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COURSE OF LECTURES 
 
 UPON THB 
 
 DEFENCE 
 
 siA-coAST OF m irao states 
 
 DELIVERED BEFORE THE 
 
 U. S. NAVAL WAE COLLEGE 
 
 BVT. BRIG.-GEN. HENRY L ABBOT, U. S. ARMY 
 
 Colonel Corps of Engineers 
 
 NOVEMBEE, 1887 
 
 NEW YORK 
 D. VAN JSrOSTI^AND 
 
 23 MUKRAY AND 27 WARREN STREET 
 1888 
 

 Copyright, 1888, 
 Bt W. H. FARRINGTON". 
 
 ^33 4^/ 
 
CONTENl'S. 
 
 FIRST LECTURE. 
 
 GENERAL CONSIDERATIONS. 
 
 Introduction — The Art of War as Applied to Coast Defence ; Strat- 
 egy; Grand Tactics ; Logistics ; Art of the Engineer — Proba- 
 ble Nature of the Attack ; Needful Calibres ; Number of Guns; 
 Guns Ashore and Guns Afloat ; Naval Tactics against Forts 5-40 
 
 SECOND LECTURE. 
 
 ECONOMY IN COAST DEFENCE. 
 
 Limit of Judicious Outlay — Economic Value of Different Elements; 
 General Analysis ; Case of Non- Disappearing Barbette Mount- 
 ing; Case of the King Mounting for 50-Ton 12-Inch Rifles; Case 
 of the Duane Lift ; Case of an Armored Casemate ; Case of a 
 Revolving Turret ; General Conclusions 41-6G 
 
 THIRD LECTURE. ^ 
 
 SELECTING THE SITE ; HORIZONTAL FIRE. 
 
 Sites to Prevent Bombardment or to Cover Anchorages — Sites to 
 Prevent a Forced Passage ; Height and Character of the Posi- 
 tion ; Development of Front ; Submarine Mine Requirements — 
 Horizontal Fire ; Range and Position Finders ; Revolving Tur- 
 rets ; Armored Casemates ; Lifts ; Disappearing Gun Batteries; 
 Non-Disappearing Gun Batteries ; Flanking Guns for Mined 
 Zones ; Magazines 67-101 
 
 FOURTH LECTURE. 
 
 MORTARS AND SUBMARINE MINES. 
 
 Vertical Fire ; Advantages of Rifling ; Carriages and Platforms ; 
 Mortar Batteries ; Economy of Mortars— Submarine Mines ; 
 General Conditions ; Attacks by Daylight ; Attacks by Night or 
 in Fogs ; Attempted Passage by Force 102-134 
 
 FIFTH LECTURE. 
 
 SEA-COAST FORTRESSES. 
 
 Historical Resumfi of Coast Defence in America— Resistance to 
 Projectiles ; Armor ; Masonry ; Earth — Approximate Formu- 
 lae— Fortification of the Site Selected— Naval Co-operation. 135-1 64 
 
First Lecture, 
 
 GENERAL CONSIDERATIONS. 
 
 Introduction— The art of war as applied to Coast Defence ; strategy ; 
 grand tactics ; logistics ; art of the Engineer — Probable nature of 
 the attack ; needful calibres ; number of guns ; guns ashore and 
 guns afloat ; naval tactics against forts. 
 
 In accepting the invitation to lecture before the 
 Naval War College on our Coast Defences, I duly- 
 appreciated not only the courtesy extended by it to 
 the body of Military Engineers which I represent, but 
 also the assistance to be received from an interchange 
 of views upon debatable points where the duties of 
 the land and naval forces follow parallel lines and 
 demand mutual co-operation of the most cordial 
 character. Good cannot fail to result from dropping 
 occasionally the technical study of our respective 
 specialties, and taking a general view of what is 
 needed by the country to prevent its thousands of 
 miles of coast line from opening to an enemy modes 
 of attack where heavy blows may be delivered with 
 little risk, and where decisive results may be at- 
 tained without affording us a chance of bringing our 
 power as a nation to bear. 
 
 The great mass of our population is now, and 
 from the nature of things must remain, ignorant of 
 the requirements of National Defence. The duty of 
 considering what should be done, and how it should 
 be done, has been devolved upon a little band of pro- 
 fessional Army and Navy men, largely graduates of 
 West Point and Annapolis, small in numbers and 
 
6 General Considerations. 
 
 with no ready mode of interchanging views. Yet we 
 are expected to elaborate a wise and comprehensive 
 system of coast defence ; and when the evil day 
 comes we shall justly and mercilessly be held re- 
 sponsible if, blinded by professional technicalities, 
 we have failed to grasp the problem in its entirety. 
 We are too much tempted to forget that our respon- 
 sibility is by no means limited to details. We are 
 expected to form broad and harmonious views of 
 what the Nation needs ; and only in this way shall 
 we secure for our opinions that weight which unan- 
 imity among experts always carries with intelligent 
 men who feel themselves to lack technical informa- 
 tion. What the Army and Navy agree in recom- 
 mending will not be lightly thrust aside ; and I know 
 of no better mode of inducing unanimity of opinion 
 than the plan of mutual co-operation in study intro- 
 duced by the founders of the Naval War College. 
 
 In preparing these lectures I have borne in mind 
 the professional character of the audience, which 
 wrould render details on such subjects as modern 
 ^uns, modern armor, modern torpedoes, and subma- 
 Tine mines as wearisome as a twice-told tale ; they 
 will only be touched upon when necessary to make 
 my meaning clear. On the other hand, it would tax 
 your patience to spend time in elaborating details of 
 land construction, such as foundations, strength of 
 materials, and other technicalities of the profession 
 which, of vital importance to the constructor, can 
 have no interest to a naval officer. In a word, I shall 
 try to present the general subject of Coast Defence 
 from the point of view of an Army Engineer, omit- 
 ting technicalities with which you are familiar and 
 also those in which you have no interest. In return 
 I shall be grateful for suggestions as to any matters 
 which may appear doubtful as seen from a naval 
 point of view. 
 
Art of War Applied to Coast Defence, 
 
 THE ART OF WAR AS APPLIED TO COAST DEFENCE. 
 
 General Brialmont justly observes in his latest 
 treatise on Fortification that the defence of a sea-coast 
 resembles that of a chain of rugged mountains. At 
 most points it is unassailable. The few deep bays 
 and mouths of rivers, which have attracted commerce 
 and caused the erection of cities and the establish- 
 ment of dock-yards and naval stations, are like the 
 natural passes through the mountains that have 
 created the roads and villages by which the enemy 
 must move to the attack. 
 
 There is, however, a marked difference in the na- 
 ture of this attack. The army advances like a swarm 
 of ants, imposing in numbers but weak in individual 
 power ; the fleets approach like a platoon of ele- 
 phants in the days of Alexander, terrible as individ- 
 uals, but few in number and handicapped by difficul- 
 ties in the use of their weapons. 
 
 It is only two centuries since admirals stepped 
 from the qaarter-deck to command armies in the 
 field, and since generals won victories upon the 
 water by applying land tactics. The Services have 
 long been distinct, but it does not follow that we 
 may not still derive mutual benefit by approaching 
 this problem of coast defence from our different 
 standpoints, and applying principles learned in dif- 
 ferent fields of duty. 
 
 This is the more true because works of coast de- 
 fence are less a matter of pure fortification than an 
 application of technical details which are becoming 
 more complex from year to year. The Engineer 
 charged with planning them is compelled to study 
 the subject somewhat from a naval standpoint, be- 
 cause the arrangements of all defensive works are 
 regulated by the mode of attack; and the latter, 
 which has undergone radical changes in the last few 
 
8 General Considerations. 
 
 years, is, in the absence of actual experience in war, 
 still far from being detinitely established. Neverthe- 
 less, in its general features, Coast Defence is a prob- 
 lem to which many rules derived from land opera- 
 tions are applicable. 
 
 The Art of War is usually subdivided by military 
 writers into five principal branches : Strategy, Grand 
 Tactics, Logistics, Elementary Tactics, and the Art 
 of the Engineer. Kules of each of these branches, 
 except perhaps of Elementary Tactics, find an appli- 
 cation more or less important in the problem of Sea- 
 Coast Defence. 
 
 Strategy. — The art of making war upon the 
 map is especially concerned with the selection of the 
 points for permanent occupation, and with the opera- 
 tions of the fleets which in coast defence represent 
 the movable forces of the Nation. No principles are 
 better established than (1) that the mass of our forces 
 should be thrown upon fractions of the enemy ; (2) 
 that, so far as practicable, we should operate upon 
 his communications without endangering our own ; 
 (3) that the effort should be energetic and in concert 
 throughout the theatre of war ; and (4) that even in 
 a defensive campaign vigorous offensive operations 
 should never be neglected when practicable. 
 
 Every principle of strategy is therefore violated 
 in adopting for sea-coast defence a plan which con- 
 templates the leaving of our important strategic po- 
 sitions without permanent fortifications, and looking 
 to defending them by fractions of our Navy shut up 
 in them at the outbreak of war. Such a project 
 would find its parallel in an army subdivided, in- 
 terned in strong places, and left to be overmastered 
 successively by the united strength of the enemy. 
 All experience in land campaigns warns us that by 
 such a system defeat would be assured before the 
 first gun was fired. 
 
Art of War Applied to Coast Defence, 9 
 
 From this point of view it is evident that in se- *^ 
 lee ting the positions on our sea- coast to be perma- 
 nently defended, we must have regard not only to 
 security for our navy-yards and depots, for our 
 great fleet, of coastwise trading vessels, for our im- 
 portant cities — in a word, for the points which a 
 hostile fleet bent on scourging us into accepting 
 peace by inflicting pecuniary damages would select 
 for attack — but also to providing safe rendezvous for 
 our fleets whence they can sally at will to assume 
 the offensive. 
 
 The necessity of leaving our fleets free to carry, so 
 to speak, the war into the enemy's country whenever 
 occasion offers, is no new theory resulting from the 
 peculiar conditions of sea-coast defence to-day. The 
 idea was urged in the Senate by Mr. Webster, with 
 his usual eloquence, in 1838 ; and was so well ex- 
 pressed by Admiral Dupont in 1851 that I cannot do 
 better than quote his exact language. He wrote : 
 
 " I beg leave to express an emj^hatic dissent from 
 all theories having for their object the substitution 
 of active ships of war for permanent works. This 
 would be placing the Navy in a false position before 
 the country ; giving it duties to x)erform for which 
 its organization is inapplicable ; preparing for its 
 future discredit and loss, through failures to execute 
 that which should never have been undertaken, 
 which is not embraced in the general scope and de- 
 sign of a naval establishment. 
 
 ''To retain the Navy for harbor defence was en- 
 tertained at the commencement of the last war with 
 England ; the proposition to do so sx3rung from the 
 apprehension that it could not compete with the 
 vastly superior English force upon the ocean. But 
 at that time some brave and sagacious officers in the 
 high ranks saved the Navy from the fate that threat- 
 ened it, and to these gentlemen it owes all its sub- 
 
10 General Considerations. 
 
 sequent honors, usefulness, and prosperity. If any 
 such ideas prevail at this day, in or out of the ^yo- 
 fession, those holding them would do well to pause 
 and consider wliat the Navy would have lost, and 
 what the country would have lost, if our ships of war 
 had at that eventful period been deprived of the op- 
 portunity of filling so bright a page in the Nation's 
 history by their achievements ui)on the ocean." 
 
 These opinions as to the true strategic functions of 
 the Navy are now, it is believed, generally accepted, 
 and plans for coast defence should be so arranged as 
 to give them full effect wherever possible ; ^.e., any 
 complete system must be planned to furnish safe 
 bases along the coast from which offensive operations 
 can be undertaken and in which security may be 
 found in the event of disaster. 
 
 This matter was carefully considered by the Endi- 
 cott Board of 1886, and provision was made for such 
 rendezvous at Portland, at Boston, at Narragansett 
 Bay, at New York, at the Delaware, at Hampton 
 Roads, at the mouth of the Mississippi, and at San 
 Francisco ; /.e., at eight of the eleven ports at which 
 fortifications were reported as ''most urgently re- 
 quired." Great Britain has already prepared two 
 such rendezvous in our waters for her own use — one 
 at Halifax and one at Bermuda ; and rumor reports 
 that she has another in view in the near future at 
 Victoria. 
 
 Strategic considerations of a special character are 
 suggested in connection with Portland Harbor ; they 
 give it a prominence to which the wealth and import- 
 ance of the city itself could advance no claim. It is 
 the terminus of the Grand Trunk Railroad and the 
 natural winter outlet of the Dominion of Canada. 
 Its importance is iDerfectly appreciated by Great 
 Britain. Colonel Strang, R.A., in a lecture before 
 the Royal United Service Institution in 1879 used the 
 
Art of War Applied to Coast Defence. 11 
 
 following language : ^'Without the Canadian Pacific 
 Canada is a cul-de-sac. The struggling nationality- 
 resembles a young giant whose careless parents al- 
 lowed one nostril to be stuffed up by the loss of the 
 unfrozen seaports of the State of Maine ; and now,, 
 after giving up Oregon and the San Juan passage, 
 that other Canadian nostril, we are threatened with 
 the secession of British Columbia, which can neither 
 be defended nor traded with. . . . Fortunately at 
 Halifax we have retained some of the ultimce rationed 
 regum et populorum. We need not, therefore, discuss 
 the defence of this fortress and harbor, which, how- 
 ever valuable in other senses, can in no sense be 
 considered a safe base for operating in the inland 
 defence of Canada ; for the treaty of 1842, which 
 handed over the State of Maine, sends a wedge of 
 territory up to within a few miles of the inter- colo- 
 nial railroad which a handful of troopers could at 
 any moment render unserviceable in a night, thus 
 cutting off retreat to Halifax or succor from thence 
 to the upper provinces. It is true that detachments 
 were sent from Halifax during the Trent diiSculty ; 
 but the United States were at that time disunited 
 States." 
 
 The value of Portland as a temporary British 
 naval station during a war with the United States 
 would be sure to attract attention ; and if, in case of 
 heavy American reverses, our opponent should be in 
 a position to demand a land indemnity as one of the 
 conditions of peace, as did Germany in the late war 
 with France — to whom the idea doubtless seemed as 
 preposterous at the outset as it does to us to-day — 
 probably no section of the country would be so likely 
 to be desired as this magnificent port. For this rea- 
 son it behooves us to hold it strongly against any 
 possible attack. If Metz and Strasbourg had been 
 unoccupied by a German army when fehe terms of 
 
12 General Considerations. 
 
 peace were agreed upon, they might have escax)ed 
 their fate. 
 
 The strategic importance of Boston in a naval war 
 is self-evident. A small force here would cover the 
 entire coast from Cape Cod to New Brunswick 
 against marauding expeditions detached from a 
 fleet operating against New York. It forms the 
 natural base for fitting out offensive operations 
 against Halifax and the St. Lawrence. Lastly, when 
 properly defended, it would afford refuge to the whole 
 fleet of New England fishing and coasting vessels. 
 
 Narragansett Bay covers the entrance to Long 
 Island Sound and all the small harbors on its shores. 
 An enemy passing Montauk Point would leave his 
 communications at the mercy of a much smaller fleet 
 lying here behind land defences affording security 
 against direct attack. Gardiner's Bay, at the east- 
 ern end of Long Island, would be perhaps a better 
 position ; but it is not so easily defended by forts, 
 and it lacks the importance of Narragansett Bay in 
 other respects. Admiral Simpson, in whose profes- 
 sional judgment I have great confidence, has always 
 urged the importance of a large naval establishment 
 at New London, not only from its natural advan- 
 tages, but also from its strategic relations to Long 
 Island Sound. Should such an establishment ever 
 be created there, the' local question of its land de- 
 fences would be simple. 
 
 The supreme importance of New York, the com- 
 mercial metropolis of our Atlantic seaboard, is un- 
 questioned. No demonstration is needed either as 
 to the necessity of local defence or as to the facilities 
 the port offers for offensive sallies in every direction. 
 
 Hampton Roads bear to Chesapeake Bay a rela- 
 tion similar to that of Narragansett Bay to Long 
 Island Sound. A small force driven from the ocean 
 by a superior fleet could take refuge behind a forti- 
 
Art of War Applied to Coast Defence. 13 
 
 lied line based on Fortress Monroe, and from this 
 secure position could threaten the passage between 
 the Capes so effectually that no enemy could afford 
 to operate against Baltimore or Washington without 
 leaving behind at least an equal detachment to cover 
 his only route of communication witli the ocean. 
 
 The lleet charged with the general defence of the 
 Gulf Coast would find its principal base on the Mis- 
 sissippi ; where, stationed centrally, it could operate 
 at any point between the Capes of Florida and the 
 Rio Grande so soon as the telegra|)h made the ap- 
 proach of the marauders known. It goes without 
 saying that, in case of a war with Spain, Key West 
 would become a place of great strategic importance 
 by reason of its vicinity to Cuba, and the facilities 
 it offers as a base for land operations against that 
 island and for blockading its coasts. Controlling 
 as it does the narrow channel leading from the South 
 Atlantic Coast to the Gulf of Mexico, it must be 
 firmly held in any maritime war, and especially in 
 one with France or Great Britain, which have pos- 
 sessions in the West Indies. 
 
 The relations of San Francisco to the Pacific 
 Coast are similar to those of New Orleans to the 
 Gulf of Mexico ; and in addition it would be our base 
 for any offensive operations on the Pacific, at least 
 until a new fortified position at Puget Sound is de- 
 manded by the growth of population in that direc- 
 tion. 
 
 These views as to the strategic points along our 
 seaboard are based upon three beliefs : (1) that it 
 will be long before we shall have a Navy strong 
 enough to carry the war across the Atlantic and thus 
 keep the enemy at home ; (2) that present indications 
 of awakened interest warrant the opinion that we 
 shall soon have a Navy which, if afforded secure 
 points of refuge, would by frequent sallies make its 
 
14 General Considerations , 
 
 influence felt against an attacking fleet too strong to 
 be faced in a pitched battle, thus extending indirect 
 protection to the small ports along our entire sea- 
 coast ; and (3) that if we neglect to prepare these 
 places of refuge, our new Navy may be swept from 
 the ocean, as was the Huascar^ or may be ignomi- 
 niously captured in our harbors, as happened to the 
 Danube squadron in the late Russo-Turkish war, 
 and as has happened to fleets again and again in 
 days gone by. 
 
 If we should fritter away our resources in con- 
 structing armored ships with a view to chaining 
 them in harbors where local conditions make a land 
 defence more economical — and this statement is true 
 for all our ports except San Francisco and the mouth 
 of the Mississippi — we should not only waste money 
 but should also create a Navy ill-suited to perform 
 the duties which sound strategic principles demand 
 of that arm of the service. In my judgment, the 
 Navy, like cavalry, loses half its power if not threat- 
 ening the offensive. 
 
 I make no reference to the strategic use of tor- 
 pedo-boat flotillas, because I am not sufiiciently in- 
 formed as to their ability to keep the sea in tempes- 
 tuous weather, concerning which there appears to be 
 some difference of opinion since the recent French 
 evolutions. Of one thing, however, I am sure. 
 These boats will play a very imi)ortant part in con- 
 nection with our projected land defences, as will be 
 more fully elaborated hereafter. 
 
 Grand Tactics. — Grand tactics treat of the art 
 of well combining and well conducting battles. In 
 the shock of armies manoeuvring for position much 
 is necessarily left to chance, because neither com- 
 batant is possessed of the plans and views of his op- 
 ponent, and accident or lack of time may compel the 
 neglect of well- recognized rules. A seaport to be 
 
Art of War Applied to Coast Defence. 15 
 
 fortified sliould be carefully studied in advance, and 
 with ample time and means no such mistakes are 
 justifiable. 
 
 On land the weak positions of a line of battle are 
 usually the flanks ; and if the line be too strong and 
 well occupied for a front attack, the assailant usually 
 manoeuvres to turn one of them. But when the 
 enemy is confined to his ships he can move only by 
 navigable channels ; we may with certainty foresee 
 what, if any, flank ox)erations will be practicable, 
 and by preparing to meet them may compel him to 
 either attack where we have carefully prepared a 
 battle-field .to give us every advantage, or, as has 
 often happened, to abandon his intention of attack- 
 ing. This latter sliould he the aim of the Engineer 
 in fortifying a harhor^ for it is an accepted principle 
 never to seek a battle unless the chances of advan- 
 tage which will accrue in case of success shall pre- 
 ponderate over the chances of loss if defeated ; and 
 this condition can rarely if ever be fulfilled in a bat- 
 tle fought to prevent the occupation of an important 
 harhor by a hostile fleet. 
 
 The maxims of grand tactics applicable to coast 
 defence teach us the following : (1) to provide for of- 
 fensive movements of our own torpedo-boats, and of 
 our armored ships if any be present. This princi- 
 ple forbids the closure of channels by obstructions 
 which cannot be passed by our own vessels ; (2) to so 
 place our land guns as to assure their mutual sup- 
 port and their most effective service against the 
 enemy. Mutual support is important to prevent the 
 overwhelming of one battery by the concentration of 
 superior fire, which is always to be expected in a 
 deliberate attack. In discussing the defences of 
 Spezzia the Italian engineers laid great stress upon 
 this point ; and a position which would permit an 
 enemy to bombard the docks and navy-yard at a 
 
16 General Considerations . 
 
 range of only 4.6 miles was advocated, and I think 
 has been adopted, rather than secure a longer range 
 at the expense of exposing isolated turrets to a con- 
 centric fire ; (3) to guard well the flanks by closing 
 all unnecessary channels, and thus compel the enemy 
 to make a direct attack or to make none at all — the 
 application of this principle has been already con- 
 sidered ; (4) to provide means for offensive returns 
 against countermining oj)erations in the absence of 
 torpedo-boats of our own. This is the true function 
 of movable torpedoes operated and directed from the 
 shore. A purely passive defence, whether on land or 
 sea, is rarely successful. 
 
 Logistics. — This branch of the art of war is con- 
 cerned with the preparation in advance, with the pro- 
 per storage, and with the transportation of all ma- 
 terial needful for use in connection with the opera- 
 tions of an army. In sea-coast fortification it has to 
 do with supplies of all kinds, and with preparations 
 to receive and store them. Thus magazines and 
 shell-rooms ample to contain the immense quantities 
 of ammunition demanded by modern guns, and, yet 
 absolutely bomb-proof, are a necessity. Bomb-proof 
 cover for the garrison, the stores, and the military 
 material ; safe covered passages for the movement of 
 ammunition in action ; protected routes for introduc 
 ing the electric cables of the submarine mines ; and 
 many other matters too numerous to mention, per- 
 taining to the domain of logistics, press upon the 
 attention of the military engineer. The Navy has 
 troubles of its own of a like character ; but I think 
 neither branch of the service has much to learn from 
 a study of rules in logistics evolved from the expe- 
 rience of armies in the field. 
 
 The Art of the Engineer. — This branch of the 
 art of war, which as applied to coast defence includes 
 locating, planning, and constructing the fortifica- 
 
Art of War Applied to Coast Defence. 17 
 
 tions, largely forms the subject of these lectures. It 
 calls for an appreciation of the power and of the 
 weakness of modern ships of war, of modern ord- 
 nance and torjDedoes, and, in general, of the most 
 effective and economical methods of securing every 
 possible advantage to the defence by applying such 
 means as are available. Each element must be con- 
 sidered and weighed as to its relative cost and rela- 
 tive efficiency. The funds allotted to sea-coast de- 
 fences by all nations are limited, and what is wasted 
 in injudicious expenditure will certainly be sub- 
 tracted from some needful outlay. For example, 
 nothing could be easier than to make an impregnable 
 fort if cost were left out of consideration. Armor- 
 plates, whether steel, or compound, or wrought iron, 
 or chilled cast iron, can be made thick enough to 
 keep out the projectiles of any gun now existing or 
 which ever can exist. If three feet of armor will not 
 do it, ten feet will. There is no limit to the secu- 
 rity attainable in a land battery, where any weight 
 whatever can be supported. But the skill of the 
 engineer lies in a judicious estimate of what is need- 
 ful and of what is superfluous, and in making his 
 plans and applying his funds accordingly. 
 
 This principle has always governed the Engineer 
 Department. By skilfully applying it to a problem 
 all the elements of which were then known and ad- 
 mitted of computation. General Totten was able to 
 give to the country what at their date were perhaps 
 the most perfect sea-coast fortifications the world has 
 ever seen, and to accomplish the task with funds 
 which Congress was willing to grant. 
 
 But this is the age of progress. The introduction 
 of the screw-propeller led to the use of guns throw- 
 ing shells which no ships could endure, and hence 
 to the introduction of armor. Then followed the long 
 struggle for supremacy between ordnance and armor, 
 
18 General Considerations. 
 
 which unsettled all ideas and made the problem one 
 rather of prophecy thali of knowledge. This was the 
 condition at the close of the civil war. It was the 
 judgment of the best officers of the Corps of En- 
 gineers, shared and carried into effect by Gfeneral 
 Humphreys, that the time was ill-suited for the selec- 
 tion of a permanent system ; but that all funds avail- 
 able could be wisely applied to inaugurating a system 
 of earth- works which would meet the needs of the 
 moment and would remain useful when a more defi- 
 nite estimate of what could be accomplished in ar- 
 mored ships and ordnance was possible. 
 
 This time has now come — at least as to the essen- 
 tial elements — and it is my purpose in these lectures 
 to consider each point in sufficient detail to give a 
 fair idea of the proposed system, from the point of 
 view of a military engineer. 
 
 It should be understood at the outset that the de- 
 fence of each important locality forms a study in it- 
 self. Nature has nowhere given us sites combining 
 every desirable feature. The Engineer must avail 
 himself of every natural advantage to the utmost, 
 and must deal with natural defects in such a manner 
 as to secure the maximum of strength at the mini- 
 mum of cost. 
 
 This mode of approaching the subject reveals the 
 base metal of which many theories of defence are 
 constructed. One savant informs us that inexpensive 
 submarine mines, easily improvised, are sufficient to 
 close any harbor ; another proposes movable torpe- 
 does under control from the shore, or from armored 
 rafts at anchor, as the needful panacea ; another 
 simply advocates a line of turrets, armed with mod- 
 ern high-power guns ; another finds a perfect de- 
 fence in a few disappearing guns fired from pits ; 
 another would trust to a swarm of torpedo-boats of 
 the approved type ; while another pins his faith 
 
Art of War Applied to Coast Defence. 19 
 
 solely upon a fleet of armored ships of war. The 
 truth is, such crude assertions, stamp the utterer as 
 a military quack. All of these devices, and others, 
 find useful applications ; but as soon as a serious 
 study of our harbors is made it becomes apparent 
 that there are locations where, so far from being suf- 
 ficient, each of them in turn is quite inapplicable. 
 There is no medicine which will cure all the ills to 
 which flesh is heir ; and the same is eminently true 
 of an exposed sea-coast. To-day a satisfactory solu- 
 tion can in general be secured only by a complex 
 combination of many elements, varying according to 
 locality to an extent which forbids any summary not 
 •couched in the most comprehensive terms. Each 
 individual case must be discussed on its own 
 merits. 
 
 In general, an important seaport well defended 
 implies : (1) the effective obstruction of all water ap- 
 proaches against the enemy, leaving free entrance 
 and exit for our own vessels ; (2) protection for these 
 •obstructions, and security for their operators and 
 their flanking guns against escalade by boat parties ; 
 {3) so heavy a fire of modern high-power guns and 
 mortars over all the approaches as to defy the most 
 powerful armored fleet able to operate in the chan- 
 nels leading to these auxiliary defences ; (4) a heavy 
 flanking flre of medium and small projectiles over 
 the obstructed zone; (5) provision for offensive re- 
 turns against armored counterminers ; (6) the power 
 ■of illuminating the obstructions by night, so far as 
 this is physically possible ; (7) a swarm of torpedo- 
 Iboats which, safe behind the barrier, are always 
 ready to sally out and carry the war to the enemy's 
 fleet when favorable opportunities occur. 
 
 Harbors of minor importance may be sufficiently 
 -def ended upon less elaborate systems ; but at the 
 ports which the Fortification Board of 1886 reported 
 
20 General Considerations. 
 
 as " most urgently requiring defences" it would be 
 criminal to neglect any of those named. 
 
 The first matters for consideration in deciding 
 how any particular position shall be fortified are the 
 calibres and numbers of the heavy guns needful to 
 overpower the enemy's fire. These will be determin- 
 ed in accordance with our estimate of what he can 
 bring to the attack, and what tactics will probably be 
 adopted in making it. 
 
 I naturally feel some difladence in discussing this 
 branch of my subject before Naval experts ; but as 
 the question is a vital one for Army engineers, I 
 shall undertake the task, hoping to receive candid 
 criticism as to any points concerning which my con- 
 clusions may appear to be at fault. 
 
 PEOBABLE NATURE OF THE ATTACK. 
 
 The calibre of the land guns must be sufficient to 
 pierce the armor of the enemy at a two-mile range, 
 and to compete with his artillery on at least equal 
 terms. His possible armament and armor are both 
 fixed by the available depth of water in the channel 
 of approach. Since the guns of most modern ships 
 will pierce the armor they carry at considerable 
 ranges, a rough estimate of what calibres we should 
 provide may be formed by studying the armament of 
 modern ships in connection with their draught and 
 the depth of water in the channel to be defended. 
 
 Needful Calibres. — Thus, taking the British 
 Navy as an example, the Benhow, Renown, and Sans- 
 pareil each carry two 110- ton B. L. guns, with from 
 ten to thirteen 6-inch or larger high-power guns. 
 They all draw 27 feet. No vessel with a less draught 
 is now armed with 110- ton guns. The ColUngwood, 
 Conqueror, Hero, Colossus, and Edinburgli each, 
 carry either four or two 12-incli 43-ton guns, with 
 
Probable Nature of the Attack, 21 
 
 four, five, or six high-power 6-inch guns ; and the 
 Inflexible^ four 16-inch 80-ton guns. Their draught 
 ranges from 24 feet to 26 feet. The belted cruisers 
 Orlando^ Undaunted,, Australia,, Narcissus^ and 
 Galatea each carry two 9.2-inch 18- ton guns, and ten 
 high-power 6-inch guns. Their draught is 22>^ feet. 
 As a rule no armored ships draw less than 20 feet, 
 except the so-called Coast Defenders, which draw 
 about 18 feet ; but unarmored cruisers drawing only 
 16 feet could, in the present condition of our sea- 
 coast armament, work great destruction at ranges 
 where our gtins would be powerless to reply. This 
 class carries about 10 guns, varying between 9 inches 
 and 6 inches in calibre ; and a swarm of gunboats 
 drawing less than 16 feet carry muzzle-loading 10- 
 inch 18-ton guns. 
 
 No discussion of the power of these guns is need- 
 ful here ; I will only recall that their muzzle energies 
 are approximately as follows : 
 
 That of the 16j<-inch llO-ton B. L. gun is 57 000 
 foot-tons. 
 
 That of the 16-inch 80-lon M. L. gun is 30 000 
 foot-tons. 
 
 That of the 12-inch 46-ton B. L. gun is 24 000 
 foot-tons. 
 
 That of the 12-inch 43-ton B. L. gun is 15 000 
 foot-tons. 
 
 That of the 9.2-inch 18-ton B. L. gun is 9 000 foot- 
 tons. 
 
 That of the 10-inch 18-ton M. L. gun is 5 000 foot- 
 tons. 
 
 That bf the 6-inch 4-ton B. L. gun is 2 500 foot- 
 tons. 
 
 The estimate to be placed upon the offensive 
 power of these guns will of course depend upon the- 
 nature of the proposed works ; for example, a 6-inch 
 gun, little to be feared by a turret or an armored 
 
 u 
 
22 General Considerations. 
 
 casemate, might by its rapidity of fire be more for- 
 midable against an exposed barbette than even a 100- 
 ton gun. In such cases shrapnel-fire becomes spe- 
 cially dangerous. Its effect is terrible, provided the 
 projectile be exploded at exactly the right place ; 
 fortunately for open barbettes, precision of fire is 
 diflBcult to secure on shipboard, and no perfect time- 
 fuse exists. 
 
 Another element of the armament of modern ships 
 must not be forgotten — the rapid-firing and machine 
 guns. Their record at Alexandria was a poor one, 
 but improvements are constantly making and they 
 will certainly be brought against forts. The best de- 
 fence is shoal v^ater or submarine mines, which for- 
 bid approach within a thousand or twelve hundred 
 yards' range ; but wlien it is not possible to secure 
 this advantage, guns on low sites, without cover dur- 
 ing loading, must be regarded as of little value. 
 
 After studying the map of the entrance to be de- 
 fended, in connection with lists of war-ships, which 
 for all navies are easily accessible, the engineer can 
 form a fair estimate of the calibres of the guns likely 
 to be brought against him. Two points should not 
 be forgotten : (1) Coast Defenders of comparatively 
 little draught can carry the largest modern guns, and, 
 although they would not be allowed to leave their 
 regular posts of duty in a war with a formidable 
 maritime power, they may be expected on our shores 
 for many years to come ; and (2) the moral effect of a 
 few land guns of larger calibre than any carried by 
 the fleet is very great. The influence of General Tot- 
 ten was powerfully exerted to secure the introduction 
 of the 15-inch S. B. gun when that was supposed to 
 be quite beyond the ability of ships to carry ; the 
 ^'largest gun possible" is a time-honored maxim 
 with us, and I think the projects of the Corps of En- 
 gineers for our chief harbors will always provide for 
 
Probable Nature of the Attack. 23 
 
 a few of tlie most powerful guns which the genius of 
 the age can fabricate successfully. 
 
 As stated above, our largest guns should at least 
 be able to pierce the armor of the enemy at a two- 
 mile range. This limit is adopted, partly because 
 ships must approach to that distance to seriously an- 
 noy land guns properly mounted; partly because, with 
 ships and forts more or less shrouded in smoke, pre- 
 cision of fire on our part is not to be expected at 
 longer ranges ;. and partly because the area of the 
 ship protected by her heaviest armor forms but a 
 small per cent, of that exposed to our blows, and she 
 may receive great injury from shots powerless to 
 pierce her at the water-line. 
 
 Number of Guns. — The next point for conside - 
 ration is the number of the guns likely to be brought 
 against the port under study, by the most powerful 
 enemy. The number which a single vessel of each 
 class carries has already been noted ; the present 
 question is therefore restricted to the local problem 
 of how many ships can be placed in position. For 
 ports of the first class the basis of the estimate 
 should be the full strength of possible attack ; for 
 ports of minor importance the Engineer will be guid- 
 ed by his judgment as to the size of the fleet likely to 
 be detached for the purpose. 
 
 The determination of the length of the front of 
 attack is a simple matter of map and dividers. Draw 
 circles with radii varying from one to three miles, 
 the centre being the fort under consideration, and 
 note the lengths which fall upon water of sufficient 
 depth and otherwise suitable for occupation by war- 
 ships. The probable distance and the maximum de- 
 velopment of the attack can thus be estimated with 
 precision. 
 
 How near together the ships can be safely manoeu- 
 vred will depend upon the strength of the current 
 
24 General Considerations. 
 
 and the nature of the channel, whether clear or ob- 
 structed by shoals, reefs, or suspected torpedoes. 
 At Alexandria, where there was no need of crowding, 
 about four ships occupied one mile. At Charleston, 
 on April 7, 1863, the monitors in a difficult channel 
 formed at intervals of "one cable length," or at the 
 rate of about eight monitors per mile. At the attack 
 on Fort Fisher on December 24-25, 1864, as well as 
 that of January 13, 1865, the favorable position and 
 calm weather offered exceptionally advantageous 
 conditions to the fleet. The monitors were ordered 
 to be anchored '^not more than one length apart." 
 The diagram accompanying Admiral Porter's official 
 report of the final attack indicates that the first line 
 (14 vessels) occupied a development of three-quarters 
 of a mile ; the second line (12 vessels) a development 
 of three-quarters of a mile ; and the third line (14 
 vessels) a development of one mile. The diagram of 
 the December attack (which formed part of the offi- 
 cial order for the engagement) does not materially 
 differ in respect to length of development. The Ad- 
 miral evidently designed to deploy his vessels at the 
 rate of about fifteen to the mile. 
 
