l^r 
 
 GIFT OF 
 Miss J, T. Vinther 
 
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MANUAL 
 
 Military Field Engineering 
 
 FOR THE USE OF 
 
 OFFICERS AND TROOPS OF THE LINE. 
 
 PREPARED AT THE 
 
 UNITED STATES INFANTRY AND CAVAIvRY SCHOOL 
 
 BY THE 
 
 Department of Engineering, 
 
 Capt. Wm. D. Beach, 3d Cavalry, Instructor. 
 
 SIXTH EDITION 
 
 REVISED BY 
 
 Major Wm. D. Beach, 10th Cavai^ry, 
 
 Member of the War College Board. 
 
 Capt. E. a. Root, 10th Infantry.- 
 Capt. T. H. Si^avens. Quartermaster, U. S. A. 
 
 The Hddson-Kimberly Publishing Co., 
 Kansas City, Mo. 
 
 I.ONDON: 
 W. H. AI,I,KN & CO. (I^imited), 
 
 13 Waterloo Place, S. W. 
 Publishers to the India Office. 
 

 Entered according to the Act of Congress in the year 1897, by the 
 
 hudson-klmberly publishing cc, in the office of the 
 
 I^ibrarian of Congress, at Washington. 
 
 Cop*YRi6HTEi5 1902, ^y'the* * 
 
 HUDSON-KlM^ERiY PC^M^ICSIING C©MI»AK{Y, 
 
 GIFT OF 
 
PREFACE. 
 
 The necessity existing at the Infantry and Cavalry School 
 for a text-book on Field Engineering, including the various 
 military expedients recognized in our service, is deemed suffi- 
 cient reason for the following pages. 
 
 Most of the subjects treated of in this volume may be found 
 in various military works published in our country during the 
 past twenty-five years, but the fact remains that no one book 
 has covered the required ground, nor has their revision been of 
 very recent date; while, at the same time, the new field gun and 
 small calibre rifle have necessarily modified previously exist- 
 ing profiles of Field Works and Shelter Trenches. 
 
 Access has been had to corresponding publications of the 
 Germans, French, English and Austrians, as well as to our 
 own Official Rebellion Records and many other available 
 sources, native and foreign. 
 
 It has been the endeavor to limit the scope of this work to 
 subjects considered indispensable as a part of a line officer's 
 education. 
 
 •The following Assistant Instructors in the Department of 
 Engineering — viz.: 1st Lieut. E. A. Root, 19th Infantry; 1st 
 Lieut. W. C. Wren, 17th Infantry, and 1st Lieut. T. H. Slavens, 
 6th Cavalry, have been associated with the undersigned in the 
 preparation of this volume. 
 
 WM. D. BEACH, 
 Captain, 3d Cavalry, 
 U. S. Infantry and Cavalry School, 
 
 Fort Leavenworth, Kansas, July, 1894. 
 
 921579 
 
Headquarters of the Army, Adjutant-Generars Office, 
 
 Washington, March 25, 1895. 
 Circular No. 4. 
 
 With the approval of the Secretary of War, the special study 
 of the books, pamphlets, orders, etc., hereinafter named, by 
 officers of the army subject to examinations for promotion, is 
 recommended: 
 
 Manual of Field Engineering— Captain W. D. Beach, 3pd 
 Cavalry. 
 
 By command of Lieutenant-General Schofield. 
 
 [Signed] GEO. D. RUGGLBS. 
 AdJutant-OmeraL 
 
PREFACE TO THE FIFTH EDITION. 
 
 A fifth edition of this manual having been called for, the re- 
 visers have made certain alterations and additions which seem 
 to them warranted by experiences which have fallen to their lot 
 during the Spanish-American War and Philippine insurrection. 
 
 The peculiar difficulties confronting a rapidly advancing army 
 are such as to render familiarity with various military expedi- 
 ents only a degree less important than an intimate acquaintance 
 with one's weapon. The efficiency of a command may be para- 
 lyzed by the lack of a practicable road or by reason of a broken 
 bridge as effectually as by tactical blunders or failure to 
 reconnoiter. 
 
 Hasty intrenchments are more than ever important, and there 
 seems little reason to doubt, judging from our experience before 
 El Caney and at San Juan Hill, that odds of ten to one will here- 
 after be necessary in order to successfully assault trenches de- 
 fended by good infantry armed with a magazine rifle. This de- 
 duction was originally made by Colonel A. L. Wagner, A. A.-G., in 
 a report on El Caney, and is borne out by a critical study of the 
 fight at San Juan Hill and various actions during the Boer War 
 in South Africa. 
 
 Recent experiences but render more certain the assertion that 
 the assailant will usually find it necessary to intrench, the de- 
 fender always. 
 
 Upon the line officer in the future as in the past will devolve 
 the responsibility of tracing and directing the construction of 
 shelter trenches as well as making intelligent use of expedients 
 in bridging, rafting, road-building or camping. 
 
 As modern civilization tends to diminish the number of men 
 skilled in handicraft, so much the more important does it become 
 that all officers should require greater familiarity with what 
 are ordinarily termed ''military expedients." Results may be 
 reached in many ways, but their attainment with economy of life 
 and treasure marks a soldier skilled in his art, a leader worthy 
 the best traditions of the military service. 
 
 W. D. B 
 
 Fort Leavenworth, Kansas, August, 1902. 
 
List of Books Consulted in the Preparation of this Work. 
 
 Aide Memoire, R. E Vols, j-2, 
 
 A Move for Better Roads L, A. Haupi, 
 
 Appleton's Cyclopaedia of Applied Mechanics, Vols, 1-2, 
 
 Civil Engineering Wheeler, 
 
 Cours de Fortification Passagere De Guise, 
 
 Ecole de Fortification de Campagne French, 
 
 Elements of Field Fortification Wheeler, 
 
 Engineering News Magazine, 
 
 Engineer's Pocket-Book Trautwine, 
 
 Field Fortification Turner. 
 
 Field Fortification Hutchinson, 
 
 Field Works Brackenbury^ 
 
 Field Works Used in War, (Translation 
 
 from the German) Wilson, 
 
 Good Roads Magazine, 
 
 Gun Powder and High Explosives Walke, 
 
 International Cyclopaedia Dodd, Mead & Co* 
 
 Journal of the Military Service Institution 
 
 of the U. S. 
 Journal of the U. S. Cavalry Association, 
 
 Manual for Engineer Troops Duane, 
 
 Manual of Military Engineering Ernst, 
 
 Manual for Railway Engineers G, L, Vose, 
 
 Manuel de Fortification de Campagne. . . . Brialmont, 
 Manuel des Travaux de Fortification de 
 
 Campagne, par un Capitaine d'Infanterie. 
 
 Manuel de Fortification Plessix and Legrand, 
 
 Manual of Heavy Artillery Tidball, 
 
 Military Bridges Haupt, 
 
 Military Bridges. Chester. 
 
 Military Engineering, Instruction in Chatham Course, 
 
 Military Land Mines Mercur. 
 
 Military Transport Furse, 
 
 Modern High Explosives Eissler, 
 
 Notes on Military Hygiene A. A. Woodhull, 
 
 Official Records of the Rebellion, U. S . . . . War Department, 
 
 Organization and Tactics Wagner, * 
 
 Pionier Taschenbuch, Berlin, 1893 Official, 
 
 Report of Chief Signal Officer, U. S., 1893. . War Department, 
 
 Roads and Railroads Chester. 
 
 Roads and Railroads Gillespie* 
 
 Roads, Stieets, and Pavements Gitlmore, 
 
 Temporary Fortification Chester. 
 
 The American Railway Scribner, 
 
 U. S. Bridge Equipage and Drill . . , , War Department 
 
TABLE OF CONTENTS. 
 
 Chapter. Page. 
 
 I. General Principles 7 
 
 II. Fire, Projectiles and Penetration 11 
 
 III. Field Geometry 15 
 
 IV. Hasty Intrenchments, Gun Pits and Epaule- 
 
 ments 21 
 
 V. Clearing the Ground 28 
 
 VI. Obstacles 32 
 
 VII. Field Works 39 
 
 VIII. Working Parties 57 
 
 IX. Revetting Materials and Revetments 61 
 
 X. Field Casemates and Magazines .-. 73 
 
 XI. Field Works in Combination 78 
 
 XII. Siege Works 84 
 
 XIII. Defense of Localities 88 
 
 XIV. Use of Cordage and Spars 105 
 
 XV. Spar Bridges 118 
 
 XVI. Floating Bridges 140 
 
 XVII. Roads 168 
 
 XVIII. Railroads 175 
 
 XIX. Telegraph and Telephone Lines 186 
 
 XX. Demolitions 191 
 
 XXI. Camping Expedients 205 
 
 Plate. 
 
 1, 2 
 
 3, 4 
 
 5, 6 
 
 7, 8 
 
 9-15 
 
 16 
 
 17, 18 
 
 19, 20 
 
 21 
 
 22, 23 
 
 24-29 
 
 30-33 
 
 34-40a 
 
 41-49 
 
 50 
 
 51-53 
 
 54 
 
 55-57 
 
 58-60 
 
WLA.lSlxy^s.1^ 
 
 OF 
 
 MILITARY FIELD ENGINEERING 
 
 CHAPTER I.— General Principles. 
 
 1.— Military Field Engineering may be defined to be the art 
 of utilizing the materials at hand for the attainment of the secu- 
 rity, effectiveness, health and comfort of an army in the field. 
 
 The modern rifle has vastly increased the value of cover, both 
 iu attack and defense, and rendered necessary the application of 
 ihe principles of fortification to an army in the field. The result 
 to be obtained in all fortification is to so strengthen a position, by 
 artificial means, that a force occupying it may successfully resist 
 or subdue another attacking it. 
 
 2.— Fortification is divided into two general classes, viz.: 
 
 (^(7j— Permanent. 
 
 ^&;— Temporary or Field Fortifications. 
 
 With the former this manual has nothing to do. 
 
 3.— The latter division includes three quite distinct classes. 
 
 The first comprises all works devised for the temporary protec- 
 tion of important points, such as cities, arsenals, bridges, fords, 
 positions, etc., and are techuicallv known as Field Works. 
 
 7 
 

 9 , * (?e»^<3ti Principle*. 
 
 ''1?Iie*sec\)rfd c6in]prt1^es"the various devices of the engineer for 
 reducing a fortified place by means of parallels and approaches, 
 called Siepe Works. 
 
 The third division relates particularly to the quickly made 
 defenses by which an army in the presence of an enemy protects 
 itself; these are known as Battle Intrenchments or Hasty Intrench- 
 merits, 
 
 4.— A Defensive Position is one affording protection from 
 the shot and observation of an enemy and, at the same time, com- 
 manding the ground in front, within range. 
 
 A position of perfect defense is not possible, but the following 
 general principles are to be fulfilled as nearly as circumstances 
 will permit. 
 
 (1) The defenders' position should conform to the special tacti- 
 cal requirements of the occasion* and should be such as to favor 
 the use of their relatively, strongest arm. 
 
 (2) It should be made impossible for the enemy to obtain nat- 
 ural cover during his advance. In other words, the position should 
 have a free field of fire. 
 
 (3) The defenders should be protected from the fire and view of 
 the enemy by cover so arranged as not to interfere with counter- 
 attacks. 
 
 (4) The advance of the enemy should be hindered by obstacles 
 so arranged that he may be checked while under the fire of the 
 defenders. 
 
 (5) Communications should be such that the defenders may 
 freely move from one part o^ the position to another, while the 
 contrary should obtain witb respect to the enemy's ground in 
 front. 
 
 The chief requisite of a defensive position is a free field of fire, 
 especially at short and mid ranges. If the position is judiciously 
 selected the field of fire will generally be obtained without much 
 difficulty, but the advantages of the position and the effect of the 
 fire may be enhanced by temporary fortifications. The cutting 
 down of slight ridges which might afford cover for th^e enemj 
 
 ♦A. r>ure1v defensive nosition . for instan^'e, mig-ht have its flanks resting- on im- 
 passfible obstacles, and thns be secure from a turning movement, but this same 
 position ♦^ig'ht be found to be a faulty one were a quick offensive movement, by 
 the defenders, contemplated. 
 
General Principles, ^ 9 
 
 within effective range or the removal of hedges, fences, etc., may 
 sometimes be of more benefit than the actual preparation of 
 defenses. 
 
 In the present advanced state of efficiency of fire-arms, artificial 
 cover is, however, of greater importance than ever before. Con- 
 structed in the right place, at the proper time, field fortifications 
 may render indispensable service, while their neglect may insure 
 defeat. 
 
 5.— While formerly it was the special province of the Engineer 
 to lay out and supervise the construction of defensive works, it 
 has now, under the changed condition of warfare, become the work 
 of the Line as well, and it may be laid down as an accepted rule 
 that the defensive arrangements for a given position are to be 
 made by the troops which are to occupy it. 
 
 These changes have affected the art in many ways. The field 
 works now constructed are simpler, ruder, less regular, and less 
 angular than before. An army in the presence of an enemy always 
 fortifies, whether in camp, in bivouac, or in line. 
 
 6.— Rapidity of execution renders necessary the adoption of 
 fixed types of works in the exercises in time of peace; but these 
 types will sometimes be susceptible of modification in their real 
 application. However, even in war, the endeavor should be to 
 approximate to the regulation forms, for they are deduced from 
 experience and observation, and realize, as well as possible, for 
 each particular case, the best conditions of resistance compatible 
 with rapidity of execution. 
 
 The advantage of regulation types is understood at once when 
 it is borne in mind that, upon the battle-field, there should be no 
 hesitation; everyone should stick to his individual role in order 
 to unite efficiently in combined action. 
 
 Thorough study and frequent practical exercises, conducted 
 methodically, are indispensable In order to escape feeling one's 
 way, with the loss of time that an insufficient instruction renders 
 inevitable. Upon the battle-field a few minutes may decide the 
 fate of armies in each other's sight. 
 
 7.— Fortification, which at first glance may appear to dominate, 
 as representing the "security" and * 'effectiveness" of an army. 
 
10 General Principles. 
 
 the other and apparently less important subjects relating to health 
 and comfort, is, however, so intimately connected with them that 
 neglect of one may render all the others useless. Thus, ^'bridges," 
 "roads," and "railroads" may, under certain conditions, relate par- 
 ticularly to the effectiveness and security of an army, in con- 
 nection with Fortification, while under other circumstances they 
 may be as important as various "camping expedients" in the 
 attainment of "health" and "comfort." 
 
CHAPTER II.— Fire, Projectiles and Penetration. 
 
 8.— Pire as regards its direction is classified as follows: 
 
 (1) Prontal, when it is delivered at right angles to tlie front 
 of the enemy's line, and sometimes so termed when delivered 
 straight to its own front. 
 
 (2) Oblique, when the direction of the fire is at an oblique angle 
 to the front of the enemy's line. 
 
 (3) Enfilade, which is delivered from positions on the prolon- 
 gation of the enemy's line. In this case, the line of fire sweeps 
 the enemy's front. When fire is used to sweep along the front of 
 a defensive line and thus enfilade the assailants as they approach 
 the position, it is known as flanking fire. 
 
 (4) Reverse, when delivered so as to strike troops or lines oj 
 defense from the rear. 
 
 (5) Cross, when the lines of fire from different positions cross 
 on or in front of the enemy's line. 
 
 As regards its trajectory it is classified as 
 
 (1) Direct, when delivered at seen objects at moderate angles 
 of elevation— in the case of artillery when delivered at seen objects, 
 with service charges at elevations not exceeding 15". 
 
 (2) Indirect or Curved, when delivered with small-arms against 
 an unseen object protected by a seen covering obstacle— in the case 
 of artillery, as above, or with guns, howitzers or mortars with 
 reduced charges at angles not exceeding 15°. Thus firing over an 
 intervening hill at troops sheltered behind it would be an example 
 of indirect fire. 
 
 (3) High Angle, when used at angles exceeding 15**. 
 
 (4) Grazing, when the projectile travels approximately parallel 
 to the ground. 
 
 (5) Plunging, the muzzle is required to be depressed. 
 
 9.— The Artillery Projectiles used in the U. S. Army are sJiell, 
 shrapnel and canister. 
 
12 Fire, trojtctiU^ and Penetration. 
 
 i&neii.— toiieii may be classiiieu as commou sliell aud torpeuo 
 jsiiell. Tlie commou sliell is "a noliovv cast-irou or steel eylmder 
 with au ogival Head closed ai oue end and niled witn powder." 
 Tlie torpedo sliell is Ulled witii gun-cottou, or otiier liigli explo- 
 sive. Either shell may be ciiaracterized as a llyiug mine, the 
 chief object of which is to destroy material objects at a distance, 
 though the commou shell may also be effectively used against 
 troops. 
 
 10.— Shrapnel differs from common shell in being filled with 
 bullets, and having only a sufficient bursting charge to rupture 
 the envelope and release the bullets, which then move with a veloc- 
 ity which the projectile had at the moment of bursting. The bul- 
 lets are assembled in circular layers and held in position by "sep- 
 arators," which are short cast-iron cylinders with hemispherical 
 cavities into which the bullets fit. The shrapnel for the 3.2 inch 
 gun contain 1G2 bullets i^ in. in diameter, and weighing 41 to the 
 lb. The total number of bullets and individual pieces in the shrap- 
 nel is 201 when assembled, and many more after bursting. 
 
 11.— Canister, which is practically obsolete, is made of sheet- 
 iron or tin in the shape of an ordinary can, and is filled with bul- 
 lets held in place by filling the interstices between the bullets with 
 saw-dust, sulphur or rosin; the can is ruptured and its contents 
 dispersed by the discharge of the piece. 
 
 12.— The charges in the shell and shrapnel are exploded by 
 means of a combination fuse; by combination fuse is meant one 
 that may be arranged to explode the charge either on impact, by 
 percussion, or at a given time by certain arrangement of the parts 
 of the fuse. 
 
 13.— Field Guns range up to 6000 yds., but will be seldom usea 
 at a range greater than 2500 yds. 
 
 14.— The XJ. S. Magazine Bifle, when used as a single loader, 
 has fired 21 aimed shots in one minute, and when used as a maga- 
 zine rifie, 23 shots in one minute; its range is over 3000 yds. and it 
 is sighted to 1900 yds. 
 
 The average heights over which fire may be delivered are as 
 follows: Man standing, 4 ft. 4 in.; kneeling, 3 ft.; lying down, 1 ft.; 
 field guns, 3 ft 
 
I^irt, rrojtvH(A^ and Penetration. id 
 
 iu.— Xiie lolluvviii^ Luicivuefcjs ol maLeiial may be couisiaered ab 
 jji'ool: agaiust small-arm projectiles at all ranges: 
 
 ;baud 30 in. 
 
 Jiiartn 3y in. 
 
 i:>os8y or ini'Ly oxuaiiu 60 in. 
 
 ijiabiou niled wuu eartn 1 
 
 Well-made fascines '6 
 
 fciaud bag well packed, neaaer 1 
 
 ** stretcjLier 2 
 
 stacked sod 79 in. 
 
 Packed snow 79 in. 
 
 Soit wood 40 to 49 in. 
 
 Oak or other bard wood 24 in. 
 
 Grain sheaves piled 16 ft. 
 
 Iron plate 7-16 in. 
 
 Steel plate % in. 
 
 ♦Masonry brickwork with broken joints 20 in. 
 
 Crib of broken stone 8 in. 
 
 Against field artillery. 
 
 Sand 10 ft. 
 
 Earth 13 ft 
 
 Clay 17 ft. 
 
 Snow well packed 27 ft. 
 
 Masonry (for a short time; 40 in. 
 
 *A wall two bricks thick, breaking the joints, will stop any one 
 bullet, but after a time the bricks will ibe smashed and some bul- 
 lets get through. 
 
 A well-built wall with fine joints set in cement mortar, 9 inches 
 thick, is practically bullet-proof. 
 
 A 24 -inch sun-dried brick wall is fairly bullet-proof a short 
 time after setting. 
 
 15a. — ^The mean penetration of shells from siege gims, with a 
 striking velocity of about 800 feet, is: 
 
 6-inch 8- and 10-inch 
 Guns. Guns. 
 
 Feet. Feet. 
 
 Sand, mixed with gravel 9.84 11.48 
 
 Light earth 13.12 16.73 
 
 Light earth, loose (newly stirred up) 14.76 20.34 
 
 Clay (argillaceous earth) 21.33 27.89 
 
14 Fire, Projectiles and Penetration. 
 
 Dlmeoasions of craters made by 6- and 8.5-iiicli shells: 
 
 6-lnch. 8.5-inch. 
 
 Diam. Depth. Diain. Depth. 
 Feet. Feet. Feet. Feet. 
 
 Clayey earth 16.48 4.9 22.3 6.9 
 
 Calcareous sandstone 13.1 3.3 16.4 3.9 
 
 Concrete 9.8 3 11.5 3.3 
 
 Rough masonry 9 2 6.6 3 
 
 Note, — ^With delayed-action fuses, shells burst after gaining a 
 certain penetration. The maximum effect of the bursting charge 
 will be found on the line of least resistance. 
 
CHAPTER III.— Field Geometry. 
 
 16.— Before proceeding to that portion of field engineering 
 which involves geometry some of its simplest applications will be 
 explained. 
 
 17. — Slopes. Tlie usual description of a slope is by a fraction, 
 the numerator being the height and the denominator the base. 
 Thus, in PL 1, Fig. 1, the vertical height is l-6th part of the base, 
 and the slope is read as 1 on 6. In Fig. 2, the slope is 6 on 1. 
 
 18.— To lay out a Right Angle: First Method. Let A be a 
 point in the line BC, Fig. 3. Lay off from A the equal distances 
 AD and AE. With a radius greater than AD, and with D and E 
 as centers, describe arcs cutting each other at X. Join X with A. 
 Then is XA perpendicular to BC. 
 
 Second Method. Find a point such that the distances are in the 
 proportions of 3, 4 and 5: then will the angle included between the 
 two shorter sides be a right angle Thus (Fig. 4) with chain or 
 tape measure the distance AD equal to 4 yds. Place one end of 
 tape at D, the other at A, pulling it out and making XD equal to 5 
 yds., XA equal to 3 yds. 
 
 Third Method. At extremity of line, as A (Fig. 4), assume any 
 ))oint as C. Measure distance CA, set a stake on line BA at a dis- 
 tance from C equal to CA, as D. Set a third stake on line CD at X, 
 making CX equal to CD. Then will XA be perpendicular to 
 BA. 
 
 19. — To erect a perpendicular to a line from, a point without. 
 Ivet X (Fig. 5) be the point without, then, with X as a center, and 
 a distance greater than XA as radius, describe an arc cutting BC 
 at D and E. With D and E as centers, and with a radius greater 
 than DA, describe arcs cutting each other at Y. Join X and Y. 
 Then will XY be perpendicular to BC. 
 
 20.— -To bisect a given angle. Let BAG (Fig. 6) be the angle. 
 With A as a center, and with any convenient radius, as AD, 
 —2- 
 
PLATE 1. 
 
 •Figure 1. 
 
 Figure 2. 
 
 Figure 3. 
 
 B '.D 
 
 Figure 4 
 
 /E c 
 
 X 
 
 cK 
 
 Figure 5 . 
 
 Figure 6. 
 
 Figure 7y 
 
 A * c ' 
 
 Figure 10. 
 
 D ' B 
 
 B D" 
 
 E C 
 
 B C 
 
 Figure 11 
 
 .X 
 
 Y 
 
Field Geometry. 17 
 
 aescribe an aic cutting AB and AG at E and D. With D and E as 
 centers, describe arcs cutting eacli otlier at X. Join X with A. 
 The liue XA bisects the angle BAG. 
 
 21. — To lay out an equilateral triangle constructing adjacent 
 angles of 60 "" and 120"^. Let AB (Fig. 7) be a given line. Lay 
 off from B any convenient distance, as BE. Then, with B and E 
 as centers, and a radius equal to BE, describe arcs cutting each 
 other at D. Join D with E and B. The angles DEB, DBE and 
 EDB are each equal to 60°. The angle AED is equal to 120°. 
 Combining this method with that of slopes an angle of almost any 
 number of degrees can be laid out. 
 
 22. — To lay out an angle equal to a given angle. Let X 
 (Fig. 8) be a point in the line AB, from which it is required to lay 
 out an angle equal to OEG. Fix the points O and G at convenient 
 distances from E. From X lay off Xg equal to OE. Then, with 
 X and G as centers, and EG and OG as radii respectively, strike 
 arcs intersecting at F. Join X and F. The angle FXG is equal to 
 the angle GEO. 
 
 23. — To draw a line parallel to a given line and at a given 
 distance from it. Let AB (Fig. 9) be the given line. From any 
 two points, as G and D, erect perpendiculars. On these lay off the 
 required distance CE and DF. Join E and F. 
 
 24. — To find the distance between any two points when it 
 cannot be measured directly. First Method. To find AO, take 
 a point B in line with AO and from this point (Fig. 10) lay off any 
 convenient angle, as ABG. At D make EDG equal to ABG. Meas- 
 ure BG, DG and DE, putting E in the line GO. From similar 
 triangles 
 
 BO X DE 
 
 BO : BG :: DE : DG ;•. BO = 
 
 DG 
 
 From the result thus found, subtract the distance AB. The 
 remainder is the distance AO. 
 
 Second Method. (Fig. 11.) Mark B in prolongation of the line 
 AO. Assume any point as G. Lay off AF, making AG equal to 
 GP: also BE, making BG equal to GE. Prolong EF until a point 
 K is found in line with GO. Measure FK. This is the required 
 distance. 
 
18 Field Oeometry, 
 
 25. — ^Areas. To find the area of a rectangle. Multiply the 
 base by the height 
 
 To find the area of a trapezoid. Multiply the sum of the two 
 parallel sides by the perpendicular distance between them and 
 take half the product. 
 
 To find the area of a triangle. Multiply the base by the alti- 
 tude and take half the product. Or, 
 
 Area = V s (s — a) (s — b) (s — c) 
 in which s is the half sum of the three sides a, b, and c. Or, 
 
 Area = % a b sin O 
 in which a and b are two sides and C the included angle. 
 
 26.— The Field Level (PI. 2, Fig. 1) consists of three strips of 
 wood, A, B and C, each ^ in. thick and 2 in. wide. A being 62 in. 
 long, B and C each 44.42 in. The distance between centers on A is 
 60 in., on B and C 42.42 in. This makes a right angle between B 
 and C. There is a thumb nut at E clamping the arm B to the arm 
 A when the level is used. The screw at F projects, holding the 
 arm B, when folded, up. There is a stud at H, affording an attach- 
 ment for a plumb bob. There are permanent joints between B 
 and C, and A and C. 
 
 Fig. 1 shows the level and its joints, plumb bob for reading 
 slopes, and spirit level. Fig. 2 shows side for protracting angles. 
 
 27. — Uses of Level. The level may be used as follows: 
 
 (1) As a spirit-level, the level being on the edge C. 
 
 (2) As a square for setting out a right angle. 
 
 (3) As a protractor. 
 
 (4) For setting off slopes. 
 
 (5) As a mason's level with a plumb bob. 
 
PLATE 2. 
 
PLATE 3. 
 
 SHELTER TRENCH. 
 
 - LYING- 
 
 FiG.4. 
 
 SPLINTER PROOF, 
 
 (earth cover omitted). 
 
 Fig. 5 . SHELTER rof^ SUPPORTS oh RESERVES. 
 
 HEAD LOG AND 
 BRUSH-WOOD LOOPHOLE, 
 
 LOOP-HOLE 
 
 !rfl6i«97 
 
CHAPTER IV.— Hasty Intrenchments, Gun Pits and 
 Epaulements. 
 
 28. — The intensity of fire made possible by the fire-arms of 
 to-day renders some form of shelter on the field of battle impera- 
 tive. Circumstances may occur when advancing lines of skirmish- 
 ers will find natural shelter, but in many cases artificial cover will 
 have to be constructed on the spot. 
 
 Fortifications used on the field of battle depend, as to their posi- 
 tion, extent and use, on the ground; in conformity to this idea 
 they are constructed at the time of the battle, and not before. 
 
 They are called *' Battle" or ^^East<y'^ Intrenchments, and should 
 fulfill the following conditions: 
 
 (a) The thickness of earth embankment should be such that it 
 will not be liable to penetration by small-arm projectiles or shrap- 
 nel fragments. %^ 
 
 (h) The intrenchments should conform to the average heights 
 over which men can fire in the various positions,— viz. : lying prone, 
 1 ft.; kneeling, 3 ft: standing, 4 ft. 4 in.; and at the same time the 
 height of earth embankment above the natural surface of the 
 ground should be small, for the reason that the trenches can thus 
 be more easily concealed and are less liable to be struck by artil- 
 lery projectiles. 
 
 Hasty or Battle Intrenchments consist of cover for 
 
 (1) Skirmishers, lying, kneeling or sitting. 
 
 (2) Firing Line, Supports and Reserves, kneeling, sitting or 
 standing. 
 
 (3) Gun Pits and Epaulements. 
 
 r59. — The shelter trench for skirmishers lying down is shown 
 in Fl. 3, Fig. 1. It gives earth protection of a thickness of 2^ feet; 
 this thickness of loose earth will stop small-arm projectiles under 
 ordinary circumstances. The average time required by one man 
 to make 5 ft. (2 paces) of this trench is, with large pick and shovel, 
 15 minutes; with small intrenching spade, 20 to 25 minutes. 
 
 The number of skirmishers that can use this trench is usually 
 computed as two for each five feet of length, although three. may 
 occupy this space by lying partially on their left sides. In firing, 
 the left elbow rests on the berm. 
 
 30. — For men kneeling in two ranks, cover is gained by deep 
 ening the trench already dug to 1 ft. 8 In. and making it 5 ft. wide 
 
22 Hasty Intrenchments, Chin Pits and Epaulements. 
 
 with an embankment in front having a height of 1 ft. 4 in. and a 
 resulting thicliness of about ^Vo ft. (Fig. 2.) 
 
 The average time required by one man to transform 5 ft. of the 
 trench ''lying" into the trench "lineeling" is, with large pick and 
 shovel, 25 minutes; with small intrenching spade, 45 minutes. 
 
 Infantry in double rank kneeling can fire from this trench, the 
 number of rifles being computed at 4 for each 5 ft. length of trench. 
 The kneeling trench affords protection to men sitting, but hori- ^ 
 zontal fire from this position is impossible. The step at a would 
 only appear in the converted trench. 
 
 31. — Cover standing is obtained by deepening the kneeling 
 trench to 4 ft, leaving a step 20 in. high and 3 ft. wide next 
 the front wall, so as to facilitate leaving the trench to the 
 front and at the same time allowing a protected passage in 
 rear. The step serves as a banquette for men firing over the 
 embankment. 
 
 The embankment is given a height of 2 ft., the resulting thick- 
 ness being about 5^ ft. (Fig. 3.) 
 
 The average time required by one man to transform 5 ft. of 
 the trench "kneeling" into the trench "standing" is, with large 
 pick and shovel, 1 hour.* 
 
 32. — When isolated trenches for single skii^misliers lying are 
 desired, they should be made with the same section as that shown 
 in Figure 1 and have a length of 1 pace. Isolated kneeling trenches 
 for two men should also have a length of 1 pace, but the 
 rifle pit or isolated slielter standina should be 5 ft. in length on 
 account of difficulty in constructing a smaller one. The last read- 
 ily accommodates three men, two of whom can fire over the 
 embankment, while the third, standing in the 4 ft. trench, pro- 
 tects the flanks. 
 
 33. — When necessary to intrench supports and reserves, the cover 
 
 -The orditiRry form of ^Danish hastv intrenchment for fire, standing and cover 
 sitting:, kneeling- or crouching is a trench abont two feet wide and four feet deet), 
 having vertical sides and no embankments. This type of trench does not readilv 
 permit relieving or re inforcing the occupants an'^. as it is too narrow to permit 
 rarrving the wounded out. there re.«n1ts extreme snfFerine. since the injured mu.st 
 lie at the bottom and run th^ risk of being trampled upon. This trench has the 
 advantage however of affording a .email target for the enemy's artillery. 
 
 The f^ermans claim that the surface presented to .<;hrapnel bullets by a man 
 Iving down is nracticallv the .<5ame as a man standing in the open: therefore they 
 do not believe in broad s"Hallow trenche.s. Thev advocate the making of trenches 
 in the natural soil with the fresh earth carried away, or used fo- dummy trenches 
 so as to deceive the enemy's artillerists and prevent execution from shrapnel fire. 
 
Hasty Intrenchments, Gun Pits cmd Epaulements. 23 
 
 kneeling or standing should be used in parallel rows close to one 
 another. (Fig. 5.) 
 
 In the construction advantage should be taken, where possible, 
 of plows for loosening the earth. Two or three plows following 
 each other at intervals can be used to great advantage. 
 
 34. — The trenches here illustrated are all made on level 
 ground and are simply Ujpes showing the best forms and giving 
 general ideas as to the time required to construct cover.* On 
 slopes they must be modified so that the tops of tlie embank- 
 ments are, in general, parallel to the ground; they may also be 
 varied according to the kind of earth, sand requiring less thick- 
 ness of embankment and gentler slopes than clayey soil, while 
 sod mixed with earth allows greater penetration than earth 
 without it. 
 
 35. — The location of trenches depends primarily on tactical 
 situations, and secondarily on the nature of the ground. 
 
 Primarily, they should always occupy a position giving the 
 greatest development of fire, and hence are generally located 
 near tJie crest of the most ahrupt slope— i. e., near the *'mAlitary 
 cresty (See par. 153.) Tlie exact position is determined "by plan- 
 ing the eye at a distance above the ground equal to the proposed height 
 of embankment, and then selecting that line which gives a clear field of 
 fire to the front. 
 
 As to the secondary consideration, it is desirable in locating 
 trenches to avoid stony ground and that close to the edges of 
 woods, the former on account of the liability to flying frag- 
 ments should the embankment be struck by an artillery projectile, 
 and the latter by reason of the difficulty in constructing the 
 trenches. 
 
 36. — ^Intervals in line of trenches. In all trenches except 
 those for skirmishers lying down, intervals in the line should be 
 left for the passage to the front of artillery and cavalry— this 
 is especially necessary when cover standing is used. The inter- 
 vals may vary in width according to circumstances, but should 
 never be so wide as to preclude their defense by the trenches 
 adjoining the opening. 
 
 37. — Splinter-proofs. When troops are required to remain 
 
 *Cover from view only can. of course, be obtain'^d much more quickly, but a 
 penetrable cover is hardly more than a target to invite an enemy's fire. 
 
24 Hasty Intrenchments^ Chin Pits and Epaulements. 
 
 in the trenches for any considerable period, they should be pro- 
 vided with splinter 'proois or shelters of some kind. Planks, old 
 lumber, doors, etc., or, in their absence, small poles, may be used. 
 They should be laid with one end on the embankment, the other 
 resting on the ground in rear of the trench, and then covered with 
 3 or 4 inches of earth. This defense, while not proof against burst- 
 ing shells, will protect the men from dropping bullets and shrapnel 
 fragments. (Fig. 4.) 
 
 38. — Concealment of shelter trenches. Endeavor should 
 always be made to disguise the location of shelter trenches 
 by covering the sides toward the enemy with branches, weeds, 
 sod, etc. 
 
 39. — The advantages and disadvantages of the shelters for 
 men lying and kneeling may be briefly summarized as follows: 
 
 Advantages. 
 
 (1) They present but little difficulty to the advance of the 
 defenders' cavalry or artillery over them, and are easily sur 
 mounted by the occupants when the advance is ordered. 
 
 (2) They will stop rifle bullets. 
 
 (3) They offer but a small target to the enemy's artillery fire. 
 
 (4) They are quickly and easily made. 
 Disadvantages. 
 
 (1) The embankments being low, the field of fire may be lim 
 ited by small folds in the ground (care in selecting their position 
 may partially remedy this disadvantage). 
 
 (2) In wet weather they may become untenable by reason of 
 mud. 
 
 40.— lioop-holes may be provided by half Imbedding head-logs 
 in the embankment, or resting them on sand-bags on top of it, ana 
 leaving spaces beneath for the rifle. Or the loop-hole may be 
 formed with four sand-J)ags, as shown In Fig. 7. Brushwood may 
 also be used with an earth cover, either alone or in connection with 
 a head-log, as shown in Fig. 6. 
 
 Loop-holes for rifles splay inward, for field guns, outward. 
 
 The hest practice is not to use JisadAogs or loop-holes (unless in 
 case of an inferior force acting solely on the defensive), as their 
 use impels men to hesitate to leave cover when the advance is 
 ordered. 
 
PLATE 4. 
 
 
 -ts^ 
 
 FIGURES. 
 
 
 -»'6"^ 
 
'^6 Hasty Intrenchments, Gun Pits and Epaulements. 
 
 40a. — Cover for guns may be obtained in two ways. 
 
 (1) By means of Chun Pits; made by digging a tiole of a size suffi- 
 cient to partially conceal the gun and gun detachment, and form- 
 ing an embankment in front wuth the excavated earth. (PI. 4, 
 Figs. 1, 2 and 3.)* 
 
 (2) By means of Chin Epaulements; made by constructing an 
 embankment in front of the gun which rests on the natural surface 
 of the ground. In this form the gun detachment would be par- 
 tially sheltered in the pits from which the earth for the embank- 
 ment is taken. (Figs. 4 and 5.) 
 
 Circumstances would control the selection of the kind of cover, 
 If any, for field guns. The disadvantages of gun pits are the same 
 as those of shelter trenches, but pits give more complete protection 
 to the gun. (See par. 153.) 
 
 ♦Figs. 1, 2 and 4, PI. 4, are from U. S. Artillery Drill Regulations. 
 
PLATES. 
 
CHAPTER v.— Clearing the Ground. 
 
 41. — The tools more especially used in the field may be divided 
 into two classes. 
 
 (1) Intrenching tools, such as the pick, the shovel (long and 
 short handled, the spade, the picket shovel, and the hunting knife. 
 
 (2) Cutting tools, such as the ax, the hand ax, the log saw, 
 the hand saw, the linked felling saw, the gabion knife (pruning 
 knife), the hunting knife, the bush hook and the wire cutter. 
 (PI. 5 and 6.) 
 
 42. — The choice of a defensive position in which the foreground 
 is free from obstructions and favorable to the defenders' fire is of 
 the utmost importance: more or less clearing, however, will usu- 
 ally be necessary. Clearing must be systematically done, and, as 
 in all other work, should be undertaken by complete organizations 
 or parts of organizations under their own officers. 
 
 43.— The extent (theoretical) to which the foreground should be 
 cleared is equal to the effective range of the defenders' weapons. 
 Practically, as wide a space within this limit, is to be cleared, as 
 is consistent with the time and labor available. Brushwood and 
 standing timber most often screen the enemy's advance and steps 
 should be taken to remove them. 
 
 44.— The tools usually employed in felling heavy timber are 
 the ax and the log saw, the former being the most common, al- 
 though inexperienced men acquire familiarity with the latter more 
 quickly. When using the ax the cut should be commenced on the 
 side toward which it is desired the tree should fall, ropes being 
 used to incline it in that direction, if necessary; if immaterial 
 which way the tree falls, then attack it on the side toward which 
 it leans; after cutting it a little more than half through change 
 over to the other side and commencing about six inches higher 
 up, cut until it falls. In using the saw it may be necessary to 
 
Clearing the Grornid. 29 
 
 wedge the cut or use other means in order to keep the saw free: 
 the teeth should be set wide. 
 
 Both saw and ax may be used, in which case the ax should be 
 used on the side toward which the tree is to fall and the saw on 
 the other side. (PI. 6.) 
 
 45. — Trees would ordinarily be cut within a foot of the ground 
 because a greater height would afford cover. A man should cut 
 down a hard wood tree 1 ft. in diameter in 10 minutes and one of 
 soft wood of the same size in one-third the time. The hand ax, 
 hand saw, and hunting knife are useful in felling small trees, ropes 
 being attached to bend them, and the cut being made on the 
 convex side. 
 
 Felled timber must be removed, if of such a size as to afford 
 shelter to the enemy. It is utilized in making field casemates, 
 magazines, etc. 
 
 46. — Brushwood can be cleared at the rate of about 12 sq. yards 
 per man per hour. The men should be extended at about 4 paces 
 interval, using the bush hook, hatchet, or hand ax, together with 
 the gabion or hunting knife. 
 
 47. — Grain, grass, or weeds must be trampled by men in line, 
 mowed, or burnt. 
 
 48.— Hedges, fences, and walls, if not perpendicular to the 
 front, must be removed. Live hedges should be pulled to one side 
 in order to give the axmen greater freedom. (PI. 6.) Fences can 
 ordinarily be demolished with axes, walls by battering them down 
 or blowing them down with explosives. (Chapter XX.) 
 
 Buildings may be battered down, burned, or demolished by 
 explosives according to circumstances. In the case of buildings 
 and walls it will usually be necessary to remove the debris, which 
 can be used for filling hollows. 
 
PLATE 6. 
 
 
 Cutter. 
 
 Jt — — vvwvvvvvvWw'vvvvvvvv^ Wvvvvvvv^ 
 
 IL,LnkGci I^eLlLnpr ScxLv. 
 
 ig 
 
 /KuQTur. 
 
 -^ /n/antry ^ p 
 
 ado. 
 
 EUROPEAN. 
 
 .M- 
 
PLATE' 7.' 
 
 'Figure 1. 
 
 Figure 2, 
 
 Figure 12: '^^ 
 
 -8- 
 
CHAPTER VL—Obstacles. 
 
 49.— Obstacles have for their object the holding of the enemy 
 under fire while checliing his advance and breaking up his 
 formation. 
 
 (1) They must be within the effective zone of the defenders* fire 
 and must be so arranged as to offer the least obstacle possible to 
 an advance from the side of the defense. 
 
 (2) They must be concealed as far as possible from the view of 
 the assaulting party, so that they may come upon them as a 
 surprise. 
 
 (3) They must be diflicult of removal under fire, and, if possi- 
 ble, should be of such construction as will necessitate the use of 
 tools not usually carried by troops. 
 
 (4) They should, if possible, be so placed as to be secure from 
 the fire of the enemy's artillery, and so constructed that, if strtck 
 by his projectiles, they will suffer small damage. 
 
 (5) They must offer no shelter to the enemy. 
 
 50.— Abatis, on account of the ease with which it can be con- 
 structed, is the obstacle most used. 
 
 It consists of branches of trees about 15 feet long, laid on the 
 ground, butts pointing to the rear, all small twigs being cut off, and 
 all large branches pointed and interlaced. ThB abatis should be 
 5 feet high. 
 
 The branches are secured to the ground by forks, wire, or by 
 logs laid over the butts of the branches. The use of wire to hold 
 down the branches is recommended, and when used should be also 
 passed from branch to branch so as to form an additional en- 
 tanglement. When more than one row of abatis is used the 
 branches of one row overlap the butts of the next one in front. 
 (PI. 7, Figs. 1 and 2.) 
 
 The abatis most easy of construction is that made by felling 
 trees towards the enemy in such manner as to leave the fallen 
 part still attached to the stump; the branches are then pointed as 
 described before. (Fig. 5.) This is called slasMng. 
 
 ,51.— Abatis is often placed in the front of works when the 
 ditch is so shallow as to present little or no obstacle to an assault. 
 When so used they are placed upright and well tamped in. In all 
 cases, especially when small branches are used, it is better to sink 
 
Obstacles. 33 
 
 the butts in triangular pits, and, when tlie branclies are in place, 
 fill in with earth and tamp well. (Figs. 3 and 4.) 
 
 In all cases where exposed to artillery fire a glacis should be 
 constructed in front of an abatis, so as to protect it from injury. 
 
 52. — Low Wire entanglements are formed by driving into the 
 ground stakes projecting about 18 in. The stakes should be driven in 
 rows about 6 feet apart, the stakes in each row being opposite in- 
 tervals in adjacent rows. The heads of the stakes are connected 
 by stout wire wound around them. To make this more effective, 
 do not clear the ground, but allow bushes, brush, etc., to remain in 
 place. (Fig. 6.) Use 1 ft. of wire to 1 sq. foot of ground covered. 
 
 53. — High Wire entanglements are constructed in the same 
 manner, except that the stakes should be at least 4 ft. high, and 
 placed 6 to 8 feet apart. The head of each stake is connected 
 with the foot of the stake diagonally opposite, the line of posts in 
 front and rear being finished off as fence panels with barbed 
 wire. The use of barbed wire is not advised for the interior 
 crossed work on account of the danger and difficulty in working 
 with it. 
 
 Roughly, 1 yard of wire is necessary for each square foot of 
 entanglement. Ten men can make about 9 square yards of this 
 entanglement in one hour. This work does not require trained 
 men. Wire entanglement, either high or low, is useful on the 
 glacis of field works, as it holds the attacker under fire at the most 
 favorable point. (Fig. 7.) 
 
 54. — ^Palisades consist of rows of trunks of trees or of squared 
 trunks, 8 or 10 feet high, planted close together and pointed on 
 top. When material is at hand, ribband pieces should be spiked 
 on the inside along their tops about a foot or two below the 
 points to hold them steady. They are used to advantage in the 
 bottoms of ditches or to close the gorge of field works. (PI. 8, 
 Fig. 1.) 
 
