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Cornell University Library 
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 Notes on seacoast fortification constrijc 
 
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 3 1924 030 766 046 
 
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 Cornell University 
 Library 
 
 The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924030766046 
 
NUMBER 61 
 
 OCCASIONAL PAPERS 
 
 ENGINEER SCHOOL 
 
 UNITED STATES ARMY 
 
 NOTES ON 
 
 SEAGOAST FORTIFICATION 
 CONSTRUCTION 
 
 By 
 COL. EBEN EVELETH WINSLOW 
 
 CORPS OF ENGINEERS, U. S. ARMY 
 
 PREPARED UNDER THE DIRECTION OF THE CHIEF 
 
 OF ENGINEERS, U. S. ARMY, FOR USE 
 
 AT THE ENGINEER SCHOOL 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 
 1920 
 
 5v 
 
 (; fi I'.' I'- i 
 
CONTENTS. 
 
 Page. 
 
 Preface 5 
 
 Chapter I. Historical 7 
 
 Chapter II. Administration 25 
 
 Chapter III. Armor and armament 33 
 
 Chapter IV. Material used in emplacement Construction 49 
 
 Chapter V. Ammunition supply, storage, and service 71 
 
 Chapter VI. Batteries and emplacements, general design 101 
 
 Chapter VII. Emplacement details 159 
 
 Chapter VIII. Mortar batteries 199 
 
 Chapter IX. Dryness, heating, and ventilation 225 
 
 Chapter X. Blast effects -. 261 
 
 Chapter XI. Uses of electricity in fortifications 269 
 
 Chapter XII. Fire control 303 
 
 Chapter XIII. Night illumination of battlefields 369 
 
 Chapter XIV. Submarine mining - 407 
 
 Chapter XV. Summary 431 
 
 LIST OF PLATES. 
 
 Plate I. Some of the details of ammunition service apparatus. 
 
 Plate II. Some of the details of ammunition service apparatus. 
 
 Plate III. Emplacements for two 3-inch guns (balanced pillar mounts) 1898 type. 
 Drawing based on Mimeograph No. 30. 
 
 Platb IV. Emplacements for two 3-inch guns (pedestal mounts) 1902 type. Drawing 
 based on fifth supplement to Mimeograph No. 30. 
 
 Plate V. Emplacements for two 3-inch guns (pedestal mounts) 1903 tjrpe. Drawing 
 based on sixth supplement to Mimeograph No. 30. 
 
 Plate VI. Emplacements for two 5-inch guns (balanced pillar mounts) 1897 type. 
 Drawing based on Mimeograph No. 18. 
 
 Plate VII. Emplacements for three 5-inch guns (pedestal mounts) 1899 type. Draw- 
 ing baaed on Mimeograph No. 33. 
 
 Plate VIII. Emplacements for two 6-inch guns (pedestal mounts) 1900 type. Draw- 
 ing based on Mimeograph No. 40. 
 
 Plate IX. Emplacements for two 6-inch guns (pedestal mounts) 1901 tj'pe. Drawing 
 based on plans of Battery Montgomery. 
 
 Plate X. Emplacements for two 6-inch guns (pedestal mounts) 1902 type. Drawing 
 based on second supplement to Mimeograph No. 40. 
 
 Plate XI. Emplacements for two 6-inch guns (disappearing carriages) 1903 type. 
 Drawing based on Mimeograph No. 59. 
 
 Plate XII. Emplacements for two 6-iQch guns (disappearing carriages) 1912 type. 
 Drawing based on plans oi batteries designed for Panama Canal. 
 
 Plate XIII. Emplacements for two 10-inch guns (disappearing carriages) 1894 type. 
 
 Drawing based on the design of a battery built at Fort Monroe. 
 Plate XIV. Emplacements for two 10-inch guns (disappearing carriages) 1896 type. 
 Drawing based on Mimeograph No. 4. 
 
 (3) 
 
Plate XV. Emplacements for two 10-iach guns (disappearing carriages) 1898 type. 
 Drawing based on Mimeograph No. 22. 
 
 Plate XVI. Emplacements for three 10-inch guns (disappearing carriages) 1900 type. 
 Drawing based on Mimeograph No. 36. 
 
 Plate XVII. Emplacements for two 10-inch guns (disappearing carriages) 1903 type. 
 Drawing based on Sixth Supplement to Mimeograph No. 36. 
 
 Plate XVIII. Emplacements for two 12-inch guns (disappearing carriages) 1896 type. 
 Drawing based on Mimeograph No. 4. 
 
 Plate XIX. Emplacements for two 12-inch guns (disappearing carriages) 1898 type. 
 Drawing based on Mimeograph No. 24. 
 
 Plate XX. Emplacements for two 12-inch guns (disappearing carriages) 1903 type. 
 Drawing based on Mimeograph No. 66. 
 
 Plate XXI. Emplacements for two 12-inch guns (barbette carriages) 1915 type. 
 Drawing based on general outline plans. 
 
 Plate XXII. Left emplacement of a battery of two 14-inch guns (disappearing car- 
 riages) 1908 type. Drawing based on Mimeograph No. 109. 
 
 Plate XXIII. Emplacement for one 14-inch gun (disappearing carriage) M variety 
 of 1912 type. Drawing based on a battery actually constructed. 
 
 Plate XXIV. Emplacement for one 14-inch gun (disappearing carriage) S variety of 
 1912 type. . Drawing based on a battery actually constructed. 
 
 Plate XXV. Emplacements for two 14-inch guns (disappearing carriages) W variety 
 of 1912 type. Drawing based on a battery actually constructed. 
 
 Plate XXVI. Emplacements for two 14-inch guns (disappearing carriages) L variety 
 of 1912 type. Drawing based on a battery actually constructed. 
 
 Plate XXVII. Batteries lor sixteen 12-inch mortars. 1892 and 1894 types. Draw- 
 ings based on batteries actually constructed. 
 
 PlSte XXVIII. Batteries for eight 12-inch mortars. 1898 and 1906 types. Draw- 
 ings based on Mimeograph No. 27 and its first supplement. 
 
 Plate XXIX. Battery for eight 12-inch mortars. 1912 type. Drawings based on 
 general plans. 
 
PREFACE. 
 
 In the fall of 1906 the author of these notes was relieved from duty 
 in charge of the Norfolk engineering district, and was sent to the 
 Engineer School at Washington Barracks as director of military 
 engineering. The Norfolk district, from which he came, had, during 
 his tenure of the district, been an exceedingly active one as far as 
 fortification construction was concerned, and had been the principal 
 site of the joint Army and Navy maneuvers in 1905. Furthermore, 
 during the years 1903 to 1906 a large amount of experimental Coast 
 Artillery work had been in progress at Fort Monroe. 
 
 Immediately after arrival at Washington Barracks he began to 
 prepare, in connection with the course in military engineering, a 
 series of lectures on the details of seacoast defense, which were 
 delivered during the winter of 1906 and 1907. During the following 
 summer these lectures were revised, almost to the extent of being 
 practically rewritten, and as thus revised were used during the 
 winter of 1907 and 1908, being issued at this time not as lectures- 
 but in typewritten form, each student oflBcer being furnished with 
 his own individual copy. 
 
 These lectures were not intended to be complete in themselves, 
 but were intended to be studied in connection with Engineering 
 Department mimeographs and with certain engineering drawings and 
 photographs, all of which were placed in the study rooms for use of 
 the student officers. To these other papers and drawings frequent 
 reference was made in the lectures. In addition to the lectures, 
 mimeographs, drawings, and photographs there was prescribed a 
 "course of reading," consisting of certain stated pages in certain pub- 
 lications, copies of which were placed in the study rooms for the aid 
 of the student officers. 
 
 During the spring and summer of 1908 the lectures were again 
 subject to revision and as thus revised were published in the early 
 part of 1909 as "Occasional Papers No. 35, Engineer School, United 
 States Army." 
 
 Since the publication of these papers the author has had practically 
 continuous experience in fortification matters, having designed and 
 constructed most of the fortifications of the Hawaiian Islands and 
 having designed all the fortifications constructed up to this time in 
 the Panama Canal Zone, and having been for four years in charge of 
 the fortification desk in the office of the Chief of Engineers. Before 
 leaving this desk he has thought it well to again revise his lectures 
 under the title "Notes on Seacoast Fortification Construction." 
 
 (5) 
 
The original lectures were not intended as a textbook on the gen- 
 eral subject of fortification or on the application of fortification to 
 seacoast defense, but merely as a compilation of matter for the use 
 and assistance of those Engineer ofiicers whose duties require them 
 to undertake the detailed design or construction of emplacements or 
 other features of seacoast fortification work. 
 
 It will be noted that in connection with many of the items covered 
 in these notes considerable historical matter is inserted. This has 
 been done not because of any special importance attached to this 
 matter historically, but merely because it is thought that one of the 
 best ways to prevent mistakes in the future is to call to the attention 
 of the designing and constructing officers the defects and mistakes of 
 the past. 
 
 Washington, D. C, July, 1919. 
 
Chapter I. 
 HISTORICAL. 
 
 Before going into a description of the detailed construction of sea- 
 coast batteries, and their accessories, it would appear to be well to 
 give a brief historical sketch of the development of seacoast defense 
 in the United States ; for in order to thoroughly understand existing 
 conditions in our seacoast-defense work a general knowledge of the 
 antecedent history of the subject is necessary. 
 
 The history of seacoast fortifications in this country dates back to 
 before the Revolutionary War, but most of the fortifications built 
 at that time were small and of minor importance. For some 10 years 
 after the Revolutionary War, and during the formative period of 
 our, Government, but little additional work seems to have been done. 
 
 In his annual message, submitted in December, 1793, President 
 Washington urged upon Congress the necessity of placing our sea- 
 coast in a condition of complete defense, and a few months later in 
 same session a committee of the House of Representatives submitted 
 to the House a report giving an estimate for the construction of 
 fortification at important points, and making a few reconmienda- 
 tions as to the kind of works that shoidd be built. Based upon this 
 report, the first appropriation for fortification construction was made 
 in the spring of 1794. 
 
 The Secretary of War at once issued to the constructing engineers 
 certain general instructions as to the character of the fortifications 
 to be built. He directed that, owing to the small size of the appro- 
 priation, the works should be comparatively inexpensive, consisting 
 of earthen parapets revetted with timber or sod. When located at 
 distant points the batteries should be buUt into a closed work or 
 redoubt, but in general the defense on the land side was to be 
 provided for by small blockhouses. The redoubts were to be adapted ' 
 to garrisons of about 500 men each, and the blockhouses to detach- 
 ments of about 50 men each. The Secretary left to the judgment of 
 the constructing engineers the question as to whether the redoubts 
 should have embrasures or the fire should be in barbette. He, 
 however, regarded it as very important that a reverberatory furnace 
 for heating cannon balls red hot be erected in each battery. 
 
 Thus was our first system of seacoast defense begun. Appropria- 
 tions were small and the works which were buUt were of rather a 
 minor character. A few years later, however, more extensive plans 
 
 (7) 
 
8 
 
 were adopted and more important permanent works were begun. 
 Fort Constitution in Portsmouth Harbor, Fort Independence in 
 Boston Harbor, Fort Adams at Newport, and a number of other 
 forts date back to this period. 
 
 Work had been carried on in this way for about 12 years under 
 appropriations totaUng about $1,300,000, when in the latter part of 
 the year 1805, our foreign relations became embarrassed, and in 
 December of that year the President, in submitting his annual message 
 to Congress, called attention to the damage done our ports, and to 
 ships sheltered in them, by the enemy's privateers and by pirate 
 vessels, and to the necessity of completing our seacoast defenses. A 
 few months later Congress made a largely increased appropriation 
 for fortification work. Still larger worfe were soon planned and 
 begun, and when, in 1812, war broke out with England, enough work 
 had been done to put our most important harbors in a fair state of 
 defense, though of course during the war, numerous earthworks and 
 other hasty defenses were added. 
 
 Taken as a whole, these defenses accomplished their purpose 
 fairly well during the war, as is shown by the comparative freedom, 
 of the coast ports from naval raids. The only attacks made upon 
 our regular defenses wei'e repulsed and such landings as were made 
 were at undefended places. Had our mobile army been efficient 
 the enemy would have been able to accomplish little. 
 
 The real beginning of our seacoast defenses dates from about 1816; 
 that is, shortly after the close of the war with England. 
 
 The Corps of Engineers had been established in 1802, in connec- 
 tion with the Military Academy, but for the next few years it con- 
 sisted of but little more than the Military Academy itself. By 
 1815, however, the corps had grown in size and importance, and 
 Gen. J. G. Swift, then Chief of Engineers, was directed by the Sec- 
 retary of War to send various engineer officers to examine the 
 different ports of the country, to prepare plans for defensive works, 
 and to submit estimates of the cost of the same. In December, 
 1815, Gen. Swift submitted an estimate to Congress of $838,000 
 as the cost of the work considered immediately necessary, and in 
 the following April Congress appropriated this hitherto unequaled 
 sum for defensive works. 
 
 In the same year, 1816, there was appointed a permanent- board 
 of Engineer officers to prepare plans for defensive works. A dis- 
 tinguished French officer. Gen. Bernard, was induced to come to 
 this country and become the senior member of the board. This was 
 the beginning of the Board of Engineers for Fortifications, which 
 has been in continuous existence since that time. 
 
 Immediately after the organization of this board, it proceeded to 
 make a study of the defense of our various harbors atid to prepare 
 plans for defensive works. Among the first of the forts designed 
 
by this board was Fort Monroe, the largest mclosed work ever con- 
 structed in this country. This fort contains seven bastions, and 
 has a wet ditch If nules in length. Its armament was to consist of 
 over 400 guns. 
 
 From time to time this board submitted to the Secretary of War 
 reports containing plans and estimates for special defenses, which, 
 were considered of a confidential character and were not printed, but 
 under date of February 7; 1821, a more general report was submitted 
 containing a general study of the subject of fortifications. In this 
 report it is stated: 
 
 It will be seen that most of the existing forts only defend single points, and satisfy 
 only a few essential conditions; and that they have not been planned with a view 
 to the defense of the frontiers, considered as one great and combined system, whose 
 several parts should be connected, and should mutually support each other. The 
 navy yards (excepting that of Charlestown, near Boston) have all been improperly 
 placed; the conveniences for the erection of the necessary establishments having 
 alone been taken into consideration, while all the other requisites for points so impor- 
 tant, such as security of attack by sea or land, facility for receiving all kinds of build- 
 ing materials in time of war, as well as in time of peace, vicinity to a place of rendezvous, 
 have been overlooked. 
 
 A defensive system for the frontiers of the United States is therefore yet to be created; 
 its bases are: First, a navy; second, fortifications; third, interior communication 
 by land and water; and, fourth, a regular army and well-organized militia; these 
 means must all be combined so as to form a complete system. 
 
 The navy must, in the first place, be provided with proper establishments for con- 
 struction and repair, harbors of rendezvous, stations, and ports of refuge. It is only 
 by taking into view the general character, as well as the details of the whole frontier, 
 that we can fix on the most advantageous points for these naval depots, harbors of 
 rendezvous, stations, and ports of refuge. 
 
 After determining the general and connected system of naval depots, harbors of 
 rendezvous, stations, and ports of refuge, the commission in the next place traced 
 the scheme of fortifications necessary to protect this system, and at the same time to 
 guard the whole frontier against invasion. The forts projected by the commission 
 for this purpose satisfy one or more of the following conditions: 
 
 1. To close important harbors to an enemy and secure them to the navy of tho- 
 country. 
 
 2. To deprive an enemy of strong positions, where, protected -by his naval supe- 
 riority, he might fix permanent quarters in our territory, maintain himself during 
 the war, and keep the whole frontier in perpetual alarm. 
 
 3. To cover our great cities against attack. 
 
 4. To prevent as much as possible the great avenues of interior navigation from 
 being blockaded by a naval force, at their entrances to the ocean. 
 
 5. To cover the coastwise and interior navigation, and give to our Navy the means 
 necessary for protecting this navigation. 
 
 The board then took up in detail the various ports in the country, 
 showing why and where fortifications were necessary to each. The 
 report then continued: 
 
 From the general exposition which we have given, it will be seen that all the forti- 
 fications projected by the board are not of the same pressing necessity, nor of like 
 importance; that some are required immediately and that the commencement of others 
 
' 10 
 
 may be delayed. In classing them, we shall observe that the works of the most urgent 
 necessity are those which are destined to prevent an enemy, in time of war, from 
 forming a permanent establishment, or even a momentary one, on the soil of the 
 Union; those which defend our great naval arsenals, and those which protect our chief 
 commercial cities. 
 
 In the second grade we will place those which defend stations for our Navy, and 
 commercial cities of secondary importance, which, either from natural or articficial 
 defenses, existing works, etc., are not entirely without protection, and can wait until 
 the chief and more important points are secured, at least against a first attack. 
 
 Finally, in the third class, we will range the works which will complete the defensive 
 ' system in all its parta but whose construction may, without imminent danger, be de- 
 ferred until the frontier has received all the successive degrees of strength which the 
 gradual erection of the forts of the first and second class will give to it. 
 
 The board then gave consideration to the number of men neces- 
 sary to garrison each fort both in peace and war, and then to the cost 
 of the defensive works. The total estimate was about $11,000,000. 
 The board then continued: 
 
 It is proper to add that though the expense of these works be great, that expense Is 
 never to be renewed, while with troops, on the contrary, the expense is annually 
 repeated if not increased until the end of the war. Besides the disbursements for 
 fortifications are works in time of peace, built slowly, and to an extent, exactly corre- 
 sponding with the financial prosperity of the country. Armies, however, are most 
 wanted, and must be paid in periods of great emergency, when the ordinary sources 
 of revenue are dried up, and when the Treasury can only be kept supplied by resort 
 to means the most disagreeable to and the most burdensome upon the people. 
 
 The defense of oiir maritime frontier by permanent fortifications, and even the 
 expense of erecting these fortifications, will thus be real and positive economy. 
 The points of attack being reduced to a few, instead of awaiting an attack on every 
 point, and holding ourselves everywhere in readiness to repel it, we shall force an 
 €nemy to direct his efforts against these.few points, with which we shall be well ac- 
 quainted beforehand, and which we shall have disposed to withstand all his attempts. 
 There is no doubt that such circumstances will render an enemy more backward in 
 risking his expeditions, and that we shall not only therefore be better able to resist 
 attack, but that we shall also be less frequently menaced with invasion. 
 
 Some prominent military writers have opposed the principle of fortifying a mari- 
 time frontier. The practice of every nation, ancient and modern, has been the same 
 in this respect. On a land frontier a good, experienced, and numerous infantry may 
 dispense with permanent fortifications, although they would prove excellent auxili- 
 aries and supports when properly disposed and organized; but though disciplined 
 troops can, rigorously speaking, without their aid, cover and protect a frontier, undis- 
 ciplined troops never can. On a maritime frontier the case is totally different. Troops 
 can not supply the place of the strong batteries which are disposed along the important 
 places. The uncertainty of the point on which an enemy may direct his attack, the 
 suddenness with which he may reach it, and the powerful masses which he can con- 
 centrate at a distance out of our reach and knowledge, or suddenly, and at the very 
 moment of attack, are reasons for erecting defenses on every exposed point, which may 
 repel his attack, or retard it until reinforcements can arrive, or the means of resistance 
 be properly organized. By land we are acquainted with the motions of an enemy, 
 with the movements and directions of the columns; we know the roads by which he 
 must pass. But the ocean is a vast plain without obstacle; there his movements are 
 performed out of our sight and knowledge, and we can receive no intelligence of hia 
 approach until he has already arrived within the range of the eye. In a word, the 
 
11 
 
 vulnerable points of a seacoast frontier are left to their fate, if they are not covered by 
 permanent fortifications; and their only chance of safety must then depend upon the 
 issue of a battle, always uncertain, even when regular and well-disciplined troops , 
 inured to danger, have been assembled beforehand, and have made all possible prepa- 
 ration for the combat. 
 
 If we overlook for a moment the many points of the maritime frontier which the 
 enemy might invade with the most serious consequences to the United States; if we 
 suppose that there exists no object on that frontier worth the trouble and expense of a 
 great expenditure, these fortifications will even yet be highly necessary; for we still 
 have one great object to attain — the security of avx Navy. This can not be protected 
 ■without fortifications, especially in struggling with an adversary superior in numbers 
 and jealous of a supremacy on which may ultimately depend his political importance. 
 A navy can neither be augmented nor secured without fortifications, nor can it enjoy 
 without them the advantages which the localities of the frontier might otherwise afford. 
 Accidents may and must happen to it; and it is only in closed and fortified harbors that 
 ^t can repair the losses and disasters of a course of war, and from them, when refitted 
 and refreshed, recommence its operations. England, herself, notwithstanding the 
 great naval superiority which she posseses at this moment over the rest of the world, 
 and the excellent organization of her militia, strengthens and augments the fortifica- 
 tions of her frontier every day; and no nation of Europe, France excepted, poBsesses a 
 stronger and more complete system of permanent defenses along its coast. 
 
 Lastly, the defensive system of our seacoast by permanent fortifications being com- 
 pleted, and the Union being protected against all danger of invasion from that quarter, 
 ahe can direct all her resources toward her Navy. Her national quarrels wiU then all 
 be decided upon the ocean, and no longer upon her own territory; her wars will all be 
 maritime; a species of warfare in unifion with the institutions of the country less costly 
 in men and money, and which, by keeping oft all aggressions from her own territory, 
 will preserve untouched her industry, her agriculture, her financial resources, and all 
 the other means of supporting a just and honorable war. 
 
 As for the garrisons which these forts will require in time of war, a small portion of 
 them, equal in number to the garrisons necessary in time of peace, may be composed 
 of regular troops; the surplus of militia practiced to the maneuvers of artillery; for the 
 greatest part of the troops required for the defense and service of these great coast 
 batteries should be composed of Artillery. 
 
 To this end every State might organize a certain number of battalions of militia 
 Artillery, proportioned to the exigencies and armament of the forts upon its coast, or 
 "within the sphere of activity of its military force. These battalions should be within 
 call of the forts so long as no invading expedition is announced, but as soon as some 
 operations of an enemy should menace the frontier, they should throw themselves into 
 the forts, and remain there as long as the precise point of attack should remain uncer- 
 tain. This system of defense for the coast was established in France, where it suc- 
 ceeded very well. It appears to us to harmonize as well with the institutions and 
 spirit of the country as with the principles of economy, which should direct and govern 
 all the expenses of the Government. 
 
 If to our general system of permanent fortifications and naval establishments we 
 connect a system of interior communications by land and water, adapted both to the 
 defense and to the commercial interests of the country; if to these we add a well-con- 
 stituted regular army, and perfect the organization of our militia, the Union will not 
 only completely secure its territory, but preserve its national institutions from those 
 violent shocks and revolutions which, in every age and in every nation, have been 
 too often incident to a state of war. 
 
 In the present report we have taken no account of the interior and land frontiers of 
 the Union; they have not yet been sufficiently reconnoitered to enable us to give an 
 exact idea of the system of defensive works which they may require. All that we 
 
12 
 
 can say by anticipation is that, from their general topographical features, these fron- 
 tiers can be covered, at a very moderate expense, by such a defensive system that no 
 enemy will be able to invade them without exposing himself to disasters almost in- 
 evitable; and that the armies of the United States, supposing all her warlike prepara- 
 tions well organized beforehand, will be enabled, at the very opening of the first cam- 
 paign, to carry the theater of war beyond her own territory. 
 
 A few years later tlie board submitted another general report upon 
 the means and works of the defensive system which it considered was 
 for the best interest of the United States to adopt. This report states : 
 
 The means of defense for the seaboard of the United States, constituting a system , 
 may be classed as follows: First, a navy; second, fortifications; third, interior communi- 
 cations by land and water; and fourth, a regular army and well-organized militia. 
 
 The navy must be provided with suitable establishments for construction and re- 
 pair, stations, harbors of rendezvous, and ports of refuge, all secured by fortifications,, 
 defended by regular troops and militia, and supplied with men and materials by th& 
 lines of intercommunication. Being the only species of offensive force compatible 
 with our political institutions, it will then be prepared to act the great part which its 
 early achievements have promised, and to which its high destiny will lead. 
 
 Fortifications must close all important harbors against an enemy, and secure them 
 to our military and commercial marine; second," must deprive an enemy of all strong- 
 positions, where, protected by naval superiority, he might fix permanent quarters in 
 our territory, maintain himself during the war, and keep the whole frontier in per- 
 petual alarm; third, must cover the great cities from attack; fourth, must prevent, as^ 
 far as practicable, the great avenues of interior navigation from being blockaded at their 
 entrance into the ocean; fifth, must cover the coaiitwise and interior navigation by 
 closing the harbors and the several inlets from the sea which intersect the lines of com- 
 munication, and thereby further aid the navy in protecting the navigation of the 
 country; and, sixth, must protect the great naval establishments. 
 
 From time to time in later years similar reports were made by the- 
 Board of Engineers, but it is not considered necessary to quote from 
 them. 
 
 Under the supervision of the Corps of Engineers and upon plans- 
 prepared by the Board of Engineers, work on our seacoast defenses wa& 
 continued with fair regularity until the outbreak of the Civil War. Of 
 course, modifications and improvements in the method of construc- 
 tion were made from time to time, but, taken as a whole, the works 
 were carried out on one general system. 
 
 The locations selected for defensive works were usually in close 
 proximity to the navigable channels, and generally where the chan- 
 nels were rather narrow. This brought them frequently quite close, 
 to the cities and harbors they were intended to protect. Where the 
 channels were wide, defenses were built on both sides, and in some 
 cases artificial islands were constructed on shoals so that defenses 
 might be built closer to the navigable channels. A prominent ex- 
 ample of this kind of Work is Fort Wool (formerly Fort Calhoun),, 
 situated on an artificial island built by depositing riprap on a shoal 
 at the mouth of Hampton Roads, Va. 
 
13 
 
 In most cases the larger forts consisted of a closed enceinte sur- 
 rounded by a ditch with a high scarp wall. On all sides from which 
 a land attack was to be feared the ditch was finished on the outside 
 with a revetted counterscarp, covered way, and glacis. These ditches 
 were usually dry, although where conditions made it possible, as at 
 Fort Monroe, a wet ditch was provided. The trace of the works was 
 usually on the bastioned system, and a thorough system of ditch 
 defense was always provided, sometimes by casemates in the flanks 
 of the bastions, sometimes by counterscarp galleries, and sometimes 
 bj^ caponnieres. On the land fronts complicated outworks were not 
 uncommon, and demilunes were quite numerous. 
 
 The crests of all these forts were lined with heavy guns in barbette, 
 the heaviest being placed on the water fronts. In some localities the 
 fire brought to bear on the water was increased by water batteries 
 constructed outside the ditches. At other places everything exterior 
 to the ditch was omitted on the sea front, the curtains of the bastions 
 on these fronts being armed with casemated guns. 
 
 In some extremely important localities, tall seacoast batteries were 
 constructed, consisting of several tiers of masonry casemates sur- 
 mounted by a barbette tier at the top. The battery of this character 
 which was most nearly completed was at Fort Wadsworth, Staten 
 Island, but other batteries of the character were begun at other places, 
 such as Willets Point (now Fort Totten),"Long Island Sound, N. Y., 
 and at Fort Wool, Ya. 
 
 As a general rule, in the North and East, where stone was obtain- 
 able, the forts were built of granite, but on the south Atlantic and Gulf 
 coasts, where stone was not obtainable, brick was the building 
 material commonly used. 
 
 Shortly before the Civil War there was introduced into the case- 
 mates of the forts what was caUed the "Totten embrasure," named 
 after its inventor, Gen. Totten, afterwards Chief of Engineers. This 
 consisted of a pair of heavy wrought-iron shutters hinged on either 
 side of the opening. When the gun was ready to fire, the shutters 
 were pushed by hand nearly all the way open; when the gun was fired 
 the blast of the discharge opened the shutters aU the way and they 
 then bounded back shut, and were caught and held by a spring latch 
 and thus concealed and protected the detachment while reloading 
 the gun. 
 
 At the beginning of the Civil War the fortifications in the Southern 
 States fell at once into hands of the Confederates and were prepared 
 for defense by their Engineer officers, many of whom had previously 
 served in the United States Corps of Engineers. The Confederates 
 at once hastily finished all incomplete works and added greatly to the 
 strength of the completed ones by throwing up earthwork batteries. 
 That such a system of seacoast defenses was quite efficient was 
 
14 
 
 demonstrated during the Civil War. In spite of the size and strength, 
 of our Navy, the naval attacks on the forts were repulsed in almost 
 every case, and when the seacoast forts were captured, it was usuaUj^ 
 only by the aid of land forces and frequently after regular sieges. 
 
 History Since the Civil War. 
 
 The period of the Civil War and a few years preceding and following- 
 it was one of rapid development in the manufacture of guns and 
 armor and in naval architecture. The introduction of steam power 
 for propelling ships removed them from their dependence on winda 
 and tides and gave them the power of approaching forts and of 
 retreating at will. The use of wrought iron as side armor, by de- 
 creasing the vulnerability of ships, increased their chances in conflict 
 with shore batteries. The power of naval guns had been increased 
 so that they were able to successfully attack the masonry walls of 
 fortifications. From these changes there resulted, therefore, a change 
 in the art of seacoast defense. 
 
 In .1865 the Board of Engineers was directed by the Chief of Engi- 
 neers to consider what modifications in seacoast defense the experience 
 of our Civil War and contemporaneous developments abroad had 
 rendered desirable in our seacoast defense. The board was in addi- 
 tion directed to report specifically upon the possibility of substituting 
 wrought-iron armor for masonry work and upon the advisability of 
 moimting our guns, so that when not in use they might slide down, 
 behind the parapet. 
 
 The board gave these subjects careful consideration and, after con- 
 siderable deliberation, submitted a long report, their principal recom- 
 mendations being to the effect that our seacoast defenses should 
 preferably consist of powerful batteries of guns of the largest caliber ,^ 
 that the disappearing gun carriage should be introduced, that mortar 
 batteries should thereafter play an important part in seacoast defense 
 for firing against the decks of vessels (their weakest portion), that 
 torpedoes and physical obstruction of channels should be used where ' 
 possible, that it was no longer advisable to use granite casemate 
 batteries, and that armor as a substitute for granite fronts or for use 
 in connection with granite in casement fronts had not as yet proved, 
 satisfactory. 
 
 From the close of the war up to 1875 small appropriations were 
 made annually for fortification construction, and with the money 
 thus provided considerable work was done. Much repair work and 
 rebuilding was necessary, especially along the south Atlantic and 
 Gulf coasts. At many places new earthen batteries were constructed, 
 generally exterior to the enceinte, the guns being mounted in barbette. 
 The disappearing carriages were not generally introduced, though: 
 experiments had shown the "King carriage," invented by Maj. W. R. 
 King, Corps of Engineers, to be serviceable. 
 
15 
 
 The barbette guns were usually grouped in paii's and, to prevent 
 enfilade, the pairs were separated by thick traverses of earth extend- 
 ing high above the crest of the parapet; service magazines were usu- 
 ally built in these traverses. The guns employed at this time were 
 the 10 and 15-inch muzzle-loading smoothbores; the 10-inch guns 
 being subsequently altered into 8-inch rifles, and the 15-inch guns 
 into 11-inch rifles. 
 
 After 1875 Congress ceased for several years to make further 
 appropriations for the construction of seacoast batteries, contenting 
 itself with small and utterly inadequate appropriations for the preser- 
 vation and repair of existing fortifications. This condition existed 
 for nearly 15 years, and it was not until August, 1890, that Congress 
 began again to appropriate for battery construction. 
 
 In thus neglecting our seacoast defenses. Congress was acting 
 directly contrary to the advice of the Corps of Engineers, as the Chief 
 of Engineers never failed, in his annual report, to submit a strong 
 plea for renewal of the work. On pages 4 to 18 of the Annual Report 
 of the Chief of Engineers for 1880 there will be found an especially 
 strong plea for resuming work on the defenses, and in the report for 
 1881, pages 399 to 415, there is a letter to the Chief of Engineers 
 from Col. Gilmore, of the corps, which is worth study. 
 
 On March 3, 1885, Congress passed an act authorizing the forma- 
 tion of a board to be composed of Army and Navy ofiicers and of 
 civilians to examine into and report upon the subject of seacoast 
 defenses. This board was shortly afterwards appointed by the Presi- 
 -dent, and became known as the "Endicott Board," from its senior 
 member, Secretary of War Endicott. This board, dividing itself into 
 committees, made a long and careful study of the different features 
 of seacoast defense, and, in 1886, submitted its report. 
 
 The report of the board is quite lengthy and takes up first the 
 general subject of where fortifications should be established. It then 
 selects the places which should be fortified, gives in detail the forti- 
 fications which should be provided in these places, and mentions the 
 order in which the work should be done. It also makes a very careful 
 summation of the number and caliber of guns which should be em- 
 placed with the cost thereof, and of all other elements of the defense. 
 
 In 1890, Congress decided to act upon the recommendation of the 
 Endicott Board, and in August of that year made an appropriation 
 for the construction of seacoast defenses, the first for 16 years. The 
 amoimt of this first appropriation was $1,200,000. Other appro- 
 priations followed, the annual average being about a half million 
 dollars until 1896. In this and the following few years, the amounts 
 were still larger. 
 
16 
 
 The first appropriation which was made by Congress was directed 
 to be distributed between Boston, New York, and San Francisco, and 
 the next year Hampton Eoads was added to the list. In the later 
 appropriation acts no restrictions as to the distribution of the appro- 
 priation were made. 
 
 From the firs't appropriation allotments were made for bar- 
 bette batteries at San Francisco, for disappearing 8-inch guns in 
 New York Harbor, for a 12-inch gun-lift battery at Sandy Hook, 
 and for mortar batteries at Sandy Hook and at the Presidio, San 
 Francisco. Work on these and other batteries was pushed rapidly, 
 though progress on the disappearing emplacements was delayed until 
 the Ordnance Department could develop a suitable type of disap- 
 pearing carriage. 
 
 The estimates that were submitted by the Endicott Board were 
 necessarily based upon the gun carriages, types of emplacements, 
 etc., known at the time (1885 and 1886), but before actual work was 
 begun many improvements and developments had been made. How- 
 ever, the Endicott Board had made liberal allowance for such im- 
 provements and contingencies, and these estimates were so well made 
 that they remained, for about 20 years, the official basis upon which 
 annual requests for funds were made to Congress. That is, in each 
 annual report the Chief of Engineers would make a statement of the 
 total amount which had been appropriated, the number of guns 
 which had been mounted, and number of emplacements which had 
 been provided for. This was compared with the figures of the Endi- 
 cott Board, and the diflFerences were stated as being the nmnber of 
 guns stUl to be mounted, the nmnber of emplacements still to be 
 built, the amount of money still to be appropriated. 
 
 In the meantime, however, there had been a rapid development, 
 not only in the manufacture of ordnance and in the construction of 
 emplacements, but in auxiliaries, such as fire control, searchlight 
 illumination, etc. 
 
 Accordingly, the President, under date of January 31, 1905, 
 organized what is officially known as the National Coast Defense 
 Board and what is informally known as the Taft Board, Secretary of 
 War Taft (afterwards President) having been the presiding officer of 
 the board. After due consideration, this board submitted a report 
 which is now the basis of estimates. 
 
 The report of the Taft Board is much shorter than that of the 
 Endicott Board report and should be read by all students of fortifi- 
 cation history. It first reviews briefly the Endicott Board report 
 and the conditions which required the formation of that board. 
 It suggests certain new harbors as being worthy of fortifications — 
 the entrance to Chesapeake Bay, the eastern entrance to Long Island 
 Sound, our insular possessions, and the entrances to the Panama 
 
17 
 
 Canal. It suggests some slight modification in the character of 
 guns to be mounted, and especially the introduction of the 14-inch 
 gun as the standard seacoast defense gun in preference to the 12-inch, 
 which had theretofore been considered the largest gun. The report 
 also laid great stress upon the importance of searchlights and adequate 
 fire-control systems. 
 
 Finally, the board made a summary of the cost of all the work 
 recommended by it and recwnmended that this cost be taken as the 
 new basis of estimates and appropriations. 
 
 As had been the case with the Endicott Board report, the Taft 
 Board report, after its submission to the Secretary of War, thence to 
 the President, and thence to Congress, was assumed as the standard 
 upon which seacoast defense shoidd be based. The various sugges- 
 tions of this report as to searchlight and fire-control installation, and 
 as to other details, were all carried into effect by the War Department. 
 
 Unfortunately, however, the principal xise made of this report 
 seems to have been as a basis of estimates. Thus, the War Depart- 
 ment in submitting its annual report to Congress stated each year 
 that the Endicott Board report, as modified by the Taft Board 
 report, recommended a certain number of guns of each caliber, that 
 there had been emplaced or provided so many gims of that character, 
 and that therefore there remained so many to be emplaced and so 
 many to be provided; that the board estimated the total cost of 
 emplacement construction as so much; that so much had been 
 appropriated by Congress, and that the balance, therefore, was the 
 amount still to be appropriated. Similarly with regard to fire con- 
 trol and searchlights. 
 
 In thus making the figures compiled by the Taft Board an un- 
 changeable basis of estimates, the War Department was but con- 
 tinuing the policy which had been customary, at least since the 
 acceptance of the report of the Endicott Board. Moreover, the 
 department was but carrying out the suggestions of the Bernard 
 Board, for, as may be noted in one of the quotations in the early 
 part of this chapter, the Bernard Board in advocating the construc- 
 tions of fortifications around our frontiers used as an argiunent the 
 statement that the expense of a fortification construction once 
 incurred would never have to be renewed, while, on the other hand, 
 the cost of maintaining a mobile army was one that must be repeated 
 annually. 
 
 A century ago, when, in spite of the impetus of the Napoleonic 
 wars, the apphcation to military art of mechanical inventions and 
 developments was proceeding but slowly, and when the portions of 
 fortifications in the immediate vicinity of the gun emplacements 
 were constructed of earth which could be easily changed at will, it 
 might have been considered fairly true that fortifications once 
 173341—20 2 
 
18 
 
 constructed could be expected to remain fairly efficient for quite a 
 number of years. 
 
 This, however, is no longer true. Inventions are being made by 
 the thousands, and the adaptation to military affairs of recent in- 
 ventions and discoveries is being made by leaps and bounds. An 
 emplacement, at least, in the immediate vicinity of the guns consists 
 usually of concrete, which once set is permanent and which costs 
 several times as much to remove as to put in place. 
 
 That it is dangerous to rely upon a fortification remaining fairly 
 up to date, even for a period of but two or three decades, is shown 
 by the disastrous failure of the Belgian fortifications- in the summer 
 of 1914 to stop the advance of the German army. 
 
 The fortifications of the Belgian cities had been constructed only 
 about a quarter of a century. They had been designed by the 
 foremost fortification engineer of the day. They had been built to 
 withstand the fire of guns larger than any which it was then thought 
 possible to transport with a field army, and the armament consisted 
 of even heavier guns. However, before these fortifications were 
 three decades old they were confronted by the advancing German 
 Army bringing forward guns of a size never before used with a field 
 army and theretofore considered available for fortress use only. 
 These heavy gims outclassed the Belgian ,guns and fired projectilea 
 which the defenses were not intended to withstand. As a result, 
 before many days had passed the Belgian fortifications had been bat- 
 tered out of existence. 
 
 Making a text of this occurrence, the Chief of Engineers in Novem- 
 ber, 1914, submitted to the Chief of Staff a memorandum on the 
 subject of "The Obsolescence of Seacoast Emplacements," which 
 reads in part as follows : 
 
 In connection with the easy capture by the Germans of Belgian fortresses and the 
 inability to withstand modern ordnance shown by fortifications built more than 20 
 years ago and designed to withstand guns of that time, the Chief of Engineers con- 
 siders it advisable to bring certain facts connected with our existing seacoast fortifica- 
 tions to the attention of the Chief of Staff. 
 
 On the eastern shore of the United States — ^that is, on the Atlantic and Gulf coasts — 
 there have been emplaced since 1890 two hundred and seventy-two 12-inch mortars 
 and eighty-one 12-inch rifles, 64 of the latter being mounted on disappearing carriages 
 and 17 on barbette carriages. These guns constitute the primary armament, and iu 
 this connection no attention will be paid to the guns of smaller caliber. 
 
 Of these" emplacements for the larger guns, 248 of the mortar emplacements and 
 60 of the 12-inch emplacements were designed and begun prior to the Spanish War- 
 The last mortar emplacements were designed and begun in 1900-1901, and the latest 
 type 12-inch emplacements, namely, Batteries Parrott, at Port Monroe, and Wheaton,. 
 on Narragansett Bay, were planned and begun about 1903 and were practically ready 
 for use in 1905. 
 
 Of the ships of the United States Navy now carried as first-line battleships, the 
 very oldest, the Michigan and the Souffi CaroUna, were designed an(J begun in 1905, 
 or about the time the latest of our eastern seacoast batteries were completed. 
 
19 
 
 Judged by the naval stiKndard, therefore, we have not on the Atlantic coast a single 
 """fiist-Iine" emplacement. '■• ' , 
 
 In our FaiJfic defenses conditions are in general the same as on the Atlantic x:oa8t. 
 Of the 104 mortar emplacements and twenty-four 12-inch rifle emplacements whicit 
 have been built, only two, the 12-inch emplacements at Fort Worden, inay be con- 
 sidered as Mrly modem, having been designed in 1908. However, work is' about 
 to be b^fim on new defenses at San Bi^ and Los Angeles. 
 
 For many years the Navy Department has been educating public opinion and- 
 die ideas of Congressmen to the fact that the life of a' battleship is limited; that after 
 a comparatively small number of years it must be relegated to what is caUed the 
 second line; after a few years more it must go in reserve for emergency use only. 
 Slid, when 20 or 25 years of age, is to be dassed as obsolete and can be considered 
 agifitted only to be broken up, or to be used, like the San Marcos (fonneiiy the battle- 
 ship Texas), as a target forits more modem sisters. 
 
 With vessels and floating craft there Sre, of course, other things to be considered 
 beaid^ armor and armament, such as the huU, the propelling machinery, and the 
 deatrudable nature of the very material used in coKstmction; but the reasons for 
 i^^jsting Eiiips to the second line or to the reserve are not usually defects in the- 
 hull or propelling machinery, but rather the obsolescence of the armament,~armorr; 
 or other matters directly .connected with offense or defense. 
 
 In Gpnnection with this obsolescence' of battleships the Navy Department, year 
 by year, preBents^tements to Gdngress. to the effect that in order to keep the Navy- 
 efficient and up to date a certain number of battleshijis must be laid down each year, 
 this number usually being stated at four. 
 
 Unfortunately, the War Departinent has not seen fit td adopt a similar policy, but 
 Uiis permitted it to be understood that a seacoast battery, once constructed, remains' 
 IHaetically.Mdefinitely up to date. For instaneie, from 1890 until about the time 
 of the formation of the Taft Board in 1905, the department each year in its annual 
 report would state that, based upon the report ot the Endicott Board and the revision:- 
 of certain projects up to date, it was estimated that a certain number of emplacements 
 of each caliber were necessary to complete the defenses of the country, that a certaii* 
 number had been constrfiieted, and that the difference represented the number to 
 be built.- 
 
 In the report of the Taft Board in 1905 no'attiempt was made to bring the subject 
 of seacoast fortiflcations up to date, thbugh new estimate were made of the number 
 -iX guns still to be emplaced and of the cost of doing this work. However, since the 
 report of the btiaTd, the same policy as to estimates mentioned above has been essen- 
 tially fbUowed, and npwhere in the report of the Taft Board nor in the aimual reports 
 of the department is attention called to the fact that our emplacements rapidly get 
 «ut of date, and to keep our coast defenses efficient fortification construction must- 
 go on practically continually." 
 
 As a partial step toward keeiping the batteries up to date estimates were submitted 
 by the Taft Board for modemiziiig older batteries, and, under this head, approxi- 
 ]nately-$l,09b,000 has been provided by C!oiigress. With the funds thus provided 
 much work has been done; In unptoving projectile hoists and -widening loading plat- 
 forms so as to pro-vide easier and more efficient ammunition service and thereby 
 inBuie\greatei' rapidity in fire; in the installation of ventilating apparatus and the 
 pieveiition ofd^BpnesS' in our .ms^iazines; and in the introduction of other modem 
 aj^liancee. Such mede^iz3ng-,;liweve», is really analogous to the repairs and over- 
 ' hauling which are periodically done on our battieships and in spite of wMch periodical 
 •overbaWling our battleshiju stiiU grow out of date. Consequently, it can never be 
 l^^pt^ iMt &j3x Emplacements can be kept up to date by merely tinkering with 
 
20 
 
 :i O'tfr-a0|kEoaist, .tatteriesr.jWtiieii ^biijiifi. ■w!e*e>.d99ighed, to witiisliaaiidr^ttMP -pf, the, ijgj ,9A# ;, 
 a fkir factor of mieij was, provided to allow for the fMare adwB^eiifipljin 'ordSaiil^ 
 The time ,elapso4'J!i«''^eA«er,>S%|e,='Si!S,5^^^ ,hafl«;feje,ea.Bo gi-eat and the - 
 
 adiraiaCes ia ordnaaee have Ibeek so rapid that maBy of our older ina^ifipes are npf; 
 adequately protected against BMSiera fia-v^l; fifles . In may ea?es,; of course, thjesad^fc 
 tionaLnecessairy. proteetiom-can b« added by excavating e&nd- a,nd'-mt^^fieyr. coiih 
 Crete to the front of the concrete walls', or by placing more sand in front, of lihe^exfcfe; 
 iiig isaiiSi^ioteetion. Usmally, however, thisr can not bj^ done wilihout; to sojme: ext^jit 
 rfe^imeitag the are of fire of ^e 'gii% ■ ,^ ,' : ,^ . , - '" 
 
 ,• fcny of oiir feSi^eiiesifesalso deficient ia o^^rhgadipfbteQtiom, 'sia^©,, at tijie-jtMie;- 
 tji^j5 were planned, high angle, fiire from naval vfessejswas jaot possible.! It is pasiibliili 
 to add'&e additional iirateetioa by increasing the jeoncrete cover or by the additi^, 
 of iron pjlrt^,; but in very many cases the addition «f this new pi'ateetion dan but 
 result in the reduction of the available field of fire of <3ie gun. : i <if^j 
 
 I Jt#iesse;ttti8Sl,vif ourseaeoastifojtificatiQiia are to be kept, i^< to date andtobeefflcfeiif*; 
 againSti modem (tiavies,i1fhat our coast-defense gtrnfiste^lslt. fee. at least as powerful aB, 
 fli^, gun* which may he brought against -them on shiflioairij that is, our coast gunSi 
 miist te at iteast aia gteat a eaMbes and must have at l^at as great a range as &e naValt 
 Svmac-, -!i^/;t ■: ,; . ,;- !•< ■iv.,,i,--;»c!.-vir j-w i.""5 - ".■ : ■.■..-. ■ ••'[.■' •{■ 
 
 Asia shown- by the aceompanytng tafelej jaost of our em)pUiicem^t8;0n ^otb "were. 
 diesigned pricffi;to the; Spanish War, since which time there have been enoranflljBp; 
 adviaftoea in naval ahdiseaeossterdaaneei,! and, if our seacoast batteries are to be 
 broMght up to date/ these smaller guds which- they contwn must be replaced by mofe 
 powerful ones. - ': 
 
 ' : To adapt oug ,eBiplaceme,nts to more powerful ordnance' reqjaaies not only that^new 
 k mirjages 4»oB.ld be constmeted .batjihat ilihe very lessenitals of the emplacementt|; 
 should ibe altered|;:i)eq'uai^g #e(piittiingt.awas''of largft amounts of old concrete andi_ 
 theiplacing of teiijge aniounts.of new concrete, the cost of which changes would be a 
 very toge percentage of th6,is6sl of new gm^lacefliejitsit .. , «, 
 
 In iact, when everything is consideredi the need of; additional proteotioi to tiiB. 
 magazine^ the need of more,convenientsaimmuni4g.oniseivicey together with the need 
 of a complete rebliilding of the emplacement,, aili the loading ^latf oran. and its vieini^ii 
 in order to adapt our older batteries to the new and larger guns; econoiny and effldenQy} 
 wU uauallji! reqjlpe ■'ffiat ,ii^ eraf fefijllg" iiew ^ordnance entirely new emplaceaientBf 
 Bbould be designed and built and thati(ihe;©ldl•QI^e^.?hould be abandoned. !■• ^'- 
 
 In deBigniBgand building fflifl-Wjemplaoenienitsj of comise,- ewiy efEoEtishouM. be 
 
 made to ^tosade for reasonable advances.in the near future, for -there is every reaa^af 
 
 to beUeve that such ad'waniees will continue, but ©tpiejieneeiin the past, would seeso.; 
 
 , to sjiow Alust it is^not within the, limit, of human sinteHigence to properly ^df|^ 
 
 the .advances of. the futu!!!e*'i- ,. ■;-'■'*■' . ■'■'!< -.^ •: ' . . '■'■n'ysM; 
 
 Consequently, based upon the same reasoning as is usedihy the Uavyiaitg.repiortai- 
 to Oongreaa, that a certain niimbeE of battleships miastjannuially be laid diQ^!* if the 
 -Navy;is|to be kOpt'fairl^up to date, it TKojufld Appear proper that the War Departmsi^ 
 p&oMdirepOEttO'CaiailressitMajt.in ordsfito keep oui.seagpast forJifiiEations; up- to date 
 it isimefeggfpy.lhiiifr'eadiSyear a Qertaim nuDEiber of s^aCoast em,placementB Should be, 
 autihoi5iz.ed,i.' ' ■•'--t, , „i:..; ,. ;, ,.., .. ,,.■,;- ,.i,«,.,,,, . ■■ '.^t ?»traji 
 
 ^Vhat USaia number should sbe tsi^f ^eouf ges'. a ii&atter of iadgment,! hni it ie the .^islij^ 
 of the .Ohiefiiof Bngjneerg- that .wef cart Aot. expect, that our aefccoast foifefiGatiiing.dial4- 
 alifays remain even,feirly'up to,d?6te:';fladess ipro^sasiona are made aanually-for replaMg>i 
 from 4'to,^ peree&t of .our«tapla0jaenitSj ;' • 1 • >• •' r ;i..;: 
 
 , ■ ,At psesenit, aaihasrheeaphosnti theje}afB»no emjrfajpements., on our Atlantic, aitdfgnuM-'. 
 Q^pufejs^iidjonly two om tto Jaiciflc j|0flst|:that weie. not desiggf^di.more than 10 yeaas. 
 -ago. " ^dnseqiiently, to enable vps to 'catch up as it werOj eiflaplaceMent cottstruclaQ^ 
 must for the next few yiea^s be capied on at a greater rate even tlfan wolild be required 
 
21 
 
 by the percentage just stated. The Chief of Engineers considers it his duty, therefore, 
 to urge that appropriations be made for emplacing each year for the next 10 years 
 or 80 an average of not less than 8 major-caliber guns and 24 seacoast mortals. 
 
 In order to emphasize this mattef, the Chief of Engineers, in his 
 annual report submitted in the summer of 1915, inserted the following: 
 
 When designed and constructed our seacoast batteries were thoroughly modem 
 and fuUy adequate for the purpose for which they were intended, but the work o f 
 battery construction has in the past few years been allowed to practically cease and 
 has not kept pace with the recent progress in naval development. 
 
 It can not be too emphatically stated that the art of fortification is a progressive 
 one. It must continually grow to keep pace with the new discoveries which give 
 it special advantages or to meet and offset progre^ in the development of naval vessels 
 and armament against which the forts are expected to contend. However carefully 
 planned and constructed, a battery must always pertain to the date when completed 
 and must be out of date in so far as relates to things which have been discovered or 
 developed since the batter}' was planned. 
 
 Seacoast defenses are designed to fight naval vessels and to thus protect certain 
 cities, harbors, or other utilities from bombardment by an enemy's vessels within 
 any of the area covered bj' the seacoast guns. In locating and designing batteries 
 the range and power of the naval guns, as well as the number of such guns which can 
 be brought against these fortifications, must be given consideration, and, unless our 
 fortifications are to become obsolete, changes in any of the elements of na\ral offense 
 must be met by corresponding changes in seacoast batteries, and these changes must 
 in most cases consist not merely of modifjdng the older emplacements by affording 
 additional protection for the gun platforms and magazines against the increased power 
 of naval guns, or in mounting more powerful guns in these older emplacements, but 
 rather in the construction of absolutely new batteries in new locations. The older 
 batteries were necessarily designed and located so as to obtain the maxdmum effect 
 with guns of the range of those to be mounted in those emplacements. If the guns 
 which were to be mounted in those older batteries had been of loiter range, the 
 locations of the batteries would in many cases have been different, and if more power- 
 ful and longer range guns be mounted in those older batteries a large proportion of 
 this increased power and range wiE in most cases be lost. 
 
 For the above reasons it should be noted that a fixed project for seacoast defenses 
 can never be adequate, and its obsolescence must begin before it can be completed. 
 
 For the first few years after the report of the Taft board was sub- 
 mitted, seacoast construction in this country, in general, was restricted 
 to the completion of batteries previously begun, or to the installa- 
 tion of fire-control and other accessories. The new batteries that were 
 begun were mainly in our tropical possessions and in the Panama 
 Canal Zone. 
 
 About 1912, however, battery construction was resumed in the 
 United States, principally on the Pacific coast, and studies were 
 made of the work covered by the Taft board project for the defense 
 of the entrance to Chesapeake Bay. 
 
 In its report submitted in the autumn of 1914 upon the project 
 for the defense of the entrance to Chesapeake Bay, the special board . 
 which had been oi^anized to consider the matter invited the atten- 
 tion of the War Department to recent developments in seacoast 
 
22 
 
 defense which appeared to make desirable a revision of all seacoast 
 defense projects. About the same time the Chief of Engineers sub- 
 mitted the paper on obsolescence quoted above. 
 
 His attention having been thus called to the matter, the Secretary 
 of W&T decided to organize ia the War Department an agency known 
 as the War Department Board of Eeview for the revision of seacoast 
 defense projects. This board consisted of the Chief of Staff and his 
 principal assistant, and of the Chief of Engineers, Chief of Ordnance, 
 Chief of Coast Artillery, and the president of the War CoUege. It 
 at once commenced a study of all the projects for seacoast defense 
 of the United States and, within about a year, submitted its recom- 
 mendations as to the modifications which it thought should be made 
 in these projects. 
 
 In a number of cases no additional emplacements were recom- 
 mended, but in the more important defenses important modifications 
 were reported as being necessary. In the meantime the 16-iQch 
 rifle had been developed by the Ordnance Department and was 
 recommended for installation as the primary gun in the new fortifi- 
 cations, to be mounted generally on disappearing carriages providing 
 for an elevation up to 30°. The 16-inch mortar was recommended 
 as the standard mortar, to be emplaced ia batteries of the same 
 general type of the Panama Canal mortar batteries. 
 
 It having been brought 16 the attention of the board of review that 
 there were on hand and not in use a number of 12-iach guns which 
 had been manufactured by the Ordnance Department as "spares" 
 to take the place of the standard 12-inch guns which had been installed 
 in our seacoast defenses, as these guns wore out, and since it was 
 probable that they would not be used for this purpose, the board of 
 review recommended that these guns be emplaced immediately, 24 
 in the United States and 12 in the insular possessions, and ia order 
 to give these guns the maximum range possible, it was recommended 
 that they be mouated on barbette carriages, permitting an elevation 
 of from 30° to 35°. 
 
 The recommendations of the board of review as to the construction 
 of 12-inch long-range emplacements have been carried out, but work 
 on its other projects has not as yet been begun, although the Ordnance 
 Department has done some work on the construction of the 16-inch 
 guns and carriages. The reason for this is, that before work could be 
 begun, the United States became involved in the recent war and 
 during the war the efforts of the Ordnance and Engineer Depart- 
 ments were devoted to work immediately connected with the war, 
 consequently it was not until about the time of the armistice that it 
 was possible, without neglecting war work, to devote attention again 
 to the seacoast-defense situation. 
 
23 
 
 In the meantime, in connection with land operations abroad, there 
 had been a rapid development of large-caHber railroad artillery and 
 the War Department has referred to a committee of the General 
 Staff the consideration of the question as to the effect that this 
 development should properly have upon seacoast projects — that is, 
 to what extent in the future our seacoast guns should be mounted 
 on railroad cars and to what extent permanent emplacements should 
 be built. Pending the receipt of the report of this committee, the 
 work of designing seacoast emplacements has been temporarily 
 suspended. 
 
Chapter II. 
 ADMINISTRATION. 
 
 The duties of the Corps of Engmeers of the Army are prescribed 
 in certain paragraphs of Army Regulations with which aU Engineer 
 officers should be familiar. These paragraphs, however, are subject 
 to amendment and are in fact frequently amended. Therefore, no 
 attempt will be made to quote them here. 
 
 Among the duties of the Corps of Engineers as laid down by Army 
 Regulations are the design and construction of permanent fortifi- 
 cations. In this country but few attempts have been made at the 
 construction of permanent fortifications, except on our sea and lake 
 shores and on the coasts of our insular possessions consequently so 
 much -of the duties of the Corps of Engineers as pertain to permanent 
 fortifications have been performed almost exclusively in connection 
 with coast fortifications. 
 
 The work of the Engineer Department is carried on under the com- 
 mand and supervision of the Chief of Engineers, who is assisted by 
 certain officers and civilian employees in his office. The construc- 
 tion work is in charge of the district Engineer officers who are sta- 
 tioned in various places conveniently located with respect to the 
 work. In order that this work may be properly coordinated and 
 supervised, the Engineer districts are united into a number of groups 
 called Engineer divisions which are imder the supervision and general 
 control of senior officers called division Engineers. 
 
 In connection with the fortification work, the Chief of Engineers 
 receives assistance, especially in the way of advice, from the Board 
 of Engineers, or, as it is sometimes called, the "Board of Engineers 
 for Fortifications." This board consists normally of three Engineer 
 officers of high rank who have had considerable experience in forti- 
 fication matters, and, in addition, of a younger officer detailed as 
 recorder of the board. 
 
 As was noted in the Chapter I, on historical matters, the Board of 
 Engineers is a very ancient organization, dating back to about 1816. 
 At one time the seat of the board was in Washington, later it was 
 moved to New York City, where it is now. 
 
 In addition to the Engineer officers, who are regularly members 
 of the board. Ordnance officers or officers of the Coast Artillery have 
 occasionally been detailed on the board. 
 
 (25) 
 
26 
 
 The principal duties of the Board of Engineers as laid down by 
 Engineer Department Regulations, which have remained practically 
 unchanged for many years, are as foUows: 
 
 There shall be Board of Engineers whose duty it shall be to revise, as may be di- 
 rected by the Chief of Engineers, from time to time, projects of permanent fortifi- 
 cations required for the defense of the territory of the United States, and works of 
 river and harbor improvement; also to consider and to report upon such other matters 
 as may be referred to it by the Chief of Engineers. 
 
 It shall be the duty of the mem,bers of the bdard, whenever required by the Chief 
 of Engineers, to inspect and report upon any of the works of construction or other 
 of the operations of the Engineer Department, the inepection reports to be made to 
 the board and by it submitted to the Chief of Engineers, with such remarks as it may 
 deem proper. 
 
 The board shall consist of not less than three officers to be designated by the Chief 
 of Engineers, with the sanction of the Secretary of War. 
 
 As will be seen from the above quotation, the functions of the 
 Board of Engineers were formerly quite broad, and it was their duty 
 when caUed upon to do so, to formulate a general project for the de- 
 fense of any harbor, or to modify, existing defense projects. In con- 
 sidering such a fortification project, it was their duty; to decide upon 
 the general character of the defense to be provided; to fix upon the 
 number of guns of different cahbers which should be emplaced, and 
 to select the locations for the emplacements; to make general designs 
 for the emplacements themselves; to decide if a submarine mine 
 defense was necessary and the character of the defense; to fix upon 
 the number of searchhghts needed, their location, etc. The recom- 
 mendations of the board were made to the Chief of Engineers, and 
 were forwarded by him to the Secretary of War. When approved 
 by the Secretary of War they became the "approved project" for 
 the defense of that locality. 
 
 In recent years, however, that is to say, since the organization of 
 the General Staff, and the enactment of legislation providing for a 
 Coast' Artillery Corps and a Chief of Coast Artillery, who is ex officio 
 a member of the General Staff, the duties of making or revising coast 
 defense projects have devolved upon certain sections of the General 
 Staff or upon special War Department boards formed for the pur- 
 pose. Consequently, the Board of Engineers, in connection with 
 seacoast defense, has no longer the important functions that it for- 
 merly had. However, there still devolves upon it the preparation 
 of typical plans for seacoast defense structures. 
 
 The plans of the Board of Engineers are usually pubhshed to the 
 Engineer Department in the form of Engineer Department mimeo- 
 graphs. Though not strictly confidential in the true sense of the 
 word "confidential," access to the mimeographs is supposed to be 
 restricted to the officers of the corps, or to other persons whose 
 duties require it. 
 
27 
 
 In the case of minor structures the mimeographs are usually quite 
 simple, but when they relate to more extensive works, such as typical 
 emplacements for large guns, they go into considerable detail and 
 consist of a text and of a number of drawings. These show, not only 
 the general outlay of the emplacements or other structures, with 
 <iimensions and elevations, but also in considerable detail the pro- 
 visions for drainage, ventilation, heating, lighting, etc. 
 
 When any battery or other fortification structure is to be built 
 in any Engiaeer district, as much information as may be necessary 
 is sent the district officer. In the case of a battery he is notified as 
 to the location selected for the battery, the number and caUber of 
 the guns to be emplaced, the fields of fire to be covered by the guns 
 and the general purpose of the battery. Appropriate mimeographs 
 are sent to him, or he is referred to certain numbered mimeographs 
 if they have already been furnished him. 
 
 With the data furnished him, it is the duty of the district officer 
 to work out and prepare the detailed designs of the work. In so 
 doing, however, he should not make the mistake, as has been done 
 once or twice, of slavishly following the mimeograph drawing in all 
 details. The mimeograph plans are, of course, made to suit general 
 or average conditions and aU of the general conditions are almost 
 never fulfilled at any one locality. For instance, an emplacement 
 mimeograph shows a certain angular .field of fire for the gun with 
 reference to the capital of the battery, but this may not in all cases 
 suit the particular site. It is the duty of the district officer, there- 
 fore, to make a careful study of the site and its surroundings, especially 
 as to the direction of the capital of the battery, the relative angular 
 fields of fire of the diflFerent guns of the battery, the sides of the guns 
 on which the magazines are to be placed, the elevation of the battery 
 with reference to the surrounding ground, the possibUity of con- 
 cealment, etc. In addition, the district officer must work out all the 
 details of the foundations, the drainage, water supply, ventilation, 
 lighting, communications, etc., and in doing so he should include in 
 his designs the latest improvements of which he may have heard, 
 whether these were learned from mimeographs or in some other 
 way. 
 
 The detail of plans of the structures are forwarded by the district 
 officer to the division Engineer, who gives them careful study, and, 
 by correspondence with the district officer, causes any alterations 
 that he may consider necessary to be made. The plans are then 
 forwarded to the Chief of Engineers, iu whose office and in that of 
 the Chief of Coast Artillery they are agaru examined. If foimd 
 satisfactory, they are forwarded to the War Department for approval, 
 and are finally returned to the district Engineer with directions to 
 build the emplacements upon the designs as approved. 
 
28 
 
 ' A similar routine is foUowed with the designs for range stations, 
 searchUght buildiags, mine defense stations, etc. 
 
 During the period of construction, Army Eegulations place the 
 structures within the exclusive control of the Engineer Department, 
 but it is of course proper and suitable that the constructing officer 
 should, from the very beginning and through all the stages of con- 
 struction, freely and frequently discuss the various features with, 
 the local Coast -Artillery authorities. 
 
 When a structure is completed, the district Engineer officer pre- 
 pares the so-called "transfer drawings." These should contain not- 
 only the general plans of the structure but in addition when neces- 
 sary, special instructions for the care of the structure or the care 
 of the plant. In the case of a large battery, separate drawings- 
 shoiild usually be prepared of the general design of the emplacement, 
 of its electric system, of its drainage system, of its ventilating system, 
 and so on. Some of these, of course, may sometimes be combined 
 in a single drawing and, in the case of a smaller battery or a building, 
 a single drawing may include data as to all'these features. 
 
 When the transfer drawings have been prepared they are forwarded 
 through the division Engineer to the Chief of Engineers with a letter 
 announcing the completion of the battery or building. The drawings 
 are then inspected in the office of the Chief of Engineers, and if found 
 to be satisfactory they are forwarded to the War Department for 
 formal approval. In due time instructions are issued by the Chief 
 of Engineers to the district officer to formally transfer the structure 
 to the garrison. At the same time, through military channels, the 
 local Coast Artillery commander is ordered to formally receive the 
 structure from the Engineer ofiicer. 
 
 Upon receipt of these instructions at the locahty, it is expected 
 that the district Engineer ofiicer and the local Coast Artillery com- 
 mander, or an officer detailed by him, will make a joint personal 
 inspection of the structure. After this inspection has been made, 
 the keys, if any, are transferred by the Engineer officer to the Artil- 
 lery commander, and any portable property is at the same time trans- 
 ferred by means of the usual invoices and receipts. The Artillery 
 district commander is expected to give the district Engineer officer 
 a formal acceptance of the structure, stating at the time such criti- 
 cisms as he may desire as to the condition of the structure, its design, 
 suitability for the purpose intended, etc. 
 
 Funds. 
 
 To carry on the fortification construction work of the Corps of 
 Engineers, funds are necessary, and these funds are provided by 
 congressional appropriations. 
 
29 
 
 In the summer of each year there are prepared in the office of the 
 Ohief of Engineers, upon the basis of data received from district 
 ■officers, estimates of the funds which it is considered should be appro- 
 priated for the fiscal year to begin on the 1st of July of the following 
 summer. These estimates are submitted to the Secretary of War 
 and, after more or less modification by his direction, are combined 
 ^th other War Department estimates and, at the beginning of the 
 next regular session of Congress, are subn^itted through the Treasury 
 Department to the House of Kepresentativ|s. 
 
 The various estimates are referred to certain committees of the 
 House of Representatives, and in due time these committees hold 
 learings upon the different estimates. 
 
 During a committee hearing upon an Engineer Department esti- 
 mate, the Chief of Engineers and his assistants who have special 
 inowledge of the estimates are called before the committee and are 
 closely questioned as to the detailed piu-poses for which the funds 
 are desired and as to the needs of the particular amounts stated in 
 the estimates. Upon the basis of the formal estimates before them 
 and of the explanations which have been made to them, the committee 
 prepares a draft of the fortification bill for the consideration of the 
 House of Representatives. 
 
 Eventually the bill is passed by the House and goes to the Senate, 
 where it is referred to a Senate committee. This committee also 
 usually holds brief hearings and requests additional information as 
 to certain items. The Senate committee then returns the appro- 
 J)riation bUl to the Senate, usually suggesting a few amendments. 
 The bin is then considered and passed by the Senate with or without 
 amendmeits. 
 
 If the Senate has made amendments, the bill ultimately goes to a 
 conference committee appointed by the two houses, which adjusts 
 all differences and recommends to the House and Senate what may 
 be called a compromise bill. This is ultimately passed by the House 
 and Senate, and, when signed by the President, becomes a law. 
 
 Most of the appropriation items included in appropriation bills are 
 for specific purposes, and of course the funds so appropriated can be 
 expended for those purposes only. Not infrequently even an appro- 
 priation item has attached to it specific conditions, and of course the 
 funds appropriated can be expended only under the conditions stated. 
 
 However, it was feared that a statement in the fortification appro- 
 priation bill that money was appropriated for the construction of a 
 particular gun battery would be publishing to the world information 
 which is considered desirable should remain secret. Consequently, 
 the items in the fortification appropriation bill are usually expressed 
 in general terms only. Thus, instead of stating that the appropria- 
 tion is to cover the construction of a certain battery of a certain num- 
 
30 
 
 ber of guns at one place, and another battery at another place, the 
 bill contains a lump-sum appropriation for the construction of "gun 
 and mortar batteries." Similarly with other items. 
 
 However, though the items of the fortification appropriation bill 
 are usually stated in general terms only and legally are of very gen- 
 eral application, yet it should be noted that the biU is drawn up onlyr 
 after committee hearings on the estimates, and during these com- 
 mittee hearings the Chie f ^E ngineers, or his assistants, state to th& 
 committees the exact wqjKlKitended to be done with the funds asked 
 for. Though, therefore, in no way legally restricted by the wording; 
 of the law, the Engineer Department considers itself bound to allot 
 and expend the funds appropriated for the specific purposes whick 
 were stated to the committee at the committee hearing and for no 
 others. 
 
 The Chief of Engineers, after consultation with the Chief of Coast 
 Artillery and with such Other officials of the War Department as mayr 
 be officially interested, allots the funds made available for the forti- 
 fication work of the Engineer Department, to specific items of work- 
 in the different Engineer districts, and the prosecution of these items 
 of work is then left to the district Engineer officers. 
 
 As has been stated, the construction work of the Corps of Engineers 
 is carried on under the command and supervision of the Chief of 
 Engineers, and does not in general come within the jurisdiction of the 
 department commanders. However, in connection with the appro- 
 priation for the maintenance and upkeep of fortifications, which is: 
 ordinarily known as the appropriation for "preservation and repair," 
 some special remarks appear necessary. 
 
 Up to a few years ago, it was customary for the Engineer depart- 
 ment to consider the maintenance work done under the appropria- 
 tions for preservation and repair, as essentially of the same character 
 as the actual construction work. The appropriation would be dis- 
 tributed to the various engineer districts and it was left to the dis- 
 cretion of the district Engineer officer to select from the many items 
 of needed work those which should be attended to. Consequently, 
 the district Engineer officer performed this class of work, as he did 
 the construction work, under the direction of the Chief of Engineers 
 and independently of any supervision by the department commander 
 or the local Artillery officers. 
 
 The department commanders are, however, responsible for the 
 condition of military affairs in their respective departments and 
 where a particular department contains sea-coast fortifications, the 
 department commander is to a certain extent responsible for the 
 condition in which these fortifications are kept. It is customary 
 for each department commander to inspect all the fortifications in 
 his department, at least once every year. During such inspection 
 
31 
 
 trips, it" is quite probable that be will see some particular item of 
 maintenance work which be may think should be given precedence 
 and be attended to at once. If this should happen, all that he was 
 able to do under the former method of carrying on the fortification 
 maintenance work was to request the district Engineer officer to 
 attend to this item, but he was without authority to direct that this 
 particular piece of work should be done. 
 
 The present Chief of Engineers, ^faj. Gen. William M. Black, just 
 before being appointed Chief of Engineers, had served as department 
 Engineer on the staff of the department commander of the Eastern 
 Department. His attention was thus called to the somewhat 
 anomalous condition of leaving entirely outside of the jurisdiction' of 
 the department commander, the preservation and repair of the forti- 
 fications, for the upkeep of which the department conmiander is in 
 a sense responsible. Shortly after becoming Chief of Engineers, 
 Gen. Black suggested to the War Department the desirability of 
 modifying Army Regulations on this subject, and the result has been 
 that the work of preservation and repair of fortifications is now 
 divided into two different classes of work, first, work involving 
 structiu-al changes, and second, ordinary preservation and repair 
 work not involving structural changes. This latter work has been 
 placed under the control of the department commander, and, in so 
 far as this work is concerned, the district Engineer ofiicers are placed 
 Tmder the orders and supervision of the department commander. 
 The other class of work, that is, work involving structural changes, 
 remains imder the supervision of the Chief of Engineers in the same 
 manner as fortification construction work. 
 
 In actual practice the maintenance work is provided for in the^ 
 following manner: Shortly after a fortification appropriation bill 
 becomes a law a certain portion of it is set aside for repairs and modi- 
 fications involving structural changes, and the remainder is assigned 
 to ordinary nonstructural preservation and repair. The fimds of 
 the first class are allotted and distributed in the same manner as if 
 they were for fortification construction work. The latter class of 
 funds is distributed among the various mihtary departments accord- 
 ing to their respective needs, as shown by estimates previously 
 received. 
 
 A department conunander is informed by the War Department that 
 a certain amount of the appropriation for preservation and repair 
 has been set aside for maintenance work in his department. He 
 then allots these fimds, usually upon the advice of his department 
 Engineer, among the different Engineer districts within his depart- 
 ment and notifies the War Department of this allotment. He gives 
 to the different Engineer officers such instructions with regard to 
 the fortification maintenance workes he may desire. 
 
32 
 
 As soon as the War Department is informed as to the desires of a 
 department commander with regard to the distribution of the forti- 
 fication maintenance fmids, the Chief of Engineers takes steps to 
 have the funds allotted, in accordance with the wishes of the de- 
 partment commander, . to the different district Engineer officers. 
 The latter then expend the funds under the supervision of the depart- 
 ment commander. 
 
Chaptee III. 
 ARMOR AND ARMAMENT. 
 
 Before going into the detailed discussion of fortification construc- 
 tion, which is the maia subject of this work, it may be well to devote 
 a short chapter to two closely related subjects, armor and armament. 
 
 ARMOR. 
 
 The object of armor is the protection of personnel, and, to some 
 extent, of materiel, against the gunfire of the enemy. The kind of 
 armor to be use-^ must, of course, depend directly upon the character 
 of gunfire against which it is to provide protection. Protection 
 against gunfire can be obtained in several ways: By the use of earth 
 especially sand; by the use of masonry, stone, or concrete: and by 
 the use of metal armor. 
 
 Earth protection is of course the cheapest and in some ways the 
 most eflicient, but in order to obtain protection against modern 
 large projectiles a considerable thickness of sand is necessary. Fur- 
 thermore, it is not possible to design a sand parapet sufficiently 
 thick to give perfect protection without at the same time seriously 
 interfering with the active features of the defense. 
 
 Masonry and concrete provide, for the same thickness, a greater 
 resistance against the penetration of projectiles than do earth or 
 sand, and in certain locations adapt themselves much better to the 
 active features of the defense. They are, however, for the same 
 bulk and also for the same amount of protection agaiast penetration, 
 much more expensive than earth or sand. 
 
 Steel armor, especially of the most modem type, opposes for a 
 given thickness the greatest resistance to the penetration of pro- 
 jectiles. It is, however, extremeh' expensive, and on account of its 
 high cost its use has been restricted to those situations where its 
 peculiar efficiency counterbalances the high cost. 
 
 The use of brass armor in the form of a shield carried by a fighting 
 man dates back before the dawn of history. The invention of 
 methods of working iron caused the brass shield to be replaced by 
 the iron shield, and until the early middle ages it was customary for 
 all heavily armored soldiers to be provided with shields. 
 
 Increase in skill in working iron permitted the principle of a shield 
 to be extended from the original shield to body armor covering 
 practically the entire body, and, in the case of a mounted man, his 
 173341—20 3 (33) 
 
34 
 
 horse also. The increasing power of missile weapons, however, 
 made an increase in the thickness of armor necessary, until soon the 
 weight of body armor became too heavy for a man to carry when on 
 foot, and rendered him unwieldly even on horseback. Finally, not 
 many centuries after the invention of gunpowder, armor fell into 
 generaUdisuse, except in the case of helmets or cuirasses carried by 
 certain kinds of mounted troops. 
 
 Armor was introduced as a protection for ships shortly before the 
 time of our Civil War, and during that war its efficiency was proven. 
 Because of its relatively great resisting power to the penetration of 
 projectiles in proportion to its weight, and since in ship construction 
 the question of weight is one of prime importance, a resort to steel 
 armor for ship construction became necessary in spite of its high 
 cost. On shore its use has been far less common than on shipboard, 
 because in shore batteries there is ordinarily ample space to make 
 possible the use of the much cheaper earth or sand protection and 
 the question of weight is usually of no importance. 
 
 During the last two decades of the last century, metal armor, 
 'especially cast iron, was much used in fortification construction in 
 certain sections of Europe. Some of the land guns were mounted 
 in armored turrets similar in general character to the naval turrets 
 of the day, and some were mounted in armored casemates the fronts 
 of which were somewhat similar to the fronts of turrets. Further- 
 more, armor was used also as the protection against overhead fire in 
 certain mortar batteries, and also to protect observation stations 
 and disappearing searchlights. 
 
 In this country the use of armor on land has in general not met with 
 muchfavorexceptforafewspecial purposes. Bullet-proof shields have 
 been used with the limbers of field guns, and shields sufficient to 
 withstand the projectiles of field guns have been used on field guns. 
 The 6 and 8 inch barbette seacoast guns have likewise been provided 
 with shields, and emplacements for these guns had to be so designed 
 that the shields could be used. Armored casemate mounts, however, 
 for seacoast guns have never been used, and the only actual use of the 
 armored turret has been in the fortifications of Manila Harbor. 
 
 Eecent wars, however, have given quite an impetus to the use of 
 armor in connection with land operations. Armored locomotives 
 and cars were used in the South African War, and were developed in 
 this country to a considerable extent in connection with possible 
 operations in Mexico. The armored automobile was utilized to 
 some extent in the early stages of the recent war and from it there 
 have been developed the so-called tanks. 
 
 Apparently, during the war, there has been practically no develop- 
 ment of steel armor in connection with emplacements of heavy guns, 
 nor would it appear that any further development of this matter is 
 
35 
 
 probable since the present tendency appears rather toward making 
 the guns portable than to providing for them heavily armored per- 
 manent emplacements. 
 
 ARMAMENT. 
 
 The Ordnance Department manufactures the guns and the gun 
 carriages to be used in seacoast defense. When these guns are to be 
 movmted iu fixed emplacements, the Engineer Department builds 
 the emplacements. 
 
 GUNS. 
 
 The guns for which the Engineer Department has been called upon 
 to provide emplacements are of mamy different calibers: — less than 
 3-inch guns, 3-inch, 4-in'ch, 4.7-iQch, 5-inch, 6-inch, 8-inch, 10-inch, 
 12-inch, 14-inch, and 16-inch guns, and 12-inch and 16-inch mortars. 
 
 This multiplicity of different calibers originated under a number of 
 different circumstances, and the best-informed officers are now in 
 favor of reducing the number of different calibers, the tendency 
 being toward the adoption of a standard small-caliber gun, a standard 
 medium-caliber gun, a standard large-caliber gun, and a standard 
 large-caliber mortar. 
 
 The 4.7-inch gun was introduced into our seacoast defenses during 
 the Spanish War. At that time the number of rapid-fire guns avail- 
 able in this country was very small, and it was necessary to make 
 purchases abroad. The 4.7-inch Armstrong gun was available at 
 that time for purchase and was about equivalent in power to our 
 standard 5-inch gun. Consequently, a number of these 4.7-inch 
 Armstrong guns were purchased. At first they were installed in 
 hastily constructed emplacements at a large number of om seacoast 
 forts. Tins work was done with all the rapidity possible, using any 
 sites available, and of course, as was to be expected, a number of 
 the sites chosen at that time proved afterwards to be far from suitable. 
 Furthermore, the arrangements for magazines and storerooms 
 which had been hastily improvised, were not, in general, satisfactory 
 for permanent use. As a result a number of these guns had to 
 be reemplaced, and iu so doing, the tendency has been to group 
 them into batteries of three or four guns each. It is not probable 
 that any more guns of this caliber will be purchased or manufactured, 
 and consequently, before long, this caliber of gun will have been 
 eliminated from our seacoast defenses. 
 
 The 5-inch rapid fire gun was decided upon at a time when it was 
 thought that the principle of rapid fire could not be applied to a 
 larger gun. This has proven not to be true, and rapid-fire 6-inch 
 and 8-inch guns can now be made. Consequently the 5-inch gun 
 also may be considered as an obsolete type. 
 
36 
 
 The 6-inch guns first made were not fitted for rapid fire and a 
 number of them were mounted on disappearing carriages, ■with which 
 what is called rapid fire is not possible. It now appears that this 
 gun is well adapted to rapid fire and consequently it has become a 
 standard medium-caliber rapid-fire gun. 
 
 The 8-inch gun was the, first one for which a satisfactory disappear- 
 ing carriage was developed. Tt was not long, however, before a similar 
 carriage was developed for the 10-inch gun, but after that there was 
 quite a delay before a satisfactory 12-inch carriage could be manu- 
 factured, in the meantime quite a number of 8-inch a;nd 10-inch 
 guns were manufactured and were moxmted in a few cases in barbette 
 emplacements, but to a greater extent on disappearing carriages. The 
 development, hov/ever, of a satisf actor}^ 1 2-inch disappearing carriage 
 soon did away with the manufacture of 8-inch and 10-inch guns and 
 cairiages. Most of the remaining 8-ineh guns were dismoimted during 
 the recent war and, although a number of 10-inch guns are still in 
 commission, the 10-inch gun also may be considered as an obsolescent 
 type. 
 
 ' The first of the 12-inch guns to be emplaced for seacoast defense 
 were but 30 cahbers long, and as a number of these guns had been 
 manufactured and were available, and a satisfactory 12-inch disap- 
 pearing carriage had not at that time been developed, a very large 
 number of these guns were mounted on barbette carriages, even in 
 locations where disappearing carriages would have been more suit- 
 able. As soon, liowever, as the disappearing carriages became avail- 
 able it became customary to mount practical^ all new 12-inch guns 
 on disappearing carriages. ' 
 
 Although the 30-caliber 12-inch gun was much more powerful 
 than the 10-inch and 8-inch guns, it was soon found to be deficient 
 in power at extreme ranges, and a change was made to the 35-caliber 
 gun and emplacements for a number of these longer gims were built. 
 It soon* appeared, however, that the powder pressure necessarj^ to 
 obtain the full initial velocity out of this long 12-inch gun was so 
 great and the consequent internal temperature so high that the erosion 
 in the guns was excessive. On account of the apparent short life of 
 these guns it was decided to substitute for them in future emplace- 
 ments the 14-inch gun, which wiih lower powder pressures would, 
 on account of the heavier projectiles, have at long ranges the same 
 or even a greater striking power. This change was recommended by 
 the Taft Board. It was for this reason that the 14-inch gun was intro- 
 duced into seacoast work. Subsequently it was improved and became 
 the standard large-cahber gun at the time the Panama and later Phil- 
 ippine batteries were designed. 
 
37 
 
 Many years ago, as an experiment, the Ordnance Department 
 constructed a 16-inch gun. This remained for many years at Sandy 
 Hook out of use, but a few years ago it was taken to Panama and 
 installed on a disappearing carriage specially constructed for it. 
 
 In very recent years, however, the manufacture of very long 
 16-inch guns, up to 50 calibers in length, has been found to be per- 
 fectly practicable, and the present poHcy of the War Department is 
 that the 50-caliber 16-inch gun is to be. the standard major-caliber 
 weapon hereafter. 
 
 Mortars. 
 
 Prior to the appointment of the Endicott Board there had been 
 developed and were in use in this country many different calibers of 
 mortars, from the small 4-inch portable Coehorn mortar for use in 
 siege works up to a large 2n-inch mortar for seacoast ■«'ork. All of 
 them were smooth bore and muzzle loading and their length did not 
 exceed .3 feet or so as a maximum. At the time of the Endicott 
 Board, liowevor, the efficiency of the mortar for seacoast use had 
 apparently been so effectually demonstrated that the Ordnance 
 Department took tip the manufacture of breech-loading howitzers of 
 considerable length. Since these howitzers were to be used in the 
 same manner as the older mortars, the name "mortars" was applied to 
 them and has stuck to them ever since. 
 
 The ffrst guns of this type were the 12-inch howitzers or mortars 
 and this remained until a few years ago the standard seacoast mortar. 
 
 By the time the Panama fortifications were under consideration, a 
 satisfactory 12 inch mortar, 15 calibers long, had been developed by 
 the Ordnance Department, and this then became the standard type. 
 More recently still a 16 inch mortar or howitzer has been developed, 
 and it is understood it is this mortar that will hereafter be furnished 
 for seacoast use, practically to the exclusion of smaller sizes. 
 
 GUN MOUNTS AND CARRIAGES. 
 
 At the time that our modern fortifications were started the only 
 types of moimts in seacoast use were the barbette mount and the 
 tmret. Disappearing guns were in their infanc}-, although a number 
 of types had been invented in this country and the experiments with 
 some of them had been satisfactory. 
 
 About the first successful type of disappearing gun carriage to be 
 invented was the "King carriage," the invention of Maj. William H. 
 King of the Corps of Engineers. This type of carriage was a modifica- 
 tion of the standard barbette carriage in use at that time, the essential 
 difference being that the gun carriage instead of sliding with friction 
 up a slightly inclined plane when the gun was fired, slid downward at 
 an angle of about 30° behind the parapet, raising vertically by means 
 of a cable a heavy counterweight which soon overcame the energy 
 
38 
 
 of recoil and brought the gun and top carriage to rest. This carriage 
 was developed shortly after the Civil War and was successfully tested 
 at Fort Wadsworth, Nev,' York B arbor. At this time, however, as 
 Was stated in the historical sketch, practically no new seacoast defenses 
 were beirig constructed in this country aad consequently this type of 
 carriage was never adopted for use. 
 
 In the earlj- eighties, however, with the revival of interest in 
 seacoast defense matters, a number of types of disappearing carriages 
 were experimented with until there was developed the BufFmgton- 
 Crozier type. This type of carriage was first developed satisfactorily 
 for the S-inch rifle and subsequently for the 6-inch, the 10-inch, the 
 12-inch, the 14-inch, and 16-inch rifles. 
 
 As far as is known the first guns ever mounted in a turret were 
 those on the original Monitor. As a result of the victory over the 
 Mernmar the turret became the standard method of mounting large 
 guns on shipboard, the dreadnaught battleship of the present day 
 having all of its major-caliber guns mounted in turrets. As a rule 
 2-gun turrets have been the standard, but in the very recent past a 
 3-gun turret has been adopted, in our Navy at least, as the standard. 
 
 In spite of the great success of the turrets for moimting naval guns 
 and their occasional use in mounting land guns in Europe, they have 
 never become popular for mounting land guns in the United States. 
 
 Between the j^ears 1911 and 191*^ there were designed and built on 
 one of the islands in Manila Bay two turrets, in each of which were 
 installed two 14-inch guns. The idea of mounting the guns on this 
 island in turrets originated with Capt. John J. Kingman, Corps of 
 Engineers, then on construction duty in the defenses of Manila, 
 because, on. account of the small size of the island, it was the only 
 method by which a sufficient number of guns could be emplaced on 
 it. According to his original proposition it was proposed that the 
 Engineer Department should purchase from the Navy Department 
 and install on the island the standard naval turrets ^^^th their guns. 
 It was later decided by the War Department that the manufacture 
 of mounts for seacoast guns pertained to the Army (^'rdnance Depart- 
 ment and this department was therefore directed to design and man- 
 ufacture the turrets and carriages for these guns. Much dola\ , how- 
 ever, resulted, and it was not until iniS that the turrets were finally 
 completed and the guns mounted. 
 
 The project for the defense of the eastern end of Long Island Sound 
 as revised in 1916 by the War Department Board of Review, included 
 a turret for two 16-inch guns at one of the forts in these defenses. 
 The installation of this turret was delayed by the breaking out of the 
 big war and since the war, although the matter has been much 
 discussed, no definite, decision seems to have yet been taken. Should 
 it be decided to install these gims in a turret it is the opinion of the 
 
39 
 
 Engineer Department that the quickest and most satisfactory 
 arrangement would be to purchase a naval turret from the Navy De- 
 partment. The reasons for doing this are as follows: A turret is a 
 very complicated piece of machinery and it is the general experience 
 of human nature that no new and complicated piece of machinery was 
 ever invented that did not, when first constructed, develop a number 
 of weaknesses. Turrets have been in use in the Navy for many 
 years and practically all the weak points have been shown up and re- 
 moved; consequently, the chances of obtaining a satisfactory turret 
 would appear to be many times greater by adopting bodily the naval 
 tmret which has already been perfected, rather than by trusting to 
 the hasty development of a new type of turret by a department prac- 
 tically without previous experience in such a matter. 
 
 COMPARISON OF DIFFERENT TYPES OF MOUNTS. 
 
 The relative merits, advantages, and disadvantages of the three 
 types of seacoast gun carriages, viz, the barbette, the disappearing, 
 and the turret moimts, have been much discussed, and some 16 or 18 
 years ago a number of articles on the subject appeared in our service 
 journals, which can be referred to by persons specially interested in 
 these affairs. The articles, of course, discussed the matter according 
 to then existing conditions. Since that time, however, as will appear 
 later, many new conditions have arisen, and it would appear well to 
 briefly review the matter here. 
 
 The facts would appear to be that each of these types of mounts 
 has its advantages and its disadvantages, and while each would appear 
 to be the most suitable for certain conditions, no one of them is the 
 best suited to all. 
 
 The Barbette Mount. 
 
 The barbette mount has the great advantage of being capable of 
 firing in any direction horizontally and to almost any angle of eleva- 
 tion. When fitted, however, for fire horizontally or at an angle of 
 depression throughout the whole ^60° of traverse, the gun and carriage 
 must necessarily be exposed to view above all surrounding objects 
 and must be very conspicuous and give the minimum protection to 
 the detachment. If mounted lower and so as to be less conspicuous, 
 its field of fire wUl be somewhat reduced. 
 
 With the small caliber guns, where fixed ammunition is fired and 
 where the ammunition does not weigh too much to make loading 
 possible when the gun is at any angle of elevation, the barbette 
 mount has the additional advantage of permitting the most rapid 
 fire. In the larger caliber guns, however, where the ammunition is so 
 heavy that the gun must be loaded when in a practically horizontal 
 position, or even at a slight angle of depression, it is evident that a 
 barbette gun must have its elevation changed from that used in firing 
 
40 
 
 down to the loading position, and when loaded, must be again trained 
 in elevation. This does not permit the rapid loadiag and firing which 
 is possible with the diasppearing gun where the gun recoils into the 
 same loading position and with its breech at the same elevation 
 whatever be the angle of elevation at which the gun may be laid at the 
 time. 
 
 Incidentally, also, the barbette mounts for large guns heretofore 
 used in this country have been somewhat crude in their provisions for 
 ammunition service. 
 
 When a barbette gun is trained in elevation it rotates about a hori- 
 zontal axis through the trunnions, and if the angle of elevation be 
 considerable and the length of the gun in rear of the trunnion be quite 
 great, as is the case with large guns, the breech of the gun when 
 trained for a high angle of elevation drops down considerably below 
 the trunnions. This makes it necessary, therefore, either that a gun 
 should be so mounted that its trunnions are at a considerable height 
 above the base on which it rests, or else that a space be provided into 
 which the breech of the gun may recoil when the gun is trained high 
 in elevation. 
 
 In the standard form of barbette mount heretofore adopted in this 
 country for the larger guns, this depression of the breech has been 
 made possible by raising the trunnions high above the ground. The 
 gun must be loaded in practically a horizontal position and the men 
 actually doing the loading must for convenience stand upon a plat- 
 form from 4 to 4^ feet below the axis of the gun. This has been made 
 possible by attaching to the gun carriage a long horizontal metal plat- 
 form which rotates as the gun is moved in azimuth. When the gun is 
 elevated and the breech depressed the breech drops down through a slot 
 to the floor of this platform. This platform extends far enough to the 
 rear of the gun to give room for the ramming detachment. The only 
 means heretofore provided with these barbette carriages, for raising pro- 
 jectiles up to the gun is by the old-style crane, and loading guns with 
 projectiles raised by the crane has been found not to be a very rapid 
 process. Consequently, these barbette guns have been much slower 
 in loading and firing than the disappearing guns of the same caliber. 
 
 However, in the type of carriage provided for the high-angle 12- 
 inch rifles, of which quite a number have reteently been emplaced in 
 this country, the base of the carriage has been set in a large gun well, 
 and when the gun is elevated the breech is depressed through a slot 
 in a metal platform covering this gun well and revolving in azimuth 
 with the gun. When the gun is horizontal the breech projects 
 slightly behind and outside the gun well, and the projectile carried 
 on the usual type of projectile truck can be brought right up to the 
 breech of the gun and can be rammed into the breech in the same man- 
 ner as is done with the disappearing carriage. The loading can, 
 
41 
 
 therefore, be done almost as rapidly as in the disappearing carriages. 
 It is necessary, however, that after the gun has been fired once it be 
 brought down to the horizontal before it can be loaded, and after the 
 loading is completed the gun must once again be trained in elevation. 
 The time necessary for this large angular movement exceeds that re- 
 quired for the disappearing gun to rise into battery and to recoil after 
 filing, so that even with the unproved barbette moimt the rate of 
 fire must be slower than with the disappearing carriage. 
 
 It is understood that the barbette mounts proposed by the Ordnance 
 Department for use in the futm^e with large guns, approximate, in 
 general characteristics, to those used with the recently emplaced 
 12-inch guns, at least in so far as the possibilities of rapid loading are 
 concerned. 
 
 Disappearing Mount. 
 
 The disappearing carriage has the great advantage that the gun in 
 the loading position is invisible and, in batteries made on the hori- 
 zontal crest principle, there is nothing that can be seen by the enemy 
 to show the location of the guns or the number of any battery. 
 Concealment is therefore attained. This type, in addition, has the 
 great "advantage of giving the maximum protection to the lower and 
 more dehcate parts of the gun carriage and to the detachment, not 
 only against direct hits but also against the fragments of a projectile 
 that may faU short and detonate. Although it might appear that, 
 against projectiles with a large angle of fall, the protection given by a 
 disappearing emplacement against a direct hit is much more apparent 
 than real, yet the experiments at Fort Morgan in the spring of 1916 
 showed clearly that against the fragments of projectiles striking short 
 and detonating, the parapet of a disappearing emplacement does 
 provide much real protection to the detachment. In addition, there 
 is no doubt that the feelingof protection possessed by the detachment 
 should make the handling of the gun in action much better and more 
 rehable than when the men feel that they are exposed. 
 
 When the disappearing carriages were first proposed and developed 
 it was expected that combats between ships and seacoast forts would 
 be carried on in general at comparatively short ranges, and conse- 
 quently high angles of fire were not considered necessary, nor was 
 protection considered necessary against projectiles having more than 
 a comparatively small angle of fall. Consequently, 15° was the maxi- 
 mum angle of elevation possible with the early disappearing carriages 
 developed in this country. 
 
 Within the last decade, however, there has been a rapid increase in 
 the range at which guns have been fired, either in experiment or in 
 actual combat. Naval engagements have been fought at ranges 
 approximately 25,000 yards and naval guns are now mounted so as 
 to be able to fire at as high as 45° elevation. 
 
42 
 
 In a combat with ships capable of such high angle fire and having 
 such a long range, a seacoast battery with guns whose elevation is 
 hmited by the carriage would be at a great disadvantage. Conse- 
 quently, there has been a demand by the Coast Artillery that the 
 seacoast guns hereafter to be emplaced should be capable of firing 
 at an elevation which will give the maximum range of the gun. 
 
 The original disappearing carriages were designed for 15° of eleva- 
 tion, and this remained for many years the standard. In more recent 
 years, however, some of these carriages, especially those at Panama 
 and in the tropical possessions, have been modified so as to permit 
 20° of elevation. Much beyond this it would appear impossible to go 
 with the present type of disappearing carriage or, in fact, with any 
 type of disappearing carriage. 
 
 On account, therefore, of the impossibility of providing sufficient 
 angles of elevation it is beheved that the disappearing carriage must 
 in the future be considered as unsuitable for seacoast defense gen- 
 erally, and as a type of carriage not to be used except in a few special 
 locations where, for special reasons, it is considered advisable to with- 
 hold certain guns from long-range use for firing later at compara- 
 tively close ranges. Under such conditions, on account of the ease of 
 manipulation and rapidity of fire, the disappearing carriage may still 
 prove extremely satisfactory. 
 
 The disappearing carriage also has an additional great advantage 
 in that at whatever angle of elevation a gun may be laid, the axis in 
 the loading position is practically horizontal, and its breech is at 
 practically the same elevation, so that the projectile trucks once set 
 may be used for rapid loading irrespective of how the gun may be 
 laid in elevation. This permits the gun to be kept constantly laid 
 on the target both in azimuth and elevation. When tripped, it rises 
 promptly into the proper position for firing and as it fixes it recoils 
 into exactly the proper position for loading. This type of carriage 
 therefore lends itseK to the most rapid handling of ammunition and 
 rate of fixing, the 12-inch disappearing guns having been actually 
 loaded and fired at less than 20-second intervals as against practically 
 2-mLnute intervals for barbette guns of the same size. 
 
 The disappearing carriage of the standard and most used type has, 
 however, the great disadvantage that it practically limits the possible 
 arc of traverse to approximately 170° and also limits the possible 
 angle of elevation to about 30°. In the older types of disappearing 
 carriages this Umit to the elevation at which the guns could be fired 
 was in some cases 20°, but usually 15° only. 
 
 The restriction in the horizontal angle through which the gun can 
 be fired is encountered, not because the gun and carriage if mounted 
 in the open could not be traversed through the full 360°, but because 
 of the existence of the parapet which is necessary to give the advan- 
 
43 
 
 tages of conceabnent of the position of the gun while loading and of 
 protection to the gun carriage and detachment. 
 
 In order that the parapet may offer the maximum protection, it 
 must be built as close as possible to the gun — -that is, with its vertical 
 face but a foot or so in front of the position of the muzzle of the gun 
 when the gun is iu the loading position, and the crest of the parapet 
 must be at such a height that the gun will just clear when it rises into 
 the firing position when set for fire at the maximum angle of depression 
 at which it is proposed to use the gun. 
 
 In order that the gun may be fired directly to the rear of its normal 
 direction of firing, ample space must be provided for its recoihng into 
 a loading position when fired to the rear, and the parapet must there- 
 fore be placed so far to the front (that is, in the direction of the breech 
 end of the gun when firing to the rear) that the breech will not strike 
 the parapet during recoil. 
 
 In the standard form of disappearing carriage, the vertical axis 
 about which the gun and carriage rotate in azimuth is usually from 
 8 to 12 feet forward of the center of length of the gun in loading 
 position, or, in other words, from 16 to 24 feet nearer to the muzzle 
 than to the breech of the gun. 
 
 If, therefore, a disappearing emplacement is to be designed so that 
 the gun can fire to the rear, it is necessary that the parapet be moved 
 from 16 to 24 feet farther awa}^ from the axis of the gim well, and if 
 the emplacement is to be used for firing at any angle of depression 
 the height of the parapet must be much reduced. 
 
 Not only will such a parapet provide much less concealment and 
 protection from the enemy's projectiles, but it would also have the 
 great disadvantage that the muzzle of the gun when fired will not 
 project over the parapet but will be to the rear of the rear face of 
 the parapet. Consequently, the blast of discharge will be reflected 
 back into the emplacement. It has been found to be necessary that 
 the muzzle of the gun project at least 5 feet over the crest of a parapet 
 in order that none of the direct blast may be reflected back into the 
 emplacement. To fire a gun with its muzzle well to the rear of the 
 parapet would be to endanger the entire detachment, as well as the 
 material in the emplacement from damage by blast. 
 
 Although the standard and most generally used form of disappear- 
 ing carriage hmits the horizontal angle through which the gun can be 
 fired, this has not been true of two special tjrpes of disappearing 
 mounts which have been used or suggested. 
 
 In one of these types the gun well, instead of being cyhndrical, 
 as is usual, was made annular, and consists of the space between two 
 cylinders. The coxmterweight hung down in this annular space and 
 rotated when the gun was rotated in azimuth. This type of carriage 
 
44 
 
 was tried Tvith the lO-inch guns in certain of oiir seacoast batteries, 
 but is understood not to have been a complete success. 
 
 The other type of carriage is the most modern all-around type of 
 16-inch disappearing gun carriage designed by the Ordnance Depart- 
 ment. In this the well is extremely large and the axis of the well 
 passes unusually near the center of the length of the gun in the 
 loading position. Building the parapet a few feet in advance of its 
 ordinary position and yet not so far but that the muzzle of the gun 
 in battery projects far enough over it, there is room for the breech to 
 recoil even should the gun be aimed directly to the rear. The gun, 
 however, can not be loaded in this position, and before it can be 
 loaded it must be traversed into some azimuth in which loading is 
 possible. 
 
 Turret Mounts. 
 
 The turret mount has the advantage that it may be fired in any 
 horizontal direction and can be adapted to use at a degree of elevation 
 which wUl make use of the maximum range of the gun. This mount 
 provides almost complete protection for the gun carriages and for 
 the personnel, and for all portions of the guns except the ends pro- 
 jecting outside of the turret. It also lends itself well to mechanical 
 means of loading, and in the latest forms of naval turrets an extremely 
 rapid rate of firing has been obtained, even with guns as large as 
 16-inch. 
 
 Turrets have, however, the great disadvantage of enormous cost 
 and though comparatively invulnerable, yet experience has shown 
 that in action it may not infrequently happen that a turret as a whole 
 may become jammed either as the result of a direct hit or a hit 
 around the base. When this occurs, of course, the turret becomes 
 practically useless, as the guns can be fired in but one direction only. 
 
 Where there is but little space and where it is a question, as in ship 
 construction, of keeping down the weight as much as possible, the 
 turret is undoubtedly the best type of mount, in spite of its cost and 
 other defects. Where there is no scarcity of space and ease of hand- 
 ling and rapidity of loading are to be desired, the disappearing car- 
 riage is probably better. 
 
 Portable Mounts. 
 
 Prior to the recent war it seems to have been generally considered 
 by military experts that the 6-inch direct fire gun, and possibly the 
 8-inch or 9-inch Howitzer, were the largest guns which were capable 
 of being transported upon carriages from which they could be fired. 
 That this was not true was shown by the surprise sprung by the 
 Germans in their campaign in Belgium in 1914. They proved their 
 ability to transport and to use guns of much larger caliber than those 
 mentioned, with the result that the guns mounted in the Belgium 
 
45 
 
 permanent fortifications were hopelessly outclassed and these fortifi- 
 cations were soon destroyed. 
 
 This gave a great impetus to the development of portable artOlery, 
 both for transportation on paved highways and on railroad trains, 
 with the result that nearly a year before the war closed the Germans 
 had brought up and were firing a gun having a range of some 60 or 
 70 miles. This gun was, however, fired from an elaborate em- 
 placement. The Alhes mounted on railroad carriages guns of 
 14-iiich caUber which had a range of 18 miles. 
 
 It would appear that these portable railroad guns are mounted on 
 two essentially different characters of mount. First, those to be 
 fired from the cars themselves with but a slight preparation of the 
 foundation; second, those which were not intended to be fired from 
 the cars themselves but which, before firing, were to be transferred 
 to prepared bases, after which the cars, or at least the wheels of 
 the cars, were to be removed. 
 
 The first type has the great advantage that it can be put in action 
 quickly, but the great disadvantage that it permits of being fired 
 only in the direction of the length of the car, or within a degree or 
 two of azimuth on either side of the axis of the car. Consequently, 
 when its azimuth has to be frequently changed, the car has to be 
 removed to a track laid in a curve, the general control of azimuth 
 being obtained by the exact place in the curve at which the car in 
 placed and the final setting in azimuth by moving the gun slightly 
 on the car. 
 
 When firing upon a fixed land target which can not be moved, such 
 as a town, manufacturing plant, raOroad station, etc., this small 
 degree of control in azimuth may be aU that is necessary, but it is 
 evident that a gun moimted in this manner can not be used satis- 
 factorily in firing against ships, urdess at anchor, and certainly can 
 not be made to follow the motions of a rapidly moving ship. 
 
 In the second type of carriage, where the gun has to be moved 
 from the car to a base prepared in advance, the railroad car is, in 
 reality, only a form of portable or travelling carriage. It has the 
 advantage of a greater range in azimuth, for when the gun is once 
 mounted on such prepared base its azimuth is practically unhmited. 
 It has, however, the great disadvantage that it can not be put in 
 action or withdrawn from action rapidly, since the preparation of the 
 base and transfer of the gun from car to carriage will require con- 
 siderable time, as wiU the reverse process of making the gun agaia 
 portable. 
 
 That guns mounted on portable carriages may fulfill an important 
 function in seacoast defense is undoubtedly true, but exactly to 
 what extent they should be used and to what extent the fixed emplace- 
 ment should be retained is a question for the future to decide. 
 
46 
 
 PROJECTILES. 
 
 The size aiid weight of projectiles vary, not only with the size of 
 the gun from which they are to be fired, but for other reasons. In 
 other words, the Ordnance Department, in a number of cases, fur- 
 nishes for a single gun, projectiles of more than one kind. 
 
 In some cases the" different types of projectiles furnished for the- 
 same gun differ mainly in length and weight. Thus for use with the 
 mortars, long heavy projectiles are issued for work at comparatively 
 short range where the striking velocities are limited, and lighter and 
 shorter projectiles for work at very long ranges to attain which it ia 
 necessary that the shells go very high. In the latter case the 
 striking velocity is great and this makes up for the small weight of 
 the projectiles. 
 
 In other cases the projectiles, though of practically the same size- 
 and weight, differ principally in the thickness ol the walls of the shell,, 
 the size of the chamber, and the amount of explosive carried. 
 Strongly built shells with thick walls are necessary for armor 
 piercing, in spite of the fact that they make it necessary to limit the 
 amount of explosive carried. On the other hand, for inflicting th& 
 greatest damage on unarmored ships or the unarmored portions of 
 armored ships, thin-walled shells carrying large quantities of explo- 
 sives are most efficient. 
 
 In connection with the subject of projectiles there is one develop- 
 ment of the last few years which has somewhat seriously affected the 
 Engineer Department; that is the comparatively recent change in 
 the shape of the projectiles for large guns. 
 
 A few years ago it was discovered by experiment that by lengthen- 
 ing the point of the projectile, that is, by increasing the radius of the 
 curve of the ogive, the resistance which the air offered to the passage 
 of the projectile was much reduced, with a consequent increase in 
 the range and velocity of the projectile, and a flattening of the 
 trajectory. 
 
 Apparently the present adopted standard is that the radius of the 
 ogive should be approximately equal to 7 calibers, which makes the 
 length of the point more than 2^ calibers; thus with the 14-inch 
 projectiles the radius of the ogive is approximately 97 inches, whicK 
 brings the tangency of the ogive and the cylindrical portion of the 
 projectile about 36 inches from the point. The cylindrical portion 
 is about 27 inches long, which makes the total length of the pro- 
 jectile 63 inches, or about 4^ calibers. 
 
 The projectile hoists which were installed in the early emplace- 
 ments were, of course, designed to raise the projectile of the day, and 
 though some allowance was made for slight increases in length the 
 allowance was, in general, not sufficient for the great increase caused 
 
47 
 
 by the introduction of the new type. Consequently it became 
 necessary to change practically all the hoists which had been in- 
 stalled prior to about 1911. 
 
 This has been done under an appropriation for modernizing and 
 it has now been completed in all 12-inch emplacements, and is about 
 to be completed in all 10-inch emplacements still to be retained in 
 commission. The 8-inch gun being an obsolescent type, it has been 
 decided to be not worth while to change the projectile hoists in the 
 emplacements for that caliber of gun, nor has this been done in a 
 number of the very old 6-inch batteries, the projectiles of which can 
 be carried by hand. 
 
 Besides merely lengthening the projectile, this change in shape 
 indirectly had another very important effect. The center of gravity 
 is left only an inch or two to the rear of the point of tangency of the 
 ogive and cylindrical portions. This renders the projectile some- 
 what difficult to roll on a horizontal table or on horizontal rails 
 because the center of gravity is so near the end of the cylindrical 
 surface on which the rolling is done that any slight resistance is apt 
 to swing the projectile around and cause it to roll in another direction. 
 
Chapter IV. 
 
 MATERIAL USED IN EMPLACEMENT 
 CONSTRUCTION. 
 
 In the earliest permanent fortifications of which jve know, the 
 faces of the walls exposed to the enemy were buUt either of stone or 
 of brick masonry and this type of construction persisted until after 
 the introduction of gunpowder. 
 
 The earlier cannon were of exceedingly low power and the fhght 
 of the projectiles was quite erratic, and though they soon showed 
 their ability to damage masonry walls, considerable time was required 
 to do this, and it must have seemed to the fortification engineers of 
 the day that if the walls could be made a little more resistant to 
 camion fire they might be able to withstand considerable bombard- 
 ment. The attempt was therefore made to strengthen the walls by 
 increasing the thickness of their faces, by building counterforts in 
 the wall, by the use of relieving arches, etc. 
 
 The use of these expedients made the walls much more resistant 
 but in course of a few centuries the power of cannon increased so 
 much thajt they were able to destroy these strengthened walls also, 
 and it was found that no masonry construction could withstand the 
 continuous bombardment of cannon. Consequently the use of ma- 
 sonry was entirely done away with, wherever exposed to continued 
 land bombardment, and earthen parapets were substituted instead. 
 
 At first sight it would appear that if masonry can not withstand 
 cannon fire, earth can not either — that is, any projectile that can 
 destroy masonry will certainly penetrate and destroy a mass of earth. 
 This is undoubtedly true, but if a projectile passes through a mass of 
 earth, the loose earth above falls into and fills the hole made by the 
 passage of the projectile and the net result is merely a slight groove 
 in the surface. If a projectile enters into a mass of earth and ex- 
 plodes, some earth is blown up into the air. A considerable portion 
 of it, however, falls back into the crater from which it came and 
 although a well-pronounced crater may be made, the same amount 
 of earth is in the parapet as was there before, although somewhat 
 differently placed. A second projectile entering the earth and ex- 
 ploding near by wiU not improbably fiU, or partially fill, the hole 
 made by the first, and so on. If it is possible by night to repair some 
 of the damage done by the day, an earthen parapet wOl withstand 
 an almost indefinite bombardment. 
 173341—20 i (49) 
 
50 
 
 Consequently, in all land fortifications earthwork has for many 
 years been relied upon as the main agency to resist the enemy's 
 projectiles. 
 
 For several centuries after it had been found necessary to discard 
 in land forts the use of exposed masonry walls, such walls were still 
 used on the sea fronts. This was considered possible because the fire 
 from ships was always more or less erratic, the ships being subject 
 to wave action; and it seemed quite improbable that a sufficient num- 
 ber of projectiles from a ship would strike a waU close enough to the 
 same spot to have any real battering effect. Furthermore, the ships 
 at the time were built of wood and were thus quite vulnerable; they 
 were propelled by sails, which rendered them, to a certain extent, at 
 the mercy of the wind and waves. It was clear, therefore, that they 
 would never dare to attempt a sufficiently prolonged bombardment 
 of a masonry land fort to be able to seriously damage the masonry 
 walls. 
 
 However, about the time of our Civil War it became customary to 
 use armor to protect the exposed sides of warships. The introduc- 
 tion of steam a few years before had made it possible for the ship to 
 go where it would and to approach or retreat from a fort as it desired. 
 It thus became possible for armored steamships to attempt a pro- 
 longed bombardment of a seacoast fort, and it was soon shown that 
 by such a bombardment the masonry walls of the sea front could be 
 destroyed. It, therefore, became necessary, on the sea fronts of the 
 seacoast forts also, to do away with masom-y walls and to rely on 
 earthen parapets to resist bombardment. 
 
 SAND. 
 
 Consequently, it is the modern idea that in seacoast fortifications, 
 as in land forts, the main protection against the enenay's projectiles 
 is the mass of earth, or as it is called, the "parapet," and that concrete 
 protection is to be used only on special occasions, such as in the blast 
 apron in front of the muzzle of the gun, where earth would be blown 
 out when the gun is fired, or in retaining walls where it is necessary 
 that the rear of a mass of earth stand vertically. 
 
 Although referred to under the general name of "earth," it is pref- 
 erable that the mass of a parapet shoidd be composed not of clay 
 or loam but of sand, since it has been found that a projectile entering 
 a mass of sand appears to have a tendency to deflect upward and to 
 leave the sand without penetrating very far. In other words, pro- 
 jectiles striking in sand have a tendency to ricochet in much the same 
 manner as they do upon striking water. 
 
 This tendency has been greatly increased in the recent past by the 
 modifications made in the shape of projectiles in the way of increas- 
 ing the length of the point. This change was made to decrease the 
 
51 
 
 resistance offered by the air to the flight of the projectile, and to thus 
 increase the range of the gun, but indirectly it has had the effect of 
 increasing the tendency of a projectile to ricochet upon striking 
 sand. As a projectile of this type enters sand it packs under the 
 point and tends to deflect the latter upward. This tendency is so 
 great that it has been found that it is almost impossible to make 
 lengthy projectiles penetrate very far into a sand parapet without 
 curving upward and coming out through the top. 
 
 This was very noticeable in the experiments conducted at Fort 
 Morgan, Ala., in March, 1916, when naval vessels fixed at an emplace- 
 ment specially constructed for the purpose. All the projectiles fixed 
 by the Xavy, that did not detonate upon impact, emerged from the 
 sand after a short penetration only. On practically horizontal sur- 
 faces the projectiles, even though striking with an angle of fall of 18°, 
 penetrated not more than 3 or 4 feet deep before they curved upward 
 and emerged from the sand, and even where detonation occurred 
 apparently at the time of greatest penetration, the craters were not 
 more than 5 feet deep. 
 
 Not only did the projectiles ricochet from the horizontal sand sur- 
 face, but this was also the case where they struck the front slopes of 
 the parapet. In one case a projectile struck the exterior slope of 
 the sand parapet making an angle of approximately 40° with that 
 surface. It penetrated the sand only a short distance and emerged 
 40 feet away from the point of entrance. Apparently at no time was 
 it more than 8 feet below the surface. 
 
 Ordinary earth and clay do not seem to possess this tendency to 
 deflect projectiles to anywhere nearly as great an extent as sand, 
 and consequently sand should be used in parapets instead of earth 
 and clay, even if it is necessary to go to considerable expense to 
 obtain it. This is especially true of the parapets in front of guns and 
 in front of and on top of magazines. 
 
 SAND FILL. 
 
 On account of the comparatively high cost of concrete as compared 
 with sand, attempts have frequently been made to substitute sand 
 for a portion of the mass of concrete in emplacements. Thus, 
 beneath the floors of the first-story rooms sand has been used in place 
 of filling up with concrete. Occasionally also, especially in the 
 smaller emplacements, sand has been used under the loading plat- 
 form, as will be noted on some of the drawings. (See Pis. V, "\T^I, 
 and IX.) There have also been cases where voids can well be left ux 
 the concrete and these have been filled with sand. This last, however, 
 is believed to be hardly necessary as a better method is to build rough 
 box-like frames and to cover them completely with concrete, thus 
 leaving actual voids in the mass. However, in the more modern 
 
52 
 
 batteries it has been customary, wherever a void has been left, to 
 place a door into it and to prepare it so that it can be used for storage 
 purposes if needed. 
 
 Wherever sand is to be used for filling voids and is to be covered by 
 concrete it is of course necessary for the future safety of the concrete 
 that the space be entirely filled with earth or sand, and that there be 
 no space left for subsequent settlement of this earth or sand filling. 
 In order to insure this, it is necessary that there be no place left for 
 the sand to escape. Thus, if the sand filling has to be placed upon a 
 mass of broken stone, the broken stone must first be covered with a 
 ayer of concrete, for otherwise the sand in time could jar down into 
 the voids of the stone. Likewise, to prevent the earth from escaping 
 sideways, it should be inclosed within solid walls. 
 
 Furthermore, as the earth filling is put in place it must be carefully 
 settled. Occasionally an attempt is made to settle earth by pumping 
 water on it as it is put in position but this has not been proved to 
 be perfectly satisfactory. Indeed, no method of packing an earth fill 
 seems to be as safe and satisfactory as to place it in layers from 3 to 
 4 inches thick and then to ram each layer thoroughly before putting 
 the next upon it. 
 
 MASONRY AND CONCRETE. 
 
 Although the sand parapet is supposed to constitute the main 
 resistance to an enemy's projectiles, yet it can not be used to the 
 entire exclusion of masonry. There are places, even on the exterior 
 of a battery, where vertical walls are required, and the rooms, gal- 
 leries, etc., must have walls and ceilings. Furthermore, the floors 
 must be smooth so that the ammunition trucks may be rolled thereon. 
 In all such places masonry or concrete is required. 
 
 Experience has shown that where the muzzle of a gun extends over 
 earth or grass and the gun is fired a considerable amount of earth 
 and dust is blown away by the discharge of the gun and continuous 
 firing makes quite a crater. To avoid this it has become customary 
 to place immediately under the muzzle of the gun and for some 
 distance to the front, a concrete blast apron made so thick and so 
 strong as not to be destroyed by the blast. 
 
 About the only masonry now used in emplacement construction is 
 concrete, and this concrete does not differ in its essential qualities 
 from the concrete in use in ordinary commercial life. 
 
 In the early nineties when the construction of the modern concrete 
 emplacements was begun, Portland cement was not manufactured in 
 this country and could be obtained only from abroad and at a high 
 price. There were, however, a number of brands of so-called natu- 
 ral or Rosendale cement made in America that could be pur- 
 chased much more cheaply. Consequently, for reasons of economy, 
 
53 
 
 Rosendale cement was used, at least in most of the gun emplacements 
 constructed on the Atlantic coast. Shortly thereafter, however, 
 there was a rapid development in the Portland cement industry in 
 this country, and since ahout the time of the Spanish War the only 
 cement used has been Portland. 
 
 The specifications which have been used in the purchase of this 
 cement have been the standard of the Engineer Department in aU its 
 work and no fiu-ther remarks are necessary concerning them. 
 
 The aggregate used in concrete has in general been broken stone, 
 though gravel is equally good when available and cheaper than stone. 
 
 As a general rule, the sand which has been used has been that 
 available in the immediate vicinity. A large proportion of our 
 emplacements have been located on sand beaches, so that sand has 
 been very plentiful. Frequently this sand has not been very sharp 
 and has not made as good concrete as other sand, yet on account of 
 its abundance it has been more economical to use this sand even with 
 an increased percentage of cement than to purchase other and better 
 sand and use the normal proportion of cement. 
 
 Our modern emplacements contain a great many granolithic 
 walks and wide ceilings supported by reinforced concrete slabs. In 
 all such places very strong concrete is necessary and consequently 
 the custom has arisen of using in certain cases two qualities of sand, 
 the better quality for granolithic and slab work, and the poorer 
 quality where mere mass concrete only is desired. This was done to 
 a great extent in the Hawaiian Islands. The batteries there were, 
 as a rule, built where there was an abundance of coral sand ; that is, 
 sand formed by disintegrated coral. The concrete made with this 
 sand was not strong enough for slab work, but it could be used for 
 mass work. For slabs or granolithic work, however, where strength 
 was desired, the sand which was used was obtained by pulverizing 
 lava rock. This lava sand was quite expensive, costing from $2 to 
 $2.50 per yard, delivered at the site of the battery, whereas the coral 
 sand being plentiful in the vicinity cost almost nothing. 
 
 The proportions of the various ingredients of concrete are deter- 
 mined in the same way as in the concrete used for civil engineering 
 work. Where great strength is necessary, proportions as high as 
 1, 2J, and 5 are used, in some cases even 1, 2, 4. In mass concrete 
 1, 3, 6, or even 1, 3 J, 7 are frequently used. 
 
 Mixing and Placing of Concrete. 
 
 In the first concrete emplacements built but little care seems to 
 have been taken in the mixing and ramming of the concrete. It 
 seems to have been thought at that time that about all that was 
 needed was mass and that ramming was not very necessary to make 
 the concrete strong. Occasionally the concrete was dumped in by 
 the skipful, the surface being then tamped a little, but the effect of 
 
54 
 
 this tamping did not, of course, extend very far down into the ma,ss. 
 Sometimes it was customary to dump the skips while moving, which 
 would thus scatter the cement considerably, and wherever the con- 
 crete fell it was tamped to some extent. 
 
 At this time it was customary to mix the concrete extremely dry, 
 laboratory experiments having shown that dry concrete properly 
 rammed was stronger than if mixed wet. This was all well enough 
 for laboratory work, but it did not do in practice, because it was 
 impossible to insure that the concrete would be rammed well enough 
 to get the little water that it contained completely distributed 
 through it. 
 
 The consequence was that although mass was obtained and appar- 
 ently the necessary strength, the concrete prepared in this way was 
 as a rule quite porous, in some cases about" as porous as a sieve. 
 Water would seep readily through it and much difficidty was later 
 found in keeping this seep water out of the rooms and magazines. 
 This subject will be discussed later in the Chapter on Dryness, etc. 
 
 Finding that mixing the concrete with more water made it easier 
 to ram, the next tendency was to make the concrete too wet — ^so wet 
 in fact that it could ncg; be rammed but could be merely puddled. 
 
 The opinion of the engineering world is still divided as to v.-hat is the 
 best amoimt of water to use in mixing concrete and as to the best 
 method of placing it, but as the requirements of concrete for fortifi- 
 cation purposes are essentially the same as those for other construc- 
 tion purposes, the matter will not be further discussed here. 
 
 Construction Plant. 
 
 It is not necessary to go into this subject since the problem is the 
 same as has to be solved in connection with other concrete construc- 
 tion. 
 
 Planes of Weakness. 
 
 When concrete emplacement construction was first begun it seems 
 to have been the idea that the emplacement should be made as mono- 
 lithic as possible. To accomplish this, the work was sometimes run 
 continuously day and night, and when day work only was used, it 
 was customary upon resuming work after the overnight's delay to 
 carefully brush off and wash off the surface of the old concrete, to 
 dampen this surface, and then apply to it a layer of mortar before 
 beginning the deposit of the new concrete. It was thought that by 
 this means the new concrete would be bonded to the old and that an 
 essentially monolithic condition would be obtained. It has been 
 found, however, that new concrete does not bond well to old, and 
 that the monolithic character desired was not obtained. 
 
 It was soon discovered, moreover, that the irregular settlement 
 which appears inevitable, and the irregular expansions and contrac- 
 tions due to temperature changes, cause cracks to occur in a large 
 
55 
 
 mass of concrete. If left to chance these cracks may occur at the 
 worst places possible, and consequently, since it is known that they 
 will occur in any case, it is desirable to insure that when they do 
 occur they will occur at places where no harm can be done. 
 
 For this reason there are usually left in emplacement construction 
 what are called "planes of weakness." The method of creating one 
 of these planes of weakness is simply to build the separate parts 
 independently; that is, one section is built up against a wall of smooth 
 framework placed along the desired plane of weakness. When this 
 section is completed, the framing is torn down and the next section is 
 then built. These sections, built separately in this manner, do not 
 bond. In the early days layers of building paper would be placed 
 between them, but this has been found not to be necessary. 
 
 The gun block of a large emplacement is buUt so as to be separated 
 from all the concrete work around it by planes of weakness. This 
 gun block is built soMd and heavy. It supports the gun and carriage 
 which are both heavy. To the gun block is transmitted directly the 
 shock of the discharge and consequently it is much more liable to 
 settle than the portions around it. By surrounding it with planes of 
 weakness it is left so that it can settle independently and without 
 causing cracks in the neighboring concrete. Similarly the heavy 
 parapet in front of the loading platform is usually separated from the 
 mass behind it by planes of weakness and is sometimes divided up 
 into lengths by planes of weakness extending from front to rear 
 through the parapet. In the more modern type of emplacements, 
 when the magazines are surrounded by air spaces, planes of weakness 
 are frequently located so that they pass along these air spaces. (See 
 Plate XXV.) 
 
 Mimeograph No. 8 pubhshed in 1896 says: 
 
 Cracks having appeared at more than one locality it seems expedient to call the 
 special attention of officers of the Corps of Engineers engaged in fortification \vork to 
 the necessity of providing for planes of weakness between portions of the concrete 
 masses which differ in dimensions and weight, or which rest on different foundation 
 strata. Such planes of weakness should be provided at all places where cracks are 
 liable to form from settlement or from unequal expansion and contraction. Particular 
 care should be given to the gun platform. As designed it possesses ample strength 
 where it can rest on a good foundation. Where a firm subbase is not found, provision 
 should be made for strengthening it. It is particularly necessary that it should rest on 
 a uniform stratum. No portion of it should be joined to or rest on any portion of the 
 parapet mass. 
 
 SURFACE FINISH OF CONCRETE. 
 
 In building the early emplacements, especially where Kosendale 
 cement was used, it was customary to use very rough lumber for the 
 forms. After these forms were taken away the siu-face of the con- 
 crete would of course be very rough and irregular, and in order to 
 make it look better it was plastered over and given a nice finish. 
 
56 
 
 For a while the coarse concrete finished in this manner looked very 
 well, but it was soon found that the plaster coat would not as a rule 
 stand the effect of frost, and would peel off nearly everywhere. With 
 Portland cement concrete this peeMng off does not occur so frequently, 
 but it has happened at times and where it has peeled off the effects 
 are uglier than if it had never been put on at all. 
 
 For the above reasons the practice is becoming more and more 
 common of making the concrete framing of dressed boards carefully 
 planed, finished on all four sides, and neatly put together with all 
 joints exactly vertical or exactly horizontal. With care in placing 
 the concrete, or by making the proportions of the aggregate a little 
 less in the portion to be placed next to the boards, or by puddling 
 the concrete with the end of a spade as it is placed against the framing, 
 that portion against the boards is made very smooth and when the 
 framing is removed the surface is unbroken and shows off very well 
 the grain of the wood. Under such conditions no plaster coat is 
 necessary. 
 
 In this connection it may be noted that as a rule the wetter con- 
 crete is mixed, the easier it is to get a nice finish. However, where 
 the concrete is to be mixed very wet, great care must be taken in 
 building the framing, and the thinnest joints possible must be used. 
 When wetted, of course, the boards swell slightly and the joints 
 become waterproof. Otherwise the surplus water in the concrete 
 may leak out, carrying with it much of the cement and thus weaken- 
 ing the concrete in addition to interfering with its appearance. 
 Granolithic Finish. 
 
 In finishing a nearly smooth horizontal surface which is to be used 
 as a pavement or walkway, the same care is necessary as in finishing 
 any granolithic walk. The concrete near the surface is mixed quite 
 rich in cement and the surface layer contains none of the larger aggre- 
 gate. As soon as placed, the concrete is pressed down to squeeze out 
 the water and as it begins to get its set it is carefully rubbed down 
 with a wooden float. Strictly horizontal surfaces should, in general, 
 be avoided, drainage slopes being provided wherever possible. This, 
 however, is a matter which will be discussed more in detail in the 
 chapter on Dryness, etc. 
 
 It is usual in laying pavements to do the work in alternate blocks 
 so as to insure that any cracks that may subsequently occur wLU occur 
 along the joints and will not mar the appearance of the pavement. 
 Blast Apron. 
 
 In finishing the concrete apron immediately in front of a gun, great 
 care must be taken to insure that the concrete shall not be cracked 
 up by the effect of the blast and subsequently be blown away. In 
 the earlier batteries it was customary to finish the concrete up to ■ 
 
57 
 
 within from 6 to 8 inches of its final level and then later to lay a sort 
 of pavement upon it. Such construction, however, was quickly 
 cracked and blown away, this thin layer not being properly bonded 
 to the concrete below. With the increasing power of guns, the diffi- 
 culty of preparing a proper concrete a.pron has also increased, and 
 the method now considered best is to lay the last 4 or 5 feet or so of 
 the parapet as nearly monolithic as possible. The regular work of 
 placing the concrete is stopped when within 4 or 5 feet of the final 
 level. Arrangements are then made so that the remaining concrete 
 can be put in place without interruption, and this is done as, rapidly 
 as possible and is continued completely to the surface itself, which is 
 smoothed off and floated down without delay and before the concrete 
 below it can have reached its final set. 
 
 In the older batteries where Rosendale cement was used it was 
 practically impossible to make the concrete in front of the guns 
 sufficiently strong to withstand the blast, and to overcome this 
 weakness resort was occasionally had to substituting Portland cement 
 in this section of an emplacement. Occasionally, also, the attempt 
 was made to use thick metal blast plates held down by long bolts, 
 but these were found to be unsatisfactory. Fortunately, however, 
 it was discovered that properly prepared Portland cement concrete 
 is sufficiently strong to withstand the blast effects, and where put 
 in as above described the blast aprons have been found to be satis- 
 factorily dm-able. 
 
 Corners and Edges. 
 