 These facts, I think, warrant the conclusion that 
 the larger ships of war of to-day, under the most 
 favorable conditions, may be expected to deploy in a 
 single line at the rate of about ten to the mile, but 
 that in a contracted and unfavorable channel not 
 more than five of them would be likely to make the 
 attempt. Indeed, some individual vessels are claimed 
 to require a mile in which to manoeuvre with safety to 
 their neighbors. In fine, my studies induce the be- 
 lief that, allowing to each vessel six effective guns of 
 calibres varying from six inches upwards, according 
 to her draught, we must anticipate a possible fire at 
 the rate of thirty to sixty guns j)er mile of available 
 development, depending upon the nature of the site. 
 
Prohahle Nature of the Attack. 25 
 
 The next point for consideration is the old and 
 much-mooted question of relative efficiency between 
 land guns and those mounted on shipboard. This 
 question is open to intelligent differences of opinion, 
 but, as the Engineer must commit himself to some 
 definite estimate upon which to regulate the aTma- 
 ment, I will state my own opinion, with some of the 
 grounds upon which it is based. 
 
 Guns Ashore and Guns Afloat. — Formerly it 
 was a maxim accepted by French engineers that one 
 gun on shore was able, when properly mounted and 
 served, to contend successfully with from eight to 
 thirty on shipboard. This rule, derived from expe- 
 rience in such contests in olden times, was verified 
 in the naval attack on Sebastopol, where ''an earth- 
 en battery mounting only five guns, but placed on 
 the cliff at an elevation of 100 feet, inflicted grievous 
 injury on four powerful English ships of war, and 
 actually disabled two of them, without itself having a 
 gun dismounted and without losing even one man." 
 But the rule was founded on conditions no longer 
 existing. The ship guns of that period were small in 
 calibre ; were crowded closely together ; were cov- 
 ered by bulwarks of oak, which, when struck by such 
 projectiles as were used in coast batteries, afforded 
 little j)rotection ; the ship was soon buried in smoke, 
 which prevented the scores of gunners either from 
 seeing how to aim or from being guided with any 
 precision by orders from aloft ; and, lastly, the ar- 
 mament was not readily brought to bear by reason of 
 the unwieldy nature of the ship, which floated at 
 the mercy of baffling winds and shifting currents, 
 with her masts and sails exposed to destruction by a 
 single lucky shot. 
 
 A modern duel between ships and forts is fought 
 under very different conditions. The ships are more 
 or less protected by armor in all vital parts; the 
 
26 General Considerations. 
 
 motive power, deep under water and carefully with- 
 drawn, by the mode of manoeuvring, from direct fire, 
 is comparatively little exposed to injury; the guns 
 are much fewer in number, and the smoke, although 
 still a serious cause of inaccuracy of aim, will hardly 
 form the impenetrable veil which hung about the old 
 three- decker in action, and its evil effects can be 
 more easily counteracted ; moreover, the reduced size 
 of the crews, and the protective armor (if the latter 
 be sufficiently substantial for its work), will reduce 
 casualties, and, leaving torpedoes out of the ques- 
 tion, the hideous carnage of old naval contests will 
 no longer appall the crew. 
 
 ' On the other hand, it must not be forgotten that 
 the risk of injury when struck by an effective- 
 modern projectile is far greater for the ship than for 
 the land battery. The latter may be disfigured by 
 huge craters in the parapet, a few men may be killed, 
 and a few guns may be dismounted, but so long as 
 the magazines are secure no overwhelming disaster is 
 to be feared. But one projectile which has forced its 
 way into the complex mechanism covered by the 
 armor plating of the ship may annihilate, at a single 
 blow, the offensive power of an Italia^ of an Inflexi- 
 ble^ or of a Trafalgar. Moreover, the shij) fires from 
 an unstable deck, at varying and uncertain distances, 
 and always more or less annoyed by the smoke of her 
 own guns ; the land battery, aided by the modern 
 system of position-finding, is comparatively unaffect- 
 ed by smoke and can direct its fire with greater pre- 
 cision than the ship, and with vastly greater certainty 
 than in the days gone by. 
 
 One question formerly stoutly contested has been 
 practically answered so many times in late years that 
 there is no longer any difference of opinion upon the 
 subject : every one now admits that a fleet can force 
 a passage past a line of batteries of equal or even of 
 
Probable Nature of the Attack. 27 
 
 superior armament, provided tlie channel be unob- 
 structed. Hence in studying recent experience we 
 may leave this class of operations entirely out of con- 
 sideration, and confine our attention exclusively to 
 instances of pitched battles between armored ships 
 and forts. Combats of this kind are inevitable when 
 the channel is obstructed by mines properly .defend- 
 ed ; and I shall ask your attention to a few instances 
 which throw light on the problem, although it must 
 be admitted that experience is still lacking on which 
 to formulate definite rules — if, indeed, it will ever be 
 possible to formulate rules where so great variations 
 exist in the protection afforded by different types of 
 armored ships and by different modes of mounting 
 and protecting land guns. Still, experience is the 
 only safe guide, and use should be made of all that is 
 available. 
 
 On May 15, 1862, an earthen battery situated 
 on Drewry's Bluff about 100 feet above James Ri- 
 ver, and without bomb-proof cover, was attacked 
 by two iron-clads, the Galena and the Monitor^ and 
 by three wooden vessels, the Aroostook^ the Port 
 Poyal, and the JVaugattick. The iron clads anchored 
 at from 600 to 1 000 yards range, where a double pile 
 obstruction, reinforced by hulks, pre^^ented a nearer 
 approach ; the wooden vessels anchored about 1 300 
 yards below. After fighting for about three and a 
 quarter hours the fleet was repulsed ; the Galena had 
 expended nearly all her ammunition and had suf- 
 fered severely, being hulled several times. The 
 Monitor and apparently the wooden vessels were not 
 seriously injured ; but Lieut. -Commander Jeffers, 
 commanding the Monitor, reported : "So long as our 
 vessels kept up a rapid fire they rarely fired in re- 
 turn, but the moment our fire slackened they re- 
 manned their guns. It was impossible to reduce such 
 works, except by the aid of a land force." 
 
28 General Coitsiderations. 
 
 Tlie armament of the Galena consisted of 9-inch 
 Dahlgreii smooth-bores and Parrott rifles ; the Moni- 
 tor carried two 15-inch guns ; the armament of the 
 wooden vessels is not stated in the ofiicial reports. 
 
 When Fort Drewry was captured, in 1865, the 
 water-bearing guns consisted of one 7-inch Brooke 
 rifle, with six 10-inch and three 8-inch Rodman 
 smooth-bores. I was personally informed by Major 
 Drewry, who had commanded in the action of May 
 15, 1862, that at that date he had only three Rodman 
 smooth-bores in position, the others having been 
 added subsequently. 
 
 This was, I believe, the first decisive contest be 
 .tween our armor-clad vessels and a land battery. 
 Although the result was a disappointment, and the 
 vessels were repulsed with loss by a greatly inferior 
 force, it must not be forgotten that the trial took 
 place under conditions which gave many advantages 
 to the land forces — the narrowness of the river even 
 permitting them to annoy the fleet with musketry. 
 
 The next typical pitched battle between guns 
 ashore and guns afloat took place at Fort Sumter on 
 April 7, 1863. The day was calm and all the con- 
 ditions were favorable to the fleet. 
 
 Fort Sumter at that date consisted of an un- 
 finished masonry work having a single tier of case- 
 mates, strengthened by such means as the Con- 
 federates had found practicable after its occupation. 
 The masonry was largely shell concrete faced with 
 brick ; the scarp was 8 feet thick (5 feet in front 
 of the recess arch and 11 feet at the piers). The site 
 was a small artificial island. 
 
 The armament which repulsed the attack of Ad- 
 miral Dupont was mounted in Fort Sumter, Fort 
 Moultrie, and in the batteries on Sullivan's Island. 
 The Confederate official report gives the following 
 ;statement of the guns and mortars used in the battle : 
 
Prohahle Nature of the Attack. 29 
 
 GUNS AND MORTARS IN USE ON APRIL 7, 1863. 
 
 
 m 
 
 m 
 
 OD 
 
 . 
 
 rri 
 
 ts 
 
 J3 
 
 
 
 
 
 
 
 •c 
 
 .- flj 
 
 
 
 
 
 Fort or Battery. 
 
 
 % 
 
 CD 
 
 « 
 
 .2 
 
 1 
 
 so 
 
 a 
 
 IS 
 
 s 
 
 11 
 
 1 
 
 5 
 
 3 
 
 2 
 I 
 
 Fort Sumter 
 
 4 
 
 2 
 
 2 
 
 8 
 
 7 
 
 1 
 
 13 
 
 7 
 
 44 
 
 Fort Moultrie 
 
 
 
 
 9 
 
 
 5 
 
 5 
 
 2 
 
 21 
 
 Battery Bee 
 
 5 
 
 
 
 1 
 
 
 .. 
 
 
 
 6 
 
 Battery Beauregard.. 
 
 •• 
 
 . . 
 
 
 1 
 
 
 1 
 
 
 
 2 
 
 Cumraiiigs Point 
 
 1 
 
 1 
 
 .. 
 
 
 
 .. 
 
 
 
 2 
 
 Battery Wagner 
 
 
 •• 
 
 •• 
 
 
 
 1 
 
 •• 
 
 
 1 
 
 Total 
 
 10 
 
 3 
 
 2 
 
 19 
 
 7 
 
 8 
 
 18 
 
 9 
 
 76 
 
 Fort Sumter fired 831 rounds ; Fort Moultrie, 868 
 rounds ; Battery Bee, 283 rounds ; Battery Beaure- 
 gard, 157 rounds ; Cummings Point, 66 rounds ; Bat- 
 tery Wagner, 22 rounds ; total, 2 227 rounds. In all 
 21 093 pounds of powder were used. 
 
 The fleet consisted of the New Ironsides^ the 
 Keokuk^ and seven monitors. Twenty-three guns 
 were used in the action : seven 15-inch Dahlgrens, 
 fourteen 11-inch Dahlgrens, and two 150-pounder rifles. 
 One hundred and thirty-nine shots were flred by the 
 fleet (124 of them at Fort Sumter). The 15-inch guns 
 were charged with 35 pounds of powder, the 11-inch 
 guns with 20 pounds, and the 150-pounders with 
 16 pounds. 
 
 Admiral Dupont reported the range of the moni- 
 tors as from 550 to 800 yards, that of the Ironsides 
 being not less than 1 000 yards ; his ordnance officer, 
 Lieut. A. S. Mackenzie, reports the ranges as from 
 550 to 2 100 yards ; tlie Confederate engineers give 
 
30 General Considerations. 
 
 them as from 900 to 1 500 yards, averaging 1 200 
 yards. 
 
 The engagement lasted two and one-half hours. 
 As to the result, Admiral Bahlgren reported: "I^o 
 ship had been exposed to the severest fire of the 
 enemy over forty minutes, and yet in that brief period 
 five of the iron-clads were wholly or partially dis- 
 abled ; disabled, too, in that which was most essential 
 to our success — I mean in their armament or power 
 of inflicting injury by their guns. . . . The other 
 iron-clads (2 out of 7), though struck many times 
 severely, were still able to use their guns, but I am 
 convinced that in all probability in another thirty 
 minutes they, too, would have been likewise dis- 
 abled." 
 
 The official rej)orts of the captains commanding 
 the iron-clads indicate that the fleet, exclusive of the 
 Bew Ironsides^ received 346 hits. The New Ironsides 
 was struck several times, but the exact number ap- 
 pears not to have been reported. The KeoJculc was 
 sunk, where her guns were subsequently secured by 
 the Confederates. One man was killed and at least 
 twenty-two men were wounded on shipboard during 
 the action. 
 
 Upon the Confederate side, General Beauregard 
 states: "Not more than 34 shots took effect on the 
 walls of Fort Sumter." "Fort Moultrie and other 
 batteries were not touched in a way to be considered." 
 The injuries to Fort Sumter were by no means dis- 
 abling, and the total casualties on land were three 
 men killed by the accidental explosion of an ammu- 
 nition-chest, and eleven men wounded— five of them 
 by the same accident. 
 
 The next conspicuous duel between armored ships 
 and forts was at Fort Fisher, North Carolina. This 
 fort had a water-front and a land-front, both consist- 
 ing of substantial sand batteries ; the land-front had 
 
Frobable Nature of the AttacJc. 31 
 
 an oblique lire upon the sea. The worli was well 
 provided with traverses and bomb-proofs, but the 
 former were so conspicuous that they marked the gun 
 positions with great distinctness. The site was a low, 
 sandy point between the ocean and Cape Fear River. 
 The offing afforded unlimited development to the 
 fleet. 
 
 Carrying out the plan of a co-operative attack in 
 aid of tlie land forces, Admiral Porter ordered his 
 monitors to anchor at a range of about 800 yards, and 
 his wooden vessels in three lines at from 1 100 to 
 1 800 yards. Tlie former were to fire deliberately 
 upon the land-front (from within a dead angle where 
 the enemy could reply only at great disadvantage) in 
 order to prepare the way for an assault ; the latter 
 were to maintain so terrific a storm of shot and shell 
 over the fort as to prevent the enemy from serving 
 his guns. These tactics were successful, and the 
 Confederates were soon driven to take temporary 
 refuge in their bomb-proofs. 
 
 Immediately after the capture of the fort on Jan- 
 uary 15, 1865, I personally made an inventory of the 
 armament, with notes as to its condition. The fol- 
 lowing were the water-bearing guns : On the land 
 front, one 10-inch Rodman, five 8-inch Rodmans, 
 five old 32-pounders, one old 24-pounder, seven 6.4- 
 inch rifles, one 4.2-inch rifle ; total, 20 guns. On the 
 water-front, nine 10-inch Rodmans, four 8-inch Rod- 
 mans, two 8-inch rifles, two 7-inch rifles, five 6.4-inch 
 rifles ; total, 22 guns. The grand total which could 
 have been used against the fleet was 42 guns. Of 
 these, eight guns and eight carriages (16 in all) were 
 disabled on the land-front, and one gun on the water- 
 front (it evidently had burst in action). This state- 
 ment includes all injuries by direct impact of shot, 
 or by destruction of carriages, or by the ■i:)iling of 
 sand in front of the guns ; they represent the wliole 
 
32 General Considerations. 
 
 damage effected by one of tlie most tremendous bom- 
 bardments of modern times directed against an open 
 barbette battery on a low site. 
 
 The following was the effective armament of the 
 fleet, as furnished to me by the Bureau of Ordnance, 
 Navy Department. It includes all the pivot guns 
 and half the broadside gans of the vessels in ac- 
 tion, excluding the small bronze guns as of no value 
 for such service : ten 15-inch Dahlgrens, 20 11-inch 
 Dahlgrens, two 10 inch Dahlgrens, one hundred and 
 thirty-four 9-inch Dahlgrens, eighteen 8-inch Dahl- 
 grens, sixteen 32-pounders, eight 8-inch Parrott rifles, 
 twenty-four 100-pounder Parrott rifles, two 60- 
 pounder Parrotts, two 50-pounder Dahlgrens, twen- 
 ty-seven 30-pounder Parrotts, twelve 20-pounder 
 Parrotts, making a total of 275 guns of all calibres 
 used against the land defences. 
 
 This bombardment silenced the Are of the fort and 
 enabled an assault to be delivered without the pre- 
 liminary operations of a siege — an assistance of the 
 most important character ; but that the damage to 
 the works should be as unimportant as it actually 
 was, seemed at the time almost incredible to the eye- 
 witnesses. If the garrison had not been provided 
 with ample bomb-proofs, a surrender might probably 
 have occurred ; but, as it was, the men took shelter 
 until the flre slackened to favor the assault, and then 
 they exhibited anything but demoralization. Still, 
 it must not be forgotten that such a result to-day 
 would be decisive in favor of an attack to force a 
 passage ; for unless the land guns can be served con- 
 tinuously the flanking arrangements will be destroy- 
 ed, and the mines will be removed with but little 
 risk. 
 
 These three examples, concerning which all the 
 essential facts are known, have been selected as typi- 
 cal contests between guns ashore and guns afloat at 
 
Probable Nature of the Attack. 33 
 
 the beginning of tlie era of armor and of heavy guns 
 on shipboard. They certainly prove that our iron- 
 clad fleet could not contend with any chance of suc- 
 cess against an equal, or even against a very inferior, 
 land armament. 
 
 The same was true at that epoch in Europe, as 
 appears from the result of the attack of the Italian 
 fleet upon the island of Lissa in July, 1866. Al- 
 though full data respecting this two-day engagement 
 are lacking, enough is known to justify the claim of 
 the Austrians "of having driven back the Italian 
 iron-clad ships, incapable of resisting the fire of the 
 forts which command the harbor." Just as a third 
 attack was about to be made, including a landing of 
 troops to storm the works, the arrival of the Aus- 
 trian fleet terminated the attempt. 
 
 The land works consisted of masonry forts and 
 earthen batteries, which appear to have usually had 
 high sites. They were distributed among three har- 
 bors, and "the whole of the defence presented a 
 front of nearly 100 guns." The latter were all of an 
 old type, of which the largest were smooth- bores 
 throwing solid shot weighing ^^ pounds, and rifles 
 throwing elongated shot weighing 60 pounds. 
 
 The armored fleet consisted of 12 ships, carrying 
 248 guns. Their armament "contained all the latest 
 improvements which the modern art of war had up 
 to that date invented." There were also 8 unarmor- 
 ed ships carrying 360 guns, and 16 despatch-boats. 
 
 The bombardment of Alexandria affords the only 
 example available for testing more recent progress, 
 and even that fails to exhibit what the latest type of 
 guns can accomplish against land batteries. 
 
 The foits at Alexandria were mostly low barbette 
 batteries, with a few old masonry works still less de- 
 fensible against modern attack. The garrison was 
 demoralized by being in rebellion against its own 
 
34 General Considerations. 
 
 government, which was supported by the hostile fleet. 
 The only circumstance in favor of the rebels was the 
 possession of a few Armstrong guns. 
 
 On the northern line there were 20 Armstrong 
 M. L. rifles (four 10-inch, nine 9-inch, five 8-inch, and 
 two 7-inch), thirteen 40-pounder Armstrong B. L. 
 rifles, and 62 smooth-bores which were little used. 
 On the inner line there were seven Armstrong M. L. 
 rifles (one 10-inch, one 9-inch, and five 8-inch), with 
 one 40-pounder Armstrong B. L. rifle, and 76 smooth- 
 bores which were little used. 
 
 The working broadside of the offshore squadron 
 opposed to the northern line the fire of '^^ M. L. rifles 
 (two 16-inch 81-tons, one 12-inch 25-tons, fifteen 10- 
 inch 18 tons, two 9-inch 12-tons, and six 8-inch 9- 
 tons). These were supplemented later by three more 
 of 25 tons, two of 18 tons, and two of 81 tons. 
 
 The working broadside of the inshore squadron 
 employed th6 following heavy guns, all muzzle-load- 
 ing rifles : four 12-inch of 25 tons, five 9-inch of 12 
 tons, and four 8-inch of 9 tons ; total, 13 guns. 
 
 In Captain Goodrich's Keport, from which these 
 data are extracted, is a table of numerical ratios 
 showing 'Hhe phases which the engagement either 
 assumed or might have been made to assume." It is : 
 
 Fort Pharos 4 land to 33 ship (actual). 
 
 Fort Adda 5 land to 28 or 33 ship (actual). 
 
 Bas-el-Tin Lines. . 7 land to 26 ship. 
 Light-house Fort . 4 land to 26 ship. 
 Fort Mex 5 land to 14 or 16 ship (actual). 
 
 Taking into consideration the relative calibres as 
 well as numbers, it is plain that this action affords 
 no fair comparison between the fire of guns on land 
 and those on shipboard ; but it has value as a test of 
 the effect of modern guns on batteries of the kind 
 engaged. Three thousand one hundred and ninety- 
 
Probable Nature of the Attack. 36 
 
 eight rounds, of which 1 731 were 7 inches and up- 
 ward in calibre, were fired by the fleet. Captain 
 Goodrich writes: "To the unprejudiced observer 
 the most striking characteristics of the bombardment 
 ^re, without doubt, the excessive apparent and the 
 slight real damage done to the fortifications. . . ." 
 "The forts at Alexandria were badly bruised, but 
 the more modern parapets were not seriously harmed. 
 In the generality of cases the real damage they sus- 
 tained could have been easily repaired in a single 
 night. If the bombardment was directed against the 
 forts in this their defensive capacity, it must be pro- 
 nounced a failure. If its object was the dismounting 
 of the new rifled guns, it must be conceded that such 
 results as attended the work of the inshore squadron 
 (only one gun of this type being seriously affected), 
 or even such as were achieved by the offshore squad- 
 ron (less than one-half being permanently disabled), 
 do not justify the verdict of success." 
 
 The action at Alexandria, rightly or wrongly, has 
 certainly tended to reduce the estimate lately enter- 
 tained by engineers as to the accuracy of fire to be 
 expected from shrapnel and machine guns on modern 
 ships of war — the peace practice at Inchkeith notwith- 
 standing. Although siege howitzers on land have 
 proved their ability to breach concealed scarps and 
 rsearch out nopks and corners of fortresses with show- 
 ers of descending shrapnel-balls, it now appears that 
 no such practice is to be apprehended from vessels. 
 Although machine and rapid-firing guns are murder- 
 ous at suitable ranges on land, their fire proved to be 
 far less terrible from the gunboats. Moreover, this 
 fire can be neutralized by forbidding an approach to 
 within less than 1 000 yards. In addition, it has been 
 practically learned that high-power guns, with their 
 flat trajectories, are unfavorable for shrapnel-fire 
 ;against earth-works. The spread of the balls is be- 
 
36 General Considerations. 
 
 lieved to be often less tlian live degrees, and mucli of 
 the effect depends on obtaining a rapid fall in the 
 shell itself before explosion. General Sir Andrew- 
 Clarke, R. E., late Inspector-General of Fortifications, 
 sums up a recent discussion of the subject with this 
 language: ''As regards searching effect, ships are 
 now in a worse position than they w^ere fifty years 
 ago, and when re-armed with new guns tlieir power 
 will in this respect be still further diminished." He 
 also states: ''At Alexandria the fieet carried about 
 seventy 1-inch 4-barrel I^ordenfelts and expended 
 more than 16 000 bullets. The expenditure of Gat- 
 ling ammunition was only 7 000 rounds, and of Mar- 
 tini bullets 10 000. As to the results obtained opin- 
 ions differed. It is submitted, how^ever, that the 
 number of hits on the guns and carriages of the de- 
 fence may fairly be taken to afford some indication 
 of those results. The hit of a Nordenfelt bullet on 
 iron is generally unmistakable, but it is evidently 
 possible that grazes at a very acute angle might have 
 escaped observation. The total number of hits on 
 guns and carriages was seven, and even this mode- 
 rate number requires qualification." 
 
 I think, after this review of the best data upon the 
 subject, no one will advocate a fixed ratio of compa- 
 rison between the efficiency of guns ashore and guns 
 afioat. The Engineer must carefully consider the 
 question for his local problem and make his own esti- 
 mate, taking into account the natural advantages and 
 disadvantages of the position, and how far his art can 
 be applied to increase the relative power of the land 
 armament. One consideration must not be overlooked 
 for a position of first-class importance, especially 
 when the approaches are unfavorable to the fleet. 
 The enemy may not be able to bring all his force to 
 bear at the same time, but his reserves may be able to 
 supply losses and maintain the attack with unbroken 
 
IB vigor ; 
 
 Probable Nature of the Attack, 37 ^ 
 
 vigor ; while the land batteries, having no reserves, will 
 become less and less able to meet it as their guns be- 
 come dismounted. 
 
 Personally, while according a relatively higher 
 efficiency to naval armaments as compared with land 
 guns than was warranted by experience before recent 
 improvements, I am convinced that ship guns can 
 never hope to contend with similar land guns on any- 
 thing like equal terms when the latter are properly 
 placed in position and properly served. In fine, I 
 think engineers would agree tliat for a port of first- 
 class importance the armament should never be al- 
 lowed to fall below that of the enemy in calibre, and 
 that in number of guns we should rarely mount less 
 than half of what can be deployed against the works 
 in line of battle. With such an armament, well dis- 
 posed upon a favorable site, and well served, I should 
 have no fear of the result, and indeed one much 
 weaker would have a fair chance for success. 
 
 It only remains to consider how a land position is 
 likely to be attacked by a fleet. 
 
 Naval Tactics against Forts. — At Port Royal, 
 in November, 1862, Admiral Dupont captured the 
 land defences (Forts Walker and Beauregard) by a 
 system of tactics which consisted in keeping his fleet 
 (unarmored) in constant motion upon an elliptical 
 curve which brought the ships within a range of 
 about half a mile of the forts in passing. These 
 forts, armed with 35 small guns, only two being rifled, 
 were earthen batteries of slight command and ill- 
 fitted to endure so powerful an attack as that of his 
 squadron. Still, at that date these tactics were 
 highly admired, and were even claimed by some en- 
 thusiasts to mark a new era in such operations. 
 
 Similar tactics were tried at Alexandria in 1882^ 
 the speed being about five miles per hour, but with- 
 out a satisfactory result. Captain Goodrich states : 
 
38 General Considerations. 
 
 V The outside squadron having tried both modes of 
 attack, under weigh and at anchor, definitely solved 
 one important problem. There remains no possible 
 doubt that ships engaging forts not superior to them 
 in force will gain more in accuracy of fire by anchor- 
 ing than in safety by keeping under way." These 
 views accord with statements of Royal Engineer offi- 
 cers and with my own belief ; for I think that land 
 guns will hereafter be so protected in positions of 
 importance that they will have little to fear from the 
 inaccurate practice inseparable from motion. 
 
 Accepting, then, as a maxim that a first-class 
 naval attack upon a well-fortified position will be 
 made at anchor, or at any rate from fixed buoys to 
 indicate the precise range to the gunners, the defence, 
 aided by the modern system of position-finding, can 
 count upon all the advantages resulting from supe- 
 rior stability of platform, freedom from the annoy- 
 ance of smoke, and a better knowledge of the range. 
 
 But what ranges will ships select when the chan- 
 nel allows a choice % The preponderance of profes- 
 sional opinion is that it will be as short as the power 
 of the land guns will permit. If that power be in- 
 sufficient to penetrate the armor, ships will approach 
 very closely to increase their precision of fire as 
 much as possible. Their targets are guns and maga- 
 zines, and all shots that fail to attain them are 
 thrown away, although great apparent damage may 
 result to earthen parapets and to masonry walls. , 
 
 At Lissa the fleet forced the fighting, ranges of 
 300 and 400 metres being mentioned in the report. 
 
 At Alexandria the outside squadron began the 
 action at a minimum range of about 1 500 yards. Of 
 the inshore squadron the flagship was anchored at 
 1 300 yards, while the Penelope drifted several times 
 broadside on from that distance to 700 yards. The 
 Inflexible and Temeraire fired at very much greater 
 
Probable Nature of the Attack, 39 
 
 distances — between 3 000 and 4 000 yards. These 
 long ranges were criticised by Captain Goodricb as 
 "needlessly great." He states: ''The outside ves- 
 sels could have gone to within 1 000 yards on the 
 northwest side of the Light-house fort and 800 yards 
 abreast the Ras-el-Tin lines ; to within 500 yards of 
 Fort Adda and 200 yards of Fort Pharos. Along 
 the southern line the ships could easily have gotten 
 within 400 yards of all the batteries. This would 
 have prevented the Temeraire from shelling Mex, 
 but it is believed that the gain would have outbal- 
 anced the loss. It can hardly be doubted that the 
 boldness of this move would have been rewarded by 
 the speedier and more extensive dismounting of the 
 guns, which was confessedly the chief object of the 
 attack. Shrapnel and canister from a portion of the 
 ships' batteries, supplemented by the machine guns 
 at a more appropriate range than that originally 
 adopted, would have prevented return fire from the 
 shore ; and the remainder could have been concen- 
 trated on each gun in the forts in succession until 
 bowled over. Close range and a stable platform, 
 however, are necessary for such refinement of prac- 
 tice." 
 
 I think there can be little doubt that such consid- 
 erations will commend themselves to Naval Com- 
 manders ; and they must be met by at least a few 
 guns of the largest calibre, and by outlying sub- 
 marine mines where nature permits too close an 
 approach to the works. A shoal in the near front is 
 a great merit in a position for a battery. The ship 
 must necessarily fight under disadvantages as to pre- 
 cision of fire, and it is the business of the Engineer to 
 secure the full benefit of this advantage by forcing 
 an action at long range. 
 
 If this be desirable for horizontal fire, it is abso- 
 lutely essential for vertical fire. With mortars the 
 
40 General Considerations. 
 
 force of impact depends upon the fall of the projec- 
 tile, which fall is a direct function of the range ; 
 hence with this class of ordnance very short ranges 
 are to be forbidden to the enemy at any cost. 
 
 To sum up these conclusions as to the probable 
 nature of an attack by a modern fleet upon a sea-coast 
 fortress of the first class, I am disposed to believe : 
 (1) that we should be prepared to meet the largest 
 calibres which the draught of water in the channel will 
 admit ; (2) that from five to ten ships, carrying from 
 thirty to sixty guns of six- inch calibre and upward, 
 should be estimated for each mile of the line of battle 
 — the character of the approaches determining the 
 precise number ; (3) that the attack will be made at 
 anchor, or at least from fixed buoys, in order to in- 
 crease the precision of fire ; and (4) that it will be 
 made at as close quarters as possible. The Engineers 
 should provide for a land armament at least equal in 
 calibre, and perhaps half as large in number of guns, 
 as that which can be deployed against the works. All 
 approach to within less than 1 000 yards must be 
 forbidden, use being made of submarine mines if 
 deep water renders them necessary for this purpose. 
 Witli a reasonably favorable site, well occupied, I 
 consider that such preparations would probably de- 
 ter attack and would certainly give large odds in 
 favor of the land defences. 
 
Lecture IL 
 
 ECOIVOMY IN COAST DEFENCE. 
 
 Limit of judicious outlay — Economic value of different elements ; gen- 
 eral analysis ; case of non-disappearing barbette mounting; case of 
 the King mounting for 50-ton 12-inch rifle ; case of the Duane lift; 
 case of an armored casemate ; case of a revolving turret ; general 
 ' conclusions. 
 
 Before proceeding to consider details it will be 
 well to discuss with some care the fundamental basis 
 upon which they all rest. Are outlays for coast de- 
 fence demanded by the needs of the country ; and, if 
 so, how large an amount should be asked of Con- 
 gress ? How far are projects for coast defence to be 
 influenced by the question of expenditure ? 
 
 LIMIT OF JUDICIOUS OUTLAY. 
 
 From one point of view expenditures for sea- 
 coast defences should be regarded simply as a neces- 
 sary business outlay entailed by the possession of 
 wealth, and should be governed by the usual rules of 
 Insurance, so far as they can be applied. A citizen 
 of New York pays a certain percentage of his prop- 
 erty towards the support of a fire department, be- 
 cause he is convinced that the outlay is demanded by 
 true economy as a protection against loss by fire ; he 
 pa\ s another tax to maintain a police department to 
 afford security against individual violence and rob- 
 bery ; he contributes his assessments in support of 
 the National Gruard, because he knows that mobs are 
 a danger to life and property which timely precau- 
 tions alone can, control ; finally, not satisfied with 
 
42 Economy in Coast Defence. 
 
 these precautions, his business instincts teach him to 
 pay large sums for insurance, to reimburse him for 
 losses which may probably overtake him in spite of 
 all his forethought. It seems amazing, to one who 
 has reflected upon the subject, that this same man 
 appears to forget that war, liable at any time to 
 occur, may result either in the burning of his prop- 
 erty under circumstances which will cripple the lire 
 department, disperse the police and National Guard, 
 and bankrupt the insurance companies, or else will 
 subject him to enormous impositions to purchase ex- 
 emption from utter destruction. Surely all history 
 proves that this danger is real, and should arouse 
 public sentiment to demand that the lethargy which 
 for a dozen years has paralyzed us shall cease, and 
 that the general government, without further delay, 
 shall attend to its duty of providing for the national 
 defence. 
 
 It must not be overlooked that, in some important 
 particulars, funds invested in sea coast fortresses are 
 far more advantageous than ordinary insurance. 
 Thus, instead of merely distributing the loss among 
 many individuals, they prevent it altogether. More- 
 over, large continuous outlays are not required. The 
 works are imperishable and the annual premiums are 
 therefore small. A port once provided with ade- 
 quate defences remains in security until new progress 
 in the art of war demands modifications. In a word, 
 their utility is as permanent as anything hum^n. 
 
 But, it may be asked, what has this problem in 
 political economy to do with the duty of the military 
 engineer \ I answer. Much. He should regulate his 
 plans and estimates upon the same principles which 
 determine the size of the fire department, the strength 
 of the police force, and the organization of the Na- 
 tional Guard. His problem is more complex, be- 
 cause the elements are more uncertain, the field is 
 
r 
 
 Limit of Judicious Outlay. 43 
 
 broader, and constructive damages constitute a larger 
 element ; but, after all is said, the matter reduces it- 
 self to dollars and cents. If, ignoring the question 
 of cost, the engineer demands a larger outlay than 
 business principles will warrant, he rightly fails to 
 command the confidence of those whose duty it is to 
 scrutinize the necessity for expenditures before vot- 
 ing appropriations. 
 
 When preparing a project for defence the first 
 matter for consideration is, therefore, what sum can 
 judiciously be expended. This by no means signifies 
 exact figures, like those for the cost of a mass of con- 
 crete or of an iron shield ; there are many elements 
 to be considered, some of which can be measured by 
 the gold standard, while others can hardly be so 
 gauged. As an example of the first class, the port 
 may contain a great city, and the assessed valuations 
 for real estate and personal property are always ac- 
 cessible, while fair estimates of the value of exempt 
 and untaxed real estate and personal property may 
 usually be obtained with some degree of exactitude. 
 If a hostile fleet succeeds in forcing its way into the 
 harbor, the property which lies at its mercy will 
 either be destroj^ed or will be ransomed at a price 
 which may range, according to circumstances, even 
 up to a full cash valuation of all property subject to 
 destruction. This valuation, of course, will exclude 
 the cost of land, of water- works, of gas-mains, of roll- 
 ing stock of railways, of bonds and specie, and of 
 all other non-destructible or removable property. 
 What is needed, therefore, by the engineer in his 
 estimates for this class of probable damages is a fair 
 valuation of the total destructible property. 
 
 When preparing a paper on Coast Defence which 
 was read before the Military Service Institution in 
 1885, Captain Eugene Griffin, Corps of Engineers, 
 corresponded with collectors and receivers of taxes, 
 
,44 Economy in Coast Defence, 
 
 boards of assessment, and collectors of ports, and 
 consulted reports of Tax Departments and other 
 official documents of a similar character, with a view 
 ito obtain a fair estimate of the destructible property 
 -exposed to an enemy in eight of the eleven ports af- 
 terward (1886) reported by the Endicott Board as 
 '' most urgently requiring fortifications or other 
 defences." The three ports not included were the 
 Xiake ports, Hampton Roads, and Washington. 
 
 Captain Griffin presents the results of his re- 
 ^searches in tabular form ; and they convey much 
 information useful for reference in this connection. 
 The figures are based on valuations for the year 1884, 
 ithree years ago. But the records show that during 
 the past ten years there has been in New York City 
 an average annual increase of $40 000 000 in the total 
 assessment valuation for real estate and personal 
 property. Last year this increase was $50 000 000. 
 We should therefore accept Captain Griffin's figures 
 as now considerably under the true values. 
 
 His grand total of destructible property for these 
 -eight ports (Portland, Boston, Newport, New York, 
 Philadelphia, Baltimore, New Orleans, and San Fran- 
 cisco) is $4 529 177 244. The estimate of the cost of 
 fortifying these same eight ports upon a liberal scale, 
 presented by the Endicott Board (including $18 875- 
 000 for five floating batteries and their armament, to 
 be used at San Francisco and New Orleans), is 
 $90 018 150, or a gross sum not quite two per cent, of 
 the value of the destructible property now at the 
 mercy of any maritime enemy. Extending these 
 expenditures over a term of ten years, as is projjosed, 
 they would amount to an annual expenditure of 
 two-tenths of one per cent, of the destructible prop- 
 erty. 
 