 55. — Praises are palisades arranged horizontally or much in- 
 clined and are often used at the foot of the exterior slope and at 
 the top of the counterscarp; in the first position they point down 
 and in the second upward. In each case, the ribband or strip is 
 spiked on underneath and laid against the ground near the edge of 
 scarp or counterscarp, as the case may be, another one being spiked 
 
PLATE a 
 
Obstacles, 35 
 
 to the inner end of the f raise on top; thus the outer ones give good 
 bearing surfaces and do not break up the crest, and the inner one 
 gives a bearing for staking and tying down. The slopes described 
 above are given so that unexploded shell will always roll away 
 from the parapet. (PI. 7, Figs. 9, 10 and 13.) 
 
 Fraises may with advantage be made of barbed wire in the 
 form shown, care being taken that all wire when finished is on 
 top of the wooden supports. The advantage of this variety of 
 fraise is that it is little damaged by artillery fire and is very difll- 
 cult of removal. (PI. 7, Fig. 13.) 
 
 When time is pressing fraises may be made of branches of trees 
 with the butts well sunken and staked down. (PI. 7, Fig. 12.) 
 
 56. — Crows' feet, Chevaux-de-frisey and planks full of spikes have 
 been used in the past as obstacles to an advance, but the two 
 former are not now issued for use in our service, and the latter is 
 one not easily made in the field. Such obstacles require much 
 time and material in their construction and are not treated of 
 here, as they do not fall properly in the domain of Field Engineer- 
 ing; their value in any event is not commensurate with the diffi- 
 culty of their preparation. (PI. 8, Figs. 2 and 6.) 
 
 57. — Small Pits or troup de loup are square on the top, 3 feet 
 on a side, and are pyramidal in shape; they are 2 ft. 6 in. deep, and 
 have a pointed picket driven in the center of each. 
 
 In digging these pits a glacis should be formed in front of the 
 row nearest the enemy, and, to avoid filling the pits with earth 
 thrown from the others, the row farthest from the glacis should 
 be commenced first. One man can make 10 pits per day in easy 
 soil. (PI. 7, Figs. 8 and 11.) 
 
 Small pits may be surmounted by a low wire entanglement, 
 making a very serious obstacle. 
 
 58. — Fords may be made impassable by strewing them with 
 harrows, points up. 
 
 59. — A Fougass is a mine so arranged that upon explosion a 
 large mass of stones or shells are projected towards the enemy. 
 (PI. 8, Fig. 3.) 
 
 To make a fougass, dig a hole in the shape of a frustum of a 
 cone, inclining the axis in the direction of the enemy, so as to 
 make an angle with the horizon of about 45 degrees. The sides 
 
36 Obstacles. 
 
 should splay outwards at an inclination of 12 degrees from the 
 axis. The powder charge is placed in the bottom of the hole- 
 preferably in a box— and in front of this a platform of wood 
 about 3 inches in thickness: on this are piled stones, brick, etc. 
 The mine is exploded by means of electricity or common fuse. 
 Care must be taken in digging the hole for the fougass that the 
 line of least resistance is in all cases in the axis of the hole; to he 
 sure of this, throw the excavated earth upon the crest towards the 
 defenders' side and ram well, allowing earth to enclose the sides of 
 the excavation in the manner shown in cut. 
 
 Fougasses are useful in defending boat-landings, roads, etc. 
 
 The following empirical formula may be taken for determining 
 the charge of powder for fougasses: P = -^, in which P and s 
 represent the weight in pounds of the powder and stone. 
 
 When broken up, a cubic foot of limestone weighs 96 1T)S. 
 
 60. — Land Mines are small mines placed in the line of ad- 
 vance of the enemy and exploded either by electricity or fuse 
 from the defense. The small mines are made by digging holes 
 from 2 to 3 yards deep, placing the charge in a box in a recess 
 excavated in one side of the hole, and refilling with the excavated 
 earth, tamping well. The wires are carried back in a small trench 
 to the work. In common earth, the charge for 2 yards deep is 
 about 25 lbs., and for 3 yards deep about 80 lbs.; the diameter 
 of the crater formed will be about twice the depth of charge. 
 (PI. 8, Fig. 4.) 
 
 ♦To determine the quantity of explosive necessary for use in 
 a **common" mine, multiply eleven-sixths of the cube of the line 
 of least resistance in yards by the quantity of explosive required 
 to throw out one cubic yard. 
 
 Quantity of gunpowder necessary to throw out a cubic yard of 
 material (Macaulay): , 
 
 Pounds. Ounces. 
 
 Light sa ndy earth 1 13 
 
 Hard sand 2 
 
 Fat earth mixed with sand and gravel 1 10 
 
 Wet sand 2 2 
 
 Earth mixed with stone 2 4 
 
 * "Military T^and Mines," Mefcur. 
 
Obstacles. 37 
 
 Pounds. Ounces. 
 Clay with tufa 2 8 
 
 Fat earth mixed with pebbles 2 12 
 
 Rock 3 10 
 
 New brickwork or masonry 2 2 
 
 Inf ^ior brickwork or m-asonry 2 11 
 
 Good new brickwork or masonry 3 10 
 
 Good old brickwork or masonry 4 11 
 
 The following formula gives the relation beween the charge 
 for common and overcharged or undercharged mines: 
 
 C' = c iVs^+Vs)^; 
 
 C — charge for common mine (lbs.); 
 
 r = radius of crater; 
 
 C = charge for undercharged or overcharged mines (lbs.) ; 
 
 L = length of line of least resistance. 
 
 The following formulae give charges for common mines: 
 
 With explosive gelatine, 
 
 C--1-17 (L + % (r — L) )3; 
 
 With gunpowder, 
 
 e = l-10 (L+ % (r — L) )3; 
 
 C = charge in pounds; 
 
 r = crater radius in feet; 
 
 L = line of least resistance in feet. 
 
 In common mines, 
 
 L-^r. 
 
 61. — Barricades are used to prevent the passage of the enemy 
 through roads, streets, and defiles generally. 
 
 They may be made of any material at hand, paving stones, 
 overturned carts, barrels filled with earth, stones, and articles of 
 like nature. They should be built so that a passage is always left 
 for the defenders, but means should be at hand to close the open- 
 ing quickly— a wagon may be used for this purpose, being drawn 
 away from the opening when a passage is desired. 
 
 The houses on either side should be loop-holed and used to 
 flank the defense. Overturned wagons, broken furniture and 
 debris from the adjacent houses make a very good obstacle and 
 should be placed in front of the barricade to ward off cavalry 
 charges. (PI. 8, Pig. 5.) 
 
PLATE .9. 
 
CHAPTER VII.— Field Works. 
 
 62. — When a position is to be held for a considerable period and 
 when time is available, more deliberate defenses than the Hasty 
 or Battle Intrenchments (Chapter IV.) are constructed. These are 
 known as Field Works and usually require a minimum of 6 hours 
 for construction. The conditions to be fulfilled, besides those nec- 
 essary for a defensive position (Chapter 1.), are. 
 
 (1) That they must afford protection against both rifle and 
 artillery fire. 
 
 (2) That they must be of suitable size for the garrison that is 
 to occupy them. 
 
 (3) That they should have suitably constructed casemates to 
 shelter the garrison at night. 
 
 Field works may be constructed for the defense of a single ob- 
 ject, as a bridge, a ford, etc., or they may occupy the key points in 
 a long line of defense, in which case they should be located so as 
 to afford mutual protection, the intervening space either being left 
 open or occupied by shelter trenches. 
 
 Before proceeding to the study of Field Works, a brief synopsis 
 of the technical terms used in connection with them will be 
 necessary. 
 
 63.— A Parapet is a bank of earth thrown up to cover the 
 defenders while firing. 
 
 64. — The Trace of a work is its outline in plan: the term is 
 often applied to the horizontal projection of its Interior crest. 
 (PI. 9, Fig. 1.) 
 
 65. — The Profile is a cross-section of the work made by a plane 
 perpendicular to the interior crest. (Fig. 2.) 
 
 In the profile, the various parts are named as follows: 
 
 a. Banquette slope, e. Exterior slope. D. Ditch. 
 
 b. Banquette tread, f. Berm. i. Interior slope of glacis. 
 
 c. Interior slope. g. Escarp. k. Glacis. 
 
 d. Superior slope. h. Counterscarp, t. Trench. 
 
 66. — The Interior Crest is the intersection of the Interior 
 and Superior slopes: sometimes called the magistral line, ("a" 
 Fig. 1.) 
 
40 Field Works. 
 
 67.— The Exterior Crest— that of the Superior and Exterior 
 slopes. C'b*' Fig. 1.) The thickness of parapet is the horizontal 
 distance between interior and exterior crests. 
 
 68. — A Traverse is a bank of earth inside a work to protect 
 some portion of it from direct fire. When the protection afforded 
 is from reverse fire, the traverse is sometimes called a Parados. 
 (Figs. 8 and 4.) 
 
 69. — An Embrasure is a revetted opening in the parapet, 
 through which field guns may fire. It is said to be Direct or 
 Oblique according to whether its axis is perpendicular or inclined 
 to the line of parapet. 
 
 70. — A Gun Bank is a raised mound, by means of which Held 
 guns may fire over the parapet. Guns thus placed are said to be 
 en barbette. 
 
 The relative advantages of Embrasures and Gun Banks are as 
 follows:— 
 
 Embrasures afford greater protection to the gunners, but 
 
 (a) They afford a very limited field of fire. 
 
 (b) They weaken the parapet and require frequent repairs. 
 
 (c) The place of the gun when not in action cannot well be used 
 by Infantry. 
 
 The conditions as to Gun Banks are the converse in each case. 
 
 71. — The Command of a work is the height of its interior crest 
 above the ground on which it is constructed, ("m" Fig. 2.) 
 
 72.— Its Relief is the height above the bottom of the ditch, 
 ("o" Fig. 2.) 
 
 73.— The Plane of Site is a plane tangent to the ground on 
 which the work is constructed. 
 
 74. — The Terreplein is the surface of the ground inside the 
 work and does not, of necessity, coincide with the plane of site, 
 since the whole interior of the work— i. t'., the terreplein— may be 
 lowered for the purpose of securing more cover. 
 
 When the banquette tread is more than 2 feet above the terre- 
 plein, its slope may be stepped with fascines or planks: this has 
 the advantage of giving more interior space, but tends to produce 
 confusion on the part of the defenders, especially in a night 
 assault. 
 
Field Works. 41 
 
 75. — The interior slope is usually made as steep, up to four on 
 one, as the revetment will stand. 
 
 76. — The superior slope is necessary in order to secure the best 
 fire effect on the ground immediately in front of the work. It 
 weakens the parapet near the interior crest, however, and this 
 defect increases as the slope is made steeper; hence, it should be 
 as slight as is consistent with good fire effect. 
 
 The degree of this slope is regulated by the principle that fire 
 from rifles resting on its surface should not pass more than three 
 feet above the glacis, or, when there is no glacis, above the outer 
 edge of the ditch. It will thus depend on 
 
 (1) The command of the work. 
 
 (2) The inclination of the plane of site. 
 
 (3) The distance from the interior crest to outer edge of ditch. 
 The slope should not exceed one on four; one on six (normal) is 
 
 better, and then, if necessary, make a glacis of the requisite 
 height. 
 
 77.— The exterior slope should be as gentle as two on three, if 
 possible, owing to the fact that steeper slopes are soon destroyed 
 by artillery fire. 
 
 78. — The Berm may be as great as 6 ft. in width; ordinarily it 
 would not be greater than 2 ft., while in favorable soil none may 
 be left at all. 
 
 Advantages of berm: 
 
 (1) It relieves the edge of the ditch from the weight of the par- 
 apet and thus prevents caving, in loose soil. 
 
 (2) It enables the parapet to be thickened. 
 Disadvantages: 
 
 (1) It affords a footing in an assault. (This, however, may be 
 partially remedied by use of obstacles.) 
 
 79. — The slope of the escarp and counterscarp should be equal 
 to or greater than the exterior slope, the counterscarp being as 
 steep as the earth will stand. 
 
 80.— The Glacis snould be parallel to the superior slope, in 
 order to get the best fire effect from the crest. 
 
 81. — If the parapet does not require much earth, and the ditch 
 is required as an obstacle, it may be made triangular in cross-sec- 
 
42 Field Works. 
 
 tion. This form gives ,the greatest depth and prevents the assail- 
 ants from forming in the ditch, but it is difficult of construction. 
 Eight feet may be talven as the extreme depth of ditch and twelve 
 feet as the extreme lieight of parapet. The' width of the ditch 
 varies with the amount of earth required— 12 ft. at the top being 
 a minimum. 
 
 A parapet with trench and ditch affords cover iu the shortest 
 time possible: each foot of depth in the trench means 2 ft. of 
 cover, plus the additional protection afforded by the earth from 
 the ditch. 
 
 A parapet with ditch alone affords greater cover to the ground 
 in rear and better command of ground in front, but its height 
 makes it more conspicuous. 
 
 82.— Referring to traces of various works (PI. 9, Fig. 5)— 
 
 a, is a salient angle. 
 a' is a shoulder angle. 
 
 b, is a reentrant angle. 
 
 c, c, c, are faces. e, e, is the gorge. 
 
 d, d, d, are flanks. f, is the capital. 
 83. — Field Works are classified with reference to their 
 
 trace, as 
 
 (1) Open, which have thick parapets on exposed sides, the rear 
 or gorge being open. 
 
 (2) Closed, in which the thick parapet is continuous. 
 
 (3) Half-Closed, which only differ from the "open" in that 
 the gorge is closed by obstacles, stockade work, or shelter 
 trenches. 
 
 Advanced works within rifle range of the main defensive line, 
 as well as those in positions where the flanks are secure (as a 
 bridge head), should usually be "open." Works in main line and 
 advanced works beyond rifle range should be "half-closed"; those 
 in isolated positions or on the flanks of a defensive line— "closed." 
 
 Open works have the advantage over closed, of affording greater 
 freedom of movement to the defenders, and, in the event of cap- 
 ture, of being exposed to fire and assault from the works in rear. 
 
 Closed works, while affording greater protection from assault, 
 are liable to have their parapets exposed to enfilade or reverse fire, 
 besides which the available interior space is much reduced. 
 
PLATE 10. 
 
44 Field Works. 
 
 84.— Forts and Redoubts (Closed Works) are distinguished 
 by tlie former having reentering angles, thus affording defense 
 of the ditch from the parapet, both conditions being lacking in 
 redoubts. 
 
 Redoubts, as compared to forts, are of simpler trace, do not re- 
 quire so large a garrison, and afford better frontal fire; but, as 
 they have no ditch defense (unless caponiers and counterscarp 
 galleries are constructed), they should be traced to support one 
 another. 
 
 85. — With respect to caponiers (PI. 20) and counterscarp gal- 
 leries—the former, if sunken, as is usually necessary for protection 
 against artillery fire, may become untenable in rainy weather; 
 while communication with the latter is diflicult and may, by the 
 enemy, be rendered impossible. The objections to these forms of 
 ditch defense are so great, and their use so limited, where proper 
 frontal fire and obstacles are possible, that their construction is 
 seldom necessary. 
 
 86.— The Sector of Fire is a term used to designate the angular 
 space in front of a work which is swept by its fire (30° on each 
 side of a perpendicular being considered the limit of oblique rifle 
 fire.) Thus, a straight line of parapet has a sector of fire of 60° 
 (PI. 10, Fig. 1), while, in a redan, it varies with the angle at the 
 salient. With a salient of 120°, the sector of fire is evidently 120° 
 (Fig. 2); with a 60° salient, there will be an undefended space of 
 60°. (Fig. 3.) This undefended space may be done away with by 
 blunting the redan. (Fig. 4.) A redan with shoulder angles 
 (Fig. 5) furnishes a ditch defense in front of the shoulders and does 
 away with part of the dead space in front of the salient, but it is 
 diflicult of construction and is not usually resorted to. 
 
 87.— For reasons given in Chapter XI., it is often desirable to 
 place the guns outside the work; in which case some plan like 
 Fig. 6 may be adopted, the single line representing a shelter 
 trench. 
 
 88.— Defilade of Field Works. In order that Field Works may 
 fulfill the condition of screening the occupants from the fire and 
 view of an enemy, the problem of defilade arises. 
 
 This may be defined as the operation of regulating the direction 
 and command of the earth cover so that the interior of the work 
 is protected from the direct fire of an enemy. 
 
Field Works. 45 
 
 The problem resolves itself into two distinct parts— 
 
 (1) Dcfiladiny in plan, 
 
 (2) Defilading in section. 
 
 89. — Defilading in plan. This involves the selection of the 
 trace of the work (its position having been previously chosen). 
 The trace will vary with the plane of site, the terrain in the im- 
 mediate vicinity, the proximity of high ground that the enemy 
 may occupy, and the time available for construction. A plane of 
 site sloping to the rear is obviously the easiest to^ defilade, and 
 one sloping toward the enemy the most difficult. Salients should 
 occupy commanding ground, the lower portion being taken for 
 the reentrants or for the gorge. The longer faces of a work should 
 lie in the direction of lower or inaccessible ground, so that they 
 cannot be enfiladed. 
 
 With commanding ground in front, the work is more difficult 
 to defilade in proportion to its depth; therefore, have longer faces 
 opposed to the high ground and make the work as shallow as is 
 consistent with other conditions. 
 
 As a rule, the longer faces of a work must lie so that the de- 
 fenders can bring as direct a fire as possible in the direction of 
 expected attack. 
 
 All the foregoing conditions as to defilading in plan cannot, in 
 the usual case, be satisfied, but the object to be attained must be 
 kept constantly in view, and, in selecting the trace for a work, an 
 officer's ability will be shown by the skill with which he harmon- 
 izes the various diverse requirements. 
 
 After the careful selection of the trace, as already indicated, 
 and marking it by pickets, the problem is completed by defilading 
 tlie proposed work in section. 
 
 90. — Defilading in section* With a horizontal site and only 
 level ground toward the enemy, a constant command of 8 ft. is 
 sufficient to protect the whole interior of the work. 
 
 On an irregular site, or when necessary to place a work in a 
 position commanded by higher accessible ground, the necessary 
 protection of 8 ft. may be attained in one of three ways— 
 
 (1) By raising a parapet. 
 
 <2) By lowering the terreplein. 
 
 (3) By use of traverses, parados, bonnets, etc. 
 
FTrATE 11 
 
 Pi^re 1. 
 
 ^ Plani^4- -^#^- - "■- ;^V 
 
 Figure. 2. 
 
 Figure 3. 
 
 
 ^J;QK 
 
 Figure 4, 
 
Field Works. 47 
 
 To determiue bow niucli protection is needed, suppose, for ex- 
 ample, the proposed worli is a lunette. Plant poles at the salients 
 of sufficient length to reach the interior crest of completed work. 
 Place two pickets at the gorge, about G ft. apart, .one on each side 
 of the capital, and a third 8 ft. to the front. Tie a string to the 
 rear pickets, 3.5 ft. from the ground, the string passing round the 
 third stake. (PI. 11, Fig. 2.) Taking position behind the horizontal 
 string, have an assistant move the string on the forward picket 
 until it comes into the plane fixed by the eye, the horizontal string 
 and the highest point of the dangerous ground. This plane, 
 which is now established by the string triangle, is called the tan- 
 f/cnt plane. A plane parallel to this and 4.5 ft. above it is l^nown 
 as the plane of defilade. (Fig. 1.) The proper height of parapet at 
 the salient and shoulder angles is now fixed by sawing off the 
 poles 4.5 ft. above the points in which the tangent plane cuts them. 
 This will evidently give 8 ft. cover at the gorge, at which point 
 the height of parapet of the flanks is 8 ft. 
 
 If it is found that the required height of parapet exceeds 12 ft., 
 the plane of defilade may be lowered not to exceed 1.5 ft. This will 
 still give 6.5 ft. protection at the gorge. 
 
 If this proves insuflicient, either traverses must be resorted to 
 or the terreplein at the gorge lowered. 
 
 91. — To defilade a work from two or more heights, the plane 
 must be tangent to the two heights to which angles of elevation 
 are the greatest. As three points fix a plane, it follows that the 
 tangent plane would usually contain but a single point of the' 
 string at the gorge; hence, the problem is solved by reversing the 
 string triangle — i. e., fixing the apex at the gorge 3.5 ft. above- the 
 ground, and the two extremities of the base within the proposed 
 work and far enough apart to allow the two heights to be seen 
 between them. An assistant at each of the forward stakes ad- 
 justs the string as directed. (Fig. 3.) The problem is then com- 
 pleted as in the previous case. 
 
 92. — It is sometimes advisable, when a single plane of defilade 
 gives too great a command, to use two planes; the portion of the 
 interior of the work on the side tow^ard H (Fi^. 4) being defiladed 
 from it, and that on the other side from the height H'. This 
 method exposes the faces and flanks to reverse fire and renders 
 traverses (parados) necessary. 
 
48 Field Works. 
 
 93.— The height of a traverse (which should be such that a 
 shot grazing it will pass 2 ft. above the parapet it is to cover) is 
 found as follows: 
 
 Assume that the traverse is to be on the capital of a lunette. 
 
 The problem of direct defilade with two planes having been 
 solved, and the poles at angles of the works having been sawed off 
 to indicate the proper height of interior crest in order to defilade 
 the work as far as the capital, the height of traverse to protect a 
 flank from reverse fire is found thus: Measure down from the 
 tops of the poles at the extremities of the flank any convenient dis- 
 tance, as 3 feet,* mark the points and connect them by a string. 
 This string and the opposite height determine a plane which will 
 cut rods held vertically on the capital, at a distance of 5 feet below 
 the required top of the traverse (2 ft. plus the distance measured 
 down on the poles). Proceed in a similar manner, using the other 
 hill and its opposite flank. The greater of the two results fixes 
 the height of that portion of the traverse. In the same manner. 
 Its height to protect the faces from reverse fire may be found. 
 By reference to Fig. 4 this will be readily understood. 
 
 This method, while not absolutely accurate, will give results 
 near enough for all practical purposes, with the error on the side 
 of safety. Traverses or Parados are the usual protection against 
 reverse and enfilade fire, and, although sometimes used to protect 
 parts of a work from direct fire, this is usually attained either by 
 raising the parapet, by lowering the terreplein, or by both these 
 methods combined. 
 
 94.— Profiling. After the trace of the work has been decided 
 upon, the problem of defilade solved, the poles at the angles cut 
 off as indicated, and the cross-section of the parapet decided upon, 
 the next step is to erect profiles which shall correspond to this 
 cross-section. These profiles are, if practicable, to be made of 
 strips or battens 1 in. x 2 in., and placed at intervals of about 10 
 yds. along each face and flank, as well as at each angle. 
 
 For parapets not over 6 ft. in height, stakes may at once be 
 driven into the ground and strips nailed to them, but for higher 
 parapets it is more convenient to make the profile on the ground, 
 merely driving short pickets in place of the long stakes In the first 
 
 *The idea beinsf to have the string: behind which the observer stands, when 
 looking towards the height, at about the level of the eye. 
 
PLATE 12. 
 
PLATE '13 
 
 CJi N N O o 
 
 .<0 »fi T- o o 
 
 ■ -^ o <^- ^ ^ 
 
 C ^ o-d <3> 
 
 m 
 
Field Works. 51 
 
 Instance. When completed, the profile is up-ended and nailed to 
 the pickets. (Fl. 12, Fig. 1.) If strips cannot be obtained, the 
 entire profile, except the uprights, may be made of twine. The 
 profiles at the angles of the works, known as oblique or angle pro- 
 files, will evidently differ from the others in length, while their 
 height, on level ground, remains the same. The position of any 
 point of the angle profile, as, for example, the exterior crest, is 
 fixed by finding the intersection of the prolonged exterior crest 
 lines of the face profiles. This result is accomplished by standing 
 on the farther side of the second profile from the angle and lin- 
 ing in an assistant who holds a rod vertically at the angle, one end 
 of the rod resting on the ground. After the profiles are in place, 
 twine should be stretched between them to indicate the various 
 crest lines. The outer edge of the battens marks the extent of 
 the fill, except in the case of the interior slope, which is marked by 
 the inner edge when the slope is to be revetted. 
 
 95. — Calculation of Dimensions of Earthworks. Tfie Com- 
 mand of the proposed work having been fixed by the requirements 
 of defilade, and the thickness by the character of fire expected, 
 it becomes nece>ssary to calcailate the dimensions of the excavations, 
 so that theij ivill furnish enough, and no more, earth than is required. 
 The size of embankments and trench are, by the nature of the 
 problem, fixed, as is the depth of ditch; hence the only variable is 
 width of ditch, which is found as follows: 
 
 Assuming the relief to be constant and the profile, for example, 
 to be as shown in PI. 13, make a sectional sketch of the proposed 
 work at any point except an angle. Calculate the sectional area 
 of parapet, glacis, and trench, in square feet, and from the sum of 
 the first two subtract the last: the remainder divided by the as- 
 sumed depth of ditch, in feet, will give the mean width of ditch, 
 from which, knowing the slope of escarp and counterscarp, 
 the width at top and bottom can readily be found. 
 
 96.— Earth in embankment occupies, for a time, about one- 
 twelfth more space than it did originally if untamped, but this In- 
 crease is not usually taken into account in the computations for 
 ascertaining the width of ditch. If the earth is tamped it occupies 
 about 1-10 less space. When the relief of a work is not constant, 
 It is evident that, in order to get the proper amount of earth, 
 
52 Field Works. 
 
 either the depth or the width of ditch must vary. On account of 
 the labor required in raising earth, the limit of depth is taken at 
 8 ft; for a similar reason, the maximum height of parapet is 
 taken at 12 ft. Whatever the depth of ditch assumed, it is always 
 constant. The required width at any point is found by means of 
 a section of the work, as already explained, a section near the 
 extremities of each face determining the wudth of ditch for that 
 entire face. 
 
 97. — An excess of earth will occur at the salients and a defi- 
 ciency at the reentrants, although this may be partially obviated 
 by making the shovelers throw toward the reentrants. 
 
 98. — Drainage of the trench must be provided for at the time 
 the work is constructed. If the fall is toward the gorge, an open 
 drain will suffice; but if in any other direction, a covered draiu 
 (PI. 50) should be left to carry the water to the ditch. 
 
 Construction of Field Works. The details of construction 
 and dimensions of earthworks will change with varying require- 
 ments and soil, but there are certain general principles that 
 should be followed in all. 
 
 99.— As to profile: The Normal (PI. 14, Fig. 2) fulfills the 
 conditions as to simplicity, protection against field artillery (in 
 most soils), command of the ground in front, and cover stand- 
 ing, in the trench. The trench is stepped and steps revetted to 
 facilitate mounting the banquette, while the berm is omitted to 
 deprive the assailants of a foothold. The command may be in- 
 creased either with or without constant relief, the parapet thick- 
 ened or reduced, and the trench made into a casemate without 
 changing the type of this profile. 
 
 100.— As to garrison: For ordinary field works, the garri- 
 son is usually computed at 2 men per yard of interior crest; but 
 for isolated works, this estimate should be increased by one-half. 
 Embrasures and gun-banks each reduce the interior crest line 
 available for troops, by 5 yards. 
 
 101. — As to laying out tasks: Cutting lines must be marked 
 by tape or pick, computations made, and the exact size of the task 
 for each relief determined in accordance with the rules given in 
 Chapter VIII. 
 
 As an example of laying out tasks, assume that an earthwork 
 
PLATE 14. 
 
PIATE 15. 
 
Field Works. 55 
 
 with normal profile and constant command of 6 ft. is to be made 
 on a level site. 
 
 Before work is commenced, the outer and the cutting lines of 
 ditch and trench must be marked. As fatigue parties cannot be 
 expected to excavate eartii and at the same time preserve the 
 proper slopes, the usual method followed is to dig vertically as in 
 dicated by the cutting lines and afterward form the slopes by cut 
 ting off the steps. 
 
 The cutting lines for the task of the 1st Relief would be made 
 oil the ground, as indicated in section and plan. (PI. 14, Fig. 1.) 
 The 1st Relief having finished, cutting lines for task of 2d Relief 
 would then be marked out; and finally, the 3d Relief would com- 
 plete the slopes of ditch and parapet, and finish any work not com- 
 pleted by the other reliefs. 
 
 When not practicable to revet the banquette and trench steps, 
 the risers may be sloped back at about six on one. 
 
 When necessary to throw earth more than 12 ft. horizontally, 
 extra shovelers should be provided at the rate of 1 to each 2, or 2 
 to each 3 diggers, depending upon the soil and the distance it is to 
 be thrown. 
 
 102.— Gun-banks, when made, are usually placed in the sali- 
 ents, for the reasons that the guns will have a greater field of 
 fire and it is at this point that the earth of which they are made is 
 in excess. PI. 12, Fig. 2 shows a gun-bank on a straight line of 
 parapet, and Fig. 3 one at a salient. The top is horizontal and 3.5 
 ft. below the interior crest: this distance may vary, however, for 
 different pieces. All slopes are one on one, except the ramp, or 
 roadway leading up to the bank; this may be as steep as one on 
 four, but a gentler slope is better. The width of ramp should be 8 
 ft. The level surface of the bank extends back 24 ft. from the para- 
 pet and a log or fascine is half sunken and picketed near the front, 
 for a hurter. The width of bank for a single gun is 15 ft. At a sali- 
 ent (PI. 12, Figs. 3 and 4) the angle is filled in by a straight revet- 
 ment from 6 ft. to 15 ft. long and the superior slope reduced to cor- 
 respond to lines joining its extremities with the exterior crest 
 salient. This forms what is known as a "pan coup6." 
 
 103. — Embrasures for field guns would be used in positions 
 where the fire is required to be in one direction only; for example, 
 
56 Field Works, 
 
 to sweep a road, bridge, or ford; or in the flank of a work to 
 cover ground in front of an adjacent work. 
 
 PI. 15, Fig. 1, shows the horizontal projection and the section of 
 an embrasure. It is made at the same time as the parapet, by 
 making the sole "s" parallel to the superior slope. The cheeks, 
 "c, c," are vertical at the throat, "e," and have a slope of one on 
 one at the other extremity; their height should never exceed 4 ft. 
 
 The usual method of forming an embrasure is to stretch a string 
 nlong the line of fire; at the throat lay off 1 ft. on each side of it, 
 and at a distance of 5 ft. from the throat lay off 1.5 ft. in a similar 
 manner. Right lines joining the corresponding points so deter- 
 mined will mark the outer lines of the sole, which will splay one 
 on ten. Each throat gabion is vertical, the extreme ones being in- 
 clined throe on one; the slope of the intermediate ones is secured 
 by alignment top and bottom on the extreme ones. Each gabion 
 is anchored independently of the others, so that one may be torn 
 out without seriously injuring the embrasure. 
 
 104. — By the Merlon is meant that portion of the parapet be- 
 tween two embrasures and above the soles. Embrasures should, 
 as a rule, never be closer together than 15 ft. ; otherwise the merlon 
 is too mucli weakened. 
 
PLATE 16. 
 
 Fig-l. 
 
 Fio.3. 
 
 i ', 1 
 
 i ' I ■ 
 
 '4'^" 
 
 
 
 
 5' 
 
 5' 
 
 :5" 
 
 ^' 
 
 5* 
 
 6' 
 
 "3^' 
 
 
 
 
 
 4' 4-' 4-' 4' 4' 
 
 Fig.4, 
 
 
 
 * 
 
 '^, 
 
CHAPTER VIII.— Working Parties. 
 
 Occasion may arise, as, tor example, at night, in the presence of 
 an enemy or even with a large working party, when a well-estab- 
 lished system of talking and uandling tools, distributing and reliev 
 ing worlving parties, etc., will be a paramount importance. 
 
 105. — Organization of Working Parties. The nature of the 
 required worlv having been decided upon, the estimate of and the 
 application for the requisite number of men and tools devolves 
 upon the officer charged with its execution. 
 
 A working party of the requisite strength (which should include 
 a reserve of 1-lOth) should be furnished, as far as possible, from a 
 complete organization, a company, a battalion or brigade, and not 
 from detachments of different organizations. 
 
 106. — Responsibility. The party should be divided into re- 
 liefs and the task each is to accomplish made plain before it begins 
 work. Tlie officers and non-commissioned officers of the working 
 party are responsible for the amount of work done. 
 
 107. — Taking Tools. The first relief, having been formed 
 in single rank with rifles slung across the back, is marched to the 
 parli where the tools have previously been laid out, either in rows 
 (PI. 16, Fig. 1) or in heaps. (Fig. 2.) The relief in the former case 
 is advanced in line to the row and each takes a pick in the left 
 and a spade in the right hand; in the latter case the party in col- 
 umn of files is marched between the piles, each in turn receiving 
 a pick in the left and a spade in the right hand. The relief is 
 then marched in column of fours or twos to the point where the 
 work is to begin. 
 
 108. — Carrying Tools. In carrying picks and spades the 
 handles are grasped near the iron, which is held vertically, the 
 arras extended and the hands close to the side. In turning, the 
 point of the pick should be lowered and the blade of the shovel 
 raised, and when marching, either in line or in column, the han- 
 dles should be splayed outward, in order to prevent interference. 
 The necessity undei* certain circumstances of preserving silence 
 makes the above precautions important at all times as a matter of 
 training. 
 
Working Parties. 59 
 
 109. — Extending the Working Party. VVlieu tlie tirst re- 
 lief approaclies the designated point it is lialted, ttien brolten in- 
 to column of Hies and direction cnanged, if necessary, so tiiat tlie 
 iiead of tlie column approaclies in a direction parallel to and about 
 3 yds. in rear of tlie tape marking tiie front edge of proposed exca- 
 vation. (Fig. 3.) When the leading tile is opposite his place the 
 command is given: 
 
 {1) On riylit (or lojtj into line at tico paces inter vat. (2) March. 
 (3) Detachment. (4) Halt. 
 
 The command "Halt" is given when the leading file is 1 yd. iu 
 rear of the tape. While the line is forming, the correct positions 
 are at once taken, as follows: 
 
 Each man on arriving at the line extends his arms horizontally, 
 holding them thus until his own position and that of the man fol- 
 lowing him are established by touching hands. As soon as each 
 man has his position he drives his pick into the ground on the left 
 of his own task and lays his shovel on the ground, parallel to and 
 at a distance in the rear of the tape equal to the width of his task 
 from front to rear. 
 
 Rifles are then unslung, belts and canteens removed, and all 
 having been placed on the ground three paces directly to the rear 
 of task, butts of rifles toward the front, the men sit or lie down be- 
 hind their shovels until the order ^'Commence work," 
 
 110.— Extension of 2d and 3d Reliefs. Each man of the 1st 
 relief, after completing his task, scrapes his tools and lays them 
 together in rear of the trench. 
 
 The task being completed, each man secures his accoutrements 
 and rifle, and then, under direction of his officers, closes in to the 
 left (or right), forming column of fours, which is then marched 
 back to camp. 
 
 As an incentive to rapid work, each relief should be allowed to 
 return to camp on the completion of its task. 
 
 If the working party be large and the work of a complicated 
 nature, each relief should arrive in successive detachments and 
 their location on the work should have been previously designated, 
 so that there need be no delay or confusion, even at night. 
 
 Work should not be commenced until the distribution of the 
 entire relief is complete, since any change after work has begun 
 tends to confusion, loss of tools, and delay. 
 
60 Working Parties. 
 
 111.— -Tasks. An untrained workman can excavate in ordi- 
 nary soil one cubic yard of eartli per liour for four consecutive 
 liours. As some men work slower than otliers, however, it is 
 usual to estimate at 6 hours per man for the lifting of 4 cu. yds. 
 of earth from a trench 3.5 to 5 ft deep and throwing the same a 
 horizontal distance of 10 ft. 
 
 When it is necessary to throw the earth more than 12 ft hori- 
 zontally, extra shovelers should be provided for rehandling it, in 
 the proportion of 1 shoveler to every 2 diggers. 
 
 When exposed to the enemy's fire, a skirmish line is kept well 
 to the front and the earth first excavated is thrown close to the 
 edge of the ditch, forming a screen which is gradually thickened; 
 under other circumstances the earth first excavated is thrown 
 farthest. 
 
 Five feet, or two paces, is the usual distance apart for men to 
 work, but they may be posted as close together as 4 ft., while using 
 the heavy pick and shovel. As a precaution against injury to ad- 
 jacent workers, the men should swing the pick in a direction per- 
 pendicular to the tape. 
 
 112.— Working parties may be extended at less or greater in- 
 tervals by making the corresponding changes in the commands: 
 when this is done, it will usually be necessary to verify intervals. 
 
 When necessary to complete a task in the shortest possible time, 
 or when the men available greatly exceed the number of tools, 
 working parties should be formed in double rank, two men being 
 assigned to each set of tools, which should be carried by the front 
 rank man. When working in this manner with a double relief, 
 the men, under direction of non-commlssjoned oflScers, should 
 change off every 10 or 15 minutes. 
 
 Officers having general supervision of the work should not be 
 changed at the same time the reliefs are. 
 
 The sizes of tasks based on the 4 yd. rule may be arranged as 
 shown in diagram. (Fig. 4.) For arrangement of tasks in difficult 
 soil, see PI. 14. 
 
CHAPTER IX.— Revetting Materials and 
 Revetments. 
 
 113.- A Revetment is a facing used to liold up an embank- 
 ment at a steeper slope tlian it would assume naturally. 
 
 1 14.— Revetting Materials. Tlie revetments most commonly 
 used in field engineering are made either of brushwood in the 
 rough, fascines, gabions, hurdles, planks, timber, sods, sand-bags, 
 pisa, adobe, bamboo, or of a combination of two or more of these. 
 
 115.— Brushwood, which is used in making the first four, 
 should be of willow, birch, ash, hickory, or hazel, and is most pli- 
 ant when not in leaf: it may be of any size when used in the rough, 
 but should not exceed an inch in butt diameter for gabions and 
 hurdles and 2.5 in. for fascines and pickets. 
 
 The working party cuts and binds the brushwood in bundles 
 of about 40 lbs. each, putting the large and small in separate piles 
 with butts in the same direction. For convenience, the detail 
 should be divided into three parts— one for cutting, one for sort- 
 ing and binding, the other for carrying and, if necessary, loading. 
 Tools required and time necessary are as in ''Clearing the Ground'* 
 (Chap. v.). 
 
 116.— Withes (PL 17, Fig. 1), which are used for binding and 
 sewing, are made by twisting pliant rods. The butt is held under 
 the left foot and the twisting commenced at the small end, care 
 being taken to avoid breaking or kinking the rod. The pliancy of 
 the rod may be increased by heating it. In using the withes for 
 binding, an eye is made at the small end, then the withe is passed 
 round the bundle, the butt passed through the eye and twisted 
 until a kink is formed, when the butt is thrust (buried) in the 
 bundle. 
 
 117.— Fascines. A fascine is a bundle of rods tightly bound 
 together. It has a length of 18 ft., a diameter of 9 in., and weighs 
 about 140 lbs. 
 
 Pascine Rack. The fascine is made In a cradle rack of five 
 equidistant trestles (Figs. 2 and 4), the outer ones being 16 ft. 
 apart; the crotches are each 2.5 ft. above the ground and aligned. 
 The stakes for the trestles should be from 2.5 to 4 in. in diameter 
 
PLATE 17 
 
Revetting Materials and Revetments. 63 
 
 and from 5 to 6 ft. in length. Those for the outer trestles are first 
 driven and securely bound together with wire or rope, then a line 
 is stretched from crotch to crotch and the interior trestles made 
 in a similar manner; the stakes should be driven firmly into the 
 ground and each should have a length of 2 ft. above the crotch. 
 
 Fascine Choker. For the purpose of gauging the circum- 
 ference of the fascine and for cramping it in binding, the fascine 
 choker (Fig. 3) is used. It consists of two stout bars or hand- 
 spikes, 4 ft. long, to each of which is attached a collar 18 in. from 
 the end, the collars being connected by a stout chain, to which 
 are attached two gauge links 28 in. apart. The choker is used by 
 a man on each side of the rack taking a bar of it and resting the 
 short end on top of the fascine, chain being underneath (Fig. 4, 
 "a"); then each passes his bar over to the other (the short ends 
 passing around and under the fascine), and each bears down on 
 the end of his lever. (Fig. 4, "b.") 
 
 Making the Fascine. The trestles having been prepared, 
 the fascine is made by laying brushwood, trimmed if practicable, 
 in them, the pieces breaking joints and crooked ones being partly 
 sawed or cut through. The rods should extend from 18 in. to 2 ft. 
 beyond the extreme trestles and the bunch made of uniform size 
 throughout. (Fig. 4.) 
 
 The choker should be used occasionally for testing the size, and 
 when of such dimensions throughout that the gauge rings meet, 
 the fascine is bound. This should be done with wire or tarred 
 rope, which is passed twice round the fascine and securely fas- 
 tened, the bindings being 12 in number, the two outer ones 3 in. 
 outside the extreme trestles and the others at intervals of about a 
 foot and a half. This allows the fascine to be cut into lengths of 
 6 or of 9 ft. Five men require about an hour to make a fascine. 
 
 118.— Gabions. Gabions are open cylinders 2 ft. in exterior 
 diameter by 2 ft. 9 in. in height, varying in weight from 35 to 50 
 lbs. : they are made of brushwood, strap iron, iron bands or sheet iron 
 and from 9 to 14 pickets each. The interlaced brushwood in gabions 
 is called the watling or web. Gabion pickets should be 3.5 ft. in 
 length and from an inch to an inch and a half in diameter. The 
 rods for the web should be from one-half to three-fourths of an 
 inch in diameter, although smaller may be used. Wicker gabions 
 
64 Revetting Materials and Bevetments. 
 
 are most easily made with the aid of a gabion form, wliich is a 
 circular piece of board 21 iu. iu diameter, with equidistant notches 
 on its circumference, the number of notches depending on the size 
 of the brushwood and running from 9 to 14. (Fig. 5.) 
 
 The construction of the Wicker Gabion (Fig. 7) is as follows: 
 Watling. The gabion form is laid on level ground and a 
 picket driven vertically in each notch, the thick and thin ends of 
 the pickets alternating. The form is then slipped up the pickets 
 about a foot and held firmly in place by means of a rope, which is 
 tied loosely round the pickets just below the form and then tight- 
 ened by a rack stick (Fig. 6), the rope holding the pickets firmly 
 in the notches. The rods for the web having been stripped of 
 their leaves, the web is commenced by laying the butts of two rods 
 in adjacent spaces between pickets, resting on the form. The rear 
 rod, passing outside the second picket, is then bent inward, pass- 
 ing over the first rod, inside the third picket, and then out. (Fig. 
 5.) The other rod, which is now the rear one, is similarly treated 
 and the watling continued by using the rods alternately. This 
 method of watling is called pairing. On coming to the end of a 
 rod a fresh one is laid alongside and woven with it for a short dis- 
 tance. The web is continued to within 3 in. of the ends of the 
 pickets, care being taken to keep the pickets vertical and to make 
 the web close by frequent use of the mallet. 
 
 Sewing. To prevent the web from coming off the pickets it 
 is then sewed with wire, heavy twine, or withes, in four places, as 
 follows: Take an end of a withe in each hand, the middle of it 
 resting on top of the web, pass the ends of it through the web about 
 6 in. down the sides, one from without inward and the other from 
 within outward; pull taut by bearing downward. Pass the ends 
 through the web again G in. farther down and tighten as before. 
 Proceed in the same manner a third time and then bury the ends 
 of the withe in the web. The sewing should be at equal inter- 
 vals and the two ends of the withe, when pushed through the 
 web, should be separated by two or three of the watling rods; wire 
 is much easier worked and more durable than withes. The partly 
 completed gabion is now inverted, the form removed, and the wat- 
 ling continued as before, until the gabion has a height of 2 ft. 9 in., 
 when it is completed by again sewing as before explained. The 
 ends of the pickets that were driven Into the ground are now 
 
Revetting Materials and Revetments. 05 
 
 trimmed to within 3 in. of tlie web and sharpened, the opposite 
 ends sawed off to within an inch of the web, and a carrying picket 
 driven through the sides of the gabion perpendicular to the axis 
 and a few inches from it. 
 
 Three men should make a gabion in an hour. 
 
 119.— Wicker Gabion Without the Gabion Form. Where 
 the form is not at hand, the wicker gabion is made by first 
 describing on the ground a circle with a 10.5 in. radius and then 
 driving the pickets at equidistant intervals on this line. The 
 watling is commenced at the ground and run up to the full height, 
 care being taken by frequent gauging to keep the dimensions 
 accurate. It will be necesary for one man to devote his entire 
 attention to keeping the pickets in position, while a second makes 
 the web, and a third prepares the rods. Three men should 
 make a gabion, without the form, in an hour and a half to two 
 hours. Instead of sewing, the gabion may be finished by driving 
 four forked pickets (Fig. 8) in the web alongside of the gabion 
 pickets. 
 
 120.— The Hoop or Strap Iron Gabion. This is more dura- 
 ble and more quickly made than the wicker gabion, but is 
 heavy, weighing 55 lbs., and liable to splinter dangerously. The 
 form for this gabion is used solely for gauging and shaping the 
 bands. 
 
 To make the hoops, describe on a wooden platform a circle 
 with a 1 ft. radius and divide it into 6 equal parts. Make auger 
 holes at points of division and insert in them wooden pins about 
 5 in. long and triangular in cross section, the bases of the tri- 
 angles being on the interior of the circle. (Fig. 9.) Wrap the 
 strap iron once tightly round the pins, thus forming an hexagonal 
 hoop. Mark the point where the hoop is to be joined, then remove, 
 punch, and rivet it. As the iron is usually 1 in. wide, the com- 
 pleted gabion will require 33 of these hoops. 
 