 Though concrete is strong and generally a serviceable material 
 for battery constructions salient corners of it, such as door jambs, 
 the comers at turns in corridors, etc., are apt to be chipped off by 
 things accidentally striking them. Consequently, the custom has 
 grown up of rounding off or beveling all such corners. The rounding 
 off requires a special form of molding. The beveling can be easily 
 arranged by inserting in the corner of the framing a triangular piece 
 of wood made by splitting a square piece of scantling along the 
 diagonal of its cross section. 
 
 Some officers in order to make their work look better build such 
 exposed corners of pressed brick and sometimes they insert stone 
 lintels, etc. These details, although they add to the appearance of 
 the battery, are believed to be unnecessary and unduly expensive. 
 
 Tinting Concrete Surfaces. 
 
 In connection with the finish of concrete work there is another 
 
 subject frequently of great importance. Concrete when hard and 
 
 dry is nearly white and the glare from such a surface when exposed 
 
 ' to sunlight, especially in the Tropics, is very disagreeable. In order 
 
 to avoid this, it is desirable if possible to darken this surface. 
 
58 
 
 One method of doing this is by mixing lampblack in the concrete 
 that is to be used near the surface. Powdered blue stone or red 
 stone is also frequently used for this purpose. When first completed, 
 the granolithic surfaces made with powdered stone or lampblack 
 are much darker than concrete in which some darkening substance 
 has not been used. It has been found, however, that all such con- 
 crete quickly wears lighter. 
 
 Frequently, too, the same end has been accomplished by applying 
 to the surface when completed a water-mixed paint. A dull green 
 was used for this in connection with the Panama fortifications and 
 has proved very successful not only on pavements but also on 
 vertical walls. 
 
 For the vertical concrete walls around the loading platform some 
 form of darkening also is desirable. One method used for this pur- 
 pose was to apply to these walls a cement wash containing lamp- 
 black. Since lampblack itself is not soluble in water, it is usually 
 dissolved in wood alcohol or some other cheap solvent, and is then 
 added to the water used in mixing up the cement wash. It is applied 
 by means of a brush. Walls when freshly painted this way are very 
 nice looking, but unfortunately the lampblack has a tendency to 
 wear away irregularly and the walls soon become splotchy. 
 
 Another method of darkening the walls has been the application 
 of boiled linseed oil applied quite frequently in coats until the wall 
 has absorbed enough oil to give it a proper hue. Sometimes a little 
 pigment has been mixed up with this linseed oil. This linseed-oil 
 coat is supposed to have the additional quality of making the wall 
 waterproof, but it has been found in a number of cases that the 
 concrete has been injured by the oil. 
 
 The conditions as to excessive glare from the concrete surfaces are 
 quite reversed in the interior of batteries, where as much illumina- 
 tion as possible is needed, since the personnel have to go frequently 
 back and forth from outside to inside. Consequently, the better 
 the light reflecting qualities of the interior paving and walls, the more 
 generally will light be diffused within the interior of the battery and 
 the better will be the general illumination of the interior. Concrete 
 walls are of course not perfectly white, and it improves the general 
 diffusion of light within an emplacement to paint the walls and 
 ceilings white. Several varieties of paint have been found suitable 
 for the purpose and some of the formulas for these have been published 
 in mimeographs or circulars. 
 
 The white paint on the walls and ceilings should, of course, be 
 restricted to concrete surfaces. Paint should never be applied to 
 tile surfaces or the surface of porous bricks, for the paint fills up the 
 pores of the tiles or brick and thus prevents them from accomplish- 
 ing their proper function. (See Chapter on Dryness, etc.) 
 
59 
 
 Effect of Oil on Concrete. 
 
 In connection with the concrete work, not only of emplacements, 
 but even more especially of some of the smaller buildings, the effect 
 which oils may have on the concrete must be given consideration. 
 This matter should likewise not be overlooked in connection with 
 concrete used in civilian construction. 
 
 If, after concrete has become thoroughly set and hard, oil be 
 applied to it or be allowed to fall upon it no immediate effect is seen, 
 except possibly a staia or a change in color. Experience has shown, 
 however, that certain forms of oil applied to concrete have a tendency 
 to cause a slow disintegration, and the conditions which cause this 
 disintegration have as yet not been thoroughly determined, either 
 as to the varieties of oil which will cause this action or as to the 
 amount which has to be present or the circumstances under which 
 it has to be applied. 
 
 Spme years ago tests were made by the department upon neat 
 cement briquettes which had been previously tested in a machine 
 and which had been found sufficiently strong to withstand tensile 
 strains of more than 800 pounds per square inch. When several 
 months old, some of these briquettes were painted with coatings of 
 different kinds of oil and some of them were placed in saucers con- 
 taining different varieties of oil. For a considerable time no change 
 was noted, then there developed in certain of the briquettes a sort 
 of crumbling or disintegration and in some six months or so a few 
 of the briquettes had been disintegrated into what might be called 
 a mass of powder saturated with oil. These experiments were 
 somewhat contradictory as to the kinds of oil which produced this 
 effect, there being at least one case where two briquettes, painted 
 apparently imder the same conditions and with the same kind of 
 oil, were acted upon very differently, one being completely disinte- 
 grated and the other being almost uninjured. 
 
 This matter is of considerable importance when for any reason it 
 is desired to paint a concrete surface, since the oU used in the paint 
 may affect the integrity of the concrete. Plain boiled hnseed oil, 
 apphed to a monohthic concrete surface, darkens the sm^ace and 
 apparently has no tendency to cause disintegration, but, if applied 
 to a plaster coat placed over a concrete surface, it seems to accelerate 
 the rapidity with which the plaster will peel off, the oil working its 
 way through the plaster coat and dissolving the imperfect bond 
 between the plaster and the concrete surface upon which it was 
 placed. 
 
 Cases have also happened where the oil drippings from a gun 
 carriage have caused a softening or disintegration of the concrete 
 paving- below. Often, however, no such effect has been noticed. 
 So, whether the cases where disintegration has occurred have been 
 due to the peculiarities of the cement used, to the particular brand 
 
6U 
 
 of oil, or to some special peculiarities of the case, has not yet been 
 determined. 
 
 However, there is one thing in connection with the effect of oil on. 
 concrete that would appear to be certain, and that is that the action 
 may be extremely slow, and that when a particular brand of oil has. 
 been applied to a concrete surface and nothing apparently has hap- 
 pened for some time the conclusion should not hastily be jumped at 
 that no harm has been done. 
 
 As far as the knowledge of the writer of these notes goes, the effect 
 of oil on concrete and, for that matter, the effect of sea water on con- 
 crete are both problems which have not yet been thoroughly solved. 
 That they may have been solved is not improbable, and that if they 
 have not yet been, they wiU be before long is practically certain,, 
 but until something much more definite has been learned about 
 them it is thought that the constructing officers should exercise con- 
 siderable care in permitting oil to be applied to concrete. For the 
 present, therefore, it is believed to be safer to use water-mixed paints 
 instead of oil paints wherever it is necessary to paint a concrete- 
 surface. 
 Roof Construction. 
 
 In the first designs for emplacements, it seemed to be considered 
 necessary to make all the ceilings full center arches, and all the bat- 
 teries begun in the very early nineties were built this way. Thus, 
 the first mortar batteries, built at the Presidio, San Francisco, and 
 at Sandy Hook, New York Harbor, and the earlier gun batteries, built 
 at Fort Monroe, are of this type. (See Pis. XIII and XXVII.) 
 
 When the rooms and galleries were quite narrow these fuU center 
 arches did not place the ceilings very high, but when it was found 
 that the width of these rooms was not sufficient and that wider rooms 
 had to be provided the lost vertical space became a serious obstacle, 
 and to avoid this the batteries were designed with fiat roofs supported 
 by I beams extending aU the way across the room from wall to wall. 
 
 This type of construction seems to have been introduced about 
 1895. Comparatively large beams were used. Where a corridor or 
 passageway was about 4 feet wide, a 4-inch beam was used. In 
 rooms 12 and 14 feet wide, 10-inch beams were provided, and so on 
 up. The beams, of course, were made long enough to extend at 
 least a foot into each side waH and, in order to distribute the pressure 
 which they would bring to bear upon the walk supporting them, 
 special plates of cast iron were inserted under them. This latter 
 provision, however, was done -away with as it was found to be un- 
 necessary. 
 
 These beams were, in general, placed parallel and 2 feet apart, 
 center to center, and the portions of the ceiling between each two 
 beams were made in the shape of a flat segmental arch. Generally 
 
61 
 
 the concrete in this arch was exposed to sight, but in a few places the 
 corrugated sheet-iron arches provided to hold up the concrete as it 
 was put in place were left after the concrete set. 
 
 It was shortly found that the framings for these small arches were 
 difficult to put into position and were expensive. The experiment 
 was therefore tried of doing away with them and making the ceihng 
 between the beams perfectl}^ flat. In a report issued by the Board 
 of Engineers in July, 1890, and published as a mimeograph, it is said: 
 
 The ceilings of magazines should be flat. Arches between ceiling beams are 
 unnecessary. 
 
 Of course, in this form of roof construction the lower flanges of the 
 ceiling beams were exposed to view, and incidental^ to the moist air 
 of the magazines. To protect them from rust they were painted, 
 but it was soon foimd that it was difficult to keep them so thor- 
 oughly painted as to prevent them from rusting. 
 
 The next step, therefore, in ceiling construction was to embed these 
 beams in the ceiling about 2 inches above the exposed surface of the 
 •ceiling. 
 
 This was accomphshed by building the walls about 2 inches above 
 the ceiling level before placing the beams. Incidentally, also, before 
 any beam was put in place the framing over which it was to go was 
 covered with a layer of concrete, some 2 or 3 inches in thickness, 
 from which all large stones had been removed. The beams were 
 then put in place and the concrete dumped between them, binding 
 the whole mass together so that when the framing was removed the 
 beams were hidden and were not seen. 
 
 The type of construction mentioned above, with the beams either 
 hidden or exposed, was continued for a considerable time; in fact, 
 until the invention of the different systems of reinforcing concrete by 
 deformed steel bars. In 1903 the Board of Engineers recommended 
 that thereafter this latter type of construction be utilized in em- 
 placements and the mimeographs publishing the plans of the 1903 
 types of 12-inch emplacements showed, in addition to other things, 
 the sizes and locations of the reinforcing bars necessary. 
 
 Steel Reinforcement. 
 
 In designing the reinforcing for the concrete work used in em- 
 placements it has been considered necessary to adopt rules as to the 
 amount of reinforcement required which differ considerably from 
 those used in designing the concrete slabs ordinarily used in the con- 
 struction of buildings intended for civil purposes. 
 
 In the latter it is considered that when a concrete ceiling slab is 
 
 once put into position it wiU remain indefinitely, and consequently 
 
 the entire thickness of the concrete, except possibly a very small 
 
 ^allowance for wear at the top, can be counted on as assisting to bear 
 
 the stresses that wiU come on the compression side of the slab. 
 
62 
 
 In designing emplacements, however, especially the wide roof 
 spans over the magazine spaces, it is to be assumed that the u'pper 
 portion of the mass of concrete is subject to the destructive effects 
 of projectiles that may strike it or may penetrate it slightly and 
 then explode. Furthermore, as will be mentioned in the chapter 
 on Dryness, it is frequently necessary to place in the interior of this 
 mass an intermediate waterproof surface. For these two reasons, 
 and in order to be on the side of safety, it is usual in designing the 
 reinforced concrete roofs over magazines to assume that only so 
 much of the thickness of the concrete as is absolutely essential is 
 acting to help support the weight, and that all the concrete above 
 this minimum thickness is to be considered as in no way adding to 
 the strength of the beam but as acting merely as so much additional 
 dead weight to be supported. For instance, in one case where the 
 roof span was 27 feet and the thickness of the concrete 12 feet, it 
 was assumed that the total weight to be supported wotild approxi- 
 mate 1,800 pounds* per square foot of ceUing surface, and that there- 
 fore the weight on the portion of the slab 1 foot wide and extending 
 entirely across the span would be approximately 50,000 pounds. 
 A beam 1 foot wide and 27 feet long would have to be about 36 inches 
 deep, assuming the amount of steel reinforcement as slightly less 
 than 1 per cent of the cross section. The reinforcement was there- 
 fore designed as if the total depth of the beam was 36 inches and the 
 weight of all the rest of the concrete was considered as being sup- 
 ported by this slab 36 inches thick. This permitted the interme- 
 diate waterproof surface to be so designed as to come just above this 
 36 inches of the ceiling surface. 
 
 Apparently this is somewhat unduly expensive in the matter of 
 steel, because it is evident that a good deal of the concrete above 
 this slab will actually act in compression to help support the load, 
 and the strain on the steel will not be as great as that computed-. 
 However, there is always the possibility that a projectUe or a bomb 
 may penetrate through the earth blanket and actually enter the 
 concrete a short distance and there explode, not only shattering the 
 concrete to a considerable extent but actually bringing a sudden 
 blow upon the supporting slab. 
 
 The rule above mentioned is ordinarily applied only to the wide 
 ceiling slabs over the magazines and galleries in the traverse, to the 
 ceiling slabs of the rooms under the loading platform, and to the ceil- 
 ings of corridors, or galleries, or shell recesses opening through the 
 parapet in front of the loading platform. In other cases of reinforc- 
 ing, such as the cantilever stairways and platforms, and in the short 
 lintels over doors and windows where there are no intermediate 
 waterproof surfaces to interfere, the reinforcing is designed according 
 to the rules usual in civil construction. 
 
63 
 
 The reinforcement of concrete columns is usually made of plain 
 steel bars and not of deformed bars, and these bars are usually bonded 
 or wired together at intervals to prevent them from spreading. 
 
 FOUNDATIONS. 
 
 So far as its foundations are concerned, a gun emplacement is 
 nothing more or less than a masonry structure, and exactly the same 
 precautions should be applied in constructing the foundation of a 
 gun emplacement as would be considered necessary in constructing 
 the foimdation of any heavy masonry structure, whatever the pur- 
 pose for which it is intended. 
 
 Unfortimately, the location of a gun battery is fixed by other con- 
 siderations than stability of foundations, and the preparation of a 
 satisfactory foundation is frequently a serious engineering problem. 
 
 Another consideration which increases the foundation difficulty is 
 that the weight of a gun emplacement is quite unequally distributed^. 
 Thus the concrete parapet is solid. The gun platforms are much 
 lower than the parapet and it is evident the weight of the gun and 
 carriage is much less than if the gun block were extended upward 
 in solid concrete to the level of the crest of the parapet. Farther 
 to the rear is the loading platform, and in large emplacements, rooms 
 or other voids are usually placed under the loading platform so that 
 the weight per square foot of foundation under the loading platform 
 is much less than under the gun block, and the weight per square 
 foot under the gun block is much less than under the parapet. 
 
 Similarly, in the traverses between the guns, the weight is un- 
 equally distributed. Immediately in front of the magazines the 
 concrete is buUt solid in order to insure protection to the ammuni- 
 tion. The magazine spaces are, of course, empty but are covered 
 by a thick concrete roof. Farther -to the rear there are the hoist 
 rooms and stiU farther rooms or corridors below and open corridors 
 above. 
 
 Consequently, both near the guns and through the traverses, em- 
 placements are much heavier per square foot of area in front than in 
 the rear. If the emplacements are built upon ground that is yield- 
 ing or which rests upon a compressible stratum, it is but natural to 
 expect that the settlement will be greater in front than in rear, and 
 that, taken as a whole, there will be a tendency for the emplacement 
 to tip forward. 
 
 This has actually occured in many oases, and has not infrequently 
 gone so far as to interfere with the drainage system of the battery. 
 It is the usual custom to give loading platforms a sUght slope to the 
 rear to encourage rain water to run in that direction. The drainage 
 slopes given have usually been from about 1 to 2 per cent, and when- 
 ever the tipping due to irregi^^r settlement has exceeded this the 
 
64 
 
 drainage has been reversed and the water, instead of running off the 
 loading platform to the rear, has had a tendency to run forward 
 toward the foot of the parapet. 
 
 In a few fortification sites, especially those on the New England 
 coast and on the Pacific coast, the soil has been found to be rocky 
 and sufficiently strong to stand any reasonable weight, and trouble 
 has not been experienced from irregular settling. Along the middle 
 Atlantic, South Atlantic, and Gulf coasts, however, no rock or abso- 
 lutely stable foundations are found, and, in general, emplacements 
 have been located upon sandy coasts where the normal level of the 
 site is only from 5 to 15 feet above tide level. Where this sand rests 
 upon rock, packed gravel, or hardpan, it is not difficult to prepare 
 a suitable foundation. Sand itself, when confined, is incompressible, 
 and aU that it is usually necessary to do under the conditions men- 
 tioned is to excavate the sand down to about the level of groundwater, 
 and then to begin to lay the concrete upon the saturated sand with- 
 out other precautions than spreading the foundations of the walls. 
 This is the ordinary method of construction and has in general 
 worked well. "WTiere undue settlement has occurred it has ordi- 
 narily been found to have been due to strata of mud or other com- 
 pressible material underlying the sand at no great depth. 
 
 In a few places it has been known that the sand is of comparatively 
 recent formation or that it contp,ins considerable mud or there may be 
 reasons to believe that some thin mud strata of unknown compress- 
 ibility underlie the sand. In such cases resort has frequently been 
 had to covering the entire area of the battery by a reinforced con- 
 crete slab, made suHiciently strong to take up the weight of the 
 structure and transmit it fairly uniformly to the foundation. In the 
 early constructions of this character the steel reinforcement was 
 made by inserting heavy I bea-ms in the foundation. First a tier 
 of I beams would be placed with the beams from 2 to 3 foot centers. 
 Immediately above this would be placed another tier at right angles. 
 In the latest structures, instead of using I beams in this manner 
 steel reinforcing bars have been used, so placed and so bent with 
 regard to shear as to distribute the weight of the structure uniformly 
 to the foundation. 
 
 Where it is known that the substrata can not be relied upon to 
 hold up the heavy weights, foundation piles must be driven, and these 
 piles should be so distributed as to make the weight to be borne by 
 each approximately the same. Where the piles are driven so as to 
 be always submerged ordinary pine pUes will sufiice. Where they 
 are to extend above the ground-water level either creosoted piles 
 or preferably concrete piles should be used. 
 
 In a few cases, especially in the Tropics, considerable difficulty has 
 been met with in connection with the foundations of batteries. 
 Thus, under one of the forts in the Hawaiian Islands it was learned 
 
65 
 
 by making borings and the sinking of test pits that for a depth of 
 at least 60 feet the underlying earth consisted of disintegrated coral, 
 fine coral sand, and alluvial mud mixed most irregularly. Scattered 
 irregularly through this mass were large coral bowlders with many 
 fragments of so-called finger coral; that is, fragments from 2 to 12 
 inches long and from about one-quarter of an inch to 2 inches in 
 diameter. 
 
 In the preliminary drilling into this mass of earth, the pipe used to 
 make the boring sank with extreme ease, and it was decided to build 
 the batteries upon long concrete piles. When, however, the attempt 
 was made to drive these long piles considerable difl&culty was experi- 
 enced. Occasionally the piles would run up against a limip of coral, 
 which either had to be pushed out of the way or penetrated. After 
 the battery was completed, very slight and fairly regular settlement 
 was experienced except at one place, and that was under one of the 
 gun blocks where, strange to say, the piles were more difficult to 
 drive than anywhere else. 
 
 For a smaller battery the gun blocks were founded on piles, which 
 held perfectly. The magazine traverse, however, was built upon a 
 reinforced concrete slab. It was figured that this slab might settle 
 about 12 inches, and it was hoped it would settle fairly uniformly: 
 In fact, it settled about 10 inches in the rear and sHghtly less than 13 
 inches forward. Since the tilt thus caused was not sufficient to inter- 
 fere with the drainage system no trouble has been caused. 
 
 At another one of the Hawaiian forts it was found that the site of 
 a battery was underlaid at a distance of about 20 to 30 feet by a thick 
 coral ledge. The portions of the battery which were considered im- 
 portant — that is, the gun blocks, magazines, etc. — ^were all foundec 
 on piles driven through the soft strata to the coral ledge, and no 
 material settling was experienced. The parapets were built without 
 piles, and when raised nearly to full height work was stopped on them 
 and they were allowed considerable time to settle. When it was found 
 that settlement had about ceased, the parapets were then brought up 
 to shghtly more than full height, a small allowance being made for 
 subsequent settlement. 
 
 In the Panama batteries, except in one locality, there was no doubt 
 about the capability of the foundations to support the battery. The 
 exception was an island where the soil consisted of a soft mud under- 
 laid by coral. Piles were driven through the mud to the coral and 
 the batteries built upon the pUes. In the case of two batteries no 
 material settlement occurred. In the third and largest battery, how- 
 ever, the weight apparently proved too great for the Coral stratum^ 
 which seems to have broken through, permitting the battery to settle 
 considerably and irregularly. 
 173341—20 5 
 
66 
 
 The problem of foundations is important and is purely a local one^ 
 dependent upon .condition of the site. The constructing engineer 
 should therefore make a cartful investigation and study of the local 
 conditions and do the best he can under the circumstances. Fre- 
 quently the best that can be done is to divide the battery by planes of 
 weakness into several sections, which may thus settle separately and 
 independently; to then buUd the battery nearly to the top, to permit 
 the settlement to occur, and subsequently to put the finishing touches 
 to the battery. 
 Encroachments by the Sea. 
 
 Experience has shown that the sand beaches along most of our 
 seashores on the Middle, South Atlantic, and Gulf coasts are con- 
 stantly making or cutting away. Apparently this action is somewhat 
 periodic; that is, where a beach is cut away at one time it is apt to be 
 subsequently built up again, and, on the other hand, a beach built up 
 far in advance of its normal location may be cut away again. In 
 some cases the beaches are built up by storms and cut away under 
 normal conditions of wave and sea, and in others they are cut away 
 during storms and are subsequently built up to their normal posi- 
 tions between storms. 
 
 Occasions have arisen where it has become necessary to build a 
 battery so close to one of these fluctuating beaches as to be within 
 possible danger, at least temporarily, from an extreme case of erosion. 
 It is essential in such cases that the battery should not be allowed to 
 be undermined. If it is built upon piles, the sand can be temporarily 
 washed from under it without injuring the concrete work of the bat- 
 tery. Subsequently a change of conditions may wash the sand back 
 under the battery and build up the beach in front of it. Of course, 
 wherever this occurs the sand parapet is lost and has to be replaced. 
 
 For these reasons, where batteries have been placed close to a beach 
 and there seems to be a tendency to possible encroachment by the sea 
 it has been customary to build sea walls or groins along the beach 
 in front of the batteries and to fiU up between the sea wall and the 
 battery to at least the level of extreme high tide. Sometimes where 
 these extreme high tides occur only very infrequently the sand flat 
 has been left a few feet below such level and the lower 2 or 3 feet of 
 the parapet has been revetted with rock. 
 
 The place where the greatest difficulty of this character has been 
 experienced is at Galveston, where the natural level of the sand beach 
 is quite low. Within the last few decades, however, this vicinity 
 has been visited by severe tropical hurricanes accompanied by high 
 water, rising to as much as 15 f«et above ordinary low tide. The 
 first storm of this character washed away all the sand parapets and 
 undermined and destroyed the concrete work of the batteries not 
 built upon piles. Where the concrete work was founded upon piles 
 
67 
 
 it was not injured, and the sand could, of course, be replaced. Subse- 
 quently a strong sea wall was built in front of one of these forts. The 
 question of building similar waUs in front of the other has frequently 
 been discussed, but up to the present has been considered as not justi- 
 fiable on account of the high cost. 
 
 STEEL AND IRON. 
 
 Steel and iron are used in fortification construction and equipment: 
 In ordinary structural steelwork, such as towers, either fixed 
 or disappearing, and in roof trusses, etc. 
 
 As I beams for reinforcing ceilings or fortification slabs. 
 In columns for supporting ceilings or the rails of bridge 
 cranes. 
 
 For reinforcing concrete, in the form of simple or deformed 
 steel bars, wire mesh, or expanded metal. 
 As metal laths used in plastered walls. 
 As rails for railroads, tramways, or troUey tracks. 
 As piles for supporting wharves. 
 
 As pipes for water supply, sewage disposal, or speaking tubes,. 
 As stairways or ladders, either in emplacement construction or 
 in connection with towers. 
 
 As handrails for platforms, staii-ways, and in other dangerous 
 places. 
 
 In doors and windows, either solid or grating, and in manhole 
 and ventilator frames and covers. 
 
 In hold-down bolts for the base rings of gun carriages. 
 In the curbing around the top of gun weUs. 
 In ringbolts for maneuvering purposes. 
 
 In machinery such as engines, generating sets, trolleys, ammu- 
 nition hoists, and the receiving and delivery tables for the same, 
 or in service and storage tables, etc. 
 In electrical fittings. 
 As tools. 
 
 In many miscellaneous ways. 
 In general, the uses of iron and steel for the purposes mentioned 
 do not differ from similar uses in commercial life, and the iron and 
 steel work for these uses is usually bought under the standard com- 
 mercial specifications. In the following cases only do any special 
 remarks appear to be needed: 
 
 For use in reinforcing concrete ceiling slabs and foundations de- 
 formed steel bars are in general preferred to plain bars, and it seems 
 to be considered advisable to use several smaller bars rather than a. 
 few larger bars. As a rule the largest bar used is the l^-inch, although 
 If-inch are occasionally found in special places. Larger bars are 
 apparently never used. For reinforcing columns, plain bars with 
 
68 
 
 occasional bands to prevent spreading seem to be preferred. Wire 
 mesh, and expanded metal are much used for reinforcing thin concrete 
 waUs, and, along with metal lathing, as the support for plastered or 
 stucco walls. 
 
 In a number of early emplacements the handrails used were too 
 small. Not only did they not look well, but they bent too easily. 
 Consequently, it is now the custom not to use handrails smaller 
 than 3 inches. The handrails themselves and all the different 
 kinds of fittings are on the market and are described in the manu- 
 facturers' catalogues. 
 
 Hold-down bolts for the base rings of gun carriages have to be 
 specially made and under special specifications. This matter will 
 be more fully discussed in the portion of Chapter VII relating to the 
 subject. 
 
 In the early days it was the custom to permit district officers to 
 purchase machinery and electrical fitting^ through their own district 
 offices, but this led to so much dissimilarity between districts that 
 all this work was concentrated, first, in a single district office and 
 later in the main Engineer Depot. Generator sets, ammunition 
 hoists, electrical fittings, etc., are all now standardized and can be 
 obtained by district officers through the Office of the Chief of 
 Engineers or the Engineer Depot. 
 
 TIMBER. 
 
 Wood and timber are used in fortification construction: 
 For concrete framing. 
 For building various kinds of houses. 
 
 For ceilings, floors, and doors of buildings built otherwise 
 of fireproof material. 
 
 For the interior fittings of buUdings, such as benches, stools, 
 chairs, tables, etc. 
 
 For stairways in fortifications. 
 For building wharves, etc. 
 In the early days it was customary to use only rough lumber for 
 concrete framing. This, however, required the finishing of all 
 concrete walls after the framing was removed. To avoid this the 
 custom was adopted of using smooth, dressed lumber for concrete 
 framing, so that no subsequent plastering of the walls was necessary. 
 As a rule, light, thin lumber should not be used, the best results 
 having been obtained by making the surfacing of tongued and grooved 
 umber, nearly 2 inches thick, and having faces about 6 inches wide. 
 The studding also must be fairly large so as not to bend perceptibly 
 between braces. 
 
 For many years it was customary to build of timber many of the 
 important fortification buildings, such as range stations, plotting 
 rooms, switchboard rooms, mining casemates, searchlight stations, 
 
69 
 
 etc. Where these structures were isolated, the fire risk was but 
 slight, but when it became customary to group the buildings the 
 risk became greater, for a fire in one building might destroy others 
 also. Consequently, buildings of this class are now, as a rule, built 
 of fireproof or fire-resisting material. Timber, however, is still 
 used for the temporary offices and storerooms used by the Engineer 
 Department during construction, and for small temporary or peace- 
 time structures around emplacements, also occasionally for dormi- 
 tories and other nonessential buddings, so located that their de- 
 struction would not endanger other buildings or interfere with the 
 defense. 
 
 In casemates, switchboard houses, etc., even when otherwise fire- 
 proof, the ceilings and floors of rooms to contain much wiring are 
 frequently made of timber so as to facilitate the attachment of 
 wires. The doors, doorframes, and window frames of such buildings, 
 as well as of other fire-proof buildings, are likewise frequently mad© 
 of wood. 
 
 Benches, stools, chairs, tables, etc., are required in nearly all 
 classes of structures, and for the comfort of the personnel these are 
 made of wood. 
 
 In a number of cases wooden stairways have been built so as to 
 permit easy access to the crests of parapets of emplacements during 
 drills and target practice. These being considered originally as 
 temporary, or, at least, peace-time constructions, were frequently 
 built of wood. These wooden stairways, of course, rotted away 
 in time and, as a rule, have been replaced by concrete stairs. 
 
 Most of the torpedo wharves heretofore built have been of timber, 
 as is usual in civil life. In a few cases, though, reinforced concrete 
 wharves are now being substituted. 
 
 GLASS. 
 
 Window glass used around fortifications should, as a rule, be of 
 extra thickness and of extra good quality. Where blast effects are 
 to be feared wire glass should be used. 
 
 TILES. 
 
 The structural tUes ordinarily used in civil constructions are 
 usually burnt quite hard to give them strength and are left quite 
 rough and are fitted with small dovetailed grooves to catch hold of 
 the mortar. In emplacement construction the tiles are desired 
 principally on account of their porosity and water-absorbing qualities. 
 Medium burned tiles are, therefore, to be preferred, and since the 
 tUes are to be left in view in the completed work one face, at least, 
 of each tile should be left fairly even and smooth. 
 
 The tile ducts used for the underground installations of electric 
 wires and cables need be only of the usual commercial quality. 
 
Chapter V. 
 AMMUNITION SUPPLY, STORAGE, AND SERVICE. 
 
 The term "ammunition storage" explains itseK. "Ammunition 
 supply" includes manufacturing the ammunition, transporting it to 
 the vicinity of the battery, moving it into and storing it in the maga- 
 zine. "Ammunition service" is the term appUed to the movement 
 of ammunition from the magazine to the gun. 
 
 The Engineer Department is interested in two main movements of 
 the ammunition: First, in ammunition supply, the handling of the 
 ammunition from the point in the vicinity of the battery where it is 
 delivered by the Quartermaster Department to its storage place in 
 the magazine; second, in ammunition service, the movement of the 
 ammunition from the magazine to the gun. 
 
 The first of these movements of ammunition, bringing it to the 
 magazine, is a process properly performed in time of peace or, at least, 
 before the particular fort becomes actually engaged. Ordinarily, 
 therefore, no special haste is necessary in thus moving the ammuni- 
 tion and usually there is an ample number of men available. Never- 
 theless, all batteries should be so designed that all the handling of 
 ammunition necessary in getting it into and storing it in the magazines 
 can be done easily and without undue physical demands upon the 
 personnel. It is probable, of course, that after war is begun additional 
 ammunition may have to be sent to certain batteries, but the hand- 
 ling of this ammunition, at least in the immediate vicinity of the 
 batteries, can evidently not be done during an engagement. It must, 
 therefore, be handled between engagements when no very great haste 
 should be necessaiy. 
 
 The movement of ammunition in ammunition service must be very 
 rapid and it is the duty of the Engineer Department to so design its 
 emplacements that each and every step of the ammunition service 
 may be performed with such speed that the ammunition can be carried 
 to the breech of the gun at least as rapidly as it can be loaded into the 
 gun and fired; and so that the rate of fire which can be obtained from 
 the gun shall be hmited by considerations other than the functioning 
 of the portion of the ammunition service for which the Engineer 
 Department is responsible. 
 
 In addition to these two main movements of ammunition there are 
 two others in which the Engineer Department may be interested: 
 First, such movement as may be necessary from time to time during 
 storage, such as rearranging the ammunition so as to place what has 
 
 (71) 
 
72 
 
 not yet been used where it can be more readily handled when it 
 becomes necessary to serve it to the guns; second, replacing in the 
 magazine ammunition which had been carried to the gun, but which 
 had not been fired. This is very frequently necessary in drill and may 
 be necessary in time of war, at the end of an action. 
 
 In providing means for handling ammunition, the Engineer Depart- 
 ment is merely called upon to solve a particular case of what is probably 
 the most conunon problem that is presented to mechanical engineers — 
 the movement of heavy weights. Furthermore, neither in the total 
 amount of material to be moved nor in the size of the largest indi- 
 vidual pieces do the difficulties to be met with in handling ammunition 
 begin to compare with those which are successfully overcome daily 
 in commercial hfe. Nevertheless, there are certain conditions con- 
 nected with the handling of ammunition, especially in serving it to 
 the gun, that make the problem somewhat unique. 
 
 The appliances provided for the handling of ammunition in ammu- 
 nition service must be absolutely and thoroughly rehable. They 
 must be such as to require? no time for adjustment when called upon 
 for use. They must be capable of being left absolutely without 
 attention for a considerable time, many weeks and perhaps monthSj 
 and yet must be instantaneously available. They must be strongr 
 capable of standing considerable abuse, and of being operated by 
 untrained or poorly trained men. In fact, they should be so simple 
 in operation that practically no training is required, yet when called 
 upon for use they must be capable of handling the ammunition rapidly 
 and under conditions where even seconds of time are important. In 
 many cases they are installed in locations where they are subject to 
 extreme dampness and other corrosive agencies and yet must not be 
 injured by these agencies. They must be used frequently under con- 
 ditions where the men are cramped for space and where the illumina- 
 tion is extremely poor. AH these conditions must be given considera- 
 tion by the fortification engineer, who must, in spite of them, provide 
 simple, fool-proof, thoroughly rehable, and sufl&ciently rapid means 
 of handling the ammunition. 
 
 The means which must be provided for moving ammunition and, 
 for that matter, any other class of articles, depend, of course, upon the 
 weight and bulk of the pieces to be moved. - 
 
 For guns not larger than 5-inch, the projectiles and the powder are 
 ordinarily stored and transported to the gun in the form of complete 
 cartridges, put up in metallic cases, similar, except as to size, to the 
 metallic cartridges used in the Infantry rifle. These complete car- 
 tridges weigh so little that they can be easily transported by hand 
 and no mechanical handling apphances are necessary. 
 
 For gims larger than 5-inch, the powder and the projectiles are 
 usually stored, handled, and loaded separately. 
 
73 
 
 The 6-inch projectile weighs about a hundred pounds and can easUy 
 be carried short distances by hand. When, however, it has to be 
 carried any great distance horizontally, or has to be raised to any 
 considerable height, a mechanical appliance is desirable, though not 
 essentia'. 
 
 The 8-inch pro j ectile weighs approximately 3 00 pounds ; the 1 0-inch, 
 600 pounds; the 12-inch, 1,000 pounds; the 14-inch, 1,600 pounds; 
 and the 16-inch, about 2,400 pounds.. To handle projectiles of these 
 weights mechanical appliances are essential. 
 
 The powder for the 6-inch gun is usually put up in a single cartridge, 
 neither too large nor too heavy to be easily transported by hand. 
 The 8-inch powder charge, likewise, is not too heavy to be carried by 
 hand. If the charge for a gun larger than 8-inch be put up in a single 
 cartridge the charge becomes too heavy for manual transportation 
 and, moreover, becomes quite large and unwieldy. 
 
 Up to about two or three years ago the powder charges for even the 
 largest guns were furnished by the Ordnance Department in several 
 cartridges, weighing as a rule not over 80 pounds each, the 10-inch 
 charge consisting of two cartridges, the 12-inch and the 14-inch, of 
 four, and the 16-inch charge of six cartridges. These comparatively 
 small cartridges could, therefore, be easily handled by hand. 
 
 However, experience has shown that when the charge for a large 
 gun consists of several cartridges there is apt to be an irregularity in 
 the rate of ignition of the charge when the gun is fired. This results 
 in irregularity in powder pressure which affects initial velocity of the 
 projectile and therefore the range. To avoid this, it is understood to 
 have been tentatively decided by the Ordnance Department that 
 hereafter the charges for all gxins, at least as large as the 14-inch, shall 
 be put up in a single cartridge. Whether or not this is to be done also 
 for the 16-inch is understood to be stiU under discussion. Certainly 
 the storage and handUng of the 16-inch charge, which weighs about 
 600 pounds and is nearly 9 feet long, would be much simplified if it 
 can be divided into at least two cartridges. 
 
 AMMUNITION SUPPLY. 
 
 Tn its full meaning, the tei'm ammunition supply inchides manu- 
 facturing the ammunition, transporting it to the seacoast fort, mov- 
 ing in to the vicinity of the particular battery, carrying it into the 
 magazine, and storing it away in the magazine. The manufacture 
 of the ammunition pertains to the Ordnance Department; transport- 
 ing it to the fort, to the Quartermaster or Transportation Corps; 
 moving it, after it reaches the fort, to a place in the vicinity of the 
 battery is usually a function of the Quartermaster or Transportation 
 Corps, though, as will be noted, the Engineer Department may be 
 interested in a waj'; carrying the ammunition to the magazine and 
 
74 
 
 storing it therein is a question in which the Engineer Department is 
 interested to the extent that it must supply all appliances necessary 
 for this movement of ammimition. 
 
 The movement of ammunition from the point where it reaches the 
 post to the vicinity of the battery is one which in time of peace has 
 to be but seldom [)erforraed, for after the magazines are once filled 
 the only movement of ammunition necessary will be to replace that 
 expended in target practice and this is usually quite small. For 
 these reasons, it has seldom been considered necessary to provide 
 special transportation facilities for ammunition supply. 
 
 Prior to startiag work on a battery, it is customary for the Engi- 
 neer Department to build a railroad to the battery for bringing in 
 the materials used in construction. After the battery is constructed, 
 it was formerly customary for the Engineer Department to remove 
 this railroad. In some cases, however, the railroad was left and 
 was turned over to the Quartermaster Corps for maintenance and 
 for such operation as, might be necessary in carrying supplies to the 
 battery. In a few places, as at Fort Monroe, this railroad, origin- 
 ally constructed by the Engineer Department, has become an impor- 
 tant transportation feature of the post and is utilized for carrying 
 troops back and forth to drill. In others, however, the railroad is 
 used but seldom and is not always maintained in the best of con- 
 dition. 
 
 It is the opinion of many Engineer officers, however, that the 
 provision of proper facilities for bringing ammunition and other 
 supplies to the battery should be considered when the battery is 
 under construction. This was done by the writer in connection 
 with all the Panama fortifications designed by him. Tn every case 
 it was planned that the railroad tracks provided for construction 
 purposes should, as the battery approached completion, be extended 
 to some part of the emplacement, whence the movement of ammuni- 
 tion to the magazine could be conveniently made. (See Plates 
 XXIII, XXIV, and XXV.) The plans of all the batteries show 
 these supply tracks, and they show, in addition, trolley rails extend- 
 ing over the tracks, so that the projectiles, if desired, can be picked 
 up by a trolley directly from the railroad cars in which they are 
 brought to the battery and can be moved by trolleys to the'shell 
 room: the same means also can be used, if desired, for handling 
 powder. 
 
 In one battery built on the top of a high hill, an elevator was 
 pro-vdded. The shaft extended from a tunnel dug into the foot of 
 the hill, up to the magazine floor, several hundred feet higher. For 
 ammunition supply in another battery a cableway was provided for 
 taking ammunition from the railroad cars at near sea level up to 
 the end of a corridor passing in rear of the various emolacements. 
 
75 
 
 In most of the older batteries built several years ago in this coun- 
 try no such provisions were made: although in connection with the 
 use of ammunition cranes, which were needed, at least as an alter- 
 native method, for raising the projectiles to tlie loading platform, 
 trolley tracks quite frequently led all the way to the rear doors of 
 the emplacements. (See Plates XV to XX.) Consequently, in 
 ammimition supply, if the projectile could be carried or rolled to 
 within reach of the trolley, the movement for the remainder of the 
 way to the shell room was simple. In fact, even after the use of 
 the cranes was abandoned, and the cranes themselves were removed, 
 the trolley rails were retained on account of their usefulness in 
 ammunition supply, and quite frequently were extended out by 
 brackets so as to project as much as 5 feet or so behind the rear face 
 of the emplacements. 
 
 The means to be provided for bringing ammunition to (vithin 
 reach of the trolley rails and trolleys are rather difficult to standard- 
 ize because they are to such a great extent dependent upon local 
 conditions. They must, therefore, be left to the local officers. 
 
 AMMUNITION STORAGE. 
 
 Ammunition for small caliber guns, that is, S-inch and under, 
 which, as has been stated, is usually issued as fixed ammunition put 
 up in metallic cartridges, is usually supplied by the Ordnance Depart- 
 ment, and is transported to the battery in wooden boxes or cases 
 containing several rounds. It is usually kept in the form in which it 
 is received until just before it is to be used, when the boxes are 
 broken open. Its storage, therefore, consists simply in piling up the 
 boxes in the most convenient arrangement. 
 
 For 6-inch and larger guns the powder and the projectiles are 
 stored and served to the gun separately. 
 
 Projectile Storage. 
 
 It was formerly customary to store projectiles in rows along the 
 walls of the shell room with their points toward the wall so that the 
 bases could be gotten at for inspection or placing fuzes. The lowest 
 tier of projectiles was usually laid on a pair of timber sldds 3 or 4 
 inches in thickness, and similar skids were placed between the suc- 
 cessive tiers. For convenience in placing the projectiles in their 
 rows, and in subsequently serving them to the guns, trolley rails were 
 fastened to the ceilings of all 8-inch and larger batteries, passing 
 over the centers of gravity of the projectiles in each row. No trol- 
 leys are provided in the shell room of 6-inch batteries because the 
 projectiles are not heavy enough to require them. The number of 
 6-inch projectiles for which storage space is to be provided in the 
 shell room is expected to be too great to permit storage in two rows 
 only. It is intended, therefore, that in addition to the rows along 
 
76 
 
 the walls, other rows will be placed down the center of the shell 
 rooms, so arranged, of course, that the bases of all jjrojectiles wilt 
 be along a passageway. These additional rows are usually shown 
 on the mimeograph drawings of the 6-inch batteries. (See Mimeo- 
 graph No. -59.) 
 
 The method of storing larger projectiles so close to the walls 
 proved to be somewhat inconvenient, and in preparing the draw- 
 ings for the ] 4-inch emplacements, pubUshed in 1908 (mimeograph 
 109, Plate XXII), the shell rooms were arranged for two rows of 
 projectiles, leaving not only a passageway between the rows but 
 also between the points of the projectiles aiid the walls. 
 
 These Resigns embodied also another neAv idea, that of storing the 
 lower tier of projectiles not on the floor but on special storage tables, 
 approximately of the same height as the receiving tables of the 
 hoists. This was intended to facilitate ammunition service, and will 
 be again referred to under that heading. 
 
 In the Panama batteries, the idea of keeping the projectiles away 
 from the walls was adhered to, but instead of having two rows down 
 the center of the shell rooms, two shell rooms are provided for each 
 gun, the projectiles being stored down the center of the room with 
 one passageway on each side of the row. (See Plates XXIII to 
 XXVI.) The other new idea of the 1908 type of 14-inch emplace- 
 ment was likewise adopted, but in part only. Instead of having shell 
 tables extending the whole length of the shell rooms, they were 
 provided at the service ends only, each table being large enough to 
 hold eight projectiles ready for instant service. The tables are at 
 just the proper height to permit the projectiles to be rolled directly 
 into the shell trucks. By using short shell tables only, the floor of 
 the rest of the shell room is left for projectile storage and a. much 
 larger number can be stored. This being a matter of ammunition 
 service, it will be again referred to under that heading. 
 
 In the Panama mortar batteries still another idea of projectile 
 storage is tried, that of raising the floors of the shell rooms, except 
 near the doors, to nearly the height of the service table; this likewise 
 was intended to facilitate the service of the projectiles. 
 
 Wherever two types of projectiles are furnished, it is expected that 
 they will be segregated in the shell rooms, either by piling them in 
 different rows or at least in different parts of the same row. 
 
 Powder Storage. 
 
 Powder is usually put up in hermetically sealed metallic cases and, 
 for transportation, these are inclosed in wooden boxes or cases and 
 are carried into the magazines in this shape. Sometimes the metallic 
 cases are left in these wooden boxes and sometimes the wooden 
 boxes are broken open. The cases containing the individual car- 
 tridges are cylindrical and, as long as the charges for all largei- guns 
 
77 
 
 were put up in several cartridges, the lengths of these cylinders, as 
 a rule, did not much exceed their diameter. It was customary to 
 store them in the magazines with their axes vertical, piling, if neces- 
 sary, some cases on top of others. 
 
 It was feared that during a rapid engagement when much powder 
 had to be handled there might be considerable confusion between 
 the empty cases and those which had not yet been emptied. To 
 avoid this it was proposed to store the powder cartridges in metal 
 racks in which they might be classified. The designs of the 14-inch 
 emplacements shown in Mimeograph 109 and the plans of the powder 
 magazines for^'he Panama fortifications were all based on the suppo- 
 sition that the metallic cases holding the cartridges would be stored 
 in the magazines in such racks. The cartridge cases were to be laid 
 on their sides in the rack, with their ends projecting into the passage- 
 way. When a cartridge was desired, the solder strip was to be pulled 
 off without moving the cartridge case from the rack. This loosens 
 the top of the case and the cartridge is then pulled out, leaving the 
 •case still fastened in its proper place. 
 
 The idea of storing the powder cases in racks as described, was 
 abandoned because, before the racks could be provided, it had been 
 decided by the Ordnance Department to furnish the powder for these 
 large guns in single cartridges. These single cartridges are very 
 large and in some oases are heavy enough to be quite unwieldy. 
 Magazines for the storage of the long cartridges should preferably 
 be of quite different shape from those most suitable for the storage 
 of the small ones and, consequently, the magazines actually provided 
 for the recent batteries are not as conveniently shaped and a,rranged 
 as they woidd have been had the change been foreseen. 
 
 The question of the best method of storing and handling these 
 long and unwieldy cartridges is now being studied and, as far as is 
 known to the writer, a definite and thoroughly satisfactory solution 
 has not as yet been developed. In some batteries it was proposed 
 to store the cartridges in the same manner as projectiles, that is, 
 lyxQg on their sides, crossways in the room, and with passageways 
 between the ends of the cases and the side walls of the magazines. 
 Of course, they would be stored several tiers high. For convenient 
 handling, a pair of twin trolley tracks was to be installed on the 
 oeiling with twin trolleys to pick up both ends of the case at the 
 same time.' A powder service table, likewise, was to be provided. 
 However, all such installations of powder trolleys and powder service 
 tables have had to be suspended pending a final determination of the 
 question as to the exact form in which the powder is to be furnished 
 T)y the Ordnance Department. 
 
 One difficulty that has been met with in handling the long single- 
 cartridge powder charges for very large guns is in getting the car- 
 tridges out of the metallic cases. To open the case at one end and 
 
78 
 
 attempt to lift or pull the cartridge out may result in tearing it unless 
 special canvas ribbons have been provided that pass around the base 
 of the cartridge, and even with them it appears almost necessary to 
 tip the case up till its base is considerably higher than its open end. 
 It has been suggested that both ends of this case might be opened 
 and that the cartridge might be pushed out from the base. Another 
 suggestion has been that to avoid having to handle the very flexible 
 long cartridge it might be carried in the metallic case itself all the 
 way to the breech of the gun and be pushed right through the case 
 directly into the breech of the gun. 
 
 The question of powder storage has also been somewhat compli- 
 cated by the practice, now customary with the Coast Artillery, of 
 what is called "blending" the powder just before target practice. 
 They open up a number of the metallic powder cases and then open 
 and repack the cartridges, putting in each new cartridge an equal 
 amount from each of the old ones. This is supposed to insure a 
 more uniform action of the powder. 
 
 Sometimes the blending is done in the magazine, sometimes in a 
 special small room, and sometimes outside of the battery. In some 
 batteries a special small rehandling room has been provided for the 
 purpose. Such a rehandling room is specially necessary at mortar 
 batteries, where charges of several different weights have to be put 
 up for fire in the different zones. This will be discussed more at 
 length in the chapter on mortar batteries. 
 
 AMMUNITION SERVICE. 
 
 As has been stated, ammunition service is the movement of the 
 ammunition from the magazines to the gun, and is a process which 
 must be performed with the maximum possible speed. In considering 
 the speed of ammunition service, it is not so much a question of the 
 total time necessary for any particular projectile or powder charge to 
 get from the magazine to the gun, but rather of the time interval 
 between successive projectiles or powder charges. The magazines 
 must be in a safe place and may be quite distant from the gun, so 
 that there may be several different stages in the service of the ammu- 
 nition. The critical time, therefore, is not the total time needed for 
 serving any piece of ammunition, but the interval between successive 
 charges ir the slowest stage of the ammunition movement. In time 
 of war a battery is supposed to be always in commission, and at least 
 partially manned. On the approach of the enemy, more or less 
 timely notice may be expected from the intelligence service, and when 
 he is known to be m the vicinity, as many stages of the ammunition 
 service as may be necessary can be performed in advance- even to 
 partially loading the gun, so that the gun can be fired promptly when 
 the enemy comes within range and fire can be continued rapidly 
 thereafter. •' , 
 
79 
 
 In the discussion in this chapter, ammunition service will be con- 
 sidered in its general principles only, the detailed appUcation to each 
 particular type of emplacement being considered in the next chapter 
 on the general subject of emplacement design. In that chapter the 
 gradual development of the different types of emplacement will be 
 discussed; for each type, the character of ammunition service de- 
 signed for it will be stated and it will thus be shown historically how 
 ammunition service has been gradually improved. 
 
 In the service of ammunition and, for that matter, in ammunition 
 supply also, the ammunition may have to be moved either hori- 
 zontally or vertically, or ia a combination of these two directions. 
 Since the apphances for horizontal and vertical movement differ 
 somewhat, they will be discussed separately. 
 
 Horizontal Movement. 
 
 Ammunition can be, and in fact is, moved horizontally ia several 
 different ways: By hand; by handbarrows; by cars or trucks; by 
 being rolled on a horizontal surface such as the floor, a table, or 
 steel rails; or by being suspended from a trolley moving on a trolley 
 rail usually fastened to or hung from the ceiling. 
 
 Moving ammunition by hand is the method used in practically 
 all cases when the weight of the individual parts to be carried is 
 small enough to permit it. It is used to the exclusion of other meth- 
 ods in the service of 5-inch guns and all smaller guns, and in the 
 powder service of the 6-inch gun. Occasionally, in addition, it is 
 used for carrying the 6-inch projectiles and the individual cartridges 
 that make up the powder charges of the larger guns. 
 
 In moving ammunition by hand, the movement may be all on the 
 same level or it may be up or down stairways or ramps. In some 
 cases, one man will carry the ammunition all the way from the 
 magazine to the gun, and in others it is passed from hand to hand; 
 or it may be picked up by one man from one place and be pushed or 
 carried by him to another place, where it will be picked up by an- 
 other man. None of these cases, however, require further discus- 
 sion. 
 
 The method of moving ammunition by means of handbarrows, 
 carried by two or four men, is now the standard method of powder 
 service for large guns. The barrows are either fiirnished by the 
 Ordnance Department or are improvised by the detachment. They 
 are sufficiently large to carry all the cartridges that go to make up 
 a complete powder charge, or to carry the single large cartridge if 
 the powder be put up in that form. 
 
 The trucks for carrying projectiles and powder along the hori- 
 zontal or nearly horizontal floors of rooms, corridors, galleries, and 
 platforms are usually furnished by the Ordnance Department, al- 
 
80 
 
 though in a few cases of very special emplacements the trucks have 
 been specially designed and furnished by the Engineer Department. 
 
 The trucks usually furnished by the Ordnance Department for 
 carryiag 6-inch projectiles are designed to carry several at a time, 
 crossways on the truck. These, trucks carry the projectiles from 
 the magazine to or as near ithe guns as they can go, and at this place 
 members of the detachment pick up the projectiles and carry them 
 by hand to and insert them in the breech of the gun. 
 
 The trucks furnished by the Ordnance Department for use with 
 the larger guns have usually been designed for carrying the projec- 
 tiles only, one at a time, the powder being carried by hand or by 
 handbarrows. For several years, how&ver, a type of truck was 
 standard for use with large gims which carried the projectiles in a 
 main tray high up and the four cartridges of the powder charge in 
 two side trays lower down. (In figure 1, Plate I, there is a drawing 
 of the rear elevation of such a truck.) The trucks for carrying pro- 
 jectiles only are quite similar except that the powder trays are 
 omitted. 
 
 The trucks for larger projectiles carry the projectiles lengthwise 
 and at such a height that they can be pushed directly into the breech. 
 It was intended by the Ordnance Department that the projectile 
 trucks should be roUed slowly up to the breech of the gun and that 
 the ramming should, be done while the projectile was at rest. Start- 
 ing a heavy projectile along the loading tray by pushing is, however, 
 somewhat difficult and to avoid this there has grown up in the 
 Artillery the habit of rushing the shot truck agaiast the breech of 
 the gun on the run. The moment the truck strikes the breech it 
 stops, but the projectile by its inertia is thrown forward into the 
 breech of the gun, and, after a little practice, the detachment be- 
 comes so skiUful that the men at the rammer are able to place the 
 head of it against the breech of the projectile before the latter stops, 
 and the ramming of the projectile into the breech of the gun Is thus 
 effected almost without labor. It is needless to say that this method 
 of operation tends to batter up and wear out the projectile trucks 
 and is, therefore, opposed by the Ordnance Department. It does, 
 however, have the great advantage of ease and rapidity of service 
 and wiU probably be continued in practice. 
 
 In order to make the ramming of the projectile into the gun as 
 easy' as possible, the breech of the gun in the loading position should 
 be at that height which makes the ramming most convenient. It 
 has been found by experience that the best elevation for manipulat- 
 ing the rammer is when the center of the breech of the gun is about 
 46 inches above the level of the platform on which the detachment 
 stands. Consequently, the elevation of the loading platform when 
 
81 
 
 built is usually so arranged with regard to the other portions of the 
 gun carriage as to make about this difference of level. 
 
 In order to provide for the possible breakdown of trucks, it is 
 usual for the Ordnance Department to furnish several for each gun. 
 This, in addition to providing spare trucks for emergency use, makes 
 it possible to keep several of them loaded and in close proximity to 
 the guns. These trucks when not in use have to be stored away and 
 recesses for this purpose are shown in many of the mimeographs. 
 (See Plates XVI, XVII, and XX.) Usually the truck recesses are 
 located in the parapet wall along the front face of the loading plat- 
 form. In the older emplacements it was not unusual to floor over 
 the wells, which formerly held the balanced platform hoists and to 
 use the recesses thus made for storing the spare trucks. (See Plates 
 XIV and XVIII.) 
 
 A projectile is more or less cylindrical in shape and moving it 
 horizontally by rolling on a smooth surface would naturally suggest 
 itself to anyone. In fact, as will be noted hereafter, rolling the 
 projectiles for a short distance along a floor formed one of the regular 
 stages of the ammunition service of the earliest disappearing em- 
 placements. 
 
 The old-style projectiles with blunt points could be rolled quite 
 easily and when roUed would travel straight with no tendency to 
 change direction. The modern long-point projectile, however, has 
 its center of gravity so far back as to make it somewhat difficult 
 to roU, since any shght obstacle has a tendency to cause it to swing 
 or spin around. 
 
 Rolling projectiles, however, has an important disadvantage. AU 
 projectiles now used are fitted with copper bands to take the rifling 
 of the bore of the gun and thus give the projectile, in its flight, a rota- 
 tion about its axis. This copper band projects from the circum- 
 ference of the shell and if the shell be rolled along a floor or table 
 having a hafd surface the copper band is quite apt to be injured. 
 Consequently, whenever projectiles have regularly to be rolled 
 horizontally, arrangements are usually made so that this motion 
 takes place on rails, imbedded in a table and so spaced that the 
 copper bands will come between the rails and will, therefore, not be 
 damaged as the projectile is roUed. Such an arrangement of rails 
 is made on the receiving and delivery tables of all hoists, and on the 
 service and storage tables in all shell rooms. (Figures 3 and 4, 
 Plate I.) 
 
 Powder cartridges when in the metal cases in which they are 
 shipped and stored can of course be moved by roUing, but this is apt 
 to injure the cases and should be resorted to but seldom. The 
 wooden dummy cartridges of the same size and weight as real powder 
 cartridges, which are sometimes furnished for and used at drills, 
 173341—20 6 
 
82 
 
 can, however, be rolled readily and with impunity. This, though, is 
 not true of the real cartridges which are usuaUy more or less bumpy 
 and soon lose their shape. Consequently, m designing the special 
 hoists intended for raising powder cartridges, it was necessary to 
 build the receiving and delivery tables on quite a slope. 
 
 For moving ammunition horizontally, the method of suspending it 
 from trolleys has many advantages. With properly designed rails 
 and trolleys, friction is very small and the rails, attached as they 
 usually are to the ceilings, are quite out of the way. Of course, these 
 trolley rails should, as a rule, be practically horizontal throughout 
 their whole length; though, where there is a gentle slope to the ceiling 
 and it is in the direction of the main movement, there is no reason 
 why the trolley rails should not also be given a slight slope, provided 
 the slope is not so great as to cause the trolleys to start to roll of 
 themselves. When the trolley rails pass through rooms, galleries, 
 or corridors where the ceiling elevations differ, it is usual to attach 
 them to the lowest ceiling and, in other rooms, to suspend them at the 
 same level by suspension rods attached to the higher ceilings. 
 
 In the earliest form of trolley rail, an ordinary I beam was attached 
 to a flat ceiling by bolts through its upper flange, or suspended by 
 hangers where the ceiling was high. This I beam form of trolley 
 rail had the great advantage that considerable spans could be made 
 with it and when the sections of the I beams used as trolley rails were 
 of considerable length no difficulty was met with in keeping the rails 
 in proper alignment. 
 
 The first forjn of trolley used with the I beam trolley rail consisted 
 of a pair of wheels running on the lower flange on either side of the 
 beam, and held together by a U-shaped yoke hanging down under 
 the beam. Some difficulty was met with in connection with this 
 form of trolley. Each wheel, of course, revolved about its own axle 
 and the two axles had to be held in their proper relative positions 
 by the yoke. Through some faulty construction or for^ some other 
 reason these yokes had a tendency to bend outward and to allow one 
 or both wheels to drop. 
 
 The next form of rail used and the one that has probably been used 
 more than any other is the so-called "Coburn" trolley track, manu- 
 factured by the New Jersey Foundry & Machinery Co. (See figure 6, 
 Plate I.) The Coburn rail is in the shape of an inverted letter fjr 
 with the lips turned inward and upward. The trolley wheels are 
 inside of this rail and roll in the grooves made by the upturned lips, 
 the suspension bars hanging down between the lips. Theoretically, 
 one double trolley wheel might suffice, at least for small loads. 
 But in fortifications no use is made of so simple a form. The simplest 
 form applied to practical uses consists of a pair of double wheels, 
 placed one behind the other and connected by a horizontal bar' 
 
83 
 
 from the center of which is hung another suspension bar. Of course, 
 any weight placed on this suspension bar is transmitted equally to 
 the two double wheels. When a heavier load is to be carried, two 
 suspension bars, each supported by a pair of double wheels, can be 
 brought together and be themselves connected by a longer horizontal 
 bar to the center of which the load can be applied. This method, 
 which transmits the weight equally to four double trolley wheels all 
 in tandem, is the one in most common use in fortifications. 
 
 The trolley rail itself is supported at intervals by hangers some- 
 what similar in general shape to the rail itself, but having in addition 
 upper flanges by which it can be bolted to the ceilicg. (See figure 6, 
 Plate I.) All of the details of this trolley system are shown in the 
 pamphlet issued by the manufactm-er and usually sent to Engineer 
 oflScers upon request. 
 
 This form of trolley rail has the disadvantages, first, of requiring 
 more headroom than the I beam rail because all loads must be 
 attached well below it; and second, of being maniifactured in short 
 lengths only, and therefore somewhat apt to get out of line. On the 
 whole, however, this system has given satisfaction and for some 10 
 years or so was the standard for fortification use, at least in trolley 
 systems consisting merely of a single line of rail or of simple loops 
 only. 
 
 Frequently, however, it is desirable in any trolley system to have 
 switches so that the trolley may be sent over either one of two alterna- 
 tive routes. With the old form of I beam track and with the Cobiu"n 
 tracks also, these switches are somewhat difficult to build so as to 
 make them accident proof, as there is always the possibility of their 
 being turned the wrong way when the trolley arrives. 
 
 This difficulty has been obviated in a new trolley system invented 
 a few years ago by a Mr. James Y. Moore of the firm of Chisholm- 
 Moore Co., of Cleveland, Ohio. This system made use of an ordinary 
 I beam as the trolley rail and of a specially designed "frog" having 
 no movable parts so that it can not get out of order. (See figm-e 7, 
 Plate I.) A 7-inch I beam and frog are used for handling the 12 inch 
 and 14 inch projectiles and an 8-inch I beam and frog for the 16-inch 
 projectiles. The wheels of the trolley, which are very easy running, 
 roll on the lower flanges of the beam, one on each side, and are held 
 together by a well and strongly built yoke. On approaching . the 
 frog, the trolley chain is pulled to one side, the trolley automatically 
 switches to the side toward which the chain is pulled, and takes one of 
 the two branch tracks that make an angle of 24° with each other 
 and of 12° with the line of the main-line track produced. When 
 moving in the reverse direction, the trolley passes easily from either 
 branch track back to the main line. For use with this trolley and 
 frog, Mr. Moore has invented an easy-hoisting differential block and 
 
84 
 
 a new form of telescoping shell tongs which saves considerable head- 
 room, which in magazines is an important item. He has developed, 
 in addition, a new form of fastening, which permits the hold-up 
 bolts to be inserted in the concrete ceiling when poured and yet gives 
 considerable play when the I beam is to be put in place. All of these 
 details are shown in the pamphlet published by the manufacturer. 
 The trolley system has so many advantages that it was adopted as 
 the standard in the Panama and most of the more recent batteries. 
 In designing an emplacement, the layout of the trolley tracks is 
 a subject which shoidd receive more thought than apparently has 
 always been devoted to it. 
 
 In the old mimeograph drawings of gun emplacements, paths for 
 the trolley tracks are shown. These paths pass over the storage piles 
 of projectiles and, of course, over the receiving tables of the hoists, 
 and they sometimes extend to the outer doors, for use with the cranes, 
 and in ammunition supply. (See Plates XV to XX.) Unfortunately, 
 however, they have usually been what may be called "single track" 
 only. That is, when a particular trolley had been used to bring a 
 projectile from the shell room to the receiving table of the hoist 
 it had to be pushed back over the same path before it could be again 
 used. Of course, several trolleys might be used at the same time and 
 they might be manipulated in a gang, being pushed forward and 
 back together, but this inevitably means some loss of time somewhere. 
 To obviate this trouble there was introduced in the 12-inch battery 
 constructed by the writer at Fort Monroe in 1904 and 1905, the policy 
 of laying out the paths of all trolley tracks, or at least the portions of 
 these paths necessary for ammunition service, in loops, so that when 
 one trolley has been used to bring a projectile from the shell room 
 to the receiving table of the hoist, it may be pushed on around the 
 loop and thus not interfere with the use of subsequent trolleys on the 
 same loop. By doing this and by having a sufficient number of 
 trolleys, the shells can be handled at any desired rate. 
 
 The system of laying out all ammunition service trolley tracks 
 in loops is now the standard policy and has not only been introduced 
 in all recent emplacement designs, as will be seen by examining the 
 plans of the Panama batteries both direct fire and mortar, but in 
 many cases has been applied' to the older batteries, the trolley sys- 
 tems of which have been altered. (See Plates XXI to XXVI and 
 XXIX.) 
 
 In addition to the trolley rails necessary in ammunition service, 
 additional trolley rails should be extended to the exterior of the 
 battery for use in ammunition supply. These ammunition supply 
 trolley tracks should extend not only to the doors but should also, if 
 possible, be carried farther so as to pass over the cars or vehicles' in 
 
85 
 
 whicli the projectiles are to be brought to the battery. (See Plates 
 XVIII to XXV.) 
 
 Moving Ammunition Vertically. 
 
 In order to be able to raise heavy projectiles an appliance for 
 seizing hold of them is necessary, and for this pxu-pose projectile tongs 
 are used. For each size of large projectiles the Ordnance Department 
 fm-nishes projectile tongs which work on much the same principle as 
 ice tongs, there being, however, three prongs instead of two, two on 
 on one side of the projectUe and the third on the other, located so as 
 to close between the two. To take hold of a projectile, these tongs 
 are opened wide and are then placed around it as nearly over the 
 center of gravity as can be estimated. The tongs are then closed and 
 clamped and the projectile is ready to be moved. 
 
 With these ordnance tongs, however, several inches of vertical 
 height are lost between the projectile and the eye in which the hook 
 of the chain is inserted. This loss of distance becomes important in 
 some cases where head room is scarce. 
 
 To avoid this trouble and, incidentally, to improve the tongs in 
 other details, the same Mr. Moore who invented the trolley-rail frog 
 mentioned above, invented also a new type of projectile tongs in 
 which the third prong telescopes between the other two when the 
 tongs are opened. These tongs can be used with any form of trolley, 
 but when used with the Chisholm-Moore trolley, for which they were 
 specially designed, they save fully 15 inches of head room, as com- 
 pared with the form of Yale & Towne block and the Ordnance shell 
 tongs which were formerly the standards. 
 
 For raising projectiles short distances, especially in connection with 
 the use of a trolley, and occasionally even for raising projectiles 
 through a considerable vertical height, the appHance most commonly 
 used is a differential block, the friction of which is sufficient to pre- 
 vent the projectiles descending of its own weight but yet is so small 
 as to permit it to be raised or lowered by overhauhng the operating 
 chain without any undue expenditure of energy. 
 
 The old form of Yale & Towne differential or "Triplex" block has 
 for many years been the standard appliance used for this purpose, 
 and stiU is quite serviceable. For places, however, where there is 
 but scant head room, or in new emplacements where the provision of 
 much head room increases the cost of the work the newly-invented 
 Chisholm-Moore differential block has many advantages and has been 
 adopted as the standard in the Panama and other recently con- 
 structed fortifications. 
 
 Of course, in raising projectiles by means of these differential blocks 
 considerable energy must be expended, and the question has been 
 several times considered as to whether or not it would be desirable 
 to install special electric apphances for doing this work. After careful 
 
86 
 
 consideration, however, it has been decided thart; since the distance 
 which the projectiles have to be raised by these blocks is usually not 
 great, the amount of work saved would not be sufficient to compensate 
 for the complications necessarily involved in the installation of electric 
 power. In very exceptional cases where the projectiles have to be 
 raised great distances it might pay to use electrically operated blocks. 
 
 In the interior of the earhest emplacements, where ceilihgs were 
 available for attaching trolley rails, the differential block just men- 
 tioned was the appliance used for raising the projectiles from the 
 floor. Outside of the magazines the platforms were uncovered and 
 troUey rails could not be used, so cranes were substituted. 
 
 These cranes (see figures 1 and 2, Plate II) consisted essentially of 
 a vertical rod or bar, bent at its upper end so as to extend out hori- 
 zontally some 3 or 4 feet. At the outer end of this bent portion 
 there was attached for suspension purposes a ring or hook. The foot 
 of the crane was inserted in a socket or bearing plate, usually some 
 2 feet or so from the foot of the vertical wall, and the crane was 
 held in a vertical position by passing through a coUar in a bracket 
 attached to the upper part of this wall. By rotating the crane about 
 its vertical axis, the suspension ring would describe a circle in a 
 horizontal plane, and this gave articles suspended from it a small 
 horizontal movement. 
 
 The actual hoisting was done by different methods; in some cases 
 a differential block was used, similar to those in the magazines though 
 having a little greater vertical range. In other cases, a regular block 
 and fall was installed, the hoisting line being led to a winch attached 
 to the vertical part of the crane. Sometimes the block and fall 
 would be omitted and a single line would be used for hoisting, passing 
 through a pulley suspended from the ring and thence to the winch. 
 Several of the early mimeographs were devoted to the details of 
 these cranes, but being obsolete, no further reference to them is 
 necessary. When the crane was used for ammunition service in the 
 older emplacements the projectile to be raised was rolled to within 
 reach of the crane, which picked it up and raised it to above the level 
 of the loading platform. The crane was then swung around and the 
 projectile lowered into a projectile truck on the loading platform. 
 
 In the emplacements designed about 1894 to 1896 the crane was 
 an essential portion of the ammunition service provided. Later 
 emplacements were, as a rule, provided with platform hoists or 
 standard chain hoists and the cranes became no longer necessary. 
 However, it continued for several years to be the custom to install 
 cranes as an alternative method of raising projectiles should the 
 regular projectile hoists be for any reason out of commission. They 
 are shown on all emplacement designs issued by the Engineer Depart- 
 ment up to and including the designs for the 14-inch emplacement, 
 
87 
 
 published in 1908 as mimeograpli 109. However, in a few years the 
 projectile hoists showed themselves to be so rehable that the cranes 
 were not used. Later it became the custom not to install cranes in 
 new emplacements, and eventually they were removed from the old 
 emplacements in which they had been installed and were scrapped. 
 
 Cranes somewhat similar in general desigii to those used in emplace- 
 ments were, imtil very recently, installed by the Ordnance Depart- 
 ment for ammunition service in connection with large barbette 
 carriages. The cranes for this purpose were mounted upon the long 
 metal loading platforms attached to and forming part of the rear of the 
 barbette carriages and revolving with the carriages as they moved 
 in azimuth. The actual hoisting was sometimes done by a differ- 
 ential block and sometimes by a windlass. Occasionally, however, 
 where the distance the projectile had to be raised was large, a simpler 
 and somewhat more rapid method of hoisting projectiles was used 
 with these cranes. A block and fall was attached to the suspension 
 ring. The hoisting line, instead of going to the winch on the crane, 
 passed down and through a snatch block at the base of the crane 
 and thence out horizontally. On the level platform around the base 
 of the gun carriage was stationed a gang of from 8 to 12 men who, 
 by seizing hold of the hoisting hne and walking away with it, could 
 rapidly raise the projectile. 
 
 When, by means of a crane, the projectile is raised to the level of 
 the breech of the gun, the crane is swung around so that the point 
 of the projectile is inserted ia the breech. The hoisting line is then 
 gradually slacked away as the projectile is rammed into the gun. It 
 requires considerable care to do this well and quickly. 
 
 The handling of projectiles by means of cranes was somewhat 
 slow, and about 1896 there was substituted for the cranes an apparatus 
 known as the "balanced platform hoist." (See figures 5, 6, and 7, 
 Plate II.) This apparatus consisted of two platforms about 3 
 by 4 feet, operating in two wells a few feet apart. The platforms 
 were connected by means of a wire rope so that one would counter- 
 balance the other and, consequently, as one went up the other would 
 go down. A wire rope was attached to one of these platforms and 
 passed thence up over pulleys at the top of the well, to and around 
 the operating wheels of a winch, up over pulleys at the top of the 
 other well, and thence down to the other platform. The length of 
 the wire cable was supposed to be such that when one of the plat- 
 forms was exactly on the level of the magazine floor, the other would 
 be exactly on the level of the loading platform. By operating the 
 winch, the upper platform would be lowered to the magazine floor 
 and the lower platform would be raised to the loading platform 
 level. 
 
88 
 
 These platforms were made of such a size as to just contam the 
 standard ammunition truck used at that time. (See figure- 1 , Plate I. ) 
 This truck had an upper and central tray for carrying the projectiles 
 and two lower side trays, one on each side, for carrying the powder 
 cartridges. A truck would first be rolled to or near the shell room 
 and a projectile placed on the central tray, thence it would travel 
 past the powder room and the powder would be placed on it. The 
 truck was then rolled on to the lower platform of the platform hoist 
 and, at about the same time, an empty truck would be placed on the 
 upper platform. The winch was operated, raising the loaded truck 
 and bringing down the unloaded one. When the loaded truck 
 reached the loading platform level, it would be rolled out for service 
 to the gun and at the same time the empty truck would be rolled 
 out on the magazine floor for loading. Since the platforms exactly 
 balanced each other, as did the trucks, the net weight to be moved 
 in any case was merely that of the ammunition. 
 
 These winches were intended to be operated normally by an electric 
 motor, but arrangements were made so that,'in the absence of electric 
 power, the winch could be operated by hand. 
 
 When new, the platform hoists worked quite well, but unfortu- 
 nately, as they began to wear and the wire ropes stretched, it seemed 
 to be almost impossible to keep the lengths of the ropes properly 
 adjusted, and if this were not done, the platforms would not come to 
 the level of the floors at the same time which made it somewhat 
 difficult to roll the trucks on or off the platforms. 
 
 In the meantime, however, several officers had been experimenting 
 with continuous chain hoists. Such a hoist (see figures 1 and 5, Plate I) 
 consists essentially of two exactly similar sprocket chains, formed into 
 loops of the same length. The upper bends of these two chains pass 
 over and are supported by two exactly similar sprocket wheels fas- 
 tened to the same axle which is supported by a frame work on the 
 upper level of the emplacement. The loops of the chains, of course, 
 hang down and in the lower bends of these loops are hung two exactly 
 similar sprocket wheels, likewise attached to an axle. This axle 
 fits into bearings in two side frames and has on it, in addition to the 
 sprocket wheels, a gear wheel, geared up with the other wheels of a 
 winch. By working the mechanism of the winch, the lower sprocket 
 wheels are turned, thus causing one part of each chain to go up and 
 the other to go down. At intervals along these chains, and at the 
 corresponding links of the two chains, are attached carriers which, 
 of course, go up and come down with the chains. As the carriers 
 are moved up they pass through slots in a specially designed table 
 called the receiving table and pick up from this table the ammunition 
 which is to be raised. This ammunition they carry up and eventually 
 
89 
 
 deliver to an especially designed table called the delivery table, which 
 is located on the upper level of the emplacement. 
 
 The detailed drawings and descriptions of the different chain hoists 
 which from time to time have been developed, as well as instructions 
 for their care and operation, have been published by the Engineer 
 Department in Mimeograph 46, its different supplements, and the 
 drawings accompanying them. To correctly understand all the details 
 of the hoists an examination of these mimeograph drawings will bo 
 necessary, but outline drawings showing the general principles are 
 given in Plate I. 
 
 There are two essentially different classes of these hoists known as 
 the front delivery and the rear delivery tjrpe. In the front delivery 
 hoist, the lable upon which the ammunition is delivered by the carriers 
 is practically directly over the receiving table from which the ammuni- 
 tion is taken up. In the rear delivery hoist (figure 5, Plate I), the 
 ammunition is carried over the axle of the top sprocket wheel and 
 is delivered on the opposite side of this axle, and therefore of the 
 hoist. 
 
 The choice of the words "front," and "rear" or "back," to dis- 
 tinguish these two classes of hoists, is unfortunate, because, in almost 
 all other phases of fortification work the words "front" and "rear" 
 have special techinical meanings. The word "front" always means 
 the direction toward the enemy and the word "rear" the direction 
 away from the enemy. 
 
 Fortunately, however, in this particular case, the use of the words 
 "front" and "back" has not, and probably will not, cause much 
 confusion, because the front delivery hoists soon became obsolete. 
 They were intended for use in a type of emplacement designed before 
 the invention of the hoist. (See Plate XV.) Shortly after its inven- 
 tion, this type of em.placement was discarded and no others were 
 built. All subsequent emplacements were designed for the rear 
 delivery hoist and all the designs have been such that the delivery 
 tables of these hoists actually point toward the rear of the emplace- 
 ment. 
 
 There are three general types of hoists that have been used. In 
 the first, the load is carried by bracket carriers held out nearly hori- 
 zontal from the chains by means of wheels rolling in guides. (Figure 1 , 
 Plate I.) In the second, which is very similar to the first, the carriers 
 are pushed up by the chains from below and have to be moved in 
 grooves or guides to keep them from turning over. In the third type, 
 the carriers are hung from chains, and being, therefore, in a position 
 of stable equilibrium, grooves or guides are not necessary. (Figure 5, 
 Plate I.) The first two types, which are very similar, are known as 
 the Hodges types, they having been developed by Capt. (now ^[aj. 
 Gen.) Harry F. Hodges, Corps of Engineers. The third type is 
 
90 
 
 known as the Taylor-Kaymond hoist, from the two engineer officers 
 -who were specially concerned in its development, Capt. (now Brig. 
 Gen.) Harry Taylor and Capt. (now Lieut. Col.) R. R. Raymond. 
 
 The first type was used in the 6-inch and 8-inch emplacements; 
 .the second, in the 6-inch, 8-inch, and 10-inch emplacements; the 
 thhd, in all sizes of emplacements up to and including the 14-inch. 
 
 All of these types are readily adapted to rear delivery. The second 
 type was also eas-ily adaptable to front delivery, the carriers, as they 
 approached the delivery table, being forced by their grooves to move 
 out toward the table and to roll or push the projectiles thereon. As 
 the chain continued upward the carrier then fell down in an inverted 
 position and in that position passed over the upper sprocket wheel 
 and down the descending part of the chian. As it passed around 
 the loop at the bottom of the chain, the carrier was pushed back into 
 its proper position. 
 
 The adaptation of the third, or Taylor-Raymond, type of hoist to 
 front dehvery was somewhat awkward, as will be noted from figure 
 2, Plate I. In this type of front-dehvery hoist, the receiving table 
 is placed on the side of the winch on which the chains descend and 
 is made very low. As the carriers ia their descent approach the 
 receiving table, they are thrown out horizontally by guides and as 
 the chain continues around the lower sprocket wheel the carriers 
 by a sort of scoop motion draw the projectiles into themselves. In 
 order that a projectile may be scooped up from the receiving table 
 it must be in exactly the right place at the right time, and to insure 
 this there is an escapement, operated by stops on the chain, which 
 permits the projectile to roU into this position only at the proper 
 moment. 
 
 The receiving tables of the hoists are ordinarily built so as to be 
 about 3 feet or shghtly more above the floor, as this has been found 
 to be a very convenient height. (Figures 4 and 5, Plate I.) The 
 dehvery table (figures 1, 3, and 5, Plate I) is located on the loading 
 platform level and its elevation has to be carefuUy adjusted to that 
 of the projectile tray of the ammunition truck, the height of which 
 is governed by the elevation of the breech of the gun above the load- 
 ing platform level. As the projectile is delivered by the hoist upon 
 the dehvery table, it rolls to the rear untU it comes against the buffers 
 of an escapement. When an ammunition truck is in proper position 
 just in rear of this escapement (figure 1, Plate I) the escapement 
 is operated, allowing one projectile and one only to roll from the 
 delivery table to the shell tray of the truck. When the elevation 
 of the dehvery table has been properly adjusted, the edge of the shell 
 tray of the truck should be a very small fraction of an inch below the 
 rear end of the rails of the dehvery table. 
 
91 
 
 AE the types of continuous chain hoist have been fitted with electric 
 motors for operation by electric power and this is supposed to be 
 the normal method of using them. For emergency use, however, 
 in case the electric power should fail, cranks have been provided for 
 iand operation, although, of course, at much less speed. The normal 
 <5hain speed for electric operation is at the rate of about 25 or 30 feet 
 a minute and the carriers are usually spaced so that five or six carriers 
 pass both the receiving table and the dehvery table each minute. 
 As originally designed, it was expected that one carrier would take 
 the projectile and the two succeeding carriers, the powder cartridges 
 to fire this projectile, so that two full charges could be dehvered by 
 a hoist in about a minute. Later, when it was found to be somewhat 
 dangerous to raise both powder and projectiles by the same hoists, 
 all of the carriers of the hoist became available for handling pro- 
 jectiles. It was then found possible to spread the carriers a httle 
 farther apart and to reduce the chaia speed, still deliveriag projectiles 
 at a rate of not less than three per miaute. This, for large guns, is 
 faster than they can be fired. The 6-inch projectiles can be sent 
 up at a rate of from six to eight per minute. 
 
 Hand operation is, of course, much slower but it has been found 
 that four men, two to each crank, can without undue fatigue raise 
 12-inch projectiles faster than, under ordinary circumstances, they 
 can be fired, provided the men are reMeved every few minutes. 
 
 The projectile hoist is ordinarily worked by electricity and it is the 
 duty of the detachment at the receiving table on the lower story to 
 feed the projectiles rapidly to the hoist. These men, of course, can 
 not see and can not know the rapidity with which the projectiles 
 are being removed from the dehvery table above, and there is, there- 
 fore, danger of the projectiles being sent up faster than they are 
 used. In this case the dehvery table wiQ soon become filled and, if 
 filled, a projectile coming up on a succeeding carrier and not finding 
 a place on the dehvery table would be hable to be pushed off and fall 
 down through the hoist well. Of coTirse it is the duty of the detach- 
 ment at the dehvery table to prevent this by having the hoist stopped. 
 This can be done by calling down through the hoist well, but as there 
 might be so much noise and confusion that the call would not be 
 heard, an arrangement is made so that they can, themselves, stop 
 the hoist. There is installed alongside of the dehvery table on the 
 upper level a small electric switch, which, when opened, automatically 
 stops the electric motor operating the hoist. The hoist can not be 
 started again until the upper switch is closed. This will be again 
 referred to in the chapter on electrical installation. 
 
 In aU emplacements built up to about 1908, but one projectile 
 hoist was installed, the cranes being rehed upon as a reserve or 
 emergency means of raising projectiles shoidd the hoist become 
 
92 
 
 disabled. An additional precaution, however, the 1908 design for 
 the 14-inch emplacements (mimeograph 109, Plate XXII) provides 
 two hoists for each emplacement. 
 
 The second projectile hoist was provided not only as a spare in 
 case the first one should get out of order, but for the following reasons : 
 It was expected that the Ordnance Department would supply for 
 each caliber of gun at least two kinds of sheU, either shells of different 
 weight or an ordinary shell and a high explosive shell. It might 
 happen in the midst of an action that it would become desirable to 
 change from one type of projectile to another. With but one hoist 
 it would be difficult to make such a change, for until aU of the pro- 
 jectiles of the old type then en route to the gun had been disposed of, 
 either by firing them or laying them aside, the projectiles of the new 
 type could not begin to arrive, since they would have to pass through 
 all the stages of ammunition service up to the gun. With two hoists 
 in operation, two different kinds of projectiles could be on the way 
 to the gun at the same time, or the action might be started with the 
 dehvery table of one hoist filled with one kind of projectile and the 
 dehvery table of another hoist with another kind, so that the change 
 from one type of projectile to another could be made practically 
 instantaneously. 
 
 To provide an arrangement of this general character in an old 
 battery where but a single hoist is in use, there was experimentally 
 provided at Battery De Eussy, Fort Monroe, in 1905, an additional 
 "double dehvery table." This double dehvery table was placed 
 immediately in rear of the regular dehvery table of the hoist and had 
 two sections, each holding four projectiles, and could be rolled from 
 one side to the other so that either section of the special double 
 dehvery table would be in rear of the regular dehvery table. One 
 section would be kept in rear of the hoist and would be in constant 
 use, the projectiles being rolled from the regular hoist delivery table 
 right along to the special delivery table as fast as they could be 
 received. The other section would be kept to one side in reserve. 
 
 It was assumed that an action would be started with both sections 
 of the double dehvery table fiUed or partially filled, one with one kind 
 of projectile and the other with another kind. If the action was to be 
 started with one kind of projectile, the section of the double dehvery 
 table containing that particular kind of projectile would be moved 
 in rear of the hoist, and that kmd of projectile would be the one sent 
 up by the hoist and the one carried to the gun. If the order came to 
 change, projectiles of the new type would be taken from the other 
 section .of the dehvery table untU that type of projectile began to 
 come up on the hoist. Then the table would be shifted and the new 
 type of projectiles as they came up would be passed right along the 
 delivery table to the truck. 
 
93, 
 
 This double delivery table was used for some four or five years, but 
 it was finally decided to be unnecessary and was discarded and 
 scrapped. Since all modem batteries of the two-story type are 
 provided with two hoists, it is not probable that the construction 
 of another double dehvery table will ever be necessary. 
 
 In one of the earlier designs for 6-uich barbette rapid-fire emplace- 
 ment (mimeograph No. 40), it was considered desirable that a deliv- 
 ery table holding a greater number of projectiles should be provided 
 and quite a complex form of such table was shown in the drawings. 
 (See figures 3 and 4, Plate II.) First there was the ordinary delivery 
 table immediately behind the hoist and provided with the usual 
 escapement; immediately in the rear of the escapement, and running 
 from side to side on a track was a transfer car, to which projectiles 
 could be delivered by the proper working of the escapement. This 
 transfer car would hold six projectiles, and when in its position im- 
 mediately in the rear of the delivery table, these projectiles could be 
 rolled right across it, to the middle section of a thi-ee-soction reserve 
 table. However, by fiUuig the transfer car and then by moving it to 
 the right or left on the rails set in the platform for the purpose, it could 
 be placed immediately in the rear of the right or of the left section 
 of the reserve table. 
 
 From the reserve table the projectiles were to be taken by hand 
 to the gun or were to be carried on a special form of truck to a posi- 
 tion more nearly in rear of the gun. Since each section of the re- 
 serve table would hold 12 projectiles, the transfer car 6, and the 
 delivery table at least 3, not less than 45 projectiles could be con- 
 veniently stored on this complicated apparatus. 
 
 As far as is known, however, no battery of the particular type for 
 which this table was designed was ever constructed, and it is prob- 
 able, therefore, that no triple reserve table was ever used. 
 
 As has been stated, the projectile hoists are designed to be operated 
 normally by electric power, and in case this power gives out, then by 
 hand. 
 
 As an additional precaution, arrangements are usually made for 
 storing a few projectiles in niches on the loading platform level. 
 Provisions for doing this were frequently made by constructing 
 ofl&cers, although not shown in the mimeograph designs. However, 
 in mimeograph 109, published in 1908, and showing designs for 14- 
 inch emplacements (Plate XXII), niches on both faces of the para- 
 pet are shown, each containing small emergency storage tables for 
 projectiles. These storage tables are provided with the same form 
 of escapement as the dehvery tables of the hoists and the projectiles 
 can be moved from them to the shell trucks exactly as from the 
 delivery tables. By storing projectiles of different kinds on these 
 different emergency tables, a rapid change of projectiles during an 
 
94 
 
 action can be made quickly and easily. Later, during a lull in the 
 engagement, the tables can be filled again. To fill them the pro- 
 jectiles are carried on the regular truck to the emergency storage- 
 tables and are rolled on to the tables by reversing the regular action; 
 of the escapement. 
 
 When the ammunition hoists are used, the projectile, when once 
 elevated in the shell room by the block on the trolley to about the- 
 level of the receiving table of the hoist, is moved the rest of the way 
 to the breech of the gun with but little expenditure of humian energy,, 
 none being needed at any stage to raise the projectile higher. How- 
 ever, in raising the projectile from the floor to the level of the re- 
 ceiving table, considerable human energy must be expended. This; 
 was especially true in the older batteries where the supply of ammu- 
 nition normally kept on hand was so small that the piles of pro- 
 jectiles were ordinarily but one tier high and never more than two. 
 
 In order to reduce the amount of labor necessary in raising the 
 projectiles up to the. level of the receiving table, there were tried ex- 
 perimentally in Battery Parrott, Fort Monroe, hoists with what 
 were called "depressed" receiving tables. The winches and lower 
 portions of the hoists, instead of being set upon the magazine floor 
 level, as is usual, were placed in pits slightly below the magazine' 
 floor and slight modifications were made in the design of the receiv- 
 ing tables so that they were at the level of the floor. The pits ex- 
 tended along the sides of the receiving table so that the men working 
 there would not have to stoop so low. 
 
 In this battery, therefore, a projectile stored upon the floor of the 
 shell room may be rolled all the way along the floor to the receiving 
 table. If the projectiles be stored on skids, all that is necessary is 
 to raise it with the troUey hoist just far enough to clear the skid, 
 and to then push it horizontally and lower it a few inches to the re- 
 ceiving table. In other words, in ammunition service, with this 
 style of hoist, no raising of the projectile has to be done by human 
 energy. 
 
 Apparently this new design should have worked well, but it was 
 finally decided by the officers concerned that the labor of stooping 
 over and handling projectiles on or near the floor was more fatiguing 
 than to raise them up to the usual receiving table level. This type 
 of hoist was, therefore, never used again. 
 
 In the 1908 design for 14-Lach emplacements (mimeograph 109, 
 Plate XXII), the trouble encomitered in raising the projectiles was 
 avoided by building for them in the shell rooms long storage tables, 
 the levels of which were exactly the same height as the receiving 
 tables of the hoists. In this type of emplacement two projectile 
 hoists were provided and, immediately to the front of each receiv- 
 ing table, a storage table. By means of removable sections of rails, 
 
95 
 
 the storage tables can be made practically continuous with the re- 
 ceiving tables, so that, if desired, projectiles of the first tier can be 
 roUed all the way from the storage tables to the receiving tables. 
 Should there be suflficient projectiles to require storage in two tiers,, 
 removable rails were to be provided which could be placed upon the 
 top of the first tier, and a removable receiving table was also pro- 
 vided, so that the projectiles of the second tier could likewise be rolled 
 all the way to the removable receiving table. 
 
 In this system of ammunition service, the trolley in the shell room 
 is not essential in ammunition service, although it is very useful in 
 ammmiition supply or later for shifting projectiles from one place to 
 another. It could also be used in ammunition service as an alter- 
 native to the rolling of the projectiles if foimd more convenient. 
 
 The operation of raising projectiles with the differential blocks 
 is quite fatiguing if done rapidly, but is not especially so when done 
 slowly. In order, therefore, to obviate the necessity of operating 
 the differential blocks rapidly, it has become the custom to install 
 at the service end of shell rooms what may be called "service" 
 tables. These service tables are of the same height as the trays of 
 the projectile trucks and are fitted at the service end with escape- 
 ments, similar to those at the end of the dehvery tables of the hoists, 
 so that projectiles can be rolled right from the service tables into the 
 trays of the trucks. 
 
 An arrangement of this kind was first shown in the 1906 type of 
 mortar battery, supplement to mimeograph No. 27 (see figure 7, 
 Plate XXVIII), and since that time they have become a standard 
 fitting for mortar battery shell rooms. 
 
 Similar tables sufficiently large to hold eight projectiles each were 
 designed to be installed ui the shell rooms of aU the Panama heavy 
 direct-fire guns. In these batteries the loading platform is on the 
 same level as the floor of the magazine, and, consequently, hoists are 
 not needed for ammunition service. The projectiles are rolled 
 directly from the tables at the service end of the shell rooms to -the 
 trucks and are carried by the trucks to the guns. In all cases, both 
 in the mortar batteries and the Panama type of battery, it is ex- 
 pected that an action should find the service tables fiUed with pro- 
 jectiles. As these are fired away, they are to be replaced from the 
 piles of projectiles in the rear, but as several trolleys and their blocks 
 can be used simultaneously, the work of raising the projectiles should 
 not be exhausting. 
 
 A still handier method of storing projectiles is shown in the de- 
 signs of the Panama mortar batteries (Plate XXIX). In this case 
 the ceilings of the shell rooms are made quite high and the floors, 
 except near the doors, are raised between 2 and 3 feet above the floors 
 of the entrance galleries, that is, to such a level that the second tier of 
 
96 
 
 projectiles stored on these floors is at exactly the same height as the, 
 projectiles resting on the service tables. In moving the projectiles 
 from the shell rooms proper to these service tables, therefore, the 
 third and fourth tier of projectiles would have to be lowered in 
 placing them on the service tables, the second tier would have to be 
 moved practically horizontally, and the first tier only would have to 
 be raised by an amount equal to their own diameter plus the thick-, 
 ness of a projectile skid. 
 Powder Service. 
 
 When the balanced platform hoists were used, the trucks raised 
 by these platforms carried both the powder and projectile. When 
 these platforms were replaced by the endless chain hoists it was but 
 natxu-al that the hoists should also be expected to carry up the powder 
 as well as the projectiles, and, consequently, the early hoist drawings 
 show one carrier raising a projectile and the two following carriers 
 the powder. This powder charge is shown as consisting of four car- 
 tridges, two of which were carried by a single carrier. (See Gg. 1, 
 Plate I.) The dummy drill cartridges worked very well with the 
 hoists, but when actual powder cartridges were used, it was found 
 that they did not roll down the gentle slope of the delivery table as 
 readily as did the projectiles, and, therefore, had a tendency to choke 
 up this table at its front end. It therefore became necessary to 
 stop using these hoists for raising powder and to use them for pro- 
 jectiles only. 
 
 The next step was to build separate powder hoists. Three types 
 of these were d,ev eloped for use under different circumstances, and 
 many were installed in different large batteries throughout the country. 
 
 Of these three types of powder hoist, the most successful was some- 
 what similar in its general characteristics to the Taylor-Raymond 
 projectile hoist, except that the cari'iers consisted of loosely hanging 
 canvas bags, which were hoisted on a slope of about 30° or 40° in- 
 stead of vertically, as in the projectile hoists. To insure that the 
 cartridges would roll out of the way as soon as they reached the de- 
 livery table, this table was built on a very decided slope. 
 
 'However, after powder hoists had been installed in many bat- 
 teries, it was decided that it was not advisable to use them. It had 
 already been found that the carrying of powder from the delivery 
 table of the hoist to the' gun on the same truck as the projectile was 
 not very convenient. This part of the powder service was performed 
 by men carrying the cartridges on their shoulders, the trucks being 
 used for projectiles only. Shortly afterwards there was introduced 
 for carrying the powder a sort of handbarrow carried by two or four 
 men and which could hold all of the cartridges at once. The next 
 step was to do away entirely with the powder hoist and to have the 
 powder carried on these handbarrows or by hand all the way from 
 
97 
 
 the powder magazine on the lower level up to the loading platform 
 on the upper level. 
 
 This is the standard method now in use and is, of course, equally 
 adaptable to the use of the single cartridge charge. Whether or not 
 it will be continued with the new proposed long 16-inch cartridge re- 
 mains to be seen, but it is the opinion of the author that before long 
 some special foijm of 16-inch powder truck will have to be developed. 
 
 As showing the general character of the anmiunition service pro- 
 vided in the modern battery, I quote from the letter submitting to 
 the Chief of Engineers the plans for two of the 14-inch Panama 
 batteries : 
 
 In the ammunition service proper of these batteries, hoists are not to be used. 
 Each gun has its own.double-shell room on the same level as the loading platform, and 
 each double-shell room has two shell tables, so that two classes of projectiles can be 
 kept available for instant use. Each shell table is large enough to hold eight projec- 
 tiles, while in the rear of each a total of about 63 projectiles may be easily piled in not 
 more than three tiers, so that 142 projectiles for each gun can be conveniently stored; 
 nd by placing the projectiles closer together this number can be increased to 172, and 
 by using a fourth tier still more can be stored. As the projectiles are vssed from the 
 shell table, others are to be placed on the shell table by trolleys from the piles in the 
 rear. 
 
 The powder magazine of each battery has a capacity of 140 charges (four cartridges 
 in each) stored in racks, five cartridges high. By making use of four tiers only, a total 
 of 112 charges can be stored. It is expected that those stored in the fifth tier will be 
 moved to the lower tiers in the racks during lulls in the engagement. 
 
 As the use of the fifth tier of cartridges may prove inconvenient, it has been consid- 
 ered necessary to provide additional powder storage, which has been provided in one 
 long room on the left side of the right traverse of Battery Bumside, this now being in- 
 tended as a reserve poWder magazine for all four of the 14-inch gims, the powder 
 beiag removed from this reserve magazine to the regular powder magazines during 
 intervals in an engagement. 
 
 OTHER MOVEMENTS OF AMMUNITION. 
 
 In addition to the moving of ammunition necessary in ammunition 
 supply, such as carrying the ammunition into the magazine, and, in 
 ammunition service, taking it from the magazine to the gun, it is 
 sometimes desirable to move it at other times. 
 
 Where this is merely a question of rearranging the projectiles or 
 powder in the shell room or powder magazine, no special arrangements 
 are necessary; the same appliances which were used for getting the 
 ammunition into the magazine, such as the trolley rails and trolleys, 
 being available likewise for shifting it around. 
 
 There occurs, however, in certain batteries, an intermediate stage 
 in ammunition storage when the movement of the anmiunition be- 
 comes necessary. 
 
 In the early emplacements, when the amount of ammimition which 
 it was considered should be kept on hand was not large, it was ex- 
 pected that all of this ammunition would be kept in storage under 
 173341—20 7 
 
98 
 
 conditions which would make its service to the gun rapid and easy. 
 More recently, however, the allowance for ammunition has been 
 much increased. All storage space is expensive, and it has, in some 
 cases, been considered unnecessary to go to the extra expense of 
 making the magazines and shell rooms of these batteries so large that 
 all of this enlarged supply of ammunition may be kept in what may 
 be called "service storage." . ' 
 
 This condition arose specially in two of the batteries in the Panama 
 fortifications. (See Plate XXV.) Here only half of the ammunition 
 supply is kept in service storage. For each of the guns in each of 
 these batteries there are upper magazines and upper shell rooms on 
 the same level with; the loading platforms and in which are kept the 
 ammunition that is ready for instant service. Immediately below 
 these and on a lower floor are magazines and shell rooms of prac- 
 tically the same size as those above but in which the ammunition is 
 supposed to be kept only in what maybe called "supply storage." 
 
 During an engagement, ammunition will be taken, of course, from 
 the upper or service magazines, and the supply kept there is much 
 greater than can ever be used in a single engagement. In the inter- 
 vals between an engagement, it is intended that the ammunition 
 taken from the upper or service magazines and used in the engage- 
 ment will be replaced by bringing up ammunition from the lower or 
 supply magazines. 
 
 This movement of the ammunition from the supply to the service 
 magazine, which is to be done between engagements, or possibly 
 during an engagement, by the surplus men of the detachment, is. one 
 in which no haste is necessary and consequently the hoists need not 
 be very rapidly moving. Those actually installed are comparatively 
 simple, are operated by electrical means, and raise the ammunition 
 through openings extending from the floors of the upper magazines 
 to the ceilings of the lower ones. Since the conditions in these bat- 
 teries are quite unique, this apparatus can hardly be considered 
 standard and no special description is necessary here, but the draw- 
 ings of this apparatus can doubtless be obtained by officers who may 
 have need for them. 
 
 Another movement of ammunition which quite frequently becomes 
 necessary is sending back to the powder and shell rooms, ammunition 
 which has not been used. In action, of course, all the ammunition 
 taken to the gun presumably will be fired, though there may at the 
 end of an engagement be a small amount to be returned. In drill,, 
 however, the ammunition is not fired and, therefore, has to be 
 restored to the magazine. 
 
 Consequently, all the modern projectile hoists have been so de- 
 signed that not only can the projectiles be raised from the magazine 
 to the loading platform, but so that they can likewise be taken back 
 
99 
 
 from the loading platform to the magazine level. 7n the Hodges 
 hoist this was an operation requiring considerable care, but in the 
 Taylor-Raymond rear-delivery hoist it can be done quite readily, 
 the projectile being pushed out on the fingers of the delivery table 
 so that the carrier moving in the reverse direction can pick it up 
 and carry i* over and down to the receiving table. As soon as it 
 rests on the fingers of the receiving table, it has, of course, to be 
 rolled back on this table. If this is not done, the next carrier as it 
 descends will be caught on this projectile and trouble may result. 
 
 In order to avoid such trouble, the mechanism of the winch of the 
 hoists is so made that though the hoists may be operated for raising 
 projectiles either by electricity or by hand, they can be used by 
 hand only in the reverse direction for lowering projectiles. The 
 lowering by hand is, of course, quite slow; the men operating the 
 handle are close to the receiving table of the hoist and are easily 
 able to look out and see that the projectiles are moved out from the 
 fingers of the receiving table as fast as they are delivered there by 
 the descending carriers. 
 
 In the early days, as was stated, it was intended that these am- 
 munition hoists should be used, not only for raising projectiles, but 
 also for raising powder, but among the instructions issued for the 
 operation of these hoists was one to the effect that they should never 
 be used for lowering powder, and there was an appliance attached 
 to the frame of the upper sprocket wheel which made it impossible 
 for this to be done excepting by improper manipulation. 
 
 The actual powder cartridges are so delicate as not to stand very 
 much handling. Consequently, it is customary at drill not to use 
 actual powder cartridges, but to use dummies of essentially the same 
 size and shape. These, of course, can stand more or less rough han- 
 dling, but in order that the detachment might not get in the habit of 
 sending these dummies back to the magazines by the hoists, and 
 later inadvertently do the same thing with actual powder cartridges, 
 the attachment mentioned was added to the hoist so as to prevent 
 the powder dimmiies, which are of somewhat greater diameter than 
 the projectiles, from being sent backward over the sprocket wheel. 
 
 The development of special powder hoists was made several years 
 after the introduction of projectile hoists, and only after several 
 occurrences had shown the danger of using the same hoist for powder 
 and projectiles. When the design of these powder hoists was under- 
 taken, some method of getting the powder back to the magazine was 
 considered desirable. Consequently, several of the types of powder 
 hoists were provided with chutes by means of which dummy car- 
 tridges, and for that matter genuine cartridges also, coidd, if desired, 
 be returned to the magazine. A rough outline of such a chute is 
 shown on sheet 3 of the drawings accompanying mimeograph 109. 
 
Chapter VI. 
 
 BATTERIES AND EMPLACEMENTS, GENERAL 
 
 DESIGN. 
 
 In its most common use in connection with military' matters the 
 word "battery" is a tactical expression and means a complete 
 Artillery unit. In Field Artillery the battery consists of the ofl&cers, 
 enlisted men, horses, a definite number of guns, and the equipment 
 pertainiug thereto. In fixed Artillery, of course, the horses are 
 omitted and the battery, considered as a perspnnel unit, is not in all 
 cases definitely assigned to any particular guns. 
 
 By extension, the term "battery" is frequently applied to a group 
 of guns mounted in emplacements which are so located as to form a 
 convenient tactical unit. 
 
 Unfortunately, in assigning troops to guns mounted in fixed 
 emplacements, the battery considered as a personnel unit has not al- 
 ways been assigned so as to accord with the battery considered as a 
 group of guns. Usually this has been done, but occasionally a 
 battery (personnel) has been assigned to two or more batteries of 
 guns, and less often, two or more batteries (personnel) have been 
 assigned a single battery of guns. 
 
 The word "emplacement" is a structural term only and refers to 
 so much of a battery (of guns) as pertains to any one gun; that is, 
 the gun block, loading platform, parapet, magazines, storerooms, etc. 
 
 Since, with smaller guns, the battery usually consists of more 
 than one gun, an emplacement is generally part of a battery. Occa- 
 sionally, however, especially where the gun is a very large one, the 
 battery consists of but a single emplacement, and in such a case the 
 term "battery" may be used structurally as essentially synonymous 
 with the term "emplacement." 
 
 In designing an emplacement it is desirable that it should be 
 known in advance whether or not the gun to be mounted therein is 
 to form a tactical battery of itself, or is to be united with another 
 gun or group of guns to form a tactical battery, because the best 
 arrangement of observation stations, plotting rooms, the duct sys- 
 tems, speaking-tube communications, and other matters connected 
 with fire control depends upon this fact. 
 
 Occasionally what is structurally a single battery, designed to be 
 so used tactically, has for tactical reasons arising subsequently been 
 subdivided into smallesr batteries. Thus, at the time of or prior to 
 
 (101) 
 
102 
 
 the Spanish War it was customary to consider 16 mortars as forming 
 a tactical unit and, consequently, the mortar batteries then started 
 were designed with this understanding. Since that time tactical 
 reasons have required these older batteries to be divided tactically 
 into two batteries of eight mortars each, and this in turn has 
 required quite a number of changes in the provision for the fire-control 
 system, etc. 
 
 EMPLACEMENTS. 
 
 The principal purpose of a gun emplacement is to provide a firm 
 and unyielding support for the gun and carriage and convenient plat- 
 forms and passageways for the personnel, so that the gun may be 
 loaded, manipulated, and fired with the greatest amount of ease and 
 the maximum speed possible. It should also give to the armament 
 and to the personnel as rnuch protection as may be possible from the 
 fire of the enemy and from the action of the elements. It should 
 provide a safe and convenient storage place for the ammunition and 
 other supplies pertaining to the gun, and should, to such an extent 
 as may be possible, provide for the comfort and convenience of the 
 personnel. 
 
 It is evident that in its general characteristics an emplacement 
 must be' a compromise. For instance, we can make the parapet of 
 the emplacement sufficiently thick and sufiiciently high to furnish 
 complete protection to the personnel, armament, and ammunition, 
 but this can be done only by sacrificing the usefulness of the gun 
 by reducing the field of fire. Furthermore, it has generally been 
 found that, as we increase the thickness of the walls, and therefore 
 the protection afforded to the magazines against the enemy's fire, 
 we increase the difiiculties due to condensation of moisture. 
 
 Perhaps more important still, the question of cost must always be 
 considered. The appropriations applicable to the construction of 
 gun emplacements have always been and probably always wUl be 
 small, and the necessity of getting as much as possible out of every 
 dollar requires that we seek general efl&ciency rather than absolute 
 perfection in any one detail. Consequently, in designing an emplace- 
 ment all the functions that it must fulfill must receive consideration 
 and undue attention may not be given any one function. 
 
 Types of Emplacements. 
 
 The general character and type of an emplacement necessarily 
 varies greatly according to the size of the gun to be mounted therein, 
 the type of carriage upon which the gun is to be mounted, the char- 
 acter of fire which it is expected to bring to bear upon the enemy, and 
 the extent of the field of fire. 
 
 In designing the details of any gun emplacement it must always 
 be remembered that the emplacement is intended to provide rapid 
 and efficient service for the gun and that the gun is not merely an 
 
103 
 
 excuse for the existence of the emplacement. Consequently, aU of 
 the details of an emplacement must be given careful consideration 
 and must be so designed as to make the service of the gun as rapid, 
 as easy, and as efiScient as possible. Unfortunately, it has frequently 
 occurred in the past that the designers of a gun carriage have made 
 no effort to keep in view the engineering requirements of the emplace- 
 ment and have introduced features which gave considerable trouble 
 to the Engineer Department, even where, with slight modifications 
 which would have served the ordnance requirements equally well, 
 other features could have been used which were much better adapted 
 to the engineering needs. Fortunately, in more recent times this 
 trouble has to a great extent been avoided by a closer haison between 
 the proper branches of the Offices of the Chief of Engineers and the 
 Chief of Ordnance. 
 
 The Ordnance Department prepares the drawings of the gun 
 carriages and of the guns and it is for the Engineer Department to 
 make its designs of gun emplacements conform to the gun carriages 
 designed by the Ordnance Department. Under present arrange- 
 ments, before the Ordnance Department definitely decides upon the 
 more important details of the gun carriages which may affect the 
 engineering features, the Chief of Ordnance usually sends to the 
 Chief of Engineers prints of these designs in a preliminary shape. 
 These preliminary drawings are criticised in the Office of the Chief of 
 Engineers and, in a number of cases, modifications in the Ordnance 
 drawings have been made at the request of the Engineer Department, 
 The Engineer Department has been called upon in recent times to 
 provide emplacements for guns less than 3-inch in cahber, for 3, 4, 
 4.7, 5, 6, 8, 10, 12, 14, and 16 inch guns. These gims have been 
 mounted on carriages of several different types which may be classi- 
 fied as follows : Portable mounts, barbette mounts, masking mounts, 
 disappearir^ mounts, antiaircraft mounts, mortar mounts, gun-hft 
 mounts, turret mounts, and railroad mounts. The emplacements 
 which are buUt by the Engineer Department must, of course, be 
 suited to the type of carriage on which the guns are to be mounted. 
 
 All of these terms designating the types of gun carriages explain 
 themselves except perhaps the masking mount. This was a modifi- 
 cation of the barbette mount, formerly used for comparatively small 
 guns only — that is, guns up to and including the 5-inch. The gun was 
 attached to the top of a pillar operating ia a well. When the gun 
 was to be fired this pillar was raised and locked in the elevated posi- 
 tion. The gtui was then operated essentially as if it were on a bar- 
 bette mount. When, however, the gun was not in use, the pillar 
 could be lowered into the well, at the same time raising a counter- 
 weight, and the gun would drop down into a niche in the parapet and 
 would be hidden from sight. 
 
104 
 
 This gun was thus supposed to unite the advantages of concealment 
 and protection which pertain to the disappearing mount, and the 
 advantages of rapidity and ease of fire pertaining to the baxbette 
 mount. Quite a number of emplacements of this character were 
 built and the guns were mounted therein. Theoretically this plan 
 should have worked well and if it had, it would have been extremely 
 useful. Apparently, however, insuperable mechanical difficulties 
 seem to have developed in this type of carriage, and consequently it 
 was thought well to do away with its use. Later, the emplacements 
 which had already been built for the balanced pillar mount were 
 altered for the regular barbette or, as it is sometunes called, the 
 "pedestal" mount. 
 
 For the portable mounts, which have heretofore been applied to 
 very small guns only, all that has been provided is a smooth platform 
 upon which the wheels might roll, sometimes with a low parapet in 
 front and sometimes without. Occasionally, ring bolts have been 
 inserted in the platform so that chains could be used to check the 
 extent of recoil. 
 
 The emplacements upon which turrets were to be constructed have, 
 up to the present, been built in but one place, Manila Bay. The de- 
 sign of the turrets was briefly discussed in a preceding chapter and the 
 Emplacements were so special as to require, for a full understanding, 
 a study of the drawings. They will, therefore, not be further dis- 
 cussion here. 
 
 . Recently, in connection with field operations abroad, railroad 
 mounts have been successfully developed for guns of comparatively 
 large size and such gxms and mounts will doubtless be used in the 
 future in seacoast defense. The idea, however, is only in its infancy 
 and the character of emplacements which the Engineer Department 
 may have to build for these guns has not yet been decided, so it is 
 not possible to discuss the matter fm-ther here. 
 
 The batteries built for mortars are so different in their general 
 characteristics from those built for* direct fire guns that the subject 
 will be treated separately in Chapter VIII. 
 
 The general types and characteristics of the emplacements built for 
 the other types of carriages will now be discussed. In this discussion 
 the terms "front" and "rear," "right" and "left" will be used in 
 their strictly military sense; the front of an emplacement being 
 always the part toward the expected position of the enemy; the 
 rear being in the direction away from the enemy; and right and left 
 as they would appear to a man facing the enemy. In this connection 
 it might be well to note that in all drawings of an emplacement or 
 portions of an emplacement, the direction of the enemy should always 
 be toward the top of the drawing. 
 
105 
 
 For convenience in this discussion, the emplacements will be divided 
 into three classes, as follows : 
 
 Emplacements for small caliber guns. 
 Emplacements for medium caliber guns. 
 Emplacements for large caliber guns. 
 
 Under the term "small caliber guns" as here used, will be included 
 those of 5-inch caliber and smaller. The "medium caliber guns" re- 
 ferred to will be the 6-inch gun only. The 8-inch and larger guns 
 will be discussed under the head "large caliber guns." 
 
 The reason for including guns up to 5-inch under the terms "small 
 caliber guns" is because the ammunition for all such guns is ordinarily 
 served to them in fixed metallic cartridges containing both the powder 
 and projectile, these cartridges being similar, except as regards size, 
 to the cartridges used in the Infantry rifle. The ammunition service 
 consists merely of carrying the cartridge to the gun and of inserting 
 it in the breech, whence the metallic case is ejected when the gim is 
 fired. 
 
 The 6-inch gun is included in a class by itself and called the "medium 
 caliber gun," because, though in the ammunition service of this size of 
 gun the powder and projectile are handled separately as is done in all 
 the larger guns, yet the shell is not too heavy to be picked up and moved 
 by hand. Consequently mechanical appliances for handling the pro- 
 jectiles are not necessary. 
 
 For the 8-inch gun and all larger guns, the projectiles are too heavy 
 for easy hand manipulation and mechanical appliances are, there- 
 fore, necessary. 
 
 EMPLACEMENTS FOR SMALL CALIBER GUNS. 
 
 The emplacements which have been built by the Engineer Depart- 
 ment for guns of smaller caliber than 3-inch have, as a rule, consisted 
 merely of a gun block sufficiently large and sufficiently heavy to 
 hold the gun securely when it is fired and no discussion of such em- 
 placements would appear to be necessary. 
 
 This has also been practically true of the emplacements built for 
 the 3-inch antiaircraft rifles heretofore furnished by the Ordnance 
 Department, the gun block for this gun, however, requiring the con- 
 struction in it of a shallow gun- well. 
 
 Most of the small caliber guns which have had to be regularly em- 
 placed have been the 3-inch, 4.7-inch, and the 5-inch guns. The 4.7 
 rifles were mainly Armstrong guns purchased by the United States 
 from England during the Spanish War. They were about as powerful 
 as the standard 5-inch guns then in use in the United States, and con- 
 sequently the emplacements built for them were essentially similar 
 to the standard 5-inch emplacements and no further description is 
 necessary here. 
 
106 
 
 The Board of Engineers' type plans for 3-inch emplacements were 
 published in Mimeograph 30 and its various supplements and for the 
 5-inch emplacements in mimeographs 16, 18, and 33. Outline draw- 
 ings showing the more important details of the most characteristic of 
 these designs have been prepared and accompany these notes as 
 Plates III, IV, V, VI, and VII. 
 
 Plate III shows' what is known as the 1898 type of 3-inch emplace- 
 ment designed for 3-inch guns on balanced pillar or masking mounts; 
 Place IV shows the 1902 type of 3-inch emplacement for 3-inch guns 
 on pedestal mounts; and Plate VII, the 1899 type of 5-inch emplace- 
 ment for 5-inch guns on pedestal mounts. In their essentials, these 
 types are exceedingly similar. In all of them, the emplacement con- 
 sists of but little more than a loading platform, upon which the men 
 stand while loading and firing the gun, and of a magazine. In front 
 of the emplacement there is a low parapet about 3 feet high which 
 gives some protection to the personnel, additional protection being 
 given by the shields with which such guns are usually provided. The 
 crest of this parapet over which the gun is fired is on the same level 
 as the top of the roof of the magazine. Consequently the floor of the 
 magazine has to be some 10 feet or so below the loading platform 
 level. The magazines provided for the 5-inch guns are 13 by 22 feet 
 and for the 3-inch guns 9 by 15 feet. About 7 or 8 feet of head room 
 is allowed in the magazine, the ceilings of which are of concrete from 
 5 to 7 feet thick. The roof over the magazine, when viewed from a 
 distance, forms with the crest of the parapet a practically unbroken 
 horizontal line. 
 
 The low parapet in front of the loading platform, except occa- 
 sionally in the center emplacements of batteries consisting of more 
 than two guns, is built in the arc of a circle, the radius of which is 
 about 7i feet in the 3-inch emplacements and about 11 feet in the 
 5-inch emplacements. Behind the gun the loading platform extends 
 horizontally backward, for a distance about equal to the radius of 
 the front circle, to the top of a fhght of from six to eight steps leading 
 directly to the rear and down to an intermediate or terreplein level, 
 some 7 feet or so below the crest of the parapet. From the platform 
 •of this intermediate level another flight of steps runs downward 
 parallel to the front of the battery to near the door of the magazine. 
 
 The ammunition for these guns is fixed, consisting of a metallic 
 cartridge loaded with powder and clamping the base of the projectile, - 
 similar, except as to size, to the cartridge for the Infantry rifle. 
 This ammunition is furnished by the Ordnance Department in boxes 
 containing several cartridges. The method of ammunition service 
 proposed is that these boxes shall be broken open in the magazine, 
 and individual cartridges shall then be carried by hand out of the 
 magazine door and up the two short flights of steps to the detachment 
 
107 
 
 around the gun. In order to make it possible to keep a few rounds 
 of ammunition close to the gim in case of emergency, ammunition 
 recesses, ammunition shelves, or platforms are usually provided on 
 the sides of the loading platform. Such recesses are shown on 
 Plates III and VI and the platforms on Plate VII. 
 
 Plate VI shows designs prepared in 1897 by the Board of Engineers 
 for emplacements for 5-inch guns mounted on balanced pillar mounts. 
 While in general similar to the S-inch emplacement described above 
 (Plate VII) , the loading platform differs in important particulars. 
 The concrete part of this platform was nearly 7 feet below the crest 
 of the parapet and the loading platform proper consisted of a metal 
 platform attached to the gun carriage, which rose when the gun was 
 lifted into the firing position. The loading detachment, of course, 
 stood on this metal platform and the ammunition was handed up to 
 them by members of the detachment standing on the concrete 
 platform below. 
 
 In the emplacements built for guns on balanced pillar or masking 
 mounts, gun-weUs were necessary and niches were left in the sides of 
 the walls of the emplacements, into which the gun could be lowered 
 when it was not in use. In this position it was, of course, hidden 
 from the sight of the enemy, and the top of the battery as viewed 
 from the front consisted of a practically unbroken horizontal line, 
 giving no indication of the position of the gun. The balanced piUar 
 mount was later abandoned by the Ordnance Department and all 
 emplacements built for such mounts were altered so as to be suitable 
 for the pedestal or regular barbette moimt. 
 
 The early emplacements consisted of but httle more than the 
 magazine, the loading platform, and the stairway between. In a 
 few cases, however, observation stations or crow's nests were built 
 on a flank of the battery (see Plates III, VI, and VII) and under this 
 crow's nest a small bomb-proof relocating or plotting room was 
 provided. Plate IV shows the addition of small storerooms under 
 the stairways. 
 
 In most cases, the 5-inch guns were mounted in individual em- 
 placements, but occasionally they wfere grouped into batteries of two 
 or three guns each. The 3-inch guns were usually grouped either 
 into batteries of two guns or four guns, individual emplacements 
 being practically never used. When the guns were grouped into 
 batteries, the 5-uich emplacements were intended to be about 
 45 feet apart, gun center to gun center, and the 3-inch guns about 
 29 feet. 
 
 When the attempt was made to man at the same time all the 3-inch 
 guns of a battery, it was soon found that difficulties were met with 
 due to the effect of the blast of one gun upon the detachment at the 
 next. A gun could be fired directly to the front without any dis- 
 
108 
 
 comfort to the detachment at the next gun, but if it was fired at any- 
 material angle of traverse from the capital the blast effect soon 
 became so great that the men could not stay at the next gun, conse- 
 quently it was evident that in future batteries the guns should be 
 placed farther apart. 
 
 The first attempt to do this is shown on Plate IV. The designs 
 shown in this plate, sometimes called the 1902 type of 3-inch emplace- 
 ment, are for a two-gun battery having both magazines between the 
 guns. This separates the gun centers to an interval of 42 feet. 
 Otherwise, the design resembles closely the 1898 type. (Plate III.) 
 
 A more efficient attempt to avoid the trouble from blast was 
 described in 1903 in the sixth supplement to mimeograph 30. (See 
 Plate V.) The guns are shown as spread farther apart, 62 feet 
 center to CMiter and, in order to still further diminish the effect of the 
 blast of one gun upon the men at the other, the roof of the magazine 
 between the guns is shown as rising in a gently rounded mound of 
 earth, the crest of which, at the center, is about 7 feet above the 
 loading platforms. Both magazines are located in the traverse 
 between the guns, and they are made 12^ by 22 feet, a considerable 
 increase in size over the plans of the older 3-inch emplacements. 
 Furthermore, since the magazines did not fill up all the space between 
 the guns, a storeroom 10 by 12 feet is provided between the magazines. 
 
 For convenience in ammunition service the stairway leading from 
 the magazine level to the loading platform is broken into two addi- 
 tional levels. The intention was that the boxes containing several 
 rounds of ammunition should be brought by hand from the maga- 
 zines and should be lifted up and placed on the lower of these two 
 additional levels. There the boxes were to be broken open, the 
 individual cartridges being handed to naen on the next level who 
 placed them on shelves provided on that level for that purpose. 
 From these shelves the cartridges were to be handed to members of 
 the loading detachment at the gun. 
 
 In order to provide space for the members of the detachment on 
 these different levels, the stairway leading down from the loading 
 platform was made only about 3 feet wide. 
 
 Since these plans were published in 1903, a large number of 3-inch 
 emplacements based on them have been constructed, the guns in all 
 cases being mounted in pairs. In a few of the more recent batteries, 
 however, improvements have been made in the ammunition service. 
 A niche about 2 by 5 feet and high enough for a man to stand in has 
 been left in the rear comer of the magazine wall on the side toward 
 the gun, the bottom of the niche being about 2 feet above the floor 
 of the magazine. Between the upper part of this niche and the 
 shelf on the upper level behind the loading platform an opening was 
 left so that a man standing in the niche can push the cartridges by 
 
109 
 
 hand directly out on to the ammunition shelf. When this was done 
 the lower of the two additional levels was omitted and the stairs 
 leading downward from the loading platform were moved to the outer 
 flank. (The location and general outline of the niche are shown 
 dotted on the rear elevation on Plate V.) 
 
 It wiU be noted that the protection given the magazine, as shown 
 in all these plates, consists of about from 6 to 8 feet of concrete and 
 of about from 20 to 24 feet of sand. This was estimated to be suffi- 
 cient to protect these guns against a 6-inch projectile. 
 
 No arrangements for the prevention of condensation are shown 
 in any of the drawings, this being a detail left to the constructing 
 officer. In actual construction many of the emplacements had 
 built into the magazine walls, a foot or so from the interior surface of 
 these walls, vertical tiers of porous tiles. 
 
 About 1909 another important change was made in the last type 
 of emplacements — a battery commander's station being added above 
 the rear of the traverse. This was usually built with concrete walls 
 about 4 feet high, over which was placed a light corrugated iron 
 roof with observation slots in front and on the sides. Above the 
 roof were placed boards facing the guns, on which data as to the 
 range of the target could be displayed. Part of the side and rear 
 edges of the earth fill over the traverse was removed so as to provide 
 walkways from the loading platforms to the batterj^ commander's 
 station. 
 
 TWO MAIN TYPES OF MEDIUM AND LARGE CALIBER EMPLACEMENT. 
 
 Before going further into the detailed discussion of emplacements 
 for 6-inch and larger guns, it would appear well to distinguish be- 
 tween the two essentially different types in accordance with either 
 of which these emplacements may be designed. 
 
 These two types are sometimes called respectively the "two story" 
 and the "one story" types, and sometimes they are designated as 
 the "horizontal crest t3i^e" and the "horizontal ammunition service 
 type." 
 
 In the earthem emplacements constructed during and just after 
 the Civil War, the guns were mounted on barbette carriages and were, 
 therefore, always visible. In order to obtain a sufficient volume of 
 fire they were mounted fairly close together along a parapet, although 
 it was customary, wherever infilade fire was feared, to place frequent 
 traverses in the line of guns so as to reduce the effect of this enfilade 
 fire. In general, the guns were emplaced in pairs, two guns in the 
 interval between two traverses. 
 
 These traverses extended high above the parapet and, in fact, 
 above the guns and, therefore, were visible from a considerable 
 distance. The guns then in use were mounted in barbette and were 
 
110 
 
 always exposed to view, the ranges used at the. time were compara- 
 tively short, and since the guns themselves were not concealed no 
 concealment was lost by the exposure of the traverses to view. 
 
 When, however, the disappearing principle was introduced into 
 seacoast gun carriages so that the gun in the loading position was 
 entirely out of sight, it became desirable to conceal, if possible, the 
 position of the gun.' It appeared to be desirable to reduce the height 
 of the traverse to that of the parapet, so that when seen from the 
 front, the emplacement appeared with an unbroken horizontal crest, 
 no guns being visible and no traverses indicating the approximate 
 positions of the guns. The early designs for disappearing emplace- 
 ments as prepared by the Board of Engineers were aU based on this 
 idea. 
 
 Unfortunately, in attempting to keep this unbroken horizontal 
 crest one great disadvantage was introduced, that is, the lowering 
 of the magazines far below the level of the gun in the loading position. 
 
 The Ordnance Department's designs for disappearing carriages 
 place the loading platform, upon which are moved the ammunition 
 trucks bringing projectiles to the guns, from 9 to 11 feet below the 
 crest of the parapet in front of the gun. The larger of these figures 
 is just about the thickness of concrete considered necessary for the 
 roofs over the magazines and, consequently, in this type of emplace- 
 ment, the ceilings of the magazines could not be higher and usually 
 must be lower than the pavements of the loading platform. When 
 it is considered that in aU the magazines considerable head room is 
 necessary, especially in the shell rooms where trolley rails are re- 
 quired for moving projectiles, it will be seen that if the horizontal 
 crest is to be maintained, the floors of the magazines are pushed 
 down far below the loading platform level and there results a two- 
 story type of emplacement, a lower or first story containing, the 
 powder and shell rooms, and a second or upper story with the 
 floor upon the loading platform level. 
 
 In service the ammunition must, of course, be raised from the 
 magazine level to the loading platform level. In small emplace- 
 ments (that is, for 5-inch or smaller guns) where the ammunition is 
 handled by hand, this difference of level is not so important and in 
 the 6-inch emplacements not of great importance, but in the larger 
 emplacements where the projectiles are too large and heavy for hand 
 manipulation and where, therefore, mechanical means are necessary 
 for raising them complications necessarily ensue. In the first 
 emplacements constructed the hoists for raising ammunition were 
 somewhat crude, but they were soon improved until they became 
 mechanically almost perfect. Nevertheless, the necessity for using 
 hoists was one which it was desired to avoid if possible. 
 
Ill 
 
 It was therefore suggested as possibly desirable that the larger 
 gun emplacements should be designed so as to provide what may be 
 called horizontal ammunition service, the floor of the magazine being 
 essentially on the same level as the loading platform so that no hoists 
 are necessary. 
 
 The difference of level between the floors and magazines and the 
 tops of the roofs over them is fixed within small limits by the need 
 of sufficient head room in the magazines and the necessity of pro- 
 viding sufficient cover over them. The difference in level between 
 the loading platform and the crest in front of the gun is also fixed 
 within small limits by the type of gun carriage, and consequently, 
 if the loading platforms and the floors of the magazines are to be 
 placed on essentially the same level, the top of the roofs over the 
 magazines must project far above the crest of the parapet in front 
 of the loading platform. The approximate position of the gun is 
 indicated to the enemy because it must be at about the center of the 
 distance between two traverses and the advantage of concealment 
 obtained with the horizontal crest type of battery is lost. 
 
 In other words, in designing an emplacement we can obtain hori- 
 zontal ammunition service or we can obtain a horizontal crest, but 
 we can not obtain both. We can build a disappearing battery to 
 provide concealment of the location of the gun or we can build a 
 battery so as to provide the easiest form of ammunition service, but 
 we can not build a battery which wiU provide both of these ad 
 vantages. 
 
 The horizontal-crest type of battery means a two-story type, and 
 is sometimes referred to as such. With the type of battery providing 
 horizontal ammunition service the battery is essentially on one story 
 and it is therefore sometimes called the one-story type of battery. 
 
 In the discussion above these two types of battery have been 
 considered as if the two types were found in the emplacements for 
 heavy guns only, because in emplacements for heavy guns the two 
 types are most distinct, one requiring and the other not requiring 
 ammunition hoists. However, the same distinction may be made 
 if desired in the batteries for small caliber guns. Thus the original 
 design for balanced pillar or masking mounts was based upon the 
 horizontal-crest idea, the guns when lowered to their niches being 
 hidden from sight and there being therefore nothing to make a break 
 in the evenness of the crest. The magazines were likewise on a lower 
 level and the emplacements were therefore essentially of the two- 
 story type. 
 
 For guns with masking mounts the horizontal crest type of battery 
 provided a complete concealment of the position of the gun, but with 
 the pedestal type of barbette guns no such concealment was possible 
 because the gun was always in sight. Consequently in preparing 
 
112 
 
 the 1903 design for emplacing the 3-inch pedestal guns (see Plate V) 
 no attempt was made to adhere to the horizontal crest, the top of 
 the traverse between the guns rising in a gently rounded surface a 
 considerable distance above the crest of the parapet in front of the 
 gun. However, the magazine is kept just as low as it was in the 
 former type of 3-inch emplacement, so that this type of design com- 
 bines neither the advantage of the horizontal crest providing con- 
 cealment nor of horizontal ammunition service. The horizontal 
 crest was not necessary because the guns were in barbette and hori- 
 zontal ammunition service was not considered necessary because 
 the ammunition was not heavy. Keeping the magazines low 
 increased the angle of traverse over which the guns could be fired. 
 
 EMPLACEMENTS FOR MEDIUM CALIBER GUNS. 
 
 ix-Inch Emplacements. 
 