 Let us now see how this compares with the pre- 
 miums paid for other insurance in New York. The 
 

 Limit of Judicious Outlay, 45 
 
 City pays over $1 500 000 annually for the support of 
 its lire department and over $6 000 000 annually for 
 insurance against fire— aggregating, say, $7 500 OOO. 
 It pays over $500 000 annually for its courts, its pri- 
 sons, and the support of its criminal classes, and over 
 $4 500 000 annually for its police department— or a 
 total of upward of $5 000 000 as its insurance against 
 minor disorders and robbery. The cost of the Na- 
 tional Guard, which represents insurance against 
 mob violence, is not less than $617 000, of which the 
 State pays $400 000 for cost of camp-ground, pay of 
 troops in camp, annual allowance for clothing, drills, 
 etc.; the county contribution for rent of armories, 
 janitors, etc., in New York and Brooklyn, is $117 000 ; 
 the balance, $100 000, is the estimated private outlay 
 of the members themselves. 
 
 The aggregate annual insurance against these 
 three dangers, fractions included, is, say, $13 800 000. 
 The corresponding total destructible property in 1884 
 was $1 855 303 043. The total annual insurance 
 against these ordinary dangers in the City of New 
 York is, therefore, eight-tenths of one per cent, of its 
 destructible property, or four times the percentage 
 proposed as an annual expenditure for ten years for 
 the most important coast defences of the Nation. 
 
 The financial question, therefore, resolves itself 
 into this : Is it or is it not judicious for the Nation to 
 pay in ten years for protecting, during a term of 
 many years, the property exposed to destruction in 
 its eight principal ports, as high a premium as New 
 York pays continuously every 2.5 years to protect 
 itself against, loss by tire, by robbery, and by vio- 
 lence \ It would certainly appear that business prin- 
 ciples demand such an expenditure. 
 
 But this basis for considering tlie matter is a very 
 inadequate one, even from a financial point of view. 
 The Nation is bound to supply its coasting trade 
 
46 Economy in Coast Defence. 
 
 with some refuge from cruisers in case of war ; and 
 this cannot be done so long as even its chief ports are 
 open to the enemy. The same remark is true now, 
 and must remain so for some years, even for the 
 Navy itself. Our navy-yards are all exposed to sud- 
 den raids. We are even debarred from seeking re- 
 prisals with our new cruisers ; for, with our port& 
 open to the enemy, we should pay in cash for every 
 capture as soon as it was made. Precedents for this 
 ready mode of keeping our Alahamas in check are 
 not wanting ; for a similar system was enforced 
 against France during the late war, to protect bodies 
 of German cavalry scouting through the country. 
 
 But if these interests, which can be measured in 
 dollars and cents, demand attention by every recog- 
 nized business i)rinciple, how shall we estimate the 
 National humiliation we invite by slumbering on in 
 our present unprotected condition, while the rest of 
 the world is so actively awake ? The stars and 
 stripes, held aloft at so fearful a cost twenty-five 
 years ago, are now exposed to insult by second and. 
 third-rate powers whose geographical positions, even, 
 are hardly known to our populace. If this exposure, 
 so well understood by Army and Navy men, were 
 appreciated by the country at large, should we have 
 been allowed to sink to such a condition % 
 
 I dwell upon this branch of my subject because 
 the facts should be emphasized, (1) that there is ur- 
 gent necessity for action ; and (2) that engineers 
 limit their estimates for coast defence to reasonable 
 sums. The nation has increased so rapidly that our 
 people still gauge their ideas of military exj)endi- 
 tures by a scale long since outgrown. Because the 
 sums appear large when stated in dollars and cents, 
 the enormous interests involved are forgotten and an 
 outcry of extravagance is raised. All that engineers 
 demand is a fair hearing, and a discussion of a busi- 
 
Limit of Judicious Outlay, 47 
 
 ness question upon business principles and in a busi- 
 ness-like way. 
 
 Before quitting tlie subject let us, to fix ideas, 
 attempt to consider a little more mathematically the 
 problem what stlm {x) the nation ought to expend 
 annually on its fortifications — every consideration 
 which cannot be measured by a gold standard being 
 ignored. 
 
 Clearly this sum will be directly proportional to 
 the value ( F) of the property exposed to capture, 
 and directly proportional to the average frequency 
 of war with maritime powers, which may be ex- 
 
 W 
 
 pressed by the fraction p- , in which W denotes the 
 
 number of years of war, and F the number of years 
 of peace, noted during a period sufficiently long to 
 afford a fair average. The sum to be expended will 
 be inversely proportional to the efficiency of the ex- 
 isting defences, which may be represented by the 
 
 fraction -; — -, in which B denotes the price of an 
 
 adequate system, and B, the part of this price already 
 paid. The sum to be properly expended will also be 
 inversely proportional to {F\ a quantity representing 
 the fear of our retaliation or of an attack by other 
 enemies while involved with us, and the improbability 
 of our own inauguration of war. Hence, represent- 
 ing by (7 a numerical constant, we may write : 
 
 X=: 
 
 c y^ 
 
 S .— FFS 
 F 
 
 S—S, 
 
 From this equation it appears that x can be zero ; 
 i.e., that the Nation can afford to pay nothing for 
 defences, only upon the condition that W =: 0, or 
 that Sz=: S^, or that Z^= co ; or, in other words. 
 
48 Economy in Coast Defence. 
 
 wlien the millennium has come, or when adequate 
 defences are completed, or when every maritime 
 power so dreads our strength, or the hostility of its 
 neighbors, that our wealth offers no sufficient tempta- 
 tion to declare war against us or to give just provo- 
 cation for war on our part. But few will claim that 
 wars have ceased, or that our defences are perfect, or 
 that our naval power is so vast as to spread terror 
 throughout the world. The uncertainty of the rela- 
 tions between the great powers was probably our 
 salvation during the civil war; but it is a slender reed 
 upon which to rest our only hope when our exposed 
 wealth is measured in thousands of millions, and is 
 increasing with wonderful rapidity from day to day. 
 Moreover, it will be noted that this condition {F = 
 00 ) implies that we have made up our minds to en- 
 dure any insult or outrage rather than have recourse 
 ourselves to the ultima ratio regum. The Monroe 
 doctrine must be abandoned ; we must see the Sand- 
 wich Islands pass under a foreign protectorate, if 
 such be the pleasure of a commercial rival ; our 
 fisheries must be left without that protection which 
 every government owes to its citizens ; the Isthmus 
 canal, when completed, may be used to discriminate 
 against us, even to the extent of ruining our commer- 
 cial interests, without arousing us to action ; in a 
 word, we must humble ourselves to admit that we 
 have no rights which any nation possessed of an 
 armored fleet is bound to respect. That the Ameri- 
 can people will ever consent to occupy a position so 
 humiliating is a supposition not to be named. In- 
 deed, the belligerent shrieks which are always raised 
 by newspapers and demagogues when our foreign 
 political horizon becomes overcast, and the excite- 
 ment which stirs the better class of our population as 
 well, afford ample evidence that even although de- 
 feat were certain, the government would never be al- 
 
Limit of Judicious Outlay. 49 
 
 lowed to avoid a just quarrel. For these various 
 reasons we cannot assume i^ = go ; and therefore, 
 logically, our sea-coast must be adequately defended. 
 
 But let us go a little further, and, by assigning 
 fair numerical values to the quantities in this general 
 formula, try to estimate in a very general manner 
 what sum business principles demand shall be ex- 
 pended next year upon the defences of New York 
 City. Since 8, is practically zero, both that quantity 
 and /S' disappear. From Captain Gfriffin's researches, 
 and the rapidly increasing wealth in the City during 
 the past three years, Y may now be assumed at 
 $2 000 000 000. One consideration, however, must 
 not be forgotten. Although this amount represents 
 the total property which would be the prize of a 
 hostile fleet forcing its way into New York Harbor, 
 and which at its option might be destroyed, a much 
 smaller ransom might probably be accepted ; because 
 a certain percentage of this value actually carried off 
 in gold might be more imi^ortant to the captor than 
 the forcing of a larger loss upon us. What per- 
 centage might be demanded as a ransom would de- 
 pend upon the local circumstances of the case ; bat 
 certainly, in view of recent similar assessments, ten 
 per cent. ($200 000 000) must be regarded as a mode- 
 rate demand. 
 
 The values of W and P must be derived from our 
 actual experience as a nation. During the 111 years 
 which have elapsed since the Declaration of Indepen- 
 dence we have passed about nine years in actual 
 warfare with Great Britain ; and have been in such 
 imminent danger of foreign interference during the 
 late civil war, to say nothing of threatened hostilities 
 with France in the latter part of the last century, 
 and with Spain on several recent occasions, that, in 
 prudence, say 3 years more should be added. Hence 
 W becomes 12, and F becomes 99. But it may be 
 
50 Economy in Coast Defence. 
 
 objected to these figures that our present strength as 
 a nation is so much greater than it was in the earlier 
 years of our national existence that they afford no 
 fair indication for the future. This argument might 
 have weight if our offensive power upon the sea had 
 increased ^ar/^a552^ with our wealth. That form of 
 national strength alone can be considered, since our 
 ability to raise armies on land does not enter into 
 the problem when confronted with an enemy across 
 the water. Offensive power upon the ocean deters 
 maritime attack, but exposed wealth invites it. 
 Hence it is the ratio between these quantities at dif- 
 ferent periods of our national existence which is to 
 be considered : and it may safely be affirmed that 
 never before in our whole history has this ratio been 
 more unfavorable than it is to-day. 
 
 The quantity i^, the general character of which has 
 already been considered, is more difficult to express 
 numerically. Mathematically it is a ratio of which 
 the numerator is unity and the denominator a pro- 
 per fraction — i.e., the denominator is zero for abso- 
 lute security and unity for existing war. What val- 
 ue shall be assigned is a matter of judgment ; but 
 perhaps our past history affords the fairest measure. 
 We have been engaged in actual war (not including 
 Indian wars) about one-seventh of our national exist- 
 ence, and I shall therefore assume F to be — =7. 
 
 Making the above substitutions in the formula, an4 
 noting that from the values assumed for the several 
 
 quantities C becomes — -, we have the numerical 
 
 value : 
 
 ^ aiX_20W 000000X12^ 4gg j^g_ 
 7X99 
 
 But this sum which, upon business principles, 
 should be expended upon the defences of New York 
 
Limit of Judicious Outlay. 51 
 
 €ity during the coining year, exceeds by fifty per 
 <3ent. the amount recommended by the Endicott 
 Eoard [$2 394 850]. Hence that Board under-esti- 
 mated rather than over-estimated the business risks 
 and necessities involved in the problem of the de- 
 fence of New York, and, more generally, in that of 
 •our sea- coast and Lake frontier. That they did not 
 ignore financial considerations is shown by the fol- 
 lowing quotation from their report : 
 
 '' A comparison can now be made of the estimates 
 for modern works with those made in 1840, when the 
 old system of coast- defence had received considerable 
 -development and was being pressed toward comple- 
 tion. The population of the country at that time 
 was 17 000 000, and the estimate of cost, including 
 the amounts already expended, was $57 131 541, be- 
 ing at the rate of $3.35 per head. 
 
 ''The population in 1880 was 50 000 000, and the 
 estimate for the coast defence is $126 377 800, or at 
 the rate of $2.52 per head. 
 
 ''The valuation of property in 1880 was $43 642- 
 '000 000 ; that of 1840 was about $4 000 000 000, and 
 it is to be seen that the ratio of the estimate for de- 
 fences to the wealth of the country at the present 
 time exhibits a still more favorable comparison. 
 
 "In 1840 the cost of the line-of-battle ship, then 
 representing the most formidable means of attack 
 against coast defences, was about $550 000, and the 
 cost of the corresponding war-ship of the present day 
 is about $5 000 000. While the ships have increased 
 in cost ninefold, the estimate of the defences to re- 
 sist them has increased only between two and three 
 fold." 
 
 The present humiliating condition of the country, 
 arising from the neglect of this subject, can hardly 
 l)e expressed in more forcible language than that at- 
 tributed to Hon. Robert T. Lincoln, who when Secre- 
 
52 Economy in Coast Defence. 
 
 tary of War was in a position to have his attention 
 officially directed to the matter. He is quoted as re- 
 cently saying: '* During my term as Secretary of 
 War you recall there was a diplomatic difficulty 
 with Chili. I was in trepidation for some time lest 
 she should send an iron-clad up the coast and exact a 
 heavy tribute — millions of dollars, in fact — from San 
 Francisco, under threat of laying the city in ashes, 
 which she could easily have done. Any of the great 
 naval powers of the world could do such a thing — 
 along our Atlantic seaboard, for instance — in case of 
 trouble. Of course, had we entered upon war with 
 Chili, she would have got the worst of it in the end ; 
 but it would have taken time enough to obtain a navy 
 before we could have even begun offensive opera- 
 tions. In point of fact, there is much latent hostility 
 against us among foreign nations, and it would often 
 be easy to bring on a war. But we are not in condi- 
 tion for it, and all the world knows it. Hence our 
 foreign policy lacks self-respect and a proper asser- 
 tion of our nation's dignity and power. We would 
 be at first at the mercy of foreign States in case of 
 hostilities, and our government has to be humble in 
 its diplomacy in consequence." 
 
 ECOJS^OMIO VALUE OF DIFFERENT ELEMENTS. 
 
 It is certain, for reasons which need not be dis- 
 cussed, that in this country appropriations will never 
 exceed a fraction of the sums which might economi- 
 cally be applied in coast defence. Hence not only 
 should estimates never cover extravagant or merely 
 ornamental work, but the constant aim should be to 
 provide the most effective and economical parts of 
 the system first. In a word, funds must be applied 
 where they will yield the quickest return in defensive 
 strength. By following this course, and only by fol- 
 lowing this course, will the engineer be acquitted if 
 
Economic Value of Different Elements. 63 
 
 disasters, largely resulting from ill-judged parsimony 
 in appropriations, should hereafter afflict the Nation. 
 
 But the ground is sometimes taken that where 
 cost comes in conflict with the best mode of fortify- 
 ing a particular site, cost must yield. The best sys- 
 tem must be adopted, no matter at what expense. If 
 a 16-inch gun is better than a 10-inch gun, it must be 
 had ; if a turret is superior to a lift or to a disappear- 
 ing carriage, it must be built. In a word, cost is to be 
 considered only when it becomes so enormous as to 
 forbid any hope of obtaining the needful appropria- 
 tions. In my judgment, in the present defenseless 
 condition of the coast this is a very mistaken view of 
 the case. 
 
 For example, suppose a million dollars were grant- 
 ed by Congress for beginning the work of defending 
 New York Harbor. The construction of a turret for 
 two 110-ton guns on the site of Fort Lafayette would 
 not, in my judgment, be a judicious application of the 
 money. Such a turret is needed and should be built ; 
 and if our government exhibited as much interest in 
 Coast Defence as does Russia or Italy it would cer- 
 tainly be promptly built. Still, the funds could be 
 better applied under the peculiar conditions exist- 
 ing here. There is no probability of our being able 
 for some years to fabricate 110- ton guns ; and until 
 we can do so the turret has no practical value — for 
 there is no chance that Congress will import guns 
 from Europe. One million dollars expended in sub- 
 marine mines, operating casemates, cable-shafts and 
 galleries, mortar batteries, lifts, and disappearing- 
 gun batteries, would produce a, much quicker re- 
 turn, and would at least enable some defence to be 
 made, and at a much earlier date, than if the money 
 were sunk in the turret. 
 
 But we may go even farther, and reach the same 
 conclusion upon the supposition that the ordnance 
 
54 Economy in Coast Defence, 
 
 will be on liand ready for mounting as soon as the 
 turret is completed. No doubt a turret at Fort La- 
 fayette mounting two 110-ton guns would have enor- 
 mous influence in deterring an attack ; but thirty-two 
 12-inch rifled mortars, six 12-inch rifles, mounted 
 say, one on a lift and five on disappearing carriages, 
 behind substantial earth parapets, and an effective 
 system of mines, with casemates, cable- galleries, etc., 
 complete, all of which could be provided for a million 
 dollars, would yield a better return for the invest- 
 ment. 
 
 I dwell upon this point because it is well worthy 
 of consideration, and because it is probable that 
 many officers, both of the Army and Navy, may not 
 entirely agree with me. We see clearly what is the 
 most powerful element, and are inclined to insist on 
 procuring it, no matter what may be the cost. If 
 funds were liberally provided to meet the needs of the 
 service, there would be no question that this is the 
 right principle ; but we know to our sorrow that this 
 is not the habit of legislators. Funds are given 
 sparingly and, what is worse, irregularly. In my 
 judgment they should be applied so that the aggre- 
 gate defensive return shall be the greatest, even at 
 the temporary sacrifice of some of the more expensive 
 and powerful elements. The whole case may be put 
 in a nutshell. St)oner or later war will surprise us, 
 and we shall have to do the best we can with very in- 
 adequate means. This ought not to be so ; but it will 
 be so, in spite of all efforts to the contrary. Hence, 
 in my Judgment, funds should now be applied as we 
 shall wish that they had been applied when we find 
 ourselves compelled to fight with but few chances of 
 success in our favor. An Inflexible would be a 
 precious possession ; but I think the 50 first-class 
 torpedo-boats, which, according to the money stan- 
 dard, she represents, would be of more service in the 
 
Economic Value of Different Elements, 55 
 
 defence of our extensive sea-coast if the war-cloud 
 were to burst to-day, or at any time within half a 
 dozen years, and very probably, indeed, at any time 
 within the next twenty years. I fear we shall never 
 have the coast properly defended until another war 
 like that of 1812 teaches our people that coast de- 
 fence is a live issue. In a paper read before the 
 Essayons Club of the Corps of Engineers, many years 
 ago, Major W. R. King discussed this question ; and 
 I quite agree with his conclusion that "cost is not 
 only a proper standard of comparison in engineering 
 matters, but to disregard it, or to speak of adopting a 
 certain material or mode of construction regardless of 
 cost, is simply a misapplication of terms." Our peo- 
 ple thoroughly understand the cash standard in tlieir 
 private business, and we must do the same in this 
 matter of coast defence, or some day we shall rue its 
 neglect. If these premises are sound the conclusion 
 is far-reaching for both services. 
 
 The problem of a new Navy is under solution by 
 naval men. The Army problem is now before us for 
 consideration ; and, to illustrate the principles which, 
 in my judgment, should govern in such studies, I ask 
 you to consider how a gross sum to be expended for 
 the defence of New York should be allotted among 
 different objects of expenditure ; and, to simplify 
 this discussion, I will limit it to the very practical 
 question. How should one million dollars be expended 
 in purchasing and placing in position 12-inch 50-ton 
 rifles ? 
 
 General Analysis. — Evidently the maximum 
 serviceable number of guns will be obtained by 
 placing them upon simple barbette carriages standing; 
 upon the shore, without protection, remote from each 
 other, and with no provisions for loading other thau 
 by hand. This would represent one extreme solu- 
 tion. The other would be to mount one gun in all 
 
56 Economy in Coast Defence. 
 
 the security and with all the facilities for rapid load- 
 ing.which could be obtained by expending the whole 
 balance of the appropriation on these accessories. 
 Between these limits what would be the most econo- 
 mical and hence the most judicious investment of the 
 iunds ? 
 
 I shall assume three fundamental principles 
 which, although perhaps sometimes modified by 
 special conditions, are in general true. They are, (1) 
 that the object to be sought is the maximum possible 
 number of well-directed shots fired against the en- 
 emy during the engagement ; (2) that the economical 
 value of a gun-carriage and mounting is directly 
 proportional to the number of shots it permits to be 
 ;S0 fired, provided this number does not exceed the 
 limit which the gun can safely endure ; (3) that the 
 economical value of an artificial protection for the 
 :gun and carriage is inversely proportional to the 
 •dangerous area through which it permits the shot of 
 the enemy to attain essential parts of the mechan- 
 ism. 
 
 In an exhaustive discussion of the problem other 
 •elements would find a place — such, for example, as 
 diminished efficiency resulting from restricting eleva- 
 tion and traverse in return for cover. Practically, 
 however, these are believed to be of so nmch less 
 importance that they may be waived. Thus lifts can 
 be arranged for an all-round fire unlimited as to 
 elevation ; a revolving turret allows a full traverse of 
 360 degrees, and all the elevation (15 degrees) which 
 is of much value against shipping ; the disappearing 
 carriage affords only about 120 degrees in traverse, but 
 is unlimited as to elevation ; in fine, the armored case- 
 mate is the only form of protection now advocated 
 ivhich seriously restricts the field of fire. But few 
 positions demand an all-round field ; and, more gen- 
 erally, conditions as to the offensive elements of the 
 
Economic Value of Different Elements, 57 
 
 battery are so dependent on the particular site that 
 they may be ignored in a general discussion. Lo- 
 cally they must be duly considered by the Engi- 
 neer. 
 
 In reasoning upon such questions the use of al- 
 gebraic formulae is almost a necessity, and I shall 
 therefore ask your indulgence for introducing the 
 method here. 
 
 Let 
 
 c?=duration of engagement in minutes. 
 
 ^= minimum interval between shots which the gun 
 
 will endure. 
 ^,=interval between shots, loading by hand. 
 ^//=interval between shots, loading by stored power. 
 a=area of target, in square feet, presented by an: 
 
 unprotected gun and carriage. 
 a^=area of target, in square feet, presented by a 
 
 protected gun and carriage. 
 w=number of minutes before the enemy by his fire 
 can disable the unprotected gun and carriage. 
 m,=number of minutes before the enemy by his fire 
 
 can disable the protected gun and carriage. 
 F=cost of a 12-inch 50-ton gun mounted without 
 
 protection, on a hand-loading carriage. 
 >S^= funds available for purchasing and placing 
 
 in position 12-inch 50-ton rifies. 
 a?= number of guns that should be mounted with J3,. 
 ^=: maximum percentage of V to be expended in- 
 increasing rapidity of fire. 
 J/=maximum percentage of V to be expended for 
 cover of gun and carriage. 
 Considering first the matter of rapidity in loadings 
 we have for the number of rounds fired by hand^ 
 
 — ; and for the number of rounds fired by stored 
 ^/ 
 
 power, — -. The difference between these quantities 
 
58 Economy in Coast Defence. 
 
 will be the number of rounds gained by improve- 
 ments in loading, providing, of course, that t^^ be not 
 made less than t. Factoring this gain, one factor 
 being the number of rounds with hand-loading, the 
 other {T) will express the maximum fraction of Y 
 which can economically be expended for machine- 
 loading. Hence : 
 
 d d d t, — t 
 
 ^11 ^/ ^/ ^// 
 
 (1) ^z=i=A/- 
 
 IN'ext, considering the question of cover for the 
 gun, by following the same course of . reasoning as 
 above we have : 
 
 
 e->) 
 
 M-- 
 
 m,—m 
 m 
 
 But since m : m/.\a, : a^ the numerical value of this 
 ratio will not be changed by writing a^ for m and a 
 for m,. Hence : 
 
 a — a, 
 
 Jf= 
 
 a. 
 
 But by revolving turrets, by lifts, and by disap- 
 pearing gun-carriages, the gun and carriage may be 
 removed entirely from the sight of the enemy for a 
 greater or less time between shots. By revolving 
 turrets and lifts its protection is thus nearly absolute 
 when in the position of loading ; and by disappear- 
 ing gun-carriages it is but little less so, being then 
 subject only to danger from shots on the rapidly 
 descending branch of their trajectory. Let us now 
 
Economic Value of Different Elements, 59 
 
 introduce these elements into the calculus, and de- 
 cide how much we can afford to pay for such extra 
 protection. This may be computed, with all needful 
 precision, by giving a coefficient to a, in the last 
 equation. Thus, if b denote the quotient of the thne 
 during \^hich the gun is exposed between two conse- 
 cutive shots by the whole time between two conse- 
 cutive shots, h a, will represent the mean area serv- 
 ing as a target ; and we have only to substitute h a^ 
 for a^ in the above value for M, giving for this class 
 of gun protection : 
 
 a — ha, 
 
 (^2) M^ 
 
 ha 
 
 Strictly speaking, h should be a little less than the 
 fraction above indicated, because this mode of mount- 
 ing gives the power of entirely withdrawing from 
 danger any particular gun upon whose emplacement 
 the enemy is concentrating his fire, and, while he is 
 thus wasting ammunition, taking advantage of the 
 comparative security of our other guns (against 
 which he must have temporarily reduced his fire) to 
 overwhelm him with deliberate practice. Since the 
 gun has to be moved, however, this advantage will 
 probably be offset by a small lengthening in the time 
 between shots— /. 6., by a small increase in t^,. Both 
 these details may be neglected, because their differ- 
 ence is too small a quantity to be considered in an 
 analysis so general as this. 
 
 In combining these several elements into one equa- 
 tion, it must be remembered that the fractional co- 
 efficients represent the maximum percentages of the 
 cost of the gun and mounting to be economically ex- 
 pended in the improvements which the terms of the 
 formula represent ; and hence that new coefficients 
 must be added to reduce the values thus found to the 
 actual percentages necessary to secure the desired 
 
60 Economy in Coast Defence, 
 
 improvements. Let A and B represent such coef- 
 ficients, respectively, and we may write : 
 
 X V + AxV T-\- BxVM^S 
 
 S 
 
 (3) x = 
 
 V (1 + A T+BM) 
 
 Proceeding to numerical applications of these for- 
 mulse, let us first compute the largest price which can 
 judiciously be paid for appliances for loading supe- 
 rior to those available in hand-work. Assuming t to 
 be 5 minutes, i, to be 10 minutes, and t,^ to be 5 min- 
 utes, equation (1) indicates : 
 
 y_ 10-5 _^ 
 5 
 
 That is, a sum equal to the cost of the gun mount- 
 ed without cover for hand-loading, or say $70 000, 
 may be expended to reduce the time of loading from 
 10 minutes to 5 minutes. The actual cost of such im- 
 proved facilities would not probably exceed $20 000, 
 liberally estimated. Hence the numerical value of A 
 (the quotient of 20 000 by 70 000) becomes, say, 0.3. 
 
 In discussing the question of cover, five kinds of 
 mounting will be considered: the simple barbette car- 
 riage behind an earthen parapet ; a King disapx)ear- 
 ing-carriage behind an earthen parapet ; a lift of the 
 pattern elaborated by General Duane ; an armored 
 casemate, and a revolving turret. To make the com- 
 parison exact it would be necessary to know the pre- 
 cise dimensions of the gun, of the carriage, and of the 
 exposure with each kind of cover. I shall only at- 
 tempt to make use of values closely approximate to 
 the truth. 
 
 When a 12-inch gun is mounted without cover 
 upon a carriage made after the old barbette centre- 
 pintle pattern for hand-loading only, it offers a tar- 
 
Economic Value of Different Elements^, 61 
 
 get of about 70 square feet to a direct fire from the 
 front, and of about 175 square feet to a fire perpen- 
 dicular to its flank. These areas are computed upon 
 the assumption that shots may arrive at any angle 
 between the horizontal and a fall of 10°; and, also, 
 that if they pass 2 feet below the level of the traverse- 
 rails they will disable the gun. Intentional ricochet 
 fire is ignored as no longer probable, especially 
 against guns on bluffs. Since the fire may come 
 through a wide arc in front, a mean of the two areas 
 above given, or 125 square feet, will be assumed as a 
 fair value to represent the target presented to the 
 enemy. 
 
 Case of a Non-disappearing Barbette.— A shot 
 striking the superior slope in front of the gun ten feet 
 or less from the interior crest would undoubtedly 
 disable the gun. The descending branch of a trajectory 
 having a fall of ten degrees, passing through this 
 point, would intersect the platform near the rear tra- 
 verse-wheels. The protection afforded to the gun by 
 this mode of mounting is tlierefore much less than 
 would appear at first sight. Indeed, the area of the 
 exposed target, computed upon the assumptions 
 above made for the unprotected gun, has still the 
 large value of about 80 square feet. Hence, by equa- 
 tion (2), 
 
 ^^125-(1X80)^0.56 
 1X80 
 
 Hence $70 000x0.56, or $39 200, is the maximum 
 sum which can economically be expended for this 
 mode of mounting. The average actual cost of such 
 a battery would probably not exceed $20 000, show- 
 ing that it is judicious to give even this insufficient 
 protection to the gun. Indeed, on very high sites, 
 like the bluffs bordering the Golden Gate, these 
 figures give an exaggerated idea of the defects of the 
 system. 
 
62 Economy in Coast Defence, 
 
 The value of B for this kind of mounting (20 000 
 divided by 39 200) is 0.51. 
 
 Case of the King Mounting for the 50-ton 
 13-inch Rifle. — The gun in its firing position ex- 
 poses a target of about 80 square feet ; and in its load- 
 ing position, perpendicular to the parapet, a target of 
 about 40 square feet — computed on the same prin- 
 ciples as above. 
 
 Major King estimates that the gun can be fired 
 with steam-power deliberately once in six minutes ; 
 but by improved machinery it could doubtless be 
 fired once in five minutes. Assume it to be exposed 
 in the firing position one minute, and in the loading 
 position perpendicular to the parapet four minutes, 
 and ha, becomes 
 
 S^^t^X^ ^ 48 square feet. 
 
 And from equation (2) we have : 
 
 ^^125-48^1 go 
 48 
 
 Hence $70 000X1. 60=$112 000 is the largest sum 
 which can be paid judiciously for this mode of mount- 
 ing. The actual cost of such a battery, including 
 the extra cost of the carriage, would probably not 
 exceed $25 000. Hence the value of B (25 000 di- 
 vided by 112 000) becomes 0.22. 
 
 Case of the Duane Lift.— The gun in its firing 
 position will expose a target of about 80 square feet, 
 and in its loading position will be entirely covered. 
 Assume it to be fired once in 5 minutes, during which 
 it is exposed 2 minutes, then ha^ becomes : 
 
 ?^^ = 32 square feet. 
 
Economic Value of Different Elements. 63 
 
 And from equation (2) we have : • 
 
 Jf=l^ii:?? = say 2.90 
 
 Hence $70 000x2. 9=$203 000 is the maximum 
 which should be expended for this mounting. The 
 actual extra outlay is estimated at about $80 000 ; 
 and the value of B (80 000 divided by 203 000) be • 
 comes 0.40. 
 
 Case of au Armored Casemate.— The gun is 
 constantly exposed, forming a target which may be 
 estimated at 20 square feet. Hence from equation (2) : 
 
 M=. ^^^~ ^^ c= say 5.25 
 20 ^ 
 
 Hence $70 000x5.25=$367 500 is the maximum 
 judicious outlay. The actual extra cost of such a 
 mounting will probably be $200 000. Hence for B 
 (200 000 divided by 367 500) we have 0.55. 
 
 Case of a Revolving Turret. —The gun will ex- 
 pose a target of about 20 square feet, for, say, two 
 minutes out of five. Hence 
 
 5« -20X2^8. 
 
 and from equation (2) we have : 
 
 M=- 1^5^!^ =: say 14.62 
 
 8 
 
 Hence $70 000x14.62^$! 023 400 is the maximum 
 price which should be paid for this mounting. But 
 the actual extra cost would probably nearly or quite 
 equal this sum, and B is therefore unity. 
 
 General Conclusions.— Equation (3) solved with 
 these values exhibits the comparative results (shown 
 in the following table) of the expenditure of one mil- 
 lion dollars for providing 12-incli 50-ton rifles. The 
 figures in the second column show the number of 
 guns, firing once in five minutes and mounted as de- 
 
64 
 
 Economy in Coast Defence. 
 
 signaled in the first column, which can economically 
 be placed in position ; and the figures in the third 
 column, the number of such guns which can actually 
 be mounted. The fourth column gives the number of 
 shots which can be fired per hour by the number of 
 guns indicated in the third column. The fifth column 
 exhibits the relative life accorded by the different 
 mountings, assumed to be measured by the inverse 
 ratio of their exposures. The sixth column contains 
 the quotients of the products of the figures in the 
 fourth and fifth columns by that product for the 
 guns mounted with ''no cover, hand-loaded." These 
 quotients perhaps exhibit, as correctly as such an ap- 
 proximate analysis permits, the economic merit of 
 the investments — upon the supposition that the en- 
 gagement is to last long enough to make the theory 
 of probabilities applicable. Local conditions may 
 materially modify the figures. 
 
 ECONOMIC COMPARISON OF DIFFERENT MOUNTINGS. 
 
 MOUNTING. 
 
 No cover, hand-loaded 
 
 Simple barbette 
 
 King disappearing...-. 
 
 Duane lift 
 
 Armored casemate 
 
 Revolving turret 
 
 NUMBER OF 12-INCH 50-TON GUNS IN POSITION 
 FOR $1 000 000. 
 
 7.7 
 4.9 
 3.4 
 2.2 
 1.0 
 
 14.0 
 9.0 
 8.7 
 5.9 
 3.4 
 1.0 
 
 84 
 108 
 104 
 71 
 41 
 12 
 
 1.0 
 
 1.6 
 2.6 
 4.0 
 6.2 
 15.6 
 
 1.0 
 2.1 
 3.2 
 3.4 
 3.0 
 2.2 
 
Economic Value of Different Elements. 65 
 
 From this point of view it would appear that the 
 Duane lift and the King disappearing carriage offer 
 the largest return for funds invested in mounting 
 50-ton guns. King's old-model carriage, mounting a 
 25-ton 15-inch Rodman gun, was thoroughly tested, 
 and was successful ; and there is no doubt that his 
 improved pattern, designed for larger guns, should 
 be experimented with at once. 
 
 This comparison as applied to the revolving turret 
 requires qualification. For sea-coast use they can be 
 and usually are made to contain two guns, because 
 this involves less cost per gun than when only one is 
 thus mounted. Moreover, sea- coast turrets are not 
 favored for guns of so small weight as 50 tons. The 
 table, therefore, must not be taken to imply more 
 than it actually expresses. Upon the basis of the 
 above computation, a much more favorable result 
 than appears above would be shown for mounting 
 two 110-ton guns in a single turret. 
 
 It will be noted that the moral effect of the pro- 
 tection, real or fancied, afforded by cover in front is 
 left to be taken into account by coefficients to the 
 sixth column of the table, based on individual judg- 
 ment. It is safe to assume that guns mounted in the 
 open would be deserted under the fire of a modern 
 fleet long before they could be dismounted. Men be- 
 hind a parapet which conceals the enemy feel com- 
 paratively safe ; and, by the doctrine of chances, 
 considerable time will elapse before a shot striking 
 where the cover is weak disabuses them of the belief 
 in its efficiency. At the siege of Petersburg the 
 two lines were within murderous musketry range of 
 each other, and rope mantelets to cover the gun-em- 
 brasures were a necessity. The first pattern was 
 bullet-proof, but too heavy for convenience, weighing 
 over 500 pounds. Subsequently a lighter pattern 
 which would not certainly stop bullets was used. It 
 
66 Economy in Coast Defence, 
 
 served all purposes. The enemy rarely fired at them, 
 believing that the shots would be thrown away ; and 
 our men were as happy behind them as they had 
 been when perfectly protected. War, like all things 
 human, has its successful shams, and cover more 
 apparent than real is often valuable. 
 
Third Lecture, 
 
 SELECTING THE SITE— HOEIZONTAL FIRE. 
 
 Sites to prevent bombardment or to cover anchorages — Sites to prevent 
 a forced passage ; height and character of the position ; development 
 of front ; submarine mine requirements — Horizontal fire ; range 
 and position-finders; revolving turrets; armored casemates; lifts; 
 disappearing-gun batteries; non-disappearing-gun batteries; fiank- 
 ing guns for mined zones ; magazines. 
 
 With American engineers tlie objects sought in 
 preparing works of coast defence are : (1) to forbid 
 distant bombardment; (2) to control important an- 
 chorages ; and (3), by far the most common and the 
 most urgent, to close important channels. Descents 
 in force are little to be feared, and of outlying coal- 
 ing stations we have none. 
 
 The elements of a first class system for Coast 
 Defence, as already stated, are : (1) high-power guns 
 and mortars for keeping the armored ships of the 
 enemy at a distance ; (2) land fortifications to liold 
 the position ; (3) obstructions in the channels of 
 approach ; (4) flanking guns, movable torpedoes, and 
 the electric light to cover the obstructions ; (5) vi- 
 dette and torpedo boats to watch the enemy and 
 make offensive returns. These elements are of pri- 
 mary importance, and they are the only elements 
 which can be so regarded ; their relative importance 
 at different sites will vary, but, according to modern 
 engineering principles, no site is thoroughly defended 
 unless all of them are represented. 
 
 These elements hardly admit of intercomparison 
 as to relative importance. Each must be sufficiently 
 elaborate to fulfil its special function at the locality. 
 