 To make the gabion, place a hoop on the ground and an- 
 other on it in the positions shown. (Fig. 10.) Drive a picket 
 vertically in each of the triangular spaces, then place the remain- 
 ing hoops alternately over the first and second. Drive nails in 
 four of the pickets outside the extreme hoops to keep the gabion 
 intact. 
 
 121.— The Sheet Iron Gabion. This gabion is made of a piece 
 
^^ Revetting Materials and Revetments. 
 
 of sheet iron 2 It. U iu. x 6 it. 4 in., riveted or wired togetlier along 
 its shorter edges. 
 
 122.— Hurdles. The hurdle is a brushwood mat 2 ft. 9 in. 
 wide by 6 ft. long, the length corresponding very nearly to the 
 circumference of the gabion. An even number of pickets, usually 
 10, is used in making it, the extreme pickets being somewhat 
 heavier than the interior ones. (Fig. 11.) 
 
 Construction of Hurdles. Describe on the ground an arc 
 with an 8 ft. radius, measure off 6 ft. of this arc and drive 10 
 gabion pickets along it at intervals of 8 in. (Fig. 11.) Commence 
 the watling in the center space on the ground by randing— i. e., 
 working with a single rod alternately inside and outside of the 
 pickets; on reaching the end picket the rod should be twisted as 
 a withe, so as to avoid breaking it, and then returned toward the 
 center in the same manner as at first. When approaching the 
 end of a rod another should be laid alongside of and randed with 
 it for a distance of two or three pickets. Pairing, as in gabions, 
 should be resorted to in finishing the top and bottom of the web, 
 and the hurdle should then be sewed as described for the gabion. 
 When the rods used in watling are very small the process of slew- 
 ing should be resorted to: this is the same as randing with the 
 exception that 2 or 3 rods are laid alongside each other instead of 
 using them singly. Slewing makes weaker work than randing. 
 Three men should make a hurdle in two hours; two work at the 
 web and the third prepares the rods. The completed hurdle 
 weighs about 50 lbs. The hurdle is made on a curve and after- 
 ward flattened as much as possible, because it is found that by 
 so doing it is less liable to warp than if made flat. It should be 
 placed in a road or revetment with the concave side toward the 
 earth. 
 
 123.— The Continuous Hurdle is usually preferred for revet- 
 ting purposes to single ones joined. It differs from the latter 
 in that the pickets are driven at once, at intervals of 12 to 18 in. 
 according to their thickness, in the position the revetment is to 
 occupy, but at a slightly gentler slope, so as to allow for straight- 
 ening when the earth is tamped. It is constructed by randing or 
 slewing, two men being assigned a task of 10 or 12 ft. in length, 
 which they should finish to a height of 4 ft. and anchor, in from 
 one-half to three-quarters of an hour. 
 
PLATE 18. 
 
 Revetments. 
 
 Figure 3. 
 
 Figure 4. 
 
68 Revetting Materials and Revetments. 
 
 124.— Planks, when used for revetting, should be placed 
 edgewise and held in position by stout stakes, which should be 
 anchored. They make a neat, durable and quickly made revet- 
 ment. 
 
 125.— Round timber from 3 to 8 in. in diameter may be used 
 in the same manner as planks, but the revetment is more diflScult 
 of construction and is not so durable. 
 
 126.— Sod for revetting purposes is cut of a uniform size— 18 
 in. long, 9 in. wide, and 4 in. thick. They should be laid in alter- 
 nate rows of headers and stretchers, grass down, breaking joints, 
 and perpendicular to the slope. The top layer should be all head- 
 ers and have the grass up; alternate rows should be pinned secure- 
 ly, using split pickets, if possible, as with them there is less liabil- 
 ity of splitting the sod than when round ones are used. Two men 
 should lay from 70 to 100 sods per hour, depending upon whether 
 or not pickets are used. 
 
 127.— Sand-bags are made of coarse canvas or bagging 
 material, and, when empty, measure 2 ft. 8 in. by 1 ft. 4 in. When 
 filled they are supposed to contain 1 cubic ft. of earth; it is found 
 in practice, however, that a cubic yard will fill from 48 to 50, mak- 
 ing their average size 1 ft. 6 in. long, 10 in. wide, and 6 in. thick. 
 Each bag has eyelet holes near the mouth through which a stout 
 cord passes, to expedite tying, when filled. 
 
 For filling sand-bags the working party is divided into squads 
 of 6: 2 with shovels, 1 with a pick, 1 to hold the bag, and 2 to tie. 
 
 Each squad fills 150 bags per hour. This task may be consid- 
 erably increased, however, in easy soil or with trained men, and 
 the rapidity of the work more than doubled by having a double 
 relief and keeping the men constantly changing. 
 
 128.— Revetments. Brushwood Revetment is made by driv- 
 ing pickets at intervals of about 12 in. along the foot of the 
 proposed slope. The top of the pickets when driven should be 
 as high as the proposed revetment, and the pickets should be 
 anchored by wire to logs or stout stakes in the parapet. Loose 
 brushwood is laid closely behind the stakes and earth tamped 
 against it, the construction of the parapet going on at the same 
 time. 
 
 Brushwood revetment is rapidly made in daylight, but is neither 
 durable nor sightly. 
 
Revetting Materials and Revetments. 69 
 
 129.— The Fascine Revetment. (PI. 18, Fig. 1.) This is 
 made by laying the fascines in single rows of stretchers, breaking 
 joints, each fascine being pinned to the parapet by 5 or 6 pickets, 
 and every second or third row securely anchored. 
 
 Six-foot fascines should be used occasionally as headers. The 
 bottom fascine is sunk about one-third of its diameter by excavat- 
 ing a shallow trench. The construction of parapet and revetment 
 proceed simultaneously. Slope should not be greater than four 
 on one. The defects of this revetment are the weight of the fas- 
 cines, the large quantity of brushwood required, and the fact that 
 the fascines are held in place by anchors and pickets in the earth 
 which they support. 
 
 130.— The Gabion Revetment. (Fig. 2.) This is made by 
 first sinking a row of fascines about 3 in. at the foot of the slope, 
 so as to give an inclination of four on one to the gabions resting 
 partially on them. Earth is tamped behind and in the gabions, 
 and sod or sand-bags placed on top. Where greater height is 
 required two rows of gabions may be used with two fascines, well 
 picketed, between them. 
 
 Gabions make one of the strongest and most durable revet- 
 ments, their own weight when filled being usually sufficient to 
 retain the embankment. 
 
 131.— Hurdles. These make a poor revetment unless the 
 method is followed of constructing a "continuous hurdle'' at the 
 same time with the parapet. To do this, the pickets are driven 
 along the foot of the slope at an inclination of about three on one, 
 when the final slope is to be four on one. The watling is made 
 continuous by randing or slewing, each two men having four 
 paces of hurdle as a task, and taking care to work in their rods 
 with those of adjacent sections. (Fig. 3.) 
 
 132.— Plank or Timber Revetment. (Fig. 4.) This is made 
 by driving heavy stakes into the ground at the proper angle, plac- 
 ing the planks or timbers behind them, then filling in and tamp- 
 ing firmly. The stakes must be anchored. This revetment Is 
 neat and durable. 
 
 133.— Sod Revetment. (Fig. 5.) This is made by laying the 
 sod in alternate layers of headers and stretchers, grassy side down, 
 breaking joints and perpendicular to the face of the revetment. 
 
70 Revetting Materials and Revetments, 
 
 Each sod should be well settled before another is placed on it and 
 the top laj^er should be headers with grass up. It is well to 
 pin alternate rows by means of split pickets, three-fourths of an 
 inch in diameter and 9 in. long. This revetment is made of uni- 
 form thickness throughout by using double rows of stretchers. 
 If the grass is long it should be mowed. If the sod is very wet 
 when laid the revetment will crack in drjung. Two men well 
 supplied with sod should lay two paces of revetment, four and 
 one-third feet high, in an hour. 
 
 This revetment has the advantage of not splintering like 
 gabions, fascines and boards, but should not be used when other 
 material is obtainable, because ordinarily it will not stand long 
 at a steep slope (three on one being about the Itniit), cannot be 
 used when very dry or frozen, and requires great care to build 
 properly. 
 
 134.— Sand-bag Revetment. (Fig. 6.) This is made by lay- 
 ing alternate rows of headers and stretchers, breaking joints, and 
 perpendicular to slope, seams of stretchers and chokes of headers 
 .being put in the embankment. Men working in pairs lay the 
 bags, settling them firmly in place with a mallet or spade. This 
 revetment is not very durable, but the bags are easily transported, 
 may be used with any soil, and are invaluable in making hasty 
 repairs and loop-holes. 
 
 135.— A very durable revetment (Fig. 7), much used in the 
 defenses of Washington, 1861-5, was made of posts (oak, chestnut, 
 or cedar) cut in lengths of 5.5 ft. and placed side by side, at a slope 
 of six on one. The footing was a 2 in. plank laid in a trench exca- 
 vated for the purpose. The tops of the posts were sawed off 16 
 in. below the interior crest and capped by a half-round timber, 
 all being securely anchored in the parapet. Crowning was com- 
 pleted to the requisite height with sod. 
 
 All revetments that are liable to splinter should be crowned to 
 a height of at least 8 in. with sods, sand-bags or earth. 
 
 136.— Pisa Revetment is made of earth and clay, to which 
 has been added enough water to reduce the mixture to a working 
 consistency. A trench 6 in. deep and 18 in. wide is first dug, its 
 nearest edge marking the foot of the revetment. Pickets, of 
 suflficient length to reach the top of the proposed revetment, are 
 
Revetting Materials and Revetments, 
 
 71 
 
 firmly driven, at the proper angle, about 2 in. from the near edge 
 of the trench, at intervals of about a yard, and then anchored. 
 Boards placed on edge are now laid against the pickets on 
 the trench side. The trench is then filled with the mixture, 
 tamped, and more added, other boards being placed on top of the 
 first, as required, and the mixture forced closely against them. 
 The construction of the parapet goes on at the same time with 
 the revetment. When completed, the pickets and boards are 
 removed. This revetment is neat and durable, but cannot be 
 rapidly made. 
 
 137. — Adobe Revetment. The adobe is a sun-dried brick, 
 about IS in. X 9 in. x 4.5 in., and when carefully laid with the same 
 bond as given for sod or sand-bag, forms a neat and very durable 
 revetment, exceeding in the latter respect any of the other varieties 
 mentioned. 
 
 137a. — Bamboo Revetment. Where material is available green 
 bamboo split into strips an inch and a half wide makes an excel- 
 lent revetment. It is constructed by randing in the same manner 
 as the "continuous hurdle," care being taken to have the adjacent 
 strips break joints. 
 
 The following table shows amount of various materials re- 
 quired for 300 running feet of 4 ft. 4 in. high revetment: 
 
 Kind of Revetment 
 
 Fascines 
 
 Gabions 
 
 Sod 
 
 Sand-bags 
 
 Pickets 
 
 Fascines 
 
 Gabion 
 
 Sod 
 
 Sand-bag 
 
 30 
 6 
 
 50 
 
 267 
 
 400 
 
 1867 
 
 867 
 
 150 
 1000 
 
PLATE 19. 
 
 Field Casemates. 
 
CHAPTER X.— Field Casemates and Magazines. 
 
 138.— In all field works, protection against both weatlier and 
 liostile fire must be provided for the garrison. 
 
 These shelters are constructed by building a chamber of wood 
 sufficiently strong to bear the necessary earth covering, and by 
 protecting this in front by an embankment thick enough to with- 
 stand direct artillery fire. 
 
 Two general forms are used: 
 
 (1) Those which, after providing complete protection from 
 direct fire, have their roofs sloped to the rear at an angle greater 
 than the angle of descent of the enemy's projectiles, generally 
 about one on four; and 
 
 (2) Those which have horizontal roofs, the earth covering being 
 so high and massive as to protect against artillery fire by its thick- 
 ness alone. 
 
 The first class is preferable, the work of construction being very 
 much less than in the second class, as the embankment is not so 
 high and the earth on the roof does not require to be thicker than 
 16 in., as it has to resist only the dropping fire of small-arms and 
 the fragments from bursting shrapnel. Moreover, it gives much 
 easier drainage to the ditch in rear. 
 
 139.— The construction of the timber part of the casemate is 
 practically the same in both cases. The vertical timbers being 
 rough tree trunks, about 1 ft. in diameter, placed at intervals of 
 3 or 4 ft., and strutted when necessary. The roof timbers in sim- 
 ple casemates being not less than 8 in. in diameter and the inter- 
 stices filled with small poles or brush. In case the protection has 
 to be proof against vertical fire of mortars, the earth mask on the 
 roof must be 6 ft. in thickness and a correspondingly stronger 
 timber construction must be provided: these are shown in PI. 19, 
 Figs. 1 to 7. 
 
 In calculating floor space, each man should have from 9 to 18 
 sq. ft.; the former when crowded, the latter when not. 
 
 139a. — The following Is a bomb-proof construction which would 
 be safe under the fire of projectiles having a bursting charge of 
 9.9 pounds of explosive gelatine and a penetration of 5 feet before 
 bursting: 
 
74 Field Casemates and Magazines. 
 
 1. Frames of 8-by-8-inch pine, 5.5 feet high and 6.5 feet wide 
 in the clear, with upper corners braced, spaced 10 inches apart. 
 
 2. Sides of poles or botards outside the frames. 
 
 3. On top: (a J a longitudinal layer of double thickness of rail- 
 road iron or a double thickness of 4-by-6-inch timbers; (h) cross 
 layer of fascines; (cj longitudinal layer of 8-by-8-inch oak; (dj 9 
 feet of earth; (ej 20 feet of earth on exposed side. 
 
 140.— Magazines are of two kinds: First, those intended to 
 hold the temporary supply for guns or troops when in action; and. 
 Second, those intended for the purpose of storing ammunition in 
 large quantities. 
 
 The first variety consists of recesses in the interior slope of the 
 epaulement— barrels or gabions are excellent and when not obtain- 
 able may be replaced by empty ammunition boxes placed in holes 
 excavated for their reception. 
 
 Magazines of the second class are used only in works of great 
 defensive value and then only when ample time is available. 
 They are made in the same general manner as the casemates 
 heretofore described, except that great care must be taken to 
 render the structure as dry as possible and to secure good venti- 
 lation. 
 
 141.— The general plan of execution of these works is as 
 follows:— 
 
 (1) Magazine shown in PI. 20, Fig. 1. 
 
 The mask in front should be 20 ft. thick. The roof consists of 
 a row of timbers or logs 8 in. in diameter, overlaid with steel rails, 
 and then covered with a paulin, well tarred if possible. On this 
 is placed 16 to 18 in. of earth. The ends are made of logs, 12 in. 
 in diameter, planted in a double row, Breaking joints. The en- 
 trance is at either one or both ends according to circumstances. 
 The doors, 2 ft. 6 in. in width, are made of planks crossed, and are 
 hung next to the front wall of trench, opening into a passage 
 formed by a row of upright logs parallel to those on the end of 
 the magazine. At the end of the passage farthest from the first 
 door a second one is hung, opening into the magazine. The ver- 
 tical timbers in front and rear of trench support a revetment of 
 planks or hurdles. The floor should be raised at least 6 in. from 
 the bottom of the trench to guard against dampness. Care should 
 be taken to facilitate the draining of all water that falls on the 
 
PLATE 20. 
 
 ]\I^agazine behind naranet. 
 
 Tu/o S'tortecl Block HousQ, 
 
 Ca/ionier in front ofwalL 
 
7(5 Field Casemates and Magazines. 
 
 roof, and that the trench itself is drained away from the ends of 
 the magazine. 
 
 142.— Another form is as follows:— Determine the space need- 
 ed for storage of ammunition. Then build the timber work as 
 in the preceding, first excavating to a depth of 4 or 5 ft. over 
 the entire site. There will be no ends to be closed by timbers. 
 The roof is made of timbers 12 in. in diameter, well supported by 
 uprights of sam<) size and long enough to give sufficient head 
 room. The sides and ends should be revetted with planli, if pos- 
 sible, and the floor raised 6 in. above the earth. The center of 
 the roof is raised a foot above the sides and surmounted by a 
 layer of 6 in. of earth, well tamped; over this is laid a paulin and 
 the earth mask is then placed over all to the thickness of 8 ft.; 
 the covering mass in front should not be less than 20 ft. in thick- 
 ness. Entrance is gained by means of a doorway opening into 
 a passage which communicates through a return with the inte- 
 rior of the magazine. Doors made of crossed planks are hung 
 as indicated in the plan. If time is available, and the planks 
 at hand, an interior chamber should be formed, leaving an air 
 space around the magazine proper; and inlets may be constructed, 
 care being taken that they are not situated in exposed positions 
 and that their course is such as to prevent the entrance of sparks. 
 The roof should be rounded off so as to afford the easiest drain- 
 age. If the earth excavated is not sufficient to cover the roof, 
 the necessary amount may be taken from a trench dug around the 
 outside. 
 
 This form of magazine may with advantage be placed in a 
 traverse. 
 
 143.— In case timber is not at hand, gabions and fascines may 
 be used to build the magazine in the manner shown In PI. 20. 
 
 144.— Block Houses are defensible shelters for infantry, al- 
 though, under certain circumstances, they contain artillery. 
 
 They are generally used for the purpose of flanking defenses 
 whose fire cannot reach into the ditch. 
 
 They are constructed either of upright timbers set in the ground 
 close together, or horizontal timbers laid one upon the other; the 
 timbers being in two rows, breaking joints in each case, or, if both 
 methods are used, the outside row should be horizontal and the 
 
Field Casemates and Magazines. 11 
 
 iuuer vertical. They should have at least 6 ft. of head room and 
 should not be less than 9 ft. wide, as this allows one row of beds 
 only. The roof should be of solid construction and covered with 
 earth to the thickness of 2 ft. and should project 2 ft. over the 
 wall to protect from dropping fire. 
 
 The walls should be masked with earth as high as possible and 
 a ditch dug around the entire building. Loop-holes are made at 
 the height of 4 ft. 4 in. and are cut according to circumstances, 
 as described in Chap. XIII. If necessary, block houses may be 
 sunk in the ground, but a limit of 4 ft. in depth should be observed. 
 The shape will conform to the necessities of the case. 
 
 145a. — The Spanish Block House is a modified form of the 
 one d^escribed; it is loopholed for two or three tiers of fire, and 
 as asecondary defense of especial value if attacked by artillery, 
 it has shelter trenches far enough in front to escape splinters from 
 the house. (See Par. 191.) 
 
 145.— In isolated positions they are advantageously made 
 cruciform, thus presenting an opportunity for flanking each face 
 of the house. When in wooded and mountainous countries, 
 where artillery is not to be feared, these houses may be made with 
 two stories, built so that the angles of the upper story project over 
 the sides of the other, forming a machicoulis gallery, thus prevent- 
 ing the occupation by the enemy of the dead space in front of 
 the straight walls. 
 
 146. — Caponiers are sunken block houses placed in the ditch 
 of fortified places to prevent their occupation by the enemy: they 
 are loop-holed about 18 in. from the ground, so as to have the most 
 effective plane of fire. (PI. 20.) 
 
 147.— Tambours are essentially block houses, having for their 
 object the protection of angles, and the flanking of sides of build- 
 ings, and are especially useful in defending doors of buildings. 
 
CHAPTER XI.— Field Works in Combination. 
 
 148.— Where several field works are used in conjunction, either 
 as an intrenched position or in the investment of a fortress, city, 
 or other important point, they constitute what is linown as a Line 
 of Works. 
 
 A Line of Works may be continuous, that is, forming, together 
 with natural obstacles, an unbroken line, or, with intervals, by 
 which it is understood that the works are distinct, either support- 
 ing each other or not, and the spaces between them not impassable 
 by reason of natural obstacles. 
 
 149.— Lines with intervals have the following advantages over 
 continuous UneSt viz. :— 
 
 (a) They involve less labor. 
 
 (b) The garrison of the defenders may be smaller. 
 
 (c) They allow greater freedom of movement for counter- 
 attacks. 
 
 The general principle to be followed in their construction con- 
 sists in forming a line of fortified points or pivots. These points 
 or pivots detain the enemy's advance, since he would hardly pass 
 them and expose his flanks and rear, while a continued unsuccess- 
 ful attack on the strongly fortified pivots would open the way for a 
 counter-attack by the defenders. 
 
 When, however, the defense is intended to be solely passive, 
 which would be the case while awaiting reinforcements, or when 
 the enemy greatly outnumbers the defenders, the intervals would 
 be obstructed by felling trees or using any available obstacles, 
 since counter-attack is not contemplated. 
 
 In the use of lines with intervals, if the general defensive line 
 is straight the works could be blunted lunettes with flanks traced 
 so as to protect the front of adjacent works. If on a convex curve, 
 the capitals should radiate from a common center, while on a curve 
 concave toward the enemy, the capitals should converge and the 
 front of each work might be a straight line. 
 
 When impracticable to construct the main works of a line with 
 intervals, within supporting distance (600 yds. for infantry and 
 2000 yds. for artillery)* of each other, intermediate works retired 
 
 ♦Continuous dangerous space for Springfield Magazine rifle is about 600 yds. 
 
Field Works m Comhination. 79 
 
 from the main line, not more than half the interval, may be 
 used. 
 
 In PI. 21, Fig. 6, is shown such an arrangement, the pivots being 
 single works while the artillery is retired from the main line and 
 supported by infantry in shelter trenches. 
 
 Where the interval is as great as 1500 yds. it is advisable to 
 strengthen the pivots considerably, forming groups, the individ- 
 ual works of each group being so traced as to afford mutual de- 
 fense. (PI. 15, Fig. 2.) Each group in this latter arrangement 
 forms a strongly fortified point of support and would usually have 
 sufiicient strength in itself to resist assault. 
 
 150.— Sometimes, when the defense of a line is of vital import- 
 ance to the defenders, a double line of works is employed, the front 
 line being shelter trenches or open field works of slight profile, 
 the second line, not over 500 yds. in rear of the first, being field 
 works of strong profile. 
 
 151.— Artillery should, as a rule, be placed outside of and some- 
 what retired from the works and protected by their own gun-pits 
 or epaulements, for the reasons— 
 
 (1) That the works gain much in simplicity and rapidity of 
 construction. 
 
 (2) That this disposition draws the enemy's artillery fire from 
 the works and renders it more scattering. 
 
 (3) Greater mobility is given to the defender's artillery in case 
 of advance or retreat. 
 
 (4) A better tactical position for this arm can often be secured 
 than the one selected for infantry. 
 
 152.— As examples of continuous lines, PI. 21, Fig. 1, is known 
 as the redan trace with curtains. Fig. 2 is a modification of Fig. 
 1, the redans being blunted. Fig. 3 is the tenaille trace. Fig. 4 
 is a tenaille and redan trace. The cr^maillere trace (Fig. 5) has 
 long faces and short flanks. 
 
 With respect to the continuous lines above mentioned, the 
 preference on a level site would usually be given to the trace shown 
 in Pigs. 1 and 2, the artillery being placed in the most favorable 
 position along the curtains, with machine guns in the most im- 
 portant redans. 
 
 The tenaille and the tenaille and redan trace (Figs. 3 and 4) 
 -6- 
 
PLATE 21. 
 
 riG.l. 
 
 FIG.2. 
 
 FIG.5. 
 
 (^^^^ ^% FIG,6. ^t ^ 
 
Field Works in Gomhmation, 81 
 
 are objectionable, in that they involve more labor, cannot bring as 
 direct a fire to the front, and the faces are liable to enfilade when 
 the salient angles approach 90°, while on the other hand, if a 
 salient, as "S," Fig. 4, approaches 120°, mutual defense of the 
 faces, *'f" and "g," would be lacking, thus making the redan, "R," 
 necessary. This trace may, however, be rendered unavoidable by 
 the conformation of the ground. 
 
 The cr6maillere trace finds special application in a position such 
 as is indicated in Fig. 5, viz., joining two points, one at the top and 
 the other at the bottom of a slope, the short flanks affording but 
 limited opportunity for enfilade fire. 
 
 153.— The strength of a defensive position lies in a great 
 measure in the proper utilization of the accidents of the ground; 
 thus, the traces that have been mentioned may have to undergo 
 considerable modification to be appropriate to the varieties of 
 terrain constantly met. It is evident that, in a broken or hilly 
 country, one by preference would occupy the heights. These, from 
 a tactical point of view, possess the advantage of overlooking 
 the low ground in front, besides the great advantage of conceal- 
 ing from the enemy the movements of our own troops in rear; but, 
 since all else must be subordinated to fire effect, it is evident that 
 such a line on the heights should be selected that the defenders 
 may completely cover the ground over which the enemy must 
 approach. This naturally leads to the inquiry as to how that line 
 may be determined. 
 
 Heights, great or small, usually present the profile shown 
 in Fig. 7, that is to say, they have a steepest slope, "b c," which 
 is joined to the crest and to the valley below by the two gentler 
 slopes, "a b" and *'c d." In order, then, to beat the zone "b c" it 
 is necessary to occupy the crest "c" or some point below it on this 
 slope. To distinguish this crest from others, it will be called the 
 military crest. 
 
 With the Inclination of this steepest slope greater than one on 
 four, it is unusual to construct anything but shelter trenches 
 along the military crest, the artillery being retired sufficiently and 
 placed in such positions as to command a good view of the rest of 
 the field. With gentler slopes, however, the artillery may be 
 placed at intervals along the military crest, the intermediate spaces 
 being held by infantry in shelter trenches. 
 
82 Field Works in Combination. 
 
 A better disposition than this, where the ground permits of it, 
 is to place the infantry trenches part way down the slope in front 
 of the militai-y crest, the artillery occupying a position in rear of 
 and close to the crest, so that little more than the muzzles of the 
 pieces are visible. In this case, care must be taken that the infant- 
 ry* trenches do not mask the fire of the artillery. 
 
 In choosing a defensive position the ground should be viewed 
 from the highest point in the vicinity, and by frequent practice the 
 eye so trained that the military crest is at once apparent and the 
 slopes instinctively classified with respect to their use by the 
 different arms. 
 
 Finally, the distance to a number of visible permanent points 
 in front of the works should be determined and recorded, so that 
 there may be no necessity for range finding during the enemy's 
 advance. 
 
PLATB 22. 
 
 WigA 
 
 v^# Fi^.2. 
 
 Fie 3 
 
 WiSi4, 
 
CHAPTER XII.— Siege Works. 
 
 154.— When it becomes necessary to besiege a place, it may be 
 approached by common trench worli or by some form of sapping. 
 As the common trench and the flying sap are the work of Infantry, 
 they alone will be referred to. 
 
 155.— The method of providing the working party with tools, 
 laying out the work, and extending the working party is described 
 in Chap. VIII. It is to be noted, however, in work of this char- 
 acter, thai ichen extending along a zig-zag, upon reaching the angle 
 the order of forming up must he reversed. Thus, if the column from 
 b to c (PI. 22, Fig. 1) were forming on the left, upon reaching e f, 
 it would form on the right. 
 
 156.— Common Trench Work. This may be used as a par- 
 allel, an oblique approach, or communication. The work done 
 by reliefs in constructing a parallel is shown in Fig. 2. In this 
 case, as musketry fire must be provided for, the second relief cuts 
 out the top step. Should it be necessary to revet the bottom step, 
 fascines for this purpose may be carried by the second and third 
 reliefs. This may be and usually is omitted until the parallel is 
 completed. Fig. 3 shows the common trench used as an oblique 
 approach or communication. Should the trench be found wide 
 enough the task of the third relief may be omitted. 
 
 157.— The Flying Sap (Fig. 4) is similar to common trench 
 work, except that in the former case the embankment is revetted 
 with gabions. 
 
 In taking tools, each man of the first relief is, in addition to his 
 pick and shovel, provided with two gabions. In laying out the 
 tools, a shovel should be fastened in one gabion by being placed 
 between tAvo of the gabion pickets, handle of the shovel inside. 
 A pick should be secured in the other gabion by having its point 
 pushed under the pairing rods, handle Inside. The gabion with 
 shovel is taken in the right hand, the one with pick in the left: 
 both gabions being carried by carrying pickets. 
 
 158.— The extension in the flying sap is made from single 
 r^nk on the right or left, and differs from the extension In com- 
 
Siege Works. 85 
 
 mon trench work in that the interval, in the former case, is the 
 width of two gabions. Each man, on coming into line, place© 
 his gabions so that they touch each other along the inner edge of 
 the tape, takes out his tools and lays them down, as explained for 
 working parties in Chap. VIII., and waits for the command, *'Com- 
 mence work." In commencing work, the gabions should first be 
 filled; hence the position of each pair of gabions should be recti- 
 fied before this command is given. 
 
 159. — Each branch of a zig-zag should receive such direction 
 as not to expose it to enfilade fire from any point of the defenses. 
 Its prolongation should, therefore, fall outside of the most ad- 
 vanced salient of the collateral works. Ordinarily it would not 
 be longer than 100 yds. A parallel should be stepped in order to 
 facilitate an advance from it. 
 
 160.— A portion of the parallels and approaches used in the 
 capture of Fort Wagner, Morris Island, S. C, September 7th, 1863, 
 is shown in PI. 23. 
 
PLATE 23. 
 
TLATE 24. 
 
 Figure 1 
 
CHAPTEB XIII.— Defense of Localities. 
 
 161.— Walls. Should the enemy close on them, walls must be 
 so prepared that they will neither screen nor cover him, nor per- 
 mit his firing from them. To prevent this, obstacles may be 
 placed in front, or a ditch may be dug outside which will place him 
 so far below the top of the wall or the bottom of the loop-holes 
 that he cannot fire over the one or through the other. A total 
 height of G ft. will prevent this, or, in case of loop-holes close to 
 the ground, the maximum height should not be greater than 1 ft. 
 from the outside, or an embankment made in rear 18 in. high. 
 
 Notwithstanding these precautions, walls may still give cover; 
 hence they should be flanked when possible. 
 
 162.~In preparing walls for defense, the following cases 
 arise:— 
 
 (1) A wall less than 4 ft. high. Sink a small trench on the In- 
 side to gain additional cover. Fire over the top. (PI. 24, Fig. 1.) 
 Head cover should be provided with logs, sand-bags, or sods, sand- 
 bags being the best, sods next. 
 
 Additional protection against artillery may be obtained by heap- 
 ing earth from the ditch In front against the wall, the thickness 
 depending on the kind of artillery the wall Is to resist. 
 
 If this should be done, the ditch should not be too close to the 
 wall. A trench should be dug In rear to give cover to the supports, 
 or for the firing line when not firing from the wall. 
 
 (2) A wall between 4 and 5 ft. can be used as It stands, subject 
 to the same modifications as In the preceding case. (Fig. 2.) 
 
 (3) Between 5 and 6 ft. a wall can be notched. The tops of 
 the notches may be filled with sand-bags, sods, etc. (Fig. 3.) 
 
 (4) Should the wall be higher than 6 ft., a platform or staging 
 must be raised Inside to enable the men to fire over the wall or 
 through the notches, or else the wall must be loop-holed. 
 
 163. — ^Loop-Holing. Loop-holes for fire should not be closer 
 than 2 ft. 6 in.; ordinarily they should be 3 ft. To find the height, 
 Tiold fhe riffe in flie fiosHion intended to he used. 
 
 164.— To make a loop-hole In a wall (Fig. 4), 14 In. or less In 
 thickness, begin on the inside, to prevent the splay being toward 
 
Defense of Localities. 89 
 
 the outside, by detaching a stretcher: the adjacent header on the 
 outside can then be knocked out and the loop-hole roughly shaped. 
 Outside dimensions, 4 in. wide by 3 in. high. Interior dimensions 
 will depend on the nature of the ground over which fire is to be 
 delivered. For horizontal fire increase the breadth, for elevated 
 or depressed fire increase the height. 
 
 In walls of ordinary thickness, a loop-hole can be made in 
 about 15 minutes, a notch in about 5 minutes. 
 
 165.— For a thick wall (Fig. 4), the small part should be at the 
 center, the loop-hole splayed to the front and rear, for it will do 
 this anyway. The side toward the enemy may be stepped, in 
 order that bullets striking it may flatten. Loop-holes of observa- 
 tion should splay towards the outside. 
 
 All loop-holes, when not in use, should be blinded. 
 
 166.— The height or position of the loop-hole is influenced as 
 follows:— 
 
 (1) 1 ft. above the ground. Men lying down in a shallow exca- 
 vation. Earth heaped up to 18 in. in rear prevents the enemy 
 from using the loop-holes should he close on the wall. The loop- 
 holes are a diflScult mark for the enemy and sentries at night can 
 watch the sky line. Cannot be used where ground in front is 
 broken. 
 
 (2) Loop-holes 2 ft. 3 in. Sitting. Position easy, but must have 
 a deep ditch in front. 
 
 (3) Loop-holes 3 ft. Kneeling. Position strained and must 
 have a deep ditch in front. 
 
 (4) Loop-holes 4 ft. 4 in. Standing. Good command, but easier 
 mark for enemy: ditch necessary, but not so deep as In cases 2 
 or 3. 
 
 (5) Loop-holes 6 ft. or more. Men standing on banquette. Best 
 position for view or fire; no ditch in front; banquette strengthens 
 wall, but takes longer to prepare wall in this manner; more sus- 
 ceptible to artillery fire. 
 
 167.— In order to allow a double tier of fire, walls should be at 
 least 9 ft. high. (Figs. 5 and 6.) 
 
 168.— Fences. Fences should be removed or left standing 
 according to their position or direction. Wire fence forms a good 
 obstacle; a rail or plank fence forms a screen and may be banked 
 
PLATE 25. 
 
 Figure 1, 
 
 Fig^ure 2 
 
 y^ 
 
 Fioure 3 
 
 Figure 6 
 
 } ^Figure 7- 
 
 Figure 9. 
 
 Figure 10. 
 
Defense of Localities. 91 
 
 witli earth to give cover. If fence is of stone it may be treated as 
 explained for walls. 
 
 169.— Hedges. Almost the same principles as explained for 
 walls apply to hedges. A hedge primarily acts as a screen, but to 
 resist projectiles must be banked up with earth. 
 
 Hedges possess the following advantages: (1) With little labor 
 afford good cover. (2) Serve as a screen and also as a revetment. 
 (3) Act as an obstacle to the enemy. 
 
 To derive these advantages hedges can be treated as follows:— 
 
 (1) A hedge with a ditch on the defenders' side. Can be used 
 as it stands, the ditch being converted into a trench, widened and 
 improved if necessary. (Fig. 7.) 
 
 (2) A hedge with a ditch on the enemy's side. Deepen the 
 ditch if necessary, and throw the earth to the defenders' side to 
 give cover. If this is not possible, scatter the earth and dig a 
 trench in rear. (Figs. 8 and 9.) 
 
 (3) A hedge with ditches on both sides. Deepen the ditch on 
 the enemy's side, using the earth to obtain cover. Trench on de- 
 fenders' side may be deepened. (Fig. 9.) 
 
 (4) Hedge on sloping ground. Gain cover by a small trench in 
 rear; scarp away the ground in front, forming a glacis. (Fig. 10.) 
 
 (5) High and strong hedges. When time is available, may be 
 treated as in Fig. 11. This is advantageous where additional com- 
 mand is required. 
 
 (6) A sunken road with hedges on both sides. Dig a shelter 
 trench In rear of the hedge on defenders' side and utilize the earth 
 to form a breastwork. Cut down the hedge .on the enemy's side, 
 entangling it to form an obstacle. 
 
 (7) Hedge without ditches. Excavate a shelter trench on de- 
 fenders' side and bank up the earth against the hedge as a breast- 
 work. 
 
 Weak places in hedges should be closed up with boughs, stakes, 
 wire, etc., as a strong hedge, in addition to being a screen, forms a 
 very efficient obstacle. 
 
 170.— Embankments may be defended:— 
 
 (1) Narrow Embankments. By occupying the inner edge bet- 
 ter cover is obtained, but, unless the bank is both low and narrow, 
 there is a dead space in front at the foot of the outer slope. (PI. 
 25, Fig. 1.) 
 
92 Defense of Localities. 
 
 (2) Broad Embankments. By occupying the front edge, a bet- 
 ter field of fire is obtained, but less cover can be provided for 
 the firing line, and the supports are exposed when coming into 
 action. (Fig. 2.) 
 
 171.— Cuttings are usually defended on the defenders' side, 
 since in this case retreat is easy and the cutting itself forms an 
 obstacle to the enemy's advance. But for active defense the front 
 edge may be held, and then a forward movement is possible. In 
 this case a means of retreat must be provided. 
 
 172.— Fig. 3 shows a case where the fall of the ground admits 
 of both sides of the cutting being occupied, giving a double tier of 
 fire. The command of the higher edge over the lower should be 
 about 6 ft. 
 
 173.— In case of a road cut, as in Fig. 4, the upper fence may 
 be used to sustain a breastwork, while the hedge below may be 
 converted into an obstacle. 
 
 174.— Woods.— (PL 26, Fig. 6.) Preparation of edge of wood 
 occupied. The edge of a wood should be put in a state of de- 
 fense and an abatis is the readiest means of doing it. The sali- 
 ents should first be prepared, the reentrants next, and then roads 
 entering the wood from the enemy's side. Instead of an abatis, 
 the outer trees may be left standing and an entanglement made 
 by packing in among them smaller trees cut about 10 to 20 paces 
 to the rear. This clearing will serve as a communication all round 
 the edge of the wood. 
 
 If a reentrant bend is deep the abatis or entanglement may be 
 carried straight across it and flanked from the adjacent salients. 
 In case of a road, a lunette may be used instead of the abatis or 
 entanglement. In case there is not time to prepare the entire 
 edge of the wood, the salients may alone be prepared, the flanks 
 of the defense being turned back for a short distance into the 
 wood. 
 
 175.— Preparation of woods lying beyond. Woods beyond, 
 within rifle range of the line of defense, but too far to the front to 
 be occupied, and too extended to be felled, should have an abatis 
 or entanglement on the rear side to act as an obstacle. 
 
 176.— Cover. Trench digging is difficult on account of the 
 roots, but when possible it should be done. Cover is generally 
 obtained from the natural features. Trees, unless very large and 
 
PLATE 26. 
 
 Fig. 6. 
 
94 Defense of Localities, 
 
 standiug thickly, do uot give complete protection against artillery 
 lire. Troops as supports and reserves, if not so far to the rear as 
 to preclude their seeing through the wood to the front, may be 
 covered by log walls and trenches. 
 
 177. — communications, (a) There must be good radial com- 
 munication as well as free movement along the boundary in rear 
 of the firing line. 
 
 (h) Roads and paths for bringing up the supports must be clear- 
 ly marked by blazing as well as by posting sentries at all cross 
 roads. 
 
 (c) In dense woods, preparations should be made for blocking 
 up roads by cutting trees on either side of them nearly through, 
 to be pulled down across them in case of retreat. 
 
 178.— Second and third lines may be placed along any open 
 space, brook, or broad road, parallel to the front. In case of brook, 
 the brook should be in front of defenders* position. 
 
 179.— Artillery should generally be placed outside of the 
 wood on the flanks. If placed in the wood, batteries should be 
 placed far apart, near good roads, masked as much as possible, 
 and each gun having more than one position. Reentrants are 
 desirable. 
 
 The number of defenders is estimated at 2 to 3 men per yard of 
 front. 
 
 180.— Stockades. Stockades are timber defenses, made by 
 placing one or more rows of timbers or rails upright or horizon- 
 tally, and so close to one another as to keep out rifle bullets, loop- 
 holes being made, through which flre is delivered. They have the 
 advantages of combining a parapet and an obstacle in one, giving 
 good cover and ample interior space, and of being easily guarded 
 against surprise. On the other hand, they require considerable 
 time for construction, a certain amount of skilled labor, and are 
 easily destroyed by artillery fire. 
 
 181.— Stockades would be employed:— 
 
 (1) Where timber is plentiful. 
 
 (2) When artillery fire is not to be resisted. 
 
 (3) When acting purely on the defensive. They are useful for 
 the rear faces or gorges of half-closed works, and may be a good 
 deal used in the defense of houses, streets, villages, and even woods. 
 
Defense of Localities. 95 
 
 182.— stockades of vertical timbers. Vertical timbers should 
 be close together, planted iu the ground to a depth of 3 or 4 ft, 
 according to their size and weight, pointed or spiked at the top, 
 and loop-holed at intervals. A ribband must be spilled along the 
 inside, near the top, to keep the timbers close together. 
 
 183.— PI. 25, Figs. 5, G, and 7, show stockades with squared tim- 
 bers; Fig. 8 with round timbers squared where they touch and the 
 joint between every two trees made good on the inside by a 
 smaller tree. 
 
 184.— The loop-holes should be made in the crack between the 
 timbers, in order to avoid weakening them, half being cut out of 
 each. (Fig. 9.) In round timber, two saw cuts will make a loop- 
 hole. (JFig. 10.) 
 
 185.— The loop-holes should be cut before the timbers are placed 
 in position and the same precautions in regard to them as given 
 in walls should be observed. A loop-hole can be cut in from 10 to 
 15 minutes. 
 
 186.— In the foregoing cases, where the stockade is built of tim- 
 bers placed vertically, squared timbers are preferred, as they are 
 more easily fastened together and the joints made bullet-proof. 
 In round timbers the logs should be as straight as possible. If 
 very crooked, two complete rows will be required. 
 
 One N. C. O. and 10 men will erect 15 running feet of stockade 
 of squared timber, with one tier of loop-holes, in 8 hours. 
 
 187.— Stockades of horizontal timbers, iron rails, fascines, or 
 logs. (PL 26.) 
 
 Fig. 1 shows stockade of rails and ties. Can only be used for a 
 very short distance, as it will involve an immense amount of plant. 
 Can be used to cover guns, close a road, and is more properly a 
 barricade. 
 
 Fig. 2 shows a stockade or log breastwork, banked in rear with 
 earth held in place by planks or hurdles and stakes. 
 
 Fig. 3 shows a stockade or breastwork of logs and fascines. 
 
 188.— Stockade work, both vertical and horizontal, can be used 
 for the construction of tambours (Figs. 4 and 5) and caponiers for 
 flanking walls or stockades and covering entrances. Tambours 
 may be triangular or rectangular in shape, arranged for one or two 
 tiers of fire, and covered with a splinter-proof roof. 
 -7- 
 
96 Defense of Localities. 
 
 189.— Buildings. Buildings may be used for defense, either 
 singly or in combination;-- 
 
 (aj As tactical points in the battle-field, held either as advanced 
 posts, or as supporting points in the line or on the flanks, or as 
 rallying points to cover retreat. 
 
 (bj As keeps to a more extensive position, such as a wood, vil- 
 lage, etc. 
 
 (cj As an isolated post on the lines of communication. 
 
 190.— In order to admit of use as a defensible post, a building 
 should possess the following requisites:— 
 
 (1) Solidly built of soft stone, brick, or adobe. 
 
 (2) Large enough to hold at least half a company. 
 
 (3) Sheltered from distant artillery fire; otherwise the building 
 cannot be held against infantry or cavalry. 
 
 (4) Well selected for the object in view. 
 
 (5) Low, flat roof. 
 
 (6) Clear field of fire obtainable. 
 
 (7) Shape in plan affording flank defense. 
 
 191.— The building should be looked upon as a keep, or second 
 line of defense, a first line being prepared at a minimum distance 
 of 40 yds. to the front, this distance being the least that will 
 give the defenders immunity from splinters caused by shells strik- 
 ing the building. 
 
 192.— In falling back, the first line should retreat pasty not 
 into the house, which should by this time be occupied by the sup- 
 ports. The garrison of the house may be estimated at two men to 
 each door, window", or loop-hole, with a reserve of one-fourth, tac- 
 tical unity being in this, as in all similar cases, adhered to as much 
 as possible. 
 
 193.— The following are the steps which must be taken in has- 
 tily preparing a house for defense:— 
 
 (aJ Remove the inhabitants, also all easily combustible mate- 
 rial, and provide water and heaps of earth in each room. 
 
 (b) Barricade doors and ground-floor Tvindows (bullet-proof if 
 possible), also mask inaccessible window^s, and remove all glass. 
 
 (c) Make loop-holes in doors, shutters and walls, and, in the 
 case of a sloping roof, remove tiles or slates. 
 
Defense of Localities. 97 
 
 (dj Clear away cover in the viciuity as far as time and means 
 will allow. 
 
 (ej Open up communication throughout and prepare a means of 
 retreat. 
 
 194.— The same precautions as to loop-holing walls apply in case 
 of buildings. On the ground lioor the horizontal dimensions of a 
 loop-hole should be greatest; on upper floors, the vertical dimen- 
 sion. If an artillery attack is feared, shelter trenches should be 
 provided outside the building on the flanks. 
 
 195. — Barricades for Doors may be made in the following 
 ways:— 
 
 (a) Fill boxes, barrels, cupboards, etc., with earth and place 
 them against the door inside. 
 
 (h) Build a wall of brick, stone, flag-stones, or hearth-stones, 
 against the door inside, and support by a shutter or another door. 
 
 (c) If railway plant is available, pile ties horizontally on one 
 another and secure with telegraph wire. 
 
 (d) Pile lumber inside the door and fix with blocks nailed to 
 the floor. 
 
 (e) Other methods may be employed in accordance with mate- 
 rial available. 
 
 196.— Should a door be reserved for use, it should be in a re- 
 entering angle of the building, if possible, and protected from fire. 
 A couple of chests filled with earth and placed on rollers may be 
 used to secure the door. Similarly it may be possible to place iron 
 or wood on the door, thus rendering it bullet-proof. 
 