 The designs prepared by the Board of Engineers for 6-inch emplace- 
 ments were published in Mimeographs 31, 40, and 59. Plate VIII 
 sliows in outline the designs of 6-inch emplacements prepared by the 
 Board of Engineers in 1900 for guns on pedestal mounts with shields. 
 These designs were subsequently pubMshed in mimeograph No. 40. 
 
 The drawings showed a 2-gun battery of the 2-story type, the lower 
 story containing two shell rooms, one for each gun, a magazine for 
 the joint use of both guns, and a room for general use marked on th& 
 drawing as the "guard room." The upper story is on two levels, 
 one about 4^ feet higher than the other. The uppermost level con- 
 sists of the gun or loading platforms on which a,re located the pedestals 
 of the two guns 20 feet apart, center to center. In front of the gun is 
 a low parapet about 2 J feet high. The lower level of the upper story 
 is called the "terreplein" and is connected with the upper level by a 
 broad flight of steps. At the center of this terreplein level there is a 
 "powder recess" in which there can be placed temporarily a few 
 charges of powder available for instantaneous use. At both flanks of 
 the terreplein level and immediately over the shell rooms of the lower 
 story are the openings of the shell hoists. From the extreme sides 
 of this terreplein level there are shown two ramps running down to 
 the level of the lower story. For more convenient communication 
 between the two stories a double stairway is placed in the rear of 
 the center of the battery leading from the lower story up to the 
 terreplein. 
 
 The powder service was intended to be by hand, the cartridges 
 were to be picked up from the magazine and carried out through the 
 entrance to the shell room to the rear stairs, up the stairs, and thence 
 direct to the gun or to the powder recess. The projectiles could be 
 carried by hand over the same route as the, powder, or they could be 
 raised by means of hand operated mechanical shell hoists from the re- 
 
113 
 
 ceiving tables in the centers of the shell rooms up to the dehvery 
 tables on the terreplein level. The design of the receiving tables was 
 quite complex. It was described in the chapter on ammunition sup- 
 ply and service and is illustrated in outline in figures 3 and 4 of 
 Plate II. 
 
 In preparing designs for these emplacements the idea of reducing 
 condensation was evidently kept in mind as there is shown a 6-inch 
 air space built around the walls in front of the magazine and on the 
 inner sides of the shell room; while at the rear numerous doors and 
 windows were provided which when left open should provide fairly 
 efficient ventilation. Unfortunately, however, the air space has no 
 exterior openings and ends in the tile facing in front of the battery. 
 It was therefore what may be called a blind air space. The necessity 
 for this air space wiU be more fully discussed in the chapter on 
 dryness, etc. 
 
 The designs shown have several disadvantages; first, the gims are 
 placed so close to each other that if either be fired at any considerable 
 angle of traverse from the capital the blast from the gun wiU certainly 
 interfere with the detachment at the other gun. Furthermore, the 
 guns are so close together that an enemy's shell striking in the imme- 
 diate vicinity of one wiU almost certainly put the other out of action 
 also. The disadvantages arising from this close spacing of the guns 
 were noticed very shortly after the issuance of the mimeograph and 
 the first officer called upon to design an actual battery, based upon 
 the mimeograph, suggested a change to what may be called the 
 "Montgomery or 1901 type." (See PI. IX.) 
 
 In this latter type the guns are separated by a distance of 52 feet 
 which gives considerable protection to the detachment at one gun 
 from the blast of the other. The arrangement of the lower floor also 
 is quite different. The two shell rooms are drawn from the flank 
 toward the center where they are imited into a single shell room, 
 each gun, however, being provided with a separate hoist. The powder 
 magazine is placed in the center of the battery in front of the shell 
 room. The room for general use, disignated as a "guard room" in 
 the old design, has been broken into two and these have been placed 
 on the flanks of the shell room. As in the other design, there is a 
 double stairway in the rear of the battery, but instead of the tops of 
 the stairways being in the center and the feet outward, the feet of 
 the stairways are placed one on either side of the center door of the 
 shell room and the tops are spread out to the flanks in rear of the 
 guns. 
 
 As in the other design, the upper story has two levels, the terreplein 
 level and the gun platform level. On the terreplein level, instead of 
 the single center powder recess two smaller recesses are provided, one 
 173341—20 8 
 
114 
 
 in rear of each gun. The projectile hoists, instead of delivering the 
 projectiles on delivery tables on the terreplein level, are now so fixed 
 as to roll the projectiles out on the floors of the gun platform levels 
 in rear of and not far from the guns. On the gun platform level at 
 the center of the battery, a crow's nest or battery commander's 
 station is provided. 
 
 In the drawings no special arrangement for preventing condensa- 
 tion is shown, but in the actual construction of the only battery built 
 on these plans a layer of tiles was built in the magazine walls. How- 
 ever, this battery is so small and so many doors and windows are 
 provided on its rear that when these doors and windows have been 
 kept open there has almost never been any condensation. 
 
 The protection given the shell rooms in Plate VIII and the maga- 
 zines in Plate IX consists of about 6 feet of concrete and 22 feet of 
 earth, sufficient, it was calculated, to more than keep out J;he 6-inch 
 projectiles of the day. 
 
 In 1902, the Board of Engineers prepared new type plans for 6-inch 
 barbette guns which were published as a second supplement to 
 Mimeograph No. 40 and the general outlines of which are shown on 
 Plate X. The type of emplacement shown differs from all the plans 
 discussed heretofore in that it is essentially of the one-story type and 
 provides what may be called "horizontal ammunition service." 
 The guns are separated by an interval of 94 feet and between them is 
 the magazine, built in a high traverse, which rises at its center some 
 20 feet above the floor of the magazine and some 13 feet above the 
 level of the loading platform around the guns — these platforms being 
 approximately 7 feet higher than the floors of the magazines. 
 
 The pedestals of the guns are located near the centers of wide, 
 gently-sloping loading platforms, nearly 24 feet in diameter. In 
 front these loading platforms are partially protected by a low parapet 
 about 2 feet high, and to the rear they are partially surrounded by a 
 so-called "banquette" some 3 feet wide and on a level about 3^ feet 
 lower. About 20 inches below the banquette is the truck platform 
 which slopes very gently to the rear and toward the traverse down, to 
 the level of the floor of the magazine, the slopes not being too steep 
 for the easy rolling of trucks loaded with powder or projectiles. 
 
 For ammunition service the Ordnance Department was to provide 
 small cars or trucks which would hold several complete charges. 
 These trucks were to be loaded inside the magazines and were then to 
 be pushed along the floor of the magazine and of the truck ple^tform 
 until they were close to the banquette and in rear of the gun in which- 
 ever direction it might be pointed. Members of the detachment stand- 
 ing on the banquette were then to lift the powder and projectiles from 
 the truck and hand them to other members of the detachjnent on the 
 loading platform, who would carry them to the gun. 
 
115 
 
 The traverse was quite large and roomy. It contained a powder 
 room about 12 by 35 feet for the common use of both guns, and a 
 shell room about 12 by 38 feet, likewise for both guns. Four other 
 rooms for general use were provided, each being designated for some 
 supposed particular use, as shown on the plan. At the rear of the top 
 of the traverse there is shown a battery commander's station reached 
 by a double flight of stairs. 
 
 No special arrangements for preventing condensation are shown in 
 these drawings, the details being left to the commanding officer. 
 
 These plans were the first to indicate an earthen blanket over the 
 concrete roof of the magazine, but as this is clearly shown on the 
 drawing no further description of it is necessary. 
 
 About the time that the designs just discussed were published, the 
 Ordnance Department succeeded in perfecting the details of the 6-inch 
 disappearing carriage and the Board of Engineers at once proceeded 
 to prepare a typical design for emplacements for these carriages. 
 These, the 1903 type plans, were subsequently published in Mimeo- 
 graph 59 and the main details are shown on Plate XI. 
 
 As will be noted by comparing Plates X and XI, these new designs 
 for the disappearing emplacements are very similar to those of the 
 barbette emplacements, both containing the high center traverse and 
 being of the one-story type. The principal differences are: The pro- 
 vision in the disappearing plans of much wider loading platform* 
 extending out more than 27 feet from the centers of the gunweUs 
 and the provision of a powder passage connecting the front of the 
 two loading platforms and extending from side to side of the traverse 
 immediately in front of the powder magazine. Doors are cut from 
 the powder magazine into this powder passage which thus serves 
 not only to permit more efficient ventilation for the powder maga- 
 zines but also to provide a protected passageway for powder service 
 which is thus made distinct from the projectile service. 
 
 The widening of the loading platforms makes it necessary to sepa- 
 rate the guns about 125 feet, approximately 31 feet more than in the 
 barbette plans, and the use of the disappearing principle permits the 
 parapet to be raised to some 7 feet above the loading platform. The 
 loading platform, itself, was lowered until it is about 5 feet only above 
 the level of the magazine floor instead of 7 feet, as in the barbette 
 emplacements. This permits a verj'^ great reduction in the slope of 
 the truck platform floor, which is now made almost level. 
 
 With the exception of the introduction of the powder passage 
 which has been mentioned, the traverse is essentially similar to that 
 of the barbette design. 
 
 After the publication of the two mimeographs mentioned but few 
 modifications were made in 6-inch emplacement designs for a period 
 of some 9 or 10 years, during which time many batteries were built 
 
116 
 
 iiji various sections of the country, based on these standard plans, 
 In a few places no provisions for preventing' condensation were made, 
 reliance being placed upon the ventilation of the battery which the 
 wide powder passage rendered easy; in others, as at Fort Wool, Va., 
 the walls and ceilings of the shell rooms and powder rooms were 
 faced with tiles and an air space was left between the wall tiles and 
 the wall proper. 
 
 In some of the batteries following this general design the traverse 
 was altered considerably, the rooms marked "Storeroom" and "Stor- 
 age battery room" were omitted and the "Guard room" and "Office" 
 were merged into a single room about 10 feet measured fore and aft, 
 and about 22 feet measured across the battery. This reduced the 
 depth of the traverse by about 10 feet. In batteries thus modified, 
 which were seriously exposed to flank fire from either side, the en- 
 trance to the traverse from the loading platform on the exposed side 
 was made at the rear of the traverse and not on the side, as shown 
 in the plates. 
 
 The magazine protection shown is about 11 feet of concrete and, 
 in the center, about 10 feet of sand — sufficient to withstand the 
 6-inch projectile of 1902 or 1903. 
 
 Although not shown on the plates, recesses were usually provided 
 in the side walls of the emplacement for telephone booths, for storing 
 sponge and rammer staves, and for other miscellaneous purposes. 
 
 About 1912 plans were prepared for the 6-inch emplacements for 
 the defenses of the Panama Canal. These differed considerably from 
 the plans just discussed and are shown in general outline on Plate 
 XII. 
 
 As will be noted by a comparison of the drawings, the same general 
 arrangement of guns and magazine traverse is retained. The bat- 
 tery is of the one-story type and practically horizontal ammunition 
 service is provided. 
 
 The most striking differences between the Panama and previous 
 designs are the great thickening of the earth blanket over the con- 
 crete roof of the magazine, which thus raises the top of the traverse 
 much higher, the provision of gentle sand slopes on the sides of the 
 loading platform instead of the concrete walls of the old designs 
 and the placing of the entrance to the shell room in rear of the traverse 
 instead of on the side, thus making the entrance of an enem.y's pro- 
 jectile much less probable. 
 
 Another quite important difference is the omission of the banquette 
 level, the truck platform being raised up to and merged with the 
 loading platform. The difference between the level of the floor of 
 the shell room and that of the loading platform immediately around 
 the gunwell steps is made about 3 feet, and the distance between the 
 magazine and the gun is sufficient to permit this change in level to 
 
117 
 
 be made by a pavement having a grade of less than 3 per cent, up 
 which the loaded trucks can be easily pushed. 
 
 The guns are shown as separated by a distance of, 175 feet, the 
 increase being necessitated by the space required for the sand side 
 slopes. 
 
 The same arrangement of having a shell room and powder room 
 common to both guns is retained and the powder passage hkewise is 
 retained, but, in order to increase the overhead protection of the 
 powder room, its floor has been lowered about 3 feet below the floor 
 of the shell room, convenient stairs being provided between the two. 
 The powder passage likewise is lowered, so that additional stairs are 
 required between it and the loading platform. 
 
 The center traverse is shown as having in the rear of the shell 
 room a plotting room, surmounted by a battery commander's sta- 
 tion, and connected by range indication tunnels with indicating 
 boards on the left side of the loading platforms. Rooms for the 
 comfort of the officers and enlisted men also were provided as shown. 
 
 As will be noted, also, no special provisions are made for preventing 
 condensation, such provisions being unnecessary, since the batteries 
 were buUt in the Tropics, where the temperature remains practically 
 the same all the year round, and where, therefore, there is practically 
 no condensation. 
 
 As it so happens that most of the 6-inch Panama batteries are 
 built in fairly close proximity to emplacements for large guns and, 
 therefore, may presumably be struck by large projectiles aimed at 
 the emplacements of the large guns, it was considered essential that 
 the magazines of these 6-inch guns be given the same amount of 
 protection as the magazines of the large guns. In most cases, also, 
 one flank of the battery was .considered much more exposed than the 
 other and was, therefore, given slightly increased protection. 
 
 All but two of the 6-inch guns which have been emplaced at Pan- 
 ama having been provided by the Ordnance Department with dis- 
 appearing carriages, it was not considered necessary to prepare any 
 typical 6-inch barbette plans. Only one such battery was buUt in 
 the Panama defenses and its design was based upon the Montgomery, 
 or 1901, type. Many modifications, however, were required by 
 local conditions and the necessity of providing dormitories and other 
 arrangements for the comfort of the garrison. The designs of this 
 battery, therefore, are quite special and wiU not be further discussed 
 here as the plans themselves wUl doubtless be available for any officer 
 who may desire to examine them. 
 
 LARGE-CALIBER EMPLACEMENTS. 
 
 When about 1890 emplacement construction was resumed in this 
 cotmtry, it was the policy of the War Department, based upon the 
 recommendations of the Endicott Board, that in general aU large- 
 
118 
 
 caliber guns should be mounted on disappearing carriages. Barbette 
 mounts were to be used in a few special locations only, such as where 
 the available sites were very high. Consequently, no type plans for 
 large-cahber barbette emplacements were prepared. 
 
 Owing, however, to the delay in manufacturing satisfactory dis- 
 appearing carriages and to the- excitement preceding and incident to 
 the Spanish War, quite a number of 8-inch guns and some 10-inch 
 and 12-inch guns were actually mounted in barbette, and the work 
 was in many cases hurriedly done. 
 
 The 8-inch guns which were so mounted were usually located in 
 some older fortifications. The carriages were placed on flat concrete 
 platforms into which the bolts for holding down the base ring were 
 inserted. In many cases the magazines already in existence were 
 utihzed; in others, special magazines were built. In either case, the 
 ammunition service consisted essentially of rolling the projectile and 
 powder on trucks to the vicinity of the gun. * There the projectile 
 was picked up by a crane attached to the rear platform which formed 
 part of the gun carriage. 
 
 The barbette emplacements constructed for 10 and 12 inch guns 
 were usually designed, as far as might be appUcable, upon the then 
 standard type of two-story disappearing emplacements, the maga- 
 zines and shell rooms being in a lower story and hoists being used to 
 hft the ammunition up to the platform on which the base ring stood, 
 which was usually about from 5 to 8 feet below the crest of the parapet. 
 The ammunition was raised to the platform by means of the hoist and 
 was then roUed in a truck to near the breech of the gun. Here^the 
 projectile was picked up by a crane mounted on the steel breech plat- 
 form attached to and forming part of the gun carriage. 
 
 These barbette batteries varied considerably as regards these de- 
 tails and since no one type was ever developed into what may be 
 called a standard, and no others like them will ever be buUt, a fur- 
 ther discussion here appears unnecessary. 
 
 Gun Lift Battery. 
 
 The first emplacements built for heavy guns so they might disap- 
 pear from sight while being loaded was the large gun-Uft battery 
 built at Sandy Hook in the early, nineties. This battery was built 
 for two 12-inch guns. Each gun and its carriage was mounted on a 
 heavy metal platform. When loaded and ready to fire, the entire 
 platform with the gxm and carriage was raised from below by hy- 
 draulic pressure until it had reached the proper level. After the gun 
 was fired it was lowered until it disappeared from sight behind a par- 
 apet. The gun was then loaded from covered chambers in the rear. 
 
 Although in a hmited sense a mechanical success, at least to the 
 extent that the gun worked properly and could be used, this battery 
 was nevertheless exceedingly slow in action, firing one shot from each 
 
119 
 
 gun every five minutes. Furthermore, it was a very expensive in- 
 stallation and no more batteries of this type were ever started. Some 
 years later the original battery was abandoned. 
 
 Disappearing Emplacements. 
 
 The first of the standard Crozier disappearing carriages to be per- 
 fected was the 8-inch. This was very shortly followed by the 10-inch 
 and not long afterwards by the 12-inch. By 1894, the Board of 
 Engineers had prepared typical plans for the 8-inch and 10-inch 
 disappearing emplacements. A few years later they prepared other 
 and improved type plans for the 8-inch, 10-inch, and 12-inch em- 
 placements. Subsequently, about 1902 and 1903, new and quite 
 different type plans were pubUshed for the ] 0-inch emplacement and 
 a short time later, for the 12-inch. Since, however, each particular 
 type of 10-inch disappearing emplacement differed from the corre- 
 sponding types of the 8-inch and 12-inch in dimensions only, the dis- 
 cussion here will be restricted mainly to a description of the 10-inch 
 emplacement with incidental reference to special details embodied in 
 the 12-inch designs. The 8-inch emplacement designs have been 
 pubhshed with mimeographs 8 and 25 and their supplements; the 
 10-inch emplacement designs, with mimeographs 8, 22, and 36, and 
 their supplements; the 12-inch emplacement designs, with Mimeo- 
 graphs 8, 24, 66, and supplements; and the 14-inch emplacement 
 designs with mimeograph 109. 
 
 1894 Types of Disappearing Emplacements. 
 
 The first type of disappearing emplacement for large-caliber guns 
 is what may be called the 1894 type. On Plate XIII there is an out- 
 line drawing showing the most complete form of this type of em- 
 placement, this drawing being taken from the original drawing of a 
 battery constructed at Fort Monroe, Va., in 1894. It is interesting 
 as showing the narrow loading platforms and crude character of 
 ammunition service provided, as well as the contracted and inade- 
 quate magazine space and the total lack of provision for keeping the 
 magazines dry. 
 
 The guns are separated by an interval of 124 feet and are located 
 behind a high, thick parapet finished on the top with a strictly hori- 
 zontal crest. Immediately in front of each gun the line of the para- 
 pet is shghtly hollowed out and in rear of the gun is a raised structure 
 intended to be used as a loading platform. The magazines are 
 located to the right of their respective guns in Hi-defined traverses 
 which do not rise above the crest of the parapet. 
 
 The general type is the one which afterwards grew into the stand- 
 ard two-story emplacement, but in these first designs the two stories 
 were not well defined — instead there were several different levels. 
 
120 
 
 First and lowest, there was the magazine level on which were the 
 powder magazine and shell room, an entrance gallery, and the bottom 
 of the hoist well, all with their floors at the same general elevation, 
 about 24 feet below the crest of the parapet. Next there was what 
 may be called the crane level, because upon it were placed the bases 
 of the cranes used for hfting the projectiles up to the loading plat- 
 form. The floor of this level was not, however, strictly horizontal; 
 in front it was about 7 feet above the magazine floor, but it. had 
 quite a slope downward and to the rear so that as it passed around 
 behind the room under the loading platform it was about 3 feet 
 lower. At the right-hand front corner of the crane level there was 
 an entrance into the traverse, forming what is sometimes called the 
 lobby. This lobby, at the rear, abutted on the hoist well. The ceil- 
 ing of the lobby and of the hoist well were at the same elevation and 
 continuous, but there was a difference of 7 feet in the elevation 
 of the floors. Third, there was the working platform level about 3 
 feet higher than the crane level and extending around the base of the 
 gun carriage. Fourth, there was the loading platform level, ap-, 
 proximately 4 feet above the working platform level, 7 feet above the 
 crane level, 14 feet above the magazine level, and about 10 feet below 
 the crest of the parapet. On this level is the comparatively narrow 
 loading platform upon which the men stand while ramming projec- 
 tiles or powder into the guns. 
 
 AH the rooms and galleries in the traverse were made with their 
 ceflings in the form of full center arches, furnishing about 8 feet head 
 room at the center. A trolley rail was attached to the ceihng of 
 the shell room and extended out through the gallery to the edge 
 of the hoist well. Another trofley rail, some 7 feet higher, extended 
 fore and aft along the ceihng of the hoist well and along the ceiling 
 of the lobby to the dqor which opened on the crane level. 
 
 The projectile service in this type of battery was somewhat com- 
 plex and crude. The shell was first to be picked up in the sheU. 
 room by means of a differential hoist running on the lower trolley 
 rail. The troUey was then to be pushed through the gallery and to 
 the end of the lower trolley rail at the side of the hoist well. Here 
 the projectile was to be lowered to the floor, to be pushed out under 
 the center of the hoist well, and to be picked up by another differ- 
 ential block attached to a trolley running on the upper trolley track. 
 By means of this differential block it was to be raised up until it 
 was slightly higher than the floor of the lobby. This trolley was 
 then to be rolled on the upper trolley track along the ceihngs of 
 the hoist well and of the lobby to the doorway on the crane leVel. 
 Here the projectile was to be again lowered to the ground and roUed 
 to within reach of the crane by which it would be raised up and 
 deposited upon a truck on the loading platform level. This was th6 
 
121 
 
 normal method of projectile service, at least for handling loaded 
 sheU. It was provided, however, that a few solid shot might be 
 stored on the floor of the room under the loading platform. These 
 could be rolled out of one of the doors of this room and picked up by 
 one of the rear cranes which would hoist them up and place them 
 on trucks on the loading platform. 
 
 The powder could be handled in much the same way as the projec- 
 tiles or, preferably, the individual cartridges which were not too 
 large to be carried by one man, would be cariied by hand up to the 
 loading platform. For this, however, it should be noted that the 
 conveniences were few. There were no stairways connecting the 
 magazine level with the crane level on the magazine side of the 
 emplacement; consequently, the man with the powder charge com- 
 ing from the magazine had to walk well to the rear of the emplace- 
 ment and thence up a ramp to the crane level, then he had to walk 
 well forward and up a flight of stairs to the level of the working plat- 
 form. Here he had to climb another fhght of stairs to the loading 
 platfojm level. The route of the powder might be somewhat short- 
 ened by having the man who picked up a cartridge carry it to another 
 man standing on a stool at the foot of the hoist well who could lift 
 it up and hand it to a third man in the lobby. 
 
 In this design there was apparently no deficiency in parapet pro- 
 tection. Immediately in front of the gun the concrete parapet was 
 20 feet thick with 4.5 feet of earth in front, while the horizontal pro- 
 tection in front of the magazine measured at the level of the ceiling 
 was not less than 50 feet of concrete with 30 feet of earth in front of 
 that. 
 
 A particularly noticeable feature of this design was the utter 
 insufficiency of magazine space and the inadequate size of the load- 
 ing platform. The powder magazine was but 8 by 16 feet. The 
 shell room was 6 by 16 feet, but the projectile storage space was 
 supplemented by the room under the loading platform, some 3^ 
 feet wide, which was intended to be used for storing solid shot. 
 
 The loading platforms stood up quite isolated — they were not con- 
 nected with each other or with anything else. They could be reached 
 only by the two stairways connecting each with its working plat- 
 ,form. The loading platform was only 13 feet wide, which was barely 
 sufficient for handhng the projectile truck and left almost no space 
 for the ramming detail. Furthermore, the loading platform was 
 finished off in front by a vertical wall descending 4 feet to the work- 
 ing platform, which made it quite dangerous for the detachment. 
 Handraihngs could not be placed here without interfering with the 
 service of the gun, though, of course, they were erected along the 
 rear edge and the ends of the loading platform. 
 
122 
 
 A serious defect in the original design was the small size of the 
 gun well, which was barely large enough to hold the counterweight. 
 Before the gun could be mounted it became necessary to make a 
 hole from the crane level through into the bottom of the gun well 
 in order that the blocking used in mounting the gun and carriage 
 might be withdrawn. - 
 
 Another noticeable feature was the absence of anything like 
 proper arrangements for ventilation or for prevention of dampness. 
 The only openings into the magazine space were two doorways, and 
 in the early emplacements these doorways were closed with sohd 
 doors, so that when they were closed there was no circulation of air at 
 all. Consequently there was much condensation. Furthermore, 
 in aU such batteries the concrete was made of Rosendale cement 
 and in practically all eases was so porous as to permit much seepage 
 of water through it. Attempts were made subsequently at the 
 Fort Monroe battery to diminish this seepage by covering the con- 
 crete roof of the emplacements with layers of tar or asphalt. These 
 attempts, however, were only partially and very temporarily suc- 
 cessful. 
 
 Crude though this 1894 design was, yet it is easy to see how it 
 grew into the subsequent two-story type. The crane level was done 
 away with entirely, the floors of the rooms under the loading plat- 
 forms being lowered to the same level as the floors of the magazine. 
 The loading platform was much enlarged to the front and to the 
 sides, so as to touch the parapet and traverse walls,, while to the 
 rear it was extended by a corridor passing along the rear of the maga- 
 zine traverse and connecting the loading platforms of the two or 
 more emplacements. The loading platform and the working plat- 
 form were connected by a set of circular steps concentric with the 
 axis of the gun well. The hoist well was enlarged and was fitted -_ 
 for the mechanical hoisting apparatus for lifting the ammunition 
 up to the level of the loading platform. 
 Subsequent Designs. 
 
 Following the 1894 design above described, quite a number of 
 successive plans were prepared by the Board of Engineers, each an 
 improvement upon the preceding. In these successive designs more 
 space was provided for ammunition storage and provisions were* 
 made for decreasing the amount of dampness; the loading platforms 
 were widened and were much improved; and, incidentally, a great 
 many improvements were made by the Ordnance Department in 
 the design of the gun carriage. 
 
 The ammunition service especially was improved, there being sub- 
 stituted for the cranes, balanced platform hoists, by which the ammu- 
 nition trucks already loaded with both powder and projectiles could 
 be raised from the floor of the magazine to the loading platform. 
 
123 
 
 Subsequently, improved chain hoists were substituted for these bal- 
 anced platform hoists. 
 
 1896 Type of Disappearing Elmplacements. 
 
 An outline dravdng of the 1896 type of 10-inch disappearing 
 emplacement is shown on Plate XIV and of the 12-Lnch emplace- 
 ment on Plate XVIII. By the time these designs were prepared 
 the emplacements had evolved into their typical two-story form, 
 there being a lower story or magazine level and an upper story or 
 loading platform level, while the top of the battery was still finished 
 off in an unbroken horizontal plane. In the 12-inch design, Plate 
 XVIII, the floors of all the rooms of the lower story are at exactly 
 the same elevation, but in the 10-inch design, Plate XIV, the floors 
 of the rooms under the loading platform are shown as being about 
 3 feet higher than those in the traverse. 
 
 The means of communication between the two stories have been 
 somewhat improved over the 1894 type. At the rear of the right 
 side of each loading platform, a wide staircase connects this platform 
 with the lower level and in front of the same side of the loading 
 platform another staircase runs from the working-platform level 
 down to the lower level. These designs are the first to show the wide 
 annular steps connecting the loading and working platforms. 
 
 As compared with 1894 type, the loading platform has been much 
 widened and extended. It now extends to the parapet wall in front 
 and to the traverse walls on both sides. The rear of the platform in 
 the lO-inch emplacement is about 32 feet from the axis of the gun 
 well and in the 12-inch it is- about 41 feet. Each loading platform 
 has also been extended by means of a so-called "truck corridor," 
 in rear of a portion of the traverse, so as to provide a convenient 
 location for the upper outlet of the ammunition hoist, but the loading 
 platforms are still isolated from each other, the truck corridor not 
 having been extended completely across the traverse between the 
 two emplacements. 
 
 The magazine space has been much increased over the 1894 type, as 
 will be seen by a comparison of the size of the powder and shell rooms 
 of the emplacements as shown on Plates XIII and XIV. Those 
 shown on the latter plate hava more than twice the floor area of 
 those on the former. Solid shot are still to be stored in the room 
 under the loading platform, which has been much increased in size. 
 The ammunition service has been greatly improved by providing in 
 each emplacement fom* hoists wells for the use of four differential 
 blocks, or for the installation of two pairs of balanced platform hoists, 
 which coiild hoist the already loaded ammimition trucks from the 
 magazine level up to the loading platform. 
 
124 
 
 For convenience in handling the projectiles, trolley tracks are 
 shown. These trolley tracks in both the 10-inch and 12-inch em- 
 placements pass from the shell room through the gallery and im- 
 mediately in front of the hoist wells. In the 12-inch emplacements 
 (Plate XVIII) another trolley track leads from the shot room under 
 the loading platform through this same gallery. In the 10-inch 
 design, however (Plate XIV), the ceilings pf the shot room and of 
 the gallery are on different levels and consequently a continuous 
 movement by trolley is not possible, although by using first one and 
 then another trolley track, the shot may be taken by troUey from the 
 shot room to the hoist wells. As an alternative method of handling 
 projectiles iri the 12-inch emplacements, in case the ammunition 
 hoist should get out of order, the trolley tracks are extended to the 
 rear doors of the shot room, and cranes are provided in the rear of 
 these doors for lifting the projectiles up to trucks on the loading 
 platform. The last mentioned trolley tracks leading from the rear 
 doors of the shot room to the shell room, can be used also in taking 
 the projectiles into the shell room. These particular trolley tracks 
 are not shown in the 10-inch plans and it is, therefore, necessary in 
 emergency ammunition supply in these emplacements, to roll the 
 projectiles on the floor out through the doors until they come within 
 reach of the cranes. 
 
 Plates XIV and XVIII both show on the lower story — in addition 
 to the powder, shell, and shot rooms — guard rooms, a storage battery 
 room, a stpreroom for general use, and a relocating room. They 
 each show on top of the battery a small observation station, or crow's 
 nest as it is sometimes called. In the 12-inch emplacements the 
 crow's nest is reached by a stairway from the loading platform and 
 in the 10-inch by a stairway leading directly from the relocating room- 
 In these designs the powder magazine is given a protection meas- 
 ured horizontally at the level of the ceiling, of not less than 20 feet 
 of, concrete and 50 feet of earth, while the parapet protection in 
 front of the gun consists of about 20 feet of concrete and 30 feet 
 of earth. 
 
 As a provision for decreasing the amount of condensation, small 
 6-inch air spaces are shown, passing around the front and sides of 
 the rooms in the traverse and in front of the rooms under the loading 
 platform. Unfortunately, however, these air spaces are shown as 
 blind and have no outlets for drainage ; and, as wUl be noted on the 
 chapter on dryness, it was not unusual for seep water to accumulate 
 in these blind air spaces and to seep through them into the magazines 
 or other rooms, so that though intended to decrease the difficulties 
 due to dampness, these air spaces occasionally made matters worse. 
 However, these designs are an improvement over the 1894 type in 
 providing possible ventilation, the number of doors opening on to 
 
125 
 
 the rear face being much increased and these, if left open, permit 
 some circiilation of air. 
 
 These designs show also a considerable increase in the size and 
 depth of the gun well, but as the size of the gun well is fixed by the 
 Ordnance Department this is an improvement for which the Engineer 
 Department is not entitled to credit. 
 
 1898 Type. 
 
 Outline drawings of the 1898 type of 10-inch emplacements are 
 shown on Plate XV and of the 1898 ty'pe of 12-inch emplacements on 
 Plate XIX. 
 
 These designs, like the preceding ones, are of the two-story type, 
 all the rooms on the first story having their floors on the same eleva- 
 tion. The principal improvement over the 1896 .type consists in 
 the extension of the truck corridor completely across the rear of the 
 center traverse so as to connect the two loading platforms, thus per- 
 mitting the personnel to walk from one to another, and also allowing 
 an ammunition truck to be rolled from one loading platform to the 
 gun at the other. It is thus made possible, in case the ammunition 
 hoist of one gun should get out of order, to supply that gun from the 
 ammunition hoist of the other. In view of this possibility and of the 
 improvement in ammunition lifts, it was considered unnecessary to 
 furnish more than a single pair of balanced platform hoists for each 
 gun. The truck corridors of the left guns are shown as covered by 
 spHnter-proof Concrete roofs, while those of the right gun are open 
 to the sky. Why this was done is not known to the writer. 
 
 Another important improvement in this new type is in placing the 
 forward stairway between the two stories in such a position that its 
 lower end is in the magazine space instead of being on the other flank 
 of the gun, as in the 1896 type. 
 
 Still another improvement was in providing three crow's nests for 
 the battery instead of one, as in the 1896 type. One of these crow's 
 nests is located on each flank of the battery and one about the center, 
 and they are all placed much farther to the rear than in the 1896 type, 
 so as not to be interfered with as much by the blast effect when the 
 gun is fired. All are reached by ladders instead of by stairways like 
 those in the 1896 drawings, and this makes them slightly less easy to 
 get to. 
 
 Another important difference from the 1896 type is the provision 
 of an earth cover in the rear of the magazines. A few years later, 
 however, this earth cover was considered unnecessary and was removed 
 from most of the batteries where it had been placed. 
 
 The 1898 type plans of 10-inch emplacements, Plate XV, differ from 
 the corresponding type plans of the 12-inch emplacements, Plate XIX, 
 and from all the other 10-inch and 12-inch type plans shown. Plates 
 XIV, XVI, XVII, XVIII, and XX, in the important particular 
 
126 
 
 that the trolley rails from the shell rooms and the galleries through 
 which the trolley rails pass are located in rear of the hoist wells- 
 instead of in front of them as in all the other plans. So long as there 
 were installed in emplacements of this type, the balanced platform 
 hoists for the use of which these emplacements were designed, no 
 trouble was experienced from this difference, for it is just as easy, if 
 not a httle easier, to pull the loaded ammunition truck backward^ 
 from the hoist platform to the loading platform, as it is to push it 
 forward as had to be done in the other design of emplacement. How- 
 ever, when the balanced platform hoists had proved to be difficult to 
 keep in adjustment and it appeared desirable to substitute for them 
 the continuous-chain hoists diiSculties began to arise, for the chain 
 hoist had to carry up the projectiles and deliver them to a dehvery 
 table on the loading-platform level, practically vertically over the 
 receiving table on the magazine level. This required the front- 
 delivery type of chain hoists. When, therefore, it became necessary 
 to install chain hoists in this type of 10-inch^mplacements, of which 
 quite a large number were built, and in the similarly arranged 8-inch 
 and 12-inch emplacements, of which a few were built, use had to be 
 made of the somewhat awkward front-delivery type of hoist, of 
 which the lower portion is illustrated in figure 2, Plate I, instead of 
 the much simpler and more satisfactory back-delivery hoist illus- 
 trated in figures .3, 4, and 5 of the same Plate I. 
 
 Except for the items mentioned and a slightly different arrange- 
 ment of the rooms on the lower story, the 1896 and 1898 types are 
 essentially alike. 
 1900 Type. 
 
 About 1900, plans of another type of large disappearing emplace- 
 ment were prepared. Outline drawings of the 10-inch emplacement 
 of this type are shown on Plate XVI. 
 
 In these plans there was a considerable rearrangement and an 
 increase in the number of the rooms on the lower story, as will be 
 seen by comparing Plates XV and XVI. This type of emplacement 
 is adapted to the use of the back delivery chain ammunition hoists. 
 The projectiles are carried up by the hoists and are delivered on 
 delivery tables opening through the front walls of the truck corridors. 
 The truck corridor of the left gun is again shown as covered, while 
 those of the other two are open to the sky. 
 
 Although not needed for ammunition service, cranes are still 
 shown for emergency use in case the ammunition hoists get com- 
 pletely out of order. For use with the crane or in ammunition 
 supply, trolley rails are shown as running to the rear doors of the 
 shot room. As a possible alternative method of getting projectiles 
 from the lower to the upper story, long ramps are shown on both 
 flanks of the battery. An ammunition truck could in this way be 
 
127 
 
 pushed down to the lower story and, in cases of emergency, be loaded 
 there and then pushed to the flanks of the battery and up one of 
 these ramps to the loading platforms of the guns. The shape of the 
 rear of the loading platform level is also somewhat improved by 
 making it a straight line parallel to the line of the gun centers, thus 
 improving the communication between the diEEerent loading plat- 
 forms. 
 
 Another improvement is in providing two rear stairways instead 
 of one for getting from the lower story up to the loading platform. 
 Unfortunately, however, these rear stairways are located immedi- 
 ately behind the gun and are, therefore, directly in the way of all 
 movements requiring the mounting or dismounting of the gun or 
 carriage. It was assumed, of course, that the gim and carriage 
 would be mounted once for all but experience has shown that, on 
 account of repairs and alterations, the process has to be repeated 
 not infrequently, and when this is done, stairways in rear of the 
 center of the loading platform have been found somewhat in the way. 
 
 The stairway connecting the working platform with the magazine 
 space shown in this plate as circular. It is understood that this was 
 done in order to make less probable the entrance of an enemy's 
 projectile. However, circular stairways are by no means as con- 
 venient to go up and down as if they were straight. These plans 
 show ladders for climbing from the loading platform up to the crest 
 of the parapet. Although not shown on the other older plates, it 
 had been customary almost from the very beginning to install such 
 ladders. Stairways instead of ladders are provided for gettiag to 
 the crow's nest; this is an improvement. 
 
 The blind air spaces around the magazines and rooms are shown 
 on this plate as on the plates of the preceding types. The number 
 of doors and windows opening from the rooms on the lower story is 
 much greater on this plan than in the preceding ones, and other 
 openings for ventilation connect the different rooms with one another 
 and with the corridors, galleries, and stairways, so that the ventila- 
 tion in this new design is much better than in the older ones. 
 
 Recesses under the front parapet wall are shown for storing spare 
 ammunition trucks and there are other recesses intended to be used 
 for telephone booths in several different places. 
 
 The amount of protection afforded the magazine and guns ia this 
 tj^e of emplacement is shown as only about four-fifths of that in the 
 older types. 
 
 1903 Type. 
 
 About 1903 there were prepared by the Board of Engineers the 
 drawings of a greatly improved type of emplacement. The 10-inch 
 plans were published in the sixth supplement to Mimeograph 36, 
 
128 
 
 and are shown in outline on Plate XVII. The 12-inch plans were 
 published in Mimeograph 66, and are shown in outline on Plate XX. 
 
 Among the principal improvements in this new type design are: 
 The great increase in size of the loading platforms; the provision of 
 two ammunition hoists per gun; the provision of a special room for 
 the motor generator of the Ordnance Department; the substitution 
 of regular staircases built into the side walls of the loading platforms 
 for the ladders previously used for climbing from the loading plat- 
 form to the top of the battery; and, most important of all, the 
 greatly improved methods for keeping the magazines and other 
 rooms of the battery dry. 
 
 The loading platforms in the 10-inch emplacements are increased 
 in size, to a depth of about 43 feet measured from the axis of the 
 gunwell, and a width of 40 feet on each side of the gunwell to the 
 side wall of the emplacement. The 12-inch emplacements are made 
 about 52 feet deep, measured from the axis of the gunwell to the 
 rear of the loading platform, and 48 feet wide, measured on each 
 side of the gunwell to the side wall of the emplacement. These 
 increases in the size of the loading platforms were made principally 
 because it was expected that longer guns would be mounted in these 
 emplacements and ample space was desired for handling the long 
 sponge and rammer staffs. 
 
 Two shell hoists were provided for each gun, not only for the pur- 
 pose of providing an additional means of raising projectiles should 
 a single hoist get out of order, but also in order to make it possible 
 to change rapidly from one type of projectile to another. Cranes 
 are shown as an alternative method of raising projectiles should the 
 hoists get out of order. 
 
 The corridor connecting the two loading platforms is made about 
 12 feet wide and perfectly straight, and on this corridor there open 
 the hoist wells, the Ordnance Department motor generator rooms, 
 the telephone booths, and the storerooms. Both truck corridors are 
 shown as covered by splinter-proof roofs. 
 
 The arrangement of the rooms on the lower floor is somewhat 
 simplified by having fewer rooms and making these larger. Under 
 each loading platform there are three large rooms, surrounded in 
 front, and on the sides by a wide air passage, while at the rear they 
 open on a corridor. In each traverse, likewise, are three large rooms, 
 a shell room, a powder room, and a large and conveniently arranged 
 hoist room. The hoist room has an air passage in front and on one 
 flank, while on the rear and on the other flank it opens on the 
 outer air. 
 
 The shell and powder room taken together are built as an inside 
 house in a large magazine space. Between the two is a thick brick 
 wall that serves also to hold up the roof of the magazine space, but 
 
129 
 
 the other walls are thin brick walls that do not extend up to the 
 ceiling of the magazine space but only to separate frame and copper 
 roofs. Since these roofs are easy of access they can easily be kept 
 water-tight so that seep water can not get into the shell or powder 
 rooms. The free circulation of air permitted aroimd the thin walls 
 and roof of the powder and shell rooms tends to insure that these 
 waUs will practically always have the same temperature as the outside 
 air. Consequently, when this air is permitted to enter these rooms 
 there is no condensation. The effect of the air passage on dryness 
 and condensation will be discussed much more fully in Chapter IX, 
 which is devoted to such subjects. 
 
 As an aid to prevention of dampness, the air passages passing 
 around the various rooms, which on the former plans, were shown 
 as blind, are now widened to 2 feet, and are made so as to open 
 on the rear face of the emplacement at several places, and to connect 
 with the various corridors, galleries, and stairways. Incidentally 
 also, numerous ventilators leading from the air spaces on the lower 
 story up to openings on the side and front waUs of the loading plat- 
 forms were shown in the mimeograph, but are omitted from the 
 outline drawings on the plates. There is thus insured, through the 
 air passages, a good circulation of air, the need of which is described 
 Chapter IX. 
 
 However, in spite of the greatly improved provisions for inducing 
 a circidation of air, the plans were deficient in not providing sufficient 
 windows, in showing only solid doors, and in not providing gratings 
 that could be locked and thus keep out intruders while still permitting 
 the free circulation of the air. Incidentally, the air passages in a few 
 places had an unnecessary number of sharp bends which always 
 interfere to some extent with the circulation of air. 
 
 The front stairways end on the lower floor in passageways close 
 to the doors of the powder rooms, thus making these stairways con- 
 venient for serving powder when carried by hand. By using the 
 guard rooms as passageways the lower ends of the front stairways 
 are readily accessible from behind the battery. In the 10-inch plans 
 (Plate XVII), the upper end of these front stairways is on the loading 
 platform; in the 12-inch plan (Plate XX), on the working platform; 
 but the difference is one of convenience and is not important. The 
 rear stairways are made double and the mistake is again made of 
 placing them directly behind the guns. 
 
 The observation stations are shown as metal platforms reached by 
 metal staircases projecting out from the rear of the emplacement 
 proper. Three are provided, one at either flank of the battery and 
 one neiar the center. 
 
 173341—20 e , 
 
130 
 
 The amount of protection afforded to the magazine, measured 
 horizontally at the ceiling, is about 15 feet of concrete and 45 feet 
 of earth. The protection in front of the gun is about 15 feet of con- 
 crete and 40 feet of earth. These figures are slightly smaller than in 
 the 1896 and 1898 types, but are slightly larger than in the 1900 type 
 and are stated in the mimeograph as b^^ing sufficient to keep out the. 
 Navy 12-inch projectile even -wjth its muzzle velocity. i- 
 
 On one of the sheets of the mimeograph an alternative arrangement 
 of the battery with both magazines placed between the guns is shown, 
 but in the magazine space of this alternative plan the mistake, was 
 apparently made of placing the powder rooms . outside of the shell 
 rooms instead of the reverse, which is the natural and convenient 
 arrangement. 
 
 The few defects of the 1903 type mentioned above were to a con- 
 siderable extent corrected in the first battery built according to these 
 type plans; Battery Parrott, a two-gun, 12-inch disappearing battery 
 completed at Fort Monroe in 1905. In this battery the air spaces 
 were made with fewer angles than is shown in the type design all the 
 rooms were lined and ceiled with porous tiles or porous bricks, and^ 
 in place of the double stairway in the center of the rear of each load- 
 ing platform, two staircases were provided for each loading platform, 
 one on either side. ' 
 
 1908 Type. 
 
 After the publication of the mimeograph showing the 1903 type 
 designs, emplacement construction in this country almost ceased, 
 although there were a few 12-inch, emplacements of that type con- 
 structed. 
 
 The Ordnance Department completed its preliminary designs for 
 the 14-inch disappestrihg caiTiage about 1907, and the Board of En- 
 gineers at once started to design emjilacements for that gun and 
 carriage; The designs prepiared by the board were very similar to 
 the 1903 designs, but before being published they were much improved 
 and were redrawn in the Office of the Chief of Engineers, so it was not 
 until 1908 that they were issued as Mimeograph 109. Outline draw- 
 ings of this ty^e design are shown on plate XXII. 
 
 However, although outline drawings of this new type accompany 
 these notiBs, it is believed that it is highly desirable that any officer 
 studying the subject in earnest should obtain access to the mimeo- 
 graph, both text and drawings) and should careftiUy examine them. 
 These are the latest mimeograiph plans of large gun emplacements 
 issued by th6 Engineer Department. They are quite complete and 
 go into many details which can not be shown on outline drawings. 
 The details referred to are those of the contour liries, gutters, drainsy 
 mosquito-proof smnps, and other matters connected with the drainage 
 system; the air vents, ventilators, gratmg windows, and doors of the 
 
131 
 
 ventilating system; the tile linings of the walls and ceilings; the de- 
 tails of the water-proofing system; the location of the electric lights 
 and lighthoods, and of the ducts and conduits of the electric system; 
 the routing of the speaking tube system; the hydrants, basins, etc., 
 of the water supply and sewerage system; the details of the hoist 
 installation, troUey tracks, shell tables, powder racks, emergency 
 shell and powder recesses of the ammunition service system; the 
 interior waterproofing surface of the Marshall system of water- 
 proofing; the details of the reinforcing bars, steel coliunns, etc., and 
 the dets^led arrangement of the observation slots and observation 
 openings of the battery commander's station and the plotting room. 
 
 The drawings of the 1908 type, both in the mimeograph and on the 
 accompanying plate show only the left half of a two-gun battery, 
 the other half of the battery being supposed to be syxometrically 
 arranged. Both magazines are located between the guns. 
 
 In its main characteristics this type of emplacement design re- 
 sembles somewhat closely the 1903 type. It is of the two-story type, 
 the upper story containing the wide loading platforms which are 
 connected by a covered truck corridor, and the lower story, three 
 groups of rooms, one group under each loading platform and the 
 other in the traverse. 
 
 The loading platforms are shown much larger than in the 1903 
 designs, because they are intended for the 14-inch gxm which is longer 
 than the 12-inch. These platforms are 62 feet deep, measvu-ed in 
 rear of the gun well and 58 feet wide from the gun center to the side 
 wall. 
 
 The covered truck corridor is 12 feet wide, measured in the clear, 
 between the rear wall of the traverse and the columns, and, immedi- 
 ately in front of this corridor and opening on it, are the shell hoist 
 rooms, the powder hoist rooms, the truck storage rooms, and the 
 plotting room. 
 
 On the lower story there are five rooms under the loading platform, 
 the increase in the number of rooms over the 1903 type being made 
 possible by the increase in the size of the loading platform. As in 
 the 1903 type, these roortis under the loading platform have an air 
 passage in front of them and on their flanks. In addition to this air 
 passage around these rooms, there is another fore and aft passage, 
 extending along the capital of the emplacement from the front air 
 passage to the rear corridor, this separating these five rooms into two 
 groups. On the lower story of the traverse there are, as in the 1903 
 type, a shell room, a powder room, and a hoist room for each gxin, 
 while in the center of the battery small additional rooms are provided 
 for the use of the officers, either as offices or sleeping rooms. Im- 
 mediately in front of the hoist rooms an air passage runs from one side 
 of the traverse to the other, being connected at its ends with the 
 
132 
 
 fore and aft air passages under the edges of the loading platfoims, 
 and at the center of the battery with a special short air passage which 
 extends through to the main rear corridor. In front of the powder 
 room and shell room a passageway 5 feet wide extends not only 
 completely across the traverse but, in addition, a short distance 
 farther in either direction to th.e feet of the stairways which lead 
 up to the working platforms. By using either of the "long store- 
 rooms" as a passageway, this front passageway can easily be reached 
 from the main rear corridor. 
 
 As additional inducements to a steady circulation of air through 
 the emplacement, the mimeograph drawings show niunerous vents 
 passing through the walls near the ceilings from one room to another 
 or from the rooms to the air passages. In addition, several 2-foot 
 ventilators are shown as passing upward from the air passages to the 
 side or front walls of the emplacement or to the top of the battery. 
 Numerous windows are shown in all of the rooms that open on the 
 truck or main corridors and all door and window openings are fitted 
 with gratings as well as with solid doors and windows. Included 
 among the doorways to be fitted with gratings as well as solid doors 
 are the outer doors of the air passages, all the doors of the shell and 
 powder rooms, and the doors of the shell hoist and powder hoist 
 rooms. 
 
 The shell room and the powder room of each emplacement are 
 shown as absolutely separate structures, each built in a large maga- 
 zine space. This carries out still further the ideas first shown in the 
 1903 plans, in which the powder room and the shell room are shown 
 as semiseparate structures; that is, only one of the walls of each room 
 serves to hold up the roof of the magazine space. 
 
 All of the walls of the powder room and the shell room, as well as 
 their ceilings, are shown as lined with tiles or porous brick. In fact, 
 this is likewise true of all the rooms in the battery. The ceiling tiles 
 are to be of special shape, designed for use in Battery Parrott, Fort 
 Monroe, and shown on Sheet IV of Mimeograph 109. 
 
 The mimeograph drawings show the emplacement waterproofed 
 according to a system described in the mimeograph text. This system 
 known as the Marshall system, consists principally of an interior 
 water-proof surface, as described in the chapter on dryness, etc. 
 As a further means of preventing or reducing the amount of water 
 entering the concrete through the hair cracks which are so apt to 
 form in an exposed horizontal concrete surface, a system of reinforcing 
 bars inserted a few inches below the surface is shown in the mimeo- 
 graph drawing as extending throughout the whole roof of the traverse 
 as well as in the pavings of the loading platforms. 
 
133 
 
 TJbe method of storing ammunition in this type of emplacement is 
 quite different from that shown in the older types. The projectiles 
 «re to be stored not on the floors of the shell rooms, but on shell 
 tables built of concrete and containing a tile layer to prevent the con- 
 duction of heat away from the surface of the table. The lower tier of 
 projectiles is to rest on steel rails built into the table, and these rails 
 are of the same height as those in the receiving table of the hoist. 
 Short removable rails are to be provided across the passageway, so 
 that the projectiles may be rolled directly from the storage table to 
 the receiving table of the hoist, although in case it is desired to do so, 
 the projectiles can be handled by a trolley running on a trolley rail 
 which passes over the center of gravity of the projectiles on the storage 
 table and over the receiving table of the hoist. 
 
 When the number of projectiles to be stored in the shell room is more 
 than sufficient to fill one tier, skids are to be placed upon the lower 
 tier of projectiles and a second tier placed on these skids. For the 
 easy service of the projectiles of the second tier, it is proposed to install 
 a removable upper set of rails across the passageway and a removable 
 upper receiving table on the hoist, so that the projectiles of the second 
 tier likewise may be rolled directly to a receiving table. Consequently 
 the use of a trolley is not actually required in the ammunition service 
 of a battery of this type. 
 
 For the storage of additional projectiles, if necessary, it is pro- 
 posed to make use of the long storeroom under the loading platform, 
 and to make this possible, the trolley rails of the shell room have been 
 extended to and through this long storeroom. In connection with 
 the trolley system it should be noted that, in general, it is laid off m a 
 series of loops so that as soon as one trolley has delivered its load it 
 can be moved on again around the loop without interfering with the 
 motion of succeeding trolleys. Where necessary to go from one loop 
 to another, switches and connecting tracks have been installed. In 
 addition, for the purpose of ammunition supply, a trolley rail has 
 been extended from the hoist room to the rear corridor and across 
 that corridor where it projects in the form of a cantilever from the 
 rear face of the battery. It was recommended in the mimeograph 
 text that the "Cob urn" trolleys and trolley track be used, they being 
 the most satisfactory type known at the time. 
 
 In accordance with the custom of the times the plans show ammuni- 
 tion cranes placed in rear of the truck corridor just over the cantilever 
 extensions of the trolley rails. However, in the batteries constructed 
 on this type the cranes were not installed. 
 
 As in the '1903, and in some of the earlier designs, the projectiles 
 when served to the gun are carried up from the shell room by means 
 of a hoist, which delivers them on a delivery table in the truck 
 corridor. The delivery table is fitted with an escapement to permit 
 
134 
 
 one projectile at a time to be rolled into the ammunition tnick, which 
 is then pushed to the loading platform. 
 
 At this point in ammunition service, however, a modification was 
 intended to be introduced and was shown in the mimeograph drawmgs- 
 At the time these drawings were prepared the Ordnance Department 
 proposed to do the ramming by a mechanical rammer operated on a 
 special loading car, which was to run on rails set in the loading plat- 
 form in a circular track concentric with the axis of the gun well. 
 These rails were shown on the original mimeograph drawings, but have 
 been omitted from the plate. 
 
 This loading car was to be attached to the gun carriage and was to' 
 move around the track as the gun carriage was moved in azimuth. 
 It was intended that the projectile truck with the projectile on it 
 should be run up alongside the loading car. The projectiles would 
 then be rolled from the truck to the receiving table of the loading car, 
 and when the gun had fired a shot and had recoiled into its loading 
 position the new projectile would be mechanically rammed from the 
 loading car into the gun. The same rammer was then to ram the 
 powder in in the same manner. However, before any emplacements 
 foliowing these designs were built the Ordnance Department decided 
 not to introduce the loading car or the mechanical rammer. Con- 
 sequently, the circular loading track was omitted and the Ibading plat- 
 forms were finished off smooth as in the former types of emplacements. 
 The old method of serving ammunition by running the loaded pro- 
 jectile truck against the breech of the gun and ramming the projectile 
 in by hand was retained. 
 
 The mimeograph drawings show steel powder racks in the powder 
 rooms for the storage of powder, a charge of which was to consist of 
 four cartridges. For raising the powder from the powder room to the 
 truck corridor a special powder hoist was to be installed, and in con- 
 nection with this powder hoist a powder chute is shown for the return 
 to the magazine of unused powder or of the dummy cartridges used in 
 drill. 
 
 One powder hoist and two projectile hoists are provided for each 
 gun, the two projectile hoists being intended to permit a rapid change 
 in the kind of projectile whenever it might be necessary. 
 
 For the emergency storage of a few projectiles close to the gun, 
 recesses are shown in the front walls of the loading platform, in which 
 are to be installed emergency shell tables large enough to hold four 
 projectiles each. These emergency shell tables are of the same 
 height as the delivery tables of the hoists and are fitted with similar 
 escapements. Similarly, an emergency powder shelf 'for storing 
 temporarily a few rounds of powder is shown in the front wall of the 
 truck corridor near the loading platform. 
 
135 
 
 The plotting room is placed immediately in front of the center of 
 the truck corridor and has a door and windows opening on it. Over 
 the center of the truck corridor, and therefore very nearly over the 
 plotting room, is placed a battery commander's station, and between 
 the two, large openings are left so that the battery commander in the 
 battery commander's station can look iato the plotting room and see 
 what is going on there and can talk to the personnel at the plotting 
 board. The battery commander's station has a concrete roof and is 
 fitted with observation slots and windows similar to those in use in 
 fire-control stations. 
 
 Immediately in rear of the battery commander's station and run- 
 ning the whole width of the traverse is the battery commander's 
 walk at the same height as the floor of the battery commander's 
 station. From any point on this battery commander's walk a clear 
 view of the field of fire can be obtained over the battery, and from 
 either end of the walk a person can look down into one of the loading 
 platforms. 
 
 The plans show a power room in the battery, one of the rooms imder 
 the loading platform being utilized for that purpose. It is intended 
 that there should be installed in this power roona two of the standard 
 25-kilowatt, gasoline-actuated generating sets, with their radiators. 
 Normally, the fans are to blow the heated air from the radiators to the 
 outside, but in order that it may be possible to warm up the battery 
 in the early spring and thus reduce the amount of condensation later, 
 a hot-air flue is shown as passing from the power room across the entire 
 front of the battery. At various places this flue is connected with the 
 front passageway by branch flues, controlled by dampers, by the 
 proper operation of which warm air can be thrown in at any point 
 of the emplacement. The reason for this expedient will be explained 
 in Chapter IX on dryness, etc. 
 
 In the mimeograph drawings, this hot-air flue is shown as circular 
 in cross section and about 4 feet in diameter. In the batteries 
 actually constructed there has been substituted for' the hot-air flue 
 a passageway about 2^ feet wide by 6^ feet high, and doors have been 
 substituted for the dampers. ' 
 
 For communication between the lower and upper stories there are 
 the interior stairways connecting the front passageway with the 
 working platforms, and five other stairways in rear of the battery, one 
 in the rear of the center of the battpry, and one on each side of each 
 loading platform. The sides of the loading platform are considered 
 better positions for these stairways than tne center, as in the former 
 position the stairways will not interfere with or be injured by the proc- 
 ess of mounting the gun or carriage. For communication between 
 the loading platform level and the battery commander's walk three 
 stairways aie provided, one in tne center of the battei> behind the 
 
136 
 
 plotting room and the others at each flank of the trav^eise. For 
 reaching the top of the battery, stairways are provided on each side 
 of each loading platform; aad lor getting from the battery com- 
 mander's walk to the top ot the traverse, a stairway on each side of the 
 battery commander's station. All exterior stairways and the battery 
 commander's walk are shown as built of rekiforced concrete, supported 
 by reinforced concrete brackets, projecting as cantilevers from the 
 rear walls or columns of the battery. 
 
 The mimeograph drawings likewise show hand rails wherever they 
 are considered necessary, such as on all exterior stairways and along 
 the rear of the loading platform, of the truck corridor, and of the 
 battery commander's walk. 
 1912 Type of Disappearing Emplacements. 
 
 When, in 1908, mimeograph 109 was published, and for several 
 years thereafter, emplacement construction in this country was quite 
 inactive and consequently no emplacements following the 1908 design 
 were actually built, though in the next few -years in our tropical 
 possessions, quite a number of 14-inch emplacements and some 
 12-uich emplacements were built along the general lines of mimeo- 
 graph 109. 
 
 In the meantime, however, the question was being agitated as to 
 whether the general type previously used in designing disappearitrg 
 emplacements for heavy guns was the most satisfactory. These 
 designs aU followed the two-story type, which had the disadvantage 
 of requiring in ammunition service that the ammunition be raised 
 from the lower or magazine level to the upper or loading platform 
 level. However, this type of construction was supposed to possess 
 the great advantage of concealing the exact position of the gun, which 
 was accomplished by placing the crest of the whole battery in a 
 horizontal plane. As long as nothing was allowed to project verti- 
 cally above this horizontal plane, this important advantage was 
 retained, but for a few years back it had become customary to build 
 battery commander's stations in rear of the batteries, so as to project 
 above the crest Hne. A battery commander's station of the kind 
 with a splinter-proof concrete roof had been embodied in the 1908 
 designs and is shown on Plate XXII. This battery commander's 
 station is visible to the enemy, its position with respect to the gtm 
 can be npted whenever the gun appears in battery, and thereafter 
 the battery commander's station may be used as an piming point for 
 projectiles directed not only at the station itself but also those 
 directed at the gun. In this way the principal advantage of the 
 two-story type battery — that is, concealment of the position of the 
 guns, is lost; while the principal disadvantage, the necessity of using 
 mechanical hoists, is retained. 
 
137 
 
 The question was, therefore, discussed as to. whether it might not 
 be advisable to change to the one-story type of battery providing 
 horizontal ammunition service. Consequentiy, when in the summer 
 of 1911 the writer of these notes was detailed as the designing engi- 
 neer of the Panama fortifications he was directed by the Chief of 
 Engineers to design the heavy emplacements on the one-story, 
 horizontal ammunition service plan. 
 
 The detailed designs of the 14-iach batteries were completed in 
 1912, and consequently this type of design is properly called the 
 "1912 type;" but as it was first worked out in connection with the 
 Panama fortifications, it is ordinarily known as the Panama type 
 of emplacement and is several times referred to by that title in these 
 notes. 
 
 Plate XXIII shows the outline drawings of one variety of this 
 type, called the "1912 (M) type" and Plate XXIV, another variety 
 called the "1912 (S) type." A comparison of these two plates wiU 
 show that these two varieties are exceedingly similar. The first 
 or "M" variety is suited to locations where fiank fire is not to be 
 expected and where, therefore, it is safe to have the truck corridor 
 enter the magazine traverse in the most direct way — that is, from the 
 side. The " S" variety is intended for locations where the possibility 
 of flank fire is considered too great to permit an opening into the 
 magazine from the side of the loading platform. This entrance must, 
 therefore, be made from the rear. 
 
 The essential principle of both varieties is horizontal ammunition 
 service; each emplacement having a loading platform, a corridor, two 
 shell rooms, and two powder rooms, aU on the same level — the fioors 
 of all being continuous and, except for slight drainage slopes, at 
 exactly the same elevation. 
 
 In this type of battery both of the shell rooms and both of the 
 powder rooms open on the truck corridor, and at the truck corridor 
 end of each of the shell rooms there is placed a service shell table, 
 large enough to hold eight projectiles, and fitted at its service end 
 with an escapement similar to that ordinarily used on the delivery 
 tables of ammunition hoists. When the time comes to serve a pro- 
 jectile to the gun, a truck is run up alongside the escapement end 
 of the shell table, which is just high enough for the purpose, and a 
 projectile is rolled from the shell table to the truck in exactly the 
 saine manner as is done in the older typc'of emplacements from the 
 delivery table to the truck. The projectile is then pushed directly 
 from this shell table to the breech of the gun. The powder is picked 
 up by the powder detachment, at the service end of the powder 
 magazine, and is carried to the gun either by hand or in a hand- 
 barrow. Consequently, in the ammunition service of this battery 
 no mechanical hoists are required. 
 
138 
 
 A trolley track is shown passing in a loop around through both 
 shell rooms and over both shell tables. The troUeys and differential 
 blocks are to be used for raising the projectiles from the floor of the 
 shell rooms where they are normally stored and placing them on the 
 shell tables. Not less than four trolleys are furnished for each gun 
 and, consequently, the work of keeping the shell table filled should 
 be easily done as fast or faster than the projectiles can be carried 
 away by trucks and can be fired by the guns. The trolley track is 
 shown in the form of a loop so that- when one trolley has deposited 
 its shell upon the shell table, it can be run on around the loop and 
 not interfere with the motion of succeeding trolleys. Iii each variety 
 of this type of emplacement an extension of this trolley track is shown 
 as running back to the rear part of the emplacement where it passes 
 over a railroad track on a level sufficiently below that of the truck 
 corridor to permit a loaded railroad car to pass under the trolley 
 rail. Since this railroad track is connected with the main railroad 
 system of the post, the movement of projectiles into the magazine 
 in ammimition supply is made quite simple and easy. In all these 
 new types of emplacements the troUey rails are composed of 7-inch 
 I beams, and the Chisholm-Moore trolleys, differential blocks, tongs, 
 and frogs are used. 
 
 The powder magazines were designed upon the idea that the powder 
 charge would be furnished in four cartridges which were to be stored 
 in specially designed steel powder racks. Before, however, these 
 racks were actually built and placed in the batteries the question was 
 raised as to whether it would not be desirable to put up the powder 
 charge in a single cartridge, for which, of course, the racks designed 
 for the four-cartridge ^charge were unsuited. Consequently these 
 racks were never built. 
 
 This type of emplacement has the advantage of horizontal ammu- 
 nition service but it has the disadvantage that with the floor of the 
 magazine and loading platform on the same level, the head room and 
 cover necessary for the magazine cause the magazine traverse to 
 project high into the air above the parapet in front of the gun. 
 However, in actual construction, the top of this traverse is rounded 
 off in a gentle slope and at the long range from which it is expected 
 it will generally be viewed by the enemy, the battery can not be 
 said to be imduly conspicuous. 
 
 In front of the loading "platform there is shown the usual variety 
 of parapet consisting of a concrete wall about 20 feet thick with a 
 thick mass of earth in front. In the immediate vicinity of the gun 
 and in the angle bounded by the limiting lines of fire of the gun, 
 the interior crest of the parapet is made horizontal and its top is 
 finished off with the elevations and slopes required by the necessity 
 of clearing the field of fire. However, toward the sides of the loading 
 
139 
 
 platform, the crest of the parapet instead of being horizontal as in 
 the old two-story type of battery, rises slightly as it proceeds from 
 the gun thus giving greater protection to the loading platform and, 
 in the "M" variety, to the truck corridor entrance of the magazine. 
 
 A very essential difference in this type of battery from the preceding 
 types is the abandonment of the concrete side walls of the emplace- 
 ment and the substitution for them of sand slopes rising gently from 
 the edge of the loading platform up to the cover over the magazine 
 traverse on one side and up to the top of the flanking traverse on 
 the other. 
 
 At both of the locations where the original emplacements of this 
 type were built, fire from the rear was not possible and, consequently, 
 it was not necessary to protect the gun and emplacement from such 
 fire. The rear of the loading platforms is, therefore, left open so that 
 an enemy's projectile wiU find nothing to stop it in its flight to the 
 rear. In a few other emplacements, however, fire from the rear was 
 not only possible but probable and the construction of a parados 
 was, therefore, essential. This will be discussed a httle later. 
 
 The two varieties of emplacements shown on the tw(t plates differ 
 mainly, as was stated above, in the location of the truck corridor 
 entrance. In the "M" variety, Plate XXIII, this entrance is at 
 the front of one flank of the loading platform, consequently the 
 truck corridor is perpendicular to the capital oi the battery and the 
 shell rooms and powder rooms are parallel to this capital. In the 
 "S" variety, Plate XXIV, the truck corridor enters the traverse 
 from the rear and essentially parallel to the capital of the battery, 
 and the powder magazine and shell rooms are, therefore, essentially 
 perpendicular to the capital of the battery. The ari'angement of 
 the other rooms in the traverse must, of course, accord with the 
 arrangement of the powder rooms and shell rooms, and, incidentally, 
 with the topography of the site. Of the rooms and passages in the 
 traverse, the most essential are, of course, the truck corridor, the 
 powder rooms, *and the shell rooms, but in addition to these both 
 plates show a plotting room, a power room, a storeroom, a guard room, 
 and a latrine. No air passages are provided for inducing a circula- 
 tion of air and no tile hnings are used because the emplacements 
 built in accordance with the plans shown are located in the Tropics, 
 where the temperature is nearly uniform throughout the year and 
 where, consequently, no trouble is experienced from condensation. 
 However, in order to make the magazines less uncomfortable when 
 a number of men are working in them, it was considered desirable 
 in a number of the Panama batteries to install fans for artificial 
 ventUation. One such is shown on Plate XXIV. 
 
 The power rooms in both varieties are each large enough for the 
 installation of two standard gasoline actuated generating sets with 
 'their radiators, and in order to prevent the hot air blown out by the 
 
140 
 
 radiators from being drawn back into the engine room, the radiator 
 flues are shown ending a considerable distance from the power room. 
 The gasoline tanks are located outside of the emplacement. This 
 was always done when possible, and as an additional precaution the 
 tanks are placed in pits about three or four feet deep. After the 
 tanks are placed in their pits and the pipe connections are made,, 
 the pits are filled with sand so that no part of the tank except the 
 filling pipe projects above the ground. 
 
 In all 14-inch batteries built in the last few years, even though 
 structurally composed of two emplacements, each emplacement has 
 been fitted so that tactically it may be used as an independent bat- 
 tery. That is, each gun is provided with its own battery commander's 
 station and plotting room. In order that persons in the battery 
 commander's station may obtain a clear view of the field of fire, it 
 is essential that the battery commander's station be placed on top 
 of the traverse ; furthermore, to get as far away as possible from the 
 blast of the gun it has to be at the rear of the traverse; and it should 
 be sufficiently to one side to permit a view to be obtained from it 
 of the gun, and of a part of the loading platform. This fixes its 
 position within narrow limits. In order that the usual voice-tube 
 communication between the battery commander's station and plot- 
 ting room may be possible, the plotting room has to be practically 
 under the battery commander's station, and in order that the plotting 
 room may be given the maximum protection, it is necessary to place 
 it on approximately the same level as the powder rooms and shell 
 rooms. , 
 
 The difference in elevation between the plotting room and the 
 battery commander's station thus rendered necessary is so great in 
 the "M" and "S" varieties that there remains sufficient space for 
 an intermediate story. This is utilized in both these varieties as 
 a place for an officer's room and toilet, the doors and windows of 
 which are shown on the rear elevations and sections, as are the 
 stairways leading from the lower story to the int^mediate story" 
 and thence to the battery commander's walk and battery com- 
 mander's station. 
 
 The battery commander's station shown has a one-level floor 
 and is an open station, though for the convenience of the personnel 
 in peace time pipes for holding an awning are indicated on the drawing,. 
 
 The drawings show also the tunnel connecting the plotting room 
 and the mechanical range indicator on the left of the gun. The 
 mechanism of this indicating apparatus is operated from the plotting- 
 room; the data is displayed in a niche cut in the upper part of the 
 stairs around the working platform. After the original plans of 
 these batteries were completed, they were modified at the request 
 of Gen. Weaver, then Chief of Coast Artillery, by providing, on the 
 
141 
 
 left side of the loading platform of each gun, a time-range board 
 and for the use of the men operating this time-range board, the data 
 displayed by the mechanical range indicator to the detachment at 
 the gun is also shown at another place where it can be seen by the 
 men operating this time-range board. 
 
 The drawings show also the passageway and stairway for proceed- 
 ing from the working platform down into the gun well. It leaves 
 the loading platform in front of the gun and proceeds around and 
 •downward and enters the gun well between two of the hold-down 
 bolts. For convenience in getting to the mechanical-indicator 
 -apparatus this stairway connects with the mechanical-indicator 
 tunnel. 
 
 Another variety of the 1912 or Panama type of emplacement which 
 may be called the "W" variety is shown on Plate XXV. At first 
 sight it would appear that the plans shown on this plate are a return 
 to the two-story type of battery, but a study will show this is not 
 true. ' The upper story of this variety, considered by itself, is a 
 <;omplete one-story battery, each gun having its loading platform, 
 its truck corridor, its shell room, and its powder room on the same 
 level. Consequently the service of ammunition is horizontal and 
 310 hoists are needed in ammunition service. 
 
 The battery of two guns shown on this plate is, therefore, reaUy 
 of the one-story type, although it resembles the two-story type. 
 The reason for building it in this way was that the site where this 
 particular battery was to be built was exceedingly low. To build 
 the battery on this level would have required that the bottoms of 
 the gun wells be sunk so far below sea level that they would be difficult 
 and expensive to build and also would, in all probabihty, subse- 
 <iuently give trouble in keeping water out. In order to reduce this 
 trouble within reasonable hmits, it was evidently necessary to raise 
 the battery quite a number of feet into the air and, after a study 
 •of the subject, it appeared well to raise it so high as to give room for 
 an additional story under the loading platform level, which in this 
 •case is also the magazine level. 
 
 This makes it possible to Teduce slightly the size of the magazine 
 on the loading platform level, part of the ammunition, only, being 
 kept in this, what may be called "service magazine," the remainder 
 l)eing kept in the "storage magazine," located on the lower story 
 ■directly under the service magazine. The service magazine contains 
 more ammunition ready for immediate service than will probably 
 •ever be used in a single engagement, and it is intended that between 
 ■engagements the ammunition that has been fired shall be replaced 
 hj raising into the service magazine some of the reserve ammunition 
 previously stored in the storage magazine on the lower story. For 
 oonvenience in raising powder and shell from the lower story to the 
 
142 
 
 upper, openings through the ceiling of the storage magazine to the 
 floor of the service magazine are shown. Special mechanical hoists 
 were installed in these openings and, since this is a process for which- 
 extreme haste is not necessary, the refinements necessary in the hoists 
 of the two-story type of battery are not needed. TroUey tracks are 
 showTi on both stories, those on the lower one being extended to 
 the rear so as to be available for ammunition supply. 
 
 The arrangement of the front parapet wall, of the sand slopes on 
 the sides of the loading platform, of the rounded-off top of the center 
 traverse, of the battery commander's walk and battery commander's 
 stations, and of the stairways leading to them are quite similar to 
 those of the "M" and "S" types shown on Plates XXIII and XXIV. 
 
 Raising of the battery sufficiently high for an additional story 
 under the loading platform and service magazine level, leaves much 
 spare space on this lower story. Structurally, only the concrete walls 
 necessary for supporting the upper story are required. In some 
 places the voids are, for reasons of protection, shown as filled with 
 sand, but the rest of them were left open and fitted as rooms. They 
 are furnished with doors and windows and, on the deta.iled plans, are 
 shown as being electrically lighted and are thus available for use. 
 On Plate XXV some of these rooms are shown as being assigned to 
 particular uses^ — reserve powder rooms, reserve shell rooms, officers' 
 room, plotting rooms, latrine, power room, guard room, storerooms, 
 pump rooms, etc. The other rooms are not marked and are, of 
 course, available for miscellaneous use. 
 
 The plotting room is placed on the lower story in order to give it 
 the maximum protection possible. In this case, instead of the indi- 
 cator tunnel leadiug from belcfvr the floor of the plotting room, it is 
 intended that the wires and shafts of the mechanical indicating 
 apparatus shall pass out just below the ceiling of the plotting room, 
 through openings left in the intervening walls, to the proper place 
 under the loading platform on the left side of the guns. 
 
 The power room is shown as occupied by four standard 25 kw. 
 generator sets. Only a part of this power is for use at this battery 
 itself, the remainder being required by neighboring batteries,_search- 
 lights, etc., or as a reserve. 
 
 In spite of the elevation to which the loading platform in this 
 battery was raised, the bottom of the gun well still remains some 
 6 or 7 feet below mean tide level. The natural drainage of such, 
 wells is, of course, impossible, and in the heavy rainstorms wnich 
 occur in the tropics considerable water will, of course, find its way 
 into them. It is, therefore, considered necessary to install pumps for 
 removing this water, and pump rooms are shown located on the sides 
 of the passageways leading into the gun wells. 
 
143 
 
 The great width of the loading platform required by the 14-inch 
 gun and the provision of sand slopes on the sides of the loading 
 platforms, make it necessary to separate the gims to about 320 feet, 
 center to center. This makes tJie battery quite long, and it is con- 
 sidered necessary to install six stairways for communication between 
 the lower story and the loading platform level. 
 
 The main line of railroad behind the battery was a part of the main 
 post railroad system and was connected with the Panama Railroad. 
 The sidetrack behind the center of the battery passes under the 
 cantilever extension of the trolley rail and was intended for use in 
 ammimition supply. 
 
 In the drawings of this battery, and, in fact, also in Plates XXIII 
 and XXIV, so-called "breech recesses" are shown as cut in the 
 front parapet wall, a few feet to the right of each gun. These are 
 required to provide space for opening the breechblocks after the gun 
 has been fired in the farthest possible position to the left. 
 
 The main important featxu-es of the large Panama emplacements 
 are illustrated on one or more of these three plates, XXIII, XXIV, 
 or XXV, but there are, in addition, a few details of some of the bat- 
 teries that would appear to deserve mention. 
 
 In addition to the battery illustrated as the "W" variety on 
 Plate XXV, there w^as another battery built in two stories, but for 
 quite a different reason. The "W" battery had a story built under 
 it, as it were, because the site was so low; this was done in the other 
 battery because the site was so high. It was built on a high conical 
 hill, and in order to avoid the cost of cutting the hill down too low, 
 it appeared to be well to keep the battery high by reducing the size 
 of the traverse. This was done, as in the "W" variety, by storing 
 some of the ammunition in service magazines on the loading platform 
 level, and some in storage magazines on a lower level, and by dividing 
 the other essential rooms between these two stories. 
 
 In a few of the Panama batteries where the conditions were specially 
 suitable an earth cover was placed over the concrete roof of the 
 traverse in a manner similar to that shown on Plate XXVI. When 
 this was done a different method of waterproofing was used. Instead 
 of using the Marshall system of an interior waterproof layer within 
 the mass of concrete, the waterproofing was done on the upper surface 
 where the waterproof material is protected by the sand covering from 
 exposure to the atmosphere. 
 
 The only two-gun battery illustrated is the " W" variety on Plate 
 XXV. In this battery the magazines of both guns are arranged and 
 are entered from the rear as in the "S" variety, Plate XXIV. Some 
 of the other two-gun batteries have their magazines arranged as in 
 the "M" variety, Plate XXIII. The two magazines are between the 
 guns, and the truck corridors of both emplacements enter the traverse 
 
144 
 
 from the side, close to the parapet in front, and nieet in the center 
 of the battery. The two truck corridors thus provide a continuous 
 passageway from one loading platform to the other. 
 
 A few of the Panama emplacements are so located that fire from 
 the rear would appear to be possible, and parados were therefore 
 considered necessary. When built, the parados extends completely 
 around the rear of the loading platform from the outer flank to the 
 magazine traverse, and is made as if it were an extension of the flank 
 traverse in a manner similar to the parados shown for the left em 
 placement of the battery illustrated on Plate XXVI . On the outer 
 flank the elevation of the top of the parados is the same as that of 
 the flank traverse and the elevation increases as the parados passes 
 in rear of the loading platform until it merges into the top of the 
 magazine traverse. In front the parados slopes down to the rear 
 edge of the loading platform in a slope at least as gentle as the sand 
 slopes on the sides of the loading platform. 
 
 In all emplacements where it was necessary to build parados the 
 magazines and the entrances to them are arranged as in the "M" 
 variety (PI. XXIII) ; that is, the truck corridor opens from the front 
 of the side of the loading platform. The shell and powder rooms, 
 of course, open on this truck corridor but the other rooms — store- 
 room, plotting room, officers' room, and latrine — are placed in the 
 rear of the shell and powder rooms and open on a rear gallery which 
 can be reached by a fore and aft gallerj^ connected with the truck 
 corridor. When the emplacement forms part of a battery, the rear 
 gallery is usually made continuous from emplacement to emplace- 
 ment, passing thi-ough the parados. Where this gallery passes in rear 
 of the loading platform an entrance is made to the rear gallery from 
 the loading platform and provides an alternative route of going from 
 the loading platform into the rooms of the traverse. For passage 
 between the plotting room and the battery commander's station, 
 a staircase is built up from the rear gallery near the door of the plot- 
 ting room to the battery commander's walk not far from the battery 
 commander's station. 
 
 The type of Ifi-inch emplacement built at Panama is similar to the 
 1912 type of 14-inch emplacements just described except for the 
 necessary increase in dimensions. The main difference is in the pas- 
 sageway doivn into the gun well. In order to get the large I beams 
 needed for moimting the gun. carriage through this passageway it had 
 to be made straight. The entrance is in rear of the loading platform, 
 and thence the floor of the passageway slopes down to the bottom of 
 the gun well. 
 
 The standard horizontal protection for the magazines of all these 
 batteries is the equivalent of 35 feet of concrete, which was calculated 
 to be about 25 per cent greater than sufficient to give protection 
 
145 
 
 agaiust the largest naval gun afloat at the time the batteries were 
 designed. 
 
 Not long after the development of the 1912 type of design for use 
 primarily in the Canal Zone, batteries of the same general design were 
 started in this country. As was to be expected the detailed designs 
 pf these batteries show some modifications from the 1912 type designs 
 described above, but the modifications are hardly sufficient to justify 
 considering these new designs as a new type. They are, therefore, 
 considered rather as a new variety of the 1912 type. Plate XXVI 
 shows the outlines of one of these newer batteries and may be called 
 the "L" variety of the 1912 type. 
 
 This Plate XXVI shows a two-gun, one-story, horizontal ammu- 
 nition service battery which, due to the topography of the site, has 
 certain peculiarities special to itself and these peculiarities, therefore, 
 can not be considered as typical. In the first place one gun is em- 
 placed a few feet higher than the other, but the difference is so small 
 that it can be easily overcome in the scarcely perceptible slopes of 
 the connecting corridors and galleries, so that, as far as tlae movements 
 of persons or trucks are concerned, the loading platforms may be 
 considered as essentially on the same level. Secondly, as wiU be 
 noted, the right loading platform is open to the rear, while the left 
 has a parados behind it. The parados is necessary in this case not 
 to protect the battery from fire from the rear, but because of the 
 presence of a hiU behind the left emplacement. However, the front 
 slope of this parados, the entrance into it, and the gallery through it 
 are quite similar to the same elements of the Panama batteries, where 
 parados were necessary and may, therefore, be considered to illus- 
 trate those elements of the Panama batteries. 
 
 The most important modifications shown in the battery illustrated 
 on Plate XXVI, which cause it to be considered as a new variety, 
 are the earth blanket over the traverse and the arrangement of the 
 shell and powder rooms. 
 
 The concrete roof of the traverse is covered by a blanket of sand 
 from 9 to 12 feet thick and the thickness of the concrete roof has, 
 therefore, been reduced to about 9 feet. This was done occasionally 
 in the Panama batteries, but is now to be considered as an essential 
 element of this later variety of the Panama type of design. The use- 
 fulness of the earth blanket has become even more apparent since the 
 Fort Morgan experiments of March, 1916, showed how probable it is 
 that the long-pointed projectiles of the present day will ricochet 
 from a mass of sand without penetrating more than a very few feet. 
 
 The addition of the earth blanket over the surface of the concrete 
 has made it possible to insure the water-tightness of this concrete 
 roof at its upper surface and no interior waterproof surface is con- 
 sidered necessary. 
 173341—20 10 
 
146 
 
 The plans of this new variety show also a slight change in the 
 arrangement of the rooms within the magazines. The truck corri- 
 dors enter the magazine space as they do in the "M" variety (Plate 
 XXIII), that is from the side close up imder the parapet; but, after 
 getting well into the magazine space, the corridors change direction 
 and proceed straight to the rear, piarallel to the capital of the battery. 
 The shell rooms and the powder rooms are laid out parallel to the 
 line of gun centers, as in the "S" variety, but the shell rooms are in 
 front of the powder rooms, instead of in rear of them as in the "S" 
 variety. After passing to the rear, past the shell rooms first and 
 then past the powder rooms, the truck corridors end in a wide area 
 way which extends from one side of the traverse to the other. In 
 front, where the truck corridors enter the traverse, each is extended 
 a few feet beyond where it changes direction, in a sort of shell trap, 
 to catch and hold comparatively harmless any enemy's projectile 
 that might by any chance be able to find its way into this entrance 
 to the traverse and there explode. 
 
 This battery being built at a place where but little trouble has been 
 experienced with condensation, no inside air passages were considered 
 necessary, except the one connecting the truck corridors immediately 
 in front of the forward shell room, which by separating the thin front 
 wall of this shell room from the thick concrete parapet in front should 
 serve to equalize the temperature of this thin wall with that of the 
 air. 
 
 The plotting rooms, power rooms, etc., have been located on the 
 front side of the areaway but still within the body of the traverse, 
 while a few of the less important rooms have been placed on the rear 
 side of this areaway in a house which is provided with much less 
 overhead cover. 
 
 The battery commander's stations are, as usual, placed on top of 
 the rear of the traverse and on the fianks. They are reached by two 
 stairways, one at each side of the traverse, and are connected by a 
 battery commander's walk. The battery commander's stations 
 shown have their fioors on two levels for the reasons which will be 
 described in the chapter on Fire control and the battery commander's 
 walk is placed on the lower level. It is thus too low to provide a 
 view over the traverse, but is connected with the top of the traverse 
 by two stairways running up the sand slope in front of the battery 
 commander's walk. 
 
 Criticisms. 
 
 Shortly after the Panama batteries were built, they were criticized 
 by a number of officers for their somewhat high cost; for their alleged 
 unnecessary extravagance in the protection furnished the gun, 
 materiel, and personnel; and for the arrangements for the comfort of 
 the detachments. At first these criticisms were made casually, but 
 
147 
 
 after they had reached a semioflicial status, the writer of these notes, 
 who had been the designing engineer of the fortifications, thought it 
 necessary to reply to the criticisms and did so in a long letter ad- 
 dressed to the Chief of Engineers. The substance of this letter was 
 subsequently embodied in the annual report of the Chief of Engineers 
 for 1918, from which I quote the following: 
 
 It has been proposed that it woiild be better and more economical to emplace sea- 
 coast guns in a much more simple way than has been the custom; to mount them in 
 barbette, in the open, without protecting parapets; to remove the magazines some 
 distance from the guns and, on accoimt of their decreased liability of being hit, to 
 make corresponding reductions in the thickness of their walls and ceilings; incidently , 
 to minimi ze the ammunition-handling apparatus within these magazines and to 
 simplify the emplacements generally by doing away with the provisions customarily 
 inserted for the care and comfort of the detachment. It has been argued that such a 
 policy would be in the interests of economy. 
 
 The cost of the gun carriage and of the emplacement are but two factors ia the total 
 cost connected with the gun, and by no means the largest factors. For every gim that 
 ifl emplaced there must be the personnel to man it, consisting of officers, noncommis- 
 sioned officers, and privates, all of whom must be paid, rationed, and maintained. 
 For the maintenance of this personnel, barracks, quarters, hospitals, storehouses, 
 administration buildings, etc., must be built, military posts must be purchased and 
 built and maintained, including their water supply, sewerage, lighting, and other 
 incidentals. Such detachments are required for the gun and for the gun alone, and 
 consequently all items relating to the pay, subsistence, and maintenance of the gun 
 detachment are just as much charges connected with the gun as are the cost of the 
 carriage and emplacement. 
 
 Certain of these costs, such as the purchase of sites, the manufactiu-e of the gun and 
 carriage, the construction of emplacements, barracks, quarters, hospitals, and other 
 buildings, and the installation costs of water supply and sewerage, are expenses which 
 are made once for all. Other expenses, such as pay, salaries, subsistence, heat, light, 
 fuel, water, and the maintenance of guns, emplacements, barracks and quarters, roads, 
 etc . , are continuing expenses and go on from day to day and year to year. In attempt- 
 ing to make a comparison or summation which include items of first cost as well as 
 those of continuing costs, we must reduce the two to a common basis, either by capital- 
 izing the running expenses or by converting first cost into running expenses by taking 
 into account interest on the original investment and the probable serviceable life of 
 the utility. 
 
 Making the comparison by means of the second method, we have for each enlisted 
 man his pay varying with length of service and grade, his subsistence, clothing allow- 
 ance, his pro rata share of the ffi-st cost and upkeep of the barracks, quarters, hospitals, 
 posts, roads, sewers, etc. Calculations made about a year or so ago in connection 
 with Army reorganization bills before Congress, indicated that the annual cost of a 
 priva,te figured in this way, was probably about $900 to $1,000 a year, and that this 
 annual cost mounted rapidly through the various grades of noncommissioned officers 
 and officers until a total of from six to eight times this figure was reached in the case of 
 field officers. 
 
 Basing calculations on the 14-inch guns, it is found that the personnel consists of 
 about 70 officers and enlisted men, whose total annual cost amounts to about $90,000. 
 The first cost of a disappearing emplacement for a 14-inch gun was estimated recently 
 at about $200,000 depending. Of course, upon location. Assuming 25 years as the 
 utility life of the emplacement, figuring the interest on the original cost at 3 per 
 cent, we will get what might be called the annual r unn ing cost at 7 per cent of the first 
 cost. Seven per cent of the first cost is $14,000 and adding to this $3,000, the cost of 
 
annual maintenance, we get as the annual cost pertaining to the emplacement about 
 117,000, equivalent to the upkeep of 16 or 18 enlisted men, or about one-fourth of the 
 size of the required gun crew. Similar figures make the annual cost pertaining to the 
 gun carriage about equivalent to the upkeejp of 7 or 8 enlisted men, or one-ninth of 
 the crew. , 
 
 In addition to the personnel, emplacement and gun carriage factors, there are many 
 other items of expense, such as the cost of the gun itself, of the power plant, etc.; 
 dividing these costs by the estimated life of each item, adding interest and main- 
 tenance and summing up, it is found that the amount is in all something over $130,000 
 per 14-inch gun per annum. So that the annual charges against a 14-inch emplace- 
 ment are, for fixed constructions, $17,000; armament, $23,000, and personnel, $90,000. 
 Of these items of annual cost, that relating to the personnel is by far the largest, amount- 
 ing to fully two-thirds of the whole, while the items relating to the gun carriage and to 
 the elements ordinarily included in the emplacement are respectively only about 
 one-tenth and one-fifth of the personnel cost. Consequently, an increase or decrease 
 of a certain percentage of the cost of the emplacement or carriage will have a much 
 smaller influence on the total cost than a change 6f the same percentage in the per- 
 sonnel cost. 
 
 The cost of a gun carriage for a particular gun depends upon the type, whether it is 
 disappearing or barbette; whether it is all-round fire or limited fire; but it is under- 
 stood that in the case of large guns, the difference between the cost of carriages of dif- 
 ferent types does not vary greatly, and as a rule is less than one-fourth of the actual 
 cost of the carriage. Since the annual cost of the carriage itself is shown to be only 
 about 5 or 6 per cent of the total annual cost connected with the gun, a change of 
 one-fourth or one-fifth in this one item would mean a change of but little more than 
 1 per cent of the whole, and, consequently, any modification in the type of a car- 
 riage that would decrease by two men the size of the detachment, necessary for the 
 service of the gun, would pay for itself. 
 
 The object of the parapet in front of the gun is to protect the gun and its detachment 
 from the enemy's fire and incidentUy for the psychological purpose of giving the mem- 
 bers of the gun detachment a sense of security in action, and thus increasing the rapid- 
 ity and accuracy of the fire. Whether or not the parapet is needed, that is, whether 
 the detachment should stand behind the parapet or in the open, or whether the gun 
 should disappear behind the parapet or remain always in the open, is still a disputed 
 question, but experiments made some two years ago indicated clearly and conclusively 
 that a parapet in front of a disappearing gun is a real protection to both the gun and 
 personnel and that a fair proportion of projectiles which, in the absence of a parapet, 
 would have struck and detonated in the immediate vicinity of the gun emplacement 
 and would have done serious damage to the gun and personnel, were caught by the 
 parapet and were either deflected or were detonated under sjich conditions as to do no - 
 damage to the gun emplacement or the silhouettes representing the detachment; and 
 that, furthermore, this parapet caught a large number of fragments from projectiles 
 detonated a short distance in front of the gun which, in the absence of the parapet, 
 would have passed among the personnel with considerable probability of causing 
 casualties. Calculations show that the cost of the parapet in front of a gun is less than 
 one-seventh the cost of an emplacement, and the annual cost pertaining to the emplace- 
 ment does not exceed one-seventh of the total annual cost connected with the gun. 
 Consequently, the part of the annual cost connected with the parapet is but 2 per 
 cent of the whole annual cost, and if this parapet gives sufficient protection to enable a 
 gun to fire 2 per cent more shots at the enemy before the gun is knocked out than 
 would be the case if the parapet were not there, it would appear, neglecting the items 
 of protection given to the men, that the parapet will have paid for itself. That it 
 will do many times more than this is clearly shown by the experiments mentioned. 
 Furthermore, where there are such parapets to give protection, the probable casualties 
 
149 
 
 among the gun detachments will probably be much smaller, and the number of ad- 
 ditional men which should be kept immediately on hand to replace losses in time of 
 action, would be much less than were there no parapet. The portion of the annual 
 cost pertaining to the parapet is equivalent to no more than the cost of two or three 
 privates. If, therefore, the parapet will permit the number of the reserves available 
 to replace casualties to be reduced by two or three, the parapet will have paid for itself 
 by reduction in the personnel item of cost without considering its effect upon the pro- 
 tection of the gun and carriage. 
 
 Wherever placed, magazines and shell rooms must have sufficient protection to 
 prevent their destruction by hostile projectiles, for the result of the explosion of the 
 magazine of a large gun would probably be so disastrous, not only in the destruction of 
 life and property, but in the demoralization of the garrison, that such an occurrence 
 ^must be prevented, if possible, Such magazines must, therefore, be given thorough 
 protection against aircraft bombs and against direct hits of the enemy's projectiles. If 
 built in plain sight and so close to the gun as to be struck by projectiles aimed at the 
 gim there is the danger, of course, of repeated hits in the same place and slightly 
 greater protection is necessary, but the cost of this additional protection is so small 
 compared with the total cost of protecting the magazine as to make but a small percent- 
 age in the total cost. 
 
 The further the magazine is from the gun the greater the time necessarily required 
 for the ammunition service and the greater the amoimt of labor expended, and since 
 the rate of fire against rapidly moving vessels must be as rapid as possible, the farther 
 the magazine is from the gun the larger in general is the size of the detachment which 
 must be kept on hand ; and as a result, the size of the personnel item of cost will in general 
 increase much more rapidly than the cost of magazine construction can decrease by 
 permissible reductionin protection. The same is true as to the simplification of ammu- 
 nition service in the magazine. Any reduction in the installing of appliances for the 
 mechanical handling of projectiles must be accompanied by a corresponding increase 
 in the size of the detachment, and since the total annual cost connected with mechani- 
 cal appliances for handling ammtinition and magazines is probably much less than the 
 annual cost pertaining to a single private, a reduction in the cost of emplacement con- 
 struction due to the omission of these appliances would seem to be the very reverse of 
 ' economy. 
 
 In time of war, when a hostile fleet is known to be in the vicinity, it may be expected 
 to attack at any time , and the officers and men must remain habitually in the immediate 
 vicinity, and anything that adds to the comfort and mental composure of the detach- 
 ment or that decreases the time taken for necessary absences, increases the efficiency 
 of the detachment in time of action, and incidentally decreases the number of men 
 whose maiutenance is necessary for the service of the gun. 
 
 A seacoast gun is designed to combat naval vessels, and can be so used only wheii 
 the vessels come within range and observation and only as long as the vessels so remain. 
 The destructive power of such guns is Icnown to the enemy, and he will therefore 
 naturally attempt to escape damage by remaining within the fire of the guns for the 
 shortest time possible. TMs means that the ammunition service of such guns should 
 be designed "to be as rapid as possible, and to go to the cost of building guns and car- 
 riages, of emplacing them, and of making provision annually for the personnel, and 
 then to attempt to make a saving in any of the small items so as to unfavorably affect 
 the rapidity of service is not only .uneconomical but is po-fitively wasteful. 
 
 In suggesting greater simplicity of emplacements the critics have, it is believed, 
 entirely overlooked fhe fact that of the total items of cost connected with seacoast 
 guns, the personnel items are by far the largest, and that the items of the first cost of 
 emplacement construction, et<-., though comparatively large, really make up but a 
 very small proportion of the total. Careful study has been given to this matter, and 
 the calculations which have been made clearly and conclusively show that the addi- 
 
150 
 
 tional amounts which must be expended in providing rapid amnuuilion serviee and 
 
 in protection of the gun and personnel muoh more than pay for themselves in the 
 
 increased rapidity and accuracy of fire, in the increased protection of the gun carriage 
 
 and personnel, and in a permissible reduction in the strength of the gun detachment. 
 
 The men whose services are dispensed with are thus made available for use in the 
 
 field. 
 
 16-inch Emplacement Designs. 
 
 No 16-inch emplacements based on the designs above described 
 have as yet been built in this country, though many tentative designs 
 for such emplacements have been prepared. 
 
 In the year 1914, the question of what modifications should be 
 considered as desirable in the projects for the seacoast defense of 
 about a half dozen different locahties in the United States was under 
 consideration, either by formally appointed boards or by groups of 
 officers gathered together by mere informal War Department routine. 
 The reports of such boards or groups of officers were to the general 
 effect that thereafter the 16-inch rifle should be considered as the 
 main primary weapon for seacoast defense and that these guns should 
 be mounted in single-emplacement batteries and usually on disap- 
 pearing carriages. As these reports were accepted by the War 
 Department and, in the cases of the more formal boards, received 
 formal departmental approval, the recommendations contained in 
 these reports may be considered to have become the policy of the 
 War Department. 
 
 The tentative designs for the 16-inch emplacements required by 
 these projects resembled closely the 1912 or Panama type of heavy 
 disappearing gun emplacements, though, of course, the necessary 
 changes in dimensions had to be made to fit the emplacements to the 
 16-inch instead of the 14-inch guns. The blanket of sand over the 
 traverse pertaining to the "L" variety (illustrated on Plate XXVI) 
 was used in aU cases. The arrangements of the magazines and other 
 rooms of the traverse usually followed the " L" variety (Plate XXVI). 
 although the arrangements pertaining to the "M" variety (Plate 
 XXIII) and to the "S" variety (Plate XXIV) were adopted in some 
 cases. Most of these emplacements were to be bmlt in localities 
 where trouble from condensation had been experienced in the older 
 batteries, and consequently special arrangements for preventing, 
 or at least reducing, the amount of condensation were considered 
 necessary — such as semidetached magazine houses and provisions for 
 artificial heating similar to those shown on Plate XXI. The rear 
 faces of the traverses were usually made as concrete walls opening on 
 area ways as shown on Plate XXVI, although in some cases the rear 
 of the traverses had to be given both rear and overhead protection, 
 which required that the rooms in the rear open on a gallery instead 
 of on an open area way. The battery comcniander's stations were all 
 
151 
 
 planned with the two-level floors such as are shown on Plates XXI 
 and XXVI. 
 
 The designs just described were used as bases for preparing the 
 estimates of cost to be submitted to Congress, but no actual construc- 
 tion work was ever commenced. 
 
 In the meantime war had broken out in Europe and among its 
 early developments were the greatly increased range of heavy artil- 
 lery and the use of very large gtrns for firing at land targets. The 
 standard disappearing carriage in customary use in this country 
 restricted the angle of elevation at which the gun might be fired to a 
 maximum of about 20°, and furthermore required the construction 
 in front of the gun and carriage of a parapet which restricted the 
 horizontal angle of fire to an azimuth arc of about 170°. The restric- 
 tion in elevation reduced the range of the 16-inch gun to far below the 
 ranges then in actual use, not only on land but also in naval engage- 
 ments. It was was therefore considered important that this state 
 of affairs be corrected promptly, and the Ordnance Department 
 undertook to design a 16-inch disappearuig gim carriage which woiild 
 be capable of all-round fire and would permit firing to an elevation of 
 at least 30°. This would give a range of considerably over 30,000 
 yards. 
 
 To design and build such carriages would, however, require time, 
 and as a provision for the immediate futiu-e the Chief of Ordnance 
 suggested that there be mounted on barbette carriages, which could 
 be quickly manufactured, some 12-inch guns which the Ordnance 
 Department had on hand, these guns having been manufactured some 
 years before as spares to replace the emplaced 12-inch guns as the 
 latter wore out. 
 
 This suggestion of the Chief of Ordnance was approved by the War 
 Department Board of Keview, and the Ordnance Department began 
 at once the manufaotiu-e of long-range barbette carriages for these 
 12-inch guns. These carriages permit the gun to be fired up to an 
 angle of not less than 30° and are capable of aU-round fire. The base 
 ring is set in the bottom of a deep gun well. Around the upper part 
 of the gun carriage there is attached a horizontal metal loading 
 platform some 4 feet below the axis of the gim trunnions. This 
 metal platform revolves with the gun carriage and through a slot in it 
 the breech of the gun sinks down as the gun is trained at a high angle 
 of elevation. 
 
 1915 Type of 12-inch Barbette Emplacements. ~ 
 
 As soon as the Ordnance Department had completed the drawings 
 of the long-range barbette 12-inch gim carriages, the Engineer 
 Department proceeded to design an emplacement for it. The type 
 of emplacement designed for these guns, which in all cases have been 
 mounted in pairs, is shown on Plate XXI. 
 
152 
 
 It will be noted that this emplaoement is of the one-story type. 
 The gun well is surrounded by a circular concrete pavement on the 
 same level as and continuous with the metal loading platform of the 
 gun carriage and forming therefore the loading platform of the 
 emplacement. When the gun is to be loaded it has to be turned in 
 elevation until its axis is horizontal, which brings this axis about 4 
 feet above the loading platform. The ammunition truck is brought 
 up against the breech of the gun and the projectile is rammed into 
 it in exactly the same manner as has been customary in disappearing 
 emplacements. In other words, the ammunition service is similar 
 to that heretofore adopted in disappearing emplacements. After the 
 gun has been loaded it, of course, has to be trained to the proper 
 elevation for firing. 
 
 The arrangement of the ammunition space, as shown in Plate XXI 
 and, in fact, of the entire magazine traverse, is similar to that shown 
 for the upper story of the " W" variety of the 1912 type of disappear- 
 ing emplacement (Plate XXV). Being intended for construction in 
 cold climates where condensation is difficult to prevent, the shell and 
 powder rooms are shown as semidetached houses built in the maga- 
 zine space. Tile lining for the rooms is indicated and arrangements 
 are shown by which the hot air from the radiator can be blown 
 through the emplacements. The usual trolley tracks for carrying 
 projectiles are shown; also a system of double trolley tracks on the 
 ceilings of the powder rooms for handling the powder charges, which 
 were expected to be furnished in single long cartridges. The rear 
 corridor shown on the plate is to be fitted so that it may be closed in 
 at the rear by metallic shutters sliding on the columns. It is intended 
 that this corridor shall be closed in by these shutters in bad weather, 
 when the battery is manned but is not in action, and thus provide a 
 partially protected dormitory for a part at least of the personnel. 
 The battery commander's station is shown as of the two-level type, 
 which will be described in the chapter on fire control. 
 
 The surroundings of the loading platform, however, vary greatly 
 from the former types. The parapet is entirely done away with 
 and the loading platform consists practically of an open and exposed 
 circular concrete pavement, from which a concrete walk leads off ta 
 the rear and thence into the truck corridor of the traverse. As has 
 been stated, the axis of the gun is only about 4 feet above the level 
 of the loadmg platform and if the gun is to be fired horizontally or 
 if the men at the gun are to have a sight on the target it is evident 
 that no parapet is possible. According to the design of such emplace- 
 ments as shown on Plate XXI, each gun is capable of fire at eleva- 
 tions from zero up to 30° through 275° of traverse; and of fire at an 
 angle of elevation of from 10° to 30°— that is, of the long range fixe 
 for which these emplacements were specially designed — ^f or the remain- 
 
153 
 
 ing 85° of traverse. Taking the two guns of the battery together, 
 for 190° of traverse the firing of both guns is possible from zero 
 elevation up to 30°, and for the other 170° of traverse one gun can 
 be fired at zero elevation and up and the other gun from 10° up to 30°. 
 
 There are a few cases, however, where the conditions as to depths 
 of water in the vicinity of the site of the emplacement make it un- 
 necessary ever to fire the gun at less elevation than about 10°, and 
 in order to provide concealment and at least the feeling of protection 
 to the personnel of the emplacements buUt in these locaMties, it was 
 suggested that a parapet composed of sand without any concrete 
 whatever be built around the loading platform, located far enough 
 away not to be disturbed by the blast of the gun, and built up not 
 quite to the line of the trajectory at the lowest elevation at which 
 the gun might be called upon to fire. Designs embodying this 
 form of parapet were approved by the War Department but, before 
 emplacement construction had reached the state of parapet building, 
 the department changed its mind and the parapets were ordered not 
 to be buUt. A sketch of a section of such a parapet is shown dotted 
 in Plate XXI. 
 
 In one case, as an experiment, it was decided to build the loading 
 platforms of the battery only, omitting the magazines entirely, and 
 to utilize as magazines existing structures quite a distance from the 
 guns. The moving of ammunition from the magazines to the guns 
 was to be performed by motor trucks. 
 
 This type of battery construction is surely carrying to a maximum 
 the proposed simplicity of batteries suggested by critics of the 
 Panama batteries. However, as was to be expected, the ammuni- 
 tion service of this battery, after the loading platforms only had 
 been, completed, proved to be quite unsatisfactory and requests 
 were subsequently made by the local Artillery authorities for the 
 completion of the magazines between the guns and these have now 
 been about completed. 
 
 Later Developments. 
 
 While the first long range 12-inch batteries were under construc- 
 tion, the Chief of Engineers received from the Chief of Ordnance a 
 preliminary and advanced copy of the drawings of the new 16-inch 
 disappearing gun carriage which was to be capable of all-round 
 fire up to an elevation of at least 30°. In this type of carriage, aU- 
 round fire is made possible by increasing the diameter of the gun 
 well, by making other changes in the gun carriage which place the 
 axis of the gun well not far in front of the center of the length of the 
 gun when it is in the loading position, and by moving the parapet 
 immediately in front of the gun a few feet farther from the center 
 of the gun well than it woiild naturally be in a limited fire emplace- 
 ment. 
 
154 
 
 • 
 
 This change, however, does not more the parapet wall as far away 
 from the gun center as is the muzzle, so that the muzzle still projects 
 well over the parapet when fired. 
 
 This change in the position of the parapet makes it possible to 
 revolve the gun while in the loading position until it points to what 
 is normally the rear of the emplacement, and in this position, with 
 the l)reech of the gun toward what is normally the direction of the 
 enemy, the gun may be tripped and fired, and there is ample room 
 for recoil. Of course, the gun can not be loaded in this reversed 
 position, but as this firing to the rear is expected, in general, to be 
 necessary only at land targets, at which fire is usually delivered 
 quite deliberately, the necessity of moving the gun in azimuth 
 before it can be again loaded and of moving it back again when 
 loaded is not considered a very serious objection. 
 
 The first emplacements designed for this type of gun carriage were 
 but modifications of the plans previously prepared in 1914 and 1915 
 and which were briefly described a few paragraphs above. In these 
 new designs, of course, some additional changes had to be made. 
 The emplacement, in the immediate vicinity of the gun well, had, 
 of course, to be suited to the new gun carriage which required, 
 among other things, pushing the parapet in front of the gun a little 
 farther away from the gun well. To enable the gun to be fired 
 toward the flank at zero elevation, the top of the flank traverse 
 and the crest of the parapet on the side toward the flank traverse 
 were both lowered to the elevation of the crest of the parapet in 
 front of the gun. The magazine traverse was retained as of about 
 the same general design as in the 1912 and 1915 plans (PJates XXI, 
 and XXIII to XXVI), because this permitted horizontal ammuni- 
 tion service. Of course, the top of ■ this traverse projected high 
 above the top of the parapet in front of the gun and prohibited 
 horizontal fire over an arc of about 80° of azimuth, but throughout 
 even this limited arc of azimuth, long range fire was still possible 
 at all angles of elevations from about 6° or 7° up. The type of 
 emplacement designed, therefore, permitted horizontal fire through 
 about 280° of azimuth and long range fire through the remaining 
 80° of azimuth. This it was thought would be sufficient at practically 
 every location where it might be necessary to emplace one of these 
 guns. 
 
 However, in order to.be prepared, should it be considered necessary 
 that in any location the gun should be so emplaced as to fire as low 
 as zero elevation throughout the whole 360° of traverse, drawings 
 were prepared of still another type of emplacement, and as an aid 
 to a study of this type, a model was made and deposited in the 
 OflEice of the Chief of Engineers. 
 
155 
 
 If fire is to be possible at zero elevation for the complete 360° 
 of traverse, it is evident that no part of the emplacement can rise 
 quite as high as the trunnions of the gun when in the firing position. 
 The elevation of the trunnions above the loading platform is not 
 sufficient to keep the top of the magazine traverse below the eleva- 
 tion of the trunnions and stUl permit horizontal ammimition service. 
 Consequently, this change necessitates a return to the Iwo-story 
 type of emplacement, one story consisting of the loading platform 
 level, and the other or lower story of what may be called the magazine 
 level. 
 
 In this type of design the loading platform is made practically 
 horizontal and of the size required by the 16-inch gun. In front of 
 the gun and of the sides of the loading platform there is provided 
 the usual type of concrete and sand parapet, the curved part of the 
 parapet in front of the gun and the faces of the parapet in front of 
 the sides of the loading platform,' however, being made symmetrical 
 Tv^ith respect to the center line of the loading platform, which may 
 be called the capital of the battery. The crest of the parapet through- 
 out is made of the same elevation as immediately in front of the 
 gun, and toward each flank this parapet becomes merged into the 
 flank traverses. These flank traverses, one on either side of the 
 gun, run back parallel to the capital of the battery. Their crests 
 are at the same elevation as the crests of the parapet in front of the 
 gun. On the lower story, that is, the magazine level, these flank 
 traverses contain numerous rooms and a corridor, aU of which have 
 concrete roofs covered with a blanket of sand. This sa d blanket 
 is rounded off on top, and on the side toward the gun is merged 
 into the sand slope on that side of the loading platform; while on 
 the side away from the gun it merges into the topography of the site. 
 
 The corridor of the lower story of each flank traverse extends 
 from front to rear throughout the entire length of the flank traverse, 
 and in front is continued imder the whole width of the parapet, so 
 that the corridor is continuous from the rear of one flank traverse 
 around under the parapet and back to the rear of the other flank trav- 
 erse. In the flank traverses, there are rooms on both sides of this cor - 
 ridor and similarly in the portion of the corridor under the parapet there 
 are rooms both in front and rear of the corridor. The rooms imder the 
 parapet are utilized as service magazines both for shell and for 
 powder, while the rooms in the flank traverses are utilized as storage 
 powder magazines for powder not expected to be available for imme- 
 diate service, as rehandling rooms for powder, as power rooms, 
 plotting rooms, officers' rooms, storerooms, etc. 
 
 For raising projectiles from the lower or magazine level up to the 
 loading platform level, hoists or elevators arfe to be installed, their 
 upper openings being in the parapet wall immediately in front of the 
 
156 
 
 loading platform and close to the gun. The exact form of hoist to be 
 used has not been definitely decided. One suggestion considered is 
 the installation of standard projectile hoists, similar to those used in 
 the older two-story type of emplacements. Another is the installa- 
 tion of platform hoists, on which may be raised the loaded ammuni- 
 tion trucks. In one sketch,- these platform hoists rise vertically and 
 in another they run up on inclined rails, the upper position being 
 immediately in front of the face of the parapet wall and the lower 
 position, immediately in the rear of the corridor of the lower story. 
 
 It has been tentatively decided that the powder service should be 
 by hand up stairways to be provided near the gun, although study 
 had been given to the provision of special powder trucks and hoists. 
 
 The plans as drawn show concrete pavements leading from the 
 rear of the loading platform and extending around and into the rear 
 of the flank traverses. These concrete walk ways, however, are not 
 to be made level, but are to have a g'entle slope like long ramps, which,, 
 leaving the rear of the loading platform at the upper level, would by 
 the time they get well into the corridors of the flank traverse have 
 dropped down to the level of the floors of these corridors. It has 
 been suggested that these long ramps might be convenient for 
 returning the ammunition trucks to the lower story should it be 
 decided that the system of ammunition service shall involve raising 
 the loaded trucks from the magazines to the loaded platform level. 
 Furthermore, the slope of the ramps is not so great but that a loaded 
 ammunition truck can, with the assistance of an additional man or 
 two, be pushed from the magazine level up to the loading platform 
 in case anything should happen to the projectile hoists. 
 
 Among the new features embodied in these designs are the pro- 
 vision, in the power room, of air compressors and tanks which, hy 
 means of suitable pipes and hose, can furnish compressed air to the 
 gun for use in blowing the gases from the bore in the same manner 
 as is done in the turrets of battleships; and the provision of hot-air 
 flues extending from the radiators in the power rooms to the annular 
 space surrounding the gun well just below the base ring level. In. 
 this manner, hot air can, when desired, be blown around under the 
 gun carriage and thus be available for melting snow and ice in 
 wintry weather, so that there will be no danger even in winter time 
 that the gun carriage will freeze up. 
 
 During the year 1918 it was urged by several officers who had 
 just returned to this country after service abroad that an elevation, 
 of 30°, and the ranges made possible by this elevation, are not 
 sufficient, and that aU guns must hereafter be emplaced so as tO' 
 be capable of firing up to such an elevation as will give the maximum 
 range which is possible with the gun; This necessarily means an 
 abandoimient of the disappearing principle and the mounting of the 
 
157 
 
 guns in barbette, somewhat in the same manner as is done in the 
 1915 type of barbette long-range 12-inch carriage. 
 
 To accord with this demand, the Ordnance Department has recently 
 prepared tentative designs for a 16-inch barbette gun carriage, 
 capable of firing the gun at practically any elevation. The base ring 
 of this gun carriage is to be set down at the bottom of a gun well as 
 in the 1915 long-range 12-inch barbette gun carriage. Attached to 
 the gun carriage and revolving with it there is an elevated metal 
 loading platform. When the gun is elevated for firing the breech 
 drops down through a slot in this elevated loading platform and 
 when the gun is depressed for loading the breech rises through this 
 slot. It is proposed by the Ordnance Department, in order that the 
 ramming of the projectile into the gun may be easily done, that the 
 gun shall normally be loaded when set at an angle of depression of 
 about 7°. Since the trunnions are only a few feet above the metal 
 loading platform, it is evident that if the gun is to be so emplaced as 
 to be able to fire throughout the 360° of azimuth at zero elevation 
 no part of the emplacement can rise even quite as high as this trun- 
 nion level. 
 
 Plans of an emplacement in which such guns can be used have 
 been tentatively prepared in the Ofl&ce of the Chief of Engineers. 
 The gun well is in the center of the emplacement and is surrounded 
 by a loading platform on the same level as the metal loading platform 
 ■of the gun carriage. This concrete loading platform is not wide and 
 on the outside it is surrounded by an annular V-shaped trench, 
 into which the muzzle of the gun can drop when in the loading 
 position. Outside of this trench the sand rises again to the level of 
 the loading platform. It then continues out very nearly horizon- 
 tally until it merges with the topography beyond the limits of the 
 emplacement. 
 
 The magazines, shell rooms, and other necessary rooms of the 
 emplacement are aU on a lower story and surround the gun well. 
 They open on a series of corridors or galleries, the entrances to which 
 from the outside are located in what is generally the rear of the 
 ■emplacement. The method of ammunition service proposed is to 
 load certain trucks with projectiles and others with powder and to 
 place the loaded trucks on platform hoists which will rise up through 
 trapdoors in the concrete loading platform in much the same manner 
 £LS is done in raising and lowering merchandise from or to the base- 
 ments of stores where these basements project out under city side- 
 "walks. . The trapdoors themselves are to automatically open and 
 ■close, as the hoists come up or go down. 
 
 Up to the present time the Ordnance Department drawings of this 
 type of carriage are reported as tentative, and consequently the plans 
 for the emplacement just described must be considered as a study 
 only. 
 
Chapter VII. 
 EMPLACEMENT DETAILS. 
 
 In the preceding chapter, the general history of the evolution of 
 the design of heavy-gun emplacements has been brought up to 
 include the latest designs prepared. Attention wiU now be given 
 to the details of the emplacements, including a few general matters 
 applicable to all emplacements. 
 
 Number of Guns in a Battery. 
 
 Uniting several emplacements structurally into a single battery 
 has some advantages and some disadvantages. 
 
 Among the advantages is reduction of cost. That this is true 
 will be seen at once if we assume that we have the plans already 
 drawn for a number of one-gun emplacements. Each of • these 
 emplacements must, of course, be given protection not only in the 
 front but also on both flanks. If now we combine two of them so as 
 to form structurally a single battery, it is evident that in so doing 
 we may omit the flank protection on one side of one emplacement 
 and on the other side of the other emplacement. Consequently, a 
 two-gun battery will generally require less work and will cost less 
 than two single-gun emplacements. 
 
 If several emplacements are united into a single battery, the 
 ammunition stored in the magazine of one gun can easily be moved 
 to and be used in another gun if the ammunition of the latter gim 
 should become exhausted or if there should be a breakdown in its 
 ammunition service. Consequently, it is permissible that the 
 reserve stock of ammunition for a battery of several emplacements 
 be somewhat less than the sum of the reserves which should be 
 kept on hand if the emplacements be separated. 
 
 Uniting several emplacements into a battery has the additional 
 advantage of making it much easier for one officer to supervise the 
 work of all the emplacements and thus conduces to unity of action. 
 
 Another advantage in having several emplacements united into a 
 battery and, incidentally, in having the guns of a battery emplaced 
 close together, is the ease of handling fire-control data. As will be 
 described in the chapter on fire control, the range and azimuth of 
 the target and the other data required for aiming guns are usually 
 calculated for one gun of a battery, which is known as the " directing" 
 gun. Before this data can be used by another gun, corrections must 
 be made and, in general, the closer the guns are together, the smaller 
 
 (159) 
 
160 
 
 the relocating corrections will be and the more easily and more 
 accurately these corrections can be made. Consequently, if several 
 guns are united in a battery, original fire-control data need be 
 obtained for one gun only, the data required for the other gun being 
 obtained by relocating, wnile if the guns are separated in several 
 batteries the data must, in general, be obtained sepaiately for each 
 battery. 
 
 On the other hand, placing guns so close together that they form 
 part of a single battery has a number of disadvantages. In the 
 first place, as will be explained more at length further on, when guns 
 are too close together the blast of one gun, when discharged obliquely 
 toward another, may interfere with the detachment at the next 
 gun or may even drive it away from that gun; whereas, when em- 
 placements are mounted ia single-gun batteries, one gun can usually 
 be fired directly over the other battery without seriously interfermg 
 with work in that battery. 
 
 Another important disadvantage in having gxms placed too close 
 together is that one may be struck by an enemy's projectile aimed 
 at the other. Owing to the very long ranges now used, there will 
 probably be a considerable horizontal deviation in the fall of the 
 enemy's projectiles and the greater the distance over which a given 
 number of guns are distributed, whether in one battery or several 
 batteries, the less, in general, will be the chances of having one em- 
 placement hit by projectiles aimed at another. 
 
 In addition to the important factors mentioned which should 
 have an influence in determiaing to what extent emplacements 
 should be grouped into batteries, there is another element which, 
 though theoretically of secondary importance as far as the efficiency 
 of the action of the battery is concerned, is yet quite important in 
 other ways. This element is the question of quartering and messing 
 the persoimel pertaining to a battery. 
 
 For each gun there must be a detachment of a certain strength, 
 some men to maneuver and aim the gun, some to handle the ammuni- 
 tion in the magazines, some to serve the ammunition, and some to 
 load it in the gun; others are required for fire-control work and for 
 other purposes. In general^ the strength of the detachment will 
 depend upon the size of the gun, the method in which it is mounted, 
 and upon the ease of ammunition service. In order that team work 
 may be obtained, it is evidently desirable that the men should be 
 trained to work together and that, in general, the same men should 
 be kept together. In other words, there should be a particular 
 unit of men assigned to each particular gun and to each particular 
 battery. 
 
161 . 
 
 In peace times it- is customary for the men to be quartered and 
 messed in regular barracks at considerable distances from the guns. 
 In order that they may be well acquainted with each other and with 
 their officers and noncommissioned officers, and that the noncommis- 
 sioned officers and officeis may know the men, it is very desirable 
 that the organization foi handling the guns should be the same as 
 the organization for quartering and messing; in other woids, that 
 the personnel of a batters should be quartered and messed together 
 and undei the control of the same officers who are to control the 
 battery in action. 
 
 At first sight it would appear that the simple solution of this 
 problem is to have the size of the barracks adjus{^ed to the size of 
 the personnel pertaining to a particular batteiy, but experience 
 has shown that it is convenient to organize the personnel of an 
 artillery post for quartering and messing into companies of approxi- 
 mately the same size, the company being a command appropriate 
 to the rank of captain, as is normally the command of a single bat- 
 tery. Consequently, it would seem that convenience as well as 
 efficiency will be best obtained, if the emplacements are so com- 
 bined into the batteries that the number of men necessary for one 
 batttery will be approximately equal to that necessary for other 
 batteries, and will, at the same time, form a company of convenient 
 size for quartering and messing. 
 
 Apparently, in the early days of modern-emplacement construc- 
 tion the question of the number of guns which could best be united 
 in a battery was not given very careful consideration, for in examin- 
 ing our older batteries we notice so many apparently inexplicable 
 inconsistencies. Thus it was not infrequent to mount 5-inch guns 
 in single-gun emplacements considerably scattered, while the emplace- 
 ments of large guns were at times united with as many as three in a 
 battery; again, at one post, immediately next to a battery of two 
 6-inch barbette guns, there is a battery of three 12-inch disappear- 
 ing guns. 
 
 In general, in the early days it was customary to group 3- 
 inch and smaller emplacements four in a battery, and aU larger guns 
 two in a battery or in some cases in multiples of two. However, 
 where large guns were united structurally in batteries in multiples 
 of two, it was probably with the expectation that these structural 
 batteries would be subdivided into tactical batteries of two guns each. 
 
 In recent times the advantages and disadvantages of having guns 
 united into batteries have received more careful consideration and, 
 judging from the action of the War Department in the last few years^ 
 it would appear that the adopted policy is about as follows: That 
 3-inch guns should be grouped either two or four in a battery; 
 173341—20 ^11 
 
162 
 
 that 6-inch guns should be mounted two in a battery; that 12-inch 
 barbette guns should likewise be mounted two in a battery; but that 
 12-inch disappearing guns and all larger guns should be mounted 
 in single-emplacement batteries, and when, for any special reasons, 
 two such large emplacements are structurally united, they should 
 tactically be manned and operated as if they were single-emplace- 
 ment batteries. 
 Relative Position of Gun aind of Magazine. 
 
 An examination of the plans prepared by the Board of Engineers 
 for disappearing batteries (Plates XIV to XX, inclusive) shows that 
 in all cases the magazines are placed on the left of the loading plat- 
 forms. Unfortunately, this fact has been taken by some officers 
 to mean that this is the only normal and proper location. This, 
 however, is not true, for there is nothing in the construction of the 
 gun or carriage or in the system of ammunition service to make it 
 preferable to place the magazine on any particular side of the gun. 
 In fact, the arrangement of gun and magazine shown on the drawing 
 probably originated in this way. The original drawings of the 
 Board of Engineers happened to be made with the magazines on the 
 left sides of the guns, and this was continued in subsequent draw- 
 ings because it was easier for the draftsmen to stick as closely as pos- 
 sible to the old ones. That it was not the intention of the Board of 
 Engineers to imply that the left side of the gun is the normal side for 
 the magazine is further shown by the fact that a number of the early 
 mimeographs which originated with the Board of Engineers, in 
 addition to the main arrangement of guns and magazines for which 
 the details are worked out, show other and alternative outline ar- 
 rangements and in many of these the magazines are shown on the 
 right of the guns. Furthermore, in the Board of Engineers' plans 
 the left emplacement is usually shown as designed as if it were for 
 the flank gun of a battery of a number of guns, the 170° of possible 
 arc of traverse being generally so distributed as to show 20° of fire 
 in rear of the line of gun centers prolonged and 60° of arc of fire to 
 the right of the capital of the emplacement. On the other hand, 
 the right emplacement is drawn as if it were a center emplacement, 
 its arc of fire being Hmited to 140° of azimuth, 70 on either side of 
 the capital, since 70° is considered as about the maximum per- 
 missible departure from the capital which wiU not interfere too 
 seriously with the men in the next emplacement. 
 
 The greater part of our seacoast batteries have been built on one 
 side or the other of an entrance to a harbor. The enemy is to be pre- 
 sumed to approach from the sea and, consequently, for each par- 
 ticular battery there is one special side from which the enemy may 
 be expected to come. This side, for convenience, we may call the 
 exposed side. The question may now well be asked as to whether it 
 
163 
 
 is advisable that the magazine should be placed on the exposed side 
 or on the unexposed side of the gun. 
 
 In answer to this question it may be said that in the form of em- 
 placement based on the horizontal crest idea it really makes very 
 little difference whether the magazine is on the exposed or on the 
 unexposed side of an emplacement. If the magazine be placed on 
 the side of the gun toward the enemy, the members of the detach- 
 ment serving ammunition from the ammunition hoists to the gun 
 wiU be a little less exposed than if they were on the opposite side; but, 
 on the other hand, the projectile truck and the powder wiU have to 
 be carried farther to reach the breech of the gun if they come from 
 the side toward the enemy than if they come from the opposite 
 side. Consequently, the relative advantages and disadvantages of 
 these two positions about balance. 
 
 However, in the one-story type of emplacement, in which the maga- 
 zine is placed in a traverse reaching high above the parapet, the load- 
 ing platform is much better protected from an approaching enemy 
 if the magazine be on the exposed side. Furthermore, if the maga- 
 zine be on this side, it is permissible to have its main entrance in 
 the most convenient place, that is, on the side of the emplacement 
 as in the "M" variety of the 1912 tjTpe (Plate XXIII), rather than 
 in the rear, as in the "S" variety. (Plate XXIV.) 
 
 Where there are two guns and but two guns in a battery, there is 
 a considerable advantage in placing the magazines of both guns 
 between them, because this separates the guns farther and not only 
 reduces the blast effect of one gun in the other emplacement, but also 
 makes one gun less likely to be hit by a projectile aimed at the other. 
 Distance Between Consecutive Guns. 
 
 In the seacoast fortifications built before and during the Civil 
 War the guns were mainly smoothbores, and in order to overcome 
 the inherent inaccuracy of the fire of such guns and still bring an 
 effective fire to bear, a large number of such guns were necessary. 
 This required that the guns be mounted quite close together, although 
 in order to reduce the damage that might be done by enfilade, it was 
 necessary to place traverses at intervals along the line of guns. This 
 close grouping of guns was continued in the design of our seacoast 
 defenses long after the necessity for it had passed, and even after the 
 introduction of rifling and other means of improving the accuracy 
 of fire had made it possible t-o make use of fewer guns and to fire 
 them with greater individual care. 
 
 Ttxe tendency to the close grouping of guns was shown in almost 
 all of our batteries designed prior to the Spanish War. Thus the 
 early designs for the 3-inch emplacements showed the guns as mount- 
 ed only 29 feet apart. (Plate III.) Similarly, the oldest designs 
 for the 5-inch emplacements (Plate VI) showed the guns but 45 feet 
 
164 
 
 apart, and the first mimeograph of the 6-inch barbette emplacement 
 showed those guns as only 20 feet apart center to center (Plate VIII), 
 it being necessary in order to obtain this close grouping to adopt 
 the inconvenient arrangement of placing both guns between the two 
 magazines. 
 
 However, it was not very long after emplacements based upon 
 these early designs were built before it was discovered that if a 
 gun were fired at only a slight angle from the line of gun centers, 
 the blast effect was so great as to interfere with the detachment 
 at the next gun. 
 
 About 1904 and 1905 a series of tests were made at Fort Monroe 
 and elsewhere, under direction of a board, to determine the minimum 
 distance which should be allowed between gun centers for different 
 sizes of guns and for different angles of fire. The report of this board 
 is pubhshed in mimeograph No. 89, and indicates it to be desirable 
 that thereafter guns should be emplaced farther apart than they had 
 been shown in the early designs, and also that where it could be done 
 without sacrificing other valuable considerations the traverses be- 
 tween guns could weU be rounded up to above the level of the guns 
 in the firing positions. 
 
 To reduce the blast effect and to make it less probable that one 
 gun will be hit by a projectUe aimed at the other, as well as for other 
 reasons, there has been in recent years a steady tendency to spread 
 guns farther apart. Thus the most recent 6-inch guns have been 
 emplaced 170 feet center to center (see Plate XII), as against 20 feet 
 for the battery shown on Plate VIII, while the heavy gun batteries 
 have grown in width from the 124 feet, gun center to gun center, 
 shown for the 10-inoh emplacements on Plates XIII to XVI, up to 
 275 feet for the two-story 14-inch emplacement shown on Plate XXII, 
 and 320 feet for the Panama 14-inch batteries shown on Plate XXV. 
 In .several recent fortification projects single heavy gun emplacements 
 have been placed about 300 yards apart, gun to gun. 
 
 However, in attempting to obtain the advantages that foUow a 
 wide spacing of the guns, the matter should not be overdone, for 
 an unnecessarily wide spacing of guns in a battery needlessly 
 increases the cost of the battery. Consequently, to separate the 
 guns of a battery any farther apart than is necessary to ptovide 
 conveniently large loading platforms and sufficiently protected 
 magazines, is wasteful. 
 
 GUN BLOCK. 
 