68 Selecting the Site, 
 
 Thus, obstructions cannot replace Mgh-power guns ; 
 neither can high-power guns replace flanking guns ; 
 nor can any or all of them replace fortifications, 
 or vidette and torpedo boats, which are essential to 
 guard against surprise and to make the offensive re- 
 turns so necessary to any defence in war. When 
 these five elements are judiciously combined and 
 sufficiently developed, they may be trusted to do 
 their work without further assistance, provided the 
 site is favorable. 
 
 Considerable latitude is allowed in the composi- 
 tion of these elements. 
 
 Thus, obstructions may consist of electrical buoy- 
 ant or ground mines, self-acting mines not under con- 
 trol, floating barricades, sunken hulks and piling, 
 or sometimes even imaginary obstacles believed to be 
 real by the enemy. 
 
 The high-power guns required are not the same at 
 different localities ; as a general rule their power 
 need not much exceed what the draught of water per- 
 mits to be brought against them, and they may be 
 mounted, according to circumstances, in armored 
 turrets, in armored casemates, on lifts, on disappear- 
 ing carriages, or sometimes even in open barbette. 
 Mortars in pits will be largely used. 
 
 A good flanking fire may often be had from 8-inch 
 or 10-inch smooth-bore guns firing canister, grape, 
 shrapnel, and shells; but machine guns, and even low- 
 power rifled cannon, may play an important part. 
 Movable torpedoes under control from the shore and 
 the electric light also fall under this class. 
 
 Our cavalry of the sea will certainly comprise fast 
 torpedo-boats, and not impossibly submarine boats of 
 the Nordenfelt class ; while it goes without saying 
 that such ships of war as can be spared from their 
 more important and more legitimate field of duty 
 will add powerfully to the defence. 
 
Sites to Prevent Bombardment. 69 
 
 Evidently a modein fortified position on the coast 
 is like an organ with many pipes and stops ; and to 
 produce harmony, care and good judgment in the 
 setting-up and skill on the part of the player are re- 
 quired. We have now to deal with the setting-up. 
 
 Having, by applying the principles enunciated in 
 former lectures, formed definite ideas as to the stra- 
 tegic importance of the works and as to the scale 
 upon which they are to be constructed, the first duty 
 of the Engineer is to select the site. This requires a 
 thorough understanding of the fiYQ elements in their 
 various forms, and a practical knowledge of their 
 several requirements for efficient service. 
 
 In actual practice nature often leaves but little 
 choice in fixing upon the best site; but in a theoretical 
 consideration of the subject it is well to decide what is 
 desirable in this connection. The object is to prepare 
 a field of battle in advance where our guns shall 
 overpower anything the enemy can bring against us ; 
 where they shall be placed in position in a manner 
 to combine maximum offensive power with minimum 
 vulnerability; where the channel shall be unfavorable 
 for manoeuvres and easy to obstruct ; and, in a word, 
 where we shall have, every advantage. 
 
 SITES TO PREVENT BOMBARDMENT OR COVER ANCHOR- 
 AGES. 
 
 Unquestionably a primary object in view is to se- 
 cure the place to be defended against distant bom- 
 bardment, which, so long as the enemy is kept out- 
 side the barrier erected in his path, is his natural 
 mode of attack. At some places situated on great 
 rivers or in deep indentations of the coast — as, for 
 example, at New Orleans, at Philadelphia, at Balti- 
 more, and at Washington— this problem is easy ; at 
 others— as, for example, at the Naval Depot formerly 
 projected at the Dry Tortugas, which is situated 
 
70 Selecting the Site, 
 
 upon a small island surrounded by a narroAV cordon 
 of sand-keys and coral-reefs, outside of which tlie 
 enemy could deploy and maintain tlirougli an arc of 
 360° a concentrated lire at easy ranges — the problem 
 to-day admits of no solution, and the project lias been 
 abandoned. Between these extreme conditions we 
 have many harbors which must be defended, and the 
 question arises in each case what kind and amount of 
 tire mxust be j)rovided, and what other means may be 
 employed to convince the naval commander that he 
 has more to lose than to gain from the contingent ad- 
 vantage of shelling the port at long range. This prob- 
 lem involves : (1) the effective range of modern high- 
 power guns mounted on shipboard ; (2) the amount 
 of damage they will probably inflict upon the port in 
 question ; and (3) what kind and amount of land-fire 
 and what other expedients will best produce the de- 
 sired conviction that bombardment is inexpedient. 
 Each of these questions admits of diJ3ferences of 
 opinion, and I can only give my own. 
 
 I. As to the extreme ranges to be expected from 
 naval guns, I assume, with Lieut. Very and others, 
 that from 13° to 15° is the maximum practicable ele- 
 vation for guns on shipboard. At 14° Krupp's 30,5- 
 centimetre gun, 35 calibres long, has thrown its pro- 
 jectile about 6.5 miles. Without entering into a dis- 
 cussion of the subject, which in this company would 
 be travelling over familiar ground, I will state that 
 as an engineer officer I have little expectation that 
 bombardment from shipboard will ever be seriously 
 attempted at ranges exceeding six or possibly seven 
 miles ; and bearing in mind the tremendous shock 
 upon the deck which cannot be avoided in such prac- 
 tice, the immense number of shots required for ef- 
 fective work where the results cannot be accurately 
 noted, and the short life even of the best modern 
 high-power guns, I do not believe that we have much 
 
Sites to Present Bomhardment 71 
 
 to fear at so long ranges, or, indeed, at ranges consid- 
 erably less than those named. That these views are 
 entertained abroad is sufficiently shown by the dis- 
 cussion of the problem for Spezzia., mentioned in a 
 former lecture, where the engineers considered 4.6 
 miles as sufficient to secure even their chief naval 
 establishment against unendurable annoyance. 
 
 Even in conservative England the dangers of bom- 
 bardment at panic ranges are discounted. Colonel 
 Schaw, R.E., the well-known Deputy Director of 
 AVorks for Fortification, said, in a lecture delivered be- 
 fore the Royal United Service Institution less than a 
 year ago : " Bombardments are now possible at ranges 
 of 8 000 to 10 000 yards distance, which would have 
 seemed fabulous in former days ; and although the 
 actual destruction produced by a bombardment may 
 be less than would be at first siglit thought probable, 
 yet, if ammunition be plentiful, it is undoubtedly 
 very serious, and may be disastrous if magazines be 
 exploded or important storehouses set on fire. 
 
 ^^ Dockyards are perhaps less inflammable now 
 than they were in former days, as iron enters so 
 largely into the construction of ou^ ships ; yet a great 
 quantity of wood and otlier materials that can be set 
 on fire must be found in every dockyard, and, in any 
 case, the bursting of large shells containing many 
 pounds of powder, or perhaps dynamite, will work 
 great havoc." 
 
 It will be noticed that he limits the dangerous 
 range to from 8 000 to 10 000 yards— ^^^., from 4.5 to 
 6.0 miles. 
 
 In the discussion which followed the reading of 
 the paper, Captain Henderson, Royal ISTavy, made 
 use of the following language: ^'I doubt the effi- 
 ciency of bombardment at long ranges by ships under 
 way (for ships cannot anchor for this purpose if ex- 
 posed to gun-fire or Whitehead attack), against uii- 
 
72 Selecting the Site, 
 
 seen objects, without any knowledge of the damage 
 done ; for the sliort life of breech-loadiiig heavy rilled 
 guns necessitates every shot being carefully hus- 
 banded." No speaker criticised this conclusion or 
 suggested a longer range as dangerous. Like contin- 
 uous picket-liriug on the lines of an army, the re- 
 sults will not compensate the outlay, for reasons in- 
 dependent of the ballistic power of the guns. 
 
 II. As to the damage which can be iniiicted at 
 these extreme ranges, experience at Charleston, 
 Yicksburg, Petersburg, and even Paris, has slio\^n 
 that many siege projectiles may fall within the limits 
 of a city without compelling a surrender. The laiger 
 sizes of naval shells will produce more destructive 
 results, and, among buildings like those in the lower 
 part of New York, they would probably prove unen- 
 durable ; but in a sparsely settled city like Galves- 
 ton I should not ajpprehend a decisive result. 
 
 III. As to what expedients are best to deter ves- 
 sels from indulging in distant bombardment, or to 
 cover important anchorages, I attach great importance 
 to a well-directed fire from many heavy mortars, in 
 pits quite out of sight, having a range of 5 miles, and 
 so mounted as to bring their fire perfectly under the 
 control of one officer. By mounting them compactly 
 on centre-pintle carriages, with traverse-circles grad- 
 uated to 360° from a common origin of azimuths, this 
 is easily accomplished, as will appear in the next 
 lecture. Supplemented by outlying groups of de- 
 tached mines to be fired by judgment, and by a 
 swarm of fast torpedo-boats ready to rush upon the 
 enemy when enveloped by the smoke of his own 
 gnns, these mortars, I think, would soon bring about 
 the desired frame of mind. 
 
 In fine, with proper arrangements, I believe little 
 is to be feared from distant bombardment when our 
 defensive works are placed at six miles outside the 
 
Sites to Prevent a Forced Passage. 73 
 
 object to be defended, be it a densely populated city, 
 a depot, a navy-yard, or a port crowded with vessels 
 of commerce. Still, if ten miles be practicable at rea- 
 sonable expense, no engineer to-day would probably 
 choose a less distance for works to prevent distant 
 bombardment. 
 
 SITES TO PREVENT A FOKCED PASSAGE. 
 
 In selecting a line for blocking the entrance, cer- 
 tain local conditions are desirable — snch are a single 
 channel, a favorable height and character of banks, 
 a well-developed front for ourselves, a contracted 
 front of attack, and a channel easy to obstruct ; the 
 latter calling for moderate depth, small tidal range, 
 gentle curients, water sufficiently turbid to conceal 
 mines, and a muddy bottom to bury the electric 
 cables. Each wilFbe considered in turn. 
 
 Height and Character of the Position. — A 
 low site near the sea- level possesses a single advan- 
 tage over one moderately high — it favors ricochet fire. 
 But in the days of smooth-bore guns and wooden 
 ships this was the most effective kind of tire known, 
 because a small error in elevation or a variation in 
 strength of powder did not prevent destructive hits. 
 For this reason water-batteries were often placed at 
 the water's edge, even when such locations involved 
 extra expense in foundations. Fort Wadsworth, in 
 New York Harbor, is an example in point. 
 
 With rifled guns this advantage has lost much of 
 its value, even against unarmored ships, because after 
 striking the water the projectile often diverges widely 
 from the plane of tire. Still, as many old smooth- 
 bore guns will continue to be used for the flanking of 
 submarine mines when attacked by boats, ricochet 
 fire is not entirely obsolete even to-day. Against 
 armored ships it conld no longer be used, because 
 after even one grazing impact on water so much of 
 
74 Selecting tlie Site, 
 
 the velocity is lost as to destroy the effective energy 
 of the largest projectile. 
 
 On the other hand, a low site for land guns entails 
 many disadvantages.* (1) It affords no direct fire 
 upon the deck of a ship, which, being her most vul- 
 nerable point, should always be attacked. (2) It en- 
 ables ships to dispense witli high angles of fire, for 
 which the mode of mounting their guns in a measure 
 disqualifies them. (3) It places the hostile guns on 
 shipboard on an equality with land guns as to energy 
 of impact — an advantage which nature denies them 
 in attacking a high battery. For example, a 16-inch 
 rifle, firing projectiles weighing one ton from a bluif 
 200 feet high, will have its efl'ective energy of imx)act 
 increased 200 foot-tons by gravity — a matter worth 
 considering wlien striking a'' plunging blow upon a 
 3-inch steel deck. A similar gun returning this fire 
 from shipboard will lose an equal amount of energy 
 in the projectile, which must be raieed against grav- 
 ity to the top of the bluif ; the ship will therefore be 
 handicapped to the extent of 400 foot-tons for every 
 shot jn a duel fought under such conditions. (4) 
 The depression of the axis of the land gun fired fi'om 
 a high site tends to make the trajectory more nearly 
 normal to the deck, while the corresj)onding elevation 
 of the axis of the gun on shipboard tends, at short 
 ranges, to make its trajectory still more oblique to 
 the parapet, and especially more oblique to inclined 
 armor. (5) A high site compels the ship to keep her- 
 self at a certain distance in order to bring the guns 
 to bear, and thus interferes with the precision of fire 
 needful to dismount land guns attacked from a mov- 
 ing gun platform like the deck of a shij). Even*nt 
 Fort Mex, a low w^ork at Alexandria, out of 920 shots 
 fired at 14 guns piactically en harhette by five ar- 
 mored ships at ranges from 1 000 to 3 800 yards, two 
 land guns were perhaps grazed but none were dis- 
 
Sites to Prevent a Forced Passage. 75 
 
 abled b.v direct hits ; and only direct hits can place 
 a gun properly mounted on a bluff Jiors de combat. 
 
 These considerations make it evident that where 
 nature has provided moderately high sites (say from 
 100 to 200 feet) they should be occupied by the for- 
 tifications of to-day. The question w^as not so simple 
 in 1864, vs^hen it was brought seriously to the atten- 
 tion of a special Board of Engineers convened, in 
 view- of the tlien recent changes in guns and of the 
 introduction of armor, to report what should be done 
 in respect to fortifications under actual construction. 
 We were not prepared at that date to entirely sacri- 
 fice the advantages of ricochet fire ; but no data 
 existed to decide definitely how much would be lost 
 by placing the guns considerably above the water. 
 
 The problem, about this time, was discussed ana- 
 lytically in a paper written by Prof. C. A. Schott, of 
 the Coast Survey, at the instance of General A. P. 
 Howe, Inspector of Artillery, IT. S. A., and his re- 
 sults were submitted by the latter in a report to the 
 Chief of Engineers. Mr. Schott based his computa- 
 tions upon the assumption that the angle of re- 
 bound from the water was equal to the angle of 
 incidence — an assumi)tion which I could not accept. 
 After the war was over, in the summer of 1865, acci- 
 dent placed my brigade of volunteer artillery troops 
 for a short time in the Defenses of Washington ; 
 and I took advantage of the opportunity to investi- 
 gate the problem by firing shots with 15-inch guns at 
 the heights of 36 feet and 103 feet above the waters of 
 the Potomac. These data I subsequently subjected 
 to mathematical analysis ; and General Haskin, of 
 .the Artillery, kindly checked the results by firing, in 
 1867, at Fort Schuyler, New York Harbor, with an 
 8-inch Rodman gun and a 24-pounder, at heights 
 above the water of 38 feet and 15 feet respectively. 
 This investigation led to definite formulae and con- 
 
76 Selecting the Site. 
 
 elusions, which are reported in full in Professional 
 Papers No. 14 of the Corps of Engineers. 
 
 Briefly, the results may be stated as follows : Re- 
 bounds cease when the angle of incidence increases to 
 about 8 degrees, whether fired from heights of 15 
 feet or 103 feet. The angles of rebound at the first 
 and subsequent impacts are always greater than 
 those of incidence ; and they follow a law which was 
 experimentally deduced. The loss in the ricochet 
 trajectories of the 15-inch gun, caused by increasing 
 its height above the water, proved to be not so great 
 as had been imagined. For example, with spherical 
 shells, weigliing 344 lbs. and having an initial veloci- 
 ty of 1 166 feet per second (assuming that such projec- 
 tiles are dangerous to unarmored vessels when mov- 
 ing with a velocity not less than 300 feet per second 
 at a height above the water not greater than 25 feet), 
 the lengths of dangerous ricochet trajectories are as 
 follows : 
 
 HEIGHT OP GUN. 
 
 DANGEROUS TRAJECTORY, 
 
 TOTAL TRAJECTORY. 
 
 FEET. 
 
 YARDS. 
 
 YARDS. 
 
 10 
 
 3428 
 
 4152 
 
 36 
 
 3122 
 
 4457 
 
 60 
 
 1924 
 
 3758 
 
 104 
 
 821 
 
 2706 
 
 150 
 
 481 
 
 1934 
 
 200 
 
 291 
 
 1508 
 
 250 
 
 63 
 
 1117 
 
 With residual velocities not less than 400 feet, and 
 heights of projectiles above the water surface not 
 greater than 20 feet, these figures become : 
 
 HEIGHT OF GUN. 
 
 DANGEROUS TRAJECTORY. 
 
 TOTAL TRAJECTORT. 
 
 FEBT. 
 
 YARDS. 
 
 YARDS. 
 
 10 
 
 3007 
 
 4152 
 
 36 
 
 2311 
 
 4457 
 
 60 
 
 1174 
 
 3758 
 
 104 
 
 433 
 
 2706 
 
 150 
 
 204 
 
 1934 
 
 200 
 
 57 
 
 1508 
 
 250 
 
 50 
 
 1117 
 
I 
 
 Sites to Prevent a Forced Passage. 11 
 
 With the smooth-bore ordnance in service when 
 our i3rovisional earthen-battery system was phinned, 
 it is plain that a trajectory useful for ricochet fire for 
 fully one-quarter of a mile was secured, even with 
 our guns raised 100 feet above the water ; and when- 
 ever this height was available it tvas selected in locat- 
 ing the works. We would do the same, for stronger 
 reasons, with the ordnance of to-day. 
 
 There are, of course, limits which should not be 
 exceeded in raising guns above the water. With a 
 depression of 7°, which is about the maximum pro- 
 vided for by modern carriages and mountings, the 
 dead angle in front of a gun 200 feet above the water 
 would cover 543 yards ; at 400 feet above the water 
 this space would be 1 086 yards wide. If a deep 
 channel past the position lay within this space, it 
 would evidently be necessary to place at least part 
 of the armament at a lower level. 
 
 The height of the site exercises a controlling influ- 
 ence upon die mode of mounting and covering the 
 guns. The object sought is to combine the widest 
 possible range and traverse with the least risk of 
 being silenced by the enemy's Are. If the site be low 
 and the adjacent water deep, the position is very 
 unfavorable and an open barbette mounting is inad- 
 missible ; for the ships would approach within less 
 than 1 000 yards, and with shrapnel and machine-gun 
 lire would render it impossible to serve the guns. 
 Turrets for 100-ton guns and casemates or lifts for 
 50-ton guns are imperative for such sites. With 
 heights 300 or 400 feet above tide the conditions are 
 far more favorable, and open barbette batteries may 
 be constructed with reasonable chances of effective 
 service. For intermediate heights, especially if 
 shoal water or mine fields prevent the near approach 
 of the vessels, disappearing guns in barbette batteries 
 may be trusted to do good service. On cliffs 500 feet 
 
78 Selecting the Site. 
 
 high, like some of those which border the Golden 
 Gate, land guns, however mounted, have enormous 
 advantages : the target is enlarged by the area of the 
 deck, the fire is pluno;ing, the enemy at short ranges 
 has difficulty in elevating his guns, and his shots, 
 pass over with little i'all. On the other hand, provi- 
 sion must be made to cover the dead angle left near 
 the shore. 
 
 When a choice is given between a low site near 
 the water and a bluff in rear, the question of relative 
 cost will often decide whether a more powerful gun 
 en barhette on the bluff or a less powerful gun in a 
 more expensive form of battery near the water shall 
 be preferred. Equal armor-piercing power at a two- 
 mile range should be secured. 
 
 There are, of course, other matters connected with 
 the banks besides height which have influence in 
 selecting the site. Forests are always advantageous, 
 because they favor concealment ; and for mortar bat- 
 teries, from which no sight of the enemy is required, 
 this is so important that, if not in siiu^ trees will 
 often have to be cultivated. The character of the soil 
 and of the foundation ; the absence of ledges of rock, 
 which will enhance the cost of construction ; and 
 many other matters pertaining to the details of the 
 profession, must have due consideration, although 
 they need not be dwelt upon here. 
 
 Development of Front. — The batteries of the 
 defence should be widely distributed : (1) to avoid 
 accumulations of smoke, which interfere with the 
 accurate firing demanded of modern guns ; this mat- 
 ter is more serious than formerly when far smaller 
 charges were burned, and when shorter ranges and 
 ricochet tiring rendered precision in pointing less im- 
 portant ; (2) to avoid the concentration of fire which 
 can be brought against a contracted site ; shots aimed 
 at one gun, under such circumstances, may take effect 
 
Sites to Frenent a Forced Passage. 79 
 
 upon its neighbor, and bursting sliells or accidental 
 explosions will cause the maximum of destruction ; 
 (8) because a widely -developed land front favors 
 cross-fire, which is exceedingly effective upon some 
 types of modern sliijjping, such, for example, as that 
 of the Benbow^ wliere 110-ton guns are exposed eii 
 barbette. Fighting "head on" maybe thus rendered 
 impracticable, except at too long ranges to be ef- 
 fective. 
 
 On the other hand, in selecting the position the 
 enemy should be forced, when possible, to make use 
 of a contracted front ; he will thus not only be sub- 
 jected to the inconveniences named above, but also 
 may be prevented from developing his full power, 
 and will certainly be thrown into confusion should 
 some of his vessels become unmanageable during the 
 engagement. 
 
 The map and the ground should both be studied with 
 a view to selecting a site combining the two advantages 
 of a wide development of fire for ourselves and a* 
 contracted front for the enemy. For example, the 
 choice may lie between occupying projecting head 
 lands where our guns must be massed on the sea- 
 shore, and where the enemy may develop his attack 
 from a semi-circle, with all his vessels advantugeously 
 placed ; or choosing an interior position where our 
 guns may be scattered widely while his front is re- 
 stricted to a narrow channel. In such cases the latter 
 site will always be selected by an engineer. A long, 
 narrow gorge opening in rear into a small bay, or a 
 sharp bend in the channel, will usually be occupied 
 by the defence rather than a position still farther to 
 the rear which enables the enemy to deploy in the 
 bay or to escape from a dangerous triangle. The ap- 
 proaches to Melbourne present a good example of the 
 first class of positions; and the East Kiver entrance 
 to New York harbor, one of the second. The i)osi- 
 
80 Selecting the Site. 
 
 tion at the Narrows is a familiar illustration where 
 the natural conditions oft'er great advantages to the 
 defence. 
 
 Submarine Mine Requirements. — Shallow wa- 
 ter, gentle currents, and small tidal range should 
 have great weight in choosing a site for blocking the 
 channel, whether by tlie older plans or by submarine 
 mines, which to-day afford the best and simplest 
 mode of so doing available to the engineer. Under 
 certain circumstances these conditions may of them- 
 selves modify the selection of the position ; for where 
 the mines are, there must also be an array of land 
 guns to cover them. San F'rancisco is a case in point. 
 
 This matter will be rendered more clear by con- 
 sidering briefly a few details. The smaller a buoyant 
 torpedo is made, the more easy it is handled and the 
 more likely will it be to remain effective for a long 
 period. Even in still water enough buoyancy must 
 be given to support tlie torx^edo-case, the charge, the 
 mooring ropes, and the electric cable ; in a strong- 
 current its depressing effect must also be taken into 
 account or the torpedo will sink too deep to be struck 
 by a passing vessel. With our spherical pattern tlie 
 buoyancy varies with the cube of the radius, wliile 
 the great circle cross-section varies with the square 
 of the radius. But the horizontal thrust due to the 
 current is directly proportional to the great circle 
 cross-section, and may be estimated in pounds per 
 square foot, when applied to the spherical surface of 
 our adopted pattern, by taking one-half of the square 
 of the velocity in feet. That is, a spherical torpedo 
 32 inches in diameter, having 6 square feet of cross- 
 section, w^hen moored in a current of 7 feet per sec- 
 ond, will experience a horizontal thrust of about 
 6 X ^ X 7' = 147 pounds. But this thrust is also ap- 
 plied to the mooring and electric cable, which in 
 water 50 feet deep about doubles its intensity — giving 
 
Bites to Prevent a Forced Passage. 81 
 
 in tills case a horizontal thrust of about 300 pounds 
 to be overcome by buoyancy additional to what is 
 required in still water. But to obtain increased buoy- 
 ancy sufficient to prevent the torpedo from being 
 carried below the draught of the vessel, its size and 
 hence the above figures must also be increased— and 
 increased very considerably— since the gain varies 
 only as the cube of the radius, while the increased 
 thrust varies as the square of that quantity. 
 
 These figures give an idea of the great difficulties 
 which beset the submarine miner wlien he has to con- 
 tend with a strong current. Great depths are hardly 
 less objectionable; for not only is the increased 
 weight of mooring and cable (about one pound per 
 running foot) to. be supported, but also the admissi- 
 ble angular deflection to prevemt too great depression 
 of the torpedo is rapidly reduced, and the absolute 
 buoyancy needful from this cause is correspondingly 
 increased. Practically a depth of 100 feet with a 
 current of 7 feet per second fixes the admissible 
 limit within which submarine mining is effective in 
 our harbors ; and defensive positions must be chosen 
 accordingl}^. 
 
 Excessive tidal ranges, such as prevail in the 
 English Channel (20 feet and upward), can only be 
 overcome by a double system of mines— one for low 
 water, and another in rear of the first for high water. 
 Very fortunately we are not afflicted with such tides 
 on our coast, where 10 feet is about the maximum 
 in any harbor of first-class importance ; hence this 
 double system is not necessary in our projects for 
 submarine mines. 
 
 After duly considering these matters of distant 
 bombardment, practicable height of batteries, nature 
 of the soil, development of front for himself and 
 contraction of front for the enemy, depth of water, 
 and the tidal range and velocities of cu/rents at the 
 
82 Selecting the Site, 
 
 different stages, the engineer selects his site or sites 
 and proceeds to study the extent to be covered by his 
 submarine mines, the needful armament, and the ex- 
 act character and location of his works. 
 
 HOKIZONTAL FIKE. 
 
 An early matter for consideration is : What sliall 
 constitute the land armament and how shall it be 
 placed in i)osition ? Tliis subject was referred by Con- 
 gress for report to a special Board, of wliich the Secre- 
 tary of War, Judge Endicott, was president— consist- 
 ing of two officers of the Engineer Corps of tlie 
 Army, two officers of the Ordnance Department of 
 the Army, two officers of the line of the Navj^, and 
 two civilian experts in steel manufacture. 
 
 This Board, in January, 1886, endorsing the views 
 of the Board of Engineers and of the last Armament 
 Board (July, 1884), recommended, exclusive of old 
 guns now on hand, the adoption of modern high- 
 ])Ower guns fabricated entirely of steel. For the land 
 defence of the twenty-seven most important seaports 
 of the United States the following calibies and num- 
 bers were specified, viz. : 44 16-inch guns, 6 14-inch 
 guns, 203 12-inch guns, 222 10-inch guns, 102 8-inch 
 guns, 4 6-inch guns, 700 12-inch rifled mortars, and 
 24 10-incli rifled mortals ; also 5 floating batteries, 
 150 toriDedo-boats, 12 special torpedo-gunboats for 
 the Lakes, and 6 161 submarine mines. 
 
 Summing up the total new armament recom- 
 mended for the twenty seven ports, we find 581 guns 
 of all calibres and 724 mortars. The 16-incli 110-ton 
 guns are recommended to be mounted in revolving 
 turrets ; the smaller calibres in armored casements, 
 on lifts, or on disappearing or non-disappearing car- 
 riages, according to the peculiarities of the sites. The 
 mortars are to be served in groups from pits entirely 
 concealed, when practicable, from the enemy's view. 
 
Horizontal Fire. 83 
 
 I shall confine myself to-day to discnssing the 
 different modes of providing for the horizontal fiie. 
 
 The power and character of the proposed gnns, 
 and reasons for their selection, are so familiar to all 
 present that time wonld be wasted in discussing 
 them ; but a fe\v words upon recent improvements 
 in land- pointing will not be out of place. 
 
 Range and Position Finders. — The change 
 from many small guns to few large guns in coast 
 defence has vastly increased the importance of mak- 
 ing every shot tell. For this reason the subject of 
 range- finding has received much study of late years, 
 and many devices have been presented for trial. For 
 sea-coast works where an altitude of not less than 
 fifty or sixty feet can be obtained, the principle 
 which seems to lend itself best to the requirements 
 of the problem is that of ''depression angles" : ix., 
 the angle is measured between the horizontal and a 
 line drawn to the water- surface at the object whose 
 distance is desired ; this being the parallax of the 
 known height of the instrument above the water 
 as seen from that object, the distance may either 
 be determined by calculation or be read from a scale 
 on the instrument. The accuracy attained by some 
 of these new devices is wonderful. One of the best, 
 known as the Watkin Depression Range-Finder, is 
 claimed to give an error of only about half a dozen 
 yards at a range of 2 000 yards. 
 
 Where the site is low the use of horizontal angles 
 becomes necessary ; and two observers at a consider- 
 able distance from each other, or a very delicate and 
 costly instrument with a short base, may be employ- 
 ed, according to circumstances. 
 
 But there is another difficulty inherent to modern 
 practice— viz., the volumes of smoke caused by burn- 
 ing so large charges, which makes it very desirable 
 to know more than the simple dista nce to th e object. 
 
84 Selecting tlte Site. 
 
 This necessity, and the advantages which grow out of 
 having one general system of range-finding instead of 
 isolated measurements, have led to the introduc- 
 tion of *' position-finders." These instruments de- 
 fine the ship's exact position at any instant of time ; 
 and by having the maj) divided into squares some 
 forty or fifty yards on the edge, and supplying lists 
 at the batteries giving the corresponding elevation 
 and azimuths, the guns, even when completely shroud- 
 ed in smoke, may be served with precision by orders 
 telegraphed from a distant station where the fleet is 
 in view. 
 
 The first system of position finding was devised 
 by Mr. Madsen, and was introduced at Copenliagen 
 in the war of 1864 by Colonel Ernst, of the Danish 
 Engineers. It was a complex system of triangula- 
 tion by theodolites, under electrical control from a 
 central station. 
 
 This plan was succeeded by the well-known Dis- 
 tance-Measurer of Siemens, by which, through the aid 
 of electricity, a light arm is caused to move over a 
 chart at a distant station, always retaining its paral- 
 lelism to the axis of the governing telescope. The 
 complexity of this system and the practical diffi- 
 culties attending it are the chief objections, and they 
 apply to the similar plan of Major Watkin, R.A., 
 submitted in 1867. In all of these three methods 
 the system of corresponding squares on the chart and 
 on the water forms the basis of the operation, and it 
 is evident that any well-considered plan of tiiangula- 
 tion can be adapted to the same principle. Major 
 Watkin' s electrical position-finder was tried at Pick- 
 lecombe Battery in actual practice at a moving tar- 
 get, and with decided success. 
 
 When a height of not less than 60 or 80 feet above 
 the water can be had. Major Watkin has modified his 
 range-finder to give azimuths as well as distances ; 
 
Horizontal Fire. 85 
 
 and llius, at a single station wlncli may be far reniov- 
 I^Led from smoke or hostile artillery practice, tlie point- 
 '^^ing of every gun in every battery may be regulated 
 by ordinary telegrapliy — the actual iiring may be done 
 at the battery or by electricity from the observing 
 station. This system is now adopted in the English 
 land service, and no doubt the same, or something 
 imilar, will hereafter be used in all sea-coast fort- 
 resses. Suitable stations are easily prei)ared at most 
 of our ports. 
 
 Speaking of this system before the Royal United 
 Service Institution within less than a year, Colonel 
 Schaw, R.E., Deputy Director of Works for Fortifi- 
 cation, said : ''This sounds too complicated and sci- 
 entific to be practicable ; but seeing is believing. The 
 S3'stem is no longer a project, but an accomplished 
 fact, which I have witnessed in successful operation, 
 and which I hope may soon be applied to every im- 
 portant battery we possess. . . . The percentage of 
 hits will be probably increased tenfold." 
 
 Moiiiitiiig Land Guns. — Reverting to how 
 land guns should be mounted, it is to be noted that 
 so soon as a resort is had to horizontal fire we are 
 compelled to face the problem of how best to en- 
 counter the flying asteroids now to be expected in 
 naval warfare. Five principal plans are in use to- 
 ay — turrets of various types ; armored casemates ; 
 ifts by which the gun with its platform complete is 
 raised to fire over the parapet, and then lowered at 
 once for cover while reloading ; disappeaiing car- 
 riages operated in a similar manner from a fixed 
 platform, but utilizing the force of recoil to raise the 
 gun ; and the open barbette mounting. 
 
 One remark is to be made emphatically at the 
 outset. No matter what kind of protection is chosen, 
 some of the defenders will be hurt. It appears to be 
 expected in some quarters that the same men who are 
 
 n 
 
86 Selecting the Site. 
 
 to be disciplined to endure the loss of one-tliird of 
 their numbers in serving a light buttery in action, are 
 to be guaranteed entire safet}^ as to life and linib in 
 serving the armament of a sea-coast fortress. This 
 is asking too much of the engineer, and is raising 
 a false standard by which to judge of his work. 
 Wh-ere blows are to be received measured b}^ the im- 
 pact of the New York obelisk dropx)ed from the top 
 of Trinity Church steeple, it is idle to look for ab- 
 solute security. Let us hope, before the time comes, 
 to have in readiness works offering reasonable 
 chances of safety ; but if not, our soldiers may be 
 trusted not to disgrace the flag. If there were no 
 risks to be encountered, the service would cease 
 to be war and soldiers would become mere laborers. 
 
 Revolving Turrets. — The details of revolving 
 turrets, with their machinery and gun-carriages, are 
 so similar to like arrangements on shipboard that 
 time would be wasted in discussing them. 
 
 Land turrets are surrounded by a massive 
 masonry glacis, below which, and properly covered, 
 are the magazines, the shell-rooms, the engine and 
 boiler rooms, the quarters for the garrison in war, and 
 such store-rooms for coal, etc., as are necessary for 
 the service of the guns. All these appurtenances 
 may be thoroughly protected ; and in this resjject 
 land turrets have decidedly the advantage over those 
 on shipboard, which must always be liable to become 
 unserviceable from any seiious injury to the ship 
 itself, whether caused by a gun, by a mortar, by 
 a submarine mine, or even hy a rock or shoal. 
 
 On land serious difficulty is experienced in pre- 
 venting fragments, dislodged from the masonry 
 glacis in the near vicinity of the base of the turret, 
 from becoming wedged in a manner to prevent its 
 rotation. This is attempted to be obviated in the 
 Dover turret by embedding in the masonry two ver- 
 
I 
 
 Horizontal Fire. 87 
 
 tical wroiiglit-iron plates parallel to each other, on 
 circumferences concentric with the turret. Gruson 
 j)rovides a massive glacis ring of chilled cast-iron, 
 buried in part under the masonry, but curving to 
 the rear to form half of a roof of a chemin des rondes 
 passing around the concealed truss which supports 
 the weight of the turret. The bottom surface of the 
 turret itself forms the other half of .this roof. The 
 junction between the two, near the crown of the arch, 
 is well protected against impact by the curved form 
 of both parts ; and the space between the plates is 
 too small to admit fragments of stone large enough 
 to stop rotation against the power of the engines. 
 This arrangement appears to be excellent. 
 
 The tendency at present is to replace the cylin- 
 drical form of turret by that of a cupola, with curved 
 surfaces inclined to the horizon — the object being to 
 break and deflect the projectiles by opposing only an 
 oblique surface. This form, admirable everywhere 
 else, entails serious consequences round the embra- 
 sures by the excessive cutting away of the metal 
 necessary to accommodate the gun. Protection im- 
 mediately over the chase is certainly apparent rather 
 than real ; and, worse still, the effect of a very pow- 
 erful blow upon the iron mass between the two em- 
 brasures, where it has little or no lateral support, 
 becomes, to say the least, doubtful; experiment here- 
 tofore has thrown no light on this difficulty. In 
 these two particulars the new form is far inferior to 
 the old ; it is the price paid for the unquestioned 
 advantages resulting from obliquity of imx)act. Un- 
 fortunately the weak place falls immediately in front 
 of the guns, where it can be least favored by rapid 
 and skilful manipulation of the revolving mechanism.. 
 A shattering blow here could not but be fatal to both 
 guns. 
 
 Another form of two-gun turret, known in Eng- 
 
88 Selecting the Site. 
 
 land as the CoUingwood mounting, is attracting 
 attention for land uses. The embrasures of the ordi- 
 nary turret are omitted, and the gun, mounted upon 
 a hydro-pneumatic carriage, is lired in barbette. The 
 breecli is lowered for loading, leaving the muzzle 
 always exposed. The iiitejior space is covered with 
 a steel deck, with openings to .permit raising and 
 lowering the guns. In this arrangement rotation is 
 given by a turn-table, the heavy armored walls re- 
 maining fixed in position ; they are made of inclined 
 iron covered entirely with masonry in the form of a 
 glacis. 
 