 197.— Windows. Windows must be barricaded as explained 
 for doors. If provided with shutters, these should be utilized. 
 Upper windows require to be bullet-proof only high enough to 
 cover the defenders. Bedding is no protection against modern 
 rifles, but may be used to mask windows of upper floors. If tim- 
 ber is used it should be placed vertically and nailed to horizontal 
 ribbands strutted back to the floor. 
 
 198.— If the house is large and strong and is to be held to the 
 last, in addition to the foregoing the following preparations should 
 be made:— 
 
 (1) Arrange for storage of provisions and ammunition. 
 
 (2) Set apart a place for a hospital. 
 
PLATE 27 
 
 Pig.l 
 
 Pig 2 
 
 Kff.e, 
 
Defense of Localities. 91i 
 
 (3) Prepare latrines. 
 
 (4) Loop-hole partition walls and upper floors. 
 
 (5) Make ready barricades to cover retreat from one part of the 
 building to another. 
 
 (6) If artillery is feared, shore up the floors and cover them 
 with about 3 in. of earth. 
 
 199.— Should the construction of the house not afford suffi- 
 cient flank defense, it can be improvised in the shape of tambours 
 or caponiers, but the labor involved in their construction is consid- 
 erable and they would only be undertaken for the defense of a 
 very long wall or to cover an important entrance or communi- 
 cation. 
 
 For the latter purpose a machicouUs gallery is sometimes em- 
 ployed. (PI. 27, Fig. 3.) This is made by removing the wall of 
 the upper story where a window occurs down to the level of the 
 floor, running out two or three long balks so as to project a few 
 feet beyond the wall, the other ends being secured down to the 
 floor. On these planks are nailed, with holes cut through to act 
 as loop-holes, and a musket-proof parapet of planking, sand-bags, 
 etc., is built all around. A projecting veranda offers a favorable 
 position for this arrangement. 
 
 Second method: If a regular gallery can not be made, holes 
 may be cut in the wall at a convenient height for a man to fire 
 downwards when leaning over, and a screen of wood or other 
 material may be secured outside for protection. (Fig. 4.) 
 
 If neither of the foregoing methods be possible, holes may be 
 made in the roof, through which grenades may be thrown on the 
 enemy. 
 
 200.— The materials most likely to be useful in preparing a 
 house for defense are sand-bags, stout timbers, such as railway 
 ties, large boxes, chests, barrels, coal-boxes, furniture and bed- 
 ding. 
 
 201.— PI. 27, Figs. 1, 2, and 5, illustrate the more important 
 points in the defense of a house. 
 
 202.— Farms. Farms should be defended according to the 
 nature of the surface covering, the ground and the improvements, 
 and may involve the preparation for defense of walls, hedges, cut- 
 tings, embankments, buildings, woods, etc. Owing to their posi- 
 tions, farms may become very important and a great amount of 
 
100 Defense of Localities. 
 
 fighting take place for their possession. They may occur either 
 in the main line of a position, as an advanced post in front, or as a 
 reserve station or rallying point in rear. 
 
 203.— Fig. 6 shows the principles of defense applied to a farm 
 lying in advance of a stream, which is a point that requires to be 
 strongly held. From the position of the farm it must be held Jife 
 an advanced post. 
 
 The firing line is established along the fences bounding the 
 fields and orchard. The farm buildings are loop-holed and can 
 be held should the firing line be forced, while the fire from the 
 house would render occupation of the farmyard by the enemy 
 difiicult. Further to the rear, the wood is strongly prepared for a 
 final position, as shown in the figure. 
 
 204.— The rear of an advanced post should be left weak and 
 open to facilitate recapture. 
 
 205.— Villages. Villages can be rapidly prepared for defense 
 and, under favorable circumstances, obstinately defended; conse- 
 quently they are valuable supporting points in a defensive line. 
 Owing to the effect of modern artillery and the liability of burst- 
 ing shells to set villages on fire, great precautions have to be taken 
 in the preparation for defense. 
 
 206.— A village, when properly prepared and defended, may 
 have the following advantages:— 
 
 (a) Can be rapidly placed in condition for defense. 
 
 (h) Defense may be obstinate — thus giving time. 
 
 (c) Conceals the strength of the defenders. 
 
 (d) Provides a certain amount of cover rfrom fire. 
 (ej Shelter from the elements. 
 
 On the other hand:— 
 
 (a) The garrison is scattered, and hence the difllculty of 
 supervision. 
 
 (b) When under artillery fire, splinters may cause many 
 casualties. 
 
 fc) Liability to be set on fire by shells. 
 
 207.— A village may be held with the following objects In 
 view:— 
 
 fa) As a supporting point in the main line of defense. 
 (h) As an advanced post in front of the main line. 
 
PLATE 2&, , .'. 
 
102) D^pyfenee of Localities. "^ 
 
 (0) As an independent post. 
 
 (d) As a reserve station or rallying point in rear. 
 
 In the first case, strengthen the front and flanks. The rear 
 should be prepared to resist infantry. In the second case, the 
 distance from the main line will govern the amount of prepara- 
 tion. If very distant, should be prepared for all-round defense. 
 If within rifle range, the rear should be left open, so that in case 
 the village is taken, recapture will be facilitated. In the third 
 case, if an independent post, must be prepared for an all-round 
 defense. In the fourth case, if in the rear of the main line, must be 
 prepared for a protracted, all-round defense. 
 
 208.— -Whether or not a village is to be held will depend on:— 
 
 (1) Its tactical value as compared with the number of men re- 
 quired to defend it. 
 
 (2) Whether it is practicable to provide a suflScient garrison for 
 its defense. 
 
 (3) Whether It will be possible to demolish the village entirely, 
 in order to deprive the enemy of the cover It provides. 
 
 (4) On the form and nature of the surrounding country— i. 6., 
 no commanding ground within artillery range, foreground easily 
 prepared and the unimpeded advance of the defenders' troops In 
 the required direction easily arranged. 
 
 (5) On the shape of the village— whether broadside, salient, or 
 circular. 
 
 (6) Nature and materials of the houses. 
 
 209.— The first points to determine in preparing a village for 
 defense are how much of it will be defended, whether there are 
 buildings suitable for a keep or citadel, and whether or not these 
 are properly located. 
 
 210.— The arrangements for defense would be made in the fol- 
 lowing order:— 
 
 (1) Clear the ground toward the enemy. (See Chap. V.) 
 
 (2) Cover for the firing line, supports, and reserves. (See 
 Chap. IV.) 
 
 (3) Creating obstacles. (See Chap. VI.) 
 
 (4) Preparing communications. (See Chap. XVII.) 
 
 (5) Constructing retrenchments, citadels, or keeps. (See "Build- 
 ings.") 
 
Defense of Localities. 103 
 
 211.— The garrison of a village may be estimated at two men 
 to the yard of perimeter to be defended. 
 
 212.— Salient Village. (PL 28, Fig. 2.) The successive lines 
 of defense must be carried well out to both sides and the flanks 
 well protected; otherwise the enemy may turn them and avoid 
 fighting in the streets. 
 
 213.— Broadside Village. (Fig. 1.) Here the outside fences 
 must be more utilized than the actual buildings, as the latter are 
 open to fire from artillery. 
 
 214.— Circular Village. (PI. 29.) Great attention must be paid 
 to the proper division of the village into sections for defense and 
 preparing and making the communications. 
 
 215.— In any of the foregoing cases, if cover does not exist foi 
 supports and reserves, it must be provided, as the village will prob- 
 ably be shelled before being assaulted. 
 
 If artillery is to be used it should be placed on commanding 
 ground, inaccessible, if possible, to the enemey, and so that its 
 fire will sweep those parts most favorable to the enemy's advance. 
 
PLATE 29. 
 
CHAPTER XIV.— Use of Cordage and Spars. 
 
 216.— A rope is composed of three or more strands of fibrous 
 material, iron or steel, twisted together. The strands of fibrous 
 ropes are formed of threads; of iron and steel ropes, of wires. The 
 size of rope is denoted by its diameter in inches,* and rope is gen- 
 erally sold by the pound. Fibrous ropes when new and dry stretch 
 considerably, when wet they contract; advantage is often taken of 
 the latter fact to tighten temporary lashings. Manila rope is only 
 about % as strong as hemp rope; tarred ropes only about % as 
 strong as untarred. 
 
 217,— A rule approximating to the breaking weight of a new rope, 
 in tons of 2,000 lbs., is to take one-fourth the square of the circum- 
 ference in inched. The strength of pieces from the same coil may 
 vary 25 per cent. 
 
 Ropes in daily use should not be worked up to greater than 1-5 
 their breaking loads, to meet the reduction in strength by wear 
 and exposure. 
 
 218.— The following table gives the approximate breaking 
 loads and weights of new Manila ropes, Swede's hemp center 
 Iron pliable ropes of 6 strands of 19 wires each, and hemp center 
 Steel pliable ropes of 6 strands of 19 wires each, Manufacturers' 
 Tests: 
 
 Diam. ii 
 inches 
 
 Breaking loads in lbs. 
 
 1-4 
 
 3-8 
 
 7-16 
 
 1-2 
 
 5-8 
 
 3-4 
 
 7-8 
 
 1 
 
 IV4 
 
 m 
 1% 
 2 
 
 Manila 
 
 ^780" 
 
 1,280 
 
 1,562 
 
 2,250 
 
 4,000 
 
 5,000 
 
 7,500 
 
 9,000 
 
 14,000 
 
 20,250 
 
 30,250 
 
 36,000 
 
 Iron 
 
 Steel 
 
 Weig-ht per 100 
 ft. in lbs. 
 
 Manila |I™",t 
 
 Minimum Size of 
 
 Sheaves in feet 
 for Iron and Steel 
 
 5,000 
 
 6,200 
 
 7,600 
 
 11,000 
 
 17,500 
 
 23,000 
 
 32,000 
 
 54,000 
 
 78,000 
 
 108,000 
 
 130,000 
 
 12,000 
 
 15,000 
 
 24,000 
 
 36,000 
 
 50,000 
 
 66,000 
 
 104,000 
 
 154,000 
 
 212,000 
 
 250,000 
 
 ^ 1 
 
 ... 1 
 
 
 5 1 
 
 26 
 
 1 
 
 61-81 
 
 29 
 
 iy2 
 
 8 ' 
 
 35 
 
 2 
 
 13.5 
 
 70 
 
 2% 
 
 16.5 
 
 88 
 
 3V4 
 
 24 
 
 120 
 
 3% 
 
 30 
 
 158 
 
 4 
 
 45 
 
 250 
 
 5 
 
 66 
 
 365 
 
 evz 
 
 97 
 
 525 
 
 7% 
 
 15 1 
 
 630 
 
 9 
 
 *In the Navy the size of rope is denoted by its circumference in inches, 
 method used should be distinctly stated. 
 
 The 
 
106 Use of Cordage and ^pars. 
 
 219.— Knots, Hitches, etc. The standing part of a rope is any 
 part not an end. 
 
 A bight is a loop formed in a rope. (PI. 30, Fig. 1.) 
 
 Whipping is securing the end of a rope with twine to prevent 
 it from fraying out. (Fig. 1.) 
 
 Parceling is wrapping a rope to prevent chafing or cutting 
 against a rough surface or sharp edge. (Fig. 1.) 
 
 Stopping is fastening two parts of a rope together without a 
 crossing or riding. (Fig. 1.) 
 
 I^eizi'ng is fastening two parts of a rope together with or with- 
 out riding and finishing with crossings or f rapping turns. (Figs. 
 5 and 17, f rapping turns not shown.) 
 
 Nippering is taking turns crosswise between the parts to jam 
 them, finishing with crossings or frapping turns, latter not shown 
 in figure. (Fig. 1.) 
 
 Splicing is joining the ends of ropes by opening the strands 
 and placing them into one another (Figs. 2 and 3), or by putting 
 the strands of the ends of a rope between those of the standing 
 part (Fig. 4.) The splice is about % weaker than main rope. 
 
 Rolli/ng or stopper hitch, for fastening a rope to a strap or tail 
 block, and to secure a fall while being shifted on a windlass or 
 capstan. (Fig. 5.) 
 
 Overhand Icnot, to prevent the end of a rope from fraying out, 
 from slipping through a block, and the beginning of several other 
 knots. (Fig. 6.) 
 
 Figure of 8 knot, for same purpose as overhand knot and used 
 in making ansk piers. (Fig. 7.) 
 
 Square or reef knot, for joining the ends of two ropes the same 
 size. (Fig. 8.) 
 
 Thief knot (Fig. 9), with ends on opposite sides, and Granny knot 
 (Fig. 10), by crossing the ends the wrong way, both looking like 
 square knots, are to be avoided, as they will not hold. 
 
 Single how or slip knot. (Fig. 11.) 
 
 Square how, which can be cast off. (Fig. 13.) 
 
 Marlinspike hitch, used in putting on lashings, etc. (Fig. 12.) 
 
 Sheepshank, used to shorten a rope temporarily without cutting. 
 (Fig. 14.) 
 
 Two half lutches, for fastening the end of a rope around its own 
 standing part (Fig. 15.) 
 
PLATE 30. 
 
 » 
 
 FIG.1. 
 
 jjxxxnn 
 
 IVhipping J>*^SPV. 
 
 IG,2. 
 
 7 — y 
 
 -vT'v-v^ Nipperwig 
 or Seizing ' " 
 
 FIG. 6. 
 
 ^""""^ Rdltng or i^/f/K'i Hitch, seizing 
 
 ^ye Splice Ym. - fIG.9. . FIG. 10. 
 
 FIG. 11.,^ FIG.12. 
 
 •FIG.8.. 
 
 Sinole bow <n-skp knot, -n^ 7l^ .^ Square or': Ohie/C Granny 
 
 FIG. 13. __ Marli?^pvP.e . ^^^pjQ ^4 ^ 
 
 FIG. 17. ^J^^I^^/'^^^^M^ 
 
 Wecu/etiknot 
 or Sheet bervd. Bend 
 
 FIG.22. 
 
 Timber hitch. 
 
 EM_ 
 
PLATE 51. 
 
 FIG. I 
 
 FIG, 2 
 
 FIG 3^ FIG.4.^ FIG.5. 
 
 on a bi^t 
 
 rIG6. 
 
 XiOrkis he(td 
 
 ^FIQIO. 
 
 FIG.13. 
 
 ' Jtack lashing^ 
 
 nG.i5. 
 
 licick /askirtg- 
 
 FIG.14. 
 
 Square ZMshzng- 
 
 FIG.16. 
 
 \ear Lushing 
 
 Gin iashin^ EAJf. 
 
Vse of Cordage and Spars. 109 
 
 Round tturn and two Juiif hitches, to secure guys to stakes, etc. 
 (Fig. 16.) 
 
 Fisherman's bend or Anchor knot, for fastening a rope to an 
 anctior or ring. (Fig. 17.) 
 
 Weaver's knot or sheet bend, for joining ropes of different sizes 
 without jamming. (Fig. 18.) 
 
 Double sheet bend, more secure tlian the single bend. (Fig. 19.) 
 Glove hitch, for fastening a rope to a spar; the end may after- 
 wards be stoppered to its own part. The clove hitch differs from 
 two half hitches only in being made around a spar cr other rope 
 instead of around its own standing part. (Fig. 20.) 
 
 Timber hitch jams when made round a timber. (Fig. 21.) 
 Bowline, to form a temporary loop at the end of a rope. (Fig. 
 22.) 
 
 Bowline on a bight, to mal^e a loop on a bight. (PT. 31, Fig 1.) 
 Cafs paw, for applying a purchase or tackle to the fall of an- 
 other. (Fig. 2, the beginning; Fig. 3, how applied.) 
 
 Blackwall hitch, for fastening the end of a rope on a block in the 
 simplest manner, or fastening a rope in a hook. (Fig. 4.) 
 
 Mousing is a seizing placed around a hook to prevent it from 
 spreading or unhooking. (Fig. 4.) 
 
 Carrick bend, to fasten guys to a derrick. (Fig. 5.) 
 Lark's head, for fastening a bight to a ring. (Fig. 6.) 
 Capstan or Prolonge, making fast a spar. (Fig. 7.) 
 Wall knot, for finishing off the end of a rope to keep from un- 
 stranding (Fig. 8), by passing the strands, as shown, then drawing 
 them down into a knot. 
 
 Frapping is passing a rope around a lashing to keep the turns 
 together. (Figs. 14, 15 and 16.) 
 
 Straps are rings used for attaching tackles to spars or ropes. 
 (PI. 33, Figs. 1, 2 and 6.) 
 
 220.— To make a short splice. (PL 30, Fig. 2.) Unlay strands 
 of each end for a convenient length; take an end in each hand, 
 place end to end, strands sandwiching, and grasp the three strands 
 from opposite rope in left hand. Take a free strand, pass it over 
 the first strand next to it, then through under the second and out 
 between the second and third from it, then haul taut. Pass 
 each of the remaining six strands in same manner, first those of 
 
110 Use of Cordage and Spars. 
 
 oue end and then tliojse ot the other, and bo continue as far as 
 desired. 
 
 221.— To make a long splice. (1^ ig. 3.) Unlay strands of each 
 end, three or four times longer than for short splice, and place end 
 to end as described. Unlay one strand a considerable distance and 
 fill up its space with opposite strand from other rope, and twis» 
 them together. Do the same with two strands on other rope. 
 Open remaining strands, divide in two, make overhand knot with 
 opposite halves, and lead ends as in short splice. Cut off the other 
 two halves. Do the same with the other pairs of strands 
 where twisted together. Before cutting off any of the half strands, 
 first stretch, roll under the feet, and pound the rope well. This 
 splicing does not increase the size of the rope and is used where 
 the splice is to run through blocks. 
 
 222.— To make an eye splice. (Fig. 4.) • Unlay one end for 
 ghort distance, lay strands upon the standing part so as to form 
 the desired sized eye. Put first end through the strand next to 
 it. Put second over that strand and through second. Put third 
 through third strand on other side of rope and so continue. This 
 forms a permanent loop in end of rope. 
 
 223.— To sling a box or barrel. Lay a strong strap under 
 it, spreading the parts, and pass one bight through the other; or 
 make a long loop with a bowline and sling as shown on PI. 31, 
 Fig. 9. If one head is out stand barrel up, put one part of a strap 
 under middle of bottom, take a half hitch over top with each part 
 just over bilge hoops and exactly opposite; or place rope under 
 barrel, bring up over top, make overhand knot, open it out and slip 
 each half down over hoops, fasten end to standing part with bow- 
 line. (Fig. 10.) 
 
 224.— Rack lashings (Figs. 11, 12 and 13) are made with a 1-3 
 in. rope, 18 ft. long, with a loop at one end, and a rack stick 2 ft. 
 long, 1%. in. in diameter, having a cord 4 ft. long through one end, 
 by passing the rope two or three times around the side rail and 
 balk, and, after making it fast, twisting It tightly with the rack 
 stick. 
 
 225.— Transom lashing. (Fig. 14.) The spars are laid across 
 each other at right angles, a clove hitch is made on one of the 
 spars, the end then twisted around its standing part, then three 
 
2L4IE'32. 
 
 FIG.1. _FI&2 PIG.3. • FIG.4. 
 
 FIG. 7. 
 
 Sinole 
 
 vket lafiecket \t\ 
 
 pZ rfr Treble, 
 
 rullet, gock block 
 
 FIG 6. 
 
 FIGS. 
 
 (TtT/, 7 Hrry Block 
 
 FIG.IO 
 
112 Use of Cordage and Spars. 
 
 or more turns are taken around ibe spars, under one and over the 
 other, keeping outside previous turns on one spar and inside on the 
 other. Several trapping turns are then talien between the 
 spars and the end fastened on one of the spars with a clove 
 hitch. Used in lashing transoms to standards in bridge-building. 
 
 226.— Shear lashing. (Fig. 15.) The spars are laid parallel, a 
 couple of inches apart, on a block, a clove hitch made on one spar, 
 then five or six turns taken ai'ound both spars without riding. 
 Several frapping turns are then taken between the spars and the 
 end fastened on one of the spars with a clove hitch. This is used 
 in rigging shears for hoisting heavy weights, etc. 
 
 227.— Gin lashing. (Fig. IG.) The three spars are laid par- 
 allel, a couple of inches apart, the butts of the two outside ones 
 in one direction, that of the middle one in the opposite direction. 
 A clove hitch is made on one spar, then five or six loose turns 
 taken, passing over and under, without riding. Several frapping 
 turns are taken in each interval and the end fastened on one of 
 the spars with a clove hitch. 
 
 228.— Blocks, Tackles, etc. A pulley consists of a wheel, hav- 
 ing a grooved rim for carrying a rope, turning in a frame. (PL 
 32, Fig. 1.) 
 
 A block (Figs. 2 and 3) consists of one or more grooved pulleys 
 or sheaves turning on an axle, called a pin, mounted in a casing 
 or shell, which is furnished with a hook, eye or strap on one end, 
 by which the block may be attached to something, and sometimes 
 with a becket on the other end for attaching ropes, etc. It is 
 used to transmit power, or change direction of motion, by means 
 of a rope or chain passing round the movable pulleys. Blocks are 
 single, double, treble or fourfold, according as the number of 
 sheaves or pulleys is one, two, three or four. The size of blocks 
 is expressed by the length of the shell in inches. A common style 
 of Ferry Block is shown in Fig. 5. 
 
 A snatch block (Fig. 4) is a single block with a notch cut in one 
 cheek so as to receive the standing part of a fall without the trou- 
 ble of reeving and unreeving the whole. 
 
 A running block is one attached directly or indirectly to the ob- 
 ject to be raised or moved; a standing block is one fixed to some 
 permanent support. 
 
Use of Cordage and Spars, 1 1 3 
 
 229.— A tackle consists of two or more blocks with a rope rove 
 ttirougii tliem for use in lioisting. 
 
 230.— Tlie parts of all ropes between the points of fastening 
 and sheaves are called standing parts; the parts between the 
 sheaves are called running parts; the part to which the power is 
 applied is called the fall. 
 
 231.— To overMul a tackle is to separate the blocks; to round in 
 is to bring the blocks closer together. 
 
 A tackle is said to be block and Uock or two blocks when the en- 
 tire fall is hauled through so the blocks are in contact. 
 
 232.— Before reeving a rope in a block, it should be stretched 
 out its full length. Tackle should not be allowed to twist; to pre- 
 vent it, insert a bar in the block or between the running parts and 
 use it as a lever to hold straight. If allowed to make one complete 
 turn with two single blocks, the friction will increase the resist- 
 ance about 40 per cent. Ropes should not be too large for blocks, 
 the rule being, ''Small ropes and hig blocks.^' 
 
 233.— Power of Tackle. Theoretically, the power necessary 
 to just balance a weight, with a tackle of two blocks, is equal 
 to the weight divided by the number of ropes at the running 
 block, including the standing part if attached to it. 
 
 234.— To produce motion, however, a greater power is required 
 to overcome friction and stiffness of rope. It has been found by ex- 
 periment that to do this about 10 per cent of the theoretical power 
 necessary to balance must be added to itself for each of the 
 sheaves over which the rope passes, the blocks being in good con- 
 dition and well oiled. If not in good condition and not well oiled, 
 the per cent may be as high as 30 for each sheave. 
 
 235.— The formula P = ^^^^ is used to determine the power 
 required to raise a weight with a simple tackle, in which P = the 
 power required, W = the weight to be raised, S = the number 
 of sheaves, and R = the number of ropes at running block, in- 
 cluding standing part if attached to it. If it is required to find 
 how great a weight a certain power will lift, the formula is 
 W =^3^. Power is gained only at the loss of time. The power 
 moves as many times faster and farther than the weight as the 
 number of ropes at the running block. No advantage is gained 
 
PLATE 33. 
 
Use of Cordage and Spars. 115 
 
 by using, in one fall, a greater number of sheaves than two 
 treble blocks, but further advantage may be gained by a combina- 
 tion of blocks and tackles.* 
 
 236.— A squad of men hauling on a fall exert a pull of about 
 80 lbs. (or half their weight) each, the fall being nearly horizontal. 
 
 237.— A Derrick (Fig. 7) usually consists of a single spar or 
 leg, held up by four guys, and having a tackle lashed to the top, 
 used for hoisting or lowering heavy bodies within a circle whose 
 diameter equals % the height of the spar. When made of two 
 legs (Fig. 8), they are mortised into a cap on top and a sill at the 
 bottom, only two guys being required, a fore and back, but three 
 are better, one fore and two back. The weight can only swing 
 between the legs. The holdfasts for the guys should be at a dis- 
 tance from foot of derrick at least twice its height. The foot 
 should be secured from slipping by being let into a hole in the 
 ground or otherwise. 
 
 238.— Shears (PI. 33, Fig. 1) consist of two spars, of a size suita- 
 ble for the weight to be raised, lashed together at the cross. 
 
 A tackle is fastened at the lashing by a strap passed around it 
 or otherwise, the hook moused, and holdfasts are required as for 
 two-legged derrick. 
 
 Two-legged derricks and shears should not lean to exceed 1-3 
 of their height, and each leg should have about % this Inclination, 
 or 1-6 their height. 
 
 239.— A Gin (Fig. 2) is a tripod formed of three poles. The two 
 outside ones are called legs, the third one the pry-pole. Gins re- 
 quire no guys. Weights can only be lifted vertically. 
 
 240.— In using derricks, shears, and gins, the fall is generally 
 led through a snatch-block lashed on a leg near the bottom, 
 thence to a crab, windlass, or capstan. Derricks frequently 
 have fastened on their legs a winch for transmitting the power. 
 (PI. 32, Fig. 10.) 
 
 241.— A "Windlass (Fig. 12) consists of a horizontal axis fast- 
 ened in a frame and turned by means of cranks or handles. The 
 rope may either be fastened to the axis or passed two or three 
 times around it, hauled taut, the free end being held, and taken 
 in by men in the rear. 
 
 *The formula P = — ^^-^ is merely a simplified form of the equation 
 p = ( W -{- rV W S ) -^ R. (See par. 234.) 
 
116 Use of Cordage and Spars, 
 
 242.— A Capstan (PI. 32, Fig. 9, and PI. 33, Fig. 3) consists of 
 an upright barrel, either smooth or ribbed, arranged about a spin- 
 dle. Above the barrel is the head with holes to receive the ends of 
 levers or bars by which the barrel is revolved. The rope is passed 
 and held as explained for a windlass. 
 
 243.— Holdfasts are stout wooden stakes driven into the 
 ground, or other arrangements used for securing purposes. 
 
 An essential point to be considered before moving or suspend- 
 ing heavy weights is the nature and condition of the securing 
 points, together with the strain that will be brought upon them. 
 In the first instance, it is better to make them more secure than 
 seems to be absolutely necessary, as, when they once begin to 
 give way, it is difficult to strengthen them. PI. 33, Figs. 4, 5. 6 
 and 7, show some of the various methods of making them, 
 also PI. 40a. 
 
 243a.— An improvised Field Capstan, which is but an adapta- 
 tion of the Spanish windlass, is shown in cut. One end of the rope 
 is made fast to the object which is to be moved and the other end 
 to a holdfast. A lever, a, is inserted in a bight of the rope and one 
 end of it placed against an upright bar, h. The lever is then car- 
 ried round and round the bar, which revolves and gradually winds 
 the rope upon itself as it approaches the holdfast. The bar h can 
 be held upright more readily if the lever a is long enough for men 
 to work at both ends of it. 
 
PLATE 3^. 
 
 M0 
 *iil: 
 
CHAPTER XV.— Spar Bridges. 
 
 244.— Military Bridges are not required to fulfill all the condi- 
 tions of ordinary bridges. Tliey are constructed for special and 
 immediate purposes, usually with unskilled labor, and of such 
 materials as can be procured on or near the spot. That the bridge 
 built shall be strong enough to bear the heaviest load intended to 
 be crossed is the first requisite; celerity and simplicity of con- 
 struction next. 
 
 245.— PI. 34 is an illustration of what was done in building 
 Military Railroad Bridges under unfavorable circumstances in 
 time of war with troops of the line, very few of whom were 
 mechanics, many could not even handle an ax, none were trained 
 to the duty, and none were engineer troops. This bridge was built 
 by General Haupt over Potomac Creek, Va., during the Rebellion, 
 and was 80 ft. high and 400 ft. long. It consisted of three tiers 
 of trestles on top of cribs 12 ft. high. The timber used was chiefly 
 round sticks, cut in the woods near by, and put together without 
 bolts, simply with spikes and wooden pins, and when finished, was 
 crossed by 10 to 20 heavily loaded trains per day. This kind of 
 work, however, properly belongs to a special construction corps, 
 but it falls to the lot of the ofllcers and men who first arrive at a 
 stream on the ordinary, roads, where there are no means of cross- 
 ing, to construct an improvised bridge with such tools and of such 
 materials as may be available. 
 
 246.— The plans and expedients which follow have been select- 
 ed with a view to their being types of bridges that can be con- 
 structed by troops having no other tools than axes and augers, and 
 such materials as growing trees found in the vicinity, and beams, 
 boards, ropes, wire, nails, etc.. obtained from neighboring houses 
 and towns. The purposes for which the bridge is to be used, the 
 nature of the crossing, velocity of stream, and kind of bottom, will 
 determine its strength, kind, size. etc. 
 
 247.— For a common road bridge, the load is assumed to be h 
 maximum when covererl with men. estimated at 120 lbs. to the 
 square foot, Plns the woisrht of the bridge, usually taken at about 
 80 lbs. per lineal foot. For roas^ons which are evident, the bridge 
 should be as shovf ns possible, with good approaches. Swampy, 
 high, or steep banks should be avoided. 
 
 248.— Bridges usually take their names from some part of their 
 
Spar Bridges. 119 
 
 construction, as Trestle, Truss, Pile, Suspension, or Floating Bridges. 
 The distance between supports (determined by the strength of 
 the balks to bear the desired load) is called the bay or spcm, and 
 the corresponding part of the bridge the span. The superstruct- 
 ure, consisting of the stringers or balks, the floor, the side-rails 
 and the fastenings, is of the same nature for each kind, as shown 
 in PI. 35, Fig. 1. The ends of the balks rest on cross-pieces of the 
 supports called transoms; on the balks (of which there are usually 
 five) are laid chess or poles, forming the floor; on top of the 
 floor, over the outside balks, are laid side-rails or poles, which 
 are securely fastened every 4 or 5 ft. to the balks beneath by 
 rack lashings. Hand-rails (Fig. 2) should always be provided on 
 each side of the roadway. The usual width of military bridges is 
 9 ft. in the clear, between side-rails; 6 ft. will answer for Infantry 
 in column of twos, and Cavalry by file; 2.5 ft. for Infantry in 
 single file. 
 
 249.— For determining the strength of the materials to be used, 
 all errors should be on the side of safety. The practical method 
 is to place the ends of the timber on low supports, as far apart 
 as they will be in bridge; as many men as can then step on it 
 and jump up and down; or It is otherwise arranged so as to 
 bring as great a weight upon it as It will have to bear at any time 
 in bridge. 
 
 Where small poles of the usual number would not be strong 
 enough, a greater number must be used until the desired strength 
 is gained. 
 
 250.— Transoms must be strong enough to bear all the weight 
 that may be brought upon one bay of the bridge, considered as 
 distributed dead load on the transom. 
 
 251.— T/?c load in pounds which any timber resting on two 
 points of support will safely bear, concentrated at its center, may 
 
 be approximately determined by the formula 1-3 x -p x O, in 
 which b = the breadth in inches, d = the' depth in inches, 1 = the 
 length in feet between supports, and C is a constant in pounds for 
 the particular material of the beam.* 1-3 Is the fraction of the 
 
 *C is determined by takine^ a piece 1 in. square and 1 ft. longbetween supports, 
 loading- it at the center until it breaks, then to the applied load adding one-half 
 the weight of the piece between supports, and the sum will be C; or. a piece of 
 any convenient size and length can be used, afterwards deducing what the 
 breaking weight would be for a piece 1 in. square and 1 ft. long, remembering 
 that the breaking weight varies directly with the width, as the square of the 
 depth, and inversely as the length. 
 
PLATK 35. 
 
 jg£fil 
 
Spar Bridges. 121 
 
 breaking weight used for safety. It would, in all cases, be better 
 to use a smaller fraction of the breaking weight, as 1-5 or 1-6; or 
 even 1-8 in structures designed to be of a lasting character. The 
 formula is for a rectangular beam, but for a cylindrical timber 
 whose mean diameter equals the side of a square beam, use 6-10 
 of what the formula gives. 
 
 252.— Weight brought on a hridge by the passage of troops, taken 
 as distributed live load for Infantry and Cavalry: Infantry in 
 column of twos or fours, about 225 lbs. per lineal foot. Infantry 
 when crowded at a check in fours, about 550 lbs. per lineal foot. 
 Cavalry in column of twos, about 230 lbs. per lineal foot. Cavalry 
 when crowded at a check, about 350 lbs. per lineal foot. When 
 Artillery carriages cross a bridge, the weight is not equally distrib- 
 uted, but is greatest when the wheels bearing the heaviest load are on 
 the center. 
 
 253.— A uniformly distributed dead load produces only one- 
 half the strain of an equal dead load concentrated at the cen- 
 ter. A moving or live load produces twice the strain of a dead 
 load. A uniformly distributed live load equals a concentrated 
 dead load. 
 
 Table of Constants C, for finding the breaking load of various 
 materials by the formula^x-pxC when concentrated at cen- 
 ter of beam supported at both ends. From Trautwine's 
 "Engineer's Pocket Book": 
 
 Ash, white 650 Elm 350 Oak, red & black..550 
 
 Ash, swamp 400 Hemlock 400 Pine, white 450 
 
 Ash, black 300 Hickory 700 Pine, yellow 500 
 
 Beech, white .450 Hickory, pig nut. 500 Pine, pitch 550 
 
 Beech, red 550 Locust 600 Poplar 550 
 
 Birch, 450 Mahogany 450 Spruce 450 
 
 Cedar 250 Maple 550 Sycamore 500 
 
 Chestnut 4.50 Oak, white & live.600 Walnut 450 
 
 254:.— The cubic contents of a log is appioximately equal to 
 0.7854 times the square of the mean diameter times the lengfh, 
 or the area of the mean section multiplied by the length; or the 
 square of one-fifth the mean circumference times twice the length, 
 all in feet. 
 
 255.— In calculating the strength of a round timber or spar, 
 
122 Spar Bridges. 
 
 its mean diameter is used, because such a spar, if overloaded, will 
 break at center, instead of at small end.* 
 
 256.— The following table gives the weights in pounds per 
 cubic foot of various materials: 
 
 Iron, cast 450 Chestnut 40 Spruce 31 
 
 Iron, wrought 487 Cottonwood 35 Sycamore 37 
 
 Lead 710 Hicliory 43-49 Walnut , .38 
 
 Steel 488 Maple 48 Clay .120 
 
 Ash 38-47 Oal£ 45-60 Earth 72-120 
 
 Cedar 35 Pine 34-40 Gravel & sand..90-130 
 
 Green timbers weigh from 1-5 to 1-2 more than those in table. 
 
 257.— When spars are used for ballis, they must be arranged 
 so as to have alj butts or all tips together on a transom. They 
 should have good overlap and be well lashed to each other and to 
 the transoms. To allow for settling, the center is generally made 
 higher by about 1-30 the span. 
 
 258. — Stringer Bridge. For spams of 25 ft. or less, if timber is 
 available, the simplest form of stringer bridge could be built, as in 
 Fig. 2, of 6 balks, 30 ft. long, reaching clear across, covered with 
 small poles 4 to 6 in. in diameter, 12 ft. long, for a floor. Side-rails 
 would be laid on the floor over the outside balks and either lashed 
 or pinned to the balks. Hand-rails would be as shown, or a rope 
 stretched across would answer. Time of construction — 1 hour. The 
 balks could be jumped across as shown in either Figs. 3 or 4. 
 
 259. — Scarped Bridge. If stringers of length to reach across 
 
 *For a bridee constructed as in Fig. 2, with six balks, to determine the safe 
 load it will carry, the application will be about as follows: 
 
 The balks being of ^-ellow pine, ""O in in diameter at fhe center, 25 ft. be- 
 tween supports, the formula gives yV X g^ X ^%^ x500 = 4,000 lbs. as the safe load 
 each balk will bea^- concentrated at the center, including its own weight. Cal- 
 culating for five balks, on the supposition that the two outside ones receive only 
 one-half the strain of the center ones, they will bear 5 x 4,000 lbs. = 20,000 lbs. 
 f oncentrated at center. From this deduct half the weight of the balks and floor 
 concentrated at center, found by multiplying one-half the cubic contents by the 
 weight per foot; for the six balks this will be 
 
 6 X H fP)' X .7854] X 25 x 40 = 1,636.25 lbs. 
 For the floor of seventy-five 4-in. poles, each 12 ft. long, the weight will be 
 75 X * X [ (^^2 x .7854] x 12 x 40= 1,570.86 lbs 
 
 20,000 lbs. — 3,207.11 lbs. -- 16.792.89 lbs., the capacity of the bridge concentrated at 
 the center. Infantry niarchine: in column of fours crowded by a check would 
 cause a load of onlyabout 13,750 lbs. Cavalry in column of twos crowded by a 
 check only about 8,750 lbs. 
 
 Similarly, knowing the span, the kind of material at hand, the weight to be 
 borne, etc., the size of timbers required can be deduced; or, having the size and 
 kind of the timbers, weight to be borne, etc., the greatest length that can be 
 spanned can be determined by the above formula. 
 
PLATE 36. 
 
124 Spar Bridges. 
 
 cannot be obtained or are too heavy to handle easily, a scarped 
 bridge as in Fig. 5 might be made, requiring only axes and augers. 
 The shore stringers, 25 ft. long, 10 in. in diameter, six on each 
 shore, have their bridge ends scarped on upper side 18 in., then 
 pushed out 10 ft., their shore ends being well anchored down and 
 loaded with roadway. Six short stringers, 8 ft. long, 10 in. in diam- 
 eter, three on each shore, scarped 18 in. on under side of each end, 
 are passed over gap and laid on shore stringers. Two 2-in. auger 
 holes are bored at each end through both stringers and wooden 
 pins driven through, and the flooring completed. 
 
 260.— Paine's Bridge. (Fig. 6.) If timber is abundant and 
 stream not over 6 ft. deep, select trees up stream. Fell, and trim 
 off branches. Bore two 3-in. auger holes near butt ends 3 in. apart, 
 making an angle of 30° with each other, and a third hole, making 
 an angle of 45°, between them nearer the butt. Cut and insert in 
 outside holes legs long enough to raise the butt the desired height 
 of bridge. Float down stream, butt end first, to position of bridge. 
 On arriving in line of bridge, the log is turned on its feet, the tip 
 sinking to bottom. The brace leg is then inserted down stream 
 in last hole, making an angle of 45°. Log after log is thus placed, 
 balks rolled up and put into position and leveled, and the floor laid 
 in the usual way. 
 
 261. — Trestle Bridges. For spans of 25 ft. or over, when bot- 
 tom can be touched clear across, some form of trestle bridge will be 
 the easiest of construction. 
 
 262.— The Six-legged Trestle. In PI. 36, Fig. 1, the trestle con- 
 sists of 6 legs, 4 vertical and 2 inclined; the two vertical legs on 
 each side are fastened to two short sills by 2-in. pins. The ends of 
 the two inclined legs are cut on an angle, driven into position, and 
 held by 2-in. pins passing through the transom from above. They 
 serve as braces and supports. A short horizontal piece pinned to 
 each pair of vertical legs supports the transom, which is also 
 pinned. On top of the projecting ends of the vertical legs a cap 
 piece can be pinned to form hand-rails. The trestle is made on 
 shore, floated to its place in bridge, and erected with the aid of a 
 float held at the proper distance from last trestle by a pole on each 
 side, having the lengths of the spans marked by pins which engage 
 the transoms of the trestles. The transoms are only temporarily 
 lashed in position at first, but after the trestle is erected in its 
 
^par Bridges, 125 
 
 proper place the proper height for it is determined by bringing 
 the 2 distance poles horizontal, or a little above the horizontal if 
 a camber is to be given, then pinning or spiliing on the short hori 
 zontal pieces. If accurate soundings have been made across the 
 stream on the lines of the legs of the trestles, then the trestles can 
 be completed on shore before launching. The balks are then 
 run across and pinned and roadway finished. If there occurs 
 unequal settling, the roadway can be raised by blocking up under 
 the transoms on the short horizontal pieces. 
 
 263. — The Tie-block Trestle. Fig. 2 is another form of tres- 
 tle, consisting of only two legs, about 8 in. in diameter. 
 The transoms are in pairs, across which two blocks are spiked at 
 each end into notches, as shown. This trestle can be used on 
 hard, uneven bottom. The trestle is formed on shore, held in 
 shape by the rope, and rack stick across the top, then floated into 
 place. Two poles, longer than two spans, are then run out; on the 
 projecting ends are pins to prevent the trestle slipping off, and on 
 near end a rope for fastening to transoms of second trestle back. 
 Having caught the trestle on the ends of the poles under the 
 transom, it can be raised to a vertical position by men bearing 
 down on the rear, and held by means of ropes; it is then lowered 
 into position, legs in a vertical plane. The transoms are then 
 adjusted to their proper elevation by striking on under side, if 
 too low, then tightening rope; or by slackening the rope and strik- 
 ing on upper side if too high. . When properly adjusted, the rope is 
 tightened, pinching the legs between the blocks; the braces are 
 then spiked or pinned on, the rope removed, the balks laid and 
 pinned, and the poles shoved out for the next trestle. 
 
 264. — The Four-legged Capped Trestle. Where sufficient lum- 
 ber can be procured, the most expeditious and probably the best 
 method will be as follows: (Pig. 3.) With the balks and chesses 
 for each span, form a raft, or as many as may be desired, the length 
 of a span. Form a trestle by placing four legs parallel and 4 ft. 
 apart from center to center. Spike a pole across near the bottom 
 and ono near the top to keep them together. The first, or any tres- 
 tle, having been set, float a raft against it and make fast; bring the 
 trestle to be set up to the other end; force the legs under the raft a 
 distance a little less than the depth of the water. Tie a rope around 
 the outside legs at **f" with a bow-knot, to hold from slipping un- 
 
126 Spar Bridges. 
 
 der, ana others to the top pole, by means of which it is raised to a 
 vertical position, when it is dropped to the bottom by slackening 
 off on lower ropes. As soon as it is dropped,another raft is brought 
 up, tied, and another trestle put into position, and so continued. 
 Each trestle, as soon as it is in position, is then capped by nailing 
 two boards horizontally on opposite sides of legs with tops in same 
 plane. (Fig. 3, a.) Braces arie then spiked on the legs. Saw off the 
 two inside posts even with the tops of boards. Spike a 2-in. plank 
 across the top of posts and boards. Lay the balks, spike them, 
 remove the raft, and move it into position to raise another trestle. 
 If boards cannot be procured for capping, round sticks may be 
 used as in Fig. 3, b, by cutting the two inside legs off 5 or 6 in. 
 above the horizontal poles, then spiking two short pieces across 
 the poles against the outside legs and one in center on which the 
 cap piece or transom will rest. Advantages are — work can be 
 commenced in any number of places at the same time; no accu- 
 rate soundings required so long as poles are sufficiently long; cap- 
 ping and bracing do not retard work; different squads can be at 
 work at same time, etc. 
 
 265. — The Two-legged Trestle. If only axes and rope are 
 available, trestles may be made by lashing their parts together. 
 (Fig. 4.) Having determined the height of the roadway above 
 the bottom of the stream, mark this height from the butts on 
 both leg;s, then mark the position of the transom on the legs, 
 allowing for the thickness of the balks; also mark on the transom 
 the width of roadway between side-rails plus 3 ft, for points 
 of crossing of legs, the distance apart of legs depending on 
 width of roadway. Give the legs a splay outwards at the bottom 
 of 1-6 and mark on legs and ledger the points of lashing. All be- 
 ing ready, lay the transom on a couple of supports 3 or 4 In. high, 
 inside the position of the legs, lay on the legs in their proper posi- 
 tions, on the legs lay the ledger. With the square lashing fasten 
 the four points of crossing. Next, lay on the braces, butts and 
 one tip on same side as ledger and one tip on side of transom. 
 Lash the butts with square lashings. Square the trestle by mak- 
 ing the diagonals equal, measuring from the center of ledger lash- 
 ing on one leg to the center of transom lashing on opposite leg. 
 When these diagonals are made equal the tips are lashed with 
 square lashings and the braces at the middle with a cross lash- 
 
Spar Bridges. 127 
 
 iiig. Ledger and braces can be of ratlier light timber. Tlie tres- 
 ues can be floated into position and raised as already described, 
 or run out and down from the end of the bridge, which is more 
 difticult. They are kept vertical by lashing the balks to the 
 transoms, and longitudinal bracing from one to another. 
 
 266.— A Three-legged Trestle (ri. 37, Fig. 1) may be made 
 by first lashing two legs together considerably higher than the 
 roadway is to be, then lashing the pry -pole just below to one of 
 the legs, all with shear lashings. Stand the trestle up, spread 
 out legs till butts rest on the vertices of an equilateral triangle 
 whose sides are ^> height of trestle, then lash three light ledgers 
 to the legs by round lashings. On the outside of the pry-pole 
 and leg to which it is fastened are lashed short pieces, by square 
 lashings, on which rest two longer pieces, separated by the legs, 
 which are lashed together by the shear lashing. On these longer 
 pieces rest the transoms. With these trestles lighter material 
 can be used; they stand without bracing, but are difficult to place; 
 accommodate themselves to inequalities of surface; the roadway 
 may be readily raised or lowered. If material is available, they 
 are readily made with spikes. 
 
