maximum. The greatest value of a variable quantity or magnitude, in 
 opposition to minimum, the least. 
 
 Maximum Ordinate. The vertical distance between the line of sight and 
 the summit of the trajectory. 
 
 Maximum Pressure. The greatest pressure in the bore of a firearm. The 
 pressure indicated by the pressure gauge. 
 
 Maximum Range. The greatest range obtainable by using the maximum 
 elevation permitted by the carriage. 
 
 Mean Lateral Deviation. The arithmetical mean of the lateral deviations 
 of the points of impact of a series of shots, from the center of the target. 
 
 Mean Longitudinal Deviation. The arithmetical mean of the longitudinal 
 deviations of all the points of impact of a series of shots, from the center of the 
 target. For example, if six shots were fired and struck as follows: No. 1 
 50 yards over. No. 2 10 yards short. No. 3 10 yards over. No. 4 30 
 yards over. No. 5 2 yards over. No. 6 12 yards short. The mean longi- 
 tudinal deviation would be 114^-6 = 19 yards. 
 
 Measure of Uniformity. The regularity in the velocity given by a number 
 of consecutive shots. It is calculated by taking the mean observed velocity, 
 and from it deducting the difference in velocity of each shot, and dividing the 
 sum of the differences by the number of shots fired. 
 
 Mechanic. A specially qualified artilleryman holding the grade of that 
 name in a coast artillery company. Insignia: Two crossed hammers of red 
 cloth. 
 
 Mechanics. The science which treats of the nature of forces and of their 
 actions on bodies, either directly or by the agency of machinery. 
 
 Medium-Caliber Guns. Guns of 4-inch, 4-7-inch, 5-inch and 6-inch 
 caliber. 
 
 Melinite. A high explosive compound of foreign manufacture 
 
 Melting and Thawing Explosives. The explosive shell filler maximite is 
 melted by placing it in a copper watertight vessel and immersing it in a boiling 
 water bath, the temperature being kept practically at 212 degrees F. Dyna- 
 mite is thawed by putting the cartridges or sticks of frozen dynamite in a water- 
 tight vessel and immersing it in warm water. If sufficient time is available 
 a better method would be to leave the boxes open for several hours in a warm 
 room or by taking the cartridges out of the boxes and laying them on a shelf 
 in a room at which the temperature is about 70 degrees F., and thus allow the 
 cartridges to thaw out gradually. 
 
 Mensuration. The act or process of measuring. That branch of applied 
 geometry which gives rules for finding the length of lines, the areas of surfaces, 
 etc., from certain simple data of lines and angles. 
 
 Mercurial Barometer. An instrument used in the meteorological station 
 to determine the pressure or density of the atmosphere. 
 
 Meteorological Message. The message sent to fire commanders by a 
 meteorological observer. It includes the barometer and thermometer readings, 
 the atmosphere reference numbers and the velocity and azimuth of the wind. 
 
 Meteorological Observer. An enlisted man in charge of the meteorological 
 station. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 37 
 
 Meteorological Station. A station containing instruments for obtaining 
 and sending out to the various primary stations data relating to the density 
 of the atmosphere and the velocity and direction of the wind. 
 
 Micrometer. An instrument, used with a telescope, for measuring minute 
 distances or apparent diameters of objects which subtend minute angles. The 
 measurement given directly is that of the image of the object formed at the 
 focus of the object glass. 
 
 Micrometer Caliper or Gauge. A caliper or gauge with a micrometer 
 screw for measuring dimensions with great accuracy. 
 
 Military Crest. The military crest is that part of a hill or mountain, from 
 which all or a greater part of the downward slope within range can be seen 
 and subjected to direct fire. It generally differs from the actual or topo- 
 graphical crest, which is at the highest point or watershed. 
 
 Mine. See SUBMARINE MINE. 
 
 Mine Command. Such portions of submarine defenses and rapid-fire guns 
 for the protection thereof as may be efficiently controlled by one man. 
 
 A mine command consists normally of one or more rapid-fire batteries, with 
 the necessary elements for a complete mine system, including proper installation, 
 control and repair of the mine fields. There may be more than one mine com- 
 mand in a battle area, depending upon the size of the harbor and the mine 
 defenses necessary for the protection thereof. 
 
 Mine Commander. A coast artillery officer assigned as such in orders from 
 district headquarters. He exercises both administrative and tactical command 
 of a mine command. 
 
 As an administrative officer it is his duty to have his command supplied 
 with all material necessary for carrying out the improved scheme of submarine 
 defense. In this he is assisted by a property officer, who is responsible to the 
 mine commander for the material and equipment of the command. 
 
 Tactically the mine commander is responsible to his battle commander for 
 the condition of the submarine defense material of his command and the effi- 
 cient service thereof at drill or in action. 
 
 He is responsible for the instruction of the officers and men of his command 
 in all matters pertaining to the care and use of the mine defense material and 
 rapid-fire guns assigned to his command. 
 
 In battle -command drill and in action he undertakes to destroy such vessels 
 crossing the mine field as the battle commander may direct. When ordered 
 to exercise independent fire action he fires the mines in accordance with his 
 own judgment. He exercises the same command over rapid-fire batteries 
 assigned to the mine command, as is the case in fire commands. 
 
 He has control over and is responsible under the battle commander, for, 
 the use of the mine field searchlights. 
 
 Mine Company. A company assigned to the service of submarine mines. 
 
 Mine Field. The area of water in which submarine mines are planted. 
 
 Mine-Field Lights. Searchlights that may be used for searching when 
 no attack on the mine field is anticipated, and to illuminate the channel for the 
 purpose of aiding the entrance of friendly vessels. During an attack on the 
 mine field their function is to deceive the enemy by searching over an area 
 outside the field. The mine field should not be illuminated until the enemy's 
 boats approach one of the fields. 
 
38 THE SERVICE OF COAST ARTILLERY 
 
 Mine-Field Officer. A coast artillery officer in charge of laying and main- 
 taining the mine field. 
 
 He is responsible that the planting and loading sections perform their duties 
 correctly and that proper material is used in the assembling and planting of 
 mines ; that all precautions for safety are taken in loading, planting and taking 
 up of mines. 
 
 Mine Planter. A seagoing tug 150 feet in length and about 30 feet beam. 
 It has large deck space forward and little rigging. It is equipped with booms, 
 winches, davits, catheads, triplex blocks, etc., necessary in handling and plant- 
 ing assembled mines. 
 
 Mining Casemate. A protected building containing the controlling mech- 
 anism of the mine defense. 
 
 Minus Correction. When conditions require the use of a range less than 
 the actual range it is termed minus correction. 
 
 Minus Deflection. A piece is said to have minus deflection when its axis 
 points to the left of the target. 
 
 Misfire. The failure of a powder charge to explode. In case of a misfire 
 in artillery practice the breech will not under any circumstances be opened for 
 ten minutes, nor until the primer has been removed, except when the primer 
 is seated in the cartridge case. 
 
 Miter Wheel. See BEVEL WHEEL. 
 
 Moat. See DITCH. 
 
 Mobile Torpedo. Ordinarily a cigar-shaped metal case containing an 
 explosive charge and firing device; intended to run under the surface of the 
 water and attack the hull of an enemy's vessel. There are two classes, dirigible 
 and automatic. The former is controlled by electrical or other cables; the 
 latter carry their own propelling agent and keep a given direction automatically. 
 The latest type of automobile torpedo, known as the Whitehead torpedo, is now 
 used almost exclusively. This torpedo is made of steel or phosphor-bronze, 
 about 15 feet long and 19 inches in diameter, divided into compartments and 
 carrying a large explosive charge forward which is fused and explodes on impact. 
 Their functions in coast defense are as adjuncts to fixed mines, to cover waters 
 of channels too deep or too swift to mine. They are usually fired from above 
 water from launching tubes located ashore. 
 
 Monitors. Armored vessels with very low freeboard and 10-inch and 
 12-inch gun turrets, one fore and one aft, of 11-inch armor. Average dis- 
 placement 3,000 to 4,000 tons ; length 250 feet ; beam 50 to 60 feet. Armament 
 usually consists of 10-inch and 12-inch guns and light rapid-fire guns on upper 
 decks. The principal functions of monitors are to supplement the regular 
 fortifications of coast defense. 
 
 Mortar. A cannon employed to throw projectiles at high angles of eleva- 
 tion. Their length of bore is small in comparison with the caliber. 
 
 Mortar Battery. The entire structure erected for the emplacement, pro- 
 tection and service of one or more pits of mortars. 
 
 Mortar Company. A company assigned to the service of mortars. 
 
 Mortar Pit. See PIT. 
 
 Mount. See CARRIAGE or MOUNT. 
 
 Mounting Cannon. The mechanical maneuvers necessary to place coast 
 cannon in position. 
 
 
DEFINITIONS, ABBREVIATIONS AM) SIGNS 39 
 
 Movable Armament. Small caliber guns on wheeled mounts, such as the 
 Colt automatic and Gatling machine gun. 
 
 Movable Carriage or Wheeled Mount. A carriage or mount provided with 
 wheels for ready transportation of the piece mounted thereon. 
 
 Mushroom Head. The front face of the obturator. 
 
 Muzzle. The front end of a cannon, including the mouth of the bore, the 
 face and the swell. 
 
 Muzzle Velocity. The rate of travel at which a projectile leaves the muzzle 
 of a cannon. It is sometimes called initial velocity. 
 
 Nitro-Cellulose Powder. The name applied to a form of smokeless powder 
 used in modern ordnance, in which cellulose (unspun cotton waste) is the base. 
 
 Nitro-Glycerine Powder. The name applied to a form of smokeless powder 
 used in modern ordnance, in which nitro -glycerine is the base. 
 
 Non-commissioned Staff Officers. The Coast Artillery Corps non-commis- 
 sioned staff officers consist of sergeants major, senior grade; master electri- 
 cians, engineers, electrician sergeants, first class; electrician sergeants, second 
 class; master gunners, sergeants major, junior grade, and firemen. They are 
 appointed after due examination, and receive warrants signed by the Chief of 
 Coast Artillery. 
 
 Nose. A name sometimes given to the point of projectiles. 
 
 Object Glass. The glass in a telescope which is placed at the end of the 
 tube nearest the object. 
 
 Oblique Fire. Fire which is directed obliquely to the object fired at. 
 
 Observation Firing. A term applied to one of the three methods of ex- 
 ploding submarine mines, i.e., where the time of firing is given from the mine 
 commanders' station. 
 
 Observation Telescope. A telescope used in target practice and in action 
 to observe the striking point of shots. 
 
 Observer. A member of the fire-control section who is in charge of and 
 uses an observing instrument. Insignia: First Class. Red triangle with a 
 red bar below within a yellow circle. Second Class. Same as first class, 
 omitting the bar. All to be of cloth. 
 
 Observing Interval. The time in seconds between two consecutive obser- 
 vations on a target (between two signals of the time interval bell) during track- 
 ing. The regular interval for guns is 15 seconds, and for mortars 30 seconds. 
 
 Observing Room. The room of a primary station in which the position - 
 finding instrument and necessary accessories are located. 
 
 Observing Station. A position constructed in a favorable place for observ- 
 ing the field of fire. A protected position constructed in a parapet or traverse 
 for the purpose of observation, commonly called " Crow's Nest." 
 
 Obturating Primer. A primer of any type so constructed as to prevent the 
 escape of powder gas through the vent. 
 
 Obturator. In gunnery, any device for preventing the escape of gas; the 
 term includes the entire mechanism. 
 
 Obturator Head. The mushroom head of the breechblock. 
 
 Occult Light. The act of screening or shutting off the beam of a search- 
 light. 
 
 Offensive Return. An offensive return, during an engagement of mobile 
 troops, consists in the assumption of the offensive by the defender with the pur- 
 
40 THE SERVICE OF COAST ARTILLERY 
 
 pose of recovering ground just captured by the enemy, and of returning to the 
 original position. 
 
 Ogive. That curve of the head of a projectile which terminates at the 
 point. 
 
 Oil Room. A room in the emplacement for the storage of oil. 
 
 Oils. The principal oils used in the coast artillery service are : Hydroline, 
 for filling recoil cylinders. Synovial, for lubricating the breech recess and 
 breechlock of cannon, and general lubrication of the carriage. Light Slushing, 
 for slushing the bore of cannon and all exposed surfaces of the carriage. Lubri- 
 cant No. 4^, for filling grease cups. Linseed (boiled), for use on retraction 
 ropes, mixing paints, etc. Kerosene, for cleaning purposes. 
 
 Omniscope. An apparatus used in the Lake type of submarine boats for 
 observation, sighting and steering. 
 
 One-Pounder. A rapid-fire gun whose projectile weighs one pound. The 
 caliber 1.457-inch pompom, Vickers-Maxim gun is an example of this type. 
 
 Open Sight. See SIGHT. 
 
 Opposite Angles. When two lines meet and cross each other four angles 
 are formed, and the opposite angles are equal to each other. 
 
 Orders of Fire. 1. Unrestricted Fire. When the only limitation imposed 
 by the fire commander upon the action of a battery is the assignment of a target, 
 the fire is said to be unrestricted. This is the normal fire action of a battery. 
 
 2. Restricted Fire. When the range at which to fire, the number of shots, 
 the firing interval, or any other limitation except as to target, is imposed upon 
 the action of a battery, the fire is said to be restricted. 
 
 In unrestricted fire, and also in restricted fire when the rate is not specified, 
 the fire should be as rapid as possible. 
 
 Ordnance. The term applied to artillery armament and the accessories and 
 stores pertaining thereto. 
 
 Ordnance Machinist. A civilian expert ordnance machinist, resident at 
 each coast artillery fort. 
 
 Ordnance Officer. See ARTILLERY DISTRICT ORDNANCE OFFICER, POST 
 ORDNANCE OFFICER. 
 
 Ordnance Sergeant. A non-commissioned staff officer charged with the care 
 and preservation of all ordnance property at a coast artillery fort. Chevrons 
 and Insignia: Three bars inclosing a shell and a flame. All to be of black 
 cloth piped with red. 
 
 Orientation. The process of adjusting an instrument, gun or mortar in 
 azimuth. 
 
 Orientation Table. A table showing the azimuths and distances of various 
 points in a harbor. 
 
 Out of Commission. A term applied to armament and fire-control stations 
 that are not in such condition that they could be made ready for service in 
 24 hours. 
 
 Out of Service. A term applied to armament and fire-control stations to 
 which no manning party is assigned but which could be made ready for service 
 in 24 hours. 
 
 Outposts. Detachments thrown out from a force for the purpose of pro- 
 tecting it from surprise. 
 
 Outside of a Beam. A point is said to be outside of a searchlight beam 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 41 
 
 when it lies on the outer side of a line passing through the axis of the beam as 
 seen from the battle commander's station. 
 
 Paints on Projectiles. Projectiles are painted so as to show the material 
 used in their manufacture, their armor-piercing qualities, their center of gravity 
 and their character. 
 
 Pantograph. A device used on the plotting board of a fire-command sta- 
 tion, to relocate for data for use at any battery in that command. 
 
 Parade Slope or Wall. The rear slope or wall of an emplacement. 
 
 Parados. Earthworks in rear of a battery for protection against fire from 
 the rear. It may have interior, superior, exterior and traverse slopes. 
 
 Parallax. An apparent displacement of an object observed through a 
 telescope, due to the real displacement of the observer, so that the direction 
 of the object with reference to the observer is changed. 
 
 In optics, parallax is an apparent displacement of the image upon the cross- 
 wires in a telescope when the eye is moved across the eye-piece. It is due to the 
 non-coincidence of the cross-wires with the focal plane of the objective. Both 
 the image, as formed by the objective, and the cross wires, should lie in the 
 focus of the eye-piece, i.e., in the same plane. 
 
 The image may be moved back and forth by moving the objective in or out, 
 but the plane of the cross wires is fixed. When the two are brought into the 
 same plane the image is brought upon the cross- wires. To accomplish this the eye- 
 piece should first be focused on the cross-wires so that they appear most distinct, 
 the irregularities of the wires being very apparent. There should be no image 
 visible during this operation, that is, the objective should either be thrown out 
 of focus by turning the focusing knob either all the way out or in; or the tele- 
 scope should be pointed to the sky. The eye-piece should then be moved until 
 the inner and outer limits of distinct vision of the wires are found, and then set 
 at the mean position. The telescope should then be pointed toward the object 
 and moved until the image also comes into focus accurately. If parallax is 
 now found it should be removed by refocusing. 
 
 The adjustment of the eye-piece will be correct for the same observer re- 
 gardless of the range and object sighted upon, but it may be necessary to refocus 
 the objective when the range differs materially. 
 
 Parallel. Parallel planes and lines are the same distance apart at all points; 
 if prolonged they will never meet. 
 
 Parapet. That part of a battery, composed of earth, timber, stone, metal, 
 etc., which give protection to the armament and personnel from front fire. 
 
 Patrol Boats. Boats of the torpedo-boat destroyer type. During fog or 
 thick weather they are necessary to guard the mine fields and such independent 
 mine groups as are not covered by the shore defenses; also, at night, they 
 patrol the approaches within the battle area with the object of preventing the 
 small craft of the enemy from stealing into the inner waters, under cover of 
 darkness of the land shadows. In case searchlights are occulted or fail, the 
 boat patrol is the only means available to discover any movement of the enemy 
 and give the alarm. 
 
 Pawl. A pivoted tongue, sliding bolt or catch, adapted to fall into notches 
 or indental spaces in such a manner as to permit motion in one direction and 
 prevent it in the reverse, as in a windlass. 
 
 Penetration of Projectiles. The ability of a projectile to overcome the 
 
42 THE SERVICE OF COAST ARTILLERY 
 
 resisting qualities of an armor plate by completely or partially perforating it. 
 The ability to perform this function depends on the relative merits of the 
 particular projectile, the plate against which it is fired, the striking velocity 
 and the angle of impact. 
 
 Percussion Cap. A cap in which the method of explosion is due to a blow; 
 used in fixed ammunition. 
 
 Percussion Fuse. A fuse which is armed or prepared for action by the 
 shock of discharge and acts upon impact. 
 
 Percussion Primer. The type of primer used in fixed ammunition which 
 is exploded by a blow of the firing pin. 
 
 Periscope. An apparatus used on the Holland type of submarine boat, for 
 observation, sighting and steering. 
 
 Perpendicular. Exactly upright or vertical ; at right angles with the plane 
 of the horizon. When two lines so intersect each other as to form four equal 
 angles they are said to be perpendicular to each other. 
 
 Personnel. The personal composition of any organized group of officers 
 or men which has for its purpose the accomplishment of some service. 
 
 Picket Boats. Any speedy boat or boats stationed outside the battle area 
 to watch for the enemy and give warning of his approach. 
 
 Picric Acid. A detonating and disruptive explosive of high order used as 
 a base for explosives or shell fillers. 
 
 Piece. The name applied to any type of cannon, whether gun or mortar. 
 It is also used as a matter of convenience to designate both cannon and carriage 
 when the cannon is mounted. 
 
 Pit. That part of a mortar emplacement designed for mounting one or 
 more mortars, usually four. 
 
 Pit Commander. A non-commissioned officer (gun commander) in charge 
 of a mortar pit. 
 
 Plane. A surface without curvature which has length and breadth but no 
 thickness; a surface real or imaginary, in which, if any two points are taken, 
 the straight line which joins them lies wholly in the surface. 
 
 Plane of Departure The vertical plane containing the line of departure. 
 
 Plane of Direction. The vertical plane containing the line of direc- 
 tion. 
 
 Plane of Sight. The vertical plane containing the line of sight. 
 
 Planter. See MINE PLANTER. 
 
 Planting Section. A section of the enlisted personnel of a mine company, 
 consisting of men required afloat. It is divided into a planter detachment and 
 the small boat detachments. 
 
 Plotter. A specially qualified enlisted man in charge of the plotting board 
 at a fire-control station. Insignia: Red triangle with a red bar below within 
 a yellow circle, all to be of cloth. 
 
 Plotting Board. A device used in the position-finding service to quickly 
 plot to scale the data sent from the position-finding instruments, and in con- 
 nection with range and deflection boards, to determine the corrected data for 
 firing. It consists essentially of a semi-circular drawing board with a radius 
 of 45 inches, made of well-seasoned lumber. It has mounted upon it the neces- 
 sary scale arms and gun center to determine the rate of travel of the 
 target both in range and azimuth for use on the range and deflection boards. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 43 
 
 By means of the gun arm the range and azimuth to the target from the directing 
 point of the battery is found. 
 
 Plotting Room. The room in which the plotting detachment works. It is 
 usually located below and communicates with, the instrument room of the 
 battery commander's station, or with the observing room of the primary 
 station. 
 
 Plunging Fire. Fire in which the line of departure passes below the hori- 
 zontal plane. 
 
 Plus Correction. When conditions require the use of a range greater than 
 the actual range the correction is called plus correction. 
 
 Plus Deflection. A piece is said to have plus deflection when its axis points 
 to the right of the target. 
 
 Point. That which has neither length, breadth, nor thickness only posi- 
 tion, In communicating numerals a word used as a mark of division, i.e., a 
 period. For example, 106.20 would be expressed: "One-zero-six-point-two- 
 zero." 
 
 Point Fuse. A firing device inserted in the point of a shell not intended to 
 penetrate; as shrapnel. 
 
 Point of Fall. The point of intersection of the trajectory where it crosses 
 the horizontal plane passing through the muzzle of the gun. See THEORETICAL 
 RANGE 
 
 Point of Impact. The point where the projectile first strikes on meeting 
 an opposing body, 
 
 Pointing. The operation of giving a piece the direction and elevation neces- 
 sary to hit the target. When the sight is used it is called "aiming"; when 
 the sight is not used, it is called "laying." 
 
 Position Angle. See ANGULAR ELEVATION. 
 
 Position Finder. An instrument for locating a target. See AZIMUTH 
 INSTRUMENT, DEPRESSION POSITION FINDER, HORIZONTAL POSITION FINDER, 
 and SELF-CONTAINED POSITION FINDER. 
 
 Position-Finding System. The system of position finding includes: 
 
 1. The horizontal base system, which employs azimuth reading instruments 
 in stations at the ends of a base line, and a plotting board. 
 
 2. The depression -position finding system, which employs a depression -posi- 
 tion finder at a considerable elevation above the sea level, and a plotting board. 
 
 3. The emergency system, which ordinarily employs a self-contained instru- 
 ment located at the battery, with or without a plotting board. 
 
 Post Adjutant. A coast artillery officer responsible, under the post com- 
 mander, for the various reports, returns, rosters, details, records, orders and 
 communications pertaining to the administration of a post. It is his duty to 
 sustain the reputation, discipline and harmony of the command under all circum- 
 stances. He is assisted by a sergeant major and as many clerks as may be 
 required. His tactical duties are those prescribed for regimental or battalion 
 adjutants of infantry and, unless otherwise assigned, communicating officer of a 
 fire command. 
 
 Post Artillery Engineer. A coast artillery officer holding all engineer and 
 signal property at a post on memorandum receipt to the district artillery 
 engineer, and, except when it is so held by the commanding officer of a com- 
 pany or detachment assigned to the mine defense, he holds mine property in 
 
44 THE SERVICE OF COAST ARTILLERY 
 
 the same manner. He is responsible to the post commander for the care, 
 preservation and efficiency of all engineer and signal property under his control. 
 He is charged with the supervision, test and maintenance of the electrical and 
 lighting plants, also searchlights and lines of electrical communication. He is 
 assisted by master electricians, engineers, electrician sergeants, firemen and 
 such additional enlisted men as may be necessary. His tactical duties are 
 those of searchlight officer unless otherwise assigned. 
 
 Post Commander. The senior coast artillery officer assigned to dutv at an 
 artillery post. He has control, within the limits of the post and subject to 
 higher authority, of all matters relating to coast artillery, its personnel and 
 material. He appoints the post staff officers on duty at the post, corresponding 
 to those of an artillery district, unless the headquarters of an artillery district 
 is stationed at the post, in which event the artillery district staff officers serve 
 as the corresponding post staff officers. 
 
 Post Commander's Flag. See FLAG OF POST COMMANDER. 
 
 Post Commissary Sergeant. A post non-commissioned staff officer in im- 
 mediate charge of all commissary stores and property at a post. Chevrons and 
 insignia: Three bars and a crescent (points to the front), all to be of cadet 
 gray cloth. 
 
 Post Flag. The national flag, 20-foot fly and 10-foot hoist. Hoisted daily 
 in pleasant weather. 
 
 Post Non-commissioned Staff. Ordnance sergeants, post commissary ser- 
 geants, and post quartermaster sergeants. 
 
 Post Ordnance Officer. A coast artillery officer charged with the care of 
 all ordnance property not charged to battery commanders. He holds all ord- 
 nance property and stores pertaining to the modern seacoast armament at the 
 post on memorandum receipt from the artillery district ordnance officer. He 
 is responsible that batteries out of service are kept in such condition that they 
 can be prepared for service upon not more than 24 hours' notice. He is assisted 
 by the post ordnance sergeants and necessary assistants. His tactical duties 
 are those of a company officer unless otherwise assigned. 
 
 Post Quartermaster. An officer charged with the care and supervision of 
 all quartermaster property at a post, as well as the receipt and issue of all 
 quartermaster stores, etc. His tactical duties, if a coast artillery officer, are 
 those of company officer unless otherwise assigned. 
 
 Post Quartermaster Sergeant. A post non-commissioned staff officer in im- 
 mediate charge of all quartermaster property at a post. Chevrons and Insignia: 
 Three bars of buff cloth and insignia of Quartermaster Department. 
 
 Post Telephone Switchboard. A central telephone station. 
 
 Powder. See GUNPOWDER. 
 
 Powder Blast. The force of the powder gas for a short distance in front 
 of the muzzle, which acts destructively on objects close at hand lying within 
 its path. 
 
 Powder Cases. Cases in which powder is contained in shipment from 
 arsenals or storage until used. Three types are in common use; the zinc 
 storage case with balata washers; the wooden storage case; and the metallic 
 cartridge case hermetically sealed. The latter is rapidly replacing all the 
 others in the service. 
 
 Powder Chamber. The chamber in the bore for the reception of the powder 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 45 
 
 charge; it is usually cylindrical, but frequently conical and sometimes ellip- 
 tical. It is between the breech recess and the centering slope, which unites 
 it with the forcing cone. 
 
 Powder Chart. A graphic chart used to determine the velocity to be 
 expected from a given charge of powder considered as a function of the tem- 
 perature of the powder. 
 
 Powder Chute. In gun emplacements an inclined well or shaft for returning 
 cartridges or dummies to magazine. 
 
 Powder Hoist. A device for raising powder from the magazine to the 
 loading platform. 
 
 Powder Hoist Well. The shaft through which the powder hoist operates. 
 
 Powder Magazine. See MAGAZINE. 
 
 Powder Room. See CARTRIDGE ROOM. 
 
 Power and Light Equipment. Equipment including engines, dynamos, 
 storage batteries, motors, electric and other kinds of lights, and all material 
 and supplies pertaining thereto. 
 
 Power Room. A room in the battery provided for the necessary motor 
 generators, induction motors and switch-boards. 
 
 Power Section. A detachment of the enlisted personnel of a mine com- 
 pany consisting of the operators and assistants required at the power plants, 
 searchlights and mining casemate of a mine command. 
 
 Power Station or Plant. The principal source of supply of energy, 
 usually electrical, for the power system of the fortifications and stations. 
 The plant consists of a sufficient number of direct connected units to supply 
 all the power needed for the entire installation under conditions of full load. 
 
 Predicted Firing. Firing at which guns and mortars are given direction 
 and elevation corresponding to a predicted point. 
 
 Predicted Point. A point on the course of a moving target, as ndicated 
 on the plotting board at which it is predicted the target will arrive at the ex- 
 piration of an assumed interval of time. This interval of time is called the 
 predicting interval. 
 
 Predicted Time. The time at which the target should reach a predicted 
 point. 
 
 Predicting Interval. See PREDICTED POINT. 
 
 Predicter. An accessory of the mortar plotting board used to locate the 
 position of the predicted and set-forward points. 
 
 Preponderance. The excess (moment) of weight of that part of the piece 
 in rear of the trunnions over that of the front, or the converse. It is measured 
 by the force expressed in pounds necessary to balance the cannon when resting 
 freely on the trunnions. 
 
 Pressure Cylinder. A soft copper cylinder used in crusher gauges which 
 is compressed by the explosion of the charge. 
 
 Pressure Gauge. See CRUSHER GAUGE. 
 
 Primary Armament. The armament of a coast artillery fort used to attack 
 the side, turret and deck armor of war vessels, and carry large explosive charges 
 into their interiors. It includes the 8-inch, 10-inch, 12-inch, 14-inch and 
 16-inch guns, and 12-inch mortars. 
 
 Primary Station. The principal station of a base line. See BASE-END 
 STATION. 
 
46 THE SERVICE OF COAST ARTILLERY 
 
 Primer. A wafer, cap, tube or. other device for communicating fire to the 
 powder charge. There are five classes of primers used in the U. . S. Coast 
 Artillery service, namely: Friction, percussion, electric, combination and 
 igniting. 
 
 Priming Charges. A charge consisting of black powder, quilted in each 
 end of the bag containing the sections of smokeless powder for the purpose of 
 igniting it. 
 
 Prismatic Powder. A molded gunpowder hexagonal in shape, with a 
 single round perforation through the center of the grain. It is either brown or 
 black in color, depending upon the color of the charcoal used. The black 
 prismatic powder is made of the ordinary black granulated powder, the " can- 
 non powder" grain being taken as a base. 
 
 Probability Factors. A table of factors which, multiplied by the width of a 
 zone containing fifty per cent, of the hits, will give the width of zones contain- 
 ing any other percentage of hits. 
 
 Probability of Error. As referred to gunnery, is that particular error in 
 any direction in which it is an even chance will not be exceeded by any shot. 
 It is based upon the rule that when the value of any quantity or element has 
 been determined by means of a number of independent observations, each one 
 liable to a small amount of accidental error, the result of determination will also 
 be liable to some uncertainty. The probable error, therefore, is the quantity, 
 which is such that there is some probability of difference between the determi- 
 nation and the true absolute value of the thing to be determined, exceeding or 
 falling short of it. The probable error of a gun, in any direction, is a distance 
 measured in that direction from the center of impact, of such length that it is 
 an even chance that it will not be exceeded by a single shot, and for which it 
 can be predicted that in the long run 50 per cent, of all shots fired will have 
 a less error. 
 
 Probable Zone. The space bounded by two parallel straight lines of such 
 length that by the theory of probabilities 50 per cent, of the points of impact 
 will probably be found. 
 
 Profile Board. A thin plate or board having its edge so cut as to represent 
 the outline of an object ; it is used to prove the models of the breech and other 
 exterior parts of a gun. 
 
 Progressive Powder. An explosive or propelling agent of low order; for 
 example, the charcoal and nitro-cellulose powders. The explosion of powders 
 of this kind is marked by more or less progression. The mass is ignited at one 
 point and the combustion proceeds progressively over the exterior exposed 
 surfaces and then at right angles to these surfaces. 
 
 Projectile. A term applied to a missile usually thrown from a firearm by 
 some explosive, to strike and destroy some distant object. The principal parts 
 of a modern projectile include the point or nose, the ogive, the bourrelet, the 
 base, the rotating band and the fuse hole. 
 
 Projector. The technical name of a searchlight. 
 
 Proof of Gunpowder. A certain test made on separate lots of gunpowder 
 before it is accepted by the War Department. 
 
 Proof Plug. See CRUSHER GAUGE. 
 
 Property Officer. The senior company officer of a mine command. He is 
 responsible to the mine commander that requisitions are made for the necessary 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 47 
 
 apparatus and material for the mine defense. He has direct charge of all 
 property appertaining to the care, loading and planting of submarine mines. 
 
 Protractor. A mechanical instrument used for laying out and measuring 
 angles on paper. 
 
 Pyramidal Target. A material target in the form of a pyramid, covered 
 with canvas painted vermilion, divided into rectangles 2 feet wide, which are 
 painted alternately vermilion and white. This pyramid is mounted on a 
 float made of two parallel sills of timber, joined by transoms, two diagonal 
 braces and a prow to which a suitable bridle is attached for towing. This 
 target is used as a fixed target for all trial shots, and in case the material target 
 for heavy guns has not been furnished, two of these targets are towed 60 feet 
 from center to center, with a red streamer suspended from a wire or hemp line 
 at the middle point between them, to represent the material target. For 
 service practice with mortars this target is used to represent the center of a 
 circular hypothetical target 100 yards in diameter. For subcaliber practice 
 with mortars this target without canvas covering but with a flagstaff and flag 
 is used. 
 
 Quadrant. The quarter of a circle or the quarter of the circumference of a 
 circle ; an arc of 90 degrees. See GUNNER'S QUADRANT. 
 
 Quadrant Angle of Departure. The angle between the line of departure 
 and the horizontal plane through the muzzle. It is obtained from the angle 
 of departure by correcting for the angular elevation or depression of the target, 
 including curvature of the earth. 
 
 Quadrant Elevation. The angle between the horizontal and the axis of 
 the bore when the piece is pointed. It is obtained from the angle of departure 
 by correcting for the angular elevation or depression of the target including 
 curvature of the earth and for jump. 
 
 Quartermaster. See ARTILLERY DISTRICT QUARTERMASTER and POST 
 QUARTERMASTER. 
 
 Quartermaster Sergeant. See POST QUARTERMASTER SERGEANT. 
 
 Quick-Firing Guns. A British term for rapid-fire guns. 
 
 Quickness of Burning. The rapidity with which a grain of powder is 
 consumed. When it is said that the powder is too quick or too slow for a gun, 
 the quickness of burning through the "critical dimension" of the grain is re- 
 ferred to. 
 
 Rack. A bar or arc, having teeth that engage with those of a gear wheel 
 or worm. 
 
 Radial Vent. A vent extending at right angles to the axis of the bore. 
 
 Radius. Any line extending from the center to the circumference of a 
 circle : it is one-half the diameter. 
 
 Rammer. A rod provided with a graduated brass ring ; used for properly 
 seating a projectile in the bore of seacoast cannon. 
 
 Ramp. An inclined plane or foot-path, serving as a means of communica- 
 tion from one level to another. 
 
 Rampart. A broad embankment of earth around a place upon which a 
 parapet is raised. A structure forming the substratum of every permanent 
 fortification. 
 
 Range. The range in gunnery is the horizontal distance from the muzzle 
 of the gun to the target. The word is applied in a general sense to other hori- 
 
48 THE SERVICE OF COAST ARTILLERY 
 
 zontal distances, as, for instance, to the distance between the position finders 
 and the target, or between a position finder and a splash, etc. 
 
 The range of a shot is the horizontal distance from the center of the gun 
 to the point where the projectile first strikes. 
 
 Range-Azimuth Table. A table of ranges and the corresponding azimuths 
 from a gun to points in the center of the main ship channel or channels. It is 
 kept at the gun and used for firing without the use of the range-finding 
 apparatus. 
 
 Range Board. A device for obtaining the range corrections which must be 
 made for wind, atmosphere, tide, velocity, and travel of target during the 
 observing interval and time of flight. 
 
 Range Deviation. The difference between the range to the target and the 
 range to the point of impact. 
 
 Range Difference. The difference in range of a point from any other two 
 points, as, the difference between the range to the target from the directing 
 gun, and the range to the target from any other gun of the same battery. 
 
 Range Finder. An instrument for determining the range to a target or 
 object, from some fixed point. 
 
 Range Keeper. A specially qualified member of the fire-control section, 
 who operates the time range board and calls out the range to the range setter 
 as often as may be necessary to insure the piece being kept at proper elevation. 
 In restricted fire at a specified interval he keeps the time and indicates to the 
 chief of detachment the proper time to trip the gun. 
 
 Range of Ballistic Tables. See THEORETICAL RANGE. 
 
 Range Officer. A coast artillery officer in immediate charge of all or a 
 part of the fire-control section. 
 
 He is stationed at the battery plotting-room. He is responsible to the 
 battery commander for the condition of the material pertaining to the fire- 
 control service, for the instruction of the fire-control personnel and for the 
 efficiency of that service in general. Upon opening the station he should make 
 careful inspection of the equipment, verify the adjustment of the position- 
 finding instruments, plotting-board, etc. After satisfying himself that every- 
 thing is in order and receiving the reports of the chiefs of details, he reports to 
 the battery commander: "Sir, fire-control stations in order," (or reports defects 
 he cannot readily correct). 
 
 In battle and fire-command drill or action, he receives directly from the 
 fire commander and executes orders, as to the assignment of targets. When 
 direct communication between the fire commander and the battery commander 
 is impracticable he receives directly and executes other orders pertaining to the 
 fire action of the battery. He is responsible to the battery commander for the 
 prompt and accurate transmission to the battery commander of orders received 
 by him from the fire commander. 
 
 At the close of the drill or action he directs stations to be closed, inspects 
 them and reports to the battery commander, handing him all records pertaining 
 to the work at his station. 
 
 Range Rake. An instrument made in the form of an ordinary rake. 
 The main arm is shaped like a gun stock with the cross arm extended at front 
 end. At a convenient distance on the main arm is placed a guide peg repre- 
 senting the rear sight, while on the cross arm pegs are placed at intervals of one- 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 49 
 
 half of an inch to represent points, each point having a value in mils equal 
 to 1/1000 the length of the towline connecting the target with the tug upon 
 which the observations with the range rake are taken. To use the range rake 
 the observer takes position at a point in the center of the stern of the tug and 
 aims the rake so that the line of sight from the guide peg will pass over the 
 center peg on the cross arm and thence to the target. At the instant the splash 
 of the shot occurs, the observer, keeping the rake pointed as above described, 
 sights over the guide peg and in the direction of the splash, observing which peg 
 on the cross arm is in line with the splash. For example, if a shot struck five 
 divisions of the rake beyond the target (or five pegs), assuming the value of 
 each peg at 10 mils, the reading in mils would be 50; if the towline wet mea- 
 sured 295 yards, the shot would have struck 14.75 yards over. This is obtained 
 as follows: 50 X 295 -=-1000 = 14.75 yards. 
 
 Range Scale. The graduations in yards either on the range scale arc of 
 rapid fire guns, or the quadrant arc of large-caliber guns. 
 
 Range Setter. A specially qualified member of the gun section who lays 
 the gun for range. 
 
 Range of a Shot. See RANGE. 
 
 Range Table. A properly constructed range table for a particular piece, 
 containing the range, time of flight, drift, etc., for each elevation. 
 
 Rapid-Fire Gun. A single-barrel breech-loading gun provided with breech 
 mechanism, mounting, and facilities for loading, aiming and firing with great 
 rapidity. The breech mechanism is operated by a single motion of the handle 
 or lever. The smaller calibers use fixed ammunition. 
 
 Rapid-Fire Gun Carriage. See CARRIAGE or MOUNT. 
 
 Rate of Fire. The average rate of fire of heavy caliber guns with service 
 charge should be about one shot in forty or fifty seconds. 
 
 Ratings. A particular class or grade to which enlisted men belong. In the 
 coast artillery they may be rated as sergeants major, master electricians, 
 engineers, electrician sergeants, master gunners, firemen, casemate electricians, 
 observers, plotters, chief planters, chief loaders, gun commanders, gun pointers 
 and gunners. 
 
 Ready. At gun batteries, a signal given to indicate to the gun pointer that 
 the piece is ready to be fired. At mortar batteries, a signal given to the battery 
 commander that the mortars\are ready to be fired. 
 
 Rear Slope. The rear slope to the parade in rear of the battery. 
 
 Receiving Table. The hoist table on which ammunition is placed prepara- 
 tory to raising it to the loading platform level. 
 
 Recoil. The backward movement of the gun on firing. It is measured by 
 the distance which some point on a gun or carriage travels during recoil. See 
 SECTOR OF EXPLOSION. 
 
 Recoil Cylinder. The hydraulic cylinder attached to the carriage for con- 
 trolling the recoil of the piece. 
 
 Reconnaissance. An examination of a territory or military position, for 
 the purpose of obtaining information necessary for directing military operations. 
 
 Reconnaissance in Force. A demonstration conducted in the same general 
 manner as a regular attack. It is made for the purpose of drawing the fire 
 of the defense, discovering his strength, dispositions, location of batteries, etc. 
 
 Recorder. An enlisted man stationed at each battle- and fire -commander's 
 
50 THE SERVICE OF COAST ARTILLERY 
 
 station who keeps an accurate written record of all orders and communications 
 received and transmitted by the battle or fire commander. 
 
 Records of Firing. Data taken during target practice or that relating to 
 the gun, carriage, conditions of loading, laying, etc., which would be of value 
 in connection with future firings. 
 
 Rectangular Target. See MATERIAL TARGET. 
 
 Redoubt. Usually a roughly constructed field-work of varying shape in 
 which all or nearly all the angles are salient angles. They are usually employed 
 only in positions in which a small body of troops desire to make a very vigorous 
 defense. 
 
 Reference Numbers. Arbitrary numbers used to avoid "plus" and 
 "minus," "right" and "left," in data for firing. These numbers are used on 
 the graduations of scales on devices of the position-finding equipment to avoid 
 liability of error by the use of one set of numbers instead of two sets. Without 
 reference numbers it would be necessary to have one set of numbers for plus, 
 and another set for minus corrections. For example, if the wind curves on the 
 range board were numbered in both directions from zero, there would be a 
 "plus" 10-mile wind curve and a "minus" 10-mile wind curve. In use it 
 would be comparatively easy to make the mistake of taking the plus 10, instead 
 of the minus 10. The corresponding reference numbers, however, for wind 
 would be 60 for plus 10, and 40 for minus 10 (50 being the zero). In this 
 manner the liability of error is minimized. 
 
 Regulations. Under the Constitution of the United States, any rules for 
 the government and regulation of the army made by Congress. Regulations 
 imply regularity and signify fixed forms; a certain method, order or precise 
 determination of functions, rights and duties. It embraces administrative 
 service, system of tactics, and the regulation of service in campaign, garrison 
 and in quarters. 
 
 Reinforce. See BREECH REINFORCE. 
 
 Relay. The command given when mortars are not to be fired as laid, but 
 are to be fired on the next data furnished. 
 
 Relocation of a Target. Any process whereby having the location of a 
 target from one point, its range and azimuth from some other point may be 
 determined without further observation. 
 
 Remaining Velocity. The velocity of a projectile at any point of the 
 trajectory. 
 
 Reserve Table. A table in a sheltered position for reserve ammunition. 
 
 Resistance of the Air. The retarding effect of the air on projectiles 
 during their flight. 
 
 Restricted Fire. See ORDERS OF FIRE. 
 
 Retardation. The velocity a projectile loses in consequence of a resisting 
 medium. 
 
 Retractor. A device for withdrawing the empty cartridge shell rearward 
 from the bore of small -calibe red guns. 
 
 Reverse Fire. Reverse fire is when the object is fired at from the rear. 
 
 Ricochet. The rebound of a projectile along a surface. 
 
 Rifle. A cannon or gun with the interior surface of its bore grooved with 
 spiral channels or cuts, thus giving the projectile a rotary motion. If the 
 interior surface of the bore is smooth, the cannon is known as smooth bore. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 51 
 
 Rifling. The spiral grooves cut in the surface of the bore of a rifle for the 
 purpose of giving a rotary motion to the projectile. 
 
 Rifling, Twist in. See TWIST OF RIFLING. 
 
 Rimbases. The masses of metal uniting the trunnions with the trunnion 
 band. 
 
 Ring Resistance Fuse. A base or point fuse used in charged shell and 
 shrapnel. The name is derived from the manner in which the firing pin is main- 
 tained in its normal or unarmed position by a brass split-ring spring. 
 
 Roadstead. A water area where ships may ride at anchor some distance 
 from the shore. An anchorage off shore. 
 
 Rocket. A projectile set in motion by forces residing within itself, usually 
 used for signaling. 
 
 ^ Rotating Band. The copper band encircling projectiles near their base 
 for the purpose of giving them angular rotation in passing through the rifling 
 of the bore. 
 
 Rotation. The act of a body turning on its axis. 
 
 Rotation of Projectile. The act of the projectile turning upon its axis 
 during the time of flight. 
 
 Round. A round of ammunition includes a projectile, charge and primer. 
 To fire one round is to discharge one shot from each gun of a battery. 
 
 Roving Light. A searchlight intended to search the battle area within the 
 field not covered by fixed lights. 
 
 Row. See HOOPS. 
 
 Rubber Impression of the Bore. An impression taken on rubber and 
 used to determine the amount of erosion or other irregularities of any portion 
 of the bore. 
 
 Safety Lanyard. A safety device attached to seacoast cannon consisting 
 of a lanyard wound on a drum working against the action of a spring and 
 attached to the gun. It is so arranged, by means of a ratchet and pawl, that a 
 pull on the firing lanyard can not be transmitted to the primer until the gun 
 is in battery. 
 
 Salvo. To fire all the mortars of a pit or battery, or the guns of a gun 
 battery simultaneously. 
 
 Salvo Fire. Fire concentrated from one or more batteries against a salvo 
 point. 
 
 Salvo Point. A point, the azimuth and range of which are known and 
 conspicuously posted in the battery ; at which a concentrated fire from one or 
 more batteries may be directed. Certain points in narrow channels are usually 
 selected as salvo points. 
 
 Salvo Table. A table giving ranges and azimuths of salvo points. 
 
 Scarp. In field fortification the wall of the ditch adjacent to the parapet. 
 It is always made at as large an angle as the nature of the soil will permit, 
 the design being to offer the greatest possible obstacle to the assailant. The 
 opposite wall or side is called the counterscarp. 
 
 Scout Ships. Speedy seagoing ships that patrol at a distance off shore, 
 to discover the approach of the enemy and signal information thereof to the 
 signal stations ashore. 
 
 Screw Box. The breech recess of seacoast cannon. 
 
 Searchlight. A high-power electric arc light, used for night illumination. 
 
52 THE SERVICE OF COAST ARTILLERY 
 
 Searchlights are classified as, Fixed Lights, Roving Lights, Illuminating Lights, 
 Mine Field Lights and Battle Lights. The standard diameters are the 60-inch 
 and the 36-inch lights. A few 30-inch and 24-inch lights are still in use. 
 
 Searchlight Area. The area of land or water illuminated by a searchlight. 
 
 Searchlight Observer. A member of a searchlight detachment equipped 
 with a night glass, stationed outside of fixed or roving lights at such distance 
 that he can detect readily any vessel passing into the beam. 
 
 Searchlight Officer. A coast artillery officer in charge of the searchlight 
 system covering a battle area, and the manning party assigned thereto. His 
 station is at the battle-command station, or within speaking distance of the 
 battle commander. He is responsible to him for the condition of the search- 
 light material and for the efficiency of the searchlight system. At night drill 
 and in action he stands ready to execute the orders of the battle commander 
 as to searching the battle area. When deemed necessary by the battle com- 
 mander, the searchlight officer may temporarily take charge of the mine-field 
 lights. He is responsible for the instruction of the personnel assigned to the 
 control and operation of the searchlights, and by frequent inspections sees that 
 they are thoroughly familiar with their duties and the prescribed method of 
 searchlight control. In performing his duties from the battle commander's 
 station he should be constantly on the alert to see that no vessel enters the battle 
 area without being detected either by himself or one of his observers, and should 
 so direct the searchlights as to promptly pick up any vessel entering the 
 harbor. 
 
 Searchlight Operator. An enlisted man specially trained in the care and 
 operation of searchlights. 
 
 Searchlight Range. The distance at which a target can be illuminated 
 sufficiently for identification and range-finding purposes. The maximum 
 effective illuminating range on a clear night would be approximately 8,000 
 yards for horizontal-base range-finding system; for purposes of water-lining 
 the target in using the vertical base system the range would be approximately 
 6,500 yards. 
 
 Searchlight Tower. An elevated structure containing the searchlight and 
 its operating mechanism. 
 
 Seat of the Charge. The form of that part of the bore of a firearm which 
 contains the charge. 
 
 Secondary Armament. The armament of a coast artillery fort used to 
 defend the mine field; to attack lightly armored or unarmored ships, the upper 
 works, etc., and personnel of war ships and defend the inner waters against 
 small boats and landing parties. It includes 3-inch guns, small-caliber guns, 
 and machine guns when on fixed mounts. 
 
 Secondary or Auxiliary Power Plant. A reserve unit of power supply 
 usually located at each battery, to furnish it with power in case the central 
 power plant or main source of power supply fails or is put out of action. 
 
 Secondary Station. A position-finding station furnished with an author- 
 ized range-finding instrument upon which readings are taken simultaneously 
 with those at the, primary station if the horizontal-base system is used; or 
 upon which range and azimuth readings are taken if the vertical -base system 
 is used and it is desired to make observations and obtain data taken from that 
 position. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 53 
 
 Sector. A plane figure part of a circle, inclosed between two radii and the 
 included arc. 
 
 Sector of Explosion. At the moment a cannon is fired, there is a sort of 
 spherical sector of fire formed in front of the piece, called sector of explosion. 
 The extremity of this sector presses against the rear end of the bore while the 
 external portion of it terminates in the air, which it compresses and drives in 
 every direction; the air thus forming a support, the sector reacts with its full 
 force upon the rear end of the bore and causes the recoil of the piece. 
 
 Segment. A piece of metal in the form of the sector of a circle, or part of 
 a ring. 
 
 Self-Contained Horizontal Position Finder. A position-finding instru- 
 ment containing a horizontal base line within itself. This base line is from 
 eight to twenty-five feet in length. 
 
 Semi-Automatic Machine Guns. Rapid-fire guns in which the force of 
 recoil is used to operate the breechblock, but not to load and fire the piece. 
 See AUTOMATIC MACHINE GUNS. 
 
 Separate Observing Room. An observing room which does not adjoin a 
 plotting room or other observing room. 
 
 Separate Plotting Room. A room in which the plotting board is located 
 and used; instead of being located in the primary station. 
 
 Sergeants Major. Coast artillery corps non-commissioned staff officers 
 assigned to duty as assistants to adjutants in administrative functions. Their 
 tactical duties are the same as those of regimental or battalion sergeants major 
 of infantry and any coast artillery duty pertaining to their proper position. 
 Chevrons : Sergeant Major, Senior Grade. Three bars and an arc of three bars. 
 Sergeant Major, Junior Grade. Three bars and an arc of two bars. All to be 
 of red cloth. 
 
 Service Charge. The maximum quantity of powder that is perscribed to 
 be used in any seacoast cannon. 
 
 Serving Table. A table for keeping a supply of projectiles convenient to 
 the breech during loading. It is usually mounted on wheels. 
 
 Serving the Vent. The term implies the removing of the old primer from 
 the obturator, inserting a new one, adjusting the slide of the firing attachment, 
 attaching the firing wire or lanyard and cleaning the vent. 
 
 Set-Back Point. A point on the course of a target determined in a similar 
 manner as a set-forward point, but in the opposite direction. 
 
 Set-Forward Point. A point on the course of the target in advance of a 
 predicted point, at a distance from the latter equal to the distance passed 
 over by the target during the time of flight of the projectile for that particular 
 range. 
 
 Set-Forward Ruler. A celluloid rule that may be used in the position - 
 finding system for mortars, to determine the set-forward point; It consists of 
 a time-of-flight scale in seconds, a travel scale in yards and a scale giving yards 
 of travel during time of flight plus one minute. It is arranged in the form of a 
 slide rule. 
 
 Shears. A form of tackle consisting of two spars lashed together at one 
 point, forming an inverted V. 
 
 Shell. A steel or cast iron projectile the center of which is hollowed to be 
 filled with the bursting charge. 
 
54 THE SERVICE OF COAST ARTILLERY 
 
 Shell Filler. See BURSTING CHARGE. 
 
 Shell Room. The room for the storage of projectiles. 
 
 Shell Tracer. A device attached to the base of a projectile which enables 
 its flight to be followed. In the daytime a yellow smoke is emitted, and at 
 night a bright flame. 
 
 Shimose Powder. A high explosive of Japanese manufacture. 
 
 Shot. A term applied to all solid projectiles. 
 
 Shot Chamber. That part of the bore in which the projectile is seated. 
 It includes part of the centering slope and the rear portion of the forcing 
 cone. 
 
 Shot Gallery. A gallery or room in the emplacement for the storage of 
 projectiles. 
 
 Shot Hoist. A device for raising projectiles from the hoist room to the 
 loading or truck platform. 
 
 Shot Hoist Well. The shaft through which the shot hoist operates. 
 
 Shot Room. The room in earlier emplacements for the storage of shot. 
 
 Shot Tongs. A mechanical device used to encircle the projectile at the 
 center of gravity to facilitate handling. 
 
 Shrapnel. A projectile composed of a number of spherical balls inclosed 
 in a cast iron case, with a bursting charge in either point or base to scatter 
 the missiles. The point is armed with a combination fuse. It is distinguished 
 from shell by this point. 
 
 Sight. An instrument by which the gun pointer gives the gun the proper 
 direction for firing. Sights are of two classes, open and telescopic. The former 
 consists of two points which are brought into line with the target by the unaided 
 eye ; the latter uses the magnifying power of the telescope and is the standard 
 sight. 
 
 Sight Deflection. The horizontal angle between the line of sight and the 
 axis of the piece. It is used to correct for conditions of drift, wind, and move- 
 ment of target tending to cause deviation. 
 
 Sight Elevation. The elevation measured from the line of sight; it is the 
 angle between the line of sight and the axis of the bore when the piece is pointed. 
 It is obtained from the angle of departure by correcting for jump. 
 
 Sight Standard. A vertical steel post supporting the sight. 
 
 Signal Rocket. An ordinary skyrocket used in fortress warfare and exer- 
 cises, as a means of communication. 
 
 Signal Station. A station located if practicable at a height sufficient to 
 give a sky background, from which visual signals are displayed. 
 
 Signs. See PAGE 65. 
 
 Six-Inch Gun. A rapid fire gun from 40 to 50 calibers in length and of 
 6-inch caliber; mounted either upon disappearing or pedestal carriage. 
 
 Six-Pounder. A rapid-fire gun of 2.24-inch caliber. The name denotes 
 the proper weight for the projectile of the piece. 
 
 Small Boats. Launches, cutters, gigs and j^awls, use d in connection with 
 submarine mine work, boat drill and transportation. 
 
 Small-Caliber Guns. Guns of 3-inch caliber, 6 and 1-pounders. 
 
 Smokeless Powder. The name given to nitro-cellulose and nitro-glycerin 
 gunpowder. 
 
 Smooth-Bore Cannon. See RIFLE. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 55 
 
 Sound Travel. The rate of travel of sound. Under normal conditions it is 
 approximately 1,150 feet per second. 
 
 Specific Gravity. The ratio of the weight of a body to the weight of an 
 equal volume of water, in the case of solids and liquids ; and to an equal volume 
 of air in the case of gases; taken as the standard or unit. 
 
 Sphero-Hexagonal Powder. A black gunpowder in the form of a small 
 ball with a six-sided ring around the middle. 
 
 Spline. A rectangular piece fitting grooves like key seats in a hub or shaft, 
 so that while the one may slide endwise on the other, both must revolve to- 
 gether. 
 
 Sponge. A swab used for cleaning the chamber and bore of guns and 
 mortars. 
 
 Sprocket Wheel. A toothed wheel that engages the links of a chain. 
 Spur Ring. A ring having radial teeth on the circumference. 
 Spur Wheel. A gear wheel having external radial teeth on the circum- 
 ference. 
 
 Staff. For administrative and other purposes, the staff of a coast artillery 
 fort includes an adjutant, surgeon, artillery engineer, ordnance officer, quarter- 
 master and commissary. 
 Standards. See COLORS. 
 
 Stand Fast. A command at which cannoneers halt until the previous 
 command is repeated. When one member makes a mistake this command 
 is given before the mistake is corrected. 
 
 Star Gauge. A device for measuring the diameter of the bore of cannon. 
 It is used during the manufacture and when it is necessary to determine if any 
 enlargement of the bore has t^fcen place. 
 
 Storage Magazine. A building provided for the storage and preservation 
 of powder or explosives; located so as to be protected from the fire of the 
 enemy. 
 
 Storehouse. Every coast artillery fort is provided with one or more store- 
 houses for the care and storage of accessory material. 
 
 Storeroom. A room in the emplacement for the storage of necessary ma- 
 terial. 
 
 Storm Flag. The national flag 8-foot fly by 4-foot 2-inch hoist. Hoisted 
 in stormy or windy weather. 
 
 Strategy. The art of moving an army in the theater of operations with a 
 view to placing it in such a position, relative to the enemy, as to increase the 
 probability of victory, increase the consequences of victory, or lessen the con- 
 sequences of defeat. 
 
 Strength. The number composing any military body. 
 Striking Angle. The angle which the line of impact makes with the hori- 
 zontal plane. It is equal to the angular depression of the point of impact plus 
 the angle between the line of impact and the line of shot. 
 Striking Energy. See ENERGY OF PROJECTILE. 
 
 Striking Velocity. The velocity of the projectile at the point of impact. 
 vSubcaliber Platform. A steel platform attached to the breech of large- 
 caliber guns upon which the breech detail stands to load the subcaliber tube 
 during practice. After the platform is attached the piece is placed in battery. 
 At batteries not equipped with the prescribed pattern a platform of wood is 
 
56 THE SERVICE OF COAST ARTILLERY 
 
 constructed by lashing heavy planks to the sighting platforms so that they 
 will extend about six feet in rear of the breech; flooring is then nailed to the 
 planks. 
 
 Subcaliber Quadrant Scale. Scales used on gun carriages to set the piece 
 in elevation during subcaliber practice in place of the regular service scale. 
 They are constructed for ranges in yards corrected for height of site and 
 curvature, and are used in the same manner as the regular quadrant scale. 
 
 Subcaliber Tube. A small caliber gun which is seated in the bore of a gun 
 of larger caliber; used for target practice with ammunition of smaller charges 
 and caliber than the gun in which it is used. In rapid fire guns this device is 
 contained in a dummy projectile. They are classified as 30/100-inch caliber, 
 1-pounder, and 18-pounder. 
 
 Submarine Boat. Small boats capable of maneuvering under the surface 
 of the water. There are two types, namely: Holland and Lake. On the sur- 
 face they have the appearance of a small monitor; when submerged only the 
 conning tower, hood and sighting apparatus are visible; when completely 
 submerged only the signal mast is visible and this only when desired or when 
 submergence is not great. They fire torpedoes from one or two tubes in all 
 three positions. Average length 60 to 70 feet; beam 11 to 14 feet; speed 
 10 to 12 knots; partially submerged 8 to 10 knots; submerged 8 knots. 
 
 Submarine Boat Signal Flag. A flag of bunting showing a black fish on 
 a white surface and surrounded by a red border. This flag is flown from the 
 tender or parent vessel attending submarine boats. Its function is to notify 
 shipping that a submarine boat is below the surface of the water in the 
 vicinity. 
 
 Submarine Defense Equipment. Submarine defense equipment includes 
 submarine mines, mobile torpedoes, obstructions and all material pertaining 
 to the placing and service of these means of defense. 
 
 Submarine Defenses. Submarine defenses include submarine mines, 
 mobile torpedoes, marine obstructions and submarine boats. 
 
 Submarine Mine. A submerged stationary torpedo consisting of an explo- 
 sive charge and firing device, inclosed in a water-tight steel case, to be fixed 
 in position in a channel which it is desired to close against the passage of an 
 enemy's vessels. They are classified as mechanical, when they are exploded by 
 means of a firing device ; and electrical, when exploded by electricity. 
 
 Superior Slope. The top slope of a parapet or traverse. 
 
 Supplementary Station. An auxiliary base-line station used to furnish 
 data in place of the secondary station in case said station is put out of action, 
 or to furnish data over a field of fire not covered by the secondary station. 
 
 Surface. The exterior part of anything that has length and breadth; the 
 outside, as the surface of the earth. 
 
 Surveyor's Transit. An angle-measuring instrument similar in its essential 
 parts to the azimuth instrument, but of more delicate and complicated design. 
 It may be used to measure both horizontal and vertical angles as well as give 
 the magnetic bearing. Its principal parts are shown by name and detail in 
 chapter on Fire-Control Instruments, etc. 
 
 Swell of the Muzzle. The enlargement of the exterior of the gun at the 
 muzzle. 
 
 Symbol Charts. See VESSEL CHARTS. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 57 
 
 Tackle. A purchase formed by reeving a rope through two or more blocks, 
 for the purpose of hoisting. 
 
 Tactical Chain of Artillery Command. The combined tactical units of 
 seacoast defense. 
 
 Tactical Command. Command at drill and during action. 
 
 Tactical Responsibility. Responsibility for all matters affecting the effi- 
 ciency of a tactical command. 
 
 Tactics. The art of drilling troops, and of handling and maneuvering them 
 in the presence of the enemy. See BATTLE TACTICS. 
 
 Take Cover. A command which can be given at any time, at which all 
 numbers not designated to remain at their post move at a run to some desig- 
 nated place under cover. As a rule this command is given in mortar batteries 
 only. 
 
 Tangent. A line lying in the plane of a circle and touching the circumference 
 at one point. 
 
 Tangent of an Arc. That part of the tangent which, touching the arc at 
 one extremity, is limited by the line passing through the other extremity and the 
 center of the circle. 
 
 Tangential Force. A force which acts on a moving body in the direction 
 of the tangent to the path of the body, its effect being to increase or diminish 
 the velocity; distinguished from a normal force, which acts at right angles to the 
 tangent and changes the direction of the motion without changing the velocity. 
 A ricochet shot or a foul tip in base ball, are examples of applied tangential 
 force. 
 
 Targ. The piece of metal used to indicate the intersection of the arms on 
 the plotting board. 
 
 Target. The object at which guns or mortars are pointed ; as a boat, ship 
 or other object, whether stationary or moving. 
 
 Target or Vessel Tracking. The process whereby successive positions of a 
 moving target are plotted on a chart or plotting board. It includes the observa- 
 tions made by the observers at the position-finding instruments, the plotting 
 of the results of these observations on a plotting board at the same time tracing 
 thereon the plotted track of the course of the target. 
 
 Telautograph. An electro-mechanical instrument by means of which the 
 movement of an attached pencil used by a person in writing at one end of the 
 circuit, will automatically trace or reproduce the characters, as written, at the 
 other end. 
 
 Telephone. An instrument by means of which a sound produced at one end 
 of a wire is reproduced at the other end. There are two types in use the 
 Service Telephone, used in temporary installations; and the Composite Artillery 
 Type Telephone, used in permanent installations. 
 
 Telescopic Sight. A combination sight and telescope used for the aiming 
 of guns at ranges greater than an object could be distinguished with the naked 
 eye. The advantage of telescopic sights are the increased power of vision ; large 
 decrease in personal error ; and the great facility and accuracy of aiming a gun 
 at the greater ranges. See SIGHT. 
 
 Ten-Inch Gun. A seacoast cannon usually 35 to 40 calibers long and of 
 10-inch caliber. 
 
 Terrain. The ground, its configuration and natural and artificial diversifi- 
 
58 THE SERVICE OF COAST ARTILLERY 
 
 cation. The topographical character of the country, region or tract, as viewed 
 from a military standpoint. 
 
 Thawing Explosives. See MELTING AND THAWING EXPLOSIVES. 
 
 Theater of Operations. All the territory an army may desire to invade, 
 and all that it may be necessary to defend. 
 
 Theoretical Range or Range of Ballistic Tables. The horizontal distance 
 from the muzzle of the gun to that point of the descending branch of the tra- 
 jectory, called the point of fall, which is at the level of the muzzle of the gun. 
 This definition of the theoretical range is strictly accurate and is conveniently 
 applicable in using quadrant elevation, as with mortar fire; but in using sight 
 elevation it is more convenient, assuming the principle of the rigidity of the 
 trajectory, to define the theoretical range as the distance from the muzzle of 
 the gun to the point of intersection of the trajectory with the line from the muz- 
 zle to the target, the distance being measured along this line. The point of 
 intersection is called the point of fall. 
 
 Theory of Probability. See PROBABILITY OF ERROR. 
 
 Thermometer. An instrument for measuring temperature. 
 
 Three-Inch Gun. A rapid-fire gun 40 to 50 calibers long and of 3-inch 
 caliber. Commonly called "Fifteen Pounder." 
 
 Throttling Bar. A bar in the recoil cylinder to regulate the size of the 
 orifice through which the oil escapes from one side of the piston head to the 
 other. 
 
 T-I Bell. See TIME-INTERVAL BELL. 
 
 Tide Gauge. A mechanical device used to register the height of 
 tide in feet and hundredths above the datum plane (mean low water). 
 It consists essentially of a float connected with an automatic registering 
 device. 
 
 Tide Indicator. A device operated electrically to indicate height of tide 
 in all primary stations. It is operated by a controller located in the tide 
 station. 
 
 Tide Station. A station at which periodical readings of height of tide are 
 made, recorded and sent to the various primary stations throughout the fire- 
 control command. 
 
 Time Fuse. A fuse which ignites the bursting charge at some fixed time 
 after the projectile leaves the muzzle. 
 
 Time-Interval Bell. A bell with electrical attachment, located in all em- 
 placements, primary and secondary stations, for the purpose of sounding 
 simultaneous signals to indicate the observing interval. Commonly called 
 "T-I Bell." 
 
 Time of Flight Scale. A scale giving the time of flight in seconds for any 
 particular muzzle velocity and projectile, for ranges from one to twelve thousand 
 yards. The term is also applied to the travel of the vessel in yards during the 
 time of flight for any projectile at the range considered. In the case of mortars, 
 the term is applied to the time of flight scale on the predicter, which gives the 
 yards of travel during the time of flight plus one minute. 
 
 Time-Interval Recorder. The ordinary stop-watch. 
 
 Time-Range Board. A board to show range of target from battery at any 
 instant. It is placed on the emplacement wall and is operated on data from 
 the plotting room. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 59 
 
 Tool Room. A room in the battery for the storage of necessary tools and 
 implements. 
 
 Torpedo. An explosive device belonging to either of two distinct classes 
 of submarine destructive agents intended for use in time of war. The torpedo 
 proper to which the name properly applies, is a cigar-shaped vessel designed 
 for offensive subwater attack against the enemy's ships. The other class to 
 which the name is applied is a purely defensive weapon and is more correctly 
 termed submarine mine. It consists of an explosive charge inclosed in a water- 
 tight case which is submerged and anchored in channels, etc. See MOBILE 
 TORPEDO. 
 
 Torpedo Boats. Long, low and narrow war vessels modeled after torpedo- 
 boat destroyers. They have no armor protection. Average speed, 22 to 29 
 knots, tonnage 103 to 107 tons. Armament, three to five one-pounders and 
 three torpedo tubes. They are nothing more than metal shells three-eighths 
 of an inch thick. They are necessary for each important fortified point, to meet 
 and repel attacks made by the enemy's torpedo boats on the shipping at anchor 
 inside the line of fixed defenses; to attack large ships of the enemy when 
 opportunity offers, and protect the mine fields. 
 
 Torpedoboat Destroyers. Long, low and narrow war vessels, with high 
 bow and higher freeboard forward than aft. They have no armor protection. 
 Average speed 29 to 31 knots, tonnage 275 to 740 tons. Armament, six to 
 eight 14 and 6-pounders, and two torpedo tubes. Their functions in connec- 
 tion with coast defense cover the same general duties as those of torbedo boats, 
 except that they have better seagoing qualities. 
 
 Torpedo-Detonating Pierce Fuse. A delayed action fuse used to detonate 
 high-explosive bursting charges in mortar projectiles. 
 
 Torpedo Shell. A deck-piercing shell with an unusually large explosive 
 cavity, fired from mortars for the purpose of carrying a large explosive charge 
 to the decks of war vessels. 
 
 Towing Target. Any target which is capable of being towed behind a 
 boat, 
 
 Tracking. The method employed in locating the course of a vessel on the 
 plotting board, by taking simultaneous readings at the two base-end stations 
 at regular intervals, and plotting the location of the target at the instant of eac h 
 observation. See TARGET OR VESSEL TRACKING. 
 
 Trajectory. The curve described by the center of gravity of the projectile. 
 The path of a projectile in its flight through the air from the muzzle of the 
 gun to the point of impact. 
 
 Transit Instrument. See SURVEYOR'S TRANSIT. 
 
 Travel of Projectile. The distance from the base of a projectile in its seat 
 in the bore to the muzzle of the gun. 
 
 Travel of Target. The distance passed over by the target in the time of 
 flight. It is also used to express the distance passed over by the target in an 
 observing interval. 
 
 Traverse. In fortification, the structure perpendicular or oblique to the 
 parapet wall, protecting the armament and personnel from flank fire. In gun- 
 nery, a term used to indicate the horizontal travel of the piece either to the 
 right or left, 
 
 Traverse Slope or Wall. The side slope or wall of the traverse. 
 
60 THE SERVICE OF COAST ARTILLERY 
 
 Traversing Indicator. A device used by gun pointers to control the 
 traversing of a gun without command. 
 
 Tray. See LOADING TRAY. 
 
 Trial Shots. Shots fired before practice or action to determine, for guns, 
 the muzzle velocity to be used; for mortars the range and deflection correc- 
 tions to be applied. 
 
 Trinitrotoluol. A detonating and disruptive explosive of high order used 
 as a base for shell fillers. 
 
 Tripping. The act of releasing the counterweights of a disappearing car- 
 riage, thereby carrying the piece in battery, i.e., moving the top carriage 
 forward so that the muzzle extends over the parapet. 
 
 Trolley. A mechanical device for transporting projectiles on horizontally 
 suspended tracks. 
 
 Truck. See AMMUNITION TRUCK. 
 
 Truck Platform. If the ammunition trucks run on a different surface 
 from that of the loading platform, this surface is called the "truck plat- 
 form." 
 
 Truck Recess. The spaces built in the parapet wall for the storage of 
 ammunition trucks. 
 
 Trunnion Band or Hoop. The hoop around a cannon, of which the 
 trunnions form a part, located at about the center of gravity. 
 
 Trunnion-Sight Bracket. A bracket attached to the right trunnion of a 
 gun, which may be used for holding the telescopic sights. 
 
 Trunnions. Trunnions are cylinders designed to rest in bearing surfaces 
 of carriages, called "trunnion beds," their axis being perpendicular to the axis 
 of the bore, and ordinarily in the same plane; they connect the gun with the 
 carriage and transmit the force of recoil from one to the other. 
 
 Twelve-Inch Gun. A seacoast cannon usually thirty-five to forty calibers 
 in length and of 12-inch caliber. 
 
 Twelve-Inch Mortar. A seacoast mortar usually nine to ten calibers in 
 length and of 12-inch caliber. 
 
 Twist of Rifling. The inclination of the grooves to the axis of the gun at 
 any point in the bore. The twist is said to be increasing when the inclination 
 gradually increases from the breech to the muzzle; uniform when the inclina- 
 tion is constant. Twist is generally expressed in terms per caliber, viz. : one 
 turn in 40 calibers, meaning that the projectile makes one complete revolution 
 in passing over a length of the bore equal to 40 calibers. 
 
 Tube.^The inner wall of the bore of a built-up gun extending usually from 
 the breech to the muzzle, ordinarily made one piece. 
 
 Tug Observer. A coast artillery officer detailed by the post commander 
 for duty aboard a tug engaged in towing and maneuvering targets during 
 subcaliber or service target practice. His principal duties are to supervise 
 the use of the camera or range rake in taking range deviations (overs and 
 shorts) . 
 
 Tug Officer. A coast artillery officer in charge of a tug engaged in towing 
 and maneuvering targets during subcaliber or service target practice. The 
 actual maneuvering of targets from the tug is under the supervision of the 
 master of the tug, subject to the orders of the tug officer. 
 
 Union Jack. A flag of bunting consisting of 46 white stars, in six rows, 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 61 
 
 the first, third, fourth and sixth rows to have 8 stars, and the second and fifth 
 rows 7 stars each, in a blue field. 
 
 Unit. A military body acting together. Military units are divided into 
 two classes, i.e., administrative units, which include those necessary for the 
 proper care, housing, clothing, feeding, instruction, disciplining and keeping of 
 military records ; and tactical units, which are organized and equipped with a 
 view of their highest efficiency in action. 
 
 Unrestricted Fire. See ORDERS OF FIRE. 
 
 Vedette. A mounted sentinel. 
 
 Velocity. The common term used to denote speed, or rate of motion. 
 Velocities with guns vary from 2,000 to 3,000 feet per second, with mortars 
 from 550 to 1,300 feet per second. 
 
 Velocity of Combustion. The rate of burning of a powder grain. 
 
 Velocity of Rotation. The rate of motion of a body around its axis, as a 
 wheel, as distinguished from progressive motion of a body in the direction of a 
 distant point. In gunnery it is the rate of motion of the projectile at any 
 point in the trajectory around its longer axis. 
 
 Velocity of Translation. The rate of travel of the projectile in the direction 
 of its flight. 
 
 Vent. A small channel leading from the exterior to the powder chamber 
 for ignition of the powder charge. 
 
 Ventilators. The shafts or flues with movable covers for ventilation, 
 leading from interior galleries or air spaces and opening through the superior 
 slope. 
 
 Vernier. A small auxiliary scale enabling the measurement of hundredths 
 (or minutes and seconds) in connection with the main scale. 
 
 Vertical. Perpendicular to the plane of the horizon. The line of direction 
 through the center of the earth which is taken up by the plumb bob when 
 freely suspended by a line and allowed to come to rest. 
 
 Vertical Angle. An angle whose sides lie wholly in the vertical plane. 
 
 Vertical Base System. The system of range finding in which the azimuth 
 and range are determined by one position-finding instrument, located at either 
 of the (horizontal) base-end stations. The base line in this system extends 
 from the horizontal axis of the trunnions of the instrument vertically to mean 
 low-water level. The vertical base feature of the position-finding instrument 
 is used exclusively in this system. 
 
 Vessel Charts. Charts, usually blue prints, used in the identification of 
 targets. These charts consist of a system of vessel symbols giving a classifica- 
 tion in outline of warships in connection with funnels and masts. 
 
 Vertical Plane. Any plane which passes through a vertical line or con- 
 tains the line of the plumb bob when freely suspended by a line and allowed to 
 come to rest. 
 
 Vertex of an Angle. The point at which the sides of an angle meet. 
 
 Vessel Tracking. See TARGET OR VESSEL TRACKING. 
 
 Vickers-Maxim Gun. A rapid-fire gun of 1.457-inch caliber, usually called 
 "one-pounder." 
 
 Water Front. That portion of the defenses bearing upon the navigable 
 water areas that may be open to an enemy. 
 
 Wheeled Mount. See CARRIAGE or MOUNT. 
 
62 THE SERVICE OF COAST ARTILLERY 
 
 Winch. A machine operated by steam or other motive power, used on 
 mine planters for raising anchors and other heavy weights. It consists of a 
 drum, crank and the necessary gearing arranged for gaining power. 
 
 Wind-Component Indicator. A device used in primary stations of the 
 fire-control system to indicate to the operators of the range and deflection 
 boards, the reference numbers corresponding to the range and deflection com- 
 ponents of the wind as sent from the meteorological station. 
 
 Wind Vane. A device pertaining to the meteorological station, which 
 indicates the azimuth of the wind. 
 
 Wireless Station. A station located within the fortification in which wire- 
 less telegraph apparatus is installed. 
 
 Worm. A short threaded portion of a shaft, constituting an endless screw r 
 formed to mesh with a gear wheel. 
 
 Xylol. A colorless oily inflammable liquid, used in the bath for making 
 the 135-degree stability test of nitro-cellulose powder. 
 
 Zero. The point from which instruments, etc., are graduated. In com- 
 municating numerals it is a word used to indicate a cipher or naught. For 
 example, 340.30, would be expressed: "Three-four-zero-point-three-zero." 
 
 Zone Energy. A term denoting the relative armor-piercing power of 
 different guns. It is estimated by the number of foot-tons per inch of the 
 shot circumference. At the muzzle this power is a maximum, but owing to 
 the resistance of the air it gradually diminishes during flight. 
 
 Zone Mort. A French military expression denoting the space in which 
 the projectile has lost its strength, or is spent. 
 
 Zone of Fire. A term synonymous with specified fire areas. In mortar 
 firing it is the particular area in which projectiles fall for a given charge of 
 powder when the elevation is varied between minimum and maximum. The 
 several zones of fire for the 12-inch steel mortars are, 1st Zone, 2,210 to 2,970; 
 2d Zone, 2,600 to 3,431 ; 3d Zone, 3,070 to 4,030; 4th Zone, 3,631 to 4,800; 
 5th Zone, 4,429 to 5,940; 6th Zone, 5,520 to 7,476; 7th Zone, 7,027 to 9,250; 
 8th Zone, 8,758 to 12,019 yards. 
 
 In the case of rifle fire the defensive area between the guns and 4,000 yards 
 range, is known as the "inner defense zone/' between 4,000 and 8,000 yards 
 range, as the "middle defense zone;" and between 8,000 and 12,000 yards 
 range, as the "outer defense zone." 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 63 
 
 ABBREVIATIONS. 
 
 A.R.F All-round fire. 
 
 A.P Armor-piercing (shot or shell). 
 
 B' Primary station of a battery. 
 
 B" Secondary station of a battery. 
 
 B'" Supplementary station of a battery. 
 
 BC Battery commander's station. 
 
 B.C Battery commander. 
 
 B.L.L Bolt-locking lug. 
 
 B.L.R Breech-loading rifle. 
 
 C Battle commander's station. 
 
 C.A.C Coast artillery corps. 
 
 C.A.D Coast artillery district. 
 
 C.A.D.R Coast artillery drill regulations. 
 
 C.E Corps of engineers. 
 
 C.I Cast-iron (shot or shell). 
 
 D.C Disappearing carriage. 
 
 D.C.L.F Disappearing carriage limited fire. 
 
 D.P Deck piercing. 
 
 D.P.F Depression-position finder. 
 
 D.R Drill regulations. 
 
 D-S Driggs-Schroeder or Driggs-Seabury. 
 
 E Emergency station. 
 
 F' Primary station of a fire command. 
 
 F" Secondary station of a fire command. 
 
 F"' Supplementary station of a fire command. 
 
 F.A Frankford Arsenal; field artillery. 
 
 F.C Fire commander. 
 
 f.s Feet per second. 
 
 H.P.F Horizontal position finder. 
 
 I Illuminating light. 
 
 I. V Initial velocity. 
 
 M. . . . . Mortar; model. 
 
 M' Primary station of a mine command. 
 
 M" Secondary station of a mine command. 
 
 M"' Supplementary station of a mine command. 
 
 M'-M' Double primary station of a mine command. 
 
 M"-M" Double secondary station of a mine command, 
 
 Met Meteorological station. 
 
 Mi Mark one, meaning, first modification. 
 
 mi Miles. 
 
 M.L.R Muzzle-loading rifle. 
 
 M.V Muzzle velocity. 
 
 O Separate observing room. 
 
 O.D Ordnance department. 
 
 P Separate plotting room. 
 
 P. . . . Pressure. 
 
64 THE SERVICE OF COAST ARTILLERY 
 
 P.S.B Post telephone switchboard. 
 
 Proj Projectile. 
 
 R Rifle. 
 
 R.F Rapid fire. 
 
 S Searchlight. 
 
 S.E Striking Energy. 
 
 SS Signal station. 
 
 S.V Striking velocity. 
 
 Sub. Cal Sub-caliber. 
 
 T Tide station. 
 
 T Torpedo. 
 
 T.D Torpedo-detonating (Pierce fuse). 
 
 T. I. Bell Time-interval bell. 
 
 V Velocity. 
 
 W Weight. 
 
 W.D War department. 
 
 WS Wireless station. 
 
 Q.F Quick-firing. 
 
 Q.M.D Quartermaster department. 
 
 W.& S Warner & Swasey. 
 
DEFINITIONS, ABBREVIATIONS AND SIGNS 65 
 
 SIGNS. 
 
 Primary Station of a Battery (o) 
 
 Secondary Station of a Battery I g"| 
 
 Supplementary Srat/on of a Battery I g'"| 
 
 Battery Commander's Station (BCi 
 
 Battle Commander's Statioh T ... (^CB 
 
 Emergancy Station ofa Battery. C^\ 
 
 Primary Station of a F/re Command (F^ 
 
 Secondary Station of a Fire Command. I p" I 
 
 Supplementary Station of a F/re Command I p'"j 
 
 Illuminating Light I | I 
 
 Primary Station of a Mine Command. . Mvn 
 
 Secondary Station of a Mine Command ___________________________ |M"| 
 
 Supplementary Station of a M/ne Command. _____________________ \M" f \ 
 
 Doub/e Primary Station ofaMine Command. _______________________ (M^Cm 
 
 Double Secondary Station of a Mine Command. __________________ |M"-|-M"| 
 
 Meteorological Station ______________________________________________ |[7Tj| 
 
 Separate Observing Room ______________________ , ____________________ ^0^ 
 
 Separate P/ott/ng Room ______________________________________ ^ _______ /^\ 
 
 Post Telephone Switchboard ______ ^ ____________________________ pv/j 
 
 Searchlight- _____________________________________ _________ [sj 
 
 Searchlight 36 inch. ___________________ __ _______ \36\ 
 
 Searchlight 6O inch _______ _______________________ 160) 
 
 Tide Station. ______________________ ! ______________________ Il 
 
 Signal 'Station ________________________________ _ _______________ || - - 
 
 Wire/ess Station,... ______ 
 
CHAPTER II 
 THEORY AND PRINCIPLES OF COAST DEFENSE 
 
 THE fundamental object of coast defense in the general accepta- 
 tion of the term is to afford suitable means of protection to the coast 
 line with a view to resisting invasion by an enemy. Harbor defense 
 is that branch of coast defense which has for its object the protection 
 of important harbors and cities situated on or near the sea, as well as 
 the securing of adequate anchorages and bases for the navy in time of 
 hostilities. Thus coast defense in the largest sense becomes not only 
 protective in its strength but a productive contributor to the nation's 
 ability to carry on war beyond her coast line. 
 
 It is not practicable to fortify the entire extent of the coast in 
 such a manner that an enemy in command of the sea could not land 
 upon some portion of it. The cost of such an undertaking would 
 be excessive, and the maintenance and number of men required as a 
 personnel would make it prohibitive. It is essential, however, that 
 certain selected points shall be permanently fortified, and in their 
 selection the following conditions should be considered: 
 
 First. The value of the property accumulated at such points and 
 the importance of this property to the function of commercial pursuits, 
 as well as the value of such points to the enemy. 
 
 Second. The importance of defending convenient, well-protected 
 and sheltered harbors or anchorages for naval and military bases, and 
 preventing the occupation of such points by the enemy. 
 
 The means of defending the coast line are divided into two general 
 units. The first of these comprehends the fortifications manned by the 
 Coast Artillery troops proper; which include the personnel of the 
 Regular Coast Artillery Corps, assisted by the Coast Artillery Reserve. 
 The fortifications are protected against attack of small landing parties, 
 by infantry troops, called Coast Artillery Supports. 
 
 The second general unit comprehends the troops necessary to pro- 
 tect unfortified portions of the coast line. 
 
 The functions of the navy are not within the scope of this work. 
 
 66 
 
THEORY AND PRINCIPLES OF COAST DEFENSE 67 
 
 However, the navy is prepared, by reason of its mobility, to carry on 
 offensive warfare. The means of protecting unfortified portions of the 
 coast line are also tactically offensive in their action, while the harbor 
 defenses or fortifications are purely defensive. Ships of the line and 
 smaller craft such as monitors, scout ships, torpedo boats and submarine 
 boats may be attached to the land forts and assigned as floating 
 defenses unless it is desirable that they be otherwise engaged. Their 
 functions consist of assisting the artillery defense at any point or points 
 required in the plans of defense. 
 
 The functions of the coast artillery troops proper, are the manning 
 and operation of the armament of coast forts, the control of 'the sub- 
 marine defense and the location of such marine obstructions as may 
 be found necessary at the entrance of harbors. 
 
 The coast artillery supports are charged with the duty of flank and 
 land front security and information, as well as the protection of the 
 fortifications against attack by small parties of the enemy landed close 
 to their flanks, thus making sure that the coast artillery troops proper 
 shall not be harassed or annoyed in the performance of their proper 
 duties. 
 
 The function of the coast guard is the protection of unfortified 
 portions of the coast line lying adjacent to fortifications, such protec- 
 tion being sufficient to resist the most powerful landing parties of the 
 enemy and prevent the capture of the fortifications, together with the 
 cities and harbors they defend. In this duty they will be supported 
 by field armies. 
 
 THE THEORY OF DEFENSE 
 
 Before entering into a discussion of the various phases of fortress 
 warfare it is appropriate to weigh the efficacy of fire to be delivered 
 by the two combatants. It is evident that fire from ships cannot be 
 delivered at as great an accurate range as that available to the guns of 
 coast fortifications. The enemy is at a disadvantge in not being able 
 to use the higher elevations with any degree of accuracy, which neces- 
 sarily reduces his maximum effective range. In this connection atten- 
 tion may be called to the fact that the turret openings in the later 
 types of battleships allow a twenty-degree elevation, which, with a 
 12-inch gun will give an extreme range of something like 21,000 yards. 
 It is conceded, however, that accuracy cannot be obtained at a range 
 exceeding say 10,000 to 12,000 yards, and this requires the ability to 
 see the target, which would be extremely difficult if modern seacoast 
 
68 THE SERVICE OF COAST ARTILLERY 
 
 batteries be the targets. On the other hand, the maximum accurate 
 effective range of the land defenses is approximately 12,000 yards, or 
 about seven miles, with moving targets easily identified. 
 
 It may be stated that the relative value of a battery ashore to that 
 of one afloat is not a matter of gun against gun; it is a function of the 
 relative degree of protection which each enjoys, as well as the volume 
 of fire each can deliver. The protection afforded the battery of a 
 seacoast fortification is much greater than that afforded the guns of 
 ships. 
 
 The protection of a large-caliber gun mounted afloat, with its 
 mechanism and ammunition, is limited to the necessities of compromise 
 as to space and weight which pertain to all marine construction, while 
 that of the gun ashore is limited only by that of cost. Apart from the 
 question of its immediate protection, the gun afloat is necessarily 
 dependent upon its platform, that is, upon the safety of the ship upon 
 which it is mounted, and this is vulnerable throughout its entire under- 
 water body to a mine or submarine boat, and, to a lesser degree, to shot 
 and shell. If a ship is sunk the guns which it carries, together with the 
 mobility which constitutes their special value, are destroyed and lost 
 to their country for the remainder of the war. 
 
 It is right that a war vessel should take this risk when involved in 
 a contest against her proper antagonist the warships of the enemy 
 but it is indeed an exceptional case when a vessel should accept or 
 involve herself in a contest with shore batteries and mine fields. The 
 cost even of success in such a contest would probably be too great. 
 Again, fortifications have a decided advantage in the means afforded 
 them to determine the necessary data for laying the guns, while owing 
 to the shortness of base lines in the range-finding system afloat, the 
 data determined therefrom must necessarily be less effective than that 
 obtained by the longer base lines used ashore. It must also be remem- 
 bered that the shore gun, with its emplacement and disappearing car- 
 riage, is completely protected from the fire of the gun afloat and in most 
 cases is entirely hidden from view, at the same time having a clear 
 definition of the target. 
 
 ATTACKS FROM THE SEA 
 
 In order that definite plans of defense may be formulated, it is 
 necessary to assume that the enemy will make one of the several forms 
 of attack herein outlined: 
 
 Frontal Attack. If it is assumed that the enemy will make a 
 
THEORY AND PRINCIPLES OF COAST DEFENSE 69 
 
 frontal attack, that is, will attempt after bombardment, to run by 
 the fortifications, the best means and principles to follow would neces- 
 sarily be to have fortifications strong enough to repel such an attempt 
 by graded artillery fire in the outer defense zones. To conduct an 
 effective bombardment the enemy's vessels would in all probability 
 steam successively to a buoy anchored at a known distance from the 
 works, deliver their fire and go out again. 
 
 It is scarcely probable, however, that a frontal attack would take 
 place at any of the more strongly fortified positions. Nevertheless, if 
 the armament at these points compels the enemy to land in order to 
 effect their capture, such armament is fulfilling its proper function in 
 the role of defense. 
 
 This form of attack would be impracticable until the enemy had 
 obtained command of the sea. As long as such command was in doubt, 
 it would be his purpose to seek our fleet and engage it. If unsuccessful, 
 it is hardly to be expected that he would attempt a frontal attack 
 upon any fortification with the intent of entering a fortified harbor. 
 A frontal attack must, therefore, take up such form more for the purpose 
 of locating positions of the batteries than an attempt to run by. 
 
 Moreover, if a direct fr/mtal attack of the enemy should be successful 
 in silencing the fortifications, neither the ships themselves nor their 
 personnel have the requisite tactical organization to complete the 
 victory by landing. They are not able to supply the necessary number 
 of men to take actual physical possession of the fortified points secured, 
 capture the guns and other property, guard the large number of prisoners 
 taken, and overcome the defense of the coast artillery supports, the 
 coast guard and other available troops. It is therefore necessary that 
 the enemy's army be present and ready to land when the attack is 
 negotiated, and such a condition is not likely to exist until after com- 
 mand of the sea had been obtained. 
 
 The " Run By." The object of a fleet in attempting to run by 
 fortifications would be to enable it to enter a harbor and operate in the 
 rear, as well as to make such a blow felt by the destruction or capture 
 of the property in such harbors. The matter of a " run by " has become 
 a most difficult problem for a fleet and especially a foreign fleet oper- 
 ating against the United States since the development of the present 
 mine system. Without the mine fields, it is conceded as being possible 
 for the fleet at full speed, at night and under favorable conditions of 
 smoke, fog, etc., to run by the batteries without being discovered, or 
 without the batteries being able to deliver an effective and deliberate 
 fire. To accomplish this under present conditions, however, all regard 
 
70 THE SERVICE OF COAST ARTILLERY 
 
 for the mine fields must be left out of consideration. They must be 
 made ineffective by counter mining the success of which is indeed 
 very doubtful, if at all effective or by cutting the cables beforehand. 
 The location of the mine fields will always be kept a secret, so the 
 matter of cable cutting must necessarily be done in order to assure 
 success, although how such an operation will be successful is extremely 
 hard to outline when consideration is given to the authorized floating 
 defenses. The only other means available for the enemy would be that 
 of dragging for cables, in which event it would be necessary, for success, 
 to cover almost the entire ground occupied by the mines, and it is 
 hardly possible that this operation would be effective under the condi- 
 tions of security maintained by the floating and shore defenses, and 
 the character of the mines themselves. 
 
 Leaving out of consideration the matter of fog, etc., the coast 
 batteries are practically as effective at night with the searchlights in 
 action, as they are in the daytime; and for an enemy to effect a "run 
 by," it must necessarily first put the searchlights out of action. These, 
 together with the range-finding stations, and other fire-control stations, 
 while apt to be rendered unserviceable by a chance shot, can only be 
 successfully destroyed by landing parties. 
 
 It may therefore be stated that a successful " run by " can only be 
 accomplished when the mine fields have been put out of action. The 
 days of the "run by" fortifications, like those of charges by massed 
 bodies of infantry, belong to the warfare of the past rather than to that 
 of the future. 
 
 Landings. During the second period of a war, or after the navy 
 had been rendered ineffective, the object of a victorious enemy would 
 probably be to obtain final decision upon the issues by invading 
 United States territory with landing parties, or troops landed from 
 transports, etc. There are many points on the coast at which an army 
 might be landed, but to make such invasion effective and at all perma- 
 nent, a suitable base must be obtained, that is, possession taken of a 
 good harbor with terminal facilities for supplies, etc. 
 
 From both military and naval standpoints, such a port must be 
 captured or established by the enemy before he can make his occupation 
 effective and secure. It is reasonable to suppose he would try to effect 
 a landing, and by that means attempt to capture a fortified point, rather 
 than attempt it from the water side, as under the conditions of this 
 assumption it is supposed a combination of armament and mines will 
 effectively prevent any modern navy from entering a fortified harbor. 
 
 Bearing in mind historical cases of attacks on fortifications, namely, 
 
THEORY AND PRINCIPLES OF COAST DEFENSE 71 
 
 Sevastopol and Port Arthur, the above assumption would seem reason- 
 able, as both of these fortifications were captured from the land side. 
 The allied fleets in the first instance, and the Japanese in the second, 
 had command of the sea, maintained a blockade and kept their com- 
 munications open, but left the reduction of the strongholds to the 
 slow but certain process of siege operations. At Sevastopol the British 
 and French men-of-war in concert on one occasion, attacked the harbor 
 forts ineffectively and with considerable loss to themselves. 
 
 More recently at Port Arthur, the Japanese vessels did not even 
 expose themselves to the fire of the Russian land batteries, but waited 
 for their army to reduce the fortifications from the land side. 
 
 The general considerations attending combat with landing parties, 
 belong to the functions of the coast artillery supports, the coast guard 
 and the field army. It is one of the problems that confront comman- 
 ders of mobile troops. 
 
 It is practically safe to assume that the enemy would attempt to 
 effect a landing only under one of three conditions. 
 
 The first of these would be when he found a suitable unfortified 
 place, uncovered or but sparsely occupied by troops, and so situated 
 that it would be impossible to mobilize an army from the surrounding 
 country of such strength, and in time, to defend or prevent the landing. 
 Such a point might be found along the coast, particularly if the plans 
 of the enemy were drawn with marked strategical insight. In other 
 words, with the real idea of landing at the north a series of feints or 
 false landings, apparently in force, might be demonstrated at the south, 
 or vice versa. 
 
 At first glance we might consider such a line of reasoning as unsound, 
 if not altogether impossible, under the assumption that the force neces- 
 sary to accomplish such an enterprise would prevent its execution, 
 particularly in view of the facilities for information and transportation 
 afforded us by reason of our commercial telegraphs, railways, etc. 
 Indeed, it would be impracticable, if we were contending with a second- 
 class power or one or moderate limits of credit or men. However, 
 before Napoleon, in the Marengo campaign, emerged from the Great 
 St. Bernard Pass, after the passage across the Alps, few military special- 
 ists could have been found who would have admitted the possibility or 
 likelihood of such an enterprise. The late Colonel Wagner, in com- 
 menting upon this feat, remarks that it would have been impossible at 
 the present time with the facilities now enjoyed for information. He 
 continues, however, that in all probability Napoleon would have won 
 with as much ease to-day as he did yesterday; and the facts that 
 
72 THE SERVICE OF COAST ARTILLERY 
 
 front us are that with all our enterprise and ingenuity, our cables, 
 telegraphs, newspapers and fleets, a few years ago Cervera's fleet came 
 over from Spain and unknown to us sailed into the harbor of Santiago 
 de Cuba without being detected and without the slightest material 
 strategic attempt being made to turn our heads to any other point 
 than Cuba. 
 
 The questions of time and means are undoubtedly the leading things 
 to be considered. Landings in force have the advantage of a powerful 
 covering base, namely, the protecting fleet. Against this base no force 
 of mobile troops would be effective. The length of time necessary to 
 bring up and land an army with its necessary impedimenta is an 
 extremely difficult problem to solve. The period, however, should not 
 be in excess of the time required for the United States to mobilize a 
 force strong enough to give it combat of enough effectiveness to prevent 
 its advance to the nearest fortified point, for with the latter taken, the 
 fleet kept until that time beyond the range of the shore batteries 
 would sail quietly in and anchor. 
 
 With our navy destroyed or at points not accessible, and barring 
 storms that might temporarily dislodge its base, the danger from landings 
 in force may be considered as of grave import. 
 
 The second condition under which landings could be effected on 
 unfortified portions of the coast, would be after bombardment by the 
 fleet. The means of protection against such fire is a function of the 
 engineers, and a consideration to be dealt with in the plans of defense 
 of unfortified portions of the coast. The duty of the personnel, how- 
 ever, of the mobile army, coast guard, and coast artillery supports are 
 attached closely to the means provided in these plans. Their func- 
 tions might be characterized as those of a purely tactical nature, 
 while the plans themselves belong rather to the science of strategy. 
 In other words, no plan of defense could go to the length of explaining 
 exact tactical dispositions. These must of necessity be left to the 
 professional abilities of the commanding officer on the ground. Hence, 
 in preparing himself, his officers and men, for the duty to be performed, 
 there are set rules that should be studied theoretically and developed, 
 if possible during peace time. It has been said, with much good 
 reason, that it is not well to await an ideal condition of affairs in 
 military instruction, but to make the best of things as they are, to 
 economize time and utilize means as effectively as surrounding 
 circumstances admit. 
 
THEORY AND PRINCIPLES OF COAST DEFENSE 73 
 
 PLAN OF LAND DEFENSE 
 
 Before drawing up the plan of land defense for the locality considered, 
 it will be necessary to make a careful examination of the ground in the 
 vicinity with reference to the following details: 
 
 (a) The best general line to be occupied by the infantry. 
 
 (6) The best positions for mobile artillery. 
 
 (c) The most favorable lines of advance for the enemy, should he 
 succeed in effecting a landing. 
 
 (d) The weak flank of the position, and the most favorable ground 
 for counter attack. 
 
 (e) Ground for the reserve, for the general reserve, for mounted 
 troops, and for rallying positions in case of retreat. 
 
 In order to conceal the main position as long as possible, advanced 
 lines may be established in front of the main trenches. Trenches should 
 never be constructed so as to bring the troops against the sky line. 
 
 FIELD COMBAT 
 
 The established rules of field combat, briefly, are as follows: An 
 engagement generally presents three distinct phases, namely, the 
 preparatory stage, the decisive action and the completion. 
 
 The corresponding distribution of troops should be such as to carry 
 out the following plan: 
 
 (a) To engage the enemy, wherever he may attempt to land, with 
 sufficient troops to stop him. 
 
 (6) To withhold a part of the available forces for a powerful effect 
 at the decisive point or moment. 
 
 (c) To maintain a reserve, screened from the enemy's view and 
 protected from loss, to take part in a vigorous pursuit in case of success, 
 or to avert complete disaster by disputing his advance in case of failure. 
 
 In combat against landings in force these phases would not neces- 
 sarily be fully developed ; the preparatory stage might be brief and the 
 decisive attack begun suddenly. Such combat is necessarily offensive 
 and has the advantage of the choice of position, which should be se- 
 lected so as to afford shelter to the defenders from bombardment and if 
 possible screen them from view. Ranges in the foreground should be 
 measured and marked. 
 
 The manner of occupying a position will vary with the nature of the 
 ground, and with the strength and character of the troops available. 
 It is therefore impracticable to apply fixed rules. 
 
74 THE SERVICE OF COAST ARTILLERY 
 
 The troops available will generally be divided into two principal 
 parts one for occupation of the intrenchments, including local reserves ; 
 and the other the general reserve for reinforcing parts of the line and 
 for the delivery of the decisive counter-attack or of the offensive return. 
 
 Should the enemy succeed in gaining a position threatening the line 
 of defense, or penetrate that line, a counter attack becomes imperative, 
 and the sooner it is made the better, so that the enemy may not have 
 time to strengthen the ground he has gained. Such local counter- 
 attacks are the special duty of the local reserves; they are made upon 
 the initiative of officers in command of subdivisions of the defense. 
 
 Should the enemy attempt an assault he will be met with rapid fire 
 and a counter charge with fixed bayonets. Every available man should 
 be brought up and the enemy struck in flank if possible. If the de- 
 fenders are successful and the assailants abandon the offensive the 
 enemy should be pursued vigorously. If retreat on the part of the de- 
 fenders is necessary, some artillery and intact infantry should occupy 
 the rallying position and the remainder of the troops endeavor to gain 
 the cover of the rallying position and there reorganize. 
 
 FIRE IN FIELD COMBAT 
 
 Fire direction is a function of the company commanders. Their 
 instructions as to the general direction and character of the fight as 
 well as the part their companies are to take in it are received from the 
 next higher commanders. From the beginning of the action collective 
 concentrated controlled fire should be delivered. To each platoon and 
 section there should be allotted a certain subdivision of the enemy's 
 line at which to fire, so that the distribution may be evenly divided 
 along the assailant's front. 
 
 Fire control, in so far as it pertains to seeing that the orders for fire 
 are implicitly obeyed, that proper ranges are used, that men are sup- 
 plied with ammunition, that ammunition is not wasted and that the 
 fire is concentrated on the portion of the enemy's line designated, is the 
 duty of the lieutenants and non-commissioned officers. 
 
 NIGHT ATTACKS 
 
 The third condition under which an enemy would endeavor to effect 
 a landing would be either at night or in foggy weather. In discussing 
 this condition the night operations of the defense should be considered. 
 
THEORY AND PRINCIPLES OF COAST DEFENSE 75 
 
 On the assumption that the enemy would attempt to land, outside of 
 the range of the guns of permanent fortifications, night operations of the 
 defense should be studied with a view of rapid concentration of troops 
 for the decisive attack. Nothing but the most general rules for the 
 defensive can be prescribed. The outposts must exercise the utmost 
 vigilance, and the dispositions must be such that the line of resistance 
 can be stubbornly held and quickly reenforced. Whenever practicable 
 the position should be covered with obstacles, and successive echelons 
 placed in positions favorable for the assumption of the offensive. 
 Arrangements should be made to enable them to form their ranks with 
 the least possible delay. 
 
 Smoking, talking, laughing and other noises in ranks should be 
 prohibited. The watches of all officers should be set with those of the 
 commanding officer. 
 
 The infantry should withhold its fire as long as possible and open 
 with volleys. 
 
 Small Landing Parties differ from landings in force in that their 
 objects are: (1) to procure information as to the position and strength 
 of the land defense, condition of the land front, the armament, and 
 morale, etc. ; (2) to annoy the garrison by attacks in the nature of recon- 
 naissance in force; (3) to attempt gaining admission to the fortifica- 
 tions by stealth or subterfuge for the purpose of destroying power 
 plants, searchlights, etc. 
 
 Men landing from boats under these conditions are always at a 
 disadvantage and are especially subject to severe loss from the fire 
 of the movable armament assigned to fortifications, as well as the rifle 
 fire of the coast artillery supports. Indeed, such landing parties have 
 little or no importance if an efficient system of outposts and patrols is 
 constantly maintained. 
 
CHAPTER III 
 ORGANIZATION AND PERSONNEL 
 
 THE Regular Coast Artillery troops are organized as a corps, and 
 assigned to artillery districts. The coast artillery reserve is composed 
 of regiments, battalions and companies of the organized militia perma- 
 nently assigned to fortifications at or adjacent to their home stations. 
 The regular Coast Artillery troops and the coast artillery reserve together 
 constitute the coast artillery troops proper. 
 
 Coast artillery supports are not a part of the Coast Artillery troops 
 proper. They consist of mobile troops of the line of the Army. When 
 assigned as such they are under the immediate orders of the Artillery 
 District Commander. 
 
 The coast guard is not a part of the coast artillery troops proper. It 
 consists of mobile troops of the line of the army. It is placed at 
 strategical points near fortified portions of the coast line. It is organ- 
 ized the same as a field army. 
 
 TACTICAL 
 
 For tactical purposes artillery districts are divided into Battle 
 Commands, Fire Commands, Mine Commands, and Battery Com- 
 mands. The function of each is described in the DEFINITIONS. 
 
 ADMINISTRATIVE 
 
 For purposes of drill and administrative organization the Regular 
 Coast Artillery Corps is divided into companies and assigned to coast 
 artillery forts or posts. The strength of companies is prescribed in 
 regulations. There is no battalion or regimental organization, except 
 in the coast artillery reserve, when at their home stations, where pro- 
 visional regimental or battalion organization is maintained. 
 
 In the regular service the Company, Post, District, Department, 
 and War Department constitute the administrative channel. 
 
ORGANIZATION AND PERSONNEL 77 
 
 PERSONNEL 
 
 The personnel of the Regular Coast Artillery Corps consists of a 
 Chief of Coast Artillery, officers assigned to duty at the War Depart- 
 ment, officers assigned to the Coast Artillery Board, officers assigned to 
 the Coast Artillery School, officers assigned to the headquarters of each 
 division or department in which coast artillery is located, and other 
 officers and enlisted men designated as follows: 
 
 District Commander, Battle Commander, Fire Commander, Mine 
 Commander, Battery Commander, Range Officer, Emplacement Officer, 
 Communication Officer, Searchlight Officer, Property Officer, Mine- 
 Field Officer. The duties of each will be found in the DEFINITIONS. 
 
 STAFF OFFICERS 
 
 For administrative purposes coast artillery officers are assigned to 
 the following staff positions: At each headquarters of an artillery 
 district, an Artillery District Adjutant, District Artillery Engineer, 
 Artillery District Ordnance Officer, and Artillery District Quarter- 
 master. 
 
 At coast artillery forts or posts the corresponding post staff officers 
 are appointed. The duties of each will be found in the DEFINITIONS. 
 
 COAST ARTILLERY RESERVE OFFICERS 
 
 A coast artillery reserve officer assigned to any of the commands 
 enumerated above, when taking part in drills or exercises at a coast 
 artillery fort or post, or when mustered into the service of the United 
 States, performs the same duties so far as compatible with those noted 
 for regular officers, unless otherwise directed by competent authority. 
 
 If a regular and a reserve officer of equal rank are acting together, as 
 contemplated in the preceding paragraph, the reserve officer would act 
 as assistant to the regular officer. In cases where regular and reserve 
 officers are assembled together on duty, reserve officers take precedence 
 next after all regular officers of the same rank, irrespective of the 
 seniority of such reserve officers. 
 
 COMMANDS APPROPRIATE TO GRADE 
 
 Colonels of coast artillery are usually assigned to staff duty at the 
 War Department, on the Coast Artillery Board, as commandants of the 
 Coast Artillery School, and as artillery district commanders. 
 
78 THE SERVICE OF COAST ARTILLERY 
 
 Lieutenant-colonels as artillery district commanders, battle, fire, 
 or mine commanders, and commanders of coast artillery forts or posts. 
 
 Majors as battle commanders, fire or mine commanders, and as 
 commanders of coast artillery forts or posts. 
 
 Captains as battery commanders and in command of mine, gun, or 
 mortar companies. Also as commanders of small coast artillery forts 
 or posts. 
 
 Lieutenants as communication, searchlight, property, mine-field, 
 casemate, range or emplacement officers; assigned to companies, or 
 staff duty. 
 
 All field and line officers of coast artillery are subject to detail as 
 staff officers or on special duty. 
 
 NON-COMMISSIONED OFFICERS, ETC. 
 
 In the Coast Artillery Corps the following non-commissioned officers 
 and graded men are authorized: 
 
 Sergeant Major, Senior Grade; Sergeant Major, Junior Grade; First 
 Sergeant; Quartermaster Sergeant; Sergeant; and Corporal. 
 
 In addition to the above the following ratings are authorized: 
 
 Master Electrician; Engineer; Electrician Sergeant, First Class; 
 Electrician Sergeant, Second Class; Master Gunner; Fireman; Gunner, 
 First Class; Gunner, Second Class; Gun Commander; Gun Pointer; 
 Plotter; Observer, First Class; Observer, Second Class; Casemate 
 Electrician; Chief Planter; Chief Loader. The duties of each will be 
 found in the DEFINITIONS. 
 
 Other positions to which the enlisted personnel are detailed are as 
 follows: Mechanic; Range-Setter; Meteorological Observer; Tide- 
 Observer; Assistant Plotter; Range-correction Computer; Deflection- 
 Computer; Primary Arm-Setter; Secondary Arm-Setter; Telauto- 
 graph Operator; Telephone Operator; Range Keeper; *Reader; Search- 
 light Operator; Searchlight Watcher; Wireless Operator; Recorder; 
 Orderly; Musician; Cook. 
 
 Chiefs are assigned to the various sections, detachments and details 
 shown in the drill regulations. 
 
CHAPTER IV 
 GUNNERY AND BALLISTICS 
 
 IN this chapter it is intended to make the ballistic formulas which 
 are necessary to the practical artilleryman less formidable than the 
 term implies, with the hope that gunners will not instinctively avoid 
 them. One need not be an expert mathematician in order to be a 
 practical gunner and successfully apply ballistic formula. 
 
 As concerns the artilleryman, ballistics is divided into two classes: 
 First, that which relates to the behavior of the projectile in the gun, 
 known as " Interior Ballistics/' and second, that which deals with the 
 projectile's action in its flight through the air, called " Exterior Bal- 
 listics." It is believed that a comprehensive understanding will be 
 had of each, if the explanation is preceded by a few words on gunnery, 
 or the art and science of operating the guns to which both Interior 
 and Exterior Ballistics are to be applied. 
 
 GUNNERY 
 
 The Gun. A gun may be called the simplest form of gas engine. 
 To move the projectile through the bore requires the expenditure of 
 energy. The energy which produces the force to propel the projectile 
 is heat, and the heat carrier is gaseous, hence the term " gas engine." 
 
 This machine or gun is made entirely of steel; its essential parts 
 being a tube, jacket, breech-bushing, and the A, B, C and D rows of 
 hoops. The number of hoops has been successively reduced 'and their 
 length increased, as steel manufacturers have become able to make 
 larger forgings; and this increase in the length of hoops has greatly 
 augmented the efficiency of guns. 
 
 The tube is enveloped by a jacket and the several rows of hoops; 
 it is inserted into the jacket from the breech end and a shoulder upon 
 its exterior abuts against a corresponding one near the front end of the 
 jacket. The outside diameter of the tube is successively reduced from 
 the front end of the jacket, to the muzzle, by 6 shoulders. The jacket 
 projects to the rear of the tube a sufficient distance to allow room for the 
 
 79 
 
THE SERVICE OF COAST ARTILLERY 
 
 screw box, or breech recess. Figures 
 1, 2 and 3 illustrate the method of 
 construction of seacoast cannon. 
 The 8-inch gun, model 1888 (Fig. 1), 
 is here used for purposes of demon- 
 stration, by reason of its being the 
 first of the modern types of built-up 
 gun construction. In this model 
 the jacket and C-l hoop, the C-l and 
 C-2 hoops, and the C-2 and C-3 
 hoops, are not directly locked to- 
 gether. The remaining C-hoops, three 
 in number, are locked together with 
 a lip on the forward hoop by over- 
 lapping a lip on the rear one, the 
 contact surface of the rear one being 
 a frustum of a cone, with the smaller 
 base at the breech end. 
 
 In front of the C-5 hoop is a key 
 ring, which being part in a groove 
 of the tube and part in front of the 
 hoop, prevents forward motion of 
 any of the C-hoops in the rear. The 
 C-6 hoop is fastened to the tube by 
 three radial securing pins. Overlap- 
 ping the front end of the jacket and 
 covering the C-l, C-2 and part of 
 the C-3 hoops, there are three 
 D-hoops, locked together by lips 
 similar to those on the C-hoops and 
 having three radial securing pins 
 passing into the D-3 and the C-3 
 hoops. Five A-hoops, the second of 
 w T hich is the trunnion hoop, cover 
 the jacket and part of the D-l hoop. 
 
 The trunnion hoop has the shock 
 of discharge transmitted to it 
 through a shoulder on the jacket. 
 Into the portion of the jacket pro- 
 jecting beyond the breech and the 
 tube is screwed the steel breech 
 
GUNNERY AND BALLISTICS 
 
 81 
 
 bushing, which on its interior is threaded to receive the breechblock. 
 The breech bushing is secured against unscrewing by four spline screws, 
 halved into it and the jacket. A space of 0.05 inch is left between the 
 breech of the tube and the breech bushing. At the interior of this 
 
 HoopsArow 
 
 j / Hoops B row 
 
 "\\ Ijffify 
 
 \ x 1 ^'"^ 1 
 
 /?' 24* 36" 48 
 
 FIG. 2. 
 
 
 
 joint there is a copper ring, given a compression of 0.01 inch between 
 the tube and bushing. 
 
 The trunnion band is also a hoop, by which connection is made with 
 the carriage of the piece. The trunnions are the cylindrical arms 
 supporting the piece when mounted. 
 
 j r-Breech Bushing. 
 ^Copoer Ricking 
 __[ r~^ ? -^ 
 
 55^ 
 
 >/ >"^-/?V^V / >P J 
 
 ^L 
 
 a/ y je' 
 
 ! Jacket! ^Gas Check 5eal:\ \/fc^/%'-Trunnion Hoop. 
 
 Centering Slope- -' 
 k /4/./2S' 
 
 FIG. 3. 
 
 The rim bases are the shoulders uniting the trunnions with the 
 trunnion band. The face of the trunnion and the face of the rim bases 
 are their end surfaces. The section of the gun between the rear of the 
 trunnion band and the breechplate is called the breech reinforce, while 
 
82 THE SERVICE OF COAST ARTILLERY 
 
 the section between the front of the trunnion band and the front of the 
 muzzle is called the chase. 
 
 The bore is the hollow portion in the center of the piece, and is 
 subdivided into the following parts, commencing at the breech end 
 of the tube: Gas check seat (conical), powder chamber (cylindrical), 
 centering slope, forcing cone, shot chamber and the main bore. The 
 centering slope is used for the purpose of bringing the axis of the pro- 
 jectile to coincide with the axis of the bore, the copper rotating band 
 on the projectile also stopping it at its proper distance forward, by 
 seating it in the slope. At the junction of this slope and the forcing 
 cone the rifling commences, beginning flat and gradually increasing 
 to its proper height and gauge. The tube is closed at the breech end 
 of the gun by the breechblock. 
 
 THE BREECH MECHANISM 
 
 The breech mechanism of the gun considered consists of the breech- 
 block, obturator,' breechplate, rotating crank, tray latch, securing 
 latch and hinge pin. 
 
 In studying the breech mechanism, probably the best method is to 
 dismantle it. The illustration shown in Fig. 4 gives an excellent idea 
 of the location of parts herein described, as well as an illustrated nomen- 
 clature of this model of breech. The principal parts of the breech- 
 blocks are 3 threaded sectors, 3 slotted sectors, 2 guide grooves, vent 
 cover and translating stud. The block is threaded with a V thread 
 with rounded top; the rear portion is left unthreaded to prevent the 
 entrance of dust. The threaded portion is divided into 6 equal seg- 
 ments, 3 threaded and 3 slotted. The 2 guide grooves are cut in the 
 bottom slotted sector 30 degrees each side of the element of the unlocked 
 block ; they fit upon, and pass over the rails of the console or tray when 
 the block is drawn to the rear. In the model considered, two handles 
 are cut out of the solid metal upon the rear end of the block, for use in 
 case of failure of the mechanism. 
 
 The vent cover is a steel arm, mounted in a mortise in the block, 
 and suspended on the vent-cover screw. By means of a shoulder in the 
 bronze bushing, which is stationary in the breechplate, the vent cover 
 is constrained to move when the block is rotated, so as to cover the vent, 
 over which it remains until the block is returned to is locked position. 
 The translating stud, attached to the rear face of the block, by a screw 
 in a slotted seat, projects radially from the face of the block. When 
 
GUNNERY AND BALLISTICS 
 
 83 
 
84 THE SERVICE OF COAST ARTILLERY 
 
 the latter is rotated the 60 degrees necessary to unlock it the stud 
 revolves into the groove in the translating roller. 
 
 The obturator consists of the mushroom head and stem, gas-check 
 pad, front and rear exterior split rings, filling-in disk, obturator-spindle 
 nut, locking-nut and the obturator-spindle washers. The vent is 
 drilled through the spindle in front of which there is a copper bushing- 
 plug forced into an undercut on the face of the mushroom head; in 
 passing through this plug, the vent contracts from 0.2 to 0.1 inch, or 
 one-tenth of an inch. This bushing may be replaced when badly 
 eroded. The rear end of the vent channel (old model) is elongated 
 and threaded for an obturating primer, used to ignite the charge. 
 
 The gas-check pad is made of asbestos and tallow, inclosed in a 
 canvas cover. 
 
 The exterior split rings are of steel, split diagonally through one 
 side. They are slightly larger than the conical seat and are sprung 
 together in being forced into place. 
 
 The interior ring is of similar construction but slightly smaller than 
 the spindle. The filling-in disk acts as a washer in the rear of the pad, 
 a shoulder on its front face supports the interior edge of the rear split- 
 ring, and a fillet on the rear face of the mushroom-head performs the 
 same office for the front split-ring. 
 
 The obturator-spindle nut is screwed on the rear end of the stem 
 with a right-hand thread; it draws the obturator head and gas check 
 to a bearing against the face of the block; it abuts against the spindle 
 washers, and has under its front edge a thin steel spring washer designed 
 to keep out dust. In rear of the spindle nut is a locking nut, screwed 
 on with a left-hand thread, designed to prevent the spindle from 
 unscrewing. 
 
 The four obturator-spindle washers are alternately bronze and 
 steel. The object of having one of bronze and one of steel is to reduce 
 friction, taking advantage of the principle that metals of different 
 kinds, bearing upon each other, have less friction than those of the same 
 kind. They are assambled with a bronze washer in front, and the others 
 alternately steel and bronze. 
 
 The breechplate is a steel casting attached to the breechface by 
 12 large screw bolts. Its function is to cover the rotating gears and 
 connect the tray with the gun by means of the hinge pin. On it are 
 mounted the rotating gears and their journals, the gear segment actuated 
 by them, the bronze bushing seat of the gear segments, and the securing 
 latch. On its rear face are the hinge-pin ears, and the rear-sight seat. 
 The recess in its face acts as a catch for the tray latch. 
 
GUNNERY AND BALLISTICS 85 
 
 The bronze bushing for the gear segment is permanently attached 
 to the plate by 4 screw bolts in a recess in its front face. It supports 
 the gear segment in rear and on its outer surface and is provided with 
 oil channels in its face, to facilitate lubrication. 
 
 The rotating crank and gears are the means of unlocking the block. 
 They consist of the gear segment, rotating pinion, the rotating crank 
 and associate parts. The steel gear ring encircles the breechblock and 
 is mounted in the bronze bushing; from this ring projects radially the 
 gear segment of 70 degrees, in which gear teeth are cut. 
 
 The gear ring fits over the cylindrical portion of the block with a lug 
 extending inward into the upper right-hand slotted sector prolonged 
 to the rear to receive it. It acts as a key in this slot to cause the block 
 to rotate. When the latter is withdrawn from the screw box, the 
 slotted sector slides from under the lug. 
 
 The pinion is a small gear whose function is to rotate the gear 
 segment into which it meshes. Its journal, mounted in a bronze sleeve 
 seated in the upper part of the breechplate, extends to the rear beyond 
 the face of the breechplate, and has the rotating crank mounted upon 
 its square end, secured by a nut and stay pin. By it the pinion is 
 turned, which rotates the gear segment, and in turn, the block. Over 
 the two faces of the pinion there are oil holes, closed by screws, for the 
 lubrication of the rotating gears. 
 
 There is a spring catch mounted in the face of the crank arm, by 
 which the gear system is locked when the breech is closed and the block 
 rotated to its firing position. This catch consists of a bolt, a spiral 
 spring, a housing nut and a winged nut. The bolt is seated with its 
 head projecting to the front, through the crank arm. Its forward end 
 is beveled on one side, and squared on the other. It is held in bearing 
 against its seat by a spiral spring on its back, compressed by the housing 
 nut screwed over it. The rear end of the bolt is threaded and has a 
 winged nut mounted upon it, having the projecting lug on one side. 
 When the nut is revolved ISO degrees, so that the bolt presents its 
 beveled side in the direction of rotation, the crank may be revolved, 
 carrying the gear segment to either of its extreme positions. The 
 handle of the rotating crank is covered with a loose sleeve to facilitate 
 turning. 
 
 By the rotation of the block, the translating stud on the block is 
 revolved into the thread of the translating roller, and the block is in 
 position to be drawn directly to the rear of the breech recess onto the 
 tray. 
 
 The tray or console is of bronze, mounted in the rear of the breech 
 
B6 THE SERVICE OF COAST ARTILLERY 
 
 and supported by a hinge pin on the right-hand side, the ears being 
 cast in the breechplate. The parts are the tray proper, the translating 
 roller and crank, the tray latch, and the catch for the securing latch. 
 
 The translating roller is seated in a right-hand thread in the upper 
 surface of the body of the tray; it has two independent threads cut in 
 opposite directions on its surface. The translating stud engages in the 
 left-hand thread in the roller. 
 
 The translating crank is mounted on the squared end of the roller. 
 The rotation of this crank causes the roller to screw in its right-hand 
 thread, and hence, travel back in the tray, drawing the block with it. 
 It also causes the translating stud, attached to the block, to travel 
 as a nut in the left-hand thread. Thus a double motion of translation 
 is given to the block, drawing it onto the tray by fewer revolutions of 
 the crank than if either of the threads acted upon it singly. In the 
 reverse motion, the tray latch serves to secure the tray to the face of the 
 breech, while the block is translated into its seat in the screw box. 
 
 The tray latch is mounted in a longitudinal slot in the web on the 
 under side of the tray, on a latch bolt. Its front end terminates in a 
 hook lip which engages in a catch seat recessed in the breechplate. 
 On its rear end is a transverse handle. A spring bolt mounted in the 
 tray, above the latch, holds it so that it cannot be unlatched while 
 its bolt is covered by the translating roller. When the latter is 
 quickly withdrawn beyond it, the relation between the excess of weight 
 in front of the latch journal and the tension of the bolt spring is such 
 that the jar will unlatch it. The tray may then be swung about its 
 hinge pin until caught by the securing latch, thus uncovering the screw 
 box. The securing latch is mounted in a recess in the breechplate, 
 through which its handle protrudes on the left, and its catch end on the 
 right. Its pivot is a screw bolt passing through the lower hinge ear, 
 hinge pin and breechplate. Its latch lip engages in a catch on the diag- 
 onal web of the tray. It may be released by lifting the handle, or 
 pressing down the latch end. 
 
 The hinge pin is a cylindrical bar mounted in two ears on the side 
 of the breechplate; it is lubricated from an oil hole in the upper hinge 
 ear. It is entered from below and held in position by the same screw 
 bolt upon which the securing latch is pivoted. 
 
 The type of gun construction described in this chapter is known as 
 the " built-up " cannon, designed to utilize, to the best advantage, 
 the elastic qualities of the metal. No portion of the bore of a gun 
 should be strained, either at rest or during firing, beyond its elastic 
 limit. 
 
GUNNERY AND BALLISTICS 87 
 
 The elastic limit of a metal is that point beyond which, if it is 
 strained either by extension or compression, a permanent set will take 
 place. There is an elastic limit of compression, as well as extension, 
 and if the metal is strained beyond either limit, permanent deformation 
 will occur. If the strain is continued, a rupture will take place when 
 the ultimate strain is exceeded. In a gun made of a single piece of 
 homogeneous steel in its natural condition, with no initial compression 
 or extension, the metal at the bore cannot be stretched by the expansion 
 of the powder gases beyond the limit of elasticity for extension without 
 a permanent " set'" taking place. If, however, the gun of the same 
 exterior dimensions be made of concentric tubes, properly assembled, 
 so that the metal at the surface of the bore is contracted to its elastic 
 limit for compression, this surface will, in firing, stand a corresponding 
 stress necessary to stretch it back to the normal condition of the first 
 cannon, and, therefore, it may be further strained so as to utilize the 
 elastic qualities for extension. As the greatest strain is at the bore, 
 this portion of the wall is compressed, when at rest, up to its elastic 
 limit for compression, and it is extended, when under the stress of the 
 powder gases, nearly or quite up to its elastic limit for extension. 
 It is to obtain this greater tangential strength that modern cannon are 
 built up in the manner just described. The tangential strength of a 
 cannon is the resistance it offers to being torn apart in a plane parallel 
 to its axis. 
 
 RIFLING AND ITS TWIST 
 
 In order to give elongated projectiles angular velocity of rotation, 
 and thereby cause them to rotate around their longer axis, spiral 
 grooves are cut in the bore of seacoast cannon. Attached to the base 
 of projectiles is a soft copper band, which is forced into the grooves 
 when the gun is fired. This band being rigidly attached to the pro- 
 jectile, the motion of rotation is transmitted to the projectile, and it 
 turns around its longer axis as it moves through the bore. This rota- 
 tion of the projectile around its longer axis gives greater accuracy of 
 flight, by keeping the projectile tangent to the trajectory, thereby 
 presenting the surface of least resistance to the air and thus giving 
 greater range and penetrative power. 
 
 As stated in the ' DEFINITIONS, grooves are the spiral cuts made in 
 the bore, and lands the spaces between two adjacent grooves. 
 
 Although a great factor in the accuracy of fire, rifling is also the 
 source of weakness in guns, due to the erosive effect of the powder 
 
88 THE SERVICE OF COAST ARTILLERY 
 
 gases on the bore at the junction of the lands and the grooves. Since 
 first introduced into gun construction, the tendency has been to reduce 
 the depth, and increase the number of grooves. In the United States 
 coast artillery service, the number of grooves is usually 6 times the 
 caliber, their width approximately thirty-seven one-hundredths of an 
 inch, and their depth from six to seven one-hundredths of an inch. 
 
 The rifling commences at the junction of the centering slope with 
 the forcing cone. The tops of the lands, at this point, are cut down so 
 that less power is required at first to force them through the copper 
 rotating band on the projectile. The twist of rifling, i. e., the inclina- 
 tion of the grooves to the axis of the bore at any point, increases from 
 1 turn in 50 calibers at its origin, to 1 turn in 25 calibers at a point 
 several inches in rear of the muzzle, and retains this latter twist uni- 
 formly up to the muzzle. In other words, the projectile, at the start, 
 would make one complete revolution around its longer axis in passing 
 over a distance of 400 inches for an 8-inch rifle, 500 inches for a 10-inch 
 rifle and 600 inches for a 12-inch rifle; its velocity of rotation gradually 
 increasing as it passes through the bore until at a point near the muzzle 
 its velocity is such that it would make one complete revolution in passing 
 over a distance of 200 inches for an 8-inch rifle, 250 inches for a 10-inch 
 rifle and 300 inches for a 12-inch rifle, or the projectile is turning twice 
 as fast as at the start. The twist is then uniform to the muzzle in order 
 to steady the projectile as it leaves the gun. 
 
 When the inclination of the grooves is constant, the twist is said to 
 be uniform. When it increases gradually from the breech towards the 
 muzzle, the twist is said to be increasing. In the United States service, 
 the rifling of seacoast guns and mortars is increasing for the guns 
 from 1 turn in 50 calibers at the breech, to 1 turn in 25 calibers 
 at a distance of about 2 calibers from the muzzle, from which point 
 to the muzzle it is uniform; for mortars, from 1 turn in 40 or 42 
 calibers, to 1 turn in 20 or 25 calibers. 
 
 With rapid-fire guns, the twist is different in most cases. In the 
 6-pounder (Driggs-Seabury and Driggs-Schroeder) the twist is from 
 to 1 in 26 calibers. In the 4-inch (Driggs-Schroeder), and the 6-inch 
 rifle, model of 1905, it is practically the same. The twist in the 
 4.72-inch Armstrong, 40 caliber, is from 1 in 100 to 1 in 34 calibers, 
 and the same gun, 50 calibers long, has a twist of rifling from 1 in 
 600 to 1 in 30 calibers. 
 
 The necessity for the increasing twist of rifling will be readily under- 
 stood when it is considered that as the projectile starts from its seat, 
 on the first part of its travel through the bore, the pressure of the 
 
GUNNERY AND BALLISTICS 89 
 
 powder gases rise to a maximum, and the angular velocity is impressed 
 upon the projectile at this point also. It is necessary, therefore, that 
 the least resistance to starting be offered by the projectile at this point. 
 With an increasing twist, the projectile takes the grooves gradually, 
 and the strain on the gun is not very great. With uniform rifling, the 
 gun would be submitted to the greatest pressure due to the starting, 
 and at the same time would be subjected to the greatest pressure due 
 to the rotation of the projectile, which would unnecessarily strain the 
 gun. As the projectile moves along the bore, the pressure of the powder 
 gases falls off while the twist is gradually increasing until it reaches 
 the final value necessary to impart the desired angular velocity to the 
 projectile. The pressures are thus more uniformly distributed along 
 the bore and the gun strained less at the start, while the final velocity 
 of rotation is as great is if the rifling had been uniform. 
 
 THE PROJECTILE IN THE GUN 
 
 Explosion, the principle of propulsion employed in modern artillery, 
 is simply the expansion of gases released by the decomposition of 
 chemical substances. The gases thus liberated exert an equal pressure 
 at all points on the surfaces which they touch. The propulsive energy 
 of these forces is controlled and regulated by the mechanism of the gun, 
 and absolute precision in their use is the first condition both of safety 
 and efficiency. 
 
 The potential energy stored up in a pound of powder, when expand- 
 ing to infinity, is capable of doing 576 foot-tons of work. In the bore 
 of the gun the space in which gases are free to expand is limited, and 
 the gases from a pound of powder expanding to the volume of the bore 
 do approximately only 75 foot-tons of work. This therefore is the usual 
 energy available to do the total work in the gun. The other 501 foot- 
 tons of energy cannot be utilized because of the limited length and 
 diameter of the bore. Again, a considerable portion of the total work 
 in the gun is lost in heating the gun; expanding the walls of the gun; 
 driving the column of air in front of the projectile out; driving out the 
 products of combustion, deforming the rotating band; overcoming the 
 friction in the bore; giving rotation to the projectile, and finally, 
 accelerating the projectile, that is, gradually increasing its velocity 
 from rest until it attains its final initial velocity at the muzzle with 
 which the projectile starts in its path through the air. 
 
 As the principal object is to give acceleration to the projectile it is 
 important to know how much of the total work in the gun can be 
 
90 THE SERVICE OF COAST ARTILLERY 
 
 Utilized for this purpose. The ratio of the useful work to the total 
 energy of the powder is called the " coefficient of useful effect/' or the 
 " coefficient of efficiency," and has been shown by experiment to be 
 between 80 and 90 per cent, of the total work in the gun. If a charge 
 of powder is burned in a rigid space, that is, one that has a fixed capacity, 
 the expansive force of the gas will at any instant depend upon the 
 amount of gas that has been formed and its mean temperature. As the 
 amount of gas and its temperature increase the expansive force will 
 increase. If at any instant the space in which the powder is burning 
 be increased, the other conditions remaining the same, the expansive 
 force will decrease. In a gun, the space in which the powder is burning 
 has a fixed capacity until the projectile starts to move, after which the 
 space increases. The pressure on the walls of the gun and on the base 
 of the projectile at any instant depends upon the expansive force of 
 the gas at that instant, as well as the increase of expansive force due 
 to an increase of the amount of powder burned, or to temperature. 
 If this is greater than the decrease of expansive force due to increase 
 in the space it occupies, the pressure on the walls of the gun and on the 
 base of the projectile is increasing. When the decrease, due to the 
 increase in the space, is greater than the increase due to the amount 
 of powder burned, or to temperature, the pressure falls off. 
 
 Theoretically, the last atom of powder should be converted into gas 
 as the projectile leaves the bore. The more gradually the projectile is 
 evolved, the less the strain on the gun; but the greater must be the 
 length of the bore in order that all the power-charge may be converted 
 into gas before the projectile leaves the bore. 
 
 What happens in a gun is this: The explosion of the powder-charge 
 gives rise to a large amount of gas, which expands, and the pressure 
 from the same acting on the base of the projectile starts the projectile 
 to move in the bore of the gun. The pressure increases up to a certain 
 amount and as the space in which the powder charge is burning is 
 increasing as the projectile moves through the bore, the pressure com- 
 mences to fall off. The greatest pressure acting on the base of the 
 projectile is called the maximum pressure, and this is the pressure 
 indicated by the crusher gauge. For any gun, the maximum pressure 
 must not be exceeded. 
 
 The form and size of the powder grain should be so regulated as to 
 produce the greatest possible initial velocity with a maximum pressure 
 not exceeding that which is allowed for the gun. It is sufficient to say 
 that within certain limits, the larger the grain, the less will be the 
 initial burning surface per pound of powder, and the less will be the 
 
GUNNERY AND BALLISTICS 91 
 
 maximum amount of pressure produced for a given charge of powder. 
 Due to this fact, the larger the grain, the larger the charge of powder 
 that can be used, as a rule, and therefore a greater muzzle velocity. 
 As the size of the grain is increased the percentage of the grain which 
 will be consumed while the projectile is in the bore is decreased, leaving 
 a certain portion of each grain unburned when the projectile leaves 
 the muzzle. For this reason, the size of the powder grain can be in- 
 creased within certain limits only. When the point is reached at which 
 the weight of the unburned powder will equal the additional amount 
 of powder which has been put in the chamber, no further increase of 
 velocity can be obtained. If we continue to increase the size of the 
 grain without increasing the charge the velocity will fall off. 
 
 For each class of gun, therefore, there is a limit to the size of grain, 
 which must not be exceeded. There is also a limit in the opposite 
 direction and it is possible to produce dangerous pressures in a gun by 
 using a small charge of powder where the grain is too small for the gun 
 in question. For this reason, powder should not be used in a gun for 
 which it is not designed, or it should be used in a gun of smaller caliber 
 than that for which it is designed, and never for one of larger caliber. 
 The rate at which gas is emitted from a burning grain is dependent 
 upon its rate of burning, and the area of the burning surface. 
 
 The ratio of burning increases with the pressure and also with the 
 temperature of the inflamed gases. The larger the grain, the less will 
 be the area of burning surface, per pound of powder, and the slower 
 will be the rate of emission of gas for the same rate of burning. For 
 every grain of powder, no matter what form, there is always one dimen- 
 sion, which, when burned through, the entire grain is consumed. This 
 dimension is known as the " least dimension," and is sometimes called 
 the " critical dimension " of the grain. In the multi-perforated 
 grain, the kind used with modern seacoast guns, or with smokeless 
 powder, the critical dimension is the thickness of the web between the 
 perforations. For example : If two tubular grains are the same length, 
 one of them one-half inch in diameter and the -other one inch in diameter, 
 both having the same thickness of wall (one eighth-inch) it is manifest 
 that as soon as the wall is burned through both grains will have been 
 consumed. The grain which is one inch in diameter would weigh about 
 twice as much as the other, and twice the amount of gas would be evolved. 
 For similar guns, the critical dimension of the grain should be in pro- 
 portion to the caliber of the gun. 
 
 When a grain is said to be too large or too small for a gun, too 
 quick or too slow for a gun, it is the critical dimension that is referred 
 
92 THE SERVICE OF COAST ARTILLERY 
 
 to. The denser the powder, the slower will be the combustion. An 
 extremely hard and very smooth grain is difficult to ignite. Uniformity 
 of action of powder is dependent upon the ignition and inflammation of 
 the charge. By ignition is meant setting fire to the charge, and by 
 inflammation is meant the spread of the fire from grain to grain over the 
 surface and into the perforations of the several grains. It is desirable 
 to produce as nearly as possible a simultaneous ignition of the entire 
 charge in order to eliminate the variation in the rate of emission of 
 gas, due to an irregular spread of inflammation from grain to grain. A 
 charge composed of large grains inflames quicker than one composed 
 of small grains; this is due to the larger opening between the grains. 
 A grain with large or multi-perforations inflames more readily than one 
 with small perforations. The longer the grain, the slower will be the 
 inflammation with the same-sized perforations. Black powder ignites 
 very readily, which is just the opposite of the smokeless powder, which 
 is now the standard powder and which requires a large amount of 
 flame to insure instantaneous ignition. For this reason an igniting 
 charge of black powder is put in the base of each section of the charge 
 of smokeless powder used in large caliber guns. 
 
 From what has been said, it can readily be seen that a charge com- 
 posed of large grains will burn more slowly and exert less strain on the 
 gun than one composed of small grains. Hence the danger of using 
 the same weight of charge of black powder in place of that of smokeless 
 powder or powder of large grains, is obvious. 
 
 The glazing of gunpowder, which smooths and hardens the surface 
 of the grain, is done to retard the ignition and make it a slower-acting 
 powder. Moisture in powder also reduces the rate of burning and con- 
 sequently, the velocity and pressure. Uniformity in size, shape, 
 density, surface smoothness, and toughness of the grain are essential 
 in order to obtain uniform results of velocity. The maximum pressure 
 and muzzle velocity are also affected by the density of loading, which 
 is fully defined in the DEFINITIONS. 
 
 It is important that the projectile should always be seated so that 
 its base will be at the same distance from the face of the breech, in 
 order that the volume of the powder chamber will be more nearly 
 constant for each charge. The smaller the space the higher will be the 
 initial velocity and the greater the pressure. Again, it is important 
 that the powder charge for each round fired should be the same length. 
 The length of the cartridge for any powder chamber should not be 
 less than nine-tenths (9-10) the length of the chamber. This is neces- 
 sary in order to eliminate what is known as wave motion. It has been 
 
GUNNERY AND BALLISTICS 93 
 
 found by experiment that if a cartridge is much shorter than the 
 powder chamber, it is liable to produce a motion of air in the gases 
 formed in the chamber which greatly increases the maximum pressure 
 on the breech. It has been found that in long chambers wherein 
 simultaneous ignition and inflammation is difficult, wave motion is 
 more apt to occur, in which cases abnormally high local pressures have 
 been produced. It is in order to contain the required amount 
 of powder without giving the chamber undue length that in modern 
 construction the powder chamber of the guns have been given greater 
 diameter than that of the main bore. 
 
 The causes affecting the velocity and pressure may be summarized 
 as follows: First, the size, shape, density, surface smoothness, and 
 toughness of the grain. Second, the length of the bore and the con- 
 struction of the gun. Third, the increase or decrease of the weight 
 of the charge. Fourth, the density of loading. 
 
 THE PROJECTILE IN ITS FLIGHT, OR THE TRAJECTORY 
 
 The projectile in flight will be considered, for convenience of expla- 
 nation: first, in the plane of departure, ignoring deviating effects; 
 second, the entire trajectory, including the -effects of wind and drift. 
 
 The projectile in its flight is influenced by: 1. The expansive force 
 of the powder gases which gives it the initial velocity of translation. 
 2. The force of gravity. 3. The resistance of the air. These forces 
 determine its trajectory. 
 
 The weight and dimension of the projectile as well as the shape of 
 its head also affect the path of its flight, but only because they act upon 
 the retardation of the projectile due to the resistance of the air. 
 
 Under the influence of the expansive force of the powder gas the 
 projectile would move with uniform velocity in a straight line or in 
 continuation of the axis of the bore. 
 
 The actual velocity of the projectile as it leaves the muzzle of the 
 gun is difficult to determine. It is, however, usually measured by 
 means of an instrument called the chronograph, at some point a short 
 distance from the muzzle. The velocity thus obtained is called in- 
 strumental velocity at the point measured from the muzzle. By 
 means of ballistic formula this instrumental velocity may be reduced 
 to what it would be, under the laws of resistance, at the muzzle. The 
 velocity thus calculated is called " muzzle velocity," as it is assumed 
 to be the initial velocity of the projectile in the trajectory. In other 
 words it is the velocity, which under the laws of resistance of the 
 
94 
 
 THE SERVICE OF COAST ARTILLERY 
 
 atmosphere when computed with ballistic formula, would give the 
 projectile a velocity equal to the instrumental velocity at the point 
 measured by the chronograph. 
 
 If the gun were fired where there is no resistance to the air, or in 
 vacuo, and leaving out of consideration the effect of gravity, the pro- 
 jectile would move in a straight line with uniform velocity and would 
 pass through equal distances for each second of its flight. For example, 
 
 FIG. 5. 
 
 if a projectile had an initial velocity of 2,000 feet per second, it would 
 pass through 2,000 feet during each second of its flight, or referring to 
 diagram (Fig. 5) it would pass in each second over OA, AB, BC, these 
 distances being equal in each case. 
 
 If the same gun were fired in air, horizontally, without considering 
 the action of gravity, it would move in the same straight line, but the 
 distance passed over during each successive second of its flight would 
 
 FIG. 6. 
 
 gradually decrease, that is, the projectile would lose velocity in conse- 
 quence of the resistance of the air. In such a case the distance passed 
 over during each second of its flight would be, referring to Fig. 6, the 
 distances OA, AB, BC. 
 
 Under the influence of gravity alone the space through which the 
 projectile will fall in vacuo is determined by the simple formula: 
 Space (S) in feet equals one-half of the acceleration of gravity (g), 
 mean value 32.16 feet per second, times, seconds squared (/ 2 ), or in 
 
GUNNERY AND BALLISTICS 
 
 95 
 
 other words, (S = %gt 2 ) a projectile will fall through 16.08 feet the first 
 second; at the end of the second second the projectile will have fallen 
 64.32 feet; at the end of the third, 144.72 feet, and at the end of the 
 fourth, 257.28 feet. Therefore, if the same gun were fired in air 
 horizontally, the projectile is, due to the influence of gravity, drawn 
 towards the center of the earth with a uniformly accelerated velocity, 
 
 and disregarding the retardation due to the resistance of the air in 
 falling the projectile would be, referring to Fig. 6, at points a, b, c, in 
 its path, instead of at the points A, B, C, referred to in Fig. 5. 
 
 In the air the projectile is retarded in its fall by the resistance 
 offered to it which would tend to retard it, so that, strictly speaking, 
 
 the distances given above are not absolutely correct. However, due 
 to the small velocity of fall obtained in direct fire, the errors are so small 
 that they may be disregarded. Therefore, under the conditions of the 
 initial velocity, force of gravity, and resistance of the air, the path of 
 the projectile disregarding drift and wind, would be as shown in Fig. 8. 
 The resistance which the air offers to the projectile is proportional 
 to the cross-sectional area exposed, and the square of the velocity. 
 
96 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Referring to figures 7, 8 and 9 it is evident that a gun may be fired 
 so as to produce trajectories similar to those illustrated, that is: First, 
 the trajectory which is entirely above the horizontal plane, or where 
 the target is above the level of the horizontal plane, passing through 
 the muzzle; second, where the target is on a level with the plane, 
 passing through the muzzle, and third, where the target is below 
 the horizontal plane, passing through the muzzle, which is the usual 
 trajectory found in practice. 
 
 In order that the terms may be thoroughly understood, the different 
 elements of the trajectory are indicated. 
 
 The horizontal trajectory is the one considered in all fundamental 
 ballistic computations. It is very seldom, in actual practice, that the 
 target is in the initial plane; therefore, the trajectory most commonly 
 found in practice is the trajectory described where the target is below 
 the horizontal plane passing through the axis of the gun. It is there- 
 
 \^fftifht of &"* 
 
 Water Level 
 
 FIG. 9. 
 
 fore evident that some means of applying the computations for the 
 horizontal trajectory, or the values given in the range table, must be 
 devised to apply to the trajectory in the three cases heretofore men- 
 tioned. This is accomplished by a method known as the principle of 
 rigidity of the trajectory, which may be defined as follows: The prin- 
 ciple of the rigidity of the trajectory assumes that the relations existing 
 between the elements of the trajectory and the chord representing the 
 range are sensibly the same, whether the latter be horizontal or inclined 
 to the horizon. 
 
 The acceptance of this principle assumes that knowing -the angle of 
 departure necessary to hit a certain point at a horizontal range " X " 
 from the gun and on the same level, the angle of departure necessary 
 to hit a certain point " h " feet below the level of the gun would be 
 obtained by subtracting the value of the position angle from the 
 angle of departure of the horizontal trajectory. 
 
GUNNERY AND BALLISTICS 97 
 
 Likewise if the target is above the level of the gun the position 
 angle would be added to the angle of departure of the horizontal 
 trajectory. Both of these are shown graphically in Figs. 7 and 9. 
 
 The power of a projectile to overcome the resistance of the air is 
 dependent upon its weight, dimensions, and shape of its head. It is a 
 well-known fact that given two balls, one a baseball, and one a light 
 hollow rubber ball of the same size, the heavy ball can be thrown 
 further than the light ball. This is because its greater weight gives it 
 more power to overcome the resistance of the air. If the two balls 
 were of the same weight, one being larger than the other, the larger ball 
 would meet with more resistance than the smaller one because there 
 would be more surface exposed to the resistance of the air. Applying 
 this principle to ballistics, a number is given, known as the ballistic 
 coefficient, which expresses the power of a projectile to overcome the 
 
 resistance of the air. It is expressed by C=/ - in which delta sub 
 
 oca 2 
 
 one is the standard density of the air; delta, the density of the air 
 when firing; w, the weight of the projectile in pounds; c, the coefficient 
 of reduction, depending for its value upon the smoothness of the pro- 
 jectile and its steadiness in flight; and d, the diameter of the projectile 
 in inches; / is known as the altitude factor. Two other factors are 
 frequently introduced into the equation in order to account for the 
 increased wind effect on the projectile as it rises, indicated by the symbol 
 fw and may be either negative or positive depending upon whether a 
 rear or head wind component is considered. The other factor is known 
 as the reducing factor, which takes into account the oblique presentation 
 of the projectile to the resistance of the air; this factor is expressed by 
 the Greek letter "gamma" (f) and its value is based upon experimental 
 
 firings. The complete coefficient then becomes C = -^-f a -f w . 
 
 For similar projectiles, that is, projectiles which have proportional 
 dimensions and the same shape head, the ballistic coefficient is directly 
 proportional to the weight of the projectile and inversely proportional 
 to the area of cross-section, or is proportional to the square of the 
 diameter; that is, C=W, divided by D squared. 
 
 It is a well-known fact that a long-tapered tool can' be forced into a 
 resisting medium more readily than one having a shorter taper; that 
 is, the sharper the instrument, the less power it requires to force it 
 through the medium. This same principle is true of projectiles passing 
 through the air the longer the taper of the head, the less power required 
 to force it through the air, because the area exposed to the resistance of 
 
98 THE SERVICE OF COAST ARTILLERY 
 
 the air is less. We may, therefore, consider that the sharpening of the 
 head of a projectile increases its power to force its way through the air, 
 which is equivalent to increasing its weight. 
 
 The coefficient of form, represented by " c" is usually taken as 
 unity, and depends for its value upon the results of experimental 
 firings. 
 