 The question of the kind of armor is still an open 
 one for land turrets. They have been actually con- 
 structed of wrought iron and of chilled cast iron, the 
 latter being now generally preferred on the Continent 
 of Europe ; they liave never been made either of 
 compound plates or of steel. The chief reason for 
 giving preference in naval constructions to com- 
 pound or steel armor — less weight for equal protec- 
 tion—loses much of its force when applied to a 
 land turret. The subject will be considered more 
 fully in a subsequent lecture, and I will now simply 
 express my opinion that judgment in this country 
 should be held in suspense for the piesent. 
 
 There are serious objections to the use of any 
 form of turret in coast -defence. They are enormous- 
 ly expensive ; they somewhat restrict the elevation 
 of the guns ; and, like all complex machines, they 
 are liable to become unserviceable in action by a 
 single lucky shot which may jam a gun in its em- 
 brasure, or by any chance accident to the mechanism 
 which may^render it impossible to revolve the turret 
 or to serve the ammunition. On the other hand, they 
 afford more perfect cover to the guns, the personnel, 
 and the machinery for loading and pointing than 
 any other known mode of protection ; they simplify 
 
\ 
 
 Horizontal Fire. 89 
 
 the carriage (a matter of no small importance with 
 guns of this weight), since no azimuth motion aside 
 from that of the turret itself is required ; they afford 
 an all-round lire ; in the event of an overpowering 
 concentration upon a single turret they permit all 
 vulnerable parts to be withdrawn temporarily from 
 action by revolving the embrasures to the rear ; and, 
 lastly, where nature has too much restricted the area 
 of the site, they compress into the smallest space the 
 maximum possible offensive power. 
 
 The balance between these merits and demerits 
 evidently becomes more favorable as the weight and 
 power of the guns increase. In our projects turrets 
 are proposed only for the 16-incli 110-ton gun, or for 
 larger calibres if such should ever become necessary, 
 and for low sites where a wide field of fire is demand- 
 ed. Under such conditions it must be remembered 
 that their cost, although great, is less than half of 
 the sums which have been expended for similar guns 
 to be brought against us on armored ships, and less 
 even than tliat of single buildings in our great cities, 
 which without tlieir protection may be reduced to 
 heaps of ruins. Twenty-two of them were recom- 
 mended by the Endicott Board. 
 
 Armored Casemates. — This mode of covering 
 guns so much restricts their field of fire that it has 
 only a limited application. About 15 degrees in 
 elevjition and 60 degrees in traverse (80 on each side 
 of the perpendicular) are all which can be given. If 
 a larger traverse is demanded, the best way is to in- 
 crea,se the number of guns and dispose them on a 
 polygon giving the needful dispersion. A hexagon 
 is usually the best form to select, because all the 
 guns on two adjacent fronts can be brought to bear 
 upon a vessel lying on the line bisecting the angle 
 included between these fronts. If a polygon of a 
 greater number of sides be selected, there will be a 
 
90 Selecting the Site. 
 
 wasteful overlap of fire ; if of a less number of sides, 
 there will be a dead angle which will be taken advan- 
 tage of by a skilful Naval Commander — as was done 
 in selecting the anchorage for the iron-clad vessels at 
 the bombardment of Fort Fisher. 
 
 This kind of protection permits no temporary 
 withdrawal of the armament from action, either for 
 repairs or to escape a concentration of hostile fire ; 
 and this objection is aggravated by the fact that per- 
 haps no form of battery is so difiicult to design to 
 meet the conflicting requirements of the problem. 
 
 The old composite form of iron shields and ma- 
 sonry merlons has long been out of date. An all- 
 iron scarp is now universally adopted, with a single 
 tier of guns, and with the magazines, etc., in case- 
 mates below them where perfect protection can be 
 given. For low^ sites this form of battery affords 
 better cover than any other except turrets. The cost 
 is materially reduced by combining several guns in 
 the same battery ; it is usual to consider from three 
 to five as the minimum number. They are necessarily 
 crowded in a small space, and the annoyance of 
 smoke in preventing accurate aim may well be feared. 
 The question of the kind of armor to be nsed is the 
 same as for turrets. It is still an open one in our 
 service. 
 
 Until the dimensions of gun and carriage are defi- 
 nitely determined it is impossible to form precise 
 rules for the interior space needful in a casemate. A 
 sufficiently close approximation for all general pur- 
 poses may be had, however, from the English rule, 
 which is based on large experience wath modern guns 
 and iron structures. It is in substance the follow- 
 ing : Strike an arc from the pintle as a centre, with 
 a radius of 24.5 feet ; the space included between the 
 extreme lines of fire, with four feet beyond them, 
 will afford enough floor space for any gun np to the 
 
Horizontal Fire, 91 
 
 S12.5-mcli of 38 tons. The 12-inch 43-ton B. L. gun 
 requires a radius of ^'o.^ feet, and one of 28.5 feet is 
 favored. A clear height of 9 feet is sufficient. 
 
 Casemate magazines are usually now placed in a 
 second tier under the guns, fitted with suitable lifts 
 for supplying ammunition. These lifts should be 
 placed in the rear piers, enlarged slightly for the 
 purpose, where danger of accidental explosions com- 
 municating to the magazines below is at a minimum, 
 and where the space required for serving the guns 
 is not encroached upon. 
 
 Reducing the size of the gun makes comparative- 
 ly little difference in the cost of the casemate, which 
 is chiefly dependent upon the size of the armament 
 to be brought against it. Hence only one type, 
 suited to the 12-inch 50- ton gun, is proposed for our 
 service, and it is restricted to low sites. Casemates 
 for eighty of these guns were recommended by the 
 Endicott Board. 
 
 Lifts. — This class of mounting dispenses with the 
 use of armor entirely, or at any rate restricts its use 
 to a light bomb proof roofing which ma}^ be sometimes 
 used to stop fragments of shells and shrapnel-balls. 
 The gun and its platform are placed behind a suita^ble 
 parapet, and by hydraulic power, with or without the 
 aid of counterpoises, are raised and lowered at plea- 
 sure. When in the firing position the gnn has all the 
 capacity as to elevation and traverse afforded by the 
 best barbette carriage, even, if necessary, being given 
 a traverse of 360 degrees; but no sooner is its work 
 done than it sinks out of sight and is loaded, so 
 far as horizontal fire is concerned, in perfect safety. 
 
 Guns have been actually mounted upon this prin- 
 ciple for several years at Cronstadt and at Alexan- 
 dria ; and the Temeraire and other armored vessels 
 carry guns disposed in a similar manner. General 
 Duane, when president of the Board of Engineers, 
 
92 Selecting the Site. 
 
 gave careful study to the subject, and devised two 
 types, one v^rith and the other without counterpoises, 
 which met with such favor before tlie Endicott Board 
 that tlie construction of 54 of them was recommended 
 for the defence of the Coast. 
 
 Lifts are usually restricted to the mounting* of the 
 12- inch 50- ton gun, and are preferred for medium 
 heights where a wide traverse is required. They 
 would serve an excellent purpose as the chief defence 
 of secondary ports where the depth of water in the 
 channel will not permit the entrance of vessels carry- 
 ing a more powerful armament than the 12-inch gun. 
 The cost is estimated at $100 000 per gun, and it is 
 greatly to be desired that the construction of one of 
 them should at once be undertaken, to enable the 
 minor details to be perfected by trial. 
 
 This mode of mounting x>ossesses so many and 
 such incontestable merits that a few details may 
 prove interesting. The two types devised by Gene- 
 ral Duane differ only in the mode of applying power 
 to the raising and lowering of the platform. They 
 have in common a substantial parapet to resist the 
 lire of the heaviest gun which can be brought against 
 them Usually the front of this parapet would be of 
 earth, but near the guns it must be of massive ma- 
 sonry, presenting only a horizontal surface to the fire 
 of the enemy. The crest is broken by semi-circular 
 recesses, 50 feet in diameter, to receive the guns, 
 which are placed at a minimum distance of 74 feet 
 apart. The centres of these semi-circles are live feet 
 in front of the crest, giving a horizontal angle of fire 
 of 180 degrees. The arrangements behind the para- 
 pet dispense with the use of traverses — a very great 
 advantage, as their absence destroys the usual clue 
 to the position of the guns. The latter are mounted 
 on any form of low centre-pintle barbette carriage, 
 which is supported by a circular platform 26 feet in 
 
Horizontal Fire. 93 
 
 diameter. This platform, wlieri in the firing position, 
 forms x>art of the masonry floor of tbe recess, the 
 reference being six feet below the crest. This floor 
 extends' unbroken to the rear for 50 feet from the 
 centre of motion of the gun. Covered by it are two 
 tiers of casemates for magazines, shell-rooms, etc.; 
 and in front of them on the side of the gun is a long 
 gallery, parallel to the crest, for communications, 
 hydraulic macliiiiery, etc. The circular platform 
 rests on a trussed staging, and can be lowered 14 feet 
 to the loading position. The muzzle of the gun in 
 the firing position extends well over the crest. After 
 the recoil, if not already there, it is traversed to the 
 front, where, within an angle of 60 degrees, the floor- 
 ing is cut away to form a recess to receive the muzzle 
 in lowering. Loading is done from a fixed position, 
 tlie usual shot-lift supplying the ammunition in front 
 of an hydraulic rammer lo force it home in the gun. 
 
 As already stated, the foregoing arrangements are 
 common to both of General Duane's devices. In one 
 of them the gun platform is lowered and raised by 
 means of six counterweio-hts and an hydraulic ac- 
 cumulator which communicates by pipe with the 
 gun-lift. The counterweights are connected by wire 
 ropes, running over drums, to the foot girders of the 
 platform staging. The total weight of gun, platform, 
 and staging is greater than the combined weight of 
 the counterweights, causing the gun to descend when 
 connection with the accumulator is turned off and the 
 waste-cock of the gun-lift is opened. The pressure of 
 the accumulator, when transmitted to the ram of the 
 gun-lift, is greater than the preponderance of the gun 
 and staging, and will raise them to the firing position. 
 
 The other device is operated without counter- 
 weights by a more powerful hydraulic ram, in the 
 manner usual to such mechanism. Experiment is 
 needed to determine which is the better arrangement. 
 
94 Selecting the Site, 
 
 Disappearing Gun-Batteries. — The invention 
 of a (Carriage which, without change of level in the 
 platform, shall remove the gun from sight when fired, 
 and by this motion shall store up the power need- 
 ful to raise it again when wanted, has long engaged 
 the attention of engineers as well as of artillerists. 
 
 The advantages of such a mode of mounting are 
 great. (1) The gun is exposed to injury only during 
 the firing. If overpowered it may remain under 
 cover, always ready to resume action when the ene- 
 my is tired of throwing away his ammunition. In a 
 word, such a battery can never be ''silenced'' until 
 the guns are hit. (2) The greater part of the person- 
 nel is permanently under cover, and the casual- 
 ties will consequently be few. (3) When guns are 
 mounted in this manner no satisfactory reconnois- 
 sance can be made by the enemy. I attach no little 
 importance to this matter, having myself experienced 
 a like difficulty in land operations. The Confederates 
 sometimes withdrew tlieir field-guns from the bar- 
 bettes, so that the most careful scrutiny gave no 
 information as to the artillery fire to which a charge 
 would be subjected. As soon as the assault was de- 
 livered, flanking guns would appear as if by magic, 
 and with results far exceeding wliat would have been 
 accomplished if tbeir position had been known and 
 our guns had been disposed accordingly. 
 
 Many different disappearing carriages have been 
 devised. No less than favQ distinct systems have 
 been introduced, but most of them are applicable only 
 to guns of small calibre. The Aloncrief counterj^oise 
 carriage will only carry guns about five tons in 
 weight. King's carriage, which alone has had a 
 practical trial in this country, has proved itself suc- 
 cessful with the 15-inch 25-ton smooth-bore gun ; and 
 his new adaptation for a 12-incli 50-ton gun ought to 
 be experimentally tested, without delay, in competi- 
 
Horizontal Fire. 95 
 
 tion with the Buffington and any other device which 
 promises success. The Moncrief hydro-pnenmatic 
 carriage, the Rendel carriage, tlie Raskasoff carriage, 
 and other types are favorably regarded abroad. 
 Armstrong now furnishes a disappearing carriage for 
 guns 70 tons in weight. 
 
 The excessive length of modern high-power guns, 
 and the loading at the breech, have increased the 
 difficulty of properly covering this type of carriage — 
 not only from the greater weights to be handled, 
 but also from the comparatively exposed position of 
 the cannoniers, which is so far removed from the 
 parapet that curved fire becomes annoying. 
 
 A special form of battery suited to receive the 
 new King carriage has been devised by the Board of 
 Engineers. The gun may be loaded from the extreme 
 rear ; but being exposed in that position to shrapnel 
 fire, and to shot descending at an angle of ten or 
 more degrees, x>rovision has been made»for revolving 
 the gun to a position parallel to the crest, and there 
 loading it from a j)assage in a bomb-proof traverse, 
 which contains, in sub-casemates, the magazines, shell- 
 rooms, etc. The cost of this battery is small, about 
 $15 000, and its efficiency in positions of moderate 
 height will be great. Cover is estimated at the rate 
 of 70 feet of sand, or its equivalent in concrete or 
 stone masonry. The gun is lowered 8 feet. In ex- 
 tending the battery an interval of 124 feet is left 
 between guns. The traverses rise 11 feet above, and 
 the terreplein is 12 feet below the level of the crest. 
 A sunken passage 6 feet below the terreplein affords 
 secure communications and fair cover for men en- 
 gaged in loading in the open. 
 
 Non-disappearing Gun-Batteries.— Probabl y 
 new batteries of this class will be restricted to ex- 
 ceptionally high sites, where they will certainly be 
 troublesome to the enemy. Simplicity and economy 
 
96 Selecting the Site. 
 
 are their chief merits. The only part of our present 
 armament which could with any chance of success 
 reply to the fire of modern guns is thus mounted, 
 and most of the batteries were constructed to admit 
 of the introduction of the old King carriage, if de- 
 sired. 
 
 It is to be noted, however, that although now 
 viewed with suspicion from perhaps exaggerated esti- 
 mates of the efficiency of shrapnel and of rapid- 
 firing guns on shipboard, there are indications that 
 where vessels can be kept at a distance this mode of 
 mounting may again receive favor. Thus the French 
 have adopted a simple barbette mounting for the 
 heavy armament (four 46- ton guns) of the Admiral 
 Dwperre and for other ships ; and the English have 
 followed their example in the Imperieuse^ the War- 
 spite^ and even in the Benhoio. Nay, more, the 
 heaviest guns now mounted in English land defences 
 (the four lOQrton Armstrong guns at Gibraltar and 
 Malta) are placed in barbette behind a high jiarapet 
 about 100 feet above the water. They are provided, 
 however, with a complete under-cover system of 
 loading. 
 
 The change from muzzle-loading to breech-loading 
 lias, upon the whole, done much to increase the effi- 
 ciency of barbette batteries. Although the cannoniers 
 are stationed further from the parapet, and are there- 
 fore more exposed to curved tire, the gun itself is a 
 great protection to them, especially at high elevations ; 
 and cover against small missiles is easily given by 
 steel hoods enveloping the breech. 
 
 Flanking Guns for Mined Zones.— None of 
 the modern high-power guns are well adapted for use 
 in flanking, being too heavy and too few in number 
 to be effective in such work. Machine and rapid- 
 firing guns will doubtless play an important part in 
 such operations, especially for new works where no 
 
Horizontal Fire. 97 
 
 flanking arrangements now exist. Where old ma- 
 sonry works are available, they will be measurably 
 serviceable, even with their present armament (usually 
 10-inch and 8 inch Rodman smooth-bores) ; for a heavy 
 fire of canister, grape, shrapnel, and shell is as 
 effective now as it ever was against launches and 
 small craft, which, if permitted to countermine, would 
 work the worst damage to the mines. Such vessels 
 abound in every fleet, and provision to meet them is 
 to be considered first. A few of ^the converted 8-inch 
 rifles now on hand, judiciously distributed among the 
 old forts, may prove serviceable against regular 
 counterminers. 
 
 Probably the idea will suggest itself to every one 
 that to depend on the old works to cover the flank- 
 ing guns of the mines is to rest on a broken reed ; 
 because they can be so easily breeched from a dis- 
 tance by the fleet, and because, under such a fire, the' 
 cannoniers would be driven from the guns. But it 
 must be remembered that countermining is most to 
 be dreaded at night, when little can be accomplished 
 by distant fire ; and that by day the ships, while at- 
 tempting to destroy the old works, will be themselves 
 subjected to the deliberate practice of the high-power 
 guns. Experience leads me to believe that a heavy 
 artillery fire upon an enemy's field battery will be 
 sure to compel a reply, and I see no reason to doubt 
 that the same is true on shipboard. Some of the 
 flanking guns would doubtless be placed liors de 
 Goinhat by occasional shots, and sometimes the tem- 
 porary withdrawal of the cannoniers will doubtless 
 be expedient ; but whatever be the demerits of the 
 old stone forts, a deficiency in number of guns is not 
 one of them. They swarm on every front, and par- 
 ticularly on those not visible to the enemy at a dis- 
 tance, from which their fire to flank the mines will 
 largely be required. The problem to destroy at long 
 
98 Selecting tlie Site. 
 
 ranges tlie efficiency of every one of scores of flank- 
 ing guns, wliile suffering from the tire of higli-power 
 guns, will, I think, be neither simple nor satisfactory 
 to tlie attacking party. Judging by the precision of 
 lire shown at Alexandria, the enemy will be liors de 
 combat before it is accomplished ; and while even a 
 few of the guns can be served liis fleet of launches 
 must remain idle. Wliile fort's of this type will 
 never be constructed in the future, they can still be 
 made use of in the plan of defence to-day ; and to 
 condemn them entirely is, in my judgment, a very 
 great mistake. 
 
 Where new works are to be constructed, wdi ether 
 for the flanking of mines or for repelling boat parties 
 attempting to land, so much use will be made of the 
 latest type of small ordnance that I shall give a brief 
 summary of some particulars which have an import- 
 ant bearing on land defences, even at the risk of re- 
 calling facts familiar to every one present. 
 
 The machine guns of Gatling, Gardner, Norden- 
 felt, and Maxim usually fire bullets of 0.45 inch cali- 
 bre, although Nordenfelt and Maxim both supply 
 patterns firing 1-inch steel projectiles. The rapidity 
 with which the small calibres can be served ranges 
 from 600 to 1 200 rounds per minute; they w-ere de- 
 signed to replace infantry fire, but are nov/ regarded 
 as better suited for defending positions than for 
 active field service. The Nordenfelt and Maxim inch 
 bolts were designed to pierce the light armor of tor- 
 pedo-boats. The. Maxim 0.45 inch projectiles are 
 fired automatically at the rate of 660 per minute, and 
 his inch bolts at the rate of 280 per minute ; the lat- 
 ter pierce an inch of iron at 100 yards. 
 
 Hotchkiss revolving cannon are made of calibres 
 37 mm. (1-pounder), of 47 mm. (3 pounder), and of 53 
 mm. (4-pounder). They fire shells designed to replace 
 light- artillery projectiles up to a range of at least 
 
Horizontal Fire. 99 
 
 2 000 yards (extreme range 5 000 yards). Served at 
 full speed, the smaller calibres have attained a rate of 
 600 shots per minute, and, when aimed, of 17 shots 
 per minute. A special flank-defence pattern (40 mm.) 
 is designed for sweeping ditches. The live barrels 
 are rifled on different pitches, ranging from 1 to 6.7 
 turns, which enables them to distribute 1 f)00 projec- 
 tiles per minute with admirable uniformity and 
 without change of aim, over a space 300 yards long 
 and 50 feet wide. 
 
 Rapid-firing hand- loaded guns are especially de- 
 signed for repelling the attacks of torpedo-boats, 
 and they will play an imi:)ortant part in flanking 
 mined zones. The Hotchkiss Company fabricates 
 them upon modern high-power principles, 82 to 34 
 calibres long. About 1 200 yards is their fighting 
 range, their rapidity of fire varying from 20 to 10 
 shots per minute, according to the care with which 
 they are aimed. Very gives the following as their 
 steel-penetrating power : 
 
 Calibre 37 mm., or 1-pounder : 0.8 inches at muzzle ; 
 
 0.4 inches at 1 200 yards. 
 Calibre 47 mm., or 3 pounder : 1.7 inches at muzzle ; 
 
 0.8 inches at 1 200 yards. 
 Calibre 57 mm., or 6-pounder : 3.5 inches at muzzle ; 
 
 1.75 inches at 1 200 yards. 
 Calibre ^^ mm., or 9-pounder : 4.0 inches at muzzle ; 
 
 2.25 inches at 1 200 yards. 
 Calibre 100 mm., or 33-pounder : — inches at muzzle ; 
 
 — inches at 1 200 yards. 
 
 Iron penetrations are one-third greater. These 
 guns all fire steel shells, common shells, shrapnel, and 
 case or canister. The three smaller calibres have 
 non-recoil mounts, and the others recoil mounts ; 
 they are also sometimes mounted on a miodified case- 
 mate carriage, or like field artillery. 
 
100 Selecting the Site. 
 
 The Elswick Company is now fabricating a 4.7- 
 inch 30- pounder pattern which has a muzzle velocity 
 of 1 900 feet per second, and which can be fired iit the 
 rate of 10 shots per minute ; and designs for a 70- 
 pounder have been completed. Should this gun prove 
 successful a very important departure in light can- 
 non of high power may be at hand. 
 
 Rapid-firing guns are also receiving attention at 
 Essen. A 15.5-pounder was tested last February 
 which gave a muzzle velocity of 1 990 feet per second 
 and a rapidity of 22 shots per minute. 
 
 These machine and rapid-firing guns have all 
 come into general use since our civil war, but they 
 are now universally adopted. When skilfully ap- 
 plied they will be of great service in meeting our 
 needs resulting fiom widely distributing batteries in 
 Coast Defence. 
 
 Magazines. — Magazines, of course, are always 
 l^laced, so far as possible, out of sight of the enemy, 
 and where his projectiles cannot penetrate. The 
 latter condition is far more difficult to fulfil than 
 formerly, and the problem often becomes perplexing. 
 The Royal Engineer rule a few years ago required 
 18 feet of granite or other masonry ; but they now 
 allow 40 feet, and Captain Lewis states (1884): "It is 
 probable that for the immediate present the 40 feet of 
 protection aimed at with our magazines is sufficient, 
 but it will not be so for long." 
 
 With turrets, casemates, and lifts, and at con- 
 tracted sites, the natural place for magazines is in 
 a tier of casemates under the guns. They should al- 
 ways be buried under ground when practicable. 
 
 The usual rule for capacity is based on having 100 
 rounds of cartridges and 100 rounds of shell on hand, 
 and not more than four guns are allotted to one ser- 
 vice magazine. 
 
 In future permanent magazines no attempt will 
 
Horizontal Fire, 101 
 
 • 
 be made to preserve the powder dry by excluding 
 moisture from the room. Experience has shown that 
 this is impossible to accomjjlish in many cases ; and, 
 moreover, the huge size of modern charges will forbid 
 their preparation at the time of firing. The cart- 
 ridges must be put up in advance, and in water-proof 
 cases whicli will serve to keep them dry indefinitely. 
 
 The necessity of precautions to prevent the acci- 
 dental explosion of a cartridge en route to the gun 
 from communicating fire to the magazine, is receiving 
 attention abroad. Safety-traps in lifts and swinging 
 mantelets in magazine passages are recommended ; 
 also that no more wood- work about a cartridge-lift 
 than is absolutely necessary should be allowed. 
 
 No greater disaster can occur during a bombard- 
 ment than the explosion, of a large magazine. Two 
 land batteries were silenced from this cause at Lissa 
 in 1866, and two at Alexandria in 1882. The sur- 
 render of the Castle of San Juan d'Ulloa to the 
 French fleet in 1838 was due to a like catastrophe. 
 At the storming of Foit Fisher, JS". C, in January, 
 1865, a shell from a 15-inch naval gun reached and 
 crushed the plank sheathing of the large traverse ma- 
 gazine at the principal salient near the Blakely rifle ; 
 and had the fuse done its duty many lives lost in 
 the subsequent assault mi^ht have been saved. It 
 is safe to assert that provisions to prevent such acci- 
 dents ill future will engage the attention of the En- 
 gineers of every Nation. 
 
Fourth Lecture. 
 
 MORTARS AND SUBMARINE MINES. 
 
 Vertical fire ; advantages of rifling ; carriages and platforms ; mortar 
 batteries ; economy of mortars— Submarines mines ; general condi- 
 tions ; attacks by daylight ; attacks by night or in fogs ; attempted 
 passage by force. 
 
 The introduction of armored ships of war, besides 
 increasing the calibre of land guns and modifying the 
 nature of their carriages, of their mountings, and of 
 their cover, has brought into so much greater promi- 
 nence two old elements of coast defence that it may 
 almost be said to have created them. I refer, of 
 course, to vertical fire and to submarine mines. 
 TJiese modes of counter-attack directly assail what is 
 now, and what must continue to be, the most vulner- 
 able parts of the ship— her deck and her bottom. 
 They have another peculiar merit : their attack ad- 
 mits of no reply in kind. They are weapons which 
 cannot be used by ships against forts, except mortars 
 in occasional river operations like the bombardment 
 of Fort Jackson, below New Orleans. With vertical 
 fire, the least roll of the sea or the least swinging to 
 the anchor must be fatal to anything like precision. 
 
 For these reasons I suppose a discussion of mor- 
 tars and submarine mines, rather more elaborate than 
 has been given to the use of guns, may be of 'interest 
 to Naval Officers. 
 
 VERTICAL FIRE. 
 
 For the defence of our entire coast the Fortifica- 
 tion Board of which Secretary Endicott was presi- 
 
Vertical Fire. 103 
 
 dent, endorsing the views held by tlie Board of Engi- 
 neers, recommended 581 high-power guns of all cali- 
 bres, and 724 heavy mortars, or, as they are now 
 often called, rifled howitzers. The proportion between 
 the number of guns and mortars shown by these fig- 
 ures differs so enormously from that accepted by the 
 best authorities a quarter of a century ago, that the 
 reasons for the change demand consideration. 
 
 They are, in brief, (1) Because the blow is struck 
 preciselj^ where armored protection is least effective, 
 and where either shot or shell are most destructive in 
 their effects. Indeed, in their power of encountering 
 such missiles ships have retrograded since the close 
 of the civil war, when it was proposed to give the 
 Kalamazoo a solid deck tliroughout of three inches 
 of wrought iron strongly supported. Now the ten- 
 dency seems to be to sink the protected deck below 
 the water-line, and thus to provide a shell-trap where 
 the effect of the explosion will be increased to the 
 maximum by confinement. In plunging fire the mor- 
 tar trajectory is incomparably more effective than 
 that of cannon. The latter, with the gun at a height 
 of 100 feet, attains an angle of incidence of 10 degrees 
 only at a two-mile range, and at a height of 500 feet 
 only at a mile-and-a-lialf range ; and this with low- 
 power guns. Modern high-power guns have still 
 flatter trajectories, and are therefore still less fitted 
 for effective plunging fire, (2) Because of the greatly 
 increased precision of modern vertical fire resulting 
 from the introduction of rifling, from improved sys- 
 tems of range-finders, and from a disposition and 
 mode of mounting which devolves the responsibility 
 of aiming upon a single officer stationed where he 
 can accurately watch the effect of his shots and cor- 
 rect errors as soon as they occur. Formerly this 
 responsibility fell upon the individual gunnere, who 
 were often annoyed by smoke and confused by the 
 
104 Mortars and Submarine Mines, 
 
 fall of projectiles other tlian their own around tlie 
 target— a difficulty aggravated by the long time of 
 flight as compared with tliat of guns. (3) Because 
 vertical Are cannot be silenced, even on land, when 
 the mortars are properly covered. The artillery con- 
 test at the digging of the Dutch Gap Canal on James 
 River in 1864 is a case in point. The excavation, 
 across a narrow neck between two bends, covered an 
 area of 30 000 square feet, being 500 feet long by 60 
 feet wide. The bank opposite the upper end of the 
 cut, held by the enemy, was low ; that opposite the 
 lower end, held by ns, was a bluff j^robably 80 feet 
 above the water. Moreover, a signal-tower, 120 feet 
 high, on this bluff, gave an excellent opportunity to 
 overlook the whole ground, the river here being only 
 400 yards wide. To interrupt the digging of the 
 canal, the enemy i)laced in front of it, at ranges vary- 
 ing fi'om 600 to 800 yards, four or Ave siege-mortars 
 in sunken batteries concealed behind clumps of trees 
 and provided with bomb-proof cover. Their lire 
 sunk the dredge and harassed the working par- 
 ties ; and to compel their silence became an impor- 
 tant object. Seven siege-mortars and five guns were 
 placed in position near the cut, where they had a 
 crossfire at short range; and a skilful officer. Cap- 
 tain Pierce, First Connecticut Artillery, fired about 
 4 000 shots, taking advantage of the tower to direct 
 his aim, and of the guns to prevent the Confederate 
 cannoniers fiom watching the effect of their firing. 
 He interfered with their practice, but he could not 
 compel their silence. This duel, and much other fir- 
 ing at Petersburg, convinced me that a mortar bat- 
 tery, well placed, well constructed, and well served, 
 cannot be silenced. If this be true in respect to a 
 land attack, how much more true is it in resx^ect to 
 .a naval attack, where no target is presented for 
 horizontal .fire,. and where vertical fire is not to be 
 
Vertical Fire, 105 
 
 feared ! In fine, sliips may sometimes compel the 
 silence of land gnns, but they must endure vertical 
 fire so long as they remain within range. (4) Be- 
 cause of the relatively small cost of mortars, as com- 
 pared with that of guns, both for fabrication and for 
 cover against an enemy's fire. This advantage per- 
 mits them to be used in large numbers without exor- 
 bitant demands upon the Treasury. Some of these 
 points will bear elaboration. 
 
 Advantages of Rifling. — The trajectory of pro- 
 jectiles fired under high angles differs materially 
 from that of ordinary gun practice ; and to appreci- 
 ate the effect of rifiing mortars this difference must be 
 understood. Fired with an elevation of, say, 45 de- 
 grees, the shell receives an initial velocity which can 
 be resolved into two equal components, one horizon- 
 tal and the other vertical. Both components will be 
 gradually reduced by the resistance of the air (acting 
 nearly in proportion to their squares), but the ver- 
 tical component is also directly opposed by gravity, 
 which soon brings it to zero. This will occur near 
 the highest point of the trajectory. Gravity, still 
 acting, will then communicate a velocity in the reverse 
 direction, which will increase proportionately to the 
 square roots of the distances passed over, until the re 
 sistance of the air, making itself felt more and more, 
 will at last establish an equilibrium, and the compo- 
 nent will become unvarying. The name "final ve- 
 locity" is usually applied to this, the maximum 
 theoretical velocity which can be used against a ship. 
 Unfortunately, from an engineer point of view, its 
 value is not great, being for a 10-inch round shot, 
 580 feet ; for a 15-inch round shot, 700 feet ; and for a 
 20 inch round shot, 790 feet. These values are theo- 
 retical limits which can never be reached, although 
 they may be approached in long-range practice. 
 
 The vertical component has so small an average 
 
106 Mortars and Submarine Mines. 
 
 value that, within the limits of ordinary firing, the laws 
 applicable in vacuo give results differing but slightly 
 from exact accuracy. Hence, within these limits, the 
 vertical velocity of impact of a mortar projectile may 
 be assumed to be that which would be acquired by a 
 heavy body falling in vacuo a height equal to one- 
 fourth of the horizontal range in feet. At elevations 
 above 45 degrees, the charge remaining the same, the 
 height attained is greater and the range is less ; and 
 hence, in obtaining a given range^ the useful compo- 
 nent of the velocity is doubly increased. At 60 de- 
 grees elevation the height is one-half greater and the 
 range is one-tenth less, and at 75 degrees elevation 
 the height is four-fifths greater and the range one- half 
 less than at 45 degrees. 
 
 From these well-known laws thefollowing approx- 
 imate rules result for estimating the vertical velocity 
 (in feet j)er second) of mortar projectiles at impact, 
 the firing being done at the water level. This vertical 
 component of course measures the effective velocity 
 upon which deck-perforation depends. 
 
 At 45 degrees elevation the vertical component is 
 four times the square root of the range in feet. 
 
 At 60 degrees elevation the vertical comx)onent is 
 4.9 times the square root of the range in feet. 
 
 At 75 degrees elevation the vertical component is 
 5.3 times the square root of the range in feet. 
 
 Having thus formed an estimate of the effective 
 velocities attainable at different high angles and at 
 different langes, the next point to be considered is 
 the energy necessary to accomplish the perforation of 
 the deck. 
 
 Actual experiments in this direction with vertical 
 fire are few in number. One fact noted by General 
 Duane at the attack on Fort McAllister throws some 
 light on the subject. A 10 inch mortar-shell, loaded 
 with sand and thrown by the fort at a range of about 
 
Vertical Fire, 107 
 
 1 800 yards, just penetrated the deck of one of our 
 monitors, which was plated with 1.5 inches of iron. 
 Assuming that the shell weighed 100 pounds, and that 
 it was fired at 45 degrees elevation, its vertical energy 
 at impact was about 1.9 foot-tons per inch of its 
 circumference. A 13-inch shell fired under like 
 conditions would have had 3.1 foot-tons, and would 
 probably have endangered the vessel. 
 
 Trials in England, about 1871, proved that a 13- 
 inch mortar-shell at 4 200 yards would easily pene- 
 trate a strong deck covered with 1.5 inches of 
 wrought iron under 4.5 inches of wood plank- 
 ing (energy, 7.1 foot-tons per inch of circumference) ; 
 and that at 2 800 yards it would penetrate a similar 
 deck covered with one inch of wrought iron under 4.5 
 inches of wood planking (energy, 4.7 foot -tons per 
 inch of circumference). 
 
 In the absence of experimental data derived from 
 modern vertical fire, recourse must be had to the 
 behavior of plating when tested in the ordinary 
 manner. It is most convenient to assume wrought 
 iron as the basis of comparison, because its resistance 
 is governed by more definite laws than that of any 
 other kind of armor ; and, although the different 
 formula3 representing these laws are not entirely 
 accordant, they are fairly so for small penetrations. 
 They indicate that to pierce three inches of wrought 
 iron requires from 12.5 to 14.5 foot- tons of energy per 
 inch of the shot's circumference. But this energy 
 for a falling projectile is : 
 
 ^^ WV ^ WY' 
 
 2 240 X 2^ X 27tB ~ 906 000^ 
 
 This formula shows, since Fis a function of the 
 range and i:>ointing, that when these are fixed the 
 only way to increase the energy at impact is to in- 
 crease the weight relatively to the radius. But this 
 is precisely the effect of rifiing; and herein lies the 
 
108 
 
 Mortars and Submarine Mines. 
 
 first advantage resulting from its use. For example, 
 tlie weight of a 12-inch solid shot is about 215 pounds ; 
 that of the corresponding elongated projectile is about 
 625 pounds. Here, therefore, is a gain of nearly 200 
 per cent, in the effective force of impact — a gain 
 which, by reason of the low velocities inherent to ver- 
 tical fire, is of great importance. It may even be in- 
 creased at short ranges, if deemed expedient ; Krupp 
 fires a projectile weighing 759 pounds from a 28-cen- 
 timetre (11-inch) howitzer at 58° elevation. 
 
 The following table exhibits the destructive ener- 
 gies of a service 12-inch rifled-mortar projectile fired 
 at different angles and ranges. It illustrates one char- 
 acteristic difference between horizontal and vertical 
 fire : with the former we must shorten the range and 
 lessen the elevation, and with the latter we must 
 lengthen the range and increase the elevation, to in- 
 crease the destructive effect. 
 
 FALLING ENERGY OP A12-INCn 625-LiB. RIFLED PROJECTILE. 
 
 
 rOOT-TONS PBK INCH OP 
 CIRCUMFEatENCB. 
 
 Bang©. 
 
 
 § . 
 
 a <v 
 
 O a> 
 
 ■ft 
 
 Half-mile 
 
 4.9 
 S.7 
 
 19.4 
 29.1 
 
 3a& 
 
 48.6 
 
 7.3 
 14.6 
 
 29.2 
 43.7 
 58.3 
 72.9 
 
 8.5 
 
 One mile ,. ... ....... 
 