 267.— The Four-legged Trestle, second form. (Fig. 2.) Two 
 two-legged trestles are made, one being 12 to 18 in. narrower than 
 the other, depending on the size of legs, so that they will lock when 
 put together. The transoms are placed on same side as ledgers, 
 instead of on opposite sides. The butts of the single trestles are 
 placed a distance apart equal to half the height, then locked at 
 the top, the transoms lashed at the ends, longitudinal braces 
 lashed at the ledgers, the tips tied and racked together. Some- 
 times used with light material, also as steadying points in a long 
 bridge of two-legged trestles. One similar to it can be made of 
 sawed timber and spikes and placed in position as shown in Figs. 
 3 and 4, if the materials are available. 
 
 26S. — Crib Piers. In sluggish streams with muddy bottoms an.i 
 not over 6 ft. deep, where timber is abundant, crib piers may be 
 used. (Fig. 5.) The cribs are built in the woods, the foundation 
 logs being pinned together, the others simply notched. The logs 
 then marked, taken down, carried or floated into position, and re- 
 built, poles being generally set to mark the corners. As the crib 
 is built up it gradually sinks, or a tray may be formed Inside and 
 loaded with stones. The balks and flooring are laid as usual. 
 9 
 
FLATS 3!? 
 
FLAtli 38. 
 
 FIG.l. 
 
 FIG. 4. Single Lock . 
 
 ab must not bo less tkani Op cd 
 
 Ji^ 
 
^^0 Spar Bridges. 
 
 269.— rUa bridyas are scarcely adapted to an emergency, from 
 the time and preparation required in tlieir construction, but on 
 lines of communication, from tlie ciiaracter of tlie bottonl or the 
 dangers from floating objects, resort may be had to them. 
 
 J270.— For driving the piles, a monkey (Fig. 8) is made of a 
 block of wood 3 ft. long, 12 in. in diameter, with four 1.5 in. pins 
 at top and four on the sides for handles. --ur men standing on 
 a platform on the pile drive it down, their own weight thus assist- 
 ing, or they may be driven from a raft built as in Fig. 6. After 
 the piles are driven they are straightened, braced, their tops sawed 
 off level, the caps placed on and pinned (PI. 38, Fig. 1), and the 
 roadway laid as usual. Piles near shore may be driven as in Fig. 7. 
 
 271.— For crossings greater than 25 ft. and too deep to use any 
 of the above forms, resort must be had to some form of truss 
 bridge. The trusses may be put together either by lashing or 
 with pins, or by combinations of both. \ 
 
 272.— PI. 38, Fig. 2, represents the ordinary King-post Truss 
 for spans up to 40 ft. The bridge is put together on the bank, 
 then pushed forward half its length, using rollers under each 
 truss, as shown. A trestle is then leaned forward from opposite 
 bank, and, when truss is over It, the trestle is raised and the end 
 of the truss carried over to the opposite bank. 
 
 273.— Fig. 3 represents the Queen-post Truss for spans up 
 to 50 ft. It is constructed and carried across similarly to the pre- 
 ceding one. 
 
 274.— Fig. 4 shows the Single Lock for spans of 30 ft. It con- 
 sists of two frames similar to the two-legged trestle on PI. 36, 
 Fig. 4. A section of the gap is first marked out on the ground on 
 each bank with the positions of the footings indicated. On these 
 the legs are laid and the positions for lashing the transoms and 
 ledgers marked. The frames are then put together opposite the 
 position they are to occupy (one on each bank), butts towards the 
 gap. One frame is made 15 to 18 in. wider than the other so they 
 will lock, and the footings should be likewise prepared. The dis- 
 tance between legs at transom of narrower frame Is at least 18 in. 
 more than width of roadway between side-rails. With the above 
 exceptions, the frames 'are made like the two-legged trestles. The 
 splay of the legs Is very slight, generally about 1 ft. between tran- 
 som an I ledger. Stout stakes are then driven at the rear, fore and 
 
Spar Bridges. 131 
 
 back guys are attached to the tips of each frame, the fore guys 
 crossed over the stream, those of narrower frame in center. Foot 
 ropes are also attached to each leg near the butts with timber 
 hitches and a turn taken around the stakes at the rear. The frames 
 are then shoved over the banks till they balance (PI. 40, Fig. 1), 
 then brought to a vertical position by hauling on the fore guys, 
 and lowered into their places by easing off on the foot ropes, 
 after which they are pulled over and locked. A couple of balks 
 are then run out, then the fork transom is put into place and the 
 balks rested on it. The remainder of the balks are then run out, 
 placed on the fork transom, lashed, and the roadway completed 
 as usual. If good places for footings cannot be secured, then 
 other means must be provided. 
 
 275.— i^or spcms up to 45 or 50 ft., the Double Lock (PI. 39, 
 Fig. 1) may be used. In this it will be noticed that the balk- 
 bearing transoms are not the transoms first lashed to the frames 
 In making them, but those which are sent out after the frames 
 are in position. This must be remembered in marking the posi- 
 tions of the transoms on the legs of the frames. In this the 
 two frame? are made as described for tTie single lock, except that 
 they are of the same width. They are launched as described, 
 and pulled forward until their tops are about 1-3 the span apart. 
 Two straining beams are then run across, the road-bearing tran- 
 soms fastened on top of them in the positions previously marked. 
 The frames are held by the back guys until all is ready, when 
 they are eased off and the bridge locked. The roadway is then 
 laid as usual. 
 
 27Q.—For spans greater than 45 or 50 ft., where timber of suffi- 
 cient size is obtainable, the Single Sling or Treble Sling may be 
 used. The frames are made as has been described, with the fol- 
 lowing additional observations: 
 
 In the Single Sling (Fig. 2), in marking the positions of the dif- 
 ferent spans, the three locking pieces must be at least 9 or 10 ft. 
 above the roadway. The fork piece is hauled into position by 
 snatch blocks lashed to the top of each leg of narrower frame, 
 after which the blocks are used to get the center transom tempo- 
 rarily Into position, when It Is slung by the ropes that are to hold 
 It, by taking several turns around It and the locking pieces with- 
 out riding, and afterwards twisted up to the proper heljrht with 
 a pole. 
 
PLATE 39. 
 
 Double Lock 
 
 Straining bear^i 
 
 T. T Road bearing transarM 
 45 pn, 
 
 Plgl. 
 
PLATE 4^. 
 
 _ -^. 
 
 
 FIG. 5 
 
134 Spar Bridges. 
 
 277.— In the Treble Sling (Fig. 3) there are three slung tran- 
 soms, one from th^ forks and one from the standards on each side 
 of the middle. The frames are constructed as ah-eady described 
 (PI. 40, Fig. 2, being one in plan.) If necessary, the frames may 
 be strengthened by additional braces on them and further braced 
 back to the banks by ropes attached to holdfasts and otherwise 
 as suggested on PL 40, Figs. 4 and 5, vertical braces being shown 
 in Fig. 3. 
 
 278.— Other expedients for crossing small gaps are the use of 
 wagons in various ways for supports, brushwood made Into 
 gabions, fascines, etc. (Figs. 6 and 7.) 
 
 279.— A light, portable truss (Fig. 11) can be made, where 
 boards are obtainable, by describing two arcs of circles with 
 radii 151 ft., on opposite sides of a 60 ft. chord, then driving 
 stakes on the arcs at intervals of about 2 ft., against which 5 
 layers on top and 6 layers on bottom of boards 1 in. thick x 12 
 In. wide, breaking joints, are bent and securely nailed together 
 every 4 in. with tenpenny nails. The lower side of truss is made 
 gne board thicker than the upper and is completed by driving 
 6 in. spikes througli every 6 in. This truss will be about 6 ft. 
 deep, and, allowing 2 ft. at each end for resting on supports, will 
 bridge a span 56 ft. 
 
 The sides are connected every 5 or 6 ft. by vertical pieces' of 
 plank and two 1-in. iron rods, the latter on the sides of the verti- 
 cals, towards the middle. If iron rods are not obtainable, rope or 
 wire should be wrapped around both and twisted tightly. The 
 angles at the ends are filled with wedge-shaped pieces and the 
 ends securely bolted, hooped, or wrapped. (Fig. 9.) For greater 
 rigidity, light diagonal braces may be inserted in the panels. 
 The top can be made straight instead of curved if so desired. 
 
 These trusses are used in pairs and are applicable to a variety 
 of structures and to spaces of considerable width. Two such 
 trusses with a central support of trestles, crib- work, or boats, may 
 be used for 116 ft. (Fig. 11); three such trusses for 176 ft., etc. 
 In experiments with such trusses in bridges, 1800 lbs. per lineal 
 foot has been applied before breaking; and by covering the boards 
 with pitch and tar before nailing together, inserting % In. bolts 
 in pairs every foot of length on lower side, and nailing boards 
 against the edges, 3500 lbs. per lineal foot was applied before 
 breaking. 
 
Spar Bridges. 135 
 
 280.— Suspension* Bridges. For spans greater than 60 ft.. 
 and when timbers for frames cannot be procured, some form of 
 suspension bridge might be used. Although applicable to longer 
 spans, and the materials more easily transported, they take longer 
 to make than other kinds. 
 
 The cables may be of iron chains, iron, steel or fibrous ropes, 
 or of boards nailed together. 
 
 281.— PI. 40a, Fig. 1, shows one with the roadway hung below 
 the cables, with a camber 1-30. At the center, the roadway 
 should be at least 1 ft. below the cables. The width of roadway 
 between side rails should be only slightly wider than wagon-wheel 
 tracks. (Fig. 2.) On the banks, the cables are supported by tim- 
 ber piers (Fig. 3), having a broad cap (Fig. 4), rounded on top, 
 over which they pass at a distance apart of 9.5 ft. The cables 
 must be securely anchored at the rear to heavy logs sunk 4 or 5 
 ft. in the ground, or otherwise, and drawn in until the sag is only 
 1-10 pr 1-12 of the span. 
 
 282.— In Fig. 5, part of the roadway is hung below and a part 
 rests on the cables, the greatest slope of road being 1 on 6 for 100 
 ft. span and 1-10 sag. The cables are only 7 ft. apart. 
 
 283.— In Fig. 6, the roadway is built on trestles supported on 
 the cables. For spans 130 ft. sag 1-12, the frames form the sides 
 of equilateral triangles of 10 ft. each. To construct it, the curve 
 of the cables is traced on the ground, the trestle legs laid on it and 
 marked where they cross the road and cable; those for each half 
 of the bridge are ranged in order on the banks, connected together 
 as placed on the cables and hauled out, connected at the center, 
 the curve of the cables adjusted and the bridge completed. 
 
 284.— Fig. 7 is a suspension bridge of which the cables are 
 made of boards nailed together in several thicknesses laid hori- 
 zontally, breaking joints; the ends are spread apart and wedge- 
 shaped blocks inserted and anchored by several rows of posts, as 
 shown in Fig. 8. Each cable, as made, is drawn across by ropes, 
 anchored, and the trestles placed from both ends at the same 
 time. Last of all, spikes long enough to reach entirely through 
 the cable are driven every 4 to 6 in. 
 
 285.— Fig. 11 is a similar bridge supported on trestles 16 ft. 
 long, not exceeding 20 ft. high, placed at intervals of 40 ft., over 
 which suspends the two board cables, 14 ft. apart. On these are 
 
PUTE 40a. 
 
Spar Bridges. 137 
 
 placed low trestles, 3 ft. high, dividing the spans into lengths of 
 20 ft. each; 25 ft. balks are used and the roadway laid as usual. 
 The cables are made of six thicknesses, of 1 in. boards 12 in. 
 wide, breaking joints, nailed and spiked every 4 to 6 in., and bolt- 
 ed by pairs of % in. bolts every foot. Three thicknesses of boards 
 are first nailed together and drawn across, the ends anchored, and 
 then the other three boards added. 
 
 286.— For light foot bridges (Fig. 10), across narrow gaps, wire 
 from fences, if available, could be used for the cables by twisting 
 a number together and passing them over crotches of trees and 
 anchoring to stumps, etc., in rear, and then laying the walk simi- 
 lar to some of the methods previously shown. 
 
 287.— So various are the conditions to be met in constructing 
 bridges that seldom will any one type meet the requirements, but 
 by the application of good judgment and resource, with the sug- 
 gestions here offered, almost any gap of reasonable width may be 
 crossed, if not by one type or another, then by a combination of 
 several to meet the emergency. 
 
 The varying strength of timbers makes it almost impossible to 
 give exact dimensions for the different spars to be used in the 
 different types, but a general idea may be obtained below of the 
 amounts and average dimensions of medium strength timber, as 
 yellow pine. For weaker timbers some of the sizes will have to 
 be increased, while for stronger ones there will be an excess of 
 strength if the sizes given are adhered to, but the desire to be on 
 the side of safety warrants the use of amounts which might, by a 
 careful mathematical calculation, appear to be excessive. 
 
 The timbers for transoms, ledgers, braces, balks, flooring and 
 side rails should be selected of as nearly a uniform diameter 
 throughout as possible and will be so considered in giving dimen- 
 sions. For legs or standards the diameter at tip will be given. 
 
 For a 9 ft. roadway with 15 ft. spans, 5 balks 20 ft. long x about 
 6 in. in diam. are used, and placed 2^ ft. apart from center to cen- 
 ter. For the flooring are used poles 11 to 12 ft. long x 4 to 5 in. 
 in diam. For side rails 2 poles 20 ft. long, 4 to 6 in. in diam. 
 
 For each Six-legged Trestle (PI. 36, Fig. 1) 4 vertical and 2 
 bracing legs 6 in. diam.; 1 transom 12 ft. x 8 in.; 2 foot pieces 3 ft. 
 X 8 in.; 10 oak pins 2 in. diam. 
 
 For eacli Tie-block Trestle (Fig. 2) 2 legs 8 in. d!am.; 2 tran- 
 
138 Spar Bridges. 
 
 soms 15 ft. X 8 in.; 4 tie blocks 2 ft. x 5 in. x 6 in.; 2 braces 3 ft. x 
 
 2 in. X 6 in.; 24 spikes, 1 rope, 1 rackstick. 
 
 For each Capped Trestle (Fig. 3) 4 legs 8 in. diam.; 2 braces 
 12 ft. X 4 in.; 2 braces 15 ft. x 5 in.; 3 boards 12 ft. x 2 in. x 12 in.; 
 4 ropes, spikes. 
 
 For each Two-legged Trestle, lashed (Fig. 4), 2 legs 4 ft. 
 longer than height of trestle, 5 to 7 in. tip; 1 transom 15 ft. x 9 in.; 
 
 1 ledger 16 ft. x 4 to 6 in.; 2 braces 3 to 5 in. diam.; 6 ropes 30 ft. x 
 ^ in. diam.; 3 ropes 15 ft. x % in. diam. 
 
 For each Three-legged Trestle, lashed (PI. 37, Fig. 1), 6 legs 3 
 to 5 in. tip; 4 transom bearers 6 ft. x 3 to 4 in.; 4 sticks 2 ft. x 2 to 
 
 3 in.; 6 ledgers 2 to 3 in. diam.; 1 transom 15 ft. x 9 in.; 12 ropes 
 30 ft. X ^ in. diam.; 6 ropes 15 ft x i^ in. diam. 
 
 For each Four-legged Trestle, lashed (Fig. 2), twice the 
 amount given for each two-legged trestle, plus 2 ledgers, and 6 
 lashings 15 ft. long. 
 
 For each Single Lock (PI. 38, Fig. 4) 4 legs 22 to 25 ft. x 7 
 in. tip; 1 fork transom 15 ft. x 10 in.; 2 frame transoms 15 ft. x 6 
 in.; 2 ledgers 15 ft. x 4 to 6 in.; 4 braces 20 ft. x 3 in.; 2 shore sills 
 15 ft. X 6 in. LasMn{/s, 4 transom 50 ft. x ^ in.; 14 ledger and 
 brace 30 ft. x % in.; 10 balks 20 ft. x 1-3 in.; 4 foot 50 ft. x 1 in.; 8 
 guy 150 ft. X 1 in. 
 
 For each Double Lock (PI. 30, Fig. 1) 4 legs 22 to 25 ft. x 7 in. 
 tip; 2 straining beams 25 ft. x 8 in.; 2 road transoms 15 ft. x 10 in.; 
 
 2 frame transoms 15 ft. x 6 in.; 2 ledgers 15 ft. x 5 to 6 in.; 4 
 braces 20 ft. x 3 in.; 2 shore sills 15 ft. x 6 in. Lashings, 8 transom 
 50 ft. X 5^ in.; 14 ledger and brace 30 ft. x % in.; 10 balk 20 ft. x 
 1-3 in.; 4 foot 50 ft. x 1 in.; 8 guy 150 ft. x 1 in.; besides axes and 
 other tools, and anchorages, holdfasts, etc., on banks. 
 
 For each Single Sling (Fig. 2) 4 legs 35 to 45 ft. x 6 in. tip; 
 
 3 top and fork transoms 15 ft. x 6 in.; 3 road transoms 15 ft. x 10 
 in.; 2 ledgers 15 ft. x 4 to 6 in.; 4 braces 20 ft. x 3 in.; 2 shore sills 
 15 ft. X 6 in.; 10 balks 30 ft. x 6 in.; 4 side rails 30 ft. x 4 to 6 in. 
 Lashings of same number, size and length as for Double Lock. 
 Stiffening will require additional spars and lashings, depending 
 upon the method used. 
 
 For each 'I?reble Sling (Fig. 3) 4 legs 50 ft. x 6 in. tip; 5 road 
 transoms 15 ft. x 10 in.; 3 top and fork transoms 15 ft. x G in.; 2 
 
Spar Bridges. 139 
 
 lower ledgers 15 ft. x 4 to 6 in.; 4 lower braces 20 ft. x 3 in.; 4 upper 
 braces 18 ft. x 3 in.; 2 shore sills 15 ft. x 6 in.; 15 balks 5 ft. longer 
 than 1-3 span x 6 in.; 6 side rails 5 ft. longer than 1-3 span x 4 to 
 G in.; 6 sling racking sticks 10 ft. x 4 in. Lashings, 4 foot 50 ft. 
 X 1 in.; 8 guy 150 ft. x 1 in.; 24 ledger and brace 30 ft. x ^^ in.; 
 8 transom 50 ft. x % in.; 40 or 50 balk 20 ft, x 1-3 in. Stiffening 
 will require additional spars and lashings, depending upon the 
 method used. 
 
 For Suspension Bridge 200 ft. long (PL 40a, Fig. 1) 4 to 8 ca- 
 bles 180 ft. X 1 in.; 16 cable seizings of yarn 18 ft. long; 12 lash- 
 ings 50 ft. X 2-3 in.; 10 lashings 30 ft. x ^^ in.; 100 lashings 20 ft. 
 X 1-3 in.; 2 steel wire cables 400 ft. x 1 2-3 in.; 4 standards 26 ft. x 
 10 in. tip; 4 braces 22 ft. x 3^^ in. tip; 2 caps 12 ft. x 10 in.; 2 sills 
 
 15 ft. X 10 in.; 4 back struts 36 ft. x 4 in. tip; 4 side struts 32 ft. x 
 3 in. tip; 4 cable props 30 ft. x 5 in. tip; 4 horizontal ties 30 ft. x 
 3 in. tip; 21 transoms 10 ft. x 6 in.; 80 balks 13 ft. x 6 in.; 40 side 
 rails 20 ft. x 6 in.; for anchorages 16 spars 5 ft. x 7 in. tip; 2 spars 
 
 16 ft. X 20 in.; 2 spars 16 ft. x 12 in. % round; 10 spars 16 ft. x 8 
 in. % round; 4 back ties 50 ft. x 2-3 in. steel rope; 4 ties 35 ft. x ^ 
 in. steel rope; 40 slings total 600 ft. x % in. steel rope; 4 guys 50 
 ft. x 1 in.; 4 rope ladders. 
 
 For Suspension Bridge 100 ft. long (Fig. 5) 4 to 8 cables, 12 
 cable seizings, 4 lashings, 12 lashings, 30 lashings as above; 2 
 cables 180 ft. x 3 in. hemp or 2 in. steel; 2 anchor spars 18 ft. x 15 
 in.; 10 transoms 12 ft. x 4 in.; 4 balks 25 ft. x 6 in.; 10 side rails 20 
 ft. X 4 in. ; materials for piers depending on circumstances. 
 
 For Suspension Bridge 130 ft. long (Fig. 6) 4 to 8 cables, 12 
 cable seizings, 9 lashings, 104 lashings, 280 lashings as above; 4 
 cables 200 ft. x 2 2-3 in. hemp or IV2 in. steel; 2 anchor spars 18 ft. x 
 18 in.; 44 trestle legs 13 ft. x 3 in. tip; 44 braces 15 ft. x 2 in. tip; 22 
 transoms 9 ft. x 4 in.; 80 ledgers 12 ft. x 2 in.; 20 cable ledgers 12 
 ft. X 5 in.; 2 shore sills 10 ft. x 5 in.; 48 balks 14 ft. x 5 in.; 28 side 
 rails 20 ft. x 5 in.; materials for piers depending on circumstances. 
 
 Besides the above materials, there will be required tools for 
 cutting timber, tackles for raising frames, shovels, pickets, etc., 
 and, where not mentioned, the ordinary amounts of balks, chess, 
 side rails, etc. 
 
CHAl»TEJt XVl.- tloating Bridged. 
 
 288.— The passage of a stream may be effected, in many cases, 
 as described in the preceding chapter. If the methods there laid 
 down are not suitable or expedient, and the stream cannot be 
 forded, then resort must be had to ferrying by boats, rafts, flying 
 bridges, or to floating bridges. 
 
 289.— The selection of a place and means of crossing a river 
 is determined by a reconnaissance, which should be as detailed 
 and extensive as circumstances will permit, and embrace the 
 following:— / 
 
 (a) The nature of the banks. 
 
 (h) The nature of the bed. 
 
 (c) Position and depth of fords. 
 
 (d) Strength of the current. 
 
 (e) Whether tidal or otherwise. 
 
 (f) Probability and extent of floods. 
 
 290.— Fords. A stream with a moderate current may be 
 forded by infantry when its depth does not exceed 3 ft., and by 
 cavalry and carriages when its depth is about 4 ft. The requi- 
 sites of a good ford are:— 
 
 (a) Banks low, but not marshy. 
 
 (h) Water attaining its depth gradually. 
 
 (c) Current moderate. 
 
 (d) Stream not subject to freshets. 
 
 (e) Bottom even, hard, and tenacious. 
 
 291.— In a mountainous country, the bed of a stream is likely 
 to be covered with large stones, rendering the passage of car- 
 riages impracticable. In level countries, the bed of the stream 
 may be composed of mud or quicksand, rendering passage by 
 fording impossible. In some cases, the bottom is composed of 
 fine sand, which is hard enough, but which, by the action of the 
 hoofs of the animals, is stirred up; the current then carries the 
 sand away and the ford is deepened, perhaps so much as to be- 
 come unfordable. The best bottom is coarse gravel. 
 
 292.— Fords are usually found In the wider and more rapid 
 parts of a stream. A straight reach gives the most uniform 
 depth. At bends, the depth will generally be greater at the con- 
 cave bank and less at the convex. (PI. 41, Figs. 1 and 3.) 
 
PLATE 41. 
 
 -i^ ^ 
 
1^2 Floating Bridges. 
 
 293.— To determine the position of a ford:— 
 
 (1) A number of mounted men may be sent across wherever 
 there is a probability of the river being shallow enough. 
 
 • (2) Most certain method. Float down the stream in a boat, 
 keeping in the swiftest part of the current, where the water is 
 usually deepest. Hang a sounding line of the proper length over 
 the stern. When this touches bottom, sound across the stream. 
 
 When a ford is discovered, it should be marked by stakes; re- 
 markable objects on the shore should be noted; and a stake 
 planted at the water's edge and marked, in order that any rise 
 in the water may be at once evident. 
 
 294.— A stream, otherwise unfordable, may be passed:— 
 
 (1) By crossing it in a slanting direction. (Fig. 2.) 
 
 (2) When the unfordable portion is not over 8 or 10 yards, this 
 may be filled in with fascines loaded with stones. (Fig. 4.) 
 
 (3) When the bottom is muddy, it may be covered with bun- 
 dles of coarse grass, rushes, or twigs, sunk by means of stones. 
 
 (4) A portion of the water may be diverted from its natural 
 channel. (Fig. 5.) 
 
 295.— In passing a stream by fording, if it is deep and the cur- 
 rent at all swift, the following precautions should be taken:— 
 
 (a) Troops passing in column should do so at a considerable 
 interval, in order to avoid choking the stream. 
 
 (h) If boats are to be had, a few should be stationed below the 
 ford, to assist men who may be carried down by the current. 
 
 (c) If boats cannot be procured, mounted men may perform 
 the duties described in the foregoing provision. 
 
 (d) In place of provisions "b'* and "c," a life line, held up by 
 casks, may be stretched across the stream. 
 
 (e) In order to break the force of the current, cavalry may be 
 stationed in the stream, above the point of crossing. 
 
 296.— After a freshet, a ford should always be reexamined, 
 lest some alteration may have taken place in the bed of the 
 stream. The banks of a stream to be forded should, if necessary, 
 be cut down. 
 
 The velocity of a stream may be determined by throwing in a 
 light rod, so weighted as to stand vertically. Note the distance 
 passed over in a certain number. of seconds; then, 7-10 the mean 
 number of feet per second gives the velocity in miles per hour. 
 
Floating Bridges. 143 
 
 297.— Ice. In high latitudes, duiiug the winter, rivers are fre- 
 quently covered with ice of sufficient thickness to sustain the 
 heaviest loads. This means of passing a stream should be used 
 with great circumspection. A change of temperature may not 
 only suddenly destroy the natural bridge, but render the river 
 impassable by any method, for a considerable time, in conse- 
 quence of floating ice. 
 
 298.— Ice, in order to allow of passage, should be of the follow- 
 ing thickness:— 
 For Infantry, single file, 2 yds. distance, on a line of 
 
 planks 2 in. 
 
 For Cavalry or light guns, with intervals 4 in. 
 
 Heavy field-pieces 5 to 7 in. 
 
 Heaviest loads 10 in. 
 
 299.— When there is any doubt as to the strength of the ice, 
 two tracks of plank may be laid for the carriage wheels to run 
 on, or the wagon may be transformed into a kind of sled by fas- 
 tening two planks under the wheels. (Fig. 6.) 
 
 The thickness of ice may be increased, when the temperature 
 is low, by throwing water on it. When a stream is frozen on each 
 side but open in the middle, in consequence of the velocity of the 
 current, a boom stretched across the open space will often check 
 the velocity sufiiciently to allow the water to freeze. 
 
 300.— If a stream cannot be forded, it may be crossed by fer- 
 rying or by constructing a bridge. Ferrying may be by boat, 
 raft, or flying bridge; rowed, sheered, or hauled across. 
 
 301.— Ferrying by Boat. All boats available should be 
 collected and taken to the chosen point of passage. The banks of 
 the stream, if steep, should bo cut down to facilitate embarkation. 
 The landing should be farther down the stream than the point 
 of starting. The boats should be arranged along the shore and 
 numbered. Entrance to the boats should be by file, the soldiers 
 taking positions on opposite sides alternately. Where the water 
 is shallow near the shore, the boat should not approach the bank 
 so closely as to ground as the men file in. The unloading should 
 be made in the same manner as the embarkation — i. e., by file 
 alternately from each side of the boat. During the transit, the 
 men should remain in position and not rise up suddenly when the 
 boat lurches. 
 
 In passing artillery, the piece should be dismounted. Horses 
 
144 Floating Bridges. 
 
 should, ordinarily, be made to swim. However, if the boats are 
 large enough, the bottoms may be covered with plank, and the 
 horses placed crosswise, facing alternately up and down stream. 
 
 302.— Ferrying by Raft. Rafts may be made of logs, lum- 
 ber, casks, and other material suitable for the purpose. Their 
 construction is the same as explained for piers of bridges, hence 
 only two expedients will be mentioned here. 
 
 303.— The Canvas Raft. No other material being available, 
 small rafts can be constructed by the use of canvas about 8 x 
 12 ft, and brushwood. Wet the canvas to make it water-proof, 
 and lay it out on the ground. Across the width place sticks in 
 layers, the longest near the middle. The sides should be strength- 
 ened by heavy sticks placed lengthwise. The pile of sticks 
 should be about 4 ft. wide in the center and sloping off slightly 
 towards the ends, 3 ft. high and 8 ft. long. Over this pile a sec- 
 ond piece of canvas, after being wet, should be placed. The 
 sides of the canvas on the ground are now drawn over toward 
 each other and lashed securely with a lariat. The ends are folded 
 neatly, brought up towards each other, and lashed. If care is 
 taken to w^et the canvas thoroughly and make it water-tight, this 
 raft will carry three troopers with their arms and accouterments. 
 By lashing several together, a larger number of men, with their 
 arms and accouterments, can be carried. 
 
 304.— Rafts of Skins. Bags, made of the skins of animals, 
 Inflated with air or stuffed with hay or straw, can be utilized for 
 crossing streams, and have been used from ancient times. 
 
 305.— Rafts are more suitable for the embarkation and landing 
 of troops of all arms than boats. They will carry a larger num- 
 ber each trip, are not so easily injured by the fire of the enemy, 
 and draw little water. On the other hand, they cannot be navi- 
 gated with the same facility as boats, move much more slowly, 
 and hence keep the troops much longer under fire; cannot be 
 directed with certainty on a fixed point when the stream is rapid, 
 and, If the passage is to be effected secretly, the time required for 
 their construction Is too long to admit of their use. 
 
 306.— The Floating Bridge.* This may be formed of two 
 
 _*A simple modification of the floating bridge is an expedient used in the Philip- 
 pine Islands for floating wagons across deep streams. 
 
 This is merely to run the vehicle into the stream astride of two bancas (narrow 
 dugouts), the axles resting on the gunwales and the boats as far apart as the 
 hubs of the wheels will allow. Wagons can thus be readily crossed without un- 
 loading, provided the bancas are large enough to support the weight. 
 
Floating Bridges. 145 
 
 boats covered with a platform, constructed as follows:— (PI. 42, 
 Fig. 1. — The lashings and side rails are omitted.) From 5 to 7 
 beams of the same thicliness are laid across the two boats, the 
 intervals between the beams being equal, and such that the cover- 
 ing planks extend 1 ft. beyond the extreme beams. The interval 
 between the boats is such as to allow the beams to extend 2 ft. 
 beyond the gunwales. The beams are lashed to the boats, the 
 covering planks are kept in place by 2 side rails, laid directly over 
 the outer beams, and lashed down to them; the extreme planks 
 should be nailed down. 
 
 The floating bridge can be navigated by oars with nearly the 
 same facility as a boat. 
 
 307.— The Rope Ferry. The rope ferry, which is used in slug- 
 gish streams, consists of a floating support, either a raft, float- 
 ing bridge, or a large boat. It is drawn by hand along a rope 
 stretched from shore to shore. 
 
 308.— The Trail Bridge. This is employed in streams not 
 more than 150 yds. in width, and whose current is not less than 3 
 ft. per second, or 2 1-10 miles per hour. The rope must be main- 
 tained above the surface of the water, and, consequently, must be 
 drawn very tightly by means of a windlass, blocks, and falls, or 
 similar expedients; it must, also, at each bank, be raised some dis- 
 tance above the water.* (PI. 42, Fig. 3.) 
 
 *A convenient expedient for tightening the rope when no blocks are at hand is 
 here shown. 
 
 Another rope "r" is attached to the ferry rope *'R" at "a" by a stopper hitch and 
 then passed round the holdfast and through a loop "b" in the ferry rope: power is 
 then applied as indicated by the arrow, the slack of the ferry rope being taken in 
 at "c." When the ferry rope is taut, enough the attached rope "r" is eased off 
 thus letting the strain come gradually upon the cable again. 
 
PLATE 42. 
 
 Fig.l. 
 
 Fig. 2. 
 
J PLATE 43. 
 
148 Floating Bridges. 
 
 The raft, or boat, is attached to a pulley, which runs on a sheer 
 line, and by means of a rudder is given such a position that its 
 side makes an angle of about 55° with the direction of the cur- 
 rent. The angle of 55° with the current divides its force against 
 the side of the boat into two components: one, perpendicular to 
 the sheer line, which is counteracted by the resistance of this 
 line; the other, parallel to it, which moves the boat. A boat for 
 this kind of ferry should be narrow and deep, with nearly ver- 
 tical sides. 
 
 If a raft is used, it should be lozenge-shaped, the acute angle 
 being about 55°. When two sides are parallel to the current, the 
 up-stream side will then be in the most favorable position for 
 passage. (PI. 43, Fig. 8.) 
 
 309.— The Flying Bridge. The character of the float for 
 this ferry is the same as in the preceding case. (PI. 41, Fig. 7; 
 PI. 42, Fig. 2.) This bridge is resorted to when the stream is 
 wider than 150 yds. The strain on the sheer line being very 
 great, it is replaced by a cable anchored in mid-stream, in which 
 case the float would swing between two landing piers; or by two 
 cables, one anchored on either bank, the float swinging between 
 four piers. The latter requires less skill in manipulation. The 
 angle w^hich the float makes with the current is the same as that 
 of the **trail" bridge. A sharp bend may be utilized for anchor- 
 ing the cable, as shown in PI. 42, Fig. 4. 
 
 The length of a swinging cable should be 1% to 2 times the 
 width of the stream. The cable should be supported on inter- 
 mediate buoys or floats, to prevent it dragging in the water. 
 
 310.— Floating Bridges are composed of a roadway and its 
 supports. The roadway is explained in the preceding chapter. 
 The supports are floating, as pontons, boats of commerce, rafts 
 of barrels, logs, lumber, inflated skins of animals, or other mate- 
 rial. The supports are called floating piers. It is from the char- 
 acter of the support that the bridge derives its name. 
 
 311.— In constructing a floating bridge, the site should be first 
 selected and the icidth of the stream measured. 
 
 In selecting a site, the following points should be noted:— 
 
 (a) Proximity to a road. As the approaches to floating 
 bridges, having frequently to be constructed across meadows, give 
 
Floatmg Bridges. 149 
 
 * mucli trouble, they should be as short as possible. For a similar 
 reason, marshy banks are undesirable. 
 
 (h) The bed of the stream, if anchors are required, should 
 afford good holding ground. 
 
 (cj A bridge can be best defended if constructed at a reenter- 
 ing bend of a river. 
 
 (dj Use can frequently be made of islands to economize 
 material. 
 
 312. — In measuring the loidth of the stream, if it cannot be 
 done directly, some one of the methods explained in Chap. III. 
 can be used. 
 
 313.— It should be remembered that a wide roadway gives 
 greater steadiness than a narrow one. In making calculations 
 for buoyancy, the weight of a 9 ft. roadway may be taken at 80 
 lbs. per running foot. 
 
 314.— Piers. Of whatever material the floating pier is made, 
 the following points should be observed:— 
 
 (1) The available buoyancy of each pier should be sufficient to 
 support the heaviest load that can be brought on one bay of the 
 bridge. 
 
 (2) Piers should be connected with each other, at their extremi- 
 ties, by tie balks or lashings. 
 
 (3) To insure steadiness, the length of a pier should be at least 
 twice the width of the roadway. 
 
 (4) The water way between piers should, if possible, be more 
 than the width of two piers, never less. 
 
 315. — Piers of open boats. In forming a pier of open boats, 
 the following precautions should be taken:— 
 
 (1) The boat should not be immersed deeper than within 1 ft. 
 of the gunwale. 
 
 1 2) If the water is rough, or the current extremely swift, -a 
 boat should not be immersed deeper than within 1 ft. 4 in. of the 
 gunwale. 
 
 (3) Boats should be placed in bridge with bows up stream or 
 toward the current. 
 
 (4) If the stream is tidal, the bows of the boats should be alter- 
 nately up and down stream. 
 
 (5) Unless the boat is very heavy and strong, the balks should 
 
150 Floating Bridges. 
 
 not rest on the gunwales; a central transom should be impro- 
 vised by resting a timber on the thwarts, or seats, blocking up 
 from underneath and bringing the weight directly on the keel- 
 son. (PI. 43, Figs. 6 and 7.) 
 
 (0) T/arge boats should be placed where the current is swiftest, 
 also as the first and last boats in bridge. 
 
 316.— The buoyancy of a boat may be found by one of the 
 following rules:— 
 
 (1) To find the available buoyancy load the boat with unarmed 
 men to a safe depth. Multiply the number of men thus loaded by 
 160. The result will be the available buoyancy in pounds, 
 
 (2) If the boat is afloat and empty, the available buoyancy may 
 be found by calculating the volume between the then water line 
 and the "safe load" line, and multiplying by 62%. 
 
 (3) To find the total buoyancy. If the boat is of nearly uni- 
 form section, the area of the section multiplied by the length of 
 the boat will give the cubic contents. A cubic foot of water 
 weighs 621^2 pounds. 
 
 Hence, If the dimensions of a boat are taken in feet, the con- 
 tents will be cubic feet, and this, multiplied by 62%, will give the 
 displacement of the boat: from this subtract the weight of the 
 boat: this will give the total buoyancy. 
 
 317.— To find the length of a bay. First find the avail- 
 able buoyancy of the boat. Then find the weight per running 
 foot of the load the bridge is to bear, and to this add the weight 
 per running foot of the roadway. Divide the available buoyancy 
 by this sum. The quotient will be the distance in feet from center 
 lo CRnter that boats should be placed apart. Thus: — Suppose th'- 
 weight per running foot is 480 lbs., that the roadway is 80 lbs. 
 per running foot. .*. 480+80=560. The available buoyancy is 
 found by one of the preceding rules to be 5,600 lbs. .*. 5,600 -^ 
 560=10, the distance in feet between centers of boats. 
 
 318.— The open boats may be:— (1) Those of commerce usually 
 found on streams. (2) Regularly constructed pontons. (3) Im- 
 provised boats. 
 
 The first class requires no description. The second class com- 
 prises the canvas ponton used In the Advance Guard Train, and 
 the boat or barge used in the Reserve Train, of the U. S. 
 
Floating Bridges. 
 
 151 
 
 319.— The table below gives the dimensions of the ponton In 
 the U. S. Advance Guard Train, shown in PI. 47. 
 Canvas Ponton 21' x 5' 4" x 2' 4". Weight, 510 lbs. 
 Balks 22' x 4y2" x 4y2". 
 Side Rails same as BalliS. 
 Chess 11' X 12" X 1%". 
 
 WEIGHTS FOR ADVANCK GUARD TRAIN. 
 
 Wag"on. 
 
 Total. 
 
 lbs. 
 
 1 lbs. 
 
 lbs. 
 
 1,750 
 
 1,985 
 
 3,735 
 
 1,750 
 
 1,856 
 
 3,606 
 
 1,750 
 
 2,060 
 
 3,810 
 
 1,700 
 
 1,938 
 
 3,638 
 
 1,217 
 
 1,166 
 
 2,385j 
 
 Ponton 
 Chess .. 
 Trestle 
 Tool. . . 
 Forge. . 
 
 320.— The table below gives the dimensions of the ponton in 
 the U. S. Reserve Train, shown in PI. 48. 
 
 Ponton 31' x 5' 8" x 2' 7". Weight, 1,600 lbs. 
 Balks 27' x 5" x 5" for a 20' span. 
 Trestle Balks 21' 8" x 5" x 5". 
 Chess 13' X 12" x IVa". 
 Side Rails same as Balks. 
 
 WEIGHTS FOR RESFRVE TRAIN. 
 
 
 Wagon. 
 
 Ivoad. 
 
 Total. 
 
 Ponton 
 
 lbs. 
 2,200 
 1,750 
 2,200 
 1,700 
 2,217 
 
 lbs. 
 2,900 
 2,280 
 2,635 
 2,100 
 1,166 
 
 lbs. 
 5,100 
 
 Chess 
 
 4,030 
 
 Trestle 
 
 4,835 
 
 Tool 
 
 3,800 
 
 Forge 
 
 3,383 
 
 
 
 321.— Improvised Boats. To reduce the amount of transpor- 
 tation required by an army is a very important consideration; 
 hence the value of the following expedients. 
 
 322.— The Crib Ponton. This boat is 18 ft. long, 5 ft. wide, 
 2% ft. deep and covered with canvas. Construction. (1) Let 
 stakes 4 ft. long, 2^^ in. in diameter, and 2 ft. apart, be driven into 
 the ground (PI. 44, Figs. 1, 2 and 8), to tlie depth of about 1 ft., so 
 as to enclose a space of the proper si^e for the top of the boat 
 
PLATE 44. 
 
 Fig 1. 
 
 Illllll 
 
 Pig. 2 
 
 ^ 4fh^U 9 /d ^ ' > ^'hA'^J^ ^ 
 
 Fig. 3. 
 I I I I 
 
 Fig.4. 
 
 Fig. 6. 
 
 Fig.7 
 
 ! ^^ 4 
 
 Fig.a 
 
 Fig. 5. 
 
 iniuinii iiiiiiniiuiiiuiiiiiHnnnm iMi 
 
 ■aWRHIHH^WPWWW 
 
Floating Bridges. 153 
 
 The tops of the stakes should be In the same horizontal plane. 
 This may be tested by placing a sti*aight-edge on them. Those 
 that are too high can then be driven down. 
 
 (2) Nail boards against the outside of the stakes, extending 
 4 in. over their tops. 
 
 (3) Cross-pieces, of the same diameter as the stakes, are laid 
 across the tops and pinned down upon them with wooden pins. 
 
 (4) Nail the side boards to the ends of the cross-pieces, and 
 cover the bottom of the boat, which in its inverted position is 
 now on top, with boards, and nail the projecting edges of the 
 side boards to the bottom securely. 
 
 (5) Finish boarding sides and ends to the proper depth. 
 
 (6) The frame is now ready to be covered with canvas. For a 
 boat of the foregoing dimensions, the canvas should be 23% ft. x 
 10% ft., about 6 in. being allowed for lap. The canvas may be put 
 together in any number of pieces by daubing the edges of the 
 seams with a water-proof composition and connecting them with 
 ordinary carpet tacks. 
 
 (7) The canvas having been prepared, it should now be coated 
 with a water-proof composition. Tallow, put on hot, will do if 
 nothing better can be found. 
 
 (8) Place the canvas on the frame, coated side downward. Tack 
 the canvas to the frame and cover with water-proof composition. 
 
 (9) Spike or pin 2 or 3 stout poles to the bottom longitudinally 
 (not shown in drawing) to keep the bottom from abrading. If 
 these poles are allowed to project about 6 in. at each end, they 
 will assist in launching. 
 
 (10) Loosen the stakes from the ground by means of levers. 
 Turn the boat over and saw off the stakes about 2 in. below the 
 top edge of the side and end boards. 
 
 (11) Pin stout poles to the top of the stakes on the sides and 
 ends, and nail the side and end boards securely to them. 
 
 (12) The side poles should project about 6 in. beyond the ends 
 corresponding to those on the bottom, and be lashed to the bot- 
 tom poles by means of a rope loop and rack stick. (Not shown in 
 drawing.) 
 
 (13) Turn the canvas over the top poles and tack ft down. The 
 boat Is finished. 
 
 323. — Th^ Box Ponton. In localities where planks and hoards 
 
154 Floating Bridges. 
 
 can be conveniently procured, pontons may be constructed very 
 expeditiously by placing two partitions of 2 in plank, each 5 ft. 
 long and 2% ft. high, in parallel positions, on the top and ends of 
 which boards are nailed. (PI. 44, Fig. 4.) The box thus formed 
 to be covered with pitched canvas, as described in the mode of 
 constructing crib pontons. Where sound lumber is at hand, the 
 box ponton will be more easily and expeditiously constructed 
 than the crib ponton, but if plank is not at hand it may be prefer- 
 able to use poles or split timber rather than wait for it. 
 
 324.— Wagon Body Ponton. Ordinary wagon bodies, cov- 
 ered with water-proof canvas or India rubber blankets, may be 
 used either as boats or pontons. The small capacity of the 
 wagon body requires such pontons to be placed more closely, to 
 compensate for it. 
 
 325. — ^Piers of Barrels. In order to determine the number of 
 barrels necessary to form a pier, the buoyancy of a barrel must be 
 calculated. This maybe done by one of the following rules:— 
 
 (1) Find the contents of the barrel in gallons and multiply this 
 by 8 1-3; the result will be almost the total buoyancy in pounds. 
 
 (2) By the formula 
 
 5c2 1 — W = X 
 in which c is the circumference of the barrel in feet half way be- 
 tween the bung and the extreme end; 1 is the length in feet, ex- 
 clusive of projections, measured along a stave, and W is the 
 weight of the barrel in pounds; x being the total buoyancy. 
 If the barrel is closed, 9-10 of the total buoyancy equals the avail- 
 ahle buoyancy. 
 
 326. — To find the distance between two piers of barrels: Find 
 the available buoyancy of each barrel. Multiply this by the num- 
 ber of barrels in the pier. This gives the available buoyancy of the 
 pier. To the weight per running foot that the bridge is to bear 
 add the weight per running foot of the superstructure. Divide 
 the available buoyancy of the pier by this sum; the quotient will 
 be the required distance in feet between centers of piers. 
 
 327. — In regard to piers of barrels, the following should be 
 noted: 
 
 (1) That piers of barrels, when in bridge, should always be rig- 
 idly connected to each other at their ends by tie balks. 
 