 Should a projectile not keep its head on in flight, the value " c" 
 would necessarily be greatly increased above unity, and therefore, 
 decrease the ballistic coefficient, or decrease the projectile's power to 
 overcome the resistance of the air. 
 
 Considering now the deviating effects upon a proj ectile in its flight, 
 which are those due to drift and wind, we find that the path of the pro- 
 jectile, instead of being as shown in Fig. 6, or lying in the vertical 
 plane of departure, describes a curve of double curvature, the horizontal 
 projection of which is shown in plan in Fig. 10. The only case in which 
 the projectile would remain in the plane of departure is when the wind 
 exactly equaled the deviating effect, due to drift. The first deviating 
 
 Horizontal projection. 
 FIG. 10. 
 
 effect, or that of drift, is due to rifling of the gun, which causes the pro- 
 jectile upon leaving the muzzle, to drift to the right for guns witn the 
 twist of rifling to the right. 
 
 The wind has considerable effect upon the flight of projectiles. In 
 the United States coast artillery service it may be designated in two 
 ways: First, by its azimuth, and second, by what is known as the 
 " clock convention." That is, a wind blowing from the west is said to 
 have an azimuth of 90 degrees; a north wind, an azimuth of 180 degrees. 
 The clock convention refers the wind to the line of direction; that is, 
 the observer is suppqsed to be at the center of a clock dial, the figure 
 12 pointing towards the target. A head wind is known as a 12-o'clock 
 wind; a rear wind, as a 6-0' clock wind; a wind directly from the right, 
 as a 3-o' clock wind; and a wind from the left, as a 9-o' clock wind, and 
 so on, the entire circle being divided into 12 sections, following the 
 known figures of the clock dial. The direction of the wind as sent to 
 each primary station is given in azimuth by means of the aeroscope. 
 
 The effect of the wind upon a projectile is directly proportional to 
 the wind velocity; that is, if a one-mile wind will shorten the range 
 
GUNNERY AND BALLISTICS 99 
 
 5 yards, a ten-mile wind will shorten it ten times as much, or 50 yards. 
 Again, if a one-mile wind will cause the projectile to deviate 3 yards to 
 the right or left, a ten-mile wind will cause the same projectile to deviate 
 approximately 30 yards. The effect of a head or retarding wind is to 
 shorten the range. A wind blowing in the direction of the range, 
 that is, a 6-o'clock wind, would tend to increase the range. A 3-o'clock 
 wind would cause the projectile to deviate to the left, and a 9-o' clock 
 wind to deviate to the right. A wind blowing from any other direction 
 than those stated would cause a change in range and deviation. 
 In such cases, it is necessary to determine the component of the wind's 
 velocity which affects the range, and also the component which would 
 cause it to deviate. The component which affects the range and which 
 is parallel to the line of direction, is called the range component; while 
 that component which acts at right angles to the line of direction is 
 known as the deviating component. The range component of a 1 
 o'clock wind, for example, is 87 per cent, of the wind's velocity; the 
 deviating component is 50 per cent, of the wind's velocity. That is, if a 
 wind had a velocity of 20 miles per hour, its range component would be 
 17 miles per hour and its deviating component would be 10 miles per 
 hour. The velocity of the wind is determined by an instrument called 
 the anemometer. 
 
 AIMING AND LAYING 
 
 In order to give a gun the direction and elevation necessary to hit 
 the target, it must be properly aimed, or laid to the data previously 
 determined by the methods hereafter outlined. The term " aiming " 
 will be employed when using the sights, and " laying " when the gun is 
 given direction by means of the azimuth circle, and elevation by means 
 of the elevation scale or quadrant. The three cases of pointing are as 
 follows : 
 
 Case I. When direction and elevation are both given by the sight. 
 In this case the sight is placed on the gun trunnions. 
 
 This method is used only with rapid-fire guns not provided with 
 quadrant-range scales. In using the sight the gun pointer for the first 
 shot sets the elevation scale to the deflection ordered. He observes the 
 splash caused by the shot and corrects the deflection for the next shot. 
 This is done by keeping the vertical hair on the designated point on the 
 target by traversing the carriage until the shot strikes and then bisecting 
 the splash with the vertical hair by turning the deflection screw. The 
 difference between the readings of the deflection scale after bisecting 
 
100 THE SERVICE OF COAST ARTILLERY 
 
 on the splash and the original reading then gives the error made, and 
 the setting in deflection should be corrected accordingly. The vertical 
 wire is then brought back to the target by traversing the carriage. 
 
 Case II. When direction is given by the sight and elevation by the 
 range scale on the carriage. 
 
 The sight in this case is placed upon the bracket on the sight 
 standard. It is the normal method used with guns of the primary 
 and usually intermediate armament. Corrected ranges are sent to the 
 guns for the next bell every fifteen seconds and the range scale set 
 accordingly by the range setter. The gun pointer keeps the sight set 
 at the deflection received from the plotting room until after the first 
 shot, and traverses or directs the traversing so as to keep the vertical 
 wire on the target. With the disappearing carriage the traversing is 
 stopped long enough for the projectile to be put in the gun. The gun 
 pointer fires or gives the command " fire," and then observes the fall 
 of his shot and corrects the deflection as previously explained, unless 
 otherwise ordered by the battery commander. 
 
 Case III. When direction is given by laying the gun in azimuth by 
 the azimuth circle, and the elevation by quadrant or range scale on the 
 carriage. 
 
 This case is used for mortars, and for guns when conditions are such 
 as to prevent the using of Case II. 
 
 ACCURACY OF FIRE AND PRACTICE 
 
 Accuracy of fire depends upon: 1. The accuracy of the gun. 
 2. The uniform action of the carriage during recoil. 3. The uniform 
 action of the powder. 4. The uniform weight of the projectile. 5. 
 The uniformity of loading. 
 
 Accuracy of practice depends upon: The accurate working of the 
 personnel: (a) Correct location of the target. (6) Accuracy of cor- 
 rections for wind, drift, travel of target and conditions of the atmosphere, 
 etc. (c) Accuracy of the gun pointer and range setter, (d) Correct 
 judgment upon observation of fire. 
 
 From the above it is readily seen that the " accuracy of fire " is 
 measured by the mean distance -of the points of impact of all the shots 
 in a group from the center of impact, or the center of the points of 
 impact of the group of shots, while the " accuracy of practice " is 
 measured by the distance of the center of impact from the center of the 
 target. For example: 
 
GUNNERY AND BALLISTICS 101- 
 
 Five shots are fired at a fixed target at a range of 7,000 yards. 
 The shots all fall within a rectangle 10 yards long and 5 yards wide, 
 and the average distance of the five shots from the target is 200 yards 
 short and 5 yards right. 
 
 The accuracy of fire was excellent, but the accuracy of practice 
 very poor. 
 
 Ballistic Symbols and Simple Formulas. 
 
 /. s. stands for " foot-seconds," which is the unit of measure for 
 velocities. For example: 32.16 f. s. is read 32.16 foot-seconds, and 
 means that the body considered is moving at the rate of 32.16 feet 
 per second. 
 
 w (small w) means " weight/' and in ballistic formulas stands for 
 the weight of the projectile in pounds. 
 
 d (small d) means " diameter," and in ballistic formulas stands for 
 the diameter or caliber of the projectile in inches. 
 
 #1 (delta sub one) stands for the density of the air two-thirds 
 saturated with -moisture, at standard temperature and barometric 
 pressure, usually taken at 60 F. and barometer 30 inches. 
 
 F written after figures denoting temperature means "Fahrenheit," 
 which is the name given to the kind of thermometer in common use 
 in this country. 60 F. therefore is read sixty degrees Fahrenheit. 
 
 d (delta) stands for the density of air, two-thirds saturated with 
 moisture, for the readings of the thermometer and barometer taken 
 at the time of firing the particular shot under consideration. 
 
 <N 
 
 -4 is read delta sub one divided by delta, and means the density of 
 
 standard air divided by the density of air at the time of firing the 
 shot. 
 
 A coefficient is a number written before any symbol to indicate how 
 many times the symbol is to be taken. Thus, 2g means twice gravity, 
 or 2X32.16 = 64.32. 
 
 c (small c) in ballistic formulas is called the " Coefficient of Reduc- 
 tion or Form." It is introduced in order to convert the result obtained 
 for a projectile of a particular form to that for a projectile of some 
 other form and is determined by experiment. 
 
 C (large C) in ballistic formulas is called the " Ballistic Coefficient" 
 It depends upon the density of the air and the weight, diameter, and 
 
 form of the projectile, and might be written -^ --^ (omitting reference 
 
102 THE SERVICE OF COAST ARTILLERY 
 
 to altitude, wind and reducing factors). This last expression is read, 
 delta sub one divided by delta, multiplied by w divided by cd 2 , which 
 means density of standard air divided by density of the air at the time 
 of firing, multiplied by the weight of the projectile in pounds divided by 
 the coefficient of reduction multiplied by the square of the diameter of the 
 projectile in inches. 
 
 V (large V) stands for muzzle velocity. That is, the number of 
 feet per second at which the projectile is moving when it leaves the 
 muzzle. 
 
 v (small v) stands for the velocity in f. s. of the projectile at any 
 point of its trajectory. 
 
 Va) (v sub omega) stands for the velocity in f. s. at the point of 
 fall. 
 
 i?o (v sub zero) stands for the velocity in f. s. at the summit of the 
 trajectory. 
 
 cf) (phi) stands for the angle of departure of the projectile. 
 
 6 (theta) stands for the angle which the tangent to the trajectory 
 at any point makes with the horizontal. In the ascending branch this 
 angle will always open outward from the gun, and will therefore be re- 
 garded as positive. At the summit of the trajectory the tangent will 
 be horizontal, and theta will therefore become zero. In the descending 
 branch the angle will open inward, that is, towards the gun, and will 
 therefore be regarded as negative. 
 
 w (omega) represents the angle of fall, that is, the angle at which 
 the projectile strikes the horizontal plane passing through the muzzle 
 of the gun. The angle of fall (aj) is always greater than the angle of 
 departure (</>). 
 
 x (small x) represents the horizontal distance from the muzzle to 
 any point within the range of the projectile. 
 
 y (small y) represents the height of the projectile above the horizontal 
 plane passing through the muzzle of the piece at any point of the 
 trajectory. 
 
 x and y are called the co-ordinates of any point of the trajectory, 
 x representing the horizontal distance of the point from the muzzle 
 of the piece, and y its vertical distance above the horizontal plane 
 passing through the muzzle, x is known as the abscissa of the point, 
 and y as the ordinate. Taken together they are called the coordinates 
 of the point. 
 
 X (large X) represents the horizontal range, that is, the distance 
 from the muzzle to the point where the projectile first grazes the hori- 
 zontal plane passing through the muzzle. 
 
GUNNERY AND BALLISTICS 103 
 
 T (large T) represents the time of flight in seconds, that is, the 
 time it takes the projectile to travel from the muzzle to the point where 
 it first grazes the horizontal plane passing through the muzzle. It is 
 the " T " for the range X. 
 
 t (small t) represents the time of flight to any point within the range 
 of the projectile. It is the " t " for the range x. 
 
 E (large E) stands for the energy of the projectile in foot -tons. 
 It is equal to the weight of the projectile in pounds multiplied by the 
 square of its velocity and divided by 4480 times gravity. The equation 
 
 r> 
 
 being E= foot-tons. 
 
 A TTOvJw 
 
 TT (pi) represents the ratio between the diameter and the circum- 
 ference of a circle. It is equal to 3.1416. 
 
 e (small e) represents the energy of a projectile per inch of circum- 
 ference. It sometimes appears in problems of penetration. The 
 
 wife 
 equation is 0=777^ foot-tons, which may be thus interpreted: 
 
 Energy per inch of circumference equal to weight of projectile X square 
 of its velocity, and divided by 4480 X 3. 141 6 X diameter of projectile X 
 32.16. 
 
 W (large W) stands for the velocity of the wind in f. s. 
 
 W x (read W sub x) represents the velocity of the wind parallel 
 to the range. 
 
 W y (read W sub ~y) represents the velocity of the wind normal, 
 that is, at right angles to the range. 
 
 u (small u) represents the horizontal progress of the projectile 
 in f. s. 
 
 p (rho) represents the resistance of the air to the motion of the 
 projectile in pounds. 
 
 T (tau) stands for the thickness of armor in inches. 
 f a (small f sub a) represents the altitude factor and depends for 
 its value upon the height the projectile rises above the level of the 
 gun. 
 
 f w (small f sub w) represents the wind factor and takesin to con- 
 sideration the effect of the wind on the projectile as it rises. 
 
 ?/o (small y sub zero) represents the maximum ordinate or height 
 in feet to summit of trajectory. 
 
 Z, A, Log B', T' and LogV are functions from Table II, Artillery 
 Circular M. 
 
104 THE SERVICE OF COAST ARTILLERY 
 
 FORMULAS 
 For use with Table II, Artillery Circular M. 
 
 = 
 
 7 *- 
 
 ; 
 
 = v cos 10 sec 
 
 ?/o = a"oC tan 
 tan aj = B' tan < 
 
 W COS 
 
 w = - L = u cos o sec w : 
 
 cos 
 
 4480^' 
 
 For a given weight of charge the velocity increases slightly with 
 the temperature of the powder at the instant of firing, and for a given 
 increase of temperature this increase in velocity varies with the initial 
 velocity. 
 
 For all lots of powder tested recently the charges have been adjusted 
 to give the prescribed velocities when fired at the standard temperature 
 of 70. In the earlier tests only the temperature of the air was recorded, 
 and for these lots but slight error will result from taking this as the 
 temperature of the powder. 
 
 According to the data available at present, the following table gives 
 the corrections for temperature. 
 
GUNNERY AND BALLISTICS 
 
 105 
 
 I 
 
 Normal Initial Velocities. 
 
 
 1 
 
 833 
 
 917 
 
 980 
 
 1056 
 
 1148 
 
 1220 
 
 2000 
 
 2100 
 
 2150 
 
 2200 
 
 2250 
 
 2400 
 
 2600 
 
 
 10 
 
 27 
 
 30 
 
 32 
 
 34 
 
 38 
 
 40 
 
 65 
 
 67 
 
 69 
 
 71 
 
 72 
 
 77 
 
 84 
 
 
 
 
 
 26 
 
 29 
 
 31 
 
 33 
 
 37 
 
 39 
 
 63 
 
 66 
 
 67 
 
 69 
 
 70 
 
 75 
 
 81 
 
 
 To be 
 
 10 
 
 25 
 
 28 
 
 29 
 
 31 
 
 35 
 
 37 
 
 60 
 
 62 
 
 64 
 
 66 
 
 67 
 
 71 
 
 77 
 
 
 deducted 
 
 20 
 
 23 
 
 26 
 
 27 
 
 29 
 
 32 
 
 34 
 
 55 
 
 58 
 
 59 
 
 61 
 
 62 
 
 66 
 
 71 
 
 
 ^ fromnor- 
 
 30 
 
 20 
 
 23 
 
 24 
 
 25 
 
 29 
 
 30 
 
 49 
 
 51 
 
 53 
 
 54 
 
 55 
 
 59 
 
 64 
 
 
 (mal ini- 
 
 40 
 
 17 
 
 19 
 
 20 
 
 21 
 
 24 
 
 25 
 
 41 
 
 43 
 
 44 
 
 46 
 
 46 
 
 49 
 
 53 
 
 
 t i a 1 ve- 
 
 50 
 
 13 
 
 14 
 
 15 
 
 16 
 
 18 
 
 19 
 
 30 
 
 32 
 
 33 
 
 34 
 
 34 
 
 36 
 
 39 
 
 
 locity. 
 
 60 
 
 7 
 
 8 
 
 8 
 
 9 
 
 10 
 
 10 
 
 17 
 
 18 
 
 18 
 
 19 
 
 19 
 
 20 
 
 22 
 
 
 
 
 70 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 To be 
 
 80 
 
 9 
 
 9 
 
 10 
 
 11 
 
 12 
 
 13 
 
 21 
 
 22 
 
 22 
 
 23 
 
 24 
 
 26 
 
 28 
 
 
 added to 
 
 90 
 
 19 
 
 21 
 
 22 
 
 24 
 
 26 
 
 28 
 
 46 
 
 48 
 
 50 
 
 50 
 
 52 
 
 56 
 
 60 
 
 
 normal 
 
 100 
 
 32 
 
 35 
 
 37 
 
 41 
 
 44 
 
 47 
 
 77 
 
 81 
 
 82 
 
 84 
 
 87 
 
 92 
 
 100 
 
 
 initial 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 velocity. 
 
 NOTE This table applies to lots tested at a temperature of 70. 
 
A cute Angle Obtuse Angle 
 
 A BD = Right Angle 
 
 Parallel Lines 
 
 B 1 Primary Station 
 B"Secondary Station 
 
 Parallel Lines 
 
 -" 
 
 CB &AB 'Perpendicular 
 Lines A 
 
 / \ Triangles 
 
 Sea/en* \^ //sosce/es\ / Eauilot0raf\ /Isosceles 
 
 Acute Angled Triangles ffight AngledTriangles Obtuse Angled Triangles 
 
 Polygons 
 
 Triangle Square _ Hexagon Octagon Concentric Circles ELLIPSE (Elliptical') 
 
 ADBE 'Circumference *.* Angle 
 
 Azimuth angles are 
 measured from the 
 South Oina clock- 
 wise directi'on.as 
 angle OA'/IO' 
 
 ADorBD'Arc 
 
 orCBorCD- Radius ^ Chord- BP D,am-BOC~ Arc -AC 
 X y- Opposite Angles 
 D/ometer 
 
 Quadrangular Cylinder Cylindro-Conicle 
 
 A* Fulcrum W- Weight 
 
 B ere/ Gear 
 
 Spur P. ing 
 
 Inferno/ or Angu/ar GearWhee/' 
 
 FIG. 10a. Geometrical Magnitudes, Etc. 
 
 106 
 
CHAPTER V 
 ARMAMENT 
 
 THE seacoast armament of the United States is a development of the 
 last twenty-five years. The construction of the first type of 8-inch 
 breech-loading rifle for coast defense purposes was undertaken in 1883 
 and completed at the West Point foundry three years later. In 1888 
 Congress began making appropriations for seacoast armament and has 
 continued the policy ever since. The present system of coast defense 
 is the result. 
 
 All the large-caliber guns now mounted have been designed, manu- 
 factured and mounted since 1888. In fact, it was not until 1895 that 
 the modern material began to be turned over to the coast artillery, and 
 the greater part of the present armament has been installed since 
 1897. 
 
 The United States has been, until recently, wedded to built-up gun 
 construction of steel forgings. Of late, however, the Ordnance Depart- 
 ment has taken up the manufacture of the wire-wound type of built-up 
 gun and is at present manufacturing a 14-inch rifle of that type. 
 
 Designs of a 6-inch wire-wrapped rifle and a new design of 12-inch 
 wire-wrapped mortar were recently completed. In the case of the 
 mortar the employment of the wire wrapping is said to decrease the 
 weight by something like 30 per cent ; while the cost is greatly reduced 
 by the fact that the cost of the wire per pound is less than one-half 
 that of steel forgings which it replaces. The new mortars have a breech 
 mechanism similar to that of the later seacoast rifles, which will greatly 
 increase the rapidity of loading. 
 
 The disappearing carriage system was adopted by the Endicott 
 Board in 1886, after exhaustive inquiry and careful consideration by 
 the officers who composed it. It was later accepted by the joint com- 
 mittee of Congress that had the general subject of coast defense in 
 charge. The disappearing system has always challenged that of the 
 barbette on two important points : First, that of the protection afforded 
 the gun, its carriage and personnel. Second, inability to discover the 
 position of batteries until they open fire. While the disappearing sys- 
 
 107 
 
108 THE SERVICE OF COAST ARTILLERY 
 
 tern has these advantages, its cost is greatly in excess of that of the 
 barbette system, to say nothing of the difference in the care and atten- 
 tion required by the two types. 
 
 COAST ARTILLERY ARMAMENT 
 
 Coast artillery armament is classified as PRIMARY, INTERMEDIATE, 
 and SECONDARY. 
 
 PRIMARY ARMAMENT 
 
 16-lNCH BREECH-LOADING RIFLE, MODEL OF 1895 
 
 The general drawing, Fig. 1, indicates the method of construction. 
 A series of this type of gun was recommended by the Endicott Board 
 for the defense of the harbors of New York, San Francisco, Boston and 
 Hampton Roads. In point of energy and range it is the largest gun 
 in the world. 
 
 It is of the built-up forged-steel type and consists of a tube, jacket, 
 2 C hoops, 3 B hoops, 1 D hoop, trunnion band or hoop, trunnion rim- 
 bases, Creech plate, breech-block, breech bushing, screw box, copper 
 rotating ring, powder chamber, forcing cone, centering slope, shot 
 chamber and main bore. 
 
 The breech mechanism (Stockett) is practically the same as that of 
 the 10-inch rifle, model of 1895, shown in Fig. 13, except in dimensions; 
 the breechblock having a diameter of 26 inches and total length of 27 
 inches. The threaded portion is divided into 12 sectors, six threaded 
 and six slotted, each sector being 30 degrees and corresponding to sim- 
 ilar sectors in the breech recess; the rotating and translating racks are 
 cut out of a solid block, the console or tray is made of cast steel. The 
 bore has 96 grooves, twist of rifling one turn in 50 calibers to one turn 
 in 25 calibers. 
 
 Total length 591 inches, with a diameter at the breech of 60 inches, 
 gradually diminishing to 28 inches at the muzzle. Weight 127 'tons; 
 length of bore 35 calibers; weight of projectile, capped, 2,400 pounds; 
 weight of propelling charge, nitro-cellulose powder, 612 pounds; weight 
 of bursting charge, high explosive, for A.P. shot, 46.1 pounds; for 
 A.P. shell, 139.3 pounds. 
 
 Muzzle velocity 2,150 foot-seconds. Muzzle energy 76,904 foot- 
 tons. Maximum pressure 38,000 pounds per square inch. Maximum 
 elevation permitted by the carriage 15 degrees, corresponding range 
 
ARMAMENT ' 109 
 
 15,558 yards. Penetration Krupp cemented armor, normal impact at 
 muzzle, 42 inches. 
 
 Only one gun of this type has been built and it has never been 
 permanently mounted. 
 
 14-lNCH BREECH-LOADING RIFLE, MODEL OF 1907 
 
 Guns of this caliber were recommended by the Chief of Ordnance 
 in 1906, based upon the recommendation of the National Coast 
 Defense Board, which consisted of officers of the army and navy. The 
 question of erosion as affecting the accuracy and life of seacoast cannon 
 caused the Ordnance Department to consider means of increasing the 
 caliber of high-power guns and decreasing the velocities used, at the 
 same time retaining the maximum gun power or increasing it. The 
 importance of these deliberations may be understood when it is stated 
 that the 12-inch B.L. rifls, Model of 1900, with a muzzle velocity of 
 2,500 feet per second, is not expected to last through an engagement of 
 more than one and one-half hours' duration, assuming that the rate of 
 fire permissible with this piece is used, this result being due to the 
 rapid rate at which the bore is worn away under high conditions of 
 loading and firing. 
 
 It was therefore decided that in order to meet the evil effects of this 
 gun erosion, high velocities and heavy powder pressures should be 
 abandoned, and return made to the custom of firing heavier projectiles 
 with smaller velocities, at the same time retaining equal or greater 
 gun power. It may thus be seen that the larger caliber gun was only 
 decided upon after considerable experience and careful study on the 
 part of the Ordnance Department. 
 
 It may be said in connection with the above, that it is entirely 
 feasible to reline guns, but the cost of inserting new liners is consider- 
 able, especially when it is observed that the guns have to be dismounted 
 and transported from their position in coast forts to some ordnance 
 arsenal, where the work of relining is done. 
 
 The 14-inch gun is designed primarily for the defense of wide channels 
 and harbors where the highest gun power is required. Its general 
 construction and nomenclature are practically the same as that of the 
 12-inch B.L. Rifle. The muzzle velocity is 2,100 foot-seconds. Pene- 
 tration in Krupp armor, normal impact at ,500 yards, 12 inches. The 
 life of this gun with the muzzle velocity indicated may be taken at 10 
 years, with the regular service practice firing. 
 
110 THE SERVICE OF COAST ARTILLERY 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 
 
 This rifle follows the general method of built-up forged steel con- 
 struction. It consists of the tube, jacket, 6 C hoops, 2 D hoops, 4 B 
 hoops, 5 A hoops and other parts as indicated in Fig. 1 . 
 
 The breech mechanism (interrupted screw system) is the same as 
 that of the 10-inch rifle, model of 1888; except in dimensions, and that 
 roller or ball bearings are introduced into the tray hinge, to carry 
 easily the greater weight. The bore has 72 grooves, twist of rifling, 
 one turn in 50 calibers to one turn in 25 calibers. 
 
 Total length 439.9 inches; weight 52 tons; length of bore 34 
 calibers; weight of projectile, capped, 1,046 pounds; weight of pro- 
 pelling charge, nitro-cellulose powder, 268 pounds; weight of igniter 
 charge 7 pounds; weight of bursting charge, gun cotton, for A. P. 
 shot, 13 pounds; for A.P. shell, 39.4 pounds. 
 
 Muzzle velocity 2,250 foot-seconds. Muzzle energy 36,824 foot- 
 tons. Maximum pressure 38,000 pounds per square inch. Maximum 
 range 15,134 yards. Penetration in Krupp cemented armor, at 5,000 
 yards, 13 inches. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1888, Mi 
 
 This rifle is similar in construction and power to the original model, 
 except that it has 5 C hoops, 2 D hoops, 3 B hoops and 4 A hoops. 
 Only a few of this modification were made. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1888, MiJ 
 
 This rifle is similar in construction and power to the original model, 
 except that it has 3 C hoops, 1 D hoop, 3 B hoops and 3 A hoops. 
 
 Total length 442.56 inches; weight 51 tons; length of bore 35 
 calibers. 
 
 Maximum range 11,636 yards. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1888, Mn 
 
 This rifle is similar in construction and power to the original 
 model, except that it has 2 C hoops, 1 D hoop, 3 B hoops, and 3 A 
 hoops. 
 
ARMAMENT 111 
 
 12-INCH BREECH-LOADING RIFLE, MODEL OF 1892 (1896) 
 
 This rifle was originally called the model of 1892. Its breech 
 mechanism was changed to a design similar to the model of 1895 
 except that the operating crank was above instead of below the tray. 
 After the change the rifle was called the model of 1896. Only one 
 was made. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1895 
 
 This rifle is similar in construction and power to the model of 
 1888 Mn, except that its total length is 442.56 inches; length of bore 
 35 calibers and maximum range 11,636 yards. 
 
 The breech mechanism (Stockett) is the same as that of the 10-inch 
 rifle model of 1895, except that the number of turns of the operating 
 crank and the number of teeth on compound gear and worm wheel 
 are increased. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1895, Mi 
 
 This rifle is practically the same as the original model. 
 
 The breech mechanism is the same as that of the 10-inch rifle, 
 model of 1895, except in dimensions, and that the number of turns of 
 the operating crank and the number of teeth on the compound gear 
 and worm wheel are increased. 
 
 12-lNCH BREECH-LOADING RIFLE, MODEL OF 1900 
 (See Plates I, II and III) 
 
 This rifle is exceedingly powerful. It is similar in construction to 
 the model of 1888, except as follows: 
 
 Stockett breech mechanism is provided (for description, see 10-inch 
 B.L.R. Mod. 1895). 
 
 Total length 504.3 inches; weight 59 tons; length of bore 40 
 calibers; weight of propelling charge, nitro-cellulose powder, 325 
 pounds; weight of igniter charge 9 pounds; weight of bursting charge, 
 gun cotton, for A.P. shot, 13 pounds; for A.P. shell, 39.4 pounds. 
 
 Originally the muzzle velocity of this model was 2,550 foot-seconds, 
 with a muzzle energy of 47,299 foot-tons. With this velocity it is 
 capable of penetrating 12 inches of latest type battleship armor, with 
 
112 
 
 THE SERVICE OF COAST ARTILLERY 
 
 normal impact of 8,700 yards; 11 inches at 10,000 yards, and 7 inches 
 at all fighting ranges. In developing this energy, however, the high 
 temperature due to the smokeless powder and great increase in volume 
 of gas, produces an erosion of the bore, which materially shortens 
 the life of the gun. 
 
 This fact caused the reduction of the service muzzle velocity to 
 2,250 foot-seconds, which has normally increased the life of the gun 
 from 4 to 5 years, to at least 12 years, in peace time. 
 
 With the present velocity its penetration at 5,000 yards is 13 inches. 
 Maximum pressure 38,000 pounds. Maximum elevation permitted 
 by the carriage 10 degrees; maximum range at this elevation 13,513 
 yards. 
 
 FIG. 11. Pit of 12-inch Mortars. 
 
 12-lNCH CAST-IRON MORTAR, MODEL OF 1886 
 (Cast-Iron Body, Steel Hooped) 
 
 This mortar is constructed of cast iron, reinforced by two rows of 
 short steel hoops; that is, 7 A hoops, breaking joints with 6 B hoops. 
 It is of the built-up type, the method of construction being shown in 
 Fig. 2. Mortars have 110 breechplate; the breechblock is supported 
 by the cast iron body and has screwed to its rear face a face plate, 
 commonly called, the "banjo," to which is attached the block handle 
 or handles. 
 
 The breech mechanism of mortars (see Fig. 12 and Plates IV, V and 
 VI) is practically the same for all models, except those of the wire- 
 
.. 
 
ARMAMENT 
 
 113 
 
114 THE SERVICE OF COAST ARTILLERY 
 
 wrapped type noted at the beginning of this chapter. In all the models 
 described herein the points of difference are of a minor character. In 
 this particular model the threads of the breechblock have the ratchet 
 section instead of the V used in the all-steel mortars, and the gear-rack 
 teeth are cut on the exterior of the segment instead of on the interior, 
 as in the later models. 
 
 The breech mechanism of mortars, with the exceptions noted 
 above, consists of the breechblock, obturator spindle, tray, hinge r 
 face plate, rack, translating roller, tray latch, securing latch or tray 
 back latch, firing mechanism of safety-bar slide, and associate parts. 
 
 The breechblock is threaded with a V thread with rounded top. 
 The rear portion is left unthreaded to prevent the entrance of dust. 
 The threaded portion is divided into six equal sectors, three threaded 
 and three slotted. The guide grooves fit upon and pass over the 
 rails of the tray when the breechblock is drawn to the rear. The face 
 plate (or " banjo"), is attached to the breechblock by five screws 
 and a dovetail tenon fitting in a transversely slotted seat. The arm 
 has a rectangular mortise cut perpendicularly to the axis of the breech- 
 block, through the upper end, in which the rotating pinion and rotating 
 crank gear are housed. ^ 
 
 The rotating crank gear (the lower one when the arm of the face 
 plate is pointing upward) is mounted upon an axle which extends to 
 the rear and has the rotating crank mounted upon it. This rotating 
 crank gear meshes into a larger one above it, the rotating pinion, 
 which is mounted upon a second axle also having its bearings in the 
 walls of the mortise. The bearings are bushed with bronze. The 
 rotating gear is mounted on the latter journal, in front of the arm. 
 This rotating gear meshes into a circular rack, geared on the interior, 
 and bolted upon the rear face of the breech in a recess cut for the 
 purpose. This rack is now cut in the solid metal of rear face of the 
 A3 hoop. The rear face and upper surface of the rack are flush with 
 the face of the breech and upper surface of the mortar. 
 
 Rotating the rotating crank turns the rotating crank gear, which 
 turns the rotating pinion and the rotating gear, which, being engaged 
 in the rack, travels in it and causes the breechblock to rotate. The 
 rotating crank has a lock consisting of a housing, two studs, a spring 
 and a handle. The housing is screwed into the rear side of the face- 
 plate arm. The front stud is mounted in a cylindrical recess in the 
 housing and extends through the face-plate arm. It moves in a 
 groove of varying depth in the breech of the gun. A rear stud enters 
 the rotating-crank arm from the front, extends to the rear, and has a. 
 
* THE 
 
 { UNIVERSITY 
 
 OF 
 
ARMAMENT 1 15 
 
 handle screwed upon the extension. About its shank is a spiral spring 
 with its front bearing against the rear of the rear stud head. The 
 front face of the rear stud is crowned, enabling the crank to pass the 
 housing by compressing the spring. As long as the front stud moves 
 in the shallow portion of its groove in the breech it entirely fills the 
 recess in the housing. 
 
 When the rotation of the breechblock is completed and the front 
 stud arrives at the well at the end of the groove, thus being free to 
 move forward, the pressure of the spring forces the rear stud into 
 the recess in the housing, latching the rotating crank. It follows 
 that the rotating crank is also latched at any time that the breech- 
 block is not fully translated home. In the earlier models there is no 
 handle, and only one stud, which is crowned and fits into a seat on the 
 front face of the rotating-crank arm, latching the rotating crank. 
 As in the later model, the rotating crank is enabled to pass the housing 
 by compressing the spring. A handle of steel or bronze is attached 
 to the face plate. 
 
 Obturator Spindle 
 
 The obturator spindle, tray, and translating roller are similar to 
 those used in the 8-inch, 10-inch, and 12-inch rifles, Model of 1888. A 
 hinge set into the face of the breech and secured by four screws is 
 provided with two lugs in which the hinge pin is mounted, and with 
 two cylindrical bosses which fit in corresponding cavities in the face of 
 the breech. The translating stud attached to the rear face of the 
 breechblock projects vertically from the face of the block. It is 
 shaped like the sector of a thread in a nut. Previous to 1896 it was 
 made cylindrical in form. When the block is rotated through the 
 arc necessary to unlock it, the translating stud revolves into the groove 
 in the translating roller. 
 
 The obturator spindle consists of the spindle (head and stem), 
 pad, front and rear split rings, small split ring, filling-in disk, obturator 
 nut, and the obturator-spindle washers. The vent is drilled through 
 the spindle, in the front of which there is a copper bushing plug forced 
 into an undercut on the face of the head. Vents are now drilled to a 
 diameter of 0.200 inch thoughout with a radius of 0.025 inch at front 
 end. This bushing may be replaced when badly eroded. 
 
 The front and rear rings are of steel, split diagonally through 
 one side. They are slightly larger than the conical gas-check seat, 
 and are sprung together in being forced into this seat. The small 
 split ring is of similar construction, but slightly smaller than the 
 
116 THE SERVICE OF COAST ARTILLERY 
 
 obturator-spindle stem. The rear filling-in disk acts as a washer 
 in rear of the pad. A shoulder on its front face supports the interior 
 edge of the rear split ring, and a fillet on the rear face of the obturator- 
 spindle head performs the same office for the front split ring. The 
 obturator nut is screwed on the rear end of the stem with a left-hand 
 thread; it draws the obturator-spindle head, gas-check pad, and 
 split rings to a bearing against the face of the breechblock. It abuts 
 against the obturator-spindle washers and has under its front edge a 
 thin steel dust cover. This obturator nut is now provided with a 
 clamp screw to clamp it on obturator spindle to prevent its rotation, 
 thus doing away with the old locking nut. In some of the earlier 
 models the obturator nut has a right-hand thread. 
 
 The four obturator-spindle washers are alternately bronze and 
 steel. They reduce the friction between the obturator nut and the 
 rear face of the breechblock recess and enable the breechblock to be 
 rotated independently of the gas check, during the first part of its 
 movement in unlocking. They are assembled with a bronze washer 
 in front and the others alternating steel and bronze. 
 
 The translating roller is seated in a right-hand thread in the upper 
 surface of the body of the tray. It has two independent threads cut 
 in opposite directions on its surface. The translating stud engages 
 in the left-hand thread. The translating crank is mounted on the 
 squared end of the translating roller. The rotation of this crank 
 causes the roller to unscrew in its right-hand thread and travel back 
 in the tray, drawing the breechblock with it. It also causes the trans- 
 lating stud attached to the breechblock to travel as a nut in the left- 
 hand thread. Thus a double motion of translation is given to the 
 breechblock, drawing it on to the tray by fewer revolutions of the 
 crank than if either motion were used singly. 
 
 The tray latch secures the tray to the face of the breech while the 
 breechblock is entering or being withdrawn from its seat in the breech 
 recess. It is mounted in a longitudinal slot in the web on the under 
 side of the tray, on a tray-latch pivot. Its front end terminates in a 
 hook lip, which engages in the tray-latch catch when the tray is against 
 the face of the breech. On its rear end is a transverse handle. A 
 tray-spring bolt mounted in the tray above the tray latch holds it 
 so that it can not be unlatched so long as the tray-spring bolt is covered 
 by the translating roller. 
 
 When the latter is quickly withdrawn beyond it, the relation 
 between the excess of weight in front of the tray-latch journal and the 
 tension of the tray-spring bolt spring is such that the jar will unlatch 
 
OF THE 
 
 ER 
 
 OF 
 
AKMAMENT 117 
 
 it. The tray-latch catch is a recess cut into the face of the breech. 
 When the tray is swung around so as to fully uncover the breech, it is 
 held by the tray-latch, which is mounted in a mortise in the hinge on a 
 tray-back-latch bolt passing through the hinge. This tray-back latch 
 engages a tray-back-latch catch on the tray. It is released by lifting 
 the tray-back-latch handle at its left end. 
 
 Action of Breech Mechanism. When the breechblock is in the 
 firing position the threads are in bearing with those of the breech recess; 
 the face plate is inclined 60 degrees to the right; the rotating crank 
 is pointed toward the vent and is held in position by the rotating- 
 crank lock; the tray is against the face of the breech; the tray latch 
 is engaged in its catch; the translating stud is 60 degrees to the left of 
 its seat in the translating roller; the translating crank is vertical with 
 the crank pointing downward, and the pad and split rings are in the 
 gas-check seat. 
 
 To Open the Breech. Pull out the rotating-crank lock, turn the 
 rotating crank three turns in direction indicated by the arrow marked 
 "open" on the face plate. The threads of the breechblock are now 
 opposite the slotted sectors of the breech recess, the face plate is 
 vertical, the rotating crank points downward, and the translating 
 stud is in the translat ing-roller thread. Then turn the translating- 
 roller crank three turns in a direction opposite that of the hands of a 
 clock, ending with a quick motion to bring the breechblock to its final 
 position in the tray with a jar which will release the tray latch. Grasp 
 the tray handle and swing the tray about the hinge pin till the tray- 
 back latch engages in its catch. The breechblock swings around 145 
 degrees and clears the breech for loading. 
 
 To Close the Breech. Release the tray-back latch by raising its 
 left end; swing the tray against the face of the breech by taking hold 
 of the tray handle; turn the translating roller three turns in the direc- 
 tion of the hands of a clock; then turn the rotating crank three turns 
 in the same direction. It is not necessary to count the number of 
 turns either in opening or closing the breech, as there are stops for 
 all motions. 
 
 To Remove and Dismount the Breech Mechanism. Turn the rotating 
 crank until the translating stud is out of its seat m the translating 
 roller, thus bringing the face plate to its vertical position, remove the 
 translating roller; grasp the breechblock handle and withdraw the 
 breechblock on to the tray as far as possible, so that the obturator 
 spindle head will clear the breech recess; raise the tray latch and 
 swing the tray around ; remove the obturator-spindle nut and washers, 
 
118 THE SERVICE OF COAST ARTILLERY 
 
 then take off the breechblock by passing a rope through it and slinging 
 it, using a gin or crane. 
 
 The face plate, when necessary, can then be removed by taking 
 out the screws, but this should not be done except at the gun factory. 
 
 In case any nuts are to be removed, their pins should be driven 
 out carefully, using a drift so as not to batter them. 
 
 The tray is removed as follows: Remove the tray latch, block up 
 under the tray or sling it securely and remove the hinge pin. The 
 tray -back latch is removed after removing the tray. 
 
 To Assemble the Breech Mechanism. Put on tray-back latch, 
 then the tray, then the tray latch; put on the breechblock on the 
 tray (by using a sling as before) ; put in the obturator spindle, then the 
 obturator nut and washers, swing the tray around against the face of 
 the breech; push the breechblock home; rotate it slightly and put in 
 the translating roller. 
 
 The above order of assembling assumes that the face plate has 
 not been removed from the breechblock. In case it has, it should be 
 put on before the breechblock is put on the tray. 
 
 If, after firing, the breechblock can not be unlocked by the rotating 
 crank, remove the obturator nut and obturator-spindle washers, and 
 then unlock the breechblock, leaving the spindle in the gun. Then 
 remove the spindle by inserting a heavy timber in the muzzle and 
 striking the head until it is loosened, being careful not to allow the 
 spindle to drop. 
 
 The bore has 68 grooves; twist of rifling, one turn in 42 calibers 
 to one turn in 25 calibers. 
 
 The total length is 129 inches; weight 14.25 tons; length of bore 
 9 calibers; weight of. projectiles, deck-piercing shell, capped, 1,046 
 pounds and 824 pounds. With 1,046-pound projectile the powder 
 charges, nitro-cellulose powder, are issued made up, to give velocities 
 for zones as follows: First zone 560 foot-seconds; second zone 610 
 foot-seconds; third zone 670 foot-seconds; fourth zone 743 foot- 
 seconds; fifth zone 837 foot-seconds; sixth zone 910 foot-seconds. 
 With 824-pound projectile, seventh zone 1,050 foot-seconds. Weight 
 of propelling charge approximately 33 pounds; weight of igniter 
 charge 1.25 pounds. 
 
 Muzzle energy, between 6,298 arid 6,544 foot-tons. Maximum 
 pressure 27,500 pounds per square inch. Maximum range, with 45 
 degrees elevation, 9,557 yards. Minimum range, with 65 degrees 
 elevation, 2,225 yards. 
 
THE 
 
 UNIVERSITY 
 
 OF 
 
ARMAMENT 119 
 
 12-lNCH CAST-IRON MORTAR, MODEL OF 1886, M 
 
 This mortar is similar in construction and power to the original 
 model, except that it has 5 A hoops. 
 
 12-lNCH STEEL MORTAR, MODEL OF 1886-90, Mi 
 
 This mortar is similar in construction and power to the model of 
 1890, except that it has 5 A hoops breaking joints with 5 B hoops. 
 
 Total length 129.25 inches; weight 12 tons; twist of rifling, one 
 turn in 40 calibers to one turn in 25 calibers. Only a few of this model 
 were made. 
 
 12-lNCH STEEL MORTAR, MODEL OF 1890 
 
 This mortar is similar in construction to the model of 1886, except 
 that it has a tube, jacket, breech bushing, 2 C hoops, 1 D hoop, 3 A 
 hoops and other parts as shown in Fig. 3. 
 
 The breechblock is supported by the jacket through the breech 
 bushing. The two C hoops are shrunk on the tube from the front, 
 each having a shoulder abutting against one on the tube. Four 
 securing pins, screwed through the C2 hoop into the tube prevent 
 the C hoops from moving to the front. The D hoop is put on from 
 the front and abuts against the shoulder on the jacket, covering the 
 joint between it and the Cl hoop. The Al hoop, assembled from the 
 rear, abuts against a shoulder on the D hoop and covers the joint 
 between the jacket and the D hoop. The A2 hoop, or trunnion hoop, 
 abuts against a shoulder on the jacket. 
 
 The bore has 72 grooves; twist of rifling one turn in 40 calibers to 
 one turn in 20 calibers. 
 
 The total length is 141.125 inches; weight 13 tons; length of 
 bore 10 calibers. The powder charges, nitro-cellulose powder, weigh 
 from 54 to 62 pounds; igniter charge 1.25 pounds. With 1,046 pound 
 projectile the powder charges are issued made up, to give velocities 
 for zones as follows: First zone 550 foot-seconds; second zone 600 
 foot-seconds; third zone 660 foot-seconds; fourth zone 725 foot-seconds; 
 fifth zone 810 foot-seconds; sixth zone 915 foot-seconds; seventh zone 
 1,050 foot-seconds. With 824-pound projectile, eighth zone 1,300 foot- 
 seconds. 
 
 Muzzle energy between 9,647 and 10,077 foot-tons. Maximum 
 pressure 33,000 pounds per square inch. Maximum range, with 45 
 degrees elevation, 12,019 yards. Minimum range, with 65 degrees 
 elevation, 2,210 yards. 
 
120 THE SERVICE OF COAST ARTILLERY 
 
 12-INCH STEEL MORTAR, MODEL OF 1890, Mi 
 (See Plates IV, V and VI) 
 
 This is the latest type of built-up forged steel mortar. It is 
 practically identical with the original model. 
 
 10-lNCH STEEL MORTAR, MODEL OF 1890 
 
 This mortar is similar in construction to the 12-inch model of 1890. 
 
 Total length 117.1 inches; weight 7.5 tons; length of bore 10 
 calibers. 
 
 Weight of projectile 604 pounds; weight of charge, including 
 igniter, 604 pounds. 
 
 Muzzle velocity 1,150 foot-seconds. Muzzle energy 5,287 foot- 
 tons. Maximum pressure 33,000 pounds per square inch. Maximum 
 range 10,798 yards. This type was entirely experimental and very 
 few were made. 
 
 10-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 
 (See Plates VII and VIII) 
 
 This rifle is similar in construction to rifles previously described. 
 It has 7 C hoops, 5 A hoops, 2 D hoops, and 4 B hoops. 
 
 Weight 30 tons; total length 30.6 feet; length of bore 34 calibers; 
 the bore has 60 grooves; twist of rifling, one turn in 50 calibers to one 
 turn in 20 calibers. 
 
 The breech mechanism, commonly called the " interrupted screw 
 system," consists of the breechblock, obturator, breechplate, rotating 
 crank and gears, tray, translating roller, translating crank, tray latch, 
 tray back latch, hinge pin, and associate parts as shown in Plates 
 VII and VIII, and Fig. 4. The principal parts of the breechblock 
 are the threaded sectors, the slotted sectors, the guide grooves, and 
 the translating stud. 
 
 The block is threaded with a V thread with rounded top. The 
 rear portion is left unthreaded to prevent the entrance of dust. The 
 threaded portion is divided into eight equal sectors, four threaded and 
 four slotted. The two guide grooves are cut in the two bottom slotted 
 sectors 30 degrees each side of the lowest element of the unlocked 
 breechblock. They fit upon and pass over the rails of the tray when 
 the breechblock is drawn to the rear. 
 
 The breechblock is slotted across its breech face for a rotating lever 
 
ARMAMENT 121 
 
 which may be attached by two screw bolts. The translating stud 
 projects radially from the rear face of the block and is secured in its 
 seat by a screw. 
 
 When the breechblock is rotated the ^cessary to unlock 
 
 it, the stud revolves into the groove i ng roller. The 
 
 obturator consists of the spindle, pad, tl ., and small split 
 
 rings, the filling-in disc, the obturator ma aie obturator-spindle 
 
 washers. The vent is drilled through the swindle, in the front of which 
 is a copper bushing forced into an undercut in the face of the mushroom 
 head. This bushing permits of being replaced when badly eroded. 
 In passing through this plug, the vent contracts from two-tenths to 
 one-tenth of an inch. The rear end of the vent channel is enlarged and 
 threaded for an obturating primer used to ignite the charge. 
 
 The pad is made of asbestos and tallow with a canvas covering. 
 The front and rear split rings are of steel, split diagonally through 
 one side. They are slightly larger than the conical seat, and are 
 sprung together in being forced into place. The small split ring is of 
 similar construction, and fits tightly over the spindle. The filling-in 
 (or gas-check) disc acts as a washer in rear of the pad; a shoulder on 
 its front face supports the interior edge of the rear split ring; a fillet 
 on the rear face of the obturator-spindle head performs the same office 
 for the front split ring. The obturator nut is screwed on the rear end 
 of the spindle with a right-hand thread in the earlier guns, and in the 
 later with a left-hand thread; it abuts against the spindle washers, 
 draws the obturator spindle head and pad to a bearing against the 
 face of the block, and has under its front edge a thin steel-spring washer, 
 designed to form a tight joint over the recess for the spindle washers 
 to prevent the entrance of dust, sand, etc. It is provided with a clamp 
 screw to prevent the obturator nut from unscrewing. 
 
 The four obturator spindle washers are alternately bronze and 
 steel, assembled with one of the former in front. They reduce the 
 friction between the spindle nut and the rear face of the block recess, 
 enabling the block to be rotated independently of the pad, leaving the 
 latter in its seat until the block is unlocked. 
 
 The breech plate is a steel casting attached to the breech face by 
 two large screw bolts. On it are mounted the rotating mechanism, 
 securing latch, and the hinge lugs. A recess in. its face acts as a catch 
 for the tray latch. The rotating mechanism for the block consists of 
 the rotating ring, the bronze bushing, the rotating gears, and the 
 rotating crank and associate parts. The steel rotating ring encircles 
 the breechblock and is mounted in the bronze bushing. From this 
 
122 THE SERVICE OF COAST ARTILLERY 
 
 ring projects radially the gear segment of 70 degrees, in which the teeth 
 are cut. The gear ring fits over the cylindrical portion of the block, 
 with a lug extending into the upper right-hand slotted sector, which 
 is prolonged to the rear to receive it when the block is locked. This 
 lug acts as a key in the sector to constrain the block to rotate, and 
 when the latter is withdrawn from the screw box the slotted sector 
 slides from under the lug. 
 
 The bronze bushing is attached to the breech plate by four screw 
 bolts and is lubricated by oil channels in its face. 
 
 The rotating gears are three in number two single and one com- 
 pound; the first, single, called the rotating-crank pinion, is solid with 
 its journal, which works in bronze bushings and extends through the 
 breech plate, the rotating crank being mounted on the rear end and 
 secured thereon by a nut and pin. The intermediate gear, also single, 
 works into the larger wheel of the compound gear. The latter is in one 
 piece, forming two gears of different diameters; the smaller engages 
 the gear segment, and thus, by the crank, the breechblock is rotated. 
 
 There is a spring catch called the rotating-crank box, mounted on 
 the rear face of the rotating crank, by which the gear system is locked 
 when the breech is closed and the block rotated to its locked position. 
 This lock consists of two locking bolts, each controlled by a spiral 
 spring which hold the bolts down in the locking recess in the breech 
 face of the gun. These locking bolts act alternately, that is, one locks 
 the rotating crank when the breech is closed and ready for firing, and 
 the other locks the rotating crank in its horizontal position when the 
 breech is open and ready for loading. These bolts are manipulated 
 by means of a small crank which is provided with inclined or beveled 
 surfaces at its pivoted end. These surfaces come into contact with 
 lugs formed on the outer end of the locking bolts, and by swinging the 
 small crank to the right the breech can be opened, and to the left the 
 breech can be locked. The handle of the rotating crank is covered 
 with a loose sleeve. 
 
 By the rotation of the block the translating stud is revolved into 
 the thread of the translating roller, and the block is in position to be 
 drawn directly to the rear out of the breech recess on to the tray. 
 The tray, of bronze, is mounted in rear of the breech, supported on the 
 right-hand side by a huge pin working in lugs on the breech plate. 
 The associate parts are the translating roller and crank, the tray latch, 
 and the catch for the securing latch. 
 
 The translating roller is seated in a right-hand thread in the upper 
 portion of the tray and has also cut upon it a left-hand thread in 
 
ARMAMENT 123 
 
 which the translating stud works. The action of the crank causes 
 the roller to unscrew in its right-hand thread and the translating stud 
 attached to the block to travel as a nut in the left-hand thread, drawing 
 the block with it; thus the translation of the block is given by fewer 
 revolutions of the crank than if either were used singly, and has only to 
 travel one-half the distance. 
 
 The tray latch secures the tray to the face of the breech; it is 
 pivoted in a longitudinal slot on the under side of the tray, has the 
 front end terminating in a hook lip, which engages in its seat in the 
 breech plate, and has a transverse handle on its rear end. A spring 
 bolt, mounted in the tray, holds the latch so that it can not be released 
 while its bolt is covered by the translating roller. When the latter 
 is quickly withdrawn beyond the bolt, the relation between the excess 
 of weight in front of the latch journal and the tension of the tray- 
 spring bolt is such that the jar will unlatch the tray. Just in rear 
 of the latch spring is a bolt, passing through the web of the tray and 
 into a recess in the roller when the block is withdrawn, thus preventing 
 any motion of the block to the front when in the loading position. 
 
 This bolt is operated by a lever hinged to the web of the tray, one 
 end entering the slot in the bolt, the other joined by a link, which, 
 in its turn, is joined to the tray latch. When the latch is unfastened its 
 rear end is forced downward by the spring bolt, thus, through the 
 connections, raising the lock bolt" into its seat in the roller; when 
 the latch is fastened the lock bolt moves downward out of its seat. 
 
 The tray latch being unfastened, the tray may be swung to the 
 right until caught by the securing latch. This latch is mounted in a 
 recess in the breech plate, through which its handle protrudes on the 
 left and its catch end on the right; its pivot is a short screw, with 
 countersunk head located in the breech plate directly back of the 
 tray hinge. The latch engages in a catch on the diagonal web of the 
 tray, arid may be released by lifting the handle or pressing down the 
 latch end. 
 
 The hinge pin is a cylindrical bar, mounted in two lugs on the 
 right side of the breech plate; it is entered from below and held in 
 position by two small screws through the tray hinge, thus locking 
 hinge and pin together. An oil hole in the upper hinge lug permits 
 of the pin being lubricated. 
 
 Action of Breech Mechanism. When the breechblock is in the 
 firing position the threads are in bearing with those in the breech 
 recess; the rotating crank is vertical; the rotating-crank lock bolt is 
 bearing in its recess. The translating stud is 45 degrees to the left 
 
124 THE SERVICE OF COAST ARTILLERY 
 
 of its seat in the translating roller; the tray latch is engaged in its 
 catch; the rotating ring is rotated to extreme right-hand position 
 and the gas-check pad is in its seat. 
 
 To Open the Breech. Turn the winged nut of the rotating crank 
 catch (lock) 180 degrees to the left; turn the rotating crank in the 
 direction of the hands of a clock, as indicated by the arrow marked 
 "open" on the breech plate, until the translating stud is in the trans- 
 lating-roller thread ; the rotating crank latch (lock) will then be opposite 
 the upper steel lock plate, which has a recess in its center to receive it; 
 the guide grooves in the breechblock will be opposite the guide rails in 
 the tray. Turn the translating crank in a contraclockwise direction 
 four times, ending with a quick motion to bring the block into its 
 final position in the tray with a jar, which will release the tray latch 
 and swing the tray until the securing latch engages the catch. 
 
 To Close the Breech. Release the securing latch; swing the tray 
 to the face of the breech; reverse the motion of the translating crank 
 until the breechblock is seated, then that of the winged nut of the 
 rotating-crank catch (lock), and that of the rotating crank. 
 
 To Remove and Dismantle the Breech Mechanism. The operations 
 are the reverse of those described for assembling it. If, after firing, 
 the block can not be unlocked by the rotating crank, put on the 
 rotating lever and endeavor to turn the block. If this fail, remove 
 the obturator nuts and washers and unscrew the block, leaving the 
 obturator in the gun. If the block can not be unscrewed, remove 
 the tray and breech plate. Support the tray by blocking and take out 
 the hinge-pin bolt and remove the hinge pin and tray. Then support the 
 breech plate by blocking and turn out the breech-plate screws, loosen- 
 ing all before any are entirely removed, and taking out the top and side 
 ones last. To avoid marring the thread, let one man hold a heavy 
 screw-driver in the slot and a second turn its blade with a screw 
 wrench, catching the blade near the screw head. Put on the rotating 
 lever and unscrew the block. The breech plate should not be taken 
 off unless it be absolutely necessary; if necessary to remove it, an 
 eyebolt, which screws into the oil hole, is provided for convenience 
 in handling. If the block can be unlocked, but not drawn back, aid 
 the translating roller by gently ramming on the face of the obturator, 
 interposing a hard-wood block between the rammer and the obturator. 
 
 To Assemble Breech Mechanism. The tray will be swung in the 
 loading position, in which it is held by the tray-back latch. The 
 translating roller must be removed if it should have been put into the 
 tray previously, but this should not have been done. The obturating 
 
f 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
ARMAMENT 125 
 
 spindle with the gas-check pad will be removed from the breechblock, 
 a rope sling will be passed over the threads around the center of the 
 breechblock and at right angles to its axis, the block being in trans- 
 lating position i. e., the translating stud at its rear end points down- 
 ward. The sling will be attached to the hook of the loading crane or 
 the gin. The breechblock will be hoisted until it can be swung 
 into the screw chamber; it will be inserted as far as the rope per- 
 mits. A handspike will be inserted into the spindle cavity, and by 
 means of this two or three men can hold the block in place while the 
 position of the rope sling is being changed farther back. The block 
 will now be forced into the breech recess and rotated till the rotating 
 crank reaches its vertical terminal position. 
 
 The tray will now be swung to the breech plate ancT the translating 
 roller screwed into the tray for the first time. The translating roller 
 should not be screwed home with the tray in any other than the firing 
 position, otherwise the rear end of the tray latch would have to be 
 lifted up to the proper height to prevent interference between the 
 lock bolts and the translating roller. 
 
 In case neither loading crane nor gin are available, the shot truck 
 may be utilized. The breechblock is rolled onto the truck by means 
 of a plank ramp, and supported thereon in its proper position by 
 means of bits of wood. The shot truck will then be adjusted to the 
 proper height and angle and the breechblock forced into the breech 
 recess and rotated, as above described. 
 
 The operation of inserting and adjusting the obturating spindle is 
 as follows : The breech will be opened and breechblock and tray swung 
 into the loading position. The obturator spindle, with the split rings 
 and pad in place, will be inserted into the breechblock and will be 
 secured by screwing up the obturator nut on the rear end of the spindle. 
 The breechblock is then translated and rotated into the firing position 
 and the wrench applied to the large nut, which is tightened as much as 
 possible by one man. The clamping screw on the obturator nut should 
 then be tightened. This screw should be set up only moderately hard. 
 The spindle is properly adjusted if while it has no play longitudinally, 
 it can be turned round freely by taking hold of the obturator-spindle 
 (mushroom) head with both hands. 
 
 This last adjustment may have to be repeated after a few rounds 
 have been fired, if it is found that the spindle has any longitudinal 
 play. 
 
 Weight of projectile, capped, 604 pounds; weight of propelling 
 charge, nitro-celullose powder, 155 pounds; weight of igniter charge, 
 
126 THE SERVICE OF COAST ARTILLERY 
 
 4 pounds; weight of bursting charge, gun cotton, 22.4 pounds, for 
 A.P. shell; 7.5 pounds for A.P. shot. 
 
 Muzzle velocity 2,250 foot-seconds. Maximum pressure, 38,000 
 pounds per square inch. Muzzle energy, 21,293 foot-tons. Maximum 
 range 12,259 yards. Penetration in Krupp cemented armor at 5,000 
 yards 9.8 inches. 
 
 10-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 Mi 
 
 This rifle is similar in construction and power to the Model of 1888, 
 and differs only in having 5 C hoops. 
 
 10-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 Mil 
 
 This rifle is similar in construction and power to the Model of 1888, 
 and differs only in the following points: 
 
 2 C hoops, 1 D hoop, 3 A hoops, and 3 B hoops. 
 
 The steel breech plate and bronze bushing used in the other models 
 are replaced in this one by a bronze plate. 
 
 10-lNCH BREECH-LOADING RIFLE, MODEL OF 1895 
 
 This rifle is similar in construction and power to the Model of 1888, 
 and differs only in the following points: 
 
 Total length 369.1 inches; weight 30 tons; length of bore, 35 
 calibers. 
 
 The breech mechanism, known as the Stockett system (see Fig. 
 13 and Plates IX and X), consists of the breechblock, block-locking 
 device, obturator, tray, tray latch, hinge, compound gear worm-wheel, 
 worm and shaft, hinge pin and nut, rotating crank, ball bearings and 
 bronze bushings for worm shaft. 
 
 The breechblock has 6 threaded and 6 slotted sectors. From the 
 rear face, to the right, projects a rotating lug with teeth, into which 
 mesh the teeth of the compound gear. Projections on the upper and 
 lower edges of this lug strike against the gear and limit the rotation 
 of the block in both directions. A translating rack is cut in the slotted 
 sector which is at the same height as the compound gear when the 
 block has been fully rotated for withdrawing. The function of this 
 rack in conjunction with the compound gear, is to withdraw the 
 breechblock, swing it and the tray into the loading position, and in 
 closing the breech to perform the reverse operation. The breech- 
 block has two guide grooves each 30 degrees from the lowest element of 
 
ARMAMENT 
 
 127 
 
 the block, when it is in position for withdrawing, and ending in shoulders 
 near the front face. 
 
 There are two short grooves, midway between the guide grooves 
 and parallel to them at opposite ends of the block, ending in inclined 
 shoulders; they form seats for the toes of the tray latch when the 
 block is withdrawn. 
 
 The block-locking device consists of a bell-crank lever pivoted 
 to the breech face near the upper end oLthe hinge pin, the longer arm 
 of which is connected to a spring-controlled locking bolt, which is 
 
 ft Thrust Bearings 
 
 Shaft Bu shiny. 
 Worm Shaft 
 
 FIG. 13. 
 
 seated in the breech face, its lower end being engaged in a notch cut 
 into the periphery of the block. The short arm of the bell crank is 
 arranged to fit into a notch cut into a cap fitted to the upper end of 
 the hinge pin. The bell crank is provided with an operating handle 
 for controlling the locking bolt. The block-locking bolt must be 
 tripped from its seat in the breechblock before the breech mechanism 
 can be opened, that is, before the breechblock can be rotated. During 
 the rotation and translation of the block the short arm of the bell- 
 crank lever is out of its notch in the hinge-pin cap and is bearing against 
 
128 THE SERVICE OF COAST ARTILLERY 
 
 the periphery of the cap; this holds or supports the locking bolt in 
 its upward or unlocked position, so that there is no interference between 
 the locking bolt and the breechblock when the latter is being closed. 
 The locking bolt works automatically when the breech mechanism is 
 closed, but must be operated by hand before the breechblock can be 
 rotated for opening. 
 
 The obturator is of the same construction as for the model 1888 
 gun, except that ball bearings are used instead of spindle washers. 
 The tray is of steel, mounted in rear of the breech, and consists of 
 two guide rails, a cylindrical hinge, and a heavy connecting web. A 
 hinge pin passing through two lugs on the hinge plate supports the 
 tray. A tray latch, with locking bolt and spring, is also provided. 
 The tray latch consists of the latch proper, and its catch, with latch 
 spring, locking bolt and spring, and the operating stud. 
 
 The latch proper is a steel lever, pivoted by a bolt to the web of 
 the tray. It has a toe and handle at the rear end, and a toe and hook 
 at the front end. The front toe is bored through for the passage of 
 the operating stud, and there is a seat on the upper surface of the 
 latch for the latch spring. The latch spring is spiral, and is seated in 
 the lower face of the web and the upper space of the front half of the 
 latch. The locking bolt is cylindrical, and has a spiral spring in rear, 
 constantly pushing it forward. The operating stud, which controls 
 the locking bolt, passes through the front toe of the latch. The tray- 
 latch catch is a steel stud, screwed into the breech, and is of a shape to 
 receive the hook of the latch. The hinge plate is of steel, and is 
 assembled by seven screw bolts to the breech of the gun, on the right- 
 hand side. Its rear face is flush with the breech, and has two lugs 
 for the hinge pin. The lower end of the plate is bored out to receive 
 the worm and shaft, and its bearings. 
 
 The hinge pin is cylindrical, with a flange on top, a square surface 
 for the bronze worm-wheel beneath the lower lug, and a thread for a 
 securing nut below the wheel. Just below the upper lug, at opposite 
 extremities of a diameter, are two splines, upon which the compound 
 gear is assembled. The upper lug hole is large enough to permit 
 these splines passing through, and the pin is correspondingly enlarged 
 at the upper end. The compound gear is assembled between the upper 
 hinge lug and the hinge, and is secured from rotating on the pin by the 
 splines that fit into two grooves on the inner surface of the gear. The 
 latter is formed by first cutting large tooth-shaped screw threads, 
 and then cutting longitudinal grooves at regular intervals, thus forming 
 a combined spiral gear (to rotate the block), and a pinion (to operate 
 
ARMAMENT 129 
 
 on the translating rack). A ball-bearing washer of steel is placed 
 between the hinge and lower hinge lock, to reduce friction in swinging 
 the tray and block. Between the ends of the worm and bronze 
 bushing are placed hardened steel ball bearings, to reduce the friction 
 clue to the end thrust. The outer end of the shaft is squared to receive 
 the crank, the handle of which has a loose-fitting brass sleeve to 
 facilitate operation. 
 
 Action of the Breech Mechanism. The block, when in firing position, 
 has its threads engaged in those of the breech recess, and is provided 
 with a locking bolt fitted in a recess in the breech face of the gun, 
 having its lower end seated in a notch formed on the periphery of the 
 block. The upper teeth of the rotating rack are engaged in those of 
 the compound gear; the tray is latched to the breech; the rear toe 
 of the latch projects above the upper surface of the tray; the front 
 toe is on a level with this surface, and the rear face of this toe retains 
 the latch locking bolt in its recess. 
 
 To Open the Breech. First release the locking bolt from its seat 
 in the block by pressing downward on its handle. The crank is then 
 turned continuously towards the muzzle, until the tray comes to rest 
 against the hinge. As the crank is turned, the teeth of the compound 
 gear, working in those of the rotating rack, cause the block to rotate 
 to the left until its guide grooves are opposite the guide rails of the 
 tray. In this position the lower shoulder on the lug strikes the lower 
 surface of the gear, preventing further rotation of the block. The 
 teeth of the gear then engage in the translating rack, and the block 
 is withdrawn. At the end of its travel it strikes the inclined surface 
 on the rear toe of the tray latch, forcing it down against the action of 
 the latch spring, thus unlatching the tray. The front toe of the latch 
 then rises and engages in its groove in the block; the locking bolt 
 moves forward and enters its seat in the latch, forcing the operating 
 stud to the front. The block is prevented from moving to the rear 
 on the tray by the bearing of the guide rails against the shoulders 
 of the guide grooves, and from moving forward, by the front toe of 
 the latch. The block and tray swing with the hinge pin to the right, 
 until the tray rests against the hinge. In this position the crank 
 handle is horizontal and in front of the shaft, the weight of the frame 
 being sufficient to retain the block and tray in place, without a back 
 or securing latch. 
 
 To Close the Breech. The crank is turned to the rear, until the 
 projecting shoulder on the upper surface of the rotating lug strikes 
 the gear. As the block is locked to the tray, turning the crank to the 
 
130 THE SERVICE OF COAST ARTILLERY 
 
 rear swings both block and tray to the left until the tray strikes the 
 breech of the gun. The operating stud, projecting through the front 
 of the latch, being pressed back by bearing against the breech, forces 
 the locking bolt into its recess and releases the tray latch in front. 
 The first small forward motion of the block when the tray strikes the 
 breech releases the rear toe of the latch, and the latch spring forces 
 the hook over the catch, thus locking the tray to the breech. The 
 block now being free to move forward, is forced home by the translating 
 rack and gear and rotated to the right by the rotating lug and gear, 
 until in the firing position again, when the projection on the upper surface 
 of the lug strikes the gear, preventing further motion. 
 
 To Assemble the Breech Mechanism. The breech recess, also all 
 surfaces of contact with parts of the breech mechanism, will be care- 
 fully cleaned and any traces of rust removed. 
 
 All parts of the breech mechanism will be carefully cleaned also. 
 
 In assembling the breech mechanism, the worm shaft with its 
 ball bearings will be put into place first. Insert one ball bearing 
 into seat at inner end of worm recess. Assemble other ball bearing 
 on worm shaft outside of worm and insert worm shaft with this ball 
 bearing into recess. Then put the threaded bronze bushing into place 
 and screAV entirely home, when its collar will be in perfect contact with 
 the hinge plate. 
 
 The tray (console) will be assembled next, with its ball bearing 
 tray latch, and catch bolt. The hinge pin will be slipped into place 
 to support the tray and allow it to be swung into position to receive 
 breechblock. The obturating spindle with the gas-check pad, split 
 rings, and disk will be removed from the breechblock so that block 
 can be suspended by a rope sling through hole in breechblock. This 
 rope sling to be hung from a gin or crane erected for the purpose. 
 
 The breechblock will be hoisted until its guide grooves are opposite 
 the guide rails of the tray, and will be pushed on from the front of tray 
 (as stops would prevent the opposite), taking care that the breech- 
 block is horizontal. 
 
 Note that in the 12-inch rifle the tray must be rotated till its front 
 surface is parallel to the axis of the gun when the block is being slid 
 into place, as otherwise the rear of block would not clear the upper 
 hinge lug when the block is well in the recess. 
 
 Disengage the rope. 
 
 Swing tray with block against end of gun, push the block into 
 breech recess of gun, shoving it entirely home, but do not rotate it. 
 
 The tray should now be supported by blocking or otherwise, so 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
ARMAMENT 131 
 
 that the hinge pin may be withdrawn. After which hold in position 
 the spiral gear with the face having cylindrical hub uppermost, the two 
 teeth marked .4. and B being inserted into spaces marked A and B on 
 rotating rack of block. The vertical line engraved on the spiral gear 
 must now be coincident with that on the upper hinge lug. Insert 
 hinge pin with vertical line thereon coincident with above and lower 
 gently through spiral gear and tray and lower hinge lug, but not below 
 the latter. Hold in this position while bronze worm wheel is put into 
 place, as follows: The worm wheel has upper face marked "Top," 
 and the marked spaces on wheel must engage the similarly marked 
 teeth of the worm. The worm wheel should now be rotated by the 
 worm (so that proper engagement of teeth is preserved) until the line 
 engraved upon the wheel coincides with the before-mentioned vertical 
 line of hinge lugs and spiral gear and hinge pin. Then hinge pin can 
 be lowered completely into place, and nut at bottom screwed on, and 
 the locking pin driven through nut and hinge pin. 
 
 The crank handle should be placed upon the worm shaft in the 
 position indicated by the engraved line and the set screw. 
 
 The insertion and securing of the spindle will be performed as 
 follows: With the breechblock in loading position, the spindle, with 
 split rings, gas-check pad, and gas-check disk upon it, will be inserted 
 into the block. The large ball bearing will be put in place upon rear 
 end of spindle projecting through block, and spindle secured by 
 screwing up by hand the spindle nut. 
 
 The adjustment of the spindle is the same as described for model 
 of 1888 guns. 
 
 To Remove and Dismount the Breech Mechanism. The operations 
 are the reverse of those given above. 
 
 The maximum elevation of the carriage is 15 degrees, corresponding 
 range, 14,062 yards. 
 
 10-lNCH BREECH-LOADING RIFLE, MODEL OF 1900 
 
 This is the latest type of 10-inch rifle. It is similar in construction 
 to the model of 1895, and differs only in the following points: 
 
 Total length 420 inches; weight 34 tons; length of bore 40 
 calibers. The first guns constructed of this model had rifling consisting 
 of 60 grooves; twist, one turn in 50 calibers to one turn in 25 calibers. 
 The later guns of this model have 90 grooves; twist, increasing from 
 to 1 caliber. The powder chamber is made cylindro-cenical, instead 
 of cylindrical, as in all other types of this caliber. 
 
132 THE SERVICE OF COAST ARTILLERY 
 
 Weight of propelling charge, nitro-cellulose powder, 205 pounds; 
 weight of igniter charge 4 pounds; weight of bursting charge, gun 
 cotton, A.P. shell 22.4 pounds; A. P. shot 7.5 pounds. 
 
 Muzzle velocity 2,250 foot-seconds. Muzzle energy 26,169 foot- 
 tons. 
 
 Maximum pressure 38,000 pounds per square inch. Maximum 
 elevation permitted by the carriage 12 degrees; corresponding range 
 14,162 yards. Penetration in Krupp cemented armor, at 5,000 yards, 
 11.6 inches. 
 
 8-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 
 
 This rifle is one of the earliest models of the built-up forged steel 
 type, and was for that reason taken as an example and described in 
 detail in the chapter on Gunnery and Ballistics. 
 
 Total length 278.52 inches; weight 14.50 tons; length of bore 
 32 calibers. The bore has 48 grooves; twist of rifling, one turn in 50 
 calibers to one turn in 25 calibers. Weight of projectile, capped, 
 316 pounds; weight of propelling charge, nitro-cellulose powder, 80 
 pounds; weight of igniter charge 1.5 pounds; weight of bursting 
 charge, gun cotton, A.P. shell 11.5 pounds; A.P. shot 4 pounds. 
 
 Muzzle velocity 2,200 foot-seconds; Muzzle energy 10,683 foot- 
 tons. Maximum pressure 38,000 pounds per square inch. Maximum 
 elevation permitted by the carnage 12 degrees; corresponding range 
 11,019 yards. Penetration in Krupp cemented armor, at 5,000 
 yards, 6.8 inches. 
 
 8-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 Mi 
 
 This rifle is similar in construction and power to the Model of 1888, 
 .and differs only in the following points: 
 
 5 C hoops. The size of the D hoops altered slightly. 
 
 8-lNCH BREECH-LOADING RIFLE, MODEL OF 1888 Mil 
 
 This rifle is similar in construction and power to the model of 1888 
 Mi, and differs only in the following points: 
 
 2 C hoops; 1 D hoop; 4 A hoops. Jacket increased slightly in 
 length. Bronze breech plate. 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
ARMAMENT 133 
 
 INTERMEDIATE ARMAMENT 
 
 6-lNCH QUICK-FIRING ARMSTRONGS GUN 
 
 (See Plates XI and XII) 
 
 This rifle is manufactured by the W. G. Armstrong Company, 
 England. It consists of a tube, jacket, 2 C hoops, 1 A hoop, 1 D hoop, 
 and a breech ring. 
 
 It is constructed entirely of steel, and is designed for obtaining 
 great rapidity of fire. For this purpose it is mounted on a special 
 mounting, and is not provided with trunnions, but is carried by a 
 cradle which encircles the gun, and in which it slides when recoiling. 
 This cradle is provided with trunnions on which the gun and cradle 
 are balanced. The breech of the gun is surrounded by a breech ring 
 which has a projecting arm on it for connecting the gun with the recoil 
 cylinder, which forms part of the cradle. The mechanism for closing 
 the breech is of the interrupted-screw system, so arranged that it 
 can be quickly opened or closed by a single movement. The gun is 
 provided with electrical firing gear, connected with an electrical pistol, 
 fixed to the mounting in a convenient place, so that the man laying 
 the gun can fire while looking over the sights. It is also provided with 
 a percussion arrangement for mechanical firing in case of failure of the 
 electrical gear. The gun sights are fixed to the gun cradle, and do 
 not therefore recoil with the gun. The powder is contained in a metallic 
 cartridge case, the base of the projectile resting against the front end 
 of this case. 
 
 Breech Mechanism (Plate XII) . The breech of the gun is closed by 
 a screw formed in two steps, the front step being tapered and of less 
 diameter than the rear; both steps have three portions of their threads 
 removed, each one-sixth of a turn, the threads on one step standing 
 opposite to the blank spaces on the other; this arrangement distributes 
 the strain all round the circumference of the breech screw. The 
 interior of the gun at the breech is prepared in a similar manner, and 
 admits of the breech screw being swung into place and locked by a 
 simple mechanism to be described. 
 
 The breech screw is supported by a carrier, on which it is free to 
 revolve through an angle of 60 degrees; the carrier is hinged to the 
 right side of the breech ring, so that the screw can swing clear of the 
 breech opening for loading. The screw is secured on the carrier by 
 means of the stop bolt. The breechblock is unscrewed and with- 
 
134 THE SERVICE OF COAST ARTILLERY 
 
 drawn from the gun by a single horizontal movement of the hand- 
 locking lever, which is pivoted on the right side. 
 
 A projecting pin is screwed into the rear face of the breech screw, 
 and enters a traversing bush in the sliding block. This block slides 
 in a seat in the carrier, and is connected to the hand-locking lever 
 by the link. When the breech is open the screw is prevented from 
 turning on the carrier by a spring catch on the carrier, which engages 
 a notch in the screw as it is withdrawn from the gun; when closing 
 the breech the catch comes in contact with the face of the gun, thus 
 releasing the screw and leaving it free to be screwed home. 
 
 It is impossible to fire the gun until the breech is completely locked. 
 This is insured by means of a safety gear consisting of a pawl fitted 
 to a spindle. The pawl engages a lip on the striker, and prevents the 
 latter from touching the primer while the hand lever is in the unlocked 
 position. On the lower end of the spindle is formed a lever with a 
 projection which engages in a recess on the hand lever. Another pro- 
 jection is formed on the lever, which is acted upon by the sliding block 
 so that the pawl is retained in position by a key on the spindle falling 
 into a notch in the carrier, while the hand lever is drawn clear in 
 unscrewing the breechblock. 
 
 When the hand lever is in the locked position, it is held there by 
 the torsion of the spiral spring when the gun is elevated. 
 
 The striker is secured in the carrier by a retaining nut, and can be 
 readily removed by slightly withdrawing it and turning the nut a quarter 
 of a turn. 
 
 To fix the striker it is pushed into the gun, and the retaining nut 
 turned to the right or left. 
 
 Electrical Firing Gear. This gear consists of an insulated firing 
 needle fitted in the axis of the breech screw. The needle is surrounded 
 by a spiral spring, which holds it against the electrical primer in the 
 base of the cartridge case. The needle is provided with a projection 
 at the rear end by which it is drawn back, the projection being acted 
 upon by a lever on the spindle. On the lower end of the spindle is 
 fitted a pawl, having a projecting piece on the under side, which is 
 held in a cam groove cut in the hand lever. When the hand lever 
 is moved away from the locked position, the spindle is revolved b}^ its 
 projecting piece working in the cam groove, thus causing the pawl 
 to engage the projection, and draw the needle back a sufficient distance 
 to effectually prevent it from making a contact with an electric primer. 
 
 Two brackets are provided, one fitted to the gun, while the other 
 is fitted to the gun cradle. These brackets carry the insulated electric 
 
1 
 
ARMAMENT 135 
 
 cable and the contact pieces on the ends of these cables, the contact 
 pieces being forced out by springs so that their contact is always 
 insured. The cable from the needle passes to the bracket on the gun, 
 and there contact is made through the contact pieces to the cable 
 attached to the bracket on the gun cradle, which is connected to the 
 electric firing pistol. This pistol is fitted to the mounting in a con- 
 venient position for the man who lays and fires the gun. A three-cell 
 electric battery is placed on the mounting; one of the terminals 
 of this battery is connected to the pistol and the other to the mounting 
 as an earth connection. The brackets are detachable and can be 
 easily removed, which allows a spare cable to be readily applied if 
 required. 
 
 An alternative electrical firing gear is also provided, which can be 
 immediately put into action if the other one becomes short circuited 
 or the insulation fails. It consists of a long cable, having a split pin 
 at one end, which is pushed into a hole in the head of the needle. The 
 other end is connected to the terminal of the battery. About the 
 middle of the cable is a firing key, which is held in the hand of the 
 man who lays the gun. On pushing down the end of this firing key 
 the circuit is completed and the current passes direct from the battery 
 to the needle, and thus fires the gun. 
 
 Before connecting this alternate cable to the battery and the 
 needle, the parts of the other cables, which are connected to the battery 
 and the needle, should be removed. 
 
 Percussion Firing Gear. This gear is fitted to the retaining nut, and 
 consists of a spring trigger with loop to receive the lanyard. 
 
 To fire by percussion the firing pin or needle is pulled to the rear 
 until it is caught by the trigger, which retains it until the latter is 
 displaced by the -lanyard attached to the trigger loop. This leaves 
 the firing needle free to travel forward and strike the primer. 
 
 When firing with this gear the adapter is screwed into the base of 
 the cartridge case and the percussion primer placed into its chamber 
 in the adapter. 
 
 When the trigger is displaced the projection on the head of the 
 trigger is moved into a slot provided in the carrier, which prevents 
 the retaining nut from being turned if the lanyard is pulled in an 
 upward direction. 
 
 Cartridge Extractor. The cartridge is started by the extractor, 
 which only has sufficient motion to insure its being free for the remainder 
 of the extraction, the conical shape of the cartridge case and chamber 
 rendering a small motion sufficient for this purpose. The cartridge 
 
136 THE SERVICE OF COAST ARTILLERY 
 
 is then completely withdrawn and laid in the recess by means of a hand 
 extractor, which readily fits over and firmly holds the primer. 
 
 The mechanical extractor is worked by the carrier in opening 
 the breech screw. It consists of a lever passing through one side of 
 the gun and fitting into the groove for the rim of the cartridge case 
 in such a manner that when it is turned about its own axis the fitted 
 part acts as a lever and presses the cartridge to the rear. 
 
 The extractor is brought back into its place as the breech is closed 
 by means of a strong helical spring outside the gun. This spring also 
 serves as a buffer to prevent the breech screw and carrier being swung 
 too violently around. The extractor is fitted on the right-hand side, 
 so that it is out of the way of loading or damage from a projectile 
 when the latter is being entered into the gun. 
 
 The bore has 24 grooves; twist, from to 1 in 30 calibers. The 
 powder chamber is conical. 
 
 Total length 249.1 inches; weight 6.6 tons; length of bore 40 
 calibers; weight of projectile 106 pounds; weight of propelling charge, 
 nitro-cellulose powder 19 pounds; Cordite 13.3 pounds; weight of 
 bursting charge, Maximite or Explosive D, 4.3 pounds. 
 
 Muzzle velocity 2,150 foot-seconds. Muzzle energy 3,400 foot- 
 tons. Maximum pressure 34,000 pounds per square inch. Maximum 
 elevation permitted by the carriage 16 degrees; corresponding range 
 10,185 yards. Penetration in Krupp cemented armor, at 5,000 yards, 
 2.9 inches. 
 
 6-lNCH RAPID-FIRE GUN, MODEL OF 1897 
 (See Modification I) 
 
 6-lNCH RAPID-FIRE GUN, MODEL OF 1897, Mi 
 (Ordnance Department Model) 
 
 This rifle follows the general method of built-up forged-steel con- 
 struction. It is of American manufacture. It consists of a tube, 
 jacket, 4 A hoops (one of which is the trunnion hoop), 2 C hoops, 1 D 
 hoop. The powder chamber is cylindrical. 
 
 The breech mechanism consists of the breechblock, gear segment, 
 block carrier, lever, pinion, latch, obturator, and associate parts. 
 
 The breechblock is cylindrical, with an axial hole for the reception 
 of the spindle and washer. The front part of the block for a short 
 distance back is reduced in diameter. This reduced part or nose of 
 
ARMAMENT 137 
 
 the block leaves a space in the breech recess of the gun, in which fouling 
 may collect without interrupting the working of the block. 
 
 On the outer surface of the block is cut a V-shaped screw thread 
 with rounded top and bottom. This screw thread is divided circum- 
 ferentially into eight equal parts, and the threads cut from the alternate 
 sectors. The sectors from which the threads are cut are called the 
 slotted sectors, and permit the entry of the block past the correspond- 
 ing threaded sectors in the breech recess. The threaded sectors of the 
 block are then engaged with the threaded sectors of the recess by 
 revolving the block through an angle of 45 degrees about its longi- 
 tudinal axis. Portions of the threaded sectors on the block are cut 
 away and parts of the slotted sectors deepened to provide clearance 
 between the block and breech recess when the former is swung to or 
 from the piece. 
 
 The rear end of the block is turned down to a smaller diameter, 
 and the cylindrical surface thus formed is prolonged into the block 
 and increased in length by means of an annular groove cut in the 
 rear face of the block. This cylindrical surface is called the guide 
 cylinder, and the annular groove, the guide groove of the block. That 
 portion of the rear face of the block which lies outside of the guide 
 groove is called the stop flange. When the block is withdrawn the 
 stop flange strikes the bottom of the stop groove in the block carrier 
 and limits the rearward motion of the block. The guide cylinder 
 supports the breechblock in the carrier and guides it in its motions of 
 rotation and translation. The guide flange of the block carrier fits 
 into the guide groove of the block and assists in supporting and guiding 
 the latter. Four oil holes are drilled radially from the exterior of 
 the block to the bottom of the guide groove to facilitate oiling the bear- 
 ing surfaces. These holes also act as air vents. An oil hole cut radially 
 in the nose of the block and closed by a screw is provided for oiling 
 the front face of the block. 
 
 The locking recess is cut in the surface of the guide cylinder. The 
 depth of this locking recess gradually increases from rear to front, 
 beginning at zero at the rear and terminating at the front end in a 
 well, called the locking recess. When the block is withdrawn the inner 
 end of the latch bolt drops into the locking recess and locks the block 
 positively to the block carrier. 
 
 The gear segment is attached to the rear end of the breechblock 
 by a spline and two screws. It consists essentially of a segment of 
 a bevel gear and a short rack, which mesh with a pinion pivoted on 
 the block carrier and actuated by the lever. Part of the periphery 
 
138 THE SERVICE OF COAST ARTILLERY 
 
 of the pinion is cut into a bevel gear and another part into a pinion, 
 meshing with the corresponding parts of the gear segment. The 
 bevel-gear parts rotate the block and the rack-and-pinion parts trans- 
 late it. These motions are successive; the termination of the motion 
 of rotation in opening the breech brings the rack and pinion into the 
 proper position to withdraw the block, and the termination of the 
 motion of translation in closing the breech brings the bevel-gear seg- 
 ments into mesh to rotate it. 
 
 The block carrier is a steel casting pivoted by means of a hinge pin 
 to a hinge plate attached to the jacket on the right side of the breech. 
 As its name indicates, its principal office is to support the block in its 
 various movements. It is bored to take the breechblock guide cylinder. 
 On the front face of the carrier surrounding this bore is a projecting 
 ring called the guide flange which enters the guide groove of the block 
 and assists in supporting and guiding it. An annular groove, called 
 the stop groove, cut in the front face of the carrier at the base of the 
 guide flange, increases the length of the latter, and forms a stop against 
 which the stop flange of the breechblock strikes, limiting the motion 
 of the block to the rear. 
 
 A lug projects to the rear from the lower part of the block carrier 
 and forms a seat for the pinion. The latter is mounted on this seat 
 upon a pivot in the form of a screw bolt which passes through the 
 pinion and screws into the lug. This screw-bolt pivot is prevented 
 from unscrewing by the pivot nut which is screwed on it under the 
 lug. The lever for actuating the pinion is fitted upon a square 
 extension upon the latter. The free end of the lever terminates in a 
 vertical handle. 
 
 The latch is a locking device for the block carrier. It consists 
 of the lock bolt, latch spring, latch lever, and latch-lever pivot, mounted 
 in the block carrier, and the latch-bolt seat and tripping stud secured 
 to the breech face of the piece by screws. The latch bolt lies in a 
 radial hole drilled through the block carrier. The end of the bolt 
 nearer the axis of the block is tapered to facilitate its entering the 
 locking recess in the breechblock guide cylinder. It is also slightly 
 beveled on the end so that it will the more easily ride out of the locking- 
 recess and up the inclined bottom of the groove. The outer end of 
 the bolt has a mortise cut through it in which one end of the latch 
 lever works. This end of the latch bolt is also slightly beveled to make 
 it ride out of the latch-bolt seat. The latch-bolt seat is a lug secured 
 to the breech face by two screws. (There are a few guns in service 
 having the latch-bolt seat and tripping stud in the form of screw 
 
ARMAMENT 139 
 
 bolts screwed directly into the breech face of the piece.) Through it 
 is drilled a radial hole into which the latch bolt enters when the carrier 
 is against the breech of the piece. 
 
 The latch lever is pivoted in a circumferential slot cut in the exterior 
 surface of the carrier. The latch-lever pivot is a small screw bolt 
 inserted from the outer base of the carrier. One end of the lever 
 works in the mortise in the latch bolt; the other end is broadened, 
 forming a shoulder against which a spiral spring, called the latch-lever 
 spring, bears. This spring is compressed between the block carrier 
 and the latch-lever shoulder, by means of the tripping stud. This 
 operation withdraws the latch bolt from the breechblock. When the 
 block is swung away from the breech, the inner end of the latch bolt 
 rests in the locking recess and locks the block to the carrier. In this 
 position the upper end of the latch lever, against which the spring 
 bears, projects slightly beyond the exterior surface of the carrier. 
 In closing the breech, just before the carrier comes in contact with 
 the breech face of the piece, this projecting part of the lever strikes 
 the beveled surface of the tripping stud and is forced toward the axis 
 of the block. This motion of the lever lifts the latch lock from the 
 locking recess and leaves the block free to be translated through the 
 block carrier. 
 
 The tripping stud is a lug secured to the breech face by two screws. 
 Its inner face is beveled so as to trip the latch as just explained. The 
 complete action of the latch is as follows: With the breech closed, the 
 outer end of the latch bolt rests in the latch-bolt seat, locking the 
 block carrier to the breech face; the inner end of the latch bolt bears 
 against the guide cylinder of the block and, at the end of the motion 
 of rotation of the block in opening the breech, rests in line with the 
 end of the latch groove. When the block is withdrawn the bolt rides 
 down the inclined bottom of the latch groove and its outer end is 
 withdrawn from the latch-bolt seat, freeing the block carrier from 
 the breech. At the end of the motion of withdrawal the inner end of 
 the latch bolt enters the locking recess in the breechblock. As the bolt 
 carrier is swung away from the piece the end of the latch lever clears 
 the tripping stud so that the full force of the latch spring comes into 
 play and the latch bolt is forced to the bottom of the locking recess, 
 securely locking the block to the carrier. In closing the breech the 
 action of the latch is the reverse of that just given. 
 
 With breech open the block is locked to the carrier. As the latter 
 is swung against the breech face, the tripping stud, by means of the 
 lever, raises the latch bolt far enough from the bottom of the latch- 
 
140 THE SERVICE OF COAST ARTILLERY 
 
 groove locking recess for the end of the bolt to ride on the inclined 
 bottom of the groove as the block is moved forward through the block 
 carrier. As the bolt rides up the inclined bottom of the latch groove 
 its outer end enters the latch-bolt seat and locks the block carrier to 
 the breech face. 
 
 The obturator is composed of the following parts: The spindle, 
 front and rear exterior split rings, interior split ring, pad, filling-in 
 disk, spindle nut, and spindle-ball washer. 
 
 The object of the obturator is to prevent the escape of gas from 
 the powder chamber to the rear during firing, and to transmit to the 
 breechblock the stress of firing resulting from pressure of gases upon 
 the bottom of the bore. 
 
 The spindle is mounted in the block in the spindle recess, the rear 
 end of the stem is threaded for the spindle nut, while the front end is 
 enlarged into a mushroom-shaped head which forms the bottom of the 
 bore of the gun. 
 
 The vent is axial and is drilled through the spindle. A copper 
 bushing, forced into an undercut in the face of the mushroom head, 
 protects the vent from erosion and enables repairs to be easily made. 
 In passing through this copper plug the vent is reduced in diameter, 
 and the rear end of the vent is formed into a primer seat to take the 
 primer used to ignite the charge. 
 
 The split rings are of steel accurately finished, and split diagonally 
 through one side. The exterior ones are made of slightly greater 
 diameter than the gas-check seat in the gun and are sprung into place. 
 The interior one is slightly smaller than its seat on the spindle. The 
 filling-in disk is a steel washer interposed between the gas-checking 
 device and the front face of the breechblock. A slight shoulder on 
 the rear face of the mushroom head supports and centers the front 
 split ring. The rear split ring is similarly held by an offset on the front 
 face of the filling-in disk. 
 
 The gas-check pad is a disk of asbestos and tallow, compressed 
 under heavy pressure and covered with canvas. It forms a yielding 
 medium for the transmission of pressure to the block. Under the 
 pressure of firing the plastic nature of the pad causes it to press outward 
 toward the gas-check seat and inward against the spindle, forcing the 
 split rings firmly against their seats and completely stopping the passage 
 of gas. 
 
 The spindle-ball washer consists of two steel rings with a groove 
 cut in one face of each ring to form a pocket for twenty f-inch hardened- 
 steel balls. The rings with the balls between them are held together 
 
ARMAMENT 141 
 
 by a cylinder of ^-inch copper, which lines the bore of the rings and 
 has its ends flanged outward over their end faces. The washer is 
 interposed between the spindle nut and the breechblock and reduces 
 the friction between them when the block is rotated. 
 
 The spindle nut is screwed on the rear end of the stem of the 
 spindle, and holds the spindle in its position in the block. It is turned 
 on the exterior, provided with a screw-driver slot, and plainly stamped 
 to indicate direction of unscrewing. 
 
 The spindle key extends radially downward through the carrier 
 and block, and its inner end enters a longitudinal slot cut in the stem 
 of the spindle. It acts as a stop for limiting the rotation of the block, 
 and also prevents the spindle from turning. 
 
 A slot is cut in the guide cylinder in which the key moves during 
 the rotation of the block, and thus the firing mechanism is always 
 held in an upright position. 
 
 To Open the Breech. With the block closed the lever lies parallel 
 to the face of the breech, with handle to the left. Moving the handle 
 to the rear and right, describing an arc about the pinion pivot as a 
 center, rotates the block through an angle of 45 degrees and disengages 
 the threaded sectors on the block from those in the breech recess. A 
 further movement of the handle about the same center draws the block 
 to the rear until the stop flange strikes the bottom of the stop groove 
 and the head of the latch bolt comes opposite the locking recess. This 
 movement of the block to the rear frees the gas check from its seat 
 in the gun sufficiently to enable the block, supported by the carrier, 
 to be swung out of the recess and to one side of the piece about the 
 block-carrier hinge pin as a center. At the end of the motion of 
 withdrawal the outer end of the latch bolt is withdrawn from its seat, 
 freeing the block carrier from the breech face of the gun so that a 
 further motion of the lever handle to the right swings the block carrier 
 and block away from the piece. During this movement the inner 
 end of the latch bolt enters the locking recess in the block and locks 
 the block in position in the block carrier. 
 
 To Close the Breech. Move the lever handle to the left as far as 
 it will go. The action of the various parts of the mechanism is the 
 reverse of that given above. When the breech is open it will be noted 
 that the block is locked to the block carrier and that, until it is unlocked, 
 relative motion of the lever handle with reference to the block and carrier 
 can not occur, so that the first movement of the lever handle to the 
 left swings the block into its recess and the carrier against the face 
 of the piece. The action of the latch now frees the block from the 
 
142 THE SERVICE OF COAST ARTILLERY 
 
 carrier and locks the latter to the piece. Further motion of the lever 
 handle first forces the block forward in the breech recess and then 
 rotates it to its seat. 
 
 The movement of the lever handle to open or close the breech 
 above described is one continuous motion. 
 
 To Remove and Dismount Breech Mechanism. Detach firing cable 
 from contact piece. Pull outward on slide stop and lift slide from 
 housing. Rotate operating lever until it stands perpendicular to the 
 face of the breech. Remove the yoke. The housing may then be 
 withdrawn to the rear, bringing with it the safety lever. Open the 
 breech. Remove the gear segment. Remove the breechblock stop. 
 Take out the latch-lever pivot. and remove the latch-lever spring and 
 bolt. The block is then free to be removed from the carrier. Drive 
 out the pivot pin and remove the pivot nut, unscrew the pivot and the 
 pinion and lever are then free to be removed from the carrier. Drive 
 out the hinge pin, being careful to support the carrier while doing 
 so, and the carrier is then freed from the piece. 
 
 To Assemble the Breech Mechanism. The operations are the reverse 
 of those given above. 
 
 Total length 277.85 inches; weight 7.25 tons; length of bore 
 44.6 calibers. The bore has 36 grooves; twist, one turn in 50 calibers 
 to one turn in 25 calibers. 
 
 The weight of the projectile is 106 pounds; weight of propelling 
 charge, nitro-cellulose powder, 29.75 pounds; weight of bursting 
 charge, Maximite or Explosive D, 4.3 pounds. Maximum pressure 
 38,000 pounds per square inch. Muzzle velocity 2,600 foot-seconds. 
 Muzzle energy 4,973 foot-tons. Maximum elevation permitted by 
 carriage 15 degrees; corresponding range 11,799 yards. Penetration 
 in Krupp cemented armor, at 5,000 yards, 3.78 inches. 
 
 6-lNCH RAPID-FIRE GUN, MODEL OF 1900 
 (See Plates XIII and XIV) 
 
 This rifle is of Ordnance Department manufacture. It is similar 
 in construction to the model of 1897, and differs only in the following 
 points: 2 A hoops. Powder chamber considerably larger in diameter 
 and shorter in length. Thread of the breechblock cut in a breech 
 bushing, instead of into the jacket. 
 
 This model of gun is made in two types, one for use on disappearing 
 carriage and the other for rapid-fire carriage, the gun used on the 
 former being slightly heavier than that used on the latter. 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
 =4 LI FOR] 
 
ARMAMENT 143 
 
 Total length 310.4 inches; weight 8.5 tons; length of bore 50 calibers. 
 
 The powder chamber is cylindro-conical. The breech mechanism 
 is the same as that of the model 1897 Mi excepting that the loading 
 tray pivot has a solid head and is screwed into the breech face of the 
 rifle. 
 
 Weight of propelling charge, nitro-cellulose powder, including 
 igniter, 42 pounds ; weight of bursting charge, Maximite or Explosive 
 D, 4.3 pounds. Muzzle velocity, 2,600 foot-seconds. Muzzle energy 
 6,180 foot-tons. Maximum pressure 36,000 pounds per square inch. 
 Maximum elevation permitted by carriage, 15 degrees; corresponding 
 range, 13,077 yards. Penetration in Krupp cemented armor at 5,000 
 yards, 3.94 inches. 
 
 6-lNCH RAPID-FIRE GUN, MODEL OF 1903 
 
 This rifle is practically identical in construction to the model 
 of 1900, except in breech mechanism. It is slightly heavier for use 
 on disappearing carriage. 
 
 The first guns of this model to be manufactured had the same number 
 of grooves in the bore and the same twist of rifling as the model of 1897 
 Mi. The later guns have 54 grooves, with a twist of rifling to 1 
 in 25 calibers. 
 
 The breech mechanism consists of the breechblock, block carrier, 
 operating spool, operating lever, rack, latch, obturator, loading tray 
 and associate parts. 
 
 The breechblock is in the form of a truncated ogive with the interior 
 hollowed out, forming a central cylindrical stem, which is prolonged 
 beyond the rear face of the block. Through the center of the stem is 
 an axial hole for the reception of the obturator spindle and obturator 
 spring. The front part of the block for a short distance back is reduced 
 in diameter, leaving a space in the breech recess of the gun in which 
 fouling may collect without interrupting the working of the block. 
 On the outer surface of the block is cut a screw thread with rounded 
 top and bottom. The rear face of the thread is more inclined to the 
 surface than the front thread. This screw thread is divided circum- 
 ferentially into 12 equal parts, and the thread cut from alternate 
 sectors. A stop groove is cut through the stem of the block to allow 
 the spindle key to pass into the spindle groove. The spindle key 
 thus serves the purpose of a breech block stop. 
 
 A roller is attached to the block by an axle screwed into the block. 
 This roller works in the roller groove of the operating spool entering 
 
144 THE SERVICE OF COAST ARTILLERY 
 
 the groove at the beginning of rotation in closing the breech, and 
 remaining in the groove until the end of the rotation in opening the 
 breech. The functions of the roller are to act as a lock to prevent the 
 rotation of the block under firing pressure, to give the slow arid powerful 
 thrust to the block at the beginning of rotation in opening the breech, 
 and a complete rotation of the block in closing the breech after the 
 rack tooth disengages. 
 
 A translating groove is cut in the surface of the block. The trans- 
 lating stud on the opposite spool works in this groove, to cause a trans- 
 lation of the block. On the rear end of the breechblock stem are two 
 teeth which engage the teeth of the rack to cause rotation of the 
 breechblock. 
 
 The block carrier is pivoted by means of the hinge pin, to the hinge 
 lugs of the hinge plate. It is provided with a central hub bored to 
 take the stem of the breechblock. 
 
 A groove is cut in the inside of the hub to allow the teeth on the block 
 stem to pass in assembling. A slot is cut through the hub to permit 
 the spindle key to pass into the stop groove. The upper end of the 
 spindle key is held in a slot cut in the upper part of the block carrier. 
 
 The firing lever passes through, and is pivoted in the same slot, 
 the firing lever pivot passing through the spindle key, and holding it in 
 place. On the rear face of the carrier a horizontal groove is formed 
 to carry the rack. The slide stop is screwed into the top surface in 
 the upper wall of the rack groove. 
 
 The operating spool is placed vertically between the two block- 
 carrier hinge lugs. The hinge pin passes vertically through the center 
 of the spool. That portion of the hinge pin within the spool is squared, 
 causing the spool to rotate with the hinge pin. The roller groove is 
 cut in the surface of the spool. The translating stud is formed on the 
 surface of this spool. A groove is cut near the top of the spool for the 
 upper latch stud. A notch is cut in the lower edge of the spool to 
 receive the end of the latch body in locking together the spool and 
 carrier while the block is swung away from the breech. 
 
 The operating lever fits over the squared end of the hinge pin, and 
 is held in place by a nut. The breech mechanism is actuated by the 
 operating lever acting through the operating spool. When the breech 
 is closed, the operating lever lies against the face of the breech, and 
 is held in this position by the lever latch. The lever latch consists 
 of a bolt with vertical motion in a housing, and pressed downward by 
 the lever-latch spring. The housing is attached to the breech plate 
 by the housing screws. Th6 downward motion of the latch bolt is 
 
ARMAMENT 145 
 
 limited by a stud on its upper end, striking the ends of the groove in 
 the housing in which the stud travels. When the operating lever 
 is against the breech, the head of the bolt enters a corresponding 
 depression in the top surface of the operating lever, holding the lever 
 against the breech. 
 
 The rack has a horizontal motion in a groove in the rear face of the 
 block carrier. A tooth on its inner end engages between teeth on the 
 stem of the breech block. A lug on the outer end of the rack works 
 in the rotating grooves in the spool. A housing is formed on the rear 
 face of the rack for the rack lock. The rack-lock bolt has a vertical 
 motion in this housing, and is pressed upward by a spring. A handle 
 is screwed into the lower end of the rack-lock bolt. The upper motion 
 of the bolt is limited by a shoulder on the handle striking the housing. 
 The upper end of the bolt enters a slot in the side of the firing mechan- 
 ism, causing the slide to move horizontally with the rack. By pulling 
 down the handle the bolt is withdrawn from the notch in the slide, 
 allowing the slide to operate independently of the rack. 
 
 The latch is housed in a notch cut through the lower hinge lug of 
 the block carrier, and held in place by the latch retainer. A stud on 
 the upper end of the latch rides in a groove cut in the operating spool, 
 and actuates the slide. A similar stud rotates in the groove cut in the 
 lower hinge plate lug. When the block carrier is against the breech, 
 the lower stud rests in a vertical portion of the groove of the hinge-lug 
 pallet, locking the carrier in position during rotation and translation 
 of the block. In opening the breech, when the translation of the block 
 is complete, the latch is elevated by the upper stud, causing the lower 
 stud to rise onto the vertical groove and free the carrier from the face 
 of the breech. At the same time the upper end of the body of the latch 
 enters a notch cut in the operating spool, locking the spool and block 
 carrier together while the block is swung away from the breech. The 
 action of the latch in closing the breech is the reverse of that in opening. 
 The latch retainer consists of a block of steel provided with a ring 
 handle and a spring catch. It is inserted in the latch slot in the hinge 
 lug, and holds the studs of the latch in their grooves. It is prevented 
 from dropping out of the slide by the latch-retainer spring. 
 
 The principal parts of the obturator are the mushroom head, 
 spindle, front and rear exterior split rings, interior split ring, pad, 
 filling-in disk, and spindle spring. They operate in a manner similar 
 to those described for other breech mechanism. 
 
 The loading tray provided remains in the breech recess at all times. 
 The center section of the tray is cut away to a width equal to one 
 
146 THE SERVICE OF COAST ARTILLERY 
 
 of the sectors of the breechblock, leaving a solid section of the same 
 width on each side. A lip is formed on the front edge and one on the 
 rear edge of the tray, extending downward. These lips rest in annular 
 grooves in the breech recess, holding the tray in place when the breech 
 is opened, and guiding the tray during its rotation with the breech- 
 block. When the breech is open, the solid sections of the tray cover 
 the two lower threaded sectors of the breech recess. The tray is 
 prevented from being displaced laterally by a shoulder in the rear 
 groove 011 the right side and by the loading-tray latch on the left side. 
 The loading-tray latch consists of a bolt with radial motion in a hole 
 bored through the gun, and pressed inward by a spring. When the 
 breech is closed, the lower threaded sector of the block enters the solid 
 sector of the tray. At the same time, the block bearing against the 
 inner end of the tray-latch bolt forces it outward and frees the tray. 
 During the rotation, the threaded sector of the block working in the 
 slotted sector of the tray carries the tray upward to the left, uncovering 
 the two lower threaded sectors of the breech recess to permit their 
 engagement into their corresponding threaded sectors of the block. 
 
 To Open the Breech. Grasp the handle of the operating lever, 
 and carry it to the right. The roller causes the block to rotate until 
 the rack tooth engages the teeth on the block stem. The remaining 
 operations are the reverse of those described in closing the breech. 
 
 To Close the Breech. Grasp the handle of the operating lever, and 
 carry it to the left until the lever latch engages. The operating spool 
 turns with the lever. During the first part of this motion, the latch 
 body is entered in its notch in the spool, causing the block carrier to 
 swing with the spool until the carrier strikes the breech. At this 
 time the latch body drops out of its notch in the spool, freeing the 
 spool from the carrier. The downward motion of the latch causes the 
 lower latch stud to enter the vertical portion of the groove in the hinge- 
 lock bolt, locking the carrier against the breech. As the spool con- 
 tinues to rotate, the translating stud enters the translating groove 
 and the block is forced forward into the breech recess. At the end 
 of the translation, the translating stud leaves the translating groove, 
 freeing the spool for further rotation. The rack stud now enters the 
 rotating groove and the rack is forced to the left, acting through the teeth 
 to rotate the block to the right. Before the rotation of the block is 
 complete, the racking tooth passes beyond the teeth on the stem of 
 the block, the edge of the left tooth of the stem being faced off for 
 this purpose. The roller, actuated by the cam shaped roller groove, 
 then completes the rotation of the block. The lower part of the roller 
 
ARMAMENT 147 
 
 groove is so shaped that the roller acts as a stop to prevent the block 
 from rotating under firing pressure. 
 
 To Remove and Dismount Breech Mechanism. Open the breech, 
 withdraw the latch retainer and remove the latch. The breechblock 
 is now free to be translated and rotated as if it were in the breech 
 recess. Hold the block carrier and rotate the operating lever until 
 translation of the block is completed. Remove the firing lever pivot 
 pin and pivot. Lift the firing lever out of its slot in the block carrier. 
 Lift the spindle key out of its slot in the block carrier. If the spindle 
 key seems to stick, move the operating lever slightly to and fro until 
 the key is free. 
 
 Continue the rotation of the operating lever until rotation of the 
 block is completed. Detach firing cable from the firing-cable bracket. 
 Support the housing of the firing mechanism, and with the wrench 
 provided for the purpose rotate the mushroom head to the left until 
 the housing is free from the spindle, when the housing may be with- 
 drawn to the rear by holding down the rack-lock bolt. 
 
 Remove the spindle from the block and remove the spindle spring. 
 The operating lever should now be rotated a short distance farther. 
 This causes the teeth on the end of the stem to enter the groove pro- 
 vided for them in the hub of the carrier. The stem of the block may now 
 be removed from the carrier. Slide the rack to the left out of its groove. 
 Remove the hinge-pin nut and take off the operating lever. Support 
 the block carrier and drive out the hinge pin, using a copper drift. 
 The block carrier and operating spool are now free to be removed. 
 
 To remove the loading tray, press down on the tray-latch bolt and 
 lift the tray from its place. 
 
 To dismount the lever latch, force the latch bolt upward until the 
 stud is free of its groove. Turn the bolt 180 degrees until the stud 
 points to the left, when the bolt may be lowered out of the housing, 
 the stud passing through a groove cut in the housing for this 
 purpose. 
 
 To Assemble the Breech Mechanism. Place the hinge-lug bushing 
 in its seat so that one of the diagonals of its rectangular interior will 
 be perpendicular to the face of the breech. Place the carrier bushing in 
 its seat so that one of the diagonals of its rectangular interior will lie 
 in the plane of the carrier. Support the carrier so that its plane is 
 perpendicular to the face of the breech, placing its lugs in position to 
 receive the hinge pin. Place the spool between the lugs of the carrier, 
 and turn so that the circular lower end of the roller groove faces the 
 body of the carrier. Insert the hinge pin carefully, using no force 
 
148 THE SERVICE OF COAST ARTILLERY 
 
 unless positive that the rectangular holes in the spool, hinge-lug 
 bushing, and carrier bushing are in line. 
 
 Place the operating lever on the hinge pin so that the lever lies in 
 the plane of the carrier and screw on the hinge-pin nut. Rotate the 
 operating lever slightly to the left and enter the stem of the breech- 
 block in the carrier until the roller enters the roller groove. Place 
 the rack in its groove. Press the block toward the carrier, at the 
 same time rotating the operating handle slightly to the right and 
 entering the stud of the rack in the rotating groove. 
 
 Assemble the obturator and firing-mechanism housing, being careful 
 to stop the rotation of the mushroom head when the ejector drops 
 into its slot in the spindle. The slide must be assembled in the housing 
 before the housing is assembled to the spindle. Rotate the operating 
 lever until rotation of the block is completed. 
 
 Assemble the spindle key and firing lever; rotate the operating 
 lever until translation of the block is completed. Insert the latch. 
 On one end of the latch the dovetail projection from the latch retainer 
 is cut away. This is the lower end of the latch. Assemble the latch 
 retainer. 
 
 6-lNCH RAPID-FIRE GUN, MODEL OF 1905 
 
 This is the latest type of 6-inch rifle and differs in construction 
 from the model of 1903 only in the following points: 
 
 1 A hoop, which extends forward of the trunnion hoop and is locked 
 to the D hoop by a locking hoop. Form of powder chamber cylindrical. 
 
 5-lNCH RAPID-FIRE GUN, MODEL OF 1897 
 
 This gun follows the general method of built-up forged-steel con- 
 struction. It consists of a tube, jacket, locking hoop, breech mechan- 
 ism and associate parts. 
 
 The tube forms the bore and powder chamber, and is reinforced 
 by the jacket and locking hoop. The method of assembling is similar 
 to that of larger calibers. The object of the locking hoop is to lock 
 the tube and jacket in place, thus preventing any backward movement 
 of the jacket. It has a shoulder on its inner surface which bears against 
 the front face of a corresponding shoulder on the tube just in front 
 of the forward end of the jacket. The breech end of the jacket projects 
 beyond the rear face of the tube and forms a recess which is threaded 
 with a V-shape thread with rounded top and bottom, slotted for the 
 interrupted screw mechanism; this forms the seat for the breechblock. 
 
ARMAMENT 149 
 
 The powder chamber is cylindrical and has the breech end slightly 
 enlarged to form a conical gas-check seat which permits the easy 
 insertion and withdrawal of the gas-checking device. There is also a 
 conical slope and forcing slope. The twist of rifling is increasing from 
 one turn in 50 calibers to one in 25 calibers; there are 30 grooves in 
 the bore. 
 
 The breech mechanism consists of the breechblock, gear segment, 
 block carrier, lever, pinion, latch, obturator, and associate parts. 
 The breechblock is cylindrical with an axial hole for the reception of 
 the spindle and washer. 
 
 The front part of the block for a short distance is reduced in 
 diameter; this allows a space in the breech recess of the gun in which 
 fouling may collect without interruption to the working of the block. 
 
 The outer surface of the block has cut upon it a V-shaped screw 
 thread with rounded top and bottom; this screw thread is divided 
 into 8 equal parts and the threads are cut from alternate sectors. 
 The sectors from which the threads are cut are called the slotted 
 sectors; while those alternating with them are called the threaded 
 sectors. The sectors from which the threads are cut permit the 
 entry of the block past the corresponding threaded sectors in the 
 breech recess. By revolving the block through an angle of 45 degrees 
 with its longitudinal axis, the threaded sectors of the block are engaged 
 with the threaded sectors of the recess. In order to provide sufficient 
 clearance for the breechblock to swing away from the piece certain 
 parts of the threaded and slotted sectors are cut away. 
 
 The rear end of the block is turned down to a smaller diameter, 
 and the cylindrical surface thus formed is prolonged into the block 
 and increased in length by means of an annular cut in the rear face of 
 the block. This cylindrical surface is called the guide cylinder; the 
 annular groove being called the guide groove of the block. That 
 portion of the rear face of the block which lies outside of the guide 
 groove is called the stop flange. When the block is withdrawn the 
 stop flange strikes the bottom of the stop groove in the block carrier 
 and limits the rearward motion of the block. The block is guided 
 and supported in its motions of rotation and translation by the guide 
 cylinder. The block is provided with four oil holes drilled radially 
 from the exterior of the block to 'he bottom of the guide groove; this 
 is to facilitate oiling of the bearing surfaces as well as acting as air 
 vents. 
 
 A locking recess is cut in the surface of the guide cylinder gradually 
 increasing in depth from rear to front; when the block is withdrawn 
 
150 THE SERVICE OF COAST ARTILLERY 
 
 the inner end of the latch bolt drops into the locking recess and locks 
 the block to the carrier. 
 
 The gear segment is attached to the rear end of the breechblock 
 and consists essentially of a segment of beveled gear and a short rack, 
 which mesh with a pinion pivoted on the block carrier and actuated 
 by the lever. Part of the periphery of the pinion is cut into a beveled 
 gear and another part into a pinion, meshing \vith the corresponding 
 parts of the gear segment. The beveled gear part rotates* the block 
 and the rack and pinion parts translate. The termination of the 
 motion of rotation in opening the breech brings the rack and pinion 
 into the proper position to withdraw the block, and the end of the motion 
 of translation in closing the breech brings the beveled gear segments 
 into mesh and thus rotated. 
 
 The block carrier is a steel casting provided by means of a pivoted 
 pin to a hinged plate attached to the j acket on the right side of the 
 breech; its function is to support the block in its various movements. 
 
 For actuating the pinion, a lever is fitted on a squared extension of 
 the lug; the free end of the lever terminates in a vertical handle. 
 
 The latch consists of the latch bolt, latch spring, latch lever and 
 latch-lever pivot; which are mounted in the block carrier; and the 
 latch-bolt seat and tripping stud, which are secured to the breech face 
 of the piece by screws. The function of the latch is to lock the block 
 to the carrier. When the block is swung away from the breech, the inner 
 end of the latch bolt rests in the locking recess and locks the bolt to 
 the carrier. In this position the upper end of the latch lever, against 
 which the spring bears, projects slightly beyond the exterior surface of 
 the carrier. When the breech is closed, just before the carrier comes 
 in contact with the breech face of the piece, this projecting part of the 
 lever strikes the beveled surface of the tripping stud and is forced 
 toward the axis of the block. The lever lifts the latch bolt from the 
 locking recess and the block is then free to be translated through the 
 block carrier. 
 
 A summary of the complete action of the latch may be stated as 
 follows: With the breech closed, the outer end of the latch bolt rests 
 in the latch-bolt seat, locking the block carrier to the breech face of the 
 gun; the inner end of the latch bolt bears against the guide cylinder 
 of the block, and at the end of the motion of rotation of the block 
 in opening the breech, rests in line with the end of the latch groove. 
 When the block is withdrawn the bolt rides down the inclined bottom 
 of the latch groove and its outer end is withdrawn from the latch-bolt 
 seat, freeing the block carrier from the breech of the piece. At the end 
 
*> OF THE 
 
 UNIVERSIT 
 
ARMAMENT 151 
 
 of the motion of withdrawal the inner end of the latch bolt enters 
 the locking recess in the breechblock. When the block carrier is 
 swung away from the piece the end of the latch lever clears the tripping 
 stud so that the full force of the latch spring comes into play, and the 
 latch bolt is forced to the bottom of the locking recess, thus securely 
 locking the block to the carrier. When the breech is closed the action 
 of the latch is the reverse of that just given. With the breech open, 
 the block is locked to the carrier. When the carrier is swung against 
 the breech face of the piece, the tripping stud, by means of the lever, 
 raises the latch bolt far enough from the bottom of the latch-groove 
 locking recess for the end of the bolt to ride on the inclined bottom 
 of the groove as the block is moved forward through the block carrier. 
 As the bolt rides up the inclined bottom of the latch groove its outer 
 end enters the latch-bolt seat and locks the block carrier to the breech 
 face of the piece. 
 
 The obturator consists of the spindle, front and rear exterior split 
 rings, interior split ring, pad, filling-in disk, spindle nut, and spindle-ball 
 wajsher. Its purpose is to prevent the escape of gas from the powder 
 chamber to the rear during firing, and to transmit to the breechblock 
 the stress of firing resulting from the pressure of the gases upon the 
 bottom of the bore. 
 
 The gas-check pad is a disk of asbestos and tallow, compressed under 
 heavy pressure and covered with canvas. It forms a yielding medium 
 for the transmission of pressure to the block, and under the pressure of 
 firing the plastic nature of the pad causes it to press outward toward 
 the gas-check seat and inward against the spindle, forcing the split 
 rings firmly against their seats and completely stopping the passage of 
 gas. 
 
 The spindle-ball washer consists of two steel rings with a groove 
 cut in one face of each ring to form a pocket for twenty hardened- 
 steel balls. The washer is interposed between the spindle nut and 
 the breechblock for the purpose of reducing the friction between them 
 when the block is rotated. 
 
 To Open the Breech. When the block is closed the lever lies 
 parallel to the face of the breech, with the handle to the left. Moving 
 the handle to the rear and right rotates the block through an angle of 
 45 degrees and disengages the threaded sectors on the block from 
 those in the breech recess. The further movement of the handle 
 draws the block to the rear until the stop flange strikes the bottom 
 of the stop groove and the head of the latch bolt comes opposite the 
 locking recess. This movement of the block to the rear frees the 
 
152 THE SERVICE OF COAST ARTILLERY 
 
 gas check from its seat in the gun sufficiently to enable the block, 
 supported by the carrier, to be swung out of the recess and to one side 
 of the piece about the block-carrier hinge pin as a center. At the end 
 of the motion of withdrawal the outer end of the latch bolt is with- 
 drawn from its seat, freeing the block carrier from the breech face of 
 the gun so that a further motion of the lever handle to the right swings 
 the block carrier and block away from the piece. During this move- 
 ment the latch bolt has locked the block to the block carrier. 
 
 To Close the Breech. The lever handle is moved to the left as 
 far as it will go. The action of the various parts of the mechanism 
 in closing the breech is the reverse of their action in opening it. 
 
 To Remove, Dismount and Assemble Breech Mechanism. -See 
 method under 6-lNCH R.-F. GUN, MODEL OF 1897 Mi. 
 
 Total length 231.6 inches; weight 7,583 pounds; length of bore 
 45 calibers; weight of projectile 58 pounds; weight of propelling 
 charge, nitro-cellulose powder, 16^ pounds; weight of bursting charge, 
 A. P. shell 2.3 pounds of gun cotton; C.I. shell 2 pounds of rifle powder; 
 shrapnel .75 pounds of rifle powder. 
 
 Muzzle velocity 2,600 foot-seconds. Muzzle energy 2,721 foot- 
 tons. Maximum pressure 38,000 pounds per square inch. Maximum 
 elevation permitted by carriage 15 degrees; corresponding range 
 10,431 yards. Penetration in Krupp cemented armor, at 5,000 yards, 
 2.36 inches. 
 
 5-lNCH RAPID-FIRE GUN, MODEL OF 1900 
 
 This rifle is similar in construction to the model of 1897, except 
 that it has 2 A hoops, 2 C hoops, and 1 D hoop. The powder chamber 
 is cylindro-conical. 
 
 The breech mechanism in this model has the guide groove tapered 
 instead of cylindrical; there is no spindle key; the rotation of the 
 block is limited by a breechblock stop; there is an automatic loading 
 tray of bronze. 
 
 Total length 258.5 inches; weight 11,120 pounds; length of bore 
 50 calibers; weight of projectile. 58 pounds; weight of propelling 
 charge, nitro-cellulose powder, 26 pounds. 
 
 Muzzle velocity 2,600 foot-seconds. Muzzle energy 3,623 foot- 
 tons. Maximum pressure 36,000 pounds per square inch. Maximum 
 elevation permitted by the carriage 15 degrees; corresponding range 
 11,791 yards. Penetration in Krupp cemented armor, at 5,000 yards, 
 2.89 inches. 
 
ARMAMENT 153 
 
 4.72-lNCH QUICK-FIRING ARMSTRONG GUN, 50 CALIBERS 
 
 (See Plate XV) 
 
 This rifle follows the general method of built-up forged steel con- 
 struction. It consists of a tube, jacket, and what in the service would 
 be termed 2 C hoops, and 1 A hoop. In order to obtain great rapidity 
 of fire a special mount is provided. The gun has no trunnions. It 
 is carried in a cradle which encircles it and in which it slides when 
 recoiling; this cradle is provided with trunnions upon which the gun 
 and cradle are balanced. The powder chamber is conical. The 
 breech is surrounded by a breech ring which has a projecting arm on 
 it for connecting the gun with the recoil cylinder, which forms part 
 of the cradle. The mechanism for closing the breech is of the inter- 
 rupted screw type, so arranged that it can be quickly opened or 
 closed by a single movement. 
 
 The breech mechanism is practically the same as 6-inch Armstrong 
 rifle, except that it is smaller in dimension, and is of the screw form 
 in two steps, the front step being tapered and of less diameter than 
 the rear. Both steps have three portions of their threads removed, 
 each one-sixth of a turn; the threads on one set standing opposite 
 to the blank spaces on the other; this is done in order to distribute 
 the strain all around the circumference of the breech screw. The 
 interior of the gun at the breech is prepared in a similar manner and 
 admits of the breech screw being swung into place and locked by a 
 simple mechanism provided. 
 
 The breech screw is supported by a carrier on which it is free to 
 revolve through an angle of 60 degrees; the carrier is hinged to the 
 right side of the breech ring so that the screw can swing clear of 
 the breech recess for loading. A stop bolt is provided for securing 
 the carrier and the block together. A projecting pin is screwed into 
 the rear face of the breechblock, and enters the traversing bush in 
 the sliding block. This block slides in a seat in the carrier and is 
 connected with the hand-locking lever by the link. The block is 
 prevented from turning on the carrier when open by a spring catch 
 which engages a notch in the block as it is withdrawn from the 
 gun. When the breech is closed the catch comes in contact with the 
 face of the gun, releases the block and allows it to be screwed 
 home. 
 
 A safety gear consisting of a pawl and spindle, the pawl of which 
 engages a lip on the striker and prevents the latter from touching 
 
154 THE SERVICE OF COAST ARTILLERY 
 
 the primer until the block is completely closed and locked, makes it 
 impossible to fire the gun until everything is safe. 
 
 To Open the Breech. The breechblock is unscrewed and withdrawn 
 from the gun by a single horizontal movement of the hand-locking 
 lever, which is pivoted on the right side. A reverse movement com- 
 pletely closes and locks the block. 
 
 Total length 236 inches; weight 6,160 pounds; length of bore 49 
 calibers. The bore has 26 grooves, twist of rifling 1 turn in 600 
 calibers to one turn in 30 calibers. Weight of projectile 45 pounds; 
 weight of propelling charge, nitro-cellulose powder, 8.2 pounds; cordite 
 10.5 pounds. Weight of bursting charge, strong head steel shell, 2 
 pounds of high explosive; steel shell 4.5 pounds of high explosive; 
 cast iron shell 1.2 pounds of rifle powder; shrapnel .125 pound of 
 rifle powder. 
 
 Muzzle velocity 2,600 foot-seconds. Muzzle energy 2,111 foot-tons. 
 Maximum pressure 34,000 pounds per square inch. Maximum range 
 11,211 yards. 
 
 Penetration in Krupp cemented armor with uncapped projectile, 
 at 5,000 yards, 1.3 inches. 
 
 4.72-lNCH QUICK-FIRING ARMSTRONG GUN, 45 CALIBERS 
 This rifle is similar in construction to the 50-caliber model of the 
 same make, with the following exceptions: 
 
 Total length 212.6 inches; weight 5,958 pounds; length of bore 
 44 calibers. Number of grooves in bore 26; twist of rifling increasing 
 from to 1 in 30 calibers. Weight of projectile 45 pounds; weight of 
 propelling charge, nitro-cellulose powder, 8.2 pounds, cordite 10.5 pounds. 
 Muzzle velocity 2,570 foot-seconds. Muzzle energy 2,063 foot-tons. 
 Maximum range 11,110 yards. Penetration in Krupp cemented armor 
 with uncapped projectile, at 5,000 yards, 1.27 inches. 
 
 4.72-lNCH QUICK-FIRING ARMSTRONG GUN, 40 CALIBERS 
 This rifle is similar in construction to the 50-caliber model of the 
 same make, with the following exceptions: 
 
 Total length 194.1 inches; weight 4,648 pounds; length of bore 
 40 calibers. Number of grooves in bore 22; twist of rifling from one 
 turn in 100 calibers to one turn in 34 calibers. Weight of propelling- 
 charge, nitro-cellulose powder, 7.5 pounds; cordite 5.5 pounds. 
 
 Muzzle velocity 2,150 foot-seconds. Muzzle energy 1,444 foot- 
 tons. Maximum range 9,669 yards. Penetration in Krupp cemented 
 armor with uncapped projectile, at 5,000 yards, 1.3 inches/ 
 

 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
ARMAMENT 155 
 
 4-IxcH RAPID-FIRE DRIGGS-SCHROEDER (ir.\ 
 
 This rifle follows the general method of built-up forged-steel con- 
 struction. Manufactured by the American Ordnance Company. 
 
 Total length 166.5 inches; weight 3,613 pounds; length of bore 
 40 calibers; twist of rifling to 1 in 25 calibers; weight of projectile 
 33 pounds; weight of propelling charge, nitro-cellulose powder, 7.5 
 pounds; weight of bursting charge approximately 4.5 pounds of high 
 explosive for shell, 2 pounds for strong-headed shell. 
 
 Muzzle velocity 2,300 foot-seconds. Muzzle energy 1,212 foot- 
 tons. Maximum pressure 34,000 pounds per square inch. Maximum 
 range 8,864 yards. 
 
 SECONDARY ARMAMENT 
 (See Plate XVI) 
 
 3-IxcH (15-POUNDER) R. F. GUN, DRIGGS-SEABURY MODEL OF 1898 
 
 This rifle follows the general method of built-up forged-steel 
 construction. Manufactured by the Driggs-Seabury Company. It 
 consists of a tube, jacket, and breech bushing. 
 
 The breech mechanism (Figs. 14 and 15) consists of the block, the 
 carrier plate, the carrier-plate ring and its screws, the block-locking 
 spring, the operating lever and pin, the lever-catch plunger, spring and 
 cotter pin, the firing pin and spring, the sear, the sear spring, the 
 extractor, and the hinge pin. 
 
 The principal parts of the breechblock are three threaded sectors, 
 three slotted sectors, the thread for the carrier ring, the operating- 
 lever slots, the recess for the firing pin, the rotating stop, and the seat 
 for the block-locking spring. 
 
 The thread is V-shaped, rounded at top and bottom, and for about 
 f inch in rear is continuous; the remainder is divided into six equal 
 sectors, three threaded and three slotted. The continuous thread 
 engages in that of the carrier-plate ring, and the threaded sectors 
 engage those of the breech recess. The slotted sectors of both blocks 
 and recess are cut away sufficiently to permit the block to enter the 
 recess when swung about the hinge pin. The slot for the block-locking 
 spring is so placed that when the threads of the block are disengaged 
 from those of the breech recess the spring enters the slot of the locking- 
 block and carrier plate together. 
 
156 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Extractor 
 
 Hinge Pin. 
 \ \ \ Carrier Plate. 
 
 FIG. 14. 
 
 Carrier P/ng. 
 Block. 
 
 Block-Jock in 
 Bolt * Spring 
 
 FIG. 15. 
 
ARMAMENT 157 
 
 The carrier plate has a lug, at right angles to its face, through which 
 passes the hinge pin, and which is so shaped as to operate the extractor 
 in opening the breech. Two lugs, projecting from the rear face, carry 
 the operating-lever pin, and the lower one also furnishes the seat for 
 the lever-catch mechanism. A lug on the front face is bored out to 
 receive the firing pin and its spring, and is assembled into the cavity 
 of the block. The carrier plate is bored from the right-hand side to 
 receive the sear and its spring. The rotating stop groove is annular, 
 ends in a shoulder, and is cut in the front face of the carrier plate. 
 
 A slot for the operating lever is cut through the carrier plate, and 
 another for the cocking toe is cut partly through. The front face of 
 the carrier plate is counter-sunk to receive the carrier-plate ring, which 
 is assembled to it by means of two screws, the holes for which are 
 centered by a rib on the carrier plate and a corresponding groove on 
 the carrier-plate ring. 
 
 The carrier-plate ring is threaded on its inner surface to receive 
 the breechblock, and is assembled to the carrier plate by two screws. 
 A groove in the front face seats the block-locking spring, has a rib 
 part of its length, and ends at the interior of the ring in a recess for 
 assembling the spring and for the seat of its locking lug. The threads 
 are slightly cut away in two places to make a clearance for the operating- 
 lever. 
 
 The block-locking spring is assembled to the carrier-plate ring by 
 means of a dovetail groove. At the lower end of the spring there is 
 a lug that locks the block to the ring when the spring is not compressed; 
 when it is compressed, one side of the lug on the spring forms a contin- 
 uous surface with the thread of the ring, permitting rotation of the 
 block. 
 
 For all guns after number 80 a modified form of block-locking bolt 
 and spring is employed. 
 
 The locking bolt for securing the block to the carrier in the open 
 position passes through the carrier-plate ring, being forced forward 
 by its spring. When in the forward position a projection on the 
 bolt enters a recess in the rear face of the block, locking it to the 
 carrier. When the carrier is closed the locking bolt is forced to the rear 
 and held there, its front end being in contact with the face of the breech. 
 
 The operating lever is assembled to lugs on the rear face of the 
 carrier plate and consists of the lever proper, the operating knob, 
 the cocking cam, the handle, the seat for the pin, and the seat for the 
 lever-catch plunger. The lever passes through the carrier plate, the 
 knob engaging in its seat in the block and forcing it to rotate when 
 
158 THE SERVICE OF COAST ARTILLERY 
 
 the lever is turned about its pin. The cocking cam engages a lug on 
 the firing pin and is so shaped that in opening the breech the pin is 
 retracted until caught and held by the sear. The lever projects to 
 the front sufficiently to form a locking lug that, by the final motion 
 in closing, is seated in a groove in the rear face of the block, thus 
 preventing rotation of the block due to pressure of the powder gas. 
 The final movement of the lever in closing, and the first in opening, is 
 perpendicular to the face of the plate, the pin hole being elliptical for 
 the purpose. The seat for the lever-catch plunger is on the under side 
 of the lever. The handle makes a right angle with the lever and is 
 vertical. 
 
 The lever-catch plunger, with its spring, is assembled in the lower 
 lever lug and is secured in place by the cotter pin passing through 
 the lower end of the plunger. The mechanism prevents rotation of the 
 handle during counter recoil. 
 
 The firing pin and spring are assembled in their seat in the carrier 
 plate, the pin, when released, passing through an aperture in the 
 front of the block. The pin has, at the rear end, a cocking lug and 
 a notch for the engagement of the sear, and in front a shoulder for 
 the spring. The spring is coiled around the pin and abuts against 
 the shoulder on the pin in front and the carrier plate in rear. 
 
 The sear and its spring are assembled to the carrier plate in a seat 
 bored parallel to the right-hand horizontal radius. The sear is so shaped 
 at its inner end as to hold the firing pin in its retracted position, except 
 when rotated upward. The outer end of the sear terminates in a 
 short lever, carrying an eye for the lanyard; near this eye there is a 
 seat for one end of the sear spring, the other end of which is secured 
 in the carrier plate, the tendency of the spring being to keep the sear 
 rotated downward. 
 
 The extractor passes through a slot in the right side of the jacket 
 into the breech recess, is assembled to the jacket by two studs fitting 
 into grooves, and is operated by a lug on the carrier plate, so shaped as 
 to give the extractor a quick, lateral motion for the purpose of throwing 
 the case clear of the breech. The hinge pin assembles the carrier 
 plate to the jacket. 
 
 Action of Breech Mechanism. Immediately after the gun has been 
 fired the block threads engage those of the breech recess, the operating- 
 lever is against the carrier plate, the locking lug on the lever is seated 
 in its groove in the block, the lever-catch plunger is in its seat, the firing 
 pin is forward against the primer, and the block-locking spring lug 
 forms a part of the carrier-ring thread. 
 
ARMAMENT 159 
 
 To Open the Breech. Rotate the handle to the right until the 
 carrier comes to rest against the jacket. At the beginning of the 
 movement to open the breech, the locking lug on the lever is with- 
 drawn from its seat, the knob causes the block to rotate from left to 
 right until the threaded sectors, are disengaged from those of the 
 breech recess, the stop on the block strikes the shoulder of its seat 
 when this disengagement is complete, and the block swings clear of the 
 breech recess. During the rotation of the lever the cocking cam 
 retracts the firing pin, which is then held by the sear. As soon as the 
 carrier has moved far enough from the face of the breech, the block- 
 locking spring is released and locks the block to the ring. 
 
 To Close the Breech. Rotate the handle to the left until the lever 
 brings up against the carrier plate. The block-locking spring is com- 
 pressed by striking the breech, and then the action of the mechanism 
 is that of opening, reversed, except that the firing pin is not affected. 
 For drill purposes an. empty cartridge case should be inserted in the 
 chamber, ac otherwise, unless care is taken that the operating lever 
 is left firmly against the breech after closing, snapping the lock is 
 liable to break the firing pin. 
 
 To Assemble the Breech Mechanism. Seat the extractor. Put 
 the carrier plate in position and insert the hinge pin. Put the lever- 
 catch plunger spring in its seat, insert the plunger, press it down, and 
 enter the cotter pin. Seat the block-locking spring in the carrier 
 ring. Place the carrier ring in the carrier plate and insert the securing 
 screws. Close the carrier plate until it rests against the breech of 
 the gun. Insert the sear and its spring, guiding the end of the latter 
 into its seat in the carrier plate. Assemble the firing-pin spring to 
 the pin. Swing the carrier plate away from the breech, seat the firing 
 pin in the stem of the plate, keeping the guide rib downward, and 
 compress the spring until the pin is held by the sear. A block of 
 wood should be used against the point of the pin in compressing the 
 spring. 
 
 Place the breechblock on the stem of the carrier plate, compress the 
 block-locking spring, and rotate the block to the left until the stop 
 comes in contact with the shoulder of its groove in the carrier plate. 
 Release the block-locking spring. Place the operating lever in position 
 and insert the lever pin. Close the breech. 
 
 To Dismount the Breech Mechanism. Reverse the operations of 
 assembling, being sure that the firing pin is cocked before beginning. 
 
 The other parts of the breech mechanism, except the extractor, 
 may be first assembled to the carrier plate and then the whole assembled 
 
160 THE SERVICE OF COAST ARTILLERY 
 
 to the gun; dismounting may be similarly effected by first removing 
 the mechanism as a whole. 
 
 Total length 154.5 inches; weight 1,782 pounds; length of bore 
 50 calibers. The bore has 24 grooves; twist of rifling 1 in 50 to 1 in 25 
 calibers. Weight of projectile, shot, shell, or shrapnel, 15 pounds; 
 weight of propelling charge, nitro-cellulose powder, 5 pounds. 
 
 Muzzle velocity 2,600 foot-seconds. Muzzle energy 703.8 foot- 
 tons. Maximum pressure 34,000 pounds per square inch. Maximum 
 elevation permitted by carriage 12 degrees, corresponding range 7,849 
 yards. Penetration in Krupp cemented armor, at 5,000 yards, 
 uncapped projectile, .77 of an inch. 
 
 3-lNCH (15-POUNDER) RAPID-FlRE GUN, MODEL OF 1902 
 
 (See Plate XVII) 
 
 This rifle follows the general method of built-up forged-steel con- 
 struction. It consists of a tube, jacket, hoop, breech mechanism, etc. 
 The tube is enveloped by a jacket and hoop for a distance of 84 inches 
 from the breech end. 
 
 The breech mechanism consists principally of the block, carrier plate, 
 latch, carrier hub, operating lever, link extractor and firing mechanism. 
 
 The block is cylindrical in form, 4.4 inches long, 5.7 inches in exterior 
 diameter, except at the rear end, where there is a collar with an exterior 
 diameter of 6.7 inches. The part in front of the collar consists of four 
 threaded and four slotted sectors of about equal area. The metal 
 in each of these sectors is cut away sufficiently to allow the block to 
 swing clear of its recess. A boss on the rear face of the block forms 
 a seat for the link pivot. A stud screwed into the rear face of the block, 
 carrying an insulated copper plug, forms half of the circuit breaker 
 for the electric firing mechanism. The block is bored axially to a 
 diameter of 2.5 inches, and a depth of 2.4 inches from the rear face. 
 The bore is continued through the block on a diameter of 4.69 inches, 
 and the front end being counter-bored to a diameter of 2.1 inches. 
 The bore in the front end is threaded and a plug having an axial hole 
 for the firing pin is screwed into .it. A spline screw prevents this plug 
 from turning. The larger diameter bore at the rear end is also threaded, 
 the thread being rectangular in form, and having the same pitch as 
 that on the exterior of the breechblock. A slot on the left-hand side 
 of this bore allows for movement of the breaker when the block is 
 in its closed position. A notch in the collar of the block forms a seat 
 for the latch when the block is locked to the carrier. 
 
ARMAMENT 161 
 
 The carrier consists of a steel plate having a lug for the hinge pin 
 at right angles to its face. This lug is so shaped as to operate the 
 extractor when the breech is opened. The plate is bored and threaded 
 the same as the interior of the block, and on line with the axis of the 
 gun when the breech is closed. 
 
 The latch locks the block to the carrier when its threads are dis- 
 engaged from those of the breech recess, and locks the carrier to the 
 gun when the threads of the block are engaged or partly engaged 
 with those of the breech recess. When the carrier is being closed 
 against the breech of the gun, an inclined face on the latch slides against 
 a similar face on the recess in the breech of the gun, withdrawing the 
 latch from the notch in the collar of the breechblock, and allowing 
 the block to rotate. At the same time, a lug on the latch is forced into 
 an undercut part of the recess in the breech of the gun, and held there 
 by the collar of the breechblock, thus locking the carrier to the gun. 
 
 The carrier hub is a bronze cylinder with rectangular head at the 
 rear end. It forms the connection between the breechblock and the 
 carrier, and contains the firing mechanism complete. 
 
 The firing mechanism is of the type known as continuous-pull per- 
 cussion, combined with electric. It consists of the following parts: 
 Firing pin with insulation, firing-pin sleeve, firing-pin guide and firing- 
 pin shoulder, firing-pin spring, pin and breaker pin, cocking link and 
 stud, cocking-stud block. For electric firing, when the block is closed, 
 the firing pin projects about 5/100 inch, or enough to make contact 
 with the primer. The firing pin is completely insulated, and is connected 
 with the circuit breaker by an insulated cable with standard connections. 
 
 Action of the firing mechanism is as follows : Supposing the gun to 
 be loaded and the block closed. The firing-pin guide is pressed forward 
 by the firing-pin spring against the front firing-pin shoulder. The 
 firing pin is thus pressed forward against the primer. The connection 
 is now complete for electric firing. Unless held back by the primer, 
 the projection of the firing pin in this position is about 5/100 inch. 
 For percussion firing the breaker is pulled to the rear until the cocking 
 piece is left from the firing-pin sleeve. In this movement, the firing 
 pin is pulled to the rear about 8/10 inch. When released, the spring 
 drives it forward until the firing-pin guide strikes the breechblock 
 plug. The inertia of the firing pin and sleeve then carries them 1/10 
 inch further forward. Total projection of the firing pin in percussion 
 firing is 15/100 inch. 
 
 The operating lever of the breech mechanism is hinged to the block- 
 carrier hinge pin. It is connected to the block by a single link with 
 
162 THE SERVICE OF COAST ARTILLERY 
 
 the hinge pivots in the block and lever. A latch fitting in a seat in the 
 link pivot in the breechblock locks the lever when the block is closed. 
 
 The extractor is hinged on a pin through the lugs on the right- 
 hand side of the gun. The rear end of the tube is slotted to allow for 
 increased thickness of the inner arm of the extractor. This inner 
 arm grasps the rim of the cartridge case. The outer arm has a cammed 
 surface against which another cammed surface on the carrier plate slides 
 when the latter is opened. These two cammed surfaces are so shaped 
 as to give the extractor an accelerated movement which ejects the 
 cartridge case clear of the gun. 
 
 To Open the Breech. Rotate the handle to the right until the 
 carrier plate comes to rest against the extractor. By this movement 
 the lever-latch plunger is withdrawn from its seat, thereby allowing a 
 further pull on the lever to rotate the block contra-clockwise by means 
 of the link through an angle of 45 degrees. The threads of the block 
 are now disengaged from those of the breech recess. The block latch 
 is situated in its notch in the collar of the breechblock, thereby locking 
 the carrier plate to the breechblock and enabling one by further pulling 
 on the lever handle to swing the block clear of the breech recess. 
 During the rotation of the block the cam on the breechblock plug 
 retracts the firing pin by means of the lock on the firing-pin sleeve. 
 When the rear of the carrier plate strikes the extractor, its inner arm 
 is caused to move to the rear, thus extracting the cartridge case. 
 
 To Close the Breech. Rotate the handle to the left until the 
 lever latch seats itself and further motion is impossible. During this 
 operation the latch recess in {he breech of the gun draws the latch 
 out of its notch in the block, thereby allowing the block to be 
 rotated in a clockwise direction. The latch then locks the carrier 
 to the gun, and is prevented from unseating itself by the collar of 
 the block. 
 
 To Assemble the Breech Mechanism, First assemble the latch and 
 spring to the carrier plate, then the extractor and carrier plate to the 
 gun. In putting in the carrier-plate hinge pin, the carrier should 
 be made to turn the carrier plate so that an arrow marked on it comes 
 opposite a corresponding arrow marked on the gun. . Assemble the 
 insulation on the firing pin, then put the front shoulder over the 
 insulation and the firing-pin guide over the front shoulder, the rear 
 shoulder and firing -pin spring on the firing-pin sleeve, and then slip 
 the sleeve over the firing-pin insulation. The insulation washer, nut 
 and taper pin on the rear are placed to the rear end of the firing pin. 
 The breaker, with spring pin and cocking link are assembled to the 
 
ARMAMENT 163 
 
 carrier hub. Screw the carrier hub into the carrier plate until its 
 front end is flush with the front face of the plate. Push the assembled 
 firing pin to its place in the front end of the carrier hub, at the same 
 time pulling back on the breaker. Hold the breechblock in the closed 
 position against the front face of the carrier plate. In this position 
 screw the carrier hub to its seat and tighten the locking screw. The 
 operating lever and link are assembled and the block rotated until the 
 latch locks it to the carrier plate. 
 
 To Dismount the Breech Mechanism. The operations for dis- 
 moimting the breech mechanism are the reverse to those given above 
 for assembling it. 
 
 Total length 154.35 inches; weight 1,950 pounds; length of bore 
 50 calibers. Fixed ammunition is used; also projectiles as described 
 for the Driggs-Seabury gun. 
 
 3-lNCH (15-POUNDER) RAPID-FlRE GlJN, MODEL OF 1903 
 
 This rifle is of Ordnance Department manufacture and corresponds 
 to the Bethlehem Model of 1902, except in power. 
 
 Total length 170 inches; weight 2,692 pounds; length of bore 
 55 calibers; weight of projectile 15 pounds; weight of propelling 
 charge, nitro-cellulose powder, 6.06 pounds. 
 
 Muzzle velocity 3,000 foot-seconds. Muzzle energy 935.8 foot- 
 tons. Maximum pressure 41,000 pounds per square inch. Penetration 
 in Krupp cemented armor, at 5,000 yards, with uncapped projectile, 
 .85 of an inch. 
 
 2.24-lNCH (6-PouNDER) R. F. GUN, DRIGGS-SEABURY MODEL OF 1898 
 
 This rifle follows the general method of built-up forged-steel con- 
 struction. It consists of a tube, jacket, hoop and breech mechanism. 
 The tube in enveloped by the jacket and hoop for a distance of about 
 52 inches from the breech end, the two being locked together by a 
 bronze sleeve screwed on and locked in place. 
 
 The sleeve is machined so as to form upon each side of its exterior 
 two parallel bearing surfaces by which the gun is supported in the 
 mount. 
 
 MECHANISM OF THE GUN 
 
 The jacket extends beyond the rear end of the tube far enough 
 to form a breech recess and is cut away at the bottom to receive the 
 block. 
 
164 THE SERVICE OF COAST ARTILLERY 
 
 The bore is composed of a cartridge seat, forcing slope and main 
 bore. There are 24 grooves in the first six guns manufactured and 
 18 grooves in the others. The twist of rifling is from to 1 turn in 25.8 
 calibers at the muzzle. 
 
 The breech recess is cut away at the top to form two steps against 
 which corresponding projections on the block abut, and on each side 
 to receive the operating lugs and the pivots of the extractor. The 
 end of the tube is cut away also to receive the arms of the extractor. 
 A hole is drilled through each cheek for the operating shaft. 
 
 The breech mechanism (known as the drop-block system) consists 
 of the block, operating shaft, cam sleeve, locking spring, extractor, 
 percussion-firing lock, operating handle and associate parts. 
 
 On the top of the breechblock are formed two locking shoulders 
 arranged in steps, and on its sides two operating lugs and rotating 
 stops, on the lower side of which the extractor-cam surface is formed. 
 