 The gun block is the portion of the emplacement which supports 
 the gun carriage and the gun. Its size and mass must,. therefore, be 
 such as to make it safe from overturning by the shook of discharge. 
 The size and shape of the gun block must, of course, be such as to fit 
 the carriage and consequently, it must be largely designed to accord 
 
165 
 
 with the Ordnance Department drawings of the carriage. In fact, 
 except for a few details such as drainage, bringing in electric cables, 
 etc., the Engineer Department, in preparing gun-block designs, has 
 but little freedom or responsibility. 
 
 In small and medium caliber barbette emplacements, the gun 
 block is usually quite simple in design, its upper surface being nearly 
 flat and merging off into the loading platform (see Plates III to IX). 
 In the older masking emplacements the gun block was likewise quite 
 simple, although it contained the gun well in which the counterweight 
 was raised and lowered. 
 
 In the larger disappearing gun emplacements, however (Plates 
 XIV to XX and XXII to XXVI) , the gun block is quite large and 
 complex. It is usually separated from other portions of emplace- 
 ments by "planes," or more "properly, surfaces of weakness." 
 
 In the center of the gun block is the gun well, cylindrical in shape. 
 (See Plate XXIII.) The upper edge of the cylindrical wall of the 
 gun well lies in a horizontal surface, called the "base ring level." 
 The base ring level is usually from 4 to 10 feet wide and is sur- 
 rounded by a vertical cylindrical wall from 2 to 4 feet high, the axis 
 of the cylinder being coiacident with the axis of the gun well. The 
 upper edge of this cylindrical wall, in turn, hes in a horizontal surface, 
 called the working platform level. In front this working platform 
 level usually extends outward to the parapet wall, while on the rear 
 and at the side it ends at the foot of a flight of from four to eight 
 circular steps that leads upward from the working platform level to 
 the loading platform level. 
 
 The gun block is usually separated from the parapet by a cylindrical 
 surface of weakness, coincident with the inner surface of the parapet 
 wall. (Consult mimeograph 109.) The gun block is likewise sepa- 
 rated from the loading platform by another cylindrical surface of 
 weakness. This latter surface of weakness is sometimes cDincident 
 with the riser of the uppermost of the circular steps connecting the 
 working and loading platforms, and sometimes it is a few feet farther 
 away from the axis of the gun well, so that structurally a portion of 
 the loading platform forms in reality the upper surface of the gun 
 block. This cylindrical surface of weakness, however, must not be 
 pushed so far from the gun as to lie behind the breach for, if that be 
 done, and if any inequality of settlement between the gun block and 
 the mass under the loading platform occurs, there will be a slight 
 break in the surface over which the loaded ammunition truck must 
 be rolled in ammunition service. 
 
 Where there is an annular air space surrounding the gun block, as 
 in the designs shown in mimeograph 109, Plate XXII, it is usual to 
 make the surface of weakness pass through the center of this air 
 space so that any leakage will find its way into the air space, whence 
 
166 
 
 it can easily be drained away. (See vertical section on left edge of 
 sheet 2, mimeograph 109.) 
 
 In many respects the most convenient location for the surface of 
 weakness between the gun block and loading platform mass is at the 
 riser of the upper step, as was suggested above. In case it is placed 
 there, the loading platform is usually given a continuous drainage 
 slope away from the top of this riser. Where the surface of weakness 
 is placed slightly farther outward, it is usual to make the intersection 
 of the surface of weakness with the loading platform the crest of the 
 latter, the portion of the loading platform within this surface of 
 weakness draining toward the steps and the portion outside to the 
 rear. 
 Working Platform. 
 
 The concrete part of the working platform level should be at 
 exactly the same elevation as the metal part of the working platform 
 attached to and rotating with the gun carriage. The working plat- 
 form is, of course, completed before the base ring is set, consequently 
 in setting the base ring, care must be taken so that not only is it 
 made perfectly level, but also that it is set at such an elevation as to 
 place the concrete and metal parts of the working platform at exactly 
 the same elevation so that they form praotically a continuous 
 horizontal plane. 
 
 Although it was not done in the early days, it has been customary 
 for the past few years to provide a metallic curb at the interior edge 
 of the concrete working platform. (See sheet 7, mimeograph 109.) 
 This curb is made of a standard angle iron with a horizontal face of 
 from 3 to 4 inches and a vertical face from 4 to 6 inches. This curb 
 must be bent until it is exactly circular in shape, and this bending 
 must be so accurately done as not to permit a variation anywhere of 
 more than one-eighth of an inch from the proper horizontal distance 
 from the vertical axis which is used as a standard in setting the 
 hold-down bolts. This degree of accuracy is necessary because the 
 metal-working platform whose exterior edge is circular revolves just 
 inside of this curb. 
 
 It is usual in large emplacements to make this curb of several pieces 
 of angle iron jointed together, using as fish plates pieces of smaller 
 angle iron. These small angle irons can, of course, be placed on the 
 outside of the curb only. 
 
 The anchor bolts holding the curb in position are usually com- 
 posed of one fourth-inch or three-eighths-inch rods, countersunk 
 where their heads appear on the cylindrical surface. To hold the 
 bolts firmly in place as the concrete is placed around th6m, nuts are 
 passed over the bolts and are screwed tight against the outside 
 vertical face of the angle iron. After passing a few inches horizon- 
 tally, these bolts bend diagonally downward and, near their outer 
 
167 
 
 ends, the last 2 or 3 inches is again bent sharply downward almost 
 vertically. Of course, after these bends are made in the anchor 
 bolts it is impossible to get the nuts on them, so that it is cus- 
 tomar}' to insert the anchor bolts in the angle iron and to then 
 screw up the nuts so as to hold them firmly in position before doing 
 the bending. 
 
 The heads of the bolts holding the fishplates must likewise be 
 countersunk. 
 
 The curb must be very acciirately set in position before the concrete 
 is placed around it. The horizontal face of the angle must be abso- 
 lutely level and at exactly the proper height, and no part of the 
 vertical face must vary by more than an eighth of an inch from the 
 proper distance from the axis of the gun well and of the cylinder pass- 
 ing through the bolts that are to hold down the base ring of the gun 
 carriage 
 
 In order to provide drainage for the concrete part of the working 
 platform and prevent water from running over the ciu-b, it is custom- 
 ary to give this part a shght slope outward to a small shallow gutter 
 placed on the working platform level against the riser of the bottom 
 step. This gutter must be provided with drain pipes, preferably 
 leading outw^ard and downward to the air passage where there is one. 
 
 Base Ring Level and Hold-Down Bolts. 
 
 Upon the gun block rests what is called the "base ring" of the 
 gun carriage, which supports the weights of the gun and carriage and 
 transmits these weights and the shock of discharge to the gun block. 
 In large gim" carriages the base ring is composed of heavy pieces of 
 cast iron, usually made in sections and bolted together so as to form, 
 as far as is practicable, a single ring. Its upper surface is planed 
 into a smooth conical path, upon which there move the rollers. The 
 rollers are conical and the point of intersection of the axes of these 
 cones lies in a v^ertical line passing through the center of the base 
 ring, so that as these rollers move around they roll without sliding. 
 On top of the rollers there is what is known as the racer, which 
 rolls around on them and which supports the remainder of the gun 
 carriage. 
 
 In smaller barbette gims the base ring is merely a flange at the 
 base of the pedestal. 
 
 The base ring is held tight to the gun block by a number of hold- 
 down or anchor bolts furnished by the Engineer Department and in- 
 stalled by that department during the construction of the gun block. 
 The number of hold-down bolts necessary, their size and distribution, 
 are fixed by the Ordnance Department, and are shown upon Ordnance 
 Department drawings which are furnished to tne Engineer Depart- 
 ment. The constructing engineer must see that the location of 
 
168 
 
 these bolts and their size accuratelj- agree with the requirements of 
 these Ordnance Department drawings. 
 
 Of coarse, in order that the bolts maj^ be accurately set a templet 
 has to be made. This, imder the circumstances, is not a difficult 
 thing to do, though great accuracy is required. Ordinarily the tem- 
 plet is made of wood. The hold-down bolts are pushed through the 
 templet 'and are bolted in place. The templet is then carefully 
 fixed in position so that the bolt's are exactly in their proper places 
 and the concrete is set around the bolts. 
 
 In a few of the early emplacements" constructed it was found, when 
 the attempt was made to set the base ring, that it did not accu- 
 rately fit the bolts. To avoid this, some constructing officers, when 
 the base ring happened fco anive before the gun block was built, 
 made use of the base ring as a templet. However, the base ring 
 of a large gun is so heavy and unwieldy that this is not believed to be 
 good practice. 
 
 In order to allow a little play for the bolts, a few constructing 
 officers have been in the habit, when the concrete had been brought 
 up so as to cover about the lower half of the bolts, of placing over the 
 upper half of each bolt a piece of pipe a little larger than the bolt. 
 The concrete is then placed around the pipe and the pipe is after- 
 wards pulled out, leaving a little play, so that the bolt may be bent a 
 fraction of an inch or so in an}'^ direction. I.,ater this space is filled 
 with grout. 
 
 This, however, is not believed to be a good practice. The bolt 
 holes bored in the base ring allow a little play for the bolts, and the 
 accuracy obtained in setting the bolts should be such that this 
 amoun t of play is sufficient. 
 
 Unfortunately, when the base rings for one of the long-range 
 12-irich carriages was, in the autumn of 19 IS, sent to the emplace- 
 ment designed for it, it was discovered that one of the bolt holes in 
 the base ring had been bored 2 inches out of place. To have mounted 
 this base ring in this emplacement would have required either that 
 a new bolt hole be bored or that one of the hold-down bolts be cut 
 out and be reanchored in the concrete. Fortunately, however, it 
 was not necessary to do either of these things, because an emplace- 
 ment for a similar carriage in another place had not been started and 
 the base ring which had been improperly bored was sent to this new 
 place, and the bolts in that emplacement were set so as to fit this 
 particular base ring. 
 
 The hold-down bolts have at their upper ends hold-dovi^n nuts to 
 })ress the base ring firmly agauist the gun block, and above these 
 hold-down nuts lock nuts are added to prevent the hold-down nuts 
 from shaking loose from the repeated shock of discharge when the 
 gun is fired. 
 
169 
 
 At the lower end of the hold-down bolt there is an anchor plate 
 with, of course, a nut below it to keep the bolt from pulling through 
 the anchor plate. Incidentally, unless there is a nut above the anchor 
 plate also, there is a possibility that in placing concrete around the 
 anchor plate some small lumps of concrete may get between the 
 plate and the nut below it. When the base ring is set later the. strain 
 put upon the nuts at the top of the bolt may not be sufficient to 
 break up the concrete lump and raise the bolt up so that the bottom 
 nut comes firmly in contact with the anchor plate. These small 
 concrete lumps may subsequently be broken by the shock of firing 
 the gun, and this would leave a little pla}^, which may cause trouble 
 later when the gun is again discharged. To avoid this trouble the 
 anchor plate should be held firmly between two nuts, which should 
 be screwed up hard before. the concrete is set around the bolt. 
 
 As a general rule the anchor plates are about 12 inches square and 
 about an inch thick, although other dimensions are sho^vn on some 
 of the drawings. 
 
 In small guns, instead of having the anchor bolts held down by 
 individual anchor plates, an anchor ring is sometimes provided 
 through which all the bolts pass. 
 
 As was stated above, the hold-down bolts are furnished by the 
 Engineer Department, and one of the earlier mimeographs (mimeo- 
 graph No. 10, issued in 1896) gave specifications for the manufacture 
 of these bolts. These specifications were subsequent^ amended and 
 were published as a supplement to mimeograph No. 10 and are as 
 f ollo'^vs : 
 
 ANCHOR BOLTS AND NUTS FOR 12-INCH MORTARS AND 8, 10, AND 12 INCH GO.N 
 
 Anchor bolts are to be of soft open-hearth structural steel. 
 
 Each finished bolt must be stamped with the melt number, and one extra bolt for 
 test purposes must be supplied with the lot made from any particular melt; said boll 
 to be selected at random by the agent of the United States. 
 
 Tensile strength, limit of elasticity, and ductibUity shall be determined by test 
 pieces cut from a selected bolt. 
 
 The bending test shall be made upon a test piece cut from a selected bolt and ma- 
 chined to 1 inch square in cross section. 
 
 The material shall fulfill the following tests: 
 
 Ultimate tensile strength, from 56,000 to 62,000 pounds per square inch; el9,stic 
 limit, not less than one-half the ultimate strength; minimum elongation, 25 per cent 
 in 8 inches; minimum reduction of area at fracture, 50 per cent; shall bend 180° 
 flat on itself without fracture on outside of bent portion. 
 
 The finished bolts must be free from injurious seams, flaws, cracks, and have a 
 workmanship finish. 
 
 Anchor plates to be of a tough gray cast iron, free from injurious cold shuts or blow 
 holes, cored and beveled as shown on the platform sheets; the holes in the anchor 
 plates to be roughly finished to fit the bolts; the surface under the head of the bolt 
 affording a through bearing. 
 
170 
 
 Bottom nuts of anchor bolts to be square and one-half inch thicker than United 
 States standard, of best quality of wrought iron, hot pressed, and of same quality 
 and finish as bottom nuts, conforming to the United States standard in size, except 
 thickness, of jam nuts. 
 
 The hold-down bolts, of course, have to be inserted in the concrete 
 when the gun block is constructed. In order to preserve the thread 
 at the top of the bolt it is customary to leave the nuts on throughout 
 the process of building the gun block and, in order to preserve the 
 nuts and the upper ends of the bolts from the concrete and moisture, 
 it is customary to tie them up with oUed rags which can afterwards 
 be removed. These rags are, of course, allowed to remain on the 
 bolts until the base ring arrives. 
 
 The first step in mounting the gun carriage is to set the base ring. 
 The rags and nuts are removed from the top of the bolts and the ends 
 of the bolts are carefuUy cleaned and oiled. The base ring is then 
 carefully manipulated over them and slowly lowered with jacks 
 until it is set in place. 
 
 It is essential, of course, that the roller path of a large gun be 
 absolutely horizontal, and great care must, therefore, be exercised 
 in setting a base ring to see that it is carefully -leveled. In order to 
 insure this, each base riag is provided with a few so-called levelii^ 
 bolts. These screw through the base ring and press against leveling 
 or thrust plates furnished by the Ordnance Department and for 
 which recesses must be left when the concrete is finished off near the 
 heads of the hold-down bolts. (See sheet 1, mimeograph 109.) 
 
 After the base ring has been lowered over the hold-down bolts, 
 these leveling bolts are carefully adjusted so as to make the base ring 
 absolutely level and at the proper elevation. There should be left 
 under the base ring and between it and the concrete surface of the 
 gun block a space of from one-half an inch to 1 inch. This space is 
 then to be filled with grout. 
 
 As was stated before, in setting the base ring of a large gun there 
 is one matter of special importance and that is that it should be set at 
 exactly the proper height so as to bring the level metal platform, 
 known as the working platform, which revolves as the gun revolves, 
 exactly in the same horizontal plane with the concrete part of the 
 working platform level. The curb of the working platform level 
 should, therefore, be taken as the basis on which all other levels 
 around the gun block are based, and when the base ring is set its 
 exact elevation and the amount of grout which is to be placed under 
 it should be so adjusted as to bring the metal part of the working 
 platform to exactly the proper elevation. 
 
 The grout used in setting the base ring consists of a very thick 
 and dry cement paste composed of neat cement and water. This is 
 forced .under the base ring until the entire space is filled and fiUed 
 
171 
 
 solidly. The cement is then given a few days in which to harden, 
 leveling bolts are loosened, and the hold-down bolts carefully tightened 
 up. An examination is then made to see if the base ring is still level; 
 and if so, the mounting of the other parts of the carriage may be 
 proceeded with. 
 
 The Chief of Ordnance has stated that m setting the base ring for a 
 large seacoast gun a variation of one-fiftieth of an inch is not permissi- 
 ble. Specially designed machinist's levels are therefore required, 
 and in order that the blame for any error may fall on the proper 
 department it is customary for a base ring never to be set except in 
 the presence of and under the supervision of an Ordnance officer 
 or an Ordnance Department mechanic. 
 
 The actual grouting of the space under the base ring is done by the 
 Engineer Department. 
 
 At new posts, where emplacements are under construction and 
 there is no Artillery garrison, the handling of the base ring and the 
 mounting of the carriage is done by the Engineer Department, that is, 
 by Engineer Department civihan employees working under the 
 supervision of an Engineer officer. At garrisoned posts where 
 artillery is available, the Artillery soldiers mount the gun and 
 carriage, the Engineer Department giving such assistance as may be 
 necessary and always grouting the base ring. Wherever large guns 
 and carriages are to be mounted or remounted, the Ordnance De- 
 partment should, in general, be represented by an Ordnance officer 
 or by a designated civilian Ordnance employee. 
 
 As a rule the Ordnance Department drawings make no allowance 
 for the gx-out under the base ring and constructing officers should, 
 therefore, be careful to finish the surface upon which the base ring 
 is to rest half an inch or so lower than the Ordnance Department 
 drawings would indicate and should then see that the base ring is 
 set not only absolutely level but at exactly the proper elevation? 
 
 Care should also be taken, in finishing the upper surface of the 
 concrete of the base ring level, to leave recesses for the leveling 
 plates. Space also should be left for the joints of the base ring where, 
 as in very large guns, it is furnished in more than one piece. In addi- 
 tion, a groove, annular in shape, should be left for the elevating 
 mechanism to revolve in. The bottom of this groove should be so 
 arranged as to drain to pipes set at a few lo^ points. In high emplace- 
 ments these drain pipes shoidd lead outward to the gutter in the air 
 passage; in low emplacements, inward to the gun well. 
 
 On the inner face of the gun block, or it might be better to say 
 in the wall of the gun well, recesses should be left for the Ordnance 
 Department terminal box. (See sheet 7, mimeograph 109.) Grooves 
 for speaking tubes, electric cables, and flexible connections should 
 likewise be left. 
 
172 
 
 Gun Well. 
 
 The main purpose of the gun well is to provide space in which the 
 counterweight may rise and fall. In the old ma&king mounts the 
 counterweight exactly balanced the gun and pedestal. It dropped 
 down when the gun rose to the firing position and was raised when, the 
 gun dropped down to the concealed position. These wells, of course, 
 were not very large. (See Pis. Ill and VT.) 
 
 With the disappearing carriages the counterweight fulfills two 
 functions: Fh^t, the work done in raising the counterweight as the 
 gun recoils serves io absorb some of the energy of recoil; and, second, 
 when the counterweight is allowed to descend it raises the gun into 
 the firing position. 
 
 In the oldest form of disappearing emplacements (1894 type, see 
 Plate XIII) the counterweight wells were made so small that the 
 counterweight nearly filled the well, and it was foimd extremely diffi- 
 cult to put the counterweight in position as the gun was being 
 mounted. In order to improve on this, an opening from the flank:, 
 was cut into the bottom of the gun well, through which opening a man 
 could crawl and through which he could pull out any cribbing which 
 had temporarily been placed under the counterweight. Similar openr- 
 ings were installed in some of the earlier masking emplacements. 
 (See Plate VI.) 
 
 The next improvement was to make the gun well very much larger 
 so that the counterweight fills up but a very small proportion of the 
 space within the well. This permits communication wires, electric- 
 light wires, speaking tubes, etc., to be carried into the well and through 
 it to the gun carriage. 
 
 Until the development of the Panama type of emplacement, the 
 only method of getting into the gun well after the gun and carriage had 
 been mounted was by means of a ladder hung downward from the 
 upper part of the gun carriage to near the bottom of the well. This, 
 however, was found to be inconvenient, and in the Panama type of 
 battery a special passageway is provided leading down into the gun 
 well. This makes it easy for a person at any time to go from the 
 loading platform into the well. (See Plates XXIII, XXIV, and 
 XXV.) Such a passageway was especially necessary in the Panama 
 16-inch disappearing emplacements, where long and heavy steel 
 I beams had to be carried into the gun well for use in mounting the 
 gun and carriage. 
 
 Of course, the rain that falls upon the gun or carriage drains into 
 the gun well. Some form of drainage is therefore essential. When the 
 gun well was small the amount of water which would accumulate in it 
 was also small, but as the gun well and the space around the loading 
 pktform which drains into it increased, the amount of water which 
 might accumulate also increased and a corresponding allowance had 
 
173 
 
 to be made for this increased drainage. To catch the drainage, a 
 sump is placed in the floor of the gun well and the floor is drained 
 toward this sump. Sometimes the sump is placed centrally, but more 
 often at one side. 
 
 In general, as will be discussed in the chapter on drainage, all por- 
 tions of an emplacement should be provided with natiu"al drainage, 
 and when the emplacement is located on a high site it is usually pos- 
 sible to provide such drainage even for the gun-well sump. However, 
 the gun wells necessary for the standard large disappearing emplace- 
 ments are so verj' deep that when these emplacements are constructed 
 along the low sand beaches of the South Atlantic and Gulf coasts the 
 floors of the gun wells are pushed down well below mean sea level, 
 and therefore below the level of ground water. Natural drainage for 
 such low wells can not be provided. Of course, with proper con- 
 struction, no seep water should find its way into these wells, but rain 
 water does, and the only way of removing it is by bailing or pumping. 
 Consequently, in one of the Panama batteries where the bottom of the 
 gun well is several feet below sea level, special pump rooms had to be 
 provided on the sides of the corridors leading into the gun wells. In 
 these pump rooms small hand pumps were installed. In general, 
 the amount of water which can accumulate in such a gun well should 
 be very small, and it was thought that power pumps were not neces- 
 sary and that hand pumps would suflace. (See Plate XXV.) 
 
 LOADING PLATFORMS. 
 
 The loading platform is the name given to the level space surround- 
 ing the gun and carriage upon which the members of the detachment 
 stand while placing the ammunition in the gun. In small emplace- 
 ments the loading platform is not large (see Plates III to VII) and 
 from its rear there is usually a flight of steps leading down to the 
 magazine. 
 
 In the medium caliber, rapid-fire, barbette emplacements the load- 
 ing platform is slightly larger. Occasionally it is considerably lower 
 than the trimnions so that the gun can be loaded while aimed at a 
 •onsiderable elevation. In such guns there is frequently attached 
 to the base of the gun carriage a metal platform that revolves with it, 
 and upon this platform one or two of the detachment engaged in 
 aiming and firing the gun usually stand. 
 
 In the larger disappearing emplacements (Plates XIV to XX and 
 XXII to XXV) the gim platform is very wide, and upon it are rolled 
 the ammunition trucks, bringing the ammunition to the breech of 
 the gun. One of the reasons why this platform has to be wide is to 
 provide room for the detachments handling the sponge and rammer 
 staves. Of course it is necessary to sponge the gun only occasionally, 
 either after quite a number of rounds have been fired or after firing 
 
174 
 
 has ceased. The rammer, however, must be used every time the 
 gun is loaded. 
 
 In the very early designs (Plate XITI) the loading platforms were 
 very deficient in size and width. The movements of the detach- 
 ment were quite cramped and consequently rapid loading was not 
 possible. However, a short time later it became customary to build 
 emplacements with very wide loading platforms. This permits the- 
 projectile truck to be pushed up to the breech of the gun on the run. 
 When the truck strikes the breech it stops suddenly, but the projectile, 
 by its inertia, bounds into the breech, and the ramming detachment 
 soon become so skillful that they can place the head of the rammer 
 against the base of the projectile as it bounds into the gun and can 
 ram it all the way home without its actually stopping. To make such 
 an action possible, an amply wide loading platform is necessary. 
 
 As an indication of the increase in the size of the loading platform, 
 it should be noted (Plate XIII) that in the 1894 type of 10-inch 
 emplacements the handrailing at the rear of the loading platform 
 was but 34 feet from the axis of the gun well, while in the 1903 type 
 (Plate XVII) this distance had been increased to 41 feet. In the 190a 
 type of 12-inch emplacement (Plate XX) the depth of the platform 
 measured from the axis to the gun well to the handrailing in the rear 
 is 52 feet. In the designs of the 14-inch emplacement (Plates XXII 
 to XXVI) the loading platform is about 62 feet deep measured from 
 the axis of the gun well to the foot of the surrounding earth slope, and 
 in the 16-inch Panama emplacements this distance is 72 feet. 
 
 When it was discovered that the loading platforms that were built 
 at the early batteries were not sufficiently large, it was, of course, 
 impossible to widen them sidewise because of the concrete traverses 
 that could not be moved. It was, however, possible to increase the 
 depth of the emplacements to the rear, and under the appropriations 
 for modernizing emplacements a large number of the loading plat- 
 forms of the older emplacements were increased in .depth. This was 
 done at the same time that new hoists were introduced in these 
 emplacements and new stairw^ays built, and the net result was a great 
 improvement in these old emplacements. 
 
 In designing a loading platform, the size of the gim well, of the load- 
 ing platform, of the steps around it, and of the parapet wall in front of 
 the gun and along both faces of the parapet must be fixed so as to 
 accord with the Ordnance Department drawings of the gun carriage. 
 In most of these details practically no choice is left to the Engineer 
 Department, except as to the details of drainage, but the location and 
 direction of the face walls of the parapet can be somewhat modified 
 if desired. 
 
 The Ordnance Department drawing, showing as much of the details 
 of the gun carriage as are necessary for the Engineer Department to 
 have in designing the gun block and loading platform (which drawing 
 
175 
 
 is ordinarily known as the "Ordnance Department platform sheet") 
 usually shows the distance of the end of the rammer staff from the 
 axis of the gun well when the head of the rammer is placed against the 
 base of the projectile on a truck pushed against the breech of the gun. 
 To permit the projectile to be loaded "on the run," the depth of the 
 loading platform must be 3 or 4 feet greater than required by the 
 Ordnance Department drawing. 
 
 In designing the loading platform, a circle of the radius obtained 
 in the manner just described is drawn with the axis of the gun well 
 as a center. A tangent of this circle drawn parallel to the line of gun 
 centers gives the position of the rear edge of the loading platform, and 
 lines drawn parallel to the capital of the emplacement through the 
 points of intersection of the circle with the face walls of the parapet 
 gives the locations of the side walls of the emplacement. Where 
 the loading platform is to be surrounded by sand side slopes and a 
 parados, the locations of the foot of the side slopes and of the foot of 
 the parados are given by the circle referred to. 
 
 The principal object pi the loading platform is to provide a con- 
 venient place for the detachment while loading the gun. Its eleva- 
 tion should, therefore, be fixed primarily at that which will make the 
 service of the gun most convenient. In the large disappearing em- 
 placements, the axis of the gun in the loading position is practically 
 horizontal and the elevation of the breech is practically the same 
 whatever be the elevation at which the gun may be set for firing. It 
 has been found that the ramming of the projectile is most convenient 
 when the axis of the breech of the gun is from 46 to 48 inches above 
 ^ the loading platform. Consequently, the loading platforms are built 
 at such an elevation as to place them about this distance below the 
 breech of the gun when in the loading position. 
 
 For drainage purposes, as will be explained more at length on the 
 chapter on dryness, etc., all loading platforms are given a slight 
 drainage slope and some portions of this platform are, therefore, 
 slightly lower than others. Since, however, the elevation of the load- 
 ing platform is fixed by the convenience of loading the gun, the govern- 
 ing elevation must be that of the portion of the loading platform im- 
 mediately below the breech of the gun in the loading position. The 
 elevation of this part of the loading platform being fixed, the contours 
 of other portions are arranged so as to provide proper drainage 
 slopes. 
 
 When the loading platforms are so built as to drain away from the 
 gun and the plane of weakness around the gun block is placed at the 
 riser of the topmost of the steps connecting the loading and working 
 platforms, the top of this topmost step is made the highest point and 
 is placed at such an elevation that, allowing for the drainage slope, 
 the circle on the loading platform under the breech of the gun as it 
 
176 
 
 revolves in azimuth will be at exactly the proper elevation for load- 
 ing. Where, as in the design shown in mimeograph 109, (Plate XXII) , 
 the cylindrical surface of. weakness comes directly over the air space, 
 the intersection of this surface of weakness with the loading platform 
 is the crest of the loading platform and the elevation of this crest 
 must be so fixed as to place the circle under the breech at its proper 
 elevation. 
 
 In the two-story batteries the loading platforms are a story above 
 the ground and for the safety of the detachment, hand railings are 
 placed along the rear of the platform. In one-story emplacements 
 such hand rails are, of course, not needed. To avoid the nuisance of 
 having water run over the rear edge of the loading platform of a two- 
 story emplacement, a gutter with suitable drains is usually placed 
 immediately in front of the hand railing. 
 
 Parapet Walls. 
 
 The front of the loading platform abuts agamst the parapet wall, 
 and in the older emplacements the sides of the loading platform 
 abutted against the concrete side walls of the emplacement. Ordi- 
 narily these front and side walls are made vertical for some 6 feet or so 
 above the loading platform level. At about this elevation the walls 
 usually project about 4 or 6 inches, forming what is called the "over- 
 hang." The face of the overhang is usually vertical up to near the 
 top of the wall where it is finished off with a 45° bevel, 12 inches in 
 the vertical and 12 inches on the horizontal. The overhang provides 
 a convenient protection under which the electric light sockets and 
 cables can be attached to the front and side walls. In the early em- 
 placements the bottom of this overhang was made strictly horizontal 
 but it was found that this permitted the rain water, running down 
 the face of the overhang above, to pass in drops along the bottom of 
 the overhang to the side wall and thence down the face of this wall. 
 To avoid this it is now customary to place in the bottom surface of 
 the overhang and about an inch from its outer edge a small groove 
 made by nailing a strip of beading to the framing before the concrete 
 is put in place. 
 
 Portions of the side and front walls of the emplacements are fer- 
 quently used as locations for telephone booths, for the openings of 
 ventilators from the air passages and galleries below, for recesses for 
 storing ammunition trucks, and, in the 14-inch emplacement (see 
 mimeograph 109 and Plate XXII), for reserve projectile tables. 
 
 The front part of the side walls are also used in some emplacements 
 (see mimeograph 109, Plate XXII) as locations for the stairways 
 leading from the loading platform up to the top of the parapet. 
 
177 
 
 Maneuvering Rings. 
 
 When it became necessary to mount the guns in the very first 
 emplacements built, it was found that no arrangements had been 
 made for the attachment of the blocks and falls necessary for handling 
 the large pieces of the carriage and the guns. There was, therefore, 
 introduced into emplacement construction the custom of inserting 
 maneuvering rings. These rings are of wrought iron or mild steel 
 and are made by bending into an annular form a piece of 1-inch to Ih- 
 inch bar steel, the interior diameter of the ring being about 6 inches. 
 The rings pass through the eye of a staple extending into and firmly 
 anchored in the concrete front or side walls. At first the staples 
 were allowed to project beyond the face of the wall so that the 
 rings hung down against it. Subsequent designs, however, have 
 shown these rings set in recesses. 
 
 Usually three maneuvering rings were installed in each emplace- 
 ment but in large ones, especially those with the concrete side walls, 
 five were provided. 
 
 Parapets. 
 
 The word "parapet" is derived from the Italian and in that 
 language it means a protection in front of a man, rising up as high 
 as his chest. Originally it referred to a protection for Infantry built 
 only to such a height as to protect the bodies of the men behind it, 
 while still permitting them to fire muskets over it. By extension, 
 however, the word was later used to indicate any similar protection 
 whatever its height. 
 
 For a while the attempt was made by certain mihtary engineers 
 to reserve the word "parapet" for its original meaning, an embank- 
 ment for protecting Infantry, and to use the word "epaulement" for 
 the higher protection used with cannon in siege and similar batteries. 
 Strictly, this was not correct, for by its derivation epaulement means 
 a protection shoulder high. In time, however, the attempt to use 
 different words, one for an Infantry parapet and the other for an 
 Artillery parapet, failed, and at present the word parapet is used for 
 all protecting embankments, whatever their height; not only In- 
 fantry parapets some 4 or 5 feet high, but even the parapets in 
 front of disappearing emplacements, which in some cases are 15 feet 
 high. Occasionally even the term parapet is used to include the 
 protection of concrete and sand in front of a magazine. 
 
 When, in the early nineties, work was begun upon the designs of 
 our modem seacoast emplacements, it seems to have been consid- 
 ered by the designers that the main protection against hostile pro- 
 jectiles was to be obtained by a thick concrete parapet. Such a 
 parapet was expensive and, for economical reasons, earth or sand was 
 substituted for the concrete in the forward part of the parapet, 
 173341—20 12 
 
178 
 
 because the same amount of protection could be obtianed at less cost 
 with a comparatively thin concrete wall, having sand in front of it, 
 than if concrete were used throughout. 
 
 Since that time our ideas have been changed. It has been found 
 that when concrete is struck by a projectile it is shattered and that 
 the scattering fragments of the concrete are exceedingly dangerous. 
 Furthermore, the impact of a shell upon concrete is apt to cause the 
 shell to detonate upon contact. 
 
 On the other hand, when a projectile strikes a bank of sand there 
 are no large fragments of the parapet that can do any damage. Be- 
 fore the projectile can detonate, it is certain to penetrate some dis- 
 tance into the sand and when the detonation does occur the mass of 
 sand above the shell serves to blarket the explosion and to reduce 
 the scattering of the fragments of th > shell. 
 
 Moreover, the damage done to concrete by the impact of projec- 
 tiles can be repaired only by rebuilding the parapet and this takes 
 time, whereas the damage done to an earthen parapet by the impact 
 of projectiles or even by the detonations can be easily repaired by 
 simply filling up the holes with earth. 
 
 For the above reasons, the sand part of the parapet is now regarded 
 as the main protection and concrete ik used only, where there is not 
 space enough tor a sufficient quantity of sand, where it is necessary 
 to have vertical walls, or where it is necessary to build an apron that 
 can stand the blast of the guns. 
 
 In the fall of 1915, there was constructed at Fort Morgan, Ala. 
 a test emplacement, and in March, 1916, this emplacement was fired 
 at by naval vessels. The result of these tests was to show that 
 naval projectiles striking a sand parapet, even in the exterior slope, 
 will penetrate the sand but a short distance before being deflected ■ 
 iipward and out, and that in a properly constructed disappearing 
 emplacement, about the only vulnerable portion is the concrete blast 
 apron within a few feet of the gun. 
 
 It was, therefore, decided to make another set of experiments to 
 determine what was the best manner of constructing the part of the 
 parapet immediately in front of a gun. The actual experiments 
 took place at Sandy Hook in September, 1917, and the report upon 
 these tests should be carefully studied. 
 
 Several types of parapets were tested and the result was, in general, 
 to show that apparently the best type of construction for this part of 
 the parapet was to buUd it of concrete, reinforced in three directions, 
 this type having shown its ability to withstand a continued bombard- 
 ment better even than a concrete parapet surmounted by a heavy 
 plate of steel armor. It was shown that as each projectile struck 
 the reinforced concrete parapet it loosened small fragments of con- 
 crete. These fragments, however, as a rule, were small, and th© 
 
179 
 
 total amount knocked off by any projectile was not lai-ge. It was 
 e\ddent that in order to produce any effective result a large number 
 of projectiles would have to strike in practically the same spot. 
 
 In connection with the designs of the recent emplacements built 
 for the long-range 12-inch rifles, some studies were made of a new 
 type of parapet to be composed of sand only and to contain no 
 masonry whatsoever. These parapets were designed for guns mount- 
 ed on barbette carriages capable of being fired at a high angle of eleva- 
 tion and placed in locations where the conditions as to depths of 
 water in the probable area of fire are such that firing at a less eleva- 
 tion than 10° would probably never be necessary. It was proposed 
 for such emplacements to move the parapet so far to the front that 
 it would not be injured by the blast of the gun; to make it quite 
 thick, and to build the interior and exterior slopes at the natural 
 slope at which the sand would stand. The top of the parapet, 
 usually called the superior slope, was to incline inward and downward 
 at an angle of 10° toward the gun, and was to be at such an elevation 
 as to be only a few feet below the trajectory when the gun was fired 
 at the minimum angle of 10°. Such a direction for the slope of the 
 top of a parapet is contrary to the usual practice. In order to provide 
 for drainage, it is customary to give slight slopes to the tops of all 
 parapets, aud these slopes usually incliae downward and outward in 
 order to provide a clear field of view and of fire. With this new type 
 of emplacement, the fire was to be indirect so no view was necessary. 
 In fact, the principal object sought was concealment, and the higher 
 the parapet the better the concealment. The parapet, of course, 
 could not be high enough to intercept the trajectory, and by making 
 the outer crest the higher, a better concealment could be obtained 
 and the top would be more nearly parallel to the trajectories of the 
 enemy's projectiles. 
 
 Although the plans of several batteries having parapets of this new 
 type received the approval of the department, no such parapets 
 were actually built. Before the actual work had reached the stage 
 of parapet construction, it was decided to do away with parapets 
 entirely so that the men at the guns might see the target and so the 
 guns, if desired, might be fired at zero elevation. 
 
 Side Walls of Emplacements. 
 
 The adoption of the idea of relyiag upon sand, rather than upon 
 concrete, as the main protection against an enemy's projectiles, 
 caused a considerable modification in the type of battery construc- 
 tion. In all the typical batteries designed prior to 1909, the loading 
 platforms were shown as having vertical concrete side walls. It was 
 known, of course, that these side walls might be struck by a projectile 
 coming from an oblique direction and passing a few feet over the 
 crest of the parapet, but it was thought that projectiles striking a side 
 
180 
 
 wall at a slight angle would be deflected to the rear without being 
 detonated and would do little or iio damage. It has more recently- 
 been shown, however, that projectiles filled with high explosives and 
 fitted with quick-acting fuses mil probably be detonated by such a 
 contact with a concrete side wall, and that this detonation may be 
 sufficiently powerful to scatter the fragments of the shell about the 
 loading platform. 
 
 To avoid this, concrete side walls were not used, in the 1912 typ6 
 of batteries, and for them were substituied gently sloping masses of 
 sand. This was done with the idea that a projectile striking sand 
 at a sUght angle would probably be deflected away without explod- 
 ing, or else would bury itself some distance in the sand beford 
 detonating. 
 Retaining Walls. 
 
 In more recent emplacement designs, retaining walls, except 
 immediately in front of the loading platform, are not carried all 
 the way to the top of the mass of earth which they retain. They 
 stop some 5 feet or more below the crest of the earth in front, which, 
 for this remaining distance, is sloped upward from the top of the 
 wall. This was done because experience has shown that in moat 
 cases projectiles striking on a nearly flat surface of sand penetrate 
 only a few feet before being deflected upward. Consequently, the 
 tops of retaining walls when kept low will, in aU probabiUty, never 
 be hit, and if so, wiU be damaged only at the top. 
 
 Amount of Protection to be Afforded. 
 
 When, in 1890, the Board of Engineers began to design our 
 modern fortifications, the concrete which they prepared to use was 
 to be made of Rosendale cement, and it was assumed that the pro- 
 tection given by such concrete against the penetration of projectiles 
 was about twice as great as that offered by sand. In 1893 the 
 board submitted a report to the effect that the amount of protection 
 necessary in large emplacements against heavy naval guns was the 
 equivalent of about 45 feet of concrete, or 90 feet of sand. 
 
 In 1896 they stated — 
 
 It, is assumed that the maximum cover of 70 feet of sand or its equivalent will 
 afford sufficient protection for the guns, 90 feet for the magazines; this distance 
 being measured horizontally at the level of the exterior crest. The vertical cover 
 over the body of the magazines should be equivalent to 6 feet of concrete. The 
 boncrete wall in front of the gun should be at least 20 feet thick. In computing 
 these equivalents 1 foot of concrete is regarded as equal in resisting power to 2 of 
 sand or 3 of earth. Wherever concrete is used as cover against projectileB it 
 is intended that as many bowlders or large rocks should be embedded irregularly 
 in the mass' as are consistent with its uniting into one monolith; the object of this 
 being to deflect projectiles. This should be done even at the risk of increasing the 
 cost. 
 
181 
 
 It was upon the basis stated in this quotation that the protection 
 afforded the magazines, as shown in the early 'mimeographs, was 
 mainly designed, although, as was noted in the discussion of the 
 different types of emplacement in the preceding chapter, modifica- 
 tions were occasionally made — the protection shown on the mimeo- 
 graph being sometimes reduced somewhat below the standards 
 stated in the quotation. 
 
 The concrete to which the Board of Engineers referred in 1893 
 and 1896 was concrete made with Rosendale cement. Shortly after 
 the Spanish War, however, the use of Rosendale cement was dis- 
 continued, and Portland cement was thereafter used exclusively. 
 This change increased the strength and the resisting power of the 
 concrete, and from then on the resistance of 1 foot of concrete was 
 considered to be the equivalent of about 3 feet of sand — an increase 
 of about 50 per cent over the ratio adopted by the Board of Engi- 
 neers for Rosendale concrete. Consequently, we find in the text of 
 the mimeographs relating to the 1903 designs for 10-inch and 
 12-inch emplacements, the board adopting as the standard amount 
 of protection: 
 
 Horizontal protection, front of magazine, to feet of concrete, 45 of sand; equivalent 
 to 30 feet of concrete. 
 
 Horizontal protection, front of gun, 15 feet of concrete, 40 of sand; equivalent to 
 about 28 J feet of concrete. 
 
 Vertical cover over magazine, 10 feet of concrete. 
 
 In Mimeograph 109, showing the typical designs for 14-inch 
 emplacements and prepared in 1908, the same standard was 
 adopted, except that the vertical concrete cover of the magazine 
 was made 12 feet of concrete instead of 10 as previously recom- 
 mended. 
 
 In designing the Panama batteries the standard amount of 
 protection given was the equivalent of 35 feet of concrete or 105 
 feet of sand measured in the horizontal. Against projectiles, with 
 an angle of fall of 2°, the protection was decreased to 30 feet of 
 concrete; for an angle of fall of 5°, to 26 feet of concrete; for an 
 angle of 15°, to 21 feet of concrete; for an angle of fall of 45°, to 
 18 feet of concrete, with 12 feet of vertical overhead protection. 
 These figures were based upon exposed concrete, but wherever 
 . possible sand was substituted for concrete upon a basis of 3 feet of 
 sand being equal in resistance to 1 foot of concrete. 
 
 Since the Panama batteries were designed the Fort Morgan 
 experiments have shown the great efficiency of sand as a protection 
 against modern projectiles, especially in its tendency to deflect 
 projectiles upward and outward. Apparently, therefore, the stand- 
 ard of protection given to the Panama batteries was somewhat 
 excessive. Instead' of providing 20 feet of concrete and 45 feet of 
 
182 
 
 sand in front of a magazine, it is believed that 10 feet of concrete 
 and about 45 to 60 feet of sand would have been sufficient. Over 
 the magazine the sand should be so distributed as to be never less 
 than 10 feet thick, measured vertically, and 14 feet thick, measured 
 at an angle of 45°. Moreover, the outer upper edge of the concrete 
 in front of the magazine should be sloped to an angle of 45° for 
 a distance of 5 feet or so. For overhead cover it is thought that 
 7 or 8 feet of concrete is sufficient, provided there is 10 feet of sand 
 above it. Where it is not possible to get this thickness of sand the 
 thickness of the concrete should be slightly increased. 
 
 One fact that will probably be noticed from a study and comparison 
 of the older mimeograph designs of emplacements is that the amount 
 of magazine protection provided was apparently dependent upon 
 the size of the gun to be emplaced, the larger the guns the thicker 
 the parapet. This was based upon the idea that the smaller batteries 
 would probably be the natural target for the enemy's smaller guns, 
 the medium caliber batteries for his medium caliber guns, and the 
 larger batteries for his main armament. Consequently, the 3-inch 
 emplacements were designed to withstand the fire of naval rapid-fire 
 batteries. The 5-inch and 6-inch emplacements were designed to 
 withstand the fire of 6-inch naval guns, and the large gun emplace- 
 ments the fire of the largest guns carried by any ships that could 
 approach the battery. 
 
 If we could be certain that a heavy projectile would never be aimed 
 at or strike a smaller battery, this might do very well, and when the 
 batteries are scattered and the probable range small, it might be safe 
 to risk it, but where small gun batteries are located in close proximity 
 to larger ones, the former may probably be struck by large projectiles 
 aimed at the latter, and since the explosive of the magazine of even 
 a small battery would be quite demoralizing, this portion, at least, 
 of the smaller batteries should be given almost if not quite as much 
 protection as those of the larger batteries. 
 
 Stones in Concrete of Parapets. 
 
 It was the custom in the first of our modern emplacements to- 
 place in the concrete of the parapet, especially in front of the maga- 
 zine, large irregular shaped stones and bowlders, it being supposed 
 that a projectile that might penetrate the concrete would be deflected^ 
 at the surface of the bowlders. That is, the bowlders in the concrete 
 were supposed to make it more impenetrable. In general^ these 
 bowlders cost more than the equivalent volume of concrete but, 
 nevertheless, it was considered that they were of sufficient value to 
 justify the additional expense. 
 
 The improvement in cement has made the bowlders no longer 
 necessary, and this is especially true now that the sand is considered 
 as the principal protection rather than the concrete. Occasionally, 
 
183 
 
 of course, large masses of stone may be available and can be placed in 
 mass concrete at less expense than the equivalent mass of concrete, 
 so that their use is economical, but in general it is considered desirable 
 to use them only in foundation work and not in parapets or in front 
 of magazines. 
 
 Sodding. 
 
 The necessity of having a clear field of fire for the guns and a 
 clear sight from the observing stations in rear of the parapet, make it 
 necessary to finish off the upper surfaces of the parapets of batteries 
 in fairly regular planes having slight drainage slopes. 
 
 Of course, to prevent these slopes from being washed by rain, it 
 is necessary to sod them. In our northern States these surfaces are 
 sodded by actually placing sod. In the southern States, however, 
 it is customary to plant little tufts of Bermuda grass at intervals 
 and to keep them watered. These tufts soon spread rapidly and 
 cover the entire slope with a nice sod. 
 
 In general, of course, grass will not grow well on bare sand. It 
 is, therefore, customary to put between the sand and the sod a layer 
 of soil or garden loam. When Bermuda grass is used it is necessary 
 to cover over the sand with a thin layer of soil or clay.- 
 
 During rainy seasons sodded slopes take care of themselves if the 
 grass be occasionally cut and the weeds be kept out, but in long 
 droughts the grass may die and it has, therefore, been customary 
 for a number of years to install hydrants in convenient places in all 
 batteries, the so-called hydrants consisting frequently of merely 
 a faucet with screw threads for attaching hose. Not only do these 
 hydrants serve for irrigation in the dry season but they also make it 
 possible to wet the earth thoroughly before the guns are fired in 
 target practice and thus to reduce the dust raised by the blast. 
 
 Camouflage or Concealment. 
 
 The custom of sodding the slopes of fortification^ originated many, 
 many years ago and at a time when the range of gun was so small as to 
 make an attempt at concealment unnecessary. Unfortunately, in 
 many places, such sodded slopes are quite conspicuous and invite 
 attention at once to the existence of a battery. 
 
 This is, -of course, to be avoided if possible, and some years ago 
 instructions were issued that trees should be planted between the 
 batteries and the shore with the idea that the trees would grow up 
 and would eventually conceal the location of the battery. Occa- 
 sionally, also, fine bushes, shrubs, and small trees were planted 
 along the outer slopes of the batteries. 
 
 These lines of trees, however, unless there are a good many in the 
 vicinity, invite attention to the fact that they are concealing some- 
 thing and presumably a battery. Where an entire post has trees in 
 front of it or where a post is situated in the vicinity of improved land, 
 
184 
 
 these trees may be all right but a better form of concealment is to 
 make the batteries appear from the sea as much like the surrounding 
 country as possible. 
 
 This was especially attempted in the experimental eniplacement. 
 constructed in 1915 at Fort Morgan. 
 
 This battery was located a half a mile or so from the main post. 
 It was placed right in the midst of a line of natural sand dunes. Some 
 of these sand dunes were bare, others were covered with irregular 
 splotches of vegetation, bushes, wild grass', small trees, etc. 
 
 In building the emplacement care was taken not to injure any of 
 the bushes or vegetation in the neighborhood. The emplacement 
 itself was given a generally rounded contour not unlike that of most 
 of the sand dunes. The sand used in the parapet was that taken 
 from the vicinity and appeared just like the sand exposed in the 
 dunes. In order not to make the area of bare sand around the 
 parapet too large and thus too conspicuous, a number of bushes w ere 
 transplanted from neighboring sand dunes and were made to grow 
 on the parapet so that in its general appearance from the sea there 
 was nothing to distinguish the emplacement from the sand dunes 
 in which it was placed. 
 
 Unfortunately, it was found that the strong winds had a tendency 
 to blow some of the sand away and some of it into the emplacement 
 and around the mechanism of the gun. It was evident, therefore, 
 that some method of preventing this was necessary and the method 
 attempted was to cover over the sand in the parapet with burlap 
 fastened to stakes driven at about 2-foot intervals. This burlap 
 was about the same color as the sand and, therefore, was not con- 
 spicuous but it was soon found that the strongest winds sucked some 
 of the sand through the burlap, and to prevent this, it was found 
 necessary to give the burlap a coating of grout composed of sand and 
 cement. 
 
 Unfortunately, such treatment can be considered as a temporary 
 expedient only, since walking on the burlap had a tendency to tear 
 it and in spite of its cement wash, it was of little durability. The 
 problem of permanently fixing sand under these conditions is, there- 
 fore, not yet solved. 
 
 The attempts made to conceal this battery were so successful that 
 the naval officers stated that at ranges of 5,000 yards they were 
 unable to distinguish the parapet from the neighboring sand dunes, 
 and this even after they had visited the battery and noticed its loca- 
 tion with relation to the surroundings. They therefore requested 
 that some mark be given them in order to show them at what they 
 were to shoot. This was done by building a large target 12 feet by 
 12 feet immediately in front of the gun and by attaching red streamers 
 to certain poles erected in the vicinity. 
 
185 
 
 The concealment just considered is concealment from horizontal 
 sight only. The modern development of air craft, however, requires 
 the concealment from observers in the air also. The earthen sur- 
 faces of the parapet are not so difficult to conceal since they can be 
 sodded or be otherwise made to resemble the surrounding landscape, 
 but it is exceedingly difficult to conceal the concrete surfaces, such as 
 the loading platform or the passage ways leading to it. These smooth 
 surfaces are, of course, necessary for the operation of the Ordnance 
 trucks and apparently can be concealed only by some form of manu- 
 factured camouflage or netting such as was generally used in France 
 for concealing field guns. Whether or not such a method is practi- 
 cable is a question yet to be worked out, but it is hoped that experi- 
 ments will soon be made. 
 
 Communications. 
 
 The word "communications" is ordinarily used in a military sense 
 to include the means which are provided for getting from one place 
 to another. As used in connection with emplacement construction, 
 it includes the corridors, galleries, passageways, stairways, ramps, 
 ladders, etc. 
 
 The communications provided in early emplacement construction 
 were, in general, not as convenient as might have been desired. They 
 were not numerous and, in general, the corridors and passageways 
 were too narrow. From time to time improvements have been made 
 as wiU be noted by comparing the successive designs of the emplace- 
 ments for the same sized guns, and more especially by comparing the 
 earliest designs (Plate XIII) with the latest mimeograph designs 
 issued by the Engineer Department (Plate XXII). 
 
 In the 1894 type of emplacements (see Plate XIII) the loading 
 platforms of the different guns of a battery were not connected at all 
 but were separate and independent. Consequently, there was no way 
 of going from one to the other except by descending the stairs and 
 ramps to the parade level and by climbing again up the ramp and 
 stairs to the loading platform of the other gun. This was incon- 
 venient not only as regards the movements of personnel but also as 
 regards the possible movement of ammunition. If ammunition had 
 been raised to the loading platform of one gun it could not be moved 
 to that of another gun except by this roundabout way. 
 
 Consequently, we find that in the 1898 type of emplacements 
 (Plates XV and XIX) the loading platforms of the different guns of 
 a battery are connected by a corridor which passes in the rear of the 
 traverse between the^uns. Not only did this permit the commanding 
 officer or members of the detachment to move readily from one load- 
 ing platform to another but it also made it possible to roll quickly 
 to one gun, ammunition from the loading platform of another. In 
 this way there is provided a reserve alternative method of getting 
 
186, 
 
 ammunition to any gun in case its own ammunition hoist should 
 become, disabled or temporarily out of order. 
 
 Not only were such corridors provided in new emplacements built 
 during and after the Spanish War but, about 1903 to 1905, similar 
 corridors were added to the older emplacements which had been 
 built without connecting corridors between the loading platforms. 
 
 Such a corridor passes in rear of the traverse, and in front of it is 
 the vertical concrete rear wall of the traverse, so that the corridor is 
 quite well protected from the enemy's fire. The wall in the front of 
 the corridor, therefore, became a very convenient location for the 
 outlet or delivery table of the shell hoist. Incidentally, also, the wall 
 immediately in front of this corridor was found a very convenient 
 place for the Ordnance Department motor generator room, for tele- 
 phone booths, for emergency powder recesses, and in 1908 and later 
 designs, for the plotting rooms. 
 
 At first this corridor connecting the loading platforms was called 
 by several different names, but after it became the usual location for 
 the delivery table of the ammunition hoist, it became customary to 
 call it the " truck corridor, ' ' because it was principally used for .rolling 
 the ammunition trucks from the ammunition hoist to the loading 
 platform. In the early drawings, the truck corridors are shown as 
 without roofs, but the desirability of having at least the delivery 
 tables of the hoists protected from the weather soon became evident 
 and small corrugated iron roofs were placed over the tables in many 
 of the emplacements. In the 1898 ajid 1900 type plans (Plates XV, 
 XVI, and XIX), splinter-proof roofs were placed over some of the 
 corridors but not over others, and in the 1903 type plans (Plate 
 XVII and XX) all of the corridors were shown as completely covered. , 
 This has been the rule since that time. 
 
 In the Panama batteries, since the ammunition is kept on the same 
 level as the loading platform, ammunition hoists are not necessary, so 
 the truck corridors pass directly from the loading platforms to the 
 service ends of the shell rooms of the magazines. Where flank fire is 
 not to be feared (see Plate XXIII), the truck corridor opens on the 
 side of the loading platform close up under the front parapet, and 
 thus passes into the magazine space approximately perpendicularly 
 to the capital of the emplacement. The shell rooms and, magazines 
 therefore run fore and aft with respect to the capital of the battery. 
 Where there are two emplacements of this type united structurally 
 into a single battery, the two truck corridors are frequently connected 
 so that a passage from one emplacement to the other is provided. 
 
 Where, however, fla,nk fire is to be feared the truck corridor runs 
 backward from the rear of the loading platform around to the flank 
 and enters the magazine from the rear in a fore and aft direction, 
 approximately paraUel to the capital of the emplacement. (See Plate 
 
» 187 
 
 XXIV.) In this case the service ends of the magazines and shell 
 rooms of course open on this truck corridor, and, consequently, the 
 length of the magazines and shell rooms is approximately perpen- 
 dicular to the capital. 
 
 Where rear fire also is to be expected the rear of the magazine is 
 carefully covered and the rear corridor or passageway leaves the 
 loading platform through a parados. Consequently the whole of such 
 a passageway is under cover. In all such cases the attempt was made 
 to provide at least two passageways between the magazine and the 
 loading platform, so that in case one was destroyed the other might 
 be used. 
 
 In the earlier two-story emplacements the rooms on the lower floor 
 usually opened directly upon a pavement or sidewalk. Subse- 
 quently, in connection with modernizing, the loading platforms were 
 widened and extended over the pavements, being supported at the rear 
 by columns. The pavements were thus converted into covered lower 
 corridors communicating with the rooms on the lower floor. This 
 arrangement having been found very convenient, we find in the 1903 
 type of emplacement (Plates XVII and XX) a similar lower corridor 
 passing in rear of the rooms under the loading platform, and similar 
 arrangements will be noted on the 1908 type (Plate XXII) connecting 
 the hoist rooms of the different emplacements. 
 
 In the 1894 type of emplacements (see Plate XIII), it will be noted 
 that there is an attempt at a commimication between the magazines 
 and the crane level. This conmiunication was useful only for passing 
 projectiles because the difference in elevation between the floors of the 
 two levels was too great for persons to step up and no stairway was 
 provided. In a few cases temporary stairways or ladders were sub- 
 sequently added. These improvised stairways made it possible to go 
 quickly from the magazine to the crane level whence it was possible, 
 by means of the stairways already built, to proceed to the loading 
 platforms. This method of commimication proving quite useful, we 
 find in aU subsequent types of two-story emplacements a direct com- 
 munication by means of a stairway between the magazine space and 
 the loading platform. This communication usually opened on the 
 wall in front of the loading platform, sometimes on the loading plat- 
 form level and sometimes on the working platform level. (See Plates 
 XIV to XX.) 
 
 In the 1903 type of 6-inch disappearing emplacements (Plate XI), 
 a passageway intended for powder service was designed to pass in front 
 of the magazines from the front corner of one loading platform to the 
 front corner of the other. This interior and thoroughly protected 
 passageway proved so useful that a similar passageway was provided 
 in the 1908 type of 14-inch emplacement (Plate XXII), passing on 
 the lower story completely in front of the magazine space, from one 
 
188 , 
 
 side of the magazine traverse to the other, and comnmnicating by- 
 stairways with the working platforms of the two guns and through 
 the long store rooms with the rear corridors of the lower story. 
 
 For access to the loading platforms, all of the oMer emplacement 
 designs show stairways passing from the lower level up to the loading 
 platform.. In the 1894 type these stairways were quite inconveni- 
 ently arranged. (See Plate XIII.) Improvements were made in 
 later emplacement designs, but the stairways, as a rule, were located 
 directly in rear of the center of the loading platform. (Plates XVI, 
 XVII, and XX.) As has been stated in. the preceding chapter, this 
 central position has been shown to be an inconvenient location for the 
 stairways, so in the 1908 type (Plate XXII) it was abandoned and 
 two stairways, one on either flank of the loading platform, were used 
 instead. 
 
 It is frequently necessary for an officer or some member of the^ 
 detachment to go from the loading platform to the top of the parapet. 
 Some of the earUer mimeographs (Plate XVI) provided ladders for 
 tliis purpose, and most of the earlier emplacements constructed had 
 these ladders. Such ladders were usually inconvenient, and in later 
 batteries stairways are provided instead. 
 
 The return to the one-story type of battery, as in the Panama 
 batteries, has, of course, done away with the necessity for the stair- 
 ways formerly connecting the two stories of an emplacement, but it 
 has thrown the battery conunander's station, crow's nest, etc., very 
 high in the air, and it has required the construction of special stairways 
 leading to them. The method of doing this will be noted in connec- 
 tion with the designs of the Panama batteries. (See Plates XXIII to 
 XXVI.) 
 
 In the Panama batteries, where the earth side slopes have super- 
 seded the concrete side walls, stairways leading from the loading plat- 
 forms to the top of the parapet are not as necessary as they formerly 
 were, since, when communication this character is necessary, a person 
 can run up the earth slope. If this be considered undesii-able, a con- 
 crete stairway can be built close up to the parapet wall. 
 
 Stairways, when needed, may be made of wood, metal, or concrete. 
 Within the interior of emplacements, concrete stairs are the most 
 convenient and have been generally used. The stairways on the 
 exterior of an emplacement may be built of metal or of concrete. It 
 would appear that, in general, metal stairways have been used, the 
 treads being made corrugated or otherwise roughened, so as to avoid 
 trouble from sleet. In the more recent emplacements in the tropics, 
 however, all exterior stairways have been made of concrete, a popular 
 type of construction being reinforced concrete in the form of canti- 
 levers projecting from the rear faces of the batteries. 
 
189 
 
 In the old types of fortifications constrilcted just prior to the Civil 
 War and, in fact, for many centuries before that, communication 
 between the different levels of a fortification was usually provided by 
 tamps, up which the gUns of the day, which were usually mounted on 
 wheels, might be rolled. In the more modern fortifications, ramps 
 are very seldom employed. However, in the 1894 type of 10-inch 
 emplacement (Plate XIII) they are used for communication between 
 the crane and the parade levels, while in the plans shown oii Plates 
 VIll and XVI, ramps are provided on the flanks of the battery for 
 communication between the two stories. Very gentle ramps have 
 also been sometimes used in modern batteries for communicalioh 
 bejtween the loading platforms where, on account of the peculiar cir- 
 cuinstances of the site, the different guns were emplaced nearly, but 
 not quite, on the same level. Such cases, however, were unusual and 
 can not be considered as standard. 
 
 Rooms, Magazines, etc. 
 
 In the fortifications built during and before the Civil War it was 
 customary to build the main magazine in some secluded and thor- 
 oughly protected place, small service magazines, containing enough 
 power for single actions, being usually installed in the traverses 
 between the guns. 
 
 In designing the early modern emplacements there was too great 
 a tendency to economy in magazine space, the magazines being small 
 and somewhat inconveniently arranged, as has been shown in dis- 
 cussing the various types of emplacements. Not only were the maga- 
 zines small, but in order to give them thorough protection they were 
 hidden away in the body of concrete where they could receive no 
 natural fight and where ventilation was difficult. In hardly any other 
 feature of gun emplacements has there been as much improvement 
 from the early to the present types of emplacement, as in the char- 
 acter of the magazines and storerooms, in the amount of space allowed 
 for them, in their convenience in location, in their ventilation and 
 protection from dampness, and in the arrangements made for furnish- 
 ing both natural and artificial fight. This improvement is well shown 
 by a comparative study of the successive types of emplacements. 
 
 The magazine taken as a whole consists of the powder magazines 
 and of the shell rooms. The powder magazine, of course, requires the 
 maximum aruount of protection possible, the shell rooms not neces- 
 sarily quite so much. Consequently, in a number of emplacements 
 the sides of galleries and corridors and the space under the loading 
 platform have been utifized for storing shells, although very fre- 
 quently this has resulted in the serving of such shells being somewhat 
 inconvenient. 
 
190 
 
 In the more modern batteries, therefore, the shell rooms have been 
 specially designed for this purpose and, except under the improbable 
 condition of the supply of projectiles being much greater than can be 
 stored in the shell room designed for them, it should not be necessary 
 to utilize for the storage of projectiles any space not specially designed 
 for this purpose. 
 
 In order to provide sufficient head room for the propef operation of 
 the trolleys, the ceiling height of shell rooms where .trolleys are to be 
 used should never be less than 8 feet in 12-inch or smaller emplace- 
 ments. For 14-inch emplacements, the Panama standard was 8 feet 
 6 inches and for 16-inch emplacements 9 feet. The standard height 
 of powder rooms has been 8 feet, but if the single cartridge charge is 
 to be adopted as a standard the ceiling height of 16-inch magazine 
 must be made at least 9 feet 6 inches. 
 
 The ceiling height in 6-inch and smaller emplacements may, if 
 jiecessary, be reduced to 7 feet 6 inches, but this is not desirable 
 unless absolutely essential. 
 
 The early emplacements provided merely powder rooms and shell 
 rooms. A little later storerooms for general pm-pose were provided, 
 also power rooms. Still later it became necessary, in the larger 
 emplacements, to provide motor generator rooms for the special . 
 apparatus provided by the Ordnance Department for the operation 
 of the electrical elevating and traversing gears installed on the larger 
 gun carriages. In some of the emplacements also, specially designed 
 rooms were provided for taking care of oils and waste provided by the 
 Ordnance Department for the preservation of the gun carriages. 
 Some of the older emplacements provided what were known as 
 "relocator" rooms for use in connection with fire control. In the 
 more modern emplacements this room is known as the "plotting 
 room" and will be further discussed in the chapter on fire control. 
 
 Latrines. 
 
 Seacoast batteries, as a rule, are located at some distance from 
 the barracks in regular use and sanitary reasons require that latrines 
 be provided either in the batteries or in their immediate vicinity. 
 In the early constructions outside latrines were always provided, 
 usually of temporary frame construction. These were frequently 
 unsightly and in many cases soon became unsanitary. Consequently 
 the custom later grew up of providing latrines in all new emplace- 
 ments, certainly in all larger ones and usually in all smaller ones 
 where they were not located in close proximity to large emplace- 
 ments with sufficient latrine accommodation. It would appear to 
 be needless to say that during the wintertime all plumbing is subject 
 to damage by freezing unless the buildings or rooms be kept heated. 
 This heating is not always possible in emplacements and, conse- 
 
191 
 
 quently, resort must be had at such times to special forms of frost- 
 proof plumbing of which there are many varieties on market. 
 
 In addition to the latrines it is now customary to install in emplace- 
 ments washbasins for the men and separate toilet facilities for the 
 officers. In the Tropics, at least in the Panama batteries, shower 
 baths also were provided. 
 
 In a few locations in the Panama fortifications, especially on the 
 islands at the Pacific end of the canal, there was a question as to a 
 possible insufficiency in the fresh-water supply. Arrangements were 
 therefore made for the installation of two water-distributing systems, 
 one for salt water and one for fresh water. Water for the showers and 
 all flushing was, of course, salt, the fresh water being retained for use 
 at the washbasins, for irrigating the slopes, and for washing out the 
 batteries at certain places where it was thought that salt water might 
 be injurious. 
 
 In this connection it should be noted that the sewers from the 
 latrines should be kept careluUy separate from the drains for removing 
 rainwater or seep water only, this being done not only within the limits 
 of the emplacements but also outside. 
 
 Quarters and Dormitories. 
 
 The question as to whether or not there should be provided in 
 seacoast emplacements dormitories, kitchens, etc., for the garrison is 
 one which has been much discussed. In connection with the design 
 of the Panama batteries and especially the more isolated of these, 
 sketch designs were presented to the Chief of Coast Artillery, showing 
 how dormitories for the Coast Artillery detachment could be pro- 
 vided. After thinking over this matter he informed the Engineer 
 Department that they would not be needed and that he considered it 
 preferable to camp the detachments in the immediate neighborhood 
 of the battery. In a number of the 12-inch long-range batteries 
 constructed in 1918 the rear corridor of the battery has been fitted 
 so it may be closed in and used as a dormitory, and in other 
 cases special dormitories have been provided in a parados where one 
 had to be built. In the turret batteries constructed on El Fraile 
 Island in Manila Bay the Engineer Department has provided dormi- 
 tories and all other provisions for the care and comfort of both the 
 conamissioned and enlisted personnel. 
 
 If it should be decided that the manning detail of the battery should 
 in time of peace be quartered in the battery it is not improbable that 
 barracks for the detachment could be constructed just about as 
 cheaply in connection with the battery as elsewhere, but until the 
 Artillery policy of this country changes it may be taken as extremely 
 probable that in time of peace the troops will be housed and will live 
 away from the batteries and under somewhat more comfortable con- 
 ditions than could be provided in barracks intended for use mainly 
 
192 
 
 in time of war. Consequently it would appear that the provisiob of 
 barracks or dormitories at the battfefieS for use in time of war only 
 would be an expense whi6h could hardly be justified, for in general 
 there will be space enough in some of the spare rooms of the battery 
 or its vicinity for at l6ast some of the detachment on duty to sleep 
 during war time. 
 
 ' The question Ss to whethet in any particular case dormitory space 
 should be provided in any battery is one that is to be determined by 
 local conditions especially applicable to the case. 
 Keys and Locks. 
 
 ' The multiplicity of doors in emplacements, all of which must be 
 provided with locks, naturally led to a complication in the question 
 of keys. At first nearly every door had a different key, and this 
 required of course that anyone desiring to enter or inspect all portions 
 of a battery should take a large bunch of keys. The next step was 
 to inake the locks in a system with a master key, so that one key only 
 would have to be carried. This was found to be unsatisfactory and 
 a duplication of locks was next suggested so that one key might 
 open all the locks in the battery. It was found best, however, to 
 make a distinction between the locks of magazines and the locks of 
 other rooms. Consequently it was decided to have all the locks, of 
 all the doors to the magazines of a battery duplicates of one another 
 and therefore opened by the same key. Similarly the locks to all 
 the other rooms were to be duplicates of one another but different 
 from the magazine locks. This made it necessary to carry but two 
 keys to get into all the rooms and magazines of a batter}'. 
 
 Additional complications were introduced later, however, when 
 range stations were built for the battery. The range detachment 
 was usually a more or less separate detachment from the remainder 
 of the company assigned to the battery, and the responsibility for 
 the fire-control property was placed on a different man, so that it 
 was thought by some officers better to have a new set of locks for the 
 range stations. Some battery commanders, however, prefer to have 
 on the range stations a lock similar to the general lock of the battery. 
 
 Another disputed question connected with the subject of keys is 
 what kind of locks should be used on the power room of a battery. 
 The battery commander and his mechanic must, of course, have 
 access to the power room in order to turn on and off the power for 
 lights and motors and, on the other hand, the care of this power room 
 rests with the Artillery engineer. If the same lock is put on the 
 power room as on the rest of the battery, it will permit the Artillery 
 engineer and his subordinates to enter any part of the battery. This 
 was not thought to be advisable, so that in some cases it has been 
 considered best to put a different lock on the power room. 
 
193 
 
 Another important question was the number of keys to be furnished 
 for each lock. It is, of course, important that too many keys should 
 mot be furnished, for if this be done it will be difficult to keep track 
 of all of them and some may fall into the hands of improper persons. 
 
 In the older system, where each door had a special lock, two keys 
 were usually furnished, one for the battery mechanic and the other 
 ior the use of the battery commander. When the keys were dupli- 
 cated the same custom continued, two keys for each set of locks being 
 "furnished. However, compUcations soon grew up in this matter 
 by the necessity in some cases of furnishing additional keys to range 
 ■detachments. The question of the keys to the power rooms also 
 gave trouble. In most posts, also, the post commander wanted to 
 have a set of keys reserved for his own use and kept in the hands of 
 the post adjutant, so the number of keys which should be furnished 
 ior different locks has not remained settled. (See mimeograph No. 64 
 and its supplements.) 
 
 There was a question also as to whether the Engineer oflElcer, at 
 the time of the formal transfer of a new battery, should turn over 
 keys to the battery commander or to the post commander. The 
 proper course is, the author believes, for him to turn over the full 
 number of keys to the post commander, and leave with him the 
 responsibility for their proper distribution. 
 
 Another debated question was the kind of lock to be used, whether 
 it should be a mortise lock or a padlock. Many officers at first 
 seemed to favor the mortise lock, as they are undoubtedly the safest. 
 
 Personally, however, the writer favors the padlock for a number of 
 reasons. It has been found that in some doors the blast effect of 
 the discharge of a heavy gun on mortise locks is to bend the bolts 
 and make the lock difficult or impossible to open. If padlocks are 
 properly installed, no such action is possible. Furthermore, the 
 use to which any particular room may be put changes from time to 
 time, and the system of keys desired by the battery commander is 
 also subject to change. Padlocks lend themselves readily to such 
 changes; mortise locks do not. 
 
 Another and perhaps more important reason still for preferring 
 padlocks is that not infrequently an officer decides that he would 
 like to inspect a battery or a room of a battery, when he does not 
 have a key, or when he finds that it has been lost or has been mis- 
 placed. Experience shows that in such a case the officer is going to 
 get into the battery, and in doing so a padlock can be forced without 
 injuring anything else except the lock itself. A mortise lock can 
 usually be violated only with -severe injury to the door, and the cost 
 of such repairs is much greater than the mere replacing of a padlock. 
 173341—20 13 
 
194 
 
 • 
 
 If padlocks are used, each padlock should always be attached by a. 
 chain, so that when not in iise it will hang near its proper place and 
 can not be inislaid. 
 
 Another question in connection with keys has frequently been 
 brought up by the loss of a key. If it has been entirely lost no trouble 
 can follow, but if it has been stolen or has fallen into the hands of an 
 improper person he would be able to go where he should not. Some 
 Artillery officers, therefore, as soon as a key has been lost, have asked, 
 not for a new key, but that a new lock be installed. When each door 
 had a particular lock, the replacement of this single lock was a minor 
 matter, but where the loss of a key means that a whole set of locks 
 must be replaced, the expense is not small, as will be readily under- 
 stood when it is stated that in one of the batteries at Fort Monroe, 
 75 locks of one kind (all duplicates) were installed. 
 
 In selecting the particular kind of locks to be used in emplacements,. 
 it must be remembered that the locks are to be installed in locations 
 where moisture is certain to be present, at least occasionally. Con- 
 sequently, locks made of iron or steel, or having iron or steel parts, 
 should not be used: Locks made of solid brass are best, but bronze 
 locks are also permissible. However, in purchasing bronze locks, 
 the district officer must be certain that the locks to be purchased are 
 really made of solid bronze and are not really steel locks with merely 
 a bronze finish. Bronze finished steel locks are on the market and 
 are frequently known by the name of "bronze," but when such 
 locks are exposed to ihoisture the dampness soon finds its way through 
 the bronze finish, causes the steel below to rust, and the locks not only 
 soon become unsightly, but frequently get out of order. 
 
 Where two or more different systems of locks are installed in an 
 emplacement, the different systems must not be merely different 
 combinations of the same variety of lock but must differ from each 
 other as much as possible so that a mere glance at any lock will show 
 instantly to which system it belongs. Furthermore, the keys for the 
 different systems should also vary greatly and must differ so much 
 that there can be no mistaking which key belongs to any lock. 
 
 Before being turned over to the Artillery, each and every key 
 transferred should have attached to it a metal tag, stamped so as to 
 indicate exactly to which battery and to which particular system the 
 key pertains; such as "Parrott, General," "Eustis, Magazine," or 
 "Church, Fire Control." It is also convenient to add to the tag, 
 in addition to the names of the battery and systSmi, a number, and 
 this same number should be stamped not only on the key tag but 
 also on all the locks belonging to the system. For convenience, each 
 of the systems of locks at any fort should have a separate and dis- 
 tinguishing number and the Engineer officer should have in his 
 office a record of these numbers for use in furnishing additional locks 
 or keys. 
 
193 
 
 The question of the system of locks to be installed and of the number 
 of keys of each kind to be furnished is evidently one of administration 
 proper, and all questions of this character should be decided by the 
 Artillery authorities; in any special case by the post commander, and 
 in cases of general policy by the chief of coast artillery upon the 
 recommendation of the Coast Artillery Board. 
 
 The question of keys for batteries and other structures has lain 
 dormant since the United States entered into the World War, largely 
 because all the batteries and other structures have been in commis- 
 sion, the troops being kept habitually close to the batteries and 
 sentinels being always on duty. However, with, the return to peace 
 conditions, it is to be expected that the question of keys will be 
 again raised, and consequently the above historical data has been 
 inserted, so that if any Engineer officers should be called upon to 
 act in connection with the question of keys, they may know some- 
 thing of the history of the case. 
 
 Speaking Tubes and Voice Tubes. 
 
 Speaking tubes in emplacements are, of course, designed to allow 
 oral communication between different portions of an emplacement. 
 Occasionally, speaking tubes have been used in connection with fire 
 control, but, in general, fire-control communication has been by 
 telephone rather than by speaking tubes, and speaking tubes have 
 been used for general purposes only and not for transmitting fire- 
 control data. 
 
 In some of the very earliest emplacements speaking tubes were 
 installed for talking from one loading platform to another or from a 
 loading platform to magazines, etc. In the early batteries, however, 
 the tubes, as a rule, were small, 1 inch and occasionally smaller pipe 
 being used. These pipes were inserted directly in the concrete 
 without any attempt being made to surroimd them by a sound in- 
 sulator. Owing to the small size of the tubes, they were not effective 
 at any great distance, and owing to the way in which they were put 
 in the concrete they would gather up the rumbling due to the move- 
 ment of trucks along the corridors or over the loading platform, or 
 of the movement of the trolleys along the trolley rails. Consequently, 
 whenever the battery was in use, there came from these speaking 
 tubes such a roaring or rumbling as to make conversation through 
 them extremely difficult. 
 
 It being found that the speaking tubes which had been installed 
 were practically useless, their installation in emplacement construc- 
 tion fell, for a number of years, into disfavor. 
 
 However, some experimenting on this line was done, and it was 
 shown by these experiments that by increasing the size of the tube, 
 eliminating all sharp corners, and substituting easy bends instead, 
 the speaking tubes could be made quite useful. Furthermore, it was 
 
196 
 
 found that the trouble due to rumbling could be largely eliminated 
 by suspending the speaking tubes from the ceilings of rooms, galleries, 
 air spaces, etc., and by insuring that when they passed through walls 
 they did not actually touch the concrete of the wall. 
 
 Speaking-tube systems installed according to this new practice 
 have been placed in the recent batteries constructed in Hawaii, 
 Panama, and on the Pacific Coast, and are understood to work quite 
 satisfactorily. 
 
 Not only have tubes been used for communication between two 
 places, but occasionally a tube has been split into two branches, one 
 running to a plotting room and the other to the battery commander's 
 station above it, so that a person at the other end of the tube may 
 talk either to the plotting room or to the battery commander's 
 station or possibly to both at the same time. 
 
 To make such an arrangement successful, however, a carefully 
 designed manifold must be placed at the points where the tube 
 branches. 
 
 A "voice tube" is really a large speaking tube, but the term at 
 present is restricted to the large pipe connecting a battery com- 
 mander's station and the plotting room which, in modern construc- 
 tion, is always placed nearly vertically beneath the battery com- 
 mander's station. The standard voice tube now used is an iron pipe 
 8 inches in diameter. Its upper end is about 4 feet above thel floor 
 of the battery commander's station and usually about 2 feet from one 
 of its side walls. Its lower end projects a few inches below the ceiling 
 of the plotting room and is usually located about 2 feet from a side 
 or end wall of this room. 
 
 By means of this tube the battery commander in the battery com- 
 mander's station, or his representative, can look doAvn into the 
 plotting room, can talk easily and deliberately to a member of the 
 plotting room detachment, and can see his face also. 
 
 To prevent rain or trash dropping through the voice tube into the 
 plotting room a removable cover is attached to its upper end. 
 
 In all cases where voice tubes have so far been installed they have 
 been placed vertically or at least have been only very slightly in- 
 clined to the vertical and their lengths have been comparatively 
 short. 
 
 As an illustration of the speaking-tube system installed in modem 
 batteries, I quote the part relating to speaking tubes from the report 
 of the designing engineer, submitting to the chief of engineers the 
 design of some of the Panama 14-inch batteries: 
 
 For intercommunication between the different parts of each battery and between 
 the two batteries a comprehensive system of speaking tubes has been provided. 
 Speaking tubes with extensions to the battery commander's station connect each 
 plotting room with every other plottiag room and battery commander's station, so 
 that a man in any battery commander's station or plotting room can talk to a man in 
 any other battery commander's station or plotting room. 
 
197 
 
 The plotting rooms are connected by tubes leading through the information tunnel 
 to terminals located on the left side of the front of each of the working platforms, 
 5 feet above the level of these platforms and at the foot of the stairs connecting the 
 working with the loading platforms. It is understood that from these terminals a 
 flexible extension is to lead to a headpiece carried by a man on the working platform 
 of the gun carriage; but as this arrangement of flexible headgear appears to be some- 
 what awkward, an alternative has been provided by which these speaking tubes, instead 
 of leading to the terminal just mentioned, may be carried into the gun well and to a 
 point in the gun well near the Ordnance Department terminal box, and the Ordnance 
 Department is now experimenting as to the possibility of further extending this tube 
 by flexible connections to tubes on the gim carriage. 
 
 At the plotting-room ends of the tubes mentioned in the preceding paragraph 
 exte^ons are had to the battery commander's station, and the connections are such 
 *hat each gun is connected with both of the plotting rooms and battery commander's 
 ^tations of its battery, so that the gun may be controlled from either of the battery 
 commander's stations or plotting rooms of the battery to which it pertains. 
 
 In the truck corridors near the magazine and shell rooms are located the terminals 
 of other speaking tubes, each magazine being connected with both of the plotting 
 rooms and the battery commander's stations of the battery to which it pertains, so 
 that the ammunition service of either emplacement may be controlled from either 
 of the battery commander's stations or plotting rooms of its battery. 
 
 Other speaking tubes connect each plotting room with the power room. 
 
 AU speaking tubes are routed as far as possible in the open air, except when they 
 pass through walls, where they should be covered with a, sound insulator. The 
 standard size of speaking tube is 3 inches, except for branches, where 2-inch tubes 
 are sufficient. 
 
 In the installation of speaking tubes in emplacements one matter 
 that should not be overlooked is their drainage. In the earlier em- 
 placements, when it was customary to place the speaking tubes 
 right in the mass of concrete, it was not unusual for water to find 
 its way into the speaking tubes through the joints of the pipes or 
 in other ways. This water would, of course, tend to accumulate^ in 
 low places and occasionally would completely fill some short lengths 
 of the pipes forming the speaking tube, and would thus absolutely 
 stop the passage of the sound waves. 
 
 With the larger pipes now used and the present method of sus- 
 pending them in the air the accumulation of water in the tubes is 
 quite rare, but, nevertheless, it is still possible that water may find 
 its way into the tubes, possibly' through their outlets or terminals. 
 Consequently, it is well to provide for the drainage of the pipes by 
 boring small drip holes at low places. Where a drip hole is placed 
 in an air passage or at some other location where the dripping water 
 can do no harm the hole may be left open. At other places it is 
 well to insert in the hole a pet cock which can be opened for occasional 
 drainage, habitually, however, being kept closed. 
 
 The standard size of the pipes to be used for speaking tubes is now 
 3-inch. Where, in the neighborhood of plotting rooms and battery 
 commander's stations, the main tube is divided into two branches, 
 2-rnch pipes are sufficient. 
 
Chaftee \1II. 
 MORTAR BATTERIES. 
 
 Mortars date back to almost the very beginning of the use of gun- 
 powder, a mortar throwing stones high into the air by the explosive 
 force of gunpowder being the natural successor of the older mechani- 
 cally biiilt engines which threw large stones and other missiles over 
 the walls of fortified places. Consequently at the siege of Constan- 
 tinople, in the middle of the fifteenth century, we hear of the use of 
 large mortars throwing stone balls weighing from 700 to 1,000 
 poimds. 
 
 For some time after the siege of Constantinople the development 
 of mortars seems to have almost ceased, attention being given rather 
 to the improvement of direct-fire gims which were able to make 
 breaches in masonry walls than to mortars whose function was to 
 throw missiles over the walls. 
 
 A century or two later, however, the use of mortars again became 
 quite general in connection with the sieges of fortified places, the 
 mortars being used to throw explosive projectiles over the walls and 
 into the interior of the besieged places for the purpose of doing 
 material damage and, incidentally, of affecting the morale of the 
 garrison. The use of mortars, however, seems to have been restricted 
 to sieges, and their use against ships seems not to have been attempted. 
 
 The ships of that day were, of course, buUt entirely of wood, and 
 their wooden sides could be easily penetrated by the direct fire of 
 guns. It was, therefore, not necessary or desirable, in firing against 
 ships, to resort to high angle fire falling upon the decks, especially 
 since the .fire of mortars was much more erratic than that of direct- 
 fire guns using a comparatively flat trajectory. The chances of 
 getting a hit with a mortar were, therefore, much less than with a 
 direct-fire gun. 
 
 In this connection it is interesting to note that as early as 1809 the 
 construction of a mortar battery at Bedloe Island, New York 
 Harbor, was proposed as a means of preventing an enemy from 
 anchoring in the upper part of New York Bay. Although as far 
 as is known this was a imique example in the United States of the 
 emplacement of mortars primarily for use against ships, yet it is to 
 be assumed that there must have been a number of cases where the 
 same thing was done abroad. 
 
 (199) 
 
200 
 
 At about the time of the American Civil War an important change^ 
 was made in naval architecture. Metal armor came into use for 
 strengthening the sides of ships, and actual experience with the 
 monitors, used during the Civil War showed that the sides of ships 
 could be made almost impenetrable. It then occurred to certain 
 engineers that the decks of vessels were as vulnerable as they had 
 ever been, and that, therefore, it would be well to resort to mortar 
 fire for dropping projectiles upon these unarmored decks. We thus 
 find, in 1869, that the Board of Engineers submitted a report irt 
 which they advocate the introduction into our seacoast defenses of 
 large caliber mortars. The following is quoted from this report : 
 
 To prevent the occupation, as an anchorage, of a roadstead, there ia nothing more- 
 effectual than the mortar. It is believed, though never yet extensively introduced 
 for that purpose, that it may be made an efficient agent of defense against ironclada 
 of the channels of approach to our cities and ports; and if so, its emplacement involves 
 none of the embarrassing questions of iron construction. It is well known that there- 
 are no projectiles of which sailors have greater dread than those from mortars, and 
 that the invulnerability of the sides of an armored vessel can be but very imperfectly 
 extended to her deck. On the other hand, the difficulty of hitting by vertical fire- 
 an object of as small an area as the deck of a vessel is conceded. But when it is under- 
 stood that considerable accuracy of mortar fire can be attained against stationary 
 objects, such as vessels in position or arrested temporarily by obstructions, at distances- 
 not exceeding the width of most ship channels, and that the increased effect of a 
 successful shot will in some degree compensate for inferior accuracy, as compared 
 with the gun, the mortar will readily be accepted as one of the most efficient means 
 of defense against the modern means of attack. 
 
 At about this time Congress was making small appropriations for 
 battery construction, and from the appropriations made during the 
 years 1870 and 1871, allotments were made for the construction of 
 three seacoast mortar batteries, one in Boston Harbor, one in the 
 Delaware Eiver, and one at San Francisco. 
 
 The mortar batteries then constructed bore but little resemblance 
 to the present typical mortar batteries, in fact they consisted merely 
 of flat platforms built behind parapets some 9 to 12 feet high. For 
 the large 13-inch mortars, these mortar platforms were 15 feet square. 
 They were composed of two cross layers of 12 by 12 inch timbers 
 placed in contact, and the upper layer of timber was covered with a 
 wrought iron plate. In general, these mortar batteries had no parados- 
 and no side protection except the usual earthen traverses in which, 
 were placed the service magazines. 
 
 The Boston mortar battery, however, was constructed on an island,, 
 in a position such that it might become subject to the enemy's fire 
 from several directions. Side and rear earth protections were, there- 
 fore, considered necessary for this battery, and as constructed it 
 consisted essentially of three pits 16 feet deep and having earthen 
 side slopes. The pits were about 40 by 50 feet on the bottom and. 
 each contained four mortars. 
 
201 
 
 This battery was, in its general characteristics, a sort of anticipation 
 of the type of mortar battery which later became the standard, but 
 since it was the only battery of the kind constructed at the time it 
 was evidently not considered as a standard type but as one suited 
 to very special local conditions. 
 
 Shortly after the nortar batteries mentioned were completed, 
 battery construction practically ceased in this country for nearly 
 20 years, not being resumed until about 1890. During this period 
 the suitability of mortars for seacoast use was qmte actively discussed. 
 
 Although it was admitted by all that mortar projectiles falling 
 upon the deck of a vessel would undoubtedly penetrate and do great 
 damage, their use was opposed by many on account of the inherent 
 inaccuracy of mortar fire. To overcome this defect Gen. Henry L. 
 Abbot, Corps of Engineers, who, during the Gvil War, had com- 
 manded a mortar battery at the siege of Petersburg, proposed to 
 group a number of mortars together and to fire them at the same time 
 and with their axes parallel thus increasing the chances of making a 
 hit. In other words, he proposed to adopt, in using mortars against 
 ships, the same method used by bird hunters, who, instead of loading 
 their guns with a single bullet, make use of a charge containing many 
 small shot. 
 
 To illustrate his idea. Gen. Abbot, in the early eighties, constructed 
 at WiUets Point (now Fort Totten) a mortar battery consisting of four 
 deep mortar pits placed with their centers on the corner of a rectangle, 
 the pits being separated from one another by two traverses crossing 
 each other at right angles. In each pit were placed four mortars 
 and in the traverses were galleries for intercommunication, maga2dnes, 
 storerooms, etc. This was the forerunner of the seacoast mortar 
 battery. 
 
 About this time the accuracy of mortar fire was much increased by 
 substituting for the old stubby smooth-bore mortars a short-rifled 
 howitzer. This made them much more useful for seacoast work 
 and in 1888 the Board of Engineers submitted a report from which 
 I quote as follows: 
 
 The increasing importance of vertical fire in coast defense resulting from modem 
 improvements in constructing, mounting, and serving mortars; the large number 
 likely to be introduced into our seacoast defenses as soon as work is resimied, and the 
 fact that local peculiarities of site exercise comparatively little influence upon the 
 plan of a mortar battery, have led the board to consider the details of a typical con- 
 etruction and theoretical discussion of the same by Gen. H. L. Abbot, which, so far as 
 practicable, shall unite desirable and exclude objectionable features. The result is 
 presented by accompanying drawing No. 1, designed for a site exposed to an all-round 
 fire and which requires no explanation except as to its general principles. 
 
 Although rifling mortars, and mounting them upon carriages which admit of ready 
 handliag and pointing, has done much to increase precision of vertical fire, the chief 
 reason which has brought the weapon forward so prominently of late is that, while the 
 attack which they deliver upon the deck is one of the most dangerous that a ship can 
 
202 
 
 receive, large numbers of them can be mounted at very moderate cost in such a manner 
 that they can hardly be injured even by the most powerful naval guns of the day. 
 The chief objection to them has been their lack of precision of fire as compared with 
 that of guns of similar calibers. 
 
 But in addition to improving the ordnance itself, much may be done to increase 
 precision of fire by constructing the battery upon proper principles. Many mortars 
 should be mounted in compact groups, each group constituting, so to speak, a unit to 
 be controlled and pointed as a single piece by a single officer. Under such conditions, 
 fire against a nearly stationary enemy will be far more effective than is generally be- 
 lieved. To secure the greatest concentration of the mortars of each group without 
 mutual interference, and without encroaching upon the space needful for bombproof 
 cover, should be the governing idea in designing a battery for vertical fire. 
 
 Pour mortars may be served in a single pit by providing a bombproof shelter for the 
 cannoneers from which they can fire the mortars simultaneously by electricity. 
 
 Four such pits, containing a total of 16 mortars, will form a suitable group for the 
 command of a captain of artillery. It remains to arrange the pits to fulfill the funda- 
 mental condition that all the mortars shall be fired with identical elevations, azimuths, 
 and charges. On the one hand, the lateral and longitudinal separation of the 
 pits must be sufficient to afford space between them ample for magazines, loading 
 rooms, and bombproof cover for the garrison. On the other hand, the extreme distance 
 between pits must be limited to the extreme dispersion of the projectiles of a single 
 mortar; or there will be an area of safety in the middle of the field of fall. Lateral 
 dispersion being much less than longitudinal dispersion, this condition fixes a much 
 narrower limit for admissible separation of the pits in a direction across the plane of 
 fire than in a dii'ection parallel to' that plane. Indeed, in a lateral direction, this 
 extreme Ijmit can hardly be avoided, but it is easy to secure a decided overlapping of 
 the rectangles in a direction parallel to the plane of fire. As appears from the drawing, 
 these conditions are fulfilled when the centers of the outer mortars in each pit lie on a 
 circle 150 feet in radius, the extreme lateral separation being 140 feet, and the extreme 
 longitudinal separation being 265 feet. 
 
 » * « « » * # 
 
 While this discussion illustrates the great advantage resulting from combining 
 mortars in groups of sixteen, the board is well aware that there are localities where 
 such a grouping will not be suited to the site. We are, nevertheless, of the opinion 
 that they should never be mounted in groups of less than four. 
 
 A few years later, in 1893, Gen. Henry L. Abbot, Corps of Engineers, 
 who from the very beginning had been one of the most ardent advo- 
 cates of the use of mortars in seacoast defenses, wrote for the Artillery 
 Journal the following: 
 
 Mortars in coast defense possess incontestable advantages. 
 
 (1) The blow is delivered precisely where armored protection is least effective and 
 in a direction which threatens danger to the magazines, the engines, the boilers, and 
 the other vitals of the ship covered against horizontal fire by the water and heavy 
 armor; and even if these vitals are not reached by the projectile the explosion of its 
 charge of 100 pounds of high explosive will occur in the shell trap above the protected 
 deck where the secondary armament and the bulk of the crew are fully exposed. 
 
 (2) The mortar battery may usually be located where it is concealed from the 
 enemy, and where no effective reply is practicable. This so materially reduces cost 
 that the number of mortars may be multiplied without extravagant outlay and their 
 comparative lack of precision thus be corrected. 
 
 (3), Another merit of vertical fire is that the force of the blow increases with the range 
 instead of diminishing, as in horizontal fire, the vertical velocity within ordinary 
 limits of practice being measured by the square root of twice the acceleration of 
 
203 
 
 gravity into the fall. The latter may be taken roughly at one-fourth of the range for 
 an angle of elevation of 45°. At 60° of elevation the fall is one-half greater (and the 
 range one-tenth less), and at 75° elevation the fall is four-fifths greater (and the range 
 one-half less) than at 45° These vertical velocities unfortunately are not great, being 
 below 1,000 feet, and hence the energy required for penetration must be obtained by 
 using large calibers with their considerable weights of projectile. With our new 
 12-inch mortars these weights range from 625 to 1 ,000 poimds. 
 
 It mav be noted in this connection that experience at Sandy Hook has shown that 
 with elevations exceeding about 65° there is difficulty in causing the axis of the pro- 
 jectile to remain parallel to the trajectorj', and hence the use of higher angles is not 
 favored. It is also found that the service of the piece is facilitated by selecting one of 
 five fixed charges of suitable grades of powder, and regulating the range by sUghtly 
 varying the elevation between 45° and 65°, rather than by the old method of depend- 
 ing wholly upon a variation of the charge. 
 
 The extensive use of vertical fire in the siege of Petersbiu^ by the volunteer artil- 
 lery troops under my command, as well as the previous preparatory training the 
 raiment received when stationed in the defenses of Washington, first drew my 
 attention strongly to this kind of fire. The results achieved proved the mortar, even 
 in the crude form then in service, to be one of the most effective weapons on the Unea 
 of the Army; but experience equally demonstrated that it required careful treatment 
 to bring out its good points. Improved modes of pointing over that prescribed in 
 the textbooks, systematic mixing of the powder for the day's firing to obtain uni- 
 formity of action, equalizing the weights of the shells, and many other points no 
 longer necessary to mention in connection with the modem type proved to be essen- 
 tial to satisfactory service. One practical difficulty, however, was found to be in- 
 herent in the system, and it impressed itself upon the mind as something which 
 should be corrected, even with the large targets usual in field service, before all the 
 efficiency possible could be seciured. For use against so small a target as a ship this 
 difficulty would become still more^important; it is simply the impossibility of regu- 
 lating the pointing by individual gimners when many pieces are directed at the same 
 object. In gun practice the short time of flight enables each gunner to perceive 
 where hi^ gun projectile strikes, and to regulate his pointing accordingly. With the 
 long times of flight, characteristic of vertical fire this is no longer the case. Shells 
 are falling so thickly around the target that with a flight of many seconds he can no 
 longer distinguish which is his own shot, and his aim may thus remain uncorrected 
 because he imagines that he is doing much better than is really the case. ^\Tiere, as 
 in the case of a siege battery, the target remains immovable this difficulty may in a 
 measure be overcome by determining and recording for future use the pointing of 
 each piece separately; but against a target shifting position like a ship, I am satisfied 
 that no dependence can be placed on individual pointing. One man must regulate 
 the firing of a whole group of mortars to secure satisfactory results. 
 
 These considerations suggest how the engineer may assist the artillerist materially 
 by designing the battery so that the fire of many pieces can be controlled as a unit 
 by a single officer, stationed where he can observe the impacts. The problem is 
 simple, and has been solved to develop this principle. 
 
 For example, say, 16 mortal's are grouped in a single square pit in close juxta- 
 position. Evidently all of them would call for a common pointing, which may be 
 given mechanically by the gunners with the aid of a horizontal azimuth circle on 
 each platform, with the lines connecting the zero and 180° point all parallel to each 
 other, use being made, of course, of identical elevations and charges. Such a battery 
 would fulfill the purely theoretical conditions of the problem, but any artillerist will 
 see that its service would be impracticable, because the needful magazines; and bomb- 
 proofs and routes of supply for the ammunition would be lacking. 
 
204 
 
 In actual firing from a group of mortars it is quite certain that the dispersion of the- 
 projectiles would differ from that indicated by these computed rectangles, inasmuch 
 as the different mortars could never be served so as to give identical trajectories parallel 
 to each other; but thie greater and more irregular dispersion resulting from this cause^ 
 would be of immense benefit, because the overlapping of the different zones would 
 be disposed in a manner to cover more ground and with more uniformity. The 
 great difBculty in all firing is to make the center of impact coincide with the tai^et^ 
 and this is to a measure overcome by the certain wandering of the shots from their 
 theoretical positions. Assuming that the pieces are well served with the assistance 
 of modern position finders, these figures make it evident that no ship could remain, 
 at anchor at this range (4J miles) with impunity. 
 
 But certain conditions other than ballistic are demanded to enable the gunners to- 
 perfectly perform their duties; these are met as follows in the batteries under con- 
 struction: 
 
 (1) There must be ample room about each mortar for loading; this is secured with 
 the adopted carriage when the four pintles of each pit are placed at the corners of 
 a square 20 feet on the side. 
 
 (2) Bombproof cover must be furnished to protect the men from the blast at firing, 
 and for passages for conveying the ammunition in safety from the magazines to the- 
 mortars; this is provided to the extent of over 350 running feet, 10 feet wide. 
 
 (3) Convenient magazine accommodations must be given; there are two, each with. 
 a floor space of 580 square feet, disposed at right angles to the long gallery, and with. 
 anterooms and entrances so placed that two adjacent pits ca^n be served independently 
 of the other two, without requiring the different detachments to pass each other im 
 the gallery. Capacity over 100 rounds is provided, the shells (loaded but without, 
 fuzes) being stored chiefly along one side of the long gallery. 
 
 (4) The ammunition will be served on truck cars running on tracks, with overhead 
 facilities for loading. 
 
 (5) The whole interior will be lighted by incandescent lamps, run by a small dynamo- 
 under bombproof cover. 
 
 (6) All firing, of course, will be done by electricity; and 
 
 (7) Where arrangements for resisting attacks by boat parties are necessary they 
 will consist of a counterscarp 15 feet h^h, with a ditch 30 feet wide, flanked by counter- 
 scarp galleries at two angles diagonally opposite to each other. Two machine guns in' 
 casemates will thus sweep each of the four ditches. Musketry fire over the approaches' 
 'will be obtained by field intrenchments on the top of the central covering mass^ 
 prepared by the garrison after the outbreak of hostilities. 
 
 To secure the highest possible accuracy with this system, care should be taken by 
 the Ordnance Department to insist on well graduated azimuth and vertical circles,, 
 and any failure in this respect should cause instant rejection of the defective work. 
 The engineer can not be too careful to place all the platforms horizontal, with the- 
 lines connecting the zero and 180° marks truly in the meridian. Of course, any 
 other position for these lines would serve equally well for a single battery, so long as 
 they are parallel to each other; but the true meridian is named in the instructions of 
 the Chief of Engineers in order to assist the commanding artillery officer at a central 
 station where the position of the enemy is supposed to be known, to designate the- 
 first trial azimuth to be used at any mortar battery in the harbor. 
 
 One of these batteries can be served either by volleys of 16 mortars, by volleys of 
 four mortars, or by single pieces. The latter method will naturally be used in obtain- 
 ing the exact range and azimuth after the position of the enemy is approximately 
 determined by the position finder. The effect of the conditions existing in the upper 
 atmosphere will thus be determined by actual trial, and the commanding officer will 
 have every detail under his control, and will be enabled to bring into play the highest 
 professional skill and good judgment. It is to be hoped that at an early day the: 
 
205 
 
 •completion ot eeveial of theee batteries will permit r^:ular practice to be had by the 
 artillery troops stationed in the neighboring fortifications, and that by this means 
 the entire system may be put to a practical test. Practice over a land range would 
 afford data of extreme value, as by marlring the projectiles with a cold chisel, as was 
 done in the preliminary training of my regiment in the defenses of ^ ashington, it 
 -would be possible to discuss the trajectory of each piece separately, and thus obtain 
 precious infoiination respectLog group firing which can no where be found in existing 
 lecords. Indeed, experimental investigation in this new field can hardly fail to lead 
 "to useful conclusions as to the best modes of serving modem mortars. 
 
 Original of 1892 Type of Mortar Battery. 
 
 Modem seacoast battery construction was resumed in this country 
 About 1891 and among the first batteries started were two mortar 
 batteries, one at Sandy Hook, New York Harbor, and the other in 
 the defenses of San Francisco, Calif. 
 
 The general design of these batteries was based upon Gen. Abbot's 
 original mortar battery buUt at WUlets Point, there being four 
 mortar pits and four mortars in each pit. An outline drawing of 
 one of these batteries is shown in figures 1, 2, and 3, Plate XXVII. 
 
 The mortar pits had their centers on the corners of a rectangle 
 about 140 by 255 feet, the long direction of the rectangle being such 
 as to pass through the center of the expected field of fire. The pits 
 were separated from one another by earthen traverses whose direc- 
 tions were parallel to the sides of the rectangle and which inter- 
 sected at the center of the rectangle. On the outside the mortar 
 jpits were surrounded by an earthen parapet of the same height as 
 the traverses — that is, about 40 feet above the floor of the pits. 
 
 Each mortar pit was a rectangle 40 by 65 feet, the sides being 
 parallel to the sides of the large rectangle and the longer dimensions 
 l)eing parallel to the longer dimension of the large rectangle. The 
 centers of the mortar weUs were placed near the front of the mortar 
 pits (that is, the side toward the enemy) and were 20 feet from each 
 other and 10 feet from the sides and front of the mortar pit. The 
 rear of each mortar pit was finished as a paved platform upon which 
 the projectile trucks could be maneuvered. 
 
 The two mortar pits at the front of the large rectangle were con- 
 nected by a cross gallery 8 feet wide extending from one pit to the 
 other, throTigh the long center traverse, this gallery being parallel 
 to the shorter sides of the rectangle and being located so as to connect 
 the rear of the two front pits. A similar gallery connected the rear 
 of the two rear pits. 
 
 The center points of these two cross galleries were connected by a 
 long central gallery located in or under the long central traverse. 
 This long central gallery was 10 feet wide and had extensions at the 
 front and at the rear beyond the front and rear cross galleries. 
 
206 
 
 This long central gallery was intended, first, for communication,, 
 and second, as a storage place for projectiles which were to be stored 
 four or five deep in tiers close to the sides of the long gallery, the 
 points against the side walls and the butts lying along the sides of 
 the somewhat narrow passageway which was left. 
 
 The space in and under the central cross traverse was utiUzed for 
 powder magazines, of which there were two, 58 by 10 feet. There 
 were also two powder handling rooms and two other rooms which 
 could be used for general storage or for power purposes. 
 
 To the ceiling of the long gallery were attached three trolley rails, 
 one on either side over the centers of gravity of the projectiles which 
 were stored along the sides 'of this gallery, and the third along the 
 middle. The side troUey rails were intended for handhng projectiles^ 
 the trolleys running on these rails being provided with differential 
 blocks by which the projectiles could be raised to the height desired. 
 The central trolley rail was for the purpose of handling powder. 
 
 The fundamental idea upon which this type of mortar battery was 
 based was that, in general, the whole 16 mortars should be fired in 
 a salvo, and in rapid fire this required that the 16 mortars be loaded 
 at once. This meant that the 8 projectile trucks for the 8 mortars 
 at the front end of the battery would be loaded at the same time at 
 that end of the long gallery — that is, four for each trolley rail; and 
 similarly for the 8 projectile trucks for the 8 mortars at the rear 
 end of the battery. To accompHsh the handling of these projectiles 
 with this speed it was necessary that there be 4 trolleys on each track 
 at each end of the battery. Each of these trolleys would be placed 
 over a projectile, the projectiles would be raised with the differen- 
 tial blocks as high as necessary and the trolleys would then be 
 roUed until they were over the trucks. It is evident that the 
 projectiles for the farther trucks had to pass over the intermediate 
 ones. When over the proper trucks the projectiles would be lowered 
 into them and then pushed to their respective mortars. 
 
 This required that 8 trucks be loaded at the same time in the 
 small contracted space at one end of the long gallery, where there was 
 little room to maneuver the trucks around and, as a result, the pro- 
 jectile service was slow and inconvenient. 
 
 Nor was the powder service much more convenient. For the 
 handling of the powder for the 8 mortars at either end of the 
 battery, a low platform was used, carried by trolleys running on the 
 center! troUey rail. This platform was long enough to carry eight 
 charges of powder. It was pushed near the entrance to the magazine 
 and the powder charges would be loaded on it. The platform was 
 then pushed to the end of the gallery whence the powder was to be 
 carried by hand to the mortars. 
 
207 
 
 Experience with the first mortar batteries soon showed that they 
 had a number of unportant defects. The pits were too small and too 
 cramped for the rapid loading of the mortars. The use of the long 
 galleries as stors^e places for projectiles interfered with free inter- 
 communication, consequently the ammunition service of these bat- 
 teries was slower than was desired. 
 
 The worst trouble experienced with these batteries was, however, 
 the blast effect. The discharge of the mortars, especially when all 
 four in one pit were fired at once, had a tendency to drive out of the 
 pit all the air that was in it, and since the pits were closed on all four 
 sides the outside air coidd not readily flow in to fill the partial vacuum 
 created. From this vacuum in the pits a wave of rarefaction was 
 started which ran into the galleries, corridors, and rooms of the trav- 
 erses, doing great damage there, blowing doors ofiE the hinges, des- 
 troying electric fights, and causing considerable discomfort to the 
 personnel. Incidentally, also, the result of this blast would, not 
 infrequently, cause the earth of the steep side slopes of the pit to 
 shde into the pits. 
 
 In the earhest mortar batteries, the mortar pits were surrounded 
 by vertical walls about 3 feet high. On top of these walls there was 
 a berm, and from this berm the earth sloped up ^vith the steepest 
 slope at which it would stand. In some of the batteries buUt a Httle 
 later, the vertical walls were made from 10 to 12 feet high, with earth 
 slopes above. This raising of the side walls of the pits made it still 
 more difficult for the air to get in to fill the partial vacuum caused by 
 firing the mortars, and it was in the batteries buUt in this latter way 
 that the earth slopes were most readily destroyed by the blast effects . 
 In fact, in a number of these batteries, it became necessary before 
 stabifity could be insured, to abandon, the use of sod on the slopes 
 of the pits and to revet these slopes with a concrete covering all the 
 way to the top. 
 
 1894 Type of Mortar Battery. 
 
 In the meantime it had been discovered that the accuracy of the 
 new mortars was greater than had been anticipated and that the 
 dispersion of the shots was much less than had been expected. Con- 
 sequently it appeared that greater accuracy would be obtained if, 
 instead of aiming all 16 mortars of the battery with their axes parallel, 
 a special setting should be used in each pit. 
 
 When the system of aiming the mortars of each pit independently 
 was adopted, there was no longer any reason for adhering to the rec- 
 tangular distribution of mortar pits, and consequently, in several of 
 the hew batteries which were begun about 1894, or shortly thereafter, 
 the pits, instead of being placed on the comers of a rectangle, were 
 placed in a fine normal to the main direction of fire. Figures 4 and 5, 
 
208 
 
 Plate XXVII, show the grovmd plan of one of the batteries of this 
 type, which we may call the 1894 type of mortar battery. 
 
 In this arrangement, the protection provided for the pits on the 
 side toward the enemy becomes a long parapet extending along the 
 front of the entire battery, and the space within and under this parapet 
 is utiUzed for magazine and storage purposes. The entrances to the 
 magazines are through doors opening at the left side of the front of 
 «ach pit, and the space immediately in front of each of these doorways 
 is widened out into what is called a lobby. 
 
 Each pit is separated from the adjoining pits by a short fore-and- 
 .-aft trayerse extending backward from the front parapet to beyond 
 the rear of the pits. In plan, the rear of each traverse is rounded 
 off and the rear slope is, therefore, conical. To the front and on 
 both sides, the pits are finished off with the usual vertical concrete 
 walls with earth slopes above the tops of the walls, but to the rear 
 all protection is omitted thus leaving the pits open in that direction 
 and permittiiig the easy inflow of air when the mortars are fired. 
 This diminished the blast effect to a considerable extent. 
 
 .The space within the parapet in front of each pit, and part of the 
 space in front of the traverse to the right of the pit, is utUized as the 
 magazine space, so that each pit has its own shell room and its own 
 powder rooms. The shell rooms are immediately in front of the pits 
 and the powder rooms are in front of the shell rooms. As the shell 
 rooms pertaining to the four pits are interconnected by galleries, 
 each shell room with the next, there is provided under the parapet a 
 continuous passageway from one side of the battery to the other. 
 
 The projectiles are stored along the two sides, that is, the front side 
 and the rear side, of the shell room, with a troUey rail over each. At 
 the inner end of each shell room, these two trolley rails are imited 
 into one by a rail making a half circle, and, at the end of the shell 
 room toward the lobby, both troUey rails extend into the lobby and 
 to the outer door of the lobby, where they end. 
 
 Since at any time but four projectiles, one for each mortar in a 
 pit, have to be placed on trucks in each lobby, only two projectiles 
 have to be handled on each trolley rail, which makes the' loading of 
 the trucks simpler and more rapid than in the older or 1892 type of 
 battery where four projectiles had to be handled on each rail. 
 
 The powder magazines are parallel with and lie in front of the shell 
 rooms. Each powder magazine consists of two rooms opening into 
 each other, a storage room and a rehandling room, the latter for use 
 in preparing powder charges of the proper weight. The rehandling 
 room opens into the lobby, so that in this type of battery the powder 
 does not have to be carried between two long lines of projectiles as in 
 the original type. The powder service is, therefore, much simpler 
 and more satisfactory. 
 
209 
 
 The drawings of this type of battery show a relocating room, and 
 opening from it, a small concrete tower containing a spiral staircase 
 leading up to a small crow's nest built in at the highest point of the 
 battery. The relocating room is so situated that no daylight can 
 reach it and has but httle ventilation. In practice, these rooms were 
 found to be damp and were practically never used for the puQ)ose for 
 which designed. The crow's nests, likewise, were found to be com- 
 paratively inaccessible and were soon abandoned. 
 
 The plans of this type of battery show also two connected power 
 • rooms situated like the relocating room, in a damp and badly venti- 
 lated place. The power rooms were also found to be too dark and 
 damp for use, and were shortly abandoned for other rooms specially 
 built outside of the battery proper. No air passages or other arrange- 
 ments for preventing dampness are shown on the plans or were in- 
 stalled in the batteries of this type. 
 
 The most serious trouble experienced in this type of battery has 
 been the severe blast effect. The entrance to the lobby, as will be 
 noted on the drawing, is in front of the pit, and if the mortars are 
 fired toward or approximately toward the front, their lines of fire 
 pass almost directly over this entrance to the magazine. As a result, 
 the blast effect in the magazine space, although not as severe as in 
 the original type of battery, is yet too great for comfort and has fre- 
 quently done considerable damage. 
 
 1898 Type of Mortar Battery. 
 
 In 1898 there were published, as Mimeograph 27, the designs of a 
 new type of mortar battery, outline drawings of which are shown in 
 figures 1, 2, .3, and 4, Plate XX^T^II. As by this time it had been 
 decided that 16 mortars were too many to be handled satisfactorily 
 as a single tactical battery, this 1898 type is based upon the idea that 
 the tactical battery shall consist of eight mortars only, that is, two 
 pits with four mortars in each. As in the 1894 type, the pits are 
 placed in a line perpendicular to the general direction of fire. The 
 pits are, however, considerably larger than in the 1894 type, being 
 in plan about 67 feet by 71 feet, but like the 1894 type, the pits have, 
 on the front and flank sides, vertical concrete walls with earth slopes 
 above. To the rear the pits are left open. 
 
 Instead of utilizing the space under the parapet for magazine and 
 storage purposes, as is done in the 1894 type, use is made of the space 
 under the central and two flank traverses. In each of these traverses 
 long fore-and-aft walls extend nearly the whole length of the traverse, 
 dividing the interior space into long rooms which open at the rear 
 on covered corridors. These corridors are closed at the sides but 
 are entered from the rear through wide doorways. With this method 
 of construction, the rooms in the traverses are well protected from the 
 173341—20 14 
 
210 
 
 effects of the blast and the blast effects in them have been practi- 
 cally negligible. 
 
 The rear parts of two of the central long rooms of the central 
 traverse and of the most distant long rooms of each of the flank 
 traverses are designated as powder magazines, there being a powder 
 magazine for each two mortars instead of for each four mortars as 
 in the l'S94 type. However, the powder magazines are not divided 
 as in the 1894 type into storage rooms and rehandling rooms and 
 this is a defect that later bad to be corrected. 
 
 The long room next to each powder room is used as a shell room, 
 and, in front, this shell room extends around so as to utilize for 
 storing shells the front part of the long room of which the rear part 
 is used as the powder magazine. There is thus provided a very 
 capacious shell room for each two mortars. 
 
 As is usual, the projectiles are stored along the sides of the shell 
 rooms and over each pile of projectiles there is a trolley rail. At 
 the rear, the trolley rails extend not only to the doors of the sheill 
 rooms but completely' across the ceihngs of the corridors and even 
 as cantilevers well out from the rear face wall of the corridor. The 
 projectiles are raised by the blocks of the troUeys, are then moved 
 on the trolley rails out to near the end of the outside extensions, and 
 are there lowered into the trucks. Since in this type of battery there 
 is a shell room for each two mortars and there are two trolley rails 
 in each shell room, there is a trolley rail for each mortar and only 
 one projectile at a time has to be loaded from each rail. 
 
 The drawings show the long rooms on the left sides of the central 
 and of the right flank traverse as "bombproofs." It was intended 
 that as soon as the mortars were loaded, the personnel would take 
 refuge in these bombproofs and in this way might escape the blast 
 effect and at the same time be sheltered from the enemy's projec- 
 tiles. Small rooms in rear of the bombproof are designated as firing 
 rooms, it being intended that the firing cables should be led into 
 these rooms and that the firing magneto should be operated there. 
 
 The plans show also a small observing station or crow's nest on 
 the top of each of the flank traverses and a relocating room located 
 on the lower level near the foot of the stairway leading up to each 
 of these crow's nests. 
 
 Two power rooms, one for the generating plant and one for a storage 
 battery, are provided in the left-flank traverse. Six-inch blind air 
 spaces are provided as a partial attempt to reduce condensation. 
 
 The type of battery just described remained the standard in this 
 country for quite a number of years and a niunber of batteries were 
 constructed on these plans. From experience, a number of defects 
 were developed and, as a result, slight modifications in plans were 
 made from time to time. Among the defects that may be mentioned 
 
211 
 
 the most important appeared to be the small size of the powder rooms, 
 as compared with the shell rooms, and the omission of the rehandling 
 rooms. Furthermore, it was fomid that the attempt to diminish the 
 blast effect had been somewhat overdone and that the powder rooms 
 and shell rooms were a little too inaccessible. They could have been 
 made more accessible by opening the corridors on the sides, that is, 
 directly into the pits. Special bombproof rooms for the personnel 
 were found to be unnecessary, as there was ample space in the corridor 
 or in rear of the traverse for the detachment to stand in as the 
 mortars were fired. 
 1906 Type of Mortar Battery. 
 
 The defects found in the 1898 type of battery were corrected from 
 time to time in the detailed plans of the batteries built according to 
 that general type, and finally, in 1906, these improvements were 
 embodied in new plans which were published as a supplement to 
 Mimeograph No. 27. The groimd plans of this type are shoAvn in 
 figure 7, Plate XX\'T[II. These new plans, which may be called the 
 1906 type of mortar battery, hardly differ from the 1898 plans suffi- 
 ciently to be designated as a separate type and might be considered 
 as a variation of the 1898 type. 
 
 The two types resemble each other closely, the main difference 
 being in the arrangement of the rooms in the traverses. In the 1898 
 type there are 10 long rooms altogether, and these are irregularly dis- 
 tributed among the traverses, while, in the 1906 type, there are 12 
 such rooms, distributed 4 in each of the 3 traverses. The four long 
 rooms next to the pits are used as shell rooms, the whole of the next 
 four rooms are used as powder magazines and each powder magazine 
 is divided into two parts, the front part being intended for storage 
 pxu^oses and the rear for rehandling purposes. The two outer long 
 rooms of the flank traverses are used for miscellaneous purposes, as 
 storerooms, guard rooms, officers' rooms, and power rooms. No 
 relocating or plotting room is provided, as at the time these plans 
 were prepared plotting rooms were usually provided in connection 
 with the primary observing stations. The corridors are made quite 
 open to the rear, their roofs being supported at the rear by columns 
 only. To the flank, the corridors open directly on the loading 
 platforms. 
 
 The greatest improvement shown in the drawings of the 1906 type 
 is the provision of shell tables at the corridor ends of the shell rooms. 
 The one slow and laborious step in handling projectiles is raising 
 them from the floor to the height of the trays of the projectile trucks. 
 This is done ordinarily by means of the differential blocks of the trol- 
 leys, and the work is laborious and, if done rapidly, exhausting. To 
 avoid this -there is provided in each shell room of this new type of 
 mortar battery two shell tables located at the rear or corridor end 
 
212 
 
 of the shell room, one table being located under each trolley track. 
 These shell tables, each of which wUl hold 12 projectiles, are built dt 
 such a height as to permit the projectiles to be rolled from the tables 
 directly into the trays of the shell trucks, and each table is provide^ 
 at its corridor end with an escapement which, when not in use, will 
 keep the projectiles from rolling off of the table and which, when 
 operated, will permit one projectile at a time to be rolled onto the 
 truck. 
 
 The main mass of projectiles is stored in piles in the front part ot 
 the shell rooms from which they are to be moved by trolleys to the 
 shell tables. It is assumed that an engagement will find the shell 
 tables completely filled, and as the projectiles are carried from the 
 tables to the guns they are to be replaced by others brought from 
 the piles in the front parts of the shell rooms. By making use of 
 several trolleys on each trolley rail and with a sufficiently large 
 detachment, these projectiles can be raised and can be placed on the 
 shell tables without undue physical strain on the members of the 
 detachment. 
 
 Although not shown on the drawi.ngs on Plate XXVIII, the mimeo- 
 graph plans of this type of battery (supplement to mimeograph 27) 
 showed an observing station or crow's nest on the top of each fiank 
 traverse -and a small battery-commander's station on top of the rear 
 of the central traverse. This station had concrete walls and a con- 
 crete roof and was reached by stairs leading down to the rear. No 
 battery-commander's walk is provided. The mimeograph drawings 
 show also mortar booths to the rear of one fiank of each pit. These 
 booths, which will be described in the chapter on fire control, are 
 shown in figures 5 and 6, Plate XXVIII. 
 
 No air passages were shown in the plans, but the mimeograph draw- 
 ings showed numerous ventilation openings connecting the various 
 rooms and passing from some of the rooms to the outside air. 
 
 For several years after the publication of the supplement to mimeo- 
 graph 27, but few mortar batteries were constructed and, consequently, 
 batteries of the 1906 type are not very common. However, the shell 
 tables, description of which was included in the same mimeograph, 
 were added in a number of the batteries built previously in accord- 
 ance with the 1898 type plans. 
 1912 Type of Mortar Battery. 
 
 All of the types of mortar batteries heretofore discussed were de- 
 signed for 12-inch mortars. By about 1910, however, it had become 
 evident that the 12-inch mortars were, not sufficiently powerful nor 
 had they sufficient range, even when the light, or 700-pound, pro- 
 jectiles were used. The Ordnance Department, therefore, began the 
 design of a 14-inch mortar and of a carriage for it. As soon as the 
 preliminary drawings of the 14-inch mortar carriage were received 
 
213 
 
 in the office of the Chief of Engineers, the Engineer Department began 
 the work of designing a mortar battery for these 14-inch mortars. 
 
 Meanwhile the design was modified to a 12-inch mortar, 15 cahbers 
 long, and the designs for the batteries were modified to correspond. 
 These batteries were first built in Panama and this type is therefore 
 often mentioned as the "Panama" type. 
 
 In the meantime, experience with the older mortar batteries had 
 shown that the simultaneous loading and aiming of four mortars in 
 a single pit is somewhat difficult. To reach the front mortars the 
 projectile trucks have to be pushed past the rear ones, and when the 
 mortars are pointed in certain directions it is difficult to so maneuver 
 the projectile trucks as to reach the breeches of the front mortars. 
 To avoid injuring the men as the result of blast, no mortar in a pit 
 can be fired while any other mortar in the same pit is being loaded 
 and the rate of firing the mortars is, therefore, dependent upon the 
 rate of loading the mortar which is the most difficult to get at. Con- 
 sequently, the rate of fire possible with four mortars in a pit was 
 found to be too slow. 
 
 As a result of this, it had become customary to use only two of the 
 mortars in a pit at a time, preferably the rear two. In some cases, 
 even the front mortars had actually been removed from the pits, 
 leaving the rear two mortars only. 
 
 Incidentally, the increase in the length of the mortars had resulted 
 in an increase in the accuracy of mortar fire and it now appeared 
 unnecessary to continue the practice of firing as many as four mortars 
 at a time at a single target. For this purpose two mortars appeared 
 to be sufficient and it was, therefore, decided that in the new 14-inch 
 batteries but two mortars would be placed in a pit and that they would 
 be placed side by side. It further appeared desirable to provide a 
 fire control installation which would permit each pair of mortars to 
 be fired independently. 
 
 However, to maintain a sufficient volmne of fire it appeared to be 
 advisable, as a general rule, to retain eight mortars in a group, even 
 though for tactical purposes the group might be subdivided. 
 
 To emplace eight mortars in a line and to locate the shell rooms 
 and powder magazines in the traverses between the pits, as had been 
 done m the 1898 and 1906 types (Plate XXVIII), would result in 
 making the battery unduly wide. Furthermore, the increase in the 
 range of naval guns and in the angle of fall of naval projectiles made 
 it appear undesirable to continue the practice of storing powder in 
 the traverses. Consequently, there was a return to the idea of utilizing 
 the front parapet for magazine space as had been done in the 1894 
 type of battery, (Plate XXVII.) 
 
214 
 
 The particular trouble that had caused the abandonment of the 
 1894 type of mortar battery had been the severe blast effects in the 
 magazine, due to the fact that the doors of the magazines were located 
 in the front walls of the pits, and therefore in front of the muzzles 
 of the mortars when fired in the most usual direction. This difficulty 
 had been avoided in the 1898 and 1906 types (Plate XXVIII), by 
 placing the entrances to the magazines rearward of the pits. Con- 
 sequently, in this new type of mortar battery, it was decided that, 
 though the interior of the front parapet should be utilized as magazine 
 space, the entrances to the magazines should be from the rear of the 
 pits through the traverses, which had to be provided in any case to 
 reduce the possible damage from enfilade fire. 
 
 Outline drawings of this 1912 type of mortar battery are shown on 
 Plate XXIX, these drawings being based upon the general plansfor this 
 type of mortar battery and not on the plans of any particular battery. 
 Although the general plans showed a battery of eight mortars located 
 two in each of four pits, it was expected that for tactical piu-poses the 
 structural battery of eight mortars would be subdivided into two 
 tactical batteries of four mortars each. In fact, in all cases where 
 structural batteries of eight mortars have actually been built, they 
 ,have been subdivided tactically, to the extent even of giving each 
 tactical battery of four mortars a special name, and of assigning to 
 it a separate tactical organization of troops. 
 
 The mortar pits, which are separated, one from another, by 
 traverses having splinter-proof concrete roofs, are 75 feet wide by 
 45 feet deep, measured from the front wall to the rear of the pit. 
 The two mortars in a pit are emplaced 30 feet apart, center to 
 center, and the center of each is about 22^ feet from the front wall and 
 from the side wall of the pit. 
 
 The space within and under the front parapet is utilized for maga- 
 zine purposes. The shell rooms are immediately in front of the pits 
 and are separated from them merely by a concrete waU of such thick- 
 ness as would appear necessary for protection. The powder maga- 
 zines are in front of the shell rooms. 
 
 Due to the great width of the pits and the fact that there are but 
 two mortars in each pit, the width of the mortar battery is now suffi- 
 cient to make it possible to provide a sheU room and a magazine for 
 each mortar, instead of one for each two mortars, as in the 1896 and 
 1906 types (Plate XXVIII), and one for each four mortars as in the 
 1894 type. (Plate XXVII.) In each of the traverses there is a 
 gallery which, at the rear, opens to the side on the mortar pits and, 
 in front, extends forward as far as the front, walls of the powder 
 magazines. The shell rooms open on these galleries, and as, at their 
 inner ends, the two contiguous shell rooms run into each other, there 
 is provided through the shell rooms a continuous covered passage 
 way from one side of the battery to the other. 
 
215 
 
 Each powder magazine is divided into two rooms, a storage room 
 and a rehandling room, the two being connected by a door. Each 
 rehandling room has an additional door that opens on the front end 
 of one of the galleries. For convenience in passing from the storage 
 room of one magazine to the storage room of the contiguous magazine, 
 a doorway is shown between them, but it is intended that this door- 
 way shall be closable by two heavy solid metal doors so as to decrease 
 the danger of an accidental explosion in one magazine being communi- 
 cated to the next. 
 
 In the 1906 type of mortar battery (PI. XXVIII), there had been 
 introduced the idea of placing at the service ends of the shell rooms, 
 shell tables for storing a limited nmnber of projectiles ready for 
 instantaneous service. The introduction of these tables had simpli- 
 fied the projectile service of mortar batteries, consequently this same 
 idea is retained in this 1912 type of mortar battery. In fact an 
 improvement is made, for instead of having but one shell table for 
 each mortar, two shell tables are now provided for each. 
 
 During the interval between the adoption of the 1906 type of mortar 
 battery and the preparation of the plans for the 1912 type, it had 
 become customary for the Ordnance Department to fiu-nish to aU 
 mortar batteries several different types of projectiles; heavy projec- 
 tiles for short ranges, light ones for long ranges, projectiles having 
 thick walls for piercing deck armor, and projectiles having thinner 
 walls and high explosive charges for use against cruisers whose 
 deck armor protection is but slight. The shell tables provided in 
 the 1906 types of mortar battery, that is, one shell table per mortar, 
 had siraplified to a considerable extent the projectile service of the 
 mortar battery as long as a single type of projectile had to be used, 
 but it appeared that this system would not be thoroughly satisfactory 
 ia case it became necessary, in the middle of an action, to change from 
 one type of projectile to another. 
 
 In order that a rapid change may be made as easily as possible, 
 it was decided to provide in the new type of mortar battery, two shell 
 tables for each mortar, this being rendered easily possible since there 
 is now a shell roona for each mortar instead of one for each two mortars 
 as in the 1906 type. It is assumed that these two shell tables wiU 
 be loaded with different types of projectiles, one table being used for 
 the type actually being fired and the other table having placed upon 
 it projectiles of that type which wiU most likely be called for if a 
 change in type is desired. If, therefore, the tables are used in this 
 manner and it becomes necessary in time of action to change from 
 one type of projectile to another, all that is necessary is for the pro- 
 jectile truclffi when coming for new projectiles to go to the other 
 table. 
 
216 
 
 Each shell table is fitted at its gallery end with an escapement of the 
 usual form, which permits one projectile, and but one at a time, to 
 be rolled from the shell table into the tray of the truck. When loaded, 
 the truck is pushed through the gallery to its rear end, and thence, 
 at the proper time, to the breech of the mortar. When the projectile 
 has been rammed into the mortar, the truck returns through the gallery 
 to the proper shell table to be reloaded with a new projectile. 
 
 The galleries in the traverses which lie between two pits are made 
 17 feet wide because along these galleries there have to be pushed 
 trucks pertaining to two mortars. In the galleries of the flank trav- 
 erses through which the trucks of but one mortar have to go, the width 
 is made but 13 feet. The widths here stated are those now standard, 
 but in a few of the earlier batteries of th,is type actually built the 
 galleries were made slightly narrower. 
 
 While the plans of this type of mortar battery were in preparation, 
 serious study was given to the question as to whether the shell tables 
 should be placed at the gallery ends of the shell rooms and the trucks 
 should be loaded there and be pushed through the galleries, or as to 
 whether the shell tables should be located at the rear ends of the 
 galleries. Some officers were in- favor of one method of ammunition 
 service and some of the other. Finally, however, it was decided, 
 with the assent of the Chief of Coast Artillery, that the system shown 
 on the plans should be adopted. 
 