 17.1 
 
 Two miles 
 
 34.1 
 
 Three miles 
 
 51.2 
 
 Four miles 
 
 68.2 
 
 Five miles 
 
 
 
 
 As already stated, it requires from 12.5 to 14 5 
 
Vertical Fire. 109 
 
 foot-tons \)QV inch of the shot's ckcumference to pen- 
 etrate a 3-iiich wroLiglit-iron deck. Hence at a range 
 of one mile and npward the fire becomes dangerous. 
 
 The second merit of rifling is that it vastly in- 
 creases the serviceable range. With the old smooth- 
 bore i3-iiich mortar the full charge was 20 pounds, 
 giving a range of 4 200 yards, of which not more than 
 2 200 yards were effective against a 3-inch deck. 
 With the 12-incli rifled mortar these figures are 60 
 pounds and 9 000 yards, of which 7 200 yards are 
 effective. Here, therefore, we have a gain of 325 per 
 cent. It is this merit that makes the new mortar so 
 useful in opposing the distant bombardment of cit- 
 ies by modern high-power guns on sliij)board. No 
 admiral would exj)ose his ships to receive such blows 
 on their decks without serious concern ; and, as will 
 soon appear, all we have to do is to multiply numbers 
 and provide suitable emphicements to obtain an occa- 
 sional hit, even at very long ranges. 
 
 But this suggests the third advantage of rifling — 
 increased precision of fire. It would at first sight ap- 
 pear paradoxical that rifling can be beneficial with 
 this class of ordnance. As used in guns it tends to 
 keep the axis of the projectile always pamllel to it- 
 self. But in vertical tire this would make the shell 
 fall sideways, which, by increasing the resistance of 
 the air, would reduce the vertical velocity, and by op- 
 posing an unsymmetrical shape would probably cause 
 an irregular flight. But experience, the only sure 
 guide in such matters, proves these anticipations to 
 be groundless. About a dozen years ago experiments 
 were made at Shoeburyness to test the matter. A 
 large target was inclined at such an angle as to re- 
 ceive the trajectory at right angles to its plane ; and 
 it was perforated by a round hole, not by one shaped 
 like the longitudinal cross-section of the projectile, 
 as would have been the case, to a greater or less ex- 
 
110 Mortars and Submarine Mines. 
 
 tent, if the axis had remained parallel to itself. A 
 little flag was then placed in the open fuse-hole, and 
 the spectators could distinctly perceive that the axis 
 remained nearly parallel to the trajectory. Knowing 
 the fact, it appears probable that the short length of 
 the bore in the mortar limits the velocity of rotation 
 just sufficiently to prevent tumbling, but not enough 
 to prevent the resistance of the air from forcing the 
 projectile to turn to a position of tangency. How- 
 ever this may be, nothing is more certain than that 
 precision of tire has been vastly increased by rifling, 
 as will appear from the following statement : 
 
 During the civil war 268 shots were fired in the 
 Defences of Washington, at a range of about half a 
 mile, to determine the precision of fire of smooth- 
 bore siege-mortars in the hands of good troops, under 
 fair service conditions. It was found that with the 
 10-incli mortar the average distance from the point 
 of impact to the centre of the target was 40 yards, 
 and that six-tenths of the shells fell within this 
 radius. With tlie 8-inch mortar these numbers were 
 .^0 yards and five-tenths of the shells respectively. 
 With the 24-pounder Coehorn mortar (for which this 
 range is too great) about half the shells fell within 80 
 yards of the centre of the target. With mortars, as 
 with guns, the accuracy of fire increases with the 
 weight and density of the projectile ; and it was esti- 
 mated that, with proper care, a 20-incli smooth-bore 
 mortar would throw at least half of its projectiles 
 within 30 yards of the centre of the target at a range 
 of 1 000 yards : i.e.^ the chances should be even that 
 the shell will fall within a circle of which the area 
 is 26 000 square feet. But the area of the deck of 
 modern war-ships varies between about 4 000 and 
 16 000 square feet, the mean (250 by 50 feet) being 
 about 12 500 square feet. Hence, by the theory of 
 probabilities, about one out of eight 20-inch mortar- 
 
VerUcal Fire, 111 
 
 shells (smooth-bore) should strike her at 1 000 yards 
 from the battery ; at 2 000 yards her danger would 
 not be very materially reduced ; at 3 000 yards the 
 uncertainty of fire would so much increase that it was 
 estimated that not more than one shot in twenty-five 
 would take effect. Let us now see how these figures 
 compare with the results to be expected from the 
 modern 12-inch rifled mortar. 
 
 At the Bucharest experiments of 1885-86 some 
 valuable data were obtained as to the precision of fire 
 of Krupp's 21-centimetre siege-mortar. The range 
 was 2 761 yards, or a little more than a mile and a 
 half. The charge was 6.6 pounds of powder. The 
 projectiles were either common shell weigliing 200 
 I)ounds, or steel shells weighing the same but longer 
 and carrying a larger bursting charge (24 pounds in- 
 stead of 10.5 pounds). The elevation varied between 
 53° and 56°.5. 
 
 Two mortars were used : 70 shell were fired at the 
 French cupola, and 94 at the German. The firing oc- 
 curred on four days, that at the French cupola com- 
 ing first. ' The following figures show separate analy- 
 se's, an evident improvement taking place during the 
 practice : 
 
 FRENCH CUPOLA. GERMAN CUPOLA. 
 
 Extreme lateral dispersion. . 273.4 yds. 76.5 yds. 
 Extreme dispersion in range. 393.7 '' 273.4 " 
 Average lateral dispersion. . 16.2 " 9.7 " 
 
 Average dispersion in range. 44.2 '^ 39.5 '' 
 
 Out of these 164 shells, 70, or nearly one-half, fell 
 within a rectangle around the target of which the area 
 was about 17 000 square feet (20 x 80 metres). Hence, 
 the area of the deck being 12 500 square feet, about 
 one projectile out of five or six fired from this siege- 
 mortar at a range of 1.5 miles should strike a modern 
 war-ship at anchor. The exact percentages, comput- 
 ed by the theory of probabilities, are, for the head-on 
 
112 
 
 Mortars and Submarine Mines, 
 
 position 17^ and 30i^ per cent., and for the broad- 
 side position Wyi and 14 per cent, respectively. 
 
 With mortars large enough to be used in coast de- 
 fence experimental data are not so full as could be 
 desired, because the firing has not been made under 
 service conditions. The chief causes of bad practice 
 are to be attributed : (1) to mechanical inaccuracies in 
 the mortar and carriage ; (2) to want of uniformity in 
 the ammunition ; (3) to errors in pointing ; (4) to v^^ind 
 and other unfavorable conditions ; (5) to the excite- 
 ment of action — although to this last little weight 
 should be accorded in mortar practice against ship- 
 ping, for the gunners will be covered so perfectly 
 against any return that the veriest coward should re- 
 main cool. 
 
 Precise data are available to estimate the effect 
 of the first-named causes of inaccuracy (mechanical 
 defects and variable ammunition) in Krupp's tables 
 of firing at Meppen : 
 
 GERMAN PRACTICE WITH 28 CENTIMETRE (11-INCH) 
 HOWITZER. 
 
 
 
 
 
 
 
 EXTREME 
 
 1 
 
 MEAN 
 
 
 w. 
 O 
 
 1 
 
 1 
 1 
 
 o 
 
 
 i 
 
 DISPERSION. 
 
 DISPERSION. 
 
 DATE. 
 
 "3 
 ■'3 
 
 
 "3 
 '5 
 
 i 
 
 
 a 
 
 w 
 
 
 ^ 
 
 
 
 0) 
 
 5 
 
 2 
 
 
 "i^ 
 
 
 
 
 
 •Si 
 5 
 
 a 
 
 To 
 
 1 
 
 a 
 
 \ 
 
 
 
 p 
 
 lbs. 
 
 lbs. 
 
 yds. 
 
 yds. 
 
 yds. 
 
 yds. 
 
 yds. 
 
 Mar. 30, 1887. 
 
 5 
 
 58 
 
 13 
 
 506 
 
 1993 
 
 36 
 
 5 
 
 11.9 
 
 1.6 
 
 July 9, 1886. 
 
 5 
 
 58 
 
 19 
 
 759 
 
 2 158 
 
 13 
 
 13 
 
 5.4 
 
 3.3 
 
 June 28, 1886 
 
 8 
 
 58 
 
 33 
 
 759 
 
 4 019 
 
 46 
 
 15 
 
 13.0 
 
 4.7 
 
 Mar. 14, 1879. 
 
 10 
 
 45 
 
 42 
 
 475 
 
 8 513 
 
 145 
 
 24 
 
 35.0 
 
 4.5 
 
 May 14, 1886. 
 
 10 
 
 45 
 
 62 
 
 475 
 
 10 787 
 
 130 
 
 54 
 
 36.2 
 
 10.4 
 
 Applying the calculus of probabilities to the last 
 
Vertical Fire. 
 
 118 
 
 two records, it ax)pears that nearly one rifled shell out 
 of two (65 per cent, in the head-on position and 15 
 per cent, in the broadside position) should strike 
 the deck of a war-sliip at a range ol 4.8 miles ; and 
 that nearly one out of four (81 per cent, in the head- 
 on position and 14 per cent, in the broadside position) 
 should take effect at a range of 6.1 miles. These fig- 
 ures, of course, give an exaggerated idea of what can 
 be expected in service, because the other causes of 
 inaccuracy above named are ignored. What numeri- 
 cal coefficient should be adopted to correct for these 
 omissions is a matter of individual judgment. 
 
 The follown'ng are some results of experimentill 
 firing with an 11-inch mortar in Russia in 1885. The 
 princip;d objects were the testing of new carriages, 
 and the determination of the maximum charge 
 under the condition that the pressure in the bore 
 should not exceed 1 900 atmospheres. These charges 
 were fixed, after firing 400 rounds with fiiD and 200 
 with reduced charges, at 46.9 pounds with a cast- 
 iron 1)1*0 jec tile weighing 477 pounds, and at 45 
 pounds with a steel projectile weighing 559 pounds, 
 the grade of powder being "large grain." I give 
 the table showing the abstract of this firing in full, 
 because it illustrates a subject concerning which 
 little information, is accessible : 
 
 RUSSIAN PRACTICE WITH 11-lNCH MORTAR. 
 
 
 Weight 
 of pro- 
 jectile. 
 
 Weight 
 charge. 
 
 Initial 
 
 veloc- 
 
 ity. 
 
 Pressure 
 at base 
 of bore. 
 
 Bange 
 
 at 
 43° 30'. 
 
 Probable deviation. 
 
 PROJECTILES. 
 
 In range. 
 
 In direc- 
 tion. 
 
 Cast iron 
 
 if 
 
 Steel 
 
 lbs. 
 
 477 
 
 477 
 559 
 559 
 559 
 559 
 
 lbs. 
 36.1 
 
 46.9 
 
 18.0 
 
 27.1 
 
 36.1 
 
 45.1 
 
 feet. 
 758 
 
 938 
 
 482 
 
 613 
 
 735 
 
 840 
 
 atmos. 
 
 1875 
 
 1700 
 
 yds. 
 5 668 
 
 7 412 
 
 2 343 
 
 3 597 
 
 5 014 
 
 6 431 
 
 yds. 
 24.0 
 
 28.3 
 
 17.6 
 
 13.2 
 
 19.8 
 
 26.2 
 
 yds. 
 4.4 
 
 6.5 
 
 3.3 
 
 «< 
 
 2.2 
 
 << 
 
 3.3 
 
 <( 
 
 4.4 
 
 
 
114 Mortars and Submarine Mines. 
 
 The wonderful precision attained in this practice 
 proves that the Krupp firing analyzed above was not 
 exceptional, and the same conclusion is warranted by 
 recent records of firing with a 12- inch mortar at 
 Sandy Hook. It must, therefore, be admitted that 
 modern improvements in vertical fire have kept pace 
 with those in guns. Indeed, in a recent analytical 
 accuracy table it appears that the probability of 
 hitting, with the projectiles of a 9-inch mortar, a first- 
 class ship of war lying at a known distance diagon- 
 ally to the plane of fire, is 62 per cent, at 1.3 miles, 
 51 per cent, at 2.6 miles, and 32 per cent, at 4.0 
 miles. In other words, it is about half that of Ijitting 
 the same ship with a rifled gun of similar calibre. 
 
 These results of the practice ground are not with- 
 out confirmation in actual service. On May 10, 1877, 
 a Russian shell from a 6-inch rifled mortar (one of 
 four in position near Braila, on tlie Danube) "pene- 
 trated the deck of one of the largest Turkish moni- 
 tors, the Luftl-Djelil^ and exploded in the powder- 
 magazine. She blew up and sank instantly, with all 
 her crew of 17 officers and 200 men. The ship was 
 a twin-screw, iron- clad, sea-going monitor, carrying 
 four 150-pounder Armstrong guns." 
 
 The latest development in mortar practice is the 
 reported ability to throw large explosive charges of 
 wet gun-cotton. It is stated on good authority that 
 in Germany shells containing 110 pounds are now 
 fired with safety from a 28-centimetre mortar. If 
 this claim be verified it marks an important advance ; 
 because the long range of the piece will enable it to 
 throw its projectile beyond the mined zones, and 
 thus avoid the objection fatal to the pneumatic dyna- 
 mite gun that it assists the enemy in countermining. 
 
 Carriages and Platforms. — No better evidence 
 can be desired of the low estimate which until within 
 a few years has been placed upon the value of verti- 
 cal fire than the crude mode of mounting universally 
 
Vertical Fire. 115 
 
 adopted. Every practical requirement of precision 
 was ignored ; hence, in my judgment, the small part 
 which mortars formerly played in projects for sea- 
 coast defence. Since their value has been better 
 understood, the old mortar bed with its eternal 
 ."heave, heave, heave," and the absurd pointing-cord 
 and old wooden quadrant, have disappeared, and 
 artillerists everywhej-e are giving intelligent consid- 
 eration to the subject. It is now appreciated that so 
 long as every gunner must point his piece indepen- 
 dently, the slow flight of the projectile will prevent 
 him from recognizing the splash of 'his own shell 
 from those of others ; and hence the more numerous 
 the mortars the worse will be the firing. 
 
 All this is changed in the new system. Mortars 
 are now mounted upon chassis like guns, and the 
 traverse-circle is graduated so that they can be accu- 
 rately pointed in any desired vertical plane. The ze- 
 ros of graduation for the entire group to be served 
 together are given the same relative position with re- 
 spect to the meridian, so that all can be set to fire in 
 any desired set of parallel planes. By this system 
 the captain regulates every shot ; and if the mortars 
 are all loaded with equal charges, set at equal angles 
 of elevation, and adjusted to the same azimuth, the 
 shells should fall, simultaneously if so desired, over an 
 area not greatly larger than that of the battery itself. 
 
 One curious fact, which has a bearing upon the 
 practicability of firing at high angles on board ship, 
 has been developed quite recently in experimenting 
 with new mountings. The increase of weight in pro- 
 jectile and charge has so largely increased the shock 
 on the carriage, and especially on the platform, that 
 radical changes are demanded. 
 
 Thus some recent experiments in Italy, conducted 
 by the Artillery and Engineer Committee with a 28- 
 centimetre (11-inch) howitzer mounted on an ordinary 
 carriage, with a charge of 42 pounds of powder and 
 
116 Mortars and Submarine Mines, 
 
 elevations varying from 30 to 60 degrees, liave proved 
 that the shock transmitted to the platform is sur- 
 prisingly difficult to resist. A platform of gianite, 24 
 inches thick, laid on a substratum of concrete 3 feet 
 thick, was soon cracked and thrown out of level. A 
 second platform, covering a wider area of concrete., 
 and with larger granite blocks, better distributed, 
 shared the same fate. The third trial was with a bed 
 introducing an elastic element. Upon the concrete 
 foundation was placed a layer of granite 16 inches 
 thick ; upon this was laid a double la^^er of oak 
 beams, each 10 inches thick ; upon this was a layer 
 of cast-iron plates, 4 inclies thick, with bevel joints. 
 Even this structure developed injurious cracks and 
 settling, although still serviceable after 244 rounds. 
 Finally, for the fourth trial, a platform identical 
 with the last received an additional top layer of 1.5 
 inches of wrought-iron plates. This structure en- 
 dured the tiring of 1 225 rounds without becoming 
 unserviceable, and was approved for adoption. 
 
 But the use of wood in the construction of per- 
 manent works has always been regarded with dis- 
 favor by Engineers, and it is quite natural to find, as 
 we do, that efforts are making to introduce the ele- 
 ment of elasticity in some other way. It is now 
 sought to modify the carriage in su^li a manner as to 
 reduce the shock on the platform ; and two different 
 patterns, one by the El:=wick Ordnance Company and 
 the other a Russian device by Lieutenant E-askasoff, 
 are under trial. 
 
 The Elsvvick pattern has yielded so favorable re- 
 sults with a 28 centimetre (11-incli) howitzer at Spez- 
 zia that the Italian government is reported to have de- 
 cided to order a large number for service. The prin- 
 ciple is to break the shock of recoil by interposing 
 an elastic buffer. The chassis-rails slope to the rear 
 at an angle of 60 degrees to the horizon. The top 
 carriage, resting thereon, is supported by two hydro- 
 
Vertical Fire, 111 
 
 pneumatic buffers fixed below and in prolongation of 
 the cliassis-rails. Each cylinder contains two cham- 
 bers, connected by a valve which can be regulated 
 from without. One chamber is filled with glycerine 
 and receives the recoil ram ; tlie other contains a 
 supply of glycerine and air. When the liowitzer is 
 fired the force of recoil drives the rams into their 
 chambers, and, displacing the columns of glycerine, 
 forces it out through non-return valves into tlie outer 
 chambers. This increases the normal tension of the 
 contained air and glycerine from 750 pounds to 1 150 
 pounds to the incli. To raise the carriage again to 
 the firing position the valve is opened between the 
 cylinders, and the equalization of pressure tlius ef- 
 fected does the work. The whole carriage, mounted 
 on a live ring, is readily turned to any desired azi- 
 muth by ordinary training gear. Facilities for bring- 
 ing the axis of the piece to a horizontal position for 
 convenience in loading are provided. The axis of 
 the liowitzer can be raised or lowered 15 degrees from 
 its mean elevation of 60 degrees in firing, thus permit- 
 ting of elevations ranging from 45 to 75 degrees. 
 The carriage supj)lied to the Italian government is 
 said to be adapted to receive an li-inch howitzer. 
 
 The new Russian carriage is similar in principle 
 to that of the Elswick Company, but, instead of the 
 hydro-pneumatic apparatus, use is made of an hy- 
 draulic cylinder and a system of steel-disc springs. 
 It has been adapted to an 11-incli mortar made on the 
 Krupp system and 12 calibres long. The action is 
 entirely automatic. The Committee desire to com- 
 bine low as well as high angles of fire, and thus are 
 compelled to sacrifice some advantages i^eculiar to 
 each. Tlie chassis-rails slope to the rear at an angle 
 of only 35 degrees. The carriage admits of an ex- 
 treme elevation of 25 degrees above this sloping 
 plane, or of 60 degrees as referred to the horizon. 
 The extreme recoil is said to be about two and a half 
 
118 Mortars and Submarine Mines. 
 
 feet. Several hundred rounds have been fired with- 
 out injury to a pattern of platform which with an 
 ordinary carriage Avas completely shattered. 
 
 It is quite certain that modern mortars will re- 
 quire some such mounting as has just been described, 
 and I think few matters connected with our new land 
 armament are more urgently in need of attention. 
 The Ordnance Department is alive to the necessity, 
 and it is to be hoped that Congress will soon provide 
 means for making the trials. With the old form of 
 carriage, or with any form which does not provide 
 a buffer, our Engineers will probably be forced to 
 introduce wood into the platforms. But, although 
 experiments have been made in this direction with 
 creosoted timber, no success lias been had in prevent- 
 ing decay when exposed for long periods ; and in all 
 probability the outbreak of war would find such plat- 
 forms either unlaid or unserviceable. 
 
 Mortar Batteries. — In these days, when Engi- 
 neers are compelled to deal so much with the terrific 
 energies of modern horizontal fire, it is a relief to find 
 one kind of effective ordnance which can be mounted 
 and served with almost absolute safety from behind a 
 simple earthen parapet. No embrasures with their 
 conflicting conditions are to be devised, and an ample 
 thickness of earth is all tliat is needful. But even 
 this statement does not present the case with suf- 
 ficient strength. The battery may be entirely con- 
 cealed from the enemy — indeed, would usually be so 
 concealed by natural inequalities of the ground, or 
 by bushes or trees. Even a view of the ship from 
 the battery itself is unnecessary, for the fire will al- 
 waj^s be regulated from a distant point. In a word, 
 with the smoke of our firing as the only target for 
 hostile guns, and with vertical fire (not to l)e had on 
 shipboard) only to be dreaded, it is easy to under- 
 stand why mortar-b^tteiies are simple as comx)ared 
 with all others. 
 
Vertical Fire, 119 
 
 There are, however, certain matters which must 
 not be ignored. In order that the projectiles shall 
 fall sufficiently near together to make the fire effec- 
 tive, it is essential that the mortars shall be massed, 
 thus constituting, as it were, a single piece. Four 
 mortars may be placed in one pit, and by disposing 
 four of these pits symmetrically round a common 
 centre very convenient arrangements for serving are 
 secured. A compact battery containing 16 mortars 
 logically results from this reasoning, and that num- 
 ber is suitable for the command of a single officer. 
 Such a combination constitutes, in effect, a single 
 gigantic musket throwing a charge of buckshot of 
 which each pellet weighs a quarter of a ton ! 
 
 The radius of the circle is fixed by the following 
 considerations : On the one hand, the lateral and 
 longitudinal separation of the pits must be sufficient 
 to afford space between tliem ample for magazines, 
 loading-rooms, and bomb-proof 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, else 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 direction parallel 
 to that plane. Indeed, in the former direction the 
 extreme limit can hardly be avoided ; but in the 
 latter it is easy to secure a decided overlapping of 
 the rectangles. 
 
 These conditions are fulfilled when the centres 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. 
 
 The arrangements in the battery are simple. One 
 long bomb-proof extends parallel to the usual plane 
 
120 Mortars and Submarine Mines. 
 
 of fire, with debouches into each pit near its extrem- 
 ities ; the magazines, shell-rooms, engine-rooms, etc., 
 are X)laced nnder the cross-embankment, with conjmu- 
 nications opening into the middle of the {;entral 
 bomb-proof. The firing will all be done by electricity 
 from the bomb-proof, permanent leading wires to the 
 mortars being laid in advance ; all the work of 
 loading, except the actual insertion of the shells iti 
 the mortars, will also be done under cover ; tlie 
 cannoniers will be exposed only when loading ; and, 
 lastly, nothing but accident can bring a hostile shell 
 to interrupt the steady prosecution of the firing. 
 
 The service of su(;h a battery in action would be 
 something like the following: The captain woukl 
 take his station at a point from which he could see 
 the enemy engaged at some work, as, for example, at 
 countermining in our mined channel. From his chart 
 and a position-finder he would determine the 
 elevation, charge, and azimuth for a trial shot. 
 Giving his orders by telephone, he would watch the 
 splash of the shell, and, estimating the deviation, 
 would give orders for the second shot accordingly. 
 Having succeeded in dropping one shell in close 
 vicinity to the enemy, he would order the whole 
 battery to adopt the same elevation, cliarge, and 
 azimuth, and to fire by volleys of 4 or of 16 mor- 
 tars, as seemed best. After that, countermining, 
 which to be eifective must be strictly local, could be 
 carried on only under great disadvantages ; and even 
 in an attempted distant bombardment the only safeiy 
 for the fleet would. lie in so frequent a change of 
 position as to destroy any precision of fire. 
 
 To fix ideas upon the probable distribution of the 
 projectiles f lom such a battery containing sixteen 12- 
 inch rifled mortars, I have discussed the foregoing 
 German and Russian data with ll-inch mortars, 
 which afford the best available criterion for judging 
 of the performance of the latest sea- coast types. The 
 
Vertical Fire. 
 
 121 
 
 two records are remarkably accordant ; and, combin- 
 ing those at 4.8 and 4.2 miles (8513 and 7412 yards) as 
 of equal weight, they give the following results when 
 discussed by an application of the method of least 
 squares. 
 
 The 16 projectiles, being fired under identical 
 conditions, should fall in relative positions corre- 
 sponding to those occupied by the mortars themselves. 
 But the units of each sub-group of four, being situated 
 at the angles of a square only 20 feet on the edge, 
 may be treated as a compound unit in the computa- 
 tion. The mean rectangle containing half of the pro- 
 jectiles of a single mortar, derived from the combined 
 records, is 28 feet wide and lt52 feet long in the plane 
 of fire. Hence, by the law of error, the following 
 rectangles result : 
 
 PERCENTAGE RECTANGLES IN MORTAR PRACTICE AT 
 4.5 MILES. 
 
 Zone. 
 
 Length- 
 
 Width. 
 
 Area. 
 
 Receives 
 
 Per Cent. 
 
 Feet. 
 
 Feet. 
 
 Sq. Feet. 
 
 Percent 
 
 20 
 
 62 
 
 11 
 
 653 
 
 4 
 
 40 
 
 136 
 
 22 
 
 2 103 
 
 16 
 
 CO 
 
 202 
 
 35 
 
 4 332 
 
 36 
 
 80 
 
 308 
 
 53 
 
 9 287 
 
 64 
 
 100 
 
 648 
 
 112 
 
 56 201 
 
 * 
 
 100 
 
 An over-lapping tinted diagram is next prepared, 
 showing these rectangles in their proper relative 
 positions ; and the number of projectiles, in a 
 volley from four mortars, falling in 1 000 square, 
 feet of each tint is inscribed thereon. By plac- 
 ing a tracing of the Inflexible^ also subdivided 
 into sections of 1 000 square feet, in any desired 
 position on this diagram, it is easy to estimate her 
 danger, and to form a definite idea of the degree of 
 
122 
 
 Mortars and Submarine Mines. 
 
 precision which is needful in the officer's determina- 
 tion of the locus of the ship when directing the firing. 
 The following results have been reached by this 
 method. To define the different positions occupied by 
 the middle of the ship, they are referred to a rect- 
 angular system of co-ordinate axes, parallel to the 
 sides of the rectangles of dispersion and central to 
 the field of fall. In the *' diagonal" position the 
 keel of the ship makes an angle of 45 degrees Avith 
 the axis of X. The shots per hour are computed 
 upon the supposition that six volleys are fired, 
 which is certainly within what may reasonably be 
 expected. The range, it will be remembered, is about 
 four and a half miles. 
 
 PROBABLE PRACTICE AT THE JKFLEXIBLJE WITU 11-INCH 
 MORTARS AT 4.5 MILES. 
 
 Position op the Ship. 
 
 (FEET) 
 
 Hits per 
 Volley. 
 
 Hits per 
 Hour. 
 
 Effective iier 
 cent, of 
 Shots. 
 
 Head on. 
 
 Central 
 
 0.93 
 
 5.6 
 
 5.8 
 
 (( 
 
 X = 60;Y = 
 
 3.24 
 
 19.4 
 
 20.3 
 
 (( 
 
 X = 60; Y = 122 
 
 2.84 
 
 17.0 
 
 17.8 
 
 Broadside. 
 
 Central 
 
 2.21 
 
 13.3 
 
 13.8 
 
 Diagonal. 
 
 Central 
 
 2.24 
 
 13.5 
 
 14 
 
 
 X :- 50 ; Y = 
 
 1.87 
 
 11.2 
 
 11.7 
 
 
 X = 100 ; Y = 
 
 1.40 
 
 8.4 
 
 8.8 
 
 
 X = 150 ; Y = 
 
 0.69 
 
 4.1 
 
 4.3 
 
 
 X - . ; Y = 100 
 
 2.27 
 
 13.6 
 
 14.2 
 
 
 X -_ ; Y = 300 
 
 1.69 
 
 10.1 
 
 10.5 
 
 
 Xr^O Y = 300 
 
 0.82 
 
 4.9 
 
 5 1 
 
 
 X = 0; Y = 400 
 
 0.33 
 
 2.0 
 
 21 
 
 
 X = ; Y = 500 
 
 0.07 
 
 0.4 
 
 05 
 
Vertical Fire. 123 
 
 From this table it appears that the fire of this bat- 
 tery, when armed with 11-iiich mortars, covers a space 
 800 feet long and 300 feet wide so effectively, at a 
 range of four and a half miles, that the Inflexible, 
 within its limits, would probably be struck from 
 two to nineteen times per liour. 
 
 It is, of course, to be understood that computations 
 of this character afford only approximate indications 
 of wliat can be attained in service ; but they do show 
 that with this form of battery slight errors in adjust- 
 ing altitudes, azimuths, and charges will have far less 
 effect than when the same number of mortars are 
 pointed and served separately. The combination of 
 several somewhat erratic projectiles in one volley 
 tends to eliminate individual lack of precision and to 
 distribute the fall over the dangerous area even more 
 uniformly than theory requires. The risk in occupy- 
 ing the field of fire is enormously increased ; and even 
 one such 16-mortar battery, skilfully served, should 
 go far to deter a ship from anchoring anywhere 
 within a range of from one to five miles with a view 
 to the bombardment of a distant city. 
 
 Economy of Mortars.— The cost of mortars 
 themselves is small compared with that of guns, for 
 they are not so much exposed to excessive powder- 
 pressures, and may perhaps be made even of cast 
 iron if any trustworthy mode of loading at the breech 
 Ccin be adapted to that material. The additional 
 weight needful with cast iron is perhaps no disad- 
 vantage in view of the difficulty of controlling recoil ; 
 but experience at Sandy Hook indicates that breech- 
 loading is essential to give the regular and uniform 
 velocity of rotation upon which precision of fire de- 
 pends. With muzzle-loading in so short a bore, the 
 expanding sabot acts irregularly, and the shells are 
 liable to tumble or to take up a wabbling flight incon- 
 sistent with uniformity of range. 
 
324 Mortars and Submarine Mines. 
 
 The cost of a mortar-battery is trifling as com- 
 pared with that for guns. Including masonry maga- 
 zines for a large supply of ammunition, bomb proofs 
 of ample size for all the needs of tbe garrison, and en- 
 gine and boiler-rooms for supj^ilying power for serv- 
 ing the pieces, the cost would range from $2 000 to 
 $6 000 per mortar, according to the local requirements 
 of the site. I constructed at Willets Point in 1872 
 a 16-mortar battery embodying the above principles, 
 at a total cost of $25 000. 
 
 But, it may be asked, why do not mortar-batteries, 
 with all these merits, solve the problem of a modern 
 coast armament, and thus render unnecessary the 
 heavy expense of high-power steel guns and armored 
 defences in which to mount them % Two defects in- 
 herent in vertical fire furnish the answer. It can 
 only be used with effect upon vessels under way by 
 the aid of a tlieoretically peifect system of position- 
 finding ; and from lack of energy in the projectiles it 
 is little to be dreaded at short ranges. If the enemy 
 can approach much within a mile, no destructive 
 blow will be struck by a descending projectile flred 
 pven at 75° elevation. The best held for horizontal 
 lire is thus the worst for mortars ; they are allies but 
 not substitutes. 
 
 SUBMARTl^E MI:NES. 
 
 General Conditions. — The following are the 
 general conditions which military engineers consider 
 should be fulfllled by this system of channel ob- 
 structions : 
 
 First. The mines must be so arranged as to admit 
 of the safe passage of our own vessels, while they 
 can instantly be rendered dangerous to the enemy. 
 This condition can only be fulfilled by employing 
 electricity as the igniting agent. When there are 
 several parallel channels, it may be admissible to 
 
Submarine Mines. 125 
 
 close some of them by self-acting mines ; but such 
 instances are exceptional, not the rule. 
 
 Second. Mines which can be exploded only by 
 judgment, at tlie will of an operator on shore, 
 have a very limited api^lication. In the night, or 
 a fog, or the smoke of a bombardment, or when 
 several vessels are a]3proaohing abreast, or when 
 the water is deep, or when the channel is wide, 
 the chances of failure are very great. Indeed, 
 the destructive range of practicable charges is so 
 limited that, if the ship be constructed with double 
 cellular bottom and water-proof compartments, 
 judgment-firing has become nearly obsolete for 
 any but very narrow channels. In general, there- 
 fore, the system must be automatic, the explosion 
 occurring in consequence of the touch of the ene- 
 my; but it should also admit of j^idgment-liring 
 by groups when desired. 
 
 To meet the ccmtingency of interference by our 
 own vessels, or the use of defensive outriggers by 
 the enemy, provision must be made to delay the ex- 
 plosion after contact, if desired, until the order to 
 lire can be given by "the officer directing the defence. 
 Since the apparatus must be operated in a casemate, 
 from which no view of the channel can be had, this 
 condition implies not only an arrangement of the ap- 
 paratus by which a contact may report itself without 
 firing the mines, but also a telegraphic communica- 
 tion with the ramparts. As a vessel moving at a 
 high rate of speed will remain only a few seconds 
 within dangerous range of a mine, a perfect code sys- 
 tem is essential. 
 
 Third, The mines should be so disposed as to 
 cover a large area of the channel. It is not enough 
 to oppose a narrow belt of danger. The waters 
 well to the front of the forts, under their close lire, 
 and far to the rear, must be dreaded by the enemy. 
 
126 . Mortars and Submarine Mines. 
 
 Fourth. Since the mines may remain in position 
 for long periods, the system must provide electrical 
 tests, by which the condition of every part may 
 often be verified in detail; and it must also be ar- 
 ranged to admit of rex-)airs in case of need. 
 
 Fifth. All of the mechanical arrangements of 
 the mine must be simple, enduring, and strong 
 enough to resist shocks from friendly vessels and 
 from the explosion of neighboring mines ; and special 
 precautions against twisting and undue dex)ression by 
 currents must be taken for all floating parts. 
 
 Sixth. Every practicable auxiliary expedient 
 should be adopted. Movable torj^edoes controlled 
 from the shore, and the electric light, are obvious 
 aids. In addition, the operating apparatus should 
 be arranged to provide for the automatic firing of 
 flanking guns in case of any disturbance of the sys- 
 tem by the enemy under cover of night or fog. The 
 electric cable should have sufficient weight to sink 
 into the mud in favorable localities, thus increasing 
 the difficulty of boat-grappling ; strong hemp cables, 
 weighted at short intervals, should be anchored in 
 the mine field with the same object in view ; and, 
 lastly, dummy mines and false buoys should not be 
 neglected. 
 
 As to the disposition of the mines in the channel 
 engineers are not entirely agreed. Some limit them 
 to two or three well-defined lines which cannot be 
 traversed because the least distance between contigu- 
 ous mines is less than the width of a ship of war. One 
 fatal objection to this mode of planting is, in my judg- 
 ment, that, with the practical difficulties to be en- 
 countered in most places, it is impossible to plant 
 mines so near together without bringing some of them 
 accidentally, in so close proximity that one explosion 
 will endanger the neighboring mines. A still stronger 
 objection to the plan is that it greatly favors the 
 
Submarine Mines. 127 
 
 kind of attack we have most to dread, that by counter- 
 mines. Such minute refinements are out of place 
 under water. If it is known or believed that the chan- 
 nel for three or four miles is thickly studded with 
 effective mines, the enemy will never attempt to run 
 past until he has found some way of opening a 
 reasonably safe passage. Nothing is so certain as 
 chance in such cases ; and the knowledge that the 
 individual mines are none of them nearer than even a 
 couple of hundred feet of each other will not induce 
 a wise man to try to run the gauntlet unless he can 
 see them. In other words, I believe that it is the total 
 number of the mines rather than great exactness of 
 location which will best bar the passage. But, on the 
 other hand, it would be almost impossible to thorough- 
 ly defend a channel without having some regular sys- 
 tem of working. The cables would become hopelessly 
 entangled, so that no repairs of tiie system would be 
 possible, if each mine were planted independently of 
 the others. Hence the use of the multiple (seven- 
 cored) cables leading to separate groups becomes a 
 necessity ; and these groups can be planted more 
 readily by assigning definite positions to the mines. 
 Moreover, by placing three mines on each separate 
 cable, each of them will explode singly if struck ; 
 while all three will be exploded simultaneously when 
 fired at the will of the operator on shore. The 
 efficiency of the whole system will be increased by 
 this mode of planting, and the use of the enormous 
 chai'ges favored in France and in some other countries 
 will be avoided. 
 
 For these and other reasons it appears desirable to 
 cut the field by continuous lines, with ample inter- 
 vals between mines to prevent them from becoming 
 mutually destructive when fired ; and to fill the gaps 
 between lines by single-cable mines admitting only of 
 automatic action. Upon this system it is possible to 
 
128 Mortars and Submarine Mines. 
 
 thorougUy obstruct a large area of cliannel without 
 increasing to an extravagant extent the total number 
 of individual mines. 
 