 The block is drilled through transversely for the insertion of the 
 operating-cam sleeve and an axial seat is formed in the rear for the 
 firing "lock. The locking shoulders engage against the steps at the 
 top of the breech recess; the under surfaces of the operating lugs 
 are in contact with the cams of the sleeve while the upper surfaces 
 bear against the top of the slots in the sides of the breech recess. 
 
 The rotating stops limit the rotation of the operating shaft to the 
 rear and are partly cut away to clear the jacket when the breech is 
 open. The extractor-cam surface is so shaped as to give a throw to 
 the extractor at the end of its movement. 
 
 The seat for the firing lock is cylindrical except at the forward end, 
 where it is shaped for the passage of the point of the firing pin; the 
 rear end is counter bored to a larger diameter and threaded to receive 
 the firing lock. 
 
 A seat for the pin of the bracket-locking spring is cut in the rear 
 face of the block. 
 
 The operating shaft is mainly cylindrical with a journal at the right 
 end and another near the left. Adjoining these journals on the inside 
 the shaft is made hexagonal to fit corresponding seats in the sleeve. 
 There is a slot for the locking spring, also for the key on the inside of 
 the handle; the slot is wider than the key. This permits a small amount 
 of rotation of the handle around the shaft. 
 
 The cam sleeve consists of two cams joined by a hollow cylinder. 
 The interior of each end is made hexagonal to fit the operating shaft, 
 and the cams are shaped to act with the operating lugs of the block. 
 
 The operating handle is a hollow rod with a lug at one end bored 
 
ARMAMENT 165 
 
 out to receive the left end of the operating shaft. A key let into the 
 lug works in the corresponding slot in the operating shaft and a short 
 slot is cut on the right or inner face of the lug for the seat of a lug on 
 the locking spring. 
 
 The locking spring is a steel bar with two lugs on one side and a 
 third at the o-uter end. This last secures the operating handle; the 
 next one, in conjunction with the handle, operates the spring and 
 locks the shaft to the jacket, while the third serves to lock the shaft 
 in the gun. 
 
 The extractor is roughly Y-shaped. Two flanges on the arms 
 engage the rim of the cartridge case, the stem forms the toe by which 
 the extractor is operated, and two pivot lugs serve to support the 
 extractor in the jacket. 
 
 The percussion-firing lock is called a continuous-pull firing mechan- 
 ism; that is, one in which the pull on the lanyard first compresses the 
 firing spring and then releases it, allowing the spring to drive forward 
 the pin. It consists of the firing pin, the pawl, the firing spring, the 
 bracket bearing, the trigger, the trigger spring, and the bracket- 
 locking spring. 
 
 The firing pin is mainly cylindrical, with the taper point and a 
 shoulder in front and a flattened section in rear. A slot for assembling 
 the firing pin to the bracket bearing is cut just forward of the flattened 
 portion, a small hole is drilled in rear of the head of the firing pin to 
 hold the end of the firing-pin spring, six longitudinal grooves are cut 
 in the head for gas vents and two holes are drilled through the flattened 
 section, one for the pivot to which the pawl is assembled and the other 
 for the lanyard. 
 
 The pawl is slotted to fit the rear of the firing pin and has a pivot 
 hole and a seat for a small pin. The firing spring is a coiled steel-wire 
 spring that abuts against the head of the firing pin in front and the 
 bracket bearing in rear. The front end is seated in a small hole in 
 the pin and the rear is held between the bracket and a shoulder in a 
 counterbore in the block. The bracket-bearing screws into the block, 
 closing the firing-pin cavity, and serving as a support for the rear of 
 the firing pin. It also carries an arm upon which the firing trigger is 
 pivoted. It is provided with a pin, which, working on a longitudinal 
 slot in the firing pin, prevents the latter from turning. On its rear 
 face is riveted the bracket-locking spring, a leaf spring formed in a 
 half circle and carrying at its end a pin which is pressed into a seat in 
 the block when the bracket is screwed home. 
 
 The trigger is an arm pivoted on the bracket bearing and carrying 
 
166 THE SERVICE OF COAST ARTILLERY 
 
 the cocking toe. Near the upper end a hole for attaching the lanyard 
 is drilled, and below this it is slotted for the stop pin on the pawl. 
 The trigger spring is of coiled steel wire assembled around the trigger 
 pivot, having one end in the bracket arm and the other in the trigger. 
 Its function is to force the trigger to the front or normal position after 
 firing. 
 
 Action of the Breech Mechanism. Immediately after firing, the 
 block is in its seat in the breech recess, the operating handle is to the 
 front, the lugs on the locking spring are in their seats in the handle 
 and the jacket, the operating lugs on the block are supported in the 
 vertical portions of their slots by the cams on the cam sleeve, the 
 flanges of the extractor engage the rim of the case, the pivot lugs of 
 the extractor are in the rear part of their slots, the point of the firing 
 pin is flush with the front face of the block, and the cocking toe is 
 forward of the pawl. 
 
 To Open the Breech. Rotate the handle to the rear. During the 
 first part of this movement the handle rotates about the shaft, com- 
 pressing the locking spring and releasing the lug from its seat in the 
 jacket; then the operating shaft and cam sleeve rotate together to 
 the rear, and the cams are moved so as to permit the operating lugs, 
 and consequently the block, to descend until the latter is disengaged 
 from the shoulder at the top of the breech recess; (if the block does 
 not descend by its own weight, the operating cams bearing on tops of 
 the rotating stops force it down.) In this position the cams abut 
 against the rotating stops and cause the block to rotate with 
 the operating shaft until stopped by the flanges at the bottom 
 of the breech recess between the checks of the jacket. During the 
 rotation of the block the extractor cam surface strikes the stem of 
 the extractor and forces the pivot lugs forward in their slots, causing 
 the arms of the extractor to move to the rear sufficiently to loosen 
 the case in its seat; when the pivot lugs bring up against the shoulder 
 of the slots, the cam surface continuing to act rotates the extractor 
 about the lugs, giving a quick throw that fully ejects the case. 
 
 To Close the Breech. Rotate the handle smartly to the front until 
 it comes to a stop. The action of the mechanism is the reverse of 
 opening. 
 
 To Fire the Gun. Insert the hook of the lanyard in the eye of 
 the trigger and pull until the firing pin is released. The cocking toe, 
 except when forced oo the rear, is constrained by the trigger spring 
 to remain against the face of the bracket bearing, forward of the pawl, 
 so that when the trigger is pulled, carrying the toe to the rear, the 
 
ARMAMENT 167 
 
 pawl and consequently the firing pin go with it. As the toe rotates 
 while the pawl is forced to move in a straight line, the latter is released 
 when it has been retracted about f inch, and moving forward under 
 the action of the spring, the pin impinges against the primer. When 
 the tension on the lanyard is released the trigger moves forward, under 
 the action of its spring, until the toe strikes the bracket bearing. In 
 this movement the pawl is first rotated by the toe, clearing the latter, 
 and afterwards rotated back by its pin, passing into the slot in the 
 trigger arm. The firing toe and pawl are thus again ready for firing. 
 The point of the firing pin is kept normally flush with the front face 
 of the block, because the firing-pin spring, being fastened at both ends 
 and properly adjusted, works in both directions and holds the pin in 
 that position. In firing, the momentum given the pin by the spring 
 carries it beyond its point of rest with sufficient force to explode the 
 primer. 
 
 In case the firing toe does not engage the pawl, rotate the pawl to 
 the front with the hand. The gun may be fired, in case the trigger 
 becomes injured, by attaching the lanyard directly to the eye of the 
 firing pin. In case of a misfire additional blows may be given the 
 primer by slacking on the lanyard to allow the toe to again engage 
 the pawl. 
 
 To Assemble the Breech Mechanism. The shoulder bar being out, 
 put the block in place from below, and hold it firmly against the top 
 of the breech recess; insert the extractor, arms upward, flanges next 
 to the tube, and engage the pivot lugs in their slots; lower the block, 
 let go the extractor, and incline the block so that the cam-sleeve seat 
 is clear. Place the cam sleeve in position, larger end to the left, so 
 that the cams lie between the operating lugs and the rotating stops; 
 keeping a rearward pressure on the cam sleeve as long as possible, 
 move the block slowly into the open position; by a pressure underneath 
 the block, line up the holes for the operating shaft; place the locking 
 spring in its slot in the operating shaft and seat the latter, keeping the 
 slot on top, and compressing the spring; put on the operating handle, 
 partly close the block, and screw the firing lock home until the pin 
 of the locking spring enters its seat; close the breech; the handle 
 should then point to the front and be nearly parallel to the axis of the 
 bore. The firing lock is furnished assembled. 
 
 To Dismount the Breech Mechanism. Reverse the operation of 
 assembling. The locking spring must be compressed until its locking 
 lug is free from the circumferential slot in the left cheek of the gun; 
 the block should be supported by the hand while the shaft is being 
 
168 
 
 THE SERVICE OF COAST ARTILLERY 
 
 driven out. For this operation use a piece of wood or a copper 
 drift. 
 
 Sights. Telescopic sights have been issued with some of these guns 
 and mounts. When so issued th6y are placed, when in use, upon a 
 sight bracket which is fastened to the right trunnion of the oscillating 
 slide of the mount. Such brackets are attached to all mounts of the 
 modification of this model. 
 
 Total length 118.12 inches; weight 845 pounds; length of bore 50 
 calibers; weight of projectile 6 pounds; weight of charge, nitre-cellulose 
 powder, 1.35 pounds; nitroglycerine 1.25 pounds. 
 
 Muzzle velocity 2,400 foot-seconds. Muzzle energy 240 foot-tons. 
 Maximum pressure 37,460 pounds per square inch. Penetration in 
 Krupp cemented armor .4 inch. 
 
 2.24-lNCH (6-PouNDEn) R. F. GUN, DRIGGS-SEABURY MODEL OF 1900 
 
 (See Fig. 16) 
 
 FIG. 16. 2.24-inch (6-pounder) R. F., D.-S. Gun, M. 1900. Interrupted Thread 
 Breech Mechanism. Mounted on Wheeled Mount. 
 
 This rifle is essentially the same as the model of 1898, except 
 that the breech recess in the jacket is differently shaped and is 
 threaded and slotted to accommodate the interrupted-thread mech- 
 anism. 
 
ARMAMENT 169 
 
 MECHANISM OF THE GUN 
 
 The breech mechanism (known as the interrupted-thread system) 
 consists of the block, carrier plate and ring, operating lever, hinge pin, 
 lever pin, firing mechanism, locking bolt and spring, extractor, and 
 associate parts. 
 
 The breechblock has two full threads at the rear end on which the 
 carrier-plate ring is screwed. In front of these there are three threaded 
 and three interrupted sectors. The interior of the block is hollowed out 
 to receive the hub of the carrier plate which carries the firing mechanism. 
 The front end of this cavity is conical, corresponding in shape to the 
 head of the firing pin, and serves as a stop to limit the forward move- 
 ment of the pin. A small safety screw, inserted from the front face 
 of the block, projects into this cavity. Its function is described in 
 connection with the description of the firing pin. A cylindrical pro- 
 jection on the rear face of the block forms a stop which, rotating in a 
 limited annular groove in the front face of the carrier plate, limits 
 the rotation of the block. 
 
 The carrier plate carries all the mechanism for operating the block 
 and the firing mechanism. It is hinged to lugs on the gun and has 
 two projecting lugs on its rear face to which the operating lever is 
 hinged. On the front face is a projecting hub which supports the 
 block and within which the firing pin and mechanism are placed. 
 On its front there is also a counterbored seat in which the carrier-plate 
 ring is set and secured by two screws. 
 
 A bolt for locking the block to the carrier in the open position 
 passes through the carrier-plate ring, being forced forward by its spring. 
 When in the forward position a projection on the bolt enters a recess 
 in the block, locking it to the carrier. When the carrier is closed the 
 bolt is held in the rear, its front end being in contact with the face of 
 the breech. 
 
 The operating lever projects through a slot in the carrier plate 
 and has a knob in front bearing in a slot in the rear face of the breech- 
 block. The lever-pin hole in the operating lever is elongated, and a 
 locking lug is formed on the front edge of the lever, which, at the final 
 motion of closing, is made to enter a slot in the rear face of the block, 
 thus preventing rotation of the block due to the powder pressure. 
 The lever-catch plunger in its spring are assembled in the powder- 
 lever lug. Their object is to prevent rotation of the operating lever 
 in counter recoil. 
 
170 THE SERVICE OF COAST ARTILLERY 
 
 The extractor has trunnions resting in slots in the hinge-pin lugs. 
 It is operated by a cam surface on the carrier plate. 
 
 The firing mechanism consists of the firing pin and spring, the pawl, 
 the trigger, and trigger spring, and the lanyard button. The firing 
 pin is composed of two parts, the body and the head. The body is 
 cylindrical, except for a short distance near the center, where it is cut 
 away on one side to clear the cocking toe on the trigger. At this 
 point also a lug is formed upon the top of the pin to which the pawl is 
 pivoted. The rear cylindrical part has two longitudinal grooves as 
 gas vents, and the end of the pin is provided with a lanyard eye. The 
 front end of the body of the pin is drilled and tapped to receive the head, 
 which is screwed in and secured by a small pin. The head itself is 
 cone-shaped, the apex being drawn out and hardened to form the firing 
 point. The base of the cone is grooved longitudinally to permit the 
 escape of gas in the event of a blow-back. A circular recess is made 
 in the side of the cone in which the end of the safety screw pin is seated 
 when the block is closed and locked. At other times the rotation of 
 the block has removed the screw from its position opposite the recess 
 and it bears against the side of the firing-pin head, thus preventing 
 the projection of the pin through the block and the resulting possi- 
 bility of a premature discharge. 
 
 The firing-pin spring is a coiled steel spring mounted on the body 
 of the firing pin between its head and the pawl lug. The front end is 
 bent to fit into a hole drilled in the body close to the head, while the 
 rear end is brought forward over the coils parallel with the body, and 
 in its normal position abuts against the shoulder at the front of the 
 block. In this position the firing point is held retracted within the 
 block, as a movement to the front would extend the spring. In the 
 firing the momentum of the firing pin carries it forward beyond its 
 point of rest and against the action of the spring far enough to explode 
 the primer. To remove the firing spring it is necessary to take off 
 the firing-pin head. 
 
 The trigger is an arm having at one end a lug to form a long pivot 
 bearing and at the other a hook over which the lanyard button passes. 
 Upon one side of the arm is formed the cocking toe which engages the 
 pawl, and on the same side near the upper end is a short slot in which 
 a projecting pin on the pawl is caught in the forward movement of 
 the trigger after firing. 
 
 The trigger spring is coiled around the trigger pivot and secured 
 at both ends. Its action is to force the trigger forward after firing 
 and thus engage the pawl again in readiness for the next shot. 
 
ARMAMENT 171 
 
 The lanyard button is a straight piece, slotted out to pass over 
 and engage the hook on the trigger, and also provided with a lanyard 
 eye at its rear end. It extends to the rear through a hole in the carrier 
 plate, and is prevented from being drawn to the front through the 
 plate by a button-shaped enlargement. 
 
 To Open the Breech. The first motion of the operating lever to 
 open moves it to the rear, due to its elongated pivot bearing, and 
 unlocks the lug on its front edge from the slot in the breechblock. 
 The knob on the operating lever then causes the block to rotate until 
 its threads are unlocked from those of the breech recess. Further 
 rotation of the blgck around its axis is prevented by its stop reaching 
 the end of the groove in the carrier plate; rotation, as a whole, takes 
 place around the hinge pin. As soon as this rotation begins the lock- 
 bolt spring presses the bolt forward, locking the block to the carrier 
 plate, and the extractor is constrained to move on its cam bearings, 
 causing the point to withdraw the cartridge case at first slowly and 
 then rapidly. 
 
 The operation of closing the block is the reverse of the above. 
 
 The firing mechanism, being of the continuous-pull type, is not 
 operated in any way by the operation of the block. 
 
 To Fire the Gun. Insert the hook of the lanyard in the eye of 
 the lanyard button and pull until the firing pin is released. Pulling 
 the lanyard button causes the trigger to rotate around its pin. The 
 cocking toe of the trigger catches the pawl and the firing pin is pulled 
 to the rear against its spring until the short arm slides off the pawl, 
 when the firing pin is released and is driven forward by its spring. 
 When the pull on the lanyard is released the trigger spring rotates 
 the trigger forward, causing the toe to pass the pawl. The long arm 
 then strikes a pin on the pawl, causing the pawl to rotate downward, 
 so as to be caught by the toe of the trigger, when the firing mechanism 
 is again ready for firing. 
 
 To Assemble the Breech Mechanism. Seat the extractor. Put in 
 the block-locking bolt and spring in the carrier plate. Assemble 
 the carrier ring in the carrier plate, securing it by the screws, top and 
 bottom. Slide the firing pin with its spring and pawl assembled into 
 its seat from the front of the carrier plate. Slip the trigger containing 
 its spring into place from beneath, taking care that the exposed end of 
 the spring enters its seat in the carrier plate; insert the trigger pin 
 carefully so as not to displace the coils of the spring. Pass the lanyard 
 button from the rear through the slot in the carrier plate and hook it 
 over the trigger, lifting the pawl so that the trigger may be pulled 
 
172 THE SERVICE OF COAST ARTILLERY 
 
 back far enough for that purpose. Holding the trigger in that position 
 by means of the lanyard button, slip the block over the hub of the 
 carrier plate and screw it home in the carrier ring. Seat the carrier 
 plate on the gun with the block exposed and insert the hinge pin. Put 
 the lever-catch plunger and spring in its seat, press it down and enter 
 the cotter pin. Push in the block-locking plunger, rotate the block 
 to its closed position and insert the operating lever in its seat. In 
 this position the lever will be home against the carrier plate. Insert 
 the operating-lever pin and enter its cotter pin. Swing the block 
 and carrier to the full open position by means of the lever, and by 
 further pulling the latter rotate the block to its proper position for 
 entering the breech. 
 
 If an attempt is made to close the breech before the last operation 
 the block will jam. 
 
 To Dismount the Breech Mechanism. Reverse the preceding ope- 
 rations. Care should be taken not to snap the firing pin except when 
 the block is closed and locked, as in any other position the firing-pin 
 head will strike the end of the safety screw. A few such blows will 
 bend or break this screw. 
 
 2.24-lNCH (6-PouNDER) R.-F. GUN, AMERICAN ORDNANCE Co. Mm 
 
 This rifle follows the general method of built-up forged-steel con- 
 struction. It consists of a tube, jacket, hoop, and breech mechanism. 
 The tube is enveloped for a distance of 42.90 inches from the breech 
 end by the jacket and hoop. The jacket is assembled from the rear, 
 the end of the tube abutting against a shoulder in the former. The 
 hoop is assembled from the front, the two parts being locked together 
 by a bronze sleeve with screws over the joint, and is held in place by a 
 key. A shoulder formed in the tube abuts against a corresponding 
 shoulder in the hoop and prevents forward movement of the tube. 
 The exterior of the bronze sleeve is machined to form parallel bearing 
 surfaces or guides by which the gun is supported in the mount. 
 
 The portion of the jacket in the rear of the tube is enlarged to form 
 the recess for the breechblock and extractors. 
 
 The bore, which is 50 calibers in length, is composed of a seat for 
 the cartridge, a forcing slope, and a main bore, which is 2.244 inches 
 in diameter between lands. 
 
 The rifling begins at a point 12.873 inches from the breech end of 
 the tube with a right-hand twist, increasing from to 1 turn in 26.36 
 calibers at the muzzle. 
 
ARMAMENT 173 
 
 The top of the breech recess is rounded and has four circumferential 
 grooves into which corresponding ribs on the block fit when the latter 
 is locked. Seats for the pivots of the extractors are drilled on either 
 side near the front of the breech recess, and a transverse hole or bearing, 
 for the main bolt is drilled through each cheek. A guide bolt is also 
 screwed into each cheek, the end projecting slightly into the breech 
 recess. 
 
 Breech Mechanism. These guns are fitted with the Driggs-Schroeder 
 breech mechanism, the principal parts of which are the block, face plate, 
 main bolt, cam, operating handle, lever lock, lever-detent spring, 
 extractors and firing mechanism. 
 
 The general shape of the block is the same as that of the breech 
 recess. On its rounded top are formed four ribs which serve to lock 
 the 'block in the firing position and transmit the thrust to the jacket. 
 On each side of the block is a curved slot in which work the ends of 
 the guide bolts. Undercut slots are cut in the front and rear faces 
 of the block to receive the face plate and the sear, and its interior is 
 hollowed out for the cam and the firing pin. Recesses are also cut in 
 each side of the front face for the extractors and surfaces for operating 
 the same, formed on the sides of the block. 
 
 Access to the interior of the block is gained through an opening 
 in the front face, which, when the block is assembled, is closed by 
 the face plate. The latter is a steel plate seated in an undercut slot 
 and secured in place by the front end of the sear spring. It is drilled 
 to permit the passage of the point of the firing pin, and has a thumb 
 notch for easy assembling. 
 
 The main bolt consists of two cylindrical surfaces of different 
 diameters joined by a hexagonal seat for the cam. It passes through 
 an elongated hole in the block and the cylindrical ends fit into the 
 supporting bearings drilled through the cheeks of the breech recess. 
 On the smaller end which projects through the left cheek the operating 
 handle is fitted and secured to it by a feather lug and the lever lock. 
 The lever lock is a circular-shaped lever pivoted to the operating 
 handle just above the lug and carrying on its under side a projection 
 which passes through a seat in the lug and engages in a seat in the 
 main bolt, thus securing the handle in place. 
 
 The handle is prevented from movement in counter recoil by the 
 lever-detent spring, a spring circular in shape and dovetailed to the 
 handle lug. The free end partly embraces the lever-stop pin when 
 the breech is closed, thus preventing movement of the handle. 
 
 The cam is a short sleeve mounted upon the main bolt within the 
 
174 THE SERVICE OF COAST ARTILLERY 
 
 block. It has a projecting cam surface which bears against the interior 
 of the block and controls the movement of the latter, and in addition 
 a shoulder, which by engaging an arm on the firing pin, cocks the pin 
 during the opening movement. 
 
 There are two extractors, one on each side. Each consists of an 
 arm, slightly bent, on which is formed at right angles a pivot that 
 seats in a bearing drilled in the side of the breech recess. 
 
 The upper end of the arm carries the flange which engages the 
 cartridge case, while on the ower end is formed a cam which works 
 against a corresponding surface on the block. 
 
 The Firing Mechanism is composed of the firing pin, the firing-pin 
 spring, the sear, and the sear spring. 
 
 The firing pin consists of a cylindrical body carrying on the under- 
 side the full-cock stud and the cocking arm and terminating in an eye 
 for the drill-washer support in rear. On the upper side of the front 
 end of the body is formed a lug, which is drilled and slotted to receive 
 the split stem of the point. The firing-pin point is made in the form of 
 a short spring split pin, the split end of which carries two locking 
 shoulders. The lug on the firing-pin body is slotted to permit the 
 passage of these shoulders, so that when the head is pressed home 
 and partly rotated a bayonet joint is formed. The spring effect tends 
 to spread the locking shoulders and prevent accidental rotation of 
 the head. The firing spring lies between the lug of the firing pin in 
 front and a shoulder of the block in rear. 
 
 The sear is a simple slide working in an undercut slot in the rear 
 face of the block. Actuated by the sear spring, it presses up against 
 the firing pin and engages the full-cock stud when the pin is retracted. 
 Near its lower end a projecting lanyard eye is formed. 
 
 The sear spring is a flat spring enlarged at both ends, the rear end 
 being notched to engage the sear, while the front end is cylindrical 
 and serves both as a fulcrum for the spring and as a retaining pin for 
 the face plate. 
 
 In the open position the block is supported by the tray, a channel- 
 shaped forging, which is secured to the rear ends of the cheeks by 
 screws. 
 
 To Open the Breech. Turn the operating handle smartly to the 
 rear. This movement unlocks the main bolt by releasing the lever- 
 detent spring from the stop pin, and rotates the main bolt and cam. 
 The first movement of the latter starts the retraction of the firing pin. 
 As soon as the latter is retracted within the block the cam begins to 
 act on the block, forcing it down until the ribs on the block clear the 
 
ARMAMENT 175 
 
 grooves in the gun. The cam and guide bolts then cause the blocks 
 to rotate backward around the main bolt until its front face is parallel 
 to the axis of the gun. During this movement the firing pin has been 
 fully retracted and caught by the sear. As the block rotates backward 
 the lower arms of the extractor follows the cam surfaces on the former, 
 causing the extractors to start the empty case slowly at first and after- 
 ward to eject it quickly. 
 
 The breech is closed by fuming the operating handle to the front. 
 The block is first turned, then raised and locked, the firing pin being 
 left in the full-cock position. 
 
 To Fire the Gun. Pass the lanyard beneath the tray and hook 
 it into the eye on the sear. A quick pull on the lanyard will draw 
 drown the sear and release the firing pin. To permit of snapping the 
 firing pin for drill purposes and without a cartridge case in the gun, a 
 rubber ring, called the drill washer, is slipped over the rear end of the 
 firing pin and held in place by the washer support, which passes through 
 the eye on the end of the pin. When the trigger is snapped under 
 drill conditions this rubber ring acts as a buffer between the rear face 
 of the block and the support and thus lessens the shock on the firing 
 pin. 
 
 The drill washer does not interfere with firing the gun, and should 
 be left on at all times in order to avoid the possibility of snapping the 
 trigger without it. 
 
 To Dismount the Breech Mechanism. Cock the firing pin either 
 by opening and closing the breech or by pulling it to the rear with 
 the breech-mechanism tool until the sear engages. Remove the handle, 
 having first raised its locking lever. 
 
 Withdraw the main bolt, supporting the block from beneath by the 
 hand; remove the block by lowering it until the ribs on top are dis- 
 engaged, and then withdrawing it straight to the rear until clear of 
 the gun. 
 
 Lay the block on its right side on a wooden surface, withdraw the 
 sear spring from the front and slip out the face plate; turn the block 
 face down and pull down the sear, thus liberating the firing pin and 
 spring; lift up the block, and the cam, firing pin, and spring will drop 
 out clear. 
 
 Care should be taken to see that the firing pin is cocked before 
 attempting to remove the face plate; otherwise the point of the pin 
 will be bent or broken by the plate. If there is no wood surface con- 
 venient for snapping the firing pin into, hold it back with the tool and 
 ease it forward on removing the sear. 
 
176 THE SERVICE OF COAST ARTILLERY 
 
 To Assemble the Breech Mechanism. Reverse the preceding 
 operations. Put in successively the firing spring, firing pin, and cam; 
 the front side of the latter is marked "Out." Put on the face plate, 
 being careful to see that the firing pin is retracted while so doing. 
 Insert the sear spring and engage the notch at its rear end with the sear. 
 Replace the block in the breech in the closed position and insert the 
 main bolt, bringing the arrow on its head in line with the arrow on the 
 cheek in order to insure the proper location of the cam on its hexagonal 
 seat. Put on the handle and close the locking lever into its seat, taking 
 care that it is pushed home. 
 
 FIRING MECHANISM, MODEL OF 1903 
 
 USED ON ALL 8-lNCH, 10-lNCH AND 12-INCH RlFLES, AND 12-INCH 
 
 MORTARS 
 
 (Plates V and IX) 
 
 The principal parts of the firing mechanism, of the above model, 
 are hinged collar, housing, slide, and firing leaf. 
 
 The hinged collar embraces the rear end of the spindle, two' ribs 
 on its inner surface engaging in corresponding grooves in the spindle. 
 
 The housing screws over the hinged collar, which is threaded to 
 receive it, and a spring catch locks the collar to the housing when it is 
 fully screwed home. The collar is thus prevented from opening and 
 secures the housing to the spindle. 
 
 A guide bar projects from the right side of the housing into a longi- 
 tudinal groove cut in the block recess and causes the housing to rotate 
 with the block. 
 
 The slide travels vertically in grooves cut in the rear face of the 
 housing and when in its lowest position holds the primer to place in 
 the primer seat. Its motion is limited by the slide stop on the left side 
 of the housing. The slide catch serves to lock it in place when lowered, 
 and to support it at the proper height to allow the primer to be inserted 
 when raised. 
 
 The ejector is an L-shaped piece with trunnions at its angle, about 
 which it swings, and which enter two slots cut for them in the housing. 
 The lower arm of this extractor is fork-shaped and hangs over the mouth 
 of the primer seat under the head of the primer. The horizontal arm 
 projects to the rear into a recess in the slide, and when the latter is 
 lifted this arm is carried upward and the ejector rotated about its 
 
ARMAMENT 177 
 
 trunnions so as to throw the horizontal arm to the rear, ejecting the 
 primer. 
 
 The firing leaf is pivoted to the slide at its upper end. It has a 
 vertical slot cut in its lower edge through which the wire of the primer 
 projects when the slide is in its lower or locked position. At the 
 right-hand lower corner of the leaf is an eye into which the lanyard 
 is hooked for friction firing. When the leaf is drawn to the rear it 
 engages the button on the end of the primer wire and draws the wire 
 out and fires the primer. 
 
 Electric connection with the primer is made through the two brass 
 arms of the contact clip which embrace the head of the primer. The 
 contact clip is held in place by a housing which is secured to the rear 
 face of the leaf. The electric-cable terminal is made of a piece of steel 
 rod bent at a right angle. To one arm is attached the electric cable; 
 the other arm is slit to form a spring which is inserted into a hole in 
 the contact-clip housing on the firing leaf. 
 
 A safety bar prevents accidental firing of the piece by the lanyard 
 before the breech is locked; and a circuit breaker serves to prevent 
 firing the piece by electricity before the breech is locked. 
 
 The first motion of rotation of the block to unlock the breech 
 forces the safety bar inward so as to engage the leaf and prevent its 
 being drawn to the rear, while at the same time the electric circuit is 
 broken by the same movement of rotation. 
 
 A safety lug on the right side of the housing engages a groove in 
 the firing leaf and prevents the latter from being drawn to the rear 
 before the breechblock is rotated to its locked position. The last part 
 of the motion of lowering the slide makes electric connection with the 
 primer. It will be seen from this that accidental firing of the piece is 
 impossible until the breech is locked and the slide of the firing mechan- 
 ism is in its lower or locked position. 
 
 The circuit breaker is of bronze and consists of two principal 
 pieces which are brought together when the block is rotated to its 
 locked position. A plunger working under the pressure of a spring- 
 serves to make electric contact between the two pieces. Both parts 
 of the circuit breaker are insulated from the piece by vulcanized 
 fiber. The electric cable is attached to the circuit breaker by a spring- 
 fork. 
 
 Instructions for the Care and Use of Seacoast Firing Mechanism, 
 Model of 1903. While this mechanism forms part of a heavy gun, it 
 is in itself small and light; the several parts are very closely adjusted, 
 and it has been necessary to make the clearances very small. The 
 
178 THE SERVICE OF COAST ARTILLERY 
 
 greatest care must be exercised, therefore, in keeping the mechanism 
 well oiled and free from rust and dirt. 
 
 It should not be left on the gun when not in use, but should be 
 kept habitually in the small box provided for it, and stored in the 
 armament chest. 
 
 To Assemble the Mechanism on the Gun. Clasp the hinged collar 
 over the end of the spindle with the two ribs of the collar engaging 
 in the corresponding grooves of the spindle, keeping the hinge at the 
 top. 
 
 Take the mechanism in the right hand, holding the collar with the 
 left, and put the mechanism over the end of the collar, screwing the 
 latter to the left until the catch on the under side of the mechanism 
 engages and locks it into position. While doing this, see that the guide 
 bar which projects from the right side of the mechanism enters the 
 groove cut in the breechblock for it, and that the pin on the safety- 
 bar slide (which is attached to the gun), enters the hole in the outer 
 end of the safety bar of the mechanism. 
 
 Do not attempt to use the mechanism until it is absolutely certain that 
 the collar has been screwed entirely home and locked. 
 
 After the primer has been inserted lower the slide until the catch 
 engages in the notch of the housing. 
 
 Be sure the slide is entirely down before attempting to fire the piece; 
 otherwise the primer may be blown to the rear, endangering the lives 
 of the detachment. 
 
 To Dismount the Mechanism. To remove the mechanism from the 
 spindle, draw the collar catch to the rear and unscrew the hinged collar. 
 
 To remove the slide from the housing, draw the slide stop out 
 to the left as far as it will go. The slide may then be lifted from the 
 housing. 
 
 To remove the firing leaf and slide catch from the slide, start the 
 split pin which passes through the leaf pivot by pressing it against the 
 bench or other surface and then draw it out. The pivot is then free 
 to be removed, and its removal frees the leaf and slide catch from the 
 slide. 
 
 The collar catch may be removed by unscrewing the screw at the 
 lower edge of the housing. 
 
 The slide stop may be removed by unscrewing it from the housing 
 with the wrench provided for that purpose. The slide stop should not 
 be removed except when necessary to repair it or to replace a broken 
 spring. 
 
 The contact-clip housing may be removed from the leaf by unscrew- 
 
ARMAMENT 179 
 
 ing the nut on the under side of the leaf. The contact clip is held 
 to place in its housing by spring pressure only, and may be removed 
 by drawing or pushing downward after the cable terminal has been 
 removed. 
 
 FIRING MECHANISM 6-lNCH R.-F. GUN, MODEL OF 1903 
 
 The principal parts of this firing mechanism are the housing, slide, 
 firing leaf, ejector, contact clip, and firing cable. 
 
 The housing is screwed on the rear end of the obturator spindle 
 and does not rotate with the block, due to the action of the spindle 
 key. A groove on the rear face of the housing carries the slide, which 
 has a horizontal motion on the right side of the axis of the gun limited 
 by the slide stop. 
 
 A notch on the under side of the slide receives the rack-lock bolt. 
 The left end of the slide is V-shaped, with the point of the V to the 
 right. The point of the V is extended to the right by a notch cut 
 through the slide. When the slide is in position, breech closed, the 
 stem of the primer passes through the notch, the base of the primer 
 being supported by the body of the slide. 
 
 The firing leaf is a vertical lever, pivoted to the slide by the firing-leaf 
 pivot and pivot pin. A horizontal notch is cut into the left side of 
 the lower arm of the firing leaf. The stem of the primer passes through 
 this notch when the slide is in the firing position. 
 
 The contact clip is attached to the firing leaf by the clip housing 
 and housing nut. The housing is insulated from the slide by the clip- 
 housing insulation. When the slide is in firing position, the clip 
 embraces the button on the end of the primer stem, forming electrical 
 connection with the primer. 
 
 The firing cable is connected to the clip housing by the firing- 
 cable terminal, consisting of a split pin with enlarged end, held in 
 place by friction. The other end of the firing cable is similarly attached 
 to the firing-cable bracket on the breech of the gun. The lower arm 
 of the firing lever lies against the upper arm of the firing leaf when 
 the slide is in firing position. When the lanyard is drawn to the rear, 
 the lower end of the firing lever presses the upper end of the firing- 
 leaf to the front, causing the lower end of the leaf to strike the primer 
 button and draw it to the rear, exploding the primer. 
 
 When the rack moves to the right in opening the breech, the rack 
 lock carries with it the slide, leaving the primer free to be ejected and 
 freeing the leaf from contact with the firing lever. 
 
180 THE SERVICE OF COAST ARTILLERY 
 
 In closing the breech the leaf does not come in contact with the 
 firing lever nor the contact clip embrace the primer button until the 
 rotation of the block is practically completed. By drawing downward 
 on the rack-lock handle, the slide is freed from the rack and may 
 be moved independently, to permit the placing of a primer in the vent 
 without opening the breech. 
 
 The ejector consists of a horizontal lever, pivoted to the housing 
 of the firing mechanism. The right end lies in a groove cut in the end 
 of the spindle. This end is forked, the fork partially surrounding 
 the mouth of the vent and lying in front of the rim of the primer. 
 The left end of the ejector is broadened to be struck with the hand. 
 The ejector spring, acting on the left end of the ejector, holds the fork 
 normally in its groove in the spindle. One side of this groove is beveled 
 to allow the fork to ride out of the groove in dismounting the mechan- 
 ism. When the left end of the ejector is struck, the fork acts on the 
 rim of the primer to throw the primer clear of the vent. 
 
 FIRING MECHANISM, 6-lNCH R.-F. GUN, MODEL OF 1905 
 
 The firing mechanism for this model of gun is very similar to that 
 of the model of 1903. The essential differences are given below: 
 
 The mechanism consists of a housing, slide, firing lever, firing leaf, 
 safety plunger, ejector, and circuit breaker. 
 
 The slide is operated entirely by hand and carries 'a handle for 
 this purpose. The slide catch holds the slide in its firing position. 
 
 The catch consists of a lever pivoted at the base of the handle. 
 A hook on one end of the catch engages a shoulder on the housing. 
 The hook is pressed forward by the slide-catch spring. The hook is 
 disengaged from the shoulder by the pressure of the hand on the other 
 arm of the catch in grasping the slide handle. 
 
 The safety plunger has a vertical movement in a slot cut in the 
 spindle key and extended in the carrier. The upper end of the plunger 
 carrier is a stud, which works in a groove in the spindle key to guide 
 the plunger and limit its downward movement. The plunger is 
 pressed downward by the plunger spring. When the breech is fully 
 closed, the lower end of the plunger enters a notch cut in the surface 
 of the gear segment. When rotation of the block in opening the breech 
 begins, the plunger is forced upward out of the notch. The upper end of 
 the plunger now engages a shoulder on the firing lever, preventing any 
 movement of the lever until the breech is again fully closed. 
 
 The circuit-breaker housing is attached to the carrier by two 
 
ARMAMENT 181 
 
 screws. Two contact pins pass vertically through the housing and 
 are held in place by the contact-pin nuts screwed on their lower ends. 
 The circuit-breaker is arranged so that when the breech is closed, 
 the contact plungers are carried by the operating lever under the 
 contact pins, thus completing the firing circuit only when the breech 
 is fully closed. 
 
 FIRING MECHANISM, G-INCH R.-F. GUN, MODEL OF 1897 Mi; AND 5-lNCH 
 R.-F. GUN, MODEL OF 1897 
 
 This mechanism is intended for use with a combination electric 
 and friction primer. It consists of the following principal parts: 
 Slide, slide housing, ejector, firing leaf, contact-clip, firing cable, circuit 
 breaker and safety bar. 
 
 The housing is attached to the rear end of the spindle by means of 
 an interrupted screw thread and is secured in place by a spline screw. 
 
 The slide has a vertical movement in guides which project from the 
 rear portion of the housing, and its movement is limited by the slide 
 stop, which has a horizontal movement in a slot cut in the housing, 
 its inner end projecting into a groove in the side of the slide. The 
 slide stop is pressed inward by a helical spring. 
 
 The firing leaf is pivoted at its upper end to the slide against which 
 it lies flat when in its normal position. 
 
 A notch is cut through both the slide and the leaf, so that when 
 in its lowered position the slide supports the head of the primer against 
 the pressure of the powder gases, while allowing the primer wire to 
 extend through the notch. 
 
 When the leaf is swung to the rear, its rear face catches the button 
 at the end of the primer wire and explodes the primer. 
 
 The contact clip makes electrical connection with the primer by 
 bearing against the button on end of primer wire when the slide is 
 in its lowered position. The contact clip is held in a housing which 
 is secured to the firing leaf by the housing nut and is insulated from 
 the leaf by the housing insulation. 
 
 One end of the firing cable is attached to the clip housing by the 
 firing-cable terminal, consisting of a split pin with enlarged end held 
 in place by friction, the other end attached to the circuit-breaker 
 contact piece. 
 
 The circuit-breaker contact piece is secured to the outside of the 
 gear segment by two screws and insulated therefrom. When the block 
 is rotated in closing, the circuit-breaker contact piece comes into 
 
182 THE SERVICE OF COAST ARTILLERY 
 
 contact with the circuit-breaker contact pin, making electrical connec- 
 tion with one of the firing leads. 
 
 The circuit-breaker contact pin and spring are inclosed in a housing 
 which is attached to the block carrier by two screws and insulated 
 therefrom. The pin is held against the contact piece by the pressure 
 of its spring. The end of the firing lead is secured to the circuit-breaker 
 housing by a fork. The firing lead is held in place by the cable clamp 
 screwed to the block carrier. 
 
 The ejector consists of a horizontal and a vertical branch with 
 two trunnions near the angle. It is supported in the housing by these 
 trunnions, and in its normal position, the lower branch, which is in the 
 form of a fork, hangs vertically over the mouth of the primer seat, 
 engaging the rim of the primer on two sides. The horizontal branch 
 projects to the rear into a recess cut in the front face of the slide. The 
 lower end of this recess is a cam surface. When the slide is raised, 
 this cam surface forces the horizontal branch upward, ejecting the primer. 
 When the slide is lowered, the ejector drops into position against 
 the mouth of the primer seat. 
 
 The safety bar is a lever pivoted in the slide housing and actuated 
 by a stud on the gear segment working in a slot cut through the outer 
 end of the safety bar. At the beginning of rotation of the block in 
 opening the breech the inner end of the safety bar rotates inward, 
 entering a slot in the right side of the firing leaf, thus preventing any 
 movement of the firing leaf, except when the breech is fully closed. 
 
 To Dismount Mechanism. Open the breech. Unscrew safety-bar 
 pivot and remove safety bar. Detach firing cable from circuit-breaker 
 contact piece. Pull outward on slide stop and lift slide from housing. 
 Unscrew housing spline screw and revolve housing 90 degrees to the 
 right, when the housing may be drawn to the rear from the spindle. 
 Unscrew the spindle nut and the spindle-key screw, and remove the 
 spindle key. 
 
 Be careful not to remove spindle nut and spindle key before opening 
 the breech, as in that case the split rings are liable to drop down and 
 prevent the withdrawal of the block. 
 
 The spindle, split rings, pad, etc., are then free to be removed 
 from the block. 
 
 Take out the two gear-segment screws and drive off the gear 
 segment, using a copper drift to prevent injury to the gear segment. 
 
 Take out the latch-lever pivot and remove the latch lever, spring, 
 and bolt. The block is then free to be removed from the carrier. 
 Drive out the pivot pin and remove the pivot nut, unscrew the pivot, 
 
ARMAMENT 183 
 
 and the pinion and lever are then free to be removed from the carrier. 
 Drive out the hinge pin, being careful to support the carrier while 
 doing so, and the carrier is then free from the piece. 
 
 FIRING MECHANISM, 5-lNCH R.-F. GUN, MODEL OF 1900 
 
 This mechanism is practically the same as used in the model 1897, 
 except as follows: The housing of this mechanism is attached to the 
 spindle by means of a yoke. The firing mechanism turns with the 
 block during rotation. The safety lever lies in a groove in the surface 
 of the guide cylinder. 
 
 A projection on the front end of the safety lever rides in a groove 
 cut in the block carrier. When the breech is fully closed, this projection 
 enters a well cut at the end of the groove in the block carrier, allowing 
 the hook on the rear end of the safety lever to drop and free the firing 
 leaf. At the beginning of rotation of the block in opening the breech 
 the safety-lever hook rises and prevents any movement of the firing 
 leaf. 
 
 ADJUSTING GAS-CHECK PADS 
 
 Experience has shown that, as a rule, gas-check pads are too 
 tight. It has been customary, because of the simplicity of the method, 
 to adjust the pad with the breech open by tightening the spindle nut 
 until the pad could just be turned by hand. In cold weather when the 
 pad is relatively rigid this adjustment is satisfactory; in warm weather, 
 however, the pad being more plastic is forced outward readily till it 
 extends beyond the surface of the split rings. When this occurs, even 
 though the pad can be turned by hand, the pad is not in proper adjust- 
 ment, since when forced into its seat it will be pressed over the rear 
 ring and injured. As the object of the pad is to form a perfect gas 
 check at the rear of the tube, the best adjustment is made with the 
 pad seated. 
 
 To Adjust Pads, Close the breech, having the spindle nut loose, 
 but not so loose as to permit slipping of the pad or split rings; rotate 
 the block until one-half of the rotation has been accomplished. With 
 the mechanism in position, screw up the spindle nut as tight as it can 
 be screwed with the wrenches provided. 
 
 With the new spindle nut, having a locking device, it is necessary 
 to insert the end of a screw-driver in the opening of the nut in order to 
 spread it sufficiently to allow its rotation without rotating the spindle. 
 
184 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Lock the spindle nut and rotate the breechblock until the breech 
 is completely closed. This last operation presses the pad in its seat, 
 due to the forward motion of the block. 
 
 The pad is now in proper adjustment for firing. 
 
 GUN 
 
 ID 
 
 REAR ADAPTER FRONT ADAPTER 
 
 ADAPTER CLAMP WEDGE 
 
 LOCATING GAUGE 
 
 BRISTLE SPONGE 
 
 SPONGE ROD 
 
 1=3 
 
 HANDSPIKE 
 
 ADJUSTING WRENCH FOR M. 1888-1895 
 
 n 
 
 CLAMPING WRENCH 
 
 U 
 
 HAND EXTRACTOR 
 
 VENT CLEANER 
 
 OIL CAN 
 
 CLIP EXTRACTOR 
 
 SPINDLE PLATE SCREW WRENCH SECURING SCREWS 
 
 L_\ 
 
 FIG. 17. 
 
 THE 1-POUNDER AND 2.95-INCH SUBCALIBER GUNS 
 
 As the name implies, the subcaliber tube is in reality a gun of lesser 
 caliber than the gun in which used. It is inserted into the bores of 
 seacoast cannon for the purpose of providing a means of practicing 
 
ARMAMENT 
 
 185 
 
 in firings with these guns under conditions resembling those of service 
 practice, the difference being that the projectile of the subcaliber 
 gun is of much smaller caliber when compared to the bore of the larger 
 gun. 
 
 The principal parts of a type of subcaliber tube are shown in detail 
 in Fig. 17. 
 
 A statement of the various sizes of tubes provided for use in sea- 
 coast cannon, as well as the interehangeability of the same, is given 
 in the following table: 
 
 INTERCHANGEABILITY OF SUBCALIBEK GUNS. 
 
 Subcaliber 
 
 of 1900. 
 Subcaliber 
 
 of 1900, 
 Subcaliber 
 
 of 1888. 
 Subcaliber 
 
 of 1888, 
 Subcaliber 
 
 of 1888, 
 
 guns for 5-inch guns, model 
 
 guns for 6-inch guns, models 
 
 1903, and 1905. 
 
 guns for 8-inch guns, model 
 
 guns for 10-inch guns, models 
 1895, and 1900. 
 guns for 12-inch guns, models 
 1895, and 1900. 
 
 * Subcaliber guns for 4-inch Driggs- 
 
 Schroeder guns. 
 
 * Subcaliber guns for 5-inch guns, model 
 
 of 1897. 
 
 * Subcaliber guns for 6-inch guns, model 
 of 1897. 
 
 Subcaliber guns for 4.72-inch and 6-inch 
 Armstrong guns. 
 
 Are interchangeable ; that is, these guns 
 will all fit into the 5-inch guns, model 
 of 1900; 6-inch guns, models of 1900, 
 1903 and 1905; and 8-, 10-, and 12- 
 inch guns of all models when fitted 
 with the proper adapters. 
 
 They will not fit in the 4-inch Driggs- 
 Schroeder 5-inch and 6-inch guns, 
 model of 1897, and 4.72-inch and 
 6-inch Armstrong guns, as these guns 
 must have subcaliber guns fitted with 
 special rear adapters forming a per- 
 manent part of the subcaliber gun. 
 
 Are interchangeable in 4-inch Driggs- 
 Schroeder guns, and 8-, 10-, and 12- 
 inch guns of all models when fitted 
 with the proper adapters. 
 
 Are interchangeable in 5-inch guns, 
 model of 1897, and 8-, 10-, and 12-inch 
 guns of all models when fitted with 
 the proper adapters. 
 
 Are interchangeable in 6-inch guns, 
 model of 1897, and 10- and 12-inch 
 guns of all models when fitted with 
 the proper adapters. 
 
 Are interchangeable, respectively, in all 
 4.72-inch and 6-inch Armstrong guns, 
 and 10- and 12-inch guns of all models 
 when fitted wtih the proper adapters. 
 
 * The 4-inch Driggs-Schroeder, 6-inch 1897, and 6-inch Armstrong subcaliber 
 guns should have adjusting wrench holes, if not already provided, drilled in the 
 breech face, if these guns are ever mounted in 10- or 12-inch guns. 
 
 Each caliber and model of gun requires a special adapter which can not be used 
 in any other model of gun. 
 
 The 2.95-inch subcaliber guns for 12-inch mortars, model of 1886, are not inter- 
 changeable with those for 12-inch mortars, model of 1890. 
 
 The directions for assembling and using the tubes are practically 
 the same for all guns, so that an explanation of the 1 -pounder sub- 
 caliber tube used in the bores of 8-, 10-, and 12-inch B.-L. Rifles will 
 serve as a guide: 
 
186 THE SERVICE OF COAST ARTILLERY 
 
 To Assemble the Tube. First see that the chamber and bore of 
 the subcaliber gun, and of the gun itself, are perfectly clean. Remove 
 the blank pressure plugs from the mushroom head and put on the 
 obturator spindle plate with its two screws. This is done by using 
 the securing screw wrench. The screw heads should be tightened well 
 upon the plate. Then insert the loading tray to prevent injuring 
 the adapters on the breech threads. 
 
 The subcaliber gun with its adapters should now be inserted into the 
 chamber of the large gun by pushing it forward with a handspike 
 sufficiently far to cause the front adapter to seat fir-mly in the slope 
 of the powder chamber. It is tapered so that it will fit this slope. 
 With the 10- and 12-inch rifles, model of 1900, the subcaliber gun should 
 be supported with a handspike while the bronze shoe is slipped under 
 the rear adapter. 
 
 When the subcaliber gun is as far forward as it can go remove 
 the handspike and insert locating gauge in the chamber of the sub- 
 caliber gun with its flange pulled to the rear. Then completely close 
 the breech of the large gun and open it again and note whether the 
 flange of the locating gauge is flush with the face of the subcaliber gun. 
 If the gauge protrudes revolve the subcaliber gun left-handed. If 
 below the face of the subcaliber gun turn the gun right-haniled. One 
 complete turn of the gun will make a difference in the distance from 
 the face of the subcaliber gun to the mushroom head of 1/10 of an inch. 
 This adjustment is made with the adjusting wrench, having its lugs 
 entered into the holes in the rear face of the gun. 
 
 The subcaliber gun should be adjusted in this manner until the 
 flange of the locating gauge is brought exactly flush wiien the breech 
 is closed. The thread clamp screw should be tightened with the 
 clamping wrench so that the subcaliber gun will be prevented from 
 turning. The gun is then ready for firing. 
 
 To Use the Subcaliber Gun. Insert a subcaliber cartridge, close 
 the breech and fire as with the regular ammunition. The breech is 
 then opened, the empty cartridge case removed after each round 
 with the hand extractor. Should a cartridge case stick so that it can 
 not be removed with the hand extractor, use the clip extractor, which 
 is provided for such emergencies. It may be necessary to pass a light 
 rope through the eye of the clip extractor in order to apply greater 
 force against the face of the breech. 
 
 To Dismount the Tube. Insert the loading tray and loosen up 
 both clamp screws. Then insert the handspike, leaving same to support 
 the weight, and remove the adapter shoe. Then pull the subcaliber 
 
ARMAMENT 187 
 
 gun to the rear and out. Should the gun stick attach a rope over the 
 enlargement of the breech and pull out, being careful that the gun does 
 not come to the rear too rapidly after being released. 
 
 It is important that the subcaliber gun be Unloaded and then 
 loosened before the adapter shoe is removed from under the rear 
 adapter, because if the shoe is removed before the gun is loosened 
 the lowering of the breech of the subcaliber gun will cause the front 
 adapter to bind in its seat and considerable difficulty will be had in 
 removing the tube. Care should be taken in assembling and dis- 
 mounting in order to prevent the turning surfaces of the adapters 
 from striking the threads of the breech recess or any other hard sub- 
 stance and burring them. Care should also be taken in loading not 
 to drive the point of the shell against the edge of the chamber of the 
 subcaliber gun. Both guns should be thoroughly cleaned and oiled 
 after firing. 
 
 CARRIAGES FOR COAST ARTILLERY CANNON 
 
 The method of mounting seacoast guns determines the design of 
 emplacements. Conversely, the design of emplacements also has 
 a bearing upon the suitability of mounts for guns. It is evident that 
 the principal object of an emplacement is to provide a firm, unyielding 
 support for the gun and carriage, so that the gun may be loaded, 
 manipulated and fired under conditions giving the greatest protection to 
 the personnel and armament from the fire of the enemy. 
 
 Elements influencing the selection of type of carriage may be briefly 
 stated as follows: 
 
 1. Rapidity of Fire. With large guns (10- and 12-inch calibers) 
 greater rapidity of fire is undoubtedly obtained with the disappearing 
 type of carriage. The advantage in time and less fatigue of men are such 
 as to give a decided preference for the disappearing mount. When 
 the caliber of the gun is six inches or less the advantage obtained by 
 the use of the disappearing type of carriage may be considered as nil, 
 and for calibers less than six inches the non-disappearing type is 
 decidedly preferable. 
 
 2. Exposure of Gun, Carriage, or Mount. With the non-disappear- 
 ing carriage without a shield, substantially every man working at the 
 gun, except those on the elevating cranks, is exposed to direct fire; 
 while with the disappearing carriage and direct laying (Case I and II) 
 only one man is exposed. In indirect laying (Case III) none of the 
 personnel are exposed for small angles of fall. 
 
188 THE SERVICE OF COAST ARTILLERY 
 
 Considering the non-disappearing type of carriage illustrated by 
 the Armstrong Pedestal Mount with shield, it may be stated that the 
 gunner has better protection than with any other type of mount. 
 The gun, however, on a non-disappearing carriage is exposed at all 
 times; while with the disappearing type it is only exposed, in direct 
 laying, for the few seconds required for aiming; and for indirect laying 
 it is exposed for even a shorter time, that is, while the piece is actually 
 being fired. 
 
 The damage, caused by a shot hitting the disappearing type of 
 carriage, when exposed to the direct fire of the enemy, is more apt 
 to be greater and more serious than the damage, from the same shot, 
 to the non-disappearing type; due to the numerous additional devices 
 required in the former type. 
 
 Carriages for coast artillery cannon are classified as follows: 
 
 1. According to the nature of the cover afforded by the emplace- 
 ments, into: 
 
 Barbette (Barbette Proper, Pedestal Mount, Special Mounts), 
 
 Disappearing, 
 
 Masking Mount, 
 
 Casemate, 
 
 Mortar. 
 
 2. According to the axis of rotation about which they are traversed, 
 into: 
 
 Front Pintle, 
 Center Pintle. 
 
 3. According to the area of fire covered by them, into: 
 
 Limited Fire, 
 All-around Fire. 
 
 BARBETTE 
 
 Barbette Proper. This class of carriage includes the non-dis- 
 appearing types, with guns that remain above the parapet for loading 
 and firing. Carriages of this type may be either front pintle or center 
 pintle, limited fire, or all-around fire. A type of this class of carriage 
 is illustrated in the 12-inch barbette carriage shown in Plate XVIII. 
 The carriage is of the center pintle form and consists essentially of the 
 following parts: A base ring resting upon the masonry platform, a 
 traversing roller ring, a combined racer and chassis, and a top carriage 
 containing the trunnion beds and the recoil cylinders. 
 
 The base ring is of cast iron, in one piece, 10 feet 8 inches in 
 diameter, secured to the platform by sixteen 2-inch bolts through 
 
ARMAMENT 189 
 
 the flange. The lower roller path, with an outside diameter of 96.7 
 inches, is on its upper surface. 
 
 The pintle rising from the center of the base ring is a right 
 cylinder, 8.05 inches high and 37.97 inches in diameter, with an oil 
 groove on its outer surface. Upon the lower roller path rests a circle 
 of twenty forged-steel conical rollers securely held in place by two 
 concentric distance rings. The distance rings are kept concentric 
 by ten separators, bolted between them, and the system is held con- 
 centric with the pintle by flanges on the inner ends of the rollers. 
 
 The combined racer and chassis is of cast iron, made in one piece, 
 with transoms and inner and outer strengthening ribs. The lower 
 surface, constituting the upper roller path, rests upon the traversing 
 roller-ring system. Four forged-steel clips are bolted to its lower 
 exterior surface with five If-inch tap bolts. The lips of these clips 
 engage under a corresponding flange on the base ring. Between these 
 clips is a dust guard, in four sections, extending around the traversing 
 roller-ring system. A circular flange on the interior of the racer 
 constitutes the pintle ring, and extends down over the pintle on the 
 base ring. 
 
 The top carriage rests upon eight steel rollers, 8 inches in diameter, 
 mounted on a U-shaped recess in the top of the chassis rails. These 
 rollers are bushed with bronze and mounted upon 2-inch screw axles 
 seated in the walls of the recess. The chassis rails have an inclination 
 upwards and to the rear, of four degrees, and are strengthened by 
 three transoms. The piston rods pass through lugs which project 
 upwards from the front ends of the rails and are secured by the piston- 
 rod nuts and check nuts. The front surface of these lugs and of 
 the rails is planed as a seat for a shield to protect the gu ners. 
 
 The top carriage h of steel, cast in one pi ce. It consists of the 
 two trunnion bed side frames in which are cast the two recoil 
 cylinders united by a transom passing under the gun. 
 
 Flanges upon the recoil cylinder are clipped over corresponding 
 flanges on the chassis rails. The cylinders are 8^ inches in interior 
 diameter, fitted each with a piston rod 3i inches in diameter, having 
 a piston with a clearance of 0.1 of an inch all around. During the 
 recoil the pistons remain stationary, and the top carriage with the 
 recoil cylinders is drawn over them. Uniform resistance in the 
 cylinders is obtained by the passage of the liquid from front to rear, 
 through varying orifices caused by throttling bars whose inner faces 
 are curved. There are two throttling bars in each cylinder, and each 
 piston has rectangular slots, one on each side, which fit over thorn. 
 
190 THE SERVICE OF COAST ARTILLERY 
 
 The sectional areas of these bars are such that the orifices for the 
 flow of liquid vary with the position of the piston during recoil so 
 as to obtain the desired resistance in the cylinder. The energy of 
 recoil is taken up by the resistance which the fluid offers to being 
 driven through the orifices. 
 
 After recoiling, the gun returns to the firing position by the 
 action of gravity, the slope of the chassis rails being sufficient to 
 permit the top carriage to move forward on the rollers. The rear 
 end of each cylinder is closed by a screw plug-cover which has in 
 its front face a cylindrical cavity 5 inches deep with rounded bottom, 
 and the end of the piston rod fits into this cavity w r ith a clearance 
 of .0075 of an inch on the diameter. When the gun returns to the 
 firing position the liquid caught in the cavity can only escape by 
 the small clearance, thus acting as a buffer to check the velocity at 
 the end of the return into battery. At the front end of the recoil 
 cylinder there are the usual stuffing boxes, with glands and fol- 
 lowers. 
 
 A copper equalizing pipe entering immediately behind the glands 
 connects the front ends of the cylinders. By this means the pressure 
 in both cylinders is always the same. The recoil should be about 
 40 inches. 
 
 The cylinders are provided with filling and emptying plugs suitably 
 placed. 
 
 The cap squares are dovetailed and secured by two 1-inch tap 
 bolts. 
 
 The carriage is traversed by a chain, coupled through its end 
 links to two ear bolts passing through lugs cast on the outer vertical 
 surface of the base ring below the roller path. By means of nuts 
 on these bolts the length of the chain may be given all necessary 
 adjustment. 
 
 Wrought-iron bolts are mounted vertically 8 inches each side of 
 the longitudinal axial (plane) bolted upon a racer. A rectangular 
 slot is mortised through the lower end of these bolts, in the walls 
 of which are mounted 1^-inch steel bolts which serve as axles for 
 pulleys for changing the direction of the traversing chain, to carry 
 it up over a sprocket wheel splined to a worm gear in front of it. 
 This sprocket wheel and worm gear are mounted on a horizontal 
 steel axle bolt in a bearing cast on the racer. 
 
 The traversing worm gear engages in a worm keyed on a transverse 
 through shaft, mounted in bronze bush bearings in brackets cast 
 on and projecting to the front from the chassis rails. On the squared 
 
ARMAMENT 191 
 
 ends of the traversing shaft there are crank levers IS inches long, 
 with handles covered with loose brass sleeves. 
 
 Pointing in elevation is given by a rack, bolted by two l|-inch 
 bolts to the elevating band on the gun. A pinion, mounted upon 
 a short cross shaft, engages in the rack. This elevating pinion shaft 
 is mounted in a bearing drilled in the top carriage over the rear end 
 of the right-recoil cylinder. On the outer end of the same shaft 
 there is keyed a friction clutch disk, fitting in a ground seat in the 
 outer face of the worm gear, and is brought to a bearing in its seat 
 by a nut on the end of the shaft. By this clutch excessive stress on 
 the elevating system is relieved during firing. 
 
 This worm gear engages in a worm splined upon a vertical shaft 
 having its bearings in two lugs on the outside of the top carriage. 
 On the lower end of this worm shaft there is splined a bevel gear 
 which takes in a second bevel gear upon the main elevating shaft; 
 this is supported, parallel to the top surface of the right chassis 
 rail, by the two wrought-iron brackets bolted to the outer face of 
 the latter. This second bevel gear slides upon the squared section 
 of this shaft, being carried back and forth in the recoil of the top 
 carriage by an arm cast upon the latter, through which the hub of 
 the gear extends, secured by a nut abutting against the front side 
 of the arm. There is a hand wheel on the rear end of the shaft for 
 the use of the gunners. The front end has anothe bevel gear mounted 
 thereon, which engages in a bevel gear mounted on a transverse 
 through shaft, having its bearings in bronze sleeves, bolted to the 
 chassis rails, near their forward ends, as bushings of holes drilled 
 in the same. On each end of this shaft there is a bronze handwheel 
 to assist in elevating the gun. 
 
 For the shot hoist there is a through shaft journaled in the rear 
 ends of the chassis rails above the upper roller path, with a bronze 
 bushed middle bearing in the lug projecting from the rear transom. 
 This shaft is held against lateral motion by a collar on the outside 
 of each chassis rail. A bevel gear keyed upon this shaft under the 
 right chassis rail takes in a bevel gear splined on the lower end of 
 the vertical shaft journaled in two other lugs extending from the 
 rear transom. Above this latter gear there is a worm splined on this 
 same vertical shaft, which worm takes in a segment of a worm wheel 
 keyed upon a second shaft called the shot-hoist shaft, parallel to 
 the first through shaft. The bearings of this last shaft are in 
 brackets extending to the rear from the chassis side frames, and 
 cast in one piece with them. 
 
192 THE SERVICE OF COAST ARTILLERY 
 
 A lever mounted upon a squared section of this second shaft, 
 terminating in a fork with slotted ends, is' designed to receive the 
 trunnions of the projectile tray, support being given lower down on 
 the tray by a third arm projecting below the fork. Power is applied 
 to the crank levers on each end of the first shaft. By the rotation 
 of these cranks the tray, with its projectile, is lifted to the position 
 for ramming. The handles of these levers are covered with loose 
 brass sleeves. 
 
 The shot is brought to the gun in a tray, resting upon a three- 
 wheeled truck or shot barrel, consisting of a body, two cast-iron 
 14-inch truck wheels, mounted on a wrought-iron axle, and a cast- 
 iron 5-inch caster wheel, mounted in a wrought-iron fork. 
 
 The loading platform consists of a flooring 45 inches above the 
 terreplin, supported by boiler -iron brackets strengthened by T irons 
 riveted along the edges. It is inclosed by a wrought-iron tubing 
 rail. A set of four straps on each side gives access to the platform. 
 These are supported by side pieces and struts bolted to the plat- 
 form. A slot through the middle of the flooring permits the shot 
 to be lifted by the hoist to its position opposite the breech of the 
 gun, into which it is pushed and rammed by cannoneers standing on 
 the platform. A separate loading tray is placed in the gun to protect 
 the threads. 
 
 The carriage permits of the gun being traversed through 320 
 degrees, and elevated from minus 7 degrees to plus 18 degrees. 
 
 The cylinders should be filled with neutral oil before firing. 
 
 Pedestal Mount (see Plate XVII). The pedestal mount or carriage 
 is one of the barbette class well illustrated by the 15-pdr. barbette 
 carriage, model of 1903, which consists of a pedestal, pivot yoke, 
 cradle, traversing and loading mechanism, shield, shield supports, 
 and shoulder rests, with the necessary peep and telescopic sights, 
 firing mechanism, and electrical attachments. 
 
 Pedestal. The pedestal is made of cast steel, and has the general 
 form of the frustum of a cone united at its top to a cylindrical 
 section and at its bottom to a base, in the flange of which are 
 drilled holes for the fourteen foundation bolts and three leveling 
 screws. Two hand-holes covered with water-tight plates are pro- 
 vided for cleaning the interior. The joints of the covers are made 
 water-tight by means of Garlock's gasket packing. There are twelve 
 holes equally spaced for the foundation bolts, and two extra holes 
 drilled so as to enable the use of this pedestal in emplacements of 
 the 15-pounder barbette carriage, model of 1902. 
 
ARMAMENT 193 
 
 The exterior of the cylindrical part is finished and forms a seat 
 for the traversing worm wheel. Beneath this seat on the front of 
 the pedestal is a boss to which the friction band is secured by a 
 stud bolt. An annular boss is cast in the bottom of the pedestal. 
 This boss is bushed with bronze and forms a bearing for the lower 
 end of the pivot yoke. The upper interior cylindrical part of the 
 pedestal is also bushed with a bronze bearing. These two bearings 
 serve to keep the pivot yoke in a vertical position. The weight of 
 the revolving parts is supported by a ball thrust bearing inserted 
 between the end of the pivot yoke and the bottom of the cylindrical 
 recess formed by the annular boss at the bottom of the base of the 
 pedestal. 
 
 Pivot Yoke. The pivot yoke is of cast steel, and has a cored 
 conical stem from which rise two vertical cheeks. In the cheeks 
 are bronze-lined trunnion beds for the trunnions of the cradle. These 
 beds are fitted with interchangeable dovetailed cap squares bolted 
 to the cheeks. Finished recesses are formed in the outer faces of 
 the cheeks of the pivot yoke into which the shield supports are fitted 
 and bolted. There is an annular projection under the cheeks of 
 the pivot yoke to which is bolted a cover to protect the traversing 
 worm wheel. The cored holes in the stem of the pivot yoke are 
 closed with plugs to prevent the entry of water into the bearings 
 of the pedestal. The rear faces of the cheeks are finished so as to 
 receive a bracket containing the traversing and elevating mechan- 
 isms. This bracket is bolted to the rear faces of the cheeks by six 
 bolts. There are four oil holes provided in the pivot yoke for oiling 
 its upper bearings in the pedestal, and an oil pipe leading from a 
 fifth hole to the thrust bearing through the cored hole in the pivot 
 yoke enables that bearing to be flooded with oil. 
 
 Cradle. The cradle, of cast steel, has a cylindrical body bored 
 out to receive the counter-recoil spring, on the upper surface of 
 which are guides, lined with bronze, for the recoil clips of the 
 gun. 
 
 Two side pieces extending upward from the cradle body have 
 trunnions which fit in the bronze-lined trunnion beds in the pivot 
 yoke. The outer ends of the trunnions are finished to receive the 
 front-sight brackets. 
 
 Pads near the rear end of the cradle, on either side, are finished 
 for the rear-sight brackets and shoulder guards. The right side of 
 the cradle at the rear end has a boss finished with a vertical hole to 
 receive the semi-automatic breech mechanism when used. 
 
194 THE SERVICE OF COAST ARTILLERY 
 
 At the bottom part of the rear end of the spring cylinder is a 
 slotted lug to which is attached the inner elevating screw. 
 
 The counter-recoil spring is a single helical spring, with round 
 cross-section, and at assembled height it is about 12 inches shorter 
 than at free height. It is assembled from the front, and the rear 
 end rests against a flange on the interior of the spring cylinder and 
 the forward end rests against a flange on the front recoil-cylinder 
 head. The counter-recoil spring is coiled between the interior of 
 the spring cylinder and the exterior of the recoil cylinder. 
 
 The recoil cylinder is of forged steel, finished all over, and 
 threaded at the ends to receive the front end rear recoil-cylinder 
 heads. There are flexible vulcanized fiber packings making oil- 
 tight the front and rear ends of the recoil cylinder. The piston rod 
 passes through a stuffing box in the front recoil-cylinder head. 
 
 The stuffing box consists of a finished bronze follower on the 
 piston rod, screwed into a box in the front recoil-cylinder head, and 
 compressing five rings of Oarlock's hydraulic waterproof packing 
 between a flange in the box and a forged-steel gland, divided into 
 halves and retained in position on the follower by a spring-steel 
 ring. 
 
 The front cylinder head is provided with filling and drain holes, 
 each to be closed by a bronze washer-head filling and drain plug. 
 
 The spring cylinder head is of cast steel and receives the piston- 
 rod pull. It also receives the thrust of the counter-recoil spring at 
 assembled height, when the lug of the gun is disconnected from the 
 rear cylinder-head stud, in mounting and dismounting the recoil 
 system. The instruction plate is mounted on the spring-cylinder 
 head. 
 
 The piston rod and piston are in one piece, made of forged steel, 
 finished to receive a bronze piston liner and bored out to receive the 
 counter-recoil buffer. This buffer is made of Tobin bronze, finished 
 so as to be screwed into the rear recoil-cylinder head from the inside. 
 
 There are three throttling grooves in the interior of the recoil 
 cylinder. 
 
 Recoil and Counter-Recoil Systems. The action of the carriage 
 is as follows: When fired the gun recoils to the rear about 9 inches 
 in the cradle, carrying with it the recoil cylinder and thereby com- 
 pressing the counter-recoil spring. A small portion of the energy 
 of recoil is taken up in compressing the counter-recoil spring, but 
 the greater portion of the energy is absorbed by the resistance offered 
 by the liquid being forced through the orifices of the throttling 
 
ARMAMENT 195 
 
 grooves. The width of the grooves is uniform, but their depths are 
 proportioned so that the areas of the orifices vary with the position 
 of the piston during recoil, and will be such as to give, with the aid 
 of the counter-recoil springs, a constant resistance throughout the 
 length of recoil. The pressure in the cylinder is therefore a uniformly- 
 decreasing one. The counter-recoil buffer is tapered so that the 
 escape of oil during counter recoil through the varying diametral 
 clearances between the buffer and the walls of its hole will offer such 
 resistance as will control the motion of the gun during its return, 
 and finally bring it to rest when the recoil piston reaches the rear 
 end of the cylinder. 
 
 Elevating Mechanism. The elevating mechanism consists of a 
 handwheel actuating through suitable connecting shafts and bevel 
 gears, a double screw with right-hand outer threads and left-hand 
 inner threads. The outer elevating screw is of forged steel and turns 
 in a bronze elevating nut and cap. It receives its rotary motion 
 from the elevating bevel gear by means of two keys sliding in longi- 
 tudinal grooves cut in the outside of the screw. The inner screw 
 has a left-hand thread and has its upper end attached to the slotted' 
 lug on the bottom of the rear end of the spring cylinder. The 
 elevating-screw nut is pivoted on trunnions so as to allow the 
 necessary rotation, corresponding to different angles of elevation. 
 The elevating-screw nut is provided with an elevating-screw nut 
 cap bolted to it by four bolts. The elevating-screw cap has a hole 
 and plug, and the elevating-screw nut has a hole fitted with a plug 
 for draining. 
 
 The elevating bevel gear is of bronze, and the pinion is of forged 
 steel. The pinion is keyed onto the elevating intermediate shaft 
 which receives its motion from the handwheel by the elevating 
 handwheel shaft and a set of elevating handwheel shaft gears inclosed 
 in gear covers. 
 
 The elevating handwheel shaft has a bearing near the hand- 
 wheel in a bracket secured to the shoulder rest. The elevating gear 
 bracket cap has a bearing for the lower end of the elevating hand- 
 wheel shaft and serves as a cap for the trunnions of the elevating- 
 screw nut. 
 
 Traversing Mechanism. The traversing mechanism consists of the 
 travers ng worm wheel, traversing worm shaft and worm, one pair 
 of bevel gears, one traversing shaft, and one traversing handwheel. 
 It is all designed, however, so that another handwheel can be placed 
 on the right-hand side if necessary. The traversing worm wheel is 
 
196 THE SERVICE OF COAST ARTILLERY 
 
 I 
 
 seated on the exterior cylindrical top of the pedestal, and is retained 
 
 in position by the friction band, a shoulder on the pivot yoke, and 
 a shoulder on the pedestal. 
 
 The friction band is made in halves and united by a stud bolt 
 screwed into a boss on the front of the pedestal. By means of a 
 bolt a certain amount of friction, between the friction band and 
 the traversing worm wheel, secures the traversing worm wheel to 
 the pedestal rigidly enough to allow the thrust of the traversing 
 worm shaft to traverse the gun, but it does not secure it so rigidly 
 that the teeth of the traversing worm wheel might be inj ured by 
 the sudden shock of discharge. 
 
 There is a spring between the bolthead and the lug on the friction 
 band so that when the bolt is tightened enough to give sufficient 
 friction to enable the gun to be traversed without slipping, it will yet 
 permit slipping in case undue strain is brought on the teeth of the 
 worm wheel. The spring serves to regulate and keep uniform, during 
 rotation, the pressure on the worm wheel. The traversing worm 
 shaft is assembled with its worm in the traversing-gear case. 
 
 A pair of bevel gears, in a cast-iron bevel-gear cover, serve to 
 transmit the motion of the traversing handwheel' and traversing 
 handwheel shaft, to the left end of the traversing worm shaft. The 
 traversing handwheel shaft is supported in its proper position by 
 two brackets containing suitable bearings. One bracket is bolted 
 to the elevating-gear bracket and the other is bolted to the shoulder 
 rest. 
 
 Shoulder Guard. A bronze shoulder guard, attached to the 
 left side of the cradle by four bolts, carries the firing mechanism, 
 and protects the gunner on the left side from injury during recoil 
 and counter recoil of the gun. 
 
 Shield and Supports. The shield consists of a 2-inch nickel-steel 
 plate bent to shape, shielding the gun and detachment from the 
 front only. It is pierced with two ports, one for sighting and one 
 for the gun. The shield is supported by two shield supports bolted 
 to the pivot yoke. 
 
 The center of gravity of the shield, supports, pivot yoke, gun, 
 and charge is so arranged that it falls through the center of the ball- 
 thrust bearing in the pedestal, thus limiting as much as possible the 
 force necessary to elevate and traverse the gun. 
 
 Shoulder Rest. The carriage is provided with a shoulder rest 
 bolted to the pivot voke on the left side. It is of cast steel, and the 
 shoulder end has mounted upon it a 2.4-inch rubber tube. The 
 
ARMAMENT 197 
 
 shoulder rest is finished, near its center, to receive a bracket con- 
 taining the traversing and elevating shaft bearings. 
 
 The right side of the pivot yoke is finished so that a shoulder rest 
 for the right-hand side may be attached, if it is desired to use two 
 sights and two gunners. 
 
 Special Mounts. In addition to the types of carriages described 
 above there are some few special types found in the service. The 
 designs of these carriages, strictly speaking, place them under some 
 one of the classes previously given, but the details of their construc- 
 tion are such as to make it desirable to classify them separately. 
 
 The carriages for the 4.72- and 6-inch Q.-F. Armstrong Guns 
 (Plates XI arid XV) are examples of such carriages and a descrip- 
 tion of the former follows: 
 
 The mounting consists of: 
 
 1. A cradle including hydraulic recoil cylinder, trunnions, bar 
 and drum sights, and other parts and fittings complete. 
 
 2. A carriage of steel in the shape of a Y, fitted with trunnion 
 bearings for the cradle, and having a long pin, forming the pivot 
 of the carriage. 
 
 3. A circular shield with roof supported from the carriage by 
 means of elastic stays or supports. 
 
 4. An elevating bracket, fixed to the carriage carrying the elevat- 
 ing gear, shoulder piece, and firing pistol. 
 
 5. A pedestal or socket for receiving the pivot pin of the car- 
 riage. 
 
 Cradle. The cradle is a single casting of gun bronze, and com- 
 prises the frame through which the gun recoils, the hydraulic recoil 
 cylinder, trunnions, spring box, and reserve oil tank. The trunnions 
 of the cradle are supported by bearings machined in the Y-piece, 
 the cradle moving with the gun when it is elevated or depressed. 
 The hydraulic recoil cylinder is directly underneath the gun; it is 
 provided with a piston and rod, forged in one piece. The piston 
 rod passes through a gland at the rear of the cylinder, and is 
 fitted to a projecting arm on the breech of the gun. The cylinder 
 is also fitted with a valve key, controlling ram, drain hole, and 
 air hole. 
 
 The action of the carriage on firing is as follows: The gun slides 
 back within the cradle, the force of the recoil being transmitted by 
 the arm on the gun to the piston, and the resistance offered by the 
 oil (with which the cylinder is filled) to the motion of the piston 
 gradually overcomes the force of the recoil. The valve key is of such 
 
198 THE SERVICE OF COAST ARTILLERY 
 
 a form as to produce, by varying the size of the opening in the piston 
 during recoil, an approximately uniform pressure in the recoil cylinder. 
 The controlling ram is fitted to regulate the velocity of the gun when 
 returning to the firing position. The spring box is under the front 
 part of the cradle. It contains two spiral springs for the purpose 
 of returning the gun and retaining it in the firing position after 
 recoil. The reserve oil tank is cast on the right side of the cradle 
 and is always in free communication with the recoil cylinder. Any 
 leakage which may occur from the cylinder is filled up from the 
 tank. A suitable filling hole is provided at the top. The cradle is 
 provided with bosses for the sights, and with eyes for dismounting 
 purposes. 
 
 Carriage. The carriage of Y-piece carries the cradle and forms the 
 pivot upon which the gun and mounting revolve. The elastic stays 
 for shield and elevating and training-gear bracket are attached to the 
 sides of the carriage, an undercut groove being arranged for the latter 
 in the casting. At the base of the pivot pin is fitted a hardened-steel 
 ring, forming a path for the hard steel balls, upon which the Y-piece 
 revolves. 
 
 Pedestal. The pedestal consists of a hollow steel- casting in the 
 form of a cone; the bottom of the casting forms a socket for the forged- 
 steel pivot on the carriage, and is provided with a bronze bush at the 
 lower end to receive the foot of the pivot. A ball bearing consisting of 
 spherical balls of steel is fitted to take the weight of the pivot and to 
 facilitate the training of the mounting. 
 
 Elevating Gear. The elevating gear is carried by a steel bracket, 
 fixed to the left side of the Y-piece. It is actuated by a handwheel, 
 which is placed in a convenient position to be worked by the man 
 laying the gun. The handwheel drives by means of a pair of miter 
 wheels a worm which works the worm wheel. On the inner end of the 
 shaft carrying this worm wheel a pinion is fixed, which gears with the 
 elevating arc attached to the carriage. 
 
 The elevating gear is provided with a frictional driving arrangement, 
 as follows : The boss of the worm wheel is hollow, and contains a series 
 of friction rings, part of which are of steel, and are keyed to and turn 
 with the shaft, while the remaining rings are of manganese bronze, 
 and are keyed to and turn with the worm wheel. These friction rings 
 are placed alternately, and are pressed together by means of a spring- 
 steel washer and a nut on the extreme end of the shaft. By adjusting 
 this nut the rings are pressed together sufficiently to produce the 
 requisite friction to prevent the gun running down at extreme recoil, 
 
ARMAMENT 199 
 
 but at the same time allows the gun to move slightly when fired with- 
 out giving motion to the whole of the gear. The nut is to be tightened 
 up if the gun runs down when fired. An adjustable pointer is fitted 
 so that the amount of elevation may be read off the back of the elevating 
 arc, which is graduated for that purpose. 
 
 Training Gear. The training gear is fitted on the left side of the 
 carriage, in a convenient position for being worked by the man at the 
 shoulder piece. It consists of a gun-metal worm wheel, with a hollow 
 boss, by which it is supported in the top of the pedestal, and which 
 also forms a top bearing for the pivot of the mounting. A worm, carried 
 in a gun-metal bracket fixed to the carriage, engages with the worm 
 wheel, the worm wheel is fixed to a steel shaft and is worked by means 
 of toothed gear at the rear, actuated by the handwheel. 
 
 A gun-metal friction block, which presses against the boss of the 
 worm wheel, is fitted with a clamping screw in the pedestal. Friction 
 between the block and the worm wheel is caused by the handle, 
 and is sufficient to enable the mounting to be rotated. By slackening 
 the clamping screw the mounting is free to be trained by the shoulder. 
 
 Shield. The mounting is fitted for its own protection, and that of 
 the men working the gun, with an outer circular shield 4J inches thick, 
 and inner flat vertical shield 3 inches thick of steel plate. The outer 
 shield has side wings 2 inches thick and a flat roof 1 inch thick. 
 
 The shield is provided with apertures for laying the gun. 
 
 Instructions for Filling the Recoil Cylinder. Depress the gun and 
 take out the filling and air plugs. Fill through the filling hole in the 
 reserve oil tank until the oil outflows through the air hole; replace 
 the air plug, and fill in until the oil overflows at the filling hole; then 
 replace the filling plug. 
 
 DISAPPEARING CARRIAGE 
 
 In this type of carriage the gun is raised above the parapet for 
 firing and recoils under cover for loading. Plates I, II, and III show 
 in detail the Disappearing Carriage, Limited Fire, Model of 1901; the 
 details of which are as follows: 
 
 The Carriage is designed to mount guns of either the model of 
 1895 or the model of 1900. It embodies many additions and improve- 
 ments on the previous models, the principal ones of which are general 
 stiffening of the structure, the turntable being 3 inches deeper; a sighting 
 platform along each side of the carriage, accessible by ladders in front 
 and in rear; sight-laying apparatus, with new 3-inch objective telescopic 
 
200 THE SERVICE OF COAST ARTILLERY 
 
 sight arranged to be used by a man on the sighting platform, who has 
 under his own immediate control all operations of laying and firing, if 
 desired; electric motor as well as hand appliances for the operations of 
 traversing, elevating, depressing, and retracting the gun; the control of 
 the electric-motor equiqment from either the sighting or the working 
 platform; connections for electric firing either by the man at the sight 
 or by the battery commander (in salvo) ; the addition of a safety appli- 
 ance for electric firing and of a safety lanyard attachment, which prevents 
 firing before the gun is in battery; a traversing brake near the auxili- 
 ary traversing controller; improved lubricating appliances, and new 
 counter-recoil buffers, which permit of sufficient counterweight being 
 used to bring the gun into battery in from five and one-half to seven 
 seconds. 
 
 Stops can be so arranged as to permit traversing either 60, 70, 90, 
 or 110 degrees either side of the "front" of the battery, and the piece 
 can be elevated from 5 degrees depression to 10 degrees elevation, 
 stops being arranged to limit the depression to either horizontal or 
 2.5 degrees depression when the height of the parapet requires it. 
 
 When in the execution of mechanical maneuvers it may become 
 necessary to traverse the piece breech to the front, which can be done 
 with gun in battery; the fixed stops and the cams of the traversing 
 controller stops must be removed and care exercised that the electric 
 cable in the pit is not injured by traversing the counterweight against it. 
 The elevating system is so constructed that the gun is at an angle of 
 about 4 degrees elevation when in the loading position if recoiling to the 
 thirty-third notch with any angle of elevation in battery. 
 
 Action of Carriage. Upon firing the piece the gun-lever axle is 
 moved to the rear by the recoiling energy of the gun, carrying the top 
 carriage with it. The lower ends of the levers move vertically upward, 
 being constrained by the crosshead traveling on the vertical crosshead 
 guides. The trunnions of the gun move downward and to the rear. 
 The energy of recoil is absorbed partly by raising the counterweight and 
 partly by the movement of the masses up the inclined chassis rails, but 
 principally by the resistance of the recoil cylinders; and when the gun 
 comes to rest it has the proper loading angle. After loading, the pawls 
 are tripped, and the excess of the moment of the counterweight over the 
 moment of the gun, enables it to raise the gun to the firing position. 
 If this excess be small, the velocity of counter recoil will be slow; but 
 if more counterweight be added, the velocity will increase and the time 
 required for going into battery decrease. 
 
 Principal Parts. The carriage consists of the following principal 
 
ARMAMENT 201 
 
 parts, viz.: Base ring, azimuth circle and pointer, traversing roller 
 system, racer, clips and dust guards, chassis and transoms, top carriage 
 and recoil rollers, recoil and counter-recoil system, gun levers, crosshead, 
 tripping gear, counterweight, elevating arm, band and slide, elevation 
 and range scales and pointers; elevating, traversing, and retracting 
 systems; working platform, sighting standards and platforms, sight 
 standard and laying mechanism, safety lanyard attachment; electric 
 safety firing attachments; electric motor equipment for traversing, 
 elevating and depressing, and retracting the gun, conduits, wiring, 
 and illumination; accessories, including ammunition trucks, shot tongs, 
 and implements. 
 
 Base Ring. The base ring, 19 feet in diameter, is made of cast iron, 
 in halves, bolted and keyed together, and is held in position on the 
 foundation by twelve 2.75-inch bolts. Twelve screws for leveling the 
 base ring are set against steel plates through which the foundation bolts 
 pass. 
 
 The base ring, in addition to having the lower roller path on its upper 
 surface, has an annular flange near its inner edge forming the pintle for 
 the carriage. This flange has near its top edge a lip inward under which 
 the clips engage, and on its top edge the azimuth circle. The inner edge 
 of the lip is rabbeted to receive the felt and steel inner dust-guard strips. 
 The outer annular flange on the ring projects downward into the plat- 
 form and upward outside of the traversing rollers. The cavities on each 
 side of the roller path are drained into the pit through passages closed 
 by screw plugs in the inner edge of the ring. 
 
 Tapped holes can be found inside of the pintle flange for attaching 
 the traversing stops in any required position. 
 
 The base ring is marked "front" and "rear" in raised letters cast 
 on the top surface between bolt holes. 
 
 Azimuth Circle and Pointer. A brass azimuth circle, attached 
 by countersunk screws to the top of the pintle of the base ring, is 
 graduated in degrees, the numbers of which are to be added after the 
 carriage is erected in its emplacement. The top of the racer is cut 
 away on the left side to expose the azimuth circle and the micrometer 
 pointer and the subscale, fastened to the racer. The subscale has 
 slotted holes to give it a lateral motion for adjustment, after which it 
 is fixed in position by two dowels. It is graduated and stamped in 
 decimals of a degree, the least reading being 0.1 of a degree. The 
 micrometer screw, actuating the pointer, is graduated to a least read- 
 ing of 0.01 of a degree. The subscale and pointer is protected by a 
 hinged bronze cover. 
 
202 THE SERVICE OF COAST ARTILLERY 
 
 Traversing Roller System. The racer rests and is traversed upon 
 a circle of twenty-four live, conical, traversing rollers, whose axes are 
 maintained in the radial position by bearings bolted to distance rings. 
 They are of forged steel, solid, with a journal beyond each end and 
 with flanges on their inner, small ends. 
 
 The distance rings are cast together, of steel, and made up in six 
 sections, bolted together, and have bolted on their upper surfaces the 
 bronze bearings for the traversing rollers. The bearings are formed 
 with a loop on top by means of which any roller with its bearings can 
 be lifted out of the ring through the holes at the racer joints. 
 
 The system is kept concentric with the pintle by the flanges on the 
 rollers in centrifugal contact with the inner edge of the roller path on 
 the base ring. The inner edge of the path on the racer is of a larger 
 diameter so as not to come in contact with the flanges. 
 
 Racer. The racer is made of steel, 17 feet and 10 inches in diameter, 
 cast in halves, bolted and keyed together with the joints on the side 
 of the carriage. On each side of the joints are two openings, with 
 removable cover plates, through which four recoil rollers may be lifted 
 out at a time for cleaning. 
 
 It is of box section, and, in addition to having the upper roller path 
 on its under surface, has an annular flange lined with bronze near its 
 inner edge and fitting over the pintle, with 0.04-inch diametral clearance. 
 
 Upon its top surface the chassis and transom are bolted, doweled, 
 and keyed, and on its outer wall the working platform and traversing- 
 controller stop brackets are bolted to pads. 
 
 Two oil holes on each side near the chassis with connecting grooves 
 provide means for oiling the pintle. 
 
 The traversing-roller journals are oiled by removing four oil plugs 
 on each side near the racer. In this case the oil drops into annular 
 grooves on top of the distance rings and must be supplied between 
 each roller, thus requiring traversing 90 degrees. 
 
 Two additional oil holes, placed 30 degrees on each side of each joint 
 and closed with 0.75 bronze countersunk screws, are for occasional use. 
 
 Clips and Dust Guards. Two clips in front and one in rear are 
 bolted down on top of the inner edge of the racer and engage under 
 the lip inside of the pintle flange. The rear clip extends still lower in 
 the form of a lug, which strikes the stops, limiting the traversing 
 movement. 
 
 A dust guard, of angle iron, in six sections, with handles, is bolted 
 to the top edge of the outer flange on base ring. 
 
 Felt, and steel pinching strips, inclosing the roller system dust tight, 
 
ARMAMENT 203 
 
 are bolted to the top edge of the dust guard outside and the pintle 
 flange inside of the roller paths, the felt being compressed against the 
 opposite racer surfaces. The dust-guard sections, with their felt strips, 
 are easily removed. 
 
 Chassis and Transoms. The chassis of cast iron is bolted, doweled, 
 and keyed to the racer and are united at their front and rear ends by 
 cast-steel transoms, also bolted to the racer. The rear transom carries 
 the elevating slide and gearing. The upper surfaces of the chassis 
 form the recoil-roller path and slope 1 degree and 20 minutes to the 
 front to facilitate the return of the piece to the firing position, thus 
 reducing the necessary preponderance of the counterweight. 
 
 The chassis also provide the necessary bearings or supports for all 
 the mechanism and, with the racer, supports for all the minor attach- 
 ments. 
 
 The crosshead guides are machined flush on the inside and near the 
 front end. They extend from below the racer to above the top of the 
 piston-rod lugs. 
 
 Stops are machined in rear of the lugs against which the top carriage 
 and recoil rollers come to a rest when entirely in battery. 
 
 Top Carriage and Recoil Rollers. The top carriage, which is 
 similar to that of an ordinary barbette carriage, is made of steel, cast 
 in one piece. It consists of two side frames containing the beds for the 
 gun-lever axles, and two recoil cylinders, all united by transoms. It rests 
 upon two sets of 13 live recoil rollers which are bushed with bronze 
 and run on steel axles set into movable steel cages. The rollers are of 
 forged steel and flanged on both ends to guide the top carriage upon the 
 chassis. They move to the rear with the top carriage at half its speed 
 and travel half as far. 
 
 Lugs project from the lower front part of the top carriage, which 
 serve as fulcra for pinch bars held horizontally and engaging with teeth 
 cast on the chassis rail, by which arrangement the top carriage may be 
 moved forward to the firing position against the stop if for any cause it 
 should fail to come fully into battery. When time permits, the top 
 carriage should always be brought fully into battery (against the stops) ; 
 but, if desired, the gun may be fired when the top carriage is as much as 
 3 inches out of battery with perfect safety and with no bad results other 
 than inaccuracy in the elevation of the gun, unless this elevation be 
 given by telescopic sight on gun trunnion, or by quadrant on the 
 gun. 
 
 Clips projecting from the lower rear part of the top carriage engage 
 under flanges on the top of the chassis to prevent the carriage from 
 
204 
 
 THE SERVICE OF COAST ARTILLERY 
 
 tipping forward upon striking the stops in returning to the firing 
 position. 
 
 The axle beds in the side frames are provided with caps clipped on 
 and secured from lifting off by four studs each, having nuts and check 
 nuts. The caps and beds are lined with bronze half bushings. 
 
 Recoil and Counter-recoil System. Figure 18 shows the general 
 arrangement of the hydraulic brake and its connections in its 
 essential principles and in relative positions of parts for disappearing 
 carriages "in battery." 
 
 The recoil cylinders are lined with cast iron and are 13 inches in 
 interior diameter, with piston rods 4.75 inches in diameter, having 
 pistons and counter-recoil buffer plungers forged solid with them. The 
 
 gecliort. fr-fr shstxrisiff maximum 
 ^ tsfan SeecuZ of t/te 
 
 Coast -fer Jfecei 
 
 o/ienintrs tstnision 
 juuxd closed a* &te 
 esu* of Met recoeC. 
 
 Stecoil J 
 
 I , 
 
 Jtecotz 
 
 I 
 
 GENERAL METHOD OF CONTROLLING THE ENERGY 
 OF RECOIL IN GUN CARRIAGES. 
 
 FIG. 18. 
 
 rods are secured by nuts and check nuts to upright lugs on the chassis, 
 and extending through the rear cylinder heads, their rear ends are 
 supported by brackets bolted to the chassis. At the ends of the 
 cylinders there are the usual stuffing boxes with glands and followers. 
 The counter-recoil buffers are formed by annular projections cast 
 on the rear cylinder heads, which fit into the cylinder and are supported 
 by its walls, and which are bushed with bronze inside. In the recesses 
 thus formed fit tapering plungers on the piston rods. When the gun 
 returns to the firing position the liquid caught in the recesses in the 
 cylinder heads can escape only through the small clearance between 
 the plunger and the walls of the recess, thus acting as a hydraulic 
 buffer or dashpot to check the velocity at the end of the return " into 
 
ARMAMENT 205 
 
 battery." At the front end of the chassis rails counter-recoil stops 
 are provided to prevent the bottoming of the buffer plungers in the 
 annular recesses. Against these stops the top carriage abuts when in 
 the firing position. 
 
 Each cylinder has one filling hole near its front lower end. 
 
 That portion of the cylinder above the level of the filling holes 
 (about 750 cubic inches in each cylinder) is intended to be empty, this 
 being for the purpose of allowing the oil sufficient space in which to 
 expand when heated by weather or the friction developed in firing, 
 and to provide a space into which the plunger of the counter-recoil 
 buffer may be withdrawn. This withdrawal is accomplished so rapidly 
 in recoil that the oil cannot flow through the small clearances and fill 
 the seat of the buffer without the development of a very high .pressure 
 in the cylinder, which would be undesirable. 
 
 To secure equal resistance and equal fluid pressure in the two cylin- 
 ders an equalizing pipe connects their front or pressure ends. In this 
 pipe is an emptying coupling by which the whole recoil system can be 
 emptied of oil. From this coupling a connecting pipe extends back 
 tc the throttling valve, and from this valve pipes connect with the rear 
 ends of the cylinders. 
 
 Bronze plugs are provided, to be screwed into the cylinders in place 
 of the equalizing and throttling pipes, thus continuing the piece in 
 action should the pipes be destroyed. 
 
 During the recoil the pistons remain stationary and the top carriage 
 with its cylinders is drawn over them. Each piston is slotted through 
 its opposite sides and two throttling bars lie in the slots and are bolted 
 the whole length of each cylinder. Their sectional area is such that 
 the orifices for the flow of the liquid vary with the position of the piston 
 during recoil so as to attain the desired resistance in the cylinders. 
 
 In any hydraulic brake the resistance is greater as the velocity of 
 the piston in the cylinder is greater and as the openings for the passage 
 of the liquid are less. The velocity of retarded recoil of the top car- 
 riage being variable and a constant resistance being desired, the orifices 
 are usually varied in such manner that the relation between the velocity 
 and the area of the orifices is at all points such as to give a nearly con- 
 stant resistance. 
 
 Uniform resistance to the motion of the top carriage is obtained, its 
 motion retarded and finally stopped and the energy of recoil taken up, 
 principally by the resistance which the oil in the cylinders offers to 
 being forced from one side of the piston to the other, through the fol- 
 lowing openings: 
 
206 THE SERVICE OF COAST ARTILLERY 
 
 1. The clearance between the walls of the cylinder and the piston, 
 necessary for working movement. This opening is of constant area. 
 
 2. The orifices between the throttling bars and their slots in the 
 piston. These openings vary with the profile of the throttling bars, 
 since the slots, which are partly closed by these bars, are of constant 
 area. 
 
 3. The opening of the throttling valve which controls the flow 
 through the pipes connecting the front and rear ends of the cylinders. 
 This opening is of constant area during recoil, but can be completely 
 closed or changed to suit different conditions of loading and to correct 
 for any other conditions that would cause a variation in the length of 
 recoil. 
 
 The two throttling bars in each cylinder are constructed of constant 
 width having only a sufficient lateral clearance in the slots for working 
 movement, and of varying depth, the profile being so designed that the 
 area of the orifices (the portions of the slots not filled by the bars) for the 
 escape of the oil past the piston increases from beginning of motion up 
 to the point where the velocity of retarded recoil of the top carriage 
 is greatest; beyond this point the velocity of retarded recoil of the top 
 carriage is continually decreasing and the area of the orifice decreases 
 also until it becomes zero at the end of recoil. The orifices have at 
 each point of recoil such a relation to the velocity of retarded recoil of 
 the top carriage at that point as to give merely a constant resistance to 
 the motion of the top carriage. This results in a merely constant fluid 
 pressure in the cylinders. 
 
 The areas of the orifices have to be calculated for a particular set 
 of conditions of loading, and any variation in these conditions will 
 change the length of recoil of the top carriage, and consequently the 
 height and inclination of the breech of the gun in the recoil position. 
 As the standard conditions of loading do not always exist, it has been 
 found desirable to provide means for varying the resistance of the 
 hydraulic recoil brake in order that the prescribed length of recoil 
 (bringing the gun into the prescribed loading position) may be obtained 
 under any conditions, standard or not standard as, for example, when 
 charges other than full service are fired. 
 
 For this purpose the equalizing pipes between the front ends of tho 
 cylinders are connected with the throttling pipes between their rear 
 ends through the emptying coupling and a throttling valve, providing 
 oil passages from the front or pressure to the rear side of the pistons, 
 which can be completely closed or changed in area. (This throttling 
 valve can be adjusted to give openings varying by 0.025 square inch from 
 
ARMAMENT 207 
 
 zero to 0.55 square inch.} The graduations of the valve are stamped on the 
 top of the body, there being 11 divisions, numbered 0, 0.05, 0.10, etc. 
 (One complete turn of the valve effects the change of 0.05 square inch in 
 the opening. One-half turn effects a change 0.025 square inch.) One 
 complete turn of the valve yoke generally changes the length of recoil by 
 the equivalent of 3 or 4 notches on the crosshead rack. This is liable 
 to vary by a notch or more for different carriages or for the same car- 
 riage under different conditions. 
 
 The setting of the valve best suited to different conditions o f loading, 
 full or practice charges, etc., can be determined only by experience in actual 
 firings with each particular carriage. For carriages on which new buffer 
 valves have been attached see how to set valves as described under 
 " BUFFER VALVE." Different carriages may require different settings, 
 and the same carriage may even at different times require different set- 
 tings for the same conditions of loading if it is in a materially different 
 condition as to cleanness and lubrication of the working parts, etc. It 
 is necessary, therefore, that careful records be kept, not only of the 
 setting of the valve, the conditions of loading and recoil, but also of 
 the elevation of the piece and any abnormal condition of the carriage 
 which might affect the freedom of its operation. These records should 
 be studied in the light of all these circumstances to obtain perfect work- 
 ing. However, the ammunition trucks are so designed that the loading 
 position may vary somewhat without material inconvenience, and it is 
 generally possible after a few firings with a carriage to determine the 
 setting of the valve which will result in the gun coming into a proper 
 loading position for any conditions of loading. For full charges the 
 valve should, in the lack of experience with the particular carriage, be opened 
 to about 0.15 square inch, but not more. 
 
 A padlock is provided for locking the valve yoke in any position 
 to guard against accidental or unauthorized changes in the position of 
 the valve after it has been set. The valve should habitually be kept 
 locked, but this should not be understood as discouraging examination 
 and manipulation of the valve, which are, on the contrarj^ highly 
 desirable for the sake of familiarizing the personnel with its construc- 
 tion and operation. 
 
 For all charges, the cylinders should be filled to the level of the filling 
 holes, removing for this purpose both plugs so as to permit the air to 
 escape. 
 
 A neutral oil, of specific gravity about 0.85 (such as the "hydro- 
 line" at present issued), is used, and with this oil the working pres- 
 sure in the cylinders is about 1,200 pounds per square inch. A denser 
 
208 THE SERVICE OF COAST ARTILLERY 
 
 oil would cause a higher pressure in the cylinders and therefore shorten 
 the recoil slightly. 
 
 For the purpose of reducing the shock of accidental excessive recoil, 
 recoil buffers, made up of alternate layers of balata and steel plates, 
 are placed on brackets bolted to the rear of the chassis, where they 
 will be struck by the upper ends of the gun levers if the gun is re- 
 tracted or recoils beyond its proper position. 
 
 The notches between the ratchet teeth cut on the front faces of 
 the crosshead clips are numbered from the top, the numbers being 
 opposite the notches on brass strips screwed to the crosshead. When 
 the top pawl teeth, indicated by brass arrows screwed to the pawl 
 levers, engage in the thirty-third notch the gun is in its calculated 
 loading position, below which it 'should not be retracted. By a proper 
 adjustment of the throttling valve the recoil of the gun should not 
 vary much from this position. The ammunition truck will, however, 
 permit the gun to be loaded anywhere between its position when the 
 pawls engage in the twentieth notch and the lowest possible position- 
 gun levers on the balata counter-recoil buffers. 
 
 In case the gun recoils far enough for the pawls to engage, but not 
 sufficiently for loading, it may be brought down by the use of the 
 retracting gear. 
 
 From the foregoing description of the recoil system it should be 
 evident that should the carriage recoil too freely the proper correction 
 is in a diminution of the opening of the throttling valve, not in an 
 increase of the counterweight. On the other hand, the counterweight 
 alone should be changed to correct or modify the counter-recoil. 
 
 The amount of counterweight can be determined by trial. However 
 much of the counterweight furnished be used, it will not materially 
 affect the length of recoil. 
 
 On account of the efficient counter-recoil buffers, considerably more 
 counterweight (5,000 or 6,000 pounds or more) can be employed on 
 this carriage than is necessary to bring the gun to the firing position, 
 without injury to the buffer or cylinders or injurious shock to any part 
 of the carriage. This extra counterweight acts to accelerate the counter- 
 recoil and thus the time of going into battery completely is reduced to 
 5^ to 7 seconds from the instant of tripping. 
 
 Gun Levers. The two levers are made of cast steel connected 
 near their upper ends by a cast-steel yoke firmly bolted, and at a point 
 a little below their middle by the forged-steel gun-lever axle, which is 
 fastened to the lever by bolts passing through its heavy flanges. The 
 gun levers are supported by this axle, the projecting ends of which 
 
ARMAMENT 209 
 
 serve as trunnions supported by and rotating in the axle beds in the 
 top carriage. 
 
 The upper arms of the levers support the gun and from their lower 
 ends the counterweight is suspended by crosshead pins. 
 
 The trunnion beds are provided with cap squares clipped on and 
 secured from lifting off by two studs each, having nuts and check 
 nuts. The caps and beds are lined with bronze half bushings. 
 
 Crosshead. The crosshead, of cast steel, is connected by pins to 
 the gun levers and from it the counterweight is suspended by four 
 keyed rods. 
 
 Clips formed in one piece with the crosshead are lined with bronze 
 and engage over crosshead guides cast on the inside of the chassis 
 rails. These guides constrain the crosshead to move in a vertical 
 direction. 
 
 Ratchet teeth are cut on the front faces of the clips, to be caught 
 by pawls pivoted to the chassis rails, and in this way the counter- 
 weight is held up and the gun is prevented from returning to the firing- 
 position after recoiling. 
 
 Tripping Gear. After the gun is loaded it is permitted to rise to 
 the firing position by raising the tripping levers until they unlatch, 
 and immediately leaving them in that position. 
 
 The action is entirely automatic after the pawls are latched out of 
 engagement and the gun starts into battery. After the crosshead 
 teeth have passed entirely below the pawl teeth and the gun is nearly 
 in battery the pawl levers are released from the latches by the auto- 
 matic action of dogs on the crosshead, and are returned by the moment 
 of the weight of the tripping levers, to their proper positions ready to 
 engage the crosshead when it again rises. The pawls may be tripped 
 by the use of one or both levers. The levers should not be raised 
 while the gun is in battery, but should the pawls become latched out 
 of engagement at this time, the rising of the crosshead will again release 
 them for engagement. 
 
 Counterweight, Bottom Plates, and Suspension Rods. The 
 bottom plate, of cast steel, and the four rods which suspend it from 
 the crosshead form the cage which carries the lead counterweight. 
 The counterweight is piled in the cage in layers of different thicknesses, 
 each layer consisting of two or more pieces. There are 72 smaller 
 pieces on top provided with rings for easy handling. These weigh in 
 all about 5,967 pounds. By adding or removing some or all of these 
 smaller weights the counterweight can be readily increased or dimin- 
 ished. The total amount of lead counterweight furnished with the 
 
210 THE SERVICE OF COAST ARTILLERY 
 
 model of 1895 rifle is 98 pieces, weighing approximately 142,011 
 pounds, and forming a pile, including bottom of cage, 7 feet 10.25 
 inches high. That furnished with the model of 1900 rifle is 102 pieces, 
 weighing approximately 164,705 pounds, and forming a pile 9 feet 
 high. In some carriages there is an extra layer 3.6 inches thick, the 
 first nine layers being 6.35 inches instead of 6.75 inches thick. The 
 total height and weight are the same. 
 
 The amount of lead counterweight sent with each carriage is 
 designed to be 5,000 or 6,000 pounds in excess of that required to 
 raise the gun to the firing position under normal conditions. No mat- 
 ter what charge be used, the counterweight used should be such as will 
 raise the gun completely to the firing position in about five and one- 
 half to seven seconds, but should never be such as to cause the top 
 carriage to strike the counter-recoil stops with great shock. In its 
 lowest position the counterweight hangs in a well formed in the con- 
 crete platform concentric with the base ring 12 feet 6 inches in diame- 
 ter and not less than 93 inches in depth, measured from the under side 
 of the base ring. Access to the bottom of the pit is obtained by means 
 of a ladder and a manhole in the right inside platform. 
 
 Elevating Arm, Band, and Slide. The elevating arm of cast 
 steel carries a fixed double-ended pin at its lower end, rotating in 
 bearings in the elevating slide, and has two solid bronze-bushed bear- 
 ings at its upper end for the elevating-band trunnions. 
 
 The band is of cast steel, with inserted trunnions screwed to their 
 conical seats and with teats on their inner end, which enter shallow holes 
 in the gun at accurate distance from the trunnions on each side and in 
 the same horizontal plane with them. The band is tightly clamped 
 around the gun by two heavy bolts. Their inside diameters are for 
 the gun of the model of 1900, 48.5 inches, and that for model of 1895 
 44.5 inches. 
 
 The elevating slide is moved by the elevating-gearing system, in an 
 inclined guideway machined on the rear face of the rear transom, which 
 guideway allows it the movement necessary to change the elevation of 
 the gun from 5 degrees depression to 10 degrees elevation. There is 
 provided a removable stop, to be placed in holes in the right side of 
 the guideway and above the slide, limiting the depression to either 
 or 2.5 degrees, as may be required by the parapet over which the gun 
 is to be fired. 
 
 While theory requires, in order that the gun when recoiled to the 
 thirty-third notch shall always return to the same angle for loading, 
 with the breech at the same height, whatever may be the firing angle, 
 
ARMAMENT 211 
 
 that the elevating slide and its guideway shall be circular and struck 
 with radii, using the center of the trunnion on the elevating band, 
 when the gun is in the loading position, as a center, yet the expenses 
 of manufacture have made it desirable to make the slide and guideway 
 straight. These are so placed, however, as to cause only a slight varia- 
 tion in the height of the breech and in the loading angle. 
 
 Range and Elevation Scale and Pointer. To the elevating slide 
 is bolted a bronze elevating scale carrying straight German silver 
 scales, graduated in degrees and minutes of elevation and in yards of 
 range. 
 
 On account of the character of the motion of the parts the distances 
 between the successive degree marks on the elevation scale are not the 
 same, requiring the scale to be graduated by the use of a clinometer 
 supported by a rest placed in the muzzle of the gun, after the gun is 
 mounted upon the carriage, at the time of the shop test. 
 
 As the ranges corresponding to different angles of elevation above 
 the horizontal depend upon the height at which the gun is mounted 
 above the sea level, the range scale must be graduated after mounting, 
 the ranges corresponding to the different angles of elevation for the 
 height above sea level, and for the muzzle velocity normally used must 
 be calculated from the range tables and formulas and marked upon the 
 scale in the proper place. This should never be done except under the 
 supervision of the Ordnance Department. 
 
 In smooth contact with the scale and attached to the rear transom 
 by bolts in oblong bolt holes is a range and elevation pointer, having, 
 on account of the oblong bolt holes, a motion to permit any needed 
 adjustments, after which it is to be fixed in position by two dowels. 
 
 There has been attached for trial upon the first carriage of this 
 model a circular elevation and range scale which, if found satisfactory, 
 will be substituted for this straight scale upon succeeding carriages. 
 The advantages of such a scale are that it can be placed outside of the 
 chassis, where it is more convenient for reading, and that it can be made 
 of greater length with corresponding increase of the size of the smallest 
 sub-division. It consists of a circular wheel carrying the graduated 
 scale at its outer circumference and mounted upon a shaft which has 
 keyed to its inner end a pinion engaging in a rack bolted to the ele- 
 vating slide in the place of the straight scale. The up and down 
 motion of this rack rotates the pinion and shaft and the circular wheel 
 carrying the scale. The pointer is similar to that for the straight 
 scale except it is curved. 
 
 It is probable that the range scale will be improved by making 
 
212 THE SERVICE OF COAST ARTILLERY 
 
 each range graduation correct for all muzzle velocities from the minimum 
 now in use to the maximum probably obtainable in the future. These 
 graduation lines will of necessity be curved so that one end will be 
 correct for the minimum velocity, the opposite end for the maximum 
 velocity, and intermediate points for intermediate velocities. A sliding 
 index or pointer will be used to indicate the correct elevations for 
 corresponding velocities. 
 
 In use, and knowing approximately the velocity to be given the 
 projectile, the pointer is adjusted across the scale so as to intersect 
 that point on the line which indicates the elevation required for the 
 expected velocity. Should the shot fall 100 yards short, the pointer 
 is readjusted to intersect that point which will indicate the required 
 increase in elevation. 
 
 It follows that, with the pointer set to correctly indicate the point 
 in the 6,000-yard line for the velocity used, if the wheel be rotated so 
 that the pointer intersects the 3,000-yard line it indicates the correct 
 elevation for that range for the same velocity. 
 
 Elevating System. Two handwheels are attached to the ends of 
 the elevating shaft, to be manipulated by two men standing on the gun 
 platform, one at each wheel. These wheels actuate through a train of 
 bevel and spur gearing, a forged-steel elevating screw operating the 
 bronze elevating slide nut. This slide nut actuates the elevating slide, 
 to which the lower end of the elevating arm is pivoted, through the 
 medium of two helical springs, interposed to relieve the arm from shock 
 due to the downward thrust when firing with the gun elevated. 
 
 Upon this carriage no separate spring buffer stops are provided, as 
 the buffer springs between the slide and nut fulfill the requirements. 
 At the limit of depression of the gun the slide strikes a positive stop 
 and the nut is stopped by the spring; at the limit of elevation the nut 
 strikes a positive stop and the slide is stopped by the spring. 
 
 In order to render the power required for elevating and depressing 
 as nearly equal as possible, the downward thrust of the elevating screw 
 in depressing is borne by a ball-thrust bearing placed beneath the ele- 
 vating-spur gear and inclosed with it on top of the rear transoms. 
 When depressing the gun by raising its breech (during which opera- 
 tion the men at the wheels have to overcome a certain preponderance, 
 due to weight of elevating arm, etc.), the top disk of the ball bearing 
 rotates with the elevating-spur gear upon the rolling balls and the fric- 
 tional work to be overcome is reduced. 
 
 When elevating the gun by lowering its breech the preponderance 
 above mentioned assists instead of opposes the motion. Therefore, to 
 
ARMAMENT 213 
 
 prevent the slide from running down, due to the weight upon it, during 
 this operation as well as in firing, the top disk is arranged with ratchet 
 teeth to be engaged by pawls, which prevent its rotating in the direction 
 for elevating by locking it to the transom. By this locking device the 
 ball-thrust bearing is thrown out of action when elevating and the 
 elevating-spur gear is obliged to turn on a bronze washer interposed 
 between it and the fixed top disk of the ball bearing, thus increasing 
 the frictional resistance over what it would otherwise have been. 
 
 Counterbalance Device. In order to still " further equalize" the 
 power required for elevating and depressing, an attachment has been 
 designed for this carriage, called a " counterbalance device." This con- 
 sists of a weight hung by a double wire rope which passes over pulleys 
 and is attached to the elevating slide nut so as to oppose and partially 
 counterbalance the weight of the slide and half the weight of the 
 elevating arm. 
 
 The use of too much balance weight will result in an upward thrust 
 on the elevating screw, conducing to serious wear on the under side of 
 the screw bearing. 
 
 Traversing System. For pointing in azimuth by hand power, 
 two crank handles may be attached to the traversing shaft and manipu- 
 lated by two men standing on the working platform, one at each crank. 
 From this shaft motion is transmitted by two pairs of bevel gears to 
 the vertical shaft in bearings on the chassis and racer, the pinion at the 
 lower end of which engages in the circular traversing rack bolted to 
 the base ring and by its .rotation causes the racer and all parts carried 
 thereon to rotate upon the rollers and around the pintle surface. 
 
 While the construction of the carriage itself permits it to be trav- 
 ersed 360 degrees, stops are provided which are to be screwed to the 
 inside of the pintle above the traversing rack, limiting the movement 
 in azimuth as may be required by the emplacement in which the gun 
 is mounted. 
 
 To prevent excessive shocks to the traversing gearing or other parts, 
 due to striking obstructions or to too sudden application of power, 
 etc., the intermediate bevel gear wheel is not keyed to the shaft, but 
 centered upon and held frictionally by three disks, free to move longi- 
 tudinally on two feathers made solid on the pinion shaft, and pinched 
 between a solid collar above and an adjusting nut below. The nut is 
 locked by being jacked apart with a set screw at a cut which extends 
 partly across. 
 
 The friction surfaces are provided with oil grooves, which together 
 with the spaces between the disks, are to be kept filled full with oil 
 
214 THE SERVICE OF COAST ARTILLERY 
 
 through a hole in the top end of the shaft. The adjusting nut should 
 be set up just enough to rotate the carriage by hand without slipping. 
 It is intended that in rotating by power suddenly applied the disks 
 shall slip at first, and thus pick up the load gradually. 
 
 Traversing Brake. In a convenient position on the racer, outside 
 of the left chassis and near the azimuth pointer and the controller 
 auxiliary handle is the traversing brake. This consists of a vertical 
 guide attached to the racer, in which slides a brake clamp with a toe 
 designed to grip under the lift on the inside of the pintle when pulled 
 up against the latter by the brake screw. This screw is threaded into 
 the upper end of the brake clamp and when screwed down by a clock- 
 wise motion (as viewed from above) of the handle, its lower end bears 
 upon a hardened plate upon the racer, and thus draws up the brake 
 clamp and sets the brake. A notched flange on the upper portion of 
 the screw bolt enables the handle to be set at a convenient position, in 
 which it is retained by screwing down the nut above it. This handle 
 engages under a spring catch in its "off" position to keep it out of the 
 way. 
 
 Retracting System. For hauling the gun down by hand two re- 
 movable crank handles may be attached to the retracting crank shaft 
 and maneuvered by eight men standing on the gun platform, four 
 working on each crank. The retracting crank shaft actuates through 
 a train of three pairs of spur gearing, two drums, to which are fastened 
 by corrugated clamps two wire clamps, which wind upon the drums. 
 A ratchet and pawl prevents the load from overhauling the gearing. 
 From the drums these ropes pass around guide pulleys in rear of the 
 recoil buffers and are hooked to the upper ends of the gun levers. 
 These ropes remain with the carriage, and when not in use are wound 
 upon the drums until the ropes project but a short distance from the 
 guide-pulley brackets. 
 
 For rapid and easy overhauling of the ropes, two small speed cranks 
 are fixed to the crank shaft back of crank handles. To save time these 
 should also be used to wind up the slack of the rope before placing the 
 crank handles on the shaft. In hauling down, care should be exercised 
 that both ropes are under equal tension. 
 
 After taking up the slack in the ropes and putting some strain on 
 them, they should be vibrated slightly, and if found to be unequally 
 loaded, adjustment should be made at the rope clamps on the drums. 
 After the loop of the rope is placed over the hook on the gun levers, 
 and while winding up the slack, special care should be taken that the 
 rope is guided to the pulleys without any kinks or any slack and that 
 
ARMAMENT 215 
 
 the coils lie smoothly upon the drums without crossing the ridges be- 
 tween the grooves. 
 
 On account of the extra counterweight used to decrease the time of 
 going into battery, the operation of retraction requires the application 
 of considerably more power than would otherwise be the case. Retrac- 
 tion by hand power will, therefore, be found somewhat difficult. This 
 is, however, not expected to be objectionable, as retraction by the 
 electric motor supplied is regarded as the normal practice, retraction 
 by hand being provided for use principally in case of trouble with the 
 electrical plant. 
 
 In case retraction by hand is desired to be habitually used, as for 
 example during the drill season, the amount of counterweight may be 
 reduced to about 158,000 pounds for use with the gun of the model of 
 1900, or to about 135,000 pounds for use with the gun of the model of 
 1895. With these reductions in the counterweight, the time required 
 for the gun to go into battery will be increased to about twelve or 
 thirteen seconds. 
 
 Retracting Gear, Clutch, and Brake. To permit the most rapid 
 overhauling of the wire ropes possible there has been added a spring- 
 engaging claw clutch for rotating the drum shaft from the drum gear 
 in retracting. With the clutch thrown off, the ropes can be drawn out 
 quickly, revolving the drums Lnd shaft rapidly in the drum gear. 
 
 In order to prevent overrunning and injury to the ropes a band 
 brake is added, gripping the hub of the left drum upon lifting a crank 
 handle. The clutch is thrown off by drawing a loop handle on the left 
 side until the feathers are drawn out and permit the handle to be given 
 a quarter turn, which locks the clutch off with the spring compressed. 
 
 When enough rope is overhauled the brake handle is raised to stop 
 the shaft, the loop is given a quarter turn back to permit the feathers 
 to enter, and the spring moves the clutch, on its feathers in the drum 
 shaft, to engagement. 
 
 Working Platform. The outside platform of plates and angles is 
 flush with top of racer, is supported on radial cast-steel brackets bolted 
 to it, and covers the recess around the turntable flush with the fixed 
 part of the platform. 
 
 The inside platforms, supported by the racer and chassis, cover the 
 sides of the counterweight well. On the right side a manhole and 
 ladder are provided for entering the well. 
 
 Sighting Standards and Platforms. These platforms of plates 
 and angles extend along each side of the carriage, supported in front 
 by brackets bolted to the top of the crosshead guides on the chassis and 
 
216 THE SERVICE OF COAST ARTILLERY 
 
 in rear by standards bolted to the racer and chassis. The brackets and 
 standards are of steel castings. 
 
 A flight of steps is provided at the front and rear end of each plat- 
 form. Hand rails and a screen to protect the gunner's body from the 
 elevating arm during recoil of the piece are also provided. These 
 platforms furnish not only a station for sighting and pointing and 
 firing (by electrical power), but also a convenient means of access to 
 the gun, retracting hooks, trunnion beds, etc., for oiling or other pur- 
 poses, e. g., for inserting a new primer. 
 
 Sight Standard. This standard is a steel casting, seated and 
 clamped in a split socket in the top of the left standard. It extends 
 forward as a bracket, forming a' pivot and guide for the sight arm 
 which carries the combined bar sight with the new 3-inch telescope. 
 The pivot is at such height that the sight lines may be depressed 6 
 degrees if necessary, when firing gun at 5 degrees depression, and still 
 pass over the crest of the parapet. 
 
 Counter-set screws are provided at the socket for making a slight 
 adjustment in rotation and in fixing the standard, the line of collima- 
 tion of the telescope and open sights in a vertical plane, parallel to a 
 vertical plane through the axis of gun. 
 
 To this standard is also attached the bracket supporting the con- 
 troller extensions and handles, the firing pistol, and the box protecting 
 the rheostats for adjusting the lights which illuminate the sight grad- 
 uations. 
 
 For use on the right trunnion, the telescope sights in service are the 
 models of 1896 Mi, of 1897, of 1898, and of 1898 M, described in 
 Chapter VII. 
 
 Sight-Laying Mechanism. A pair of bevel gears transmits the rota- 
 tion of the elevating-wheel shaft to the sight-elevating screw, which, 
 working in a threaded bearing in the sight-elevating slide, causes the 
 latter to move up or down in a guideway formed upon the rear of the 
 left standard near its base. To this slide is pinned the lower end of 
 the sight-elevating arm, which is partly inclosed in the standard, and 
 to the upper end of which is pivoted the rear end of the parallel arm 
 and the lower end of the sight-arm link. 
 
 To the upper end of the sight-arm link is pivoted the rear end of 
 the sight arm. The front sight arm and the parallel arm being of the 
 same length between centers of pivot holes and their front ends being 
 pivoted in fixtures attached to the standard, and these pivots being at a 
 distance from each other equal to the length of the sight-arm link, a 
 true parallel motion is secured between these two arms; and the sight- 
 
ARMAMENT 217 
 
 elevating arm and gearing are so proportioned that each of these arms 
 is kept always at the same angle of elevation as the axis of the gun. 
 The sight-arm link is inclosed in the standard, and the parallel arm is 
 in a bracket, attached to the standard, which protects it but which is 
 open at the top. 
 
 The sight-elevating screw is not solid with or keyed to the bevel 
 gear by which it derives rotation from the elevating shaft, but is fric- 
 tionally held thereto by the pulling down of its cone head into a friction 
 seat in that gear by a nut on the screw, which, through a washer, presses 
 against a bushing, which, in turn, presses against the bottom of the gear. 
 The washer has a feather entering a slot in the screw, to insure its rota- 
 tion with it. The nut is slit half through transversely and furnished 
 with a set screw to permit jamming it on the threads after the screw is 
 adjusted. After loosening the nut, the sight-elevating screw may be 
 freed from its gear and rotated by the hexagon lower end, and the 
 sight-elevating gearing thus be moved, for adjustment, independently 
 of the gun-elevating mechanism. 
 
 The parallel arm has a true upper surface which furnishes a seat for 
 a level for testing horizontality thereof. The parallel arm is, for this 
 reason, also placed at a convenient height for a man standing on the 
 gun platform. After adjusting the parallel arm to be horizontal when 
 the gun is horizontal, the nut on the sight-elevating screw should be 
 screwed up tight against the washer, bushing, and gear, while motion 
 of the screw is prevented by a wrench applied to its lower end. The 
 nut should then be jammed by its set screw. 
 
 By these means the bevel gear is firmly held to the sight-elevating 
 screw, and any motion of the elevating slide, being accomplished by a 
 rotation of the elevating shaft, produces through this bevel gear and 
 its mate a rotation of the sight-elevating screw, which, in turn, causes 
 the sight-elevating slide to move in the same direction as the elevating 
 slide. Thus the sight-elevating arm is moved up or down, causing in 
 the parallel arm and sight arm an angular movement the same as the 
 movement produced in the gun itself. 
 
 In the final adjustment of the combined telescopic and bar sight the 
 horizontality of the parallel arm may be slightly disarranged. 
 
 Lanyard Safety Attachment. This is to prevent the firing of the 
 piece by a pull, accidental or otherwise, upon the lanyard before the 
 gun has risen to the firing position; that is, before it has been raised 
 to such a height that the projectile will clear the parapet. It consists 
 of an incased reel, attached to the elevating band, upon which a short 
 cable is automatically wound by a spiral spring, and locked, except 
 
218 THE SERVICE OF COAST ARTILLERY 
 
 when piece is in battery, by a ratchet and pawl. One end of a short 
 lanyard is hooked to the primer and the other to the end of this cable. 
 The long lanyard in the hands of the cannoneer is also hooked to this 
 cable. A pull on the lanyard, when gun is out of battery, cannot 
 unwind the cable, pull the short lanyard, or fire the primer. When 
 gun rises in battery, a cam on the elevating band passing under the 
 pawl lifts it out of engagement with the reel, which can then be un- 
 wound, permitting the primer to be fired. 
 
 The initial tension of spring should be sufficient only to wind up the 
 cable with lanyards attached. It may be adjusted by loosening the 
 nut on the spring shaft and with wrench on the squared end of shaft 
 (projecting from the center of the case) withdraw the locking pin and 
 wind up or unwind the spring, returning the locking pin to one of the 
 quarter-turn positions and tightening nut. 
 
 Electric Safety-Firing Attachments. The carriage is arranged 
 to permit electric firing either individually (by a key on the sighting 
 platform or one on the working platform) or in salvo (by a key in the 
 battery commander's station). To arrange for firing by whichever of 
 these methods is desired, a double-pole, double-break, double-throw 
 switch in the Signal Corps' outlet box is turned to the proper [indicated] 
 position. This connects with a source of electrical power two of the 
 four wires from this switch to the carriage, namely, either the two 
 wires tapped directly into power mains in the emplacement (for indi- 
 vidual or " gun " fire) or the two wires leading back through the battery 
 commander's firing key to the power mains (for battery or salvo fire). 
 The latter two wires are led without any interrupting switch or key to 
 the "safety-firing switch" on the left chassis (connecting with the 
 front lug of the top carriage). 
 
 The former two wires are broken at the two firing keys on the car- 
 riage in such manner that the closing of either key closes the circuit; 
 they then go to the safety-firing switch. This switch is designed to 
 break the firing circuit automatically as soon as the top carriage has 
 recoiled. The firing circuit cannot be reclosed at this point until the 
 top carriage returns to battery (within 2.5 inches of its prescribed firing 
 position). The circuit is even then not reclosed automatically, but is 
 to be closed by the intentional act of a cannoneer after the gun is laid 
 and otherwise ready to fire. Thus the battery commander cannot 
 fire the gun before the gun commander has completed the laying, etc., 
 and is ready. 
 
 However, as it may be desirable in firing, piece by piece, to obtain 
 the maximum rapidity of action by firing immediately the gun comes 
 
ARMAMENT 219 
 
 into battery, the switch is so arranged that it may be set to make con- 
 tact automatically when the top carriage is in battery. Then the piece 
 can be fired by pressure of one of the firing keys. This must never 
 be so set, however, for battery fire, as a shot might be lost or someone hurt 
 by the battery commander firing after the gun was in battery but before 
 it was properly laid or before all cannoneers were in safe positions. 
 This setting for automatic action should never be made except by express 
 order. 
 
 The Safety-Firing Switch is essentially a double-pole, single-brake, 
 single-throw knife switch, the body carrying the two knife blades being 
 pivoted to the chassis and the double blades, or sockets for the knives 
 to make contact with, being fastened to the lug of the top carriage. 
 When the top carriage is in battery the sockets are directly above the 
 knife blades, and if the body is raised by hand until the blades engage 
 in them the circuit will be closed at this point, and the spring grip of 
 the sockets upon the blades will support the weight of the body and 
 keep the contact made until the top carriage moves to the rear and 
 releases the blades, when the body will swing downward about its pivot 
 on account of its own weight. 
 
 As long as the top carriage is not in battery it is evident that con- 
 tact cannot be remade, since the sockets are not within reach of the 
 knife blades. Even when the top carriage returns to battery there is 
 no tendency of the body to rise (against its own weight) and make 
 contact, so that it must be lifted by a man. 
 
 The automatic remaking of contact is secured when ordered by 
 raising the support which holds the body always in its upper position, 
 in which case the blades will engage in the sockets as the top carriage 
 comes into battery. 
 
 Electric Motor Equipment. The carriage is provided with a com- 
 plete electric motor equipment. This consists essentially of a motor, 
 with its controller and other adjuncts, for traversing the carriage, and 
 another motor, with its controller and other adjuncts, for either retract- 
 ing or elevating and depressing, according to whether the maneuver 
 lever is set to throw the idler gear carried by it into mesh with the gear 
 on the retracting .or that on the elevating shaft. 
 
 The motors are of the completely inclosed type, supported by cast- 
 steel brackets bolted to the inner side of the left chassis. 
 
 The traversing motor has a pinion upon its shaft which engages 
 directly with a gear upon the traversing crank shaft. There is no means 
 of throwing this gear out of mesh, and consequently the motor arma- 
 ture rotates when the carriage is traversed by hand. 
 
220 THE SERVICE OF COAST ARTILLERY 
 
 The elevating and retracting motor shaft extends through a bearing 
 in the opening in the chassis, and in an improved design is supported 
 at its outer end by a bracket bearing. A cast-steel maneuvering lever 
 is arranged to oscillate on the motor shaft and to carry an idler gear 
 on a fixed pin and in mesh with the motor pinion, between its branches. 
 The top end of the lever is guided in and may be pinned, in three 
 different positions, to an arc attached to the chassis over the motor 
 shaft. 
 
 With the lever in the forward position the idler is in mesh with a 
 gear on the retracting crank shaft, in which case the motor will retract, 
 and with the lever in the rear position the idler meshes with the gear 
 on the elevating- wheel shaft and the motor elevates or depresses the gun. 
 When pinned in the mid position the idler is free from both gears and 
 the motor armature will not be revolved by elevating or retracting by 
 hand. 
 
 This lever also throws the commutation switch so that in retracting 
 two rheostats in multiple enable the motor to do more work than when 
 elevating or depressing the gun. 
 
 The lever should never be left unpinned, and should never be shifted 
 when the motor or any part of the gearing is in motion. Care should 
 be taken in shifting that the teeth of the idler are opposite spaces in the 
 gears. 
 
 The two controllers, one for the traversing, one for the elevating- 
 retracting motor, are placed side by side on a frame bolted to the 
 working platform immediately in rear of the left standard. By turn- 
 ing the shafts of these controllers by the handles provided, the elec- 
 trical connections within are changed in such combinations as to start, 
 stop, and give the different speeds of motion provided for. When 
 turned to the off position the connections are so arranged that a short 
 circuit is made from brush to brush, thus closing the circuit through 
 the armatures of the motors while the field magnets remain energized. 
 Forced rotation of the armatures then cause the motors to work as 
 generators, which requires that work to be done by the force which 
 rotates them. The motors under these circumstances are therefore brakes. 
 
 This brake effect does not become operative in the elevating-retract- 
 ing motor until the controller reaches the off position, so that if the 
 handle be turned quickly to that position while the gearing is running 
 at full speed the motor armature would be rotated rapidly and the 
 strains due to the brake action would be severe. The traversing motor, 
 however, does operate as a brake to reduce the speed of traversing when- 
 ever the controller handle is turned toward the off position that is, 
 
ARMAMENT 221 
 
 whenever the controller is set to a slower speed than that at which the 
 motor is running.. This is due to the fact that this motor has a cur- 
 rent of variable voltage supplied to it, the voltage determining the rate 
 at which the motor runs as a motor. If the motor be actually running 
 at a higher speed than that for which the controller is set, its counter 
 electromotive force exceeds the impressed voltage, thereby generating 
 a current which tends to reverse the direction of rotation of the gener- 
 ator that is, to drive it as a motor. This, of course, requires work to 
 be done by the force tending to rotate the traversing motor at the 
 higher speed, and as this force is the inertia of the moving carriage, 
 the result is that the speed is slowed down by this braking action. 
 Therefore, when the controller comes to the off position the carriage 
 should have less remaining velocity to be overcome by the brake effect 
 of the motor when short-circuited than would otherwise be the case, 
 and the carriage therefore is brought to rest more promptly and at the 
 same time with less strain. To secure the full effect of this action the 
 controller handle should be turned rather slowly, so that the retarding 
 brake action may be of some duration. 
 
 The elevating-retracting controller has wired between it and the 
 motor a commutation switch, automatically set by throwing the maneu- 
 ver lever, so that when elevating or depressing, the upper rheostat 
 only is inserted, permitting the motor to operate at 4 horsepower, and 
 when retracting the second rheostat is thrown in multiple with the 
 first, thus permitting the motor to operate at 8 horsepower. 
 
 Resting upon the squared upper end of the shaft of each controller 
 is a shaft called the " controller extension," which reaches to a con- 
 venient height above the sighting platform and has its upper end squared 
 to receive the controller handle and thus permit rotation of the con- 
 troller shaft, and operation of the motor, from the sighting platform. 
 This controller extension may be lifted without releasing any catch, 
 and the controller handle may be put upon the squared upper end of 
 the controller shaft for operation from the gun platform. 
 
 In addition to the above, the traversing controller has its shaft 
 connected by two pairs of bevel gears to a short vertical shaft on the 
 racer near the azimuth pointer. The handle may be placed on this 
 shaft and the traversing controller operated from this point when it is 
 Desired to lay the gun to a given azimuth by the scale and pointer 
 (Case III). Only one set of controller handles is provided (that is, one 
 handle for each of the two controllers), and are marked to show the 
 direction in which the handle should be moved to produce motion in 
 the direction stated. The hand of the operator indicates the direction 
 
222 THE SERVICE OF COAST ARTILLERY 
 
 of motion and may be regarded as the pointer. (To simplify the action 
 as much as possible the direction of motion of the handle of the travers- 
 ing controller is the same as the motion of the gun) . 
 
 The farther the handles are moved from the "off" position the 
 greater is the resulting speed. As any mass acted on by a force re- 
 quires time to acquire its maximum velocity, so the carriage requires 
 a short time to acquire the velocity corresponding to any position of the 
 handles. It is well, therefore, to move the handles somewhat slowly 
 in changing speed to avoid getting up more speed than is desired. 
 Too sudden turning of the handle, moreover, imparts a greater acceleration 
 and correspondingly severe strain upon all parts. It may result in break- 
 age, and is very apt to cause opening of circuit breakers (due to over- 
 load), which will mean a short delay to close them, which may be of 
 importance in action or target practice. 
 
 There are two circuit breakers on the carriage, one for each motion, 
 placed in an iron box bolted to the under side of the rear projection of 
 the left chassis. They are capable of adjustable setting, and should be 
 set to open at about 40 amperes for the traversing and about 70 am- 
 peres for the elevating retracting motor. Any electrician sergeant will 
 understand how to set them. When a circuit breaker opens on account 
 of overload, the handle swings over from the right to the left, the circuit 
 is broken, and no current can pass. To reclose the -breaker remake the 
 circuit, and allow the current to pass again simply move this handle 
 back to the right. 
 
 If the carriage were traversed up to the positive stops at high speed 
 with electric power, damage would probably result. To prevent this 
 an automatic traversing controller stop is provided. A cam is bolted 
 to the base ring near the extreme limit of traversing "muzzle right/' 
 which, when struck by the lt shipper " (an arm fixed to the shaft carried 
 by the racer), presses this shipper gradually outward in such manner 
 that, by suitable gear connections, the traversing controller shaft is 
 gradually turned to the off position. Thus the speed of the carriage 
 is reduced and the traversing is finally stopped. By shifting the cam 
 until the correct position is found the carriage may be traversed at 
 full speed to the stop, and will come to rest very close to the extreme 
 position allowable. Once set by the Ordnance Department, this cam 
 should not be shifted. A similar cam actuating another shipper on the 
 same shaft limits the left traversing. In spite of these safety stops 
 it is recommended to slow the carriage down as it approaches the end of 
 its allowed motion. 
 
 No such safety stops are provided for the elevating, depressing, or 
 
ARMAMENT 223 
 
 refracting on account of the complication involved and the smaller 
 necessity existing. In these operations safety and proper action will 
 depend upon that proper care in manipulation which all machines 
 should receive. At the same time, should these motions accidentally 
 be continued until the limiting positive stops are struck, it is probable 
 that nothing more serious than opening of the circuit breaker would 
 result. 
 
 A detailed description of the electrical equipment furnished by the man- 
 ufacturers should be studied by those in charge. It will be found to 
 relate more particularly to the electrical features of the equipment, those 
 with which the officer in charge of the post electrical plant and his assist- 
 ants are principally concerned, while the above notes have dealt with 
 mechanical features and with appliances and operations with which the 
 officer in charge of the armament and the gunner and cannoneers 
 operating the carriage are most directly concerned. 
 
 The following data and suggestions relative to operation of the 
 motor equipment, as well as those heretofore mentioned incidentally 
 to the description, are based upon the experience so far had with these 
 equipments, and are subject to revision in the light of more extensive 
 experience, but will be found useful as guides to the proper use and 
 care of the equipment, and as criteria for judging its condition: 
 
 (a) There is nothing to prevent the running of both motors simul- 
 taneously. If the power supply is inadequate, this will simply result 
 in diminution of speed. 
 
 (b) Hand cranks should be removed from shafts when operating elec- 
 trically, as they rotate at considerable speed and might injure cannon- 
 eers getting within reach of them. 
 
 (c) Especial care, should be taken to keep all bearings and gears con- 
 nected with the system well oiled (oil before each drill, without fail) ; 
 but the amatures, field coils, and conductors should be kept, as far as 
 possible, free from oil, which injures their insulating material. 
 
 (d) Sparking at commutators and other contacts should be promptly 
 investigated by an electrician and corrected if possible. 
 
 (e) Care should be taken that the commutator brushes on all machines 
 are set with the proper lead. Generally these are set once for all, and 
 care is only necessary to see they are not shifted. 
 
 (/) Avoid injury to machines and conductors by blows from tools, 
 cannoneers' feet, etc. 
 
 (g) Do not turn the controller handles on or off suddenly. They 
 may be shifted with considerable rapidity, but all manipulation should 
 be gentle and easy. 
 
224 THE SERVICE OF COAST ARTILLERY 
 
 (h) Avoid running past the desired setting. It is easier and quicker 
 to stop a little short and perfect the setting by successive small move- 
 ments. 
 
 (i) Very small movements may be obtained by turning the con- 
 troller handles slightly from the off position and then turning back 
 immediately to the off position. 
 
 (/) Avoid running clear up to the limits of allowed movement, 
 especially at the higher speeds. 
 
 (k) Always have the circuit breakers on the carriage set to open 
 at a lower current than the corresponding breakers on the switch-board 
 panel. The breakers on the carriage are put there to permit reclosing 
 with the least loss of time, and to avoid the necessity of communicating 
 with the man in charge of the panel and motor-generator set, which 
 will be installed under cover at a distance. 
 
 (/) See that all binding posts are tightly set to insure good con- 
 tacts. 
 
 (m) All operations should be performed as frequently as possible 
 to keep all components in proper running order and to familiarize the 
 personnel therewith and enable them to gain that facility of handling 
 without which much of its efficiency and usefulness will be sacrificed. 
 
 In regard to the motor-generator set and switch-board panel: 
 
 (a) Follow carefully the directions for putting this system into 
 action. 
 
 (6) Watch the circuit breakers, and, if either opens, close it promptly 
 in order to avoid delays in the service of the piece. 
 
 (c) Measure the speed of the motor-generator set from time to time 
 to insure that it is running properly 
 
 (d) Supply as nearly constant voltage to this set as possible, in 
 order that its speed and the voltage supplied by it to the traversing 
 motor may be as calculated. Otherwise, the speeds of the carriage 
 will not be as calculated. 
 
 ((?) Take frequent reading of the voltage and amperage shown by 
 the instruments on the switch-board, and keep as full record as prac- 
 ticable of these readings with note of attendant circumstances. These 
 records should always show the voltage correspondingly in time to the 
 amperage entered. 
 
 (/) The motor-generator set running light (switch to carriage open) 
 should require, on a 110- volt circuit, about 6 amperes. The speed 
 should be 1650 revolutions per minute. 
 
 (g) The voltage and current supplied by this set to the traversing 
 motor are variable, being controlled by the traversing controller, 
 
ARMAMENT 225 
 
 and should range from to 110 volts with current from 12 to 25 
 amperes. 
 
 While starting or accelerating speed, the current may be expected 
 to run up to 40 or 50 amperes, occasionally. 
 
 (h) The voltmeter on the switch-board, as installed in the earlier 
 carriages, does not measure this voltage, but the line voltage that 
 supplied to the motor-generator set and to the elevating-retracting 
 motor. To measure the voltage given out by this set it will be necessary 
 to change the connections of this meter or to connect a portable volt- 
 meter across the terminals of the generator of the set. In later carriages 
 the voltmeter will have a double-throw switch, enabling it to be thrown 
 into either circuit desired. This modification is to be made for the 
 earlier carriages. 
 
 (i) The voltage of the current supplied to the elevating and retract- 
 ing motor is that of the line, generally 110 volts. The amperage should 
 vary between 10 and 20 amperes for elevating and 20 to 30 amperes 
 for depressing (if no counterbalance), and should average 45 to 55 
 amperes for retracting with 164,500 pounds counterweight and model 
 of 1900 gun (near commencement but after fairly under way) and be 
 about 5 amperes higher near the termination of retraction. For 6,000 
 pounds less counterweight the current for retracting is about 15 am- 
 peres less. There will be a temporary current, considerably higher, 
 while the first resistance to starting from rest is being overcome. With 
 a gun of the model of 1895 the power for elevating and retracting is 
 about as above. With this gun and 142,000 pounds counterweight, 
 retraction requires 30 to 40 amperes, and with 137,000 pounds counter- 
 weight about 25 to 35 amperes. 
 
 In regard to traversing: 
 
 (a) With the gear ratio applied to the earlier carriages the carriage 
 may be traversed at maximum speed at the rate of one revolution in 
 about one to one-and-a-quarter minutes, and at minimum speed corre- 
 sponding to one revolution in fifty to fifty-five minutes. As the above 
 maximum is unnecessarily rapid and the minimum not as slow as 
 -desirable, an increase in the gear ratio is to be made which will give a 
 maximum speed corresponding to one revolution in two minutes (en- 
 abling the sight line to follow a vessel traveling about 50 miles per 
 hour at 500 yards range) and a minimum continuous speed of one rev- 
 olution in seventy minutes (enabling the sight line to, follow a vessel 
 traveling about 9 miles per hour at 3,000 yards range). Moving tar- 
 gets with slower angular velocity may be readily followed without 
 .appreciable error by successive movements of the controller handle to 
 
226 THE SERVICE OF COAST ARTILLERY 
 
 the minimum-speed position, bringing it back immediately to the off 
 position. Practice will develop great facility in this respect. 
 
 In regard to elevating and depressing: 
 
 (a) Care should be taken in these operations not to approach the 
 limits of movement at high rate of speed. By slowing down, the full 
 limits of movement may be attained without risk. 
 
 (6) The gun may be elevated from 5 to +10 degrees in about 
 thirty-five seconds. 
 
 (c) The gun may be depressed from +10 to 5 degrees in about 
 thirty-five seconds. 
 
 (d) The above times are the results of trials with the model of 1900 
 gun; for the model of 1895 gun they are about the same. 
 
 (e) These times are subject to considerable variation, as they include 
 the time required to get up speed and to slow down. They are only 
 approximate. 
 
 In regard to retracting: 
 
 (a) The model of 1900 gun with 164,700 pounds, or the model of 
 1895 with 146,000 pounds, of counterweight can be retracted in about 
 two and three-fourths to three minutes. 
 
 (b) With about 5,000 pounds less of counterweight in either case the 
 gun can be retracted in about the same time. 
 
 (c) In starting retraction, turn the controller handle slowly, in order 
 that the starting strains and current be not unnecessarily high. 
 
 (d) Be careful not to retract so far that the gun levers strike the 
 recoil buffers. 
 
 (e) Do not allow the gun to go into battery with the ropes attached. 
 The excessive moment of the heavy counterweight produces an unde- 
 sirably high velocity of rotation of the gearing and motor armature. 
 
 Conduits, Wiring, and Illumination. Incandescent, 16-candle 
 power lamps of standard form are provided for the general illumination 
 of the carriage ; 8-candlepower candelabra lamps are provided for the 
 scales and pointers and throttling valves, and 2-candlepower miniature 
 lamps are furnished with the new bar sight to illuminate the scales and 
 the reticule inside of the telescope. All lamps are shaded so as to 
 illuminate only the parts intended. The azimuth and elevation 
 pointer lamps are lighted by one key; the lamps for the sight are 
 lighted up to a sufficient intensity by small rheostats, all other lamps 
 having each a key. 
 
 All electrical conductors for the motor equipment, for the lamps, 
 and for the firing circuits upon the carriage, enter the counterweight 
 well through a duct in the concrete, the opening of which is in the rear 
 
ARMAMENT 
 
 227 
 
 wall of the well a short distance below the base ring. Thence they 
 hang in a flexible cable or bundle, with sufficient slack to permit trav- 
 ersing through the allowed angle, and enter a vertical pipe conduit 
 near the center of rotation. Thence the individual conductors are led 
 to the several points at which their current is to be used. 
 
 The wiring system is, as far as possible, inclosed in a conduit system 
 of wrought-iron pipe, fittings, junction boxes, etc., all with interior 
 insulation and outlet insulators at the ends of pipes. The lighting and 
 firing wires only are, at points where armored conduit could not well 
 
 .00 
 
 .04 
 
 .03 
 
 .12 
 
 .16 
 
 .05 
 
 .00 
 
 be used, made up with thimbles hung on twisted hooks, and so carried 
 to their destination. 
 
 The Buffer Valve (Fig. 18) .The corrected setting of the buffer valve 
 is determined by tripping the gun several times and varying the buffer 
 valve settings until a satisfactory counter-recoil is obtained. Noting 
 the setting of the buffer valve, then obtain from the chart shown in 
 Figure 19 the proper setting for the throttling valve. The chart shows 
 curves marked buffer and throttling, plotted to give the areas of orifice 
 due to different settings of these two valves. 
 