 The projectiles are normally to be stored in the portions of the 
 shell rooms inward from the shell tables. There are to be two 
 rows of projectiles, one near the front and one near the rear side of 
 the shell rooms, the projectiles in each row being stored with their 
 points to the rear. The lowest tier in each row is to be placed on 
 timber skids and similar skids are to be placed between successive 
 tiers, it being intended that, if there are enough of thena to require 
 it, the projectiles may be stored as many as four tiers high. 
 
 Trolley tracks are attached to the ceilings of the shell rooms and 
 pass above the centers of gravity of the projectiles in the two rows, 
 and the troUeys running on these trolley tracks are to be used for 
 carrying the projectiles to the shell tables. 
 
 As has been stated before, the most laborious part of ammunition 
 service is in raising the projectiles up to a sufficient height to place 
 them on the shell tables. To reduce this labor as much as possible, 
 the idea has been introduced of raising the floors of the portions of 
 the shell rooms utilized for storage purposes about 30 inches above 
 the level of the floors of the galleries and of the shell rooms in the 
 vicinity of the shell tables. This raising of the floors of the interior 
 portions of the shell rooms places the second tier of projectiles as 
 stored in the shell rooms at practically the same level as the pro- 
 jectiles that are on the shell tables. Consequently, in ammunition 
 
217 
 
 service, the projectiles which are stored on the fourth or on the 
 third tiers have to be lowered in moving them to and placing them 
 on the shell tables, and this lowering, of coiu^e, can be done practi- 
 cally without expenditure of energy. When the projectiles of the 
 second tier have to be moved to the shell table all that is necessary is 
 to raise them up just sufficiently to clear the skids and they can then 
 be carried horizontally to the tables. The only projectiles, there- 
 fore, which have to be really raised in moving them from their 
 storage places to the shell tables are those of the lowest tier, and 
 these have to be raised only by an amount equal to shghtly more 
 than their own diameter. 
 
 The system of trolley tracks proposed for this new type of mortar 
 battery is shown on Plate XXIX and, as wiU be noted, the idea of 
 laying out the troUey tracks in loops has been carefully carried out, 
 one loop of the troUey track passing over the two rows of projectiles 
 and the two shell tables pertaining to each shell room. Additional 
 troUey tracks are shown connecting these various loops in such a 
 manner as to make it easily possible, by means of a troUey, to move 
 a projectUe from any part of any shell room to any part of any 
 other shell room of the battery. In addition, troUey tracks are 
 shown as extending through each of the gaUeries, connected at the 
 front ends of the gaUery with the trolley tracks of the two contiguous 
 sheU rooms, whUe at the rear ends of the gaUeries they pass over 
 the ammunition supply railroad track. 
 
 The raising of the floors of the storage portions of the shell rooms, 
 of course, requires that the ceilings be raised also, and since the 
 trolley raUs have to be extended from the shell rooms through the 
 gaUeries, this means that the ceilings of the gaUeries have to be 
 high as well. The plans show them about 11 feet above the floors 
 of the gaUeries. This has the advantage, however, of permitting 
 the troUey rails to be extended to the rear horizontaUy across the 
 railroad track which passes in rear of the pits and permits, in am- 
 munition supply, the projectiles to be picked up by troUeys directly 
 out of the railroad cars in which they are brought to the battery. 
 
 The drawings on the plate show a railroad track in rear of the 
 pits and also a switch leading out from this track to the rear. This 
 switch is supposed to be connected with the main railroad system of 
 the post, so that projectUes and other suppUes can be brought by 
 rail all the way to the battery. If there is no such post railroad 
 system and ammunition supply has to be by wagon or truck, there 
 should be constructed in rear of the pits, a paved roadway instead 
 of the railway. The trucks or wagons with the projectiles can, in 
 this case, be driven under the trolley raUs. 
 
 It wUl be noted that in rear of the central traverse of each tactical 
 mortar battery, that is, each battery of fom- mortars or half of the 
 eight shown on the plate, there is shown what is known as a 
 
218 
 
 "plotting house." This plotting house is one of the special new 
 features of this type of battery and came about as a result of the 
 evolution of the design of plotting rooms for mortar batteries which 
 will be discussed in the chapter on fire control. 
 
 The floor of the plotting house is on the same level as the floor of 
 the pits. Each plotting house consists of one large room, about 
 16 by 32 feet, or about twice the size of the standard plotting 
 room. . Consequently, there is space enough in the main room of 
 this plotting house for two complete plotting boards with their 
 respective auxiliary apparatus and personnel. If all four mortars 
 of a tactical battery are to be fired at the same target, only one of 
 these plotting boards needs to be used at a time, but if it is desired 
 to fire each half of the mortar battery, that is, each pair of mortars, 
 at a different target, both the plotting boards are needed, using 
 different fire-control data, and each working out special aiming data 
 for its own two mortars. 
 
 In front, this main large room of the plotting house is extended 
 to both flanks in the form of alcoves, in which is to be operated the 
 mechanical indicating apparatus which displays the aiming data 
 to the men in the pit by means of figures showing through slots in a 
 small turret over the alcove. This mechanical indicating apparatus 
 will be described more at length in the chapter on fire control. 
 
 The roof of the plotting house is intended to be used as a station 
 for the officer in immediate command of operations at the battery. 
 This roof is surrounded by hand railings and is reached by con- 
 venient stairways, one on either side of the plotting house. In 
 order that the officer and others may be protected to some extent 
 from the sun or rain, pipe awning frames are provided over which 
 a removable canvas cover can be stretched. 
 
 An officer on the roof of the plotting house is placed in such a 
 position that he can see everything that is going on in the two pits 
 of his battery,, and by means of a megaphone can give instructions 
 to the men in the pits. By voice tubes he can communicate with 
 the men in the plotting room beneath him. He has speaking-tube 
 -communication (not shown on drawings) with his powder and 
 shell rooms, with the other plotting house, and with both battery 
 commander stations. By walking to the proper places at the front 
 corners of his roof, he can observe exactly what data is displayed 
 by the indicating apparatus to the. men in the pits. By crossing 
 the bridge in front of the plotting house he can proceed to the roof 
 of the traverse and thence, by convenient stairs, either up to the 
 top of the parapet in front or downward into the pit. 
 
 The drawings show two battery commander stations located one 
 on the top of each flank of the battery. The stations shown are of 
 the standard size, 15 feet by 15 feet, and are of the two-level type. 
 
219 
 
 The earliest batteries of this type were all deigned for construction 
 in ravines from which a view of the field of fire was not possible 
 £Lnd no battery commander stations were shown on the drawings. 
 Later, however, it was considered desirable to insert such stations 
 on the general typical plans from which the drawings on Plate 
 XXTK were made, and, as by this time the two-level battery com- 
 mander station had become standard, the stations are shown as 
 of that type. 
 
 Where mortar batteries have been actually biiilt in ravines, as 
 was the case in nearly all of the mortar batteries at Panama and in 
 aU of those recently built on the Pacific coast, battery commanders' 
 stations at the batteries would have been useless and were, therefore, 
 •omitted. In such cases, other stations located at sites affording a 
 good view were provided for the battery commanders' use and good 
 telephone communications were provided between these stations and 
 the batteries. 
 
 In designing this type of mortar battery it was expected that, 
 wherever possible, mortar batteries would be located in ravines or 
 behind hills, being thus hidden from the sight of the enemy and 
 receiving from the hills a considerable amount of protection from 
 the enemy's fire. However, it was known that iu some cases it 
 might be necessary to build the battery in the open, where it would 
 be exposed to fire. In such cases it is, of course, necessary that the 
 magazines be thoroughly protected. The drawings show such a bat- 
 tery, the magazines beiag given the same amount of protection as 
 the magazines of the 1912 type of direct-fire battery; that is, the 
 equivalent of 35 feet of concrete or 105 feet of sand. 
 
 Most of the mortar batteries built according to these plans have 
 been located ia the Tropics or in locahties in the United States where 
 trouble from condensation has not been experienced, and special 
 arrangements for preventing condensation were not necessary. The 
 typical plans, however, from which the drawings on the plates were 
 made, are intended for use in places where condensation troubles 
 have been experienced. They therefore show an air passage extend- 
 ing completely around the front of the entire battery from the power 
 room on one flank to an outlet on the other. Arrangements are to 
 be made by which the hot air blast from the radiators of the gener- 
 ating sets in the power room may, when desired, be turned through 
 this air passage so as to warm up the thin wall between the air pas- 
 sage and the powder magazines. By properly regiilating the soMd 
 doors in the openings between this air passage and the front of the 
 galleries, warm air can be taken into any portion of the battery as 
 desired. 
 
220 
 
 The designs shown on the general plans, from- which the drawings 
 on Plate XXIX were taken, were intended for general use. Conse- 
 quently, the rear ends of the flanks of the battery were purposely 
 shown as unfinished, the method of finishing these ends and the 
 question as to whether or not a parados should be provided being 
 left to the constructing officer, as details directly dependent upon 
 the conditions at each site., Several of the rooms in the left flank 
 traverse are marked as intended for special purposes, such as the 
 power room, the latrine, storerooms, etc. The rooms on the right 
 flank are not specially assigned, nor are any rooms set aside for the 
 special use of officers. All these matters also were left to the de- 
 signing officer, who was expected to arrange one of these rooms for 
 the special use of officers and to provide with it a conveniently 
 located toUet. 
 
 Special ventilation shafts, not shown in the drawing, have usually 
 been provided over the waUs between the shell rooms and the powder 
 magazines. In these shafts, suction fans have been installed for 
 drawing the air out from the shell rooms and the powder magazines 
 and thus ventilating them. The arrangements for this ventilation, 
 for electric conduits, for electric lighting, for speaking tubes, and many 
 other details are not shown on the outline drawings. Officers desir- 
 ing information on the subject should obtain access to the drawings 
 of the batteries of this type actually constructed. 
 
 The 1912 type of mortar battery just described is the present 
 accepted standard, having been used in aU 14-inch mortar batteries 
 recently designed and, with the necessary changes in dimensions, for 
 all 16-inch mortar batteries likewise. 
 
 One of the mortar batteries recently erected on the Pacific coast 
 has some novel features which may be weU worth mentioning. The 
 battery is built in a ravine up which it was necessary to maintain a 
 previously existing roadway. The battery consists of four mortars; 
 that is, two in each of the two pits, but the relation between the 
 normal direction of fire and the axis of the ravine is such that instead 
 of placing the pits side by side, as is usual, it was necessary to place 
 them one behind the other. Owing to the slope of the bottom of 
 the ravine, the pits had to be built with their floors on different ele- 
 vations. The ravine is so narrow that the battery extends com- 
 pletely across it, and the roadway which it is necessary to maintain 
 is therefore located on a ramp, built in tunnels, passing up through 
 the battery, and so connected with the different pits that it can be 
 used for ammunition supply and for moving in the mortars and 
 carriages. 
 
221 
 
 CONSTRUCTION DETAILS. 
 
 In matters affecting the kind of cement used, the manner of mixing 
 and placing the concrete, the prevention of dampness, the shape and 
 size of the rooms, the method of roof construction, and in many 
 other details, the development of the mortar battery went on in 
 exactly the same way as was the case with the direct-fire emplace- 
 ment. This has been noted in other chapters. However, there are 
 some details of mortar-battery construction which appear to deserve 
 special comment. 
 
 Size of Paraj>et. 
 
 If the sections of parapets shown in the early typical drawings of 
 mortar batteries be compared with the sections of parapets shown on 
 the drawings of direct-fire emplacements of about the same date, it 
 wUl be noticed that the amount of protection provided for mortar bat- 
 teries is much greater than that given the magazines of direct-fire 
 batteries. I must confess that I have never been able to see the reason 
 for this, for the mortar batteries are no more liable to be made targets 
 by the enemy and are no more essential to the defense than the direct- 
 fire batteries. In fact, it seems to me that, compared with direct- 
 fire batteries of the same time, in some of the earher mortar batteries 
 the parapets were made needlessly large. 
 
 Locations. 
 
 From a study of the plans of the earlier mortar batteries actually 
 built, it would appear that frequently as much advantage as was pos- 
 sible was not taken of the accidents of the ground providing both 
 concealment and, to a considerable extent, protection. A battery 
 intended for direct fire must, of course, be so placed that nothing 
 intervenes between the battery and its target, but a mortar battery, 
 which uses high angle fire and indirect auning only, can well be placed 
 behind hills or other natural obstacles. 
 
 With a direct-fire gun, the closer it is to the target the greater the 
 effect of its projectiles, and, consequently, direct-fire batteries should 
 in general be pushed as far to the front as possible. With mortar 
 fire, however, the farther away the target is the higher in general 
 the projectile must go to reach the target and the greater will be 
 the velocity of fall and the penetration. Within limits, therefore, 
 the farther away a mortar is the more efficient is its fire, while, on 
 the other hand, there is for each type of mortar an inferior limit 
 within which its fire is not effective. 
 
 For these reasons, it follows that mortar batteries can, hi general, 
 be withdrawn to the rear, and since they must necessarily use indi- 
 rect methods of aiming there is no reason why they can not be placed 
 behind hiUs, sand dunes, woods, or in rear of existing buildings. If 
 some such fairly protected location be available, the mortars them- 
 
222 
 
 selves need be given no additional protection and the only extra 
 protection it is necessary to provide is a comparatively light cover 
 for the magazines. 
 
 Unfortunately, on our Atlantic coast the conditions at the sites- 
 have been such that it has been almost impossible to ever find pro- 
 tected locations for mortar batteries, but on the Pacific coast and 
 in the Tropics mortar batteries have frequently been placed behind 
 hUls or in ravines. 
 System of Zones. 
 
 The old smooth-bore mortars were usually fired at an elevation 
 of exactly 45°, this being done because errors of elevation at this; 
 angle have less effect upon the range than at any other angle of 
 elevation. Since the angle of elevation of the mortars was fixed, 
 changes in range were obtained by varying the size of the charge of 
 powder. Tables were kept in the powder magazines and, as soon 
 as the range was known or was guessed at, the proper charge of 
 powder was weighed out. This made it necessary, of course, to 
 weigh out each charge of powder, which, if done accurately, required 
 time. 
 
 With the rapid fire required under modern conditions there is no 
 time to weigh out the charges. Furthermore, modern smokeless- 
 powder must be kept, almost up to the very instant of discharge, 
 in hermetically sealed packages. Consequently it is necessary ta 
 prepare in advance charges of several different weights. It is pos- 
 sible to have only a limited number of different sizes of charge in 
 storage, so the custom arose of making the main change in range 
 by using charges of these different sizes and obtaining further varia- 
 tions in the range by changing the elevation at which the mortar is 
 fired from 45° up to about 60°. As the elevation is changed within 
 the limits mentioned, any one particular weight of charge wiU cover 
 the distance between certain ranges, and as the mortar is rotated in 
 azimuth each charge will cover a comparatively wide annular belt 
 or zone. Each weight of charge has, of course, its own zone, but in 
 order to leave some leeway when the change from one charge to the 
 other is made, it is desirable that these zones should overlap slightly. 
 
 The inferior hmit of mortar fire is, of course, fixed by the range 
 resulting when the smallest charge is fired at 60° elevation. As the 
 angle of elevation of the mortar is reduced from 60° to 45°, the 
 range is increased and the outer limit of zone No. 1 is fixed by the 
 range obtained when the smallest charge is fired at 45° elevation^ 
 The size of the next charge is necessarily fixed as that which, when 
 fired at 60° elevation, wiU give a slightly shorter range than the 
 smallest charge fired at 45°. The outer limit of zone No. 2 is, of 
 course, fixed by the range given by the second charge at 45° eleva- 
 tion, and so on. 
 
223 
 
 It is, of course, essential that exactly the proper charge of powder 
 be used each time, because the elevation given to the mortar is 
 based primarily upon the size of the charge of powder. The mortars 
 are usually fired as rapidly as possible, and consequently, when the 
 time comes for the charge to be taken to the gim it must be picked 
 up hastily in the magazuie and carried rapidly to the mortar. In 
 haste of this character it would appear that mistakes might be made 
 tmless great care is exercised. 
 
 In order to render it almost impossible for such mistakes to be 
 made the stall system of storage has been adopted. In this system 
 each powder magazine is divided by light webbed-wire partitions into 
 stalls. Each stall is to contain all the charges of one weight and 
 none of any other weight. Information as to the particular charge 
 to be used is given by the illumination of a red electric lamp over 
 the entrance to the particular stall containing the proper charge of 
 powder. This lamp is wired in series with a bell. At the proper 
 time one of the detachment in the plotting room or in the mortar 
 booth inserts a plug in a particular hole and this simultaneously 
 strikes a single stroke on a gong placed in the magazine and illumi- 
 nates a red lamp over the door of the stall containing charges of 
 the desired weight. All that the powder man has to remember is 
 that when the beU rings he is to pick up a charge of powder from 
 under the red lamp and carry it to the gun. 
 
 In order to insure that the red light in the magazine will always be 
 shining when the plug is inserted in the plug board, it is customary 
 to place the lamp over the stall in series with the lamp over the 
 _plug board. If then the lamp over the plug board is shining, the 
 man at the board knows that the red lamp is shining over the stall 
 corresponding to the hole in which the plug has been inserted. 
 
 As the bell rings only once, that is, when the plug is inserted in a 
 hole in the plug board, it is necessary to move the plug only when 
 the charge is to be carried to the gun. If the same charge is to be 
 repeated, the plug is removed an instant and is then reinserted in 
 the same hole. 
 
 A zone system of signals, based upon the above principles, was 
 designed by the writer and was installed at the mortar battery at 
 Fort Monroe for test by the Coast Artillery Board. It worked so 
 well that it was afterwards adopted bodily and a description of it 
 was published as a Signal Corps fire-control mimeograph. 
 
Chapter IX. 
 DRYNESS, HEATING, AND VENTILATION. 
 
 DRYNESS. 
 
 It might appear that the subjects to be jomtly considered in this 
 chapter are sufficiently distinct and are sufficiently important to 
 justify being treated in separate chapters. It has been found, how- 
 ever, that one of the most difficijlt things to prevent, in attempting 
 to keep magazines dry, is the condensation of moisture carried 
 into the emplacements as watery vapor in the air. Fiu-ther, it has 
 been shown that condensation can be much reduced by proper venti- 
 lation and by the application of artificial heat. It is, therefore, con- 
 venient to combine the treatment of these three subjects in a single 
 chapter. 
 
 Damage Done by Moisture. 
 
 The presence of water or moisture in the rooms, galleries, or maga- 
 zines of emplacements is always to be avoided if possible. Formerly 
 it was objectionable principally on account of its effect on powder. 
 More recently, however, it is to be avoided rather on account of the 
 damage it may do to machinery and of its effect on electrical instal- 
 lations. 
 
 Until the comparatively recent past about the only class of powder 
 used in seacoast defenses was the so-called black' powder. Not only 
 could wet powder not be ignited, but since black powder was a 
 mechanical mixture of certain ingredients and some of these ingredi- 
 ents were soluble in water, exposure to moisture was almost certain to 
 injure the powder. Even if the powder was thoroughly dried there- 
 after, it would usually be found that its strength had been impaired, 
 and the extent to which this impairment had gone was irregular and 
 usually indeterminable. 
 
 In those days, for transportation and storage, powder was usually 
 packed in barrels which were made as nearly water-tight as possible. 
 It was, however, occasionally necessary to open powder barrels and 
 imless extreme care was taken in refastening those barrels that had 
 been opened, the powder was subject to injury, some of its ingredients 
 being hygroscopic and having a tendency to absorb moisture from the 
 air, especially when the atmosphere was nearly or completely satu- 
 rated. For the above reasons, great care was necessary in keeping 
 these older powder magazines dry. 
 173341—20 15 (225) 
 
226 
 
 The powder now used is a chemical combination rather than a 
 mechanical mixture. Usually the powder contains volatile ingredi- 
 ents, and for this reason it is considered essential that it be trans- 
 ported and be stored in hermetically sealed cases. Into the cases 
 moisture can not penetrate. Consequently, in so far as the effect 
 upon the powder is concerned, the presence of moisture in magazines 
 is less objectionable than it formerly was. 
 
 Existing emplacements, however, especially those built for larger 
 guns, contain trolley tracks, trolleys, and hoists or other machinery. 
 The iron or steel parts of all such machinery are subject to injury 
 from rust, and although most of the exposed surfaces can be pro- 
 tected by being kept painted or covered with grease, yet it is almost 
 impracticable to entirely protect those surfaces where wear takes 
 place in actual use. 
 
 Electricity, also, is used in emplacements of all sizes, in connection 
 with the lighting, power, and telephone systems. Moisture is a fre- 
 quent source of electric leakage, grounds, and short circuits. In 
 general, of course, electric leakage is so small that the loss is almost 
 inappreciable in circuits receiving their power from dynamos and in 
 occasional use only; but when the source of power is a storage bat- 
 tery, the slow and continuous leakage due to moisture has not infre- 
 quently been the cause of running down the battery and of consid- 
 erable injury thereto. 
 
 By the use of properly insulated wires and cables, the leakage, in 
 general, can be kept within reasonable bounds, but on switchboards 
 and in electric switches and fixtures leakage is somewhat difficult to 
 avoid if moisture be present. Grounding and short circuits must, of 
 course, be avoided, especially in magazines or in galleries where 
 powder is handled, for it is possible that a spark, due to a short 
 circuit, might ignite the powder. 
 
 Another serious source of damage due indirectly to the presence 
 of moisture is the damage to the insulation of electric cable caused 
 by seep water. It has been found that water seeping through masses 
 of concrete dissolves and carries with it certain elements which are 
 very injurious to the lead coverings and even to the rubber insulation. 
 Care must, therefore, be taken to prevent seep water from falling 
 on or passing over wires and cables. 
 
 Although, as stated, the effect of moisture upon powder is no longer 
 to be feared, yet on account of the effects of moisture upon the electric 
 and mechanical systems, it is fully as important now as it ever has 
 been to keep moisture out of emplacements. 
 
 Sources of Moisture. 
 
 Water may get into the galleries and magazines of emplacements 
 in several ways. 
 
227 
 
 (a) It may come in through the drainage systems designed to carry 
 water away, either by the clogging of the system or by the backing 
 up of water due to storms and tides. 
 
 (6) It may come in by seepage of ground water through the walls 
 or floors of emplacements where such emplacements have been built 
 in excavation below the level of the ground. 
 
 (c) It may come in in the form of rain or melted snow, absorbed in 
 the surface of the concrete from above and working its way by seepage 
 through the mass. 
 
 (d) It may come in the form of moisture carried in the atmosphere 
 and deposited by condensation on the ceilings, walls, or floors, or upon 
 articles stored in the emplacement. 
 
 Since the methods for preventing the entrance of moisture differ 
 to a considerable extent according to its source, each of these sources 
 of dampness will be treated separately. Furthermore, the treatment 
 will, in general, be divided according to the means which should be 
 applied in new emplacement construction, and to such means as may 
 be available for stopping the trouble in old and existing emplacements 
 in the original construction of which proper precautions were not 
 taken. 
 
 Drainage. 
 
 Rain, of course, falls upon the roofs of batteries and upon other 
 exposed places such as the loading platforms, sidewalks, etc. Snow, 
 likewise, falls on such surfaces and eventually melts. Furthermore, 
 it is not infrequently necessary to cleanse off the floors of the plat- 
 forms and sometimes of the interior rooms, either by rinsiug them 
 with water carried in buckets or by turning the hose on them. 
 
 It is evidently desirable that water, whatever may have been its 
 origin, should not be allowed to stand on the floors. Consequently, 
 drainage slopes are always provided in the granolithic floor finish, 
 not only of out-door platforms and sidewalks but also in the floors of 
 interior rooms, magazines, galleries, and corridors. 
 
 The steepness of this drainage slope should, of coiu-se, depend upon 
 the circumstances of the particular case; upon the area to be drained 
 and the amount of water which may be expected. The slope should 
 in aU cases be as great as may be necessary for easy drainage, but 
 frequently considerations other than those connected with drainage 
 put a limit to these slopes. 
 
 Especially is this true where projectiles and other material have 
 to be trucked over floors of galleries or platforms. In such cases it 
 is desirable for easy trucking that these surfaces be made as nearly 
 level as possible and that the drainage slope be reduced to a minimum. 
 
 On large surfaces and on sidewalks a slope as great as one-half 
 inch to the foot is used quite frequently, but this is about as steep as 
 is ever required for drainage purposes only, and where steeper slopes 
 
228 
 
 have been used in emplacement construction it has been not to aid 
 drainage but in order to overcome differences of level between the 
 floors at two parts of the emplacement. 
 
 Of course, in the interior of magazines the direction of the drainage 
 is usually toward the outlet. Thus the floors of rooms usually slope 
 toward the doors. In small rooms this slope is, for convenience, 
 made in a single plane, except in cases where the door is located in 
 the middle of one wall and occupies but a small percentage of this 
 side of the room; here the floors near the door are sloped toward the 
 door, and flat valleys sometimes occur at the junction between the 
 different planes, in the larger rooms the drainage slopes are some- 
 what more complex. Usually they are such as to cast the water from 
 the center of the floor toward the walls. Sometimes the floors slope 
 two ways, with a ridge down the middle, and sometimes even toward 
 the four sides. Occasionally, however, the floors are made to slope 
 toward the center line, which is finished as a sort of flat valley. 
 
 The floors of galleries, corridors, passageways, etc., are usually 
 sloped to a gutter at one side. Frequently they are made to slope 
 both ways to gutters on both sides, and occasionally the slope is 
 lengthwise of the corridor or gallery, with no gutter on either side. 
 
 Loading platforms, as a general rule, are made to slope outward, 
 the highest portions in small barbette emplacements being at the 
 base ring, and, in the larger emplacements, at the top of the steps 
 leading down to the gun well. 
 
 The sidewalks in the rear of batteries, as a rule, slope to the rear 
 and are finished with curbs and gutters such as are found in city 
 streets. 
 
 Gutters. 
 
 Occasionally, as in the loading platform of the typical 6-inch 
 disappearing battery (Plate XI), the drainage slopes are made con- 
 tinuous to the edge of the platform and the water is allowed to run 
 down over the edge. Usually, however, the water cast off by the 
 drainage slopes of floors and platforms is collected in gutters along 
 the edges; that is, along the walls of- rooms and galleries, the side 
 walls of loading platforms, and along the rear of the loading plat- 
 forms. (Plate XXII.) 
 
 These gutters vary in size from 2 or 3 inches in width and 1- inch 
 in depth, the usual size of gutters around the walls of rooms, up to a 
 width of from 4 to G inches and a depth of 3 inches for gutters which 
 carry more water. In special places, where an accumulation of 
 water occurs, the gutters are made much larger so as to be almost 
 like city gutters, jn some localities subjected to tropical rains 
 drains as large as a foot or more in width and a foot or so in depth 
 have been found to be necessary. 
 
229 
 
 Drainage slopes are, of course, necessary in the bottoms of gutters. 
 Such slopes usually ^tary from one-quarter inch to a foot up to one- 
 half inch or more to a foot. 
 
 The design of the gutter system should, of course, be given careful 
 consideration. The gutters should be placed so as to interfere as 
 little as possible with the movements of the personnel. This requires 
 that in rooms and galleries they be placed verj- close to the walls, and, 
 where they pass in front of doorways, that door sills be built across 
 the gutter, the water being passed through by pipes built through 
 or under the door siU. • n such cases, of course, arrangements should 
 be carefully made so that water does not accumulate where the 
 gutter enters or leaves the pipe through the sill. 
 
 in a few cases where gutters of considerable size have to run for 
 considerable distances under walks which are in frequent use, iron 
 gratings over such gutters are essential so that they may periodically 
 be cleaned out. 
 
 Sumps, 
 
 As a rule the gutters are so designed as to carry the drainage to 
 sumps, whence the water is carried away by pipes which extend 
 either vertically downward or nearly horizontally under the floors. 
 In the smaller batteries there are, as a rule, no sumps within the 
 emplacement proper, but in the larger ones minor sumps within the 
 limits of the emplacement are not infrequent. These interior sumps 
 must, of course, be drained either into the larger gutters at the rear 
 of the emplacements or to larger sumps outside. To prevent, or at 
 least delay, the clogging up of sumps and of the drain pipe leading 
 from them, it is well to have the sumps built fairly deep, with the 
 bottom of the sump several inches below the bottom of the outlet 
 pipe. This allows quite a little space at the bottom of the sump in 
 which sand can accumulate, and if these smnps are cleaned out with 
 sufficient frequency, the sand and debris can never rise up to the 
 level of the outgoing drain and thus clog the drain pipes. (See 
 detail on sheet 6, mimeograph 109.) 
 
 Of course, sumps so constructed will frequently have water stand- 
 ing in them, and to prevent these little pools from becoming breeding 
 places for mosquitoes the sumps should be covered, below the 
 regular grating, by a sheet of copper mosquito screen. 
 
 The drainage from the interior sumps in one-story emplacements, 
 or from the sumps in the lower story of two-story emplacements, 
 must usually be carried away by pipes laid under the floors, but from 
 the upper story of two-story emplacements this drainage can very 
 frequently be carried directly downward into the gutters on the lower 
 story. For instance, the drainage from the sumps of the gutters on 
 the sides and front of the loading platforms is frequently carried 
 directly do.wnward by means of pipes into the air spaces beneath. 
 
230 
 
 and thence by pipes along the walls of these air spaces into the 
 gutters on the sides of the floors of these air spaces. 
 
 The portion of the drainage of the loading platform that goes to 
 the rear is sometimes allowed to run completely to the rear of the 
 emplacement and thence over the edge of the step, as has been noted 
 in the platforms of the 6-inch emplacements (Plates IX, X, and XI, 
 and mimeograph No. 59). In the larger two-story emplacements, 
 however, it has been found that this rain water, running over the 
 rear of the loading platform and falling down along the rear of the 
 corridor of the lower story, is objectionable. It is now customary, 
 therefore, to catch this drainage in a gutter built along the rear of 
 the platform and to drain this gutter at proper intervals by pipes 
 passing directly downward through the concrete to downspouts 
 attached, as a rule, to the columns along the rear of the corridor. 
 
 Whatever arrangements may be made for the drainage of the 
 sumps, care must be taken in all cases that these drain pipes be made 
 fairly straight and that, wherever possible, the outlets be placed so 
 that they can be reached. These outlets are, therefore, usually 
 located either in the face of the curb of the walk in rear of the battery, 
 or in the walls of the large sumps. It is also well to make these 
 drain pipes larger than might be necessary merely for drainage pur- 
 poses, in order that in case they should become clogged up in any way, 
 it may be possible either to work a rod or wire through them, or even 
 to wash them out with a small hose. When the drain pipes are very 
 long, it is well to provide, at suitable intervals, hand holes or other 
 arrangements for cleaning out the drains. 
 
 Drainage of Stairways. 
 
 Stairways, whether the treads be of concrete or iron, should also 
 be given a drainage slope. In general, it is desirable that the treads 
 never be made strictly horizontal but be given slight slopes so as to 
 tend to keep the water running down the steps. 
 
 If the treads of steps be made strictly horizontal or slope the wrong 
 way, rain water has a tendency to accumulate on them. This is not 
 only disagreeable to people who have to use these steps, but in the 
 winter and spring it tends to increase the accumulation of ice on these 
 steps and, therefore, to make them unduly dangerous. A place where 
 this difficulty is noticeably present is the steps of the State, War, 
 and Navy Building in Washington. Whether this is due to faulty 
 design, or to the fact that the building, and therefore the top of the 
 steps, have settled more than the bottom of the steps, and have thus 
 reversed the slopes of the treads, is not clear. 
 
 Drainage of Gun Wells. 
 
 In some of the older disappearing emplacements where the gun 
 wells were small, it was not imusual to use these gun wells to some 
 extent as intermediate sumps by turning into them an unnecessary 
 
231 
 
 amount of drainage. As the gun wells became larger and deeper, 
 their bottoms were thrown down so low as to make their direct 
 drainage difficult and steps were always taken to keep as much water 
 as possible from getting into these wells. Thus the loading platforms 
 were so built as to always slope away from the guns and thus dirert 
 the drainage of the loading platform away from rather than toward 
 the gun wells. Water falling on the steps around the guns must, of 
 course, be drained inward toward the gun wells and eventually passes 
 downward over the curb of the loading platform level to the base 
 ring level. This base ring level was frequently drained into the gun 
 well itself and Ordnance Department platform sheets even now 
 sometimes indicate this method of drainage. Generally, however, it 
 is better not to do so, and in the larger and more recent emplacements 
 an annular gutter has been built on the base ring level to catch all 
 the water which may fall to this level. At convenient places around 
 this gutter sumps have been provided from which pipes lead diag- 
 onally downward and outward, carrying this drainage water into 
 the air spaces around the outside of the gun blocks and not into the 
 gun wells. (See mimeograph 109, sheet 7.) 
 
 The gun wells in the 14-iach and 16-inch disappearing emplace- 
 ments of recent design are so deep, and the sites selected for the 
 batteries have frequently been so low, that in several cases the 
 bottoms of the gun wells have been placed well below sea level. 
 Natural positive drainage for such gun wells is, therefore, impossible, 
 and it has been necessary to provide pumps for this piirpose. With 
 care in constructing the gun blocks the seepage of ground water into 
 these gim wells should be avoided, but rain falling actually on the 
 gun and carriage and water used for washing the gun and carriage, 
 of course fall into the gun well. In the floor of the gun well, there- 
 fore, a sump has been provided in which this water accumulates. 
 Along the route of the passageway leading into the gun well, a little 
 pump room has been built and, by means of pumps placed in these 
 pump rooms, the removal of the water is easy and simple. In general, 
 as has been stated, .the water to be removed is rain water only and 
 the quantity usually is not so great as to prevent it from easily being 
 removed by hand pumps. Power pumps, therefore, are not con- 
 sidered necessary for this ptu-pose. (See Plate XXV.) 
 
 General Drainage. 
 
 The general principles of the drainage of emplacements, and for 
 that matter, of other fortification structures, have been laid down 
 above. The matter is extremely simple in its principles, and in 
 small structm-es it is simple in practice, but in the larger and more 
 complicated types of emplacements, the whole subject of drainage and 
 especially the fixing of the slopes of the floor is not as simple as at 
 first sight it might appear. The floor levels in many places are fre- 
 
232 
 
 quently kept within close limits by considerations not connected 
 with the drainage system^ Thus the ceiling levels are frequently 
 fixed by the heights of trolley rails, the ceiling clearance of the room 
 by the character of the material to be stored in the magazine, arid 
 thus it is not possible to raise the floors of certain rooms to the levels 
 necessary to make the drainage simple. 
 
 Frequently, also, reverse slopes are necessary in various galleries 
 and corridors, all of which must be taken into consideration in the 
 design of the drainage system. 
 
 For the ordinary student, it is not necessary to go into such details, 
 but it is suggested that before the inexperienced officer undertakes to 
 design the drainage slopes of emplacements, he should give careful 
 study to the expedients already successfully adopted; examining 
 carefully the mimeograph sheets showing the drainage sheets of 
 typical batteries and the drawings of a few of the more complicated 
 batteries where difficulties arose, such as the drainage systems of 
 batteries Webb, Warren, and Mower, Panama Canal fortifications. 
 
 Drainage and Sewage to be Kept Apart. 
 
 In this connection one thing is of especial importance, and that is 
 that the ordinary water draining from a battery must be kept en- 
 tirely separate and distinct from the sewerage system, not only 
 within but also without the battery. 
 
 Failures in Drainage Systems. 
 
 The seashore of the Atlantic and Gulf coasts of the United States, 
 where many of the early emplacements were built, is generally- veiy 
 low, flat, and saijdy. The sand is very porous, rain water seeps into 
 it rapidly, and consequejitly, in many cases, the Engineer officers 
 who designed these early emplacements thoiight that it was un- 
 necessary to provide complicated drainage systems to carry away 
 the water from batteries, and that all that it was necessary to do was 
 to have the drain pipes extend from the sumps downward into the 
 sand. This was almost always the character of drainage provided 
 for the larger sumps in the rear of batteries, and sometimes even of 
 the minor sumps in the interior of the emplacements. It was the 
 usual method of draining gun wells, the bottoms of which were 
 quite low. 
 
 For a time this system of drainage worked fairly well, but in almost- 
 all cases it was found eventually that these pipes down into the sand 
 became clogged up, partly due to the carbonate deposited by seep 
 water, and, to a much greater extent, to waste oil from the machinery 
 and gun carriages. The result was that the sand below these sumps. 
 in time became almost impervious to water. To remedy this, attempts 
 were made to break up the hardened sand by driving down bars, 
 but this was a temporary expedient only. EveiltuAlly, in practi- 
 
233 
 
 cally every case, positive drainage from these older sumps has had 
 to be provided, sometimes at considerable expense, as it frequently 
 required the cutting of long drainage openings through several feet 
 of concrete. 
 
 Fortunately, the difficulties of keeping open such indirect drainage 
 systems were noticed in the early days and all batteries built subse- 
 quently have been provided from their inception with positive 
 drainage. In the future, therefore, the matter will probably be of 
 interest merely historically and as something to be avoided. 
 Stoppages. 
 
 Sand, earth, fragments of waste, trash, etc., are apt to accumulate 
 on the floors of the rooms and platforms of batteries. Periodically 
 these are swept away by members of the detachment in charge of the 
 battery, and unfortunately the gutters and especially the sumps have 
 been found very convenient places into which to sweep this material. 
 In fact, the writer has seen a battery mechanic using the end of his 
 broom handle to jam into the end of a downspout, material which 
 could not otherwise be packed therein. It is needless to say that 
 the smnps and downspouts can easUy be clogged up in this way. 
 
 Occasionally complaints have been made to Engineer district 
 officers that certain drainage pipes of emplacements had become 
 clogged up, and an intimation has been given that it was due to 
 defect in design, when the facts were that the clogging had been due 
 solely and entirely to the improper use of these drainage pipes and 
 sumps as deposit places for sweepings. The fault, therefore, instead 
 of being with the Engineer Department, has been the lack of disci- 
 pline in the detachment. 
 
 The instructions issued for the care and maintenance of emplace- 
 ments always should, and generally do, state clearly and distinctly 
 that all sand, fragments of waste, and sweepings should be carefully 
 gathered up and be removed by hand from the battery, and should, 
 under no circumstances, be swept into gutters or sumps. These 
 nstructions should be rigidly enforced. 
 Reversals in Drainage Due to Settlement. 
 
 The heavy masses of concrete of the parapets and in front of maga- 
 zines, of course, weigh more per square foot of horizontal area than 
 the rear parts of emplacements where there are rooms and galleries. 
 Where the foundations of batteries have not been above reproach, 
 due probably to the existence of mud substrata under the sand, the 
 inevitable settlement has gone on irregularly, the heavier front 
 portions of the emplacements settling more than the rear portion. 
 Of course, this difference in settlement has not been great, but it has 
 in many cases been sufficient to overcome the slight drainage slopes 
 of only one or two per cent originally given to the platforms and 
 
234 
 
 gutters. After the settlement of such batteries, the loading plat- 
 forms, instead of shedding their drainage water to the rear, have had 
 a tendency to throw it forward against the front walls of emplace- 
 ments,' whence it has in some cases been able to find its way into thr 
 rooms and the magazines below. 
 
 In such cases it has been necessary to hollow out gutters along the 
 front edges of these loading platforms a few inches from the front 
 walls and to carry these gutters sideways and thence backward along 
 the side walls until the drainage water can be disposed of. 
 
 Storm Tides and Floods. 
 
 As a rule our seacoast emplacements have been built along the . 
 seashore and except in a few cases, such as the forts near the mouth 
 of the Mississippi River, their drainage has been little interfered 
 with by river floods". 
 
 However, along the exposed beaches of the South Atlantic and 
 Gulf coasts, our fortifications are directly exposed to the very high 
 tides accompanying storms and great damage has been done by 
 such storms. 
 
 Perhaps the worst trouble of this kind has occurred in the defenses 
 of Galveston, where the level of the water in the harbor during one 
 or two of the very noticeable storms of the past few years, has risen 
 to an elevation of fifteen feet or so above the mean low water level ;' 
 that is, to several feet above the level considered proper for the maga- 
 zine floors when the older batteries were designed. The magazines 
 and galleries of the first floor have, therefore, been flooded to a level 
 of 2 or 3 feet, partly by water backing up through the drainage sys- 
 tem, but more generally by the high water which covered to a con- 
 siderable depth the parade grounds in the rear of the battery. 
 
 It is, of course, highly desirable that the floors of rooms, galleries, 
 and magazines of batteries built on the seashore should be above any 
 possible reach of high storm tides, and sufficiently above any storm- 
 tide level to admit the installation of a complete system of positive 
 drainage for all parts of the batteries, except possibly the gun-wells. 
 Where any doubt exists as to whether this has been done in the older 
 batteries, it is well to raise the parade grounds around the battery 
 completely above any possible level of storm tides, and if positive 
 drainage has been provided, to place check-valves in these drains so 
 that water can not flow backward through them. 
 
 If this be done, it ought to be possible to keep the batteries from 
 being flooded even though the actual level of the floors may be below 
 the level of the storm tides. Such storms are usually not of long 
 duration, the seepage of water through the ground into the battery 
 will be slow, and such water as does seep through or work back 
 through the drainage system or accumulate in the battery due to 
 
235 
 
 the heavy rains which usually accompany such storms, can ordinarily 
 be kept out by pumping or even by bailing. 
 
 In general, in our middle and South Atlantic and Gulf coasts, it 
 would appear that 10 feet above high tide level should be sufficiently 
 high for the magazine floors and in a number of places magazines 
 have existed at lower levels than this for many years without any 
 trouble being experienced. This question, however, is in all cases 
 one to be decided by local conditions, and usually where fortifications 
 are likely to be needed, there are records available to the designing 
 «ngineer which should give some clear indications as to how high it is 
 necessary to build the floors of batteries. 
 
 Ground Water. 
 
 In a few localities in Xew England and on the Pacific coast, bat 
 teries have been built where econonaic conditions or conditions con- 
 nected with concealment have required that the magazines of bat- 
 teries be built in excavation. In some cases these excavations have 
 placed the floors of the magazines several feet below the natural 
 siu^ace of the ground and below the level where the ground water 
 xisually stands, at least at certain seasons of the year. 
 
 Where such conditions exist, care must always be taken, and 
 always should have been taken, to see that means of escape for this 
 ground water are provided. The outer surfaces of the side walls 
 should be waterproofed and against them should be placed porous 
 layers, either of tile or of broken stone. Along the bottom of the 
 walls, porous tile pipes should be laid with slightly open joints em- 
 bedded in a mass of broken stone. These tile pipes should lead to 
 sumps outside of the battery and should be made of sufficient size to 
 carry away ground water as fast as it can 'accumulate. These tile 
 pipes, taken in connection with the waterproofing of the wall surface 
 and the porous tiles against the walls, should prevent the accumula- 
 tion of water against these side walls whence it might seep into the 
 battery. 
 
 There have been cases in the older batteries where water has 
 seeped up through or around the floors of the rooms. It was custom- 
 ary to build the walls of the room first, leaving the floor space bare. 
 These floors were subsequently filled up by earth or gravel to bring 
 them approximately to the proper lev^ei, and the granolithic floor was 
 then put in place. In such cases, when the level of ground water 
 rose up iiigh enough, water has seeped up through the cracks between 
 the floor and the walls. Such occurrences have been rare, but the 
 possibility should be kept in mind in future battery construction, 
 and sufl&cient arrangements for ground-water drainage should be 
 inade to prevent it. 
 
236 
 
 Seepage. 
 
 Rain and snow fall upon the upper surface of an emplacement 
 whether this surface be composed of earth or of concrete. This rain 
 water and melted snow must, of course, be disposed of. In order 
 to encourage the rapid running away of this water, drainage slopes 
 are always provided, but frequently, for reasons not connected with 
 drainage, it is necessary to make concrete surfaces very nearly flat. 
 Water falling on such surfaces drains away slowly, and before this- 
 has happened some portions of it may he absorbed into the concrete- 
 mass, through the very fine cracks called "hair cracks" and through 
 the larger settlement cracks. Water once entering concrete in this- 
 manner works its way downward and may eventually appear in the 
 interior of a battery as seep water. 
 
 Not only is seep water in a battery objectionable from its wetness, 
 but it has been found also that seeping water dissolves carbonates 
 in its passage through the concrete, and after the water enters the 
 interior of the battery and begins to evaporate, the carbonate is 
 precipitated and becomes visible in the form of stains upon ceilings 
 and walls and occasionally in the form of stalactites or stalagmites. 
 Such deposits are objectionable on account of their appearance, and 
 it has also been found that seep water is exceedingly destructive to 
 the lead covering of electric cables, to some extent to the rubber 
 insulation, and also occasionally to the felts and tars used in water- 
 proofing. , ^ 
 
 The concrete of the earlier fortifications was made with Rosendale 
 cement and was usually mixed very dry as was the custom in those 
 days. Such concrete; therefore, was quite porous, and seepage 
 through it was exceedingly plentiful. This trouble has, to a large 
 extent, been corrected in the later batteries b}' the use of Portland 
 cement only, and by improvements in the manner of mixing and 
 placing the concrete. Settlement cracks have been lessened by 
 greater care in preparing foimdations, and by leaving "planes of 
 wealaiess" at convenient places, so that the formation of cracks 
 which appears to be inevitable will occur only at places where expected 
 and where no harm will be done. 
 
 This entrance of seep water to the magazine can be controlled at 
 three places: 
 
 (a) By stopping it at the exterior surface and preventing it from 
 entering the concrete; 
 
 (I) By stopping it and diverting it away by means of an interrtiedi- 
 ate waterproofing layer; 
 
 (c) Or by stopping it and disposing of it as it tries to enter the rooms 
 and galleries. 
 
237 
 
 Exterior Waterproofing. 
 
 The method of preventing water from entering the upper and 
 exterior surface of the concrete depends to a considerable extent 
 upon whether or not this surface is to be exposed to the air or whether 
 it is to be covered by a blanket of earth. 
 
 Where there is no blanket of earth, and the upper surface of the 
 concrete is exposed to the atmosphere, the entrance of water can be 
 prevented, or at least greatly reduced, by giving to the concrete a 
 sufficient drainage slope; that is, by diverting the water away as 
 rapidly as possible and before it has a chance to seep in. 
 
 The next very important step is to make this upper surface of the 
 concrete as waterproof or as water resisting as possible. 
 
 It has been found that when the concrete surface is made quite 
 rich in cement and is properly manipulated, it can be made practically 
 waterproof at first. Unfortunately, concrete is a poor conductor of 
 heat. Its surface, when exposed to the sun's heat and to the cool- 
 ness of night, is subjected to considerable variations in temperature, 
 with consequent expansions and contractions. The interior masses, 
 being subjected to much smaller temperature changes, are subject 
 to much smaller contractions and expansions, and, as a result, the 
 larger linear changes in the dimensions of the surface layer have a 
 tendency in time to cause hair cracks to form in this layer. Once 
 forntied, these hair cracks widen Mttle by little, extend deeper and 
 deeper into the concrete, and through capOlary action tend to draw 
 in seep water. 
 
 As an aid to reducing seep water, there was introduced some years 
 ago, at the suggestion of Col. (now Maj. Gen.) W. L. Marshall, a 
 layer of crossed steel bars (see mimeograph 109, sheets 2 and 4) 
 placed a few inches below the exterior surface. It has been found 
 that while these .steel bars do not absolutely prevent hair cracks 
 from forming, yet they are a great preventive to the enlargement 
 and spreading of these hair cracks. 
 
 Many attempts have been made to keep water out of concrete by 
 covering its surface with a waterproof layer. Tars, asphaltum, and 
 felt have been used for the purpose. The efficacy of tars and asphal- 
 tum in waterproo&ig depends upon their plasticity; that is, their 
 ability to expand and subsequently to contract under temperature 
 changes without losing their consistency and cohesion, and while 
 still retaining their waterproofing quahties. Unfortunately, it has 
 been found by experience that this plasticity, although lasting for 
 a considerable time, is not absolutely permanent. In time, either 
 due to the evaporation of volatile elements or to internal chemical 
 changes, this plasticity is lost to a considerable extent, and thereafter 
 tars and asphalts have a tendency to crack up, to separate from the 
 concrete beneath, and to scale off in small particles. 
 
238 
 
 These changes take place moFst readily where the tar and asphaltum 
 is exposed to the air and sun, and, consequently, where temperature 
 changes are greatest. When protected from the sun and air by a, 
 blanket of earth, the changes go on much more slowly, and where 
 layers of pine tar (as distinguished from coal tar) have been utilized, 
 the plasticity and waterproofing quahties of ttie tar would appear 
 to last almost indefinitely. Thus the writer has seen at Fort Monroe 
 the uncovering of some brick casemates over 50 years old. They 
 had been waterproofed with a thick layer of pine tar, over which was- 
 a layer of sand and earth sodded on the top. When the earth and 
 sand were removed, the tar was found to be so plastic that finger 
 prints could easily be made in it. Again, in the city of Washington, 
 in the destruction of an old building some few years ago, a cellar 
 was removed which extended well below the ground-water level and 
 which, nevertheless, had always been perfectly dry and free from 
 leakage. The waterproofing of this cellar consisted of thick brick 
 walls waterproofed on the outside by a thick layer of pine tar, while 
 under the floor was a layer of pine tar inserted between two courses- 
 of brick. 
 
 For waterproofing purposes, pine tar seems to retain its plasticity 
 much longer and, therefore, to be preferable to coal tar. It was 
 stated to the writer some years ago by a chemist that this was prob- 
 ably due to the comparative absence of sulphur in pine tar and its 
 almost certain presence in coal tar, this sulphur eventually causing 
 a chemical change in some of the other components of the tar which 
 were necessary to insure this plasticity. However, pine tar is now 
 almost unobtainable and coal tar will usually have to be used instead. 
 
 Many attempts have been made at various times to use asphaltum 
 for the purpose but though in most cases this asphaltum has worked 
 well for short times, it has never proved to be ^durable and it is 
 believed that experience" with it has been sufl&cient to prove its 
 unsuitability for this purpose. 
 
 • When concrete is to be covered by an earthen blanket, there is 
 usually no difficulty in making it thoroughly waterproof. It is 
 necessary merely to provide a proper drainage slope for the concrete,, 
 to cover it with a layer of tar, asphalt, or waterproofing felt, to pro- 
 vide outside of this a layer of porous tiles containing open passage- 
 ways which win permit any water to rapidly drain away, and to 
 provide sufficient drainage for this water when it has reached the foot 
 of the wall. With such an arrangement, seep water will ordinarily 
 not be able to enter the concrete. But should it be subsequently 
 found that there was any defect in the waterproofing, or should any 
 defect occur later and subsequent to the original construction, it is a 
 comparatively simple matter to remove the ea,rthen blanket to 
 correct the defect and then to replace the earth. 
 
239 
 
 In the chapter describing the general character of emplacements, it 
 was stated that the most modern designs provide for the covering 
 with earthen blankets of practically all of the concrete except the tops 
 of retaining walls, blast aprons in front of the guns, loading platforms, 
 and walks or passageways. Consequently, in such batteries, the 
 waterproofing is much simplified over the older types where the 
 concrete over the magazines and the traverses was exposed to the air 
 in practically horizontal planes. About the only place where diffi- 
 culty in waterproofing is to be expected now is in the rooms under 
 the loading platform in the few cases where the two-story type of 
 battery is to be built and such rooms are to be installed. 
 
 Attempts have been made many times to render exposed exterior 
 surfaces of concrete waterproof by painting them with some water- 
 proofing mixture. Ldnseed oil made more Hquid by the addition of 
 naphtha or gasoline has been tried but not with great success, espe- 
 cially siuce the linseed oil has occasionally a tendency to cause the 
 disintegration of the concrete. Occasionally, special patent prepa- 
 rations have been used for this purpose with apparent success for a 
 short time. 
 
 For the above reasons, it is thought by the writer to be better in 
 future construction not to resort to any of these patent preparations 
 but to rely for the water-tightness of the concrete upon a rich and 
 carefully floated surface, upon a cross-layer of reinforcing bars a few 
 inches below the surface to prevent the seepage cracks from growing, 
 and to then install somewhere within the mass of the concrete an 
 interior waterproof surface as will hereinafter be described. 
 
 The above remarks relate, of course, to new construcjtion only, but 
 frequently in the past the engineer has been confronted with the 
 problem of stopping seepage water in older batteries and many 
 different solutions have been attempted. 
 
 In a number of cases the seepage can be traced to a few very 
 noticeable cracks on the surface, and the method of cming this has 
 generally been to cut out the sides of the cracks until they are suffi- 
 ciently large for the ptupose, to thoroughly clean the new surfaces from 
 dust and dirt, to paint these surfaces with tar apphed hot, and then 
 to fill the cracks with an elastic compound which will not flow in 
 hot weather and wfll still retain its pltisticity in cold weather. Tar 
 as a rule has not been foimd to be durable for this purpose. Asphalt 
 has proved a failure. Webster cement is said to last better. 
 
 In some cases an attempt has been made to cover an entire loading 
 platform through .which there was considerable seepage into the 
 rooms below, with a regular asphalt covering. Usually this experi- 
 ment has resulted in failure as it has been found that wherever the 
 asphalt is made sufficiently plastic to remain uncracked in cold 
 weather it becomes so soft in hot weather that the wheels of the 
 
240 
 
 heavy trucks sink into it and, consequently, the labor of moving the 
 trucks is very much increased. 
 
 Intermediate Waterproof Surfaces. 
 
 The use of an intermediate -waterproof surface to prevent seep 
 water from entering the rooms, galleries, and magazines of emplace- 
 ments is an invention of Maj. (now Maj. Gen.) W. L. Marshall, Corps 
 of Engineers. The theory upon which its use is based is as follows: 
 
 Where concrete surfaces are exposed to great extremes of heat and 
 cold and, therefore, to extremes of expansion and contraction, the 
 formation of cracks appears unavoidable and these cracks, once 
 formed, have a tendency in time to extend farther and farther into 
 the concrete mass, at least as far as the concrete is monolithic. 
 
 Within the concrete mass temperature changes and, therefore, 
 expansions and contractions, are much smaller than at the surface and 
 take place so much more slowly that temperature cracks are not apt 
 to form. If, therefore, within the mass of the concrete we can pro- 
 vide a waterproof surface, and can so separate it from the exterior 
 concrete that cracks can not be transmitted to it, this interior 
 surface should remain waterproof practically indefinitely. 
 
 Gen. Marshall therefore proposed to provide within the interior 
 of the mass a properly drained waterproof surface and to separate 
 it from the concrete above it by a layer of sand 'and fine gravel 
 through which a crack could not be transmitted. That is, he pro- 
 posed to make a waterproof surface and to provide it with proper 
 drainage slopes leading to drains which would carry the water away 
 where it can do no harm. When thoroughly hardened this water- 
 proof surface Was to be covered by a layer several inches thick of sand 
 and of fine gravel through which, of course, the water could percolate 
 and drain away. Above the sand and gravel he proposed to install 
 a stratum of concrete made very lean in cement and mixed so dry 
 that no cement water would leak from it to the sand and gravel be- 
 low it. Above this dry layer of concrete he again started his regvilar 
 concrete construction and continued it to the outer surface. 
 
 Being protected from sudden temperature changes this interior 
 surface should remain uncracked indefinitely, and any water that 
 might seep to it will be diverted away by it in the direction to which 
 drainage is provided and pass off through the sand until the drain 
 pipe is reached. 
 
 In construction, the concrete near this interior waterproof surface 
 is made quite rich in cement, and the surface is very carefully treated 
 and floated so as to be thoroiighly waterproof. To prevent any 
 hair cracks developing, as the surface hardens, and before construc- 
 tion work can be carried further, it must be carefully protected 
 during the hardening process. As an aid to this it has been found 
 desirable, especially in the tropics, to allow the hardening to take 
 
241 
 
 place under water. That is, the regular means of drainage is tem- 
 porarily plugged up and as soon as the initial set of this surface has 
 been obtained, water is allowed to flood slowly over the surface and 
 to rise to a sufficient depth to cover it entirely. The concrete thus 
 gets its final set and does its hardening under water. After some 
 three or four weeks have elapsed, the water is allowed to run oflF and 
 the surface to dry. WMle drying it must be exposed, of course, to 
 the atmosphere, but must be kept thoroughly protected from the sun. 
 After it has dried the surface is ready for the layer of sand, gravel, etc. 
 
 Gen. Marshall did not consider that the addition of tar or felt to 
 this surface was necessary, but in most recent cases the constructing 
 officers have painted the waterproof surface with tar and covered it 
 with felt immediately after it had become thoroughly dry, thus 
 providing an additional precaution. 
 
 Where an intermediate concrete surface is to be built in a battery, 
 there is one possible source of trouble which should be kept in mind 
 by the designing officer, and that is the tendency which has occa- 
 sionally been shown for an over-lying mass of concrete, under the 
 influence of continuous temperature changes, to move bodily but 
 slowly over an underlying stratum, where the two are separated by a 
 comparatively smooth and nearly horizontal joint. The separating 
 stratum of sand, between the waterproof surface on the one hand, and 
 the mass of concrete above it, could easily permit such a bodily move- 
 ment. Such a movement might, therefore, be expected to take place 
 in time if means are not taken in the beginning to prevent it. 
 
 Stopping Seep Water as it Tries to Enter Rooms or Galleries. 
 
 A problem of this kind should present itseK in the future only in the 
 case of the older batteries, for if an emplacement has been properly 
 designed and constructed the entrance of seep water will have been 
 prevented by one of the methods mentioned above or the seep water 
 will be diverted by an intermediate waterproofing surface such as 
 has just been described. 
 
 There are, however, a number of our older batteries where proper 
 care was not taken at the time of construction, and where seep water 
 enters the room and must be stopped or carried away as it does enter- 
 Fortunately, however, all of these poorly designed and constructed 
 earlier batteries have already or will shortly become obsolete. 
 
 The first and simplest method which suggests itself is, of course, to 
 paint the wall surface with some water-repellent substance applied as 
 an emulsion or as a paint. There are a number of widely advertised 
 substances on the market for doing this. The method has been tried 
 m.any times, and at first, in a munber of cases, has appeared to work 
 well. It has in fact worked weU for an indefinite period in some few 
 173341—20 16 
 
242 
 
 cases where the hydraulic pressure never became great. In general, 
 however, when the seep water has been unable to enter the room on 
 account of the substance applied" to the wall, it has backed up in the 
 cracks or paths through which it seeped uutil the hydrauHc pressure 
 has become so great that the water began again to make itself ap- 
 parent at the same place as before, in spite of the water-repellent 
 application, or showed itself in some other place, sometimes indeed 
 in the form of an increased amount of seepage at the other place. 
 
 The next step was to catch and carry away the entering water by 
 building what is practically an independent house in the old room or 
 magazines. Many fairly successful methods of doing this will be 
 found noted under the head "Technical details" in a number of 
 older annual reports of the Chief of Engineers. 
 
 Sometimes these interior rooms have had their own independent 
 walls separated from the original wall surfaces by air spaces, and 
 sometimes they have consisted merely of a roof. 
 
 These interior walls have usually been constructed either of brick 
 or timber; the roofs usually of timber covered by an impervious 
 surface such as felt or sheet metal. Sometimes the roofs have been 
 made of corrugated iron or copper without the timber. 
 
 All of these constructions, as long as they remained intact and in 
 good condition, have been fairly successful ia catching and diverting 
 the seep water, and incidentally, by providing thin walls surrounded 
 by air spaces, they have to a considerable extent reduced condensa- 
 tion. However, all these interior structures require space and reduce 
 the dimensions originally given to the room. In the older batteries 
 the rooms were barely large enough anyhow, and this reduction in 
 their dimensions has been quite serious, especially as regards ceiling 
 height or, as it may be called, "head room. " 
 
 Moreover, wherever timber was used for this purpose, it decayed 
 quite rapidly except where a very expensive quality of cedar was 
 used. Frequently, too, the timber or fiber used, not long after the 
 interior rooms were constructed, has become moldy, smelly, and in 
 many other ways objectionable. 
 
 In one case a characteristic difficulty occurred in connection with 
 an interior roof. This was in the mortar battery at Fort Monroe. 
 This battery is one of the oldest of the seacoast batteries constructed. 
 Rosendale cement was used ia its construction and the concrete was 
 exceedingly porous. Apparently the exterior surface of the concrete, 
 where it was covered by sand, was imperfectly waterproofed, for 
 before long large quantities of seep water appeared in the battery 
 after nearly every heavy rain, forming stalactites and stalagmites in 
 the rooms and galleries. 
 
243 
 
 Fortunately, this battery has been built with considerable head- 
 room, but the rooms were too narrow to permit any interior walls 
 to be built. Consequently, the method of damp proofing was to 
 construct an interior ceiling of corrugated copper, sloping from a 
 central ridge to small gutters which were cut in the side walls. These 
 gutters were drained at intervals through down spouts likewise cut 
 into the side walls. 
 
 At first, and for a number of months, this interior roofing was quite 
 successful, but finally, one by one, leaks b^an to appear at the joints 
 where the corrugated sheets lapped and soon increased rapidly until 
 they became very objectionable. Investigation showed that the 
 cause of the trouble was that the gutters and the down spouts had 
 become almost completely stopped up by the stalagmites deposited 
 by the seep water. The seep water, being in this way prevented 
 from passing out through the drainage system provided, backed up 
 until it appeared through the joints in the roof. To remedy this 
 trouble, it was necessarj- to remove portions of the roof and to clean 
 out the stalagmites from the gutters and spouts. This done, the 
 system again worked well, but the cleaning has had to be repeated 
 periodically. 
 
 Condensation . 
 
 Of all the moisture in batteries that brought in by the atmosphere 
 and deposited by condensation is the most difficult to combat. 
 
 The natural laws governing the carrving of watery vapor in sus- 
 pension in the atmosphere and the subsequent condensation of this 
 watery vapor, are really quite simple, yet they are quite frequently 
 misimderstood and many of the remedies which hare been suggested 
 have been such as to do more harm than good. 
 
 Natural Laws Governing Evaporation and Condensation. 
 
 Air possesses the abilitj- to pick up and carry in suspension within 
 itself watery vapor in a gaseous form. The weight of watery vapor 
 per cubic foot of air which can thus be canied depends on the tem- 
 perature of the air and increases rapidly with an increase in tem- 
 perature. This amount of vapor is shown in tables found in engi- 
 neering handbooks, which may be examined if desired. In general, it 
 may be stated that within the limits of ordinary atmosphei-ic tempera- 
 ture, say, from 10° to 100° F., a rise of temperature of 10° increases by 
 about 50 per cent the ability of the air to hold moisture in suspension, 
 while a rise of temperature of about 35° practically triples the amount 
 of moisture which the air can carry. 
 
 When the air contains within itself the maximum amount of watery 
 vapor which,- at its temperature, it is able to carry, it is said to be 
 "saturated." When it contains less, it is not saturated. The degree 
 of saturation is usually expressed in the form of a percentage, indi- 
 
244 
 
 eating the ratio between the actual amount of watery vapor present 
 and the maximum amount of watery vapor which the air at that tem- 
 perture can carry. 
 
 If a mass of air not fully saturated is brought in contact with or 
 passes over a pool of water or a wet surface, the air has a tendency to 
 pick up moisture from these sources, and this process will continue 
 either until all of the water has been evaporated or until the air has 
 become fully saturated. 
 
 If, on the other hand, for any reason whatsoever such as cooling, 
 the amount of water carried by the air becomes greater than it is able 
 to hold at its new temperature; or, as it is sometimes stated, the air 
 becomes temporarily supersaturated, the watery vapor present in 
 excess of that necessary for saturation will be given up by the air. 
 This moisture ceases at once to exist in the form of vapor and is 
 transformed into very minute drops of water. Where very numerous 
 these minute drops becpme visible in the form of fogs or clouds. 
 They have a tendency to slowly settle through the air and to be 
 deposited in the form of dew or condensation upon any convenient ob- 
 ject. When the cooling is due to the passage of the air over or along 
 cooler surfaces, the deposit usually and naturally takes place on these 
 surfaces. 
 
 Since the ability of the air to carry watery vapor in suspension 
 varies rapidly with the temperature, the percentage of saturation 
 may be changed by a change in the temperature of the air and without 
 the addition or subtraction of any watery vapor. If the temperature 
 be raised, the ability of the air to carry watery vapor increases ; that is, 
 the amount of water necessary for saturation increases and, conse- 
 quently, the proportion which the amount of watery vapor actually 
 present bears to that necessary for saturation is decreased and there 
 is thus a decrease in the percentage of saturation. Consequently, if 
 saturated air be heated, the percentage of saturation is reduced and, 
 as thus heated, the air possesses the abihty to take up and carry an 
 additional quantity of moisture. 
 
 If, on the other hand, the temperature of the air falls, its ability 
 to carry watery vapor is decreased, and the ratio that the amoimt of 
 watery vapor actually present bears to that necessary for saturation; 
 that is, the percentage of saturation, is therefore increased. If the 
 cooling be continued far enough, the ratio between the amount of 
 vapor present and that necessary for saturation will become unity, 
 and any further cooling wiU be followed by the deposit of moisture or, 
 as it is called, condensation. The temperature at which this occurs 
 is called the dew point. 
 
 From the above statement of natural laws we can now lay down the 
 fundamental rules to be used in designing means for reducing con- 
 densation in emplacements. 
 
245 
 
 Anything which sen-es to raise or to Iceep up the temperature of the 
 air, or of the surfaces with which the air is to come in contact, serves to 
 increase the ability of the air to hold moisture in suspension, and, there- 
 fore, tends to reduce condensation. 
 
 Anything which acts to lower or to Iceep down the temperature of the 
 air, or of the surfaces with which the air is to come in contact, serves to 
 reduce the ability of the air to hold moisture in suspension and tends to 
 increase condensation. 
 
 In other words, the prevention of condensation is largely a question 
 of raising or Tceeping up the temperature of our emplacement walls. 
 Loss of Heat. 
 
 We leam in our study of heat that, in general, heat can be added to 
 or taken away from objects in three ways, and in these ways only: 
 Radiation, conduction, and convection. 
 
 Radiation. 
 
 The temperatures of the ceiling and of different portions of the wall 
 surfaces of an emplacement are, under ordinary circumstances, so 
 nearly the same that any heat lost by radiation from one surface or 
 part of a surface is equalized by the radiation received from the other 
 surfaces. Consequently in the interior of emplacements radiation as 
 a source of warming or cooling may, for aQ practical purposes, be 
 neglected. 
 
 Conduction. 
 
 When the wall surfaces are cooler than the mass of concrete, heat 
 is conducted from the mass of concrete to the wall surfaces and the 
 temperature of these surfaces is raised. When the temperature of the 
 wall surface is above that of the mass of concrete, heat is conducted 
 from the surface to the interior and the surface temperature is reduced. 
 
 The former of these two conditions — that is, when the temperature 
 of the center of the mass is greater than that of the wall surface — 
 occurs only ditring the fall and early winter months when the tem- 
 perature of the concrete is greater than that of the air and there is no 
 tendency to condensation. Consequently at such times it is im- 
 material, so far as condensation is concerned, whether the mass of the 
 walls be a poor or a good conductor of heat. 
 
 On the other hand, in the spring and summer when condensation 
 difficulties are greatest, the temperature of the air, and incidentally 
 the temperature of the wall surfaces, is above that of the mass of the 
 concrete, and there is a constant tendency to a loss of heat from the 
 wall sm^aces by conduction into the interior of the mass. To reduce 
 condensation it is essential, according to the rules deduced above, that 
 the temperature of the wall surfaces be kept up as much as possible, 
 and consequently anything that tends to reduce the loss of heat by 
 
246 
 
 conduction tends to keep up the temperature of the wall surfaces 
 and to reduce condensation. We may, therefore, state the rule: 
 
 Efforts 'should he made to reduce the heat conductivity of the interior 
 walls, especially near the surfaces of the walls. 
 Convection. 
 
 The change of the temperature of the walls of an emplacement by- 
 convection goes on constantly, whenever there is a current of air 
 passing through the battery. If the air be cooler than ths battery 
 walls, the temperature of the walls is lowered by the loss of heat 
 absorbed by the air in its attempt to rise to the same temperature as 
 the wall surfaces. If the air be warmer than the walls of the battery, 
 then the walls are warmed by convection; that is, by heat given off 
 by the air not only due to the cooling of the air but also in the form of 
 latent heat due to condensation. This requires a discussion of the 
 natural laws relating to the property called "latent heat." 
 
 Latent Heat. 
 
 If a mass of water be slowly heated its rise of temperature will be 
 closely proportionate to the amount of heat added, and this will 
 continue until the boiling point is reached. Thereafter the addition 
 of heat will result in the change of water to the vaporous form of 
 steam, and no rise in temperature wiU occur until all the water has 
 been transformed into steam. In other words, the heat which is 
 added after the water has reached the boiling point results, not in 
 change of temperature, but in change of form. It has been found 
 by experiment that the amount of the so-called latent heat necessary 
 to transform any quantity of water into steam is very large, approxi- 
 mately 960 times the amount of heat necessary to raise the tempera- 
 ture of the same quantity of water 1° F. 
 
 In the cooling down the reverse process takes place. As heat is 
 given off by steam its temperature slowly decreases until the boiling 
 point is reached, then follows the condensation of the steam into 
 water, and during this condensation all of the latent heat which was 
 taken up in the process of boiling is given off. 
 
 When evaporation or condensation takes place at temperatures 
 below the boiling point, there is the same phenomenon of the absorp- 
 tion and giving off of latent heat as at the boiling point, and the 
 amount of latent heat per pound of water thus absorbed or given 
 off does not differ very greatly from that absorbed or given off at 
 the boiling point. 
 
 That is, in order that the evaporation of water may take place, 
 the adddition to the water of the latent heat necessary for vaporiza- 
 tion must take place, and this heat will be obtained by absorption 
 from the temperature heat of the remainder of the water or of other 
 substances with which the water is in contact. This is noticed in 
 the cooling which usually accompanies evaporation. 
 
247 
 
 On the other hand, whenever condensation takes place this 
 condensation is accompanied by the giving off of latent heat, which 
 thus becomes sensible and has a tendency to retard the cooling of 
 the air containing the moisture and to warm up the objects upon 
 which the moisture is condensing. Condensation of itself is, therefore, 
 not an unmixed curse, because it is necessarily accompanied by the 
 giving up by the watery vapor of the latent heat of vaporization. 
 Every bit of heat thus given out raises the temperatm-e of the wall 
 turfaces and by just so much diminishes the amount of condensa- 
 sion which will subsequently take place. 
 
 Although, as has been stated, moisture in emplacements is usually 
 to be avoided, yet there are places where it is much more objection- 
 able than at others. Near machinery and electric switchboards 
 condensation is to be avoided, but in corridors and passageways it 
 can ordinarily do but little damage, and in the air spaces of the most 
 modem types of batteries condensation can do no harm at all, while 
 the latent heat given off during the process of condensation is an 
 advantage. 
 
 Therefore, in order to encourage the warming of the battery walls 
 by convection, it is desirable to increase the circulation of air through- 
 out the battery whenever the outside air is warmer than the interior 
 wall surfaces, and to do this so that, if possible, condensation will 
 take place, not at points where it is objectionable, but at places 
 where it can do no special harm. To accomplish this our most 
 modem batteries have been designed with 2-foot air passages 
 around all the magazines and other principal rooms. (See Plates 
 XVII, XX, and XXII.) They communicate directly with the out- 
 side air in the rear and, by means of stairways, corridors, and ventila- 
 tors, with the front and side walls of the loading platforms. They 
 are provided with two separate systems of doors, solid doors to cut 
 off ventilation and grating doors which keep out intruders, while 
 still permitting ventilation. A proper use of these solid doors 
 requires that they be kept closed whenever the temperature of the 
 outside air is below that of the wall surfaces inside, but that they 
 be opened wide whenever the reverse'is true. Ventilation around 
 and through the battery is thus encouraged under conditions which 
 win slowly warm the battery up, and the inevitable condensation 
 takes place principally in the air spaces where it can do no harm 
 and where it in reality does good by warming up the wall surfaces 
 on which the condensed drops of water are deposited. 
 Wet and Dry Bulb Thermometers. 
 
 The fact that evaporation requires the addition of the latent heat 
 of vaporization is made use of in an apparatus used to measure the 
 dew point of the air, and therefore incidentally the degree of satura- 
 tion. As this instrument is in common use in our coast defenses 
 
248 
 
 and as the theory of its use well illustrates one of the laws govern- 
 idg condensation and evaporation, it may be well to briefly describe 
 it here. 
 
 This apparatus is known technically as the psychrometer, or in 
 more ordinary language as the wet and dry bulb thermometer. It 
 consists of two thermometers exactly alike mounted close together 
 on a portable stand. The bulb of one of these thermometers is 
 dry, the other is surrounded by a thin layeir of cotton or wick, which 
 leads from the bulb to a bottle or tube containing water, so that the 
 cotton aroimd the bulb is kept always moist. If the instrument be 
 kept stUl, especially in saturated air, these two thermometers wiH 
 read alike. When evaporation, however, is taking place the mercury 
 in the wet bulb is cooled by the evaporation of the water from the 
 cotton or wick and there is a difference in the reading of the two 
 thermometers. 
 
 When it is desired to use this instrument for measuring the dew 
 point it is taken to the place where the measurement is desired and 
 is rapidly swung round and round in the air. The motion of the 
 thermometer through the air causes evaporation from the cotton 
 cloth covering the wet bulb, and this evaporation cools off the mercury 
 in that biilb, the cooling process continuing as long as evaporation 
 takes place. Theoretically, this evaporation will not cease until 
 the temperature of the surface of the wet cloth, and, presumably, 
 therefore, the temperature of the mercury in the wet bulb, has been 
 lowered to that, which, with the amount of moisture actually present 
 in the air, corresponds to a condition of saturation. 
 
 The wet bulb will indicate the dew point of the air and recourse 
 to a table will show the amoimt of moisture present per cubic foot 
 of air. The dry bulb wiU continue to give the actual temperature 
 of the air, and the table will show the amount of moisture which 
 the air at that temperature is able to hold. The ratio between the 
 amount of moisture actually present and that which can be carried 
 at the temperature gives the percentage of saturation. 
 
 Extent and Character of Temperature Changes in Emplacements. 
 
 Modern emplacements, as a rule, are composed of large masses of 
 concrete, the walls and ceilings, for protective reasons, being made 
 very thick. The outer surfaces of this concrete, such as the roofs, 
 loading platforms, and the rear walls, are exposed to atmospheric 
 agencies, and the temperatures of these surfaces do not, as a rule, 
 vary greatly from the temperatures of the air. In simamer, with 
 the sun's rays beating down upon them, these surfaces become very 
 warm and this heat is slowly conducted to the interior of the concrete 
 mass. In winter, on the other hand, the exposed surfaces radiate 
 their heat and by beiag covered with ice and snow or by being in 
 contact with cold air they cool off to approximately the atmospheric 
 
249 
 
 temperature. This cooling, likewise, is slowly transmitted to the 
 interior. 
 
 To determine, if possible, the character and extent ot the tempera- 
 tm-e changes within the mass of concrete, some experiments were 
 made at Fort Monroe during 1903 and 1904. A description of these 
 experiments is not necessary, as only the results are important. 
 These results showed that in general the temperature of the interior 
 of a ruass of concrete passes through a seasonal change, failing in 
 the autumn and winter and rising in the spring and summer. The 
 amplitude of the change, however, was shown to be only about hah 
 of the atmospheric changes of temperature, and, furthermore, the 
 lowest temperature followed in time considerably after the coldest 
 weather of the winter and the highest temperature occurred con- 
 siderably after the greatest heat of the summer. 
 
 As a result of this lag in the temperature changes, it was evident 
 that there were likely to be days in the spring or early summer when 
 the temperature of the interior of the concrete mass might be 40° 
 or so below that of the atmosphere; on the other hand, that there 
 would be times iu the early winter when a similar difference but in 
 the reverse direction might be expected. 
 
 That the temperature changes in the interior of a mass of concrete ^ 
 would be less than those of the atmosphere, and that the extremes 
 of the seasonal temperature changes would lag somewhat behind 
 those of the atmosphere had, of course, been anticipated, but it was 
 not expected that the differences in temperature and the lag would 
 be as great as was indicated by the experiments. 
 
 The results obtained from these experiments, however, gave a clear 
 explanation of the phenomenon already noticed, that the amount of 
 condensation in batteries of similar construction but in different 
 locaMties seemed to depend to a great extent upon the amplitude of 
 the atmospheric temperature changes. That is, on the middle and 
 north Atlantic coasts, where the difference between the winter and 
 summer temperature is very great, condensation is extremely diffi- 
 cult to deal with. On the Pacific and Gulf coasts, where the general 
 temperature changes are smaller, condensation is very much more 
 easily prevented, while in the Tropics, where the seasonal temperature 
 changes are extremely small, condensation is practically negligible. 
 
 Condensation in Emplacements. 
 
 Our seacoast fortifications are necessarily located on the seashore 
 where, due to the influence of the ocean, the percentage of saturation 
 is quite high. This is especially true during the spring and early 
 summer when, for several hours nearly every day, the wind blows 
 from the sea, bringing in air that is not only warm, but which is 
 always nearly, if not entirely, saturated. Consequently, along our 
 
250 
 
 seacoasts in the summer time the dew point is usually only a few 
 degrees lower than the atmospheric temperature. 
 
 When such warm, moisture-bearing air finds its way into an em- 
 placement or battery and comes in contact with the cool ceiling and 
 wall surfaces, condensation is to be expected. 
 
 At first sight it might appear that we could reduce the amount of 
 condensation in one of three ways: 
 
 (1) By taking the moisture out of the air. 
 
 (2) By preventing warm air containing moisture from entering the 
 battery. 
 
 (3) By reducing the tendency to condensation of the moisture 
 which is in the air entering the battery. 
 
 The first method, to remove the moisture from the air, is evidently 
 not practicable. The second method, to prevent moist air from enter- 
 ing a battery, is incompatible with the opening of the doors and 
 windows which is necessary when the battery is in use. Conse- 
 quently, we can rely on the third method only, which is to reduce the 
 tendency to condensation of the moisture which actually finds its 
 way into the battery. This, as has been stated in the rules above, 
 can be done only by increasing or keeping up the temperature of the 
 emplacement walls. 
 
 If into a room the walls of which are cold, there be introduced a 
 quantity of warm, moist air, there wiU, of course, be a deposit of 
 moisture and this deposit will be greatest near the doors or windows 
 where the air first comes in contact with the cool walls. As the air 
 cools off condensation wiU take place, but the heat .lost by the air in 
 cooling, as well as the latent heat given off by condensation, will be 
 absorbed by the walls. Consequently, as the air cools off the walls 
 warm up, and this process — the cooling of the air and the warming 
 of the walls — will continue until the walls and the air are practically 
 of the same temperature. The condensation will continue until the 
 amount of vapor stiU remaining in suspension is just that necessary 
 to produce saturation at the temperature to which the air has now 
 fallen. After this condition has been reached, the cooling of the air 
 and the condensation of moisture wiU go on much less rapidly and 
 only as the heat is conducted from the walls into the interior of the 
 mass of concrete. This is a process that is far from rapid. 
 
 If the rooms of a battery, which have been kept closed aU winter 
 and are at a temperature far below that of the outside air, be opened 
 in the early summer time, the warm, moist air rushes in and the inside 
 air rushes out until there has been one complete interchange of air. 
 Condensation wiU take place, but the amount of moisture, though 
 considerable, wiU not be excessive and wUl be limited to the difference 
 between the amount of moisture the air contained when it entered 
 
251 
 
 and the amount which it can contain in suspension when reduced to 
 the temperature of the magazine walls. 
 
 If instead of this single interchange of air, however, we have con- 
 ditions such that there is a fairly rapid circulation of air through the 
 battery, entering at one point and leaving at another, each portion 
 of the air as it passes through will deposit its own quota of moisture 
 and the total amount of moisture deposited may be considerable. 
 However, as this warm air passes through the battery it transmits 
 to the walls temperature heat as the air cools off and latent heat as 
 moisture condenses. It thus gradually warms up the walls. If the 
 circulation of air be sufficiently rapid, the surface of the walls will, 
 before long, be raised to approximately the temperature of the air, or 
 if the air be not completely saturated, to the dew point. After this, 
 provided there is no increase in the amount of moisture carried in 
 the air, no further condensation can take place except that due to 
 the slow loss of heat by conduction from the waU surface into the 
 interior. In other words, the passage of warm air through a battery 
 has a tendency to heat it up, even though this heating be accom- 
 panied by condensation, and eventually, if the circulation be rapid 
 enough, the condensation will cease. 
 
 If, however, as sometimes occurs, the passage of the moist air 
 through the battery or portion of a battery takes place quite slowly, 
 so that heat is transmitted from the air to the walls only at the same 
 speed as it is lost by conduction from the wall surface into the in- 
 terior, we have the worst possible condition, as condensation may go 
 on indefinitely. 
 
 When, therefore, a circulation of moisture-bearing air is permitted 
 through a battery, this circulation should be made to take place as 
 rapidly as possible. 
 
 Means Taken to Prevent Condensation. 
 
 It would appear well at this stage of the discussion to give a short 
 historical resumS of the means which have actually been taken to 
 prevent or reduce condensation in batteries. 
 
 When fortification construction was resumed in the early nine- 
 ties and the earlier batteries, emplacements, and casemates were 
 designed, the idea of condensations being objectionable seems never 
 to have occurred to the designers. No means for preventing this 
 condensation were provided and, with the designs adopted, condensa- 
 tion was inevitable. However, it was not long after these emplace- 
 ments were completed before it was found that the magazines and 
 galleries were disagreeably wet, and it thus became evident that some 
 provisions to reduce condensation must be included in the designs 
 of all emplacements to be built thereafter. 
 
252 
 
 At first the methods of preventing, or at least of reducing, conden- 
 sation were left to the constructing officer, but before long they began 
 to appear in the mimeograph designs. The first method shown in 
 the mimeographs was based upon the maxim stated above, that of 
 reducing the heat conductivity of the wall surface. This was done 
 by inserting small air spaces 5 or 6 inches wide ia the walls around 
 the magazines and shell rooms. (See Plates VIII, XIV to XVI, 
 XVIII, and XIX.) 
 
 Unfortunately, the idea of water seeping into these air spaces does 
 not seem to have occurred to the builders and, consequently, many 
 of them were made blind^ — that is, no provisions were made for their 
 drainage. The concrete, at the time, was made of Rosendale cement. 
 It was usually mixed quite dry and was, therefore, very porous so 
 that water could seep through it easily. This water frequently 
 found its way into the air spaces, and once inside woul^ run rapidly 
 to the floors of the spaces, whence it would try to seep away. Un- 
 fortunately, the seep water usually contained carbonates in solution 
 and these carbonates had a tendency to make deposits upon the 
 floors of the air spaces which made them less permeable and thus 
 seriously interfered with the seepage of water away from them. 
 Consequently, the water would seep in faster than it would seep 
 out and often the spaces became filled. From the air spaces it was 
 but natural for the water to seep through the thin walls into the 
 magazines and galleries and it thus became a source of trouble.. 
 To avoid this, it became necessary ia many cases to drive drainage 
 holes into these air spaces so that they would readily empty. 
 
 The next step was the introduction of the 2-foot air passages first 
 shown in the drawings of the 1903 type of 10 and 12 inch emplace- 
 ments. (See Plates XVII and XX.) These air passages are just 
 outside of the magazines and principal rooms of the batteries. The 
 walls separating the passages and the rooms or magazines are thin 
 and the loss of heat by conduction from the surface of magazine 
 walls can, therefore, not be great. Furthermore, the circulation of 
 air through the air spaces and the condensation of moisture therein 
 warm up the walls of the magazines. These air spaces thus tend to 
 reduce condensation in two ways; first by reducing the conduction 
 of heat away from the wall surfaces of the magazines and store- 
 rooms, and. second, by warming up these wall surfaces from the 
 outside. 
 
 To act efficiently in the manner mentioned, it is evident that the 
 circulation of air must be rapid. As first designed, the air spaces 
 had apparently an unnecssary number of sharp turns. It is a well- 
 known fact that every angle in a ventilating passage impedes the 
 motion of air and, consequently, to encourage a rapid motion of the 
 air the number of angles should be made as small as possible. 
 
253 
 
 AltlioTigh these air spaces opened on the rear face of the battery, 
 their connections with the front and side walls of the loading plat- 
 form were not sufficient and there was but little to induce the cir 
 culation of air through them. 
 
 These deficiences were noted and were, to a great extent, corrected 
 in the design of the 14-inch emplacement shown in mimeograph 109. 
 (Plate XXII.) In the designs shown in the mimeograph, the air 
 spaces under the loading platform and around the gun block are 
 built in gentle curves instead of sharp angles. Frequent openings 
 are provided to the long gallery extending from one side of the bat- 
 tery to the other in front of the magaziae space. Communications 
 are also provided leading up to the loading platforms and, in addition, 
 numerous ventilators are shown connecting the air spaces with the 
 front and side walls of the loading platforms. 
 
 The most readily appUcable method of reducing the heat con- 
 ductivity of the walls themselves is to introduce voids close to the 
 surface; that is, to build the wall surfaces of porous bricks or of tiles, 
 which not only are porous, but which contain numerous voids and are 
 therefore very poor heat conductors. In the cases of several recent 
 batteries, the method just mentioned has been tried and has been 
 very successful. The poor conductivity of the tile and porous brick 
 surfaces reduces the amount of condensation. Such condensation 
 as does occur is not only absorbed by the porous bricks or tiles and 
 thus becomes invisible, but by its latent heat it raises the temperature 
 of the surfaces of these bricks and tiles to the dew point. Of course, 
 such bricks or tUes can absorb only a limited amount of moisture, 
 but in the cases in which it has been tried, this capacity for absorb- 
 ing moisture has never yet been reached, for from time to time con- 
 ditions are such as to permit the evaporation from the tiles and 
 bricks of part of the moisture which they have previously absorbed. 
 
 Not only has this method of tile lining been apphed to the wall 
 surfaces but to the ceUings also. A design of tile roof for installation 
 in ceilings supported by reinforced bars is shown on sheet 4 of mimeo- 
 graph 109. This system of ceiling tUes consists of alternate rows of 
 two kinds of tUes, one shaped like the letter X and the other trape- 
 zoidal. The X-shaped tiles are about 6 inches high, 5 inches wide 
 on the base and at the top, and about 3 inches thick at the 
 middle, both the top and the bottom halves having an air space run- 
 ning through them. The trapezoidal tiles are about 3 inches high, 
 7 inches wide at the base, and 9 inches at the top. They have three 
 air spaces through them. When placed in the ceiling, the concrete 
 extends in a dovetail down over the trapezoidal tUes and between 
 the top halves of the X-shaped ones and this dovetail contains the 
 steel reinforcing. By its shape, this concrete extending downward 
 supports the X-shaped tiles through the dovetail forming the upper 
 
254 
 
 half of tlie X, and in turn the dovetails formed by the lower half of 
 the X's serve to hold up the trapezoidal tiles. This system of tile 
 ceiling thus permits reinforcing bars to be inserted at intervals of 
 about 12 inches center to center; it holds the ceiling tiles absolutely 
 securely; and presents on its visible surface a flat smooth tile surface. 
 
 Another method which has been tried successfully- in some of the 
 smaller batteries — that is, batteries where the walls are thin — is to 
 introduce in the body of the wall, a few inches from its inside surfaces, 
 layers of tiles. Where this is tried, however, a method for draining 
 from the tiles water which may seep into them must be provided. 
 
 Another and still more radical application of the principle of making 
 the walls of magazines poor conductors, is to build the shell rooms and 
 powder magazines as independent houses within the open magazine 
 spaces. These interior magazine houses are built with thin walls 
 lined on the inside with porous brick; they are covered with roofs, 
 waterproof on the outside and lined with porous material on the in- 
 side. Furthermore, in order to prevent condensation on the floor, 
 due to the conduction of heat away from it to the concrete mass 
 below, tiles are built into the floor immediately below the granolithic 
 floor surfaces and similar layers have been designed for installation 
 in the concrete shell tables slightly below the upper surface of these 
 shell tables. (See sheet 3, mimeograph 109, and Plates XVII, XX, 
 and XXII.) 
 
 In order to prevent, as far as possible, moist air from getting into 
 the magazine houses while it is passing over and warming up the outer 
 surfaces of their walls, these interior magazine houses should be fur- 
 nished with soUd doors and, for use at certain other times, with 
 grating doors also. 
 
 A battery built in the manner described, well ventilated, with 
 2-foot air spaces passing around the main rooms and magazines 
 and connected with one another and with the outside air by corridors, 
 stairways, ventilating tubes, etc., and with the interior of the maga- 
 zines and main storerooms tile lined, should remain perfectly dry 
 under all weather conditions, provided that the ventilating system 
 is properly operated. Whenever the atmospheric temperature is 
 below that of the battery, it is advisable that the doors to all air 
 spaces and other ventilating openings be kept closed and that the 
 battery itself be opened no oftener and no longer than is absolutely 
 necessary. 
 
 When, however, the atmospheric temperature is above that of 
 the battery, the circulation of air, at least through the air spaces 
 and over and around the independent magazine houses, should be 
 encouraged to the greatest extent possible, so that the battery may 
 be warmed up as quickly as possible; this being based upon the 
 principle heretofore stated that anything that tends to raise or keep 
 
255 
 
 tip the temperature of the wall surfaces of an emplacement tends to 
 reduce condensation. The rule may therefore be stated that the 
 ventilation system should ie so manipulated as to encourage the passage 
 of air through the battery when the air is warmer than the wall surfaces 
 of the battery, and wiU, therefore, tend to warm up the battery, and so as 
 to discourage the passage of air through the battery when the air is colder 
 than the wall surfaces. 
 
 As a means of increasing the circulation of air through the battery 
 when the temperature conditions are suitable, some officers have 
 thought it well to provide windsaUs, the tubes of which can be in- 
 serted into ventilators so that the wind will blow down into the in- 
 terior of the battery. Others, for a similar reason, have provided 
 at the outlets of certain ventilator shafts opening on the top of the 
 battery, cowls similar to those sometimes used to improve smoky 
 chimneys. Of course, aU such arrangements as cowls and wind- 
 sails must be removed whenever the guns are to be fired, even in 
 target practice. 
 
 The introduction of air passages around rooms and magazines, of 
 both sohd and grating doors, and of ventilating pipes leading to 
 openings around the walls of the loading platform which can be closed 
 or opened at will, while it has made possible complete control of 
 the ventilation of the battery has, of course, somewhat compUcated 
 this control. The greatest efficiency can be secured from these 
 apphances only by proper manipulation, that is, by opening or clos- 
 ing at the proper time. Up to the present time such proper manipu- 
 lation has seldom been possible to secure. Consequently, the 
 writer is not in favor of adding windsails and cowls to the ventila- 
 tion system of batteries, and beUeves it is better and safer to restrict 
 the ventilating system to the doors, windows, air passages, and a 
 few ventilating openings. It should be easy to insure that the 
 ventilators on the loading platform and the sohd doors of the air 
 spaces should be opened in warm weather and should be kept open 
 for some time. It seems, however, too much to expect that they 
 will be opened and closed frequently, or that good judgment will be 
 shown in selecting the times when they ^ill be opened and closed. 
 With the comparatively small force kept in time of peace at our 
 eeacoast batteries, and with the multifarious duties incumbent upon 
 the officers, it seems impracticable to rely upon the proper manipu- 
 lation of a comphcated system of ventilation. Simplicity, therefore, 
 rather than compHcation, should be aimed at and the installation 
 of comphcated apparatus is not only a needless expense but fre- 
 quently it will be so manipulated as to do more harm than good. 
 
 If it could be insured that aU the officers serving at batteries were 
 properly instructed in the physical laws governing condensation, 
 the proper manipulation of a ventilating system might be expected. 
 
256 
 
 but it has been found that not only are such principles not under- 
 stood by the junior ofl&cers, but even that improper instructions are 
 " sometimes issued from the War Department. 
 
 As an example of the latter, the following should be noted. A 
 number of years ago the Engineer Department was requested by the 
 Artillery to install at aU batteries thermometers and psychrometers, 
 the psychrometers for outside use and the thermometers for inside 
 use. Pamphlets giving instructions for the use of these thermometers 
 and psychrometers were issued from the War Department and in 
 my opinion these instructions were based on fundamentally wrong 
 principles. 
 
 The instructions directed that the battery commanders should 
 frequently make readings of the psychrometers and thermometers 
 and that whenever the dew point of the atmosphere was found by 
 the psychrometer to be above the temperature of the interior of 
 the battery, as shown by the thermometer, the battery was to be 
 kept tightly closed. Whenever, on the other hand, the dew point 
 of the atmosphere was found to be below the temperature of the 
 battery, the doors were to be opened and ventilation was to be 
 encouraged. 
 
 Apparently these rules were based upon the idea that the intro- 
 duction of air into the battery when the dew point was below that 
 of the temperature of the battery would cause no condensation and 
 would probably result in the evaporation of such moisture as was 
 present in the battery. As far as this goes, the theory is correct, 
 but it should be noted that on the seashore there is usually no ma- 
 terial difference between the dew point and the atmospheric temper- 
 ature. Consequently the dew point can be materially lower than 
 the temperature of the battery only when the atmospheric tempera- 
 ture was lower and the carrying out of the instructions would result 
 in the opening of the battery for ventilation only when the atmos- 
 pheric temperature was materially cooler than that of the battery. 
 The result would necessarily be the continued cooling of the battery 
 and, if the principle were carried far enough, there would be fewer 
 and fewer times when it would be permissible, under the rule, to 
 open the battery. The carrying out of this system, while it might 
 lead to the occasional evaporation of some moisture, would con- 
 tinually cool off the battery, and would, therefore, tend to increase 
 the condensation when, on a warm moist day, it finally became 
 necessary to open it. 
 
 In fact, I do not hesitate to say that the principles upon which the 
 instructions were based were fundamentally wrong, since, as has 
 been shown above, the proper use of the ventilating system must be 
 based upon doing all that is possible to warm up the battery and to 
 keep it from cooling off. 
 
257 
 
 Reducing Condensation at Older Batteries. 
 
 As has been stated, many of the older batteries constructed were 
 designed without any idea of the extent to which condensation would 
 take place. Where condensation in these old batteries has been 
 most objectionable the dampness has usually been increased by seep 
 water, and the methods of preventing this have been discussed under 
 that head. In many cases, however, where undue seepage did not 
 take place, condensation was very bad and steps to ameliorate this 
 condition became necessary. The most effective means to accom- 
 pUsh this have usually been based on the idea of improving the 
 ventilation of the battery and the circulation of air through it. The 
 first batteries that were constructed were, of course, provided with 
 windows and doors where considered necessary. When the battery 
 was in use these doors and windows were open, permitting a circula- 
 tion of air. When the battery was not in use, in order to insure the 
 safety of the contents of the battery, these doors and windows were 
 closed. As only sohd doors and sohd shutters had been provided, 
 the closing of the doors and windows practically stopped the cir- 
 culation of air through the battery. 
 
 In order to avoid this, it has become customary in all new batteries 
 to provide solid and grating doors at all doorway openings and to 
 provide gratings at aU windows so that both the doors and windows 
 can be left open for ventilation, the gratings providing for the safety 
 of the contents of the battery. 
 
 This same idea has been apphed to many of the older batteries, it 
 having been the pohcy of the department for a number of years to 
 provide gratings for the door and window openings of such batteries 
 as fast as funds permitted. 
 
 Of coinse, to be most efl&cient as a means of preventing condensa- 
 tion, the sohd doors and windows of these older batteries should be 
 manipulated in the same way as has been mentioned above for the 
 air-space openings — that is, they should be kept open whenever the 
 outside air is warmer than the temperature of the interior wall sur- 
 faces, and should be kept closed whenever the outside air is colder. 
 Such a careful manipulation has not been possible to attain, but 
 where it has been possible to induce the battery commanders to leave 
 the sohd doors and window blinds open, even continuously, condi- 
 tions as to condensation have been much improved. 
 
 It is a well-known fact that in many cases, batteries that had been 
 notoriously wet and uncomfortable, when provided with sohd doors 
 habitually kept closed, have been made fairly dry by the mere ex- 
 pedient of adding gratings and leaving the sohd doors and windows 
 open all the time. Of course, occasionally during the first warm, 
 moist days of early spring some condensation has been present, but 
 173341-^20 n 
 
258 
 
 the continuous circulation of air as the winter changes into spring^ 
 has been sufl&cient to begin the warming up of the batteries, so that 
 by the time the weather conditions are such as to be favorable for 
 condensation the difference in the temperatures of the wall surface 
 and of the outside air wiU be so small as to be rapidly overcome by 
 the latent heat given off by a small amount of condensation. Conse- 
 quently, except for occasional days in the early spring and summer,, 
 such batteries have been fairly dry. When, therefore, there is any 
 doubt as to the possibility of having the solid doors and windows 
 opened and closed at the proper times, the doubt should be solved by 
 leaving them always open. 
 
 HEATING. 
 
 Until within the last few years the idea of heating fortifications 
 artificially as a means of preventing condensation was not given con- 
 sideration. To be sure, oil lamps or oil stoves had sometimes been 
 used to dry out the air in mining casemates and thus reduce the 
 leakage in the electrical apparatus. Stoves had sometimes been 
 placed in the plotting rooms of batteries and fireplaces had been pro- 
 vided in some of the rooms intended for offices, but a general heating; 
 up of emplacements was not considered practicable. 
 
 In 1903 and 1904 some suggestions were made and experiments 
 were tried (see mimeograph 61, supplement 8) as to the effect of 
 heating up a battery in the early spring by means of an apparatus 
 for heating the air, a fan for blowing the heated air into the battery,, 
 and canvas air ducts for conducting it were needed. Apparently 
 this plan was efficacious when tried, and it was thought that one or 
 two applications in the early spring of each year should warm up 
 the battery sufficiently to prevent condensation during the foUowing^ 
 summer. The apparatus, however, was unwieldy and its general 
 adaptation was not tried. 
 
 The next step in connection with the heating up of batteries fol- 
 lowed the adoption of gasoline-operated generating sets as the stand- 
 ard power plant for battery use. The cylinders of the engines of the 
 sets are cooled by circulating water and, except in a very few cases 
 where sea water is available, economy in the use of this circulating^ 
 water requires that it be itself cooled by air. That is, the circulating^ 
 water, after being warmed up by passing around the cylinder walls, 
 is pumped through a radiator cooled by a blast of air driven by an 
 electric fan. The air corriing from this radiator is, of course, heated 
 up as it cools the water and when the radiator was first used in the 
 same room as the power plant it soon heated the air of the power 
 room so as to make it too hot for the attendants. It therefore 
 became necessary to install the radiator in a separate room and under 
 such conditions that it could draw air from the power room and force 
 the heated air outside through a window or flue provided for the pur- 
 
259 
 
 pose. It thus served not only to cool off the water but to ventilate 
 the power room. 
 
 The availabiUtj' of a blast of hot au- such as that given off by the 
 radiator natiu-all^- suggested the possibihty of using this blast in the 
 spring and early summer for warming up the wall surfaces of an 
 emplacement and thus preventing condensation. 
 
 The first arrangement of this kind proposed is shown in mimeo- 
 graph 109 (Plate XXII) where, near^ne end of the battery, there is 
 shown a power room. The radiator is to be so placed that its hot 
 air blast can be passed through a large flue extending from one end 
 of the battery to the other in front of the line of magazines and 
 storerooms. Openings into this flue are shown at various places 
 and it was stated in the text accompanying these plans that in these 
 openings there were to be installed dampers so that the flow of hot 
 air into any particular part of the battery could be regulated as 
 desired. 
 
 The first battery built on the general type of mimeograph 109 was 
 Battery Randolph at Honolulu. In this battery there was sub- 
 stituted for the circular flue, a passageway about 2^ feet wide by 6i 
 feet high, having doorways at nimaerous places. Doors placed in 
 these doorways were installed to take the place and perform the 
 function of the dampers suggested by the mimeograph. The use of 
 a passageway was considered preferable to the large flue because it 
 permitted men to pass through and clean it out when necessary. 
 
 After this battery was built, however, experience showed that 
 the climatic conditions were such at the locality, and generally in 
 the tropics, that condensation does not occxir, consequently, the 
 provision for warming up the battery was an imnecessary precau- 
 tion. It was, therefore, not installed in the large batteries subse- 
 quently built in the Philippines and on the Canal Zone. 
 
 But the idea of using this hot blast of air for warming batteries is 
 a perfectly practical one and should hereafter be installed in all bat- 
 teries constructed in continental United States or wherever climatic 
 conditions are such that condensation occurs. In fact, this idea has 
 been utilized in aU the long-range 12-inch batteries recently con- 
 structed in this country. 
 
 If the blast from these generating sets is allowed to spread at aU 
 times through the emplacements, the heating would frequently be 
 overdone and the rooms and magazine spaces would become too 
 warm for comfort and possibly hot enough to affect the powder in 
 storage. Wherever therefore, a radiator is so installed as to make 
 possible its use for warming up the battery, this disposal of the air 
 should be an alternative only and thoroughly under control by 
 doors or dampers. Normally the hot blast should be discharged to 
 the outside air through flues or passageways provided for the pur- 
 pose and only occasionally should it be blown into the battery. 
 
26a 
 
 It is further proposed in future emplacement constructioi^ to 
 provide means so that the hot air blast can, when needed, be used 
 to melt any ice, snow, or sleet that may fall or form upon the gun 
 carriage or in its vicinity. 
 
 VENTILATION. 
 
 Wherever human beings are working, ventilation is necessary to 
 provide fresh air for breathing and to carry off the vitiated air 
 which has been breathed. For this reason, to some extent at least, 
 the ventilation of the magazines and galleries of emplacements is 
 necessary. 
 
 In general, the number of men working in the interior of batteries 
 is small, and since it has not been customary to provide dormitories 
 in the emplacements built in the continental limits of the United 
 States, the circulation of air coming through the doors and the 
 windows necessary for the entrance of light have been found suffi- 
 cient for the detachments working inside. The encouragement of 
 ventilation has, therefore, not been found necessary by any cir- 
 cumstances connected with the health or physical condition of the 
 naen. 
 
 In the tropics, however, different conditions exist, and this is 
 specially true of the Panama Canal fortifications. Owing to the 
 exposure to hostile fire of the sites where many of the Panama bat- 
 teries are built, it was considered necessary in many cases to build 
 them almost of the type of subterranean tunnels and rooms. The 
 atmosphere of the Isthmus is always quite warm and usually nearly 
 saturated and, therefore, for the comfort as weU as for the health of 
 the garrison, it was considered necessary to provide artificial ven- 
 tilation for these batteries. 
 
 Thus it was thought necessary to install in by-passes at the en- 
 trances to certain batteries (see designs of Batteries Burnside, Buell, 
 and Warren, Panama fortifications) large 5-foot fans which would 
 draw air from the outside and force it into the batteries. The vari- 
 ous corridors were provided with solid doors which could be closed, 
 and by proper manipulation of these doors this forced air could be 
 prevented from running back into the entrances from which it came 
 and could be distributed as desired through all the rooms and gal- 
 leries of the batteries. 
 
 In certain other places where a number of men might be expected 
 to be gathered together, such as plotting rooms and latrines, small 
 suction fans operating in air ducts were installed to draw off the 
 vitiated air and force it outside. 
 
 In the portions of this chapter in which the subject of condensation 
 Avas treated, the importance of sufficient ventilation" as an aid to de- 
 creasing condensation was discussed. It need not, therefore, be 
 repeated here. 
 
Chaptee X. 
 BLAST EFFECTS. 
 
 One of the greatest difficulties with which the fortification engi- 
 neer has had to deal in connection with modem fortification work 
 is the terrifically destructive effects of the discharge of high-power 
 guns. Xot only is this blast effect imcomfortable and dangerous to 
 the personnel, but it does great material damage. The sodded slopes 
 in front of the gun are frequently torn up and, occasionally, even the 
 concrete blast aprons are seriously cracked and damaged. In ex- 
 treme cases thick metal blast aprons have broken away from their 
 fastenings. Window panes are broken, even at considerable dis- 
 tances from the gun, and in the vicinity of the gun, window sashes- 
 are frequently torn out bodily. Doors are burst open, sometimes 
 due simply to the breaking of the locks, but in many instances doors 
 have been spht open or have been bodily torn from the hinges. 
 Xot infrequently, wooden doors as much as 3 inches thick have been 
 split in two. Sometimes where small houses have been located in 
 the vicinity of the gun and the doors and windows were not opea 
 when the gun was fired, not only have these doors and windows been 
 destroyed, but the very walls and roofs have been seriously injured. 
 In extreme cases, interior waterproof ceUings have been broken down 
 or seriously damaged. Electric lights are destroyed, sometimes by 
 the breaking of the filaments, and sometimes bj' the shattering of 
 the bulbs. 
 
 It seems to have been thought for a considerable time that the 
 principal blast damage was due to the wave of pressure coming from 
 the muzzle of the gun, but later study has shown that though in 
 front of the plane of the muzzle the greater part of the damage may 
 be due to this wave of pressiu-e,.yet in the rear of the muzzle, and 
 especially in the interior rooms and passageways, damage appears 
 to be done more by a wave of rarefaction following the first wave of 
 pressure. When a gun is fired, the air in front of the muzzle is 
 blown forward. A vacuum is formed and the attempt of the sur- 
 rounding air to rush in and fill this vacuum causes a wave of rare- 
 faction te proceed outward from the gun. It has been shown that 
 this wave ©f rarefaction may be reflected much in the same way 
 that sound waves are reflected and where the original and reflected 
 waves are in accordance, greatly increased damage m.ay be done- 
 In a few cases the damage seems not to have been due directly 
 
 (261) 
 
262 
 
 either to the wave of pressure or the wave of rarefaction, but rather 
 to an excessive vibration set up as the resultant of these two and the 
 following waves. 
 
 Often also the blast effects are quite erratic, if not inexplicable. 
 There have been occurrences where a gun fired at a certain azimuth 
 or elevation does no damage at all. A very slight change in either 
 azimuth or elevation wiU result in great blast damage and a very- 
 slight additional change will again reduce the damage so much that 
 it may be considered as negligible. Occasionally, also, where sev- 
 eral successive shots are fired without any change whatsoever in. the 
 aiming of. the gim, the blast from some of the shots has done consid- 
 erable damage, while that from others has done none at all. 
 
 As indicating some of the peculiarities of blast effects, I will men- 
 tion a few incidents which have come to the personal attention of 
 the writer. Some years ago, during target practice at Fort Monroe, 
 there was in rear of one of the flanks of a 12-inch battery a small 
 frame house used as a tool house. Orders had been given that all 
 the doors and windows in this house should be opened before the 
 guns were fired, but through some mistake this was not done, and 
 the first gim was fired with all the doors and windows closed. The 
 result was that the windows on three sides of the house were all 
 badly broken, and the door which is on the fourth side was split. 
 The window glass was all drawn outward from the windows and the 
 entire effect was as of an explosion inside of the house. 
 
 During the summer of 1906 at Fort Monroe a recently constructed 
 12-inch battery had its guns proof-fired. This battery is based 
 essentially upon the plans shown in mimeograph 66 (Plate XX), 
 there being a number of rooms located on the magazine level under 
 the loading platform of the battery and having windows opening on 
 a corridor under the rear of the loading platform. "Before the guns 
 were fired all these windows were opened, but one of them seems 
 not to have been securely fastened back and, as a result of the fire 
 of the first shot, it closed. When the second shot was fired the glass 
 ia this window was pulverized and was all sucked outward, that is, 
 to the rear, under such pressure that some of it was drawn horizon- 
 tally a distance of fuUy 30 feet, while falUng a vertical distance of 
 only 5 or 6 feet. Where the windows were opened and fastened 
 open, no damage was done. 
 
 At one time at the mortar battery at Fort Monroe (see figure 4, 
 Plate XXVIl), the four guns of one pit were fired in salvo and in 
 a direction which threw their line of fire approximately over the 
 doors entering the magazine. There had been placed in the lobbies 
 of this pit a short time before a number of blue prints mounted in 
 picture fraines with glass fronts. Nearly all of these glasses were 
 broken at the first fire, the glass being always drawn out. In some 
 
263 
 
 cases, even tlie blue prints were sucked oflf the boards to which they 
 were attached, and in another place, where only about half of the 
 glass was drawn out of the frame, the blue print was sucked par- 
 tially through the hole in the glass. At the same time, quite a num- 
 her of the sections of the corrugated damp-proof ceiling were drawn 
 downward as if by suction from below. 
 
 Another somewhat unusual effect of the blast occurred in one of 
 the powder magazines at the Fort Monroe mortar battery. This 
 magazine was about 50 feet long by 10 feet wide and was entered 
 hy a 3-foot door, situated at one end and close to one of the side 
 walls. The magazine had recently been divided up by wooden par- 
 titions into a number of stalls for experimentation with the zone 
 storage system. Before the mortars were fired, the door to the 
 magazine was left open, but in spite of this precaution serioiis damage 
 was done. The stall partitions near the center of the magazine were 
 practically torn to pieces, those about half way between the center 
 and the ends were slightly damaged, while those nearest the ends 
 were not affected at all. This indicated clearly that the effect of the 
 Ijlast had been to set up in the magazine a vibration of air, the ends 
 of the magazine acting as nodes and the center as the ventral section. 
 
 A few years ago, there was built within the crater of an extinct 
 volcano in the Hawaiian Islands a mortar battery intended primarily 
 for land defense. This battery consisted of four mortars — that is, 
 two pits of two mortars each. Within the traverse between the pits 
 there were located certain rooms intended for fire control and power 
 purposes. The mortar pits were quite small and were surrounded 
 by high vertical walls, with a result that, when the mortars were 
 tested, it was found that the blast effects were very serioiis, especially 
 in the galleries connecting the two pits and in the rooms opening 
 thereon. This was doubtless due to the small size of the pits and 
 the way in which they were smrounded by walls. 
 
 Instances of blast effect were described in the Engineer mimeo- 
 graphs Nos. 45, 63, 81, 100, and their supplements, and also in the 
 twenty-fifth supplement to mimeograph 48. 
 
 From the above recorded instances, from many others which have 
 come under my casual observation, and from talks I have had with 
 other officers of much more experience, it would appear that the 
 hlast damage in rear of a battery, and especially in its interior, is 
 due principally to the initial wave of rarefaction and, secondly, to 
 the vibrations of the air following this initial wave. 
 
 Interesting though a record of the damage done by blast may be, 
 it is of value to the fortification engineer only in so far as it is a guide 
 to him for future construction, by showing him what conditions 
 shoiild not be repeated. Frequently, in the preceding chapters, ref- 
 erences have been made to damage due to blast effects and to the 
 
264 
 
 modifications which have been made in the designs in an attempt to 
 avoid blast damage in the future, or at least to bring that damage 
 within permissible limits. 
 
 In general, it may be said that it has been found that the more 
 nearly open and free of obstruction the space around the gun is the 
 less will be the blast effect, for under such conditions the outside air 
 may rush freely in to fill the vacuum caused by the discharge of the 
 gun. This is very clearly shown from the fact that the blast effects 
 in the more modern mortar batteries which are open freely -to the 
 rear are much less than in the older batteries where the mortars were 
 located in pits completely surrounded by high parapets. Further- 
 more, the wider platforms of the more modern direct-fire guns have 
 caused the blast effects in such emplacements to be much less th^n 
 with the contracted platforms of the older type emplacements, and 
 this in spite of the increase in the size of the guns. 
 
 The precautions that should be taken to prevent blast from injuring 
 or damaging houses, doors, windows, and other objects depend upon 
 the relative position of the object and the gun, the size of the gun, 
 and the direction in which it is usually firpd. In general, except in 
 their immediate vicinity, no material blast damage wiU be caused 
 by small or medium caliber guns; it is only from large caliber guns 
 that great blast damage is to be feared. 
 
 In localities 200 yards or more from a large caUber gun, except in 
 a direction in which it is possible for the gun to be fired, it is usually 
 not considered necessary to take any special precautions in house 
 construction, but it is well, whenever it is known that a gun is to 
 be fired, to open the doors or windows of all houses or other structures. 
 If the doors and windows be opened, it is not probable that damage 
 will be done to them, but opening the doors and windows has some- 
 times transferred the blast effects to' the interior of the building, and 
 in a few cases has resulted in having the doors of closets broken or 
 pulled open. 
 
 Occasionally, also, the plaster ceilings of houses have fallen when 
 a gun situated even more than 200 yards away has been fired, but 
 to what extent this has been due to the blast waves sent through 
 the air, and to what extent to vibrations transmitted through the 
 ground, can not be definitely determined. "Vyiiatever the cause, so 
 much damage of this character was done in certain locations by tlie 
 discharge of heavy guns that it became customary several years ago 
 to use as the ceilings of officers' quarters at seacoast forts not ordinary 
 plaster on laths, but a specially manufactured ceiling composed of 
 stamped and painted sheet metal nailed to the ceiling rafters. 
 
 Within less than 200 yards of a large caliber gun it is necessary, 
 as a rule, to take special precautions in building construction. 
 Especial^ is this true of plotting rooms ajid battery commander 
 stations when built in or close to either direct fire or mortar batteries. 
 
265 
 
 When lopated well in rear of the plane of the muzzle, and when all 
 the doors and windows have always been opened during firing, frame 
 buildings and buildings composed of plaster on metal lathing have 
 as a rule been fairly successful in withstanding the effects of blast. 
 But in a number of cases where such biuldings were placed on the 
 rear slopes of the traverses of mortar batteries of the 1894 type (see 
 figure 4, Plate XXVII) and the mortars were fired obhquely toward 
 them, they have been much damaged. The frame buildings were 
 badly wrecked and the plaster was cracked or shaken off of the 
 plaster buildings. Reinforced-concrete structures io such locations 
 have usually stood the blast perfectly. 
 
 Windows are, of course, especially liable to be damaged by blast, the 
 window panes being cracked and broken or, in extreme cases, the sashes 
 being broken to pieces. In order to avoid damage to the windows 
 they should also be open when the gun is fired. When quite distant 
 from the gun, the ordinary vertical sHding sashes that leave free about 
 half the area of the window opening have usually withstood the 
 effects of the blast, though sometimes some of the panes have been 
 broken. In more exposed locations the window sashes that have 
 stood the blast effect best are those rotating about vertical axes", so 
 that when the gun is about to be fired, the windows can be opened 
 and can be set so that the motion of the air wave is parallel to the 
 window surface and not perpendicular to it. In the rooms opening 
 on the corridors under the loading platforms of heavy guns (see PI. 
 XXII), a method of mounting windows that has been found particu- 
 larly serviceable has been to rotate each sash about a vertical axis 
 passing through its center, the sash rotating on special pivots inserted 
 in the top and bottom of the window frame (see sheet 5, Mimeograph 
 109). 
 
 In general, it has been found advisable anywhere in the vicinity of 
 fortifications to use a better quality and thicker glass than that 
 ordinarily used in windows. In some special locations it has become 
 necessary to use wire glass. This was especially true in the glass roofs 
 over the observation rooms at the top of the fire-control towers where 
 they were built in the vicinity of gun batteries, and in the windows 
 of the observation openings of the battery commander stations of 
 mortar of l^eayy direct-fire gun batteries. 
 
 It shouild be imnecessary to state that whenever guns are to be 
 fired, the doors and windows in all buildings, permanent and tem- 
 porary, in the vicinity of the battery should be opened, and should 
 l»e securely fastened open, so that they may not be closed by the 
 blast of one shot and be destroyed by the next. 
 
 It has been customary, when a battery is turned over by the en- 
 gineer department to the Artillery, that drawings showing certain 
 detpil3 of the battery be fiunished to the commanding officer. In 
 
266 
 
 addition, copies of these drawings were usually posted in the bat- 
 tery. These drawings were usually in the form of blueprints, and 
 for many years it was customary to mount them in picture frames and 
 hang them on the walls of the rooms or of the corridors of the bat- 
 teries. In the older batteries it was not unusual for the glass in these 
 frames to be broken by the blast, and sometimes the frames themselves 
 were badly injured. So much damage of this character was done that 
 a few years ago it was decided that thereafter these blueprints, in- 
 stead of being framed like pictures, should be attached to sheets of 
 galvanized sheet metal. The blueprints are glued to the metal sheets, 
 are varnished to protect them from dampness, and are then posted 
 in the batteries. (See Mimeograph 103.) 
 
 In the early days searchlights were sometimes injured by blas^. 
 Fortunately, however, this did not occur very frequently, because in 
 order to prevent the searchlight beam from interfering with the sight 
 of the men at the guns or in the battery commander stations, the 
 searchlights were placed at least a few hundred yards to one flank 
 or the otter of the battery, and this was usually sufficient to preserve 
 them from the effects of the blast. The damage to the searchlights 
 which has happened has been not the breaking of the mirrors, which 
 are so mounted to prevent this, but the destruction of the so-called 
 front doors. In the older form of searchlight mechanism used prior to 
 about five years ago, a front door was necessary in order to keep the 
 air currents from causing the arc to fUcker. However, with the 
 modem high intensity searchlights, such front doors have been found 
 to be mmecessary and the use of them has been abandoned, so that 
 in the future there will be no front doors to be injured. 
 
 As regards the effect of blast on the personnel, there would appear 
 to be many contradictions. For instance, it is found that the de- 
 tachments with a little cotton in their ears can stand around the base 
 of the gun carriage or on the sighting platform of the 12-inch, 14-inch, 
 and 16-inch guns without any special discomfort, although the de- 
 structive effect of the blast is very great in those localities. It is 
 further found that, as far as the effects on the nervous system are 
 concerned, the shocks of the 5-inch and 6-inch guns appear to be 
 much more powerful than those of the 12-inch and 14-inch guns, 
 although the intensity of the blast and the material damage is vastly 
 less. 
 
 In an attempt to study quantitatively the effect of blast from guns, 
 there was invented nearly 20 years ago by Col. (then Capt.) Edward 
 H. Schulz, Corps of Engineers, a so-called "blast meter," which is 
 described in the first supplement to Mimeograph 81 and in the draw- 
 ings pertaining to it. This first blast meter was based upon the idea 
 that it was the wave of pressure that did the greatest amount of 
 damage, and as originally constructed, it measured pressure only 
 
267 
 
 Xater, however, it was modified by Col. Schnlz so that it could be 
 adjusted to measure rarefaction. 
 
 Comparatively recently Col. Schulz has agaia taken up the study 
 of the measurement of blast effects, and has invented a new type of 
 Tjlast meter the readings of which depend upon the breaking strength 
 of paper stretched over holes of dififerent sizes. This last form of 
 Mast meter is illustrated and described at some length in a recent 
 nimiber of Professional Memoirs (Vol. XI, No. 57). 
 
 The readings of these different forms of blast meters have, as a 
 Tule, been fairly consistent one with another, but imfortunately they 
 do not seem to bear any well-defined ratios to the physiological effects 
 upon individuals or the amounts of physical damage done by the blast. 
 So far as concerns damage to the superior slope of the parapet and 
 to objects ia front of the plane of the muzzle, the readings of the 
 l)last meters seem to be fairly in accord with the severity of the blast 
 «ffects, but when it is a question of the damage done in rear of the gun 
 or in the rooms and iuterior passage ways of a battery, the blast 
 meter indications would appear to be no criterion upon which to 
 l)ase an estimate of the damage which will be done. 
 
Chaptee XI. 
 USES OF ELECTRICITY IN FORTIFICATIONS. 
 
 It is proposed to give in this chapter a brief outline of the applica- 
 tion of electricity to fortification uses, but without going at all deeply 
 into the subject of electrical engineering. 
 
 Historical. 
 
 When, about 1890, the construction of our modem fortifications 
 was begun, the use of electricity for lighting and power purposes 
 had reached a considerable commercial development. Consequently, 
 we find arrangements for the use of electricity in the first emplace- 
 ments built, and one of the very earliest of the Engineer Department 
 mimeographs gives a description of the electric lighting plant installed 
 in the San Francisco mortar battery, the earliest mortar battery begun. 
 
 Although it had been planned to use electricity for lighting piurposes 
 in all the new emplacements, the funds available for that piupose were, 
 prior to the Spanish War, so small that comparatively little was accom- 
 plished. Under the spur of the excitement caused by the sinking of 
 the Maine and the practical certainty of an early war with Spain, 
 Congress made a large appropriation to prepare the coimtry for 
 defense. Out of this so-called "National defense fund," and other 
 emergency appropriations made shortly thereafter, a large amount 
 was allotted for fortification piu:poses and a considerable proportion 
 of this was expended in the purchase and installation of electric plants, 
 the building of power houses, etc. 
 
 As is the case with all emergency work, the electrical installations 
 were hurriedly made. Almost any kind of a boiler and engine that 
 was available was purchased, and it is needless to say that time 
 proved that a number of these hastily installed plants were quite 
 unsuited for fortification use. 
 
 As a general rule the plants installed were operated by steam, 
 though another variety of engine purchased quite extensively was the 
 Homsby-Akroyd oil engine. Occasionally these plants were placed 
 in already existing rooms. More frequently, however, they were 
 installed in small power houses hastily constructed in rear of and 
 under the protection of the emplacements. 
 
 The first plants were intended for lighting only and were, in general, 
 merely large enough to fiimish power for this purpose. However, 
 after the electric plants were once installed, it was but natural that 
 
 (269) 
 
270 
 
 the idea should arise of using them for other purposes than Ughting^ 
 such as furnishing power for electric motors. The first step of this 
 character -was the use of electric motors to operate the old balanced 
 platform hoists in the earlier 8 and 10 inch emplacements, and as these 
 platform hoists were removed and replaced by chain hoists, motors 
 for operating these chain hoists were installed at the same time. 
 
 At first, nearly all matters connected with the design and installa- 
 tion of electric plants were left to the constructing officers, and as a 
 natural result the installations in different sections of the country 
 differed greatly. It became evident that some effort must be made- 
 to standardize electrical equipment and bring it to some degree of 
 uniformity. 
 
 It is, of course, not practicable to secure absolute uniformity in all 
 our electric plants at all fortified posts, for the conditions to be met 
 with vary too greatly ; but the advantages in having the fewest possible 
 number of different types is too obvious to require argument. That 
 the type of design at one fort should be similar to that at others is 
 advisable, because Artillery officers and enlisted men are frequently 
 transferred from one station to another, and it is, of course, desirable 
 that they should find the electric installation at the new station so 
 nearly like that at the old that they wiU be able to apply at the new 
 post the knowledge which they obtained at the old. 
 
 But, though it is desirable that the installations at the different 
 forts should be somewhat similar, it is by no means as important as 
 that the installation in the different plants at any one fort should be 
 alike. Many reasons may require that the personnel in charge of ^ 
 plant in one battery be called quickly to take charge of the plant in 
 another battery at the same post, and the plants should be so much, 
 alike that these men as they go from one to another will know exactly 
 how to operate them. 
 
 This is especially true of switchboards; that is, the switches used 
 for the same purpose should have the same relative position on all 
 switchboards. Indeed, this question of similarity of switchboards i& 
 believed by the writer to be so important that he would, in some 
 cases, unhesitatingly recommend the duplication of existing switch- 
 boards rather than the introduction of a possible improvement on a. 
 single new switchboard unless it is intended that a similar improve- 
 ment shall shortly be added to all. 
 
 As early as 1896 the Board of Engineers gave consideration to the 
 subject of electrical installations and submitted to the Chief of Engi- 
 neers a report published in Mimeograph No. 13. This mimeograph, 
 which is now practically obsolete, discussed the general subject of the 
 installation of emplacement electric plants and submitted specifica- 
 tions of a rather general character for the guidance of constructing 
 officers. Steam power seemed to be preferred, although the oil 
 
271 
 
 engine was favorably recommended. Storage batteries, or as they 
 were called at that time, "accumulators," were recommended as 
 reserves. It was pointed out that without some such reserve it 
 would be necessary, every time it is desired to light up a single room 
 of an emplacement to start the steam plant; with a storage battery 
 in commission all that is necessary is to throw the proper switches. 
 For the wiring, the board recommended ordinary okonite covered 
 wire and suggested the use of pipe conduits wherever the wiring was 
 to go through masonry. Although, in general, all the lights were to 
 be controlled by a single switch at the main switchboard, branch 
 circuits controlled by separate switches were suggested in special 
 places and the necessity was noted of having fuses at the points where 
 the circuits branched. An estimate was given of the number of 
 electric lamps required and it should be noted that this is a very small 
 fraction of those now considered necessary. 
 
 In 1900 a board of Engineer officers was organized by the Chief of 
 Engineers for the purpose of considering the subject of electric 
 installations, and this board continued in existence for a number of 
 years, with, however, changes in membership from time to time. 
 
 The first report of this board is published in Professional Papers 
 No. 27, Corps of Engineers, which is well worth reading. It recom- 
 mended steam as the standard prime mover. The electric system 
 was to be direct-current. Storage batteries were to be used as 
 reserves, and in order to be able to charge the batteries fully without 
 causing the dynamos to be operated at exceedingly high voltages, 
 the plan was suggested of cutting the storage battery in halves and 
 charging these halves in parallel, but connecting them in series for 
 discharge and use. A form of switchboard for accompHshing this 
 was shown in the report, the wiring of which was shown in a diagram. 
 
 The principle of charging the storage battery in halves in parallel 
 and discharging it in series is an excellent one, but the method of 
 regulating the voltage recommended by Professional Papers No. 27 
 was not the best one. 
 
 The voltage of a storage battery cell, and therefore of an entire 
 storage battery, when first charged is quite high, but as the charge is 
 used the voltage is reduced. The battery is stiU in usable condition 
 when the voltage has dropped by as much as 15 per cent of its 
 maximum. Now, it is evident that where a storage battery is to be 
 used for lighting purposes, a sufficient number of cells must be placed 
 in it to leave its voltage as it approaches a state of complete discharge, 
 slightly greater than that required for fighting purposes or, say, 
 115 volts at the switchboard. This means that when the storage 
 battery is freshly charged its voltage wiU be some 15 or 20 volts too 
 high. If wlule in this condition, the fuU power be turned on a small 
 number of incandescent lights, they wiU quickly be burned out. 
 
272 
 
 In practical use, therefore, it is necessary to reduce the voltage of 
 the storage battery and this can be done in two ways, hf the ihtto- 
 duction of rheostats in the circuit, or by cutting out a few of the cells. 
 The former method was the one recdmmended by Prof essional Papers 
 No. 27. 
 
 Three rheostats are shown, a smad one in circuit with each half of 
 the storage battery for use in regulating the voltage of that half 
 during the charge, and a large one in the main circuit beyond where 
 the two half circuits are joined together for general use. That is, the 
 main current passes always through a large rheostat. While the 
 battery is being charged, the current divides and half runs through 
 each half of the storage battery and through one of the smaller 
 rheostats. When, during discharge, the two half circuits are put in 
 series, the tliree rheostats are, of course, in series and as much resist- 
 ance can be put in as may be necessary. 
 
 With an open circuit, the voltage at the bus bars is that of the 
 storage battery, whether or not aU the resistance of the rheostats 
 be connected in. It is intended that when a load is placed upon the 
 battery the voltage shall be regulated by the main rheostat, resistance 
 being cut out as the load is increased. This means, however, that 
 every time the load is increased or diminished, the rheostat adjust- 
 ment must be made. If it is not, and the load be suddenly decreased, 
 a few electric lights left in circuit will be Uable to burn out; if the 
 load be suddenly increased, the lights will get very dim. Where the 
 storage battery was used for furnishing power for lights only and where 
 the lights could be turned on or off only in groups, the case was not 
 so bad, but where the same storage battery was used for furnishing 
 power for operating hoists, the load of which was extremely inter- 
 mittent and irregular, this system required that there should, at all 
 times, be a. man at the switchboard, practically with his eyes on the 
 voltmeter and his hand on the rheostat wheel. For th^se reasons, 
 in systems combining light and power, this arrangement did not 
 work well and it became evident that a change must be made. 
 
 After a year or so of attempting to operate the storage batteries 
 with the voltage regulated by rheostats, and at the same time experi- 
 menting in a few places with the end cell method of regulating the 
 voltage, the latter was found to be preferable and was introduced in 
 all electric plants about 1904 and 1905. 
 
 In the end cell method of regulating the voltage there is, on the 
 switchboard, a so-called end-ceU switch, consisting of a number of 
 points to any one of which the switch can be turned. These points 
 are connected successively to the end of the battery and to the 
 connections between the successive cells. By turning the end cell 
 switch to the point corresponding to the end of the battery all of the 
 
273 
 
 cells are placed in 'series. By turning it to the next point, the end 
 cell is cut out; to the next point, two cells are cut out, and so on. 
 