 There are two other mine systems which require 
 special arrangements. The object of one is to obstruct 
 a restricted area available for occupation in conduct- 
 ing a distant bombardment ; this is specially easy if 
 the water be so shalloAvas to permit the use of ground- 
 mines. A few large and carefully located charges, 
 arranged preferably for judgment-tiring (so that their 
 discovery by sweeping shall be made as difficult as 
 possible), will reinforce mortar-firing in a very ef- 
 fective manner. Such mines, technically called "de- 
 tached groups-," will certainly be used to cover an- 
 chorages like that near Coney Island, whence a ves- 
 sel, without crossing the bar, might annoy Brooklyn. 
 The system permits the use of cable too much de- 
 teriorated for automatic firing, and may have an ex- 
 tended application under certain contingencies. 
 
 The other special system is emi)loyed when we can 
 afford to sacrifice one or more channels because we 
 have the use of a better one defended by electrical 
 mines. Such an obstruction would be made by the 
 use of self-acting mines, dangerous alike to all comers. 
 The only remark I have to make in respect to this class 
 is that no pattern which fails to fulfil three conditions 
 should be received with favor. These conditions are, 
 iV) that no safety arrangement which requires the act 
 of the planting party to remove is admissible ; (2) that 
 some arrangement to cause the immediate explosion 
 of the charge if the mine goes adrift is essential ; and 
 (3) that every possible means should be taken to make 
 the removal difficult. There appears to be a differ- 
 ence of opinion among engineers as to this last point ; 
 but I think it arises from overlooking the fact that 
 it is impossible to easily remove ourselves what an 
 enemy informed as to the mechanism cannot also 
 
Submarine Mines. 129 
 
 readil}^ clear away. No compromise in such a case 
 is possible. If we want efficiency we must pay tlie 
 price by incurring difficulty in oijening the channel 
 when the need for tlie obstructions has passed. 
 
 This same class of self-acting mines may some- 
 times find useful employment in repairing injuries 
 done to a regular system of electrical mines by coun- 
 termining. To be of much use the passage opened by 
 the enemy must be well marked and buoyed. A few 
 self-acting mines dropped in it by night would prove 
 extremely dangerous ; and such mines are very easily 
 handled and rapidly planted. All that is necessary 
 to render the expedient easy of application is to 
 adapt the special parts of the self-acting mechanism 
 to the ordinary electrical mine, so that when desired 
 it may be planted to act in either capacity. 
 
 To operate electrical submarine mines success- 
 fully, large voltaic batteries and delicate apparatus 
 of various kinds are indispensable. To expose this 
 material to boat attacks, or even to distant bombard- 
 ment, would be inadmissible, for even a slight in- 
 jury here might open the channel to the enemy. 
 The operating ai:)paratus is the most vulnerable pait 
 of the sj^stem ; hence the accepted principle that 
 mines must be served from strong land fortifications. 
 A sunken gallery leads from the water edge at lowest 
 tide, under the foundations of the fort, to a vertical 
 shaft oiDening into a bomb-proof casemate which 
 contains the apparatus. This apparatus is connected 
 with the ramparts by telegraph, so that the engineer 
 is fully informed as to what is electrically reported 
 by the ndnes, and at the same time is able to see 
 what the enemy is doing and to take measures ac- 
 cordingly. 
 
 Attacks by Daylig'ht. — Where the defence is 
 believed to be weak, shii^s, by the use of outrigger 
 frames or wire-rope crinoline, may try to explode at 
 
130 Mortars and Submarine Mines. 
 
 a safe distance such mines as may chance to be en- 
 countered. But with electrical mines the engineer 
 will simply delay the explosion until the torpedo has 
 passed under her bottom ; or, if such devices should 
 ever be made really practicable, he will plant his cir- 
 cuit-closer buoys a little in rear of his mines, and 
 thus cause the explosion to occur precisely where he 
 wants it. Finally, the crinoline being certainly 
 swept away by the first explosion, the ship will be 
 left, encumbered by the wreck, among other mines 
 equally dangerous. 
 
 Should divers be sent forward to destroj^ the sys- 
 tem, so soon as their work is revealed by the electri- 
 cal indications a mine fired in the vicinity will at 
 once put an end to their labors. 
 
 If old hulks, steered by electricity, be sent for- 
 ward to explode the mines in the channel, or if rafts 
 provided with grapnels be allowed to drift in with 
 the tide, the engineer will switch off his batteries ; 
 and, although injury may result, a terrible uncertain- 
 ty will be left to the enemy as to how many perfect 
 mines may still be waiting to receive him. 
 
 Remembering that a cleared and buoyed passage 
 is a sine qua non for the fleet, and that by daylight 
 the guns of the fort will sweep the mined zone with a 
 murderous fire, the uncertainty of any unsystematic 
 attack is apparent. The only successful method of 
 attacking land mines has been shown, by the experi- 
 ence of centuries, to be by countermines, and I be- 
 lieve that future wars will teach the same lesson for 
 sea mines. 
 
 Steam-launches, controlled by electricity or other- 
 wise, or small, heavily armored vessels made for the 
 purpose, will move up to the supposed outer limit 
 of danger ; will plant from one to four 500-pound 
 counteruiines ; will back off, and by exploding them 
 by electricity will destroy any mines in the immedi- 
 
I 
 
 Submarine Mines, 131 
 
 ate vicinity. The vessel will then steam forward into 
 the vortices and plant one or more buoys. By re 
 peating this operation it is clear that n safe channel 
 maybe opened and plainly marked ; and that, finally, 
 the fleet will be free to move rapidly tli rough it past 
 the guns. 
 
 These countermining operations, however, will be 
 neither expeditious nor safe. The vessel will neces 
 sarily indicate her successive positions of rest, and 
 the mortars and guns will prepare volleys for her 
 reception at i)oiiits where her exact locus is known. 
 Movable torpedoes under control from the shore will 
 assail her below the armor belt, however massive that 
 may be. By night new mines will be dropped in her 
 buoyed channel. In fine, the delays, disasters, and 
 murderous struggles familiar in land-mining will in 
 future wars find their counterparts on the sea. 
 
 Attacks by Night or in Fog^s.— Under such 
 conditions the firing of the guns and the operating 
 of the mines cannot be so intelligently directed by 
 the defence ; but, on the other hand, the enemy can 
 derive little information as to the details of the dam- 
 age inflicted, unless he sends boats forward to work 
 systematic mischief and to drop buoys accordingly. 
 How to defend the mines against boat attacks con- 
 ducted when shrouded from view becomes, therefore, 
 an important engineering problem. The best of all 
 assistance can be rendered by a flotilla of naval j)ick- 
 et and torpedo-boats ; but when they cannot be had, 
 four useful auxiliaries may be employed — fouling- 
 lines, automatic action of the guns, the electric light, 
 and, last but not least, movable torpedoes under con- 
 trol from the shore. I shall say a few words as to 
 how engineers propose to make use of each of these 
 auxiliaries. 
 
 Nets to foul propellers are too well known for 
 discussion. As a defence against attempts to grapple 
 
132 Mortal's and Submarine Mines. 
 
 the cables, whether by drifting rafts, or by the some- 
 what fanciful scheme of mortar-boats throwing grap- 
 nels, or by ordinary steam-launches or small boats, 
 a few hawsers anchored in front of and among the 
 mines will certainly be found useful. They should 
 be attached to the heavy anchors or blocks of stone 
 used to hold them in position, by short lashings, to 
 prevent them from being drawn under the mud. 
 Multiple cables for mines soon bury themselves by 
 their own weight in the soft bottom of many of our 
 harbors ; and, as a harmless hawser can only be de- 
 tected by raising it, the enemy must either lose time 
 in so doing, or, if use be made of explosive grapnels, 
 he will be led to over-estimate the damage he is in- 
 flicting. 
 
 Main lines of mines should be so arranged as to 
 be swept throughout their length by the fire of 
 flanking guns. These guns, charged with canister, 
 grape, or shrapnel, according to the range, should be 
 trained by daylight to sweep their respective fields. 
 Cables extended to the mining casemate place these 
 guns, in groups, in connection with the electrical 
 system, and any injuries to mines or cables will at 
 once draw the fire of the guns ]3ointed to annoy the 
 boat which has done the mischief. The artillery offi- 
 cers are thus informed that parties are grappling and 
 that their position lies in a certain direction. Know- 
 ing the latter, they will keep up such a fire as will 
 stop or, at any rate, greatly harass the boats. 
 
 As to the utility of the electric light in channel 
 defence, I think a better idea can be formed after it 
 has been more fully tried in war. Before firing be- 
 gins it will doubtless be very useful, but so soon as 
 the air becomes obscured by smoke from the guns, or 
 from smoke-balls burned for the purpose, experience 
 leads me to doubt its value. It will be most useful 
 in clear, dark nights ; in bright moonlight nights, 
 
Sabmarine Mines. 133 
 
 and especially in fogs, I think little dependence 
 will be placed on its assistance by engineers. 
 
 Tlie usual dispositions of the apparatus in a fort- 
 ress are to place the engines and dynamo in a bomb- 
 proof casemate, and to throw the beam from a station 
 near the water-level, either directly or by reflectors, 
 according to circumstances. Stations sliould be du- 
 plicated and be placed near the flanl<LS of the position, 
 to avoid smoke driven by the wind. 
 
 In the absence of an effective tire of artillery, and 
 particularly when special vessels shall have been 
 constructed for countermining, movable torpedoes 
 controlled from the sliore can be made to play an 
 important part. Unless the currents are strong there 
 is no urgent need of very high speed, say above 10 
 miles per hour. The most valuable jjoints, from 
 an engineer standpoint, are : (1) Invulnerability to 
 fire, whether of machine guns, of rapid-firing guns, 
 or of cannon throwing grape and canister. (2) Ca- 
 pacity to carry three or four hundred pounds of the 
 explosive. (3) A range of at least two miles. (4) 
 The power of diving under any simple boom pro- 
 tection, such as a sbip could easily improvise from 
 lier spare stores. The ordinary service conditions, 
 such as being under perfect control, presenting a 
 small target, etc., etc., of course are essential. All 
 these conditions can be fultilled in practice, and I 
 entertain no doubt that such boats will form an im- 
 portant but subordinate element in every perfect sys- 
 tem of coast defence. 
 
 Much has been said of late as to the probability 
 of torpedoes of this class being superseded by large 
 charges of dynamite or other high explosives, thrown 
 by pneumatic mortars (usually called guns), and pro- 
 vided with fuses which cause explosion either at im- 
 pact or when submerged. In advance of official re- 
 ports it would be premature to foim any decided 
 
 f/T^ Of THt ^ 
 
 (UNIVERSITY j 
 
134 Mortars and Submarine Mines. 
 
 opinion on the subject ; but it is certain that one 
 fatal objection would lie to this proposed application 
 — we could liardly fail to damage our mines, and thus 
 perform for the enemy work which it is the part of 
 wisdom to force him to undertake himself. The con- 
 trollable torpedo causes one explosion under the bot- 
 tom of the counteiminer, and tliis is far preferable 
 to many explosions well distributed by ourselves 
 among the mines upon which our successful defence 
 depends. 
 
 Attempted Passage by Force, — After the ene- 
 my imagines that he has opened a clear channel 
 through the mined field he will attempt to force a 
 passage. The following preparations will be natu- 
 rally made : The position of tlie commanding officer, 
 of the chief of artillery, and of the engineer in 
 charge of the mines will be at some selected place 
 where smoke from the guns will not be likely to an- 
 noy them ; where the instruments, so far as possible, 
 can be kept under cover ; and where a good view can 
 be had of the mined zone. Two electric cables ter- 
 minate at this station. One extends to the mining 
 casemate for telegraphic communication ; the second 
 leads to the other extremity of a base line, for 
 triangulatitms to fix exactly the position of the enemy 
 — unless, indeed, some superior method of position- 
 finding be used. 
 
 The map of the channel being always at hand, 
 with the locus and condition of the mines and the 
 successive positions of the enemy as he approaches 
 laid down upon it, the commanding ofiicer will always 
 understand the state of affairs ; and the engineer can 
 direct the service of his mines, and the artillery offi- 
 cer that of his guns, under every possible advan- 
 tage. 
 
Fifth Lecture, 
 
 SEA-COAST FORTRESSES. 
 
 Historical resume of Coast Defence in America — Resistance to projec- 
 tiles; armor; masonry; earth — Approximate formulae — Fortifica- 
 tion of the site selected — Naval co-operation. 
 
 Having, in the " previous lectures of this course, 
 passed in review the general principles of the art of 
 war applicable to sea-coast defence, the probable 
 nature of the naval attacks which will be brought 
 against the works, the financial aspects of the ques- 
 tion, the selection of suitable positions for the bat- 
 teries, mines, etc., and the character of the several 
 elements composing them, it remains to consider how 
 the latter are to be combined at any site to constitute 
 a sea-coast fortress. 
 
 If our coasts were entirely devoid of defensive 
 works the problem would be different from that now 
 presented. To take a broad view of the subject it is 
 needful to appreciate what the existing works were 
 designed to accomplish, to understand their construc- 
 tion in some detail, and to consider what use can be 
 made of them under the changed conditions of the 
 problem now presented. I shall, therefore, first ask 
 your attention to a brief outline of the development 
 of sea- coast fortification in this country. 
 
 HISTORICAL KESUME OF COAST DEFENCE IN 
 AMERICA. 
 
 Previous to the Revolution our seaport towns 
 were villages, and naval establishments and military 
 
136 Sea-coast Fortresses. 
 
 depots were unknown. The harbors of Boston, New 
 York, Philadelphia, Charleston, etc., had been pro- 
 tected by a few insignificant earthen forts ; but at the 
 outbreak of war the sparse population and long 
 coast line enabled the mother- country to use the 
 ocean for her base, and to operate where she wished 
 until the French appeared on the scene. A small 
 work of sand and palmetto-logs in Charleston harbor, 
 however, under the command of Colonel Moultrie, de- 
 cisively repuls^ed the attack of a British fleet of two 
 frigates and six sloops of war (80 guns against 270) 
 in 1776, and thus taught our people the value of for- 
 tifications. The battle lasted ui3ward of ten hours, 
 and its result gave a local respite from the calamities 
 of war for two and a half years. 
 
 Shortly after peace had been declared Washing- 
 ton urged the necessity of defending the coast, and 
 the French troubles drew popular attention to the 
 subject. Fort Columbus, Castle Williams, and Cas- 
 tle Clinton (now known as Castle Garden) were built 
 in New York harbor ; and in nearly all of our chief 
 ports batteries made their appearance, but they were 
 of so defective design, and so weak and perishable 
 in material, as to have no permanent value. This 
 (known among engineers as our second system of de- 
 fence) did, however, some service in the war of 1812. 
 New York and Boston were blockaded, not occu- 
 pied ; but the shores of Long Island Sound and 
 Chesapeake Bay were ravaged, and the whole New 
 England coast was kept in terror by raiding expe- 
 ditions. This bitter experience bore fruit, and no 
 sooner had the war ended than the defence of the 
 Atlantic seaboard was seriously taken in hand. 
 
 In 1816 a Board of Engineers was constituted to 
 examine the sea-coast and to prepare plans for defen- 
 sive works, subject to the revision of the Chief of En- 
 gineers and to the sanction of the Secretary of War. 
 
Coast Defence in America. 137 
 
 This important Board, which at the outset consisted 
 of General Simon Bernard, Colonel William McRee, 
 and Lieutenant-Colonel J. G. Totten, may justly be 
 said to have originated the first permanent system of 
 coast defence on this continent. Indeed, at that date 
 European treatises on fortifications scarcely touched 
 on this branch of the subject, so little was science 
 supposed to be concerned in the throwing-up of bat- 
 teries to contend with ships. 
 
 Perhaps no better idea of the problem before the 
 Board of Engineers can be given than by quoting 
 the language of a contemporary writer, a British of- 
 ficer who had taken part in the expedition against 
 Baltimore. He wrote : 
 
 ''America must be assaulted only on her coasts. 
 Her harbors destroyed, lier ship]3ing burned, and her 
 seaport towns laid waste, are the only evils she has 
 reason to dread. ... 
 
 ''To the plan proposed, of making desert- the 
 whole line of coast, it may be objected that by so do- 
 ing we should distress individuals and not the gov- 
 ernment. But they who offer this objection forget 
 the nature both of the people whose cause they 
 plead and of the government under which they live. 
 
 "In a democratical government the voice of the 
 people must at all times prevail. The members of 
 the House of Representatives are the very persons 
 who, from such proceedings, would suffer most se- 
 verely, and we all know how far private suffering 
 goes to influence a man's public opinions. . . . 
 
 "By compelling the constituents to experience 
 the real hardships and miseries of warfare you will 
 compel the representatives to a vote of peace. . . . 
 Burn their houses, plunder their property, block up 
 their harbors, and destroy their shipping in a few 
 places, arfd before you have time to proceed to the 
 rest you will be stopped by entreaties for peace." 
 
138 Sea- coast Fortresses. 
 
 The Board of Engineers, in a report dated in 1826, 
 gave a general resume of the principles which had 
 guided their labors, and of the progress which had 
 already been made. I shall quote two sentences 
 which specially relate to the subject now under con- 
 sideration : 
 
 ''The means of defence for the seaboard of the 
 United States, constituting a system, may be classed 
 as follows : First, a navy ; second, fortifications ; 
 third, interior communications by land and water ; 
 and, fourth, a regular army and well- organized 
 militia. ..." 
 
 "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 perpetual alarm ; third, 
 must cover the great cities from attack ; fourth, must 
 prevent as far as practicable the great avenues of in- 
 terior navigation from being blockaded at their en- 
 trances to the ocean ; fifth, must cover the coastwise 
 and interior navigation by closing the harbors and 
 the several inlets from the sea which intersect the 
 lines of communication, and thereby further aid the 
 navy in protecting the navigation of the country ; 
 and, sixth, must protect the great naval establish- 
 ments." 
 
 We will now consider briefly the character of the 
 individual works constructed in inaugurating this 
 conjprehensive system. 
 
 Ever since the general introduction of gunpowder 
 into warfare, the rule has been recognized that no 
 masonry must be exposed to the fire of land guns ; 
 but this rule was not deemed applicable wllen ships, 
 themselves much more vulnerable than stone walls. 
 
Coast Defence in America. 139 
 
 carried the guns. Moreover, the distinguishing char- 
 acteristic of the line- of -battle ship of that day was 
 her enormous concentration of fire. To reply with 
 equal chances of success, many land guns were de- 
 manded ; and space was lacking for them at most 
 sites, unless advantage were taken of the facilities to 
 pile tier above tier afforded by a masonry scarp. 
 
 The use of the casemate in flank defence may be 
 traced back to the early part of the sixteenth cen- 
 tury ; but the Marquis de Montalembert, writing near 
 the close of the eighteenth centuiy, had lecently 
 given the invention an extraordinary development 
 To the needs of sea-coast fortification casemates were 
 peculiarly well adapted, and he had presented special 
 designs for the piirpose. The forts constructed to de- 
 fend the roadstead and harbor of Cherbourg in 1786 
 were patterned after these designs ; and other Euro 
 pean nations followed in the same track. As already 
 stated. Colonel Williams introduced casemates into 
 this country by the construction of Castle Williams 
 and sister forts in 1807 ; and the Board of Engineers 
 adopted them as the basis of the permanent system. 
 
 Time is lacking to trace the development of that 
 system, and the successive improvements introduced 
 by General Totten during the construction of the 
 works. They were radical, especially as to the de- 
 tails of the embrasure ; he reduced the dangerous 
 opening from 28 square feet to about 10 square feet, 
 and this with an increased traverse and elevation for 
 the gun. He was also the first to introduce iron for 
 defensive purposes into sea-coast forts. This innova- 
 tion resulted from a series of experiments carried out 
 at West Point between the years 1852 and 1855. The 
 throats of all embrasures constructed after 1858 were 
 reinforced by 8-inch wrought-iron plates set into the 
 masonry ; and, during the loading of the guns, the 
 embrasure openings were closed by iron shutters two 
 
140 Sea-coast Fortresses. 
 
 inches thick and proof against the largest grape. 
 There is one sentence in General Totten' s report upon 
 these experiments, dated March, 1857, which is pa- 
 thetic as showing that the shadow of the great change 
 about to occur in naval warfare, which was destined 
 even before his death to sweep away the system of 
 forts he had elaborated by the labor of liis wliole life, 
 had made itself perceived. He wrote in 1857 : 
 
 " Were it not for the vastly greater cost, the whole 
 scarp might be faced with iron — indeed, might be 
 made of iron only ; but, until there shall be much 
 stronger reasons than now exist, or are now antici- 
 pated, for believing that well-constructed masonry 
 batteries may be breached by naval broadsides, the 
 cheaper construction can be safely followed — espe- 
 cially as, should such a necessity ever arise, they may 
 be externally plated with iron." 
 
 The actual construction of works upon General 
 Totten's system covered a period of 45 years, termi- 
 nating about a year before the close of the civil war. 
 They are masonry structures, usually placed but lit- 
 tle above the water-level, rising into one, two, or 
 three tiers of casemates and surmounted by a tier in 
 barbette. The scarps are built without any bonding 
 of the masonry into the supporting piers (which 
 would cause unequal settling on such sites as most of 
 these works occupj^). In all the later works the 
 scarps of the water-fronts are 8 feet thick ; where 
 tliey are backed by the piers of the casemates the re- 
 inforcement amounts to 2% feet ; the masonry of the 
 casemate arch, above the level of the communication 
 arch, extends a solid support to the whole structure 
 over 30 feet thick ; immediately in front of the guns, 
 at the " recess," there is a small space where the 
 thickness is reduced to 5 feet. In some of the earlier 
 works the casemate arches were sprung at the level 
 of the barbette tier and covered four guns each, the 
 
Coast Defence in America. 141 
 
 two of the second tier resting on a wooden floor ; but 
 all the later scarps are solidly backed against single 
 arches. In plan these works are usually hexagonal, 
 often truncated on the land side. The superiority of 
 the hexagon arises from its permitting the casemate 
 guns on adjacent fronts to be fired in parallel planes 
 at their extreme traverse (30 degrees). This covers 
 and prevents a dead angle at the salient between 
 them. Where there is a barbette tier, the guns, ad- 
 mitting of a traverse of 60 degrees from the front in 
 each direction, strongly reinforce the fire of the case- 
 mate guns over this naturally weak angle. 
 
 So soon as the work of fortifying the coast was 
 resumed after the civil war a radical change of sys- 
 tem occurred. Masonry Avas provisionally aban- 
 doned, and earth was substituted for every kind of 
 cover. Under this system, which continued until ap- 
 propriations ceased in 1875, many batteries were 
 built at important positions ; and they will serve a 
 good purpose, notwithstanding the rapid progress in 
 guns which has occurred since they were built. Af- 
 ter 1870 these earthen batteries were constructed to 
 receive, if desired, the pattern of the King disaj^pear- 
 ing carriage designed for the 15-inch gun. 
 
 All the sites now owned by the United States suit- 
 able for the erection of defensive works, contain 
 specimens of the different types just described ; and 
 it is therefore a live question what shall be done 
 with them when work is resumed. As stated in a 
 former lecture, many of the old masonry forts, with 
 their old armament, will be not without value for the 
 necessary flanking of the submarine mines ; and the 
 later earthen batteries may often be modified to re- 
 ceive guns of the new type. But the general problem 
 compels the consideration of a subject which I have 
 heretofore passed over — the relative and absolute re- 
 sistance opposed by different kinds of materials, such 
 as armor, masonry, and earth, to modern projectiles. 
 
142 Sea-coast Fortresses. 
 
 llESrSTAlS^CE TO PROJECTILES. 
 
 Armor.— -The armor question is by no means the 
 same for land fortifications as for ships. The ele- 
 ment of weight, so important when displacement 
 is involved, demands far less consideration when 
 the solid earth supplies foundations. The ratio be- 
 tween resistance and weight has decided the matter 
 for naval uses, steel or comp.ound armor being now 
 universally adopted. The decision for forts is still 
 an open one. Heretofore Engineers have confined 
 themselves either to wrought iron or to the Gruson 
 chilled cast iron, no steel or compound armor having 
 yet been used or strongly advocated for use in coast- 
 wise works. 
 
 Wrought-iron armor localizes the injury better 
 than steel or compound armor, and thus saves the 
 general structure ; the Gruson metal breaks up and 
 deflects the projectile, and absorbs the remaining en- 
 ^^^Y by so large a mass that its strength to receive 
 farther shocks is often not seriously impaired. Cap- 
 tain Bixby, Corps of Engineers, in a recent official 
 report upon duties which had been assigned to him 
 in Europe, sums up the case in what I regard as a 
 fair statement, except perhaps that he lays hardly 
 enough stress upon the fact that chilled cast iron 
 does not admit of subsequent thickening, while the 
 other kinds may readily be reinforced if necessary. 
 He states : 
 
 '^ At the present date heavy armor (from 12 to 
 40 inches thick) is very expensive, its cost, firmly 
 mounted in place, being approximately as follows : 
 wrought iron, from $200 to $350 per ton ; steel-faced 
 wrought iron or surface-hardened steel, from $400 to 
 $600 per ton ; chilled cast iron, from $150 to $200 per 
 ton. . . . 
 
 *' Taking into consideration the cost of bolts, 
 bolt-holes, and other means of assemblage, and the 
 
Resistance to Projectiles. 143 
 
 cost of fitting and setting up the armor, the same 
 amount of money will, roughly speaking, furnish a 
 steel-faced wrought- iron or surface-hardened steel 
 armor of 20 inches thickness, a wrought-iron armor 
 of 40 inches thickness, or a chilled cast-iron armor of 
 60 inches thickness. E-ouglily speaking, the steel- 
 faced wrought iron or surface-hardened steel is least 
 heavy, the strongest in proportion to its thickness ; 
 the wrought iron is easiest to make, easier worked, 
 easier added to, best against racking shots, localizes 
 best the effect of a shot, can best be penetrated and 
 even perforated without being actually destroyed, 
 and can best have the amount of penetration calcu- 
 lated in advance ; the chilled cast iron is easiest and 
 quickest made, can be given any shape, requires the 
 least working, is easiest and quickest placed in posi- 
 tion, is never penetrated, always shivers in pieces the 
 striking projectiles, generalizes best the effect of a 
 striking projectile, provides the greatest weight or 
 mass to receive the total living force of the striking 
 projectile, has no bolts to be knocked off on its inte- 
 rior, and sends off the fewest splinters on its interior. 
 The steel has undoubtedly the advantage around the 
 edge of embrasures, and wherever thickness or 
 weight is undesirable or inadmissible, also wherever 
 it can be backed by a great thickness of less expen- 
 sive masonry ; the chilled cast iron has undoubtedly 
 the advantage . . . .wherever weight or mass is an 
 advantage ." 
 
 In the matter of bolts, wrought-iron armor re- 
 quires one to each 10 or 12 square feet of surface ; 
 compound or steel armor requires one to each four 
 square feet of surface ; chilled cast iron dispenses 
 with bolts entirely. 
 
 Wrought-iron, steel, and compound or steel-faced 
 armor are so familiar to naval officers that no time will 
 be given to their further discussion. Gruson chilled 
 
144 Sea-coast Fortresses. 
 
 casfc iron, being inapplicable to floating structures, is 
 probably less studied, and the following short ex- 
 tracts from a publication by Julius von Schutz, En- 
 gineer of Gruson's Works, which has just left the 
 press, may perhaps be not uninteresting : 
 
 *^ The Gruson chilled cast iron is a mixture of dif- 
 ferent blends of pig-iron, cast in chill, to which it owes 
 its hardness. 
 
 " In accordance with the two chief qualities whicli 
 he sought to obtain, Gruson chose two sorts of pig- 
 iron for his principal materials, each of which pos- 
 sessed one of the desired qualities — a highly carbon- 
 ized steel-hard, white iron, and a soft gray iron. 
 
 ''Although it appeared impossible, by the mere 
 mixture of the two metals, to combine hardness and 
 toughness in the same stratum of iron, another way 
 of solving the problem, to produce a hard surface on 
 a soft, elastic interior, seemed less difficult if it were 
 possible to combine the two different materials to- 
 gether with such a gradual change of their respective 
 properties that no marked line of separation should 
 occur ; and this is tlie problem which Gruson, after 
 years of effort, succeeded in reaching in such a man- 
 ner that even at the present day his chilled cast iron 
 possesses a superiority over that of other makers. 
 
 '' Gruson attained his object by a seemingly simple 
 procedure. By the use of iron forms, or moulds for 
 casting, he prevented, by a rapid cooling of the surface, 
 the always existing tendency in a fluid casting for 
 the carbon to separate off in scales of graphite. 
 
 '' It would be foreign to the scope of this compila- 
 tion to specify the details of the manufacture of the 
 chilled cast iron, and we will only describe the peculiar 
 structure which characterizes the broken section of a 
 piece of the Gruson chilled cast iron. The exterior 
 layer is of a flne fibrous character, which passes, with- 
 out visible lines of separation, into the granular s true- 
 
Resistance to Projectiles, 145 
 
 ture of tlie so-called mottled iron, which in tnrn 
 gradually assumes the character and line crystalline 
 structure of the gray soft iron. This is the great dif- 
 ference which distinguishes Gruson chilled cast iron 
 from tliat of other manufacturers, in whose iron the 
 line of separation of the layers is always more or less 
 distinctly marked, and the edge between the hard and 
 soft metal visibly seen. . . . 
 
 ''To his plates he gave a curved form, which in 
 vertical section approaches that of a quadrant of an 
 ellipse. Such a surface, by its hardness, deflected the 
 shot striking it, and besides it possessed this advan- 
 tage, that, by reason of their arched form, the plates 
 supported one another and retained their position by 
 their weight, without the necessity of securing them 
 by bolts." 
 
 I have already shown that it would be unwise to 
 devote the first funds granted by Congress for coast 
 defence to the purchase of armor of any kind ; it is 
 certain that whatever is purchased must be manufac- 
 tured in this country; the facilities for working heavy 
 masses here are steadily increasing ; the struggle be- 
 tween the different kinds of armor has not ceased in 
 Europe; and when the time conies for purchasing, the 
 choice may be affected by conditions materially dif- 
 ferent from those now existing. For these reasons 
 the Corps of Etigineers has never committed itself to 
 a definite choice. We know that wrought-iron armor 
 8 feet wide, 10 inches thick, and weighing from 10 to 
 12 tons can now be rolled in this country; that larger 
 plates could soon be fabricated were there any de- 
 mand for them; that probably the same will soon be 
 true for steel, and that, if sufficient inducements were 
 offered, works for making the Gruson chilled cast iron 
 would be quickly established. In my judgment, 
 therefore, it is the part of wisdom for us in this mat- 
 ter to say with the Russians : " I sit upon the bank 
 and there I await the wind." 
 
146 Sea-coast Fortresses. 
 
 Masonry. — Very few experiments have been made 
 to determine the penetration of modern ordnance in 
 masonry. 
 
 In 1877 an unfilled Palliser shell was fired from a 
 12.5-inch 38-ton gan at a mass of masonry at Shoe- 
 buryness. The projectile weighed 800 pounds, its 
 striking velocity was 1 405 feet, and its energy 10 080 
 foot- tons. The masonry was an old experimental 
 casemate, somewhat shaken by previous firing ; it 
 was 16 feet by 12 feet by 16 feet liigh. The shell, after 
 passing through 6.5 feet of granite and Q.Q feet of 
 brick and Portland cement concrete, was found on the 
 floor of the casemate. The wall was completely 
 wrecked. 
 
 In 1881 the cast-iron 100-ton gun made in Italy 
 was fired at a steep rock face. The projectile, vveigli- 
 ing 2 200 pounds and striking with a velocity of 1 456 
 feet, had an energy of about 32 000 foot- tons. The 
 penetration was over 20 feet. 
 
 A concrete butt at Dungeness was fired at with 
 smaller ^projectiles in 1881. The concrete had been 
 made of rounded shingle about two years before, and 
 was not so solid as if the material had been more 
 angular. The following were the maximum penetra- 
 tions, the energies being respectively 5 738, 1 989, and 
 1 555 foot-tons : 
 
 A 10-inch M. L. rifle of 18 tons : Palliser shell, 
 17 feet ; common shell, 13.8 feet. 
 
 A 6-inch B. L. rifle of 80 cwt.: Palliser shell, 12.6 
 feet ; common shell, 10.8 feet. 
 
 A 6.6-inch M. L. rifle of 70 cwt.: Palliser shell, 
 8.2 feet ; common shell, 8.4 feet. 
 
 In 1883 a muzzle-loading 80- ton gun was flred at a 
 masonry target at Shoeburyness built for the pur- 
 pose. The projectile was chilled cast iron, 1 700 
 pounds in weight. The striking velocity was 1 580 
 feet per second, giving an energy of about 30 000 
 foot-tons. There are some discrepancies in different 
 
Resistance to Projectiles, 147 
 
 statements respecting the details of this experiment. 
 I was informed on the spot a few days after the tiring 
 that the shot passed through 9 feet of granite, 6 feet 
 of good Portland cement concrete, and tlien encoun- 
 tered a brick wall 5 feet thick, the whole forming one 
 solid wall, backed by buttresses of concrete 20 feet 
 thick. The brick wall deflected the shot from its 
 course, and it curved to the right and finally to the 
 front, after passing over a total distance of about 25 
 feet. The shot broke up. 
 
 Another similar shot was fired at a mass of Port- 
 land cement concrete about 40 feet thick, made about 
 9 months before. The penetration was 32 feet (Cap- 
 tain Lewis, R.E., says 34 feet) on a straight course ; 
 the mass was also badly cracked. 
 
 Another similar shot was fired at a compound 
 plate of steel-faced wrought iron, 12 inches thick, 
 secured without any elastic backing to a masonry 
 mass 20 feet thick, like that first described. The shot 
 bulged and just penetrated the plate, so that its j^oint 
 appeared at the back, and the injury to the masonry 
 was insignificant. 
 
 Another similar shot was fired at a wrought-iron 
 sandwich target backed in the same manner. The 
 target consisted of two 8-inch plates, separated and 
 backed by 5 inches of wood. The shot traversed the 
 shield and granite, resting at the concrete just behind 
 it (penetration, 16 inches of iron, 10 inches of wood, 
 and 9 feet of masonry). 
 
 In 1884 the 12-inch 43-ton gun was fired at the same 
 target at Shoeburyness, which had been repaired for 
 the purpose. Captain Lewis, R.E., states that it 
 now consisted of 14 feet of granite and Portland 
 stone, 2 feet of Portland cement concrete, and 6 feet 
 of brick. The shot weighed 715 pounds, its striking 
 velocity was 1 804 feet per second, and its energy 
 16 300 foot-tons. The penetration was 11.3 feet, and 
 the granite was much shattered and displaced. 
 
148 Sea-coast Fortresses, 
 
 In firing at the concrete butt with this gun, the 
 striking velocity was reduced to 1 524 feet per second, 
 giving an energy of 11 620 foot-tons. The penetra- 
 tion was 24 feet, and a large mass 2 feet thick flaked 
 off from the front. 
 
 The two 8 inch wrought-iron plates used as a fac- 
 ing, attacked by the same gun, reduced the penetra- 
 tion in the granite to 5.9 feet. 
 
 A mass of concrete 17 feet thiclv was faced by 
 three 1-inch plates of wrought iron and backed by 
 the granite wall. The result with the 43-ton gun was 
 unsatisfactory, the concrete disintegrating ; ba<t Gen- 
 eral Inglis, K-.E., states that the latter was not prop- 
 erly set. 
 
 Captain Lewis, E..E., gives the following as the 
 results derived from the firing at the bombardment of 
 Alexandria: ''The maximum x>enetration of blind 
 shell, 9-inch or lO-inch, into the soft rubble scarp of 
 Fort Adda, was from 8 to 9 feet. A 9-inch Palliser 
 burst with 4 feet penetration. A 16-inch common 
 shell burst with 8 feet 6 inches penetration, and made 
 a crater about 10 feet in diameter at the face of the 
 wall. This was one of the best results obtained. The 
 shell struck near the base of the wall. Range about 
 1 500 yards. 
 
 ''At Fort Pharos the 10-inch shell, common and 
 Palliser, penetrated the 8-foot rubble walls of the 
 casemates and burst inside." 
 