228 THE SERVICE OF COAST ARTILLERY 
 
 Using the buffer-valve setting as an ordinate, enter the chart and 
 obtain the amount that the throttling valve should be closed to obtain 
 the proper recoil corresponding to this buffer-valve setting. This 
 amount will be found on the left-hand vertical scale and will be the 
 horizontal line intersected by the buffer-valve setting-line and the 
 buffer-valve curve. For example, suppose that the emplacement book 
 records show at last target practice that the throttling valve set at 
 .16 gave the proper recoil. In trial after the attachment of the buffer 
 valve, setting the same at 30, the amount of change in the setting of 
 the throttling valve would be obtained from the chart by following 
 up the vertical line marked 30 until it intersected the buffer-valve 
 curve, then following the horizontal line to the left and reading its 
 value and the area of orifice in square inches. This will be found to be 
 approximately .06 square inch. Subtracting this from .16 gives .10 
 as the proper setting of the throttling valve. It must be remembered 
 that any change in the opening of the buffer valve necessitates a corre- 
 sponding opposite change in the throttling valve unless it is desired 
 that the length of recoil be changed. 
 
 MASKING PARAPET MOUNT 
 
 In this type of carriage the gun remains above the parapet for 
 loading and firing, but can be lowered below the level of the crest 
 of the emplacement for concealment. The 15-Pounder R.-F. Gun, 
 Driggs-Seabury, is mounted usually on this type of carriage and is 
 shown in detail in Plate XVI. 
 
 The principal parts of the mount are the outer base, the inner base, 
 the counterweight, the counterweight chains, the chain wheels, the 
 operating shaft, the pivot socket and bar, the pivot socket clamping 
 wedge, the pivot yoke, the ball-bearing washer, the horizontal clamp, 
 the vertical clamps, the oscillating slide, the recoil sleeve, the recoil 
 cylinder and piston rod, the shoulder bar, the elevating mechanism, 
 the sight drum and gearing, and the shield and braces. 
 
 The outer base is set into a concrete foundation and forms the 
 ultimate support for the entire mechanism. It is cylindrical in shape, 
 with a circular hole in the bottom for the lower part of the inner base 1 , 
 and two flanges, of which the top one is for the holding-down bolts, 
 while the other, by means of connecting ribs, supports the first. The 
 inner top edge is cut away, making a surface inclined 15 to the axis 
 of the base and serving to help center the inner base. 
 
 The inner base is, roughly, a cylinder with a broad flange at the 
 
ARMAMENT 229 
 
 top. At the lower end is a turned surface that fits into the hole in the 
 bottom of the outer base, and 3 inches from the edge of the flange and 
 on the under side is a surface, inclined 15 to the axis, that fits into the 
 corresponding surface of the outer base. On inner surface of the inner 
 base are formed two vertical ways for the pivot-socket bar diametri- 
 cally opposite to each other, and at the top of these, chain-wheel 
 recesses with supports and holes for the pin and the shaft. Near the 
 chain-wheel recesses, there are two handholes with covers, and the front 
 edge of the flange carries a lug for the operating lever and the ratchet- 
 wheel pawl. The interior is bored to receive the pivot socket, and the 
 upper edge has two holes for the clamp bolts. The two bases are held 
 together by eight bolts. 
 
 The counterweight is a cast-iron ring .weighted with lead. It is 
 raised and lowered between the two bases, and it has two grooves to 
 correspond to the ways of the inner base, and two shackle plates for 
 attaching the chains. 
 
 There are two counterweight chains; they pass over the wheels 
 and are attached by shackles to the counterweight and by eyebolts 
 to the pivot-socket bar. 
 
 The chain wheels are assembled to the inner base, one by a pin and 
 the other by the operating shaft; the first is bushed with bronze and 
 the second has a slot for a spline on the shaft. The wheels have sockets 
 for the links of the chain. 
 
 The operating shaft carries the right-hand chain wheel, extends to 
 the front through the lug on the inner base, and is squared near the end 
 for the ratchet. The ratchet wheel is assembled to the shaft by a 
 taper pin and the lug carries the ratchet-wheel pawl. 
 
 The pivot socket is cylindrical in shape and is raised and lowered 
 in the inner base by a bar, to which the chains are attached, and which 
 passes through the socket. Two bronze collars give a bearing surface 
 on the exterior, while the interior of the upper part is bored out to 
 give two bearing surfaces for the pivot yoke. A \veb forms the support 
 for the ball-bearing washer. In front and slightly above the upper 
 brass collar is the clamp pad, the lower surface of which makes a slight 
 angle with the collar. 
 
 The^ pivot-socket clamping wedge is shaped to the socket in rear 
 and is fastened to the top of the inner base by two screw bolts passing 
 through slots in the clamp. These slots are at the ends of the clamp, 
 one being open, while the other is closed. Both permit motion of the 
 clamp to right or left without wholly removing the bolts. On the 
 upper portion of the clamp, next the socket, there is an inclined surface 
 
230 THE SERVICE OF COAST ARTILLERY 
 
 corresponding to that of the clamp pad and terminating horizontally 
 at both ends. The clamp is operated by means of a lug. 
 
 The pivot yoke is Y-shaped; the stem seats in the pivot socket and 
 the arms furnish the trunnion beds. It rests on the ball-bearing washer, 
 and those that are made of steel have two bronze collars for the bearing- 
 surfaces. Both arms have threaded seats for the vertical clamps and 
 lugs on the inside to prevent the slide from springing under the pressure 
 of the clamps. Four lugs, two on each arm, are bored out for the 
 shield braces, and the seat for the horizontal clamp is cut at the top of 
 the front part of the stem. The cap squares are secured by screw bolts. 
 
 The ball-bearing washer is seated on the web of the pivot socket 
 and supports the pivot yoke. It consists of a row of hardened steel 
 balls, inclosed between two steel washers shaped to fit them, and con- 
 nected by a copper thimble. 
 
 The horizontal clamp is assembled to the pivot yoke, and consists 
 of a lever and a wedge. The lever is curved and has, near its inner end, 
 a projection that passes through the wedge and is assembled to the pivot 
 yoke by a set screw or a filister head screw. An eccentric cam on the 
 projection operates the wedge and retains it in place when once set 
 home. The lower part of the wedge is shaped to the interior of the 
 pivot socket. 
 
 The two vertical clamps are bent handles terminating at one end 
 in a screw thread. They are assembled to the arms of the pivot yoke 
 and operate by friction against the slide. 
 
 The oscillating slide is a casting, made of bronze in the mounts 
 first issued and of steel in those of later design. The bronze slide 
 consists of two cheeks connected by a loop and web; the loop is under 
 the front part of the cheeks and the web is across the front of the 
 loop; a hole for the piston rod is bored through the web. On the 
 inside of each cheek there are two guides for the sleeve, and at the rear 
 end of these are screwed two filling pieces. Near the front there are 
 two trunnions, and directly under these two lugs giving bearing sur- 
 faces for the vertical clamps. 
 
 Too great elevation is prevented by stops at the rear ends of these 
 lugs. The left trunnion has a projecting axis for the shoulder arm, 
 an elevating rack is screwed to the left cheek of the slide, and a counter- 
 recoil buffer of leather is placed on the inside of the web. In the steel 
 slide the tops of the cheeks are also connected by a strong web and the 
 loop is strengthened by two diagonal braces extending to the rear ends 
 of the cheek. The leather buffer is omitted in the steel slide. 
 
 Since manufacture the bronze oscillating slides have been strength- 
 
ARMAMENT 231 
 
 ened by a transom bolted across the top and two diagonal braces bolted 
 to the sides to and the loop connecting them. 
 
 The recoil sleeve screws over the jacket and hoop of the gun and is 
 keyed in position; it is shaped to fit the guides of the slide, and has a 
 loop with a beveled surface in rear, against which abuts a shoulder on 
 the cylinder. A lug in front stops the counter-recoil. The recoil 
 sleeve was made of bronze in mounts of early manufacture, but in later 
 mounts they are of steel, with the guide surfaces faced with bronze. 
 
 The cylinder has a smaller diameter in front than in rear, the two 
 portions being joined by an inclined curved surface. On the interior 
 the smaller part is cylindrical and is intended as a seat for the spring. 
 
 The travel of the piston is limited to the larger part of the cylinder. 
 Constant resistance is obtained by the passage of the liquid from one 
 side of the piston to the other through varying orifices, depending upon 
 the varying diameters of the interior. These diameters vary with the 
 position of the piston in such a way as to obtain the desired resistance. 
 The piston rod and head form one piece, the latter being of the same 
 diameter as the front of the larger portion of the cylinder. Springs of 
 a circular or rectangular cross-section abut against the piston head and 
 the front end of the cylinder. There is a cylinder head in the rear, and 
 stuffing-box glands front and rear. The forward end of the piston rod 
 is threaded for two nuts. A vent and filling hole are placed in the side 
 of the cylinder. 
 
 The shoulder bar is pivoted to the left trunnion, kept in position 
 by a washer and screw bolt in the trunnion, the shoulder-bar guide is 
 elevated and depressed by a worm and rack; the bar is shaped to give 
 a grip for the hand and carries the indicator for the elevation scale, 
 the complete sight drum, the sight, the elevating handwheel and worm, 
 and the shoulder piece. 
 
 The elevating mechanism consists of a rack, screwed to the oscillating 
 slide, and a worm, spring, ball-bearing washer, and handwheel assembled 
 on a vertical shaft to lugs on the shoulder-bar. 
 
 The sight drum and gearing consists of an indicator drum, with a 
 guard, a cover, a coil spring, a clamp bolt and nut, and a rack. The 
 cover fits inside the drum inclosing the spring, the cover and drum 
 being screwed together. The spring has one end secured to the drum 
 and the other to a bolt which is screwed into the shoulder-bar. An 
 axis and pinion projects from the indicator drum, the former being 
 seated in the shoulder bar and the latter engaging the rack on the 
 shoulder-bar guide. The indicator drum has, on the outer cylindrical 
 surface, a German silver strip on which the ranges are marked. The 
 
232 THE SERVICE OF COAST ARTILLERY 
 
 whole is assembled to the shoulder bar by the clamp bolt and nut. 
 The guard is screwed to the shoulder bar and has a rectangular cut 
 that permits a view of the graduated strip; there is a small pointer 
 at one side of this opening for indicating ranges. 
 
 The shield is a plate so bent that the two parts make an angle of 
 135 with each other. The gun and the line of sight pass through 
 apertures, and there are holes for the bolts used to assemble the shield 
 to the braces; these latter are four in number and are supported in 
 lugs on the pivot yoke. 
 
 The lanyard is a cord wound with brass wire and passing through 
 three guides; one on the breech of the gun, another on the sleeve, 
 and the third on the left cheek of the slide. There is a handle on one 
 end and a button on the other, while a small check nut, held in place 
 by a set screw, prevents too much slack near the breech. 
 
 THE DRIGGS-SEABURY 6-POUNDER PARAPET MOUNTS 
 
 (See Fig. 16) 
 
 The later mounts supplied by this company differ in several details 
 from the earlier ones. Though all are designated on the name plate as 
 model 1898, those of later manufacture are described herein as model 
 1898 modified. 
 
 The principal parts of the model 1898 mount are the axle, the wheels, 
 the pivot socket, and ball-bearing washer, the trail flasks, the trail 
 piece, the spade, the trail wheel and cradle, the trail-traverse roller, 
 the pivot yoke, the horizontal and vertical clamps, the recoil sleeve, 
 the recoil cylinder and piston rod, the counter-recoil spring, the 
 shoulder bar, the shield and braces, the anchorage and the ammunition 
 boxes. 
 
 The axle is a square bar of forged steel, terminating at each end 
 in an arm for the hub of the wheel and bent to the front in the center 
 to make room for the pivot socket. The wheels, washers, linchpins 
 and fasteners are similar to those on field carriages for 3.2-inch guns. 
 
 The pivot socket is a steel casting, rectangular in shape; the two 
 sides being extended front and rear beyond the ends to form four 
 flanges to which are riveted the trail flasks. In front, at the bottom, 
 a horizontal flange is similarly formed and rests upon the curved part 
 of the axle. The interior is bored to form two cylindrical bearing 
 surfaces for the pivot yoke, one at the top and the other near the bot- 
 tom, the space between being cored out to prevent contact with the yoke. 
 
ARMAMENT 233 
 
 In the bottom of the socket a hole is drilled for the pivot bolt, and a 
 shallow circular groove formed with four small drainage holes. 
 
 A seat for the horizontal clamp is formed by drilling and partly 
 threading a hole through the right side, and two stops are placed on 
 top in rear to limit the rotation of the pivot yoke. A ball-bearing 
 washer, consisting of a row of hardened steel balls, held between two 
 steel washers by means of a copper thimble, rests on the bottom of the 
 pivot-socket cavity and supports the weight of the pivot yoke and 
 assembled parts. 
 
 The two steel trail flasks are riveted to the flanges of the pivot 
 socket and the axle brackets in front and to two transoms and the 
 trail piece in rear. The construction is further stiffened by riveting 
 steel angles to the inside lower edges of the flasks which also serve as 
 supports for the trail-wheel bearings and for the bottom of the trail 
 toolbox. This toolbox is a compartment formed between the trail 
 flasks by the two transoms, and closed by a hinged lid on top. A 
 step, a handle, and the fastenings for the handspike are riveted to the 
 outside of the right flask, and a step, a handle, and the fastenings for 
 the sponge rod to the left, flask. 
 
 The trail piece is a bronze casting which contains the lunette and 
 seats for the handspike, spade pin, the trail-wheel cradle pin, and the 
 traverse roller. The spade is hinged to lugs on the upper side of the 
 trail piece by a pin, and by this arrangement can either be placed in 
 position for use or rotated over the end of the trail and laid upon the 
 latter out of the way. 
 
 The trail-wheel cradle carries the trail wheel at one end and is 
 pivoted to the trail piece at the other. The cradle may be secured in 
 either of two positions by means of a pin, which passes through the 
 hollow axle of the wheel. In the lower position this pin is inserted 
 through bearings on the under side of the trail and in the upper the pin 
 is passed through the flasks. When secured in the lower position the 
 wheel supports the trail, while in the upper it is raised between the 
 flasks and the trail rests on the ground. 
 
 The traverse roller is ellipsoidal in shape and is assembled to the 
 trail piece beneath with the axis at right angles to that of the trail 
 wheel. Its function is to permit easy movement of the trail in aiming. 
 
 The pivot yoke is Y-shaped, the stem seating on the ball-bearing 
 washer in the pivot socket and the arms forming the trunnion beds. 
 Two bearing surfaces are turned on the stem to fit those in the socket, 
 and its base is drilled and tapped for the pivot bolt. 
 
 The upper bearing is slotted for the horizontal clamp and the right 
 
234 THE SERVICE OF COAST ARTILLERY 
 
 arm is drilled for the vertical clamp. On each arm there are two lugs 
 through which the shield braces pass. The cap squares are secured by 
 screw bolts. 
 
 The horizontal clamp consists of a screw bolt, the outer end of which 
 is bent to form a lever handle, a pad, and a button. On the inner side 
 the pad is knurled and shaped to the pivot yoke, while on the outer 
 side it has an undercut groove, open at the top, in which the button 
 is held. Rotation of the pad is prevented by a stud on the lower edge. 
 
 The oscillating slide is a bronze casting consisting of two cheeks 
 connected at their lower edges by a web. On the outside of each 
 cheek there is a trunnion and on the inside two guides in which the 
 sleeve works; the right-hand cheek also has seats for the shoulder bar 
 and the vertical clamp bolt. A hole for the piston rod is drilled through 
 the front of the web, and a filling piece is screwed on the rear end of 
 each cheek between the guides to prevent the sleeve and gun running 
 out of the slide in the operation of mounting, or whenever the piston 
 rod is disconnected from the slide. 
 
 The vertical clamp consists of a screw bolt and a lever handle, 
 the latter provided with a lug at one end and threaded for the bolt. 
 A circular slot is cut in a flange on the right side of the oscillating slide 
 to form a seat for the head of the bolt. The circular head of this bolt 
 is cut away on the inside top and bottom to the width of the radius 
 of the slot in the slide. The lug thus formed works in the slot and 
 prevents turning of the bolt, while the remaining circular portion of 
 the head is in contact with the inner side of the flange of the slide, 
 and serves to clamp the latter when the bolt is drawn in by screwing 
 on the handle. 
 
 The recoil sleeve, which is also a bronze casting, screws over the 
 jacket and hoop of the gun and is keyed in position. It has bearings 
 on each side formed to fit those of the slide and a heavy loop beneath 
 bored out for the insertion of the recoil cylinder and shaped to fit 
 against a shoulder on the latter. An eye in a lug on top affords a con- 
 venient attachment for handling the gun in mounting and dismount- 
 ing. 
 
 The recoil cylinder is of bronze and is closed by a stuffingbox in 
 front and a head and stuffingbox in rear. At about the center a cir- 
 cumferential rib or shoulder is formed on the exterior, which abuts 
 against the loop on the sleeve. The interior of this front portion of the 
 cylinder is bored cylindrically and merely affords the additional length 
 required for the counter-recoil spring over that needed for the move- 
 ment of the piston in recoil. The part of the cylinder in rear of the 
 
ARMAMENT 235 
 
 exterior shoulder is that in which the piston head works and is bored 
 larger. 
 
 The piston and all cross-sections of the cylinder are circular; the 
 oil, therefore, always has an annular opening to pass through while 
 being forced from one side of the piston to the other as the cylinder 
 and piston move relatively to each other. This opening is the annular 
 clearance to the piston (and is equal to the area of cross-section of the 
 cylinder minus the area of cross-section of the piston). This opening 
 is varied by giving the cylinder a different area of cross-section at each 
 point of recoil. The greatest area of cross-section of the cylinder is at 
 the point at which the velocity of retarded recoil is the greatest. The 
 areas are so varied relative to the velocity of retarded recoil that the 
 resistance to recoil (that is, the pull on the piston rod) is nearly con- 
 stant. 
 
 These mounts were designed to use a mixture of glycerin and water 
 in the cylinders, and the earlier mounts as issued w r ere supplied with 
 this mixture. No issues of glycerin are made, however, as the Ordnance 
 Department has found a neutral oil to be superior. This oil, called 
 "hydroline," is now issued and used in these as well as all other hy- 
 draulic recoil cylinders. 
 
 Through the side of the cylinder near the rear end, a filling hole is 
 drilled, closed with a small screw plug. 
 
 The piston head and rod are formed from one piece of steel. The 
 rod extends on both sides of the head, the portion in front, which is 
 longer and larger in diameter, ending in an eye and being threaded for 
 the piston-rod nuts, while the part in rear of the head projects through 
 the rear stuffingbox and serves as a support and guide for the head 
 during recoil. The counter-recoil spring is a coiled spring strung upon 
 the rod in front of the head and abutting against the head and the front 
 end of the cylinder. 
 
 The shoulder bar is a straight bronze arm the forward end of which 
 is shaped to slide into an undercut seat on the oscillating slide. A leaf 
 spring on the bar locks it in its seat. The rear end of the bar is fitted 
 with a wooden shoulderpiece suitably padded with a piece of rubber 
 hose. A bronze handle and a guide or deflector to prevent the ejected 
 cases from hitting the gunner are attached to the left side of the shoulder- 
 piece. 
 
 The shield consists of a steel plate about J inch thick, which is at- 
 tached to the carriage by the four shield braces passing through lugs on 
 the pivot yoke. The upper part of the shield is bent to the rear, 
 forming an angle of 135 degrees with the lower vertical part, and suitable 
 
236 THE SERVICE OF COAST ARTILLERY 
 
 apertures are cut out for the gun, the line of slide, and bolts of the 
 braces. 
 
 The anchorage consists of one V-rod, two anchor bolts and nuts, 
 two anchor plates, and one axle brace and anchor stirrup. 
 
 The brace and stirrup is a steel plate, assembled to and under the 
 ammunition and axle brackets. The stirrup is directly beneath the 
 pivot socket, is braced and reenforced from the rear, and has a hole 
 for the hook of the V-rod. The angle end of the V-rod terminates in a 
 hook through which a pinhole is drilled. The two ends of the rod are 
 permanently connected to the anchor bolts by eyes, and the anchor 
 plates are assembled on the bolts by nuts. 
 
 Two ammunition boxes, each holding nine rounds, are carried on 
 brackets on the axle, on either side of the pivot socket. These boxes 
 are rectangular in shape and, except the door, which is of steel, are 
 made of malleable-iron sheets. The interior is fitted with three tran- 
 soms or partitions, two of malleable iron and one of wood, provided 
 with holes for receiving the ammunition. The door is lined on the 
 inside with felt, is hinged at the bottom, has two steel hangers to support 
 it when open, and is closed by a hasp. Two handles are riveted on each 
 box, and two trunnion bars, one front and one rear, pass through near 
 the bottom and project slightly on either side. 
 
 The brackets which support these boxes fit over the axle, are bolted 
 to the brace, and each has two undercut lugs in the front, into which 
 the trunnion bars of the boxes slip, and two slotted lugs in rear. The 
 rear lugs are drilled and tapped for the screw bolts, which serve as pivots 
 for the box holders. These holders are clips, fitted with springs to 
 retain them in place, which swing over the rear trunnion bars of the 
 ammunition boxes and secure them in place. 
 
 MORTAR CARRIAGES 
 
 The method of mounting mortars is such as to require the classifi- 
 cation of their carriages under a special head. A strict interpretation 
 of the definitions of the other classes readily shows that they are neither 
 barbette, disappearing, masking parapet, or casemate, but rather a 
 combination of the two principal classes. The 12-inch B.-L. mortar 
 mounted on spring return carriage is shown in Plate IV and Fig. 11. 
 
 The carriage is designed to deliver all-around high-angle fire, of 
 from 45 to 65 degrees elevation. It is prevented from creeping after 
 set in azimuth by a traversing brake which must be released before 
 pointing the piece in azimuth. 
 
ARMAMENT 237 
 
 With the 800-pound projectile and full charge, the recoil is approxi- 
 mately 19 inches, measured on the piston-rods. 
 
 The horizontal piece, when fully counter-recoiled, is 54 inches above 
 the loading platform, and the projectile, in loading, is wheeled directly 
 into the breech recess, the tray of the ammunition trucks forming the 
 loading trays. 
 
 It is arranged for either lanyard or electric firing, and in the latter 
 case the pieces may be fired independently or the entire four in a pit 
 at once, from the outlet box, or the battery commander from his station 
 may fire either by pit or by battery. 
 
 After loading, the piece must be again elevated to 43 degrees before 
 the electric connection for firing is automatically made. 
 
 In lanyard fire, the lanyard is hooked into the stopper of the lanyard 
 attachment in the floor plate, the attachment lanyard giving a direct 
 pull on the primer. 
 
 Action of Carriage. Upon firing, the piece and top carriage rotate 
 to the rear and downward about the fulcrum shaft, compressing the 
 counter-recoil springs and forcing the crossheads and piston downward 
 until the resistance in the recoil cylinders stops the motion, after which 
 the compressed counter-recoil springs immediately return the piece to 
 the loading and firing height. The movement of the crank pins through 
 the arc of a circle causes the recoil cylinders and guides to oscillate 
 about their trunnions. 
 
 Principal Parts. The carriage consists of the following principal 
 parts, viz.: Base ring and floor plates, traversing roller system, racer, 
 top carriage or saddle, recoil system, counter-recoil springs and buffer 
 stops, elevating system, traversing system, azimuth circle and pointer, 
 elevation quadrant, lanyard attachment, electrical attachments, and 
 shot trucks and tongs. 
 
 Base Ring. The base ring is of cast iron in one piece, and is secured 
 in its position by twenty-four 1.75-inch anchor bolts. The outer flange 
 of the base ring, 14 feet in diameter, which contains the bolt holes, rests 
 upon the upper step of the well, whose surface is 24.5 inches below the 
 floor level of the emplacement. 
 
 The top surface is turned, forming the lower roller path and a 
 vertical annular flange forms the male part of the pintle. The traversing 
 rack is attached on the inside below the roller path. 
 
 Eight brackets, rigidly supporting the azimuth circle castings, are 
 bolted to the outer flange, these brackets and castings, together with 
 the radial angle irons whose outer ends are embedded in the concrete, 
 furnishing the support for the circle of cast iron removable floor 
 
238 
 
 THE SERVICE OF .COAST ARTILLERY 
 
 plates. There are sixteen plates, retained in position by countersunk 
 screws. 
 
 Traversing Roller System. The racer rests and is traversed upon 
 a circle of twenty-four live, conical, traversing rollers of forged steel, 
 with a single flange. The rollers are 7.5 inches in maximum diameter, 
 and their axes are held in the radial position by a cast-steel distance 
 ring in six sections, in which their bronze-bushed journals have bearings. 
 The distance ring has oil grooves finished around its top edges, reaching 
 through oil tubes in the racer. 
 
 Racer. The racer is of cast iron in one piece, 13 feet 9.5 inches in 
 diameter. Its lower surface is turned, forming the upper roller path, 
 corresponding to the lower roller path on the base ring. The outside 
 annular flange extends downward, fitting over the pintle with 0. 063-inch 
 diametral clearance. It is of cellular structure, and upon its front edge 
 are cast two lugs or brackets, to which the top carriage or saddle is 
 
 GENERAL METHOD OF CONTROLLING THE ENERGY 
 OF RECOIL IN MORTAR CARRIAGES. 
 
 FlG. 20. 
 
 pivoted by means of a forged steel fulcrum shaft. On each side of the 
 longitudinal openings are openings and supporting bearings for the 
 recoil cylinders. The reenforce piec'es, one on either side of the opening, 
 have been added to the original racers to give additional strength at 
 these points. Three removable oil plugs permit oiling the pintle and 
 trave sing rollers. 
 
 Top Carriage. The top carriage or saddle, of cast iron, consists 
 of two arms connected by a heavy web. The upper ends of these arms 
 form the trunnion beds in which the mortar is mounted and carry the 
 crank pins which operate the recoil brake. The saddle is inclined to the 
 rear at an angle of about 41 degrees, the lower ends being held by the 
 fulcrum shaft. Between the fulcrum and the trunnions are placed 
 openings for the spring guide rods and the seat for the cap of the rock- 
 ing counter-recoil springs. 
 
 Recoil System. Fig. 20 shows the general arrangement of the 
 
ARMAMENT 239 
 
 hydraulic brake and its connections in its essential principles and in 
 relative positions of parts for mortar carriages "in battery." 
 
 The recoil is checked by two hydraulic cylinders with return pas- 
 sages. These cylinders are provided with trunnions and oscillate in 
 brackets bolted to the top of the racer on each side of its central opening, 
 their lower ends extending some distance below the racer. 
 
 They are of cast-steel, 7.75 inches interior diameter arid are fitted 
 with 3.5-inch forged-steel piston rods working through stuffing-boxes 
 at both ends of the cylinders. Each stuffingbox contains six rings of 
 0.625-inch-square Garlock water-proof hydraulic packing. 
 
 About the middle of the rod a piston is formed out of the solid, on 
 which is formed a bronze bushing. The connecting or return passages 
 are formed along one side between the ends of each cylinder, entering 
 the upper end immediately above the head, and five holes 0.7-inch in 
 diameter are bored at proper intervals, connecting the passages with the 
 cylinders. The energy of recoil is taken up by the resistance which the 
 fluid offers to being driven through these holes, which are successively 
 closed by passage of the piston over them. Plugs are provided for 
 closing or partly closing the holes. The upper face of each piston 
 has an annular recess, which, at the end of the counter recoil, passes 
 over the annular projection or buffer on the upper, bronze, cylinder head. 
 The fluid thus imprisoned being able to escape by the clearance only, 
 its resistance gradually checks the movement and consequently the 
 mortar returns gently to the firing position. 
 
 Each cylinder has one filling hole, on its rear side, near its upper end. 
 
 For all charges the cylinders should be filled to the level of the filling- 
 holes, removing for this purpose both plugs, so as to permit the air to 
 escape. 
 
 A neutral oil of specific gravity of about 0.85 (such as the hydroline 
 at present issued), is used, and with this oil the working pressure in 
 the cylinders is about 4,000 pounds per square inch and the piston-rod 
 compression about 150,000 pounds. A denser oil would cause a higher 
 pressure in the cylinders and therefore shorten the recoil slightly. 
 
 To give the proper recoil the throttling plugs should be arranged in 
 each cylinder, from top to bottom, as follows: First hole closed; second 
 hole half open; third hole quarter open; fourth and fifth holes open. 
 
 To facilitate inspections, the tops of the throttling plugs have been 
 stamped with a "C," "," "J," and "0" to indicate whether the holes 
 are closed, half open, quarter open, or open. 
 
 The recoil system is at present undergoing certain changes which 
 when completed will result in the return passageway being entirely 
 
240 THE SERVICE OF COAST ARTILLERY 
 
 closed. In place of this passageway three channels about 2| inches 
 wide and varying in depth from .02 to .087 inch have been cut the 
 length of the recoil cylinder. 
 
 If it is desired to measure the recoil, it can be done on one of the 
 piston rods by making several turns around it with fine twine and ty ing- 
 it tightly just where the piston rod enters the stuffingbox. The 
 height of the twine above the stuffingbox, after firing, will indicate the 
 counter recoil, which will also be the recoil if the mortar has returned 
 to the firing position. If it does not return to the firing position the 
 springs should be compressed as hereafter described. 
 
 The lower ends of the hydraulic cylinders are connected by an 
 equalizing pipe, in which is made an emptying coupling, so that the 
 resistance and the pressure in both cylinders shall be equal. The 
 coupling is provided for emptying the cylinders at a convenient po.int. 
 
 Bronze plugs are provided which can be used to replace the equaliz- 
 ing pipes thus continuing the piece in action after their injury. On 
 the top of each cylinder are bolted two guides of cast steel, between 
 which moves a sliding crosshead, into which the upper end of the 
 piston-rod is secured by means of a collar and nut. The crossheads are 
 assembled over the crank pins, of forged steel, which are forced into 
 the saddle, just below the trunnion beds, by hydraulic pressure and 
 riveted. 
 
 Counter-Recoil Springs and Buffer Stops. The saddle is sup- 
 ported at a point about one-third of its length from the fulcrum shaft 
 by five columns of springs. Each column consists of five double-coil 
 helical springs, threaded on a rod of forged steel. These five rods, 
 arranged in a row side by side, are used to give the necessary initial 
 compression to the springs in assembling the carriage, and afterwards 
 serve simply to guide the springs laterally. 
 
 The lower ends of these spring columns rest in a springbox, of cast- 
 iron, and the upper ends bear against a spring cap. 
 
 The springbox is hung, by means of trunnions, in two brackets, of 
 cast iron, bolted to the upper surface of the racer, which permit it to 
 oscillate during recoil to the different inclinations of the spring columns. 
 The spring cap, performing essentially the same office above as the 
 springbox does below, is a thin rectangular steel casting fitting over 
 the top of the spring columns, and having upon its upper surface a 
 well-rounded knife-edge bearing. During recoil this bearing rocks in a 
 groove running across the lower surface of the saddle web. Both the 
 spring cap and box are perforated to allow the ends of the spring rods 
 to pass freely through them. 
 
ARMAMENT 241 
 
 As an additional precaution against shock when returning to the 
 firing position, buffer stops are provided. These are made up of 
 alternate layers of balata and steel plates, and are held between the 
 guides under the caps. The cross heads moving between the guides 
 during counter-recoil strike these buffers when the mortar returns to 
 the firing position, and are maintained in pressure contact under the 
 guide caps by the counter-recoil springs. 
 
 Elevating System. A circular rack of cast steel is bolted longi- 
 tudinally to the mortar on the under side, so that the center from which 
 its pitch line is struck is at the intersection of the axis of the trunnion 
 and bore. This rack engages in a pinion of forged steel mounted on a 
 heavy shaft on the under surface of the saddle web, to which motion 
 is given by gears connecting with a second shaft extending across the 
 upper face of the saddle web and bearing a hand wheel at each end. 
 The saddle web is cored out to permit the passage of the rack in ele- 
 vating. 
 
 The mortar is held in the loading and firing positions by means of 
 a hand nut on the handwheel shaft, which locks that shaft by pressing 
 the steel handwheel pinion against an adjoining bushing, which together 
 form a conical friction clutch. To protect the teeth on the elevating 
 gearing from injury, which may be caused by the inertia effects of the 
 handwheel during the change of elevation in recoil, the elevating shaft 
 has keyed to it a friction cone. This cone fits into the bronze elevating 
 gear, which is loose on its shaft and engages the steel pinion on the 
 handwheel siiaft. By means of a washer and nut the bronze elevating 
 gear may be forced onto the friction cone with any desired pressure, 
 i. e., with sufficient pressure to prevent slipping during elevating or 
 depressing or an undue amount of slipping during the recoil. The 
 friction between cone and gear will be sufficient if the united effort of 
 two men applied to the handwheels is required to cause a slipping when 
 an attempt is made to depress below the minimum. 
 
 An elevation lock is to be applied to lock the mortar in the hori- 
 zontal position against the elevating stop while loading. It consists 
 of a latch bolt with a lever for withdrawing it, arranged on the top of 
 the carriage, engaging with a strike on the elevating rack. It is operated 
 by the cannoneer at the right elevating handwheel. 
 
 Traversing System. The circular traversing rack on the inside of 
 the base ring has meshing with it a pinion on a vertical shaft which 
 passes down through the racer and having at its upper end a worm- 
 wheel. Motion is given the latter by means of two cranks mounted 
 on a worm shaft. The worm shaft, worm wheel, and the part of the 
 
242 THE SERVICE OF COAST ARTILLERY 
 
 vertical shaft above the racer are incased in a cast-iron standard, which 
 has oil and drain holes conveniently placed and also so arranged that 
 the worm and the gear rim run in oil. 
 
 In order to maintain the piece without further movement until fired, 
 after having been set in azimuth, it is expected that a traversing brake 
 will be applied. 
 
 It has been arranged with a pedal in the rear of the cast-iron 
 standard which carries the gearing and so as to be maintained "on" 
 by a coil spring acting to set the brake levers to grip the top and 
 bottom surfaces of the traversing rack, thus retaining the carriage in 
 a fixed position. When about to traverse, the cannoneer at the 'crank 
 places a foot on the pedal, compressing the spring and permitting free 
 movement. 
 
 Azimuth Circle and Pointer. A brass circular strip in eight sections 
 about 1 inch wide graduated to degrees, is attached to the top side 
 of the azimuth-circle castings which surround the racer. Attached to 
 the racer is a small brass pointer or subscale. This pointer is sub- 
 divided to 0.05 of a degree and stamped in hundredths of a degree. 
 After final adjustment it is dowel-pinned to the racer. 
 
 An improved azimuth pointer has been tested. It has a deflec- 
 tion scale for wind and moving targets to be used in combination with 
 deflection scales for the drift of the different projectiles used with the 
 piece. Adjustments are quickly made by means of thumb wheels 
 actuating pinions meshing in fixed racks. 
 
 The whole is protected by a cast-iron cover which, when raised, 
 exposes an electric light for illuminating the scales. 
 
 Elevation Quadrant. To save time in bringing the mortar to the 
 desired elevation and to avoid inaccuracy in placing the quadrant and 
 holding it against its seat a special elevation quadrant has been de- 
 signed. This quadrant is similar to the gunner's quadrant, but perma- 
 nently attached to the right rim-base of the mortar and consists of a 
 bracket with a toothed arc and an arm hinged at the other end. The 
 arm is telescoped and its front bushing carries a bubble, a microm- 
 eter, and a toothed sector which is constantly pressed outward by a 
 spiral spring. The teeth of the sector engage in the teeth of the arc 
 which are cut in degrees, from 45 to 75 degrees. The micrometer, which 
 gives a limited movement to the arm, is graduated to a least reading 
 of 1 minute. The cannoneer at the right-handwheel adjusts the quad- 
 rant at the required angle of fire and when the mortar is loaded sets its 
 elevation by the bubble. 
 
 Lanyard Attachment. In using the firing mechanism, model of 
 
ARMAMENT 243 
 
 1903, at high-angle fire, it is necessary that -the direction of lanyard 
 pull shall be approximately that of the axis of the piece and that 
 the lanyard be arranged to not interfere with the loading opera- 
 tions. 
 
 A short lanyard is attached to the underside of a stopper in the 
 top of the racer in rear of its central opening and extends below a 
 sheave on the pit ladder and thence upward to the firing mech- 
 anism. 
 
 While loading, its hook is placed in an eye screw at the lower edge 
 of the breech. 
 
 The long lanyard is hooked into the eye on the top of the stopper 
 and the stopper and short lanyard drawn to the rear to fire. 
 
 Electrical Attachments. These consist of the firing circuit inclosed 
 in flexible metallic conduit and with its safety attachments and the 
 illumination circuit also inclosed. 
 
 The safety firing switch is designed to prevent firing the mortar 
 electrically until it has been elevated to 43 degrees. It consists of 
 a circuit-breaker attached to the saddle on the right side of the opening 
 for the elevating rack, and a steel cam in the form of an arc of a circle 
 subtending 40 degrees, which is fastened to the right side of the elevating 
 arc. The circuit-breaker holds a plunger, which is constantly pressed 
 outward by a spiral spring, breaking the circuit. On the end of the 
 plunger is a roller which, when the mortar is elevated 43 degrees, moves 
 up an incline on the cam, pressing the plunger and closing the circuit. 
 The plunger is held in this compressed position as the elevation is further 
 increased so that the circuit remains closed at all elevations at which 
 the mortar is fired. 
 
 For general illumination, hooded 16-candlepower incandescent lamps 
 are advantageously placed, the usual 8-candlepower candelabra lamps 
 being placed at the azimuth circle and elevation quadrant. 
 
 All electrical conductors enter the well through a duct in the con- 
 crete, thence they hang in flexible metallic conduit with sufficient slack 
 to permit traversing through the required angle, continuing in a conduit 
 system of wrought-iron pipe, junction-boxes, etc., with interior insu- 
 lation. 
 
 Shot Trucks and Shot Tongs. The shot trucks (Fig. 11) for this 
 carriage are constructed so as to admit of passing the shell directly 
 from the truck into the mortar. Each truck consists of a light rec- 
 tangular framework of steel mounted on four rubber-tired wheels and 
 carrying a pan, in which the shell lies horizontally and at the proper 
 height for loading. This shell pan projects to the front and is designed 
 
244 THE SERVICE OF COAST ARTILLERY 
 
 to enter the breech of the mortar and to supply the place of the usual 
 loading tray. Two straight wooden bars which slip into sockets on 
 each side of the truck serve as handles and the two rear wheels are 
 swiveled to facilitate turning. 
 
 Shot tongs are also provided for placing the projectile on the shot 
 trucks. 
 
CHAPTER VI 
 EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 Explosives. Explosives are divided into three classes, namely: 
 
 Low Explosives or progressive or propelling explosives, which 
 include those used as propelling agents in guns or mortars. 
 
 High Explosives or detonating and disruptive explosives, which 
 are used in shells, torpedoes, mines and for demolitions of all kinds. 
 
 Fulminates or detonators or exploders, which are related to high 
 explosives and used to originate explosive reaction in the first two classes. 
 
 The three classes are distinguished by the character of their explosive 
 reaction, which places them in three distinct divisions in so far as their 
 action is concerned, namely: 1. Explosion proper: explosion of low 
 order; progressive explosion; combustion. 2. Detonation: explosion 
 of high order. 3. Fulmination: a characteristic type of explosion 
 produced by the fulminates. 
 
 Low Explosives. The low explosives are progressive and consist 
 of the charcoal powders and nitrocellulose powders. The charcoal 
 powders are divided into black charcoal powder and brown charcoal 
 powder. 
 
 Black Charcoal Powder has the following ingredients: 75 parts 
 by weight of nitre (saltpetre), 15 parts by weight of charcoal, 10 parts 
 by weight of sulphur. 
 
 Nitre is a salt found in nature as an incrustation on the surface of 
 the soil in certain tropical countries, resulting in such instances from 
 the decomposition of organic matter in the presence of moist alkaline 
 earths. The decomposition of organic matter produces ammonia, which, 
 combining with the oxygen, produces nitric acid. The acid, acting 
 on other salts of potassium, produces the nitrate which in solution 
 percolates through the soil and is left after evaporation as an incrusta- 
 tion on the surface. 
 
 Nitre is also produced artificially by the nitre-bed process. A 
 finely mixed lot of animal and vegetable matter, together with lime- 
 stone, old mortar, wood ashes and any alkaline material, is piled in a 
 high, narrow bed on an impervious floor. One side of the bed is exposed 
 
 245 
 
246 THE SERVICE OF COAST ARTILLERY 
 
 to the prevailing wind, and the opposite side is terraced, the terraces 
 inclining toward the then formed gutters. In these gutters urine from 
 stables is thrown. The temperature is to be kept between 60 and 70 
 degrees F. The chemical action above described takes place in the 
 body of the heap and the soluble nitrates percolating through the mass 
 of the heap appear after evaporation on the exposed side as an incrus- 
 tation. 
 
 The crude nitre obtained from this source contains the nitrates of 
 magnesium and calcium and the chlorides and sulphates of the alkalies 
 and alkaline earths. Before being used nitre has to be separated from 
 these. This is accomplished by making use of the principle of the 
 relative solubilities in water of the substances at different temperatures. 
 The nitre crystallizes first on cooling, leaving the impurities in solution. 
 The most objectionable impurity of those mentioned is the chlorides, on 
 account of their hydroscopic quality. Nitre should always be freed 
 from them and before being used is always tested to determine if they 
 are present. . 
 
 Nitre is distinguished from most other nitrates by the form of its 
 crystals, which are long six-sided prisms; and from most salts other than 
 nitrate by its deflagration when heated on charcoal. 
 
 The value of nitre in explosives is due to the fact that it supplies 
 oxygen to the combustible elements present. Five-sixths of its oxygen 
 is available for its combination with any combustible, the nitrogen 
 coming off from its decomposition being given off in the free state. 
 The temperature of its chemical union with any combustible is very 
 high, as the oxygen is supplied in very concentrated form and not 
 mixed with nitrogen as in the case of air. It has been found that the 
 amount of oxygen in a cubic inch of nitre will occupy 3023 cubic inches 
 at atmospheric pressure and temperature of 60 degrees F. The fact 
 that all nitrates used in explosives act as carriers of oxygen, and break 
 up on the application of heat, thus increasing the temperature of the 
 chemical reaction, makes them of special value in their use as an in- 
 gredient of explosives. 
 
 Carbon or Charcoal is present in nearly all military explosives. Its 
 function in all cases is to combine with oxygen, forming CO or CO 2 or 
 both, the combination producing an elevation of temperature. In 
 explosive mixtures it occurs in the form of pulverized charcoal. 
 
 Charcoal for military purposes is obtained by the destructive 
 distillation of wood, such as willow, alder, dogwood and rye straw. 
 The lighter woods are preferable and are usually used. The charring 
 is done in a metallic cylinder placed in a retort over a furnace fire. The 
 
EXPLOSIVES, PROJECTILES, PRIME KS AND FUSES 247 
 
 effect of heat is to drive off all the volatile parts of the wood, as wood 
 naphtha, water, etc. Charcoal made by this process is called cylindrical 
 charcoal to distinguish it from the common pit charcoal. After charring, 
 the charcoal should be exposed to the air for about two weeks before 
 grinding up for powder. The reason for this delay after charring is 
 the danger of spontaneous combustion. About 30 per cent, of the weight 
 of wood is obtained in the form of charcoal. Charcoal used in the 
 manufacture of brown powder is made from rye straw and is under- 
 charred. Freshly charred charcoal pulverized and 'stored over two 
 feet deep will ignite spontaneously. The charcoal used in black powders 
 contains between 75 to 80 per cent, of carbon, 3 to 5 per cent, of hydro- 
 gen, 10 to 23 per cent, of oxygen and about 2 per cent, of ash. That used 
 in the manufacture of brown powder contains 45 to 48 per cent, of 
 carbon, 5 per cent, of hydrogen, 45 per cent, of oxygen and the remainder 
 is ash. 
 
 Sulphur. The sulphur used is that commonly found in the volcanic 
 districts of the United States, Mexico and Italy. It is usually found in 
 chemical combination in nature in the sulphides and sulphates. The 
 common ores which produce sulphilr are those of iron sulphates (FeS), 
 galena (PbS), zinc-blende (ZnS), black sulphide of antimony (Sb 2 S 3 ) 
 and cinnabar (HgS). The sulphur is obtained from these native ores 
 and from iron and copper pyrites by direct distillation and subsequent 
 refining to free the sulphur from impurities. The value of sulphur as 
 an ingredient of gunpowder is that it reduces the temperature of ignition 
 and produces in the chemical union with oxygen a higher temperature 
 than with carbon, as well as increasing the rate of combustion and 
 pressure of the gases produced. 
 
 MANUFACTURE. As a preliminary step each of the ingredients is 
 purified and then pulverized by grinding. The charcoal is ground in 
 a machine resembling a large coffee mill, and the nitre and sulphur 
 in a mortar mill. The latter consists of a pair of circular-edged rollers 
 traveling around a circular cast-iron bed and revolving about a com- 
 mon horizontal and vertical axis. 
 
 The nitre or sulphur is then spread evenly over the bed to a depth 
 of from one to two inches and reduced to a fine powder. After grinding, 
 the pulverized material of each kind is passed through a sifting reel 
 which consists of a frame cylinder covered with wire cloth, 32 meshes 
 to the inch. The reel is revolved slowly until the particles are fine 
 enough for incorporation. The remainder is reground. 
 
 The sifted materials are weighed out in the relative proportions 
 given above and placed in bags, each lot weighing 50 pounds. These 
 
248 THE SERVICE OF COAST ARTILLERY 
 
 bags are then taken to. the mixing machine, which consists of a copper 
 drum mounted on a horizontal shaft, the capacity of the drum being 
 about 150 pounds. The shaft of the drum is hollow and through it 
 passes a second shaft which carries a series of arms or fliers, and revolves 
 in a direction opposite to that of the first shaft. The process of mixing 
 takes about five minutes. The mixed material is placed in bags 
 which are laid on their side to prevent the ingredients separating 
 in layers according to their specific gravities. They are handled 
 carefully in transportation without jarring or shaking for this same 
 reason. 
 
 The ingredients are now incorporated in the incorporating mill. 
 This is the most important step of the whole process, the object being 
 to bring the ingredients into the closest possible contact so that each 
 particle of the resulting cake will be composed of all the ingredients in 
 their proper proportion. 
 
 The mixed ingredients are spread evenly over the bed of the mill, 
 the layer being not more than one-half nor less than one-fourth of an 
 inch thick. If too thick the incorporation is defective, and if too thin 
 or less than one-fourth of an inch in thickness there is danger of an 
 explosion. 
 
 After the charge has been spread over the bed it is moistened with 
 distilled water, the quantity used depending on the state of the atmos- 
 phere. It is important to secure a uniform moistening, as the nature 
 of the product depends much upon this. The time for incorporation 
 is from three to four hours and the product is called " mill cake." 
 This cake should have a uniform blackish gray color without any white 
 or yellow specks. 
 
 These cakes are put in tubs and placed in small magazines where 
 they are exposed to the action of the air so that all workings, i. e., 
 several charges, may contain about the same percentage of moisture 
 2 to 3 per cent, of water is necessary for good results in the subsequent 
 pressing 
 
 So far as the chemical requirements are concerned the process is 
 now completed, and the subsequent operations have for their object 
 physical effects, and depend upon the use to which the powder is to be 
 put. In order that it may have its rate of burning regulated, the size, 
 density and form of the grain must be fixed. To do this the mill cake 
 is now taken to the breaking-down machine, where it is broken up into 
 lumps of uniform size. The breaking-down machine consists essentially 
 of two pairs of grooved cylinders arranged one pair above the other. 
 The mill cake is passed through these rollers, by which it is broken up 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 249 
 
 into lumps of uniform size. The product after leaving the breaking 
 down machine is called " powdered meal." 
 
 Now in order to granulate the powder it is first pressed into solid 
 compact cakes, called " press cakes." This is done in a hydraulic 
 press, which consists of a press box strong gun-metal box having three 
 of its sides hinged and an hydraulic ram. In filling the press box it is 
 laid on one side and the upper side laid back, the metal plates being 
 held apart in a frame. The powdered meal is now filled in between 
 them, the side is closed down and the box revolves so that it comes 
 under the ram of the hydraulic press. After it is in place pressure is 
 applied and the powdered meal compressed in a hard, compact cake. 
 Pressed cake is then broken up into grains by passing it through 
 the granulating machine. This machine consists of a series of tooth 
 and grooved rollers, the clearance between which and the character 
 of the grooves of teeth being adjusted for the kind of powder 
 desired. 
 
 Under the rollers of the granulating machine are arranged three 
 separate screens. The upper one has eight meshes to the inch, the 
 second sixteen and the third is a copper wire cloth. The screens have 
 a slight slant and the powder collected on each is put in a separate 
 bin. The powder caught on the top screen is too large and is reworked; 
 that on the second screen is common powder; that on the third screen 
 is rifle powder; and that which passes through the lower screen is powder 
 dust. 
 
 To remove the sharp corners of the grains and to free it from the 
 dust the powder is passed through the dusting machine. This consists 
 of horizontal cylindrical frames covered with canvas having 24 meshes 
 to the inch. Several barrels of the powder are placed in these cylinders 
 and the cylinders revolved at about 40 revolutions to the minute. The 
 dusting process requires about one-half hour. It is sometimes desirable 
 to glaze powder, the object being to protect the grain to some extent 
 from moisture and from the formation of dust in transportation. 
 This is accomplished by placing a small quantity of pulverized graphite 
 with the powder grains in a barrel-like receptacle and revolving the 
 latter for a short time. By this process the graphite adheres to the 
 powder grains and forms a smooth surface. 
 
 The final operation in the manufacture of black powder is to remove 
 the excess of moisture by drying. This is done by spreading the powder 
 out over shallow canvas-bottomed frames arranged in tiers over a 
 steam radiator and subjected to a temperature of 130 degrees F. for 
 about eighteen hours. This process causes the production of some 
 
250 THE SERVICE OF COAST ARTILLERY 
 
 dust, and the powder is redusted. Black powder is packed in hundred- 
 pound packages. For commercial use oak barrels with cedar hoops 
 are used, but that for military purposes is packed in the zinc powder- 
 case described in the DEFINITIONS. 
 
 Black Prismatic Powder is made from the ordinary black granu- 
 lated powder, the cannon powder grain being taken as a base. It is 
 made by reworking the black powder by moistening it with 10 per cent, 
 of water and forming it into prisms to the action of a prism p^ress. This 
 press consists essentially of two sets of powerful stamps operating 
 reciprocally through openings in a heavy mould plate. The mould 
 plate has a series of hexagonal moulds in it and is placed so as to be 
 horizontal in the press. The bottoms of these moulds are formed by 
 the ends of the lower series of stamps, each of which has seven needles 
 projecting upwards through perforations in the stamps. The upper 
 series of stamps has also similar perforations. The powder is placed 
 in a hopper the bottom of which has a sliding charging plate which 
 contains a series of measures corresponding to the moulds of the mould 
 plate. The charging plate with its measures filled with powder slides 
 over the mould plate until the measures are directly over the moulds 
 into which the powder drops. The charging plate then slides back. 
 The press is then put in operation, the upper stamps descend into the 
 moulds and the needles pass up into the perforations of the upper 
 stamps and form the perforations of the prisms. By the reciprocating 
 action of the press when the upper stamps have reached their lowest 
 point and begin to ascend, the lower stamps follow them up until the 
 ends of the lower stamps are flush with the top of the mould plate and 
 the upper end -perforating needles. When this position is reached the 
 lower stamps stop and the upper ones continue upward, leaving pris- 
 matic grains free to be pushed off by the edge of the charging plate 
 as it returns carrying a new charge. 
 
 Sphero-hexagonal Powder is a black powder made in a similar 
 way as the prismatic powder just described. It receives its name 
 from the form of the grain, which consists of two half spheres with 
 a narrow six-sided hexagonal prism at the diameter. 
 
 Brown Charcoal Powder has the following ingredients: 80 parts 
 by weight of nitre, 16 parts by weight of charcoal, 3 parts by weight of 
 sulphur and 1 part by weight of moisture. The charcoal is made of 
 rye straw and is under-charred. The color of the powder, which is a 
 brown or cocoa color, is due to this fact. The method of manufacture 
 and the ingredients are the same as described for the manufacture of 
 black charcoal powder. Brown powder burns more slowly than black 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 251 
 
 powder, and with lower pressure in the chamber of the gun. The 
 explosion is more uniform and the stresses produced in the bore 
 of the gun are not so great, thus increasing the endurance of the 
 gun. 
 
 Brown Prismatic Powder is made in exactly the same way as that 
 described for black prismatic powder, the brown granulated powder 
 being taken as the base. 
 
 Nitrocellulose or Smokeless Powder is an explosive compound. It 
 is distinguished from an explosive mixture like the charcoal powders 
 in which the ingredients are mixed mechanically, in that the con- 
 stituents are brought together through a chemical reaction. The 
 word powder is misleading as applied to modern propellants, in that 
 they are made in a variety of forms which do not bear any resemblance 
 to a powder, but take the shape of tubes, cord, strips, flakes or 
 cubes. 
 
 Nitrocellulose is the base of all smokeless powders. Its molecule 
 contains carbon, hydrogen and oxygen, so that when conditions favor- 
 able to the combination of these elements are produced, the gaseous 
 oxides of carbon and water vapor are formed. 
 
 Any substance whose molecules contain carbon, hydrogen and oxy- 
 gen in the proportion to give CO, or CO 2 and H 2 O may become an 
 explosive. One w T hich is so constituted and at the same time has weak 
 molecular, bonds due to the presence of some other element or radical, 
 is an explosive. 
 
 The principal ingredients of nitrocellulose powder consist of 
 cellulose, nitric acid, sulphuric acid, ether and alcohol. The manu- 
 facture of nitrocellulose powder consists of the following essential 
 steps : 
 
 Cleaning. The cotton waste or cotton rags are brought into the 
 washing house in large bales. These are broken open and put into 
 the washer. This consists of a large iron tank with pipes running 
 through the center. The tank is filled with a solution of caustic soda, 
 and the cotton waste about 175 pounds of caustic soda to 200 pounds 
 of the cotton waste. The washer is slowly revolved, keeping the 
 mass constantly agitated. The temperature is retained at 120 to 
 130 degrees F., and the washing continues for four hours, the object 
 being to remove any oil or grease from the waste or rags. After being 
 washed for four hours the product is taken from the washhouse to the 
 centrifugal wringer and wrung as dry as possible, after which it is 
 returned to the washer and washed in clear, pure water. It is then 
 wrung out a second time in the centrifugal wringer and taken to the 
 
252 THE SERVICE OF COAST ARTILLERY 
 
 picker, which consists of two horizontal toothed cylinders revolving 
 in opposite directions. The cotton waste is then placed on a wooden 
 apron arid fed into the picker, which tears it apart, removing all knots 
 and tangles and delivers it in finely shredded strips about an inch long 
 and one-quarter of an inch wide. 
 
 Drying. The cotton from the picker is collected in boxes and 
 taken into the drying house, where it is placed in large wooden bins 
 having perforated bottoms. Hot air at a temperature of 90 to 105 
 degrees C. is forced up through the bins as the cotton is turned from 
 time to time by hand. The process of drying requires about eight 
 hours, at the end of which time the cotton should not contain more 
 than five-tenths of one per cent, of water. 
 
 Nitrating. The cotton, having been dried, is placed in air-tight 
 cans and taken to the nitrating house. The object of packing it in air- 
 tight cans is to prevent the dry cellulose from absorbing water from 
 the air. The nitrating is done in a centrifugal machine. One can 
 of the dry cotton, containing about 16 pounds, is placed in the nitrating 
 machine with 900 pounds of mixed acids consisting of 50 per cent, 
 sulphuric and 28 per cent, nitric. The mixed acids are drawn from 
 a large tank called the mixed acid tank. The charge is kept in the 
 nitrating machine for about 30 minutes, during which time it is turned 
 over with iron forks. In becoming nitrated the cotton increases in 
 weight about one-half, the 16 pounds of cellulose giving about 24 pounds 
 of nitrocellulose. It will be noted that the process of nitration changes 
 the cotton or cellulose into nitrocellulose or cellulose nitrated. The 
 powder contains about 12.6 per cent, of nitrogen as well as free acids and 
 alkali used in the manufacture, and some unnitrated cellulose. At 
 the end of 30 minutes the drain cocks of the nitrating machine are 
 opened, the machine started, and spent acid forced out by centrifugal 
 action. 
 
 Purification. The rest of the process, which is very essential to 
 the production of stable smokeless powder, consists in removing the 
 impurities left in the nitrocellulose in the manufacture. The free 
 acids and unstable nitro by-products must be removed in order that 
 the nitrocellulose may be kept, even in the dry state, at ordinary 
 temperature without deterioration. Nitrocellulose is taken at once 
 from the nitrating machine and immersed in a large quantity of pure 
 water, and left there for eight hours, two changes of water being made 
 during that time. It is then taken to the centrifugal machine and, 
 while revolved in this, cold water is played upon it with a hose for 
 about ten minutes. The machine is then revolved at its highest speed 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 253 
 
 and the nitrocellulose wrung as dry as possible. When about 1,000 
 pounds has been treated in this manner, it is given a definite number 
 known as its "lot number/' which it retains throughout its manu- 
 facture, and all subsequent operations are recorded in reference to this 
 number. The size of a lot may sometimes vary, depending upon the 
 place of manufacture. The lot is now taken to the purifying tanks, 
 which are large wooden tanks with steam pipes arranged over the 
 bottom. Steam circulates through these pipes and keeps the cellulose 
 znd water at the desired temperature. Pure water is put in the tank 
 and one lot put in. The lot is kept in the purifying tanks for two 
 days, the temperature being kept at 80 degrees C., and the water is 
 renewed three times during this period. At each renewal the tempera- 
 ture is increased to 100 degrees C. for 2 hours. The mass is kept 
 agitated by revolving arms set at different angles. From the purify- 
 ing tanks the nitrocellulose is taken to the centrifugal machine, where 
 it is washed with pure cold water from a hose for ten minutes. It 
 then goes to the pulper. 
 
 Pulping. The pulper is an ordinary pulping machine used in paper 
 mills. It consists of an oval-shaped vat or tank with a horizontal 
 shaft passing across its narrowest dimension. On one end of this 
 shaft is a drum which has on its outer surface a series of parallel knife 
 edges. Directly below the drum is a concentric surface with a second 
 series of knife edges. Pure water circulates slowly throughout the vat, 
 running in at one point and overflowing at the other. From 600 to 
 1,000 pounds of nitrocellulose from the purifying tank is placed at one 
 time in the pulper. The drum in revolving pulls the cotton down and 
 forces it between the two series of knife edges, cutting it finer and 
 finer until the whole mass is a smooth, even, fine pulp, about the con- 
 sistency of corn meal. This requires about six hours. The contents 
 of the vat are submitted to an acid test from time to time, to determine 
 if any free acid is being liberated as the pulping proceeds. Should 
 the test show the presence of free acid, sufficient sodium carbonate 
 is added to neutralize the acid. 
 
 Poaching. The poacher consists of a large deep cylindrical vat 
 with a propeller-shaped wheel on a vertical axis near its bottom. Steam 
 pipes are placed over the bottom. The cotton is taken from the 
 pulper and put in the poacher, and subjected to the action of a boiling 
 carbonate of soda solution. It is then rewashed in cold water as in 
 the purifying vats, the process continuing for three days, having twelve 
 changes of water, and two hdurs boiling at each change. The propeller 
 keeps the mass circulating throughout the entire process. The iiitro- 
 
254 THE SERVICE OF COAST ARTILLERY 
 
 cotton is then taken from the poacher and dumped into a large volume 
 of pure cold water which is contained in a large trough. An endless 
 belt of coarse cotton cloth which, at some distance outside of the 
 trough, passes between two rollers, circulates through the trough. As 
 the belt moves through the mass of suspended cotton a certain quantity 
 adheres to it, and the belt carries this up through the rollers, which 
 squeeze out the surplus water. The cotton is detached Trom the belt 
 by a scraper, and falls into receptacles placed on the other side of the 
 rollers. The cotton is now in the form of small thin flakes and is 
 called "pyro," and contains about 58 per cent, of water. At this 
 point it is submitted to careful laboratory tests. If this mass was 
 now compressed into blocks it would be in the usual form of gun- 
 cottori. 
 
 Dehydrating. The pyro is now taken to the dehydrating press 
 and the water is extracted by means of alcohol, which is forced through 
 the pyro by air pressure, the alcohol displacing the water. Sufficient 
 alcohol is left in the cotton to accomplish its colloidization, when ether 
 is added in the next operation. About 15 pounds of pyro is placed in 
 the cylinder of the dehydrating press and subjected to a pressure of 
 200 pounds to the square inch. This forms it into a cylindrical cheese. 
 Not all of the water is forced out by this pressure, so about 14 pounds 
 of alcohol is let into the cylinder. Air is now admitted over the alcohol 
 and subjected to a pressure of 100 pounds to the square inch. This 
 forces the alcohol through the pyro, the liquid flowing out through the 
 pipe below. First water comes out, then a mixture of water and 
 alcohol, and finally alcohol of full strength. A pressure of 3,000 pounds 
 per square inch is now put on the cheese, and more of the alcohol forced 
 out, enough remaining, however, for colloiding. 
 
 Colloidization. The pyro-cheese, weighing about 17 pounds, 
 is taken from the dehydrating press to the colloiding machine, which 
 is an ordinary kneading machine. Three of the pyro cheeses are 
 broken up and put into the kneader with about one-half of their weight 
 of ether. The kneader is started and the charge is mixed until all the 
 ether is absorbed, which as a rule requires about two hours. At the 
 end of this time the colloiding is finished, and the product should be 
 a smooth compact colloid with a clear amber or light-brown color. 
 The colloid is pressed into a cake by hydraulic pressure, and should 
 show a few white spots when finished, which are caused by air 
 bubbles. 
 
 Granulation. The colloid cake is now put through the macaroni 
 press, which is a hydraulic press having small holes in the bottom of 
 
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256 THE SERVICE OF COAST ARTILLERY 
 
 its cylinder. The .colloid is forced by a pressure of 500 pounds through 
 these small holes and falls in a receptacle below in macaroni-like strings. 
 The object of this operation is to free the colloid from air bubbles 
 and to blend it better. The macaroni-like strings are collected and put 
 into the final press, where they are pressed into a cake^ known as the 
 powder cake. The powder cake is put through the die press, which is 
 a horizontal press with a cone-shaped cylinder, into the apex of which 
 is fitted the die with needles of the proper size for the perforation. 
 The continuous pressure forces the colloid into the cone and out through 
 the die, the needles making the perforations. The rope-like cylinder 
 of the diameter of t]jie powder grain is carried on rollers along the table 
 on which the press rests, until it reaches a point where it is cut into 
 grains of the proper length by a revolving disc. The die can be changed 
 so that any size grain may be formed. 
 
 Drying. The grains from the die press are collected in cans with 
 woven wire bottoms and are taken to the solvent-recovery house, 
 where hot air is forced up through the grains. This hot air carries 
 off a portion of the solvent, and the grains shrink accordingly. The 
 powder is now taken to the dry house, where it kept from two to four 
 months in a drying temperature from 100 to 105 degrees F. 
 
 Lot Number. A record is kept of each "pyro lot," and several of 
 these lots are allowed to accumulate, after which they are blended 
 and receive a "lot number." The blend lot number is indexed and is 
 that which reaches the service. 
 
 Cordite. This is a British smokeless powder composed of 37 parts 
 guncotton, 58 parts nitro-glycerine, and 5 parts vaseline. This powder 
 gives very high muzzle velocities with low pressures, but the temperature 
 of its explosion is so high as to cause a rapid erosion of the bore. For 
 this reason the percentage of nitroglycerine has gradually been reduced 
 and the result is given in the new powder called "Cordite M. B." which 
 contains 58 parts guncotton, 37 parts nitroglycerine and 5 parts 
 vaseline. 
 
 Brown Prismatic Powder may be used in the 8-, 10-, and 12-inch 
 rifles and the 12-inch mortars. As this powder rapidly deteriorates 
 it may be necessary to increase the charge to the capacity of the 
 chamber to obtain the proof velocity. This involves the building up 
 of charges, the operation* of which, in the case of this powder, consists 
 of stringing the grains on wires to make the required height of the charge, 
 as shown in the following table: 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 257 
 
 
 
 Length of 
 
 
 
 
 I 
 
 Section 
 (Number of 
 
 Full Charge. 
 
 Maximum 
 Charge. 
 
 
 1. 
 
 Prisms.) 
 
 
 
 
 u * 
 
 g 
 
 g 
 
 A 
 
 .s . s 
 
 .4 
 
 .S , 
 
 
 |6 
 
 s 
 
 
 *> c 
 
 got 
 
 || 
 
 ill 
 
 
 3.5 
 
 3 
 
 03 
 
 '53 ^ 
 
 .^6^ 
 
 
 .20 w 
 
 
 fe 
 
 i 
 
 a 
 
 J 
 
 AH 
 
 f 
 
 * 
 
 8-inch breech-loading rifle . 
 
 2 
 
 23 
 
 24 
 
 135 
 
 31 
 
 154 
 
 34 
 
 
 2 
 
 30 
 
 31 
 
 280 
 
 48 
 
 320 
 
 55 
 
 
 / 3 
 1*1 
 
 18 
 18 
 
 1-8 
 19 
 
 380 
 110 
 
 76 
 61 
 
 450 
 110 
 
 85 
 61 
 
 
 12-inch breech-loading mortar, cast- 
 
 
 
 
 
 
 
 
 iron hooped 
 
 1 
 
 
 14 
 
 75 
 
 61 
 
 81 
 
 61 
 
 12-inch breech-loading mortar 
 
 1 
 
 
 19 
 
 105 
 
 61 
 
 110 
 
 61 
 
 
 
 * Cone Section. 
 
 After the charges are built up the black powder priming charge is 
 placed in position on top of the charge and the serge silk bags slipped 
 down over the form. The charge is then inverted and another priming 
 charge placed on what is now the top. The bag is then sewed up with 
 silk thread; then weighed; and, in the case of mortars, the zone 
 number marked thereon. 
 
 For brown prismatic powder either one of two forms of igniter may 
 be used, namely: 1. Seven black prisms in the center of the bottom 
 layer of each section of the cartridge. With this igniter the bottom 
 of the bag next to the vent must be cut when loaded to insure ignition. 
 2. In this case the bag is made with a double bottom; the outside 
 thickness is of the same cloth as the bag, but the inside thickness is 
 of a lighter cloth such as that used in field and siege cartridges. About 
 2 ounces of rifle powder for the 8-inch rifle and 3 ounces for the 10- and 
 12-inch sections are spread between these two bottoms, more thickly 
 toward the middle, the bottom is then quilted in about 1-inch squares 
 to retain the powder in place. 
 
 Each lot of powder or cartridge issued is marked for the weight of 
 charge and proof velocity and pressure; these are to be considered the 
 standard for that powder, unless subsequent changes are announced 
 in orders. The propelling charges of smokeless powder for both the 
 reserve supply and target practice are issued in hermetically sealed 
 cartridge storage cases. 
 
 No changes in these powder charges are allowable without the ex- 
 press authorization contained in orders or in instructions from the 
 hief of Ordnance. Changes in charges should always be made with 
 
258 THE SERVICE OF COAST ARTILLERY 
 
 care, even when, by calculation, the pressures appear to be within 
 the safe limits. All lots of smokeless powder that have been tested 
 in recent years, except those specially noted, have been adjusted to 
 give the prescribed muzzle velocity when fired at the standard temper- 
 ature of 70 degrees F. When powder is used at any other temperature 
 than that of the standard, correction must be made therefor. See 
 "Powder chart." In some of the earlier tests of lots of smokeless 
 powder, only the temperature of the air, and not that of the powder 
 at the time of firing was recorded. 
 
 To avoid irregular and sometimes excessive pressures, the total 
 length of charge of guns should really equal the length of chamber,, 
 and should never be less than 9/10 of that length. When reduction 
 of the charge is found necessary care must be taken that the new 
 cartridge made is firm and that the bag is of the necessary diameter 
 and uniform over its length. The requirement as to length of charge 
 is not necessary in the case of mortars. 
 
 Smokeless powder may be used in all types of guns. Before build- 
 ing up charges of smokeless powder or before using those that are 
 issued already built up it is necessary that the entire amount of powder 
 to be used is thoroughly blended. 
 
 Blending. The method of blending powder just prior to its use 
 is as follows : A suitable floor space is first covered with paulins around 
 the outer edge of which are placed boards (1x12 inches), supported by 
 brackets to keep them in place and prevent the powder from scattering. 
 All the powder to be used is taken from the cases and bags, and placed 
 in a single pile in the center of the covered space. Ten men, provided 
 with wooden shovels, form 10 circumferential piles by shoveling care- 
 fully from the bottom of the large center pile to the tops of the 10 
 smaller piles until the center pile is exhausted. The powder from the 
 10 small piles is then shoveled from the bottom of each to the top of 
 the large center pile, each shovelful being scattered over the pile as 
 much as possible during the operation. The operation of shoveling 
 from the center pile to the 10 small piles and back again forms one 
 cycle of the blending process, and to thoroughly blend a lot of powder 
 requires 5 cycles. 
 
 Nitroglycerin and nitrocellulose powders must not be blended 
 together. Each charge should always be made up from the same 
 lot of powder. 
 
 In blending smokeless powder it should not be done in the direct 
 rays of the sun. 
 
 Only powders of the same lot are blended together. Charges for a, 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 259 
 
 given zone, weight of projectile or model of gun, should not be changed 
 for any other zone, weight of projectile or model of gun. 
 
 With nitrocellulose and nitroglycerin powder charges, the bag is 
 opened and the powder charge shoveled in. The section is then laid 
 on a table and rolled to get it as compact as possible before beginning 
 to lace it. To avoid bulging in the center, the lacing is commenced 
 at the middle and carried towards each end, in order to keep the section 
 of uniform diameter. 
 
 In lacing, place the point of the needle close to and outside the seam 
 or plait, letting the needle come out between it and the expansion 
 plait and pass over the latter; lace from left to right and right to left, 
 taking stitches about one and one-half inches apart. After lacing 
 about 4 inches of the length of the bag, draw the lacing taut and tie 
 the twine, so that if the twine should break in handling, the section 
 cannot lose more than 4 inches. 
 
 Cartridge bags for 5 and 6-inch rapid-fire guns have no extension 
 plait. 
 
 The dimensions of the sections of cartridges of smokeless powder 
 made up with the average charges of powder are given in the following 
 table : 
 
 
 Charge. 
 Pounds. 
 
 Cartridge (or Section.) 
 
 Number 
 of 
 Sections. 
 
 Diameter, 
 Inches. 
 
 Length, 
 Inches. 
 
 5-inch rapid-fire gun, model 1897 
 5-inch rapid-fire gun, model 1900 
 6-inch rapid-fire gun, model 1897 
 6-inch rapid-fire gun, models 1900, 1903 and 
 1905 
 
 16.4 
 23.0 
 
 29.7 
 
 39.1 
 80.0 
 155.0 
 205.0 
 275.0 
 325.0 
 33.0 
 62.0 
 
 1 
 1 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 4 
 4 
 1 
 1 
 
 5.25 
 5.75 
 6.00 
 
 6.90 
 8.25 
 10.25 
 12.00 
 * 12.25 
 f 14.00 
 10.75 
 12.00 
 
 27.00 
 34.50 
 32.00 
 
 41.00 
 24.00 
 30.00 
 J 33.00 
 18.25 
 20.25 
 15.00 
 20.00 
 
 8-inch rifle 
 10-inch rifle, models 1888 and 1895 
 
 10-inch rifle, model 1900 
 12-inch rifle, models 1888 and 1895 
 
 12-inch rifle, model 1900 
 12-inch mortar, cast-iron, hooped 
 
 12-inch mortar, steel 
 
 
 * 12.25 to 13. 
 
 t 14 to 14.5. 
 
 I 33 to 35. 
 
 20.25 to 21.25. 
 
 Igniting Charges. These charges are composed of black rifle 
 powder. As explained above they are placed in position at each end 
 of the sections of the charge, their function being to properly ignite 
 the less inflammable charge of smokeless powder. 
 
260 THE SERVICE OF COAST ARTILLERY 
 
 The weight of igniting charges will be found in the table of weights 
 of powder charges, etc., on page 255. 
 
 Blank Ammunition. Blank ammunition is used in firing salutes, 
 for maneuver firings, and for the morning and evening gun, and for 
 instruction purposes. 
 
 All firings with blank ammunition, whether with breech or muzzle- 
 loading guns, is under the personal supervision of a commissioned 
 officer who is present at the firing and directs it. Whenever more than 
 1 round is fired from any gun or guns he sees that the chamber of 
 breech-loading guns and the bore of muzzle-loading guns is carefully 
 sponged out with a damp sponge, to extinguish sparks and remove 
 powder residue after each round and before the insertion of another 
 round. 
 
 Care must be exercised to see that the sponges are not worn and 
 that they thoroughly fill the chamber or bore. The interval between 
 rounds of blank ammunition should be sufficient to allow thorough 
 sponging of the chamber or bore and examination to ascertain that all 
 sparks have been extinguished. 
 
 Guns using metallic ammunition are employed whenever practicable 
 in firing blank ammunition; in their absence breech-loading guns 
 using loose ammunition should preferably be used. 
 
 Muzzle loaders are used only when breech loaders are not available. 
 When using muzzle-loading guns a sufficient number should be employed 
 to avoid the necessity of firing the same gun until a reasonable interval 
 has elapsed. 
 
 The cartridge bags for muzzle-loading guns or breech-loading guns 
 not using fixed ammunition are of silk, chemically treated to make 
 it as non-inflammable as possible, and the cartridges are made to measure 
 in length at least 1^ times the diameter. 
 
 It has been found difficult to tie the open end of the cartridge bags 
 heretofore used for blank charges in such a manner as to prevent that 
 end opening and permitting powder grains to leak out. The cartridge 
 bags now issued have both ends alike. There is an opening left between 
 the circular disk forming the front end of the bag and the body, which 
 should be closed by sewing after the charge has been inserted. 
 
 The post ordnance officer before issuing cartridges for blank am- 
 munition firing to organizations sees that the bags are in sound condi- 
 tion and that no powder can escape therefrom, and the bags are inspected 
 further as to their condition in this respect by the commissioned officer 
 in charge of the firing before their use. 
 
 Unless all the above conditions be fulfilled blank ammunition should 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 261 
 
 not be fired with breech-loading guns using non-metallic ammunition 
 or with muzzle-loading guns. 
 
 Blank metallic ammunition for saluting and maneuver purposes 
 is assembled at posts. For this purpose there are issued saluting 
 cartridge cases, saluting powder in bulk, tight-fitting felt wads, primers, 
 adapters, etc.; also reloading, decapping, and cleaning outfits. The 
 cartridge cases are issued unprimed, with primers in separate moisture- 
 proof tin boxes, and are not primed until just before inserting the 
 powder charge and the wad. Cartridge cases should never be primed 
 after the powder charge has been inserted. 
 
 The same care must be exercised in sponging the chamber with guns 
 using metallic ammunition as with guns using non-metallic ammunition. 
 
 Saluting cartridge cases for 6-pounder, 15-pounder, 4-inch, 4.72-inch, 
 and 6-inch guns may be distinguished from service cartridge cases by 
 the fact that they are considerably shorter than the service case. 
 Service cases of the above calibers will under no consideration be used 
 in the preparation of blank ammunition. For all other guns using 
 metallic ammunition the service case and the saluting-cartridge case 
 are the same. 
 
 Primers will not be removed from the hermetically sealed cases in 
 which they are received until they are to be used. They are made a 
 tight fit in the primer seat of the cartridge case, and should be pressed 
 into place with the inserting press and not hammered in. 
 
 In preparing saluting ammunition the following instructions must 
 be observed: 
 
 (a) Before assembling, the saluting case should be inspected to see 
 that it is thoroughly clean and dry. The primer will then be inserted 
 with the inserting press ; after which the proper weight of loose powder 
 will be poured into the case and shaken down. 
 
 (b) A felt wad will next be inserted and pressed down hard until 
 it rests squarely on the powder charge. 
 
 (c) The wad will then be made fast to the cartridge case, to prevent 
 its being dislodged in handling, in the following manner: Pour rub- 
 berine paint upon the surface of the wad and case until it forms a layer 
 over the surface about a sixteenth of an inch thick. Allow the case 
 to stand from 10 to 20 minutes, until the paint has dried and been 
 partly absorbed by the wad. Then pour in an additional amount of 
 paint around the edges of the wad to entirely seal the joint between 
 the wad and the cartridge case, and also to form a layer on the side of 
 the cartridge case from .02 to .03 of an inch in thickness. 
 
 The rubberine paint is very tough and strongly adhesive, and if 
 
262 
 
 THE SERVICE OF COAST ARTILLERY 
 
 used as directed will prevent danger of wads dropping out in 
 handling. 
 
 The wads, when issued, are a tight fit in the cartridge case for which 
 they are intended. If, after storage, it is found that any have shrunken 
 so as to fit loosely they should not be used, but a report on their condition 
 made to the proper authority in order that they may be replaced. 
 
 If rubberine paint is not available, any other quick-drying paint 
 issued by the Ordnance Department for coating cavities of projectiles 
 may be used instead. 
 
 Blank ammunition for saluting purposes and for morning and 
 evening gun should be made up in lots of 25 cartridges (the number 
 of primers contained in a box), but a new lot should not be made up 
 until two or three days before the supply on hand is exhausted. 
 
 WEIGHTS OF SALUTING POWDER CHARGES 
 
 Gun. 
 
 1-pounder subcaliber 
 
 6-pounder (2.24-inch) rapid-fire gun 
 
 2.95-inch subcaliber tube 
 
 3-inch wrought-iron gun, saluting * . , 
 15-pounder (3-inch) rapid-fire gun. . 
 
 3-inch gun (M. L.) 
 
 6-pounder (3. 67-inch), bronze 
 
 4-inch rapid-fire gun 
 
 4.72-inch rapid-fire gun, Armstrong . , 
 5-inch rapid-fire gun (Ord. Dept.) . . , 
 
 6-inch rapid-fire gun, Armstrong 
 
 6-inch rapid-fire gun (Ord. Dept.) . . 
 
 8-inch converted rifle 
 
 8-inch smoothbore gun 
 
 10-inch smoothbore gun 
 
 8-inch rifle 
 
 10-inch rifle , . . 
 
 12-inch rifle 
 
 12-inch mortar. . 
 
 Charge. 
 
 5i ounces saluting powder, 
 li pounds saluting powder. 
 
 1 pound 6 ounces saluting powder. 
 
 11 pounds saluting powder. 
 
 2 pounds saluting powder. 
 
 1 pound mortar or saluting powder. 
 1 pound mortar or saluting powder. 
 
 4 pounds saluting powder. 
 
 5 pounds saluting powder. 
 5 pounds saluting powder, f 
 5 pounds saluting powder. 
 8 pounds saluting powder. f 
 7 pounds saluting powder. 
 7 pounds saluting powder. 
 10 pounds saluting powder. 
 
 12 pounds saluting powder. f 
 18 pounds saluting powder. f 
 30 pounds saluting powder, f 
 18 pounds saluting powder. f 
 
 * This gun uses the standard 6-pounder saluting case, 
 t Used during maneuvers only if specially authorized. 
 NOTE. Smokeless powder will not be used for blank charges. 
 
 Blank metallic ammunition should be assembled under the personal 
 supervision of a commissioned officer, who should be held responsible 
 that tbe ammunition is prepared and the wads secured as prescribed 
 above, and who will mark the cartridge cases with his initials to indi- 
 cate that the round has been assembled properly, and no blank metallic 
 ammunition on which his initials do not appear will be used. Cases 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 263 
 
 should be marked in such manner that the marks may be removed 
 after the charges have been fired. 
 
 The primer-inserting press issued is made especially for the 15- 
 pounder seacoast gun, bushings being provided for guns of less caliber 
 using fixed ammunition. Each post is furnished with one of these 
 presses and such bushings as may be required, also decapping and 
 cleaning outfits. 
 
 Metallic powder barrels of 25 pounds capacity or over should be 
 returned to the depot or arsenal from which shipped; when emptied, 
 care should be taken to store in a dry place. 
 
 The table on the opposite page shows the authorized weights of 
 blank charges used in saluting, etc. 
 
 High Explosives. The high explosives are disruptive, and consist 
 of the shell-fillers, those used in torpedoes, mines and for demolition 
 purposes. Those in general use are: Gun cotton, nitroglycerine, picric 
 acid, dynamite, explosive "D," maximite, trinitrotoluol and blasting 
 gelatine. 
 
 The action of explosives of this class is entirely different from 
 that of those of the low order. In this case the explosion is not con- 
 fined to the surfaces of the substances exploded, but appears to progress 
 radially in all directions throughout the mass from the initial point. 
 The time is extremely short and the effect is to transfer the explosive 
 from the solid or liquid state to the gaseous state in an almost inappre- 
 ciably brief interval. The gases are increased very rapidly in volume 
 and pressure by the heat of the combination. 
 
 Gun Cotton. This explosive is a nitrocellulose of high nitration 
 or containing more than 12.9 per cent, of nitrogen. 
 
 Its manufacture is practically the same as that described for nitro- 
 cellulose powders, except that the process is discontinued before 
 colloidization takes place. When made for military purposes the 
 purified pulp is taken from the poacher to a stuff chest by suction. 
 This chest consists of a large vat with an air-tight top. Through the 
 center of the vat passes a vertical shaft upon which are mounted a 
 number of paddles. The purified pulp having been sucked up into 
 the stuff chest is kept agitated by these paddles so that, the pulp will 
 be evenly distributed in suspension through the liquid. From the 
 stuff chest the pulp is drawn into the moulding press. This is a 
 hydraulic press made of bronze and containing four moulds. The 
 pulp is run into these moulds and a pressure applied for about four 
 minutes. The mould press blocks are then placed in the mould of 
 the final press and a pressure of from 6,000 to 7,000 pounds is appliedc 
 
264 THE SERVICE OF COAST ARTILLERY % 
 
 While in this press they are stamped with the name of the manufac- 
 turer, the lot and the year. 
 
 The blocks from the final press contain about 15 per cent, water, 
 but before being issued for storage they should be soaked in pure water 
 until they contain about 25 per cent, of water. 
 
 Gun cotton is recommended for use (when wet) for mines, torpedoes 
 and demolitions of all kinds. Its great value as a disruptive agent 
 rests upon its great force and in its safety in manufacture, storage 
 and handling. It is less liable to accident or spontaneous explosion 
 than any other explosive now used, and when kept in storage in a wet 
 state it is non-explosive except with a powerful detonator or a small 
 piece of dry gun cotton. 
 
 Cold has no effect on dry gun cotton. If wet and exposed to 
 freezing and thawing, the compressed cakes or disks will flake off on 
 the surface; the -freezing also causes the mass of the cake or disk to 
 open out and be less compact. Variations of temperature between 
 32 degrees and 135 degrees F. have no effect on either the physical 
 or chemical condition of gun cotton. Even when dry it is not liable 
 to explode by a blow or friction unless very closely confined and com- 
 pressed. When wet in any form it cannot be ignited by flame, and a 
 wet disk when thrown into a fire will first dry out on the outer surface 
 and burn there, continuing this progressively until consumed. 
 
 Gun cotton when wet explodes more brusquely than when dry, 
 because the water in the pores being incompressible increases the 
 velocity of the explosive wave. It has been found by experiment 
 to detonate wet gun cotton with a dry priming charge of gun cotton, 
 the main charge and priming charge must be in intimate contact, 
 that is, they must not be separated by material of any great thicknesss. 
 
 Owing to its safety in handling and storage it is of great value as 
 an explosive for submarine mines and is used almost exclusively for 
 that purpose when it can be procured. 
 
 It is ordinarily packed in a wooden zinc-lined case, the lid of which 
 has an opening with a screw top, in which water is periodically poured, 
 in order to keep the charge thoroughly saturated or up to its wet 
 weight. These cases are weighed quarterly and should they be found 
 to weigh less than their registered gross weight the deficiency is made 
 by adding distilled water. 
 
 Dry gun cotton is used as a priming charge for submarine mines and 
 comes packed wet in glass jars. Before being used for this purpose it is 
 necessary to dry the charge, in a warm room, until weighing on two 
 successive days fails to show any loss due to evaporation. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 265 
 
 In color gun cotton varies from white to light yellow and is usually 
 issued in the form of compressed cakes or that of the pulp form. 
 
 Nitroglycerine consists of glycerine, nitric acid and sulphuric acid. 
 
 The process of manufacture is as follows : A large amount of glycerine 
 is nitrated by gradually allowing a small amount of glycerine to enter 
 into the presence of mixed acids in succession. The acids, which 
 consist of two parts by weight of sulphuric acid specific gravity 1.845, 
 to one part of nitric acid specific gravity 1.150, are placed in a lead- 
 lined chamber above which is a tank containing the glycerine, the two 
 being connected by a pipe having a coil with numerous fine holes on 
 the bottom of the acid chamber. A pipe running into the top of the 
 glycerine tank supplies compressed air, which forces the glycerine down 
 into the acids. If the temperature of the acid chamber rises above 
 86 degrees F. and cannot be controlled by stopping the admission of 
 glycerine the compressed-air pipes leading into this chamber are opened 
 and the acid tanks cooled by the expansion of the air. If the tempera- 
 ture still rises the contents of the chamber are drawn off into the safety 
 tanks. It requires about one hour to charge the apparatus, nitrate 
 and discharge the contents. The nitroglycerine should then contain 
 about 92 parts of glycerine and 189 parts of nitric acid. When the ni- 
 tration is completed a cock is opened and the contents are drawn off 
 by gravity into the separating tank. 
 
 The separating tank is provided with a cock near the top for drawing 
 off the nitroglycerine into the washing tank and three at the bottom lead- 
 ing respectively to a safety tank, a waste acid tank and a second separat- 
 ing tank. It is arranged so that the compressed air can be admitted if 
 heating develops, and should this not be effective the liquid can be 
 drawn off into the safety tank. The nitroglycerine separating from the 
 waste products rises to the top and is drawn off into the washing tank, 
 the waste products being drawn off at the bottom. 
 
 In the washing tank the nitroglycerine is kept under pure water, 
 compressed air being forced through the liquid to keep the temperature 
 below 86 degrees F. In a few minutes after the air is shut off the 
 liquids separate, and the nitroglycerine, being the heavier, settles to the 
 bottom and is drawn off through a cock at the bottom of the tank. 
 The liquid is rewashed and then filtered to remove any foreign particles. 
 The final product is allowed to stand in a w^arm room for several days, 
 during which time a small quantity of water will arise to the top and 
 may be removed by skimming and absorbing. 
 
 Nitroglycerine is made from chemically pure ingredients, and should 
 have the appearance of a water-white oily liquid without any odor. 
 
266 THE SERVICE OF COAST ARTILLERY 
 
 Some commercial nitroglycerines have a yellow color, more* or less deep. 
 When free from water it is transparent; the presence of water makes 
 it milky. It has a slightly sweet taste, gives a burning sensation, is 
 very poisonous and a small quantity absorbed through the skin, mouth 
 or nostrils causes a severe headache, followed by giddiness and fainting; 
 and, if sufficient quantity has been taken, produces rigor and uncon- 
 sciousness. 
 
 Pure nitroglycerine freezes at about 4 degrees C. , and does not melt 
 from the frozen state until about 11 degrees C. In the frozen state it is 
 less sensitive to shock than in liquid shape but the process of thawing 
 is very dangerous and should never be attempted over a naked flame 
 or by direct contact with the heated metal. The only safe way to thaw 
 nitroglycerine is in a water bath the temperature of which should never 
 be allowed to rise above 50 degrees C. When frozen, nitroglycerine is 
 very liable to explode over a naked flame or hot metal. Liquid nitro- 
 glycerine is not sensitive to flame and will extinguish a match plunged 
 into it; an incandescent platinum wire will be cooled down, the nitro- 
 glycerine being volatilized. A small quantity of the liquid ignited 
 in the open air will burn quietly, but if the quantity be large and in, 
 any way confined an explosion will be sure to occur. It will explode 
 by a shock under certain conditions, as when pinched between two 
 rigid surfaces of metal or rock, and it will be detonated if a bullet is 
 fired into the mass. 
 
 In handling nitroglycerine rubber gloves should be used, and all 
 friction and shock avoided. As now manufactured it does not deteri- 
 orate very rapidly, and if care is taken to see the vessels or crocks in 
 which it is stored or transported do not leak there should be no danger 
 in handling. Its dangerous qualities are due to creeping and sweating. 
 In storage liquid nitroglycerine is covered with a layer of water. Its 
 chief value is found in the manufacture of dynamite, an accelerator for 
 smokeless powders and for blasting purposes. 
 
 Picric Acid. This is an explosive derived from the nitration of 
 phenol or carbolic acid. Both picric acid and its salts are largely used 
 in detonating and disruptive explosives. Lyddite, melinite, shimose 
 powder and ecrasite consist for the most part of picric acid, in fact, 
 lyddite is simply melted picric acid. 
 
 Picric acid has been found by experiment to be too sensitive as a 
 shell filler for armor-piercing shell, although it has been used success- 
 fully as a shell filler for field-artillery projectiles. Its process of manu- 
 facture is as follows: 
 
 Equal quantities by weight of phenol and concentrated sulphuric 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 267 
 
 acid are mixed in an iron vessel, stirred and heated by steam at a 
 temperature between 212 and 250 degrees F. From time to time tests 
 are made to see if the mixture formed is soluble in cold water. When 
 this is so the mixture is allowed to cool and twice the quantity of water 
 is added. The. nitration then takes place in earthen vessels standing 
 in running water which can be heated by steam pipes. In these re- 
 ceivers 3 parts by weight of nitric acid is placed and 1 part of the 
 mixture described above, is added. The latter is allowed to run in 
 gradually at first, as the reaction is violent. Afterwards it becomes 
 sluggish and then steam is turned on and the temperature of the 
 solution raised to restore the chemical action. 
 
 The picric acid formed separates at first into a syrupy liquid, be- 
 coming crystallized on cooling. It is separated from the other liquids 
 by a centrifugal machine and is washed in the same machine with pure 
 warm water. The crystals are further purified by re-dissolving in warm 
 water, re-crystallizing and finally drying. 
 
 The crystals are long, flat and lemon-colored. It has a bitter taste, 
 is partly soluble in cold water but entirely so in hot water, giving a 
 solution of a bright yellow color. It stains the skin and is used as a 
 yellow dye. If heated suddenly it will explode, and if added to any 
 potassium salt forms a very sensitive explosive and must be handled 
 with great care. The combination of picric acid with metal bases such 
 as lead, iron and potassium makes an exceedingly sensitive compound, 
 and for this reason care must be taken in filling iron shells with picric 
 acid or its derivatives. 
 
 Of all the picrates of salts of picric acid there is only one that is 
 suitable for use as an explosive, and that is ammonium picrate, which 
 unlike the metallic picrates, is insensitive to shock. 
 
 Dynamite. This term is used in both a general and special sense. 
 As a general term it includes all mixtures of nitroglycerine with solid 
 substances, in which the latter hold the liquid nitroglycerine in absorp- 
 tion. The solid substance is called the base and may be an explosive 
 or combustible material. In this sense smokeless powders, such as 
 cordite, having nitroglycerine as an accelerator, partake of the nature 
 of dynamite, but the name is used with reference to explosives designed 
 for disruptive purposes only. 
 
 In a special sense the term refers to the product obtained by mixing 
 liquid nitroglycerine with a fine, usually white, siliceous earth called 
 kieselguhr. This earth has marked absorbent properties due to its cel- 
 lular structure, and having once absorbed liquid nitroglycerine holds it 
 tenaciously. Kieselguhr will absorb nitroglycerine to the extent of over 
 
268 THE SERVICE OF COAST ARTILLERY 
 
 80 per cent, of the weight of the mixture. The amount of nitroglycerine 
 absorbed in any case determines the class of dynamite. That con- 
 taining 75 per cent., the highest commercial percentage, is called 
 dynamite No. 1; 50 per cent, nitroglycerine, dynamite No. 2; 30 per 
 cent, nitroglycerine, dynamite No. 3. In each case of the classes of 
 dynamite mentioned above a little sodium carbonate is always added to 
 neutralize any free acid that may be formed. 
 
 The commercial names for the several classes of dynamite are as 
 follows: Dynamite No. 1, Giant or Atlas powder; Dynamite No. 2, 
 Atlas powder B, Giant powder No. 2, and Rendrock; Dynamite No. 3, 
 Vulcan and Judson powders. 
 
 In the manufacture of dynamite the following steps are taken: 
 1. Kieselguhr is converted into a powder by the action of heat in a 
 furnace. 2. It is then ground between rolls, passed through fine 
 sieves, dried and packed in bags and stored in a drying atmosphere. 
 3. When the kieselguhr is dried until it contains not more than 5 per 
 cent, of water it is spread over the bottom of a lead-lined trough and 
 nitroglycerine is pored over it and mixed thoroughly. 4. The mixture 
 is then rubbed through sieves, first through one containing 3 meshes to 
 the inch, and then through one containing 7 meshes to the inch. 5. The 
 bulk dynamite is pressed into cylinders about 1 inch in diameter and 
 8 inches long. These cylinders are called sticks or cartridges, and are 
 carefully wrapped in paraffine paper. Enough of the cartridges to weigh 
 50 or 100 pounds are packed in sawdust in wooden boxes. In appear- 
 ance dynamite manufactured in this way has a light brown to reddish- 
 brown color and resembles brown sugar. 
 
 Dynamite in the military service is used as a standard explosive for 
 submarine mines and in demolitions. It is more sensitive than gun 
 cotton and requires great care in handling and storage. It is more 
 sensitive when thawed than in its usual or frozen condition. 
 
 Due to the fact that it contains nitroglycerine, which is one of the 
 most sensitive explosives, dynamite can be exploded by friction or 
 shock. In storage, in magazines where the temperature is apt to be 
 high it will deteriorate quite rapidly, such deterioration being indi- 
 cated by its damp, pasty condition or green spots on the paraffine 
 wrappers. In such cases care must be taken not to slide the boxes in 
 moving. It should also be destroyed in the open air when it has reached 
 this state of deterioration. 
 
 Explosive " D ". This explosive is a picric acid derivative. It is 
 a compound of picric acid with certain other elements which it has 
 been thought to the best interests of the service to keep secret. It is 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 269 
 
 used extensively as a shell filler, due to the fact that it is least sensitive 
 to shock of all the explosives considered. It is not fusible, that is, 
 it cannot be melted or liquefied. Shells are filled with it by compres- 
 sion, that is, the explosive is put in the cavity of the shell in small 
 quantities and thoroughly tamped with either a copper or wooden 
 tamper or mallet, until the cavity is completely filled. 
 
 The relative force of explosive "D" for actual density of loading 
 as compared with that of gun cotton is practically twice as great. It is 
 perfectly safe in manufacture and free from very injurious effects on the 
 workmen. It is insensitive on impact and stands the maximum shock 
 of discharge safely. It is non-hygroscopic and stable in storage. It 
 resembles powdered sulphur very closely in appearance. 
 
 Maximite. This explosive is also a picric acid compound, the com- 
 position of which has been kept secret. It is fusible and a suitable 
 explosive for armor-piercing shell. It differs from explosive "D" in 
 that it is melted when used to fill shells. Also in the requirement that 
 the metal of the shell must be protected with rubberine paint before it 
 is put in. In all other requirements as a service shell filler it is prac- 
 tically similar and equal to explosive "D." 
 
 It resembles explosive "D" except that it is much darker, having a 
 light brown or buff appearance. 
 
 Trinitrotoluol. This explosive is rapidly superseding picric acid 
 as a basis for shell fillers. It is slightly less powerful than picric acid 
 but possesses many advantages over it, one of which is that it will not 
 form dangerous combinations with other bodies with which it may come 
 in contact, whereas picric acid in contact with certain metals forms very 
 unstable and dangerous picrates. Trinitrotoluol is not unpleasant to 
 work with, nor does it disfigure like picric acid. 
 
 Blasting Gelatine. This is the most powerful explosive known. 
 It is 17 per cent, greater in strength than dynamite No. 1. It differs 
 from ordinary dynamite in that the usual pressure does not cause the 
 nitroglycerine to exude, and it is not affected by the action of water 
 except on the surface. The ingredients are nitroglycerine and soluble 
 nitrocellulose, about 90 per cent., of the former to 10 per cent, of the 
 latter. 
 
 In manufacture the mixing is done in troughs at a temperature of 
 122 degrees F., with wooden spades, and when the mass is so gelatinized 
 as to make it difficult to work with spades, it is kneaded by hand like 
 bread dough until it has a smooth, even consistency. It is then removed 
 and allowed to cool, when the mass becomes a firm, jelly-like substance, 
 yellow or light brown in color, and soft enough to be cut by a knife. 
 
270 THE SERVICE OF COAST ARTILLERY 
 
 The finished product is placed in a machine very much like an ordinary 
 sausage-making machine and forced out in a long cable and cut to the 
 desired lengths by a bronze knife. The cylindrical sticks are then 
 wrapped with paraffine paper. 
 
 The initial shock required to detonate blasting gelatine is six times 
 greater tnan that required to detonate ordinary dynamite, and for this 
 reason it is far less sensitive to sympathetic explosion or explosion by 
 influence. When frozen it is more sensitive to shock than dynamite, 
 but freezing does not seem to affect its explosive force. The same care 
 must be exercised in thawing as in the case of ordinary dynamite. A 
 small quantity of it burns in the open air without exploding and it will 
 burn in mass quietly unless some part reaches the exploding tempera- 
 ture, 204 degrees C. It is very stable under the action of heat, but its 
 sensitiveness is increased thereby. 
 
 This explosive is far too violent for many purposes, and it has 
 therefore been necessary to incorporate with the gelatine some suitable 
 base, such as sodium nitrate and wood pulp, with a view of regulating 
 the force of explosion. Explosives of this kind are called gelatine 
 dynamites and consist of 65 parts by weight of blasting gelatine to 
 35 parts by weight of the base described. It has been found that by 
 adding 10 per cent, of camphor to blasting gelatine it will not explode. 
 It cannot be used as a shell filler and is only suitable for purposes of 
 demolition. 
 
 Fulminates. The characteristic feature of fulmination is that it is 
 more brusque than in the other two classes. The explosive blow is 
 not prolonged and it is therefore much sharper than in the case of other 
 explosives. The heat of the first phase of the explosion is also very 
 great, due to the fact that the molecules of the fulminate are endothermic, 
 that is, they increase the temperature, and this in itself tends to in- 
 crease the sharpness and energy of the blow on the initial molecule. 
 Such a sharp molecular blow is thought to be particularly effective in 
 breaking up the molecular bonds of the disruptive class, and in this 
 way an explosion of the highest order is obtained. The abruptness 
 of the explosion of fulminates and the consequent shortness of blow, 
 combined with the concentration of very great heat at the point of 
 ignition, causes the fulminates, or as they are frequently called, de- 
 tonators or exploders, to be of great value as originators of detonations 
 and explosions in the first two classes. 
 
 Exploders or Detonators. The essential ingredient of all caps 
 and detonators is fulminate of mercury, which is formed from metallic 
 mercury, nitric acid and alcohol. The quantity of fulminate in any 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 271 
 
 particular exploder depends upon the kind of explosive used. It may 
 require some other ingredient to be mixed with the fulminate, such as 
 chlorate or nitrate of potassium, sulphide of antimony, etc., to give the 
 character to the initial explosive blow. 
 
 The manufacture of fulminate of m rcury is as follows: Equal 
 parts by weight of mercury and nitric acid (specific gravity 1.38) are 
 mixed in a glass carboy. The nitric acid dissolves the mercury and 
 when completely dissolved the contents are allowed to cool. The 
 solution is then well shaken to secure uniformity, and emptied into a 
 second carboy, which contains 10 parts of ethyl alcohol, and is there 
 kept at a temperature of 60 degrees F. After a few minutes the re- 
 action begins, the liquid boils and white vapors of nitric and acetic 
 ether, carbonic acid, etc. rise and pass off. The crystals of fulminate 
 of mercury separate in the form of small gray-colored needles in about 
 fifteen minutes afterwards. When the reaction is completed the pro- 
 duct is allowed to cool, it is then filtered and washed with pure water 
 until no trace of acid is found. The fulminate is then placed in a 
 drying atmosphere out of the direct rays of the sun and allowed to dry 
 until it contains not more than 15 per cent, of water. 
 
 The finished product is usually made up in packages containing 
 120 grains. When packed it contains 15 per cent, of water and is 
 hermetically sealed to prevent evaporation, as it is much more sensitive 
 to shock and friction in the dry state. When it is necessary to dry it 
 for use in caps and detonators great care must be exercised. The tem- 
 perature must be kept below 104 degrees F. It should not be kept in 
 stoppered bottles and especially not in bottles having glass stoppers, 
 as the friction of the moving and inserting of the stopper might detonate 
 a particle of the fulminate caught in the neck of the bottle. It is 
 exploded by a moderate blow of a hammer, by heat and by friction. 
 
 Fulminate of mercury is used very little except in caps and de- 
 tonators. Powdered glass and sulphide of antimony are frequently 
 used with it to increase its sensitiveness to percussion. 
 
 PROJECTILES 
 
 Projectiles used in seacoast cannon are designed primarily to over- 
 come the resistance offered by armor plate to their entrance into the 
 vitals of war vessels, or to carry a bursting charge into a destructive 
 radius. The power of a projectile to accomplish this depends upon the 
 shape of the projectile upon impact, the possibility of its breaking up, 
 and the amount of heat developed upon striking a plate. In the 
 
272 THE SERVICE OF COAST ARTILLERY 
 
 manufacture of projectiles it is very difficult to make them exactly 
 alike, that is, exactly homogeneous. This variation even extends to 
 projectiles made in the same foundry. 
 
 It is generally agreed that the dissipation of energy stored in a 
 projectile when it strikes a target may be accounted for, (1) in heating 
 the target; (2) in heating the projectile; (3) in changing the form of 
 the projectile; (4) in changing the form of the target. From the 
 standpoint of results obtained, all but the last of these are a waste. 
 
 The amount of energy in the projectile which, upon impact takes 
 the form of heat, can be approximately estimated. It has been found 
 that the temperature upon impact is sufficiently great to ignite a bursting 
 charge of black powder which requires a heat of 540 degrees F. Again 
 a bright red spot, even on bright days, can be observed at the instant 
 the projectile strikes the plate, which shows that the plate in the im- 
 mediate vicinity of the impact is heated to a high degree of temperature. 
 
 The penetrative effect of a projectile depends upon, (1) its shape; 
 (2) its material; (3) its energy and diameter; (4) the angle at which 
 it strikes the target; (5) whether it is capped or uncapped. 
 
 The shape believed to accomplish the best results is that of a 
 cylindrical body with ogival head, the latter having a radius of from 
 two to two and one-half calibers, that is, the radius of the curve forming 
 the head is drawn from the arc of a circle the diameter of which is from 
 two to two and one-half times the diameter of the projectile. 
 
 The material best suited for projectiles designed to pierce armor is 
 that which will neither break up on impact nor change its shape. 
 Forged oil-tempered steel of special treatment and composition has 
 been found to come nearest to fulfilling these conditions. 
 
 The energy of a projectile necessarily depends upon its weight which, 
 for any given projectile, is a function of its diameter. The best weight 
 for a projectile of given diameter is generally found by obtaining the 
 
 value of the ratio , in which w is the weight of the projectile and d 
 a 3 
 
 the diameter. 
 
 The smallest angle of impact (measured from the surface of the plate) , 
 at which a projectile will hold or bite, is called the biting angle. See 
 Fig. 8. For plates of different materials, this angle changes. For 
 plates of comparatively soft material, such as wrought iron and low 
 steel, or if the plate is overmatched, the shot will bite at a slightly less 
 angle than in the case of face-hardened steel, owing to the fact that the 
 plate bends slightly on impact. For face-hardened armor the biting 
 angle cannot be mathematically seated. As a general rule it may be 
 
PLATE XIX 
 
 Types of 
 
 1. Friction Primer, Axial Vent. 
 
 2. Friction Primer, Radial Vent. 
 
 3. Friction Primer, Sub. Cal. Firing. 
 
 4. Obturating Friction, Old Model Vent. 
 
 5. Obturating Friction, Siege, New Vent. 
 
 6. Drill Primer, Old Model Vent. 
 
 7. Drill Primer, New Model Vent. 
 
 8. Electric Primer, Axial and Radial Vent. 
 
 9. Obturating Electric, Old Model Vent. 
 
 10. Electric Primer for use with Armstrong 
 Adapter. 
 
 Primers. 
 
 11. Combination Electric and Friction, New 
 Vent. 
 
 12. Percussion for use with Armstrong Adapter. 
 
 13. 110-Grain Percussion Primer. 
 
 14. 20-Grain Percussion Primer. 
 
 15. Percussion Primer, Battery Cup. 
 
 16. 20-Grain Saluting Primer. 
 
 17. Igniting Primer. 
 
 18. 20-Grain Igniting Primer. 
 
 19. 110-Grain Igniting Primer. 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 273 
 
 defined as that angle at which the component of the energy of the 
 projectile, normal to the plate, is- sufficient to smash in the hard face, 
 the projectile at the same time holding together long enough to penetrate. 
 A projectile has its greatest penetration at normal impact and its 
 penetrative power decreases as the angle of impact increases, but not 
 in exact proportion. 
 
 All armor-piercing projectiles are now fitted with soft steel caps, 
 which, under favorable angles of impact, increase their penetrative 
 effect when attacking hard-faced armor. The cap as adapted in the 
 service consists of a cylindrical piece of soft steel about half a 'caliber 
 of the projectile in diameter, bored out to a depth of about two-thirds 
 of its length to fit over the nose or point of the projectile. It weighs 
 
 FIG. 21. Armor Plate after Attack by Capped and Uncapped Projectiles, 
 ordinarily about 2^ to 5 per cent, of the weight of the projectile. 
 A recess or cavity in the interior, that is, between the nose 
 of the projectile and the cap when assembled, contains a lubricant, 
 usually graphite. The cap is made fast by a small cylindrical groove cut 
 in the nose of the projectile, the cap being forced on under pressure. 
 In the case of cast-iron projectiles used in tests and practice, the nose 
 is cut off, the head bored to receive a threaded portion of the cap which 
 is screwed into place, the object being to make the practice projectile 
 identical in weight and shape to those used in service. 
 
 The theory of the action of the cap, which seems most reasonable, 
 is that when the mass consisting of the projectile and cap meets the hard 
 face of the plate, the latter acts as a buffer against the hard and im- 
 penetrable surface, and elastically dishes the plate on impact. The 
 cap is strong enough to transmit the stress of impact, and at the same 
 time the projectile proper is not stopped as suddenly as in the case of 
 
274 THE SERVICE OF COAST ARTILLERY 
 
 one not capped, but continues to advance through the cap, which, being 
 soft, is comparatively easy and when the point reaches the plate it 
 finds the latter already dished practically to its elastic limit. Again, 
 it gives the projectile a most decided advantage in having the tendency 
 of preventing the projectile from breaking up on impact. 
 
 Fig. 21 is a photographic view of a 6-inch cemented armor plate 
 against which were fired two shots from a 6-inch gun, at practically 
 the same velocity. The projectiles in both cases were alike, excepting 
 that the first was uncapped while the other was capped, similar to that 
 shown in the view. The striking energies were virtually the same; 
 but the uncapped projectile failed to penetrate and broke up on impact, 
 the nose remaining embedded in the plate. The capped projectile,, 
 on the other hand, made a clean hole through the plate and was recovered 
 whole, with the exception of a small piece broken from the point as 
 shown in the illustration. 
 
 In the matter of acceleration of penetration, for normal impact 
 against cemented plate, with velocities exceeding 1,800 f. s., the use 
 of the cap will add about one-sixth to the penetrative power of the 
 projectile; at angles of impact greater than 30 degrees the advantage 
 gained by the cap is nil or almost so; with velocities less than 1,800 
 f. s., the cap is practically useless. Recently tests have been made 
 with a new form of cap, and good results obtained. This cap is 
 more pointed and covers the entire ogive, which has given rise to the 
 term " long nose" to projectiles so capped. 
 
 SERVICE PROJECTILES 
 
 Armor-Piercing Shot are made of forged steel with a small cavity 
 designed primarily to facilitate the tempering and hardening process. 
 The cavity may be filled with a "shell filler" consisting of a high 
 explosive bursting-charge. They are armed with a delayed action 
 fuse, thus permitting of the perforation of armor plate before the bursting 
 charge is ignited. (See Fig. 22). 
 
 Armor-Piercing Shell are made of forged or cast-steel with a 
 larger cavity than that of shot. They are designed to carry a large 
 bursting-charge of high explosive and to attack the thinner side armor 
 of battleships or the vertical armor of cruisers. They are also provided 
 with a delayed action fuse. 
 
 Deck-Piercing Shell are made of forged or cast-steel with a cavity 
 of about the same dimensions as armor-piercing shell. They are 
 provided with a torpedo detonating pierce fuse. 
 
l?/rKr> mortar she//. Torpedo, forged step/. 
 
 m 
 en 
 
 en 
 
 
 
 n 
 
276 THE SERVICE OF COAST ARTILLERY 
 
 Cast-iron Shot are used exclusively for tests and service target 
 practice. Their weight and dimensions are identical with the armor- 
 piercing shot. 
 
 Torpedo Shell are made of forged steel and are designed to carry a 
 very large bursting charge of high explosive onto the decks of war 
 vessels. They weigh either 800 or 1000 pounds, and are provided 
 with a major-caliber base detonating fuse. 
 
 The table on opposite page gives the weights of projectiles and their 
 armor piercing capacity: 
 
 PAINTS FOR PROJECTILES 
 
 To distinguish the character of metal of which projectiles are made 
 and their armor-piercing qualities, as well as the position and nature 
 of their bursting-charge, conventional colors are prescribed for use on 
 the exterior. The body color of all projectiles is black. 
 Colors to Distinguish the Character of Metal. 
 
 Forged or Wrought Steel Blue gray. 
 
 Cast-Steel Warm gray. 
 
 Cast-Iron Olive green. 
 
 Chilled Iron Light green. 
 
 Brass Light yellow. 
 
 Copper Light reddish brown. 
 
 The colors above named are also used to indicate the degree of armor- 
 piercing quality of the projectile, as well as the position of its center of 
 gravity, the latter being essential to facilitate the raising and lowering 
 of projectiles with shot tongs. 
 
 To indicate the degree of armor-piercing quality, a greater or less 
 portion of the head is painted with the color corresponding to the 
 metal. The band indicating the center of gravity is also of the color 
 corresponding to the metal. It is one-half caliber wide and extends 
 equally above and below the position of the center of gravity. It may 
 also be employed with the smaller calibers of projectiles to indicate 
 the character of the metal. 
 
 Colors to Distinguish the Character of the Bursting Charge. 
 
 Gun cotton White. 
 
 Explosive "D" or Dunnite Deep (chrome) yellow. 
 
 Maximite Dark buff. 
 
 Rifle or Charcoal Powder Vermilion. 
 
 The bursting-charge color is applied to the base and the cylindrical 
 portion of the body in rear of the copper rotating band. Until the 
 projectile is filled, these portions may remain black. 
 
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 S 1^,-g . "^ "5 ; '~1'~1 
 
278 THE SERVICE OF COAST ARTILLERY 
 
 On Armor-Piercing Shot, the whole head, including the soft-metal 
 cap, and the center of gravity band, is painted blue gray. The charge 
 color appears as stated above, if the projectile is a cored shot. 
 
 On Armor-Piercing or Deck-Piercing Shell, one-half of the head, 
 measured from the point; and the center of gravity band, is painted 
 blue gray. The charge color appears as stated above. 
 
 On Chilled-Iron Shot, one-half of the head, measured from the 
 point; and the center of gravity band, is painted light green. The 
 charge color appears as stated above, if the projectile is a cored shot. 
 
 On Cast-iron Shot, the center of gravity band is painted olive green 
 
 On Torpedo Shell, the center of gravity band is painted blue gray. 
 The charge color appears as stated above. 
 
 On Shrapnel, the entire body is painted black, with a band of 
 vermilion on the head below the fuse to indicate a front charge, or on 
 the cylindrical portion of the body in rear of the copper rotating band 
 to indicate a base charge. Those used for fixed ammunition are 
 painted all black above the copper band. 
 
 On cannister, the entire body is painted black. 
 
 Before the paint is applied the surfaces should be cleaned and all 
 grease or oil removed. It should be applied by brush and rubbed on 
 evenly, particularly on parts required to fit the bore closely. Care is 
 necessary that the junction of two colors does not overlap to produce 
 inequalities of thickness. ,The thickness of the coating generally must 
 be limited to the least amount required to produce the color. 
 
 The cavities of cored shot, shell and shrapnel made to contain a 
 bursting-charge of powder are coated with "Turpentine Asphaltum 
 Varnish, best quality." The process consists of thoroughly cleaning 
 the cavity of all greasy matter and pouring in the liquid, then rolling 
 and turning the projectile to insure even distribution, and pouring out 
 the excess. The projectile is then allowed to stand with the fuse hole 
 down for a time sufficient to insure thorough draining of excess. The 
 residue from fuse threads is removed by means of a cloth soaked in 
 benzene and a tap. The fuse hole is left open for the circulation of air 
 until after the coating has hardened. 
 
 The "body" of coating can be increased by a second coating after 
 the first has dried, or by thickening the varnish, through evaporation, 
 before applying. 
 
 Cored shot or shell which are charged with picric acid compounds 
 are first coated on the interior with paraffin or rubberine paint No. 2, 
 the process consisting of melting the wax and pouring it in as described. 
 
 The object of these coatings is to prevent the generation of the 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 279 
 
 sensitive qualities produced in some explosives when exposed to iron 
 or steel, such qualities causing them to detonate from the slightest 
 friction. 
 
 PRIMERS 
 (See Plate XIX) 
 
 Primers are devices used to ignite powder charges in guns. They 
 are classed, according to the method by which the ignition is produced, 
 into friction primers, electric primers, percussion primers and igniting 
 primers. There is also a combination primer so constructed that it 
 may be fired by either of the two methods named above. Primers 
 known as obturating primers, in addition to affording a means of 
 igniting a charge, also act as a gas check and prevent the escape of 
 powder gases through the vent by closing it. 
 
 Friction Primers. Primers of this class consist of those exploded 
 by frictional heat; they are composed essentially of a body of brass or 
 Tobin bronze; a friction pellet, composed of a mixture of sulphide 
 of antimony; chlorate of potash; sulphur; ground glass; and usually 
 a matrix, used to hold the other parts together, such as beeswax or 
 tar; a toothed or serrated wire, to ignite the friction pellet by fric- 
 tional heat when forced through it; and the priming charge of blac : 
 powder. It is essential that there shall be no escape of gas, either 
 through or around the primer body on discharge, especially in case of 
 high-power guns, therefore most of the primers of this class, especially 
 those used in seacoast cannon, are made obturating. The friction 
 primers in use are the obturating friction primer for siege and sea- 
 coast cannon shown in Fig. 23. The primer illustrated in Fig. 23 
 was designed for use with old-model vents and are gradually being 
 replaced in the service by the primers for the new-model vent shown in 
 Fig. 29, which is commonly known as the button primer. 
 
 In addition to the friction primers above described, the primer 
 shown in Fig. 24 ; known as the drill primer for new-model vents, has 
 been designed to take the place of the relatively expensive combination 
 electric-friction primer for use in drill, saluting and subcaliber practice. 
 The method of operation of the friction primer consists in pulling the 
 serrated end of the copper wire through the friction composition. The 
 pull on the lanyard draws the serrated wire through the friction com- 
 position and ignites it; the flame communicates to the rifle powder and 
 thence through the vent to the powder charge in the gun. 
 
 The lanyard should be pulled from a position as near to the rear of 
 the gun as possible. A strong, steady pull from one man with as short 
 
280 
 
 THE SERVICE OF COAST ARTILLERY 
 
 BODY (BRASS) 
 
 SAFETY BLOCK (BRASS) 
 
 SERRATED WIRE (BRASS) 
 
 GAS CHECK (BRASS) 
 
 PAPER CYLINDER 
 FRICTION COMPOSITION 
 PRIMER CHARGE 
 LOOSE RIFLE POWDER 
 
 PRIMER CHARGE 
 CLOSING CUP (BRASS) 
 
 FIG. 23. 
 
 REAR WIRE (BRASS) 
 
 (BRASS) 
 SERRATED WIRE (BRASS) 
 
 -GAS CHECK (BRASS) 
 PAPER CYLINDER 
 
 FRICTION COMPOSITION 
 
 PRIMER CHARGE 
 LOOSE RIFLE POWDER 
 
 CLOSING CUP (BRASS) 
 
 FIG. 24. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 281 
 
 a lanyard as practicable should be used. Where a long lanyard is used, 
 the slack causes the force to be applied slowly, increasing the chances 
 for a misfire. 
 
 If a primer cannot be fired by one man, it should be rejected and 
 another used. Two men pulling on a lanyard will injure the firing 
 mechanism, in case one is used. When a primer is pulled and fails 
 to fire it should be removed from the vent ; the wire should immediately 
 be bent around the primer through an angle of 180 degrees to prevent 
 it from being used again. 
 
 The obturating friction primer for new-model vent shown in Fig. 25, 
 was designed to increase the rapidity of fire of all guns, as it is more 
 readily inserted in the gun and after use more easily taken out of the 
 vent. In order to use a primer of this kind it became necessary to add 
 
 BUTTON (BRASS) 
 WIRE (BRASS) 
 
 BODYCTOBIN BRONZE) 
 
 SERRATED CYLINDER 
 '& GAS CHECK 
 'VULCANITE WASHER 
 -FRICTION COMPOUND 
 T r"p T nw 
 
 N 
 
 (BRASS) 
 
 PRIMER CHARGE .THREE 
 'CYLINDERS (20 GR.lf 
 ^LOOSE RIFLE POWDER 
 PRIMER CHARGE CONTD. 
 END CLOSING CUP 
 
 FIG. 25. 
 
 a new firing mechanism to the breechblocks of the guns in which it is 
 used. The head of the primer is firmly held by the firing mechanism, 
 so that the primer cannot be blown out at the discharge of the piece. 
 The firing wire is engaged and pulled by a slotted lever actuated by the 
 pull on the lanyard. 
 
 This primer consists of a brass body with a brass firing wire passing 
 loosely through the hole in the serrated cylinder, the end of the wire 
 being flush with the end of the cylinder when the nut on the wire bears 
 against the interior shoulder. The friction composition, pressed into 
 the brass case, surrounds the cylinder above the serrations. A vul- 
 canite washer holds the friction composition in place and prevents it 
 from crumbling when the pull is applied. The nut screwed to a bearing 
 
282 THE SERVICE OF COAST ARTILLERY 
 
 on the case holds the assembled parts in place. Three holes through 
 the nut permit the passage of the flame from the friction composition 
 to the priming charge of powder. 
 
 The action of the primer is as follows: When the wire is pulled, 
 ignition of the friction composition is effected. The conical end of the 
 cylinder is pulled to its seat in the body of the primer, and prevents 
 escape of gas to the rear. 
 
 One of the late improvements in this primer is its arrangement by 
 which the wire may be moved forward without carrying the cylinder 
 and the friction composition with it, and therefore without danger of 
 firing the primer in case the wire is pushed back after a primer has been 
 taken from a vent in case of a misfire. In the earlier models the teeth 
 were formed on the wire, and it was found when a primer had failed 
 to fire it might be fired accidentally in case the wire was pushed back. 
 
 Drill Primer. This primer is shown in Fig. 24. It is constructed 
 practically the same as the primer just described except that its parts 
 are more cheaply made. It is the only primer issued unassembled. 
 The button wire, body, serrated wire, cylinder of smokeless powder 
 and friction composition are furnished separately. The rifle powder, 
 closing caps and necessary assembling tools are furnished for assembling 
 and disassembling the drill primers. 
 
 The serrated wire with the friction composition is first inserted in 
 its seat in the body and the button wire screwed on the end. The body 
 is then filled with 25 grains of loose rifle powder and the end closed 
 with the brass cap. To prevent the displacement of the cap, the end 
 of the primer is sealed with a composition furnished for that purpose. 
 
 Drill primer cases are intended to be reloaded as many times as 
 possible, and for this purpose the drill primer kit consists of 30 primer 
 cases, 30 button wires, friction pellets, closing caps, loading tools and 
 a resizing die for priming cases. The drill primer costs approxi- 
 mately five cents, and with proper care a drill primer case will stand 
 about ten firings before becoming unfit for further use. To preserve 
 the cases they should be carefully cleansed with a hot solution of lye 
 immediately after firing, and thoroughly dried before being put away. 
 The resizing die is used for the purpose of readjusting the shape of the 
 primer cases that have become swollen or bent out of shape. 
 
 Electric Primers. Primers of this class consist of those exploded 
 by an electric wire heated to incandescency. The service electric 
 primer consists essentially of the primer body, the lead wire or wires, the 
 platinum wire bridge, the gun cotton primer charge, the primer charge 
 proper and the insulating parts. The essentials of an electric primer 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 283 
 
 are that it should be simple in construction, thoroughly free from short 
 circuits, sure in its action when the proper current is applied, uniform 
 as to the firing current, and so constructed that the obturation of the 
 gas is complete through and around the primer body. The amount of 
 current usually required to fire an electric primer is, under ordinary 
 conditions, 75/100 of an ampere. The electric primer for axial and 
 radial vents is shown in Fig. 26, and consists of the parts indicated 
 thereon. It is the only two-wire electric primer found in the service. 
 The circuit between the two wires is completed across the platinum 
 
 -INSULATED WIRE 
 (COPPER) 
 
 SLEEVE (COPPER) 
 CARTRIDGE 
 
 STEM WRAPPING 
 HARDWOOD PLUG 
 GUN COTTON 
 WIRE BRIDGE 
 (PLATINUM) 
 PRIMER CHARGE 
 
 (BLACK POWDER) 
 STEM(COPPER) 
 
 BEES WAX 
 AND TAR 
 
 FIG. 26. 
 
 GUN 
 
 COTTON 
 
 IGNITING 
 PELLETS 
 
 CLOSING 
 CUP 
 
 INSULATED WIRE 
 
 VULCANITE BUSHING 
 BODY(TOBIN BRONZE) 
 
 VULCANITE WASHER 
 LEATHER WAS 
 CONTACT PLUG 
 INSULATING C 
 PLATINUM WIRE BRIDGE 
 CONTACT CUP(BRASS) 
 CLOSING SCREW( BRASS) 
 PAPER WASHER 
 IGNITING POWDER 
 
 FIG. 27. 
 
 bridge and the electric current passing over the circuit heats the wire, 
 igniting the gun cotton surrounding the bridge, which in turn ignites 
 the primer charge. 
 
 The electric primer for siege and seacoast cannon with old model 
 vents is shown in Fig. 27, and is used generally in the same cannon as 
 the obturating friction primer shown in Fig. 23. The principal parts 
 are indicated on the cut. The copper wire, insulated throughout its 
 entire length in the primer body, is threaded to the brass contact plug. 
 After these two parts are assembled, the metal of the contact plug is 
 
284 
 
 THE SERVICE OF COAST ARTILLERY 
 
 crimped in around the wire to prevent accidental unscrewing. The 
 vulcanite washer, the lead washer, and the insulating cylinder, insulate 
 the contact plug from the primer body. The front end of the contact 
 plug fits into the counterbore in the rear end of the vulcanite insulating 
 cylinder. The front end of the vulcanite insulating cylinder is counter- 
 bored to the contact cup, which is bored centrally to the hole leading to 
 the primer cavity. The interior of the primer body is threaded as 
 shown for the closing screw. Both the contact plug and the contact 
 cup extend beyond the ends of the insulating cylinder, so that when the 
 closing screw is set up tight all the interior parts referred to are held 
 firmly together. 
 
 NTAC' 
 
 CUP (BR 
 ING CYLIJ 
 INSULATING PLUG 
 CONTACT PLUG (BRASS) 
 PLATINUM WIRE BRIDGE 
 GUN COTTON IGNITER 
 
 PRIMER CHARGE 
 
 END CLOSING DISK 
 (CARD BOARD) 
 
 FIG. 28. 
 
 A platinum wire bridge of 2/1000 of an inch in thickness is soldered 
 to the front end of the contact plug to the contact cup. The electrical 
 connection of the primer body is secured through the threads of the 
 closing screw. The platinum wire bridge is surrounded with a small 
 priming charge of dry gun cotton, so that when the bridge is heated 
 by the passage of the electric current the gun cotton is ignited, which 
 in turn ignites the pellets. These pellets are composed of 21 grains 
 of compressed black powder. On the discharge, the pressure of the gas 
 forces the contact plug against the washers and also forces the thin walls 
 of the primer out against the primer seat, thus producing an effective 
 gas check. 
 
 The 110-grain electric primer shown in Fig. 28 is designed for use "in 
 all guns employing metallic ammunition, and equipped with electric 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 235 
 
 firing attachments, such as the 3-inch R. F. gun, model of 1902, and all 
 of the Armstrong seacoast guns in the service. The parts are indicated 
 in detail in the cut. The electric element of the primer consists of a 
 wire bridge soldered to the contact disk, which is then pressed to the 
 bottom of the contact cup; the contact cup is then pressed into the 
 insulating cylinder, in which it is made a snug fit; a small quantity of 
 gun cotton is placed around the bridge, after which the insulating plug 
 is assembled in the open end of the contact cup. The contact plug, 
 which is centrally bored for the passage of the flame, and the platinum 
 bridge is assembled with the boss or projection fitting into the end of the 
 
 BUTTON (BRASS) 
 WIRE (BRASS) 
 
 SUPPORT 
 
 FOR BRIDGE 
 GUN COTTON 
 
 LOOSE POWDER- 
 
 INSULATING 
 CYLINDER 
 
 (PAPER) 
 SS) 
 
 BODY (TOBIN BRONZE) 
 SERRATED CYLINDER 
 AND GAS CHECK 
 
 , WASHER (VULCANITE) 
 FRICTION COMPOSITION 
 CASE FOR FRICTION 
 
 COMPOSITION 
 (PLATINUM WIRE BRIDGE 
 CONTACT NUT 
 
 ? (VULCANITE) 
 COMPRESSED POWDER 
 E1ID CLOSING CUP (BRASS) 
 
 FIG. 29. 
 
 insulating plug, the bridge passing out through the central hole and 
 being soldered into a groove in the surface of the contact plug. 
 
 The diaphragm separating the recess for the electric element from 
 the black powder^ cavity is centrally bored to permit ready passage of 
 the flame from the gun-cotton igniter when the primer is fired. 
 
 Combination Electric Friction Primer. Primers of this class consist 
 of those which can be exploded by either a frictional heat or by an 
 electric wire heated to incandescency, or both. The primer shown in 
 Fig. 29, known as the combination electric and fricting primer (button 
 primer) has been adopted for use in seacoast cannon provided with 
 
286 THE SERVICE OF COAST ARTILLERY 
 
 new model vents and will eventually be used in all seacoast cannon 
 except those provided with percussion firing ammunition. Its great 
 advantage is that it is readily inserted and removed from its seat. 
 It provides two methods of firing and permits greater rapidity of fire. 
 Its essential parts are marked in detail in the figure. 
 
 The friction composition of this primer consists of the following 
 ingredients: 50 parts by weight of chlorate of potash, 27 parts by 
 weight of sulphide of antimony, 10 parts by weight of sulphur and 13 
 parts by weight of ground glass. No matrix is used with the com- 
 position, the ingredients being thoroughly incorporated and inserted 
 as a finely pulverized powder into the case and pressed into a solid 
 pellet which surrounds the cylindrical part of the serrated cylinder 
 so that the teeth of the latter are not imbedded in the composition 
 but rest on the compressed pellet. 
 
 The electric element consists of a paper cylinder which surrounds 
 the wire insulating it from the firing mechanism, the insulating plug 
 insulates it from the primer body. The friction composition pellet, 
 which is a non-conductor of electricity, insulates the serrated cylinder, 
 which is electrically connected with the wire from the walls of the 
 primer body. The support for the platinum wire bridge, when the 
 primer is assembled by screwing the closing screw into the front end 
 of the case, presses tightly against the end of the wire, making the elec- 
 trical connection at this point. The vulcanite cap insulates the prongs 
 of the support from the closing screw. The platinum wire bridge is 
 soldered to the support and to the closing screw. The case, into the 
 front of which the screw is threaded, screws into the primer body as 
 shown on the drawing. The electric circuit is thus completed between 
 the button and body of the primer across the platinum bridge. The 
 priming charge of gun cotton surrounds the bridge inside the prongs 
 of the support. 
 
 The frictional element is operated by pulling the teeth of the serrated 
 cylinder quickly through the pellet of friction composition which is 
 ignited by frictional heat and fires the -primer. The electrical element 
 is operated by the passage of the electric current over the bridge, 
 which ignites the gun cotton and in turn fires the primer. 
 
 Percussion Primers. Primers of this class consist of those which 
 can be exploded by a sharp blow or frictional shock. The 'essential 
 parts of a simple percussion primer are the primer cup, the anvil and 
 the percussion composition. With the exception of the tin-foil covering 
 all metal parts of percussion primers are made of brass. Percussion 
 primers are used in all guns provided with percussion-firing mechanism, 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 287 
 
 such as the 1 -pounder pom-pom, the 1.65 Hotchkiss, the 6-pounder 
 rapid-fire gun, the 4.7 and the 6-inch Armstrong gun, and the 3-inch 
 15-pounder r. f. gun. The ingredients of the friction composition con- 
 sist of the following mixture : Chlorate of potash, sulphide of antimony, 
 glass and sulphur. Formerly the composition of all service primers 
 contained a large percentage of fulminate of mercury, but on account 
 of the danger involved in handling these primers in shipment, its 
 use has been discontinued. 
 
 To insure the ignition of smokeless powder charges in cartridge 
 cases it is necessary that primers either contain in themselves, in addition 
 to the percussion composition, an auxiliary charge of black powder, 
 or that an auxiliary charge of loose black pow r der be placed at the 
 rear of the cartridge case to communicate the flame from the percussion 
 primer and thoroughly ignite the smokeless powder. 
 
 All percussion primers now used in the service, except the primer 
 known as battery cup, shown in Fig. 30, contains an igniting charge 
 of black powder in addition to the essential elements named above. 
 
 PERCUSSION-PRIMER CUP 
 BODY (BRASS) 
 
 PERCUSSION COMPOSITION 
 TIN FOIL 
 
 FIG. 30. 
 
 The amount of loose black powder required as an igniting charge 
 for smokeless powder to give anywhere like uniform ignition is relatively 
 large, with the result that considerable fouling of the gun occurs when 
 the igniting charge is used. This is at all times objectionable, but is 
 especially so with machine guns. This objection has resulted in the 
 development of two sizes of percussion primers, one known as the 
 110-grain percussion primer, for use in all cartridge cases from the 
 1 -pounder to the 6-inch Armstrong, and the other known as the 20-grain 
 percussion primer, which is used in the smaller calibers of guns. 
 
 The 110-grain percussion primer, shown in Fig. 31, consists of the 
 parts indicated in the cut. The body is 3J inches long, and is drawn 
 from a disk of cartridge metal. In the rear of the body a recess or 
 pocket for the percussion primer is formed. The percussion primer 
 consists of a cup, a percussion composition and the anvil, is assembled 
 and inserted as a unit into the pocket. A hole is drilled through 
 the diaphragm separating the pocket from the cavity containing the 
 compressed charge to allow passage of the flame from the percussion 
 primer. 
 
288 
 
 THE SERVICE OF COAST ARTILLERY 
 
 The, primer charge consists of 110 grains of black powder inserted 
 under a pressure of 36,000 Ibs. per square inch. Eight radial holes are 
 drilled through the primer and compressed powder. The powder is 
 pressed into the primer body around a central wire, which is then 
 withdrawn, leaving a longitudinal hole the full length of the primer. 
 
 BODY (BRASS) 
 PERCUSSION-PRIMER 
 CUP AND COMPOSITION 
 
 ANVIL 
 
 COMPRESSED POWDER 
 
 (110 GR.) 
 TIN FOIL 
 
 END CLOSING WAD 
 (PAPER) 
 
 FIG. 31. 
 
 This compression of the powder with the longitudinal hole increases 
 the time of burning of the powder charge, and causes the primer to burn 
 with a torchlike rather than an explosive effect, making the ignition 
 of the smokeless powder charge more complete. This primer has been 
 
 PERCUSSION-PRIMER CUP 
 PERCUSSION COMPOSITION 
 COMPRESSED POWDER 
 TIN-FOIL COVERING 
 
 END CLOSING WAD (PAPER) 
 
 FIG. 32. 
 
 adopted for use in all cartridge cases from the 6-pounder to the 6-inch 
 Armstrong inclusive, and requires no rear igniting charge. 
 
 The primer is a drive fit in its seat in all cartridge cases in which 
 it is used, and for this reason a special press for the insertion of the 
 primer is provided. 
 
 The 20-grain percussion primer shown in Fig. 32 has been adopted 
 
PLATE XX 
 
 1. Point Fuse, Minor Caliber. 
 
 2. Base Fuse, Minor Caliber. 
 
 3. Base Fuse, C High. 
 
 4. Centrifugal F Fuse Altered C. 
 
 5. Centrifugal F Fuse. 
 
 6. Centrifugal S Fuse Altered A. 
 
 7. Centrifugal S Fuse. 
 
 Types of Fuses. 
 
 8. Centrifugal 12 M Fuse. 
 
 9. 15-second F.A. Combination Fuse 
 
 10. Combination Fuse 28-second High. 
 
 11. Combination Fuse 28-second Low. 
 
 12. Erhardt Combination Fuse. 
 
 13. Krupp Combination Fuse. 
 
 14. Combination Fuse, F.A. 21-second. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 289 
 
 for use in cartridge cases for 1-pounder subcaliber tubes, percussion 
 firing, 1-pounder machine guns, and the 1.65 Hotchkiss. Its con- 
 struction is practically the same as that of the 1 ID-grain percussion 
 primer, the main difference being that the primer charge consists of 
 
 PERCUSSION-PRIMER CUP 
 PERCUSSION COMPOSITION 
 ANVIL 
 
 LOOSE POWDER(20 (JR.) 
 
 END CLOSING WAD (PAPER) 
 FIG. 33. 
 
 only 20 grains of compressed powder inserted under the same pressure 
 as the larger primer. 
 
 For saluting purposes the percussion saluting primer, shown in 
 Fig. 33, has been adopted. It is used in all saluting cases for guns 
 designated as using 110-grain percussion primers. 
 
 VENT CLOSING DISK (PAPER) 
 BODY (BRASS) 
 OBTURATING CUP (BRASS) 
 OBTURATING VALVE (BRASS) 
 
 PRIMER CHARGE 
 
 END CLOSING WAD 
 (PAPER) 
 
 FIG. 35. 
 
 FIG. 34. 
 
 FIG. 36. 
 
 For use in the smaller guns the percussion primer battery cup, 
 shown in Fig. 30, is used in all fixed ammunition. 
 
 Igniting Primers. Primers of this class consist of those which con- 
 tain no means of ignition within themselves, but require for their 
 ignition an auxiliary friction or electric primer which is inserted in 
 
290 THE SERVICE OF COAST ARTILLERY 
 
 the vent of the piece in the same manner as for service firing. Igniting 
 primers consist essentially of a brass body, an obturating cup, an 
 obturating valve, a vent-closing disk, an end-closing wad, and a 20-grain 
 primer charge. They are assembled as shown in Figs. 34, 35, and 36. 
 The saluting igniting primer, shown in Fig. 35, is designed for use in 
 cartridge cases for 18-pounder subcaliber guns in firing blank charges 
 of black powder. 
 
 The action of the primer is as follows : The flames and gases from the 
 auxiliary primer cut through the vent in the cap and drive the obturating 
 valve, which is normally in the rear of the cup, closing the vent forward, 
 allowing the flames to pass around and enter the primer cavity through 
 the vent in the diaphragm, and thus igniting the primer charge. The 
 pressure of the gases at once react on the obturating valve and drive 
 it to the rear, closing the vent in the obturating cup, at the same time 
 expanding the walls of the cup in the recess, making a gas check at 
 both these points. 
 
 The powder charge of this primer consists of 20 grains of loose 
 rifle powder. 
 
 The flame from the service primer alone would not be sufficient to 
 ignite properly the smokeless powder charge in the cartridge case, and 
 therefore the igniting primer is used. 
 
 The 110-grain igniting primer is identical in form and dimensions 
 with the 110-grain percussion primer, and is designed for use in cart- 
 ridge cases for subcaliber practice with the 18-pounder subcaliber guns 
 only. Its action is the same as that described for the saluting igniting 
 primer. Its primer charge consists of 110 grains of rifle powder. 
 
 The 20-grain igniting primer, shown in Fig. 36, bears the same 
 relation to the 20-grain percussion primer as the 110-grain igniting 
 primer does to the 110-grain percussion primer. It is designed for use 
 in cartridge cases for the 1 -pounder subcaliber guns in subcaliber 
 practice, and requires no igniting charge of black powder. 
 
 FUSES 
 
 (See Plate XX) 
 
 Fuses are devices used to ignite or detonate bursting charges con- 
 tained in projectiles. They are classified: (1) According to their 
 construction, as Ring-Resistance; Centrifugal; Combination; Detonat- 
 ing. (2) According to their use, as Time, Percussion, Combination 
 Time and Percussion. (3) According to their location in the projectile, 
 as Point or Base. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 291 
 
 The essential elements common to all fuses of whatever class are 
 safety in handling and transportation; certainty in action when fired; 
 suitability for use in projectiles of different calibers; simplicity in 
 construction ; cheapness of manufacture ; stability in storage and 
 method of assembly. 
 
 Ring-Resistance Fuses are made both for base and point insertion, 
 and consist essentially of a fuse stock or body, firing-pin sleeve, split- 
 ring spring, firing pin, percussion primer and fuse cap. 
 
 There are two classes of resistance fuses manufactured, the " high 
 resistance" and the "low resistance/' so called because the arming 
 resistance of the ring is relatively high or low, that is, the resistance 
 of the spring requires a greater or less shock to arm them. High- 
 resistance fuses are safe under all ordinary conditions of handling and 
 transportation, and may be transported fixed in the projectiles in which 
 it is intended to use them. Low-resistance fuses cannot, on account 
 of the danger of premature arming, be transported inserted in projectiles. 
 They are shipped in hermetically sealed boxes, and, to prevent prema- 
 ture arming of the plunger in handling, the firing-pin sleeve and firing 
 pin are locked together by means of a safety wire passing through them 
 and the body of the fuse. Just before using, this wire must be pulled 
 out, after which the fuse may be screwed into the projectile. 
 
 All the fuses of this class issued to the service at present belong to 
 the high-resistance class, the only low-resistance fuses at present issued 
 to the service being the 22-secorid combination fuse, low resistance, 
 for use in a 7-inch mortar shot. All service fuses are stamped to show 
 the distinguishing letter of designation and place of manufacture. The 
 point fuses have a right-hand thread, which, in connection with the 
 right-hand twist of rifling, has a tendency to tighten in its seat on 
 discharge. For the same reason all base fuses have a left-hand thread. 
 
 The arming resistance of ring-resistance fuses is tested in the course 
 of manufacture with a static machine, which gives the weight necessary 
 to force the sleeve over the firing pin against the resistance of the split- 
 ring spring. They are also tested by assembling them in shell and 
 dropping the shell upon a steel plate. 
 
 Ring-resistance fuses are also percussion in their character, that is, 
 the shock of discharge prepares the fuse for action and the shock of 
 impact causes the fuse to act. A type of ring-resistance point-percussion 
 fuse for minor caliber guns is shown in Fig. 37 (before arming and 
 after arming). The same type of fuse for base percussion is shown 
 in Fig. 38. 
 
 The fuse itself is a small affair relatively, but its importance cannot 
 
292 
 
 THE SERVICE OF COAST ARTILLERY 
 
 be overrated. All percussion fuses carry an interior mass called the 
 plunger, whose forward movement, when the shell is retarded, causes 
 the firing pin to strike a percussion primer and explode it. Before 
 firing the fuse must be in a " safe " or " unarmed " condition, in which 
 
 BEFORE ARMING 
 
 AFTER ARMING 
 
 85- 
 
 TIN-FOIL DISC 
 
 PRIMER CHARGE 
 
 (BLACK POWDER) 
 
 PRIMER SHIELD 
 
 (BRASS) 
 
 BODY (BRASS) 
 PERCUSION- 
 PRIMER CUP 
 PERCUSSION- 
 PRIMER SCREW 
 PERCUSSION 
 
 COMPOSITION 
 FIRING PIN 
 
 IRING PIN 
 
 SLEEVE 
 SPLIT-RING 
 LOCKING GROOVE 
 CLOSING SCREW 
 
 FIG. 37. Ring Resistance Point Percussion Fuse. For minor cailbers. 
 
 the pin cannot reach the primer, and during the flight of the projectile 
 it must be in the "ready" or "armed " position. Either or both of the 
 forces exerted on the plunger to give it the longitudinal and angular 
 accelerations communicated to the projectile may be utilized to trans- 
 
 BEFORE ARMING 
 
 PRIMER 
 CHARGE 
 PRIMER 
 SHIELD 
 Q3RASS) 
 
 LOCKING 
 GROOVE 
 
 CAP (BRASS) 
 CLOSING- 
 DISC (BRASS) 
 PRIMER- 
 SCREAK BRASS) 
 PERCUSSION- 
 COMPOSITION 
 FIRING PIN- 
 
 SPLIT-RING 
 
 SPRING (BRASS) 
 
 BODY( BRASS) 
 
 FIG. 38. Ring Resistance Base Percussion Fuse. For minor calibers. 
 
 form the plunger from the "safe" to the "ready" position. The 
 fuse is made principally of hard rolled brass. The body which forms 
 a housing for the parts of the fuse is struck at the head with a radius 
 corresponding to that of the shell in which used. Two slots are formed 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 293 
 
 in the head for a spanner wrench for insertion and removal of the fuses 
 from the projectiles. The outside of the body is turned and threaded, 
 and the interior, after being bored out for the plunger and primer parts, 
 is threaded for the closing screw. The front end of the plunger cavity 
 is bored out to form a recess for the primer, and is threaded with a 
 left-hand thread in the interior for the primer screw. A hole in the 
 top of the primer screw permits the firing pin to strike the primer on 
 impact, and allows the flame to come from the primer in the rear and 
 ignite the shell charge. The primer screw holds the primer cup in 
 place, which is longer than the recess in the primer screw, so that when 
 the latter is screwed down hard it bears upon the bottom of the primer 
 recess. 
 
 The primer cup has two chambers separated by a solid vented par- 
 tition; the lower chamber holds the percussion composition, which is 
 held in place by the primer shield, which also restrains the firing pin 
 during the flight of the projectile. 
 
 In unarmed or safe condition of the fuse, the split ring rests on a 
 conical slope on the firing pin and sustains the firing pin on the sleeve. 
 The resistance of this ring to the expansion necessary to force it ov.er 
 the slope is less than the force required to transmit the maximum ac- 
 celeration of the projectile to the sleeve, thus insuring the arming of 
 the fuse in the bore of the gun on discharge. The percussion com- 
 position of all service fuses consists usually of the following ingredients : 
 Chlorate of potash, sulphide of antimony, sulphur, ground glass and 
 shellac. The ingredients are mixed dry, alcohol being added to absorb 
 the shellac. 
 
 The action of the fuse is as follows. When the piece is fired the 
 sleeve moves to the rear, and is locked to the firing pin, the point of 
 the firing pin projecting beyond the sleeve and thus arming the fuse. 
 As the projectile meets the atmospheric retardation the plunger grad- 
 ually creeps forward until stopped by the primer shield. When the 
 projectile strikes, the firing pin pierces the shield and the thin layer 
 of percussion composition, and ignites the primer charge. This is 
 done by a small portion of the composition being caught between the 
 point of the firing pin and the anvil. 
 
 The action of the base percussion fuse and the function of its parts 
 are the same as those for the point percussion, the only essential differ- 
 ence being the position of the primer with reference to the shell charge. 
 In the case of the point fuse the flame from the primer has to pass 
 either through or around the plunger from front to rear, but in the case 
 of the base fuse the flame does not have to cross any intervening space. 
 
294 
 
 THE SERVICE OF COAST ARTILLERY 
 
 BEFORE ARMING 
 
 PRIMER DISC 
 (TIN FOIL) 
 TIRING PIN 
 LINK (BRASS) 
 PERCUSSION 
 PLUNGER 
 
 ARMING RE- 
 SISTANCE 
 BOLT & NUT 
 PERCUSSION- 
 PLUNGER BUSH- 
 
 PRIMER CLOSING 
 * SCREW 
 
 CLOSING CAP SCREW 
 PRIMER CUP 
 RESTRAINING DISC 
 __._ PIN (BRASS) 
 PERCUSSION PLUNGER 
 
 AFTER ARMING 
 9 
 
 ROTATING FIN(BRASS) 
 30DY (BRASS) 
 
 FIG. 39. Centrifugal Base Fuse F. 
 