 When the storage battery is first charged, the voltage of its cells is 
 high and all of them are not required to give the proper voltage, 
 so the end cell switch is turned to such a point as to place in action 
 only as many cells as are necessary. As by use the voltage of the 
 battery gradually decreases, one cell after another is added to the 
 circuit, so that the terminal voltage of the portion of the battery 
 used remains practically the same. 
 
 In the switchboard arranged for use with the end cell switch method, 
 the same rheostats are needed as before because they are all necessary 
 during the process of charging, but the connections are so made on 
 this switchboard that when the main batters' switch is thrown to 
 discharge, the small rheostats are left out of the circuit and the main 
 rheostat is short circuited. 
 
 One of the great difficulties foimd in maintaining the early fortifica- 
 tion lighting plants was that they were used so Mttle that it was diffi- 
 cult to keep them in order, for machinery of all kinds deteriorates 
 much more rapidly when not in use than when in use. The question 
 then arose as to whether it might not be desirable to use these plants 
 for regular garrison lighting. This would not only insure that they 
 would be kept in order, but it would also give the garrison a much 
 needed experience in taking care of the plants. 
 
 This subject was referred for consideration to the Board of Officers 
 above referred to and they submitted two reports on the subject, one 
 published as Mimeograph No. 41 and the other as a Supplement to 
 Professional Papers No. 27. In the former, the lighting of garrisons 
 by fortification plants was recommended under certain conditions. 
 The latter report related principally to the method of lighting garrison 
 buildings when at considerable distances from the fortification plant. 
 For such cases, the use of alternating current was recommended, 
 this to be obtained from the direct current by the use of motor 
 generators. Suggestions were also made in this report as to the ust 
 of "boosters" for reinforcing the voltage of direct current lines at 
 points distant from the plant so as to make up for the line loss. 
 The board further recommended that duplicate generating plants be 
 installed as reserves rather than storage batteries. 
 
 In 1903, the board submitted another report published as Mmeo- 
 graph No. 75, discussing according to the standards of the times 
 the relative advantages and disadvantages of direct current and 
 alternating current for central plants, and inclining to the opinion 
 that a direct current installation was generally preferable. 
 
 In 1906, in the Taft Board report, the subject of electrical installa- 
 tions is touched upon and a central plant is recommended for all 
 fortified posts, with reserve plants in each battery or group of batteries 
 173341—20 18 
 
274 
 
 clirect-current power is preferred to alternating current. Remarks 
 on this subject on pages 16, 35, and 36 of this report might weU be 
 read. 
 
 Since the report of the Taft Board the installation of electric power 
 in our fortifications has been steadily progressing and has been slowly 
 undergoing a sort of evolution. The results of this evolution have in 
 some respects been almost the opposite of what was evidently con- 
 sidered probable by that board. These developments will be dis- 
 cussed, each in its proper subdivision of this chapter. 
 
 ELECTRIC INSTALLATIONS. 
 
 In some important respects, the requirements which it is essential 
 that fortification electric installations shall fulfill are quite different 
 from those governing in commercial plants. In ^ commercial life 
 certainty of action, though an important desideratum, is usually not 
 considered as necessary as economy in operation. In fortification 
 plants, on the other hand, economy in operation is but of minor 
 importance, as compared with reliability and certainty of action. 
 A commercial plant is in operation day after day and all day. Econ- 
 omy, therefore, is of prime importance, and an occasional temporary 
 breakdown, though it may mean a loss of time and in one or more ways 
 a loss of money, is not an irremediable disaster. Fortification jplants, 
 on the other hand, are, in time of peace, usually run at intervals only; 
 they find their real use only in time of action,, and at such a time a 
 breakdown wiU, in all probability, prove disastrous. Consequently, 
 in selecting or designing electric machinery or fittings for installation 
 in fortifications, care must be taken to select only those which are 
 thoroughly reliable, and these must be installed so as to give them 
 the maximmn possible protection against injuries caused by accident 
 or the efforts of the enemy. 
 
 The safety of an electric plant requires that it be thoroughly pro- 
 tected from hostile projectiles — in fact, in the early emplacements it 
 appeared to be considered about as important to give protection to the 
 power room as to the magazine. Consequently, in the first emplace- 
 ments designed, the power rooms were located well in the interior 
 of the emplacements in positions somewhat similar to the magazines. 
 These rooms were dark and usually damp, and it was soon discovered 
 that an electric plant in such a position would rapidly deteriorate. 
 Furthermore, the electric leakage, especially on the switchboard, 
 was considerable. 
 
 An additional trouble due to dampness arose wben the attempt was 
 made to place storage batteries in these damp rooms. (See Plates 
 XIV, XV, XVIII, and XIX.) It was found that water would con- 
 dense in the storage-battery cells, filling them in some cases to over- 
 flowing and reducing the strength of the solution. The surplus 
 
275 
 
 liquid had, of course, to be siphoned out at intem^als and new acid 
 had to be added to bring the solution up to proper strength. So 
 much trouble was caused in this way in the earlier storage batteries 
 installed in such damp rooms that it soon became customary to 
 remove them, and the generating plants as well, to temporary build- 
 ings located outside of the emplacements, frequently in partially 
 exposed positions. 
 
 The next step, of com^e, was to utUize for miscellaneous storage 
 pxu^poses the rooms in the eniplacement which had been intended for 
 the power plants and from which, in some cases, the electric plants 
 had been removed. The result was that had it been found necessary 
 to move the electric plants hastily back from their supposedly tem- 
 porary locations, there would have been no place to put them because 
 the rooms previously assigned to that purpose had been utUized 
 for other purposes. 
 
 Beginning, however, about 1902 or 1903, a change in pohcy was 
 made, and in' all emplacements thereafter constructed power rooms 
 were provided which were not only well ventilated and free from 
 condensation but were so located as to be fairly well protected from 
 hostde fire. (See Plates XVII and XX to XXVI.) 
 
 LOCAL AND GENERAL SYSTEMS. 
 
 In seacoast fortifications the guns are usually concentrated into 
 small groups called batteries. The batteries are sometimes built 
 close together and sometimes are scattered over a large area. Elec- 
 tricity is needed for one or more purposes at every battery but may 
 be provided in two ways — by making the electric installation in each 
 battery or contiguous group of batteries, separate and independent 
 from the installations in other batteries or groups of batteries ; or by 
 making the installations in all of the batteries parts of. a single large 
 installation. The former is sometimes called the "separate plant 
 system" and the latter the " central plant system." 
 
 If rehance be placed on the central plant system, each battery is 
 dependent for its electric power upon an electric connection with the 
 central plant. Not only is this, as it were, putting aU our eggs in the 
 same basket, but experience has shown that electric cables are quite 
 subject to injury or destruction. The essential requirement of 
 reliability, therefore, points to the adoption of the "separate plant 
 system." 
 
 It is therefore desirable that, as far as possible, the electric installa- 
 tion in each large battery, or group of contiguous smaller batteries, 
 should be practically independent of the installations in other bat- 
 teries, and should not be absolutely dependent for power upon a con- 
 nection with a central plant or a plant in another battery. 
 
276 
 
 It is much more economical, however, to operate a central plant 
 having power equal to the combined power of .several smaller plants 
 than it is to operate the several smaller plants independently and 
 simultaneously. Furthermore, it frequently happens that the de- 
 mand for electric power at any one battery or section of the forti- 
 fications is very small, so small in fact as hardly to make it worth 
 while to start up the local plant. It is probable, however, at every 
 large group of fortifications that there will at aU times be some de- 
 mand at some part of the fortifications sufficient to justify running 
 the central plant on a small scale. Consequently, in time of peace, 
 both economy and convenience point to having a central plant 
 practically always in operation, local plants or the plants in local 
 systems being utilized only sufficiently to keep them in good order. 
 Need of Reserve Sources of Power. 
 
 It has been shown that in selecting or designing any portion of a 
 fortification electric installation, reliability and certainty of action 
 are the prime desiderata. But, unfortunately, however great the 
 care that may be taken in selecting or in designing electrical apparatus, 
 an occasional breakdown is sure to occur. Should such a breakdown 
 happen in time of action, it woiild be disastrous. It is essential, 
 therefore, that in case of such a breakdown we have an additional 
 or reserve source of power "to fall back upon; that is, we must have 
 a duplicate source of power for use in case the main source is destroyed 
 or in case the connection with the main source is cut. In fact, we 
 must go further and must have other means to fall back upon in case 
 all our sources of electric power should fail. 
 
 These ideas have been carried out in our fortification construction. 
 Thus there are usually provided two sources of electric power which 
 are available for lighting. In case both of these sources should be cut 
 off, aU our esmplacements are provided with lamp recesses and 
 "reserve lanterns" for use in these lamp recesses. Up until a few 
 years ago, the reserve lanterns were oil lamps; now they are merely 
 small, portable, electric' lanterns operated by low-voltage dry bat- 
 teries, similar in their essentials to the flash lights in such common use 
 in conmiercial life. 
 
 Similarly, our ammunition hoists are normally operated by 
 electric power, but they are aU built so that in case the electric power 
 should absolutely fail the hoists can be operated by hand. Similar 
 arrangements are made wherever else electric motors are installed. 
 
 The principle of having a reserve source of electric power was in- 
 cluded in the reports of the first board of Engineer officers on elec- 
 trical installations referred to above. They recommended, for each 
 battery, a steam engine as the prime source of power and a storage 
 battery as a reserve. The idea was that the storage battery should 
 at all times be kept charged nearly up to the maximum, or at least 
 
277 
 
 that the begmning of an engagement should find it so chained. Dur- 
 ing action the steam engine itself would be used, but in case the en- 
 gine should become disabled the storage battery could instantly be 
 put into service. This was the theory of the case, but the facts are 
 that a storage batters', to be in good condition, must be charged 
 and discharged at fairly frequent intervals. Consequently the cus- 
 tom gradually grew up in peace time of running the engine only once 
 every week or so to charge the storage battery, and of utilizing the 
 storage battery as the actual source of power between these times 
 of charging. This may have been convenient and may have pre- 
 served the storage batteries, but it was directly opposed to the theory 
 of reserves. 
 
 For several years the standard type of installation was essentially 
 like that just described, the steam engine as the primary source of 
 power and the storage battery as the reserve. It was soon found, 
 however, that storage batteries are expensive to install and, at least 
 imder the conditions met with in fortifications, are even more expen- 
 sive to maintain. Storage batteries for general fortification use were, 
 therefore, gradually done away with and they are now no longer 
 standard except imder very special conditions, such as in connection 
 with the 'submarine mining system and in certain telephone instal- 
 lations. 
 
 The gradual abandonment of the storage battery required that 
 omething should be substituted for it as a reserve source of powers. 
 It therefore became customary, about the time of the abandonment 
 of the storage battery, to install in our fortifications as reserve sources 
 of power, additional electric generators operated by prime movers. 
 These were as nearly as possible like the main sources of power. 
 
 In this character of installation, the generators forming the main 
 source of power and those constituting the reserves are duplicates of 
 one another. In large batteries or groups of smaller batteries the 
 total demand is sufficient usually to require that two or more standard 
 gasoline sets be installed. Where this is true, other and similar 
 generator sets are installed as reserves, but it is usually not consid- 
 ered necessary to install as reserves as manj' sets as are needed in the 
 main source of power. Thus, where two sets are required to furnish 
 aU the power that may be needed, it is usually considered sufficient 
 to install a third set as a reserve for either of the other two. Where 
 three sets are required to supply the maximum demand, a fourth set 
 may be considered as a sufficient resers'e. 
 
 A steam plant as the prime source of power, and more especiall}' as 
 a reserve, has the great disadvantage in that it can not be started 
 quickly. In fact, an hour is about the least time upon which it is 
 safe to count for getting a steam plant in full operation. Of course 
 this time might be shortened by getting up fires in all steam plants at 
 
278 
 
 the beginning of an action and keeping these fires banked until called 
 upon; but when we consider the speed of modern naval vessels and 
 the extreme ranges at which actions may be commenced, an attempt 
 to adopt this policy would mean practically that we would have to 
 keep up fires all the time in all the steam plants. Consequently, the 
 steam plant came to be considered as unsuitable for a reserve. 
 
 Internal combustion engines, on the other hand, can be started 
 more quickly than the steam plants. This is only partially true of 
 the old oil engines and is one of the reasons for doing away with them. 
 The gasoline engine, however, has now been brought to a high stage 
 of perfection and is in very general use; it can be started instantane- 
 ously and consequently has been adopted as the standard, not only 
 for reserve plants, but also for the main plants in all local installations. 
 
 The first gasoline engine installed for fortification purposes was at 
 Fort Wool, Va., during the manoeuvers of 1905. A number of de- 
 fects developed in this engine and the same type was therefore not 
 used again. A few years later, however, under the charge of Col. 
 Harry Taylor, then district Engineer officer at New London, Conn., a 
 number of other types were tried and as a result there was devel- 
 oped a satisfactory type of 25 kilowatt, gasoline actuated, direct 
 connected, generating set. For several years thereafter, tHe work of 
 perfecting this engine was continued and there are now hundreds of 
 them in the service. 
 
 Central Plant. 
 
 For the reasons and under the circumstances stated above, there was 
 gradually evolved the idea of having at each large fortification post 
 a large central plant as the main source of power and to have in the dif- 
 ferent local systems the standard gasoline engines as reserves. This 
 central plant should in general be so located as to be thoroughly pro- 
 tected from hostile fire. As it can well be utilized for garrison light- 
 ing in time of peace, this will insure that it will always be in good 
 order and that well-trained men will always be available for its 
 operation. 
 
 The character of the central plant which should be used is one upon 
 which entire agreement has not been reached. If it were intended 
 merely for fortification purposes, certainty of action would take pre- 
 cedence over economy, but since the central plant must be run almost 
 constantly in peace time, the question of economy should be given 
 more weight than is usually considered necessary in fortification 
 plants. ^It seems to be generally considered that in most cases a 
 steam plant is the most economical and, if the plant is large enough, 
 use might be made of very high pressure engines with condensers. 
 Some experts advocate a modern form of steam turbine. This, how- 
 ever, is strictly a question of electrical engineering and will not be 
 further touched upon here. 
 
279 
 
 The central plant should preferably be composed of a number of 
 separate units, each unit being practically complete in itself. Yet to 
 insure flexibility, it is desirable, if it can be done without too much 
 complication, to so design the system of piping that any engine can 
 be run from any boiler. The total capacity of the central plant 
 should be at least great enough to supply all the needs of the de- 
 fense while stiU keeping back a reserve. An additional slight reserve 
 is also an advantage, especially should it be desirable during time of 
 action to use electric power for garrison purposes. The individual 
 units, or at least some of them, should be so small as to take care on 
 an economical scale of what may be called the minimum requirements. 
 During time of peace, as many of the units as may be needed at one 
 time will be in operation but it is desirable that these units be utilized 
 in some kind of rotation so that all the units wiU be kept in good con- 
 dition at all time. 
 
 Local Plants. 
 
 In time of action it is not improbable that either the central plant 
 may be injured or that the connections with one or more of the local 
 systems wiU be cut off. It is essential, therefore, that each of the 
 local systems have its independent source of power which can be 
 quickly put in operation should the central plant be cut off. In time 
 of peace, these reserve plants wiU be but seldom needed, but each one 
 should be operated from time to time so as to insure its being in good 
 condition when necessity requires that it be called upon. 
 
 Alternating or Direct Current. 
 
 In our local systems electricity is used for lighting. The voltage 
 must be that suitable for the electric lamps to be used, and unless we 
 are going to have different sets of lamps, the voltage of one local 
 system must be the same as the voltage of the others. Although 
 theoretically not necessary, it is evidently desirable that our electric 
 lamps should be interchangeable among all batteries; that is, that 
 aU om local systems should be of the same voltage. At present 
 the consensus of opinion seems to be that the voltage at the lamp 
 terminals shall be about 110 to 112 volts. 
 
 As far as the lamps are concerned it is immaterial whether we use 
 the direct current or alternating current power, and if desirable we 
 may switch from one kind of power to the other at will, provided 
 that the voltage of the two be the same. 
 
 Ease of connection would, in general, indicate that our motors 
 should require the same voltage as the lamps. As far as the kind 
 of power is concerned we can install either alternating current 
 motors or direct current motors but we can not change instanta- 
 neously from one kind of power to the other unless our motors are so 
 wound as to make this change possible and this, in general, is not 
 true. Consequently, as far as our light and motor requirements are 
 
280 
 
 concerned, we have a free choice as to whethei" our electric system 
 should be direct current or alternating current. 
 
 In the first electric installations, the storage battery was the 
 reserve source of power. This battery necessarily gives off direct 
 current and direct current only, and as long as storage batteries were 
 used as reserves it was but natural that direct current installations 
 should be exclusively used in fortification work. 
 
 The complete abandonment of storage batteries as a reserve 
 soiu-ce of power, however, leaves the question as to whether the 
 installation shall be direct current or alternating current, dependent 
 merely upon which is more suitable for the purposes for which electric 
 power is required. As has been stated before, either may be used 
 for lighting and a change from the one to the other may be made 
 instantaneously. Either kind of power may likewise be used to drive 
 electric motors, but as motors are wound for either one kind of power 
 or the other the change can not be made after the motors are once 
 installed. 
 
 The most modern form of emplacement is the one-story type in 
 which projectile hoists are not needed. Furthermore, the Ordnance 
 Department seems to be opposed to installing electric motors on 
 gun carriages for traversing or elevating. Consequently, about the 
 only motors to be used in future emplacements are those installed 
 by the Ordnance Department on the gun carriages for retracting 
 purposes. And for this purpose either alternating current motors 
 or direct current motors would appear equally suitable. There is 
 now, therefore, no reason as far as emplacement use is concerned, 
 why an alternating current system of power is tiot as good as a 
 direct current. 
 
 The alternating current system has the great advantage of per- 
 mitting the transmission of electric power to considerable distances 
 with but slight line loss. With the growing tendency to spread out 
 the defensive works and to plan small rapid-fire batteries, range 
 finding and searchlight stations at considerable distances from the 
 main batteries, the reduction of line loss is becoming more important. 
 Alternating current systems are becoming more and more popular 
 in commercial life and it is the opinion of the writer that for general 
 fortification purposes, the advantages of an alternating current 
 installation far outweigh the disadvantages. 
 
 It should be noted, however, that the use of the alternating current 
 system requires the introduction of high voltage currents, at least in 
 the transformer room. For safety, it is considered necessary that 
 these transformers be installed either in separate rooms or in separate 
 alcoves in the power rooms, so that they may not endanger the 
 personnel. 
 
281 
 
 The first installation in seacoast fortifications of alternating cur- 
 rent power on a large scale was made by the writer, then the local 
 district engineer at Fort Monroe, Va., in preparation for the joint 
 Army and Navy maneuvers of 1905. This was done for the following 
 reasons: It had been decided to attempt to supply electric power 
 sufficient to operate at least 10 searchlights, to light all the batteries, 
 range stations, etc., to operate at the same time all the motors on 
 the hoists and gun carriages. Sufficient electric plants to *do this 
 were not available and funds for purchasing electric plants were not 
 sufficient. There was, however, in operation in the neighboring 
 towns of Newport News and Hampton, an alternating current 
 system, used for lighting and for power purposes. It was, therefore, 
 decided to make connection with this commercial plant. This was 
 done by means of large transformers located in the power house of a 
 certain battery. Thence alternating current power was distributed 
 to all local systems. In each local system there was installed a set 
 of transformers and a motor generator. The transformers reduced 
 the current of the alternating current^ystem to that which was con- 
 sidered safe to aUow to enter the local power rooms, 110 in small 
 plants and 220 in large ones. With this reduced voltage the alter- 
 - nating current motors of the motor generators were operated, the 
 generator ends giving off direct current at the standard voltage of 
 115. By this means it became possible with the funds available to 
 provide sufficient electric power for all purposes. 
 
 During these maneuvers and afterwards this system worked so 
 well that it was later decided to make it permanent. A new central 
 plant to furnish three-phase alternating current at 2,300 volts was 
 installed in the power plant building of the large new Coast Artillery 
 School. The distributing cables from this system are installed in 
 conduits and pass to the power rooms of all the local systems. Here 
 there are installed the transformers and the motor generators. !Many 
 of the latter, now in operation, are the same as were purchased in 
 1905. 
 
 For the new fortifications at Los Angeles and San Diego on the 
 Pacific coast, alternating cmrent power was already available from 
 a commercial source and was utilized for post lighting before the 
 construction of the modem fortifications. Consequently an alter- 
 nating current system of power was installed in the new emplace- 
 ments recently constructed. 
 
 ELECTRIC WIRING AND FITTINGS. 
 
 In electrical installation for lighting purposes in the earlier bat- 
 teries, the wires and fittings used were those common in commercial 
 life at that time. The wire was the ordinary rubber-covered type, 
 the lamp sockets were the usual sockets mounted on porcelain 
 
282 
 
 bases, attached to wooden blocks fastened to the walls, and the 
 switches were commercial throw-switches with porcelain bases. 
 
 Wiring. 
 
 As has been stated, these earlier batteries were extremely damp, 
 not only from condensation but from seep water. The moisture 
 deposited by condensation caused large electrical leakage and the 
 seep Walter showed a tendency to destroy the insulation of the wiring 
 wherever it came in contact with it. 
 
 The next step seems to have been to install the rubber wires in 
 pipe conduits. These pipes were made so as to screw into metal 
 junction boxes installed wherever the circuit branched or where a 
 light or other fitting was to be installed. It was thought that by 
 installing the wiring in piping it would be protected from seep water. 
 Unfortunately, however, a considerable portion of this pipe was 
 buried in the concrete, and in spite of all that could be done it 
 Seemed as if seep water would find its way into these conduits and 
 would destroy the insulation and eventually ground the system. 
 After several years' experience, therefore, this system was abandoned. 
 
 The next step was to abandon the rubber-covered wire entirely 
 and to make use of lead-covered cables. In some cases these cables 
 were attached by insulated hangers to the walls and ceilings so as to 
 be in plain sight, and in other cases attempts were made to bury the 
 lead cable in the concrete. Unfortunately, however, it has been 
 found that seep water destroys the lead coverings of cables even 
 more rapidly than it affects the rubber insulation, so wherever lead 
 cables are buried in concrete, trouble is soon experienced with them, 
 and even where they are exposed to view care must be taken to 
 protect them from seep water. 
 
 Exposed wiring has the advantage of easy inspection and if the 
 hangers are properly insulated, electric leakage will probably not 
 occur. Unfortunately, this exposed isviring proved disadvantageous 
 in those locaHties where the discipline of the personnel was not what 
 it should be. Most seacoast forts are located where there is good 
 fishing and the sight of so much lead seems to have proven an irresist- 
 ible temptation to the would-be fishermen of the garrison who, in 
 attempting to strip off the lead for their sinkers, were not always as 
 careful as they might have been to, avoid harm to the rubber insula- 
 lation under the lead or damage to the copper cores. 
 
 To avoid the class of injury just mentioned, as well as other 
 mechanical injuries, the next step was to make use of armored cables 
 attached by hangers to the walls or ceilings. This was the method 
 recommended by a board of officers appointed some eight or ten 
 years ago to give consideration to and submit reports upon the best 
 type of wiring and electrical fittings for fortification use. It is now 
 the standard practice. 
 
283 
 
 On account of the excessive dampness in the old emplacements, 
 considerable leakage occurred at aU switches which, at first, were 
 ordinary throw switches. To avoid this source of leakage it soon 
 became customary to provide as few branch circuits as possible, 
 leaving practically the entire lighting system of an emplacement as a 
 single circuit, controlled by a switch on a panel board ia the engine 
 room. Here the heat from the engine soon dissipated the dampness 
 and the electrical leakage was, therefore, comparatively small. 
 
 This system of having the entire emplacement hghted by a sickle 
 switch had the great disadvantage that if anything happened to any 
 part of the circuit no part of the battery could be lighted. 
 
 The next step, therefore, was to divide up the battery iato sections, 
 each Lighted by a special circuit and each circuit operated by a 
 special switch on a panel board in the engine room. This gave rise 
 to the panel-board system. With the improvements made in the 
 new batteries ia the way of preventiag condensation and dampness 
 from other sources, it became possible, and it was much more con- 
 venient, to place other panel boards at different portions of the battery 
 Most modem large emplacements have several panel boards. 
 
 Wherever the panel board system is introduced, the' cable connect- 
 ing the panel board and the main switchboard in the engine room is 
 not tapped between. At the panel board there is a lai^e switch 
 so that the circuit can be broken there ia case it is necessary. At the 
 engiae room end, the cable leads off from one of the switches on the 
 maia distributing panel, which usually is fused, though occasionally 
 circuit breakers are substituted for the fuses. 
 
 The distributing panel boards must, of course, be made so as to 
 withstand the shock and blast of the guns when fired. They must be 
 so located as to be protected from seep water and reduce condensa- 
 tion to the minimum. Condensation can be prevented to a great 
 extent by making the panel boards of comparatively thin slate, and 
 by mounting them so as to be held several inches from the wall by 
 strips of wood or other heat-insulating material. In such a position 
 there can be no conduction of heat from the panel board to the 
 wall and with the air circulating freely both in front and behind the 
 panel, its temperature, shoidd remain always practically that of the 
 surroimding air. 
 
 In some of the earUer installations, the Artillery battery command- 
 ers requested that these panels be placed in boxes so that they 
 coidd be kept locked and this request was complied with. Since it is 
 very desirable that a person, by a glance at the board, should be 
 able to see whether any particular branch circuit is switched on or 
 off, the front doors of the panel boards first installed were made of 
 glass. Unfortimately, these glass fronts were often broken by the 
 blast of the guns during target practice, and it therefore became cus- 
 tomary to substitute for the glass a copper wire netting. 
 
284 
 
 Boxing-in the panel board interfered witli the free circulation of 
 air around it, even though the front door was of netting, and conse- 
 quently there would usually be more or less condensation and slight 
 electrical leakage. To avoid this there were designed tightly closed 
 panel boards with doors which shut into rubber rabbets, thus inclosing 
 the panel board in an air-tight case. 
 
 The object of having the panel boards inclosed air-tight is to 
 prevent condensation, but it should be noted that whenever the box 
 is closed the air contains the same percentage of moisture as the air 
 in the emplacement at the time the box is closed. If, thereafter, the 
 temperature should faU, condensation will necessarily take place 
 inside the box, and what is more, when once this has taken place 
 evaporation can not occur until the temperature of the box is raised. 
 
 It is the opinion of the author that it should not be necessary to 
 place the panel board in a box at aU or to lock it up. With proper 
 care no unauthorized persons should be in the neighborhood of a 
 panel board, and with the proper discipline no unauthorized mem- 
 bers of the detachment would ever attempt to throw the switches 
 on the board. 
 
 It is believed, therefore, that the most satisfactory form of panel 
 board is an open one. It should be located in a convenient place and 
 be so mounted that there will be practically no condensation. 
 
 It should, of course, be unnecessary to state that all the branch 
 circuits of a distributing panel board should be properly fused. 
 Wherever a distributing panel board is used, it is very convenient 
 to have on it a small pilot light, not only for the purpose of lighting 
 the board and making it easier to read the names of the respective 
 switches, but also for indicating whether or not the power is on and 
 is properly connected in the power room. This panel Hghts should, 
 therefore, be connected into the circuit below the main switch of 
 the panel board so as to be in operation whether the main switch is 
 thrown in or out. 
 
 The cables feeding these distributing panel boards are usually 
 quite large and should be used for this purpose and no other. They 
 should not be tapped between the panel board and the switchboard 
 in the power room. In a properly designed battery it should be 
 possible to lay the main line cables of this character in conduits and 
 if this be done, the cables need not be armored. 
 
 This same thing is true of the cables feeding the hoists. Ordinarily, 
 the projectile and powder hoists of any emplacement are very close 
 together and the current feeding the hoists is large enough to justify 
 a cable beiag used for this purpose and this purpose only. This cable 
 should lead back from the neighborhood of the hoist to the switch- 
 board in the power room, preferably through a conduit. If a conduit 
 is available, it is not necessary that these large cables should be 
 
285 
 
 armored. In the hoist room this cable may go directly to the con- 
 troller of the hoist if there be but one, or if there is more than one 
 hoist, to a small branch panel board conveniently located with 
 respect to the different hoists. 
 
 As was stated, it is now the standard practice that emplacement 
 wiring should be exposed, the cable being lead covered and armored 
 and attached to the ceilings or walls by hangers. This is strictly 
 true of the branch circuits leading from the panel boards to the hghts 
 themselves. Ordinarily, the panel board is located either in one of 
 the principal galleries or corridors or in one of the principal rooms of 
 the emplacement, and the wires leading from this panel board to the 
 other rooms pass along the ceiling of galleries and corridors. Where 
 they pass through walls, they do so through short pieces of pipe, 
 either iron or terra cotta, installed when the walls are built. The 
 2-foot air passages needed for ventilation and dryness frequently 
 foma very convenient routes for these cables, since there is usually 
 not much passing of people through them, and consequently the 
 cables installed there are fairly free from the danger of accidental 
 mechanical injuries. 
 
 The main large cables leading from the panel boards back to the 
 power room are usually installed in conduits put in place when the 
 emplacement is built. Usually these conduit lines are installed 
 under the floors and lead from the power room through the main 
 corridors or galleries. At intervals, manholes or handholes are 
 placed and these are, of course, necessary wherever the conduit line 
 branches. 
 
 In one battery- the experiment was tried with considerable success 
 of installing the conduit Unes in the ceiling just above the reinf orcir^ 
 bars iostead of under the floor. The conduits used were of fiber duct 
 and were laid a single tier deep. At intervals, handholes were left 
 which were closed by hinged doors that could be swung down when 
 access was necessary. 
 
 The number of conduits necessary in emplacements is usually not 
 large. One conduit is needed, of course, for each light panel board 
 and one for each hoist panel board. One should lead to the ordnance 
 motor generator room if there be one, and one also to the gun well 
 of large guns. Other conduits are desirable for bringing fire-control 
 wires into the battery and these conduit lines must, of course, be 
 connected with the interbattery system of conduits. 
 
 Duct System. 
 
 In the earlier fortifications, the emplacement electric systems were 
 usually local, there being a separate plant for each large emplacement 
 and it being rather unusual for this plant to be used for other purposes. 
 Where it became necessary to use it for other purposes, the connecting 
 cables or wires were usually strung in the air on poles. 
 
286 
 
 Hanging the power cables on poles, of course, made them quite 
 vulnerable, and the next step was to use lead^covered cables and 
 simply bury them in the ground. 
 
 As long as these buried lead-covered cabks were not interfered with 
 they worked all right, but unfortunately it became frequently neces- 
 sary to lay other cables in the vicinity or to dig trenches for water 
 pipes, sewers, etc., and in digging into the ground the lead-covered 
 cables were often injured. Consequently, it became customary 
 wherever cables were buried in the ground, to use armored cables 
 exclusively. 
 
 Later on, in connection principally with fire-control conmaunica- 
 tion, the system of instaUing fiber or terra-cotta ducts was introduced 
 and the number of such conduits was always made sufficient to 
 provide for the battery and other power and fighting cables. 
 
 Duct systems are provided for fire-control cables, for power cables, 
 and for the cables required in submarine miaes, but as the require- 
 ments of the last mentioned are usually somewhat pecufiar they will 
 not be further referred to in this place. 
 
 Apparently the best form of duct system now used consists of 
 terra-cotta multiple-duct tUes embedded in concrete. The trench 
 is first dug, a foundation of a few inches of concrete is laid on the 
 bottom, the tUes are then put into place and are afterwards sur- 
 rounded on the sides and covered on the top with concrete. 
 
 Another and alternative form of duct system which has proved 
 very satisfactory, especially in certaia of our tropical possessions 
 where the breakage of tiles in transit rendered the tile system very 
 expensive, is a fiber-duct system. These fiber ducts can be pur- 
 chased in the market of diEEerent diameters and usually in 5 or 6 foot 
 lengths. They are laid in concrete in much the same way as the tile 
 ducts and usually in such a manner that the different ducts break 
 joints. 
 
 Ordinarily, it is customary to install but one cable in each duct, 
 although if the cables are small and are available so that they can be 
 drawn in at the same time, it is possible to lay two or three small 
 cables in one duct. 
 
 For convenience in the installation of these cables, manholes are 
 required. In general, the cables are furnished in thousand-foot 
 lengths. It usually is considered necessary to have manholes where 
 the different cables join, and as it is somewhat inconvenient to haul 
 in a full thousand feet at a time, it is usual to build about two addi- 
 tional manholes in each thousand feet of duct fine. This places 
 the manholes in a line of ducts about 325 feet apart. Additional 
 manholes must also be provided wherever two conduit fines intersect 
 or where a conduit fine branches. 
 
287 
 
 In cases where the power cables carry only direct currents and 
 where the voltage does not exceed 250, it is permissible to lay power 
 cables and telephone cables in the same line of conduits, but of course 
 in different ducts. 
 
 Where, however, the power system is alternating current and 
 especially where the voltage carried is high, power cables should have 
 conduit lines different from the lines used for telephone communica- 
 tion. Xot only is this due to the danger of crosses where high- 
 tension power cables and telephone communication cables pass 
 through the same manholes, but because it is found that where 
 alternating-current cables are laid parallel and fairly close to telephone 
 cables, the alternations of current cause a ringing sound in the tele- 
 phone which interferes with the hearing. 
 
 The installation of conduits has now reached a stage where the 
 shape of the manholes has become standardized and drawings of the 
 standard manholes should be examined and studied. 
 
 Between manholes a conduit line should be made as straight as 
 possible. In general, it should be graded so as to drain to one or the 
 other of the manholes, and great care should be taken to be certain 
 that there are in a conduit line no depressions between manholes in 
 which water may accumulate. 
 
 Cables which are to be inserted in the conduit system should always 
 have a waterproof covering of lead, even if they are not armored. 
 All joints should be made at manholes only, should be well and care- 
 fully made and waterproofed, the lead sheaths of the two cables 
 being connected by a lead sleeve carefully soldered to both sheaths. 
 
 If properly installed, such a system wiU not be injured should 
 water get into the manholes or conduits. Of course, it is better 
 that the water be kept out if possible, and wherever drainage is 
 available the manholes should be properly drained. In many 
 localities where conduit installations are placed, however, the bottoms 
 of the manholes and the conduits themselves will not infrequently 
 lie below the groimd-water level and it is inevitable that ia time these 
 conduits wiU fill with water. If this happens no damage shoidd 
 occur to the cables if they are properly waterproofed and whenever 
 any work is to be done on the cables it is a simple matter to pump 
 out the manholes. 
 
 There have, however, been cases where the ground water seeping 
 into the conduit system has in time pitted the lead covering of the 
 cables and of course leaks and grounds have resulted. This occurred 
 in the defenses of Honolulu just westward of the moimtain known as 
 Diamond Head. Immediately to the westward of this mountain 
 there was originally a large swamp or flat. This had been reclaimed 
 iato a park and the flow of water concentrated in a well-defined 
 stream over which there were a n\tmber of bridges. The lowland 
 
288 
 
 was quite extensive and when it became necessary to lay conduits, 
 economy pointed out that the conduit system should pass through 
 the park rather than make a very long detour around it. 
 
 At certain seasons of the year the level of ground water rises up 
 to within a few inches of the surface of the ground, and of course 
 the manholes and conduits in this part of the system are flooded 
 and remain full of water. For a number of months the system 
 worked all right, then grounds began to appear and soon became 
 worse and more numerous. An investigation was made and the 
 cables were found to be badly pitted, apparently due to the action 
 of the ground water. This ground water was essentially swamp 
 water and contained much vegetation in solution, and some of 
 these vegetable salts had evidently acted upon the cables. It 
 therefore became necessary to re-lay a portion of the conduit line 
 on a long detour in the higher ground around the original swamp. 
 
 Fittings. 
 
 When it first became necessary to wire emplacements for lighting, 
 the fittings selected were those used in commercial hfe. These were 
 the usual types of porcelain lamp bases, switch bases, and so on. 
 On account of the dampness always present in these older emplace- 
 ments there was much electrical leakage from these fittings, and it 
 soon became evident that special fittings would have to be used. 
 
 The next step was to use metal boxes for all fittings, the wires 
 being carried into' them through pipes screwed into the boxes. The 
 top of the box, where it was a mere junction box, was made solid. 
 Where lamps or switches were to be installed the tops were specially 
 prepared for or made a part of these fixtures. These tops were 
 screwed on tight, and the rabbets into which they fitted were usually 
 lined with rubber so that the joints would be what was considered 
 air-tight. 
 
 In the early days there was no standard design for these boxes, 
 and the selection of the type to be used in any emplacement was 
 left to the district officer. He usually had to choose a type that 
 happened to be available in the locality. The earlier boxes were 
 screwed to the walls or ceilings through holes in the base, and it 
 was attempted to make these openings water-tight. However, 
 whenever the guns were fired the shock was distributed through the 
 concrete of the emplacement, causing a vibration, and quite fre- 
 quently this vibration would loosen the screws or would destroy 
 the waterproofing around them. Water would begin to seep into 
 the boxes, especially where their bases were screwed to the ceihng. 
 Once in the box, of course, the water was apt to cause grounds or 
 short circuits. 
 
289 
 
 It was evident, therefore, that another form of box was necessary, 
 and one was designed that is fastened to the ceihng or walls by 
 exterior lugs. Some of the boxes are, of course, used for making 
 joints in the circuits. In all such cases these joints should be 
 thoroughly waterproofed, using almost the same care as is done in 
 joining electric cables to be installed in conduits, where it is supposed 
 they may occasionally be covered with water. 
 
 Some of the boxes are, of course, used for switches. Many forms 
 of switches have been tried, the most common form being that 
 manufactured by the General Electric Co. and shown in their cata- 
 logue. As long as this switch is always turned in the same direction 
 this type works satisfactorily, and it has a ratchet arrangement 
 provided with a spring to prevent it being tiuned in the wrong 
 direction. With intelligent handling no difficulty should have been 
 experienced with this form, but unfortunately the type of enlisted 
 man frequently met with can not be trusted with the handling of 
 delicate switches. They seem to think that if you turn the switch 
 in one direction to turn on the light, you would naturally reverse 
 the direction to turn it off. The fact that the switch seemed to 
 work hard in the reverse direction did not deter them, and they 
 would frequently use sufficient force to break it. It therefore 
 became necessary to use specially designed switches. It should be 
 noted that all switches when inclosed in a box should have on the 
 outside easily legible marks to show when the switch is on and when 
 it is off. This is desirable also with snap switches. 
 
 Where the box is used as a lamp base not only must there be the 
 socket for screwing in the lamp (and this should preferably be of the 
 spring type), but there must also be a screw thread for screwing on 
 the protecting globe. This goes outside of and over the lamp and 
 should screw down water-tight. Outside of this globe there is 
 usually provided a basket metal work guard for protecting the 
 globe and the bulb inside from mechanical injuries. 
 
 Lamps. 
 
 The lamp ordinarily used is the standard carbon filament 16 
 candlepower lamp designed for a voltage of about 110 to 112. Occa- 
 tionaUy, however, 32-candlepower lamps are used, and in a few 
 cases even larger ones have been provided. In range stations, 
 dormitories, casemates, etc., which are ordinarily situated so far 
 away from the nearest large gun as to be free from blast effects, the 
 ordinary carbon filament used in commercial Kfe is satisfactory, and 
 even the Mazda and other sensitive filament lamps can be used. 
 Such sensitive filament lamps have the advantage of providing more 
 light for the same expenditure of current than the carbon filament. 
 173341—20 ^19 
 
290 
 
 But in gun emplacements, 'especially on or in close proximity to 
 the loading platform, the blast effect and the vibration or shock 
 are usually so great that nothing except carbon filaments will stand, 
 and these ordinarily have to be of special manufacture — that is, 
 their carbon filaments have to be unanchored, since it is found that 
 anchored filaments are broken too frequently. 
 
 Incidentally also it has been found that in such locations the 
 ordinary fixed lamp sdcket is not suitable since the shock .trans- 
 mitted through it has a tendency to break even the unanchored 
 carbon filaments. Spring sockets shoxild therefore be used. Not 
 only have these spring sockets been found to greatly diminish the 
 breakage of the filaments,! but. lamps screwed into them do not have 
 the tendency to gradually unscrew and get loose, as has been found 
 to be true of the ordinary sockets. 
 
 It having been found that there was an excessive tendency for 
 fortification lamps to disappear from batteries and other similar 
 places, it was thought to be necessary to have the lamps marked 
 specially. In recent years fortification lamps have usually been 
 bought under specifications requiring that bulbs should have etched 
 on them the letters "U. S. E. D." or something similar. 
 
 The subject of the best designs for electric fittings to be used 
 around emplacements has been considered from time to time by 
 various boards, and some three or four years ago standard forms of 
 fittings were adopted, and the main Engineer depot at Washington 
 Barracks was intrusted with their manufacture and purchase. It 
 was at that time ordered that all constructing engineers who might 
 have need of such Jittings should submit requisitions to be filled by 
 the Engineer depot. 
 
 The details of the standard fittings have been very carefully 
 thought out, and there are now available forms of fittings which 
 are suitable for practicably every use that can arise in fortification 
 structures. Drawings of these fittings and perhaps samples will 
 doubtless be made available to ofiicers who need them. 
 
 In dormitories, casemates, fire-control stations, and other buildings 
 isolated from batteries these special fittings are not required, and 
 such buildings can be wired very much in the same general way as 
 buildings in civil life, this wiring usually being governed by what are 
 called underwriters' rules. 
 
 DIFFERENT USES OF ELECTRICITY. 
 
 At the present time electricity is used in fortification work in the. 
 following ways: 
 
 First. For searchlights. 
 
 Second. For illuminating emplacements of all kinds, range sta- 
 tions, etc. 
 
291 
 
 Third. For lighting the range scales on the guns and on the range 
 finding instruments and for lighting the wires of observing telescopes. 
 Foiirth. For operating hoists. 
 Fifth. For gun maneuvering apparatus. 
 Sixth. For firing guns from a distance. 
 Seventh. For telephone communication. 
 Eighth. For operating range-iudicating apparatus. 
 Xinth. For furnishing power for telautographs. 
 Tenth. In connection with submarine mines. 
 
 Electric Power for Searchlights. 
 
 The power for operating a searchlight can be obtained from a 
 central plant, from a local battery plant, or, where the searchlight 
 is isolated, from a special searchlight plant. Where the searchlight 
 is mounted in a fixed location, and this location is within easy reach 
 of a connection with a central plant, it is not infrequent to connect 
 the searchlight with the central plant, but since this connection may 
 be cut off at a critical moment, it is customary to provide the search- 
 light with a special plant of its own as a reserve. Similarly, when a 
 searchlight is located not too far from a battery, connection with the 
 electric system of the battery is frequently made. In such a case, 
 also, a reserve plant is needed. The standard searchhght plant for 
 a 60-inch searchlight is a 25-kilowatt generator. 
 
 The tendency in the recent past, however, has been to mount two 
 searchlights in the neighborhood of each other and so close together 
 that either can be used to illuminate the same field, and yet not so> 
 close together as to make both subject to destruction if a shell should 
 strike or explode near one. Each searchlight is given its independent 
 power plant, but in order to make the system more flexible, each 
 searchlight is ordinarily connected with or is connectible with the 
 power plant of the other. 
 
 Searchlights require direct current, so when a connection is made 
 with an alternating current central plant or another source of alter- 
 nating-current power, it is necessary to provide a motor generator 
 at or near the searchhght to furnish the direct current necessary- for 
 the light. Although a slightly lower voltage might be used with 
 searchlights, it is customary, in order to keep to the general standard, 
 to run the local searchlight plants at about 110 to 115 volts, the 
 standard for lighting plants. 
 
 In connection with antiaircraft operations during the recent war 
 there has been a great development in portable searchhghts, and in 
 portable powerplants for them. Portable searchlights were, of course, 
 intended primarily for antiaircraft work; but with the addition of 
 distant control mechanism, and in certain cases of some method of 
 raising the light to a height, these searchlights will probably be quite 
 serviceable for fortification use, as will also the portable power plants. 
 
292 
 
 Two separate types of automobile portable power plants have been 
 secured, one consisting of what is practically the standard 25-kilowatt 
 generating set, mounted on a large automobile truck, with a separate 
 engine for operating the truck; and the other a generating set carried 
 on a truck, the engine of which is so designed as to be used either for 
 propelling the truck or for operating the genierator. 
 
 In addition, a portable searchlight plant has been designed for 
 operation on railroads. The plant consists of two cars, one a search- 
 light car containing the searchlight plant, and the mechanism for 
 elevating it to a height of 40 feet or so, and the other a car containing 
 a standard 25-kilowatt set to furnish power. 
 Use of Electricity for Lighting Emplacements, etc. 
 
 As far as the use of electricity for lighting emplacements, range 
 stations, etc., is concerned, the conditions are closely analogous to 
 those found in civil life, except for the necessity of protection from 
 hostile fire, and of avoiding the difficulties due to dampness and the 
 blast effect from the guns. 
 
 In the earliest emplacement installations it was customary to have 
 all, or nearly all, of the lights of the emplacement operated by a single 
 switch in the power room. Only occasional use was made of special 
 branch circuits, as in lighting a magazine or some other room not in 
 frequent use. It is needless to say that with such a system, if you 
 wanted to light a single room, or a single part of a room, it was neces- 
 sary toJight the entire battery. This system had the further great 
 disadvantage that a single short circuit would make the entire 
 battery dark. 
 
 The main reason for this character of installation was the extreme 
 dampness of the old emplacements which caused the switches to be 
 almost always a source of electric leakage. We therefore find that 
 the earlier boards in their reports discouraged the use of branch 
 circuits. However, with the armored cable now furnished for elec- 
 tric installation, with the standard type of switches now in use, and 
 with the arrangements for ventilation and prevention of dampness 
 which have been installed in the more modern batteries, there is no 
 longer any reason why switches should be a source of trouble and why 
 it should not be permissible to divide up the lights into as many 
 separate circuits as may be convenient. Lately, therefore, the cus- 
 tom has been introduced of dividing an emplacement up into a num- 
 ber of different circuits, one for the loading platform lights, one for 
 the magazine lights, one for storeroom lights, one for air space lights, 
 and so on. As a rule, these branch circuits contain from seven to 
 twelve 16-candlepower lamps each. 
 
 At first the plan was tried of having these separate circuits operated 
 by ordinary switches placed around the walls, but the difficulty of 
 keeping these numerous switches in order caused them to be aban- 
 
293 
 
 doned and for them were substituted distributing panel boards con- 
 veniently located. Each panel board is connected with the main 
 switchboard in the power room by a cable which is not tapped between 
 the two points. In small batteries, only one panel board is used; in 
 lai^er ones, two, and sometimes four. In a few cases panels with as 
 many as 16 or 18 branch circuits have been used, but a better prac^ 
 tice would seem to be to use more panel boards, with not more than 
 10 or 12 branches on each. 
 
 The greatest difficulty that has been met with in properly lighting 
 the loading platforms of heavy direct fire gun em^placements is the 
 blast damage done in such places by the guns when discharged. 
 
 In order that the operation of loading the gun ma}^ be done rapidly, 
 t is essential that the loading platform be properly illuminated, and 
 yet this illumination must not be so strong as to make the location 
 of the emplacement visible to the enemy by the glare. 
 
 This illumination has been attempted in two ways; thp first being 
 by lights around the walls immediately imder the ovefnang. The 
 lamps installed there must, of course, be very strong and have unan- 
 chored filaments. They must be held in place by spring sockets and 
 protected by heavy glass globes mounted in metal basketwork 
 frames. Incidentally, also, in order that the glare from any of these 
 hghts may not interfere with the man at the sighting telescope as 
 the gun is pointed in different directions, each one of these lamps must 
 have its own independent key so it can be turned on or off at wiU. 
 
 The other method of illuminating the loading platforms is by the 
 so-caUed "footUghts" hung from the handraUing at the rear of the 
 platform and provided with screens so adjusted as to prevent the 
 ight from shining over the parapet. 
 
 In the Panama and similar one-story emplacements where the 
 loading platform is surrounded by sand slopes the foothghts are 
 attached to posts set in the ground. AH footlights should be keyed. 
 
 In addition to the lights mentioned above, should anything go 
 wrong about the gun carriage, some form of portable light is very 
 useful. Consequently two standard Engineer Department keyed 
 sockets for the attachment of portable lights are installed on the 
 front walls of a gun emplacement, one on either side of the capital 
 of the emplacement. It is intended that whenever an emplacement 
 is in use at night the portable lamps shall be brought out from the 
 storehouse and the ends of the cables be attached to the correspond- 
 ing sockets, the cables being coiled up until the lamps are needed. 
 
 Another and very convenient place for portable hghts is on the 
 gun carriage itself. When the early emplacements were built, it 
 was not considered necessary to carry electric-hght wires into the 
 gun wells, and no arrangements for doing this were made. Conse- 
 quently when it became necessary to estabhsh lights on the gun 
 
294 
 
 carriages great difficulty was rnet with in getting the cables in. In 
 some cases long holes from the gun well to some neighboring portion 
 of the emplacement had to be cut at great expense. In fhe more 
 recent batteries, however, arrangements for carrying cables, and 
 for that matter speaking tubes, too, to the gun weUs have been pro- 
 vided as will be noted by an examination of the detailed drawings 
 of the Panama emplacements. 
 
 With small, rapid-fire guns which are mounted in barbette and 
 under conditions, therefore, such that the illumination of the loading 
 platform is not possible in action, sockets for attaching portable 
 lamps are fastened to the gun pedestals and lighting cables are led 
 to them. 
 
 The blast of mortars is so very great as frequently to destroy even 
 the best form of wall electric light yet developed. Consequently 
 these wall lights can not be relied upon for the illumination of 
 mortar pits^ti action, although they are extremely serviceable for 
 drill purposes. Occasionally they are not destroyed when the 
 mortars are fired. It having become evident that some other method 
 of lighting the mortar pits was necessary, a method by means of 
 reflecting cones was developed by the writer at Fort Monroe for the 
 maneuvers of 1905. These cones were attached about 20 feet above 
 the ground to posts planted in rear of the mortar pits. The cones 
 were composed of galvanized iron, painted white on the inside, and 
 were so adjusted in direction that the axes of the cones prolonged 
 passed about through the center of the floor of the pits. At the 
 inside of the upper end of the cone was inserted a base to which 
 was attached three 32-candlepower electric lights. It was found 
 by experiment that, except when the mortars were turned around 
 so as practically to face directly toward the cones, the electric 
 lights in them would withstand the blast, and that the illumination 
 given by two cones is more than ample. 
 
 In the more recently constructed mortar batteries the cone lights 
 have been attached to brackets on top of and near the rear of the 
 side walls of the mortar pits. (See Plate XXIX.) 
 
 One of the rooms in an emplacement which has to be particularly 
 well lighted is the plotting room. The plotting is usually done 
 with pencil, and therefore good illumination is necessary. Further- 
 more, a number of men are employed around the plotting board, 
 and the illumination must be such as to avoid shadows as much 
 as possible. The standard method of illuminating the plotting 
 board is by four 32-candlepower lamps attached to the ceiling 
 directly over it and placed on the corners of a square about 3^ 
 or 4 feet on the side. Additional lights have to be located where 
 they will give the best illumination on the various correction boards, 
 etc. Such lights should preferably be hooded. There must also 
 be other lights for the general illumination of the room. 
 
295 
 
 The illxiniiiiation of the power room must be so designed as to 
 give ample light at the smtchboard and on critical parts of the 
 engine. Portable lights, also, are frequently of great assistance. 
 
 As an illustration of the general character of the electric-lighting 
 system installed in modern batteries, the following is quoted from 
 the report of the designing engineer in submitting to the Chief of 
 Engineers the plans for one of the modem large Panama batteries: 
 
 The conditions are such that artificial illumination will be required, even by day, 
 in the magazines, galleries, and rooms of these batteries. The artificial lighting is 
 to be done ordinarily by electricity, and in case electricity temporarily fails, then by 
 the standard emergency lanterns. Recesses for these emergency lanterns are shown 
 on the drawings, around the loadtDg platforms, in the truck corridors, the shell rooms, 
 and opposite the magazine doors, but as the supply of these reserve lanterns will 
 always be limited their use has generally been restricted to these locations. These 
 lanterns are not sufliciently powerful to be of use for plotting purposes, and the emer- 
 gency illumination by them of the other parts of the battery would not appear to be 
 desirable. 
 
 In general, each group of from 7 to 12 lights is formed into a separate circuit, 
 fed by a cable leading back untouched to a distributing panel, of which there are 4 
 located in convenient pla,ces in the rear gallery. On these distributing panels are to 
 be located the operating switches for the branch circuits, and in general they will 
 be the only switches on those branch circuits; but in the plotting rooms and 
 oflScers' rooms and in a few other special locations wall s^s^.tches and specially keyed 
 lights are considered necessary. The distributing panel is to be connected through a 
 switch to the main cable extending into the power room and should have a small 
 pilot lamp set in a keyed socket. The figures on the drawings of the distributing 
 panels show the number of branch circuits now estimated as required and the extra 
 spare connections considered necessary for future growth . 
 
 Two general methods of artificially illimiinating the loading platforms are shown — 
 one a line of footlights set around the rear of the platform, as directed in mimeograph 
 93, and the other a line of lights located under the overhang of the front parapet 
 wall. AH these lights should be provided with keyed boxes, so that any light which 
 may temporarily interfere with the view of the men on the sighting platforms of the 
 guns, or of the officers in the battery commander's stations, may be darkened. 
 
 Sockets for portables are shown in the battery commander's stations, around the 
 wall in front of the gun well, and around the steps in the rear of the gun well. 
 
 The x)ower, lighting, and fire-control wires to the gun carriages are to be connected 
 through the Ordnance Department terminal boxes set in niches in the rear walls of 
 the gun wells. All these wires are to be routed from the plotting room through the 
 tunnels and passageways. 
 
 The electric-light and power wiring shown is to be generally of the exposed type 
 attached to the walls or ceilings, except when passing through walls. In passing 
 through walls the wires are to go through short conduit pipes to be inserted in the 
 walls when built. 
 
 The cables and fixtures used are to be of the Engineer Department standard type. 
 
 The positions of lights and distributing panels and the routing of electric cables 
 as shown on the drawings are to be considered to some extent as diagrammatic, the 
 details being left to the constructing officer. 
 
 For the convenience of handHng fire-control wires and power cables, a series of 
 electric conduits has been provided in these batteries. The main conduit system 
 consists of a line of conduits laid imder the floor of the rear gallery and extending 
 from end to end of the gallery. From this main line, branch conduits communicate 
 
296 
 
 with each plotting room, with the power room, and with the lower level of the 
 island, the latter conduits being laid under the stairs of the entrance galleries. The 
 conduit lines extend to the extreme right eivd of the rear gallery, whence they may be 
 extended to any fire-control stations which may be constructed. The number of 
 ducts which it is considered necessary to provide in each portion of this conduit 
 system is noted on the plans. 
 
 From the conduit manholes in rear of each plotting room branch conduit,s are to 
 extend, two to the wiring recesses of the plotting room, one to the wall of the rear 
 ' gallery (for the lighting main), and one to the indicating apparatus manhole for the 
 power mains leading to the gun carriage. * 
 
 In the operating room of casemates, the lights must be so dis- 
 tributed to give ample illumination on the various switchboards, 
 and portable lights conveniently arranged for seeing behind the 
 boards are frequently of great assistance. 
 
 The illumination of observation stations requires considerable 
 thought and care. For an observer to see through a telescope at 
 night, it is usually necessary that everything around him should 
 be as dark as possible. Furthermore, any glare or gleam coming 
 from a range station may attract the attention of the enemy to its 
 existence, and may therefore attract the enemy's fire and endanger 
 the station. Both of these requirements therefore, would point 
 to there being no lights in a range station. However, it is frequently 
 desirable, especially in a battery commander's or fire commander's 
 station, to consult charts or maps or other papers. Wherever 
 illumination fo^this purpose is necessary it shoidd be provided by 
 carefully hooded lights in the extreme back part of the station, 
 the lights being so located, hooded, and screened that no glare can 
 reach the observer or can show through the observation openings. 
 
 A somewhat perplexing problem that frequently arises is the 
 illumination of outlying observation stations, small dormitories, 
 and small rapid fire batteries, when these structm-es are located 
 far away from other portions of the defenses. These observation 
 stations and dormitories will probably be but infrequently used at 
 night during peace time, and as has just been stated, in actual war 
 ■time but little light, if any, should be permitted in the observation 
 stations. Consequently, it would appear almost as if it were a 
 useless expense to provide electric lighting connections to such 
 stations or dormitories. On the other hand, of course, fire-control 
 cables must be carried to the stations and it would cost but little 
 more to install a small power cable at the same time. It is the 
 opinion of the author, however, that unless there are quite a number 
 of these stations in fairly close proximity to one another, it is an 
 unnecessary expense to provide electric lighting. For ordinary 
 illumination, oil lamps can be used and the illumination of range 
 scales and telescope cross hairs can be done by dry batteries. 
 
297 
 
 The same thing, it is believed, is true of most rapid fire batteries. 
 These guns are necessarily mounted in barbette and no light can be 
 permitted on the platforms when in use at night. The ammunition 
 usually comes fixed and httle Hght would appear to be needed in 
 the magazines. Such as is needed could be proA-ided by reserve 
 lanterns. 
 
 Unless, therefore, such batteries are grouped together, it is be- 
 lieved that ther all might well be left without electric light con- 
 nections. If there are, however, several batteries grouped together 
 it may be worth while to install for lighting the group a small 
 detached electric plant, but it is evident that for such purpose the 
 standard 25 kw. sets are too large. For small groups, possibly 5 
 kw. sets might be provided. Up to the present, however, no 
 standard set of this size has been adopted by the Engineer department. 
 Lighting Range Scales and the Cross Hairs of Telescopes. 
 
 The small lights used to illuminate the range scales of rapid-fire 
 guns and position-finding instruments, the cross hairs of range- 
 finding telescopes, and the sighting telescopes on gun carriages 
 are from about one-haK a candlepower to 2 candlepower. These 
 lamps are furnished by the Ordnance Department and at first the 
 power was provided by a dry battery. However, as the dry batteries 
 furnished for this purpose proved to be somewhat unsatisfactory a 
 new arrangement was adopted. The Ordnance Department now 
 furnishes with the lamps a suitable rheostat. Coimection is made 
 with the ordinary lightiog maios furnished by the Engineer Depart- 
 ment and carrying about 110 volts. This voltage is cut down 
 by the rheostat to the voltage necessary for the lamps. Occasion- 
 ally also, the expedient is adopted of placing several of these small 
 voltage lamps in series across a 110 volt circuit. 
 
 Power for Ammunition Hoists. 
 
 The use of electric power for operating motors is exceedingly 
 common in commercial life and the use of such motors for operating 
 hoists in fortifications has nothing unusual about it. The standard 
 form of electric hoist is operated by an ordinary shunt motor, there 
 being a clutch so that the hoist itself can be thrown in or out of gear. 
 The motors are started when the clutch is out and the hoist itself 
 not connected. When the motor is running full speed the clutch is 
 thrown in and the hoist starts to move. After it has attained fuU 
 speed it is ready to take up ammunition. 
 
 As in all motors, in order to prevent a sudden rush of current on 
 starting there is a starting rheostat, the resistance of which is 
 gradually cut out as the motor gains speed. This rheostat and the 
 switches connected with it are operated by a form of controller, in 
 general not unlike that used on street cars. The motor is started 
 
298 
 
 by turning the controller handle to the first notch; as the motor 
 gains speed the handle is moved from notch to notch, and when 
 nearly at full speed the handle is thrown all the way around, cutting 
 out all the resistance of the starting rheostat. This handle is so 
 connected with the brushes that if the circuit be at any time broken 
 the connection between the handle and the brushes is broken and a 
 spring returns the l?rushes to the starting position. In order to 
 start the motor again, it is necessary to push the handle all the way 
 back and pick up the brushes again. 
 
 This arrangement is utilized in a very ingenious way to prevent 
 accidents with the ammunition hoists. The controller operating a 
 hoist is usually located in the hoist room on the lower story. The 
 projectiles are raised and are rolled out by the hoist on a delivery 
 table on the loading platform. It is, of course, possible that there 
 may be a delay on the loading platform and the projectiles may 
 not be taken away as fast as they are carried up. If the delivery 
 table be fxill and an attempt is made by the hoist to place on the 
 table another projectile for which there is no room, there is danger 
 that it may fall down through the hoist opening and do considerable 
 damage. ^ To avoid this, the circuit passing through the automatic 
 clutch that holds the brushes to the controller handle passes also 
 through a small switch placed on the loading platform level along- 
 side the delivery table. If the attendant at ithe delivery table 
 sees that there is any tendency for the table to become overloaded 
 he opens the small switch, thus releasing the clutch that holds the 
 brushes to the controller handle. The spring throws the brushes 
 back to the starting position and the hoist instantaneously stops. 
 
 In connection with the use of electricity for operating the hoist 
 motors there is one point that should be noted, attention having 
 been called to it by a peculiar occurrence at Fort Hamilton some 
 years ago. As has been described, projectiles are brought to the 
 receiving table of a hoist by a trolley running on a troUey rail 
 attached to the ceiling. When over the receiving table, the pulley 
 block is slackened off slightly and the projectile is lowered to the 
 table. The receiving table is connected with the frame of the 
 hoist upon which is mounted the operating motor. Now it so 
 happened that at Fort Hamilton the negative wire of the motor 
 was grounded to the frame of the hoist and therefore was electrically 
 connected with the metal of the receiving table. Incidentally, the 
 troUey rail passed close to and was in metallic contact, with a lamp 
 socket in the ceUing in which the positive wire happened to be 
 grounded. Theoretically, according to the knowledge of the time, 
 the grounding of one side of the electric system in one part of an 
 emplacement and of the other side at another place should have 
 made the electric current complete and should have been at once 
 
299 
 
 indicated in the power room by the blowing of a fuse or the opening 
 of a circuit breaker. 
 
 It was at that time supposed that concrete in mass was a good 
 conductor of electricity and that a piece of bare metal in contact with 
 the concrete was effectirely grounded. This has been found not to 
 be true unless the concrete is saturated with water. Dry concrete 
 partakes largely of the nature of a conglomerated limestone, or 
 marble which is but a form of limestone, and is such a poor conductor 
 that it is frequently chosen as a material of which to make switch- 
 boards. In fact, as is noted in the chapter on dryness and condensa- 
 tion, dry concrete is not only a poor conductor of electricity but is 
 also a poor conductor of heat. 
 
 At Fort Hamilton, therefore, we had a case of the trolley rail 
 being grounded on one side of an electric circuit and of the hoist 
 frame and receiving table being grounded to the other side. While 
 in this condition a projectile was brought to the receiving table 
 hanging from the trolley. As it approached the table one of the 
 detachment with his hand on the projectile touched the table with 
 the other hand and received a shock. A few seconds later the point 
 of the projectile swung around so as to touch one of the sides of the 
 receiving table making a distinct spark, and what is more, the pro- 
 jectile after touching the side of the table swung away and hung 
 so as to leave but a short interval between the projectile and the 
 receiving table and there was thus formed between the two a distinct 
 iron arc similar to the carbon arc which is used in the electric arc 
 light. 
 
 Fortunately, no damage was done, but it should be noted that at 
 that time it was customary to use the same hoist not only for raising 
 projectiles but for raising powder. Had this arc occurred in the 
 neighborhood of powder there would have been great danger that 
 the powder on the receiving table might have been set on fire much 
 in the same manner as had actually occurred a short while before in 
 the turret of one of the battleships. When this sparking occurred, 
 the cause was not known, but an investigation showed the facts to 
 be about as I have stated. 
 
 The remedy is exceedingly simple — to bond aU sections of the 
 trolley rail and of the hoist together. Had this bonding been in 
 place, as soon as the grounds occurred, one on the positive and one 
 on the negative side of the electric system, a short circuit would have 
 been formed through the metal connections, and either a fuse would 
 at once have been burned or a circuit breaker on the switchboard 
 would have been thrown and attention would have been called to the 
 occurrence. 
 
300 
 
 Power for Maneuvering Gun Carriages. 
 
 The installation of electric apparatus for maneuvering gun car- 
 riages was somewhat delayed due to the fact that the gun carriage 
 and everything connected with it is manufactured by the Ordnance 
 Department, whereas the electric power comes from the Engineer 
 Department. Formerly there was a lack of coordination between the 
 two departments which has happily been corrected since. 
 
 The Ordnance Department decided to install motors on its large 
 gun carriages for traversing, for operating the elevating mechanism, 
 and for retracting the guns. 
 
 In connection with the traversing it is necessary "that the gun should 
 be kept pointed on the target as the latter moves, and as the target 
 may move across the field of fixe of the gun with an infinite variety of 
 speeds, the motor operating the traversing mechanism must be cap- 
 able of very delicate adjustments in speed. A special motor generator 
 is installed in a special room of the emplacement convenient to the 
 gun-weU. The motor generator receives power from the Engineer 
 Department cables and furnishes power to the traversing motor 
 which is of such a character as to permit an adjustment to any- 
 desired speed. 
 
 The earliest traversing motors did not give complete satisfaction 
 and the Ordnance Department, for a while at least, abandoned the 
 idea of installing them, leaving the traversing gear to be worked by 
 hand. Whether or not it is the intention to install traversing motors 
 on the new gun carriages is not known, but it is believed that it 
 should be done. 
 
 The other two uses of power on gun carriages, that is, elevating 
 and retracting, are performed by the same motor and no such delicate 
 adjustment in speed is necessary as in traversing. This single motor 
 is so arranged that it can be thrown in gear at will either with the 
 elevating mechanism or with the retracting mechanism. 
 
 Firing Circuits. 
 
 The use of electricty for firing guns has long been considered as 
 desirable and it was at one time intended to use the regular source 
 of power for this purpose. Later, however, this idea was abandoned 
 as being too dangerous. Where electric firing is to be used it is done 
 by special batteries or magneto machines, the circuits being kept 
 entirely separate from those used for lighting or power purposes, 
 even to the extent of being carried in separate conduits. This is 
 largely a matter for the Ordnance Department, the only duty of the 
 Engineer Department being to install the necessary conduits. 
 Power for Telephones. 
 
 Telephones, telephone wires, and all the incidental accessories 
 are furnished by the Signal Corps. Prior to a few years ago they 
 were likewise installed by the Signal Corps, the work as a rule being 
 
301 
 
 done by civilian electricians and hired labor. A little later skilled 
 noncommissioned officers of the Signal Corps were employed to super- 
 vise this work. 
 
 A few years ago, however, while the Signal Corps still retained the 
 control of the purchase and issue of all telephone material, the actual 
 wiring was left to be done in garrisoned posts under the supervision 
 of the ArtillerT Engineers, and in new fortifications by the Engineer 
 Department. 
 
 As a source of electric power, the Signal Corps has sometimes 
 furnished independent generators, sometimes motor generators which 
 receive their power from Engineer department cables, and sometimes 
 storage batteries which are charged from the Engineer department 
 power lines. Xo further reference will, therefore, be made to this 
 subject here. 
 
 Power for Range Indicator Apparatus. 
 
 Electricity has occasionally been used for operating the apparatus 
 for indicating to the men at the guns the range of the target or the 
 other data needed for laying the guns. This being a matter closely 
 connected with fire control, will be discussed in the chapter on that 
 subject. 
 
 Power for Telautographs. 
 
 A telautograph is an appliance which by electrical means repeats 
 at a distance a supposed facsimile of what is being written on the 
 transmitting telautograph. That is, as a man with a telautograph 
 pencil -mites his name on the receiving telautograph, his autograph 
 is repeated at a distance, so as to be almost exactly like the original. 
 This apparatus can, therefore, theoretically be used for the rapid 
 transmission of v.Titten data. 
 
 The only attempt that was ever made to use telautographs in 
 fortification service was as a substitute for or as a supplement to 
 telephone transmission of fire-control data. The subject will, there- 
 fore, be discussed principally in the chapter on iire control. 
 
 Both the receiving and transmitting telautographs had to be fur- 
 nished with direct current at approximately the same voltage. In 
 the initial experiments the telautographs had been connected with per- 
 fectly regular soiirces of power and worked fairly well, but when 
 the}" were introduced into fortification service and were connected 
 with the fortification electric systems they failed to work. It was 
 not until the experiment was tried of connecting the telautographs to 
 storage batteries, used for the time being for no other purpose than 
 furnishing power for them, that they could be made to work satis- 
 factorily. For this and other reasons which will be noted in the 
 chapter on fire control, the use of the telautographs was aban- 
 doned, so that the subject of power for them is of historical interest 
 only. 
 
302 
 
 Power for Submarine Mining, 
 
 The power needed in the operation of the submarine mining system^ 
 is usually obtained from a special generator installed by the Artillery. 
 In connection with the generator they install also a storage battery 
 charged from it, so the Engineer department is not concerned in this 
 use of electric power. 
 
 Personnel. 
 
 When the electric plants were first introduced in emplacements, 
 not only were they installed by the Engineer department, but they 
 were cared for and operated by civilian employees of that department 
 working directly under the orders of the district engineer officers, but 
 of course operating the plants when directed by the Artillery com- 
 manders. In a few places, such as during the maneuvers of 1903 
 at Portland, Me., the attempt was made to operate the electric plants 
 by a detachment of Engineer soldiers working under an Engineer 
 officer. 
 
 This arrangement of having electric plants operated by the Engineer 
 department was not satisfactory to the Artillery, and at about the 
 time the torpedo system was turned over to the Artillery the electric 
 plants were turned over also. An electrical school for the education 
 of Artillery soldiers and noncommisioned officers was opened at 
 Fort Monroe, and these men when sufficiently instructed were placed 
 in charge of the electrical plants. 
 
 In Artillery districts there is an Artillery district engineer on the 
 staflf of the Artillery district commander. In each coast defense 
 there is a coast defense Artillery engineer, and at each large post 
 there is a post Artillery engineer. These Artillery engineers are in 
 command of all the electrical sergeants, firemen, privates, etc. 
 detailed in charge of the electric plants. 
 
Chapter XII. 
 FIRE CONTROL. 
 
 In the lectiire on this subject in the original notes, the matter was 
 gone into quite extensively, but since it is probable that the experi- 
 ence of the recent war will soon be reflected in radical changes in the 
 fire-control system the matter will be but briefly touched on in this 
 chapter. 
 
 The term "fire control" is used with two separate and independent 
 meanings; first, the assignment to each particular gun of its particular 
 target and the regulation of the rapidity of fire at this target; and 
 second, the communication to the detachment around the gun of the 
 exact location of its particular target in such a manner as to insure 
 that the gun will be fired with such azimuth and elevation as to 
 secure a hit on the particular portion of the particular target assigned. 
 The first of these two operations might better be caUed "fire regula- 
 tion" and the second, "position finding." 
 
 FIRE REGULATION. 
 
 In the chapter on gun batteries and emplacements it was stated 
 that a "battery," as the word is used in reference to seacoast artillery, 
 ordinarily includes from two to four emplacements, though occa- 
 sionally one large gun emplacement may by itseK constitute a bat- 
 tery. The command of such a battery is appropriate to the rank 
 of captain. 
 
 The concerted action necessary for success in all military affairs 
 requires that the different batteries in any one harbor or portion of a 
 harbor should not be allowed to do their fighting independently, but 
 should be under the command and control of higher officers. Conse- 
 quently, it has become customary to combine several battery com- 
 mands into a higher command called a "fire command," appropriate- 
 to the rank of major. 
 
 In general, the different batteries composing a fire command 
 woidd be of gims of the same general cahber and covering in general 
 the same field of fire. That is, in a large fort or collection of forts, 
 the large cahber guns would be divided into one or more fire com- 
 mands, the medium cahber guns would form other fire commands, 
 and the smaller rapid fire guns stUl others. The command of subma- 
 rine rniTiing matters and of the smaller gims detafled specially to pro- 
 tect the mine field would form another so-caUed "mine command" 
 assimilated to a fire command. 
 
 (303) 
 
304 
 
 In the same way that the battery commands are organized into 
 fire commands, the fire commands are organized into a more impor- 
 tant command known as a "battle command" under the control of a 
 battle commander normally of the rank of colonel. In most cases a 
 battle command would include practically all of the defenses of a 
 single harbor, but in very large and important harbors such as New 
 York, San Francisco, etc., there might be several independent battle 
 commands all organized into still larger commands known as the 
 "fortress command" under a fortress commander, who would ordi- 
 narily be a general officer. 
 
 It is, of course, essential that the fortress commander should be 
 kept in close communication by telephone or other means with his 
 battle commanders, the battle commanders with their fire com- 
 manders, and the fire commanders with their battery commanders. 
 Similarly there must be communication between a battery commander 
 and the various parts of his battery, his observation stations, his 
 plotting room, etc., and between the observation stations and the 
 plotting room. 
 
 In this connection, however, it should be noted that the organiza- 
 tion of batteries into fire commands, and fire commands into battle 
 commands is a tactical organization only. For general administra- 
 tive purposes the organization is somewhat different. 
 
 The administrative organization is based upon the seacoast fort, 
 each fort as a rule being treated, as far as administration is concerned, 
 as a separate post. In a few cases, smaller forts which are ungarri- 
 soned or very slightly garrisoned, are treated as subposts. The 
 different forts in any one harbor are usually united into a higher 
 command. Formerly this command was known as a Coast Artillery 
 district, the next superior administrative commander being the 
 commanding general of a military department. 
 
 About 8 or 10 years ago, however, it was considered desirable to 
 interpose a more general Coast Artillery commander between the 
 Coast Artillery district as then organized and the department com- 
 mander. The term "Coast Artillery district" was selected for these 
 more general commands and the designation of the command for- 
 merly called a "Coast Artillery district" was changed to a "coast 
 defense." 
 
 In general, therefore, there is now a coast defense for each harbor, 
 though in the larger harbors such as New York, where there is more 
 than one entrance, there might be a coast defense for each entrance, 
 or one of these entrances even may be divided into more than one 
 coast defense. Thus in New York Harbor there is one coast defense 
 for the eastern entrance and two for the southern, one at the Narrows 
 and one at Sandy Hook. 
 
305 
 
 The coast defenses along one general stretch of coast line are 
 formed mto a Coast Artillery district, which is usually commanded 
 hy a colonel of Coast Artillery, but sometimes by a brigadier general 
 whose prior service has been in the Coast Artillery. These Coast 
 Artillery district commanders are under the supervision of the 
 department commanders. 
 
 This organization and in fact the entire present mUitary organiza- 
 tion into territorial mihtary departments would appear to be some- 
 what anomalous and will, in all probabihty, be changed before long. 
 
 POSITION FINDING. 
 
 In target practice with the small arms rifle the soldier aims at the 
 target, making on his sight a vertical correction for the range and a 
 lateral correction for windage, drift, etc. If the range is not known 
 it is guessed at or is determined by the fall of the bullets. The range 
 at which a small arms rifle is fired is usually comparatively small and 
 in general can be determined with sufficient accuracy by the methods 
 just mentioned. However, when the range of the target is known 
 from other means this information should be used and every possible 
 expedient should be made use of that will increase the accuracy of 
 the fire. 
 
 The ranges of the old muzzle-loading seacoast guns used dming 
 our Civil War and before were comparatively small, the fire of the 
 guns themselves was quite erratic, and consequently, guessing at the 
 range or its determination by actual firing sufficed. 
 
 This is, however, no longer true of the guns now mounted in sea- 
 coast defense. Many of these have an available range of over 20,000 
 yards and the next gims to be emplaced will probably have a range 
 of nearly double this or even more. For seacoast firing at such 
 ranges, guessing at the range is out of the question and something 
 more accurate must be attempted. 
 
 The simplest method of determining a distance which can not be 
 actually measured is by triangulation, and this is the method used 
 for range finding in seacoast defense. In determining the distance 
 of an object we may do our triangulation either in the horizontal 
 plane or in a vertical plane. Both methods are in actual use and 
 we may, therefore, have a horizontal position-finding service or a 
 vertical position-finding service. 
 
 HORIZONTAL POSITION FINDING. 
 
 Triangulation in the horizontal plane is based upon the assumption 
 that we have two points whose distance apart is known and that we 
 have at both points instruments which may be used for measming 
 horizontal angles. The line of known length connecting the two 
 points is called the base hne. If the transits at the two ends of the 
 173341—20 2a 
 
306 
 
 base line are pointed at each other with their verniers set at zero 
 and the telescopes are then pointed at the same distant object and 
 the angles are read, we have the simplest form of triangulation. 
 We have a triangle the length of one side of which is known and 
 two angles of which have been xneasm-ed, and a few minutes' calcu- 
 lation will give the distance of the object from either or both ends 
 of the base line. Knowing these, the distance and direction of th,is 
 object from any other known point in the same plane also can be 
 calculated. 
 
 If the target whose position is being determined is not moving, 
 the transits may be sighted on it at any convenient time for each, 
 or in fact the same transit may be used, measuring the angle at one 
 end of the base hne and then being taken to the other end of the 
 base line and used in measuring that angle. If, however, the target 
 is in motion it is evident that the sighting of both telescopes must 
 be made simultaneously. 
 
 If time and good computers were available we might resort in all 
 cases to calculation to determine the distance of the target, but 
 time is of the utmost importance, for the target is moving, and 
 recourse is therefore had to graphics — that is, to the determination 
 of the position of the target by plotting. 
 
 The simplest and in fact the original form of the plotting board 
 was rectangular. The base line was drawn to the proper scale near 
 one of the sides of the board. The position of the two ends of the 
 base line, A and B, was plainly marked by points. With the points 
 A and B as centers fairly large circumferences were drawn on the 
 board, and these circumferences had the degrees marked off and 
 numbered, the zero in the case of each circumference being toward 
 the other end of the base line, and the numbering of the graduations 
 increasing in the clockwise direction on one circumference and in the 
 counter-clockwise direction on the other. For use in plotting, pins 
 were inserted in the board at the points A and B and strings were 
 fastened to the pins. The ends of these strings were held by two 
 men called "plotters" to whom, by telegraph or telephone, were 
 communicated as promptly as possible the readings of the two tele- 
 scopes. Upon receiving the reading of the telescope at one end of 
 the actual base line, the proper plotter would promptly stretch his 
 string so that it passed through the corresponding division of the 
 proper circle. The other plotter would in the same way stretch his 
 string so that it would pass through the division on his side corre- 
 sponding to the reading of the telescope at his end of the base line. 
 The intersection of the two strings would indicate the position which 
 the object had at the instant the two telescopes were read. This 
 intersection could be marked by a small dot on the paper and the 
 distances of the target from the two base end stations could be read 
 off with the proper scales. 
 
307 
 
 Furthermore, if on the same board the actual position of the gun 
 with reference to the two base end stations was marked, a circle 
 drawn with this point (which we wiU call G) as the center, and the 
 degrees marked on this circle so as to accord with the degree marks 
 on the azimuth circle of the gim carriage, a string or ruler from G 
 to the dot indicating the position of the target would give the range 
 and direction of the target from the gun. 
 
 The somewhat crude and primitive form of plotting board just 
 described was the one actually in use less than 30 years- ago. It 
 contained the essential principles of the more modem plotting board, 
 but many necessary refinements have been introduced. 
 
 On the earhest plotting board used, three circles were actually 
 drawn, one with each end of the base line as the center, and one 
 with the position of the gun as the center. The zeros of the circles 
 drawn about the ends of the base line were on the line connecting 
 the base ends, one circle was graduated in one direction and one in 
 the other. The zero of the circle about the point of the gun was 
 fixed by actual observation from the direction of the zero of the 
 azimuth circle of the gun. 
 
 If we have to calculate the distances of the target from the ends 
 of the base line it is evidently easiest to use the base line as the zero 
 line, but where a position is determined by plotting and not by calcula- 
 tion, nothing is gained by using the base line as the zero line, and 
 there are many advantages if all the angles read and plotted 
 are true azimuths counted from the same zero of azimuth. The 
 Artillery service in this coimtry has selected the south as the zero 
 of azimuths, and all angles are measm-ed from the south around by 
 the west to the north, east, and finally to the south again. The 
 azimuth circles of all gun carriages are graduated in degrees, and 
 the numbers stamped upon these azimuth circles are such that 
 when the vernier reads zero or 360° the gun will be pointed due 
 south. Similarly, all position-finding instrtiments are set so that 
 when the vernier reads zero the instrimient will be pointed due 
 south. Consequently, when any two telescopes or a gun, or a gun 
 and a telescope, have the same azimuth reading, the telescopes or 
 guns win, as far as azimuths are concerned, be parallel. 
 
 On any plotting board in constant use, the paper must be fre- 
 quently changed, and the graduation of different circles on the paper 
 requires very careful work. With the large number of different 
 lengths of bases used, the Hthographing of these circles is hardly 
 practicable, and the custom grew up of placing the graduations and 
 the mmabers not on the circles but around the edgra of the board 
 where the radii prolonged would intersect the edges, in much the 
 same way as in the rectangular protractor. In this manner the 
 graduation for any one station or for any position of the gun can be 
 
308 
 
 put around the edge of the board once for all, and the paper or maps 
 upon which the plotting is to be done can be changed as frequently 
 as may be necessary. This means, however, that around the edges 
 of the plotting board we will have at least three sets of graduations 
 in close proximity one to another, and in times of excitement even 
 the best trained plotter might easily make a mistake by using the 
 WTbng set of graduations. 
 
 To avoid the multiplicity of graduations there was devised a plot- 
 ting apparatus based on the principle of the old form of parallel 
 ruler which used the principle of the equality of -the opposite sides 
 of a parallelogram. In making use of this new principle, bars or 
 rulers have been substituted for strings as being more convenient 
 and because distances could be marked off on them. 
 
 The plotting from one of the stations, we will say station A, was 
 done by a ruler pivoted at A. This ruler was placed in position by 
 using a set of graduations around the edge of the plotting board 
 based upon the point A as the center. In plotting from the point 
 B two parallel connected rulers were used, one, the real marker, 
 actually pivoted at B, and the other or auxiliary ruler pivoted at A. 
 These two rxilers were kept always parallel by being connected at 
 about the middle of their length by a bar equal in length to the 
 distance AB and pivoted to the rulers at the same distances from 
 A and B, respectively. This connecting bar therefore remained 
 always equal and parallel to the base line AB, and consequently the 
 two rulers pivoted at A and B were always parallel to each other. 
 If the auxiliary ruler which was pivoted at A was located in posi- 
 tion by the reading on the graduations centered at A, then the ruler 
 that was pivoted at B would evidently indicate the same azimuth 
 on a circle centered at B. Consequently, both the A ruler and the 
 B ruler could be set by using the same set of graduations, the A 
 ruler by direct use of the graduations around" the edge of the board, 
 and the B ruler through the principle of parallelism and by use of 
 the auxiliary ruler actually pivoted at A. 
 
 For reading azimuths and distances from the gim an additional or 
 gun arm is used. This is pivoted at the point G, but for reasons 
 which will appear later its azimuth is read, not by using the gradua- 
 tions around the edge of the board, but by using the graduations on a 
 special small metal azimuth circle, the zero of which is adjustable. 
 Consequently, under this system only one set of azimuth graduations 
 is required around the edge of the plotting board. 
 
 The system of plotting so far developed therefore consists of a 
 plotting room and two base end stations. At both stations, in the 
 plotting room and on the platform close to the gun, are small electric 
 bells, all of these bells being connected electrically with one master clock 
 which causes all of them to give a single tap simultaneously and at 
 
309 
 
 intervals of 10, 15, 20, or 30 seconds, as may be desired. At eacli 
 end of the base line there is an azimuth instrument oriented so as 
 to read true azimuths. A man looking through the telescope keeps 
 the vertical hair upon the previously designated portion of the target. 
 As he follows the moving target with the telescope the vernier moves 
 slowly over the scale and is watched by another member of the 
 detachment. Every time the bell taps the last-mentioned observer 
 reads the azimuth and communicates it at once by telegraph or 
 telephone to the corresponding plotter at the plotting board. This 
 plotter, immediately upon receiving this communication, sets his 
 ruler and, as the bells have tapped in the two observing stations at 
 the same instant, the settings made by the two plotters are of the 
 same time, and the intersection of the rulers will indicate the position 
 of the target at the actual instant the bells rang in the two observing 
 stations. This point of intersection of the rulers is marked by a 
 dot on the plotting board, and the gun arm can then be moved by the 
 chief plotter to this intersection. The reading of the scale on the 
 gun arm and of the azimuth on the gun azimuth circle, will give the 
 distance and direction which the target had with reference to the 
 gun at the instant the bell tapped. This information or certain 
 deductions from it are then at once transmitted to the gun detach- 
 ment for assistance in aiming the gun. 
 
 It is at this point, however, that the principal difficulty comes in. 
 If the gun be pointed with ihe azimuth and range just determined, it 
 will be aimed) not where the target is at the moment of aiming, but 
 where the target was when the bells rang in the observing station 
 some seconds before. Furthermore, even if at the time of firing the 
 vessel was actually at the spot at which the gun was aimed it would 
 have moved before the projectile could reach it. Consequently it is 
 obvious that there are two very necessary corrections which must 
 be made if the projectile is to hit the target; first, the correction for 
 the travel of the target during the time between the observation of 
 the target and the time of firing the gun, and second, for the travel 
 of the target during the time of flight of the projectile. 
 
 If a dot be placed upon the board showing the position of the target 
 at each tap of the bell, the direction of motion and the speed of the 
 target wiU soon be shown by the row of dots and their distances apart. 
 If it be assumed that the motion of the target wiU continue for some 
 little time in the same direction and at the same speed, its position 
 can be approximately determined for any particular moment in the 
 future, and the gun can be aimed for the position the target will be 
 in at that moment; or better still, since the distance of the target 
 from the gun is known, the time of flight of the projectile can be 
 jSgured out, the motion of the target diuing that time can be calcu- 
 
310 
 
 lated and allowed for, and the gun can be aimed for a time corre- 
 sponding to the arrival of the projectile at the target. 
 
 This allowance for the motion of the target can be made roughly 
 by taking a scale and continuing the line of dots forward to the 
 calculated time of arrival of the projectile. The gun arm could then 
 be moved to this point and the reading of the direction and distance 
 made directly. In actual practice, however, this is done in a much 
 better way. 
 
 As I have stated before, the gun arm makes use, not of the azimuth 
 graduations around the edge of the plotting board, but of the gradua- 
 tions on a special metal azimuth circle centered at the point G. The 
 zero of the vernier of this azimuth circle is adjustable and the zero 
 of distances along the gun arm is also adjustable. Instead, therefore, 
 of pointing the gun arm to the predicted position of the target on the 
 plotting board and reading off on a fixed scale and azimuth circle a 
 predicted range and a predicted azimuth, the gun arm is kept pointed 
 to the ppsition of the target as last plotted and the readings to a 
 predicted point are made by adjusting the zeros of the azimuth circle 
 and of the range scale of the gun arm. 
 
 In working out the corrections for the motion of the target, it is 
 convenient at the same time to make other corrections — a correction 
 for the drift of the projectile depending upon the shape of the point, 
 a correction for the effect of the wind, a correction for the difference 
 in air resistance due to variations, barometric pressure, and a cor- 
 rection for a possible variation in the initial velocity of the projectile 
 due to the temperature of the powder, etc. 
 
 These corrections are mechanically worked out by two members 
 of the plotting detachment on two corrector boards especially 
 designed for the purpose and fm-nished by the Ordnance Department, 
 one giving the correction in azimuth and the other the correction in 
 elevation. These boards are reaUy mechanical integrators and the 
 methods of using them are given in pamphlets that describe them and 
 in the Coast Artillery manuals. 
 
 At the beginning of the plotting on any target, the zeros of the 
 azimuth circle and of the range scale of the gun arm are set at their 
 absolute positions. The first plotting gives the approximate range 
 and the subsequent plottings give the motion of the target. As soon 
 as the correctors get the approximate range they note it up on their 
 corrector boards and later the travel. They then quickly and 
 mechanically sum up the different corrections for these and the other 
 items and then set off the correction by changing the zeros of the gun 
 azimuth circle and of the distance scale on the gun arm. 
 
 At first sight it might appear that the application of these cor- 
 rections makes the aiming of a gun very complicated, but it must be 
 remembered that barometric pressure changes but slightly in an hour 
 
311 
 
 or so and that the average direction and velocity of the wind, not 
 considering gusts, also remain fairly steady. The termperature of 
 the air and the temperature of the magazine change slowly. The 
 total correction to be applied is never very great and the changes in 
 this correction from time to time are exceedingly small. Conse- 
 quently, by the time the fourth or fifth plotting has been made the 
 corrections will have been noted and the zeros moved. Thereafter 
 the changes in the amount of the corrections wiU be very slight and 
 only occasionally will any movement of the zeros be necessary. It 
 thus becomes possible to transmit to the gun detachment an azimuth 
 and range which if used ia the aiming will cause the projectile and 
 the target to arrive at the same point at the same instant. 
 
 Of course, aU corrections in aiming based upon an allowance for 
 the motion of the target, assume that the direction and speed of the 
 target wiU remain practically imchanged from the time of observa- 
 tion to the time of arrival of the projectile. If the direction and 
 speed of the target should be changed quickly and irregularly such 
 corrections will do but little good, but it must be remembered that the 
 targets at which heavy seacoast guns wiU be fired are usually very 
 large vessels. On account of their mass the speed of these vessels 
 can be changed but slowly, and when they turn they turn slowly and 
 in circles of large radius. 
 
 THREE METHODS OF AIMING. 
 
 If the method of position-finding above described be tised, it is 
 not necessary that the aiming detachment see the target at all. To 
 obtain success in this method of aiming, however, it is necessary that 
 both base end stations be kept in good working condition, and that aU 
 communications be kept intact, so that all the data necessary may 
 reach the plotting room and be sent thence to the gun. It is of 
 course not impossible that during an action one of the position-finding 
 stations may go out of commission or that one or more of the com- 
 munication lines may be cut. In order that such an occurrence may 
 not absolutely put the gun out of action it must be possible to fire 
 without recourse to such an elaborate position-finding system. 
 
 There have, therefore, been adopted three methods of aiming: 
 
 Case 1. — Where the gun receives practically no information as to 
 azimuths or ranges from a plotting room. 
 
 Case 2. — ^Where the range and elevation are given from the plotting 
 room, but the azimuth is determined by direct sighting with certain 
 corrections for the motion of target, etc. 
 
 Case S. — ^Where both the range and azimuth are sent from the 
 plotting room as has been described above. 
 
312 
 
 For use in cases 1 and 2 a modern seacoast disappearing-gun car- 
 riage has an elevated platform where the gunner stands and observes 
 the target through a sighting telescope. At this sighting telescope he 
 is, of course, exposed to view -and to fire. 
 
 In firing by case 1 the gunner points his telescope directly at the 
 target, guessing at the range from the first shots and making such 
 subsequent corrections in range and azimuth as may appear to be 
 necessary from observation of the fall of the projectiles. 
 
 In firing by case 2 the gunner on the sighting platform uses the 
 telescope, but he obtains his range and some data as to corrections in 
 azimuth from the plotting room. In using this case the same general 
 data as in case 3 are sent to the plotting room. The plotting is done 
 as in case 3 and, as in case 3, information as to range and elevation 
 is sent to the loading detachment, but instead of sending data as to the 
 azimuth at which the gun should be aimed, there is merely sent to the 
 gunner at the sighting platform, information as to the total of the 
 corrections in azimuth. This he makes use of by setting the axis 
 of his telescope a little to the right or left so that it does not point 
 in the same horizontal direction as the gun, but in such a direction 
 that if the cross hair of the telescope be kept on the target when the 
 gun is fired, the projectile wiU go not to the spot at which the tele- 
 scope is pointed, but to the spot at which the target will be when the 
 projectile has gone that distance. 
 
 In actual service, case 2 is the one most used by our seacoast 
 artillery since it has the great advantage that the firing of a gun at 
 any particular instant is not necessary as in case 3. 
 
 Of all the corrections in azimuth which are applied, the largest 
 is usually that due to the motion of the target and this correction 
 changes slowly. Therefore, if case 2 be used and the proper correc- 
 tion for aU elements be once sent to the gun and applied to the 
 sighting telescope, subsequent corrections will be infrequent and 
 slight, and if the gunner keeps the vertical hair constantly on the 
 target the gun wUl be constantly kept trained in azimuth and can 
 be fired, as far as azimuth is concerned, at any instant. 
 
 Likewise, the member of the detachment at the elevating wheel 
 keeps the gun set at the elevation sent him from the plotting room.^ 
 Since this elevation wiU evidently change at a fairly uniform rate, 
 a skilled man soon learns to change the elevation continuously, and 
 at such a rate that it will always agree accurately with the elevations 
 received from the plotting room just as they are received. The 
 gun will, therefore, be always trained in elevation and can be fired. 
 w;henever it is loaded and just as rapidly as it can be loaded. 
 
 In firing by case 3, on the other hand, it is essential that the gun 
 be fired at exactly the movement for which the aiming data were 
 calculated. 
 
313 
 
 Mortar Fire. 
 
 Mortars are usually mounted in deep pits from \rhich the tai^et 
 can not be seen. Consequently, case 3 is the only one applicable to 
 mortar firing. 
 
 The initial velocity of mortars is much less than that of direct-fire 
 guns and the projectiles are fired at high angles, and, consequently, 
 the time of flight is much greater than that of direct-fire projectiles — 
 in some cases as much as one minute and a half or two minutes. 
 Furthermore, it is not possible in mortars as in direct-fire guns to 
 keep the mortars constantly trained in azimuth and elevation. They 
 can be loaded only when their axes are horizontal and must be 
 trained, in elevation at least, after they have been loaded. Further- 
 more, the blast effect of the discharge of mortars is so great that time 
 must be given to the men to withdraw several yards to the rear. 
 Consequently, some time must elapse from the time when the mortar 
 is set to the time when it is fired. During this time and that required 
 for the plotting and transmission of data, it is possible that either the 
 direction or speed of the target may have changed, and in order not 
 to waste ammunition in case this should have occurred an additional 
 precaution is used in mortar firing. 
 
 In addition to the base-end observing stations, there is an addi- 
 tional station provided at which the battery commander or some espe- 
 cially designated man is stationed. At the same time that the data 
 for loading are sent to the detachment in the pit, information is sent 
 to this special station as to the azimuth which the target shoidd 
 have from that station at the particular moment that the mortar 
 should be fired. The azimuth instrument in this station is set at this 
 a2dmuth and the observer looks through it. If, when the instant 
 for firing comes, the target is passing over the vertical wire, the 
 mortars are fired. If the target is very nearly there they are fired 
 at the instant the target crosses the vertical hair, because the differ- 
 ence between the azimuth at which the instrument is set and that 
 used in setting the mortars has been calculated for the time for 
 flight. If, however, when the calculated moment for firing arrives 
 the target is far off from its predicted position, the observer knows 
 that something is wrong and withholds fire until after a new pre- 
 diction has been received and the mortars have been relaid. The use 
 of this additional instrument, therefore, acts as a check upon the 
 plotting and aiming system. 
 
 SHORT HORIZONTAL BASE SYSTEM. 
 
 The system of horizontal position-finding just described is based 
 upon the use of a very long base line and telescopes at both ends of this 
 base line. Accuracy in the use of this system is possible only when 
 the exact length of the base line is known, when the zeros of azimuth 
 
314 
 
 of the two instruments are exactly parallel, and when the instru- 
 ments are read at exactly the same moment. Furthermore, it may 
 happen that while a target can be seen very clearly from one station, 
 smoke or some other obstacle may interfere with its view from the other 
 station. 
 
 In order to overcome these and other difficulties an attempt has 
 been made to utilize short self-contained horizontal base instruments. 
 
 The essential principle of these instruments is as foUows: Two 
 similar object glasses are mounted a known horizontal distance apart 
 and with their optical axes horizontal and parallel. Immediately 
 behind each object glass a prism or mirror is placed in such a position 
 as to change the direction of the rays of Hght 90° in a horizontal plane 
 so that after passing through the prisms the rays wUl travel approx- 
 imately toward the other object glass. Midway between these 
 object glasses a pair of prisms is placed, one for the rays coming from 
 each object glass, these prisms being so arranged as to again turn the 
 rays of light 90° in a horizontal plane and so that these rays become 
 parallel to the directions which they had after they passed through 
 the object glasses. These central prisms are, in addition, so con- 
 nected up with the eyepiece as to fuse the rays of light together, 
 with the result that the observer, looking into the eyepiece sees two 
 images in the same field and nearly superposed. Incidentally, also, 
 these prisms are so arranged as to caiise the image as seen by the 
 eyepiece to be erect. 
 
 Under normal conditions the two images seen through the eyepiece 
 wUl be exactly superposed only if they are images of an object at an 
 infinite distance away. The images of objects at finite distances can 
 be made to superpose exactly by the rotation of one or both mirrors 
 or main prisms, or by the rotation of an auxiliary prism interposed 
 in the path of the rays of Hght coming from one of the object. glasses. 
 To make the two images of any object at a finite distance exactly 
 coincide, a rotation of this auxiliary prism is necessary and the amount 
 of the rotation required is dependent upon the distance of the object. 
 If we know the amount of movement necessary to make the images 
 of an object coincide, we can figure out the distance of the object or, 
 what is better, the scale showing the amount of this rotation can be 
 so marked as to indicate, not the amount of rotation itself, but the 
 distance of the object, in yards or as such other units as may bfe 
 desired. 
 
 What the instrument really does is to measure the angle subtended 
 at the target by the distance between the two object glasses and to 
 convert this angle into distance. The angle is always very small and 
 becomes smaller the greater the distance of the object. The accuracy 
 of the reading of the instrument depends, therefore, upon the accuracy 
 of the reading of a very small angle. Furthermore, the use of the 
 
315 
 
 4 
 
 instrument depends upon the exact superposition of the two images 
 of an object. In order that the superposition may be exact the out- 
 lines of the objects must be very clear and distinct, and the farther 
 away the target is the greater the difficidty in obtaining in a tele- 
 scope clear and distinct views of it. 
 
 The instrument, therefore, has hmitations and though many types 
 have been tried none have been foimd satisfactory for reading long 
 ranges. 
 
 The longer the instrument, of course, the greater the base line used 
 in the triangulation, but as the length increases there seems to be an 
 increase in the difficulty of keeping the instrument rigid under tem- 
 perature changes. 
 
 At the present time there has been adopted in the service a short 
 horizontal-base instrument which seems to be quite satisfactory in 
 reading ranges for rapid-fire guns up to about 6,000 yards under good 
 atmospheric conditions. Larger instruments have also been intro- 
 duced and are effective at slightly increased ranges. It is possible 
 that the future may show that it is possible to develop still better 
 instruments, but it is the opinion of the writer that owing to the 
 optical principle upon which these instruments work and the diffi- 
 culty of obtaining very distinct images of distance objects, it will 
 never be possible to develop self-contained horizontal-base instru- 
 ments that will be even fairly effective in any except most unusual 
 atmospheric conditions at ranges greater than 10,000 yards. 
 
 This instrument reads the distance of the object from the instru- 
 ment, and it can be made so as to read azimuths, in addition. It is 
 ordinarily used with rapid-fire guns and is mounted not far from the 
 guns, so that the distance shown by the instrument will be approxi- 
 mately the range of the target from the gun. Xo plotting, therefore, 
 is necessary and slight errors of range are of but little importance. 
 To be of use with guns not near the instrument, plotting or reloca- 
 tion is necessary. 
 
 VERTICAL BASE POSITION-FINDING SYSTEM. 
 
 The principle upon which the use of the vertical base position-finding 
 system is founded is triangulation in a vertical plane, making use of a 
 right triangle whose sides are as follows: First, a vertical line down- 
 ward from the position of the instrument to the projection of this 
 point upon the plane of sea level ; second, the horizontal line from the 
 ioot of the vertical line to the target; third, the line from the target 
 to the telescope. Since the triangle is a right triangle it is necessary 
 to measure but one of the acute angles. The direct measurement of 
 the angle at the target is, of course, impracticable, but the other 
 acute angle, that at the telescope, is available and can be measured. 
 
316 
 
 It should be noted, 'however, that in the cases vvhich happen in 
 -practice the vertical side of the right triangle is always much smaller 
 •;#han the horizontal side, the elevation of the instrument practically 
 never exceeding a, few hundred^ feet and the distance of the target 
 being seldom less than a thousand yards. Consequently, of the two 
 acute angles of the triangle the one at the target is usually quite 
 small and the one at the telescope is not much less than a right angle. 
 
 In practice, therefore, it has been found simpler to measure, not 
 the angle between the vertical line and thQ line from the telescope 
 to the target, but the complement of this angle, that is, the angle of 
 depression of the line to the target below the horizontal plane passing^ 
 through the telescope. This angle of depression is equal to the angle 
 of the triangle at the target and is always fairly small. 
 
 The sites chosen for the stations to be used in this system are 
 usually the highest that are available or that can be made available, 
 consistent of course with other requirements, such as a fair degree of 
 concealment, convenience of location with respect to the gun, a clear 
 view of the probable field of fire, etc. 
 
 The instruments used are of special design and of very careful 
 manufacture. The telescopes are large and powerful. The ob- 
 server looks through the telescope at the target and moves the tele- 
 scope until the horizontal hair appears to coincide with the water line 
 of the target. 
 
 All that is then necessary is to measure the angle of depression, 
 and to make the calculation for the distance which is mathematically 
 equal to the length of the vertical base of the triangle divided by the 
 tangent of the angle of depression (which angle is equal to the angle 
 of the triangle at the target). Since, with a given length of vertical 
 base, the distance of the target is a function of the angle of the de- 
 pression, it is simpler and easier in practice to have the calculations 
 worked out beforehand and to have the scale on the instrument sa 
 graduated as to read, not angles, but the calculated distances to the 
 target. 
 
 In spite, however, of aU possible care in the design of the instru- 
 ment and skill in its manufacture, this system of position finding^ 
 possesses certain inherent difficulties which place a limit upon the 
 degree of accuracy obtainable. Some of these difficulties are de- 
 pendent upon the difficulty of the determination of the actual length, 
 of the vertical base, and the remainder upon the difficulties in obtain- 
 ing a proper value for the angle of depression. 
 
 The upper end of the vertical base is, of course, the center of the 
 instrument. This point is fixed and its elevation can be measured,, 
 with any desirable degree of accuracy, with reference to a selected 
 bench mark, to mean sea level, to mean fiigji water, to mean low 
 ^ater, to the zero of any fixed tide gauge, or to any other fixed point; 
 but the quantity which should properly enter into the calculation of 
 
317 
 
 the distance of the target is not the elevation of the instrument above 
 any one of the planes mentioned, but the difference in elevation be- 
 tween the instrument and the actual point of the target apparently 
 intersected by the horizontal hair of the telescope. 
 
 The targets used with this system are, of course, intended to be 
 the enemy's vessels, and the attempt is made to waterline these ves- 
 sels as seen in the telescope. This is where the difficulties come in. 
 In the first place, the level of the water surface in aU our harbors, and 
 hence the length of our vertical base line^ varies with the tide. The 
 difficulty due to tidal rise and fall is, however, one that is easy to elim- 
 inate since the height of the tide at any moment can be predicted 
 closely by tidal tables, or what is better, can actually be observed 
 on a tide gauge. Information as to the height of the tide at any mo- 
 ment can be quickly transmitted to the observer at the iustrument 
 "who can make the proper adjustment of his instrument. The tidal 
 «rror is, therefore, one for which proper correction can be made from 
 time to time. 
 
 To waterline the target, however, that is, to fix the cross hair of the 
 telescope on the portion of the target that the water is just touching 
 is not an easy thing to do. Warships are painted a dark green not 
 greatly different from the apparent color of the water when seen at a 
 distance and due to the reflection of the ship in the water the exact 
 determination of the water line is difficult even when the ship is not in 
 motion. When the ship is in motion and when there are waves the 
 difficulty is much increased. 
 
 In all our harbors there is always more or less wave action. Some 
 of the waves are small, splash up against portions of the target, and 
 are depressed in others. But these smaller waves, although some- 
 "what confusing to an imtrained observer, do not give as much 
 trouble as the longer swells which raise and lower the target without 
 showing visibly upon it. These long swells are always present to a 
 greater or less extent; they are of irregular periodicity, and are 
 almost certain to influence the readings of the instrument. 
 
 When a vessel is in motion the water is always banked up at and 
 near the bow. A little distance further astern the level of the water 
 against the side is much depressed, thence to the stem of the vessel 
 the water level, is alternately raised and lowered. 
 
 The extent to which the water is banked up in some places and 
 depressed in others depends upon the speed of the vessel and is greater 
 the faster the vessel is going. To look through a telescope at a mov- 
 ing vessel and attempt to water line it is extremely difficult. Even 
 the best trained observers are very prone to make mistakes, usually 
 in the way of assuming that the waterline is higher than it really is. 
 
 It might appear at first sight that the errors which would be made 
 in water lining a vessel, due to the causes mentioned, would be com- 
 
318 
 
 paratively small, only a few feet at most. This may be true, but it 
 should be noted that the effect of errors of this character is really to 
 change the length of the vertical base line which is used in calculation. 
 If, for instance, the vertical base line is approximately 50 feet and an 
 error of 5 feet should be made in water lining the vessel, this error is 
 one-tenth of the length of the base, and the calculated distance would, 
 therefore, be in error by approximately one-tenth of that distance. 
 
 The difficulties of waterlining increase rapidly with the distance 
 of the target both because of decreasing visibility and the difficxilty 
 of seeiog the troughs of the waves against the vessel and, therefore, 
 of placing the horizontal cross hair so as to about balance the crests 
 and troughs. 
 
 In the measurement or observation of the angle of depression there 
 are other sources of error, a minor one due to the curvature of the 
 earth's surface, and a more serious one due to refraction. 
 
 The curvature of the earth's surface is an element which must be 
 taken into consideration. The departure of the surface of the earth 
 from a horizontal plane increases approximately as the square of the 
 distance. The error thus introduced is an easily calculable quantity; 
 it can, therefore, be allowed for with a fair degree of accuracy. 
 
 Refraction in the vertical plane is always Resent in the passage 
 of light rays through the atmosphere and is due to the decreasing 
 density of the air as one ascends. 
 
 For observation on stars near the zenith, refraction is almost 
 negligible except for use in very careful astronomical observations, 
 but for observations on stars at or near the horizon refraction becomes 
 very great, the general effect being to elevate the apparent horizon 
 by more than one-half a degree of arc. If the elevation of our instru- 
 ment is about 100 feet, and it is frequently much less than that, and 
 the distance of the target is 10,000 yards, and it is frequently much 
 more than that, our vertical base line is only about one three-hun- 
 dredth of the horizontal distance to the target. Consequently the 
 angle of depression with which we are dealing is only about one-fifth 
 of a degree or approximately one- third of the amount of refraction. 
 Consequently, it is evident' that refraction in depression position 
 finding is an extremely important element. 
 
 Were refraction constant, however large it might be it could be 
 allowed for, but unfortunately it is not a constant quantity. 
 
 TTie line of sight from the instrument to the water line of a distant 
 target passes for a considerable distance through air that is almost 
 in contact with the water and the temperature of which is to a con- 
 siderable extent affected by the temperature of the water as well as 
 by the temperature of the air above. The larger part of our seacoast 
 forts are situated at the entrances to navigable harbors. The depth of 
 water in the harbors is usually not very great and the sun is apt to 
 
319 
 
 ■warm up these comparatively shallow harbors to several degrees above 
 the temperature of the ocean outside. With the ebbing of the tide 
 the warm water passes to the sea, usually in well defined currents, 
 so that the water in our harbors and over which our depression posi- 
 tion finding telescopes have to look are apt to contain irregular 
 streaks of warmer and cooler water with considerable resulting 
 irregularity in refraction. 
 
 When depression position finding instruments were first intro- 
 duced it was the idea of their inventors that the amount of refraction 
 could be easily calculated when the reading of the local barometer and 
 thermometer were known and could then be allowed for. It was soon 
 found out, however, that this was not true and that even an approxi- 
 mate determination of the effect of refraction could be arrived at 
 only by actual observation at the tim^; that is, by sighting the tele- 
 scope at some object in the water whose position was known. 
 
 The objects whose position and distance from the instruments are 
 known are called "datum points" and consist usually of piles or 
 clusters of piles or of some similar structures. 
 
 At first it was thought that a single datum point would be all that 
 was necessary, but it was soon discovered that a telescope adjusted 
 on a datimi point at a comparatively short distance would not neces- 
 sarily read the correct distances when sighted at a datum point much 
 farther away. Consequently, a multiphcity of datum points was 
 found to be necessary, and the attempt was made to place datum 
 points, some at about 3,000 yards from the observation stations, 
 others at about 6,000 yards, and stiU others at about 9,000 yards. 
 
 The observing instruments used are adjustable for two corrections ; 
 one, a tidal correction intended to allow for the varying length of the 
 vertical base; and the second, a refraction correction intended to 
 allow for atmospheric refraction. In practice, both corrections have 
 to be used together to allow for refraction. The instrument is first 
 adjusted for the tidal correction, according to the reading of the tide 
 gauge. It is then sighted at a distant datimi point and adjusted by 
 the refraction correction adjustment so as to read the correct distance 
 of that datum point. It is next turned to a nearer datum point and, 
 if it does not read correctly and adjustment is made as if for tidal 
 difference so that the instrument will read the correct distance to this 
 nearer datum point. With care and the alternate use of the two 
 datum points, it is usually possible to adjust the instrument so that 
 wOl read fairly correctly the distances to both the near and the far 
 datiun points and will presumably, therefore, give approximately 
 accurate readings for distances between the two and for distances 
 slig htly beyond the farther datum point. 
 
 The methods of making these adjustments are given at length in 
 the manuals on the subject and need not be gone into further here. 
 
320 
 
 In spite of the fact that more care and thought seems to have been 
 expended upon the development of the depression position finding 
 instrument than on any other observation instrument, the best that 
 can be said of it is that except under unusually favorable circumstances 
 it gives approximate distances only. 
 
 Of course, the longer the vertical base — that is, the higher the 
 instrument — the less the probable error of its reading. Where very 
 high sites are available the instrument is therefore quite serviceable, 
 but unfortunately the country is so fiat along the greater part of the 
 coasts that high sites are not available and we can raise our position- 
 finding instruments to high elevations only at the expense of making 
 the stations quite conspicuous. 
 
 The first experiments with the depression position finding instru- 
 ments were made at Fort Wadsworth, New York Harbor, where 
 fairly high sites were available, where the water was comparatively 
 quiet, and where the ranges at which observations were made were 
 not very great. 
 
 The results of these experiments were so satisfactory and the sim- 
 plicity of the vertical-base system which read distances directly 
 without plotting was so great, compared with the long horizontal- 
 base system, which requires the simultaneous readings from two ends 
 of a base line and the subsequent plotting of position, that it was 
 adopted as the standard position-finding system for seacoast use. 
 
 It was then believed that a vertical base 60 feet long would give 
 sufiiciently accurate readings at the ranges desired and the Board of 
 Engineers at once designed instrumental towers to be used along our 
 low sandy beaches. This tower consisted of a steel framework sup- 
 porting a house at the top. The pillar or pier for supporting the 
 instrument was built independently of the tower proper and con- 
 sisted of a concrete column going aU the way to and into the ground. 
 To keep this column from vibrations due to the wind, it was sur- 
 rounded by a metal cylinder attached to the tower framework, but 
 nowhere touching the concrete of the column, nor was the floor of the 
 observing room allowed to touch the column. 
 
 The first' of these towers buUt was a one-story tower, the plotting 
 being done on one side of the same room containing the instrument. 
 Before any additional towers were constructed, however, the plans 
 were changed slightly so as to make the upper part of the tower con- 
 sist of two stories, an upper room for observation and a lower one 
 for plotting. The plans for these towers are shown in mimeograph 
 No. 42 and its supplements. 
 
 It so happened that just at the time that this type of tower was 
 adopted as a standard, a large appropriation for fire control was 
 available and many towers were ordered to be built, distributed prac- 
 tically along our whole coast. At small forts only one or two of these 
 
321 
 
 towers were built, but at some of the larger ones as many as eight 
 were constructed. 
 
 Unfortunately, the harbor entrances at all of our South Atlantic 
 and Gulf ports, and occasionally elsewhere, are bounded by low sandy 
 shores. No sooner did these towers begin to spring into actual 
 existence on the low sandy beaches than it became clear that they 
 were entirely too conspicuous. Occasionally it happened, near the 
 north end of the Fort Monroe reservation, that towers could be built 
 in the midst of woods or had a wooded background which made it 
 possible to conceal them, but in most places no such background ex- 
 isted and it was evidently impossible to conceal the towers. Being, 
 as it were, the head and brains of the whole &e-control system, it 
 was expected that they would naturally be the targets used by the 
 enemy. It was, therefore, thought that they were too vulnerable 
 and the type was abandoned. In fact, before many of them were 
 actually completed they had been declared to be obsolete. 
 
 Experiments were then made with lower stations, some having an 
 instrumental height of 40 feet, some of 30 feet, and some of 15 feet 
 only. These were found not to be satisfactory and finally the idea 
 of depending exclusively upon this depression position-finding system 
 had to be given up except for localities where high sites were available, 
 and even then for comparatively short ranges only. 
 
 THE THREE SYSTEMS OF RANGE FINDING. 
 
 We have, then, three essentially different systems for determining 
 ranges: First, the long horizontal-base system; second, the seK- 
 contained short horizontal-base system; and third, the vertical-base 
 system. 
 
 The first, the long horizontal-base system, is the most accurate, 
 but there are a number of adherent disadvantages in such a system. 
 First, in order that the position finding may be sufficiently acciu-ate 
 the base must be very long and must be suitably oriented with regard 
 to the direction of the target. Locations for suitable base end stations 
 are not always available. Then again, if there are a number of vessels 
 coming in at the same time, and if the vessels happen to be of the 
 same class, as is quite probable, in future attacks, it is quite difficult 
 to insure that the instruments at the two ends of the base hne will be 
 sighted at the same ship. This difficulty increases with the length 
 of the base line. A ship that appears the farthest to the right from 
 one station may not necessarily so appear to the other, or the one that 
 appears foremost or rearmost from one station may not have the 
 same relative position from the other. Unless, therefore, the ship it 
 is desired to use as a target has very special characteristics that dis- 
 tinguish it from the other ships, mistakes in the identity of thie target 
 may easily be made. 
 173341—20 ^21 
 
322 
 
 In fact, during the maneuvers of 1905 at Fort Monroe, a mistake- 
 of this kind actually did occur. In making the run by, the larger 
 ships were preceded by destroyers making a smoke cloud. Through 
 this smoke the battleships could be seen but dimly. The target 
 used by one end of a base line was not the same as that used by the 
 other. When plotted from these erroneous^ observations it so- 
 happened that thb first point plotted looked as if it might be the- 
 actual location of a ship, but as the plotting was continued the mis- 
 take became evident as the plotted path, instead of following the 
 channel, passed right through the position of a big stone fort. 
 
 The depression instrument is much less accurate than the hori- 
 zontal base system, but with this instrmnent only one view of the 
 target is necessary and no errors due to failure of icleatification can 
 occur. However, in order to make this instnunent available at all, 
 the target must be seen with sufficient clearness to make" it easy to 
 water line. 
 
 The short self-contained horizontal base system is much less accu- 
 rate than the long horizontal base system, but is probably more 
 accurate than the vertical base system when used from low sites, 
 and less acc^u•ate than the vertical base system used from high sites. 
 Identification . 
 
 After the errors in the use of the vertical base system due to re- 
 fraction were found to be irremediable, and the possibilities of errors 
 due to mistakes in identification in the use of the long horizontal 
 base system had been shown, it was suggested that the two systems 
 might be used together so as to avoid both errors. That is, it was 
 proposed that the instruments at both ends of the horizontal base 
 should be depression instruments fitted with azimuth circles. When 
 the target had been designated, not only would the azimuths to the 
 target be read but the approximate range as shown by the depression 
 principle also. The position of the target given by the azimuth read- 
 ings from the two ends of the base line would then be marked on the 
 plotting board and if this position accorded fairly well with the dis- 
 tances from the two stations as shown by the reading of the dfe- 
 pression angle, it was considered that it might be safely assumed that 
 both instruments were pointing at the same target. If not, it would 
 be evident that a mistake had been made in the identification of the 
 target and the cause of this trouble would be at once investigated 
 and corrected. 
 
 POSITION FINDING FOR BATTERIES. 
 
 In the preceding discussion the subject of position finding has 
 been discussed as if each gun had its own independent base line and 
 plotting room. Although nowadays this is to a great extent true of 
 the larger guns that are being installed, it is not true now of the 
 
323 
 
 smaller guns, and has only recently been true of the larger ones. 
 Structurally, emplacements have \isuaUy been united into batteries 
 of two, three, or four, and, in general, it has been expected that all 
 the guns of a battery wovdd use the same target at the same time. 
 Theoretically, if t\ro gvms of a battery are aimed with the same 
 azimuth and elevation, the two points of fall of the two shots should 
 be at the same distance apart as the two guns and the line joining 
 them should be parallel to the line connecting the gun centers. This 
 might at times throw the gun off the target and a correction is some- 
 times necessary. In practice, therefore, it has been customarv to 
 determine the range and azimuth of the target from one point of 
 the battery known at the directing point, usually one of the gun 
 centers, a point midway between the gun centers in a two-gun battery 
 or the location of the middle gun in a three-gun battery. The azi- 
 muth and elevation with which a gun not at the directing point of a 
 battery shoidd be fired are, of course, very sHghtly different from, 
 what they would be if the guns were at the position of the directing 
 point, but the difference is not great either in azimuth or elevation, 
 seldom amounting to as much as a haK of a degree in azimuth and 
 more than a very small fraction of a degree in elevation. 
 
 The actual differences can easily be calculated, or better stiU they 
 may be shown graphically on what is called a 'difference chart."' 
 When the azimuth and elevation corresponding to the directing point 
 are received at the gun, the corresponding differences can be quickly 
 read off this chart and can then be applied in aiming the gun. 
 
 Battery Commanders' Stations. 
 
 It would appear at first sight that the logical station of a battery 
 commander is at his battery, and at such a position at his batteiy 
 as to enable him to best oversee the work of the detachment. As 
 has been stated, the earher emplacements constructed contained in 
 each battery a plotting or relocating room, and consequently when 
 the battery commander was at the battery he could at the same 
 time oversee the plotting or relocating. 
 
 When the plotting room was moved to an observation station 
 either in connection with the depression position finding system oi 
 with the horizontal position finding system, it was evident that the 
 battery commander could not personally oversee both the operations 
 in the battery and the operations in the plotting room. Either he 
 must stay at the battery and leave the supervision of the plotting 
 to one of his subordinate officers, or he might go to the primary 
 station and leave the supervision of operations at the battery to one 
 of his assistants. In general, of course, it woiild appear that his 
 proper place was at the battery. 
 
324 
 
 With the adoption, about 1904, of what was called the Barrancas 
 system other cbnditions were introduced. As will later be explained 
 more in detail, the essential principle of this system was the installa- 
 tion of equal and parallel base lines, and this was obtained by haying 
 a set of primary stations collected together in one group, and a set 
 of secondary stations in a similar group. In general, there was a 
 group of primary stations for each fire command, the fire commander 
 occupying the central primary station and the other primaries being 
 assigned to the different batteries. This system was invented by. 
 an officer who at the time was of the rank of major and a fire com 
 mander, and in order to insure that the system would work well he 
 wanted to have his battery commanders near him. He therefore 
 required that each battery commander should take station at his 
 primary station, leaving affairs at his battery to the charge of his 
 lieutenants. 
 
 It was intended that the fire commander should select the vesse 
 to be used as the target for each battery and should then telephone 
 each battery commander as to the target he should use, but in order 
 to be sure that a battery commander was using the proper target, 
 the fire commander might walk into the battery primary, which was 
 only a few feet away, and see that the instrument was actually 
 observing the proper target. Or without even telephoning, the fire 
 commander might, if he desired, walk into a primary station and 
 himself point the telescope on the proper target. This system, of 
 course, contributed largely to the unity of action of the different 
 batteries of a fire command and was quite satisfactory to the fixe 
 commanders. The captains, however, were in this manner located 
 at considerable distances away from and frequently out of sight of 
 their batteries and in positions where their responsibilities were in 
 fact comparatively small. It was natural, therefore, that the cap- 
 tains should clamor for a system which would send them back to 
 their batteries. 
 
 When the towers for use with the depression position finding 
 system had been built at Fort Monroe there were several cases where 
 the towers were located slightly to the flank of and to the rear of 
 the batteries to which they pertained, especially was this true in 
 the case of the most powerful battery then in commission at that 
 fort, a three-gun 12-inch battery. 
 
 It was soon discovered by the commanding officer of this battery 
 that from the observing room of the tower he could obtain an ex- 
 cellent view of operations on at least two of his loading platforms, 
 and that by means of a megaphone he could communicate his in- 
 structions to the detachments in those emplacements. Consequently, 
 when it was decided that the captains should go back to the bat- 
 teries there was a demand that stations be built for them from which 
 
325 
 
 they could not only see what was going on at the batteries but could 
 also observe the effects of their fire. 
 
 The typical plans of the older batteries all showed small crow 
 nests on the flanks of the batteries, but in general these crow nests 
 were too small for occupancy by more than a single observer, and 
 moreover, they were very inconveniently placed for an officer whose 
 duties required that in addition to observing he should supervise 
 the work of the battery. (See Plates XIV to XX.) 
 
 At the same time when the subject of providing battery command- 
 ers' stations at the batteries was being considered, the writer of these 
 notes was the constructing officer at Fort Monroe, Va. The most 
 modern 12-inch battery, Battery Parrott, was about to go into com- 
 mission and there happened to be in rear of it a part of the old 
 system of fortifications, a water battery then being demoUshed. The 
 suggestion was therefore made to the battery commander assigned 
 to this battery that an experimental station for him might be built 
 on the top of the old water battery. Trial showed that the old 
 battery was a little too far to the rear of the new one, and the experi- 
 mental station was therefore located immediately in rear of the center 
 of the new battery. 
 
 This experimental battery conmiander station was built of scrap 
 lumber saved from the concrete framework. In connection with it 
 there was provided a plank battery commander walk on the same 
 level as the floor of the station and extending from one side to the 
 other of the central traverse of this battery, immediately behind the 
 traverse and just in front of the station. At the end of this walk 
 stairways led down to the loading platforms, and thus permitted the 
 battery commander to proceed quickly from the station to either of 
 the loading platforms. The height of the battery conmiander station 
 Was such that a person in the station or on the walk could just see 
 over the top of the battery, which was of the horizontal crest type. 
 The station was roofed over and was provided with the character of 
 observation windows then standard in fire-control stations. Beneath 
 the station and about on the loading platform level there was built a 
 plotting room, and by means of an opening in the floor of the station 
 the battery commander could look into the plotting room and see, 
 if -he desired, exactly how the plotting was being done. As soon as 
 completed this experimental station was put in use, and as experience 
 showed them to be desirable modifications were made, these modifi- 
 cations being easily possible because the structure was of timber. 
 
 Finally, after about a year's experience, a satisfactory type of 
 battery commander station was developed and the original experi- 
 mental station was replaced by concrete. Similar structures were 
 soon built for many other batteries throughout the country (see the 
 thirty- third supplement of mimeograph No. 42). The type of station 
 
326 
 
 thus evolved consists essentially of a small two-story concrete strucr- 
 ture. The upper story is for observation by the battery commander 
 and his assistants and contains some telescopes and such other 
 observation instruments as may be necessary. It is placed on such 
 a level that the battery commander can look over the top of the 
 hattery and can have a clear view of the field of fire of the battery. 
 The lower story, which is on about the loading platform level, eoni- 
 tains the plotting room. CommuMcation^— that is, speaking — be- 
 tween the two levels is provided for by means of a large voice tube 
 connecting the battery commander's room with the plotting room 
 and there is a conveniently located stairway which permits a person 
 to go quickly from one room to the other. = In order that the battery 
 commander may be able to move rapidly from his station to either 
 of the loading platforms or, if he desires, to go merely to a position 
 from which he can see into the platform, there passes in either direc- 
 tion from the battery commander station an elevated walk known 
 as the battery commander walk. The floor of this walk is at the 
 same level as the floor of the battery commander station so that a 
 person standing on it can see over the top of the battery. It is 
 located immediately behind and is attached to the rear wall of the 
 central traverse and at each end has steps going down into the 
 loading platform. 
 
 The battery commander stations built in accordance with the plans 
 just described proved so satisfactory that it was decided to embody 
 a station possessing all the most desirable features in the mimeo- 
 graphed plans of the next disappearing emplacements to be pub- 
 lished. This was therefore done in mimeograph No. 1 09 (Plate XXII) , 
 which gives the plans of the emplacements for 14-inch guns. 
 
 The stations added to the older batteries were necessarily built in 
 rear of the batteries because it was evidently impossible to incorporate 
 them in the main structure of the emplacements. It is evident, how- 
 ever, that the stations, and what is more important still, the plotting 
 rooms, would be better protected from flank fire if they had actually 
 been built into the central traverse. This, of course, it was possible 
 to do in batteries to be thereafter constructed and the station and 
 plotting room are shovm in mimeograph No. 109 (Plate XXII) as 
 built into and forming part of the central traverse. 
 
 In the battery commander stations built in the rear of the top of 
 the traverse the floor is a few feet below the level of the top of the 
 emplacement, but at such an elevation as to enable an observer to 
 easily look over the traverse. The stations are shown, as covered by 
 a splinter-proof concrete roof and observation windows are shown 
 around three sides of the station of a design which had already been 
 shown to be satisfactory. 
 
327 
 
 The batterj- commander's walk in this design is quite similar to 
 those built for the older batteries, passing along the rear of the cen- 
 tral traverse and behind the battery commander station which is 
 entered from the walk. At each end of the battery commander's 
 walk, as in the old design, there is a staircase leading downward to 
 the upper platforms of the main staircases, which extend downward 
 from the loading platform to the ground level. They therefore serve 
 to provide easy communication, not only from the battery com- 
 mander's walk to the loading platform, but also from the battery 
 commander's walk to the ground. 
 
 In the design shown in mimeograph Xo. 109 (Plate XXII) the 
 plotting room is placed not directly beneath the battery commander 
 station, but is pushed farther forward into the body of the traverse, 
 leaving behind the plotting room a corridor which serves as a com- 
 mimication not only to the plotting room but also between the two 
 loading platforms. 
 
 In order that the battery commander in his station may be able 
 to talk conveniently to persons in the plotting room, there are pi"o- 
 vided wide slots extending from the ceiling of the plotting room rear- 
 ward and upward to the front wall of the battery commander station. 
 These slots are so shaped that, in addition to talking through them, 
 the battery commander can actually observe what is being done on 
 the plotting^ board. (See detail on sheet 2, mimeograph 109.) 
 
 Mimeograph 109 remained the standard upon which large gim 
 emplacements were designed until it became necessary to design the 
 Panama batteries. These batteries, as has been stated, were of the 
 new one-story horizontal ammunition service type, the magazines 
 having their floors on the same level as the loading platform and 
 having their concrete ceilings surmounted by earthen covers. 
 
 A battery commander's station has been provided for each emplace- 
 ment and is located on top of the rear of the magazine traverse, and 
 on the side of that traverse toward the loading platform. The side 
 slopes of the traverse have been so designed as to permit a partial 
 view of the loading platform to be obtained from the battery com- 
 mander station. (See Plates XXIII, XXR^ and XXV.) The floor 
 of the station is sunk into the top of the traverse and is placed at 
 such a height that a view can just be obtained over the traverse. 
 The front and side walls are, of course, of concrete but are raised 
 only from 4 to 6 inches above the level of the surrounding earth 
 and are finished off on top in slopes running down to the earth. 
 
 The station is entered from the rear and can be reached by a walk 
 "which leads sideways to the side slope of the loading platform or by 
 & staircase which leadu downward to the magazine level. 
 
328 
 
 The plotting room is placed on the loading platform level which^ 
 in this case, is the same as the magazine level and is almost vertically- 
 under the battery commander station, the usual voice tube communi- 
 cation between the two being provided. 
 