 Comparing these results with those of former fir- 
 ing with less powerful guns, and allowing for the 
 reduced effect of the ranges likely to be used in war, 
 it appears that not less than 30 feet of good granite 
 masonry, or 40 feet of good concrete masonry, is ad- 
 missible in sea-coast forts where it is to be exposed 
 to direct fire, and that even these thicknesses are not 
 sufficiently great to resist a prolonged bombardment. 
 English engineers now protect their magazines wftth 
 
llesistance to Projectiles. 149 
 
 40 feet of masonry, but an increased thickness is an- 
 ticipated. 
 
 Resistance of Earth. — The resistance of earth 
 to penetration of modern ordnance is so variable, not 
 ordy from difference of consistency but also from the 
 tendency of the projectile to change direction and 
 pass out at the top of the parapet, that it is not easy 
 to frame a rule for suitable thickness. Clay opposes 
 a local resistance like wrought iron ; sand seems to 
 wedge in front and thus resists as would a cone 
 pressed at the vertex. This difference is marked and 
 characteristic, and preference should therefore al- 
 ways be given to sand where it can be obtained at 
 reasonable expense. The tendency to curve upward, 
 always present, appears to increase with the range — 
 possibly because the velocity of fall continues at the 
 base after the point is engaged. However this may 
 be, the fact occasioned much surprise at the bom- 
 bardment of Alexandria, where no x)rojectile, even 
 those of the 80-ton gun, penetrated the sand parapet 
 to a greater depth than 20 feet before coming out at 
 the top. 
 
 Firing at Fort Monroe in 1866-67 with a M. L. 12- 
 iuch rifled gun, with projectiles varying from 500 to 
 600 pounds in weight, and velocities ranging from 
 1 100 to 1 300 feet per second, indicated that penetra- 
 tions should not be estimated at less than 20 feet. 
 
 The Italian 100-ton gun (cast iron) was fired at a 
 sand parapet in 1880-1, the projectile weighing 2 200 
 pounds, the striking velocity being 1 453 feet, and the 
 energy being 32 000 foot-tons. The penetration in 
 five shots varied between 39 and 47 feet. One of 
 their 10-incli guns at a range of 1 100 yards gave a 
 penetration of 24 feet into earth or 20 feet into sand. 
 
 At Woolwich, in 1880, the 12-inch M. L. rifled gun 
 gave a maximum penetration of 6Q feet in sand. 
 Older experiments at Shoeburyness, with a butt of 
 
150 Sea- coast Fortresses. 
 
 stiff marsh clay, gave as a mean penetration of 23 
 shots with a 13.3-inch rilled gun, 36.5 feet, the maxi- 
 mum being 50 feet ; and as a mean penetration of 43 
 shots with a 9.2-inch rifled gun, 32 feet, the maximum 
 being 40 feet. 
 
 The rule given by Captain Lewis, R.E., in 1882, 
 as the result of English trials with siege artillery of 
 the present type, is that the extreme j^enetration of 
 earth in feet is about four times the calibre in inches. 
 
 In the Lydd experiments of 18S5 two shots were 
 fired with a 9.2-inch B. L. gun, at a range of 1 200 
 yards, against a clay parapet 30 feet thick with 
 an exterior slope of 45 degrees. The first shot pene- 
 trated 13 feet into the parapet ; the second went 
 through, lowering the interior crest 3.5 feet. About 
 61.9 cubic yards were removed. No such results were 
 obtained with sand, or with a loam consisting of 
 two parts sand and one part clay. 
 
 The U. S. Board of Engineers, making allowance 
 for probable increased calibres and for craters which 
 may be expected in action, have adopted 70 feet be- 
 tween crests as the proper thickness to be given to 
 sand parapets, although, in view of the facts above 
 stated, the probability of penetration with a less 
 thickness would not appear to be sufficiently great to 
 require all old parapets to be increased to this stan- 
 dard. 
 
 APPROXIMATE FOEMUL^. 
 
 When planning and studying sea-coast fortresses 
 a few rules, in a form to be easily remembered, are 
 convenient to assist in roughly estimating the proba- 
 ble effect of tiring. 
 
 Such are : 
 
 For Weight of Projectiles. — The cube of the 
 radius in inches gives the weight in pounds of the 
 solid spherical projectile. Modern armor-piercing 
 
Approximate FormidcB. 151 
 
 projectiles usually range from 8.3 to 4 times this 
 weight. Another form of this rule (corresponding to 
 a multiplier of 4) is to take half the cube of the cali- 
 bre of the gun in inclies for the weight in pounds. 
 
 For Velocity of Projectiles of High-Power 
 Guns. — A cliarge of one-fourth of the weight of the 
 projectile will give a velocity of about 1 500 or 1 600 
 feet per second ; and a charge of one-half that weight, 
 a velocity of about 2 000 or 2 100 feet per second. 
 These are muzzle velocities ; to estimate striking 
 velocities up to a range of about 6 000 yards subtract 
 from them' one- tenth of the range in yards ; for longer 
 ranges the loss is less rapid. 
 
 For Energy in Foot-Tons.— Take seven-mil- 
 lionths of the product of the square of the velocity 
 in feet by the weight of the projectile in pounds. 
 
 For Penetration of Wrouglit-Iron Plates. — 
 Under favorable service conditions, the thickness in 
 inches of wrought-iron armor pierced by a suitable 
 projectile, may be estimated, with about as much pre- 
 cision as the subject admits, by taking one-thou- 
 sandth of the product of the calibre in inches by the 
 velocity of the projectile in feet per second. This 
 rule, suggested by Captain Orde Browne, R.A., de- 
 pends for its accuracy upon the constancy of the 
 ratio between the weight of the spherical shot and of 
 the elongated projectile of the same calibre. It is not 
 far from true in ordinary practice with armor-pierc- 
 ing projectiles. Common shells can be put through 
 wrought-iron plates about half a calibre thick. 
 
 For Limit of Resistance of Steel-Faced and 
 Steel Armor. — The compound plates and steel 
 plates now manufactured mnst be disruj^ted rather 
 than perforated ; and their extreme resistance (not 
 materially different for these two kinds of armor) is 
 usually estimated in terms of the thickness of 
 wrought iron which opposes an equivalent resistance 
 
152 Sea-coast Fortresses. 
 
 to perforation. This has been shown by many trials 
 to vary between one-quarter and one-half greater 
 thickness, the latest accepted value being one-third 
 greater thickness — i.e., a 9 inch steel or compound 
 plate is equivalent to a 12-iiich wrought-iron plate, 
 since a projectile which will perforate the latter will 
 usually disrupt the former. It must not be forgot- 
 ten, however, that much depends upon the projectile 
 itself. When the latter is broken up by the shock 
 its work on the plate is greatly and irregularly re- 
 duced ; and until quite recently this rupture ap- 
 peared to be unavoidable with very hedvy armor. 
 Within a year, 'however, a 16.5-inch St. diamond 
 steel battering shell, with a striking velocity of only 
 1 410 feet per second and an energy of only about 
 24 000 foot-tons, traversed, entire, a 19.7-inch Creusot 
 steel armor-plate, and fell 400 metres beyond it, 
 upset one-quarter of an inch ! Also 12-inch Holtzer 
 projectiles have penetrated 16-inch compound plates 
 practicall}^ uninjured. 
 
 There is little utility in attempting to construct a 
 formula to predict the effect of the imp)act of so di- 
 verse projectiles as have been used in firing at steel 
 and compound armor, but I fin(^ the results of many 
 of the experiments to be fairly represented by the 
 following rule : A steel or compound plate with ordi- 
 nary backing rarely fails to yield to a projectile hav- 
 ing an energy in foot-tons represented by sixty times 
 the square of its thickness in inches. 
 
 For Resistance of Chilled Cast Iron.— No for- 
 mula for the resistance of this kind of armor has 
 been generally accepted. Gruson's rule for the maxi- 
 mum thickness in inches to be given to his plates is 
 the product of a constant by the fourth root of the 
 energy in foot-tons to which it is to be exposed. His 
 constants are : For port-plates 0.29 ; for side-plates, 
 0.27 ; for glacis-plates with earth in front, 0.22 ; and 
 
Fortijication of the Site Selected, 153 
 
 for glacis-plates with granite in front, 0.20. For in- 
 land fortifications tliese constants are increased ten 
 per cent. 
 
 FORTIFICATEON OF THE SITE SELECTED. 
 
 Coast defences differ radically from ordinary for- 
 tifications, in that tliey are not expected to resist an 
 attack by formal land approaches. They must be 
 planned to resist capture by surprise or by storm, 
 but not by regular saps. Moreover, our sea-coast 
 fortresses of to-day will be much less exposed to 
 boat attack than were those planned in 1816. Not 
 only lias the increase of population and the exten- 
 sion of railroad and telegraphic communication ren- 
 dered it vastly more easy to concentrate reinforce- 
 ments, but the reduction of crews in naval v^ar-ships 
 has lessened the force available for landing opera- 
 tions. 
 
 For these reasons the idea of constructing a fort- 
 ress to contain all the water-bearing guns within its 
 enceinte has long been abandoned. The ordnance is 
 now distributed in detached batteries, each provided 
 with minor defensive arrangements suited to the 
 locality, while the whole position is made secure by 
 a central keep. This 'is usually a small enclosed 
 work, fortified on the principles recognized in land 
 constructions. It should be concealed from the view 
 of hostile shipping ; should contain or flank the 
 casemate for operating the submarine mines ; and 
 should command as many of the detached batteries 
 as the site will permit. 
 
 Four kinds of fire are requisite to contend against 
 a modern fleet : (1) A sufficient array of armor-pierc- 
 ing guns to attain the vital parts behind a belt of 
 steel about 20 inches thick, at ranges of 1 500 to 
 2 000 yards. (2) Guns throwing large common shells 
 
154 Sea- coast Fortresses. 
 
 to destroy the upper works, which in the more recent 
 types include an area so much larger than the ar- 
 mored belt that this kind of fiie is the most effective 
 at ranges exceeding 2 000 yards. High-power guns 
 of moderate calibres, or even a less efficient armament, 
 will serve this purpose. Rapidity of fire, calling for 
 many guns, is needful. Here the use of high explo- 
 sives in shells, which (if not now) is certain to be soon 
 available, will play its most important part. (3) Ver- 
 tical lire from heavy mortars, to attack the lightly 
 armored decks at ranges exceeding 1 500 yards ; and 
 (4) Light guns, inclading machine and mpid-firing 
 guns as well as the old types throwing canister, 
 shrapnel, and shells, to flank the submarine mines, 
 repel boat attacks, and contend with the torpedo- 
 boat armament of the ships if they can approach 
 sufficiently near to bring it into play to annoy the 
 cannoniers in serving our high-power guns. At long 
 ranges machine-gun fire is useless because its effect 
 cannot be noted. 
 
 No precise rules can be laid down for fixing the 
 relative proportions of these different types in a mod- 
 ern armament ; the engineer must study his special 
 problem and be governed by local conditions. In 
 little else can his professional skill be better dis- 
 played. The principles which should determine the 
 number of battering guns and their largest calibres, 
 have already been considered. 
 
 In planning the works the chief objects are : to 
 dispose separate gun batteries in such a manner as 
 to cover the field of fire thoroughly without leaving 
 dead angles, and to permit effective concentration 
 upon the more important channels ; to place the 
 mortar batteries where they will be concealed as much 
 as possible from view, and where their smoke shall not 
 interfere with the guns ; to locate the submarine 
 mining casemates where they will be secure against 
 
Fortification of the Site Selected. 155 
 
 bombardment ; and, finally, to make the needful pro- 
 visions against surprise by boat parties. 
 
 The separate batteries will be much more scat- 
 tered than formerly — partly to avoid mutual interfer- 
 ence by smoke, which, being dependent on the amount 
 of powder burned, will, unless provided against, be a 
 more serious annoyance than ever before ; and partly 
 to x)i'event the enemy from obtaining that concentra- 
 tion of fire which his reduced number of guns will 
 render more than ever desirable. The new phases of 
 modern warfare have thus introduced a dispersed 
 order in sea- coast batteries as well as in the shock of 
 armies in the field. 
 
 Machine guns will play an important part in de- 
 fending such a system of works against assault. 
 They concentrate within a small space the fire of 
 whole regiments under the old system ; they may be 
 withdrawn from view, and be made safe from cap- 
 ture, at small expense ; and, lastly, they avoid the ne- 
 cessity of providing bomb-proof quarters for a large 
 garrison. Still a reserve, in moderate numbers, is a 
 necessity ; and provision for cover during bombard- 
 ment, and a strong keep to serve as a rallying point 
 in case of a formidable attack, wdll form a part of 
 every important sea-coast fortress of to-day. Trous 
 de loups, wire entanglements, ordinary arrangements 
 for ditch defence, etc., will of course be provided ac- 
 cording to local needs, but works of this character 
 will be largely left to be placed by the garrison so 
 soon as war is declared. 
 
 Before a fortress can be planned some definite es- 
 timate must be formed as to the size of its war gar- 
 rison. The rule abroad is to determine the number of 
 cannoniers needful to serve all the guns likely to be 
 in action at the same time, and the number of the 
 guards ; to allow three reliefs for these duties, and to 
 the total thus found add the number of men proba- 
 bly to be detailed on special duties. 
 
156 Sea- coast Fortresses. 
 
 Sucli a garrison would be much larger than would 
 be available in this country without reinforcements 
 of volunteers ; and in general it should be ample to 
 defend the works against boat attacks, which usually 
 could not be effectively supported by the iire of the 
 fleet at the moment of assault. Provision for quar- 
 tering such a garrison will therefore suffice in plan- 
 ning the defences. 
 
 To determine the lines of the batteries wdiich, in 
 whole or in part, constitute the general trace of the 
 works, the following is the usual procedure. Circles 
 are drawn on the map, with the battery under consid- 
 eration as a centre. The bounding radii of fire will 
 be determined by the width of field open to occu- 
 pation by the fleet ; and if this differs materially at 
 tlie different pi acticable ranges, separate studies must 
 be made and the best compromise be effected. Each 
 mode of mounting has a maximum angle of distribu- 
 tion of fire — a revolving turret has 360 degrees, a 
 casemate 60 degrees, an ordinary barbette 120 de- 
 grees, etc. If the desired bounding radii, fixed as al- 
 ready explained, include a less angle than that per- 
 mitted by the selected mode of mounting, the crest of 
 the battery will be a straight line perpendicular to 
 the bisecting radius ; if not, the crest should be a 
 broken line — and in general an angle of about 60 de- 
 grees will be most advantageous. With casemates 
 this angle is decidedly the best. Having drawn the 
 crest-line upon the map, note whether or not it is ex- 
 posed to be flanked or enfiladed by shipping, and ex- 
 amine the locality itself to learn whether a slight 
 change of position would reduce the cost of construc- 
 tion. The different batteries are thua successively 
 established. 
 
 The traverses and parados are next to be con- 
 sidered, Traverses are desirable between all large 
 high-power guns mounted in barbette : (1) to sux)ply 
 
Fortification of the Site Selected. 157 
 
 magazines and sliell or loading rooms ; (2) to prevent 
 the blast of adjacent j:>ieces from interfering with 
 each other ; (3) to limit the effect of an exploding 
 shell ; (4) to cover the guns against enfilade fire, if 
 that be practicable from the water. On the other 
 hand, if raised considerably above the level of the 
 parapet, as has usually been the custom, they serve 
 to define the exact position of the gun to the enemy ; 
 and, with the increased precision of fire to be ex- 
 pected from shipsf,under favorable conditions, this is 
 a serious objection. Some of the reasons for their 
 existence do not absolutely compel them to be 
 raised much above the crest of the parapet, and per- 
 liaps, where there is no danger of enfilade, future 
 practice may limit them to that height. With dis- 
 appearing guns, especially, this would reduce the 
 target to a long, ill-defined line with nothing to indi- 
 cate their position except an occasional appearance 
 at the moment of firing. 
 
 Recent difiicalties which have arisen in respect to 
 the x)arados are more perplexing. Its only raison 
 d'etre is to afford protection against reverse fire, to 
 which coast batteries are sometimes unavoidably ex- 
 posed. No one has ever proposed to use the device 
 unnecessarily, because when a projectile is coming 
 over the parapet a highway to speed the parting 
 guest is an instinctive provision. But experiment 
 lias shown that even when parados are unavoidable it 
 it is not easy to fulfil the conflicting conditions they 
 impose. Allowing for an angle of fall of 15 degrees, 
 a parados must be placed quite near the gun or else 
 be built to an excessive height. But if it be built too 
 near, the effect of shells from the front, of the size 
 now employed by ships, is disastrous. Quantities of 
 earth, especially .if frozen, stones, gravel, and splin- 
 ters of shell, are thrown back so* freely by such pro- 
 jectiles that the Italian engineers, after practical ex- 
 
158 Sea-coast Fortresses. 
 
 periments, have decided 95 feet behind the platform 
 to be not an excessive distance for parados exposed to 
 guns of a larger calibre than six inches. Up to and 
 including that calibre Q^ feet proved sufficient ; field 
 and siege guns caused no dangerous splinters. But 
 a distance of 95 feet with a fall of 15 degrees calls for 
 a parados rising at least 25 feet above the crest. 
 Evidently they will be avoided whenever practicable, 
 and, when unavoidable, will demand special studies 
 in each case. 9 
 
 Of late the attention of engineers has been strong- 
 ly drawn to the importance of concealing sea-coast 
 batteries by every practicable expedient. To in- 
 crease precision of fire, gunners on shipboard will 
 take advantage of surrounding objects which have a 
 known relation to the position of the guns, and they 
 will correct errors in pointing by noting the bursting 
 of percLission-shells, or columns of dust thrown up 
 by shot. Hence those sites are* most advantageous 
 which do not favor such methods. For example, 
 forests behind the battery give an uncertain horizon, 
 while if the guns are clearly defined against the sky 
 it is comparatively easy to adjust the sights. If the 
 slope in front is wooded or grown up with brush it is 
 not easy to perceive the exact point where a projec- 
 tile has struck ; while a battery placed upon a long, 
 smootli slope which continues to rise to the rear, is as 
 unfavorably situated as the bull's eye of a target. A 
 battery retired a short distance behind the crest of a 
 bluff affords a very uncertain clue to its range. A 
 rocky slope increases the chance of ricochet shots 
 taking effect, while a steep earthen slope stops the 
 projectiles. 
 
 Evidently in the future we must sacrifice neat 
 crests and beautiful slopes, so far as the service of the 
 guns and protection against washing by storms will 
 permit ; trees and bushes must be planted on the 
 
Fortification of the Site Selected. 159 
 
 parapets and behind the batteries to prevent a clear 
 definition of the guns ; the latter themselves must be 
 colored to harmonize with tlieir surroundings in sum- 
 mer and winter ; in a word, dispersion and conceal- 
 ment, as contrasted with concentration and armor, is 
 the hitest phase which the question has assumed. 
 This solutiou has been strongly advocated by Gen- 
 eral Sir Andrew Clarke, recently Inspector-General 
 of Fortifications in England ; and no doubt, as ship- 
 guns improve in power and accuracy, engineers will 
 study every expedient to aggravate the difficulty of 
 aiming from the unstable decks to which, fortunately 
 for us, they are confined. 
 
 Another matter must not be overlooked in con- 
 structing batteries for high-power guns — the effect of 
 the blast. The direct blow of the gases is not so 
 severe as might be expected. A smooth layer of 
 stone or concrete three feet thick, under and in front 
 of the muzzle of a 12-inch gun, saves the parapet 
 from degradation ; but there is another effect which 
 in confined positions is formidable. The partial 
 vacuum created behind the blast has a tendency to 
 burst open doors and light recesses, break windows, 
 etc., by the pressure of the air behind them. This 
 effect has long been noted at the explosion of maga- 
 zines. Iron bars 2.5 inches wide and 0.5 inches thick, 
 securing the doors of shell recesses, are reported to 
 have been bent outward by the vacuum created by the 
 blast of a 9-inch rifled gun. Large embrasures in case- 
 mates have caused the breaking open of doors of shot- 
 lifts, and have shaken uj) the cannoniers most un- 
 pleasantly. To meet this difficulty, free passages for 
 the air to enter should be supplied, and casemates 
 should never be closed in rear. 
 
 Some experiments were made in 1872-73, in New 
 York harbor, to test the effect of the blast of a 15- 
 inch smooth-bore gun charged with 100 pounds of 
 
160 Sea- coast Fortresses. 
 
 mammoth j)owder and a sliot weigUing 460 pounds. 
 The conclusion reached by the Board conducting the 
 experiments was that a second battery Q5 feet below 
 the first and 200 feet in advance, the ground between 
 being a somewhat broken slope of earth, would be 
 beyond the range of injury from the blast or from 
 unburned grains of powder ; but at 54 feet in front 
 and 12 feet below the muzzle there would be danger 
 from the latter, a screen of inch boards having been 
 riddled under like conditions. It was also inferred 
 that intermediate irregularities of ground, in the na- 
 ture of high screens, would tend to further reduce 
 the effects of the blast at a second batter3^ and that 
 a sufficiently high scarp (height not determined) 
 would justify placing a second barbette battery at its 
 foot. The Board, however, guarded itself by recom- 
 mending that, before a second barbette battery was 
 placed in front of the high battery, "a few experi- 
 mental shots should be fired in order to test the force 
 of the blast at points of the intended site." 
 
 I think that, with the high-power guns and slow- 
 burning powder of to-day, no engineer would care to 
 dispose two barbette batteries so that one should fire 
 over the other, under conditions even approaching 
 those favored by this Board. 
 
 In fine, then, a sea-coast fortress of to-day, suited 
 to the needs of this country, consists of a central 
 keep provided with bomb-proof quarters and ar- 
 ranged for a vigorous defence ; of detached high- 
 power gun batteries (turrets, iron casemates, lifts, 
 barbette batteries for disappearing guns, open bar- 
 bette batteries, etc., according to circumstances), 
 so placed as to sweep the channel and approaches, 
 but with ample space between their sites to prevent 
 mutual interference ; of detached mortar batteries, 
 usually in rear of the guns, and, so far as possible, out 
 of sight of the enemy ; of machine guns in covered 
 
Fortification of the Site Selected. 161 
 
 positions to sweej) slopes and approaches, and the in- 
 terior of the batteries in case of surprise ; of wire and 
 other entanglements to check the advance of tbe es- 
 calade parties from boats ; of secure operating rooms, 
 cable-shafts, galleries, and flanking guns for the 
 mined zones ; of position-finders suited to the local- 
 ity, for determining ranges and controlling the fire of 
 the guns and the operation of the mines from the 
 station of the commanding officer ; of snitable ar- 
 rangements for sweeping the approaches by the elec- 
 tric light, and for using movable torpedoes under 
 control from the shore. In countries where there is 
 danger of powerful descents upon the coast more 
 attention is paid to the defence of the position against 
 assault ; but with us little is to be feared in that di- 
 rection. Few modern fleets could afford to land more 
 than 1 500 or 2 000 men for that purpose, and, with 
 our reserves of local troops added to the regular gar- 
 rison, w^e should be able to hold the works with the 
 preparations indicated. 
 
 The cost of such a fortress is less than might be 
 imagined, and very far less than would be demanded 
 by a system of floating batteries. Thus the Fortifi- 
 cation Board, of which Secretary Endicott was presi- 
 dent, after a careful study of the subject, estimated 
 that the first cost of one floating battery, complete 
 except the armament, would be $3 300 000. Let us 
 see what could be prepared for that sum in the way of 
 a sea-coast fortress, adopting a liberal scale of ex- 
 penditure, increased in nearly every important item 
 over the figures of that Board : 
 
162 Sea-coast Fortresses. 
 
 FIRST COST OF A SEA-COAST FORTRESS COMPLETE, EX- 
 CEPT THE GUNS. 
 
 One 2-gUTi turret for two 16^-iiich 110- ton 
 
 guns $1 000 000 
 
 Ten lifts for ten 12-incli 50- ton guns 1 000 000 
 
 Ten disappearing batteries for ten 12-inch 
 
 50 ton guns 450 000 
 
 Three batteries for forty-eight 12-inch mor- 
 tars 192 000 
 
 Four hundred mines and cables, etc., com- 
 plete 200 000 
 
 Two operating casemates for the same, 
 
 with cable shafts, etc 100 000 
 
 One keep, with flanking arrangements for 
 
 the batteries 200 000 
 
 Add contingencies, 5 per cent 158 000 
 
 Total $3 300 000 
 
 The floating battery carries two 16 J^ -inch 110- ton 
 guns and one 10-inch 27- ton gun, and is exposed to 
 torpedo attacks and to rapid deterioration. The fort- 
 ress mounts two 16;^ -inch 110- ton guns, twenty 12- 
 inch 50-ton guns, forty-eight 12-incli mortars, four 
 hundred mines with their adjuncts ; and they are ex- 
 posed neither to torpedo attacks, nor to escalade, nor 
 to rapid deterioration. Bearing in mind the import- 
 ance of economy, these figures permit of no difference 
 of opinion as to how funds should be invested in 
 cases where a land fortress will accomplish the de. 
 sired object ; and this is the case in all but two of 
 our cjiief seaports. 
 
 NAVAL CO-OPERATION. 
 
 We have seen that, from the standpoint of a mili- 
 tary engineer, a sea-coast fortress bears a relation to 
 
Naval Co-operation. 163 
 
 the naval strength of the nation similar (o that of 
 an entrenched camp to *the land forces. It affords 
 security to the port and depots, a refuge to the com- 
 mercial marine, and a base of operations for the fleets. 
 So far as the position permits, the means of defence 
 should be conflned to the land ; in that way only can -' 
 economy, permanency, and security against torpedo 
 attacks be secured. Moreover, any floating defence 
 is always liable to be transferred to some other held 
 to meet a pressing emergency, real or imagined, and 
 the enemy may thus succeed by skilful manoeuvres in 
 stripping his proposed point of attack of elements 
 vital to its projected plan of defence. It is therefore 
 an accepted axiom with us that, so far as possible, 
 our system of land defences shall be independent of 
 floating supx)ort. 
 
 But this, like all other rules, has its exceptions. 
 Thus, for example, nature may offer no facilities for 
 defensive works. A large city, like many of our 
 Lake ports, lying upon a straight shore with no bay 
 or river approach admitting of defence intervening 
 between itself and an anchorage within bombarding 
 range, is practically at the mercy of the power hold- 
 ing control of the water. Other sites, like San Fran-o 
 Cisco Bay, by reason of deep water, strong currents, 
 and unfavorable topography, may justify the great 
 cost of floating defences to complete the land system. 
 Yet other sites, like the mouth of the Mississippi, '■ 
 may i^resent engineering difficulties in the way of 
 foundations which render it cheaper to float the 
 heavy guns on water rather than on mud. 
 
 But in addition to these special cases where the 
 aid of floating batteries is counted upon by the land 
 forces, there is one duty of vital importance in a vig- 
 orous defence which is solely naval. No entrenched 
 camp would be left without outposts to watch the 
 approach of the enemy, or without sorties to harass 
 
164 Sea- coast Fortresses. 
 
 him when he has made lijs appearance. Tlie land 
 defences are immovable and would lose half their 
 value if not supported by an active naval force. It is 
 not great guns that we shall need ; they can usually 
 be mounted far more economically on land. It is 
 the power of making offensive returns, in the nature 
 of sorties, that we lack ; and for supplementing this 
 deficiency we shall everywhere need naval co-opera- 
 tion. Present indications lead to the belief that the 
 modern torpedo-boat is lit ted for this work. Its high 
 speed would render it as useful as is cavalry for 
 scouting ; its terrible weapon would make it more 
 dreaded than the '^ masked battery" so often heard 
 of in the early days of the civil war ; while its 
 power of combining in flotillas, and assailing individ- 
 ual armored shi^^s of the first-class by night or when 
 obscured by the smoke of their own guns, might lead 
 to results as decisive as those achieved by the column 
 of Macdonald on the field of Wagram. 
 
 These needs in our latest system of coast defences 
 are strongly appreciated by engineers, and weliope 
 that they may be seriously considered by naval offi- 
 cers, who will know how they can best be met by ex- 
 isting or by modified types of torpedo-boats. I can- 
 not but believe that in no other form can funds for 
 ' ' coast defenders "be so usefully applied. O ur forts 
 have been likened to chained w^atch-dogs, and in one 
 sense it is a true comparison ; but we must not forget 
 that the dog is chained in front of the office safe, 
 where he is most needed, and that there are better 
 ways of assisting him than by locking an unchained 
 friend in the same apartment. 
 
INDEX. 
 
 Alexandria, bombardment of, 24, 
 33, 37, 38, 101. 
 
 Armament for coast, 82. 
 
 Armor, kinds compared, 142; fab- 
 rication of the Gruson, 143 ; kind 
 not yet adopted, 88, 90, 145 ; re- 
 sistance of wrought iron, 151; 
 resistance of steel and compound, 
 151; resistance of chilled cast 
 iron, 152. 
 
 Art of the Engineer, 16. 
 
 Attack by fleet, nature of, 40, 129, 
 131, 134; reasons for, 137. 
 
 Bombardment distant, the prob- 
 lem, 69; effective range, 70 ; in- 
 juries from, 72; how to meet, 72, 
 128. 
 
 Boston, strategic relations of, 12. 
 
 Calibres in naval warfare, 20. 
 
 Casemates, exposure in, 63; de- 
 scription of, 89 ; space within, 90 ; 
 how to locate, 156. 
 
 Charleston, naval attack on, 24, 28, 
 136. 
 
 Cost of Coast defence, judicious 
 limit of, 41; estimate for chief 
 ports, 44; compared with insur- 
 ance in New York, 45 ; other 
 reasons for incurring, 45, 52; 
 proper annual, 47; analysis for 
 New York City, 49 ; former out- 
 lays for, 51 ; funds how applied, 
 52; fortresses versus "Coast de- 
 fenders," 161. 
 
 Danube, mortar-fire on, 114. 
 
 Disappearing gun batteries, ex- 
 posure in, 62; description of , 95; 
 merits and demerits, 94. 
 
 Draught of war-ships, 20. 
 
 Drewry's Blufl", naval attack on, 
 27. 
 
 Dutch Gap, mortar-fire at, 104. 
 
 Earth, resistance of, 149. 
 
 Elements of Coast defence, 19, 67, 
 138, 153, 160. 
 
 Formulae approximate, (see Rules 
 approximate). 
 
 Forts existing, utility of, 97, 141; 
 history of, 135; description of, 
 138. 
 
 Fort Fisher, naval attack on, 24, 
 30, 90, 101. 
 
 Fort Sumter, naval attack on, 28. 
 
 Fortification of site, discussion of, 
 153; armament for, 153; plan- 
 ning the works, 154 ; size of gar- 
 rison, 155; general trace, 156; 
 the keep, 153; traverses, 156; 
 parados, 157; concealment, 158; 
 effect of blast, 159 ; cost of, 161. 
 
 Grand tactics, in Coast defence, 14. 
 
 Gulf Coast, strategic relations of, 
 13. 
 
 Guns, mounting analyzed, 55; ex- 
 posure without parapet, 60; ex- 
 posure as non-disappearing bar- 
 bette, 61 ; exposure on the King 
 carriage, 62; exposure on the 
 Duane gun-lift, 62; exposure in 
 casemates, 63; exposure in tur- 
 
166 
 
 Index. 
 
 ret, 63; economic comparison of 
 mountings, 64; height above wa- 
 ter, 73, 77; modes of mounting, 
 82, 85; extreme effective range, 
 70; flanking submarine mines, 
 96, 154; power of, 21; calibres 
 needed, 20; number of, 23; 
 ashore and afloat, 25, 37; ma- 
 chine, 35, 98, 155; rapid firing, 
 99; relative numbers, 153. 
 
 Hampton Roads, strategic relations 
 of, 12. 
 
 Horizontal fire, nnmber required, 
 83; how mounted, 85. 
 
 Lifts (gun), exposure in, 62; de- 
 scription of, 91. 
 
 Lissa, naval attack on, 33, 38, 101. 
 
 Logistics in Coast defence, 16. 
 
 Machine guns, details respecting,. 
 98; precision of, 35; for local 
 defence, 155. 
 
 Magazines, rules for constructing, 
 91, 100; explosion of, 101. 
 
 Masonry, resistance of, 146. 
 
 Mortars, number required, 102; 
 merits of, 103; demerits of, 124; 
 advantages of rifling, 105: ve- 
 locity of fall, 106; energy to 
 crush deck, 106, 108; efi:ective 
 range^ 109; precision of fire, 109; 
 practice in defences of Washing- 
 ton, 110; practice at Bucharest, 
 111; practice at Meppen, 112; 
 practice in Russia, 113; high ex- 
 plosives in, 114; disposition in 
 battery, 119. 
 
 Mortar batteries, plan of, 118 , ser- 
 vice of ,.120; distribution of fire, 
 120; cost of, 124. 
 
 Mortar carriages, Elswick, 116; 
 Raskasoff, 117; need of experi- 
 ments with, 118. 
 
 Mortar platforms, 114; Italian ex- 
 periments with, 115. 
 
 Narragansect Bay, strategic re- 
 lations of , 12. 
 
 Naval co-operation, 8, 68, 72, 131, 
 162. 
 
 Non-disappearing gun batteries, 
 exposure in, 61 ; where used, 95. 
 
 Pacific Coast, strategic relations of, 
 13. 
 
 Parados, 157. 
 
 Position-finders, 84. 
 
 Pneumatic dynamite gun, 114, 133. 
 
 Portland, strategic relations of, 10. 
 
 Port Royal, naval attack on, 37. 
 
 Range-finders, 83, 
 
 Rapid-firing guns, details respect- 
 ing, 99; see also Machine guns. 
 
 Ricochet fire. 73, 75. 
 
 Rules approximate, weight of pro- 
 jectile, 150; velocity of projec- 
 tile, 151; energy of projectile, 
 151; penetration of wrought-iron 
 armor, 151; resistance of steel 
 and compound armor, 151; re- 
 sistance of chilled cast-iron ar- 
 mor, 152. 
 
 Sea-coast fortresses, discussed, 135 ; 
 history of our, 135; duty of, 138; 
 mir third system, 138; our pro- 
 visional system after the civil 
 war, 141 ; now proposed, 153. 
 
 Sebastopol, naval attack on, 25. 
 
 Ships of war, draught of, 20; de- 
 ployment of, 23; guns per mile 
 of line, 24; attack on land de- 
 fences, 40; ranges they seek, 38; 
 tactics against forts, 37; deck 
 protection, 103. 
 
 Shrapnel fire, 35. 
 
 Site for works, to deter bombard- 
 ment, 69 ; to prevent passage, 73 ; 
 discussion of height, 73 ; develop- 
 ment of front, 78; submarine re- 
 quirements, 80; selection of, 67; 
 see also Fortification of site. 
 
 Spezzia, defences of, 15, 71. 
 
 Strategy naval, in Coast defence, 
 8, 13 ; naval bases demanded by, 
 10. 
 
Index. 
 
 167 
 
 Submarine mines, depth of water, 
 81: inllueiice of eiirreiits, 80; 
 tidal range. 81 ; conditions to ful- 
 fil, 124, 138: disposition of, 130: 
 detached groups, 138; self-act- 
 ing, 138; operating casemate for, 
 131): attacked by day, 129: at- 
 tacked by night, 131; ttanking 
 guns of, l;)2: electric light for, 
 133; movable torpedoes for, 133; 
 passMu:^ throuiih, by force^ 134, 
 
 Torpedo-boats (naval), utility of. 
 14, 11), 54. 68, 73: largo numl)erj» 
 needed, 108. 
 
 Tori:)edoes, movable, conditions to 
 be nu»t, 133. 
 
 Travei-ses, 150. 
 
 Turrets, exposure in. OiJ; descrip- 
 tion of, 86: metal of, 88; merit. s 
 and demerits of, 88. 
 
 Vertical tiro, discusst^d, 103: theory 
 of, 105, 109 'r see also Mortars. 
 
14 DAY USE 
 
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 I^PRlSlSTieT ^ 
 
 KfcC'DLO AFR l/t-4fHA0S 
 
 "STANFORD 
 
 m^M'm^m^ii 
 
 OCT 8 1974 
 
 IHRY2 5 1977 
 
 SAN niE GO-SlQ 
 
 INTERLIBRARY LOAN 
 
 AUG 3 1978 
 
 LD21A-50to-2,'71 
 (P2001sl0)476 — A-32 
 
 General Library 
 
 University of California 
 
 Berkeley 
 
K 03n^l