 PRIMER DISK BEFORE ARMING 
 (TIN FOIL) 
 
 PRIMER DISK 
 (TIN FOIL) 
 
 FIRING PIN 
 
 LINK(BRASS) 
 
 PERSUSSION 
 
 PLUNGER 
 
 PERCUSSION 
 PLUNGER BUSHING 
 
 AFTER ARMING 
 
 PRIMER CLOSING SCREW 
 CLOSING CUP SCREW 
 
 PRIMER CUP (BRASS) 
 RESTRAINING DISK 
 FIRING PIN (BRASS) 
 PERCUSSION PLUNGER 
 ARISING RESISTANCE 
 BOLT AND NUT 
 ARMING RESISTANCE 
 SPRING 
 ROTATING FIN 
 
 BODY (BRASS) 
 
 FIG. 40. Centrifugal Base Percussion Fuse. Medium and major caliber. 
 BEFORE ARMING 
 
 PRIMER DISK: 
 
 (TIN FOIL) 
 
 PRIMER DISC 
 (TIN FOIL) 
 
 FIRING PIN 
 LINK 
 
 PERCUSSION 
 PLUNGER 
 BUSHING 
 
 PRIMER CLOSING SCREW 
 CLOSING CAP SCREW 
 PRIMER CUP 
 RESTRAINING DISK 
 FIRING PIN 
 
 PERCUSSION PLUNGER 
 ARMING RESISTANCE 
 BOLT AND NUT 
 
 ARMING RESISTANCE 
 
 SPRING 
 .ROTATING FIN 
 
 BODY (BRASS) 
 
 FIG. 41. Centrifugal Base Fuse, 12M. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 295 
 
 Centrifugal Fuses depend for their action on the centrifugal force 
 developed by the rotation of the projectile. The increased rapidity 
 of fire renders it necessary for all fuses to be transported fixed in pro- 
 jectiles, as too much time would be lost under war conditions if fuses 
 had to be unpacked and inserted during an engagement. The require- 
 ment also that the projectiles fused shall be handled and transported 
 with absolute safety is a reason which led to the development of the 
 centrifugal fuse. 
 
 As has been stated in the case of ring resistance fuses, or any fuse 
 the action of which depends upon the longitudinal stresses developed 
 by the pressure of the powder gases of the gun on discharge, the con- 
 ditions of safety of handling and certainty of action were imposing 
 ones. 
 
 A centrifugal fuse is armed by the centrifugal force developed by the 
 rotation of the projectile, and is safe until the maximum velocity of 
 rotation is nearly attained. The three principal types of centrifugal 
 fuses are shown in Figs. 39, 40 and 41. The fuse body or stock and 
 the primer parts of the centrifugal fuse do not differ materially from the 
 corresponding parts of ring-resistance fuses. The body of the centrif- 
 ugal plunger is in three parts, nearly semi-cylindrical in shape, which 
 when the fuse is at rest, are held together by the pressure of a spiral 
 spring contained in the cylindrical bushing which is secured to one of 
 the plunger halves. The spring exerts its pressure on the other half 
 cf the plunger through a bolt. Pivoted in a recess in one-half of the 
 [-lunger is the firing pin, which, when the fuse is at rest, is held with its 
 point below the front surface of the plunger by the lever action of the 
 link which is pivoted in the other half. Under the action of centrif- 
 ugal force developed by the rapid rotation of the projectile the two 
 halves of the plunger separate. This separation causes the rotation of 
 the firing pin, the point of which is then held in advance of the front 
 surface of the plunger, ready, on impact of the projectile, to pierce the 
 brass primer shield and ignite the percussion composition. When the 
 fuse is armed the end of the link rests on the axis of the firing pin, thus 
 affording support to the firing pin when it strikes the percussion primer. 
 The separation of the plunger parts is limited by a nut coming to a 
 bearing on a shoulder on the bushing, so as not to permit the diameter 
 of the expanded plunger to equal the interior diameter of the fuse 
 stock. 
 
 A rotation piece is screwed into the head of the fuse stock, and 
 engages in a corresponding slot cut through the bottom of both plunger 
 halves and insures the rotation of the plunger with the shell. The 
 
296 
 
 THE SERVICE OF COAST ARTILLERY 
 
 BEFORE ARMING 
 
 CONCUSSION OR 
 
 TIME PLUNGER 
 
 POWDER RING 
 
 RETAINING RING 
 BRASS WASHER 
 
 GAS CHECK CUP 
 PELT GAS CHECK 
 
 BASE COVER 
 
 CAP (BRASS) 
 SAFETY PIN 
 SPLIT-RING SPRING 
 CLAMPING RING 
 
 PERCUSSION 
 COMPOSITION 
 TIMS TRAIN 
 CQITE(LEAD) 
 CONE COVER 
 TIME TRAIN 
 
 BODY (BRONZE) 
 
 PERCUSSION 
 
 PRIMER 
 PERCUSSION 
 FIRING PIN 
 
 SLEEVE 
 
 PAPER DISC 
 
 \. X' JUJ.lkAJV4 J- JL, 
 
 0\PERCUSSION 
 \ FIRING PIN 
 
 ^SPLIT RING PER- 
 CUSSION PLUNGER 
 
 'CLOSING SCREW 
 
 FIG. 42. Combination Fuse, 15-second (Frankford Arsenal). 
 
 AFTER ARMING 
 
 CONCUSSION FIRING- 
 
 PIN (STEEL) 
 VENTS . 
 
 CONNECTING TUB: 
 CLOSING SCREW 
 
 CONE DOWEL PINS 
 
 (BRASS) 
 WRENCH HOLE 
 COVER DOWEL PINS 
 
 FIG. 43. Combination Fuse, 15-second (Frankford Arsenal) 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 297 
 
 strength of the spring is so adjusted that the fuse will not arm until 
 its rapidity of revolution is a certain percentage of that in the shell 
 in which it is used, and that it will certainly arm when the rapidity of 
 revolution approximates that expected in the shell. Should the parts 
 of the plunger be accidentally separated and the fuse armed by a 
 sudden jolt or jar in transportation or handling, the reaction of the 
 spring will immediately bring the plunger to the unarmed position. 
 
 Centrifugal plungers are used as base percussion fuses in the small, 
 medium, and large-caliber guns, howitzers and mortars, also as base- 
 detonating fuses in the medium and large caliber as well as the per- 
 cussion plunger in combination fuses. 
 
 The greater simplicity and cheapness of the ring-resistance fuse and 
 its greater certainty of action make it more suitable for use whenever 
 practicable. 
 
 Combination Fuses used in the service are point insertion and 
 combine the elements of time and percussion arranged to act indepen- 
 dently in one fuse body. Combination fuses contain two plungers and 
 two primers, arming and firing by concussion and percussion, respec- 
 tively. The concussion plunger arms and fires the percussion primer 
 by shock of discharge in the bore of the gun and ignites the time ele- 
 ment. The percussion plunger is armed by the shock of discharge and 
 fires its primer on impact. 
 
 There are at present two general classes of combination fuses in 
 the service, differing principally in the details of the time-train elements. 
 In the first class this element consists of a wire-drawn lead tube filled 
 with meal powder wound in a spiral groove around the lead core. In 
 the second class this element consists of two superposed trains of meal 
 powder compressed with heayy pressure in annular grooves in disks 
 of brass. 
 
 The first class is shown in Figs. 42 and 43, the second class is repre- 
 sented in Figs. 44, 45 and 46. JiTo more fuses of the first class are to 
 be manufactured, those of the second class having been found far 
 superior in many respects. The combination fuse of the first class 
 cannot be reset, while those of the second class can be reset many times 
 if desired. This fuse is also superior in that it has greater uniformity 
 of action clue to the improvement in the time-train feature. The 
 fuses of class one have the time-train element composed of the concus- 
 sion or time plunger, the firing pin, the cone, the time train, the cone 
 cover, the cap and the clamping nut. The plunger is cylindrical in 
 shape and contains the fulminate primer in a recess in its base. Its 
 upper extremity is pierced to receive a safety pin which retains the 
 
298 THE SERVICE OF COAST ARTILLERY 
 
 plunger in its safe or unarmed position in handling and transportation. 
 When the safety pin is removed, which is done just before firing, the 
 weight of the plunger rests on the split-ring spring. The action of the 
 latter on discharge is similar to that of the split-ring spring of other 
 ring-resistance fuses already described. 
 
 The cone is an alloy of soft metal held in place on the fuse body 
 by a clamping nut and a groove at the bottom, and is prevented from 
 turning by four steel dowel pins. The lip on the bottom of the cone, 
 entering the groove in the body, acts as a gas check to prevent the 
 ignition of the powder in the connecting tube. On the exterior of 
 the cone is a left-handed groove which carries the time train, and this 
 time train communicates at its lower end with the priming charge 
 in the tube and thence with the magazine. The time train is formed 
 of a lead tube filled with meal powder and is wire drawn. 
 
 The cone cover is of brass, and is held in place by a cap and pre- 
 vented from turning by a small pin projecting from the body and fitting 
 in a slot on its lower edge. On the exterior of the cone is a left-handed 
 groove corresponding to that on the time train, and this groove is 
 pierced with holes numbered from 1 to 15 or 1 to 21 or 1 to 28 as the 
 case may be, these numbers corresponding to the number of seconds, 
 the spaces between the holes being divided into 5 equal parts, or fifths 
 of seconds. The percussion element may consist of either the ring- 
 resistance plunger or the centrifugal plunger, depending upon the type 
 of fuse considered. 
 
 The action of the fuse is as follows: As a time fuse: A hole is 
 punched through the cover, time train and lead cone, at the point in 
 the cover corresponding to the number of seconds desired. Before 
 loading the safety pin is removed, and this allows the time plunger to 
 rest on the fuse body, where it is held by the split-ring spring. The 
 projectile is then inserted in the gun. By the shock of discharge the 
 split-ring spring is expanded and the plunger forced to the rear, the 
 primer striking the firing pin and exploding. The flame from the 
 primer passes through the four radial holes and ignites the ring of 
 compressed powder. The only vent for these gases is a punched hole, 
 and they ignite the time train at that point. The train burns and 
 ignites the powder in the tube and the magazine. The flame from 
 the magazine passes through the percussion primer and percussion- 
 plunger chamber and ignites the bursting charge in the shell. 
 
 As a percussion fuse: The percussion plunger arms by shock of 
 discharge and fires the percussion primej on impact as in other per- 
 cussion fuses. The percussion plunger is grooved or fluted to permit 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 
 
 299 
 
 ready passage of the flame from the front to the rear. In order to use 
 this fuse in base charge shrapnel an extension piece is necessary, and 
 is screwed in the base of the fuse in place of the bottom-closing screw. 
 The ignition of the pellet of compressed powder in the extension piece 
 transmits the flame through the central tube to the base charge. 
 
 BEFORE ARMING 
 
 TIME OR CONCUSSION PLUNG 
 SPLIT RING SPRING (BRASS) 
 FRONT CLOSING CAP (BRONZE 
 FIRING PIN (BRASS) 
 UPPER TIME TRAIN RING 
 
 (BRONZE) 
 CLOTH WASHER 
 
 LOWER TIME TRAIN RING 
 CLOTH WASHER 
 
 PERCUSSION PRIMER 
 POWDER MAGAZINE 
 
 LINEN GAUZE 
 
 BODY (BRONZE) 
 FRONT CLOSING CAP 
 VENT TO UPPER TRAIN 
 .COMPRESSED POWDER PELLET 
 .UPPER TIME TRAIN ( COM. POW.) 
 
 OMPRESSED POWDER PELLET 
 IN VENT TO LOWER TRAIN 
 
 OWER TIME TRAIN 
 
 (COMPRESSED POWDER) 
 
 COMPRESSED POWDER PELLET 
 IN VENT TO LOWER TRAIN 
 
 ENT LEADING TO MAGAZINE 
 PERCUSSION PLUNGER 
 BOTTOM CLOSING SCREW 
 
 FIG. 44. Combination Fuse, 21-second, Model of 1907. 
 
 BEFORE ARMING 
 
 ?IMB OR CONCUSSION PLUNGER 
 5) - 
 
 UPPER TIME TRAIN (COMPRESSED POWD! 
 COMPRESSED POWDER PELLET IN 
 LEADING TO LOWER TIME TRAIN 
 
 COMPRESSED POWDER PELLET. IN VENT 
 LEADING TO MAG1ZINE 
 VENT LEADING TO MAGAZINE 
 
 POWDER MAGAZINE 
 
 ROTATING DEVICE (BRASS) 
 LINEN GAUZE 
 
 BODY (BRONZE) 
 
 FRONT CLOSING 
 CAP (BRONZE) 
 
 _._. TIME TRAIN 
 RING (BRONZE) 
 CLOTH WASHER 
 LOWER TIME TRAIN 
 ^IWG (BRONZE 
 LOTH WASHER 
 
 ERCUSSION PRIMER 
 CENTRIFUGAL 
 PERCUSSION PLUNGER 
 CLOSING CUP (BRASS) 
 CLOSING SCREW(BRASS) 
 WASHER (BRASS) 
 
 FIG. 45. Combination Fuse (Centrifugal) 21-second (Frankford Arsenal). 
 
 The latest types of combination fuses are those shown in Figs. 
 44, 45 and 46, and belong to class two. The body of the fuse and the 
 front closing cap are machined from bronze castings. The upper and 
 lower time-train rings are turned from hard rolled rods of Tobin bronze. 
 An annular groove in the shape of a horseshoe is milled in the lower 
 face of each of the time-train rings. Meal powder is compressed in 
 these grooves under a pressure of 70,000 pounds per square inch, 
 forming a time train of necessary length. 
 
 The time element of this fuse consists of the following parts: The 
 
300 
 
 THE SERVICE OF COAST ARTILLERY 
 
 time or concussion plunger, the split-ring spring, the firing pin, the vent 
 leading to the upper time train, the compressed powder pellet, lower 
 time train, the compressed powder pellet in the vent leading to the 
 powder magazine. 
 
 The upper ring is prevented from rotating by pins which are halved 
 into the fuse body and the inner circumference of the ring. A vent is 
 drilled through the walls of the percussion chamber and is exactly 
 opposite a hole in the inner surface of the upper time train leading to 
 the end of the train from which the direction of burning is anti-clock- 
 wise. Another hole is drilled through the upper face of the lower 
 
 EXTERIOR 
 
 RETAINING WIRE 
 
 COMPRESSED POWDER PELLET 
 IN UPPER TIME- TRAIN VENT 
 COMPRESSED POWDER PELLET 
 IN LOWER TIME- TRAIN VENT 
 FUZE SETTER STUD(BRASS) 
 
 FIG. 46. Combination Fuse, 21-second, Model of 1907. 
 
 time-train ring, to the end of the lower time-train groove from which 
 the direction of burning is clockwise. The lower time-train ring is 
 immovable and is graduated on its outer edge in a clockwise direction 
 from to 21, each full division corresponding to one second of time of 
 burning in flight. These divisions are subdivided into five equal parts 
 corresponding to one-fifth seconds. A fixed pin or stud is provided on 
 the lower or graduated time-train ring, which enters a notch of the 
 corrector ring or fuse setter when set in a fuse. An arrow on the 
 lower side of the fuse stock is the datum line for the fuse settings. 
 
 A vent is drilled through the flange of the fuse stock to the powder 
 magazine, and leads to the same end of the lower time train as the 
 vent last described; that is, the end which the direction of burning is 
 clockwise when the fuse is at its " O " setting. 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 301 
 
 The action of the time feature of the fuse is as follows: Assume 
 first the zero setting as shown in Fig. 46. The time plunger arms and 
 fires the primer which it carries as in the case of the first fuse described. 
 The flame from the primer passes out through the vent drilled through 
 the walls of the concussion plunger chamber and ignites the pellet at 
 the end of the upper time train (see Fig. 44) , down through the vent 
 through the upper surface of the lower time train, to the end of the 
 lower time train and thence through the vent to the magazine, 
 the flame from which is transmitted to the base charge in the 
 shrapnel. 
 
 It will be seen that for the zero setting of the fuse the origin of both 
 the upper and lower time trains are in juxtaposition. For any other 
 setting, say 12 seconds: The vent through the upper face of the lower 
 time train changes its position with respect to the vent leading to the 
 beginning of the upper time train and the vent leading to the powder 
 magazine, both of which points are fixed by the angle subtended 
 between the 0- and the 12-second settings. For this setting the flame 
 passes out through the vent drilled through the walls of the concussion 
 plunger chamber and burns on the upper time train in an anti-clock- 
 wise direction until the vent drilled through the upper surface of the 
 lower time train is reached, where it passes down to the beginning 
 of the lower time train and burns back in a clockwise direction to the 
 position of the vent leading to the powder magazine, whence it is trans- 
 mitted by the pellet of compressed powder. 
 
 If the fuse is set for 21 seconds, the vent through the upper face of 
 the lower time train is opposite the end of the upper time train and 
 the end of the lower time train is opposite the vent leading to the 
 powder magazine. It will be seen that to reach the magazine and 
 burst the shrapnel, the entire length of time train in both rings must 
 be burned. 
 
 As the annular grooves in the lower face of each ring for the powder 
 trains do not form complete circles, a solid portion being left between 
 the ends of the grooves, the fuse can be set at the safety point quoted, 
 which is indicated by the letter S, in which position the fuse cannot 
 be exploded. 
 
 The fuse is provided with cloth washers glued to the upper surface 
 of the time-train ring and to the upper face of the flange on the fuse 
 stock, the function of these washers being to provide a gas check and 
 prevent a premature action of the fuse. The percussion elements of 
 the fuse consist of the percussion plunger and ordinary percussion 
 primer. The fuse is also provided with a centrifugal percussion plunger 
 
302 
 
 THE SERVICE OF COAST ARTILLERY 
 
 which will take up immediately the rotation of the projectile when a 
 rotating device, which consists of jaws fitted over the corresponding 
 flat surfaces on the plunger, is fastened to the fuse body. 
 
 Detonating Fuses are for use in shell containing high explosives. 
 They are made for point and base insertion, the former being used in 
 the field shell, the latter in siege and seacoast projectiles. The de- 
 tonating fuse differs from the simple percussion fuse heretofore de- 
 scribed in having in addition to the percussion elements a detonating 
 element or one which will produce an explosion of high order when 
 burst in a projectile containing a charge of high explosive. 
 
 DETONATING FUSES 
 
 Official Designation of Fuse. 
 
 Weight 
 of Fuse, 
 in 
 Pounds. 
 
 Projectiles in which Used. 
 
 Minor caliber base detonating 
 
 0.195 
 
 In 6-pounder and 2 38-inch steel shell 
 
 
 
 Picric acid bursting charge. 
 
 Special " S " base fuse, with 100 grain 
 detonator 
 
 65 
 
 In 3-inch r.f. gun, steel shell tapped in 
 base for this fuse To be super- 
 
 
 
 seded by medium caliber base deto- 
 nating fuse. 
 
 Medium caliber base detonating fuse . 
 
 1.5 
 
 In all steel projectiles for guns from 
 2.95 to 7 inches (inclusive) in caliber. 
 
 Armor-piercing base detonating fuse 
 (modified) . . 
 
 7 09 
 
 In 8- 10-, and 12-inch rifle A. P. shot 
 and shell adapted to the fuse To 
 
 
 
 be superseded by major caliber 
 detonating fuse. 
 
 Major caliber base detonating fuse . . 
 
 2.908 
 
 In 8-, 10-, and 12-inch rifle and mor- 
 tar steel projectiles. 
 
 To have sufficient energy to completely detonate a high explosive 
 bursting charge in projectiles the detonating fuse must contain high 
 explosive within itself. The service detonating fuse for seacoast pro- 
 jectiles contains two explosive compounds. The reason for this is as 
 follows: All detonating fuses contain a percussion plunger either of 
 the ring-resistance type or of the centrifugal type, depending upon the 
 projectile in which used, and a percussion primer. This primer con- 
 sists of the percussion composition and an igniting charge of black 
 powder. The explosion of the primer is of low order and would not of 
 itself detonate the high explosive charge contained in the fuse. To 
 
EXPLOSIVES, PROJECTILES, PRIMERS AND FUSES 303 
 
 .accomplish this it is necessary to introduce between the percussion 
 primer and the detonating charge an auxiliary high explosive sufficiently 
 sensitive to be fired by the percussion primer and sufficiently powerful 
 to detonate the high explosive charge proper contained in the 
 fuse. 
 
 In order to contain these detonating elements it is necessary for the 
 body of the fuse to be increased in length. 
 
 The table on the preceding page gives a list of the detonating fuses 
 used in the steel projectiles containing a bursting charge of high 
 explosives. 
 
CHAPTER VII 
 INSTRUMENTS, DEVICES AND CHARTS 
 
 THE various instruments, devices and charts described in this 
 chapter may be classified as follows : 
 
 Those used in the Observing Room for finding the position of targets, 
 which include the depression position finders and the azimuth instrument. 
 Those used in the plotting room for locating and correcting the range 
 and azimuth of targets, together with the necessary signal system inci- 
 dental thereto, which include the plotting board, the range board, the 
 deflection board, the wind component indicator, the aeroscope, the time- 
 interval bell, the time-interval clock, the interrupter, the telephone and 
 telautograph. 
 
 Those used in the Meteorological Station for furnishing data to the 
 plotting rooms in connection with the condition of the atmosphere 
 and the direction and velocity of the wind, which include the ther- 
 mometer, barometer, anemometer and atmosphere board. 
 
 Those used on guns and mortars for sighting and laying; also for 
 determining the maximum powder pressure in the chamber, which 
 include the various sights, the gunner's quadrant, and the crusher 
 gauge. 
 
 The time-range board is used at the emplacement to provide 
 information for keeping the piece laid continuously for range. The 
 powder chart is, for convenience, placed herein. 
 
 Height of tide is received at the plotting rooms from the Tide 
 Station, where the data is procured from a tide indicator, and sent out 
 by means of the telephone or the aeroscope. 
 
 DEPRESSION POSITION FINDER 
 
 Depression position finders are arranged for reading both vertical 
 and horizontal angles, and therefore, may be used as either depression 
 position finders, or as azimuth instruments. Objects, when viewed 
 from an elevation, appear under different angles of depression, according 
 to their distances from the point of observation, and it is this fact that 
 
 304 
 
PLATE XXI 
 
 TIME INTERVAL BELL 
 
 STRIDE 
 
 LEVEL NUT 
 
 ERECTING PRISMS 
 AND HOLDER 
 
 EST BAR CAP 
 
 LEVEL BO 
 
 OBJECTIVE 
 END TUBE 
 
 MICROMETER 
 
 SCREW 
 
 HEIGHT SLIDE 
 KNOB 
 
 ELL RING SCREWS 
 
 ILEVATING AND 
 'Z PRESSING 
 4ANOWHEEL 
 
 PPOSITE SIDE) 
 
 STANDARDS 
 (PART OF CRADLE) 
 
 VERTICAL SPINDLE 
 BEARING 
 
 RANGE 
 POINTER 
 COVER 
 
 AZIMUTH PLATE 
 HANDLE 
 
 LAMP BRACKET AND 
 
 OPENING FOR READ 
 
 !NG HUNDREDTHS 
 
 OF DEGREES 
 
 AZIMUTH PLATE 
 BOLTS . 
 
 READING OPENING 
 [AZIMUTH CIRCLE ) 
 
 AZiMUTH CIRCLE 
 LAMP BRACKET 
 
 Warner & Swasey D. P. Finder, Type A-l. 
 
INSTRUMENTS, DEVICES AND CHARTS 305 
 
 is taken advantage of in the depression position finder when used to 
 measure vertical angles. 
 
 In principle, it is based upon the solution by observation of a vertical 
 right angle when given a side and two adjacent angles. The given 
 side, called the base, is the distance above mean low water of the pivot 
 about which the telescope of the instrument is elevated and depressed. 
 The lower angle is constant, and is equal to 90 degrees. The upper 
 angle varies with the distance of the observed object. 
 
 The principal parts of the instrument are shown in Plate XXI, and 
 consist of the telescope, the cradle, the height slide, the range drum 
 shaft, the range pointer, the range-pointer bracket and the attachment 
 for correction of the curvature of the earth and normal refraction, the 
 range drum, the vertical spindle, the azimuth circle, the azimuth worm 
 screw, the azimuth drum, the azimuth plate, leveling screws, base, 
 cables, lamp and lamp brackets. 
 
 The principal- parts of the telescope are the tube, trunnions, the cell 
 ring, the cell, the objective, the prisms, the micrometer box, cross wires, 
 micrometer screw, micrometer slide, the draw tube, the focusing nut 
 and ring, the eyepiece adapter, the eyepiece, the right and left guides, 
 the level and the dew cap. The telescope objective has a 3-inch clear 
 aperture, and is provided with powers 12 and 20. The field of view 
 is 1.85 degrees with both eyepieces. The range drum is graduated 
 every 10 yards, from 1,500 to 12,000. 
 
 To Use the Instrument after it has been properly mounted, it 
 should be first put in adjustment, and in doing this, it may be found 
 convenient to take up the different steps in the following order: First, 
 leveling. Second, adjustment of telescope. Third, orientation. 
 
 First: To level the instrument, it should be set up so that it is 
 practically level with equal lengths of leveling screws exposed. The 
 cradle can then be brought exactly level by using the leveling screws. 
 The cradle is turned so that the telescope lies parallel with, or directly 
 across two opposite leveling screws. This causes the levels to be 
 parallel with opposite leveling screws. The bubble in each level is 
 then brought to the center by turning both leveling screws either in 
 or out, depending on the way the bubble is to go, a good rule being 
 that the bubble follows the direction in which the left thumb is turned. 
 After centering the bubble with one set of screws, do the same thing 
 with the two other leveling screws, with which the other cross level is 
 parallel. The instrument should then be revolved 180 degrees, and if 
 the bubbles do not remain in the center of the levels, they should be 
 brought there in the manner just described, except that half of the 
 
306 
 
 THE SERVICE OF COAST ARTILLERY 
 
 error in level should be corrected 
 by the level-adjusting screws, 
 and the other half with the 
 leveling screws. The instrument 
 is again revolved 180 degrees, 
 and the operation repeated until 
 the bubbles of the levels remain 
 in the center of the levels for all 
 positions of the cradle. If the 
 range drum be rotated until the 
 reading is " telescope level," the 
 stride level on the telescope 
 should show the telescope to be 
 horizontal. If such is not the 
 case, the drum should be rotated 
 until this condition is obtained. 
 The screws holding the range 
 drum to the beveled gear 
 loosened, the handle being firmly 
 held, the drum should be rotated 
 until the line corresponds with 
 that on the pointer, then the 
 screws should be set up again. 
 The bubble of the level on the 
 telescope should then remain 
 stationary, while the height slide 
 is moved to any position. 
 
 Second: Adjustment of the 
 telescope. The telescope is a 
 delicate piece of apparatus, and 
 requires careful use and adjust- 
 ment. Its interior mechanism 
 is shown in Fig. 47. To obtain 
 satisfactory results, the telescope 
 should have absolute clearness 
 of vision, which requires that 
 the lenses be kept free from 
 moisture, the erecting prisms 
 should never be removed, nor 
 the objective lens removed from 
 the objective cell or ring. The 
 
INSTRUMENTS, DEVICES AND CHARTS 307 
 
 two principal and important adjustments of the telescope are the 
 adjustment of the eyepiece, and the adjustment for collimation. 
 
 To adjust the eyepiece, the objective should be turned all the way 
 in or all the way out, so that- there is no object in the field. This 
 causes a milky background for the cross wires. The eyepiece should 
 then be removed, first to its outer limit for clearness of the cross wires, 
 then to its inner limit. The observer should then try to set the eye- 
 piece at a point midway between these two positions, which position 
 should show the cross wires very distinctly, and with exact clearness. 
 
 The eyepiece, when once adjusted, should need no further atten- 
 tion unless the observer is changed. The eyepiece serves to give a 
 distinct and magnified view of the image. Its magnifying power is 
 large, and its focal range of distinct vision is very small, depending 
 upon its magnifying power. With the ordinary field instruments, it 
 is about 1/16 inch. Both the image, as formed by the objective, and 
 the cross wires, should lie in the focus of the eyepiece; that is, they 
 should be in the same plane. The image is moved back and forth by 
 moving the objective in or out, but the plane of the cross wires is fixed. 
 If the two are brought into the same plane, it is necessary that the 
 image be brought upon the cross wires. The adjustment just de- 
 scribed accomplishes this very thing; it brings the focus of the eye- 
 piece on the cross wires so they are most distinct. The objective may 
 then be moved until the image or target also comes into focus. This 
 focusing does not remain the same at all ranges, or for all observers, 
 and must be done with each pointing, if the distances are materially 
 changed. Should the image be not brought into exact coincidence 
 with the cross wires, the cross wires will appear to move slightly on 
 the image as the eye is moved behind the eyepiece. This movement 
 or apparent displacement of the target is what is known as parallax, 
 and can only exist when the cross wires do not lie in the focus of the 
 eyepiece. It is removed by refocusing the objective, which moves the 
 image until there is no perceptible movement of the wire or image as 
 the eye is shifted. In other words, they are practically in coincidence. 
 If the eye were always in the center of the eyepiece, there would be no 
 parallax, and it is for this reason that the eyepiece is covered with a 
 shield with a small hole in the center. Even with this small hole, a 
 slight movement of the eye, if the telescope is not properly adjusted, 
 will cause a perceptible angular error. 
 
 This adjustment may be summed up as follows : The eyepiece 
 adjustment is a personal adjustment, and is made once for all for any 
 given observer, but the objective adjustment depends upon the dis- 
 
308 THE SERVICE OF COAST ATILLERY 
 
 tances of the object from the instrument, and is made for each pointing; 
 that is, it may have to be changed even for the same observer at different 
 ranges. It may be considered as in perfect focus or adjustment when 
 there is no parallax. 
 
 Usually the collimation of the telescope will be correct, but if neces- 
 sary to adjust it for collimation, the telescope should be leveled, and 
 the intersection of the cross wires brought on the target, some well- 
 defined object being used, and the telescope then reversed. That is, 
 the telescope is turned over, so that what was the original top of the 
 vertical diameter is brought to the bottom. If the intersection of the 
 cross wires is not then on the same part of the target, the dew cap and 
 ring should be removed, and the cross wires brought on to the same 
 line on the target by correcting one-half of the discrepancy by means 
 of the radial screws in the object ring. This operation is repeated until 
 the intersection of the cross wires remains on the target when the tele- 
 scope is reversed. The telescope -is then accurately collimated. The 
 adjustment for parallax should be made before collimation is attempted, 
 as an error in parallax will result in the adjustment for collimation being 
 of no value, even after several attempts have been made by reversing 
 the telescope. 
 
 Third: For the proper orientation of an instrument, it is essential 
 that at least three datum points be provided. These datum points 
 are designated D-l, D-2 and D-3, the first being the short-range 
 datum point located between 2,000 and 2,500 yards, the second 
 the midrange datum point located at about 5,000 yards, and 
 the third the long-range datum point at about 9,000 yards. Datum 
 points may be either lighthouses, buoys, tripods of piles, or of any 
 design suitable in shape for clear vision at the ranges specified. If 
 cylindrical in shape, they should be at least one foot in diameter for 
 every 1,000 yards of range from the instrument, and sufficiently 
 high to be readily distinguished at high water. Each datum point 
 should have upon it a reference mark at a known height above 
 mean low water; that is, above the fixed plane of reference of the range- 
 finding instruments. These heights are usually from six to ten feet. 
 The datum points are accurately located, and their azimuth and ranges 
 from the various stations accurately determined, usually from their 
 geodetic position. 
 
 Before attemping to orient the instrument, the range drum should 
 be rotated until the reading "telescope level" is opposite the pointer. 
 The stride level on the telescope should then show the telescope to be 
 horizontal. If this is not the case, the drum should be rotated until 
 
INSTRUMENTS, DEVICES AND CHARTS 309 
 
 that condition is obtained, the screws attaching the range drum to the 
 beveled gear should be loosened, and while the handle is firmly held, 
 the drum should be rotated until the line corresponds with that on the 
 pointer, and the screws should then be set up. The telescope should 
 then be horizontal, and the reading on the range drum should be 
 " telescope level." The instrument should be set for the correct height 
 above mean low water by the height scale. Now direct the telescope 
 on datum point No. 3, the range drum having been set at the range for 
 same, and water-line by means of the micrometer screw. Then direct 
 the instrument on datum point No. 1, or the short range datum point, 
 the range pointer having been set at the range of datum No. 1, and water- 
 line by means of the height slide pinion. Repeat this operation until 
 correct readings are obtained, by water-lining by means of the range 
 crank. Then set the instrument for the range and azimuth of the 
 midrange datum point, the difference between the range reading and 
 the true range as given in the datum chart, should be less than the danger 
 space of the gun considered at that range. If it is correct, no further 
 adjustment should be made. If this difference be appreciably greater 
 than the danger space at the midrange datum point, then datum point 
 Xo. 2 should be substituted for either No. 1 or No. 3, and the set of ad- 
 justments as just described made. Should the vertical wire not be 
 exactly on the datum point when set at the correct azimuth, it should be 
 brought there by turning the azimuth zero set screws. This adjust- 
 ment, when once made, should be repeated at longer or shorter inter- 
 vals, depending on the extent of the variation of the tide, and when- 
 ever atmospheric conditions have appeared to change considerably. 
 
 The adjustment for abnormal refraction should always be made at 
 the long-range datum point, as refraction is greatest at this point. 
 The adjustment for tide can best be made at the short-range datum 
 point. The refraction surface is assumed to be an inverted cone, with 
 its apex at the foot of the vertical base. If the condition of refraction 
 is uniform through the whole 360 degrees, the axis of this cone will toe 
 vertical; otherwise, it will be inclined. When the field of fire is for 
 the same water area, it is probable that it will be sufficiently accurate 
 to consider this axis vertical, and but one set of datum points will be 
 required. 
 
 Use and Care of the Instrument. When the observer is about to 
 begin work, his first duty is to verify the level of the instrument. He 
 then adjusts the eyepiece, and focuses the telescope according to the 
 principles laid down. The instrument should then be sighted upon 
 the datum points in the order given, and the orientation verified. 
 
310 THE SERVICE OF COAST ARTILLERY 
 
 The instrument in itself embodies an automatic means of correcting 
 for the curvature of the earth, and normal refraction, which is ordinarily 
 taken as one-seventh of that of curvature. When the range crank is 
 rotated, it causes the rotation of the range-drum shaft by means of a 
 beveled gear. This rotates the range drum which is secured to the gear, 
 causes rotation of the lower arm of the lever about the lever pivots by 
 means of the worm on the shaft, and the worm segment on the arm, 
 and causes movement of the range pointer by means of the worm on 
 the shaft, and the segment on the pointer arm. The rotation of the 
 lower arm of the lever causes a corresponding movement in the forward 
 arm, which elevates or depresses the telescope by rotating it about its 
 trunnions. The rotation of the pointer arm about its bearings in the 
 pointer bracket is, at its upper end, communicated to the pointer, the 
 direction of the movement being governed by the guides. If large 
 azimuth movements are desired, the worm box crank should be turned 
 to the rear, which releases the cradle so that it will freely revolve on 
 the spindle. When the general direction has been obtained, the worm 
 should be thrown into mesh, and the movement controlled by the 
 azimuth drum, which rotates the worm and revolves the cradle about 
 the spindle and azimuth circle. If desired, a small movement can be 
 obtained by loosening the four azimuth plate bolts and moving the 
 table and all above it, with reference to the base. One of the chief 
 sources of error in tracking is due to the attempt of the observer to 
 follow in azimuth and range at the same time. It has been found that 
 the best results are obtained as follows: 
 
 When Using the Vertical Base. The vessel should be followed 
 in azimuth without attempting to water-line accurately. Keep the 
 horizontal hair a little below the water-line until the first stroke of the 
 time-interval bell, when the target should be accurately water-lined 
 by bi-secting the bow-wave, and kept accurately water-lined until the 
 last stroke of the bell, at the same time maintaining the vertical hair 
 as near as possible on the designated point of the ship. Stop the 
 instrument promptly at the last stroke of the bell to enable the reader 
 to read the range and azimuth as given on the instrument. If the vessel 
 is moving directly away from the observer, water-line on the stern. 
 If the bow-wave, or bone, cannot be seen, water-line on the side of the 
 vessel, endeavoring to take a mean of the wave lines which are made by 
 the vessel going through the water. It is not necessary to water-line 
 at the middle point of the horizontal hair. 
 
 It must be remembered in using this system, that while it is important 
 to make accurate azimuth observations, it is far more important to 
 
PLATE XXII 
 
 PRISM CASE 
 
 EYEPIECE 
 AND ADAPTER 
 
 TELESCOPE 
 DEPRESSION BAR 
 
 COMPENSATING 
 SCREW 
 
 COMPENSATING 
 BAR 
 
 TANGENT 
 SCREW. NUT, ETC. 
 
 TABLE CLAMP 
 
 DRAW TUBE 
 
 FOCUSING WHEEL 
 
 TELESCOPE TUBE 
 
 SUN 
 SHADE 
 
 TELESCOPE 
 COUNTERWEIGHT 
 
 TABLE 
 
 LEVELING SCREW 
 
 LEVELING SCREW 
 SOCKETS 
 
 Depression Position Finder, Lewis Type. 
 
*"* OF THE 
 
 UNIVERSITY 
 
 OF 
 
INSTRUMENTS, DEVICES AND CHARTS 311 
 
 water-line accurately, for in the vertical-base system, it depends upon 
 the accuracy used in determining the range. Small errors in azimuth 
 are less liable to occur than large errors in range due to faulty water- 
 lining. In attempting to water-line the side of the vessel, the cross 
 hair is often lost in consequence of the character of the background. 
 The observer, in order to obtain a good background, unconsciously 
 water-lines short; that is, he will see a little water between the hair 
 and the side of the ship. The water passing along the side of the 
 vessel forms a succession of waves, and the observer is liable to water- 
 line over or under, according as his eye catches the crest or the bottom 
 of a trough. It is therefore much better to water-line the bone whenever 
 it can be done. 
 
 When Using the Horizontal-Base System. The vessel should 
 be followed in azimjuth, keeping the vertical hair approximately on 
 the designated point until the first stroke of the time interval bell, the 
 horizontal hair being at the same time kept a little below the vessel. 
 Then bring the vertical hair accurately to the designated point, the 
 central line of a funnel or mast, and keep it there until the last stroke of 
 the bell, and then stop the instrument promptly. Observations should 
 be made on the forward military mast whenever the vessel followed 
 has one and it can be seen. In other cases, the observations should be 
 made on the forward funnel unless the range officer designates some other 
 point. It is not well to use the bow of vessels as points of observa- 
 tion, as they are not usually clearly defined, and in the horizontal-base 
 system, the bow may not always be visible from both stations. 
 
 Too much stress cannot be put upon accuracy in observations, 
 both in time and azimuth, when using the horizontal-base system, 
 because upon this accuracy depends the accuracy of range. To avoid 
 error, both instruments must be stopped instantly at the last stroke 
 of the bell. 
 
 The maximum distance at which the depression position finder 
 can be expected to give sufficiently accurate ranges may be taken 
 as a distance equal to 1,000 yards for every 10 feet of height of the in- 
 strument above mean low water. Up to this distance, the maximum 
 allowable error is one-half of one per cent, of the range, and observers 
 should be trained until they can accurately and quickly determine 
 ranges within the allowable error. 
 
 Care and Preservation of the Instrument. Position finders, 
 particularly the telescope, are delicate instruments, and should not be 
 subjected to rough usage, jars or strains. When not in use, the tele- 
 scope should be covered, protected from dust and moisture. To obtain 
 
312 THE SERVICE OF COAST ARTILLERY 
 
 satisfactory vision, the glasses should be kept perfectly clean and dry. 
 A piece of chamois skin or a clean linen handkerchief will always 
 answer for cleaning purposes, care being taken that the cleaning cloth 
 does not contain any dirt or grit. The lenses will seldom require 
 cleaning on the inside, but when necessary, they should be unscrewed, 
 and cleaned by a competent person only. The objective glass, erecting 
 prisms, should not be moved from the objective cell and ring and the 
 prism holder, except by an optician, and if they need repair they 
 should be reported to the proper authorities. The cross wires should 
 not be touched. Any dirt should be removed by blowing. The 
 instrument should be regularly . oiled at all the marked oil holes and 
 bearings with a high-grade clock oil. 
 
 LEWIS DEPRESSION POSITION FINDER, MODEL OF 1907 
 (Plate XXII) 
 
 These instruments are designed to measure ranges and horizontal 
 angles of objects from stations overlooking the sea. Ranges are 
 automatically indicated by a pointer and dial when the telescope is 
 depressed so that the horizontal cross wire coincides with the water- 
 line of the object. Horizontal angles are automatically indicated by 
 dials when the vertical cross wire of the telescope coincides with the 
 object 
 
 Ranges are measured in yards, the dials being marked for each 
 10 yards between the minimum and maximum ranges. Horizontal 
 angles are measured to one hundredths of a degree. 
 
 The principal parts are the telescope, the compensator and depres- 
 sion mechanism in the case, the azimuth dials, the 1/100 degree scale, 
 the table, body, pedestal cap and pedestal. The telescope has an 
 achromatic objective with a clear aperture of 3 inches and focus of 
 25 inches, which affords well-defined flat fields of view of 3 and 2 
 degrees when the 15- and 25-power eyepieces, respectively, are used. 
 
 The range-measuring feature consists in measuring the tangents of 
 angles of depression of the telescope when directed at the water-line of 
 an object on the sea. The range dial is spiral in form and a traversing 
 pointer indicates the range mark to be read for any position of the 
 telescope. The graduations on the range dial are exact for one height 
 of the instrument, due allowance being made for curvature of the 
 water surface and normal atmospheric refraction. This height is 
 designated the initial height and it is usually that height on the height 
 scale which locates the point of the compensating screw in the sliding 
 
PLATE XXIII 
 
 Yoke Ce.p 
 
 Trunnion 
 Clamp Screw 
 
 Telescope 
 Trunnion 
 
 Focusing Knob 
 
 Sunshade 
 
 Objective 
 Dew Cap 
 
 Adjusting Screws Slow Motion 
 Clamp 
 
 Azimuth Shield 
 Leveling Screws 
 Instrun-.ent Base 
 
 Tripod 
 
 Fhumb Screws 
 
 Telescope 
 Lamp and Bracket 
 Eye Piece Adapter 
 
 Eye Piece 
 
 Eye Lens 
 
 Cross Wire Holder 
 
 md Adjusting Screws 
 
 Erecting Prism, 
 
 Holder and Case 
 
 Reading Openings 
 
 Two Way Switch 
 
 Worm Box 
 
 Adjusting Screw 
 
 Worm Box 
 
 Illuminating Reflector 
 index Pointer Underneath 
 
 \V. & S. Azimuth Instrument. 
 
INSTRUMENTS, DEVICES AND CHARTS 313 
 
 block at a distance of 7 inches from the axis about which the telescope 
 rotates, measured horizontally along the tangent-screw rail. 
 
 When the slide block is set for this initial height the range dial 
 gives exact range readings for all ranges, but when set for greater or 
 less heights only the minimum and maximum ranges will be correctly 
 indicated. All intermediate ranges will be in error to a varying ex- 
 tent. By means of the compensator, automatic compensation is made 
 for these errors, which are caused by the varying effects of curvature 
 of the surface of the sea and atmospheric refraction when the instru- 
 ment is used at any other than the initial height above sea level. 
 These instruments are ma'de for heights from 25 to 690 feet, they 
 have interchangeable depression mechanisms, height scales and range 
 dials. 
 
 Before using the instrument the following adjustments are necessary: 
 
 1. To Adjust the Azimuth Mechanism. When moved or shipped 
 the azimuth mechanism is put out of mesh, so it is first necessary to make 
 this adjustment. On a radial line through the center of the azimuth 
 dials are four screw heads. Counting from the center of the instrument 
 out, the first and fourth are clamping screws, the second is the cover 
 screw, covering the center of the unit-degree dial, which can be removed. 
 The third is the shaft of the cam which moves the unit-degree dial into 
 and out of mesh with a gear on the body of the instrument, inside the 
 table. To adjust, loosen the two clamping screws very slightly, then 
 turn the table until the index mark nearest the center of the instrument 
 registers with any one of the hundreds and tens of degree marks. Next 
 insert a screwdriver in the slot in the center of the unit-degree dial 
 and turn it until zero (0) on this dial registers with zero (0) on the 
 fixed scale. While in this position insert the screwdriver in the slot 
 in the cam and gently turn the same until the unit-degree dial gear 
 meshes with the gear in the body, and clamp in this position. If this 
 adjustment has been properly made the azimuth mechanism will show 
 about one-hundredth of a degree of back lash, when the direction of 
 rotation of the table is reversed, and the table should turn nearly as 
 easily as it did before the gears were meshed. If the turning of the 
 table is very much harder than before, the adjustment should be re- 
 peated. 
 
 2. To Level. Follow instructions previously given for leveling. 
 
 3. To Orient. Select some datum point and turn the table by 
 means of the azimuth handwheel until the azimuth of the datum point 
 is indicated on the azimuth dials. Clamp the table to the body of the 
 instrument and insert the large pin wrench in the hole in the side of 
 
314 THE SERVICE OF COAST ARTILLERY 
 
 the pedestal cap and turn the cap until the vertical cross wire of the 
 telescope coincides with the reference mark on the datum point. The 
 level of the instrument should again be checked and releveled if neces- 
 sary. The pedestal cap is clamped to the pedestal as soon as the 
 adjustment is secured. 
 
 4. To Adjust the Telescope. The telescope adjustments are given 
 in detail for the W. and S. instruments on page 306, and are not 
 materially different for this instrument. 
 
 To Use the Instrument. 1. Set the slide block to the proper height 
 of instrument after deducting the height of tide and clamp same by 
 means of the clamping screw. 
 
 2. Next bring the telescope to bear on a datum point about 8,000 
 yards and turn the operating nut until the range pointer indicates the 
 correct range of the datum point. The horizontal wire will generally 
 be found slightly above or below the water line at the datum point. It is 
 therefore necessary to bring the horizontal wire into coincidence by 
 unclamping the clamp screw on the compensating screw and screwing 
 the latter up or down until the datum point is waterlined. The com- 
 pensating screw is then clamped to the shaft of the rack gear. Under 
 conditions of normal refraction the instrument is now ready for use. 
 In practice, however, it will be found that when the telescope is directed 
 on a nearer datum point, for example the short -range datum (2,500 
 yards), when the refraction is more than normal, the range will be less 
 than 2,500 yards when the datum point is water-lined. So in order to 
 correct for this abnormal refraction the adjustment must be made on 
 two datum points (3,000 and 8,000 yards) concurrently, until a position 
 of the sliding block is found, which will give correct range indications 
 for the two datum points. Other ranges will be slightly in error, but 
 near enough for all practical purposes. 
 
 The rules for adjustment, use and care given above for depression 
 position finders are applicable to a great extent to the azimuth instru- 
 ment and surveyors transit, the nomenclature of which instruments will 
 be found in Plates XXIII and XXIV. 
 
 THE PLOTTING BOARD 
 
 The principle upon which all plotting boards are based is the same, 
 and their value lies in the fact that they quickly give by mechanical 
 means the rate of travel of the target, the range and azimuth from the 
 target to the directing point of the battery; as well as the necessary 
 data for use on the Range and Deflection Boards. 
 
PLATE XXIV 
 
 TELESCOPE TUBE 
 
 FOCUSING SCREW 
 
 TELESCOPE 
 CLAMP SCRE 
 
 OBJECTIVE AND 
 OBJECTIVE CELL 
 
 ' EYE PIECE 
 FOCUSING SCREW 
 
 TELESCOPE LEVEL 
 
 CROSS WIRE 
 ADJUSTING SCREW 
 
 TELESCOPE LEVEL 
 ADJUSTING CAPSTAN 
 
 VERNIER 
 
 TANGENT SCREW 
 
 STANDARDS 
 MAGNETIC COMPASS 
 
 TELESCOPE 
 LEVEL SCALE 
 
 TANGENT SCREW 
 SPRING AND CUSHION 
 
 MAGNETIC NEEDLE 
 RELEASE SCREW 
 
 READING OPENING 
 
 AZIMUTH AND VERNIER 
 
 SCALES 
 
 AZIMUTH 
 CLAMP SCREW 
 
 AZIMUTH SLOW 
 MOTION SCREW 
 
 SPINDLE 
 COLLAR CLAMP 
 
 LEVELING OR 
 LOWER PLATE 
 
 LEVELING SCREWS 
 
 TRIPOD SCREWS 
 
 TRIPOD LEGS 
 
 Engineer's Transit, Gurley Model. 
 
INSTRUMENTS, DEVICES AND CHARTS 315 
 
 The plotting boards used in the coast artillery service are: 
 
 Whistler-Hearn Plotting Board, Model of 1904. 
 
 Mortar Plotting Board, Model of 1906 Mi. 
 
 Submarine Plotting Board, Model of 1906. 
 
 Fire Commander's Plotting Board. 
 
 The Whistler-Hearn Plotting Board is designated for use with 
 a horizontal base of lengths from 900 to 7,000 yards. The board can be 
 used as a right- or left-hand board. When used as a right-hand board 
 the secondary station is "on the right of the primary station (where the 
 board is located), the front being toward the principal field of fire. 
 When used as a left-hand board the secondary station is on the left of 
 the primary station. 
 
 The plotting board proper, Plate XXV, consists of a semicircular table 
 of well-seasoned lumber approximately two inches thick. The radius of 
 the board is approximately 45 inches and is so made as to allow for ex- 
 pansion and contraction and to prevent warping. The diameter plate 
 is a heavy piece of brass 7 inches wide and J-inch thick and is attached 
 to the under side of the board by bolts which pass through slotted holes 
 to allow for expansion and contraction of the board. 
 
 The base-line arm is made of bronze and extends the whole diameter 
 of the board on its upper surface, and when set at zero it is parallel to 
 the diameter plate. The main azimuth circle extends around the curved 
 surface of the table and is greater than a semicircle ; it is made of bronze 
 in several pieces and is put together in two layers, the pieces of the upper 
 layer breaking joints with the lower portion, thus forming a complete 
 metallic strip. The middle of the top portion of the circle is counter- 
 sunk to admit the insertion of a piece of zinc upon which the degrees 
 are numbered. The outer edge is notched with V-shaped notches about 
 J of an inch deep, each notch corresponding to one degree in azimuth. 
 The entire azimuth circle is bolted at its two extremities to the diameter 
 plate; all measurements therefore made on the board, whether angular 
 or linear, are independent of the table proper, the expansion or contrac- 
 tion of the wood does not in any way effect the accuracy of the board. 
 
 The station blocks are mounted on the base-line arm. One block, 
 known as the primary block, is attached to the base-line arm and fits 
 over the main pintle center; the other block, known as the secondary 
 block, is attached to the base-line arm, but is arranged so that it will 
 move laterally along the base-line arm and may be set for any length of 
 base line on either side of the main center or primary (station) block. 
 Each block is provided with a pivot or center over which the primary 
 arm, secondary arm and auxiliary arm are pivoted. 
 
316 THE SERVICE OF COAST ARTILLERY 
 
 The primary arm is a scale arm or alidade which is pivoted at the main 
 center, carried by the primary block. This arm is made of brass, steel 
 or copper, and is graduated on one edge to the scale of 300 yards to the 
 inch, the graduations representing yards in range, the smallest reading 
 being 10 yards. The secondary arm is a similar scale arm and is pivoted 
 at the center on the secondary block; it is likewise graduated for range 
 to the scale of 300 yards to the inch, the smallest reading being 10 yards. 
 
 The auxiliary arm is a similar arm but without graduations, and is 
 pivoted at the main center or at the same point on the primary block 
 as the primary arm. 
 
 The connecting bar or coupler is a brass piece connecting the outer 
 ends of the secondary and auxiliary arms; its length depends upon the 
 length of the base line for the board considered, that is, the coupler 
 would be equal to the length of the base line in inches at the scale of 
 the board. The primary and auxiliary arms are fitted with an index 
 box which slides and may be locked on the azimuth circle. The index 
 box consists of the box proper which moves on the azimuth circle and 
 is fitted with a lock called the degree lock by means of which the box 
 may be located and locked at any particular degree. The scale arms 
 pass through the boxes and by means of a rack and pinion may be 
 moved in either direction through an arc of .99 of a degree ; the pinion 
 attached to the box is actuated by a dial plate or index disk and knob. 
 The dial is graduated in one hundred parts and on its outer edge are 
 one hundred teeth; it is arranged so that one revolution of the dial 
 plate carries either arm through .99 of a degree. The dial is held 
 and locked in any desired position by a dial lock or index disk clamp 
 which fits into the teeth on the circumference of the dial and prevents 
 the movement of the arm when locked. 
 
 Over the center of the primary block is mounted the gun center , which 
 consists of two slides, the lateral adjusting slide and the longitudinal ad- 
 justing slide; the gun arm (See Plate XX VI) , the fixed limb, the movable 
 limb, the correction box, the degree tally, and the hundredths dial. 
 The lateral slide has a motion along the base-line arm, it is dovetailed 
 on a guide piece attached to the base-line arm, and can be clamped in 
 any position by means- of three set screws on the rear side which act 
 against a long gib. The guidepiece is graduated and the slide is fitted 
 to a vernier reading to one yard. When this vernier is set at zero the 
 center line of the slide passes through the main center of the board. 
 The longitudinal slide is fitted into the lateral slide so that it may be 
 moved in a direction at right angles to the base-line arm. On the longi- 
 tudinal slide is a scale and on the lateral slide a vernier by means of 
 
INSTRUMENTS, DEVICES AND CHARTS 317 
 
 which the slide may be set as desired ; the longitudinal slide carries the 
 gun-arm center. 
 
 When the vernier on the lateral slide is at zero the gun-arm center 
 is on the base line. When the longitudinal and lateral slide are both 
 set at zero the gun-arm center is directly over the main center of the 
 board or the center at which the primary arm is pivoted. The longi- 
 tudinal slide is held in position by two set screws which act against short 
 gibs; the lateral and longitudinal slides are provided so that the gun- 
 arm center may be located at such a point on the board with reference 
 to the main center as to correspond to the location of the directing gun 
 or point of a battery, to the scale of the board, and that of the primary 
 station of the battery. 
 
 The gun arm is made of German silver or aluminium. It is a scale 
 arm or alidade pivoted at the gun center, and is used to determine the 
 range and azimuth of the target from the directing point of a battery. 
 The gun-arm center consists of the gun-arm proper, the fixed limb, the 
 movable limb and the correction box (and, in the first type of board, 
 the travel scale) . 
 
 The fixed limb is a semicircular metallic piece attached to the 
 longitudinal adjusting slide by three screws. This limb carries 
 the degree index of the gun-arm azimuth circle, and the index or dial 
 for reading the fractions of a degree. The gun-arm pintle, about which 
 the azimuth circle and correction box revolve, is attached to this limb. 
 
 The movable limb is an azimuth circle. It has geared teeth on its 
 outer edge which mesh into the pinion which actuates the mechanism 
 of the hundredths dial. The degrees are graduated on the brass circle, 
 but are numbered on a strip of zinc. This limb is centered on the gun- 
 arm pintle. 
 
 The correction box is a device for mechanically making the range 
 corrections for atmospheric conditions and travel as determined from 
 the range board, and also for making, mechanically, the deflection cor- 
 rections as determined from the deflection board. The range corrections 
 are made by sliding the gun arm in or out the required distance which 
 is measured by a range difference scale on the arm. This scale is seen 
 through a reading opening, or window, in the box. The arm is moved 
 in or out by a rack and pinion. The deflection corrections are made by 
 moving the box through a given azimuth angle indicated by a scale on 
 the box. The box is actuated by a worm gear which is attached to the 
 movable limb. 
 
 The degree tally is a device for indicating the angular travel of the 
 target during a predicting interval, and is on the left of the window 
 
318 THE SERVICE OF COAST ARTILLERY 
 
 of the gun-arm azimuth circle. Over the face of the dial moves a hand, 
 the reading of which gives the angular travel in degrees. The frac- 
 tions of a degree are read from the outer graduations of the hundredths 
 dial of the gun arm. The tally scale is marked in reference numbers, 
 running from to 30, the origin, or zero, being 15. 
 
 The travel scale is a sliding scale on the gun arm used in determining 
 the change in the range of the target during the observing interval on 
 boards where the range board has not been provided with the new travel 
 scales. At the center of this scale is a pointer which is set at the in- 
 dicated range of the target at the end of an observing interval. At the 
 end of the next observing interval, by turning down the leaf, the change 
 in range for the interval will be indicated by reference numbers. The 
 leaf is held up at all other times by a spring, so as not to interfere with 
 readings of the range scale. 
 
 The gun-arm shoe is made of bronze, and is used to facilitate the use 
 of the gun arm by obviating the necessity for raising it, and also prevents 
 the bending of the other arms. It slides along the gun arm, and is held 
 in position by a friction spring. 
 
 To Set Up the Board. The trestles should be set up, and the board 
 placed on them in a horizontal position, with the diametrical spider arm 
 of the board resting on the oakum-reinforced pieces of the trestle. Care 
 should be exercised in mounting the board and removing it from its 
 box, as the azimuth circle has been carefully adjusted to the base line 
 arm and primary center, and a blow on the azimuth circle or the base- 
 line arm may destroy the adjustment of the entire board. 
 
 The direction and length of the base line having been determined, 
 loosen the screws holding the proper end of the base-line arm, and slip 
 the sliding station block on the base-line arm. The screws on the end 
 of the base-line arm should then be replaced and tightened. The small 
 gib of the sliding block should be slipped into place, and the vernier 
 attached. The small gib in the rear of the secondary station block 
 should be loosened sufficiently to adjust for the correct length of reading 
 for the base line in yards. After this adjustment is made, the gib screw 
 should be carefully tightened. An adjustment of one degree in azimuth 
 in either direction can be given to the base line, but ,50 of a degree 
 is the maximum amount necessary to be used. 
 
 To make this adjustment, slacken the clamp screws at each end of the 
 base-line arm, and also the screw directly on the end of the primary 
 station block. Set to the correct position by means of the vernier. 
 This caution is given owing to the fact that on account of the length of 
 the base-line arm there is apt to be some spring which might give a false 
 
INSTRUMENTS, DEVICES AND CHARTS 319 
 
 position with only one reading. Both verniers should be read and 
 should agree. The readings, however, should be in opposite directions. 
 Two supporting plates with two dowel pins in each are placed under 
 each end of the base-line arm to support it and prevent sagging. It is 
 not necessary to remove these in making an adjustment of the base-line 
 arm. 
 
 The primary arm for right-handed base line is marked with the 
 initials "P. R." The secondary arm for the same board would be 
 marked "S. R.," and the gun arm "G. R." The auxiliary arm is simply 
 marked "R.," on one side, and "L.,' ; on the other side. 
 
 For a left-handed plotting board the primary arm would be marked 
 "P. L.", the secondary arm "S. L." and the gun arm "G. L." The 
 "R" side of the auxiliary arm is up for a right-handed board, and the 
 " L" side is up for a left-handed board. When mounting the scale arms, 
 the primary arms should be placed next to the board being pivoted on 
 the main pintle. The auxiliary arm is pivoted on the same pintle and 
 placed on top of the primary arm. The secondary arm passes over the 
 primary, and is connected to the auxiliary arm by a coupler which has 
 the same length as the base line. The object of the coupler is to keep 
 the secondary arm parallel to the auxiliary arm, and obviate the neces- 
 sity of having more than one azimuth circle, as the auxiliary arm is 
 pivoted at the center of the main azimuth circle, or at the pintle center 
 of the board. 
 
 The azimuth readings from the secondary station being set by means 
 of the index box on the auxiliary arm, the coupler keeping the second- 
 ary arm parallel with said arm, must necessarily give the secondary arm 
 the correct direction with reference to the primary, or in other words, 
 set the secondary arm at the same azimuth. 
 
 Two index boxes are furnished with each board, one for the auxiliary 
 arm and one for the primary arm. These boxes are marked " Aux. R." 
 and "Prim. L." and the other is marked "Aux. L." and "Prim. R." For 
 a right-handed base line the index boxes marked " Aux. R." is for the 
 auxiliary arm, and the box marked " Prim. R." is for the primary arm. 
 If a left-handed board is used, the box marked "Aux. L." is for the 
 auxiliary arm, and the box marked " Prim. L." is for the primary arm. 
 
 To assemble the index boxes, set the pointer at 50, and insert the 
 rack in position according to the corresponding marks A or B, being 
 careful to see that the teeth of the pinion meshes with the teeth of the 
 rack marked 0. The rack should be held in position until the index 
 box is placed over the scale arm. Bring the arm on which the index 
 box is to be mounted over one of the places near either end of the base- 
 
320 THE SERVICE OF COAST ARTILLERY 
 
 line arm, where the azimuth circle is cut out. If a right-handed base 
 line is used, the primary index box is inserted over the azimuth circle 
 at the right-hand end of the base line, and the auxiliary arm is inserted 
 at the left-hand end of the base line, and vice versa for a left-handed 
 base line. 
 
 Be sure to hold the rack in position while the scale arm is being in- 
 serted under the rack and between the locking plate and the index box. 
 The scale arms must not be lifted too high when assembling the boxes, as 
 the arms may be bent at the pivots. If the rack has been inserted cor- 
 rectly, the pointer of the dial will move clockwise from to 99. 
 
 On the outside of each index box, on the locking plate, will be noticed 
 a small brass lip. When the edge of this lip is opposite the center of the 
 notch in the azimuth circle, the locking lever can be pulled out, thus 
 locking the index box to the azimuth circle and permitting an adjust- 
 ment up to .99 of a degree by moving the index disk on the index box. 
 Above the locking plate is a small latch, and before attempting to turn 
 the index disk, this latch must be pulled out. The movement of this 
 knob is only about one-eighth of an inch, and does not require a heavy 
 strain. After the correct reading has been obtained by setting the disk, 
 this latch is pushed in and locks the disk in position. 
 
 To mount the gun-arm center, place it over the tongue of the base-line 
 arm with the dials of the gun-arm center, toward the rear of the board. 
 Insert the lateral adjusting-slide gib according to the corresponding 
 marks on the gib and gun-arm center. Then screw up the gib screw 
 slightly, so that the gun-arm center can slide by the primary or secondary 
 station blocks, but not so tight that the gun arm cannot be moved. 
 
 To set the gun-arm center, the fixed limb must be moved to expose 
 the scales on the longitudinal adjusting slide. The fixed limb is secured 
 to the longitudinal adjusting slide by three retaining screws and the 
 gun-arm center pivot. One retaining screw is located in the rear position 
 of the gun-arm azimuth subscale, and is entered by removing the tally 
 subdial. Two screws are also located on either side of the pivot, and are 
 entered from the top of the fixed limb by turning the gun arm to the 
 left. The right end retaining screw near the pivot can be taken out, 
 and similarly by turning the gun arm to the right, the left end retaining 
 screw can be taken out. The fixed limb can then be turned to the right 
 or left about the gun-arm center pivot. The position of the gun-arm 
 center is set according to the distance in yards of the gun in front of, 
 or in rear of the base line. This adjustment is made on the longitudinal 
 adjusting slide, which has two scales on it, of 25-yard divisions, and 
 two verniers attached to enable readings to one yard. The two gib 
 
THE 
 
 UNIVERSITY 
 
INSTRUMENTS, DEVICES AND CHARTS 321 
 
 screws on the left-hand side and under the fixed limb, are then 
 tightened. 
 
 The limit of this adjustment is 1,000 yards to the front or to the rear 
 of the base line. The distance in yards to the right or left of the primary 
 station is set on the lateral adjusting slide, which also has a vernier 
 reading to one yard, with two scales each of 25-yard divisions. The 
 limit of this adjustment is 4,000 yards to the right or left of the primary 
 station. The three gib screws on the rear of the lateral adjusting slides 
 are then tightened. After the position of the gun-arm center has been 
 located, the fixed limb should be replaced. The "targ " is for the pur- 
 pose of obtaining an exact reading at the intersection of the edges o 
 the primary and secondary arms. It should be held up against the edge 
 of the secondary arm, and moved along that edge until it touches the 
 primary. This gives the intersection. Care should be taken not to 
 bring it against the edge of the primary arm with too great a force and 
 thus injure the edge of the arm. 
 
 To Orient the Board. The normal line of the board is the radius at 
 right angles to the base-line arm, when the verniers at each end of the 
 base-line arm are set at 0. The center of the center notch in the azimuth 
 circle and the center of the main pintle, establish this normal. As has 
 been stated, the base-line arm may be moved through one degree 4 
 either way, and to set the proper reading by means of verniers attached 
 to each end. 
 
 The of the base-line arm may be given any convenient degree num- 
 ber, depending upon the azimuth of the actual base line. It is con- 
 venient to number one with the nearest degree to the back azimuth; 
 that is, 180 degrees plus the azimuth of the base line. For example: 
 Assume that the azimuth of the base line is 312.26 degrees, and that 
 the base line is left-handed. Then the at the left hand of the base 
 line arm would be numbered 312 degrees, and the at the right-hand 
 end would be numbered 132 degrees. To orient the base-line arm to 
 correspond with the actual base, it is necessary to swing the base-line 
 arm clockwise to 0.26 degrees. That is, to set the left end to 
 312.26 degrees. The other of course would be set at 132.26 degrees. 
 Assume that the azimuth of the base line was 312.90 degrees, then the 
 left end would be numbered 313 degrees, and the right end 133 degrees. 
 To set the base line at 312.90 it would be necessary to swing the base- 
 line arm contraclockwise through 0.10 degrees; in other words, the 
 left-hand end is to be set at 312.90 degrees, and the right-hand end 
 at 133.90 degrees. 
 
 To orient the gun-arm center, bring the gun-arm center over the 
 
322 THE SERVICE OF COAST ARTILLERY 
 
 primary center by placing the zeros of the longitudinal adjusting slide 
 verniers and the lateral adjusting slide verniers coincident with the 
 zeros of their respective scales. See that the of the worm guard is 
 opposite 15 on the azimuth correction scale, and the scale on the microm- 
 eter head of the worm is at 0. Bring the "primary arm to the normal 
 line of the board, and be sure that the pointer of the index box on the 
 primary arm is set at 0. Place the targ against the reading edge of the 
 primary arm, and bring the gun arm carefully up against the targ. If 
 properly done, the reading edges of the primary and gun arm will now 
 coincide to the normal line of the board. Set the azimuth pointer at 
 the gun-arm azimuth window by means of the adjusting screw to the 
 whole degree of the azimuth of the 'normal. 
 
 Next set the gun-arm azimuth sub-dial indicator to by loosening 
 the screw holding the indicator in place. This will allow an adjustment 
 of J, J or j of a degree. If that is not sufficient, the tally sub-dial is 
 removed. The vernier dial face can now be adjusted within the limits 
 of 1- of one degree by loosening the retaining screw and moving the dial 
 until the pointer is at 0. 
 
 To test this orientation the gun arm should be moved away from the 
 targ, and brought up to it several times. The gun-arm center is now 
 moved to a position on the board to a corresponding position of the gun 
 as previously explained. To test the accuracy of the board, take three 
 positions of a target near the center of the board and extremes respec- 
 tively, each at about a range of 6,000 yards, and calculate trigonomet- 
 rically and see if the calculations agree with the readings given by 
 the board. 
 
 Another simple test of the accuracy of a plotting board is to plot the 
 location of the datum points with a range and azimuth of either station, 
 and then check the range and azimuth as given by the board from the 
 other station. The azimuth and range found should agree with that 
 given on the datum sheet. 
 
 Care of the Board. Too much attention cannot be given to the scale 
 arms, as the accuracy of the board depends upon the reading edges being 
 true, straight edges, and any roughness due to handling of these arms 
 will impair the accuracy of the board. If the scale on the micrometer 
 head of the worm needs adjustment, it should be made by using the 
 spanner wrench and pin wrench furnished for loosening the jam nut. 
 If the worm has any backlash, this will be due either to the fact that the 
 worm is not in close enough mesh, or that the screw at the left-hand of 
 the worm is not adjusted properly. To correct the first, release the 
 two clamp screws on the worm, and move the worm forward to the proper 
 
INSTRUMENTS, DEVICES AND CHARTS 323 
 
 mesh; then tighten the screws. To correct the second error, release the 
 jam nut by using the small end of the spanner wrench, and then adjust 
 the screw by holding the screw with the small pin wrench, and tighten 
 the jam nut. All the pivot bearings should be oiled regularly, and the 
 board kept free from dust at all times. When not in use, the index box 
 locking levers should be left released. 
 
 To Use the Board. The gun plotting board is used for batteries of 
 the primary armament and of the intermediate armament to include 
 6-inch batteries provided with a separate base line. 
 
 Readings are taken simultaneously at the base-end stations and trans- 
 mitted to the arm-setters for the primary and secondary arms of the 
 plotting board. The arm-setters lock the index box in the degree notch 
 of the azimuth called to them by the readers over their respective tele- 
 phones, locking the box in this position with the degree lock. They 
 then set the index disk of the box to the hundredths of degrees as called 
 and lock the index disk with the index clamp. When this operation is 
 completed each arm-setter calls " set," which is a signal for the plotter 
 to move the " targ " along the left edge of the secondary arm until it 
 comes to the intersection of the secondary and primary arms, which 
 point indicates the position of the target. 
 
 After the first two readings the plotter moves the gun arm up to this 
 intersection and reads and transmits the range as indicated on the gun 
 arm to the guns. These readings are sent to the guns every 15 seconds 
 and are the corrected ranges for the target being tracked. 
 
 The corrections are made as follows: The assistant plotter at the first 
 setting of the gun arm turns the hundredths dial for gun arm until the 
 'zero is opposite the pointer and also sets the degree tally so that the 
 number 15 of the degree tally scale is opposite the pointer. At the sec- 
 ond setting of the gun arm he calls off the reference number from the 
 degree tally and the hundredths dial of the gun arm. This reference 
 number indicates the angular travel of the target during the observing 
 interval and is used by the deflection computer in the operation of the 
 deflection board. The assistant plotter also sets the wind component 
 indicator to the proper azimuth which is taken from the azimuth circle 
 for the gun arm. 
 
 In Case III the assistant plotter calls off the corrected azimuth as 
 shown on the azimuth circle for gun arm and index for hundredths of 
 degree scale. 
 
 The range correction device is set at the proper reference number as 
 obtained from the range board by the range-correction computer. 
 
324 THE SERVICE OF COAST ARTILLERY 
 
 MORTAR PLOTTING BOARD, MODEL OF 1906 
 
 (See Plate XXVII.) 
 
 This board is similar to the Whistler-Hearn plotting board just de- 
 scribed, the principal difference being the mortar arm, and mortar arm 
 center. The two principal parts of the mortar arm, which, are shown 
 in detail in Fig. 48, are the range and zone scales. 
 
 The range scale gives the range of the object plotted from the mortar, 
 and in conjunction with the mortar-arm center gives its azimuth. The 
 zone scale is in 8 zones, and gives the elevation in degrees and the times 
 of flight in seconds for all ranges from 2,000 to 12,000 yards. The zone 
 scale permits of adjustment for correction. The mortar arm is pivoted 
 to the mortar-arm center by means of the mortar-arm box, and permits 
 of it being raised from the board at any time in a vertical plane. On 
 account of the increased size of the mortar-arm center over the gun-arm 
 center of the regular plotting board, a mortar-center support has been 
 provided. The instructions for adjusting, assembling and orienting the 
 Whistler-Hearn plotting board hold good in the case of this board. 
 
 To Use the Board. The mortar-plotting board is used similarly to 
 that of the gun-plotting board except that the mortar arm is provided 
 with a sliding scale, as shown in Plate XXVII, which is graduated into 
 degrees of elevations and times of flight for each zone. The two arm- 
 setters on hearing the azimuth at the signal for each observation set 
 and lock the primary and secondary arms as previously described for 
 the gun-plotting board. The plotter, as soon as he hears the command 
 "set," marks the position of the target by making a pencil mark on 
 the plotting-board chart at the intersection of the two arms. 
 
 The tracking of the target is commenced and four or more positions 
 plotted on the board at 20-second intervals. The plotter then moves 
 the mortar arm up to the last plotted position of the 20-second readings 
 and estimates where the vessel will be, providing the course is continued 
 for two minutes ahead of the time of the last plotted point. He calls 
 out the zone indicated on the mortar arm to the azimuth computer, who 
 operates the mortar deflection board, and who in turn transmits these 
 data to the booths. 
 
 The plotter also notes and remembers the time of flight indicated for 
 the range and zone in question. The position of the target is then 
 plotted either every 30 seconds or every minute. For example, it will 
 be assumed that it is plotted every minute.' In the cut, Fig. 49, the first 
 four plotted positions at 20-second intervals are indicated by the num- 
 
INSTRUMENTS, DEVICES AND CHARTS 
 Times of ' r/ig^jt /e> 
 
 tvvW^Vv/^ 
 
 325- 
 
 Zone n umber 
 
 i 1 Normal 
 
 Mo\seabfe G 
 
 FIG. 48. 
 
326 THE SERVICE OF COAST ARTILLERY 
 
 bers 1, 2, 3 and 4. The position of the target one -minute after the 
 plotted position No. 4 is indicated at 5. When this point is obtained 
 the plotter sets the leg of the predicter nearest to him at position 4 
 and the next leg to the position 5. The third leg will then indicate the 
 predicted point, and assuming the time of flight to be 50 seconds, the 
 leg of the predicter marked 50 will indicate the set-forward point. When 
 the plotter has obtained these points the mortar arm is brought up to 
 the set-forward point and the elevation read from the arm. No. 1, the 
 assistant plotter, also calls out the azimuth of the set-forward point to 
 No. 4 or the operator of the mortar-deflection board. The plotter then 
 moves the mortar arm up to the predicted point indicated by position 6 
 and calls out the range to the assistant plotter, who transmits this range 
 
 Sef Forward Point^ ^-Predicted Point 
 
 FIG. 49. Mortar Predicter. 
 
 to the battery commander's station to be used in case relocation is 
 necessary. The assistant plotter also transmits to the battery com- 
 mander's station the azimuth of the predicted point. The range and 
 azimuth as read by the plotter and assistant plotter are the range and 
 azimuth of the directing point of the battery. Should this point not 
 correspond with the position of the battery commander's station, it is 
 necessary for the battery commander to use these data to relocate from the 
 directing point of the battery to the position his instrument occupies. 
 The operator at the deflection board uses the data called to him by the 
 plotter and assistant plotter, as follows: 
 
 He first sets the cylinder of the deflection board, shown in Plate 
 XXVIII so that the whole degrees of azimuth as read to him by the 
 assistant plotter appear in the slit of the drum. He then moves the 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 327 
 
 pointer, which is carried on the drift-scale slide and used for reading the 
 azimuth subscale, to the hundredth of the azimuth read by the assistant 
 plotter. He next transmits to the booth the elevation called to him by 
 the plotter and at the same time sets the small pointer (elevation pointer) 
 on the deflection scale to the elevation given him by the plotter. In case 
 110 arbitrary correction has resulted from the observation of fire, the large 
 pointer on the deflection scale then indicates the corrected azimuth of 
 the set-forward point and No. 4 transmits this azimuth to the booths 
 as soon as he has completed the operations just described. The zone 
 number, elevation, and corrected azimuth are posted from the booths 
 so that the mortars may be laid on the data given. The battery com- 
 mander relocates from the directing point of the battery for the position 
 of his instrument and sets. his instrument at the relocated azimuth as 
 determined from the range and azimuth of the predicted point pre- 
 viously transmitted to the station by, the assistant plotter. As the target 
 comes on to the vertical wire of his instrument he signals or closes the 
 switch for firing the mortar or mortars of the pits that have signaled 
 " ready." Should the target not come on^to the vertical wire of the 
 battery commander's instrument at the proper time, he withholds the 
 fire and gives instructions to " relay." 
 
 ZONES AND VELOCITIES 
 
 The number of zones, muzzle velocities corresponding thereto, zone 
 limits, width of zones and oven-laps for the 12-inch mortar, cast-iron, 
 steel-hooped, and the 12-inch mortar, steel, are shown in the following 
 table: 
 
 g 
 
 
 *c 
 
 c 
 
 z 
 
 12-inch Mortar, Cast-iron, Steel-hooped. 
 
 12-inch Mortar, Steel. 
 
 Muzzle 
 Veloc- 
 ity. 
 F.S. 
 
 Weight 
 of Pro- 
 jectile. 
 Lbs. 
 
 rj Width 
 Zone , 
 
 Limits - Zone. 
 Yds. Yds. 
 
 Over- 
 laps. 
 
 Yds. 
 
 Muzzle 
 Veloc- 
 ity. 
 F 8. 
 
 Weight 
 of Pro- 
 jectile. 
 Lbs. 
 
 Zone 
 Limits. 
 
 Yds. 
 
 Width 
 of 
 Zone. 
 
 Yds. 
 
 Over- 
 laps. 
 
 Yds. 
 
 1 
 
 560 
 
 1046 
 
 2225-3000 775 
 
 400 
 
 550 
 
 1046 
 
 2210-2970 
 
 760 
 
 370 
 
 2 
 
 610 
 
 1046 
 
 2600-3480 880 
 
 480 
 
 600 
 
 1046 
 
 2600-3431 
 
 831 
 
 361 
 
 3 
 
 670 
 
 1046 
 
 3080-4110 1030 
 
 400 
 
 660 
 
 1046 
 
 3070-4030 
 
 960 
 
 399 
 
 4 
 
 743 
 
 1046 
 
 3710-5000 1290 
 
 400 
 
 725 
 
 1046 
 
 3631-4800 
 
 1169 
 
 371 
 
 5 
 
 837 
 
 1046 '4600-6240 1640 
 
 400 
 
 810 
 
 1046 
 
 4429-5940 
 
 1511 
 
 420 
 
 6 
 
 910 
 
 1046 
 
 5840-7319 1479 
 
 594 
 
 915 
 
 1046 
 
 5520-7476 
 
 1956 
 
 449 
 
 7 
 
 1050 
 
 824 
 
 6725-9225 2500 
 
 
 1050 
 
 1046 
 
 7027-9250 
 
 2223 
 
 492 
 
 8 
 
 
 
 
 
 1300 
 
 824 
 
 8758- 
 
 3261 
 
 
 
 
 
 
 
 
 
 12019 
 
 
 
328 THE SERVICE OF COAST ARTILLERY 
 
 In target practice with 12-inch mortars the extreme zones in which 
 practice may be held will be the sixth with the cast-iron steel-hooped 
 mortar, and the fifth with the steel mortar, except that with the steel 
 mortar mounted upon the model of 1896 Mil carriage or the model of 
 1896 carriage converted to the model of 1896 Mi carriage, practice may 
 be held in all zones. 
 
 MORTAR PLOTTING BOARD, MODEL OF 1906 Mi 
 
 This is a special plotting board, made for cases where the mortar-arm 
 center is more than 1,000 yards behind the base-line. The maximum 
 distance permitted for the mortar-arm center to be behind the base line 
 arm in this type of board is 2,000 yards. In order to meet this require- 
 ment, the lateral adjusting slide of the board has been extended towards 
 the rear, and the base-line arm moved back. The mortar arm has also 
 been changed to correspond with the other changes on this type of 
 board. 
 
 SUBMARINE PLOTTING BOARD, MODEL OF 1906 
 
 This board is the Whistler-Hearn plotting board, model of 1904, sim- 
 plified. The board is not provided with a gun arm or gun center. The 
 scale of the board is 100 yards to the inch, or in some cases, 150 yards 
 to the inch, depending upon the mine field to be plotted. The primary 
 arm, secondary arm, base-line arm and base-line verniers are slightly 
 different in construction from the regular plotting board, but tha 
 principles of the board are exactly the same. 
 
 Due to the fact that the range of the board is necessarily limited, the 
 scale on the arms has been changed to 100 yards to the inch, or 150 
 yards to the inch. The board, when assembled, adjusted and oriented, 
 has mounted upon the table a chart showing the location of the principal 
 datum points within the mine field, the outline of the entrance to the 
 harbor, the various channels, the depths of water passable by the various 
 types of battle-ships, cruisers and torpedo boats, and also the location 
 of the distribution boxes and the mines comprising the mine field. 
 
 To Use the Board. Readings are taken at the base-end stations of the 
 mine-base line simultaneously, every 15 seconds, and the primary and 
 secondary arms set at the azimuth readings sent is by the readers at the 
 base-end stations; each arm-setter indicating by calling the word "set" 
 when his arm is set at the azimuth called to him by the reader at the 
 primary or secondary instrument. 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 At this signal the plotter indicates 
 the position of the target at the inter- 
 section of the two arms by making a 
 dot with the point of a pencil. The 
 target is tracked in this manner until 
 its position is indicated to be within 
 the predicting distance of any mine of 
 the group over which the vessel will 
 pass; this distance ordinarily is taken 
 as 1J times the distance traveled by 
 the target during any observing inter- 
 val. At the last stroke of the time- 
 interval bell which would give such a 
 position the plotter starts a stopwatch, 
 and after the arm-setters have set their 
 arms to the readings sent them, the 
 plotter calls out " arms off,", at which 
 command the arm setters move the 
 primary and secondary arms out of 
 the plotter's way. 
 
 The plotter then, with the mine- 
 prediction ruler, measures the distance 
 from the last plotted point to the mine, 
 and from the last plotted point to the 
 preceding plotted position of the tar- 
 get, obtaining in the first case the dis- 
 tance the vessel has to travel before 
 crossing the particular mine in ques- 
 tion, and in the second, the travel of 
 the target during the predicting inter- 
 val. He then manipulates the mine- 
 prediction ruler shown in Fig. 50, and 
 obtains the time that it will take the 
 vessel to travel from the last plotted 
 point to the mine. 
 
 Previously the plotter has sent 
 word to the casemate the number of 
 the group and the number of the 
 mine in the group that the target, if it 
 continues its course, will pass over 
 or nearest to. At a short interval 
 
 /JT 
 
 TIME IN 15 
 
 5 
 
 e 
 
 YARDS 
 
 5ECOM&-2S 
 
 25 
 
 YA/WS 
 TO 
 
 /s 
 
 20 
 
 /oo 
 
 //o 
 
 30 
 
 75 
 
 S3S 
 
 60 
 
 Stefe 
 
 .250 
 =2.70 
 
 o = 
 o 
 
 O _Z 
 
 _ 
 
 
 
 FIG. 50. 
 
330 
 
 THE SERVICE OF COAST ARTILLERY 
 
 before the time required for the vessel to travel from the last plotted 
 point to the mine has expired (say two seconds), which is allowed for 
 transmission of message from the mine primary station to the mining 
 casemate, the plotter calls out " ready, fire." This method of plotting 
 is that used for judgment firing. The mine-plotting board is not pro- 
 vided with the gun center or gun arm. It can be used for either the 
 horizontal or vertical base system, exactly the same way as the gun- 
 plotting board. 
 
 FIRE COMMANDER'S PLOTTING BOARD 
 
 The Fire Commander's plotting board is the regular Whistler-Hearn 
 plotting board, with a pantograph attachment, as shown in Fig. 51, to 
 
 f 
 
 tCB 
 
 FIG. 51. 
 
 enable the Fire Commander to adapt his board to any base line of the 
 fire command. 
 
 The scale of the board is 300 yards to the inch. The pantograph arms 
 are so constructed that when pivoted at the pantograph pivot the stylus 
 moves through a reverse space five times greater than that moved 
 
INSTRUMENTS, DEVICES AND CHARTS 331 
 
 through by the end connected to the longitudinal slide. Hence, the 
 scale of the templet is five times the scale of the board, or 60 yards to 
 the inch. The holes in the templet represent an accurate reversed plan 
 of the centers of the observation stations, and directing guns of the 
 various batteries of the fire command considered. The names of these 
 stations and batteries are marked directly under their respective holes 
 on the templet. If the pantograph arms are moved so that the stylus 
 can be placed in the hole representing the primary or center pivot of 
 the board, the gun center will be exactly over the primary center of the 
 board. As the line through the two holes on the templet is parallel 
 to the base line, it is obvious that as the stylus is moved forward or 
 backward, right or left, the gun center or its longitudinal ordinate 
 will move reversely backward or forward, and will move reversely 
 the lateral ordinate, left or right, a distance one-fifth of that covered 
 by the reversed corresponding motion of the stylus over the 
 templet. Hence, if the 'stylus is inserted in any of the holes in the tem- 
 plet, it will place the gun center in a position exactly corresponding to 
 the particular hole used, relative to the base line, and the range and 
 azimuth as read to any plotted point will be the correct range and 
 azimuth of that point from the station or directing gun designated by 
 ''the marking of the hole in the templet occupied by the stylus. 
 Moving the gun center to the various positions it may occupy does 
 not change the orientation of the gun-azimuth dial, as the movement 
 to obtain the various positions are broken up into components parallel 
 to and normal to the base line. 
 
 In making range corrections, the clamping lever should be released 
 and the required adjustment made by moving the range dial. The gun 
 arm is at zero when the range-dial pointer indicates the reference 
 number 2,000. 
 
 In making azimuth corrections, release the knurled clamping screw 
 on the azimuth-correction plate. By turning the azimuth-correction 
 worm, the correct adjustment can be made. Read degrees directly 
 from the azimuth-correction plate, and one one-hundredths of degrees 
 from the micrometer drawn on the right-hand end of the worm. 
 
 The azimuth-correction plate is at zero when the line on the worm 
 cover coincides with the reference number 15. The micrometer drum 
 should then be at " 0." If the micrometer drum needs adjusting, re- 
 lease the clamping nut by the spanner wrench to be found in the drawer. 
 Hold the micrometer down in position with small pin to be found in 
 drawer, and tighten the nut. If the worm works too freely in its bearings, 
 it may be adjusted by the set screw and nut on the left of the worm 
 
332 THE SERVICE OF COAST ARTILLERY 
 
 bracket. If the worm has any back lash, it may be taken up by re- 
 leasing the two screws clamping the bracket to the fixed limb, and by 
 setting the bracket closer to the azimuth correction plate. 
 
 The small dial to the left of the gun-azimuth dial is called the tally 
 dial, and in conjunction with the tally sub-dial, is used for obtaining 
 angular travel of a target during a predicting interval. . The hand scale 
 is a sliding scale and is intersected in an undercut groove on the gun arm. 
 It is used for obtaining change in range of a target during an observing 
 interval. 
 
 Should the lateral and longitudinal slides become loose, due to wear, 
 they may be adjusted by the adjusting, wedge on each slide. To do this, 
 first take out hexagonal screw attaching the pantograph to the longi- 
 tudinal slide. Then by releasing the screw on the small end of the ad- 
 justing wedge., the screw on the large end may be adjusted until the 
 slide can be moved freely, but without side play. The screw on the 
 small end of the wedge is then tightened, thereby clamping the wedge. 
 It is imperative that the pantograph be disconnected from the longi- 
 tudinal slide before attempting to adjust either slide, as each must be 
 tested separately, and as there would be danger of bending the stylus 
 end of the pantograph in moving the gun center, if either slide is made 
 too tight. 
 
 The assembling, adjustments and orientation of the board are similar 
 in all respects to those of the regular Whistler-Hearn plotting board. 
 
 THE RANGE BOARD 
 
 The range board is a device by means of which the range corrections 
 for atmospheric conditions; range corrections for tide; range corrections for 
 travel of target; and range corrections for variation in muzzle velocity are 
 mechanically added and subtracted. 
 
 The total range correction, when determined, is applied to the range- 
 correction scale on the gun arm of the plotting board. 
 
 The nomenclature of the board is shown in Plate XXIX, and consists 
 of & frame in which a graphic range-correction chart is mounted. In front 
 of the chart is a balanced horizontal ruler which can be moved up or 
 down and set opposite any range on the chart. The vertical scale of the 
 chart is marked in both range and time of flight. The ruler is main- 
 tained in position by chains secured to it at each end which pass over 
 chain sprockets and are secured to a counterweight which balances the 
 ruler. A clamp, or clamping screw on the left of the frame secures the 
 ruler at any desired position. 
 
Of THE 
 
 f UNIVERSITY j 
 
 OF 
 
INSTRUMENTS, DEVICES AND CHARTS 333 
 
 On the ruler is a scale for the ruler, a bar and a pointer. The scale is 
 fixed in position on the plate of the ruler, while the bar and pointer are 
 arranged to slide horizontally. The scale, bar, and pointer, in connec- 
 tion with the chart, constitute the computing device for mechanically 
 adding algebraically the various corrections. The scale on the ruler and 
 the horizontal scale on the chart is 100 yards to the inch. 
 
 The origin of the correction scale of the gun arm on the plotting board 
 in numbered 2,000, in order that the correction to be made thereon shall 
 never be negative. This requires 2,000 to be taken as the origin of the 
 scale on the ruler. 
 
 The curves on the chart indicate the magnitude of the corrections to 
 be added or subtracted, and the ruler mechanically performs the addition 
 or subtraction. In each set of curves the horizontal distance from any 
 curve to the normal of the set (which is the heavy vertical line in the 
 center of each set of curves), is equal to the correction in yards of range 
 at the particular range considered, corresponding to the conditions repre- 
 sented by the curve, plotted to the scale of 100 yards to the inch. The 
 curves are drawn for every 2 per cent, variation in the density of the air, 
 for evory 10 foot-seconds of muzzle velocity; for every 5 feet of tide, 
 and for every 10 miles of wind. For conditions when the values lie be- 
 tween these least readings, the pointer can be set by the eye closely 
 enough for all practical purposes. 
 
 The vertical scale of the chart has a time of flight scale, one second to 
 the inch. Each range number is plotted at a point corresponding to the 
 time of flight for that particular range. 
 
 The travel device consists of a travel scale, secured by two supports 
 on the top of the box; the upper ends of the supports pass through the 
 top of the box, are threaded and provided with nuts. To adjust the 
 position of the scale the top edge of each should be about 27 inches above 
 the zero line of the chart. A travel bar is arranged along the travel 
 scale, and carries a trammel or pointer for reading the upper scale, 
 also a trammel or pointer for reading the lower scale; these are so 
 arranged as to slide freely along the travel bar. The pointer for the 
 lower reading is so arranged as to obscure the upper row of graduations 
 on the travel scale. 
 
 The normal of the travel scale is 300 and this scale is graduated from 
 the normal to the right with 10-yard divisions to a reading of 109, and 
 to the left with 10-yard divisions to 600, which number is taken as a 
 new origin for graduations on a second scale from to 900. The first- 
 described scale is the travel scale used for determining the travel of the 
 target during the predicting interval; the second scale is a tally scale 
 
334 THE SERVICE OF COAST ARTILLERY 
 
 used to determine the change in range of the target during the predicting 
 interval. 
 
 The travel device is so located that the normal is directly over the 
 normal of the prediction scale on the chart, which is also marked 300. 
 The upper row of graduations on the travel scale correspond to a fifteen- 
 second observing interval and the lower row to a thirty-second observing 
 interval. Near the right-hand end of the travel bar is an index mark, 
 and a string is attached at this point. This string passes over the travel 
 scale, through the hole in the centering stud, and around the hook eye 
 to the eye pin. A rubber band is tied to the lower end of the string to 
 keep it taut as the travel bar is moved back and forth. When the index 
 of the travel bar is set at normal the string should be over the normal 
 of the prediction curves on the chart, that is over the 300-line mark. 
 The travel scale for a 15-second time interval is so graduated that if the 
 string is set for any reference number thereon, it will intersect the hori- 
 zontal line corresponding to 15-second time of flight at a distance from 
 the normal equal to the travel represented by the number on the scale 
 at which the string is set. The scale for a 30-second time interval is so 
 constructed that under the same conditions the string will intersect the 
 horizontal line corresponding to 15-second time of flight at one-half 
 this distance. 
 
 The left end of the travel scale is graduated from right to left in ranges 
 from to 1,600; only the numbers from 1,000 up are marked on the scale 
 without the digit indicating the thousands. This is so that the scale 
 may be adapted to any range, the proper thousand number in any 
 particular case being understood or assumed. 
 
 Across the box, near the top of the board, is a bar for curve indicators 
 or pointers, on which are four curve pointers, which admit of sliding back 
 and forth. They are used to mark the particular curve which is to be 
 used in making corrections. 
 
 Near the lower edge of the ruler is the bar for the tally indicator, on 
 which the tally indicator slides back and forth. This is used to 
 indicate the amount of the total range correction in the last previous 
 operation of the board. 
 
 To avoid the use of two sets of numbers of the same 
 magnitude with plus and minus signs, reference numbers are 
 used for denoting the various curves on the chart. For example: If 
 the wind curves are numbered in both directions from 0, there would 
 be a plus 10-mile wind curve, and a minus 10-mile wind curve, and 
 it would require extreme care to avoid the wrong curve being used, so 
 in using reference numbers, the normal, or 0, is taken as 50, in which 
 
INSTRUMENTS, DEVICES AND CHARTS 335 
 
 case the reference numbers for a plus and minus 10-mile wind 
 become 40 and 60 respectively, and in this way liability of error is re- 
 duced. With the atmosphere curves, it is reasonable to assume that the 
 
 <\f 
 
 maximum variation that is ever liable to occur in the value of -- is 
 
 o 
 
 16 per cent. The normal of these curves is therefore taken as 16, and 
 the reference numbers run from to 32, and read from left to right. 
 With the wind curves, the board is constructed for a 50-mile plus or 
 minus wind; therefore, the normal is numbered 50, and the reference 
 numbers run from to 100, and read from left to right. The reference 
 numbers for the tide curves represent the actual height of tide in feet, 
 plus or minus, likewise the velocity curves are numbered with the actual 
 velocity to which they correspond*. The travel and prediction curves 
 consist of parallel vertical lines. The travel curves consist of the 
 graduations on the travel scale of the travel device, and the prediction 
 curves are the parallel vertical lines on the chart, the horizontal scale 
 of which is 100 yards to the inch. In this set of curves the 300 yards 
 is taken as the normal, and for convenience in computation, the refer- 
 ence numbers of the travel scale read from 100 to 500, from right to 
 left, while the reference numbers of the prediction scale, which is also 
 graduated from 100 to 500, read from left to right. 
 
 Adjustment. Before using the board, it is important to see that the 
 chart has been properly mounted and in the correct position. The line 
 on the print should be on the line with the upper eyelets, and the 300- 
 yard line on the chart should be in line with the two eyelets at the right. 
 The brass eyelets are placed on the left side as well as the right side of 
 the canvas chart mount so that the back side of the canvas chart mount 
 may be used for the chart for one pounder sub-caliber guns. 
 
 To Use the Board. The curve indicators or markers are first set on 
 the proper reference numbers for each set of curves. The tide-curve 
 marker is set to the tide given on the tide dial of the aeroscope indicator, 
 shown in Fig. 53. The marker for the atmosphere curve is set at the 
 reference number indicated on the aeroscope dial, giving the atmosphere 
 density per cent. The velocity curve is set at the velocity obtained 
 from the trial shots, or that assumed for the series of firings. The wind 
 curve is set at the reference number obtained from the wind component 
 indicator, shown in Fig. 52. 
 
 The travel bar is moved until the string is at normal (300) , and the 
 pointer set at the last three numbers of the first range called off by the 
 plotter. When the second range is called off, the travel bar is moved 
 until the pointer indicates the last three numbers of that range. The 
 
336 THE SERVICE OF COAST ARTILLERY 
 
 string is now set to indicate the travel during any time of flight. The 
 ruler is then set at the first range called off by the plotter. The 
 scale bar for the ruler is set at normal (2,000). The board is now 
 arranged for making the corrections for the first range called off by 
 the plotter. 
 
 The pointer is then set to the curve indicated by the curve marker for 
 tide, and the bar moved until the pointer is on the normal line of the 
 curves. The difference in the reading on the scale on the ruler between 
 2,000 and the reading shown would indicate the total correction due to 
 tide. In the same manner the corrections are made for atmosphere, 
 velocity, and wind, and finally for travel, which is made as follows: The 
 pointer is set on the string after the latter has been set fdr a particular 
 travel; the bar is then moved until the pointer is on the normal. The 
 distance through which the index is moved will be that corresponding to 
 the time of flight for the range at which the ruler is set. 
 
 If the pointer is again set on the prediction scale at a distance from 
 the normal equal to the travel during the time interval, as indicated by 
 the setting of the string on the travel scale, and the bar is again moved 
 until the pointer is opposite the normal, the index will then have added 
 or subtracted the travel during one time interval. This is necessary in 
 that it requires that there shall be added to or subtracted from the range 
 corrections for any range a correction which is equal to the travel of a 
 target during the time of flight plus the travel during the time interval. 
 In order to do this by one operation the reference numbers of the pre- 
 diction scale are made to read in the opposite direction from those on the 
 travel scale, as the travel away from the gun requires an additive motion 
 of the bar. 
 
 The numbers on the travel scale read from right to left, while the 
 numbers on the prediction scale read from left to right, so that after 
 setting the pointer opposite the string, it will be possible by moving the 
 bar in a direction to make the pointer pass the normal until it is opposite 
 the numerical value of the travel during the time interval to combine the 
 two corrections in one operation. 
 
 After these corrections have been made the scale on the ruler, as in- 
 dicated by the index on the bar, indicates the reading to which the gun 
 arm should be set and thus automatically changes the actual range to 
 that of the corrected range which is sent to the gun. For a better under- 
 standing of the board it might be well to explain that if the index of the 
 bar is set at the origin of the scale, 2,000, and the pointer thereon is set 
 on any curve and then the bar is moved to right or left until the pointer 
 is opposite the normal of that particular set of curves it is apparent that 
 
INSTRUMENTS, DEVICES AND CHARTS 337 
 
 the index will be moved along the scale bar of the ruler a distance to 
 scale equal to the distance between the curve and the normal. 
 
 The index will then indicate a number on the scale equal to 2,000, plus 
 or minus the correction corresponding to the curve used. That is, if the 
 trammel is set to the left of the normal, and the bar is moved until the 
 trammel is opposite the normal, the bar will move to the right, and as the 
 scale bar for ruler reads from left to right, the reading of the index will 
 then be greater than 2,000, and therefore the correction is an additive 
 one. For example: If the atmosphere is heavy, it requires an additive 
 range correction, as the projectile would fall short. Therefore the of 
 the atmosphere curve, which represents 16 per cent, increase in the 
 weight of the air, and the 32 curve a 16 per cent, decrease in the weight 
 of the air, and the 16 curve represents standard weight of air. Further, 
 a slight wind would require an additive range correction in order to over- 
 come its retarding effect on the projectile; therefore, the of the wind 
 curve represents a 50-mile per hour head-wind component. The 100- 
 mile wind curve represents a 50-mile per hour rear-wind component, and 
 the reference number 50 represents a 0-wind component for range. 
 
 On the side of the board opposite to the regular chart used for guns, 
 is a chart used with sub-caliber tubes, which is constructed 100 yards to 
 the inch. In order to use this chart with the plotting board, the normal 
 of the range-correction scale of the gun arm, and the ruler of the range 
 board is taken as 2,400, and a paper scale, 300 yards to the inch, is pasted 
 on the gun arm showing ranges from 1,400 to 3,500 yards. When the 
 index reading of the range board is beyond the limits of the correction 
 scale on the gun arm, the gun arm may be set by applying the following 
 rule : If the reading be between 2,500 and 3,500, subtract 1,000 from the 
 reading and set the arm accordingly, and add 1,000 to the range. For a 
 reading over 3,500 subtract 2,000 and add 2,000 to the range. To a 
 reading between 500 and 1,500, add 1,000 and subtract 1,000 from the 
 range. To readings less than 500, add 2,000 and subtract 2,000 from 
 the range. 
 
 The range-correction computer sets the range-correction scale on the 
 gun-arm center to the reading obtained from the scale on the ruler. 
 
 The range boards issued prior to December, 1906, have curves con- 
 structed to give the corrections for the actual range. Those issued after 
 December, 1906, have curves constructed to give the corrections for the 
 corrected ranges instead of the actual ranges. 
 
338 THE SERVICE OF COAST ARTILLERY 
 
 THE DEFLECTION BOARD (GUN) 
 
 The deflection board is a machine by means of which the corrections 
 for travel in azimuth during 'the observing interval, corrections for travel in 
 azimuth during the time of flight, corrections for wind, and corrections for 
 drift, are mechanically computed. 
 
 In Case III the total azimuth corrections obtained are applied to the 
 azimuth correction device on the plotting board. 
 
 In Cases I and II the total deflection correction is sent to the guns and 
 set off on the deflection scales of the telescopic sights. 
 
 The nomenclature of the board is shown in Plate XXX, and consists 
 of a base, upon which slides a movable frame called the platen. This frame 
 slides on a rod, to which it is attached by means of two trammels. On 
 the left-hand trammel there is a set screw by means of which the platen 
 may be locked to the rod. The rod in turn is attached to the base by 
 two brackets. In the left bracket is a threaded sleeve which can be 
 turned by a milled head screw or worm wheel near it, which gives a slow 
 motion to the rod and consequently to the platen. 
 
 Attached to the base at the lower side are three scales, namely, the 
 deflection scale, the travel scale, and the azimuth correction scale. On the 
 latest type of boards, the travel scale is not provided, and is no longer 
 needed for use on the board. The first two scales are fixed on the base, 
 and the other is movable. 
 
 On the left-hand side and attached to the base, is the wind arm and 
 the wind arc. Attached to the platen is the platen (travel) scale, "over 
 which moves a travel arm. The platen scale can be given two positions 
 on the platen; one corresponding to a time interval of 15 seconds, and 
 one corresponding to a time interval of 20 seconds. 
 
 The T square moves over all and slides on the rod. On the face of the 
 T square is a range scale, called the T-square scale. Attached to the left 
 side of the platen is a piece of metal called the leaf. The curved edge of 
 the leaf has a drift curve, which is used for setting the platen for drift. 
 On the leaf is a range scale which is used in setting the platen for wind 
 and drift, this is called the leaf-range scale. 
 
 The platen scale represents the travel in azimuth ; its graduations 
 represent degrees and hundredths on a scale of half of a degree to the 
 inch. It is numbered from left to right and the number at the origin is 
 15 degrees. This is a reference number to correspond to the azimuth 
 degree-tally dial on the plotting board. The deflection scale indicates 
 the deflection to be set off on the sight in Cases I and II, the scale being 
 
^SAR?' 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
INSTRUMENTS, DEVICES AND CHARTS 339 
 
 constructed to J of a degree per inch; it is numbered from left to right 
 with 3 degrees in the center; this is also a reference number, made to 
 correspond with a similar reference number on the deflection scale of 
 the sight. 
 
 The azimuth correction scale indicates the correction to be applied to 
 the gun arm on the plotting board when Case III is used; the scale is 
 constructed to \ of a degree per inch, and is numbered from left to right 
 with 15 degrees in the center, this being a reference number made to 
 correspond with the numbering on the azimuth correction device on the 
 gun arm of the plotting board. 
 
 The wind arc is graduated for wind components taken from the wind 
 component indicator. The origin (0 wind) is number 50, and when the 
 wind arm is set on this number it is perpendicular to the deflection scale, 
 and there is no wind correction so far as the deflection corrections are 
 concerned. The reference number corresponds to a left wind com- 
 ponent of 50 miles per hour, while the reference number 100 corresponds 
 to a right wind component of 50 miles per hour. 
 
 The wind arm is set to the proper reference number by the arrow 
 index. The T-square scale is graduated in yards of range plotted really 
 to a scale of times of flight. The origin for the time scale of the board is 
 the center of motion of the travel arm. The leaf-range scale is used to 
 set the platen for drift; its principal function is to set the platen for 
 a deviating wind component. 
 
 To Use the Board. (1) The wind arm is set to the proper reference 
 number, corresponding to the deflection component as taken from the 
 wind-component indicator. (2) The platen is set so that the point of 
 the drift curve corresponding to the range will be accurately over the 
 right edge of the wind arm. (3) The travel arm (right edge) , when used, 
 is set for the travel-reference number as received from the tally on the 
 plotting board. (4) Set the azimuth-correction scale so that the travel- 
 reference number is under the normal of the deflection scale. Then set 
 the T square so that the point of the scale corresponding to the range as 
 called off from the plotting board, will be accurately over the edge of 
 the travel arm. The beveled edge of the T square then indicates on the 
 deflection scale, the deflection to be used on the sight in Cases I and II, 
 and is called out and transmitted to the guns by telephone and telauto- 
 graph. The beveled edge of the T square also indicates on the azimuth- 
 correction scale, the correction to be applied to the gun arm center 
 of the plotting board, when Case III is used. 
 
 When using Case III, and when the time required to lay the guns is 
 greater than one observing interval, it is necessary to use a multiplying 
 
340 THE SERVICE OF COAST ARTILLERY 
 
 scale, which can be attached to the semicircular brass on the platen. 
 These scales are intended for use with either 15- or 20-second intervals. 
 When the multiple scale is used, instead of setting the azimuth-correction 
 scale to the same reading as that of the travel arm for travel, it should 
 be set to the reading of the multiple scale used, in which case the 
 operations will then be the same as described above. 
 
 For use during sub-caliber practice, a special leaf scale and scale arm 
 for the T square are used, which, when in place, permit of the same 
 operations of the board as in the regular drill. 
 
 MORTAR DEFLECTION BOARD 
 
 The mortar deflection board is shown in Plate XXVIII. 
 
 It consists of a cylinder on which are numbered, consecutively and 
 horizontally across the cylinder, azimuths from 1 to 21 degrees, from 
 11 to 31 degrees, etc., the last series running from 351 to degrees and 
 then to 11 degrees. 
 
 The subdivisions of degrees to five one-hundredths (0.05) of a degree 
 are indicated on the azimuth subscale. The cylinder is revolved by 
 turning the azimuth wheel or head and any desired series of azimuths' 
 brought into the slit in the drum shield. 
 
 On the carriage immediately below the azimuth subscale is the drift 
 scale mounted on the drift-scale slide. The carriage is moved by turning 
 the main traversing wheel. This carriage has on it a pointer for setting 
 to any azimuth on the subscale. 
 
 The elevation knob operates a carriage carrying the two pointers for 
 setting the elevation on the drift scale and for indicating the corrected 
 azimuth on the subscale. The " pointer " may be set for any arbitrary 
 correction on the deflection scale by turning the milled head screw. 
 
 The operation of the board is as follows: 
 
 The operator (No. 4) sets the small pointer to the elevation called out 
 by the plotter; he then brings the proper degrees on the cylinder into 
 the slit in the drum shield and sets the pointer for the subscale to azi- 
 muth of the set-forward point as called out by the assistant plotter. 
 
 The corrected azimuth of the set-forward point is then indicated by 
 the corrected azimuth pointer. 
 
 The pointer for the deflection scale should be set at normal or 3 
 degrees unless it is desired to make some arbitrary correction as the 
 result of the observation of fire. 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 341 
 
 THE WIND-COMPONENT INDICATOR 
 
 The wind-component indicator is an instrument used to determine, 
 mechanically, the two components of the wind; that is, the component 
 of the wind which affects the range, and that component which affects 
 
 FIG. 52. Wind Component Indicator. 
 
 the deflection correction. The component affecting the range is used 
 on the range board. That which affects the deflection is used on the 
 deflection board. 
 
 The instrument is shown in Fig. 52, and consists of a dial plate, on 
 the face of which are reference numbers for the range and deflection 
 components, marked with their corresponding lines. The reference num- 
 bers read from on the left to 100 on the right, and from at the 
 bottom to 100 at the top, with 50 in the center. The dial is intended 
 
342 THE SERVICE OF COAST ARTILLERY 
 
 to he held in a vertical position by means of the arm which is fastened 
 to the back of the dial in such a manner that the dial itself will not turn, 
 and in this way the figures on it will always be right side up. It is usually 
 mounted convenient to the plotting board, and where it can be seen by 
 the range and deflection computers. 
 
 Around the dial is a movable azimuth ring graduated and numbered 
 clockwise for every 5 degrees, which can be set so that 1 the azimuth of 
 wind pointer, on the bottom of the dial, points to any required degree. 
 It can be clamped to the dial in this position by 'a clamp screw imme- 
 diately behind the azimuth of wind pointer. 
 
 The target arm is mounted about a.n axle so that it may be rotated, 
 and embraces both the dial and ring. It is also bent in such a way 
 as to allow it to pass over the azimuth-ring clamp screw. It also has a 
 clamp screw by means of which it can be clamped at any desired 
 azimuth. 
 
 The target pointer passes through a slot in the squared projection 
 near the base end of the target arm, and is set to indicate any velocity of 
 the wind from to 50 miles per hour, as shown from the indicator of the 
 aeroscope. It also has a set screw by means of which it can be secured 
 at any velocity. 
 
 To Use the Board. The operator (generally the assistant plotter) 
 first sets the target pointer on the target arm to the velocity of the wind, 
 as indicated on the aeroscope, or received over the telephone from the 
 meteorological station. The azimuth ring is then set so that the pointer 
 at the bottom of the dial plate will show the azimuth of the wind as 
 obtained from the same source. The target arm is then set so that its 
 (graduated) edge shows the azimuth of the target on the azimuth ring, 
 as indicated by the gun arm of the plotting board, and it is necessary 
 that this target arm be moved to the azimuth of the target whenever 
 a reading is taken. The position of the point of the target pointer on 
 the dial plate then indicates the two components of the wind which are 
 to be used for correction purposes on the range and deflection boards. 
 If the velocity of the wind or its direction should change, the component 
 indicator should be reset and new components determined. 
 
 Taking Fig. 52 as an illustration, the range component as indicated 
 is the reference number 25, while the deflection component as indicated 
 is the reference number 35. 
 
INSTRUMENTS. DEVICES AND CHARTS .343 
 
 AEROSCOPE 
 
 The aeroscope is a step-by-step dial telegraph used for sending data 
 from the meteorological and tide stations to the several primary stations 
 of a battle command. 
 
 The apparatus consists of the meteorological controller, shown in 
 Plate XXXI, which is mounted in the meteorological station, the tide 
 controller mounted in the tide station, and the meteorological and tide 
 indicators, shown in Fig. 53, which are mounted in the various primary 
 stations. 
 
 The mechanism of the indicator consists of a wheel which is 
 rotated in either direction by the action of electromagnets operated 
 by the making and breaking keys of the controller. The shaft on 
 which the wheel of the indicator rotates carries a pointer, which, by 
 its position on a suitably graduated dial, indicates the proper data. 
 
 TIME-INTERVAL CLOCK 
 
 The time-interval clock is shown in Plate XXXII, it is installed in 
 each primary station of a battery, fire or mine command. It is used to 
 operate the time-interval bells in the stations and emplacements. The 
 bells for any command ring in unison at either 15- or 30-second intervals. 
 (Some of the first clocks installed ring bells on 15- and 20-second 
 intervals) . 
 
 The clock is spring-actuated and is provided with an arrangement of 
 hands which is the reverse of those of clocks in common use, the second 
 hand being mounted centrally and sweeping over the whole face of the 
 clock, while the hour hand and minute hands are mounted at the point 
 usually chosen for the second hand. It has three small wheels mounted 
 on a shaft, two of which are notched so as to cause steel pawls to drop 
 down and make three electrical contacts one second apart, which give 
 the three distinct strokes to the bell. The interval depends upon the 
 pawl and wheel used. The pawls are lowered to the wheels by means 
 of a rod, the position being indicated on the face of the clock. To 
 facilitate setting the bells at the primary station, secondary station and 
 battery in step, a starting and stopping button is provided; this button 
 is connected to a light spring which acts on the escapement wheel, 
 stopping and starting the same. 
 
344 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Wind Azimuth Dial 
 giving Azimuth of 
 
 Wind Velocity Dia 
 
 giving Velocity of 
 
 Wind in Miles 
 
 per Hour 
 
 Atmosphere Density 
 Dial giving percent- 
 age Density of the 
 
 Atmosphere in 
 Reference Numbers 
 
 Tide Dial 
 giving Stat of 
 Tide in Feet 
 and Hundredths 
 
 FIG. 53. Aeroscope Indicator. 
 
INSTRUMENTS, DEVICES AND CHARTS 345 
 
 THE INTERRUPTER 
 
 The interrupter is shown in Plate XXXII. It is a form of buzzer 
 arranged to provide comparatively 'slow interruptions of the time- 
 interval bell circuit. The coil of the interrupter is in shunt across the 
 signal circuit and its armature is provided with an auxiliary break, 
 which causes the armature of the single stroke bells to vibrate in unison 
 with it. 
 
 Interrupters are mounted on brackets in the primary base-end stations. 
 
 THE TELAUTOGRAPH 
 
 The telautograph is shown in Plate XXXII. It is an electro- 
 mechanical instrument which transmits and simultaneously reproduces 
 handwriting or sketches at a distance. 
 
 In the coast artillery service these instruments are used to transmit 
 data from the plotting rooms of the primary stations to the gun emplace- 
 ments and mortar emplacements. 
 
 The telautograph equipment for a battery consists of a transmitter 
 mounted in the plotting room, a receiver mounted within view of a 
 transmitter, as a " pilot " or guide receiver, and several receivers, usually 
 two, mounted in moisture-proof cases and installed on the gun carriages 
 at the battery or in an emplacement booth. The instruments are con- 
 nected to the line wires in series, the line currents passing through all the 
 receivers in turn, and all receivers write the same message simultaneously. 
 Three line wires are used, one called the " right line," which operates 
 the mechanism of the right side, and one called the " left line/' which 
 operates the mechanism of the left side. The third wire carries the 
 current which actuates the pen-lifters and relays; this is called the 
 " pen-lifter line." 
 
 The instruments require 110 volts direct current and each uses about 
 one ampere during actual operation. This power is obtained from a 
 storage battery over separate power leads and is independent of the 
 emplacement lights or motors. 
 
 Messages written on the transmitter are reproduced upon the pilot 
 receiver and similarly on all the outlying receivers, the pens moving in 
 unison with the transmitter pencil. The method of switching the power 
 on and off at the transmitter operates the paper shifting magnet in all 
 the receivers. 
 
346 THE SERVICE OF COAST ARTILLERY 
 
 THE TELEPHONE 
 
 In addition to using the telephone properly it is important that the 
 operator should have sufficient knowledge of the theory and general 
 construction of the types of telephones used in the seacoast service to 
 correct minor defects or at least determine where the troubles lie in 
 order to make intelligent report to those charged with their repair. 
 
 Anyone can use a telephone, with but little practice, but to do so 
 accurately and with such certainty .necessary in coast artillery work 
 requires careful instruction and constant training. 
 
 The standard telephone system now used in fire-control work is tech- 
 nically known as the composite, common and local battery system. The 
 several types of instruments are shown in Plate XXXII and the dia- 
 gram of their circuits is shown in Fig. 54. 
 
 The theory of the telephone may be briefly stated as follows: 
 
 The act of speaking produces sound waves of varying intensity which 
 fall upon the drum of the ear and are recognized by the auditory nerves 
 as speech. If these sound waves instead of falling upon the ear drum, 
 strike against a thin diaphragm such as that found in the transmitters 
 of the ordinary telephones, these vibrations become electrical and are 
 capable of being reproduced at the other end of the line, that is, in the 
 receiver of the distant telephone. 
 
 Referring to the diagram, Fig. 54, when the receiver r is removed 
 from the hook h current comes to the line through the retardation coil C, 
 over the line a, through the induction coil S, through contact of the hook 
 switch v, through the connection n, through the transmitter t, through 
 the connection e and back over d through the retardation coil and to 
 the other pole of the battery. 
 
 Changes in resistance of the transmitter due to the sound waves of 
 the voice striking the diaphragm cause corresponding changes in the 
 current on the line, and a change of potential (pressure) at the terminals 
 of the retardation coil inductively affects the coil T of the induction coil, 
 this induced current passes through the receiver r and the operator hears 
 himself speak; the current also goes through the transmitter, the con- 
 denser and back to coil T. The same effect as that produced in the 
 home receiver is produced in all receivers on the line, the current in the 
 distant induction coil being altered by change of potential at the 
 retardation coil. 
 
 The condenser k is introduced into the circuit to strengthen the trans- 
 mission and produce clearness of speech. Changes in the transmitter 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 347 
 
 resistance produce corresponding changes in potential between the trans- 
 mitter terminals, through I to e on one side of the condenser and through 
 the receiver and coil T to /on the other % side. The condenser will there- 
 
 JOOOOhn 
 
 induction Coil \ 
 
 TO Ohms 
 
 'ye f / on Coil 
 
 fnductionCoil \ 
 
 "FT 
 
 4O Ohms\3jg Retardation Coif 
 
 C 
 4OOhms-\ 
 
 30 Volts 
 Common Battery 
 
 Induction Coil 
 
 FIG. 54. 
 
 fore be charged and discharged through the coil T, producing current 
 ripples which will inductively affect the coil T t and tend to amplify 
 corresponding changes of current in T. 
 
348 THE SERVICE OF COAST ARTILLERY 
 
 In case of failure of the common battery the switches at 8 and S' are 
 closed, putting the local battery circuit through the primary coil P, 
 which then acts inductively on S as a secondary and tjie induced current 
 passes to the line through the distant coil $', and acts inductively on 
 the coil T and the receiver circuit. 
 
 The magneto m and the ringer g are in parallel on one side of the line 
 a, with the condenser k between them and the other line d. The magneto 
 is connected to the line through the condenser because the heavy gener- 
 ator windings of comparatively low resistance would otherwise tend to 
 cause the armature to " stick " when the crank is turned. This " stick- 
 ing " is due to the direct current on the line which would pass through 
 the armature of the magneto. 
 
 * 
 OPERATION 
 
 Selection of Operators. The operator should be of a non-excitable 
 disposition, so as to speak slowly and distinctly at all times. He should 
 articulate well and never speak too loud. No person should be selected 
 as operator until he has been tried on a line that is not working very 
 well, for a test of the suitability of his voice for the work. Too much 
 stress cannot be laid on the necessity for care in the selection of tele- 
 phone operators. 
 
 If each operator takes an interest in the instrument he uses and applies 
 proper care, the efficiency of the system will be increased twofold. The 
 talking sets should be hung in their proper places at the completion of 
 drill; hook retaining springs attached; cords kept clear of possible 
 interference; and a prompt report made of any defect found. 
 
 To Open Station. Care must be taken in this ordinary operation in 
 order to detect any evident trouble before the work begins and thus 
 avoid interruption. The following simple rules should be observed: 
 
 (a) Look over the connections to see if none is loose. These are the 
 two connections to line and the three where the head set is attached at 
 terminal block, the battery terminals, if local battery is used. 
 
 (6) Release the retaining spring and see that the hook goes all the way up 
 or till good contacts are made at v. 
 
 (c) Put the head set on and close the two-way switches to C B and 
 then to L B. In both cases a distinct click should be heard. Leaving 
 the switch on the common battery, lower and raise the hook switch when 
 the same click should be heard. Experience will teach the operator how 
 loud this click should be. A slight scratching in the transmitter should 
 be heard in the receiver. 
 
INSTRUMENTS, DEVICES AND CHARTS 349 
 
 (d) Hold hook down and ring the station and wait for a reply (unless 
 the phones are connected through a central), in which case no ringing 
 is necessary. 
 
 (e) Place the mouth near the mouthpiece of the transmitter and call 
 the other station by name. Wait for a verbal answer to the call before 
 sending any message. A little delay at this stage may result in a 
 material gain of time. 
 
 Using the Phone. Although a simple operation, too much care 
 cannot be taken to do this properly. 
 
 (a) Never shout, as this causes a rattling of the diaphragm with a 
 consequent jumbling of the sounds. 
 
 (6) Place the mouth at a distance of from one to two inches from the trans- 
 mitter and speak slowly and distinctly, not slurring over words or syllables, 
 but enunciating clearly each sound. The distance of the mouth from 
 the receiver is determined by practice and depends on the character and 
 carrying power of the voice. 
 
 It is not desirable that the air expelled from the mouth in the act of 
 speaking strike the diaphragm, as this may set up vibrations different 
 from those due to the sound wave and cause confusion. 
 
 To prevent this the voice should be directed to one side of the trans- 
 mitter, or the mouth may be placed at the side of and touching the 
 transmitter opening and the voice directed across it. 
 
 (c) Unless absolutely necessary, do not use any unusual words, ad- 
 hering to those heard every day about the guns. 
 
 (d) Endeavor to complete every sentence without break or change. 
 For this reason every important message should be written and the 
 operator should read it before beginning to transmit it. 
 
 (e) Send numerals singly, thus 4370 is sent four, three, seven, zero. 
 The use of the letter O for a zero may sound like the numeral four. 
 Mistakes due to this are known to have occurred. 
 
 Enunciate clearly and speak slowly, as each word stands by itself; the 
 adjacent words do not, as in a message, help to determine one not under- 
 stood. If it is necessary to repeat, use more care as to distinctness and 
 do not yell. 
 
 If necessary, a numeral not understood may be accentuated by count- 
 ing up to it and emphasizing it. Thus if the 4 is not understood in 
 7649 begin to count one, two, three, FOUR. 
 
 (/) In receiving, close attention is necessary; the senders hould be 
 interrupted only when absolutely necessary and the part to be repeated 
 clearly indicated. 
 
 If the sender begins to speak too loud, the receiver must caution him 
 
3.50 THE SERVICE OF COAST ARTILLERY 
 
 to speak lower and continue to do so until the best pitch of voice is 
 obtained. 
 
 All unnecessary conversation must be absolutely prohibited if satis- 
 factory results are desired. 
 
 To Close Station. Repeat to the other stations what has been 
 ordered, then hang up the head set on the hook and open the switch in 
 the local circuit if it has been used. If the head set is not to be hung 
 on the hook see that the retaining spring is made fast to insure the 
 breaking of the contact at v, Fig. 54. 
 
 TESTING 
 
 Remarks. Experience is the best guide in quickly locating and cor- 
 recting faults in the telephone, but a familiarity with the parts of the 
 phone and what each is supposed to do, together with a few rules of 
 procedure, coupled with a primary knowledge of electrical principles, 
 will enable a novice to locate trouble even though he cannot cure it. 
 
 General Principles. It is evident that the field ctf the trouble can 
 always be narrowed down considerably by disconnecting the phone from 
 the line. If, on so doing, the trouble disappears it must have been in 
 the line. In any case of trouble look carefully, but rapidly over the 
 whole phone, as the cause is sometimes quite evident to the eye, partic- 
 ularly if it is a disconnected wire or a loose joint. Failing to see 
 the trouble, proceed with the operator's test. 
 
 The troubles generally lie under five heads, as given below. Each 
 case is analyzed and the possible sources of troubles enumerated, with 
 the tests for determining which exists. The term indicated is used ad- 
 visedly in the tests because in obscure troubles the symptoms may 
 be deceptive. 
 
 A. BELL IS NOT RUNG BY ITS OWN MAGNETO 
 
 Analysis 
 
 1. Short circuit on line, or 
 
 2. Mechanical trouble in the bell, or 
 
 3. Short circuit in the phone, or 
 
 4. Open circuit in the phone, or 
 
 5. Magneto does not generate. 
 
 Operator's Test. With the receiver on the hook turn the magneto 
 handle briskly tw T o or three times. If the bell does not ring and the 
 
INSTRUMENTS, DEVICES AND CHARTS 351 
 
 magneto turns hard, i. e., with more difficulty than when the phone is 
 in good order 1. (Short, circuit on line), or, 3. (Short circuit in phone) is 
 indicated and the operator proceeds as follows, trying to ring after 
 each step: 
 
 * Inspect and see that the ends of the line and x ground wires do not 
 touch any other part after passing through the binding posts. 
 
 Disconnect the line wires, if the bell rings now, 1 (Short circuit on line) 
 is clearly indicated and should be reported, but if it does not ring and 
 still turns hard, report that 3 (Short circuit in phone) is indicated. 
 
 If the handle does not turn hard the operator takes up 2 (Mechanical 
 trouble in the bell) and sees that the striker is not bound by the metallic 
 cap over it, also that the armature can be moved by hand and that the 
 striker will touch the gongs when the armature is so moved. The first 
 trouble may be remedied, the others should be reported. 
 
 Proceed next to 4 (Open circuit in the phone) and, opening the mag- 
 neto box, see if contact is made between shaft and spring when th/* 
 handle is turned. The last may fail because the shaft is caught at some 
 place, as where it enters the box, or the collar on the shaft may have 
 slipped or the springs may be bent. The spring may be held against 
 the end of the shaft with a pencil, during a test, to insure good contact. 
 A spark seen at this contact indicates poor contact. If the operator 
 cannot easily correct these faults he should report as nearly as practicable 
 what trouble he has found. 
 
 B. BELL IS NOT RUNG BY DISTANT MAGNETO 
 
 Analysis 
 
 1. Home phone out of order, or 
 
 2. Distant phone out of order, or, 
 
 3. Line out of order. 
 
 4. Condenser circuit open. 
 
 Operator's and Expert's Test 
 
 (a) Test for 1 (Home phone out of order) by detaching the line and 
 turning the handle, and proceed as under A. 
 
 (b) Test for 2 (Distant phone out of order) at the distant phone in a 
 manner entirely similar to 1 (Home phone out of order) . 
 
352 THE SERVICE OF COAST ARTILLERY 
 
 C. CAN HEAR BUT CANNOT BE HEARD 
 
 Analysis 
 
 1. Local circuit at fault. 
 
 (a) Battery, (6) connections or wiring, (c) transmitter, 
 (d) primary coil, or 
 
 2. Distant receiver out of order, or 
 
 3. Home secondary coil short-circuited. 
 
 Operator's Test. Disconnect line wires and connect binding posts 
 with a piece of wire, thus short-circuiting the phone. Place the receiver 
 to the ear and scratch gently with the finger nail on the inside of the 
 transmitter mouthpiece. If this is distinctly -heard the local circuit 
 and receiver are all right. 
 
 If no sound results put the receiver to the ear, lower and raise hook, 
 also open and close the two-way switch. If a distant click is heard for 
 each of these, the local circuit is all right , but the transmitter may not be 
 in good order, and a report should be so made. 
 
 If no sound results, make sure that the switch contact is good, on 
 CB and LB, that the pivot is not loose, that contacts at v are good, 
 that the connections at battery terminals are good. 
 
 (Distant receiver out of order). The operator at the distant phone 
 should try the tests above given for home circuit. If these give no 
 sound in his receiver he should try another receiver, if one is available. 
 He may try a new cord or substitute pieces of wire for it. 
 
 D. CAN NEITHER HEAR NOR BE HEARD 
 
 Analysis This indicates general trouble. 
 
 1. In the phones, or 
 
 2. In the line. 
 
 Operator's Test. Go over the phone carefully, looking for poor con- 
 tacts as where an insulated wire is put in the binding posts ; binding posts 
 not screwed down tight; ends of wires passing through post and touching 
 other parts; contacts at cells and condition of cells as noted before. 
 Disconnect the line wires and test out phones as indicated. If there are 
 fuses in the line see that they are not burned out. If no trouble is 
 found to exist when the line is disconnected report line out of order. 
 
INSTRUMENTS, DEVICES AND CHARTS 353 
 
 MERCURIAL THERMOMETER 
 
 The temperature of the air is measured by means of a mercurial ther- 
 mometer. This instrument consists of a glass tube having a very small 
 bore, terminating in a bulb, and containing mercury. 
 
 It is founded on the principle that changes of temperature in bodies 
 are accompanied by proportional changes in their volumes or dimen- 
 sions. When the temperature rises, the mercury in the bulb expands 
 more than the glass and rises in the tube; when the temperature de- 
 creases the mercury contracting more than the glass descends again 
 towards the bulb. The changes in temperature, to which the thermo- 
 meter is exposed, will therefore be shown by the rising and falling of 
 the mercury in the tube. 
 
 In order to have an intelligent measure of these changes the ther- 
 mometer is provided with a fixed scale. The two fixed temperatures 
 one of melting ice, usually called the freezing point; and the other that 
 of boiling water under standard pressure, or rather the temperature of 
 the steam above the surface of boiling water have been adopted as the 
 fixed or starting points' for the graduations of thermometers. The 
 intervals between these two fixed points are divided into spaces called 
 degrees, and for coast artillery work these are divided into sub-spaces, 
 called hundredths of degrees. 
 
 The Fahrenheit thermometer is marked 32 degrees at the point of 
 melting ice and 212 degrees at the point of boiling water, the space be- 
 tween these two graduations being divided into 180 equal parts. The 
 graduations being divided into 180 equal parts. The graduations ex- 
 tend downward to zero, and usually 10 or 20 degrees below zero. 
 
 The Fahrenheit scale is generally used in connection with coast 
 artillery work, but readings made on the centigrade thermometer are 
 readily converted. The freezing point on the centigrade is marked 
 zero and the boiling point 100. It is therefore necessary, in order to 
 convert Fahrenheit readings to centigrade, to subtract 32 degrees and 
 multiply the remainder by f ; or, to convert centigrade to Fahrenheit 
 readings, multiply by f and add 32 degrees. Mercurial thermometers 
 can be relied upon down to temperatures near the point of freezing 
 mercury, or as low as minus 38 degrees. 
 
354 THE SERVICE OF COAST ARTILLERY 
 
 THE BAROMETER 
 
 The density of the air is measured by means of the barometer and 
 thermometer. The barometer depends for its action upon the principle 
 that air has weight. As is generally known, the weight of air w;ll uphold 
 a column of water the vertical height of which depends upon the height 
 above the sea level at which the experiment is conducted. 
 
 In the coast artillery service the jnercurial barometer is used prin- 
 cipally to test the adjustment of the aneroid barometer. The latter, 
 being quicker in its action, is used in connection with the thermometer to 
 determine the reference number on the atmosphere board, to be applied 
 on the atmosphere density per cent, indicator of the aeroscope. 
 
 Mercurial Barometer. This barometer consists of a glass tube about 
 a yard in length closed at the top and open at the bottom, which is 
 partially filled with mercury. The tube is suspended vertically, as shown 
 in Plate XXXI. The lower end of the tube dips into a cistern, which 
 consists of a brass casing, including three wooden pieces fastened to- 
 gether by four screws in the form of a circle. The lower portion of the 
 cistern has a leather sack, called the cistern sack, which can be raised or 
 lowered by means of an adjusting screw. It is used to bring the surface 
 of mercury in the cistern to a certain level before a reading is taken. 
 
 In preparing the instrument for use the top is first completely filled 
 with mercury. As soon as it is free to do so the column of mercury in the 
 tube sinks until it stands at a height of about 30 inches, or such that the 
 pressure of the column exactly balances that of the atmosphere. A 
 graduated scale of metal is attached to the glass and affords the means 
 of reading the height of the column of mercury. 
 
 To read the barometer first read the attached thermometer to the 
 nearest half degree 'and record it. Tap the barometer sharply with 
 the finger to free the mercury from the tube. By means of the adjusting 
 screw lower the mercury in the cistern below and then raise it until the 
 surface exactly touches the ivory point. When the mercury is per- 
 fectly clean the proper adjustment can be made by causing the ivory 
 point to exactly coincide with its reflected image in the mercury below. 
 But usually after the mercury has been in use for a short time a slight 
 film of oxide forms on its upper surface and it is necessary to determine 
 the contact by immersing the ivory point in the mercury until a slight 
 dimple is formed, and then slightly lower the screw until the dimple is 
 about to disappear. 
 
 Adjust the vernier by means of the side mill-headed screw to the top 
 
PLATE XXXI 
 
 SERVICE 
 AEROSCOPE | 
 ONTROLLER- 
 
 ANERCMD 
 AROMETE 
 
 Azimuth of 
 
 in degrees 
 terrruned from 
 wind vane 
 
 ind miles 
 per hour 
 
 letermtned from 
 
 memometer and 
 
 Density of 
 atmosphere 
 
 per cent, 
 determined from 
 itmosphere board 
 
 m 
 
 SI STANDARD 
 I 1 MERCURIAL 
 i' 8AROMETEF 
 
 Equipment of Meteorological Station. 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 355 
 
 of column of mercury until the zero line of the vernier and the bottom 
 of the hind part of the vernier in rear of the mercurial column exactly 
 coincides with the top of the meniscus, that is, tangent to the convex 
 surface of the mercury in the tube. Read the barometer scale to inches 
 and tenths between the zero point and the lowest line of the vernier. 
 Find the number of the line on the vernier which coincides most nearly 
 with the line on the barometer scale. (See Fig. 55.) This number will 
 be the hundredths of an inch of the barometer reading. Add to this 
 the inches and tenths and the result will be the barometer reading in 
 
 80.011. 
 
 20.999. 
 
 FIG. 55. 
 
 28.820. 
 
 inches, tenths and hundredths. Where a line on the vernier does not 
 exactly coincide with the line on the barometer scale the observer will 
 after practice be able to estimate the reading to thousandths of an inch. 
 Be careful in making the adjustments of a barometer suspended from 
 one end only so as not to move the barometer from its vertical 
 position. 
 
 Aneroid Barometer. The aneroid barometer, shown in Plate XXXI, 
 consists of a cylindrical metal box exhausted of air, having a lid of thin 
 corrugated metal. The lid, which is highly elastic, yields to every 
 change of atmospheric pressure and delicate springs and levers transmit 
 
356 THE SERVICE OF COAST ARTILLERY 
 
 its motions to an index that moves over a graduated scale whose divi- 
 sions are marked on the dial after comparison with the mercurial 
 barometer. 
 
 All aneroids should be frequently and carefully tested with standard 
 mercurial instruments at known altitudes in order to determine the 
 proper correction for instrumental error. The best aneroids are now 
 marked compensated and are practically free from errors arising from 
 changes of temperature in the instrument itself. 
 
 One of the chief differences between the aneroid and the mercurial 
 barometer is the fact that the aneroid acts more rapidly under rapid 
 changes of pressure than does the mercurial barometer, and care should 
 be taken to avoid errors due to the sluggishness of the mercurial bar- 
 ometer. 
 
 Aneroids are usually graduated to indicate a fall of pressure to 
 twenty inches, which would correspond to a height of a little over 
 11,000 feet. 
 
 THE ANEMOMETER 
 
 The velocity of the wind is determined by an instrument called the 
 anemometer. The type in use at seacoast fortifications is known as the 
 Robinson type, and consists of a vertical spindle having at its upper end 
 four horizontal arms at right angles to one another, bearing at their ex- 
 tremities hollow hemispherical aluminum cups whose circular rims are 
 in the vertical plane passing through the respective arms and the com- 
 mon axis of rotation. The convex side of each cup faces the direction 
 of rotation. Therefore two opposite cups have their convex surfaces 
 facing in opposite directions. The pressure of the wind against the cup 
 whose concave side receives the wind is greater than against the cup 
 whose convex side receives it at the same time. Consequently, whatever 
 the direction of the wind, the cups are caused to rotate in the same direc- 
 tion, each cup moving with its convex side forward. 
 
 On the lower portion of the vertical spindle there is a worm gearing 
 into a worm wheel, and on the arbor of this wheel another worm gears 
 into a pinion and the pinion in turn gears into the teeth on the circum- 
 ferences of the dials driven by them. The mechanism is arranged to 
 close an electric circuit at the expiration of a certain number of revolu- 
 tions of the cups. In the type in use the contact is so arranged that it is 
 closed once every 25 revolutions of the spindle, which corresponds to 
 ^ of a mile travel of wind, with certain corrections -as the velocity rises. 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 357 
 
 The connections and general arrangement of the anemometer are shown 
 in Fig. 56. 
 
 The rapidity with which the air moves past any given point of the 
 earth's surface is called the velocity of the air or wind at that point. 
 On account of the friction of the moving air in contact with the surface 
 of the earth the movement of the air is retarded near the surface. It is 
 estimated that the effect of this friction decreases from 20 to 50 per cent, 
 for the first 100 feet above the earth, and gradually diminishes until its 
 effect is nil at an elevation of 10,000 feet. For this reason anemometers 
 are installed at the highest available point in fortifications. 
 
 Anemometer 
 
 Battery 
 
 FIG. 56. 
 
 Method of Using the Instrument. As previously stated, the approxi- 
 mate velocity of the wind in miles per hour is equal to 180 divided by the 
 time between the closing of the contacts of the anemometer. An ane- 
 mometer stop watch reading to second and marked on its face in red 
 figures at the points corresponding to 40, 30, 20, 10 and 5 miles per hour 
 is used in connection with the anemometer in determining the velocity 
 of the wind. At the first closing of the contact which clicks a sounder 
 or rings a bell the stop watch is started, and at the next closing of the 
 circuit which gives the same signal the watch is stopped. The velocity 
 of the wind in miles per hour is indicated as above stated in red figures 
 upon the dial of the watch, or in case the anemometer stop watch is not 
 at hand the velocity may be obtained from the following table: 
 
358 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Seconds 
 Interval 
 Between 
 Strokes 
 of Bell or 
 Sounder. 
 
 Velocity of 
 Wind, Miles 
 per Hour. 
 
 Seconds 
 Interval 
 Between 
 Strokes 
 of Bell or 
 Sounder. 
 
 Velocity of 
 Wind, Miles 
 per Hour. 
 
 2 J 
 
 53 
 
 12 
 
 14 
 
 3 
 
 45 
 
 14 , 
 
 12 
 
 3 40 
 
 16 
 
 11 
 
 4~ 
 
 36 
 
 18 
 
 9.5 
 
 5 
 
 30 
 
 20 
 
 8 
 
 6 
 
 26 
 
 25 
 
 6.5 
 
 7 
 
 23 
 
 30 
 
 5.5 
 
 8 
 
 20 
 
 -35 
 
 5 
 
 9 
 
 18 
 
 40 
 
 4.5 
 
 10 
 
 16 
 
 60 
 
 3.0 
 
 THE ATMOSPHERE BOARD 
 
 The atmosphere board is used to determine the atmosphere reference 
 numbers to be recorded on the density dial of the aeroscope indicator. 
 It is shown in Fig. 57. 
 
 ATMOSPHERE BOARD 
 
 FIG. 57. 
 
 The board consists of a frame upon which a graphic table is mounted. 
 Along the top edge of the frame a T-square fits into a groove which runs 
 the length of the board. The arguments of the table are barometer and 
 
PLATE XXXII 
 
 Instrument Panel, Fire-Control Equipment for Primary Station. 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
INSTRUMENTS, DEVICES AND CHARTS 359 
 
 thermometer readings. The thermometer graduations are horizontal 
 and extend along the top of the table while the barometer graduations 
 are vertical and extend along the right side of the table, and for con- 
 venience of reading, are also placed along the left edge of the T-square. 
 The reference numbers are indicated on diagonal lines as shown in 
 Fig. 57. 
 
 To Use the Chart. Assuming that the thermometer shows a tempera- 
 ture of 20.10 degrees and the barometer a pressure of 29.50 inches, the 
 ruler of the T-square is moved until its left edge is made to coincide 
 wdth the reading of 20.10 degrees. The atmosphere reference number 
 will then be the nearest diagonal line cutting the barometer graduations 
 on the ruler at 29.50. An inspection of Fig. 57 will show this diagonal 
 line to be numbered 8. Therefore the reference number for the ther- 
 mometer and barometer readings taken would be 8. This number 
 would then be indicated on the density dial of the aeroscope. 
 
 SIGHTS 
 
 Sights for scacoast cannon are of two general classes, namely: Open 
 Sights, and Telescopic Sights. 
 
 OPEN SIGHTS. 
 
 2.24-inch 6-pounder, Wheeled Mount. Open tangent (front and 
 rear) sights, affixed to the gun in the ordinary manner, are issued with 
 these guns. 
 
 The front sight consists of a bracket and a cross-wire frame; the 
 latter carries two wires and is assembled in the socket of the former by 
 a stud and set screw. 
 
 The rear sight consists of a bracket, an operating knob, a pinion with 
 a sleeve, a standard, a cross arm and screw, and a cross-wire frame. 
 The bracket is slotted for the standard and, at right angles, for the 
 pinion and sleeve. The sleeve and the knob are assembled to the 
 pinion and are held in place by the pinion wheel and a spring that 
 abuts against a shoulder on the knob and a collar fastened at the outer 
 end of the pinion. 
 
 The sleeve is assembled to the bracket by a set screw, and has a ser- 
 rated surface that fits a corresponding surface on the knob, thus pre- 
 venting rotation of the latter. The knob is ordinarily held against the 
 sleeve by the spring, but may be moved along the pinion and then 
 
360 THE SERVICE OF COAST ARTILLERY 
 
 rotated, a spline on the pinion and a corresponding groove in the knob 
 causing them to rotate together. 
 
 The standard is shaped to the slot in the bracket, has the ranges 
 marked on its surface, and carries a rack that engages the pinion. The 
 cross arm is assembled to the standard by a stud and pin, is shaped to 
 receive the base of the cross-wire frame, has two bearings for the cross- 
 arm, and is graduated to mark deflections. 
 
 The cross- wire frame carries four wires arranged to give a small square 
 aperture in the center. The lower part of the frame has a zero line, is 
 made to fit into the cross arm and is threaded for the screw. This last 
 is fixed in position, and when rotated causes the cross-wire frame to 
 move to the right or left. 
 
 2.24 inch 6-pounder Barbette Mount (Driggs-Seabury) , Model of 
 1898. The open sights for this gun, with the exception of minor and 
 unimportant details, are the same as those given for the 4-inch 
 Driggs-Schroeder gun. 
 
 Three-inch, is-pounder. The open sights for these guns are the bar 
 and drum pattern, shown in Plate XV. 
 
 Four-inch Barbette Carriage (Driggs-Schroeder). The open sight 
 for these guns consists of a front sight screwed into its seat and held by a 
 set screw. The head of this sight is a hoop, the single cross wires and 
 sighting point projecting from the top of the hoop for rough aiming. 
 The rear sight is a general pattern of bar sights moving in a sight box 
 bolted to the face of the breech. The right part of the rear face of the 
 bar has a vertical rack cut in it throughout the, length, in which works 
 a small pinion controlled by a small hand wheel. The shaft of the hand 
 wheel carries a ratchet which normally engages in a pinion-fixed ratchet 
 in the wall of the sight box, being held in place by a spring. The bar is 
 graduated in yards for range, full charges, and set at a vertical latent 
 angle to give an automatic correction for drift. To correct for wind or 
 speed of target the head of the sight carries a cross bar actuated by a 
 worm, the cross bar being graduated in minutes. 
 
 4.72-and 6-inch Armstrong Q.F. Guns. The sights are of the bar 
 and drum pattern, shown in Plate XV, and consist of a carrier, which 
 is fixed to two bosses on the mounting by means of two T-headed bolts; 
 a sight bar with rack and front and rear sights; a worm wheel, pinion 
 and drum with graduated crown metal ring attached to the circumfer- 
 ence. The ring is graduated in yards. The drum is fixed to the spindle 
 by means of three screws, so as to be readily moved round for adjustment. 
 
 In order to adjust the ring, slack the screws, run the sight by means 
 of the worm gear to the " point blank " position, then move the ring 
 
INSTRUMENTS, DEVICES AND CHARTS 361 
 
 around till the zero point is in line with the pointer, then tighten the 
 screws. 
 
 The sight bar is fitted to take the electric night sights. The crosshead 
 on the sight bar gives 2 degrees deflection, right and left, and is fitted 
 with a screwed deflection window of H form, with a horizontal wire 
 stretched across. 
 
 The fore sight is furnished with an upright blade, terminating with a 
 spherical bead. 
 
 Five-inch Barbette Carriage (Model of 1896). Sights for this carriage 
 consists of a bead front sight and a small ring set in a window for a rear 
 sight. The front sight is inserted in the front-sight bracket and the 
 bead is protected by a ring. The rear-sight window is set in a crosshead, 
 giving 2 degrees deflection right or left, the smallest graduation being 
 10 minutes. The crosshead is on the upper end of a stem curved so 
 that in elevating the rear sight moves through the arc of a circle, the 
 center of which is the bead of the front sight. Rack teeth are cut in the 
 front face of the stem and are engaged by a worm operated by a small 
 hand wheel in the rear of the sight bracket. This bracket carries a drum 
 graduated in yards and arranged to be easily adjusted so as to bring its 
 zero to the pointer when the sight is brought to the " point blank " 
 position. 
 
 For 8-, 10-, and 1 2-inch B. L. Rifles. All of these guns are fitted for 
 axial sights arid are issued with screw holes filled with brass plugs. The 
 axial sights are only issued for guns mounted on barbette carriages. 
 These sights consist of a simple notched rear sight without any means 
 of elevation or deflection, and a point front sight. 
 
 TELESCOPIC SIGHTS 
 
 Three-inch (is-pounder) R. F. Gun on Masking Parapet Mount. 
 
 The sights furnished with this mount are the telescopic sight, model of 
 1899, Type A, as shown in Fig. 58, and the night sights. 
 
 The telescopic sight differs materially from all previous models. In- 
 stead of being pivoted to a trunnion casting by which it may be adjusted 
 in its seat or bracket and which permits elevation to be given, the tele- 
 scope tube consists of a substantial bronze casting provided on its 
 under side with two lugs. These lugs are about 4 inches apart and rest 
 on and inclose the ends of a flat-machined seat on the shoulder bar. 
 The sight is secured in place by two thumbscrews, one on the left side 
 of each lug, which bear against the undercut side of the seat. There are 
 no levels and no movement of the telescope with reference to its seat is 
 
362 
 
 THE SERVICE OF COAST ARTILLERY 
 
 possible. The telescope is used simply as a more effective open sight, 
 elevation being given by movement of the shoulder bar. 
 
 The interior and exterior deflection scales and the micrometer head 
 on the deflection screw are practically the same as in the model of 1898, 
 with the exception of the graduation. Both scales are graduated to 
 2 degrees 30 minutes on each side of zero, the smallest division on the 
 interior scale being 6 minutes and on the exterior scale 30 minutes. 
 
 One revolution of the micrometer head is equal to 1 degree. The 
 6-minute readings on the outer scale are obtained from the ten divisions 
 on the micrometer head. 
 
 FIG. 58. Telescopic Sight, Type "A," M. 1899, for R.-F. Guns. 
 
 The telescope is provided with a set of open sights to serve as a finder. 
 The object glass is protected by a heavy bronze disk attached to a 
 spindle about 3^ inches long, which passes through a projection on the 
 left side of the telescope tube parallel with the axis. The rear end of 
 the spindle is fitted with a short lever arm by which the disk can be 
 rotated to uncover the objective. 
 