 In the Panama batteries the battery commanders' stations are 
 usually 15 feet square and their floors are entirely on one level.. 
 Among the functions to be performed from the battery commanders' 
 stations is that of telephone or speaking-tube communication. 
 This is usually attended to by members of the detachment provided 
 with head sets. It is, of course, not essential that these telephone 
 men should be so situated as to get a view of the field of fire, and if 
 they can get such a view it is not improbable that their attention 
 might be thus distracted from their proper work. Furthermore, it 
 is thought that they are perhaps unnecessarily exposed to fire. 
 
 A modification has therefore been made in the standard design of 
 battery commanders' stations, the floor of the stations being broken 
 into two levels, the forward level at a height convenient for observa- 
 tion and the rear some 3 or 4 feet lower. The telephone speaking 
 tube terminals are placed on this lower level and stools are to be 
 provided for the telephone men, who are thus put in a position where 
 they are much safer and where their attention is not Hkely to be 
 distracted from their proper duties by the sight of what is going on 
 in the field of fire. This new type of station, with two fioor levels 
 (see Plate XXI and XXVI), may now be considered as standard. 
 The battery commander's walk is now placed on the lower level, and 
 therefore no longer affords a view of the field of fire. 
 
 In aU recent designs, both those for the Panama and for other 
 batteries, short stairways have been provided leading from the 
 battery commanders' stations up to the top of the traverse, so that 
 ready access is available should it be necessary for the battery com- 
 mander or some one else to get hastily on top of the traverse. The 
 question of the proper kind of roof for a battery commander's station 
 is still under discussion. 
 
 The first experimental battery commander's station built at Battery 
 Parrott was provided with a light frame roof for the protection from 
 the weather of the personnel and instruments. Incidentally, the 
 presence of a roof made it possible to lock the station up securely 
 when it was not occupied. v 
 
 When the standard designs of battery commanders' stations were 
 prepared it was proposed to build the stations of concrete and they 
 were provided with splinter-proof concrete roofs. The same design 
 with some improvements in detail was embodied in Mimeograph No. 
 109. (Plate XXII.) 
 
 To observe over the battery requires that the eyes of the observer 
 should be a foot or so above the upper surface. A little space must 
 be provided above the head of the observer, and if above this 8 
 
329 
 
 fairly thick concrete roof is to be built, the top of the roof necessarily 
 projects a considerable distance above the top of other portions of 
 the traverse. It is therefore more or less conspicuous and can be 
 seen by the enemy. Not only may it draw the enemy's fire, but it 
 may in addition be used by him as a point from which to locate the 
 guns. Incidentally, in time of action it might be struck and cause 
 the detonation of a projectile which, if it were not for the roof, would 
 have passed harmlessly by. 
 
 It was therefore thought that for many reasons it might be better 
 that the station, at least in time of action, should have no roof at all. 
 Consequently, in most of the larger Panama and later batteries the 
 battery commanders' stations have been provided merely with 
 removable iron-pipe framework, upon which awnings could be spread 
 to protect the detachments during drills and target practice from the 
 sun or weather. 
 
 Battery Commanders' Stations for 6-Inch and Smaller Batteries. 
 
 As was the case with the early designs for large gun emplacements,, 
 the earher designs of emplacements for small and medium cahber 
 guns usually -included small observation stations or crow's nests. 
 (See early design for 3-inch emplacement, Plate III, for 5-inch 
 emplacements, Plates VI and VII, and for 6-inch emplacements, 
 Plate IX.) The crow's nests shown on these earher drawings were 
 usually quite small; sometimes they were shown as circular, some- 
 times as square, and their diameter usually did not exceed 5 feet. 
 They were therefore intended for observation only and were hardly 
 suited for use as battery commanders' stations. The 1902-03 designs 
 for 6-inch emplacements (Plate X and XI) showed these stations 
 slightly larger, about 7 feet square, and that remained the standard 
 for 6-inch batteries Tintil the Panama 6-inch emplacements were 
 designed. These were provided with battery commanders' stations 
 similar in size, shape, and location to those provided for the large 
 Panama batteries and heretofore described. (See Plate XII.) 
 
 The 1903 designs for 3-inch emplacements (Plate V) showed no 
 crow's nests or observation stations, probably because at that time 
 it was customary to consider small rapid-fire batteries as intended 
 primarily for the protection of submarine mines. They were, there- 
 fore, assigned to the min e commands, formed part of those commands, 
 and were supposed to have httle use for battery commanders' 
 stations. However, some years later, instructions were issued to 
 build battery commanders' stations at these small batteries also. 
 These battery commanders' stations were placed at the center of 
 the rear of the top of the traverse and were reached by walks passing 
 along the rear of the top of the traverse and thence along the sides 
 to the loading, platforms of the guns. Some of the earth coveriag 
 of the toD of the traverse was removed to provide space for the 
 
330 
 
 station and the walk ways leading to it. The station was surrounded 
 by thin concrete walls. Usually it was provided with a corrugated 
 iron roof. 
 
 Battery Commanders' Stations at Mortar Batteries. 
 
 In the drawings of the 1898 type of mortar battery (Plate XXVIII), 
 smaU crow's nests are shown on top of the flank traverses, and where 
 mortar batteries of this type were built in such positions that the 
 fields of fire could be seen from them, such crow's nests were usually 
 provided. These crow's nests, however^ were small and usually not 
 well fitted for the use of a battery conmiander. 
 
 In 1905 there was in session at Fort Monroe a board of Artillery 
 officers revising the Drill Kegulations for Seacoast Artillery. The 
 writer was at that time constructing officer there and had recently 
 completed the experimental battery commander's station at a large 
 direct-fire battery, described a few pages above. He therefore 
 offered to undertake the development of a battery commander's 
 station for mortar batteries. 
 
 The mortar battery at Fort Monroe is of the type shown in figure 
 4, Plate XXVII, and consists of four mortar pits in a line with four 
 mortars in each pit. The pits are open to the rear and are separated 
 from each other by traverses extending backward from the front 
 parapet. To the rear these traverses end off in gently rounded slopes. 
 Shortly before the time mentioned this battery had for tactical 
 purposes been divided into two smaller tactical batteries of eight 
 mortars each, and each tactical battery had, therefore, a traverse 
 extending backward between its two pits. 
 
 The top of the rear slope of the central traverse of one of these 
 smaller tactical batteries was selected as the site for the experimental 
 battery coiomander's station. The station was built high up on the 
 rear slope of this central traverse and was placed at such an elevation 
 that it was just possible to see over the top of the battery. At first 
 the station, which was about 5 feet wide by 7 feet deep, consisted 
 merely of concrete walls on three sides, the rear being open. The 
 concrete walls were about a foot thick and 5 feet high measured 
 above the concrete floor, while in front they projected about a foot 
 above the upper surface of the earth of the parapet. In the center 
 of the station was a pier for the battery commander's telescope. 
 No roof was provided at first, but some months later, at the request 
 of the local battery commander, a light frame and supposedly 
 removable roof was added, with the understanding that the roof 
 was a mere temporary convenience for protection during drills. 
 However, before long the garrison had found it convenient to suspend 
 electric wires from the framework of the roof so that it could not 
 have been removed without disarranging a large part of the wiring. 
 
331 
 
 Just behind the battery-commander station and on a level a few feet 
 below the floor of the station a plank walk was built extending out to 
 both flanks far enough to permit a person standing near the end of 
 the walk to easily see down into the mortar pit. 
 
 A few months later, in connection with this battery-commander 
 station, a plotting room was constructed farther down in the rear 
 slope of the central traverse, as will be described hereafter. 
 
 Within the next year or so somewhat similar battery-commander 
 stations were built at several of the older mortar batteries, one of 
 which is described in the twenty-third supplement to mimeograph 
 42, issued in 1906. This mimeograph shows designs for a concrete 
 battery-commander station for mortar batteries. The station is about 
 6 feet wide by 10 feet deep, has reinforced concrete walls and roof, and 
 the usual observation slots. Xo battery-commander walk was pro- 
 vided, as the conditions did not permit it, nor was a plotting room 
 built in connection with the battery-commander station. 
 
 A few years later the writer, then the district offit er at Honolulu, 
 designed an improved battery-commander station and plotting room 
 for the mortar battery then under construction for the defenses of 
 Honolulu. The battery was of the 1906 type of mortar battery. 
 (Plate XXVITI.) The plotting room was built just over the roof of 
 the rooms in the central traverse and near the rear of that traverse. 
 The battery-commander station was placed over the front end of 
 the plotting room and was provided with a reinforced concrete roof 
 and observation slots. Xo battery-commander walk was buUt, be- 
 cause a fairly good view of the pits could be obtained from the battery- 
 commander station. However, to enable an officer to quickly get 
 down closer to the pits, short flights of steps were provided from the 
 door of the plotting reom down to the roofs of the alcoves of that 
 room. These alcoves had been added to the plotting room to take 
 care of the shafts of the mechanical data indicators and extended 
 from the side waJls of the plotting room diagonally sideways and 
 backward until they overhilng slightly the side walls of the mortar 
 pits. It was therefore possible for a person upon the roof of one 
 of these alcoves to walk out imtil he was practically over the edge of 
 the pit. 
 
 In 1913 and 1914 battery commanders' stations of two different 
 types weriB built at the two tactical batteries of eight mortars each 
 into which the original Fort Monroe mortar battery had been divided. 
 It was at one of these batteries that there had been buUt the original 
 experimental battery-commander station described a few paragraphs 
 above, and just below it had been buUt the plotting room. The 
 plotting room was constructed of plaster upon metal lathing. It 
 had been gradually knocked to pieces by the effect of the blast and 
 needed to be replaced. Consequently, at this battery a new concrete 
 plotting room was buUt, located, like its predecessor, in the rear slope 
 
332 
 
 of the central traverse of the battery. Over the front part of this 
 plotting room was built the new battery-commander station, which 
 was quite similar to the original experimental one, having concrete- 
 walls on three sides and a door to the rear. No roof was provided,, 
 and a removable frame for stretching a canvas awning was added 
 over it. The roof of the plotting room in rear of the battery com- 
 mander's station was utilized as a sort of battery commander's plat- 
 form and was extended toward each flank by a concrete walk which, 
 led out far enough to enable the battery commander from its end to. 
 see into the pit. 
 
 A hole was cut in the floor of the battery commander's station, and' 
 over it was stretched a thick wir6 grating. This, in turn, was cov- 
 ered by a removable cast-iron cover. By raising the cover it was pos- 
 sible for the battery commander in his station to see through the- 
 grating what was going on in the plotting room and to talk to the- 
 detachment working therein. 
 
 The battery commander station and plotting room at the other 
 tactical haW of the original large mortar battery was a little more- 
 elaborate but of the same general character. The plotting room, in- 
 stead of being 15 feet square, was made 18 feet square, and 
 the battery commander station was enlarged from 6 by 7 J feet to- 
 7 J by 11 feet. This battery commander station, like the other, was 
 not provided with a roof, an awning frame being provided instead. 
 In one important respect this station differed from the other — - 
 its floor was made on two levels. The upper or front level was made- 
 4 by 7J feet and contained a pier for the battery commander's instru- 
 ment. The other level, about 4 feet lower and connected with th& 
 upper level by steps, occupied the remaining space of the station, 
 and on this lower level were placed the telepljione terminals, so that 
 the men at the telephone would be somewhat protected and would 
 not be likely to have their attention distracted by the sight of what 
 was going on in the field of fire. 
 
 As in the other station, the roof of the rear of the plotting room 
 was utilized as a battery commander platform, and a battery com- 
 mander walk was extended in both directions toward the pits.. 
 This walk, of course, was too low to permit a person standing on it 
 to see over the mortar battery, and it was therefore considered neces- 
 sary at each end of this walk to build up a pulpit to the same height 
 as the floor of the battery commander station. On each of these 
 pulpits there was installed a pedestal for a telescope. 
 
 The battery commander station just described was the first one 
 to include the two-level idea, which has since been adopted as the 
 standard for battery commander stations for both mortar and direct- 
 fire batteries. (See Plates XXI, XXVI, and XXIX.) 
 
333 
 
 All the mortar batteries built witlun the last few years, either in 
 "the Canal Zone or elsewhere, have been located in ravines or behind 
 hills, from which no view of the field of fire can be obtaiaed, conse- 
 <juently battery commander stations provided at the ■ batteries 
 wotdd have been useless. It was necessary, therefore, to build lor 
 the use of the battery conmiander and at a distance from the battery 
 a station somewhat similar to the ordinary fire-control observing 
 station, which will hereafter be described. Moreover, it was con- 
 sidered necessary to provide at the battery itself a convenient 
 location from which the officer in actual command might supervise 
 what is going on. Consequently, the roof of the plotting house 
 (see Sheet XXIX) has been finished off as a sort of a platform for 
 the battery commander. ^ 
 
 The plotting house has its floor about on the same level as the 
 floors of the pits and is located behind the central traverse. The roof 
 of this house has been surrounded by handrails, and stairways have 
 been built leading up to it. From this roof the battery commander, 
 or such other officer as may be on duty, can readily see what is going 
 on in the pits, and by the use of a megaphone can give commands and 
 instructions to the men there; by the use of the voice tubes he can 
 communicate with the detachment in the plotting rooms below him; 
 by means of speaking tubes he can talk to members of the detach- 
 ment in the magazines and storerooms; and by going to either of 
 the front corners of his platform he can see exactly what information 
 is being displayed for the guidance of the men in the pit. For his 
 protection from the sun or rain an awning has been provided which 
 can be put up or be taken down, as he may desire. 
 
 PLOTTING ROOMS. 
 
 In the early nineties, at the time when the first modern batteries 
 were imder construction, and when fire control, or, as it was then 
 called, "position finding," was beginning to be developed, it was 
 planned that the plotting of the path of the target should be done 
 in a room situated in a thoroughly protected position within one of 
 the emplacements of the battery. At that time the determination 
 of the position of the target with reference to the ends of the base 
 line was called "locating" the target, and the adjustment of this 
 data to suit the position of any particular gun was known as "re- 
 locating." Consequently, the earlier emplacement designs, show 
 rooms marked "Relocating rooms." (See Plates XIV, XV, XVIII, 
 and XIX.) 
 
 As has been stated previously, the interior rooms of most of these 
 old batteries were damp and disagreeable. Furthermore, the noise 
 made by firing the guns, the rimibling of the loaded trucks on the 
 platforms, and the rattling of the chains and troUeys used in pro- 
 
334 
 
 jectile service all tended to produce confusion in these relocating 
 rooms. It was therefore decided, at least in time of peace, to abandon 
 the use of these rooms and to do the plotting elsewhere. A move was 
 made to some conveniently located existing building or to some frame 
 structure specially built for the purpose and located usually in the 
 rear of and close to the battery. 
 
 However, at about the same time as the plotting boards were being 
 removed from the relocating rooms of the batteries to other temporary 
 but more comfortable locations, the first depression position-finding 
 instruments were under test. In the first form of this instrument the 
 plotting was done upon a map attached to the extended front part of a 
 large and unwieldly base upon which the instrument was mounted. 
 This, however, was soon foimd to be somewhat awkward, and it was 
 then arranged that the plotting should be done upon a separate board 
 in the same room as the instrument. 
 
 The original towers built for the use with the depression position- 
 finding instrument were designed with a view of doing the plotting at 
 the base of the instrument, and but one room was provided at the top 
 of the tower. Later, the attempt was made to do the plotting upon a 
 separate plotting board in the same room, but as it was fo\md that 
 the room was too small for doing this conveniently, all subsequent 
 towers were built with two-story houses at their tops, the idea being 
 that the plotting should be done in a room one story below the 
 observing room. 
 
 The designs for such a tower are shown in mimeograph 42, where it 
 will be noted that the upper story or instrumental room forms a sort 
 of loft over the center part of the Jjlotting room on the lower story, 
 the floor of the upper story not extending over all of the lower story. 
 Communication by talking between one story and the other can easily 
 be held. The plotting room was about 15 feet square, but the large 
 instrumental pier passed through its center so that the plotting board 
 had to be placed in a comer. 
 
 As has been stated before, the first towers that were built soon 
 proved to be too conspicuous and the attempts to use lower stations 
 having shown the impracticability of relyiag upon the vertical base 
 system for low sites, there was, about 1903, a return to the horizontal 
 base system and new designs for stations for use with this system 
 were, in 1903, published in the sixth supplement to Mimeograph 42. 
 
 The .use of the towers having shown the desirability of having a 
 plotting board located close to at least one observing station, the 
 same arrangement was carried out in the new system, one of the 
 pair of observing stations at the end of a base line being made quite 
 large, about 30 by 16 feet, so as to contain in the front part an observ- 
 ing room and in the rear a plotting room. The other end of the base 
 line was occupied as the site of a so-called "secondary" station, which 
 
335 
 
 was made merely large enough to contain the azimuth instrument. 
 The usual size of the secondary station was 10 by 10 feet, though 
 sometimes it was made even slightly smaller. 
 
 The first instruments that were used in these horizontal base 
 stations were those that had been designed and pTirchased with a 
 view to use with the vertical base system. In order not to waste the 
 use of the depression principle, for which the instruments were 
 designed, an attempt was made to keep the instnunental height of 
 the stations as close as possible to 40 feet, so that the depression 
 principle of range finding could be used for identification purposes. 
 Where placing these instnmients at 40 feet made them too con- 
 spicuous, it was said to be permissible to reduce the height to 35 feet, 
 or even in some cases to 32 feet in locations where the range of the 
 tai^et was limited. 
 
 Barrancas System. 
 
 The successful working of any one base line of a horizontal position- 
 finding system requires that both the observation stations of this 
 base line should remaia intact and that the telephone communication 
 between both the stations and the plotting room shoiild not be bro- 
 ken. The stations themselves, if they can be seen, will not improbably 
 be selected as targets by the enemy and the communicating cables, 
 even thotigh placed in undergroimd conduits, may be injured by the 
 enemy's fire. Consequently, the entire system possesses considerable 
 vulnerability. 
 
 It was thought possible that it might occur in action that one of 
 the stations of one base line might be put out of commission dTiring 
 action, or that its communications might be cut, and in order that 
 the gun itself might still receive data which could be used, it was pro- 
 posed that the commimication lines should be so designed that the 
 data pertaining to any one base line could be sent to and be used by 
 the plotting rooms of other gims than its own. 
 
 It was planned, therefore, that all the communicating telephone 
 cables should pass through a central telephone switchboard room, and 
 that there should be installed in this room a somewhat comphcated 
 set of switchboards so designed as to permit the data coming from 
 the base line of any battery to be sent, not only to the plotting room 
 of that battery but in addition to be duphcated in other plotting 
 rooms. 
 
 Now, in order that the data coming from any base line may be 
 available for plotting on any plotting board, it is essential that the 
 base hne should be equal in length and should have the same azimuth 
 as the base line for which the plotting board was designed. 
 
 To render possible the use of an interchangeable set of base lines, 
 it was essential that these base lines be equal and parallel, and, 
 furthermore, in order to avoid too great relocation errors, it was 
 
336 
 
 •essential that the primary stations of these base lines be grouped 
 iairly close together. 
 
 This system was invented by Maj. Whistler of the Coast Artillery, 
 and as the first set of experimental stations was built at Fort Barran- 
 cas, Pensacola Harbor, Fla., the system became known as the "Bar- 
 Tancas system." This system consisted of a row of primary station 
 with their instrumental piers on a straight line and from about 16 to 
 ^0 feet apart. The secondary stations were likewise grouped in a 
 parallel line and with their instrumental piers at the same distance 
 apart. 
 
 Although based upon the idea of making the system less vulnerable 
 by the interchangeabUity of base lines, it became apparent soon after 
 these groups of stations were completed that this system was itself 
 ■quite vulnerable, since the comparatively close grouping of the sta- 
 tions pertaining to different base lines made it not improbable that 
 more than one station would be destroyed at a single time. Espe- 
 cially was this true in connection with the first sets of stations which 
 were built entirely of wood. 
 
 Furthermore, any one base line can cover satisfactorily but a com- 
 paratively limited field of fire and is, therefore, thoroughly suitable 
 •only for guns having essentially the same field of fire as its stations 
 have field of view. The different batteries in a harbor seldom cover 
 ■exactly the same areas, and it seldom happens,-therefore, that a single 
 l)ase line is very well suited for the use of more than one or two 
 batteries. So when the attempt was made to adapt the Barrancas 
 system of equal and parallel base lines to our different seacoast 
 fortifications, and to select sites for the observation stations, it was 
 found not to be adaptable to very many locations. The system was 
 later abandoned and subsequent layouts have been based upon the 
 idea of selecting for any particular battery of guns the base line best 
 suited for the field of fire covered by the guns and, in general, to make 
 the selection of sites for base ^nd stations without regard to their 
 suitabihty for the use of other guns or their relation to the base lines 
 ,to be used for other guns. 
 
 As was noted in the discussion of battery commander's stations, the 
 grouping of the plotting rooms in the primary stations of the Bar- 
 rancas system had another purpose in view, that of making it possible 
 for the fire commander to go into any of the plotting rooms of the 
 batteries of his fire command and to personally oversee the plotting 
 carried on in these different plotting rooms. 
 
 When, however, the close grouping of the primary stations was 
 done away with there was no longer any reason for keeping the 
 plotting rooms at the primary stations, and since with the abandon- 
 ment of the Barrancas system, the battery commanders were moved 
 back to the batteries, it began to be considered desirable to move the 
 
337 
 
 plotting rooms also. This was accordingly done, beginning with the 
 experimental plotting room of Battery Parrott at Fort Monroe, 
 described above. 
 
 From this historical sketch of the peregrinations of the plotting 
 rooms, and incidentally of the battery commander's stations, it is 
 seen that they both started at the battery; that they were both 
 moved away to the so-called primary stations; and that eventually 
 both came back to the battery again. This is a ciirious example of 
 how things sometimes go all around the circle only to come back to 
 the place from which they started. 
 
 The relocating rooms of the earlier batteries were usually about 8 
 by 12 feet and in some cases even smaller, and the earlier temporary 
 stations built in rear of battery for relocating or plotting purposes 
 were no larger. By the time, however, of the development of the 
 Barrancas system, the plotting system had become somewhat com- 
 plicated. There was in each plotting room not only the plotting 
 board, but the corrector boards for azimuth and elevation, a map 
 case, and other furniture. To provide space for aU this it became 
 necessary to increase the size of the plotting room to not less than 
 15 by 16 feet which has since become the standard. More recently, 
 however, it has become necessary to slightly lengthen the plotting 
 rooms in order to accommodate in one end of the room a mechanical 
 indicating apparatus for transmitting data to the guns. 
 
 Plotting Room at Mortar Batteries. 
 
 As was stated a few paragraphs before, in describing the experi- 
 mental battery commander station constructed about 1905 at the Fort 
 Moiu"oe mortar battery, a plotting room was built for that battery 
 farther down the rear slope of the central traverse. This plotting 
 room was set into the rear slope of the traverse. It was entered by a 
 stairway coming up the slope from the rear, and in the front of the 
 plotting room the stairway was continued up to the battery com- 
 mander's station. The first station, built of timber, was soon injured 
 by blast effects and was very shortly replaced by a similar and slightly 
 larger room built of cement plaster construction, as was then standard. 
 This structure also was seriously injured within a few years and as 
 has been stated was, about 1913, replaced by a concrete structure 
 set well into the traverse and described a few pages above. From 
 this plotting room, in all its various stages, attempts were made to 
 operate mechanical indicating apparatus for displaying in the pits 
 the data for aiming. 
 
 The general idea of the first plotting room at the Fort Monroe 
 
 mortar battery was copied and improved upon in the designs of the 
 
 mortar batteries built in the Hawaiian Islands. The plotting rooms 
 
 there constructed were made of concrete and were set well into the 
 
 173341—20 22 
 
338 
 
 rear end of the central traverse at an elevation well above the floors 
 of the pits. From the side •walls of the plotting room small alcoves, 
 extended out to the flank and obliquely to the rear, and in these 
 alcoves were installed the shafts of the mechanical indicating appa- 
 ratus which displayed the data through slots at the ends. The- 
 alcoves extended over the rear corners of the central traverse and. 
 were so turned as to directly face the pits. They were so high in. 
 the air as to be easily seen from any point in the pit without the line- 
 of sight being interfered with by other persons or by the mortars. 
 
 In connection with the design of the Panama type of mortar bat- 
 teries (see Plate XXIX) a regular plotting house was provided 
 immediately in the rear of the central traverse of the battery. The- 
 interior of this house is about 16 by 32 feet; that is, about twice the 
 size of the regular plotting room, so as to accommodate the plotting 
 boards, one for each pit. It thus permits the two pits to be handled 
 tactically as if they were different batteries. In front this plotting 
 room is extended toward either flank in the form of an alcove for the- 
 mechanical indicating apparatus which displays data in a turret over 
 this alcove at such an elevation as to be seen from any portion of th& 
 pits. In the plotting houses so far built no partitions have been used 
 to separate the two parts of the plotting rooms, but should it ever be- 
 desired such partitions could be easily built. 
 
 As has been stated, the roofs of these buildings have been prepared 
 so as to make convenient stations for the ofiicer in immediate com- 
 mand of the work of the batteries. 
 
 It is customary for the Engineer Department to provide for alL 
 pilotting rooms, seats or benches around the plotting boards, arrange- 
 ments for hanging on the walls the corrector boards and other fire- 
 control apparatus, hooks for hanging up hats and coats, a locker or- 
 cupboard for keepiQg maps, and a folding shelf or table upon which, 
 the maps and" drawings may be spread out for examination. 
 
 PLOTTING BOARDS. 
 
 In the preceding parts of this chapter an outline has been given of 
 the principles underlying both the horizontal and vertical position- 
 finding systems and of the methods of graphically plotting the 
 observations made on the target by the telescopes at the observing- 
 stations. The first plottiug boards used were rectangular in shape- 
 and were usually of home-made manufacture. As they developed, 
 however, and became more delicate, more careful construction became 
 necessary, and their manufacture and issue was made a fimction of 
 the Ordnance Department. 
 
 The plotting boards gradually increased in complexity and soon 
 there were several types in use. However, by the time of the joint 
 Army and Favy maneuvers of 1905 there had been developed a> 
 
339 
 
 standard form of board known as the "WMstler-Heam" plotting 
 board, after its inventors, Maj. Whistler and Capt. Heam of the 
 Coast Artillery. This board was the first to make use of the prin- 
 ciple of parallelism previously described. In size and shape it con- 
 sists essentially of a segment, slightly more than 180° of a circle, 
 having a diameter of about 5 feet. Carefully made notches indicating 
 the degrees are placed around its circumference and the ends of the 
 plotting bars are fitted with wedge-shaped pieces which slip into the 
 notches of the board. The fractional parts of a degree are set off 
 by means of micrometers on the ends of the plotting bars. 
 
 The earlier of these plotting boards were fitted for use with one 
 particular base line only. Subsequently improvements were made so 
 that by inserting a connecting arm of the proper length any plotting 
 board can be quickly adjusted to any length of base line. 
 
 The field of view which can be satisfactorily covered by any one 
 base line is, of course, considerably less than a half circle, because as 
 points approach the ends of the base line prolonged the angle sub- 
 tended at the target by the base line becomes less and less; and when 
 plotting is attempted the intersection of the lines from the two base 
 ends becomes very acute. Consequently any base hne is available 
 for use only in a sector covering not more than about 160° of azimuth 
 arc from the center of the base line, and the same limited area is 
 about all that can be satisfactorily plotted with the normal form of 
 plotting board. For observation in other directions auxiliary base 
 lines are usually necessary. With the form of plotting board first 
 used additional plotting boards were needed, one for use with each of 
 the auxiliary base lines. However, there was afterwards developed 
 a form of plotting board which could be modified when necessary 
 so as to permit plotting throughout the 360° of azimuth arc. 
 
 The correctness of the plotting as done by pins and strings on the 
 original crude plotting boards, or by bars with the later Whistler- 
 Heam plotting boards, is dependent upon the correct reading of the 
 azimuths indicated by the scales on the observing instruments which 
 are kept trained on a moving target and are therefore in motion, 
 upon the correct transmission by telephone of the azimuth readings 
 thus obtained, and upon the correct setting of the azimuth strings or 
 bars on the plotting board. In all of these steps errors are possible, 
 and though with skilled observers the chance of making errors is 
 small and any errors made will probably not be large, yet they are 
 still possible. It would appear that a number of these sources of 
 error would be avoided if these plotting bars could by mechanical or 
 electrical means be kept always parallel to the lines of sight of the 
 corresponding observing instruments. 
 
340 
 
 This idea is not new. In fact, more than 30 years ago the Engineer. 
 School at Willets Point obtained from England a mechanical appa- 
 ratus for doing this very thing. ' It had been invented for use in 
 submarine mining at a time when experiments were in progress 
 having in view the development of a system of submarine mining 
 which would make it possible, from the shore, to explode any par- 
 ticular mine whenever desired. The effective use of this method of 
 firing submarine mines necessarily required that the course of the 
 enemy's vessel through the mined field should be carefully followed 
 on a map upon which were indicated the positions of the mines. 
 
 With the apparatus referred to, the map was placed upon an ex- 
 tended base in front of one of the observing instruments. Attached 
 to the instrument and moving with it in azimuth was a ruler, so 
 iastened to the telescope that the edge of the ruler would always be 
 parallel with and exactly below the line of sight of the telescope. 
 At another point on this board — that is, the point corresponding to 
 the location of the secondary base-end station — there was pivoted 
 a,nother ruler. This ruler was so connected electrically with the 
 observing instrument at the secondary station as supposedly to be 
 kept always parallel to the line of sight of the telescope at that 
 -station. Electric machinery at that time had not been very well 
 developed, and in actual practice the secondary ruler moved by jerks 
 and jumps and was seldom even approximately parallel to the line 
 of sight of the telescope. The instrument, therefore, although beauti- 
 ful in theory would not work very well in practice and its use was 
 abandoned. 
 
 Comparatively recently, that is, during the last year of the recent 
 war, the same idea was revived for use in connection with the plotting 
 of the movements of aircraft. In this case the plotting is done upon 
 the upper surface of a plate of slightly translucent glass. Instead of 
 using intersecting rulers, the plotting is done by means of the inter- 
 section of two well-defined beams of light that are thrown along the 
 undersurface of this glass plate. These beams are pivoted at the 
 two points corresponding to the positions of the observing stations. 
 They are rotated electrically by an apparatus that is supposed to 
 keep them always parallel to the lines of sight of the observing instru- 
 ments, and since the light beams are without mass and therefore have 
 no inertia it is easier to keep them up to exact parallelism with the 
 axes of the telescopes than is the case with material bars/ or rulers. 
 As far as is known to the writer at the present time, this instrument 
 has not passed beyond the experimental stage, but the writer is 
 assured that the results of the first experiments have been decidedly 
 promising. 
 
 Should this system be shown to be practicable it will do away with 
 a number of the complications of the present system of plotting and 
 -wiU avoid several sources of error. 
 
341. 
 
 The Whistler-Hearn plotting board was designed with the idea ol 
 using in plotting a scale of 1 to 18,000, that is, 500 yards to the inch. 
 The standard size of board was fixed at that which would permit 
 plotting with this scale up to distances of slightly more than 12,000 
 yards, which at that time was considered as about the maximum 
 range at which it was probable that seacoast guns would be fired. 
 When, some six or eight years later, it was considered desirable to 
 increase ranges to about 20,000 yards, it was thought that the same 
 plotting boards could still be used by changing the scale to 1 in 36,000, 
 that is, to 1 ,000 yards to the inch. 
 
 Even when the,ranges were supposed to be limited to 12,000 yards 
 it was found that in order to make the plotting fairly accurate the 
 base line had to^be from 2,200 feet to 2,500 feet in length. When 
 the possible ranges were supposed to be increased to 20,000 yards,. 
 4,000 feet had to be looked upon as the proper length of base line, 
 with a minimum length of about 3,500 feet. Wherever it has become 
 necessary to lay out base lines of lengths approaching the figures just 
 given, great difficulty has usuaUy been met with in finding suitable 
 sites; and, what is more, the sites that are available have not infre- 
 quently been so placed with reference to each other and to the field 
 of fire as to make errors of identification pf the target not improbable. 
 
 Events in the World War have shown the necessity of giving con- 
 sideration to much greater ranges still, up to 35,000 or possibly 40,000 
 yards. The problem of position finding at these ranges is one for 
 which, up to the present time, no satisfactory solution has been 
 found. The base lines woiild have to be at least 3,000 yards in 
 length. In order tp be able to see the hull of a target 35,000 yards 
 distant, the observer, even in clear weather, would have to be con- 
 siderably more than 200 feet above sea level and such high sites are 
 usually not available on our sea shores. From stations as high as 
 are available, with the conditions of low visibiUty which ordinarily 
 exist along our sea shores, the masts and funnels only of the ships 
 will be in sight, and they will usually be seen but dimly. 
 
 Position-finding under these conditions and at such distant targets 
 is almost certain to be vmsatisfactory. No assistance ia the identifi- 
 cation of targets can be given by the depression principle and the 
 observation of the results of fire will usually be impracticable from 
 the shore. It would therefore appear that it will be necessary, for 
 finding the position of such distant targets and controlling fiire on 
 them, to rely upon some form of aircraft. 
 
 For long-range fire on shore where the targets are fixed, aircraft 
 control of artillery fire is understood to have been very satisfactory, 
 but this does not necessai-ily prove that aircraft will be very successful 
 in the control of fire at sea where the targets themselves are in motion 
 and where there is nothing fixed which can give the observer in an 
 
342 
 
 airplane any certain information as to the speed of the target. 
 Consequently, it is thought probable that at these extreme ranges 
 accuracy of fire wiU be found to be unobtainable. If that be the 
 case, material damage to an enemy's vessels wiU occur but seldom, 
 and the effect of fire upon him, if any, wiU be more moral than 
 material. 
 
 FIRE-CONTROL BUILDINGS. 
 
 The buildings usually provided by the Engineer Department for 
 fire-control purposes are the observing stations, plotting rooms, 
 battery commanders' stations, fire commanders' stations, ^battle 
 commanders' stations, switchboard rooms, meteorological stations, 
 signal and radio stations, dormitories, and occasionally power houses. 
 Observing Stations. 
 
 The first system of position finding used was the horizontal 
 system. The observing station was at first extremely simple,' con- 
 sisting of but little more than a pier upon which could be mounted 
 the observing instrument ,which was a mere transit or simple azimuth 
 instrument. To a neighboring post were led a pair of telephone 
 wires to which a portable telephone could be attached. 
 
 These stations were placed in the open and in positions from which 
 good views could be obtained of the fields of fire of the guns. No 
 houses or other fixed protections were provided and when necessary, 
 the observer protected himself and his instriunent from the sun or 
 rain by using a large umbrella similar to those in frequent use by 
 siirveyors. When not occupied, such stations were not protected 
 in any way. Consequently, aU the instnmients had to be portable 
 and were taken away by the detachment when -the drill was over. 
 
 The next step was to provide over these stations small houses 
 which could be locked up so that the instruments could be left in the 
 stations even when not in use. The stations were usually built of 
 wood and were fitted with wide observation slots through which 
 the^ telescopes could look. 
 
 The next important step in the development of observing stations 
 was taken about 1900, in connection with the vertical base position- 
 finding system. It consisted in the erection of tall towers. One or 
 two experimental towers were built first of different materials, but 
 before long a tower composed of metal framework became the standard. 
 (The Board of Engineers' designs for §uch a tower are published as 
 mimeograph 42.) 
 
 On the first one or two experimental towers, the houses at the tops 
 were made but one story high, but on all of the subsequent towers and 
 on the mimeograph designs the houses were aU two stories high. 
 The lower story of the house consisted of the plotting room, about 
 15 feet square, in one corner of which was placed a steel column for 
 
343 
 
 inounting a small azimuth instrument. The observing room was a 
 sort of loft over the center of the plotting room. In the center of 
 the observing room the depression position instrument was moimted 
 -upon a concrete pier running all the way down to the ground and not 
 connected at any point with the metal framework or with any portion 
 of the buidling. This concrete column was protected from the wind 
 l)y an outside metal cylinder forming part of the metallic frame work 
 of the tower, but nowhere touching the concrete coliunn. This was 
 done in order that the vibrations in the tower or house, due to the 
 -wind or other causes, might not be communicated to the pier and 
 thus to the instrument. 
 
 The mimeograph drawings show the telescopic height to be about 
 46 feet above the base of the tower or about 50 feet above the groimd 
 on which the tower was built. Usually an effort was made to increase 
 the height of the tower or to so locate it that the telescope would be 
 not less than 60 feet above sea level. 
 
 In nearly all cases, the houses at the tops of the towers were built 
 of timber and for convenient hghting were covered with a slanting 
 roof of painted wire glass. Observation slots were provided at the 
 proper height around all four walls of the observing room, while 
 around the plotting room somewhat similar windows were provided 
 ior ventilation as well as for observation. The houses were reached 
 lay metal stairs built partly within and partly without the metal frame- 
 work of the tower. 
 
 The next type of station generally introduced was developed in 
 1903 for use in connection with the Barrancas system. The plans for 
 this type of station were published in the sixth supplement to 
 mimeograph 42. The Barrancas system was based upon the hori- 
 zontal position-finding system, there being for each base line a 
 primary station and a secondary station. The instruments to be 
 used in the stations were those that had been purchased for use with 
 the vertical base position-finding system, and for this reason it was 
 considered desirable to keep the instrument heights of these stations 
 Tip to at least 32 feet and to 40 feet if possible. As most of the localities 
 where the stations were to be built were low, the typical designs show 
 the primary and secondary stations as three-story houses, although, 
 of course, where they were to be built on higher sites, only as many 
 stories as were necessary were to be provided. 
 
 The secondary station was a small frame structure about 10 feet 
 square with a stairway on the outside. The upper story was the 
 observing room. The instrumental pier was built of concrete and 
 went all the way down to and into the ground. No part of the house 
 was allowed to touch this pier. On account of the small size of the 
 rooms of the first and second stories, and the fact that the instru- 
 mental pier went through them, these rooms were of but little use 
 though they were occasionally used as storerooms. 
 
344 
 
 The primary stations were larger, being in plan about 16 by 29 feet. 
 The important story of the building was, of course, the upper one 
 and this was built on two levels. The upper level, which was in 
 front, contained the observing room with the instrumental pier, 
 while the lower level in rear consisted of the plotting room, about 
 15 by 16 feet, with its floor at an elevation about 5 feet lower than 
 the floor of the observing room. The two floors were connected 
 by a suitable stairway. The main reason for lowering the floor of 
 the plotting room below the floor of the observing room was in order 
 to permit observation from the observing room in all directions, to 
 the rear as weU as to the front. The story or stories below the 
 plotting room were used as dormitories or storerooms. 
 
 In the original mimeograph design the stairway from the ground 
 to the upper stories is shown as built on the outside of the building, 
 and this was the method of construction actuaUy adopted in the 
 greater number of stations of this type now in existence. However, 
 it was found that in snowy or sleety weather, men using the outside 
 staircase, especially when going between the dormitory and plotting 
 room, were apt to track into these rooms water and dirt, and con- 
 sequently mimeograph directions were given that thereafter the 
 stairway between the different stories should be built inside of the 
 structures and not outside. (Nineteenth supplement to mimeograph 
 No. 43.) 
 
 In the primary stations of this character which were first con- 
 structed, the roofs over the plotting rooms were made of tin in order 
 that they might be very flat. It was discovered, however that in a 
 heavy rain the noise of the rain falling on a tin roof is so great as to 
 interfere with plotting. It was, therefore, prescribed that thereafter 
 the roof should be made of tar and gravel because the rain falling on 
 such roofs makes much less noise than when the roof is of tin. 
 
 The first crude observing stations had been built of timber because 
 of its cheapness. The houses at the top of the towers were likewise 
 of frame construction. The Barrancas system was developed at 
 Fort Barrancas in Pensacola Harbor, a locality noted for its good and 
 abundant timber. Consequently these stations also were naturally 
 built of that material, and when the system was extended to other 
 communities the stations there also were usually built of timber. 
 
 All frame structiu-es are, of course, subject to destruction by fire, 
 but the fire risk in single isolated frame structures is not. very great. 
 Fires are not allowed in the stations and the members of the detach- 
 ment are not permitted to smoke in them. Incidentally, also, the 
 destruction in a small frame building when struck by an enemy's 
 shell is likely to be no greater than in a similar building constructed 
 of any other material. 
 
345 
 
 When, however, the stations are built in groups as required by the 
 Barrancas system, the fire risk is much increased, since it becomes 
 quite probable that if one station should catch fire several others also 
 will be destroyed. 
 
 It therefore became evidently desirable to construct stations, 
 especially when grouped together, of noninflammable materials. 
 Of the several experimental stations built at different places of such 
 materials, that developed in Portland, Me., upon the suggestion 
 of Capt. Sewell, Corps of Engineers, under the direction of Maj. 
 William M. Black, now major general. Chief of Engineers, was the 
 most satisfactory, and the type of construction there developed soon 
 became the standard. This type of construction (see Mimeograph 
 100) consists of using timber studding for the framework of the 
 building. The walls are composed of cement plaster laid upon metal 
 laths or expanded metal nailed to the studding. In a few cases only 
 the outside sm^ace of the structure was plastered, but generally the 
 inside was plastered also. The roofs of these structures were, as a 
 rule, composed of tin laid upon a timber framework and sheathing. 
 
 Structures of this type proved to be exceedingly durable if properly 
 built. When not too near the guns they stood the effects of blast 
 fairly well. Consequently this method of construction soon became 
 the standard, not only for observing stations, but for switchboard 
 rooms, power houses, and many other small fortification structures. 
 
 In the fortifications of New York Harbor, many of the observing 
 stations were built of brick, the plotting rooms being lined with white, 
 faced brick so as to make the illumination easier. In several other 
 places quite elaborate structures were buUt, sometimes of reinforced 
 concrete. But in the large majority of fire-control stations built 
 the plastered type of construction was used. 
 
 Most of the sites of the observing stations built in connection -with 
 the Panama fortifications were located on hills, and in order to give 
 as much protection as possible and to conceal the stations, the walls 
 and floors were usually buUt of concrete and set down about 4 or 5 
 feet into the ground. In designing these half-sunken stations, an 
 important question that came up was whether or not the stations 
 should be roofed; and, if so, what kind of roof should be provided. 
 
 An open station lends itself readily to concealment, especially if 
 it is well sunken in the ground, but it exposes the detachment, and 
 incidentally the instruments in the station, to the sun and rain. 
 Furthermore, it is practically impossible to lock up an open station 
 so that when it is not occupied the instrimaents or fittings are pro- 
 tected from theft or damage by casual or unauthorized visitors. 
 
 On the other hand, a roof over an observation station has a tend- 
 ency to make it conspicuous. In order that observing may be possi- 
 ble, nothing in front may rise above the level of the telescope. Some 
 
346 
 
 ^ead room above the instrument must be provided for the observer, 
 and the roof, of course, must project above this. Consequently a 
 •covered station is bound to be more or less conspicuous and may- 
 draw fire, or may be used as an aiming point for fire directed at the 
 guns. 
 
 The details of the Panama observing stations, especially the ques- 
 tion of roofs, were frequently talked over by the designing engineer^ 
 -who is the author of these notes, with the Chief of Coast Artillery and 
 his assistants. Finally, as a result of these consultations, it was 
 decided that where stations were to be constructed in close proximity 
 to the batteries and where their concealment was therefore most 
 essential, a sort of compromise should be adopted. For peace condi- 
 tions a roof was to be provided over the station, but the roof was to be 
 so designed that by the removal of a few bolts it might be reduced 
 to sections of a size and weight capable of being handled by one or 
 two men. In this way, the roof may quickly be removed and re- 
 placed. It was intended that the detachment should be drilled 
 occasionally in removing and replacing the roof. Whether or not 
 this is done is not known to the writer. 
 
 These removable roofs provide shelter during peace time to the 
 personnel against the very hot tropical sun or the very hard tropical 
 rains. In addition, they permit these stations during the intervals 
 between drills to be safely closed and locked. When the time for 
 action comes, however, the roofs can be quickly removed and there 
 will remain nothing conspicuous enough to attract the attention of 
 the enemy or to draw his fire. 
 
 Although, in general, the Panama fire-control observing stations 
 buUt in fairly close proximity to the batteries were- designed with 
 removable roofs, those stations located where concealment could be 
 easily provided were provided with fixed ' splinter-proof concrete 
 roofs. In many cases these concrete roofs were covered over with 
 earth upon which it was intended that the growth of vegetation should 
 be encouraged, in order to make the stations blend in with the 
 appearance of the surroundings and thus serve to more effectively 
 camouflage them. 
 
 Observing stations constructed within the last few years at places 
 other than at Panama have been built in this same general manner, 
 special emphasis in all cases being laid upon the concealment of the 
 positions of the stations. In some cases where the stations, lookout 
 from the face of a bluff, the observation slots have been fitted with 
 removable covers composed of sheet tin. This tin was first placed 
 over the face of the bluff and hammered until it was just about as 
 rough as this face. It was then painted in splotches of the same 
 general color as the bluff and before the paint was dry it was sprinkled 
 with powder formed by grinding up stone taken from the face of the 
 
347 
 
 bluff. Consequently in roughness and color these observation slots 
 appear in every way to resemble the bluff. In other places, where 
 stations were built on low sites in the naidst of vegetation, care was 
 taken not to injure the vegetation and the art of camouflage was 
 called upon to conceal not only the position but if possible the very 
 ■existence of the station. 
 
 In all observing stations the engineer department always provides 
 benches around the telescope for the comfort of the observer, and such 
 map lockers and shelves as may be necessary. 
 
 For comfort in cold weather it is, of course, customary to provide 
 heat, usually by small oil stoves in the plotting rooms. The same 
 thing was sometimes tried in the observing rooms. For observation, 
 liowever, the windows of the slots must be open, and if this is d^e 
 when the temperature of the observing room is much above that on 
 the outside, the heated air escaping through the observation windows 
 causes the air to appear to boU when the attempt is made to use the 
 telescope. Consequently, accuracy of observation and heating of 
 the observing rooms are not compatible, and when actual observations 
 have to be made the observing rooms must be left unheated. 
 
 In the description given above of the evolution of fire-control 
 stations, the stations described have been those intended for use in 
 connection with the gun fire of batteries. Similar stations have, of 
 cotu^e, been used in connection with submarine mining. The main 
 difference between the stations now constructed for battery use and 
 those for submarine mining use is that it is prescribed that the latter 
 shall always be double — that is, in pairs, two primary stations and the 
 twa plotting rooms being provided at one end of the base line and 
 two secondary stations at the other. 
 
 Observation Slots. • 
 
 Where uncovered stations are used the line of sight of the telescope 
 passes above the walls of the station. Where roofs were provided 
 over the stations, observation slots or windows had, of course, to be 
 provided on all sides toward which it was expected it might ever be 
 necessary to observe. 
 
 For the convenience of the men at the telescope, seats or benches 
 were provided surrounding the instrumental pier and raising the 
 observer to a convenient height for looking through the telescope. 
 (Thirteenth supplement to mimeograph No. 42.) The height of the 
 telescope was fixed, and as far as observation with the telescope alone 
 was concerned, a comparatively narrow observation slot would usually 
 suffice, except where the site of the station was high and it was 
 necessary to observe both distant targets and those at a comparatively 
 short distance away. However, it was soon found to be essential to 
 make these observation slots of such a width that not only could the 
 men at the telescope easily see through them but that men standing 
 
348 
 
 on the floor of the observing room could do so also. In order to pro- 
 vide for the difference in height of men, it appeared necessary to make 
 the slots at least 12 inches high, and this was the standard used in 
 nearly all of the first observing stations built. It was found, how- 
 ever, that this made it necessary for extremely tall men to stoop 
 down in order to see out, so it was considered desirable to make the 
 observation slot at least 15 inches high. 
 
 Since, in general, a wide field of view is necessary from these sta^ 
 tions, it is evident that it is not practicable to provide for opening 
 the observing slots by sliding the sashes horizontally. The attempt 
 was therefore made to hinge them along their upper edge so that 
 they opened inward and upward, being supported when open by 
 chains or hooks from the ceiling. This was found to prevent the 
 taller observers getting very close to the slots and also made it difficult 
 to prevent rain water from leaking in when the slot was closed. 
 
 The next attempt was to hinge the sashes on the outside at the 
 lower edge so that the sashes would open outward and downward 
 against brackets provided to support the sashes a little below the 
 horizontal. In general, this worked very well and was the standard 
 for many years. However, when the attempt was made to keep the 
 observation slots open in heavy rains it was found that the rain 
 beating on these open sashes had a tendency to splash into the 
 station. ■ An attempt was made to stop this by building wide eaves 
 to the houses, but it was found to be impracticable to extend the 
 eaves far enough to prevent the splashing. 
 
 The next attempt was to hinge the windows on the outside at the 
 top and to raise them upward and outward. A method of doing this 
 mechanically by means of levers and a long shaft operated by chains 
 is shown in the forty-seventh supplement to mimeograph No. 42. 
 This method did not work thoroughly satisfactorily, and finally, in 
 1908, there was developed by Maj. Chittenden, Corps of Engineers, 
 then the constructing officer in the Seattle district, what is now the 
 standard method of suspending these sashes. Suspended from the 
 eaves of the building are hooks, specially designed so as to catch and 
 hold the sashes when they are pushed open slowly. To release the 
 sashes they are quickly pushed up a little bit higher and are then 
 quickly lowered. (This matter is described in the fiftieth supple- 
 ment to mimeograph No. 42, and a drawing of the kind of hook 
 intended for this purpose is shown on sheet 2, mimeograph 109.) 
 
 This method of suspending the sashes of observation slots has been 
 adopted in practically all recent designs, not only of observing sta- 
 tions but also of battle commanders' stations, fire commanders' sta- 
 tions, etc. 
 
349 
 
 Wiring Slots. 
 
 A very convenient improvement adopted in the Panama observing 
 stations, battery commanders' stations, plotting rooms, and other 
 stations, is the so-called "wiring recess." This consists of a recess 
 extending around all sides of the room from 6 to 12 inches above 
 the floor. The recess is 6 inches high, extends some 4 inches into 
 the walls, and is covered by pieces of removable brass plate. The 
 conduits or pipes for bringing in wires end in this recess. The cables 
 or wires are led in the recess around the room, then at the proper 
 place each is led out through a small length of pipe or a notch cut in 
 the wall. (Plate XXI.) 
 
 Periscopic Stations. 
 
 While the question of roofs for the Panama fire-control station 
 was being discussed with the Chief of Coast ArtUlery, it was suggested 
 by the writer that if periscopic observing instruments could be 
 developed it might be possible to build an observing station which, 
 while having a concrete roof, would yet not be seen, ihe periscopic 
 instrument could project through the roof of the station and the roof 
 could be drawn down behind a parapet, leaving visible merely the 
 object end of the instrument, and this would be too small to readily 
 be seen. 
 
 Although the periscope as an instrument for observation of a 
 battlefield from a protected position behind a parapet received its 
 first great development in connection with the World War, the prin- 
 ciple is not at all new nor in fact is its application to Coast Artillery 
 use. 
 
 During the years 1904 and 1905 there was in session in Fort 
 Monroe, Va., a board preparing or revising the Drill Regulations for 
 Seacoast Artillery. Maj. Hamilton Rowan, of the Coast Artillery, 
 was a member of this board. There came up for disciission by the 
 board the question as to whether or not a heavy seacoast gun shoidd 
 be provided with a sighting platform and a sighting telescope. The 
 objection was raised that an observer on the sighting platform would 
 be very much exposed, and to avoid this exposm-e Maj. Rowan sug- 
 gested the possibility of using the periscopic principle, so that the 
 observer could stand down on the working platform and do his observ- 
 ing by means of a periscope from that thoroughly protected position. 
 Accordingly, Maj. Rowan supervised the making of a periscope and 
 tried it on the carriage of a 10-inch gim. The first instriunent was 
 somewhat crude. It made use of mirrors instead of prisms and had 
 a number of mechanical and optical defects. Consequently, the 
 attempt to vse it was a failure and the experiments were unfortunately 
 stopped. 
 
350 
 
 At the time of Maj. Rowan's experiment the use of prisms in tele- 
 scopes was in its infancy, but this principle h^ since been greatly 
 developed; to such an extent that at present' the erection'-of images 
 in telescopes and field glasses is accomplished almost exclusively by 
 arrangements of prisms and not by additional lenses. In the 
 standard field glasses used at the present time, the rays of light, after 
 passing through the object glass, pass through a pair of prisms which 
 make two 90° changes of direction in the horizontal plane, so that the 
 rays of light are now proceeding generally toward the object glass. 
 The rays then pass through another pair of prisms which make two 
 more 90° changes of direction, this time in a vetical plane, sending 
 the rays of light once again toward the eyepiece and incidentally 
 forming an image, which is erect. Similarly, the large telescopes 
 now used with the standard azimuth instruments and with the 
 standard depression position-finding instnmients, make use of the 
 same principle, having two sets of prisms, both of which change the 
 direction of the rays of light 180°, one set causing an offset in the 
 vertical plane and the other in the horizontal plane. 
 
 In other words, the rays of light, after passing through the object 
 glass and proceeding in a general direction toward ^the eyepiece, are 
 reversed once so as to travel back again toward the object glass, and 
 again a second time so as to travel toward the eyepiece. Incidentally, 
 in these changes of direction, the rays of light at one time m.ake an 
 offset in the horizontal plane, and at another time in the vertical 
 plane. If now, the various lenses and prisms were so placed with 
 reference to one another that all the various offsets and travel in the 
 horizontal direction were made as small as possible, thus concentrat- 
 ing in a vertical direction and travel that may be necessary, nearly 
 all of the focal length of the object glass could be used in vertical 
 travel, and the eyepiece of the telescope could be placed quite a con- 
 siderable distance below the object glass. The observer could then 
 be located under the shelter of a concrete roof, the telescope projecting 
 through a small hole in this roof and the object glass being above 
 the roof and looking toward the target. 
 
 The general principles of such a periscopic observation instrument 
 were suggested by the writer to the Chief of Coast Artillery and to 
 certain representatives of the Ordnance Department at the time 
 when the design of the Panama fortifications was first under con- 
 sideration. It is understood that an instrument based on these ideas 
 is now about ready for experimental test. 
 
 As is to be expected in all new instruments, it is probable that 
 mechanical or optical defects will be found, but it is to be hoped that 
 this time these defects will not cause the matter to be dropped. The 
 writer of these notes is confident that it is a perfectly possible thing 
 
351 
 
 to develop and to manufacture a satisfactory observing instrument 
 making use of the periscopic principle. 
 Plotting Rooms and Battery Commander Stations. 
 
 The designs of these rooms and stations have all been discussed 
 in the earlier parts of this chapter and need not, therefore, be treated 
 here. 
 
 Fire Commiuiders* Stations and Battle Commander Stations. 
 
 In its general design, a fire commander's station is a combination 
 of an observing station and of a battery commander station. It is 
 fitted with the regular observing instrument movmted upon its. 
 instrumental pier, and with observing slots on as many sides as may 
 be necessary. In addition to a regular observing instrument on its. 
 concrete pier, there is usually provided a small iron pipe attached 
 to the floor of the station for holding a smaller telescope or observing 
 instrument. Usually a plotting room is provided for use in connection 
 with the station, and not infrequently there is a secondary station at 
 the other end of a base line. 
 
 The most noticeable difference between a fire commander's station 
 and other observing stations is in the provision of telephone booths. 
 
 After the abandonment of the Barrancas sjrstem and the moving 
 back to the batteries of the battery commanders and the plotting 
 rooms, the fire commanders were left with rather meager communi- 
 cations with their battery conmianders, the only . communication 
 possible being by the ordinary telephone. This was soon found to be 
 unsatisfactory. 
 
 The fire commander has to be kept in close commimication with 
 each of his battery commanders and with each of the searchlights 
 under his control. To attempt to keep up this communication 
 through a central telephone station was found to be too slow and 
 unsatisfactory, and it was evident that the fire commander must have 
 a separate and special wire to each battery and each searchUght. To 
 have in the fire commander's station a separate telephone for each 
 one of these lines was found to produce confusion, and it was therefore 
 decided to place the fire commander's end of these individual tele- 
 phone lines, not in his station proper, but in booths. 
 
 For convenience and protection these booths were usually placed 
 on a lower story. For communication with the telephone booths, 
 -.peaking tubes were introduced between them and the fire com- 
 mander's room. A separate speaking tube was provided to each 
 booth, and in addition, for use in case it became desirable to give at 
 one time the same orders to all the booths, a co mm on speaking tube 
 connecting with all the booths was introduced. By means of this 
 common speaking tube a person in the fire commander's room can 
 speak to the operators at all the telephones at once. 
 
352 
 
 When a battery commander or a searchlight operator desires to 
 communicate with the fire commander he telephones the information 
 to the man in the telephone booth at the fire, commander's station, 
 who, by means of an electric bell or buzzer, calls up the speaking tube 
 operator in the fire commander's room and gives him the message. 
 Communication in the reverse direction is done in the same manner, 
 the individual tubes being used in all cases where biit one booth is 
 to be communicated With. 
 
 However, in addition to the telephones and tubes just described, 
 the fire commander is usually provided with a special form of tele- 
 phone fitted with a number of levers or buttons by the proper manipu- 
 lation of which he can communicate directly with any of his battery 
 commanders or searchlight operators over a separate line that does 
 not pass through the telephone booth. 
 
 In general, a battle commander's station does not differ much 
 from a fire commander's station. Telephone booths for communica- 
 tion between the battle commander and the various fire commanders, 
 searchlight station, etc., are necessary, as in the fire commanders' 
 stations. 
 
 In a few places the battle commanders' stations have been made 
 somewhat more complicated. One type is shown in the twenty- 
 eighth supplement to mimeograph No. 42. In another case, rooms 
 which,' in emergency, may be used as sleeping rooms by the battle 
 commander and- the officers of his staif have been built as part of a 
 battle commander's station. In general, however, this has not 
 been done. 
 
 Switchboard Rooms. 
 
 The first switchboard rooms that were built were introduced in 
 connection with the Barrancas system and they had to be quite 
 large for in them there had to be installed the complicated switch- 
 boards required by that system, which were so wired that the data 
 from anypair of base-end stations could be transmitted to any plot- 
 ting room or to as many plotting rooms as might be desired. Although 
 not now needed for the purpose just mentioned, switchboard rooms are 
 still essential for the operation of the present telephone systems. 
 Incidentally, they also frequently contain the motor generators and 
 storage batteries needed to provide power for the operation of the 
 telephone system. 
 
 Sometimes existing older buildings or rooms in them have been 
 utilized as switchboard rooms. Sometimes special houses have been 
 built, but the same method of construction has not at all times been 
 used. Sometimes the switchboard rooms have been built of timber, 
 sometimes of plaster, and sometimes of concrete. Plans of several 
 types of switchboard rooms were published in the twenty-ninth, 
 thirtieth, fortieth, and forty-third supplements to mimeograph No. 42. 
 
353 
 
 In more recently built switchboard rooms it has been found con- 
 venient to provide, under the floor of the room, a shallow basement 
 or cellar for handling wires. The electric conduits or ducts are led 
 mto this basement, and in the basement the wires or cables can be 
 handled easily and can be led up through openings in the floor to the 
 switchboard room proper at^convenient places. 
 Meteorological Station. 
 
 The meteorological station is a small station usually about 12 by 12 
 feet, located at some fairly high and convenient place. It is used 
 for obtaining data as to the velocity of the wind, its direction, the 
 height of the barometer, the temperature of the air, etc., all of which 
 data are transmitted when needed to the various battle commanders' 
 stations, fire commanders' station, plotting rooms, etc. 
 
 Usually the meteorological stations have been located in existiag 
 buildings. Frequently an old and abandoned fire-control tower 
 has been used for the piu-pose. Where a new station has had to be 
 built, the method of construction followed has been the same as was 
 standard at the time and place for the construction of other fire- 
 control structures. 
 
 Signal aind Radio Stations. 
 
 A number of years ago, before it became customary to install 
 radio apparatus on the torpedo planters and on the tugs that towed 
 the targets used in target practice, the need was felt of some con- 
 venient method of signaliag between the shore and these boats. 
 
 Occasionally the attempt was made to direct the boats by a simple 
 system of displaying flags in some conspicuous place. Later a trial 
 was made of signaling by means of a searchlight beam, placing in the 
 beam a mechanical shutter by the opening and closing of which a 
 system of dots and dashes could be sent. In one place, where no 
 searchlight was available, an attempt was made to erect in front of 
 the conspicuous exterior slope of a certain battery, a large mechanical 
 shutter composed of planks which could be turned edgeways or 
 flatways and by means of which signaling dots and dashes could be 
 carried on. 
 
 No improvised means of this character, however, proved thoroughly 
 satisfactory and requests were made to the Engineer Department for 
 the erection of special stations fitted for signaling to the torpedo 
 planters and target-towing tugs. One of the first such stations was 
 erected at Fort Monroe. 
 
 The principal use of this signal station was with the kinds of com- 
 munication just mentioned, but it was thought that as the station 
 had to be built for these purposes, it might just as well be arranged 
 so as to be available for other kinds of signalii^ a,lso. Hampton 
 Koads, on the shores of which Fort Monroe is located, is a favorite 
 173341—20 2& ' <i:^ 
 
354 
 
 rendezvous for oiir Navy and, consequently, the signal station was 
 arranged so as to be available for signaling between the shore and 
 the ships. Many methods of signaling are used by the Navy, and 
 the shore station was to be so designed that any or all of them might 
 be used. 
 
 This station was, therefore, erected in a prominent location not 
 very far from the main wharf and well to the flank of all the batteries, 
 so that though it was very conspicuous, it in no way interfered with 
 the fire of any of the batteries. Not only is the station too far from 
 the batteries to be used as an aiming point by the enemy, but since 
 this kind of signaling is considered as a peace time proposition only, 
 the station can readily be destroyed if it should be thought that its 
 existence during time of war might endanger the defense. 
 
 The station consisted of a three-story timber building. In order 
 to protect the first story from dampness its floor was raised about 3 
 feet above the ground and it was entered by a short flight of steps. 
 For communication between the other stories an exterior staircase 
 was provided, running up three sides of the building and connecting 
 with the roof. The roof, which was made of ordinary sheet tin, was 
 surrounded by a handrailing and in order to protect the tin it was 
 covered by a flooring consisting of narrow planks laid with intervals 
 between them. 
 
 This roof was used as a station by men communicating with vessels 
 by wigwag or semaphore flags, or by men attaching or detaching 
 flags to halyards hanging from the long yardarm of a tall mast 
 erected a few feet from the station. 
 
 The upper story of the building was fitted as an observing room. 
 Around three sides of it there were inserted observation windows 
 similar to those standard in fire-control stations, and at a convenient 
 point in the room a pipe pier was fastened to the floor and was fitted 
 as a mount for an ordinary telescope. Men on the lookout were to 
 be stationed in this obsetving room both day and night and it was 
 to be their duty, in addition to exchanging signals with the vessels, 
 to give the post commander notice of the approach or departure of 
 all naval and other vessels, when and where such vessels anchored, 
 and also when they might change anchorage. 
 
 The middle story of the building was intended as a dormitory and 
 was fitted for the comfort of the detachment. The lower story con- 
 tained a lavatory, a toilet, and the rest of the room was used for 
 storage purposes. 
 
 By means of this station and the taU mast erected close to it and 
 really forming part of it, it was possible to interchange with the Navy 
 signals in many different ways ; by wig-wag flags, by semaphore flags, 
 by the display of flag signals from the yardarni, by the electric 
 Ardois signals, by large semaphores attached to the mast, which 
 
355 
 
 could be lighted at night, and in many other ways. Incidentally, 
 also, the station was in close and direct telephone communication 
 with the radio station. 
 
 The signal station just described was the first one of the character 
 erected, but it was to a great extent copied in many other seacoast 
 forts, of course with a number of modifications required by local 
 conditions. 
 
 When, a few years later, it became customary to fit up the torpedo 
 planters and some of the target-towing tugs with wireless apparatus, 
 conununication between the shore and the tugs had, of course, to be 
 carried on by wireless, and this required the erection on the shore of 
 regular wireless stations. Wireless comnuinication is considered as 
 something which it is essential to retain during war, consequently 
 it is important that the masts for supporting the antennae should be 
 erected permanently in inconspicuous places; if possible where they 
 can not be seen from, the sea, and in any case where they can not 
 "serve as aiming points for directing fire at batteries or other impor- 
 tant structures. 
 
 The masts themselves and all the aerial apparatus are furnished 
 by the Signal Corps. Generally they have been installed by the 
 garrison, although in a few cases the actual erection of the masts and 
 the rigging up of the antennae have had to be done by the Engineer 
 Department. 
 
 The operating houses for the radio system have been built by the 
 Engineer Department. In a few places they have been reinforced 
 concrete structures, but more generally have been of plaster on metal 
 lathing. They have ordinarily been located in positions where 
 ample protection was available. 
 Dormitories. 
 
 Specially constructed dormitories have generally been considered 
 necessary only for isolated groups of fire-control stations. Being 
 intended for war use only, they have been of quite simple construc- 
 tion and no special remarks concerning them appear necessary. 
 Where electric power has been available, dormitories have been 
 wired for electric hghts, but in more isolated positions no special 
 means for Ughting have been installed, it being intended that rehance 
 should be placed upon ordinary oil lamps. 
 Power Houses. 
 
 Generally, the primary source of power for operating fire-control 
 telephones has been the regular fortification power system; motor 
 generators being used to reduce the voltage to that required by the 
 telephone system. The motor generators required and the storage 
 batteries, when necessary, have usually been placed in one of the so- 
 called "switchboard rooms." 
 
356 
 
 Occasionally, however, special bouses for fire control, use have been 
 required, and when required have been erected by the Engineer 
 Department. Such stations, however, have been similar, except in 
 size, to the regular power house erected for general fortification use 
 and no general remarks concerning them is necessary. 
 
 COMMUNICATION OF DATA. 
 
 With any of the systems of position finding as outlined in the earlier 
 parts of this chapter, it is evident that the information that has been 
 obtained must be transmitted from the observing instruments to 
 the plotting room and from the plotting room to the guns. Where 
 the distance is not great, as for instance where the plotting is done 
 in the same room with one of the position-finding telescopes, the 
 information may be transmitted orally either by shouting or by 
 means of a small voice or speaking tube. Where the distance is great, 
 however, information has to be sent by the telegraph, telephone, or 
 telautograph. 
 
 All three methods have been used, but of the three, the telephone 
 is the only one that has proved satisfactory . In practice, the observ- 
 ers and the receivers aU wear head sets, so that they can speak in a 
 low tone of voice directly into the transmitters. The telephone 
 receivers are held by the head sets close to the ears of the plotters, so 
 that this method of communication is not interfered with by the talk- 
 ing of other persons or by other noises, nor does it interfere with any 
 other conversation that may be carried on at the same time. The 
 telephone is now customarily used, even where the distance through 
 which the data have to be transmitted is but a few feet, since in this 
 way there is no possible source of error as to the source of the exact 
 piece of information which is heard. 
 
 Telautograph. 
 
 The telautograph is an instrument by which something written at 
 one place is -reproduced electrically in a facsimile at another. The 
 pencil used in writing is attached to two cords wound up on two 
 cylinders placed about a foot apart. As the pencil moves these cyl- 
 inders wind or unwind according to the length of the cords from the 
 cylinders to the pencil. The receiving instrument has a writing pencil 
 connected by rods with two points corresponding to the two positions 
 of the cylinders on the transmitter. By electrical means, as the trans- 
 mitting cylinders wind or unwind, the rods of the receiving instru- 
 ment are drawn in or pushed out, so that theoretically the writing 
 done by the receiving pencil is a facsimile of that done by the trans- 
 mitting pencil. 
 
 The use of this instrument for transmitting fire-control data was 
 advocated, because it was feared that just at the time that a member 
 of the gun detachment was receiving information by telephone as to 
 
357 
 
 the setting of the gun, the receipt of this information might he inter- 
 fered with by the noise of the discharge of a neighboring gun, by the 
 rumbling of the ammunition trucks, or some other noise. It appeared 
 well, therefore, to have the information appear before the man in 
 plain sight, so that he would see it as well as hear it. 
 
 Many experiments were made in the. attempt to adapt the telauto- 
 graph to seacoast artillery use, but many difficulties were met with, 
 some electrical and some mechanical. The telautographs were at 
 first connected electrically with the regiilar post electric systems 
 wnich, at the time, were based on the use of storage batteries. It 
 was soon found out, however, that the fluctuations in the voltage of 
 the terminals of the storage batteries, due to the irregular demands 
 for power in connection with ammunition hoists, caused the telauto- 
 graphs to work most irregularly and badly. The attempt was then 
 made to connect them to the generators, but even the ordinary fluc- 
 tuations at the dynamos themselves were found to be too great for 
 the successful working of the telautographs. Still further experi- 
 ments were made, until it finally appeared that the telautograph 
 would work satisfactorily only when it received its power from a 
 storage battery which, for the time being, was used for nothing else. 
 Many of the supplements to Mimeograph 48 treat of this subject and 
 are of considerable interest. 
 
 Mechanically, the first telautographs used in gun emplacements 
 were thrown out of adjustment by the shock of firing, at least when 
 attached firmly to the walls of the emplacements. Later they were 
 hung on specially designed springs, and these springs were even- 
 tually so well perfected that under the best of conditions the telauto- 
 graphs seemed to work fairly well even when fastened to the gun 
 carriages. However, although the telautographs would work fairly 
 well when under expert supervision, without such expert control 
 they would soon get out of order. It therefore appeared that they 
 were too delicate for general Coast Artillery use and they were 
 ultimately discarded. 
 Telephone Wires and Cables. 
 
 Except in the immediate vicinity of a telephone or in a switch- 
 board room, individual telephone wires are seldom used, cables 
 containing many pairs of wires being preferred. 
 
 In the earher installations, these telephone wires and cables, as 
 well as power cables, were usually strung in the air on poles, but as 
 thus strung they were considered to be somewhat vulnerable and 
 subject to being broken, not only by the direct fire of the enemy's 
 projectiles, but by fragments of exploding projectiles as well. 
 Furthermore, it was feared that under some circumstances they 
 might be easily cut by a malicious person. Consequently, it soon 
 became customary to make the permanent installation of all com- 
 
358 
 
 municati'on cables in duct systems buried several feet below the 
 surface of the ground. These duct or conduit systems are installed 
 by the Engineer Department and, of course, as the system of com- 
 munication becomes more and more complex, these duct systems 
 become more and more extensive. These subjects were discussed 
 at some length in the chapter on electrical installations and the 
 discussion need not be repeated here. 
 
 MECHANICAL DATA TRANSMISSION. 
 
 When the plotting rooms were located at a considerable distance 
 from the batteries, as was generally the case when the towers per- 
 taining to the vertical-base position-finding system were in use, 
 or when the Barrancas system was in vogue, the only proper method 
 of transmitting to the detachment around the gun carriage the 
 data needed for aiming the gun was by telephone. Telephone com- 
 munication is not always reliable, especially when there is much 
 noise and confusion, and it was in an attempt to remedy this con- 
 dition that the telautograph was introduced. 
 
 About the time that it was finally admitted that the telautograph 
 was unsuited to seacoast artillery Work, the plotting rooms were 
 moved back to the batteries and it seemed as if it should be possible, 
 by mechanical means, to transmit the data needed for aiming the 
 ^un in a form which should be visible as well as audible. 
 Mechanical Transmission of Aiming Data at Mortar Batteries. 
 
 The mechanical transmission of aiming data seems to have been 
 first attempted in mortar batteries, and this was but natural because 
 it was at mortar batteries that the need of such mechanical trans- 
 mission was first felt. At a direct fire gun, the azimuth data has 
 to be transmitted to but one man, the elevation data to another, 
 but this can be done most easily by telephones, and head sets can 
 be worn by these two men. In mortar batteries, four mortars have 
 to be set simultaneously and with the same data. With four mortars 
 in a pit and four loading trucks moving around, it was found to be 
 impracticable to have the men setting the mortars wear telephone 
 head sets. It was therefore very desirable that the required data 
 should be displayed at a place where it could be seen by all the 
 men engaged in setting the mortars. 
 
 About 1903, there was developed in Portland, Me., a form of so- 
 called "mortar battery booth." Plans of this booth were published 
 in the sixteenth supplement to Mimeograph No. 48, and are shown 
 in outline in figures 5 and 6 on Plate XXVIII. (It should be noted 
 that on this plate the drawings of the booth have been made ■ as 
 if it were viewed by a person in the pit looking at the booth, which 
 is in rear of the pit. This view best illustrates the use of the booth, 
 but makes these drawings an exception to the general rule that in 
 
359 
 
 all fortification drawings tlie top of tlie sheet should always be the 
 direction toward the enemy.) 
 
 As shown on the drawing the booth is a reinforced concrete 
 structure about 7 by 8 feet in plan, with about 6^ feet headroom 
 inside. The walls and ceUings of the building, as well as the shding 
 metal door, are all made strong enough to stand the effect of the 
 blast and it is therefore possible to locate such booths only a few 
 feet to the rear of a mortar pit. The booth was to be located in 
 rear of the right side of the pit and from the rear of the left side of 
 the booth, which is the side toward the axis of the pit, the aiming 
 data is displayed by chalk figures written upon shding sections 
 of blackboard. The method of operation is as follows: The shding 
 blackboards are drawn into the booth, the desired data is written 
 on them, or on as many of them as may be necessary and the boards 
 are then pushed out so as to be visible to the men in the pits. For 
 use at night, these boards are, of course, illimiinated by electric 
 lights in shielded hoods not shown on the drawing. In the front 
 left-hand corner of the booth windows are shown by which the 
 men inside can see what is going on in the mortar pit. For these 
 windows, metal frames with thick glass were used, similar to the 
 bull's-eye windows used on shipboard. 
 
 The booth was directly connected by telephone with the plotting 
 room. The aiming data, as soon as it was worked up in the plotting 
 room, was transmitted by telephone to the men in the booth who 
 quickly wrote it on the blackboards and then slid them out for the 
 information of the men in the pit. If desired, it was planned that 
 the mortars might be fired from the booth. 
 
 It was discovered soon after these booths were, bmlt and placed 
 in service that the figures written hiuriedly on a blackboard were 
 not always easily legible, ^t least at the distances from which they 
 had to be viewed. Moreover, blackboards when once wet by heavy 
 rains are somewhat difficult to write upon, and finrthermore, the 
 figures written on them may be removed by a driving rain. This 
 type of mortar booth, therefore, although quite widely used, was 
 never thoroiighly satisfactory. 
 
 At about the same time that this form of booth was being developed 
 at Portland, experiments with the same idea ia view were in progress 
 at Fort Monroe in connection with the work of the board on the revi- 
 sion of Seacoast Artillery Drill Regulations. The first experimental 
 work of this character was done on a temporary frame structm-e 
 that happened to be in rear of one of the pits of the Fort Monroe 
 mortar battery so that changes could be easily made. As a result 
 of these experiments, a new and improved form of mortar booth 
 was evolved and samples were erected in rear of all the pits of this 
 battery. 
 
360 
 
 This Fort Monroe type of mortar booth (not shown in any of the 
 plates) was similar in construction to the Portland booth, above 
 described. It was of approximately the same size, its walls and roof 
 were built of reinforced concrete, and its door was of heavy sheet 
 metal. It differed from the Portland booth, however, in displajdng 
 the data on its front and not on the side. Consequently it was 
 placed in rear of the center of the pit instead of in rear of the right 
 side. 
 
 In this case the figures or letters were painted on wooden slides mov- 
 ing horizontally and were displayed to the men in the pit through 
 slots cut in a metal plate inserted in the front face of the booth. 
 These slots were so arranged that the figures indicating the degrees 
 and fractions of a degree of azimuth and Of elevation read downward, 
 but in order that there might not be any Confusion between the two 
 sets of figures, the azimuth and the elevation figures were consid- 
 erably offset to the side, one from the other, and were plainly distin- 
 guished by the letters A and E, painted above them. 
 
 The slides with the figiu-es painted on them moved horizontally, 
 and in addition to the figures painted on their front sides which 
 a]f)peared to the men in the pits through the slots, other and smaller 
 figures were painted on the rear sides of the slide and were, therefore, 
 visible to the men in the booth. These figures were so arranged that 
 when any figure, as for instance 3, appeared through a slot to the men 
 in the pit, the figure 3 on the rear of the same slide showed between 
 two vertical bars to the men on the inside. Consequently, the officer 
 or noncommissioned officer in charge of the booth could see at any 
 moment from inside exactly what data was displayed to the men in 
 the pit. 
 
 It was in a booth of this type that the plug board for the operation 
 of the zone signal system in the powder nragazines was operated. 
 
 The first mortar booths buUt, both of the Portland type and of 
 the Fort Monroe tjrpe, were located on the same level as the floor of 
 the pit. Consequently, the sight of the men in the pit whose duties 
 required them to see the data displayed was frequently cut off by 
 persons passing between them and the booth. In fact, the mortars 
 themselves, when aimed at certain aziniuths, would frequently cut 
 off the view of the men setting them. Consequently, it soon becamfe 
 evident that data, to be easily seen by men at wOrk at the mortats, 
 jnust be displayed on a level well above the floor of the pit. 
 
 In addition, the types of mortar booth referred to are not suitable 
 for plotting purposes and the aiming data heseded hkd to be trans- 
 mitted to them by telephone from a plotting room. This, of course, 
 introduced a possible source of error. 
 
361 
 
 Fortunately, it soon became possible to avoid such errors because, 
 very shortly after the first mortar booths were built, the plottii^ 
 rooms were moved back to the mortar batteries and it became pos- 
 sible to operate the display apparatus directly from the plotting 
 rooms. As has been stated, it was at Fort Monroe that the first 
 expeiimental plotting rooms were built at mortar batteries, and in 
 connection with them the attempt was made to operate directly 
 from the plotting room elevated data display boards which would 
 show to the men in the pits the aiming data, so high up that then- 
 view could not be cut off either by the mortars themselves or by 
 other persons moving around. 
 
 The display boards used consisted of iron plates supported by iron 
 framework weU up in the air. The data displayed consisted of 
 figures or letters painted on the front sides of vertical metal slides, 
 and appeared through slots as the metal slides were raised or lowered. 
 The slides were moved by means of wires passing around pulleys at 
 the top of the display board and passing thence nearly horizontally 
 through the air to the plotting room, which they entered through 
 openings near the ceiling. 
 
 In one form of this display apparatus the single-wire system was 
 used, the metal sKde being made heavy and gravity being relied 
 upon to pull it down; in another form, an attempt was made to use 
 the two-wire system; there being, in addition to the wire attached to 
 the top of the slide, another wire passing from the bottom, around 
 a pulley at the bottom of the display board, thence up to another 
 pulley at the top of the board, and thence into the plotting room. 
 In other words, each slide formed part of a continuous wire circuit. 
 Of the two systems the one wire gravity system seemed to work 
 more satisfactorily. 
 
 The Fort Monroe mortar battery was of the 1894 type (Plate 
 XXVII), and the experimental plotting room was built on the rear 
 slope of the traverse between two mortar pits. The same data was 
 always displayed to both pits at the same time. Consequently, the 
 wire coming from the slide of one display board in one pit passed 
 through the plotting room and thence to another slide on the display 
 board in the other pit. As the shde in one display board was pulled 
 up, the slide in the other display board went down, but since the 
 figures were painted so as to increase upward on one board and so as to 
 increase downward on the other, the same figures were always dis- 
 played at the same time on both boards. This arrangement had the 
 advantage that the corresponding slides on the two boards counter- 
 wtoghted each other and they could be made so heavy as to be cer- 
 tain to always take up all the slack in the wire. As the wire passed 
 through the plotting room it was attached to a slide which, at a 
 proper place, displayed to the persons in the plotting room the same 
 
362 
 
 data as was displayed to the men in the pits on the two display 
 boards. 
 
 Although, on the whole, this system has worked fairly well, a num^ 
 ber of mechanical difficulties have been encountered. In the first 
 place, it was found that the wires had a tendency to continually 
 change their lengths, and consequently it was necessary to place 
 several turn-buckles in each of them and to readjust their lengths 
 at frequent intervals. Again, the wires, when rapidly operated, had a 
 tendency to slip off the pulleys or to get caught in them, and what 
 was worse, in snowy or sleety weather the entire system w^ apt to 
 be completely frozen up. 
 
 Occasionally, also, a slide would stick and would fail to take up all 
 the slack. It might, therefore, display an erroneous number. It 
 was in an effort to overcome this trouble that the attempt was made 
 to use the two-wire system. In this system, each slide, with the 
 wires attached to it, formed a complete loop and if any part of the 
 loop was moved, the whole loop had to move as well. In this double- 
 wire system, however, the changing length of the wires gave even 
 more trouble than in the single-wire system and where it had been 
 tried a return was made to the single-wire system. 
 
 In the first of these systems tried at Fort Monroe, the shdes in the 
 plotting room were arranged on the rear wall one above another and 
 moved horizontally. In the new plotting rooms installed in 1913 
 and 1914 the shdes were placed on the side walls of the room and 
 moved vertically. This latter method seems to have proved the 
 better. 
 
 Still another and quite different type of mechanical data display 
 apparatus was installed in the Honolulu mortar battery completed by 
 the author in 1910. This battery is a two-pit mortar battery of 
 the 1906 type. (See PI. XXVIII.) The plotting room was built 
 in on the top of the rear of the central traverse. On each side of this 
 plotting room a sort of tunneled alcove was constructed leading out 
 diagonally to the rear and toward the mortar pit. The data display 
 board was placed at the end of the front side of this tunnel directly 
 over the side of the mortar pit and so high up as to be easily visible from 
 all portions of the pit. The data shown consists of figures painted 
 on the cylindrical surfaces of drum-like wheels, displayed through 
 plots cut out at proper places on the display boards. These drums are 
 manipulated by shafts leading from the plotting room and, of course, 
 give indications at the plotting room ends of the shafts of the figures 
 which are displayed at the outer ends to the men in the pits. 
 
 Unfortunately, certain mechanical difficulties have developed in 
 this apparatus. In order that the figures displayed to the men in the 
 pit might be of the proper size, the drums had to be quite large and 
 this made them heavy. The shafts, likewise, were quite long and had 
 
363 
 
 to be strongly built so that whenever a drum had to be moved there 
 was considerable inertia to overcome, and considerable practice was 
 required in order to properly manipulate the apparatus. An officer 
 interested in the subject should inspect the drawings of this Battery 
 Harlow apparatus. 
 
 Some two or three years after the completion of the Honolulu 
 mortar batteries and the installation in them of the mechanical data 
 display apparatus just described, there was developed the 1912, or 
 Panama type, of mortar battery, the outline drawings of which are 
 shown on Plate XXTK. One of the special new features of this type 
 of moitar battery is the plotting house, one such plotting house being 
 built just in rear of the central traverse separating the pits of each 
 tactical mortar battery, which consists of four mortars eipbraced two 
 in each of two mortar pits. 
 
 On the ground floor of the plotting house there is the large double- 
 size plotting room and from each of the front comers of this room 
 there extends out sideways a rectangular alcove about 7 by 8 feet in 
 size and intended for the operation of the mechanical data display 
 apparatus pertaining to the mortar pit on the corresponding side of 
 the traverse. 
 
 The data is displayed to the men in the mortar pit through slots 
 cut in the face of a data display plate set in the front wall of a rec- 
 tangular turret located over the center of the alcove. Measured on 
 the inside, this turret is about 3 by 9 feet in size and its ceiling is 
 about 5 feet above the ceilings of the alcove and plotting room, so 
 that the turret projects up well above the roof of the plotting house. 
 The turret is set somewhat obliquely to the sides of the plotting house, 
 so that a line from the center of the turret and perpendicular to its 
 length passes about over the center of the mortar pit. 
 
 The details of the data-indicating apparatus are quite simple and 
 are shown fairly clearly on the inset on the right-hand side of Plate 
 IXXIX. Fastened by brackets to the front wall of the turret there is a 
 long horizontal fixed shaft, about which, as upon an axle, there re- 
 volve the 10 or 12 display wheels. The rims of these display wheels 
 are about 20 inches in diameter and consist of cylindrical surfaces 
 3 inches wide and more than 5 feet in circumference. On these 
 cylindrical surfaces are painted the figures or letters which are dis- 
 played to the men in the pit through the slots cut at the proper 
 places in the data display plate. This data display plate is tilted 
 slightly to the front so that a line normal to the siirf ace of the plate 
 and passing through its center will about pass through the eyes of a 
 man standhig on the pavement at the center of the mortar pit. 
 
 Firmly attached to each of the display wheels, and therefore revolv- 
 ing with it, there is a sprocket wheel over which hangs a short length of 
 sprocket chain. From each end of the sprocket chain there hangs a 
 
364 
 
 short lerigth of wire or wire rope. The wire rope attached to the rear 
 end of the sprocket chain, that is, the end farthest from the pit, is; 
 Sbttached to the upper end of an index slide, while that attached to 
 the front end of the sprocket chain passes down and around a pulley 
 or sheave attached to the floor and thence up to the lower end of 
 the same index slide. At a convenient height there is firmly attached 
 to the front wire a nicely shaped grip, by means of which the oper- 
 ator can cause the index slide to move up and down. This causes 
 the figures on the rim of the display wheel to revolve behind the 
 slot in the data display plate on the front face of the turret. As 
 this index shde is moved lip or down in the alcove it passes jiist 
 behind a horizontal index plate and, through a slot in this plate, 
 the figures or letters painted on the front surface of the index slide 
 appear to the operator. These are so painted that the letter or figure 
 showing to the operator in the alcove through the slot in the index 
 plate is always the same letter or figure that is displayed from the 
 rim of the display wheel through the slot in the data display plate to 
 the men in the pit. 
 
 The joirits where the wire ropes are attached to the index slide are 
 both made adjustable, so that the circuit of the wires, chain, and 
 index slide can be easily kept at the proper length, and so that the 
 index slide can be placcid at just the proper place in the circuit as to 
 indicate properly. Furthermore, and in order to properly balance 
 the circuit aiid avoid any tendency to move of itself, a counterweight 
 is attached to either the front or rear wire as required. 
 
 In order that the circuit may have a tendency to stop at such places 
 as will accurately center the figures in the display slot, there is placed 
 above the axle at the top a small weighted lever with a roller at its 
 end. This rolls around the surface of a star wheel firmly attached 
 to the display wheel. This roller tends to stop the wheel at certain 
 places only, that is, just when some one figure is exactly centered 
 behind the display slot. 
 
 The operator in the alcove stands in front of the apparatus with 
 his back to the mortar pit, where he can see into the plotting room. 
 As he receives instructions from the plotting detachment, he manip- 
 ulates the index slides, and he knows that the data shown to him 
 through the slots in the index plate are always exactly the same as 
 are displayed from the data display plate of the turret to the men 
 in the pit. In order to keep his feet from accidentally getting; 
 caught in or injiuing the wires or the floor pulleys, a so-called "kick 
 board" is attached to the floor between his feet and the pulleys. 
 
 The drawings show 11 complete index slides and circuits, 5 for 
 indicating the degrees and fractions of a degree of azimuth, 4 for the 
 degrees and fractions of a degree of elevation, 1 for the zone, and 1 
 for the type of projectile. Of course the same system is adaptable 
 
365 
 
 to a larger or smaller number of circuits. If it should appear to be 
 advisable, the azimuth figures of the display apparatus could be 
 painted one color, the elevation figures another, etc. 
 
 The electric lights for illuminating the data display board at night 
 are indicated in .the drawings. The apparatus under the alcove is 
 lighted at night by electric lights which are not shown. For the 
 illumiaation of this interior apparatus in the day time three bull's-eye 
 windows, not shown on the drawing, are provided. These bull's-eyes 
 are located in the front and side walls of the alcove, and are placed so 
 high up above the floor that they can not readily be used to look out 
 of, so there is no temptation to the operator to permit his attention 
 to be diverted from his proper duties in order to see what is going 
 on in the pit. As the bull's-eye windows are quite exposed to blast, 
 they must be made of specially strong glass such as is used in the 
 portholes of ships. 
 
 At some batteries, a hinged shutter was added to the front of the 
 tmret so that it could be lowered down in front of the display plate 
 and thus cut off all view of the plate from the pit. Where the shutter 
 has been added, it is intended that it shall normally- be left down. 
 The apparatus will be. set while invisible from the pit. When all 
 data have been properly set, this shutter will be raised thus display- 
 ing them all to the pit at the same moment. When the mortars have 
 been laid, the shutter will be lowered again thus cutting off the view 
 of the display plate. 
 Mechanical Display Apparatus at Rapid-Fire Batteries. 
 
 Very shortly after it was found to be possible to mechanically dis- 
 play aiming data at mortar batteries, the attempt was made to do the 
 same thing at rapid-fire batteries. A concrete booth was built in rear 
 of the center of the battery and the display apparatus was installed 
 above its roof. The apparatus was very simple. The figiires were 
 painted on the front face of circular disks. Behind each disk and 
 attached to the same axle was a sprocket wheel. The sprocket chains 
 passed down to a similar disk within the booth. By moving the disks 
 the proper figures were displayed to the men at the gims and the 
 same figures were visible to the men in the booth. The original dis- 
 play apparatus was based upon never having to display a range as 
 great as 10,000 yards. Since no graduations less than 10 yards were 
 used, all that were necessary were three changeable figures and a 
 fixed zero for the unit digit. Consequently the apparatus required 
 but three disks and was exceedingly simple, but if necessary for 
 ranges greater than 10,000 yards, a fourth disk could have been 
 used. One form of the apparatus is illustrated in the fifty-second 
 supplement to mimeograph No. 48. 
 
366 
 
 Mechanical Display Apparatus at Large Gun Emplacements. 
 
 Shortly after it became customary to build concrete plotting rooma 
 in rear of the central traverses of heavy gun batteries, as has been 
 previously described, an attempt was made to operate from these 
 plotting rooms mechanical data display boards. In most cases the 
 means employed were horizontal shafts attached by brackets to the 
 rear face of the emplacements, just belo# the level df the loading 
 platforms and truck corridors and just above the ceilings of the lower 
 , story. These shafts were operated by sprocket wheels placed on 
 them immediately in rear of the plotting rooms, the sprocket chains 
 passing up to other sprocket wheels in the plotting rooms. 
 
 Immediately in rear of the center of each of the loading platforms, 
 a small display board was built containing drums with figures painted 
 on their cylindrical surface. These appeared through slots to the 
 view of the men on the loading platform. In the larger batteries 
 where the gims were rather far apart, the shafts had to be quite long; 
 and consequently possessed considerable inertia. It required a good 
 deal of force to start them rotating, and considerable strength and 
 skill to stop them at exactly the proper place. To obviate this diffi- 
 culty the attempt was made to do away wi1>h the use of shafts and 
 to substitute wires extending all the way from the plotting room to 
 the display apparatus and back again, passing en route over or 
 around as many pulleys as might be necessary. All these wires were 
 made in continuous circuits, but considerable difficulty was met with 
 in trying to keep the circuits at exactly the proper length and in pre- 
 venting the wires from jumping occasionally off of the pulleys so that, 
 taken as a whole, the display apparatus using wires was not as suc- 
 cessful as when shafts were used. 
 
 All the types of apparatus just described displayed the data in a 
 box buUt in rear of and only a few feet above the floor of the loading 
 platform, and therefore in a position such that the men aromid the 
 gun were extremely likely to have their view of the displayed data 
 cut off by the movements of other men of the detachment. It was 
 evident therefore, that to be more readily usable the data must be 
 displayed in a more convenient place. 
 
 In the 1912 type of direct-fire battery (Plates XXIII to XXVI) 
 each gim has its own plotting room. In each emplacement a tunnel 
 was built, starting from a pit cut in the floor of the plotting room and 
 proceeding to a point imder the steps connecting the loading and 
 working platforms at a point directly to the left of the gun center, 
 the data being displayed through slots cut in the uppermost of these , 
 steps. 
 
 Similar arrangements were made in the 6-inch Panama batteries 
 (Plate XII), pits being cut under the floor of the plotting room which 
 served for both the guns of the battery.- From these pits imder the 
 
367 
 
 plotting room, tunnels were dug to the left sides of the loading plat- 
 forms where the display apparatus was located. 
 
 The mechanical apparatus for use in these Panama batteries was 
 quite unique and the detailed drawings should be obtained and 
 studied. 
 
 As will be noted, many forms of display apparatiis have at times 
 been tried — ^horizontal slides, veridical slides, shafts, wire, and 
 sprocket wheels, etc. Up to the present time no type of apparatus 
 can be considered as standardized. 
 
 Of course, where data are displayed by any of the apparatus 
 mentioned, arrangements have been made for illuminating the display 
 boards at night. This illumination, of course, must be sufficiently 
 powerful to make the letters and figures easily legible but yet must 
 not be so bright as to cast a glare visible to the enemy, or so as to 
 interfere by glare or otherwise with the sight of observers on the 
 sighting platforms of the guns, or in battery commander or range 
 stations. Consequently, all lamps used must be so hooded as to 
 throw their light on display boards and nowhere else. 
 Electrical Data Transmitters. 
 
 Owing to the considerable distances over which the mechanical 
 apparatus for transmitting data had to be extended in some batteries, 
 the difficulties due to the varying lengths of the wires, if wires were 
 used, or to the weight and consequent inertia of the long shafts 
 required, it appeared that a somewhat simpler apparatus might be 
 designed to be operated by electricity. As early as 1905, an experi- 
 mental attempt was made at Fort Monroe to operate by electrical 
 means a data indicating board. At the display end of this apparatus, 
 the numbers to be displayed to the men in the mortar pit were painted 
 on the peripheries of small drums, and these drums were connected 
 electrically with somewhat similar but smaller drums on the appa- 
 ratus in the plotting room. As the drums in the plotting room were 
 moved by hand, the drums in the pits were supposed to be operated 
 by electricity so as to move synchronously. At first, when tested 
 without firing the mortars, this apparatus worked quite well, but it 
 appeared to be imable to withstand the shock of firing. Conse- 
 quently, it was abandoned, but in the opinion of the author this was 
 done much too soon and before the possibilities of the apparatus had 
 been thoroughly tested. Somewhat similar but modified forms of 
 the same apparatus have been tried occasionally since, but none 
 have been successful. 
 
 About a year ago another form of electrical indicating apparatus 
 was tried in one of the 1915 type of barbette batteries at Sandy 
 Hook. This apparatus works on exactly the same principle as the 
 display boards frequently installed over the doors of hotels and 
 theaters for displaying the number of carriages which it is desired 
 
368 
 
 to call. For each digit to be used, quite a number of electric light 
 bulbs are installed, and by illuminating certain of thpse lights at a 
 time the desired digit is roughly outlined. By night these figures 
 are easily visible, but the apparatus has been installed so that it c^-n 
 be used by day also, the display boards being placed in shaded 
 black painted recesses. This apparatus has been but recently 
 tested and is imderstood to have worked very 'well, but whether pr 
 not it will be found to function satisfactorily in service only the 
 future can tell. 
 
 TIME-RANGE BOARDS. 
 
 In one of the early stages of the development of the fire-control 
 system, the plotting of ranges was to a ceratin extent done on the 
 loading platforms. A blackboard was erected on each loading plat- 
 form in such a position as to be easily seen by the men at the range 
 wheel of the gun carriage. . On the blackboard were painted in white 
 a series of vertical and horizontal lines which could be numbered 
 at their ends. From thne to , time, every 20 or 30 seconds as 
 might be decided upon, the calculated range of the target was re- 
 ceived by telephone from the plotting room and was promptly plotted 
 upon this time range board, one set of lines being used to indicate 
 ranges, and the other seconds of time. Some 20 or 30 seconds 
 later another range would be received and would be promptly 
 plotted on the blackboard by another dot. After a few dots had thus 
 been made on the time range board, it was easily possible with a ruler 
 to prolong the line of dots across the board, and from this line to 
 roughly predict the range the target would have at any subsequent 
 time. 
 
 A few years later, however, after the introduction of the Whistler- 
 Hearn plotting board and its refined apparatus for making all the 
 various corrections that might be necessary, the use of the time 
 range board on the loading platform appeared no longer necessary 
 and it was abandoned. 
 
 Still later, shortly after Gen. Weaver became Chief of Coast Artil- 
 lery, he thought it well to restore the use of the board. At his 
 -request, specially constructed time-range boards with mechaiujcal 
 arrangements for easy plotting were made by the Engineer Deparjt- 
 ment and were installed on the loading platforms of the batteries 
 then in existence. As about this time tJie detailed designs of the 
 Panama batteries were approaching completion, they were modifiied 
 so as to include the time range boards. In addition, the designs of 
 ihe m,echanioal data transmitting apparatus for large guns were 
 modified so that this data, besides being displayed in the steps on the 
 left side of the gun where it could be seen by the men at the range 
 wheel of the gun carriage, would be displayed also in another place 
 where it could be seen by the men working at the time range board. 
 
CHAPTER XIII. 
 NIGHT ILLUMINATION OF BATTLE FIELDS. 
 
 The best and most available method now known of iUuminating 
 the battle area ia front of a seacoast fort is by means of searchlights. 
 A searchlight or, as it is frequently called, a "projector," consists 
 essentially of a strong electric arc hght placed in the focus of a con- 
 cave reflectiag mirror which, by reflection, projects the rays of light 
 f allin g upon the mirror into a beam composed of rays parallel or 
 nearly parallel, and thus permits the night iUumiaation of distant 
 objects. 
 
 The electric arc is dependent for its formation upon a powerful 
 electric current and as long as the only known source of electricity 
 was a galvanic battery, the arc hght remaiued but httle more than a 
 laboratory toy. It did not become a practicable apparatus for gen- 
 eral use imtil after the development of electric generators operated 
 by steam engiaes or other prime movers. Though, for this reason, 
 the electric-arc searchlight is a comparatively modem invention, 
 the night iUumiaation of battle fields is by no means new, specially 
 built fires having at times been used for this purpose since the earhest 
 dawn of history and probably before. Furthermore, ia a night 
 assault on one of the forts ia Charleston Harbor during the Civil War, 
 Gen. Gihnore (whose regular commission was in the Corps of Engi- 
 neers) made a fairly successful attempt at battle-field illumination by 
 means of a mirror and what was at that time called a "calciimi^' 
 light, the light of which comes from a piece of lime heated to iacan- 
 descence by beir^ placed ia an oxyhydrogen flame. 
 
 Shortly after the Civil War there was established at Willetts Point, 
 (now Fort Totten, Long Island, New York Harbor), an Ei^iaeer 
 school, and as early as 1872 experiments were made at this school with 
 a view to determiaiag the possibhty of using searchhghts for sea- 
 coast defensive purposes. A few years later, a small searchhght was 
 purchased and shortly thereafter it became customary to have 
 regular night drills with this searchlight for the purpose of tracking 
 vessels moving through a supposedly mined field. The light, how- 
 ever, was a small one and ia these night drills no attempt seems to 
 have been made to illumiaate targets at a greater distance than from 
 1,500 to 2,000 yards. 
 
 173341—20 24 (369) 
 
370 
 
 In 1886, in the report of the Endicott Board, the subject of search- 
 lights is referred to and it was recommended that 200 hghts be pur- 
 chased and installed in the seacoast defenses of the United States. 
 Nothing is said as to the way in which this estimate of 200 was 
 obtained. 
 
 Although about this time but httle was being done in this country, 
 the manufacture of searchlights was developing abroad quite rapidiyi 
 and, in 1893, as an advertisement; there was exhibited at the Chicago 
 World's Fair a 60-inch searchlight of German manufacture, along 
 with its special generating plant. This searchlight and generator 
 were purchased by the United States, and after the close of the 
 Exposition were sent to the Coast Artillery school at Fort Monroe 
 and installed there. 
 
 After the installation of this hght, drills and experiments were 
 carried on quite regularly at Fort Monroe as had been done at Fort 
 Totten. With these exceptions but little was done in searchlight 
 matters until the outbreak of the Spanish War when, with a part of 
 the large amount of emergency funds at once made available by 
 Congress, some forty-odd searchlights were purchased, The greater 
 portion of these were 30-inch hghts, there being a few 24-inch and a 
 few 36-inch; the latter, the largest size obtainable in this country. 
 The searchlight mechanisms and everythiag connected with them, 
 except the mijiTors, were of American manufacture. The mirrors, 
 however, could not be obtained ia this country and had to be pur- 
 chased abroad. 
 
 Up until the transfer, in the spring of 1901, of submarine mining 
 from the Engineers to the Coast Artillery, searchlight matters seemed 
 to have been handled lai^ely as an accessory to submarine mines. 
 The original use of the searchhght at Willetts Point had been for 
 tracking a vessel proceeding through a supposedly mined field, and 
 in the report of the Endicott Board the use of searchlights seems to 
 have been considered as a necessary adjunct to submarine mines. 
 In the annual estimates submitted by the War Department to Con- 
 gress, the cost of purchasing searchlights was included in the esti- 
 mates for submarine mine material and was so included in the annual 
 reports of the Chief of Engineers. 
 
 However, in 1901, probably as one of the indirect results of the 
 transfer of the submarine mining system to the Coast Artillery, the 
 subject of searchlights was taken up anew and separately, and the 
 1901 fortification appropriation act contained an item of $15,000 for 
 the purchase and installation of searchlights and the electric plants 
 pertaining to them. Since then the two subjects have been kept 
 separate. 
 
371 
 
 In this same year, 1901, the Board of Engineers made a careful 
 study of the niimber of searchlights needed ia our seacoast defenses 
 and recommended the installation of 344 lights, including 24-inch 
 lights, 30-inch lights, and 36-inch lights; the latter being the laigest 
 then available. 
 
 In the next year, 1902, the Board of Engineers submitted another 
 long report. In it they stated that the 60-inch light, which had 
 just appeared, was a most satisfactory large light, having a probable 
 range under ordinary atmospheric conditions of from 6,000 to 8,000 
 yards, as against 4,000 to 6,000 yards for the 36-inch light. They 
 further recommended that searchlights should be placed as near the 
 shore as possible so as to take fuU advantage of their comparatively 
 short range, but that their positions should be thoroughly concealed 
 during the day time. They reconmiended that as far as the uses of 
 the lights were concerned, they be divided into two classes, searching 
 lights and illuminating lights; the former to be the more powerful, 
 located well in advance, and so disposed as to cover all avenues of 
 approach; and the latter to be more retired, preferably to positions 
 in the flanks of the batteries to which they pertained, and to be used 
 for Oluminating vessels whose presence had been detected by the 
 searching lights. The board further drew attention to the fact that 
 the crossing of searchlight beams should be avoided if possible, as it 
 is very diflicult to see, through one searchlight beam, a target illu- 
 minated by another. 
 
 The above-mentioned reports of the Board of Engineers on the 
 subject of searchlights were published in Engineer ilimeograph 39 
 and its supplements. An additional supplement was published in 
 the fall of 1904 containing a report by Maj. S. W. Roessler, the dis- 
 trict Engineer officer at Portland, Me., upon the use of the search- 
 lights in the maneuvers of that year m that vicinity. 
 
 In 1904 it was decided that during the year 1905 the Army and 
 Navy would cooperate in joint maneuvers in Chesapeake Bay and its 
 tributaries. In preparation for these maneuvers, arrar^ements 
 were made to mount at least 10 searchlights in the defenses of 
 Hampton Roads and to provide power for these lights. A detailed 
 report on this subject was published in Mimeograph No. 91 in which 
 there are related in some detail the difficulties that were encountered 
 and defects that were developed during the preparations for these 
 maneuvers, the steps that were taken to correct the defects, and the 
 improvements that should be made in future. 
 
3^2 
 
 By the time of the organization of the Taft Board in 1905, the 
 importance of searchlights for nocturnal battlefield illumination had 
 been fully realized. The Taft Board therefore gave careful consid- 
 eration to the subject and on page 19 they state as follows: 
 
 The varioxia combined Army and Navy maneuvers and exercises have clearly dem- 
 onstrated their importance for disclosing the presence of an enemy at night. When, 
 properly located, the lights illuminate the ships so that the system of range finding, 
 fire control and direction becomes as eflSlcient at night as dtiring the day for accii- 
 rately fixing the position of the ships, and does away with the advantages the dark- 
 ness woxild give the attack in attempted "run by" or in forcing a passage. 
 
 Because of the effect of beams of light on each other and on auxiliaries of defense, 
 experiments have demonstrated that the proper number and locations of searchlights 
 in each harbor are matters that can be determined only after repeated local trials, and 
 as a consequence the preparation of an estimate of the cost of perfected searchlight 
 apparatus for all of the defended harbors, which is more than a fair approximation, 
 is impracticable. The estimate submitted is based on a study of the fortified harbors, 
 with no provision for any reserve. 
 
 Later on, on page 39 of their report, they state as follows: 
 
 Searchlights, originally intended for protecting the mine fields against counter- 
 mining operations at night, have become an indispensable adjunct to an eflScient 
 gun defense. Experiments made with searchlights during various combined Army 
 and Navy maneuvers and exercises show the necessity for — 
 
 1. Searching lights for illuminating and searching all waters of approach. 
 
 2. lUimiinating lights for lighting up the hostile ship during its advance after 
 discovery by the searching light, in order that its exact location with respect to the 
 guns may be constantly determined by the system of range finding, fire control and 
 direction. 
 
 The most powerful lights are required for "searching," and the illuminating light 
 must give a beam of sufficient intensity to light up the target for the effective ranges 
 of the guns. The 24-inch and 30-inch projectors have shown lack of power to do the 
 work required, and at present the 36-inch and the 60-inch lights are the adopted types. 
 
 The location of the lights in any particular harbor is a matter of the'greatest import- 
 ance, as serious disadvantages may otherwise result to the defense, due to the effect 
 of interfering beams of light on each oiher and on other auxiliaries of defense. It has 
 been clearly demonstrated that proper locations can be determined only after sys- 
 tematic and intelligent local experiments made by the troops using powerful search- 
 lights, moved and grouped at will. Upon the locations from which all the avenues 
 of approach can be properly illuminated depends the number of lights required in 
 each case. Such experimentation has as yet been very limited, and, therefore, accu- 
 rate estimates can not be prepared. The one submitted is based on an assignment 
 of two searching lights to the battle commander, and an illuminating light to each 
 fire commander without any reserve. Whether a greater number of lights will be 
 required can only be determined after careful arid extensive experiments. 
 
 In the report of the Taft Board it is stated that, with the proper 
 use of searchlights, fire control and fire direction will become as effi- 
 cient by night as by day. Subsequent events, however, woxild 
 appear to indicate that in making this statement the board was 
 unduly optimistic. 
 
 From the quotations made above from the report of the Taft 
 Board, it will be noticed that the recommendation is made for the 
 use of the 36-inch and the 60-inch searchlights only; the 36-inch for 
 
373 
 
 illuminating miae fields and the targets of rapid-fire guns, but the 
 60-iiich searchlight to be used, to the exclusion of the smaller sizes, 
 for distant searching or illumiaation. However, very shortly after 
 the acceptance of the Taft Board report, there was a tendency to 
 push the location of the mine fields much farther to the front and 
 beyond the effective range of 36-inch searchlight. Consequently, 
 only a few years after the submission of the Taft Board report, it 
 was found that the 36-inch searchhght was not powerful enough, 
 thus leaving the 60-inch light as the only size suitable for sea-coast 
 use. 
 
 Among the other recommendations of the Taft Board was one to 
 the effect that the number of searchlights needed iu any harbor and 
 their proper location should be determined only by trial. This 
 recommendation was adopted by the War Department and there 
 were therefore, gathered together a number of portable 36-inch 
 searchlight outfits. These were tentatively combiaed into a so- ' 
 called "Searchhght brigade" and were placed ia charge of Capt. 
 (now Brig. Gen.) W. C. Davis of the Coast ArtUlery Corps. The 
 searchhght brigade was first mobilized in Portland Harbor, Me. 
 The searchhghts were located at certain places and were then moved 
 aroTind from place to place until it was considered that the question 
 of the number of hghts necessary and of their proper location had 
 been satisfactorily determined. The searchhght brigade was then 
 moved to another harbor, and so on, until all the principal harbors 
 on our coast had been visited. 
 
 From the acceptance of the Taft Board report until the entrance 
 of the United States into the recent World War, regular but small 
 appropriations available for searchhght purchase and installation 
 were made annually, and with the funds thus made available, con. 
 siderable progress was made in the purchase and installation of the 
 searchlights called for by the various harbor defense projects and in 
 the substitution of 60-inch hghts for the smaller ones. 
 
 Usually, at least in later years, there have been avaUabie in 
 addition, small allotments from the appropriations for Engineer 
 equipment which have been used in the development and purchase 
 of portable searchlights for use with a field army. These aUotments, 
 however, and the appropriations for coast defense searchhghts have 
 been too small to permit of much experimental or development 
 work. For that reason, improvements in =earchhghts have been 
 made much more slowly than was desirablr 
 
 But in spite of the scarcity of funds, coni lerable had been accom- 
 plished; the most important progress made »)eing in the development 
 of two satisfactory types of high intensity lights, as will hereafter 
 be mentioned, and in the development of the manufacture in this 
 cotontry of satisfactory searchlight mirrors. 
 
374 
 
 As soon as the United States entered into the World War, greatly 
 increased appropriations became available for searchlight work, and 
 with the funds thus made available and due to the impetus given by 
 the war, many developments have been made, especially in the 
 way of incireasing the portability of the searchlights and of their 
 generating sets. 
 
 MECHANISM AND PARTS OF THE SEARCHLIGHT. 
 
 In its older form, and in the form still standard for seacpast work, 
 a projector consists essentially of a cylindrical metal drum having a 
 diameter slightly greater than that of the mirror. When in operation, 
 the axis of this drum is horizontal and points toward the object to 
 be illuminated. At the rear end of the cylinder is the mirror set 
 in its frame and, at the front end, the so-called "front door," com- 
 posed normally of plate-glass strips. The carbons, between the 
 ends of which the arc is formed, are held in position with their ends 
 in or near the focus of the mirror by means of two clamps on the 
 arms of the lamp mechanism, which is located in a box attached to 
 the bottom of the drum. 
 
 Opposite each other on the sides of the drum, and in such a position 
 that the line joining them is horizontal and passes through the center 
 of gravity of the drum and contents, there are attached the trunnions. 
 About the horizontal axis formed by these trunnions, the drum can 
 be revolved so that its axis and, therefore, the beam of light wiU 
 move in a vertical plane. The trunnions rest in the sockets at the 
 top of two arms, the lower ends of which are fastened to the upper 
 plate of the searchlight base. This upper plate of the searchlight 
 base can be revolved about a vertical axis and in this way the axis 
 of the drum, and therefore the beam of the searchlight is moved 
 in azimuth. 
 
 Lamps. 
 
 The only source of light which up to the present time has been 
 found suflSiciently powerful for distant illumination in connection with 
 seacoast defense is the electric carbon arc — that is, the arc that is 
 formed by two pieces of carbon which are placed in contact and are 
 then suddenly separated while a strong electric current is passing 
 from one to the other. When this happens, not only does the electric 
 arc between the two pieces of carbon give off a great deal of light, 
 but the ends of the two pieces of carbon become heated to incan- 
 descence and give off even a greater quantity. It is found that due 
 to the passage of the electric current through the arc, the ends of the 
 two pieces of carbon are slowly consumed and that this wearing away 
 takes place differently in the two carbons. The negative carbon is 
 worn away almost to a point, while the end of the positive carbon is 
 cut out into theiorm of a crater. The surface of this crater is apparr 
 
375 
 
 ently the hottest place connected with the arc and gives off the 
 greatest amount of light. 
 
 It has been found that the most satisfactory arc is formed when the 
 positive carbon is considerably larger than the negative one. Since the 
 negative carbon is the smaller and is worn into a point, and since the 
 larger portion of the light comes from the crater of the positive 
 carbon, it is customary in searchlights to place the positive carbon 
 in the axis of the mirror, exactly at the focus, and with the cratfer 
 pointing toward the mirror. The negative carbon is placed between 
 the positive carbon and the mirror in such a way as to cut off as 
 little light as possible. Usually this negative carbon is in direct 
 prolongation of the positive one. Sometimes, however, it is set at a 
 slight angle. 
 
 In order that the arc may burn properly several things are essential. 
 First, the carbons must he placed Ln contact and an electric current 
 must be passed through them before an attempt is made to strike 
 the arc; next, the carbons must be drawn quickly a short distance 
 apart, thus striking the arc; and third, after the arc is struck, the 
 carbons must be kept exactly the proper distance apart, because it is 
 found that slight variations in the length of the axe make considerable 
 differences in the amount of light that is given off. Furthermore, as 
 the carbons are consumed they must be fed together so as to make 
 up for the consumption, and this must be done in such a manner as to 
 keep the center of the crater of the positive carbon exactly in the 
 focus of the mirror. Since the two carbons are consimied at different 
 rates, this is not a simple matter. 
 
 The method by which the arc is struck, its length regulated, and 
 the carbons fed up is called the "regulation of the light." The 
 mechanism for doing all this miist operate practically automatically. 
 It is located, in the old form of searchlight, in the box just outside of 
 the lower part of the drum, the arms holding the carbon passing up 
 from the lamp box through slots in the shell of the drum to the 
 clamps holding the carbons in their proper position. 
 
 It is not proposed to go into any further details regarding this 
 mechanism, because it is not easy to understand without numerous 
 drawings and preferably a lamp itself to examine. 
 
 Rheostat. 
 
 The automatic regulation of the length of the arc is made simpler 
 by the fact that the carbon arc has a high electric resistance. Con- 
 sequently, slight changes in the length of the arc make considerable 
 variations in the amount of the electric resistance in the circuit and, 
 therefore, in the strength of the current which is flowing. By placing 
 the coil of an electromagnet in series with the arc, the strength of 
 this magnet will vary Avith the varying lengths of arc, and the magnet 
 can be so placed that its tendency wiU be to move the carbons, or 
 
376 
 
 one of them, in sucK a direction as to tend to counteract the changes 
 in the length of the arc as fast as they occur. 
 
 With an extremely short arc, the drop across the arc is about 55 
 volts, and this drop increases with the length of the arc up to 70 or 
 75 volts. It might appear, therefore, that a voltage of about 80 is 
 aU that is necessary at the terminals ot the searchlights. Experience, 
 hqwever, has shown that in order that a searchl^ht may burn stead- 
 ily, it is essential that there be a considerable resistance in the circuit 
 in addition to that of the arc. It is therefore necessary to put a 
 rheostat in series. This is usuaUy mounted close to the lamp, and 
 in addition to merely steadying the current, the rheostat can be used 
 so as to be of great assistance in the regulation of the arc. 
 
 Where a searchlight is mounted very close to a source of power 
 fiu-nishing the ordinary voltage of 110 volts, the rheostat must be 
 heavy enough to consume all of the voltage not necessary for the 
 operation of the lamp. However, in order to give additional pro- 
 tection to the power plant, and incidentally to reduce the noise from 
 the generator, it is customaiy to place the power plant a considerable 
 distance from the searchlight and to make the connection by a length 
 of cable. The electric resistance of this cable acts in the same way as 
 the resistance of the rheostat and makes it unnecessary to have a 
 very large rheostat in the vicinity of the lamp. 
 
 Carbons. 
 
 The ordinary electric arc light had for several years been in use for 
 street and factory illumination before the attempt was made to 
 utilize it in the modern form of searchlight. Of course, a satisfactory 
 type of carbon for the older arc lights had been developed, but when 
 the attempt was made to use more powerful arcs in the searchlights 
 these older forms of carbon were found unsatisfactory, and it was 
 seen to be necessary to develop different sizes and different types of 
 carbon for the diffbrent sizes and types of searchlights. The greater 
 the intensity of the current to be used, the larger it was found the 
 carbons must be, the standard carbons required by the 60-inch light 
 having a diameter of 2 inches for the positive and 1 inch for the 
 negative. The most satisfactory arc was formed between these car- 
 bons with a current intensity of from 180 to 200 amperes. 
 
 It was only after considerable difficulty and much experimentation 
 that carbons of the proper quality were obtained, and even in a 
 single lot of carbons some would seem to burn well and some not. 
 It was noticed that when a brand new box of carbons was received 
 from the factory and opened, the first carbons usually burned very 
 well and the others might or might not burn satisfactorily. For a 
 long time the cause of this, irregularity was puzzling, but it was 
 finally discovered that it was due to the carbons having a tendency to 
 absorb the moisture from the atmosphere and that they burned well 
 
377 
 
 only when perfectly dry. The first carbon taken out of the can, 
 which had been hermetically sealed, was dry and burned well. If 
 the can were immediately sealed up, the others would burn well also, 
 but if they were allowed to lie around in the air, they would absorb 
 moisture and burn badly, at least for a considerable time after being 
 put in the lamp. 
 
 It was, therefore, found to be necessary before using the carbons 
 in the lamp to heat and dry them. When the lamp was ia operation, 
 the carbons to be next used could easily be placed in or near the drum 
 and in this way would be heated up before they were needed. This 
 was all right after the hght was in operation but of course with the 
 first carbon tlie arc would flicker. It was soon found that the way 
 to avoid this was to put the carbons in the lamp considerably before 
 it was put in operation and then to pass through them a current 
 sufficiently strong to shghtly heat them up but not strong enough 
 to strike the arc. 
 
 High Intensity Lights. 
 
 Even with the best type of carbon the old simple carbon arc 
 searchlights were deficient in illuminating power and attempts were 
 naturally made to increase this. 
 
 The most natural way that suggested itself was to increase the 
 intensity of the current. By using the same size carbon and in- 
 creasing the current density per unit of surface of the crater of the 
 positive carbon, the temperature of the sm^ace of the crater would 
 be increased and this would increase the amount of hght given oflf. 
 When this was tried, it was found that the edges were apt to flake 
 off, leaving the crater irregular in shape and actually decreasing 
 instead of increasing the amoxint of hght given off. 
 
 After careful dehberation, it was finally decided that in all prob- 
 abihty this breaking off of the edges of the crater was due to the high 
 temperature of these edges, and the next attempt was to keep the 
 edges of the crater cool by blowing along the surface of the positive 
 carbon a blast of cool vapor or air. 
 
 The first successful attempt to do this seems to have been with 
 vapor of alcohol. This vapor, of course, would catch fire as it ap- 
 proached the arc but the temperature of combustion was much less 
 than that of the edges of the crater, and so these edges were kept 
 comparatively cool and did not break off as they did without the blast. 
 This is the principle of the so-called "Beck" hght. 
 
 Later, another and more successful light was developed in which 
 the blast consists of plain air. This is the method adopted in the 
 so-called "Sperry" hght. 
 
 After considerable experimentation, it was found that it was pos- 
 sible by the use of these blasts of cool air or vapor to keep the edges 
 of the crater cool and thus prevent them from cracking off, while at 
 
378 
 
 the same time greatly raising the temperature of the surface of the 
 interior of the crater by a great increase in the current density. 
 
 This increase in the ciurent density could be secured in two ways, 
 either by keeping the same size carbon and increasing the strength 
 of the electric current, or by keeping the same strength of current 
 and decreasing the size of the carbon. To avoid the necessity of 
 changing the generating plants fitted for use with searchlights, the 
 second of these plans for increasing the current density was followed. 
 The size of the carbon was decreased while still maintaining the 
 standard cmrent of from 180 to 200 amperes. 
 
 Of course, this required something of a change in the quality of 
 the carbons used, but there has now been developed as* the standard 
 positive carbon for use with the 60-inch searchlights, one which is 
 copper-plated on the outside, having a smaU but specially prepared 
 core and being but about five-eighths of an inch in diameter. The 
 diameter of the negative carbon is approximately half of this size. 
 Since the new positive carbon is about five-eighths of an inch in 
 diameter, or sUghtly less than one-third of the size of the 2-inch 
 carbon which was standard in the old searchhghts, it is evident 
 that the current density is approximatiely ten times greater. This 
 great increase in the current density has resulted in a correspondingly 
 great increase in the temperature of the surface of the crater, and in 
 the emission of a very much greater quantity of light. Furthermore, 
 the reduction in the size of the surface from which the light is given 
 off has resulted, as will be shown hereafter, in a much greater con- 
 centration of the beam. 
 
 The steadiness of the arc and the regularity of consumption of the 
 different sides of the crater have further been much improved by 
 an attachment which slowly rotates the carbons about their axes as 
 they are consumed. 
 
 Experiments are now under way with a view to the development 
 of still more powerful hghts which will make use of currents approxi- 
 mating five hundred amperes. This, of course^ will require larger 
 carbons, it being probable that the positive carbon will be approxi- 
 mately 1 inch in diameter. 
 
 The new high-intensity mechanism was naturally appHed first to 
 the old form of searchlight with the drum and the front door. In 
 fact, although a few brand new lights were purchased, the first gen- 
 eral use of the high-intensity principle was made by modifying the 
 old searchlights, keeping the drums and front doors practically as 
 they were and inserting the new lamp mechanism in place of the old. 
 This was the status at the entrance of the United States into the 
 World War. 
 
379 
 
 Shortly thereafter ample funds for searchlight development be- 
 came avaUable, and among the tests and measm-ements made were 
 some to determine the extent to which the glass front door was an ab- 
 sorbent of light. That it absorbed some hght was known, but that 
 it absorbed much was not beheved to be true, and it was a consider- 
 able surprise, therefore, when it was found that this front door ab- 
 sorbed nearly one-fourth of the hght reflected from the mirror and 
 reduced the eflaciency of the beam to that extent. 
 
 The object of the front door of the old lamp was to prevent the 
 flickering of the arc, due to the irregular air currents which might 
 have entered through an open front. The xise of the strong, con- 
 centrated air-blast of the high intensity mechanism did away with 
 any possibihty of iuterference by these hght irregular air ciurents, 
 and consequently, after the high intensity mechanism was intro- 
 duced, the front door was no longer a necessity. 
 
 The two most essential parts of the searchhght left after the aban- 
 donment of the use of the front door were the lamp mechanism and 
 the mirror. The only function now performed by the drum was to 
 hold the mirror and the lamp mechanism in their proper relative 
 positions and it would appear that there might be a simpler and 
 lighter construction for doing this. 
 
 An attempt was therefore made to do away with the drum, mount- 
 ing the mirror merely in a frame, on the bottom side of which was at- 
 tached the lamp mechanism. In the meantime, however, the type 
 of lamp mechanism which had been found to work extremely well 
 when the searchlight was used either horizontally or at moderate 
 angles of elevation only, failed when the beam was directed nearly 
 to the zenith as was frequently necessary in antiaircraft work. A 
 new mechanism had to be devised which would satisfy this require- 
 ment. 
 
 In this way there was slowly developed what is called the "dish- 
 pan" type of searchlight. This consists essentially of a mirror and 
 its frame, the lamp mechanism being contained in a comparatively 
 small cylinder which is inserted from the rear through a hole cut 
 through the center of the mirror. 
 
 Doing away with the drum, the front door, and other portions of 
 the mechanism resulted in a great decrease of weight. This made it 
 possible to use lighter arms for supporting the mirror and lamp, and 
 this, in turn, permitted the use of a hghter base. By omitting from 
 the base the distant control mechanism (which was found to be 
 unnecessary in antiaircraft Hghts) the weight of the new 60-inch 
 dish-pan hght, even including the weight of the small rubber-wheeled 
 car for moving it arovmd, was reduced to approximately 650 pounds, 
 as against the 6,000 or 7,000 pounds of the old standard 60-inch sea- 
 coast hght. 
 
380 
 
 The various improvements which have been described, the high- 
 ihtensity arcs and the abandonment of the front doors, have greatly 
 increased the illiiminating range of the searchlights. In a test a few 
 years ago ait Fort Monroe with the high-intensity lights, it was found 
 that both the "Beck" and "Sperry" lights would, under ordinary 
 atmospheric conditions, give srdBB.cient illumination at 13,000 yards, 
 in these tests the front doors were used and the lights tested did not 
 have all the latest improvements. With the addition of these im- 
 provements and with the abandonment of the front door, it is be- 
 lieved that the normal illuminating range of the best 60-inch search- 
 light miay be placed at approximately i5,00t) yards. 
 
 Mirror. 
 
 Theoretically, the best form of mirror is parabolic. If the mirroi-s 
 were truly parabolic and if all the light issued from a point truly at 
 the focus of the mirror, all the rays which strike the mirror would, 
 after reflection, be parallel. In fact, however, the light actually does 
 not issue from a geometrical point but from practically the entire 
 surface of the crater of the positive carbon. , Consequently, with a 
 single exception, none of these luminous points can be exactly at 
 the focus of the mirror. Rays of light issuing frpm a luminous point 
 slightly to the side of the focus of a parabolic mirror are, after reflec- 
 tion, nearly parallel to one another, but they are not parallel to the 
 beam of light made up of the reflected rays which issue from a point 
 exactly in the focus. Consequently, even with a truly parabolic 
 reflector, the rays of light tend to diverge somewhat and this di- 
 vergence is greater the greater the luminous area from which the 
 rays come. The smaller the size of the luminous crater, therefore,, 
 the less will be the divergence of the rays. This is one of the reasons 
 why the beams of the modern high intensity lights are less divergent 
 than those of the old standard lights, the diameter of the positive' 
 carbon of these new high intensity 60-inch lights. being about flve- 
 eighths of an inch, or about one-third of the diameter of the positive 
 carbon of the older standard lights. 
 
 The object of the searchlight being to illuminate a distant object 
 as brightly as possible, it is necessary, in order to get the maximum 
 amount of illumination of this distant object, that the beam of any 
 searchlight should be as little divergeij.t as possible. Consequently, 
 the light, to be efficient, must always be kept properly focused. If 
 the luminous point be too close to the mirror the rays on leaving 
 have a tendency to diverge. If the luminous point be too far away 
 from the mirror, the rays have a tendency to converge at a point 
 some distance to the front, and after crossing that point to diverge 
 again. The net result, therefore, when the light is out of focus in 
 either direction, is the divergence of the beam and this decreases 
 the intensity of the distant illumination. 
 
381 
 
 The subject has been sometimes discussed as to whether search- 
 light mirrors should be short focused or long focused. Of course, 
 with a mirror of the same diameter, the nearer it is to the light the 
 larger the spherical angle centering at the light that will be iater- 
 cepted by the mirror, and the larger the percentage of rays coming 
 from any point that will be reflected from the mirror. However, 
 the closer the mirror is to the light, the greater will be the divergence 
 of the axes of the beams of rays from different points of the crater. 
 So in illumination at a great distance, what is gained in one way 
 may be lost in another. Furthermore, the closer the mirror is to 
 the arc, the greater the tendency to heat up, damage, crack, or 
 distort the mirror. In fact, it would appear that the best focal 
 length for a searchlight mirror is a question that can be determined 
 by experimentation only, and the present adopted standard seems 
 to be about as satisfactory as any. 
 
 The mirrors which, up to the present time, have been found most 
 satisfactory for searchhght work are of silvered glass, although 
 many experiments have been made with metal mirrors. 
 
 Up to some eight or ten years ago it was not possible to obtain 
 satisfactory glass searchlight mirrors manufactured in this country 
 and all of the mirrors used had to be obtained from abroad. The 
 few attempts that had been made in this country to manufacture 
 glass mirrors had failed, and the annual appropriations available 
 for the piirchase of searchlight mirrors were so small that it hardly 
 seemed to the glass manufacturers that it was worth while to go to 
 the expense of installing special machinery to make such mirrors- 
 However, about 1910, with an increase in the size of the annual 
 appropriations, the Engineer officers engaged in 'the purchase of 
 searchlight mirrors succeeded in getting an American manufacturer 
 interested in the subject and a few years later very successful 60- 
 inch mirrors were turned out. Since that time, all glass mirrors 
 purchased have been of domestic manufacture and, under the impetus 
 of the enormous expenditures of the recent war, other manufac- 
 turers were induced to go into the business and have succeeded ia 
 making satisfactory mirrors. Consequently this country is no 
 longer dependent upon foreign manuf actiu-e. 
 
 A glass mirror, however, requires careful handliag; in fact, several 
 have been broken while being screwed into their frames. Others, 
 on accoimt of not being properly annealed, have been cracked by 
 the heat of the arc, especially when exposed to a sudden blast of 
 <;ool air. Furthermore, experiments have indicated that a glass 
 mirror when struck by a bullet is apt to be badly shattered, whereas 
 a properly made mirror may be pimctured many times by small-arms 
 bullets without being broken or even having its reflectiag power 
 seriously diminished. 
 
382 
 
 In order, therefore, to obtain if possible a mirror which will be 
 less vulnerable, experiments have been made for very many years, 
 both in this coimtry and abroad, looking to the development of 
 metal mirrors. 
 