Floating Bridges. 155 
 
 (2) That the tie balks should be lashed to both gunnels of each 
 pier. 
 
 (3) That while the roadway balks may not be lashed to the 
 gunnels and to each other, it should be done if there is much 
 sway to the bridge. 
 
 328. — Piers of Open Barrels. This is the simplest and most 
 convenient method of using barrels for piers, as it requires only 
 a few nails and poles, dispensing with ropes, which are sometimes 
 hard to procure. 
 
 To make a raft of this kind, as shown in PI. 44, Figs. 5 and 6, 
 stand 10 or 12 barrels side by side, touching each other; nail 4 
 poles across the* outside of the barrels, two at top, two at bottom, 
 the nails being driven from the inside into the poles, which, as 
 the heads are out, can easily be done. Place another row of bar- 
 rels beside the row thus fastened together and nail them to the 
 two poles of this row. Nail two poles to the outside of the second 
 row of barrels, one at top and one at bottom; push the barrels 
 thus connected into the water. 
 
 If too many rows are connected on land they will become too 
 heavy to handle. Any number of rows, however, can be attached 
 in the manner described above. When the raft is completed, the 
 projecting ends of the poles outside are lashed together, and, at 
 the points of contact of the barrels, a stout wire nail should be 
 driven through and clinched. 
 
 329. — The total buoyancy of a barrel may be calculated by the 
 formula given above. If this should be 400 lbs., the safe load for 
 smooth water would be at least 300 lbs.; that is, the available 
 buoyancy is about % the total buoyancy. A square raft of 10 
 such barrels to a side would carry safely 30,000 lbs. 
 
 330.— Piers of Closed Barrels. The usual method of forming 
 large barrels into a pier is shown in PI. 43, Figs. 1 and 2. The fol- 
 lowing are the successive steps in its construction:— 
 
 Stores required for a pier of 7 barrels: 7 barrels; 2 gunnels; "2 
 slings; 12 braces. 
 
 To build a pier of the foregoing stores, 1 N. C. O. and 16 men 
 will be required. The detachment is marched to the site on 
 which the material is placed and forms the barrels into piers by the 
 following commands and means, 4 men being detailed as gunnel- 
 men and 12 as bracemen. 
 
156 Floating Bridges. 
 
 (1) Align barrels. At this command, the barrels are brought to 
 the designated place by the bracemen and aligned, touching each 
 other, bung uppermost. 
 
 (2) Place gunnels. At this command, the gunnels are placed 
 on the outer ends of the barrels by the gunnelmen. 
 
 (3) Adjust slings. At this command, gunnelmen bring up 
 the slings and stand at the ends of the gunnels, the bracemen be- 
 ing opposite the intervals between the barrels. The gunnelmen at 
 one end place the eyes of the slings over the ends of the gunnels, 
 and those at the other end secure the slings to the ends of the 
 gunnels by a round turn and two half-hitches. The bracemen 
 keep the slings under the ends of the barrels with their feet. A 
 sling is made of 1 in. rope and of sufficient length for an eye splice 
 1 ft. long, at one end. 
 
 (4) Fasten braces. At this command, the bracemen, having 
 provided themselves with braces, pass the eye of the brace under 
 the sling in the center of their interval the end passed through 
 the eye and the brace hauled taut, the sling being steadied by 
 either foot. The brace is then brought up outside the gunnel, 
 directly over the eye, and a turn round the gunnel taken to the 
 left of the standing part. 
 
 (5) Haul taut. At this command, each braceman removes 
 his foot from the sling and hauls up the standing part of his 
 brace with his right hand, holding on to the turn with his left; 
 as soon as the brace is taut, the turn is held with the left hand 
 and the remainder of the brace in a coil is placed on the barrel to 
 the left. 
 
 (6) Cross braces. At this command, each braceman takes the 
 brace of the man opposite him from the barrel on his right, pass- 
 ing it between the standing part of his brace and the barrel on 
 his left, then back between his brace and the barrel on his right, 
 keeping the turn below the figure of eight knot on his own brace. 
 The end is then placed on the barrel on his right. Each man then 
 takes back his own brace from the barrel on his left, passes it un- 
 der the gunnel to the left of the standing part, places one foot 
 against the gunnel and hauls taut. 
 
 (7) Rock and haul taut. The bracemen, assisted by the gun- 
 nelmen, at this command, rock the pier backwards and forwards, 
 the bracemen taking in the slack of their braces. ^ 
 
Floating Bridges. 15'V 
 
 (8) Steady. At this command, the bracemen cease rocking 
 and take a turn round the gunnel to the left of the previous 
 turns. 
 
 (9) Secure braces. At this command, the braces are made fast 
 by two half -hitches round the two parts of their own braces, close 
 lo the gunnels, drawing the two parts close together and placing 
 the spare ends of the braces between the barrels. 
 
 (10) Turn the pier to the right and adjust sling. At this 
 command, the bracemen on the left side, assisted by the gunnel- 
 uien, turn the pier on its right side. The bracemen on the left 
 feide adjust the left sling. 
 
 (11) Lower the pier, turn to the left, and adjust sling. 
 xVt this command, the bracemen on the left, assisted by the 
 i»:unnelmen, lower the pier. The bracemen on the right, assist- 
 ed by the gunnelmen, then turn the pier to the left. The 
 bracemen on the right then adjust the right sling. The pier is 
 complete. 
 
 331. — Should the barrels be very small, they may be put to- 
 gether as above described, forming small piers. These can then be 
 united in one large pier by cross gunnels. 
 
 332. — Another method of forming barrels into a pier is as fol- 
 .ows:— (Figs. 3 and 4.) 
 
 Fasten the braces to a balk, two braces for each barrel. Stretch 
 out the braces perpendicular to the balk and lay the barrels bung 
 uppermost, end to end, on each side of the balk, each barrel over 
 its own braces. Upon the cask lay two gunnels, fastened together 
 at the ends and one or two intermediate points by lashings, the 
 distance between the gunnels being less than a bung diameter of 
 a barrel. Secure the braces to the gunnels by two round turns and 
 two half-hitches. The lashings connecting the gunnels are then 
 racked up. The two end gunnel lashings are lashed to the balk 
 beneath the barrels and these lashings are racked up taut. The 
 pier is then complete. 
 
 333.— The barrels may be held in a frames as shown In PI. 44, 
 Mgs. 7 and 8. 
 
 334.— Piers of Logs. In order to determine the number 
 of logs necessary to form a pier, the buoyancy of a log must be 
 calculated. 
 
158 Floating Bridges. 
 
 To find the total buoyancy of a log. Multiply the solid con- 
 tents of a log by the difference between the weight of a cubic foot 
 of the log and a cubic foot of water. 
 
 335.— To find the solid contents of a log. 
 
 (1) Take a mean of the girths or circumference at the ends in 
 feet and decimals. Square this mean and multiply it by the dec- 
 imal .07956. Multiply this product by the length of the log in 
 feet. 
 
 (2) Multiply twice the square of 1-5 of the mean girth by the 
 length of the trunk. 
 
 336.— The weight per cubic foot of the timbers usually met 
 with will be found in Chap. XV. 
 
 337.— Required the total buoyancy of a pine log whose mean 
 girth is 6 ft. and whose length is 35 ft. 
 
 Applying rule 2, we have 
 
 2X|X|X35 = lOOi cu. ft. 
 
 100 i X (62^ — 40) = 100 f X 221^ = 100.8 x 22.5 = 2,268 lbs. 
 
 As lumber absorbs water, the available buoyancy is taken as 5-6 
 the total buoyancy. 
 
 338.— To form a pier of logs. (PI. 43, Fig. 5.) The larg- 
 est and longest logs should be selected. Branches and knots 
 should be trimmed off. The ends of the logs should be painted if 
 the raft is to be used any length of lime. The raft should be 
 built in the water. Select a place where there is little current 
 and where the bank slopes gently to the stream. Throw the tim- 
 ber into the water and moor it close to the shore. Note the nat- 
 ural position of each log in the water before putting it in the rart. 
 The up-stream end of each log should be drawn on shore and bev- 
 eled to a whistle shape, so as to present less obstruction to the 
 action of the current. 
 
 Arrange the timber in the position it is to have in the raft, the 
 butts alternately up and down stream, the up-stream ends forming 
 a right angle, salient up stream. The first log is brought along- 
 side the shore and the end of a plank or a small trunk of a tree 
 fastened with trenails or spikes to it about 3 ft. from each end. 
 The log is then pushed off a little, a second log brought up under 
 the transoms and in close contact with the first. The second log 
 is then spiked like the first, and so on for each remaining log. 
 Care must be taken to place the whistle ends up stream with the 
 
PLATE 45. 
 
PLATE 46. 
 
PLATE 47. 
 
PLATE 48 
 
Floating Bridges. 163 
 
 bevel underneath, and to spike the transoms perpendicular to the 
 logs. If the stream is very gentle, the up-stream ends of the logs 
 need not be placed as in Fig. 5, but may be parallel to the 
 transoms. 
 
 Another metJiod is to lash the logs together and fasten on the 
 transoms with spikes or trenails. Or, lash the logs together and 
 lash the transoms to the logs, tightening the lashings with rack 
 sticks. 
 
 339.— Two additional transoms should be placed on the raft 
 by whatever method employed in putting on the first. They 
 should be the distance of the roadway or platform apart, at equal 
 distances from the center of gravity of the raft, and bear upon all 
 the logs. In order to obtain sufficient buoyancy, and allow suf- 
 ficient water way, several courses of timber may have to be em- 
 ployed. For use in a bridge, a raft should have an available 
 buoyancy of 15,000 lbs. 
 
 340.— If the raft is to be used as a flying bridge, it should have 
 the shape of a lozenge. (PI. 43, Fig. 8.) 
 
 341.— Anchors. Anchors for the U. S. Advance Guard Bridge 
 Train weigh 75 lbs., and for the Reserve Train 150 lbs. These 
 will be sufficient for moderate streams. An anchor with the 
 names of the various parts Is shown in PI. 45, Fig. 1. 
 
 342.— The distance of the anchor from the bridge should be 
 at least 10 times the depth of the stream; otherwise the bow of 
 the boat or ponton will sink too deep in the water. The direction 
 of the cable must be the same as the current. The anchor cable 
 should be of 1 in. rope and attached to the anchor ring by a fish- 
 erman's bend. A buoy might be attached to the anchor by means 
 of a i/^-in. breast line, in order to mark its position and serve as 
 a means of raising it. The breast line is attached to the buoy 
 ring by a fisherman's bend and round the shank of the anchor, 
 close to the crown, by a clove hitch. 
 
 343.— The number of anchors will depend on the strength of 
 the current. It is generally sufficient to cast an anchor up-stream 
 for every alternate boat or ponton, and lialf that number down- 
 stream. If the stream is rapid, every boat should be anchored 
 up-stream. 
 
 If very rapid, the bridge must be secured to a hawser, as shown 
 In PI. 46, Fig. 1. If the bridge is short, ropes can be stretched 
 
164 Floating Bridges. 
 
 from the piers to the banks. (Fig. 2.) If anchors are scarce, one 
 may be attached to two piers. (Fig. 3.) 
 
 Before being cast, the anchor should be well stocked. Rafts 
 of casks or timbers bring a greater strain on anchors than boats 
 or pontons. 
 
 344.— Substitutes for Anchors. One or two spare wheels 
 with tires and felloes removed. (PI. 45, Figs. 3 and 4.) Two or 
 more pick-axes, laid together or fixed on one handle. (PI. 46, Fig. 
 4.) A harrow with lengthened teeth, loaded with stones. Ga- 
 bions filled with stones. Large stones or railway irons. Nets 
 filled with stones. Frame filled with stones. (PI. 45, Fig. 2.) 
 
 Care must be taken to allow the anchor to fall in good holding 
 ground. For this purpose, a direction oblique to the current may 
 sometimes be allowed. 
 
 345.— Forming Floating Bridges. Floating bridges may 
 be formed in the following ways:— 
 
 (1) By successive pontons or boats. 
 
 (2) By parts. 
 
 (3) By rafts. 
 
 (4) By conversion. 
 
 346.— By Successive Pontons. (PI. 49.) This may be done 
 in two ways:— 
 
 (1) By adding to the head of the bridge, the tail being station- 
 ary. This method requires the roadway material to be carried an 
 increasing distance. The men, however, do not have to work in 
 the water. 
 
 (2) By adding to the tail of the bridge, the head, already con- 
 structed, being constantly pushed into the stream. The materials 
 do not have to be carried so far as in the first case, but it requires 
 a number of men to work in the water and Is not advantageous 
 where the bank is steep. 
 
 In the first method, those boats or pontons which cast up- 
 stream anchors should be moored above the approach to the 
 bridge, the others below. 
 
 347.— By Parts. (PI. 49.) In this method, the boats or pon- 
 tons are brought close to the shore above the bridge. For con- 
 venience in putting the parts together several chess are laid from 
 the bank to the interior gunwale of one boat or ponton. The 
 boats or pontons forming the part are then brought in place and 
 
PLATE -49. 
 
166 Floating Bridges, 
 
 balks placed on them. The chess forming the roadway are then 
 placed on the balks, excepting a sufficient number at each end of 
 the part to allow for the insertion of a bay between the parts. 
 The parts, all constructed as dh-ected, are then placed in position, 
 each part carrying enough material to construct the connecting 
 bay. The parts are joined with each other and with the abut- 
 ment bay, which has been previously constructed. 
 
 348.— By Bafts. Each raft formed of 2 or more piers is con- 
 structed complete and the rafts come into the bridge in succes- 
 sion. Each of the methods, bridge by raft and bridge by parts, 
 has the advantage of simultaneously employing, a large number 
 of men. (PI. 49.) 
 
 349.— By Conversion. (PI. 49.) In this method, the bridge 
 is put together entire along the shore above the selected site. A 
 tributary stream may be advantageous for this purpose. The 
 bridge is then floated toward the site, care being taken to prevent 
 the pivot end from touching the shore and the wheeling end from 
 turning too fast. 
 
 350.— The various methods above described may be combined 
 in the construction of one bridge. 
 
 The connection of the bridge with the shore may be made by 
 allowing the balks to rest on an abutment sill let about 1 ft. into 
 the ground, or by a trestle. 
 
 351.— If the stream is to remain ojieu to traffic, it is well to 
 liave two or more rafts in mid-stream, arranged to swing so as to 
 allow boats to pass, or the halves of the bridge may be swung for 
 this purpose. Usually the passage is made by allowing the rafts 
 or halves to swing with the current; they are then brought back 
 against the current. 
 
 352.— Floating Objects. Some arrangement should be made 
 to protect the bridge from floating objects. This mav be done:— 
 
 (1) By a guard of observation, stationed above the bridge, pro- 
 vided with boats containing anchors, grapnels, hammers, chains, 
 etc. The object may be turned ashore, or, if this is not possible, 
 an anchor may be attached to it to break its momentum. 
 
 (2) By a floating stockade, constructed of trees united by 
 chains and forming a continuous barrier to floating objects. Its 
 direction should be about 20° with the current. 
 
 (3) By constructing the bridge by rafts and withdrawing the 
 menaced part, thus allowing the object to float past. 
 
Floating Bridges. 
 
 167 
 
 352a. — Improvised Floating Bridge.* A practical improvised 
 floating bridge having a wagon-road 10 ft. wide was constructed 
 at Molo, Island of Panay, P. I., across a tidal stream 300 ft. wide, 
 and is described as follows: 
 
 Floating piers at intervals of 10 ft, consisting of bundles of 
 25 bamboo poles ("a"), supported the roadway, which consisted 
 of a mat of interwoven bamboo strips ("b") resting on a bamboo 
 corduroy ("c"), which in turn rested on four hard wood balks, 
 2l^ in. X 4 in. in cross-section ("d"). Rattan lashings were used 
 throughout and aprons were improvised at the shore ends of the 
 bridge to allow for the 3-ft. rise and fall of the tide. 
 
 In anchoring, advantage was taken of the piles of a former 
 bridge, as shown in sketch. The bamboo crib ("e"), built loosely 
 around the pile, rose and fell with the tide and prevented the 
 bridge from floating either up or down stream. The buoyancy of 
 this bridge was such that infantry in column of fours did not 
 bring the balks into the water. 
 
 ♦This bridge was constructed, using native labor, by Captain B. F. Cheatham, Q. 
 M. U. S. Array, in June, 1899, and was still in use a year later. 
 
CHAPTER XVII.— Roads. 
 
 353.— The frequent necessity, in the field, for the construction 
 of a short piece of road, or the repairing of existing roads, malves 
 it important that all who may at any time have this worli in 
 charge should be familiar with the principal requirements of it. 
 
 354.— Two desirable conditions in a road are that it be straight 
 and level; where both cannot be obtained, straightness is sacri- 
 ficed to levelness. Other things being equal, the length of a road 
 may often be advantageously increased 20 ft. for every foot of 
 vertical height avoided. 
 
 355.— Limiting Gradient. As levelness cannot always be ob- 
 tained, various considerations fix limits for the steepness, called 
 limiting gradients, which are to be used only when unavoidable; 
 thus, for a very short distance, as an approach to a bridge, the lim- 
 iting gradient may be 1-10; a grade of 1-12 should not exceed 100 
 ft.; one of 1-15 should not exceed 200 ft.; 1-20 should ordinarily be 
 the limiting gradient for easy travel, while 1-30 to 1-35 is still 
 better. 
 
 356.— Compared to what he can draw on a level, a horse can 
 draw only about 90 per cent on a grade of 1-100, 80 per cent on 
 1-50, 50 per cent on 1-24, and 25 per cent on 1-10, but for a short 
 distance he can exert 6 times his ordinary force. 
 
 357.— A road should, if possible, always rise continuously to 
 its highest point and nowhere descend partially again. 
 
 358.— Width. For military purposes roads should be wide 
 enough to allow wagons going in opposite directions to pass each 
 other easily; this is usually taken at 16 ft. For wagons going in 
 one direction only or with turnouts at intervals, and for Infant- 
 ry in column of fours, or cavalry in column of twos, 9 ft. will suf- 
 fice, and for pack animals 6 ft. At turns in a zig-zag road up a 
 hill the road should be level and the width increased from % to %. 
 
 359.— Form. The best for the upper surface is that of two 
 planes inclined at an angle of about 1-24 and joined by a slight 
 curve 5 ft. long. (PI. 50, Figs. 1, 2 and 13.) 
 
 Between the road and ditches should be flat mounds raised 6 
 in. or more above the surface, with sloping sides covered with 
 sods or stone next to road, forming with roadway the gutters: 
 
Sub'Q drain SubOcfraJr, 
 
 £arth sides 
 
 Metal Center ■^"''^'' -^^^^s 
 
170 Roads. 
 
 they serve also to hold up the road material and as warnings at 
 night of the proximity of the ditch. 
 
 On the hillside the surface should be a single plane inclined 
 towards the hill. (Figs. 3, 4, 5, 7 and 8.) 
 
 360.— Road-bed. The surface of the road-bed should be dug 
 out or built up and solidly compacted, either by rolling or ram- 
 ming, and when ready to receive the road material should be of 
 the same shape as the surface of the finished road, with shoulders 
 at the sides to retain the material in place. (Fig. 13.) 
 
 On hillsides of gentle slope, the road-bed is usually made of 
 half cutting and half filling, the lower side of the slope being 
 stepped to retain the earth excavated (Fig. 3); on steep slopes it 
 is often necessary to both step the slope and build a retaining 
 wall of stone (Fig. 4), or of logs (Fig. 5), or of other materials; on 
 very steep slopes it may be necessary to build retaining walls on 
 both sides (Fig. 7); while in rocky formations the excavated hill- 
 side may be left nearly vertical. (Fig. 8.) 
 
 361.— Drainage. Nothing is of greater importance in road- 
 building than proper drainage. It is the life of a road. In a 
 level country it is necessary to raise the road-bed to keep it 
 always free from water. None must be allowed to remain on the 
 surface and all must be drained from beneath. To accomplish 
 this -ditches must be dug on both sides of a road on level ground 
 and in cuttings, from 2 to 3 ft. below the road-bed and of a width 
 depending on the amount of water to be discharged. (Figs. 1 
 and 2.) In wet places, low-lying lands, clayey and springy soils, 
 the ditches must be deeper and sub-drains 3 to 5 ft. below the 
 road, emptying at intervals into the side ditches, must be made to 
 keep it dry. (Fig. 1.) 
 
 Rain falling on the surface of the road is collected in the gut- 
 ters on the sides and run into the side ditches by drains at fre- 
 quent intervals. 
 
 On a hillside, between the road and the hill is the ditch, from 
 which the water is discharged through culverts or covered drains 
 under the road into the natural watercourses. Catch drains 
 along the top of the cutting are made to prevent the slopes being 
 washed down and the water from above finding its way to the 
 road, 
 
Roads. 1*71 
 
 Wlieie open ditches are liable to become filled, some kind of 
 covered drain must be used. (Figs. 5, 10, 11 and 12.) 
 
 Tiieoretically, a road should be perfectly level, but for pur- 
 poses of drainage, in the direction of its length, it should have at 
 least a slope of 1-125. 
 
 On a steep road, shallow paved water tables extending oblique- 
 ly across the road are sometimes necessary to catch the water 
 running down the road and carry it to the gutters, or small 
 mounds crossing the road obliquely are substituted. (Fig. 9.) 
 
 362. — The surface of a road ought to be as smooth and as hard 
 as possible, for which purpose various liinds of covering material 
 are put on the bed. 
 
 As the road-bed must be kept thoroughly dry at all times by 
 the ditches intercepting all ground water, so the stone or other 
 covering must be so thoroughly rolled and compacted that no 
 water falling upon the surface can possibly find its way down to 
 the foundation and through it to the bed. 
 
 363.— When roads are made of broken stone the material in 
 the Telford class is composed of two parts: the foundation and 
 the covering. (Fig. 1, right half.) The foundation consists of 
 a uniform thickness of not less than 5 in. of any durable broken 
 stone with bases about 5 in. x 10 in. laid close together by hand, 
 larger faces down, firmly wedged with smaller stones in the in- 
 terstices, and the whole sledged and rolled to a uniform sur- 
 face. Then a thin layer of binding material, as clay or loam, is 
 sprinkled over it and rolled. On this is put the covering, consist- 
 ing of a layer of about 3 in. of broken stone of uniform, well- 
 shaped cubical pieces which will pass through a ring from 2 to 
 21^ in. in diameter, and rolled to a uniform, compact surface. 
 Then another layer of binding material is added and well rolled. 
 Another layer of stones, 3 in. thick, of sizes from 1 to 2 in. in diam- 
 eter, is next spread and rolled as before. On this may be spread 
 another binding coat, well rolled, then a thin layer of fine screen- 
 ings or fine gravel free from dirt. Often, where traffic is light 
 and expense large, a single layer of broken stone 4 in. thick is put 
 on the foundation. 
 
 364.— In the Macadam class (Fig. 1, left half) the hand-laid 
 foundation is not used, but generally three layers, each from 3 to 
 
^Td Roads. 
 
 -k m. Liiick, ui biuJieu biune and bmdiiig cout«, as described abuve, 
 are spread aud rolled until smoota and compact. 
 
 For light trallic a single layer ot 4 in. is sometimes used. 
 
 365.— Tlie best stone is a compact, tine-grained syenite, basalt 
 or trap rock. Hornblend, actinolyte, dioryte, and some other 
 rocks make good material. Quartz and flint, though very hard, 
 are brittle, ditflcult to work, and not so good. Granite, on ac- 
 count of mica in it, breaks up and grinds away too easily. Gneiss 
 is poorer than granite. Slatey rocks generally break up too eas- 
 ily. Limestone, generally too soft, grinds away easily, making a 
 very disagreeable dust. Softer stones may be used for the foun- 
 dations and lower layers, but only the hardest and toughesi 
 should be used for the coverings. 
 
 366.— Earth roads require even greater care in draining, grad- 
 ing, and forming the surface than those described, and a trans- 
 verse slope, not less than 1-20, to hasten the flow of surface water 
 to the gutters. No sods or vegetable refuse should be allowed in 
 grading or filling ruts, only gravelly earth, if obtainable. 
 
 Roads are frequently made with a metal portion in the center 
 and earth roads, called wings, on the sides. (Fig. 2.) 
 
 367.— It is almost impossible to construct a road of clay which 
 will be good in wet weather, but a very sandy road may be im- 
 proved by working a little clay in it. 
 
 368.— For gravel roads the bed is first formed as described. 
 The gravel is screened to remove stones larger than 2% in. in 
 diameter and such as are less than % in.; and all earthy matter. 
 A layer of the screened gravel, 4 or 5 in. thick, is then spread and 
 rolled, then another layer of 3 or 4 in., which should also be well 
 rolled. 
 
 869.— Repairs. Ruts appearing should be immediately filled 
 in, and traffic directed over all parts of road Before spreading 
 stones, all mud should be cleaned off and the surface picked up a 
 little to allow the new stone to bind into the old, wet weather be- 
 ing preferred, or the stones should be sprinkled. Ditches and 
 culverts must be cleaned as needed. 
 
 370.— In crossing marshy ground that cannot be well drained, 
 corduroy roi4s made of logs of suitable lengths laid side by side 
 across the road, over which is spread a covering of earth or gravel, 
 are sometimes used. 
 
Roads. 173 
 
 371.— Brushwood, made into fasciues and hurdles, may be 
 used the same way as a foundation. With fascines, the top row 
 should extend across the road and be of a length equal to the 
 width of road. (Fig. 6.) 
 
 372.— Where lumber is the cheapest material, plank roads may 
 be built by first laying parallel rows of sleepers or sills flush 
 with the ground, about 4 ft. apart, in the direction of the road, on 
 which boards, 3 in. thick by 9 to 12 in. wide and 8 ft. long, are 
 placed crosswise. 
 
 373.— The construction of communications to all parts of a 
 position to facilitate the movement of troops, etc., from one part 
 to another, is almost always a certain necessity. These would 
 rarely be more than temporary, but, if made on the lines indi- 
 cated, as far as time and requirements permitted, so much the 
 better. 
 
 374.— Roads and paths may have to be cleared through woods; 
 wet places made passable by corduroying or filling up with brush, 
 fascines, etc.; and approaches made to ascend steep places. 
 
 Wherever roads cross or separate, signs should be put up tell- 
 ing exactly where each leads. 
 
PLATE 51 
 
 FIG.l 
 
 FIG.2. 
 
 Pi.ATm 
 
 a a D D D D 
 
 FIGS. /fartfrrd fl-esaed^eeim. FIG 5: 
 
 FIG. 4. 
 
 FIG6. 
 
 ^f^m V 
 
 w 
 
 FIGS. 
 
 IntfrUtkingiolis FIG 7 
 
 Fiaa 
 
 I 
 
 BRIOCE RAIL JOfff] 
 
 FIG;10. 
 
 n. m.m.m M. 
 
 Em 
 
 Crossing 
 
 FIG.12. 
 
CHAPTER XVIIi.— Railroads. 
 
 375.— In military operations, the principal duties of troops in 
 connection with railroads will be either ther repairing of lines that 
 have been partially destroyed, or the destruction of lines to pre- 
 vent their use by the enemy. 
 
 376.— A railroad, as existing in its completed form, will be 
 briefly described to indicate the state to which it should be 
 brought hy repairs after destruction, and to so familiarize one 
 with it as to suggest methods of most effectually destroying it. 
 
 377.— A railway line consists of a series of straight lines of 
 different lengths, called tangents, which are joined by curves. 
 The road-bed is first prepared with a smooth hard surface (slop- 
 ing slightly from the middle to each side for drainage) from 10 to 
 12 ft. wide for a single track, and from 21 to 25 ft. for a double 
 track. On this is placed the ballast, from 12 to 24 in. thick, of 
 broken stone, gravel or cinders, etc., for the pui-pose of distribut- 
 ing the load over a larger surface, holding the ties in place, carry- 
 ing off the rainwater, affording a means of keeping the ties up to 
 grade line and giving elasticity to the road-bed. 
 
 378.— The ties are generally of wood, hewn flat on top and 
 bottom, from 7.5 to 9 ft. long, 6 to 10 in. wide, and about 7 in. 
 deep. It is customary to sink them about half their depth into 
 the ballast. Their object is to hold the rails in place and furnish 
 an elastic medium between the rails and ground. The distance 
 apart is usually 2.5 ft. from center to center, but depends upon 
 weight of engines and strength of rails. They should be uni- 
 formly spaced to distribute the weight equally. 
 
 Tie plates (PI. 51, Figs. 3 and 7) are often used to prevent the 
 rails from crushing into the ties. 
 
 379.— Tests of metal ties in the interests of economy and eflS- 
 ciency have been made with satisfactory results. On some level 
 portions of the N. Y. Central R. R. are used the Hartford pressed 
 steel tie (Figs. 1 and 2), to which the rails are fastened by clamps 
 bolted to the tie. 
 
 380.— The form of rail used in the United States is shown in 
 Fig. 3, being the "T" rail, which varies in weight from 12 to 100 
 lbs. per yard. The mean dimensions of 80 lb. rails are given on 
 wi2- 
 
1^6 Railrodda. 
 
 left-hand side of figure and of 100 lb. rails on right-Land side. 
 They are placed 3 ft. apart for narrow gauge, 4 ft. 8.5 in. for 
 standard gauge, while 6 ft. is the broadest gauge in the United 
 States, measured from inside to inside of head. The tops of rails 
 must be slightly inclined to fit the cones of the wheels. 
 
 381.— The weak part of a track is at the joints. The old 
 method of using chairs under the ends of rails has about ceased, 
 the practice now being to fish the joints by plates (Fig. 1), and 
 angle irons. (Fig. 3.) Tliere are also used what are known as 
 the Reinforced rail joints (Fig. 4), Bridge rail joints (Fig. 8), Dou- 
 ble Girder rail joints. (Fig. 9.) 
 
 382.— Rails are fastened to the ties by spikes, the best being 
 made with sharp, chisel-edge points, clean, sharp edges, and 
 smooth surfaces, so as to cut and press aside the fibers of the 
 wood, instead of tearing them. Attempts to increase the hold- 
 ing power by jagged or twisted spikes have been unsuccessful. 
 On bridges, interlocking bolts (Fig. 6) are much used instead of 
 spikes. To keep the track in the right line, allowance must be 
 made for the contraction and expansion of the rails, by not plac- 
 ing them in contact at the joints, and the holes for the bolts must 
 be elongated. 
 
 383.— The centrifugal force of a train passing around a curve 
 tends to throw the wheels against the outer rails, which is par- 
 tially counteracted by raising them to throw the center of gravity 
 inward and cause the car to slide inward. Each rail in a curve 
 ought to be bent to fit the curve before being laid. 
 
 384.— On single tracks, there are laid at occasional intervals 
 short pieces of track, called sidings, to enable trains to pass one 
 another. The arrangement for passing from one track to another 
 is the switch, which consists of a single length of rails, movable at 
 one end by a lever, so as to connect with either pair of rails. The 
 simplest form is the stub switch (Fig. 10), which leaves one line 
 always open while the other is continuous. The one in common 
 use is the split or point switch. (Fig. 11.) Various devices are 
 used for locking and interlocking switches, to avoid accidents. 
 At the points where the inner rails cross is placed a frog (PI. 52, 
 Fig. 1), which enables the wheels to pass over the inner rail of 
 the other track. 
 
PLATE 52. 
 
 FIGl 
 
 FrG:8. 
 
 f/4- 
 
178 Railroads. 
 
 385.— Orosbiugjs occur where two tracks intersect, and consist 
 of four frogs and corresponding guard rails. (PI. 51, Fig. 12.) 
 
 386.— Wliere one main line passes to another is called a junc- 
 tion and the ordinary switch is used. In crossing from one track 
 to a pai'allel track the rails are arranged as in PI. 52, Fig. 2. 
 
 387.— A wye, from a similarity to the letter "Y," is an arrange- 
 ment of tracks for turning around engines and cars and connect- 
 ing cross-roads. (Fig. 3.) 
 
 388.— Turntables are platforms, turning on rollers upon an 
 underground circular track, used to transfer engines and cars 
 from one track to another and to turn them around. 
 
 389.— The locomotive engine is the power on railroads. They 
 weigh up to 232,000 Ihs. without tender, and to 292,000 lbs. for 
 passenger to 365,000 lbs. for freight, with tender, and draw 2,400 
 or more tons on a level. The amount of coal consumed being from 
 40 lbs. to 70 lbs. per mile run. 
 
 390.— The rolling stock consists of passenger cars for about 60 
 persons, 48 to 52 ft. long, 9.5 ft. wide, w eighing from 40,000 lbs. 
 to G0,000 lbs.; sleeping cars for 64 passengers, 60 to 70 ft. long, 
 9.8 ft. wide, weighing 60,000 lbs. to 90,000 lbs.; mail, express and 
 baggage cars, 45 ft. long, 9.3 ft. wide, weighing about 27,000 lbs.; 
 freight cars consist of Box, Refrigerator, Hay, Furniture, Oil, 
 Stock, etc., and are about 34 ft. long, 8.5 ft. wide, weighing from 
 20,000 lbs. to 30,000 lbs., capacity 20 to 30 tons; flat cars, 34 ft. long, 
 weighing 16,000 lbs. to 19,000 lbs. Height of top of box cars above 
 rails about 15 ft. Freight cars are being rapidly provided with the 
 M. C. B. automatic couplers. (Fig. 4.) 
 
 391.— The buildings consist of passenger and freight depots, 
 engine houses, fuel sheds, water tanks, repair shops, and section 
 houses. At convenient points are generally located yards where 
 stock can be loaded and unloaded. It may sometimes be neces- 
 sary, however, to load and unload animals and supplies in the 
 field along a railroad where there are no platforms or other con- 
 veniences, which must then be built. 
 
 392.— A simple form of ramp, in the absence of anything 
 better, could be made by taking 3 or 4 planks 3 in. thick, 10 to 12 
 in. wide, and 10 to 14 ft. long, fastening them together side by 
 side, preferably by footholds nailed across on top and several 
 cleats on. the bottom; otherAvise, by lashing, wiring or by stakes 
 
Railroads. 179 
 
 at the bottom when in position, and we9ges in the car door. The 
 ends on the .s^round should be slightly sunken and rested against 
 a cross beam. Ropes should be hung along the sides and blankets 
 or canvas hung on them. Props of some kind, as sacks of grain, 
 bales of hay, etc., can be placed under the middle to strengthen 
 it if necessary. 
 
 393. — Another form of portadU rarnp, which could be carried 
 on all railroad trains where they might be needed, consists of 6 
 long timbers 4 in. x 4 in. x 14 ft., 6 short timbers 4 in. x 4 in. x 6 
 ft., 24 boards 1.5 in. x 12 in. x 6 ft. with footholds nailed length- 
 wise on one side. 
 
 To load or unload horses, rest the ends of three or four of the* 
 long timbers, equally spaced, on the car floor, the other ends resting 
 against a short timber, sunk in the ground and staked down. On 
 these place the boards forming the floor; on each side of the ramp, 
 on the boards, lay a long timber and fasten the ends to the timbers 
 underneath. The boards should have cleats on under side to 
 prevent slipping sideways. If necessary, some of the remaining 
 boards can be set edgewise between posts of the short timbers 
 as an Intermediate support. 
 
 394. — To unload a number of cars, enough men can be placed un- 
 der the ramp, near the car, to raise it high enough to allow the car 
 to be removed and another run in place, thus avoiding taking 
 the ramp apart for each car. 
 
 S95— -Semi-permanent platforms and ramps may be made as in 
 Figs. 6 and 7, if rails and boards are available. 
 
 396.— To load or unload tcagons and guns from a flat car, place 
 the ramp against one end (Fig. 8), using four long timbers for 
 stringers on which the boards are placed, the other two long tim- 
 bers being used for side rails. Support underneath with boards 
 set on edge, held between some short timbers, or with bales of 
 hay, sacks of grain or otherwise, as necessary. A couple of 
 boards can be used to run the wheels from the car on to the ramp 
 and others at the foot of ramp to carry the wheels across the rails. 
 The lower ends of the stringers should abut against a tie, if pos- 
 sible: if not, they should be staked down. 
 
 397.— PI. 53 is a design of a portable ramp devised by Major 
 E. G. Fechet, 6th IT. S. Cavalry. The ramp consists of 7 boards 
 1,5 Jp, 3C T J^« ^ 1? ^t- joined together In three sections (2 for the 
 
- K 
 
 Major £. C.Fschft, 
 
 e"*^ Cavalry, , 
 
 US.At^Y, 
 
 £.A.1^C.a: 
 
Railroads. 181 
 
 outside, "A," "A"; and 3 for the middle one, "B"); by wooden 
 strips *'C," 1 in. thick, and 2 in. wide, bolted to the upper surfaces, 
 1 ft. between centers; these strips also serve as footholds. Along 
 the middle of the outside boards extends a side rail, "D," 3 in. x 
 3 in., held firmly by the iron straps, "E," ^ in. x 2 in. On the out- 
 side of each side rail are 3 sockets *'F," for standards **G" 3 ft. 
 high, along the tops of which are to be stretched ropes or chains 
 from which canvas or blankets are hung. On the under side of 
 each section 3 ft. apart are bolted iron cleats, "H," 0.5 in. x 2 in., 
 beginning at 18 in. from the ends. On the ends of each section are 
 bolted iron claws, "K," for catching the car floor or door slide, to 
 prevent slipping when in position for use. The three sections are 
 held together for use by 4 iron tie bars, "L," 0.5 in. x 2 in., which 
 are placed under the cleats "H," and the whole firmly keyed as 
 shown. This form of ramp may be made longer or shorter, nar- 
 rower or broader, as desired. By taking out the standards it may 
 be hung on the side of a car between a door and end. It is easily 
 taken apart and transported in a wagon, and as easily put to- 
 gether when needed. It is designed to combine both strength 
 and lightness. It weighs about 400 lbs. complete. 
 
 398.— Disabling and destroying railroads. Under the head 
 of disahling will be mentioned means, the effects of which will 
 only temporarily interrupt traffic,, leaving the road repairable af- 
 ter some delay. 
 
 399.— Under destroying, such as are more serious in their 
 effects; either causing extensive repairs or a change of route to 
 avoid them. 
 
 400.— The disabling of railroads will usually be done by raid- 
 ing parties of cavalry, while the destroying of them may be done 
 by such parties or by specially detailed troops trained for such 
 service. 
 
 401.— It must be understood that no railroad is to be destroyed 
 except upon the orders of the oflScer commanding' In the field. 
 If otherwise, and It should be taken from the enemy, the dam- 
 age done might seriously embarrass future operations. Before 
 ordering any destruction the questions will arise — "Is destruction 
 absolutely necessary?'* "Will it be of no further use and is every 
 hope of regaining it gone?" "Are the advantages to be gained 
 BulBcIent to compensate for the damage that will be done?* AW 
 
182 Railroads. 
 
 the attending circumstances should be carefully considered, es- 
 pecially if in one's own country. The choice of points for de- 
 struction and the most effective means are subjects for study. It 
 is useless to destroy anything that will not seriously embarrass 
 traffic. 
 
 402. — A railroad may be disabled by removing rails at vari- 
 ous intervals, then destroying or hiding them; or, if a large num- 
 ber of men are at hand, select a high embankment, line the men 
 along on one side of the track, disconnect the rails at each end of 
 the line of men, then, at a signal, they raise the track on edge and 
 let rails and ties together go over the embankment. Thus treated, 
 rails and ties must be separated before being replaced. An im- 
 provised wrench for removing nuts on fish-plates is a bolt with 
 two nuts on it, just far enough apart to grasp the nut to be re- 
 moved. (PL 52, Fig. 5.) If time is an object, remove outside 
 rails on a curve, or disconnect a joint on each side and throw them 
 as a switch to derail the train either on an embankment or in a 
 cut, or use explosives as described in Chap. XX. 
 
 By laying rails across a pile of burning ties until red hot in the 
 middle they may be easily bent around a tree or telegraph pole; 
 they may be twisted by heating, as above, then using bars or pick- 
 axes placed in the holes in each end and working in opposite 
 directions. 
 
 They may be torn from the ties and twisted cold by using Gen. 
 Haupt's "TJ"-shaped rail-twister, shown on PI. 40, Fig. 8. Ten 
 men with two twisters, two axes, two stout pieces of rope 35 ft. 
 long, can tear up and twist a rail in 5 minutes. The junctions of 
 lines are important points to attack to disable a track. 
 
 Water tanks may be rendered useless for a time by breaking 
 holes in them, removing pistons from pumps, etc. Fuel, ties, and 
 small bridges may be burned. Engines may be disabled by burn- 
 ing out the flues. Temovirig or breaking different parts of the ma- 
 chinery, filling suction pipes of pumps with waste, or by removing 
 bolts from eccentric straps, etc. Cars may be disabled by removing 
 couplers, axle boxes, breaking or removing trucks, etc. The use 
 of mines under the tracks, so arranged as to be exploded by the 
 passing of trains, is an effective method of interrupting traffic and 
 "shaking the morale of troops being transported. 
 
 403,— To destroy a railroad, if time is Bufflclpnt, remove roll- 
 
Railroads, 183 
 
 ing stock, rails, etc., to the rear. Otherwise, destroy large bridges, 
 if of wood, by burning, using oil if it can be obtained, or by ex- 
 plosives, as in Chapter XX.; if of iron, steel, or masonry, by ex- 
 plosives, as in Chapter XX. If there are tunnels on the line, 
 select longest ones and blow them in at as many points as possi- 
 ble, or cause two wild trains to collide in the middle, afterwards 
 blowing in the ends. Those with sandy soil are the best. Deep 
 cuttings with retaining walls may be filled in by use of explo- 
 sives. If trees, poles, wires, etc., can be mixed in— so much the 
 better. Blow up tanks and engines, burn all fuel, cars, repair 
 supplies, etc. Fire a cannon ball through engines. 
 
 404.— The repair of railroads will best be accomplished by 
 a construction corps having some of the elements of permanency 
 in its organization; or, at least, by small squads of experienced 
 men, to which others could be added by temporary detail, when- 
 ever active operations require such increase. They should be 
 established as near to where their services may be needed as 
 possible. 
 
 405.— Bridges should, in the beginning, be classified and num- 
 bered, so that a single reference to the class and number will give 
 complete information as to its character, dimensions, etc. At 
 designated points will be kept on hand, already prepared for put- 
 ting in bridge, suitable materials for the repair of each class. 
 This was done by the Union Army from 1861 to 1865, so that, 
 when word was received that a certain bridge had been destroyed, 
 by a reference to the class and number the reconstruction corps 
 started out carrying with it just what was needed to repair the 
 bridge. Even complete trusses for the larger class of bridges 
 were prepared and kept ready for use. 
 
 406.— Tunnels and cuts which have been filled up can gener- 
 ally be cleared only from the two ends. 
 
 407.— Rails, fish-plates, spikes, ties, etc., will be kept in store 
 at secure places, for repairing any portions of destroyed track. 
 Rails which have been simply bent can be straightened by various 
 means. Gen. Haupt's method was as follows: Two ties were 
 placed on the ground, across these two more ties' and on top a 
 single tie. which was cut across one-half the depth of the rail 
 to receive It and prevent It turning. Weight was applied at the 
 two ends of the r^!l hy m^n benrtngr down on poles placed there^ 
 
184 Railroads, 
 
 on. The rail being moved back and forth until strai;?htened, re- 
 quiring from 4 to 5 minutes. Rails which had been heated and 
 bent to a very sharp angle required more time, necessitating re- 
 neating and hammering until straightened. For this purpose, at 
 special points, were prepared furnaces consisting of two parallel 
 walls of bricli, stone or clay, with a kind of grate. The straight- 
 ening table consisted of a large, square timber as long as a rail, 
 on which were securely fastened three rails, as in PI. 52, Fig. 9, 
 on which the heated rail was laid and hammered until straight- 
 ened. Twisted rails require rerolling before they can be again 
 used. 
 
- H-ATE 54. 
 
 Fia7. 
 
 7IG.8 
 
 yMM|MMM«H«B^HM«eM 
 
 WJ^ 
 
CHAPTER XIX. -Telegraph and Telephone Lines. 
 
 408.— In order that telegraphic messages may be sent from 
 one point to another, it is necessary that there be a continuous 
 metallic conductor from the first to the second point, and that 
 this conductor be insulated from contact with the ground or with 
 anything leading to the ground. The conductor used in construct- 
 ing permanent lines is of galvanized iron wire, generally of size 
 No. 9. In military lines it is generally somewhat smaller on ac- 
 count of the weight, and sometimes of bare copper wire about No. 
 14. The wire is carried on poles and tied to glass or other insu- 
 lators which are attached to the poles. 
 
 409.— Poles should be not less than 22 feet in length nor less 
 than 7 and 5 inches in diameter at the larger and smaller ends 
 respectively, but may be as much longer and larger as de- 
 sired, and should be stripped of bark and pointed at the 
 upper end. The holes for poles should be not less than 1-6 the 
 length of the pole in depth. The poles should be raised as shown 
 in PI. 54, Fig. 1, and held vertically while the excavated earth is 
 thoroughly tamped in from bottom to top; after the hole Is com- 
 pletely filled, the earth should be made into a small mound so as 
 to shed water. 
 
 410.— When the brackets are attached to the pole directly, a 
 seat should be cut !n the pole with a hatchet and the bracket 
 should be nailed on, using 1 twenty-penny and 1 forty-penny 
 nail. Where the poles are intended to carry several wires, cross- 
 arms are bolted to the poles, fitting into seats cut for them. The 
 arms carry brackets not less than 15 in. apart. The arms should 
 not be less than 20 in. from one another. Not less than 25 poles 
 to the mile should be used, and usually the number is increased 
 to 30. 
 