 Data for Telescope 
 
 Field of eyepiece 26^ 
 
 Power of telescope 3^ 
 
 Field of view 7-- 
 
 Diameter of objective .;t ........ 1J inches 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 363 
 
 As in the case of the model of 1898 the telescope is non-inverting, but 
 the erect image is obtained by the use of an erecting eyepiece instead of 
 prisms. This eyepiece consists of three plano-convex lenses mounted 
 in a brass tube which is screwed into the main tube from the rear. A 
 capstan-headed screw on the right side of the main tube screws into a 
 collar in the inner tube and determines the position of the latter. The 
 sliding diaphragm containing the cross hairs is placed in rear of this 
 eyepiece. 
 
 Two-inch Telescopic Sight, Model of 1902. This sight is shown in 
 detail in Fig. 59. Its general description is as follows: 
 
 FIG. 59. Combination Open and Telescopic Sight, 2-inch, M. 1902. For R.-F. Guns. 
 
 The sight is attached to the cradle by means of a front and rear 
 bracket. The front sight bracket is securely keyed to an extension of 
 the left trunnion of the cradle, and locked by a screw. It is not intended 
 to be removed except when necessary to protect it from injury in dismounting 
 the shield or cradle. The rear-sight bracket is attached to the elevating 
 rack bracket by means of two 0.75-inch conical head screws and one 
 0.75-inch headless screw. It is further secured by a horizontal spline 
 and a vertical key. The front-sight bracket is bored vertically at the 
 
364 THE SERVICE OF COAST ARTILLERY 
 
 upper end to receive the sight post. A keyway is provided in the bracket 
 and a key in the sight post to prevent the latter turning in the bracket, 
 and the sight post is provided with a nut and locking pin at its lower 
 end. At its upper end the sight post is hinged to the sight pivot ty 
 means of a bronze hinge pin 0.81 inch in diameter, screwed into one of 
 the prongs of the sight post and secured by a taper pin. This hinge pin 
 forms the axis of rotation of the sight bar in elevation and should never be 
 removed from the sight post. 
 
 The upper end of the sight pivot forms a seat for the sight-bar head, 
 which is drilled to slip over it and is secured by a nut with a taper pin 
 so as to be free to revolve around the axis of the pivot. The sight pivot , 
 therefore, forms the axis of rotation of the sight bar in azimuth and should 
 never be removed from the sight bar except when absolutely necessary for 
 cleaning purposes. 
 
 Rear-sight Bracket. The rear sight bracket is a steel forging which, 
 with its cover, a bronze casting, is milled out in such a way as to form 
 bearings for the mechanism necessary to elevate and depress the sight. 
 About half of these bearings are in the steel bracket and half in the 
 cover. Near the top the sight bracket is bored to a depth of 1 .752 inches 
 and a diameter of 2.35 inches. The center of this bore is further drilled 
 to a depth of 0.66 inch and a diameter of 0.625 inch, the object being to 
 form a bearing for the sight-elevating pinion and wormwheel. This 
 part, which is of bronze, in one piece, is drilled 0.625 inch diameter on 
 the pinion end. The gear cover is milled to a diameter of 2.35 inches in 
 line with the bore of the sight bracket, but in the gear cover a projection 
 0.623 inch in diameter and 0.877 inch long at the center of the bore is not 
 cut away and forms the left-hand bearing of the sight-elevating pinion 
 and wormwheel. 
 
 A horizontal slot 0.8 inch wide and 1.9 inches deep is cut through the 
 rear-sight bracket near its middle part. Two bronze bushings suitably 
 fitted into this slot form bearings for the sight-elevating worm which 
 gears into the worm wheel above described. A spline on the gear 
 cover also fits into this slot and helps to keep the gear cover in 
 position. The sight-elevating worm shaft has a hand wheel at each end. 
 
 A slot on the proper radius is cut in the gear cover for the sight-ele- 
 vating rack. At the upper end of this slot, at the rear, and on the left- 
 hand side the gear cover is cut away to make the graduations on the 
 sight-elevating rack visible. 
 
 Sight Holder. The sight holder, of bronze, is riveted to the rear end 
 of the sight bar and forms an extension of it. Directly above the sight 
 bar is the seat for the telescope, consisting of two hinged ring clamps, 
 
INSTRUMENTS, DEVICES AND CHARTS 365 
 
 the forward one of which is provided with a slot to take the spline of the 
 telescope. An extension of the sight holder to the left is bored and 
 tapped to receive the peep-sight tube, consisting of a bronze tube with 
 an interior diameter of 0.812 inch. The peep-sight plate is drilled at the 
 center 0.125 inch in diameter, forming the peep. It rests against a 
 shoulder of the tube, being held in position by a ring screwed into the 
 end of the tube. It is held and adjusted laterally by three screws 
 through the walls of the tube bearing against its edges. 
 
 Front Sight. The front sight consists of a ring carrying two German 
 silver cross wires and attached to a stem fitted with a bayonet joint, by 
 which it is attached to the sight-bar head. 
 
 Telescope. The telescope consists of a brass tube about 16 inches 
 long and 1.78 inches in exterior diameter, except at the forward end, 
 where the tube is enlarged to an exterior diameter of 2.25 inches, and 
 at the two bearing surfaces, where the exterior diameter is 1.875 inches. 
 
 The object glass, 1.75 inches in diameter, held in a brass ring with a 
 knurled head, is screwed into the front end of the tube. 
 
 The eyepiece consists of two lenses held in brass rings screwed into 
 the ends of a brass tube 2.65 inches long, which slides in the rear end of 
 the main tube of the telescope. This short tube is slotted out at the top 
 and is provided with a rack placed at the side of the slot. The rack 
 engages with a pinion provided with a knurled head and having its 
 bearing in the main tube of the telescope. By turning the knurled 
 head the eyepiece is adjusted for focus. 
 
 Horizontal and vertical cross lines are etched upon the forward lens 
 of the eyepiece and scales for horizontal and vertical deflection. 
 
 The horizontal scale is graduated to 0.05 degree and numbered to 
 0.2 degree. The vertical scale is graduated to 0.001 of the range and 
 numbered to 0.004 of the range. 
 
 The distance between the centers of the bearing surfaces of the tele- 
 scope is 6 inches. The forward bearing surface is provided with shoul- 
 ders to prevent longitudinal motion in the telescope carrier and a spline 
 to prevent rotation. Between the two bearing surfaces the top of the 
 main tube is slotted out to permit the placing of a set of Brashear erect- 
 ing prisms. These are held in an adjustable brass frame and are covered 
 by a cap which is screwed to the main tube by six screws. 
 
 Both the object glass and eyepiece are protected by swinging 
 covers. 
 
 For night illumination a small tube for the lamp enters the main 
 tube on the right-hand side just forward of the front bearing. Just for- 
 ward of this a mirror is provided, which, by means of a knurled head, 
 
366 THE SERVICE OF COAST ARTILLERY 
 
 can be swung in or out of the center line of the telescope. Arrows 
 on the knurled head and on the telescope indicate when the mirror is 
 in the axis of the telescope. 
 
 Two-inch Telescopic Sight (Model of 1906). This sight is designed 
 for use on the 15-pounder R.F. gun, model of 1903. It consists of a 
 telescope, sight bracket, cradle, with the open-sight attachments con- 
 sisting of the sight shank, deflection worm box and head of shank, range 
 drum, gear cast cover and cover for range drum, elevating worm, the 
 fulcrum, the yoke, deflection scale, elevating-gear shaft and necessary 
 lighting cables. 
 
 The sight bracket is bolted to the carriage at its lower end. The 
 cradle is assembled at the forward end of the front-sight bracket by 
 means of the fulcrum, the fulcrum axis for bearings in the two sides of 
 the front sight bracket permitting rotation for elevation and deflection, 
 and the fulcrum is a short vertical shaft on its outside to which the for- 
 ward end of the cradle is assembled so as to allow rotation in azimuth. 
 At the rear end the cradle is assembled to the sigl^t shank by means of 
 the sight-shank head and the deflection worm. The latter is seated in 
 the sight-shank head, which thus forms the deflection-worm box and 
 meshes into a worm segment cut in the cradle. The front and rear faces 
 of the deflection box and the head of the sight shank are arcs of circles 
 having their common center on the axis of the vertical shaft fulcrum. 
 
 The elevation of the sight and the rotation of the range drum are 
 accomplished by the elevating gear, consisting of the elevating worm, 
 elevating-gear shaft with its worm gear and spur- gear, the latter two 
 being in one piece. The elevating worm engages the worm gear and the 
 spur gear engages the sight-shank rack. The piece on which these two 
 gears are mounted is cut on a square section of the elevating-gear shaft, 
 which is also the range-drum shaft, the range drum being mounted and 
 held in place by the friction of a washer bearing against the drum and 
 the friction of the drum on a shoulder of the shaft. A German silver 
 ribbon spring about eleven feet long is secured at one end to the ele- 
 vating-gear shaft and is wound several times around the shaft, and has 
 the other end secured to the gear-case cover. 
 
 By rotating the elevating worm the elevating-gear shaft is moved, 
 adding to or releasing the tension on the spring, at the same time de- 
 pressing or elevating the cradle by means of the sight shank also rotating 
 the range drum. The object of the spring is to equalize the force re- 
 quired to depress or elevate the cradle. A range pointer is attached to 
 the cover, which is bolted to the sight bracket. The elevation scale is 
 of German silver dovetailed into the rear face of the sight shank, and 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 367 
 
 reads from zero to 16 degrees, the least reading being 6 minutes, or 
 .10 of a degree. 
 
 The range pointer is a piece of German silver dovetailed into the gear- 
 case cover just opposite the lamp bracket and the range-drum elevation 
 scale. The deflection scale, of German silver, is dovetailed into.the rear 
 end of the cradle. The numbers on the scale are reference numbers, 
 three (3) representing the original or central position of the scale. The 
 interval between whole numbers is equal to one degree of arc. The 
 lowest reading of the scale is 6 minutes, or .10 of a degree. 
 
 The deflection scale index is cut on a German silver plate, secured to a 
 lug projecting from the rear of the sight shank. The principal parts of 
 
 OBJECTIVE 
 CELLS AND RING 
 
 LAMP BRACKET FOR 
 ILLUMINATING CROSS WIRES 
 
 EYE PIECE. FIELI 
 AND EYE LENS 
 
 FIG. 59A. 2-inch Telescopic Sight, M. 1906, for 3-inch R.-F. Guns. 
 
 the telescope are the tube, the objective, the Porro erectingvprisms, the 
 draw tube, cross- wire holder, the focusing sleeve, the focusing ring and 
 the eyepiece. 
 
 The telescope is shown in Fig. 59A. The telescope is secured in position 
 on four accurately bored projections on the cradle by the front and rear 
 telescope clamps, each of which is machine-finished to proper bearing 
 on the upper portion of the telescope to secure proper alignment of the 
 optical axis and to insure the vertical wires being held vertically. The 
 telescope has a 2-inch aperture. The magnifying power of the eyepiece 
 is 8 and the sight has a field of 4^ degrees. 
 
 Three-inch Telescopic Sight (Model of 1904). This sight is shown 
 in Plate XXXIII and is designed for use either on barbette or disap- 
 pearing carriages. 
 
368 THE SERVICE OF COAST ARTILLERY 
 
 Sights for Barbette Carriages. The principal parts are the telescope, 
 the sight bracket, the cradle, the open sights, the sight shank with de- 
 flection-worm box and head of sight shank, the range drum, the gear- 
 case cover and cover for range drum, the elevating worm, the fulcrum, 
 the yoke^ the cables and electric lamps, the deflection scale, the elevation 
 scale, the deflection worm and the elevating gear shaft. 
 
 The sight bracket is bolted to the carriage by means of the feet. The 
 cradle is assembled at the forward end to the sight bracket by means of 
 the yoke and fulcrum. The yoke shaft seats in the sight bracket and is 
 keyed in place; the fulcrum axes have bearings in the two sides of the 
 yoke permitting rotation for elevation and depression, and the fulcrum 
 has a short vertical shaft on its under side to which the forward end of the 
 cradle is assembled so as to allow rotation in azimuth only. At the rear 
 end the sight shank is assembled between the sight bracket and the gear- 
 case cover, being held in place by the gear-case cover and the elevating 
 gearing. The cradle is assembled to the sight shank by means of its 
 head (which is also the deflection-worm box) and the deflection worm, 
 the latter being seated in the box and meshing into a worm segment cut 
 in the cradle. The front and rear faces of the deflection box and head 
 of sight shank are arcs of circles having their common center on the 
 axis of the vertical shaft of the fulcrum, and the front and rear faces of 
 the sight shank and its seat are arcs of circles having their common 
 center on the central line of the fulcrum axes. 
 
 The elevation of the sight and the rotation of the range drum are 
 accomplished by the elevating gearing, consisting- of the elevating worm 
 and the elevating-gear shaft with its worm gear and spur gear, the latter 
 two being on one piece. The elevating worm engages the worm gear 
 and the spur gear engages the sight-shank rack. The piece on which 
 these two gears are cut is mounted on a squared section of the elevating- 
 gear shaft, which is also the range-drum shaft. The range drum is also 
 mounted on this shaft and is held in place by the friction of a nut on a 
 washer bearing against the drum and the friction of the drum on a 
 shoulder of the shaft. A ribbon spring 11 feet long and of German 
 silver is secured at one end to the elevating-gear shaft, is wound several 
 times around the shaft, and has the other end secured to the gear-case 
 cover. The cover is bolted to the sight bracket. By rotating the ele- 
 vating worm, the elevating-gear shaft is turned, adding to or releasing 
 tension on the spring, depressing or elevating the cradle by means of 
 the sight shank and rotating the range drum. The spring serves to 
 equalize the force required to depress and elevate the cradle. The gear- 
 case cover and the bracket serve to protect the elevating gearing, the 
 
INSTRUMENTS, DEVICES AND CHARTS 369 
 
 spring, and the range drum. The range-scale pointer is attached to 
 the cover. 
 
 The elevation scale is of German silver, is dovetailed into the rear face 
 of the sight shank, and reads to 6 minutes from zero to 16 degrees. The 
 pointer is on a piece of German silver dovetailed into the sight bracket 
 just opposite the lamp bracket for range drum and elevation scale. 
 
 Deflection is obtained by rotating the deflection worm which is seated 
 in the deflection-worm box and meshes into a worm segment cut into the 
 cradle where the box is seated. 
 
 The deflection scale, of German silver, is secured to the rear end of 
 the cradle and reads to 0.05 of a degree, which equals 3 minutes, over 
 an arc of 4 degrees, beginning with 1 degree on the right. The 
 3-degree mark gives no deflection. The pointer plate is secured to a 
 bracket which is screwed to the under side of the sight shank head. This 
 bracket has, at the rear end, the deflection lamp bracket and a lug that 
 works in a groove in the end of the cradle. 
 
 The open sight consists of a peep sight in rear and a cross sight in 
 front, the former mounted on the eye and telescope clamp, and the latter 
 on the cross-sight holder. It is for use in picking up an object quickly. 
 
 Each sight is provided with three small electric lamps of about 2 
 candlepower; those originally furnished with the first 405 sights have 
 a voltage of 3.75 to 4.75, and an amperage from 0.75 to 1, while those 
 that will be used for replacements and for sights to be manufactured 
 have the voltage from 5.5 to 6.5, with an amperage from 1.25 to 1.35. 
 One of these lamps illuminates the cross wires, giving bright lines in a 
 dark field, and the other two illuminate the scale pointers and adjacent 
 parts of the scales. They are connected with the electric circuit by the 
 cables and plug connections. The lamp that illuminates the cross wires 
 is placed in a holder that is screwed to the eye end of the telescope tube 
 on the right-hand side. Two small mirrors deflect the rays of light 
 through two elongated openings cut through the telescope tube 90 de- 
 grees apart. These openings are so arranged that the light from each 
 mirror is thrown upon the full length of the wire opposite. 
 
 The principal parts of the telescope are the telescope tube, the objec- 
 tive, the Porro erecting prisms, the draw tube, the cross- wire ring, the 
 adjusting sleeve, the adjusting ring, and the eyepiece. 
 
 The telescope tube is the principal piece to which the other parts are 
 assembled. The objective is triple, is seated in a cell that screws into 
 the forward end of the telescope tube, and gives a 3-inch clear aperture. 
 The Porro erecting prisms are two in number, secured in place by a 
 bronze frame. There are no cemented surfaces, as in the Brashear- 
 
370 THE SERVICE OF COAST ARTILLERY 
 
 Hastings prisms used in former types, which reduces the chance of injury, 
 renders replacement easier, and facilitates cleaning. 
 
 The cross wires are secured to a ring by four clamps, and are at right 
 angles to each other. The cross-wire ring is carried in a holder which is 
 secured to the draw tube by screws. The draw tube is assembled to the 
 focusing sleeve so as to allow longitudinal motion of the former when 
 the focusing ring is rotated, and to force rotation of the tube when the 
 focusing sleeve is rotated. The sleeve is screwed into the rear end of the 
 telescope tube by a thread of tight fit, so that it is difficult to rotate. 
 The focusing ring is seated on the focusing sleeve by a threaded surface, 
 its motion being limited by the telescope tube in front and the focusing 
 sleeve nut in rear. When turned, it transmits to the draw tube and 
 reticule its longitudinal motion only. 
 
 The eyepiece consists of the eyepiece tube, the field lens, the eye lens 
 in its holder, and the eye-lens cover. The eyepiece tube is screwed into 
 the draw tube and carries the field lens and the eye lens with its holder, 
 the cover being screwed to the latter. There is an amber glass shade in 
 a holder that is pivoted so that it may be used or not, as desired, and 
 which is provided to protect the eye from a glare of light. The eyepiece 
 serves to magnify the image at the cross wires and to concentrate the 
 rays of light in the eye. 
 
 The front end of the telescope is provided with a movable shutter for 
 the protection of the objective. 
 
 The clear aperture of the telescope is 3 inches, the focal length is 
 17.25 inches, the magnifying powers of the two eyepieces are 12 and 20 
 diameters and the fields are 3.6 degrees for the 12-power eyepiece and 
 2.6 degrees for the 20-power. 
 
 The image is direct, the erecting being secured by the Porro prisms, 
 each of which twice totally deflects the rays of light at an angle of 90 
 degrees so that it emerges parallel to the entering ray and in the original 
 direction. The paths of two rays of light are shown in Fig. 47, giving 
 an illustration of the erecting process, in which, however, the 90-degree 
 angles are not all projected as 90 degrees, because of the relative posi- 
 tions of the prisms. The eyepiece of power 12 should generally be used, 
 as the higher power so magnifies the particles in the atmosphere as 
 to cause blurring on any but a dark -day. 
 
 The telescope is secured in position by six accurately bored projec- 
 tions, four on the cradle and one on each clamp. A locating lug on the 
 front clamp fits into a recess on the telescope, thus bringing the vertical 
 wire plumb. 
 
 For those carriages in which the gun is carried in a cradle, the sight 
 
INSTRUMENTS, DEVICES AND CHARTS 371 
 
 bracket is bolted by means of the feet to seats which form parts of the gun 
 cradle, and when the sight is properly assembled to the carriage and the 
 elevation and deflection readings are zero, the optical axis of the tele- 
 scope and the axis of the bore of the gun will remain parallel at all ele- 
 vations. Therefore, if the sight be set at the elevation required for the 
 range of the object to be fired at, and then be laid upon it, the gun will 
 automatically receive the same elevation. Since the deflection move- 
 ment of the sight is independent of the gun, and deflection necessary 
 may be given without affecting the elevation. 
 
 The sight brackets for barbette carriages are lefts and rights. 
 
 SIGHTS FOR DISAPPEARING CARRIAGES 
 
 The sights for disappearing carriages differ from those for barbette 
 in that they are all alike for the same type of carriage (the range drums 
 all being on the left side) ; a sight arm is substituted for the sight bracket, 
 and a different method of attachment is used. 
 
 The sight arm differs from the sight bracket in shape, has an elevation 
 guide, and the feet of the sight bracket are replaced by seats for two pins. 
 
 Disappearing carriages, after model of 1901, are supplied with two 
 sight standards, one right and one left. The elevating mechanism for 
 the gun may be operated by a handwheel assembled to the left end of 
 the elevating shaft, which is supported by a bracket attached to the left 
 sight standard. This shaft connects through bevel gearing with an in- 
 clined shaft (passing through the sight standard), the upper end of 
 which connects by bevel gearing with a third shaft that carries a maneu- 
 vering handwheel. The middle portion of the inclined shaft is threaded, 
 and carries a nut to which is attached a sight-elevating arm, the upper 
 end of which is a swivel fork. The top of the sight arm ends in a hori- 
 zontal flange surmounted by a cylindrical axis, upon which is centered 
 a sight-arm bracket, with a flange resting upon the flange of the sight 
 standard. This bracket has a small motion in azimuth and can be set 
 in its proper position by lugs and adjusting screws, then clamped by screw 
 bolts passing through its flange and into that of the sight standard. 
 The bracket has two arms extending forward, and the sight arm is 
 assembled between them by a pin passing through the front ends of the 
 two arms of the bracket and the front seat in the sight arm. The sight- 
 elevating arm passes through the bottom of the bracket and is assembled 
 to the sight arm by a pin passing through the sight arm and the fork of 
 the sight-elevating arm. The sight-arm bracket has two guide ways, 
 
372 THE SERVICE OF COAST ARTILLERY 
 
 between which travels the elevation guide of the sight arm. The ele- 
 vating shaft operates the elevating *screw, on which travels a slide to 
 which the elevating arm is pivoted at one end, the other end being 
 pivoted to a band on the breech of the gun. The inclined shaft is in two 
 pieces, joined by a coupling, so that the gun and telescope can be set 
 independently and the connection can afterwards be made. 
 
 The relations of the pitches of threads, the number of teeth in gears 
 and pinions, the angles of the elevating screw and the inclined shaft, and 
 the lengths of parts are of such that, if the optical^axis of the telescope 
 and the axis of the bore of the gun be set parallel at zero elevation and 
 deflection, they will so remain at any elevation. Rotating either hand- 
 wheel elevates or depresses the gun and the sight arm at the same time 
 and through equal angles. Therefore the principles of operating the 
 sight are the same as already described for barbette carriages. 
 
 The right sight is mounted similarly to the left, except that it has no 
 connection with the elevating mechanism of the carriage, the rear of 
 the sight arm being assembled by a pin passing through it and two lugs 
 on the sight-arm bracket. This sight can be used only for following an 
 object in azimuth, since the sight arm remains stationary. 
 
 SIGHTS OF NEARLY SAME DESIGN AS MODEL OF 1904 
 
 There are in service 26 sights, numbered from 1 to 26, both inclusive, 
 which are nearly the same as those described above. The differences 
 are due to substituting in the latter Porro double reflecting prisms for 
 the Brashear-Hastings erecting prisms used in the former. 
 
 The telescopes of these sights are differently shaped from the model of 
 1904, being practically symmetrical about the axis; they are longer by 
 about 3J inches, the peep sight is directly over the eyepiece, the rear 
 clamp is differently shaped, the sides upon which the shutter and clamps 
 are hinged have been reversed, the adjusting arrangements for the cross- 
 wire ring are different, and the diameters of bearings on the telescopes 
 and cradles for seating the telescope are ^ inch smaller than on the 
 model of 1904. 
 
 METHOD OF ASSEMBLING SIGHTS AND LOCATING POINTERS 
 
 For Barbette Carriages. In assembling the brackets for the barbette 
 carriages, great care should be taken to see that the seats are level in both 
 directions, and that burrs, paint, and rust are removed from them and 
 the feet of the brackets. A small obstruction of this kind will throw the 
 
INSTRUMENTS, DEVICES AND CHARTS 373 
 
 sight shank out of plumb. In setting up the bolts, all should be brought 
 to a firm bearing before any are set up tight. 
 
 Neither the elevation nor the deflection pointer is marked by the 
 manufacturer of the sights, since there is no adjustment for either on 
 the carnage. The elevation pointer should be cut at the works of the 
 builder of the carriage to allow for any possible inaccuracy in the seats 
 and the deflection pointer should be put on at the emplacement after 
 the gun is mounted. 
 
 After the sight is assembled to the carriage and while the gun is at 
 zero elevation the sight should be accurately leveled and the pointer cut 
 exactly opposite the zero of the elevation scale. 
 
 The position of the deflection pointer may be determined by setting 
 up two screens at right angles to the axis of the gun, one more distant 
 from it than the other, and measuring the horizontal distance on each 
 screen between the points in which the line of sight and the axis of the 
 bore intersect it. When these two distances are equal, the vertical 
 planes through the line of sight and the axis of the bore are parallel arid 
 the pointer should be cut exactly opposite the 3-degree mark on the 
 deflection scale. 
 
 For Disappearing Carriages. The elevation pointer should be cut 
 at the emplacement, and both sights should have the work done while 
 mounted on the left sight standard. The gun and the sight should be 
 leveled accurately and independently, and the pointer should then be 
 cut exactly opposite the zero elevation scale, the set screw of the coupling 
 having been previously seated and the coupling clamped. The elevating 
 mechanism of the carriage should be so marked by the builder that it can 
 be assembled with all parts in correct relation without leveling. 
 
 The deflection pointer is cut by the manufacturer of the sight, but the 
 vertical planes of the line of sight and the axis of the bore of the gun 
 should be brought parallel at the emplacement, using some method such 
 as outlined for barbette sights and rotating the sight-arm bracket with 
 the deflection pointer set at the 3-degree mark. When the sight is in 
 the correct position, the bracket should be clamped and a light line cut 
 so as to extend over both the flange on the bracket and that on the sight 
 standard. The sight for each side of a carriage should be set on its own 
 sight standard. 
 
 The range drum for all sights must be graduated after the height of 
 the emplacement above sea level is known. 
 
 Adjustments. The cross wires are rendered distinct by screwing the 
 eyepiece in or out, and this adjustment has no other object. If the tele- 
 scope is frequently used by the same observer, the eyepiece can be reset 
 
374 THE SERVICE COAST ARTILLERY 
 
 at the correct position by using the graduations on the outer rim in con- 
 nection with the pointer on the focusing-sleeve nut. After bringing the 
 cross wires into distinct vision by adjusting the eyepiece, the wires may 
 be brought into the focal plane by turning the focusing ring until the 
 object appears distinctly and does not seem to shift when the eye is 
 moved from side to side of the eyepiece. This adjustment is impossible 
 if the object is too close to the telescope' 100 yards is usually 
 sufficient. 
 
 The cross wires may be adj usted to bring them into vertical and hori- 
 zontal planes by removing the focusing-sleeve nut, unscrewing the focus- 
 ing ring until spanner holes appear in the focusing-sleeve, placing a 
 spanner wrench in the holes and tapping the handle of the wrench with 
 a very light hammer. This adjustment should be made with the tele- 
 scope in the cradle and trained on a plumb line, and only those thoroughly 
 familiar with the instrument should attempt it. 
 
 The adjustment of the cross wires of the sights numbered from 1 to 26 
 is made by unscrewing the focusing-sleeve nut and the focusing ring until 
 access is given to the capstan-head adjusting screws that secure the 
 cross-wire ring. These screws should be loosened the adj ustment made 
 and the screws again set up. 
 
 To adjust the tension of the range-drum spring, run the sight-shank 
 rack out of mesh, turn the balanced handwheel to the right to relievo 
 tension or to the left to increase tension and re-engage the rack. When 
 the cradle and telescope are in place and the elevation is 8 degrees, the 
 force required to rotate the handwheel should be the same for both 
 directions. This adjustment must never be made after the drum is 
 graduated, and the cradle must first be disengaaed from the head of the 
 sight shank. 
 
 Care and Preservation. Telescopic sights are necessarily delicate 
 instruments and must not be subjected to rough usage, jars, or strains. 
 When not in use, the telescope should be kept in its leather case and 
 should be stored in a dry place. It should be occasionally examined to 
 insure its not being corroded by tannic acid from the case and all traces 
 of dust or moisture should be removed before putting it away. 
 
 To obtain satisfactory vision, the glasses should be kept perfectly 
 clear and dry. In case moisture collects on the glasses, place the tele- 
 scope in a gentle warmth; this is usually sufficient to remove it. A 
 piece of chamois skin or a clean linen handkerchief will answer for clean- 
 ing purposes, care being taken that the cleaning material does not contain 
 any dirt or grit. The glasses will seldom require cleaning on the inside; 
 but, when necessary, they should be unscrewed, and by a competent 
 
INSTRUMENTS, DEVICES AND CHARTS 375 
 
 person only. The object glass must always be kept screwed home, except 
 when removed for cleaning. 
 
 The erecting prisms should not be removed, except by an optician, 
 and if they need repair, report should be made to the proper authority. 
 Removal is apt to disturb the adjustment, and finger marks or lint will 
 cause difficulty. 
 
 The cross wires are unprotected when the eyepiece is removed, and 
 great care must be exercised not to touch them, as they are very delicate. 
 No attempt should be made to clean them, except by blowing. 
 
 The sight bracket (or arm) and cradle should never be removed from 
 the carriage unless the carriage is dismounted. When not in use these 
 parts should be kept covered by hoods provided for the purpose. All 
 bright parts should be kept thoroughly oiled, special care being given 
 to the worm box, sight shank, and bearings for the telescope, which are 
 of steel. Care should be taken not to remove the oil in putting on the 
 hood. The oil should be wiped off before use. The hood should be re- 
 moved and the sight brackets (or arms), etc., examined at least once in 
 every two weeks, and tho cradle should be removed in elevation and 
 deflection so that as much as possible of the sight shank and worm box 
 can be inspected. 
 
 Special care should be taken in the use of the three small electric 
 lamps, as they are fragile. The resistance should be carefully regulated, 
 since a small increase in voltage will burn them out. It is desirable to 
 first throw in a comparatively large resistance and then adjust until the 
 proper illumination is obtained. Each lamp should seat in its receptacle 
 not less than one and one-half turns. 
 
 The Scott Telescopic Sight. The telescopic sights in service are the 
 model of 1896 Mi, the model of 1897, the model of 1898, and the model 
 of 1898 M. See Plate XXXIV. 
 
 These sights consist of a telescope mounted on an adjustable frame 
 on which are trunnions and a projecting lug by which the sight and its 
 frame are attached to either a gun or gun carriage by means of a bracket 
 or sight holder. 
 
 For attaching the sight to a gun a trunnion bracket is fastened to the 
 right trunnion in which the sight frame is placed and secured so as to 
 hold the telescope during the shock of discharge. 
 
 For attaching the sight to a barbette carriage a sight bracket is fast- 
 ened to the rear part of the right chassis. The upper end of this bracket 
 has a vertical face, to which is attached the sight bracket which holds 
 the sight and its frame. 
 
 Disappearing carriages are provided with sight standards attached to 
 
376 THE SERVICE OF COAST ARTILLERY 
 
 either the right or left chassis rail. On the upper part of the standard 
 are two lugs, slotted to receive the sight holder. The outsides of these 
 slots are closed with caps, in each of which is a clamping screw for se- 
 curing the sight holder when adjusted to a convenient height for the 
 gunner. The upper end of the sight holder is arranged to receive the 
 sight and its frame. 
 
 A catch band is placed on the models of 1898 and 1898 M sights, to 
 which the end of the retainer is secured. With the models of 1896 Mi 
 and 1897 sights the end of the retainer is secured to the lower bar of the 
 sight frame. 
 
 The line passing through the centers of the trunnions is called the axis 
 of revolution of the sight or the axis of the sight trunnion, and is parallel 
 to the optical axis of the telescope at zero elevation. 
 
 The sight bracket, which is the same for all models of sights, is pro- 
 vided with two V's and a leveling screw. The sight trunnion is seated 
 in the V's and the leveling lug between them bears against the leveling 
 screw. The latter, working against the lug, levels the sight. 
 
 The overbalancing of the sight and the method of suspension to the 
 bracket enable the sight to be used for reverse laying. The undercut in 
 the cross level exposes the bubble for adjustment. 
 
 A strap fastened loosely to the frame is used for carrying the sight. 
 
 For each sight there is provided a leather case in which the sight is 
 carried and kept. 
 
 Telescopic Sight, Model of 1896 Ml, consists Of a telescope carried 
 by an adjustable frame, as above described. The telescope is supported 
 by having its forward end pivoted and secured to the frame, while the 
 other end has a sliding motion along the elevation arc, through contact 
 with the vernier piece. The telescope is an ordinary non-inverting one, 
 provided with an achromatic objective composed of two lenses in contact 
 and a Ramsden eyepiece to magnify the image formed by the objective. 
 
 The non-inverting telescope is obtained by inserting the Hastings- 
 Brashear compound erecting prism between the sliding diaphragm 
 and the objective. This compound prism consists of two prisms 
 having angles of 30, 60, and 90, laid with their 30 angle toward 
 each other on a parallel-sided glass plate, and on the other side of 
 this plate is laid a third prism having a true 90 angle. Successive 
 reflections at the surfaces of these three prisms erect the image with- 
 out any lateral displacement of the rays of light other than that 
 necessary for the purpose, and without lengthening the telescope 
 tube, or diminishing the field of view. This compound prism is 
 mounted in a frame provided with two sets of screws by means of 
 
PLATE XXXIV 
 
 DEFLECTION SCALE 
 
 OF DEGREES AND 
 
 HALF DEGREES 
 
 Telescopic Sight, M. 1898 Mn. Mounted on Hagood Tripod Mount. 
 
INSTRUMENTS, DEVICES AND CHARTS 377 
 
 which it is adjusted after being assembled in the telescope. Just 
 forward of the sliding diaphragm the telescope tube is cut away on 
 top to admit the prism and its frame. Two screws passing through 
 flanges on the latter secure it to the tube and determine its position. 
 A roof-shaped plate screwed to the telescope tube protects the prism 
 from dust or mechanical injury. 
 
 Mechanism of the Telescope. Within the telescope is a sliding 
 diaphragm or frame carrying a vertical platinum cross wire 0.001 inch 
 in diameter; also a thin glass reticule, a horizontal and a vertical 
 scale; also a horizontal line which takes the place of the horizontal 
 cross wire in telescopic sights of other models. The vertical wire 
 indicates deflection, and the intersection of the wire and horizontal 
 line is laid on the object sighted. Lateral motion is given the dia- 
 phragm by a deflection screw on the right side of the telescope. 
 The movement of the vertical wire is a little more than 2 on each 
 side of the zero of the deflection scale, and the scale itself is 
 graduated to 0.05 to indicate this movement. On this scale the 
 degree marks are numbered, the 'half degrees being indicated by the 
 number 50. The vertical scale reads to 3' 26", equal to .001 of 
 the range. It is intended to assist in estimating distances, errors of 
 range, etc. 
 
 The telescope is properly focused when the plane of the cross 
 wires is in the position of distinct vision and the image of the object 
 is in the same plane as the cross wires. To accomplish this condition 
 both the eyepiece and the objective are given the necessary motions 
 within the telescope tube. 
 
 The motion of the eyepiece is given by screwing or unscrewing 
 it in its housing, and that of the objective by a focusing screw collar 
 back of the sunshade. 
 
 In sighting, the intersection of the cross wires is brought to bear 
 on the image of the object sighted; and this process is precisely the 
 same as bringing the intersection of the cross wires on to a material 
 object in the same plane as the cross wires, and, provided the focusing 
 is correct for each observer, there can be no variation in the sight- 
 ing. 
 
 The elevation arc, the center of which is on the horizontal axis 
 of the telescope, is graduated from 7 to +22, but owing to the 
 space occupied by the vernier these limits for practical purposes are 7 
 and +16. 
 
 The vernier reads to 2'. It is fastened to the vernier piece on 
 the telescope forward of the deflection screw and is provided with 
 
378 THE SERVICE OF COAST ARTILLERY 
 
 two set screws, one at each end, for the purpose of securing it to this 
 piece, as well as for purposes of adjustment. 
 
 The rocking-worm spindle is a distinct feature of this sight; and 
 the change was made to provide for a constant pressure of the worm 
 spindle in the worm rack, and to prevent uneven wear of the 
 latter. 
 
 The line of sight at zero deflection is the optical axis of the tele- 
 scope. 
 
 A level is attached to the left side of the telescope. Its axis is 
 parallel to that of the sight trunnions, or axis of revolution of the 
 sight. This level enables the sight to be used as a quadrant in its 
 own bracket. 
 
 Open sights on top of the telescope are provided to enable the 
 gunner to quickly bring an object into the field of the telescope. 
 
 The angle of elevation is given by turning a milled-head microm- 
 eter screw which actuates a worm spindle; and the latter engaging 
 in the worm rack cut in a projection on the right side of the telescope 
 gives the desired angular motion to the telescope about its horizontal 
 axis. For one complete turn of this micrometer screw the telescope 
 is elevated or depressed 1. 
 
 Any backlash between the worm spindle and the worm rack is 
 overcome by means of a spring pressing upward against the bottom 
 side of the telescope. 
 
 The micrometer screw which actuates the worm spindle is gradu- 
 ated to minutes. It is provided on top with two small screws which 
 secure the collar on which the graduations are made. Unscrewing 
 them, the collar can be turned and the vernier and micrometer readings 
 made to agree. 
 
 To obtain a correct angle of elevation it is essential that the eleva- 
 tion arc should be truly vertical for all angles of elevation of the 
 gun, and for any inclination the gun trunnions might have to the 
 horizontal. This is accomplished by means of a cross level, fastened 
 to the under side of the frame, parallel to the horizontal axis of the 
 telescope, and perpendicular to the axis of revolution of the sight. 
 The cross level is provided with two openings, one on the top and one 
 on the bottom, to permit of easy observation in direct and reverse 
 laying. 
 
 Telescopic Sight, Model of 1897, differs from model of 1896 Mi in 
 having a slightly larger field of view (5 12'); a larger objective (1.2 
 inches), and a power of nine. 
 
 The glass reticule and vertical scale are omitted, and the engraved 
 
INSTRUMENTS, DEVICES AND CHARTS 379 
 
 horizontal line is replaced by a horizontal platinum wire of .001 inch 
 diameter. 
 
 Deflection is given by moving the sliding diaphragm along a* 
 graduated horn deflection scale placed below the diaphragm. The 
 movement permitted is about 2 15' on each side of the zero of the 
 scale, the latter being graduated to indicate the movement. The 
 degree marks only are numbered, and the value of the smallest division, 
 3', is indicated by the symbol -^ directly under the zero hole of the 
 scale. The vertical crosswire indicates the .amount of deflection. 
 
 Telescopic Sight, Model of 1898, is a new design, similar to the earlier 
 models described, in its method of attachment to the sight bracket, 
 but differing from them in general construction and in the more 
 important details. 
 
 The sight consists of two principal parts, the trunnion casting 
 and the telescope, which is pivoted to the casting at its forward end. 
 
 The trunnion casting is made of phosphor-bronze on account of 
 its great hardness, elasticity, and the resistance to corrosion. This 
 casting comprises the trunnions, the leveling lug, the bearing for the 
 horizontal axis of the telescope, and the elevation arc with the bearing 
 for the elevating- worm spindle. 
 
 To provide for interchangeability, the dimensions of the trunnions 
 and leveling lug are made the same as in the other telescopic sights. 
 
 The bearing of the horizontal axis of the telescope is drilled 
 through the trunnion casting near the 'forward trunnion. The eleva- 
 tion arc and the bearing for the elevating-worm spindle constitute 
 one piece. This latter bearing is practically dustproof, being closed 
 entirely in rear, and having only sufficient opening in front for the worm 
 rack to engage. 
 
 The elevation arc is graduated as in the other sights. 
 
 The fundamental line of all the telescopic sights is the axis of 
 revolution defined by the trunnions, and since the elevation arc and 
 the bearing for the horizontal axis of the telescope form, as they do, 
 a part of the. casting which contains the axis of revolution, it follows 
 that such a construction is all that can be desired. 
 
 The telescope is attached to the trunnion casting by its horizontal 
 axis and the worm rack. The horizontal axis, or pivot of the telescope, 
 projects through the trunnion casting. Within the bearing for this 
 pivot is an annular groove which contains a spiral spring, one end of 
 which bears against the trunnion casting and the other against the 
 telescope. This spring serves to overcome any backlash in the worm 
 rack when the telescope is moved in altitude, and being placed under 
 
380 THE SERVICE OF COAST ARTILLERY 
 
 considerable strain in fitting it in its groove, the pressure it exerts 
 against the telescope in every position is practically uniform. 
 
 The worm rack on the left side of the telescope projects into the 
 opening in the trunnion casting and engages with the elevating-worm 
 spindle. 
 
 The telescope can be run out and disengaged entirely from the 
 worm spindle without affecting the adjustment of the telescope. 
 
 The micrometer screw on the elevating-worm spindle is graduated 
 to 1', and its adjustments are made as in the other sights. 
 
 The vernier is attached to a vernier piece on the left side of the 
 telescope, and is adjusted by means of two screws working into the 
 vernier piece, one at each end, and against two shoulder pieces bearing 
 against the vernier. This adjustment differs from that in the other 
 sights in that a given turn of an adjusting screw produces an opposite 
 movement in the vernier. 
 
 The vernier reads to 2'. 
 
 The telescopic level is fastened to the right side of the telescope. 
 
 The level is a minute one, the bubble moving .1 of an inch for 1' 
 of elevation. 
 
 For giving deflection, a set of platinum cross wires, one vertical 
 and one horizontal, and two scales, one inside and one outside, are 
 provided. The vertical cross wire is attached to a sliding diaphragm 
 actuated by the deflection screw on the right' side of the telescope. 
 In giving deflection, this vertical wire moves along the interior horn 
 scale, and indicates the reading. In addition, this diaphragm has a 
 pointer, which at the same time moves along the outside silver scale, 
 giving the reading without looking into the telescope. The tele- 
 scope is cut away at this place to make room for the outside scale, and 
 to reveal the pointer. In order that the pointer should give a correct 
 reading, the screw actuating the fixed diaphragm is accurately cut, 
 and the backlash is overcome by two spiral springs working against the 
 sliding diaphragm. 
 
 The horizontal cross wire is attached to a fixed diaphragm placed 
 behind the sliding one. For the purpose of adjustment, this dia- 
 phragm can be given a slight motion in a vertical direction and secured 
 in the correct position. 
 
 The interior horn scale is graduated to 2 30' on each side of the 
 zero. The smallest division is 3'. This scale is held and adjusted 
 as in the other telescopic sights; on the scale is engraved IU-FIRE L, 
 indicating the direction of motion for the vertical cross wire in order 
 to direct the gun to the left or right of the object sighted. 
 
INSTRUMENTS, DEVICES AND CHARTS 381 
 
 The cross wires and the fixed and sliding diaphragms are exposed 
 to view by unscrewing the four screws holding the cap, which contains 
 the socket for the eyepiece. 
 
 The outside scale is graduated to degrees and half degrees, the 
 3' readings being obtained from the micrometer-deflection screw. 
 The inscription R< FIRE >L is also engraved on this scale. 
 
 The micrometer-deflection screw which actuates the sliding dia- 
 phragm is graduated on its collar, with two series of figures from 
 to 9 in opposite directions. Each division equals 3', and a complete 
 turn of the screw moves the sliding diaphragm 30'. One series of figures 
 gives the correct reading when the deflection movement is for firing 
 to the left and the other series for the contrary movement. 
 
 L 
 
 On the telescope near the graduated collar is engraved J , indi- 
 
 R 
 
 eating the direction of rotation of the micrometer deflection screw 
 for firing to the left or right of the object sighted. 
 
 The cross level is attached to the under side of the telescope and 
 is provided with an opening at the top for direct laying and one at 
 the bottom for reverse laying. The level tube fits in a larger tube 
 cast with the telescope, and for the purpose of adjustment is provided 
 with four radial set screws which fit in a flare at one end of the level 
 tube and bear against the outside tubes. 
 
 The level is a 3' one, the bubble moving a tenth of an inch for a 
 change of inclination of 3'. 
 
 The telescope attached to this sight was especially designed to 
 give a large field of veiw, an erect image, and the maximum amount 
 of light the eye will receive under the most unfavorable conditions. 
 
 The field of view of a telescope depends on its power and the field 
 of the eyepiece. Ordinarily the field of an eyepiece rarely exceeds 
 40, but in this case, besides making the eyepiece achromatic, the 
 field was increased to nearly 50. An increase of this amount in the 
 field of the eyepiece is always accompanied by lack of perfect definition 
 at the margin of the field. By dividing the field of the eyepiece by 
 the power of the telescope, its field of view is obtained. In this tele- 
 scope the field of the eyepiece is 48, and the power is 8, consequently 
 the field of the telescope is 6. 
 
 The power of 8 was selected as sufficient for proper magnification 
 of the deflection scale, and any power above 8 would have corre- 
 spondingly diminished the field of view. 
 
 The erect image is formed by the insertion of a Hastings-Brashear 
 erecting prism between the eyepiece and the objective. The opening 
 
382 THE SERVICE OF COAST ARTILLERY 
 
 for the insertion of the prism and its frame is made in the under side 
 of the telescope tube. 
 
 The eye receives the maximum amount of light through a tele- 
 scope of this character, when the diameter of the pencil of light 
 emerging from the eyepiece is equal to that of the pupil of the eye. 
 The diameter of the emerging pencil is equal to the diameter of the 
 objective divided by the power of the telescope. To fulfill this condition 
 the diameter of the objective is made 1.25 inches; the diameter of 
 the emerging pencil of light is therefore nearly -J- inch. Except at 
 night, when the pupil of the eye may dilate to J- inch, the telescope is 
 adapted to all conditions of light. 
 
 The loss of light in the telescope is due to absorption in the lenses 
 and prism, and when these are made of the best glass and the sur- 
 faces carefully prepared, the loss of light is reduced to a minimum. 
 
 The objective is focused by a focusing collar back of the sun- 
 shade. 
 
 The eyepiece is focused by screwing or unscrewing it in its bearing, 
 which forms part of the cap covering the deflection scale and cross 
 wires. 
 
 The sunshade with the dew cap is retained in place by a small set 
 screw which permits the sunshade to be pulled in or out, and rotated 
 about the telescope. 
 
 The telescope tube is made of thick brass, so that it may be handled 
 without danger of bending or the sight losing its adjustments. 
 
 Use of the Sight. There is a tendency, among those making a 
 first acquaintance with the telescopic sight, to think it a very compli- 
 cated instrument, having little in common with the ordinary sights, 
 and that to learn how to use it is a difficult matter. As a matter of 
 fact it is simply a sight in the form of a telescope; and every rule 
 learned about elevation, etc., is precisely the same as with the ordinary 
 sights, only of easier application, the operations being mechanical; 
 besides the telescope and its elevating gear, there is only the means of 
 attaching it to the gun, which a little information will make quite 
 clear. 
 
 The advantages gained by the use of the telescopic sight are: 
 
 Increased accuracy of fire due to 
 
 a. Power of vision. 
 
 b. Elimination of personal error. 
 
 (a) Power of vision. Objects, indistinct to the naked eye, in 
 some lights almost invisible, can be seen clearly, and accurately aimed 
 at, even at the extreme range of effective fire. 
 
INSTRUMENTS, DEVICES AND CHARTS 383 
 
 A short-sighted man can see and aim just as well as a man with 
 good eyes. 
 
 A particular part of the object can be aimed at, instead of an 
 indistinct whole, and no part of the object is obscured, as so often 
 happens with the ordinary front sight. 
 
 (6) Elimination of personal error. A -fine cross wire has to be 
 brought mechanically on to the object a much easier thing than 
 aiming exactly with, a full sight, and everyone must aim the same 
 providing the focusing is correct. 
 
 Before using a sight,, the case containing it should be slung over 
 the gunner's shoulder, and the sight should not be removed until 
 the gunner has reached the sighting platform. While the sight is 
 in the case, the cover should be kept fastened. 
 
 In removing a sight from its case, take hold of the strap fastened 
 to the frame or to the telescope. 
 
 See that the objective is screwed home. Neglect of this precaution 
 may give rise to a large error, since the optical center of the objective 
 may not coincide with the axis of the screw, and a change in the position 
 of the optical center involves at once a change in the line of sight. 
 
 The focusing screw collar has slightly more movement than is 
 necessary for solar focus, and the telescope is first focused by focusing 
 the eyepiece, which is done by screwing the eyepiece until the cross 
 wires, with every roughness on them, are distinctly visible. On account 
 of the coarseness of the cross wires, this is not a very sensitive method 
 of focusing the eyepiece, and final focusing may be necessary after the 
 objective is focused. The objective is focused by directing the telescope 
 on a distant object and turning the focusing collar until, on shifting the 
 eye over the eyepiece, the intersection of the cross wires remains on 
 the same point of the object (or, in other words, there is no parallax). 
 The distant object selected for this purpose should possess sharp out- 
 lines. Telegraph wires, signposts, or buildings are excellent for the 
 purpose. The general landscape, possessing, as it does, soft outlines, 
 should not be used. 
 
 When the objective is focused, should the image not be clearly 
 defined, then the eyepiece is not correctly focused, and it must be 
 screwed until the definition is satisfactory. 
 
 An objective once focused is correct for all observers, but the 
 eyepiece requires focusing for each individual. 
 
 Unless disturbed, an objective once focused will remain so indefi- 
 nitely. 
 
384 THE SERVICE OF COAST ARTILLERY 
 
 The Sight as used in Gun Laying 
 
 The sight is now ready for use in gun laying. 
 
 To set the sight for deflection, take hold of it with the left hand, 
 and, looking into the telescope, move the deflection screw with the 
 thumb and forefinger of the right hand until the required deflection 
 is obtained. 
 
 Right deflection corrects for deviation in firing where the shots 
 fall to the left of the target, and left deflection the contrary. 
 
 To avoid confusion, the model of 1897 sight has engraved on the 
 body of the telescope, and beside the deflection screw controlling 
 the sliding diaphragm, the expression "Drift correction/' and an 
 arrowhead to indicate the direction of motion to make the correction. 
 
 The inscription, "Drift correction/' was placed on the sight as a 
 guide in the movement of the cross wires to correct for various deviat- 
 ing causes. It must not be understood that the sight corrects for 
 drift only. 
 
 In the model of 1898 sight and model of 1898 M sight, the inside and 
 outside deflection scales, and the telescope near the micrometer, deflec- 
 tion screws have engraved on them the direction of the movement of 
 the vertical cross wire in order to direct the gun to the left or right of 
 the object sighted. 
 
 Should the shot fall to the right of the target, to make the correction 
 the vertical cross wire is moved the proper amount in the direction 
 indicated by the arrowhead pointing toward the letter L. Looking 
 into the telescope, this motion is to the right. 
 
 Should the shot fall to the left of the target, the movement of the 
 vertical cross wire is in the contrary direction and as indicated by the 
 arrowhead pointing toward the letter R. 
 
 It is readily seen that the sliding diaphragm moves to the right 
 to correct for drift, or for a similar deviating cause. 
 
 These sights correct for drift, wind, and speed of target. 
 
 To set the sight for elevation, turn the micrometer screw control- 
 ling the elevating-worm spindle until the required elevation is obtained. 
 
 Since the worm rack is not apt to wear uniformly, it is preferable 
 to depend entirely on the vernier for the 2' readings, and to use the 
 graduations on the collar of the elevating screw for the odd minute. 
 
 Let the angle of elevation required be 2 35'. To set the sight, 
 turn the elevating screw until the arrow on the vernier points to 
 2 30', now turn the same screw until the second graduation from 
 
INSTRUMENTS, DEVICES AND CHARTS 3S5 
 
 the arrow on the vernier is brought into line with the graduation 
 on the elevation arc just in front of it. The reading is now 2 34', 
 and to obtain the required elevation, turn the micrometer screw 
 through the extra minute indicated on the graduated collar. 
 
 The sight is now ready to be placed in its bracket on the gun 
 trunnion, and in seating it be very careful to bring the leveling lug 
 to bear gently against the leveling screw. If this one precaution is 
 heeded, the sight will ordinarily never lose its adjustments. 
 
 The sight is leveled by turning the leveling screw until the bubble 
 in the cross level comes to its -center. 
 
 Looking along the telescope, or through the open sights, or along 
 the axis of the sight trunnions, the gun carriage is quickly traversed 
 until the target is brought into the field of view. 
 
 If the target appears below the intersection of the cross wires, 
 depression is required; if above the intersection of the cross wires, the 
 gun must be elevated. If the target is seen to the right of the cross 
 wires, the gun carriage must be traversed "muzzle right"; if to the 
 left, "muzzle left." 
 
 With barbette carriages, owing to the slight preponderance of the 
 breech of the gun, it is preferable in order to overcome any backlash 
 in the elevating gearing that depression should be the last opera- 
 tion. 
 
 The intersection of the cross wires having been brought on that 
 part of the target aimed at, look at the cross level, and if the bubble 
 is still in the center, the gun is correctly laid. If the bubble is not 
 in the center of the cross level, the gun is not correctly laid, and the 
 sight must be releveled and the operation of laying repeated until 
 the condition obtains that when the sight is directed on the target the 
 bubble shall be in the center of the cross level. In sighting a gun 
 mounted on a seacoast carriage, the axis of the gun trunnions being 
 horizontal, the bubble will remain in the center of the cross level during 
 the entire operation of laying. The last act of the gunner before firing, 
 .should be to see whether or not the bubble is in the center of the cross 
 level. 
 
 The telescopic level enables the gunner to use the quadrant angle 
 of elevation, in which case the sight is first set for deflection only, 
 and the gun is aligned with the telescope at a convenient angle of 
 -elevation. The gun having been aligned on the target, the sight is 
 set for the required quadrant angle of elevation, and the gun elevated 
 or depressed until the bubble in the telescopic level comes to its center. 
 
 Using the sight as a quadrant has the advantage of eliminating 
 
386 THE SERVICE OF COAST ARTILLERY 
 
 any error due to refraction, which is likely to be present where the site 
 of the gun is at an elevation above the target. 
 
 A correction must be applied to the angle of elevation to obtain 
 the quadrant angle, depending on the height of the gun site above the 
 target. Both angles are alike when the gun and target are on the same 
 level. 
 
 For reverse laying, the sight is reversed in its bracket and leveled , 
 the cross level being exposed on its under side to render the bubble 
 visible. 
 
 When the sight is placed in the bracket on the sight standard of 
 a disappearing or barbette carriage, it is leveled as before; but in this 
 position it can only be used for giving direction, and accordingly is 
 set for deflection only, the elevation of the gun being given by the 
 elevation arc. 
 
 Tests and Adjustments of the Sights. The principles involved 
 in the construction of telescopic sights require : 
 
 1. That the line of sight at zero deflection and elevation and tlie 
 axis of the telescopic level should be parallel to the axis of revolu- 
 tion. 
 
 2. That the axis of the cross level should be perpendicular to the 
 elevation arc and to the axis of revolution. 
 
 3. That the sight trunnions should be of equal diameter. 
 
 4. That the sliding diaphragm carrying the cross wires should 
 move in setting the sight for deflection parallel to the axis of the cross 
 level. 
 
 In addition to the above, the following tests are prescribed for 
 each sight: 
 
 A test of the elevation arc and deflection scale for accuracy. 
 
 A test of each level for sensitiveness. 
 
 A test of the telescope for definition, field of view, and power. 
 
 Before making any tests of a sight, see that the objective and the 
 eyepiece lenses are clean, and that the objective is screwed home. 
 
 1. Test for parallelism of the line of sight at zero deflection and 
 elevation to the axis of the telescopic level and to the axis of revolution 
 of the sight: 
 
 To make this test, it is desirable to have a stand on which to place 
 the sight, a striding level to level the trunnions, and an engineer's 
 Y level. 
 
 To make the examination, place the trunnions on the stand, level 
 them with the striding level, make the cross level read zero, and then, 
 by means of the elevation micrometer screw, make the telescopic 
 
INSTRUMENTS, DEVICES AND CHARTS 387 
 
 level read zero. This will bring the axis of the level and the axis of 
 the revolution into parallel planes, which are horizontal. 
 
 Then see if the vernier reads zero on the arc. If it does not, either 
 make it do so by means of the proper adjusting screws or note the 
 error. 
 
 The vernier is adjusted by means of two set screws, one at either 
 end of the vernier, so arranged that, by unscrewing one of the screws 
 and screwing up the other, the vernier can be adjusted in the required 
 direction. 
 
 To make the zero of the micrometer divisions on the milled head 
 screw for elevating agree with the zero of the vernier, loosen the two 
 small screws on top of the brass head, then turn the collar carrying the 
 divisions into the proper position, and tighten the two small screws. 
 
 Next, focus the telescope of the sight on a distant object, set up 
 the engineer's Y level, focus it on a distant object, adjust it carefully 
 to indicate a level line, and make sure that there is no parallax in the 
 eyepiece of either telescope. That being done, and the telescope of 
 the level being collimated on the telescope of the sight, with the object 
 glasses 2 or 3 inches apart, look into the telescope of the level and see 
 if its horizontal wire coincides with the horizontal pointer or horizontal 
 cross wire in the sight. If there is any error, note its amount. 
 
 In the model of 1896 Mi sight, this error can be corrected by adjust- 
 ing horizontally the line on the glass reticule, the latter being adjustable 
 after loosening the two screws which secure it and its frame in a vertically 
 adjustable frame which in turn is held by two screws. 
 
 To remove the eyepiece cap so as to render the reticule and frames 
 accessible first remove the four screws at the right of the eyepiece 
 which secure the split housing for the deflection knob, when two other 
 screws will be exposed which must also be removed in addition to the 
 two screws at the left of the eyepiece, when the cap can be removed 
 by drawing it directly toward the operator. 
 
 In the model of 1897 sight this error can be corrected by the adjust- 
 ing screws of the erecting prism, tilting the line of collimation suffi- 
 ciently to compensate for the error; these sights are, however, being 
 fitted as rapidly as possible with a vertically adjustable diaphragm, 
 to which the horizontal wire is attached similar to the model of 1898 
 sight, and when so equipped the erecting prism should not be dis- 
 turbed. This diaphragm has a small screw and opposing spring, by 
 means of which, after loosening the three screws which hold it in place, 
 the diaphragm can be adjusted very minutely and clamped securely 
 as before. 
 
388 THE SERVICE OF COAST ARTILLERY 
 
 In the model of 1898 and 1898 M sights, the error is corrected by 
 moving in the direction required the diaphragm carrying the hori- 
 zontal wire. These sights are being equipped with the fine adjust- 
 ment above described. 
 
 This test shows whether or not the line of collimation of the tele- 
 scope is parallel to the axis of revolution in the horizontal plane. It 
 yet remains to be seen whether it is parallel in the vertical plane; 
 For that purpose revolve the sight on its trunnions through an angle 
 of 90, so as to bring the cross level vertical, and then having again 
 brought the engineer's level into position, look through it into the 
 telescope of the gun sight, and notice whether or not the horizontal 
 wire of the level cuts the extreme tip of the horizontal pointer or the 
 intersection of the cross wires when the deflection scale reads zero. 
 If they do, all is well; if not, by means of the deflection screw, move 
 the horizontal pointer or cross wires until its extreme tip or their 
 intersection touches exactly the horizontal wire of the engineer's level. 
 The eye end is closed by a cap, held by four screws which must be 
 unscrewed. When this is done, the deflection scale will be exposed, 
 and it will be seen that it is held in place by two small screws. Loosen 
 these screws, shift the scale so as to make its zero coincide accurately 
 with the pointer or cross wire; tighten the screws so as to clamp the 
 scale firmly, and replace the cap which carries ,the eyepiece. If these 
 operations are properly performed, the deflection scale will be brought 
 into perfect adjustment, but it should be again tested with the engineer's 
 level to make sure that such is the case. 
 
 To determine whether the axis of the telescopic level is parallel to 
 the axis of the sight trunnions or axis of revolution, revolve the sight 
 through a small angle about its trunnions, the level and trunnions 
 both being horizontal; if the parallelism is present, the bubble will 
 remain in the center of the level; if not, the instrument maker only 
 can correct it. 
 
 2. Test to determine whether the axis of the cross level is perpen- 
 dicular to the elevation arc, and to the axis of revolution of the sight: 
 
 Place the sight in its bracket with the axis of the V bearings 
 approximately horizontal, and level the cross level. Suspend* a plumb 
 line of sufficient length to subtend the elevation arc about 15 yards 
 from the sight, and move the sight until the intersection of the cross 
 wires bears accurately on the top of the line. Now move the tele- 
 scope in altitude until it is sighted on the bottom of the line. If the 
 intersection of the cross wires bears accurately on the bottom of the 
 line, the axis on the cross level is in a plane perpendicular to the eleva- 
 
INSTRUMENTS, DEVICES AND CHARTS 389 
 
 tion arc. If not, adjust the cross level in the model of 1896 Mi and 
 model of 1897 sights, as follows: 
 
 Unscrew, by half a turn at a time, each of the two screws of the 
 level, just sufficiently to admit of a piece of paper being inserted under- 
 neath the proper screw end of the level. 
 
 The paper must be rectangular, having a piece cut out of it in 
 order that it may envelop the screw on three sides. One thickness 
 of foolscap paper raises the level about 1'. 
 
 If the pointer was to the right, raise the level on the left side; if 
 to the left, on the right side, by means of the piece of paper put under- 
 neath. 
 
 Finally, screw the screws home equally, and with moderate force. 
 Re apply the test, and if found correct make a scratch across the heads 
 of the screws to the metal of the sight. If not correct, the operation 
 must be repeated. 
 
 To make the adjustment in the model of 1898 sight, unscrew the 
 screw cap on the right end of the cross-level casting. This will expose 
 the level tube with four adjusting set screws. The position of these 
 screws will at once suggest the correct ones to adjust to make the 
 correction. 
 
 To complete the test, the experiment must be repeated with the 
 axis of the V bearings at the maximum elevation the experiment 
 will permit. 
 
 If, then, the intersection of the cross wires follows the plumb line 
 the axis of the cross level is truly at right angles to the axis of revolu- 
 tion and to the elevation arc. If not, then in the model of 1896 Mi 
 and model of 1897 sights the adjustment must be made by unscrewing 
 the two screws holding the cross level and forcing sidewise one end of 
 the level sufficient to correct for the error, and then tightening the 
 screws. If there is not sufficient play in the screw holes to make the 
 correction, the sight should be returned to the maker. In the model of 
 1898 the correction is made by adjusting the set screws of the level tube 
 so as to move it sidewise. 
 
 Repeat the preceding experiment for test of the adjustments 
 made. 
 
 3. Test for equality in the diameters of the sight trunnions: 
 
 Use a Brown & Sharpe micrometer, measuring each diameter 
 with the utmost care. With skill the measurement can be made 
 to one five-thousandth (0.0002) part of an inch, and if the trunnions 
 differ by more than that they should be returned to the maker for 
 correction. 
 
390 THE SERVICE OF COAST ARTILLERY 
 
 The striding level will answer the purpose even better than the 
 micrometer calipers. 
 
 4. Test for the horizontal movement of the sliding diaphragm 
 when the sight is leveled: 
 
 This test can be made in conjunction with the test for the par- 
 allelism of the axis of revolution and the line of sight at zero deflection 
 and elevation. The telescope of tho sight being adjusted and its line of 
 sight at zero deflection and elevation horizontal, and the telescope 
 of the Y level being horizontal and collimated on that of the sight, 
 when the horizontal pointer or cross wires should coincide with the 
 horizontal wire of the Y level. Move the sliding diaphragm carrying 
 the pointers or cross wires, when, if the sight is in adjustment, the 
 coincidence should remain undisturbed during the deflection of the 
 pointers or cross wires. If the horizontal pointer or cross wire rises 
 above or falls below the horizontal wire in the level, the sight is not in 
 adjustment, and the defect can only be remedied by the maker. 
 
 5. To test the vertical arc, the most convenient plan will be to 
 fasten the instrument on a stand with the vertical arc lying hori- 
 zontally, and point the telescope on some distant object, in such a 
 direction that the vernier is near one extremity of the arc. Read 
 the arc, and then point on another distant object so situated as to 
 bring the vernier nearly to the other extremity of the arc, and ' read 
 the arc again. The difference of these two readings will be the angular 
 distance between the objects. Then remove the gun sight, set an 
 ordinary theodolite in its place, and measure the angle between the 
 same objects with it. If all is right, the arc as measured by the 
 theodolite should be the same as that indicated by the gun sight. In 
 making this test care must be taken to place the center of the theodolite 
 as nearly as possible in the position which was occupied by the horizontal 
 axis of the telescope of the gun sight. The vertical limb of the transit 
 may be used for the same purpose when there are facilities for doing so. 
 If it is thought best, collimated telescopes can be used instead of 
 distant objects. 
 
 6. To determine the value of the horizontal scale of the gun sight, 
 set up a theodolite in such a position that its telescope collimates on 
 the telescope of the gun sight, and measure on the limb of the theodolite 
 any convenient number of the divisions of the horizontal scale of the 
 gun sight. Dividing the arc thus measured by the number of divisions 
 will give the value of each single division. When using collimated 
 telescopes, always take the precaution to focus each one on a distant 
 object before collimating. 
 
INSTRUMENTS, DEVICES AND CHARTS 391 
 
 7. Examine the telescope by measuring its aperture in inches, 
 its focal distance in inches, and its magnifying power. The best 
 method of determining the magnifying power is by means of a double- 
 image dynameter, but it is not necessary to employ such an elaborate 
 apparatus in the present case. It will suffice to take the clear aperture 
 of the objective between the points of a pair of dividers and prick it 
 down on a piece of paper. Then, with the same pair of dividers and 
 a magnifying glass, take the diameter of the pencil of light emerging 
 from the eyepiece, and find how many times that is contained in the 
 clear aperture of the objective by using the last opening of the dividers 
 to step the distance between dots laid down when the objective was 
 measured. The result will be the magnifying power. Finally, examine 
 the definition of the telescope, and note whether or not it is satisfactory. 
 
 An accurate determination of the focal distance of the telescope 
 is not necessary. The telescope being focused on a distant object, 
 it will suffice to measure the distance from the front of its objective 
 to the pointers, and then deduct two-thirds of the thickness of the object 
 glass. 
 
 For determining the field of view the following method is suggested : 
 When the telescope of the sight and transit instrument are colli- 
 mated on each other, the diameter of the field of view can be deter- 
 mined by pointing the transit first on one end of the diameter and 
 then on the other, reading the angles and taking the difference. 
 
 8. A test to determine the sensitiveness of the telescopic level: 
 Bring the bubble to one end of its run by means of the elevation 
 micrometer screw on the telescope and note the reading on the arc 
 of elevation. Then, by means of the elevating screw, bring the bubble 
 to the other end of its run, and again read the arc of elevation. The 
 difference of these two readings is the amount of arc corresponding 
 to the distance traversed by the bubble in passing from one end of its 
 run to the other. This should be at the rate of not less than 1 inch for 
 10' of elevation. There seems to be no convenient way of testing the 
 sensitiveness of the horizontal level, except by taking it off, fastening 
 it on the telescope, and then testing it in the same way as the telescopic 
 level. 
 
 The preceding tests and adjustments, on which the efficiency of 
 the sights depends, are carefully made during manufacture, and unless 
 a sight is tampered with, or subjected to rough treatment, it is most 
 unlikely to ever lose its adjustments. In manufacture the adjustments 
 are all made with a limiting error of 1'. 
 
 In service it is desirable that the sights should frequently be 
 
392 THE SERVICE OF COAST ARTILLERY 
 
 tested, and where there are facilities the methods laid down should 
 be followed. 
 
 The adjustments must not, however, be made except by an officer 
 authorized to do so by the Chief of Ordnance, and if a sight is found 
 by trial to be out of adjustment the fact should be reported to 
 proper authority. 
 
 At a fortification where the facilities are few for making the pre- 
 ceding tests, the following methods are outlined for the guidance of 
 the officer conducting them: 
 
 Tfre test for the equality of the sight trunnions, the accuracy of 
 the elevation arc and deflection scale, the sensitiveness of the levels, 
 and the horizontal motion of the sliding diaphragm can be dispensed 
 with, since the sights before issue to the service have been tested for 
 these requirements, and from the construction of the sight, it is obvious 
 that these requirements can always be obtained. 
 
 A bracket mounted accurately on a horizontal gun trunnion will 
 .answer all the purposes of an efficient support for the sight during 
 these tests. 
 
 1. Test for the parallelism between the line of sight at zero deflec- 
 tion and elevation, and the axis of revolution: 
 
 Test each sight independently by setting it at zero deflection and 
 elevation, and laying it on a mark about 3,000 yards distant, and 
 revolving the sight about its axis of revolution. If the line of sight 
 is parallel to the axis of revolution, the tip of the pointer or the inter- 
 section of the cross wires will remain exactly on the same distant 
 mark. If not, deflect the sliding diaphragm and elevate or depress the 
 telescope until the tip of the pointer, or the intersection of the cross 
 wires, remains exactly on the distant mark. Note the errors in eleva- 
 tion and deflection. If the error in elevation or deflection exceeds 1' 
 the sight must be readjusted. Select that sight which has the minimum 
 errors as the standard sight. 
 
 2. Test for parallelism between the axis of the telescopic level 
 and the axis of revolution of the sight: 
 
 With all the sights set at the true line of sight for zero deflection 
 and elevation, elevate or depress the gun until the telescopic level 
 reads zero. Revolve the sight about its axis of revolution through 
 an angle of about 5. If the axis of the telescopic level is parallel 
 to the axis of revolution, the bubble should not leave the center of 
 the level. 
 
 3. Test for the cross level being at right angles to the axis of 
 revolution of the sight: 
 
INSTRUMENTS, DEVICES AND CHARTS 393 
 
 Level the cross level of each sight. Elevate the gun through an 
 angle about 20, when the bubble should remain stationary in the 
 center of the cross level. 
 
 4. Test for the cross level being at right angles to the vertical arc: 
 
 Lay on a distant mark with the sight set at zero deflection and 
 elevation. Elevate the gun through an angle of about 15. Now 
 depress the telescope until the intersection of the cross wires cuts the 
 point aimed at. If it does not do so the level is not at right angles to 
 the arc, and the arc is not vertical. 
 
 Select the sights that have fulfilled the preceding tests satis- 
 factorily and set each one at 10 elevation and zero deflection, and 
 lay each one carefully on a distant mark. 
 
 The sights should be interchangeable to within 1', and this test 
 will verify all the preceding tests except 2. If the sights show a 
 disagreement in elevation which cannot be accounted for in the pre- 
 ceding tests, then set each sight at the zero elevation, and if the 
 disagreement still holds, it is due to the trunnions not being of the 
 same diameter and the trunnions must have been injured. 
 
 After a sight has been in use for some time the micrometer of 
 the elevating w T orm may be found not to agree with the vernier. This 
 is due to a slight wear of the worm rack, and when the vernier and 
 micrometer are made to agree at zero, it will sometimes be found 
 that, owing to uneven wearing of the rack, they cannot be made to 
 agree at other angles of elevation. When the difference is considerable 
 the sight should 'be provided with a new rack. 
 
 THE GUNNER'S QUADRANT 
 
 This instrument (Fig. 60) is used on all kinds of guns and mortars ; 
 either to give the elevation directly or to verify the angles obtained by 
 ordinary sights. On the 12-inch mortars two seats for the feet of the 
 quadrant are squared off on the upper side of the piece in rear of the 
 trunnions; with other pieces, the quadrant should be applied to 
 surfaces perpendicular or parallel to the axis of the bore. There are 
 three models in service 1892, 1897, and 1898. 
 
 The quadrant is composed of two main parts the body, carrying 
 the graduated arc, and the movable arm, carrying the index and 
 the level. The movable arm also carries a graduation in minutes from 
 to 60, and the level, which is capable of a longitudinal movement 
 along the arm, carries a second index for reading this scale. 
 
394 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Degrees are read upon the graduated arm of the body, minutes 
 by the sliding level, and scale on the movable arm. 
 
 The graduated arc is provided on the inside with a toothed circular 
 rack, each tooth of which corresponds to a degree mark. The mov- 
 able arm is hollow and holds a spindle which carries on its end a small 
 toothed sector. A spiral spring contained inside the hollow arm 
 constantly urges the spindle and sector outward, thereby engaging the 
 teeth of the sector with those of the graduated arc and holding the arm 
 in any position it may be placed. To move the arm it is necessary 
 
 ARC". (TEETH ONE 
 DEGREE EACH)- 
 
 FOOT '''/?, VERNIER, 
 BEARINGS CLAMP SCREW 
 
 VERNIER 
 
 FIG. 60. Gunner's Quadrant. 
 
 to press back the sector against the action of the spiral spring until 
 its teeth clear those of the graduated arc ; the arm may now be moved to 
 a new position, and when the pressure is removed from the sector 
 its teeth will again engage with those of the graduated arc. 
 
 The principle by which the scale of the movable arm is constructed 
 to read to minutes is as follows: 
 
 The movable arm is a portion of the arc of a circle. 
 
 The level is a chord of this circle, and the angle between any two 
 of its positions will, therefore, be that subtended by the arc over 
 which the index moves. 
 
INSTRUMENTS, DEVICES AND CHARTS 395 
 
 To Use the Quadrant. It should be remembered that a correction 
 must be made to the angle of elevation used with the sight to obtain 
 the quadrant angle of elevation, and that this correction depends on 
 the difference in height above sea level of the axis of the trunnions 
 and the target. 
 
 QE =SE+the angular elevation of the target, 
 or when target is below the level of the gun, as is the usual case: 
 QE=SEihe angular depression of the target. 
 
 For Angles of Elevation. Set the quadrant at the required quadrant 
 elevation by placing the index mark of the sector of the movable 
 arm opposite the required degree mark on the graduated arc of the 
 body, and by sliding the level along the arm until its index is opposite 
 the required minute division of the scale of the movable arm. All 
 elevations below 45 (both degrees and minutes) are read from the 
 scales on one side of the quadrant, and those above 45 from the scales 
 on the other side of the quadrant. 
 
 Place the quadrant on its seats or on surfaces parallel or perpen- 
 dicular to the axis of the bore, always being careful to keep the side 
 of the graduated arc in use to the left, looking in the direction of the 
 target, and keep the arrow showing the line of fire pointing in the 
 direction of the target. Elevate the piece until the bubble of the level 
 comes to rest at the center. This will be the elevation required. 
 
 For Angles of Depression. Proceed as above, except that the 
 side of the graduated arc in use should be kept to the right, looking in 
 the direction of the target, and the arrow showing "direction of fire" 
 should point away from the target. 
 
 It will thus be seen that any elevation or depression in degrees 
 and minutes from to 90, within the limits imposed by the method 
 of mounting, can be given by this quadrant. It will be noticed that 
 it is graduated on one side from to 44 and on the other from 45 
 to 89. The extra degree on both sides will be given by the sliding 
 level. It will also be noticed that if 45 be given on the one side by 
 moving the arm to 44 and the index on the level to 60', and the quadrant 
 be then placed to give readings above 45 without changing the arm or 
 level, it will still record 45; for the position of the level to give a reading 
 of 60' above 44 is also the position to give a reading of 0' above 45, 
 and the main index will be found to stand at 45 on the opposite side 
 of the graduated arc. 
 
396 THE SERVICE OF COAST ARTILLERY 
 
 Model of 1898. The method of setting this quadrant for a given 
 reading is the same as in the other models, using the graduation on 
 either side of frame. Its use is simplified in that it is only necessary 
 after having set it for a given angle of elevation or depression to place 
 it on its seat on the gun with the arrow marked " Line of fire, elevation," 
 or " Line of fire, depression/' as the case may be, pointing toward the 
 target. 
 
 CRUSHER GAUGE 
 
 The crusher gauge for seacoast cannon is used for determining the 
 maximum pressure exerted in the bore of the gun during service firing. 
 Pressures are required to be taken not only at proof firings and tests 
 
 FIG. 61. Crusher Gauge Outfit. 
 
 of powder and ammunition, but also in service target practice. There 
 are three standard outfits of crusher gauges, namely, those for large- 
 caliber guns, those for intermediate, and those for small-caliber guns. 
 
 The outfit used for large-caliber guns is shown in Fig. 61, and is 
 designed for use in all cannon above 6 inches in caliber. 
 
 The gauge is inserted in the mushroom head of the breechblock in 
 each gun, two crusher gauges being us d. ^ blank plug similar in 
 external appearances to the crusher gauge is furnished to protect the 
 gun when the regular gauge is not in its seat. This may be seen by 
 referring to Plate X. 
 
INSTRUMENTS, DEVICES AND CliVRTS 397 
 
 To Prepare Crusher Gauge for Use, the closing cap is removed by 
 holding the housing fast with the housing wrench in the left hand and 
 unscrewing the closing cap with the closing-cap wrench in the right hand. 
 In the medium-caliber crusher gauge outfit the teat wrench, the tee, 
 and reamer wrench are used in place of the housing and closing-cap 
 wrenches respectively. The piston is pushed out with the gas-check 
 inserting tool. The piston and the interior of the crusher gauge should 
 then be thoroughly cleaned with oil and cotton waste and freed from 
 moisture. It should also be determined that the piston enters the bore 
 freely at both ends. The parts of the crusher gauge being in order, 
 put a drop of oil on each end of the piston and insert piston in the bore. 
 Take the pressure cylinder which is to be used in recording the 
 pressure and enter it in the cylinder holder until it is held in the 
 middle of its length. Then insert pressure cylinder in the crusher gauge 
 with the fingers so that it rests on end in the center of the piston. 
 Place the washer on top of the housing and screw in the -closing cap, 
 setting it up tightly by means of the wrenches. The gas check is then 
 placed in the bore above the piston, bottom of the cap next to the piston, 
 and with the gas-check inserting tool set it down on the piston until 
 there is no play between piston head and pressure cylinder underneath, 
 which should now remain firmly held between piston head and closing 
 cap. The crusher gauge is now ready for insertion in the gun. 
 
 After firing dip the crusher gauge into a bucket of water to remove 
 fouling and then wipe dry. Unscrew the closing cap, using the wrenches 
 as above described; shake pressure cylinder and cylinder holder out 
 of the gauge and push the piston and gas check out with the gas-check 
 inserting tool. Remove the cylinder holder from the pressure cylinder, 
 wipe the latter clean, and place it in the properly numbered hole in 
 the chest, or measure it immediately if time is available. The piston 
 and interior of crusher gauge should then be cleaned and oiled as pre- 
 viously described before again being inserted in the gun. A new pressure 
 cylinder and generally a new gas check will be required for each round. 
 The washers should be carefully inspected for cracks or unusual 
 hardening of the metal before being used. 
 
 Pressure Cylinders. Two sizes of pressure cylinders are furnished, 
 the larger being designated the cannon-pressure cylinder, and the 
 smaller, the small-arms pressure cylinder; the latter being used in 
 minor-caliber crusher-gauge outfits. These cylinders are made from 
 copper rods, about 99 per cent pure copper. The rod is drawn once 
 after annealing and every precaution in composition and treatment is 
 taken to make the metal homogeneous. 
 
398 THE SERVICE OF COAST ARTILLERY 
 
 These cylinders are subjected to initial compressions of from 2,000 
 to 7,000 pounds per square inch less than the standard maximum 
 powder pressure expected in the guns in which they are used, the object 
 being to reject all pressure cylinders which do not come within certain 
 prescribed limits of variation in set (shortening) due to this com- 
 pression, and to eliminate abnormal results by reducing the amount 
 of set produced by the powder pressure. These cylinders are made 
 up in lots of several thousand and tarage tables are prepared for the 
 various lots. Pressure cylinders are measured by the micrometer 
 before and after firing, and the amount of compression is the difference 
 between these readings. In making these measurements care should 
 be taken to secure a light but firm contact of the measuring surfaces 
 at the ends of the pressure cylinder. They should not be squeezed. 
 After the set in inches is obtained by subtracting the length " after 
 firing" from the length " before firing" and obtaining the set in inches 
 from the pressure-record pamphlet, the tarage table should be entered 
 and the corresponding pressure obtained. 
 
 TIME-RANGE BOARD 
 
 The time-range board is a device to provide information for keeping 
 the piece laid continuously for range, so that if an observation is lost 
 or the rate of change in range received from the plotting room indicates 
 an error, the range setter may look at the board and set the range on 
 the range scale, on the carriage of the gun, in accordance with the data 
 indicated thereon. It is placed on the emplacement wall (when 
 actually in use) at a point where it can be plainly seen by the range 
 setter. It is operated by the range keeper, on data received from the 
 plotting room. 
 
 The board is shown in Fig. 62. It consists of an oblong frame 
 containing a thousands scale, with two reading openings. This scale 
 is numbered from 11 to 1 on the left-hand end, and from 2 to 12 on 
 the right-hand end. It is operated by moving a knob in the slot on 
 the upper portion of the board. 
 
 A hundreds scale running the length of the board is marked on its 
 outer surface just under the reading openings of the thousands scale. 
 The hundreds scale is graduated so that readings 300 yards greater or 
 less than the number indicated in the reading openings of the thousands 
 scale may be obtained. 
 
 Below the hundreds scale and extending the length of the board 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 399 
 
 there is a plug rack with holes which 
 divide the hundreds scale into ten- 
 yard divisions. 
 
 A prediction scale graduated from 
 to 350 yards in both directions slides 
 in a groove underneath the plug rack 
 of the board. 
 
 To Use the Board. The first cor- 
 rected range received from the plotting 
 room is indicated on the board by 
 the operator. The left-hand reading 
 opening is used when the range is 
 increasing, and the right-hand read- 
 ing opening is used when the range 
 is decreasing. 
 
 For example : Assume the first cor- 
 rected range to be 5,430 yards, target 
 moving out. The thousands scale is 
 moved until the figure 5 appears in 
 the left-hand reading opening. The 
 zero of the prediction scale is then 
 moved directly under the third hole 
 from the right of figure 4 on the hun- 
 dreds scale and a plug inserted. At 
 the next reading sent to the gun and 
 called out, say 5,580, the zero of the 
 prediction scale is moved until it is 
 directly under the eighth hole to the 
 right of figure 5 on the scale for hun- 
 dreds and a plug inserted. The pre- 
 diction scale is then read between 
 plugs, that is from zero of the predic- 
 tion scale back to the first plug insert- 
 ed. The reading will be found to be 
 150, in other words the range to the 
 target is uniformly increasing at the 
 rate of 150 yards every 15 seconds, 
 or every predicting interval. There- 
 fore the range for one prediction ahead 
 will be indicated under the reading 
 150 to the right of zero on the predic- 
 
 lOa 
 
 CD O- 
 
 CD- 
 
iOO THE SERVICE OF COAST ARTILLERY 
 
 tion scale, or as 5,730. A plug is therefore inserted in the third hole 
 to the right of 7 on the scale for hundreds. The operation above 
 given is repeated as each range is received and the rear plugs taken 
 out. 
 
 The board is used in a similar manner in the case of a target coming 
 toward the battery or when the range is decreasing; for example, suppose 
 the first range received to be 6,600 and the second 6,500. A plug is 
 inserted under the 6 of the scale for hundreds and when the second 
 range is called out the zero of the prediction scale is set directly under 
 5 of the scale for hundreds as shown on plate and a plug inserted. The 
 reading between plugs (from zero to right) will be found to be 100 
 and as the range is decreasing a plug should be inserted above 1 
 (100) to the left of zero on the prediction scale. or directly under 4 of 
 the hundreds scale; the combined reading of the board will then be 
 6,400. 
 
 POWDER CHART 
 
 The powder chart is used to determine the velocity to be expected 
 from a given charge of powder considered as a function of the temper- 
 ature of the powder. It is shown in Fig. 63. 
 
 The chart consists of a board upon which the chart is mounted; 
 along thfe" top edge of the board a T square fits into a groove which runs 
 the length of the board. Along the top edge of the chart a velocity 
 scale is marked, with graduations to represent 10 foot-seconds to the 
 inch. The scale reads from left to right with the normal velocity of 
 the gun placed in the middle and designated by a vertical line extending 
 the width of the chart. A convenient length for the chart is 20 inches, 
 which allows for a variation of 100 foot-seconds on each side of the 
 normal. 
 
 Across the face of the chart is drawn a temperature-velocity curve 
 plotted to rectangular co-ordinates. The ordinates are the temperatures 
 and the abscissae are the corresponding variations from the normal 
 muzzle velocity. 
 
 The left edge of the T square is graduated in degrees Fahrenheit, 
 beginning at 10 degrees at the bottom and ending at 100 degrees at the 
 top. A convenient scale is 10 degrees to the inch, which requires a 
 chart about 13 inches wide. 
 
 A horizontal line extends across the chart so that it will pass 
 through the 70 mark on the T square; this line designates the normal 
 temperature. 
 
INSTRUMENTS, DEVICES AND CHARTS 
 
 401 
 
 To Use the Chart. For powder tested to give the normal velocity 
 of the chart at 70 F., the T-square is set so that the actual temperature 
 as indicated on the scale of the T square lies on the temperature velocity 
 curve, and the velocity that may be expected from such powder will 
 be indicated on the velocity scale at the top of the chart, at the inter- 
 section of the left edge of the T square and this scale. 
 
 For powder tested and adjusted to give the normal velocity at any 
 other temperature than 70, the T square is set for the temperature 
 at which the powder was tested and the velocity read as in the first 
 
 n 
 
 r 
 
 Normal Temperature 
 
 -too 
 
 90 
 80 
 70 
 
 POWDEIH 
 
 FIG. 63. 
 
 case. The T square is then set for the actual temperature of the powder 
 and another velocity determined. The difference between the first 
 velocity obtained and the velocity obtained from the temperature 
 setting will give the algebraic difference to be added to the normal 
 velocity for the gun in question, and the same will be the velocity 
 to be expected from the charge used. 
 
 For example: Assume that the normal velocity is 2,250 f.s. The 
 velocity obtained by setting the T square at the test temperature was 
 2,240 f.s. The velocity for temperature setting, or the actual temper- 
 ature of the powder in question, say, is 2,280 f.s. The difference 
 would then be +40 f.s.; or, this added algebraically to the normal 
 velocity would give 2,290 f.s. as the probable velocity to be expected 
 from the powder in question. 
 
CHAPTER VIII 
 SEARCHLIGHTS 
 
 IN developing the maximum efficiency of searchlights, when acting 
 in conjunction with fixed defenses, the following requirements are 
 suggested by a recognized expert on searchlight defense.* 
 
 They should be located with consideration to their ability to search 
 effectually the approaches of the battle area, with a view to the early, 
 discovery and identification of the enemy. For this purpose advanced 
 roving lights on portable or disappearing towers should be placed some 
 4,000 yards in front of the outside line of the primary armament, where 
 practicable, and observers placed still further to the front and in 
 telephonic communication with the battle commander. The purpose 
 of this is obvious when it is remembered that the effective range of the 
 primary armament is 12,000 yards, while that of the 60-inch light is 
 approximately 8,000 yards, as shown in the accompanying table. 
 
 The second consideration is their ability to illuminate continuously 
 with minimum interference, a number of targets simultaneously in. 
 any part or parts of the battle area. This can be accomplished by so 
 disposing the lights that as the target passes in through successive zones 
 of the battle area it can be picked up and covered by searchlights 
 assigned to each zone before it is out of reach of the lights of the preced- 
 ing zone. Further to prevent interference, the lights should be placed 
 on the flanks of all stations and guns pertaining to their respective 
 zones. 
 
 The third consideration concerns the ability of the lights to illuminate 
 landing positions and points from which the fortifications could be 
 readily attacked from the flanks or rear by raiding parties of the enemy. 
 This condition may be overcome by a judicious employment of the 
 outermost roving lights, or other lights in special positions, and when 
 
 * Namely, Major W. C. Davis, C. A. C., II. S. A., from whose article, published in 
 the Journal of the U. S. Artillery, May-June, 1909, most of the information in 
 regard to the tactical use of searchlights is drawn. 
 
 402 
 
SEARCHLIGHTS 403 
 
 necessary, supplemented by portable lights, controlled by the coast 
 artillery supports, along the land front. 
 
 The fourth consideration is their ability to cover mine fields and 
 channels leading to inner harbors against the operation of torpedo 
 boats and other craft. This condition is met by having a number of 36- 
 inch lights, on sights from 15 to 25 feet above high water, with beams 
 held fixed or nearly so, across the channel, or covering the mine field 
 and its approaches. .Where channels are narrow, diverging lenses 
 can be used. The 36-inch projector is effective under good weather 
 conditions up to 3,000 yards, using a concentrated beam (angular 
 divergence about 2 degrees). At this range the beam has a diameter 
 of approximately 120 yards. At 2,000 yards and at 1,500 yards the same 
 intensity of illumination can be obtained (as with the concentrated beam 
 at 3,000 yards) by employing lenses giving 12 to 40 degrees' divergence. 
 Such lenses should be employed, in good weather, to increase the time 
 required by a vessel to traverse the beam. 
 
 Another consideration of importance in connection with the search- 
 light defense is the providing of relieving lights to replace lights 
 temporarily or permanently disabled. This can be accomplished either 
 by having duplicate lights installed whenever practicable, or by assign- 
 ing one light to another's relief. 
 
 The effective protection of advanced searchlights from capture 
 or destruction by the enemy must also be considered. In this con- 
 nection no searchlight should be advanced so far to the front, or 
 otherwise sited, that an armored ship can attack it effectively without 
 exposing herself to destruction from the high-power guns of the forti- 
 fications. At night a searchlight is a very difficult target to hit, and 
 when properly made and emplaced can only be put out of action by a 
 direct hit on the projector. It is believed this is not likely to occur 
 until the vessel has advanced to close range, say about 2,500 yards, 
 where its secondary armament can be used to full advantage. Should 
 the enemy, under these conditions, succeed in obtaining the range, 
 so that the projector should appear to be endangered, the light should 
 be suddenly occulted leaving no target for him to fire at,. and probably 
 leading him to the false conclusion that the projector had been destroyed 
 or disabled. Under such conditions the advanced light has served its 
 purpose, for it has revealed the enemy, who should now be covered by 
 a searchlight further to the rear. If the advanced light, as previously 
 suggested, is placed not more than 4,000 yards in front of the first line 
 of primary armament, the ship, when she has closed to within 2,500 
 yards from the light, would be less than 6,500 yards from the primary 
 
404 THE SERVICE OF COAST ARTILLERY 
 
 armament of the defense a situation which she should not be able 
 to maintain for any appreciable time. 
 
 All advanced searchlights should be protected from torpedo boats 
 and small craft by a suitable force of coast artillery supports, supple- 
 mented by a few field guns. In the daytime these lights should be run 
 under cover and their position concealed from the enemy. 
 
 TYPES OF PROJECTORS 
 
 The number of searchlights necessary for the proper illumination of 
 the water area covered by any particular fort depends upon the size 
 of the area in question and the importance attached to its defense. 
 Two types of projectors have been adopted in the U. S. Coast Artillery 
 service, namely the 36-inch and the 60-inch. Both of these types 
 are provided with parabolic reflectors. The beam proceeding from 
 them, even when the arc is most perfectly in focus, is not a cylinder, but 
 the frustrum of a cone; the 36-inch light having an angular divergence 
 of 2^ degrees, and the 60-inch light a divergence of from 2^ to 3 degrees, 
 from the projector outward. The approximate diameter of the beam 
 at various ranges is shown in the following table: 
 
 Range, yards .............. 1000 2000 3000 4000 5000 6000 7000 8000 
 
 36-inch \ ,. ,, f , , 40 80 120 160 200 240 280 320 
 
 80 50 100 150 200 250 300 350 400 
 
 From this table it will be seen that the illuminating power of the 
 beam follows the quadric law, varying inversely with the square of the 
 distance. 
 
 In passing through the air the elements of the beam encounter 
 various impurities, such as particles of moisture, dust, carbon, etc., 
 which absorb, reflect, and refract rays of the light, causing the beam 
 to fall off rapidly in intensity and giving rise to a considerable amount of 
 diffused light. Due to this cause the beam, as it passes through the 
 air, is visible; its distinctness varying inversely with the clearness of 
 the atmosphere, and directly with the darkness of the night. 
 
 The diffused light above referred to, radiating at right angles from 
 the beam, lights up with considerable brightness objects two or three 
 hundred yards from the beam, and when the beam is held just above 
 the water, gives rise to the " reflected ray" or beam, so often observed 
 and mentioned in the coast artillery service. The clearer the atmos- 
 phere and the brighter the direct beam from the searchlight, the less 
 
PLATE XXXV 
 
 36-inch Searchlight (Proiector). Showing movable truck, and apparatus 
 for electrical control. 
 
SEARCHLIGHTS 405 
 
 luminous becomes the "reflected beam"; but in no case does the 
 "reflected beam" ever approach the brightness of the direct beam; 
 and a target passing through the "reflected beam" is never seen as 
 clearly, other conditions being the same, as it would appear in the direct 
 beam of the light. 
 
 The atmospheric conditions affecting the penetration of the search- 
 light beam are the same as those affecting sunlight; that is, fog, mist, 
 snow, rain, smoke, etc., reduce the effective range of the beam in pro- 
 portion to their respective densities. 
 
 Xo definite rule can be made as to the exact range at which a target 
 in a searchlight beam should be visible, the range varying with respect 
 to the condition of the air; the intensity of the light; the color and 
 shape of the target; the position of the observer with respect to the 
 target and light; the ability of the observer; the suitability of the 
 telescope; and the character of the background. 
 
 Atmospheric conditions are at their best when the air is free from 
 moisture and smoke, and when the moon and stars are entirely obscured 
 by clouds. The beam then has great penetration and the law of 
 contrast brings the target out into clear relief. 
 
 The intensity of the light depends directly upon the candle power. 
 The average intensities of the German projectors, using 125 to 150 
 amperes, are 61,000,000 and 180,000,000 standard candle-power, 
 respectively; that is, the 60-inch projector has three times the candle- 
 power of the 36-inch projector. 
 
 When a searchlight beam impinges on a ship a portion of the light 
 is absorbed, while the balance is reflected in various directions, according 
 to the well-known law that the angle of reflection is equal to the angle 
 of incidence. The percentage of light absorbed depends upon the color 
 and kind of paint and the character of the reflecting surface. Thus a 
 dark-colored ship is less conspicuous than one painted white, and a ship 
 the lines of which are irregular and broken is not as conspicuous as 
 one having a smooth outline. 
 
 All stations and guns using the same type of illuminating light 
 should be on the same side of the light and the light should be con- 
 trolled from that side. The projector, for efficient service, should not 
 be less than 150 yards from the flank of the nearest battery or position 
 finder that the searchlight is to serve. That within any practicably 
 attainable range in elevation (other conditions remaining constant) 
 the greater the difference in level between the observer and the search- 
 light, the better the illumination of the target always excepting the 
 case where the observer or the projector is so near the water as to be 
 
406 
 
 THE SERVICE OF COAST ARTILLERY 
 
 interfered with by the curvature of. the earth. It may be stated that 
 the two greatest objections to the high-siting of searchlights in the 
 U. S. Coast Artillery service, are: (1) That it may give too great a 
 "searchlight dead space/' so called when the beam is projected so as 
 to strike the water at a certain range, inside of which vessels may pass 
 under the beam unilluminated and unobserved. (2) High-sited 
 searchlights are of no value whatever in harbors where high fog prevails 
 where the water underneath may be perfectly open for navigation. 
 
 The ability of the observer usually depends upon* the amount of 
 practice he receives at night. A good illustration of the influence of 
 training is seen in pilots of boats at night or where fog is prevalent. 
 The acuteness of vision by which a pilot will discern landmarks at night 
 or through a fog seems wonderful to a landsman, who, standing by his 
 side, is unable to see anything. 
 
 Experience teaches that the best telescope for night work is one 
 with a large objective and low magnifying power. 
 
 Channels whose hilly shores are rough and irregular, or are heavily 
 wooded, offer special difficulties for observers, as do also the shadows 
 thrown on the water by high hills or mountains. These difficulties 
 are apparent in the daytime and at night are even more in evidence. 
 Under such conditions, a small dark-painted craft, like a torpedo boat, 
 stealing in close to the shore, is a most difficult object to detect. 
 
 APPROXIMATE RANGES 
 
 The following table summarizes the approximate ranges at which 
 targets should be visible in good weather, and under other favorable 
 conditions. 
 
 Color of ship. 
 
 Vessel seen, but 
 outline obscure. 
 
 Form clear enough 
 for horizontal 
 tracking. , 
 
 Target can be 
 water- lined. 
 
 36" 
 
 60" 
 
 36" 
 
 60" 
 
 36" 
 
 60" 
 
 White 
 'War paint" 
 
 8000 
 6000 
 5000 
 
 12000 
 9000 
 7000 
 
 5500 
 4500 
 4000 
 
 8000 
 6500 
 5500 
 
 4500 
 4000 
 3500 
 
 6500 
 6000 
 4500 
 
 Black 
 
 
 The service of searchlights is officially defined in the U. S. Coast 
 Artillery Drill Regulations. 
 
SEARCHLIGHTS 407 
 
 COMPONENTS OF SEARCHLIGHTS 
 
 In addition to their tactical classification searchights are classified 
 with reference to the size of their mirrors or reflectors. The two 
 standard sizes found in the U. S. Coast Artillery service are, as previously 
 stated, the 36- and 60-inch. The standard 36-inch light, with apparatus 
 for electrical control, etc., is shown in Plate XXXV. 
 
 The principal parts of a searchlight are the lamp, mirror, drum, 
 lamp box, glass front door, standards, pedestal, turntable, training 
 mechanism. 
 
 (a) Lamp. The lamp of the latest type of searchlight in service 
 is shown in Plate XXXVI, and its mechanism is as follows: 
 
 A, negative carbon holder; 
 
 B, positive carbon holder; 
 
 C, clamping screws for carbon clamps; 
 
 D, vertical adjusting screw for positive carbon clamp; 
 
 E, horizontal adjusting screw for positive carbon clamp; 
 
 F, negative carbon support; 
 
 G, positive carbon support; 
 H, lamp frame; 
 
 K, main lamp contact shoes; 
 L, hand feed screw; 
 Af, focus nut for focusing screw; 
 
 N, stud of lamp switch for cutting out feeding magnet; 
 0, ratchet and pawl; 
 P, feeding magnet armature; 
 Q, contact of circuit breaker; 
 R, adjusting screw for ratchet arm; 
 S, starting magnet; 
 T, feeding magnet; 
 U, adjusting spring for feeding magnet. 
 
 The lamp is for producing the light, starting and feeding the arc, and 
 is operated through its mechanical arrangement by the electric magnets 
 named in the nomenclature. The circuits of the lamp are shown in 
 Figs. 64 and 65. The current is brought to the searchlight by the 
 power cables and enters the pedestal, going directly to the main switch 
 of the lamp; from there it is taken by leads to the contact rings attached 
 to the turntable. 
 
 There are two circuits the series circuit, which includes the arc, 
 
408 
 
 THE SERVICE OF COAST ARTILLERY 
 
 and the feed-magnet circuit in shunt with it. The series circuit is 
 from the positive contact shoe to the series magnet, thence through 
 the positive carbon holder to the arc, back through the negative carbon 
 holder to the negative contact shoe, and after passing through the series 
 
 FIG. 64. Circuits and Lamp Mechanism 
 
 magnet the circuit is connected to the frame, the frame being a part of 
 the circuit. The feed magnet circuit is from the circuit-breaker spring 
 (positive) to the other circuit-breaker contact, then to the feed magnet 
 and through the main switch to negative line. 
 
 The Action of the Lamp is as Follows : When the circuit is closed 
 the resistance in the air gap prevents any current from flowing in the 
 arc circuit, and the voltage across the carbons will be practically that 
 of the source of power. This difference of potential or pressure causes 
 sufficient current to pass in the shunt circuit, so that the feed magnet 
 
SEARCHLIGHTS 
 
 409 
 
 attracts its armature and thus draws the pawl into the ratchet while 
 turning it through a small angle. The act of drawing the armature 
 breaks the shunt circuit at the circuit-breaker contact, and the attrac- 
 tion ceasing, the spring returns the armature to its initial position. The 
 
 Circuit 
 
 Feet/iflq Ma j nets 
 *!__ Positive Carbon 
 
 io 
 contact* 
 
 FIG. 65. Circuit Breaker, etc., Searchlight Lamp Mechanism. 
 
 voltage across the arc is not changed since the first movement of the 
 ratchet, so the operation will be repeated and continue until the carbons 
 touch each other. When the carbons touch a large flow of current makes 
 the starting magnet attract its armature, which operates to pull the 
 
410 , THE SERVICE OF COAST ARTILLERY 
 
 carbons apart, forming the arc. It takes a short time for the crater to 
 burn properly, and until this is done the arc will not have the proper 
 length. As soon as this is attained the feeding magnet will keep the 
 carbons the proper distance apart, since it acts when the proper voltage 
 across the arc is exceeded, this adjustment being made by the spring 
 attached to the feed magnet armature. 
 
 The attractive power of the magnet depends urjon the current 
 passing around the core, which necessarily is proportional to the 
 difference of voltage across the arc and the resistance of the magnet 
 winding. The feed spring is arranged to resist an opposing force equal 
 to the force of attraction, so that whenever this force is exceeded 
 which indicates that the voltage across the arc has been exceeded 
 and that the carbons are too far apart, the current will flow 
 around the feed magnet and the feeding magnetism will commence 
 to operate, feeding the carbons closer together and maintaining the 
 proper arc. 
 
 (6). The Arc. If two pieces of carbon are joined by wires to the 
 terminals of a battery of sufficient electro-motive force, or to a generator 
 of electric current as just described, and are then brought into contact 
 for a moment and drawn apart a short distance, as is done with the 
 lamp of a searchlight, a kind of electric flame called the electric arc 
 or voltaic arc is produced between the points of the carbons, and a 
 brilliant light is given off by the white-hot points of carbon electrodes. 
 Before contact of the carbons is made the difference of potential or 
 pressure between the points is insufficient to cause a spark to leap 
 across even 1/10,000 of an inch of air space, but when the carbons are 
 made to touch by the feeding mechanism of the lamp a current is 
 established. On separating the carbons the spark at parting volatilizes 
 a small quantity of carbon upon the points. This carbon vapor, being a 
 fairly good conductor, allows the current to continue to flow across 
 the gap, provided it is not too wide, and as the carbon vapor has a 
 high resistance it becomes intensely heated by the passage of this 
 current, and the carbon points become highly heated, giving off a 
 white light. The temperature of the arc at this point is estimated to 
 be 6.000 degrees C. The greater part of the light is given off from the 
 points of the carbons themselves, though their temperature is not as 
 high as the arc, due to the principle that solid matter is a better radiator 
 than gaseous. The volatilizing from the positive electrode or carbon 
 causes it to become hollowed out or cup-shaped, forming the crater. 
 Due to the gap between the two carbons being small, particles of the 
 volatilized carbon are deposited on the negative carbon, and this tends 
 
SEARCHLIGHTS 411 
 
 to point it. The amount of light emitted from the crater depends upon 
 the amount of current and the carbons used; that is, their size, or the 
 incandescent area exposed. 
 
 The normal current for the 36-inch light is 130 amperes, while the 
 normal voltage across the arc is 60; for the 60-inch light the normal 
 current is 200 amperes, and the normal voltage across the arc is 65. 
 For any particular light it may be found that better practical results 
 are obtained by slight variations in the values given, as it has been 
 found in practice that nearly every light has its individual factor. 
 An arc may be made and maintained by either direct or alternating 
 current, but for searchlight purposes an arc from pure carbon electrodes 
 supplied with direct current has been found to be the best, and is the 
 method used in coast defense. 
 
 (c) The Mirror. The reflector is a parabolic mirror and its object 
 is to project the light reflected from the arc in parallel rays to the 
 target. As is knoVn, the angle made by a reflected ray of light with 
 the normal and the reflecting surface is equal to that made by the incident 
 ray, so by the use of a parabolic reflecting surface, when the light is in 
 focus the reflected rays are parallel. 
 
 The mirror is so mounted in a brass frame that it is securely pro- 
 tected against concussion, and provision is made for expansion due to 
 heat. The mirror should always be kept dry to prevent spotting or 
 frost due to moisture, and prior to its use should be cleaned by dusting 
 with a soft brush or with a piece of chamois skin after it has been care- 
 fully shaken out to prevent the presence of grit, which would result 
 in scratching the mirror. It must be remembered that the presence of 
 dirt or dust will greatly reduce the amount of reflected light. It has 
 been found from observation that the direct rays of the sun damage 
 reflectors to a considerable extent, therefore they should not be exposed 
 unnecessarily. 
 
 (d) The Drum. The drum and lamp box are together a casing for 
 the lamp and reflector. The drum is pivoted on trunnions that bear 
 on standards which are bolted to the turntable. It can be given 
 vertical motion on the trunnions or a horizontal motion on the rollers, 
 or both together, such being necessary for training the beam. The lamp 
 rests on guides fastened to the lamp box, so arranged as to be moved 
 forward or backward by turning the focusing screw, the head of which 
 is shown in the cut referred to. 
 
 (e) Lamp Box. The lamp box is shown in detail in Plate XXXVI, 
 and is used to carry the lamp and feeding mechanism, and carries the 
 contacts for transmitting the current to the lamp proper. 
 
412 THE SERVICE OF COAST ARTILLERY 
 
 (/) Glass Front Door. The glass front door is provided for the 
 protection of the lamp and mirror. It is made up of a circular frame 
 carrying strips of glass about two inches wide of varying lengths 
 depending upon the diameter of the projector considered. 
 
 (g) Standards. The light is provided with two standards or up- 
 right arms, which are bolted to the turntable at the lower extremity 
 and carry the trunnions at the top, supporting and carrying the drum 
 and its contents and give the light the necessary motions for training. 
 
 (h) Turntable. A turntable attached to the horizontal training 
 motor through a gear train is used to give the beam horizontal motion. 
 
 (k) Pedestal. The pedestal is that part of the light beneath the 
 turntable carriage. On its interior surface the training motors are 
 arranged to give both the horizontal and vertical motions of the beam. 
 
 (1) Training Mechanism. Training normally is by means of an 
 electrically controlled mechanism, but there is an auxiliary mechanism, 
 so that in case the electric control fails the training may be done by 
 hand at the light. 
 
 The electric control consists of two training motors located in the 
 pedestal and connected electrically with the controller located in the 
 station from which the light is operated. The vertical training motor 
 through a gear train transmits a vertical motion to the beam, and the 
 horizontal training motor through a gear train drives a pinion which 
 engages with the pinion on the turntable, giving the beam horizontal 
 motion. 
 
 ESSENTIALS OF EFFECTIVENESS 
 
 The essentials of an effective searchlight, aside from its tactical 
 location, may be stated as follows: 
 
 a. A proper power supply. 
 
 b. Good arc, which necessarily means good carbons. 
 
 c. The proper focusing of the beam. 
 
 d. Careful operation of the training mechanism. 
 
 e. A good operator of the searchlight controller. 
 
 The first depends upon the installation and is beyond the control of 
 those ordinarily charged with the care and operation of searchlights. 
 The second is within the power of those charged with the care and 
 operation of the searchlight, and the steps necessary to obtain a good 
 arc may be summarized as follows : 
 
 1. Begin with a new set of carbons. 
 
SEARCHLIGHTS 413 
 
 2. Secure them in their holders with the negative carbon that is, 
 the smaller one nearest the mirror. 
 
 3. See that they are in alignment that is, that the axis of the 
 positive carbon is approximately in prolongation with that of the 
 negative. Should they not be properly aligned, adjust them by means of 
 the adjusting screws indicated in Plate XXXVI. 
 
 Make sure that the carbons are clamped securely, so that when the 
 drum is elevated they will not be thrown out of alignment, or drop back 
 and spread the arc, giving it abnormal length. The carbons should have 
 about f of an inch play between the tips when separated. Then bring 
 the carbon tips approximately in the focus of the beam by means of the 
 focusing screw. The drum is marked, that is, the finder in the drum 
 is marked to indicate this position. If the start is made with carbons 
 that have been used before and the crater is not evenly formed, part 
 should be broken off and reamed out before the start is made. 
 
 5. Feed the carbons together by turning the feed screw until they 
 nearly touch and turn the current on. 
 
 6. Keep the current as near normal as possible, as this assists the 
 crater in forming properly. 
 
 7. After the lamp has been operated long enough for all parts to reach 
 their normal temperature and the arc has become normal, run the 
 carbons apart slowly and note the voltmeter reading at the first stroke 
 of the magnet. If the voltage is above the normal voltage as given 
 across the arc for the lamp in question, loosen the feed spring U shown 
 in Plate XXXVI, until proper adjustment is made. Should the volt- 
 age be below the normal, tighten the same screw. It is necessary 
 that this adjustment be made when the lamp is in the horizontal 
 position. 
 
 8. Focus the lamp by bringing the arc directly on the cross wires 
 of the ground-glass finder and note if the rays leave the mirror parallel. 
 
CHAPTER IX 
 SUBMARINE MINES, SMALL BOATS, ETC. 
 
 IN case of heavy fog, or at night when an attack is unexpected, or 
 even when expected, the possible failure of searchlights makes it impera- 
 tive to provide some final means of defense. An adequate submarine 
 defense has been developed in the U. S. Coast Artillery service, and 
 consists of a submarine mine containing an explosive charge, a firing 
 device, and the necessary arrangement for testing and signaling. The 
 whole is inclosed in a water-tight case, and is intended to be submerged 
 in the waterway or entrance to important harbors, and naval bases. 
 
 A submarine mine is not a torpedo, although frequently referred to 
 as such. The device just described, when submerged the proper depth 
 under water, and anchored in position, is a submarine mine, while a 
 torpedo consists of a case containing a charge of explosive, a firing device, 
 and a device for propelling it through the water. The submarine mine 
 is fixed in position, and its functions are purely defensive, while the 
 torpedo is both defensive and offensive. 
 
 Submarine mines are of two distinct classes with regard to their use 
 in respect to position, and are classified as buoyant and ground mines. 
 The buoyant mine is one that floats in position, and has such an excess 
 of buoyancy that if it were not anchored in position as shown in Fig. 
 66, it would float on the surface. These mines are designed to be 
 submerged and held in position by anchors. A ground mine consists of 
 a case containing an explosive and a firing device, and is heavier than 
 the amount of water it displaces, and therefore, requires no anchor, 
 and sinks to the bottom. 
 
 Mechanical and Electrical Types. Submarine mines are further 
 classified as mechanical or electrical, depending upon their means of 
 firing. 
 
 A mechanical mine is a non-controllable mine, and may be either 
 electrical or purely mechanical. They carry their own firing apparatus, 
 and when once planted, are equally dangerous to our own and to the 
 enemy's vessels. They are non-controllable to such an extent, and such 
 
 414 
 
SUBMARINE MINES, SMALL BOATS, ETC. 
 
 415 
 
 ng Buoy 
 Distribution JBoxJZuoy- - 
 
 .P/antrry &uoy f?o/>e. 
 
 Mooring Rope- 
 
 Distribution 
 
 -Sf 
 
 '* c. 
 
 tiple 
 S.C Ca'Je 
 
416 THE SERVICE OF COAST ARTILLERY 
 
 a menace to the commerce of friendly nations and non-combatants that 
 their use in modern warfare is rapidly being dispensed with. 
 
 The electrical mine adopted in our system and in most modern 
 systems, is controllable and can be made perfectly safe or equally 
 dangerous by the manipulation of the electrical features. The electrical 
 mine is arranged so that it may be fired at the will of the operator; 
 on contact with an enemy's vessel, or after a contact and a signal has 
 been given. 
 
 To properly protect the entrance to a harbor or naval base, it is 
 thought that at least three lines of submarine mines a.e essential. 
 The exact location of these different lines of mines involves considera- 
 tions with reference to the other defenses of the harbor considered. 
 Their location must also depend upon the width and depth of the 
 channel, the swiftness of the current, conditions of tide, bottom, and 
 difficulties of planting. 
 
 A mine field must be properly protected by shore batteries in order 
 to become effective. Mine-fields which are susceptible to raids by 
 the enemy may be considered as not fulfilling their proper function, as 
 their protection would require the explosion of mines when tampered 
 with, which is not the proper function of a submarine mine defense. 
 The proper protection for the mine fields is that of rapid-fire shore 
 batteries, submarine boats and torpedo boats, in order that raiding 
 parties of the enemy may be met in the same manner in which such 
 tours are ordinarily carried out. 
 
 The ideal location of a mine field would be that which would require 
 the vessels of a hostile fleet to be held in the zone of most effective fire 
 of the heavy guns. This zone lies between 4,000 and 8,000 yards from 
 the main defenses of a harbor, and is beyond the interior limit of effective 
 mortar fire. It can readily be seen, therefore, that any mine field 
 which would break up the formation of an enemy's fleet in this effective 
 zone, in addition to the possibilities of the total destruction of the 
 vessels themselves by the mines, would result in the fleet being exposed 
 to the destructive fire of the heavy batteries where that fire is most 
 effective. In the location of mine fields it is also essential that the 
 outer line be sufficiently extended so that in case of fog, thick weather, 
 and darkness, the presence of the enemy will be made known before 
 it is too late to prevent an effective run-by. 
 
 The essential elements of a mine command consist of the fire-control 
 system, the rapid-fire batteries, the mining casemate, the loading room, 
 a storehouse for mine material, sufficient cable tanks for the storage 
 of submarine mine cable, the searchlight system, the magazine and 
 
SUBMARINE MINES, SMALL BOATS, ETC. 417 
 
 explosives, as well as a means to transport and handle this material, the 
 necessary boats for carrying out the duties of putting the mines in 
 position, the repair of the mine fields, and some means for the test, 
 care and preservation of the above elements. 
 
 The Fire-Control System. The fire-control stations of a mine com- 
 mand are provided with range finders, and in the mine primary station 
 a telescope, a plotting board, a prediction ruler, time-interval bell, 
 stop watch, and the necessary telephones to the post switchboard, 
 mining casemate, searchlights, loading room, and rapid-fire gun 
 batteries. The operation of the apparatus is similar to that of the other 
 fire-control stations. The use of the plotting board has been fully 
 expained under the heading " Submarine Plotting Board." 
 
 The Mining Casemate. This is usually a substantial building either of 
 masonry or frame, one story high, and about 30 X60 feet in dimensions. 
 It is located in such manner as to protect it from attack from the 
 land front as well as fire delivered from the entrance to the harbor. 
 
 The equipment of the mining casemate is necessarily kept a secret. 
 Its purpose, however, is to explode the mines at the proper instant, 
 and to control and test them after they are planted. 
 
 The Loading Room. The duties of the loading room include 
 the mechanical and electrical operations necessary for preparing the 
 mines for planting. Such operations are divided as follows : 
 
 1. Making turk's-heads: 
 
 (a) Single-conductor cable. 
 (6) Multiple cable. 
 
 2. Making telegraph joints. 
 
 3. Making okonite joints: 
 
 (a) Uniting two single-conductor cables. 
 
 (6) Uniting multiple cable and seven-branch cables. 
 
 (c) Uniting multiple cable and mine cables. 
 
 (d) Uniting mine cable to loading wire. 
 
 4. Preparing compound plug for buoyant mine. 
 
 5. Loading and testing compound plugs. 
 
 6. Loading mines. 
 
 7. Assembling a group of mines. 
 
 8. Attaching mooring sockets to cable. 
 
 (a) Preparing mooring ropes rule for lengths. 
 
 9. Insulating exposed cable ends. 
 
 The loading room is in charge of a non-commissioned officer (Chief 
 Loader) , who is selected for his knowledge of the subject. In performing 
 
418 
 
 THE SERVICE OF COAST ARTILLERY 
 
 his duties he should keep the detachment busy at such parts of the work 
 as the several details are best fitted to perform, exercising care that 
 no accident occurs from carelessness or neglect; to make the necessary 
 electrical tests; to keep himself informed as to the general progress of 
 the work so that no part may fall behind and create unnecessary delay ; 
 and finally to allow no unauthorized persons in the building. 
 
 Making a Turk's-Head. In submarine telegraph cables the armor 
 is jointed by a long running splice with the iron wires, similar to the 
 splicing of a rope to run through a block. In case of necessity, the 
 same device may be employed in the mine service, but the method of 
 turkVheads is greatly to be preferred when junction boxes are at hand 
 and it must be exclusively used in connecting the cable to the mines. 
 
 To make a turk's-head (Fig. 67 a), one private equipped with a navy 
 
 C 
 
 FIG. 67. 
 
 knife, cutting pliers, hammer, turk's-head collar (large or small), and 
 about 14 feet of marline is required. 
 
 If the object be to splice a single-conductor cable, or to unite a 
 multiple cable to several cables, the turk's-head will be made first; but 
 if it be desired to attach the cable to a mine or mine buoy, the free 
 end will first be passed through the clamping hole of the mine cap. 
 In either case, the turk's-head will be made in the following manner: 
 
 Trim the end square; at 15 inches from it place a wrapping of four 
 or five turns of marline overlapping each other round the cable, and 
 finally secured by a square knot, to form a stop for the collar; slip on the 
 collar, flat side first until it rests against the stop of marline; unwrap 
 the jute covering, and bend it back regularly over the collar; do the 
 
SUBMARINE MINES, SMALL BOATS, ETC. 419 
 
 same with the iron wires and the interior hemp serving; cut off the 
 iron wires with the pliers, removing about 4 inches from one, and 6 
 inches from the next, alternately; trim off about 4 inches from the 
 jute and hemp wrapping; bend the iron wires separately to closely fit 
 the collar (making two right angles with the pliers) and arrange the 
 ends smoothly along the cable; engage the end of a strand of marline 
 under one of the wires near the collar, and wrap it regularly and closely 
 around the cable, until a point about one inch beyond the end of the 
 jute and hemp is reached; then, secure the free end of marline with 
 two half hitches. About 12 feet of it are required. Where time is 
 important the wrapping of marline may be reduced to a couple of half 
 hitches (near collar) drawn tight. 
 
 In case no collars are at hand, a wrapping of marline of similar 
 form may be substituted. 
 
 If the object be to splice one cable to another, the turkVheads are 
 placed in their clamps in a single junction box, the cores are jointed, 
 and the parts of the junction box are bolted together, great care being 
 observed not to injure the exposed parts of the cores coiled inside, and 
 to see that the wrappings of the turk's-head are so firmly clamped that 
 no motion is possible. 
 
 If a multiple cable is to be connected to single-conductor cables, a 
 distribution box will be used. The turkVheads will first be secured; 
 then the cores will be united; lastly, the box will be bolted or keyed 
 together. 
 
 If the cable is to be jointed to a mine or mine buoy, the turk's-head 
 is first drawn up until the swell is in contact with the cap, and the clamps 
 are then bolted fast. It is essential that the clamps shall take a firm 
 hold; and if the iron jaws touch, it is sufficient proof that there is not 
 enough marline wrapping. Afterwards the cores are jointed, and the 
 cap is immediately screwed to its seat. Care must be taken to avoid 
 any unnecessary bending or twisting of the cores, and no pulling what- 
 ever must be allowed. 
 
 Telegraph Joint. (see Fig. 676). The ends of the wires to be 
 jointed are bared and brightened for about 1^ inches, the bared ends 
 are laid across each other at an angle of about 45 degrees, the point of 
 crossing being about one-third the distance from the insulation of 
 the ends. With a pair of pliers, grasp the two wires firmly at the cross- 
 ing; then wind closely and tightly the free end of each wire around 
 the short bared part of the other, shifting the pliers, if necessary, after 
 wrapping one end and before beginning on the other, so that the two 
 wrappings begin as close together as possible. The two windings 
 
420 THE SERVICE OF COAST ARTILLERY 
 
 should run in opposite directions. The end of each wire at the end of 
 the wrapping is trimmed or hammered down so as to leave no projecting 
 sharp points. When completed in the manner described the joint 
 should not give in either direction. To insulate the joint a piece of 
 rubber tape, 2 inches long, is cut from the roll, the cut running in a 
 diagonal direction across the strip. Beginning well back on the insula- 
 tion the tape is applied under strong tension, each turn overlapping 
 the preceding one by about one-third of its width. This winding is 
 continued forward and backward, sometimes in a straight and sometimes 
 in .a diagonal direction, until the strip is used up and a substantial 
 insulation is secured. The end of the rubber tape is secured by firm 
 pressure continued for several seconds; a little rubber cement may 
 be used to insure adhesion. This joint is used in connecting the fuses. 
 
 Okoriite Joint. This joint is now prescribed for use in uniting all 
 conductors of cables placed under water or exposed to dampness. 
 The following is prescribed as the method of making the okonite joint: 
 
 The ends are bared and cleaned, then beveled like a sharpened 
 lead pencil (see Fig. 67 c), using a very sharp navy knife; roughen 
 the beveled part and half an inch of the insulation with the knife or file 
 and wipe clean with gasoline. 
 
 The wires may be joined in three ways: 
 
 1. By using a brass jointer, in which case about f inch of the ends 
 of the conductor is bared; the wire is secured by compressing the 
 longer diameter. Smooth off any rough edges with a file. 
 
 2. By a telegraph joint, in which case about 4 inches of the ends 
 of the conductor should be bared. 
 
 3. By the following method: bare about 4 inches of the ends of 
 the conductors, separate the wires of each for about 2 inches, cut out 
 the center wire, and spread out the others radially; then put the two 
 ends together as in splicing a rope, each wire opposite the space between 
 two in the other end; bend the wires of one end through the spaces of 
 the other and wrap them closely and regularly around it; then do the 
 same with the other end. If carefully done, the joint will be of smaller 
 diameter than the telegraph joint. 
 
 In either method, work the wrapping tightly with the pliers and be 
 careful to have no protruding ends. The joints, unless sleeves are 
 used, should show about 2 inches of bare wire when wound. With 
 sleeve only a little bare wire should show on either end of the sleeve. 
 Be careful not to touch the beveled insulation with the fingers, and 
 handle the bare wire as little as possible. 
 
 Now cover the bevels and joints with a thin coat of okonite rubber 
 
SUBMARINE .MINES, SMALL BOATS, ETC. 421 
 
 cement, allowing the solvent to evaporate thoroughly; cut a two and one- 
 half inch piece of okonite tape with diagonal ends and, beginning at 
 the beveled insulation, cover the joint by applying the tape under such 
 tension that its width is about two-thirds its normal value. 
 
 The layers of tape should overlap and should be stretched as applied, 
 not before beginning the joint. 
 
 Repeat the above with a piece of tape about eight inches long, 
 beginning well back on the insulation. 
 
 If tinfoil be on hand, cover with this and then with Manson tape; 
 heat in the edge of a torch or alcohol flame, turning so as to expose the 
 entire joint until the Manson tape becomes slightly pasty; the time 
 will be about one minute; take off the tape and tinfoil and re-cover 
 with two layers of Manson tape. 
 
 Gasoline or alcohol on a piece of waste answers well for heating 
 joints in a boat. 
 
 The object of heating is to convert the tape into one compact 
 mass which offers the same resistance as the original insulation of the 
 wire. 
 
 The joints may be made without the rubber cement, but it requires 
 much more care in heating to get proper vulcanization. 
 
 Loading Mines. The mine cases are carried from the storeroom 
 to the loading room on the platform cars provided, and placed on the 
 loading skids with the caps up. The caps are removed and placed 
 nearby, washers, nuts, and keys being placed near them. All screw 
 threads are then thoroughly cleaned by use of kerosene and the neces- 
 sary cleaning brushes. The mine case itself should be wiped out, 
 and, if it has been in the water previously, dried out. The explosive 
 detail then brings the explosive from the magazine to the loading room 
 and it is inserted in the mine case through the loading hole. If dynamite 
 is the explosive used, a loading funnel should be placed in the loading 
 hole before any of the cartridges are inserted in the mine case. Care 
 should also be taken that the cartridges are not broken, and that 
 canvas is placed on the floor around and underneath the mine case. 
 Only one box of explosive for each mine being loaded is allowed in the 
 loading room at any one time. When the proper amount of explosive 
 has been placed in the mine case the screw threads are thoroughly 
 cleaned with button brushes and then coated with rubberine or other 
 waterproof material. The compound plugs, having been assembled, 
 are then screwed home with the socket wrench, a loading washer being 
 first placed between the plug and the mine case. Sufficient force 
 should be used in screwing the compound plug home to insure making 
 
422 THE SERVICE OF COAST ARTILLERY 
 
 the joint water-tight. The end of the lever inserted in the openings 
 of the socket wrench should be tapped several times with a mallet to 
 insure tightening. The mine cases are then put in the testing tank, 
 and, if time is available, allowed to remain there for at least twenty-four 
 hours before the test is made to determine whether the circuits have 
 been correctly made and the joints made water-tight. This test can 
 either be made by running or by extending the milliammeter lead 
 from the mining casemate to the loading room and taking a reading 
 of each mine, as is done after planting; or, the test may be made by 
 using a portable voltmeter and four dry cells. The test should show 
 the resistance of the loaded mine to be between 2,200 and 2,400 ohms. 
 
 Duties on the Water. Time will usually be of the utmost importance 
 when a channel is to be mined, and success will very largely depend 
 upon the officer in charge of the harbor mine defense in so arranging 
 the work as to avoid delays and keep everyone constantly and actively 
 employed. For the work on the water specially constructed boats 
 known as "mine planters" are fitted up for quickly placing the mines 
 in position. In addition to a mine planter it is necessary to have at 
 least four small boats. One of these, known as the distribution-box 
 boat, is equipped with a gasoline engine, and should be provided with 
 its own power for hoisting the distribution box and at least a 500-pound 
 anchor. The other three boats are the ordinary yawl boats. Assuming 
 that a group of mines has been loaded, assembled and placed on the 
 planting wharf, the duties on the water would be carried out in some 
 such order as given below: 
 
 The chart showing the approved scheme of mine defense is first 
 consulted and the locations of the distribution boxes noted. These 
 positions are also marked on the mine plotting board. The mine 
 planter, with the necessary buoys and anchors, proceeds to the mine 
 field, and from some prearranged signals from the base-end stations 
 drops anchors with the keg buoys attached at the positions of the 
 distribution boxes as indicated on the mine plotting board. The mine 
 field is next laid out. 
 
 It is next . necessary to take soundings along the line of mines in 
 order to determine the lengths the mooring ropes and the lengths the 
 single conductor cables should be cut. If automatic anchors are used 
 such information as may be required about the depth of water can 
 usually be obtained from charts, but such information is not sufficiently 
 accurate for planting with the ordinary anchors. 
 
 The soundings are made either with the launch from the mine 
 planter or the distribution-box boat assisted by the yawl boats. The 
 
OF THE 
 
 UNIVERSITY 
 
 OF 
 
SUBMARINE MINES, SMALL BOATS, ETC. 423 
 
 launch moves along the line of mines and takes soundings at the proper 
 intervals, these readings being recorded in a blank book showing the 
 number of the mine and the time of day. It is necessary that the tide 
 station be manned during this time and the operator in charge instructed 
 to keep a record of the time of day and the tide readings taken at 
 least every fifteen minutes. 
 
 The planter then lays the multiple cable from the shore terminal 
 to the distribution box for each group. The multiple cable is cut and 
 the end passed to the distribution-box boat, usually by a heaving line. 
 The men in the distribution-box boat make a turk's-head upon the end 
 of the multiple cable and finally put it in the proper slot in the dis- 
 tribution box. As a precautionary measure for recovery of the 
 distribution box should it be pulled overboard during the operations 
 of planting, it is well to buoy the multiple cable about 100 yards in 
 rear of the distribution box. As soon as the end of the cable has been 
 put in the slot, the conductors of the multiple cable are spread out 
 preparatory to identification. 
 
 In numbering the conductors at the mining-casemate end, or shore 
 end, they are numbered clock-wise, commencing with the marked 
 numbers. At the distribution box they are numbered contra-clock- 
 wise, commencing with these same numbers, for communicating with 
 the casemate, the central conductor, is the one to which the boat tele- 
 phone is attached. 
 
 After the ends have been numbered and communication established 
 with the casemate, the casemate electrician then directs the distribution- 
 box boat to prepare the ends of the cable for test. When this has been 
 done word is sent to the casemate electrician, who makes the prescribed 
 test of the cable to determine any leaks. The ends are next tested to 
 determine if they have been properly numbered. 
 
 While these operations have been going on the mines have been 
 taken aboard the planter and arranged for planting, as shown in 
 Plate XXXVII. This is done by the detail on each side of the planter 
 preparing the mines on its side for planting. 
 
 The mine planter then moves out towards the mine field, passing 
 as close to the distribution-box boat as precautions for safety will 
 permit passing it on the starboard; that is, having the distribution- 
 box boat to port. The heaving line is thrown well forward of the 
 distribution-box boat, caught or picked up by the party in the boat and 
 secured at once to a cleat, and after the mine is dropped pulled in and 
 inserted in the proper slot for the mine in question. A temporary 
 joint is then made between it and the proper conductor of the multiple 
 
424 THE SERVICE OF COAST ARTILLERY 
 
 cable and the casemate electrician asked if the mine tests out satis- 
 factorily. 
 
 If the casemate electrician informs the boat party that the mine 
 tests all right the joint is made permanent. 
 
 After the last mine is planted the telephone is first put on the single 
 conductor and the casemate electrician informed that the boat party 
 is ready to make a joint for the last mine planted. When the last 
 joint has been made the distribution box is closed and a buoy rope, 
 attached to a buoy, is made fast to its lid. The anchor of the distribu- 
 tion-box boat is raised and the distribution box then lowered. 
 
 CARE AND PRESERVATION OF EQUIPMENT 
 
 One of the important duties that the personnel of mine companies 
 are called upon to perform is the care and'preservation of the armament, 
 material and equipment, comprising and pertaining to the mine defense, 
 which consists of the following: 
 
 At Fire-Control Stations. Position-finding instruments, plotting 
 boards, prediction rulers, azimuth instruments, telephones, time- 
 interval clock and bell, controller for searchlight and the necessary 
 charts. 
 
 At Mining Casemate. Storage battery, oil engine, generator, power 
 panel, operating boards, casemate transformers, motor generators, and 
 telephones. 
 
 At Loading Room. Telephones, traveling cranes and triplex block, 
 vises, and such tools and material as may be in the loading room for 
 use or purposes of instruction. 
 
 At Cable Tanks. 19-, 7-, and 1-conductor cable, traveling cranes, 
 triplex blocks, and apparatus pertaining to water supply. 
 
 At Boathouse. Submarine-mine yawls, oars, boathooks, oar-locks, 
 ropes and tackle for raising and lowering boats. 
 
 At Storehouse. Mine cases, compound plugs, circuit closers, anchors, 
 anchor shackles, mine shackles, mooring sockets, mooring cable, 
 distribution boxes, junction boxes, ropes, small tools and appliances, 
 traveling cranes and triplex blocks. 
 
 Paints and oils should be kept separate from other stores , either in 
 different buildings or some other convenient place. The floor where 
 such stores are kept must be covered with sand two or three inches 
 thick, and the same renewed at intervals. Kerosene oil must be kept 
 apart from other oils and paint. 
 
SUBMARINE MINES, SMALL BOATS, ETC. 425 
 
 At Magazine. Explosives. Primers and fuses are kept in a sep- 
 arate room of the magazine or some other convenient place. 
 
 At Searchlight Shelter. Searchlight, rheostat, switchboard, tele- 
 phone and necessary appliances. If the searchlight does not receive 
 its power from a central plant, add generating set to the above. 
 
 At Rapid-Fire Gun Batteries. Guns, carriages and necessary 
 equipment and appliances. 
 
 SUPPLIES, TOOLS, ETC., AND THEIR USE. 
 
 The supplies necessary for cleaning mine material are: Kerosene, 
 gasoline, benzene, alcohol, pomade, sandpaper, emery cloth, crocus 
 cloth, and cotton waste. 
 
 The tools used in cleaning mine material are: steel scrapers, wire 
 brushes, paint brushes, button brushes, chamois skin, and soft cloth. 
 
 The supplies necessary for preserving mine material are: cosmic- 
 dense, white and red lead, beef tallow, varnish, raw linseed oil, lard oil, 
 and sperm oil. 
 
 Cosmic-dense is applied to bright parts of oil engines, generators, 
 and motor-generators, when out of commission. It is also applied to 
 brass screw threads, parts of triplex blocks and trolley systems, as well 
 as to all tools that are liable to rust. It should be renewed three times 
 a year. 
 
 White lead is used for painting mines, and in lead tallow mix- 
 ture. 
 
 Red lead is used for the first coat on mines when taken from the 
 water and after rust has been removed; also for first coat on oil engines. 
 The mixture for first coat consists of 100 pounds red lead to 5 gallons 
 raw linseed oil. One gallon of paint to each ten mines. 
 
 Beef tallow (rendered) is used in white lead-tallow mixture for 
 smearing the screw threads of mine cases, steel screw threads of com- 
 pound plugs, bolts, nuts, washers, and all surfaces of flat joints. The 
 mixture consists of one part white lead, to four parts beef tallow. The 
 mixture is melted and applied to surfaces while hot. 
 
 Raw linseed oil is used in paint mixtures. For priming coat: 
 o gallons to each 100 pounds of red ,lead. For painting mine cases 
 neutral gray; 2^- gallons to each '100 pounds white lead, 2J gallons 
 turpentine, 1 gallon liquid dryer, and 1 pound lampblack. 
 
 Asphaltum varnish is used for painting anchors, distribution boxes, 
 fuse cans and plug proper of compound plugs, junction boxes, shackles, 
 sister hooks, and iron work of operating boards and power panels. 
 
426 THE SERVICE OF COAST ARTILLERY 
 
 Lard oil is used for preserving copper or brass parts and screw 
 threads. 
 
 Sperm oil is used on the iron and steel work of electrical instruments, 
 and on tools to keep them free from rust. 
 
 No oil should be used on electrical contacts. 
 
 Care of the Storage Battery. Take daily readings of the pilot cell, 
 making record of specific gravity, voltage, and temperature of the 
 cell. See that the battery is given regular weekly charge at normal 
 rate. Examine the plates with battery lamp for sulphate (white 
 deposit on the negative plate) , buckling, blistering, or anything unusual 
 in their appearance. Always keep electroylite at proper height in 
 each cell (one-half inch from top). Comply carefully with the special 
 instructions issued regarding the care of the storage battery. 
 
 Care of Dynamos and Motor Generators. See that all surfaces are 
 free from rust, dust or dirt. See that oil holes or oilers are kept filled; 
 that all connections are tight; that there are no loose nuts or contacts; 
 that brushes are in good condition, i.e., bear evenly and are not chipped 
 or covered with foreign material; that when brushes are worn they are 
 replaced in due time with new ones. 
 
 The commutator should be smooth, free from grit, and clean 
 throughout; slight inequalities should be removed by running the 
 generator with the brushes off and allowing a block of wood properly 
 beveled and covered with very fine sandpaper (not emery paper) to 
 bear evenly on the rough surface. The machine should be protected 
 with rubber or canvas paulins whenever possible. 
 
 Care of Power Panels or Operating Boards. All connections should 
 be examined to see that they are tight, contacts and switches clean, dry, 
 and free from dust, oil or gum of any description. Switches adjusted 
 so that they are not loose nor wabbly; when thrown they should make 
 or break the circuit evenly and without unnecessary sparking. No 
 verdigris should be allowed anywhere. 
 
 Care of Electric Lights. Lights should be kept clean at all times. 
 Switches should not be permitted to spark badly without being replaced. 
 Burnt-out or dim lamps should be replaced immediately. An extra 
 supply of fuses should be on hand to replace any that may be blown 
 out. Only fuses or fuse wire should be used for this purpose. 
 
 Care of the Oil Engine. All bearings should be kept smooth and well 
 lubricated. Oil cups kept constantly filled. 
 
 Before the engine is started care should be taken to see that the 
 water tank is clean and free from mud or sediment, and that it is full 
 of clean water, the water to be above level of top pipe. Oil tank full 
 
SUBMARINE MINES, SMALL BOATS, ETC. 427 
 
 of kerosene oil. Under no circumstances should gasoline oil be used 
 in the engine. Before starting see that the two cocks which supply 
 water to the vaporizer valve box water jacket are fully open; also 
 the cock on main water pipe from bottom of the tank. The spray nozzle 
 and vaporizer must be kept free from carbon. The piston must be 
 clean and well oiled; the khotal lamps clean, free from soot and always 
 filled. A small bottle of wood alcohol should be at hand for starting 
 up lamps, also asbestos wicks in cups under burners. 
 
 In frosty weather the water must be drained out of the cooling tank, 
 circulating pipes and water jacket, in order to prevent damage from 
 freezing. 
 
 Care of Machinery Being Placed Out of Commission. All bearing 
 surfaces are carefully cleaned and covered with white lead and lard oil 
 (white tallow mixture) ; all small loose parts are removed, covered with 
 cosmic, wrapped in burlap and put in a small box, when practicable. 
 The box should be plainly marked and stored under cover. The machine 
 if not already under cover should be housed or protected in some way. 
 
 Storage of Mines. Mines should be cleaned and painted, the screw 
 threads covered with the lead-tallow mixture and the holes fitted with 
 wooden plugs which have been thoroughly greased. They are then 
 stored on racks or skids in the storeroom. Mine cases should not be 
 stored in contact with each other where it can be avoided. 
 
 Small Boats. A small boat may be defined as any small open 
 vessel moved by oars. Those used in connection with submarine mine 
 work may be either cutters, gigs or yawls, usually the latter. 
 
 The curved piece of timber to which the sides of a boat are united 
 in the fore end is called the stem. The bending or rounded part forward 
 is called the bow or prow. The middle portion is called amidships. The 
 after or rear end is called the stern. Fore implies the portion forward; 
 aft or abaft means toward the stern. The longitudinal timber, or series 
 of timber scarfed together, extending from stem to stern along the 
 bottom is called the keel. That part of the bottom which is broadest 
 and most nearly flat is called the bilge. The width of a boat is expressed 
 as the beam. 
 
 When the boats are constructed of planks running fore-and-aft, 
 their edges meeting but not overlapping, they are called carvel-built. 
 When the planks run fore-and-aft and their edges overlap, they are 
 called clinker-built. When the planks run in a diagonally opposite 
 direction from the outside layer, they are called diagonal-built. The 
 seats on which the crew sit are called thwarts. When two men pull on 
 one oar it is said to be double-banked. Boats are called single- or double- 
 
428 THE SERVICE OF COAST ARTILLERY 
 
 banked, if they have one or two men to a thwart. The space abaft the 
 after thwart is called the stern-sheets. 
 
 The notches for the oars are called rowlocks', if wooden pins are set 
 in the rails they are called thole-pins; if metal forks or stirrups are used 
 they are called oarlocks. Purchases made with two blocks and a length 
 of rope (used for hoisting boats) are called boat-falls. A line made fast 
 to a ring-bolt in the stem is called the painter. 
 
 The upper rail of a boat is called the gunwale. The piece of wood or 
 metal filling across the head of a boat's rudder is called the yoke; lines 
 attached to it are called yoke-lines. The bottom boards of a boat are 
 called floorings or gratings. A small keg used for carrying fresh water 
 is called a boat-breaker. 
 
 The signal used to order boats to return is called boat-recall. 
 
 Boat Drill. The small-boat detachments place in their respective 
 boats the necessary oars, oarlocks, life preservers, buckets, and heaving 
 lines. 
 
 The men are numbered in each detachment as follows: 
 
 Nos. 1-3-5 on starboard oars, No. 1 on bow oar; 
 Nos. 2-4-6 on port oars, No. 2 on bow oar; 
 No. 7 in bow to man boathook or heaving line. 
 Non-commissioned officer at rudder. 
 
 No. 1 enters boat and makes ready to cast off bridles when boat is 
 lowered. All being in readiness, the boats are lowered at once by 
 the remaining members of the crew at the command: Lower. 
 
 When the bridles have been cast off, the No. 1 of each boat mans the 
 boathook, and holds boat alongside the ladder until the remaining 
 members of the crew take their seats. 
 
 Shove Off. At this command, No. 7, the bowman, shoves the boat 
 clear, being eareful to clear the piling in leaving the boathouse or 
 mooring. 
 
 Up Oars. The crew simultaneously seize and raise their oars to 
 the vertical position. The oars being held directly in front of them, 
 the blades fore-and-aft, and the handles clear of the bottom of the 
 boat. The oars are held by hoth hands. 
 
 Let Fall. The oars are lowered quickly into the oarlocks, brought 
 level with gunwale, blades brought horizontal, and all trimmed on 
 the aft oars. 
 
 1. Give Way Together. 2. Give Way. At the first command, the 
 men reach well forward, blades nearly vertical, and get ready for the 
 stroke. At the second command they dip their oars at the same 
 
SUBMARINE MINES, SMALL BOATS, ETC. 429 
 
 time as the stroke oar, and commence rowing, keeping stroke with the 
 men directly in front of them, and all lifting their blades to the height of 
 the gunwale on the return. Oars must not splash under any con- 
 sideration. 
 
 In Bows. In case no extra man is in the bow to man the boat- 
 hook, this command is given when making a landing alongside of a 
 vessel, or a wharf. The bow oarsmen finish their stroke, then " toss " 
 their oars into the boat, and lay them with blade to the bow. No. 1 
 then takes the boat hook and stands ready to fend off and hold the 
 landing. When the boat has sufficient headway to carry it properly 
 to the landing, the command is given. 
 
 Way Enough. This command is given while the oars are in the 
 water; the stroke is finished, and the men toss their oars all together, 
 and lay them in the boat. The oars are put next to the rail, blades 
 towards the bow. The oarsmen remain seated until given further 
 command. 
 
 1. Stand by to lay on oars. 2. Oars. This command is given if it is 
 desired to stop rowing temporarily. At the second command, given 
 while the oars are in the water, they finish their stroke, and bring their 
 oars level with the gunwale, blades horizontal, trimmed on after 
 oars. 
 
 1. Trail. 2. Oars. This command is used in passing under bridges 
 or wharfs where the room is insufficient to toss oars. The second 
 command is given while the oars are in the water; the stroke is finished, 
 the oars thrown out of the oarlocks, and are allowed to trail astern. 
 To bring the oars back inboard the command: Oars, is given. 
 
 1. Give Way, Starboard', Back-port. 2. Give Way. This command 
 is used to turn the boat short around to the port. 
 
 1. Give Way, Port, Back-starboard. 2. Give Way. Same as pre- 
 ceding command, to turn the boat to starboard. 
 
 After either command, when the boat has the desired direction, the 
 command is given: 1. Give way together. 2. Give way. 
 
 Hold Water. This command is given when it is desired to stop 
 the boat's headway. The blades of the oars are held vertically in the 
 water. To resume rowing the command: Oars, is given and the crew 
 takes the position given under the command: Let fall. 
 
 Stern All. This command is given when it is desired to move the 
 boat astern. The crew back water, keeping stroke as in the regular 
 way. To resume rowing in the regular direction, the command: Oars, is 
 given. 
 
 1. Stand by to Toss. 2. Toss. This command is given near the 
 
430 THE SERVICE OF COAST ARTILLERY 
 
 end of a stroke. The oars are raised quickly to the vertical position 
 as in up oars. 
 
 If it is desired to put the oars in the boat, the command: Boat, 
 Oars, is given, at which the oars are lowered towards the bow, and laid 
 in the boat as previously described. 
 
CHAPTER X 
 SEACOAST ENGINEERING 
 
 SE AGO AST engineering may be divided into two general classes. 
 The first comprehends the location, arrangement and construction of 
 emplacements for seacoast armament; while the second appertains to 
 the: (1) Location and measurement of horizontal base lines. (2) Tri- 
 angulation in connection with the location of horizontal base lines, gun 
 centers, and directing points of batteries. (3) The determination of 
 the true azimuth. (4) The location of pintle centers, and orientation 
 of gun and mortar azimuth circles. (5) Leveling. (6) Principles of 
 hydrographic surveying. 
 
 The first division is a function of the National Defense Board and 
 the Corps of Engineers. In this connection fortifications are situated 
 so as to be a reasonable strategic distance outside or in front of the 
 point to be defended, with a view to preventing the ships of the enemy 
 from lying within effective bombarding range of such points without 
 being liable to injury from the armament of such fortifications. 
 
 Consideration is given to the location of gun batteries: (1) With a 
 view to their efficiency under conditions described above. (2) With a 
 view of compelling the enemy to pass them in a clear waterway. (3) 
 With a view of restricting the front of the enemy, if practicable, and at 
 the same time have a convergent fire upon him. (4) With a view of 
 having the batteries at such a distance apart as to prevent the con- 
 centration of the enemy's fire upon them and still allow for mutual 
 support. (5) With a view of not masking or limiting the field of each 
 other's fire and at the same time not permitting the enemy's fire to 
 enfilade nor take them in reverse. (6) With a view to the protection 
 of their flanks and rear so that they cannot be cut off by small landing 
 parties. (7) With a view to their concealment, so that their location, 
 height, and azimuth will not be discovered by the assailants. 
 
 Consideration is given to the location of mortar batteries: (1) With 
 a view to their command of dead angles which cannot be reached by 
 rifle fire. (2) With a view, if practicable, of placing the channel in a 
 
 431 
 
432 THE SERVICE OF COAST ARTILLERY 
 
 single zone. (3) With a view, if practicable, of covering all anchorages 
 in the inner harbor. 
 
 All landing points are, when practicable, covered by rapid-fire guns. 
 
 BASE LINES, ETC. 
 
 Location and Measurement of Horizontal Base Lines. In determin- 
 ing the location of a horizontal base line the following conditions should 
 be fulfilled as far as practicable. (1) Its length should be as long as 
 possible and 2,000 yards when practicable. (2) An uninterrupted view 
 of the whole field of fire, or that portion of the field of fire which the base 
 line is to serve, should be obtainable. (3) Both base ends should be 
 in such position that they will not be exposed unnecessarily to the 
 fire of attacking vessels. (4) Both base ends should be readily access- 
 ible and the stations located so that they are invisible from the field 
 of fire. (5) Base lines crossing water areas should be so located that 
 the communication cables can be protected from raiding parties and 
 are not unnecessarily exposed to anchorage areas. (6) The direction, 
 length and general location of a base line should be such that the lines 
 of sight converging from its ends upon the target at different parts of 
 the field of fire shall intersect at favorable angles, and thus furnish 
 ranges and azimuths to the guns with a minimum of error. (7) The 
 base ends should be so located that observation from the stations will 
 not be interfered with by smoke from the batteries. 
 