 It was first attempted to build a mirror having a silver surface. 
 It was soon found, however, that in the high temperature to which 
 the surface is exposed silver soon tarnishes and loses much of its 
 reflecting power. Attempts were then made to find some form of 
 lacquer or varnish which could be applied to the silver surface and 
 which, while not seriously diminishing the reflecting power, would 
 nevertheless prevent it from tarnishing.. Experiments, however, 
 showed that although it was comparatively easy to find a lacquer 
 which would prevent the silver itself from tarnishing, the lacquer 
 showed a tendency, when exposed to the high temperature, to become 
 opaque. 
 
 Other experiments were made with mirrors having a nickel sur- 
 face and with mirrors composed of various alloys of which one, the 
 so-called "Monel" metal, appeared at first to give the greatest 
 promise. 
 
 Gold-plated mirrors were also tried, and as early as 1905, the 
 Sautter-Harl6 Co., of France, were able to manufacture a successful 
 gold-plated mirror. A number of these were pm"chased for use in 
 this country and were first thought to be fairly satisfactory. This 
 gold-plated mirror, however, gives a beam of a somewhat yellow 
 color, quite different from the bright blue color of the beam from a 
 glass or silver mirror. It was expected by some that this yellow 
 beam would show in the air greater penetrative power than the silver 
 beam, and therefore would be comparatively more efiicient at a dis- 
 tance. This promise appears not to have been fulfilled and, after 
 considerable experimentation, it has been finally decided that the 
 gold-plated mirror is not as efficient as the silver and glass mirrors. 
 
 As has been stated, the experimental development of the details 
 of searchlight mechanism, and especially of the metal mirror, was 
 largely retarded in this country by a deficiency in the funds avail- 
 able for experimentation, but this condition of scarcity of funds 
 was changed during the World War. With the increased funds, 
 rapid experimentation became possible and the manufacture of 
 metal mirrors was again attempted and on a larger scale than ever 
 before. 
 
 Instead of continuing to mold a metal disk into its approximately 
 correct shape and' then grind and polish it, a new method of manu- 
 facture was tried which is as follows: There is first manufactured a 
 convex glass mirror exactly parabolic in shape and having exactly 
 the curvature , desired for the metal mirror, but reversed. The sur- 
 face of the glass mirror is then covered with a uniformly thin coating 
 
383 
 
 of a certain kind of cement. On the outside of tliis cement layer 
 there is deposited by electrolytic means, a layer of silver and, be- 
 hind it a thicker layer of copper to stiffen the silver. The metal is 
 then strengthened by a thick- cement backing. When this has hard- 
 ened, the layer of cement between the glass and the layer of 
 silver is dissolved, and the metal mirror is left in its proper shape and 
 ready for polishing 
 
 The early mirrors made by this new process were, as was to be 
 expected, not a complete success, but it is thought by the officers 
 in charge of this development that the results have been very prom- 
 ising and that before long the successful manufacture of metal mir- 
 rors will be accomplished. 
 Front Door. 
 
 The object of the front door is to prevent the flickering of the arc, 
 and thus to steady the hght. In the earher searchlights, before the 
 front door was used, it was noted that the arc seemed to flicker badly 
 and that this tendency increased in a wind. After considerable dis- 
 cussion, it was decided that this flickering must be due largely to the 
 currents of air entering through the open front of the drum and a 
 front door of plate glass was, therefore, introduced to close this open- 
 ing. That the absence of this front door was the sole cause of this 
 flickering was not thought for a moment, but that it was a contribu- 
 tory cause was evident for the use of the front door made the light 
 much steadier. The front door therefore became an essential part 
 of the searchhght, at least as long as the simple carbon arc was used. 
 More recently, as has been noted, the introduction of the high inten- 
 sity mechanism has rendered the front door no longer necessary. 
 
 The door was hinged to the drxun on one side and was provided 
 with a fastening on the other so it could be clamped shut. When 
 opened, it provided a convenient means of getting at and adjusting 
 the mechanism in the drum. 
 
 The door consists normally of plate-glass strips set in a suitable 
 frame, the strips being cut from plane glass so as to cause no change 
 in direction of the rays of Hght as they pass through. Strips are used 
 instead of a solid piece of glass because they are more easily obtain- 
 able and if one be broken only that one has to be replaced. 
 
 In the early days of the use of searchlights, it was thought by some 
 that it might increase the usefulness of the 'hght for searching pur- 
 poses if the beam could be made sKghtly divergent in a horizontal 
 direction while still being kept as convergent as possible in the ver- 
 tical plane. It was proposed to do this by making the front door of 
 the drimi of the searchlight, not of plane glass but of prismatic ver- 
 tical strips, the angle of divergence of the prisms increasing from the 
 center of the door to the sides. It was thought that by this arrange- 
 ment the beam would cover a larger horizontal field which would 
 
384 
 
 make it possible in searcliing to move it somewhat more rapidly in 
 azimuth. 
 
 Where the objects which are being searched for are at very mod- 
 era,te distances from the hght such a diyergent ray might possibly bp 
 of use, but as a rule, on the seacoast, the objects which are being sought 
 are at or near the maximum range of the light; in other words, so far 
 away that even with the greatest possible convergence of beam thg 
 illumination is barely sufficient. After a small amount of experi- 
 mentation, therefore, this idea of prismatic strips for the front door 
 was abandoned. 
 
 Signaling Apparatus. 
 
 Long before the invention of the modern searchlight, night signal- 
 ing by means of the flash-Kght lantern had been in common Army 
 use. The introduction of this much more powerful source of light 
 natm-ally suggested that the searchlight also might be used for sig- 
 nahng pm-poses, all that was necessary being some form of movablp 
 shutter that could be placed in the beam. 
 
 The first form of shutter consisted of a set of small parallel slats 
 fastened in a frarae which was attached to the drum in front of thp 
 front door. These slats were all connected to and operated by a 
 lever. When open, the slats were in the plane of the beam, and 
 therefore obstructed Httle Mght. When closed, they hid the hght 
 completely and, by a proper manipulation of the operating lever, 
 dots and dashes could be sent as desired. 
 
 With flash-hght signaling by a lantern, it is usually necessary that 
 the hght be directed toward the person who is being signaled to, but 
 with searchlights this was soon found to. be unnecessary as a beam 
 directed at a considerable angle of elevation and in the general direc- 
 tion of the person with whom it is desired to communicate, can be 
 plainly seen and the message c^n be read from a distance of many 
 miles . 
 
 The form of shutter just mentioned consisted of metal slats and 
 was exceedingly he^vy. It threw the drum out of balance to such 
 an extent that special trunnions had to be attached for use with the 
 shutter. Furthermore, even though the ^lats were turned in the 
 plane of the beam some hght was intercepted. Consequently, an- 
 other form of shutter .was tried which worked on the iris principle, 
 like the shutters used in photographic cameras. This form has been 
 fpund to be quite satisfactory, but it is somewhat slower in operation 
 than the other. 
 
 Still another apparatus was tried consisting of a small disk tha,t 
 could be raised up betyr^en the arc and tl^e Purrpr, thus temporarily 
 killing the beam though not completely occulting the light. 
 
385 
 
 Occulter. 
 
 The slat shutter and the iris shutter just referred to have at times 
 been put to other uses than signaUng. It frequently happens that 
 a searchlight has to be put suddenly into operation, and it was the 
 experience with the old simple carbon arcs that for some time after 
 the arc was struck it flickered badly and the illumination from it was 
 not satisfactory. It was therefore proposed to keep the light always 
 in operation, or at least to hght it with the shutter closed whenever 
 it was thought the light might be needed before long. Then when 
 the light was needed suddenly, aU it was necessary to do was to open 
 the shutter. It was found, however, that not only is this expensive 
 in the consumption of the carbons, but that the energy generated by 
 the arc when shut in by the shutter and unable to escape, produces 
 such high temperatures as to cause considerable damage. 
 
 Another method of obtaining a satisfactory arc when the hght is 
 put into operation suddenly is, before the light is needed, to pass 
 through the carbons when in contact, a current not sufficient to cause 
 an arc to be struck or to h«at the carbons to incandescence. The 
 theory upon which this is based is that the ffickering of the carbon 
 when the hght is first put in operation is largely due to the sudden and 
 local increase of temperature when the arc is suddenly formed at the 
 ends of cold carbons. The smaller current passing through the car- 
 bons heats them up considerably and, consequently, when the arc 
 is struck there are not as great differences in temperatiu"e as with 
 cold carbons and the flickering is noticeably smaller. 
 
 Fortunately, however, most of the difficulty in the ffickering of a 
 newly struck arc has been done away with by the introduction of the 
 new high intensity light which can be put in operation very quickly 
 and which comes into operation with practically its fuU intensity and 
 without much ffickering. 
 
 Control Mechanism, 
 
 The movements of a searchlight, by means of which the beam is 
 thrown in any desired direction, is called "searchlight control." In 
 order that the beam may be directed in any direction which may be 
 desired, it is evident that two motions are necessary, one in azimuth 
 and one hi elevation. The one in elevation is obtained by rotating 
 the searchlight drum (or the mirror frame in the high intensity 
 searchhght) about the horizontal axis made by the trunnions which 
 support the drum or frame. The movement of the beam in azimuth 
 is obtained by revolving the upper part of the base about a vertical 
 axis. 
 
 In the original searchlights these motions in azimuth and ele- 
 vation were given by hand, the operator, of course, standing close to 
 the light. It was fotmd, however, that persons as close to the light 
 173341—20 ^25 
 
386 
 
 as the hand operators can see but little of the objects illunainated by 
 the beam and are, in fact, unable to keep the beam upon a distant 
 dim object that is in motion. For this p]irpose the person control- 
 ling the movement of the light must be at a considerable distance 
 from it. 
 
 The attempt was first made to have the hand operators directed 
 by telephone as to how the light must be moved but this proved so 
 unsatisfactory that steps were then taken to develop, if possible, a 
 mechanism by means of which the actual movements of the drum 
 would be electrically controlled from a distance. 
 
 Several very satisfactory forms were developed at an early date, 
 and by 1905 the General Electric Co. had developed a distant con- 
 trol mechanism which could be worked successfully from distances 
 as great as 4,000 feet, and under favorable conditions from distances 
 of nearly 10,000 feet. The controller used was very simple in form 
 and permitted of two speeds in elevation and four speeds in azimuth. 
 To move the beam slowly to the right, the controller handle was 
 moved to the right to the first notch and as long as it was held there 
 the beam would continue to move in azimuth to the right and at the 
 same speed. To increase the speed the handle was moved to another 
 notch, etc. To elevate the beam the controller handle was raised, 
 and to depress it the handle was lowered. As long as the handle was 
 held in one notch the control mechanism of the light would work at a 
 steady speed. When the handle was brought back to the normal 
 position, the beam would stop wherever it happened to be. 
 
 Up to 1905 no attempt seems to have been made to direct search- 
 light beams by means of azimuth readings. In telephoning to the 
 detachment at a searchlight as to the use of the hand control, or to 
 the man at the controller as to electric control, directions were stated 
 in general terms only or were referred to local objects. 
 
 It soon appeared, however, that this was rather a rough and indefi- 
 nite method of indicating directions and that greater definiteness 
 would be insured by using azimuth readings. Accordingly, azimuth 
 readings were painted around the bases of aU searchlights installed 
 in fixed positions and were so oriented that the reading of the azimuth 
 scale indicated the azimuth of the beam. For hand operation this 
 was aU that was needed but the adopted foim of distant controller 
 gave no indication to the man at the controller as to the azimuth of 
 the beam, if in operation, or as to the direction in which the light was 
 pointed, if not in operation. To successfully control searchlights by 
 means of azimuth readings, some such indication appeared to be 
 necessary. 
 
 In order to accomplish this, there was developed a new form of 
 controller known as the "step-by-step" controller. In the old Gen- 
 eral Electric form, as long as the controller handle was held to the 
 
387 
 
 right, the controlling mechanism would keep the beam moving in 
 azimuth to the right. When the controller handle was put back to 
 the normal position the motion of the searchlight would be stopped. 
 Sunilarly with motions in elevation. With this new step-bv-step 
 controller it was necessary, in order, to keep the light moving in azi- 
 muth, to keep the controller handle rotatmg and the velocity of mo- 
 tion in azimuth was regulated by the speed of rotatmg the handle. 
 As soon as the handle stopped, the motion of the beam would stop 
 too. Incidentally, as the handle was rotated figures showing the 
 azimuth of the beam would appear in the controller. 
 
 This form of controller has not, however, proved to be thoroughly 
 satisfactory. It does not permit a sufficiently rapid change of direc- 
 tion where the target has to be changed and, moreover, the motion 
 of the beam is not perfectly steady but by jumps. As an apparatus 
 for movmg the beam, it is far inferior to the older form and has the 
 sole advantage of azimuth indication. Work is therefore in prog- 
 ress now on the development of a new form of controller which it 
 is hoped wiU unite the advantages of both of the older forms and will 
 have the disadvantages of neither. 
 Cables. 
 
 Ordinarily, in order to give protection to the power plant which it 
 is not necessary to expose, the power plant and searchlight are sep- 
 arated by a considerable distance and this makes it necessary to 
 have a connection by an electric wire or cable. The cables used are 
 rubber-covered twin conductors. The size of copper has to be, of 
 course, sufficient to carry, without undue heating, the full amperage 
 necessary for the operation of the light, but as the voltage necessary 
 at the searchlight is considerably less than the 110 volts standard at 
 the generator, a loss of 20 volts or so in the passage of the current 
 through the cable is not a disadvantage. It is to a certain extent an 
 advantage as the resistance of the cable under these conditions forms 
 part of the steadying resistance which seems to be necessary for the 
 perfect operation of the lamp. 
 
 However, it should be noted that in the control mechanism there 
 are a number of motors, and these motors have been found to operate 
 best when provided with the voltage for which they were wound. ' 
 Where the voltage at the terminals of the searchlight varies rapidly, 
 or where it is much below the standard for which the control motors 
 were designed, the control mechanism has been found not to work 
 very well. At least that was the case with General Electric control 
 that was standard in 1905. To overcome this difl&culty, it became 
 customary to obtain the power for operating the control mechanism, 
 not from the searchlight terminals, but from the source of power, by 
 connecting the terminals of the control mechanism aU the way back 
 to the terminals at the source of power. This was done by making 
 
388 
 
 the searclilight power cable four-cored, two of the cores being large 
 for carrying the light current, and the other two much smaller for 
 furnishing power to the control mechanism. This was and still is 
 the standard form of cable for all searchlights furnished with distant 
 control mechanism. Where there is no distant control mechanism 
 a two-cored cable is sufficient. 
 
 The controller cable is usually 10-cored, although the number of 
 cores depends upon the type of controller used. The operation of 
 the control mechanism in the base of the lamp makes use of relays, 
 and consequently the wires of the controller cable can be quite small. 
 
 This cable is ordinarily furnished in lengths of 1,000 feet and 
 at the ends of these cables are couplings for connecting the vari- 
 ous lengths together and for connecting one end of the controller 
 cable to the controller and the other to the control mechanism at the 
 lamp. Of course, it is essential, when making these joints, that the 
 connections be made between the proper wires, and this requires that 
 the couplings should be of a special form to fit together in one way, 
 and one way only. 
 
 When possible, both the power and the controller cables are laid 
 in ducts, sometimes they are merely trenched, and in a few cases 
 they are strung in the air or on the ground. The latter is frequently 
 necessary with portable searchlights. In connection with the in- 
 stallation in ducts, it should be noted that some of the forms of coup- 
 lings used for controller cables are so large they can not be pulled 
 through ducts. In this case the couplings are removed, the cable is 
 piilled in and the couplings are then replaced on the ends. 
 Power Plants for Searchlights. 
 
 This subject was discussed in the chapter on electrical installations 
 and need not be repeated here. 
 
 CLASSIFICATION OF SEARCHLIGHTS. 
 
 A classification of searchlights according to their size is a necessary 
 and useful one. In addition to this method, the attempt was once 
 made to classify them according to the principal use for which each 
 light was intended, as follows: 
 
 First. What may be called a "sentinel beam," that is, it was 
 supposed that it might be desirable in some localities to throw a 
 searchlight beam across a channel and keep it fixed in that posi- 
 tion so that any vessel approaching would have to pass through 
 this beam. 
 
 Second. There was to be a class of so-ca,lled "searching lights" 
 which were to be swung back and forth over a specified area to 
 discover the presence of the enemy. 
 
389 
 
 Third. There was to be a class of so-called "illuminating 
 lights" for lighting up a target after its presence had been dis- 
 covered by a searching Hght. In other words, when a searching 
 light had picked up a target and observation showed it to be an 
 enemy, an illuminating light would be timaed upon the target, 
 thus freeing the searchmg light so that it might resume the 
 search for other vessels. The illuminating light would then be 
 kept upon the vessel as it proceeded on its course so that it might 
 be observed by the range-findiag stations and, if necessary, by 
 the observers at the sighting telescopes of the guns. 
 
 Fourth. There was 'to be a class of so-called " blinding" Hghts, 
 that is, lights which upon the approach of any enemy's vessel 
 were to be concentrated upon the pilot house or bridge with the 
 intention of so blinding and confusing the navigators as to inter- 
 fere with the navigation of the vessels. 
 In addition to the classifications mentioned above, there was to be 
 another classification depending upon the person who was to have 
 charge of the operation of the hght. Thus it was supposed that 
 certain lights would be kept exclusively under the control of the 
 battle commander and be known as "battle commander's hghts." 
 There would be other lights under the control of the fire coromanders 
 and called "fire commander's lights." Then the mine commander 
 would have other hghts for Ulmninating the mine field, and possibly 
 in some cases there might be even "battery commander's lights." 
 
 Of coiu^e, it was supposed to be possible that any one particular 
 searchlight might at diflferent times and imder different conditions 
 fulfill several or possibly all of the different functions, but each par- 
 ticular function was supposed to be separate and independent of the 
 others and carried out under different regulations. 
 
 For many years these distinctions were insisted upon, but it was 
 developed by experience that they were imnecessary, and all or most 
 of them have gradually fallen into disuse. 
 
 Thus it was foimd necessary to do away with the class of so-called 
 sentinel beams because, if a beam remains in a fiLxed position, an 
 enemy's vessel can approach quite close to it and keep just outside 
 of the beam. Its presence not being known, it can bring a sudden 
 fire upon the light and destroy it. It was therefore decided that it 
 was necessary to keep all lights moving to a greater or less extent, 
 so that the operation of a so-called sentinel hght became essentially 
 the same as that of a searching light. 
 
 It was also found necessary to do away with the so-caUed blinding 
 lights, for the reasons that, except at exceedingly short ranges, they 
 did not blind and all that it is necessary for the navigators of the 
 vessel upon whom the hght is thrown to do is to use dark glasses 
 
390 
 
 and to proceed on their w^ay. In fact, in the case where the location 
 of the Winding light was known to the enemy, its use really was 
 an aid to navigation. It is needless to say that if a powerful light 
 at a comparatively short range be thrown into the eyes of the navi- 
 gator of a vessel it makes him, for the time being, unable, to distin- 
 guish small objects such as small boats, buoys, etc., and it may to 
 some extent interfere with navigation. But it is to be supposed that 
 in time of war all buoys and similar aids to navigation wiU have been 
 removed, and the navigators of vessels will not rely upon such aids and 
 will steer largely by the compass. 
 
 There are thus left as the different classes of lights, only the search- 
 ing light and the iUiuninating light, and these distinctions are not 
 now considered of any special importance, as circumstances may 
 require any light to be used for either purpose. 
 
 As illustrating the methods of operation which were proposed at the 
 time the distinctions of the different classes of lights were considered 
 as important, attention is invited to Mimeograph No. 91, in which 
 there is a lengthy explanation, along with a map, showing where the 
 lights were placed and how they were intended to be used in the 
 defenses of Hampton Roads during the maneuvers of 1905. 
 
 Briefly, it may be stated that Hampton Roads empties into the 
 southwest corner of Chesapeake Bay. The general lines of the south 
 shore of the bay, which runs nearly east and west, and of the west side 
 of the bay, which runs nearly north and south, would, if prolonged, 
 intersect at the outlet of Hampton Roads, and this point, for con- 
 venience, may be called the "corner" of the bay. 
 
 The defenses of the bay during the maneuvers were located on the 
 south end of the west shore, on the west end of the south shore, and 
 upon an island located at the outlet of Hampton Roads. The most 
 easterly point that was occupied, which may be called for conven- 
 ience " Willoughby, " was located on the south shore of the bay 
 about 4 or 5 miles east of the corner, and the most northerly point 
 that was occupied, which we will caU "Buckroe," was on the west 
 shore of the bay about 3 or 4 miles north of the corner. 
 
 At each of these places, Willoughby and Buckroe, two searchlights 
 were installed, as well as a number of light field batteries. One of 
 the searchlights at each point was a so-called "sentinel" beam. The 
 light at Willoughby operated normally over an angular range of 
 about 30°, the mean of which was nearly north; and the one at 
 Buckroe operated normally over an angular range of about 30°, the 
 center of which was nearly due east. It was intended that the 
 movements of these sentinel beams should be so timed that when 
 one was at the outward limit of its arc the other would be at its 
 inward limit, so that the beams could intersect over a comparatively 
 
391 
 
 small area, situated some 3 or 4 miles north of the south side of the 
 bay and some 4 or 5 miles east of the west shore of the bay. 
 
 It so happens that at the point where the beams normally inter- 
 sected there is a large shoal marked by a lighthouse. A short dis- 
 tance south of this shoal there passes the main entrance channel from 
 the ocean, while between the shoal and the west shore there is a sec- 
 ondary channel which can be used by small boats. 
 
 With this arrangement of sentinel beams, it is evident that no 
 vessel can enter the area within the beams without passing through 
 one of them, and therefore, supposedly, being seen. 
 
 The other lights at each of these positions, WUloughby and Buck- 
 roe, were installed approximately 100 yards outside of their respec- 
 tive sentinel beams and were intended to be used as searching lights, 
 each moving back and forth in the angle, approximately equal to a 
 right angle, between the shore and its sentinel beam. The object of 
 these lights were; first, to act as a protection against a vessel that 
 might come up but stay just outside of the sentinel beam, and, second, 
 to give, if possible, earlier notice of the approach of the enemy. 
 
 The light gun batteries were installed at these points and were 
 intended, of course, for the protection of the searchlights from guns 
 in small boats. 
 
 Inside of the sentinel beams and located at advantageous posi- 
 tions among the principal batteries of the defense, were installed the 
 illuminating lights which were intended to be kept dark until it was 
 nown the enemy was approaching. 
 
 One only of these interior lights was intended for any function 
 other than illumination and that was the inmost light. This was 
 so located that its beam could be turned across the channel to Hamp- 
 ton Roads without intersecting the beams of other lights. This 
 beam passed over the supposedly mined field. It was intended, 
 should occasion arise, that this light might be kept in operation 
 over the mined field as a searching light to detect any small boats 
 that might attempt counter-mining or cable-cutting operations. 
 
 The normal use of this system of searchlights was as follows: 
 
 If either of the searching lights which were operating outside of 
 the sentinel beams detected the presence of an enemy this light 
 was to continue to illuminate the enemy as he approached. It would 
 continue to hold this vessel in its beam as the vessel approached the 
 normal range of the sentinel beams. Under these circumstances the 
 sentinel beam was to be allowed to leave its normal arc of action until 
 its beam also illuminated the enemy's vessel, but this movement was 
 to be made very slowly and carefully so as not to overlook anythii^ 
 ^e. As soon as the sentinel light had picked up the approaching 
 vessel, the searching light was left free to resume searching. 
 
392 
 
 The sentinel beam would then continue to illuminate the vessel as 
 it passed inwardly, until it had nearly reajched the inward limit of 
 the normal range of the sentinel beam. As soon as this happened, 
 one of the regular interior illuminating Hghts was to be brought into 
 action and to be used to illuminate the enemy. As soon as this 
 illuminating hght picked up tjie vessel, the sentinel beam was to go 
 back to its regular duties. 
 
 Should another enemy appear and be caught by the searching 
 hght, it would be passed on to the sentinel light, by this, to an iUunai- 
 nating light, and so on. 
 
 It seems to have been expected at that time that it might be pos- 
 sible to illuminate at one time and to use as targets almost as many 
 of the enemy's vessels as there were searchlights, but one of the 
 things that was taught by these maneuvers was that in any practi- 
 cable distribution of searchlights among batteries there is a very 
 small limit to the number of vessels which can be satisfactorily 
 illuminated at one time without requiring either the range-finding 
 instruments or the sighting telescopes on the guns to look through 
 one or more beams. 
 
 Another lesson was that whatever classification may be made of 
 these lights as, battle commander's hghts, fire commander's hghts, 
 and battery eommander's lights, nevertheless, the operation of all of 
 the lights must be under the close control of some one general, com- 
 mander; otherwise, the crossing of beams and interference with obser- 
 vation stations is certain to occur. Furthermore, it was clearly 
 shown by the maneuvers that the number of searchhghts that can be 
 used satisfactorily and simultaneously in a hmited area is itself quite 
 limited. 
 
 Still another lesson was that where there are a number of hghts in 
 operation in any one area, the control apparatus for any one search- 
 light must, in general, not be very far from the light itself, otherwise 
 the man at a controller may be unable to identify his beam from the 
 others that may be in operation. 
 
 In this connection, the following extract from the report on search- 
 lights during the 1905 maneuvers (mimeograph No. 91) may be 
 interesting: 
 
 In connection with the subject of the distant control of searchlights, it appeared to 
 me during the exercises that, except in certain limited cases, very distant control is 
 not advisable. For searching lights that are comparatively isolated, and whose beams 
 are not liable to be confused with those of other lights, long-distance control may be 
 desirable, but for illuminating lights, especially when a number of them are grouped 
 within a comparatively small area, this is not true. Under certain atmospheric con- 
 ditions, it is very hard, at a distance, to distinguish one beam from another, or to tell 
 accurately by which beam a target is illuminated. During one of the preliminary drills, 
 one officer mistook for his own another beam, and in trying to maneuver the latter, 
 and attributing his difficulty to some defect in his own controller, he unwittingly 
 
393 
 
 traversed his own beam until it extended directly across the line of sight of some of 
 the obse^^^ing stations, and for a while, put these stations out of action. With more 
 practice, such an accident might not have been possible, but there were other inci- 
 dents that convinced me, that, with many lights in simultaneous operation, each 
 operator must not be too far away from his own light to easily and clearly distinguish 
 his beam from all others. 
 
 THE LOCATION OF SEARCHLIGHTS. 
 
 Searchlights are, in general, installed with one or two objects in 
 view: First, to give notice of the approach of an enemy, and, second, 
 to iUuifiinate the vessel so that it can be used as a target for the 
 guns. 
 
 In order that our guns may be enabled to keep the enemy as far 
 away as possible, it is desirable that his presence be detected before 
 he comes within the range of the guns. 
 
 However, the range of our guns exceeds the effective range of our 
 searchlights. This has always been true and is true now. When, 
 about 1905, the effective range of our major caliber gun was supposed 
 to be 12,000 yards, the best searchlights which we then had were effec- 
 tive under ordinary conditions at 8,000 yards only. At present the 
 effective range of our searchlights has been increased to possibly 
 15,000 yards, but in the meantime the effective range of our gims has 
 gone up to 30,000 yards or more. 
 
 If our searchlights are to be able to illuminate the area near the 
 extreme range of our guns, the searchlights must be placed well in 
 advance of the guns, that is, toward the harbor entrance from the 
 batteries. This, however, must not be done to such an extent that 
 the searchlights are so far in advance of our guns as to leave them sub- 
 ject to destruction by fire from the enemy's ships, which are beyond 
 the range of our batteries. 
 
 In fixing the locations of searchlights with respect to batteries 
 and observation stations, it shoxild be noted that the searchlights 
 must not be placed so that the beam when used in any probable 
 direction will illuminate the battery or range station so it can be seen 
 by the enemy. Furthermore, the searchlight must be placed far 
 enough from the batteries so as not to be injured by the blast effect of 
 the guns. With the old standard form of searchlight, the strips of the 
 front door were quite sensitive to severe blast effect, but this difficulty 
 has b6en largely removed by the introduction of high intensity lights 
 which require no front door. 
 
 The problem of locating searchUghts with reference to observa- 
 tion stations and the sighting telescopes of the gims is made difficult 
 by the fact that it is hard to see through one searchlight beam a 
 target iUuminated by another beam. If the target be not very 
 distant and be very brightly illuminated, it can, of course, be seen 
 through the beam of another light, especially if that beam be quite 
 
394 
 
 diffused, but where the object illuminated is very distant and the 
 illumination is very dim, it can not be detected through another 
 beam. As a result, an observer on one side of a searchlight beam 
 can see almost nothing of what is happening on the other side, 
 Consequently, an observer situated between two beams that cross 
 in front of him has his field of vision, for practicable purposes,, 
 confined to the area between the two beams. 
 
 Another important matter in this connection is that, for essentially 
 the same reason that causes the difficulty mentioned in the pre- 
 ceding paragraph, an observer close to a beam can see but little of 
 the objects illuminated by it. The reason for this is evidently that 
 he is looking almost straight do-mi the length of the beam and, 
 therefore, is trying to see an object through the maximum length 
 of the beam. If, however, he is at considerable distance to one 
 side of the searchlight, his fine of vision to the illuminated object 
 will enter and pass through but a small length of the beam and 
 that will be where the beam is most diffused. The minimum dis- 
 tance to either side of the searchlight at which the observer should 
 be placed to obtain good vision, depends to a large extent upon 
 the intensity of the beam and upon the atmospheric conditions. 
 In geneial, however, it may be said that in order to see well an 
 observer should not be less than 150 yards to one side of an old-style 
 60-inch fight and 200 yards to one side of a high intensity light. 
 
 If the guns are to be fired by case 3 at a target illuminated by a 
 searchfight, the observer at the sighting telescope can see well 
 enough if the searchfight be on either side of the gun, provided it 
 is not within the minimum distance previously given. Conse- 
 quently, for case 3 firing there would be no difficulty in having a 
 searchlight for every battery and aU in simultaneous operation, 
 provided the intervals between the batteries were sufficient to 
 permit all the searchlights to be installed more than the minimum 
 distance from the nearest guns. 
 
 When, however, searchfights are to be used in connection with a 
 horizontal position finding system, the searchfight locations must 
 be chosen largely with reference to the positions of the base end 
 stations. If there is but one base line, or if the same target is to 
 be used by all the guns, the seai-chfight may evidently be located 
 either between the base end stations or on the outside of either. 
 If, however, more than one target is to be Oluminated at the same 
 time, it is evident that the searchfights must not be between the 
 base end stations, for if this were true one, at least, of the base 
 end stations would have to look through one of the beams at a 
 target iUuminated by the other. Consequently, in any harbor the 
 number of targets which can be simultaneously illuminated for use 
 with' horizontal position finding is exceedingly limited. Conse- 
 
395 
 
 quently, it would appear that the policj' will have to be to concen- 
 trate the entire armament on a very few targets at a tune, destroying 
 these before attempting to fire at other targets. 
 
 Tncidently, also, it should be noted that in the early days of 
 searchlight use, when the ranges at which it was expected to pro- 
 ^de illumination were quite small, it was proposed to mount the 
 searchlight very high and direct its beam, not at the object to be 
 illuminated, but over that object. Such a beam is, of course, 
 reflected in the water and makes the water apparently luminous 
 Itself. Dark objects are said to show up well in this illumination. 
 This was tried and for very short distances was found to work well, 
 hnt for longer distances it was of no avail because, as has been 
 stated, even when the beam is as concentrated as possible and is 
 turned directly on the target the illumination is barely satisfactory. 
 
 Smiilarly, other persons advocated the use of searchlights on the 
 opposite side of a harbor entrance from the observer, the idea being 
 that the searchlights would be thrown on or nearly on him. This 
 -would throw the dark side of the object toward him, but as the 
 object passed across the Hght it would be strongly silhouetted 
 a,gainst it and therefore would be plainly visible. This also was 
 tried and at very moderate ranges was found to work quite well, 
 but it was foTind to be absolutely valueless for use at a distance. 
 
 Height of Searchlights. 
 
 The question of the height at which searchlights should be placed 
 il, of course, but one item in the question of location. 
 
 In the early days of searchlights, when the ranges were small, 
 it was considered by some experts that they should be mounted so 
 low as to make it impossible for any vessel or boat to sneak through 
 close to the shore tmder the beam. This extreme lowness of Hght 
 Tvas soon found to be unnecessary, for under any searchlight beam, 
 "unless it be mounted at an extreme height, there will almost always 
 Tie sufficient diffused light to iiluininate a boat. 
 
 For illuminating a very distant target, all the available power of 
 the searchlight is necessary. Close to the water's surface the trans- 
 parency of the atmosphere is usually less than higher up, due to 
 the haze or spray, and this haze is considerably increased when there 
 is a wind or the water is rough or choppy. It is therefore desirable 
 that the searchlight beam, for as much as its length as is possible, 
 should pass through the higher and more transparent air. In 
 -other words, a searchlight should be mounted as high as possible. 
 
 In a few locations along our north Atlantic and Pacific coasts 
 and in the Tropics, high sites can be found that are suitable for 
 searchlight use; but unfortunately, along our middle and south 
 Atlantic coast, and along the Gulf of Mexico, the shores are aU 
 
396 
 
 low and the mounting of searchlights at an elevation presents 
 considerable difficulty. 
 
 Attempts were first made to accompMsh this by means of fixed 
 towers which woxild raise the Hghts approximately 60 feet above 
 high water. In a few, but very few, locations it was possible ta 
 build these towers in the vicinity of. woods so that they could not 
 easily be seen. In most places, however, woods and other natural 
 hiding places were not available and the towers were most con- 
 spicuous. Not only did this make them much more liable to de- 
 struction by gunfire, but it made it possible for an enemy during^ 
 the daytime to note the location of these towers, plot this location 
 on his charts, and then, at night, when the searchlights were in 
 action, they could be used as aids to navigation in much the same 
 way as our large seacoast lighthouses. 
 
 The searchUght towers which were built were sometimes con- 
 structed of timber and sometimes of steel. In both cases they 
 were of skeleton construction, consisting of four uprights and the 
 necessary horizontals and diagonal bracing. The feet of the uprights- 
 were usually set in concrete blocks on the comer of a square about 
 from 16 to 24 feet on a side, depending upon the height of the tower. 
 The platform at the top was usually about 12 feet square and was 
 roofed over, while the sides were made at least partially removable 
 so that they could be taken out of the way of the beam. Usually 
 the center of the floor of the platform was made as a removable 
 trapdoor so that the light could be puUed up to the platform or 
 let down if desired. The stairway was usually inside of the uprights. 
 In a few cases the skeleton steel framework of an abandoned fire- 
 control, tower was utilized for this purpose, the necessary alteration 
 being made at the top. 
 
 The next recourse was to disappeariag .towers which, during the 
 day, would be lowered out of the enemy's sight behind a sand hill or 
 parapet, and which, at night, would be raised into the working posi- 
 tion, with the searchlight on a platform high above the sea and 
 ground. Three types of such towers have been tried; one based 
 much upon the same principle as in the Scljerzer rolling-lift draw- 
 bridge, one based upon the somewhat similar Strauss Bascule draw- 
 bridge, and the third upon the principle of the simple counter- 
 weighted beam or lever. Of the three, the last named seems to be 
 the most efficient and has been tentatively adopted as a type. In 
 the original installations of all three of these towers, the attempt was 
 successfully, made to raise th^, light about 60 feet above the ground. 
 Drawings of all these types are in the office of the Chief of Engineer 
 and will undoubtedly be made available for the use of officers. 
 
397 
 
 Not only must a disappearing tower raise the searchlight up to the 
 proper elevation, but it must hold it there firmly and on a perfectly 
 horizontal platform. If the tower is so hght that the wind causes it 
 to vibrate, the searchlight beam will vibrate and this is almost fatal 
 to distant observation. The platform on which the searchlight rests 
 "when lifted, must be perfectly horizontal because, if not, the motion 
 of the beam in azimuth wiU have the tendency to raise or lower the 
 beam, requiring constant adjustment in the elevation. This constant 
 adjustment seriously interferes with vision. 
 
 The greatest difficulty that has been heretofore met with is in the 
 great weight of the standard seacoast light, between 6,000 and 7,000 
 pounds. This difficulty will be largely reduced in the future because 
 of the great reduction of weight in the modem dish-pan searchlight. 
 (A satisfactory control mechanism has not as yet been adopted to 
 this form of light, but it is believed, even when this is added, the 
 weight of the dish-pan searchl^ht should not exceed one-fourth or 
 one-fifth of the weight of the older light.) 
 
 Concealment and Protection of Searchlights. 
 
 If a searchlight is hit by an enemy's projectile it may be destroyed 
 or seriously injured. In the daj^ime a searchlight is of no use what- 
 soever. Consequently, the safety of the searchl^ht when not in 
 use would point to its being thoroughly protected in the daytime. 
 For this reason, in many places, searchhghts are mounted on small 
 cars which can be moved back and forth on a few feet of track. At 
 night, of course, they are moved to an operating position, but in the 
 daytime they are rolled into shelters Jbuilt behind conveniently situ- 
 ated hills or into rooms of batteries or other parts of the defensive 
 wrorks. Preferably, of course, these shelters should protect the 
 searchlights not only from the direct fire of the enemy's projectiles 
 but also give sufficient overhead protection. The latter is not always 
 possible, but protection from direct fire by putting a searchlight 
 behind a parapet is much better than no protection at all. 
 
 If protection is not possible, the next best thing to do is to conceal 
 the lights, not only for the sake of keeping them from being fired at, 
 but in order that their positions may not be spotted by the enemy 
 diiring the daytime and the Hghts be used by him at night as aids to 
 navigation. 
 
 In connection with the concealment of searchlights, quite a mmiber 
 of devices have been used at various places. Where searchlights 
 have been located on the tops of hills, arrangements have been made 
 by which they can, in the daytime, be lowered down into excavated 
 shelters. Sometimes the searchhght is lowered vertically and some- 
 times it is rolled down an inclined plane, coimterweights being used 
 in both cases. Where the searchhght drops down vertically, it is 
 usually moTinted on a platform having a roof which, when down, 
 
398 
 
 forms the roof of the shelter. This roof must" be, if possible, so 
 arranged as not to be visible either from horizontal view or from an. 
 airplane. Where the searchlight goes down an inclined plane, it. 
 usually moves into a more or less bombproof shelter. 
 
 In other places, when searchlights are to be used along a thickly^ 
 settled beach, plans have been devised for building as a searchhght 
 station, a structure which, froin the sea, wiU appear exactly similar 
 to the beach cottages. The searchhght is to be placed in the rear part 
 of a cottage and is to be so mounted that it will appear above the roof 
 of the cottage. The front rooms can be filled with sand and thus- 
 give considerable protection to the searchlight. 
 
 Officers interested in the subject should obtain for inspection, 
 plans of the disappearing installations at Diamond Head, Honolulu; 
 Tennessee Point, San Francisco; and Los Angeles. 
 
 As a method of providing protection for the searchUghts, not only" 
 during the daytime, but even when in operation at night, it has been, 
 suggested that the searchlight and its mechanism, which is quite ex- 
 pensive, might be kept behind a parapet and throw its beam upon a. 
 plane mirror at one side of the parapet which would reflect it to the 
 target which it was desired to illuminate. This means, of course, 
 the additional expense of a plane mirror and its mounting, and this- 
 plane mirror would, of course, require the distant control mechanism. 
 However, it was considered probable that the cost of the plane mirror 
 would be so much less than that of the searchlight, and that the plane 
 mirror would be so much easier to replace, that the scheme might b& 
 advisable. 
 
 As at first suggested and tried, the plane mirror was essentially on 
 the same level as the searchhght and changed the direction of ther 
 beam in the horizontal plane only. Later, it was suggested that thfr 
 same expedient might be utilized, not only to give protection to the- 
 searchlight proper by leaving it behind a parapet, but also so as to 
 elevate the beam to a sufficient height. 
 
 This could be done either by two mirrors or by one. In the former 
 case, the searchlight would throw its beam horizontally and this- 
 beam would be reflected into a vertical position by a plane mirror set 
 at an angle of 45°. At the proper elevation, and on top of a sort of 
 skeleton tower, there would be placed another mirror set also at an 
 angle of 45°, which would change the vertical beam back again to a. 
 horizontal one. By rotating this upper mirror, or rather stand, in 
 azimuth, the beam could be sent in any desired horizontal direction. 
 This method has the disadvantage of a double loss of hght due to 
 double reflection. 
 
 The other method was to place the axis of the beam in a vertical 
 line, in which case the upper plane mirror only would be needed ► 
 This would require the reflection of the beam at one mirror only. 
 
399 
 
 With a view to determining the possibilities of the use of plane 
 mirrors with searchlights and, incidentally, the loss of illuminating 
 power by this reflection,, experiments have been made in the last 
 year or two. As a whole, these experiments have been discouraging. 
 Plane mirrors of proper size have been exceedingly difficult to obtain 
 and the attempt to use a composite mirror made up of smaller mir- 
 rors has met with failure, owing to the practical impossibility of insur- 
 ing that the different individual mirrors would all be in the same plane 
 or in parallel planes. Furthermore, the loss of illuminating power 
 by this reflection has been shown to be extremely great, but to what 
 extent this large loss of power has been due to defects in the plane 
 mirrors used, and to what extent it is inherent, has not yet been 
 
 determined. 
 
 REINFORCING LIGHTS. 
 
 During the maneuvers of 1905 it was simultaneously suggested 
 by several persons that for use at extreme distances where the 
 illuminating power of searchlights was small it might be possible to 
 increase the illumination by the use of what may be called "rein- 
 forcing lights"; that is, of several lights thrown simultaneously on 
 the same target so that their combined effects might make the target 
 visible when it would not be sufficiently illuminated by one beam 
 only. 
 
 This was attempted but was found not to work well for a niunber of 
 reasons which would appear to be almost inherent. 
 
 Where a single searchlight can illuminate a target sothat it can be 
 seen only dimly and not with sufficient distinctness to be observed 
 by position finding telescopes, the addition of another light does 
 indeed increase the apparent illumination of the target and make it 
 possible to use the telescope. Where the target is fixed in position, 
 this works fairly well, but when it is attempted to keep two beams 
 on a distant moving target, great difficulties are encountered. 
 When, by a decrease in the illumination of the target, it becomes 
 evident that it has gotten out of onljbeam, it is impossible to tell 
 which beam is stiU illuminating it' and which is not. In an attempt 
 to get both be.ams back on the target, the operators are just as likely 
 to move from the target the beam that is on it, thus leaving it in 
 total darkness. By having the controllers of both beams in the 
 same station and operated by the same man, it may be possible for 
 a very well-trained operator to keep both beams on the target. 
 But for general use it would appear that the scheme is impractical, 
 even when the range is not too great to leave the object slightly 
 visible when illuminated by one beam only. 
 
 For finding a target so distant as not to be visible at aU when 
 illuminated by one beam, the scheme is absolutely useless. 
 
400 
 
 RESERVE SEARCHLIGHTS. 
 
 Up until the time when the United States became involved in the 
 World War, the project for searchlight installation of aU our defenses 
 was so far from completion that but little attention could be paid to 
 the question of reserve lights, but the possible availability for domes- 
 tic use of a large number of searchlights piu-chased for operation 
 abroad has, since the armistice, made it necessary to consider this 
 question. A searchlight is, of course, vulnerable and can be 
 destroyed. It is exceedingly, useful, and if destroyed, it should be 
 replaced almost inamediately. This means that there should be a 
 reserve light available. If a reserve light be kept close to the light 
 in operation, it may be destroyed at the same time and safety points 
 to its being kept some little distance away. The question then 
 naturally arises as to whether it would not be well to employ the 
 reserve searchlight so that it might be available not only as a reserve 
 but as an additional light. 
 
 Taking this into consideration, it would appear that it would be 
 well, where it can conveniently be done, to have two searchlights 
 placed in fairly close proximity one to the other, both so installed 
 as to be put into use quickly when needed. Normally, one light 
 only would be used. If destroyed or put out of commission for any 
 reason, the other light would take its place. In an emergency, both 
 could be used. 
 
 In places where it is probable that both searchlights would be 
 useful and might be used simultaneously for a considerable portion 
 of the time, it would appear well to have a third light in reserve. 
 
 The same principle that would indicate the practicability of reserve 
 searchlights would indicate the desirability of reserve searchlight 
 electric plants. The policy where there are two searchlights located 
 in fairly close proximity, would be that each should have its sepa- 
 rate generating plant and that there should be a third pla,nt some- 
 where in the vicinity which c^jd'-be used as a reserve for either. 
 
 Spare Mirrors. ^^. 'f ' 
 
 The most vulnerable portion of the modern searchlight is the glass 
 mirror which may be broken from many causes. This was recog- 
 nized a number of years ago and as soon as it became possible to 
 obtain in this country searchlight mirrors of domestic manufacture, 
 the policy was adopted of purchasing reserve mirrors. Some of 
 these reserve mirrors were to be normally kept in stock in the main 
 Engineer depot, a few others in minor depots in various sections of 
 country, and still others in our coast defenses. The number of 
 reserve mirrors to be kept in each coast defense was to be not less 
 than one-third of the number of each size in actual use. Such a 
 distribution was in progress at the beginning of the war but it was 
 necessarily interrupted by the demand for field searchlights abroad. 
 
4Ui 
 Portable Searchlights. 
 
 Before the installation of searchlights had heen in progress for 
 many years, it became evident that a number of the most suitable 
 locations were outside of the limits of the coast forts and were on 
 private grounds. To attempt to maintain searchlights in tunes of 
 peace in these places would he difficult and expensive, and it was 
 therefore decided that it would be desirable, if possible, to make some 
 of our searchlight outfits portable so that they might be taken to 
 these desirable outlying sites for drill purposes or during maneuvers, 
 as well as in time of war. 
 
 An attempt was therefore made to develop portable searchlights 
 and a number of 36-inch sets were actually built. These were 
 utilized later in the portable searchlight brigade, which was sent 
 from point to point in the country for the purpose of determining 
 by trial the desirable locations for searcMights. These sets consisted 
 of two units, the generator unit and the searchlight unit. They 
 were horse drawn, exceedingly heavy, and could be moved only 
 with difficulty, especially in sandy soil. To movfe them for a short 
 distance and put them in place was possible but they were not 
 portable in the sense that they could be rapidly put into position 
 and later withdrawn if exposed to too hot a fire. 
 
 In many respects the machinery of these so-caUed portable outfits 
 was quite crude and practically aU of them have since been scrapped. 
 Prior to the Japanese-Russian War the use of searchlights in 
 military operations had been advocated almost exclusively in con- 
 nection with seacoast defense, and their use in field operations 
 appears not to have been seriously considered. During the siege of 
 Port Arthur, however, searchlights proved their usefulness in con- 
 nection with such operations, and shortly thereafter it was decided 
 to be advisable to introduce portable searchlights into the trains of 
 our mobile army for use with Field Artillery. Searchlights for this 
 purpose must, of course, possess considerable mobility, in fact, 
 mobility might be almost said to be the prime desideratimi. 
 
 Prior to the entrance of the United States into the World War, 
 three sizes of such lights had been developed, a 24-inch horse-drawn 
 light for use with horse-drawn Artillery, a 30-inch motor-drawn 
 light for use with motor-drawn Artillery, and a 36-inch portable 
 light for siege use. Very few of these had actually been manu- 
 factured, but as soon as funds became available, contracts were 
 placed for the manufacture of a number ot them. In the meantime, 
 development work was in progress and this proceeded so rapidly 
 that almost before searchlights of any size could be delivered in 
 quantity, the improvements and developments that had been made 
 rendered them obsolete. 
 173341—20 26 
 
402 
 
 The different types that were tried are too numerous to describe, 
 but there were finally developed two serviceable forms of portable 
 60-inch searcKlight outfits. In one of these forms, each set consists 
 of two units, a generating' unit and a searchlight unit. The gener- 
 ating unit consists of a standard 25-lril6watt electric generator 
 mounted in an automobile truck which can be moved rapidly from 
 place to place. A 60-inch searchlight mounted on a somewhat 
 similar truck completes the outfit. 
 
 Later, a stUl more portable set was developed, consisting of a 
 single unit. The searchlight pertaining to this unit is of the dish-pan 
 type, mounted on a light car with rubber tires, the whole weighing 
 but 650 pounds. This is loaded by a portable ramp into an auto- 
 mobile truck, the engine of which propels the truck when desired, 
 or furnishes electric power for operating the searchlight when. the 
 truck is at rest. The truck contains, in addition, a considerable 
 length of cable on a reel, so that the light on its light rubber-tired car 
 can be moved a considerable distance from the generator before 
 being put into operation. 
 
 The last two kinds of portable lights mentioned were developed 
 primarily for use in anti-aircraft work and were therefore not pro- 
 vided with distant control mechanism, since it was found for anti- 
 aircraft work the control of the searchlight had to be done at the 
 light and by levers. 
 
 Before this light will be serviceable for seacoast use, it is probable 
 that distant control mechanism will have to be added. This is 
 beheved to be perfectly possible, although'it will increase the weight 
 and will to some extent affect the portability. Being intended for 
 use in anti-aircraft work, no attempt was made to elevate the light 
 above the ground. For seacoast use, the searchlights must be 
 raised, and therefore steps 'are in progress looking to the development 
 of a slightly heavier automobile searchlight outfit which contains a 
 collapsing or disappearing tower by which the searchlight can be 
 lifted to a height of approximately 40 feet. Up to the present, this 
 outfit has not yet proved practicable, but the design is said to possess 
 considerable promise. 
 
 In the meanwhile, and for use in harbors where there are available 
 railroad tracks, a railroad searchlight outfit has been developed. 
 This outfit consists of two units, one containing the generating set 
 and accommodations for the detachment, and the other the search- 
 light mounted on an elevating tower. This outfit has recently been 
 completed and is reported to be a success. 
 
403 
 
 ANTI-AIRCRAFT SEARCHLIGHTS. 
 
 The most important derelopment in searchlight matters during 
 the recent war was in connection with anti-aircraft defense. The 
 lights formerly in use had been designed to operate with their beams 
 horizontal or at only a slight elevation above the horizontal, this 
 elevation being made use of in signaling and for tactical reasons. 
 A searchlight would be put in operation with its beam elevated so 
 that the commanding officer might be certain that the beam he had 
 ordered into use had received the order. Similarly, in order that he 
 might know positively that his instructions for the extinguishing 
 of a light had been carried out, the beam would first be elevated and 
 then would be occulted while in the elevated position. There was, 
 therefore, a comparatively small limit to the elevation at which the 
 older searchlights had to be operated. 
 
 When an attempt was made to move the beams to a greater eleva- 
 tion, the regulating apparatus ceased to work. Further, under such 
 conditions, the mirrors were apt to be injured by fragments of carbon 
 falling upon them. For following aircraft, however, it is essential 
 that the searchlight beams go all the way to the zenith or possibly, 
 in a few cases, beyond the zenith. An attempt was first made to 
 obtain this high elevation by the use of reflecting plane mirrors. 
 These proved inadequate for the purpose. Fortunately a lamp 
 mechanism was soon developed which would work with the beam in 
 a vertical position, and it was found to be possible to add a screen 
 that wouid protect the mirror from the dropping of carbon fragments. 
 The final result of these developments was the portable dish-pan 
 light described above. 
 
 As far as anti-aircraft searchlight defense is concerned, the arrange- 
 ments to be made at seacoast defenses do not differ from those in the 
 efense of cities. Consequently, the matter wiU not be treated 
 further here. 
 
 OTHER METHODS OF BATTLE-FIELD ILLUMINATION. 
 
 In the early part of the World War attempts seem to have been 
 made to use searchUghts for field operations. These soon ceased 
 and as far as is kno\m to the author searchlights seem to have 
 been practically restricted during the latter part of the war to anti- 
 aircraft use only. 
 
 Searchlights having proven themselves not specially satisfactory 
 for battle-field illumination, attempts were made to Ught up the fore- 
 ground in front of the fines by means of flares. Some of these were 
 dropped from rockets, some were fired from rifles, and some from 
 specially designed mortars. These, however, were of comparatively 
 small range and fit up the ground only a short distance to the front. 
 
404 
 
 It is understood, however, that fairly successful attempts have been 
 made to inclose a flare and parachute in the projectiles of guns as 
 large as 5 inches and 6 inches. The guns are fired at .quite a high angle 
 of elevation and the projectiles are fitted with a time fuse which ex- 
 plodes the mat the proper time. The explosion is of such a character as 
 merely to blow out the base of the shell and to set the flare and 
 parachute free. 
 
 If the above idea proves to be practicable with guns of fairly long 
 range and the flares can be made so as to bum for a considerable 
 time, it would look as if they might be adopted in seacoast defense 
 for lighting up the sea at extreme ranges. As to whether or not 
 this is possible, only the future can show, 
 
 FUTURE DEVELOPMENTS. 
 
 The rapid advance that has been made in the last few-years in the 
 range of heavy artillery has, in spite of the improvements in search- 
 lights, placed the range of seacoast and naval artillery far beyond 
 the range of any searchlights that can be made. Consequently, long 
 before a hostile vessel can get within searchlight range it will have 
 come within the range of the artillery, both its own and that on shore. 
 
 Consequently, it would appear that reliance upon the beams of 
 searchlights for informing us of the approach of an enemy's vessel 
 is now a thing of the past. If we are to learn of such approach at or 
 near the extreme range of our guns, we must make use of other 
 devices and must restrict our searchhghts in all probabflity to the 
 illumination of vessels whose presence has long before been learned 
 by these other means. 
 
 Several years ago the writer suggested to the Chief of Engineers 
 and to the Chief of Coast Artillery that in the future rehance for 
 early information as to the approach of an enemy's fleet could well 
 be obtained by picket boats. It would appear possible to select, in 
 and around the entrances to many of our harbors, certain picket- 
 boat locations, and to lay to these locations telephone cables the 
 inshore ends of which would be connected to our telephone system. 
 To the outer ends of these cables would be attached buoys which 
 would float a short distance below the surface and would, therefore, 
 not be visible to the enemy. About dusk or shortly afterwards, the 
 picket boats would go out to their proper locations, locating them- 
 selves by ranges temporarily placed on shore. When in or near their 
 positions, the men in a boat woxdd grapple for the buoy and, having 
 found it, the end of the cable would be hauled into the boat and 
 telephone communication established with the shore. Such com- 
 munication would be maintained until daybreak, when the buoys 
 would be thrown overboard and the,boat would return to the harbor. 
 
405 
 
 It has been suggested that these boats might be fitted with sub- 
 marine "ears" now used under certain conditions on vessels for 
 picking up the direction of submarine fog signals. It is understood 
 that these "ears" are sensitive enough, when used from a ship at 
 rest, to give an indication of the approach of a vessel quite a number 
 of miles away, and at the same time to give a fairly close approxima- 
 tion of the direction of the approaching object. 
 
 Upon hearing an approaching ship the picket boat would at once 
 telephone to the shore, giving the azimuth of the approaching ship 
 from the boat. In general, the picket boats should be so close 
 together that an approaching ship could be heard by more than one 
 boat, and the relative azimuth indications from the boats would 
 show the location of the ship and should later render possible the 
 plotting of its course. 
 
 If desired, the ship could be fired on and although this fire would 
 probably not be very effective, it would no doubt warn the ship that 
 its presence was known and probably cause it to withdraw. 
 
 It is understood also that experiments are under way tending to 
 lead to the development of a form of sensitive anchor which by 
 dectric-magnetic means will give notice of the approach of a vessel 
 and its approximate direction. Should this develop into a practi- 
 cable apparatus, it will go far toward solving the problem of the 
 distant detection of an approaching enemy. 
 
Chapter XIV. 
 SUBMARINE MINING. 
 
 This chapter will be devoted to a brief recital of the connection of 
 the Engineer Department with submarine mining. 
 
 During the Revolutionary War some attempts seem to have been 
 made by the Americans to destroy British war vessels anchored in 
 our harbors by the use of explosives attached to the bows of sub- 
 marine or partially submerged vessels. Somewhat similar attempts 
 were repeated by the Confederates during the Civil War, and in at 
 least one case, such attempts were successful. In addition to using 
 submarines, the Confederates tried to close some of their harbor 
 channels by anchoring in them explosive mines and apparently 
 succeeded to the extent of sinking one of Admiral Farragut's mon- 
 itors when, in the siunmer of 1864, the admiral forced his way into 
 Mobile Bay. However, the question as to whether the monitor was 
 destroyed by a submarine mine planted by the Confederates or by 
 other means is one concerning which historians are not in thorough 
 accord. 
 
 The attempt of the Confederates to close some of their harbors 
 by submarine mines, and the moral effect which the supposed pres- 
 ence of these mines seems to have had upon our naval officers, drew 
 the attention of the Federal Government to the importance of mines ; 
 and their use was, in 1865, recommended by the Board of Engineers. 
 As a result, when shortly after the Civil War, the Engineer School was 
 established at Willetts Point (now Fort Totten, Long Island, N. Y.), 
 the development of a submarine mining system was assigned to that 
 school. Gen. Henry L. Abbot, Corps of Engineers, was assigned to 
 duty as conunandant of the school and the development of our sub- 
 marine mining system was largely due to his untiring efforts. In the 
 nearly 20 years during which he was connected with the school he 
 brought the system to such a high state of development that the 
 improvements that have been made since have been almost exclu- 
 sively in details, and in those details where improvements have been 
 made possible only by recent discoveries and by the development of 
 electrical and mechanical apphances unknown at the time the develop- 
 ment of the submarine mining system was under the supervision of 
 
 Gen. Abbot. 
 
 (407) 
 
408 
 
 Abbot System. 
 
 When Gen. Abbot was relieved from duty at Willetts Point about 
 1886 the system that had been developed by him was briefly as 
 follows : 
 
 The mines used were of two kinds, ground mines and buoyant 
 mines. The latter were thosecpmmonly used, and even when ground 
 mines were used they frequently had attached to them buoys which 
 when struck by a vessel would cause the mine to explode. 
 
 The mine case was made of steel approximately one-half inch in 
 thickness, the most common form consisting of two hemispheres 32 
 inches in diameter. These hemispheres were pressed out of flat 
 steel plates. At the same time there was turned up along the edge of 
 the hemisphere a rim an inch or two wide. The two hemispheres of 
 a mine case were firmly welded together along their rims and this 
 formed a spherical case, 32 inches in internal diameter. At 
 the top of the mine there was fastened a fixed ring by which the 
 mine coidd be raised or held up, and at the bottom there was left 
 an opening into which could be screwed through a water-tight joint, 
 the so-called compound plug. This opening^ was loosely covered 
 by a removable cap in which the joint between the cable and the insu- 
 lated wire entering the mine was protected. To three points sym- 
 metrically situated on the lower hemisphere were welded three long 
 bales which, at their lower ends, were united in a ring to which could 
 be attached the anchor ropes. The anchor ropes used were made of 
 steel wire and were shackled at their lower ends to heavy anchors. 
 
 The compoimd plug which was screwed into the bottom of the 
 mine case consisted of a water-tight entrance for the insulated wire, 
 a chamber to hold the priming charge and fuses, and above this 
 chamber a combined circuit closer and circuit regulator. 
 
 The insulated wire after passing through the water-tight entrance 
 in the base of the compouild plug entered the priming chamber. 
 Here two fuses in series were placed in the circuit which ended at a 
 terminal post on the circuit regulator. The priming charge of dry 
 gun cotton was placed in the priming chamber, around the fuses. 
 
 The circuit regulator was intended for firing the mine by "judg- 
 ment" — that is, without its being hit and while the current still 
 remained open at the circuit closer. The main essential parts of the 
 circuit regula;t6r were a high resistance coil of wire and a small already 
 polarized permanent steel magnet. Normally, the electric current 
 coming from the shore passed through the fuses in the priming 
 chamber, thence through the high resistance coil to the metal walls 
 of the compoimd plug, and thence through the mine case to "ground." 
 The resistance of the cdil was so great that this current was much too 
 small to affect the fuses in any way. Moreover, the direction of the 
 current was normally such that the magnetic action induced in the 
 
409 
 
 coil was of such a character as to repel the permanent magnet. 
 If, however, the direction of the current was reversed, the magnetism 
 induced in the coil was also reversed and the small permanent magnet 
 was attracted. In moving, it short circuited the high resistance 
 coU and greatly augmented the strength of the current. 
 
 The circuit closer part, intended for contact firing, consisted essen- 
 tially of a small metal ball resting in a httle hemispherical cup-like 
 hole. Normally, the electric circuit was broken here, but if the 
 mine was struck sufficiently hard or was tipped sufficiently far, the 
 metal ball would roU up along the side of its cup until it touched 
 one of a nimiber of metal springs, thus making an electric connection 
 and short circuiting the high resistance coil of the circuit regulator. 
 
 The mines were connected with the shore by insulated armored 
 electric cables lying on the bottom. At or near the shore these 
 cables passed in through cable conduits to so-called mining case- 
 mates which contained the operating apparatus. All the joints 
 of these cables were very carefully insulated, so that after a mine 
 was put in place there was a continuous insulated electric circuit 
 passing from the operating apparatus in the casemate, through the 
 core of the cable and the various junction boxes, into the priming 
 charge chamber of the compoimd plug. Here the circuit, still 
 insulated, passed through two fuses and to an insulated attachment 
 on the base of the circuit regulator where it divided into two parallel 
 branches, one passing to ground through the high resistance coil of 
 the circuit regulator and the other attempting to pass through the 
 circuit closer. 
 
 In the operating casemate were two voltaic batteries; a so-called 
 signal battery consisting of a few cells of the Daniel type similar 
 to those used in telegraph offices, and a firing battery composed of 
 some 300 "Lelanch6" cells similar to those used in electric bell 
 circuits. These two types of cells were chosen becausCj at that time, 
 the Daniel battery was the most efficient then known for use on 
 closed circuits, and the Leclanche cells for use on open circuits. 
 
 The signal battery was normally kept in circuit with the mines, 
 and caiosed a slight current to pass through the cables and the high 
 resistance coils of the circuit regulators. This current was measured 
 when the mines were planted and from time to time thereafter, 
 supposedly at least once a day. The constancy of this current gave 
 evidence as to the good condition of the mine and its connections. 
 
 If the mine was struck and tipped by a passing vessel or in other 
 ways the ball of the circuit closer would jnake connection, short-cir- 
 cuiting the high-resistance coil and largely increasing the current 
 passing through the cable. This increased current would then be 
 sxifficient to work the operating apparatus in the operating box of 
 the casemate, but was not enough, if only the signal battery were in 
 
410 
 
 the circuit, to fire the mine. However, if the firing battery also was 
 in circuit, or was brought into circuit by the mechanism of the oper- 
 ating box, the fuses would be fired and the mine exploded. 
 
 To fire the mine by "judgment" it was necessary to connect in the 
 firing battery, but in the reverse direction. The voltage of the firing 
 battery passing through the high-resistance coil of the circuit regu- 
 lator Was not of itself sufficient to fire the fuses; but if this current 
 passed through the circuit regulator in the reverse direction it re- 
 versed the magnetism of the coil, drew over the small permanent 
 magnet, and short-circuited the high-resistance coil, thus causing 
 an increase of current sufiicient to fire the fuses. 
 
 Such a mine was harmless unless the firing battery was turned on. 
 With the battery out of circuit the mine mi^ht be struck by a vessel 
 with safety to the vessel though not necessarily with safety to the 
 mine. However, if the firing battery was in circuit the mine would 
 explode upon contact, and it could, by reversing the fixing battery, 
 be fired at any desired time even without being struck. 
 
 In the electric system the so-caUed '^ single wire" was used, the 
 earth and water being utilized as the return circuit. The inner end 
 of whichever battery was in series with the mines was grounded 
 through a wire leading into the casemate, and the outer end of the 
 circuit was grounded through the mine case, which was submerged 
 in sea water.' 
 
 The mine was usually moored so as to float at low tide and in a 
 slack current about 5 feet below the surface. Had it been closer to 
 the surface it could have been seen from a distance and could proba- 
 bly have been destroyed by artillery fire. As the tide rose the water, 
 'of course, would rise higher above the mine, but fortunately in all 
 the harbors of ovoc country the tidal fluctuations are too small to 
 place the mines so deep that they could be passed over at high tide 
 without being struck; that is, unless the mine had been depressed by 
 the action of currents. 
 
 When a mine is moored in water where there is a strong current it 
 will, of' course, be pushed sideways by the current, thus causing the 
 anchor rope to assume an inclined position until an approximate 
 * equilibrium is attained between the depressing effect of the ciurent 
 and the buoyancy of the mine case. With the same strength of cur- 
 rient, and consequently the same angular displacement of the anchor 
 rope, both the horizontal movement and the vertical depression vary 
 proportionately with the depth of the water. For evident reasons 
 the xnines, when thus depressed, must not be permitted to sink so 
 low that at high tide vessels might pass over them without touching 
 them. 
 
411 
 
 Furthermore, it is advisable that the horizontal movement be re- 
 ■stncted within as narrow limits as possible. Mines are planted in 
 regularly located groups with intervals so small that it is practically 
 impossible for a vessel to pass through a group without striking at 
 least one mine. Theoretically, of course, the current effect on xnines 
 planted fairly close together should be such as to give them equal 
 and parallel displacements, but actual experience shows that this is 
 not always true, and that the irreigularities in currents are frequently 
 so great that with any considerable horizontal displacement the in- 
 tervals between the mines may become extremely irregidar, leaving 
 gaps through which a vessel might possibly be able to pass. 
 
 It was therefore considered desirable, even for mines to be fired by 
 contact, that the horizontal displacement be kept small. For mines 
 to be fired by "judgment" this is even more important. The effec- 
 tive radius of action of a mine is comparatively small, and for cer- 
 tainty of effect in "judgment" firing it is essential that the mine, at 
 the time it is fired, should be quite close to where it was expected to 
 be. Of coiirse the displacement caused by a current might be esti- 
 mated and allowed for, but such an estimate must in any case be 
 but little more than a guess. 
 
 Fortunately, it was possible to diminish to a considerable extent 
 the movements of the mine by the simple expedient of increasing 
 the size of the mine cases. The pressiu-e of the cvu-rent varies, of 
 course, with the area of the surface exposed to the ciurent, while the 
 upward or buoyant force varies with the volume of water displaced. 
 As a body increases in size its volume increases in greater ratio than 
 its area, so that the larger the mine case the greater the ratio between 
 the buoyant force and the deflecting force and the less the angular 
 deflection of the anchor ropes; consequently, the smaller the hori- 
 zontal displacement and the vertical depression of the mines. 
 
 This fact was recognized and several sizes of large mine cases were 
 designed, the largest having a volvmie equal to that of a 46-inch 
 sphere, or approximately three times that of the regular 32-inch 
 sphere. However, in order to secure as far as possible luuformity 
 in details this increase in size was made not by using larger spheres 
 but by keeping the same top and bottom hemispheres and inserting 
 between these two hemispheres cyUnders of the same diameter as 
 the hemispheres and having lengths sufB.cient to give the proper 
 
 volume. 
 
 The larger mines were intended for use in deep water or where the 
 currents were strong, as for these locations the depression of the 
 larger mines would not be as great as if the standard 32-inoh mines 
 were used. However, it had to be recognized that there might be 
 places where a large tidal variation, or the existence of very strong 
 currents, would cause even the largest mines to smk so low, either 
 
412 
 
 at high water or when the current was strongest", that vessels might 
 pass over them with comparative immunity. For such a locality it 
 was proposed to plant in comparatively close proximity two sets of 
 mines; an outer set at such depth that they would be serviceable at 
 low water, and an interior set at such depth as to be serviceable for- 
 high water. Of course this had the disadvantage that at low water 
 the high-water mines would probably float on the surface, where they 
 might be seen by the enemy and would be subject to destruction hy 
 -fire. For that reason these high-water mines were to be planted on 
 an interior line that would not be reached until the outer mine hne- 
 had been passed. With such an arrangement, however, an enemy's- 
 vessels might at high water pass over the low-water line of the mines- 
 and then remain between the two lines until low water, when the 
 high-water line of mines would float on the surface and thus be sub- 
 ject to easy destruction. Fortunately, there are no harbors in our 
 country where conditions are such as to require both high and low 
 water mines, so it has not been necessary to work out the details of 
 this system. 
 
 Theoretically, a floating mine, when the firing battery is not iit 
 circuit, may be struck by a friendly vessel without danger to the 
 vessel. However, as was shown during the Spanish War, ship cap- 
 tains prefer not to pass over mines, because they seem to fear that the- 
 mine might be cut into by a propeller blade and exploded by friction. 
 It was to avoid such trouble that the ground mine was designed. 
 
 Ground mines are intended to be used in comparatively shallow 
 water or where it is considered necessary that our own vessels be as. 
 unimpeded as possible. Of course, ground mines were best adapted 
 for "judgment firing," but where it was considered desirable to hav& 
 them converted into a kind of contact mine, small buoys containing 
 merely the circuit closers and regulators were attached to them. 
 These buoys, of course, were much less of an obstruction to naviga- 
 tion than the ftill-size mines and, containing no explosive, wer& 
 supposed to be safer for the passing vessels. Furthermore, if th& 
 if the buoy was destroyed it could be much more economically replaced 
 than a mine case. 
 
 The normal arrangement of mines was in groups called "grand 
 groups," each composed of 21 mines, or more strictly, of seven smaller 
 groups of three mines each, called "triple groups." 
 
 In Gen. Abbot's time one of the greatest difiiculties experienced 
 in the development of the torpedo system was ia obtaiaing suitable 
 submarine cables, and multiple cables containing more than seven 
 cores could not be manufactured at that time. Consequently, seven 
 mines or seven small groups of mines were all that could be operated 
 from a sulgle cable. He therefore adopted the plan of having a grand 
 group consist of seven small groups called "triple groups." The 
 
413 
 
 large seven-cored cable led first to a junction box called the "grand 
 junction box." Here each of the seven cores was jointed to a single 
 •conductor cable, leading to a so-called "triple junction box." In 
 this triple junction box the single-cored cable was connected to 
 three smgle-cored cables, each leading to a separate mine, one placed 
 100 feet in front of the triple junction box and one 100 feet on each 
 side. Since the grand junction boxes were planted about 300 feet 
 apart, the 21 mines forming a grand group, extended almost ia a 
 straight line for a length of about 2,000 feet. 
 
 The joints between the single conductor cable, connecting the 
 triple junction box with the grand junction box, and the three single 
 •conductor cables leading to the three mines were placed within 
 a so-called "cut-out box." This was done so that each of the branch 
 circuits might contain a fuse which would be in series with the fuses 
 ■of the mine and would presumably be fired at the same time. The 
 ■object of these cut-outs was as follows: Suppose one mine of a triple 
 group to be struck by an enemy's vessel and to be fired by contact, 
 the m ine case would, of coiirse, be destroyed, as would the end of the 
 cable leading to the mine. The remainder of this cable leading to the 
 triple junction box woidd be left, and ia all probability a ragged end 
 ■of the copper core would be exposed to sea water. This 'would cause 
 « ground which might greatly interfere with the proper working 
 of the remaining two mines of this triple group. To avoid this there 
 was inserted in each branch circuit in the triple junction box a cut-out 
 •or fuse. This cut-out or fuse, being in series with the fuses of the 
 mine and being exactly similar to them, woidd presumably be blown 
 -at the same time the mine was exploded, and woTild thus place the 
 -end of the branch circuit inside the cut-out box, where it would be 
 insulated, instead of in the copper core groTinded in the water. 
 
 Unfortunately the proper operation of this cut-out box required 
 that it should be loaded as to be absolutely water-tight. This, of 
 course, had to be done in the air and at atmospheric pressure, but 
 vrhen put to use the cut-out box was located at the bottom of the 
 sea where the hydrauUc pressure might be several atmospheres. 
 "With merely atmospheric pressure in the air ioside and the heavy 
 iydrauhc pressure outside, leaks into the cut-out box were very hard 
 to prevent. 
 
 With the arrangement just described, separate mines might be 
 &-ed by contact, but when "judgment firing" was attempted all 
 three mines of the triple group would be exploded simultaneously. 
 This arrangement, while quite imeconomical in the use of mines 
 has one advantage. "Judgment firing" was based upon the tracking 
 of vessels. The process of tracking was somewhat crude, and there 
 was always more or less uncertainty as to the exact location of a 
 -vessel and of the mines. If, therefore, "judgment firing" was 
 
414 
 
 resorted to only the vessel appeared to be passing, through the center 
 of the triple group, it was practically certain that one of the three 
 mines exploded would sink the vessel. 
 
 For each grand group there was in the casemates a special opera- 
 ting box. This operating box consisted essentially of seven opera- 
 ting magnets and levers, one magnet and lever for each of the cores» 
 At one end of the operating box there were a few simple electric 
 switches; up one side there passed; a bus bar connected with the 
 signal battery, and up the other another bus bar connected with or 
 connectible to the firing battery. . Each operating lever had mounted 
 on it in plain sight a number corresponding to the tactical number 
 of the triple group. Normally, with no current on, or with only the 
 small current due to the signal battery acting through the three- 
 high-resistance • coils of the circuit regulators, the lever remained 
 in a certain position. If, however, by the tipping of a mine and the 
 operation of the circuit closer, or in any other way, the current through, 
 an operating magnet was largely increased, the lever was drawn over 
 and closed a circuit which caused an electric beU to ring and throw a. 
 visible signal into plain sight near the number card of the triple 
 group, thus giving both audible and visible notice that a mine had 
 been strucli. Incidentally this motion automatically connected 
 firing battery bus bar to the cable leading to the mine. If this bus- 
 bar was at the time actually connected with the firing battery, the 
 firing current would flow into the cable and explode the mine which, 
 had been struck. If at any time it was desired to fire any triple 
 group by "judgment," the connection with the firing battery was- 
 reversed by a convenient reversing switch, the lever pertaining ta 
 the particular triple group, which it was desired to fire, was operated 
 by hand, thus by throwing the firing current, in a reverse direction,, 
 into the cable and exploding the entire triple group. 
 
 The electric bell just mentioned not only gave audible notice of 
 firing of a mine, it also performed another function in cutting off,, 
 for an interval of about 10 seconds, the firing battery from any pos- 
 sible connection with any other mine. This was done to prevent 
 the explosion of other mines whose circuit breakers might be closed 
 by the shock of the explosion or by the waves caused by the dis- 
 turbance. 
 
 At a convenient place in the operating room there was a testing 
 galvanometer. By the throwing of convenient switches this gal- 
 vanometer was placed in circuit with the cable leading to any par- 
 ticular triple group. As soon as a group had been planted this con- 
 nection was made and a note made of the galvanometer reading.^ 
 Similar readings were supposed to be made daily and the comparisoa 
 of the new and older readings showed whether or not the group con- 
 tinued in good condition and when it needed attention. 
 
415 
 
 Incidentally, also, arrangements were made by which a so-called 
 "sea cell test" could be apphed to any triple group whose galva- 
 nometer readings indicated that it was not in good condition. 
 
 For use in connection with the sea cell test, there were exposed in 
 the water near the casemate three separate plates, one of iron, one of 
 zinc, and one of copper. Different wires led from each of these 
 grounds into the casemate, and, consequently, by use of the proper 
 one of these wires, the home ground could be made with any one of 
 these three metals. If the home ground was a metal different from 
 that exposed to the water at the mine, a galvanic current would be 
 caused, due to the action of the sea water upon the two metals. 
 
 Normally the mine was grounded through its steel case, and there- 
 fore would give no current with the iron home ground but would give 
 currents with the zinc groimd or the copper ground. The top of the 
 circuit closers was composed of ziac, so if a mine filled <with water 
 there would be in addition a zinc ground, and this would be shown 
 by the sea cell test. Similarly, if there was an abrasion of the cable 
 exposing the copper core, this also would be shown. 
 
 Theoretically, the use of the sea-ceU test would give an indication 
 of the cause of the trouble with a faUing mine. In the hands of skDled 
 operators it worked very weU but for general use it was too deUcate. 
 It is of interest at the present time and is mentioned here because it 
 is understood that the same essential principles were made use of in 
 connection with the operation of the antisubmarine barrage planted 
 by our Navy in the North Sea during the World War. 
 
 The explosive used was dynamite and in Gen. Abbot's day this 
 was furnished in the form of a coarse powder. It was placed in a bag 
 around the compound plug. The mine was, of course, loaded when 
 upside down. A large bag was first inserted through the opening in 
 the base. The dynamite was placed in this bag and the compoimd 
 plug then screwed into the opening. When the mine was turned 
 back to its proper position, that is, in the position in which it would 
 float in the water, the dynanaite would fall down and close around 
 the compound plug. The p riming charge consisted of a small amount 
 of guncotton within the pruning charge chamber of the compound 
 plug, having the fuses embedded in it. When the fuses were fired, 
 they were supposed to detonate the guncotton, and this, in turn, 
 the dynamite. 
 
 In connection with the submarine mine system there is one point 
 of great importance, and that is that the destructive range of mines 
 is much smaller than was popularly supposed. In fact, the usual 
 chaise of 100 pounds of dynamite was certain to destroy a well-con- 
 structed vessel at a distance of about 20 feet only. In other words, a 
 vessel to be seriously endangered by 100 pounds of dynamite would 
 have to be in contact with or almost in contact with the mine. 
 
416 
 
 In ground mines, and occasionally in the larger floating mines, 
 larger chaises of dynamite were used and it was found by experiment 
 that the effective range of the mine was approximately proportiona 
 to the square root of the fcharge, that is, a 400-pound charge would 
 have aibout twice the effective range of a 100-pound charge. 
 
 The process of the planting of a grand group was about as follows: 
 The grand junction box was placed in a yawl which was rowed or 
 towed to the proper place, being accurately located by transits on 
 shore. When properly located it was anchored and, if it had not 
 ah-eady been done, a seven-cored cable was laid from this location to 
 the shore. The next step was to connect the seven-cored cable with 
 the grand junction box. A so-caUed "Turk's-head" was made at the 
 end of this cable and this was then fastened in the proper clamp of 
 the junction box. The ends of the individual cores of the cable 
 were then ^parated and exposed, and by means of a telegraph or 
 telephone connection made through the armor of the cable the indi- 
 vidual cores were identified with their other ends in the casemate 
 and were tagged. 
 
 The next step was to locate the triple junction boxes. These 
 with their loaded cut-out boxes, were placed in other yawls which were 
 rowed into their proper place, the center one being first located from 
 the grand junction box and the others from the center yawl. The 
 distance apart, 300 feet, was determined by a line stretched from one 
 boat to the next, the direction of the line being fixed by a range on 
 shore. After being properly located each boat was held in place by a 
 small anchor. 
 
 The next step was to lay a single-conductor cable from each triple 
 junction box to the grand junction box. These cables, whose lengths 
 could be known beforehand, were already fitted with Turk's-heads 
 before being laid and, of course, as soon as they were laid, the Turk's- 
 heads were quickly fastened to the corresponding clamp of the grand 
 junction box in the grand junction box yawl and to the proper clamp 
 of the triple junction box in the triple junction box yawl. 
 
 In the meantime there had been placed in the planting boat the 
 loaded mines, cables of the proper length for reaching from the mines 
 to the triple junction boxes (with Turk's-heads already made), anchors, 
 and anchor ropes of proper lengths. While the boat was proceeding 
 to the proper place for planting the mines, the cables and mooring 
 lines were attached to the mines, and the first mine with its anchor, 
 etc., was raised and hung over the side of the vessel preparatory to 
 planting. On arriving at the proper spot, the location of which was 
 estimated from the triple junction box boat, the mine was let go and, 
 of course, dropped to the bottom. The planter at once steamed to 
 the triple junction box boat, paying out the cable as it went, and 
 handing the end of the cable to the man in the triple junction box boat, 
 
417 
 
 who at once made the Turk's-head fast to the propeK^lamp. This 
 man then made a temporary joint between the ends of the two cables, 
 one leading to the mine and the other toward the shore. A pre- 
 liminary electrical test was made at the casemate and, if all was well, 
 the joint was made permanent. In the same way the other two 
 mines of this triple group were planted. The triple junction box was 
 then closed and lowered to the bottom and the joint pertaining to 
 that triple group was permanently made in the grand junction box. 
 The process was then continued and triple group after triple group was 
 planted. When all the mines were down the cover of the grand junc- 
 tion box was itself put on and this box was then dropped to the 
 bottom. 
 
 The above is a very general description of the system as developed 
 by Gen. Abbot. Of course, provision was made for planting mines 
 other than in grand groups and there were a number of refinements 
 in details which it is not necessary to go into here. 
 
 Later Developments. 
 
 Between the time when Gen. Abbot left Willetts Point in 1886 and 
 the outbreak of the Spanish War a few modifications were made in the 
 system. For instance, the old voltaic firing battery was done away 
 with and a dynamo was substituted in its place; experiments were 
 also made as to the desirability of substituting a storage battery for 
 the voltaic signal battery. The galvanometers upon which Gen. 
 Abbot had relied were superseded by the self-contained ammeters 
 and voltmeters which had been put upon the market, and improve- 
 ments were made in the circuit clqser and cut-out box. These changes, 
 it should be noted, were improvements in detail and changed none of 
 the essentials of the system. 
 
 Prior to the Spanish War all the Engineer captains and heutenants 
 of the Regular Service, with the exception of a few very recent 
 graduates of the Mihtary Academy, had been well instructed in the 
 torpedo system. It had also been customary, for a number of years, to 
 instruct each year about a dozen selected fine officers. A few of 
 these line officers belonged to the Infantry and Calvary but most of 
 them to the Artillery. , Of course, when the war broke out only a part 
 of these instructed ofiicers were available for torpedo work and many 
 skiUed civilian electricians had to be employed. 
 
 The greatest shortage, however, was in experienced enlisted men. 
 Previous to the Spanish War three of the four existing Engineer 
 companies had been stationed at Willetts Point. A large proportion 
 of the privates of these companies had been drilled in the mechanical 
 details of mine loading and planting, and there were quite a number 
 of noncommissioned ofiicers who were thoroughly well trained and 
 skilled in all parts of the system. However, immediately after the 
 173341—20 ^27 
 
418 
 
 outbreak of the war it became necessary to send one of these three 
 trained companies to Cuba and another to the Phihppines. Another 
 company, or a large part of it, was needed for the Engineer depot, so 
 that there was a great scarcity of Engineer soldiers for torpedo work. 
 
 Torpedo material was hastily shipped from the Engineer depot to 
 the various harbors and the mine planting was begun. In this 
 planting many difficulties were experienced. Only one regularly 
 designed mine-planting vessel was in existence and that was needed at 
 New York, so that at all our other harbors tugs or other vessels that 
 were available had to be hired and means had to be improvised for 
 handling the mines. 
 
 Much trouble also was experienced from passing merchant vessels 
 whose masters refused to obey the rules set down for navigation 
 during the planting of the mines. At least one boat engaged in mine 
 work was run down and a number of men were drowned. 
 
 However, in spite of numerous difficulties, many mines were planted 
 in our different harbors, sufficient to have exercised a strong deterrent 
 moral influence upon the enemy had he approached, even if they had 
 never been able to actually and physically prevent his entrance. 
 
 That the mines as planted were harmless to friendly vessels is 
 shown by the fact that not a single accident occurred to a friendly 
 vessel caused by a mine. That the mines are dangerous when ex- 
 ploded is shown by the number of unfortunate and fatal accidents to 
 the detachments that undertook, after the end of the war, to raise 
 and remove the mines which had been planted. 
 
 Progress Since the Spanish War. 
 
 A few years after the Spanish War the Army was generally reor- 
 ganized, and since it had been represented to Congress that the sub- 
 marine mine defense was most closely connected with the gun defense 
 of the harbors. Congress, in its wisdom, by the act of February 2, 
 1901, transferred the operation and control of the torpedo system 
 from the Corps of Engineers, which had developed it, to the Coast 
 Artillery Corps. In connection with this transfer the engineers 
 were removed from Willetts Point, which had been the home of the 
 Engineer School for over 30 years, and there was organized at the 
 location a new Artillery School of Submarine Mining to take the place 
 of the older Engineer School. 
 
 Shortly after this transfer had been made Congress made largely 
 increased appropriations for mine defense, enabling larger quantities 
 of mine materials to be purchased, many mine buildings to be con- 
 structed, and several especially designed mine-planting vessels to be 
 built. With the largely increased appropriations which were made 
 available and with the great development in electrical matters which 
 had taken place in commercial life, it was but natural that many 
 changes should be made in the torpedo system. Indeed, it would 
 
419 
 
 not have been surprising if the new body of ofl&cers to whom the 
 charge of this system had fallen should have practically torn the 
 old system to pieces. They did, indeed, make changes, but consider- 
 ing the circumstances, it is surprising how few these changes were. 
 This can but be considered as a great, though involuntary, tribute to 
 the excellent work that Gen. Abbot had done on the system. 
 
 Perhaps the most important change actually made is in the sub- 
 stitution of an alternating current for the heavy direct current for 
 firing the fuses and the substitution of an alternating current trans- 
 former for the circuit regulator. Under the new system the current 
 flowing to the mine does not pass through the fuses, but passes in- 
 stead through the primary coil of a small regulating transformer and 
 then divides, one part going to the circuit closer and the other through 
 a resistance coil to the mine case. This new arrangement has the 
 advantage of doing away with the old circuit regulator, the adjust- 
 ment of which was somewhat difficult, but it has the disadvantage of 
 placing the fuses in the secondary circuit of the small transformer so 
 that it is impossible afterwards to test them. 
 
 The signal current is still a direct current, and of course, while it 
 passes through the primary coil of the transformer, the secondary 
 coil, in which are placed the fuses, is dead. The fixed resistance coil 
 performs now the same function the high resistance coil of the circuit 
 regulator formerly performed. The circuit closer acts in the same 
 way as before and, by the mechanism in the casemate, gives notice 
 that the mine has been struck, and at the same time, if the switch is 
 turned, throws into the mine the firing current. When the firing 
 current, now an alternating current of considerable intensity, is 
 turned on, it passes through the primary coU of the small transformer 
 and induces in the secondary coil a current which passes through 
 and fires the fuses. The voltage of this firing current is suflScient 
 to fire the mine, even though the fixed resistance coil is in series, so 
 that as soon as the firing battery is turned into the mine it is fired 
 whether or not the circuit closer is in operation. 
 
 This change to an alternating, firing current, although it has the 
 disadvantage of not permitting any subsequent test of the complete- 
 ness of the circuit including the fuses, is apparently an improvement; 
 but its adoption has been rendered possible only by the recent great 
 development of alternating current apparatus. 
 
 Another important change in the system is the doing away with 
 the triple junction box and its cut-out boxes, and the substitution 
 of a 19-cored cable for the 7-cored cable. A grand group therefore 
 consists now of 19 mines mstead of 21, each mine having its separate 
 individual core extending all the way back to the casemate. It is 
 therefore possible to test each individual mine instead of each triple 
 group as formerly, and, incidentally, a single mine may now be fired 
 
420 
 
 by judgment, whereas before it was necessary to fire three. This 
 improvement was rendered possible by the fact that 19 conductor 
 cables are now manufactured, and these were not obtainable in 
 Gen. Abbot's time. 
 
 The change to a grand group of 19 mines having individual cables, 
 instead of seven groups of three mines to the group, has increased 
 by approximately three times the number of cables entering the 
 operating room, and therefore the number of individual operating 
 switches and levers. It became necessary, therefore, to do away 
 with the operating boxes, which under the Abbot system could easily 
 be spread on the shelves around the three sides of a single operating 
 space, and to substitute for them, a series of switchboards arranged 
 around the walls of the operating room. 
 
 Each grand group now has its own switchboard, each switchboard 
 being composed of 20 small square panels, arranged four wide by 
 five high. The conductor from each mine leads to its own small 
 panel; the twentieth panel is utilized for switches, signal lamps, etc. 
 The operation of the lever and the magnet on these square panels is 
 on exactly the same principle as in the old operating boxes invented 
 by Gen. Abbot, but a change in the method of mounting on the 
 switchboard has required a change in the mechanical details. 
 
 For the old signal battery, composed of voltaic cells, a storage bat- 
 tery is now utilized. This is located in a special separate room. In 
 another room, close to the operating room, there is placed an engine 
 and dynamo for charging the storage battery, as well as the motor 
 generator for furnishing the alternating firing current. The small 
 motor generator is operated by a direct current from the storage 
 battery and gives off at the generator end an alternating current 
 of the proper voltage. 
 
 The same selective system of contact or judgment firing is retained, 
 although the tendency has been, so far as drills are concerned, to 
 place more and more reliance upon judgment firing and the tracking 
 of vessels. 
 
 TACTICAL USE OF MINES. 
 
 Tactically, submarine mines partake of the nature of obstacles, 
 and though they are destructive obstacles, their use is restricted to a 
 large extent by the same conditions that affect the use of other forms 
 of obstacles in land warfare. As obstacles, their principal function 
 is to delay the advance of the enemy, and to delay him in a position 
 where he will be subjected to destructive fire from our artillery on 
 shore. In fact, submarine mines, if used otherwise than in connec- 
 tion with shore batteries, can delay only and can not entirely prevent 
 the entrance of an enemy's vessel. If not protected by gunfire, the 
 mines can and probably will be destroyed by counter mining or their 
 cable connections with the shore will be found by dragging operations 
 
421 
 
 and will be destroyed. These dragging operations will probably be 
 conducted by boats too small to operate the circuit closers and too 
 insignificant for mines, by judgment firing, to be wasted on them. 
 
 It is essential, therefore, that the mines be located within the field 
 of fire of guns on shore. In the modern system of artillery organiza- 
 tion the rapid-fire batteries of any fort, or at least a number of such 
 guns, are usually assigned to the mine commander for the protection 
 of his mine field, so that the use of these guns for the protection of 
 this mine field will not be interfered with by the lack of unity of com- 
 mand, which might occur if these guns were not under the control 
 of the mine commander. 
 
 It is, of course, advisable that the mine field should be located so 
 far to the front as to cause the enemy's vessels to halt before they 
 can come close enough to the defenses to make effective use of their 
 rapid fire guns, but at the same time the mines must not be pushed 
 so far to the front as to make their protection by their own rapid fire 
 armament inefficient, or so to make it possible for the enemy under 
 cover of darkness, fogs, or thick weather, to remove, destroy, or 
 paralyze the submarine mine defense. 
 
 MORAL EFFECT OF MINES. 
 
 One fact strongly brought into prominence in aU recent wars is 
 that the efficiency of fixed mines lies largely in their moral effect 
 upon naval commanders. The proper use of any naval vessel is 
 against other naval vessels, and a naval commander is not likely to 
 risk possible instantaneous destruction of his vessel by an unseen 
 mine unless the advantages to be gained are much greater than they 
 ordinarily are. Furthermore, the location and the number of mines 
 which may have been planted, and their condition as to efficiency, 
 wiU not generally be known to a foreign naval commander who will 
 usually give them credit for being more nmnerous and better than 
 they are. Indeed, I know one distinguished officer, who, after 
 studying carefully the manner in which the American fleet declined 
 to enter the harbor at Santiago, Cuba, which was supposed to be 
 but really was not defended by effective mines, and the way in which 
 the Japanese stayed out of Port Arthur, stated that in his opinion a 
 most efficient defense could be arranged for almost any harbor by 
 merely pretending to plant mines and then putticig up in plain sight 
 of the enemy, as if intended for a warning to our friendly vessels, a 
 large sign marked "Torpedoes." 
 
 SUBMARINE MINE BUILDINGS. 
 
 When matters connected with the operation of the submarine 
 mine system were transferred to the Coast Artillery, there was left 
 in the hands of the Engineers, the construction of the buildings per- 
 
422 
 
 taining to the submarine mine system. These buildings are the 
 mining casemates from which the mines are operated; the conduits 
 connecting the casemates with the shore; the cable terminals on 
 the shore; the cable tanks in which the cable is stored when not in 
 use; the torpedo storehouses in which are kept the mine cases and 
 other material; the loading rooms in which the mines are loaded; 
 the magazines in which the dynamite is stored; the range stations, 
 plotting rooms, and dormitories; the torpedo wharves at which 
 the mine planter is to land and receive the loaded mines; and the 
 tramways connecting the wharves with the cable tanks, storehouses, 
 loading rooms, etc. 
 Mining Casemates. 
 
 The so-called "mining casemates" are in reality not casemates 
 at all; that is, in the sense in which the word "casemate" is ordi- 
 narily used in connection with fortifications. They are in reality 
 the operating houses of the mine system and acquired the name "case- 
 mate" probably from the fact that many of the older "mining case- 
 mates" were made by mere alterations of existing casemates of the 
 old forts, which had become obsolete in so far as locations for mount- 
 ing guns was concerned. 
 
 The mining casement is really the operating house for the mine 
 system and into it are led the cables coming from the mines. In 
 its mpst modern form a casemate ordinarily consists of several dif- 
 ferent rooms; an "operating room," in which are located the oper- 
 ating boxes or switchboards, the testing instruments, and other 
 appliances used in the operation of the system; a power room, con- 
 taining the electric generating plant; a storage battery room con- 
 taining the storage battery; and a fourth room used as a dormitory 
 or oflBce room. 
 
 In the early casemates, as planned by the Board of Engineers, 
 the main consideration seems to have been to provide protection 
 and concealment, and protection seems to have been sought even 
 at the expense of efficiency of operation. As then constructed the 
 casemate consisted of a room about 12 by 18 feet in floor area with a 
 ceiling in the form of a full center arch. No steel beams were allowed 
 in the roof because it was feared that they might affect the delicate 
 galvanometers and other electrical instruments used at that time. 
 The roof and walls of the casemates were of concrete and were very 
 thick, 20 feet on the side toward the enemy and 10 feet on the 
 opposite side. Above and around this concrete was placed a large 
 pile of sand. The entrance was usually through a crooked gallery 
 opening out to the rear, so that by no chance could any projectile 
 enter the casemate. Incidentally, it may be stated that no light 
 could get in and very Uttle air, the only arrangement for ventilation 
 being a crooked ventilator pipe a few inches in diameter and extend- 
 
423 
 
 ing from tlie ceiling to some point on top of the sand fUl where its 
 outlet could be concealed. 
 
 In the center of the floor of the casemate there was a large man- 
 hole covered by a removable trapdoor and connecting with a con- 
 duit leading to the shore through which the cables were extended 
 into the casemate. Around the floor, on three sides of the opening 
 of this manhole, there was a line of tables or shelves of suitable 
 height for the operating boxes, etc. The testing appliances, the 
 batteries, and a few other fittings were kept on other shelves placed 
 under the operating tables or aroimd the walls. 
 
 In the harbors where there were older fortifications available, the 
 mining casemates were usually built in these older fortifications, 
 utilizing an abandoned casemate from which the gun had been re- 
 moved, or some other older room. The casemate openings or other 
 voids in the scarp walls were filled with concrete, the thickness of 
 the scarp wall was much increased by adding new concrete, and a 
 great deal of sand was piled aroimd it. Where no good site was 
 available within an older fortification, the casemate was an entirely 
 new structure built preferably in some existing sand dune or other 
 hiU. 
 
 Although between 1890 and 1898, quite a large number of case- 
 mates of the general character described above, were buUt in the 
 various fortified harbors of this coimtry, but httle use was made of 
 these casemates utntil the Spanish War, and it was then discovered 
 that many of them were so damp that condensation was apt to occur 
 on the electrical instruments with resulting electrical leakage. To 
 do away with the dampness, coal oil stoves and lamps were intro- 
 duced, but while these lamps were fairly efficient in overcoming the 
 dampness, they soon rendered the air almost unbreathable. 
 
 As a result of this experience, the Board of Engineers prepared 
 in 1899 a new design for a casemate which was pubhshed in Mimeo- 
 graph No. 32. In this design the thick concrete wall and the sand 
 protection were omitted from one side and were replaced by a com- 
 paratively thin wall with doors and window openings to provide 
 light and" air. On the other sides there were to be interior timber 
 walls with an air space between them and the casemate and similarly 
 there was to be an interior ceUing with an air space above. Means 
 were to be provided for artificially heating the air in these air spaces 
 and it was hoped by these means to prevent the trouble due to 
 dampness. 
 
 It was soon found out, however, that the casemate proposed was 
 too small, especially when the storage battery had to be provided 
 instead of the older galvanic battery. 
 
424 
 
 In 1903, therefore, the Board of Engineers presented a new plan 
 published as the second supplement to mimeograph No. 32. In this 
 new plan, the dimensions ot all the rooms and tne number of rooms 
 ■were increased and sleeping accommodations for the operating de- 
 tachment were provided. The casemate was now to consist essen- 
 tially of a frame building constructed in the vacant space in a large 
 concrete mass, the building being completely surrounded on aU sides 
 by an air space. The roof was to be made waterproof so that any 
 dripping or seepage through the concrete might run away. As by 
 this time the delicate galvanometers which had formerly been used 
 for measuring current and voltage had been replaced by the standard 
 self-contained ammeters and voltmeters,-no difficulty was to be feared 
 from the use of iron in the concrete, so the ceiling was shown as built 
 of reinforced concrete. On one side, that is, the side to the rear, 
 the exterior concrete wall was to consist essentially of concrete 
 columns to be pierced for doors and windows opposite the similar 
 openings of the interior frame building. 
 
 In the mimeograph instructions, it was stated that when the case- 
 mate could be built in a location where it wopld be entirely protected 
 from hostile fire, the mass of concrete even might be omitted so that 
 the oiily thing which would have to be constructed was a structure 
 essentially similar to the frame building itself. 
 
 The first casemate of this last type which was built was at Fort 
 Monroe, Va. The casemate was located on the parade level of one 
 of the bastions of the old fort, and being surrounded on aU sides, 
 except the rear, by the masonry ramparts of the old fort, this position 
 was supposed to provide sufficient protection. 
 
 The use of timber as the material for the casemate was intended 
 to reduce condensation, but of course it made the building inflamma- 
 ble. However, as at that time it was customary to build practically 
 all the observation stations of the fire control system of timber, the 
 use of timber for the casemate was in accordance with standard 
 practice. Subsequently, as was noted in the chapter on fire con- 
 trol, it became usual to build range stations not of timber but of 
 cement plaster on metal laths, and a similar change was made at 
 the same time in the construction of mining casemates. Later on, 
 some mining casemates were built of concrete blocks, some of brick, 
 and a number of reinforced concrete. 
 
 Since the adoption of the general design ot casemates just described, 
 only minor changes have been made. A casemate still consists of 
 four main rooms; at one end, a dormitory for the detachment that 
 in the daytime may be used as an office, next, a large operating room 
 with closets and a toilet, then a dynamo room, and at the other end, 
 a storage battery room. 
 
425 
 
 Formerly, it was customary to have the cables enter a well or 
 manhole imder one comer of the operating room, and from this 
 manhole trenches covered with removable sections of floor led around 
 the walls of the room a few feet away from the walls. Over these 
 trenches were placed the operating switchboards. 
 
 It was soon found, however, that it was somewhat difficult to 
 handle the cabjes in these narrow trenches and m the first casemate 
 built at Honolulu, which was designed and constructed by the author, 
 an improvement was made. In this casemate, a cellar some 4 feet 
 deep was constructed under the entire operating room and extended 
 some 3 feet to the front and rear of the operatiag room forming 
 areaways which were covered by gratings. The caole conduit en- 
 tered one of these areaways so that the ends of the cable couJd be 
 pulled iato the cellar. The object of the cellar was to simphfy the 
 handhng of the cables and to provide ventilation. When pulled in, 
 the cables are spread around the floor of the cellar and xmder their 
 particular operatmg boards and for the passage of a cable up into 
 the operating room a small hole is bored through the floor, behiad 
 the proper operating board. 
 
 The Honolulu casemate was constructed with reinforced concrete 
 walls, but for convenience in handling cables and for attaching the 
 wiring, the operating room was finished with a wooden floor and a 
 wooden ceiling. The mining casemates built a few years later in 
 the Canal Zone were of the same general character as that of the 
 Honolulu casemate, being constructed with reinforced concrete walls 
 and having a cellar imderneath the operating room. 
 
 Most of the casemates constructed by the Engineer Department 
 from 1908, up to and including the year 1917, were of the open type- 
 They were located where they would be well protected by other 
 structures from the direct fire of the enemy and consequently were 
 given no overhead or rear concrete protection. 
 
 The experience oi the World War, however, has invited attention 
 to the danger from air bombing and to the need of overhead pro- 
 tection for a structure as essential to the defense as a mining case- 
 mate. Consequently, reinforced concrete roofs siu-mounted by 
 earth covers have been added at many of the formerly existing case- 
 mates, and future casemate plans will undoubtedly provide for 
 overhead protection. 
 
 It wiU be noticed that the early standard designs for casemates 
 provided an unnecessary amount of protection, with resulting damp- 
 ness. The designs were gradually changed to the open casemates, 
 without any overhead protection whatsoever. The pendulum is now 
 swinging the other way and the standard design provides complete 
 protection both overhead and on alt sides. This tendency must, 
 however, not be allowed to go so far as to permit casemates to be 
 built without sufficient provision for dryness and ventilation. 
 
426 
 
 Cable Conduits and Terminals. 
 
 The cable conduits lead from the casemate toward the shore, and 
 if this distance exceeds 200 feet or so, the ease of handling the heavy 
 torpedo cables requires that intermediate manholes be provided. 
 The earliest conduits built were like sewers, large enough for a man 
 to crawl through, and but one conduit was provided for any case- 
 mate connection with the shore, all the cables being intended to be 
 hauled through this one. The more modern form of construction 
 however, is to use multiple terra-cotta ducts laid in concrete and 
 covered over with concrete. At intervals, these multiple conduits 
 enter into the side walls of manholes. In general, the torpedo conduit 
 lines are simUar to the fire control or power line conduits except 
 that the individual conduits should be somewhat larger. 
 
 The cable terminal is really a large manhole placed near the sea, on 
 the beach, or preferably behind a sea wall, if there is one. It is 
 provided with rings set in the walls for use in drawing in the heavy 
 cables. In fact, the same character of rings are useful in all the 
 manholes of the torpedo conduit line. 
 
 The designs of cable terminals and manholes have become stand- 
 ardized and the standard designs should be studied. 
 
 When built behind a sea wall the terminal must, of course, have 
 a connection with the sea by means of a hole cut below low water, 
 and arrangements must be made so that this hole may be stopped up 
 when not in use. When there is no sea wall, this cable terminal is 
 built in the sand beach and at such a level that it will ordinarily 
 be covered by the sand and not be seen. On the side toward the 
 land the muHiple duct conduit system enters, and on the side toward 
 the sea openings are made which are temporarily plugged with 
 wooden plugs. When the cables are to be laid, temporary trenches 
 must be dug from this cable conduit into the water. The cables 
 are then laid in these trenches and the ends passed through into 
 the terminal manhole. 
 
 Cable Tanks. 
 
 Cable tanks are designed for the storage of submarine cables, as 
 experience has shown that this cable keeps best when covered with 
 water. It consists essentially of a tank to be kept full or nearly 
 full of water, the depth of the water being sufficient to slightly more 
 than submerge the standard cable drums. For convenience in han- 
 dling the heavy drums of cable, a bridge crane with a hoist or block 
 is provided which may be moved back and forth over the cable tank. 
 The ends of this bridge crane are supported by raUs placed on lines 
 of columns' along the sides of the tank. In order to retard evapo- 
 ration, a house is usually built over the cable tank. 
 
427 
 
 About 1915, in connection with the pushing of the mine field 
 further to the front, double length torpedo cables were purchased, 
 the drums of which were, therefore, much heavier and larger, both 
 in length and in diameter, than had been proposed theretofore. 
 This rendered it necessary that the cable tanks should be made 
 deeper in order that the larger drums might be completely submerged 
 and that the cranes apd hoists should be of greater capacity in order 
 to handle the heavier cables. 
 
 The earlier cranes were provided with differential hoists similar to 
 those used for hoisting the projectUes in the shell rooms of emplace- 
 ments. In order, however, to operate these hoists, it was necessary 
 in raising the drums of cables that the operators should stand right 
 over the cable or very close to it. This required that temporary 
 planks shoTild be placed across the cable tanks whenever it was nec- 
 essary to lift out a cable and these planks frequently were in the way 
 as the cable rose up above the water. 
 
 This trouble was first remedied in the design of the cable tanks for 
 Honolulu, built by the author. In this design one of the side walls 
 of the cable tank was made much thicker so that its top might be 
 used as a walk way. The form of bridge crane provided was such that 
 all three of the motions necessary in the hoisting and operation of 
 this crane could be performed from one end of the bridge by men 
 standing on the top of this wall. 
 
 In the design of this cable tank additional improvements were 
 included. The levels of the cable tank and of the tramway leading 
 to it were so regulated that the top of the walls of the cable tank was 
 exactly on the same level as the deck of the cars running on the 
 tramway. The cable tank house was extended at one end so that 
 there was space for one car to come inside; and, on one side of the 
 entering track, a concrete platform large enough to hold two drums 
 of cable was built on the same level as the top of the tank walls. It 
 was therefore of the same height as the decks of the cars. Conse- 
 quently, from this platform, a cable drum could be rolled to a car 
 or it could be roUed from the car to the platform. In removing a 
 cable from the tank, it would be moved by the crane directly to the 
 car, if the car was there. If the car was not there, the drum would 
 be placed temporarily on the platform, thus releasing the crane, which 
 coTild bring up a second drum. When the car did come, the cable 
 drum could be rolled from the platform to the car. Similarly the 
 platform would be of service in carrying cable drums to the tank. 
 
 On the opposite side of the entrance track from this cable platform 
 was built a small testing house for the periodical testing of the insu- 
 lation of the cable. In this testing room, in order to reduce vibra- 
 tion, there was provided as a support for the instrument a concrete 
 pier running down into the ground and not touching any portions 
 of the cable tank or the walls. 
 
428 
 
 Torpedo Storehouse, Loading Room, Magazine, etc. 
 
 The early designs for these structures were pubhshed in mimeo- 
 graph No. 72 and modifications were pubhshed in mimeographs No. 
 ^2 and 100 and their various supplements. Still later designs were 
 utUized in the Panama fortifications, the drawings of which should 
 be consulted. 
 
 In the Panama fortifica-tions the torpedo storehouse consists of a 
 large concrete two-story building. Tlie lower story contains a very 
 long and wide storeroom, over which there runs a bridge crane which 
 can reach any portion of the storeroom and carry articles to or from 
 cars on the railroad track through the center of the storeroom. The 
 Tipper story is intended for various purpose's, and in order that there 
 may be no columns to interfere with the operation of the bridge crane 
 the floor of the upper story is supported by rods hanging from the 
 trusses of the wide and high roof. Kooms for. the storage of special 
 articles are provided at the ends of the storehouse. Outside, on one 
 side of the storehouse, is a wide platform on the same level as the 
 floor of the storehouse and of the platforms of the cars on the track 
 which runs alongside of it. 
 
 Many different designs have been used from time to time in buUd- 
 ing loading rooms and, since the last ones were built, the Artillery 
 Board has suggested still another change in design. So it may be 
 said that the design for loading rooms at the present time is in a 
 condition of flux and subject to modifications. 
 
 In most of the plans the loading room has been divided into at 
 least two portions, one for loading the mine cases and the other for 
 loading the compound plugs. The portion of the building intended 
 for loading the mine cases is provided with suitably shaped supports 
 for holding the mine cases in the proper position for loading; that is, 
 upside down. Occasionally arrangements have been made so that 
 the dynamite or the other explosive to be put in the torpedoes may 
 be chuted down into the torpedo from rooms above. Many of the 
 older loading rooms contain small tanks into which the mines may 
 be lowered and tested before they are sent to be planted. 
 
 Range Stations and Plotting Rooms. 
 
 For the operation of a submarine mining system by judgment 
 firing it is essential that the enemy's vessel be plotted in exactly the 
 same manner as is done in connection with the aiming of the guns 
 and as is described in the chapter on fire control. 
 
 The observation stations are of exactly the same character as the 
 observation stations connected with fire control aiid the plotting 
 rooms likewise are similar. The principal difference is that two 
 primary and two secondary stations are provided for each mine field, 
 and the plotting room is made double size, so that at least two vessels 
 At a time may be followed through the mine fields. 
 
429 
 
 Torpedo Wharves. 
 
 Wharves are needed in a submarine mining system for loading the 
 mmes on the mine planters. There is no general reason, of course, 
 why almost any wharf could not be used for this purpose, but expe- 
 nence during the Spanish War seemed to show that the operation 
 of planters at the regular wharves provided by the Quartermaster 
 Department for general post use would probably be seriously mter- 
 fered with at critical times by the movement of troops and the han- 
 dling of miscellaneous materials. Furthermore, it was considered 
 da,ngerous to handle loaded mines at the same wharves at which 
 miscellaneous materials were being handled and over which troops 
 were frequently passing. It was therefore thought advisable, when 
 it could be done, to build separate wharves for submarine mining 
 purposes, these wharves, in general, to be used for no other purposes. 
 
 As far as the construction of a submarine mine wharf is concerned, 
 no special remarks seem to be necessary, except that it should be 
 noted that the wharf is supposedly bmlt for the use of the mine 
 planters only, and therefore the deck should be bmlt of that height 
 which is best suited to the mine planters, whether or not such height 
 may be convienent for other purposes.. Whenever a mine planter is 
 provided with a derrick for handling the mines, and this is generally 
 true, no derrick will be necessary on the wharf; but as it is not im- 
 probable that, in some cases, vessels other than the regular planters 
 may be needed, it is well that a submarine mine wharf should have 
 on it at least one derrick. 
 
 The standard draft of mine planters for many years has been less 
 than 16 feet, and consequently a depth of 18 feet at low water is all 
 that has been considered necessary at mine wharves. However, there 
 has been a recent tendency to increase the draft of the planters and 
 this, of course, means increased depths of water at the wharves. 
 
 Tramways. 
 
 Tramways are required for handling loaded or unloaded mines, 
 anchors, cables, and other materials. They should lead from the 
 wharf to the cable tank, torpedo storehouses, and the torpedo load- 
 ing room. Where the tramway is intended for use with the mine 
 system only, and where no connections with any other railroads is 
 possible or desirable, the tramways used are usually narrow guage. 
 Where, however, a connection can easily be made with a railway sys- 
 tem used for other purposes, it is well that the mine tramway should be 
 of the same gauge and that a connection between the two should be 
 made. The cars for use on the torpedo tramway are supplied by the 
 Engineer Department. 
 
430 
 
 PROBABLE FUTURE DEVELOPMENT. 
 
 During the World War there has been an enormous increase in the 
 ranges used by naval and seacoast artillery and a residting probable 
 transfer of the field of any artillery action much farther to the front. 
 Consequently, to be of service in future operations, the mine field 
 must be pushed very much farther to the front than has heretofore 
 been considered necessary. This means much longer cables, greatly 
 increasing the difficulty of laying the cables and the mines; an in-_ 
 creased number of joints in the cables, which are always a source of 
 weakness; and an enormous increase in cost. Furthermore, the mine 
 fields are removed so far from the observation stations as to make the 
 the accurate tracking of vessels through them much more difficult. 
 Consequently the comparative usefulness of the Army form of sub- 
 marine mines would appear to have greatly decreased. 
 
 At the same time there has been an enormous development dur- 
 ing the war in jthe use of deep-sea mines, both those which are anchored 
 and those which are allowed to float with the current while automat- 
 ically maintaining a practically uniform depth from the surface. 
 The planting and control of these drifting mines naturally pertains 
 to the Navy, and the Navy has likewise become so expert as to be 
 able to plant anchored mines in the deep sea many miles away from 
 the coast. 
 
 These developments, along with many great improvements in the 
 mobile torpedo, would appear to have relegated the Army type of 
 submarine mine to a comparatively unimportant position. In fact, 
 it would appear as if this type of mine might almost have reached a 
 stage of obsolescence. 
 
Chaptee XV. 
 SUMMARY. 
 
 In the preceding chapters of this work, the attempt has been made 
 to gather together, for the instruction of student Engineer officers, 
 and for the assistance of such other Engineer officers as may be 
 called upon to take charge of fortification construction, a number 
 of facts which the author has learned from his experience and study 
 of the subject. There have been inserted here Mats as to the best 
 methods of doing things, reminders as to certain details which 
 an inexperienced officer might m all probability overlook, and 
 warnings as to things which should be avoided. 
 
 The attempt has been made also, by a recital of the history of 
 the development of emplacement design, to show that the accepted 
 standards are based, not upon the mere whims of designing officers, 
 but upon a sort of evolution, based upon experience that has shown 
 which of the many things attempted in the past should be retained 
 and which should be discarded. Fm-thermore, the attempt has been 
 made, as far as appeared possible, to point out the reasons which 
 appear to underhe the success or failure of the different expedients 
 tried. 
 
 It will probably have been noted that the recital of the work 
 actually done seems to cease as of a date several years ago. This 
 is because, for the last few years, there has been more or less stag- 
 nation in seacoast fortification matters in this coimtry, due largely 
 to the transfer of the interest and the energy of ail concerned to 
 the great war on the other side of the water. Consequently, these 
 notes may be considered as a sort of compilation of past history, 
 made in a well-marked interval between the past and the future. 
 
 Up to the present it has not been possible to even roughly predict 
 the effect the experiences of the World War will have upon the future 
 of seacoast fortification construction, for sufficient time has not yet 
 elapsed to permit the lessons taught by the war to be thoroughly 
 considered and digested. 
 
 During the war, there were very few instances of combats between 
 coast fortifications and naval vessels. The Allies, as far as we can 
 learn, made no effort to attack, or even to make a demonstration 
 ao'ainst, the German coast fortifications, and the same is equally 
 tme as to attacks or demonstrations by the German Navy against 
 the seacoast fortifications of the British, French, or Belgium coasts. 
 
 (431) 
 
432 
 
 To be sure, in the early portion of the war, a few German light 
 cruisers, in pursuance of the poUcy of increasing the frightfulness 
 of war, did make a few raids and bombardments of practically 
 unprotected English coast towns, but the results of such actions were 
 practically nil, and nothing, important can be learned from them. 
 
 In fact, about the only important instance during the war where 
 naval vessels made a genuine attack against seacoast fortifications 
 was at the mouth of the Dardanelles. Though much general matter 
 has appeared in print concerning these attacks, the writer has been 
 unable -to obtain any definite details from which lessons as to forti- 
 fication construction can be deduced. It is clear, however, that 
 though the fortifications were not strictly modern or up to date, 
 and the naval vessels which attacked them were quite modern, the 
 naval attack was far from successful and, after losing several ships 
 and many men, the British were compelled to cease their efforts 
 without having silenced or materially injured the fortifications, "and 
 without having been able to force their way through. 
 
 Being unable to destroy the Turkish seacoast fortifications or to 
 push past them, the British later attempted to get around them by 
 land operations, but the naval attack at the Dardanelles had warned 
 the Turks in time, and with the assistance of their German friends 
 they were enabled to thi'ow up land works and to bring sufficient 
 forces together to cause the British efforts at GaUipoH to end in 
 disaster. 
 
 During the war the writer of these notes had no actual field experi- 
 ence abroad, events beyond his control having forced him to perform 
 Ms war service in "The Army of the Potomac." Within the last 
 few weeks or months, however, he has had an opportunity of con- 
 versing Avith a large number of officers of Engineers and other 
 branches of the service who have returned from abroad. Unfor- 
 tunately, however, the ideas and opinions as to fortification matters 
 received from these different officers are exceedingly diverse, the 
 experience of nearly every officer having been more or less hmited, 
 and his ideas having been largely affected by matters which came 
 under his immediate observation. 
 
 In summing up for future use the lessons to be learned upon a 
 subject like seacoast fortifications, which were really not actively 
 involved in the recent struggle, considerable care must be taken 
 before actually changing our policies, to get a thorough and com- 
 prehensive grasp of aU that has happened. Especially must we 
 be careful not to allow our attention to be unduly attracted by what 
 we may call the dramatic incidents of the war. 
 
 In connection with artillery, the two remarkable developments of 
 the war were the enormous ranges which were sometimes xised 
 in artillery fire and the great advance in the portability of the heavy 
 
433 
 
 artillery. So striking were these two developments, that certain 
 officers hare retiimed from abroad imbued \dth the idea that all 
 guns, whatever their size and function, must be so mounted as to 
 be capable of being fired at extreme ranges and in any direction, 
 and, except where the gims are to be emplaced upon a small island, 
 that they must all be mounted on portable carriages so that they 
 may be carried from one place to another whenever 'desired. 
 
 In some respects, the great increase in the possible range of 
 artUlery must neceasarily have a great influence upon seacoast 
 fortification design. It makes it necessary that the enemy's vessels 
 must be kept much farther away from the cities or harbors than 
 was formerly considered necessary, and this means the pushing to 
 the front and outward of the seacoast fortifications, and the merging 
 of the subject of what may be called harbor defense, with the general 
 subject of coast frontier defense. 
 
 Seacoast fortifications are necessarily merely passive defenses; 
 they can not injure an enemy's vessel unless he voluntarily comes 
 within their reach. They can prevent an enemy's fleet from enter- 
 ing our important harbors, but they can not drive him away from 
 the coast, nor can they prevent him from attempting to land at a 
 minor improtected port, or on our open coast between defended 
 harbors. 
 
 Should an enemy once land on our coast he may, if he is not effec- 
 tively opposed by our mobile army, proceed to the rear of our sea- 
 coast defenses and attack them from that side, and if successful 
 in capturing our seacoast defenses from the rear he may enter the 
 harbor with his fleet and use it as a base for future operations. Or, 
 once landed, he may entirely disregard our seacoast or harbor 
 fortifications and proceed with his army to attack, from the land 
 side, the cities, the nav^' yards, or the dock yards, for the protection 
 of which the harbor defenses were designed. Or, ignoring the 
 seacoast cities and utilities, he may make a campaign against our 
 interior cities and country. 
 
 The first of these possibUities, the. landing of the enemy and his 
 then attacking our seacoast defenses from the land side, is one which 
 should of course be prevented, and this can be done only by the con- 
 struction of defenses on the land side of our seacoast forts. The 
 second possibiUty, an attack by the enemy upon the cities and 
 utilities protected by seacoast defenses, can only be successfully 
 combatted by the construction around such cities and utihties of 
 defenses on the land side, and by the organization and traimng of 
 the troops to man these defenses. The third of these possibiUties^ 
 a land campaign against our interior cities, can be prevented only 
 by the organization and formation of proper land forces. 
 173341—20 28, 
 
434 
 
 As was stated in one of the earlier chapters, most of the seacoast 
 defenses existing prior to our Civil War were provided on their land 
 side with regular defenses against land attacks. The forts then built 
 were usually closed works. On their seacoast sides they were 
 designed to combat ships, while on their land sides they were de- 
 signed so as to be able to resist land attacks, even up to a regular siege. 
 This form of design was rendered possible by the short range of the 
 guns of the day^ 
 
 Unfortunately, in the batteries and emplacements constructed 
 since the Civil War, provisions for defense on the land side would 
 appear to have been somewhat neglected, probably for the reason that 
 the increased range of artillery had caused land operations to be so 
 extensive that land defenses located close to or immediately in the 
 rear of seacoast batteries would be practically valueless, as an enemy 
 could probably put such batteries out of commission by land guns 
 emplaced at a considerable distance in the rear. Consequently, to 
 be of value the land defenses provided would have to be not defenses 
 of the seacoast batteries themselves but rather land defenses for 
 protecting the .entire group of seacoast forts, and not improbably 
 including within the defensive lines cities and other utilities. 
 
 Beginning some five or ten years ago, however, the question of th« 
 land defense of our seacoast forts, and of the cities protected by themj 
 began to again receive the attention which its importance demands. 
 Boards were appointed for drawing up the defaisive hnes, for laying 
 out the defensive works, and for gathering together data as to the 
 personnel and material necessary for such land defenses.. Much 
 information of this kind has been gathered together and placed 
 where it will be of value. 
 
 Later, beginning with the formation of the War Department 
 Board of Review, Gen. Kingman, then the Chief of Engineers, in 
 submitting to the War Department his views as to the adequacy of 
 any seacoast defense project, began the custom of urging that all 
 seacoast defense projects should be accompanied by provisions for 
 adequate mobile armies for the defense on the land side of the areas 
 supposed to be protected on the sea side by the seacoast fortifications 
 under consideration. In many of his reports, he stated to the Board 
 of Review that his assent to the board's project for the seacoast 
 defenses mentioned was based upon the supposition that before this 
 seacoast defense project could be carried into effect, proper pro- 
 vision would have been made for the organization of the mobile land 
 forces necessary for the land defense. 
 
 The increase in the range of land artillery, shown during the World 
 War to be possible, has made it necessary to move the defensive lines 
 much farther away from the cities than had heretofore been con- 
 sidered necessary, and the increase in the radius of these land line 
 
435 
 
 defense lines has, of course, correspondingly increased their perim- 
 eters and multiplied the points at which the enemy may concen- 
 trate his attack. In the protection of these defensive lines, heavy 
 mobile artillery, moving upon raib-oad tracks constructed ia advance 
 to positions likewise constructed in advance, will doubtless play an 
 miportant part. Such guns, before the enemy shall have landed, 
 may doubtless on occasions be quite useful in assisting in repelling 
 a naval attack against our protected harbors, or in keeping the 
 enemy's naval vessels at a distance from our coasts. 
 
 However, in the opinion of the author, the importance of having 
 certain armanent portable in no way detracts from the necessity of 
 having, in certain locations in our harbors, large guns permanently 
 emplaced. Seacoast guns, once permanently emplaced, are fixed and 
 will be at their proper places when required. On the other hand^ 
 there is always the possibihty that should not be overlooked, that 
 a portable gun, either through our own neglect or as a result of the 
 machinations of the enemy, may have been sent elsewhere and wUl 
 be absent when the need for its use becomes most acute. 
 
 It is the opinion of the author that the recent demands, which have 
 been made by some officers who have recently returned from abroad, 
 that all guns hereafter to be installed in seacoast defenses should 
 not only be portable but should be so mounted as to be capable of 
 all around fire and at any degree of elevation, are somewhat over- 
 drawn. They are in violation of the fundamental principle that 
 any fortification design must necessarily be a compromise between a 
 niimber of confficting elements, and that perfection in any one detail 
 can, in general, be obtained only at the expense of inefficiency in 
 some other items. 
 
 For effective use not only in fixed fortifications but in active land 
 operations as well we must have many guns of many different kinds. 
 We need light rapid fire guns for accompanying the advance of the 
 Infantry in land operations and, to some extent, for combating small 
 boats on the seacoast; we need heavier rapid fire guns for combating 
 on our sea front the secondary armament of naval vessels, and on our 
 land fronts for overcoming the enemy's fortifications and his artillery. 
 Likewise we need heavy guns for combating the heavy guns of the 
 enemy whether on shipboard or on land. No one gun can fulfill all 
 these different functions. 
 
 In oiu" seacoast defenses, every seacoast gun should have some one 
 important function to fulfill, and the gun itself, its carriage, and its 
 emplacement should be so designed as to enable it to perform this 
 one important function most efficiently. If, at the same time and 
 without lessening the ability of the gun to perform its proper function, 
 it can be so mounted and emplaced as to make it capable of perform- 
 ing some other less important functions, so much the better; but 
 
436 
 
 the arrangements made for the performance of these less important 
 functions should never be permitted to interfere with the efficiency of 
 the gun in the performance of its main function.. 
 
 The normal function of a seacoast gun is ordinarily to cover with 
 its fire a certain water area, to prevent an enemy's vessel from enter- 
 ing this water area, or to sink the enemy's vessel if it should attempt 
 to come in. Every detail of the carriage, every detail connected 
 with the emplacement, every detail of its fire-control system should 
 be so designed as to enable the gun to bring to bear on this particular 
 water area the most rapid and most efficient fire possible. If, with- 
 out interferihg with the efficiency of this character of fire, for which 
 the gun was especially designed, the gun carriage or the emplacement 
 can be so designed as to permit the gun to fire on certain land areas 
 also, so much the better, but if the attempt to make it possible for 
 the gun to fire on these land areas results in any decrease in the 
 rapidity or accuracy of the fire of this gun at an enemy's vessel in its 
 particular water area, the real value of the gun must have been 
 reduced. 
 
 In attempting to make it possible for a seacoast gun to fire toward 
 the land, careful consideration should be given as to whether this fire 
 to the rear, if required, will be long-range fire only, or as to whether 
 it will ever be necessary to fire the gun to the rear at zero elevation 
 or at an angle of depression. Long-range fire on certain land areas 
 can usually be made possible without difficulty, but as was shown in 
 describing the tentative designs of future emplacements, all around 
 fire at zero elevation is not possible with any large gun except by a 
 return to the two-story type of battery, with a resulting resort to 
 mechanical means of handling ammunition and a decrease in the 
 rapidity and reliability of ammunition service. This can but make 
 the gun less efficient in the performance of its main function. 
 
 In the opinion of the author, it ,is far from essential that all guns 
 should hereafter be mounted so as to be capable of firing at the maxi- 
 mum range. That some at least of the guns for the defense of any 
 port should be able to fire at the maximum range is of course essential, 
 but this does not necessarily imply that all guns must be capable of 
 this kind of fire. 
 
 Fire at very long ranges where the target is out of sight of the gun, 
 and where position finding is difficult, must necessarily be exceed- 
 ingly erratic and ineft'ective. Little material damage will probably 
 be done by such fire and the effect will be moral only. Nevertheless, 
 to keep the enemy's vessels as far away as possible it is essential that 
 some of our guns should be able to fire at such extreme ranges 
 
437 
 
 If the enemy has reason to believe that in the attempt to make this 
 extreme long-range fire possible we have decreased the efficiency of 
 om- short-range fire, it is not improbable that he might take the some- 
 what small risk of rushing through the area covered by our ineffec- 
 tive long-range fire, into the area where he knows that out short-range 
 fire will likewise be ineffective. If, however, he knows that the 
 closer in he gets the more effective our fire will be, he will surely not 
 dare such a risk. 
 
 It would appear to have been conclusively shown that our heavy 
 disappearing guns can be loaded and fired more rapidly and effi- 
 ciently than is possible with any barbette mounts yet designed. To 
 be sure, the range of guns on disappearing carriages is comparatively 
 limited, say to 25,000 yards, but in the opinion of the author it is 
 not improbable that there are a number of locations in our harbors 
 where it is desirable to continue to mount some of our primary guns 
 on disappearing carriages, even though this somewhat restricts their 
 range, for it will result in making the fire of these guns most rapid and 
 efficient at the ranges at which they are capable of firing. Such guns 
 will, of course, be unable to take part in an action at extreme ranges, 
 but when the time does come, if it ever should, when the enemy ap- 
 proaches within the range of these guns they wOl then be absolutely 
 and thoroughly reliable. Kjiowing such to be the case, it is quite 
 probable that the enemy will never dare to come within their range. 
 
 On a seacoast as extensive as ovirs it is manifestly impossible that 
 we can defend our entire coast. We may defend our most important 
 harbors and commercial centers, but we can not efficiently protect 
 all our smaller ports or the open seacoast between. Where we do 
 build seacoast defenses they should be strongly built, for weak defenses 
 in some respects are worse than none at all. It is much better that 
 we should have a few well defended harbors than a number of weakly 
 defended ports. In fact, our seacoast fortifications should be well 
 planned, well built, and well armed, not so much with a view of de- 
 feating an enemy when he does make an attack as in persuading him 
 not to attack at aU. 
 
 By defending oxir most important harbors the enemy will be per- 
 suaded not to attack them and will be compelled to land his army, if 
 he feels he can accomplish this successfully, on the open coast or at 
 our smaller ports which lack the wharves, the unloading facilities, 
 and the rail connections usually available only at our larger harbors. 
 The landing of enemy under such circumstances and conditions wiQ 
 necessarily be slowly done, and should give time for the concentration 
 of our mobile land forces. 
 
438 
 
 If our seacoast fortifications at any harbor have been so well de- 
 signed and built as to have deterred an enemy from attacking them, 
 to have kept him out of a harbor plentifully supplied with landing^ 
 and dock facilities, and to have forced him to land elsewhere under 
 difficult conditionSj and where proper terminal facilities are lacking, 
 they must be considered to have performed most efficiently the main 
 purpose for which they were designed. Nothing more should be 
 expected or desired of them. In fact, a seacoast fortification may be 
 said to have most efficiently performed the function for which it wa& 
 intended, if it is never called into use at all. 
 
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