 411.— Every 5th pole should be protected from lightning dis- 
 charges by having a piece of line wire run from about 6 in. above 
 tlie tor> of the r>ole to the ground. This wire must be so arranged 
 that it cannot cf)me in contact with the line wire should that 
 become unfastened. Poles should be vertical CTrept when nec- 
 essary to incline them to resist strain*? when they will be set 
 at a slight inclination in such manner that the component of 
 the strain in the direction of the length of pole will tend to 
 press it Into the ground, Where exppsefl to great strains, of 
 
Telegraph and Telephone Limes. 187 
 
 to continuously high winds, it may be necessary to guy the 
 poles: this is done with stays consisting of two or more line 
 wires twisted together and fastened near the top of the pole, the 
 ground end being attached to a section of a pole or timber suita- 
 bly anchored in the ground, as shown in Fig. 2. Where possi- 
 ble, the line of poles should be run on one side of the road and 
 far enough from it to be safe from accidental damage by pass- 
 ing wagons. Where roads have to be crossed, the wire should 
 be carried over on high poles so as to clear any possible wagon- 
 load. 
 
 412.— The insulators in common use in this country are of 
 glass and of the form shown in IT'ig. 3. The one shown in Fig. 4 
 is preferable, as it is not so liable to cause leaks on account of 
 moisture accumulating and forming a connecting film to the 
 bracket and from that to the pole. 
 
 413.— The wire is attached to the insulators by pieces of wire 
 called ties. These are generally of the same wire as the .line. 
 They are annealed and formed on an insulator and cut long 
 enough to embrace the insulator and project 3 or 4 inches beyond 
 the line wire. 
 
 414.— To hang the wire. The wire is carried up to the top 
 of the pole and the lineman places a tie on the insulator, the line 
 wire against the insulator above the tie wire, and bends the 
 ends of the tie wire upward so as to sustain the line wire. The 
 line wire is then strained by the lineman, either by means of 
 hand power or by use of the wagon carrying the reel. When 
 the line wire is stretched so that it sags but about V/o, ft. in 70 
 yds., the tie wire is wrapped around it about one and a half 
 times, finishing with the ends of the tie wire pointing towards 
 the insulator; this secures the line and completes the work. 
 (Fig. 5.) 
 
 415. — ^In open country the line wire is strung on the insulator 
 on the side towards the pole, so that, if it becomes accidentally 
 undone, the wire will not drop. If in timbered country, then 
 hang it on the side from the pole, so that when trees, etc., fall 
 against the wire It will simply tear it away from the insulator, 
 but will not break the line wire. When necessary to hang the 
 wire on trees, a regrular tree insulator should be used, and in 
 default of this, the tie shown in Fig. 6 may be used, the ends 
 
188 Telegraph and Telephone Lines. 
 
 beiug wound loosely jso as to allow of an easy lateral motion to 
 accommodate the swing of the tree. Tlie poles should be num- 
 bered at each mile so as to aid linemen to report location of breaks 
 and repairs. 
 
 Streams are crossed by hanging the wires on strong, high sup- 
 ports, taking cai*e not to strain the wire so much as to cause it 
 to break. 
 
 416.— The description of Instruments and batteries, their con- 
 nections and care, will be found in the Manual published by the 
 Signal Service of the Army. 
 
 417.— Joints. Where wires have to be joined to preserve the 
 continuity of the metallic circuit, the best joint is the American 
 twist joint. To make this clean the wires for a length of 5 or 6 
 inches, make a right-angle bend in each wire about 4 inches from 
 the end, now join the wires so that the ends project on different 
 sides and clamp both wires with a hand vise, then with a splicing 
 iron turn the ends around the line wire, making the turns as close 
 as possible; after the entire end is turned around the line wire, 
 cut off the projecting end and dip the joint into melted solder; 
 this protects the joint against rusting. The details of this 
 joint-making are shown in Figs. 7 and 8. 
 
 418.— Military lines are generally of the kind designated as 
 flying lines — i. e., they are intended to accompany the army in 
 the field, are constructed quickly for temporary use, and are as 
 quickly dismantled and taken up. The poles used are small poles 
 called lances, each about 2\<2 in. in diameter and 17 ft. in length, 
 placed 2 ft. in the ground, and run about 40 to the mile. The 
 batteries, line lances, and instruments are carried in wagons 
 which accompany the army. A detailed description of the tele- 
 gi'aph, with directions how to erect and dismantle, is found in the 
 Manual of Signals for the U. S. Army. The ordinary telephone 
 receiver (with magneto call bell) is used on the military lines; but 
 for the use of outposts, reconnoiterers and scouts a special form 
 of telephone cart and wire has been adopted, the following de- 
 scription of which is taken from the Report of the Chief Signal 
 Officer of the Army, 1892: 
 
 "The frame of this cart is constructed of bicycle tubing, and 
 30 In. bicycle wheels with heavy cushion rubber tires are used. 
 The cart Is fitted with an automatic spooling device for reeling 
 
Telegraph and Telephone Lmes. 189 
 
 up the outpost cable. Tliis device was made by F. S. Gahill & 
 Co., and is a success. The cart carries 5 reels of cable and 1 reel 
 knapsack for use in places where the cart cannot penetrate 
 owing to underbrush, etc. As the extreme width of the cart, 
 measured at the wheels, is only 26 in., it can follow any ordinary 
 path through underbrush. The weight of the cart complete 
 with spooling device, but without the reels, is only 53 pounds; 
 when loaded with reels and reel knapsack, the total weight 
 is 157 pounds. The cart is well balanced upon its axle by a 
 device which permits the point of support to be changed to bal- 
 ance the cart as the distribution of the weight is changed by 
 the cable being run out. In connection with the reel cart a tele- 
 phone kit is used, and by attaching the double connector of the 
 kit to one on the frame of the cart the telephone is kept in cir- 
 cuit and conversation can be kept up with the home station. 
 The cart with its load can be easily drawn by one man, and by 
 its use it will be possible to connect outposts with the main 
 guard, or brigade with regimental headquarters, or brigade 
 with division headquarters, in a few minutes of time. The ex- 
 perience of the English in Egypt has proved the value of the 
 field cable line in action, as by means of these lines the Com- 
 manding General was kept in communication with different 
 divisions of troops and with those actually engaged in the firing 
 line. It is proposed to fit shafts to the cart so that a horse can 
 be harnessed to it, thus securing great rapidity in running out 
 the cable. The cart carries 1 2-3 miles of cable, which can be paid 
 out as fast as a man moves with the cart, and by means of the 
 reeling apparatus and spooling device can be recovered at the 
 rate of 4 miles per hour, or as rapidly as a man can walk with 
 the cart." 
 
 419.— Faults are generally of three kinds— breaks or discon- 
 nections, leaks or escapes, and crosses or contacts. 
 
 Breaks or disconnections occur when the metallic circuit is 
 broken or cut so that either the disconnection is complete, as when 
 entirely severed; or incomplete, when partially cut or where a joint 
 is rnsted so much as to increase the conductive resistance. In 
 these cases the instruments will work weakly or fail entirely. 
 
 Leaks or escapes. Where the insulation is destroyed or is 
 defective, of where a wire comes in contact with a conductor to 
 
190 Telegraph and Telephone Lines. 
 
 the earth or with the earth itself, a portion of the current leaks or 
 escapes. When the wire is swinging, the leak will be intermit- 
 tent; when constant leakage is going on, the instruments will 
 work weakly; when the leak becomes complete, failing altogether, 
 it is called "a ground." 
 
 A cross or contact occurs when two wires, each carrying cur- 
 rents, are brought into contact; thus the instruments on one line 
 will interfere with the workings of those on the other. Generally 
 occurs from parallel wires being swung over one another by 
 the wind, or having a good conductor fall so as to touch both 
 wires. 
 
 420.— Telegraph lines should never be damaged or destroyed, 
 except in obedience to direct orders. Faults may be made by 
 connecting the wires together with small wire (this makes a bad 
 cross), or they may be connected with the lightning rods on the 
 poles, thus running them to the groun<i. 
 
 When an office is taken, the instruments should all be discon- 
 nected and destroyed or taken away; the ends of the wires should 
 be tied together. The batteries, if any, should be disconnected. 
 To destroy the line, cut down the poles and burn them and cut 
 the wire into small lengths. Subaqueous lines should be brought 
 up with a grapnel and a piece cut out and cut into small 
 pieces and thrown back into the water. Subterranean lines are 
 generally laid in conduits, and at regular intervals man-holes 
 are built to allow of repairs; the line may be detected by these 
 man-holes, the conduit destroyed, and the cables disconnected. 
 
CHAPTER XX.— Demolitions. 
 
 421.— In military operations demolitions must be made witli 
 tlie least possible expenditure of time and explosive. Neverthe- 
 less, a charge which in itself seems large for the object intended 
 may prove economical, in that it errs on the right side and a repe- 
 tition of the work is not made necessary. 
 
 Military engineers, or troops acting as such, may have to de- 
 stroy bridges, houses, walls, railroads, tunnels, stockades, pal- 
 isades, gates, cannon, etc., break up roads, fell trees and place 
 mines. On account of their portability, great destructive effect 
 and facility of handling, high explosives should generally be 
 used in all these operations. However, where ordinary gun- 
 poA^der is available, it may be used to advantage, if time permits 
 its proper placing and tamping. Gun-cotton is the standard 
 explosive for military work, and all formulas are calculated for 
 its use. 
 
 422.— Gun-cotton, as made at the U. S. Naval Torpedo Sta- 
 tion, is in blocks about 3 in. square and 2 in. thick; each block 
 is perforated to allow the insertion of a detonator, and, when dry, 
 weighs about 10 oz. When necessary to use a «maller amount 
 than 10 oz., a block may be cut, when wet, by using a saw or 
 sharp knife, care being taken to place it between two boards, so 
 that it will not flake or crack during the operation. 
 
 Gun-cotton, as furnished by the U. S. Ordnance Department, 
 is in small rectangular blocks weighing about 1-8 oz. The blocks 
 contain about 15 per cent of water, are coated with varnish, 
 and can be shipped or handled with safety. For use, a paper 
 or cardboard cylinder is made and the blocks placed in it. The 
 detonator is inserted in a prepared primer, which is placed be- 
 tween the blocks. 
 
 Gun-cotton will absorb about 30 per cent of its weight of 
 water, and, when in this condition, Is comparatively safe, as it 
 can only be ignited by fire and is difficult of detonation. When 
 packed for transportation the blocks are placed, while wet, in 
 a tin can; the can is hermetically sealed or is left so that the water 
 can be replaced when it has evaporated. 
 
 When both are well tamped, gun-cotton has an explosive force 
 
 -13— 
 
PLATE 55. 
 
 Fign-re 1. 
 
 /• / y^ 
 
 Figure 2. 
 
 ^ ------- ■ f--^ — r 
 
Demolitions. 193 
 
 two timet) as gieut as guupovvaer; wlien no tamping is used, it 
 has a force four times as great. 
 
 423.— Primers. Wet gun-cotton detonates with much greater 
 force than dry, but it is necessary that this action be set up by 
 the detonation of a dry primer of gun-cotton placed in intimate 
 contact with the w- et charge. When wet gun-cotton is carried, a 
 sufficient quantity for a primer may be taken from the wet case, 
 placed in the sun and allowed to dry; it is better, however, in 
 operations in the field, to carr:^' a small amount of dry gun-cotton, 
 so as not to waste time in drying the primer. 
 
 When used in holes, gun-cotton should be dry, as wet gun- 
 cotton is difficult to detonate under such circumstances. 
 
 424.— Dynamite. Dynamite comes in cartridges or sticks 
 weighing 8 oz. each, and may be used instead of gun-cotton. It 
 should not be used, however, if exposed to wet or if frozen. 
 Frozen dynamite can be thawed by placing it in an apparatus 
 like a glue pot, the dynamite being in the inner vessel and the 
 hot water in the outer. It must not be thawed at a fire. 
 
 Gunpowder may sometimes be used in demolitions, and when 
 so employed it should be placed in stout bags, preferably two, the 
 outer one well tarred. This is to protect from accidental explo- 
 sion occasioned by sparks from the fuse. 
 
 425.— Explosives should be placed in as close contact as pos- 
 sible with the object to be destroyed, and the packages compos- 
 ing the charge should be in intimate contact with each other. 
 
 426. — Common Detonator. The common detonator is a cop- 
 per tube, about % in. in diameter, closed at one end and partially 
 filled with fulminate of mercury, which is ignited by a fuse. 
 The ordinary blasting cap (PI. 55, Fig. 1), or detonator, is in- 
 tended for use with a fuse, and is designated as single, double, 
 or triple force, according to the amount of fulminate of mercury 
 used. In military operations it is better to use the triple- 
 force caps, as their action is sure, even on comparatively low 
 explosives.* 
 
 427.— The fuse generally used in this country to ignite these 
 detonators or caps is that made by Ensign, Bickford & Co., 
 Simsbury, Conn., the grade known as "double-taped" being the 
 
 ♦Sing-le-force caps contain 3 grs., double-force caps 6 grs., and triple-force caps 
 9 grs. of fulminate of mercury. 
 
1^^ Demolitions. 
 
 best for general work when the fuse is not expcsed to pro- 
 longed immersion in water or damp ground. When it is nec- 
 essary to use fuse for submarine explosives, the water-proof 
 fuse should be used. The rate of burning of the fuse should 
 be found by experiment before using. This is done by taliing 
 several pieces, 1 ft. long, and finding the average rate of burn- 
 ing and taking this as the standard. The rate at which this fuse 
 is intended to burn is 3 ft. per minute, but it varies somewhat, 
 so that when great nicety is required it should be tested as 
 above. 
 
 428.— To prepare a fuse and detonator for use, cut the fuse to the 
 length required, leaving a square end; insert this end in the det- 
 onator until it rests against the fulminate, taking care not tc 
 scratch the fulminate. Then crimp the copper against the fuse so 
 as to hold it firmly: this is done by means of pincers made for the 
 purpose; or, in case these are not available, any pincers or the 
 edge of a dull knife may be used, being careful not to crimp on 
 the portion of the cap containing the fulminate. 
 
 To fire t/un-cotton, insert the detonator in the hole in the prim- 
 ing-block, secure it by tying with wire or twine, and when ready, 
 light the fuse. 
 
 To fire dynamite^ a hole is made for the detonator in the end 
 of the cartridge with a sharp stick or lead pencil and the deto- 
 nator, with fuse or wire attached, is inserted; the envelope is then 
 tied around the fuse, so that the detonator cannot become de- 
 tached from the cartridge, care being taken to place the deto- 
 nator in the cartridge only about % its length, so that the charge 
 may not be ignited by sparks from the fuse before the detonator 
 is exploded. 
 
 To fire gunpowder (PL 57, Fig. 5), the fuse alone is used, being 
 placed so that the end is well centered in the mass of the powder 
 and so secure that it cannot pull out. 
 
 429.— The simple electric fuse is so constructed that, upon 
 the passage of a current of electricity through a platinum wire of 
 sufliclent strength to heat the wire to redness, some fleecy gun- 
 cotton or other inflammable material, which is wrapped around 
 the wire, is ignited. This fuse may be used to fire a detonator or 
 to ignite gunpowder. 
 
 In PI. 55, Fig. 2, is shown a fuse with a cap, which cannot be 
 
PLATE 56. 
 
 FIG.l 
 
 FIG 4, 
 
 FIG, 6 
 
196 Demolitions. 
 
 removed, containing a detonating compound; hence it can be used 
 with best effect only in compounds that can be detonated. It is 
 called the commercial fuse and detonator. 
 
 In PI. 57, Fig. 10, is shown a fuse with a cap containing a det- 
 onator. The cap can be removed and the fuse used to ignite 
 gunpowder. It is called the service fuse and detonator. 
 
 Gun-cotton and gunpowder are fired as explained in Par. 428. 
 
 To fire dynamite y push the detonator in its full length and take 
 two half-hitches, with wire, about the cartridges, so as to hold 
 everything in place. (PI. 50, Fig. 1.) 
 
 430.— The Laflin and Rand Exploder, No. 3. The current 
 of electricity is generated by means of a battery consisting of 
 several cells, or by an electrical machine. The means now gen- 
 erally used, and the one that gives surest results, is the magneto 
 machine. On account of its compactness, portability, and sim- 
 plicity, the Laflin & Rand Exploder, No. 3, is probably the best 
 for all work where electricity is to be the igniting agent. (PI. 55, 
 Fig. 3.) The machine is cased in wood, and its dimensions are 
 13x8x5^/^ in. It weighs 18 lbs. The machine will fire, under 
 favorable circumstances, 12 fuses. In order that there may be 
 no chance of failure, a greater number than 5 should not be fired 
 in military operations by this machine. 
 
 The insulated wire used to make connection between the 
 machine and fuse is carried on a reel. Fig. 3. The connecting 
 wires between machine and reel are attached by binding posts, 
 as shown in the figure. 
 
 To use the m^cMne, reel off a sufficient amount of wire, usually 
 about 250 ft., and connect with the wires of the detonator; con- 
 nect the machine with the reel, being careful not to make this 
 connection until every one is at a safe distance from the place of 
 explosion. The handle on top of the box is now lifted, with- 
 drawing the ratchet bar to its full length, and, when the time 
 arrives to fire the charge, the bar is pushed vertically down- 
 ward, moving slowly for the first inch or two, then by a rapid 
 but even pressure, till the lower end Is stopped at the bottom of 
 the box. 
 
 When more than one charge is to be fired, the wires leading 
 to the several charges should be connected, as shown in PI. 57, 
 Fig. 6, 
 
Demolitions. 197 
 
 431.— In all connection of wires, at least 2 in. of each wire 
 must be cleaned bright and well wrapped around one another, 
 as shown in PI. 55, Fig. 4; under no circumstances simply hook 
 wires together. After wires are joined, the joint should be in- 
 sulated by winding rubber tape, or wide rubber bands, around 
 so as to overlap the next previous turn. When water has to be 
 encountered, wrap with rag or a strip of linen and cover with 
 tar; or, use rubber tube as shown: the tube in this case is placed 
 on one of the wires, and, when the joint is made, is pulled over it 
 and tied tightly to the wires on either side of the joint. (PI. 57, 
 Fig. 9.) 
 
 432.— To fell trees, bore a hole at the height desired, insert 
 the charge, and fire, care being taken that the center of the 
 charge is about the center of the tree. If the charge be of a 
 length equal to or less than the diameter of the tree, the hole 
 may be bored directly through; but if greater, then two or three 
 holes, intersecting at the center, must be bored, thus putting the 
 packages of gun-cotton in intimate contact, and requiring but 
 one detonator. The charge may be calculated from the formula 
 C=ys T2, in which C is the charge in pounds and T the diameter 
 in feet. 
 
 When time is not available to bore a hole, a necklace may 
 be used. The charge may be calculated from the formula C=3T ^ 
 in which C is the charge in pounds and T the diameter in feet. 
 
 Should the charge be placed or hung against the tree, the 
 amount as given by the formula for a necklace must be increased 
 one-fourth. 
 
 To make the tree fall in a given direction a rope may be tied 
 to it, hauled taut, and secured to another tree or strong stake. 
 
 The above method of felling trees is more expensive than with 
 the ax, and is not to be resorted to except In cases of emergency 
 where time is not available for slower methods. (PI. 55, Figs. 5, 
 6, 7 and 8.) 
 
 433.— To destroy bridge timbers, if rectangular, the charge 
 is placed across the whole width of the timber. (PI. 5B, Fig. 2.) 
 The charge may be calculated from the formula C=3WT^, In 
 which C is the charge in pounds, W the width and T the thickness 
 in feet. If the timbers are circular or square, the formula re- 
 
1^8 Demolitions. 
 
 duces to C=3T«, and being the same as that for trees where a 
 necklace is used, the charge should be so placed. 
 
 When high explosives are not on hand, the bridge torpedo used 
 in the War of the Rebellion may be substituted. It consists of 
 a bolt 8 or 9 in. in length, surrounded by a tin cylinder 2 in. in 
 diameter, which is filled with powder. The ends of the cylinder 
 are closed by iron washers, and a fuse placed in one end. To 
 use this torpedo, a hole 2^ in. in diameter is bored in the timber 
 and the torpedo inserted, having its center at the center of the 
 timber; it is then exploded by means of a fuse. If necessary, 
 two may be placed in holes bored at right angles to each other. 
 (PI. 56. Fig. 4.) 
 
 434.— To destroy a wooden truss bridge, if time is available, 
 the bridge may be burned; to do this, collect brush, etc., and, if 
 possible, place it under one end so as to bum it off and cause the 
 span to drop, but if not possible, build the fire in the center of the 
 span; it will burn through and cause rupture in the center. If time 
 is not available, blow away the main brace of the panel nearest 
 to an abutment or pier; it is really necessary to blow only one side 
 down, but it is better to be sure and destroy both sides. If the 
 bridge has an arch of wood besides the truss, then destroy the 
 arch on each side. It is better to attack the span over the deepest 
 water. 
 
 435.— Palisades may be cut down with axes or saws, the cuts 
 being made near the bottom: ropes are attached to the tops of 
 the timbers to assist in bringing them down; or the earth at the 
 bottom may be dug out and the palisade pulled over. 
 
 Palisades, up to 10 in. in thickness, may be blown down, when 
 the timbers are close together, with 4 lbs. of gun-cotton per run 
 ning foot. 
 
 436.— Stockades may be cut down with axes or saws, as ex- 
 plained for palisades. 
 
 They may be blown down with 4 lbs. of gun-cotton per run- 
 ning foot. 
 
 If the timbers are squared, the blocks of cotton may be fas- 
 tened to a thin board and placed against the foot of the stockade; 
 but if of rough logs, tie the blocks together so that they may 
 adapt themselves to the form of the timbers. 
 
 When stockades are double, and separated by a distance of 
 
Demolitions. 199 
 
 one yard--25 lbs. of gun-cotton per running foot or one charge of 
 80 lbs. may be placed. 
 
 Railway-iron stockades are breached by 7 lbs. per running 
 foot. 
 
 In all cases, distribute the charge so as to cover the length 
 desired to be breached. 
 
 437.— Gates may be blown in with 50 lbs. of gun-cotton ex- 
 ploded in one charge. The charge is hung against the center of 
 gate by means of a sharpened pick or on a nail. This charge is 
 large, but gates will generally be strengthened in some manner 
 on the inside. (PI. 57, Fig. 4.) The gates of Pekin were opened 
 by a couple of shots from 3.2-inch field guns directed at the locks. 
 
 438.— Houses may be blown down or shattered by placing 
 charges in the center of the floor and closing all outlets, such as 
 doors, windows, etc. Charge according to the size, 20 lbs. being 
 sufficient for small houses. 
 
 439.— Walls. The charge should be placed against the bot- 
 tom, close to the wall, and, if possible, should be tamped. If 
 time permits, a channel may be cut in the wall at the seat of the 
 charge. The charge untamped may be computed from the for- 
 mula C=%WT 2 in which C is the charge in pounds, W the width 
 of wall to be breached, and T the thickness; W and T are in feet. 
 When tamped with earth equal to the thickness of the wall, half 
 the above charge may be used. (PI. 57, Fig. 2.) 
 
 440.— Masonry bridge piers may be destroyed by a charge 
 calculated from the formula 0= W T ^ , C, W, and T being the 
 same as in par. 439. In order to avoid using so much gun-cotton, 
 it is better to place small charges in chambers excavated as deep 
 as possible in the masonry, and explode all simultaneously; cal- 
 culate charges as for walls. 
 
 441.— A masonry bridge arch may be destroyed by attacking 
 the haunches or the crown. The haunches are the best points of 
 attack, two trenches being dug across the width of the roadway 
 down to the back of the arch. If this is not possible, attack 
 the crown. A single trench across the width of the roadway 
 may be used, but it is better to use two, each placed from the 
 crown a distance equal to one-half the width to be breached. The 
 charge untamped may be calculated from the formula 0=%WT2, 
 in which C, W, and T are the same as in par. 439. When the 
 charge is tamped with a depth of earth equal to the thickness of 
 
200 Demolitions. 
 
 the arch, one-half the amount given by the formula is used. (PI. 
 57, Fig. 3.) 
 
 442.— Tunnels may be destroyed by placing charges back of 
 the masonry at the spring of the arch. If possible, the charge 
 should be placed in a chamber excavated behind the arch and 
 well tamped. Tunnels should be blown in at several places, so 
 as to render It impossible to repair them in a short time. Charges 
 as for bridge arches. (PI. 57, Fig. 8.) 
 
 443.— To cut steel rails, use one block of gun-cotton, weight 
 8 ozs., tie the block against the web of the rail with wire or twine, 
 and, if possible, tamp well with earth, and explode. (PI. 56, 
 Fig. 8.) 
 
 To blow a piece of some length out of a rail, arrange two 
 charges of 8 ozs. as shown in Fig. 5, placing one on each side of 
 the rail at a distance apart of 5 or 6 ft.; these should be exploded 
 by use of a magneto machine, so that the action may be simul- 
 taneous in both charges; the section will be blown out and turned 
 on its center, making a large opening. 
 
 444.— Switch points may be destroyed by lodging 8 ozs. of gun- 
 cotton between the outer rail and the pivot end of the switch 
 point, being careful to tamp as completely as possible. ("A," PI. 
 51, Fig. 11.) In the case of frogs, 8 ozs. placed in the angle of the 
 frog will destroy the point and render it useless. ("A," PI. 52, 
 Fig. 1.) 
 
 A great length of railway may be disabled at a very rapid 
 rate by making use of hand-cars loaded with gun-cotton, pre- 
 pared lengths of fuse inserted into detonators, torches, and 
 copper wire for binding the gun-cotton to the rail. One non- 
 commissioned officer and seven men will be necessary; two run 
 the hand-car: two sit on the hand-car and fix the detonators to 
 the gun-cotton, prepare binding wire and hand out the charges: 
 two men receive the charges and bind them to the rails; two 
 follow at about 150 yards In rear and fire the charges as they 
 pass. 
 
 445.— To cut wrought-iron plates, the charge is found from 
 the formula C=1.5Wt^, in which C is the charge in pounds, W the 
 width in feet, and the thickness in inches. The charge should 
 be placed entirely across the plate to be cut. 
 
 446.— To cut an iron bridge beam or girder (PI. 56, Figs. 6 
 
Demolitions. 201 
 
 and 7), calculate the charge for each separate cross-section to 
 be cut, using the formula in par. 445, and add the results; the 
 sum will be the charge required. The charge is most conven- 
 iently placed on the side of the beam, reaching entirely across 
 and bound on with wire, the primer being in the center of the 
 charge. If possible, a board should be tied over the charge and 
 earth tamped around it. When time is not available for placing 
 the charge as above described, it may be laid on top of the beam 
 or on the flange. 
 
 447.— Girder bridges not longer than 20 ft. may be overturned 
 by levers and thrown off the abutments. When this cannot be 
 done, the gun-cotton charge may be calculated and placed as de- 
 scribed for iron girders. 
 
 448.— In iron truss bridges the most favorable place for the 
 charge is at the center of the span on the lower chord. When 
 the bridge is of the variety known as a deck bridge, the charge 
 should be placed on the top member. When the lower or ten- 
 sion member is composed of eye-bars, the charge should be placed 
 between alternate pairs of eye-bars as near to the coupling- 
 pin as possible. The charge may be calculated as in par. 446. 
 (PI. 57, Fig. 1.) 
 
 449.— When bridges are supported by iron or wood piers, it is 
 sometimes possible to destroy the piers, and thus bring down the 
 entire structure. In attacking a pier, it is best to blow out the 
 supports on both sides, as this will bring down all of the bridge 
 resting on the pier. The charges may be calculated, if of stone, 
 by par. 440; if of iron, by par. 445. 
 
 450.— In destroying suspension bridges, blow down the tow- 
 ers below the saddles, excavate and blow out one of the an- 
 chorages, or cut the cable with gun-cotton. The charge for 
 bridge cables is calculated as for cutting iron plates; the charge 
 must be carefully placed, so as to be in close contact with the 
 cable. If the cables are made of plates, the plates may be cut 
 with .2:un-cotton, as in the case of eye-bars cited above. 
 
 451.— Field and siege guns may be disabled by detonating 
 1% pounds of gun-cotton on the outside near the muzzle. For 
 heavier fortress guns, detonate 4 pounds in the bottom of the 
 bore, tamping with sand. Tbe carriages may be destroyed by 
 using gun-cotton, 
 
PLATE 57. 
 
 iFIG.l. 
 
 FIG. 2. 
 
 FIG. 4 
 
 FIG.3. 
 
 FIG 6, 
 
 r IG 10. ^ • Service Fuye 
 
 „ bridia 
 f. prinrlna 
 h fulTTtinqre cf mercury, 
 lo to ^4 grains. ^ 
 
 drop 
 
 chwoocL. 
 
 Z paper, discs Xeld by 
 2. 7 ^ ^oUocTipn / 
 K. plug cf beechwoot 
 
 PIG. 9. 
 
Demolitions. 203 
 
 452.— Approximate Relative Strength of Some of the High 
 Explosives. 
 
 Explosive gelatine 128.3 
 
 Nitro-glycerine 120.3 
 
 Gun-cotton 100. 
 
 Dynamite, No 1, 75 per cent Nitro-glycerine 97.8 
 
 Rack-a-rock 74.2 
 
 Dynamite, 50 per cent 72.7 
 
 453.— Destruction of Obstacles. Wire entanglements may 
 be destroyed by cutting with wire nippers, or, if they are not at 
 hand, then the ordinary hand-ax will do, taking care to cut against 
 tlie picket. 
 
 Abatis is very difficult to destroy and cannot be removed 
 while fire can be brought to bear on the spot. Pry up the pick- 
 ets with levers and attach ropes to the butts of trees and haul 
 away. 
 
 Small pickets are cut through with the ax, or, if possible, 
 pulled up. 
 
 Small pits are filled with earth, brush, or covered by planks, 
 fascines, or bales of hay. 
 
 Automatic torpedoes are easily destroyed by driving animals 
 up and down the line suspected of containing them. 
 
 454. — The following table gives in a concise form all Inlrorma- 
 tion necessary for the use of gun-cotton and gunpowder. The 
 table shows approximately the value of the different high explo- 
 sives as compared with gun-cotton. 
 
 NOTE.— Charges are in lbs.; W and T are in feet; t is in inches. 
 
 W is width of breach to be made; T or t is thickness of object 
 to be demolished. 
 
 Gunpowder is assumed to be roughly tamped with sand-bags. 
 Gun-cotton is untamped. If the gun-cotton is tamped, the charges 
 may be reduced by about one-half. 
 
 Charge of gun-cotton must be equal in length to the breach 
 which Is to be made. 
 
204 
 
 Easty Demolitions. 
 
 Object Attacked. 
 
 Gunpowder 
 
 Gun-cotton 
 
 Remarks. 
 
 Brick arch ^ 
 
 I 
 
 IWT2 
 
 2 lbs. per 
 
 foot run 
 
 iWT2 
 |WT2 
 
 The length of 
 
 bleach, W, should 
 
 ► not be less than the 
 
 height of the wall 
 
 to be brought down. 
 
 Brick wall, 2 ft. or 
 less 
 
 Brick wall over 2 ft. 
 thick 
 
 Brick piers 
 
 Hard wood {e. g.y oak, 
 
 40 to 100 
 
 3WT2 
 
 In a concentrated 
 
 elm), in any form, 
 
 lbs. for 
 
 
 charge, or for trees 
 
 whether stock- 
 
 stockade 
 
 
 not over 12 in. diame- 
 
 ade, palisade, sin- 
 
 
 
 ter, in a necklace. 
 
 gle timbers, trees, 
 
 
 |T2 
 
 In auger-hole, when 
 
 etc. 
 
 
 
 the timber is not per- 
 fectly round, T = the 
 smaller axis. 
 
 Soft wood 
 
 Half the 
 
 charges 
 wood. 
 
 
 
 for hard 
 
 
 Breastwork of hori- 
 
 60 to 80 
 
 4 lbs. per 
 
 
 zontal balks, or 
 
 lbs. per 
 
 foot. 
 
 
 earth between 
 
 5 ft. 
 
 
 
 sleepers up to 3 ft. 
 
 
 
 
 6 in. thick 
 
 
 7 lbs. per 
 
 
 Heavy rail stockade. 
 
 
 
 foot. 
 
 
 Fortress gate 
 
 200 lbs. 
 
 50 lbs. 
 
 
 Iron plate 
 
 
 #Wt2 
 
 In this case only^ t 
 is in inches. 
 
 
 
 2 •» •• 
 
 Kield or siec^e cnins 
 
 
 \h lbs. 
 
 On chase near muz- 
 
 A J.V«XV& V^X \3X.\^^^\^ ^L ULXAv? • • 
 
 
 
 zle. 
 
 Heavier guns 
 
 
 4 lbs. 
 
 In bottom of bore, 
 tamped with water or 
 
 
 
 
 
 
 sand. 
 
 First-class iron rail . . 
 
 
 10 ozs. 
 
 Touching web of 
 rail and near a chair. 
 
 First-class steel rail . . 
 
 
 8ozs. 
 
 Four rails placed 
 round the charge will 
 
 
 
 
 
 
 be cut simultaneously 
 
 
 
 
 by it. 
 
CHAPTER XXI.— Camping Expedients. 
 
 455.— There are a few general principles wliich should be ob- 
 served in selecting a camp, whether the troops are to be estab- 
 lished in bivouac, in tents or in huts. These principles relate to 
 the health and comfort of the troops, the facilities for communi- 
 cation, the convenience of wood and water, and the resources of 
 the locality in provisions and forage. 
 
 456.— For an intrenched camp the ground must be selected 
 with particular reference to its adaptability for defense and the 
 camp arranged with that object in view, at the same time observ- 
 ing as many of the other requirements as possible. 
 
 457.— Dry and healthy sites, dependent on soil: Grardte, 
 metamorpMc and trap rocks, usually; clay slates, but drinking wa- 
 ter is scarce; limestone generally, but the water is hard, clear 
 and sparkling, though sonletimes contaminated; deep permeable 
 sandstones, if the air and soil are dry; deep gravels, unless lower 
 than surrounding country; pure sand, deep and free from organic 
 matter; well-cultivated soils generally; gravelly Mllocks, the very 
 best. 
 
 458.— Unhealthy sites, dependent on soil: Magnesium lime- 
 stone; shallow sandstone underlaid with clay; clay amd alluvial 
 soils generally; rice fields; made soils usually; newVy plowed 
 ground. 
 
 459.— Healthy sites, independent of soil: The hest is on a 
 divide or saddle, unless too much exposed or without water. The 
 next best is near the top of a slope, and the southern side is prefera- 
 ble Jo the northern; banks of running rivers are good, if not 
 marshy. 
 
 460.— Unhealthy sites, independent of soil: Enclosed valleys, 
 ravines, or the mouths of long ravines, ill-drained ground, the neigh- 
 borhood of marshes, especially if the wind blows from them. If 
 forced to camp near a marsh, the windward side should be select- 
 ed, and, if possible, have a hill or a screen of woods or brush be- 
 tween the camp and marsh. Moss generally indicates marshy 
 ground. 
 
 461.— Sites affected by surrounding vegetation: Herbage, 
 or closely lying grass, is always healthy, but should be kept 
 
206 Camping Expedients. 
 
 cut and all weeds destroyed; heavy brush about a marsh should 
 not be removed. Trees, in cold countries, break the winds; 
 in hot countries they cool the ground and raay protect against 
 malarial currents; so should only be removed with judgment. 
 
 462.— In selecting camps, wood, water, and grass should be 
 secured, if possible, together with good drainage, but marshy 
 ground* should not be occupied even for a night. 
 
 Old camp-grounds should never be occupied, if avoidable; 
 instead, go as far as possible to the windward side of them. 
 
 The site having been selected, the details of castrametation, 
 or the laying out of camps for the different arms, will be found in 
 the authorized Drill Regulations of each. 
 
 463.— Water is more immediately necessary to life than 
 food. 
 
 Each man requires, in bivouac on the march, for drinking and 
 cooking 3 to 4 quarts per day, and am equal amount for washing. 
 In camps, 5 gallons per day for all purposes. 
 
 Hospitals require several times as much per man per day. 
 
 Horses, mules, and cattle require from G to 10 gallons each 
 per day for drinking. It should be soft and clean, if possible. 
 Sheep and hogs require from 2 to 4 quarts each per day. 
 
 464.—/^ is imperative J on going into camp, tJiat the supply he imme- 
 diately looked after and a guard placed over it. If the supply be 
 small, special precautions must be taken and an officer put in 
 charge. 
 
 465.— Good drinking water should be bright, colorless, odor- 
 less, free from sediment, of pleasant and sparkling taste. 
 
 Rain water, collected from a clean surface, after the atmos- 
 phere has been well washed, is the purest in nature. Springs 
 whose origins are remote from habitations, streams flowing 
 through uninhabited regions, and large lakes, furnish the next 
 best sources of supply. 
 
 466.-7/" the supply be from a lake, pond, or stream, separate 
 places for obtaining water for men and animals must be marked 
 out, and care taken that the margin is not trampled into mud and 
 the water made turbid. Where this is likely to occur when ani- 
 mals are watered direct from the source of supply, a hard bottom 
 should be formed foy them to stand on, and a barrier formed to 
 prevent them going out too far. 
 
Camping Ewped/ients. 207 
 
 It is better, wliea couveuieut, to arrange rows of sunken half- 
 barrels, or board trouglis raised above tlie ground, into wMch the 
 water can be drawn. If the supply be limited, it may be neces- 
 sary to connect the troughs to prevent waste; if not limited, each 
 should be supplied direct from the source and the overflow 
 drained off. Even when drinking from a running stream, the 
 animals below get foul water. To prevent the ground around the 
 troughs becoming muddy, it should be paved and drained along 
 the whole length and for a distance of 10 or 12 ft. back. Where 
 troughs cannot be constructed, trenches lined with puddled clay 
 may be made to answer. 
 
 Arrangements should be made so animals may be brought up 
 from one direction and leave in another without confusion or 
 crowding. 
 
 467.—// iJie supply be from a stream, the water for drinking 
 and cooking for the troops is drawn highest up; for the animals 
 to drink, next below; and for washing, bathing, etc., lowest down; 
 while all drainage should enter below where any water is 
 taken. 
 
 If the stream be small, it may be necessary to construct a 
 series of small reservoirs by building small dams across. Ani- 
 mals drink better and more rapidly where water is 5 or 6 in. 
 deep. 
 
 468.— If unavoidable, water from small ponds and shallow 
 wells should only be used after being boiled half an hour, then 
 aerated and filtered. In fact, the only safe method of treating any 
 water that is not known to be pure is to boil it thoroughly for at 
 least half an hour, or distil it, one or the other of which methods 
 should always be insisted upon. 
 
 469.—// the supply be fro7n springs, each should be enlarged 
 and surrounded by a low puddled wall, to keep out surface drain- 
 age. They may be lined with casks or barrels charred inside, or 
 gabions, afterwards working in puddled clay between the earth 
 and linings. The overflow may be received into a succession of 
 casks let into the ground close together. 
 
 Surface springs should be sought for in hollows, at the foot 
 of hills, w^here the earth is moist, the grass unusually green, or 
 the thickest mists arise mornings and evenings. 
 
 470.— If water is not immediately available, it may be neces- 
 
 -14- 
 
208 Camping Expedients. 
 
 sary to dig wells. The most expeditious means of doing so is to 
 use Well Augers. (PI. 58, Figs. 1, 2, and 3.) 
 
 471.— To dig a well, an auger is attaclied to a rod suspended 
 from a rope passing over a pulley at the top of a derrick or tripod 
 and thence to a windlass. To the auger rod is secured an arm or 
 arms, by which the auger is turned by hand and so screwed down 
 into the earth. About eight turns till the auger, which is then 
 lifted, emptied and replaced. 
 
 472.— r/te auger for hoiiiiij in quicksand (Fig. 3) is shaped simi- 
 larly to the ordinary wood-boring auger, but with a hollow shank, 
 so that, when lifted, no suction is produced. When the thread be- 
 comes loaded, the auger is drawn up into an enclosing cylinder, 
 removed from well and emptied. 
 
 473.— Driven wells. The driven tube-well consists of a tube 
 about 3 ft. long, perforated with holes, and furnished with a steel 
 point of bulbous form (Fig. 4) and as many other plain iron tubes 
 as may be necessary. 
 
 The form of the point serves to clear a passage for the sockets 
 by w^hich the tubes are screwed together. 
 
 474.— To drive a well, a tube is screwed to the point (Fig. 5) 
 and on this a clamp is fastened by two bolts at about 3 ft. from 
 the lower extremity of the point. Next, an iron driving weight, 
 or monkey, is slipped on the tube above the clamp. The tube thus 
 furnished is raised and held vertically in the center of a guide, 
 in which it is retained by a latch. The w^hole being now arranged 
 in position, ropes are made fast to the monkey and passed over 
 pulleys on the guide, and driving commenced by two men pull- 
 ing the ropes and allowing the monkey to fall on the clamp. As 
 soon as the clamp reaches the ground, the monkey is raised and 
 held up, the clamp loosened and raised 1.5 or 2 ft., tightened, 
 and the driving continued as before until the top of the tube 
 comes below the hole in the top of the guide head, when the 
 lengthening bar (Fig. 7) is dropped into the top of the well-tube. 
 The lengthening bar consists of a length of the well-tubing with 
 a smaller pipe brazed into one end and projecting about 1 ft., 
 which fits into the well-tube. This bar keeps the tube steady 
 and serves as a guide for the monkey to slide on until the top 
 of the well-tube reaches to within a foot of the ground. The 
 lengthening bar is then removed, another tube is screwed on, 
 
PLATE 58. 
 
 Pig.l 
 
 Fig. 2. 
 
 Fig.3. 
 
 
 Fig.l3. 
 
 J^Ll 
 
210 Campi/ng Expedients. 
 
 and the driving continued until water is reached. A hollow 
 iron plumb is frequently lowered into the tube to ascertain when 
 water has been reached or whether earth of any kind has got 
 into it. 
 
 Accumulations in the tube, of a loose sandy nature, can be 
 pumped up, by screwing a funnel (Fig. 8) on top of the tube, then 
 lowering into it through the funnel a small tube with a pump 
 attached. Water poured into the funnel runs down outside the 
 smaller tube and is pumped up through it, bringing the mud and 
 sand. When water is struck, and stands several feet in the tube, 
 the pump is screwed on to the well-tube. 
 
 The well can also be driven without the use of the tripod sup- 
 ports (Fig. 6), care being taken to keep the tube vertical by means 
 of guy-ropes. Such a well can be driven from 10 to 20 ft. per hour. 
 The tubes can be withdrawn without damage by reversing the 
 operations of driving. (Fig. 9.) 
 
 475.— The tube-well is not intended for piercing rock, or 
 solid stone formations, but is quite capable of penetrating very 
 hard and compact soils. When striking rock, stone, or deep beds 
 of clay, it is best to pull up the tube and try in another spot, for 
 by going a little distance off water will in many cases be found. 
 
 476.— Clarification of water. Water usually contains min- 
 eral and organic substances in solution and in suspension. ^Sub- 
 stances in solution completely disappear and cannot be entirely 
 filtered out. Substances in suspension do not entirely disappear 
 and may be filtered out. 
 
 477.— Hard water contains one or more substances, as lime, mag- 
 nesia, iron and others, in solution, which are liable to produce 
 intestinal troubles to persons unaccustomed to them. Cooking 
 vegetables in it is very difficult. Washing with it requires a 
 great deal of soap. 
 
 The hardness of water may be partially removed by boiling 
 for half an hour or so, or by adding a small quantity of wash- 
 ing soda, or by adding a couple of ounces of quicklime to 100 
 gallons. 
 
 478.— Substances in suspension may be largely removed hy pre- 
 cipitation and filtration. 
 
 479.— Precipitation is allowing such matter as will to settle 
 through Its greater specific gravity, or by inducing it to do so 
 
Ca/mping Expedients. 211 
 
 through some harmless chemical or mechanical action. For 
 which purpose may be used about 6 grains of crystallized alum 
 to the gallon, or tannin in small quantities, and letting stand sev- 
 eral hours before using; bruised cactus leaves, also tea leaves 
 that have been used, act similarly; citric acid, 1 oz. to 16 gal., or 
 borax and alum, 1-3 oz. each, or 1 to 2 tablespoonfuls of ground 
 mustard to a barrel, improves water. 
 
 480.— Piltration is mechanically arresting and attracting sus- 
 pended matter, and removing dissolved matter in the water. Fil- 
 tering materials act only for a short period and should be fre- 
 quently cleaned. 
 
 4:81, ^Materials which may he used are sponge, wool, and like 
 articles for straining, but must be constantly removed and 
 cleaned. Clean sand, gravel, and porous stone remove sus- 
 pended matter, but have little or no effect on dissolved organic 
 matter. Iron sponge, a compound of sawdust and iron oxide 
 heated in a furnace, and Garferal, sl composition of charcoal, iron, 
 and clay, are efficient for removing mineral matter. Bone-black 
 or animal charcoal, and wood charcoal, when freshly burned, ab- 
 sorb mineral matter for a couple of weeks, but their chief action 
 is on organic matter. 
 