 After the location of the base line has been agreed upon the first 
 step is to mark the base ends, which is ordinarily done by sinking a stone 
 post in the earth two or three feet and extending a few inches above 
 the surface of the ground and by indicating on the top of such post a 
 center. This is usually done by drilling a quarter or half inch hole in 
 the stone and putting in a copper plug, the center of the copper plug 
 being marked by the intersection of two of its diameters. 
 
 The actual measurement of a base line is made with steel tapes 
 usually of one-hundred foot lengths. A sufficient number of marking 
 stakes should be erected between the two ends of the base line before 
 the measuring commences. These consist of pieces of scantling about 
 3 or 4 inches in cross section or even less, sharpened at one end, and 
 sufficiently long to project about one and one-half feet above the 
 surface when driven firmly in the earth. The upper end should be 
 capped with a strip of zinc or tin. The stakes are aligned from the 
 initial point by setting a transit up, sighting on the opposite end of the 
 
SEACOAST ENGINEERING 433 
 
 base line and then clamping the instrument in the direction of the pro- 
 posed line. The marking stakes are then brought into line and driven 
 to approximately the same level. The height of the upper surface of 
 each stake above the assumed datum level should be determined by 
 using the Y level and leveling rod. 
 
 The accuracy required for base lines used in artillery work is taken 
 as 1 in 50,000, that is, a permissible error of one foot in 50,000 feet. In 
 order to obtain this degree of accuracy the temperature of the tape 
 at the time of measurement, to the nearest degree, must be taken; the 
 slope determined by stretching over stakes whose elevation above a 
 given datum are known, and the pull on the tape measured by spring 
 balances. The work should be done in cloudy weather and with little 
 wind. 
 
 The actual measurement of the base line is conducted as follows: 
 The tape is stretched over two stakes by two assistants, one in rear of 
 the rear stake and one in front of the forward stake. The spring 
 balance is attached at the forward end, and in stretching care must be 
 taken not to bring a strain on either stake. The rear end graduation 
 is made to coincide exactly with the initial point or a scratch on the 
 zinc cap of the marking stake which indicates the forward end of the 
 previous tape length. A pull of from 10 to 15 pounds is applied and 
 when the tape is sufficiently stretched the forward end is marked. 
 The thermometer should be carried about the height of the tape 
 when stretched and in such position as not to be affected by the heat 
 of the body. A reading should be taken as each stake is marked. The 
 process is repeated from one marking stake to the other until the end 
 of the base line is reached. An accurate record of the data should be 
 made. The tape should never be dragged on the ground on account 
 of possible injury thereto and the variation which would be caused in 
 the temperature of the same. The line should be measured at least 
 twice and any discrepancy at the last stake being measured by a finely 
 graduated scale. 
 
 For the accuracy desired in artillery base lines the tape should 
 not be stretched by hand, as it is impossible to hold the tape graduation 
 steady at a given point or to apply a steady pull. Any device which 
 can be placed firmly in position and which involves the principle of the 
 lever or the screw should be used to get a steady pull on the tape. 
 
 The base line having been found to consist of a certain number 
 of tape lengths, it is necessary to know the horizontal distances between 
 the ends of tape lengths before the length of the base line can be 
 calculated. These will differ among themselves on account of the 
 
434 THE SERVICE OF COAST ARTILLERY 
 
 difference in slope, temperature, etc. It is, therefore, necessary to know 
 the distance between the end marks of the tape under one set of 
 conditions as to temperature, tension and sag, in order that its length 
 under any other conditions may be calculated. 
 
 If these data cannot be obtained from the maker, recourse may be 
 had to the National Bureau of Standards, Treasury Department, where 
 the determination for tapes up to 300 feet in length is made free of 
 charge. This information will usually be given in the following form: 
 Its graduated length, say 75 feet, is the true distance between its end 
 graduations when the tape is subjected to a certain stated pull (P), 
 at a certain stated temperature (T), and when supported at points a 
 certain stated distance (/)) apart. If the tape is supported throughout 
 its entire length as when lying on a level surface, d =0. 
 
 These are called standard conditions, and will usually differ in one 
 or more particulars from those actually existing or employed at the 
 time the base line is measured. Each measured tape length therefore 
 must receive corrections in order to obtain its actual length under the 
 actual conditions. The number of these corrections are in general as 
 follows: Correction of slope or difference of level; correction for temper- 
 ature; correction for sag and correction for pull or stretch of metal. 
 
 It is thought that a clearer understanding of the method of making 
 these corrections will be obtained by taking the following example : 
 
 DATA FOR STEEL TAPE 
 
 Horizontal distance between its end graduations is 75 feet = 900" 
 when the tape is at 62 F. ; pull 10 Ibs. ; and when supported at its 
 middle point (d = 450"). 
 
 = 0.0562; log = 4.79239-10; 
 
 E = 28,200,000 ; log E = 7.45025 ; 
 
 TF = 0.0 3 68 Ibs.; \ogW = 6.83251- 10; 
 
 = 0.0024 sq.in. log S = 7.38021- 10. 
 
 PROBLEM 
 
 Measuring " base line," making all necessary corrections, i.e., slope, 
 temperature, sag and pull. 
 
 The following instruments and accessories are used in the field 
 work: 
 
SEACOAST ENGINEERING 
 
 435 
 
 Transit and tripod (complete). 
 
 Y level " " 
 
 Leveling-rod. 
 
 75 ft. steel tape. 
 
 Spring balances. 
 
 Devices for applying pull on tape (front and rear), 
 
 Stakes (2"X4", zinc-capped) (6) . 
 
 Malls (2). 
 
 Thermometer (1). 
 
 Penknife (to mark on zinc cap) . 
 
 DATA 
 L =75 ft. = 900" 
 
 P=13 Ibs. 
 
 Levels. 
 
 1. 3.478' 
 
 2. 3.264' 
 
 3. 3.785' 
 
 4. 3.795' 
 
 5. 3.104' 
 
 6. 3.098' 
 
 1. CORRECTION FOR SLOPE: 
 
 3.478' 
 3.264' 
 
 0.214' = 2.568" = hi. 
 
 3.795' 
 
 3.785' 
 
 Temperatures. 
 84 1st tape length 
 82 2d " " 
 86 3d " " 
 86 4th " " 
 87 5th " 
 
 5)425 C 
 
 85 = mean temperature. 
 
 3.785' 
 3.264' 
 
 0.521' = 6.252" = h 2 . 
 
 3.795' 
 
 3.104' 
 
 0.691' = 8.292 
 
 3.104' 
 3.098' 
 
 0.006' = .072" = h 5 . 
 
 log 2.568"= .4095950 
 2 
 
 log (2.568) 2 = .8181900 = 6.59462 = h l 2 . 
 
436 THE SERVICE OF COAST ARTILLERY 
 
 log 6.252"= .796019 
 2 
 
 log (6.252) 2 = 1.592038 = 39.088 = /i 2 2 
 h 3 2 = (.120) 2 = .0144 
 log 8.292 =: .9186593 
 2 
 
 log (8.292) 2 = 1.8373186 = 68.7573 = h 
 /i 5 2 = (.072) 2 = .005184 
 
 /H 2 = 6.59462 
 h 2 2 = 39.08800 
 
 fc 3 2 = .01440 
 
 /i4 2 = 68.75730 
 h 5 2 = .005184 
 
 C 1 
 
 " 2/i 
 
 
 - ~ -063588 
 
 2/i 2 =114.459504n r/ 
 
 2. Correction for Temperature: 
 
 C t = a(r w -7 7 
 = +0.6417 /r . 
 
 3. Correction for Sag: 
 
 c ' = lr(iSS) 2((13)2x(450)2 " (900)2(10)2); 
 
 log 900 = 2.9542425 
 6.8325089 
 
 , 2 
 
 log. 000682 
 
 log 46,777,500 = 7.6700370w 
 
 4.2892973^ 
 log (24X16900) =5.6080979 
 
 log C s = 8.6811994w .-, C s = - .047995". 
 Total C s = -.047995" X5 = 0.239975". 
 
SEACOAST ENGINEERING 437 
 
 4. Correction for Pull. 
 
 (P-P )L_ (13-10)900 ^ 2700 
 p ~ ES ~ 28,200,000 X. 0024 "67680 
 = (7 P =+ 0.03989. 
 
 Total C p = + 0.03989 X 5 = .19945" 
 
 SUMMARY OF CORRECTIONS 
 
 Ci= -0.063588" C t = +0.64170" 
 
 C s = - 0.239975" C p = + 0. 19945" 
 
 -0.303563" +0.84115" 
 
 -0.303563" 
 
 + 0.537587" 
 
 Standard length of tape = 900". 
 
 900" X 5" = 4500" = length of base line under standard conditions. 
 4500" + .54" = 4500. 54"== length of base line under local conditions at 
 
 time of measurement. 
 In feet = 375.0448'. 
 
 Triangulation in Connection with the Location of Horizontal Base 
 Lines, Gun Centers, and Directing Points of Batteries. The triangula- 
 tion stations should, when practicable, be located so that the angles 
 will each be greater than 30 degrees and less than 120 degrees. The 
 transit (see Plate XXIV) should have at least two verniers and the 
 least count should not be greater than 20 seconds. The plate of the 
 ordinary engineers transit given shows in detail its principal parts. 
 
 Before using the instrument it should be put in thorough adjustment, 
 as every transit is liable to and in general possesses errors of both 
 eccentricity and graduation. If the center of motion of the vernier 
 plate does not coincide accurately with the center of the graduated 
 plate, then as the limb is turned, the vernier will have an eccentric 
 motion with reference to the limb manifestly resulting in errors of 
 measurement. In order to eliminate these errors two verniers are 
 used whose zeros are as nearly 180 degrees apart as possible, or three 
 120 degrees apart. The mean of the readings of these verniers is 
 free from errors of eccentricity. An eccentricity of centers of 1-1000 
 inch would cause a maximum error of I' 08" on a six-inch limb with but 
 one vernier. It is not unusual for an instrument to have an eccentricity 
 of several times this amount. 
 
 Errors of graduation are in the main periodic in character, and are 
 
438 THE SERVICE OF COAST ARTILLERY 
 
 due to errors in the dividing engine in which the circles are graduated. 
 The result is a progressive closing of the intervals between successive 
 graduations in certain portions of the limb, followed by a corresponding 
 extension. Such errors are eliminated or minimized by reading each 
 angle on several different portions of the limb a process which is 
 shortened by the use of two or three verniers. 
 
 Accidental errors, as they are called, must also be eliminated as far 
 as possible. Such errors are brought to light in subsequent measure- 
 ments of an angle on the same part of the limb of an instrument with 
 fine readings giving discordant results. They are due to many and often 
 unknown causes such as the difficulty of exactly duplicating a setting 
 of the transit on a given signal pole or target and are sought to be 
 eliminated by making more than one reading of the angle on each of 
 the selected portions of the limb. 
 
 The errors just mentioned are errors found on the most perfectly 
 adjusted instrument. The following adjustments must be carefully 
 made, frequently tested and rectified: 
 
 The adjustment of the plate levels especially must be carefully made. 
 These levels indicate when the vertical axis of the instrument is truly 
 vertical. If this is not so, then the telescope when turned upon its 
 trunnions will not move in a vertical plane, and hence the horizontal 
 angle between two distant stations at different altitudes will not be 
 correctly measured. When the telescope is provided with an attached 
 level we have a very accurate means of testing or rectifying errors of 
 this kind. 
 
 Even when the axis is truly vertical the two standards may be of 
 different lengths due to lack of perfect adjustment, unequal expansion 
 or contraction, etc., thus causing the telescope to again revolve in an 
 oblique plane, and introduce errors similar to those just referred to. 
 Unlike the last, however, these errors may be eliminated by reading 
 the same angle an equal number of 'times with telescope direct and then 
 telescope inverted. To measure an angle with telescope inverted, 
 " tumble" or "transit" the telescope, leaving the trunnions in the same 
 beds, and then turn the vernier plate 180 degrees, or until the telescope 
 points to one of the stations. 
 
 The adopted methods of reading angles in triangulation work for 
 coast artillery is that known as the " repeating method." By this 
 method the limb is clamped in any position and left undisturbed while 
 pointings are made to all visible stations in succession around the 
 horizon, and both verniers read for each pointing. Angles are then 
 found by taking the difference between the proper mean reading. 
 
SEACOAST ENGINEERING 439 
 
 More in detail, the method is as follows: Suppose a transit be set 
 up over the station marked at B (Fig. 68), and accurately leveled. 
 Clamp the vernier plate a little in advance and approximately at zero, 
 but without reference to any particular setting. Turn the telescope on 
 signal at the station A , clamp the limb and do not unclamp it until the 
 set of readings about to be described is completed. Secure accurate 
 bisection of the signal by the vernier tangent screw. Read and record 
 both verniers. Unclamp the vernier, 
 point and read in the same manner 
 on D and then on C. After record- 
 ing the last reading see if the signal 
 remains accurately bisected. If not, 
 perfect the bisection, record the new 
 reading, and from this signal as a start- 
 ing point, proceed around to the left, 
 sighting on the signals successively as 
 before, but in inversed order. These 
 pointings should be entered in the 
 
 notebook as D } meaning telescope direct. Invert the telescope, turn 
 on A, and proceed to the other signals and back again as before, 
 recording the pointings as I, meaning telescope inverted. 
 
 These four pointings on all the signals constitute a set, and 
 in any. set the four pointings on any one signal are evidently read 
 by the verniers at very nearly the same point of the limb. The use 
 of opposite verniers eliminates errors of eccentricity. Inverting 
 the telescope eliminates errors of adjustment in the line of collima. 
 tion and standards. A multiplication of the pointings tends to reduce 
 accidental errors. 
 
 It should be observed that the transit is level and accurately above 
 the station before beginning each set. If, while observing, the levels 
 show a change, they should not be disturbed until the set is finished ; 
 when, if a change is considerable, the entire set of readings should be 
 rejected. The stability of the instrument on its tripod or other support 
 should receive careful attention. 
 
 The successive pointings should be made as rapidly as consistent 
 with accuracy, thus giving them a greater certainty of having them 
 made all under the same conditions, by reducing the time by which 
 unequal temperature affects on the instrument, or changes in illumina- 
 tion of the signal, may occur. 
 
 When the .sun is not obscured, especially in summer, heated air cur- 
 rents are apt to render the image of the signal so unsteady as to make a 
 
440 THE SERVICE OF COAST ARTILLERY 
 
 pointing to it very uncertain. To obtain an accurate bisection of a 
 distant signal, we must have steadiness of air and good definition. It will 
 contribute to accuracy if the transit is shielded artificially from the 
 direct rays of the sun when the weather is not cloudy. 
 
 In a wind when the transit is mounted on a tripod, it will often be 
 found difficult to center it over a station by means of a plumb bob. 
 Advantage may be taken of the method of inclosing the line and bob 
 in a gas or sewer pipe of small bore, supported on the bottom on strips 
 or blocks of wood of just sufficient height to permit seeing that the bob 
 is properly centered under the pipe. 
 
 After these various sets of readings are taken the accurate adjust- 
 ment of the triangle should be made. 
 
 The Determination of the True Azimuth. The azimuth of a line 
 is the horizontal angle between the line and a true south line running 
 from one of its extremities, the angle always being measured from the 
 south point as an origin towards the right; that is, in the same direction 
 as the increasing graduations on a watch. If the direction of the line 
 be between north and east, its azimuth will be between 180 and 270 
 degrees; if between east and south its azimuth will be between 270 
 and 360. The method of determining the true azimuth of a base line 
 in coast artillery work is that known as the determination by stellar 
 observation, or observations on Polaris. 
 
 For example, suppose in Fig. 69 that OT is the base line in question, 
 with the transit accurately centered over the point and a signal or 
 target at the other ; Z, the zenith or point directly overhead as pointed 
 out by a plumb line; HH, the horizon. Planes passing through ZA 
 will cut the sphere in circles all of which intersect the horizon at right 
 angles and pass through the zenith. These are called vertical circles. 
 One of these , ZPN, will pass through the point P where the axis of the 
 earth pierces the surface of the earth called the pole. The projection 
 of the arc ZPN on the surface of the earth gives the true meridian, 
 NOS, and N the north point of the horizon. The arc PN or the 
 altitude of the pole above the horizon is always the latitude of 0, the 
 observers' station, say 37 degrees; the remainder of the quadrant PZ is 
 called the co-latitude and is equal to 53 degrees. 
 
 The line of sight of a transit in perfect adjustment placed at and 
 pointed at N will, when revolved on the trunnions, pass successively 
 through P and Z. If there were a star permanently located at any 
 point in this arc, as at P, the determination of the azimuth OT or the 
 base line would consist simply in measuring with the transit the hori- 
 zontal angle between two objects P and T at unequal heights, in other 
 
SEACOAST ENGINEERING 
 
 441 
 
 words the angle NOT, which is the azimuth of OT reckoned from the 
 north. Increasing this by 180 degrees we will have the true azimuth, 
 SOT. 
 
 It happens, however, that there is no star exactly at the pole P, but 
 Polaris indicated as S t is about one and a fourth degrees from the pole, 
 and is the nearest star which, in the absence of clouds, can be seen 
 readily with the naked eye even in full moonlight. 
 
 So if S is the star, the angle TOB between the star and the line is 
 measured with the transit. After deducting the angle BON between 
 
 FIG. 69. 
 
 the star and the meridian we have the angle NOT, which as before is 
 the azimuth of the base line from the north. 
 
 To an observer facing the north Polaris appears to move in a circle 
 around the pole once in 24 hours in the direction of the arrow indicated 
 on the cut, with a radius of one and a fourth degrees from the pole. (To 
 give some idea of the extent of one and one-fourth degrees on the sphere, 
 it may be remembered that it is one-quarter the distance between the 
 pointers in the Dipper, or the length occupied by two full moons and a 
 half placed side by side.) 
 
 The same is true of all other stars, each within its own radius ; and 
 
442 
 
 THE SERVICE OF COAST ARTILLERY 
 
 this affords a means of both finding Polaris at any hour and locating the 
 pole approximately. The line joining the pointers passes very near 
 to Polaris and the line joining Polaris and the star at the bend of the 
 handle of the Dipper passes over the pole one and a fourth degrees from 
 Polaris. 
 
 TO DETERMINE THE TRUE AZIMUTH 
 
 The mean sun, by whose motion ordinary timepieces are regulated, 
 moves daily around the pole in a circle, with a longer radius but in the 
 same direction as Polaris. Polaris, however, moves a little faster in 
 an angular sense than the sun, completing the circuit 3.94 minutes 
 sooner. Once a year, therefore, the star Polaris will overtake the sun, 
 and the date upon which this occurs is given in the table following: 
 
 TABLE A 
 CIVIL DATES (OR EPOCHS) WHEN POLARIS PASSES THE MEAN SUN 
 
 Year. 
 
 Epoch. 
 April. 
 
 Year. 
 
 Epoch. 
 April. 
 
 Year. 
 
 Epoch. 
 April. 
 
 Year. 
 
 Epoch. 
 April. 
 
 1901 
 
 13 
 
 1909 
 
 13 8 
 
 1917 
 
 14 6 
 
 1925 
 
 15 3 
 
 1902 
 
 13 4 
 
 1910 
 
 14 2 
 
 1918 
 
 15 
 
 1926 
 
 15 6 
 
 1903 
 
 13 7 
 
 1911 
 
 14 5 
 
 1919 
 
 15 3 
 
 1927 
 
 15 9 
 
 1904 
 
 13 1 
 
 1912 
 
 13 9 
 
 1920 
 
 14 7 
 
 1928 
 
 15 3 
 
 1905 
 
 13 4 
 
 1913 
 
 14 2 
 
 1921 
 
 15 
 
 1929 
 
 15 6 
 
 1906 
 
 13 8 
 
 1914 
 
 14 6 
 
 1922 
 
 15 3 
 
 1930 
 
 15 9 
 
 1907 
 
 14 1 
 
 1915 
 
 14 9 
 
 1923 
 
 15 6 
 
 1931 
 
 16 2 
 
 1908 
 
 13 5 
 
 1916 
 
 14 3 
 
 1924 
 
 15 
 
 1932 
 
 15 6 
 
 By the use of this table the position of Polaris in its daily path at 
 any instant during the ensuing year can be determined. In other words, 
 it would be ahead of the sun by 3.94 minutes times the number of days 
 and fraction of a da,v in the interval. The position of the sun itself is 
 known by the use of the corrected watch time. For example, suppose 
 Polaris to pass the mean sun on April 14.1. The civil day beginning 
 at midnight, this date is really 2:24 A.M., April 14th. What is its posi- 
 tion in its circular path on June 24th at 4:30 P.M.? The interval to 
 the nearest tenth is 71.6 days, and 71.6 multiplied by 3.94 equals 4 
 hours and 42 minutes, which is the time Polaris is ahead of the sun. 
 The sun is, as stated, 4^ hours from the meridian. Therefore, Polaris 
 is 9 hours and 12 minutes from the meridian, or, in circular measure, 
 138 degrees from the same. It is in the first half of its daily path, or at 
 
SEACOAST ENGINEERING 
 
 443 
 
 some such point as S prime, in Fig. 69, and the hour angle is indicated 
 by the angle in the figure ZPS prime, which is equal to 138 degrees. In 
 the spherical triangle ZPS prime we have known the side ZP, which 
 is equal to the CO latitude of the station, or 53 degrees; the side S 
 prime, equal to the constant, equal to 1 degree and 13 minutes, and the 
 angle at P, equal to 138 degrees. The angle at Z may therefore be 
 computed, and it is the angular distance of Polaris west of the meridian at 
 4 :30 P.M., June 24th, which is the same as the angle BON on the surface 
 of the earth. By varying the hour angle at P from zero to 360 degrees, 
 a table of azimuths of Polaris at any latitude can be constructed for 
 each hour of the 24. The table for latitude 40 degrees north is given 
 below: 
 
 TABLE B 
 
 ANGULAR DISTANCE OF POLARIS FROM THE MERIDIAN FOR 
 DIFFERENT HOUR-ANGLES (#) IN APRIL, 1900, LATITUDE 40 
 (CALLED THE AZIMUTH OF POLARIS) 
 
 H, hours . . 
 
 
 
 1 
 
 234 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Az. minutes of arc . . 
 
 
 
 25 
 
 49 69 84 
 
 93 
 
 96 
 
 92 
 
 82 
 
 67 
 
 47 
 
 24 
 
 
 
 H, hours . 
 
 24 
 
 ?3 
 
 22 21 20 
 
 19 
 
 18 
 
 17 
 
 16 
 
 15 
 
 14 
 
 13 
 
 12 
 
 
 
 
 
 
 
 
 
 
 
 
 
 TABLE C 
 FACTOR FOR YEAR AND LATITUDE 
 
 Lat. 
 
 1900 
 
 1910 
 
 1920 
 
 1930 
 
 20 
 
 82 
 
 78 
 
 75 
 
 72 
 
 30 
 
 88 
 
 85 
 
 81 
 
 77 
 
 40 
 
 1 00 
 
 96 
 
 92 
 
 87 
 
 50 
 
 1 10 
 
 1 14 
 
 1 09 
 
 1 04 
 
 The problem of determining the true azimuth of a base line consists 
 in measuring at any convenient time the horizontal angle between 
 Polaris and the line to be established and then applying thereto the 
 angular distance of Polaris from the meridian; that is, the angular 
 distance at the moment of observation. The solution of the following 
 problem illustrates the method followed: 
 
444 THE SERVICE OF COAST ARTILLERY 
 
 Find the azimuth of the base line NO, Fig. 69, the latitude of station 
 being 37 degrees, longitude 70 degrees west. The angle between 
 Polaris and the artificial star was 200 degrees. The time of sighting 
 on star by the watch was 10 P.M., July 26, 1904. The watch was 30 
 seconds fast. 
 
 Solution. The transit is adjusted beforehand and by daylight, and 
 set up at the point 0. A post is sunk firmly in the earth at the point 
 T 1 , and on a separate surface are nailed two strips pointing in the 
 direction of the distant station where the observation is to be made, 
 or at the point 0. Between these two stripes a small box opened at the 
 rear is placed and a bullseye lantern is put in with its lens against the 
 front wall of the box. In the top over the lantern a hole is cut for the ' 
 escape of the smoke, and in the front face at the height of the lens a 
 small circular hole is cut through, the box so that the light is visible 
 from the point of observation. This hole should be made very small 
 so that the light will have the appearance of a star when sighted upon 
 with the transit. First with the telescope direct read on star and then 
 on the signal or artificial star. Invert the telescope and read on signal 
 and then on the star. For greater accuracy a second set of readings 
 may be taken. As assumed in the problem, the angle between Polaris 
 and the artificial star was found to be 200 degrees. The solution of the 
 rest of the problem is therefore as follows : 
 
 Corrected watch time=9 h 59 m 30 s standard time. 
 Local time =9 h 59 m 30 s +20 m . 
 15)5 =20 minutes. 
 
 Therefore corrected time of observation = 10 h 19 m 30 s , July 26, 1004. 
 Interval between epochs = 
 
 May 
 
 . .. 31. 
 
 June 
 
 30 
 
 Julv . 
 
 . . . 25.93 
 
 
 
 104.83 days 
 
 3. 94 m X 104.83 =412.99 m =6 h 52 m 59.4 s =time Polaris is in advance 
 of the sun. 
 
 The sun is 10 h 19 m 30 s from the meridian. 
 
 Therefore Polaris is 17 h 12 m 29 s from the meridian = hour angle. 
 
SEACOAST ENGINEERING 445 
 
 From Table B 
 Azimuth Polaris =92.83'+. 
 Correcting (from Table C) for year and latitude. 
 
 1900 1904 1910 
 
 37 .964 .949 .927 
 
 92.83' X. 949 = 88.096' = 1 28. 1' 5" 
 
 Azimuth from N=201 28' 5". 
 " S= 21 28' 5". 
 
 LOCATION OF PINTLE CENTERS 
 
 The center of the true or pintle surface of the ring is the point 
 required. This point may be obtained after the base ring has been set 
 and before the racer has been put in position, or even after the gun and 
 carriage have been mounted. For example, suppose the racer net- 
 to be in position, and that the carriage has not been mounted. A 
 tripod made of pieces of scantling is placed at the center of the pit with 
 legs properly braced to prevent motion, or built up by a box from the 
 center of the pit at the bottom until the upper surface is nearly at the 
 level where it is intended to locate the center of the base ring. Nail on 
 the top of this pile a piece of dressed pine 4x4 feet square for use in 
 making marks with a pencil or sharp pointed instrument. The diameter 
 of the base ring may be found from the official drawings, or it may be 
 measured very closely with a steel tape. With the marking point of 
 a trammel set as nearly as possible to the radius, and with the caliper 
 point bearing at the particular height against the pintle surface, strike 
 an arc across the cap. Do the same at three other points around the 
 ring 90 degrees apart, taking care that the caliper point is always at 
 the same height. If these four arcs all pass through a given point this 
 is the center sought. If not, the distance between the points of the 
 trammel should be altered until two opposite arcs slightly overlap 
 and the two points of intersection come on the cap. Over this point 
 a suitable signal with pointed end may be erected, held in a vertical 
 position by wire guys fitted with turnbuckles, and of sufficient length 
 to be seen from two or more triangulation stations. This will usually 
 require the signal to project above the parapet, necessitating a length 
 of from 15 to 20 feet, according to the caliber of the gun. Sections of 
 gas-pipe fitted together make a good signal, and one having but little 
 flexure. By this signal the pintle center is located by triangulation. 
 
446 
 
 THE SERVICE OF COAST ARTILLERY 
 
 If a trammel is not at hand and one cannot be improvised, the following 
 devices, or others which may suggest themselves, may be employed. 
 
 In Fig. 70, AB is a straightedge of scantling (supported, if necessary, 
 at intermediate points to avoid sag) laid as nearly as practicable over 
 the center, and ab marked or scratched on the cap. AB is bisected by 
 a steel tape, and the point e located, at which a perpendicular to ab is 
 erected in the ordinary manner. The straightedge is then transferred 
 to a position CD, estimated as perpendicular to the former, and the point 
 / determined as was e. The intersection of the perpendiculars at e and 
 / is the center. 
 
 FIG. 70. 
 
 FIG. 71. 
 
 It may be well to mark the points A and B permanently on the 
 straightedge by means of solid stops which will bear against the 
 pintle surface; these stops being a little nearer together than the 
 pintle diameter. The point e may then be marked on the edge once 
 for all. 
 
 Where the base ring is made in two parts, the line connecting the 
 joints is evidently a diameter of the ring, and the straightedge care- 
 fully adjusted along this diameter, and accurately bisected, gives the 
 center. 
 
 In Fig. 71, A Bed represents a scantling T square with the pieces 
 halved into each other, supported as may be necessary, and the inner 
 edge cd bisecting AB at right angles, as shown by a "square." The 
 line cd is marked on the cap, and the T square transferred to a position 
 estimated as perpendicular to the former. The intersection of the 
 two lines cd gives the center. 
 
SEACOAST ENGINEERING 447 
 
 In emplacements for an A. R. F. disappearing carriage, it will be 
 most convenient to use the inner base ring. The central blocking will 
 be very low. In emplacements for non-disappearing carriages (com- 
 monly called barbette) the diameter of the pintle surface is so small, 
 and the center so readily found and tested, that no remark is necessary. 
 
 It will be remembered that for the best results each angle of a 
 triangle should be directly measured in order that a suitable adjustment 
 may be made. In emplacements for disappearing guns, however, 
 whether L. F. or A. R. F., the pintle center cannot be conveniently 
 occupied by a transit (even though the point be carried upward by a 
 plumb line), on account of the diameter of the emplacement, and the 
 height of the parapet, over which, in the general case, it would be 
 necessary to obtain a clear view. 
 
 In barbette emplacements the transit may be very conveniently set 
 over the pintle-center so as to give a free view over the parapet. This 
 point is therefore a very advantageous observation station, and should 
 be always occupied, both as an aid to its own accurate location in the 
 triangulation scheme, and also in the location of reference points in the 
 field of fire for purposes of orientation. 
 
 With mortar emplacements, where the racers have not been put in 
 position, the same methods are applicable as in the case of emplacements 
 for disappearing guns. It will, however, usually be found necessary to 
 locate trigonometrically, not the individual mortar centers, but a single 
 directing point for the battery (which may well be on the parapet) , or 
 at most the centers of the individual pits. In the latter case the center 
 of the rectangle of the four base rings may be easily marked on the floor 
 of each pit with quite sufficient accuracy, and signals erected at these 
 points as before described. It will not be convenient to occupy such 
 pit stations with a transit; but the directing point of the battery 
 should always be occupied. 
 
 In all these cases the verticality of the signal throughout its whole 
 extent should be secured and tested by a transit, immediately before any 
 triangulation work. 
 
 To Find the Center of Motion. When the carriage and gun have been 
 mounted over a base ring properly leveled, the center of motion of the 
 gun, when turned in azimuth, will practically coincide with the center of 
 the pintle surface, and may be found with either barbette or disappear- 
 ing mounts as follows : With the gun in the firing position and at about 
 the limit of its play in azimuth, locate two points of the "line of metal" 
 (or highest element) on each portion of the contour of the gun. Snap 
 a chalk line between these points. This chalk mark on the gun lies 
 
448 THE SERVICE OF COAST ARTILLERY 
 
 directly over the center of the pintle surface. Set up a transit on the 
 parapet at a distance of 50 yards or thereabouts, and depress the gun 
 until the chalk mark is visible throughout its whole extent. (It may 
 be found desirable to raise the transit on blocks one or two feet.) 
 Traverse both gun and transit until by trial the intersection of the cross 
 wires will run accurately along the whole mark as the telescope is elevated 
 and depressed. The transit is now pointing along a diameter of the 
 pintle surface, and must not be disturbed in azimuth. Traverse the gun 
 approximately 90, bring it to elevation, and then move along the 
 chalk mark a pencil, wire, or flat-headed nail inverted, until its base 
 is accurately on the line of sight of the transit. The point thus deter- 
 mined is evidently on two diameters of the pintle surface one indicated 
 by the chalk mark, and one by the line of sight of the transit. It is there- 
 fore at the center which supposition should be tested by traversing 
 the gun through a considerable arc to the right and left. Scratch the 
 chalk mark at the exact point by the pencil or nail. Over this point a 
 small target may be set up and securely fastened to the gun, as a 
 signal for triangulation purposes, and the pintle center located trigo- 
 nometrically thereby. The pattern shown in Fig. 72 has been found 
 to answer perfectly. AB is a half-inch board about 3 by 8 or 10 inches, 
 fastened by brads to two cross shoes, whose lower surfaces are hollowed 
 out to fit the curvature of the gun hoops. Through a hole in the 
 middle of the board passes a small post P, of the proper diameter for 
 a signal, extending 10 or 12 inches above, suitably braced, and a fraction 
 of an inch below. Into the middle of its lower end is driven an iron or 
 steel point so that when the shoes are placed on the gun, this point will 
 just touch the gun or very nearly so. Openings are cut in the board and 
 it is cut away at the sides to allow of properly placing the pin over the 
 point on the chalk mark. The whole may be securely bound in place 
 by twine or straps attached to the parts of the carriage, and will be 
 immovable in any ordinary wind. 
 
 The above method of finding the center of motion applies strictly 
 only to barbette and the later models of disappearing mounts, where the 
 point in question falls either on the body of the piece or the trunnion 
 hoop surfaces which are level when the gun is at zero degrees elevation. 
 In the disappearing model of 1894, however, the point falls on the 
 sloping surface of one of the chase hoops. In observing this point 
 during the triangulation, the post P must be vertical. Therefore, when 
 the piece is traversed 90 degrees in order to locate the pencil or nail as 
 before described; the gun should not be set at zero, but at such elevation 
 that the post will be vertical when in position. This may be accom- 
 
SEACOAST ENGINEERING 
 
 449 
 
 plished by placing the target of Fig. 72 on the hoop in question and 
 testing the verticality of the post by the vertical motion of the transit, 
 altering the elevation of the gun until the desired result is obtained. 
 The elevation of the gun should not be changed during the subsequent 
 triangulation. 
 
 On account of irregularities in the contour of a gun, it will be found 
 best, in marking the line of metal, to snap the chalk line on each portion 
 of the surface separately, i.e., on the body, on the trunnion band, etc. 
 
 The line of metal may be found as follows: Clear the vent, close the 
 breech and place in the muzzle an open bore sight having white cross 
 
 FIG. 72. 
 
 threads, i.e., fine white cord or fine wire wrapped with white insulating 
 material. 
 
 Set up a transit on the parapet as before, point into the muzzle and 
 by elevating and traversing both gun and transit, bring the cross wires 
 of the transit, the cross threads in the muzzle, and the axis of the vent 
 in line. Depress the gun, and with the vertical wire of the transit, locate 
 by a pencil or other sharp point several points of the line of metal and 
 snap a chalk line as before. 
 
 With mortars, the problem of location of the directing point of the 
 battery or of the centers of the different pits, is evidently the same as 
 before the mortars were mounted. 
 
 Orientation of Gun and Mortar Azimuth Circles. These circles, 
 when received from the arsenals, have the degree marks cut on them, 
 but the proper numbering of the marks is necessarily postponed until 
 
450 
 
 THE SERVICE OF COAST ARTILLERY 
 
 the circles are in position. A brass subscale, whose least reading is 
 five one-hundredths, is screwed to the racer the screw holes being 
 slotted to permit of lateral movement and adjustment of the scale. 
 The complete orientation of a circle consists in the proper .numbering 
 of the degree marks, and the proper setting of the subscale, so that 
 when the gun points to the true South the reading shall be 0, or when 
 pointing to any object whose azimuth is known, the reading shall be 
 that azimuth. 
 
 1. Guns. In order to do this, and as a check from time to time 
 in the future, the azimuth from the pintle-center of one or more points 
 in the field of fire should be accurately determined. These points may be 
 either natural or artificial, but must be clearly visible through the 
 bore of the gun. For example, the tip of a lighthouse or other tower, 
 a spire, the vertical edge of a structure, a certain pile of a distant wharf, 
 
 FIG. 73. 
 
 or a pile or other target specially erected, a paint-mark on a vertical 
 rock cliff, or a flagstaff, would all answer. The azimuth of such points 
 from the guns should be found at the same time that the gun pintles are 
 located. For example, in case the pintle centers have been occupied 
 by a transit as on barbette mounts, the azimuth from the gun of any 
 object in the field of fire may be directly determined at the same time 
 by measuring the angle between one of the base ends (or other established 
 point) and the object in question. As this, however, does not of itself 
 give the range to such points, it is usual to determine both their range 
 and azimuth by triangulation. Thus in Fig. 73, if EF is a line whose 
 azimuth and length are known, G the gun center, and L the reference 
 point in question, then the distance and azimuth of L from G may be 
 found by sighting from E and F on each of the other three points. 
 If G and L can also be used as observing stations, it will add to the 
 accuracy of the determination. A complete solution of the following 
 problem illustrates the method: 
 
SEACOAST ENGINEERING 
 
 451 
 
 PROBLEM. To determine the azimuth and range of "lighthouse" 
 from Gun No. 2, Battery - . Same to be used as datum point 
 
 for orientation of gun. 
 
 Method. The pintle center was located as previously described. 
 
 The following observations were then made: 
 
 Station at 
 
 On. 
 
 Reading. 
 
 Angle. 
 
 Remarks. 
 
 E 
 
 F 
 G 
 
 L 
 
 3 50' 
 60 54' 
 
 117 06' 
 
 57 04' 
 56 12' 
 
 One end of base line. 
 Gun No. 2, Battery . 
 
 Point on Lighthouse. 
 
 113 16' 
 
 F 
 
 G 
 L 
 E 
 
 23 15' 1 
 41 51' / 
 105 48' 
 
 18 36' 
 63 57' 
 
 
 
 
 
 82 33' 
 
 
 See diagram, 'Fig. 73. 
 
 The following table shows the solution: 
 
 TABLE OF DATA 
 
 From 
 
 To 
 
 Azimuth. 
 
 Range, Yards. 
 
 E 
 
 F 
 
 145 47' 23" 
 
 349 184 
 
 F 
 
 E 
 
 325 47' 23" 
 
 349 . 184 
 
 E 
 
 L 
 
 259 03' 23" 
 
 6460.496 
 
 L 
 
 E 
 
 79 03' 23" 
 
 0460 496 
 
 L 
 
 F 
 
 81 50' 23" 
 
 6605.909 
 
 F 
 
 L 
 
 261 50' 23" 
 
 6605.909 
 
 L 
 
 G 
 
 *83 10' 35.1" 
 
 6179.29 
 
 G 
 
 L 
 
 t263 10' 35.1" 
 
 6179.29 
 
 G 
 
 E 
 
 22 51' 23" 
 
 534.341 
 
 E 
 
 . G 
 
 202 51' 23" 
 
 534.341 
 
 G 
 
 F 
 
 63 14' 23" 
 
 452.354 
 
 F 
 
 G 
 
 243 14' 2:;" 
 
 452.354 
 
 By proof method 83' 10' 39.8". 
 
 t By proof method 233 10' 39.8' 
 
 Solution for Azimuth and Range (only) . 
 
 Z FGE = 180 - (18 36' + 63 57') = 40 23'. 
 sin 82 33' : sin 40 23' : : EG : EF. 
 EF sin 82 33' 
 
 /. EG 
 
 sin 40 23' 
 
452 THE SERVICE OF COAST ARTILLERY 
 
 logEF= 3.0201844 
 (in ft.) 
 log sin 82 33'= 9.99632 
 
 13.0165044 
 log sin 40 23'= 9.811505 
 
 log EG = 3.2049994 
 /. EG= 1603.024 ft. = 534.341 yards. 
 Z#LF=180-(63 57' + 57 04' + 56 12') =2 47'. 
 sin6357':sin247'::#L:E'F. 
 j, 7 EF sin 63 57' 
 
 sin 2 47' 
 
 logEF= 3.0201844 
 log sin 63 57'= 9.953475 
 
 12.9736594 
 
 log sin 2 47' = 8.68627 
 
 log EL = 4.2873894 
 /. EL= 19381. 49 ft. = 6460.496 yards. 
 <2 + L=180-56 12' = 123 48'. 
 
 19381.491 - 1603.024 rpo , 
 
 tan i(G- L) = 19381 491 + 1603 .024 
 
 19381.491 19381.491 
 
 1603.024 1603.024 
 
 (1) 17778.467 (2) 20984.515 
 
 log (1)= 4.24990073 
 log cot 28 06'= .27250 
 
 4.52240073 
 
 log (2) =4.3218972 
 
 log tan J(G- L) = .20050353 
 .-. tan KG- )= 57 46' 47.9". 
 *(G + L)=61 54' 
 i(G-L)=5746'47.9" 
 
 G=11940' 47.9" 
 L= 4 07' 12.1" 
 Az. EF (given) = 145 47' 23" 
 113 16' 
 
 Az. #L = 259 03' 23" 
 
SEACOAST ENGINEERING 453 
 
 }// 
 
 Az. LE= 79 03' 23' 
 '= 4 07' 12.1' 
 
 i // 
 
 Az. LG= 83 10' 35.1' 
 
 Az. GL = 263 10' 35.1" = (gun azimuth) 
 
 Sin 119 40' 47.9": :sin 56 12': : 19381.491 :GL. 
 
 19381.491 sin 56 12' 
 '"' ' sin 119 40' 47.9" 
 
 log 19381.491- 4.2873894 
 log sin 56 12'= 9.919595 
 
 14.2069844 
 log sin 119 40' 47.9"= 9.938924 
 
 logGL = 4.2680604 
 /. GL= 18537.87 ft, = 6179.29 yards = range. 
 
 Solution for finding other sides of quadrilateral and as a check on 
 foregoing solution. 
 
 Sin 57 04': sin 40 23'::FG:EF. 
 EFsmo704' 
 
 sin 40 23' 
 \ogEF= 3.0201844 
 log sin 57 04' = 9.92392 
 
 12.9441044 
 
 loo- sin 40 23'= 9.811505 
 logFG= 3.1325994 
 
 /. FG= 1357.0606 ft. = 452.354 yards, 
 sin G:sinF::FL:GL. 
 
 GL sin G 
 ' FL= -sin^ 
 log sin 19 56.2'= 9.53273 
 log(7L= 4.26806 
 
 13.80079 
 log sin 18 36'= 9.50374 
 
 logFL= 4.29705 
 .-. FL= 19817.727 ft. = 6605.909 yards. 
 
454 THE SERVICE OF COAST ARTILLERY 
 
 Proof of Solution for L 's G and L. 
 
 _a _ 19817.729 
 
 "6 "1357.0606 
 tan i(G-L)=tan (x-4 
 log a = 4.29705 
 log 6 = 3. 132599 
 
 log tan z = 1.164451 
 
 .;. x = 86 04.95' 
 (x- 45) =41 04.95' 
 log tan 41 04.95' = 9.940427 
 
 log tan i( + ) = -78580 
 
 log tan i (#-) = .726227 
 i(-L)= 79 21.72' 
 - 80 42' 
 
 /. G= 160 03.72' = 160 03' 43.2" 
 L = 1 20.28'= 1 20' 16.8" 
 
 Having located at least two such reference points, place bore sights 
 in the breech and muzzle of the gun, the sights having black cross 
 threads, and turn the gun on one of the points as L, whose azimuth from 
 G is, for example, 263.17. Loosen the clamp SCI-EWS of trn subscale 
 and slip the scale to the right or left until its .17 division lies directly 
 over some graduation line of the circle the zero of the scale thus being 
 .17 to the left of this line.. By alternate movements of the screws, set 
 them moderately well home, taking care that the subscale does not 
 move. By means of a steel punch stamp this line 263. As the gun 
 now lies the circle reading is 263.17 degrees, as it evidently should 
 when directed on a point whose azimuth is 263.17 degrees. Proceed 
 around the circle to the left, stamping the lines successively 262, 261, 
 etc. Turn the gun on another reference point for verification. If a 
 discrepancy be found to exist the computation of the azimuths of the 
 points should be re-examined. If no error be found, the triangulation 
 should be repeated. When substantial verification has been obtained, 
 the screws should be set fully home, but without inserting dowels, as 
 these prevent subsequent adjustment of the scale. 
 
 Whether the telescopic sight may be substituted in this operation 
 for the bore sights is a matter of calculation and judgment. For 
 example, suppose a sight accurately adjusted to parallelism with the 
 axis of the bore and distant therefrom 4 feet when on the sight standard. 
 
SEACOAST ENGINEERING 455 
 
 If this sight be directed on a reference point 1,000 yards distant, the 
 gun will point 4^ minutes to the right or left, and hence the subscale, 
 if set accordingly, will always be 4^ minutes in error. When firing 
 by Case III this will cause a deviation error of about 13 yards at a range 
 of 10,000 yards. If the sight be nearer the axis, or if it be adjusted 
 to intersect the axis of the bore at 6,000 yards; or if the reference point 
 be more distant or the range less than 10,000 yards, the error will be 
 less. 
 
 Mortars. Since a view of the field of fire from mortar-pits is 
 impossible unless high trestles or blocking be erected, the use of distant 
 reference points in orienting the circles will in general be impossible. 
 There should ; whenever practicable, be at least one permanent point 
 established on the parapet (this may be a cross cut in the concrete), 
 whose azimuth from some visible point is known. From this point 
 a line of known azimuths may be run to a point near the crest of the 
 parapet, over which a transit may be set up, and by elevating the 
 mortars a view through the bore of each obtained. The remainder of 
 the operation is the same as in case of guns. It may be found that a 
 single position of the transit will answer for more than one pit. 
 
 Leveling. The principal leveling problems which need be considered 
 in connection with seacoast works are the determination of the height 
 of gun trunnions, and the trunnions of D. P. F. instruments, above mean 
 low water. 
 
 At each post will be found one or more permanent marks, called 
 " bench marks/' whose location and height above mean low water 
 have been determined and recorded. These data may be obtained 
 either from the artillery engineer of the post, or from the office of the 
 district engineer. The height of any given point above such bench 
 mark is then obtained by leveling, and to this height is added the 
 height of the bench. The result is the height of the given point above 
 mean low water. 
 
 The instruments required are the engineer's Y level and the leveling 
 rod. The adjustments of the former should be carefully made, and 
 to provide a stable rest for the latter during the work, an iron pin may 
 be carried along and driven in the ground as required. 
 
 The difference of level between a bench and any other desired point 
 may be found as follows: Set up the Y level in any convenient position, 
 from which the leveling rod, when held on the bench, will be clearly 
 visible. The rod should be balanced by hand in a vertical position. 
 Read the rod. This reading is called a back sight, and is evident!}' 
 the height of the axis of the telescope above the bench. Pace the 
 
456 THE SERVICE OF COAST ARTILLERY ' 
 
 distance from bench to instrument when possible; if not, carefulty 
 estimate the same. Send the rod forward in the general direction 
 required, a distance equal to the last, determined by pacing or estima- 
 tion. Drive the pin in the ground, and rest the rod vertically on the 
 same. Turn the instrument and read the rod, noting that the bubble 
 is level. This reading is called a foresight, and is evidently the height 
 of the axis of the telescope above the pin. 
 
 The back sight, diminished by the fore sight, is therefore the differ- 
 ence of level between the bench and pin. If the difference be positive, 
 the pin is higher than the bench; if negative, it is lower. It will be noted 
 in the foregoing that the instrument has not been changed in position 
 between the back and foresights. It has simply been turned in azimuth, 
 and its level corrected when necessary. 
 
 Now carry the instrument forward in the general direction required, 
 set up and read on the rod in its last position. This is another back- 
 sight; and in general any reading on the rod held over a point whose 
 height is known, or which may be calculated from previous readings, 
 is called a back sight, while a reading on a point whose height is as yet 
 unknown, is called a fore sight. 
 
 Continue in this manner, taking a back and fore sight at each posi- 
 tion of the instrument, the last fore sight being taken on the rod when 
 resting on the point whose height is required. Then, the sum of the 
 back sights, diminished by the sum of the fore sights, gives the elevation 
 of the final point above the bench. 
 
 For manifest reasons a cloudy day is best suited for this work, and 
 to secure stability of both instrument and rod, one should be selected 
 when there is but little wind. 
 
 For any one position of the instrument, the two sights back and 
 fore should be of about equal length. This eliminates errors due to 
 imperfect adjustment of the instrument. For example, if, when the 
 bubble is in the middle of its tube, the line of sight is inclined 
 upwards by a small angle, then it has this same inclination to the 
 horizontal on both back and fore sights; and if the lengths of the sights 
 are equal, the two rod readings will be equally in excess of their propel 
 values, the error disappearing when their difference is taken. This pre- 
 caution will also eliminate in a considerable degree the effects of unequal 
 refraction which occur, especially in summer, if the sights vary greatly 
 in length. It also eliminates the effect of the earth's curvature, which, 
 at a distance of one-half mile from the bench, amounts to 2 inches, 
 at one mile to 8 inches, at two miles to 2 feet 8 inches, etc., increasing 
 as the square of the distance. 
 
SEACOAST ENGINEERING 457 
 
 i 
 When it is impossible to make the back and foresights of equal 
 
 length, the inequality should be balanced off at the next or some 
 subsequent setting of the instrument, by making the two sights unequal 
 by the same amount in the opposite direction. 
 
 On ground which is nearly level the maximum length of sight 
 permissible depends on the state of the atmosphere. The length should 
 not be so great that the image of the target in the telescope appears 
 to "tremble" or "dance," due to currents of air of unequal density 
 between the instrument and target. In the general case from 100 to 
 200 yards is all that should be attempted for the best results. On 
 sloping ground the sights will necessarily be short. 
 
 When the height of the trunnions of a D. P. F. instrument is required, 
 a scantling or board straightedge 4 to 6 inches in width may be placed 
 on edge across the azimuth table, which has been properly leveled, 
 taking care that it is of sufficient length to project through a window, 
 door, or the sighting slit, clear of the tower and stairways. In order to 
 obtain an exit through the sighting slit, it may be necessary to lay the 
 straightedge on small blocks placed on the azimuth table. In any 
 case it should be suitably supported to prevent flexure, and its hori- 
 zontality secured and tested by a carpenter's or machinist's level. 
 Note the height of the axis of the trunnions above its datum edge, and 
 by means of a steel tape, measure the height of the latter above some 
 staple point on the ground or concrete foundation. With the Y 
 level and leveling rod, find the height of this point above the 
 bench mark as before described. We thus have all the data for 
 finding the height of the D.P.F. instrument trunnions above mean 
 low water. 
 
 Sometimes it may be found convenient to mark the level of the datum 
 edge on the outer surface or some auxiliary portion of the tower, and 
 then find the height of this mark above some point on the ground by 
 the ordinary principles of surveying. A line of levels to the bench will 
 then give the information desired. 
 
 In the case of guns, a knowledge of the heights of their trunnions 
 when in a firing position is necessary in calculating the quadrant eleva- 
 tions. It will often be found practicable to run a line of levels direct 
 from the bench mark to the gun, the last position of the instrument 
 being on the parapet and the rod resting on the cap square. Deducting 
 the radius of the cap square from the difference of level thus found, we 
 have the height of the trunnions. This will often involve zigzagging 
 up the exterior of the parapet, or running a line of levels up a ramp, 
 but may frequently be accomplished by running the line over a gradual 
 
458 
 
 THE SERVICE OF COAST ARTILLERY 
 
 slope to a point at some distance and at such an elevation that a suitable 
 view of the rod held on a cap square may be obtained. 
 
 In some cases it will be more convenient to run a line of levels to a 
 point in rear of the guns, and thence by easy stages to a point on the 
 loading platform; the height of the trunnions above the same being 
 found from the authorized drawings or by steel tape and straightedge. 
 This operation may be reversed if desired. 
 
 Sometimes it will be practicable to set up the Y level, either with 
 or without its tripod, at a point on the superior slope, and read the rod 
 held on a cap square; thus obtaining the height of the instrument above 
 the cap square. This horizontal line of sight may be transferred to a 
 D. P. F. station or other structure, or to a tree or flagstaff, the height 
 above the ground of the point thus marked being measured by a steel 
 tape. Knowing the radius of the cap square and running a line of levels 
 to the bench, we have all the data for finding the height of the gun trun- 
 nions above mean low water. 
 
 Example. Determine height of trunnions of 8" B. L. R. (barbette), 
 above mean low water. 
 
 Station. 
 
 Back Sight (Feet) 
 
 Front Sight (Feet) 
 
 Remarks. 
 
 B.M. XIV. 
 
 8.923 
 
 
 Above mean low water. 
 
 1 
 
 3.429 
 
 4.124 
 
 
 2 
 
 3.852 
 
 0.886 
 
 
 3 
 
 8.201 
 
 0.611 
 
 
 4 
 
 11 All 
 
 0.726 
 
 
 5 
 
 9.654 
 
 0.974 
 
 
 
 45.481 
 
 7.321 
 
 
 
 7.321 
 
 
 
 
 38.160 = 
 
 Height of gun trunnions above mean low water. 
 
 HYDROGRAPHIC SURVEYING 
 
 In some of our harbors it becomes desirable to determine from time 
 to time the changes which may have occurred in the depth or position 
 of one or more of the channels, the depths in certain areas outside 
 the channel, changes in the three and four-fathom contours, etc. The 
 following indicates in outline the methods to be followed in making such 
 a survey. 
 
 In general terms, soundings are made from a tug, launch or open 
 
SEACOAST ENGINEERING 459 
 
 boat at various points over the area in question, the position of the 
 boat at the moment of making the sounding being determined by 
 triangulation either from the shore or the boat. The position may 
 then be plotted on the chart, and the corresponding depth of water, 
 reduced to mean low water, marked thereon. It will be seen, there- 
 fore, that such a survey contemplates the previous determination and 
 accurate location on the chart, of several points on shore which are to 
 be used as points of reference. In other words, it contemplates a 
 shore base line, and a certain amount of triangulation. 
 
 Soundings are made at regular intervals, determined either by 
 time or distance, on straight lines over which the boat is caused to pass, 
 the lines being parallel or approximately so, and normal to the general 
 trend of the shore. These lines should not be farther apart than from 
 75 to 150 yards, and may be as much nearer as the progress of the work 
 shows to be necessary, according to nature of bottom and accuracy 
 desired. On each line soundings should be taken at distances apart 
 not greater than the interval between the lines. 
 
 If the survey is of considerable importance, a second system of 
 lines may be run at right angles to the first and the accuracy of the work 
 checked by the arrangement of interpolated soundings where the lines 
 cross. 
 
 The keeping of the boat on the line is much facilitated by the use 
 of "ranges," that is by two signals placed on the line. The boat is 
 then so steered as to keep on the range thus pointed out. The 
 signals may consist of two poles set on shore at a suitable distance apart, 
 or one pole on shore and a buoy. The range should be marked for each 
 line to be run. When buoys are to be used for the above or any other 
 purpose, their positions must be determined and plotted on the chart 
 in short, they are to be considered simply as additional points in the 
 land triangulation scheme. The same is, of course, true of any signals 
 used to indicate a range. 
 
 A suitable buoy for the purpose may be made of any light wood, 
 6 to 12 inches in diameter at top, from 3 to 5 or 6 feet long, tapering 
 toward the bottom. A through hole bored in the direction of its 
 length permits the insertion and wedging of a flagstaff. To the lower 
 end of this staff, projecting below the end of the float, is attached the 
 buoy rope. Rocks may be used as anchors. Buoys, of course, swing- 
 somewhat with the tide, and are therefore not as reliable as po'nts on 
 land. 
 
CHAPTER XI 
 CORDAGE 
 
 Yarn is formed by twisting together several fibers of hemp or other 
 material used. A number of yarns or threads twisted or spun together 
 form a strand, and three or four of these strands form a rope. 
 
 Rope is cord more than one inch ifc\ circumference, made up of hemp 
 or other fibrous material or of steel or other metallic wire. 
 Hawser is a term applied to large ropes. 
 
 Ropes are ordinarily composed of three strands laid up right-handed, 
 so that when a strand is followed away from the observer the rotation 
 will be clockwise or laid up with the sun. Hawser-laid, plain-laid or 
 right-hand rope is laid up in this manner. (PI. 38, Fig. 1.) 
 
 Shroud-laid Rope contains four strands, usually laid up right- 
 handed round a smaller rope called a heart or core. (PL 38, Fig. 2.) 
 
 Cable-laid Rope contains three right-handed ropes of three strands 
 each, laid up left-handed into one. (PL 38, Fig. 3.) 
 
 Wire Rope contains a number of wires twisted into strands, three to 
 six of which are laid up round a wire or hemp core. It is about three 
 times as strong as hemp rope, but lacks elasticity and is difficult to 
 handle. It is used principally for permanent standing rigging. 
 
 The size of a rope is expressed in inches and fractions thereof, and 
 is measured on the circumference. 
 
 Rope is either tarred or untarred; the latter is usually called white. 
 It is more suitable for tackles than tarred, as there is less waste of power 
 due to stiffness. Tarred rope is more desirable if exposed to moisture. 
 Hawser-laid rope should be coiled with the sun; cable-laid rope 
 against the sun. To allow a free circulation of air large ropes should 
 be coiled and stored on skids. Small ropes may be hung on pins or 
 hooks. Rope should not be coiled wet. Coiled rope should be uncoiled 
 at least once a year and stretched out in the sun for a few days. 
 
 Spun Yarn is made by twisting together loosely two or more tarred 
 yarns. 
 
 Marlin is two-stranded, right-handed. It is made of spun yarn 
 tightly twisted. It is harder and smoother than spun yarn. 
 
 460 
 
CORDAGE 461 
 
 Hambroline is two-stranded, right-handed; roundline three-stranded, 
 right-handed. Both are made of fine left-handed yarns. 
 
 Houseline is three-stranded, left-handed. It is made of finer 
 dressed hemp and has a smoother appearance than spun yarn. 
 
 Hemp Fiber is obtained from the hemp plant. Manila fiber is 
 obtained from a species of plantain. Coir fiber is obtained from the 
 outer husk of the cocoanut. 
 
 Right-handed rope is coiled clockwise. In uncoiling a new hemp 
 rope pass the end which is at the core through the coil to the opposite 
 side and coil it down against its lay to get the turns out without kinking. 
 Wire ropes should be coiled like a figure 8, which enables their being 
 uncoiled without kinking. 
 
 To stretch a rope, lay it out its full length along the ground, make 
 fast one end to a swivel-hook block secured to a holdfast which is clear 
 of the ground; connect the other end with the drum of a capstan or 
 winch. As soon as the capstan is worked sufficiently to make the rope 
 taut it will begin to unlay and spin the block around, thus taking the 
 twist out of the rope. When the required strain has been attained the 
 rope should be left taut for an hour or more and then coiled up. In this 
 way it may be tested for strength as well as stretched. (PL 38, Fig. 4.) 
 
 The Safe Load which can be put on a rope is very much less than 
 the breaking weight. It should not exceed one-third of the standard 
 breaking weight, and when using a worn rope or with live loads it is 
 necessary to use a larger factor of safety. Should any doubt exist as 
 to the condition of the rope a portion of it should be actually strained 
 to its breaking point, and the proper factor of safety applied to the 
 remainder, or the whole rope that is to be used tested with a ten per 
 cent greater pull than the proposed working load to be put on it. 
 
 The breaking weight of hemp rope, hawser-laid, 3-inch, 3-strand, 
 tarred, is 3 tons per fathom (6 feet) of length. Same rope white 4 
 tons. Manila rope hawser-laid tarred 4^ tons. Same rope white 4f 
 tons. Coir rope hawser-laid white 7 tons. Steel wire rope 17 tons. 
 
 The strength of other sizes, from 1 to 4 inches, can be calculated 
 from this on the principle that the strength varies with the square 
 of the circumference of the rope. Larger sizes than 4-inch are not 
 quite as strong in proportion to their size. 
 
 The strength of a chain, when the links are not longer than 5 times 
 the diameter of the iron is: Mean breaking weight in tons =24 times 
 square of diameter of iron in inches. 
 
 The Bight of a rope is any part not an end. A bight is a loop formed 
 by bending or doubling the rope. 
 
462 THE SERVICE OF COAST ARTILLERY 
 
 The Jaws are the open grooves between the strands. A rope is 
 said to be long-jawed or short-jawed as it is loosely or tightly layed up. 
 
 The Running End of a rope is the free end ; and the rest of the rope 
 is the standing part or end. 
 
 Standing Rigging comprises stationary ropes such as guys for sheers, 
 stays for derricks, etc. Guys are made fast to natural or artificial 
 holdfasts. (PI. 40, Fig. 38.) 
 
 Running Rigging comprises ropes running through blocks. (PI. 39, 
 Fig. 54.) 
 
 Whipping is the securing of the end of a rope with twine to prevent 
 it fraying out or unlaying. The method is shown in Plate 38, Figs. 
 5, 6 and 7. 
 
 Worming is filling up the jaws of a rope by laying spun yarn or 
 marlin along them to make a smooth surface for parceling or worming. 
 PI. 38, Fig. 8a shows the method. 
 
 Parceling is wrapping, with the lay of the rope, narrow strips of 
 tarred canvas round it to secure it from injury by water; also to prevent 
 the rope from being chafed or cut when brought against a rough surface 
 or sharp edge. For this latter purpose old rope or canvas suffices. 
 PI. 38, Fig. 86, shows the method. 
 
 Serving is the laying on tightly of spun yarn or other material 
 in turns round and against the lay of the rope. A serving board or 
 mallet is used to draw the service tight. (PL 38, Fig. Sd.) The method 
 is shown in PL 38, Fig. 8c. 
 
 Splicing is joining two ends of a rope together, or joining an end 
 to any part of it, by interweaving the strands in a regular manner. 
 There are three kinds of splices. 
 
 SPLICES 
 
 The Short Splice is used to connect two ends of rope not intended 
 to run through blocks. 
 
 To make the short splice, unlay for a convenient length the ends of 
 the two ropes to be joined, whip the strands of both ropes with fine 
 twine; having placed each of the strands of one rope opposite to and in 
 the interval between the corresponding strands of the other exactly as 
 shown in PL 38, Fig. 9: draw them close together, now hold the end 
 of one rope (the left) and the three strands which come from the opposite 
 rope firmly in the left hand, or if the rope be large tie the strands down 
 with marlin. Take the middle free strand and pass it over the strand of 
 
PLATE XXXVIII 
 
 1. 2. 3. 
 
 PLAIN SHROUD) CABLE 
 
 LAID LAID LAID 
 
 STRETCHING 
 
 WHIPPING 
 
 
 7. 
 "WHIPPING 
 
 28. 29. 30. 31. 
 
 THUMB FIGURE- STEVEDORE'S' % FLEMISH 
 27 . OF-EIGHT 
 
 OVERHAND 
 
 4V. 
 
 RIGGING 
 
CORDAGE 463 
 
 the other rope next to the left of it, then tuck under the second and out 
 between the second and third strands from it, then haul the splice taut. 
 It should now be identical with PL 38, Fig. 10. Now pass each of the 
 other strands in the same manner, first those of one rope and then those 
 of the other, the splice assuming the appearance of PL 38, Fig. 11. 
 Continue this same operation until the strands are used up though 
 three tucks of the strands of each rope are usually sufficient. After 
 the ends have been tucked through once, a neater finish may be obtained 
 by dividing the strands, passing one half of each for the second tuck as 
 described above and cutting off the unused half; for the third tuck 
 repeat the halving of each strand. Finish by hauling the strands well 
 through and flatten by beating with a marlinspike or mallet, and cut 
 the ends of strands off close to the rope and whip the joints with twine. 
 
 Grease may be rubbed in the strands when necessary to make them 
 flexible. 
 
 A tapering pin called a fid, if of wood, and a marlinspike if of iron, 
 should be used to open the span between strands sufficient for the 
 opposite strand to be pulled through in each case. 
 
 The Eye Splice is used to form an eye or loop in a rope. It is made 
 in a manner similar to that of the short splice. The strands are unlaid 
 as far as may be judged necessary to make three tucks. (PL 38, Fig. 12.} 
 The ends of the center and left strand are tucked through the correspond- 
 ing spaces between the strands of the standing part at a point which 
 will make an eye of the required size. (PL 38, Fig. 13.) The splice 
 is then turned over and the remaining strand is tucked under and 
 pointed to the left as indicated in PL 38, Fig. 14. The tucking over 
 and under is then continued as explained for the short splice. 
 
 The Long Splice is made to join ropes intended to run through a 
 block. To make a long splice unlay the ends of the two ropes to be 
 joined to a distance three or four times as great as for a short splice 
 and place them together. Unlay one strand for a considerable distance 
 and fill up the interval as it is unlaid w r ith the opposite strand of the 
 other rope following it up closely as shown in PL 38, Fig. 15. Twist 
 these two ends together as shown in PL 38, Fig. 16, then do the same 
 with two more strands, untwisting the strands in the opposite direction 
 from that of the first. The two remaining strands are twisted together 
 in the place where they were first crossed. Open these last two strands 
 and divide each in two, then make an overhand knot with the opposite 
 halves and lead the ends over the next strand and under the second in 
 the same manner that the strands were passed for the short splice. 
 Trim off the two halves. Do the same with the others that are placed 
 
464 THE SERVICE OF COAST ARTILLERY 
 
 together, dividing, knotting and passing them in the same manner. 
 Before trimming off any of the half strands the rope at the splice should 
 be well stretched. Sometimes the whole strands are knotted, then 
 divided and the half strands passed as described. 
 
 The long splice is from 15 to 40 per cent, weaker at the splice than 
 the rest of the rope. 
 
 Wire Rope is spliced in a somewhat similar manner (PL 38, Fig. 17). 
 This rope is usually six-stranded with a hemp core. The three alternate 
 strands of each of the parts to be spliced are first unlaid to a distance 
 of about nine feet and then cut; the hemp core is also removed the 
 same distance; the rope being first tightly bound with wire at this 
 point. The remaining strands are then unlaid and the two ropes 
 placed together as for a long splice so that the cut strands abut. 
 
 No. 1 cut strand of one rope is then unlaid and the corresponding 
 strand of the other rope is laid up in its place until all but nine inches 
 of the latter has been laid up. No. 2 strand of the first rope is then 
 unlaid and its place is filled in a similar manner by the corresponding 
 strand of the other rope up to about two feet from where the first two 
 strands met, and then each strand is cut about nine inches from where 
 they meet. In this manner all the strands are laid in, first those on 
 one side and then those on the other, the distances between the points 
 where the different ends meet being about two feet, and the whole 
 splice taking up about ten feet. The projecting ends of the strands 
 are then laid into the middle of the rope at these places, the rope being 
 partially untwisted to enable this to be done, and enough of the core 
 being removed to make room for the ends. The rope is then twisted 
 back and well hammered down with wooden mallets, and when the 
 splice has been properly made it cannot be detected after the rope has 
 been running for a day or two. 
 
 An Eye Splice in wire is made in a similar manner to that in rope, 
 but in view of the difficulty and delay involved in splicing wire rope, the 
 parts are often fastened together by means of screw clamps or clips 
 which are quickly and easily applied and give as strong a connection 
 as a splice. 
 
 Pointing is the operation of tapering the end of a rope so that it 
 will enter a hole or block more easily. (PL 38, Fig. 18, 19, and 20.) 
 
 Seizing a rope is to lash two parts of it together, or to lash two 
 ropes together, by means of spun yarn, seizing stuff, or marlin, as shown 
 in PL 38, Fig. 22, c. 
 
 Round Seizing is when the seizing material is wound round both 
 ropes without passing between them as shown in PL 38, Fig. 21. 
 
CORDAGE 465 
 
 Racking Seizing is when the seizing material is wound round the 
 ropes in figures of eight, as shown in PI. 38, Fig. 22, a. 
 
 Nippering is the binding together of two ropes^as parts of a block 
 and fall, to prevent them from slipping when the running end is cast 
 loose. It is done by seizing or passing a loop around them once or 
 twice and passing a spike in the bight and twisting it as shown ^in 
 PL 38, Fig. 22, b. 
 
 Mousing a hook is to seize the point and back to strengthen and 
 prevent it from disengaging itself from anything to which it may be 
 hooked. PL 38, Figs. 23 and 24 show the method; it is secured by a 
 square knot. 
 
 Frapping is used to draw two ropes and hold them while taking up 
 slack. PL 38, Fig. 25, shows the method. 
 
 Inside Clinch is used for fastening a stiff rope to a ring or other 
 object. It is made by passing the ends through the ring or round the 
 object, leading it round the standing part and through the bight, 
 forming a circle; a seizing is then put on the circle (sometimes two 
 seizings are put on), and the clinch will appear as in PL 38, Fig. 23. 
 
 A Strap or Sling is usually made of rope the ends of which are either 
 spliced or tied together. It is passed round the object to be moved, 
 the hook of the tackle being passed through both bights, as shown in 
 PL 39, Fig. 42, c, or through one bight after it has been passed through 
 the other one. 
 
 A Stopper is a short piece of rope, or a gasket used to keep any 
 weight suspended or to take the strain off a rope. 
 
 Lashing is the binding, or making fast, of one object to another by 
 means of ropes. 
 
 Cleats are used to prevent lashing from slipping, made by cutting 
 lengthwise, diagonally, a piece of 6X6 inch scantling 2 feet long. 
 
 Anti-twisters are contrivances employed for preventing the main 
 tackle and guys of sheers and derricks from twisting. They are made 
 by placing a handspike or smooth picket at right angles between the 
 returns as close to the moving block (or block that rotates) as possible, 
 the handspike being kept in place by lashing or drag-rope at one end. 
 held by two men or made fast to a fixed object. Another method 
 is to lash a handspike or capstan bar across the movable or rotating 
 block, with a rope attached to either end of the handspike and held or 
 made fast as before. 
 
 A Leading Block is used when a weight is to be raised and force 
 cannot be applied in the direction in which it would be most effective. 
 A single block is made fast at some point so as to lead the fall in the 
 
466 THE SERVICE OF COAST ARTILLERY 
 
 direction in which it is intended that the weight shall be hauled upon. 
 The rope is passed around the sheave of this block and can then be 
 hauled in the m oak convenient direction. 
 
 KNOTS 
 
 Overhand Knot. PL 38, Fig. 27, shows the method of tying. 
 When drawn up tight it is called a Thumb-knot. 
 
 PI. 38, Fig. 28. Thumb-knot, used to prevent the end of a rope 
 from unlaying, also used as a stopper to prevent the end of a rope from 
 slipping through a ring or eye. 
 
 PI. 38, Fig. 29. Figure-of-eight knot. 
 
 PL 38, Fig. 30. Stevedore's knot. 
 
 PL 38, Fig. 31. Flemish knot. 
 
 PL 38, Fig. 32. Flemish loop. 
 
 PL 38, Fig. 33. Chain knot. 
 
 PL 38, Fig. 34. Square or reef knot. 
 
 PL 38, Fig. 35. Thief knot. 
 
 PL 38, Fig. 36. Granny knot. 
 
 PL 38, Fig. 37. Draw knot. It is untied by pulling at the end, a. 
 
 PL 38, Fig. 38. Running or slip knot. 
 
 PL 38, Figs. 39, 40 and 41. A bowline knot. 
 
 PL 38, Fig. 42. Running bowline. 
 
 PL 38, Fig. 43 and 44. Bowline on a bight. 
 
 PL 38, Fig. 45. Anchor knot or fisherman's bend. 
 
 PL 38, Fig. 46. Prolonge knot. 
 
 PL 38. Fig. 47. Rigging knot. Used to attach guys to a derrick 
 or mast. The opening is placed over the top of the derrick and the 
 four guys are attached to the ends of the rope h and i, and to the loops 
 a and c. * 
 
 PL 38, Fig. 48, 49, and 50. Single wall knot. 
 
 PL 38, Figs. 51 and 52. Crowning a wall knot. Fig. 52 shows the 
 crown at the top, i.e., looking down the rope. 
 
 PL 38, Figs. 53 to 59. Double wall and double crown. 
 
 PL 39, Figs. 1,2, and 3. Single and double diamond knot. 
 
 PL 39, Fi s. 4 to 7. Matthew Walker's knot. 
 
 PL 39, Figs. 8 to 11. Turk's-head. The method used to insure 
 it from slipping is shown in PL 39, Fig. 12; weave the ends as shown 
 in the diamond or the wall knot. 
 
 PL 39, Figs. 13 and 14. Single bend, sheet-bend, single becket or 
 
CORDAGE 467 
 
 weaver's knot. Used for joining two ropes of different sizes or a rope 
 to another one at an eye. 
 
 PI. 39, Fig. 15. Double bend or double becket. 
 
 PL 39, Figs. 16 and 17. Carrick bend, used for joining a hawser 
 or chain. 
 
 PL 39, Fig. 18. Hawser bend. 
 
 HITCHES 
 
 PL 39, Fig. 19. Half hitch. Made by passing the running end, a, 
 of a rope round the rope or spar to which it is to be attached, then round 
 the standing part, 6, and bringing it up to the bight c. It may also be 
 seized to the standing part at d. A safe rule to adopt in all cases where 
 a knot is likely to jam or become untied is to lash the free end to the 
 standing part as shown in PL 39, Fig. 38. 
 
 PL 39, Fig. 20. Two half hitches. Round turn and two half 
 hitches. Same as two half hitches except that a complete turn is first 
 taken round the spar or other object to which the rope is to be attached. 
 
 PL 39, Fig. 21. Rolling hitch. Used to haul a spar or other 
 object in the direction of its length. 
 
 PL 39, Figs. 22 to 25. Clove hitch, sometimes used to fasten a 
 small boat to a pile or a heaving line to a cable. In the latter case one 
 or two half hitches should be taken round the cable with the free end. 
 
 PL 39, Figs. 26 and 27. Magnus hitch, or mooring knot. Used to 
 fasten a mooring rope to a pile. 
 
 PL 39, Fig. 28 and 29. Timber hitch. Used to secure a rope tem- 
 porarily to a spar to lift or haul it. 
 
 PL 39, Fig. 30. Marlinspike hitch or lever hitch. Used to draw 
 a seizing tight. 
 
 PL 39, Fig. 31. Stopper hitch. 
 
 PL 39, Fig. 32. Telegraph hitch. Used to haul a smooth spar in 
 the direction of its length. 
 
 PL 39, Fig. 33. Blackwall hitch. 
 
 PL 39, Fig. 34. Midshipman's hitch. 
 
 PL 39, Figs. 35 to 38. Cat's paw. 
 
 PL 39, Figs. 39 and 40. Sheep shank. Used to shorten a rope 
 without cutting it. 
 
468 THE SERVICE OF COAST ARTILLERY 
 
 STRAPS, ETC. 
 
 PL 39, Figs. 41 and 42. Selvagee made by planting two pickets 
 or pins at a distance apart equal to the intended length; wind rope 
 yarn round them until the selvagee is thick enough for the purpose 
 intended and then bind it together with the same yarn, half-hitched 
 round it at intervals of about 'an inch. The method of applying to a 
 rope is shown in PL 39, Fig. 42. 
 
 PL 39, Figs. 43 to 46. Gasket. Is made of rope unstranded and 
 plaited. 
 
 PL 39, Figs. 47 and 48. Sheer lashing, is used to bind together the 
 legs of sheers in such a way that the lashing will not slip when the 
 weight is suspended from it. The legs are crossed at the end near 
 where the lashing is to be, but with a less angle between them than the 
 legs will have when the sheers will be in position, so that the spreading 
 of the legs will tighten the lashing. Begin with a clove hitch round 
 one leg, then pass as many turns round both legs as may be necessary, 
 ending with two or three frapping turns round the lashing itself and 
 then fast n the end by two half hitches round one leg. 
 
 PL 39, Figs. 49 and 50. Barrel or cask sling. 
 
 BLOCKS AND TACKLES 
 
 PL 39, Fig. 51. A block consists of four parts: the shell or outside 
 framework; the sheave or grooved pulley on which the rope runs; the 
 pin or axle on which the sheave turns; and the strap (when used), made 
 of rope or iron, which encircles the shell and supports the hook and eye 
 of the block. 
 
 A mortised block is made of a single block of wood mortised (cut) 
 to receive one or more sheaves. 
 
 PL 39, Fig. 52. Heavy blocks for artillery purposes are generally 
 made of an iron or steel shell, with single, double, treble or fourfold 
 brass sheaves. 
 
 ' The size of a block is expressed by the length of the shell in inches. 
 A running block is attached to the object to be raised. A standing- 
 block is fixed to the support or holdfast. A leading block is a single 
 standing block used when power cannot be applied directly. 
 
 PL 39, Fig. 53. Snatch block, a single sheave block having an 
 opening in one side to insert the bight of a fall. 
 
PLATE XXXIX 
 
 50. 51. 
 
 BARREL MADE 
 
 SLING BLOCK 
 
 Cordage, etc. 
 
CORDAGE 469 
 
 Tackle is a purchase formed by rigging a rope through one or more 
 blocks working together. 
 
 Purchase, a tackle of any kind for gaining power. 
 
 Simple tackle, consists of one or more blocks rove with a single rope, 
 or fall. (PL 39, Fig. 54.) 
 
 Standing parts, are parts of the rope of a tackle between the fasts 
 and a sheave. 
 
 Running parts, are between the sheaves. 
 
 The fall is the part to which the hauling power is applied. 
 
 PL 40, Figs. 2, 3, and 4. Whip. The simplest form of tackle; it is 
 made by a rope rove through a single block. 
 
 PL 40, Fig. 5. Whip upon whip, so called where the block of one 
 whip is attached to the fall of another. 
 
 PL 40, Fig. 12. Gun tackle is made by reeving a rope through 
 two single blocks and making the standing end fast to the upper block. 
 
 PL 40, Fig. 14. Luff tackle is made by reeving a rope through a 
 single and a double block. Inverted it is called a watch or tail tackle. 
 
 Luff upon luff. A luff tackle upon the fall of another luff tackle 
 is so called. 
 
 Gin tackle consists usually of a double and a treble block, but may 
 consist of a single and a double block. 
 
 PL 40, Fig. 17. Single Burton consists of two single blocks with 
 the fall reeved as shown in the figure. 
 
 PL 40, Fig. 18. Double Burton, a single Burton with an additional 
 whip attached to its fall, the standing part of which is also attached to 
 the weight to be raised. 
 
 PL 40, Fig. 19. Spanish Burton, a gun tackle with a whip attached 
 to its fall. 
 
 PL 40, Fig. 20. Double Spanish Burton, a luff tackle with a whip 
 attached to its fall in the same manner as a Spanish Burton. 
 
 POWER OF TACKLE 
 
 The actual power of any tackle may be approximately calculated 
 from the theoretical power. In obtaining the latter it is assumed the 
 rope or cord used is perfectly flexible, not elastic, and that the blocks 
 have no friction. It is obviously impossible to find such a condition in 
 practice. By the power of a tackle is meant the ratio of the force 
 exerted by it to that applied to the fall. This should, more strictly 
 speaking, be termed force, and not power, as force is that which is 
 gained by a tackle. 
 
470 THE SERVICE OF COAST ARTILLERY 
 
 If a weight W, equal to P pounds, is suspended from one end of a 
 perfectly flexible and inextensible cord passing over any number of 
 frictionless pulleys, a pull equal to P pounds will have to be exerted at 
 the other end of the cord to support this weight, and every intermediate 
 portion of the cord will have a pull upon it equal to P pounds, which is 
 exerted in the direction of the cord. See PL 40, Fig. 1. This is the 
 fundamental principle of the theoretical power of any tackle. 
 
 The theoretical powers of the various tackles illustrated in PL 40, 
 Figs. 1 to 20 inclusive, are shown on the figures themselves. A simple 
 rule of obtaining the gaining power of any tackle is that the force applied 
 multiplied by the number of moving parts is equal to the power gained. 
 For example, PL 40, Fig. 15, shows one standing part (i.e., the part 
 attached from the hook of the upper block to the sheave of the lower 
 block), and four running parts; accordingly the power gained for 
 hoisting is four. The tackle inverted would give a power of five, for 
 the reason in that case the upper part moves, increasing the number 
 of running parts by one. 
 
 LEVERS 
 
 The three orders of levers are shown in PL 40, Figs. 22 to 29, called 
 respectively lever of the first class, second class, and third class. The 
 classification depends entirely on the position of the fulcrum or prop. 
 The fundamental equation of these classes of levers, under the supposi- 
 tion that the lever is straight and that the weight W and force F act 
 at right-angles to it, is as follows: lever arm L is equal to the weight 
 
 Wy.Cl 
 
 W times its lever arm Cl or the counter-lever arm; or F = -. 
 
 L 
 
 When levers are such that the weight and force do not act at right 
 angles to the lever, the perpendicular distances from the fulcrum to the 
 lines of application of the force and weight, as shown in PL 40, Figs. 
 24, 26, and 27, are taken as the lever and counter-lever arms. Taking 
 such distances, the above formula holds good, but it must be remembered 
 that in using a lever of this kind the lever arm and the counter-lever 
 arm do not usually remain constant, but change in might as the lever 
 is moved and the direction of the applied force changes with respect to 
 the lever, see PL 40, Fig. 28. 
 
 The gaining power or mechanical advantage of a simple lever is 
 
 equal to - and that, of a double compound lever is equal to 
 
PLATE XL 
 
 37. (b. ) 
 
 Cordage, etc. 
 
CORDAGE 471 
 
 L U 
 
 X in which L and L', Cl and Cl' pertain to the corresponding 
 
 v> L v> ' 
 
 parts of the two levers, see PL 40, Fig. 29. 
 
 An example of the lever of the second class is shown by the gun 
 represented in PI. 40, Fig. 30. The gun is resting on two supports, 
 the blocking in front of the trunnions representing the fulcrum 
 and the jack under the breech representing the applied force; the 
 weight supported by the jack as well as that supported by the 
 blocking can readily be determined as follows: TF=30 tons, L or ac 
 in the figure =227 inches, d or ab = H2 inches, therefore the applied 
 
 30 V 1 12 
 force or the weight supported by the jack= =14+ tons, and 
 
 _ _ i 
 
 OQ N/ 1 1 5 
 
 the weight supported by the blocking equals =15+ tons. 
 
 REVOLVING LEVERS 
 
 The three classes of revolving levers are shown in PL 40, Figs. 31, 
 32, and 33. The principle of these levers is exactly the same as that 
 enumerated in the foregoing cases. The lengths of the lever and 
 counter-lever arms are in this case the respective radii of the two 
 circles. This variety of levers is exemplified in the windlass of a gin, PL 
 40, Fig. 35; the capstan, PL 40, Fig. 46; and the crab, PL 40, Fig. 47. 
 
 DIFFERENTIAL PULLEY 
 
 The differential pulley embodies the principles of the revolving lever, 
 combined with that of a single movable block. . It consists essentially 
 of two iron pulleys of unequal diameter mounted upon a common axle 
 and rigidly attached to each other; an endless chain passes round the 
 larger pulley A (PL 40, Fig. 34), down round' the movable pulley B 
 and up round the smaller pulley mounted on the same axle with A. 
 The upper pulleys are sprocket wheels in order to prevent the slipping of 
 the chain. Weight is suspended from the lower pulley and the force 
 is applied to the chain at P. An example of the power gained by the 
 tackle, neglecting friction, is as follows: If the radius of the larger pulley 
 is 6 inches, and the small pulley 5 inches, the power of the tackle will be 
 
 /- 
 
 12, and if W equals 1200 Ibs., F would equal 100 Ibs., or 2 . - -12. 
 
 65 
 
472 THE SERVICE OF COAST ARTILLERY 
 
 GINS, ETC. 
 
 The mechanical appliances employed in fortifications for raising 
 weights are Gins, Sheers, Derricks and Cranes. In each case the 
 weight is raised by means of a tackle, either alone or in combination 
 with a Capstan, Crab, or the Drum of a hoisting engine. To raise 
 excessive weights the Hydraulic Jack is used in combination with 
 suitable crib work built up of wooden blocks. 
 
 A Gin is represented in PL 40, Fig. 35. The two poles supporting 
 the windlass are called legs, while the third is called the pry-pole, and is 
 joined with the others at the head by a bolt which also supports a clevis 
 to which the upper block of the tackle is hooked. The windlass is 
 turned by two metal handspikes which fit into brass sockets at each end. 
 Two pawls acting on ratchets at the ends of the windlass keep it from 
 turning backward. 
 
 Shoes consisting of wooden blocks are placed under the lower ends 
 of the two legs and pry-pole called the feet, to keep them from sinking 
 into the ground. That part included between the legs and pry-pole 
 after the gin is raised, is called the inside; the right and left sides are 
 the corresponding right and left sides of a man standing behind the gin 
 and facing it. 
 
 The tackle for hoisting is usually a double and treble block with 
 fall led to the windlass over which it is wound two or more times 
 to keep it from slipping, the slack of the rope being taken up by hand as 
 the windlass revolves. The feet should be as nearly as possible at equal 
 distances from each other and on the same level, in order that the 
 weight may be evenly distributed on the three supports. This is 
 essential when the maximum weight for which the gin is designed is to 
 be raised. A garrison gin, if perfectly sound, is capable of sustaining a 
 weight of 17,000 Ibs. 
 
 The detachment required to put the gin together and handle it with 
 facility is composed of one chief of detachment, one gunner and ten 
 privates. The post of the chief is in rear of the gin, but he goes wherever 
 his presence is necessary. The gunner is on the left side near the head. 
 The odd numbers are on the right, and the even numbers on the left side 
 and facing the gin. PI. 40, Fig. 36, shows their relative positions. The 
 chief of detachment superintends the placing of the windlass, and the 
 gunner the putting together of the head ; assisted by the most expert 
 privates, he reeves the fall, slings the gun or weight to be raised and 
 attends to all knottings and lashings. 
 
 The fall is either reeved on the ground and the upper block then 
 
CORDAGE 473 
 
 hoisted up to its position by means of a rope passing over the clevis; or 
 after the gin is only partly raised the upper block is hooked to the clevis 
 and the lower block to the middle brace, where it is held in the proper 
 position for reeving. The fall is then reeved by the gunner passing 
 the end of the fall through the left sheave of the upper block from 
 without to within, after which it is passed through the sheave of the 
 lower block from within to without, then up and through the upper 
 sheave of the upper block in the same direction as the first time and the 
 end then made fast to the lower block. With a treble upper block it is 
 preferable to pass the rope through the middle sheave first, as it will 
 then lead better. 
 
 Usually the gin is raised t after being put together, by raising the 
 head and bringing up the foot of the pry-pole towards the foot of the 
 leg. To raise the gin, Nos. 1 and 2 take hold of the pry-pole; Nos. 9 
 and 10 each hold down the foot of a leg to keep it from slipping; Nos. 
 3 and 4 remain at the head, and Nos. 5, 6, 7 and 8 apply themselves to 
 the legs on their respective sides. The gunner commands, Heave, and 
 the gin is raised ; shoes being placed under the pry-pole and each leg. 
 
 To move the gin after it has been raised, Nos. 1 and 2 apply them- 
 selves to the pry -pole; Nos. 9 and 10 each place a handspike under the 
 windlass from without and near the legs and assisted by Nos. 7 and 8 
 from within, they lift and move the gin in the direction indicated. 
 
 The gin is lowered and dismantled by the reverse operations pre- 
 scribed in the foregoing. 
 
 A Gin Derrick is represented in PI. 40, Fig. 37 (a and 6). It is a 
 light gin equipped with a gearing for operating the windlass. It is 
 operated like other gins except that the power is applied to the wheels 
 instead of to the handspikes. 
 
 Sheers are represented in PI. 40, Fig. 38. They are composed of 
 two legs of suitable size. The upper end is called the head, the lower 
 end the heel and the part where they are lashed together (as shown in 
 PL 39, Fig. 48) the cross. A gin may be used as sheers by removing the 
 pry-pole, replacing it by a short block of wood of equal thickness, and 
 attaching the guy ropes. Sheers are used for lifting heavy weights 
 over a wall, and for loading and unloading guns, etc. 
 
 The following table gives the approximate size and length of spars 
 required. 
 
 Weight to be Raised. Mean Diameter. Length. 
 
 3 to 5 tons 11 to 13 inches 30 to 40 feet 
 
 5 to 12 " 13 to 16 " 40 to 50 " 
 
 12 to 25 " 16 to 20 " 50 to 60 " 
 
474 THE SERVICE OF COAST ARTILLERY 
 
 In some sheers the legs are connected by a bolt through the head ? 
 as shown in PL 40, Fig. 38, instead of being lashed together as in PL 
 39, Fig. 47. 
 
 The materials necessary to equip a pair of sheers are : 
 
 Gun Tackle. Two single and two double blocks. 
 
 Main Tackle. One double, one treble and one snatch block. 
 
 Cordage. Main tackle fall, 100 fathoms (a fathom is a measure of 
 6 feet) of 3- to 5-inch manila rope; guys, 100 fathoms of 3- to 6-inch 
 manila rope; head lashing, 10 fathoms of 3- to 4-inch manila rope; 
 heel lashing (two each), 10 fathoms of 3- to 4-inch manila rope; con- 
 tingencies, 50 fathoms of 3- to 4-inch manila rope. 
 
 Straps. Main tackle, one fathom long, of 6-inch manila rope; 
 snatch block, one fathom long, of 4-inch manila rope; guys (two), 
 each one fathom long, of 4-inch manila rope; holdfasts (six), each one 
 fathom long, of 4-inch manila rope; contingencies (six), each a half 
 fathom long, of 4-inch manila rope. 
 
 Spun-yarn for mousing, stoppering, etc., one ball of 100 fathoms. 
 Two cleats, to be spiked to the heels about 6 inches from the bottom. 
 Stakes for holdfasts and heel posts; two shoes for heels or one long 
 shoe joining the two heels as in PL 40, Fig. 38. 
 
 TO RIG THE SHEERS 
 
 To rig the sheers, PL 39, Fig. 48, lay the heads of the spars on a 
 trestle about three feet high, so that they cross at about twice their 
 thickness from the upper ends, with the heels in the proper positions 
 and the distance from the cross to each heel exactly the same. Make 
 the sheer lashing, as previously described; or, if a very heavy weight is 
 to be raised, as follows: 
 
 Take a good piece of 3- or 4-inch rope, well stretched, middle 
 it and make fast to one of the legs below the cross; with one end pass 
 the requisite number of racking seizing turns (PL 38, Fig. 21) round 
 both spars, hauling each one taut, and hitch the end to the upper end 
 of the sheer-leg; with the other end pass round-seizing turns round 
 both spars, filling up the spaces between the ropes of the first turns, 
 as far up as the first rope, and pass f rapping turns round all the parts of 
 the lashing between the sheers ; finish with a square knot and seize the 
 ends with spun yarn. If necessary tighten up the lashing with wedges. 
 
 A guy strap having the splice in the center, so that the splice cannot 
 come into either bight, is then laid between the spars above the cross 
 
CORDAGE 475 
 
 and equally divided, each end led round the spar farthest away from 
 the guy for which it is intended, the ends brought back round both 
 spars, for the upper guy block to be hooked to, or the guy rope itself 
 is attached to the guy strap. The other guy strap is put on in the same 
 manner, the strain on each guy thus tending to bind the spars together. 
 
 The main tackle sling is then put on over the cross from front to 
 rear, passing over the guy straps and under the bights for the headblocks 
 (PL 39, Fig. 48.) The upper block of the main tackle is then hooked 
 through both bights of the main sling and the hook moused. 
 
 Sink or lash the shoes in proper positions. They must be on the same 
 level, and, in bad ground, prevented from sinking or slipping by placing 
 planks, brushwood or timber underneath, securing them by pickets. 
 Pickets are then driven as holdfasts for the foot ropes; for the lighter 
 sheers, two for each foot, one in front and one in rear of the shoes, so 
 as to be just inside the heels of the legs when they are on the ground and 
 a few feet to the front and rear of the shoes. For the heavier sheers 
 four are required for each foot. Make a clove-hitch with the middle of a 
 foot rope round each leg below the cleats and lead the ends to opposite 
 holdfasts where they are made fast. 
 
 Put down the holdfasts for the rear and front guys. The kind of 
 holdfasts to be used will depend upon the strain on them, the nature of 
 the ground, etc. Those shown in PL 40, Figs. 39, 40, 41, or some 
 modification of them, will generally be used, but sometimes the holdfast 
 for the rear guy will have to be sunk in the ground as in PL 40, Fig. 42, to 
 obtain a firm hold. Care must be taken to have both holdfasts on the 
 line FG (PL 40, Fig. 44) perpendicular to the line joining the heels of 
 the sheers at its middle point. 
 
 Hook the upper blocks of the guy tackles to a bowline in the end of 
 the guys, or to the guy straps, and the lower blocks to the holdfast 
 straps, and mouse all the hooks. Ordinarily the fore guy can be worked 
 without a tackle, belaying it over the holdfasts, first taking a round turn 
 over the next one to the sheers, but if the sheers have to be inclined to 
 the rear with the weight on them, the front guy should also be provided 
 with a tackle, and be as carefully secured as the rear guy. 
 
 If the sheers are not too heavy they may be raised by lifting the head 
 and hauling on the proper guy tackle, slacking the heel lashings as 
 required, and tending the opposite guy carefully to prevent the sheers 
 from falling over after passing the vertical. 
 
 If the sheers are too heavy to raise in this way, form a crutch by 
 lashing together two poles, or the legs of a gin, near their upper ends, 
 the feet of the crutch being slightly in rear of the heels of the sheers and 
 
476 THE SERVICE OF COAST ARTILLERY 
 
 temporarily secured to prevent them from slipping. Lay the rear 
 guy over the crutch and raise the crutch by means of two light guy 
 ropes until it is inclined at an angle of about 45 degrees to the front. 
 Haul on the rear sheer guy, allowing the crutch to rise as the sheers rise. 
 After the sheers are raised high enough so that the crutch ceases to act 
 it is lowered by means of its guy ropes. In general, the inclination or 
 rake of the sheers should not exceed 20 degrees, or four-elevenths of 
 their height. In this position the pull on the guy will not exceed one- 
 half the weight. An allowance of 7 or 8 degrees in the rake should be 
 made for the stretch of the guys. 
 
 After the sheers are raised hook the snatch block to a strap placed 
 below the cleat on one of the legs, or to a holdfast placed in a convenient 
 position. 
 
 PL 40, Fig. 44, represents in plan the position of the sheers, holdfast, 
 etc 
 
 AD, BC are the legs of the sheers. 
 
 F, the front guy holdfast. 
 
 G, the rear guy holdfast. 
 
 E, the center of the line AB at right angles to FG. 
 
 AC=BC. 
 
 The splay AB = J CE. 
 
 EF and EG=at least 2 AC. 
 
 DERRICKS AND CRANES 
 
 Derricks are of two kinds, standing and swinging. 
 
 A Standing Derrick (PL 40, Fig. 21) consists of a single spar and 
 is used when a direct lift or slight lateral movement is required. The 
 spar rests on a shoe and is supported in a vertical or slightly inclined 
 position by three or four guys attached to the head, making equal 
 Tingles with each other and secured at distances, from the foot of the 
 derrick, of at least twice the length of the derrick. The strap for 
 supporting the hoisting tackle rests in a groove cut in the top of the 
 spar. The guy blocks are lashed to the head of the derrick, the lashing 
 passing over the strap for the hoisting tackle, binding it to the spar. 
 Foot tackles are used to prevent the derrick from slipping and a snatch 
 block, lashed with a cleat, is secured at the foot through which to lead 
 the fall from the hoisting tackle. The top of the spar can be moved a 
 limited distance by slacking or hauling in on the proper guys, and in 
 this way the weight moved laterally. 
 
CORDAGE 477 
 
 A Swinging Derrick, as shown in PL 40, Fig. 43, consists of two 
 spars, i.e., an upright called the mast, and a swinging spar attached to 
 the mast near its base, called a boom. With this derrick a weight 
 cannot only be raised and lowered, but swung in a circle, of which the 
 base of the mast is the center, and also moved in and out from the mast 
 a distance limited by the length of the boom. The mast is held in a 
 vertical position by three or four guy ropes. Wire ropes fastened to a 
 collar on the top of the mast are usually used when the derrick is to 
 remain erected for some time. The method of supporting the boom, 
 etc., is shown in PL 40, Fig. 43, the fall being led to the drum of a hoisting 
 engine or to a capstan or crab. For steadying the weight and moving 
 it laterally, two smaller guy ropes are usually fastened to the weight or 
 to the block supporting it. 
 
 A Temporary Swinging Derrick may be rigged up by lashing the 
 guys and fastening the lower end of the boom to the mast by a rope sling, 
 and lashing the necessary blocks to the upper end of the boom and 
 mast to support the boom and the weight. 
 
 For steadying the weight and moving it laterally two smaller 
 guy ropes are usually fastened to the weight or to the block 
 supporting it. 
 
 The same precautions should be taken in erecting a derrick and 
 handling a weight with it as in operating with sheers. 
 
 To ascertain the pull on the guys and thrust on the spars of sheers 
 and derricks. Construct on paper or on the ground a diagram similar 
 to PL 40, Fig. 45. 
 
 AD to represent a vertical line. 
 
 AB the inclination of the sheers when supporting the weight. 
 
 AC the inclination of the guys. 
 
 With a scale of equal parts (as large as can be conveniently used) 
 lay off on the line AD, from A, a distance equal to the number of units 
 of weight; through the point E thus found draw EF parallel to AC' until 
 it cuts AB at F. Then the distance EF measured by the same scale will 
 represent the pull on the guy and AF the thrust on the spars. If there 
 are two spars the thrust on each one will evidently be one-half of this, 
 or rather a little more than one-half, depending on the angle which they 
 make with each other. 
 
 It must be borne in mind that the thrust on the sheers is not only 
 that due to the weight lifted, but in addition to this the amount of 
 pull on the end of the fall required to support this weight (see PL 40, 
 Figs. 12, 13, and 14). 
 
 A Crane differs but slightly from a derrick and is used for the same 
 
478 THE SERVICE OF COAST ARTILLERY 
 
 purpose, being usually supported by braces and tie rods, when necessary, 
 instead of by guys. 
 
 Light cranes are used in many of the gun emplacements to lift 
 projectiles up to the loading platform and, in case of the larger barbette 
 non-disappearing carriages, from this platform to the breech of the gun. 
 
 A Capstan (PL 40, Fig. 46), is a machine used as a strong purchase 
 for heaving or hoisting. When so employed it is held in position by 
 strong ropes or chains attached to holdfasts. The rope is passed two 
 or three times round the barrel of the capstan, the free end coming off 
 above the turns, and the standing part being attached to the weight 
 to be moved. The capstan bars are inserted in mortises in the head of 
 the capstan, and the free end of the rope is held and taken in by two 
 men seated on the ground. 
 
 Twelve men, three at each bar, are all that can be advantageously 
 employed. When additional power is required, the bars are swifted, 
 that is, the outer ends of the bars are joined by a rope lashed to each 
 bar for additional men to take hold of. In some cases horse power is 
 used. 
 
 A Crab (PL 40, Fig. 47) is used for the same purpose as a capstan; 
 but with this machine the force it applied to two winches and power is 
 gained by the operation of smaller cog wheels upon larger ones; it being 
 a compound revolving lever. 
 
 The Sling-cart is used for moving guns, or other heavy objects, short 
 distances. There are two kinds: The garrison sling-cart (PL 40, Fig. 
 48), for the heaviest weights, is attached by its pole to a limber, and 
 may be drawn by horses; the hand sling-cart is designed for moving 
 lighter weights by hand. 
 
 With the hand sling-cart the weight is raised sufficiently from the 
 ground to transport it by first attaching a sling of the proper length to 
 the weight to be moved and then raising the pole of the cart enough to 
 permit the hook on the rear of the axle being hooked into this sling. 
 The pole in this case is used as a lever, the axle and wheels being the 
 fulcrum, and the weight is raised by lowering the end of the pole. It 
 may be used for transporting any weight up to 6,000 pounds. 
 
 With the garrison sling-cart the weight is raised by first attaching it 
 to a sling, and then applying the sling to the hooks forming the lower 
 part of a powerful screw passing up through the axle of the cart. Above 
 the axle is the butt of the screw, provided with long handles by means 
 of which the screw is run up, thus raising the weight. 
 
 This sling-cart is capable of supporting 20,000 pounds; but as with 
 such heavy weights it is difficult to turn the handles of the screw to 
 
CORDAGE 479 
 
 raise it; the cart has been modified by substituting a hydraulic jack 
 for the screw. 
 
 A Sling-wagon (PL 40, Fig. 49) is also provided for moving guns 
 or heavy material. In this the weight is raised by means of a hydraulic 
 jack, and supported by pins through the vertical bars, which support 
 the weight. 
 
 THE HYDRAULIC JACK 
 
 This is a lifting apparatus operated by means of a liquid acting 
 against a piston to raise it, the pressure on the liquid being produced 
 by a force pump. There are two kinds of Dudgeon's hydraulic jacks, 
 the base and the horizontal, the principle and method of operation 
 being the same in both. There are also three sizes supplied by the 
 Ordnance Department capable of lifting 15, 20 and 30 tons respect- 
 ively. Both larger and smaller jacks than these are also manufactured, 
 and can be obtained where needed. 
 
 A sectional view of the horizontal jack is shown in Fig. 74, with the 
 names of the different parts. 
 
 Instructions for using. Fill the jack, when the ram is quite down, 
 through the screw-hole in the head, within half an inch from the top, 
 with alcohol 1 part, water 2 parts and add a tablespoonful of sperm oil. 
 
 Never fill with water, kerosene or wood alcohol. Water is dangerous 
 on account of its liability to freeze and to rust the jack when not in use. 
 Kerosene destroys the packings, and wood alcohol corrodes the metal 
 surfaces and destroys the packings. 
 
 Heavy oils and glycerin soften the packings and gum clog the valve 
 ports. 
 
 The screw in the head is not intended to fit tightly, as an air passage 
 is cut in it. 
 
 Be careful that no dirt gets into the reservoir in filling. 
 
 Occasionally clean it out and refill it, as the liquid becomes thick and 
 the jack will not then work well. 
 
 Always keep the ram quite down when not in use. 
 
 In using, place the head or the claw under the weight to be raised. 
 Put in the lever with the projection downward. Work it until the 
 weight is at the required height, or the number of inches the jack runs 
 out. Sometimes it happens that another stroke of the lever will raise 
 the weight too high; then raise the lever and push it down slowly, 
 by which a stroke will be missed. 
 
480 
 
 THE SERVICE OF COAST ARTILLERY 
 
 In most jacks there is a tell-tale hole in the cylinder which lets the 
 liquid out when the ram is raised beyond the safety point. 
 
 To lower the weight with the old-style jacks, push the lever to the 
 bottom of the stroke, take it out, and insert it with the projection 
 upward and with a slight pressure of the hand the weight will be 
 
 PUMP - 
 
 RAM 
 
 6CHE7WT/C -SECTION 
 
 V/ILVES 
 
 SECTION A77V 
 
 A. Ram. 
 
 B. Cylinder. 
 
 C. Reservoir. 
 
 D. Piston cap. 
 
 E. Knuckle. 
 
 F. Pump piston. 
 H. Piston lever. 
 
 b. Ram packing ring. 
 
 c. Ram packing ring nut. 
 
 d. Ram packing. 
 
 /. Pump small nut. 
 g. By-pass channel. 
 h. Pump-valve bonnet. 
 j. Pump-valve spring. 
 k. Nut. 
 I. Packing. 
 
 FIG. 74. 
 
 n. Pump nut. 
 
 p. Piston valve bonnet. 
 
 r. Piston valve, 
 
 s. Piston packing. 
 
 t. Piston packing ring. 
 
 w. Screw-valve tripping rod. 
 
 x. Pump valve. 
 
 lowered as slowly as required, or stopped at any point. Do not push 
 the lever down quickly, but slowly, tapping it a little with the hand. 
 
 If the valve should stick on its seat (in which case the jack will 
 not work), strike the lever a few sharp blows up and down, jarring the 
 valve and removing the difficulty. 
 
 With the latest improved jacks, that have the screw valve w; to 
 raise the weight, screw this valve down tight on its seat with the wheel 
 
CORDAGE 481 
 
 before beginning to pump. To lower, unscrew the same ; two full turns 
 are sufficient to lower as fast as required. , It can be lowered fast or 
 slowly by unscrewing the valve from its seat any distance up to two 
 turns, and can be checked by screwing the valve back to its seat. 
 
 These jacks may be used equally well in horizontal or upright 
 positions except that care must be exercised not to leave them too 
 long in a horizontal position, as there is then a leakage of the liquid 
 through the vent, and the pump, F, must always be submerged in 
 order that it may work. 
 
 A jack not in use should be kept filled and pumped up under pressure 
 at least once a month. 
 
 TO REPAIR JACKS 
 
 Instructions for Repairing Jacks. Trouble with hydraulic jacks 
 is most frequently caused by rust or by foreign substances within the 
 jack and good care is essential to keep a jack in order. Without this, it 
 is useless to expect it to give satisfaction. Rust and sand or grit will 
 soon injure the valves, packings, and polished surfaces of the cylinder 
 and pump, and these are the vulnerable parts of all hydraulic appliances. 
 
 The packing and the valves are very simple, and the following 
 directions will give all the information necessary to keep them in order: 
 
 If the filling flows over the top of the cylinder or through the cylinder 
 vent, the ram packing leaks. Remove the ram from the cylinder, and 
 if the packing is only worn, place a strip of very thin tin under it. If it is 
 broken or torn, unscrew the packing rings, put on a new papking, and 
 replace the rings. If the packing is too large, or if the ram does not run 
 down easily, take off a very little from the outside of the packing with 
 a clean file or rasp. Be careful not to take off too much, for a new 
 packing must be reasonably tight, as it will soon wear smooth. Fit 
 a new packing tight enough to require the weight of two men to force 
 down the ram, for if the packing is made too slack, it will soon leak. The 
 bottom packing seldom gives trouble, and should last for years. If, 
 however, it becomes necessary to renew it, it should be done by driving 
 it from the upper end of the cylinder to the bottom. 
 
 If the piston packing becomes worn, unscrew the head, draw out 
 the piston, renew the packings, and file off the edges to fit the pump. 
 
 To remove the piston of the horizontal jack, unscrew the cap; turn 
 back the socket until the arm is disengaged, and draw out the piston. 
 
 If the valves or valve seats become worn or scratched, unscrew the 
 
482 THE SERVICE OF COAST ARTILLERY 
 
 valve bonnets and regrind the valves with oil and very fine flour of 
 emery. Be careful not to grind the valves too much, and to wash the 
 valves and seat perfectly free from emery before replacing the valves. 
 
 The piston valve of the horizontal jack is reached by removing 
 the piston, as before described, and the pump valve by unscrewing 
 the pump-valve bonnet in the bottom of the cistern. 
 
 If the ram does not rise when pumping, examine the piston valve; 
 if the lever rises when the hand is removed, examine the pump valve. 
 
CHAPTER XII 
 MAGAZINE RIFLE 
 
 THE U. S. magazine rifle, model of 1903, caliber .30, is shown in 
 Fig. 75. It is equipped with a rear sight, model of 1905, a knife bayonet, 
 model of 1905, and gun sling, model of 1907. The appendages of the 
 rifle consist of front sight cover; the oiler and thong case (carried in 
 the butt of the stock), consisting of an oiler and dropper, thong and 
 brush complete. The accessories of the rifle consist of a brass cleaning 
 rod and screw driver. A kit of tools is issued to each company or 
 troop and to each regimental or post ordnance officer for use in repair- 
 ing the rifle and bayonet. 
 
 The rifle proper consists of 89 component parts. The bayonet 
 proper consists of 12 component parts. 
 
 The total weight of the arm, including bayonet, oiler and thong 
 case, is 9.69 pounds. The bayonet weighs 1 pound. 
 
 The total length of the gun, without bayonet, is 43.212 inches. 
 The total length of bayonet, is 20.56 inches. The total length of gun 
 and bayonet (when attached) is 58.96 inches. 
 
 The caliber is .30 of an inch. The rifling consists of four plain 
 grooves, 0.004 inch deep; the grooves are three times the width of the 
 lands. The ^wist of rifling is uniform, one turn in 10 inches. 
 
 The rifle is stamped with the Ordnance escutcheon, together with 
 the initials of the place of manufacture and the month and year; this 
 stamp is on the top in rear of the front sight stud. Those manufactured 
 prior to 1906 are stamped with the year but without the month. 
 
 The magazine holds five cartridges. The trigger pull is equal to 
 from 3 to 4^ pounds, measured at middle point of bow of the trigger. 
 
 The computed maximum range is 5,465 yards, with a time of flight 
 of 31.36 seconds. Elevation 45 degrees. Initial velocity, 2,700 feet 
 per second. Powder pressure in chamber, about 49,000 pounds per 
 square inch. 
 
 483 
 
484 
 
 THE SERVICE OF COAST ARTILLERY 
 
 I 
 
 e 
 
 POINTS IN HANDLING 
 
 If it is desired to carry the piece cocked, with a cartridge in the 
 chamber, the bolt mechanism should be secured by turning the safety 
 
 lock fully to the right. If this is not done 
 the rifle may be discharged upon turning 
 the safety lock fully to the ready position. 
 
 Under no circumstances should the firing 
 pin be let down by hand on a cartridge in 
 the chamber. 
 
 To obtain positive ejection, and to in- 
 sure the bolt catching the top cartridge in 
 magazine, when loading from the magazine, 
 the bolt must be drawn fully to the rear 
 in opening it. 
 
 The piece is habitually carried locked; 
 that is, with the safety lock at the "safe." 
 It is always locked after executing cease 
 firing. 
 
 To prevent accidents, the chamber is 
 opened and the magazine examined when 
 troops are first formed and again just be- 
 fore they are dismissed. When rifles are 
 not in use, as, for instance, when they are 
 in gun racks, etc., the trigger should be 
 pulled to relieve the strain on the spring. 
 
 The cut off is kept turned "off "except 
 when actually using cartridges. 
 
 When the bolt is closed, or slightly for- 
 ward, the cut o/f may be turned up or down, 
 as desired. When the bolt is in its rear- 
 most position, to pass from loading from 
 the magazine to single loading, it is neces- 
 sary to force the top cartridge or follower 
 below the reach of the bolt, to push the 
 bolt slightly forward and to turn the cut 
 off down, showing "off." 
 
 In aiming the rifle, care should be exer- 
 cised that the fingers do not cover the gas 
 escape hole just above and to the rear of the grasping groove on the 
 right side of the piece. 
 
MAGAZINE RIFLE 485 
 
 In case of a misfire it is unsafe to draw back the bolt immediately, 
 as it may be a case of hang fire. In such cases the piece should be 
 cocked by drawing back the cocking piece. 
 
 The bayonet is not fixed except for instruction, in bayonet exercise, 
 on guard, or when needed for purposes of defense or offense. 
 
 Experimental firing and laboratory experiments show that, all 
 other conditions being identical, the muzzle velocity of ammunition 
 loaded with smokeless powder will be increased by exposure to a higher 
 atmospheric temperature, and decreased by a lower. 
 
 Variations in the barometric pressure and the percentage of humidity 
 of the air will also cause variations in the velocity; consequently the 
 elevation for any range will vary slightly with these conditions. More- 
 over, the velocity of 78 feet stamped upon the bandoleers may vary, 
 in different issues of ammunition, 20 feet on either side of the standards. 
 The muzzle velocity obtained in different rifles also varies with the same 
 ammunition. 
 
 In adjusting the sight for elevation at any range, it must be borne 
 in mind that in addition to the allowance made for variations in the 
 velocity of the ammunition, allowance must also be made for the effect 
 of differences in light, the amount of front sight seen, the effect of 
 mirage on the target, the effect of heat developed in the gun in firing, 
 the condition of the bore as to cleanliness, the personal equation of the 
 firer, the peculiarities of individual guns, etc. 
 
 The graduations of the rear sight are correct only for the particular 
 conditions existing when they were experimentally determined, con- 
 sequently, in adjusting the sight for elevation at any range, allowance 
 must be made for whatever change in the elevation the difference 
 between the former and the present conditions produces. 
 
 DISMOUNTING AND ASSEMBLING 
 
 Figure 76 shows the bolt and magazine mechanism. They can be dis- 
 mounted without removing the stock. The latter should never be 
 done, except for making repairs, and then only by some selected and 
 instructed man. 
 
 To Dismount the Bolt Mechanism, place the cut off at the center 
 notch; cock the arm and turn the safety lock to a vertical position; 
 grasp the piece as shown in Fig. 77, raise the bolt handle and draw 
 out the bolt. 
 
 Hold the bolt in the left hand as shown in Fig. 78, press sleeve lock 
 
486 
 
 THE SERVICE OF COAST ARTILLERY 
 
 in with the thumb of right hand to unlock sleeve from bolt and unscrew 
 sleeve by turning to the left. 
 
 Hold the sleeve between the forefinger and thumb of the left hand, 
 draw cocking piece back with the middle finger and thumb of the right 
 
 Cl/T Off Sf/MOif 
 
 CUTOFF &CCTORPIN 
 
 xirc>v./-mtfr STOCK 
 
 FIG. 76. 
 
 hand, turn safety lock down to the left with the forefinger of the right 
 hand, in order to allow the cocking piece to move forward in sleeve, 
 thus partially relieving the tension of mainspring; with the cocking 
 piece against the body, draw back the firing-pin sleeve with the fore- 
 
 FIG. 77. 
 
 finger and thumb of the right hand and hold it in the position shown in 
 Fig. 79, while removing the striker with the left hand; remove firing- 
 pin sleeve and mainspring; pull firing pin out of sleeve; turn the 
 extractor to the right, forcing its tongue out of its groove in the front 
 
MAGAZINE RIFLE 
 
 487 
 
 of the bolt, and force the extractor forward as shown in Fig. 80, until 
 it is off the bolt. 
 
 To Assemble Bolt Mechanism, with the left hand grasp the rear of 
 the bolt, handle up; with the thumb and forefinger of the right hand 
 
 FIG. 78. 
 
 turn the extractor collar until its lug is on a line with the safety lug- 
 on the bolt; take the extractor in the right hand and insert the lug on 
 the collar in the undercuts in the extractor by pushing the extractor to 
 the rear until its tongue comes in contact with the rim on the face of 
 
 COCKING PIECE. 
 \ 
 
 FIG. 79. 
 
 the bolt (a slight pressure with the left thumb on the top of the rear 
 part of the extractor assists in this operation); turn the extractor to 
 the right until it is over the right lug; take the bolt in the right hand 
 
488 
 
 THE SERVICE OF COAST ARTILLERY 
 
 and press the hook of the extractor (Fig. 81) against the butt plate or 
 some rigid object, until the tongue on the extractor enters its groove 
 in the bolt. 
 
 With the safety lock turned down to the left to permit the firing 
 pin to enter the sleeve as far as possible, assemble the sleeve and firing 
 
 FIG. 80. 
 
 pin; place the cocking piece against the body and put on mainspring, 
 firing-pin sleeve, and striker (Fig. 79) ; hold the cocking piece between 
 the thumb and forefinger of the left hand, and by pressing the striker 
 point against some substance, not hard enough to injure it, force the 
 cocking piece back until the safety lock can be turned to the vertical 
 position with the right hand ; insert the firing pin in the bolt and screw 
 
 GROOVE.- 
 
 IXTBACTOR COLLAE. SAFETY LOO. 
 
 FIG. 81. 
 
 up the sleeve (by turning it to the right) until the sleeve lock enters its 
 notch on the bolt. 
 
 See that the cut off is at the center notch; hold the piece under the 
 floor plate with the fingers of the left hand, the thumb extending over the 
 left side of the receiver; take bolt in right hand with safety lock in 
 a vertical position and safety lug up; press rear end of follower down 
 with the left thumb and push bolt into the receiver; lower bolt 
 handle; turn safety lock and cut off down to the left with right hand. 
 
 To Dismount Magazine Mechanism, with the bullet end of a cartridge 
 press on the floor plate catch (through the hole in the floor plate), at 
 
MAGAZINE RIFLE 489 
 
 the same time drawing the bullet to the rear; this releases the floor 
 plate. 
 
 Raise the rear end of the first limb of the magazine spring high 
 enough to clear the lug on the floor plate and draw it out of its mortise ; 
 proceed in the same manner to remove the follower. 
 
 To assemble magazine spring and follower to floor plate, reverse 
 operation of dismounting. 
 
 Insert the follower and magazine spring in the magazine, place the 
 tenon on the front end of the floor plate in its recess in the magazine, 
 then place the lug on the rear end of the floor plate in its slot in the 
 guard, and press the rear end of the floor plate forward and inward at the 
 same time, forcing the floor plate into its seat in the guard. 
 
 CLEANING AND CARE 
 
 As the bore of the rifle is manufactured with great care in order 
 that a high degree of accuracy may be obtained, it should be attentively 
 cared for. The residuum from smokeless powder tends to corrode the 
 bore and should therefore be removed as soon after firing as practicable. 
 The following method has been practiced with good results : Using the 
 cleaning rod and small patches of cloth (preferably canton flannel), 
 clean the bore thoroughly with the patches soaked in a saturated 
 solution of soda and water. Then thoroughly dry the bore and remove 
 the soda solution by the use of dry patches, and finally oil the bore with 
 patches soaked in cosmic oil. Twenty-four hours after this first clean- 
 ing, the bore should be again cleaned as described above, as it has been 
 found that the powder gases are probably forced into the texture of 
 the steel and will, if the second cleaning is not resorted to, cause rusting 
 no matter how thoroughly the bore may have been cleaned at first. 
 If, however, a cleaning rod is not at hand, the barrel should be cleaned 
 as thoroughly as possible by means of the thong brush and rags, and 
 oiled as explained above. 
 
 To clean or oil the bore with rags, the thong brush is unscrewed, 
 the rag placed in the rag slot of the thong tip and drawn from the 
 muzzle toward the breech. 
 
 As neither the ramrod nor jointed cleaning rod is issued with this 
 rifle, the brass cleaning rod should be carried into the field whenever 
 practicable. 
 
 If gas escapes at the base of the cartridge, it will probably enter 
 the well of the bolt through the striker hole. In this case the bolt 
 
490 THE SERVICE OF COAST ARTILLERY 
 
 mechanism must be dismounted and the parts and well of the bolt 
 thoroughly cleaned. 
 
 Before assembling the bolt mechanism, the firing pin, the barrel 
 of the sleeve, the body of the striker, the well of bolt, and all cams should 
 be lightly oiled. 
 
 Many of the parts can generally be cleaned with dry rags. All parts 
 after cleaning should be wiped with an oiled rag. 
 
 The best method of applying oil is to rub with a piece of cotton 
 cloth upon which a few drops of oil have been placed, thereby avoiding 
 the use of an unnecessary amount of oil. This method will, even in 
 the absence of the oiler, serve for the cams and bearings, which should 
 be kept continually oiled. 
 
 Any part that may appear to move hard can generally be freed by 
 the use of a little oil. Sperm oil only should be used for lubricating 
 metallic bearing and contact surfaces. 
 
 For the chamber and bore, only cosmoline or cosmic should be used. 
 This should also be applied to all metallic surfaces, to prevent rusting 
 when arms are stored or when not used for an appreciable length of 
 time. 
 
 The stock and hand guard may be coated with raw linseed oil and 
 polished by rubbing with the hand. 
 
 GUN SLING 
 
 The gun sling, model of 1907, is made of four parts, the long strap, 
 the short strap and two keepers. To assemble it, the plain end of the 
 long strap is passed through the larger keeper, then through the metal 
 loop of the short strap, passing from the undressed to the dressed side 
 of the latter, then back through the larger keeper, forming the arm loop, 
 dressed side out. The same end is then passed through the smaller 
 keeper, through the lower band-sling swivel called the upper sling 
 swivel, from the butt toward the muzzle, and back through the smaller 
 keeper, the arm loop being completed by engaging the claw of the long 
 strap in the proper holes in the other end of same. The size of the 
 arm loop is adjusted to suit the individual who is to fire the piece, the 
 loop being drawn through the upper swivel until the claw comes well up 
 toward the upper swivel. The claw end of the short strap is then passed 
 through the lower swivel from muzzle to butt and brought up and 
 engaged in the proper holes in the long strap, drawing the sling taut. 
 This gives the parade position of the sling. To adjust it for firing or 
 
MAGAZINE RIFLE 491 
 
 carrying, the claw of the short strap is disengaged and re-engaged in 
 the proper holes of the short strap, no change being necessary in the 
 adjustment of the arm loop. 
 
 AMMUNITION 
 
 Ammunition for this arm is assembled in clips to facilitate load- 
 ing. Ammunition issued is as follows: 
 
 The Caliber .30 Ball Cartridge is shown in Fig. 82. It consists of a 
 case, primer, charge of smokeless powder, and bullet. The case is of 
 cartridge brass. It has a conical body joined by a sharper cone, called 
 the shoulder, to the neck, which is the seat of the bullet and very nearly 
 cylindrical. The front end of the case is called the mouth and the rear 
 
 FIG. 82. 
 
 end the head. The latter is grooved to provide for extraction of the 
 cartridge from the chamber of the rifle, and is provided with a primer 
 pocket and vent. The initials of the place of manufacture, the number 
 of the month, and the year of its fabrication are stamped on the head 
 of the case. 
 
 The primer consists of the cup, percussion composition, disc of 
 shellaced paper, and anvil. The cup is of gilding metal and contains 
 .48 grain of non-fulminate composition composed of tersulphide of 
 antimony, potassium chlorate, sulphur and ground glass. A disc of 
 shellaced paper covers the composition to protect it from moisture and 
 to prevent electrolytic action. The anvil is of brass and is assembled 
 over the paper. After the primer is assembled to the case a drop of 
 shellac is placed on the head of the primer to make the joint waterproof. 
 
 The charge is of pyrocellulose composition very similar to the 
 powders used as propelling charges in seacoast guns. The grains are 
 cylindrical, single, perforated and graphited. The normal charge 
 weighs from 48 to 50 grains, varying with the lot of powder used. 
 
 The bullet has a core of lead and tin composition inclosed in a 
 jacket of cupro nickel. It weighs 150 grains, and the point is much 
 
492 
 
 THE SERVICE OF COAST ARTILLERY 
 
 sharper and offers less resistance to the air than that of any previous 
 model. The sides of the bullet are smooth and its base flat. The 
 portion inclosed in the neck of the case is covered with a lubricant of 
 japan, wax and graphite. A pressure of at least 75 pounds is required 
 to seat the bullet in the case, resulting in the case being waterproof. 
 
 The standard muzzle velocity of this ammunition in the rifle is 
 2,700 feet per second. The instrumental velocity measured at 78 feet 
 from the muzzle is 2,640 feet per second, with an allowed mean varia- 
 tion of 20 feet per second on either side of the standard. The cartridge 
 complete weighs 392 grains, its weight varying slightly with variation 
 in the weight of the powder charge. Five cartridges are packed in a 
 clip, a drawing of which is shown in Fig. 83. The clip for dummy 
 
 FIG. 83. 
 
 cartridges has square instead of round ends and the tongues on the 
 spring are omitted. 
 
 Sixty ball cartridges in twelve clips are packed in a bandoleer which 
 is made of olive drab cloth and contains six pockets, each holding two 
 clips. It weighs, with cartridges, 3.88 pounds. Each bandoleer is 
 stamped with the number and kind of cartridges it contains, the place 
 of manufacture, the instrumental velocity and the date of loading. 
 
 FIG. 84. 
 
 The Blank Cartridge is shown in Fig. 84. It differs from the ball 
 cartridge in the charge of powder, in the bullet, and in the fact that the 
 case is tinned. The bullet is of paper, hollow, and contains a charge of 
 
MAGAZINE RIFLE 
 
 493 
 
 5 grains of "E.G." smokeless powder, which insures the breaking up 
 of the bullet on leaving the bore. This charge is retained in the bullet 
 by a drop of shellac. A coating of paraffin on the outside of the bullet 
 prevents the absorption of moisture by the paper. The propelling 
 charge is 10 grains of "E.G." powder. The cartridge is made 0.1 inch 
 shorter than the ball cartridge. This is a measure of protection against 
 the accidental assembling by the machine of a ball cartridge in a clip 
 of blank ones. 
 
 The Dummy Cartridge is shown in Fig. 85. It is tinned and pro- 
 vided with six longitudinal corrugations, also three circular holes in the 
 
 FIG. 85. 
 
 corrugated portion. The tinning, corrugations, and holes afford 
 unmistakable means for distinguishing the dummy from the ball 
 cartridge, both by sight and touch. The bullet is the same as in the 
 ball cartridge. The dummy primer has cup and anvil, but no percussion 
 composition. 
 
 The Guard Cartridge is shown in Fig. 86. It differs from the ball 
 cartridge in the charge of powder and in the fact that second-class 
 
 r 
 
 FIG. 86. 
 
 bullets having slight imperfections are used. Five cannelures encircle 
 the body of the case at about the middle, affording means for distinguish- 
 ing it from the ball cartridge by either sight or touch. 
 
 The charge consists of about 9.1 grains bullseye powder; or 16.7 
 grains DuPont Rifle Smokeless No. 1, giving a muzzle velocity of 1,200 
 feet per second. This cartridge gives good results at 100 yards and has 
 sufficient accuracy for use at 150 and 200 yards. The range of 100 
 yards requires a sight elevation of 450 yards, and ranges of 200 and 300 
 yards require elevations of 650 and 850 yards, respectively. 
 
CHAPTER XIII 
 POINTS FOR COAST ARTILLERISTS 
 
 IT is the object of these points to facilitate the study of the Drill 
 Regulations. They are given merely as suggestions of methods for 
 obtaining practical results as well as uniformity of commands during 
 drill or action. 
 
 BATTLE COMMANDERS 
 
 
 
 The general principles governing battle-command combat involve 
 the best means to pursue in order to destroy the enemy with the greatest 
 dispatch and the least confusion on the one hand, and economy of 
 ammunition and the preservation of the life of the guns by the preven- 
 tion of useless fire, on the other. 
 
 No attempt should be made to develop a regular routine of drill. 
 Each battle commander should conduct his drills according to the 
 development of the particular problem in hand, and rules as to the 
 procedure of particular batteries or fire commands should be applied 
 with reference to the development of this problem. 
 
 "General defense plans" authorized for use as suitable commands 
 during battle-command drill or action, are undoubtedly effective, since 
 they lead to a proper general understanding of fire control as it is to be 
 applied under normal conditions of combat. They unquestionably 
 tend to perfect organization among the several tactical units, but they 
 are not intended to be accepted as the only means through which a 
 battle command may be fought, as they are necessarily theoretical in 
 that their practical utility has never been demonstrated in action. 
 
 It should be borne in mind that the " normal' ' time for an attack 
 from the sea would be at night or in rainy or misty weather when great 
 difficulty is to be anticipated in locating particular ships of a column or 
 line, as, for instance, "the first and last battle ship of a column" or 
 "the ships in order in line from right to left." 
 
 Battle commanders should study to maintain control of their 
 commands even after they have passed the several subdivisions into 
 
 494 
 
POINTS FOR COAST ARTILLERISTS 495 
 
 the hands of fire or battery commanders. Experience with one of the 
 most important battle commands on the Atlantic seaboard under 
 assimiliated service conditions indicates that the ideal battle command 
 drill is that in which the several subdivisions are not committed to any 
 general line of action but are retained under the personal control of 
 the battle commander until the action has developed to a point where 
 the battle commander may safely eliminate certain targets or ships 
 from the general action by their assignment to particular batteries or 
 units. 
 
 Should the topographical or marine features of a harbor prevent 
 the assailants from attacking in any formation but that of column, 
 the concentration of fire on the leading ship by say 75 per cent, of the 
 primary armament (keeping the others in reserve) by the command, 
 " Fire at ships in order in column/' meaning, as it does, that the fire is 
 to be concentrated on the leading ship until it is out of action and then 
 changed to the next and so on, would seem to be logical, thoroughly 
 simple and practical. The moral effect of the quick destruction of 
 the leading ship would be severe on the personnel of the remaining vessels 
 and inspiring to those ashore. Again, the destruction of the first ship 
 would place her directly in the path of the others and possibly block 
 their further approach. 
 
 At this point the battle commander's action would be guided by his 
 newly acquired knowledge of the destructiveness of his armament. There 
 are no data available on which to found an absolutely sure estimate 
 as to the number of guns that can with certainty be counted on to injure 
 the fighting efficiency of a ship or sink her. Accordingly, if the battle 
 commander found at this stage of the combat that two batteries would 
 have been sufficient to destroy the ship with dispatch, the moment 
 for the distribution of the heretofore concentrated stream of fire would 
 be at hand, and the second or decisive stage of the action developed. 
 
 Should the fleet press the action, the fort or forts should remain in 
 action under the direction of the battle commander in accordance with 
 the principles already enunciated, namely that he should keep under 
 his personal control all the elements of his command until the action 
 has developed to the stage where he can safely assign ships or sub- 
 divisions of the fleet to fire or battery commanders, and thus, as before 
 explained, eliminate them from the general action. 
 
 On the other hand , should the military features of the harbor permit 
 the approach of the assailants in line or line of columns, a subdivision 
 of the fleet should receive concentrated action of say 50 per cent, of the 
 primary armament in the outer defense zone. The destruction of any 
 
496 THE SERVICE OF COAST ARTILLERY 
 
 of the ships fired upon at the longer ranges would have the same encourag- 
 ing result on the defenders and a demoralizing effect on the assailants. 
 From this stage the action would follow the same general lines as are 
 laid down above. 
 
 In order that the battle commander may accomplish the tactical 
 changes indicated, it is essential that the artillery discipline and artillery 
 drill be, through continued practice, so perfected that in actual com- 
 bat the excitement will not disurb the system of command nor cause 
 any unit to be carried away to the extent that it would commence 
 independent action without waiting orders from the battle commander. 
 
 To attain such a state of excellence in artillery drill it is most impor- 
 tant that the larger elements of the command, that is, fire and battle 
 commands, be not only frequently but habitually drilled and exercised. 
 
 BATTLE COMMAND DRILL 
 
 Battle commanders are liable to endeavor to work their commands 
 too fast during drill. They should constantly keep the fact in mind 
 that they have under their control a military machine of vast dimensions, 
 and in order that it may run smoothly each part must necessarily work 
 without needless pressure and in perfect unison. Undue haste should 
 be studiously avoided. 
 
 Floods of orders tend to clog the parts rather than facilitate their 
 action. Absolute silence in all stations should be insisted upon. Smoking 
 should be strictly prohibited. 
 
 For practice in deliberation as well as brevity, battle commanders 
 should personally dictate to their recorders all orders they desire to 
 have transmitted. They should constantly endeavor to word their 
 communications with such brevity of language as to make their tran- 
 scription comparatively easy. 
 
 All general orders to fire commanders should be given as soon after 
 the stations are opened as practicable. 
 
 The words "right," "left," " in front of," or "in back of," should not 
 be used in describing targets, etc. The words, "north," "south," 
 "east," and "west," can always be used with ease and by their use 
 the likelihood of error is greatly reduced. 
 
 Unless there is some special reason for so doing, battle commanders 
 should not specify the kind of projectile to be used, as this is a proper 
 function of the battery commanders. 
 
 As soon as reports have been received, such as: " F. C. Two, In order," 
 
POINTS FOR COAST ARTILLERISTS 497 
 
 "F. C. Five, In order/' etc., the battle commander may begin the drill 
 by designating the target or targets ; or if at night by directing fire and 
 mine commanders to search certain areas with their searchlights and 
 report any suspicious vessels to him, using his own searchlight as a 
 roving light. 
 
 The following scheme for the drill of a battle command consisting 
 of four gun fire-commands, one mortar fire-command and one mine 
 command is given as an example and may be modified in accordance with 
 the strength of armament. It calls for Fire Commander's Action in 
 one Fire Command ; Restricted Fire in one Fire Command ; Unrestricted 
 Fire in one Fire Command ; Battery Commander's Action in one Fire 
 Command; One Fire Command in Reserve, and Mine Command in 
 Action. 
 
 "F. C. One; Target in Battle Beam; Fire Commander's Action." 
 
 "F. C. Two; Prepare for Action as Reserve." 
 
 "F. C. Three; Target in Number Three Beam; Each Battery 
 Fire Five Shots at Two-Minute Interval." 
 
 "F. C. Four; * Fire at Target in Battle Beam when it arrives in 
 seventh zone." 
 
 "F. C. Five; f When target representing protected cruiser is identi- 
 fied begin Battery Commander's Action." 
 
 "Mine C. Protect Mine Field." 
 
 By interchanging the above commands a very complete battle 
 command drill can be executed. 
 
 FIRE COMMANDERS 
 
 The general principles and rules enumerated in connection with 
 battle commanders are applicable in every way to the drill or action of 
 fire commands, and should be studied with a view to their application 
 and development. 
 
 Fire commanders should remember that at forts where the horizontal- 
 base system is generally used apparent delay is frequently caused in 
 identifying targets by the secondary observer, whose position at the 
 other end of a long base line often makes it much more difficult for him 
 to find the target than the primary observer and gun pointer. In order 
 to overcome this delay, at forts where the vertical-base system can also 
 
 * F.C. Four, assumed to be mortars. 
 
 t F.C. Five, assumed to be 10-inch batteries. 
 
498 THE SERVICE OF COAST ARTILLERY 
 
 be used, fire commanders can facilitate action by issuing a general 
 order directing that as soon as the primary observer has found the 
 target, report be sent to him ("Dix, Target"*) and the vertical-base 
 system used until such time as secondary locates the target. 
 
 The establishment of uniformity in commands during fire-command 
 drill or action is necessary, as it simplifies communications and instantly 
 gives subordinates unmistakable information as to the wishes of the 
 fire commander. 
 
 The following commands, covering the general drill of fire commands, 
 are authorized. They are particularly recommended on account of their 
 studied brevity and simplicity. Fire commanders should insist that 
 officers and men charged with the transmission of communications use 
 the exact words of the text during all drills and exercises. 
 
 In case recorders are not available at battery primary stations, or 
 battery commander's stations, should the fire commander desire that a 
 message or order to a battery commander be written down upon its 
 receipt, he should first send the following: 
 
 "Dix (or, All Batteries), Prepare to write message." 
 
 When suitable preparation has been made, announcement of readi- 
 ness should be made to the F. C., as follows: 
 
 "Dix, Ready." 
 
 As soon as the batteries of a fire-command are in order, or need 
 repairs that cannot be made immediately, the following message should 
 be sent to F. C. by each: 
 
 "Dix, In order," or "Dix, T. I. Bell not ringing," or "Dix, Tele- 
 phone to guns out of order," etc., etc. 
 
 In case report of difficulty is received the F. C. should direct the 
 electrician sergeant detailed to his command to make such repairs as 
 may be needed. 
 
 The next order in sequence would be: 
 
 "All Batteries (or, Dix), Target; Steamer coming in, one funnel, 
 white band, main ship channel, west of Norton's Point Light." 
 
 When target has been identified it should be followed and F. C. 
 notified as follows: 
 
 "Dix, Target." 
 
 In case the target cannot be found after suitable effort F. C. is notified 
 as follows: 
 
 "Dix, Describe." 
 
 In this case the F. C. may send further particulars of description. 
 
 * The word " Dix " is used to designate the name of a battery. 
 
POINTS FOR COAST ARTILLERISTS 499 
 
 In case the F. C. desires a battery to take another target, the 
 following order is sent: 
 
 "Dix, Change Target. Target; Tug, towing two barges, coming 
 in, range about 10,000 yards." 
 
 In case a battery, after having identified a target, tracks same until 
 it is out of range, the following message is sent to F. C. 
 
 "Dix, Target out of range." 
 
 To indicate that a vessel is no longer to be fired upon, or is assumed 
 to have been destroyed, the following message is sent: 
 
 " Target out of action." 
 
 To place the control of a battery in the hands of the battery com- 
 mander, the following command is proper: " Dix (or, All Batteries), 
 Battery Commander's Action." 
 
 RESTRICTED FIRE 
 
 To restrict the fire during a fire command drill or action, the follow- 
 ing commands are proper: 
 
 "Dix (or, All Batteries), Fire one shot: Commence Firing." (This 
 restricts to one shot from one gun.) 
 
 "Dix (or, All Batteries), Fire one (or more) rounds; Commence 
 Firing." (A round consists of one shot from each gun of a battery.) 
 
 "Dix (or, All Batteries), Fire at two-minute interval; Commence 
 Firing." (This means that one round is to be hred every two minutes 
 by the battery or batteries designated, until "Cease Firing" is given.) 
 
 "Dix (or, All Batteries), Fire five shots, at two (three, etc.) minute 
 interval; Commence Firing." 
 
 "Dix (or, All Batteries), Fire five rounds when in range (or at 9,000 
 yards)." 
 
 "Dix (or, All Batteries), Fire at Salvo Point No. 1 (or No. 2, etc.). 
 (This requires the battery commander (or all battery commanders) to 
 fire a round at each target or vessel of a fleet as they pass the designated 
 salvo point. 
 
 UNRESTRICTED FIRE 
 
 The following commands for unrestricted fire are proper: 
 " Dix (or, All Batteries), Fire at ships in order in column; Commence 
 Firing." (This requires the battery commander or all battery com- 
 manders to concentrate fire on the first vessel in the column until it 
 is out of action and then to change to the second vessel and so on.) 
 
500 THE SERVICE OF COAST ARTILLERY 
 
 "Dix (or, All Batteries), Fire at ships in order in line from right 
 to left; Commence Firing." (This requires the battery commander 
 or all battery commanders to concentrate fire on the vessel on the 
 right of the enemy's line, until it is out of action and then change to 
 the next and so on.) 
 
 "Dix (or, All Batteries), Target under fire; Commence Firing." 
 (This requires the concentration of fire on a target or vessel already 
 being fired upon by another battery or batteries.) 
 
 "Dix (or, All Batteries), Fire at target; Commence Firing." 
 
 At the conclusion of all series of shots fired, battery commanders 
 should report as follows: 
 
 "Dix, Series completed." 
 
 In restricted fire, in case "cease firing" is given before the number 
 of shots specified have been fired, battery commanders after stopping the 
 fire should report: 
 
 "Dix (so many) shots fired." 
 
 In case the command, "Commence Firing, "is again given, battery 
 commanders should proceed to complete the series. 
 
 For the purpose of finding the comparative accuracy of ranges, fire 
 commanders may send the following order: 
 
 "All batteries: Send range of target to F. C. at next bell." 
 
 In case a party of the enemy is discovered to have gained access to 
 a fort unobserved, and provided the artillery personnel are not actually 
 engaged in action or the chances of artillery action are remote, fire 
 commanders would send the following order: 
 
 "Prepare for land defense." 
 
 At this command all men of the designated unit or units take their 
 small arms and independently rush to their positions previously 
 designated and prepare for land defense. 
 
 During artillery practice for batteries the fire commander is respon- 
 sible to the district commander for the efficiency of his batteries at 
 practice. His active duties in connection with battery practice are 
 limited to the preparations necessary for the highest efficiency, and 
 to the observance of safety precautions on the day of the practice. 
 
 When a battery commander desires to fire he requests authority 
 from the fire commander to begin; the latter gives the authority if 
 the range is safe, and the battery commander gives the command 
 "Commence Firing" as soon thereafter as practicable. 
 
 If an interruption of the fire is necessary the fire commander com- 
 mands "Cease Firing." Firing is resumed after an interruption in 
 the same manner as the original firing was begun. 
 
POINTS FOR COAST ARTILLERISTS 501 
 
 The necessary precautions for safety are laid down in the drill 
 regulations. The additional precautions to be observed during night 
 practice are as follows: 
 
 a. The dates of the practice shall be published so as to reach with- 
 out fail shipping and fishing interests. 
 
 b. The field of fire shall be patrolled before dark with a view of 
 determining whether or not vessels are anchored therein and of 
 warning approaching vessels. 
 
 c. Signal boats shall be located so as to observe any vessel approach- 
 ing the range during the firing and to signal the battery firing by rocket 
 or other means. 
 
 d. At least one searchlight shall be held on the towing tug and one 
 on the target during the firing. 
 
 e. The day and hour of firing shall be selected with a view to having 
 the practice at an hour when there is least likelihood of a vessel crossing 
 the range. 
 
 If in the opinion of the fire commander the deflection error of any 
 mortar shot is such as to imperil the safety of the field of fire, he com- 
 mands "Cease Firing" and investigates the cause of error, indorsing 
 results of his investigations on the report of the practice. 
 
 When troops are ordered for artillery practice away from their 
 home stations they shall be accompanied by the fire commander of 
 the fire command to which they belong. This fire commander shall 
 require the troops of his command to be drilled carefully before the 
 practice begins at the pieces with which such practice is to be held. 
 He shall order and supervise subcaliber practice with each piece before 
 service takes place. He shall assure himself before the practice 
 begins that each gun and fire-control section is instructed sufficiently 
 in the use of the equipment furnished to derive the fullest possible 
 benefit from the practice. 
 
 The following rules are suggested to be followed by safety officers 
 in charge of the target practice: 
 
 Vessels short of first point of fall should be considered in dangerous 
 position if within 10 degrees from either side of line of fire measured from 
 gun. 
 
 For all rounds where ricochet is expected, vessels beyond first point 
 of fall should be considered in dangerous position if within 45 degrees 
 from line of fire to the right, or if within 22^ degrees from line of fire 
 to the left, measured in both cases from first point of fall of projectile. 
 
 Any angle of elevation under 9 degrees may be expected to give a 
 ricochet. 
 
502 THE SERVICE OF COAST ARTILLERY 
 
 For angles of elevation less than 9 degrees the total range, including 
 ricochets, may be expected to be at least as great at that given by 9 
 degrees, and if near 9 degrees probably greater. 
 
 Based upon the above assumptions, the following have been deter- 
 mined to be the required clear angles to the right, measured from the 
 gun, for vessels, beyond the point of first fall of projectile, but within 
 ricochet range. These assume firings to be with high-power guns 
 and full charges: 
 
 When first point of fall is about 1 ,500 yards from gun the clear angle 
 from the gun should be about 40 degrees. When first point of fall is 
 about 4,000 yards the clear angle should be about 30 degrees. 
 
 Where first point of fall is about 8,000 yards the clear angle should 
 be about 6 degrees for an 8-inch gun or less, about 11 degrees for a 
 10-inch gun, and about 17 degrees for a 12-inch gun. 
 
 The clear angle to the left should in all cases be about one-half the 
 corresponding one to the right. 
 
 If the conditions of water are such that the targets could be 
 towed at ranges of 11,000 yards there would apparently be no danger 
 from ricochet at that range. 
 
 SEARCHLIGHT COMMANDS 
 
 At night the following searchlight commands are prescribed in 
 connection with battle, fire and mine lights: 
 
 To put occulted light into action the command would be: 
 
 "No. 1, In action." 
 
 To take a light out of action: 
 
 " Battle (or, No. 1, etc.), Out." 
 
 To have a designated light search its area, or any sector of its area: 
 
 " Battle (or, No. 1, etc.), Search right (or middle or left)." 
 
 For a light to search its entire area: 
 
 "Battle (or, No. 1, etc.), Search." 
 
 If the light is covering a target the command is "Uncover and 
 Search." 
 
 To have a light follow a target found in its area: 
 
 "Mine (or Battle, etc.), Follow." 
 
 To have a light cover a target already illuminated by another light : 
 
 " Battle, Cover No. 1," or, " Mine, Cover Battle." 
 
 To change a light from one target to another: 
 
 "No. 1, Uncover and cover Battle." 
 
POINTS FOR COAST ARTILLERISTS 503 
 
 To have a light uncover and search : 
 
 "No. 4 (or, Battle, etc.), Uncover and Search." 
 
 The command "Elevate" means for the controller operator to raise 
 the beam 30 degrees from the horizontal. 
 
 The command "Focus' 7 indicates to the operator at the light that 
 the beam requires adjusting. 
 
 The command "Spread" means to diverge the beam. 
 
 The command "Contract" means to contract the beam. 
 
 Other commands used are: "Raise," "Lower," "Raise slightly," 
 "Lower Slightly," "Right," "Left," "Halt." 
 
 To indicate a target to a battery at night, the command would be: 
 
 " Dix (or, All batteries) , Target in Battle (or, No. 4, or Mine) beam. 
 
 COMMUNICATION OFFICER 
 
 No service in the Coast Artillery is more important than the accurate 
 transmission and receipt of artillery communications. 
 
 Communication officers should point out to their assistants the 
 importance of the duty which rests upon them. They should person- 
 ally instruct their subordinates in the proper method of transmitting, 
 receiving and retransmitting orders and communications. 
 
 They should request, through their respective superiors, that men 
 detailed to this important service at the several stations in the chain 
 of communication be selected with reference to the following rules, viz. : 
 
 1. General intelligence. 
 
 2. Knowledge of artillery terms and orders. 
 
 3. Natural coolness and ability to remember a message long enough 
 to transmit it properly. 
 
 4. Experience in the use of the telephone. 
 
 5. Ability to speak in a modulated but distinct tone of voice. 
 
 6. Familiarity with the English language sufficient to enable the 
 proper pronunciation of words. 
 
 7. Complete absence of any impediment of speech or foreign accent. 
 Communication officers of fire commands are charged with the 
 
 inspection of the equipment of the station and the proper adjustment 
 of all instruments therein. 
 
 When the station is in readiness, the communiation officer reports 
 to the commander: "Sir, Station in order." 
 
 He receives all reports from batteries and transmits them to the 
 fire commander as received. After all batteries in the command 
 
504 THE SERVICE- OF COAST ARTILLERY 
 
 have reported and upon intimation from the fire commander, he reports 
 to the battle commander, as follows: 
 
 "F. C. 2, In order." (Or reports defects that cannot be repaired.) 
 