 482.— Charcoal may be made by digging in the ground a cir- 
 cular pit, some 6 in. deep by 4 or 5 ft. across, then placing a large 
 pole or bundle of brushwood vertically in the center. Around 
 this the wood to be burned is piled, forming a kind of cone. The 
 pile is then covered with brush, and on this a layer of 4 or 5 in. of 
 earth. (Fig. 10.) The center pole is then removed and a fire 
 lighted in its place, receiving air from vents left at the bottom for 
 that purpose. The fire proceeds from the center outwards, and, 
 if burning properly, the smoke is thick and white. If it does 
 not spread to every part, new vents must be made. If the smoke 
 becomes thin and a blue flame appears, it is burning too fast, and 
 vents must be stopped up or more earfh thrown on. When the 
 smoke ceases to escsne, the vents and chimney are closed and the 
 pile allowed to stand for a couple of days until it cools. 
 
 From 20 to 25 per cent of charcoal is thus obtained. 
 
 483.— A convenient portable filter (Fig. 11) is made by 
 taking a small cylinder of compressed carbon and inserting it 
 In 9, rubber tube in such a manner that the carbon end may 
 
212 Camping Expedients. 
 
 be immersed in the water, then applying the mouth to a mouth- 
 piece at the other end of the tube, and drawing the water through. 
 
 484.— The Success Filter (Fig. 12) consists of a cylindrical 
 porous stone 4 in. long by 4 in. in diameter with a hole bored in 
 one end. In this is fitted a rubber gasket, through which passes 
 an iron tube that is fastened into the bottom of a barrel, jar, or 
 bucket. The water filters through the stone into the hole inside 
 and passes out through the tube into a receiving vessel below. 
 (Fig. 13.) 
 
 By fastening the iron tube into the bottom of a large empty 
 tomato or peach can, in which the stone is placed on the tube and 
 wedged fast, then fastening a rubber tube 2 or 3 ft. long on the 
 iron tube outside of the can, a syphon filter is obtained. The 
 action is set up by exhausting the air from the stone, after the 
 can and stone are immersed in water, by sucking on the end of the 
 rubber tube until the water is started. 
 
 485.— A simple water filter may be made by stuflSng a 
 piece of sponge in a hole in the bottom of a cask, flower pot, or 
 other vessel (Fig. 14), then placing above this a layer of coarse 
 sand, then a layer of pounded charcoal 3 or 4 in. thick, then 
 another layer of coarse sand and on this a layer of coarse gravel. 
 The layers should be thick as possible, and tightly compressed, 
 and washed thoroughly clean before being used. The differ- 
 ent layers may be prevented from mixing by perforated boards, 
 or otherwise. Another form may be made as shown in Fig. 15. 
 
 486.— Casks, or barrels, charred on the inside (and occasionally 
 cleaned, brushed, and recharred), improve water. 
 
 487.— Latrines. Arriving on the site of a camp, one of the 
 first duties is to designate the places to attend to the calls of na- 
 tiire, and there dig latrines. Urinals should be placed nearer the 
 camp and of easy access. 
 
 The only exception to digging latrines Is when the command 
 is very small, is certain to march the next day, and no other 
 troops are to follow. 
 
 488.— Latrines and urinals should be so placed as not to be in 
 the course of the prevailing winds to the camp, and must be so 
 situated that they cannot pollute the watpr, either directly or by 
 iRoakage. 
 
Camping Expedients. 213 
 
 489.— A small, shallow trench will suflSce for a single night, 
 and should invariably be filled in the morning before marching. 
 
 For longer periods, a trench 2 or 3 ft. wide at top, from 2 to 10 
 ft. deep, and 12 to 15 ft. long for every 100 men, should be dug, 
 throwing the earth to the rear, from which a layer of a few inches 
 should be thrown into the trench every day, or oftener if neces- 
 sary. Lime or charcoal may also be used to deodorize the 
 soil. 
 
 It is better to increase the number of trenches than to make 
 any one trench too long. 
 
 Shallow latrines should be discarded when filled within a foot 
 of the surface, and completely filled in with earth; deep ones when 
 within 3 or 4 ft. of the surface. 
 
 All latrines should be filled in and marked before marching. 
 
 490.— In temporary camps, latrines may be provided with seats 
 of a pole and a back, and be screened by bushes, canvas, or other 
 means. (Fig. 16.) 
 
 491.— Kitchens. On going into camp, kitchens should be 
 promptly established, and in the same relative positions as if the 
 camp were going to last a month or more. A pit should be dug 
 near by for strictly liquid refuse, while solid matter should be 
 placed in a box or barrel for the police party to remove. 
 
 4:92.— When fuel is plentiful, a trench of sufficient length and 
 about 1 ft. deep may be dug to contain the fire, over which the 
 kettles are hung from supports. (PI. 59, Fig. 1.) 
 
 If fuel is scarce, then dig a trench as above in the direction of 
 the wind, but a little narrower than the diameter of the kettles to 
 be used. Plnoe the kettles over the trench and fill in between 
 with stones, clay, etc., forming a kind of flue. The draft may be 
 increased by building a chimney of sods, stones, etc., on the lee- 
 ward end and enlarging the windward end. (Fig. 2.) 
 
 If the camp is to be for a long time and the direction of the 
 wind liable to vary, a number of such trenches mav be dug 
 radiating from a common point, over which point a chimney is 
 constructed. Then, whatever the direction of the wind, the 
 trench opening in that direction can be used, the others being 
 closed. 
 
 The trenches should have a slight fall from the chimney back 
 for drainage, and a means for the water to escape. If the ket- 
 
PLATE 59, 
 
 FIGl 
 
Ca/mping Expedients. 215 
 
 ties are small or of various sizes, rests of stones, scraps of iron, 
 etc., may be placed across the trench. 
 
 A square hole may be dug for the fire with trenches for draught 
 at the corners, the kettles being placed on rests over the fire. 
 (Fig. 3.) 
 
 493.— A grillage or kind of grate about 1 ft. high, made of gas- 
 pipe or bar-iron, is sometimes used to set over the fire, and on this 
 are placed the kettles. (Fig. 4.) These are sometimes made with 
 movable joints, so as to be closed for transportation. 
 
 494. — If a covered kitchen is desired, either a trench similar 
 to Fig. 2 can be dug, or one above ground can be built with stones 
 and sods and a tent placed over it, or a cover constructed. 
 
 495.— To bake bread, when none of the portable ovens of the 
 Commissary Department are carried, improvised ovens must be 
 constructed. The simplest method is to take a barrel with one 
 head out (one with iron hoops best), lay it on its side in a hollow 
 in the ground and then plaster over with wet clay 6 to 8 in. thick, 
 then with a layer of dry earth equally thick, leaving an opening 
 of 3 or 4 in. at the top of the closed end for a flue. The staves are 
 then burned out by a hot fire, which also bakes the clay covering, 
 forming an arched oven. To bake, after heating, the front and 
 flues are closed. Or a pit may be dug from 6 to 12 in. deep and 4 
 by 5 ft. for the hearth, over this form an arch with a hurdle or any 
 other material available (Fig. 7), with a chimney at one end and 
 a door at the other. Then plaster and cover the arch as in the 
 barrel oven and bake the clay covering. 
 
 496.— An oven may be excavated in a clay bank (Fig. 6) and 
 used at once. 
 
 497.— The Buzzacott Army Field Oven (Fig. 8), which is an ar- 
 ticle of issue, is a complete camp cooking outfit, consisting of oven, 
 baking and frying pans, etc. All are securely packed together and 
 can be conveniently carried in the feed box of an army wagon or 
 on a pack animal. To use it, a bed of live coals is first obtained, 
 then the oven after being heated is placed on rests over a bed of 
 coals, and a layer of sand sprinkled evenly over the bottom of the 
 oven to prevent burning out. In this is placed the pans of pre- 
 pared food on suitable rests and the whole covered with a hood, 
 
216 Camping Expedients. 
 
 On th,e hood is scattered a layer of live coals and burning brands. 
 Broiling, frying, coffee-making, etc., may be done on top of the 
 oven by using the remaining pans, rests, etc., at the same time 
 that the interior is used for baking. 
 
 498.— Drainage. The camp beiug located, a system of sur- 
 face drainage should be carefully traced and constructed. As 
 soon as a tent is pitched it should be surrounded by a shallow 
 ditch outside, emptying into a company -ditch. The proper meth- 
 od of doing this is to have the inner edge of the ditch come just 
 inside of the skirt wall of the tent to catch the water running 
 down the side of the tent and to drain the interior. 
 
 The picket should be inside of the ditch. (Fig. 9.) To bank 
 earth up against the tent soon rots the bottom of the wall. 
 
 499.— Beds. The ground being generally too damp to lie upon 
 directly, all should sleep upon some dry material, as straw, leaves, 
 or preferably a low platform constructed of small branches and 
 poles, if available. (Fig. 10.) 
 
 If required to sleep upon the ground, one will sleep more com- 
 fortably if he scrapes out a small hollow for his hips. Straw, 
 hay, etc., for sleeping upon may be made into mats with the Malay 
 Hitch as in Fig. 11. 
 
 500.— Windbreaks. When troops bivouac, some protection 
 from wind may be obtained by building up to the windward a 
 pile of earth, sods, etc. Where trees are available, by resting a 
 pole on two forked sticks, 4 or 5 ft. high, against which branches, 
 thick end up, are piled at an angle of 45** on the windward side. 
 (Fig. 12.) Hurdles similarly placed, supported and covered (Fig. 
 18), canvas or blankets secured as in Fig. 14, straw or hay clamped 
 between poles as in Fig. 15, may be used. 
 
 By throwing up either a half or whole circle of earth 18 ft. in 
 diameter, from a ditch on the outside, some protection may be 
 obtained. On the bank so formed additional windbreaks may be 
 placed or a covering extended over it all may be made. (PI. 60, 
 Figs. 1 and 2.) 
 
 501.— In cases of prolonged occupation, if tents ar^ not avail- 
 a^ble, tfifi trppps shpyld builcl ish^ltei* pf some bJnd, 
 
PLATE 60. 
 
218 Cwmping Expedients. 
 
 Huts may be built of timber, logs, brushwood, adobe, etc., in 
 connection with straw, bark, sods and similar materials. 
 
 All huts should, if possible, have their floors raised above the 
 ground to allow free circulation of air underneath. (Fig. 3.) Only 
 in very dry soil and when not to be occupied long is it allowable 
 to sink them, if avoidable. Space between huts in the same row 
 should equal the height of walls, and passage in rear equal the 
 height of ridge. Hut sites should be well pounded. 
 
 Huts are ordinarily constructed to contain a small number of 
 men, but the sizes and details of construction will depend greatly 
 upon the site and materials available. 
 
 A very fair minimum allowance per man of bed space is about 
 2.5 ft. X 7 ft. with a passage at foot from 2 to 4 ft. 
 
 Thus, the plan for 8 men may be taken at 10 ft. x 18 ft., ar- 
 ranged as in Fig. 4. For 12 men, 15 ft. x 18 ft. For 16 men, 20 
 ft. X 18 ft. For 20 men, 25 ft. x 18 ft. 
 
 For calculating the accommodation at the above rates, allow 
 1 man per pace of length for a single row of beds and 2 men per 
 pace of length for a double row of beds. 
 
 502.— Major Smart, Medical Department, recommends as best 
 a modification of the Army of the Potomac hut, of rectangular 
 plan (Fig. 5), 7 ft. x 13 ft., height to eaves 6 ft., to ridge 10 ft; door 
 in middle of one long side, chimney opposite door on outside of 
 wall; on each side of doorway a double bunk. This hut to accom- 
 modate 4 men. 
 
 If logs are used, the ends are trimmed with an ax where they 
 lap at the corners, so they will lie one upon the other throughout 
 their length. 
 
 503.-— If made of small timber, some style, as in Fig. 6, with 
 thatched roof, might be used. 
 
 If, for any reason, it is not desirable to build huts as above, 
 forms may be used as shown in Fig. 7, or hurdles, as in Fig. 8. 
 
 504.— Sentry boxes may be made as in Fig. 9, the side cover 
 Ing consisting of watling described in Chap. IX. and the roof 
 thatched. 
 
 505.— An excellent form of bamboo hut with grass roof, as 
 shown in cut, has been successfully used In the Philippines. The 
 
Camping Expedients. 
 
 219 
 
 corner posts were made double for additional strength, the floor 
 being of bamboo strips lashed firmly to bamboo floor beams. 
 Wooden pins and rattan lashings were used throughout. The hut 
 shown is 16 ft. square, in the clear, and furnished comfortable and 
 sanitary sleeping-room for eight men on gold medal cots. 
 
INDEX. 
 
 Par. 
 
 ABATIS, consists of, how 
 
 made 50 
 
 in shallow ditch, of small 
 branches, in front of 
 
 glacis 5 
 
 how destroyed.^ 41 
 
 ADVANCED PO^T, rear of... 204 
 ANCHORS, number of, scarc- 
 ity of 343 
 
 substitutes for 344 
 
 use of 342 
 
 weights of, names of parts 
 
 of 341 
 
 aNGLiE, equal to a given 
 angle, method of laying 
 
 out 22 
 
 right, method of laying 
 
 out 18 
 
 re-entrant, salient, shoul- 
 der 82 
 
 APPROACHES, in siege oper- 
 ations constructed by 
 
 infantry 154 
 
 AREA, of rectangle, of trape- 
 zoid, of triangle, method 
 
 of finding 25 
 
 ARTILLERY, in defense of 
 
 village, where placed... 215 
 
 in woods 179 
 
 projectiles 9 
 
 to be placed outside of 
 
 works 87, 151 
 
 AX, use of 44 
 
 BALKS, bay, etc., defined... 284-285 
 BALLAST, for R.R., object of 377 
 BANK, GUN, definition of, 
 relative advantages of, 
 
 and embrasures 70 
 
 dimensions of, where 
 
 placed 102 
 
 space required for 100 
 
 BARREL, buoyancy of, how 
 
 determined 325 
 
 BARRELS, closed, piers of, 
 
 construction of 333 
 
 open, piers of, construc- 
 tion of 328 
 
 open, safe load of 329 
 
 Par. 
 BARRICADE, use and con- 
 struction of 61 
 
 for doors of buildings 195 
 
 BATTERIES, telegraph, how 
 
 carried 418 
 
 B AY, length of, how found ... 317 
 
 BEDS, camp 499 
 
 BERM, definition of, etc 65, 99 
 
 advantages and disadvan- 
 tages of 78 
 
 RINDING, fascines 117 
 
 BISECTING an angle, method 
 
 of 20 
 
 BLOCKS, description of, etc., 
 
 running 228 
 
 BLOCKHOUSE, use and con- 
 struction of 144 
 
 Spanish 145a 
 
 in isolated places 145 
 
 BOAT, buoyaiicy of, how 
 
 found 316 
 
 BOX or barrel to sling 223 
 
 ponton, construction of . . . 323 
 
 BRACKETS, .telegraph 410 
 
 BREAKING loads of ropes . . . 218 
 BREAKS in telegraph lines . 419 
 BRIDGE, anchored to haw- 
 ser 343 
 
 beams, of iron, how de- 
 stroyed 446 
 
 connection of with shore, 
 
 how made 350 
 
 computing strength of.. . 255 
 
 double lock 27^ 
 
 expedients 278 
 
 floating, description of, 
 
 modi ttcation of 306 
 
 floating, improvised 352a 
 
 flying, description of 3u9 
 
 forming, by sue cessive 
 
 pontons 346 
 
 forming, by parts 347 
 
 forming, by rafts 348 
 
 forming, by conversion . . 349 
 masonry, how destroyed. . 
 
 .....440-441 
 
 maxi num load for 247 
 
 namf of, how derived. . .248, 310 
 
 Paine's 260 
 
 pile 269 
 
222 
 
 hidex. 
 
 Par. 
 
 BRIDGE— Continued. 
 
 protection of, from float- 
 ing objects 352 
 
 railroad, repair of 407 
 
 requirements of 244 
 
 short, how anchored 343 
 
 single lock 274 
 
 single sling 276 
 
 spar railroad 245 
 
 suspension 280-6 
 
 suspension, how destroyed 450 
 
 swing 351 
 
 trail 308 
 
 treble sling 277 
 
 twenty-five feet or le«»}a.. . .258-9 
 twenty-five feet or over . 
 
 261,271,276 
 
 BROADSIDE VILLAGE, how 
 
 defended 1V\ 
 
 BliUSH huts 503 
 
 sentry boxes 504 
 
 BRUSHWOOD, bundles of, va- 
 rieties and sizes 115 
 
 rate and method of clear- 
 ing 40 
 
 roads. 371 
 
 BUILDING, defense of, how 
 regarded, first line, how 
 
 far distant 191 
 
 doors of, how barricaded, 195 
 
 flank defense of 199 
 
 how used for defense 189 
 
 loopholingof 194 
 
 materials used in defense 
 
 of 200 
 
 precautions in defense of. 19^ 
 
 removal of 48, 438 
 
 requisite of, for defense . 190 
 steps in preparing for de- 
 fense 193 
 
 windows of, how barri- 
 caded 197 
 
 BUOYANCY of casks, how de- 
 termined 325 
 
 BUZZACOTT oven, descrip- 
 tion of 497 
 
 CABLE, charge Of explosive 
 
 to cut 450 
 
 swinging, length of 309 
 
 CAMP BEDS 499 
 
 CAMPS, drainage 498 
 
 dry and healthy sites 
 
 for 457,459 
 
 selection of 455, 45«, 462 
 
 unhealthy sites for 458, 460 
 
 windbreaks for 600 
 
 C AN IS TE R. description of. . . 11 
 
 CANVAS PONTON, U. S 319 
 
 CANVAS RAFT, description of 303 
 CAPITAL of field works ... 82 
 CAPONIERS, objections to, 85, 146 
 
 stockade work used for 188 
 
 used in flanking buildings, 199 
 
 CAPSTAN, description of 241 
 
 improvised field 243 
 
 Par. 
 CASEMATES.use and general 
 
 form of 138 
 
 how constructed, floor 
 
 space in 139 
 
 CENTRIFUGAL FORCE of 
 
 train 383 
 
 CHARCOAL, uses of 481 
 
 how made ^. . . 482 
 
 CHARjGES, several exploded 
 
 at same time 439 
 
 CHESS described 248 
 
 CHEVAUX-DE-FRISE 56 
 
 CHOKER FASCINE, descrip- 
 tion and use of 117 
 
 CIRCULAR VILLAGE, how 
 
 defended 214 
 
 CLARIFICATION of water . . 476 
 
 CLAY ROADS 367 
 
 COMMAND OF WORKS, defi- 
 nition of 71 
 
 COMMON T KENCH work,how 
 
 made, uyesof 156 
 
 COMMUNICATIONS, c o n - 
 
 struction of 373,374 
 
 i n woods 177 
 
 CONCENTRATED LOAD on 
 
 bridge 253 
 
 CONDUCTOR, metallic, for 
 
 telegraph 408 
 
 CONNECTING WIRES, how 
 
 done 431 
 
 CORDUROY ROADS 370 
 
 COUNTER-SCARP, definition, 
 
 etc.... 65, 79 
 
 galleries 85 
 
 COVERforguns 40a 
 
 in woods, how obtained .. . 176 
 
 CRAB 240 
 
 CREST, exterior 67 
 
 interior 66 
 
 military 153 
 
 CRIB piers, construction of.. 268 
 ponton, construction of... 322 
 
 CROSS, in telegrjiph wires 419 
 
 CROSS ARMS, telegraph 410 
 
 CROSSING of rivers, selec- 
 tion of, how determined, 289 
 
 CROSSINGS, railroad 385 
 
 CROW'SFEET 56 
 
 CUTTING, how defended. . .171, 172 
 
 DE ' O LOAD on bridges 253 
 
 DEBRIS, removal of 48 
 
 DEFENDERS of woods, num- 
 ber of 179 
 
 DEFENSE, of fences 368 
 
 passive, with respect to 
 
 lines of works 149 
 
 DEFILADE, definition of.... 88 
 
 In plan 89 
 
 in section 90, 91 
 
 with two planes 92 
 
 DEPTH of fords 290 
 
 DERRICK, description of . . . . 237 
 
 in using 240 
 
Index. 
 
 223 r 
 
 Par. 
 DESTROYING railroads, by 
 
 whom done 399.400 
 
 by whom ordered 401 
 
 of telegrraph lines 420 
 
 DETONATOH 429 
 
 withfuse 428 
 
 electrical 429 
 
 DIGGING wells 470, 471, 472 
 
 DIMENSIONS of loopholes ... 164 
 
 DISABLING railroads 398 
 
 DISTANCE between two in- 
 accessible points.method 
 
 offlndinpT 24 
 
 D!8TRIBUTED load 253 
 
 DITCH 65,81,361 
 
 depthof 96 
 
 method of digging 1"1 
 
 DOORS, how barricaded 195 
 
 DOUBLE lock bridge 275 
 
 DRAINS, catch and covered. . 3fil 
 
 DRAINAGE of camps 498 
 
 of roads 361 
 
 DRINKING water 465-9 
 
 DRIVEN wells 473-4 
 
 DRIVING piles 270 
 
 DYNAMITE, use of with de- 
 tonator 428 
 
 EARTH, excess of at salients. 97 
 in embankments, space 
 
 occupied by 96 
 
 roads 366 
 
 EARTHWORKS, calculation 
 
 of dimension j! of 95 
 
 ELECTRICAL fuse 429 
 
 EMBANKMENT, how defend- 
 ed 170 
 
 EMBARKATION, in ferrying 301 
 
 EMBRASURE 69 
 
 used when, details and 
 
 construction of. 103 
 
 space required for 100 
 
 ENGINE, locomotive 389 
 
 ENGINEERING, Military, 
 
 Field, definition of 1 
 
 EPAULEMENT, gun 4()a, 70 
 
 relative advantage of, and 
 
 embrasures 70 
 
 EQUILATERAL TRIANGLE, 
 
 method of laying out — 21 
 
 ESCAPE in telegraph lines... 419 
 
 ESCARP 65, 79 
 
 EXPEDIENTS, bridge 278 
 
 EXPLODER, electrical 430 
 
 EXPLOSIVES, kind general- 
 
 ly used 421 
 
 table of comparative 
 
 strength of 453 
 
 EXTENDING along zig-zag.. 155 
 
 workinsr party 109, 110, 155 
 
 EXTfc:NSION on flying sap, 
 
 method of 158 
 
 EYE-BARS, how cut 448 
 
 j;yE-SPLICE, to make 222 
 
 FACES of works 82 
 
 FARMS, principles of defense , 
 
 applied to 203 » 
 
 FASCINES, size, weight, and f' 
 
 making of 117 
 
 FASTENINGS, rail 382 
 
 FAULTS in telegraph lines.419-20 
 
 FENCES, defense of * 168 
 
 removal of when 48 
 
 FERRY, the rope 307 
 
 FERRYING by boat, embark- 
 ation, and unloading 301 
 
 by raft 302 
 
 FIELD GUNS, destruction of 451 
 
 range of 13 
 
 FIELD LEVEL,description of 26 
 
 FILTERS, portable 483-4 
 
 simple 485 
 
 FILTERING water 480-1 
 
 FIRE, as regards direction, 
 
 trajectory 8 
 
 double tier of, for walls... 167 
 
 sector of, discussion of — 86 
 working parties exposed 
 
 to Ill 
 
 FLANK defense of buildings 199 
 
 FLANKS of works 82 
 
 FLOOR space in casemates. . . 139 
 FLOATING piers, essentials 
 
 of 314 
 
 FLYING BRIDGES, raft for. . 340 
 
 telegraph lines 418 
 
 sap, description of 157 
 
 sap. method of extension 
 
 along 158 
 
 FORDS, how made impassa- 
 ble 58 
 
 with sandy bottom 291 
 
 depth of, requisite of 290 
 
 in mountainous country. . 291 
 
 level country 291 
 
 how marked, position of, 
 
 how determined 293 
 
 precautions in selecting. . 295 
 
 re-examinations of 296 
 
 where found 292 
 
 FOREGROUND, extent of 
 
 clearing 43 
 
 FORM, strap iron gabion ..... 120 
 
 wicker gabion 118 
 
 of roads 359 
 
 FORMING BRIDGE by con- 
 
 version 349 
 
 by parts 347 
 
 by rafts 348 
 
 by successive pontons ... 346 
 
 FORTS, how distinguished. . . 84 
 FORT WaGNER, parallels 
 
 and approaches to 160 
 
 FORTIFICATION, classes of. 2 
 compared to other milita- 
 ry expedients 7 
 
 oblect of 
 
 subdivision of field 3 
 
 FOUGASSE.conBtruotlon.use 
 
 anachavgefor,,,,. „ \^ 
 
224 
 
 Index. 
 
 Par. 
 
 F RAISES, construction and 
 
 use of 55 
 
 FROGS 384 
 
 railroad, how destroyed. . 444 
 
 FUSE 427 
 
 how used 428 
 
 GABIONS, hoop or strap iron, 
 
 weififht and making of... 120 
 
 method of carrying 157 
 
 sheet iron, making of 121 
 
 wicker, size, weight, and 
 
 making of 118 
 
 making of without a gabi- 
 on form 119 
 
 GATES, destruction of 437 
 
 GIN, description of 239 
 
 using 240 
 
 lashing, making of. 227 
 
 GLACIS. 65.80 
 
 GORGE of works 82 
 
 GRADIENT, limitingof roads 355 
 
 GRAIN, removal of standing. 47 
 
 GRASS, removal of standing. 47 
 
 GRAVEL ROADS 368 
 
 GRILLAGE 493 
 
 GAUGE of railroads 380 
 
 GUARDING water supply . 464 
 
 GUN-COTTON 422 
 
 how detonated 428 
 
 GUN EPAULEMENTS nnd 
 
 pits 40a 
 
 GUNPOWDER, how ignited. 428 
 
 used as an explosive 424 
 
 GUTTERS 361 
 
 HARD WATER 477 
 HASTY DEMOLITION, ta- 
 bles showing charges 
 
 for 452 
 
 HEAD LOGS, use of 40 
 
 HEALTHY CAM PS 4n7. 459 
 
 HEDGES, advantages of. how 
 
 derived, principles of... 169 
 
 removed , when 48 
 
 HEIGHTS over which fire 
 
 mav be delivered 13 
 
 HITCHES, knots, etc 219 
 
 HOLDFASTS, description of. . 243 
 HOOPS, making of, for strap 
 
 iron gabions 120 
 
 HORSE, power of on grsades.. 356 
 
 HOUSES, demolition of 438 
 
 HURDLES, continuous, con- 
 
 sti'ucl ion of 123 
 
 size,weight and making of 122 
 
 HUTS, brush. 503 
 
 how made, etc 501 
 
 Army of Potomac (Major 
 
 Smart's) 502 
 
 allowance of space in ftOl 
 
 bamboo 605 
 
 of, how in- 
 
 Par. 
 
 297 
 
 ICE 
 
 thickness 
 
 CI eased 299 
 
 thickness of for various 
 
 loads 298 
 
 INFANTRY APPROACHES 
 
 in siege operations 154 
 
 INTERVALS between trench- 
 es 36 
 
 method of taking.by work- 
 ing parties 100 
 
 usual for working par- 
 ties Ill, 112 
 
 INSU L ATORS, telegraph 412 
 
 INSULATED WIRE JOINTS 431 
 INTRENCHMENTS, HASTY, 
 advantages and disad- 
 vantages of 39 
 
 concealment of 38 
 
 conditions to be fulfilled 
 
 by '28 
 
 consist of 28 
 
 for men standing 31 
 
 for skirmishers lying 28 
 
 for two ranks kneeling... 30 
 
 for supports and reserves. 33 
 
 intervals in line of 36 
 
 iFolated- 32 
 
 location of depends upon. 35 
 
 on slopes 34 
 
 Spanf sh 31 
 
 IRON PLATES, how cut 445 
 
 ISOLATED PITS b2 
 
 JOINTS for telegraph wire. . . 417 
 
 American twist 417 
 
 insulation of 431 
 
 rail 381 
 
 JUNCTIONS, railroad 386, 
 
 KING-POST TRUSS 272: 
 
 KITCHENS 491-2* 
 
 covered 494J 
 
 KNOTS, hitches, etc 219» 
 
 LANCES, military, telegraph. 418 
 
 LASHINGS, gin 227 
 
 rack 224 
 
 shear 226, 
 
 transom 225 
 
 L ATRINES 487, 490, 
 
 LEAKS in telegraph line 419 
 
 LEVEL, field, description of. 26 
 
 uses of 27 
 
 LINES, cutting of ditch and 
 
 trench,. 101 
 
 LINE, first, falling back past 
 
 housea. ,,, 192 
 
 par all ell to given line, 
 
 metliod of constructing. 23 
 LINES, fvecond and thiiBd in 
 
 woc^S. 16&- 
 
. In 
 
 Index, 
 
 Par. 
 
 225 
 
 iLOADy distributed ,dead, and 
 
 moving 253 
 
 LOADING HORSES in rail- 
 
 TOad'cats 393, 394 
 
 LOADING WAGONS on rail- 
 road cars : 3Q6 
 
 LOG, cubic contents of 254,335 
 
 buoj'^a ncy of. . . . : ...;..,. 3:^4 
 
 ILOGS, pi rs of, construction 
 
 of : 3H8^ 
 
 LONG SPLICE, to make 221 
 
 LOOPHOLES, atmensions of 164 
 height of, how influenced. 166 
 
 how made 40 
 
 in buildings 194 
 
 LOO PHOLING WALLS 163 
 
 method of 164,165 
 
 MACADAM ROADS 364 
 
 MACHICOULIS gallery, con- 
 struction of, use of 199 
 
 MAGAZINE, general plan 
 
 of 141, 142 
 
 large, small in parapet 140 
 
 of gabions and fascines. . . 143 
 rifle, range, speed, and 
 
 flreof 14 
 
 MAGNETO EXPLODE^ 430 
 
 MARKING FORDS 293 
 
 MATEKIALS for bridges 287 
 
 . for road coverings 365 
 
 revetting 114 
 
 used in defense of build- 
 ings 200 
 
 MAXIMUM LOAD for bridge 
 
 MERLON, deflnition of, rule 
 
 as to adnimum length of 
 
 METAL TIES 37 
 
 MILITARY ENGINEERS, du- 
 ties of 421 
 
 MILITARY TELEGRAPH 
 
 lines 418 
 
 MINES, land, quantity of ex- 
 plosive necessary 60 
 
 MOVING or LIVE LOADS. .. 253 
 
 104 
 
 OBJECTS, floating, protec- 
 tion of bridge from 352 
 
 OBSTACLES, conditions gov- 
 erning use of 49 
 
 OFFICE TELEGRAPH.tveat- 
 
 ment of when captured. 420 
 
 OVENS 495-6 
 
 Buzzacott 497 
 
 ORGANIZATIONS, or parts 
 of, used as working par- 
 ties 42 
 
 OVERHAUL TACKLE 231 
 
 PAINE'S BRIDGE 260 
 
 PALISADES, consist of 54 
 
 PALISADING, destruction of 435 
 
 PAIRING 118 
 
 Pm. 
 
 PAN COUPE 101 
 
 PARADOS, deflnition of 
 
 meihod of determining 
 
 \ height of 93 
 
 PARALLEL to a given line, 
 
 . method of constructing. 23 
 PARALLELS and approaches, 
 
 , Fort Wagner 160 
 
 PARAPET 63, 67,81 
 
 PERPENDICULAR to a line 
 
 method of erecting 19' 
 
 PICKETS, forked 119 
 
 gabion 118 
 
 PIERS, bridge, how de- 
 stroyed 440, 449 
 
 floating, essentials of 314 
 
 of casks, precautions in 
 
 using 327 
 
 of open boats, precautions 
 
 in using 315 
 
 of open caskn, construc- 
 tion of 328 
 
 of closed casks, construe 
 
 tlonof 330,333 
 
 of logs, construction of .338, 339 
 
 PILEBRIDGES 269 
 
 driving 2'70 
 
 PLANK ROADS 372 
 
 PLANKS, when used for re- 
 vetments 124 
 
 PLOWS, useof 33 
 
 PONTON CANVA>, U. S.. 
 crib, construction of. 
 PONT(>N, box, construction 
 
 of 
 
 reserve train, U. S 
 
 wagon body, construction 
 
 of 
 
 POLES, telegraph, how num- 
 bered 415 
 
 telegraph, how guyed, 
 number tomile,prepaia- 
 tion of, protection from 
 lightning, raising of, 
 
 size of, where run 409, 411 
 
 PORTABLE RAMP 393 
 
 fllters 483, 484 
 
 truss 279 
 
 POSITION .' defensive," deflnjl 
 tion of, chief requisite 
 
 of 4 
 
 choice of 42 
 
 strength of 153 
 
 conditions to be fulfllled.. 4 
 
 of ford, how determined. . 293 
 
 POWER of horse on slopes. . . 356 
 
 exerted by man 236 
 
 of tackle 233-5 
 
 PRECAUTIONS, additional, 
 
 in defending buildings.. 198 
 
 in fording 295 
 
 PROFILES, angle, how deter- 
 mined 94 
 
 deflnition and nomencla- 
 ture of 65 
 
 normal, of fleld works 99 
 
 319 
 322 
 
 323 
 
 320 
 
 324 
 
226 
 
 Index, 
 
 Par. 
 
 PROFILING, method of 94 
 
 PU LLE Y, descriptiou of 228 
 
 QUEEN-POST TRUSS 273 
 
 RACK, fascine, description 
 
 and use of 117 
 
 lashing to make 224 
 
 RAFT, canvas, description of, 303 
 
 for trail bridge ;W8 
 
 of skins 304 
 
 RAFTS, advantages and dis 
 
 ad vantages of :^5 
 
 for flying bridge 340 
 
 swinging, for traffic 351 
 
 RAIL Fastenings :«2 
 
 form of 380 
 
 joints 381 
 
 how cut 435 
 
 straightening 407 
 
 RAILROAD, bridge 245 
 
 crossings :^85 
 
 junction 386 
 
 wye 387 
 
 turntable 388 
 
 RAILROADS, duties of troops 
 
 in connection with 375 
 
 descri ption of 377 
 
 destroying and disabling, 
 
 by whom done 398-400 
 
 how disabled and des- 
 troyed 402, 403 
 
 repair of 404 
 
 rolling stock, buildings, 
 etc 390, 391 
 
 RAM P. port a Die 393 
 
 Major Fechet's 397 
 
 semi-permanent 395 
 
 simple form of 392 
 
 RANDING 1*22 
 
 REDOUBTS 84 
 
 RELIEFS, 1st, 2nd and 3rd of 
 working party, cutting 
 
 lines for tasks of 
 
 of field work, definition of 
 
 RESERVE TRAIN, ponton, 
 
 U. S 320 
 
 REVETMENT, definition of 113 
 making and qualities of 
 
 adobe 137 
 
 of brushwood 128 
 
 of fascines 129 
 
 of gabion 130 
 
 of hurdle and continuous 
 
 hurdle 131 
 
 of pisa 136 
 
 of plank 124, 132 
 
 of posts 135 
 
 of sand bag 133 
 
 of sod 126, 133 
 
 of timber 125, 132 
 
 of bamboo 137a 
 
 RIBBANDS 55 
 
 ROAD-BED 360 
 
 defense of 173 
 
 materials 365 
 
 101 
 
 Par, 
 
 ROADS, brushwood 371 
 
 clay 367 
 
 corduroy 370 
 
 desirable conditions in 354 
 
 drainage of 361 
 
 earih 366 
 
 form of 359 
 
 gravel 368 
 
 knowledge of 353 
 
 limiting gradients of 355 
 
 plank 372 
 
 repair of 369 
 
 surface of 362 
 
 width of 358 
 
 ROADWAY, weight of, steadi- 
 ness of 313 
 
 width of on bridges. . .248, 280-6 
 ROPE, breaking loads of, 
 
 weight of 218 
 
 composition, size of, etc . . 216 
 
 ROPE, parts of 219, 230 
 
 rule for strength of 217 
 
 expedient for tightening, 308 
 
 ROUND TIMBER, strength of, 255 
 
 RUNNING BLOCKS 228 
 
 SAG in telegraph wire 414 
 
 SALIENT village, liow de- 
 fended 212 
 
 SAND-BAGS, materials, size, 
 
 capacity, and filling 127 
 
 SAP, flying, description of.. 15V 
 
 SAW, teeth of 44 
 
 use of 44 
 
 SECTOR OF FIRE, definition 
 of and application to dif- 
 ferent traces 86 
 
 SELECTING CAMPS 455-6, 462 
 
 SENTRY BOXES 504 
 
 SEWING, liiethod of , for gabi- 
 ons and hurdles 18 
 
 SHE \R LASHINGS 226 
 
 S HE A KS, description of 238 
 
 method of using 240 
 
 SHKLL 9 
 
 charges, how exploded 12 
 
 penetration 15a 
 
 shrapnel 10 
 
 SHORT SPLICE, to make 220 
 
 SHOVEL ERS, extra, provid- 
 ed when 101 
 
 SIDINGS, railroad 384 
 
 SINGLE LOCK BRIDGE. 274 
 
 SINGLE SLING BRIDGE 276 
 
 SITE for floating bri dge, selec- 
 tion of 311 
 
 plane of, definition 73 
 
 SIZE OF TELEGRAPH 
 
 WIRE 408 
 
 SLEWING 122 
 
 SLOPE, banquette 65 
 
 description of 17 
 
 exterior 65, 77 
 
 interior 65, 75 
 
 superior 65, 76 
 
Index. 
 
 227 
 
 Par. 
 
 SMALL PITS, how made 57 
 
 how destroyed. 453 
 
 SNATCH BLOCK 228 
 
 SODS for revetments, cutting 
 
 and laying 126 
 
 SPAN, superstructure, string- 
 ers oi- balks, side rails, 
 
 etc 248 
 
 SPANS, 25-ft. or less 258 259 
 
 25-ft. or over 261. 271, 276 
 
 SPARS, arrangement of 257 
 
 SPLICE, long 221 
 
 eye 222 
 
 SPLINTEll PKOOF for Iren- 
 
 STOCKADE, advantages of, 
 
 definition of 180 
 
 how destroyed 436 
 
 kind of timber preferable 
 
 for 186 
 
 loopholes in 184 
 
 loopholes, when cut in 185 
 
 of vertical timbers 182 
 
 of same, square and round 
 
 timbers 183 
 
 of horizontal timber 187 
 
 STOCKADE, of K. R. iron, de- 
 stroyed how 436 
 
 when employed 181 
 
 work used for tambours 
 
 and caponiers 188 
 
 STRAIGHTENING KAILS.. . 407 
 STREAMS, unfordable, how 
 
 passed 294 
 
 velocity of, how deter- 
 mined 296 
 
 width of, how determined, 312 
 
 STRENGTH OF MATERIALS 249 
 
 of rope 217, 218 
 
 SUB-DRAINS 361 
 
 SUSPENSION BRIDGES 280-6 
 
 S WITCH, split and stub 384 
 
 TAB LE of breaking loads ... 218 
 
 of constant "C" 253 
 
 of weights of materials 256 
 
 showing amounts of revet- 
 ting materials for 100 
 
 linear feet of revetment, 137 
 
 TACKLE, description of 229 
 
 formula for power of 235 
 
 powerof 233-4 
 
 to prevent twisting 232 
 
 to round in, to overhaul. . . 231 
 
 TAMBOUR 147 
 
 stockade work used for. . . 188 
 
 used in flanking buildiufs, 199 
 
 TASKS (PI. 14, 16) 111, 112 
 
 laying out of 101 
 
 in constructing parallels 
 
 and approaches PI. 22 
 
 responsibility for comple- 
 tion of 106 
 
 TELEGRAPH MESSAGES. .. 408 
 
 lines, how destroyed 4'20 
 
 TELEPHONE,outpost cart for 418 
 
 Par. 
 
 TELFORD ROADS 363 
 
 TERREPLEIN 74 
 
 THICKNESS of materials 
 
 proof against small arms, 15 
 
 TIES, metal 379 
 
 wood 378 
 
 TIMBER BRIDGE, how de 
 
 stroyed 433 
 
 felled, removal of 45 
 
 kinds preferable for stock- 
 ade 186 
 
 rouu'l for revetments 125 
 
 standing, removal of 43, 44 
 
 TOOLS, carrying of by work- 
 ing parties 108 
 
 cutting, intrenching used 
 
 in the field 41 
 
 taking of, by working par- 
 ties 107 
 
 used in felling tember 44 
 
 TORPEDO, U. S. bridge 433 
 
 TORPEDOES, automatic 453 
 
 TRACE, definition of 64 
 
 selection of 89 
 
 TUANSOM, strength of 250 
 
 TllAVEKSE, definition of 68 
 
 method of determining 
 
 height of ^3 
 
 TREAD BANQUETTE 65 
 
 TREBLE SLING BRIDGE.... 277 
 
 TREE INSULATOR and tie.. 415 
 
 TKKES, cutting of 44,45 
 
 how to fell with explosives, 432 
 
 TRKNCH 65 
 
 common.nsesof.howmttde, 156 
 
 d rainage of 98 
 
 method of digging lUl 
 
 TRENCHES, advantages and 
 
 disadvantages of 39 
 
 conditions to be fulfilled 
 
 by 28 
 
 disguising location of 38 
 
 intervals in line of 36 
 
 kneeling or sitting 30 
 
 location of 35 
 
 lying 29 
 
 standing 81 
 
 Spanish 31 
 
 TROOPS, weight of on bridge, 252 
 
 TRESTLES, capped 264 
 
 tie block 263 
 
 two-legged 265 
 
 three-legged 266 
 
 four-legged 267 
 
 six-legged 262 
 
 TRUSS, king- post 272 
 
 queen-post 273 
 
 portable 279 
 
 TUNNELS, how destroyed.... 442 
 
 repair of 406 
 
 TURNTABLES, railroad 388 
 
 UNLOADING in ferrying.... 301 
 
 horses from R. R. cars.. 393, 394 
 
 wagons from cars 396 
 
 URINALS 488, 489 
 
228 Index. 
 
 Par. 
 VELOCITY of streams, how i 
 
 determined 296 i 
 
 VILLAGE, advantages and 
 disadvantages of for de- 
 fense 206 
 
 artillery, wliere placed in 
 
 defense of. 215 
 
 broadside, how defended.. 213 
 circular, how defended.... 214 
 cover for supports and re- 
 serves in 215 
 
 in defense of, precautions 
 
 necessary 205 
 
 defense of depends on.. .. 208 
 arrangements for defense 
 
 of 205 
 
 garrison of, how deter- 
 mined 211 
 
 objfcts in holding 207 
 
 salient, how defended 212 
 
 value of, for defense 205 
 
 arrangement for defense 
 of, how made 210 
 
 WAGON BODY PONTON, con- 
 struction of 324 
 
 WAGONS, prepared for cross- 
 ing on ice 299 
 
 WALLS, for double tiers of 
 
 fire 16T 
 
 discussion of as military 
 
 expedients 161 
 
 loopholing 163-5 
 
 preparation of for defense 162 
 
 removal of 48 
 
 how destroyed 439 
 
 WATER, clarification of 476 
 
 drinking 465-9 
 
 filtering 480-1 
 
 guarding 464 
 
 necessity of and amount 
 
 required 463-4 
 
 WATER TABLES on roads... 361 
 
 WATLING 118 
 
 WEEDS, removal of 47 
 
 WEIGHT of materials 256 
 
 of rope 218 
 
 of troops on bridge 252 
 
 WELLS, digging of 470-2 
 
 driven 47;^4 
 
 WIDTH OF ROADS 358 
 
 WINCH 240 
 
 WINDLASS, description of.. 241 
 WINDBREAKS, for (tamps.... 500 
 WINDOWS of buildings, how 
 
 barricaded 197 
 
 Par. 
 
 WIRR, connection of 431 
 
 entanglements, high, low, 
 
 how made 52, 53 
 
 entanglements, how de- 
 stroyed 464 
 
 how stretched, hanging 
 
 of , secured to 414 
 
 liow strung across roads.. . 411 
 how strung across streams 415 
 
 telegraph 408 
 
 tie 413 
 
 WITHES, making and use of 117 
 
 WO()D<, artillery in 179 
 
 communications in 177 
 
 cover in 176 
 
 lying beyond position 175 
 
 number of defenders of... 179 
 
 preparation of edge of 174 
 
 2d and 3d lines in 178 
 
 WORKS, constructed by 
 
 troops to occupy 5 
 
 double line of 150 
 
 fixed types of necessary. . . t> 
 groups of, intermediate, 
 
 when used 149 
 
 line of 148 
 
 advantages and principles 
 
 of 149 
 
 WORKS, field, conditions to 
 
 be fulfilled 62 
 
 calculation of cross sec- 
 tion of 95 
 
 classification as to trace. . 83 
 
 defilade of 88, 89 90, 91, 92 
 
 details of constiniction of 
 
 99, 100, 101 
 
 length of crest for as- 
 sumed garrison 100 
 
 open, closed, and half 
 closed, definitions, ad- 
 vantages, and disadvan- 
 tages 83 
 
 continuous line of, crem- 
 aillere, blunted redan, 
 redan with curtains, te- 
 naille. tenaille and re- 
 dan, trace of 152 
 
 WORKING parties, extensio»» 
 
 of 109. 110 
 
 organization of 105 
 
 whenunderfire Ill 
 
 WYE, R. R 387 
 
 ZIG-ZAG, direction of, length 
 
 of 159 
 
 extending along 155 
 
YB 49784 
 
 /f62 
 
 THE UNIVERSITY OF CALIFORNIA LIBRARY