 He communicates all orders from the fire commander to the tele- 
 phone operators on the lines over which the message is to be transmitted 
 and receives all messages sent over such lines. 
 
 When a communication is to one particular battery he can facilitate 
 its prompt and accurate delivery by personally transmitting it direct 
 by the use of the cut-off jack-set. 
 
 When telephone operators have transmitted their messages word 
 for word to the batteries to which their lines are connected and know 
 they have been received correctly, they report to the communication 
 officer, as follows: 
 
 "Dix, Message delivered/' "Richmond, Message delivered," etc. 
 
 The expression "OK" is used by a communication officer to 
 announce that a communication transmitted to him is understood. 
 To announce that he has concluded a message the letter "X" may be 
 used. For example, the communication officer calls the operators in 
 communication with Batteries Dix and Richmond; the operators 
 answer, "Dix," "Richmond." The communication officer then says: 
 
 "Target, Side-wheel steamboat coming in. X." 
 
 The letter "X" in this instance implies "end of message." It has 
 been found that where telephone operators are in booths they are apt 
 to lose time in delivering messages by not knowing just when the 
 message is complete. Accordingly the use of "X" at the end of each 
 message delivered to them signifies the end. 
 
 At the end of the drill or exercise the communication officer, upon 
 intimation of the fire commander, sends the following message: "All 
 Batteries, Close Stations." 
 
 While the above points are for the use of communication officers 
 detailed to fire commands, they are applicable to those at battle com- 
 mand stations as well. 
 
 BATTERY COMMANDERS 
 
 To battery commanders the words of the great artillerist, Napoleon, 
 apply with peculiar emphasis: "There are no poor regiments, there 
 are some poor colonels." In other words, a good battery commander 
 will always have an efficient battery. 
 
 Battery commanders should strive to obtain such a standard of 
 
. POINTS FOR COAST ARTILLERISTS 505 
 
 discipline that the battery would be able to conduct subcaliber or 
 service target practice in the same orderly manner as they would the 
 ordinary routine drill. That is, the drills should approach the con- 
 ditions of actual service to such a realistic extent that the difference 
 would not be apparent to the enlisted personnel. 
 
 The battery commander is responsible for the excellence of the 
 gunnery of his command. This excellence is judged by the accuracy 
 and rapidity with which the battery can hit the target. In this, every 
 person who actually participates in the firing has a personal liability; 
 the battery commander, the range officer, the emplacement officers, 
 each individual member of the fire-control section and the gun detach- 
 ments. Only by the united efforts of all persons concerned, working 
 in complete harmony with each other, can the best results be expected. 
 A failure in the slightest detail on the part of any one participating 
 may materially reduce the accuracy and rapidity of hitting, and thus 
 defeat the efforts of the others to attain the highest possible excellence. 
 Success in practice, if properly carried out, under as nearly as possible 
 service conditions, is by far the best evidence of the state of training 
 of a company. 
 
 Battery commanders are responsible for the team work of their 
 respective companies, without which it is practically impossible to 
 obtain results. They should employ a system of checks in order that 
 errors may be located. 
 
 By personal inspections they should know positively that the 
 military machine over which they exercise command is in proper 
 order and ready at all times for immediate action. 
 
 Before artillery practice battery commanders should satisfy them- 
 selves that all the material for the practice is ready for service. In 
 this connection the instructions contained in Coast Artillery memoran- 
 dum No. 6, W. D. 1909, have been copied without material alterations, 
 as follows: 
 
 "... It is believed that target practice is a problem capable of 
 definite solution, within the limits of accuracy allowed by the gun and 
 the ammunition; but the solution is arrived at only when all the 
 variants or sources of error, viz., ununiformity in material and methods, 
 are eliminated." 
 
 The final objective of target practice is to develop ability to hit. 
 To hit, or to throw the projectile accurately in practice or in service, 
 we must have for successive shots, uniformity in the several factors 
 that enter into the problem of gun fire, viz. : 
 
 (1) Gun and carriage (action of). 
 
506 THE SERVICE OF COAST ARTILLERY 
 
 (2) Projectile. 
 
 (3) Powder. 
 
 (4) Position -finding service (operation of). 
 
 (5) Personnel (work of). 
 
 The target-practice problem, then, reduces itself to an elimination 
 of the variants affecting these factors. 
 
 1. Gun and Carriage. Careful inspection and adjustment will be 
 made of the following: 
 
 (a) Base Rings to be Tested for Level. Place a clinometer on its 
 rest in the bore of the gun. Traverse the gun through the field of fire, 
 recording variations in level of the base ring as indicated by the clinom- 
 eter for azimuths varying by 5. Calculate, for mid-range, the range 
 corrections which should be applied for variations in level, and combine 
 these corrections with the corrections for gun displacement; modify 
 the figures painted on the base ring or on the steps of the loading 
 platform so that they will represent the total correction due to gun 
 displacement and variations in level. 
 
 In using the clinometer and its rest the bore of the gun should be 
 thoroughly cleaned and any burrs on the ends of the lands should be 
 removed to facilitate the insertion of the adaptors. The adjustment 
 of the clinometer itself should be tested. In giving the gun elevation 
 the last movement of the elevating wheel should always be in the same 
 direction. It will be found that the direction of this motion should 
 be against preponderance that is, in the direction of depression. 
 
 (6) Sight Standards. Place bore sights in the gun, and with the 
 telescopic sight on its standard, point the gun so that- the line of collima- 
 tion of the sight and the line through the axis of the bore intersect at 
 some well-defined object at or beyond mid-range. For 8-inch, 10-inch, 
 and 12-inch guns this adjustment should be made on an object at about 
 6,000 yards from the gun. The sight itself should be in adjustment 
 and the vertical wire should be in the center of the deflection scale. 
 
 (c) Quadrant Elevation Scales to be tested for Adjustment by the 
 Clinometer at 0, 5, and 10 degrees. The elevating pinion shaft projecting 
 through the chassis rail carries one or two disks, depending upon the 
 model of the carnage. There are two scales on the disk (or disks), 
 one the quadrant elevation scale, the other the range scale. The 
 quadrant elevation scale should be tested by the clinometer and the 
 results compared with the calibration record of the battery, bearing 
 in mind that the index for this scale may have been adjusted as a result 
 of the calibration firing so as not to give the actual quadrant elevation. 
 In the graduation of the range scale allowance has been made for the 
 
POINTS FOR COAST ARTILLERISTS 507 
 
 curvature of the earth and the height of the gun trunnions. The 
 relation between the graduations of the range scale and the quadrant 
 elevation scale is unalterable. This should be checked by the battery 
 commander, and he should also verify the computations upon which 
 these graduations are based and the accuracy of graduations them- 
 selves. 
 
 Wear of the elevating gearing will result in inaccuracies at certain 
 parts of the quadrant-elevation scale. The index should be adjusted 
 so as to be correct for mid-range or for the approximate range at which 
 trial and record shots will be fired. In making this adjustment, as in 
 the case of testing for base-ring level, the last movement of the elevating 
 wheel should always be in the same direction, viz., in the direction of 
 depression. It is to be noted that this corresponds to a target coming 
 toward the battery, which will be in the condition to be expected in 
 the important part of any actual engagement. With the target going 
 away from the battery it will be found impracticable to have the last 
 motion in laying the gun to be that of depression, because the gun must 
 be laid continuously. If all adjustments involving the elevating 
 mechanism are made with the last motion that of depression, the 
 carriage will be in the best adjustment for firing at a target approaching 
 the battery. It is well, therefore, at target practice, to arrange that 
 the target shall approach the battery during the firing of the record shots.. 
 
 (d) Elevating Mechanism. Examine the hand-wheel shaft and 
 bearings, all racks and pinions, elevating-rack slide and its bearing; 
 clean thoroughly and oil all bearing parts. Oil that has accumulated, 
 sand and grit should be removed. The elevating mechanism should 
 work easily and smoothly for both elevation and depression. 
 
 (e) Friction Device of Elevating Mechanism (if this device is not in 
 proper adjustment it should be removed by an ordnance machinist and 
 examined). Examine and adjust the friction clutch. The gun jumps 
 when it is fired. It may be said that correction for jump is included in 
 correction made as a result of trial shots; this correction, however, 
 will not apply unless the jump is uniform. The proper adjustment 
 of the friction clutch will tend to make the amount of the jump uniform 
 for successive shots. If the gun were in a vise there would be no 
 jump. We can conceive that if the friction device were so tight as 
 to allow no movement in the elevating device when the gun is fired, and 
 if this device as a whole were rigid, there would be no j ump. The rigidity 
 of the mount in respect to elevation and depression is, therefore, 
 dependent to a degree on the friction surfaces of the elevating gearing. 
 Jump should decrease with increased friction. 
 
508 THE SERVICE OF COAST ARTILLERY 
 
 In making the adjustment, care must be taken not to cause the friction 
 surfaces to bear too tight, otherwise the gearing will be endangered. 
 
 The main object is to secure uniformity in the action of this device. 
 The bearings of the elevating shaft should be kept clean and properly 
 lubricated. The friction surfaces should be kept clean, smooth, and 
 dry. They should not under any circumstances be oiled. Frequently 
 at. drill elevate or depress to the limit and turn the friction surfaces on 
 each other. According to the Ordnance Department pamphlet the 
 elevating arm for 12-inch carriages, model of 1896, should be held by 
 friction surfaces only so tight as will prevent the elevating arm sliding 
 down. 
 
 (/) Traversing Mechanism. Examine the crank shaft and the 
 bearings, all racks and pinions; clean thoroughly and oil all bearing 
 parts of the traversing mechanism. Clean traversing rollers and their 
 paths, and oil all bearing surfaces as often as necessary. Different 
 sections of the dust guards should be removed each month of the out- 
 door season. 
 
 (g) Recoil Cylinders (to be cleaned and filled, periodically, as required 
 by Ordnance Department pamphlet for the carriage considered). The 
 follower should not be so tight as to cause undue friction, nor so loose 
 as to allow leakage. (See C. A. D. R. instructions for packing stuffing 
 boxes and adjusting followers.) The adjustment of glands and fol- 
 lowers must be uniform for the two cylinders. Examine the cylinders 
 just before firing to see that they are/w/Z. 
 
 (h) Recoil and Counter-Recoil System. Clean crossheads and guides, 
 recoil rollers, upper and lower roller paths, and lubricate all bearings. 
 For firing; rollers, paths and piston rods should be bright and slightly 
 lubricated with thin oil. Keep grease cups full and so adjusted that 
 they function properly at all times. The gun should be tripped fre- 
 quently and time of going into battery recorded with a view to observ- 
 ing whether or not the action of the carriage is uniform. Equalizing 
 pipes must be clean and free from "settlings" or solid matter, so as to 
 allow a free circulation of oil. Throttling valves should be properly 
 set by reference to records as to action of the carriage with settings at 
 previous times, or as judgment and experience may dictate. The 
 setting of the valve depends principally upon the temperature of the 
 oil in the cylinders at the time of firing. The records of previous firings, 
 therefore, should show the setting of the valve, the amount of recoil, 
 temperature of the oil in the cylinders, and the time elapsing between 
 successive shots. It should be noted whether or not with the same 
 setting the recoil increases with shots fired at short intervals. 
 
POINTS FOR COAST ARTILLERISTS 509 
 
 (i) Breechblocks and Obturators. Once a month breechblocks should 
 be dismantled and all parts carefully cleaned. Cable and breech con- 
 tacts will be freed of all grease and dirt. Dummy pressure plugs will be 
 unscrewed occasionally and threads of pressure-plug recesses examined. 
 Prior to practice cylinders for pressure plugs will be measured, and 
 gun commanders will be instructed in the preparation of the plugs and 
 their use during practice. 
 
 Adjust the obturator so that a slight effort will be required to turn 
 the mushroom head. See that the gas-check pad is serviceable. 
 
 (j) Firing Attachments. Examine firing attachment. Take it apart 
 occasionally and clean it; oil its bearing parts so that it functions easily. 
 Men should be instructed to insert the primer by pushing on the body 
 of the primer and not on the button wire. The slide must be lowered 
 completely down. If a primer fails, its button wire should be bent back 
 over the body of the primer, so that the primer will not, by mistake, be 
 inserted again during the firing. In bending the wire back care should 
 be taken to put as little strain as possible on the, button wire in the 
 direction of the axis of the primer body, to avoid the possibility of 
 igniting friction composition in the primer. 
 
 See that the safety lanyard is in working order, if this is used; and 
 test all lanyards to see that they are strong and serviceable. 
 
 (k) Azimuth Subscales (Mortars). Check up the data upon which 
 orientation of mortars is based and verify the setting of azimuth sub- 
 scales before practice. (See Method of orienting, in chapter X, also 
 in D. R.) Having once verified the orientation data, setting of 
 azimuth subscales can be readily checked by a transit on the parapet 
 or in rear of the pit. By means of bore sights direct the vertical wire 
 of the transit on the axis of the bore and, if necessary, move the sub- 
 scale so that it indicates the correct azimuth reading. The subscale 
 should be doweled in position when correctly set. Station for the 
 transit should be located at a point near the battery from which all 
 mortars are visible and correct data for this point determined. The 
 orientation of the B. C. instrument and instruments in P. F. system 
 must agree with that of the mortars. An azimuth instrument may 
 be used for this adjustment if a transit is not available. 
 
 (1) Quadrants (Mortars). Test and adjust all quadrants. Expan- 
 sion and contraction due to sun and shade make it difficult to keep 
 quadrants in adjustment. They should be tested with the clinometer 
 as short a time before firing as possible. As the clinometer does not 
 read to 45 and the quadrant does not read below 45, an old-style 
 quadrant may be placed on the surfaces prepared for it at the breech 
 
510 
 
 THE SERVICE OF COAST ARTILLERY 
 
 and its zero determined by the clinometer. Having adjusted this 
 quadrant the attached quadrant should be compared with it at eleva- 
 tions differing by 5 between 45 and 70. 
 
 (m) Adjust sights to remove parallax and for clear definition. 
 (See Adjustment of telescopes.) 
 
 (n) Ammunition Trucks (See Fig. 87). Oil -axles. Have trays 
 clean and smooth. Trucks for disappearing carriages should be 
 
 FIG. 87. Emplacement Booth, Equipment, and Ammunition Truck. 
 
 adjusted approximately for proper height of breech in loading position 
 just before practice. Tray-elevating and depressing mechanism must 
 be lubricated and should be frequently operated. 
 
 IN GENERAL. 
 
 The bore and chamber, breechblock, and all parts of the carriage, 
 such as traversing rollers and their paths, and crosshead guides, will 
 be carefully freed of grease and dirt; only bearing surfaces should be 
 lubricated. 
 
 Uniformity in the action of the gun and carriage will be attained 
 by lubrication of bearing surfaces and by adjustment of the working 
 parts of the gun and carriage to insure smooth operation of the whole 
 
POINTS FOR COAST ARTILLERISTS 511 
 
 as a machine, (iuns should be tripped and retracted frequently. 
 Just before target practice this should be done several times a day. 
 The action of guns and carriages in firing should be observed, and a 
 careful inspection should be made of them before and immediately after 
 firing, notation being made of any change in adjustment as well as of 
 any defects in material that the firing has caused. 
 
 2. Projectiles. The weights of all projectiles to be used in a 
 practice will be adjusted as nearly as possible to standard -range table 
 weights. This may be done by filling the cavities of the projectiles 
 with sand. A difference in weight of less than 2 pounds may be 
 neglected, but anything greater than this should be taken into account. 
 
 Remove all loose paint from projectiles, making their surfaces 
 smooth; polish the bourrelets. 
 
 The rotating bands will be carefully cleaned and all oil and grit 
 removed from the grooves. Burrs on rotating bands or bourrelets 
 will be removed. 
 
 Rotating bands of projectiles will be calipered and the projectiles 
 classified in groups so that all projectiles for trial shots and all for 
 record shots will, if possible, have rotating bands of the same diameter. 
 In order that this work may have any value it must be done most care- 
 fully. 
 
 Variations in diameters of rotating bands cause variations in 
 velocities. The grouping of projectiles, therefore, according to diameters 
 of rotating bands will permit of uniform projectiles being used for trial 
 and for record shots, and differences in velocities between the pro- 
 jectiles used for trial and those used for record shots, due to ununiform 
 rotating bands, can be allowed for. 
 
 It has been determined by careful experiment that the variation 
 of 4-0.025 of an inch in the diameter of a rotating band of a 6-inch 
 projectile has given an increase of 30 f. s. in velocity. The Ordnance 
 Department specifications allow a variation of 0.003 of an inch in 
 diameter of rotating bands. 
 
 At all practices keep records as to differences in diameters of rotating 
 bands of projectiles for trial shots and corresponding range variations. 
 If all other variants have been eliminated in the trial shots, the informa- 
 tion to be obtained from these records will be of assistance to battery 
 commanders in making allowances for velocity due to differences in 
 rotating bands. 
 
 The Ordnance Department last year conducted experiments with 
 projectiles with narrow rotating bands at a battery the guns of which 
 had been fired 200 times. The projectiles with narrow bands fell very 
 
512 THE SERVICE OF COAST ARTILLERY 
 
 erratically. Projectiles with similar bands fired from new guns gave 
 normal results. The Ordnance Department has issued projectiles 
 with broad rotating bands for use at some of the batteries whose 
 guns are known to be considerably worn. (The guns of two such 
 batteries have been fired 200 times, and the third 118 times.) It is 
 hoped that these broad-banded projectiles will increase the accuracy 
 of guns that have been fired a great number of times. 
 
 NOTE. Firing with broad-banded projectiles of the new design 
 has been recently conducted. The results of this firing were most 
 satisfactory; the dispersion of shots in calibration firing was small, 
 and in the record firing 100 per cent, of hits was made. 
 
 3. Powder. Powder for heavy guns (except those using fixed 
 ammunition) will be blended as described in chapter VI. After blending 
 the sections of charges will be carefully made up. Each section should 
 be as stiff and rigid as possible, and of uniform cross-section and length. 
 This can be attained by care in relacing and by a process of kneading or 
 rolling after lacing. Weights of powder charges will be verified by an 
 officer. The following illustration indicates very conclusively the 
 advantage of careful blending.: 
 
 Last year several practices were held at a battery of 12-inch rifles 
 on disappearing carriages, with International Lot No. 9, 1907, powder. 
 This powder was carefully blended and behaved with great uniformity 
 at all practices. The powder appeared to be weak, however, and on 
 this account the Ordnance Department sent four charges of the same lot 
 to be tested for initial velocity. Two charges slightly under normal 
 weight gave the following results : 
 
 First shot I. V. 2,153 f. s. 
 
 Second shot I. V. 2,206 f. s. 
 
 Variation 53 f. s. 
 
 Two charges slightly over normal weight gave 
 
 First shot I. V. 2,369 f. s. 
 
 Second shot I. V. 2,320 f. s. 
 
 Variation 49 f. s. 
 
 These charges were tested as shipped from the arsenal and were 
 not blended. 
 
 Five charges of the same lot of powder were blended and shipped 
 for test. These charges were blended with 16 other charges which 
 
POINTS FOR COAST ARTILLERISTS 513 
 
 were used in practice. The results obtained with the five blended 
 charges were as follows: 
 
 First shot I. V. 2,198 f. s. 
 
 Second shot I. V. 2,202 f. s. 
 
 Third shot I. V. 2,212 f. s. 
 
 Fourth shot I. V. 2,203 f. s. 
 
 Fifth shot I. V. 2,215 f. s. 
 
 Maximum variation 17 f. s. 
 
 The Ordnance Department specifications for powder allow a varia- 
 tion of 1 per cent, either way from normal velocity. For a powder with 
 normal muzzle velocity of 2,250, it will be seen that the total allowable 
 variation is 45 f. s. 
 
 4. Position-Finding Service. Communications will be inspected 
 and all instruments in the position-finding service will be put in a con- 
 dition of minimum error. Check all data upon which the position- 
 finding system is based by examination of all available records and 
 calculations of involved triangulations, if necessary. 
 
 (a) Depression Position Finder. Test position finder for adjustment 
 and orientation. Instruct observer in the proper use of instrument to 
 avoid errors due to lost motion. Where targets entering the harbor 
 move across the field of fire in the same direction during their entire 
 course, azimuth-reading instruments should be adjusted by bringing the 
 vertical wire on the orientation point always in the same direction, which 
 direction should be that of the target in entering the harbor. Where 
 lost motion exists which cannot be eliminated, its effect should be 
 carefully ascertained and corrected for by the reader, especially when the 
 direction of motion of the target which is being followed is opposite to 
 that used in adjusting the instrument on the orientation point. It is 
 very important that the observer should be instructed to stop the 
 instrument on the last stroke of the bell, and in order to do this he must 
 keep the vertical wire exactly on the designated point of the target 
 during the last two or three seconds of the interval. Similarly the 
 horizontal wire, in using the instrument for determining ranges, must 
 be stopped on the water line on exactly the last stroke of the bell. 
 Observers should be trained to give particular attention to either the 
 vertical or the horizontal wire during the last seconds of each observing 
 interval, depending upon whether the azimuth or the range of the target 
 is changing most rapidly. If the azimuth is changing more rapidly 
 than the range, the last two or three seconds should be devoted 
 
514 THE SERVICE OF COAST ARTILLERY 
 
 exclusively to the setting of the vertical wire. If the range is changing 
 more rapidly than the azimuth, the last two or three seconds of each 
 interval should be devoted exclusively to the setting of the horizontal 
 wire. 
 
 (b) Plotting Board. Check orientation of base line and numbering 
 of the degrees on the azimuth circle. Verify the setting of the gun 
 center. See that the locks and all mechanical devices are in adjustment. 
 To avoid errors due to lost motion in setting arms, both arm setters and 
 the plotter should be instructed to cause the last motion of arms to 
 be always in the same direction. The proper operation of these arms 
 requires skill and care. A determination of maximum and minimum 
 errors that result from various methods of setting arms, at different 
 positions on the board, will impress upon the plotting detachment the 
 importance of uniformity in the setting of arms. The calculated and 
 plotted ranges (the latter by the method of setting arms selected as 
 being most accurate) should not differ by more than 10 yards at mid- 
 range. When the course of the target is plotted it should show uniform 
 intervals, either equal or uniformly increasing or decreasing, depending 
 upon its speed. If the interval suddenly changes the plotter reports 
 the fact to the range officer. The latter immediately looks for "the 
 trouble and takes steps to eliminate it. 
 
 (c) Range Board. The ruler should be parallel to the range lines. 
 There should be no lateral motion of the ruler. The string should be 
 properly centered. Some trouble has been experienced in the use of 
 range boards due to the fact that with the old type of range charts the 
 velocity curves did not cover the low velocities developed in practice. 
 Some officers constructed additional curves in pencil and some selected 
 arbitrarily a curve on the chart and made an additional range correction 
 on the range arm. The latter method is inaccurate when trial shots 
 and record shots are fired at different ranges and should not be used. 
 It is not expected that these difficulties will arise this year, since the 
 Ordnance Department has issued the latest revised range charts with 
 velocity curves from 2,100 f. s. to 2,400 f. s., to all heavy gun batteries. 
 If, however, velocities fall below the curves on the range board, addi- 
 tional curves in pencil should be constructed. 
 
 The following directions in the use of range boards should be observed 
 where they apply: 
 
 On range boards issued prior to December 26, 1906, the curves 
 are constructed to give corrections for the actual range. Therefore, it 
 is necessary that the operator of the board should keep the ruler set 
 at the actual range and not the corrected range. A setting to within 
 
POINTS FOR COAST ARTILLERISTS 515 
 
 100 yards of the actual range is sufficiently accurate. The operator 
 should be drilled in obtaining approximately the actual ranges from 
 the corrected ranges read by the plotter from the gun arm of the plotting 
 board. 
 
 On range boards issued December 26, 1906, and subsequently, the 
 curves are constructed to give the correction for the corrected ranges, 
 to that ranges read from the gun arm of the plotting board should be 
 used in setting the ruler. The first corrected range can be obtained 
 only by using the actual range in setting the ruler, hence it is only an 
 approximation. The second corrected range obtained by setting the 
 ruler at the first corrected range will be sufficiently accurate to use for 
 firing. It is necessary to obtain the second corrected range in firing at a 
 stationary target as well as at a moving target. 
 
 (d) Deflection Board. See that the proper leaf-range scale and T- 
 square range scale are attached and that the board is otherwise in 
 adjustment. 
 
 Examine time-interval clock, interrupter, and bell, and all telephones 
 and switches, to see that they are in good working order and properly 
 adjusted. See that all screws are tight. 
 
 5. Personnel. Substitutes should be trained for all the important 
 positions in order that unexpected vacancies may be filled. All men 
 operating telephones or other instruments will be put through the proper 
 operators' tests, and drilled with a view to eliminating personal errors. 
 Too great attention cannot be given to the minutest details. Each day 
 the drill should be conducted as in target practice, or as if the boat for 
 drill represented the enemy. At least once a week a simulated target 
 practice should be conducted at each post. Time-out will be given 
 occasionally as in practice. Any errors that are brought out in these 
 simulated practices will be investigated and eliminated. Such records 
 should be kept as will permit of careful checking of the work of each 
 individual of the personnel throughout the system. The training of 
 the personnel should be progressive; from the individual to the 
 detachment, and then to the battery. The work of the battery as a 
 unit requires co-ordination of the work of the various detachments. 
 The individual training of gun pointers should be given attention. 
 
 The range officer is responsible for the accuracy of the data trans- 
 mitted from the plotting room to the guns. He in turn should hold the 
 plotter responsible for errors that pass him undetected. As a check 
 against errors in deflection the gun pointer should be taught to associate 
 the value of deflections sent to him with the angular travel of the target, 
 which is uniform, or increasing or decreasing at a uniform rate. It is 
 
516 
 
 THE SERVICE OF COAST ARTILLERY 
 
 thought that a gun pointer can be readily trained to detect errors in 
 deflections when the fact is impressed upon him that their values should 
 be uniform or increasing or decreasing at a uniform rate. 
 
 Dummy projectiles (see Fig. 88) should be rammed with the same 
 energy as would be employed in practice. Ramming a very few pro- 
 jectiles during the drill will be of more value than going through the 
 motions any number of times. Uniform ramming is of the greatest 
 importance. If the projectile is not well rammed the powder gas will 
 
 FIG. 88. Complete Dummy Charge for 12-inch Gun. 
 
 escape around the rotating band, and there will be a loss in velocity. 
 Projectiles should be rammed with all force possible. 
 
 It has been determined by test that the variation of a few tenths 
 of an inch in the seating of a projectile will give a variation of 70 f. s. 
 in muzzle velocity, due to the fact, apparently, that powder gases 
 escape around the rotating band. The velocity in the case of the 
 projectile not being home is less than when the projectile is rammed 
 well home. (See Fig. 89.) 
 
 The following, bearing on the training of the personnel, is taken 
 
POINTS FOR COAST ARTILLERISTS 
 
 517 
 
 from a report of an officer of the Coast Artillery Corps, who has secured 
 uniformly good results in practice : 
 
 "The adjustment of the gun and carriage and the preparation of 
 
 Base 0f 
 
 <-/ Gun, 
 
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 /fa/rimer. 
 
 8-**** 
 
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 199* 
 
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 ~c*. 100*1 \/0 tt*i\/0223 
 
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 4-2-3 OS J7-J/V 37'/JJ- 
 
 ***L 
 
 " *3z .s 
 
 S*Lj*jf. ^ | 1 if" T 
 
 i 
 
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 f ^ 
 
 " 
 
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 F * 
 
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 3 
 
 
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 1 
 
 GrooKe /i'MetJ ~t(A\ r S 
 Uatff enamel, ] j 
 
 S^M im^y7 T 
 
 A> indicccfe. ftrojoer travet 
 fr 8 '- JO "- 12'm/Le, *<* 12"Mortar. 
 
 FIG. 89. 
 
 the ammunition, etc., is done before firing, when there is ample time 
 for verification, but the accuracy of the work of the personnel is 
 practically beyond the control of the battery commander after firing 
 once begins. This must be provided for by thorough training. In this 
 
518 THE SERVICE OF COAST ARTILLERY 
 
 training the methods of work used by each member of the range detach- 
 ment including the range keeper and gun pointer should be definitely 
 prescribed .... The sequence in which each member of the detach- 
 ment performs the details of his work should be prescribed, also as far 
 as possible the mental process he uses. The drill should then be 
 continued until the work of each member becomes mechanical and 
 thus, by force of habit, reduce to a minimum the errors that may occur 
 when working under conditions of excitement or fatigue. 
 
 "In developing the work of the range detachment, I worked at 
 each position in the detachment until I was thoroughly familiar with 
 the details of the work at each position. I noted the routine in which 
 each step of the work could best be done, and where errors were likely 
 to occur. I also noted where irregularities, such as the loss of one or 
 more observations, an error in reading the range or azimuth, etc., 
 were likely to occur and prescribed exactly what should be done in each 
 case, and by whom the correction of an error should be made. I then 
 prescribed in detail the methods to be used at each position and 
 required that they be strictly followed. 
 
 "If observations are lost, the plotter should so inform the guns. 
 In case of errors in the observations or in the setting of the arms, he 
 should report "lost" to the guns, unless it can be at once corrected. 
 In both cases the range keeper, having noted the rate of change in 
 range from previous data, should be able to set the disk at approximately 
 the correct range and continue to do so for several observations. 
 In transmitting the deflection to the guns the plotter should not 
 attempt to detect errors therein, as he is fully occupied with his other 
 work. 
 
 "The correctness of the work of the range detachment should be 
 continually verified at all drills. If errors occur, they should be 
 traced to the members of the detachment making them and the cause 
 for same determined and corrected. The rate of change in the corrected 
 range at which the range disk will be set will be uniform or gradually 
 increasing or decreasing, depending upon the course and speed of the 
 target. A record of the actual settings of the range disk will indicate 
 in a general way the accuracy of the work of the range detachment 
 as a whole. 
 
 "The following method is useful in verifying the work of each 
 member of the range section except the observers and readers: 
 
 "Prepare data corresponding to the track of a target having both 
 change in range and angular travel. This should be sufficient to cover 
 about one-half hour of tracking. With the plotting board, range board, 
 
POINTS FOR COAST ARTILLERISTS 519 
 
 etc., determine the following for each observation and tabulate same in 
 convenient form: 
 
 "Number of observation. 
 
 " If vertical base is used : Azimuth of the target from B' ; range of 
 the target from B'. 
 
 " If horizontal base is used: Azimuth of the target from B'; azimuth 
 of the target from B". 
 
 " Corrected range sent to the guns. 
 
 " Angular travel. 
 
 "Total range correction as applied on range correction scale. 
 
 " Deflection. 
 
 "Corrected range (corrected for gun displacement) for each gun of 
 the battery except the directing gun. 
 
 "The azimuth of the target from B' and B" or the azimuth and 
 range from B', if a vertical base is used, as given in above data, should 
 be transmitted from the proper observing station to the plotting 
 room at the usual observing intervals. The work of the range section 
 and gun detachment should proceed in the usual manner. A record 
 of the work of each member of the detachment, corresponding to that 
 noted above, should be made and should include the actual settings 
 of the range disk of each gun and the actual setting of each sight for 
 deflection. A comparison with the prepared data will show all errors. 
 To test the plotter as to the detection of errors in observations, 
 reading, etc., incorrect azimuths or ranges should occasionally be 
 transmitted from the observing room. The plotter should detect 
 these and call "lost" to the guns. Occasionally the data for one or 
 more observations should be regarded as lost and not sent to the 
 plotting room. The range keeper should have kept the range disk 
 set at the proper range from data previously sent, as above explained. 
 The records of the actual setting of the range disk will show with what 
 accuracy this has been done. 
 
 " Occasionally an incorrect range or deflection should be sent from 
 the plotting room to the guns for the purpose of testing the range 
 keepers and gun pointers. 
 
 "The above method can be used to advantage when there are no 
 targets in the field of fire or it is foggy." 
 
 Variations in Muzzle Velocity. The battery commander should 
 know what variation in muzzle velocity can be attributed to certain 
 conditions which may exist in a practice. Variation in range due to 
 a given variation in muzzle velocity and atmospheric conditions can be 
 taken from the range board. Variations in muzzle- velocity due to 
 
520 THE SERVICE OF COAST ARTILLERY 
 
 variations in weights of charges, diameters of rotating bands, length of 
 travel of a projectile in the bore, and to improper seating of projectiles 
 in the gun cannot be taken from range tables; and variations in range 
 due to variations in weights of projectiles cannot be taken directly 
 from these tables. The following formulae are reasonably accurate 
 for small variations in weights of projectiles and powder charges and 
 variation of travel of shot in the bore: 
 
 Variation in velocity due to variation in weight of projectile: 
 
 A V = - - V , in this formula w= weight of projectile. 
 
 Variation in velocity due to variation in weight of charge: 
 
 6 Aw 
 
 A V = V , in which w=weight of charge. 
 5 w 
 
 In these formulae weights of projectiles and powder charges are to 
 be taken in pounds and length of travel in inches. The effect of the 
 length of travel alone can usually be neglected, though some battery 
 commanders may be interested in accounting for it. 
 
 To illustrate the effect of only two variables, let us take the follow- 
 ing simple example: 
 
 The 12-inch rifle, model 1888, fires three trial shots at a range of 
 6,000 yards at a fixed target. The normal velocity is 2,520. Weight 
 of projectile, normal, 1,046 pounds. Weight of charge, normal, 275 
 pounds. The projectile for the first trial shot weighs 1,058 pounds. 
 The projectile for the second shot weighs the same. The third pro- 
 jectile has normal weight (1,046 pounds). 
 
 The charge for the first shot weighs 275 pounds. The charge for the 
 second shot weighs 275 pounds. The weight of the charge for the 
 third shot is 276 pounds. 
 
 Assuming that there are no other variations in projectiles and 
 powder, in the work of the personnel, or in the operation of the gun 
 and carriage, what would be the difference in range between the 1st 
 and 3d trial shots? 
 
 By the formulas above, we find that the variation in velocity due 
 to +12 pounds difference in weight of projectiles is 11.29 f. s., and 
 that the variation in velocity due to variation of + 1 pound in weight of 
 powder charge is +9.8 f. s. 
 
POINTS FOR COAST ARTILLERISTS 
 Therefore, we have 
 
 521 
 
 No. of Shot. 
 
 Weight of 
 Projectile. 
 
 Pounds. 
 
 Weight of 
 Charge. 
 
 Pounds. 
 
 Variation 
 in Muzzle 
 Velocity, 
 f. s. 
 
 Range 
 Variation. 
 
 Yards. 
 
 Range 
 Attained . 
 
 Yards. 
 
 1 
 2 
 
 1058 
 1058 
 
 275 
 
 275 
 
 -11.29 
 -11.29 
 
 -50.8 
 -50.8 
 
 5,949.2 
 5,949.2 
 
 3 
 
 1046 
 
 276 
 
 + 9.81 
 
 + 45.1 
 
 6,045.1 
 
 
 
 
 
 
 
 The difference in range between first and third trial shots, there- 
 fore, would be 95.9 yards. 
 
 This shows the effect of the combination of only two varying 
 factors. A systematic elimination of all variables which may be 
 said to be in the hands of the battery commander is necessary if the 
 problem is to be solved with any certainty. It is possible that in 
 practices where good results have been obtained there have been 
 compensating variations. Success in these cases has been due to 
 good luck, not good management. Good practice on the average will 
 result only from methodical and painstaking work at all times. 
 
 Accuracy of Fire and Practice. Battery commanders should dis- 
 tinguish between accuracy of fire of a gun and accuracy of practice of 
 a gun. Accuracy of fire is determined by the grouping of shots around 
 the center of impact of the group. Accuracy of practice is determined 
 by the distance of the center of impact from the center of the target. 
 In order to have a measure of accuracy of fire, and of practice, battery 
 commanders should know the probable errors of the guns of their 
 batteries with the ammunition used in practice. All shots of the group 
 of shots from which the probable error is determined should be fired 
 at the same elevation and under identical conditions as nearly as 
 possible. 
 
 In order to have available information as to probable errors of 
 their guns, data will be collected from trial and calibration shots from 
 the guns of each battery. For this purpose, district commanders 
 have issued a number of blank probable error cards of the type 
 shown on page 522, sufficient for carrying out the instructions indi- 
 cated. 
 
522 
 
 THE SERVICE OF COAST ARTILLERY 
 
 Probable error card. 
 
 Battery 
 
 Company Post 
 
 District 
 Date . 
 
 
 G 
 
 Ul 
 
 s . 
 
 
 
 
 CARRIAGE. 
 
 Caliber. 
 
 Model. 
 
 
 Reg. No. 
 
 
 Tact. No. 
 
 
 Kind. Model. Reg. No. 
 
 
 
 
 
 
 
 
 
 No. of 
 Round. 
 
 Serial 
 No. from 
 Piece. 
 
 
 Range. 
 
 Yards. 
 
 
 Difference 
 from Mean 
 
 
 Remarks. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Sum 
 
 
 
 
 
 
 
 
 Mean 
 
 
 
 
 
 
 
 
 (Mean error X 0.845= probable error.) 
 Probable error yards. Expectation 
 
 per centum of hits. 
 
 Each battery commander, and ordnance officers of batteries out 
 of commission, will determine and record on the probable error card 
 the probable error and expectation of hits from each group of shots 
 from each gun fired at the same elevation, viz.: Trial shots fired just 
 before target practice, and calibration shots. 
 
 Battery commanders will enter on probable error cards each group 
 of trial and calibration shots, going as far back as the records of practice 
 of their batteries show groups of three or more shots fired with the same 
 elevation. The cards will be subject to inspection by coast defense 
 officers or other officers who may be authorized to call for them. 
 
 Each probable error card will be prepared in triplicate, one copy 
 being retained with the battery records and one each being sent 
 directly, without letter of transmittal, to the Chief of Coast Artillery 
 and to the coast defense officer at department headquarters. 
 
POINTS FOR COAST ARTILLERISTS 523 
 
 An officer taking command of a battery should be materially 
 assisted by these cards, which will indicate the accuracy of fire of the 
 guns of his battery as mounted and with ammunition used from year 
 to year. He can also, by a proper combination of the several results, 
 draw conclusions as to the mean results to be expected from his battery 
 by the following process: 
 
 It is desirable, of course, to find the probable error at each range 
 at which firing takes place and thus acquire data for a curve of errors 
 as a function of the range. It is thought best, to begin with, to select 
 4,000, 6,000, and 8,000 yards as the points to determine the curve 
 and to reduce probable errors to these ranges as follows : 
 
 Superimpose the centers of impacts of all groups of shots fired at 
 odd times and at different ranges between 3,000 and 5,000 yards at a 
 point having a mid-range of 4,000 yards; all groups between 5,000 
 yards and 7,000 yards at 6,000 yards; all groups from 7,000 yards to 
 9,000 yards at 8,000 yards. 
 
 This can be done in the following manner: 
 
 Say, for instance, we have six groups of shots between 5,000 and 
 7,000 yards, each group fired at a different range. Superimpose the 
 centers of impacts of all groups at a mid-range of 6,000 yards, and correct 
 the dispersion of each shot of each group by finding the equivalent 
 of the actual dispersion in yards, in velocity, and in turn determine 
 the dispersion at 6,000 yards which this variation in velocity would 
 cause. In this way each shot of each group will be reduced to the 
 dispersion it should have at 6,000 yards. In other words, the errors 
 from center of impact of a group of shots at any range between 5,000 
 yards and 7,000 yards will be reduced to what they would be at 6,000 
 yards through velocity. Having treated all groups in this manner, 
 then the probable error will be determined from the total number of 
 shots fired between 5,000 and 7,000 yards as if they all belonged to 
 one group. In this plan we assume that velocity variation is the 
 principal source of error. This contemplates careful adjustments 
 and preparation of material. 
 
 Knowing what is the best that his guns, as mounted and with 
 ammunition used in practice, will do, the battery commander will 
 then be able to correct for observed errors with intelligence, and can 
 compare the accuracy of practice which he has obtained with the 
 accuracy of fire obtainable from his guns. Now, the probable error 
 of. any gun which is obtained as indicated above is defined as such 
 that just half the shots fired will in the long run have an error equal to 
 or less than this probable error. The mean error multiplied by 0.845 
 
524 THE SERVICE OF COAST ARTILLERY 
 
 is the probable error. The total width of the 50 per cent, zone, which 
 is compared to the target zone to determine expectation of hits, is 
 twice the probable error or 1.69 times the mean error. Ballistics, 
 Part I, by Captain Alston Hamilton, will indicate method of deter- 
 mining expectation of hits. 
 
 It is desired in practice to place the center of impact of a group 
 of shots in the center of the target zone. Therefore, in comparing 
 the 50 per cent, zone with the target zone to determine expectation 
 of hits, it should be considered that the point aimed at is one-fourth 
 the width of the danger space beyond the water line of the target. 
 This is necessary because with the present target the target zone is 
 made up of the danger space beyond the target and one-half the 
 danger space short of the target. 
 
 Calibration. Calibration has been conducted from various batteries 
 from time to time. It is the intention to continue this firing as funds 
 will allow, the batteries in service being calibrated first. Full advan- 
 tage should be taken of the information obtained from calibration 
 firing. The purpose of this firing is to enable such adjustment of the 
 range scales of the guns of a battery that all guns when set at the same 
 range reading will attain the same range. When mean errors from 
 calibration firing have been comparatively small and calibration 
 data reliable, elevation scales of the guns of a battery should be adjusted 
 to correct for differences in ranging of the guns. 
 
 In adjusting the scales of guns as a result of calibration firing, a 
 gun of the battery should be taken as the standard gun, and all guns 
 should be adjusted to this one. The gun first selected as a standard 
 will always be the standard gun of the battery. It is desirable, in the 
 first adjustment, that the standard gun should be the one whose 
 center of impact is nearest the target, and that its range scale be 
 not shifted. The range scales of the remaining guns of a battery 
 should be adjusted so that these guns when set with the same range 
 scale reading as the standard gun will attain the same range as that 
 gun. 
 
 Complete record of data obtained in calibration firing and adjust- 
 ments made as a result of this firing will be kept in battery emplacement 
 books, in order that the battery commander may have information 
 as to differences in the shooting of guns and the setting of indices to 
 secure uniformity in ranging of the guns of the battery. 
 
 The method outlined above appears to be the best from a con- 
 sideration of the information at present available. If as a result of 
 calibration firing in the future a better method is determined upon, 
 
POINTS FOR COAST ARTILLERISTS 525 
 
 proper instructions will be furnished to all concerned. Battery com- 
 manders having suggestions to make with reference to the method 
 of calibrating guns should submit them in brief, concise form, with 
 reports of calibration firing to the Chief of Coast Artillery. 
 
 After the calibration adjustment is made, then the center of impact 
 of a group of shots from the battery may be adjusted to the center 
 of the target zone, for any practice, by means of trial shots from any 
 gun of the battery. 
 
 There is given below extract from the proceedings of the board 
 which conducted calibration firing in 1908. This firing was very care- 
 fully conducted. It is thought the report will be of interest to the 
 service and useful to officers who have not had experience in calibration 
 firing. This was the most complete report of calibration firing sub- 
 mitted in 1908. 
 
 The arrangements for and details followed in the conduct of the 
 firing were" as follows: 
 
 The Station. A lighthouse 5,950 yards from the battery was used 
 as an observing station. 
 
 A wooden platform was constructed on the lower braces of the 
 tower and the range rakes mounted on the rail and securely fixed in 
 position with the middle point, reference number 50, on the target. 
 The azimuth instruments and the camera were mounted on the lower 
 platform of the lighthouse; thus a solid platform was obtained, so 
 that the movements around the instruments did not disturb their 
 adj ustment. 
 
 Local conditions made it necessary to locate the target 400 yards 
 from the station instead of 200 yards, as called for in the instruc- 
 tions. 
 
 The Target. The target, a standard pyramidal target, was anchored 
 in position by four 500-pound mine anchors. . . . 
 
 At the time the target was anchored it was found impracticable 
 to lay off the distance of 400 yards, owing to the fact that a strong 
 wind was blowing with the tide coming in. The target was anchored 
 accurately for range as determined by an azimuth instrument mounted 
 on the station; the distance by computation was found to be 525 yards. 
 Observations made daily on the target showed no material movement 
 of the target in range or direction. 
 
 Range Rakes. New range rakes were made, the points being 
 placed one-half inch apart, the value of each point being 6 yards. The 
 crosspiece was made so that it could be adjusted for various distances 
 from observer to target. Reference numbers stamped on the rakes 
 
526 THE SERVICE OF COAST ARTILLERY 
 
 were used to avoid confusion, the numbers increasing from on the left 
 to 100 on the right. 
 
 The crossarms were adjusted by a member of the board just before 
 the firing and the range rakes bolted in position with the meridian 
 line on the target. The rear sight was 43.75 inches from the cross- 
 arm, making each point 6 yards. The range observations were very 
 satisfactory. The officers charged with the work were interested, and 
 the results demonstrated that the range rake is satisfactory when used 
 in an intelligent manner. The azimuth instrument observations were 
 used as a check on the range rakes, and as such gave very satisfactory 
 results. It is believed, however, that the longer time taken to turn 
 an azimuth instrument on to the splash gives the splash time to spread 
 out, thus causing greater variations in separate readings. The value 
 of having at least one azimuth instrument was demonstrated, how- 
 ever, on the first shot, which struck 546 yards short; that is 246 yards 
 off the range rakes. This splash was caught by both azimuth instru- 
 ments. 
 
 The board procured a Panorama Kodak No. 1, Eastman Kodak 
 Company, from the War College for the purpose of observing the fall 
 of the shots. 
 
 An observer at the lighthouse caught every shot. 
 
 A table about 4 feet high was lashed to the rail of the lower balcony 
 of the lighthouse and the camera was leveled on this and the central 
 position of the lens was accurately directed on the target so that the 
 latter would appear in the same position on each negative. The 
 camera was then fixed in this position. 
 
 If there were any imperfections in the camera lens, this arrangement 
 insured that the fall of the shots would be measured under identical 
 positions of the lens, and the comparative values of the overs and 
 shorts would not be affected. 
 
 The observation by range rakes, azimuth instrument, and camera 
 are tabulated on opposite page, and columns 1, 2, and 3 give compara- 
 tive results of the three independent methods. 
 
 The differences are tabulated in columns 6 and 7. 
 
 It will be seen that the maximum difference is but 8.67 yards. 
 
 Column 5 gives the width of splash, as shown by the camera, the 
 average width being about 26 yards. 
 
POINTS FOR COAST ARTILLERISTS 
 
 527 
 
 [All measurements are reduced to yards.] 
 
 No. 
 
 Range 
 Rakes. 
 
 Azimuth 
 
 Instru- 
 ment. 
 
 Camera, 
 Inside of 
 
 Splash. 
 
 Camera 
 Outside 
 of Splash. 
 
 Width of 
 Splash. 
 
 Difference, 
 Azimuth 
 Instrument 
 and Range 
 Rake. 
 
 Difference , 
 Camera 
 and Range 
 Rake. 
 
 1 
 
 Off rk. 
 
 546.80 
 
 483.33 
 
 503.33 
 
 .20.00 
 
 
 
 2 
 
 114.00 
 
 112.50 
 
 116.67 
 
 143.33 
 
 26.66 
 
 1.50 
 
 2.67 
 
 3 
 
 168.00 
 
 164.08 
 
 166.67 
 
 196.67 
 
 30.00 
 
 3.92 
 
 1.33 
 
 4 
 
 168 . 00 
 
 167.16 
 
 176.67 
 
 200.00 
 
 22.33 
 
 0.84 
 
 8.67 
 
 5 
 
 291.60 
 
 290.56 
 
 290 . 00 
 
 320.00 
 
 30.00 
 
 1.04 
 
 1.60 
 
 6 
 
 168 . 00 
 
 171.84 
 
 173.00 
 
 196.67 
 
 23.67 
 
 3.84 
 
 5.00 
 
 7 
 
 102.00 
 
 101.56 
 
 103 . 33 
 
 126.00 
 
 22 . 34 
 
 0.44 
 
 1.33 
 
 8 
 
 114.00 
 
 111.00 
 
 106.67 
 
 143.33 
 
 36 . 60 
 
 3.00 
 
 7.33 
 
 9 
 
 84.00 
 
 82.76 
 
 83.33 
 
 108.33 
 
 25.00 
 
 1.24 
 
 0.67 
 
 10 
 
 192.00 
 
 193.78 
 
 200.00 
 
 223 . 00 
 
 23.00 
 
 1.78 
 
 8.00 
 
 11 
 
 150.00 
 
 148.36 
 
 146.67 
 
 176.67 
 
 30.00 
 
 1.64 
 
 3.33 
 
 12 
 
 126.00 
 
 128.08 
 
 121.67 
 
 150.00 
 
 28.33 
 
 2.08 
 
 4.33 
 
 13 
 
 192 . 00 
 
 187.05 
 
 200.00 
 
 216.00 
 
 16.00 
 
 4.95 
 
 8.00 
 
 14 
 
 129.60 
 
 128.08 
 
 133.33 
 
 156.67 
 
 23.34 
 
 1.52 
 
 3.73 
 
 15 
 
 225.60 
 
 220.28 
 
 220.00 
 
 256.67 
 
 36 . 67 
 
 .') . 32 
 
 5.60 
 
 16 
 
 156.00 
 
 159.36 
 
 163.33 
 
 190.67 
 
 27 . 34 
 
 3.36 
 
 7.33 
 
 17 
 
 78.00 
 
 71.56 
 
 76.67 
 
 100.00 
 
 23.33 
 
 6.44 
 
 1.33 
 
 18 
 
 144.00 
 
 140.56 
 
 150.00 
 
 173.33 
 
 23.33 
 
 3.44 
 
 6.00 
 
 Close agreement of the range rakes and azimuth instrument with 
 the photographic record shows excellent judgment and uniform care- 
 fulness on the part of the observers. 
 
 From the well-known construction of the panoramic camera and 
 its action, it is readily seen that these negatives give the exact relative 
 locations of target and splash. 
 
 The range rake and azimuth instrument observers cannot avoid 
 taking varying parts of the successive splashes, and so may make 
 errors .as great as 20 yards. 
 
 The camera record can be measured at leisure and checked as often 
 as may be desired. 
 
 The range-rake observations were taken as the official records. 
 
 Powder. The powder supplied for this firing was Nitro Gel. Inter- 
 national, Lot. 9, 1907. V. 2,250 f. s., P. 36,500, W. 257, Proj. 1046. 
 
 Owing to the damp condition of the magazine this powder had been 
 stored in a powder-storage magazine, from the date of its receipt, April 
 15, 1908, until it was brought to the fort, in June, 1908, and placed in 
 the submarine mine storeroom, where it was served to the guns as 
 needed in the firing. 
 
528 
 
 THE SERVICE OF COAST ARTILLERY 
 
 This powder gave very satisfactory results as to uniformity, but 
 the probable V. appears to have been only 2,150 f. s., while the 
 maximum pressure recorded was only 32,377 pounds. It is believed, 
 however, that the pressure was higher than this. 
 
 Projectiles. The projectiles supplied -for this firing were those 
 having the old-style cap, i.e., caps longer and of greater diameter than 
 the later ones. 
 
 Owing to age and frequent handling the rotating bands were more 
 or less deformed. 
 
 The maximum variation in seating the projectile was 0.228 inch 
 on No. 1 gun and 0.3 inch on No. 2 gun. This variation was too great 
 and was due to the use of untrained men for the service of the 
 piece. 
 
 Crusher Guages. Four crusher gauges were supplied ; these were 
 handled by an ordnance machinist detailed for that purpose and 
 supervised by an officer, the results being examined and checked by 
 a member of the board. Cylinders compressed to 32,000 pounds were 
 used for the first shot, but as the pressure of only 32,377 pounds was 
 recorded, cylinders compressed to 28,000 pounds were used for the 
 remaining shots. Even with these no compression was recorded on 
 the seventh, ninth, and tenth shots. These records are not considered 
 reliable; it is believed that the pressures were higher and more 
 uniform. 
 
 Density of Loading. The density of loading varied to some 
 extent. 
 
 Results and Records. Plotting of shots from range rakes and 
 azimuth instrument observations may be briefly tabulated as follows: 
 
 No. 1 GUN RANGE, 5980 YARDS 
 
 Shot. 
 
 Pressure. 
 Pounds. 
 
 Struck Short. 
 Yards. 
 
 First 
 
 32,377 
 
 546 
 
 Second 
 
 31 925 
 
 168 
 
 Third 
 
 28,092 
 
 291 6 
 
 Fourth 
 
 * 
 
 102 
 
 Fifth 
 
 * 
 
 84 
 
 Sixth . . . 
 
 30 035 
 
 150 
 
 Seventh 
 
 29,295,5 
 
 192 
 
 Eighth 
 
 29 046 
 
 225 6 
 
 Ninth ... 
 
 28092 
 
 78 
 
 
 
 
 Maximum variation in seating of projectile, 0.228 inch. 
 Maximum variation in distance to third section, 2.144 inches. 
 
 * Not recorded. 
 
POINTS FOR COAST ARTILLERISTS 
 
 529 
 
 No. 2 GUN RANGE, 5950 YARDS 
 
 Shot. 
 
 Pressure. 
 Pounds. 
 
 Struck Short. 
 Yards. 
 
 First 
 
 32 356 
 
 114 
 
 Second 
 
 28,092 
 
 168 
 
 Third . . 
 
 29 665 
 
 168 
 
 Fourth 
 
 29,572 
 
 114 
 
 Fifth 
 
 * 
 
 192 
 
 Sixth 
 
 29,757 
 
 126 
 
 Seventh ... 
 
 31 330 
 
 129 6 
 
 Eighth 
 
 28,092 
 
 156 
 
 Ninth 
 
 29 017 5 
 
 144 
 
 
 
 
 * Not recorded. 
 
 Maximum variation in seating projectile, 0.3 inch. 
 Maximum variation in distance to third section, 1.856 inches. 
 
 Comments and Conclusions. Lateral dispersion of fire is known to 
 be small for all modern rifled guns, as the deflections obtained in this 
 practice show. The necessary correction for such dispersion is so easily 
 determined and so readily applied in practice that it may be omitted 
 from this report. 
 
 A careful study of the results and due consideration of the con- 
 ditions and circumstances of the firing indicate to the board the follow- 
 ing conclusions: 
 
 1. That whatever erosion or other imperfection may have existed 
 in the guns themselves, the effects of stich imperfections were of least 
 importance in producing inaccuracy of fire when compared with the 
 mount. 
 
 2. That the chief source of inaccuracy was the mount; it being 
 the opinion of the board that with each of the carriages used the " jump " 
 of the gun was an important element, probably negative in value 
 and variable in amount. 
 
 3. That blending should be required at all times. 
 
 The board believes that the method of blending, while accurate, 
 is not suitable to service conditions. The board, however, is of the 
 opinion that all powder should be blended, whether in practice or in 
 service. Under war conditions powders from various sources will be 
 found at every post, all manufactured under the same specifications 
 of the Ordnance Department, but varying slightly in velocity, rate 
 of burning, etc. 
 
 Velocity for Trial Shots. Such velocity should be assumed for the 
 trial shots as will bring these shots as near as possible to the target. 
 
530 THE SERVICE OF COAST ARTILLERY 
 
 On account of the fact that a great many powders have fallen off in 
 velocity and are considerably under the velocity tabulated in general 
 orders, as determined by tests of the Ordnance Department, it may be 
 necessary for battery commanders to base their assumption as to the 
 muzzle velocity of their powder for trial shots on previous experience 
 obtained with this powder either by themselves or others in the service. 
 For this reason there is available a tabulation showing the mean results 
 obtained with the various lots of powder in use throughout the service. 
 
 Determination of Range Errors of Trial Shots. . . . All officers 
 should strive to eliminate these errors in the observation of trial shots. 
 The greatest care must be exercised by range observers on the tug in 
 observing splashes, and there should be a thorough understanding by 
 the officers on the tug and those on shore as to the method of signaling 
 to be used. Range rakes will be inspected by the officer in charge of 
 range observers before the practice. These rakes will be graduated in 
 mils. The tug will be anchored opposite to and as nearly as possible 
 at right angles to the line joining gun and target. The position of 
 tug and target immediately before and after each shot will be observed 
 by the position finders of the battery firing and these positions plotted 
 on the plotting board in order that mils can be correctly converted 
 into yards when they are signaled in. 
 
 If the first trial shot should fall too great a distance from the target 
 to permit of its accurate observation by the range party, the battery 
 commander should change the elevation, provided he believes that 
 the error was due to faulty assumption as to muzzle velocity, so that 
 the remaining shots will fall near the target. If this is done properly 
 the battery commander should then have the benefit of at least two 
 good trial shots. Having fired the trial shots, if these are normal and 
 the errors are small, the general practice is to take the mean of the errors 
 of these shots in making corrections for velocity for record shots. If 
 one or more shots are erratic, it may be the erratic shot or shots should 
 be thrown out, although this depends on the circumstances. The 
 problem must be solved on its merits in each case by the battery 
 commander and no definite rules can be laid down. With the present 
 target such assumption as to velocity for record shots should be made 
 as will place the center of impact one-fourth the width of the danger 
 space beyond the water line of the target. 
 
 Adjustment of Center of Impact. To aim at a point one-fourth the 
 danger space proper beyond the target is equivalent to aiming at a point 
 on the target 7^ feet above the water line. As the present target is 30 
 feet high (see Fig. 90) and therefore the point to be aimed at is 7^ feet 
 
POINTS FOR COAST ARTILLERISTS 
 
 531 
 
 above the water line, if we make correction for plus 7^ feet in the same 
 way as the correction is made for plus tide we accomplish the desired 
 result. It will be seen that when the trial shots are fired at one range 
 and their center of impact is adjusted for one-fourth the width of the 
 danger space beyond the target for that range, this fixed correction 
 will not be the true one when the record shots are fired at different 
 ranges. An officer of the Coast Artillery Corps has suggested, in 
 order that the proper correction may be made at all ranges, that a curve 
 be constructed on the range chart for 7J feet of tide. This curve 
 may be put on the range chart in pencil and can be placed conveniently 
 to the left of the travel scale, using the left vertical line of travel scale 
 for the normal of the curve. It should be understood that this correc- 
 
 FIG. 90. 
 
 tion for placing the center of impact in the center of the target zone is 
 in addition to the other corrections now provided for on the range board. 
 Observation of Fire. The question of the observation of fire has 
 received considerable thought and the policy in regard thereto was 
 outlined in a memorandum from the office of the Chief of Coast Artillery, 
 dated June 1, 1908. This memorandum pointed to the conclusion that 
 corrections based on observation of fire were inadvisable in the case of 
 batteries equipped with a separate position-finding system, viz., the 
 8-inch, 10-inch, and 12-inch rifles, and the more important 6-inch 
 batteries, in view of the fact that observations of overs and shorts 
 have been found to be unreliable. It was stated in this memorandum 
 as the opinion of the Chief of Coast Artillery that it was not thought 
 advisable for battery commanders to apply corrections based on 
 observations of fire until they had assured themselves, through the 
 observation of a number of shots, that there was a constant error in 
 the ranges for which the guns were laid. It is believed that the number 
 of shots upon which any correction is based should be not less than three. 
 
532 THE SERVICE OF COAST ARTILLERY 
 
 Therefore, if the battery commander by observation determines the 
 fact that three or more shots have fallen uniformly short or over, he 
 should then make an arbitrary correction to cause the remaining shots 
 to fall in the center of the danger space. Correction should not be 
 made when the fall of the shots is within the mean error as determined 
 by the trial shots. Observation of fire with heavy-gun batteries is 
 the last step in the solution of the target-practice problem. In this 
 problem we must start with the gun and eliminate all source of error 
 there first. Having done this, then if the shot does riot strike the 
 target we know that the manipulation of the gun has been -faulty; 
 that is, errors have arisen in the range finding and the proper applica- 
 tion of the data determined by the position-finding system to the guns. 
 We may say, therefore, that observation of fire is a means of correcting 
 errors in the position-finding service or the manipulation of the gun; 
 and to employ it intelligently we must assume that the errors we are 
 correcting for are constant. It will be appreciated that the most difficult 
 step in observation of fire is the correct determination of the range 
 errors. This is practically impossible excepting at very short ranges. 
 On high sites observation of fire is more feasible; even on these sites 
 the errors of shots can be correctly estimated only at short ranges. 
 When errors can be determined by observation any correction made 
 as a result thereof will be made by the battery commander and not by 
 the gun pointers. 
 
 At a test with 3-inch guns, it developed that observation of fire was 
 unreliable' except at very short ranges for the ordinary height of battery. 
 Range errors short of the target could be fairly well estimated, but 
 it was practically impossible to estimate reliably the errors of the shots 
 that fell beyond the target. As a result of this test in which a great 
 number of rounds were fired, the following conclusions on the proper 
 method of making corrections from observation of fire with rapid-fire 
 batteries were arrived at: 
 
 That range corrections based on observation of fire should be 
 made only by the battery commander. 
 
 That deflection corrections with rapid-fire guns should be made 
 by gun pointers. The training of gun pointers is, therefore, of great 
 importance. 
 
 That velocity corrections as a result of trial shots with rapid-fire 
 guns may be applied by shifting the range scale or the pointer, or by 
 correcting the ranges determined by the range finder, before these 
 ranges are posted." 
 
POINTS FOR COAST ARTILLERISTS 
 
 533 
 
 VALUE IN YARDS OF POINTS OF DEFLECTION 
 
 During subcaliber and service practice, battery commanders should 
 record and study deflections. In this connection the following table 
 will be found beneficial. 
 
 Hundred ths of degrees 
 
 5 
 
 10 
 
 15 
 
 90 
 
 25 
 
 30 
 
 35 
 
 40 
 
 45 
 
 50 
 
 
 
 
 
 
 
 
 
 
 
 
 Minutes 
 
 3 
 
 6 
 
 q 
 
 1? 
 
 15 
 
 18 
 
 91 
 
 94 
 
 97 
 
 30 
 
 
 
 
 
 
 
 
 
 
 
 
 Points 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 RANGES 
 
 
 
 
 VAL 
 
 UE I 
 
 x Y 
 
 ARD 
 
 s 
 
 
 
 1 000 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 q 
 
 10 
 
 2 000 .... 
 
 2 
 
 4 
 
 6 
 
 8 
 
 10 
 
 12 
 
 14 
 
 16 
 
 18 
 
 20 
 
 3 000 
 
 3 
 
 6 
 
 q 
 
 19 
 
 15 
 
 18 
 
 21 
 
 94 
 
 97 
 
 30 
 
 4 000 
 
 3 
 
 6 
 
 9 
 
 12 
 
 15 
 
 18 
 
 21 
 
 24 
 
 27 
 
 30 
 
 5 000 
 
 4 
 
 8 
 
 12 
 
 16 
 
 ?0 
 
 94 
 
 28 
 
 39 
 
 36 
 
 40 
 
 6 000 
 
 5 
 
 10 
 
 15 
 
 20 
 
 25 
 
 30 
 
 35 
 
 40 
 
 45 
 
 50 
 
 7 000 
 
 6 
 
 12 
 
 18 
 
 94 
 
 30 
 
 36 
 
 49 
 
 48 
 
 54 
 
 60 
 
 8,000 
 
 7 
 
 14 
 
 21 
 
 98 
 
 35 
 
 49 
 
 49 
 
 56 
 
 63 
 
 70 
 
 9 000 
 
 8 
 
 16 
 
 24 
 
 39 
 
 40 
 
 48 
 
 56 
 
 64 
 
 72 
 
 80 
 
 10,000 
 
 9 
 
 18 
 
 97 
 
 36 
 
 45 
 
 54 
 
 63 
 
 79 
 
 81 
 
 90 
 
 11 000 
 
 10 
 
 20 
 
 30 
 
 40 
 
 50 
 
 60 
 
 70 
 
 80 
 
 90 
 
 100 
 
 12,000 
 
 10 
 
 20 
 
 30 
 
 40 
 
 50 
 
 60 
 
 70 
 
 80 
 
 90 
 
 100 
 
 NOTE. This table is not exactly accurate, the value of one point at 1,000 yards is exactly 
 0.87426 yards, but as the error is less than one yard it may be used safely for all firings under 
 Case II. The value of one point may therefore be taken as .001 of the range, or equal to one mil. 
 
 All ballistic corrections which battery commanders may desire to 
 make should be sent through the primary station. They should see 
 that an accurate record is kept of all shots fired. 
 
 In battle and fire-command drills after receiving the order announc- 
 ing the kind of fire, battery commanders state the kind of projectile 
 to be used, the character of fire and command, "Commence firing/' 
 
 At target practice they see that all reports are properly and promptly 
 transmitted. 
 
 During drills men temporarily disengaged should be required to 
 remain silent and alert. No talking or smoking should be permitted 
 at emplacements or stations under any circumstances. 
 
 No person should be allowed on the parapet during drill or practice. 
 
 Battery commanders should remain constantly at their proper 
 stations unless called away for some urgent reason, in which event 
 they 'leave word where they can be found. 
 
534 THE SERVICE OF COAST ARTILLERY 
 
 The possibility of gun pointers or others being disabled should be 
 provided for and their successors named in advance. 
 
 The following are the proper commands for battery commanders: 
 
 To load and fire: 
 
 "No. 1 (or, No. 2), With dummy pi>jectile; Fire one shot, Com- 
 meiie Firing." 
 
 "No. 1 (or, No. 2), With A. P. Shot, Fire one shot, Commence 
 Firing." 
 
 "No. 1 (or, No. 2), With dummy projectile, Commence Firing." 
 
 "With dummy projectile, Fire one round, Commence Firing." 
 
 "With A. P. Shot, Commence Firing." 
 
 "With Subcaliber ammunition (or, C. I. Shot, or, Dummy Pro- 
 jectile, etc.), Commence Firing." 
 
 During battery drill battery commanders designate targets in the 
 same manner as prescribed for fire commanders. 
 
 EMPLACEMENT OFFICERS 
 
 Emplacement officers should be so familiar with the entire mechan- 
 ism of guns and carriages as to be able, if necessary, to take the place of 
 any enlisted man in the gun section. 
 
 They should be perfectly capable of making any repairs of a minor 
 nature that may be necessary during drill or action. They should 
 have a practical working knowledge of breechblocks, firing mechanisms, 
 the recoil system and stuffing boxes, as well as sights and the various 
 equipment incidental to guns and mortars. 
 
 No emplacement officer is capable of doing the work which the 
 position requires unless he has a practical working knowledge of each 
 position on the gun. 
 
 Emplacement officers should take every opportunity to teach 
 enlisted men the theory of the work, that is, the theory of pointing 
 and laying guns; the meaning of Case I, Case II, and Case III; as 
 well as the part each of them plays in the logical chain of events which 
 begins at the target, thence to the primary and secondary stations, 
 thence to the guns and back to the target again. 
 
 A close study of the illustrations found herein of the several types of 
 guns, mortars and various equipment connected therewith, will be 
 found a great help in their studies. 
 
 Emplacement officers are responsible to the battery commander 
 that all parts of the guns and carriages are in perfect working 'order 
 
POINTS FOR COAST ARTILLERISTS . 535 
 
 and that all necessary adjustments are properly made. They are 
 responsible for safety during drill and action. They should see that 
 their men work with calmness and speed, keeping constantly in mind 
 that proper seating of the projectile, careful handling of powder, proper 
 locking of the breech, proper swabbing of the powder chamber after 
 each shot, are all matters of vast importance each of which takes prece- 
 dence over speed. 
 
 Emplacement officers see that the ammunition specified is used, 
 that the artillery discipline during drill or action is constantly main- 
 tained, that men disengaged stand at ease, that in moving from place 
 to place the men do so at double time, and that all orders are 
 instantly obeyed. 
 
 RANGE OFFICERS 
 
 Range officers should be perfectly capable of operating and adjusting 
 every instrument in the fire-control stations. This knowledge should 
 be such that in case minor repairs are necessary they can make them. 
 
 Upon arrival at the station the range officer should see that each 
 man examines and properly adjusts the instrument to which he is 
 assigned and that the proper reports are made to the Plotter. The 
 reports, when no defects are found, are as follows: " B Prime, In Order." 
 "B Second, In Order." "Deflection Board, In Order." "Range 
 Board, In Order." "Telautograph, In Order." "F. C. Intelligence, 
 In Order." " B. C. Line, In Order." " Gun Line, In Order." " Secondary 
 Intelligence, In Order." 
 
 The Plotter, after having received the above reports (or reports 
 of any repairs necessary), and after making the adjustments of the 
 equipment to which he is assigned, reports to the range officer: "Sir, 
 Plotting Room, In Order" (or reports such defects as cannot be readily 
 corrected) . 
 
 The Observer, after satisfying himself that the observing room 
 equipment is in order and that the position-finding instrument is in 
 proper adjustment, reports to the range officer: "Sir, Observing Room, 
 In Order." . 
 
 After the range officer has satisfied himself by personal inspection 
 that everything is in readiness, including Secondary Station, he reports 
 to the battery commander: "Sir, Fire Control Stations, In Order" 
 (or reports any defects that cannot be readily corrected). 
 
 Upon orders being received from the battery commander designating 
 a target, the range officer commands: 
 
536 THE SERVICE OF COAST ARTILLERY 
 
 "Target (repeating the battery commander's description verbatim; 
 and adding any other information that may facilitate identification)." 
 
 After the target has been identified by the primary and secondary 
 observers and the gun pointer (or, if vertical base system is used, by the 
 primary observer and gun pointer) , the range officer commands : 
 
 "Horizontal (or, Vertical) Base, Track." 
 
 He then reports to the battery commander over the B. C. line: 
 
 "Target." 
 
 Upon orders being received from the battery commander to change 
 target, etc., the range officer commands: 
 
 "Cease Tracking. Change Target. Target (repeating description, 
 etc.)." 
 
 At the end of the drill or exercise, the range officer commands: 
 
 "Close Station." 
 
 In the case of battle or fire-command drill or action, he transmits 
 the following message from the battery commander to the fire com- 
 mander: 
 
 "Dix, In Order." (Or, reports repairs which the battery com- 
 mander deems necessary.) 
 
 When a target is assigned by the fire commander and after it has 
 been properly identified, the range officer sends the following message 
 to the fire commander: 
 
 "Dix, Target." 
 
 The range officer receives directly from the fire commander, 
 and executes, orders as to the assignment of targets; and when direct 
 communication between the fire commander and the battery com- 
 mander is impracticable, he receives directly, and executes, other 
 orders pertaining to the fire action of the battery. He is responsible, 
 however, for the prompt and accurate transmission to the battery 
 commander of all orders received by him directly from the fire com- 
 mander. 
 
 TUG OFFICER AND TUG OBSERVER 
 
 An experienced officer not belonging to the company firing, prefer- 
 ably a district staff officer, is in charge of the tug during service 
 practice. 
 
 The tug officer determines the overs and shorts for all shots except 
 the record practice of guns below 4.7 inches in caliber. He is assisted 
 by an officer or a non-commissioned officer equipped with a camera 
 or a range rake. (For description, see DEFINITIONS.) For trial shots 
 
POINTS FOR COAST ARTILLERISTS 537 
 
 both observers obtain the overs and shorts in mils. For record shots 
 of mortar batteries and of gun batteries above 4-inch the assistant 
 observer uses the camera, if available; otherwise the range rake. 
 When both observers are using range rakes, the results of the observa- 
 tions on the tug shall not be called or spoken aloud, but shall be recorded 
 without comment by the observer as soon as made. The observer shall 
 sight on the edge of the splash nearest the gun. The average of the 
 deviations determined by the observers when both are using range 
 rakes shall be recorded as the deviation normal to the line joining the 
 tug and target. When record is obtained with the camera the range- 
 rake observation shall be discarded and, under direction of the fire 
 commander, the camera record reduced to yards. The records are 
 submitted to the fire commander on the proper form, who may discard 
 the deviations reported by any observer upon satisfactory representa- 
 tion by the officer in charge of the range party on the tug that the 
 observation was probably erroneous. The points of attachment of the 
 towline to the targets and the point of the towline at the position 
 occupied by the observers on the tug shall be marked by tying cloth 
 around the towline or by other suitable means. Immediately after 
 the practice and while still wet the towline shall be detached from the 
 tug and targets, stretched, and measured accurately between the points 
 marked, under the supervision of the officer in charge of the tug, and 
 the result of this measurement shall be entered on the proper form as 
 the length of the towline. No allowance shall be made for sag. 
 
 Tug officers are responsible that the following material is on the 
 tug whenever it goes out for target practice. 
 
 One copy of current Coast Artillery Instruction Memorandum; 
 one copy of Tug Service; six forms No. 823; one red streamer; three 
 range rakes; 600 yards of towing line; 300 yards of anchor rope; 
 3 buoys; all the target anchors available; paint pot and brush, for 
 marking out subcaliber hits; two pairs of field glasses; one army 
 signal code card; two red wig-wag flags; one measuring tape; two 
 cameras; one memorandum pad. 
 
 Each launch should be equipped with a red streamer, a red signal 
 flag, and a copy of Tug Service. 
 
 Each tug should be equipped with wireless telegraph apparatus in 
 order to communicate with the officer in charge of the firing as well 
 as to promptly inform the battery commander of the range deflections 
 of trial shots. 
 
 Tug officers are responsible for the efficiency of the tug detail, 
 which should consist of the necessary number of men to handle targets, 
 
538 THE SERVICE OF COAST ARTILLERY 
 
 to watch shore signals, to read or send wig-wag signals, and to use the 
 cameras. 
 
 The actual maneuvering of targets from tug will be under the 
 supervision of the master of the tug. 
 
 All personnel detailed for tug service should provide themselves 'with 
 lunches. 
 
 Each fixed target should be anchored with two heavy anchors and 
 buoyed; a rectangular target always broadside to the battery. 
 
 As far as practicable targets should be planted the day before firing. 
 
 A fixed target should, whenever practicable, be left down as a marker 
 on the selected course for practice at a moving target. 
 
 In anchoring the tug to observe splashes or hits for fixed target, 
 always take position to left of target (as viewed from the battery) on 
 a line perpendicular to line of fire, about 200 yards when rectangular 
 target is used, 300 yards for service gun practice, and 500 yards for 
 mortar practice (subcaliber and service). Always anchor tug for trial 
 shots. For description of targets, see Pyramidal and Material Targets, 
 in the DEFINITIONS. 
 
 The nearest towed target, to the tug, for gun fire will always be 
 200 yards, and for mortars 500 yards. 
 
 Towline will always be stretched and measured wet, immediately 
 after returning from practice under the direct supervision of the senior 
 tug observer; the measured length being noted on report. 
 
 The senior tug officer will report to the Umpire and Fire Com- 
 mander, before going out, for written instructions and a harbor chart 
 with positions of targets, courses, etc., indicated thereon. This chart, 
 with report, will be returned to the Umpire immediately after the 
 return of the tug party to post. 
 
 The charted course for a moving target may often serve as a general 
 guide only, or unexpected developments may change plans ashore. 
 Consequently it may often happen that the tug will have to be run on 
 course by signals from the signal station ashore. A constant lookout 
 will be maintained for such signals, and they must be promptly and 
 accurately obeyed. 
 
 Before leaving for day's work, the senior tug officer will set his 
 watch on post time. 
 
 SHORE TUG SIGNALS 
 
 A flag will be designated on shore for the purpose of displaying the 
 firing signal, and will be used for no other purpose. The firing signal 
 
POINTS FOR COAST ARTILLERISTS 
 
 539 
 
 staff will be located in the immediate vicinity of the battery firing, 
 preferably near the center. 
 
 A long red streamer will be displayed from the firing signal staff 
 and one on the tug. In no case will firing be permitted unless the red 
 streamer is displayed both ashore and afloat. As a rule, the first 
 signal will be displayed on shore, the tug displaying its streamer as 
 soon as the range is clear. In case of danger to tug or to any other 
 boats near the field of fire, the tug will lower streamer, shore station 
 
 
 
 Anchor target. 
 5. 
 
 Take up anchor. ' 
 6. 
 
 Proceed to execute what 
 is prescribed next. 
 
 7 
 
 Indicate Score. 
 8. 
 
 Halt and await 
 further orders. 
 
 9. 
 
 Take course for practice 
 at moving target. 
 
 /O. 
 
 To your right. 
 
 To your left. 
 IS. 
 
 
 \ 
 
 Turn about. 
 
 Increase range. Decrease range. 
 
 FIG. 91. 
 
 Come in, practice ended. 
 
 immediately responding. The whistle signal of "D" 222 will also 
 be given from the tug. 
 
 During subcaliber mortar firing, on account of the difficulty of 
 catching mortar splashes, the red streamer will be run down and up 
 several times as a warning immediately after each shot is fired. 
 
 The " Maneuver" signal staff will be located in the immediate 
 vicinity of the Fire Commander's station. 
 
 The accompanying diagram (Fig. 91) represents the various 
 
540 THE SERVICE OF COAST ARTILLERY 
 
 maneuver signals as they would appear when viewed from the tug. 
 Owing to their lightness and uniformity of dimensions four ordinary 
 megaphones may be used, when available, in forming signals until 
 cones or disks are supplied. 
 
 REMARKS ON MANEUVER AND SOUND SIGNALS 
 
 The tug should drop target anchors as promptly as possible after 
 Signal No. 1 is shown on shore. If the tug is not fitted with appliances 
 for tripping anchors at word of command drop a marking buoy at once. 
 
 (a) The tug will acknowledge all maneuver signals by one long 
 blast followed by two toots in quick succession. 
 
 (6) The shore signal will be lowered as soon as the tug acknowledges. 
 If signal is One that puts tug in motion, it will continue in the direction 
 indicated until some other signal is displayed on shore. 
 
 (c) Signal up and down several times, means go slow, to be acknowl- 
 edged by the tug as soon as made out, after original acknowledgment. 
 
 (d) Signal No. 3. This means proceed to next step indicated in 
 tug officer's orders. 
 
 (e) Signal No. 4. The following designations are used: 
 
 Hit. "H" [122] 1 toot, 2 toots, 2 toots. 
 
 Over. "O" [21J 2 toots, 1 toot. 
 
 Short. "S" [212] 2 toots, 1 toot, 2 toots. 
 
 To indicate the number of hits at subcaliber gun practice; acknowl- 
 edge Signal No. 4. After marking, Signal " H," considerable pause, 
 followed by one toot for each hit. If no hits, signal " H" only. 
 
 To indicate the result of a trial shot at service gun practice, and 
 mortar practice (subcaliber and service) acknowledge Signal No. 4, 
 long pause, toot "S" or "0" as the case may be, considerable pause 
 followed by one toot for each division of the range rake. If there is 
 no deviation signal "O" only. In the case of shot off the rake, after 
 "S" or " O" give one long blast, marked pause, and one toot fcr 
 every five divisions of estimated deviation. 
 
 Make a distinct pause between toots in a series indicating hits or mils 
 so that successive puffs of steam can be clearly distinguished. 
 
 (/) Halt (No. 5) repeated means a probable intermission or delay 
 of half an hour for each repetition. 
 
 (g) Signals Nos. 7 and 8. If at a halt move in direction perpen- 
 dicular to line joining tug and Fire Commander's station, rights or 
 
POINTS FOR COAST ARTILLERISTS 541 
 
 lefts being determined as tug observer faces this station. If in motion 
 bear off in direction indicated (as tug observer faces bow) by one point 
 (about 11 degrees). To make a considerable change in direction 
 repeat necessary number of times. 
 
 (h) Signal No. 9. Tug will make a turn of 180 degrees to right. 
 If once repeated turn to left. (In either case, as observer faces bow.) 
 
 (i) Signals Nos. 10 and 11. Move directly away from or towards 
 Fire Commander's station as the case may be. 
 
 SOUND SIGNALS 
 
 Tug will use following conventional sound signals: 
 
 " D" 222 (2 toots, 2 toots, 2 toots), Danger to tug or to boats in the 
 vicinity. 
 
 "W" 1121 (1 toot, 1 toot, 2 toots, 1 toot), Something wrong on 
 board, am having trouble. 
 
 "K" 2121 (2 toots, 1 toot, 2 toots, 1 toot), All right now, am ready 
 to resume work. 
 
 "X" 2122 (2 toots, 1 toot, 2 toots, 2 toots), Have executed what 
 was ordered last (used generally after a movement requiring some 
 time to execute, has been completed as directed by Signal No. 3). 
 
 WIG-WAG SIGNALS 
 
 (a) The shore flagman will be posted near the maneuver signal 
 staff. 
 
 (b) The tug's call letter is "T". The shore station's call letter is 
 "F." 
 
 (c) The tug will never be called unless Signal No. 5 is first displayed. 
 If tug wishes to call shore, the tug will always do so from a halt. In 
 the latter case, in addition to the usual wig-wag call, the tug will toot 
 "F" (2221) 2 toots, 2 toots, 2 toots, 1 toot, 
 
 (d) Tug will acknowledge wig-wag call in the same manner as 
 prescribed in the case of maneuver signals, this in addition to the flag- 
 man's acknowledgment. 
 
 (e) The tug flagman should be posted well up on the upper deck 
 with the sky as a background, and a red flag should be used. 
 
 Whenever practicable, the shore flagman, also, should use a sky 
 background. 
 
542 THE SERVICE OF COAST ARTILLERY 
 
 NIGHT SIGNALS 
 
 For maneuvering at night, the Battle Commander's searchlight is 
 used to indicate the number of disks or cones used for each of the 
 maneuver signals. 
 
 The beam is first directed over the smokestack of the tug and 
 then swung in arcs of about 30 degrees to the right or left, as seen from 
 the tug. When both right and left are required, the right arcs are 
 made first. For example, maneuver signal No. 3 would be one swing 
 to the tug observer's right and three to his left; signal No. 6, would 
 be two swings to tug observer's right and two to his left. 
 
 WIRELESS COMMUNICATION 
 
 When wireless communication is used, the maneuver signals 
 are communicated by number, prefixed by the letter M. For example, 
 the maneuver signal indicating "Take up anchor," would be sent " M2." 
 
 OBSERVERS 
 
 Observers are trained out of drill hours, to observe fixed objects, the 
 distance of which are accurately known, until they can quickly deter- 
 mine ranges with accuracy. Officers in immediate command of 
 observers test their proficiency in the following manner: After the 
 observer has properly adjusted the instrument (as explained in 
 Chapter VII), the range and azimuth scales are covered. 
 
 The officer then indicates the object (the range and azimuth of 
 which is accurately known), and commands: "Take," at the same 
 time starting his stop-watch. As soon as the observer has completed 
 the observation, he reports, " Now." 
 
 The officer then stops the watch and personally reads the range 
 and azimuth from the scales of the instrument, making a record of the 
 readings as well as the time between "take" and "now." Several 
 points are located in a like manner and the operation repeated until 
 three observations have been made on each point. 
 
 Observers should carefully study the methods of water-lining, 
 (See Depression Position Finder, Chapter VII). They should con- 
 tinually follow the target, keeping the vertical cross-wire a shade 
 in front of the point upon which it is desired to have the instrument 
 
POINTS FOR COAST ARTILLERISTS 543 
 
 point at the third stroke of the time-interval bell, so that when the 
 traversing of the instrument is stopped on the third stroke of the bell 
 the wire will be accurately on the center of the target, or point upon 
 which it is desired to aim. 
 
 Observers should be familiar with every part of their instrument 
 and capable of its perfect adjustment and care. 
 
 GUN POINTERS 
 
 Gun pointers should practice at every opportunity, what may be 
 termed "continual aim." The difficulty of keeping the gun pointed 
 or trained directly at the required point on the target can only be 
 overcome by practice on the part of the gun pointer (and the traversing 
 detail if the gun is not operated by electricity). 
 
 In vertical-base tracking they should keep the horizontal cross-wire 
 of the sight constantly on the water line of the target, as explained 
 in the article on position finders (see Chapter VII) , and the vertical 
 cross-wire slightly forward of the point it is desired to hit. 
 
 Care should be exercised in firing service charges, to give the 
 command "Fire" (when not firing electrically) when the vertical cross- 
 wire is a shade in advance of the point it is intended to hit, for the 
 reason that there is an appreciable interval of time between the instant 
 the command "Fire" is given and the instant the projectile leaves the 
 muzzle, caused by the slow ignition of smokeless powder as well as the 
 time incidental to the pulling of the lanyard. This interval is calculated 
 at from one-sixteenth to one and one-quarter seconds, hence with a 
 rapidly moving target a slight percentage of accuracy is lost. 
 
 When the gun is fired electrically the percentage of time lost is, 
 of course, reduced to the interval consumed by the ignition of the 
 powder. 
 
 In order that accurate results may be obtained gun pointers should 
 be careful to fire the gun at the last stroke of the time interval bell 
 following the range setter's announcement "Range Set," as the calcula- 
 tions are based on the projectile leaving the muzzle at that instant. 
 
 RANGE SETTERS 
 
 The principal duty of the range setter is the accurate setting of the 
 range drum. He is responsible for the proper elevation or range of the 
 
544 THE SERVICE OF COAST ARTILLERY 
 
 piece. In case an observation is lost he sets the gun at the range called 
 to him by the operator at the time-range board. 
 
 In setting for elevation, the effects of backlash are practically 
 eliminated if the graduation is always approached from the same 
 direction that direction which depresses the piece being the best. 
 
 METEOROLOGICAL OBSERVERS 
 
 The meteorological observer is responsible for the care and adjust- 
 ments of all instruments and equipment installed at the meteorlogical 
 station. 
 
 Upon his arrival at the station he reports his presence to the battle 
 commander's station. He then adjusts the mercurial barometer by 
 means of the adjusting screw which lowers the mercury in the cistern 
 and then raises it -until the surface exactly touches the ivory point. 
 He then tests the aneroid barometer by carefully comparing its reading 
 with the mercurial barometer in order to determine the proper correction 
 to be applied for instrumental error and then notes the corrections to 
 be made if any. He then connects the electrical device of the ane- 
 mometer, adjusts the stop-watch device, if it is used in the station. 
 He notes whether the wind-vane works freely. He tests and syn- 
 chronizes the aeroscope. After satisfying himself that everything is 
 in readiness he reports to the battle commander's station: 
 
 "Meteorological Station, In Order." 
 
 He then immediately records on the aeroscope the azimuth of the 
 wind as determined by the wind vane, and its velocity, as determined 
 from ten readings of the anemometer; then reads the barometer and 
 thermometer and records on the aeroscope the atmosphere per -cent, 
 as determined from the atmosphere board. 
 
 The direction and velocity of the wind should be recorded at least 
 every twenty minutes or oftener if necessary. Any sudden change 
 either in direction or velocity of the wind of any considerable magnitude 
 should be recorded and reported at once. The relative weight of the 
 air should be recorded whenever it changes more than 1 per cent. 
 He keeps a complete record of all messages. 
 
 Meteorological observers should study carefully the description, 
 etc., of instruments appertaining to the station which appears in another 
 part of this book. 
 
POINTS FOR COAST ARTILLERISTS 545 
 
 TIDE OBSERVERS 
 
 The tide observer is responsible for the care and adjustment of 
 all equipment installed at the tide station. 
 
 Upon arrival at the station he first tests and synchronizes the 
 aeroscope, and sees that the tide-gauge is in proper order. After 
 satisfying himself that everything is in order he reports to the battle 
 commander's station: 
 
 "Tide Station, In Order/' 
 
 He then records the height of tide on the aeroscope and thereafter 
 reports the tide for every half foot. 
 
 CAMP SANITATION 
 
 Deaths from sickness have outnumbered those of violence in all our 
 wars. In the Philippines, in the eighteen months following July 1, 
 1898, 36 officers and 489 men were killed in action or died of wounds, 
 while 16 officers and 693 men died of disease. 
 
 Coast artillery camps are practically permanent and have the 
 advantage of being pitched near tide or salt water. They have more 
 or less permanent drainage and are usually adjacent to permanent 
 military hospitals. All these features facilitate proper sanitation. 
 They do not necessarily conduce to the health of troops, however, 
 unless their features are developed by the constant efforts of the 
 officers in immediate control of troops. The importance of such 
 officers making every effort to compel soldiers to comply with the laws 
 of sanitation is emphasized when it is remembered that the whole 
 military fabric rests upon the physical character of the individuals 
 composing it. 
 
 Coast artillery camps should be as widespread as tactical con- 
 siderations and convenience to the batteries will permit. 
 
 The health of all camps depends fundamentally upon: (1) food, 
 (2) water supply, (3) disposal of excreta, (4) absence of flies and other 
 germ-carrying insects, and (5) personal cleanliness. 
 
 Field cooking is of the utmost importance to the health and con- 
 tentment of a command. It is useless to expect men, however well 
 equipped, to keep the field with vigor if they cannot subsist on the 
 food supplied. Officers should personally inspect each meal and satisfy 
 
546 THE SERVICE OF COAST ARTILLERY 
 
 themselves that the food is properly cooked and served in the proper 
 proportion. 
 
 Civilian cooks of militia companies should be informed when em- 
 ployed that they will be required to submit to daily inspection as to 
 the cleanliness of their persons, underclothing, etc. The cleanliness 
 of these cooks should be a charge of the company officers, for it is a 
 well-known fact that civilian cooks and their assistants are usually 
 the most unkempt individuals in the camp, while, by reason of their 
 occupation, they should be the cleanest and neatest in appearance. 
 
 The water supply should be given careful study, and under-drainage 
 procured if possible. Proper drainage is an important element in 
 connection with the health of troops. 
 
 Constant endeavor should be made to prevent flies from carrying 
 contagion from the sinks to the food. Burning a little mineral oil in 
 the sinks and metal garbage cans helps keep down the flies. Garbage 
 cans should, when practicable, be placed in a shaded place. Tightly 
 fitting covers are absolutely necessary. Lime when issued should be* 
 sprinkled freely about the cans, and after emptying, lime should cover 
 the bottom of each can. All refuse should be burned and particular 
 care exercised to keep the camp clear of horse manure, which is a rapid 
 breeder of flies. 
 
 Company kitchens should be the special care of the officers of each 
 company, who should visit them frequently and insist upon absolute 
 cleanliness of every part thereof. They should be well screened with 
 wire netting. All food should be kept constantly covered, and when no 
 ice is provided the meat ration should be cooked as soon as received. 
 When ice is issued or provided the meat ration should not be allowed 
 to remain uncooked for over five hours after issue. 
 
 The only practical way of ridding kitchens and mess shacks of flies 
 is to starve them, and this can only be accomplished by keeping the 
 shacks barren of food particles. Orders should be issued prohibiting 
 the throwing of food of any character on the ground, and severe pun- 
 ishment follow any infraction of the order. Mess tables should be 
 cleaned or washed of all crumbs and refuse immediately after each 
 meal and the ground about the mess tables raked and cleaned of all 
 crumbs, etc. 
 
 The latrines should be kept scrupulously clean and well supplied 
 with paper and lime. They should be under the charge of an enlisted 
 man held responsible for their condition during his tour of duty. 
 This detail should be indeterminate in duration, that is, any man found 
 or reported breaking any of the rules governing the latrines should 
 
POINTS FOR COAST ARTILLERISTS 547 
 
 be assigned immediately to the work of keeping them clean, such 
 assignment continuing until some other man is found to have trans- 
 gressed the rules. 
 
 Tents should be ditched as soon as they are pitched. No circum- 
 stance, even that of extreme fatigue, should be allowed as an excuse 
 for omitting this important part of the proper pitching of tents. The 
 ditch should be dug around each tent and should be shallow; the 
 earth taken out being banked on the inner side, so that the wall of the 
 tent will fall over the mound. 'The ditch should empty into a com- 
 pany ditch arranged for a careful system of drainage. 
 
 Tent walls should be raised for several hours each day and all 
 bedding and other contents exposed to the sun. If board floors are 
 used, the boards should be loose and removed frequently and the 
 ground beneath them cleaned and aired. In the case of conical tents 
 they should be unfastened daily and folded loosely about the center 
 pole so that the ground or flooring is exposed to the sun. 
 
 When practicable tents should be pitched at such a distance apart 
 as to have adjacent to each an equal unoccupied area, so that their 
 position can be changed from one site to the other once each week. 
 
 The Conical Wall Tent contains a floor space of 212 square feet; 
 air space, 1450 feet; allowance, 20 foot soldiers, comfortable for about 
 half that number. When cots are used 6 men can be accommodated. 
 
 The Wall Tent contains a floor space of 81 square feet; air space, 
 500 feet; usually used for one or two officers. 
 
 The Common Tent contains a floor space of 57 square feet; air 
 space, 250 feet; allowance 6 foot soldiers, comfortable for half that 
 number. 
 
 Mosquito netting is a required sanitary precaution against malaria 
 where the anopheles mosquito is found and is still more important 
 against yellow fever within the habitat of the stegomyia fasciata. 
 In such regions its careful use should be enforced as a matter of 
 routine discipline. 
 
 Men should be required to keep the hair short and the teeth clean; 
 to bathe daily the head, feet, armpits, groins, anus, and genitals. 
 
 SHIP BARK BARKENTINE BRIG BRIGANTINE SCHOONER SLOOP 
 
DO 
 
INDEX 
 
 (Numbers refer to pages.) 
 
 "A" row, 1, 79. 
 Abatis, 1. 
 Abbreviations, 63. 
 Absolute deviation, 1. 
 Accumulator room, 1. 
 Accuracy of D. P. F., 311. 
 
 of fire and practice, 100, 521. 
 Adjutant, 1. 
 
 Administrative organization, 76. 
 Aeroscope, 1, 343, 344. 
 Aiming, 1, 99. 
 Air spaces, 1. 
 All-round-fire, 1, 188. 
 Ammunition, 1, 245, 491. 
 
 hoist, 1. 
 
 recess, 1. 
 
 shoes, 2. 
 
 truck, 2, 510. 
 Anemometer, 2, 356. 
 Aneroid barometer, 2, 355. 
 Angles, etc., 106. 
 
 acute, 106. 
 
 biting, 95. 
 
 clear, 502. 
 
 equilateral, 106. 
 
 iscosceles, 106. 
 
 obtuse, 106. 
 
 of departure, 2, 96. 
 
 of depression, 96. 
 
 of elevation, 22, 502. 
 
 of fall, 2, 96, 502. 
 
 of impact, 2, 95. 
 
 of incidence, 2, 95. 
 
 of jump, 2, 95. 
 
 of position, 2, 96. 
 
 quadrant, 2, 95, 96, 395. 
 
 right, 106. 
 
 scalene, 106. 
 
 striking, 2, 95, 96, 274. 
 Angular elevation or depression, 2, 95, 
 
 96, 395. 
 
 Angular velocity, 2. 
 Approaches, 2. 
 
 Apron, 2. 
 
 Arbitrary correction, 531. 
 
 deflection board, 340. 
 
 rapid-fire guns, 531. 
 Arc, 2. 
 Area, 2. 
 Armament, 2, 107. 
 
 intermediate, 32, 133. 
 
 primary, 45, 108. 
 
 secondary, 52, 155. 
 Armor, 2. 
 
 belt, 2. 
 
 piercing projectiles, 3, 274. 
 Armstrong guns, 3. 
 
 4.72-inch, 153. 
 
 6-inch, 133. 
 Artillery, 3. 
 
 garrison, 5. 
 Artillery district, 3. 
 
 adjutant, 3. 
 
 commander, 3. 
 
 commander's flag, 26. 
 
 engineer, 21. 
 
 ordnance officer, 4. 
 
 quartermaster, 4. 
 Assembling breech mechanism: 
 
 12-inch gun, see 10-in. G. 
 
 12-inch mortar, 118. 
 
 10-inch gun, 124, 130. 
 
 8-inch gun, see 10-in. G. 
 
 6-inch gun, 142, 147. 
 
 5-inch gun, 152. 
 
 3-inch gun, 159, 162. 
 
 2.24-inch gun, 167, 171, 176. 
 Assistant plotter, 78. 
 Attacks from sea, 68. 
 
 night, 74. 
 
 Atmosphere board, 5, 358. 
 Automatic firing, 5. 
 
 machine guns, 5. 
 Auxiliary : 
 
 horizontal base system, 5. 
 
 power plant, 5. 
 
 549 
 
550 
 
 INDEX 
 
 Axial vent, 5. 
 Axis, 5. 
 
 of gun, 5. 
 
 of trunnions, 5. 
 Azimuth: 
 
 correction scale, 317 
 
 determination of, 440. 
 
 difference, 5. 
 
 instrument, 5, 314. 
 
 of a point, 5. 
 
 of wind, 62, 98, 341. 
 
 setter, 5. 
 
 " B " row, 5, 79. 
 Backlash, 5. 
 Bale, 5. 
 Ballistic board, 5. 
 
 corrections, 533. 
 
 coefficient, 97. 
 
 formulas, 101, 104. 
 
 symbols, 101. 
 
 tables, 5. 
 Ballistics, 6, 79. 
 
 exterior, 79, 93. 
 
 interior, 79, 89. 
 Bandoleer, 6. 
 Banjo, 112. 
 Banquette, 6. 
 
 tread, 6. 
 
 Bar and drum sight, 6, 133, 360. 
 Barbette, 6. 
 
 carriages, 12, 188. 
 Barometer, 6. 
 
 aneroid, 355. 
 
 mercurial, 354. 
 Base-end stations, 6. 
 Base: 
 
 fuse, 6, 290. 
 
 line, 6, 432. 
 
 ring test, 506. 
 Battery, 6. 
 
 commander, 6, 504. 
 
 commander's action, 499, 534. 
 
 commander's station, 7. 
 
 commander's walk, 7. 
 
 emplacement book, 7. 
 
 field of fire, 7. 
 
 fire control, 25. 
 
 in commission, 31. 
 
 in service, 31. 
 
 location of, 431. 
 
 manning table, 7. 
 
 out of commission, 40. 
 
 out of service, 40. 
 
 parade, 7. 
 
 Battery, subcaliber practice 186, 534. 
 
 target practice, 504, 533. 
 Battle: 
 
 area, 7. 
 
 chart, 7. 
 
 command, 8, 496. 
 
 command drill, 496. 
 
 commander, 8, 496. 
 
 commander's station, 8. 
 
 flag, 8. 
 
 ships, 8. 
 
 tactics, 9. 
 Berm, 9. 
 Bevel gear, 106. 
 
 wheel, 9. 
 Biting angle, 95. 
 Bivouac, 9. 
 Black charcoal powder, 245. 
 
 prismatic powder, 250. 
 Blank ammunition, 260, 492. 
 Blank charges: 
 
 weight of, 262. 
 Blast slope, 9. 
 Blasting gelatine, 9, 269. 
 Blending powder, 9, 258, 512. 
 
 room, 9. 
 Blind shell, 9. 
 Blocks and tackles, 470. 
 Boat drill, 428. 
 Boat telephone, 9, 423. 
 Bomb, 9. 
 
 proof, 9. 
 
 Book, emplacement, 22. 
 Booth, 9 ; 510. 
 Bore, 9, 82, 510. 
 
 bottom of, 9. 
 
 length of, 9, Chap. V. 
 
 plug, 9. 
 
 sighting, 9, 454, 506. 
 Bound, 9. 
 Bourrelet, 9, 511. 
 Brackets, 9. 
 Breech, 9. 
 
 block, 10, 82, 509. 
 
 bushing, 10, 79. 
 
 detail, 10. 
 
 face of, 10. 
 
 plate, 84. 
 
 recess, 10, 80. 
 
 reinforce, 10, 80. 
 Breech mechanisms, 10. 82. 
 
 Driggs-Schroeder, 173. 
 
 Drop-block system, 164. 
 
 Interrupted screw, 82, 120. 
 
 Interrupted thread, 169. 
 
INDEX 
 
 551 
 
 Breech Mortar, 112, 113. 
 
 Stockett, 126. 
 
 6-in. Q. F. Armstrong, 133. 
 
 6-in. R. F. G., M. 1897 Mi, 136. 
 
 6-in. R. F. G., M. 1903, 143. 
 
 5-in. R. F. G., M. 1897, 149. 
 
 4.72-in. Q. F. Armstrong, 153. 
 
 3-in. D.-S. G., M. 1898, 155. 
 
 3-in. R. F. G., M. 1902, 160. 
 
 2.24-in. D.-S., M. 1898, 164. 
 
 2.24-in. D.-S., M. 1900, 168. 
 
 2.24-in. Am. Ord., 173. 
 Brown charcoal powder, 250. 
 
 prismatic powder, 10, 251, 256. 
 Brown & Sharpe micrometer, 389. 
 Buffer valve, 227. 
 
 Building-up charges, 10, 257, 258, 512. 
 Built-up cannon, 10, 80, 86. 
 Buoy, 10. 
 
 Bursting charge, 10, Chap. V. 
 Butt, 10. 
 Button-drill primer, 10, 282. 
 
 "C" row, 10, 79. 
 
 Cake powder, 10, 248, 249. 
 
 Caliber, 10. 
 
 Calibration, 10, 524. 
 
 Call to arms, 11. 
 
 Cam wheel, 106. 
 
 Cam lever grip, 106. 
 
 Camera, 526. 
 
 Camp sanitation, 545. 
 
 Cannister, 11, 278. 
 
 Cannon, 11 (see Guns). 
 
 ball, 11. 
 
 powder, 11. 
 Cannonade, 11, 
 Cannoneer, 11. 
 Canopy, 11. 
 Cap-square, 11, 111. 
 Capital, 11. 
 
 Capped projectile, 11, 272. 
 Carriages, 11, 187. 
 
 A. R. F., 188. 
 
 barbette, 12, 188. 
 
 barbette proper, 1SS. 
 
 casemate, 12, 188. 
 
 coast, 12, 187. 
 
 disappearing, 12, 188, 199. 
 
 fixed, 12, 187. 
 
 L. F., 188. 
 
 masking mount, 12, 188, 228. 
 
 mortar, 188, 236. 
 
 movable, 12, 169. 
 
 pedestal mount, 188, 192. 
 
 Carriages, parapet mount, 232. 
 
 rapid-fire gun, 12, 160. 
 
 recoil cylinders of, 204, 238. 
 
 special, 188, 197. 
 
 wheeled, 168. 
 Cartridge, 12. 
 
 bags, 12, 259. 
 
 extractor, 12. 
 
 for small arms, 491. 
 
 room, 12. 
 Case, 12. 
 Case I, 12, 99. 
 
 II, 12, 100. 
 
 III, 12, 100. 
 Casemate, 12. 
 
 battery, 12. 
 
 carriages, 188. 
 
 electrician, 12, 78. 
 
 officer, 13. 
 Casernes, 13. 
 Cast-iron shot, 13, 276. 
 Castramentation, 13. 
 Cathead, 13. 
 Center of gravity, 13, 94. 
 
 band, 13, 276. 
 
 of cannon, 13. 
 
 of impact, 13, 523, 530. 
 
 pintle, 13, 188, 445. 
 Centering slope, 13, 82. 
 Centigrade scale, 353. 
 Centrifugal force, 13, 295. 
 
 fuses, 13, 295. 
 Chamber, 13. 
 
 powder, 44, 82. 
 
 shot, 54, 82. 
 Charcoal powder, 245. 
 Charge, 13, 520. 
 Charts, 13, 304. 
 
 battle, 7. 
 
 difference, 20. 
 
 harbor, 30. 
 
 powder, 45, 400. 
 
 symbol, 56. 
 Chase, 13, 82. 
 Chassis, 13, 203. 
 Chief-loader, 13, 78. 
 
 of ammunition service, 14. 
 
 of coast artillery, 14. 
 
 of coast artillery's flag, 14. 
 
 planter, 14, 78. 
 Chronograph, 14. 
 Chronometer, 14. 
 Circle, 14, 106. 
 Circuit-closer, 14. 
 Circumference, 14. 
 
552 
 
 INDEX 
 
 Civilian cooks, 546. 
 Cleaner, 14. 
 Clear angle, 502. 
 Clinometer, 14, 506. 
 
 rest, 14. 
 Coast Artillery: 
 
 board, 14. 
 
 chief of, 14. 
 
 company, 14. 
 
 corps, 66, 76. 
 
 fort, 15. 
 
 garrison, 15. 
 
 material, 15. 
 
 memorandum, 505, 537. 
 
 posts, 15. 
 
 reserves, 15, 66, 76, 77, 494. 
 
 supports, 15, 66, 76. 
 Coast defense, 15. 
 
 officer, 15. 
 
 principles of, 66. 
 
 ships, 15. 
 
 theory of, 66. 
 Coast Guard, 15. 
 Coefficient, of efficiency, 90. 
 
 of form, 98. 
 
 of useful effect, 90. 
 Collar, 15. 
 
 Collimation, 33, 308. 
 Colors, 15. 
 
 of coast artillery corps, 15. 
 
 on projectiles, 16, 276. 
 Combination electric friction primer, 16, 
 
 285. 
 
 Combination fuse, 16, 297. 
 Command : 
 
 administrative, 76. 
 
 appropriate to grade, 77. 
 
 tactical, 76. 
 Commands : 
 
 of battery commander, 534. 
 
 of battle commander, 497. 
 
 of fire commander, 498. 
 
 searchlight, 502. 
 Commissary sergeant, 16. 
 Common electric primer, 16, 282. 
 
 friction primer, 16, 279. 
 Communication officer, 16, 503. 
 Communications. 17, 348, 503, 515, 541. 
 Composite artillery type telephone, 17, 
 
 346. 
 
 Computer, 17. 
 Concentric, 17. 
 
 Conduits, wiring and illumination of car- 
 riages, 226. 
 Cone, 106. 
 
 Cone, of dispersion, 17, 522. 
 
 of spread, 17, 522. 
 Conical, 17, 106. 
 Console, 17, 106. 
 Construction of batteries, 431. 
 Contact firing, 17. 
 Converted gun, 17. 
 Cordage, 17, 460. 
 Cordite, 256. 
 Cored shot, 17. 
 Corps of engineers, 431. 
 Corrected range, 17. 
 Corridor, 17. 
 
 wall, 17. 
 Counter, attack, 17. 
 
 recoil, 17. 
 
 recoil springs, 240. 
 
 recoil systems, 194, 204, 240, 508. 
 Countermining, 17. 
 Counterscarp, 17. 
 Counterweight, 17, 209. 
 
 well, 18. 
 Cover post, 18. 
 Cradle, 18. 
 Crane, 18. 
 
 Critical dimension, 18, 91. 
 Crest: 
 
 exterior, 24. 
 
 interior, 32. 
 Cross-fire, 18. 
 Crosshead guides, 203. 
 Crow's nest, 18. 
 Cruiser, 18. 
 Cruiser battleship, 18. 
 Crusher gauge, 18, 90, 396, 528. 
 Curvature of earth, 18, 95, 96, 313. 
 Curve, 18. 
 
 of trajectory, 95, 96. 
 Curves, range board, 333, 514. 
 Cut-off jack set, 18, 504. 
 Cylindrical, 19, 106. 
 Cylindro-conical, 19, 106- 
 
 "D" row, 19, 79. 
 Danger, range, 19. 
 
 space, 19. 
 Data line, 19. 
 Datum point, 19, 308. 
 Defense, of coast line, 66. 
 
 land, 73. 
 
 of harbors, 66. 
 
 plans, 28, 494. 
 
 zones, 62. 
 Definitions, 1. 
 i. ^flection. 19. 
 
INDEX 
 
 553 
 
 Deflection board (gun), 19, 338, 515. 
 
 board (mortar), 340. 
 
 computer, 78. 
 
 corrections, 338, 340, 505, 515, 532. 
 
 scale, 19. 
 
 value in yards, 533. 
 Delayed automatic firing, 19. 
 Delivery table, 19. 
 Density of air, 97. 
 
 of loading, 19, 93, 517, 528. 
 Department artillery officer, 19. 
 
 commander, 19. 
 
 commander's flag, 19. 
 Depression position finder, 19, 304, 513. 
 
 description of W. & S., 304. 
 
 description of Lewis, 312. 
 
 system, 304. 
 Derricks, 476. 
 
 Determining true azimuth, 440. 
 Detonation, 20. 
 Detonating fuses, 302. 
 Deviation, 20. 
 
 absolute, 20. 
 
 at target, 20, 525. 
 
 mean lateral, 20. 
 
 mean longitudinal, 20. 
 
 range, 20. 
 
 Device, obturating, 35, 115. 
 Diameter, 20. 
 Difference chart, 20. 
 Direct fire, 20. 
 Directing, gun, 20, 437. 
 
 point, 20, 437. 
 
 Disappearing carriage, 20, 199. 
 Dismounting breechblock: 
 
 12-in. gun (see 10-in. gun). 
 
 12-in. mortar, 117. 
 
 10-in. gun, 124, 129. 
 
 8-in. gun, 82. 
 
 6-in. gun, 142, 147. 
 
 5-in. gun, 152. 
 
 3-in. gun, 159 ; 162, 163. 
 
 2.24-in. gun, 167, 172, 175. 
 Displacement, 20. 
 
 gun, 29. 
 
 of any point, 20. 
 
 of ships, 20. 
 
 Distribution box, 20, 422. 
 District, (see Artillery district). 
 
 artillery engineer, 21. 
 
 commander, 4. 
 
 drill, 21. 
 Ditch, 21. 
 Double: 
 
 primary station, 21. 
 
 Double secondary station, 21. 
 Drift, 21. 
 
 corrections, 338. 
 
 Driggs-Schroeder R.-F. gun, 21, 155. 
 Driggs-Seabury R.-F. gun, 21, 155, 163, 
 
 168. 232. 
 Drill, 494. 
 
 primer, 21, 282. 
 
 regulations, 494. 
 Dry gun cotton, 263. 
 Dummy charge, 516. 
 
 projectile, 510, 516. 
 Dunnite, 21. 
 Dynamite, 21, 267. 
 
 Earthworks, 21. 
 
 Ecrasite, 21, 266. 
 
 Eight-inch gun, 21, 132. 
 
 Elasticity, 21, 87. 
 
 Electric ballistic machine, 14. 
 
 controllers, 223. 
 
 firer, 21. 
 
 motors, 219, 223. 
 
 mines, 21, 414. 
 
 primer, 21, 282. 
 
 safety firing attachment, 218. 
 Electrical : 
 
 elevating and depressing, 226. 
 
 retracting, 226. 
 
 traversing, 225. 
 Electrician : 
 
 casemate, 78. 
 
 detachment, 21. 
 
 master, 78. 
 
 sergeant, 22, 78. 
 
 Elements of trajectory, 93, 95, 96. 
 Elevating system, 200-507. 
 
 friction device, 507. 
 Elevation, 22, 502. 
 
 quadrant, 47, 395. 
 
 setter, 22. 
 
 sight, 54, 359. 
 Elliptical, 22. 
 
 Elongated projectiles, 22, 274. 
 Emergency position finder, 22. 
 
 station. 22. 
 
 system, 22. 
 Emplacement, 22. 
 
 book, 22. 
 
 booth, 510. 
 
 officer, 22, 534. 
 Encampment, 545. 
 Endurance of cannon, 23. 
 Energy of projectile, 23, 104, 272. 
 
 of recoil, 23. 
 
554 
 
 INDEX 
 
 Enfilade fire, 23. 
 
 Engineer, 23, 78. 
 
 Engineer corps, 431. 
 
 Engineering, seacoast, 431. 
 
 Engineer's transit, 314. 
 
 Equalizing pipes, 23, 204, 238. 
 
 Erosion of the bore, 23, 109, 112. 
 
 Estuary, 23. 
 
 Exploder, 23. 
 
 Exploders or detonators, 270. 
 
 Explosive, 23. 
 
 compound, 24, 251. 
 
 "D", 24, 268. 
 
 house, 24. 
 
 mixture, 24, 251. 
 Explosives, 245. 
 
 atlas powder, 268. 
 
 black charcoal powder, 245. 
 
 black prismatic powder, 250. 
 
 blasting gelatine, 269. 
 
 brown charcoal powder, 250. 
 
 brown prismatic powder, 251, 256. 
 
 charcoal powder, 245. 
 
 cordite, 256. 
 
 dynamite, 267. 
 
 ecrasite, 266. 
 
 fulminates, 245, 270. 
 
 giant powder, 268. 
 
 guncotton, 263. 
 
 high, 245, 263. 
 
 Judson powder, 268. 
 
 low, 245. 
 
 lyddite, 266. 
 
 maximite, 269. 
 
 melinite, 266. 
 
 melting, 266. 
 
 nitrocellulose powder, 251. 
 
 nitroglycerine, 265. 
 
 picric acid, 266. 
 
 rendrock, 268. 
 
 shimose, 266. 
 
 smokeless, 251. 
 
 sphero-hexagonal, 55, 250. 
 
 thawing, 266. 
 
 trinitrotoluol, 269. 
 
 vulcan powder, 268. 
 Exterior crest, 24. 
 
 slope, 24. 
 Extreme range, 24. 
 
 Face of breech, 24. 
 
 of muzzle, 24. 
 
 of rimbase, 24. 
 
 of trunnion, 24. 
 Fahrenheit scale, 353. 
 
 Field, combat, 73. 
 
 of fire, 24. 
 
 safety of, 500. 
 
 Fifteen-pounder, 24, 155, 162. 
 Fillet, 24. 
 Final velocity, 24. 
 Fire, 24. 
 
 accuracy of, 100. 
 
 all-round, 1, 188. 
 
 ara, 24. 
 
 in field combat, 74. 
 
 limited, 33, 188. 
 
 observation of, 531. 
 
 orders of, 499. 
 
 rate of, 49. 
 
 restricted, 499. 
 
 unrestricted, 499. 
 Firearm, 26. 
 Fire command, 25, 497. 
 
 grouping batteries of, 431. 
 
 target practice (service), 497. 
 Fire commander, 25, 497, 518. 
 
 appropriate rank of, 78. 
 
 assignment of, 25. 
 
 commands of, 497. 
 
 duties of, 25. 
 Fire commanders, 497. 
 
 action, 498. 
 
 plotting board, 330. 
 
 station, 25. 
 
 supervision of target practice, 500. 
 Fire control, 25. 
 
 apparatus and instruments, 304. 
 
 installation, 26. 
 
 range officer, 537. 
 
 system, 26. 
 Fire left, 26. 
 
 right, 26. 
 
 Fired standard primer, 26, 282. 
 Firing attachment, 218, 509. 
 
 interval, 26. 
 
 machine, 26. 
 
 mechanism, 174, 176, 183. 
 
 switch, safety, 219. 
 First-class gunner, 30, 78. 
 First sergeant, 78. 
 Five-inch gun, 26, 148. 
 Fixed ammunition, 26, 261, 491. 
 
 armament, 26. 
 
 defenses, 26. 
 
 light, 26. 
 
 mount, 26, 188. 
 Flag: 
 
 battle, 8. 
 
 garrison, 28. 
 
INDEX 
 
 555 
 
 Flag of admiral of the navy, 26. 
 
 of artillery district commander, 26. 
 
 of assistant secretary of the navy, 26. 
 
 of assistant secretary of war, 26. 
 
 of chief of coast artillery, 26. 
 
 of department commander, 27. 
 
 of post commander, 27. 
 
 of president of the U. S., 27. 
 
 of rear-admiral of the navy, 27. 
 
 of the secretary of the navy, 27. 
 
 of the secretary of war, 27. 
 
 of the U. S., 27. 
 
 of vice-admiral of the navy, 27. 
 
 post, 44. 
 
 storm, 55. 
 
 submarine boat signal, 56. 
 Flags, 27. 
 Flagship, 27. 
 Flanking fire, 27. 
 Floating defenses, 27. 
 Focussing telescope, 306. 
 Foot-ton, 27. 
 Force of gravity, 93. 
 Forcing, 27. 
 
 cone, 27, 82. 
 Formulas, ballistic, 101. 
 Fort commander, 27. 
 
 record book, 27. 
 Fortified point, 28. 
 Fosse, 28. 
 
 Four-inch gun, 28, 155. 
 Four point seventy-two-inch gun, 3, 153. 
 Friction, 28. 
 
 clutch, 213. 
 
 primer, 28, 279. 
 From battery, 28. 
 Front pintle, 28, 188, 445. 
 Frontal attack, 68. 
 
 fire, 28. 
 Frustrum, 28. 
 Fulcrum, 28. 
 Fulminate, 28, 270. 
 Fuses, 28, 290. 
 
 base, 290 
 
 combination, 297. 
 
 detonating, 302. 
 
 point, 290. 
 
 Gabion, 28. 
 Gallery, 28. 
 Galvanometer, 28. 
 Garrison, 28. 
 
 coast artillery, 15, 
 
 flag, 28. 
 
 gin, 28. 
 
 Gas-check pad, 28, 84. 
 
 seat, 82. 
 
 adjustment of, 183. 
 Gear wheel, 28, 106. 
 General defense plans, 28, 494. 
 
 principles, 66. 
 
 Geometrical magnitudes, etc.,. 106. 
 Gins, 472. 
 Glacis, 29. 
 
 Gravemetric density, 29. 
 Gravity, 29, 94. 
 Graze, 29. 
 Grooves, 29, 87. 
 Grouping batteries, 431. 
 Guard room, 29. 
 Gun, 29, 79. 
 
 16-inch, 108. 
 
 14-inch, 109. 
 
 12-inch, 110, 111, 112. 
 
 10-inch, 120. 
 
 8-inch, 80, 132. 
 
 6-inch, 133, 136. 
 
 5-inch, 148. 
 
 4.72-inch, 153. 
 
 4-inch, 155. 
 
 3-inch, 155, 162. 
 
 2.24-inch, 163, 164, 168, 172 
 
 1-pounder, 184. 
 
 6-pounder, 163, 164, 168, 172. 
 
 15-pounder, 155, 162. 
 
 arm, 317. 
 
 automatic, 5. 
 
 boat, 29. 
 
 carriage, 29. 
 
 center, location of, 437. 
 
 commander, 29, 78. 
 
 commander's range scale, 29. 
 
 company, 29. 
 
 construction, 79, 107. 
 
 cotton, 29, 263. 
 
 deflection board, 338. 
 
 differences, 29. 
 
 displacement, 29. 
 
 lift, 29. 
 
 machine, 5, 34. 
 
 platform, 29. 
 
 plotting board, 315. 
 
 pointer, 29, 78, 543. 
 
 powder, 30, 245. 
 
 section, 30. 
 
 semi-automatic, 53. 
 
 sling, 490. 
 
 sub-caliber, 184. 
 
 wire-wound type, 107. 
 Gunner, 30, 78. 
 
556 
 
 INDEX 
 
 Gunner's quadrant, 30, 393. 
 Gunnery, 30, 79. 
 specialists, 30. 
 
 Hang fire, 30. 
 Harbor, charts, 30. 
 
 defense, 66. 
 
 Height of D. P. F., 311. 
 High-angle fire, 30. 
 Hitches, 468. 
 Hoist, 30. 
 
 ammunition, 1. 
 
 powder, 45. 
 
 room, 30. 
 
 shot, 1. 
 
 Homogeneous, 30. 
 Hoop, 30, 79. 
 Horizontal, 30. 
 
 angle, 31. 
 
 base-line measurement, 432. 
 
 base system, 31, 311. 
 
 plane, 31. 
 
 position finder, 31, 304, 312. 
 
 range, 31. 
 
 velocity, 31. 
 Hostilities, 31. 
 Howitzer, 31. 
 Hydraulic jack, 31, 479. 
 Hydrographic surveying, 458. 
 Hygrometer, 31. 
 Hypothetical targets, 31. 
 
 Identification of target, 31, 503. 
 Igniter, 31. 
 
 charge, 31, 259. 
 Igniting primer, 31, 289. 
 Illuminating light, 31, 402. 
 Illumination, conduits and wiring, 226. 
 In battery, 31. 
 In commission, 31. 
 Independent action, 499. 
 Indication of target, 31, 503. 
 Indicator: 
 
 aeroscope, 343, 344. 
 
 tide, 304. 
 
 wind component, 341. 
 Infantry, 73. 
 Inflammation, 31. 
 Initial pressure, 31. 
 
 of rotation, 32. 
 
 of translation, 32. 
 
 velocity, 32. 
 Inner defense aone, 62. 
 In service, 31. 
 
 Inside of a beam, 32. 
 Instruments, 304. 
 Intelligence line, 32, 535. 
 Interior crest, 32. 
 
 slope, 32. 
 
 wall, 32. 
 
 Intermediate armament, 32, 133. 
 Interrupter, 345, 515. 
 
 Jacket, 32, 79. 
 Judgment firing, 32. 
 Jump, angle of, 32, 95, 507. 
 Junction box, 32, 423. 
 
 Kentledge, 33. 
 
 Knots, 467. 
 
 Laflin & Rand firing machine, 33. 
 
 Land attack, 73, 74, 75, 500. 
 
 defense, 73, 500. 
 
 front, 33. 
 Landings, 70. 
 Lands, 33, 88. 
 Lanyard, 33, 217. 
 Large caliber guns, 33, 107. 
 Lateral, 33. 
 Latrine, 33. 
 Laying, 33, 99. 
 Least dimension, 33, 91. 
 Le Boulenge chronograph, 33. 
 Length of the bore, 33. 
 Leveling, 455. 
 Levers, 472. 
 Limited fire, 33, 188. 
 Limits of fire, 33, 62. 
 Line, 33. 
 
 of collimation, 33, 308. 
 
 of defense, 33. 
 
 of departure, 33, 95, 102. 
 
 of direction, 34, 95. 
 
 of impact, 34, 95. 
 
 of metal, 447. 
 
 of shot, 34, 95. 
 
 of sight, 34, 95. 
 Litmus, 34. 
 
 paper test, 34. 
 Loading: 
 
 density of, 19, 93, 517, 528. 
 
 mines, 421. 
 
 platform, 34. 
 
 position, 34. 
 
 projectiles, 378. 
 
 room, 34, 417, 424. 
 
 tray, 34. 
 
INDEX 
 
 557 
 
 Location : 
 
 of batteries, 431. 
 
 of horizontal base lines, 432. 
 
 of pintle centers, 438. 
 
 of target, 34. 
 
 "Long nose" projectiles, 274. 
 Long roll, 34. 
 Longitudinal, 34. 
 Lot number, 256. 
 Lug, 34. 
 Lyddite, 34, 266. 
 
 Machine gun, 34. 
 
 mounts, 34. 
 
 Machinery, care of, 424, 481. 
 Magazine rifle, 4X3. 
 Magazines, 35, 525, 527. 
 Main bore, 35, 82. 
 Maneuver signals, 539, 540. 
 Maneuvering rings, 35. 
 Manning parties, 35. 
 
 tables, 35. 
 Mark one, 35, 110. 
 Marine obstructions, 35. 
 Masking mount, 35, 22 X. 
 Master electrician, 35, 78. 
 
 gunner, 35, 78. 
 Material target, 35. 
 Maul, 35. 
 
 Maximite, 35, 269. 
 Maximum, 36. 
 
 ordinate, 36, 95. 
 
 pressure, 36. 
 
 range, 36, 107. 
 Mean lateral deviation, 36. 
 
 longitudinal deviation, 36. 
 Measure of uniformity, 36. 
 Mechanic, 36, 78. 
 Mechanics, 36, 106. 
 Medium caliber guns, 36, 107, 133. 
 Melinite, 36, 266. 
 Melting explosives, 36, 266. 
 Mensuration, 36. 
 Mercurial barometer, 36, 35 
 
 thermometer, 58, 354. 
 Meteorological' message, 36. 
 
 observer, 36, 78, 541. 
 
 station, 37, 544. 
 Methods of pointing, 99. 
 Micrometer, 37. 
 
 caliper or gauge, 37, 396. 
 Military crest, 37. 
 Mine (submarine), 37, 414. 
 
 field, 37. 
 
 material, care of, 424. 
 
 Mine, planter, 38, 422. 
 
 plotting board, 328. 
 
 prediction ruler, 329. 
 Mine command, 37. 
 
 boat drill for, 428. 
 
 fire-command system, 417. 
 Mine commander, 37, 414. 
 Mine company, 37, 424. 
 Mine-field lights, 37. 
 
 officer, 38. 
 
 Mining casemate, 38, 417. 
 Minus correction, 38, 384. 
 
 deflection, 38, 384. 
 Misfire, 38. 
 Miter wheel, 38. 
 Moat, 38. 
 Mobile, army, 67, 76. 
 
 torpedo, 38, 414. 
 Monitors, 38. 
 Mortar, 38, 112, 119, 120. 
 
 arm, 325. 
 
 battery, 38. 
 
 breech mechanism, 114. 
 
 carriage, 236. 
 
 cast-iron, 112. 
 
 company, 38. 
 
 deflection board, 340. 
 
 pit, 38, 112. 
 
 plotting board, 324. 
 
 predicter, 326. 
 
 steel, 119. 
 
 velocities, 327. 
 
 wire- wound type, 107. 
 
 zones, 62, 327. 
 Motor generator, 224. 
 Motors, 223. 
 
 Mount (see Carriage), 38. 
 Mounting cannon, 38. 
 Movable armament, 39, 168. 
 
 carriage, 39, 188. 
 Multiplying scale, 338. 
 Mushroom head, 39. 
 Musician, 78. 
 Muzzle, 39. 
 Muzzle velocity, 39, 519. 
 
 probable, for trial shots, 519. 
 
 variations in, 519. 
 
 Naval attack, 68. 
 Night, attacks, 74. 
 
 signals, 542. 
 
 Nitrocellulose powder, 39, 251. 
 Nitroglycerine, 39, 265. 
 Non-commissioned officers, 39, 78. 
 Nose, 39. 
 
558 
 
 INDEX 
 
 Object glass, 39, 306. 
 Oblique fire, 39. 
 Observation, firing, 39. 
 
 of fire, 531. 
 
 telescope, 39. 
 
 Observations with D. P. F., 310, 311. 
 Observer, 39, 78, 535, 542. 
 
 1st and 2d class, 78. 
 
 meteorological, 78, 544. 
 
 tide, 78, 545. 
 
 tug, 536. 
 Observing interval, 39. 
 
 room, 39. 
 
 station, 39. 
 
 Obturating primer, 39, 274. 
 Obturator, 39, 115, 509. 
 
 head, 39. 
 Occult light, 39. 
 Offensive return, 39. 
 Officers, points for, 494. 
 Ogive, 40, 272. 
 Oil room, 40. 
 Oils, 40, 425. 
 Okonite joint, 420. 
 Omniscope, 40. 
 One-pounder, 40, 184. 
 Open sight, 40, 359. 
 
 bar and drum, 6, 133, 360, 363. 
 
 2.24-inch (6-pounder), 359. 
 
 3-inch (15-pounder), 360. 
 
 4-inch, 360. 
 
 4.72-inch, 360. 
 
 5-inch, 361. 
 
 6-inch, 360. 
 
 8-, 10-, and 12-inch, 361. 
 Opposite angles, 40. 
 Orderly, 78. 
 Orders, 496. 
 
 of fire, 40. 499. 
 Ordnance, 40. 
 
 machinist, 40. 
 
 officer, 40. 
 
 sergeant, 40. 
 
 Organization and personnel, 76. 
 Orientation, 40, 449. 
 
 table, 40. 
 
 Out of commission, 40. 
 Out of service, 40. 
 Outer defense zone, 62. 
 Outposts, 40. 
 Outside of the beam, 40. 
 Overs and shorts, 527. 
 
 Paint mixtures, etc., 425. 
 Paints, oils, etc., 425. 
 
 Paints on projectiles, 41. 276. 
 
 Pantograph, 41. 
 
 Parade slope or wall, 41. 
 
 Parados, 41. 
 
 Parallax, 41, 307. 
 
 Parallel, 41. 
 
 Parapet, 41, 533. 
 
 Patrol boats, 41. 
 
 Pawl, 41, 106. 
 
 Pedestal mount, 192. 
 
 Penetration of projectiles, 41, 109 272, 
 
 273, 277. 
 Percussion cap, 42, 287. 
 
 fuse, 42, 291. 
 
 primer, 42, 286. 
 Periscope, 42. 
 
 Permanent fortifications, 431. 
 Perpendicular, 42. 
 Personnel, 42, 76, 77, 515. 
 Picket boats, 42. 
 Picric acid, 42, 266. 
 Piece (see Gun), 42. 
 Pintle centers, location of, 188, 445. 
 Pipe, equalizing, 23, 204, 238. 
 Pit, 42. 
 
 commander, 42. 
 
 mortar, 112. 
 Plan of land defense, 73. 
 Plane, 42. 
 
 of departure, 42, 95, 98. 
 
 of direction, 42, 95. 98. 
 
 of sight, 42, 95, 98. 
 Plans, general defense, 28, 494. 
 Planter. 42, 422. 
 Planting mines, 422. 
 
 section, 42. 
 Platen scale, 338. 
 Plotter, 42, 78, 535. 
 Plotting board, 42, 314, 514. 
 
 fire commander's, 328. 
 
 gun, 315. 
 
 mortar, 324. 
 
 submarine, 328. ^ 
 Plotting room, 43. 
 Plunging fire, 43. 
 Plus correction, 43, 384. 
 
 deflection, 43, 384. 
 Point, 43. 
 
 directing, 20, 437. 
 
 fuse, 43, 290. 
 
 of fall, 43, 93, 95, 96, 502. 
 
 of impact, 43, 95. 
 Pointing, 43, 99. 
 Points for artillerists, 494. 
 Polaris, 442. 
 
INDEX 
 
 559 
 
 Position, angle, 43. 
 
 finder, 43, 304. 
 Position-finding system, 43, 310, 311, 
 
 513. 
 Post: 
 
 adjutant, 43. 
 
 artillery engineer, 43. 
 
 commander, 44. 
 
 commander's flag, 44. 
 
 commissary sergeant, 44. 
 
 flag, 44. 
 
 non-commissioned staff, 44. 
 
 ordnance officer, 44. 
 
 quartermaster, 44. 
 
 quartermaster sergeant, 44. 
 
 telephone switchboard, 44. 
 Powder (see Explosives), 44, 512, 527. 
 
 blast, 44. 
 
 blending of, 258. 
 
 cases, 44. 
 
 chamber, 44, 82. 
 
 charges, table of, 255. 
 
 chart, 45. 
 
 chute, 45. 
 
 hoist, 45. 
 
 hoist well, 45. 
 
 magazine, 45. 
 
 power expansive force, 90. 
 
 room, 45. 
 
 section, 259. 
 
 test, litmus, 34, 104. 
 Powder charge: 
 
 preparation of, 9, 258, 512, 517. 
 
 sections of, 259. 
 
 table of, 255. 
 
 weights of, 104, 259. 
 Power and light equipment, 45. 
 
 room, 45. 
 
 section, 45. 
 
 station or plant, 45. 
 Practice (see Target practice). 
 Practice, accuracy of, 100. 
 Predicted firing, 45. 
 
 point, 45. 
 time, 45. 
 
 Predicting interval, 45. 
 Predictor, 45. 
 Preponderance, 45. 
 Preparation of charges, 9, 25X. 512, 517. 
 
 of paints, 425. 
 Pressure cylinders, 45, 397. 
 Pressure gauge, 45, 397. 
 Primary arm-setter, 78. 
 armament, 45, 108. 
 station, 45. 
 
 Primer, 46, 279. 
 Priming charges, 46, 259. 
 Principles of coast defense, 66. 
 Prismatic powder, 46, 250, 251. 
 Probability factors, 46. 
 
 of error, 46, 522. 
 Probable error card, 522. 
 
 muzzle velocity, 519. 
 
 zone, 46, 522. 
 Profile board, 46. 
 Progressive powder, 46, 245. 
 Projectile, 46, 93. 
 
 in the gun, 89. 
 
 in its flight, 93. 
 Projectiles, 271, 511, 528. 
 
 armor piercing, 274. 
 
 capped, 273. 
 
 cast-iron, 276. 
 
 deck piercing, 274. 
 
 dummy, 510, 516. 
 
 energy of, 272. 
 
 filled and fused, 268, 278. 
 
 long nosed, 274. 
 
 painting of, 276. 
 
 penetration of, 41, 109, 272, 273, 277. 
 
 seating of, 516. 
 
 storage of, 278. 
 
 travel of, 59, 517. 
 Projector, 46. 
 Proof, of gunpowder. 46. 
 
 plug, 46, 396. 
 Property officer, 46. 
 Protractor, 47. 
 Pyramidal target, 47. 
 
 Quadrant, 47, 393, 509. 
 
 angle of departure, 47, 96. 
 
 elevation, 47, 395. 
 
 elevation scale test, 506. 
 Quartermaster, 47. 
 
 sergeant, 47, 78. 
 Quick-firing guns, 47, 133, 153. 
 Quickness of burning, 47. 
 
 Rack, 47. 
 Radial vent, 47. 
 Radius, 47. 
 
 Rake (see Range rake). 
 Rammer, 47, 517. 
 Ramp, 47. 
 Rampart, 47. 
 Range, 47. 
 
 azimuth table, 48. 
 
 board, 48, 332, 514. 
 
 correction computer, 78. 
 
560 
 
 INDEX 
 
 Range, corrections, 332, 514, 532. 
 
 danger, 501. 
 
 deviation, 48, 527. 
 
 difference, 48. 
 
 finder, 48, 304. 
 
 finding system, 304. 
 
 keeper, 48, 78. 
 
 of a shot, 49. 
 
 of ballistic tables, 48, 96. 
 
 officer, 48, 515, 518, 535. 
 
 rake, 48, 525. 
 
 scale, 49. 
 
 searchlight, 406. 
 
 setter, 49, 78, 534. 
 
 station, 518 
 
 table, 49. 
 Rapid-fire gun. 49, 142. 
 
 carriage, 49, 192. 
 Rate of fire, 49. 
 Rated men, 78. 
 Ratings, 49, 78. 
 Reader, 49, 78. 
 Rear slope, 49. 
 Receiving table, 49. 
 Recoil, 49. 
 
 cylinders, 49, 189, 199. 508. 
 
 systems, 194, 204, 238, 508. 
 Reconnaissance, 49. 
 
 in force, 49. 
 Record practice, 505. 
 Recorder, 49, 78, 498. 
 Records of firings, 50, 528. 
 Rectangular target, 50. 
 Redoubt, 50. 
 Reference numbers, 50. 
 Reflected ray or beam, 404. 
 Regulations, 50. 
 Reinforce, 50. 
 Relay, 50. 
 
 Relocation of target, 50. 
 Remaining velocity, 50. 
 Reserve table, 50. 
 
 Reserves, coast artillery, 15, 76, 77, 494. 
 Resistance of the air, 50, 93. 
 Restricted fire, 50, 499. 
 Retardation, 50. 
 Retractor, 50. 
 Reverse fire, 50. 
 Ricochet, 50, 501. 
 Rifle (see also Gun), 50. 
 Rifling, 51, 82, 87. 
 twist of, 60, 87. 
 Rimbases, 51. 
 
 Ring resistance fuse, 51, 291. 
 Roadstead, 51. 
 
 Rocket, 51. 
 
 Ropes, 460. 
 
 Rotating band, 51, 82, 511. 
 
 Rotation, 51. 
 
 Rotation of projectile, 51. 
 
 Round, 51. 
 
 Roving light, 51. 
 
 Row, 51. 
 
 Rubber impression of bore, 51. 
 
 Run by, 69. 
 
 Safety-firing switch, 219. 
 Safety lanyard, 51, 217. 
 Safety officer, 501, 536. 
 Salvo, 51. 
 
 fire, 51, 499. 
 
 point, 51. 
 
 table, 51. 
 Sanitation, 545. 
 Scarp, 51. 
 Scout ships, 51. 
 Screw box, 51. 
 Seacoast engineering, 431. 
 Searchlight, 51, 402. 
 
 arc, 410. 
 
 area, 52, 402. 
 
 carbons, 413. 
 
 classification of, 407. 
 
 commands, 502. 
 
 effective ranges, 406. 
 
 essentials of effectiveness, 412. 
 
 lamp mechanism, 408. 
 
 mirror, 411. 
 
 nomenclature, 407. 
 
 observer, 52. 
 
 officer, 52. 
 
 operator, 52, 78. 
 
 range, 52, 406. 
 
 tactical location, 402. 
 
 types of, 404. 
 
 tower, 52. 
 
 watcher, 78, 406. 
 Seat of the charge, 52, 517. 
 Secondary armament, 52, 155. 
 
 arm-setter, 78. 
 
 or auxiliary power plant, 52. 
 
 station, 52. 
 
 Second-class gunner, 78. 
 Sector of explosion, 53. 
 Segment, 53. 
 Self-contained horizontal position finder, 
 
 53. 
 
 Semi-automatic guns, 53. 
 Separate observing room, 53. 
 
 plotting room, 53. 
 
INDEX 
 
 561 
 
 Sergeant-major, 53, 78. 
 Service, charge, 53, 255. 
 
 practice, 505. 
 Serving table, 53. 
 Serving the vent, 53. 
 Set-back point, 53. 
 Set-forward point, 53. 
 Set-forward ruler, 53. 
 Shears, 53, 474. 
 Shell, 53, 274. 
 
 armor piercing, 274. 
 
 deck piercing, 274. 
 
 filler, 54. 
 
 room, 54. 
 
 torpedo, 59, 275, 276. 
 
 tracer, 54. 
 
 Shimose powder, 54, 266. 
 Shore signals, 538. 
 Shot, 54, 274, 276. 
 
 armor piercing, 274. 
 
 cast-iron, 274. 
 
 chamber, 54, 82. 
 
 gallery, 54. 
 
 hoist, 54. 
 
 hoist well, 54. 
 
 penetration of, 109, 277. 
 
 room, 54. 
 
 tongs, 54, 516. 
 
 trucks, 192, 510. 
 Shrapnel, 54, 278. 
 Sights, 54, 168, 359. 
 
 deflection, 54. 
 
 elevation, 54. 
 
 standard, 54, 506. 
 
 telescopic, 57, 168, 361. 
 Signal rocket, 54. 
 
 station, 54. 
 
 Signals, at target practice, 538. 
 Signs, 65. 
 
 Six-inch gun, 54, 133, 136. 
 Six-pounder, 54, 163. 
 Small arms, 483. 
 
 ammunition, 491. 
 
 boats, 54, 427. 
 
 caliber guns, 54, 155. 
 
 landing parties, 75. 
 Smokeless powder, 54, 251. 
 Smooth-bore cannon, 54. 
 Sound, signals, 540, 541. 
 
 travel, 55. 
 
 Sources of error, 505. 
 Special mounts, 197. 
 Specific gravity, 55. 
 Sphero-hexagonal powder, 55, 250. 
 Splices, 462. 
 
 Spline, 55, 106. 
 Sponge, 55. 
 
 Sprocket wheel, 55, 106. 
 Spur ring, 55. 
 
 wheel, 55, 106. 
 Staff officers, 55, 77, 78 
 Stand fast, 55. 
 Standards, 55, 506. 
 Star gauge, 55. 
 Storage magazine, 55. 
 Storehouse, 55, 424. 
 Storeroom, 55, 421. 
 Storm flag, 55. 
 Strategy, 55. 
 Strength, 55. 
 Striking, angle, 55, 95, 274. 
 
 energy, 55. 
 
 velocity, 55, 102. 
 Subcaliber: 
 
 ammunition, 255. 
 
 gun, 184, 187. 
 
 platform, 55. 
 
 practice, 186. 
 
 quadrant scale, 56. 
 
 tube, 56, 184. 
 Submarine : 
 
 boat, 56. 
 
 signal flag, 56. 
 
 defense equipment, 56, 417. 
 
 defenses, 56, 414. 
 
 mine, 56, 414. 
 
 plotting board, 328. 
 Substitutes, 515. 
 Superior slope, 56. 
 Supplementary station, 56. 
 Supports, coast artillery, 15, 66, 76. 
 Surface,. 56. 
 
 Surveyor's transit, 56, 314. 
 Swell of muzzle, 56. 
 Switchboard panel, 224. 
 Symbol charts, 56. 
 
 Table of: 
 
 angular distance of Polaris, 443. 
 blank ammunition, 263. 
 built-up charges, 257. 
 civil dates or epochs, 442. 
 deflections, 533. 
 detonating fuses, 302. 
 diameters of searchlight beams, 404. 
 dimensions of powder sections, 259. 
 effective searchlight ranges, 406. 
 factor of year and latitude, 443. 
 interchangeability of subcaliber guns, 
 185. 
 
562 
 
 INDEX 
 
 Table of, longitudinal deviations, 527. 
 
 mortar zones and velocities, 327. 
 
 muzzle velocities and pressures, 105, 
 255. 
 
 penetration, 277. 
 
 powder charges, 255. 
 
 triangulation data, 451. 
 
 velocities and temperatures, 105, 
 255. 
 
 wind velocity, miles per hour, 358. 
 Tackles, 57. 
 Tactical: 
 
 chain, 57. 
 
 command, 57. 
 
 divisions, 76. 
 
 organization, 76. 
 
 responsibility, 57. 
 Tactics, 57. 
 Take cover, 57. 
 Tangent, 57, 106. 
 Tangent of an arc, 57, 106. 
 Tangential force, 57. 
 Targ, 57, 321. 
 Target, 57, 525. 
 
 hypothetical, 31. 
 
 identification of, 31, 503. 
 
 indication of, 31, 503. 
 
 material, 35. 
 
 pyramidal, 47. 
 
 vessel tracking, 57, 304. 
 Target practice, 505. 
 
 arbitrary deflection correction, 531. 
 Team work, 505. 
 Telautograph, 57, 345. 
 Telephone, 57, 346, 515. 
 
 operator, 78, 348, 503, 515, 541 
 Telegraph joint, 419. 
 Telescope, adjustment of, 306. 
 
 leveling, 305. 
 
 orientation of, 308. 
 Telescopic sights, 57, 168, 361. 
 
 adjustments, 373 ; 385. 
 
 adjustments at forts, 392. 
 
 care of, 374. 
 
 for disappearing carriage, 371. 
 
 for rapid-fire guns, 362. 
 
 method of assembling, 372. 
 
 Scott, 375. 
 
 use in gun laying, 384. 
 Ten-inch gun, 57, 120. 
 Tents, 547. 
 Terrain, 57. 
 
 Thawing explosives, 58, 266. 
 Theater of operations, 58. 
 Thermometers, 58, 353. 
 
 Theoretical range, 58. 
 Theory, and principles, 66. 
 
 of probability, 58. 
 Three-inch gun, 58, 155. 
 Throttling bar, 58, 194, 204, 238. 
 Tide gauge, 58. 
 
 indicator, 58. 
 
 observer, 545. 
 
 station, 58, 545. 
 Time, fuse, 58, 297. 
 
 interval bell, 58, 343, 513. 
 
 interval clock, 343, 515. 
 
 interval recorder, 58, 357. 
 
 of flight scale, 58, 332, 514. 
 
 range board, 58, 398. 
 Tool room, 59. 
 Torpedo, 59. 
 
 boat destroyers, 59. 
 
 boats, 59. 
 
 detonating Pierce fuse, 59, 302. 
 
 shell, 59, 275 ; 276. 
 Towing target, 59, 536. 
 Tracer, shell, 54 
 Tracking, 59, 323. 
 Trajectory, 59, 93, 95, 96. 
 
 rigidity of, 96. 
 Transit instrument, 59, 314. 
 Travel of projectile, 59, 517. 
 
 of target, 59. 
 Traverse, 59. 
 
 slope or wall, 59. 
 Traversing, speed of, 225. 
 Traversing indicator, 60. 
 
 mechanism, 187, 508. 
 Tray, 60. 
 
 Trial shots, 60, 520, 529, 530. 
 Triangulation of base lines, etc., 437. 
 Trinitrotoluol, 60, 269. 
 Tripping, 60. 
 Trolley, 60. 
 Truck : 
 
 ammunition, 60. 
 
 platform, 60. 
 
 recess, 60. 
 Trunnion, 60. 
 
 band, 60. 
 
 hoop, 80. 
 
 sight bracket, 60. 
 T-square scale, 338. 
 Tube, 60, 82. 
 Tug observer, 60, 536. 
 
 officer, 60, 536. 
 
 signals, 538. 
 Turk's head, 418. 
 Twelve-inch, gun 60, 110. 
 
INDEX 
 
 563 
 
 Twelve-inch mortar, 60, 119. 
 Twist of rifling, 60, 87, Chap. V. 
 
 Union jack, 60. 
 
 Unit, 61. 
 
 Unrestricted fire, 61. 401), 
 
 Velocity, 61, 105. 
 
 corrections, 532. 
 
 initial, 105. 
 
 instrumental, 93. 
 
 muzzle, 91, 93, 327. 
 
 normal, 105. 
 
 of combustion. 61. 
 
 of rotation, 61. 
 
 striking, 55, 102. 
 
 table, 105. 
 
 translation, 61, 93. 
 
 trial shots, 52'.). 
 
 variations in, 519. 
 Vent, 61. 
 Ventilators, 61. 
 Vernier, 61. 
 Vertex of angle, 61. 
 Vertical, 61. 
 
 angle, 61. 
 
 base system, 61, 310. 
 
 plane, 61. 
 Vessel chart, 61. 
 
 Vessel, symbols, 547. 
 
 tracking, 61, 323. 
 Vickers-Maxim gun, 61. 
 
 Watchers, searchlight. 78, 406. 
 
 Waterfront, 61. 
 
 Weights: 
 
 of guns, Chap. V. 
 
 of powder charges, 259, 520. 
 
 of projectiles, Chap. V., 520. 
 Wheeled mounts, 61, 168. 
 Wig- wag signals, 541. 
 Winch, 61. 
 Wind, component indicator, 62, 341. 
 
 effect of, 98. 
 
 vane, 62, 544. 
 Wireless communications, 542. 
 
 operator, 78. 
 
 stations, 62. 
 
 Wiring system of carriage, 227. 
 Worm wheel, 62, 106. 
 
 Xylol, 62. 
 
 Zero, 62. 
 
 Zone energy, 62. 
 
 mort. 62. 
 
 of fire, 62. 
 Zones and velocities of mortars, 62, 327